A network option portfolio management framework for adaptive transportation planning

A real option portfolio management framework is proposed to make use of an adaptive network design problem developed using stochastic dynamic programming methodologies. The framework is extended from Smit’s and Trigeorgis’ option portfolio framework to incorporate network synergies. The adaptive planning framework is defined and tested on a case study with time series origin-destination demand data. Historically, OD time series data is costly to obtain, and there has not been much need for it because most transportation models use a single time-invariant estimate based on deterministic forecasting of demand. Despite the high cost and institutional barriers of obtaining abundant OD time series data, we illustrate how having higher fidelity data along with an adaptive planning framework can result in a number of improved management strategies. An insertion heuristic is adopted to run the lower bound adaptive network design problem for a coarse Iran network with 834 nodes, 1121 links, and 10 years of time series data for 71,795 OD pairs.     

集装箱作业系统一体化调度研究综述

目前,对集装箱作业系统的调度研究较少考虑有限资源的协同分配,也缺乏对具有自主和分散特点的多资源一体化调度及其方案自适应能力的研究.文中从一体化调度层面展开,对集装箱作业系统相关的国内外研究进行综述;采用复杂作业车间调度问题的描述方法,给出了一体化调度问题的描述原型;基于迭代式分解调度方法,构建了一体化调度问题的解决方案.     

交通拥堵反思

通过对交通拥堵进行反思,认为交通拥堵是充满活力的成功城市的伴生品,应从不同角度考虑拥堵问题.提出了十项有别于传统观点的提议,主要包括:机动性至关重要,交通拥堵是社会、经济活力的象征;道路扩容效果短暂,并会诱发潜在需求,但仍可带来一定的社会、经济效益;土地使用对出行行为的改变需要长期的努力;紧凑型发展会加剧交通拥堵;降低...     

高职院校学生心理健康问题应对及保障机制的研究与实践

大学生的心理健康教育,作为高职院校构建和谐校园的重要组成部分已日益受到重视与关注。要处理好学生的心理健康问题就必须掌握不同阶段学生的心理特征及加强保障机制的建设。文中主要介绍学院针对学生的心理健康状况,构建心理健康多层保障机制,确保良好的效果。     

Statistical and dynamical analyses of propagation mechanisms of solitary internal waves in a two-layer stratification

The blocking effect of submarine ridges on the propagation of internal solitary waves (ISWs) over the topography of the seabed results in the fission of the solitary waves that accompany the generation of reflected and transmitted waves. In this study, multivariate analysis of variance (MANOVA) is used to investigate the inseparable relationship between the transmission and reflection. An examination of the error sums of squares and cross-products (SSCP) matrix and the correction matrix shows that the correlation between the transmission (at/ai) and reflection coefficients (ar/ai) is quite low (0.284). Moreover, from multivariate testing, including Pillai’s trace, Wilks’ lambda, Hotelling’s trace and Roy’s largest root, we conclude that the ridge height has a large effect (η = 0.456) on both the amplitude of the transmitted and reflected waves, as well as large (η = 0.411) and very large (η = 0.469) effects on the amplitudes of the transmitted and reflected waves, respectively. In conclusion, the results in the present study highlight the importance of the role played by ridge height in coherent ISW transmission and reflection during oceanic wave–ridge interactions.     

Broaching prediction of a wave-piercing tumblehome vessel with twin screws and twin rudders

The new intact stability criteria which are under development at the International Maritime Organization (IMO) are required to cover a broaching phenomenon, well known as a great threat to high-speed vessels which can lead to capsizing. Some reports exist which demonstrate that their numerical models can predict a highly nonlinear phenomenon of broaching. However, additional validation studies are needed for unconventional vessels, in addition to conventional ones, to develop direct stability assessment methods for the new intact stability criteria. In this research, we selected as the subject ship a wave-piercing tumblehome vessel with twin screws and twin rudders, a design expected to be one of a new generation of high-speed monohull ships. Firstly, a series of captive model tests were conducted to measure the resistance, the manoeuvring forces, the wave-exciting forces, the heel-induced hydrodynamic forces, and the roll restoring variation for the unconventional tumblehome vessel. Secondly, the existing mathematical model which had been developed for broaching prediction of conventional vessels with a single propeller and a single rudder was extended to unconventional vessels with twin propellers and twin rudders. Finally, comparisons between numerical simulations and the existing free running model experiments were conducted. As a result, it was demonstrated that fair quantitative prediction of broaching is realised when the rudder force variation, the roll restoring variation and the heel-induced hydrodynamic force for large heel angles are taken into account.     

Parametric rolling prediction in irregular seas using combination of deterministic ship dynamics and probabilistic wave theory

In recent years there have been reports of serious accidents of parametric rolling for modern container ships and car carriers. For avoiding such accidents, a prediction method of parametric rolling in irregular seas is required. Since parametric rolling is practically non-ergodic, repetitions of numerical simulations or experiments could be not feasible to ascertain the behaviour. Therefore, in this paper, a method combining a stochastic approach with a deterministic approach in order to estimate the probabilistic index without such simple repetitions is developed. The ship's response in regular seas is estimated by solving an averaged system of the original 1-DoF roll model, and random waves necessary for occurrence of parametric rolling is achieved by using Longuet-Higgins’s or Kimura’s wave group theory. As a result, a fast and robust computation method of the probabilistic index is established. Finally, it is concluded that the proposed method is considered to be one of the useful tools for discussing the new IMO Intact Stability Code.     

Hydroelasto-plasticity approach to predicting the post-ultimate strength behavior of a ship’s hull girder in waves

Dynamic collapse behavior of a ship’s hull girder in waves is investigated; post-ultimate strength behavior is the focus. Firstly, a simulation method is proposed. Assuming that a plastic hinge is formed during the collapse of the hull girder, the whole ship is modeled as two rigid bodies connected amidship via a nonlinear rotational spring. The post-ultimate strength behavior, such as the reduction of load carrying capacity due to buckling and yielding, is reflected in the model. Hydrodynamic loads are evaluated by using nonlinear strip theory to account for the effect of large plastic deformations on the loads. A scaled model for validation of the simulation is designed and fabricated. Then a series of tank tests is conducted using the scaled model to validate the simulation results. Post-ultimate strength behavior characteristics in waves are clarified by using the numerical and tank test results. It is shown that the hull girder collapses rapidly after reaching ultimate strength, and then the plastic deformation grows until unloading starts at the collapsed section. Finally, several parametric dependencies of the extent of the collapse behavior are discussed based on a series of the simulations.     

新型分油机中的参数变量对分离效果的影响

介绍了传统分油机与新型分油机结构等特征.考虑到油、水二相的密度差,使它们在高速旋转时所受的离心力不同,因而在半径方向油、水分离.根据这一原理,对新型分油机建立相应的物理模型、数学模型并进行求解,得出影响分离效果的技术参数,经比较与实测数据相符.     

船舶失控应急的港珠澳大桥桥区水域尺度

确定桥区水域范围是保证通航船舶和桥梁安全的一个重要因素,但是目前国内外对于如何划分桥区水域的大小并没有明确的标准.以港珠澳大桥为研究对象,从桥梁的有效航宽、拖轮施救时间和船舶失控危险区域三个方面计算了桥区水域尺度.通过对各种工况的计算比较,得出港珠澳段桥区水域尺度为桥梁两侧各2 n mile.