长江江西段渡口渡船现状调查及安全管理对策探讨

长江江西段由于地处三省交界，渡船过渡依然是沿江两岸人民群众首选的最为方便、快捷的交通方式。作为长江江西段水上安全监督管理的主管机关九江海事局，近几年来按照交通部、长江海事局的要求，一直把辖区渡船的安全监督管理作为工作重点。自2005年7月1日零时起，长江江西段水上安全监督管理职责统一由九江海事局履行，     

Using a random displacement model to simulate turbulent particle motion in a baroclinic frontal zone: A new implementation scheme and model performance tests

Numerical artifacts can limit accurate simulation of turbulent particle motion when Lagrangian particle-tracking models are implemented in hydrodynamic models with stratified conditions like fronts. Yet, modeling of individual particle motion in frontal regions is critical for understanding sediment dynamics as well as the transport and retention of planktonic organisms. The objective of this research was to develop a numerical technique to accurately simulate turbulent particle motions in a particle-tracking model embedded within a hydrodynamic model of a frontal zone. A new interpolation scheme, the ‘water column profile’ scheme, was developed and used to implement a random displacement model for turbulent particle motions. A new interpolation scheme was necessary because linear interpolation schemes caused artificial aggregation of particles where abrupt changes in vertical diffusivity occurred. The new ‘water column profile’ scheme was used to fit a continuous function (a tension spline) to a smoothed profile of vertical diffusivities at the x–y particle location. The new implementation scheme was checked for artifacts and compared with a standard random walk model using (1) Well Mixed Condition tests, and (2) dye-release experiments. The Well Mixed Condition tests confirmed that the use of the ‘water column profile’ interpolation scheme for implementing the random displacement model significantly reduced numerical artifacts. In dye-release experiments, high concentrations of Eulerian tracer and Lagrangian particles were released at the same location up-estuary of the salt front and tracked for 4 days. After small differences in initial dispersal rates, tracer and particle distributions remained highly correlated (r = 0.84 to 0.99) when a random displacement model was implemented in the particle-tracking model. In contrast, correlation coefficients were substantially lower (r = 0.07 to 0.58) when a random walk model was implemented. In general, model performance tests indicated that the ‘water column interpolation’ scheme was an effective technique for implementing a random displacement model within a hydrodynamic model, and both could be used to accurately simulate diffusion in a highly baroclinic frontal region. The new implementation scheme has the potential to be a useful tool for investigating the influence of hydrodynamic variability on the transport of sediment particles and planktonic organisms in frontal zones.     

HSST将于日本2005国际博览会投入商业运营

介绍名古屋东部丘陵线的概况和该线所用的磁悬浮运输系统、磁悬浮车辆的技术特点.     

长株潭港口体系空间结构的定量分析

运用吉尼系数法、赫佛因得指数法、港口不平衡指数法三种定量分析技术研究了长株潭港口体系空间结构的演化规律,可为合理建设长株潭港口体系提供依据。     

Eco 2000机车家族的机械设计

介绍了Ｅｃｏ２０００机车家族的机械设计原则以及组件化设计思想，并简述了该机车家族的机车类型。     

大跨度双向门机设计及在航电枢纽中的应用

介绍2×800kN/2×400kN大跨度双向门机的方案设计、主要结构设计及其在大顶子山航电枢纽工程中的应用.     

A system dynamics approach to land use/transportation system performance modeling Part I: Methodology

This paper presents a system dynamics approach to simultaneous land use/transportation system performance modeling. A model is designed based on the causality functions and feedback loop structure between a large number of physical, socioeconomic, and policy variables. The model consists of 7 sub‐models: population, migration of population, household, job growth‐employment‐land availability, housing development, travel demand, and traffic congestion level. The model is formulated in DYNAMO simulation language, and tested on a data set from Montgomery County, MD. In Part I: Methodology, the overall approach and the structure of the model system is discussed and the causal‐loop diagrams and major equations are presented. In Part II: Application, the model is calibrated and tested with data from Montgomery County, MD. Least square method and overall system behavior are used to estimate the model parameters. The model is fitted with the 1970–80 data and validated with the 1980–1990 data. Robustness and sensitivities with respect to input parameters such as birth rate or regional economy growth are analyzed. The model performance as a policy analysis tool is examined by predicting the year by year impacts of highway capacity expansion on land use and transportation system performance. While this is a first attempt in using dynamic system simulation modeling in simultaneous treatment of land use and transportation system interactions, and model development and application are limited due to data availability, the results indicate that the proposed method is a promising approach in dealing with complex urban land use/transportation modeling.     

Effects of Operational and Design Parameters on the Sequence of Locking of the Wheels of Tractor-Semitrailers

It is known that loss of directional stability during braking occurs in many road accidents involving tractor-semitrailers. To minimize the undesired directional response, the correct order of locking of the wheels is of importance and should receive greater attention. This paper examines the effects of operational and design parameters on the sequence of locking of the wheels of tractor-semitrailers. The way in which the correct locking sequence may be achieved is also discussed in detail.     

Traffic assignment by trip type using volume restraint and link restraint for application in small urban areas

This research involved the development of a new traffic assignment model consisting of a set of procedures for an urbanized area with a population of 172,000. Historical, social, and economic data were used as input to conventional trip generation and trip distribution models to produce a trip table for network assignment. This fixed table was divided into three trip types: external-external trips, external-internal trips, and internal-internal trips. The methodology used to develop the new traffic assignment model assigned each of the trip types by varying the diversion of trips from the minimum path. External-external trips were assigned on a minimum path routing and external-internal trips were assigned with a slight diversion from the minimum path. Internal-internal trips were assigned with more diversion than external-internal trips and adjusted by utilizing iterative volume restraint and incremental link restraint. A statistical analysis indicated that assigning trips by trip types using trip diversion and volume and link restraint produces a significant improvement in the accuracy of the assigned traffic volumes.