基于活动的交通需求计算过程模型研究综述

为适应现代城市快速发展的要求,研究人员对交通需求预测进行了广泛深入的研究,交通需求模型在建模方法和模型功能上发生了很大变化。基于活动的方法受到广泛重视,基于活动的交通需求模型研究成为热点。其中计算过程模型被认为是最有发展前景的。文中回顾了基于活动的方法的发展过程;介绍了基于活动的方法的理论基础;总结了基于活动的交通需求计算过程模型,并分析了其中4个模型的特点;探索了模型的改进途径,展望了模型的发展应用前景。

非黏性堤防溃口发展过程计算模型

堤防是防洪工程体系的重要组成部分,一旦发生溃决将可能带来严重灾害损失,明确堤防溃口发展速率与水力要素之间的关系对于预测堤防溃决过程和洪水演进具有重要意义。通过对系列非黏性沙质堤防溃决试验结果进行整理分析,得到溃口垂向下切速率、横向展宽速率与溃口流量、溃口单宽流量之间的关系。结果表明:堤防溃口发展主要存在垂向冲刷、横向扩展2种形式;溃口发展速率与溃口流量呈正相关,但受入流流量影响,没有适用于所有工况的关系表达式;溃口发展速率与溃口单宽流量间的关系基本不受入流流量影响,下切和展宽速率与溃口单宽流量呈现指数关系;基于此关系,构建了以溃口单宽流量为参数的溃口发展过程计算模型,并对溃口垂向下切、横向展宽发展过程进行了模拟计算与对比分析,结果显示模拟情况与真实的溃口发展过程吻合较好,说明所提出的计算模型科学合理,且计算过程简洁。

堆石坝溃口流量过程计算

基于已有堆石坝研究的理论分析和模型试验成果,综合水库调洪演算、溃口泥沙石料冲刷侵蚀计算和面板折断力学分析,构建了面板堆石坝漫顶溃口流量过程计算模型,以某面板堆石坝水库为例进行溃坝计算,并与其他溃坝计算结果做了对比。结果表明,该模型合理,计算精度较高,可为类似堆石坝的溃坝后果评估提供参考。

岩体断裂的破坏机理与计算模拟

受压岩体中的裂纹问题 ,可以归结为压剪裂纹和拉剪裂纹两种类型。具体讨论了受压岩体中的斜裂纹问题和翼形裂纹问题 ,对两种不同裂纹类型的扩展机理进行了分析 ,给出了应力强度因子的计算方法。最后以受单向压缩的裂纹扩展为例 ,说明了具体的计算模拟过程。

盐城体育场钢结构屋盖卸载过程分析和监测

盐城体育场屋盖采用了空间钢桁架挑棚结构体系,最大悬挑长度达42m。由于安装时采用高达约25 m的临时支撑,因此,结构拆撑卸载过程的分析至关重要。在采用等效杆端位移法、千斤顶单元法的同时,提出了约束方程法,对盐城体育场钢屋盖的卸载过程进行数值模拟分析,为卸载过程控制提供理论依据,并和卸载监测数据结果进行实时对比,用以实现卸载过程控制。分析与比较结果表明:卸载过程计算模型合理正确,模拟分析方法准确有效,可为类似大跨度钢结构卸载过程模拟分析作参考。

粒子系统方法及其应用

介绍了粒子系统方法的基本思想、生成粒子系统某瞬间的画面的基本步骤 ,并讨论了 3 D Stu-dio MAX3 .0中的粒子系统及其应用。

多文种融合文字书写教学知识及其自动生成方法

多文种融合文字书写教学系统的教学资源具有多语源的特点,但存在知识点数据类型多、计算结构复杂等不足。为此,依据不同文种文字书写的异性与共性规律,提出基于文字书写过程计算的知识点自动生成方法。将多文种的笔画、笔画关系、部件关系等计算元按共享、分类,给出各类计算元编码空间的计算方法,定义面向各文种通用的文字书写过程计算模型,设计并实现计算模型中各计算元编码的自动生成算法。实验结果表明,该方法能准确识别各种知识要素,笔画及各类关系的识别正确率达到98.3%,与人工编码相比,录入速率提高15%,冗码率降低23%。

Kinematic Analysis and Trajectory Planning of J-Groove Welding Robot

This paper introduces the complexity and particularity of tube-sphere intersection weld(J-groove weld) and establishes the mathematical model of tube-sphere intersection trajectory.Based on the characteristics of J-groove welds,the computational process of welding gun orientation is first simplified.Then the kinematic algorithm of a welding robot is obtained according to screw theory and exponential product formula.Finally,Solidworks and SimMechanics are employed to simulate the kinematics of the welding robot,which proves the feasibility of the kinematic algorithm.

Research on the ShakeMap System with Consideration of Site Effects

In accordance with the principle of similarity in geology and topography, the Vs^30 （the average shear-velocity down to a 30m depth below the surface） approximation of sites is acquired by correlation between Vs^30 and slopes after calculating the maximum slope of topography using the 30-sec Chinese Mainland DEM （Digital Elevation Model） data set. Site-amplification factors are then quantified with Vs^30 and applied to the ShakeMap system developed by this study to revise ground-motion amplitudes on bedrock estimated from empirical relationships. Finally, the distribution of ground motion parameters on the surface is obtained. This article also introduces the calculation process, calculation models of the ShakeMap systems and related software systems. In conclusion, certain examples indicate that the ShakeMap system is feasible in the Chinese Mainland.

Study of the ship design process model for collaborative design

The ship design process model is the basis for developing the ship collaborative design system under network environment.According to the characteristics of the ship design, a method for dividing the ship design process into three layers is pat forward, that is project layer, design task layer and design activity layer, then the formalized definitions of the ship design process model, the decomposing principles of the ship design process and the architecture of the ship collaborative design (SDPM) system are presented. This method simplifies the activity network, makes the optimization and adjustment of the design plan convenient and also makes the design process easier to control and change, at last the architecture of the ship collaborative design system is discussed.

Limit analysis method for active earth pressure on laggings between stabilizing piles

Stabilizing pile is a kind of earth shoring structure frequently used in slope engineering. When the piles have cantilever segments above the ground,laggings are usually installed to avoid collapse of soil between piles. Evaluating the earth pressure acting on laggings is of great importance in design process.Since laggings are usually less stiff than piles,the lateral pressure on lagging is much closer to active earth pressure. In order to estimate the lateral earth pressure on lagging more accurately,first,a model test of cantilever stabilizing pile and lagging systems was carried out. Then,basing the experimental results a three-dimensional sliding wedge model was established. Last,the calculation process of the total active force on lagging is presented based on the kinematic approach of limit analysis. A comparison is made between the total active force on lagging calculated by the formula presented in this study and the force on a same-size rigid retaining wall obtained from Rankine's theory. It is found that the proposed method fits well with the experimental results.Parametric studies show that the total active force on lagging increases with the growth of the lagging height and the lagging clear span; while decreases asthe soil internal friction angle and soil cohesion increase.

Study of Radiative Decays D_(s1)(2536)→D_s(1968)+γand D_(s1)(2536)→D_s^(2112)+γ in CQM Model

There are some uncertain charazteristics of the Ds1（2536）, which deserves further discussion. Based on the assumption that the meson is constituted by c s, and belongs to T doublet （1^＋, 2^＋）, radiative decays Ds1（2536） → Ds（1968） ＋γ and Ds1（2536） → Ds^＊（2112） ＋ γ are studied in the CQM model The large branching ratios of them from our calculations not only indicate the process may be detected in the future experiments, but also can give a deep comprehension of the structure of it.

Analysis and evaluation of band-limited ray tracing method

From the analysis and the contrast of band-limited ray tracing method based on Kirchhoff integral, it was found that the method performs many approximations in the derivation process and omits the derivative term of the phase factor in the Kirchhoff integral. Numerical calculations and analysis show that the omission of cor-relation terms in Kirchhoff integrals has a non-negligible effect on the calculation results, and the different terms in the Kirchhoff integral have different effects on different frequency ranges. The method can be applied to ve-locity models containing complex interfaces without changing waves and continuous media. the velocity model and can be extended to elastic waves and continuous media.

A novel dynamic call admission control policy for wireless network

To address the issue of resource scarcity in wireless communication, a novel dynamic call admission control scheme for wireless mobile network was proposed. The scheme established a reward computing model of call admission of wireless cell based on Markov decision process, dynamically optimized call admission process according to the principle of maximizing the average system rewards. Extensive simulations were conducted to examine the performance of the model by comparing with other policies in terms of new call blocking probability, handoff call dropping probability and resource utilization rate. Experimental results show that the proposed scheme can achieve better adaptability to changes in traffic conditions than existing protocols. Under high call traffic load, handoff call dropping probability and new call blocking probability can be reduced by about 8%, and resource utilization rate can be improved by 2%-6%. The proposed scheme can achieve high source utilization rate of about 85%.

Air-Sea Exchange of Volatile Organic Compounds: A New Model with Microlayer Effects

The authors propose a new "three-layer" conceptual model for the air-sea exchange of organic gases, which includes a dynamic surface microlayer with photochemical and biological processes. A parameterization of this three-layer model is presented, which was used to calculate the air-sea fluxes of acetone over the Pacific Ocean. The air-sea fluxes of acetone calculated by the three-layer model are in the same direction but possess half the magnitude of the fluxes calculated by the traditional two-layer model in the absence of photochemical and biological processes. However, photochemical and biological processes impacting acetone in the microlayer can greatly vary the calculated fluxes in the three-layer model, even reversing their direction under favorable conditions. Our model may help explain the discrepancies between measured and calculated acetone fluxes in previous studies. More measurements are needed to validate our conceptual model and provide constraints on the model parameters.

STUDY ON MATHEMATICAL MODEL OF JIG PROCESS

Mathematical model is a powerful means of prediction, simulation and optimization of jig process. And it is also an important part in computer control system. Jig process is divided into two sub-processes, stratifying process serially followed by separating process. Taking stratifying process as state transition process of particles in step with jig work cycle, the mathematical model of stratifying is established with Markov chain theory; By analyzing the characteristics and float-sink data of jig, the mathematical model of separating process was submitted. The physical meaning of parameters of the models are explained; the relationship between model and partition was discussed. The fitting result was good with the model.

Wear analysis of revolute joints with clearance in multibody systems

In this work, the prediction of wear for revolute joint with clearance in multibody systems is investigated using a computational methodology. The contact model in clearance joint is established using a new hybrid nonlinear contact force model and the friction effect is considered by using a modified Coulomb friction model. The dynamics model of multibody system with clearance is established using dynamic segmentation modeling method and the computational process for wear analysis of clearance joint in multibody systems is presented. The main computational process for wear analysis of clearance joint includes two steps, which are dynamics analysis and wear analysis. The dynamics simulation of multibody system with revolute clearance joint is carried out and the contact forces are drawn and used to calculate the wear amount of revolute clearance joint based on the Archard's wear model. Finally, a four-bar multibody mechanical system with revolute clearance joint is used as numerical example application to perform the simulation and show the dynamics responses and wear characteristics of multibody systems with revolute clearance joint. The main results of this work indicate that the contact between the joint elements is wider and more frequent in some specific regions and the wear phenomenon is not regular around the joint surface, which causes the clearance size increase non-regularly after clearance joint wear. This work presents an effective method to predict wear of revolute joint with clearance in multibody systems.

Review of snow water equivalent microwave remote sensing

Accurate quantitative global scale snow water equivalent information is crucial for meteorology, hydrology, water cycle and global change studies, and is of great importance for snow melt-runoff forecast, water resources management and flood control. With land surface process model and snow process model, the snow water equivalent can be simulated with certain accuracy, with the forcing data as input. However, the snow water equivalent simulated using the snow process models has large uncertainties spatially and temporally, and it may be far from the needs of practical applications. Thus, the large scale snow water equivalent information is mainly from remote sensing. Beginning with the launch of Nimbus-7 satellite, the research on microwave snow water equivalent remote sensing has developed for more than 30 years, researchers have made progress in many aspects, including the electromagnetic scattering and emission modeling, ground and airborne experiments, and inversion algorithms for future global high resolution snow water equivalent remote sensing program. In this paper, the research and progress in the aspects of electromagnetic scattering/emission modeling over snow covered terrain and snow water equivalent inversion algorithm will be summarized.

Radiative Corrections to e^+e^-→ Zh at Future Higgs Factory in the Minimal Dilaton Model

Abstract The minimal dilaton model （MDM） extends the Standard Model by one singlet scalar called dilaton andone top quark partner called t. In this work we investigate the t-induced radiative correction to the Higgs-strahlung production process e＋e^→ Zh at future Higgs factory. We first present the analytical calculations in detail and show how to handle the ultraviolet divergence. Then we calculate the correction numerically by considering the constraints from precision electroweak data. We find that, for sinθL=0.2 and mt= 1200 GeV, the correction is 0.26% and 2.1% for SE＋E = 240 GeV, 1 TeV respectively, and a larger value can be achieved as sin θL increases.