omniomni/omni-engineering huggingface dataset:
OPC Data Access. The OPC Data Access Specification is the first of a group of specifications known as the OPC Classic Specifications.

OPC Data Access is a group of client–server standards that provides specifications for communicating real-time data from data acquisition devices such as PLCs to display and interface devices like Human–Machine Interfaces (HMI), SCADA systems and also ERP/MES systems. The specifications focus on the continuous communication of data.

The OPC Data Access specification is also known as OPC DA. OPC DA deals only with real-time data and not historical data (for historical data you need to use OPC Historical Data Access, or OPC HDA) or events (for Alarms and Events you need to use OPC Alarms and Events, or OPC AE).  There are three attributes associated with OPC DA data. These are
 a value,
 the quality of the value, and
 a timestamp.

The OPC DA specification states that these three attributes have to be returned to an OPC client making a request. Therefore, if the data source is not capable of providing a timestamp, for example, the OPC DA server must create a timestamp.

The OPC Classic specifications are based on the Microsoft COM technology and define a C/C++ interface. A standard Automation wrapper interface is also defined for access from Visual Basic, Delphi and other automation-enabled languages. Several vendors offer .NET toolkits to make the OPC interface accessible in .NET applications.

The newer OPC .NET (OPC Xi) specification is based on WCF (Windows Communication Foundation) and defines a .NET interface with the functionality of the OPC Classic specifications OPC DA, OPC HDA and OPC AE (Alarms&Events).

The more recent OPC Unified Architecture allows the same functionality but offers platform independence and optionally complex information modelling capabilities.

See also
 OPC Foundation
 Distributed Component Object Model
 OPC Unified Architecture

References

External links
OPC Programmers' Connection

Industrial automation
Scarff ring. The Scarff ring was a type of machine gun mounting developed during the First World War by Warrant Officer (Gunner) F. W. Scarff of the Admiralty Air Department for use on two-seater aircraft. The mount incorporated bungee cord suspension in elevation to compensate for the weight of the gun, and allowed an airgunner in an open cockpit to swivel and elevate his weapon (a Lewis machine gun) quickly, and easily fire in any direction. Later models permitted the fitting of two Lewis guns; while this doubled the firepower available, operation of the paired guns was more cumbersome, and required considerable strength from the gunner, especially at altitude, so that many gunners preferred the original single gun - and this became the postwar standard. In either case, the mounting was simple and rugged, and gave its operator an excellent field of fire. It was widely adapted and copied for other airforces.

As well as becoming a standard fitting in the British forces during the First World War, the Scarff ring was used in the postwar Royal Air Force for many years. Perhaps the last British aircraft to use the mounting was the Supermarine Walrus amphibian prototype.

Scarff was also involved in the development of the Scarff-Dibovsky synchronization gear.

Although it was a seemingly simple device, later attempts to emulate the Scarff ring as a mounting for the dorsal Vickers K in the World War II Handley Page Hampden bomber were failures. Handley Page had designed a carriage with ball-bearing wheels running on  a track around the cockpit. Vibration when firing shook the balls out, jamming the mounting.

In the 1930s, the Germans developed a similar system called the Drehkranz D 30 (German: "slewing ring") which was used on a number of German aircraft, most notably the Junkers Ju 52.

In British use the Scarff ring was replaced in the 1930s by specialised power-operated turrets such as those made by Boulton Paul or Nash & Thompson, aircraft air speeds having by then risen to the point where a manually-operated gun was infeasible.

The Scarff ring was also fitted to the Rolls-Royce Armoured Car vehicles of the RAF Armoured Car Companies, antecedents to the RAF Regiment.

References
 

Aviation in World War I
Hydroseeding. Hydroseeding (or hydraulic mulch seeding, hydro-mulching, hydraseeding) is a planting process that uses a slurry of seed and mulch. It is often used as an erosion control technique on construction sites, as an alternative to the traditional process of broadcasting or sowing dry seed.

Description
The hydroseeding slurry is transported in a tank, either truck-mounted or trailer-mounted and sprayed over prepared ground. Helicopters have been used to cover larger areas. Aircraft application may also be used on burned wilderness areas after a fire, and in such uses may contain only soil stabilizer to avoid introducing non-native plant species. Hydroseeding is an alternative to the traditional process of broadcasting or sowing dry seed. A study conducted along the lower Colorado River in Arizona reported that hydroseeding could be used to restore riparian vegetation in cleared land.

The slurry often has other ingredients including fertilizer, tackifying agents, fiber mulch, and green dye.

History
Originating back to the USA in the 1940s, Maurice Mandell from the Connecticut Highway Department discovered that by mixing seed and water together, the resulting mulch could be spread and sprayed over the steep and otherwise inaccessible slopes of the Connecticut expressways.

Advantages
If planting a relatively large area, hydroseeding can be completed in a very short period of time. It can be very effective for hillsides and sloping lawns to help with erosion control and quick planting. Hydroseeding will typically cost less than planting with sod, but more than broadcast seeding. Results are often quick with high germination rates producing grass growth in about a week and mowing maintenance beginning around 3 to 4 weeks from the date of application. Fiber mulch accelerates the growing process by maintaining moisture around the seeds thereby increasing the rate of germination.

Seeds are applied to tilled soil using a high pressure hose. The seeds are likely mixed into a water-based spray that often contains mulch, fertilizer, lime, or other substances that promote seed growth.

References

Agricultural terminology
Environmental soil science
Gardening aids
Habitat management equipment and methods
Lawns
Perm Airlines. Perm Airlines (Russian: Пермские авиалинии) was an airline based in Perm, Russia. It operated domestic and international scheduled and charter services within Russia and the CIS. Its main base was Bolshoye Savino Airport, Perm.

History 
The airline was established and started operations in 1968. It was formed from the Aeroflot Perm Division (Ural RCAD).
Throughout its operational history, Perm Airlines offered routes from Perm Bolshoye Savino airport to Moscow Sheremetyevo and Domodedovo airports, Ekaterinburg, Surgut, Baku, Novosibirsk and St. Petersburg (codeshare flight with St. Petersburg based Pulkovo Airlines). Furthermore, it operated charter flights to Adler/Sochi, Baikonur, Simferopol and Dubai.
As a result of an agreement between Perm Airlines and Siberian Airlines (the current S7 Airlines), all regular Perm Airlines passenger flights were carried out by Sibir Airlines.

Perm Airlines had its license revoked on May 16, 2009.

Fleet 

The Perm Airlines fleet includes the following aircraft (at May 2008):

1 Antonov An-24
2 Antonov An-26
3 Mil Mi-8T
4 Tupolev Tu-134A
2 Tupolev Tu-154B2
1 Tupolev Tu-154M
1 Yakovlev Yak-40

All three Tu-154 aircraft were leased by Sibir Airlines in 2006, to be phased out in 2008. Although the aircraft still stand at Perm Bolshoye Savino airport, the engines were removed and sold off in 2009.

Accidents and incidents 

 In October 2007, a 15-year-old boy snuck into the landing gear compartment of a Tupolev Tu-154 belonging to Perm Airlines and successfully flew to Moscow. He suffered from frostbite and had his fingers amputated. An employee of Perm Airlines was tried in the court because of his failure to inspect the plane carefully before departure.

References

External links 

  Perm Airlines (defunct)
 Perm Airlines (defunct)

Defunct airlines of Russia
Former Aeroflot divisions
Companies based in Perm, Russia
Airlines established in 1992
Airlines disestablished in 2009
Project Aqua. Project Aqua was a hydroelectric scheme proposed for the lower Waitaki River in New Zealand. Although the scheme had considerable support from some locals, it met with opposition from many other groups, and Meridian Energy decided in March 2004 not to go ahead with the project.

The plan
The plan was to divert river water at the rate of up to 280 cubic metres per second into a separate canal for six power stations. This was on top of the three dams already in the upper Waitaki. The scheme would have produced approximately 520MW of power — enough to supply a city the size of Christchurch.

Objections
The objections to the scheme included land issues, the disruption during construction, and concerns about the sustainability of the river. Meridian was working on a large scale mitigation process, whereby issues could be identified and mitigated, when the scheme was finally cancelled.

Abandonment and impact
On 29 March 2004, Meridian announced that they would not continue with Project Aqua. Among their reasons were the uncertainty in gaining access to the water, that Aqua could not come on line soon enough to meet New Zealand's growing electricity demand, the amount of money it was costing the company, design changes due to geology reports, and the Resource Management Act making it difficult to get consent for large water based projects.

Meridian's 2004 annual report states that they lost NZ$38.7 million on the project. At the time of cancellation they had spent considerably more than this, but much of the expenditure was for assets such as land that they would later sell.

Possible alternative scheme
Subsequently, Meridian proceeded to develop an alternative hydroelectric scheme along the same stretch of the Waitaki River - the North Bank tunnel project. They received water uses consents from Environment Canterbury in December 2008 but work on the project was suspended in January 2013.

References

External links 
Waitaki River Users Liaison Group
Scoop.co.nz - Press release on the proposal

Environmental issues in New Zealand
Hydroelectricity in New Zealand
Quadratic probing. Quadratic probing is an open addressing scheme in computer programming for resolving hash collisions in hash tables. Quadratic probing operates by taking the original hash index and adding successive values of an arbitrary quadratic polynomial until an open slot is found.

An example sequence using quadratic probing is:

Quadratic probing is often recommended as an alternative to linear probing because it incurs less clustering. Quadratic probing exhibits better locality of reference than many other hash table such as chaining; however, for queries, quadratic probing does not have as good locality as linear probing, causing the latter to be faster in some settings.

Quadratic probing was first introduced by Ward Douglas Maurer in 1968.

Quadratic function
Let h(k) be a hash function that maps an element k to an integer in [0, m−1], where m is the size of the table. Let the ith probe position for a value k be given by the function 

where c2 ≠ 0  (If c2 = 0, then h(k,i) degrades to a linear probe).  For a given hash table, the values of c1 and c2 remain constant.

Examples:
If , then the probe sequence will be 
For m = 2n, a good choice for the constants are c1 = c2 = 1/2, as the values of h(k,i) for i in [0, m−1] are all distinct (in fact, it is a permutation on [0, m−1]). This leads to a probe sequence of  (the triangular numbers) where the values increase by 1, 2, 3, ...
For prime m > 2, most choices of c1 and c2 will make h(k,i) distinct for i in [0, (m−1)/2].  Such choices include c1 = c2 = 1/2, c1 = c2 = 1, and c1 = 0, c2 = 1.  However, there are only m/2 distinct probes for a given element, requiring other techniques to guarantee that insertions will succeed when the load factor exceeds 1/2.
For , where m, n, and p are integer greater or equal 2 (degrades to linear probe when p = 1), then  gives cycle of all distinct probes. It can be computed in loop as: , and 
For any m, full cycle with quadratic probing can be achieved by rounding up m to closest power of 2, compute probe index: , and skip iteration when . There is maximum  skipped iterations, and these iterations do not refer to memory, so it is fast operation on most modern processors. Rounding up m can be computed by: 
uint64_t roundUp2(uint64_t v){
	v--;
	v |= v >> 1;
	v |= v >> 2;
	v |= v >> 4;
	v |= v >> 8;
	v |= v >> 16;
	v |= v >> 32;
	v++;
	return v;
}

Limitations

Alternating signs
If the sign of the offset is alternated (e.g. +1, −4, +9, −16, etc.), and if the number of buckets is a prime number  congruent to 3 modulo 4 (e.g. 3, 7, 11, 19, 23, 31, etc.), then the first  offsets will be unique (modulo ). In other words, a permutation of 0 through  is obtained, and, consequently, a free bucket will always be found as long as at least one exists.

References

External links
 Tutorial/quadratic probing

Hashing
Articles with example C code
Articles with example Java code
Search algorithms
EDACS. The Enhanced Digital Access Communication System (EDACS) is a radio communications protocol and product family invented in the General Electric Corporation in the mid 1980s. The rights were eventually bought by Harris Corporation, which eventually stopped manufacturing these devices in 2012, and ended all service in 2017.

History 
A young designer, Jeff Childress, created an autonomous radio base-station controller, known as the GETC (General Electric Trunking Card).  The GETC was a general-purpose controller with input/output optimized for radio system applications.

Childress and the team demonstrated that a smart controller could be adapted to a variety of applications, but his interest was really in fault tolerance.  

The EDACS system architecture supported large communications footprints.  By making the GETC's "trunk" among themselves, one GETC per channel, the system was designed to be inherently fault-tolerant. This provided substantial hardware reductions, and the required software efforts yielded a variety of unique features and options.

This was not a new concept in systems design; however, few other teams have embodied it cleanly into such wide distribution.

Software 
Software for system managers and radio monitors alike has been developed outside of the vendor. ETrunker is a modification to the Trunker code to work on the EDACS control channel. Users of the software can monitor and log complete system activity. See the Trunker Site for more info.

Digital Voice Modes 
The first digital voice mode developed for EDACS was GE's Voice Guard, utilizing sub-band coding for its datastream at a rate of 9600 bps. Voice quality was not great, however, with it quickly being replaced by AEGIS.

AEGIS was the second generation EDACS digital voice mode, made once again by GE, with Adaptive Multiband Encoding as its coding scheme. The voice quality was supposedly 10 times better than Voice Guard, but it was still not very great, especially compared to ProVoice.

ProVoice is Tyco Electronics' (formerly M/A-COM, Ericsson and GE) implementation of IMBE digital modulation for radio communications, being the third generation of EDACS digital voice. It is not APCO-25 compliant, but does use the same IMBE vocoder developed by  Digital Voice Systems, Inc. (DVSI). The technical difference between ProVoice and the APCO Project-25 standard is how error correction and modulation is provided to transmit the data.

References

External links 
EDACS Explained
Florida Statewide Law Enforcement Radio System (SLERS)
Harris Corporation website

Trunked radio systems
Speech codecs
OpenSky. OpenSky is a registered trademark of Harris Corporation and is the trade name for a wireless communication system, invented by M/A-COM Inc., that is now a division of  Harris RF Communications. OpenSky technology applies voice over IP transport to radio communications applications in a unique architecture.

In the mid-1990s Federal Express invited proposals for a data and voice network to the vehicular level. As the world's largest shipper, FedEx was a key opportunity, and major market players presented their existing product offerings over some time.

M/A-COM presented their concept, and won the business. They delivered a standards-based infrastructure that attempted to leverage open systems to the largest degree possible, while adapting specific input/output to meet the customer's exact requirements.

OpenSky received the direct attention of Tyco Electronics when they acquired it along with AMP Inc. Tyco Electronics funded the company to acquire the EDACS radio system team and product line. The OpenSky system has since been sold into a number of important footprints, including the entire State of Pennsylvania, and the State of New York.

On January 15, 2009, the State of New York terminated its contract with M/A-COM due to ongoing and unresolved deficiencies with the OpenSky system. On February 13, 2009, Tyco Electronics filed a complaint against the New York State Office for Technology (NY-OFT), in the New York State Court of Claims, disputing the claims made by the OFT. In the complaint, Tyco Electronics disputed many of the NY-OFT's public criticisms of both the company and the system, maintaining that SWN (which included OpenSky) ‘worked as contracted.’ The complaint also claimed the state hindered the company's ability to build the system in a timely manner, defamed the company by stating that its technology did not work, and that the state inappropriately drew $50 million from the standby letter of credit the company established for the project.

On May 29, 2009, Harris Corporation purchased Tyco Electronics Wireless Systems, including its OpenSky and other wireless communication technologies, from Tyco Electronics for US$675 million.

As of the end of 2014, it was announced that, due to ongoing problems faced by the State Police and other users, the Pennsylvania Statewide Radio Network will be replaced by a Project 25 Phase II system. It will be VHF/UHF/800 multi-band and is expected to be fully operational by the end of 2021.

References

External links
 M/A-COM Wireless Systems
 Pennsylvania Statewide Radio Network
 New York Statewide Wireless Network (SWN) and Interoperability Program

Trunked radio systems
Pierre-Arnoul de Marneffe. Pierre-Arnoul Frédéric Guy Donat de Marneffe (August 19, 1946 – July 9, 2023) was a Belgian computer scientist and professor emeritus at the University of Liège (ULiège). He studied civil engineering (mechanics section) at the Faculté polytechnique de Mons (FPMs) and obtained a PhD in applied sciences at the University of Liège (1976), in addition he obtained a Ph.D. in Computer science at Cambridge University in 1982.

His ideas expressed in Holon Programming inspired Donald Knuth in creating WEB, the first published literate programming environment.

References
 Pierre-Arnoul de Marneffe, Holon Programming. Univ. de Liège, Service d'Informatique (December, 1973).

External links 
 Holon Programming: A Survey
 University of Liège
 Literate programming

Belgian computer scientists
Walloon people
University of Liège alumni
Living people
1946 births
Rainout (radioactivity). A rainout is the process of precipitation causing the removal of radioactive particles from the atmosphere onto the ground, creating nuclear fallout by rain. The rainclouds of the rainout are often formed by the particles of a nuclear explosion itself and because of this, the decontamination of rainout is more difficult than a "dry" fallout.

In atmospheric science, rainout also refers to the removal of soluble species—not necessarily radioactive—from the atmosphere by precipitation.

Factors affecting rainout
A rainout could occur in the vicinity of ground zero or the contamination could be carried aloft before deposition depending on the current atmospheric conditions and how the explosion occurred. The explosion, or burst, can be air, surface, subsurface, or seawater. An air burst will produce less fallout than a comparable explosion near the ground due to less particulate being contaminated. Detonations at the surface will tend to produce more fallout material. In case of water surface bursts, the particles tend to be rather lighter and smaller, producing less local fallout but extending over a greater area. The particles contain mostly sea salts with some water; these can have a cloud seeding effect causing local rainout and areas of high local fallout. Fallout from a seawater burst is difficult to remove once it has soaked into porous surfaces because the fission products are present as metallic ions which become chemically bonded to many surfaces. For subsurface bursts, there is an additional phenomenon present called "base surge". The base surge is a cloud that rolls outward from the bottom of the subsiding column, which is caused by an excessive density of dust or water droplets in the air. This surge is made up of small solid particles, but it still behaves like a fluid. A soil earth medium favors base surge formation in an underground burst. Although the base surge typically contains only about 10% of the total bomb debris in a subsurface burst, it can create larger radiation doses than fallout near the detonation, because it arrives sooner than fallout, before much radioactive decay has occurred. For underwater bursts, the visible surge is, in effect, a cloud of liquid (usually water) droplets with the property of flowing almost as if it were a homogeneous fluid. After the water evaporates, an invisible base surge of small radioactive particles may persist.

Meteorogically, snow and rain will accelerate local fallout. Under special meteorological conditions, such as a local rain shower that originates above the radioactive cloud, limited areas of heavy contamination just downwind of a nuclear blast may be formed. Rain on an area contaminated by a surface burst changes the pattern of radioactive intensities by washing off higher elevations, buildings, equipment, and vegetation. This reduces intensities in some areas and possibly increases intensities in drainage systems; on low ground; and in flat, poorly drained areas.

References

Radioactivity