omniomni/omni-engineering huggingface dataset:
Acene. In organic chemistry, the acenes or polyacenes are a class of organic compounds and polycyclic aromatic hydrocarbons  made up of benzene () rings which have been linearly fused. They follow the general molecular formula .

The larger representatives have potential interest in optoelectronic applications and are actively researched in chemistry and electrical engineering. Pentacene has been incorporated into organic field-effect transistors, reaching charge carrier mobilities as high as 5 cm2/Vs.

The first 5 unsubstituted members are listed in the following table:

Hexacene is not stable in air, and dimerises upon isolation. Heptacene (and larger acenes) is very reactive and has only been isolated in a matrix. However, bis(trialkylsilylethynylated) versions of heptacene have been isolated as crystalline solids.

Larger acenes
Due to their increased conjugation length the larger acenes are also studied. Theoretically, a number of reports are available on longer chains using density functional methods. They are also building blocks for nanotubes and graphene.  Unsubstituted octacene (n=8) and nonacene (n=9) have been detected in matrix isolation. The first reports of stable nonacene derivatives claimed that due to the electronic effects of the thioaryl substituents the compound is not a diradical but a closed-shell compound with the lowest HOMO-LUMO gap reported for any acene, an observation in violation of Kasha's rule.  Subsequent work by others on different derivatives included crystal structures, with no such violations. The on-surface synthesis and characterization of unsubstituted, parent nonacene (n=9) and decacene (n=10) have been reported. In 2020, scientists reported about the creation of dodecacene (n=12) for the first time. Four years later, in the beginning of 2024, Ruan et al. succeeded in synthesizing unsubstitued tridecacene (n=13) on a (111)-gold surface. The acene was characterized by STM- and STS-measurements.

Related compounds
The acene series have the consecutive rings linked in a linear chain, but other chain linkages are possible. The phenacenes have a zig-zag structure and the helicenes have a helical structure.

Benz[a]anthracene, an isomer of tetracene, has three rings connected in a line and one ring connected at an angle.

References

 
Conductive polymers
Organic semiconductors
Boom brake. A boom brake is a device designed to control the swing of the boom on a sailboat.  The boom brake acts as a preventer when sailing downwind, and can also be used to jibe(US) or gybe(UK) the mainsail in a slow measured action.

Uncontrolled jibes often damage elements of the rig, and can inflict serious and sometimes fatal injuries to crew in the path of the boom or the mainsheet and associated hardware.

The brake usually rides on a line running perpendicular to the boom; when the boom brake is actuated, it grabs the line and either works as a preventer, or slows the boom's speed while jibing.  The brake is actuated by either tensioning the line upon which it rides or using a second line to tension the brake relative to the main line.

References
Mainsheet magazine, Vol. 23, No 2, May 2005

Sailing ship components
PL-9. The PL-9 () is a short-range, infrared-homing air-to-air missile (AAM) developed by the People's Republic of China.

History
The PL-9 program was initiated in 1986. The missile entered batch production in 1989. Two improved variants, PL-9B and PL-9C, was certified in 1992 and 2002. The latest version of the PL-9 is PL-9D.

The missile was originally designed by Dong Bingyin (董秉印) at the Luoyang Electro Optical Center, which is also known as Institute 612 and renamed in 2002 as the China Air-to-Air Guided Missile Research Institute (中国空空导弹研究院). After Dong Bingyin died, his position was succeeded by Mr. Jin Xianzhong (金先仲). The deputy general designer of PL-9 is the same deputy general designer of PL-12, Dr. Liang Xiaogeng (梁晓庚).

The PL-9C is one of the later versions of the PL-9, which also has a surface-to-air variant (DK-9). The PL-9C tactical low-altitude surface-to-air missile (SAM) was first revealed during the 1989 Paris Air Show. The launch unit is available in both towed and self-propelled arrangements. The self-propelled version has a launch complex consisting four-rail launcher and the associated target acquisition and radar and electro-optical director mounted on a 6X6 WZ551 armored personnel carrier (APC). The towed version has a four-rail launcher mounted on a four-wheel carriage. The launch unit is supported by a range of truck-mounted ground equipment for maintenance and missile testing.

Design
The PL-9 utilizes the airframe modified from the PL-5 and PL-7 missile. The seeker head is fitted with sensors from PL-8 and Python-3 missile. The missile is fitted with a cryogenic liquid nitrogen gas-cooled IR seeker capable of +/-40 degree off boresight angles. Flight control is by long span pointed delta fins at the front of the missile with Sidewinder-type slipstream driven rollerons on the aft tail fin surfaces to prevent roll and so enhance the operation of the guidance system. The missile has a maximum effective range of 35 km , although a hit at such a range is unlikely, as maximum effective range calculations tend to assume a meeting engagement against a target flying at high altitude straight at the missile, minimizing the range the missile itself needs to cover. The single-shot hit probability for a single missile launch at an approaching target is 90%. The missile can be used at a stand-alone system, or as a part of the Type 390 (DK-9) brigade (regiment)-level combined AAA/SAM air defence system. The missile entered production in 1991 and saw limited service with the PLA ground forces.

Variants
PL-9
PL-9B
PL-9C
PL-9D
DK-9 PL-9 modified surface-to-air missile.

Operators

Current operators

 Bangladesh Air Force (BAF)

 Namibian Air Force

 Nigerian Air Force

 Pakistan Air Force (PAF)

 People's Liberation Army Air Force
 People's Liberation Army Naval Air Force

See also
 PL-5
 PL-7
 PL-8
 PL-10

References
Citations

Bibliography

External links
 Chinese Defence Today
 Luoyang Electro-Optics Technology Development Centre PL-9C

Air-to-air missiles of the People's Republic of China
Surface-to-air missiles of the People's Republic of China
Short range air-to-air missiles
Circuit integrity. Circuit integrity describes the extent of a fire's effect on an electrical circuit's operation. It is a form of fire-resistance rating. Circuit integrity is achieved via passive fire protection means, which are subject to listing and approval use and compliance. Alternatively, cable construction and materials can achieve fire-resistance ratings on their own such as mineral-insulated copper-clad cable, or MI cable.

Fireproofing
Providing fireproofing for cables, cable trays, or electrical conduit, is meant to keep cables operational during a specified fire exposure and time, achieved by either:
 Cable coating with a fire retardant lowers the spread of flame along the combustible cable jacketing. 
 An enclosure constructed of fire resistive materials.

Testing and certification
Testing in Canada is in accordance with ULC-S101 as required by the local building code. 

Inherently fire resistive cables can be tested to UL 2196, Tests for Fire Resistive Cables, whereas enclosures for cables that are not inherently fire resistive can be tested to UL 1724 or USNRC Generic Letter 86-10, Supplement 1 in North America, or BS476 in the United Kingdom or DIN4102 in Germany.

For Petrochemical Industries, Offshore/ Onshore, API 2218 standards are referred as the fireproofing guidelines to address hydrocarbon fires which are more severe than the cellulosic fire profiles used in DIN 4102 and BS 476 part 20 test standards for buildings.

Shaft wall systems 
Cables can be protected from fire by enclosing them in fire resistive "shaft wall" systems which are vertical and horizontal enclosures similar to ducts.

Current test methods 
Germany has standardised testing via DIN4102 which encompasses both enclosures for cabling and bus ducts as well as inherently fire-resistive cables such as mineral insulated cables. 

North America testing includes UL1724 Standard for Tests of Thermal Barrier Systems for Electrical System Components and UL2196 Standard for Tests of Fire Resistive Cables.

Ampacity derating
If a cable is covered with a materiel which restricts heat transfer and therefore prevents it from cooling, the elevated temperature can reduce the allowable cable power  capacity (i.e., less ampacity). Derating refers to the reduction of the ability of a cable to conduct electricity.

Cladding and wrapping considerations
The added weight of the wrap systems must be included in static and seismic calculations. Fireproofing of the hanging system must also be considered. Regular maintenance must be considered, as cladding and wraps are not load-bearing and can be damaged during normal building or facility operations.

Terminals and junction box considerations
The entire circuit must be completely protected including termination points and junction boxes.

See also

 Listing and approval use and compliance
 Fire test
 Passive fire protection
 Vermiculite
 Fire protection
 Mineral-insulated copper-clad cable
 Firestop
 Certification listing

Passive fire protection
Cables
Electrical safety
Thiirane. Thiirane, more commonly known as ethylene sulfide, is the cyclic chemical compound with the formula C2H4S.  It is the smallest sulfur-containing heterocycle and the simplest episulfide.  Like many organosulfur compounds, this species has a highly unpleasant odour.  Thiirane is also used to describe any derivative of the parent ethylene sulfide.

Structure
According to electron diffraction, the C-C and C-S distances in ethylene sulfide are respectively 1.473 and 1.811 Å. The C-C-S and C-S-C angles are respectively 66.0 and 48.0°.

Preparation and reactions
It can be prepared by the reaction of ethylene carbonate and KSCN.  For this purpose the KSCN is first melted under vacuum to remove water.
KSCN  + C2H4O2CO  →  KOCN  + C2H4S  +  CO2

Ethylenesulfide adds to amines to afford 2-mercaptoethylamines, which are good chelating ligands.
C2H4S   +  R2NH  →  R2NCH2CH2SH
This process is often called mercaptoethylation.

Oxidation of thiirane with periodate gives ethylene episulfoxide.

References

Episulfides
Inkjet transfer. Inkjet transfer or inkjet photo transfer is a technique to transfer a photograph or graphic, printed with an inkjet printer onto textiles, cups, CDs, glass and other surfaces.

A special transfer sheet, usually ISO A4 size, is printed on with a regular inkjet printer. The photo has to be printed as a mirror image (except for some transfer sheets for dark materials).

T-shirt transfer

It is often a requirement of "homemade" garments (adhesive-based transfers) that they are washed inside out, only in cold water, sometimes by hand, and not be tumble dried. The heat from washing or drying conventionally, or from ironing over the transfer area, can damage the transfer or cause it to separate. These attributes generally make them less practical for frequent wear than purchased items.

The second type of transfer paper is merely a substrate which ink is deposited onto, from which it is sublimated directly into the t-shirt fibers (requires at least 50% polyester fabric).  The main advantages of this process are permanence and lack of a rough adhesive on the surface of the fabric.  This technique is used commercially, and not easily reproduced at home, since a heat press is required to heat the inks to their sublimation temperature (over 200°F) evenly.

Technique
The transfer sheet is placed ink side down (usually) onto a t-shirt or fabric and ironed (without steam) onto the cloth.  Some transfer sheets change color to signal that the transfer is finished. To create a glossy effect with adhesive-based transfers, the transfer sheet is removed after it has been cooled down. To create a matte effect, it is peeled off while still hot.

References 

Photographic processes
Paper
Computer printing
Malmquist index. The Malmquist Index (MI) is a bilateral index that can be used to compare the production technology of two economies. It is named after Professor Sten Malmquist, on whose ideas it is based. It is also called the Malmquist Productivity Index.

The MI is based on the concept of the production function. This is a function of maximum possible production, with respect to a set of inputs pertaining to capital and labour. So, if  is the set of labour and capital inputs to the production function of Economy A, and  is the production function of Economy A, we could write .

While the production function would normally apply to an enterprise, it is possible to calculate it for an entire region or nation. This would be called the aggregate production function.

To calculate the Malmquist Index of economy A with respect to economy B, we must substitute the labour and capital inputs of economy A into the production function of B, and vice versa. The formula for MI is given below.

where

Note that the MI of A with respect to B is the reciprocal of the MI of B with respect to A. If the MI of A with respect to B is greater than 1, the aggregate production technology of economy A is superior to that of economy B.

The Malmquist Index was introduced in the 1982 paper, "Multilateral Comparisons of Output, Input and Productivity Using Superlative Index Numbers", by Douglas W. Caves, Laurits R. Christensen and W. Erwin Diewert.

Notes

References

Definition on About.com

 Caves, Douglas W & Christensen, Laurits R & Diewert, W Erwin, 1982. "Multilateral Comparisons of Output, Input, and Productivity Using Superlative Index Numbers," Economic Journal, Royal Economic Society, vol. 92(365), pages 73–86, March.
 Caves, Douglas W & Christensen, Laurits R & Diewert, W Erwin, 1982. "The Economic Theory of Index Numbers and the Measurement of Input, Output, and Productivity," Econometrica, vol. 50(6), pages 1393–1414, November.
 Alexandra Daskovska & Léopold Simar & Sébastien Bellegem, 2010. "Forecasting the Malmquist productivity index," Journal of Productivity Analysis, Springer, vol. 33(2), pages 97–107, April. 
 Färe, R., Grosskopf, S., Norris, M., & Zhang, Z. 1994. Productivity growth, technical progress, and efficiency change in industrialized countries. The American Economic Review 84, pages 66–83.
 Simar, Leopold & Wilson, Paul W., 1999. "Estimating and bootstrapping Malmquist indices," European Journal of Operational Research, Elsevier, vol. 115(3), pages 459–471, June. ]
  Mayer, A. and Zelenyuk, V. 2014. "Aggregation of Malmquist productivity indexes allowing for reallocation of resources," European Journal of Operational Research, Elsevier, vol. 238(3), pages 774-785.
  Zelenyuk, V. 2006. "Aggregation of Malmquist productivity indexes," European Journal of Operational Research, vol. 174(2), pages 1076-1086.

Economic indicators
George Conrad Westervelt. George Conrad Westervelt (December 30, 1879 – March 15, 1956) was a U.S. Navy engineer who created the company  "Pacific Aero Products Co." together with William Boeing. Westervelt left the company in 1916 and Boeing changed the name of the company to the Boeing Airplane Company the following year.

Early life
George Conrad Westervelt was born in Corpus Christi, Texas to GW Westervelt and Ida Florence DeRyee (DuRy) Westervelt. He attended Corpus Christi Grammar School and Texas Military Institute, San Antonio, Texas.

Naval career

Westervelt was a 1901 graduate of the United States Naval Academy and a 1908 graduate of the Massachusetts Institute of Technology in naval architecture and marine engineering. Until 1916, Westervelt was stationed on the west coast of the United States. In 1916, he was transferred to the east coast and headed the Naval Aircraft Factory in Philadelphia from 1921 to 1927. Westervelt retired from the USN with the rank of Captain.

Aviation career

During his naval career, Westervelt was also involved in naval aviation. Westervelt became friends with Boeing and worked with him on seaplanes, co-designing the Boeing Model 1, and co-founded The Boeing Company. He left Pacific Aero Products after 1916 after being transferred to the east coast by the USN. Westervelt was assigned by the Navy Bureau of Construction and Repair to work with Curtiss Aeroplane and Motor Company on the Curtiss NC float plane and later became vice-president with Curtiss-Wright following his retirement from the USN. From 1930 to 1931 Westervelt went to China to help out with the China National Aviation Corporation.

During World War II, Westervelt was called back to active duty in April 1942 to manage military aircraft production by the Brewster Aeronautical Corporation until Henry J. Kaiser took over in 1943.

Personal life

Westervelt was married to Rieta Brabham Langhorne of Lynchburg, Virginia, on December 20, 1927, and had two daughters, Sally Cary and Effie Eda. He retired from Curtiss-Wright and became chairman of the board of the Kentucky River Coal Corporation. Westervelt died in 1956 in Florida, where he had a winter home at Jupiter Island and a ranch near Stuart, Florida.

Westervelt is buried with military honors at Arlington National Cemetery near Washington, D.C.

References

1879 births
1956 deaths
People from Corpus Christi, Texas
TMI Episcopal alumni
United States Naval Academy alumni
Military personnel from Texas
MIT School of Engineering alumni
American naval architects
Aircraft designers
Boeing people
United States Navy personnel of World War I
United States Navy captains
Businesspeople in aviation
United States Navy personnel of World War II
Burials at Arlington National Cemetery
Microlite. Microlite was once known as a pale-yellow, reddish-brown, or black isometric mineral composed of sodium calcium tantalum oxide with a small amount of fluorine. Its chemical formula is . Today it is a name of a group of oxide minerals of a similar stoichiometry having tantalum prevailing over titanium and niobium. The microlite group belongs to a large pyrochlore supergroup that occurs in pegmatites and constitutes an ore of tantalum. It has a Mohs hardness of 5.5 and a variable specific gravity of 4.2 to 6.4. It occurs as disseminated  microscopic subtranslucent to opaque octahedral crystals with a refractive index of 2.0 to 2.2. Microlite is also called djalmaite, but both names are now obsolete.

"Microlite" occurs as a primary mineral in lithium-bearing granite pegmatites, and in miarolitic cavities in granites. Association minerals include: albite, lepidolite, topaz, beryl, tourmaline, spessartine, tantalite and fluorite.

"Microlite" was first described in 1835 for an occurrence on the Island of Uto, State of Stockholm, Sweden. Another occurrence of microlite is the Clark Ledges pegmatite, Chesterfield, Hampshire County, Massachusetts. The name is from Greek mikros for "small" and lithos for "stone".

References

Additional reading
Andrade, M. B., Atencio, D., Menezes Filho, L. A., & Ellena, J. (2011). The crystal structure of a microlite-group mineral with a formula near NaCaTa2O6F from the Morro Redondo mine, Coronel Murta, Minas Gerais, Brazil (vol 49, pg 615, 2011). Canadian Mineralogist, 49(5), 1338–1338.
Atencio, D., Andrade, M. B., Christy, A. G., Gieré, R., & Kartashov, P. M. (2010). The pyrochlore supergroup of minerals: nomenclature. The Canadian Mineralogist, 48(3), 673–698.

Palache, C., H. Berman, and C. Frondel (1944) Dana’s system of mineralogy, (7th edition), v. I, 748–757

Oxide minerals
Tantalum minerals
Cubic minerals
Minerals in space group 227
Minerals described in 1835
M5 mine. The M5 is a United States minimum metal plastic cased anti-tank blast mine. The mine uses either a glass or porcelain internal case with a protective outer case, made from felt impregnated with asphalt and tar paper. The mine uses a chemical fuze rather than a mechanical one. It contains either 5.4 lb (2.4 kg) of TNT or 5.7 lb (2.6 kg) of tetrytol (a mixture of tetryl and TNT). It was used during the Second World War. The practice version, designated as M9, was also produced.

Specifications
 Weight: 15 lb (6.8 kg) or 15.3 lb (6.9 kg) 
 Explosive content: 5.4 lb (2.4 kg) of TNT or 5.7 lb (2.6 kg) of tetrytol
 Diameter: 10 inches (250 mm)
 Height: 5 inches (125 mm)
 Operating pressure:

References 

Anti-tank mines
Land mines of the United States
Roller cone bit. A roller-cone bit is a drill bit used for drilling through rock that features 2 or 3 abrasive, spinning cones that break up rock and sediment as they grind against it. Roller-cone bits are typically used when drilling for oil and gas. A water jet flowing through the bit washes out the rock in a slurry.

History 

The oil boom in the southern United States in the early 20th century lead to the need for higher efficiency drill bits for well boring. After the Spindletop Gusher, Howard R. Hughes Sr. recognized the growing demand for oil and the ineffectiveness of the standard fishtail bit against harder rock formations. The first roller cone patent was for the rotary rock bit and was issued to American businessman and inventor Howard Hughes Sr. in 1909. It consisted of two interlocking cones. American businessman Walter Benona Sharp worked very closely with Hughes in developing the rock bit. The success of this bit led to the founding of the Sharp-Hughes Tool Company. In 1933 two Hughes engineers, one of whom was Ralph Neuhaus, invented the tricone bit, which has three roller cones.  The Hughes patent for the tricone bit lasted until 1951, after which other companies made similar bits. However, Hughes still held 40% of the world's drill bit market in 2000.

Design 
Roller cone bits are characterized by the use of rolling cones at the head rather than the typical auger-type design of most drill bits. Rock hardness is one of the determining factors taken into account when selecting an appropriate drill bit. The cutting structure of the bits varies according to the rock formation. Softer formations are drilled with a roller-cone bit with widely spaced, long protruding teeth, whereas harder formations are drilled with closer-spaced and shorter-toothed bits. Roller-Cone bits are versatile and can cut through many formation types. Cones with machined heads are used in applications where tooth wear on the bit is negligible. These bits are usually machined from steel and have larger, more aggressive teeth. On the other hand, cones with tungsten inserts are used in high wear applications, where it is preferable to replace only the inserts and not the entire drill bit. They also tend to have smaller teeth.

Drilling bits are attachments that are added to the end of a drillstring to perform the cutting necessary to penetrate the many rock layers between Earth's surface and oil/gas reservoirs. Once a hole is drilled, appropriate casings may be inserted to seal the wellbore formation.

The bits are further classified based on their internal bearings.  Each bit has three rotating cones and each one will rotate on its own axis during drilling.  While the bits are fixed to the drilling rigs, the rotation of the drill pipe will be in a clockwise direction and the roller cones are rotated in an anti-clockwise direction. Each roller cone is rotated on its own axis with the help of the bearing.  Again, the bearings are classified mainly into three types: Open bearing bits, Sealed Bearing Bits and Journal Bearing bits.

External links

References 

Mining equipment
Paper density. Paper density is a paper product's mass per unit volume.  The density can be calculated by dividing the grammage of paper (in grams per square metre or "gsm") by its caliper (usually in micrometres, occasionally in mils).

The "ISO 534:2011, Paper and board — Determination of thickness, density and specific volume" indicates that the paper density is expressed in grams per cubic centimeter (g/cm3).

See also
 Grammage
 Density
 Area density
 Linear density

References

External links
 Understanding Paper Weights
 Understanding paper weight (Staples, Inc.)
 M-weight Calculator
 Paper Weight Calculator

Paper
Printing