Simulation‐based dynamic traffic assignment: Meta‐heuristic solution methods with parallel computing

The aim of this study is to solve the large‐scale dynamic traffic assignment (DTA) model using a simulation‐based framework, which is computationally a challenging problem. Many studies have been performed on developing an efficient algorithm to solve DTA. Most of the existing algorithms are based on path‐swapping descent direction methods. From the computational standpoint, the main drawback of these methods is that they cannot be parallelized. This is because the existing algorithms need to know the results of the last iteration to determine the next best path flow for the next iteration. Thus, their performance depends on the single initial or intermediate solution, which means they exploit a solution that satisfies the equilibrium conditions more than explore the solution space for the optimal solution. More specifically, the goal of this study is to overcome the drawbacks of serial algorithms by using meta‐heuristic algorithms known to be parallelizable and that have never been applied to the simulation‐based DTA problem. This study proposes two new solution methods: a new extension of the simulated annealing and an adapted genetic algorithm. With parallel simulation, the algorithm runs more simulations in comparison with existing methods, but the algorithm explores the solution space better and therefore obtains better solutions in terms of closeness to the optimal solution and computation time compared to classical methods.     

Deterministic model for dynamic assignment of time-varying traffic demand

Two algorithms are presented for assigning time-varying traffic demand to a road network during peak period. The algorithms are heuristics based on the principle of deterministic equilibrium, and they are iterative. Discrete time approach is adopted for computational simplicity. The model presented is suitable for simulating traffic flow in a road network during peak period in urban areas for strategic planning of transport systems.     

对城市化进程所带来的交通问题的思考——昆明加强公共交通解决交通问题的探讨

在城市化进程的推动下,我国的综合国力得到了提升,可是一系列的问题随之产生。交通问题成为目前许多大中城市面临的一大顽症。为此,国内外许多学者对此问题进行了广泛、深入的研究,以求寻找出解决这一问题的有效办法。自上世纪末以来,昆明市也受到了这一问题的困扰,而且越来越严重,最近一段时间以来,城市交通拥堵状况已严重影响到市民的工作、生活,成为政府和市民共同的烦恼。本文就城市发展中交通经历的三个阶段和所面临的问题、以及昆明提倡公交优先的原因、措施和个人意见进行了构思。     

An optimization‐based traffic diversion model during construction closures

During major highway construction, when lanes or entire highway sections must be temporarily closed, traffic managers would like to inform motorists of alternative routes around the construction site well in advance of the project location. This study develops a traffic diversion model to propose an optimum alternate route to drivers during a construction activity. The models and algorithms developed in this study assess a potential diversion route to optimize network performance while considering the drivers’ behaviors in following the proposed alternate route during a closure. A bilevel optimization model is proposed to minimize the total travel time of the affected network considering the link closure and a proposed alternate route for the travelers. A travelers’ route choice decision is modeled based on the user equilibrium traffic assignment, whereas a certain percentage of drivers are assumed to divert to the recommended alternate route. A sufficiently large subnetwork is selected, and a path selection method is proposed to reduce the computational effort required to optimize the model. A set of simulation experiments is conducted using the Tarrant County network in north Texas. The results show the ability of the model to improve the overall network performance during hypothetical closure scenarios.     

A performance comparison of multi-objective optimization algorithms for solving nearly-zero-energy-building design problems

Integrated building design is inherently a multi-objective optimization problem where two or more conflicting objectives must be minimized and/or maximized concurrently.Many multi-objective optimization algorithms have been developed;however few of them are tested in solving building design problems.This paper compares performance of seven commonly-used multi-objective evolutionary optimization algorithms in solving the design problem of a nearly zero energy building(n ZEB) where more than 1.610 solutions would be possible.The compared algorithms include a controlled non-dominated sorting genetic algorithm witha passive archive(p NSGA-II),a multi-objective particle swarm optimization(MOPSO),a two-phase optimization using the genetic algorithm(PR_GA),an elitist non-dominated sorting evolution strategy(ENSES),a multi-objective evolutionary algorithm based on the concept of epsilon dominance(ev MOGA),a multi-objective differential evolution algorithm(sp MODE-II),and a multi-objective dragonfly algorithm(MODA).Several criteria was used to compare performance of these algorithms.In most cases,the quality of the obtained solutions was improved when the number of generations was increased.The optimization results of running each algorithm20 times with gradually increasing number of evaluations indicated that the PR_GA algorithm had a high repeatability to explore a large area of the solution-space and achieved close-to-optimal solutions with a good diversity,followed by the p NSGA-II,ev MOGA and sp MODE-II.Uncompetitive results were achieved by the ENSES,MOPSO and MODA in most running cases.The study also found that 1400-1800 were minimum required number of evaluations to stabilize optimization results of the building energy model.     

开发性金融合作 解地方金融难题 促经济社会发展

海宁地处浙江省北部,南濒钱塘江,内陆面积近700平方公里,东距上海100公里,西离杭州60公里境内有沪杭铁路、101省道,沪杭高速公路、320国道,杭州绕城高速公路东线以及正在建设中的杭州到浦东高速公路,境内交通发达。海宁现辖8个镇,4个街道,户籍总人口64万、流动人口18万。海宁历史悠久。距今约6000年的新石器时代,就有人类在这里繁衍生息。三国吴黄武二年(公元22年)置县,称盐官县,因其境东南濒海,历代不断筑修海塘以御潮汐之患,至清乾隆年间,筑成长达二十多公里的鱼鳞石塘,海水始宁,乃易名海宁至今。海宁自古学风兴盛,民风淳厚,名人辈出。名…     

Cross‐level fragility analysis of modularized suspended buildings based on experimentally validated numerical models

Suspended buildings typically have a core as the primary and suspended floors as the secondary structures. These configurations offer visual transparency, smaller vertical components, and seismic attenuation via the primary–secondary structure interaction. Such attenuation is further enhanced by the modularization of the suspended segment which allows large drifts but prevents them from causing damage. Previously conducted shake‐table tests have confirmed these features. However, how the component performance contributes to system performance has not been quantitated. To address this gap, fragility analyses are conducted for 10‐story experimentally validated models with optimized supplemental dampers and inter‐module stiffness. Multiple limit state functions are proposed to provide a full account of damage sources. Additionally, a mapping rule from the component‐level to the system‐level limit states is developed which captures the influence of damage distribution on system‐level limit states. Results for the uncontrolled suspended building indicate that for the PGV of 0.5 m/s, the failure probabilities of the repairable and life safety limit states are 97% and 83%, respectively. These probabilities are 92% and 27% for the frame structure with viscous dampers, 58% and 5% for the passive‐controlled modularized suspended building system (MSBS), and 45% and 3% for MSBS with optimal vertical distributions of modularized secondary structure.     

Lane width‐based cellular automata model for mixed bicycle traffic flow

In this paper, an improved extended Burgers cellular automata (EBCA) model for heterogeneous bicycle traffic flow is proposed. The compressibility of bicycle traffic flow is considered as a probability, which is related to the bicycle path width. The proposed improved EBCA model is calibrated and validated using the field data collected from three sites in Hangzhou, China. The proposed model is compared with the original EBCA model that does not consider compressibility. The comparison results show that our improved model can simulate heterogeneous bicycle traffic flow better. Moreover, the proposed model overcomes the shortcoming of the other BCA models that only specific path widths can be simulated directly when lane width is determined. Lastly, the EBCA model performance in the congested regions is improved significantly.     

A decomposition scheme for parallelization of system optimal dynamic traffic assignment on urban networks with multiple origins and destinations

This paper presents a decomposition scheme to find near‐optimal solutions to a cell transmission model‐based system optimal dynamic traffic assignment problem with multiple origin‐destination pairs. A linear and convex formulation is used to define the problem characteristics. The decomposition is designed based on the Dantzig–Wolfe technique that splits the set of decision variables into subsets through the construction of a master problem and subproblems. Each subproblem includes only a single origin‐destination pair with significantly less computational burden compared to the original problem. The master problem represents the coordination between subproblems through the design of interactive flows between the pairs. The proposed methodology is implemented in two case study networks of 20 and 40 intersections with up to 25 origin‐destination pairs. The numerical results show that the decomposition scheme converges to the optimal solution, within 2.0% gap, in substantially less time compared to a benchmark solution, which confirms the computational efficiency of the proposed algorithm. Various network performance measures have been assessed based on different traffic state scenarios to draw managerial insights.     

如何解决变频调速供水设备干扰问题

通过对变频调速供水设备工作原理、常见故障、干扰来源的分析,提出了防止干扰的对策及其在实际应用中的有效抗干扰办法,从而使变频调速越来越多的应用到其他控制领域。     

城建档案馆现代化建设中怎样解决现实思想问题

我国现代化建设的飞速发展,带动了城建档案事业的大发展,城建档案工作人员的现实思想问题能否得到妥善及时地解决,直接影响着城建档案馆现代化建设的步伐。因此,在新时期加强城建档案馆全面建设中,提高思想政治工作的有效性是不容忽视的。     

An ensemble machine learning‐based modeling framework for analysis of traffic crash frequency

This study is, to our knowledge, the first in the literature to introduce a modeling framework for analyzing traffic crash frequency based on a series of ensemble machine learning (EML) methods. The main objectives of this study are fourfold: (a) to design a systematic EML‐based framework for crash frequency analysis, (b) to comprehensively compare the performance in analyzing crash frequency by different optimized EML models, (c) to identify significant contributors to crash frequency, and (d) to propose the approach to construct schemes to reduce traffic crashes. To achieve the research goal, the Highway Safety Information System database that includes records of over 1.5 million crashes is employed for model estimation and validation. We first optimize the EML models for crash analysis via the k‐fold cross‐training, including the two averaging methods of random forest and extremely randomized trees, and the two boosting methods of adaptive boosting and gradient tree boosting. Then, we assess the behavior of the optimized models, and conduct a sensitivity test to validate the stability of model performance. Furthermore, we evaluate the relative importance of features to crash frequency by using the Gini diversity index. The results indicate that the two averaging EML models can achieve desirable performance in crash frequency analysis, which outperform the two boosting EML models, in terms of predictive accuracy, generalization ability, and stability. From the results, we explore new insights into the significance of contributors to crash occurrence. Finally, we present the approach of safety improvements for transport facilities.     

浅析如何解决汽车过度发展的问题

针对汽车的过度发展引发的一系列问题,结合中国现有的国情,分析了交通问题出现的原因,通过对欧美现有理论进行参考,提出中国对汽车问题的解决方案,从而营造一种可持续发展的城市交通。     

建筑工程项目管理中存在的问题及解决措施

通过对目前我国建筑工程项目管理中存在的主要问题进行分析,得到相应的解决措施,如对建筑工人进行专业技术培训、高校应完善建筑工程项目管理课程、建筑工程项目管理创新思维等,指出只有从多方面改善和提高目前我国建筑工程项目管理中存在的问题,才能确保建筑工程顺利进行。     

浅析如何通过城市规划解决城市空间分异问题

在参阅相关书籍和资料的基础上,对城市空间分异产生的社会背景以及原因趋势进行了深入分析,并阐述了从城市规划设计以及管理方面处理空间分异问题的对策以及局限性,以达到解决城市空间分异问题的目的。     

如何解决地铁站台隧道的通风排烟问题

介绍了防排烟设计在地铁建筑设计及火灾中的重要性 ,以及目前国内地铁防排烟设施的情况 ,并详细地分析了地铁建筑的防排烟方面存在的问题及防火设计的对策     

基于交通流动态特性的交叉口复杂度模型研究

为了综合衡量城市道路交叉口空间布局形式的复杂性及交通流运行的有序性,从宏观及微观两个层面建立复杂度模型。选取冲突点及冲突概率作为影响复杂度的主要因素,应用图示法及摄影测量方法阐述冲突点的求解过程,采用统计分析及曲线拟合的方法建立冲突概率的计算模型,通过具体算例求解不同空间布局形式的交叉口在不同交通需求下的复杂度数值。结果表明:对于同一类型交叉口而言,其复杂度随流量的增加而增加;对于同一流量条件而言,不同类型的交叉口其复杂度随车道数的增加而增加。复杂度是交叉口运行状态综合性的量化指标,可应用于城市路网的规划及交叉口的安全评价中。     

An area‐based intensity measure for incremental dynamic analysis under two‐dimensional ground motion input

Incremental dynamic analysis (IDA) is a useful method in performance‐based earthquake engineering. IDA curves combine the intensity measure (IM) of ground motions with structural responses (as measured by engineering demand parameter) from nonlinear dynamic analysis. However, the curves display large record‐to‐record variability. And various IMs can lead to different results. Therefore, it is important to find a desirable IM to reduce the discreteness of the IDA results. So far, the studies on IM for IDA have been carried out by many scholars from scalar‐valued to vector‐valued, but few were based on 2‐dimensional ground motion input. To make the analysis more reasonable and practical as well as investigate the desirable IM under 2‐dimensional ground motion input, incremental dynamic analyses when ground motions are inputted in 2 directions should be investigated. In this paper, 2 combinational types of area‐based IM incorporating the influence of ground motion record components in secondary directions were proposed. To investigate the applicability, efficiency and desirable combinational form of the area‐based IM under 2‐dimensional ground motion input, incremental dynamic analysis were carried out using 2 reinforced concrete frames. Then the efficiency of the IMs was measured by the residual sum of squares and R². It is concluded that the area‐based IM with a combination by the square root of the sum of the squares (SRSS) method is the most efficient for IDA under 2‐dimensional ground motion input. The methods and conclusions will provide significant reference for studying IMs under 2‐dimensional ground motion input. Further research will focus on the applicability of the area‐based IM for tall buildings whose higher modes need to be considered.     

Prediction of residential radon exposure of the whole Swiss population: comparison of model‐based predictions with measurement‐based predictions

Radon plays an important role for human exposure to natural sources of ionizing radiation. The aim of this article is to compare two approaches to estimate mean radon exposure in the Swiss population: model‐based predictions at individual level and measurement‐based predictions based on measurements aggregated at municipality level. A nationwide model was used to predict radon levels in each household and for each individual based on the corresponding tectonic unit, building age, building type, soil texture, degree of urbanization, and floor. Measurement‐based predictions were carried out within a health impact assessment on residential radon and lung cancer. Mean measured radon levels were corrected for the average floor distribution and weighted with population size of each municipality. Model‐based predictions yielded a mean radon exposure of the Swiss population of 84.1 Bq/m³. Measurement‐based predictions yielded an average exposure of 78 Bq/m³. This study demonstrates that the model‐ and the measurement‐based predictions provided similar results. The advantage of the measurement‐based approach is its simplicity, which is sufficient for assessing exposure distribution in a population. The model‐based approach allows predicting radon levels at specific sites, which is needed in an epidemiological study, and the results do not depend on how the measurement sites have been selected.     

利用Ansys和Matlab联合求解钢筋混凝土框架结构的优化设计问题

以框架结构造价最低为优化目标,用分部优化法对框架结构进行了优化设计.利用Ansys软件建立了框架模型,计算结构内力,再利用Maflab的fmineon命令对数学模型进行优化设计.实例计算结果验证了该方法的可行性.由于采用商业应用软件,该方法具有操作简便、节省资源的优势,值得推广.