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121.
In this investigation we consider the formation of Cooper pairs near the oxygen-deficient sites in Y-Ba-Cu-O ceramic superconductors which would give rise to an energy-dependent potential as seen by conduction charge carriers. It is shown that Cooper pairs could be formed under such conditions, resulting in a supercurrent. We use the Bogoliubov transformation technique to calculate the energy gap, the energy difference, and the transition temperature of the model superconductor using certain data obtained from previous experiments. Numerical analysis shows that the superconducting current can be explained by the presence of such oscillating Cooper pairs. 相似文献
122.
123.
124.
针对无刷双馈电动机的转子磁场转换效率决定了其工作效率的问题,提出了一种隐极无刷双馈电动机隐极转子结构的优化设计方案。对作用较小的隐极转子进行优化设计,即将它们的槽型更改为半开口槽,不断改变它们的长宽比;利用有限元软件ANSYS分析不同长宽比转子结构的隐极无刷双馈电动机,获得其功率绕组励磁与控制绕组励磁分布;利用Matlab软件分解转子磁动势,获得转子磁动势的谐波含量,从而确定最有效谐波含量。实验结果表明,在设定隐极转子的长宽比分别为10、13、15、17、20的情况下,隐极无刷电动机在15倍长宽比转子结构时的能量转换效果最好。 相似文献
125.
Networks of communicating processes can be viewed as networks of stream transformers and programmed in a lazy functional language. Thus the correctness of concurrent systems can be reduced to the correctness of functional programs. In this paper such correctness is proved formally in the-calculus extended with recursion equations for functional programs. The-calculus is chosen since it allows the definition of properties by least fixed points (induction) as well as by greatest fixed points (coinduction), and since greatest fixed points are useful for formalising properties, such as fairness, of infinitely proceeding programs. Moreover, non-deterministic processes are represented as incompletely specified deterministic processes, that is, as properties of stream transformers. This method is illustrated by proving the correctness of the alternating bit protocol. 相似文献
126.
Charles A. Barrett 《Oxidation of Metals》1988,30(5-6):361-390
The effect of 0.1 at.% Zr (0.2 wt.% Zr) on the cyclic oxidation of hipped -NiAl was studied. Oxidation testing was performed in static air at 1100–1200 °C, using 1-hr exposure cycles for test times up to 3000 hr. The weight change versus time data were modeled with the COSP computer program to analyze and predict cyclic-oxidation behavior. Zr additions significantly change the nature of the scale-spalling process during cooling so that the oxide spalls near the oxide-air interface at a relatively low depth within the scale. Without Zr, the predominantly -Al2O3 scale tends to spall randomly to bare metal at relatively high effective-scale-loss rates, particularly at 1150°C and 1200°C. This leads to higher rates of Al consumption for the Zr-free aluminide and much earlier depletion of Al, leading to eventual breakaway (i.e., failure). 相似文献
127.
Marek Zaionc 《Journal of Automated Reasoning》1988,4(2):173-190
In this paper is presented an algorithm for constructing natural deduction proofs in the propositional intuitionistic and classical logics according to the analogy relating intuitionistic propositional formulas and natural deduction proofs, respectively, to types and terms of simple type theory. Proofs are constructed as closed terms in the simple typed calculus. The soundness and completeness of this method are proved. 相似文献
128.
Pavel L. Katsel Tamara M. Dmitrieva Rashid B. Valeyev Yuri P. Kozlov 《Journal of chemical ecology》1992,18(11):2003-2010
Three components of the male yellowfin Baikal sculpin pheromonal signal have been isolated from urine by diethyl ether extraction, thinayer chromatography (TLC), and high-performance liquid chromatography (HPLC). Using mass spectrometry, we have identified two of them as testosterone (T) and 11-hydroxytestosterone (11HT). These steroids are synthesized in testes during full spermatogenesis, and they are excreted in male urine with milt. The third component is not a steroid. It is more likely to be a polyene alcohol (farnesol). 2Z,6E-Farnesol possesses behavioral activity. 相似文献
129.
N. Guskos V. Lyvkodimos C. A. Londos A. Kondos S. M. Paraskevas A. Koufoudakis C. Mitros H. Gamari-Seale D. Niarchos I. Kruk 《Journal of Superconductivity》1992,5(5):457-461
EPR, XRD, and magnetic studies are presented for Pr0.5Re0.5Ba2Cu3O7– compounds (Re= La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, Tm, Yb, and Lu) in the orthorhombic and tetragonal (large oxygen deficiency) phase. For the samples with Re=Dy, Ho, Y, Er, Tm, Yb, and Lu in the orthorhombic phase, the transition to the superconducting state has been observed in the temperatures rangeT
c
between 18 and 40 K. For the samples with Nd and Yb in the tetragonal phase, EPR spectra coming from trivalent rare earth ions have been recorded. In the nonoxygenated sample Pr0.5La0.5Ba2Cu3O7–
the EPR spectrum arising from the non-Kramers trivalent praseodymium ion has been observed. A broad EPR line appearing in all our samples was attributed to superexchange interaction between copper ions over oxygen (O
2
–
) bridges. Interestingly, for the Pr0.5Re0.5Ba0.5Cu3O7– (Re = Er and Lu) compounds in the tetragonal phase at liquid-nitrogen temperature, a nonresonant microwave absorption in low magnetic fields has been detected. 相似文献
130.
Michael Morris 《Minds and Machines》1992,2(1):85-95
In his response to my Why There Are No Mental Representations, Robert Cummins accused me of having misinterpreted his views, and attempted to undermine a crucial premise of my argument, which claimed that one could only define a semantic type non-semantically by stipulating which tokens should receive a uniform interpretation. I respond to the charge and defend the premise. 相似文献