水运OD矩阵的推算模型研究

交通OD矩阵是交通量预测的基础,但由于资料调查工作量大且精度难以控制,水运OD矩阵往往难以通过调查直接得到。鉴于此,基于对现有OD矩阵推算模型的研究与分析,并结合水上运输及其运输量调查资料的特性,提出了一种利用水运港口吞吐量和水运客货运平均运距推算水运OD矩阵的计算模型,由此可推算得到水运OD矩阵,供相关分析研究之用。     

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研究印度城市道路上设置公交专用道后小汽车出行向公交转移的可能性. 借助新的混合交通流仿真模型测定设置公交专用道后公交服务水平改善状况. 基于陈述偏好入户调查的抽样数据,本文还引入其他影响出行方式转移的变量,标定出行方式选择二元Logit模型. 根据实际和预测数据,确定了公交服务水平改善条件下小汽车出行向公交转移的一系列主要影响因素. 基于两种方式出行时间差,绘制出行方式转换概率曲线,并为多变量宽值域条件下交通方式转移的预测提供一种易于操作的方法.     

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我国城市道路机动车道与非机动车道之间无物理隔离设施的情况非常普遍,因而相邻的机非交通流存在严重的相互干扰。本文利用石家庄市典型路段交通现场调查数据,定量分析了无物理隔离路段机动车和非机动车的速度特征。区分了非机动车道内非机动车的分布差异,通过各个典型位置非机动车平均速度的对比,解释了骑车人因受到相邻车道机动车影响而表现出的复杂交通行为;提出了基于时空转换思想的交通调查方法,建立了机动车速度的回归统计模型并通过了F检验,模型包含了非机动车流量和机非最小横向间距等参数,研究表明,机动车速度与以上参数之间呈一定的线性关系。     

从算术平均数谈最小一乘法与最小二乘法的区别

本文从算术平均值出发,讨论了最小一乘法与最小二乘法的区别,并用这二种方法对数据进行了回归分析。     

日本交通安全对策的借鉴与启示

尽管日本的机动车保有量和交通事故数量高于我国,但日本交通事故死亡人数远远低于我国。论文在综合介绍日本道路交通安全对策的基础上,将交通事故发生数量和交通事故造成的死亡数量与日本的乘用车保有量进行回归分析,并以虚拟变量的形式考虑了交通安全相关对策对交通事故量和死亡人数的影响。从分析结果可以看出,交通事故的发生量和死亡人数与乘用车的保有量有很大相关性,但是交通安全的相关对策对交通事故的降低和死亡人数的减少有重大影响,这对我国交通安全管理措施的制定和完善提供了积极的借鉴和启示。     

关于公交票价与私家车出行关系的研究方法

该文针对研究城市公交票价与私家车出行量之间关系的需要,提出了一种理论方法。该方法用多元线性回归模型分析了城镇居民家庭人均可支配收入、私家车出行成本等因素对私家车出行需求的影响,并在此基础上结合交叉弹性理论进一步得到公交票价和私家车出行需求之间的弹性关系。通过该方法可以量化公交票价与私家车出行需求两者之间的关系,为城市采用低价公交来制约私家车出行的政策提供一些理论依据。     

客运专线列车速度控制方式设计的优化模型及应用

在先进列车调控系统下的列车追踪间隔距离与速度分级数之间量化关系的基础上,以纯高速列车模式下的客运专线速度控制系统为对象,提出了速度控制方式优化设计的理论模型,阐述了模型构成的原理,介绍了有关参数计算的成果,并以实例作了验算。     

Development and evaluation of a hybrid travel time forecasting model

The purpose of this paper is to develop and evaluate a hybrid travel time forecasting model with geographic information systems (GIS) technologies for predicting link travel times in congested road networks. In a separate study by You and Kim (cf. You, J., Kim, T.J., 1999b. In: Proceedings of the Third Bi-Annual Conference of the Eastern Asia Society for Transportation Studies, 14–17 September, Taipei, Taiwan), a non-parametric regression model has been developed as a core forecasting algorithm to reduce computation time and increase forecasting accuracy. Using the core forecasting algorithm, a prototype hybrid forecasting model has been developed and tested by deploying GIS technologies in the following areas: (1) storing, retrieving, and displaying traffic data to assist in the forecasting procedures, (2) building road network data, and (3) integrating historical databases and road network data. This study shows that adopting GIS technologies in link travel time forecasting is efficient for achieving two goals: (1) reducing computational delay and (2) increasing forecasting accuracy.     

Transverse strength analysis of catamarans

Stresses and deformations relevant for transverse strength analysis are calculated for a 60 m catamaran by a compartment model and are compared with corresponding results from a global model. It is found that the flexibility of the partial bulkheads typical for a twin-hull Ro/Ro-vessel is so large that the interaction with the surrounding structure has to be accounted for. If springs are applied, the results are sensitive to the spring stiffness. A web frame model that does not include any bulkheads, gives large errors and is not recommended.     

Steady-state single cell model simulations of photoacclimation in a vertically mixed layer: implications for biological tracer studies and primary productivity

A numerical single-cell photoacclimation–diffusion model was constructed and used to develop criteria regarding the use of individual phytoplankton cells as tracers for vertical mixing and to illustrate how rates of vertical mixing might affect phytoplankton physiology. Both first-order and logistic representations of photoacclimation kinetics were used. Steady state was assumed for simplicity and to provide a starting point for further investigations. The modeled variance and higher moments (within a phytoplankton population) of a generic photoacclimative parameter all show trends, which are diagnostic of mixing rates and/or boundary effects. This allowed the establishment of criteria by which frequency distributions of phytoplankton physiological properties (e.g., cell fluorescence) might be used as indicators of vertical mixing. The same model can be used to predict the effects of vertical mixing on phytoplankton productivity and growth. Application of the model to both photosynthesis and carbon to chlorophyll ratios suggested that a combination of vertical mixing and hysteresis (as represented in the logistic model of photoacclimation) in acclimation kinetics can enhance specific growth rates of phytoplankton. This enhanced growth occurred as a result of mixing-induced variation in carbon to chlorophyll ratios and is in contrast to chlorophyll-specific productivity, which was maximal at low mixing rates. Differential rates of photoacclimation to upward vs. downward shifts in irradiance, may enable phytoplankton cells to better survive in a turbulent environment.