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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By removal of dirt or other unwanted material by abrasion.
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Acoustic Cavitation
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Cavitation induced by an acoustic field. Microscopic gas bubbles which are generally present in a liquid will be forced to oscillate due to an applied acoustic field. If the acoustic intensity is sufficiently high, the bubbles will first grow in size, and then rapidly collapse. High power ultrasonics usually use the inertial cavitation of microscopic vacuum bubbles for treatment of surfaces, liquids and slurries.
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Adsorption
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A process that occurs when a gas or liquid solute accumulates on the surface of a solid or a liquid (adsorbent), forming a film of molecules or atoms (the adsorbate). Most industrial adsorbents fall into one of three classes: 1. Oxygen-containing compounds (e.g.silica gel and zeolites 2. Carbon-based compounds (e.g. activated carbon and graphite) 3. Polymer-based compounds
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By adsorbing surface contaminants onto an adsorbent material. For example, wiping a surface with a cloth or sponge to remove moisture and/or dirt.
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Amphiphiles
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A chemical compound possessing both hydrophilic and hydrophobic properties. Common amphiphilic substances are soap and detergent.
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Capillary Action
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(capillarity, capillary motion, wicking) The movement of a liquid relative to a substance in contact. A result of the adhesive intermolecular forces between the liquid and the substance being stronger (or weaker) than the cohesive intermolecular forces inside the liquid. Causes a concave (or concave) meniscus to form where the liquid touches the surface. Can cause raising or lowering (e.g. mercury in glass) of the liquid.
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By removing an unwanted liquid from a solid.
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Cavitation
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The formation of vapour bubbles in a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure. Usually divided into two classes of behavior. Inertial (or transient) cavitation occurs when a void or bubble in a liquid rapidly collapses, producing a shock wave. Non-inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to energy input, e.g. acoustic field.
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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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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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By burning off unwanted material.
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Desorption
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A phenomenon whereby a substance is released from or through a surface. The process is the opposite of sorption (i.e adsorption and absorption). This occurs in a system being in the state of sorption equilibrium between bulk phase (fluid, i.e. gas or liquid solution) and an adsorbing surface (solid or boundary separating two fluids). When the concentration (or pressure) of substance in the bulk phase is lowered, some of the sorbed substance changes to the bulk state.
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Electrolysis
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A method of separating chemically bonded elements and compounds by passing an electric current through them. Electrolysis involves the passage of an electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes.
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Through electrolytic erosion at electrodes.
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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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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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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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By breaking down organic contaminants.
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Ferromagnetism
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The mechanism by which certain materials (such as iron) form permanent magnets and/or exhibit strong interactions with magnets. Responsible for commonly observed magnetism phenomena, e.g. 'fridge magnets. A material is 'ferromagnetic' only if all its magnetic ions add a positive contribution to the net magnetisation. If some of them subtract from the net magnetisation (i.e. are partially anti-aligned), then the material is 'ferrimagnetic'.
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By attracting unwanted material away from material to be cleaned, or vice versa.
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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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Hydrodynamic Cavitation
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The process of vaporisation, bubble generation and bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in local pressure.
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Hydrophile
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A physical property of a molecule that can transiently bond with water (H2O) through hydrogen bonding. This is thermodynamically favorable, and makes these molecules soluble not only in water, but also in other polar solvents.
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Soap has a hydrophilic head and a hydrophobic tail, which allows it to dissolve in both waters and oils, therefore allowing the soap to clean a surface.
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Hydrophobe
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The physical property of a molecule (known as a hydrophobe) that is repelled from a mass of water. Hydrophobic molecules tend to be non-polar and thus prefer other neutral molecules and nonpolar solvents. Hydrophobic molecules in water often cluster together forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle.
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For example, the lotus leaf effect.
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Jet
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A coherent stream of fluid (e.g. gas or liquid) that is projected into a surrounding medium, usually from some kind of a nozzle or aperture. Jets can travel long distances without dissipating.
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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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Lotus Leaf Effect
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The leaves of the sacred lotus flower (Nelumbo) are characterized by a very high water repellency (superhydrophobicity). Dirt particles are picked up by water droplets due to a complex micro- and nanoscopic architecture of the surface which enables minimisation of adhesion.
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Magnetic Field
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A vector field which surrounds magnets and electric currents, and is detected by the force it exerts on moving electric charges and on magnetic materials. When placed in a magnetic field, magnetic dipoles tend to align their axes parallel to the magnetic field. Magnetic fields also have their own energy with an energy density proportional to the square of the field intensity.
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For example, removing ferromagnetic metal contaminants
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Magnetism
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One of the phenomena by which materials exert attractive or repulsive forces on other materials. Some well-known materials that exhibit easily detectable magnetic properties (called magnets) are nickel, iron, cobalt, and their alloys; however, all materials are influenced to greater or lesser degree by the presence of a magnetic field.
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Mechanical Force
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A mechanical influence that causes a free body to undergo an acceleration.
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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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Phase Change
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The transformation of a thermodynamic system from one phase to another. Most commonly used to describe transitions between solid, liquid and gaseous states of matter, in rare cases including plasma.
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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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Plasma cleaning involves the removal of impurities and contaminants from surfaces through the use of an energetic plasma created from gaseous species.
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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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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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Solvation
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(commonly called dissolution) The process of attraction and association of molecules of a solvent with molecules or ions of a solute. As ions dissolve in a solvent they spread out and become surrounded by solvent molecules. The bigger the ion, the more solvent molecules are able to surround it and the more it becomes solvated.
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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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Sorption
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The action of both absorption and adsorption taking place simultaneously, i.e. the effect of gases or liquids being incorporated into a material of a different state and adhering to the surface of another molecule. Absorption is the incorporation of a substance in one state into another of a different state (e.g., liquids absorbed by solid or gas absorbed by liquid). Adsorption is the physical adherence or bonding of ions and molecules onto the surface of another molecule.
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Sound
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A mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard.
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Used in some cleaning applications (e.g. cleaning teeth, especially when coupled using a liquid medium)
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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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Ion Beam Sputtering can be used to polish telescope mirrors.
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Sublimation
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The change of the physical state of aggregation (or simply state) of matter directly from solid phase to gaseous phase without passing through an intermediate liquid phase.
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Suction
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The flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area.
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Supercritical Fluid
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Any substance at a temperature and pressure above its critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid. Additionally, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties to be 'tuned'.
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Supercritical Fluids (such as supercritical carbon dioxide) are used a cleaning solvenets - for example in dry-cleaning.
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Superhydrophilicity
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Under light irradiation, water dropped onto titanium dioxide forms no contact angle (almost 0 degrees). This effect is called superhydrophilicity. Examples of uses: defogging glass, enabling oil spots to be swept away by water, door mirrors for cars, coatings for buildings, self-cleaning glass, etc. Another use is the property of self-cleaning by the photodecomposition of dirt such as organic compounds adsorbed on the surface.
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Tribocorrosion
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A material degradation process due to the combined effect of corrosion and wear.
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Triboelectric Effect
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A type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated (such as through rubbing). The polarity and strength of the charges produced differ according to the materials, surface roughness, temperature, strain, and other properties.
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By attracting dirt particles away from the object to be cleaned
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Turbulence
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A fluid regime characterised by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time (flow that is not turbulent is called laminar flow).
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Ultrasonic Vibration
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Vibration at ultrasonic frequencies.
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Ultrasonic cleaners are used at frequencies from 20 to 40 kHz for jewellery, lenses and other optical parts, watches, dental instruments, surgical instruments, diving regulators and industrial parts. An ultrasonic cleaner works mostly by energy released from the collapse of millions of microscopic cavitations near the dirty surface forming tiny jets directed at the surface.
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Vacuum
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A volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in practice. Physicists often discuss ideal test results that would occur in a perfect vacuum, which they simply call 'vacuum' or 'free space', and use the term partial vacuum to refer to real vacuum.
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Through evaporation of sufficiently volatile contaminants.
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Vibration
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Mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.
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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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