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991.
S. Asghar Tasawar Hayat 《International Journal of Infrared and Millimeter Waves》1999,20(7):1413-1424
An exact solution is developed for the problem of diffraction of an E-polarized and an H-polarized spherical waves by a slit in an impedance screen. This consideration is important in the sense that point sources are regarded as better substitutes for real sources than line sources/plane waves. The two independent problems are solved using the Fourier transform, the Wiener-Hopf technique and asymptotic approximations. 相似文献
992.
993.
对自适应演化算法进行了改进,修改了变异操作中分量值会超出定义域范围的错误,改善了重组操作并不一定产生更优后代的缺点,从而大大提高了收敛到全局最优解的概率.通过将此两种算法引入微波电路的设计中,通过结果对照,证明了改进算法的优良特性. 相似文献
994.
995.
介绍了通过采用阻抗匹配与变换及参数扫描分析等方法,结合发射机合成网络的实际特性,能较好的实现中波发射机合成网络的建模与仿真. 相似文献
996.
Attachment of nickel nanoparticles on multiwalled carbon nanotubes (MWCNTs) was conducted to explore the influence of Ni loading
on the electrochemical capacitance of MWCNT electrodes. A chemical impregnation leaded to homogeneously disperse Ni particles
onto the surface of MWCNTs, and the Ni particles were found to be an average size of 30–50 nm. The capacitive behavior of
the MWCNT electrodes was investigated in 6 M KOH, by using cyclic voltammetry (CV), charge–discharge cycling, and ac electrochemical
impedance spectroscopy. CV measurements showed that the Faradaic current was found to increase with the Ni coverage, indicating
that the presence of Ni would enhance the pseudocapacitance through the redox process. Equivalent circuit analysis indicated
that both of electrical connection and charge transfer resistances accounted for the major proportion of the overall resistance
and were found to decrease with the amount of nickel. A linearity relationship between the total capacitance and the Ni population
reflected that each Ni particle exhibits an identical electrochemical activity in enhancing the electrochemical capacitance.
The overall electrochemical capacitance (including double layer capacitance and pseudocapacitance) of Ni-MWCNT electrode can
reach a maximum of 210 F/g over 500 cycles. 相似文献
997.
Seung Eon Moon Han Cheol Ryu Min Hwan Kwak Young Tae Kim Su‐Jae Lee Kwang‐Yong Kang 《ETRI Journal》2005,27(6):677-684
A phased array antenna was fabricated using four‐element ferroelectric phase shifters with a coplanar waveguide (CPW) transmission line structure based on a Ba0.6Sr0.4TiO3(BST)/MgO structure. Epitaxial BST films were deposited on MgO (001) substrates by pulsed laser deposition. To attain the large differential phase shift and small losses for a ferroelectric CPW phase shifter, an impedance‐matching‐part adding technique between the effective transmission line and connecting cable was used. The return loss and insertion loss for this technique‐adapted BST CPW device were improved with respect to those for a normal BST CPW device. For an X‐band phased array antenna system consisting of ferroelectric BST CPW phase shifters, power divider, dc block, patch antenna, and programmed dc power, the steering beam could be tilted by 15° in either direction. 相似文献
998.
999.
Suman Majumdar 《Journal of Theoretical Probability》1999,12(1):1-11
Let D be a closed subset of a real separable Hilbert space H. Let (D) denote the set of all Borel probability measures on D and (D) the set of all probabilities with integrable Laplace transform. A metric d, based on the Laplace transform, is defined on (D). Topological properties, viz., separability, connectedness, completeness, compactness and local compactness, of (D, d are investigated, and the d-topology is compared with the topology of weak convergence. 相似文献
1000.
Active control of the acoustic impedance of walls in rooms allows fine control of the reverberation in auditoria. Such active materials may use locally reacting cells comprising a transducer connected to an electronic control circuit. In this paper, a simple feedback circuit based on a linear combination of the pressure at the transducer diaphragm and the velocity of the diaphragm is presented. We then discuss the desired characteristics of a transducer dedicated to our application, and show that the isodynamic technology is an interesting candidate, especially if using rubber magnet bars. We present results from simulations involving a finite element model of such transducer, which predict a good control over two frequency decades. Preliminary experimental results obtained with a basic prototype of isodynamic transducer are encouraging, yielding an absorption coefficient approaching 1 (>0.7) from 30 up to 500 Hz. We think that far better results can be obtained (specially in the “super-reflecting” case) with closer control over the various mechanical parameters. Future work will also address the optimisation of the magnet geometry. 相似文献