omniomni/omni-engineering huggingface dataset:
Hobbit (computer). Hobbit (Russian: Хоббит) is a Soviet/Russian 8-bit home computer, based on the ZX Spectrum hardware architecture.
Besides Sinclair BASIC it also featured CP/M, Forth or LOGO modes, with the Forth or LOGO operating environment residing in an on-board ROM chip.

Overview

Hobbit was invented by Dmitry Mikhailov (Russian: Дмитрий Михайлов) (all R&D) and Mikhail Osetinskii (Russian: Михаил Осетинский) (management) in Leningrad, Russia in the late 1980s. The original circuit layout was designed on a home-made computer (built in 1979 using ASMP of three KR580 chips - Soviet Intel 8080 clones), also created by Dmitry Mikhailov. The computer was manufactured by the joint venture InterCompex.

Hobbit was marketed in the former Soviet Union as a low-cost personal computer solution for basic educational and office needs, in addition to its obvious use as a home computer. Schools would use it on the classrooms, interconnecting several machines and forming a 56K baud network. It was possible to use another Hobbit or a IBM PC compatible with a special Hobbit network adapter card by InterCompex as a master host on the network.

The Hobbit was also briefly marketed in the U.K., targeted mainly at the existing ZX Spectrum fans wanting a more advanced computer compatible with the familiar architecture. It was mentioned on Your Sinclair September 1990 and January 1991 issues; Crash April 1992 issue, and on Sinclair User August and September 1992 issues, highlighting the available Forth language and CP/M operating system.

Domestic models often did not include the TV output, the internal speaker or both. The AY8910 chip for the domestic models was sold separately as an external extension module, hanging off the same extension bus as the optional external disk drive.

Another extension was the SME (Screen and Memory Extension) board. This featured 32 KB of cache memory, some of which could be dedicated to a video text buffer in CGA mode (only supported by drivers in the FORTH or the CP/M environments; no known programs using the Sinclair-based BASIC mode used this feature). SME worked at astonishing speed - one machine code command made an output of an entire display line. SME was capable of rendering several dozens of windows per second, and its capabilities were fully utilized only in the Forth environment.

Technical details

Source:

 Z80A at 3.5 MHz
 64K RAM
 Disk drives: external 2 x 5.25" drives (up to 4 connectable) or internal 3.5" drive
 Connections: joystick (2 x Sinclair, 1 x Kempston), Centronics, RS-232, audio in/out (for cassette recorder), system bus extension
 74-key keyboard (33 keys freely programmable)
 Video output: Composite video TV out, EGA monitor
 Operating system: built in disassembler, CP/M clone called "Beta", system language switchable between English and Russian

References

Computer-related introductions in 1990
ZX Spectrum clones
Soviet Union–United Kingdom relations
Z80-based home computers
Soviet computer systems
Huff-Daland XB-1. The Huff-Daland XB-1 was a prototype bomber aircraft built for the United States Army Air Corps.

The XB-1 was the first aircraft named using just a B- designation. Prior to 1926, the U.S. Army used LB- and HB- prefixes, signifying 'Light Bomber' and 'Heavy Bomber'. The first XB-1, called the Super-Cyclops by Huff-Daland, was an extension of the earlier Huff-Daland XHB-1 'Cyclops'. It was essentially the same in size, but sported a twin tail and twin engines.

Design and development
The XB-1's gunnery arrangement was new for an American bomber, but it had been previously used by the British and the Germans during World War I. The Army Air Corps had decided that single-engined bombers such as the XHB-1 performed worse, and weren't as safe as twin-engined bombers.

Operational history
The aircraft flew for the first time in September 1927. Its original Packard engines did not provide enough power for the aircraft, and it was refitted with more powerful Curtiss Aircraft "Conqueror" engines. This new configuration was designated the XB-1B.

Three other similar aircraft designs were requested by the Army Air Corps around the same time which competed against the XB-1 for the contract. Of these three (the XB-2 Condor, the Sikorsky S-37 and the Fokker XLB-2), the Curtiss model eventually won, and only a single XB-1 was ever produced.

Specifications (XB-1B)

See also

References

External links

USAF Museum Article on XB-1
USAF Museum Article on XB-1B
Encyclopedia of American Aircraft

XB-01
Huff-Daland XB-01
Biplanes
Aircraft first flown in 1927
Twin piston-engined tractor aircraft
Aircraft with fixed conventional landing gear
Action at a distance (computer programming). Action at a distance is an anti-pattern in computer science in which behavior in one part of a program varies wildly based on difficult or impossible to identify operations in another part of the program.

The way to avoid the problems associated with action at a distance is a proper design, which avoids global variables and alters data only in a controlled and local manner, or usage of a pure functional programming style with referential transparency.

The term is based on the concept of action at a distance in physics, which may refer to a process that allows objects to interact without a mediator particle such as the gluon.  In particular, Albert Einstein referred to quantum nonlocality as "spooky action at a distance".

Software bugs due to action at a distance may arise because a program component is doing something at the wrong time, or affecting something it should not. It is very difficult, however, to track down which component is responsible. Side effects from innocent actions can put the program in an unknown state, so local data is not necessarily local. The solution in this particular scenario is to define which components should be interacting with which others. A proper design that accurately defines the interface between parts of a program, and that avoids shared states, can largely eliminate problems caused by action at a distance.

Example
This example, from the Perl programming language, demonstrates an especially serious case of action at a distance (note the $[ variable was deprecated in later versions of Perl):

Action at a distance across objects
Proper object-oriented programming involves design principles that avoid action at a distance.

The Law of Demeter states that an object should only interact with other objects near itself. Should action in a distant part of the system be required then it should be implemented by propagating a message. Proper design severely limits occurrences of action at a distance, contributing to maintainable programs.  Pressure to create an object orgy results from poor interface design, perhaps taking the form of a God object, not implementing true objects, or failing to heed the Law of Demeter.

One of the advantages of functional programming is that action at a distance is de-emphasised, sometimes to the point of being impossible to express at all in the source language.

Being aware of the danger of allowing action at a distance into a design, and being able to recognize the presence of action at a distance, is useful in developing programs that are correct, reliable and maintainable.  Given that the majority of the  expense of a program may be in the maintenance phase, and that action at a distance makes maintenance difficult, expensive and error prone, it is worth effort during design to avoid.

See also
 COMEFROM
 Loose coupling
 State pattern

References

Anti-patterns
Table engine. A table engine is a variety of stationary steam engine where the cylinder is placed on top of a table-shaped base, the legs of which stand on the baseplate which locates the crankshaft bearings. The piston rod protrudes from the top of the cylinder and has fixed to it a cross-head which runs in slides attached to, and rising from, the cylinder top. Long return rods connect the crosshead to the crankshaft, on which is fixed the flywheel.

This pattern of engine was first introduced by James Sadler at the Portsmouth Dockyard in 1798 and was house-built in that its framing was formed by the engine house, as had been common practice for beam engines.

Henry Maudslay patented an improved version of this a few years later, and other makers adopted the configuration.

It was supplied for low-speed, low-power applications around the first half of the nineteenth century. They continued to be made in a range of sizes, down to very small, with a bore and stroke of only a few inches.

The table engine was one of the first types where the engine was constructed as an independent unit, rather than being house-built. This made the engines cheaper, and more importantly quicker, to erect on site. Entire engines could be built and tested at their factory before delivery. Engines could also be pre-built, then offered for sale from stock, rather than having to be designed and constructed for each site.

One reason for the continued use of a vertical cylinder was the belief that with a horizontal cylinder, the weight of the piston within the cylinder would lead to uneven wear on the lower bore of the cylinder. This erroneous view was not dispelled until around 1830 and the increasing number of steam locomotives using horizontal cylinders without such wear problems.

Footnotes

Notes

External links

Maudslay table engine at the Science Museum, London

Stationary steam engines
Steam engines
Steam engines by layout
Laser-induced fluorescence. Laser-induced fluorescence (LIF) or laser-stimulated fluorescence (LSF) is a spectroscopic method in which an atom or molecule is excited to a higher energy level by the absorption of laser light followed by spontaneous emission of light. It was first reported by Zare and coworkers in 1968.

LIF is used for studying structure of molecules, detection of selective species and flow visualization and measurements. The wavelength is often selected to be the one at which the species has its largest cross section. The excited species will after some time, usually in the order of few nanoseconds to microseconds, de-excite and emit light at a wavelength longer than the excitation wavelength. This fluorescent light is typically recorded with a photomultiplier tube (PMT) or filtered photodiodes.

Types
Two different kinds of spectra exist, disperse spectra and excitation spectra.

The disperse spectra are performed with a fixed lasing wavelength, as above and the fluorescence spectrum is analyzed. Excitation scans on the other hand collect fluorescent light at a fixed emission wavelength or range of wavelengths. Instead the lasing wavelength is changed.

An advantage over absorption spectroscopy is that it is possible to get two- and three-dimensional images since fluorescence takes place in all directions (i.e. the fluorescence signal is usually isotropic). The signal-to-noise ratio of the fluorescence signal is very high, providing a good sensitivity to the process. It is also possible to distinguish between more species, since the lasing wavelength can be tuned to a particular excitation of a given species which is not shared by other species.

LIF is useful in the study of the electronic structure of molecules and their interactions. It has also been successfully applied for quantitative measurement of concentrations in fields like combustion, plasma, spray and flow phenomena (such as molecular tagging velocimetry), in some cases visualizing concentrations down to nanomolar levels. LED-induced fluorescence has been used in situ to delineate aromatic hydrocarbon contamination as  a cone penetrometer add on module and also as a percussive capable asset.

Applications 
 Detection of purity
 Optical tumor diagnosis
 Imaging of paleontological specimens
Detection and quantification of biomolecules and biological processes (e.g. DNA sequencing, trace protein analysis, polymerase chain reaction products, and single-cell analysis)
 In plasma diagnostics, which measures plasma properties such as the ion distribution function and velocity space diffusion and convection in a plasma

See also 
Fluorescence microscope
 Planar laser-induced fluorescence
 Ultrafast laser spectroscopy

References

Fluorescence
Plasma diagnostics
Curtiss B-2 Condor. The Curtiss B-2 Condor was a 1920s United States bomber aircraft. It was a descendant of the Martin NBS-1, which was built by the Curtiss Aeroplane and Motor Company for the Glenn L. Martin Company. There were a few differences, such as stronger materials and different engines, but they were relatively minor.

Development
The B-2 was a large fabric-covered biplane aircraft. Its two engines sat in nacelles between the wings, flanking the fuselage. It had a twin set of rudders with twin horizontal stabilizers, a configuration which was becoming obsolete by that time. At the rear of each nacelle was a gunner position. In previous planes, the back-facing gunners had been in the fuselage, but their view there was obstructed. A similar arrangement (using nacelle-mounted gun platforms) was adopted in the competing Keystone XB-1 aircraft.

The XB-2 competed for a United States Army Air Corps production contract with the similar Keystone XB-1, Sikorsky S-37, and Fokker XLB-2. The other three were immediately ruled out, but the Army board appointed to make the contracts was strongly supportive of the smaller Keystone XLB-6, which cost a third as much as the B-2. Furthermore, the B-2 was large for the time and difficult to fit into existing hangars. However, the superior performance of the XB-2 soon wrought a policy change, and in 1928 a production run of 12 was ordered.

One modified B-2, dubbed the B-2A, featured dual controls for both the pilot and the copilot. Previously, the control wheel and the pitch controls could only be handled by one person at a time. This "dual control" setup became standard on all bombers by the 1930s. There was no production line for the B-2A. The B-2 design was also used as a transport.

The B-2 was quickly made obsolete by technological advances of the 1930s, and served only briefly with the Army Air Corps, being removed from service by 1934. Following production of the B-2, Curtiss Aircraft left the bomber business, and concentrated on the Hawk series of pursuit aircraft in the 1930s.

Variants
Model 52 Company designation of the B-2.
XB-2 Prototype.
B-2 Twin-engined heavy bomber biplane. Initial production version; 12 built.
B-2A Redesignation of one B-2 fitted with dual controls.
Model 53 Condor 18 Civil version of the B-2. Six built.

Military operators

US Army Air Corps
7th Bombardment Group, Rockwell Field, California
11th Bomb Squadron - operated 1928-1931

Specifications (B-2)

See also

References

Bibliography
 Bowers, Peter M. Curtiss Aircraft 1907-1947. London: Putnam & Company, 1979. .

External links

 Curtis B-2 Condor page of Joe Baugher, part of his Encyclopedia of American Aircraft
 USAF Museum article on B-2
 

B-02 Condor
Curtiss B-02
Biplanes
Aircraft first flown in 1929
Twin piston-engined tractor aircraft
Aircraft with fixed conventional landing gear
Twin-tail aircraft
Keystone B-4. The Keystone B-4 was a biplane bomber, built by the Keystone Aircraft company for the United States Army Air Corps.

Design and development
Originally ordered by the United States Army Air Corps as the LB-13 light bomber. When the LB- designation was dropped in 1930, the first five planes were redesignated Y1B-4. (The Y1B- designation indicates that funds for the design did not come from the normal annual funds.)

The first B-3A (S/N 30-281) was converted to Y1B-4 configuration with the addition of R-1860-7 radial engines and low pressure tires. Because of more powerful engines, the performance of the Y1B-4 was a slight improvement on the B-3, but the only difference between the two planes was their engines. On April 28, 1931, the army ordered 25 improved Y1B-4s as the Keystone B-4A. This production version was part of the last biplane bomber order made by the Army Air Corps (along with 39 B-6As, identical in all respects except their make of engine), and the B-4As, delivered between January and April 1932, were the last biplane bombers delivered to the Air Corps.

Operational history
The B-4 was the last of the Keystone biplane bombers ordered by the U.S. Army in late 1931. These aircraft were used primarily as observation and reconnaissance aircraft as early as 1934 when the Martin B-10B went into operational service. Some remained in service into the early 1940s.

Variants
LB-13
Seven aircraft ordered but delivered as the Y1B-4 and Y1B-6 with different engine installations.
Y1B-4
Five pre-production aircraft, as the LB-10 but with two 575 hp (429 kW) Pratt & Whitney R-1860-7 engines.
B-4A
Production version of the Y1B-4, 25 built.

Operators

United States Army Air Corps

Specifications (B-4A)

See also

External links

Encyclopedia of American Aircraft
Photograph
USAF Museum article on B-4
USAF Museum article on LB-13

B-4
Light bombers
Keystone B-04
Biplanes
Twin piston-engined tractor aircraft
Aircraft with fixed conventional landing gear
NIB. NIB, nib or NiB may refer to:

 Nib (pen), the writing tip of a pen
 The Nib, an online comic
 Nib, partially processed cocoa bean
 Twizzlers Nibs, a candy
 Neodymium magnet or NIB (neodymium, iron, boron)
 N.I.B., a song by Black Sabbath
 .nib, Apple Interface Builder file format
 Net insurance benefit
 NiB, nickel boron, an electroless nickel alloy

In companies and organizations:

 National Irish Bank
 National Intercollegiate Band
 Nordic Investment Bank
 nib Health Funds, Australasia
 New Iberia (Amtrak station), Louisiana, US, station code
 National Internet Backbone NIB-II, the BSNL internet backbone
 Nagasaki International Television, Japan
PPI. PPI may refer to:

Science and technology

Biochemistry
 PPi, the anion P2O74−, a pyrophosphate
 Polyproline I helix
 Protein–protein interaction

Medicine
 Patient and public involvement
 Prepulse inhibition, of a later pulse
 Proton-pump inhibitor, a medication
 Psychopathic Personality Inventory, a personality test
 Psychophysiological Interaction, fMRI analysis technique

Computing
 Parallel Peripheral Interface, of the Blackfin processor
 Programmable Peripheral Interface, Intel 8255 chip
 Programmable Peripheral Interconnect, in Nordic nRF microcontrollers 
 Pixels per inch, of a display
 Productivity Products International, commercializer of the Objective-C language

Other science and technology
 Gabarit passe-partout international, in railways
 Picks per inch, a unit of textile measurement
 Plan position indicator, radar display
 Polymethylene polyphenylene isocyanate

Business and organizations
 Italian People's Party (1919) (Partito Popolare Italiano), a political party
 Italian People's Party (1994) (Partito Popolare Italiano), a political party
 Payment protection insurance
 Peace Party of India, Uttar Pradesh
 Perusahaan Perdagangan Indonesia, trading company
 Philips Phonographische Industries, later Philips Records
 Phonographic Performance Ireland, music licensing company
 Pirate Parties International
 Polly Peck International, former UK company
 Primarily Primates, primate sanctuary, Texas, US
 Productivity Products International, US software company later renamed Stepstone
 Progressive Policy Institute, U.S.
 Pakistan Press International, a  news agency

Other uses
 Pareto priority index, to prioritize projects
 Positive polarity item
 Producer price index
 Pulse Polio, immunisation campaign in India
 Port Pirie Airport, IATA airport code "PPI"
Water contact. In the hydrocarbon industry water contact is the elevation above which fluids other than water can be found in the pores of a rock.

For example, in a traditional hand-excavated water well, the level at which the water stabilizes represents the water table, or the elevation in the rock where air starts to occupy the rock pores.

In most situations in the hydrocarbon industry the term is qualified as being an oil-water contact (abbreviated to "OWC") or a gas-water contact ("GWC"). Often there is also a gas-oil contact ("GOC").

In an oil or gas field, hydrocarbons migrate into rocks and can be trapped if there is a permeability barrier to prevent upward escape.  Gas and oil are lighter than water, so they will form a bubble at the high end of the "trap" formed by the impermeable barriers.  A simple physical model of this would be a coffee cup held upside down underwater with an air bubble occupying the highest portion of the cup's interior.  The base of the bubble is the water contact.

Capillary action can obscure the true water contact in permeable media like sandstone.  Capillary pressure prevents the hydrocarbons from expelling all of the water in the pores, which creates a transition zone between the fully saturated hydrocarbon levels and the fully saturated water levels.

In poorly porous intervals, the oil-water, gas-water or gas-oil contacts can similarly be obscured, which makes estimation of hydrocarbon reserves difficult. Descriptions of the well's petrophysics will then often further qualify to delineate a gas-down-to, oil-up-to, oil-down-to and water-up-to line, clearly showing the uncertainties involved.

See also
Fluid Contact

References

Petroleum geology
NORDO. In North American aviation, a NORDO () aircraft is an aircraft flying without a radio. While sometimes used to denote small general aviation aircraft that are not equipped with a radio, the term is more commonly applied to aircraft that have experienced a radio failure while flying.

The term originates from the 5-character uppercase abbreviated notation "NORDO" displayed on controllers' radar scopes when an aircraft transmits the "radio failure" code on its transponder. An alternate explanation is that "NO RDO" was the standard note made on maintenance and equipment sheets used in military aviation, starting in the 1930s, as a code to identify planes which needed radio repairs or were not equipped with radios. The term has made its way into standard aviation jargon, used as an adjective or a noun to describe an aircraft without a radio, even among pilots and others who are not air traffic controllers.

In-flight radio failure may constitute an emergency, as determined by the pilot. Aircraft equipped with a transponder should indicate a NORDO situation by setting the appropriate transponder code: 7600 ("seven-six: radio fix"). NORDO aircraft declaring an emergency are given priority over other aircraft (providing a more serious emergency does not occur on another aircraft).

If the radio failure occurs in visual flight rules (VFR) conditions in an area where radio communication is required, the pilot is expected to continue under VFR and land when feasible. If flying under instrument flight rules (IFR) conditions, and VFR conditions exist or are encountered after the failure, the flight should be continued in VFR conditions and the pilot shall land as soon as practicable. If VFR conditions do not exist, the pilot will then continue the route last assigned by ATC. See FAR 91.185.

Air traffic control may re-establish communications with NORDO aircraft by using emergency frequencies, voice features of NAVAIDs, or aviation light signals. In the event of one-way communications (i.e. aircraft can receive only), the controller may request the aircraft make identifying turns, flash their navigational lights, transmit codes or IDENT signals on the transponder, rock their wings, etc., to acknowledge clearances or instructions.

References 

Air traffic control in the United States
Emergency aircraft operations