劣化系统最优维修策略：基于推广累积冲击模型

研究一个遭受累积冲击的劣化系统的最优维修策略. 在系统的工作时间内，任一冲击都将对系统造成损害，其损害效应具有累加性. 当累积冲击损害超过某给定水平时，系统失效. 在每个失效时刻，系统可以维修或者更换. 对一个劣化系统来说，假设引起系统失效的冲击量关于维修次数是几何递减的，并且连续的维修时间构成了一个几何递增过程. 这是一个推广的累积冲击模型，更符合可靠性的客观实际. 采用系统在前N-1次失效后维修，而在第N次失效后被替换的更换策略N，推导了长时间运行后平均费用率的精确表达，并精确地确定了最优维修策略N^*. 最后给出一个数值例子.     

多锤头碎石化震动波对水稳的影响

多锤头碎石化技术是采用多锤头式破碎设备将水泥混凝土路面破碎成混凝土块,用以限制新铺的沥青罩面上出现的反射裂缝,在遇到单幅施工或有路面时由于在均匀介质中传播时,冲击波的频率不变,而振幅将随传播距离的增大而减小,所以在靠近加铺水稳层时,应降低锤头高度。     

一类具有激波层的奇摄动非线性问题

本文研究了一类具有内激波层现象的奇摄动拟线性边值问题,在适当的条件下,用合成展开法构造出该问题的一阶渐近表达式,并利用不动点原理证明了解的存在性及其当ε→0时的渐近性质。     

二维轴对称压差方程组活塞问题的激波解

研究二维轴对称压差方程组活塞问题局部解的存在性.首先,利用轴对称的特点,选用合适的变量将原问题转化为一维问题.然后,利用Taylor展开的方法构造原问题的一个N阶近似解.进而以此近似解作为迭代的首项,通过Newton迭代法,并利用对相应线性问题所作的能量估计,最终证明其活塞问题激波解的局部存在性。     

白炽灯导通特性与导通瞬间电压相位的关系

采用微机多用实验接口线路板对白炽灯点燃过程中的电流变化暂态过程加以分析 ,结果表明 :在这个过程中 ,有象一般杂志介绍的冷态大电流冲击问题 ,而且进一步观察到了冲击电流与导通瞬间电压的相位有关 .     

Shock wave compression of poled Pb0.99[(Zr0.90Sn0.10)0.96Ti0.04]0.98Nb0.02O3 ceramics: Depoling currents in axial and normal modes

We used a 100-mm diameter gas gun to investigate the output currents due to the sudden depolarization of poled Pb 0.99 [(Zr 0.90 Sn 0.10) 0.96 Ti 0.04 ] 0.98 Nb 0.02 O 3 ceramics under shock wave compression.We conducted shock wave experiments for the normal/axial mode with the polarization vector perpendicular/antiparallel to the shock vector.The shock pressure was in the range of 0.23 to 4.50 GPa.We measured the depoling currents under short-circuit,high-impedance,and breakdown conditions.Under the short-circuit condition,the dependence of the released charge on the shock pressure demonstrates the evolution of the ferroelectric-to-antiferroelectric phase transition.The onset pressure of the phase transition is between 0.23 and 0.61 GPa,and phase transition occurs completely above 1.22 GPa.The increasing load resistance decreases the released charge and increases the released energy.The results indicate that Pb[(ZrSn)Ti]NbOceramic is a good candidate for a pulsed power generator.     

The small heat shock proteins and their clients

Small heat shock proteins are ubiquitous proteins found throughout all kingdoms. One of the most notable features is their large oligomeric structures with conserved structural organization. It is well documented that small heat shock proteins can capture unfolding proteins to form stable complexes and prevent their irreversible aggregation. In addition, small heat shock proteins coaggregate with aggregation-prone proteins for subsequent, efficient disaggregation of the protein aggregates. The release of substrate proteins from the transient reservoirs, i.e. complexes and aggregates with small heat shock proteins, and their refolding require cooperation with ATP-dependent chaperone systems. The amphitropic small heat shock proteins were shown to associate with membranes, although they do not contain transmembrane domains or signal sequences. Recent studies indicate that small heat shock proteins play an important role in membrane quality control and thereby potentially contribute to the maintenance of membrane integrity especially under stress conditions. Received 11 July 2006; received after revision 4 October 2006; accepted 10 November 2006     

冲击波下金属铜的分子动力学模拟

对4000个铜原子组成的面心立方晶体进行了近似冲击波的模拟,发现对完整晶体在一定的范围内,冲击波的强弱、外界的温度对晶体结构的影响都不大;加入少许的点缺陷后,晶体内部的应力和能量相对完整晶体变化并不显著,从而说明在考虑系统的状态方程时将带有少量点缺陷的晶体近似为理想晶体的做法是可行的．     

Al冲击熔化的分子动力学模拟

采用分子动力学模拟的方法,对金属Al的冲击熔化过程及平衡熔化过程进行实际研究,并通过对径向分布函数的观察,给出了确实可信的研究结果。     

酵母菌耐热性的最适热激条件研究

以安琪抗高温酵母菌YY为研究材料,采用30-48℃的不同温度和10～180min不同的时间对酵母菌进行热激诱导产生耐热性的研究,研究表明最适热激温度为42℃,最适热激时间为30min,产生耐热性后,在50℃处理的时间越长,活力越小,在酵母菌的不同生长时期,菌体达到一定的浓度后,耐热性的产生没有显著影响,从28℃升到热激温度42℃所需时间在30-240min内,时间越长产生的耐热性越强。