草酸根桥联手性双核铜的合成、表征、结构与磁性

分别以(8R,10R)-(-)-[4,5]-pineno-2,2′-bipyridine或(8S,10S)-(+)-[4,5]-pineno-2,2′-bipyridine(LRR和LSS)为手性配体合成双核铜络合物[Cu2(μ-ox)(LRR)2(H2O)2(ClO4)2](1)、[Cu2(μ-ox)(LRR)2(CH3COCH3)2(ClO4)2](1a)、[Cu2(μ-ox)(LSS)2(H2O)2(ClO4)2](2)和[Cu2(μ-ox)-(LRR)(LSS)(CH3COCH3)2(ClO4)2](3)(ox2-=草酸根),并探讨了其反应机理.由元素分析、电导率、紫外可见谱(UV-vis)、圆二色(CD)谱和晶体结构分析推测:该系列络合物具有草酸根桥联的双核结构,两个铜(II)离子与草酸根几乎成共平面;1a和3的晶体结构分析表明,每个Cu(II)的配位构型为拉长畸变八面体,双核分子中轴向的两个溶剂分子和两个高氯酸根互为反式配位.对映体络合物1和2的溶液CD光谱大致呈镜像对称,在可见区的极弱CD吸收峰可能源于LRR和LSS蒎烯基上的手性中心对Cu(II)d-d生色团的手性微扰产生的邻位效应.采用最小二乘法和Bleaney-Bowers方程对络合物1的变温磁化率测试数据进行拟合,求得交换积分J=-338.41(4)cm-1,表明铜(II)离子间有较强的反铁磁自旋交换作用.     

自组惠斯登电桥测电阻中的误差及分析

通过分析惠斯登电桥测电阻的误差,提出改进实验方法提高灵敏度,减小测量误差.     

测量金属导线热导率的新方法

用双臂电桥测量一定温度下铜导线的电阻,进而计算得到铜线的电导率,再根据维德曼-夫兰兹定律得到铜线的热导率.     

Efficient Monte Carlo simulation for integral functionals of Brownian motion

In the paper, we develop a variance reduction technique for Monte Carlo simulations of integral functionals of a Brownian motion. The procedure is based on a new method of sampling the process, which combines the Brownian bridge construction with conditioning on integrals along paths of the process. The key element in our method is the identification of a low-dimensional vector of variables that reduces the dimension of the integration problem more effectively than the Brownian bridge. We illustrate the method by applying it in conjunction with low-discrepancy sequences to the problem of pricing Asian options.     

Mechanical properties and deformation morphologies of covalently bridged multi-walled carbon nanotubes: Multiscale modeling

We formulate a multiscale modeling framework to investigate the deformation morphologies and energetics of covalently bridged multi-walled carbon nanotubes (MWCNTs). The formulation involves extending a previously established quasi-continuum model by incorporating the inter-wall bridging energy density function into the constitutive relations via message passing from fully atomistic simulations. Using the extended numerical model, we studied the mechanical responses of the 10-walled MWCNT with varying inter-wall bridge densities under torsion, bending, and uniaxial compression. Our simulation results show that the presence of inter-wall covalent bridges not only enhances the post-buckling rigidities of the MWCNTs, but also modifies the deformation morphologies and morphology pathways. For bending and uniaxial compression, we constructed in the space of bridge density and applied strain the deformation morphology phase diagram, where three phases, uniformly deformed phase, rippling pattern, and diamond-shaped pattern, are identified and separated by linear phase boundaries. We attribute the deformation phase transitions to the interplay of inter-wall and intra-wall interaction energies. The multiple shape transitions of MWCNTs and the elastic nature of the deformation suggest that MWCNTs can be designed as shape-memory nanodevices with tunable stabilities.     

应变式压力传感器检测电路的讨论

本文讨论了传统的应变式压力传感器检测电路，给出了改进措施，提高了视在输出，实现了零点调整，补偿了由于温度变化引起的受力弹性体的弹性系数变化和应变片灵敏度系数变化，满足了输出线性度要求。     

A Bridge Principle for Harmonic Diffeomorphisms between Surfaces

We show a bridge principle for harmonic diffeomorphisms between closed surfaces with higher genus.     

关于惠斯登电桥测电阻中几个问题的讨论

本文简述了电桥原理。提出了电桥平衡和灵敏度计算方面的两个问题，并给出了解决办法。     

ARCH模型的多变点检验

研究自回归条件异方差(ARCH)模型的多变点检验问题.提出一种拟似然比检验统计量,并在原假设下给出统计量的极限分布.在假设检验过程中得到变点个数的一致估计.数值模拟与实例分析说明了方法的合理性.