成都理工大学学生毕业设计(论文)外文译文

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毕业设计中英文翻译【范本模板】

英文The road (highway)The road is one kind of linear construction used for travel。

It is made of the roadbed，the road surface, the bridge, the culvert and the tunnel. In addition, it also has the crossing of lines, the protective project and the traffic engineering and the route facility。

The roadbed is the base of road surface, road shoulder，side slope, side ditch foundations. It is stone material structure, which is designed according to route's plane position .The roadbed, as the base of travel, must guarantee that it has the enough intensity and the stability that can prevent the water and other natural disaster from corroding.The road surface is the surface of road. It is single or complex structure built with mixture。

The road surface require being smooth，having enough intensity，good stability and anti—slippery function. The quality of road surface directly affects the safe, comfort and the traffic。

毕业设计(论文)外文参考文献译文本

武汉工业学院毕业设计（论文）外文参考文献译文本2011届原文出处IBM SYSTEMS JOURNAL, VOL 35, NOS 3&4, 1996毕业设计(论文)题目音乐图像浏览器的设计与实现院（系）计算机与信息工程专业名称计算机科学与技术学生姓名郭谦学生学号070501103指导教师丰洪才译文要求：1、译文内容须与课题（或专业）有联系；2、外文翻译不少于4000汉字。

隐藏数据技术研究数据隐藏，是一种隐秘的数据加密形式，它将数据嵌入到数字媒体之中来达到鉴定，注释和版权保护的目的。

然而，这一应用却受到了一些限制：首先是需要隐藏的数据量，其次是在“主”讯号受到失真的条件影响之下，对于这些需隐藏数据的可靠性的需要。

举例来说，就是有损压缩以及对有损压缩来说数据遇到被拦截，被修改或被第三方移除等操作的免疫程度。

我们同时用传统的和新式技术来探究解决数据隐藏问题的方法并且对这些技术在以下三个方面的应用：版权保护，防止篡改，和增强型数据嵌入做出评估。

我们能非常方便地得到数字媒体并且潜在地改善了其可移植性，信息展现的效率，和信息呈现的准确度。

便捷的数据访问所带来的负面效果包括以下两点：侵犯版权的几率增加或者是有篡改或修改其中内容的可能性增大。

这项工作的目的在于研究知识产权保护条款、内容修改的相关指示和增加注解的方法。

数据隐藏代表了一类用于插入数据的操作，例如版权信息，它利用“主”信号能够感知的最小变化量来进入到各种不同形式的媒体之内，比如图像、声音或本文。

也就是说，嵌入的数据对人类观察者来说应该是既看不见也听不见的。

值得注意的是，数据隐藏虽然与压缩很类似，但与加密解密技术却是截然不同的。

它的目标不是限制或者管理对“主”信号的存取，而是保证被嵌入的数据依然未被破坏而且是可以恢复的。

数据隐藏在数字媒体中的两个重要应用就是提供版权信息的证明，和保证内容完整性。

因此，即使主讯号遭受诸如过滤、重取样，截取或是有损压缩等破坏行为，数据也应该一直在“主”信号中保持被隐藏的特点。

毕设外文文献+翻译1

毕设外文文献+翻译1外文翻译外文原文CHANGING ROLES OF THE CLIENTS、ARCHITECTSAND CONTRACTORS THROUGH BIMAbstract:Purpose –This paper aims to present a general review of the practical implications of building information modelling (BIM) based on literature and case studies. It seeks to address the necessity for applying BIM and re-organising the processes and roles in hospital building projects. This type of project is complex due to complicated functional and technical requirements, decision making involving a large number of stakeholders, and long-term development processes.Design/methodology/approach–Through desk research and referring to the ongoing European research project InPro, the framework for integrated collaboration and the use of BIM are analysed.Findings –One of the main findings is the identification of the main factors for a successful collaboration using BIM, which can be recognised as “POWER”: product information sharing (P),organisational roles synergy (O), work processes coordination (W), environment for teamwork (E), and reference data consolidation (R).Originality/value –This paper contributes to the actual discussion in science and practice on the changing roles and processes that are required to develop and operate sustainable buildings with the support of integrated ICT frameworks and tools. It presents the state-of-the-art of European research projects and some of the first real cases of BIM application inhospital building projects.Keywords:Europe, Hospitals, The Netherlands, Construction works, Response flexibility, Project planningPaper type :General review1. IntroductionHospital building projects, are of key importance, and involve significant investment, and usually take a long-term development period. Hospital building projects are also very complex due to the complicated requirements regarding hygiene, safety, special equipments, and handling of a large amount of data. The building process is very dynamic and comprises iterative phases and intermediate changes. Many actors with shifting agendas, roles and responsibilities are actively involved, such as: the healthcare institutions, national and local governments, project developers, financial institutions, architects, contractors, advisors, facility managers, and equipment manufacturers and suppliers. Such building projects are very much influenced, by the healthcare policy, which changes rapidly in response to the medical, societal and technological developments, and varies greatly between countries (World Health Organization, 2000). In The Netherlands, for example, the way a building project in the healthcare sector is organised is undergoing a major reform due to a fundamental change in the Dutch health policy that was introduced in 2008.The rapidly changing context posts a need for a building with flexibility over its lifecycle. In order to incorporate life-cycle considerations in the building design, construction technique, and facility management strategy, a multidisciplinary collaboration is required. Despite the attempt for establishing integrated collaboration, healthcare building projects still facesserious problems in practice, such as: budget overrun, delay, and sub-optimal quality in terms of flexibility, end-user?s dissatisfaction, and energy inefficiency. It is evident that the lack of communication and coordination between the actors involved in the different phases of a building project is among the most important reasons behind these problems. The communication between different stakeholders becomes critical, as each stakeholder possesses different setof skills. As a result, the processes for extraction, interpretation, and communication of complex design information from drawings and documents are often time-consuming and difficult. Advanced visualisation technologies, like 4D planning have tremendous potential to increase the communication efficiency and interpretation ability of the project team members. However, their use as an effective communication tool is still limited and not fully explored. There are also other barriers in the information transfer and integration, for instance: many existing ICT systems do not support the openness of the data and structure that is prerequisite for an effective collaboration between different building actors or disciplines.Building information modelling (BIM) offers an integrated solution to the previously mentioned problems. Therefore, BIM is increasingly used as an ICT support in complex building projects. An effective multidisciplinary collaboration supported by an optimal use of BIM require changing roles of the clients, architects, and contractors; new contractual relationships; and re-organised collaborative processes. Unfortunately, there are still gaps in the practical knowledge on how to manage the building actors to collaborate effectively in their changing roles, and todevelop and utilise BIM as an optimal ICT support of the collaboration.This paper presents a general review of the practical implications of building information modelling (BIM) based on literature review and case studies. In the next sections, based on literature and recent findings from European research project InPro, the framework for integrated collaboration and the use of BIM are analysed. Subsequently, through the observation of two ongoing pilot projects in The Netherlands, the changing roles of clients, architects, and contractors through BIM application are investigated. In conclusion, the critical success factors as well as the main barriers of a successful integrated collaboration using BIM are identified.2. Changing roles through integrated collaboration and life-cycle design approachesA hospital building project involves various actors, roles, and knowledge domains. In The Netherlands, the changing roles of clients, architects, and contractors in hospital building projects are inevitable due the new healthcare policy. Previously under the Healthcare Institutions Act (WTZi), healthcare institutions were required to obtain both a license and a building permit for new construction projects and major renovations. The permit was issued by the Dutch Ministry of Health. The healthcare institutions were then eligible to receive financial support from the government. Since 2008, new legislation on the management of hospital building projects and real estate has come into force. In this new legislation, a permit for hospital building project under the WTZi is no longer obligatory, nor obtainable (Dutch Ministry of Health, Welfare and Sport, 2008). This change allows more freedom from the state-directed policy, and respectively,allocates more responsibilities to the healthcare organisations to deal with the financing and management of their real estate. The new policy implies that the healthcare institutions are fully responsible to man age and finance their building projects and real estate. The government?s support for the costs of healthcare facilities will no longer be given separately, but will be included in the fee for healthcare services. This means that healthcare institutions must earn back their investment on real estate through their services. This new policy intends to stimulate sustainable innovations in the design, procurement and management of healthcare buildings, which will contribute to effective and efficient primary healthcare services.The new strategy for building projects and real estate management endorses an integrated collaboration approach. In order to assure the sustainability during construction, use, and maintenance, the end-users, facility managers, contractors and specialist contractors need to be involved in the planning and design processes. The implications of the new strategy are reflected in the changing roles of the building actors and in the new procurement method.In the traditional procurement method, the design, and its details, are developed by the architect, and design engineers. Then, the client (the healthcare institution) sends an application to the Ministry of Healthto obtain an approval on the building permit and the financial support from the government. Following this, a contractor is selected through a tender process that emphasises the search for the lowest-price bidder. During the construction period, changes often take place due to constructability problems of the design and new requirements from the client.Because of the high level of technical complexity, and moreover, decision-making complexities, the whole process from initiation until delivery of a hospital building project can take up to ten years time. After the delivery, the healthcare institution is fully in charge of the operation of the facilities. Redesigns and changes also take place in the use phase to cope with new functions and developments in the medical world.The integrated procurement pictures a new contractual relationship between the parties involved in a building project. Instead of a relationship between the client and architect for design, and the client and contractor for construction, in an integrated procurement the client only holds a contractual relationship with the main party that is responsible for both design and construction. The traditional borders between tasks and occupational groups become blurred since architects, consulting firms, contractors, subcontractors, and suppliers all stand on the supply side in the building process while the client on the demand side. Such configuration puts the architect, engineer and contractor in a very different position that influences not only their roles, but also their responsibilities, tasks and communication with the client, the users, the team and other stakeholders.The transition from traditional to integrated procurement method requires a shift of mindset of the parties on both the demand and supply sides. It is essential for the client and contractor to have a fair and open collaboration in which both can optimally use their competencies. The effectiveness of integrated collaboration is also determined by the client?s capacity and strategy to organize innovative tendering procedures.A new challenge emerges in case of positioning an architect in a partnership with the contractor instead of with the client. In case of the architect enters a partnership with the contractor, an important issues is how to ensure the realisation of the architectural values as well as innovative engineering through an efficient construction process. In another case, the architect can stand at the client?s side in a strategic advisory role instead of being the designer. In this case, the architect?s responsibility is translating client?s requirements and wishes into the architectural values to be included in the design specification, and evaluating the contractor?s proposal against this. In any of this new role, the architect holds the responsibilities as stakeholder interest facilitator, custodian of customer value and custodian of design models.The transition from traditional to integrated procurement method also brings consequences in the payment schemes. In the traditional building process, the honorarium for the architect is usually based on a percentage of the project costs; this may simply mean that the more expensive the building is, the higher the honorarium will be. The engineer receives the honorarium based on the complexity of the design and the intensity of the assignment. A highly complex building, which takes a number of redesigns, is usually favourable for the engineers in terms of honorarium. A traditional contractor usually receives the commission based on the tender to construct the building at the lowest price by meeting the minimum specifications given by the client. Extra work due to modifications is charged separately to the client. After the delivery, the contractor is no longer responsible for the long-term use of the building. In the traditional procurement method, all risks are placed with theclient.In integrated procurement method, the payment is based on the achieved building performance; thus, the payment is non-adversarial. Since the architect, engineer and contractor have a wider responsibility on the quality of the design and the building, the payment is linked to a measurement system of the functional and technical performance of the building over a certain period of time. The honorarium becomes an incentive to achieve the optimal quality. If the building actors succeed to deliver a higher added-value thatexceed the minimum client?s requirements, they will receive a bonus in accordance to the client?s extra gain. The level of transparency is also improved. Open book accounting is an excellent instrument provided that the stakeholders agree on the information to be shared and to its level of detail (InPro, 2009).Next to the adoption of integrated procurement method, the new real estate strategy for hospital building projects addresses an innovative product development and life-cycle design approaches. A sustainable business case for the investment and exploitation of hospital buildings relies on dynamic life-cycle management that includes considerations and analysis of the market development over time next to the building life-cycle costs (investment/initial cost, operational cost, and logistic cost). Compared to the conventional life-cycle costing method, the dynamic life-cycle management encompasses a shift from focusing only on minimizing the costs to focusing on maximizing the total benefit that can be gained. One of the determining factors for a successful implementation of dynamic life-cycle management is the sustainable design of the building and building components, which means that the design carriessufficient flexibility to accommodate possible changes in the long term (Prins, 1992).Designing based on the principles of life-cycle management affects the role of the architect, as he needs to be well informed about the usage scenarios and related financial arrangements, the changing social and physical environments, and new technologies. Design needs to integrate people activities and business strategies over time. In this context, the architect is required to align the design strategies with the organisational, local and global policies on finance, business operations, health and safety, environment, etc.The combination of process and product innovation, and the changing roles of the building actors can be accommodated by integrated project delivery or IPD (AIA California Council, 2007). IPD is an approach that integrates people, systems, business structures and practices into a process that collaboratively harnesses the talents and insights of all participants to reduce waste and optimize efficiency through all phases of design, fabrication and construction. IPD principles can be applied to a variety of contractual arrangements. IPD teams will usually include members well beyond the basic triad of client, architect, and contractor. At a minimum, though, an Integrated Project should include a tight collaboration between the client, the architect, and the main contractor ultimately responsible for construction of the project, from the early design until the project handover. The key to a successful IPD is assembling a team that is committed to collaborative processes and is capable of working together effectively. IPD is built on collaboration. As a result, it can only be successful if the participants share and apply common values and goals.3. Changing roles through BIM applicationBuilding information model (BIM) comprises ICT frameworks and tools that can support the integrated collaboration based on life-cycle design approach. BIM is a digital representation of physical and functional characteristics of a facility. As such it serves as a shared knowledge resource for information about a facility forming a reliable basis for decisions during its lifecycle from inception onward (National Institute of Building Sciences NIBS, 2007). BIM facilitates time and place independent collaborative working. A basic premise of BIM is collaboration by different stakeholders at different phases of the life cycle of a facility to insert, extract, update or modify information in the BIM to support and reflect the roles of that stakeholder. BIM in its ultimate form, as a shared digital representation founded on open standards for interoperability, can become a virtual information model to be handed from the design team to the contractor and subcontractors and then to the client.BIM is not the same as the earlier known computer aided design (CAD). BIM goes further than an application to generate digital (2D or 3D) drawings. BIM is an integrated model in which all process and product information is combined, stored, elaborated, and interactively distributed to all relevant building actors. As a central model for all involved actors throughout the project lifecycle, BIM develops andevolves as the project progresses. Using BIM, the proposed design and engineering solutions can be measured against the client?s requirements and expected building performance. The functionalities of BIM to support the design process extend to multidimensional (nD), including: three-dimensional visualisation and detailing, clash detection, material schedule, planning, costestimate, production and logistic information, and as-built documents. During the construction process, BIM can support the communication between the building site, the factory and the design office– which is crucial for an effective and efficient prefabrication and assembly processes as well as to prevent or solve problems related to unforeseen errors or modifications. When the building is in use, BIM can be used in combination with the intelligent building systems to provide and maintain up-to-date information of the building performance, including the life-cycle cost.To unleash the full potential of more efficient information exchange in the AEC/FM industry in collaborative working using BIM, both high quality open international standards and high quality implementations of these standards must be in place. The IFC open standard is generally agreed to be of high quality and is widely implemented in software. Unfortunately, the certification process allows poor quality implementations to be certified and essentially renders the certified software useless for any practical usage with IFC. IFC compliant BIM is actually used less than manual drafting for architects and contractors, and show about the same usage for engineers. A recent survey shows that CAD (as a closed-system) is still the major form of technique used in design work (over 60 per cent) while BIM is used in around 20 percent of projects for architects and in around 10 per cent of projects for engineers and contractors.The application of BIM to support an optimal cross-disciplinary and cross-phase collaboration opens a new dimension in the roles and relationships between the building actors. Several most relevant issues are: the new role of a model manager; the agreement on the access right and IntellectualProperty Right (IPR); the liability and payment arrangement according to the type of contract and in relation to the integrated procurement; and the use of open international standards.Collaborative working using BIM demands a new expert role of a model manager who possesses ICT as well as construction process know-how (InPro, 2009). The model manager deals with the system as well as with the actors. He provides and maintains technological solutions required for BIM functionalities, manages the information flow, and improves the ICT skills of the stakeholders. The model manager does not take decisions on design and engineering solutions, nor the organisational processes, but his roles in the chain of decision making are focused on:the development of BIM, the definition of the structure and detail level of the model, and the deployment of relevant BIM tools, such as for models checking, merging, and clash detections;the contribution to collaboration methods, especially decision making and communication protocols, task planning, and risk management;and the management of information, in terms of data flow and storage, identification of communication errors, and decision or process (re-)tracking.Regarding the legal and organisational issues, one of the actual questions is: “In what way does the intellectual property right (IPR) in collaborative working using BIM differ from the IPR in a traditional teamwork?”. In terms of combine d work, the IPR of each element is at tached to its creator. Although it seems to be a fully integrated design, BIM actually resulted from a combination of works/elements; for instance: the outline of the building design, is created by the architect, the design for theelectrical system, is created by the electrical contractor, etc. Thus, in case of BIM as a combined work, the IPR is similar to traditional teamwork. Working with BIM with authorship registration functionalities may actually make it easier to keep track of the IPR.How does collaborative working, using BIM, effect the contractual relationship? On the one hand,collaborative working using BIM does not necessarily change the liability position in the contract nor does it obligate an alliance contract. The General Principles of BIM A ddendum confirms: …This does not effectuate or require a restructuring of contractual relationships or shifting of risks between or among the Project Participants other than as specifically required per the Protocol Addendum and its Attachments? (ConsensusDOCS, 2008). On the other hand, changes in terms of payment schemes can be anticipated. Collaborative processes using BIM will lead to the shifting of activities from to the early design phase. Much, if not all, activities in the detailed engineering and specification phase will be done in the earlier phases. It means that significant payment for the engineering phase, which may count up to 40 per cent of the design cost, can no longer be expected. As engineering work is done concurrently with the design, a new proportion of the payment in the early design phase is necessary.4. Review of ongoing hospital building projects using BIMIn The Netherlands, the changing roles in hospital building projects are part of the strategy, which aims at achieving a sustainable real estate in response to the changing healthcare policy. Referring to literature and previous research, the main factors that influence the success of the changing roles can be concluded as: the implementation of an integrated procurementmethod and a life-cycle design approach for a sustainable collaborative process; the agreement on the BIM structure and the intellectual rights; and the integration of the role of a model manager. The preceding sections have discussed the conceptual thinking on how to deal with these factors effectively. This current section observes two actual projects and compares the actual practice with the conceptual view respectively.The main issues, which are observed in the case studies, are: the selected procurement method and the roles of the involved parties within this method;the implementation of the life-cycle design approach;the type, structure, and functionalities of BIM used in the project;the openness in data sharing and transfer of the model, and the intended use of BIM in the future; and the roles and tasks of the model manager.The pilot experience of hospital building projects using BIM in the Netherlands can be observed at University Medical Centre St Radboud (further referred as UMC) and Maxima Medical Centre (further referred as MMC). At UMC, the new building project for the Faculty of Dentistry in the city of Nijmegen has been dedicated as a BIM pilot project. At MMC, BIM is used in designing new buildings for Medical Simulation and Mother-and-Child Centre in the city of Veldhoven.The first case is a project at the University Medical Centre (UMC) St Radboud. UMC is more than just a hospital. UMC combines medical services, education and research. More than 8500 staff and 3000 students work at UMC. As a part of the innovative real estate strategy, UMC has considered to use BIM for its building projects. The new development of the Faculty ofDentistry and the surrounding buildings on the Kapittelweg in Nijmegen has been chosen as a pilot project to gather practical knowledge and experience on collaborative processes with BIM support.The main ambition to be achieved through the use of BIM in the building projects at UMC can be summarised as follows: using 3D visualisation to enhance the coordination and communication among the building actors, and the user participation in design;integrating the architectural design with structural analysis, energy analysis, cost estimation, and planning;interactively evaluating the design solutions against the programme of requirements and specifications;reducing redesign/remake costs through clash detection during the design process; andoptimising the management of the facility through the registration of medical installations andequipments, fixed and flexible furniture, product and output specifications, and operational data.The second case is a project at the Maxima Medical Centre (MMC). MMC is a large hospital resulted from a merger between the Diaconessenhuis in Eindhoven and St Joseph Hospital in Veldhoven. Annually the 3,400 staff of MMC provides medical services to more than 450,000 visitors and patients. A large-scaled extension project of the hospital in Veldhoven is a part of its real estate strategy. A medical simulation centre and a women-and-children medical centre are among the most important new facilities within this extension project. The design has been developed using 3D modelling with several functionalities of BIM.The findings from both cases and the analysis are as follows.Both UMC and MMC opted for a traditional procurement method in which the client directly contracted an architect, a structural engineer, and a mechanical, electrical and plumbing (MEP) consultant in the design team. Once the design and detailed specifications are finished, a tender procedure will follow to select a contractor. Despite the choice for this traditional method, many attempts have been made for a closer and more effective multidisciplinary collaboration. UMC dedicated a relatively long preparation phase with the architect, structural engineer and MEP consultant before the design commenced. This preparation phase was aimed at creating a common vision on the optimal way for collaboration using BIM as an ICT support. Some results of this preparation phase are: a document that defines the common ambition for the project and the collaborative working process and a semi-formal agreement that states the commitment of the building actors for collaboration. Other than UMC, MMC selected an architecture firm with an in-house engineering department. Thus, the collaboration between the architect and structural engineer can take place within the same firm using the same software application.Regarding the life-cycle design approach, the main attention is given on life-cycle costs, maintenance needs, and facility management. Using BIM, both hospitals intend to get a much better insight in these aspects over the life-cycle period. The life-cycle sustainability criteria are included in the assignments for the design teams. Multidisciplinary designers and engineers are asked to collaborate more closely and to interact with the end-users to address life-cycle requirements. However, ensuring the building actors to engage in an integrated collaboration to generate sustainable design solutions that meet the life-cycle。

毕业设计外文文献翻译(原文+译文)

Environmental problems caused by Istanbul subway excavation and suggestionsfor remediation伊斯坦布尔地铁开挖引起的环境问题及补救建议Ibrahim Ocak Abstract：Many environmental problems caused by subway excavations have inevitably become an important point in city life. These problems can be categorized as transporting and stocking of excavated material, trafﬁc jams, noise, vibrations, piles of dust mud and lack of supplies. Although these problems cause many difﬁculties,the most pressing for a big city like Istanbul is excava tion,since other listed difﬁculties result from it. Moreover, these problems are environmentally and regionally restricted to the period over which construction projects are underway and disappear when construction is ﬁnished. Currently, in Istanbul, there are nine subway construction projects in operation, covering approximately 73 km in length; over 200 km to be constructed in the near future. The amount of material excavated from ongoing construction projects covers approximately 12 million m3. In this study, problems—primarily, the problem with excavation waste(EW)—caused by subway excavation are analyzed and suggestions for remediation are offered.摘要：许多地铁开挖引起的环境问题不可避免地成为城市生活的重要部分。

毕业设计论文中英文翻译要求

毕业设计论文中英文翻译要求Graduation Thesis Translation RequirementsEnglish translation of Graduation Thesis:1. Accuracy: The English translation of the Graduation Thesis should accurately reflect the content and meaning of the original Chinese text. It should convey the same ideas and arguments as presented in the original text.2. Clarity: The translation should be clear and easy to understand. The language used should be appropriate and the sentences should be well-structured.3. Grammar and Syntax: The translation should follow the rules of English grammar and syntax. There should be no grammatical errors or awkward sentence constructions.4. Vocabulary: The translation should make use of appropriate vocabulary that is relevant to the topic of the Graduation Thesis. Technical terms and concepts should be accurately translated.5. Style: The translation should maintain the academic style and tone of the original Chinese text. It should use formal language and avoid colloquial or informal expressions.6. References: If the Graduation Thesis includes citations or references, the English translation should accurately reflectthese citations and references. The formatting of citations and references should follow the appropriate style guide.7. Proofreading: The English translation should be thoroughly proofread to ensure there are no spelling or punctuation errors. It should also be reviewed for any inconsistencies or inaccuracies.Minimum word count: The English translation of the Graduation Thesis should be at least 1200 words. This requirement ensures that the translation adequately captures the main points and arguments of the original text.It is important to note that there may be specific guidelines or requirements provided by your academic institution or supervisor for the translation of your Graduation Thesis. Please consult these guidelines and follow them accordingly.。

毕业论文的外文译文

毕业论文的外文译文Due to the increasing importance of communication and cooperation in today's globalized world, businesses are constantly looking for ways to improve their cross-cultural communication skills. One area where these skills are crucial is in the internationalization of companies, where firms require a deep understanding of the cultural differences in order to be successful. This requires a comprehensive understanding of not only language, but also the cultural norms and values of the target market. In this thesis, we will explore the importance of cross-cultural communication in international businesses and how it can be improved.The primary challenge in cross-cultural communication is the language barrier. While English is the dominant language in international business, many firms find that it's not enough to communicate effectively with their target market. There are cultural differences in the way people use language, as well as differences in nonverbal communication such as body language and facial expressions. For instance, in Japan, it's common to nod and smile even if one does not agree with astatement, whereas in the United States, a lack of disagreement often means agreement. These differences can lead to misunderstandings in business conversations, which can ultimately harm business relationships.In order to overcome these language barriers, companies need to invest in language training for their employees. This training should focus not only on the language itself, but also on the cultural norms and values associated with the language. For example, a Japanese training program might teach students about the concepts of harmony and respect in Japanese culture, and how these values influence the way people communicate with each other. By understanding these cultural norms, employees will be able to communicate more effectively with their Japanese counterparts.Another challenge in cross-cultural communication is understanding the cultural context of business interactions. In some cultures, business is conducted in a more formal manner, with a strong emphasis on hierarchy and protocol. In other cultures, business is more informal and relaxed. Companies need to understand these differences in order to work effectively in international markets.To overcome these context challenges, companies should incorporate cultural training into their employee training programs. Cultural training should focus on the history, customs, and traditions of the target market. It should also address the specific business practices and protocol required for success in that market.In conclusion, cross-cultural communication is a key determinant of success in international businesses. In order to succeed in foreign markets, companies must have a deep understanding of the language, cultural norms, and values of their target market. This requires a comprehensive training program that not only focuses on language skills, but also on the cultural context of business interactions. With the right training and support, companies can improve their cross-cultural communication skills and achieve success in global markets.。

(完整版)_毕业设计英文翻译_及格式

毕业设计(论文)英文翻译题目专业班级姓名学号指导教师职称200年月日The Restructuring of OrganizationsThroughout the 1990s, mergers and acquisitions a major source of corporate restructuring, affecting millions of workers and their families. This form of restructuring often is accompanied by downsizing. Downsizing is the process of reducing the size of a firm by laying off or retiring workers early. The primary objectives of downsizing are similar in U.S. companies and those in other countries:●cutting cost,●spurring decentralization and speeding up decision making,●cutting bureaucracy and eliminating layers of especially they did five years ago. One consequence of this trend is that today’s managers supervise larger numbers of subordinates who report directly to them. In 1990, only about 20 percent of managers supervise twelve or more people and 54 percent supervised six or fewer.Because of downsizing, first-line managers quality control, resources, and industrial engineering provide guidance and support. First-line managers participate in the production processes and other line activities and coordinate the efforts of the specialists as part of their jobs. At the same time, the workers that first-line managers supervise are less willing to put up with authoritarian management. Employees want their jobs to be more creative, challenging, fun, and satisfying and want to participate in decisions affecting their work. Thus self-managed work teams that bring workers and first-line managers together to make joint decisions to improve the way they do their jobs offer a solution to both supervision and employee expectation problems. When you ’t always the case. Sometimes entire divisions of a firm are simply spun off from the main company to operate on their own as new, autonomous companies. The firm that spun them off may then become one of their most important customers or suppliers. That AT&T “downsized” the old Bell Labs unit, which is now known as Lucent Technologies. Now, rather than - return is free to enter into contracts with companies other than AT&T. this method of downsizing is usually called outsourcing.Outsourcing means letting other organizations perform a needed service andor manufacture needed parts or products. Nike outsources the production of its shoes to low-cost plants in South Korea and China and imports the shoes for distribution in North America. These same plants also ship shoes to Europe and other parts of Asia for distribution. Thus today’s managers face a new challenge: t o plan, organize, lead, and control a company that may as a modular corporation. The modularcorporation is most is most common in three industries: apparel, auto manufacturing, and electronics. The most commonly out-sourced function is production. By out sourcing production, a company can switch supplier best suited to a customer’s needs.Decisions about what to outsource and what to keep in- to contract production to another company is a sound business decision to contract production to another company is a sound business decision, at least for U.S. manufacturers. It appears to the unit cost of production by relieving the company of some overhead, and it frees the company to allocate scarce resources to activities for which the company examples of modular companies are Dell Computer, Nike, Liz Claiborne fashions, and ship designer Cyrix.As organizations downsize and outsource functions, they become flatter and smaller. Unlike the behemoths of the past, the new, smaller firms are less like autonomous fortresses and more like nodes in a net work of complex relationships. This approach, called the network form of organization, involves establishing strategic alliances among several entities.In Japan, cross-ownership and alliances among firms－called keiretsu－both foreign and U.S. auto parts producers. It also owns 49 percent of Hertz, the car rental company that is also a major customer. Other alliances include involvement in several research consortia. In the airline industry, a common type of alliance is between an airline and an airframe manufacture. For example, Delta recently agreed to buy all its aircraft from Boeing. Boeing Airlines. Through these agreements, Boeing guarantees that it will be able to sell specified models of its aircraft and begin to adapt their operations to the models they will be flying in the future. Thus both sides expect to reap benefits from these arrangements for many years.Networks forms of organizations are prevalent in access to the universities and in small, creative organizations. For example, the U.S. biotechnology industry is characterized by network of relationships between new biotechnology firms dedicated to research and new products development and established firms in industries that can use these new products, such as pharmaceuticals. In return for sharing technical information with the larger firms, the smaller firms gain access to their partners’ resources for product testing, marketing, and distribution. Big pharmaceutical firms such as Merk or Eli Lily gain from such partnerships because the smaller firms typically development cycle in the larger firms.Being competitive increasingly requires establishing and managing strategic alliances with other firms. In a strategic alliance, two or more firms agree to cooperate in a venture that is expected to benefit both firms.企业重组整个20世纪90年代中，合并和收购一直是企业重组的主要起源，影响着千百万的工人和他们的家庭。

毕业设计外文翻译原文

CLUTCHThe engine produces the power to drive the vehicle. The drive line or drive train transfers the power of the engine to the wheels. The drive train consists of the parts from the back of the flywh eel to the wheels. These parts include the clutch, th e transmission, the drive shaft, and the final drive assembly (Figure 8-1).The clutch which includes the flywheel, clutch disc, pressure plate, springs, pressure plate cover and the linkage necessary to operate the clutch is a rotating mechanism between t he engine and the transmission (Figure 8-2). It operates through friction which comes from contact between the parts. That is the reason why the clutch is called a friction mechanism. After engagement, the clutch must continue to transmit all the engine torque to the transmission depending on the friction without slippage. The clutch is also used to disengage the engine from the drive train whenever the gears in the transmission are being shifted from one gear ratio to another.To start the engine or shift the gears, the driver has to depress the clutch pedal with the purpose of disengagement the transmission from the engine. At that time, the driven members connected to the transmission input shaft are either stationary or rotating at a speed that is slower or faster than the driving members connected to the engine crankshaft. There is no spring pressure on the clutch assembly parts. So there is no friction between the driving members and driven members. As the driver lets loose the clutch pedal, spring pre ssure increases on the clutch parts. Friction between the parts also increases. The pressure exerted by the springs on the driven members is controlled by the driver through the clutch pedal and linkage. The positive engagement of the driving and driven members is made possible by the friction between the surfaces of the members. When full spring pressure is applied, the speed of the driving and driven members should be the same. At themoment, the clutch must act as a solid coupling device and transmit al l engine power to the transmission, without slipping.However, the transmission should be engaged to the engine gradually in order to operate the car smoothly and minimize torsional shock on the drive train because an engine at idle just develops little power. Otherwise, the driving members are connected with the driven members too quickly and the engine would be stalled.The flywheel is a major part of the clutch. The flywheel mounts to the engine’s crankshaft and transmits engine torque to the clutch assembly. The flywheel, when coupled with the clutch disc and pressure plate makes and breaks the flow of power from the engine to the transmission.The flywheel provides a mounting location for the clutch assembly as well. When the clutch is applied, the flyw heel transfers engine torque to the clutch disc. Because of its weight, the flywheel helps to smooth engine operation. The flywheel also has a large ring gear at its outer edge, which engages with a pinion gear on the starter motor during engine cranking.The clutch disc fits between the flywheel and the pressure plate. The clutch disc has a splined hub that fits over splines on the transmission input shaft. A splined hub has grooves that match splines on the shaft. These splines fit in the grooves. Thus, t he two parts are held together. However, back-and-forth movement of the disc on the shaft is possible. Attached to the input shaft, At disc turns at the speed of the shaft.The clutch pressure plate is generally made of cast iron. It is round and about the same diameter as the clutch disc. One side of the pressure plate is machined smooth. This side will press the clutch disc facing are against the flywheel. The outer side has various shapes to facilitate attachment of spring and release mechanisms. The two primary types of pressure plate assemblies are coil spri ng assembly and diaphragmspring (Figure 8-3).In a coil spring clutch the pressure plate is backed by a number of coil springs and housed with them in a pressed-steel cover bolted to the flywheel. The springs push against the cover. Neither the driven plate nor the pressure plate is connected rigidly to the flywh eel and both can move either towards it or away. When the clutch pedal is depressed a thrust pad riding on a carbon or ball thrust bearing i s forced towards the flywheel. Levers pivoted so that they engage with the thrust pad at one end and the pressure plate at the other end pull the pressure plate ba ck against its springs. This releases pressure on the driven plate disconnecting the gearbox from the engine (Figure 8-4).Diaphragm spring pressure plate assemblies are widely used in most modern cars. The diaphragm spring is a single thin sheet of metal which yields when pressure is applied to it. When pressure is removed the metal springs back to its original shape. The centre portion of the diaphragm spring is slit into numerous fingers that act as release levers. When the clutch assembly rotates with the engine these weights are flung outwards by centrifugal forces and cause the levers to pre ss against the pressure plate. During disengagement of the clutch the fingers are moved forward by the release bearing. The spring pivots over the fulcrum ring and its outer rim moves away from the flywheel. The retracting spring pulls the pressure plate a way from the clutch plate thus disengaging the clutch (Figure 8-5).When engaged the release bearing and the fingers of the diaphragm spring move towards the transmission. As the diaphragm pivots over the pivot ring its outer rim forces the pressure plate against the clutch disc so that the clutch plate is engaged to the flywheel.The advantages of a diaphragm type pres sure plate assembly are its compactness, lower weight, fewer moving parts, less effort to engage, reduces rotational imbalance by providin g a balanced force around the pressure plate and less chances of clutch slippage.The clutch pedal is connected to the disengagement mechanism either by a cable or, more com monly, by a hydraulic system. Either way, pushing the pedal down operates the dise ngagement mechanism which puts pressure on the fingers of the clutch diaphragm via a release bearing and causes the diaphragm to release the clutch plate. With a hydraulic mechanism, the clutch pedal arm operates a piston in the clutch master cylinder. Thi s forces hydraulic fluid through a pipe to the clutch release cylinder where another piston operates the clutch disengagement mechanism. The alternative is to link the clutch pedal to the disengagement mechanism by a cable.The other parts including the cl utch fork, release bearing, bell-housing, bell housing cover, and pilot bushing are needed to couple and uncouple the transmission. The clutch fork, which connects to the linkage, actually operates the clutch. The release bearing fits between the clutch fork and the pressure plate assembly. The bell housing covers the clutch assembly. The bell housing c over fastens to the bottom of the bell housing. This removable cover allows a mechanic to inspect the clutch without removing the transmission and bell housing. A pilot bushing fits into the back of th e crankshaft and holds the transmission input shaft.A Torque ConverterThere are four components inside the very strong housing of the torque converter:1. Pump;2. Turbine;3. Stator;4. Transmission fluid.The housing of the torque converter is bolted to the flywheel of the engine, so it turns at what ever speed the engine is running at. The fins that make up the pump of the torque converter are at tached to the housing, so they also turn at the same speed a s the engine. The cutaway below shows how everything is connected inside the torque converter (Figure 8-6).The pump inside a torque converter is a type of centrifugal pump. As it spins, fluid is flung to the outside, much as the spin cycle of a washing machine flings water and clothes to the outside of the wash tub. As fluid is flung to the outside, a vacuum is created that draws more fluid in at the center.The fluid then enters the blades of the turbine, which is connected to the transmission. The turbin e causes the transmission to spin, which basically moves the car. The blades of the turbine are curved. This means that the fluid, which enters the turbine from the outside, has to change direction before it exits the center of the turbine. It is this directional change that causes the turbine to spin.The fluid exits the turbine at the center, moving in a different direction than when it entered. The fluid exits the turbine moving opposite the direction that the pump (and engine) is turning. If the fluid were allowed to hit the pump, it would slow the engine down, wasting power. This is why a torque converter has a stator.The stator resides in the very center of the torque converter. Its job is to redirect the fluid returning from the turbine before it hits the pump again. This dramatically increases the efficiency of the torque converter.The stator has a very aggressive blade design that almost completely reverses the direction of the fluid. A one-way clutch (inside the stator) connects the stator to a fixed shaft in the transmission. Because of this arrangement, the stator cannot spin with the fluid - i tc a n s p i n o n l y i n t h e o p p o s i t ed i re c t i o n,f o r c i ng th e f l ui d t oc h a n g ed i re c t i o n a s i t h i t s t h e s t a t o r b l a d e s.Something a little bit tricky happens when the car gets moving. There is a point, around 40 mph (64 kph), at which both the pump and the turbine are spinning at almost the same speed (the pump alwaysspins slightly faster). At this point, the fluid returns from the turbine, entering the pump already moving in the same direction as the pump, so the stator is not needed.Even though the turbine changes the direction of the fluid and flings it out the back, the fluid still ends up moving in the direction that the turbine is spinning because the turbin e is spinning faster in one direction than the fluid is being pumped in the other direction. If you were standing in the back of a pickup moving at 60 mph, and you threw a ball out the back of that pickup at 40 mph, the ball would still be going forward at 20 mph. This is similar to what happens in the tur bine: The fluid is being flung out the back in one direction, but not as fast as it was going to start with in the other direction.At these speeds, the fluid actually strikes the back sides of the stator blades, causing the stator to freewheel on its one-way clutch so it doesn’t hinder the fluid moving through it.Benefits and Weak PointsIn addition to the very important job of allowing a car come to a complete stop without stalling the engine; the torqu e converter actually gives the car more torque when you accelerate out of a Stop. Modern torque converters can multiply the torque of the engine by two to three times. This effect only happens when the engine is turning much faster than the transmission.At higher speeds, the transmission catches up to the engine, eventually moving at almost the same speed. Ideally, though, the transmission would move at exactly the same speed as the engine, because this difference in speed wastes power. This is part of th e reason why cars with automatic transmissions get worse gas mileage than cars with manual transmissions.To counter this effect, some cars have a torque converter with alockup clutch. When the two halves of the torque converter get up to speed, this clutch locks them together, eliminating the slip page and improving efficiency.。

甲玛英文翻译

附3成都理工大学学生毕业设计（论文）外文译文拉雅褶皱冲断层带和喜马拉雅区晶体，2、拉萨地块，3、羌塘地块，松潘—甘孜可可西里—可可西里断块，4、the Kun Lun–Qiadam断块（Gansser，1980）。

这些领域可细分为小喜马拉雅变质沉积岩系列，高喜马拉雅变质岩石特提斯沉积序列，早第三纪林子宗组火山岩，冈底斯岩基的白垩系成岩区域和科希斯坦弧，其主要岩层如下：第三纪沉积的岩石中，钱塘江的古生界地层，昆仑地块和祁连地块的古生代和中生代火成岩。

读者可以参考这个庞大的系统的详细的历史（Yin and Harrison ，2000.)。

图1 喜马拉雅—西藏造山带的地质构造简图，雅鲁藏布江由西向东的缝合带位置和蛇绿岩年龄。

年龄表1中所列出，并划分地块。

生物地层年龄（沉积物）用斜体表示，缩略：SSZ, Shyok suture zone; ZSZ, Zanskar suture zone; BNSZ, Bangong Nujiang suture; YZSZ, Yarlung Zangbo Suture Zone。

主要根据不连续性结构块划分喜马拉雅褶皱冲断带：GCT, Great Counter thrust; STD, South Tibet detachment；HHT, High Himalaya thrust, MCTZ，主中央冲断带；MBT主边界断裂，MFT，主要的正面推力。

青藏高原北部的YZSZ这是世界同类中最高的，是印度大陆和欧亚板块之间的碰撞（Yin et al., 1988）。

它被细分为，从北到南，主要的为近东西向断块或地体缝合带：1、the Ayimaqin–Kunlun Mutztagh缝合；2、金沙江缝合带；3、班公湖- 怒江缝合带；4、雅鲁藏布江缝合（图1）。

这些的缝线是缝合之前的不同的洋盆片段(Yu and Zhen, 1979, Mercier and Li, 1984 and Murphy et al., 1997)。

毕设外文翻译 (英文原文+翻译)

英文翻译：PARTⅠ各种光纤接入技术Optical Fiber Technology With Various Access1 光网络主流1.1 光纤技术光纤生产技术已经成熟，现在大批量生产，广泛应用于今天的零色散波长λ0=1.3μm的单模光纤，而零色散波长λ0=1.55μm的单模光纤已开发并已进入实用阶段，这是非常小的1.55μm的波长衰减，约0.22dB/km，它更适合长距离大容量传输，是首选的长途骨干传输介质。

目前，为了适应不同的线路和局域网的发展要求，已经制定了一个非分散纤维，低色散斜率光纤，大有效面积光纤，水峰光纤等新型光纤。

长波光学研究人员研究认为，传输距离可以达到数千公里的理论，可以实现无中继传输距离，但它仍然是阶段理论。

1.2 光纤放大器1550nm波长掺铒（ER）的光纤放大器（EDFA），掺铒数字，模拟和相干光通信中继器可以以不同的速率传输光纤放大器，也可以发送特定波长的光信号。

在从模拟信号转换成数字信号、从低到高比特率比特率的光纤网络升级中，系统采用光复用技术的扩大，他们都不必改变掺铒放大器电路和设备。

掺铒放大器可作为光接收机前置放大器，后置放大器的光发射机和放大器的补偿光源装置。

1.3 宽带接入不同的环境中企业和住宅客户提供了多种宽带接入解决方案。

接入系统主要完成三大功能：高速传输，复用/路由，网络的扩展。

目前，接入系统的主流技术，ADSL 技术可以双绞铜线传输经济每秒几兆比特的信息，即支持传统的语音服务，而且还支持面向数据的因特网接入位，理事会结束的ADSL多路复用访问的数据流量，路由的分组网络，语音流量将传送到PSTN，ISDN或其它分组网络。

电缆调制解调器在HFC网络提供高速数据通信，将带宽分为上行和下行信道同轴电缆渠道，它可以提供挥发性有机化合物的在线娱乐，互联网接入等服务，同时还提供PSTN业务。

固定无线接入系统如智能天线和接收机的无线接入系统使用了许多高新技术，是一个以创新的方式接入的技术，作为目前仍滞留在今后进一步探索实践的方式最不确定的接入技术。

毕业设计论文翻译（译文+原文）

Hacking tricks toward security on network environments Tzer-Shyong Chen1, Fuh-Gwo Jeng 2, and Yu-Chia Liu 11 Department of Information Management, Tunghai University, Taiwan2 Department of Applied Mathematics, National Chiayi University, TaiwanE-Mail:****************.edu.twAbstractMounting popularity of the Internet has led to the birth of Instant Messaging, an up-and-coming form of Internet communication. Instant Messaging is very popular with businesses and individuals since it has instant communication ability. As a result, Internet security has become a pressing and important topic for discussion. Therefore, in recent years, a lot of attention has been drawn towards Internet security and the various attacks carried out by hackers over the Internet. People today often handle affairs via the Internet. For instance, instead of the conventional letter, they communicate with others by e-mails; they chat with friends through an instant messenger; find information by browsing websites instead of going to the library; perform e-commerce transactions through the Internet, etc. Although the convenience of the Internet makes our life easier, it is also a threat to Internet security. For instance, a business email intercepted during its transmission may let slip business confidentiality; file transfers via instant messengers may also be intercepted, and then implanted with backdoor malwares; conversations via instant messengers could be eavesdropped. Furthermore, ID and password theft may lose us money when using Internet bank service. Attackers on the Internet use hacking tricks to damage systems while users are connected to the Internet. These threats along with possible careless disclosure of business information make Instant Messaging a very unsafe method of communication for businesses. The paper divides hacking tricks into three categories: (1) Trojan programs that share files via instant messenger. (2) Phishing or fraud via e-mails. (3) Fake Websites. Keywords:Hacking tricks, Trojan programs, Phishing, Firewall, Intrusion detection system.1. IntroductionIncreasingly more people are using instant messengers such as MSN Messenger, Yahoo! Messenger, ICQ, etc as the media of communication. These instant messengers transmit alphanumeric message as well as permit file sharing. During transfer, a file may be intercepted by a hacker and implanted with backdoor malware. Moreover, the e-mails users receive every day may include Spam, advertisements, and fraudulent mail intended to trick uninformed users. Fake websites too are prevalent. Websites which we often visit could be counterfeited by imitating the interface and the URL of the original, tricking users. The paper classifies hacking tricks into three categories which are explained in the following sections.2. Hacking TricksThe paper divides hacking tricks into three categories: (1) Trojan programs that share files via instant messenger. (2) Phishing (3) Fake Websites.2.1 Trojan programs that share files via instant messengerInstant messaging allows file-sharing on a computer [9]. All present popular instant messengers have file sharing abilities, or allow users to have the above functionality by installing patches or plug-ins; this is also a major threat to present information security. These communication softwares also makeit difficult for existing hack prevention methods to prevent and control information security. Therefore, we shall discuss how to control the flow of instant messages and how to identify dangerous user behavior.Hackers use instant communication capability to plant Trojan program into an unsuspected program; the planted program is a kind of remotely controlled hacking tool that can conceal itself and is unauthorized. The Trojan program is unknowingly executed, controlling the infected computer; it can read, delete, move and execute any file on the computer. The advantages of a hacker replacing remotely installed backdoor Trojan programs [1] with instant messengers to access files are:When the victim gets online, the hacker will be informed. Thus, a hacker can track and access the infected computer, and incessantly steal user information.A hacker need not open a new port to perform transmissions; he can perform his operations through the already opened instant messenger port.Even if a computer uses dynamic IP addresses, its screen name doesn’t change.Certain Trojan programs are designed especially for instant messengers. These Trojans can change group settings and share all files on the hard disk of the infected computer. They can also destroy or modify data, causing data disarray. This kind of program allows a hacker access to all files on an infected computer, and thus poses a great threat to users. The Trojan program takes up a large amount of the resources of the computer causing it to become very slow and often crashes without a reason.Trojan programs that access a user computer through an instant messenger are probably harder to detect than classic Trojan horse programs. Although classic Trojan intrudes a computer by opening a listening or outgoing port which is used to connect toa remote computer, a desktop firewall can effectively block such Trojans. Alternatively, since it is very difficult for the server’s firewall to spot intrusion by controlling an instant messenger’s flow, it is extremely susceptible to intrusion.Present Trojan programs have already successfully implemented instant messengers. Some Trojan programs are Backdoor Trojan, AIMVision, and Backdoor. Sparta.C. Backdoor Trojans use ICQ pager to send messages to its writer. AIMVision steals AIM related information stored in the Windows registry, enabling a hacker to setup an AIM user id. Backdoor. Sparta.C uses ICQ to communicate with its writer and opens a port on an infected host and send its IP Address to the hacker, and at the same time attempts to terminate the antivirus program or firewall of the host.2.1.1 Hijacking and ImpersonationThere are various ways through which a hacker can impersonate other users [7]. The most commonly used method is eavesdropping on unsuspecting users to retrieve user accounts, passwords and other user related information.The theft of user account number and related information is a very serious problem in any instant messenger. For instance, a hacker after stealing a user’s information impersonate the user; the user’s contacts not knowing that the user’s account has been hacked believe that the person they’re talking to is the user, and are persuaded to execute certain programs or reveal confidential information. Hence, theft of user identity not only endangers a user but also surrounding users. Guarding against Internet security problems is presently the focus of future research; because without good protection, a computer can be easily attacked, causing major losses.Hackers wishing to obtain user accounts may do so with the help of Trojans designed to steal passwords. If an instant messenger client stores his/her password on his/her computer, then a hacker can send a Trojan program to the unsuspecting user. When the user executes the program, the program shall search for the user’s password and send it to the hacker. There are several ways through which a Trojan program can send messages back to the hacker. The methods include instant messenger, IRC, e-mails, etc.Current four most popular instant messengers are AIM, Yahoo! Messenger, ICQ, and MSN Messenger, none of which encrypts its flow. Therefore, a hackercan use a man-in-the-middle attack to hijack a connection, then impersonate the hijacked user and participate in a chat-session. Although difficult, a hacker can use the man-in-the-middle attack to hijack the connection entirely. For example, a user may receive an offline message that resembles that sent by the server, but this message could have been sent by the hacker. All at once, the user could also get disconnected to the server. Furthermore, hackers may also use a Denial of Service (DoS) tool or other unrelated exploits to break the user’s connection. However, the server keeps the connection open, and does not know that the user has been disconnected; thus allowing the hacker to impersonate the user. Moreover, since the data flow is unencrypted and unauthenticated, a hacker can use man-in-the-middle attacks that are similar to that of ARP fraud to achieve its purpose.2.1.2 Denial of Service (DoS)There are many ways through which a hacker can launch a denial of service (DoS) attack [2] on an instant messenger user. A Partial DoS attack will cause a user end to hang, or use up a large portion of CPU resources causing the system to become unstable.Another commonly seen attack is the flooding of messages to a particular user. Most instant messengers allow the blocking of a particular user to prevent flood attacks. However, a hacker can use tools that allow him to log in using several different identities at the same time, or automatically create a large number of new user ids, thus enabling a flood attack. Once a flood attack begins, even if the user realizes that his/her computer has been infected, the computer will not be able to respond. Thus, the problem cannot be solved by putting a hacker’s user id on the ignore list of your instant messenger.A DoS attack on an instant messenger client is only a common hacking tool. The difficulty of taking precautions against it could turn this hacking tool into dangerous DoS type attacks. Moreover, some hacking tools do not just cause an instant messenger client to hang, but also cause the user end to consume large amount of CPU time, causing the computer to crash.2.1.3 Information DisclosureRetrieving system information through instant messenger users is currently the most commonly used hacking tool [4]. It can effortlessly collect user network information like, current IP, port, etc. IP address retriever is an example. IP address retrievers can be used to many purposes; for instance, a Trojan when integrated with an IP address retriever allows a hacker to receive all information related to the infected computer’s IP address as soon as the infected computer connects to the internet. Therefore, even if the user uses a dynamic IP address, hackers can still retrieve the IP address.IP address retrievers and other similar tools can also be used by hackers to send data and Trojans to unsuspecting users. Hackers may also persuade unsuspecting users to execute files through social engineering or other unrelated exploits. These files when executed search for information on the user’s computer and sends them back to the hacker through the instant messenger network.Different Trojan programs were designed for different instant messaging clients. For example, with a user accounts and password stealing Trojans a hacker can have full control of the account once the user logs out. The hacker can thus perform various tasks like changing the password and sending the Trojan program to all of the user’s contacts.Moreover, Trojans is not the only way through which a hacker can cause information disclosure. Since data sent through instant messengers are unencrypted, hackers can sniff and monitor entire instant messaging transmissions. Suppose an employee of an enterprise sends confidential information of the enterprise through the instant messenger; a hacker monitoring the instant messaging session can retrieve the data sent by the enterprise employee. Thus, we must face up to the severity of the problem.2.2 PhishingThe word “Phishing” first appeared in 1996. It is a variant of ‘fishing’, and formed by replacing the ‘f’ in ‘fishing’ with ‘ph’ from phone. It means tricking users of their money through e-mails.Based on the statistics of the Internet Crime Complaint Center, loss due to internet scam was as high as $1.256 million USD in 2004. The Internet Crime Complaint Center has listed the above Nigerian internet scam as one of the ten major internet scams.Based on the latest report of Anti-Phishing Working Group (APWG) [8], there has been a 28% growth of Phishing scams in the past 4 months, mostly in the US and in Asia. Through social engineering and Trojans, it is very difficult for a common user to detect the infection.To avoid exploitation of your compassion, the following should be noted:(1)When you need to enter confidentialinformation, first make sure that theinformation is entered via an entirely secureand official webpage. There are two ways todetermine the security of the webpage:a.The address displayed on the browserbegins with https://, and not http://. Payattention to if the letter ‘s’ exists.b.There is a security lock sign on the lowerright corner of the webpage, and whenyour mouse points to the sign, a securitycertification sign shall appear.(2)Consider installing a browser security softwarelike SpoofStick which can detect fake websites.(3)If you suspect the received e-mail is a Phishinge-mail, do not open attachments attached to theemail. Opening an unknown attachment couldinstall malicious programs onto your computer.(4)Do not click on links attached to your emails. Itis always safer to visit the website through theofficial link or to first confirm the authenticityof the link. Never follow or click on suspiciouslinks in an e-mail. It is advisable to enter theURL at the address bar of the web browser,and not follow the given link.Generally speaking, Phishing [3] [5] is a method that exploits people’s sympathy in the form of aid-seeking e-mails; the e-mail act as bait. These e-mails usually request their readers to visit a link that seemingly links to some charitable organization’s website; but in truth links the readers to a website that will install a Trojan program into the reader’s computer. Therefore, users should not forward unauthenticated charity mails, or click on unfamiliar links in an e-mail. Sometimes, the link could be a very familiar link or an often frequented website, but still, it would be safer if you’d type in the address yourself so as to avoid being linked to a fraudulent website. Phisher deludes people by using similar e-mails mailed by well-known enterprises or banks; these e-mails often asks users to provide personal information, or result in losing their personal rights; they usually contain a counterfeit URL which links to a website where the users can fillin the required information. People are often trapped by phishing due to inattentionBesides, you must also be careful when using a search engine to search for donations and charitable organizations.2.3 Fake WebsitesFake bank websites stealing account numbers and passwords have become increasingly common with the growth of online financial transactions. Hence, when using online banking, we should take precautions like using a secure encrypted customer’s certificate, surf the net following the correct procedure, etc.There are countless kinds of phishing baits, for instance, messages that say data expired, data invalid, please update data, or identity verification intended to steal account ID and matching password. This typeof online scam is difficult for users to identify. As scam methods become finer, e-mails and forged websites created by the impostor resemble their original, and tremendous losses arise from the illegal transactions.The following are methods commonly used by fake websites. First, the scammers create a similar website homepage; then they send out e-mails withenticing messages to attract visitors. They may also use fake links to link internet surfers to their website. Next, the fake website tricks the visitors into entering their personal information, credit card information or online banking account number and passwords. After obtaining a user’s information, the scammers can use the information to drain the bank accounts, shop online or create fake credit cards and other similar crimes. Usually, there will be a quick search option on these fake websites, luring users to enter their account number and password. When a user enters their account number and password, the website will respond with a message stating that the server is under maintenance. Hence, we must observe the following when using online banking:(1)Observe the correct procedure for entering abanking website. Do not use links resultingfrom searches or links on other websites.(2)Online banking certifications are currently themost effective security safeguard measure. (3)Do not easily trust e-mails, phone calls, andshort messages, etc. that asks for your accountnumber and passwords.Phishers often impost a well-known enterprise while sending their e-mails, by changing the sender’s e-mail address to that of the well known enterprise, in order to gain people’s trust. The ‘From’ column of an e-mail is set by the mail software and can be easily changed by the web administrator. Then, the Phisher creates a fake information input website, and send out e-mails containing a link to this fake website to lure e-mail recipients into visiting his fake website.Most Phishers create imitations of well known enterprises websites to lure users into using their fake websites. Even so, a user can easily notice that the URL of the website they’re entering has no relation to the intended enterprise. Hence, Phishers may use different methods to impersonate enterprises and other people. A commonly used method is hiding the URL. This can easily be done with the help of JavaScript.Another way is to exploit the loopholes in an internet browser, for instance, displaying a fake URL in the browser’s address bar. The security loophole causing the address bar of a browser to display a fake URL is a commonly used trick and has often been used in the past. For example, an e-mail in HTML format may hold the URL of a website of a well-known enterprise, but in reality, the link connects to a fake website.The key to successfully use a URL similar to that of the intended website is to trick the visual senses. For example, the sender’s address could be disguised as that of Nikkei BP, and the link set to http://www.nikeibp.co.jp/ which has one k less than the correct URL which is http://www.nikkeibp.co.jp/. The two URLs look very similar, and the difference barely noticeable. Hence people are easily tricked into clicking the link.Besides the above, there are many more scams that exploit the trickery of visual senses. Therefore, you should not easily trust the given sender’s name and a website’s appearance. Never click on unfamiliar and suspicious URLs on a webpage. Also, never enter personal information into a website without careful scrutiny.3. ConclusionsBusiness strategy is the most effective form of defense and also the easiest to carry out. Therefore, they should be the first line of defense, and not last. First, determine if instant messaging is essential in the business; then weigh its pros and cons. Rules and norms must be set on user ends if it is decided that the business cannot do without instant messaging functionality. The end server should be able to support functions like centralized logging and encryption. If not, then strict rules must be drawn, and carried out by the users. Especially, business discussions must not be done over an instant messenger.The paper categorized hacking tricks into three categories: (1) Trojan programs that share files via instant messenger. (2) Phishing (3) Fake Websites. Hacking tricks when successfully carried out could cause considerable loss and damage to users. The first category of hacking tricks can be divided into three types: (1) Hijacking and Impersonation; (2) Denial of Service; (3) Information Disclosure.Acknowledgement:This work was supported by the National Science Council, Taiwan, under contract No. NSC 95-2221-E-029-024.References[1] B. Schneier, “The trojan horse race,”Communications of ACM, Vol. 42, 1999, pp.128.[2] C. L. Schuba, “Analysis of a denial of serviceattack on TCP,” IEEE Security and PrivacyConference, 1997, pp. 208-223.[3] E. Schultz, “Phishing is becoming moresophisticated,” Computer and Security, Vol.24(3), 2005, pp. 184-185.[4]G. Miklau, D. Suciu, “A formal analysis ofinformation disclosure in data exchange,”International Conference on Management ofData, 2004, pp. 575-586.[5]J. Hoyle, “'Phishing' for trouble,” Journal ofthe American Detal Association, Vol. 134(9),2003, pp. 1182-1182.[6]J. Scambray, S. McClure, G. Kurtz, Hackingexposed: network security secrets and solutions,McGraw-Hill, 2001.[7]T. Tsuji and A. Shimizu, “An impersonationattack on one-time password authenticationprotocol OSPA,” to appear in IEICE Trans.Commun, Vol. E86-B, No.7, 2003.[8]Anti-Phishing Working Group,.[9]/region/tw/enterprise/article/icq_threat.html.有关网络环境安全的黑客技术摘要：现在人们往往通过互联网处理事务。

毕业设计的论文中英翻译

Anti-Aircraft Fire Control and the Development of IntegratedSystems at SperryT he dawn of the electrical age brought new types of control systems. Able to transmit data between distributed components and effect action at a distance, these systems employed feedback devices as well as human beings to close control loops at every level. By the time theories of feedback and stability began to become practical for engineers in the 1930s a tradition of remote and automatic control engineering had developed that built distributed control systems with centralized information processors. These two strands of technology, control theory and control systems, came together to produce the large-scale integrated systems typical of World War II and after.Elmer Ambrose Sperry (I860-1930) and the company he founded, the Sperry Gyroscope Company, led the engineering of control systems between 1910 and 1940. Sperry and his engineers built distributed data transmission systems that laid the foundations of today‟s command and control systems. Sperry‟s fire control systems included more than governors or stabilizers; they consisted of distributed sensors, data transmitters, central processors, and outputs that drove machinery. This article tells the story of Sperry‟s involvement in anti-aircraft fire control between the world wars and shows how an industrial firm conceived of control systems before the common use of control theory. In the 1930s the task of fire control became progressively more automated, as Sperry engineers gradually replaced human operators with automatic devices. Feedback, human interface, and system integration posed challenging problems for fire control engineers during this period. By the end of the decade these problems would become critical as the country struggled to build up its technology to meet the demands of an impending war.Anti-Aircraft Artillery Fire ControlBefore World War I, developments in ship design, guns, and armor drove the need for improved fire control on Navy ships. By 1920, similar forces were at work in the air: wartime experiences and postwar developments in aerial bombing created the need for sophisticated fire control for anti-aircraft artillery. Shooting an airplane out of the sky is essentially a problem of “leading” the target. As aircraft developed rapidly in the twenties, their increased speed and altitude rapidly pushed the task of computing the lead out of the range of human reaction and calculation. Fire control equipment for anti-aircraft guns was a means of technologically aiding human operators to accomplish a task beyond their natural capabilities.During the first world war, anti-aircraft fire control had undergone some preliminary development. Elmer Sperry, as chairman of the Aviation Committee of the Naval Consulting Board, developed two instruments for this problem: a goniometer,a range-finder, and a pretelemeter, a fire director or calculator. Neither, however, was widely used in the field.When the war ended in I918 the Army undertook virtually no new development in anti-aircraft fire control for five to seven years. In the mid-1920s however, the Army began to develop individual components for anti-aircraft equipment including stereoscopic height-finders, searchlights, and sound location equipment. The Sperry Company was involved in the latter two efforts. About this time Maj. Thomas Wilson, at the Frankford Arsenal in Philadelphia, began developing a central computer for firecontrol data, loosely based on the system of “director firing” that had developed in naval gunn ery. Wilson‟s device resembled earlier fire control calculators, accepting data as input from sensing components, performing calculations to predict the future location of the target, and producing direction information to the guns.Integration and Data TransmissionStill, the components of an anti-aircraft battery remained independent, tied together only by telephone. As Preston R. Bassett, chief engineer and later president of the Sperry Company, recalled, “no sooner, however, did the components get to the point of functioning satisfactorily within themselves, than the problem of properly transmitting the information from one to the other came to be of prime importance.”Tactical and terrain considerations often required that different fire control elements be separated by up to several hundred feet. Observers telephoned their data to an officer, who manually entered it into the central computer, read off the results, and telephoned them to the gun installations. This communication system introduced both a time delay and the opportunity for error. The components needed tighter integration, and such a system required automatic data communications.In the 1920s the Sperry Gyroscope Company led the field in data communications. Its experience came from Elmer Spe rry‟s most successful invention, a true-north seeking gyro for ships. A significant feature of the Sperry Gyrocompass was its ability to transmit heading data from a single central gyro to repeaters located at a number of locations around the ship. The repeaters, essentially follow-up servos, connected to another follow-up, which tracked the motion of the gyro without interference. These data transmitters had attracted the interest of the Navy, which needed a stable heading reference and a system of data communication for its own fire control problems. In 1916, Sperry built a fire control system for the Navy which, although it placed minimal emphasis on automatic computing, was a sophisticated distributed data system. By 1920 Sperry had installed these systems on a number of US. battleships.Because of the Sperry Company‟s experience with fire control in the Navy, as well as Elmer Sperry‟s earlier work with the goniometer and the pretelemeter, the Army approached the company for help with data transmission for anti-aircraft fire control. To Elmer Sperry, it looked like an easy problem: the calculations resembled those in a naval application, but the physical platform, unlike a ship at sea, anchored to the ground. Sperry engineers visited Wilson at the Frankford Arsenal in 1925, and Elmer Sperry followed up with a letter expressing his interest in working on the problem. He stressed his company‟s experience with naval problems, as well as its recent developments in bombsights, “work from the other end of the pro position.” Bombsights had to incorporate numerous parameters of wind, groundspeed, airspeed, and ballistics, so an anti-aircraft gun director was in some ways a reciprocal bombsight . In fact, part of the reason anti-aircraft fire control equipment worked at all was that it assumed attacking bombers had to fly straight and level to line up their bombsights. Elmer Sperry‟s interests were warmly received, and in I925 and 1926 the Sperry Company built two data transmission systems for the Army‟s gun directors.The original director built at Frankford was designated T-1, or the “Wilson Director.” The Army had purchased a Vickers director manufactured in England, but encouraged Wilson to design one thatcould be manufactured in this country Sperry‟s two data tran smission projects were to add automatic communications between the elements of both the Wilson and the Vickers systems (Vickers would eventually incorporate the Sperry system into its product). Wilson died in 1927, and the Sperry Company took over the entire director development from the Frankford Arsenal with a contract to build and deliver a director incorporating the best features of both the Wilson and Vickers systems. From 1927 to 193.5, Sperry undertook a small but intensive development program in anti-aircraft systems. The company financed its engineering internally, selling directors in small quantities to the Army, mostly for evaluation, for only the actual cost of production [S]. Of the nearly 10 models Sperry developed during this period, it never sold more than 12 of any model; the average order was five. The Sperry Company offset some development costs by sales to foreign govemments, especially Russia, with the Army‟s approval 191.The T-6 DirectorSperry‟s modified version of Wilson‟s director was designated T-4 in development. This model incorporated corrections for air density, super-elevation, and wind. Assembled and tested at Frankford in the fall of 1928, it had problems with backlash and reliability in its predicting mechanisms. Still, the Army found the T-4 promising and after testing returned it to Sperry for modification. The company changed the design for simpler manufacture, eliminated two operators, and improved reliability. In 1930 Sperry returned with the T-6, which tested successfully. By the end of 1931, the Army had ordered 12 of the units. The T-6 was standardized by the Army as the M-2 director.Since the T-6 was the first anti-aircraft director to be put into production, as well as the first one the Army formally procured, it is instructive to examine its operation in detail. A technical memorandum dated 1930 explained the theory behind the T-6 calculations and how the equations were solved by the system. Although this publication lists no author, it probably was written by Earl W. Chafee, Sperry‟s director of fire control engineering. The director was a complex mechanical analog computer that connected four three-inch anti-aircraft guns and an altitude finder into an integratedsystem (see Fig. 1). Just as with Sperry‟s naval fire control system, the primary means of connection were “data transmitters,” similar to those that connected gyrocompasses to repeaters aboard ship.The director takes three primary inputs. Target altitude comes from a stereoscopic range finder. This device has two telescopes separated by a baseline of 12 feet; a single operator adjusts the angle between them to bring the two images into coincidence. Slant range, or the raw target distance, is then corrected to derive its altitude component. Two additional operators, each with a separate telescope, track the target, one for azimuth and one for elevation. Each sighting device has a data transmitter that measures angle or range and sends it to the computer. The computer receives these data and incorporates manual adjustments for wind velocity, wind direction, muzzle velocity, air density, and other factors. The computer calculates three variables: azimuth, elevation, and a setting for the fuze. The latter, manually set before loading, determines the time after firing at which the shell will explode. Shells are not intended to hit the target plane directly but rather to explode near it, scattering fragments to destroy it.The director performs two major calculations. First, pvediction models the motion of the target and extrapolates its position to some time in the future. Prediction corresponds to “leading” the target. Second, the ballistic calculation figures how to make the shell arrive at the desired point in space at the future time and explode, solving for the azimuth and elevation of the gun and the setting on the fuze. This calculation corresponds to the traditional artillery man‟s task of looking up data in a precalculated “firing table” and setting gun parameters accordingly. Ballistic calculation is simpler than prediction, so we will examine it first.The T-6 director solves the ballistic problem by directly mechanizing the traditional method, employing a “mechanical firing table.” Traditional firing tables printed on paper show solutions for a given angular height of the target, for a given horizontal range, and a number of other variables. The T-6 replaces the firing table with a Sperry ballistic cam.” A three-dimensionally machined cone shaped device, the ballistic cam or “pin follower” solves a pre-determined function. Two independent variables are input by the angular rotation of the cam and the longitudinal position of a pin that rests on top of the cam. As the pin moves up and down the length of the cam, and as the cam rotates, the height of the pin traces a function of two variables: the solution to the ballistics problem (or part of it). The T-6 director incorporates eight ballistic cams, each solving for a different component of the computation including superelevation, time of flight, wind correction, muzzle velocity. air density correction. Ballistic cams represented, in essence, the stored data of the mechanical computer. Later directors could be adapted to different guns simply by replacing the ballistic cams with a new set, machined according to different firing tables. The ballistic cams comprised a central component of Sperry‟s mechanical computing technology. The difficulty of their manufacture would prove a major limitation on the usefulness of Sperry directors.The T-6 director performed its other computational function, prediction, in an innovative way as well. Though the target came into the system in polar coordinates (azimuth, elevation, and range), targets usually flew a constant trajectory (it was assumed) in rectangular coordinates-i.e. straight andlevel. Thus, it was simpler to extrapolate to the future in rectangular coordinates than in the polar system. So the Sperry director projected the movement of the target onto a horizontal plane, derived the velocity from changes in position, added a fixed time multiplied by the velocity to determine a future position, and then converted the solution back into polar coordinates. This method became known as the “plan prediction method”because of the representation of the data on a flat “plan” as viewed from above; it was commonly used through World War II. In the plan prediction method, “the actual movement of the target is mechanically reproduced on a small scale within the Computer and the desired angles or speeds can be measured directly from the movements of these elements.”Together, the ballistic and prediction calculations form a feedback loop. Operators enter an estimated “time of flight” for the shell when they first begin tracking. The predictor uses this estimate to perform its initial calculation, which feeds into the ballistic stage. The output of the ballistics calculation then feeds back an updated time-of-flight estimate, which the predictor uses to refine the initial estimate. Thus “a cumulative cycle of correction brings the predicted future position of the target up to the point indicated by the actual future time of flight.”A square box about four feet on each side (see Fig. 2) the T-6 director was mounted on a pedestal on which it could rotate. Three crew would sit on seats and one or two would stand on a step mounted to the machine. The remainder of the crew stood on a fixed platform; they would have had to shuffle around as the unit rotated. This was probably not a problem, as the rotation angles were small. The direc tor‟s pedestal mounted on a trailer, on which data transmission cables and the range finder could be packed for transportation.We have seen that the T-6 computer took only three inputs, elevation, azimuth, and altitude (range), and yet it required nine operators. These nine did not include the operation of the range finder, which was considered a separate instrument, but only those operating the director itself. What did these nine men do?Human ServomechanismsTo the designers of the director, the operato rs functioned as “manual servomechanisms.”One specification for the machine required “minimum dependence on …human element.‟ The Sperry Company explained, “All operations must be made as mechanical and foolproof as possible; training requirements must visualize the conditions existent under rapid mobilization.” The lessons of World War I ring in this statement; even at the height of isolationism, with the country sliding into depression, design engineers understood the difficulty of raising large numbers of trained personnel in a national emergency. The designers not only thought the system should account for minimal training and high personnel turnover, they also considered the ability of operators to perform their duties under the stress of battle. Thus, nearly all the work for the crew was in a “follow-the-pointer”mode: each man concentrated on an instrument with two indicating dials, one the actual and one the desired value for a particular parameter. With a hand crank, he adjusted the parameter to match the two dials.Still, it seems curious that the T-6 director required so many men to perform this follow-the-pointer input. When the external rangefinder transmitted its data to the computer, it appeared on a dial and an operator had to follow the pointer to actually input the data into the computing mechanism. The machine did not explicitly calculate velocities. Rather, two operators (one for X and one for Y) adjusted variable-speed drives until their rate dials matched that of a constant-speed motor. When the prediction computation was complete, an operator had to feed the result into the ballistic calculation mechanism. Finally, when the entire calculation cycle was completed, another operator had to follow the pointer to transmit azimuth to the gun crew, who in turn had to match the train and elevation of the gun to the pointer indications.Human operators were the means of connecting “individual elements” into an integrated system. In one sense the men were impedance amplifiers, and hence quite similar to servomechanisms in other mechanical calculators of the time, especially Vannevar Bush‟s differential analyzer .The term “manual servomechanism”itself is an oxymoron: by the conventional definition, all servomechanisms are automatic. The very use of the term acknowledges the existence of an automatic technology that will eventually replace the manual method. With the T-6, this process was already underway. Though the director required nine operators, it had already eliminated two from the previous generation T-4. Servos replaced the operator who fed back superelevation data and the one who transmitted the fuze setting. Furthermore, in this early machine one man corresponded to one variable, and the machine‟s requirement for operators corresponded directly to the data flow of its computation. Thus the crew that operated the T-6 director was an exact reflection of the algorithm inside it.Why, then, were only two of the variables automated? This partial, almost hesitating automation indicates there was more to the human servo-motors than Sperry wanted to acknowledge. As much as the company touted “their duties are purely mechanical and little skill or judgment is required on the part of the operators,” men were still required to exercise some judgment, even if unconsciously. The data were noisy, and even an unskilled human eye could eliminate complications due to erroneous or corrupted data. The mechanisms themselves were rather delicate and erroneous input data, especially if it indicated conditions that were not physically possible, could lock up or damage the mechanisms. Theoperators performed as integrators in both senses of the term: they integrated different elements into a system.Later Sperry DirectorsWhen Elmer Sperry died in 1930, his engineers were at work on a newer generation director, the T-8. This machine was intended to be lighter and more portable than earlier models, as well as less expensive and “procurable in quantities in case of emergency.” The company still emphasized the need for unskilled men to operate the system in wartime, and their role as system integrators. The operators were “mechanical links in the apparatus, thereby making it possible to avoid mechanical complication which would be involved by the use of electrical or mechanical servo motors.” Still, army field experience with the T-6 had shown that servo-motors were a viable way to reduce the number of operators and improve reliability, so the requirements for the T-8 specified that wherever possible “electrical shall be used to reduce the number of operators to a minimum.” Thus the T-8 continued the process of automating fire control, and reduced the number of operators to four. Two men followed the target with telescopes, and only two were required for follow-the-pointer functions. The other follow-the-pointers had been replaced by follow-up servos fitted with magnetic brakes to eliminate hunting. Several experimental versions of the T-8 were built, and it was standardized by the Army as the M3 in 1934.Throughout the remain der of the …30s Sperry and the army fine-tuned the director system in the M3. Succeeding M3 models automated further, replacing the follow-the-pointers for target velocity with a velocity follow-up which employed a ball-and-disc integrator. The M4 series, standardized in 1939, was similar to the M3 but abandoned the constant altitude assumption and added an altitude predictor for gliding targets. The M7, standardized in 1941, was essentially similar to the M4 but added full power control to the guns for automatic pointing in elevation and azimuth. These later systems had eliminated errors. Automatic setters and loaders did not improve the situation because of reliability problems. At the start of World War II, the M7 was the primary anti-aircraft director available to the army.The M7 was a highly developed and integrated system, optimized for reliability and ease of operation and maintenance. As a mechanical computer, it was an elegant, if intricate, device, weighing 850 pounds and including about 11,000 parts. The design of the M7 capitalized on the strength of the Sperry Company: manufacturing of precision mechanisms, especially ballistic cams. By the time the U.S. entered the second world war, however, these capabilities were a scarce resource, especially for high volumes. Production of the M7 by Sperry and Ford Motor Company as subcontractor was a “real choke” and could not keep up with production of the 90mm guns, well into 1942. The army had also adopted an English system, known as the “Kerrison Director” or M5, which was less accurate than the M7 but easier to manufacture. Sperry redesigned the M5 for high-volume production in 1940, but passed in 1941.Conclusion: Human Beings as System IntegratorsThe Sperry directors we have examined here were transitional, experimental systems. Exactly for that reason, however, they allow us to peer inside the process of automation, to examine the displacement of human operators by servomechanisms while the process was still underway. Skilled asthe Sperry Company was at data transmission, it only gradually became comfortable with the automatic communication of data between subsystems. Sperry could brag about the low skill levels required of the operators of the machine, but in 1930 it was unwilling to remove them completely from the process. Men were the glue that held integrated systems together.As products, the Sperry Company‟s anti-aircraft gun directors were only partially successful. Still, we should judge a technological development program not only by the machines it produces but also by the knowledge it creates, and by how that knowledge contributes to future advances. Sperry‟s anti-aircraft directors of the 1930s were early examples of distributed control systems, technology that would assume critical importance in the following decades with the development of radar and digital computers. When building the more complex systems of later years, engineers at Bell Labs, MIT, and elsewhere would incorporate and build on the Sperry Company‟s experience,grappling with the engineering difficulties of feedback, control, and the augmentation of human capabilities by technological systems.在斯佩里防空炮火控和集成系统的发展电气时代的到来带来了新类型的控制系统。

毕业设计外文文献翻译

毕业设计外文文献翻译Graduation design of foreign literature translation 700 words Title: The Impact of Artificial Intelligence on the Job Market Abstract:With the rapid development of artificial intelligence (AI), concerns arise about its impact on the job market. This paper explores the potential effects of AI on various industries, including healthcare, manufacturing, and transportation, and the implications for employment. The findings suggest that while AI has the potential to automate repetitive tasks and increase productivity, it may also lead to job displacement and a shift in job requirements. The paper concludes with a discussion on the importance of upskilling and retraining for workers to adapt to the changing job market.1. IntroductionArtificial intelligence (AI) refers to the development of computer systems that can perform tasks that typically require human intelligence. AI has made significant advancements in recent years, with applications in various industries, such as healthcare, manufacturing, and transportation. As AI technology continues to evolve, concerns arise about its impact on the job market. This paper aims to explore the potential effects of AI on employment and discuss the implications for workers.2. Potential Effects of AI on the Job Market2.1 Automation of Repetitive TasksOne of the major impacts of AI on the job market is the automation of repetitive tasks. AI systems can perform tasks faster and moreaccurately than humans, particularly in industries that involve routine and predictable tasks, such as manufacturing and data entry. This automation has the potential to increase productivity and efficiency, but also poses a risk to jobs that can be easily replicated by AI.2.2 Job DisplacementAnother potential effect of AI on the job market is job displacement. As AI systems become more sophisticated and capable of performing complex tasks, there is a possibility that workers may be replaced by machines. This is particularly evident in industries such as transportation, where autonomous vehicles may replace human drivers, and customer service, where chatbots can handle customer inquiries. While job displacement may lead to short-term unemployment, it also creates opportunities for new jobs in industries related to AI.2.3 Shifting Job RequirementsWith the introduction of AI, job requirements are expected to shift. While AI may automate certain tasks, it also creates a demand for workers with the knowledge and skills to develop and maintain AI systems. This shift in job requirements may require workers to adapt and learn new skills to remain competitive in the job market.3. Implications for EmploymentThe impact of AI on employment is complex and multifaceted. On one hand, AI has the potential to increase productivity, create new jobs, and improve overall economic growth. On the other hand, it may lead to job displacement and a shift in job requirements. To mitigate the negative effects of AI on employment, it is essentialfor workers to upskill and retrain themselves to meet the changing demands of the job market.4. ConclusionIn conclusion, the rapid development of AI has significant implications for the job market. While AI has the potential to automate repetitive tasks and increase productivity, it may also lead to job displacement and a shift in job requirements. To adapt to the changing job market, workers should focus on upskilling and continuous learning to remain competitive. Overall, the impact of AI on employment will depend on how it is integrated into various industries and how workers and policymakers respond to these changes.。

(完整版)_毕业设计(论文)外文翻译_(原文)

毕业设计（论文）——外文翻译（原文）NEW APPLICATION OF DATABASERelational databases in use for over two decades. A large portion of the applications of relational databases in the commercial world, supporting such tasks as transaction processing for banks and stock exchanges, sales and reservations for a variety of businesses, and inventory and payroll for almost of all companies. We study several new applications, which recent years.First. Decision-support systemAs the online availability of data , businesses to exploit the available data to make better decisions about increase sales. We can extract much information for decision support by using simple SQL queries. Recently support based on data analysis and data mining, or knowledge discovery, using data from a variety of sources.Database applications can be broadly classified into transaction processing and decision support. Transaction-processing systems are widely used today, and companies generated by these systems.The term data mining refers loosely to finding relevant information, or “discovering knowledge,” from a large volume of data. Like knowledge discovery in artificial intelligence, data mining attempts to discover statistical rules and patterns automatically from data. However, data mining differs from machine learning in that it deals with large volumes of data, stored primarily on disk.Knowledge discovered from a database can be represented by a set of rules. We can discover rules from database using one of two models:In the first model, the user is involved directly in the process of knowledge discovery.In the second model, the system is responsible for automatically discovering knowledgefrom the database, by detecting patterns and correlations in the data.Work on automatic discovery of rules influenced strongly by work in the artificial-intelligence community on machine learning. The main differences lie in the volume of data databases, and in the need to access disk. Specialized data-mining algorithms developed to which rules are discovered depends on the class of data-mining application. We illustrate rule discovery using two application classes: classification and associations.Second. Spatial and Geographic DatabasesSpatial databases store information related to spatial locations, and provide support for efficient querying and indexing based on spatial locations. Two types of spatial databases are particularly important:Design databases, or computer-aided-design (CAD) databases, are spatial databases used to store design information about databases are integrated-circuit and electronic-device layouts.Geographic databases are spatial databases used to store geographic information, such as maps. Geographic databases are often called geographic information systems.Geographic data are spatial in nature, but differ from design data in certain ways. Maps and satellite images are typical examples of geographic data. Maps may provide not only location information -such as boundaries, rivers and roads---but also much more detailed information associated with locations, such as elevation, soil type, land usage, and annual rainfall.Geographic data can be categorized into two types: raster data (such data consist a bit maps or pixel maps, in two or more dimensions.), vector data (vector data are constructed from basic geographic objects). Map data are often represented in vector format.Third. Multimedia DatabasesRecently, there much interest in databases that store multimedia data, such as images, audio, and video. Today multimedia data typically are stored outside the database, in files systems. When the number of multimedia objects is relatively small, features provided by databases are usually not important. Database functionality becomes important when the number of multimedia objects stored is large. Issues such as transactional updates, querying facilities, and indexing then become important. Multimedia objects often they were created, who created them, and to what category they belong. One approach to building a database for such multimedia objects is to use database for storing the descriptive attributes, and for keeping track of the files in which the multimedia objects are stored.However, storing multimedia outside the database makes it the basis of actual multimedia data content. It can also lead to inconsistencies, such a file that is noted in the database, but whose contents are missing, or vice versa. It is therefore desirable to store the data themselves in the database.Forth. Mobility and Personal DatabasesLarge-scale commercial databases stored in central computing facilities. In the case of distributed database applications, there strong central database and network administration. Two technology trends which this assumption of central control and administration is not entirely correct:1.The increasingly widespread use of personal computers, and, more important, of laptop or “notebook” computers.2.The development of a relatively low-cost wireless digital communication infrastructure, base on wireless local-area networks, cellular digital packet networks, and other technologies.Wireless computing creates a situation where machines no longer at which to materialize the result of a query. In some cases, the location of the user is a parameter of the query. A example is a traveler’s information system that provides data on the current route must be processed based on knowledge of the user’s location, direction of motion, and speed.Energy (battery power) is a scarce resource for mobile computers. This limitation influences many aspects of system design. Among the more interesting consequences of the need for energy efficiency is the use of scheduled data broadcasts to reduce the need for mobile system to transmit queries. Increasingly amounts of data may reside on machines administered by users, rather than by database administrators. Furthermore, these machines may, at times, be disconnected from the network.SummaryDecision-support systems are gaining importance, as companies realize the value of the on-line data collected by their on-line transaction-processing systems. Proposed extensions to SQL, such as the cube operation, of summary data. Data mining seeks to discover knowledge automatically, in the form of statistical rules and patterns from large databases. Data visualization systems data as well as geographic data. Design data are stored primarily as vector data; geographic data consist of a combination of vector and raster data.Multimedia databases are growing in importance. Issues such as similarity-based retrieval and delivery of data at guaranteed rates are topics of current research.Mobile computing systems , leading to interest in database systems that can run on such systems. Query processing in such systems may involve lookups on server database.毕业设计（论文）——外文翻译（译文）数据库的新应用我们使用关系数据库已经有20多年了，关系数据库应用中有很大一部分都用于商业领域支持诸如银行和证券交易所的事务处理、各种业务的销售和预约，以及几乎所有公司都需要的财产目录和工资单管理。

毕业设计外文翻译原文

Int J Adv Manuf Technol (2014) 72:277–288DOI 10.1007/s00170-014-5664-3Workpiece roundness profile in the frequency domain: an application in cylindrical plunge grindingAndre D. L. Batako & Siew Y. GohReceived: 21 August 2013 / Accepted: 21 January 2014 / Published online: 14 February 2014# Springer-Verlag London 2014Abstract In grinding, most control strategies are based on the spindle power measurement, but recently, acoustic emission has been widely used for wheel wear and gap elimination. This paper explores a potential use of acoustic emission (AE) to detect workpiece lobes. This was achieved by sectioning and analysing the AE signal in the frequency domain. For the first time, the profile of the ground workpiece was predicted mathematically using key frequencies extracted from the AE signals. The results were validated against actual workpiece profile measurements. The relative shift of the wave formed on the surface of the part was expressed using the wheel- workpiece frequency ratio. A comparative study showed that the workpiece roundness profile could be monitored in the frequency domain using the AE signal during grinding. Keywords Plunge grinding . Roundness . Waviness . Frequency . Acoustic emission1IntroductionGrinding is mostly used as the last stage of a manufacturing process for fine finishing. However, recently, high efficiency deep grinding (HEDG) was introduced as a process that achieves high material removal rates exceeding 1,100 mm3/ mm/s [1–5]. Grinding is mainly used to achieve high dimen- sional and geometrical accuracy. However, in cylindrical plunge grinding, vibration is a key problem in keeping tight tolerances and form accuracy (roundness) of ground parts.Machine tools are designed and installed to have minimum vibration (with anti-vibration pad when required). Neverthe- less, in grinding, the interaction between the wheel and the workpiece generates persistent vibration. This leads to varia- tion of the forces acting in the contact zone, which in turn causes a variation in the depth of cut on the ground workpiece. Consequently, this creates waviness on the circumference of the workpiece. The engendered uneven profile on the work- piece surface leads to a modulation of the grinding conditions of the following successive rotations; this is called workpiece regenerative effect. The building up of this effect can take place in grinding cycles with longer duration. Similar effects occur on the grinding wheel surface; however, the process of the build up is slow [6–9].It is generally difficult to get a grinding wheel perfectly balanced manually, which is acceptable for general purpose grinding. For precision grinding, automatic dynamic wheel balancing devices are used. Though current grinding ma- chines have automatic balancing systems to reduce the out- of-balance of grinding wheels, in actual grinding, forced vi- bration is still caused by the dynamically unbalanced grinding wheels [10]. This is because any eccentricity in the rotating grinding wheel generates a vibratory motion.The stiffness of the wheel spindle and the tailstock also affects the wheel-workpiece-tailstock subsystem, which oscil- lates due to the interaction of the wheel with the workpiece. In practice, the generated force vibration is hard to eliminate completely. This type of vibration has greater influence on the formation of the workpiece profile. During the grinding process, the out-of-balance of the wheel behaves as a sinusoi- dal waveform that is i mprinted on t he workpiece s urface. T his, as in a previous case, leads to the variation of depth of cut andA.D.L.Ba t ako(*):S.Y.GohAMTReL, The General Engineering Research Institute, Liverpool John Moores University (LJMU), Byrom Street, Liverpool L3 3AF, UKe-mail: a.d.batako@ creates low-frequency lobes around the workpiece, and this is the key target of the study presented here.Other factors such as grinding parameters have to be taken into consideration in the study of grinding vibration becausethese aspects affect the stability of the process. This is because the resulting workpiece profile is the combined effect of different type of vibration in grinding [7, 11]. The studies carried out by Inasaki, Tonou and Yonetsu showed that the grinding parameters have a strong influence on the amplitude and growth rate of the workpiece and wheel regenerative vibration [12].The actual measurement of the workpiece profile is an integral part of the manufacturing process due to the uncertain-ty in wheel wear and the complexity of the grinding process. Contactless measurement and contact stylus systems were developed to record the variations of the workpiece size and roundness. However, these techniques can be used as post-process checking as it is limited to a particular set-up and must be used without the disturbance of the cutting fluid in a clean air-conditioned environment with stable t emperature [13–16].In the industry, random samples from batches are usually inspected after the grinding process. Any rejection of parts or sometimes batches increases the manufacturing time and cost. Therefore, it becomes important to develop online monitoring systems to cut down inspection time and to minimise rejected parts in grinding. Some of the existing monitoring systems in grinding are based on the wheel spindle power. However, sen-sors such as acoustic emission and accelerometers are also used to gather information of the grinding process for different appli-cation. Dornfeld has given a comprehensive view of the appli-cation of acoustic emission (AE) sensors in manufacturing [17]. Most reported applications of AE in grinding are for gap elim-ination, touch dressing and thermal burn detection [18–21].In cylindrical grinding processes, the generated chatter vibration causes the loss of form and dimensional accuracy of ground workpieces. The effect of vibration induces the formation of lobes on the workpiece surface, which are usu- ally detected using roundness measurement equipment. High- precision parts with tight tolerance are increasingly in demand and short cycle times put pressure on manufacturing process- es. This leads to the need for developing in-process roundness monitoring systems for cylindrical grinding processes.The potential of using acoustic emission to detect the formation of lobes on a workpiece during a cylindrical plunge grinding process is investigated in this work. The aim is to extract the workpiece roundness profile from the acoustic emission signal in the frequency domain. The extracted fre- quencies are compared with actual measurement in frequency domain, i.e. harmonic components. T he key frequencies o f the harmonic content are used to predict the expected profile on the ground p art.2The study of acoustic emission plunge grindingAE is an elastic wave that is generated when the workpiece is under the loading action of the cutting grits due to the interfacial and internal frictional and structural modification. The wave generated is transmitted from the contact zone through the components of the machine structure [22, 23]. In grinding processes, the main source of the AE signal is the mechanical stress applied by the wheel on the workpiece in the grinding zone [24]. The chipping action of the abrasive grits on the workpiece surface generates a multitude of acous- tic waves, which are transmitted to the sensor through the centres and the tailstock of machine. The machining condition is reflected in the signal through the magnitude of the acoustic emission, which varies with the intensity of the cutting, e.g. rough, medium or fine grinding. The key information of the machining process and its condition is buried in the AE signal. To extract any information of interest from the AE signals, it is important to identify the frequency bandwidth and study the signal in details.Susic and Grabec showed that intensive changes of AE signal relate to the grinding condition, thus the ground surface roughness could be estimated based on the measured signal with a profile correlation function [25]. A strong chatter vibration in grinding is also reflected in the recorded RMS AE signal. As vibration could generate the waviness on the workpiece, hence, the AE signal was also used to study the roundness profile [26]. A comprehensive study of the chatter vibration, wheel surface and workpiece quality in cylindrical plunge grinding based on the AE signal was carried out recently [27].In roundness measurement systems, the roundness of the part is also given as harmonic components. Generally, the frequency span given by the measurement machine is of low frequency—500 Hz and below. This is because the roundness profile deals with the waviness but not with the surface roughness that is always of higher frequency. Fricker [8] and Li and Shin [28] also indicated parts profile of frequency below 300 Hz. Part roundness profile is expressed in undula- tion per revolution. Therefore, lower frequency components are mainly targeted by t he measurement equipment, b ut higher frequency components tends to ride on top of lower carriers. In most cases, the provided frequency profile is in the range of 300 Hz [8, 28]. Therefore, this work studies the AE signal along the grinding process using the fast Fourier transform (FFT) with a particular focus on frequencies below 300 Hz. This allowed for a direct comparison between the results from this investigation and the actual roundness measurements.Figure 1 illustrates the equipment used in this study, where (a) is the configuration of the grinding machine with the location of the sensors and (b) is the roundness measurement machine. To improve signal transmission, the coating of the tailstock was removed from the location of the sensors as shown in this figure.During this study, observations of the shape of the recorded AE and the signal of spindle power indicated that there are three main phases in a typical cylindrical plunge grindingFig. 1 Experimental equipment: a grinding machine and sensors config- uration, b Talyrond 210 roundness measurement systemcycle, i.e. before grinding, actual grinding and dwell. In this work, the words ―dwell‖and ―dwelling‖are used to describe the ―spark out‖phase where the infeed stops and the grinding wheel enters a dwelling stage. For short notation, ―dwell‖is used in most figures.First phase (before grinding): at the beginning of the process, the grinding wheel approaches the workpiece in a fast infeed without any physical contact between the wheel and the workpiece.Second phase (actual grinding): when the grinding wheel gets very close to the workpiece, the rapid feed changes to the programmed infeed value then the grinding wheel gradually gets into contact with the workpiece. The phase starts with the first contact of the wheel with the part and runs until the targeted diameter is reached.Third phase (dwell or spark out): when the target diam- eter is reached, the infeed stops and the wheel stays in contact with the part. The duration of the dwelling pro- cess varies depending on the grinding conditions and is intended to remove the leftover material on the part due to mechanical and thermal deflection and to reduce the outof roundness. The grinding wheel retracts from the work- piece at the end of the programmed spark out (dwell).In this study, the power and AE signals were recorded simultaneously; however, the acceleration of the tailstock was also recorded for further investigation. The recorded signals are illustrated in Fig. 2 with a delimitation of the three phases.In addition, the actual grinding phase was subdivided to introduce the notion of ―grinding-in‖, ―steady grinding‖and ―pre-dwell‖ as depicted in Fig. 3. The steady grinding ends with a pre-dwell period. There is a transition state between the grinding in and the steady grinding states; this is where the cutting process starts entering the steady state. This is illus- trated by an ellipse in Fig. 2. During the grinding-in, the depth of cut increases from zero to a constant value per revolution, then the steady-state grinding runs under a constant depth of cut. The pre-dwell section is not an obvious technological phase, rather it is a tool used in this study.To aid the signal processing techniques, especially the fast Fourier transform and Yule Walker methods, a referenced sampling was introduced using an RPM pickup (see work- piece rotation in Fig. 3). Recording the workpiece rotation simultaneously with the AE signal helped portioning the signal to reduce processing time and to study time-varying process in the grinding.3Simulation and modellingWorkpiece responseIn this investigation, it was necessary to filter out from the recorded signals the frequencies of other parts of the grinding machine, especially the natural frequency of the workpiece. Fig. 2 Recorded power and acoustic emission signals with process phasesφ ¼ δ.2π.βð2ÞConsequently, the dynamics of the waviness Ω formed with time t at the surface of the part can be expressed as follows: Ω ¼ sin ðωt þ φÞð3ÞTherefore, the equation of the wave generated by the wheel at the surface of the workpiece was derived as follows:. Ω ¼ sin ωt þ 2πδ.βð4Þ3.3 Simulation of the workpiece profileFig. 3 Typical AE signal for one full grinding cycle with RPM outputTherefore, the workpiece response was studied using finite element analysis (FEA) and an experimental impact test to identify its natural frequency. The result of this study is depicted in Fig. 4, where it is seen that the natural frequency of the workpiece is 1,252 Hz. The outputs of the impact test and the FEA are in good agreement and show that the natural frequency of the workpiece is over 1 kHz; consequently, it will not appear in the range of low frequencies of interest.Process modellingDesignating the wheel rotational frequency by fs and the workpiece rotational frequency by fw , the ratio of these two entities was expressed as follows: β ¼ f s = f wð1ÞThe notion of frequency ratio (β) helps understanding the generation of the workpiece profile as it relates key process During the roundness measurement process, the machine uses a single trace of the stylus on the workpiece circumference to generate the profile of the workpiece. Here, the stylus is in direct contact with the measured part.However, in this study, an attempt is made for the first time to predict the final workpiece profile using process signatures extracted from the recorded signals. The link between the prediction model and the grinding process is the sensor, which collects the signal from the entire process. Therefore, the model predicts an average workpiece profile in contrary to measuring machine which gives only a single trace on the part. The procedure of capturing and extracting process sig- nature is schematically illustrated in Fig. 5.The procedure works as follows: throughout the grinding process, the acoustic emission, vibration and RPM sensor record the signals. The signals are processed using various techniques (e.g. FFT) to obtain the system response in the frequency domain. The model extracts process-inherent key dominant frequencies, and uses these frequencies and their respective amplitudes to generate the expected profile of the workpiece.The following expression in Eq. (5) is used to predict the final profile of the ground part. parameters and defines the fundamental harmonic, which naffects the part profile. In this study, it was found that the wheel-workpiece frequency ratio has a direct effect on the ∏ ¼ X i ¼1 ½αi cos ð2π t f i Þ] þ rand ðt Þ ð5Þ workpiece roundness as it constitutes the fundamental har- monic for this specific machining configuration.During the grinding process, there is a relative lag between the grinding wheel and the workpiece due to the difference in their rotational frequencies. This difference (δ) is numerically equal to the decimal part of the frequency ratio. This causes the currently forming wave to creep, with reference to the wave formed in the previous revolution of the part. By ex- pressing the wheel angular speed as ω, and the decimal part of the frequency ratio in Eq. 1 as δ, the relative shift φ of the wave on the workpiece surface was defined as follows: Where f i is the i th dominant frequency with an amplitude ofαi , and t is the time. rand (t ) is the added random noise to incorporate the randomness of grits cutting actions.4 Experimental workIn this investigation, the response of the machine tool was studied at different stages, namely idle, running by switching its components one by one and recording the signal from oneFig. 4 Workpiece response: a experiment and b FEAsingle location, and finally in operation conditions while grinding. This allowed identifying and discriminating fre- quency components belonging to the machine tools structure and those frequencies induced by noise and interference from nearby operating machineries.An analogue to digital (A/D) converter (NI 6110) was used to record the analogue signals from the power of the motor, the acceleration and the acoustic emission sensors through the tailstock. This A/D device had four channels with a sampling rate up to 5 MS/s per channel, providing a total sampling rate of 20 MS/s. This device allowed for a simultaneous four-channel sampling of analogue inputs voltage in the range of ±5 mV to42 V. The LabView software was used to control the data acquisition process during the experiments. To iden- tify the most suitable sampling, the signals were recorded at various sampling rates. The recorded signal was proc- essed using MATLAB.Sets of workpiece batches were ground using rough, medium and fine infeed. The grinding wheel speed was 35 m/s, and the workpiece was rotating at 100 rpm. In this experiment, a dwell or spark out of 10 s was applied to all grinding cycles. In total, 220 μm of material was removed from each part.The ground parts were allowed to settle down for 24 h at 19±1 °C in a temperature controlled room before the measure- ments were taken. The roundness profile of the ground parts were measured using a Talyrond 210 illustrated in Fig. 1. AFig. 5 Modelling pseudo- algorithmtypical measured workpiece roundness is illustrated in Fig. 6, where (a) is the roundness profile and (b) is the corresponding linear profile obtained by dissecting the round profile and expanding it in a line.5ResultsIn this work, various signal processing techniques were used to study the recorded signals as described above. In order to extract t he i nformation o f t he workpiece r oundness p rofile, t he acoustic emission signal was scrutinised using the above- mentioned partitioning technique. Each portion of the signal was analysed using the FFT and Yule Walker (YW) methods. However, short-time Fourier transform (STFT) and the continuous wavelet transform (CWT) were able to handle full grinding cycle signals.Figures 7 and 8 illustrate a typical power spectrum using the STFT and CWT of a full grinding cycle. Similar outputs were obtained with the FFT and YW methods; however, these last two methods required signal partitioning due to the com- putational window s ize.Figure 8 illustrates the three phases of a grinding cycle, where the frequency spectrum is given with time span along the grinding cycle. It is seen in this picture as in Fig. 7 that process-inherent f requencies a ppeared o nly d uring t he ―actual grinding‖ phase and partially in the ―dwell or spark out‖ period. Comparing STFT and CWT, it is observed that the STFT (Fig. 7) provided an aggregate frequency spectrum, when the CWT resolved each individual frequency (Fig. 8). This improved resolution allows identifying the birth of lobesFig. 6 Typical workpiece roundness measurement using Talyrond 210: a roundness profile, b corresponding linear profilein time within the grinding cycle. It opens an opportunity in studying the workpiece profile in the frequency domain. It is seen in both figures that the parasitic 50 Hz can be well discriminated f rom t he p rocess f requency. V arious f requencies up to 500 Hz that characterise the workpiece prolife are picked up in the actual grinding phase. Frequencies that dominate the spectrum towards the end of the actual grinding will poten- tially form and reside on the final part profile.Figure 9 presents the results of AE, where the sectioned signal was analysed in the frequency domain using FFT toextract the frequencies of interest. This picture displays a waterfall plot of the frequency spectrum in each phase of the grinding cycle. This study focused on the detection of process - inherent frequencies, with less attention to the actual value of the magnitude as it is subject of another investigation. It is observed in the ―before grinding ‖ section of the signal that nothing happens in the frequency domain; hence, no frequen- cy peaks were detected. In the ―grinding -in ‖ section, once the wheel hits the workpiece, several frequency peaks appear in the signal, characterising special events in the grindingFig. 7 Full grinding cycle AE signal frequency spectrum using STFTFig. 8 Full grinding cycle AE signal frequency spectrum using CWTFig. 9 Waterfall plot offrequency spectrum of a full grinding cycleprocess. The amplitudes of these frequencies increase as the process evolves into ―actual grinding ‖ due to the cutting intensity and diminish towards the end of the grinding cycle (spark out ). In this figure, the transition between the grinding phases can be observed from the variations in the frequencies and their amplitudes along the progression of the process. During the actual grinding, due to the generated vibration and the increase of the material removal, high peaks were detected. Less frequency components and small amplitude in the dwell period is due to reduced grains activities because there is no actual infeed of the wheel and the workpiece enters a relaxation stage while the wheel removes only leftover material c aused b y wheel/workpiece d eflection. Comparing the detected frequencies in the AE signal with the off-line measurement, it was identified that there is a factor of 0.6 between the two set of results in this particular test. This factor varies depending on machining configuration. Using this factor, all the detected harmonics from the frequency analysis were correlated to those from roundness measure- ment. Figure 12 gives a sample of comparative results for fine infeed grinding, showing the detected frequencies and their corresponding measured harmonics.For example, multiplying the frequency 54 in Fig. 10 (fre- quency analysis) by this factor (0.6) provides the value 32.4 (33), which is the harmonic detected by the measurement machine in Fig. 11. It is seen that the major lobes (33) formedFig. 10 Frequency content of the signal in dwell phase (fine infeed))Fig. 11 Harmonic profile from the actual measurement (fine infeed)Fig. 12 Extracted harmonics and measured values (fine infeed)on the ground workpiece in Fig. 12 as well as the other components, i.e. 48, 82, 115 and 148, were clearly detected in the AE signal as 78, 136,190 and 248 Hz.It is worth mentioning that the actual magnitude of the power spectrum of detected frequencies is not in the scope of the work presented here. This is because this work focused on the detection of process-inherent frequencies in order to develop a control strategy to improve the round- ness of the part. The control strategy and the actual magni- tude are considered in the next phase, where the system will be calibrated.The study of the frequencies in fine infeed showed that during the dwelling period (spark out), the amplitude of the detected harmonics decreases drastically. It is observed that in spark out (dwell), the amplitude of 243 Hz which was dom- inating throughout the cycle dropped and led to 54 Hz to become the dominate in the last phase in Fig. 10. This section carries important information of the final workpiece profile. The number of lobes formed on the workpiece is now defined as a product of the extracted frequencies with the defined factor. This holds true for any frequency detected and for given machining parameters configuration. The factor of 0.6 given here is adequate for this specific experimental set up used in these particular tests. However, it was identified that this factor varies as a function of process settings. The origin of this factor was identified but not stated here, as it is commercially viable for the companies pursuing further de- velopment of this work.This study confirmed that the final profile of the work- piece is the result of overlapping waves of different fre- quencies as an additive process. This is schematically illus- trated in Fig. 13. In addition, these waves have a relative translation with reference to each other due to a shifting effect caused by the relative creep of the grinding wheel with reference to the rotating workpiece as described in Eqs. (2–4). It is worthwhile stating that this work does not study the roughness which is characterised by high frequen- cy; however, it focused on the formation of lobes which are of lower frequency.This is evidenced in Fig. 14 for rough infeed grinding, where the AE signal was analysed per workpiece revo- lution in the actual steady -state grinding. This figureFig. 13 Additive effect of key harmonics forming a profile on a workpieceFig. 14 Process frequency content in steady-state grinding with rough infeedshows how different frequencies appear or disappear from revolution to revolution due to the shifting and overlapping effect. Also, the amplitude of these frequen- cies varies along the process. However, in fine infeed, it was observed that the process is dominated by two high peaks of 54 and 243 Hz (second and ninth harmonic in Fig. 12), which appeared throughout the full grinding cycle.Using the wave additive property and applying Eq. (5) allowed predicting the expected workpiece profile using the information extracted from the signal in the frequency domain. One of the examples is shown in Fig. 15 in a form of linear profile, which is obtained by dissecting the circu- lar profile and extending it along a line of 360°. The measurement machine chooses an arbitrary point and dis- sects the profile. Here, Fig. 15a is a linear roundness profile of the workpiece obtained from the actual round- ness measurement system, and Fig. 15b is the predicted (simulated) workpiece profile using the frequency compo- nents extracted from the AE signal. The point where the measuring machine cuts the profile and sets the origin of the axis 0.0°is unknown to the machine operator; there- fore, the results in Fig. 15a are shifted relative to Fig. 15b by an unknown value. However, there is a good agreement between these two profiles in terms of the surface undula- tion per revolution. This prediction will be used in the control strategy to improve the part profile well before the process enters the spark out phase.a)Simulate signal54321 0 -1-2-3-4 050 100 150200 250 300 350DegreeFig. 15 Linear workpiece profile: (a) actual measurement; (b) predicted (simulated ) profile6 DiscussionThe results show that the detected major dominant frequency in the AE signal is of importance because it indicates the number of major lobes formed on the workpiece. The other frequency components represent the small peaks on the work- piece surface. Actual workpiece measurements supported this finding. The extracted information of workpiece profile using the techniques presented here provides the room for the de- velopment of a control strategy to improve the workpiece roundness.This study showed that the formation of the workpiece profile is a function of the process parameters where the wheel and the workpiece play the key role. This is because at high rotating speeds, a slight unbalance of the wheel leads to high eccentric force, hence uneven stock removal. This is magni- fied by the effect of regular or irregular imprints on the workpiece surface. The shifting of the wheel relative to the workpiece leads to the generation of various waves on the workpiece. It was observed in fine infeed that the machining conditions are relatively stable; therefore, there were no drastic changes in the AE signal in terms of frequencies and amplitudes. However, in rough infeed with increased depth of cut and longer contact length, there is a tendency to have vibrations at high amplitude. This leads to radical changes in the cutting intensity at a regular pattern and at the pace of the fundamental frequency. An example is observed in Fig. 14 where certain frequencies appear constantly in the last three rotations (see sixth, seventh and eight rotations). If there is no shift between successive rotations, the matching of dominant frequenciesmay cause a beating effect as the wheel and the workpiece would make their contacts at the same points. Consequently, the formed lobes would become more apparent around the workpiece. An example of the beating effect is seen in the AE signal in Fig. 3 where the amplitude of the signal is modulated.Low infeed rate has a small depth of cut, short contact length and provides an increased number of lobes. However, the opposite is true in high infeed rate, where a small number of lobes is generated with higher amplitude. The higher the number of lobes, the smaller the interval between the lobes and the smoother is the profile formed. Thus, the workpiece produced using the rough infeed has higher peak with lower number of lobes, while with the fine infeed, the number of lobes is higher and the peaks are of small heights.7 Conclusions This paper provides some key relations between the process and the acoustic sounds emitted during machining. Process- inherent frequencies were successfully extracted from the AE signal and compared with the information of the measured workpiece profile. The obtained results were verified using data from the actual roundness measurement. A range of grinding parameters was covered and the outcomes correlated well with the measurements. A fundamental frequency ratio was established. A mathematical expression was derived to predict the expected profile of the machined part. The rela- tionship between the frequencies buried in the AE and those A m p l i t u d eb)。

毕业设计外文翻译英文翻译英文原稿

Harmonic source identification and current separationin distribution systemsYong Zhao a，b，Jianhua Li a，Daozhi Xia a,*a Department of Electrical Engineering Xi’an Jiaotong University, 28 West Xianning Road, Xi’an, Shaanxi 710049, Chinab Fujian Electric Power Dispatch and Telecommunication Center, 264 Wusi Road, Fuzhou, Fujian, 350003, China AbstractTo effectively diminish harmonic distortions, the locations of harmonic sources have to be identified and their currents have to be separated from that absorbed by conventional linear loads connected to the same CCP. In this paper, based on the intrinsic difference between linear and nonlinear loads in their V –I characteristics and by utilizing a new simplified harmonic source model, a new principle for harmonic source identification and harmonic current separation is proposed. By using this method, not only the existence of harmonic source can be determined, but also the contributions of the harmonic source and the linear loads to harmonic voltage distortion can be distinguished. The detailed procedure based on least squares approximation is given. The effectiveness of the approach is illustrated by test results on a composite load.2004 Elsevier Ltd. All rights reserved.Keywords: Distribution system; Harmonic source identification; Harmonic current separation; Least squares approximation1. IntroductionHarmonic distortion has experienced a continuous increase in distribution systems owing to the growing use of nonlinear loads. Many studies have shown that harmonics may cause serious effects on power systems, communication systems, and various apparatus [1–3]. Harmonic voltages at each point on a distribution network are not only determined by the harmonic currents produced by harmonic sources (nonlinear loads), but also related to all linear loads (harmonic current sinks) as well as the structure and parameters of the network. To effectively evaluate and diminish the harmonic distortion in power systems, the locations of harmonic sources have to be identified and the responsibility of the distortion caused by related individual customers has to be separated.As to harmonic source identification, most commonly the negative harmonic power is considered as an essential evidence of existing harmonic source [4–7]. Several approaches aiming at evaluating the contribution of an individual customer can also be found in the literatures. Schemes based on power factor measurement to penalize the customer’s harmonic currents are discussed in Ref. [8]. However, it would be unfair to use economical penalization if we could not distinguish whether the measured harmonic current is from nonlinear load or from linear load.In fact, the intrinsic difference between linear and nonlinear loads lies in their V –I characteristics. Harmonic currents of a linear load are i n linear proportion to its supplyharmonic voltages of the same order 次, whereas the harmonic currents of a nonlinear load are complex nonlinear functions of its supply fundamental 基波and harmonic voltage components of all orders. To successfully identify and isolate harmonic source in an individual customer or several customers connected at same point in the network, the V –I characteristics should be involved and measurement of voltages and currents under several different supply conditions should be carried out.As the existing approaches based on measurements of voltage and current spectrum or harmonic power at a certain instant cannot reflect the V –I characteristics, they may not provide reliable information about the existence and contribution of harmonic sources, which has been substantiated by theoretical analysis or experimental researches [9,10].In this paper, to approximate the nonlinear characteristics and to facilitate the work in harmonic source identification and harmonic current separation, a new simplified harmonic source model is proposed. Then based on the difference between linear and nonlinear loads in their V –I characteristics, and by utilizing the harmonic source model, a new principle for harmonic source identification and harmonic current separation is presented. By using the method, not only the existence of harmonic source can be determined, but also the contributions of the harmonic sources and the linear loads can be separated. Detailed procedure of harmonic source identification and harmonic current separation based on least squares approximation is presented. Finally, test results on a composite load containing linear and nonlinear loads are given to illustrate the effectiveness of the approach.2. New principle for harmonic source identification and current separationConsider a composite load to be studied in a distribution system, which may represent an individual consumer or a group of customers supplied by a common feeder 支路in the system. To identify whether it contains any harmonic source and to separate the harmonic currents generated by the harmonic sources from that absorbed by conventional linear loads in the measured total harmonic currents of the composite load, the following assumptions are made.(a) The supply voltage and the load currents are both periodical waveforms withperiod T; so that they can be expressed by Fourier series as1()s i n (2)h h h v t ht T πθ∞==+ (1)1()sin(2)h h h i t ht πφ∞==+The fundamental frequency and harmonic components can further be presented bycorresponding phasorshr hi h h hr hi h hV jV V I jI I θφ+=∠+=∠ , 1,2,3,...,h n = (2)(b) During the period of identification, the composite load is stationary, i.e. both its composition and circuit parameters of all individual loads keep unchanged.Under the above assumptions, the relationship between the total harmonic currents of the harmonic sources(denoted by subscript N) in the composite load and the supply voltage, i.e. the V –I characteristics, can be described by the following nonlinear equation ()()()N i t f v t = (3)and can also be represented in terms of phasors as()()122122,,,...,,,,,,...,,Nhr r i nr ni Nh Nhi r inr ni I V V V V V I I V V V V V ⎡⎤=⎢⎥⎣⎦ 2,3,...,h n = (4)Note that in Eq. (4), the initial time (reference time) of the voltage waveform has been properly selected such that the phase angle u1 becomes 0 and 10i V =, 11r V V =in Eq. (2)for simplicity.The V –I characteristics of the linear part (denote by subscript L) of the composite load can be represented by its equivalent harmonic admittance Lh Lh Lh Y G jB =+, and the total harmonic currents absorbed by the linear part can be described as,Lhr LhLh hr Lh Lhi LhLh hi I G B V I I B G V -⎡⎤⎡⎤⎡⎤==⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦⎣⎦2,3,...,h n = (5)From Eqs. (4) and (5), the whole harmonic currents absorbed by the composite load can be expressed as()()122122,,,...,,,,,,...,,hr Lhr Nhr r i nr ni h hi Lhi Nhi r inr ni I I I V V V V V I I I I V V V V V ⎡⎤⎡⎤⎡⎤==-⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦⎣⎦ 2,3,...,h n = (6)As the V –I characteristics of harmonic source are nonlinear, Eq. (6) can neither be directly used for harmonic source identification nor for harmonic current separation. To facilitate the work in practice, simplified methods should be involved. The common practice in harmonic studies is to represent nonlinear loads by means of current harmonic sources or equivalent Norton models [11,12]. However, these models are not of enough precision and new simplified model is needed.From the engineering point of view, the variations of hr V and hi V ; ordinarily fall into^3% bound of the rated bus voltage, while the change of V1 is usually less than ^5%. Within such a range of supply voltages, the following simplified linear relation is used in this paper to approximate the harmonic source characteristics, Eq. (4)112222112322,ho h h r r h i i hnr nr hni ni Nh ho h h r r h i i hnr nr hni ni a a V a V a V a V a V I b b V b V b V b V b V ++++++⎡⎤=⎢⎥++++++⎣⎦2,3,...,h n = (7)这个地方不知道是不是原文写错？23h r r b V 其他的都是2The precision and superiority of this simplified model will be illustrated in Section 4 by test results on several kinds of typical harmonic sources.The total harmonic current (Eq. (6)) then becomes112222112222,2,3,...,Lh Lh hr ho h h r r h i i hnr nr hni ni h Lh Lh hi ho h h r r h i i hnr nr hni ni G B V a a V a V a V a V a V I B G V b b V b V b V b V b V h n-++++++⎡⎤⎡⎤⎡⎤=-⎢⎥⎢⎥⎢⎥++++++⎣⎦⎣⎦⎣⎦= (8)It can be seen from the above equations that the harmonic currents of the harmonic sources (nonlinear loads) and the linear loads differ from each other intrinsically in their V –I characteristics. The harmonic current component drawn by the linear loads is uniquely determined by the harmonic voltage component with same order in the supply voltage. On the other hand, the harmonic current component of the nonlinear loads contains not only a term caused by the same order harmonic voltage but also a constant term and the terms caused by fundamental and harmonic voltages of all other orders. This property will be used for identifying the existence of harmonic source sin composite load.As the test results shown in Section 4 demonstrate that the summation of the constant term and the component related to fundamental frequency voltage in the harmonic current of nonlinear loads is dominant whereas other components are negligible, further approximation for Eq. (7) can be made as follows.Let112'012()()nh h hkr kr hki ki k k h Nhnh h hkr kr hki kik k h a a V a V a V I b b V b V b V =≠=≠⎡⎤+++⎢⎥⎢⎥=⎢⎥⎢⎥+++⎢⎥⎢⎥⎣⎦∑∑ hhr hhi hr Nhhhr hhi hi a a V I b b V ⎡⎤⎡⎤''=⎢⎥⎢⎥⎣⎦⎣⎦hhrhhihr Lh Lh Nh hhrhhi hi a a V I I I b b V ''⎡⎤⎡⎤'''=-=⎢⎥⎢⎥''⎣⎦⎣⎦,2,3,...,hhr hhiLh Lh hhrhhi hhr hhi Lh Lh hhr hhi a a G B a a h n b b B G b b ''-⎡⎤⎡⎤⎡⎤=-=⎢⎥⎢⎥⎢⎥''⎣⎦⎣⎦⎣⎦The total harmonic current of the composite load becomes112012(),()2,3,...,nh h hkr kr hki ki k k hhhrhhi hr h Lh NhLhNh n hhrhhi hi h h hkr kr hki kik k h a a V a V a V a a V I I I I I b b V b b V b V b V h n=≠=≠⎡⎤+++⎢⎥⎢⎥''⎡⎤⎡⎤''=-=-=-⎢⎥⎢⎥⎢⎥''⎣⎦⎣⎦⎢⎥+++⎢⎥⎢⎥⎣⎦=∑∑ (9)By neglecting ''Nh I in the harmonic current of nonlinear load and adding it to the harmonic current of linear load, 'Nh I can then be deemed as harmonic current of thenonlinear load while ''Lh I can be taken as harmonic current of the linear load. ''Nh I =0 means the composite load contains no harmonic sources, while ''0NhI ≠signify that harmonic sources may exist in this composite load. As the neglected term ''Nh I is not dominant, it is obviousthat this simplification does not make significant error on the total harmonic current of nonlinear load. However, it makes the possibility or the harmonic source identification and current separation.3. Identification procedureIn order to identify the existence of harmonic sources in a composite load, the parameters in Eq. (9) should be determined primarily, i.e.[]0122hr h h h rh i hhr hhihnr hni C a a a a a a a a ''= []0122hi h h h rh i hhrhhihnr hni C b b b b b b b b ''=For this purpose, measurement of different supply voltages and corresponding harmoniccurrents of the composite load should be repeatedly performed several times in some short period while keeping the composite load stationary. The change of supply voltage can for example be obtained by switching in or out some shunt capacitors, disconnecting a parallel transformer or changing the tap position of transformers with OLTC. Then, the least squares approach can be used to estimate the parameters by the measured voltages and currents. The identification procedure will be explained as follows.(1) Perform the test for m （2m n ≥）times to get measured fundamental frequency andharmonic voltage and current phasors ()()k k h h V θ∠,()()k k hh I φ∠,()1,2,,,1,2,,k m h n == .(2) For 1,2,,k n = ，transfer the phasors corresponding to zero fundamental voltage phase angle ()1(0)k θ=and change them into orthogonal components, i.e.()()11kkr V V = ()10ki V =()()()()()()()()()()11cos sin kkkkk kkkhr h h hihhV V h V V h θθθθ=-=-()()()()()()()()()()11cos sin k kkkk kkkhrhhhihhI I h I I h φθφθ=-=-,2,3,...,h n =(3)Let()()()()()()()()1221Tk k k k k k k k r i hr hi nr ni VV V V V V V V ⎡⎤=⎣⎦ ,()1,2,,k m = ()()()12Tm X V V V ⎡⎤=⎣⎦ ()()()12T m hr hr hr hrW I I I ⎡⎤=⎣⎦()()()12Tm hi hi hihi W I I I ⎡⎤=⎣⎦ Minimize ()()()211hr mk hr k I C V=-∑ and ()()()211him k hi k IC V=-∑, and determine the parametershr C and hi C by least squares approach as [13]:()()11T T hr hr T T hi hiC X X X W C X X X W --== (10)(4) By using Eq. (9), calculate I0Lh; I0Nh with the obtained Chr and Chi; then the existence of harmonic source is identified and the harmonic current is separated.It can be seen that in the course of model construction, harmonic source identification and harmonic current separation, m times changing of supply system operating condition and measuring of harmonic voltage and currents are needed. More accurate the model, more manipulations are necessary.To compromise the needed times of the switching operations and the accuracy of the results, the proposed model for the nonlinear load (Eq. (7)) and the composite load (Eq. (9)) can be further simplified by only considering the dominant terms in Eq. (7), i.e.01111,Nhr h h hhr hhi hr Nh Nhi ho h hhrhhi hi I a a V a a V I I b b V b b V +⎡⎤⎡⎤⎡⎤⎡⎤==+⎢⎥⎢⎥⎢⎥⎢⎥+⎣⎦⎣⎦⎣⎦⎣⎦2,3,,h n = (11) 01111h h Nh ho h a a V I b b V +⎡⎤'=⎢⎥+⎣⎦01111,hr hhrhhi hr h h h LhNh hi hhr hhihi ho h I a a V a a V I I I I b b V b b V ''+⎡⎤⎡⎤⎡⎤⎡⎤''==-=-⎢⎥⎢⎥⎢⎥⎢⎥''+⎣⎦⎣⎦⎣⎦⎣⎦2,3,,h n = (12) In this case, part equations in the previous procedure should be changed as follows[]01hr h h hhrhhi C a a a a ''= []01hi h h hhrhhiC b b b b ''= ()()()1Tk k k hr hi V V V ⎡⎤=⎣⎦ Similarly, 'Nh I and 'Lh I can still be taken as the harmonic current caused by thenonlinear load and the linear load, respectively.4. Experimental validation4.1. Model accuracyTo demonstrate the validity of the proposed harmonic source models, simulations are performed on the following three kind of typical nonlinear loads: a three-phase six-pulse rectifier, a single-phase capacitor-filtered rectifier and an acarc furnace under stationary operating condition.Diagrams of the three-phase six-pulse rectifier and the single-phase capacitor-filtered rectifier are shown in Figs. 1 and 2 [14,15], respectively, the V –I characteristic of the arc furnace is simplified as shown in Fig. 3 [16].The harmonic currents used in the simulation test are precisely calculated from their mathematical model. As to the supply voltage, VekT1 is assumed to be uniformly distributed between 0.95 and 1.05, VekThr and VekThi ek 1; 2;…;m T are uniformly distributed between20.03 and 0.03 with base voltage 10 kV and base power 1 MVFig. 1. Diagram of three-phase six-pulse rectifier.Fig. 2. Diagram of single-phase capacitor-filtered rectifierFig. 3. Approximate V –I characteristics of arc furnace.Three different models including the harmonic current source (constant current) model, the Norton model and the proposed simplified model are simulated and estimated by the least squares approach for comparison.For the three-phase six-pulse rectifier with fundamental currentI=1.7621; the1 parameters in the simplified model for fifth and seventh harmonic currents are listed in Table 1.To compare the accuracy of the three different models, the mean and standard deviations of the errors on Ihr; Ihi and Ih between estimated value and the simulated actual value are calculated for each model. The error comparison of the three models on the three-phase six-pulse rectifier is shown in Table 2, where mhr; mhi and mha denote the mean, and shr; shi and sha represent the standard deviations. Note that I1 and _Ih in Table 2are the current values caused by rated pure sinusoidal supply voltage.Error comparisons on the single-phase capacitor-filtered rectifier and the arc furnace load are listed in Table 3 and 4, respectively.It can be seen from the above test results that the accuracy of the proposed model is different for different nonlinear loads, while for a certain load, the accuracy will decrease as the harmonic order increase. However, the proposed model is always more accurate than other two models.It can also be seen from Table 1 that the componenta50 t a51V1 and b50 t b51V1 are around 20:0074 t0:3939 0:3865 and 0:0263 t 0:0623 0:0886 while the componenta55V5r and b55V5i will not exceed 0:2676 ￡0:03 0:008 and 0:9675 ￡0:003 0:029; respectively. The result shows that the fifth harmonic current caused by the summation of constant term and the fundamental voltage is about 10 times of that caused by harmonic voltage with same order, so that the formal is dominant in the harmonic current for the three-phase six-pulse rectifier. The same situation exists for other harmonic orders and other nonlinear loads.4.2. Effectiveness of harmonic source identification and current separationTo show the effectiveness of the proposed harmonic source identification method, simulations are performed on a composite load containing linear load (30%) and nonlinear loads with three-phase six-pulse rectifier (30%),single-phase capacitor-filtered rectifier (20%) and ac arc furnace load (20%).For simplicity, only the errors of third order harmonic current of the linear and nonlinear loads are listed in Table 5, where IN3 denotes the third order harmonic current corresponding to rated pure sinusoidal supply voltage; mN3r ;mN3i;mN3a and mL3r ;mL3i;mL3a are error means of IN3r ; IN3i; IN3 and IL3r ; IL3i; IL3 between the simulated actual value and the estimated value;sN3r ;sN3i;sN3a and sL3r ;sL3i;sL3a are standard deviations.Table 2Table 3It can be seen from Table 5 that the current errors of linear load are less than that of nonlinear loads. This is because the errors of nonlinear load currents are due to both the model error and neglecting the components related to harmonic voltages of the same order, whereas only the later components introduce errors to the linear load currents. Moreover, it can be found that more precise the composite load model is, less error is introduced. However, even by using the very simple model (12), the existence of harmonic sources can be correctly identified and the harmonic current of linear and nonlinear loads can be effectively separated. Table 4Error comparison on the arc furnaceTable 55. ConclusionsIn this paper, from an engineering point of view, firstly anew linear model is presented for representing harmonic sources. On the basis of the intrinsic difference between linear and nonlinear loads in their V –I characteristics, and by using the proposed harmonic source model, a new concise principle for identifying harmonic sources and separating harmonic source currents from that of linear loads is proposed. The detailed modeling and identification procedure is also developed based on the least squares approximation approach. Test results on several kinds of typical harmonic sources reveal that the simplified model is of sufficient precision, and is superior to other existing models. The effectiveness of the harmonic source identification approach is illustrated using a composite nonlinear load.AcknowledgementsThe authors wish to acknowledge the financial support by the National Natural Science Foundation of China for this project, under the Research Program Grant No.59737140. References[1] IEEE Working Group on Power System Harmonics, The effects of power system harmonics on power system equipment and loads. IEEE Trans Power Apparatus Syst 1985;9:2555–63.[2] IEEE Working Group on Power System Harmonics, Power line harmonic effects on communication line interference. IEEE Trans Power Apparatus Syst 1985;104(9):2578–87.[3] IEEE Task Force on the Effects of Harmonics, Effects of harmonic on equipment. IEEE Trans Power Deliv 1993;8(2):681–8.[4] Heydt GT. Identification of harmonic sources by a State Estimation Technique. IEEE Trans Power Deliv 1989;4(1):569–75.[5] Ferach JE, Grady WM, Arapostathis A. An optimal procedure for placing sensors and estimating the locations of harmonic sources in power systems. IEEE Trans Power Deliv 1993;8(3):1303–10.[6] Ma H, Girgis AA. Identification and tracking of harmonic sources in a power system using Kalman filter. IEEE Trans Power Deliv 1996;11(3):1659–65.[7] Hong YY, Chen YC. Application of algorithms and artificial intelligence approach for locating multiple harmonics in distribution systems. IEE Proc.—Gener. Transm. Distrib 1999;146(3):325–9.[8] Mceachern A, Grady WM, Moncerief WA, Heydt GT, McgranaghanM. Revenue and harmonics: an evaluation of someproposed rate structures. IEEE Trans Power Deliv 1995;10(1):474–82.[9] Xu W. Power direction method cannot be used for harmonic sourcedetection. Power Engineering Society Summer Meeting, IEEE; 2000.p. 873–6.[10] Sasdelli R, Peretto L. A VI-based measurement system for sharing the customer and supply responsibility for harmonic distortion. IEEETrans Instrum Meas 1998;47(5):1335–40.[11] Arrillaga J, Bradley DA, Bodger PS. Power system harmonics. NewYork: Wiley; 1985.[12] Thunberg E, Soder L. A Norton approach to distribution networkmodeling for harmonic studies. IEEE Trans Power Deliv 1999;14(1):272–7.[13] Giordano AA, Hsu FM. Least squares estimation with applications todigital signal processing. New York: Wiley; 1985.[14] Xia D, Heydt GT. Harmonic power flow studies. Part I. Formulationand solution. IEEE Trans Power Apparatus Syst 1982;101(6):1257–65.[15] Mansoor A, Grady WM, Thallam RS, Doyle MT, Krein SD, SamotyjMJ. Effect of supply voltage harmonics on the input current of single phase diode bridge rectifier loads. IEEE Trans Power Deliv 1995;10(3):1416–22.[16] Varadan S, Makram EB, Girgis AA. A new time domain voltage source model for an arc furnace using EMTP. IEEE Trans Power Deliv 1996;11(3):1416–22.。

成都理工大学学生毕业设计(论文)外文译文

成都理工大学
学生毕业设计（论文）外文译文
学生姓名：
学号：200708020404
专业名称：商场营销
译文标题（中英文）：对几种汽车营销模式的分析及展望（Some automotive marketing model for the analysis and prospects）
译文出处：Gary Armstrong &Philip Kotler《Some automotive marketing model for the analysis场转向买方市场．营销组织也发生了巨大的变化，三种不同的渠道模式呈现在眼前。一种是不直接零售的中间人；另一种是一般零售商，通过有形汽车市场电子商务等销售汽车．业务以销售为主，只有极少数提供维修或简单的售后服务；第三种是四位一体的专卖店，经销商直接与厂商签订合同。按照厂商的要求建立店面提供整车销售、零配件供应、售后服务和信息反馈等多种功能。这三种形式都是现代化的营销组织形式．但各有优劣，其焦点是厂商和经销商利益的平衡以及消费者不同的需求。营销组织多体的不同需要，适应不同区域市场差异。
3、营销手段
除了一般的文化营销娱乐营销等手段，信息化和服务营销将成为新形势下汽车营销的重点。互联网的开放性使得汽车消费者2 4小时进行网上订购．发送配送指令成为可能。可以预言，随着互联网应用的普及率不断提高．电子商务在整体汽车营销手段中的比重必然会大幅增加，维修服务等都能够在网上实现或通过网络提供信息支持。从现实看，参考一些成功的国际运营商，稳步实施电子商务也许是汽车厂商营销渠道变革必考虑的一个重要因素。电子商务模式下汽车营销渠道的建立，首先要求企业本身必须实行信息化管理，进一步使用产品数据管理系统(PDM)，从而优化整车以及零配件的设计与生产，使用企业资源管理系统(ER P)，降低管理成本；使用供应链管理系统(S C M)，提高上下游供应链条的运营效率。另外，汽车产品因其特有的产品特征使得汽车产品在围绕有形延伸，以战略的方式构筑个性化、多层面和全方位的汽车服务营销，如汽车改装和装饰。汽车保险和服务的个性化方案以及从买车、用车到卖车、再买车等多层面的汽车服务。汽车信贷、汽车的评估和转让等全方位的服务项目。正是适应了汽车消费的固有特征，并迎合了汽车用户对深层次服务的要求．强化汽车用户对汽车服务和汽车企业的依赖，加大制造商和经销商之间的利益联系，实施汽车销售合理化和科学化。