Microbiological pollution and ocular infection in CAD operators: an on-site investigation

A large number of workers are currently employed in tasks involving the use of computer based equipment. Much research has been carried out both on prevalence and incidence of ocular and visual disorders as well as on occupational asthenopia. Less attention has been given to investigating the possibility of a microbiological pollution of Video Display Unit (VDU) workstations and to the consequent possible development of work-related ocular infections. The authors investigated the presence of bacteria and fungi on Computer Assisted Design (CAD) workstations and in the conjunctival sac of the operators.     

Optimal scheduling of compute-intensive tasks on a network ofworkstations

In a network of high performance workstations, many workstations are underutilized by their owners. The problem of using these idle cycles for solving computationally intensive tasks by executing a large task on many workstations has been addressed before and algorithms with O(N²) time and O(N) space for choosing the optimal subset of workstations out of N workstations were presented. We improve these algorithms to reduce the running time to O(N log N), while keeping the space requirement the same. The proposed algorithms are particularly useful for SPMD parallelism where computation is the same for all workstations and the data space is partitioned between the workstations     

Comparing the effects of two school workstations on spine positions and mobility, and opinions on the workstations – A 2-year controlled intervention

A wide variety of conventional design workstations are used in schools and workstations have often been described as inappropriate for children's body dimensions. The present study aimed to investigate the effects of saddle chairs and desks with comfort curve for the body on schoolchildren's spine positions and mobility and opinions of workstations compared to conventional workstations. During the first 12-month study period, the number of participants was 98, 48 in the intervention and 50 in the control group. Since the older control group (9th graders, n = 29) decided against participation after the first 12 months, the number of participants in the entire follow-up of 24 months, was 47 (27 intervention and 20 control participants). During the follow-up, the intervention group used new chairs and desks while the controls used conventional workstations. Spine positions and mobility were measured and both groups completed a questionnaire, concerning opinions of workstations. The results indicated that no difference between groups was found when comparing workstation effects on spine positions and mobility during the whole follow-up. Schoolchildren preferred the ergonomic workstations to the conventional workstations during the first year (p < 0.001), but no difference was seen during the second year.

Relevance to industry

: The present results indicated that new design workstations had no effects on spine positions compared to conventional workstations. However, some intra-group positive effects were observed among intervention group. Therefore, the authors believe further development of both school workstations and school environment should be encouraged to ensure better long-term back health in children.     

The available capacity of a privately owned workstation environment

Powerful workstations interconnected by networks have become widely available as sources of computing cycles. Each workstation is typically owned by a single user in order to provide a high quality of service for the owner. In most cases, an owner does not have computing demands as large as the capacity of the workstation. Therefore, most of the workstations are underutilized. Nevertheless, some users have demands that exceed the capacities of their workstations. In order to effectively share the capacity of workstations, there must be algorithms that allocate available capacity and long periods when owners do not use their stations. To understand the profile of station availability, we analyzed the usage patterns of a cluster of workstations. The workstations were available more than 75% of the time observed. Large capacities were steadily available on an hour to hour, day to day, and month to month basis. These capacities were available not only during the evening hours and on weekends, but during the busiest times of normal working hours. A stochastic model was developed which was based on an analysis of the relative frequency distribution and the correlation of available and non-available interval lengths. A 3-stage hyperexponential cumulative distribution has been fitted to the observed cumulative relative frequency of available periods. The fitted distribution closely matches the observed relative frequency distribution. This stochastic model is important as a workload generator for the performance evaluation of capacity sharing strategies of a cluster of workstations. The model assists in the design of resource management algorithms that take advantage of the characteristics of the usage patterns.     

基于iSCSI的WinTarget技术在无盘教学网中的应用

无盘教学网因成本低、管理和维护方便被广泛用于各大专院校的教学.由于无盘教学网的特殊性,工作站的用户数据保存是一个令许多网络管理员难以解决的问题,本文以实例介绍利用WinTarget技术解决无盘工作站中无本地硬盘进行数据存储的难题,使得用户访问远端的存储设备就如同访问本地的硬盘一样简单方便.     

DJM: a global distributed virtual machine on the Internet

In this paper, we present the design and implementation of a novel model of distributed computing on the Internet and Intranet environment. Our model is called the Distributed Java Machine (DJM). It is a global distributed virtual machine used to realize the concept of ‘network is the computer’. DJM explores coarse-grained parallelism by using the under-utilized workstations on the network, combining the elements of object-oriented technology, distributed computing, World-Wide Web and Java programming. It can run on machines with heterogeneous hardware and software platforms without relinking or recompilation. DJM has two unique features. First, using an original applet helper mechanism, DJM allows machines without any DJM software and of different levels of ‘trust’ to work together. Secondly, DJM has implemented concurrency enhancement mechanisms (one-way message, future and redirected future) to increase the efficiency of method invocation. The prototype of DJM has been implemented and tested under both the Intranet and the Internet environments. Using the workstations from our teaching laboratories, which are already running under normal loading, experimental results show that we can achieve a speedup of about 5–8 times by 14 workstations in a Local Area Network (LAN) environment, and about 4.5 times speedup for eight workstations in a Wide Area Network (WAN) environment. © 1998 John Wiley & Sons, Ltd.     

Prophet: automated scheduling of SPMD programs in workstation networks

Obtaining efficient execution of parallel programs in workstation networks is a difficult problem for the user. Unlike dedicated parallel computer resources, network resources are shared, heterogeneous, vary in availability, and offer communication performance that is still an order of magnitude slower than parallel computer interconnection networks. Prophet, a system that automatically schedules data parallel SPMD programs in workstation networks for the user, has been developed. Prophet uses application and resource information to select the appropriate type and number of workstations, divide the application into component tasks and data across these workstations, and assign tasks to workstations. This system has been integrated into the Mentat parallel processing system developed at the University of Virginia. A suite of scientific Mentat applications has been scheduled using Prophet on a heterogeneous workstation network. The results are promising and demonstrate that scheduling SPMD applications can be automated with good performance. Copyright © 1999 John Wiley & Sons, Ltd.     

D-ISODATA: A Distributed Algorithm for Unsupervised Classification of Remotely Sensed Data on Network of Workstations

With the advent of high-speed networks and the availability of powerful high-performance workstations, network of workstations has emerged as the most cost-effective platform for computation-intensive applications. One of the major applications for the network of workstations is in the field of remote sensing, where because of the high dimensionality of data, most of the existing data exploitation procedures are computation-intensive. To test the utility of the network of workstations in the field of remote sensing we have adopted a modified version of the well-known ISODATA classification procedure which may be considered as the benchmark for all unsupervised classification algorithms. The ISODATA algorithm is an iterative method that uses Euclidean distance as the similarity measure to cluster data elements into different classes. We have designed and developed a distributed version of ISODATA algorithm (D-ISODATA) on the network of workstations under a message-passing interface environment and have obtained promising speedup. To reduce the processing load and thereby increase the throughput, the ISODATA procedure is commonly applied to only the first few principal component images derived from the original set of the multispectral images. The drawback with the principal component approach is that it is based entirely on the statistical significance of the spectra, rather than the uniqueness of the individual spectra. As, small objects and ground features would likely manifest themselves in the last principal component images, that is, eigen images, discarding them prior to classification would lead to the loss of valuable information. The significant enhancement in processing speed on the network of workstations makes it possible for us to apply our distributed algorithm D-ISODATA to the entire set of multispectral images directly, thereby preserving all the spectral signatures in the data, regardless of their statistical significance.     

Design and performance evaluation considerations of a multimediamedical database

Multimedia information management and communications systems for medical applications have been undergoing design and development. The aim of these activities has been the development of distributed computer systems providing storage, processing, and communication services required by the medical community. One of the main critical issues of such systems is the handling of multimedia information (i.e., text, images, graphics, and voice) in a uniform way and the fast access to images through the network. We present the design architecture and concepts used in our multimedia database system, along with its performance evaluation. The evaluation focuses on the response times of a multimedia medical database server, as seen by remote workstations for various retrieval and image transfer requests. For this purpose, a queueing network model was developed and simulated. Communications between the workstations and the database server are governed by the client-server model using TCP/IP and appropriate application protocols on a 10 Mb/s Ethernet LAN     

A hybrid algorithm for allocating tasks,operators, and workstations in multi-manned assembly lines

In a car, there are approximately 30,000 parts produced by many different industries. This is due to the complexity and enormity of the automotive industry chain. The vehicle assembly process comprises welding, painting, prefabrication, and final entire-vehicle assembly. The assembly line has the largest labor force, which should be arranged and balanced to increase production efficiency and reduce labor force requirements. Unlike traditional studies on assembly line balancing problems (ALBPs), this study considers the characteristics of the automotive industry, such as multi-manned workstations, minimization in terms of the numbers of operators and workstations for streamlined production, budget constraints, the optimization of both task and operator allocation among workstations, and the determination of the start/end processing time of each task at different workstations. To address these NP-hard problems, a hybrid heuristic approach that combines the procedure of building feasible balancing solutions and the simulated annealing algorithm is proposed to map out an optimal line balancing plan for multi-manned workstations and to reduce the required workspace for shop operations. Based on the design and analysis of experiments, the effects of the maximum number of allowed operators per workstation and those of the cycle time on ALBP solutions are explored. The optimal combination of algorithm parameters is also determined. The results of this study can serve as a practical reference in planning the allocation of tasks, workstations, and operators in the industry.     

High performance computing on networks of workstations through the exploitation of function parallelism

Network of workstations (NOW) has become a widely accepted form of high-performance parallel computing. As in conventional multicomputers, parallel programs running on such a platform are often written in an SPMD form to exploit data parallelism. Each workstation in a NOW is treated similarly to a processing element in a multicomputer system. However, workstations are far more powerful and flexible than the processing elements in conventional multicomputers. In this paper, we discuss how workstations in a NOW can be used to exploit more parallelism in an SPMD program, especially those induced from concurrent activities.     

Parallel efficiency of the C.R.F. method on an IBM RS/6000 cluster platform

A new numerical method for kinetic equations in several dimensions has been recently presented by Motta and Wick (1991). The method has been then applied to simple models to test its applicability to realistic physical situations. In the present paper we discuss the parallel performance of the method on a distributed memory platform based on a cluster of IBM RS/6000 superscalar workstations.     

一种基于Myrinet LANai9硬件支持的VIA原型实现

VIA定义了一种低延迟、高带宽的数据传输模型，成为集群系统通讯技术的工业标准。本文介绍VIA的产生背景和结构特征，详细阐述了清华大学在Myrinet LANai9硬件上实现 的VIA原型－MyVIA2，最后给出了几种用户层通信软件的测试结果和比较分析。     

Office productivity: contributions of the workstation

To determine if there was an economic justification for purchasing new, task-oriented and ergonomically-suitable workstations for an office in which automation was being introduced, a study was designed which examined the effect of a more comfortable and functional office setting on employee satisfaction and productivity. This study was conducted at a United States Government installation. Through task analysis questionnaires and interviews, workstation and layout requirements were defined for an organization of procurement agents and support staff. These personnel were to receive computers at their workstations-one terminal for every two people. Designs for typical workstations were created as well as a layout for two typical workgroups of 17 employees. The workstations and layout were implemented using two different types of furniture: one work group received Systems Furniture, while the other received additional pieces of their existing Conventional Furniture (Improved-Conventional). Four work groups within the same division served as the Control (received no environmental manipulation). Archival performance data consisting of workhours and the number of line items produced was formulated into a productivity ratio. Productivity of each group, as well as satisfaction ratings, were gathered before and after the application of the improved workstations. The results of the study supported the hypothesis that improvements to the workstations would significantly, and positively, impact both productivity and satisfaction. The Systems Furniture group demonstrated a significant increase in both productivity (206%) and satisfaction after moving into the new workstations, while the Improved-Conventional group showed a non-significant increase (4%) in productivity but a significant increase in workstation satisfaction. The control group did not significantly change on either measure. It can be concluded from this and other studies that satisfying office requirements can improve both productivity and employee satisfaction. This result can be translated into economic terms. The cost of providing the Systems workstations was amortized, due to space savings and increases in productivity, in only 10.8 months.     

Ergonomic studies in computer-aided design

Abstract

This paper describes the results of an ergonomic survey on interactive graphics workstations for computer-aided design (CAD). A work-sampling study was carried out to characterize the use of keyboard, digitizer tablet and video display. Subjective impressions of CAD software, CAD hardware and health aspects were collected by means of a questionnaire. Working methods and working postures were recorded on videotape. The two most important differences in comparison with other office terminals are: (i) dynamic working methods result in an absence of constrained postures in CAD operators and allow full-body exercise; (ii) CAD operators spend more time (46–68 per cent of working hours) viewing the video display than the average office terminal operator. Some ergonomic recommendations have been deduced for the construction of CAD terminals, as well as for the ergonomic improvement of existing workstations.     

Mixed model U-line balancing type-1 problem: A new approach

Avoiding work overload (imbalance) in mixed model U-line production systems entails an investigation into both balancing and sequencing problems at the same time and that is why some authors have considered both planning problems simultaneously. However because of the existing differences between planning horizons of balancing and sequencing problems (the former is a long to mid-term planning problem whereas the latter has a short term planning horizon) this simultaneous approach is only practical under very special conditions. It is also known that installation of an assembly line usually needs considerable capital investments and consequently it is necessary to design and balance such a system so that it works as efficiently as possible. To do so, in this paper, we develop a new approach to balance a mixed model U-shaped production system independent of what product sequences may be. This new approach is based on minimization of crossover workstations. Due to utilization of crossover workstations, balancing mixed model assembly lines in U-shaped line layouts is more complicated than that of straight lines. Some kind of issues including the ‘model mixes’ appearing in such workstations and the time taken for an operator to move from one side of the line to another increase the complexity of mixed model U-line balancing problems (MMULBP). Therefore it seems reasonable to develop a model in which minimizing the number of crossover workstations and maximizing the line efficiency are considered at the same time. Such a model is presented in this paper. In the proposed model, minimizing the variation of workload is also considered and taking into account operator's travel times, an extra time is assigned to workload of crossover workstations. Furthermore a genetic algorithm (GA) is proposed and a number of well-known test problems are solved by the GA and the related results are illustrated. Finally, the conclusion is presented.     

Ergonomic studies in computer-aided design

This paper describes the results of an ergonomic survey on interactive graphics workstations for computer-aided design (CAD). A work-sampling study was carried out to characterize the use of keyboard, digitizer tablet and video display. Subjective impressions of CAD software, CAD hardware and health aspects were collected by means of a questionnaire. Working methods and working postures were recorded on videotape. The two most important differences in comparison with other office terminals are: (i) dynamic working methods result in an absence of constrained postures in CAD operators and allow full-body exercise; (ii) CAD operators spend more time (46-68 per cent of working hours) viewing the video display than the average office terminal operator. Some ergonomic recommendations have been deduced for the construction of CAD terminals, as well as for the ergonomic improvement of existing workstations.     

基于MVC设计模式和Flash组件技术构建物理化学网络虚拟实验室工作站的报告

在深入研究高校物理化学实验室中常用工作站的基础上,采用MVC设计模式和Flash组件技术构建了一系列应用于物理化学网络虚拟实验室的化学工作站软件。使用者可以通过该系列软件完成数据的采集、处理以及数据曲线的绘制。对于化学工作站的操作培训和物理化学实验操作的网络学习具有较大的应用价值。     

Efficient Multiple Multicast on Heterogeneous Network of Workstations

In recent years, network of workstations/PCs (so called NOW) are becoming appealing vehicles for cost-effective parallel computing. Due to the commodity nature of workstations and networking equipment, LAN environments are gradually becoming heterogeneous. The diverse sources of heterogeneity in NOW systems pose a challenge on the design of efficient communication algorithms for this class of systems. In this paper, we propose efficient algorithms for multiple multicast on heterogeneous NOW systems, focusing on heterogeneity in processing speeds of workstations/PCs. Multiple multicast is an important operation in many scientific and industrial applications. Multicast on heterogeneous systems has not been investigated until recently. Our work distinguishes itself from others in two aspects: (1) In contrast to the blocking communication model used in prior works, we model communication in a heterogeneous cluster more accurately by a non-blocking communication model, and design multicast algorithms that can fully take advantage of non-blocking communication. (2) While prior works focus on single multicast problem, we propose efficient algorithms for general, multiple multicast (in which single multicast is a special case) on heterogeneous NOW systems. To our knowledge, our work is the earliest effort that addresses multiple multicast for heterogeneous NOW systems. These algorithms are evaluated using a network simulator for heterogeneous NOW systems. Our experimental results on a system of up to 64 nodes show that some of the algorithms outperform others in many cases. The best algorithm achieves completion time that is within 2.5 times of the lower bound.     

工作站网络系统进程迁移机制

进程迁移是工作站网络系统实现负载平衡、提高系统可用性功能的重要手段.该文提出了一种基于接收/发送方消息记录的进程迁移技术.它在消息传递库PVM(parallel virtual machine)之上实现,具有对用户程序透明、可移植性好、开销小和实现简单等特点.此技术已实际应用于作者自行研制的“并行程序运行回卷恢复与进程迁移系统—ChaRM(checkpointing-based rollback recovery and migration system)”中.