Availability measures for components maintained by repair-replacement policies

A renewal-reward process model is given for a component maintainedby a general repair-replacement policy. The point availabilityof the component at time t and its expected operating time overthe interval (0, t) are defined in terms of a pair of relatedintegral equations. These two equations are then solved numericallyto obtain values of the two measures for the policy of repairplus replacement at age .     

不同应变率下玻璃态高聚物非线性屈服后行为的唯象本构定律

基于描述高温下金属行为的方法并经过修改状态变量本构方程，本研究提出一个无定形高聚物的粘塑性行为的模型．该模型包括了应变率敏感性效应，应变软化效应和应变硬化效应．在不同应变率和低于玻璃态转变温度(Tg)范围内，利用已发表的单轴试验的实验数据给出了一个确定模型参数的方法。数值算法表明该模型能较好预示屈服后的本征软化以及随之而产生的渐进定向硬化，尤其是对无定形玻璃态高聚物．     

Ageing exploration of the energy landscape of a glass by the TSDC technique

Different thermal treatments were used in order to follow the structural relaxation of m-toluidine by thermally stimulated depolarization currents (TSDC) in the sub-T _g temperature region. In some of these thermal treatments, the ageing time, t _a, and the probing (or polarization) time, t _P, are varied independently in order to allow a clear understanding of the exploration of the energy landscape which occurs as a consequence of the structural relaxation. The TSDC results show that ageing induces a shift to higher temperatures of the TSDC peaks, in a way similar to that observed in the calorimetric heat capacity overshoot. More importantly, TSDC results show that ageing induces a decrease of the activation energies with regard to the window defined by the probing time and a sharpening of the energy distribution of the modes of motion that are present in the glass, in the studied sub-T _g temperature region.