紊流混摩区摩阻因数近似公式分析

根据对90号无铅汽油和0号柴油进行摩阻实验所取得的实测数据，对紊流混摩区的近似公式进行了误差的计算和比较，并分析了误差产生的主要原因。计算和分析结果表明：科尔布鲁克公式是紊流混摩区的较准确的计算公式，近似公式只适用于粗略的计算和数学分析。     

Locating emergency vehicles with an approximate queuing model and a meta-heuristic solution approach

In this paper, the location of emergency service (ES) vehicles is studied on fully connected networks. Queuing theory is utilized to obtain the performance metrics of the system. An approximate queuing model the (AQM) is proposed. For the AQM, different service rate formulations are constructed. These formulations are tested with a simulation study for different approximation levels. A mathematical model is proposed to minimize the mean response time of ES systems based on AQM. In the model, multiple vehicles are allowed at a single location. The objective function of the model has no closed form expression. A genetic algorithm is constructed to solve the model. With the help of the genetic algorithm, the effect of assigning multiple vehicles on the mean response time is reported.     

基于近似曲率的铁路既有线纵断面分段算法

纵断面线形的精确分段是后续铁路线路优化调整的基础。针对现有方法自动分段效果差且精度低的缺点,研究一种能够实现线形精确自动分段的算法。首先,在对比各种方法的基础上,提出一种基于测点近似曲率的线形自动分段算法,针对铁路竖曲线弧径比过小易导致的拟合病态问题,采用基于半径确定的最小二乘算法进行圆心精确定位,以提高分段点的精度。经实测数据验证该算法能自动化识别特征点位置,且具有更高的精度。     

基于近似模型的车辆操纵稳定性及平顺性的优化研究

简述了基于近似模型的车辆操纵稳定性及平顺性的优化设计方法.利用多体动力学软件ADAMS/Car建立了某轿车整车多体动力学模型,并确定了车辆操纵稳定性及平顺性的评价目标.以悬架弹簧刚度、减振器阻尼特性和横向稳定杆刚度为设计变量,利用近似优化数学模型对该轿车进行了操纵稳定性和行驶平顺性的多目标优化计算.结果表明,近似模型技术对于汽车性能的平衡优化是一种十分有效的方法.     

Game-theoretical models for competition analysis in a new emerging liner container shipping market

This paper develops three game-theoretical models to analyze shipping competition between two carriers in a new emerging liner container shipping market. The behavior of each carrier is characterized by an optimization model with the objective to maximize his payoff by setting optimal freight rate and shipping deployment (a combination of service frequency and ship capacity setting). The market share for each carrier is determined by the Logit-based discrete choice model. Three competitive game strategic interactions are further investigated, namely, Nash game, Stackelberg game and deterrence by taking account of the economies of scale of the ship capacity settings. Three corresponding competition models with discrete pure strategy are formulated as the variables in shipment deployment are indivisible and the pricing adjustment is step-wise in practice. A ɛ -approximate equilibrium and related numerical solution algorithm are proposed to analyze the effect of Nash equilibrium. Finally, the developed models are numerically evaluated by a case study. The case study shows that, with increasing container demand in the market, expanding ship capacity setting is preferable due to its low marginal cost. Furthermore, Stackelberg equilibrium is a prevailing strategy in most market situations since it makes players attain more benefits from the accommodating market. Moreover, the deterrence effects largely depend on the deterrence objective. An aggressive deterrence strategy may make potential monopolist suffer large benefit loss and an easing strategy has little deterrence effect.     

Dynamic pricing for managed lanes with multiple entrances and exits

Priced managed lanes are increasingly being used to better utilize the existing capacity of the roadway to relieve congestion and offer reliable travel time to road users. In this paper, we investigate the optimization problem for pricing managed lanes with multiple entrances and exits which seeks to maximize the revenue and minimize the total system travel time (TSTT) over a finite horizon. We propose a lane choice model where travelers make online decisions at each diverge point considering all routes on a managed lane network. We formulate the problem as a deterministic Markov decision process and solve it using the value function approximation (VFA) method for different initializations. We compare the performance of the toll policies predicted by the VFA method against the myopic revenue policy which maximizes the revenue only at the current timestep and two heuristic policies based on the measured densities on the managed and general purpose lanes (GPLs). We test the results on four different test networks. The primary findings from our research suggest the usefulness of the VFA method for determining dynamic tolls. The best-found objective value from the method at its termination is better than other heuristics for all test networks with average improvements in the objective ranging between 10% and 90% for revenue maximization and 0–27% for TSTT minimization. Certain VFA initializations obtain best-found toll profiles within first 5–50 iterations which warrants computational time savings. Our findings also indicate that the revenue-maximizing optimal policies follow the “jam-and-harvest” behavior where the GPLs are pushed towards congestion in the earlier time steps to generate higher revenue in the later time steps, a characteristic not observed for the policies minimizing TSTT.     

Dynamic pricing and reservation for intelligent urban parking management

Despite rapid advances of information technologies for intelligent parking systems, it remains a challenge to optimally manage limited parking resources in busy urban neighborhoods. In this paper, we use dynamic location-dependent parking pricing and reservation to improve system-wide performance of an intelligent parking system. With this system, the parking agency is able to decide the spatial and temporal distribution of parking prices to achieve a variety of objectives, while drivers with different origins and destinations compete for limited parking spaces via online reservation. We develop a multi-period non-cooperative bi-level model to capture the complex interactions among the parking agency and multiple drivers, as well as a non-myopic approximate dynamic programming (ADP) approach to solve the model. It is shown with numerical examples that the ADP-based pricing policy consistently outperforms alternative policies in achieving greater performance of the parking system, and shows reliability in handling the spatial and temporal variations in parking demand.     

静态GPS接收机的动态化功能改进研究

较全面地研究了静态GPS测量的机内数据处理和后处理功能的内容、要求及其最新发展。对GPS接收机内、外处理功能的配置问题进行了分析 ,提出了通过增加测站数据传输设备将传统的静态接收机的后处理的部分或全部功能前移的观点 ,并以Trimble84 0 0 0机为例 ,提出了对第二、三代接收机进行功能扩展的原则和方案     

Integrated optimisation design of a dynamic umbilical based on an approximate model

An optimised design of a dynamic umbilical requires an extreme cross-sectional stress to be maintained within an allowable limit and a fatigue life to be guaranteed to be sufficient. It should be noted that a dynamic umbilical is a typical geometric bi-scale structural system. It consists of a local cross-sectional scale and a global configuration scale, which are significantly different in terms of geometric sizes. In this study, we established an approximate model to achieve an optimised design of the dynamic umbilical by considering the parameters of local cross-sections and global configurations simultaneously. The design variables of a dynamic umbilical are independently identified and defined at both local sectional and global configuration scales in the approximate model. Furthermore, we selected the maximum tension strain and the maximum bending moment, for covering local and global properties, as the objectives to be minimised. The approximate model was observed to be effective in integrating the local and global responses into one loop so that the computational efficiency could be significantly increased. We implemented the optimisation framework on a dynamic umbilical with a lazy-wave configuration, which is considered to be a basis for a case study. Furthermore, we verified the feasibility and effectiveness of the integrated optimisation strategy by numerical simulations. Moreover, we compared the optimised dynamic umbilical properties with those without optimisation. It was observed that the fatigue life of the optimised dynamic umbilical was improved significantly, thereby indicating that the integrated optimisation methodology provides a new model and algorithm for an efficient design of the dynamic umbilical.     

波浪中螺旋桨推力变化的近似计算

螺旋桨在波浪中随船运动是前进、旋转和振荡三者的结合。本文近似计算波浪中桨流体动力性能相对于静水中性能的变化,将波浪中螺旋桨运动分解为旋转兴波和振荡兴波两部分线性迭加。利用Ｇｒｅｅｎ函数法,求解其兴波问题,给出桨推力的变化值。编制程序进行了系列数值计算。结果表明,波浪中螺旋桨推力系数变化值随桨轴浸深、桨升沉振荡频率和幅值而变化。