同步发电机Td′和Td″近似算式分析

研究对比同步发电机直轴时间常数复杂近似算式和由其导出的简易近似算式的误差。分析简易近似算式误差小于复杂近似算式误差的条件,并以45台同步发电机实际数据对其进行验证,分析近似算式传统推演方法存在的问题,研究推演简易近似算式的合理前提和方法。认为简易近似算式误差小于复杂近似算式误差的条件为σ′d>0.5,绝大多数同步发电机满足这一条件。复杂近似算式推演采用的假设条件不符合同步发电机实际,建议废弃复杂近似算式,并给出了一种直接由直轴时间常数准确算式推演简易近似算式的简明方法。

矩形明渠均匀流水深和底宽的算子分裂算法

应用算子分裂思想将矩形明渠均匀流方程分裂为两个简单算式 ,通过耦合方法建立了整个定义域内的统一近似算式 ,该算式结构简明 ,计算方便 ,精度可达

基底隔震的多层建筑结构自振频率和振型解析

本文以基底隔震的7自由度建筑结构为研究对象,参考三对角Toeplitz矩阵特征值问题的数学解法,推导了2种特定隔震层刚度条件下的各阶自振圆频率和振型的解析解,由此构造了任意隔震层刚度条件下结构的各阶自振圆频率和振型的解析算式,并用数值解的结果进行了验证。结果表明:对基底隔震建筑结构地震响应具有重要影响的第1阶自振圆频率和振型,给出了精度良好的简化算式,可供工程设计选定隔震层刚度使用。

Comparison of two kinds of approximate proximal point algorithms for monotone variational inequalities

This paper proposes two kinds of approximate proximal point algorithms （APPA） for monotone variational inequalities, both of which can be viewed as two extended versions of Solodov and Svaiter＇s APPA in the paper ＂Error bounds for proximal point subproblems and associated inexact proximal point algorithms＂ published in 2000. They are both prediction- correction methods which use the same inexactness restriction; the only difference is that they use different search directions in the correction steps. This paper also chooses an optimal step size in the two versions of the APPA to improve the profit at each iteration. Analysis also shows that the two APPAs are globally convergent under appropriate assumptions, and we can expect algorithm 2 to get more progress in every iteration than algorithm 1. Numerical experiments indicate that algorithm 2 is more efficient than algorithm 1 with the same correction step size,

Thin-bed thickness calculation formula and its approximation using peak frequency

Quantitative thickness estimation below tuning thickness is a great challenge in seismic exploration. Most studies focus on the thin-beds whose top and bottom reflection coefficients are of equal magnitude and opposite polarity. There is no systematic research on the other thin-bed types. In this article, all of the thin-beds are classified into four types： thin-beds with equal magnitude and opposite polarity, thin-beds with unequal magnitude and opposite polarity, thin-beds with equal magnitude and identical polarity, and thin-beds with unequal magnitude and identical polarity. By analytical study, an equation describing the general relationship between seismic peak frequency and thin-bed thickness was derived which shows there is a Complex implicit non-linear relationship between them and which is difficult to use in practice. In order to solve this problem, we simplify the relationship by Taylor expansion and discuss the precision of the approximation formulae with different orders for the four types of thin-beds. Compared with the traditional amplitude method for thin-bed thickness calculation, the method we present has a higher precision and isn＇t influenced by the absolute value of top or bottom reflection coefficient, so it is convenient for use in practice.

Comparison of two approximal proximal point algorithms for monotone variational inequalities

Proximal point algorithms （PPA） are attractive methods for solving monotone variational inequalities （MVI）. Since solving the sub-problem exactly in each iteration is costly or sometimes impossible, various approximate versions ofPPA （APPA） are developed for practical applications. In this paper, we compare two APPA methods, both of which can be viewed as prediction-correction methods. The only difference is that they use different search directions in the correction-step. By extending the general forward-backward splitting methods, we obtain Algorithm Ⅰ; in the same way, Algorithm Ⅱ is proposed by spreading the general extra-gradient methods. Our analysis explains theoretically why Algorithm Ⅱ usually outperforms Algorithm Ⅰ. For computation practice, we consider a class of MVI with a special structure, and choose the extending Algorithm Ⅱ to implement, which is inspired by the idea of Gauss-Seidel iteration method making full use of information about the latest iteration. And in particular, self-adaptive techniques are adopted to adjust relevant parameters for faster convergence. Finally, some numerical experiments are reported on the separated MVI. Numerical results showed that the extending Algorithm II is feasible and easy to implement with relatively low computation load.

Mechanical properties of frozen rock mass with two diagonal intersected fractures

Based on previous research results, this paper investigated the influence of fracture morphology on mechanical properties and failure modes of rock mass with two diagonal intersected fractures. This study carried out a series of triaxial compression tests on rock-like specimens with two crossed fractures under negative temperature, concluded the following conclusions. The strength and failure modes of rock mass are significantly influenced by the dips of two crossed fractures. The strength of rock mass with two frac- tures cannot simply be estimated using the method that was developed for the rock mass with a single fracture. When the intersecting angle is less than 30~, the failure plane initiates at the tip of ＂artificial rup- tures＂ and extends to the upper and lower ends of the specimen. In case of a higher dip and intersecting angle ranging from 30° to 60°, the failure plane propagates along one of these two fractures. The mechan- lca! parameters of rock mass are not only related to the trace length, but also depend on the trace !ength ratio. One could roughly calculate the strength parameters using the approximation proposed in.this paper..For the rock mass with a trace length ratio 〈0.3 （short trace length/long trace length）, the failure mode is dependent on the fracture with a longer trace length. When the trace length becomes significant and the trace length ratio approximates to 1, the failure plane propagates along two fractures, where an X-shaped.failure pattern is presented： For the rock mass with moderate frac!ures and a trace length ratio of approxlmately 1, the failure mode Is.Independent on fractures, which is simllar to .the damage pattern of intact rock. The strength, and elastic .modulus of rock mass decrease with the increase of spacing between fractures, whl!e Polsson＇s ratio is Independent on the spacing. The failure mode can be deter- mined by the area. of triangle created by two fractures. Damage occurs at the smaller triangle area first, and propagates with the two sides of the larger triangle.

Quantum entanglement of the binomial field interacting with a cascade three-level atom beyond the rotating wave approximation

In this paper, the quantum entanglement between a single mode binomial field and a cascade three-level atom is calculated mechanically without the rotating wave approximation. The numerical results indicate that the quantum entanglement at the first few periods is reduced notably due to the fact that the atom is initially in the superposition state. With increasing field parameter 17, the period of the entanglement evolution becomes obvious and the quantum decoherence phenomenon emerges in a short time.

A PROXIMAL POINT ALGORITHM FOR A SYSTEM OF GENERALIZED MIXED VARIATIONAL INEQUALITIES

This paper introduces and considers a new system of generalized mixed variational inequal- ities in a Hilbert space, which includes many new and known systems of variational inequalities and generalized variational inequalities as special cases. By using the two concepts of η-subdifferential and η-proximal mappings of a proper function, the authors try to demonstrate that the system of generalized mixed variational inequalities is equivalence with a fixed point problem. By applying the equivalence, a new and innovative η-proximal point algorithm for finding approximate solutions of the system of generalized mixed variational inequalities will be suggested and analyzed. The authors also study the convergence analysis of the new iterative method under much weaker conditions. The results can be viewed as a refinement and improvement of the previously known results for variational inequalities.

An implicit algorithm based on iterative modified approximate factorization method coupling with characteristic boundary conditions for solving subsonic viscous flows

An algorithm composed of an iterative modified approximate factorization(MAF(k)) method with Navier-Stokes characteristic boundary conditions(NSCBC) is proposed for solving subsonic viscous flows.A transformation on the matrix equation in MAF(k) is made in order to impose the implicit boundary conditions properly.To be in consistent with the implicit solver for the interior domain,an implicit scheme for NSCBC is formulated.The performance of the developed algorithm is investigated using spatially evolving zero pressure gradient boundary layer over a flat plate and a wall jet mixing with a cross flow over a flat plate with a square hole as the test cases.The numerical results are compared to the existing experimental datasets and a number of general correlations,together with other available numerical solutions,which demonstrate that the developed algorithm possesses promising capacity for simulating the subsonic viscous flows with large CFL number.

One Hair Postulate for Hawking Radiation as Tunneling Process

For Hawking radiation, treated as a tunneling process, the no-hair theorem of black hole together with the law of energy conservation is utilized to postulate that the tunneling rate only depends on the external qualities(e.g., the mass for the Schwarzschild black hole) and the energy of the radiated particle. This postulate is justified by the WKB approximation for calculating the tunneling probability. Based on this postulate, a general formula for the tunneling probability is derived without referring to the concrete form of black hole metric. This formula implies an intrinsic correlation between the successive processes of the black hole radiation of two or more particles. It also suggests a kind of entropy conservation and thus resolves the puzzle of black hole information loss in some sense.