水平地震作用下单桩横向非线性动力响应的三维有限元数值模拟

针对水平地震作用下的桩土相互作用体系,利用有限元软件ANSYS建立了单桩-地基土系统三维有限元模型。运用此模型,对系统进行考虑地基土的材料非线性和桩土界面状态非线性的单桩横向地震响应计算,并进行了自由场响应的计算。计算结果表明:土体的材料非线性与桩土界面状态的非线性特性对单桩的横向水平地震响应有着一定的影响。     

在CAN中植入时间触发机制的研究

主要论述了在普通CAN网络中植入时间触发机制的准TTCAN模型架构。首先明确了其系统结构,包括单个结点的结构以及物理和逻辑结点的划分。其次论述了QTTCAN的传输方法和出错处理机制。最后则是利用现有CAN硬件进行的仿真实验,用以论证QTTCAN的可行性和可靠性。     

Transient responses of a VLFS during landing and take-off of an airplane

The transient elastic deformation of a pontoon-type very large floating structure (VLFS) caused by the landing and take-off of an airplane is computed by the time-domain mode-expansion method. The memory effects in hydrodynamic forces are taken into account, and great care is paid to numerical accuracy in evaluating all the coefficients appearing in the simultaneous differential equations for the elastic motion of a VLFS. The time-histories of the imparted force and the position and velocity of an airplane during landing and take-off are modeled with data from a Boeing 747-400 jumbo jet. Simulation results are shown of 3-D structural waves on a VLFS and the associated unsteady drag force on an airplane, which is of engineering importance, particularly during take-off. The results for landing show that the airplane moves faster than the structural waves generated in the early stage, and the waves overtake the airplane as its speed decreases to zero. The results for take-off are essentially the same as those for landing, except that the structural waves develop slowly in the early stage, and no obstacle exists on the runway after the take-off of airplane. The additional drag force on an airplane due to the elastic responses of the runway considered in this work was found to be small in magnitude.     

Liner ship route schedule design with port time windows

This paper examines a practical tactical liner ship route schedule design problem, which is the determination of the arrival and departure time at each port of call on the ship route. When designing the schedule, the availability of each port in a week, i.e., port time window, is incorporated. As a result, the designed schedule can be applied in practice without or with only minimum revisions. This problem is formulated as a mixed-integer nonlinear nonconvex optimization model. In view of the problem structure, an efficient holistic solution approach is proposed to obtain global optimal solution. The proposed solution method is applied to a trans-Atlantic ship route. The results demonstrate that the port time windows, port handling efficiency, bunker price and unit inventory cost all affect the total cost of a ship route, the optimal number of ships to deploy, and the optimal schedule.     

城市轨道交通折返能力的估算及影响因素

重点阐述了站前、站后折返模式下的折返能力的计算方法,并分析了信号系统的选型及参数对折返能力的影响.     

贵广铁路东平水道特大桥抗震设计研究

东平水道特大桥主桥双线铁路(85.75+286+85.75)m钢桁架拱桥,为国内首座该类型铁路桥梁。桥位处抗震设防烈度为7度,主桥的地震设防为设计关键。建立主桥三维有限元抗震模型,详细研究在33号活动墩墩顶不设置或设置液体黏滞阻尼器装置对主桥的抗震影响效果,采用反应谱和时程两种分析方法,对抗震分析结果进行比较。结果表明:(1)地震反应不控制钢桁架拱桥和桥墩身结构设计,仅控制桩基础设计;(2)33号活动墩墩梁间设置纵向减隔震液体黏滞阻尼器,对32号固定墩纵向抗震响应影响不大,效果不明显;(3)给出的最小配筋率均能满足各桥墩桩基础抗震验算及预期的抗震要求。     

基于混沌理论的高速公路网短时交通流量预测研究

随着高速公路网的建成及其交通流量的不断增大,对高速路网交通流实时控制和诱导服务的需求日益突出,而高速公路网短时交通流量的预测,不仅是交通流实时控制和诱导服务的基础和依据,而且预测结果的准确性对改善高速公路网的通行能力和服务水平有重要影响。基于混沌时间序列分析和预测的理论,建立了高速公路网短时交通流预测模型,计算给定区域高速公路网多断面短时交通流量预测值,结果表明利用多维混沌时间序列法预测高速公路网短时交通流量可行且具有较高的精度。     

The Pollution-Routing Problem

The amount of pollution emitted by a vehicle depends on its load and speed, among other factors. This paper presents the Pollution-Routing Problem (PRP), an extension of the classical Vehicle Routing Problem (VRP) with a broader and more comprehensive objective function that accounts not just for the travel distance, but also for the amount of greenhouse emissions, fuel, travel times and their costs. Mathematical models are described for the PRP with or without time windows and computational experiments are performed on realistic instances. The paper sheds light on the tradeoffs between various parameters such as vehicle load, speed and total cost, and offers insight on economies of ‘environmental-friendly’ vehicle routing. The results suggest that, contrary to the VRP, the PRP is significantly more difficult to solve to optimality but has the potential of yielding savings in total cost.     

The suitability of hedonic models for cost-benefit analysis: Evidence from commuting flows

We compare two estimates of benefits arising from the construction of new bridges in south-west Norway. One estimate comes from a hedonic property value model. Rather than follow an approach which is strictly theoretically correct, we adopt Rosen’s simple first-stage approach. To investigate and validate whether this simplified approach gives a reasonable estimate, we compare it to an estimate derived from a travel demand model. We find that a variant of an ex post hedonic house price model gives very similar estimates to the estimates from the travel demand model. This supports a hypothesis that the simplistic hedonic approach is reasonable.     

Using OMP analysis to observe temporal variability in water mass distribution

Previous optimum multiparameter analyses have investigated spatial distribution of water masses and reported successful results. This study tests the method further with application to a time series to examine temporal variability in water mass distribution. Observations collected from the Sargasso Sea are utilised, mainly to detect well-documented property changes that have occurred in Labrador Sea Water, but also possible fluctuations in water mass contributions as a whole.The results show much structure and variability in the contributions of Central Water and upper deep waters in the depth range 900–2000 m. It is proposed that the passage of warm and cold core eddies is indicated by these changes in relative contributions of water masses, although quantitative comparison of satellite altimetry data with the model results is not conclusive.Significant irregularities in the distribution of Labrador Sea Water are also revealed by the model. Through-flow of modified (since the early 1990s) Labrador Sea Water is denoted in the results by an apparent absence from mid-1995 to early 1998. This suggests a transit time of 5–6 years between the Labrador Sea and Bermuda, which is consistent with observational findings described in the literature.