两亲性接枝共聚物在选择性溶剂中自组装行为的模拟研究

利用粗粒化分子动力学(CGMD)方法研究了两亲性接枝共聚物在不同选择性溶剂中的自组装行为. 分析了主链刚性及链长对自组装结构的影响. 研究结果表明, 当溶剂对主链为良溶剂而对支链为不良溶剂时, 两亲性接枝共聚物随主链刚性的增加自组装形成花状胶束、 花桥状胶束及桥状胶束, 并且组分比例对自组装结构影响很大; 随着链长的增加, 柔性链出现单花状胶束到多花状胶束的转化. 当溶剂对主链为不良溶剂而对支链为良溶剂时, 可得到近球形或椭球形核壳状胶束及束状结构; 不同链长时, 柔性接枝共聚物链均只能得到近球形的单核壳状胶束.     

高速公路封道施工路段交通流特性及通行能力分析——以杭州湾大桥内侧两条车道封道情形为例

基于交通流实测数据,针对三车道高速公路杭州湾大桥路段内侧两条车道因施工而封闭时的情形,建立元胞自动机交通流模型.根据公路养护安全作业规程和车辆行驶特点,细致划分了施工路段各区域,采用不同的换道规则来模拟不同区域中车辆的换道行为,区分车型和司机性格差异,模拟结果与实测数据吻合良好,验证了模型的有效性.通过数值模拟,研究发现封道时流量和速度随着进车率增加均有不同程度的下降,并且流量还会因施工区域长度的增加而下降.此外,通过分析封道时的道路服务水平评价指标与交通流特征值之间的关系,得出在三级服务水平以上时,道路通行能力能得到基本的保证,以此推荐了极限流量值,可为高速公路封道时的交通管理提供理论依据.     

Development of a one-way coupled diffraction/trapped air model for predicting wave loading on bridges under water wave attack

In recent years, a number of researchers have applied various computational methods to study the wave and tsunami forcing on bridge superstructure problems. Usually, these computational analyses have relied upon application of computational fluid dynamic (CFD) codes. While CFD models provide accurate results, their disadvantage is that they tend to be computationally expensive. Thus, it may be difficult to apply these techniques during risk assessment analyses. During this study, an alternative computational method was explored in which a previously-developed diffraction model was combined with a previously-developed trapped air model under worst-case wave loading conditions (i.e., when the water surface was at the same elevation as the bottom bridge chord elevation). The governing equations were solved using a finite difference algorithm for the case where the bridge was attacked by a single wave in two dimensions. Resultant water forces were computed using results from the diffraction/trapped air computations, and water force values were compared with data from three datasets. In general, excellent agreement between the diffraction/trapped air model and data was observed. The computational time associated with the model was only approximately one hour per bridge configuration, which would appear to be an improvement when compared with other computational techniques.     

断层泥显微特征研究在桥基稳定性评价中的应用

基于SEM研究了桥基断裂断层泥的原状显微结构和显微构造、石英碎砾的显微构造、表面刻蚀形貌和结构特征 ,并进一步分析和评价了断裂的抗震和抗断关键问题 ,其对系统论证在断裂带上建设特大型过江桥梁工程的稳定性具有重大实际意义 ,并为镇扬大桥工程的合理设计和安全运行提供了地质依据     

开尔文电桥测电阻及用Visual Basic处理测量数据

用开尔文电桥测量金属棒的电阻率时,电阻率的不确定度是由测量金属棒直径、长度和电阻的不确定度来决定。为了又快又准确地处理实验的测量数据,设计编制了Visual Basic程序,从而方便快捷的计算出金属棒电阻率的不确定度。     

Novel Flow Injection/Potentiometric Measurement of Slightly Soluble Salts in Small Volumes: Determination of Solubility Product Constants of Some Silver Salts

Abstract

The flow injection technique is shown to provide fast, reliable and sensitive determination of solubility product constants of silver acetate, silver sulfate, silver oxide, silver bromate and silver chloride in microliter volume samples. Potentiometric detection using electrodes of the first kind and second kind was used for measuring silver ions and chloride ions, respectively. The solubilities were determined from measurement of the silver ion concentration in the saturated solutions. In the case of silver chloride, the solubility product constant was calculated from the concentrations corresponding to the intersection of the silver ion calibration curve and the chloride ion calibration curve, i.e., where the potentials of the two electrodes are equal. Tenth-molar sodium nitrate was used for all solutions to maintain constant ionic strength. At a concentration range of 1.00 × 10^?2 ? 1.00 × 10^?5 M silver, and 1.00 × 10^?2 ? 1.00 × 10^?4 M chloride, a Nernstian response of 60 m V per decade was obtained. At a sampling rate of 50–70 samples per hour, with 50 μl sample injections, high reproducibility of measurements was achieved, with a -pL 2% relative standard deviation in measured concentrations. The scope and applications of this system are discussed.     

Correcting for Simulation Bias in Monte Carlo Methods to Value Exotic Options in Models Driven by Lévy Processes

Lévy processes can be used to model asset return's distributions. Monte Carlo methods must frequently be used to value path dependent options in these models, but Monte Carlo methods can be prone to considerable simulation bias when valuing options with continuous reset conditions. This paper shows how to correct for this bias for a range of options by generating a sample from the extremes distribution of the Lévy process on subintervals. The method uses variance‐gamma and normal inverse Gaussian processes. The method gives considerable reductions in bias, so that it becomes feasible to apply variance reduction methods. The method seems to be a very fruitful approach in a framework in which many options do not have analytical solutions.     

MatLab软件编程在随机过程教学中的运用

本文介绍数学软件MatLab在随机过程教学中的运用,通过三个实例说明在教学中运用Matlab软件编程可以将抽象的数学理论变成可视的图形,给学生带来直观的认识,进而提高学生的学习兴趣以及计算机编程水平．     

The Annihilating-Ideal Graph of a Commutative Ring with Respect to an Ideal

For a commutative ring R with identity, the annihilating-ideal graph of R, denoted 𝔸𝔾(R), is the graph whose vertices are the nonzero annihilating ideals of R with two distinct vertices joined by an edge when the product of the vertices is the zero ideal. We will generalize this notion for an ideal I of R by replacing nonzero ideals whose product is zero with ideals that are not contained in I and their product lies in I and call it the annihilating-ideal graph of R with respect to I, denoted 𝔸𝔾 _I (R). We discuss when 𝔸𝔾 _I (R) is bipartite. We also give some results on the subgraphs and the parameters of 𝔸𝔾 _I (R).