Integrating simulation and optimization to schedule loading operations in container terminals

In this paper, a simulation optimization method for scheduling loading operations in container terminals is developed. The method integrates the intelligent decision mechanism of optimization algorithm and evaluation function of simulation model, its procedures are: initializing container sequence according to certain dispatching rule, then improving the sequence through genetic algorithm, using simulation model to evaluate objective function of a given scheduling scheme. Meanwhile, a surrogate model based on neural network is designed to predict objective function and filter out potentially bad solutions, thus to decrease the times of running simulation model. Numerical tests show that simulation optimization method can solve the scheduling problem of container terminals efficiently. And the surrogate model can improve the computation efficiency of simulation optimization.     

An architectural design of control software for automated container terminals

Automation of handling equipment is a current trend in port container terminal. Because a large number of equipment of different types are involved in the handling operation, the structure of control software is highly complicated. This paper introduces an architectural design of control software and a simulation-based test-bed for testing various control rules of the control software. The suggested control system consists of a ship operation manager (SOM) and system controllers for automated guided vehicles (AGVs) and automated yard cranes (AYCs). A SOM is in charge of dispatching tasks to equipment for preplanned load/unload operations. System controllers assign equipment to the SOM and maintain the information about the location and the status of equipment. To test the control system and the operation methods of the suggested container terminal, an object-oriented simulation system was developed using Java. Using the simulation system, several operation-related issues were tested, including the postponement of dispatching decisions and the sequence rearrangement of AGVs entering transfer areas under quay cranes (QCs).     

MicroPort: A general simulation platform for seaport container terminals

Seaport container terminals are essential nodes in sea cargo transportation networks. As such, the operational efficiency of container terminals in handling containers passing through them plays a critical role in a globalized world economy. Many models and algorithms have been developed to address various decision problems in container terminals to help improve operational efficiency. These decision support tools are usually used separately for specific purposes. However, the problems they are trying to tackle are often interrelated. Therefore, in this regard, an evaluation tool which can capture as many operational conditions as possible for different decision problems is necessary. This paper introduces a general simulation platform, named MicroPort, which aims to provide an integrated and flexible modeling system for evaluating the operational capability and efficiency of different designs of seaport container terminals. The software structure of MicroPort comprises three programming layers: (1) the Functions layer; (2) the Applications layer; and (3) the Extensions layer. Different layers are bound by Application Programming Interfaces (APIs). Basic functions built in the Functions layer support the Applications layer in which major operation processes can be modeled by an agent-based method. External modules and decision support tools in the Extensions layer then use APIs to adjust the system to produce suitable simulation models for specific purposes.     

Evaluation of the floaterm concept at marine container terminals via simulation

International seaborne trade rose significantly during the past decades. This created the need to increase capacity of existing marine container terminals to meet the growing demand. The major objective of this paper is to evaluate the floaterm concept using simulation modeling and determine if it can improve terminal productivity. The main difference between floaterm and conventional marine container terminals is that, in the former case, transshipment containers are handled by off-shore quay cranes and stored on container barges. Two terminal configurations performance is compared (vessel handling times and equipment utilization) under normal and disruptive conditions. Computational experiments confirm preliminary expectations that the floaterm concept can enhance efficiency of marine container terminal operations under normal and disruptive conditions.     

Choice of loading clusters in container terminals

The storage allocation in the export yard of a container terminal determines the efficiency of container loading. Even if the yard manager has optimised the allocation of export containers to avoid rehandling, conflicts among loading quay cranes can still occur. Thus, all the possible handlings during loading must be considered when organising the yard space. In previous studies, the yard storage allocation has been assessed based on the subblock, which consists of several adjacent bays. However, to minimise all possible handlings in the loading process at the terminal, optimising more flexible storage clusters is also important. Thus, our aim in this research is to model the choice of loading clusters and derive a more flexible allocation strategy for organising the space in the export yard. A bi-objective model is built, which considers both the transportation distance and handling balance between blocks. A model aimed at minimising all possible handlings in the export yard for the loading process is also developed, and several of the insights derived can inform yard management in real-life operations. It is proven that the handling requirements have a significant effect on the choice of loading clusters, and yard managers should consider the various features of liner and loading processes when organising their storage space.     

Haptics-based virtual reality periodontal training simulator

This paper focuses upon the research and development of a prototype dental simulator for training of periodontal procedures. By the use of virtual reality and haptics technology, the periodontal simulator allows trainees to learn performing diagnosis and treatment of periodontal diseases by visualizing a three-dimensional virtual human mouth and feeling real tactile sensations while touching the surface of teeth, gingiva, and calculi with virtual dental instruments. Since periodontics requires dentists to depend primarily on tactile sensations to perform diagnostic and surgical procedures, the use of haptics is unquestionably crucial for a realistic periodontal simulator. The haptics-based virtual reality periodontal training simulator has been validated by a experiment conducted by the College of Dentistry at University of Illinois at Chicago (UIC) with faculty members and dental students, which demonstrates the scientific contribution and usefulness of the simulator as a vital part of the curriculum of the Department of Periodontics at UIC.

A case based heuristic for container stacking in seaport terminals

In this paper, we suggest a Case Based heuristic for the online container stacking management system in seaport terminals. The main objectives of the system are to determine the exact position of each import container in the storage area and to control container allocation and react to unexpected events and disturbances in an intelligent, self-organizing and real-time manner. First, we propose learning mechanisms and knowledge models for a better management of knowledge related to disturbances and container environment. This system takes into account different types of containers especially the storage of dangerous containers. For assessment of the suggested system, real data are collected from King Abdul Aziz Dammam seaport terminal (Saudi Arabia). The performance of the developed heuristic is assessed with different scenarios and compared to three other stacking strategies studied in the scientific literature. The obtained results are promising and show that the developed CBR (Case Based Reasoning) based heuristic can be efficient or similar problems, i.e. online container staking.     

Layout analysis affecting strategic decisions in artificial container terminals

As a result of a major growth in world trade, importance of the container terminals, which are the exit gates of international maritime trade, has been emphasized and the competition between these terminals has increased. In recent years, increasing competition in shallow seas, which have low berth depth and intensive trade, has caused terminal managers to investigate how the strategic decisions affect the future development of terminal operations. Due to their low berth depth, container terminals in the feeder ports of shallow seas are built artificially near coastlines. The most common layouts found in these terminals are Π, L, π, or Ψ. In this paper, simulation models were developed for the container terminals to examine the effect of transporter dispatching rules and resource allocation strategies in terms of total annual handling amount. According to the results, terminal performance is significantly affected by terminal layout design under different transporter dispatching rules and allocation strategies.     

Dynamic yard crane dispatching in container terminals with predicted vehicle arrival information

The performance of a container terminal depends on many aspects of operations. This paper focuses on the optimal sequencing of a yard crane (or YC for short) for serving a fleet of vehicles for delivery and pickup jobs. The objective is to minimize the average vehicle waiting time. While heuristic algorithms could not guarantee an optimal solution, a conventional mathematical formulation such as mixed integer program would require too much computing time. We present two new algorithms to efficiently compute YC dispatching sequences that are provably optimal within the planning window. The first algorithm is based on the well-known A^∗ search along with an admissible heuristics. We also incorporate this heuristics into a second backtracking algorithm which uses a prioritized search order to accelerate the computation. Experimental results show that both new algorithms perform very well for realistic YC jobs. Specifically, both are able to find within seconds optimal solutions for heavy workload scenarios with over 2.4 × 10¹⁸ possible dispatching sequences. Moreover, even when the vehicle arrival times are not accurately forecasted, the new algorithms are still robust enough to produce optimal or near-optimal sequences, and they consistently outperform all the other algorithms evaluated.     

虚拟制造环境中制造装备的三维建模及动作模拟

虚拟制造中，三维加工装备建模是这种活动的仿真基础之一。该文以简单车床为例，具体研究了加工装备的三维模型简化和建立，然后剖析了模型的整体结构，并按照运动和非运动部分将其分块和组合，形成了模型的装配视图，建立了每个分块的局部坐标系统。在此基础上模拟了车床的相关分块的运动，最后形成了一个具有立体视效果的模拟环境，为加工装备的具体加工过程虚拟化建立了设备基础。     

Simulation-based optimization for housekeeping in a container transshipment terminal

An important activity in container transshipment terminals consists in transferring containers in the yard from their current temporary positions to different positions closer to the point along the berth from which the containers will be boarded on departing vessels. This housekeeping process aims at speeding-up discharge and loading operations and, thus, relieving congestion. This paper introduces a heuristic procedure to manage the routing of multi-trailer systems and straddle carriers in a maritime terminal. A simulation model embedded in a local search heuristic allows a proper evaluation of the impact of different vehicle schedules on congestion and throughput. Computational experiments performed on test instances derived from real-life data show that important improvements in routing distance and vehicle waiting time can be obtained compared to the use of standard scheduling policies.     

集装箱码头三维仿真组件平台

为直观、形象地研究集装箱码头生产优化问题,采用三维仿真的方法实现集装箱码头物流信息与作业过程的可视化．基于不同业务流程的仿真要求,合理地划分静态布局、装卸设备、装卸对象、码头操作、运动学解算、数据访问、通信接口和图形渲染等组件的粒度;建立层次结构形式的组件平台,体现客观对象的逻辑关系;遵循标准COM＋规范设计岸桥、场桥和集卡等集装箱码头主要三维仿真组件．以上海振华重工（集团）股份有限公司自动化集装箱码头为例验证该组件平台的可操作性,结果表明该方法对集装箱码头装卸工艺的改进和管理水平的提升具有实际指导意义．     

Morfit Web-3D仿真建模技术及其应用

该文是一个综述性的应用报告,主要介绍了Morfit Web-3D引擎的功能以及使用它进行环境仿真建模时的作用。Morfit Web-3D引擎集成了当前许多先进的算法和技术进步的成果,采用的是基于图象的3D建模方法。它使得利用数码相机拍摄的图片可以方便地结合到虚拟场景之中,克服了虚拟现实建模过程中构造场景细节时的大量细致和耗费人力的工作。与其它虚拟现实技术相比较在建模的速度上有一定优势。该文详细阐述了Morfit场景的主要构成对象、影响场景中物体显示效果的因数、控制动态物体在场景中运动的方法及创建Morfit Web3D场景的主要步骤。最后通过一个具体实例展示了它的实际应用效果及相关程序设计方法和流程。     

Construction industry offsite production: A virtual reality interactive training environment prototype

The ‘traditional’ construction industry has constantly been challenged to improve its inherent problematic practices. Offsite production (OSP), under the umbrella of modern methods of construction (MMC), has been acknowledged as a means to help improve construction industry performance as well as meet new market demands through the provision of improved, adaptable, and sustainable buildings. However, the deployment of OSP systems, if not managed properly, may adversely affect the end result and be counterproductive. It is therefore imperative that the construction industry stakeholders learn and appreciate the specifics, merits, as well as the risks associated with OSP systems in order to achieve the desired outcomes and consequently improve industry performance.On-the-job-training (OJT) is usually sought to facilitate ‘experiential’ learning, which is argued to be particularly effective where a great deal of independence is granted to the task performer. However, OJT has been criticised for being expensive, limited, and sometimes devoid of the actual training context. In order to address the problems encountered with OJT, several virtual reality (VR) solutions have been proposed. This paper introduces one such VR solution prototype, in order to provide a risk-free environment for learning without the ‘do-or-die’ consequences often faced on real construction projects. The proffered solution provides a unique VR environment for practicing new working conditions associated with OSP practices. While the ‘scenes’ of the VR environment take place on a construction site, the environment predominantly targets professionals, such as project managers, construction managers, architects, designers, suppliers and manufacturers, to allow multidisciplinary learning to occur, and hence overcome ‘knowledge silos’ or ‘knowledge compartmentation’. The VR environment enables unforeseen problems often caused by professionals’ decisions, faulty work, and health and safety issues to occur; where the implications of which can be evaluated in respect of time, cost and resources. The VR environment proposed does not aim to resolve problems associated with OSP per se, rather aims to allow ‘things to go wrong’ and consequently allows users not only to ‘experience’ the resulting implications but also to reflect on those implications as part of the learning process. This paper discusses and presents the prototype for the first development phase of the VR interactive training environment. While the prototype was tested and validated with domain experts from industry, the research community, and academia from different EU countries, the data used in developing the prototype was constrained to one project in the UK which may limit the generalisability of results.     

Interaction with a desktop virtual environment: a 2D view into a 3D world

With the development of computer software and hardware in the past few years, it has been possible to produce effective training virtual environments on everyday personal computers with little expert training required for users or designers. However, the development of the equipment that enables this has brought little coinciding research on what features to include when designing these environments. Despite these increased advances in PC capabilities for desktop virtual environments (VEs), there are still limitations on the number of objects that can be programmed to be interactive, usually due to restrictions on programming time and cost. As a result, it is often left to the programmer to decide which of the objects included to increase the realism of the environment will be interactive and which aesthetic. The work presented in this paper is an experiment that aims to establish a guide for environment designers to aid effective environment interaction development by identifying key elements in a VE design.

SimCrane 3D+: A crane simulator with kinesthetic and stereoscopic vision

Crane operation training using virtual crane simulators has been introduced in the last decade. It can reduce the costs associated with renting actual cranes and enables operator training for a range of tasks in virtual environment. However, a critical drawback common to most existing simulators is a lack of realistic simulation for the depth perception, which usually relies on stereoscopic vision and head motion to increase the precision of depth perception. This research aimed at adopting kinesthetic vision and stereoscopic vision into a virtual crane simulator to increase its training effectiveness. Kinesthetic vision generates corrected perspective images based on the head position of the viewer. Stereoscopic vision is to generate separated images for left and right eyes respectively. A crane simulator known as SimCrane 3D⁺ was developed and implemented to achieve the goal. We performed user tests to evaluate the proposed system by both subjective and objective factors. The results showed that the system provide better simulation for depth perception. Operators increase their confidences in the tests. They also reported using SimCrane 3D⁺ is more intuitive than the simulator without stereoscopic or kinesthetic visions.     

基于Creator的三维模型的简化研究

三维模型是虚拟现实系统中重要的组成部分,在三维模型的处理中存在两个主要问题：一是载入场景文件要花费很多时间;二是即使是在高性能的PC机上,浏览场景也是一件繁重而费时的事。当鼠标移动之后,场景变换要滞后几秒钟甚至几分钟。为此需要对模型进行优化,该文从简化模型和提高渲染速度两个方面介绍了基于Creator的优化三维模型及减少载入时间的几种方法。     

实时三维声音仿真系统的设计与实现

主要论述虚拟现实环境中声音播放的原理和处理过程 ,并探讨了利用DirectSound在虚拟现实环境中实现三维实时音响仿真系统的关键技术     

The impact of Web3D technologies on medical education and training

This paper provides a survey of medical applications that make use of Web3D technologies, covering the period from 1995 to 2005. We assess the impact that Web3D has made on medical education and training during this time and highlight current and future trends. The applications identified are categorized into: general education tools; tools for diagnosis; procedures training; and collaborative training. A summary of work that has been carried out to validate these tools is also included in the survey.