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In metagenomics, binning is the process of grouping reads or contigs and assigning them to individual genome. Binning methods can be based on either compositional features or alignment (similarity), or both. | https://en.wikipedia.org/wiki/Binning_(metagenomics) |
In metagenomics, regions of the genomes that are shared between strains are typically longer than the reads. This complicates the assembly process and makes reconstructing individual genomes for a species a daunting task. Chimeric pairs that are mapped far apart in the genome can facilitate the de novo assembly process. By using a longer-jump library, Ribeiro et al. demonstrated that the assemblies of bacterial genomes were of high quality while reducing both cost and time. | https://en.wikipedia.org/wiki/Jumping_library |
In metal alloys with substitutional solute elements, such as aluminum-magnesium alloys, dynamic strain aging leads to negative strain rate sensitivity which causes instability in plastic flow. The diffusion of solute elements around a dislocation can be modeled based on the energy required to move a solute atom across the slip plane of the dislocation. An edge dislocation produces a stress field which is compressive above the slip plane and tensile below. In Al-Mg alloys, the Mg atom is larger than an Al atom and has lower energy on the tension side of the dislocation slip plane; therefore, Mg atoms in the vicinity of an edge dislocation are driven to diffuse across the slip plane (see figure). | https://en.wikipedia.org/wiki/Dynamic_strain_aging |
The resulting region of lower solute concentration above the slip plane weakens the material in the region near the pinned dislocation, such that when the dislocation becomes mobile again, the stress required to move it is temporarily reduced. This effect can manifest as serrations in the stress-strain curve (Portevin-Le Chatelier effect). Because solute diffusion is thermally activated, increases in temperature can increase the rate and range of diffusion around a dislocation core. This can result in more severe stress drops, typically marked by a transition from Type A to Type C serrations. | https://en.wikipedia.org/wiki/Dynamic_strain_aging |
In metal alloys, and for the simplifying case when there are no macroscopic or microscopic discontinuities, the process starts with dislocation movements at the microscopic level, which eventually form persistent slip bands that become the nucleus of short cracks. Macroscopic and microscopic discontinuities (at the crystalline grain scale) as well as component design features which cause stress concentrations (holes, keyways, sharp changes of load direction etc.) are common locations at which the fatigue process begins. Fatigue is a process that has a degree of randomness (stochastic), often showing considerable scatter even in seemingly identical samples in well controlled environments. Fatigue is usually associated with tensile stresses but fatigue cracks have been reported due to compressive loads. | https://en.wikipedia.org/wiki/Fatigue_cracking |
The greater the applied stress range, the shorter the life. Fatigue life scatter tends to increase for longer fatigue lives. Damage is irreversible. | https://en.wikipedia.org/wiki/Fatigue_cracking |
Materials do not recover when rested. Fatigue life is influenced by a variety of factors, such as temperature, surface finish, metallurgical microstructure, presence of oxidizing or inert chemicals, residual stresses, scuffing contact (fretting), etc. Some materials (e.g., some steel and titanium alloys) exhibit a theoretical fatigue limit below which continued loading does not lead to fatigue failure. High cycle fatigue strength (about 104 to 108 cycles) can be described by stress-based parameters. | https://en.wikipedia.org/wiki/Fatigue_cracking |
A load-controlled servo-hydraulic test rig is commonly used in these tests, with frequencies of around 20–50 Hz. Other sorts of machines—like resonant magnetic machines—can also be used, to achieve frequencies up to 250 Hz. Low-cycle fatigue (loading that typically causes failure in less than 104 cycles) is associated with localized plastic behavior in metals; thus, a strain-based parameter should be used for fatigue life prediction in metals. Testing is conducted with constant strain amplitudes typically at 0.01–5 Hz. | https://en.wikipedia.org/wiki/Fatigue_cracking |
In metal base-pairing, the Watson-Crick hydrogen bonds are replaced by the interaction between a metal ion with nucleosides acting as ligands. The possible geometries of the metal that would allow for duplex formation with two bidentate nucleosides around a central metal atom are: tetrahedral, dodecahedral, and square planar. Metal-complexing with DNA can occur by the formation of non-canonical base pairs from natural nucleobases with participation by metal ions and also by the exchanging the hydrogen atoms that are part of the Watson-Crick base pairing by metal ions. Introduction of metal ions into a DNA duplex has shown to have potential magnetic, conducting properties, as well as increased stability.Metal complexing has been shown to occur between natural nucleobases. | https://en.wikipedia.org/wiki/Nucleobase_analog |
A well-documented example is the formation of T-Hg-T, which involves two deprotonated thymine nucleobases that are brought together by Hg2+ and forms a connected metal-base pair. This motif does not accommodate stacked Hg2+ in a duplex due to an intrastrand hairpin formation process that is favored over duplex formation. Two thymines across from each other in a duplex do not form a Watson-Crick base pair in a duplex; this is an example where a Watson-Crick basepair mismatch is stabilized by the formation of the metal-base pair. | https://en.wikipedia.org/wiki/Nucleobase_analog |
Another example of a metal complexing to natural nucleobases is the formation of A-Zn-T and G-Zn-C at high pH; Co+2 and Ni+2 also form these complexes. These are Watson-Crick base pairs where the divalent cation in coordinated to the nucleobases. The exact binding is debated.A large variety of artificial nucleobases have been developed for use as metal base pairs. | https://en.wikipedia.org/wiki/Nucleobase_analog |
These modified nucleobases exhibit tunable electronic properties, sizes, and binding affinities that can be optimized for a specific metal. For, example a nucleoside modified with a pyridine-2,6-dicarboxylate has shown to bind tightly to Cu2+, whereas other divalent ions are only loosely bound. | https://en.wikipedia.org/wiki/Nucleobase_analog |
The tridentate character contributes to this selectivity. The fourth coordination site on the copper is saturated by an oppositely arranged pyridine nucleobase. The asymmetric metal base pairing system is orthogonal to the Watson-Crick base pairs. | https://en.wikipedia.org/wiki/Nucleobase_analog |
Another example of an artificial nucleobase is that with hydroxypyridone nucleobases, which are able to bind Cu2+ inside the DNA duplex. Five consecutive copper-hydroxypyridone base pairs were incorporated into a double strand, which were flanked by only one natural nucleobase on both ends. EPR data showed that the distance between copper centers was estimated to be 3.7 ± 0.1 Å, while a natural B-type DNA duplex is only slightly larger (3.4 Å). The appeal for stacking metal ions inside a DNA duplex is the hope to obtain nanoscopic self-assembling metal wires, though this has not been realized yet. | https://en.wikipedia.org/wiki/Nucleobase_analog |
In metal borides, the bonding of boron varies depending on the atomic ratio B/M. Diborides have B/M = 2, as in the well-known superconductor MgB2; they crystallize in a hexagonal AlB2-type layered structure. Hexaborides have B/M = 6 and form a three-dimensional boron framework based on a boron octahedron (Fig. 1a). Tetraborides, i.e. B/M = 4, are mixtures of diboride and hexaboride structures. | https://en.wikipedia.org/wiki/Crystal_structure_of_boron-rich_metal_borides |
Cuboctahedron (Fig. 1b) is the structural unit of dodecaborides, which have a cubic lattice and B/M = 12. When the composition ratio exceeds 12, boron forms B12 icosahedra (Fig. 1c) which are linked into a three-dimensional boron framework, and the metal atoms reside in the voids of this framework.This complex bonding behavior originates from the fact that boron has only three valence electrons; this hinders tetrahedral bonding as in diamond or hexagonal bonding as in graphite. Instead, boron atoms form polyhedra. | https://en.wikipedia.org/wiki/Crystal_structure_of_boron-rich_metal_borides |
For example, three boron atoms make up a triangle where they share two electrons to complete the so-called three-center bonding. Boron polyhedra, such as B6 octahedron, B12 cuboctahedron and B12 icosahedron, lack two valence electrons per polyhedron to complete the polyhedron-based framework structure. Metal atoms need to donate two electrons per boron polyhedron to form boron-rich metal borides. | https://en.wikipedia.org/wiki/Crystal_structure_of_boron-rich_metal_borides |
Thus, boron compounds are often regarded as electron-deficient solids. The covalent bonding nature of metal boride compounds also give them their hardness and inert chemical reactivity property.Icosahedral B12 compounds include α-rhombohedral boron (B13C2), β-rhombohedral boron (MeBx, 23≤x), α-tetragonal boron (B48B2C2), β-tetragonal boron (β-AlB12), AlB10 or AlC4B24, YB25, YB50, YB66, NaB15 or MgAlB14, γ-AlB12, BeB3 and SiB6. | https://en.wikipedia.org/wiki/Crystal_structure_of_boron-rich_metal_borides |
YB25 and YB50 decompose without melting that hinders their growth as single crystals by the floating zone method. However, addition of a small amount of Si solves this problem and results in single crystals with the stoichiometry of YB41Si1.2. This stabilization technique allowed the synthesis of some other boron-rich rare-earth borides. | https://en.wikipedia.org/wiki/Crystal_structure_of_boron-rich_metal_borides |
Albert and Hillebrecht reviewed binary and selected ternary boron compounds containing main-group elements, namely, borides of the alkali and alkaline-earth metals, aluminum borides and compounds of boron and the nonmetals C, Si, Ge, N, P, As, O, S and Se. They, however, excluded the described here icosahedron-based rare-earth borides. Note that rare-earth elements have d- and f-electrons that complicates chemical and physical properties of their borides. | https://en.wikipedia.org/wiki/Crystal_structure_of_boron-rich_metal_borides |
Werheit et al. reviewed Raman spectra of numerous icosahedron-based boron compounds.Figure 2 shows a relationship between the ionic radius of trivalent rare-earth ions and the composition of some rare-earth borides. Note that scandium has many unique boron compounds, as shown in figure 2, because of the much smaller ionic radius compared with other rare-earth elements.In understanding the crystal structures of rare-earth borides, it is important to keep in mind the concept of partial site occupancy, that is, some atoms in the described below unit cells can take several possible positions with a given statistical probability. Thus, with the given statistical probability, some of the partial-occupancy sites in such a unit cell are empty, and the remained sites are occupied. | https://en.wikipedia.org/wiki/Crystal_structure_of_boron-rich_metal_borides |
In metal matrix composites (MMCs), the additions strengthen the metal and reduce the toughness of material. In ceramic matrix composites (CMCs), the additions can toughen materials but not strengthen them. at same time. In carbon fiber reinforced composites (CFRPs), graphite fibers can toughen and strengthen polymer at same time. | https://en.wikipedia.org/wiki/Toughening |
In bulk metallic glass composites(BMGs), dendrites are added to hind the movement of shear band and the toughness is improved.If fibers have larger fracture strain than matrix, the composite is toughened by crack bridging. The toughness of a composite can be expressed: G C = V m G m + V f G f + Δ G C {\displaystyle G_{C}=V_{m}G_{m}+V_{f}G_{f}+\Delta G_{C}} where G m {\displaystyle G_{m}} and G f {\displaystyle G_{f}} are toughness of matrix and fibers respectively, V m {\displaystyle V_{m}} and V f {\displaystyle V_{f}} are volume of matrix and fibers respectively, Δ G C {\displaystyle \Delta G_{C}} is the additional toughness caused by bridging toughening. After crack propagates across through fiber, the fiber is elongated and is pulled out from matrix. | https://en.wikipedia.org/wiki/Toughening |
These processes correspond to plastic deformation and pull-out work and contribute to toughening of composite. When fiber is brittle, the pull-out work dominates the irreversible work contributing to toughening. The increment of toughness caused by pull-out work can be expressed by: Δ G C = 1 32 β 2 σ f 2 V f d τ {\displaystyle \Delta G_{C}={1 \over 32}{\beta ^{2}\sigma _{f}^{2}V_{f}d \over \tau }} where β {\displaystyle \beta } is the ratio between debond length and critical length, σ f {\displaystyle \sigma _{f}} is the strength of fibers, d {\displaystyle d} is the width of fiber, V f {\displaystyle V_{f}} is the fraction of fibers and τ {\displaystyle \tau } is the interface friction stress. From the equation, it can be found that higher volume fraction, higher fiber strength and lower interfacial stress can get a better toughening effect. | https://en.wikipedia.org/wiki/Toughening |
In metal plasticity, the assumption that the plastic strain increment and deviatoric stress tensor have the same principal directions is encapsulated in a relation called the flow rule. Rock plasticity theories also use a similar concept except that the requirement of pressure-dependence of the yield surface requires a relaxation of the above assumption. Instead, it is typically assumed that the plastic strain increment and the normal to the pressure-dependent yield surface have the same direction, i.e., d ε p = d λ ∂ f ∂ σ {\displaystyle d{\boldsymbol {\varepsilon }}_{p}=d\lambda \,{\frac {\partial f}{\partial {\boldsymbol {\sigma }}}}} where d λ > 0 {\displaystyle d\lambda >0} is a hardening parameter. This form of the flow rule is called an associated flow rule and the assumption of co-directionality is called the normality condition. | https://en.wikipedia.org/wiki/Flow_plasticity_theory |
The function f {\displaystyle f} is also called a plastic potential. The above flow rule is easily justified for perfectly plastic deformations for which d σ = 0 {\displaystyle d{\boldsymbol {\sigma }}=0} when d ε p > 0 {\displaystyle d{\boldsymbol {\varepsilon }}_{p}>0} , i.e., the yield surface remains constant under increasing plastic deformation. This implies that the increment of elastic strain is also zero, d ε e = 0 {\displaystyle d{\boldsymbol {\varepsilon }}_{e}=0} , because of Hooke's law. | https://en.wikipedia.org/wiki/Flow_plasticity_theory |
Therefore, d σ: ∂ f ∂ σ = 0 and d σ: d ε p = 0 . {\displaystyle d{\boldsymbol {\sigma }}:{\frac {\partial f}{\partial {\boldsymbol {\sigma }}}}=0\quad {\text{and}}\quad d{\boldsymbol {\sigma }}:d{\boldsymbol {\varepsilon }}_{p}=0\,.} | https://en.wikipedia.org/wiki/Flow_plasticity_theory |
Hence, both the normal to the yield surface and the plastic strain tensor are perpendicular to the stress tensor and must have the same direction. For a work hardening material, the yield surface can expand with increasing stress. We assume Drucker's second stability postulate which states that for an infinitesimal stress cycle this plastic work is positive, i.e., d σ: d ε p ≥ 0 . | https://en.wikipedia.org/wiki/Flow_plasticity_theory |
{\displaystyle d{\boldsymbol {\sigma }}:d{\boldsymbol {\varepsilon }}_{p}\geq 0\,.} The above quantity is equal to zero for purely elastic cycles. Examination of the work done over a cycle of plastic loading-unloading can be used to justify the validity of the associated flow rule. | https://en.wikipedia.org/wiki/Flow_plasticity_theory |
In metal processing, a reducing atmosphere is used in annealing ovens for relaxation of metal stresses without corroding the metal. A non-oxidizing gas, usually nitrogen or argon, is typically used as a carrier gas so that diluted amounts of reducing gases may be used. Typically, this is achieved through using the combustion products of fuels and tailoring the ratio of CO:CO2. However, other common reducing atmospheres in the metal processing industries consist of dissociated ammonia, vacuum, and/or direct mixing of appropriately pure gases of N2, Ar, and H2.A reducing atmosphere is also used to produce specific effects on ceramic wares being fired. | https://en.wikipedia.org/wiki/Reducing_atmosphere |
A reduction atmosphere is produced in a fuel fired kiln by reducing the draft and depriving the kiln of oxygen. This diminished level of oxygen causes incomplete combustion of the fuel and raises the level of carbon inside the kiln. At high temperatures the carbon will bond with and remove the oxygen in the metal oxides used as colorants in the glazes. | https://en.wikipedia.org/wiki/Reducing_atmosphere |
This loss of oxygen results in a change in the color of the glazes because it allows the metals in the glaze to be seen in an unoxidized form. A reduction atmosphere can also affect the color of the clay body. If iron is present in the clay body, as it is in most stoneware, then it will be affected by the reduction atmosphere as well. | https://en.wikipedia.org/wiki/Reducing_atmosphere |
In most commercial incinerators, exactly the same conditions are created to encourage the release of carbon bearing fumes. These fumes are then oxidized in reburn tunnels where oxygen is injected progressively. The exothermic oxidation reaction maintains the temperature of the reburn tunnels. This system allows lower temperatures to be employed in the incinerator section, where the solids are volumetrically reduced. | https://en.wikipedia.org/wiki/Reducing_atmosphere |
In metal spinning, a disk of sheet metal is held perpendicularly to the main axis of the lathe, and tools with polished tips (spoons) or roller tips are hand-held, but levered by hand against fixed posts, to develop pressure that deforms the spinning sheet of metal. Metal-spinning lathes are almost as simple as wood-turning lathes. Typically, metal spinning requires a mandrel, usually made from wood, which serves as the template onto which the workpiece is formed (asymmetric shapes can be made, but it is a very advanced technique). For example, to make a sheet metal bowl, a solid block of wood in the shape of the bowl is required; similarly, to make a vase, a solid template of the vase is required. Given the advent of high-speed, high-pressure, industrial die forming, metal spinning is less common now than it once was, but still a valuable technique for producing one-off prototypes or small batches, where die forming would be uneconomical. | https://en.wikipedia.org/wiki/Glass-working_lathe |
In metal type, the point size (and hence the em, from em quadrat) was equal to the line height of the metal body from which the letter rises. In metal type, the physical size of a letter could not normally exceed the em. A digital font's design space in digital type is called the em, which is a grid with arbitrary resolution. | https://en.wikipedia.org/wiki/Root_em |
Scaling the em to a particular point size is how imaging systems—whether for screen or print—work. In digital type, the relationship of the height of particular letters to the em is arbitrarily set by the typeface designer. However, as a very rough guideline, an "average" font might have a cap height of 70% of the em, and an x-height of 48% of the em. | https://en.wikipedia.org/wiki/Root_em |
In metal typesetting some fonts have default increased or decreased leading. To achieve this, a smaller font face is cast on the body of a larger font or vice versa. Such fonts are usually called "bastard" fonts or types. In the notation they are usually written with the face and the body size separated by a slash, like 10/12 that is a 10-point font face on a 12-point body, or 12/10, a 12-point font face on a 10-point body. | https://en.wikipedia.org/wiki/Line_spacing |
In metal typesetting, a font is a particular size, weight and style of a typeface. Each font is a matched set of type, with a piece (a "sort") for each glyph. A typeface consists of various fonts that share an overall design. In the 21st century, with the advent of computer fonts, the terms "font" and "typeface" are often used interchangeably, although the term "typeface" refers to the design of typographical lettering, whereas the term "font" refers to the specific style of a typeface, such as its size and weight. | https://en.wikipedia.org/wiki/Type_font |
For instance, the typeface "Bauer Bodoni" (sample shown here) includes fonts "Roman" (or "Regular"), "Bold" and "Italic"; each of these exists in a variety of sizes. The term "font" is correctly applied to any one of these alone but may be seen used loosely to refer to the whole typeface. When used in computers, each style is in a separate digital "font file". In both traditional typesetting and computing, the word "font" refers to the delivery mechanism of the typeface. In traditional typesetting, the font would be made from metal or wood type: to compose a page may require multiple fonts or even multiple typefaces. | https://en.wikipedia.org/wiki/Type_font |
In metallic bonding, bonding electrons are delocalized over a lattice of atoms. By contrast, in ionic compounds, the locations of the binding electrons and their charges are static. The free movement or delocalization of bonding electrons leads to classical metallic properties such as luster (surface light reflectivity), electrical and thermal conductivity, ductility, and high tensile strength. | https://en.wikipedia.org/wiki/Bond_(chemical) |
In metallic conductor systems, reflections of a signal traveling down a conductor can occur at a discontinuity or impedance mismatch. The ratio of the amplitude of the reflected wave Vr to the amplitude of the incident wave Vi is known as the reflection coefficient Γ {\displaystyle \Gamma } . Γ = V r V i {\displaystyle {\mathit {\Gamma }}={V_{\mathrm {r} } \over V_{\mathrm {i} }}} Return loss is the negative of the magnitude of the reflection coefficient in dB. Since power is proportional to the square of the voltage, return loss is given by, R L ( d B ) = − 20 log 10 | Γ | {\displaystyle RL(\mathrm {dB} )=-20\log _{10}\left|{\mathit {\Gamma }}\right|} where the vertical bars indicate magnitude. Thus, a large positive return loss indicates the reflected power is small relative to the incident power, which indicates good impedance match between transmission line and load. If the incident power and the reflected power are expressed in 'absolute' decibel units, (e.g., dBm), then the return loss in dB can be calculated as the difference between the incident power Pi (in absolute decibel units) and the reflected power Pr (also in absolute decibel units), R L ( d B ) = P i ( d B ) − P r ( d B ) {\displaystyle RL(\mathrm {dB} )=P_{\mathrm {i} }(\mathrm {dB} )-P_{\mathrm {r} }(\mathrm {dB} )\,} | https://en.wikipedia.org/wiki/Return_loss |
In metallic currencies, a government mint will coin money by placing a mark on metal tokens, typically gold or silver, which serves as a guarantee of their weight and purity. In issuing this coinage at a face value higher than its costs, the government gains a profit known as seigniorage. The role of a mint and of coin differs between commodity money and fiat money. In commodity money, the coin retains its value if it is melted and physically altered, while in a fiat money it does not. | https://en.wikipedia.org/wiki/Commodity_money |
Usually, in a fiat money the value drops if the coin is converted to metal, but in a few cases the value of metals in fiat moneys have been allowed to rise to values larger than the face value of the coin. In India, for example fiat Rupees disappeared from the market after 2007 when their content of stainless steel became larger than the fiat or face value of the coins. In the US, the metal in pennies (97.5% zinc since 1982, 95% copper in 1982 and before) and nickels (75% copper, 25% nickel) has a value close to, and sometimes exceeding, the fiat face value of the coin. | https://en.wikipedia.org/wiki/Commodity_money |
In metallic silhouette shooting only knock down steel targets featuring animals are used. | https://en.wikipedia.org/wiki/Shooting_target |
In metallic solids, electric charge flows by means of electrons, from lower to higher electrical potential. In other media, any stream of charged objects (ions, for example) may constitute an electric current. To provide a definition of current independent of the type of charge carriers, conventional current is defined as moving in the same direction as the positive charge flow. So, in metals where the charge carriers (electrons) are negative, conventional current is in the opposite direction to the overall electron movement. | https://en.wikipedia.org/wiki/Electric_conduction |
In conductors where the charge carriers are positive, conventional current is in the same direction as the charge carriers. In a vacuum, a beam of ions or electrons may be formed. In other conductive materials, the electric current is due to the flow of both positively and negatively charged particles at the same time. | https://en.wikipedia.org/wiki/Electric_conduction |
In still others, the current is entirely due to positive charge flow. For example, the electric currents in electrolytes are flows of positively and negatively charged ions. In a common lead-acid electrochemical cell, electric currents are composed of positive hydronium ions flowing in one direction, and negative sulfate ions flowing in the other. Electric currents in sparks or plasma are flows of electrons as well as positive and negative ions. In ice and in certain solid electrolytes, the electric current is entirely composed of flowing ions. | https://en.wikipedia.org/wiki/Electric_conduction |
In metalloproteins, metal ions are usually coordinated by nitrogen, oxygen or sulfur centers belonging to amino acid residues of the protein. These donor groups are often provided by side-chains on the amino acid residues. Especially important are the imidazole substituent in histidine residues, thiolate substituents in cysteine residues, and carboxylate groups provided by aspartate. Given the diversity of the metalloproteome, virtually all amino acid residues have been shown to bind metal centers. | https://en.wikipedia.org/wiki/Metalloprotein |
The peptide backbone also provides donor groups; these include deprotonated amides and the amide carbonyl oxygen centers. Lead(II) binding in natural and artificial proteins has been reviewed.In addition to donor groups that are provided by amino acid residues, many organic cofactors function as ligands. Perhaps most famous are the tetradentate N4 macrocyclic ligands incorporated into the heme protein. Inorganic ligands such as sulfide and oxide are also common. | https://en.wikipedia.org/wiki/Metalloprotein |
In metallurgical applications, wollastonite serves as a flux for welding, a source for calcium oxide, a slag conditioner, and to protect the surface of molten metal during the continuous casting of steel. | https://en.wikipedia.org/wiki/Calcium_metasilicate |
In metallurgical processes tank leaching is a hydrometallurgical method of extracting valuable material (usually metals) from ore. | https://en.wikipedia.org/wiki/Vat_leaching |
In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature, maintaining a suitable temperature for an appropriate amount of time and then cooling. In annealing, atoms migrate in the crystal lattice and the number of dislocations decreases, leading to a change in ductility and hardness. | https://en.wikipedia.org/wiki/Annealing_(materials_science) |
As the material cools it recrystallizes. For many alloys, including carbon steel, the crystal grain size and phase composition, which ultimately determine the material properties, are dependent on the heating rate and cooling rate. Hot working or cold working after the annealing process alters the metal structure, so further heat treatments may be used to achieve the properties required. | https://en.wikipedia.org/wiki/Annealing_(materials_science) |
With knowledge of the composition and phase diagram, heat treatment can be used to adjust from harder and more brittle to softer and more ductile. In the case of ferrous metals, such as steel, annealing is performed by heating the material (generally until glowing) for a while and then slowly letting it cool to room temperature in still air. Copper, silver and brass can be either cooled slowly in air, or quickly by quenching in water. In this fashion, the metal is softened and prepared for further work such as shaping, stamping, or forming. Many other materials, including glass and plastic films, use annealing to improve the finished properties. | https://en.wikipedia.org/wiki/Annealing_(materials_science) |
In metallurgy and steam engines the Industrial Revolution made extensive use of coal and coke – as cheaper, more plentiful and more efficient than wood and charcoal. Coal-fired steam engines also operated in the railways and in shipping, revolutionizing transport in the early 19th century. Kenneth Pomeranz drew attention to differences in the availability of coal between West and East. Due to regional climate, European coal mines were wetter, and deep mines did not become practical until the introduction of the Newcomen steam engine to pump out groundwater. | https://en.wikipedia.org/wiki/Great_Divergence |
In mines in the arid northwest of China, ventilation to prevent explosions was much more difficult.Another difference involved geographic distance; although China and Europe had comparable mining technologies, the distances between the economically developed regions and coal deposits differed vastly. The largest coal deposits in China are located in the northwest, within reach of the Chinese industrial core during the Northern Song (960–1127). During the 11th century China developed sophisticated technologies to extract and use coal for energy, leading to soaring iron production. | https://en.wikipedia.org/wiki/Great_Divergence |
The southward population shift between the 12th and 14th centuries resulted in new centers of Chinese industry far from the major coal deposits. Some small coal deposits were available locally, though their use was sometimes hampered by government regulations. In contrast, Britain contained some of the largest coal deposits in Europe – all within a relatively compact island. | https://en.wikipedia.org/wiki/Great_Divergence |
The centrality of coal to Industrial revolution was criticized by Gregory Clark and David Jacks, who show that coal could be substituted without much loss of national income. Similarly Deirdre N. McCloskey says that coal could easily have been imported to Britain from other countries. Moreover, the Chinese could move their industries closer to coal reserves. | https://en.wikipedia.org/wiki/Great_Divergence |
In metallurgy, a 4% picric acid in ethanol etch termed "picral" has been commonly used in optical metallography to reveal prior austenite grain boundaries in ferritic steels. The hazards associated with picric acid have meant it has largely been replaced with other chemical etchants. However, it is still used to etch magnesium alloys, such as AZ31. | https://en.wikipedia.org/wiki/Picric_acid |
In metallurgy, a flux (from Latin fluxus 'flow') is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time. They are used in both extractive metallurgy and metal joining. Some of the earliest known fluxes were sodium carbonate, potash, charcoal, coke, borax, lime, lead sulfide and certain minerals containing phosphorus. | https://en.wikipedia.org/wiki/Fluxing_agents |
Iron ore was also used as a flux in the smelting of copper. These agents served various functions, the simplest being a reducing agent, which prevented oxides from forming on the surface of the molten metal, while others absorbed impurities into slag, which could be scraped off molten metal.Fluxes are also used in foundries for removing impurities from molten nonferrous metals such as aluminium, or for adding desirable trace elements such as titanium. As cleaning agents, fluxes facilitate soldering, brazing, and welding by removing oxidation from the metals to be joined. In some applications molten flux also serves as a heat-transfer medium, facilitating heating of the joint by the soldering tool or molten solder. | https://en.wikipedia.org/wiki/Fluxing_agents |
In metallurgy, a ladle is a bucket-shaped container or vessel used to transport and pour out molten metals. Ladles are often used in foundries and range in size from small hand carried vessels that resemble a kitchen ladle and hold 20 kilograms (44 lb) to large steelmill ladles that hold up to 300 tonnes (295 long tons; 331 short tons). Many non-ferrous foundries also use ceramic crucibles for transporting and pouring molten metal and will also refer to these as ladles. | https://en.wikipedia.org/wiki/Ladle_(metallurgy) |
In metallurgy, a shape-memory alloy (SMA) is an alloy that can be deformed when cold but returns to its pre-deformed ("remembered") shape when heated. It is also known in other names such as memory metal, memory alloy, smart metal, smart alloy, and muscle wire. The "memorized geometry" can be modified by fixating the desired geometry and subjecting it to a thermal treatment, for example a wire can be taught to memorize the shape of a coil spring. Parts made of shape-memory alloys can be lightweight, solid-state alternatives to conventional actuators such as hydraulic, pneumatic, and motor-based systems. They can also be used to make hermetic joints in metal tubing, and it can also replace a sensor-actuator closed loop to control water temperature by governing hot and cold water flow ratio. | https://en.wikipedia.org/wiki/Memory_metal |
In metallurgy, alpha case is the oxygen-enriched surface phase that occurs when titanium and its alloys are exposed to heated air or oxygen. Alpha case is hard and brittle, and tends to create a series of microcracks that will reduce the metal's performance and its fatigue properties. Alpha case can be minimized or avoided by processing titanium at very deep vacuum levels. However once present on the surface, the currently applied method to remove the alpha case is by the subtractive methods of machining and/or chemical milling. | https://en.wikipedia.org/wiki/Alpha_case |
An emerging technique is to subject the metal to an electrochemical treatment in molten salts, such as calcium chloride or lithium chloride at elevated temperatures. This method removes the dissolved oxygen from the alpha case, hence restoring the oxygen-free metal. However, an unwanted consequence of the high temperature treatment is the growth of the grains in the metal. | https://en.wikipedia.org/wiki/Alpha_case |
Grain growth may be limited by lowering the molten salt temperature. Alternatively, the metal may be rolling-pressed again to break the large grains into smaller ones. == References == | https://en.wikipedia.org/wiki/Alpha_case |
In metallurgy, cold forming or cold working is any metalworking process in which metal is shaped below its recrystallization temperature, usually at the ambient temperature. Such processes are contrasted with hot working techniques like hot rolling, forging, welding, etc.: p.375 The same or similar terms are used in glassmaking for the equivalents; for example cut glass is made by "cold work", cutting or grinding a formed object. Cold forming techniques are usually classified into four major groups: squeezing, bending, drawing, and shearing. They generally have the advantage of being simpler to carry out than hot working techniques. | https://en.wikipedia.org/wiki/Cold_forming |
Unlike hot working, cold working causes the crystal grains and inclusions to distort following the flow of the metal; which may cause work hardening and anisotropic material properties. Work hardening makes the metal harder, stiffer, and stronger, but less plastic, and may cause cracks of the piece. : p.378 The possible uses of cold forming are extremely varied, including large flat sheets, complex folded shapes, metal tubes, screw heads and threads, riveted joints, and much more. | https://en.wikipedia.org/wiki/Cold_forming |
In metallurgy, exfoliation corrosion (also called lamellar corrosion) is a severe type of intergranular corrosion that raises surface grains from metal by forming corrosion products at grain boundaries under the surface. It is frequently found on extruded sections where grain thickness is not as thick as the rolled grain. It can affect aircraft structures, marine vessels, heaters and other objects. == References == | https://en.wikipedia.org/wiki/Exfoliation_corrosion_(metallurgy) |
In metallurgy, gas flushing removes dissolved gases from the molten metal prior to the material being processed. For example, before casting aluminium alloys, argon bubbles are injected into liquid aluminium using a rotary degasser. The argon bubbles rise to the surface, bringing with them some of the dissolved hydrogen. The degassing step reduces the occurrence of hydrogen gas porosity. In the steel making process, this method is used very commonly for duplex steel and some high reactivity metals. | https://en.wikipedia.org/wiki/Gas_flushing |
In metallurgy, hot working refers to processes where metals are plastically deformed above their recrystallization temperature. Being above the recrystallization temperature allows the material to recrystallize during deformation. This is important because recrystallization keeps the materials from strain hardening, which ultimately keeps the yield strength and hardness low and ductility high. This contrasts with cold working. Many kinds of working, including rolling, forging, extrusion, and drawing, can be done with hot metal. | https://en.wikipedia.org/wiki/Hot_working |
In metallurgy, materials science and structural geology, subgrain rotation recrystallization is recognized as an important mechanism for dynamic recrystallisation. It involves the rotation of initially low-angle sub-grain boundaries until the mismatch between the crystal lattices across the boundary is sufficient for them to be regarded as grain boundaries. This mechanism has been recognized in many minerals (including quartz, calcite, olivine, pyroxenes, micas, feldspars, halite, garnets and zircons) and in metals (various magnesium, aluminium and nickel alloys). | https://en.wikipedia.org/wiki/Subgrain_rotation_recrystallization |
In metallurgy, melchior is an alloy of copper, mainly with nickel (5–30%). Its name originates from Italian: melchior, which in turn is distorted French: maillechort, honoring the French inventors of the alloy, Maillot and Chorier. The term melchior sometimes refers not only to the copper-nickel alloys, but also ternary alloys of copper with nickel and zinc ("nickel silver") and even a silvered brass. Melchior is easily deformable by application of pressure, both in the hot and cold state. | https://en.wikipedia.org/wiki/Melchior_(alloy) |
After annealing, it has a tensile strength of about 40 kg/mm2. The most valuable property of melchior is its high resistance to corrosion in air, freshwater and seawater. Increasing content of nickel, iron or manganese improves corrosion and cavitation resistance, especially in sea water and atmospheric water vapor. The alloy of 30% Ni, 0.8% Fe, 1% Mn and 68.2% Cu is used in maritime shipping, in particular for the manufacture of condenser tubes. Nickel gives melchior, unlike brass and bronze, a silver color, and that property, combined with its high corrosion resistance, made it popular for the manufacture of household utensils in the Soviet Union. | https://en.wikipedia.org/wiki/Melchior_(alloy) |
In metallurgy, mineral jigs are a type of gravity concentrator, separating materials with different densities. It is widely used in recovering valuable heavy minerals such as gold, platinum, tin, tungsten, as well as gemstones such as diamond and sapphire, from alluvial or placer deposits. Base metals such as iron, manganese, and barite can also be recovered using jigs. The process begins with flowing a stream of liquid-suspended material over a screen and subjecting the screen to a vertical hydraulic pulsation. | https://en.wikipedia.org/wiki/Mineral_jig |
This pulsation momentarily expands or dilates the screen bed and allows the heavier materials to work toward the bottom. Heavier material finer than the screen openings will gradually work through the beds and the retention screen into the hutch, or lower compartment. That material, the concentrate, is discharged from this compartment or hutch through a spigot. | https://en.wikipedia.org/wiki/Mineral_jig |
If the concentrate is coarser than the screen, it will work down to the top of the shot bed, and can be withdrawn either continuously or intermittently. The lighter material, or tailing, will be rejected over the end of the jig.The mineral jig has certain advantages in placer and hardrock mill flowsheets. In gold recovery, the jigs produce highly concentrated products which can be easily upgraded by methods such as barrel amalgamation, treating across shaking tables or processing through centrifugal concentrators. In other placer operations the heavy minerals being sought are recovered efficiently and cheaply with similar high ratios of concentration. In iron, manganese, and base metal treatment flowsheets, the jigs are operated to produce marketable grades of concentrate, or, as pre-concentration devices, to reject barren gangue prior to the ore entering the fine grinding section of the mill flowsheet.The construction of the mineral jig results in maximum utilization of floor area and minimum head room requirements, permitting greater capacity per unit of operating floor area than, for example, shaking tables or other devices such as jig concentrators. | https://en.wikipedia.org/wiki/Mineral_jig |
In metallurgy, non-ferrous metals are metals or alloys that do not contain iron (allotropes of iron, ferrite, and so on) in appreciable amounts. Generally more costly than ferrous metals, non-ferrous metals are used because of desirable properties such as low weight (e.g. aluminium), higher conductivity (e.g. copper), non-magnetic properties or resistance to corrosion (e.g. zinc). Some non-ferrous materials are also used in the iron and steel industries. | https://en.wikipedia.org/wiki/Nonferrous_metal |
For example, bauxite is used as flux for blast furnaces, while others such as wolframite, pyrolusite, and chromite are used in making ferrous alloys.Important non-ferrous metals include aluminium, copper, lead, tin, titanium, and zinc, and alloys such as brass. Precious metals such as gold, silver, and platinum and exotic or rare metals such as mercury, tungsten, beryllium, bismuth, cerium, cadmium, niobium, indium, gallium, germanium, lithium, selenium, tantalum, tellurium, vanadium, and zirconium are also non-ferrous. They are usually obtained through minerals such as sulfides, carbonates, and silicates. Non-ferrous metals are usually refined through electrolysis. | https://en.wikipedia.org/wiki/Nonferrous_metal |
In metallurgy, one may encounter many terms that have very specific meanings within the field, but may seem rather vague when viewed from the outside. Terms such as "hardness," "impact resistance," "toughness," and "strength" can carry many different connotations, making it sometimes difficult to discern the specific meaning. Some of the terms encountered, and their specific definitions are: Strength – Resistance to permanent deformation and tearing. Strength, in metallurgy, is still a rather vague term, so is usually divided into yield strength (strength beyond which deformation becomes permanent), tensile strength (the ultimate tearing strength), shear strength (resistance to transverse, or cutting forces), and compressive strength (resistance to elastic shortening under a load). | https://en.wikipedia.org/wiki/Stepped_quenching |
Toughness – Resistance to fracture, as measured by the Charpy test. Toughness often increases as strength decreases, because a material that bends is less likely to break. Hardness – A surface's resistance to scratching, abrasion, or indentation. | https://en.wikipedia.org/wiki/Stepped_quenching |
In conventional metal alloys, there is a linear relation between indentation hardness and tensile strength, which eases the measurement of the latter. Brittleness – Brittleness describes a material's tendency to break before bending or deforming either elastically or plastically. | https://en.wikipedia.org/wiki/Stepped_quenching |
Brittleness increases with decreased toughness, but is greatly affected by internal stresses as well. Plasticity – The ability to mold, bend or deform in a manner that does not spontaneously return to its original shape. This is proportional to the ductility or malleability of the substance. | https://en.wikipedia.org/wiki/Stepped_quenching |
Elasticity – Also called flexibility, this is the ability to deform, bend, compress, or stretch and return to the original shape once the external stress is removed. Elasticity is inversely related to the Young's modulus of the material. Impact resistance – Usually synonymous with high-strength toughness, it is the ability to resist shock-loading with minimal deformation. Wear resistance – Usually synonymous with hardness, this is resistance to erosion, ablation, spalling, or galling. Structural integrity – The ability to withstand a maximum-rated load while resisting fracture, resisting fatigue, and producing a minimal amount of flexing or deflection, to provide a maximum service life. | https://en.wikipedia.org/wiki/Stepped_quenching |
In metallurgy, peening is the process of working a metal's surface to improve its material properties, usually by mechanical means, such as hammer blows, by blasting with shot (shot peening), focusing light (laser peening), or in recent years, with water column impacts (water jet peening) and cavitation jets (cavitation peening). With the notable exception of laser peening, peening is normally a cold work process tending to expand the surface of the cold metal, thus inducing compressive stresses or relieving tensile stresses already present. It can also encourage strain hardening of the surface metal. | https://en.wikipedia.org/wiki/Peening |
In metallurgy, recovery is a process by which a metal or alloy's deformed grains can reduce their stored energy by the removal or rearrangement of defects in their crystal structure. These defects, primarily dislocations, are introduced by plastic deformation of the material and act to increase the yield strength of a material. Since recovery reduces the dislocation density, the process is normally accompanied by a reduction in a material's strength and a simultaneous increase in the ductility. As a result, recovery may be considered beneficial or detrimental depending on the circumstances. | https://en.wikipedia.org/wiki/Recovery_(metallurgy) |
Recovery is related to the similar processes of recrystallization and grain growth, each of them being stages of annealing. Recovery competes with recrystallization, as both are driven by the stored energy, but is also thought to be a necessary prerequisite for the nucleation of recrystallized grains. It is so called because there is a recovery of the electrical conductivity due to a reduction in dislocations. This creates defect-free channels, giving electrons an increased mean free path. | https://en.wikipedia.org/wiki/Recovery_(metallurgy) |
In metallurgy, refining consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining, the final material is usually identical chemically to the original one, only it is purer. The processes used are of many types, including pyrometallurgical and hydrometallurgical techniques. | https://en.wikipedia.org/wiki/Refining_(metallurgy) |
In metallurgy, refraction is a property of metals that indicates their ability to withstand heat. Metals with a high degree of refraction are referred to as refractory. These metals derive their high melting points from their strong intermolecular forces. | https://en.wikipedia.org/wiki/Refraction_(metallurgy) |
Large quantities of energy are required to overcome intermolecular forces. Some refractory metals include molybdenum, niobium, tungsten, and tantalum. These materials are also noted for their high elastic modulus and hardness. | https://en.wikipedia.org/wiki/Refraction_(metallurgy) |
In metallurgy, selective leaching, also called dealloying, demetalification, parting and selective corrosion, is a corrosion type in some solid solution alloys, when in suitable conditions a component of the alloys is preferentially leached from the initially homogenous material. The less noble metal is removed from the alloy by a microscopic-scale galvanic corrosion mechanism. The most susceptible alloys are the ones containing metals with high distance between each other in the galvanic series, e.g. copper and zinc in brass. The elements most typically undergoing selective removal are zinc, aluminium, iron, cobalt, chromium, and others. | https://en.wikipedia.org/wiki/Dezincification_resistant_brass |
In metallurgy, solid solution strengthening is a type of alloying that can be used to improve the strength of a pure metal. The technique works by adding atoms of one element (the alloying element) to the crystalline lattice of another element (the base metal), forming a solid solution. The local nonuniformity in the lattice due to the alloying element makes plastic deformation more difficult by impeding dislocation motion through stress fields. In contrast, alloying beyond the solubility limit can form a second phase, leading to strengthening via other mechanisms (e.g. the precipitation of intermetallic compounds). | https://en.wikipedia.org/wiki/Solid_solution_strengthening |
In metallurgy, the Bower–Barff process is a method of coating iron or steel with magnetic iron oxide, such as Fe2O4, in order to minimize atmospheric corrosion. The articles to be treated are put into a closed retort and a current of superheated steam passed through for twenty minutes followed by a current of producer gas (carbon monoxide), to reduce any higher oxides that may have been formed. | https://en.wikipedia.org/wiki/Bower–Barff_process |
In metallurgy, the Darken equations are used to describe the solid-state diffusion of materials in binary solutions. They were first described by Lawrence Stamper Darken in 1948. The equations apply to cases where a solid solution's two components do not have the same coefficient of diffusion. | https://en.wikipedia.org/wiki/Darken's_equations |
In metallurgy, the Scheil-Gulliver equation (or Scheil equation) describes solute redistribution during solidification of an alloy. | https://en.wikipedia.org/wiki/Scheil_equation |
In metallurgy, the grain flow refers to the plastic deformation of crystallites during rolling or forging. == Notes and references == | https://en.wikipedia.org/wiki/Grain_flow |
In metallurgy, the partition coefficient is an important factor in determining how different impurities are distributed between molten and solidified metal. It is a critical parameter for purification using zone melting, and determines how effectively an impurity can be removed using directional solidification, described by the Scheil equation. | https://en.wikipedia.org/wiki/Differential_solubility |
In metallurgy, titanium gold (Ti-Au or Au-Ti) refers to an alloy consisting of titanium and gold. Such alloys are used in dentistry, ceramics and jewelry. Like many other alloys, titanium gold alloys have a higher yield strength, tensile strength, hardness, and magnetism than either of its constituent metals.In July 2016, researchers discovered that a titanium-gold alloy, β-Ti3Au (strictly speaking, an intermetallic), is up to 4 times harder than titanium. | https://en.wikipedia.org/wiki/Titanium_gold |
In metalogic and metamathematics, Frege's theorem is a metatheorem that states that the Peano axioms of arithmetic can be derived in second-order logic from Hume's principle. It was first proven, informally, by Gottlob Frege in his 1884 Die Grundlagen der Arithmetik (The Foundations of Arithmetic) and proven more formally in his 1893 Grundgesetze der Arithmetik I (Basic Laws of Arithmetic I). The theorem was re-discovered by Crispin Wright in the early 1980s and has since been the focus of significant work. It is at the core of the philosophy of mathematics known as neo-logicism (at least of the Scottish School variety). | https://en.wikipedia.org/wiki/Frege's_Theorem |
In metalogic, 'syntax' has to do with formal languages or formal systems without regard to any interpretation of them, whereas, 'semantics' has to do with interpretations of formal languages. The term 'syntactic' has a slightly wider scope than 'proof-theoretic', since it may be applied to properties of formal languages without any deductive systems, as well as to formal systems. 'Semantic' is synonymous with 'model-theoretic'. | https://en.wikipedia.org/wiki/Deductive_science |
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