A simulation optimization framework for ambulance deployment and relocation problems

This paper studies ambulance deployment and relocation problems, which are two of the core decisions faced by emergency medical service control centers in metropolis. The challenge in the problems is to estimate the operational performance of a deployment plan under stochastic environments. More specifically, the stochastic and dynamic nature of request arrivals, fulfillment processes, and complex traffic conditions as well as the time-dependent spatial patterns of some parameters complicate the decisions in the problems. This paper proposes a simulation optimization method that enables evaluating the operational performance of deployment plans through a detailed simulation model. For guiding the search process in the simulation optimization method, the genetic algorithm is employed in this study. On the basis of the deployment decisions, a mathematical model on ambulance relocation is also proposed for adapting to the dynamic changing environments along the time. To illustrate the proposed method’s usage in practice, a demo example about its application in Shanghai is given. Some numerical experiments are also performed to validate the effectiveness and the efficiency of the proposed methods.     

Decision rules for ambulance scheduling decision support systems

This paper studies some decision rules for ambulance scheduling. The scheduling decision rules embedded in the decision support systems for emergency ambulance scheduling consider the criteria on the average response time and the percentage of the ambulance requests that are responded within 15 min, which is usually ignored in traditional scheduling policies. The challenge in designing the decision rules lies in the stochastic and dynamic nature of request arrivals, fulfillment processes, and complex traffic conditions as well as the time-dependent spatial patterns of some parameters complicate the decisions in the problem. To illustrate the proposed decision rules’ usage in practice, a simulator is developed for performing some numerical experiments to validate the effectiveness and the efficiency of the proposed decision rules.     

A novel hybrid method for improving ambulance dispatching response time through a simulation study

Response time is the most important factor in evaluating the performance of various Emergency Medical Services (EMS). In this paper, a novel hybrid method has been proposed to improve response time for ambulance dispatching. The proposed approach uses a linear hybrid metric based on network centrality measures, nearest neighbor method and first-in first-out (FIFO) policy. Other important parameters in ambulance dispatching such as the operating environment, rate of incoming emergency calls, available resources, hospitalization probability of the patients as well as distances and locations of units are all part of information used in this proposed approach. In line with the traditional metrics used in previous works, we have adopted a linear combined metric which is adjusted according to environment parameters. Results of extensive simulation experiments show reductions in response time by as much as 42% as compared to previous methods.     

ACC design for safety and fuel efficiency: the acceptance of safety margins when adopting different driving styles

For adaptive cruise control (ACC) systems to be accepted and used safely, the transitions from cruise control mode to necessary driver intervention need to     

Ergonomic design visualization mapping- developing an assistive model for design activities

Ergonomic models and techniques are a fundamental issue in the design of comfortable and safe products and spaces. User studies, related to visualization tools are current issues in the ergonomics and design visualization literature. But researchers have begun to discover that user study is rarely straightforward, especially when drawing visualization data from interdisciplinary sources. The availability of a plethora of visualization techniques can make it difficult to determine the most appropriate technique to convey maximum possible understanding.The RT-MHV (“Real-time”– “Motion history volumes”) 3D computerized assessment model, developed by the authors, demonstrates a local risk evaluation of work-related musculoskeletal disorders (WMSDs), based on real-time and on motion history volumes. With the model, the visual display of the WMSD risk level for each body segment is defined by color-coding at points surrounding an avatar's segment, representing an actual user. The values associated with areas with an increased risk of WMSDs can be identified and iterated quickly, so as to determine the “optimal posture”. Designers can share this knowledge by recording the user's postural interactions, defined through the mapping of geometric comfort data and WMSD risk level categories.The challenge in the development process was to overcome existing “gaps” between ergonomics data and designer requirements. Further research on the RT-MHV model is recommended, principally for developing stand-alone CAD software. An aggregated statistical information database and complete body joints visualizations will be computerized in due course. 2D tabulation and statistical information relating to body joints will be made available on demand.     

The effects of safety handrails and the heights of scaffolds on the subjective and objective evaluation of postural stability and cardiovascular stress in novice and expert construction workers

Work performed on scaffolds carries the risk of falling that disproportionately threatens the safety and health of novice construction workers. Hence, objective measures of the postural stability, cardiovascular stress, and subjective difficulty in maintaining postural balance were evaluated for four expert and four novice construction workers performing a manual task in a standing posture on a scaffold with and without safety handrails at two different elevation heights. Based on a multivariate analysis of variance, the experience, scaffold height, and presence of a handrail were found to significantly affect measures of the postural stability and cardiovascular stress. At a lower level of worker experience, a higher scaffold height, and in the absence of a handrail (which may correspond to higher risk of a fall), postural stability was significantly reduced, while cardiovascular stress and subjective difficulties in maintaining postural balance increased. We emphasize the importance of training and handrails for fall prevention at construction sites.     

Integrating human factors in freight interoperability safety design

According to European Directives, it would be necessary to develop freight interoperability, defined as crossing borders from one country to another without changing either locomotive or driving crew. This project is a challenge for the railway companies that control infrastructures and traffic. The interoperability implementation implies changes in work techniques, regulation and organisation, that may affect the reliability of the systems involved, giving rise to risky situations in terms of production, regularity and safety. The purpose of this paper is to describe a proactive ergonomic approach used for the integration of human factors and safety at the early stages of design for future interoperable situations. Ergonomic analysis has been oriented within a socio-technical frame where a workstation is viewed in its technical and organisational dimensions. Three methods have been used: observations in marshalling yards and driving cabin in other countries, staff interviews and analyses of incidents and hazards. Results formed the basis for developing “a methodological guide for integrating human factors”. In a more general way, some principles for an ecological design of a safe organisational system are provided in the last section of this paper.

Powered domestic lawnmowers: design for safety

The paper describes a detailed accident investigation carried out by the Institute for Consumer Ergonomics for the Consumer Safety Unit at the Department of Trade. As such it serves to illustrate the application of two specific research techniques (i) analysis of product related accident data, and (ii) ergonomics evaluation of current models - and shows how these may be used to help in defining standards and criteria for the design of safer products. The study identified lawnmower features and activities associated with accidents recorded by the Home Accident Surveillance System. Ergonomics appraisal by expert assessment and user trials highlighted hazards associated with currently available powered lawnmowers. Performance criteria for safer design of selected features were developed with the aim of overcoming these hazards. At the end of the study liaison was sought with manufacturers to discuss how the results from the work could be used to effect.     

Proposal of a new quantitative method for postural comfort evaluation

In Human–Machine Interface (HMI) design, several parameters have to be correctly evaluated in order to guarantee a good level of safety and well-being of users (humans) and to avoid health problems like muscular-skeletal disease. ISO Standards give us a good reference on Ergonomics and Comfort: ISO 11228 regulation; it deals with qualitative/quantitative parameters for evaluating Postural Ergonomics, using a “Postural Load Index”, in push/pull, in manual loads' lifting and carrying and in repetitive actions; those parameters can represent the Ergonomics level of examined posture. While bibliographic references suggest different methods to make ergonomic evaluation like RULA, LUBA and REBA, the state of the art about comfort/discomfort evaluation shows the need of an objective method to evaluate “effect in the internal body” and “perceived effects” in several schemes of comfort perception like Moes', Vink & Hallback's and Naddeo & Cappetti's ones; postural comfort is one of the aspect of comfort/discomfort perception and this paper proposes a new quantitative method for evaluating this aspect of comfort, based on anthropometric parameters and upper limbs posture. The target of this paper is to present and test a “general purpose” method of comfort-measurement that can be applied to different industrial cases: in workspace environments, in automotive passenger compartments, in aeronautic cockpit or in industrial assembly lines.Relevance to industryThe method presented in this paper may allow industrial designers to provide an assessment of products' perceived comfort in the early stage of the product development process by making a posture-based quantitative evaluation; it also allows designers to make a comfort driven redesign of existing products' configuration for improving and innovating them.     

Maintainability and safety indicators at design stage for mechanical products

With the industrial products competition, reliability, maintainability and safety are key characteristics for availability improvement. This is mainly true in industries like automotive, aeronautic, or NC machines tools. Therefore, it is crucial to predict these characteristics as soon as possible before the manufacturing starts. This paper presents an approach to provide indicators for maintainability and safety prediction at early stage of design. The assessment procedure uses the product CAD 3D model and an associated semantic matrix gathering information on the product components criticality and reliability. Using this information we calculate indicators for the product maintainability and safety. An academic application is developed to illustrate our approach and point out the interaction between maintainability and safety constraints to determine suitable solution. In conclusion, we state on possible extensions of this approach for evaluating other product lifecycle characteristics and we give guidelines on the implementation aspects.     

Extension of optimum safety factor method to nonlinear reliability-based design optimization

In the reliability-based design optimization (RBDO) model, the mean values of uncertain system variables are usually applied as design variables, and the cost is optimized subject to prescribed probabilistic constraints as defined by a nonlinear mathematical programming problem. Therefore, a RBDO solution that reduces the structural weight in uncritical regions does not only provide an improved design but also a higher level of confidence in the design. In this paper, we present recent developments for the RBDO model relative to two points of view: reliability and optimization. Next, we develop several distributions for the hybrid method and the optimum safety factor methods (linear and nonlinear RBDO). Finally, we demonstrate the efficiency of our safety factor approach extended to nonlinear RBDO with application to a tri-material structure.     

Guaranteeing functional safety: design for provability and computer-aided verification

When autonomous robots begin to share the human living and working spaces, safety becomes paramount. It is legally required that the safety of such systems is ensured, e.g. by certification according to relevant standards such as IEC 61508. However, such safety considerations are usually not addressed in academic robotics. In this paper we report on one such successful endeavor, which is concerned with designing, implementing, and certifying a collision avoidance safety function for autonomous vehicles and static obstacles. The safety function calculates a safety zone for the vehicle, depending on its current motion, which is as large as required but as small as feasible, thus ensuring safety against collision with static obstacles. We outline the algorithm which was specifically designed with safety in mind, and present our verification methodology which is based on formal proof and verification using the theorem prover Isabelle. The implementation and our methodology have been certified for use in applications up to SIL 3 of IEC 61508 by a certification authority (TüV Süd Rail GmbH, Germany). Throughout, issues we recognized as being important for a successful application of formal methods in robotics are highlighted. Moreover, we argue that formal analysis deepens the understanding of the algorithm, and hence is valuable even outside the safety context.     

VHF宽带E类高效率功率放大器设计

使用ADS(Advanced Design System)软件仿真设计了基于28-V MOSFET器件的VHF频段30 MHz～80 MHz E类开关模式高效率功率放大器。输入端使用了宽带匹配,输出端通过开关改变后端的匹配电路和滤波器。电路实测:30 MHz～80 MHz输出功率3.2 W～7.1 W,效率从30 MHz的71.4%到80MHz的52.5%,并且具有优良的调幅线性度,可以将其应用到EER发射机。     

某飞机安全销试验夹具的仿真设计

为获得满足某飞机安全销应急断离试验要求及相关设计规范的试验夹具,采用MSC Nastran分别对3种设计方案进行强度和刚度仿真分析.考虑材料非线性和多体接触的影响,得到结构类型、尺寸和材料不同的夹具的力学响应,通过对危险部位的强度校核筛选得到符合要求的试验夹具.试验结果表明数值仿真结果准确、可靠,可为同类试验夹具的设计提供参考.     

Improving lifting motion planning and re-planning of cranes with consideration for safety and efficiency

Safe and efficient operation of cranes requires not only good planning, but also sufficient and appropriate support in real time. Due to the dynamic nature of construction sites, unexpected changes in site layout may create new obstacles for the crane that can result in collisions and accidents. Previous research on construction equipment motion planning focuses on off-line support, which considers static environment or predictable obstacles. These plans may not fit the reality when the environment has any change. In this case on-site safety and efficiency can be affected. In this research, a motion planning algorithm is proposed to efficiently generate safe and smooth paths for crane motions while taking into account engineering constraints and the path quality. Path smoothness is taken into account to provide a realistic path for cranes and to reduce unnecessary movements. A dynamic motion planning algorithm is proposed to ensure safety during the execution stage by quickly re-planning and avoiding collisions. In addition, an anytime algorithm is proposed to search for better solutions during a given time period by improving path smoothness and by reducing path execution time. The proposed algorithms are compared with other available algorithms to evaluate their performance in terms of planning and re-planning time and the cost of the path. Based on the literature review, this is the first time that dual-tree RRT algorithms have been applied to crane motion planning.     

用于大坝安全监测的长距离WSNs节点设计

针对大坝安全监测的需求,结合无线传感器网络的特点,设计了一种基于JN5139无线射频模块的用于大坝安全监测的无线传感器网络节点。简要介绍了无线传感器网络的典型网络结构,重点描述了无线传感器网络节点的硬件和软件设计,并通过在野外环境下搭建簇—树型网络,对传感器网络进行测试。实验结果表明节点数据采集准确,传输可靠。     

煤矿安全监控系统及组成设备抗干扰设计

针对现有煤矿安全监控系统及组成设备抗干扰能力较差的问题,根据国家煤矿安全监察局对煤矿安全监控系统升级改造提出的"增强系统及组成设备的抗电磁干扰能力"的要求,从设备机械结构设计、硬件电路设计、软件设计等方面阐述如何提高目前安全监控系统及组成设备的抗干扰能力。实际应用结果表明,采用本文所述抗干扰设计的设备可通过3级静电放电抗扰度试验、2级射频电磁场辐射抗扰度试验等试验项目。     

Development and Testing of a New Computerized Link Analysis System

Link analysis (LA) is a popular ergonomic tool for studying and improving the layout of workspaces. It uses a data (event) recording method to input interactions of human behavior with their environment. The traditional “pen and paper'' method of LA is cumbersome, time consuming, and gives limited outputs. To address these limitations, the computerized link analysis (CLA) system was developed and tested in laboratory and real‐world environments. CLA offers an integrated task analysis tool, including traditional LA functions (layout, event recording) with more detail for operator activities, time‐motion functions, and multioperator data recording. As well as the conventional LA results (link diagrams and link tables), there are additional outputs for time‐event lists (start/end time, duration, chronology, additional notes, importance, and operator ID), and processed link diagrams with the link direction and frequency. © 2012 Wiley Periodicals, Inc.