PERIODIC SOLUTIONS OF PLANAR SYSTEM WITH SIX DELAYS

In this paper we obtain some sufficient conditions for the existence of non-constant periodic solutions of the following planar system with six delaysOur approach is based on the continuation theorem of the coincidence degree.     

Long-Term Prediction of Creep Strain of Expanded Polystyrene

Data obtained in investigating the creep of expanded polystyrene in compression are discussed. An analysis of the results of creep tests 65–608 days long showed that the creep can be predicted for 50 years based on experiments of less duration than the 605 days indicated in EN 13163. For this purpose, it is suggested to employ a 95-fold extrapolation in time if the creep curves are described by a power function (as recommended by EN 13163) or a 50-fold extrapolation if the exponential equation proposed in the present paper is used. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 795–802, November–December, 2005.     

关于"太阳在银河系中所受引力与到银心距离r的关系"的讨论

讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系，指出引力场强g并不是与r的平方成反比，这是由于银河系的大小和形状不能忽略造成的．强调了万有引力定律的适用条件．     

NOTE ON THE OSCILLATION OF THE SOLUTION FOR GENERALIZED LIENARD EQUATIONS

Ｃｏｎｓｉｄｅｒｉｎｇｓｙｓｔｅｍ：ｘ＝φ（ｙ）－Ｆ（ｘ），ｙ＝－ｇ（ｘ）｛（Ｅ）ｉｎｗｈｉｃｈＦ（ｘ）＝∫ｘ０ｆ（ｔ）ｄｔ，ｆ（ｘ），ｇ（ｘ），φ（ｙ）ａｒｅｃｏｎｔｉｎｕｏｕｓ，ａｎｄｓａｔｉｓｆｙｔｈｅｃｏｎｄｉｔｉｏｎｓｗｈｉｃｈｅｎｓｕｒ...     

具有两台专用机,两台通用机的Q4／／Cmax问题的近似算法

本文讨论具有两台专用机、两台通用机的两组工件的同种类平行机的Q4／／Cmax问题，对这类特殊的排序问题，提出一种启发式算法，得到了最差情况下性能指标的严格的界．     

WEAK CONVERGENCE OF HENSTOCK INTEGRABLE SEQUENCES

Some relationships between pointwise and weak convergence of a sequence of Henstock integrable functions are studied, In particular it is provided an example of a sequence of Henstock integrable functions whose pointwise limit is different from the weak one. By introducing an asymptotic version of the Henstock equiintegrability notion it is given a necessary and sufficient condition in order that a pointwisely convergent sequence of Henstock integrable functions is weakly convergent to its pointwise limit.     

灰色模型的最优化及其参数的直接求法

基于灰色模型的内涵表达式和白化方程响应式均为等比级数的观点,提出了一种不用求ago值、均值,不涉及灰色微分方程,白化微分方程概念,直接求灰色模型参数a,c的方法,通过此方法建立的新模型不仅从理论上可保证是在满足给定评价标准为模拟绝对误差平方和最小(或模拟相对误差平方和最小)、给定精度条件下的最优化模型,从而结束了灰色模型只有更优,没有最优的历史.并从理论上证明了新模型具有白化指数律重合性、白化系数律重合性,伸缩变换一致性.最后通过实例编程验证该方法具有可操作性,且预测精度高,效果好.     

Almost-sure path properties of fractional Brownian sheet

The almost sure sample function behavior of the vector-valued fractional Brownian sheet is investigated. In particular, the global and the local moduli of continuity of the sample functions are studied. These results give precise information about the continuity and the oscillation behavior of the sample functions.     

Spherically symmetric static inhomogeneous cosmological models

Spherically symmetric static cosmological models filled with black-body radiation are considered. The models are isotropic about a central observer but inhomogeneous. It is suggested that the energy density of the free gravitational field, which is coupled to the isotropic radiation energy density, might play an important role in generating sufficient field (vacuum) energy (when converted into thermal energy) and initiate processes like inflation. On the central world line the energy density of the free gravitational field vanishes whereas the proper pressure and density of the isotropic black-body radiation are constants. Further, it is shown that the cosmological constant is no more arbitrary but given in terms of the central pressure and density. Also, at its maximum value the energy density of the free gravitational field is proved to be equal to one third of the combined value of radiation pressure and density.     

优化路问题的代数方法—论动态规划（Ⅱ）

本文用同一思路求解多阶段有向图中三种优化路问题:最优路、N阶最优路及多指标Pareto优化路问题,它们都服从嘉量原理,都用同一个代数公式表达它们的嘉量,并可在同一种表格中进行计算,只是所在半域不同,以本文的方法讨论动态规划中一些离散决定型典型应用问题,其提法、建模思路以及求解过程都有可观的扩大与改善。