E-commerce system simulation for construction and demolition waste exchange

This article introduces a quantitative approach to e-commerce system evaluation based on the theory of process simulation. The general concept of e-commerce system simulation is presented based on the considerations of some limitations in e-commerce system development such as the huge amount of initial investments of time and money, and the long period from business planning to system development, then to system test and operation, and finally to exact return; in other words, currently used system analysis and development method cannot tell investors about some keen attentions such as how good their e-commerce system could be, how many investment repayments they could have, and which area they should improve regarding the initial business plan. In order to exam the value and its potential effects of an e-commerce business plan, it is necessary to use a quantitative evaluation approach and the authors of this article believe that process simulation is an appropriate option. The overall objective of this article is to apply the theory of process simulation to e-commerce system evaluation, and the authors will achieve this though an experimental study on a business plan for online construction and demolition waste exchange. The methodologies adopted in this article include literature review, system analysis and development, simulation modelling and analysis, and case study. The results from this article include the concept of e-commerce system simulation, a comprehensive review of simulation methods adopted in e-commerce system evaluation, and a real case study of applying simulation to e-commerce system evaluation. Furthermore, the authors hope that the adoption and implementation of the process simulation approach can effectively support business decision-making, and improve the efficiency of e-commerce systems.     

Resource constrained project scheduling using simulation

Resource allocation is one of the most important issues of construction management. Two problems of resource allocation are of concern: resource levelling and resource scheduling. Traditionally, the resource scheduling problem is solved using either heuristic methods or optimization techniques. When heuristic methods are used, resource scheduling is treated as a subsequent problem for the CPM analysis. In this paper, the resource scheduling problem is handled using simulation, where logic dependence and resource availability limits are considered simultaneously during the time scheduling process. Simulation is applied to the resource scheduling problem at the project level. A simulation system called SIRBUS is used to schedule construction projects under resource constraints. Constant resource demand of activities is assumed, and the activity once started cannot be interrupted. Six example projects previously solved by different heuristic methods are re-solved using simulation. The results are compared with the latest heuristic models: current float technique and ranked positional weight method. In addition to the advantage that resource availability is considered during time scheduling as a starting point, which is an apparent feature of simulation, SIRBUS gives good results compared with existing heuristic methods.     

The simulation and visualization of complex human–environment interactions

The purpose of this paper is to describe ongoing research work into the development of a simulation system that integrates statistical analysis, simulation and visualization with computer modeling for analyzing the complex human–environment interactions in dynamic settings. The simulation system allows individuals to explore many facets of human–environment interactions and resulting impacts and compare these results to field-tested methods of actual conditions. More specifically, the research explores procedures for representing the human decision-making process, behavior patterns and associated impacts within a dynamic environment. This tool provides opportunities to (1) develop methods to extract from human behavior and physical systems data, rules which define how individuals communicate, and interact with each other and their environment; (2) develop automated techniques for statistically comparing actual human/environment interactions and associated impacts with simulated outcomes; and (3) the use of visualization methods for evaluating simulation outcomes against actual human–environment interactions. This research builds on data collected on human use, associated resource impacts and monitoring of environmental conditions along the Colorado River through Grand Canyon National Park. Both ecological (beach morphology, river flow rates) and social (human and recreation use and impact) data have all been collected on the Colorado River ecosystem. This data will be used to test, evaluate and demonstrate the effectiveness of simulation and visualization techniques in solving complex problems in a dynamic, sensitive ecosystem. The Grand Canyon River Trip Simulation system is currently being tested to confirm the veracity of river trip projections provided by the model.     

Measuring the global construction industry: improving the quality of data

In the context of a truly global market for construction, an international strategy is required to ensure that national and international statistical systems are able to provide accurate and valid information. In many parts of the world the collection of reliable national information on construction activity is not an easy task, and the measurement of comparable, cross-national data can be problematic. This paper considers possible strategies for the improvement of data collection systems in the context of user needs.     

石油化工真火模拟训练装置池火模拟效果评价

真火模拟训练系统已在全球多个国家投入使用,是一套较为成熟且训练效果较好的实战训练设施,是当前消防部队推行实战化练兵的主要手段,也是未来消防员实战训练的发展趋势.真火模拟训练装置燃烧系统对实际火灾场景的重构效果直接影响着消防训练效果.本文基于理论模型、数值模拟、层次分析法等方法建立了石油化工真火模拟训练装置池火模拟效果评...     

Two‐Dimensional Simulation of Turning Behavior in Potential Conflict Area of Mixed‐Flow Intersections

The potential conflict area of intersection is the space where conflicting traffic flows pass through in the same signal phase. At this area, turning vehicles interact with most traffic flows, which introduce complex features including variation of trajectories and shared‐priority phenomenon. The traditional one‐dimensional simulation oversimplifies these features with lane‐based assumption. This study integrates the modified social force model with behavior decision and movement constraints to reproduce the two‐dimensional turning process. The method is framed into a three‐layered mathematical model. First, the decision layer dynamically makes decision for turning patterns. Then the operation layer uses the modified social force model to initially generate vehicle movements. Finally, the constraint layer modifies the vehicular motion with vehicle dynamics constraints, boundary of intersection and the collision avoidance rule. The proposed model is validated using trajectories of left‐turn vehicles at a real‐world mixed‐flow intersection with nonprotected signal phases, resulting in a more realistic simulation than previous methods. The distributions of decision points and travel time in simulation are compared with the empirical data in statistics. Moreover, the spatial distribution of simulated trajectories is also satisfactory.     

Assessment of construction processes and innovations through simulation

The objectives of this research are to represent construction activities accurately, and to provide a means for assessing the impacts from using innovations. The research approach is the detailed characterization of construction processes, and the development of system and material specific dynamic process simulation models. The ongoing research program is developing a set of specific models, based on extensive empirical data, to enable the accurate modelling of all of the construction processes for a complete facility construction project. A specific process model, glass/metal curtainwall erection, demonstrates the approach, with an analysis of the impacts from a related innovation.     

有源电力滤波器的电流检测与控制方法的研究

介绍有源电力滤波器的工作原理,用PSCAD/EMTDC仿真软件对有源电力滤波器电流的检测方法和控制方法进行了仿真。仿真结果表明,有源电力滤波器采用本文所述电流检测方法和补偿电流产生的控制方法具有很好的谐波补偿效果。     

A consistent modelling methodology for secondary settling tanks in wastewater treatment

The aim of this contribution is partly to build consensus on a consistent modelling methodology (CMM) of complex real processes in wastewater treatment by combining classical concepts with results from applied mathematics, and partly to apply it to the clarification-thickening process in the secondary settling tank. In the CMM, the real process should be approximated by a mathematical model (process model; ordinary or partial differential equation (ODE or PDE)), which in turn is approximated by a simulation model (numerical method) implemented on a computer. These steps have often not been carried out in a correct way. The secondary settling tank was chosen as a case since this is one of the most complex processes in a wastewater treatment plant and simulation models developed decades ago have no guarantee of satisfying fundamental mathematical and physical properties. Nevertheless, such methods are still used in commercial tools to date. This particularly becomes of interest as the state-of-the-art practice is moving towards plant-wide modelling. Then all submodels interact and errors propagate through the model and severely hamper any calibration effort and, hence, the predictive purpose of the model. The CMM is described by applying it first to a simple conversion process in the biological reactor yielding an ODE solver, and then to the solid-liquid separation in the secondary settling tank, yielding a PDE solver. Time has come to incorporate established mathematical techniques into environmental engineering, and wastewater treatment modelling in particular, and to use proven reliable and consistent simulation models.     

Continuous and combined event-process models for simulating pipeline construction

A continuous model and a combined event-process discrete model are developed by employing the Slam II general purpose simulation language. The continuous model addressed the on-going progress of the construction process on a higher level; and the combined event-process discrete model describes the pipeline construction on the operational level. Resource sharing and related issues also are investigated in the two models through an actual gas line project adopted for the purpose of this research. A comparison of the two models provides insights into the modelling approaches. It is concluded that the combined event-process model is more flexible and more powerful for modelling complex construction operations than the continuous model, but at the price of requiring a better understanding of the actual operations and more detailed information.     

数字建筑技术及其在土木施工中的应用

建筑施工图无法完整地表达建筑物各构件的几何形状和实体数据 ,更无法体现各结构构件之间、各施工工序之间的关系数据等 ,由此 ,本文引入基于建筑施工图建立数字建筑的概念 ,用以描述土木施工过程中的所有实体数据和关系数据 ,使得设计和施工这两个阶段能有机地融合在一起 ,并为实现土木施工过程中的的实时进度控制提供基础。     

Planning gang formwork operations for building construction using simulations

Concrete formwork is a labor-intensive and time-consuming operation. Many modular formwork systems have been developed to automate the process. Such systems improve the productivity as well as the cost-effectiveness of the operation. However, proper planning for the form reuse schemes in the design as well as the construction phases of a building, including resource allocations (modular form sets, cranes, workers, etc.), and the construction sequence, is vital for ensuring a successful use of modular formwork systems. Computer process simulation techniques are employed in this research for the study of different form reuse schemes to use gang forming systems in building construction. Five form reuse schemes are identified. The CYCLONE modeling methodology is employed to develop computer models for each of them. MicroCYCLONE simulations and sensitivity analyses of the schemes, using different numbers of form sets, cranes, and labor crews, are then conducted for a real case to assess their impact on the productivity as well as the cost-effectiveness of the operation. The objective is to better understand the characteristics of different form reuse schemes and, in turn, to produce better plans for gang forming construction. Thus, the application of modular formwork systems in building construction can be facilitated.     

6自由度姿态控制的挖掘机模拟训练平台设计

针对现有挖掘机模拟训练存在的功能单一、技术含量低,视角、姿态、复杂工况作业等与实际情况差距较大,不能够满足模拟训练需要的问题,创新设计了6自由度姿态控制的挖掘机模拟训练平台。首先提出了模拟训练平台与真机具有相同的操纵系统、相同的视角、相同的姿态感受和相同的施工环境的设计要求。通过采用3屏显示方案,实现了现实设备与真机具有相同的视区和视角;通过改装XCG230LC-8驾驶室系统,设计的操控平台与真机具有相同的操作模式,最大限度地提高了操作训练水平;采用全电动6自由度动感平台,具有在模拟的性能包线范围内给驾驶人员提供一定范围内姿态角变化的动感信息的能力,从而使驾驶人员在同样环境下姿态感受与真机相同。     

Interactive fire spread simulations with extinguishment support for Virtual Reality training tools

Virtual Reality training for fire fighters and managers has two main advantages. On one hand, it supports the simulation of complex scenarios like big cities, where a fire cannot be simulated in the real world. On the other hand, fire fighting VR simulators allow trainees to experience situations as similar as possible to real fire, reducing the probability of accidents when they are practising exercises with real fire.The success of the Virtual Reality training tools also depends on how close to reality the simulation process is. This work provides fire spread algorithms for forest and urban environments, which can be used at interactive rates. Due to the interactive nature of the algorithms, the users are able to fight the fire by throwing extinguishing agents.Although the algorithms assume many simplifications of the problem, their behaviour is satisfactory. This is due to the efficient management of the cell states in a 3 m×3 m cell grid. Also the variables that have more influence on fire propagation constitute the core of the algorithms. The overall system deals with user extinguishment actions, natural and artificial firebreaks, variable wind conditions (even at a cell level) and non-contiguous fire propagation (embers and spotting fires). The unified forest/urban model leads to an object oriented architecture which supports the fire propagation algorithms. This also allows the system to compute efficiently mixed forest–urban environments.     

Construction management process reengineering: Organizational human resource planning for multiple projects

Applying the business process reengineering and organization planning philosophy, this study focuses on human resource planning in construction management process reengineering (CMPR) to develop a team-based human resource planning (THRP) method for deploying laborpower. The THRP method has two purposes; the first is to determine the maximum loading of projects the original laborpower can carry, and the second is to identify the range of laborpower required for expected project loadings in the future. The THRP method includes four phases, namely, process reengineering, data preparing, human resource allocation, and simulation. Using the THRP method, a construction company cannot only design a team-based organizational structure, but also allocate human resources based on cross-functional processes. Moreover, human resource utilizations before and after CMPR can be compared to evaluate savings attributable to the CMPR. As a consequence, optimum laborpower can be assessed, and human resources allocated to fit the changing processes and circumstances of a construction company's growing business.     

高耸结构广义人造脉动风时程模拟研究

高耸结构的风振响应要考虑非线性就必须在时域内进行,这就要发展顺风向脉动风的模拟方法。本文在了解风的基本特性基础上,利用互谱密度矩阵分解,并考虑了随高度变化的风谱,为提高计算效率和计算精度,引入了快速FFT变换技术,数值算例表明该方法切实有效可行。     

The influence of the user on the results of multizone air flow simulations with COMIS

The multizone airflow simulation program COMIS was evaluated within an International Energy Agency research program. One of the steps in the evaluation procedure is to test the user–code interface, consisting not only in the appearance of the computer screen, but also in the user guide or any other tutorial or help system. The user–code interface of COMIS was then tested through round robin tests. Two types of problems were submitted to several users: a simple and well-defined problem and a real world problem. This study first allowed great improvements of the user guide. While results for the well-defined case were very close to each other, large differences were observed for the `real world' case. Results of simulation largely depend on the user options, and users easily make modelling errors when the studied case becomes complex.     

盾构施工中的沉降监测

地铁施工由于在建筑物稠密、地下管网繁多的城市环境中建设,不仅工程测量精度要求高,而且技术密集、造价昂贵,地面沉降观测尤为重要.针对地铁施工中沉降监测主要任务及基本方法进行了总结,对盾构施工中的地面沉降监测的方法和数据分析有一定的指导意义.     

BIM在合肥南环线钢桁梁柔性拱桥施工中的应用

介绍了BIM技术的发展现状, 阐述了BIM在南环线桥梁钢结构生产、安装过程中的应用。通过应用BIM, 减少了施工技术准备阶段的工作量, 提高工作效率; 加强制造和安装过程中各参与方的协同工作; 进行施工模拟, 有利于优化施工方案。