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71.
72.
刘扬 《东莞理工学院学报》1995,2(2):26-32
本文针对传统的消除金属工作内部残余应力的热时效处理法的不足,从激振角度,运用材料力学、动力学中的振动理论等知识,并通过大量试验验证,研究了振动消除应力的方法--振动时效法的原理及其有关问题。说明这种新的方法具有节能、高效等一系列优点。 相似文献
73.
A solution to the BBGKY hierarchy for nonequilibrium distribution functions is obtained within modified boundary conditions. The boundary conditions take into account explicitly both the nonequilibrium one-particle distribution function as well as local conservation laws. As a result, modified group expansions are proposed. On the basis of these expansions, a generalized kinetic equation for hard spheres and a generalized Bogolubov–Lenard–Balescu kinetic equation for a dense electron gas are derived within the polarization approximation. 相似文献
74.
Polyethers, which are produced by alcoholysis of oxiranes, are often used as solvents in chemical plants. The spectra of the products can be influenced by the choice of the catalyst (acid or base). The results of the base-catalyzed ethanolysis of 1,2-epoxybutane are displayed. The reaction was investigated calorimetrically by varying the molar ratio between ethanol and 1,2-epoxybutane, the starting temperature and the concentration of the catalyst sodium hydroxide. Additionally, the influence of the used alcohol will be shown in one example. To determine the activation parameters, the experiments were evaluated by the nonlinear software package TA-kin v3.3. 相似文献
75.
讨论了工艺过程中产生的界面态陷阱电荷Q(it)对高频MOS-CV特性线的形变规律,提出了一种沿电压方向形变的数据处理方法,以此算出Q(it)密度在禁带中的分布,并对常规高频CV法的测量误差作了讨论和修正,由于数据的采集和处理可以由微机完成,使这种方法变得简便、准确并易于在工艺线上推广使用。 相似文献
76.
Nineteen trained soprano singers aged 18–30 years vocalized tasks designed to assess average speaking fundamental frequency (SFF) during spontaneous speaking and reading. Vocal range and perceptual characteristics while singing with low intensity and high frequency were also assessed, and subjects completed a survey of vocal habits/symptoms. Recorded signals were digitized prior to being analyzed for SFF using the Kay Computerized Speech Lab program. Subjects were assigned to a normal voice or impaired voice group based on ratings of perceptual tasks and survey results. Data analysis showed group differences in mean SFF, no differences in vocal range, higher mean SFF values for reading than speaking, and 58% ability to perceive speaking in low pitch. The role of speaking in too low pitch as causal for vocal symptoms and need for voice classification differentiation in vocal performance studies are discussed. 相似文献
77.
For structural parameters with uncertainties, interval mathematics can, in the case where the probabilistic distribution density
of uncertain variables is unavailable, deal with the influence of uncertainties in structural parameters on the response of
structures. In order to evaluate the region containing natural frequencies of structures with interval parameters, the interval
parameter perturbation method is presented in this paper. The advantage of the present method is its computational efficiency
in evaluating the region containing natural frequencies. A numerical example is used to illustrate the efficiency of the method
proposed.
The project is supported by National Youth Natural Science Foundation of China and National Outstanding Youth Science Foundation
of China. 相似文献
78.
Jacek Polewczak 《Journal of statistical physics》1989,56(1-2):159-173
A global existence theorem with large initial data inL
1 is given for the modified Enskog equation in 3. The method, which is based on the existence of a Liapunov functional (analog of theH-Boltzmann theorem), utilizes a weak compactness argument inL
1 in a similar way to the DiPerna-Lions proof for the Boltzmann equation. The existence theorem is obtained under certain condition on the behavior of the geometric factorY. The condition onY amounts to the fact that theL
1 norm of the collision term grows linearly when the local density tends to infinity. 相似文献
79.
Büttiker and Landauer studied scattering off an oscillating rectangular barrier in order to shed light on the time aspects of tunneling. The expression for the traversal time resulting from this study is controversial. In addition, doubts have recently been expressed on technical aspects of their work. In an attempt to clarify these issues, we investigate a generalization of their model to arbitrary oscillating barriers,V(x, t)=V
0(x)+V
1(x)cos t. In the process, we confirm that Büttiker and Landauer's work is technically sound. However, we show, by several examples, that no direct general relation exists between the characteristic frequency of an oscillating barrier and the duration of the tunneling process. For a wide range of realistic parameters this characteristic frequency does not even exist.This paper is dedicated to E. G. D. Cohen. 相似文献
80.
T. Katsuki 《Russian Chemical Bulletin》2004,53(9):1859-1870
The recent development of asymmetric Baeyer—Villiger oxidation of prochiral and racemic ketones is briefly summarized, focusing on the regio- and stereocontrol of the oxidation attained by regulating the stereoelectronic demand in the step of rearrangement of the Criegee intermediate.Based on the report presented at the International Conference Modern Trends in Organoelement and Polymer Chemistry dedicated to the 50th anniversary of the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences (Moscow, May 30–June 4, 2004).Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1784–1794, September, 2004. 相似文献