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Controllable pitch propeller
In marine propulsion, a variable-pitch propeller is a type of propeller with blades that can be rotated around their long axis to change the blade pitch. Reversible propellers—those where the pitch can be set to negative values—can also create reverse thrust for braking or going backwards without the need to change the direction of shaft revolution. A controllable pitch propeller (CPP) can be efficient for the full range of rotational speeds and load conditions, since its pitch will be varied to absorb the maximum power that the engine is capable of producing. When fully loaded, a vessel will need more propulsion power than when empty. | Wiki-STEM-kaggle |
Controllable pitch propeller
By varying the propeller blades to the optimal pitch, higher efficiency can be obtained, thus saving fuel. A vessel with a VPP can accelerate faster from a standstill and can decelerate much more effectively, making stopping quicker and safer. A CPP can also improve vessel maneuverability by directing a stronger flow of water onto the rudder.However, a fixed variable-pitch propeller (FVPP) is both cheaper and more robust than a CPP. | Wiki-STEM-kaggle |
Controllable pitch propeller
Also, an FVPP is typically more efficient than a CPP for a single specific rotational speed and load condition. Accordingly, vessels that normally operate at a standard speed (such as large bulk carriers, tankers and container ships) will have an FVPP optimized for that speed. At the other extreme, a canal narrowboat will have a FVPP for two reasons: speed is limited to 4 mph (to protect the canal bank), and the propeller needs to be robust (when encountering underwater obstacles). | Wiki-STEM-kaggle |
Controllable pitch propeller
Vessels with medium or high speed diesel or gasoline engines use a reduction gear to reduce the engine output speed to an optimal propeller speed—although the large low speed diesels, whose cruising RPM is in the 80 to 120 range, are usually direct drive with direct-reversing engines. While an FVPP-equipped vessel needs either a reversing gear or a reversible engine to reverse, a CPP vessel may not. On a large ship the CPP requires a hydraulic system to control the position of the blades. | Wiki-STEM-kaggle |
Controllable pitch propeller
Compared to an FPP, a CPP is more efficient in reverse as the blades' leading edges remain as such in reverse also, so that the hydrodynamic cross-sectional shape is optimal for forward propulsion and satisfactory for reverse operations. In the mid-1970s, Uljanik Shipyard in Yugoslavia produced four VLCCs with CPPs – a tanker and three ore/oil carriers – each powered by two 20,000 bhp B & W diesel engines directly driving Kamewa variable-pitch propellers. Due to the high construction cost none of these vessels ever returned a profit over their lifetimes. | Wiki-STEM-kaggle |
Controllable pitch propeller
For these vessels, fixed variable-pitch propellers would have been more appropriate.Controllable-pitch propellers are usually found on harbour or ocean-going tugs, dredgers, cruise ships, ferries, cargo vessels and larger fishing vessels. Prior to the development of CPPs, some vessels would alternate between "speed wheel" and "power wheel" propellers depending on the task. Current VPP designs can tolerate a maximum output of 44000 kW (60,000 hp). | Wiki-STEM-kaggle |
Value creation
In marketing, a company’s value proposition is the full mix of benefits or economic value which it promises to deliver to the current and future customers (i.e., a market segment) who will buy their products and/or services. It is part of a company's overall marketing strategy which differentiates its brand and fully positions it in the market. A value proposition can apply to an entire organization, or parts thereof, or customer accounts, or products or services. Creating a value proposition is a part of the overall business strategy of a company. | Wiki-STEM-kaggle |
Value creation
Kaplan and Norton note thatStrategy is based on a differentiated customer value proposition. Satisfying customers is the source of sustainable value creation. Developing a value proposition is based on a review and analysis of the benefits, costs, and value that an organization can deliver to its customers, prospective customers, and other constituent groups within and outside the organization. | Wiki-STEM-kaggle |
Value creation
It is also a positioning of value, where Value = Benefits − Cost (cost includes economic risk).A value proposition can be set out as a business or marketing statement (called a "positioning statement") which summarizes why a consumer should buy a product or use a service. A compellingly worded positioning statement has the potential to convince a prospective consumer that a particular product or service which the company offers will add more value or better solve a problem (i.e. the "pain-point") for them than other similar offerings will, thus turning them into a paying client. The positioning statement usually contains references to which sector the company is operating in, what products or services they are selling, who are its target clients and which points differentiate it from other brands and make its product or service a superior choice for those clients. | Wiki-STEM-kaggle |
Value creation
It is usually communicated to the customers via the company's website and other advertising and marketing materials. Conversely, a customer's value proposition is the perceived subjective value, satisfaction or usefulness of a product or service (based on its differentiating features and its personal and social values for the customer) delivered to and experienced by the customer when they acquire it. It is the net positive subjective difference between the total benefits they obtain from it and the sum of monetary cost and non-monetary sacrifices (relative benefits offered by other alternative competitive products) which they have to give up in return. | Wiki-STEM-kaggle |
Value creation
However, often there is a discrepancy between what the company thinks about its value proposition and what the clients think it is.A company's value propositions can evolve, whereby values can add up over time. For example, Apple's value proposition contains a mix of three values. | Wiki-STEM-kaggle |
Value creation
Originally, in the 1980s, it communicated that its products are creative, elegant and "cool" and thus different from the status quo ("Think different"). Then in the first two decades of the 21st century, it communicated its second value of providing the customers with a reliable, smooth, hassle-free user experience within its ecosystem ("Tech that works"). In the 2020s, Apple's latest differentiating value has been the protection of its client's privacy ("Your data is safe with us"). | Wiki-STEM-kaggle |
Product model
In marketing, a product is an object, or system, or service made available for consumer use as of the consumer demand; it is anything that can be offered to a market to satisfy the desire or need of a customer. In retailing, products are often referred to as merchandise, and in manufacturing, products are bought as raw materials and then sold as finished goods. A service is also regarded as a type of product. | Wiki-STEM-kaggle |
Product model
In project management, products are the formal definition of the project deliverables that make up or contribute to delivering the objectives of the project. A related concept is that of a sub-product, a secondary but useful result of a production process. Dangerous products, particularly physical ones, that cause injuries to consumers or bystanders may be subject to product liability. | Wiki-STEM-kaggle |
Holding Cost
In marketing, carrying cost, carrying cost of inventory or holding cost refers to the total cost of holding inventory. This includes warehousing costs such as rent, utilities and salaries, financial costs such as opportunity cost, and inventory costs related to perishability, shrinkage (leakage) and insurance. Carrying cost also includes the opportunity cost of reduced responsiveness to customers' changing requirements, slowed introduction of improved items, and the inventory's value and direct expenses, since that money could be used for other purposes. When there are no transaction costs for shipment, carrying costs are minimized when no excess inventory is held at all, as in a just-in-time production system.Excess inventory can be held for one of three reasons. | Wiki-STEM-kaggle |
Holding Cost
Cycle stock is held based on the re-order point, and defines the inventory that must be held for production, sale or consumption during the time between re-order and delivery. Safety stock is held to account for variability, either upstream in supplier lead time, or downstream in customer demand. Physical stock is held by consumer retailers to provide consumers with a perception of plenty. Carrying costs typically range between 20 and 30% of a company's inventory value. | Wiki-STEM-kaggle |
Shelf angle
In masonry veneer building construction, a shelf angle or masonry support is a steel angle which supports the weight of brick or stone veneer and transfers that weight onto the main structure of the building so that a gap or space can be created beneath to allow building movements to occur. | Wiki-STEM-kaggle |
Matrix (mass spectrometry)
In mass spectrometry, a matrix is a compound that promotes the formation of ions. Matrix compounds are used in matrix-assisted laser desorption/ionization (MALDI), matrix-assisted ionization (MAI), and fast atom bombardment (FAB). | Wiki-STEM-kaggle |
Data-independent acquisition
In mass spectrometry, data-independent acquisition (DIA) is a method of molecular structure determination in which all ions within a selected m/z range are fragmented and analyzed in a second stage of tandem mass spectrometry. Tandem mass spectra are acquired either by fragmenting all ions that enter the mass spectrometer at a given time (called broadband DIA) or by sequentially isolating and fragmenting ranges of m/z. DIA is an alternative to data-dependent acquisition (DDA) where a fixed number of precursor ions are selected and analyzed by tandem mass spectrometry. | Wiki-STEM-kaggle |
De novo sequencing
In mass spectrometry, de novo peptide sequencing is the method in which a peptide amino acid sequence is determined from tandem mass spectrometry. Knowing the amino acid sequence of peptides from a protein digest is essential for studying the biological function of the protein. In the old days, this was accomplished by the Edman degradation procedure. Today, analysis by a tandem mass spectrometer is a more common method to solve the sequencing of peptides. | Wiki-STEM-kaggle |
De novo sequencing
Generally, there are two approaches: database search and de novo sequencing. Database search is a simple version as the mass spectra data of the unknown peptide is submitted and run to find a match with a known peptide sequence, the peptide with the highest matching score will be selected. | Wiki-STEM-kaggle |
De novo sequencing
This approach fails to recognize novel peptides since it can only match to existing sequences in the database. De novo sequencing is an assignment of fragment ions from a mass spectrum. Different algorithms are used for interpretation and most instruments come with de novo sequencing programs. | Wiki-STEM-kaggle |
Fragmentation pattern
In mass spectrometry, fragmentation is the dissociation of energetically unstable molecular ions formed from passing the molecules mass spectrum. These reactions are well documented over the decades and fragmentation patterns are useful to determine the molar weight and structural information of unknown molecules. Fragmentation that occurs in tandem mass spectrometry experiments has been a recent focus of research, because this data helps facilitate the identification of molecules. | Wiki-STEM-kaggle |
Liquid junction interface
In mass spectrometry, liquid junction interface is an ion source or set-up that couples peripheric devices, such as capillary electrophoresis, to mass spectrometry. See the IUPAC recommendation definition as a means of coupling capillary electrophoresis to mass spectrometry in which a liquid reservoir surrounds the separation capillary and transfer capillary to the mass spectrometer. The reservoir provides electrical contact for the capillary electrophoresis. The term liquid junction interface has also been used by Henry M. Fales and coworkers for ion sources where the analyte is in direct contact with the high voltage supply. | Wiki-STEM-kaggle |
Liquid junction interface
This includes in particular nanospray ion sources where a wire made of stainless steel, gold or other conducting material makes contact with the sample solution inside uncoated spray capillaries. The principle is also applied when a stainless steel union connects a chromatography outlet to a spray capillary. Its use has a number of advantages with respect to simplification of interface or source design, easy handling and cost. | Wiki-STEM-kaggle |
Liquid junction interface
Electrolysis effects have to be controlled. Liquid junction interfaces have been used for on-line desalting in conjunction with mass spectrometry. Thereby, chromatographic material such as C18 phase was directly placed in the flow path coming from a pump or an HPLC device. In a variation of the method, fine capillaries were densely packed with chromatographic phase to form separation columns and act as electrospray capillaries at the same time. This method is commonly employed in many proteomics laboratories.It is of note that experimental designs where the direct application of high voltages to liquids to form aerosols and sprays has been described as early as 1917 in the context of not ionization, but atomization of liquids. | Wiki-STEM-kaggle |
Inlet ionization
In mass spectrometry, matrix-assisted ionization (also inlet ionization) is a low fragmentation (soft) ionization technique which involves the transfer of particles of the analyte and matrix sample from atmospheric pressure (AP) to the heated inlet tube connecting the AP region to the vacuum of the mass analyzer.Initial ionization occurs as the pressure drops within the inlet tube. Inlet ionization is similar to electrospray ionization in that a reverse phase solvent system is used and the ions produced are highly charged, however a voltage or a laser is not always needed. It is a highly sensitive process for small and large molecules like peptides, proteins and lipids that can be coupled to a liquid chromatograph. Inlet ionization techniques can be used with an Orbitrap mass analyzer, Orbitrap fourier transform mass spectrometer, linear trap quadrupole and MALDI-TOF. | Wiki-STEM-kaggle |
Quadrupole mass analyzer
In mass spectrometry, the quadrupole mass analyzer (or quadrupole mass filter) is a type of mass analyzer originally conceived by Nobel laureate Wolfgang Paul and his student Helmut Steinwedel. As the name implies, it consists of four cylindrical rods, set parallel to each other. In a quadrupole mass spectrometer (QMS) the quadrupole is the mass analyzer - the component of the instrument responsible for selecting sample ions based on their mass-to-charge ratio (m/z). Ions are separated in a quadrupole based on the stability of their trajectories in the oscillating electric fields that are applied to the rods. | Wiki-STEM-kaggle |
Sieving coefficient
In mass transfer, the sieving coefficient is a measure of equilibration between the concentrations of two mass transfer streams. It is defined as the mean pre- and post-contact concentration of the mass receiving stream divided by the pre- and post-contact concentration of the mass donating stream. S = C r C d {\displaystyle S={\frac {C_{r}}{C_{d}}}} where S is the sieving coefficient Cr is the mean concentration mass receiving stream Cd is the mean concentration mass donating streamA sieving coefficient of unity implies that the concentrations of the receiving and donating stream equilibrate, i.e. the out-flow concentrations (post-mass transfer) of the mass donating and receiving stream are equal to one another. | Wiki-STEM-kaggle |
Sieving coefficient
Systems with sieving coefficient that are greater than one require an external energy source, as they would otherwise violate the laws of thermodynamics. Sieving coefficients less than one represent a mass transfer process where the concentrations have not equilibrated. Contact time between mass streams is important in consider in mass transfer and affects the sieving coefficient. | Wiki-STEM-kaggle |
Crack growth resistance curve
In materials modeled by linear elastic fracture mechanics (LEFM), crack extension occurs when the applied energy release rate G {\displaystyle G} exceeds G R {\displaystyle G_{R}} , where G R {\displaystyle G_{R}} is the material's resistance to crack extension. Conceptually G {\displaystyle G} can be thought of as the energetic gain associated with an additional infinitesimal increment of crack extension, while G R {\displaystyle G_{R}} can be thought of as the energetic penalty of an additional infinitesimal increment of crack extension. At any moment in time, if G ≥ G R {\displaystyle G\geq G_{R}} then crack extension is energetically favorable. | Wiki-STEM-kaggle |
Crack growth resistance curve
A complication to this process is that in some materials, G R {\displaystyle G_{R}} is not a constant value during the crack extension process. A plot of crack growth resistance G R {\displaystyle G_{R}} versus crack extension Δ a {\displaystyle \Delta a} is called a crack growth resistance curve, or R-curve. A plot of energy release rate G {\displaystyle G} versus crack extension Δ a {\displaystyle \Delta a} for a particular loading configuration is called the driving force curve. | Wiki-STEM-kaggle |
Crack growth resistance curve
The nature of the applied driving force curve relative to the material's R-curve determines the stability of a given crack. The usage of R-curves in fracture analysis is a more complex, but more comprehensive failure criteria compared to the common failure criteria that fracture occurs when G ≥ G c {\displaystyle G\geq G_{c}} where G c {\displaystyle G_{c}} is simply a constant value called the critical energy release rate. An R-curve based failure analysis takes into account the notion that a material's resistance to fracture is not necessarily constant during crack growth. R-curves can alternatively be discussed in terms of stress intensity factors ( K ) {\displaystyle (K)} rather than energy release rates ( G ) {\displaystyle (G)} , where the R-curves can be expressed as the fracture toughness ( K I c {\displaystyle K_{Ic}} , sometimes referred to as K R {\displaystyle K_{R}} ) as a function of crack length a {\displaystyle a} . | Wiki-STEM-kaggle |
Radiation length
In materials of high atomic number (e.g. tungsten, uranium, plutonium) the electrons of energies >~10 MeV predominantly lose energy by bremsstrahlung, and high-energy photons by e+e− pair production. The characteristic amount of matter traversed for these related interactions is called the radiation length X0, usually measured in g·cm−2. It is both the mean distance over which a high-energy electron loses all but 1⁄e of its energy by bremsstrahlung, and 7⁄9 of the mean free path for pair production by a high-energy photon. It is also the appropriate length scale for describing high-energy electromagnetic cascades. | Wiki-STEM-kaggle |
Radiation length
The radiation length for a given material consisting of a single type of nucleus can be approximated by the following expression: where Z is the atomic number and A is mass number of the nucleus. For Z > 4, a good approximation is where na is the number density of the nucleus, ℏ {\displaystyle \hbar } denotes the reduced Planck constant, me is the electron rest mass, c is the speed of light, α is the fine-structure constant.For electrons at lower energies (below few tens of MeV), the energy loss by ionization is predominant. While this definition may also be used for other electromagnetic interacting particles beyond leptons and photons, the presence of the stronger hadronic and nuclear interaction makes it a far less interesting characterisation of the material; the nuclear collision length and nuclear interaction length are more relevant. Comprehensive tables for radiation lengths and other properties of materials are available from the Particle Data Group. | Wiki-STEM-kaggle |
Giant magnetoimpedance
In materials science Giant Magnetoimpedance (GMI) is the effect that occurs in some materials where an external magnetic field causes a large variation in the electrical impedance of the material. It should not be confused with the separate physical phenomenon of Giant Magnetoresistance. | Wiki-STEM-kaggle |
Viscous forces
In materials science and engineering, one is often interested in understanding the forces or stresses involved in the deformation of a material. For instance, if the material were a simple spring, the answer would be given by Hooke's law, which says that the force experienced by a spring is proportional to the distance displaced from equilibrium. Stresses which can be attributed to the deformation of a material from some rest state are called elastic stresses. In other materials, stresses are present which can be attributed to the deformation rate over time. | Wiki-STEM-kaggle |
Viscous forces
These are called viscous stresses. For instance, in a fluid such as water the stresses which arise from shearing the fluid do not depend on the distance the fluid has been sheared; rather, they depend on how quickly the shearing occurs. Viscosity is the material property which relates the viscous stresses in a material to the rate of change of a deformation (the strain rate). | Wiki-STEM-kaggle |
Viscous forces
Although it applies to general flows, it is easy to visualize and define in a simple shearing flow, such as a planar Couette flow. In the Couette flow, a fluid is trapped between two infinitely large plates, one fixed and one in parallel motion at constant speed u {\displaystyle u} (see illustration to the right). If the speed of the top plate is low enough (to avoid turbulence), then in steady state the fluid particles move parallel to it, and their speed varies from 0 {\displaystyle 0} at the bottom to u {\displaystyle u} at the top. | Wiki-STEM-kaggle |
Viscous forces
Each layer of fluid moves faster than the one just below it, and friction between them gives rise to a force resisting their relative motion. In particular, the fluid applies on the top plate a force in the direction opposite to its motion, and an equal but opposite force on the bottom plate. An external force is therefore required in order to keep the top plate moving at constant speed. | Wiki-STEM-kaggle |
Viscous forces
In many fluids, the flow velocity is observed to vary linearly from zero at the bottom to u {\displaystyle u} at the top. Moreover, the magnitude of the force, F {\displaystyle F} , acting on the top plate is found to be proportional to the speed u {\displaystyle u} and the area A {\displaystyle A} of each plate, and inversely proportional to their separation y {\displaystyle y}: F = μ A u y . {\displaystyle F=\mu A{\frac {u}{y}}.} | Wiki-STEM-kaggle |
Viscous forces
The proportionality factor is the dynamic viscosity of the fluid, often simply referred to as the viscosity. It is denoted by the Greek letter mu (μ). The dynamic viscosity has the dimensions ( m a s s / l e n g t h ) / t i m e {\displaystyle \mathrm {(mass/length)/time} } , therefore resulting in the SI units and the derived units: = k g m ⋅ s = N m 2 ⋅ s = P a ⋅ s = {\displaystyle ={\frac {\rm {kg}}{\rm {m{\cdot }s}}}={\frac {\rm {N}}{\rm {m^{2}}}}{\cdot }{\rm {s}}={\rm {Pa{\cdot }s}}=} pressure multiplied by time.The aforementioned ratio u / y {\displaystyle u/y} is called the rate of shear deformation or shear velocity, and is the derivative of the fluid speed in the direction perpendicular to the normal vector of the plates (see illustrations to the right). | Wiki-STEM-kaggle |
Viscous forces
If the velocity does not vary linearly with y {\displaystyle y} , then the appropriate generalization is: τ = μ ∂ u ∂ y , {\displaystyle \tau =\mu {\frac {\partial u}{\partial y}},} where τ = F / A {\displaystyle \tau =F/A} , and ∂ u / ∂ y {\displaystyle \partial u/\partial y} is the local shear velocity. This expression is referred to as Newton's law of viscosity. | Wiki-STEM-kaggle |
Viscous forces
In shearing flows with planar symmetry, it is what defines μ {\displaystyle \mu } . It is a special case of the general definition of viscosity (see below), which can be expressed in coordinate-free form. Use of the Greek letter mu ( μ {\displaystyle \mu } ) for the dynamic viscosity (sometimes also called the absolute viscosity) is common among mechanical and chemical engineers, as well as mathematicians and physicists. | Wiki-STEM-kaggle |
Viscous forces
However, the Greek letter eta ( η {\displaystyle \eta } ) is also used by chemists, physicists, and the IUPAC. The viscosity μ {\displaystyle \mu } is sometimes also called the shear viscosity. However, at least one author discourages the use of this terminology, noting that μ {\displaystyle \mu } can appear in non-shearing flows in addition to shearing flows. | Wiki-STEM-kaggle |
Yield (engineering)
In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed, some fraction of the deformation will be permanent and non-reversible and is known as plastic deformation. The yield strength or yield stress is a material property and is the stress corresponding to the yield point at which the material begins to deform plastically. | Wiki-STEM-kaggle |
Yield (engineering)
The yield strength is often used to determine the maximum allowable load in a mechanical component, since it represents the upper limit to forces that can be applied without producing permanent deformation. In some materials, such as aluminium, there is a gradual onset of non-linear behavior, and no precise yield point. In such a case, the offset yield point (or proof stress) is taken as the stress at which 0.2% plastic deformation occurs. | Wiki-STEM-kaggle |
Yield (engineering)
Yielding is a gradual failure mode which is normally not catastrophic, unlike ultimate failure. In solid mechanics, the yield point can be specified in terms of the three-dimensional principal stresses ( σ 1 , σ 2 , σ 3 {\displaystyle \sigma _{1},\sigma _{2},\sigma _{3}} ) with a yield surface or a yield criterion. A variety of yield criteria have been developed for different materials. | Wiki-STEM-kaggle |
Thermostability
In materials science and molecular biology, thermostability is the ability of a substance to resist irreversible change in its chemical or physical structure, often by resisting decomposition or polymerization, at a high relative temperature. Thermostable materials may be used industrially as fire retardants. A thermostable plastic, an uncommon and unconventional term, is likely to refer to a thermosetting plastic that cannot be reshaped when heated, than to a thermoplastic that can be remelted and recast. Thermostability is also a property of some proteins. To be a thermostable protein means to be resistant to changes in protein structure due to applied heat. | Wiki-STEM-kaggle |
Poisson's Ratio
In materials science and solid mechanics, Poisson's ratio ν {\displaystyle \nu } (nu) is a measure of the Poisson effect, the deformation (expansion or contraction) of a material in directions perpendicular to the specific direction of loading. The value of Poisson's ratio is the negative of the ratio of transverse strain to axial strain. For small values of these changes, ν {\displaystyle \nu } is the amount of transversal elongation divided by the amount of axial compression. Most materials have Poisson's ratio values ranging between 0.0 and 0.5. | Wiki-STEM-kaggle |
Poisson's Ratio
For soft materials, such as rubber, where the bulk modulus is much higher than the shear modulus, Poisson's ratio is near 0.5. For open-cell polymer foams, Poisson's ratio is near zero, since the cells tend to collapse in compression. Many typical solids have Poisson's ratios in the range of 0.2–0.3. The ratio is named after the French mathematician and physicist Siméon Poisson. | Wiki-STEM-kaggle |
Rule of mixtures
In materials science, a general rule of mixtures is a weighted mean used to predict various properties of a composite material . It provides a theoretical upper- and lower-bound on properties such as the elastic modulus, ultimate tensile strength, thermal conductivity, and electrical conductivity. In general there are two models, one for axial loading (Voigt model), and one for transverse loading (Reuss model).In general, for some material property E {\displaystyle E} (often the elastic modulus), the rule of mixtures states that the overall property in the direction parallel to the fibers may be as high as E c = f E f + ( 1 − f ) E m {\displaystyle E_{c}=fE_{f}+\left(1-f\right)E_{m}} where f = V f V f + V m {\displaystyle f={\frac {V_{f}}{V_{f}+V_{m}}}} is the volume fraction of the fibers E f {\displaystyle E_{f}} is the material property of the fibers E m {\displaystyle E_{m}} is the material property of the matrixIt is a common mistake to believe that this is the upper-bound modulus for Young's modulus. | Wiki-STEM-kaggle |
Rule of mixtures
The real upper-bound Young's modulus is larger than E c {\displaystyle E_{c}} given by this formula. Even if both constituents are isotropic, the real upper bound is E c {\displaystyle E_{c}} plus a term in the order of square of the difference of the Poisson's ratios of the two constituents.The inverse rule of mixtures states that in the direction perpendicular to the fibers, the elastic modulus of a composite can be as low as E c = ( f E f + 1 − f E m ) − 1 . {\displaystyle E_{c}=\left({\frac {f}{E_{f}}}+{\frac {1-f}{E_{m}}}\right)^{-1}.} If the property under study is the elastic modulus, this quantity is called the lower-bound modulus, and corresponds to a transverse loading. | Wiki-STEM-kaggle |
Polymer blend
In materials science, a polymer blend, or polymer mixture, is a member of a class of materials analogous to metal alloys, in which at least two polymers are blended together to create a new material with different physical properties. | Wiki-STEM-kaggle |
Precipitate-free zone
In materials science, a precipitate-free zone (PFZ) refers to microscopic localized regions around grain boundaries that are free of precipitates (solid impurities forced outwards from the grain during crystallization). It is a common phenomenon that arises in polycrystalline materials (crystalline materials with stochastically-oriented grains) where heterogeneous nucleation of precipitates is the dominant nucleation mechanism. This is because grain boundaries are high-energy surfaces that act as sinks for vacancies, causing regions adjacent to a grain boundary to be devoid of vacancies. As it is energetically favorable for heterogeneous nucleation to occur preferentially around defect-rich sites such as vacancies, nucleation of precipitates is impeded in the vacancy-free regions immediately adjacent to grain boundaries | Wiki-STEM-kaggle |
Sandwich structured composite
In materials science, a sandwich-structured composite is a special class of composite materials that is fabricated by attaching two thin-but-stiff skins to a lightweight but thick core. The core material is normally low strength, but its higher thickness provides the sandwich composite with high bending stiffness with overall low density. Open- and closed-cell-structured foams like polyethersulfone, polyvinylchloride, polyurethane, polyethylene or polystyrene foams, balsa wood, syntactic foams, and honeycombs are commonly used core materials. | Wiki-STEM-kaggle |
Sandwich structured composite
Sometimes, the honeycomb structure is filled with other foams for added strength. Open- and closed-cell metal foam can also be used as core materials. Laminates of glass or carbon fiber-reinforced thermoplastics or mainly thermoset polymers (unsaturated polyesters, epoxies...) are widely used as skin materials. Sheet metal is also used as skin material in some cases. The core is bonded to the skins with an adhesive or with metal components by brazing together. | Wiki-STEM-kaggle |
Thermosetting polymer
In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening ("curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and may be promoted by high pressure, or mixing with a catalyst. Heat is not necessarily applied externally, but is often generated by the reaction of the resin with a curing agent (catalyst, hardener). Curing results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble polymer network. | Wiki-STEM-kaggle |
Thermosetting polymer
The starting material for making thermosets is usually malleable or liquid prior to curing, and is often designed to be molded into the final shape. It may also be used as an adhesive. Once hardened, a thermoset cannot be melted for reshaping, in contrast to thermoplastic polymers which are commonly produced and distributed in the form of pellets, and shaped into the final product form by melting, pressing, or injection molding. | Wiki-STEM-kaggle |
Interstitial defect
In materials science, an interstitial defect is a type of point crystallographic defect where an atom of the same or of a different type, occupies an interstitial site in the crystal structure. When the atom is of the same type as those already present they are known as a self-interstitial defect. Alternatively, small atoms in some crystals may occupy interstitial sites, such as hydrogen in palladium. Interstitials can be produced by bombarding a crystal with elementary particles having energy above the displacement threshold for that crystal, but they may also exist in small concentrations in thermodynamic equilibrium. The presence of interstitial defects can modify the physical and chemical properties of a material. | Wiki-STEM-kaggle |
Asperity (material science)
In materials science, asperity, defined as "unevenness of surface, roughness, ruggedness" (from the Latin asper—"rough"), has implications (for example) in physics and seismology. Smooth surfaces, even those polished to a mirror finish, are not truly smooth on a microscopic scale. They are rough, with sharp, rough or rugged projections, termed "asperities". Surface asperities exist across multiple scales, often in a self affine or fractal geometry. | Wiki-STEM-kaggle |
Asperity (material science)
The fractal dimension of these structures has been correlated with the contact mechanics exhibited at an interface in terms of friction and contact stiffness. When two macroscopically smooth surfaces come into contact, initially they only touch at a few of these asperity points. These cover only a very small portion of the surface area. | Wiki-STEM-kaggle |
Asperity (material science)
Friction and wear originate at these points, and thus understanding their behavior becomes important when studying materials in contact. When the surfaces are subjected to a compressive load, the asperities deform through elastic and plastic modes, increasing the contact area between the two surfaces until the contact area is sufficient to support the load. The relationship between frictional interactions and asperity geometry is complex and poorly understood. It has been reported that an increased roughness may under certain circumstances result in weaker frictional interactions while smoother surfaces may in fact exhibit high levels of friction owing to high levels of true contact.The Archard equation provides a simplified model of asperity deformation when materials in contact are subject to a force. Due to the ubiquitous presence of deformable asperities in self affine hierarchical structures, the true contact area at an interface exhibits a linear relationship with the applied normal load. | Wiki-STEM-kaggle |
Bulk density
In materials science, bulk density, also called apparent density or volumetric density, is a property of powders, granules, and other "divided" solids, especially used in reference to mineral components (soil, gravel), chemical substances, pharmaceutical ingredients, foodstuff, or any other masses of corpuscular or particulate matter (particles). Bulk density is defined as the mass of the many particles of the material divided by the total volume they occupy. The total volume includes particle volume, inter-particle void volume, and internal pore volume.Bulk density is not an intrinsic property of a material; it can change depending on how the material is handled. For example, a powder poured into a cylinder will have a particular bulk density; if the cylinder is disturbed, the powder particles will move and usually settle closer together, resulting in a higher bulk density. For this reason, the bulk density of powders is usually reported both as "freely settled" (or "poured" density) and "tapped" density (where the tapped density refers to the bulk density of the powder after a specified compaction process, usually involving vibration of the container.) In contrast, particle density is an intrinsic property of the solid and does not include the volume for voids between particles. | Wiki-STEM-kaggle |
Friction force microscopy
In materials science, chemical force microscopy (CFM) is a variation of atomic force microscopy (AFM) which has become a versatile tool for characterization of materials surfaces. With AFM, structural morphology is probed using simple tapping or contact modes that utilize van der Waals interactions between tip and sample to maintain a constant probe deflection amplitude (constant force mode) or maintain height while measuring tip deflection (constant height mode). CFM, on the other hand, uses chemical interactions between functionalized probe tip and sample. Choice chemistry is typically gold-coated tip and surface with R−SH thiols attached, R being the functional groups of interest. | Wiki-STEM-kaggle |
Friction force microscopy
CFM enables the ability to determine the chemical nature of surfaces, irrespective of their specific morphology, and facilitates studies of basic chemical bonding enthalpy and surface energy. Typically, CFM is limited by thermal vibrations within the cantilever holding the probe. This limits force measurement resolution to ~1 pN which is still very suitable considering weak COOH/CH3 interactions are ~20 pN per pair. Hydrophobicity is used as the primary example throughout this consideration of CFM, but certainly any type of bonding can be probed with this method. | Wiki-STEM-kaggle |
Creep (deformation)
In materials science, creep (sometimes called cold flow) is the tendency of a solid material to undergo slow deformation while subject to persistent mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods and generally increase as they near their melting point. The rate of deformation is a function of the material's properties, exposure time, exposure temperature and the applied structural load. | Wiki-STEM-kaggle |
Creep (deformation)
Depending on the magnitude of the applied stress and its duration, the deformation may become so large that a component can no longer perform its function – for example creep of a turbine blade could cause the blade to contact the casing, resulting in the failure of the blade. Creep is usually of concern to engineers and metallurgists when evaluating components that operate under high stresses or high temperatures. Creep is a deformation mechanism that may or may not constitute a failure mode. | Wiki-STEM-kaggle |
Creep (deformation)
For example, moderate creep in concrete is sometimes welcomed because it relieves tensile stresses that might otherwise lead to cracking. Unlike brittle fracture, creep deformation does not occur suddenly upon the application of stress. Instead, strain accumulates as a result of long-term stress. Therefore, creep is a "time-dependent" deformation. | Wiki-STEM-kaggle |
Critical resolved shear stress
In materials science, critical resolved shear stress (CRSS) is the component of shear stress, resolved in the direction of slip, necessary to initiate slip in a grain. Resolved shear stress (RSS) is the shear component of an applied tensile or compressive stress resolved along a slip plane that is other than perpendicular or parallel to the stress axis. The RSS is related to the applied stress by a geometrical factor, m, typically the Schmid factor: τ RSS = σ app m = σ app ( cos ϕ cos λ ) {\displaystyle \tau _{\text{RSS}}=\sigma _{\text{app}}m=\sigma _{\text{app}}(\cos \phi \cos \lambda )} where σapp is the magnitude of the applied tensile stress, Φ is the angle between the normal of the slip plane and the direction of the applied force, and λ is the angle between the slip direction and the direction of the applied force. The Schmid factor is most applicable to FCC single-crystal metals, but for polycrystal metals the Taylor factor has been shown to be more accurate. | Wiki-STEM-kaggle |
Critical resolved shear stress
The CRSS is the value of resolved shear stress at which yielding of the grain occurs, marking the onset of plastic deformation. CRSS, therefore, is a material property and is not dependent on the applied load or grain orientation. The CRSS is related to the observed yield strength of the material by the maximum value of the Schmid factor: σ y = τ CRSS m max {\displaystyle \sigma _{y}={\frac {\tau _{\text{CRSS}}}{m_{\text{max}}}}} CRSS is a constant for crystal families. Hexagonal close-packed crystals, for example, have three main families - basal, prismatic, and pyramidal - with different values for the critical resolved shear stress. | Wiki-STEM-kaggle |
Dispersion (materials science)
In materials science, dispersion is the fraction of atoms of a material exposed to the surface. In general, D = NS/N, where D is the dispersion, NS is the number of surface atoms and NT is the total number of atoms of the material. It is an important concept in heterogeneous catalysis, since only atoms exposed to the surface can affect catalytic surface reactions. Dispersion increases with decreasing crystallite size and approaches unity at a crystallite diameter of about 0.1 nm. | Wiki-STEM-kaggle |
Fast ion conductor
In materials science, fast ion conductors are solid conductors with highly mobile ions. These materials are important in the area of solid state ionics, and are also known as solid electrolytes and superionic conductors. These materials are useful in batteries and various sensors. | Wiki-STEM-kaggle |
Fast ion conductor
Fast ion conductors are used primarily in solid oxide fuel cells. As solid electrolytes they allow the movement of ions without the need for a liquid or soft membrane separating the electrodes. The phenomenon relies on the hopping of ions through an otherwise rigid crystal structure. | Wiki-STEM-kaggle |
Fracture toughening mechanisms
In materials science, fracture toughness is the critical stress intensity factor of a sharp crack where propagation of the crack suddenly becomes rapid and unlimited. A component's thickness affects the constraint conditions at the tip of a crack with thin components having plane stress conditions and thick components having plane strain conditions. Plane strain conditions give the lowest fracture toughness value which is a material property. The critical value of stress intensity factor in mode I loading measured under plane strain conditions is known as the plane strain fracture toughness, denoted K Ic {\displaystyle K_{\text{Ic}}} . | Wiki-STEM-kaggle |
Fracture toughening mechanisms
When a test fails to meet the thickness and other test requirements that are in place to ensure plane strain conditions, the fracture toughness value produced is given the designation K c {\displaystyle K_{\text{c}}} . Fracture toughness is a quantitative way of expressing a material's resistance to crack propagation and standard values for a given material are generally available. Slow self-sustaining crack propagation known as stress corrosion cracking, can occur in a corrosive environment above the threshold K Iscc {\displaystyle K_{\text{Iscc}}} and below K Ic {\displaystyle K_{\text{Ic}}} . Small increments of crack extension can also occur during fatigue crack growth, which after repeated loading cycles, can gradually grow a crack until final failure occurs by exceeding the fracture toughness. | Wiki-STEM-kaggle |
Grain growth
In materials science, grain growth is the increase in size of grains (crystallites) in a material at high temperature. This occurs when recovery and recrystallisation are complete and further reduction in the internal energy can only be achieved by reducing the total area of grain boundary. The term is commonly used in metallurgy but is also used in reference to ceramics and minerals. The behaviors of grain growth is analogous to the coarsening behaviors of grains, which implied that both of grain growth and coarsening may be dominated by the same physical mechanism. | Wiki-STEM-kaggle |
Hardness tester
In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard metals such as titanium and beryllium are harder than soft metals such as sodium and metallic tin, or wood and common plastics. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, hardness can be measured in different ways, such as scratch hardness, indentation hardness, and rebound hardness. Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity. Common examples of hard matter are ceramics, concrete, certain metals, and superhard materials, which can be contrasted with soft matter. | Wiki-STEM-kaggle |
Paracrystallinity
In materials science, paracrystalline materials are defined as having short- and medium-range ordering in their lattice (similar to the liquid crystal phases) but lacking crystal-like long-range ordering at least in one direction. | Wiki-STEM-kaggle |
Polymorphism (crystallography)
In materials science, polymorphism describes the existence of a solid material in more than one form or crystal structure. Polymorphism is a form of isomerism. Any crystalline material can exhibit the phenomenon. Allotropy refers to polymorphism for chemical elements. | Wiki-STEM-kaggle |
Polymorphism (crystallography)
Polymorphism is of practical relevance to pharmaceuticals, agrochemicals, pigments, dyestuffs, foods, and explosives. According to IUPAC, a polymorphic transition is "A reversible transition of a solid crystalline phase at a certain temperature and pressure (the inversion point) to another phase of the same chemical composition with a different crystal structure." According to McCrone, polymorphs are "different in crystal structure but identical in the liquid or vapor states." Materials with two polymorphs are called dimorphic, with three polymorphs, trimorphic, etc.In some cases, polymorphism was "discovered" on a computer by crystal structure prediction first, before chemists actually synthesize the crystal in the lab. | Wiki-STEM-kaggle |
Recrystallization temperature
In materials science, recrystallization is a process by which deformed grains are replaced by a new set of defect-free grains that nucleate and grow until the original grains have been entirely consumed. Recrystallization is usually accompanied by a reduction in the strength and hardness of a material and a simultaneous increase in the ductility. Thus, the process may be introduced as a deliberate step in metals processing or may be an undesirable byproduct of another processing step. The most important industrial uses are softening of metals previously hardened or rendered brittle by cold work, and control of the grain structure in the final product. Recrystallization temperature is typically 0.3–0.4 times the melting point for pure metals and 0.5 times for alloys. | Wiki-STEM-kaggle |
Reinforcement (composite)
In materials science, reinforcement is a constituent of a composite material which increases the composite's stiffness and tensile strength. | Wiki-STEM-kaggle |
Segregation in materials
In materials science, segregation is the enrichment of atoms, ions, or molecules at a microscopic region in a materials system. While the terms segregation and adsorption are essentially synonymous, in practice, segregation is often used to describe the partitioning of molecular constituents to defects from solid solutions, whereas adsorption is generally used to describe such partitioning from liquids and gases to surfaces. The molecular-level segregation discussed in this article is distinct from other types of materials phenomena that are often called segregation, such as particle segregation in granular materials, and phase separation or precipitation, wherein molecules are segregated in to macroscopic regions of different compositions. Segregation has many practical consequences, ranging from the formation of soap bubbles, to microstructural engineering in materials science, to the stabilization of colloidal suspensions. | Wiki-STEM-kaggle |
Segregation in materials
Segregation can occur in various materials classes. In polycrystalline solids, segregation occurs at defects, such as dislocations, grain boundaries, stacking faults, or the interface between two phases. In liquid solutions, chemical gradients exist near second phases and surfaces due to combinations of chemical and electrical effects. Segregation which occurs in well-equilibrated systems due to the instrinsic chemical properties of the system is termed equilibrium segregation. Segregation that occurs due to the processing history of the sample (but that would disappear at long times) is termed non-equilibrium segregation. | Wiki-STEM-kaggle |
Modulus of rigidity
In materials science, shear modulus or modulus of rigidity, denoted by G, or sometimes S or μ, is a measure of the elastic shear stiffness of a material and is defined as the ratio of shear stress to the shear strain: G = d e f τ x y γ x y = F / A Δ x / l = F l A Δ x {\displaystyle G\ {\stackrel {\mathrm {def} }{=}}\ {\frac {\tau _{xy}}{\gamma _{xy}}}={\frac {F/A}{\Delta x/l}}={\frac {Fl}{A\Delta x}}} where τ x y = F / A {\displaystyle \tau _{xy}=F/A\,} = shear stress F {\displaystyle F} is the force which acts A {\displaystyle A} is the area on which the force acts γ x y {\displaystyle \gamma _{xy}} = shear strain. In engineering := Δ x / l = tan θ {\displaystyle :=\Delta x/l=\tan \theta } , elsewhere := θ {\displaystyle :=\theta } Δ x {\displaystyle \Delta x} is the transverse displacement l {\displaystyle l} is the initial length of the area.The derived SI unit of shear modulus is the pascal (Pa), although it is usually expressed in gigapascals (GPa) or in thousand pounds per square inch (ksi). Its dimensional form is M1L−1T−2, replacing force by mass times acceleration. | Wiki-STEM-kaggle |
Slip (materials science)
In materials science, slip is the large displacement of one part of a crystal relative to another part along crystallographic planes and directions. Slip occurs by the passage of dislocations on close/packed planes, which are planes containing the greatest number of atoms per area and in close-packed directions (most atoms per length). Close-packed planes are known as slip or glide planes. | Wiki-STEM-kaggle |
Slip (materials science)
A slip system describes the set of symmetrically identical slip planes and associated family of slip directions for which dislocation motion can easily occur and lead to plastic deformation. The magnitude and direction of slip are represented by the Burgers vector, b. An external force makes parts of the crystal lattice glide along each other, changing the material's geometry. A critical resolved shear stress is required to initiate a slip. | Wiki-STEM-kaggle |
Superplastic deformation
In materials science, superplasticity is a state in which solid crystalline material is deformed well beyond its usual breaking point, usually over about 400% during tensile deformation. Such a state is usually achieved at high homologous temperature. Examples of superplastic materials are some fine-grained metals and ceramics. Other non-crystalline materials (amorphous) such as silica glass ("molten glass") and polymers also deform similarly, but are not called superplastic, because they are not crystalline; rather, their deformation is often described as Newtonian fluid. | Wiki-STEM-kaggle |
Superplastic deformation
Superplastically deformed material gets thinner in a very uniform manner, rather than forming a "neck" (a local narrowing) that leads to fracture. Also, the formation of microvoids, which is another cause of early fracture, is inhibited. Superplasticity must not be confused with superelasticity. | Wiki-STEM-kaggle |
Charpy test
In materials science, the Charpy impact test, also known as the Charpy V-notch test, is a standardized high strain rate test which determines the amount of energy absorbed by a material during fracture. Absorbed energy is a measure of the material's notch toughness. It is widely used in industry, since it is easy to prepare and conduct and results can be obtained quickly and cheaply. | Wiki-STEM-kaggle |
Charpy test
A disadvantage is that some results are only comparative. The test was pivotal in understanding the fracture problems of ships during World War II.The test was developed around 1900 by S. B. Russell (1898, American) and Georges Charpy (1901, French). The test became known as the Charpy test in the early 1900s due to the technical contributions and standardization efforts by Charpy. | Wiki-STEM-kaggle |
Sol–gel process
In materials science, the sol–gel process is a method for producing solid materials from small molecules. The method is used for the fabrication of metal oxides, especially the oxides of silicon (Si) and titanium (Ti). The process involves conversion of monomers into a colloidal solution (sol) that acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers. Typical precursors are metal alkoxides. Sol-gel process is used to produce ceramic nanoparticles. | Wiki-STEM-kaggle |
Two dimensional (2D) nanomaterials
In materials science, the term single-layer materials or 2D materials refers to crystalline solids consisting of a single layer of atoms. These materials are promising for some applications but remain the focus of research. Single-layer materials derived from single elements generally carry the -ene suffix in their names, e.g. graphene. Single-layer materials that are compounds of two or more elements have -ane or -ide suffixes. | Wiki-STEM-kaggle |
Two dimensional (2D) nanomaterials
2D materials can generally be categorized as either 2D allotropes of various elements or as compounds (consisting of two or more covalently bonding elements). It is predicted that there are hundreds of stable single-layer materials. | Wiki-STEM-kaggle |
Two dimensional (2D) nanomaterials
The atomic structure and calculated basic properties of these and many other potentially synthesisable single-layer materials, can be found in computational databases. 2D materials can be produced using mainly two approaches: top-down exfoliation and bottom-up synthesis. The exfoliation methods include sonication, mechanical, hydrothermal, electrochemical, laser-assisted, and microwave-assisted exfoliation. | Wiki-STEM-kaggle |
Threshold displacement energy
In materials science, the threshold displacement energy (Td) is the minimum kinetic energy that an atom in a solid needs to be permanently displaced from its site in the lattice to a defect position. It is also known as "displacement threshold energy" or just "displacement energy". In a crystal, a separate threshold displacement energy exists for each crystallographic direction. | Wiki-STEM-kaggle |
Threshold displacement energy
Then one should distinguish between the minimum (Td,min) and average (Td,ave) over all lattice directions' threshold displacement energies. In amorphous solids, it may be possible to define an effective displacement energy to describe some other average quantity of interest. Threshold displacement energies in typical solids are of the order of 10-50 eV. | Wiki-STEM-kaggle |
Yield strength anomaly
In materials science, the yield strength anomaly refers to materials wherein the yield strength (i.e., the stress necessary to initiate plastic yielding) increases with temperature. For the majority of materials, the yield strength decreases with increasing temperature. In metals, this decrease in yield strength is due to the thermal activation of dislocation motion, resulting in easier plastic deformation at higher temperatures.In some cases, a yield strength anomaly refers to a decrease in the ductility of a material with increasing temperature, which is also opposite the trend in the majority of materials. Anomalies in ductility can be more clear, as an anomalous effect on yield strength can be obscured by its typical decrease with temperature. | Wiki-STEM-kaggle |
Yield strength anomaly
In concert with yield strength or ductility anomalies, some materials demonstrate extrema in other temperature dependent properties, such as a minimum in ultrasonic damping, or a maximum in electrical conductivity.The yield strength anomaly in β-brass was one of the earliest discoveries such a phenomenon, and several other ordered intermetallic alloys demonstrate this effect. Precipitation-hardened superalloys exhibit a yield strength anomaly over a considerable temperature range. For these materials, the yield strength shows little variation between room temperature and several hundred degrees Celsius. | Wiki-STEM-kaggle |
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