omniomni/omni-engineering huggingface dataset:
Privilege separation. In computer programming and computer security, privilege separation (privsep) is one software-based technique for implementing the principle of least privilege. With privilege separation, a program is divided into parts which are limited to the specific privileges they require in order to perform a specific task. This is used to mitigate the potential damage of a computer security vulnerability.

Implementation 
A common method to implement privilege separation is to have a computer program fork into two processes.  The main program drops privileges, and the smaller program keeps privileges in order to perform a certain task.  The two halves then communicate via a socket pair.  Thus, any successful attack against the larger program will gain minimal access, even though the pair of programs will be capable of performing privileged operations.

Privilege separation is traditionally accomplished by distinguishing a real user ID/group ID from the effective user ID/group ID, using the setuid(2)/setgid(2) and related system calls, which were specified by POSIX. If these are incorrectly positioned, gaps can allow widespread network penetration.

Many network service daemons have to do a specific privileged operation such as open a raw socket or an Internet socket in the well known ports range. Administrative utilities can require particular privileges at run-time as well. Such software tends to separate privileges by revoking them completely after the critical section is done, and change the user it runs under to some unprivileged account after so doing. This action is known as dropping root under Unix-like operating systems. The unprivileged part is usually run under the "nobody" user or an equivalent separate user account.

Privilege separation can also be done by splitting functionality of a single program into multiple smaller programs, and then assigning the extended privileges to particular parts using file system permissions. That way the different programs have to communicate with each other through the operating system, so the scope of the potential vulnerabilities is limited (since a crash in the less privileged part cannot be exploited to gain privileges, merely to cause a denial-of-service attack).

Examples

Dovecot 
Another email server software designed with privilege separation and security in mind is Dovecot.

OpenBSD 
Separation of privileges is one of the major OpenBSD security features.

OpenSSH 
OpenSSH uses privilege separation to ensure pseudo terminal (pty) creation happens in a secure part of the process, away from per connection processes with network access.

Postfix 
The implementation of Postfix was focused on implementing comprehensive privilege separation.

Solaris 
Solaris implements a separate set of functions for privilege bracketing.

See also
 Capability-based security
 Confused deputy problem
 Privilege escalation
 Privilege revocation (computing)
 Defensive programming
 Sandbox (computer security)

References

Computer security procedures
Algorithmic. Algorithmic may refer to:
Algorithm, step-by-step instructions for a calculation
Algorithmic art, art made by an algorithm
Algorithmic composition, music made by an algorithm
Algorithmic trading, trading decisions made by an algorithm
Algorithmic patent, an intellectual property right in an algorithm
Algorithmics, the science of algorithms
Algorithmica, an academic journal for algorithm research
Algorithmic efficiency, the computational resources used by an algorithm
Algorithmic information theory, study of relationships between computation and information
Algorithmic mechanism design, the design of economic systems from an algorithmic point of view
Algorithmic number theory, algorithms for number-theoretic computation
Algorithmic game theory, game-theoretic techniques for algorithm design and analysis
Algorithmic cooling, a phenomenon in quantum computation
Algorithmic probability, a universal choice of prior probabilities in Solomonoff's theory of inductive inference

See also
Algorithmic complexity (disambiguation)
Adams-Wilson Hobbycopter. The Adams-Wilson Hobbycopter (later named the Adams-Wilson Choppy) is a small, single-seat, open-framework helicopter designed for homebuilding, to be powered by a motorcycle engine.

Design and development
The Adams-Wilson company was formed by T.G. Adams and Paul Wilson to market plans for a simple single-seat helicopter named the HobbyCopter, of which they have built a prototype. This prototype flew successfully for the first time in November 1958. Plans were first marketed in 1958 and have been revised and revived by various designers over the years.

The Hobbycopter, (also colloquially known as the Flying Triumph), was designed to use commonly found materials that were readily available to customers. The Hobbycopter  was designed to use a motorcycle engine of about  and a variety engines have been used, including a snowmobile motor and more recently, an ultralight 2-cycle Rotax 503 engine developing .

The aircraft is available in the form of plans and some key parts for amateur construction from Vortech of Fallston, Maryland.

Variants
Hobbycopter XH-1 The prototype of the one-man open framework homebuilt helicopter powered by a  Triumph motorcycle engine.
Hobbycopter 101Production version of the XH-1 offered as a kit for $900, or as plans for $35 to homebuilders.
Hobbycopter 102Strengthened Model 101 with  Triumph and a fibre-glass cockpit enclosure.

Specifications (Hobbycopter 101)

See also

References

External links

Homebuilt aircraft
1950s United States sport aircraft
1950s United States helicopters
Single-engined piston helicopters
Hobbycopter
Aircraft first flown in 1958
Ultralight helicopters
A-B Helicopters A/W 95. The A-B Helicopters A/W 95 is an American helicopter, produced by A-B Helicopters in the form of plans for amateur construction.

By 2012 the A-B Helicopters website had been taken down and plans are no longer available.

The design was developed into the Vortech A/W 95 and plans for that version remain available from Vortech.

Design and development
The A/W 95 is a development of the Adams-Wilson Choppy, which the A/W designation acknowledges. The A/W 95 was designed to comply with the US Experimental Amateur-built rules, since the empty weight is too heavy for the FAR 103 Ultralight Vehicles rules, which stipulates a maximum empty weight of . The aircraft has a standard empty weight of . It features a single main rotor, a single-seat open cockpit without a windshield, skid landing gear and a twin cylinder, air-cooled, two-stroke, dual-ignition  Rotax 503 engine.

The aircraft fuselage is an open frame made from bolted-together and gusseted aluminum tubing. Its  diameter two-bladed extruded aluminum rotor has a chord of  and employs a symmetrical airfoil. The transmission is constructed from a belt and chain mechanism. With its standard empty weight of  and a gross weight of , the useful load is . Fuel tank capacity is , rendering a full-fuel payload of .

While the A/W 95 is primarily plans-built, during the time that A-B Helicopters was in business some pre-fabricated parts were available.

Operational history
By January 2013 two examples had been registered in the United States with the Federal Aviation Administration.

Specifications (A/W 95)

See also
Showers Skytwister Choppy
Vortech A/W 95

References

External links
Photo of an A/W 95 in flight

1990s United States sport aircraft
1990s United States helicopters
Homebuilt aircraft
Single-engined piston helicopters
AW95
ATA Cruiser. The Adams-Toman Cruiser was a US-built civil utility aircraft of the 1920s. It was a three-seat, high-wing monoplane with an enclosed cabin, and possibly a variant of the Grays Harbor Activian. Only one of this model of aircraft was ever built.

Specifications (Cruiser)

References

1920s United States civil utility aircraft
Single-engined tractor aircraft
Cruiser
High-wing aircraft
Rock sliders. Rock sliders are an aftermarket accessory popular among four wheel drive vehicle owners who engage in more serious off-road driving.

Rock sliders are typically made of heavy-duty box section steel, although they can also be made from tubular steel as well.  They run along each side of the vehicle, from just behind the front wheel to just before the rear wheel, just below the level of the door sills.  They are welded or bolted (directly, L brackets and/or U brackets) on to the vehicle's frame, and their function is to protect the door sills and door bottoms from damage when crossing large obstacles (such as rocks - hence the name). There are a variety of materials, qualities and features.

Types
Even though they serve relatively the same purpose, rock sliders come in four different types:
Classic rock sliders – intended to protect the vehicle's side but can help to get in and out of the vehicle.
Side steps with rock slider support – the general purpose is to help people get in and out of the vehicle, but additionally, the steps protect the vehicle from off-roading hazards, such as rocks.
Power running boards – an electrically powered board that gets in out and hides away whenever the doors are opened/closed. Primarily serves as a modern and lightweight side step but additionally protects the vehicle from underneath.
Rock sliders with rock skins – a combination of classy side steps and rocks skins. Rocks skins are stripes of steel usually drilled into the vehicle's body to protect it from dents, scratches, and other off-roading damage.

References 

Off-roading
Antimatter weapon. An antimatter weapon is a theoretically possible device using antimatter as a power source, a propellant, or an explosive for a weapon. Antimatter weapons are currently too costly and unreliable to be viable in warfare, as producing antimatter is enormously expensive (estimated at US$6 billion for every 100 nanograms), the quantities of antimatter generated are very small, and current technology has great difficulty containing antimatter, which annihilates upon touching ordinary matter.

The paramount advantage of such a theoretical weapon is that antimatter and matter collisions result in the entire sum of their mass energy equivalent being released as energy, which is at least two orders of magnitude greater than the energy release of the most efficient fusion weapons (100% vs 0.4–1%). Annihilation requires and converts exactly equal masses of antimatter and matter by the collision which releases the entire mass-energy of both, which for 1 gram is ~9×1013 joules. Using the convention that 1 kiloton TNT equivalent = 4.184×1012 joules (or one trillion calories of energy), one half gram of antimatter reacting with one half gram of ordinary matter (one gram total) results in 21.5 kilotons-equivalent of energy (the same as the atomic bomb dropped on Nagasaki in 1945).

Cost
, the cost of producing one millionth of a gram of antimatter was estimated at . By way of comparison, the cost of the Manhattan Project (to produce the first atomic bomb) is estimated at US$23 billion in 2007 prices. As such, Hui Chen of Lawrence Livermore National Laboratory dismissed concerns about antimatter bombs in 2008 as "unrealistic".

Antimatter-catalyzed weapons
Antimatter-catalyzed nuclear pulse propulsion proposes the use of antimatter as a "trigger" to initiate small nuclear explosions; the explosions provide thrust to a spacecraft. The same technology could theoretically be used to make very small and possibly "fission-free" (very low nuclear fallout) weapons (see pure fusion weapon).

In popular culture
An antimatter weapon is a part of the plot of the Dan Brown book Angels & Demons and its film adaptation, where it is used in a plot to blow up the Vatican City.

The Ground Zero expansion pack of the video game Quake II requires the protagonist to manufacture an Antimatter Bomb in the Munitions Plant to achieve the final objective.

In the Star Trek franchise, Federation starships are armed with photon torpedoes which contain antimatter warheads.

References

External links
 Spotlight on "Angels and Demons" – A discussion at CERN's public website on the viability of the use of antimatter for energy and weaponry
 "Air Force pursuing antimatter weapons: Program was touted publicly, then came official gag order"
 Page discussing the possibility of using antimatter as a trigger for a thermonuclear explosion
 Paper discussing the number of antiprotons required to ignite a thermonuclear weapon

Weapon
Proposed weapons
Science fiction weapons
Weapons of mass destruction
Vis-viva equation. In astrodynamics, the vis-viva equation is one of the equations that model the motion of orbiting bodies. It is the direct result of the principle of conservation of mechanical energy which applies when the only force acting on an object is its own weight which is the gravitational force determined by the product of the mass of the object and the strength of the surrounding gravitational field.

Vis viva (Latin for "living force") is a term from the history of mechanics and this name is given to the orbital equation originally derived by Isaac Newton. It represents the principle that the difference between the total work of the accelerating forces of a system and that of the retarding forces is equal to one half the vis viva accumulated or lost in the system while the work is being done.

Equation
For any Keplerian orbit (elliptic, parabolic, hyperbolic, or radial),  the vis-viva equation is as follows:

where:

  is the relative speed of the two bodies
  is the distance between the two bodies' centers of mass
  is the length of the semi-major axis ( for ellipses,  or  for parabolas, and  for hyperbolas)
  is the gravitational constant
  is the mass of the central body
The product of  can also be expressed as the standard gravitational parameter using the Greek letter .

Practical applications
Given the total mass and the scalars  and  at a single point of the orbit, one can compute:

  and  at any other point in the orbit; and
 the specific orbital energy , allowing an object orbiting a larger object to be classified as having not enough energy to remain in orbit, hence being "suborbital" (a ballistic missile, for example), having enough energy to be "orbital", but without the possibility to complete a full orbit anyway because it eventually collides with the other body, or having enough energy to come from and/or go to infinity (as a meteor, for example).

The formula for escape velocity can be obtained from the Vis-viva equation by taking the limit as  approaches :

For a given orbital radius, the escape velocity will be  times the orbital velocity.

Derivation for elliptic orbits (0 ≤ eccentricity < 1)

Specific total energy is constant throughout the orbit.  Thus, using the subscripts  and  to denote apoapsis (apogee) and periapsis (perigee), respectively,

Rearranging,

Recalling that for an elliptical orbit (and hence also a circular orbit) the velocity and radius vectors are perpendicular at apoapsis and periapsis, conservation of angular momentum requires specific angular momentum , thus :

Isolating the kinetic energy at apoapsis and simplifying,

From the geometry of an ellipse,  where a is the length of the semimajor axis.  Thus,

Substituting this into our original expression for specific orbital energy,

Thus,  and the vis-viva equation may be written

or

Therefore, the conserved angular momentum  can be derived using  and , where  is semi-major axis and  is semi-minor axis of the elliptical orbit, as follows:

and alternately,

Therefore, specific angular momentum , and

Total angular momentum

References

Orbits
Conservation laws
Equations of astronomy
Evolutionary Technologies International. Evolutionary Technologies International (ETI) was a company focused on developing database tools and data warehousing. Originally a research project at the Microelectronics and Computer Corporation (MCC) in Austin, Texas, ETI was spun off as a private company by co-founders Katherine Hammer, Robin Curle, Lisa Keeler, and Duane Voth in 1990.

ETI's technology provided a mechanism for automatically generating ETL (Extract/Transform/Load) programs based on user-defined metadata. Their first product was called EXTRACT (later changed to ETI•EXTRACT).

ETI was purchased by Versata in May, 2008.

ETI's technology was acquired by Ignite in June 2015.

References

Defunct software companies of the United States
Companies based in Austin, Texas
Lucerne hammer. The Lucerne hammer ( ) is a type of polearm which was popular in Swiss armies during the 15th to 17th centuries. It was a combination of the bec de corbin and a pronged war hammer.

Origins
The weapon originates from Switzerland, and the name comes from a discovery of many of these weapons in Lucerne, Switzerland.

Design 
The hammer-part of the Lucerne hammer is a three-to-four-pronged head mounted atop a  long polearm shaft. It bears a long spike on its reverse, and an even longer spike extending from the top. They are occasionally found to have spikes on the side of the head as well.

Use
The Lucerne hammer requires both hands for effective handling. As a modified polearm, Lucerne hammers have multiple functions in battle. The forward-pointing spike could be used for spearing, while the hammer proved effective at puncturing or smashing armour. Like many other polearms, the Lucerne hammer was also used for dismounting the enemy. The long pole increased the velocity of the head when the hammer was struck, resulting in tremendous force upon impact.

See also
 Poleaxe
 Swiss arms and armour

References

External links
Spotlight: The Medieval Poleaxe, by Alexi Goranov

European weapons
Medieval polearms
Medieval weapons

Military history of Switzerland
5M model. The 5M model is a troubleshooting and risk-management model used for aviation safety.

Original labels
Based on T.P. Wright's original work on the man-machine-environment triad at Cornell University, the 5M model incorporates a diagram of 3 interlocking circles and one all-encompassing circle. The smaller circles are labeled Man, Machine, and Medium; the intersecting space in the middle, where they all meet, is labeled Mission; while the larger circle is labeled Management:

 Man (people): including the physiology and psychology of those involved, as well as their performance and proficiency. 
 Machine (equipment): including the design, manufacture, maintenance, reliability, performance, etc. 
 Medium / measurement (environment, inspection): including weather, terrain, obstructions, lighting, etc. 
 Mission (purpose): the reason these three factors are brought together. 
 Management (leadership): the prevailing supervisory approach in terms of regulations, policies, procedures, and attitude involved in establishing, operating, maintaining, and decommissioning.

Expansion
These have been expanded by some to include an additional three, and are referred to as the 8 Ms:
Material (includes raw material, consumables, and information)
Method / mother nature (process, environment)
Maintenance

Other uses
This is also used in more general troubleshooting or root-cause analysis, such as with the Ishikawa diagram.

References

See also 
 Ishikawa diagram

Aviation safety
Quality control tools
Garden fork. A garden fork, spading fork, or digging fork (in the past also an asparagus fork, the same name as a very different utensil) is a gardening implement, with a handle and a square-shouldered head featuring several (usually four) short, sturdy tines.  It is used for loosening, lifting and turning over soil in gardening and farming, and not to be confused with the pitchfork, a similar tined tool used for moving (or throwing) loose materials such as hay, straw, silage, and manure.

A garden fork is used similarly to a spade in loosening and turning over soil.  Its tines allow it to be pushed more easily into the ground, and it can rake out stones and weeds and break up clods, it is not so easily stopped by stones, and it does not cut through weed roots or root-crops. Garden forks were originally made of wood, but the majority are now made of forged carbon steel or stainless steel.

Reflecting their differing uses, garden forks have shorter, flatter, thicker, and more closely spaced tines than pitchforks. They have comparatively a fairly short, stout, usually wooden handle, typically with a D- or T-shaped grab at the end.

A smaller version of such forks with shorter, closer-spaced, thinner tines (but a full-sized handle) is known as a border fork or ladies' fork, and is used for lighter work, such as weeding amongst other plants. Forks with broader, flatter tines are made for lifting potatoes and other root crops from the ground. A pair of forks back-to-back may used to lever apart dense clumps of roots.

See also
 Broadfork—for breaking up hardpan
 Fork
 Garden tool
 Pitchfork—for lifting loose material such as hay
 Spade

References

Sources
  (Trans. from Zeitschrift des Vereines Deutscher Ingenieure, 19 March 1921.)
 

Gardening tools
Aida cloth. Aida cloth (sometimes called Java canvas) is an open, even-weave fabric traditionally used for cross-stitch embroidery.  This cotton fabric has a natural mesh that facilitates cross-stitching and enough natural stiffness that the crafter does not need to use an embroidery hoop.

Characteristics 
Aida cloth is manufactured with various size spaces or holes between the warp and weft to accommodate different thicknesses of yarn. These are described by the count.  For example, a 10-count aida cloth would have 10 squares per linear inch. Typical sizes are 7, 10, 11, 12, 14, 16, 18 and 20 count, ranked from the coarsest to the finest count.  Traditional colours are white and ecru, though black, grey, shades of tan and brown, and other brighter colors are also available.  Aida cloth is sold in precut sheets or in bolts of 40" - 60" width at most craft stores.

Aida cloth has a tendency to fray and often needs hemming before use.  It should never be laundered prior to craft work and tends to contract when the finished item is washed in soap and water.  Hand washing improves the appearance of finished cross-stitching because Aida cloth naturally contracts in specific areas where it is embroidered.

Pronunciation 
The consensus from various discussions on Usenet group rec.crafts.textiles.needlework is that there are two ways to pronounce the word "Aida": either , as in the opera by Verdi, or . Since the name change from Java to Aida occurred not long after Verdi's opera was first performed, there has been some speculation that the cloth was renamed after the opera to take advantage of the opera's publicity.

Matty 
Matty is a fabric similar to Aida. It is another material suitable for embroidery. The fabric structure (open plain weave) makes it convenient to count threads in cross-stitch work. The material is used for various linens.

Citations

Bibliography
 

Woven fabrics
Embroidery