天体运行的介质层壳与离散轨道引论

采用介质层壳弯曲的唯象方法，在规整三维空间中给出了能量曲率方程及物体间的能量引力形式表述，其引力方程的二个条件解分别与 Newton 引力理论及 Einstein 引力理论的有关结果相近．讨论了目前分维微积分在函数方面的局限性，给出了相似扩展方程，随后通过讨论天体运行轨道的基线扩展特征，给出了天体运行的离散轨道方程，并以太阳系行星及部分卫星为例，给出了这些天体运行离散轨道方程的具体表述形式．

随机轮轨力作用下基于2.5维离散支撑模型的轨道垂向振动分析

针对轨道随机不平顺引起的钢轨高频振动响应问题,建立2.5维有限元离散支撑轨道动力学实体模型。首先结合高速车辆模型建立耦合系统垂向振动模型,进而基于虚拟激励法得到由轨道不平顺引起的动态轮轨力功率谱;然后基于2.5维离散支撑轨道数值模型,将动态轮轨力功率谱作为激励,得到轨道系统的随机振动响应。通过与格林函数结果对比,验证了本文模型的正确性。结果表明:采用2.5维有限元法及荷载等效法可快速实现无限长离散支撑实体轨道模型全频域计算,可模型钢轨的横截面变形特征;以CRH3型高速动车为例,高于2800 Hz时轨道结构的横截面开始明显变形;低于50 Hz时四个轮对处的振动加速度功率谱密度差别显著;170~3000 Hz内垫板刚度对轨道结构振动加速度影响较大。

基于轨道离散化的列车全线到站时间预测

研究列车全线到站时间预测问题,解决全天各时段列车到站时间预测。将轨道线路离散化,记录列车在轨道上的运行时刻,把运行时刻转化为到站耗时值,对多个时间段多趟列车的耗时值做平均。对得到的全线线路数据进行均值滤波平滑,制作全线路段列车运行耗时数据。当系统接收到列车位置数据时,便可通过查找耗时数据得到列车到站预测值。通过制作不同时段的列车运行耗时数据,可更精确对不同时段的列车到站耗时进行预测。

基于格林函数法的车辆—轨道垂向耦合系统随机振动分析

视钢轨为弹性欧拉梁（Euler梁）,建立离散支撑弹性轨道模型,并采用格林函数法得到全频域范围内轨道上任意点处的频率响应;结合高速车辆模型,视车辆和轨道系统为线性弹簧阻尼系统,轮轨接触为线性刚性接触,采用基于虚拟激励法的轮轨接触多点激励,以真实轨道谱为输入,计算车辆—轨道垂向耦合系统的随机振动响应,并分析不同高速轨道谱和车速对车辆—轨道垂向耦合系统随机振动的影响。结果表明：采用格林函数法可快速求解无限长离散支撑弹性轨道模型的频响特性;分析振动频率在15 Hz以上的车体及构架振动时,采用离散支撑弹性轨道模型较传统的刚性轨道模型更为准确;计算车辆—轨道垂向耦合系统的振动能量时,在15-60Hz的中频区域内,采用离散支撑弹性轨道模型得到的计算结果要高于传统的刚性轨道模型,而在高频区域内则相反;车辆—轨道垂向耦合系统的随机振动响应对轨道谱类型和车速均较为敏感。

天体运行轨道的背景介质理论导引与自相似分形测度计算的分维微积分基础

通过讨论天体运行背景介质理论的连续轨道及离散轨道这二个研究方向的基础假设,介绍了天体运行轨道的具体方程形式及理论框架概要;进一步地通过讨论天体运行轨道Binet方程的一般形式及其行星近日点进动角的解,给出了连续轨道理论与Newton理论及Einstein广义相对论的联系与区别;通过讨论天体运行轨道的分维扩展方程,给出了包括太阳系行星、天王星卫星、地球卫星、绕月航天器等在内的离散轨道(稳定性轨道)方程及其预言数据.特别地,作为对天体在较为广泛区域作用曲线的初步探讨推论,指出仅由天体引力难以形成质量密度趋于无穷大的理想黑洞.通过讨论一般函数的分维导数的位置假设及幂函数的分维导数的形式假设,进一步明晰了幂函数的分维导数、分维微分及分维积分的具体方程形式,给出分维导数与分数阶导数的区别,随后讨论了基于一般分形测度的分维微积分形式定义导出的自相似分形的测度计算方程具体形式,给出了其与目前Hausdorff测度方法(覆盖方法)的区别,并对包括三分Cantor集合、Koch曲线、Sierpinski垫片及正交十字星形等自相似分形在内的测度进行了计算分析.

柴油机燃油雾化及蒸发理论的发展

本文综述了柴油机燃油雾化及蒸发理论的发展过程及其动向.

桂北铅锌尾矿库尾砂颗粒的大气风场数值模拟研究

以平地型铅锌尾矿库尾砂颗粒为研究对象,基于离散型随机轨道模型,数值模拟不同粒径尾砂颗粒在不同风速下的迁移路径和沉积距离。研究结果表明,风速对尾矿颗粒的运动轨迹有着明显的影响。当风速为0.5m/s时,50μm尾砂迁移距离较短,无法到达计算域口;而当风速增大为2.0m/s和3.5m/s时,尾砂颗粒迁移至计算域出口的时间随之缩短,分别为2 100s和1 230s。尾砂粒径对尾砂的污染距离也有明显的影响。当风速为3.5m/s时,粒径为100μm和150μm的尾砂颗粒在距尾矿库下风向大约1 500m和800m处完全沉积,而粒径为50μm的小粒径尾砂颗粒能迁移至尾矿坝下游3 000m以外。

Orbital-Free Density Functional Theory for Molecular Structure Calculations

We give here an overview of the orbital-flee density functional theory that is used for modeling atoms and molecules. We review typical approximations to the kinetic energy, exchange-correlation corrections to the kinetic and Hartree energies, and constructions of the pseudopotentials. We discuss numerical discretizations for the orbital-free methods and include several numerical results for illustrations.

Mechanical behavior and deformation mechanism of ballast bed with various fouling materials

In order to study the interaction between various fouling particles and ballast,a multi-layer and multi-scale discrete element model(DEM)including the sleeper,ballast bed and the surface layer of subgrade was developed.Two typical fouling particles,the hard particles(sand)and soft ones(coal fines),are considered.A support stiffness test of the ballast bed under various fouling conditions was conducted to calibrate the microscopic parameters of the contact model.With the model,the influence of fouling particles on the mechanical behavior and deformation of the ballast bed was analyzed from macro and micro perspectives.The results show that the increase in the strength of the fouling particles enlarges the stiffness of the ballast bed.Hard particles increase the uniformity coefficient of the contact force bondγof ballast by 50.4%.Fouling particles increase the average stress in the subgrade,soft particles by 2 kPa and hard particles by 1 kPa.Hard particles can reduce the elasticity,plastic deformation and energy dissipation in the track structure.As the fouling particle changes from hard to soft,the proportion of the settlement in ballast bed increases to 40.5%and surface layer of swbgrade settlement decreases to 59.5%.Thus,the influence of fouling particles should be considered carefully in railway design and maintenance.

Diffusion Monte Carlo Study of Bond Dissociation Energies for BH2, B（OH）2, BCl2, and BCI

On basis of bond dissociation energies （BDEs） for BH2, B（OH）2, BCl2, and BCl, the diffusion Monte Carlo （DMC） method is applied to explore the BDEs of HB-H, HOB-OH, ClB-Cl, and B-Cl. The effect of the choice of orbitals, as well as the backflow transformation, is studied. The Slater-Jastrow DMC algorithm gives BDEs of 359.1±0.12 kJ/mol for HB-H, 410.5±0.50 kJ/mol for HOB-OH, 357.8±1.46 kJ/mol for ClB-Cl, and 504.5±0.96 kJ/mol for B-Cl using B3PW91 orbitals and similar BDEs when B3LYP orbitals are used. DMC with backflow corrections （BF-DMC） gives a HB-H BDE of 369.9±0.12 kJ/mol which is close to one of the available experimental value （375.8 kJ/mol）. In the case of HOB-OH BDE, the BF-DMC calculation is 446.04-1.84 k J/mol that is closer to the experimental BDE. The BF-DMC BDE for ClB-Cl is 343.2±2.34 kJ/mol and the BF-DMC B-Cl BDE is 523.3±0.33 kJ/mol, which are close to the experimental BDEs, 341.9 and 530.0 kJ/mol, respectively.

Discrete element method analysis of lateral resistance of fouled ballast bed

The lateral resistance of sleeper plays an important role in ensuring the stability of a railway track, which may change in the operation of railway, due to the fouling in the ballast bed. In this work, discrete element method was adopted to investigate the effect of fouling on the lateral resistance of sleeper. The shape information of ballast was captured by method of three-dimensional vision reconstruction. In order to calibrate the mechanical parameters and verify the models, a lateral resistance field test was carried out by using a custom-made device. The contact force distributions in the different parts of sleeper as well as the interaction between ballast and sleeper were discussed in depth. The results show that fouling of ballast bed evidently reduces the lateral resistance of sleeper and the decreasing degree is also related to the fouled position of ballast bed, in the order of shoulder > bottom > side.Therefore, the effect of fouling, especially the fouling in the ballast shoulder, on the lateral resistance of sleeper, should be taken into account in ballast track maintenance work.

Estimating walking access area for rail transit station based on discrete choice model

The discrete choice model is used to estimate the walking access area of rail transit stations while considering the influence of existing competition from other traffic modes. The acceptable walking access area is determined according to the willingness of passengers to walk who prefer rail transit compared with bus and automobile. Empirical studies were conducted using the survey data of six stations from the rail transit in Nanjing, China. The results indicate that the rail transit is more preferable compared with bus and private automobile in this case when excluding the influence of individual and environmental factors. It is found that passengers tend to underestimate their willingness to walk. The acceptable walking access area of every rail transit station is different from each other. Suburban stations generally have a larger walking access area than downtown stations. In addition, a better walking environment and a scarcer surrounding traffic environment can also lead to a larger walking area. The model was confirmed to be effective and reasonable according to the model validation. This study can be of benefit to the passenger transportation demand estimation in the location planning and evaluation of rail transit stations.

固-液两相流充填管道输送冲蚀磨损数值研究

为探究充填管道在输送过程中的冲蚀磨损机理，基于工程流体力学理论及颗粒输送力学模型，引入离散颗粒轨道模型、塑性冲蚀磨损模型。对某矿山复杂充填管路条件下浆体特性对管道冲蚀磨损影响进行研究。结果表明，浆体流速、黏度以及颗粒尺寸对管道冲蚀磨损影响显著，颗粒形状影响较弱。高流速下，弯管磨损最为严重。直管段磨损较轻且分布较为均匀，流速降低。主要磨损部位偏向弯管出口部位；弯管部位最大磨损值在15°-30°以及60°～75°之间；此外，粒径较小时，磨损严重程度随粒径增加而增大，粒径达到600μm后．最大磨损值随粒径增加呈现下降趋势。

On quasi-weakly almost periodic points

The core problem of dynamical systems is to study the asymptotic behaviors of orbits and their topological structures. It is well known that the orbits with certain recurrence and generating ergodic (or invariant) measures are important, such orbits form a full measure set for all invariant measures of the system, its closure is called the measure center of the system. To investigate this set, Zhou introduced the notions of weakly almost periodic point and quasi-weakly almost periodic point in 1990s, and presented some open problems on complexity of discrete dynamical systems in 2004. One of the open problems is as follows: for a quasi-weakly almost periodic point but not weakly almost periodic, is there an invariant measure generated by its orbit such that the support of this measure is equal to its minimal center of attraction (a closed invariant set which attracts its orbit statistically for every point and has no proper subset with this property)? Up to now, the problem remains open. In this paper, we construct two points in the one-sided shift system of two symbols, each of them generates a sub-shift system. One gives a positive answer to the question above, the other answers in the negative. Thus we solve the open problem completely. More important, the two examples show that a proper quasi-weakly almost periodic orbit behaves very differently with weakly almost periodic orbit.

Homoclinic orbits of first order discrete Hamiltonian systems with super linear terms

In this paper we consider the first order discrete Hamiltonian systems {x1（n＋1）-x1（n）=Hx2（n,x（n））,x2（n）-x2（n-1）=Hx1（n,x（n））,where x（n） = （x2（n）x1（n））∑ R^2N, H（n,z） = 1/2S（n）z. z ＋ R（n,z） is periodic in n and superlinear as {z} →4 ∞. We prove the existence and infinitely many （geometrically distinct） homoclonic orbits of the system by critical point theorems for strongly indefinite functionals.

DISCRETE-TIME Geo/G/1 RETRIAL QUEUES WITH GENERAL RETRIAL TIME AND BERNOULLI VACATION

This paper considers a discrete-time Geo/G/1 retrial queue where the retrial time has a general distribution and the server is subject to Bernoulli vacation policy. It is assumed that the server, after each service completion, begins a process of search in order to find the following customer to be served with a certain probability, or begins a single vacation process with complementary probability. This paper analyzes the Markov chain underlying the queueing system and obtain its ergodicity condition. The generating functions of the number of customers in the orbit and in the system are also obtained along with the marginal distributions of the orbit size when the server is idle, busy or on vacation. Finally, the author gives two stochastic decomposition laws, and as an application the author gives bounds for the proximity between the system size distributions of the model and the corresponding model without retrials.