Ablation
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The removal of material from the surface of an object by vaporisation, chipping, or other erosive processes. The term occurs in space physics associated with atmospheric reentry, in glaciology, medicine and passive fire protection. In space vehicle design, ablation is used to both cool and protect mechanical parts and/or payloads that would otherwise be adversely affected by extremely high temperatures.
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Abrasion
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The process of scuffing, scratching, wearing down, marring, or rubbing away. It can be intentionally imposed in a controlled process using an abrasive.
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Absorption (EM radiation)
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The process by which the energy of a photon is taken up by matter, typically the electrons of an atom. The electromagnetic energy is transformed to another form of energy, e.g. to heat.
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Aerobic Digestion
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A series of processes in which microorganisms break down biodegradable material in the presence of oxygen
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Anaerobic Digestion
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A series of processes in which microorganisms break down biodegradable material in the absence of oxygen. It is widely used to treat wastewater sludges and organic wastes because it provides volume and mass reduction of the input material.
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Catalysis
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The process in which the rate of a chemical reaction is increased by means of a chemical substance known as a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed. Catalysts work by lowering the activation energy for a reaction, thus dramatically increasing the rate of the reaction. As a result, products are formed faster and reactions reach their equilibrium state more rapidly.
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Combustion
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(or burning) A complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames. Direct combustion by atmospheric oxygen is a reaction mediated by radical intermediates typically produced as a result of thermal runaway, where the heat generated by combustion is necessary to maintain the high temperature necessary for radical production.
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Composting
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The aerobic decomposition of biodegradable organic matter, producing compost. The decomposition is performed primarily by facultative and obligate aerobic bacteria, yeasts and fungi, helped in the cooler initial and ending phases by a number of larger organisms, such as springtails, ants, nematodes and oligochaete worms.
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Cryogenics
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The behavior of materials at very low temperatures (typically below -150 °C, -238 °F or 123 K).
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Cryolysis
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Destruction by cold (usually in a medical context)
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Decomposition (biological)
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The break down of tissue of a formerly living organism into simpler forms of matter.
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Deflagration
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A technical term describing subsonic combustion that usually propagates through thermal conductivity (hot burning material heats the next layer of cold material and ignites it). Most 'fire' found in daily life, from flames to explosions, is technically deflagration. Deflagration is different from detonation (which is supersonic and propagates through shock compression).
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Detonation
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Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases.
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Eddy Currents
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An electrical phenomenon caused when a conductor is exposed to a changing magnetic field due to relative motion of the field source and conductor; or due to variations of the field with time. This can cause eddys of circulating current within the conductor which create electromagnets with magnetic fields that opposes the change of the magnetic field.
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Through inductive heating
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Electric Arc
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An electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air
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Electrohydrogenesis
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Electrohydrogenesis or biocatalyzed electrolysis is the name given to a process for generating hydrogen gas from organic matter being decomposed by bacteria.
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Electromagnetic Induction
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The generation of electromotive force (EMF) in a current-carrying conductor exposed to a changing magnetic field
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Through inductive heating.
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Electron Beam
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(also called Cathode Rays or e-beam) are streams of electrons observed in vacuum tubes, i.e. evacuated glass tubes that are equipped with at least two metal electrodes to which a voltage is applied, a cathode or negative electrode and an anode or positive electrode.
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Electron Impact Desorption
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Desorption arising from electron-impact induced adsorbate surface bond breaking. Molecules on surfaces may also be chemically converted to other species by electron impact
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Electrostatic Discharge
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The sudden and momentary electric current that flows between two objects at different electrical potentials
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Enzyme
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Proteins that catalyze (i.e., increase the rates of) chemical reactions. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates sufficient for life. Enzymes differ from most other catalysts in that they are highly specific for their substrates
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Erosion
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The process of weathering and transport of solids (sediment, soil, rock and other particles) in the natural environment or their source and deposits them elsewhere. It usually occurs due to transport by wind, water, or ice; by down-slope creep of soil and other material under the force of gravity; or by living organisms, such as burrowing animals, in the case of bioerosion.
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Exothermic Reaction
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An exothermic reaction is a chemical reaction accompanied by the release of heat. In other words, the energy needed for the reaction to occur is less than the total energy released. As a result of this, the extra energy is released, usually in the form of heat.
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Explosion
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A sudden increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases.
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Explosive Lens
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A device composed of several explosive charges that are shaped in such a way as to change the shape of the detonation wave passing through it; conceptually similar to the effect of an optical lens on light
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Fatigue
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The progressive and localised structural damage that occurs when a material is subjected to cyclic loading. The maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.
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Fermentation
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In an industrial context, fermentation refers to the breakdown of organic substances and re-assembly into other substances. Somewhat paradoxically, fermenter culture in industrial capacity often refers to highly oxygenated and aerobic growth conditions, whereas fermentation in the biochemical context is a strictly anaerobic process.
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Force
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That which can cause an object with mass to accelerate. Force has both magnitude & direction, i.e. it's a vector quantity. An object with constant mass will accelerate in proportion to the net force acting upon it and in inverse proportion to its mass (or the net force on an object is equal to the rate of change of momentum it experiences). Forces acting on objects may cause them to rotate or deform, or result in a change in pressure.
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Freezing
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A phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. Colloquially it is applied to water, but technically it applies to any liquid. All known liquids, except liquid helium, freeze when the temperature is lowered enough.
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Friction
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The force resisting the relative motion of two surfaces in contact or a surface in contact with a fluid (e.g. air on an aircraft or water in a pipe).
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Gear
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A gear (or more correctly a gear wheel) is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine. Geared devices can change the speed, magnitude, and direction of a power source.
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By crushing between gear wheels.
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Heating
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The act of increasing temperature.
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Hydrogen Peroxide
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(H2O2) A very pale blue liquid which appears colorless in a dilute solution, slightly more viscous than water. It is a weak acid. It has strong oxidizing properties and is therefore a powerful bleaching agent that has also found use as a disinfectant, as an oxidizer, as an antiseptic, and in rocketry. The oxidizing capacity of hydrogen peroxide is so strong that the chemical is considered a highly reactive oxygen species.
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Hydrogenation
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Hydrogenation is the chemical reaction that results from the addition of hydrogen. The process is usually employed to a reduce or saturate organic compounds. The process typically constitutes the addition of pairs of hydrogen atoms to a molecule.
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Impact Force
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A high force or shock applied over a short time period. Such a force or acceleration can sometimes have a greater effect than a lower force applied over a proportionally longer time period.
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Infrared Radiation
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Infrared (IR) radiation is electromagnetic radiation whose wavelength is longer than that of visible light (400-700 nm), but shorter than that of terahertz radiation (3-300 µm) and microwaves (~30,000 µm). Infrared radiation spans roughly three orders of magnitude (750 nm and 1000 µm).
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Ionisation
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The physical process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions.
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Jet Erosion
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A method of cutting or slicing a material using a jet of liquid or gas at high velocity and pressure, or a mixture of liquid/gas and an abrasive substance.
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Laser
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A device that emits light (electromagnetic radiation) through a process called stimulated emission.
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Laser Ablation
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The process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, but it is possible to ablate material with a continuous wave laser beam if the laser intensity is high enough.
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Light
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Light is electromagnetic radiation of a wavelength that is visible to the human eye (in a range from about 380 or 400 nanometres to about 760 or 780 nm)
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Using a high-power light source or a target susceptible to light.
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Nuclear Fission
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The splitting of the nucleus of an atom into parts (lighter nuclei) often producing free neutrons and other smaller nuclei, which may eventually produce photons (in the form of gamma rays). Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place).
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Nuclear Fusion
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The generation of power by the fusing together of atomic nuclei to form a heavier nucleus.
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Oxidation
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A chemical reaction that involves the loss of electrons or an increase in the oxidation state by a molecule, atom or ion.
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Ozone
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Ozone (O3), or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope (O2).
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Photo-oxidation
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Oxidation facilitated radiant energy such as UV or artificial light. This process is often the most significant component of weather degradation of polymers.
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Photodissociation
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A chemical reaction in which a chemical compound is broken down by photons. Any photon with sufficient energy can affect the chemical bonds of a chemical compound. Since a photon's energy is inversely proportional to its wavelength, electromagnetic waves with the energy of visible light or higher, such as ultraviolet light, x-rays and gamma rays are usually involved in such reactions.
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Plasma
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A partially ionized gas, in which a certain proportion of electrons are free rather than being bound to an atom or molecule. The ability of the positive and negative charges to move somewhat independently makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma therefore has properties quite unlike those of solids, liquids or gases and is considered to be a distinct state of matter.
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Pressure Drop
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Pressure is an effect which occurs when a force is applied on a surface. Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point. Rapid pressure drop is a useful technique for applying force or breaking objects apart.
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Pressure Increase
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Pressure is an effect which occurs when a force is applied on a surface. Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point.
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Pulsed Magnet
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Pulsed magnets can generate field strengths far in excess of conventional magnets. They come in two types: destructive and non-destructive.
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Pyrolysis
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A thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. Pyrolysis typically occurs under pressure and at operating temperatures above 430 °C (800 °F). Pyrolysis is a special case of thermolysis.
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Pyrophoricity
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A pyrophoric substance ignites spontaneously in air at or below 55 degrees centigrade. The creation of sparks from metals is based on the pyrophoricity of small metal particles. The sparking mechanism in cigarette lighters is an example. Some liquids and gases are phyrophoric.
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Radiation
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A process in which energetic particles or waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing.
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Radioactive Decay
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The process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation.
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Redox Reactions
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Redox (shorthand for oxidation-reduction) reactions describe all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of sugar(C6H12O6) in the human body through a series of complex electron transfer processes.
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Reduction
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A chemical reaction that involves the gain of electrons or a decrease in the oxidation state by a molecule, atom or ion.
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Resonance
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The tendency of a system to oscillate with larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies. At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.
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Roller
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A cylindrical device that rotates around its principle axis, typically to perform useful work, such as the compression of sheet metal between a pair of rollers.
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Shaking
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Moving something rapidly from side to side.
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Shock Wave
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A type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium (solid, liquid, gas or plasma) or through a field such as the electromagnetic field. Characterized by an abrupt, nearly discontinuous change in the characteristics of the medium. Associated with rapid rise in pressure, temperature and density of the flow. A shock wave travels through most media at a higher speed than an ordinary wave.
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Sol
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A colloidal suspension of solid particles (1-500 nanometres in size) in a liquid. Examples include blood, pigmented ink, and paint.
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Solar Energy
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Collection or use of energy from the Sun.
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Sonochemistry
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The effect of sonic waves and wave properties on chemical systems. Sonochemistry arises from acoustic cavitation: the formation, growth, and implosive collapse of bubbles in a liquid. This is demonstrated in phenomena such as ultrasound, sonication, sonoluminescence, and sonic cavitation.
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Sputtering
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A process whereby atoms are ejected from a solid target material due to bombardment of the target by energetic ions. It is commonly used for thin-film deposition, etching and analytical techniques
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Thermal Radiation
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Electromagnetic radiation emitted from the surface of an object due to the object's temperature.
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Thermal Shock
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Cracking as a result of rapid temperature change. Thermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts. This differential expansion can be understood in terms of stress or of strain, equivalently. At some point, this stress overcomes the strength of the material, causing a crack to form. If nothing stops this crack from propagating through the material, it will cause the object's structure to fail.
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Thermolysis
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(or Thermal decomposition) A chemical decomposition caused by heat. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion.
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Wear
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The erosion of material from a solid surface by the action of another surface.
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Weathering
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The breaking down of Earth's rocks, soils and minerals through direct contact with the planet's atmosphere. Weathering occurs in situ, or 'with no movement', and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, wind, and gravity.
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Wind Power
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The conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, wind mills for mechanical power, wind pumps for pumping water or drainage, or sails to propel ships.
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