932 resultados para system design


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A view has emerged within manufacturing and service organizations that the operations management function can hold the key to achieving competitive edge. This has recently been emphasized by the demands for greater variety and higher quality which must be set against a background of increasing cost of resources. As nations' trade barriers are progressively lowered and removed, so producers of goods and service products are becoming more exposed to competition that may come from virtually anywhere around the world. To simply survive in this climate many organizations have found it necessary to improve their manufacturing or service delivery systems. To become real ''winners'' some have adopted a strategic approach to operations and completely reviewed and restructured their approach to production system design and operations planning and control. The articles in this issue of the International journal of Operations & Production Management have been selected to illustrate current thinking and practice in relation to this situation. They are all based on papers presented to the Sixth International Conference of the Operations Management Association-UK which was held at Aston University in June 1991. The theme of the conference was "Achieving Competitive Edge" and authors from 15 countries around the world contributed to more than 80 presented papers. Within this special issue five topic areas are addressed with two articles relating to each. The topics are: strategic management of operations; managing change; production system design; production control; and service operations. Under strategic management of operations De Toni, Filippini and Forza propose a conceptual model which considers the performance of an operating system as a source of competitive advantage through the ''operation value chain'' of design, purchasing, production and distribution. Their model is set within the context of the tendency towards globalization. New's article is somewhat in contrast to the more fashionable literature on operations strategy. It challenges the validity of the current idea of ''world-class manufacturing'' and, instead, urges a reconsideration of the view that strategic ''trade-offs'' are necessary to achieve a competitive edge. The importance of managing change has for some time been recognized within the field of organization studies but its relevance in operations management is now being realized. Berger considers the use of "organization design", ''sociotechnical systems'' and change strategies and contrasts these with the more recent idea of the ''dialogue perspective''. A tentative model is suggested to improve the analysis of different strategies in a situation specific context. Neely and Wilson look at an essential prerequisite if change is to be effected in an efficient way, namely product goal congruence. Using a case study as its basis, their article suggests a method of measuring goal congruence as a means of identifying the extent to which key performance criteria relating to quality, time, cost and flexibility are understood within an organization. The two articles on production systems design represent important contributions to the debate on flexible production organization and autonomous group working. Rosander uses the results from cases to test the applicability of ''flow groups'' as the optimal way of organizing batch production. Schuring also examines cases to determine the reasons behind the adoption of ''autonomous work groups'' in The Netherlands and Sweden. Both these contributions help to provide a greater understanding of the production philosophies which have emerged as alternatives to more conventional systems -------for intermittent and continuous production. The production control articles are both concerned with the concepts of ''push'' and ''pull'' which are the two broad approaches to material planning and control. Hirakawa, Hoshino and Katayama have developed a hybrid model, suitable for multistage manufacturing processes, which combines the benefits of both systems. They discuss the theoretical arguments in support of the system and illustrate its performance with numerical studies. Slack and Correa's concern is with the flexibility characteristics of push and pull material planning and control systems. They use the case of two plants using the different systems to compare their performance within a number of predefined flexibility types. The two final contributions on service operations are complementary. The article by Voss really relates to manufacturing but examines the application of service industry concepts within the UK manufacturing sector. His studies in a number of companies support the idea of the ''service factory'' and offer a new perspective for manufacturing. Harvey's contribution by contrast, is concerned with the application of operations management principles in the delivery of professional services. Using the case of social-service provision in Canada, it demonstrates how concepts such as ''just-in-time'' can be used to improve service performance. The ten articles in this special issue of the journal address a wide range of issues and situations. Their common aspect is that, together, they demonstrate the extent to which competitiveness can be improved via the application of operations management concepts and techniques.

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Quality, production and technological innovation management rank among the most important matters of concern to modern manufacturing organisations. They can provide companies with the decisive means of gaining a competitive advantage, especially within industries where there is an increasing similarity in product design and manufacturing processes. The papers in this special issue of International Journal of Technology Management have all been selected as examples of how aspects of quality, production and technological innovation can help to improve competitive performance. Most are based on presentations made at the UK Operations Management Association's Sixth International Conference held at Aston University at which the theme was 'Getting Ahead Through Technology and People'. At the conference itself over 80 papers were presented by authors from 15 countries around the world. Among the many topics addressed within the conference theme, technological innovation, quality and production management emerged as attracting the greatest concern and interest of delegates, particularly those from industry. For any new initiative to be implemented successfully, it should be led from the top of the organization. Achieving the desired level of commitment from top management can, however, be a difficulty. In the first paper of this issue, Mackness investigates this question by explaining how systems thinking can help. In the systems approach, properties such as 'emergence', 'hierarchy', 'commnication' and 'control' are used to assist top managers in preparing for change. Mackness's paper is then complemented by Iijima and Hasegawa's contribution in which they investigate the development of Quality Information Management (QIM) in Japan. They present the idea of a Design Review and demonstrate how it can be used to trace and reduce quality-related losses. The next paper on the subject of quality is by Whittle and colleagues. It relates to total quality and the process of culture change within organisations. Using the findings of investigations carried out in a number of case study companies, they describe four generic models which have been identified as characterising methods of implementing total quality within existing organisation cultures. Boaden and Dale's paper also relates to the management of quality, but looks specifically at the construction industry where it has been found there is still some confusion over the role of Quality Assurance (QA) and Total Quality Management (TQM). They describe the results of a questionnaire survey of forty companies in the industry and compare them to similar work carried out in other industries. Szakonyi's contribution then completes this group of papers which all relate specifically to the question of quality. His concern is with the two ways in which R&D or engineering managers can work on improving quality. The first is by improving it in the laboratory, while the second is by working with other functions to improve quality in the company. The next group of papers in this issue all address aspects of production management. Umeda's paper proposes a new manufacturing-oriented simulation package for production management which provides important information for both design and operation of manufacturing systems. A simulation for production strategy in a Computer Integrated Manufacturing (CIM) environment is also discussed. This paper is then followed by a contribution by Tanaka and colleagues in which they consider loading schedules for manufacturing orders in a Material Requirements Planning (MRP) environment. They compare mathematical programming with a knowledge-based approach, and comment on their relative effectiveness for different practical situations. Engstrom and Medbo's paper then looks at a particular aspect of production system design, namely the question of devising group working arrangements for assembly with new product structures. Using the case of a Swedish vehicle assembly plant where long cycle assembly work has been adopted, they advocate the use of a generally applicable product structure which can be adapted to suit individual local conditions. In the last paper of this particular group, Tay considers how automation has affected the production efficiency in Singapore. Using data from ten major industries he identifies several factors which are positively correlated with efficiency, with capital intensity being of greatest interest to policy makers. The two following papers examine the case of electronic data interchange (EDI) as a means of improving the efficiency and quality of trading relationships. Banerjee and Banerjee consider a particular approach to material provisioning for production systems using orderless inventory replenishment. Using the example of a single supplier and multiple buyers they develop an analytical model which is applicable for the exchange of information between trading partners using EDI. They conclude that EDI-based inventory control can be attractive from economic as well as other standpoints and that the approach is consistent with and can be instrumental in moving towards just-in-time (JIT) inventory management. Slacker's complementary viewpoint on EDI is from the perspective of the quality relation-ship between the customer and supplier. Based on the experience of Lucas, a supplier within the automotive industry, he concludes that both banks and trading companies must take responsibility for the development of payment mechanisms which satisfy the requirements of quality trading. The three final papers of this issue relate to technological innovation and are all country based. Berman and Khalil report on a survey of US technological effectiveness in the global economy. The importance of education is supported in their conclusions, although it remains unclear to what extent the US government can play a wider role in promoting technological innovation and new industries. The role of technology in national development is taken up by Martinsons and Valdemars who examine the case of the former Soviet Union. The failure to successfully infuse technology into Soviet enterprises is seen as a factor in that country's demise, and it is anticipated that the newly liberalised economies will be able to encourage greater technological creativity. This point is then taken up in Perminov's concluding paper which looks in detail at Russia. Here a similar analysis is made of the concluding paper which looks in detail at Russia. Here a similar analysis is made of the Soviet Union's technological decline, but a development strategy is also presented within the context of the change from a centralised to a free market economy. The papers included in this special issue of the International Journal of Technology Management each represent a unique and particular contribution to their own specific area of concern. Together, however, they also argue or demonstrate the general improvements in competitive performance that can be achieved through the application of modern principles and practice to the management of quality, production and technological innovation.

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The optical regeneration is an attractive method to improve the performance of long-distance data transmission, though its application in high-speed fiber systems requires careful design consideration/optimization. In this letter we investigate 40 Gbit/s dispersion-managed fiber transmission with optical 2R regeneration based on quantum well saturable absorber and highly non-linear fiber. We demonstrate through numerical modeling a feasibility of a single channel transmission over 10,000 km using optimized system design. © 2003 Elsevier B.V. All rights reserved.

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The modulation instability (MI) is one of the main factors responsible for the degradation of beam quality in high-power laser systems. The so-called B-integral restriction is commonly used as the criteria for MI control in passive optics devices. For amplifiers the adiabatic model, assuming locally the Bespalov-Talanov expression for MI growth, is commonly used to estimate the destructive impact of the instability. We present here the exact solution of MI development in amplifiers. We determine the parameters which control the effect of MI in amplifiers and calculate the MI growth rate as a function of those parameters. The safety range of operational parameters is presented. The results of the exact calculations are compared with the adiabatic model, and the range of validity of the latest is determined. We demonstrate that for practical situations the adiabatic approximation noticeably overestimates MI. The additional margin of laser system design is quantified. © 2010 Optical Society of America.

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* The work is partly supported by RFFI grant 08-07-00062-a

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The demands towards the contemporary information systems are constantly increasing. In a dynamic business environment an organization has to be prepared for sudden growth, shrinking or other type of reorganization. Such change would bring the need of adaptation of the information system, servicing the company. The association of access rights to parts of the system with users, groups of users, user roles etc. is of great importance to defining the different activities in the company and the restrictions of the access rights for each employee, according to his status. The mechanisms for access rights management in a system are taken in account during the system design. In most cases they are build in the system. This paper offers an approach in user rights framework development that is applicable in information systems. This work presents a reusable extendable mechanism that can be integrated in information systems.

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This chapter discusses network protection of high-voltage direct current (HVDC) transmission systems for large-scale offshore wind farms where the HVDC system utilizes voltage-source converters. The multi-terminal HVDC network topology and protection allocation and configuration are discussed with DC circuit breaker and protection relay configurations studied for different fault conditions. A detailed protection scheme is designed with a solution that does not require relay communication. Advanced understanding of protection system design and operation is necessary for reliable and safe operation of the meshed HVDC system under fault conditions. Meshed-HVDC systems are important as they will be used to interconnect large-scale offshore wind generation projects. Offshore wind generation is growing rapidly and offers a means of securing energy supply and addressing emissions targets whilst minimising community impacts. There are ambitious plans concerning such projects in Europe and in the Asia-Pacific region which will all require a reliable yet economic system to generate, collect, and transmit electrical power from renewable resources. Collective offshore wind farms are efficient and have potential as a significant low-carbon energy source. However, this requires a reliable collection and transmission system. Offshore wind power generation is a relatively new area and lacks systematic analysis of faults and associated operational experience to enhance further development. Appropriate fault protection schemes are required and this chapter highlights the process of developing and assessing such schemes. The chapter illustrates the basic meshed topology, identifies the need for distance evaluation, and appropriate cable models, then details the design and operation of the protection scheme with simulation results used to illustrate operation. © Springer Science+Business Media Singapore 2014.

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ACM Computing Classification System (1998): D.2.11, D.1.3, D.3.1, J.3, C.2.4.

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Purpose – The purpose of this paper is to examine challenges and potential of big data in heterogeneous business networks and relate these to an implemented logistics solution. Design/methodology/approach – The paper establishes an overview of challenges and opportunities of current significance in the area of big data, specifically in the context of transparency and processes in heterogeneous enterprise networks. Within this context, the paper presents how existing components and purpose-driven research were combined for a solution implemented in a nationwide network for less-than-truckload consignments. Findings – Aside from providing an extended overview of today’s big data situation, the findings have shown that technical means and methods available today can comprise a feasible process transparency solution in a large heterogeneous network where legacy practices, reporting lags and incomplete data exist, yet processes are sensitive to inadequate policy changes. Practical implications – The means introduced in the paper were found to be of utility value in improving process efficiency, transparency and planning in logistics networks. The particular system design choices in the presented solution allow an incremental introduction or evolution of resource handling practices, incorporating existing fragmentary, unstructured or tacit knowledge of experienced personnel into the theoretically founded overall concept. Originality/value – The paper extends previous high-level view on the potential of big data, and presents new applied research and development results in a logistics application.

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Moving objects database systems are the most challenging sub-category among Spatio-Temporal database systems. A database system that updates in real-time the location information of GPS-equipped moving vehicles has to meet even stricter requirements. Currently existing data storage models and indexing mechanisms work well only when the number of moving objects in the system is relatively small. This dissertation research aimed at the real-time tracking and history retrieval of massive numbers of vehicles moving on road networks. A total solution has been provided for the real-time update of the vehicles' location and motion information, range queries on current and history data, and prediction of vehicles' movement in the near future. ^ To achieve these goals, a new approach called Segmented Time Associated to Partitioned Space (STAPS) was first proposed in this dissertation for building and manipulating the indexing structures for moving objects databases. ^ Applying the STAPS approach, an indexing structure of associating a time interval tree to each road segment was developed for real-time database systems of vehicles moving on road networks. The indexing structure uses affordable storage to support real-time data updates and efficient query processing. The data update and query processing performance it provides is consistent without restrictions such as a time window or assuming linear moving trajectories. ^ An application system design based on distributed system architecture with centralized organization was developed to maximally support the proposed data and indexing structures. The suggested system architecture is highly scalable and flexible. Finally, based on a real-world application model of vehicles moving in region-wide, main issues on the implementation of such a system were addressed. ^

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This research aimed at developing a research framework for the emerging field of enterprise systems engineering (ESE). The framework consists of an ESE definition, an ESE classification scheme, and an ESE process. This study views an enterprise as a system that creates value for its customers. Thus, developing the framework made use of system theory and IDEF methodologies. This study defined ESE as an engineering discipline that develops and applies systems theory and engineering techniques to specification, analysis, design, and implementation of an enterprise for its life cycle. The proposed ESE classification scheme breaks down an enterprise system into four elements. They are work, resources, decision, and information. Each enterprise element is specified with four system facets: strategy, competency, capacity, and structure. Each element-facet combination is subject to the engineering process of specification, analysis, design, and implementation, to achieve its pre-specified performance with respect to cost, time, quality, and benefit to the enterprise. This framework is intended for identifying research voids in the ESE discipline. It also helps to apply engineering and systems tools to this emerging field. It harnesses the relationships among various enterprise aspects and bridges the gap between engineering and management practices in an enterprise. The proposed ESE process is generic. It consists of a hierarchy of engineering activities presented in an IDEF0 model. Each activity is defined with its input, output, constraints, and mechanisms. The output of an ESE effort can be a partial or whole enterprise system design for its physical, managerial, and/or informational layers. The proposed ESE process is applicable to a new enterprise system design or an engineering change in an existing system. The long-term goal of this study aims at development of a scientific foundation for ESE research and development.

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The aim of this research was to demonstrate a high current and stable field emission (FE) source based on carbon nanotubes (CNTs) and electron multiplier microchannel plate (MCP) and design efficient field emitters. In recent years various CNT based FE devices have been demonstrated including field emission displays, x-ray source and many more. However to use CNTs as source in high powered microwave (HPM) devices higher and stable current in the range of few milli-amperes to amperes is required. To achieve such high current we developed a novel technique of introducing a MCP between CNT cathode and anode. MCP is an array of electron multipliers; it operates by avalanche multiplication of secondary electrons, which are generated when electrons strike channel walls of MCP. FE current from CNTs is enhanced due to avalanche multiplication of secondary electrons and in addition MCP also protects CNTs from irreversible damage during vacuum arcing. Conventional MCP is not suitable for this purpose due to the lower secondary emission properties of their materials. To achieve higher and stable currents we have designed and fabricated a unique ceramic MCP consisting of high SEY materials. The MCP was fabricated utilizing optimum design parameters, which include channel dimensions and material properties obtained from charged particle optics (CPO) simulation. Child Langmuir law, which gives the optimum current density from an electron source, was taken into account during the system design and experiments. Each MCP channel consisted of MgO coated CNTs which was chosen from various material systems due to its very high SEY. With MCP inserted between CNT cathode and anode stable and higher emission current was achieved. It was ∼25 times higher than without MCP. A brighter emission image was also evidenced due to enhanced emission current. The obtained results are a significant technological advance and this research holds promise for electron source in new generation lightweight, efficient and compact microwave devices for telecommunications in satellites or space applications. As part of this work novel emitters consisting of multistage geometry with improved FE properties were was also developed.

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This dissertation develops an innovative approach towards less-constrained iris biometrics. Two major contributions are made in this research endeavor: (1) Designed an award-winning segmentation algorithm in the less-constrained environment where image acquisition is made of subjects on the move and taken under visible lighting conditions, and (2) Developed a pioneering iris biometrics method coupling segmentation and recognition of the iris based on video of moving persons under different acquisitions scenarios. The first part of the dissertation introduces a robust and fast segmentation approach using still images contained in the UBIRIS (version 2) noisy iris database. The results show accuracy estimated at 98% when using 500 randomly selected images from the UBIRIS.v2 partial database, and estimated at 97% in a Noisy Iris Challenge Evaluation (NICE.I) in an international competition that involved 97 participants worldwide involving 35 countries, ranking this research group in sixth position. This accuracy is achieved with a processing speed nearing real time. The second part of this dissertation presents an innovative segmentation and recognition approach using video-based iris images. Following the segmentation stage which delineates the iris region through a novel segmentation strategy, some pioneering experiments on the recognition stage of the less-constrained video iris biometrics have been accomplished. In the video-based and less-constrained iris recognition, the test or subject iris videos/images and the enrolled iris images are acquired with different acquisition systems. In the matching step, the verification/identification result was accomplished by comparing the similarity distance of encoded signature from test images with each of the signature dataset from the enrolled iris images. With the improvements gained, the results proved to be highly accurate under the unconstrained environment which is more challenging. This has led to a false acceptance rate (FAR) of 0% and a false rejection rate (FRR) of 17.64% for 85 tested users with 305 test images from the video, which shows great promise and high practical implications for iris biometrics research and system design.

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Fueled by increasing human appetite for high computing performance, semiconductor technology has now marched into the deep sub-micron era. As transistor size keeps shrinking, more and more transistors are integrated into a single chip. This has increased tremendously the power consumption and heat generation of IC chips. The rapidly growing heat dissipation greatly increases the packaging/cooling costs, and adversely affects the performance and reliability of a computing system. In addition, it also reduces the processor's life span and may even crash the entire computing system. Therefore, dynamic thermal management (DTM) is becoming a critical problem in modern computer system design. Extensive theoretical research has been conducted to study the DTM problem. However, most of them are based on theoretically idealized assumptions or simplified models. While these models and assumptions help to greatly simplify a complex problem and make it theoretically manageable, practical computer systems and applications must deal with many practical factors and details beyond these models or assumptions. The goal of our research was to develop a test platform that can be used to validate theoretical results on DTM under well-controlled conditions, to identify the limitations of existing theoretical results, and also to develop new and practical DTM techniques. This dissertation details the background and our research efforts in this endeavor. Specifically, in our research, we first developed a customized test platform based on an Intel desktop. We then tested a number of related theoretical works and examined their limitations under the practical hardware environment. With these limitations in mind, we developed a new reactive thermal management algorithm for single-core computing systems to optimize the throughput under a peak temperature constraint. We further extended our research to a multicore platform and developed an effective proactive DTM technique for throughput maximization on multicore processor based on task migration and dynamic voltage frequency scaling technique. The significance of our research lies in the fact that our research complements the current extensive theoretical research in dealing with increasingly critical thermal problems and enabling the continuous evolution of high performance computing systems.

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The move from Standard Definition (SD) to High Definition (HD) represents a six times increases in data, which needs to be processed. With expanding resolutions and evolving compression, there is a need for high performance with flexible architectures to allow for quick upgrade ability. The technology advances in image display resolutions, advanced compression techniques, and video intelligence. Software implementation of these systems can attain accuracy with tradeoffs among processing performance (to achieve specified frame rates, working on large image data sets), power and cost constraints. There is a need for new architectures to be in pace with the fast innovations in video and imaging. It contains dedicated hardware implementation of the pixel and frame rate processes on Field Programmable Gate Array (FPGA) to achieve the real-time performance. ^ The following outlines the contributions of the dissertation. (1) We develop a target detection system by applying a novel running average mean threshold (RAMT) approach to globalize the threshold required for background subtraction. This approach adapts the threshold automatically to different environments (indoor and outdoor) and different targets (humans and vehicles). For low power consumption and better performance, we design the complete system on FPGA. (2) We introduce a safe distance factor and develop an algorithm for occlusion occurrence detection during target tracking. A novel mean-threshold is calculated by motion-position analysis. (3) A new strategy for gesture recognition is developed using Combinational Neural Networks (CNN) based on a tree structure. Analysis of the method is done on American Sign Language (ASL) gestures. We introduce novel point of interests approach to reduce the feature vector size and gradient threshold approach for accurate classification. (4) We design a gesture recognition system using a hardware/ software co-simulation neural network for high speed and low memory storage requirements provided by the FPGA. We develop an innovative maximum distant algorithm which uses only 0.39% of the image as the feature vector to train and test the system design. Database set gestures involved in different applications may vary. Therefore, it is highly essential to keep the feature vector as low as possible while maintaining the same accuracy and performance^