排序方式: 共有21条查询结果,搜索用时 31 毫秒
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Mostafa Dellahi Hattab Maker Guillermo Botella Enrique Alameda-Hernandez Azeddine Mouhsen 《International Journal of Circuit Theory and Applications》2020,48(6):887-905
The three-phase four-wire shunt active power filter (SAPF) was developed to suppress the harmonic currents generated by nonlinear loads, and for the compensation of unbalanced nonlinear load currents, reactive power, and the harmonic neutral current. In this work, we consider instantaneous reactive power theory (PQ theory) for reference current identification based on the following two algorithms: the classic low-pass filter (LPF) and the second-order generalized integrator (SOGI) filter. Furthermore, since an important process in SAPF control is the regulation of the DC bus voltage at the capacitor, a new controller based on the Lyapunov function is also proposed. A complete simulation of the resultant active filtering system confirms its validity, which uses the SOGI filter to extract the reference currents from the distorted line currents, compared with the traditional PQ theory based on LPF. In addition, the simulation performed also demonstrates the superiority of the proposed approach, for DC bus voltage control based on the Lyapunov function, compared with the traditional proportional-integral (PI) controller. Both novel approaches contribute towards an improvement in the overall performance of the system, which consists of a small rise and settling time, a very low or nonexistent overshoot, and the minimization of the total harmonic distortion (THD). 相似文献
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Gunapala S.D. Bundara S.V. Liu J.K. Winn Hong Mani Sundaram Maker P.D. Muller R.E. Shott C.A. Carralejo R. 《Electron Devices, IEEE Transactions on》1998,45(9):1890-1895
A 9-μm cutoff 640×486 snap-shot quantum well infrared photodetector (QWIP) camera has been demonstrated. The performance of this QWIP camera is reported including indoor and outdoor imaging. The noise equivalent differential temperature (NEΔT) of 36 mK has been achieved at 300 K background with f/2 optics. This is in good agreement with expected focal plane array sensitivity due to the practical limitations on charge handling capacity of the multiplexer, read noise, bias voltage, and operating temperature 相似文献
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Daniel Voß Wissem Zouaghi Mehran Jamshidifar Sebastian Boppel Cormac McDonnell James R. P. Bain Nils Hempler Graeme P. A. Malcolm Gareth T. Maker Maris Bauer Alvydas Lisauskas Adam Rämer Sergey A. Shevchenko Wolfgang Heinrich Viktor Krozer Hartmut G. Roskos 《Journal of Infrared, Millimeter and Terahertz Waves》2018,39(3):262-272
Aiming for non-destructive testing and security applications, we investigate transmission-mode imaging and spectroscopic sensing using terahertz (THz) pulses from a commercial optical parametric oscillator (OPO) in combination with THz detectors based on antenna-coupled field-effect transistors (TeraFETs). The Q-switched OPO generates quasi-continuous-wave THz pulses with a peak power of up to 1 W at a repetition rate between 12 and 90 Hz. The pulses are frequency-tunable between 0.7 and 2.6 THz with a typical linewidth of 50 GHz. We explore detection with fast GaN/AlGaN TeraFETs which hold the potential for multi-pixel and homodyne detection. 相似文献
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B. N. Maker T. A. Laursen 《International journal for numerical methods in engineering》1994,37(1):1-18
A finite element formulation is presented for treatment of the mechanical interaction between a rod-like object and a continuous medium, as occurs, for example, between reinforcing steel and surrounding concrete. An impenetrability constraint restricts the rod's lateral motion relative to the continuum, while an accompanying constraint allows axial slip subject to a release criterion. Satisfaction of these constraints is enforced via application of penalty and augmented Lagrangian regularizations. The proposed implementation is suitable for both static and dynamic implicit equation solving schemes, making it useful for a wide range of problems. 相似文献
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Convex grating types for concentric imaging spectrometers 总被引:1,自引:0,他引:1
The properties of convex gratings fabricated by electron-beam lithography are investigated. Three grating types are shown. The first is a single-panel, true blazed grating in which the blaze angle stays constant relative to the local surface normal. This grating provides high peak efficiencies of approximately 88% in the first order and 85% in the second order. The second grating has two concentric panels, with each panel blazed at a different angle. This type permits flexibility in matching the grating response to a desired form. The third type has a groove shape that departs from the sawtooth blazed profile to increase the second-order bandwidth. All these types are difficult or impossible to produce with conventional techniques. The gratings compare favorably with conventional (holographic and ruled) types in terms of efficiency and scatter. Simple scalar models are shown to predict the wavelength response accurately. These gratings allow the optical designer to realize fully the considerable advantages of concentric spectrometer forms. 相似文献
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Systematic investigations of the consequences of sexual abuse and clinical literature on interventions with survivors have frequently neglected the impact of sexual abuse on parenting. Grounded in both object-relations and trauma theory, this article presents a case illustration to depict the unconscious repetition of one 30-yr-old mother's childhood abusive relationship with her own child. We explore how this survivor's parenting conflicts became increasingly salient during specific developmental stages of the child, as themes of sexuality and aggression triggered unresolved conflicts, distorted cognitions, and trauma reactions. The reenactment impairs parenting in critical ways, hence increasing the risk for sexual abuse in the next generation. Strategies for interventions to modify the mother's poor parenting responses are described using a therapeutic approach that integrates concepts from psychodynamic and cognitive-behavioral theories. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Liquid-crystal blazed-grating beam deflector 总被引:12,自引:0,他引:12
A transmission-type nonmechanical multiple-angle beam-steering device that uses liquid-crystal blazed grating has been developed. Sixteen steering angles with a contrast ratio of 18 has been demonstrated. A detailed analysis of the liquid-crystal and poly(methyl methacrylate) blazed-grating deflector was carried out to provide guidance during the deflector's development. A manufacturing offset compensation technique is proposed to improve the device's performance greatly. A hybrid approach utilizing electrically generated blazed grating combined with the cascading approach described here yields in excess of 500 deflecting angles. 相似文献
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Dougherty D.J. Muller R.E. Maker P.D. Forouhar S. 《Lightwave Technology, Journal of》2001,19(10):1527-1531
Calculations of the grating spatial-frequency spectrum and the filtering properties of multiple-pass electron-beam writing demonstrate a tradeoff between stitching-error suppression and minimum pitch separation. High-resolution measurements of optical-diffraction patterns show a 25-dB reduction in stitching-error side modes 相似文献