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261.
We describe identification of seven components from Antrodia cinnamomea. Their structures were determined on the basis of spectral analysis and comparison with authentic samples. These compounds include two steroids (1, 2) (β-sitosterol and eburicol), two new steroids (3, 4) [methyl-4α-methylergost-8,24(28)-dien-3,7,11-trion-26-oate and methyl-4α-methylergost-8,24(28)-dien-3,11-dion-26-oate], two lignans (5, 6) [(+)-sesamin and 4-hydroxysesamin], and one long chain methyl ester (7) (methyl oleate). Among them, compounds 3 and 4 are first isolated from nature. 相似文献
262.
解线性及二次型规划问题增广的神经网络 总被引:3,自引:1,他引:2
本文提出了一个解线性及二次型规划问题的神经网络模型,证明了该网络是全局稳定于平衡点,而平衡点就是线性及二次型规划问题的解,该网络的优点是能够实时获得问题的精确解,且可以同时获得带等式不式约束的对偶问题解,该网络易于电路实现。 相似文献
263.
Tzong-Lin Wu Hung-Chun Chang 《Lightwave Technology, Journal of》1995,13(9):1926-1934
Based on vectorial formulations which combine the surface integral equation method and the finite-element method, a novel numerical approach is proposed for calculating the dispersion coefficients of dual-mode elliptical-core fibers with arbitrary refractive index profiles. By differentiating the original formulations involving the propagation constant β and the guided mode fields Hx and Hy once and twice with respect to the normalized frequency V, the new formulations for {dβ/dV, dHx/dV, dHy/dV} and for {d2β/dV2, d2 Hx/dV2, d2Hy/dV2 } are obtained respectively. Once {β, Hx, Hy } is solved through the eigenvalue procedure which dominates the computing time, only a few matrix manipulations are required to obtain {dβ/dV, dHx/dV, dHy/dV} and {d2β/dV2, d2Hx/dV2 , d2Hy/dV2}. Some numerical examples are examined to see the influence of different refractive index distributions with dips on the dispersions of the four nondegenerate LP 11 modes for elliptical-core fibers 相似文献
264.
A new simplified threshold-voltage model for n-MOSFETs with nonuniformly doped substrate and its application to MOSFET's miniaturization 总被引:1,自引:0,他引:1
Jiin-Jang Maa Ching-Yuan Wu 《Electron Devices, IEEE Transactions on》1995,42(8):1487-1494
The formulation, verification, and application of a new simplified 2-D threshold voltage model for n-MOSFETs with nonuniformly doped substrate profile are provided, in which the averaged normal field at the Si/SiO/sub 2/ interface in the active channel is quoted from a simplified solution of two-dimensional Poisson equation using the Green function technique. Starting with the expression of this average normal field, a simple threshold-voltage model for short-channel n-MOSFETs with nonuniformly doped substrate profile is explicitly expressed in terms of device structures and terminal voltages by considering parabolic source-drain boundary potentials. Moreover, the effects of the junction depth on the threshold voltage are examined in detail. It is shown that the DIBL effect cannot be completely eliminated by simply increasing the substrate doping concentration. Comparisons among developed model, 2-D numerical analysis, and experimental data have been made and the accuracy of the developed analytical model has been verified. In addition, a direct extension of our model to the case of uniformly doped substrates leads to a new constraint equation for device miniaturization.<> 相似文献
265.
器件尺寸按比例缩小是实现超大规模集成电路的有效途径,但寄生和二级效应却将器件限在一定的水平,本文在对比分析常温与低温下小尺寸器件效应的基础上,重点研究了MOS器件亚阈特性对器件性能及按比例缩小的影响,并根据低温工作的特点,提出了MOS器件一种低温按比例缩小规则,该原则对低温器的优化设计,从而更大程度在提高电路与系统性能具有重要的指导意义。 相似文献
266.
A new millimeter-wave omnidirectional dielectric rod metallic grating antenna is investigated theoretically and experimentally, in this paper. The radiation characteristics of the antenna are carefully investigated by a rigorous formulation for the TE01-mode and TM01-mode excitation in the Ka-band frequency range. Based on the analysis, an omnidirectional antenna excited by the TE01 mode is designed and measured. The measured results are compared with theoretical predictions and good agreement is found. Extensive numerical results are given to establish some useful guidelines for the design of the omnidirectional antenna 相似文献
267.
268.
269.
The Hawking radiation of Dirac particles in an arbitrarily rectilinearly accelerating Kinnersley black hole with electromagnetic charge and cosmological constant is investigated by using the generalized tortoise coordinate transformation. Both the location and the temperature of the event horizon depend on the time and the polar angle. The Hawking thermal radiation spectrum of Dirac particles is also derived. 相似文献
270.