Electrical breakdown or dielectric breakdown is a process that occurs when an electrical insulating material, subjected to a high enough voltage, suddenly becomes an electrical conductor and electric current flows through it. All insulating materials undergo breakdown when the electric field caused by an applied voltage exceeds the material's dielectric strength. The voltage at which a given insulating object becomes conductive is called its breakdown voltage and depends on its size and shape. Under sufficient electrical potential, electrical breakdown can occur within solids, liquids, gases or vacuum. However, the specific breakdown mechanisms are different for each kind of dielectric medium.
Electrical breakdown may be a momentary event (as in an electrostatic discharge), or may lead to a continuous electric arc if protective devices fail to interrupt the current in a power circuit. In this case electrical breakdown can cause catastrophic failure of electrical equipment, and fire hazards.
https://en.wikipedia.org/wiki/Electrical_breakdown
In optics, a diffraction grating is an optical component with a periodic structure that splits and diffractslight into several beams travelling in different directions. The emerging coloration is a form of structural coloration.[1][2] The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as the dispersive element. Because of this, gratings are commonly used in monochromators and spectrometers.
For practical applications, gratings generally have ridges or rulings on their surface rather than dark lines.[3] Such gratings can be either transmissive or reflective. Gratings that modulate the phase rather than the amplitude of the incident light are also produced, frequently using holography.[4]
https://en.wikipedia.org/wiki/Diffraction_grating
Catastrophic optical damage (COD), or catastrophic optical mirror damage (COMD), is a failure mode of high-power semiconductor lasers. It occurs when the semiconductor junction is overloaded by exceeding its power density and absorbs too much of the produced light energy, leading to melting and recrystallization of the semiconductor material at the facets of the laser. This is often colloquially referred to as "blowing the diode." The affected area contains a large number of lattice defects, negatively affecting its performance. If the affected area is sufficiently large, it can be observable under optical microscope as darkening of the laser facet, and/or as presence of cracks and grooves. The damage can occur within a single laser pulse, in less than a millisecond. The time to COD is inversely proportional to the power density.
Catastrophic optical damage is one of the limiting factors in increasing performance of semiconductor lasers. It is the primary failure mode for AlGaInP/AlGaAs red lasers.[1]
Short-wavelength lasers are more susceptible to COD than long-wavelength ones.
The typical values for COD in industrial products range between 12 and 20 MW/cm2.
https://en.wikipedia.org/wiki/Catastrophic_optical_damage
Thermal runaway describes a process that is accelerated by increased temperature, in turn releasing energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the conditions in a way that causes a further increase in temperature, often leading to a destructive result. It is a kind of uncontrolled positive feedback.
In chemistry (and chemical engineering), thermal runaway is associated with strongly exothermic reactions that are accelerated by temperature rise. In electrical engineering, thermal runaway is typically associated with increased current flow and power dissipation. Thermal runaway can occur in civil engineering, notably when the heat released by large amounts of curing concrete is not controlled.[citation needed] In astrophysics, runaway nuclear fusionreactions in stars can lead to nova and several types of supernova explosions, and also occur as a less dramatic event in the normal evolution of solar-mass stars, the "helium flash".
Some climate researchers have postulated that a global average temperature increase of 3–4 degrees Celsiusabove the preindustrial baseline could lead to a further unchecked increase in surface temperatures. For example, releases of methane, a greenhouse gas more potent than CO2, from wetlands, melting permafrost and continental margin seabed clathrate deposits could be subject to positive feedback.[1][2]
https://en.wikipedia.org/wiki/Thermal_runaway
Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop which exacerbates the effects of a small disturbance. That is, the effects of a perturbation on a system include an increase in the magnitude of the perturbation.[1] That is, A produces more of B which in turn produces more of A.[2] In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback.[1][3]Both concepts play an important role in science and engineering, including biology, chemistry, and cybernetics.
Mathematically, positive feedback is defined as a positive loop gain around a closed loop of cause and effect.[1][3]That is, positive feedback is in phase with the input, in the sense that it adds to make the input larger.[4][5] Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there will typically be exponential growth, increasing oscillations, chaotic behavior or other divergences from equilibrium.[3] System parameters will typically accelerate towards extreme values, which may damage or destroy the system, or may end with the system latched into a new stable state. Positive feedback may be controlled by signals in the system being filtered, damped, or limited, or it can be cancelled or reduced by adding negative feedback.
Positive feedback is used in digital electronics to force voltages away from intermediate voltages into '0' and '1' states. On the other hand, thermal runaway is a type of positive feedback that can destroy semiconductor junctions. Positive feedback in chemical reactions can increase the rate of reactions, and in some cases can lead to explosions. Positive feedback in mechanical design causes tipping-point, or 'over-centre', mechanisms to snap into position, for example in switches and locking pliers. Out of control, it can cause bridges to collapse. Positive feedback in economic systems can cause boom-then-bust cycles. A familiar example of positive feedback is the loud squealing or howling sound produced by audio feedback in public address systems: the microphone picks up sound from its own loudspeakers, amplifies it, and sends it through the speakers again.
https://en.wikipedia.org/wiki/Positive_feedback
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