Acoustic Levitation
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A method for suspending matter in a medium by using acoustic radiation pressure from intense sound waves in the medium. Usually used for containerless processing. Although harder to control than some other methods it has the advantage of being able to levitate nonconducting materials.
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Acoustic Radiation Pressure
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A force on a particle suspended in the field of a sound wave arising from the scattering of the acoustic waves on the particle.
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Acoustic Tweezers
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A technology for controlling the movement of objects by sound waves. In a standing acoustic field, objects will experience an acoustic radiation force that moves the objects to special regions of the acoustic field.Depending on the properties of the objects, they can be moved to either acoustic pressure nodes or pressure antinodes.
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Added Mass
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(or Virtual Mass) The inertia added to a system because an accelerating or decelerating body must move (or deflect) some volume of surrounding fluid as it moves through it.
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Adhesive
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A compound that adheres or bonds two items together. Adhesives may come from either natural or synthetic sources. Some modern adhesives are extremely strong, and are becoming increasingly important in modern construction and industry.
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Axle
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A central shaft for a rotating wheel or gear.
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Constrained in position, but not in one axis of orientation.
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Ball Bearing
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An annular bearing comprising an array of balls held within a track.
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Basset Force
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The force due to the lagging boundary layer development with changing relative velocity (acceleration) of bodies moving through a fluid.
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Bingham Plastic
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A viscoplastic material that behaves as a rigid body at low stresses but flows as a viscous fluid at high stress. A common example is toothpaste, which will not be extruded until a certain pressure is applied to the tube. It then is pushed out as a solid plug.
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Boundary Layer
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A boundary layer is that layer of fluid in the immediate vicinity of a bounding surface. The boundary layer effect occurs at the field region in which all changes occur in the flow pattern. The boundary layer distorts surrounding nonviscous flow.
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In the case of solid particles carried by a fluid.
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Brush
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A device with bristles, wire or other filaments, used for cleaning, grooming hair, applying liquids such as paint, sealing gaps between moving surfaces, deburring and other kinds of surface finishing, and for many other purposes.
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Bubble
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A globule of one substance in another, usually gas in a liquid. Due to the Marangoni effect, bubbles may remain intact when they reach the surface of the immersive substance.
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Either between bubbles, on or in the surface of the bubble.
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Chain
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A chain is a series of connected links.
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Close Packing
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A dense arrangement of equal spheres in an infinite, regular arrangement (or lattice). There are two simple regular lattices that achieve highest average density: face-centered cubic (also called cubic close packed) and hexagonal close-packed. Both are based upon sheets of spheres arranged at the vertices of a triangular tiling; they differ in how the sheets are stacked upon one another.
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Cohesion
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The action or property of like molecules sticking together, being mutually attractive. This is an intrinsic property of a substance that is caused by the shape and structure of its molecules which makes the distribution of orbiting electrons irregular when molecules get close to one another, creating electrical attraction that can maintain a macroscopic structure such as a water drop.
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Colloid
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A type of chemical mixture where one substance is dispersed evenly throughout another. The particles of the dispersed substance are only suspended in the mixture, unlike a solution, where they are completely dissolved within. This occurs because the particles in a colloid are larger than in a solution - small enough to be dispersed evenly and maintain a homogenous appearance, but large enough to scatter light and not dissolve.
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Coulomb Damping
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A type of constant mechanical damping in which energy is absorbed via sliding friction. Friction generated by the relative motion of the two surfaces that press against each other is a source of energy dissipation. In general, damping is the dissipation of energy from a vibrating system where the kinetic energy is converted into heat by the friction. Coulomb damping is a common damping mechanism that occurs in machinery.
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Cyanoacrylate
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The generic name for cyanoacrylate based fast-acting adhesives such as methyl 2-cyanoacrylate, ethyl-2-cyanoacrylate (commonly sold under trade names like SuperGlue), and n-butyl cyanoacrylate (used in veterinary and skin glues).
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Damping
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Damping is any effect, either deliberately engendered or inherent to a system, that tends to reduce the amplitude of oscillations of an oscillatory system.
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Diamagnetism
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The property of an object which causes it to create a magnetic field in opposition of an externally applied magnetic field, thus causing a repulsive effect. It is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field. Diamagnetism is generally a quite weak effect in most materials, although superconductors exhibit a strong effect.
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Diffusion Barrier
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A thin layer (usually micrometres thick) of metal usually placed between two other metals. It is done to act as a “barrier” to protect either one of the metals from corrupting the other.
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Eddy Current Damping
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The use of eddy currents to provide a damping effect.
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Elastic Recovery
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The tendancy of a material that has been stretched to return to its original shape.
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For example, through the use of an elastic band or sheet.
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Elasticity
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The physical property of a material when it deforms under stress (e.g. external forces), but returns to its original shape when the stress is removed. The amount of deformation is called the strain. The elastic regime is characterized by a linear relationship between stress and strain, denoted linear elasticity.
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Electric Field
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The space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field (that can also be equated to electric flux density). This electric field exerts a force on other electrically charged objects.
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If the solid carries an electric charge.
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Electroactive Polymer
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(or EAP) A polymer that exhibits a change in size or shape when stimulated by an electric field. The most common applications of this type of material are in actuators and sensors. A typical characteristic property of an EAP is that it will undergo a large amount of deformation while sustaining large forces.
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Electrodeposition
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The process of using electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal. Primarily used for depositing a layer of material to bestow a desired property (e.g., abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities, etc.) to a surface that otherwise lacks that property. Another application uses electroplating to build up thickness on undersized parts.
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By depositing a surrounding layer of electrodeposited material.
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Electrodynamic Bearing
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A system providing contactless electrodynamic suspension of rotating shafts based on the induction of eddy currents in a rotating conductor. When an electrically conducting material is moving in a magnetic field, a current will be generated in the material that counters the change in the magnetic field (known as Lenz' Law). This generates a current that will result in a magnetic field that is oriented opposite to the one from the magnet. The electrically conducting material is thus acting as a magnetic mirror.
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Electromagnet
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A type of magnet whose magnetic field is produced by the flow of electric current. The magnetic field disappears when the current ceases. Electromagnets are very widely used as components of other electrical devices, such as motors, generators, relays, loudspeakers, hard disks, MRI machines, scientific instruments, and magnetic separation equipment, as well as being employed as industrial lifting electromagnets for picking up and moving heavy iron objects like scrap iron.
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Electropermanent Magnet
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A type of magnet which consists of both an electromagnet and a dual material permanent magnet, in which the magnetic field produced by the electromagnet is used to change the magnetisation of the permanent magnet. Allows creating controllable permanent magnets where the magnetic effect can be maintained without requiring a continuous supply of electrical energy.
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Electroplating
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The process of using electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal. Primarily used to bestow a desired property (e.g., abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities, etc.) to a surface that otherwise lacks that property. Also used to build up thickness on undersized parts.
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Electrorheological Effect
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Electrorheological (ER) fluids are suspensions of extremely fine non-conducting particles (up to 50 micrometres diameter) in an electrically insulating fluid. The apparent viscosity of ER fluids changes reversibly by an order of up to 100,000 in response to an electric field. A typical ER fluid can go from the consistency of a liquid to that of a gel, and back, with response times of the order of ms. Sometimes called the Winslow Effect.
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Electrostatics
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The phenomena arising from stationary or slowly moving electric charges
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Faraday Wave
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(or Faraday Ripples) Nonlinear standing waves that appear on liquids enclosed by a vibrating receptacle. When the vibration frequency exceeds a critical value, the flat hydrostatic surface becomes unstable. The waves can take the form of stripes, close-packed hexagons, or even squares or quasiperiodic patterns.
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Faraday waves are used as a liquid-based template for directed assembly of microscale materials including soft matter, rigid bodies and biological entities.
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Ferrofluid
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A liquid which becomes strongly magnetised in the presence of a magnetic field. Ferrofluids are colloidal mixtures composed of nanoscale ferromagnetic, or ferrimagnetic, particles suspended in a carrier fluid, usually an organic solvent or water. The ferromagnetic nano-particles are coated with a surfactant to prevent their agglomeration (due to van der Waals and magnetic forces).
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Ferromagnetic Powder
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Ferromagnetic material in a powdered or finely divided form. Ferromagnetic materials (such as iron) form permanent magnets and/or exhibit strong interactions with magnets. Ferromagnetic materials lose their ferromagnetic properties above a characteristic temperature (the Curie Point).
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For example, ferromagnetic powder will behave more like an amorphous solid in the presence of a magnetic field.
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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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Filter (physical)
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A device (usually a membrane or layer) that is designed to block certain objects or substances while letting others through. Filters are often used to remove harmful substances from air or water, for example to remove air pollution, to make water drinkable, to prepare coffee. In domestic food and drink preparation where bulk solids are removed from liquids, this is often called a strainer.
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Flocculation
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A process of contact and adhesion whereby the particles of a dispersion form larger-size clusters.
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Foam
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A substance that is formed by trapping many gas bubbles in a liquid or solid.
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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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Friction Welding
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A class of solid-state welding processes that generates heat through mechanical friction between a moving workpiece and a stationary component, with the addition of a lateral force called 'upset' to plastically displace and fuse the materials. Technically, because no melt occurs, friction welding is not actually a welding process in the traditional sense, but a forging technique.
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Funnel
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A funnel is a pipe with a wide, often conical mouth and a narrow stem. It is used to channel liquid or fine-grained substances into containers with a small opening. Without a funnel, much spillage would occur.
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In the case of, for example, a solid in grannular, powedered or slurry form.
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Gecko-Foot Bristle Array
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The toes of the gecko adhere to a wide variety of surfaces, without the use of liquids or surface tension. The attractive forces that hold geckos to surfaces are van der Waals interactions between the finely divided spatula tipped setae (bristle array) and the surfaces themselves.
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Gel
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A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute crosslinked system, which exhibits no flow when in the steady-state. By weight, gels are mostly liquid, yet they behave like solids due to a three-dimensional crosslinked network within the liquid. It is the crosslinks within the fluid that give a gel its structure (hardness) and contribute to stickiness (tack).
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Glassy Carbon
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(also called vitreous carbon) A a non-graphitising carbon which combines glassy and ceramic properties with those of graphite. The most important properties are high temperature resistance, extreme resistance to chemical attack and impermeability to gases and liquids. Glassy carbon is widely used as an electrode material in electrochemistry, as well as for high temperature crucibles and as a component of some prosthetic devices.
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Groove
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A long and narrow indentation built into a material, generally for the purpose of allowing another material or part to move within the groove and be guided by it.
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Halbach Array
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A special arrangement of permanent magnets that augments the magnetic field on one side of the array while cancelling the field to near zero on the other side. Has many applications ranging from the humble refrigerator magnet through industrial applications such as the brushless AC motor and magnetic coupling, to high-tech applications such as wiggler magnets used in particle accelerators and free electron lasers.
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Hart's Inversor
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A mechanical linkage that can be used to convert circular motion into perfect linear motion (or vice versa). It does this without a sliding guide.
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Hinge
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A mechanical mechanism that allows mutal rotation of two joined objects around a joined common axis.
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In one axis only.
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Holes
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A hole is a confined lack of structure in some part of an object.
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Hook
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A mechanical device that is curved or bent to suspend or hold or pull something.
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Intumescent Materials
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An intumescent is a substance which swells as a result of heat exposure, thus increasing in volume, and decreasing in density. Intumescents are typically used in passive fire protection.
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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 Damping
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(or Thrust Damping) is the effect of rocket exhaust removing energy from the transverse angular motion of a rocket. If a rocket has pitch or yaw motion then the exhaust must be accelerated laterally as it flows down the exhaust tube and nozzle. Once the exhaust leaves the nozzle this lateral momentum is lost to the vehicle and thus serves to damping the lateral oscillations.
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Johnsen-Rahbek Effect
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An attractive force that occurs when an electric potential is applied across the boundary between a metallic surface and the surface of a semiconducting material. The magnitude of the force depends on the voltage and the specific materials involved.
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Knot
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A method for fastening or securing flexible linear material such as rope by tying or interweaving.
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Lewis
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A type of lifting device used to lift large stones from above. It is inserted into a specially prepared hole or 'seating' in the top of a stone, directly above its centre of mass. It works by applying principles of the lever and utilises the weight of the stone to act on the long lever-arms which in turn results in a very high reaction force and friction where the short lever-arms make contact with the stone inside the hole thereby preventing slipping.
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London Dispersion Force
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A weak intermolecular force acting between atoms and molecules arising from quantum induced instantaneous polarisation multipoles in molecules. Can therefore act between molecules without permanent multipole moments.
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Maglev
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(magnetic levitation) A system of transportation that suspends, guides and (usually) propels vehicles, predominantly trains, using magnetic forces.
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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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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 Fastener
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A device that mechanically joins or affixes two or more objects together.
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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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Memory Foam
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(visco-elastic polyurethane foam). Made from polyurethane with additional chemicals that increase its viscosity level, thereby increasing its density. Depending on the chemicals used and its overall density, it is firmer in cool temperatures and softer when warm. Higher density memory foam reacts to body heat which allows it to mould itself to the shape of a warm body within a few minutes. A lower density memory foam is pressure-sensitive and will mould more quickly to the shape of the body.
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Metastability
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A general scientific concept which describes states of delicate equilibrium. A system is in a metastable state when it is in equilibrium (not changing with time) but is susceptible to fall into lower-energy states with only slight interaction. It is analogous to being at the bottom of a small valley when there is a deeper valley close by
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Microsphere
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Small spherical particles, with diameters in the micrometer range (typically 1µm to 1000µm (1mm)). They may be used to encapsulate and transport other substances and/or control their release.
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Nanocomposite
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A multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm), or structures having nano-scale repeat distances between the different phases that make up the material. Can include porous media, colloids, gels and copolymers, but is more usually taken to mean the solid combination of a bulk matrix and nano-dimensional phase(s).
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Origami
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The traditional Japanese art of paper folding. The goal of this art is to create a representation of an object using geometric folds and crease patterns preferably without the use of gluing or cutting the paper, and using only one piece of paper. Origami only uses a small number of different folds, but they can be combined in a variety of ways to make intricate designs.
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By folding to create a box or other enclosure
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Peaucellier–Lipkin Linkage
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A mechanical linkage that can be used to convert circular motion into perfect linear motion (or vice versa). It does this without a sliding guide.
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Pendulum
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A weight suspended from a pivot so that it can swing freely
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Physical Containment
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Partial or complete enclosure of an object or substance by some physical medium, typically for the purpose of protection or restriction of movement.
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Physisorption
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(or physical adsorption) A type of adsorption in which the adsorbate adheres to the surface only through Van der Waals (weak intermolecular) interactions, which are also responsible for the non-ideal behaviour of real gases.
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Pin
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A simple mechncial device for holding objects together.
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Potential Well
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The region surrounding a local minimum of potential energy. Energy held in a potential well is unable to convert to another type of energy (kinetic energy in the case of a gravitational potential well) because it is captured in the local minimum of a potential well and so may not proceed to the global minimum of potential energy, as it would naturally tend to due to entropy.
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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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Quadruplanar-Inversor
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A mechanical linkage that can be used to convert circular motion into perfect linear motion (or vice versa). It does this without a sliding guide.
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Reaction (physics)
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In classical mechanics, Newton's third law states that forces occur in pairs: the Action and the Reaction. Both forces are equal in magnitude and opposite in direction. The distinction between action and reaction is purely arbitrary: any one of the two forces can be considered an action, in which case the other (corresponding) force automatically becomes its associated reaction.
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Rheopecty
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(or rheopexy) The rare property of some non-Newtonian fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shearing force, the higher its viscosity. Rheopectic fluids, such as some lubricants, thicken or solidify when shaken (the opposite type of behaviour, in which fluids become less viscous the longer they undergo shear, is called thixotropy and is much more common).
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Self-Assembly
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A process in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction.
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Sintering
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A method for making objects from powder, by heating the material below its melting point (solid state sintering) until its particles adhere to each other. Traditionally used for manufacturing ceramic objects. Most, if not all, metals can be sintered - especially pure metals produced in vacuum which suffer no surface contamination. Many nonmetallic substances also sinter, such as glass, alumina, zirconia, silica, magnesia, lime, ice, beryllium oxide, ferric oxide, and various organic polymers.
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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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Soldering
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A process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a relatively low melting point.
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Solenoid
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A coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create controlled magnetic fields and can be used as electromagnets.
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In the case of a ferromagnetic solid.
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Spin-stabilized Magnetic Levitation
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A phenomenon of magnetic levitation whereby a magnet or array of magnets is levitated via magnetic forces above another magnet or array of magnets, and stabilised by gyroscopic effect due to a spin that is neither too fast, nor too slow.
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Spring
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An elastic object used to store mechanical energy.
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Static Friction
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(or Stiction) Two solid objects pressing against each other (but not sliding) will require some threshold of force parallel to the surface of contact in order to overcome static cohesion. Static Friction is a threshold, not a continuous force.
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Stewart Platform
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A type of parallel robot that incorporates six prismatic actuators, commonly hydraulic jacks. These actuators are mounted in pairs to the mechanism's base, crossing over to three mounting points on a top plate. Devices placed on the top plate can be moved in the six degrees of freedom in which it is possible for a freely-suspended body to move.
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Stockbridge Damper
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A tuned mass damper used to suppress wind-induced vibrations on taut cables, such as overhead power lines. The dumbbell-shaped device consists of two masses at the ends of a short length of cable or flexible rod, which is clamped at its middle to the main cable. The damper is designed to dissipate the energy of oscillations in the main cable to an acceptable level.
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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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Supercooling
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(also known as undercooling) The process of lowering the temperature of a liquid or a gas below its freezing point, without it becoming a solid. A liquid below its standard freezing point will crystallize in the presence of a seed crystal or nucleus around which a crystal structure can form. Without any such nucleus, the liquid phase can be maintained all the way down to the temperature at which crystal homogeneous nucleation occurs.
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Tensegrity
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A structure formed by a finite network of compression, or rigid elements interconnected through tensile, or elastic elements which give the structure its overall integrity
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Thermal Contraction
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The tendency of matter to reduce in volume (contract) in response to a change in temperature or when a substance is cooled.
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Thermal Expansion
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The tendency of matter to change in volume in response to a change in temperature or when a substance is heated.
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For example by using the expansion of a solid in a limited space to result in it becoming jammed in place.
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Tuned Mass Damper
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A device to stabilise against violent motion caused by harmonic vibration. A tuned damper reduces the vibration of a system with a comparatively lightweight component so that the worst-case vibrations are less intense. Roughly speaking practical systems are tuned to either move the main mode away from a troubling excitation frequency, or to add damping to a resonance that is difficult or expensive to damp directly. .
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Van der Waals Force
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The sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral molecules. Includes Keesom Force, Debye Force and London dispersion force.
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Velcro
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A brand name of fabric hook-and-loop fasteners. It consists of two layers: a 'hook' side, which is a piece of fabric covered with tiny hooks, and a 'loop' side, which is covered with even smaller and 'hairier' loops. When the two sides are pressed together, the hooks catch in the loops and hold the pieces together. When the layers are separated, the strips make a characteristic 'ripping' sound.
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Viscous Damping
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A damping system based upon the passage of a viscous fluid through small apperture or other restriction (such as the gap between lubrictaed parts).
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Vitrification
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The transformation of a substance into a glass. Usually, it is achieved by rapdily cooling a liquid through the glass transition. Certain chemical reactions also result in glasses.
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Welding
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A process for joining materials, usually metals or thermoplastics, typically by melting the workpieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld (in contrast with soldering and brazing, which involve melting a lower-melting-point material between the workpieces, without melting the workpieces.
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Wetting
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The ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. The degree of wetting is determined by a force balance between adhesive and cohesive forces. Adhesive forces between a liquid and solid cause a liquid drop to spread across the surface. Cohesive forces within the liquid cause the drop to ball up and avoid contact with the surface.
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