Error analysis: a tool for selecting travel demand models

In developing travel demand models it is generally assumed that the base-year data used in developing the parameters, as well as the forecasted data to be used as independent variables for the design year, are of acceptable quality. The purpose of this paper is to present the application of error propagation theory in assesing the predictive quality of one type of travel demand forecasting model (multinomial logit models) and to demonstrate how error considerations can be used as a tool for identifying the optimal model. The general conclusions of this study are that: (1) it is indeed possible to quantify errors in dependent variables in logit models as a consequence of errors in independent variables; and (2) error consideration can be used as a tool for identifying the optimal model from a set of candidate models. Further research is recommended to develop better insights into the phenomenon of error propagation so that the consideration of errors can be a factor in decisions on model selection.     

NiTi合金中马氏体相的低频力学谱研究

我们用最近研制成功的LMA型低频力学谱测试系统对NiTi合金马氏体相进行了在很大频率范围内（0．003～1Hz）的低频等温力学谱和温度谱的测量．我们研究的形状记忆合金NiTi（Ni50．2at％）试样长34mm，直径1mm细丝．经一定热处理，分别在333K．343K和353K做了内耗随频率的变化的测量。实验表明：频率越小，内耗越大，也就是内耗随频率减少而增大。同时我们采用阶梯升温的方法在八个温度下每个温度测量三种频率（1Hz，0．1Hz，0．01Hz）的内耗，结果清楚地表明：不同频率下，内耗峰都出现在372K（99℃）。而且频率越低，峰高越高。这是具有相变峰的特点：相变峰的峰温不随测量频率不同而变化，相变峰高度随频率减少而增大。我们还测量了在1Hz与0．5Hz频率下内耗随温度的变化。本文用马氏体相的位错理论初步讨论了上述实验结果。     

The diffraction of plane gravitational waves by the edge of an ice cover

The diffraction of plane surface gravitational waves by the edge of an ice cover lying on the surface of an incompressible fluid of infinitely great depth is considered. The ice cover is simulated by a thin elastic plate. The wave reflection and transmission coefficients are determined when it interacts with the ice cover. A wave field is constructed in the fluid under the conditions that a periodic lumped force and a lumped moment act on the edge of the ice cover. It is shown that as the incident wavelength increases the reflection coefficient tends to zero and the transmission coefficient tends to unity.     

非负定阵元素的扰动和正定完备化

在保持非负定性不变的前提下,本文对矩阵每一元素容许多大的扰动作了进一步的研究, 将本文的结论和C．R．Johnson提出的部分正定阵的正定完备化进行比较,容易发现对已知的正定矩阵求扰动,本文的结论比用C．R.Johnson的正定完备化计算扰动形式上更简单,同时也给出了不同于C．R．Johnson的部分正定阵的正定完备化表示的另外一个公式,推出了这些正定完备化矩阵应具有的若干性质．     

Solitary waves and their bifurcations of KdV like equation with higher order nonlinearity

We investigate the KdV like equation with higher order nonlinearity ut + a(1 +bun)unux + uxxx = 0with n ≥ 1, a, b ∈ R and α≠ 0. The bifurcations and explicit expressions of solitary wave solutions for theequation are discussed by using the bifurcation method and qualitative theory of dynamical systems. Thebifurcation diagrams, existence and number of the solitary waves are given.     

Can Millimeter Waves Generate Electroporation?

Analysis of the field distributions in a single biological cell under electromagnetic wave is given. With Debye approximation, the dielectric relaxation of each part of the cell, including the extracellular and cellular media, the cell membrane and the nuclear membrane, was taken into account. Making use of some typical parameters for a cell, the voltage across nuclear and cytoplasma membranes under electromagnetic waves are calculated up to millimeter wave frequency range. The calculated result indicates that it is unlikely to generate electroporation by present available millimeter wave sources.     

拉曼放大器中放大的自发拉曼散射与拉曼开-关增益关系的研究

研究了拉曼放大器中放大的自发拉曼散射对拉曼开－关增益的影响，并提出了一种利用自发拉曼散射谱来调整拉曼放大器位曼开－关增益平坦的方法，实验采用4个波长为14xx nm的激光二极管作为抽运源，75km的G．652光纤作为传输介质，获得了C波段附近的光放大，同时对此给出了合理的理论解释。     

A comprehensive study of the long pulse Nd:YAG laser drilling of multi-layer carbon fibre composites

The results of an extensive experimental study of the free running Nd:YAG laser drilling of a multi-layer carbon fibre composite, where adjacent layers have differently orientated fibres, are reported. For holes drilled with the laser operating in fixed-Q mode at 1064 nm, parallel sections of blind holes illustrating discontinuities in the hole size along a given section direction will be shown to occur at the interface between adjacent layers. An explanation for this effect is proposed. Detailed single pulse drilling characteristics will be presented illustrating the exit hole diameter as a function of pulse energy and material thickness. These characteristics illustrate a ‘stable' drilling regime in which the exit hole diameters are least sensitive to changes in pulse energy or material thickness and a less ‘stable' regime in which they are more strongly dependent on these parameters. Drilling characteristics will be given for two different beam qualities, illustrating the greater drilling depth and reduced hole size achievable with an improved beam quality. Finally holes drilled through a 2 mm thick sample of material with multiple pulses are considered. Size distribution curves for entrance and exit holes will be presented. The total energy required (number of pulses × pulse energy) to drill through 2 mm thick material will be reported as a function of pulse energy in stationary air and argon atmospheres and in a partial vacuum, illustrating a threshold energy which is dependent upon the drilling atmosphere. The threshold energies will be discussed with reference to plasma formation and the reactivity of the drilling atmosphere.     

Correlations between dynamical properties and features of potential energy surfaces for the light atom transfer reactions O+HCl→OH+Cl AND Cl+HCl→ClH+Cl

A three-dimensional quasiclassical trajectory study of the dynamics of the light atom transfer reaction O(³P) + HCl(ν=0)→ OH + Cl was carried out employing two LEPS potential energy surfaces (I and II). Attention was focused mainly on three-dynamical properties; the oscillatory behavior of partial cross sections as a function of collision energy; the rotational excitation of the products; and the influence of reagent rotation on reactivity. Distinct differences were found between surfaces I and II with respect to these properties. The examination of individual trajectories indicated that there is a significant difference in the nature of these surfaces. While surface I is governed by weak repulsive forces, surface II is governed by strong attractive forces which tend to direct the reactants toward a collinear geometry. The present results confirm conclusions reached from an earlier study of the reaction Cl+HCl→ClH+Cl concerning correlations between dynamical properties and features of potential energy surfaces. For surfaces of the type that we termed HREP, since they are of repulsive nature and they lead to highly rotationally excited products, no significant oscillations of partial cross sections are obtained and reagent rotation promotes the reaction. On the other hand, for surfaces of the type that we termed COLD (collinearly directing), since they tend to direct the reactants toward a collinear geometry and form rotationally “cold” products, significant oscillations of partial cross sections are obtained and reagent rotation causes a decline in reactivity.     

复合体系方法测量液体力学谱

本文介绍了采用复合体系，测量得到凝聚态物质从固态到液态连续变化力学谱的一种新的实验方法。以簧振动为例，给出了解析的计算公式，以及应用条件。通过进一步综合分析，得到具有更广应用范围的近似公式，可以近似应用于其他不同的振动模式，如低频扭摆。应用新的测量方法，给出了典型小分子玻璃材料甘油和碳酸丙稀从玻璃态到液态的力学谱，观察到甘油和碳酸丙稀玻璃化转变、碳酸丙稀的再结晶、熔化和挥发的过程；测量得到挥发过程中水的质量随时间精确变化的曲线。最后，本文给出了新方法的一些应用展望。