Computation of isothermal transformation diagrams of 42CrMo4 steel from dilatometer measurements with continuous cooling

Abstract

To generally predict the mechanical properties of steels following heat treatment, the isothermal time–temperature–transformation (TTT) diagrams must be known. The isothermal kinetics of the phase transformation is influenced by the austenitisation conditions and the deformation processes. Owing to the requirements of the process chain 'integrated heat treatment following hot-forging', the steels are austenitised at a comparatively high temperature and deformed before quenching. The TTT diagrams found in the literature only treat limited austenitisation temperatures and do not generally consider different deformation levels. However, the measurements of the corresponding TTT diagrams are both costly and time consuming. In addition to this, the isothermal transformations of low alloyed steels, which transform very quickly, cannot be measured using those dilatometers which are readily available.¹ In this paper, the TTT diagrams of the 42CrMo4 steel austenitised at 1200^°C and deformed at different levels are computed from the dilatometer measurements with continuous cooling using the methods developed by Buza et al.² and Rios.³     

An Integrated Hardware/Software Data Prefetching Scheme for Shared-Memory Multiprocessors1

Both hardware and software prefetching have been shown to be effective in tolerating the large memory latencies inherent in shared-memory multiprocessors; however, both types of prefetching have their shortcomings. While software schemes require less hardware support than hardware schemes, they must generate address calculation instructions and a prefetch instruction for each datum that needs to be prefetched. Hardware schemes, however, must become progressively more complex to be able to compute data access strides and to increase the prefetching lookahead. In this paper, we propose an integrated hardware/software prefetching method that uses simple hardware that can handle most data accesses and software prefetching for the few remaining accesses. A compile time algorithm analyzes the access streams formed by array references and determines sequences of consecutive memory accesses to an access stream that can be prefetched by the hardware mechanism. This analysis is based on the relative memory locations of consecutive accesses to an access stream and the number of intervening data references between consecutive accesses to an access stream. In addition, the prefetching lookahead can be set separately for each access stream. Our approach yields an effective scheme that minimizes both CPU overhead and hardware costs. Execution-driven simulations show our method to be very effective.     

A Survey of Distributed Enterprise Network and Systems Management Paradigms

Since the mid 1990s, network and systemsmanagement has steadily evolved from centralizedparadigms, where the management application runs on asingle management station, to distributed paradigms,where it is distributed over many nodes. In thissurvey, our goal is to classify all these paradigms,especially the new ones, in order to help network andsystems administrators design a management application, and choose between mobile code, distributedobjects, intelligent agents, etc. Step by step, we buildan enhanced taxonomy based on four criteria: thedelegation granularity, the semantic richness of the information model, the degree of specificationof a task, and the degree of automation ofmanagement.     

Integrated Design for Automated Guided Vehicle Systems Using Cooperative Co-evolution

An integrated design process for automated guided vehicle (AGV) systems is proposed in this paper. There are two problems inherent in the design of systems: transporter routings and flow-path networks. They should both be solved at the same time because one depends on the other. In the present research, this issue is solved through cooperative co-evolution. For the development of co-evolution, some partner selection strategies and some evolving cycles, which are proper for design process, are evaluated. Both the transporter routing problems and the flow-path network problems are represented as different species, and a genetic algorithm is applied to them. AGV systems designed with this method are evaluated through simulations with real data. These simulations show that the proposed method makes it possible to improve the effectiveness of AGV systems.     

Quality assurance and product quality

Abstract

The basic quality assurance requirements need to be completed by means oriented towards the quality of products. In Cogema Logistics our approach is based on four principles: an integrated management system including quality, health, safety and environment; an organisation based on the responsibility of all actors, trust and transparency; a methodical approach to continuously improve the methods that are employed to achieve quality process management, corrective and preventive actions, self-assessments and various surveys; but at the same time strong procedures for controlling and monitoring all activities including technique and quality audits (external and internal), at source inspections and engineering activities inspections. This performance based approach is necessary to guarantee the effectiveness of the traditional formal quality assurance means.     

Practical design of robots operating in radiation environments

Nuclear robots must be hardened against radiation for effective operation in high-radiation environments. These robots require special components that usually have few functions, high costs and long delivery times. In the present study, we propose a modulated and hierarchical electrical circuit system for robot components such as actuators. The hierarchical system is set into a design that can withstand radiation without reducing or limiting the functionality of the robot. The hierarchical system is achieved by minimizing the variety of integrated circuit (IC) components to be used and selecting specific ICs that require radiation testing. These ICs are defined by spotted ICs with regard to the integration density and operational speed. In some cases, it is possible to select off-the-shelf IC components, but certain key IC components are needed for on-line irradiation tests, depending on robot operation reliability and the radiation environment. Since the serial numbers of off-the-shelf IC components are random, it is important that a sufficiently large number of IC components are tested under the operating conditions for statistical evaluation. If the radiation lifetime is random, then the radiation lifetime of the sorted IC components can be estimated statistically. Here, the robot user decides the operation based on this lifetime. By doing so, the experimental cost can be minimized in accordance with the proposed method at the user's operational risk. Of course, if on-line irradiation tests are performed for various types of IC components, the radiation lifetime of the robot can be predicted with a relatively high accuracy. As a result, the design of a robot that operates under certain radiation conditions, while having a certain lifetime and cost, is possible. This design technique was applied to a nuclear disaster prevention robot and the radiation lifetime of the spotted IC components was shown to be distributed randomly, indicating the validity of the proposed method.     

Performance and Efficiency in Distributed Enterprise Management

This paper is motivated by the increasing needfor scaleable, distributed management architectures forintegrated network, system and application managementwithin the enterprise network environment. Such integration, extension and wide area deploymentof management functionality impose heavy performancerequirements and produce increased management traffic.Aiming to minimize this traffic and the overall response time, we propose a distributedhierarchical caching scheme that attempts to takeadvantage of the diverse consistency requirements ofmanagement applications. We define coherency conditionsand update policies, identify the appropriateinteraction semantics, and discuss an SNMP-basedimplementation. In order to evaluate the proposed modeland to quantify the expected performance gains weconstruct a simple queuing model that provides analyticalresults on the improvement of response time and thereduction of management traffic. Finally, the analysisof experimental results provides some insight on performance improvement for specific classes ofmanaged objects.     

Materials for plasma facing components of fusion reactors

Abstract

According to current knowledge and understanding, nuclear fusion can be developed to a sustainable energy technology. Fuel is abundant and key points for fusion power production and alpha particle heating have already been demonstrated. The next step device, international thermonuclear experimental reactor (ITER), is designed to demonstrate net fusion power production and to address most of the technological issues on the way to a power reactor. There is, however, a series of materials problems related to the plasma facing components and to the structural materials which cannot be fully addressed by ITER. These developments are covered by long term development of radiation resistant low activation materials, heat sink materials, plasma facing protection materials as well as functional tritium barrier materials.

A brief survey of the current status of materials development for plasma facing applications is given in the present paper. To provide materials which can sustain the severe loading conditions in a fusion environment is a key issue in developing fusion as an economic energy technology without long lived radioactive waste.     

面向二十一世纪的柔性制造系统

通过分析柔性制造系统的关键技术及其进一步的发展研究方向，展望了21世纪柔性制造系统的发展趋势。进而阐述了在新的世纪里柔性制造系统在先进制造业中的重要作用及其发展的深远意义。     

Integrated TMN Service Management

The deregulation of the global telecommunicationindustry has seen a change in the business andoperational environment in which services are deployedand managed. The requirements have intensified toprovide a management framework for telecommunicationnetworks and services across multiple technology domainsand using multiple management technologies. This paperdescribes an integrated TMN service management architecture that provides an environment fordifferent service management functions and differentmanagement domains to be integrated. To furthersubstantiate this architecture, a system was built todemonstrate the integration concepts. The research anddevelopment work reported in this paper focuses on thefollowing two aspects of integration: first theintegration between TMN network and service managementfunctions; and next the integration between differentservice management functions. A proof of concept systemwas developed to demonstrate such integration. Itconsists of the following components: Generic service ordering and provisioning; connectionmanagement based on a generic network model concept; andservice management based upon service level agreementmanagement and customer service management concepts. This paper reports this work and theexperiences gained from this research.