A refractory material or refractory is a heat-resistant material: that is, a mineral, resistant to decomposition by heat, pressure, or chemical attack, most applied to a mineral that retains strength and form at high temperatures.. ASTM C71 defines refractories as "...non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above 1,000 °F."Refractory materials are used in furnaces, kilns and reactors. Refractories are used to make crucibles and moulds for casting glass and metals and for surfacing flame deflector systems for rocket launch structures. Today, the iron- and steel-industry and metal casting sectors use 70% of all refractories produced. Refractory materials must be chemically and physically stable at high temperatures. Depending on the operating environment, they must be resistant to thermal shock, be chemically inert, and/or have specific ranges of thermal conductivity and of the coefficient of thermal expansion.
The oxides of aluminium and magnesium are the most important materials used in the manufacturing of refractories. Another oxide found in refractories is the oxide of calcium. Fire clays are widely used in the manufacture of refractories. Refractories must be chosen according to the conditions they face; some applications require special refractory materials. Zirconia is used when the material must withstand high temperatures. Silicon carbide and carbon are two other refractory materials used in some severe temperature conditions, but they cannot be used in contact with oxygen, as they would oxidize and burn. Binary compounds such as tungsten carbide or boron nitride can be refractory. Hafnium carbide is the most refractory binary compound known, with a melting point of 3890 °C; the ternary compound tantalum hafnium carbide has one of the highest melting points of all known compounds. 1. Acidic refractories consist of acidic materials like alumina, silica, they are impervious to acidic materials, but attacked by basic materials.
Important members of this group are alumina and fireclay refractories. 2. Basic refractories consist of basic materials such as CaO, MgO, etc; these are impervious to basic materials, but attacked by acidic materials. Important members of this group are dolomite refractories. 3. Neutral refractories are made from weakly acid/basic materials such as carbon, silicon carbide and zirconia. Acidic refractories consist of acidic materials like alumina and silica, they are not attacked or affected by acidic materials, but affected by basic materials. They include substances such as silica and fire clay brick refractories. Notable reagents that can attack both alumina and silica are hydrofluoric acid, phosphoric acid, fluorinated gases. At high temperatures, acidic refractories may react with limes and basic oxides; these are used in areas where slags and atmosphere are either acidic or basic and are chemically stable to both acids and bases. The main raw materials are not confined to, the R2O3 group. Common examples of these materials are alumina and carbon.
These are used in areas. They can react to acids; the main raw materials belong to the RO group. Other examples include chrome-magnesia. For the first half of the twentieth century, the steel making process used artificial periclase as a furnace lining material. Dry press process Fused cast Hand molded Formed Un-formed Un-formed dry refractories; these shapes. These may be further divided into special shapes. Standard shapes have dimension that are conformed by most refractory manufacturers and are applicable to kilns or furnaces of the same types. Standard shapes are bricks that have a standard dimension of 9 × 4 1⁄2 × 2 1⁄2 inches and this dimension is called a "one brick equivalent". "Brick equivalents" are used in estimating how many refractory bricks it takes to make an installation into an industrial furnace. There are ranges of standard shapes of different sizes manufactured to produce walls, arches and circular apertures etc. Special shapes are made for specific locations within furnaces and for particular kilns or furnaces.
Special shapes are less dense and therefore less hard wearing than standard shapes. These are only given shape upon application; these types are better known as monolithic refractories. The common examples are plastic masses, Ramming masses, gunning masses, fettling mix, mortars etc. Dry vibration linings used in Induction furnace linings are monolithic, sold and transported as a dry powder with a magnesia/alumina composition with additions of other chemicals for altering specific properties, they are finding more applications in blast furnace linings, although this use is still rare. Based on fusion temperature, refractory materials are classified into three types. Normal refractory: fusion temperature of 1580 ~ 1780 °C High refractory: fusion temperature of 1780 ~ 2000 °C Super refractory: fusion temperature of > 2000 °C All refractories require anchorage systems suc
Martin Lee is an English former professional tennis player. Born in London, he resides in Berkshire. Lee was a promising junior. In 1995 he won the Boys Doubles at Wimbledon. A left-hander, he turned pro in 1996, he struggled with constant knee and groin problems throughout his career, which forced his retirement from the professional circuit in November 2006. Lee's best singles result on the ATP Tour was to reach the final of the Hall of Fame Championships in Newport, Rhode Island in 2001. On 11 March 2002, Lee achieved his career-high singles ranking of World No. 94, establishing himself as the British number three behind Tim Henman and Greg Rusedski. It was the first time in 23 years that Britain had three players in the Top 100. However, in November 2002 he underwent knee surgery and was out of action for 10 months, his ranking never recovered. Lee reached the second round of the men's singles at Wimbledon four times, in 1997, 2000, 2001 and 2006, he appeared in the US Open in 2001, managed to take two sets off of seeded player Sjeng Schalken, however the Dutchman prevailed 6–3 in the deciding set.
Lee's ranking ensured automatic qualification for the main draw of the Australian and French Opens in 2002, but he lost in the first round on both occasions. Overall he lost 46 ATP Tour matches. Lee won two of his three matches for Great Britain in the Davis Cup, however these were only dead rubbers. Lee lost his only live match against Thailand's Paradorn Srichaphan in straight sets. Martin Lee at the Association of Tennis Professionals Martin Lee at the International Tennis Federation Martin Lee at the Davis Cup
The Department of Chemistry is responsible for chemistry teaching and research at Imperial College London. The department has around 50 academic staff and 850 students, with around 550 studying undergraduate courses and 300 research students; the department is based in Chemistry Building along Imperial College Road, looking over Queen's Lawn, but uses the remaining section of the Royal College of Science building. The department has relocated some of its research to new facilities at the 154.4 million pound Molecular Sciences Research Hub at Imperial's new White City campus. The department ranks 9th in the QS 2018 subject world rankings; the origins of the department lie in the Royal College of Chemistry, founded in 1845 on Hanover Square, moving the next year to Oxford Street.. Its first professor was August Wilhelm von Hofmann, from the University of Giessen; the college was incorporated into the Normal School of Science as a department, the school was refounded as the Royal College of Science in 1890.
In 1907, the Royal College of Science became one of the founding institutions of Imperial College, which joined the University of London, only to leave it and become independent in 2007. In 2018 the Molecular Sciences Research Hub opened at the college's new White City campus, becoming the new centre for the department's academic research. Teaching will continue at South Kensington, students undertake research projects at the new research hub; the department offers four year undergraduate MSci courses. The department has connections with universities in Europe, allowing undergraduate master's students to study-abroad during their course, it allows students to take a year in industry, incorporate management or foreign languages into the course. All students graduating with an undergraduate degree from the department are awarded the Associateship of the Royal College of Science, ARCS; the department offers MRes courses in subject specialties as well as taking on doctors students. It offers however no taught postgraduate programmes.
The college ranks 9th on the Times Higher Education natural sciences subjects rankings, the department in particular ranks 9th in the world, 3rd in the UK after Cambridge and Oxford, on the QS World University Rankings. Domestically, the department ranks 4th in the Complete University Guide's 2019 chemistry rankings. August Wilhelm von Hofmann, first professor at the Royal College of Chemistry Martha Whiteley OBE, one of the inventors of mustard gas Sue Gibson OBE Anthony Gerard Martin Barrett FRS, FMedSci Lord George Porter OM PRS, 1967 Nobel Prize in Chemistry Frances Micklethwait MBE ARCS, first researcher into a cure for mustard gas Sir Derek Barton BSc ARCS PhD, 1969 Nobel Prize in Chemistry Sir Geoffrey Wilkinson BSc ARCS PhD, 1973 Nobel Prize in Chemistry
In number theory, the Davenport–Erdős theorem states that, for sets of multiples of integers, several different notions of density are equivalent. Let A = a 1, a 2, … be a sequence of positive integers; the multiples of A are another set M that can be defined as the set M = of numbers formed by multiplying members of A by arbitrary positive integers. According to the Davenport–Erdős theorem, for a set M, the following notions of density are equivalent, in the sense that they all produce the same number as each other for the density of M: The lower natural density, the inferior limit as n goes to infinity of the proportion of members of M in the interval; the logarithmic density or multiplicative density, the weighted proportion of members of M in the interval, again in the limit, where the weight of an element a is 1 / a. The sequential density, defined as the limit of the densities of the sets M of multiples of the first i elements of A; as these sets can be decomposed into finitely many disjoint arithmetic progressions, their densities are well defined without resort to limits.
However, there exist sequences A and their sets of multiples M for which the upper natural density differs from the lower density, for which the natural density itself does not exist. The theorem is named after Harold Davenport and Paul Erdős, who published it in 1936, their original proof used the Hardy–Littlewood tauberian theorem. Behrend sequence, a sequence A for which the density M described by this theorem is one
Uncle Joe is a 1941 American film directed by Howard M. Railsback and Raymond E. Swartley. In rural America in the 1940s, Clare Day is sent to visit her mother's brother Joe in "Baysville", Iowa when she starts going out with a modernistic artist of whom her father disapproves; the four boys who live next door to Uncle Joe remember Clare as a skinny little girl and are shocked by how grown-up she has become. Eagerly, they all vie for her attention. Uncle Joe himself is stuck in a romance of the past and fails to hear that his sweetheart Julia Jordan is going to lose her house if she can't pay the mortgage. Clare and Bill Jones construct a means to save the day. Slim Summerville as Uncle Joe ZaSu Pitts as Aunt Julia Gale Storm as Clare William B. Davidson as J. K. Day Dorothy Peterson as Margaret Day Dick Hogan as Bill Frank Coghlan Jr. as Dick Jimmy Butler as Bob Maynard Holmes as Skinny Brenda Henderson as Ann John Holland as Paul Darcey Uncle Joe on IMDb Uncle Joe at AllMovie Uncle Joe is available for free download at the Internet ArchiveAlso is related with the song Jump JIm Crow
The Assassin of Rome is a 1972 Italian historical drama film directed by Damiano Damiani. The film tells, with some historical licenses, the story of Gino Girolimoni, wrongfully accused of a series of child murders that occurred in Rome between 1924 and 1928. Nino Manfredi as Gino Girolimoni Gabriele Lavia as Tarquinio Tirabosco Eleonora Morana as Armanda Tirabosco Orso Maria Guerrini as Gianni Di Meo Guido Leontini as Apicella Mario Carotenuto as Sterbini Laura De Marchi as The servant Luciano Catenacci as Benito Mussolini Arturo Dominici as Jaccarino Ennio Antonelli as The lover of the mother of'Biocchetta' Nello Pazzafini as Fiaccarini Damiano Damiani, Gaetano Strazzulla. Girolimoni. Capelli, 1972; the Assassin of Rome on IMDb