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''life magazine'' http scientific practicescom making scientific practices matter ''classroomand beyond '' http wwwxvivonet xvivo scientific animation science communication observatory http scientixeu scientix portal science maths education europe http sciencecaseslibbuffaloedu cs national center case study teaching science nccsts http blossomsmitedu blossoms mit free science education videos http wwwidtc iuhpscom inter divisional teaching commission idtc international union history philosophy science iuhps http ihpstnet international history philosophy science teaching group

Applied science
Education
Curriculum and instruction
Science education


'''social conflict theory''' marxist based social theory argues individuals groups social classes within society interact basis conflict rather consensus various forms conflict groups tend attain differing amounts material non material resources eg wealthy vs poor powerful groups tend use power order retain power exploit groups less power conflict theorists view conflict engine change since conflict produces contradictions sometimes resolved creating new conflicts contradictions ongoing dialectic

Social science
Sociology
Social conflict theory


classic example historical materialism karl marx friedrich engels argued human history result conflict classes evolved time accordance changes society 's means meeting material needs ie changes society 's mode production example sample following consider relationship owner housing complex tenant housing complex consensus theorist might suggest relationship owner tenant founded mutual benefit contrast conflict theorist might argue relationship based


conflict owner tenant struggling relationship defined balance abilities extract resources eg rent payments place live bounds relationship set extracting maximum possible amount resources conflict take many forms involve struggle many different types resources including status however formal conflict theory foundations analysis class conflict example owner tenant understood


terms class conflict class conflict owners likely relative advantages non owners example legal system underlying relationship owner tenant biased favor owner suppose owner wishes keep tenant 's security deposit tenant moved owner 's residence legal systems based english common law owner required notify tenant security deposit withheld regain security deposit tenant must file lawsuit tenant bears burden proof


therefore required prove residence adequately cleaned move difficult even impossible task summarize example conflict theorists view relationship owner tenant built primarily conflict rather harmony even though owner tenant relationship may often appear harmonious visible harmony product law elements superstructure constrain relationship product even deeper conflict class conflict conflict theorist would say conflict theory holds explanatory power


classes develop market economies individuals compete economic gain defines class group individuals share similar position market economy virtue fact receive similar economic rewards thus person 's class situation basically market situation share similar class situation also share similar life chances economic position directly affect chances obtaining things defined desirable society see also identity politics iron law oligarchy group decision making marxist cultural analysis evidence based policy autonomy references marx karl preface


http platostanfordedu entries critical theory critical theory sociological theories marxist theory identity politics social conflict change power social political theories


western front '''trench warfare''' type land warfare using occupied fighting lines largely comprising military trenches troops well protected enemy 's small arms fire substantially sheltered artillery trench warfare became archetypically associated world war race sea rapidly expanded trench use western front starting september ref name ellis p ref trench warfare proliferated revolution firepower matched similar advances mobility resulting gruelling form warfare defender held advantage

Applied science
Military sciences
Tactics
Trench warfare


western front sides constructed elaborate trench underground dugout systems opposing along front protected assault barbed wire area opposing trench lines known man 's land fully exposed artillery fire sides attacks even successful often sustained severe casualties development armoured warfare combined arms tactics permitted static lines bypassed defeated leading decline trench warfare war following world war trench warfare became byword stalemate attrition sieges futility conflict precursors


vicksburg new zealand wars maori developed elaborate trench bunker systems part fortified areas known p employing successfully early withstand british artillery bombardments according one british observer fence round pa covered every paling loose bunches flax bullets fall drop night repair every hole made guns ref name carv b ref systems included firing trenches communication trenches tunnels anti artillery bunkers british casualty rates percent gate


pa battle ohaeawai suggested contemporary weaponry muskets cannon proved insufficient dislodge defenders trench system academic debate surrounding since book ''the new zealand wars'' historian james belich claimed northern ori effectively invented trench warfare first stages new zealand wars however criticised academics gavin mclean noting ori certainly adapted p suit contemporary weaponry many historians dismissed belich claim


baseless revisionism crimean war saw massive trench works trench warfare even though modernity trench war immediately apparent contemporaries union confederate armies employed field works extensive trench systems american civil war notably sieges vicksburg petersburg latter saw first use union army rapid fire gatling gun important precursor modern day machine guns trenches also utilized paraguayan war started second anglo boer war


russo japanese war adoption arras trenches th cheshire regiment ovillers la boisselle somme july one sentry keeps watch others sleep photo ernest brooks st lancashire fusiliers communication trench near beaumont hamel somme photo ernest brooks although technology dramatically changed nature warfare armies major combatants fully absorbed implications fundamentally range rate fire rifled small arms increased defender shielded enemy fire trench house window behind large


germans relied firepower investing heavily howitzers machine guns british lacked official tactical doctrine officer corps rejected theory favour pragmatism armies expected use entrenchments cover allow effect defences depth required deliberate approach seizing positions fire support could given next phase attack rather rapid move break enemy 's line assumed artillery could still destroy entrenched troops least suppress sufficiently


friendly infantry cavalry manoeuvre french trench northeastern france digging defending position standard practice start wwi attack frontally court crippling losses outflanking operation preferred method attack entrenched enemy battle aisne september extended series attempted flanking moves matching extensions fortified defensive lines developed race sea end german allied armies produced matched pair trench lines swiss border


associated casualties became inevitable continuous trench lines open flanks casualties defenders matched attackers vast reserves expended costly counter attacks exposed attacker 's massed artillery periods rigid trench warfare broke battle somme lines never moved far war would side able commit last reserves western front trench warfare prevailed western front germans launched spring offensive march


trench warfare also took place fronts including italy gallipoli armies also limited logistics heavy use artillery meant ammunition expenditure far higher wwi previous conflict horses carts insufficient transporting large quantities long distances armies trouble moving far railheads greatly slowed advances making impossible either side achieve breakthrough would change war situation would altered wwii greater use motorized vehicles construction trench construction diagram


british infantry manual indian infantry digging trenches fauquissart france august soldiers training trench warfare well defined fire bays connected offset traverse trenches zigzag communication trenches leading rear area early world war trenches simple lacked traverses according pre war doctrine packed men fighting shoulder shoulder doctrine led heavy casualties artillery fire vulnerability length front defended soon led front line trenches held fewer men defenders augmented trenches


barbed wire strung front impede movement wiring parties went every night repair improve forward defences small improvised trenches first months grew deeper complex gradually becoming vast areas interlocking defensive works resisted artillery bombardment mass infantry assault shell proof dugouts became high priority well developed trench least deep allow men walk upright still protected three standard ways dig trench entrenching sapping tunnelling entrenching man would stand surface


dig downwards efficient allowed large digging party dig full length trench simultaneously however entrenching left diggers exposed ground hence could carried free observation rear area night sapping involved extending trench digging away end face diggers exposed one two men could work trench time tunnelling like sapping except roof soil left place trench line


established removed trench ready occupied guidelines british trench construction stated would take men hours night complete front line trench system thereafter trench would require constant maintenance prevent deterioration caused weather shelling components breastwork trench armenti res australian light horseman using periscope rifle gallipoli banked earth lip trench facing enemy called parapet fire step embanked rear lip trench called parados


protected soldier 's back shells falling behind trench sides trench often revetted sandbags wire mesh wooden frames sometimes roofs floor trench usually covered wooden duckboards later designs floor might raised wooden frame provide drainage channel underneath static movement trench warfare need protection snipers created requirement loopholes discharging firearms observation ref name one https ww revisitedcom trench loopholes le linge trench loopholes le linge ref often steel plate used key hole rotating


piece cover loophole use ref name one german snipers used armour piercing bullets allowed penetrate loopholes another means see parapet trench periscope simplest form stick two angled pieces mirror top bottom number armies made use periscope rifle enabled soldiers snipe enemy without exposing parapet although cost reduced shooting accuracy device associated australian new zealand troops gallipoli turks


straight dug zigzagging stepped pattern straight sections generally kept less dozen meters yards later evolved combat trenches broken distinct fire bays connected traverses isolated view friendly soldiers along trench ensured entire trench could enfiladed enemy gained access one point bomb grenade shell landed trench blast could travel far early war british defensive doctrine suggested main trench system three


parallel lines interconnected communications trenches point communications trench intersected front trench critical importance usually heavily fortified front trench lightly garrisoned typically occupied force stand dawn dusk behind front trench located support travel trench garrison would retreat front trench bombarded rear located third reserve trench reserve troops could amass counter attack front trenches captured defensive


layout soon rendered obsolete power artillery grew however certain sectors front support trench maintained decoy attract enemy bombardment away front reserve lines fires lit support line make appear inhabited damage done immediately repaired aerial view opposing trench lines loos hulluch july german trenches right bottom british top left temporary trenches also built major attack planned assembly trenches would dug near front trench


could assailed three sides behind front system trenches usually least two partially prepared trench systems kilometres rear ready occupied event retreat germans often prepared multiple redundant trench systems somme front featured two complete trench systems one kilometre apart third partially completed system kilometre behind duplication made decisive breakthrough virtually impossible event section first trench system captured switch trench would dug connect second


trench system still held section first wire french soldiers struggle pass multiple lines barbed wire use lines barbed wire razor wire wire obstacles belts deep effective stalling infantry traveling across battlefield although barbs razors might cause minor injuries purpose entangle limbs enemy soldiers forcing stop methodically pull work wire likely taking several seconds even longer deadly wire emplaced points maximum


exposure concentrated enemy firepower plain sight enemy fire bays machine guns combination wire firepower cause failed attacks trench warfare high casualties liddell hart identified barbed wire machine gun elements broken regain mobile battlefield basic wire line could created draping several strands barbed wire wooden posts driven ground loose lines wire effective entangling tight ones common use coils


barbed wire delivered partially stretched called concertina wire placing repairing wire man 's land relied stealth usually done night special wiring parties could also tasked secretly sabotaging enemy wires screw picket invented germans later adopted allies war quieter driving stakes wire often stretched entire length battlefield 's trench line multiple lines sometimes covering depth methods defeat rudimentary prolonged artillery bombardment could damage reliably first


soldier meeting wire could jump onto top hopefully depressing enough followed get still took least one soldier action line wire world war british commonwealth forces relied wire cutters proved unable cope heavier gauge german wire ref name canada 's army p bangalore torpedo adopted many armies continued use past end world war ii barbed wire used differed nations german wire heavier gauge british wire cutters


upon hills named height metres hill farmhouse windmill quarry copse trees would become focus determined struggle simply largest identifiable feature however would take artillery long obliterate thereafter became name map battlefield flanders presented numerous problems practice trench warfare especially allied forces mainly british canadians often compelled occupy low ground heavy shelling quickly destroyed network ditches


water channels previously drained low lying area belgium places water table metre surface meaning trench dug ground would quickly flood consequently many trenches flanders actually ground constructed massive breastworks sandbags filled clay initially parapet parados trench built way later technique dispense parados much trench line thus exposing rear trench fire reserve line


case front breached alps trench warfare even stretched onto vertical slopes deep mountains heights sea level ortler artillery position summit near front line trench line management trench profiles adapted rough terrain hard rock harsh weather conditions many trench systems constructed within glaciers adamello presanella group famous city ice marmolada dolomites man 's land space opposing trenches referred


man 's land varied width depending battlefield western front typically though vimy ridge german withdrawal hindenburg line march man 's land stretched kilometre places quinn 's post cramped confines anzac battlefield gallipoli opposing trenches apart soldiers trenches constantly threw hand grenades eastern front middle east areas covered vast


distances factories supplying shells bullets concrete barbed wire great trench warfare west european style often occur weaponry infantry weapons machine guns british mills bomb n mk ii rod launch rifle start first world war standard infantry soldier 's primary weapons rifle bayonet weapons got less attention especially british hand grenades issued tended numbers less effective emphasis began shift soon trench warfare began


militaries rushed improved grenades mass production including rifle grenades hand grenade came one primary infantry weapons trench warfare sides quick raise specialist grenadier groups grenade enabled soldier engage enemy without exposing fire require precise accuracy kill maim another benefit soldier could get close enough trenches enemies hiding trenches could attacked germans turks well equipped grenades start war british


ceased using grenadiers anticipate siege war entered conflict virtually none soldiers improvise bombs whatever available see jam tin grenade late british mills bomb entered wide circulation end war million used since troops often adequately equipped trench warfare improvised weapons common first encounters short wooden clubs metal maces spears hatchets hammers entrenching tools well trench knives brass knuckles according semi biographical


war novel ''all quiet western front'' many soldiers preferred use sharpened spade improvised melee weapon instead bayonet bayonet tended get stuck stabbed opponents rendering useless heated battle shorter length also made easier use confined quarters trenches tools could used dig taken trench modern military digging tools rule designed also function melee weapon war progressed better equipment issued improvised arms


discarded various trench weapons used british canadian soldiers wwi display canadian war museum french soldiers sauterelle bomb throwing crossbow c specialised group fighters called ''trench sweepers'' ''nettoyeurs de tranch es'' ''zigouilleurs'' evolved fight within trenches cleared surviving enemy personnel recently overrun trenches made clandestine raids enemy trenches gather intelligence volunteers dangerous work often exempted participation frontal assaults open ground routine work like filling sandbags draining trenches repairing barbed wire man 's land allowed


used american soldiers western front pump action shotgun formidable weapon short range combat enough germany lodged formal protest use september stating every prisoner found possession guns ammunition belonging thereto forfeits life though threat apparently never carried us military began issue models specially modified combat called trench guns shorter barrels higher capacity magazines choke often heat shields around barrel well lugs bayonet anzac


six per battalion russians eight would every infantry unit american forces carried least one machine gun maschinengewehr standard issue german machine gun number entered german language idiomatic dead plain gallipoli palestine turks provided infantry usually germans manned machine guns british high command less enthusiastic machine guns supposedly considering weapon unsporting encouraging defensive fighting lagged behind germans adopting


field marshal sir douglas haig quoted saying machine gun much overrated weapon two per battalion sufficient defensive firepower machine gun exemplified first day battle somme british soldiers rendered casualties great majority lost withering machine gun fire machine gun corps formed train provide sufficient heavy machine gun teams canadians made best practice pioneering area denial indirect fire soon adopted allied armies


guidance former french army reserve officer major general raymond brutinel minutes attack vimy ridge canadians thickened artillery barrage aiming machine guns indirectly deliver plunging fire germans also significantly increased number machine guns per battalion match demand production vickers machine gun contracted firms united states every company british forces also equipped four lewis light machine guns significantly enhanced firepower heavy machine gun specialist weapon static


hundreds enemies charging open man 's land however wwi machine guns able shoot hundreds rounds per minute theory still prone overheating jamming often necessitated firing short bursts however potential increased significantly emplaced behind multiple lines barbed wire slow advancing enemy new types weapons fielded changed face warfare tactics later employed world war ii french introduced csrg chauchat spring around concept


walking fire employed weapons fielded best shooters received semi automatic rsc rifle allowing rapid fire waves attacking soldiers firing ports installed newly arrived renault ft tanks french army fielded ground version hotchkiss canon de nbsp mm used french navy primarily used destroy german machine gun nests concrete reinforced pillboxes high explosive armour piercing rounds new type machine gun introduced initially aircraft weapon bergmann lmg


modified ground use later dedicated ground version lmg n used infantry weapon european middle eastern fronts end world war later inspired mg mg well concept general purpose machine gun became known submachine gun genesis world war developed around concepts infiltration fire movement specifically clear trenches enemy soldiers engagements unlikely occur beyond range


feet mp first practical submachine gun used combat fielded german army primary weapon stormtroopers assault groups specialised trench combat around time italians developed beretta submachine gun based design earlier war artillery abbr howitzer artillery dominated battlefields trench warfare infantry attack rarely successful advanced beyond range supporting artillery addition bombarding enemy infantry trenches artillery


applied artillery pieces two types infantry support guns howitzers guns fired high velocity shells flat trajectory often used deliver fragmentation cut barbed wire howitzers lofted shell high trajectory plunged ground largest calibers usually howitzers german howitzer weighed tons could fire one ton shell critical feature period artillery pieces hydraulic recoil mechanism meant gun need aimed shot permitting tremendous increase


shell high arc relatively short distance widely used trench fighting harassing forward trenches cutting wire preparation raid attack destroying dugouts saps entrenchments british fired total mortar shells fired similarly howitzers fire direct arc mortars raised number shells smaller numerical difference mortar rounds opposed howitzer rounds presumed many related


expanded costs manufacturing larger resource intensive howitzer rounds main british mortar stokes precursor modern mortar light mortar simple operation capable rapid rate fire virtue propellant cartridge attached base shell fire stokes mortar round simply dropped tube percussion cartridge detonated struck firing pin bottom barrel thus launched germans used range mortars smallest grenade throwers


'granatenwerfer' fired stick grenades commonly used medium trench mortars called mine throwers 'minenwerfer' heavy mortar called 'ladungswerfer' threw aerial torpedoes containing charge range flight missile slow leisurely men receiving end could make attempt seek shelter mortars certain advantages artillery much portable ability fire without leaving relative safety trenches moreover mortar able fire directly trenches hard


artillery strategy tactics german trenches vimy fundamental strategy trench warfare world war defend one 's position strongly trying achieve breakthrough enemy 's rear effect end attrition process progressively grinding opposition 's resources ultimately longer able wage war prevent ambitious commander pursuing strategy annihilation ideal offensive battle produces victory one decisive engagement commander chief british forces


world war general douglas haig constantly seeking breakthrough could exploited cavalry divisions major trench offensives somme flanders conceived breakthrough battles degenerated costly attrition germans actively pursued strategy attrition battle verdun sole purpose bleed french army white time allies needed mount offensives order draw attention away hard pressed areas line french troopers using periscope popular image trench


assault wave soldiers bayonets fixed going top marching line across man 's land hail enemy fire standard method early war rarely successful common attack night advanced post man 's land cut barbed wire beforehand germans innovated infiltration tactics small groups highly trained well equipped troops would attack vulnerable points bypass strong points driving deep rear areas distance could advance


still limited ability supply communicate role artillery infantry attack twofold first aim bombardment prepare ground infantry assault killing demoralising enemy garrison destroying defences duration initial bombardments varied seconds days artillery bombardments prior infantry assaults often ineffective destroying enemy defences serving provide advance notice attack british bombardment began battle somme lasted eight days little damage either german barbed wire


deep dug outs defenders able wait bombardment relative safety guns stopped defenders time emerge usually ready attacking infantry second aim protect attacking infantry providing impenetrable barrage curtain shells prevent enemy counter attack first attempt sophistication lifting barrage first objective attack intensely bombarded period entire barrage lifted fall second objective farther back however usually expected much


infantry usual outcome barrage would outpace attackers leaving without protection resulted use creeping barrage would lift frequently smaller steps sweeping ground ahead moving slowly attackers could usually follow closely behind became standard method attack late onward main benefit barrage suppression enemy rather cause casualties material damage capturing objective half battle battle objective held


attacking force would advance weapons required capture trench also tools sandbags picks shovels barbed wire fortify defend counter attack successful advance would take attackers beyond range field artillery making vulnerable took time move guns broken ground germans placed great emphasis immediately counter attacking regain lost ground strategy cost dearly british started limit advances able meet anticipated counter attack position


strength part british artillery positioned close behind original start line took part initial bombardment ready support later phases operation guns moved germans first apply concept defence depth front line zone hundreds metres deep contained series redoubts rather continuous trench redoubt could provide supporting fire neighbours attackers freedom movement redoubts would subjected withering


enfilade fire also willing opponents make strategic withdrawal superior prepared defensive position british eventually adopted similar approach incompletely implemented germans launched spring offensive proved disastrously ineffective france contrast relied artillery reserves entrenchment life trenches distribution ''pinard'' ration wine french trench winter considered important morale studying french trenches ''the literary digest'' october hot shower bath establishment installed french engineer november individual unit 's


time front line trench usually brief little one day much two weeks time relieved st australian battalion spent days line villers bretonneux duration rare exception th battalion cef averaged front line tours six days units manned front line trenches longest portuguese expeditionary corps portugal stationed northern france unlike allies portuguese could n't rotate units front lines due lack


reinforcements sent portugal could replace depleted units lost manpower due war attrition rate casualties reinforcements forthcoming men denied leave serve long periods trenches units spending six consecutive months front line little leave time individual level typical british soldier 's year could divided follows front line support line reserve line rest hospital travelling leave training courses etc even


front line typical battalion would called upon engage fighting handful times year making attack defending attack participating raid frequency combat would increase units elite fighting divisions allied side british regular divisions canadian corps french xx corps anzacs front line anzac barber french trench sectors front saw little activity throughout war making life trenches comparatively easy anzac corps first arrived


france april evacuation gallipoli sent relatively peaceful sector south armenti res acclimatise contrast sectors perpetual state violent activity western front ypres invariably hellish especially british exposed overlooked salient however even quiet sectors amassed daily casualties sniper fire artillery disease poison gas first six months launch somme offensive british engage significant battles sector western front yet


suffered casualties men would return alive unwounded trenches sector front would allocated army corps usually comprising three divisions two divisions would occupy adjacent sections front third would rest rear breakdown duty would continue army structure within front line division typically comprising three infantry brigades regiments germans two brigades would occupy front third would reserve within front line brigade typically comprising four battalions two battalions


barbed wire trench system reconnaissance enemy 's defenses sentries listening posts man 's land would try detect enemy patrols working parties indications attack prepared pioneered princess patricia 's canadian light infantry february ref name canadasarmyp ''canada 's army'' p ref trench raids carried order capture prisoners booty mdash letters documents provide intelligence unit occupying opposing trenches war progressed raiding became part general british policy intention maintain fighting spirit


troops deny man 's land germans well intended compel enemy reinforce exposed troops artillery fire ref name canadasarmyp dominance achieved high cost enemy replied artillery ref name canadasarmyp post war british analysis concluded benefits probably worth cost early war surprise raids would mounted particularly canadians increased vigilance made achieving surprise difficult war progressed raids carefully planned exercises combined arms involved close co operation


infantry artillery raid would begin intense artillery bombardment designed drive kill front trench garrison cut barbed wire bombardment would shift form box barrage cordon around section front line prevent counter attack intercepting raid however bombardment also effect notifying enemy location planned attack thus allowing reinforcements called wider sectors dangers german machine gun position capture new zealand soldiers dead german


among debris grevillers august hundred days offensive passchendaele august mine explosion messines ridge approximately percent soldiers fought first world war died result ref name main cause death trenches came shelling gunfire diseases infections always present became massive burden sides war progressed medical procedures considerably effective previous time history still helpful antibiotics yet discovered invented result infection


caught trench often went untreated could fester soldier died injuries main killer trenches artillery fire around percent known casualties ref name ref even soldier hit directly artillery shell fragments debris high chance wounding close proximity blast artillery use increased tremendously war example percentage french army artillerymen grew percent percent ref name second largest contributor death


gunfire bullets rifles machine guns responsible percent french military casualties ref name ref war entered static phase trench warfare number lethal head wounds troops receiving fragmentation increased dramatically french first see need greater protection began introduce steel helmets summer adrian helmet replaced traditional french kepi later adopted belgian italian many armies time british developing helmets french design


rejected strong enough difficult mass produce design eventually approved british brodie helmet wide brim protect wearer falling objects offered less protection wearer 's neck americans entered war helmet chose though units used french adrian helmet disease predominant disease trenches western front trench fever trench fever common disease spread faeces body lice rampant trenches trench fever caused


headaches shin pain splenomegaly rashes relapsing fevers resulting lethargy months first reported western front british medical officer additional cases trench fever became increasingly common mostly front line troops microbiologist sir david bruce reported one million allied soldiers infected trench fever throughout war even great war ended disabled veterans britain attributed decreasing quality life trench fever sustained wartime early war gas gangrene commonly developed major wounds part


''clostridium'' bacteria responsible ubiquitous manure fertilized soil common western european agriculture france belgium dirt would often get wound rammed shrapnel explosion bullet wounded british soldiers developed gas gangrene least german soldiers died directly infection rapid advances medical procedures practices incidence gas gangrene fell entrenched soldiers also carried many intestinal parasites ascariasis trichuriasis tapeworm ref name ref parasites common amongst soldiers spread amongst


due unhygienic environment created common trench true sewage management procedures ensured parasites diseases would spread onto rations food sources would eaten soldiers ref name trench foot common environmental ailment affecting many soldiers especially winter one several immersion foot syndromes characterized numbness pain feet bad cases could result necrosis lower limbs trench foot large problem allied forces resulting american


british casualties mandatory routine daily often foot inspections fellow soldiers along systematic use soap foot powder changing socks greatly reduced cases trench foot us infantry issued improved waterproof 'pershing boot' attempt reduce casualties trench foot surprise medical professionals time outbreak typhus trenches western front despite cold harsh conditions perfect reproduction body lice transmit disease however eastern


front epidemic typhus claimed lives serbia russia also suffered globally unprecedented typhus epidemic last two years conflict exacerbated harsh winters outbreak resulted approximately million recorded deaths red army soldiers symptoms typhus include characteristic spotted rash always present severe headache sustained high fever nbsp c nbsp f cough severe muscle pain chills falling blood pressure stupor sensitivity light delirium die typhus spread body lice millions rats


called trenches home often responsible spread diseases attempts cull hordes trench rats rifle bayonets soldiers common early war rats reproduced faster could killed however soldiers still partook rat hunts form entertainment rats would feed half eaten uneaten rations well corpses many soldiers afraid rats horrors found trenches psychological impact nervous mental breakdowns amongst soldiers common due unrelenting shellfire claustrophobic trench environment


cases shell shocked soldiers executed cowardice commanders became liability often done firing squad composed fellow soldiers often unit years later would understood men suffering shell shock war british soldiers officially executed side circumvention throughout world war major combatants slowly developed different ways breaking stalemate trench warfare germans focused new tactics british french focused tanks


infiltration tactics sto truppen'' stormtroopers rising trenches attack far back th century prussian military doctrine ''vernichtungsgedanke'' stressed maneuver force concentration achieve decisive battle german military searched ways apply face trench warfare experiments new tactics willy rohr prussian captain serving vosges mountains got attention minister war tactics carried prussian military doctrine smallest units specially trained troops maneuvered massed assault positions chose next two


intended achieve surprise disrupting entrenched enemy positions aimed bypass strongpoints attack weakest parts enemy 's line additionally acknowledged futility managing grand detailed plan operations afar opting instead junior officers spot exercise initiative germans employed improved infiltration tactics series smaller larger battles increasingly successful leading battle caporetto italians finally massive german spring offensive british french german infiltration tactics sometimes called hutier


tactics others oskar von hutier general leading german th army farthest advance offensive stunningly rapid advance offensive failed achieve breakthrough german forces stalled outrunning supply artillery reinforcements could catch shell torn ground left ruined allied attacks battle somme exhausted german forces soon pushed back allied hundred days offensive germans unable organise another major offensive war 's end post war years nations


fully appreciate german tactical innovations amidst overall german defeat mining explosion mine seen french position plan ''y sap'' mine mines tunnels enemy lines packed explosives detonated widely used wwi destroy disrupt enemy 's trench lines mining counter mining became major part trench warfare dry chalk somme especially suited mining aid pumps also possible mine sodden clay flanders specialist tunneling companies usually made


men miners civilian life would dig tunnels man 's land beneath enemy 's trenches mines would packed explosives detonated producing large crater crater served two purposes could destroy breach enemy 's trench virtue raised lip produced could provide ready made trench closer enemy 's line mine detonated sides would race occupy fortify crater miners detected enemy tunnel progress would often counter mine try drive


tunnel enemy 's tunnel would detonate explosives create camouflet destroy enemy 's tunnel night raids also conducted sole purpose destroying enemy 's mine workings occasion mines would cross fighting would occur underground mining skills could also used move troops unseen one occasion whole british division moved interconnected workings sewers without german observation british detonated mines varying sizes july first day battle somme largest mines sap


mine lochnagar mine containing tons explosives blown near la boiselle throwing earth feet air small small june series mines detonated british launch battle messines average mine contained tons explosive largest feet beneath saint eloi twice average tons remarked general plumer staff evening attack gentlemen may make history tomorrow shall certainly change geography ref name ww dotcom ref craters many


first methods employing gas releasing cylinder wind favourable prone miscarry direction wind misjudged also cylinders needed positioned front trenches likely ruptured enemy bombardment later gas delivered directly enemy trenches artillery mortar shell reducing friendly casualties significantly lingering agents could still affect friendly troops advanced enemy trenches following use early soldiers made improvised gas masks urinating handkerchief putting


could suffer permanent lung damage gas easy detect scent sight phosgene first used december lethal killing gas world war times powerful chlorine much difficult detect however effective gas mustard gas introduced germany july mustard gas fatal phosgene hard detect lingered surface battlefield could inflict casualties long period even inhaled could slowly burn skin


failure tank cross anti tank trench tanks tanks developed british french means attack enemy trenches combining heavy firepower machine guns light artillery guns protection small arms fire armour battlefield mobility tracks british tanks designed rhomboid shape easily surmount barbed wire obstacles first deployed battle somme limited numbers proving unreliable ineffective first mechanical logistical issues overshadowed implementing coherent tank doctrine additional challenge traversing ground


torn apart years shell fire first battle cambrai improved tanks larger numbers demonstrated potential tank warfare though german improvised anti tank tactics including using direct fire field artillery also proved effective tank capabilities tactics improved numbers increased combined french tanks finally helped break stalemate last days war allied forces harried germans back using infantry supported tanks close air support war 's end tanks become significant element warfare proposed british plan


would employed tanks primary factor military strategy however impact tanks world war less could due late introduction inherent issues plague implementing revolutionary technology two world wars many nations developed unique tanks divergent theories tank tactics including uk france soviet union czechoslovakia japan us italy though german tank development restricted terms treaty ending world war germany successfully combined tanks plus czech tanks occupied


czechoslovakia infiltration tactics produce blitzkrieg world war ii later use side view diagram gun retractable turret block ouvrage schoenenbourg maginot line soldiers brazilian expeditionary force trench montese italian campaign world war ii world war ii decade leading world war ii french built maginot line based experience trench warfare world war maginot line extensive state art defensive system far superior previous


trench system chain massive constructions concrete iron steel fortresses bunkers retractable turrets outposts obstacles sunken artillery emplacements linked tunnel networks covered length franco german border wide supported numerous underground barracks shelters ammunition dumps depots telephone network narrow gauge railways armoured locomotives backed heavy rail artillery french military experts placed high value line saying would curb german aggression invasion force would halted long enough french forces mobilize counterattack


furthermore french military planning inter war period believed line would force germans invade belgium would allow future conflict take place french soil bypassing maginot line fighting belgian army would allow french military move best formations counter battle france germany invaded belgium best anglo french forces moved meet planned however germans recently changed plans french anticipated would happen instead attack central belgium main


survived return mobile warfare world war ii reduced emphasis trench warfare defenders commonly lacked time build battlefield defenses forced redeploy due rapidly changing strategic situation trench systems still effective wherever mobility limited front lines static around known critical objectives could bypassed quickly improvised defensive fighting positions using scrapes foxholes supplemented sand bags local materials debris rubble remain common use typically improved


expanded defenders eventually becoming full trench systems given enough time resources british trench mortar post north africa soviet soldiers running ruins stalingrad battle sevastopol red army forces successfully held trench systems narrow peninsula several months intense german bombardment western allies broke incomplete atlantic wall relative ease combination amphibious landings naval gunfire air attack airborne landings combined arms tactics infantry artillery armour aircraft cooperate closely greatly reduced importance trench


warfare however still valuable method reinforcing natural boundaries creating line defence example battle stalingrad soldiers sides dug trenches within ruins well battle hurtgen forest american german soldiers also dug trenches fox holes rugged woods forest lead continuous stalemates failed offensives lasted months reminiscent trench warfare world war addition start battle kursk soviets constructed system defence


elaborate built world war defences succeeded stopping german armoured pincers meeting enveloping salient italian campaign fought end war europe largely consisted allies storming strongly fortified german lines stretched one coast mountains coast allies broke one line germans would retreat peninsula yet another freshly prepared fortified line start battle berlin last major assault germany russians attacked


river oder german troops dug seelow heights east berlin entrenchment allowed germans massively outnumbered survive bombardment largest concentration artillery history red army attempted cross marshy riverside terrain lost tens thousands casualties entrenched germans breaking pacific war japanese used labyrinth underground fixed positions slow allied advances many pacific islands japanese built fixed fortifications iwo jima okinawa peleliu using system


tunnels interconnect fortified positions many former mine shafts turned defense positions engineers added sliding armored steel doors multiple openings serve artillery machine guns cave entrances built slanted defense grenade flamethrower attacks caves bunkers connected vast system throughout defenses allowed japanese evacuate reoccupy positions needed take advantage shrinking interior lines network bunkers tunnels pillboxes favored defense instance japanese battle iwo jima


several levels honeycombed fortifications nanpo bunker southern area islands naval air hq located east airfield number enough food water ammo japanese hold three months bunker feet deep tunnels running various directions approximately gallon drums filled water kerosene fuel oil generators located inside complex gasoline powered generators allowed radios lighting operated underground japanese caused american advance slow caused massive casualties underground fixed positions americans


eventually used flamethrowers systematic hand hand fighting oust defenders ref name ww mmdb letters ref ref name battlefleet iwodefense ref american ground forces supported extensive naval artillery complete air supremacy provided us navy marine corps aviators throughout entire battle post modern day iranian troops forward trenches iran iraq war trench warfare infrequent recent wars two large armoured armies meet result generally mobile warfare type developed world war ii however trench warfare emerged latter stages chinese civil war huaihai campaign


korean war july end cold war nato forces routinely trained fight extensive works called soviet style trench systems named warsaw pact 's complex systems field fortifications extension soviet field entrenching practices famous great patriotic war eastern front world war ii ukrainian soldier trenches war donbass example trench warfare world wars ii iran iraq war armies lacked training combined arms operations however countries often


prepared entrenched defensive positions tunnels protect supply cities bases throughout regions another problem success sides military mobility reduced drastically due hidden various land mines firm stable ground footing easy slide even get buried camouflaged anti tank trench tactics used included trench warfare machine gun posts bayonet charges booby traps use barbed wire across trenches man 's land iranian human wave attacks iraq 's extensive use chemical weapons mustard gas iranian troops ref


name benschopvan der schans ref afghan us soldiers provide security standing behind blast wall made hesco bastions zhari district kandahar province afghanistan although mainly siege unusual find extensive trench system inside outside city sarajevo siege used mainly transportation front line avoid snipers inside city pre existing structures used trenches best known example bobsleigh course trebevi used serb bosniak forces siege another example


trench stalemate eritrean ethiopian war widespread use trenches resulted comparisons conflict trench warfare world war according reports trench warfare led loss thousands young lives human wave assaults eritrea 's positions eritrean defences eventually overtaken surprise ethiopian pincer movement western front attacking mined lightly defended mountain without trenches resulting capture barentu eritrean retreat element surprise attack involved use donkeys pack animals


well solely infantry affair tanks coming afterwards secure area front line korea front lines pakistan india kashmir two examples demarcation lines could become hot time consist kilometres trenches linking fortified strongpoints korea surrounded millions land mines borders armenia republic artsakh azerbaijan amid ongoing nagorno karabakh conflict also heavily fortified trenches barbed wire two sides regularly trading fire recent example trench warfare


war donbass consolidate defend territory government rebel forces dug trenches initiated warfare reminiscent world war troops staying fighting trenches months time using cement mixers excavators lines digging network tunnels deep bunkers protection since minsk peace agreements front lines moved significantly two sides mostly fire mortars sniper shots result sides dug elaborate networks trenches deep bunkers protection cultural impact


trench warfare become powerful symbol futility war ref name g ref image young men going top parapet trench attack enemy trench line maelstrom fire leading near certain death typified first day battle somme british army suffered nearly casualties grinding slaughter mud passchendaele french equivalent attrition battle verdun french army suffered casualties trench warfare associated


mass slaughter appalling conditions many critics argued brave men went deaths incompetent narrow minded commanders failed adapt new conditions trench warfare class ridden backward looking generals put faith attack believing superior morale dash would overcome weapons moral inferiority defender british public opinion often repeated theme soldiers lions led donkeys world war generals often portrayed callously persisting repeated hopeless attacks trenches failures passchendaele sir douglas haig


often criticised allowing battles continue long lost purpose attrition haig 's defenders counter attrition necessary order cause attrition german army problems trench warfare recognised attempts made address included improvements artillery infantry tactics development tanks taking advantage failing german morale allied attacks generally successful suffered fewer casualties hundred days offensive even return mobile warfare see also harry patch


william philpott https encyclopedia onlinenet article warfare warfare https encyclopedia onlinenet homehtml online international encyclopedia first world war jeffrey lamonica https encyclopedia onlinenet article infantry infantry https encyclopedia onlinenet homehtml online international encyclopedia first world war st phane audoin rouzeau https encyclopedia onlinenet article weapons weapons https encyclopedia onlinenet homehtml online international encyclopedia first world war markus p hlmann https encyclopedia onlinenet article close combat weapons close combat weapons https encyclopedia onlinenet homehtml online international encyclopedia first world war nathan watanabe https encyclopedia onlinenet article hand grenade hand grenade https encyclopedia onlinenet homehtml online international encyclopedia first world war military doctrines military strategy subterranea geography warfare type


'''sedimentology''' encompasses study modern sediments sand silt clay processes result formation erosion weathering transport deposition diagenesis sedimentologists apply understanding modern processes interpret geologic history observations sedimentary rocks sedimentary structures sedimentary rocks cover earth 's surface record much earth 's history harbor fossil record sedimentology closely linked stratigraphy study physical temporal relationships rock layers strata premise processes affecting earth today

Natural science
Earth science
Sedimentology


predominant grain size composition past term clastic sedimentary rocks used describe silica rich clastic sedimentary rocks however cases clastic carbonate rocks appropriate term siliciclastic sedimentary rocks organic sedimentary rocks important deposits formed accumulation biological detritus form coal oil shale deposits typically found within basins clastic sedimentary rocks carbonates composed various carbonate minerals often calcium carbonate caco sub sub precipitated variety organic inorganic processes typically majority carbonate rocks composed


reef material evaporites formed evaporation water earth 's surface commonly include halite gypsum chemical sedimentary rocks including carbonates deposited precipitation minerals aqueous solution include jaspilite chert importance sedimentary rocks mi vida uranium mine redox mudstones near moab utah sedimentary rocks provide multitude products modern ancient society come utilise art marble although metamorphosed limestone example use sedimentary rocks pursuit aesthetics art architectural uses stone derived sedimentary


rocks used dimension stone architecture notably slate meta shale roofing sandstone load bearing buttresses ceramics industrial materials clay pottery ceramics including bricks cement lime derived limestone economic geology sedimentary rocks host large deposits sedex ore deposits lead zinc silver large deposits copper deposits gold tungsten uranium many precious minerals gemstones industrial minerals including heavy mineral sands ore deposits energy petroleum geology relies capacity sedimentary rocks generate deposits petroleum oils coal oil shale found sedimentary rocks large


proportion world 's uranium energy resources hosted within sedimentary successions groundwater sedimentary rocks contain large proportion earth 's groundwater aquifers understanding extent aquifers much water withdrawn depends critically knowledge rocks hold reservoir basic principles heavy minerals dark deposited quartz beach sand chennai india aim sedimentology studying sediments derive information depositional conditions acted deposit rock unit relation individual rock units


basin coherent understanding evolution sedimentary sequences basins thus earth 's geological history whole scientific basis principle uniformitarianism states sediments within ancient sedimentary rocks deposited way sediments deposited earth 's surface today sedimentological conditions recorded within sediments laid form sediments present reflects events past events affect sediments source sedimentary material


known rocks unfolded interpreted according contained sedimentary information principle lateral continuity states layers sediment initially extend laterally directions unless obstructed physical object topography principle cross cutting relationships states whatever cuts across intrudes layers strata younger layers strata methodology centripetal desiccation cracks dinosaur footprint center lower jurassic moenave formation st george dinosaur discovery site johnson farm southwestern utah methods employed sedimentologists


gather data evidence nature depositional conditions sedimentary rocks include measuring describing outcrop distribution rock unit describing rock formation formal process documenting thickness lithology outcrop distribution contact relationships formations mapping distribution rock unit units descriptions rock core drilled extracted wells hydrocarbon exploration sequence stratigraphy describes progression rock units within basin describing lithology rock petrology petrography particularly measurement texture grain size grain shape sphericity rounding etc sorting composition


sediment analysing geochemistry rock isotope geochemistry including use radiometric dating determine age rock affinity source regions recent developments longstanding understanding mudstones form challenged geologists indiana university bloomington massachusetts institute technology research appears december th edition ''science'' counters prevailing view geologists mud settles water slow moving still instead showing muds accumulate even currents move swiftly research shows mudstones may


formed fast moving waters mudstones deposited energetic conditions widely assumed requiring reappraisal many geologic records macquaker bohacs reviewing research schieber et al state results call critical reappraisal mudstones previously interpreted continuously deposited still waters rocks widely used infer past climates ocean conditions orbital variations considerable recent research mudstones driven recent effort commercially produce hydrocarbons shale gas tight oil light tight oil plays


see also clastic rocks coal geology important publications sedimentology oil shale ore genesis rock formation sequence stratigraphy vegetation induced sedimentary structures references external links earth sciences physical geography sedimentary rocks


theory syntactic nature contrast model theory semantic nature major areas proof theory include structural proof theory ordinal analysis provability logic reverse mathematics proof mining automated theorem proving proof complexity much research also focuses applications computer science linguistics philosophy history although formalisation logic much advanced work figures gottlob frege giuseppe peano bertrand russell richard dedekind story modern proof theory often seen established david hilbert initiated called hilbert 's program

Humanities
Philosophy
Logic
Mathematical logic
Proof theory


''foundations mathematics'' central idea program could give finitary proofs consistency sophisticated formal theories needed mathematicians could ground theories means metamathematical argument shows purely universal assertions technically provable math pi math sentences finitarily true grounded care non finitary meaning existential theorems regarding pseudo meaningful stipulations existence ideal entities failure program induced kurt g del 's incompleteness theorems showed


consistent theory sufficiently strong express certain simple arithmetic truths cannot prove consistency g del 's formulation math pi math sentence however modified versions hilbert 's program emerged research carried related topics led particular refinement g del 's result particularly j barkley rosser 's refinement weakening requirement consistency simple consistency axiomatisation core g del 's result terms modal language provability logic transfinite iteration theories due alan turing solomon feferman discovery self verifying theories systems


strong enough talk weak carry diagonal argument key g del 's unprovability argument parallel rise fall hilbert 's program foundations structural proof theory founded jan ukasiewicz suggested one could improve hilbert systems basis axiomatic presentation logic one allowed drawing conclusions assumptions inference rules logic response stanis aw ja kowski gerhard gentzen independently provided systems called calculi natural


sequent calculus introduced fundamental idea analytic proof proof theory structural proof theory structural proof theory subdiscipline proof theory studies specifics proof calculi three well known styles proof calculi hilbert calculi natural deduction calculi sequent calculi give complete axiomatic formalization propositional predicate logic either classical intuitionistic flavour almost modal logic many substructural logics relevance logic linear logic indeed unusual find logic resists


represented one calculi proof theorists typically interested proof calculi support notion analytic proof notion analytic proof introduced gentzen sequent calculus analytic proofs cut free much interest cut free proofs comes subformula property every formula end sequent cut free proof subformula one premises allows one show consistency sequent calculus easily empty sequent derivable would subformula


premise gentzen 's midsequent theorem craig interpolation theorem herbrand 's theorem also follow corollaries cut elimination theorem gentzen 's natural deduction calculus also supports notion analytic proof shown dag prawitz definition slightly complex say analytic proofs normal forms related notion normal form term rewriting exotic proof calculi jean yves girard 's proof nets also support notion analytic proof particular family analytic proofs arising reductive logic focused proofs characterise


large family goal directed proof search procedures ability transform proof system focused form good indication syntactic quality manner similar admissibility cut shows proof system syntactically consistent structural proof theory connected type theory means curry howard correspondence observes structural analogy process normalisation natural deduction calculus beta reduction typed lambda calculus provides foundation intuitionistic type theory developed per martin l f often extended three


way correspondence third leg cartesian closed categories research topics structural theory include analytic tableau apply central idea analytic proof structural proof theory provide decision procedures semi decision procedures wide range logics proof theory substructural logics ordinal analysis ordinal analysis powerful technique providing combinatorial consistency proofs subsystems arithmetic analysis set theory g del 's second incompleteness theorem often interpreted demonstrating finitistic consistency proofs impossible theories sufficient strength ordinal analysis allows one measure


precisely infinitary content consistency theories consistent recursively axiomatized theory one prove finitistic arithmetic well foundedness certain transfinite ordinal implies consistency g del 's second incompleteness theorem implies well foundedness ordinal cannot proved theory consequences ordinal analysis include consistency subsystems classical second order arithmetic set theory relative constructive theories combinatorial independence results classifications provably total recursive functions provably well founded ordinals ordinal analysis originated gentzen proved


consistency peano arithmetic using transfinite induction ordinal sub sub ordinal analysis extended many fragments first second order arithmetic set theory one major challenge ordinal analysis impredicative theories first breakthrough direction takeuti 's proof consistency ca sub sub using method ordinal diagrams provability logic ''provability logic'' modal logic box operator interpreted 'it provable that' point capture notion proof predicate reasonably rich formal theory basic axioms


modal logic gl complete respect peano arithmetic propositional theory provability peano arithmetic completely represented modal logic gl straightforwardly implies propositional reasoning provability peano arithmetic complete decidable research provability logic focused first order provability logic polymodal provability logic one modality representing provability object theory another representing provability meta theory interpretability logics intended capture interaction provability interpretability recent research involved applications graded provability algebras ordinal


analysis arithmetical theories reverse mathematics '''reverse mathematics''' program mathematical logic seeks determine axioms required prove theorems mathematics field founded harvey friedman defining method described going backwards theorems axioms contrast ordinary mathematical practice deriving theorems axioms reverse mathematics program foreshadowed results set theory classical theorem axiom choice zorn 's lemma equivalent zf set theory goal reverse mathematics however study


possible axioms ordinary theorems mathematics rather possible axioms set theory reverse mathematics one starts framework language base theory core axiom system weak prove theorems one might interested still powerful enough develop definitions necessary state theorems example study theorem every bounded sequence real numbers supremum necessary use base system speak real numbers sequences real numbers theorem stated


base system provable base system goal determine particular axiom system stronger base system necessary prove theorem show system ''s'' required prove theorem ''t'' two proofs required first proof shows ''t'' provable ''s'' ordinary mathematical proof along justification carried system ''s'' second proof known '' 'reversal''' shows ''t'' implies ''s'' proof carried base system


reversal establishes axiom system ''s prime '' extends base system weaker ''s'' still proving nbsp ''t'' one striking phenomenon reverse mathematics robustness ''big five'' axiom systems order increasing strength systems named initialisms rca sub sub wkl sub sub aca sub sub atr sub sub ca sub sub nearly every theorem ordinary mathematics reverse mathematically analyzed proven equivalent one five systems much recent research focused combinatorial principles fit neatly framework like rt ramsey 's theorem pairs research


successful functional interpretations yielded reductions infinitary theories finitary theories impredicative theories predicative ones functional interpretations also provide way extract constructive information proofs reduced theory direct consequence interpretation one usually obtains result recursive function whose totality proven either c represented term f one provide additional interpretation f sometimes possible characterization fact usually shown exact often turns terms


f coincide natural class functions primitive recursive polynomial time computable functions functional interpretations also used provide ordinal analyses theories classify provably recursive functions study functional interpretations began kurt g del 's interpretation intuitionistic arithmetic quantifier free theory functionals finite type interpretation commonly known dialectica interpretation together double negation interpretation classical logic intuitionistic logic provides reduction classical arithmetic intuitionistic arithmetic formal informal proof ''informal'' proofs everyday mathematical practice


unlike ''formal'' proofs proof theory rather like high level sketches would allow expert reconstruct formal proof least principle given enough time patience mathematicians writing fully formal proof pedantic long winded common use formal proofs constructed help computers interactive theorem proving significantly proofs checked automatically also computer checking formal proofs usually simple whereas ''finding'' proofs automated theorem proving generally hard informal proof mathematics literature contrast requires weeks


peer review checked may still contain errors proof theoretic semantics linguistics type logical grammar categorial grammar montague grammar apply formalisms based structural proof theory give formal natural language semantics see also intermediate logic model theory proof truth proof techniques sequent calculus notes references references j avigad eh reck http wwwandrewcmuedu user avigad papers infinitepdf 'clarifying nature infinite' development metamathematics proof theory carnegie mellon technical report cmu phil j barwise ed ''handbook mathematical logic'' north holland buss ed '' https booksgooglecom bookshl en lr id mftmdecq ukc oi fnd pg pp dq handbook proof theory ots lfjuyy fel sig jbyv cl visavkhijdf q e k v onepage q handbook proof theory f false handbook proof theory '' elsevier troelstra h schwichtenberg


''basic proof theory'' cambridge tracts theoretical computer science cambridge university press g gentzen https wwwjstororg stable investigations logical deduction e szabo ed ''collected papers gerhard gentzen'' north holland translated szabo untersuchungen ber das logische schliessen ''mathematisches zeitschrift'' v pp nbsp nbsp prawitz ''natural deduction proof theoretical study'' dover publications sg simpson ''subsystems second order arithmetic'' second edition cambridge university press h wang ''popular lectures mathematical logic'' van nostrand reinhold company external links j von plato http platostanfordedu entries proof theory development development proof theory stanford encyclopedia


hot achieve heat transfer mechanisms distinct characteristics often occur simultaneously system heat conduction also called diffusion direct microscopic exchange kinetic energy particles molecules quasiparticles lattice waves boundary two systems object different temperature another body surroundings heat flows body surroundings reach temperature point thermal equilibrium spontaneous heat transfer always occurs region high temperature another region

Applied science
Engineering and technology
Mechanical Engineering
Heat transfer


lower temperature described second law thermodynamics heat convection occurs bulk flow fluid gas liquid carries heat fluid convective processes also move heat partly diffusion well flow fluid may forced external processes sometimes gravitational fields buoyancy forces caused thermal energy expands fluid example fire plume thus influencing transfer latter process often called natural convection former process often called forced convection case fluid forced


sum internal energy system u plus product pressure p volume v joule unit quantify energy work amount heat heat transfer process function path function opposed functions state therefore amount heat transferred thermodynamic process changes state system depends process occurs net difference initial final states process thermodynamic mechanical heat transfer calculated heat transfer coefficient proportionality heat


analogies among three transport processes developed facilitate prediction conversion one others ref name faghri thermal engineering concerns generation use conversion storage exchange heat transfer heat transfer involved almost every sector economy heat transfer classified various mechanisms thermal conduction thermal convection thermal radiation transfer energy phase changes mechanisms four fundamental modes heat transfer illustrated campfire fundamental modes heat transfer advection advection transport mechanism fluid


one location another dependent motion momentum fluid conduction diffusion transfer energy objects physical contact thermal conductivity property material conduct heat evaluated primarily terms fourier 's law heat conduction convection transfer energy object environment due fluid motion average temperature reference evaluating properties related convective heat transfer radiation transfer energy emission electromagnetic radiation advection transferring matter energy including thermal energy


rapidly moving vibrating atoms molecules interact neighboring atoms molecules transferring energy heat neighboring particles words heat transferred conduction adjacent atoms vibrate one another electrons move one atom another conduction significant means heat transfer within solid solid objects thermal contact fluids especially gases less conductive thermal contact conductance study heat conduction solid bodies contact ref name abbott ref process heat transfer one place another place without movement


particles called conduction placing hand cold glass water heat conducted warm skin cold glass hand held inches glass little conduction would occur since air poor conductor heat steady state conduction idealized model conduction happens temperature difference driving conduction constant time spatial distribution temperatures conducting object change see fourier 's law steady state conduction amount heat


entering section equal amount heat coming since change temperature measure heat energy zero ref name abbott example steady state conduction heat flow walls warm house cold day inside house maintained high temperature outside temperature stays low transfer heat per unit time stays near constant rate determined insulation wall spatial distribution temperature walls approximately constant time ''transient conduction'' see heat equation occurs


temperature within object changes function time analysis transient systems complex analytic solutions heat equation valid idealized model systems practical applications generally investigated using numerical methods approximation techniques empirical study ref name abbott convection flow fluid may forced external processes sometimes gravitational fields buoyancy forces caused thermal energy expands fluid example fire plume thus influencing transfer latter process often called natural convection convective processes also move heat partly diffusion


well another form convection forced convection case fluid forced flow using pump fan mechanical means convective heat transfer simply convection transfer heat one place another movement fluids process essentially transfer heat via mass transfer bulk motion fluid enhances heat transfer many physical situations example solid surface fluid convection usually dominant form heat transfer liquids gases although sometimes discussed


refer sum heat transport advection diffusion conduction free natural convection occurs bulk fluid motions streams currents caused buoyancy forces result density variations due variations temperature fluid ''forced'' convection term used streams currents fluid induced external means fans stirrers pumps creating artificially induced convection current convection cooling convective cooling sometimes described newton 's law cooling however definition validity newton 's law cooling requires rate heat loss


convection linear function proportional temperature difference drives heat transfer convective cooling sometimes case general convection linearly dependent temperature gradients cases strongly nonlinear cases newton 's law apply convection vs conduction body fluid heated underneath container conduction convection considered compete dominance heat conduction great fluid moving convection heated conduction fast downward movement stopped due


buoyancy fluid moving convection cooled conduction fast driving buoyancy diminish hand heat conduction low large temperature gradient may formed convection might strong rayleigh number math rm ra math product grashof math rm gr math prandtl math rm pr math numbers measure determines relative strength conduction convection math mathrm ra mathrm gr cdot mathrm pr frac g delta rho l mu alpha frac g beta delta l nu alpha math ''g'' acceleration due gravity


density math delta rho math density difference lower upper ends dynamic viscosity thermal diffusivity volume thermal expansivity sometimes denoted '' '' elsewhere ''t'' temperature kinematic viscosity ''l'' characteristic length rayleigh number understood ratio rate heat transfer convection rate heat transfer conduction equivalently ratio corresponding timescales ie conduction timescale divided convection timescale numerical factor seen follows


calculations numerical factors depending geometry system buoyancy force driving convection roughly math g delta rho l math corresponding pressure roughly math g delta rho l math steady state canceled shear stress due viscosity therefore roughly equals math mu v l mu rm conv math ''v'' typical fluid velocity due convection math rm conv math order timescale conduction timescale hand order math rm cond l alpha math convection occurs rayleigh number


radiation red hot iron object transferring heat surrounding environment thermal radiation radiative heat transfer transfer energy via thermal radiation ie electromagnetic waves ref name geankoplis occurs across vacuum transparent medium solid fluid gas thermal radiation emitted objects temperatures absolute zero due random movements atoms molecules matter since atoms molecules composed charged particles protons electrons movement results emission electromagnetic radiation carries away energy radiation typically important engineering applications


hot objects objects large temperature difference objects distances separating large size compared wavelength thermal radiation rate transfer radiant energy best described stefan boltzmann equation object vacuum equation math phi q epsilon sigma math radiative transfer two objects equation follows math phi q epsilon sigma f b math math phi q math heat flux math epsilon math emissivity unity black body math sigma math stefan boltzmann constant math f math


view factor two surfaces b math math math b math absolute temperatures kelvins degrees rankine two objects blackbody limit established stefan boltzmann equation exceeded objects exchanging thermal radiation distances separating comparable scale smaller dominant thermal wavelength study cases called near field radiative heat transfer radiation sun solar radiation harvested heat power unlike conductive convective forms heat transfer thermal radiation arriving within


coarsly k nbsp c k small probe focus spot big concave concentrating mirror mont louis solar furnace france phase transition lightning highly visible form energy transfer example plasma present earth 's surface typically lightning discharges amperes million volts emits light radio waves x rays even gamma rays plasma temperatures lightning approach kelvins nbsp c nbsp f electron densities may exceed sup sup sup sup phase transition phase change takes place thermodynamic


system one phase state matter another one heat transfer phase change examples melting ice boiling water mason equation explains growth water droplet based effects heat transport evaporation condensation phase transitions involve four fundamental states matter solid deposition freezing solid solid transformation gas boiling evaporation recombination deionization sublimation liquid condensation melting fusion plasma ionization boiling nucleate boiling water boiling point substance temperature vapor pressure


liquid equals pressure surrounding liquid liquid evaporates resulting abrupt change vapor volume closed system ' 'saturation temperature'' ''boiling point'' mean thing saturation temperature temperature corresponding saturation pressure liquid boils vapor phase liquid said saturated thermal energy addition thermal energy results phase transition standard atmospheric pressure '''low temperatures''' boiling occurs heat transfer rate controlled usual single phase mechanisms surface temperature


increased local boiling occurs vapor bubbles nucleate grow surrounding cooler fluid collapse ' 'sub cooled nucleate boiling'' efficient heat transfer mechanism high bubble generation rates bubbles begin interfere heat flux longer increases rapidly surface temperature departure nucleate boiling dnb similar standard atmospheric pressure '''high temperatures''' hydrodynamically quieter regime film boiling reached heat fluxes across stable vapor layers low rise slowly temperature contact fluid surface may


seen probably leads extremely rapid nucleation fresh vapor layer spontaneous nucleation higher temperatures still maximum heat flux reached critical heat flux chf leidenfrost effect demonstrates nucleate boiling slows heat transfer due gas bubbles heater 's surface mentioned gas phase thermal conductivity much lower liquid phase thermal conductivity outcome kind gas thermal barrier condensation condensation occurs vapor cooled changes phase liquid condensation latent heat vaporization must released amount


heat absorbed vaporization fluid pressure several types condensation homogeneous condensation formation fog condensation direct contact subcooled liquid condensation direct contact cooling wall heat exchanger common mode used industry filmwise condensation liquid film formed subcooled surface usually occurs liquid wets surface dropwise condensation liquid drops formed subcooled surface usually occurs liquid


wet surface dropwise condensation difficult sustain reliably therefore industrial equipment normally designed operate filmwise condensation mode melting ice melting melting thermal process results phase transition substance solid liquid internal energy substance increased typically heat pressure resulting rise temperature melting point ordering ionic molecular entities solid breaks less ordered state solid liquefies molten substances generally reduced viscosity elevated


temperature exception maxim element sulfur whose viscosity increases point due polymerization decreases higher temperatures molten state modeling approaches heat transfer modeled various ways heat equation heat equation important partial differential equation describes distribution heat variation temperature given region time cases exact solutions equation available ref name wendl ref cases equation must solved numerically using computational methods dem based models thermal reacting particulate systems critically reviewed


peng et al ref name peng ref lumped system analysis lumped system analysis often reduces complexity equations one first order linear differential equation case heating cooling described simple exponential solution often referred newton 's law cooling system analysis lumped capacitance model common approximation transient conduction may used whenever heat conduction within object much faster heat conduction across boundary object method approximation reduces one aspect transient conduction system within object


equivalent steady state system method assumes temperature within object completely uniform although value may changing time method ratio conductive heat resistance within object convective heat transfer resistance across object 's boundary known ''biot number'' calculated small biot numbers approximation ' 'spatially uniform temperature within object'' used presumed heat transferred object time uniformly distribute due lower resistance compared


resistance heat entering object climate models climate models study radiant heat transfer using quantitative methods simulate interactions atmosphere oceans land surface ice engineering heat exposure part fire test firestop products heat transfer broad application functioning numerous devices systems heat transfer principles may used preserve increase decrease temperature wide variety circumstances heat transfer methods used numerous disciplines automotive engineering thermal management electronic devices systems climate control insulation materials processing chemical engineering


aluminized shiny mylar greatly reduce radiation heat transfer control satellite temperature devices schematic flow energy heat engine heat engine system performs conversion flow thermal energy heat mechanical energy perform mechanical work thermocouple temperature measuring device widely used type temperature sensor measurement control also used convert heat electric power thermoelectric cooler solid state electronic device pumps transfers heat one side device electric current


passed based peltier effect thermal diode thermal rectifier device causes heat flow preferentially one direction heat exchangers heat exchanger used efficient heat transfer dissipate heat heat exchangers widely used refrigeration air conditioning space heating power generation chemical processing one common example heat exchanger car 's radiator hot coolant fluid cooled flow air radiator 's surface common types heat exchanger flows include parallel flow counter flow


cross flow parallel flow fluids move direction transferring heat counter flow fluids move opposite directions cross flow fluids move right angles common types heat exchangers include shell tube double pipe extruded finned pipe spiral fin pipe u tube stacked plate type certain advantages disadvantages types heat sink component transfers heat generated within solid material fluid medium air liquid examples heat sinks heat


device records electric energy consumption intervals thermal transmittance rate transfer heat structure divided difference temperature across structure expressed watts per square meter per kelvin w sup sup k well insulated parts building low thermal transmittance whereas poorly insulated parts building high thermal transmittance thermostat device monitor control temperature climate engineering example application climate engineering includes creation biochar pyrolysis process thus storing greenhouse gases carbon reduces radiative forcing capacity


atmosphere causing long wave infrared radiation space climate engineering consists carbon dioxide removal solar radiation management since amount carbon dioxide determines radiative balance earth atmosphere carbon dioxide removal techniques applied reduce radiative forcing solar radiation management attempt absorb less solar radiation offset effects greenhouse gases greenhouse effect representation exchanges energy source sun earth 's surface earth 's atmosphere ultimate sink outer space ability atmosphere capture recycle


energy emitted earth surface defining characteristic greenhouse effect greenhouse effect process thermal radiation planetary surface absorbed atmospheric greenhouse gases radiated directions since part radiation back towards surface lower atmosphere results elevation average surface temperature would absence gases heat transfer human body principles heat transfer engineering systems applied human body order determine


body transfers heat heat produced body continuous metabolism nutrients provides energy systems body human body must maintain consistent internal temperature order maintain healthy bodily functions therefore excess heat must dissipated body keep overheating person engages elevated levels physical activity body requires additional fuel increases metabolic rate rate heat production body must use additional methods remove additional heat produced order keep


internal temperature healthy level heat transfer convection driven movement fluids surface body convective fluid either liquid gas heat transfer outer surface body convection mechanism dependent surface area body velocity air temperature gradient surface skin ambient air ref name cengel yunus cengel yunus ghajar afshin j heat mass transfer fundamentals applications mcgraw hill th edition ref normal temperature


body approximately nbsp c heat transfer occurs readily temperature surroundings significantly less normal body temperature concept explains person feels cold enough covering worn exposed cold environment clothing considered insulator provides thermal resistance heat flow covered portion body thermal resistance causes temperature surface clothing less temperature surface skin smaller temperature gradient surface temperature ambient temperature


blood vessel thickness fluid velocity flow heat transfer coefficient blood velocity blood vessel diameter fluid thickness related reynolds number dimensionless number used fluid mechanics characterize flow fluids latent heat loss also known evaporative heat loss accounts large fraction heat loss body core temperature body increases body triggers sweat glands skin bring additional moisture surface skin liquid


transformed vapor removes heat surface body rate evaporation heat loss directly related vapor pressure skin surface amount moisture present skin ref name cengel yunus therefore maximum heat transfer occur skin completely wet body continuously loses water evaporation significant amount heat loss occurs periods increased physical activity cooling techniques evaporative cooling traditional air cooler mirzapur uttar pradesh india evaporative cooling happens water vapor added


surrounding air energy needed evaporate water taken air form sensible heat converted latent heat air remains constant enthalpy latent heat describes amount heat needed evaporate liquid heat comes liquid surrounding gas surfaces greater difference two temperatures greater evaporative cooling effect temperatures net evaporation water air occurs thus cooling effect laser cooling quantum


nitric oxide convective transport heat evaporative transport latent heat remove heat surface redistribute atmosphere thermal energy storage thermal energy storage includes technologies collecting storing energy later use may employed balance energy demand day nighttime thermal reservoir may maintained temperature ambient environment applications include space heating domestic process hot water systems generating electricity see also combined forced natural convection heat capacity heat transfer physics stefan boltzmann


dispersion light photons prism '''photonics''' physical science application light photon generation detection manipulation emission transmission modulation signal processing switching amplification sensing ref name yeh ref ref name quimby ref though covering light 's technical applications whole spectrum photonic applications range visible near infrared light term photonics developed outgrowth first practical semiconductor light emitters invented early optical fibers developed history word 'photonics' derived greek word phos meaning light genitive case photos

Applied science
Engineering and technology
Materials Science and Engineering
Photonics


term photonics came common use fiber optic data transmission adopted telecommunications network operators time term used widely bell laboratories use confirmed ieee lasers electro optics society established archival journal named photonics technology letters end period leading dot com crash circa photonics field focused largely optical telecommunications however photonics covers huge range science technology applications including laser manufacturing biological chemical sensing medical diagnostics therapy display technology


optical computing growth photonics likely current silicon photonics developments successful relationship fields classical optics photonics closely related optics classical optics long preceded discovery light quantized albert einstein famously explained photoelectric effect optics tools include refracting lens reflecting mirror various optical components instruments developed throughout th th centuries key tenets classical optics huygens principle developed th century maxwell 's equations wave equations developed th depend quantum properties


light modern optics photonics related quantum optics optomechanics electro optics optoelectronics quantum electronics however area slightly different connotations scientific government communities marketplace quantum optics often connotes fundamental research whereas photonics used connote applied research development term ''photonics'' specifically connotes particle properties light potential creating signal processing device technologies using photons practical application optics analogy electronics term optoelectronics connotes devices circuits comprise electrical optical functions ie thin film semiconductor device term


electro optics came earlier use specifically encompasses nonlinear electrical optical interactions applied eg bulk crystal modulators pockels cell also includes advanced imaging sensors emerging fields photonics also relates emerging science quantum information quantum optics emerging fields include optoacoustics photoacoustic imaging laser energy delivered biological tissues absorbed converted heat leading ultrasonic emission optomechanics involves study interaction light mechanical vibrations mesoscopic macroscopic objects optomics devices integrate photonic atomic devices applications


electronic fpga applications sea mouse ''aphrodita aculeata'' showing colorful spines remarkable example photonic engineering living organism applications photonics ubiquitous included areas everyday life advanced science eg light detection telecommunications information processing photonic computing lighting metrology spectroscopy holography medicine surgery vision correction endoscopy health monitoring biophotonics military technology laser material processing art diagnostics involving infrared reflectography xrays ultraviolet fluorescence xrf agriculture robotics applications electronics expanded dramatically since first transistor invented unique applications photonics continue


emerge economically important applications semiconductor photonic devices include optical data recording fiber optic telecommunications laser printing based xerography displays optical pumping high power lasers potential applications photonics virtually unlimited include chemical synthesis medical diagnostics chip data communication sensors laser defense fusion energy name several interesting additional examples consumer equipment barcode scanner printer cd dvd blu ray devices remote control devices telecommunications optical fiber communications optical converter microwave medicine correction poor eyesight laser surgery surgical endoscopy tattoo removal industrial manufacturing use lasers welding drilling cutting various methods


surface modification construction laser leveling laser rangefinding smart structures aviation photonic gyroscopes lacking mobile parts military ir sensors command control navigation search rescue mine laying detection entertainment laser shows beam effects holographic art information processing sensors lidar sensors consumer electronics metrology time frequency measurements rangefinding photonic computing clock distribution communication computers printed circuit boards within optoelectronic integrated circuits future quantum computing microphotonics nanophotonics usually includes photonic crystals solid state devices ref name rigneaultlourtioz ref overview photonics research science photonics includes investigation emission transmission amplification detection


special properties iii v semiconductors allow implementation light emitting devices examples material systems used gallium arsenide gaas aluminium gallium arsenide algaas compound semiconductors also used conjunction silicon produce hybrid silicon lasers transmission media light transmitted transparent medium glass fiber plastic optical fiber used guide light along desired path optical communications optical fibers allow transmission distances nbsp km without amplification depending bit rate modulation format used transmission


solar cells used energy harvesting sunlight also many photodetectors based thermal chemical quantum photoelectric effects modulation modulation light source used encode information light source modulation achieved light source directly one simplest examples use flashlight send morse code another method take light light source modulate external optical modulator additional topic covered modulation research modulation format keying commonly used


modulation format optical communications last years advanced modulation formats like phase shift keying even orthogonal frequency division multiplexing investigated counteract effects like dispersion degrade quality transmitted signal photonic systems photonics also includes research photonic systems term often used optical communication systems area research focuses implementation photonic systems like high speed photonic networks also includes research optical regenerators improve optical signal quality photonic integrated circuits photonic integrated circuits pics optically active integrated semiconductor photonic devices leading commercial


increase signal noise performance make possible new benchmarks low power performance taken together high precision processing enables us pack large amounts information ultra long distance radio communications sensors photons also used detect differentiate optical properties materials identify chemical biochemical gases air pollution organic produce contaminants water also used detect abnormalities blood low glucose levels measure biometrics pulse rate photonic integrated circuits designed comprehensive


ubiquitous sensors glass silicon embedded via high volume production various mobile devices mobile platform sensors enabling us directly engage practices better protect environment monitor food supply keep us healthy lidar phased array imaging arrays pics take advantage phase delays light reflected objects three dimensional shapes reconstruct images light imaging detection ranging lidar laser light offer complement radar providing precision imaging information close distances new form machine vision


immediate application driverless cars reduce collisions biomedical imaging phased arrays also used free space communications novel display technologies current versions lidar predominantly rely moving parts making large slow low resolution costly prone mechanical vibration premature failure integrated photonics realize lidar within footprint size postage stamp scan without moving parts produced high volume low cost biophotonics '''biophotonics''' employs tools field photonics study biology biophotonics mainly focuses improving medical


'''information architecture''' '''ia''' structural design shared information environments art science organizing labelling websites intranets online communities software support usability findability emerging community practice focused bringing principles design architecture information science digital landscape ref name ref typically involves model concept information used applied activities require explicit details complex information systems activities include library systems database development today growing network active ia specialists constitute

Applied science
Library and museum studies
Information architecture


information architecture institute definition ''information architecture'' somewhat different meanings different branches information systems information technology structural design shared information environments art science organizing labeling web sites intranets online communities software support findability usability ref name emerging community practice focused bringing principles design architecture digital landscape combination organization labeling search navigation systems within websites intranets extracting required parameters data engineering designs process creating knowledge base linking different systems standards


debate difficulty establishing common definition information architecture arises partly term 's existence multiple fields field systems design example information architecture component enterprise architecture deals information component describing structure enterprise definition information architecture relatively well established field systems design much debatable within context online information ie websites andrew dillon refers latter big ia little ia debate little ia view information architecture essentially