日本寿险业效率变动实证研究:1998-2008

日本是世界上保险业最发达的国家之一.但自20世纪90年代以来随着泡沫经济的破灭,宏观经济和金融环境的恶化,日本保险业尤其是寿险业进入了停滞与调整期.面对这一情况,日本政府层面和公司层面都推出各种措施,振兴踯躅前行中的日本寿险业.利用数据包络分析(DEA)方法对1998 2008年期间日本全部寿险公司的技术效率、纯技术效率和规模效率及其变动趋势进行了测度,对日本寿险市场的发展演变历程进行全面分析,希望对中国寿险业的发展提供经验借鉴.     

Reactor scale modeling of multi-walled carbon nanotube growth

As the mechanisms of carbon nanotube (CNT) growth becomes known, it becomes important to understand how to implement this knowledge into reactor scale models to optimize CNT growth. In past work, we have reported fundamental mechanisms and competing deposition regimes that dictate single wall carbon nanotube growth. In this study, we will further explore the growth of carbon nanotubes with multiple walls. A tube flow chemical vapor deposition reactor is simulated using the commercial software package COMSOL, and considered the growth of single- and multi-walled carbon nanotubes. It was found that the limiting reaction processes for multi-walled carbon nanotubes change at different temperatures than the single walled carbon nanotubes and it was shown that the reactions directly governing CNT growth are a limiting process over certain parameters. This work shows that the optimum conditions for CNT growth are dependent on temperature, chemical concentration, and the number of nanotube walls. Optimal reactor conditions have been identified as defined by (1) a critical inlet methane concentration that results in hydrogen abstraction limited versus hydrocarbon adsorption limited reaction kinetic regime, and (2) activation energy of reaction for a given reactor temperature and inlet methane concentration. Successful optimization of a CNT growth processes requires taking all of those variables into account.     

大尺度环形液池内双层热毛细对流不稳定性

假设双层流体的交界面不发生变形,热毛细力作用于此交界面,三维数值研究了大尺度环形液池中双层流体系统在内外壁面温差加热下的热毛细对流不稳定性,其中外壁面维持高温,内壁面维持低温。计算结果显示,上下层流体的流动特性受Marangoni效应和浮力效应的影响;热毛细对流的振荡产生于内壁面附近,并沿着温度梯度的方向传播;随着温差的增大,热毛细对流的振荡逐渐增强,温度振荡波数增大。     

Fundamental uncertainty in the BAO scale from isocurvature modes

Small fractions of isocurvature perturbations correlated with the dominant adiabatic mode are shown to be a significant primordial systematic for Baryon Acoustic Oscillation (BAO) surveys which must be accounted for in future surveys. Isocurvature modes distort the standard ruler distance by broadening and shifting the peak in the galaxy correlation function. While a single isocurvature mode does not significantly degrade dark energy constraints, the general case with multiple isocurvature modes leads to biases that exceed 7σ on average in the dark energy parameters even for isocurvature amplitudes undetectable by Planck. Accounting for all isocurvature modes corrects for this bias but degrades the dark energy figure of merit by at least 50% in the case of the Boss experiment. However the BAO data in turn provides significantly stronger constraints on the nature of the primordial perturbations. Future large galaxy surveys will thus be powerful probes of exotic physics in the early Universe in addition to helping pin down the nature of dark energy.     

Temporal evolution into a more efficient stock market

Using the price change and the log return of 10 stock market indices, we examine the temporal evolution of the time scale. The 10 stock markets had similar properties. Their log-return time series had patterns and long-range correlations until the mid-1990s. In the 2000s, however, the long-range correlations for most markets shortened, and the patterns weakened. These phenomena were due to advances in communication infrastructure such as the Internet and internet-based trading systems, which increased the speed of information dissemination. We examined the temporal evolution of the time scale in the markets by comparing the probability density function of log returns for the 2000s with that in the 1990s and by using the minimum entropy density method.     

功能分子结构的组装和单分子物性:基于密度泛函理论的第一性原理计算与扫描隧道显微学(I)

在单个分子的层次上研究低维分子纳米结构的生长,理解组装机制并实现结构与特性的有效控制,是低维体系物理及其器件研究的重要内容。本文在基于密度泛函的第一性原理计算的基础上,对功能分子在金属表面上的自组装特性等进行了综述。对理论方法作了简要介绍后,综述了第一性原理计算方法在研究金属基底上分子自组装结构、界面特性、结构控制、单分子成像机制、单分子量子调控以及单分子输运性能等方面的应用。最后对基于密度泛函的第一性原理计算在解释功能分子组装与界面物理化学特性方面的发展前景进行了展望。     

一种微型温差电制冷器建模与性能分析

温差电制冷技术广泛应用在半导体的降温和制冷中,但由于半导体器件的尺寸越来越小,导致传统的温差电制冷理论和方法不再适用新的环境,尤其是在微型半导体器件中,非线性的热传导规律导致制冷模型和分析方法都发生了改变.文中在深入研究了微型半导体器件中,温差电制冷技术的工作原理和过程.在此基础上,提出了一种微型温差电制冷器的建模方法...     

前置分划板连续变焦CCD瞄准镜光学设计

针对目前国内市场遥控武器站遥控枪塔的CCD瞄准镜不能在整个焦距范围内任意视场进行瞄准射击的问题,设计了一个前置分划板连续变焦CCD瞄准镜光学系统.它不同于一般的变焦系统,该系统采用补偿组线性运动,变倍组凸轮曲线运动的变焦方式来保证像面稳定.系统变焦比为5:1,在一定焦距范围内实现连续变焦,并且通过采用分划板前置的方式,...     

Homogenization of a highly rarefied binary structure of finite diffusivity

The homogenization of a binary structure made of very small particles of general shape is performed when the diffusivity is finite and when the size of the particles has a critical value with respect to a rarefaction number. The limit problem involves an auxiliary function which can be interpreted as the solution of a problem of cellular type, thus filling the gap with classical methods of multiple scales.