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Plasma Actuator
Plasma actuators are a type of actuator currently being developed for active aerodynamic flow control (fluid), flow control. Plasma (physics), Plasma actuators impart force in a similar way to ionocraft. Plasma flow control has drawn considerable attention and been used in boundary layer acceleration, airfoil separation control, forebody separation control, turbine blade separation control, axial compressor stability extension, heat transfer and high-speed jet control. ''Dielectric barrier discharge'' (DBD) plasma actuators are widely utilized in airflow control applications. DBD is a type of electrical discharge commonly used in various ''Electrohydrodynamics, electrohydrodynamic'' (EHD) applications. In DBDs, the emitter electrode is connected to a high-voltage source and exposed to the surrounding air, while the collector electrode is grounded and encapsulated within the dielectric material (see figure). When activated, they form a low-temperature plasma between the electrode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serpentine Plasma Actuator
The serpentine plasma actuator represents a broad class of plasma actuator. The actuators vary from the standard type in that their electrode geometry has been modified in to be periodic across its span. History This class of plasma actuators was developed at the Applied Physics Research Group (APRG) at the University of Florida in 2008 by Subrata Roy (scientist), Subrata Roy for the purpose of controlling laminar and turbulent boundary layer flows. Since then, APRG has continued to characterize and develop uses for this class of plasma actuators. Several patents resulted from the early work on serpentine geometry plasma actuators. In 2013, these actuators started to get broader attention in the scientific press, and several articles were written about these actuators, including articles in AIP's EurekAlert, Inside Science and various blogs. Current research and operating mechanisms Serpentine plasma actuators (like other Dielectric Barrier Discharge actuators, i.e. plasma actu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actuator Setup
An actuator is a component of a machine that produces force, torque, or displacement, when an electrical, pneumatic or hydraulic input is supplied to it in a system (called an actuating system). The effect is usually produced in a controlled way. An actuator translates such an input signal into the required form of mechanical energy. It is a type of transducer. In simple terms, it is a "mover". An actuator requires a control device (which provides control signal) and a source of energy. The control signal is relatively low in energy and may be voltage, electric current, pneumatic, or hydraulic fluid pressure, or even human power. In the electric, hydraulic, and pneumatic sense, it is a form of automation or automatic control. The displacement achieved is commonly linear or rotational, as exemplified by linear motors and rotary motors, respectively. Rotary motion is more natural for small machines making large displacements. By means of a leadscrew, rotary motion can be adapted t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bang–bang Control
In control theory, a bang–bang controller (hysteresis, 2 step or on–off controller), is a feedback controller that switches abruptly between two states. These controllers may be realized in terms of any element that provides hysteresis. They are often used to control a plant that accepts a binary input, for example a furnace that is either completely on or completely off. Most common residential thermostats are bang–bang controllers. The Heaviside step function in its discrete form is an example of a bang–bang control signal. Due to the discontinuous control signal, systems that include bang–bang controllers are variable structure systems, and bang–bang controllers are thus variable structure controllers. Bang–bang solutions in optimal control In optimal control problems, it is sometimes the case that a control is restricted to be between a lower and an upper bound. If the optimal control switches from one extreme to the other (i.e., is strictly never in between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shock Tube
: ''For the pyrotechnic initiator, see Shock tube detonator'' A shock tube is an instrument used to replicate and direct blast waves at a sensor or model in order to simulate explosions and their effects, usually on a smaller scale. Shock tubes (and related impulse facilities such as shock tunnels, expansion tubes, and expansion tunnels) can also be used to study aerodynamic flow under a wide range of temperatures and pressures that are difficult to obtain in other types of testing facilities. Shock tubes are also used to investigate compressible flow phenomena and gas phase combustion reactions. More recently, shock tubes have been used in biomedical research to study how biological specimens are affected by blast waves. A shock wave inside a shock tube may be generated by a small explosion (blast-driven) or by the buildup of high pressures which cause diaphragm(s) to burst and a shock wave to propagate down the shock tube (compressed-gas driven). History An early study of c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tonal Versus Broadband
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Tonal may refer to: * Tonal (mythology), a concept in the belief systems and traditions of Mesoamerican cultures, involving a spiritual link between a person and an animal * Tonal language, a type of language in which pitch is used to make phonemic distinctions * Tonality, a system of writing music involving the relationship of pitch to some centered key * Tonal system, a hexadecimal (base 16) system of notation, arithmetic, and metrology proposed by Nystrom in 1859 * "Tonal", a song by the American band Bright from the album ''The Albatross Guest House'' See also *Tone (other) Tone may refer to: Visual arts and color-related * Tone (color theory), a mix of tint and shade, in painting and color theory * Tone (color), the lightness or brightness (as well as darkness) of a color * Toning (coin), color change in coins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aeroacoustics
Aeroacoustics is a branch of acoustics that studies noise generation via either turbulent fluid motion or aerodynamic forces interacting with surfaces. Noise generation can also be associated with periodically varying flows. A notable example of this phenomenon is the Aeolian tones produced by wind blowing over fixed objects. Although no complete scientific theory of the generation of noise by aerodynamic flows has been established, most practical aeroacoustic analysis relies upon the so-called '' aeroacoustic analogy'', proposed by Sir James Lighthill in the 1950s while at the University of Manchester. whereby the governing equations of motion of the fluid are coerced into a form reminiscent of the wave equation of "classical" (i.e. linear) acoustics in the left-hand side with the remaining terms as sources in the right-hand side. History The modern discipline of aeroacoustics can be said to have originated with the first publication of Lighthill in the early 1950s, when nois ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasma Sheet
In the magnetosphere, the plasma sheet is a sheet-like region of denser (0.3-0.5 ions/cm3 versus 0.01-0.02 in the lobes) hot plasma and lower magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ... located on the magnetotail and near the equatorial plane, between the magnetosphere's north and south lobes. The origin of the plasma sheet is still a subject of discussion on magnetospheric physics but it is thought that the region plays an important role on the transport of plasma around the Earth from the magnetotail towards the Sun. The plasma sheet is closely related to the convective motion of plasma on the magnetotail occurring as a result of magnetic field reconnection. References Geomagnetism Planetary science Space plasmas {{astrophysics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Noise Control
Active noise control (ANC), also known as noise cancellation (NC), or active noise reduction (ANR), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first. The concept was first developed in the late 1930s; later developmental work that began in the 1950s eventually resulted in commercial airline headsets with the technology becoming available in the late 1980s. The technology is also used in road vehicles, mobile telephones, earbuds, and headphones. Explanation Sound is a pressure wave, which consists of alternating periods of compression and rarefaction. A noise-cancellation speaker emits a sound wave with the same amplitude but with an inverted phase (also known as antiphase) relative to the original sound. The waves combine to form a new wave, in a process called interference, and effectively cancel each other out – an effect which is called destructive interference. Modern active noise control is gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Progress In Aerospace Sciences
''Progress in Aerospace Sciences'' is a monthly peer-reviewed scientific journal covering all areas of aerospace and aerospace engineering. It covers all areas of aerospace and aerospace engineering, particularly with respect to new theoretical and experimental developments and their applications in research, industry, and university. The journal aims to serve as a general-purpose aerospace journal, condensing the ever-expanding, increasingly multidisciplinary field of aerospace into one publication. The journal is intended for a broad readership - generally anyone either active or simply interested in the aerospace field. The editors-in-chief are K.J. Badcock (University of Liverpool) and M.F. Platzer (Naval Postgraduate School). It was established in 1961 and is published by Elsevier. Originally the journal published articles written in English, French, and German, but since 1972 it has been published entirely in English. About The first edition of ''Progress in Aerospace Scienc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
