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1.
T. H. Chang K. F. Pao S. H. Chen K. R. Chu 《Journal of Infrared, Millimeter and Terahertz Waves》2003,24(9):1415-1420
Self-consistent effects on the starting current of gyrotron oscillators are examined. Field profiles in the open cavity are shown to be sensitive to the interaction dynamics. This can either significantly raise or lower the oscillation threshold, particularly for the low-Q modes. The transition from resonant-mode oscillations at the low magnetic field to backward-wave oscillations at the high magnetic field is demonstrated. 相似文献
2.
The method of reverberation ray matrix is applied to analyze the dynamic behavior of structural members in trusses with pinned joints subjected to suddenly applied force. The results are compared with those in planar trusses with rigid joints. Detailed calculations are made with two types of trusses, a small laboratory model made of slender aluminum bars, and a hypothetical real size Pratt truss made of structural steel. It is found that the maximum dynamic bending strains in the members of both types of trusses are very large, comparable with the dynamic axial strains in the same member. The magnitudes of bending strains in the pinned truss differs little from those in the truss with rigid joints for both types of trusses. Such a large dynamic bending strain in a structure member, which is contradictory to the static behavior of the same truss, could be caused by the inertial force of the mass in structural members of the truss. 相似文献
3.
Stochastic choice of basis functions in adaptive functionapproximation and the functional-link net 总被引:1,自引:0,他引:1
A theoretical justification for the random vector version of the functional-link (RVFL) net is presented in this paper, based on a general approach to adaptive function approximation. The approach consists of formulating a limit-integral representation of the function to be approximated and subsequently evaluating that integral with the Monte-Carlo method. Two main results are: (1) the RVFL is a universal approximator for continuous functions on bounded finite dimensional sets, and (2) the RVFL is an efficient universal approximator with the rate of approximation error convergence to zero of order O(C/ radicaln), where n is number of basis functions and with C independent of n. Similar results are also obtained for neural nets with hidden nodes implemented as products of univariate functions or radial basis functions. Some possible ways of enhancing the accuracy of multivariate function approximations are discussed. 相似文献
4.
We have studied the isotope effect on the superconducting transition temperatureT
c ofd-wave pairing instabilities due to antiferromagnetic spin fluctuation exchange. We found that models with conventional coupling toharmonic phonon degrees of freedom and reasonable limits on coupling strength and phonon spectra, give values for the isotope exponent which are at least one order of magnitude smaller than typical observed values of in the cuprates. Models with coupling to non-linear tunneling modes in a stronglyanharmonic multi-well lattice potential and realistic coupling strengths have effectively larger isotopic mass dependences andmay therefore account for the observed magnitudes of.This work was supported by the National Science Foundation (Grant DMR-8913878 and DMR-9215123) and by the University of Georgia Office of the Vice President for Research. Computing support from UCNS, University of Georgia, and NCSA, University of Illinois, is gratefully acknowledged. 相似文献
5.
以黄金茶2号为研究对象,采用顶空固相微萃取-气相色谱-质谱联用技术建立不同等级黄金茶香气成分气相色谱-质谱指纹图谱,并通过化学计量法对两个等级的黄金茶进行判别分析。研究表明,2个等级的黄金茶中鉴定出81种香气组分,其中41种为共有香气组分。基于共有香气组分的正交偏最小二乘判别分析可以区分2个等级黄金茶,并筛选出9种差异香气组分,分别是庚醛、柠檬烯、反式-β-罗勒烯、1-辛醇、反式-4,8-二甲基-1,3,7-壬三烯、反-橙花叔醇、1,10-diepicubenol、epicubenol、十六酸甲酯。以9种差异香气组分为变量建立的线性判别方程对2个等级的黄金茶进行等级判别,自身验证和交叉验证正确率为100%。本实验结果可为黄金茶的分级提供客观量化的参考依据。 相似文献
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7.
我国是全球最大的铜消费国,铜矿资源供需矛盾问题日益突出,需大量从国外进口。本文通过对比分析东北亚地区俄罗斯、蒙古、朝鲜、韩国、日本和我国东北地区的铜矿资源概况和供需情况,明确了东北亚地区境外铜矿资源在俄罗斯、蒙古和朝鲜相对丰富,富集区分布在俄罗斯西伯利亚地区和乌拉尔地区、蒙古国北部的额尔登特地区以及与中国接壤的南戈壁和东戈壁省、朝鲜惠山-利原地区,我国与日本、韩国是东北亚地区主要的铜消费区。结合我国铜矿资源对外依存度过高的现状,发挥我国东北地区的地域优势,加强区域矿业合作,勘探、开发、利用东北亚地区铜矿资源,加大地质矿产国际合作的科研投入,深入交流与研究,将有利于缓解我国铜矿资源供需不平衡的矛盾。 相似文献
8.
9.
Pao‐San Huang 《中国工程学刊》2013,36(1):69-72
Abstract The dynamic characteristics of taper seal has been investigated. The approach is similar to Black's analysis; the stiffness and damping coefficients are derived. The results showed that the taper seals presented more stable characteristics comparing with plain seals. The practical application of this theory is increasingly used in industry. 相似文献
10.
Ronald L. Holtz Peter S. Pao Robert A. Bayles Thomas M. Longazel Ramasis Goswami 《Metallurgical and Materials Transactions A》2012,43(8):2839-2849
The fatigue crack growth behavior of aluminum alloy 5083-H131 has been systematically studied as a function of degree of sensitization for aging at 448?K (175?°C). Fatigue crack growth rates were measured at load ratios of 0.1 and 0.85, in vacuum, air, and a corrosive aqueous environment containing 1?pct NaCl with dilute inhibitor. Sensitization does not affect the fatigue crack growth behavior of Al 5083-H131 significantly in vacuum or air, at low- or high-load ratio. For high-load ratio, in the 1?pct NaCl+inhibitor solution, the threshold drops by nearly 50?pct during the first 200?hours of aging, then it degrades more slowly for longer aging times up to 2000?hours. The change in aging behavior at approximately 200?hours seems to be correlated with the transition from partial coverage of the grain boundaries by ?? Al3Mg2 phase, to continuous full ?? coverage. ASTM G-67 mass loss levels below approximately 30?mg/cm2 do not exhibit degraded corrosion-fatigue properties for R?=?0.85, but degradation of the threshold is rapid for higher mass loss levels. 相似文献