非线性约束下非完整系统的平衡稳定性

Kozlov将Liapunov第一方法推广到非线性力学系统,用来解决保守和耗散力场中,运动力学系统平衡位置的不稳定性.文中讨论的系统运动限于理想的非线性非完整约束.将势能和约束函数展开为Maclaurin级数,对其第一非平凡多项式的阶,确定了相互间关系的5种情况,并对生成的非线性非完整约束方程进行了分析.将3种线性齐次约束下的非完整系统平衡位置的不稳定定理(Kozlov,1986),推广到非线性非完整约束.另外两种情况下的新定理,也是将Kozlov(1994)的结果,拓展到非线性约束下的非完整系统.     

TiNi合金电极的表面修饰及其电催化性能

ＴｉＮｉ合金电极的表面修饰及其电催化性能胡伟康，申泮文，张允什，周作祥，汪筠（南开大学化学系，天津３０００７１）（南开大学新能源材料研究所，天津３０００７１）近几年来，储氢电极可望作为电解工业的活性阴极材料而受到了极大的关注。Ｋｉｔａ－ｍｕｒａ￣［１...     

氢化铝钠合成方法研究(Ⅱ)

氢化铝钠NaAlH_4是Schlesinger和Finbolt在1951年首次报道的。它是一种还原性能与氢化铝锂LiAlH_4十分相似的络合氢化物。由于在组成中以Na代替了Li,降低了原料成本,本应是一种比LiAlH_4应用得更为广泛的优良还原剂,但由于合成方法上的     

在数学課外工作的进行中发展学生的独立性和主动性

在本文里,打算談談維尼察(?)第四中学的学校“数学爱好者协会”的工作經驗。在数学課外工作的进行中,对于学生的独立性和主动性的发展,可通过下列的几个方面来实現: 1)形成独立閱讀的习慣。 2)搜集并編輯习題与答問題     

氢化铝钙合成方法的研究

与氢化铝锂(LiAlH_4)相似,氢化铝钙[Ca(AlH_4)_2]也是一种还原性能极强的络合金属氢化物。由于在它的组成中以Ca代替了Li,降低了原料成本。在某些特定的条件下,如还原反应在四氢呋喃(THF)中进行,使用Ca(AlH_4)_2可较大幅度地降低还原剂的使用成本。氢化铝钙是Finholt于1951年首次报道的。其合成方法之一是将氢化钙(CaH_2)与AlCl_3在THF溶剂中反应,生成Ca(AlH_4)_2 的THF合物。     

Enhancement of charging performance of quantum battery via quantum coherence of bath

An open quantum battery (QB) model of a single qubit system charging in a coherent auxiliary bath (CAB) consisting of a series of independent coherent ancillae is considered. According to the collision charging protocol we derive a quantum master equation and obtain the analytical solution of QB in a steady state. We find that the full charging capacity (or the maximal extractable work (MEW)) of QB, in the weak QB-ancilla coupling limit, is positively correlated with the coherence magnitude of ancilla. Combining with the numerical simulations we compare with the charging properties of QB at finite coupling strength, such as the MEW, average charging power and the charging efficiency, when considering the bath to be a thermal auxiliary bath (TAB) and a CAB, respectively. We find that when the QB with CAB, in the weak coupling regime, is in fully charging, both its capacity and charging efficiency can go beyond its classical counterpart, and they increase with the increase of coherence magnitude of ancilla. In addition, the MEW of QB in the regime of relative strong coupling and strong coherent magnitude shows the oscillatory behavior with the charging time increasing, and the first peak value can even be larger than the full charging MEW of QB. This also leads to a much larger average charging power than that of QB with TAB in a short-time charging process. These features suggest that with the help of quantum coherence of CAB it becomes feasible to switch the charging schemes between the long-time slow charging protocol with large capacity and high efficiency and the short-time rapid charging protocol with highly charging power only by adjusting the coupling strength of QB-ancilla. This work clearly demonstrates that the quantum coherence of bath can not only serve as the role of "fuel" of QB to be utilized to improve the QB's charging performance but also provide an alternative way to integrate the different charging protocols into a single QB.     

多孔材料夹芯的分层复合双壁面圆柱壳体中波的传播

在经典的理论框架内,对分层的复合材料壳体——多孔材料夹芯的双壁面圆柱壳体,研究自由谐和波在其中的传播.借助于一个具有同样几何特性的展开平板,评估波通过多孔夹芯层传播时大部分有效的成分.通过有效波成分的考虑,将多孔层模拟为具有等效特性的流体.因此,模型简化为一个集满流体介质的双壁面圆柱壳体.最后,评估带宽频率中结构的传播损失,并对结果加以比较.     

半导体硅上电沉积Cu/Co层状薄膜

由磁性层和非磁性层组成的人工调制层状结构多层膜,其物性和磁性都表现出与其它结构的多层膜显著不同的特点,如巨磁阻效应［’,‘l、易磁性方向的改变等”］．其性能的研究不但在磁性理论上具有重大意义,而且有望应用于高性能的磁阻敏感设备及提高磁记录密度等．因而近年来有关这方面的研究越来越引起人们的重视．目前,磁性多层膜的制备主要采用气相沉积、磁控溅射、分子束外延等真空技术．由于电沉积技术具有设备简单、操作方便等特点而成为制备多层膜的颇具活力的工艺．CO／Cll多层膜在C。层厚度较薄时具有较高室温巨磁阻（GMR）…