omniomni/omni-engineering huggingface dataset:
Comparison of mail servers. The comparison of mail servers covers mail transfer agents (MTAs), mail delivery agents, and other computer software that provide e-mail services.

Unix-based mail servers are built using a number of components because a Unix-style environment is, by default, a toolbox operating system. A stock Unix-like server already has internal mail; more traditional ones also come with a full MTA already part of the standard installation.  To allow the server to send external emails, an MTA such as Sendmail, Postfix, or Exim is required. Mail is read either through direct access (shell login) or mailbox protocols like POP and IMAP. Unix-based MTA software largely acts to enhance or replace the respective system's native MTA.

Microsoft Windows servers do not natively implement e-mail, thus Windows-based MTAs have to supply all the necessary aspects of e-mail-related functionality.

Feature comparison

Authentication

Antispam features

See also 
 Comparison of email clients
List of email archive software
List of mail server software

References 

Message transfer agents
Mail servers
Astern propulsion. Astern propulsion (as applied to a ship) is a maneuver in which a ship's propelling mechanism is used to develop thrust in a retrograde direction. Astern propulsion does not necessarily imply the ship is moving astern (in reverse); astern propulsion is used to slow a ship by applying a force in the direction of the bow of the ship, instead of the stern. The equivalent concept for an airplane is thrust reversal.

In a sailing ship astern propulsion can be achieved by the appropriate manipulation of the sails.  In square-rigged ships 'backing the sails', that is, aligning the sails so that the wind impinged on the bow surface, could provide sufficient retrograde thrust to slow or reverse the ship.  This maneuver had to be carried out with care as the rigging of masts and yards was principally designed to accept and transmit thrust in the forward direction.

In a ship with a gas turbine engine and a variable-pitch propeller, astern thrust is simply a matter of changing the propeller pitch to a negative value. Most other propeller-driven ships will reverse the direction the prop spins. For a paddle wheel ship, reversing the direction of the paddle will provide astern propulsion. Redirecting the thrust of a water jet driven craft, changing the cyclic pitch of a Voith-Schneider propulsor, or rotating an azimuth thruster 180 degrees has the same effect. As the efficiency of traditional rudders is greatly reduced when not located in the propeller wash, only propulsion systems with steerable thrust provide adequate maneuverability during astern operation.

A marine vessel is required to signal that she is operating astern propulsion by either blowing three short, easily audible blasts or by flying the Sierra signal flag (white border with one central blue square).

Some aircraft are also able to develop astern propulsion. Airships such as the R-100 could reverse the direction of rotation of some engines, so reversing the direction of thrust of the attached propeller.  This facility was used to slow down or stop the airship when mooring.

Some propeller-driven aircraft using controllable pitch propellers can change the blade pitch sufficiently to provide astern propulsion.  This facility is sometimes used to control aircraft speed in steep descents, or to taxi backwards when on the ground.  Most jet airliners and some transport aircraft use astern propulsion (more commonly termed 'reverse thrust') to slow down after landing, reducing the load on the wheel brakes and shortening the landing rollout.  Helicopters can develop thrust in any direction, including astern.

Most mechanically driven land vehicles can develop astern propulsion, although in this case the ability is more usually termed 'reverse'.  In land vehicles reverse propulsion is usually achieved through various transmission arrangements.

References

Marine propulsion
Scandium nitrate. Scandium(III) nitrate, Sc(NO3)3, is an ionic compound. It is an oxidizer, as all nitrates are. The salt is applied in optical coatings, catalysts, electronic ceramics and the laser industry.

Preparation 
Scandium nitrate can be prepared by the reaction between scandium metal with dinitrogen tetroxide.

Sc + 3 N2O4 → Sc(NO3)3 + 3 NO 
The anhydrous form can also be obtained by the reaction between scandium chloride and dinitrogen pentoxide. The tetrahydrate can be obtained from the reaction between scandium hydroxide and nitric acid.

Properties 
Scandium nitrate is a white solid which dissolves in water and ethanol. It has multiple hydrated forms, including the dihydrate, trihydrate, and tetrahydrate. The tri- and tetrahydrate exist in the monoclinic crystal system. Upon heating in air to 50 °C, the tetrahydrate transforms into the dihydrate, which at 60 °C further converts to Sc4O3(NO3)3·6.5H2O. At 140–220 °C, Sc4O5(NO3)3 is formed.

Scandium nitrate has been found to form clusters when in an aqueous solution which can affect its behavior and properties in various ways. Small Angle neutron scattering has been used in experiments to show the clusters can contain as many as 10 scandium ions. This number depends on the concentration of the original scandium nitrate in the solution.

Applications 
Scandium nitrate has been found to be a successful catalyst in chemical reactions such as Beckmann rearrangement of ketoximes to amides and the isomerization of allylic alcohols to aldehydes. The catalytic success of scandium nitrate can be increased by modifying its structure in ways such as adding a co catalyst. Scandium nitrate is also the precursor for the synthesis of other scandium based compounds such as scandium oxide or scandium hydroxide. Scandium nitrate has also been investigated for its potential in luminescent materials due to its ability to strongly emit in the blue region of the spectrum.

References

Scandium compounds
Nitrates
Scandium fluoride. Scandium(III) fluoride, ScF3, is an ionic compound.  This salt is slightly soluble in water but dissolves in the presence of excess fluoride to form the ScF63− anion.

Production
ScF3 can be produced by reacting scandium and fluorine. It is also formed during the extraction from the ore thortveitite by the reaction of Sc2O3 with  ammonium bifluoride at high temperature:
 Sc2O3 + 6 NH4HF2 → 2 ScF3 + 6 NH4F + 3 H2O

The resulting mixture contains a number of metal fluorides and this is reduced by reaction with calcium metal at high temperature. Further purification steps are required to produce usable metallic scandium.

Properties
Scandium trifluoride exhibits the unusual property of negative thermal expansion, meaning it shrinks when heated. This phenomenon is explained by the quartic oscillation of the fluoride ions. The energy stored in the bending strain of the fluoride ion is proportional to the fourth power of the displacement angle, unlike most other materials where it is proportional to the square of the displacement. A fluorine atom is bound to two scandium atoms, and as temperature increases the fluorine oscillates more perpendicularly to its bonds. This motion draws the scandium atoms together throughout the bulk material, which contracts.  ScF3 exhibits this property from at least 10 K to 1100 K above which it shows the normal positive thermal expansion; furthermore, the material has cubic symmetry over this entire temperature range, and up to at least 1600 K at ambient pressure. The negative thermal expansion at very low temperatures is quite strong (coefficient of thermal expansion around -14 ppm/K between 60 and 110 K).

At ambient pressures scandium trifluoride adopts the cubic crystal system, using the perovskite structure with one metal position vacant. The unit cell dimension is 4.01 Å. Under pressure scandium trifluoride also forms different crystal structures with rhombohedral, and above 3 GPa tetrahedral.

Scandium fluoride (ScF₃) features high transparency across UV to IR wavelengths, low optical absorption, and a low refractive index (~1.5). It exhibits nonlinear optical properties for frequency conversion and can luminesce when doped with rare-earth ions.

References

Scandium compounds
Fluorides
Metal halides
Bernhard Brænne. Bernhard Cornelius Brænne (12 November 1854 - 7 September 1927) was a Norwegian factory owner  and member of the Norwegian Parliament with the Conservative Party.

Background
Brænne was born in Trondheim, Norway. He was the son of Johan Sørensen Brænne (1817–71) and Karen Moe (1821–1901). His father was the owner of a factory owner in Trondheim. The factory that he inherited from his father specialized in textile production He graduated as a chemistry engineer from Trondheim Technical College (now Norwegian Institute of Technology) from 1875. He next studied chemistry and mechanical engineering at the Königlich-Sächsisches Polytechnikum (now Dresden University of Technology). In 1878 he took over the family business and expanded it into spinning, weaving and dry cleaning.

Career
Brænne was involved in local politics in Trondheim as a member of the city council of Trondheim 1891–1910. He served as a member of the Norwegian parliament for several periods between and 1892 and 1918.
He was appointed Minister of Labour in the cabinet of Wollert Konow on 2 February 1910, but then replaced Sofus Arctander as Minister of Trade on 11 June the same year. After the accession of the cabinet of Jens Bratlie on 20 February 1912, Brænne remained in government, again as Minister of Labour, but resigned on 23 August and was replaced by Nils Olaf Hovdenak.

References

External links 
 Bernhard Brænnes private archive exists at NTNU University Library Dorabiblioteket

1854 births
1927 deaths
Politicians from Trondheim
Norwegian Institute of Technology alumni
TU Dresden alumni 
Members of the Storting 
Government ministers of Norway
 Recipients of the St. Olav's Medal
Ministers of trade and shipping of Norway
Victor Shoup. Victor Shoup is a computer scientist and mathematician. He obtained a PhD in computer science from the University of Wisconsin–Madison in 1989, and he did his undergraduate work at the University of Wisconsin-Eau Claire. He is a professor at the Courant Institute of Mathematical Sciences at New York University, focusing on algorithm and cryptography courses. He is currently a Principal Research Scientist at Offchain Labs and has held positions at AT&T Bell Labs, the University of Toronto, Saarland University, and the IBM Zurich Research Laboratory.

Shoup's main research interests and contributions are computer algorithms relating to number theory, algebra, and cryptography.  His contributions to these fields include:

 The Cramer–Shoup cryptosystem asymmetric encryption algorithm bears his name.
 His freely available (under the terms of the GNU GPL) C++ library of number theory algorithms, NTL, is widely used and well regarded for its high performance.
 He is the author of a widely used textbook, A Computational Introduction to Number Theory and Algebra, which is freely available online.
 He has proved (while at IBM Zurich) a lower bound to the computational complexity for solving the discrete logarithm problem in the generic group model. This is a problem in computational group theory which is of considerable importance to public-key cryptography.
 He acted as editor for the ISO 18033-2 standard for public-key cryptography.
One of the primary developers of HElib.

Bibliography
 A Computational Introduction to Number Theory and Algebra, 2nd Edition, 2009, Cambridge University Press, ,

References

Courant Institute of Mathematical Sciences faculty
Year of birth missing (living people)
University of Wisconsin–Madison College of Letters and Science alumni
American computer scientists
American theoretical computer scientists
Modern cryptographers
Public-key cryptographers
20th-century American mathematicians
21st-century American  mathematicians
American number theorists
IBM employees
Living people
University of Wisconsin–Eau Claire alumni
American cryptographers
Direct shear test. A  direct shear test is a laboratory or field test used by geotechnical engineers to measure the shear strength properties of soil  or rock material, or of discontinuities in soil or rock masses.

The U.S. and U.K. standards defining how the test should be performed are ASTM D 3080, AASHTO T236 and BS 1377-7:1990, respectively. For rock the test is generally restricted to rock with (very) low shear strength. The test is, however, standard practice to establish the shear strength properties of discontinuities in rock.

The test is performed on three or four specimens from a relatively undisturbed soil sample. A specimen is placed in a shear box which has two stacked rings to hold the sample; the contact between the two rings is at approximately the mid-height of the sample. A confining stress is applied vertically to the specimen, and the upper ring is pulled laterally until the sample fails, or through a specified strain. The load applied and the strain induced is recorded at frequent intervals to determine a stress–strain curve for each confining stress. 
Several specimens are tested at varying confining stresses to determine the shear strength parameters, the soil cohesion (c) and the angle of internal friction, commonly known as friction angle (). The results of the tests on each specimen are plotted on a graph with the peak (or residual) stress on the y-axis and the confining stress on the x-axis. The y-intercept of the curve which fits the test results is the cohesion, and the slope of the line or curve is the friction angle.

Direct shear tests can be performed under several conditions. The sample is normally saturated before the test is run, but can be run at the in-situ moisture content. The rate of strain can be varied to create a test of undrained or drained conditions, depending on whether the strain is applied slowly enough for water in the sample to prevent pore-water pressure buildup. A direct shear test machine is required to perform the test. The test using the direct shear machine determines the consolidated drained shear strength of a soil material in direct shear.

The advantages of the direct shear test  over other shear tests are the simplicity of setup and equipment used, and the ability to test under differing saturation, drainage, and consolidation conditions. These advantages have to be weighed against the difficulty of measuring pore-water pressure when testing in undrained conditions, and possible spuriously high results from forcing the failure plane to occur in a specific location.

The test equipment and procedures are slightly different for test on discontinuities.

See also
Geotechnical investigation
Shear strength (discontinuity)
Tilt test (geotechnical engineering)
Triaxial shear test

References

Soil shear strength tests
Kyushu Sangyo University. was founded in 1960 in Fukuoka City, and currently has twenty departments and six graduate schools. It is a private university.

Undergraduate Faculties and departments
Faculty of Economics
Department of Economics
Faculty of Commerce
Department of Commerce
Department of Tourism Industry
Evening School of Commerce
Department of Commerce
Department of Tourism Industry
Faculty of Management
Department of International Management 	
Department of Industrial Management
Faculty of Engineering
Department of Mechanical Engineering
Department of Electrical Engineering 	
Department of Applied Chemistry and Biochemistry
Department of Department of Civil and Urban Design Engineering
Department of Architecture
Department of Biorobotics
Department of Housing and Interior Design
Faculty of Fine Arts
Department of Fine Art
Department of Craft Art
Department of Design
Department of Photography
Faculty of International Studies of Culture
Department of International Studies of Culture
Department of Regional Studies of Culture
Department of Clinical Psychology
Faculty of Information Science
Department of Information Science

Teachers
Ikkō Narahara (photographer)
Shōji Ueda (photographer)

Alumni
Shunji Dodo (photographer)
Tatsunori Fujie (basketball player)
Yuji Funayama (basketball player)
Park Joon-Kyung (footballer)
Kōji Shiraishi (film director)
Masashi Kishimoto (manga artist)
Masaaki Yuasa (film director)

Notes

External links
Official site (English)

Private universities and colleges in Japan
Universities and colleges in Fukuoka
Universities and colleges established in 1960
1960 establishments in Japan
File Compare. In computing, fc (File Compare) is a command-line program in DOS, IBM OS/2 and Microsoft Windows operating systems, that compares multiple files and outputs the differences between them. It is similar to the Unix commands comm, cmp and diff.

History
The fc command has been included in Microsoft operating systems since MS-DOS 2.11 (e.g. on the 1984/85 DEC Rainbow release) and is included in all versions of Microsoft Windows. fc has also been included in IBM OS/2 Version 2.0.

DR DOS 6.0 includes an implementation of the  command.

The command is also available in FreeDOS. This implementation is licensed under the GPLv2+.

Functionality
fc can compare text files as well as binary files. The latest versions can compare ASCII or Unicode text. The result of comparisons are output to the standard output. The output of fc is intended primarily to be human readable and may be difficult to use in other programs.

See also
 Data comparison
 comp (command)
 List of DOS commands

References

Further reading

External links

fc | Microsoft Docs
Open source FC implementation that comes with MS-DOS v2.0

DOS software
External DOS commands
File comparison tools
Microsoft free software
OS/2 commands
Windows administration
Computational scientist. A computational scientist is a person skilled in scientific computing. This person is usually a scientist, a statistician, an applied mathematician, or an engineer who applies high-performance computing and sometimes cloud computing in different ways to advance the state-of-the-art in their respective applied discipline; physics, chemistry, social sciences and so forth. Thus scientific computing has increasingly influenced many areas such as economics, biology, law, and medicine to name a few. Because a computational scientist's work is generally applied to science and other disciplines, they are not necessarily trained in computer science specifically, though concepts of computer science are often used. Computational scientists are typically researchers at academic universities, national labs, or tech companies.

One of the tasks of a computational scientist is to analyze large amounts of data, often from astrophysics or related fields, as these can often generate huge amounts of data. Computational scientists often have to clean up and calibrate the data to a usable form for an effective analysis. Computational scientists are also tasked with creating artificial data through computer models and simulations.

References

Computational science
Computer occupations
Science occupations
Mathematical science occupations
Computational fields of study
Prussian P 10. The Prussian state railways' Class P 10 were 2-8-2 "Mikado" type passenger-hauling steam locomotives built for hauling heavy express trains in the hilly terrain of the Mittelgebirge.  They were the last Prussian passenger train steam locomotives to be developed in Prussia before the state railways were merged into the Deutsche Reichsbahn (German Imperial Railway), who eventually designated them as DRG Class 39.

The design by Borsig, under the supervision of chief engineer August Meister, was ready in 1919 but, due to material shortages, no locomotives were produced until 1922.  They were three-cylinder locomotives, all cylinders driving the second coupled axle. Three sets of Walschaerts valve gear were used, the one for the inside cylinder being mainly located inside the frame, but driven from the same eccentric crank as the valve gear on the left-hand side; two eccentric rods of different lengths being attached to the same crank. 

The locomotives' heavy axle-load exceeded the 17 tonne standard specification of much of the German rail network, so they were limited to specific lines which were constructed to higher standards. A total of 260 of these locomotives were ultimately constructed and they worked primarily on the Main-Weser-Bahn between Frankfurt and Kassel, as well as the Eifel region, the Black Forest network until their replacement by Class 221 diesel locomotives, and the Gäubahn. They were the most powerful of all the state railway passenger locomotives.

The vehicles were originally equipped with Prussian 2'2' T 31,5 tenders. The Deutsche Bundesbahn fitted many of the surviving examples with Witte smoke deflectors and 2'2' T 34 tenders. The last three engines were stabled in Stuttgart and taken out of service in 1967.

39 184 is displayed in a museum located on the grounds of Alstom Transport Deutschland in Salzgitter, Germany. The museum is not accessible to the public.

The DB Museum owns 39 230, which may be viewed currently at the German Steam Locomotive Museum.

In the East German Deutsche Reichsbahn the Prussian P 10 was indispensable and was therefore included in their reconstruction programme. The 85 Rekoloks were grouped into DR Class 22.

See also 
 Prussian state railways
 List of Prussian locomotives and railcars
 List of preserved steam engines in Germany

References 

 
 
 

2-8-2 locomotives
P 10
Railway locomotives introduced in 1922
Standard gauge locomotives of Germany
Borsig locomotives
1′D1′ h3 locomotives
Passenger locomotives