Search

A new evaluation of the half-life of 241Pu has been made by combining previous results from earlier methods and techniques with further measurements of the isotopic ratio of an initially enriched 241Pu material. A correction to the previous published value has had to be made. The half-life of 241Pu is an important parameter for the measurement and control of amounts of plutonium as the decay of this isotope is usually the largest contributor to the uncertainty of estimations of the amount of total plutonium after storage. The value of the half-life together with its associated uncertainty needs to be known with a high degree of confidence. However, the half-life value of ca.14.3 a (years) means the decay of the isotope is difficult to measure over one or more half-lives using a single method or instrument. The method employed in this evaluation is designed to conform to the Guide to the Expression of Uncertainty in Measurements (GUM) (International Organisation for Standardisation, Guide to the Expression of Uncertainty in Measurement, ©ISO, ISBN 92-67-10188-9, Geneva, Switzerland, 1993)1and care was taken to ensure that all measured values over the 30 year measurement time-span have been included. The value recommended from this set of measurements is 14.325 a ± 0.024 a (k= 2). This agrees with the value from the first measurements of the same material in 1983 of 14.33 a ± 0.02 a (P. De Bièvre, P. Gallet and M. Wertz, Int. J. Mass Spectrom., Ion Phys., 51, 1983, 111).2 [ABSTRACT FROM AUTHOR]

The success of any activity and process depends fundamentally on the possibility of balancing (symmetry) needs and their satisfaction. That is, the ability to properly define a set of success indicators. The application of the developed new multi-criteria decision-making (MCDM) methods can be eliminated or decreased by decision-makers' subjectivity, which leads to consistency or symmetry in the weight values of the criteria. In this Special Issue, 40 research papers and one review study co-authored by 137 researchers from 23 different countries explore aspects of multi-criteria modeling and optimization in crisp or uncertain environments. The papers proposing new approaches and elaborate case studies in the following areas of applications: MCDM optimization in sustainable engineering, environmental sustainability in engineering processes, sustainable multi-criteria production and logistics processes planning, integrated approach for modeling processes in engineering, new trends in the multi-criteria evaluation of sustainable processes, multi-criteria decision-making in strategic management based on sustainable criteria. [ABSTRACT FROM AUTHOR]

This paper reports on a highly ambitious international study undertaken in the period 2018–2020 on the topic of convergence between biology and advanced manufacturing systems. The international team (authors of this paper) worked together to analyse the status of this convergence through the assessment of concrete examples, referred to here as demonstrators, within advanced manufacturing systems. Four independent demonstrators from different sections of the manufacturing value chain and involving bio-inspiration, bio-integration and/or bio-intelligence were selected to test the following hypothesis: "That Future Manufacturing Systems will incorporate Components, Features, Characteristics and Capabilities that enable the convergence towards Living Systems". Each of these four demonstrators have succeeded in supporting this hypothesis and in providing clear evidence to confirm that significant performance benefits may be derived through the " biologicalisation " of advanced manufacturing systems. This conclusion is of great significance for the next phases of development of manufacturing science and engineering globally. The evidence reported in this paper provides a robust basis for recommending that a deeper analysis of the implications of biologicalised manufacturing systems be undertaken. As a result of this early stage work, it is concluded that there is a high likelihood that this new convergence will lead to a major paradigm shift in advanced manufacturing. Outstanding opportunities exist for high levels of innovation in the next stages of development of advanced manufacturing processes and systems from the biological perspective. The relationship between the human and the physical manufacturing system will also change and the world of advanced manufacturing will be confronted with many new challenges including important ethical questions. [ABSTRACT FROM AUTHOR]

Purpose – No methodology has been directly proposed to address the parameter optimization problem with weight effect on the categorical response. The aim of this paper is to propose a suitable procedure to address such a problem. Design/methodology/approach – The computation of aggregation weight and neural network modeling technique were employed into forming the core architecture of the proposed approach. The consistency and difference of the weight effect between several experts or professionals can be included into the weight computation. The backpropagation neural network model is chosen to model the non-linear relationship among the control factors, the probability, and the accumulated probability of categories for a qualitative response. Findings – Weight effect for different categories of a qualitative response significantly exists in L/F manufacturing process. Including such weight effect into the L/F manufacturing analysis can achieve the parameter optimization and enhance their quality improvement. Originality/value – This paper can be viewed as the first to address the parameter optimization problem for the categorical response with the weight effect consideration. The proposed approach can aid engineers making necessary decisions about quality improvement. [ABSTRACT FROM AUTHOR]

The flatness measurement of a large 2-D flat work- piece such as a satellite solar panel substrate is a key problem in its manufacturing process. Based on the current measuring methods and the actual engineering project, a new noncontact high-precision, low-cost large 2-D flat workpiece flatness measuring system is developed, in which the techniques of oblique optical triangle measuring structure, virtual measurement datum plane, and error self-correction are adopted. By means of the oblique optical triangle measuring structure that is first proposed, the measuring area and resolution of the measuring system can be greatly increased. Meanwhile, on the basis of the techniques of virtual measurement datum plane and error self-correction, the noncontact high-precision, low-cost flatness measurement can be realized on a nonprecise large metallic platform. Experimental results on the satellite solar panel substrate indicate the correctness and effectiveness of the proposed noncontact flatness-measuring system of the large 2-D flat workpiece. Although the specific application of the satellite solar panel substrate is presented in this paper, the proposed measurement techniques and measuring system could be applied independent of the nature or use of the large 2-D flat workpieces. [ABSTRACT FROM AUTHOR]

The article presents a response to the comments made on a paper about the Shainin System engineering method. The authors make three assumptions to frame their response. First is that they follow the Juran Institute's diagnostic and remedial journeys to reduce variation in a specified output. Second, they define a cause of variation to be a process input that changes over realizations of the process, such as temperature, component dimensions in an assembly and cavity. And finally, they change the process in the remedial journey to make an improvement.

The use of precedence diagrams and estimates of task times, as the only source of engineering information for assembly line balancing (ALB), is common to most ALB techniques developed to date. This paper presents a model which incorporates the information carried by an assembly chart (or a Gozinto chart) into the ALB problem in an attempt to consider engineering objectives such as improving work methods and work enrichment in the design of assembly lines. A multi-objective approach is developed which integrates the traditional objective of minimizing the idle time of the line with the objective that a minimum number of subassemblies should be handled at each workstation. [ABSTRACT FROM AUTHOR]

Process capability indices (PCIs) have become popular as unit-less measures on whether a process is capable of reproducing items meeting the quality requirement. A reliable approach for testing process capability is to establish an interval estimate, for which we can assert that it contains the true PCI value with a reasonable degree of certainty. However, the construction of such an interval estimate is not trivial, since the distribution of the commonly used Cpk index involves unknown parameters. In this paper, we adopt the concept of generalized confidence intervals and generalized pivotal quantities to derive the generalized lower confidence bounds for providing critical information on process performance. Two practical applications in the area of process capability were considered, they include (i) assessing whether a process under investigation is capable and (ii) providing the lowest performance of the manufacturing processes from several production lines or several suppliers for quality assurance. The applicability of the derived results is also illustrated with examples. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The author comments on a paper about the Shainin engineering system. He says that his only criticism of the paper is that the authors are not as harsh in their criticism of the Shainin system. While the authors of the paper point out that the methods are most likely to work best in medium to high volume manufacturing where intervening in the process is difficult, he is not convinced that their techniques and system of implementing them would be effective in anything but the simplest sort of low-technology manufacturing processes.

Design pitfalls are defined as those obscure mistakes that can be attributed to negligence or ignorance of particular details and characteristics of the design and, in some cases, the manufacturing processes. This paper presents ten actual cases where a designer could be tempted or misled into design pitfalls that would create weird encounters during assembling or operating mechanical equipment. The pitfalls could have immediate, embarrassing consequences, or eventually lead to hazardous situations and failure in unexpected modes. The consequences of these pitfalls and their remedies are also discussed. The design examples lie in various areas such as gearing and planetary systems, bearings, and fluid power. They are classified under generic headings, some of which are seen to qualify, and are therefore suggested, as design principles, to be added to the repertory. It is deemed that this paper will stimulate further investigations leading to the identification of design pitfalls in these and other areas. [ABSTRACT FROM AUTHOR]

One of the most critical issues encountered in the area of quality engineering is the selection of an appropriate quality loss function to relate key quality characteristics of a product to its quality performance. The loss function can be used to evaluate the quality loss in terms of monetary units that enables managers to quantify unobservable costs. It aids manufacturers to evaluate quality improvement projects more rigorously, hence, the choice of paths for quality enrichment depends on the type of loss function. Although several multivariate quality loss functions have been proposed, these models only considered the-nominal-the-best (N-type) quality characteristics. The effect of other types of quality characteristics was not addressed. In this paper, a cost model is proposed to evaluate the quality level of a product with multiple the-larger-the-better (L-type) quality characteristics. An example with two quality characteristics is given to illustrate the application. [ABSTRACT FROM AUTHOR]

To obtain higher precision and accuracy in mechanical systems, a design strategy is presented in this paper including both mechanical and servo-control design methodologies to ensure higher controllability and compensation of errors due to non-modelled phenomena. Examples of physical phenomena and modelling problems that may affect the accuracy at the second order are also presented. [ABSTRACT FROM AUTHOR]

There is an important interest in compensating thermally induced errors of modular tool systems to improve the manufacturing accuracy. In this paper, we test the hypothesis whether we can predict such thermal displacements by using a nonlinear regression analysis, namely the alternating conditional expectation algorithm (ACE [Breiman & Friedman, 1985]), reliably. The data analyzed were generated by two different finite element spindle models of modular tool systems. As the main result, we find that the ACE-algorithm is a powerful tool to model the relation between temperatures and displacements. The maximal correlation is larger than 0.999 in both cases, which demonstrates the suitability of the ACE algorithm. Furthermore, preconditions for the applicability of this approach, such as the length and the support of measured data sets, are studied. Hence, this approach seems to be promising for the application to real modular tool systems. [ABSTRACT FROM AUTHOR]

Lot streaming is the process of splitting a job or lot to allow overlapping between successive operations in a multistage production system. This use of transfer lots usually results in a substantially shorter makespan for the corresponding schedule. In this paper, we study the discrete lot streaming problem for a single job in no-wait flow shops. We present a new linear programming formulation for the problem. We show that the optimal solutions are the same for the m x 2 case with or without no-wait constraints. We also present a fast, polynomial-time solution method for this case. For the general case, we prove that any solution which is 'close' to the continuous optimal solution will be a good approximation for the discrete problem. This property allows us to present two quickly obtainable approximations of very good quality. [ABSTRACT FROM AUTHOR]

Prior to the physical build of the industrial automation system, some challenges arise, such as processes' cycle times calculations, ergonomics and safety evaluation, and the integration of separate machines to the complete production shops. This, in turn, requires reconfiguring the processes and component parameters. As a result, the lifecycle of the system development is prolonged, and the potential for erroneous performance increases. In modern digital manufacturing environments, virtual engineering (VE) and virtual commissioning (VC) serve as effective tools to tackle the aforementioned problems and their consequences. The virtual models developed for VE and VC not only assist system developers in the physical build stage but also in the following stages of the system lifecycle by providing a common virtual model, a digital twin (DT), of the manufacturing processes and the product. This developed model should possess the ability to simulate the system behaviour, e.g., the mechanics, kinematics, speed and acceleration profiles. Three stakeholders are involved in the development process: the machine builder, system integrator and end user. The current work focuses on the virtual engineering approach to support the entire lifecycle of a manufacturing system from the machine builder, system integrator and end user perspectives. For this purpose, it puts forward a systematic methodology of implementing VC and VE using a toolset developed by the Automation Systems Group at the University of Warwick within an industrial project. The suggested methodology is illustrated in a case study where a digital twin of a physical station was modelled, developed and tested in parallel with the physical machine development and build. Finally, the benefits and limitations are highlighted based on the gained outcomes and the implemented activities. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a concept and a prototypical solution for the management of competences of engineers working in product development processes (PDP). Objectives are the representation of individual personnel competences, their utilisation for PDP planning activities such as the assignment of engineers to design tasks, and the support of human resources development. Main result is an instrument for the rational description of the expertise needed to process new orders and of the competencies of the engineering designers. The prototype implementation of the approach is based on a graph based structure and on rules representing competence requirements of PDP and human competence profiles, both processed by an interference mechanism. [Copyright &y& Elsevier]

The research in virtual cellular manufacturing (VCM) systems area gains momentum as markets have become more globalised. This is due to turbulent customer demands, charcterised by frequent changes in product mix and volume. Therefore, if companies are interested in implementing manufacturing systems that can be quickly restructured with minimal cost and time, the approach of virtual cellular manufacturing gives considerable benefits, VCM systems physically resemble the traditional functional layout. Within this setting, group technology (GT) philosophy is used to gain the advantages accompanying with traditional cellular manufacturing (CM) systems. VCM is being used as a philosophy with broad applicability in manufacturing sector to reduce job set-up and flow times. Decisions for pooling of jobs into families, release of part families to the shop, and temporary machine dedication will lead to improvement in shop performance i.e. in terms of job flow time and system utilisation. The goal of this paper is to develop a new concept of VCM and address its operational issues through a numerical illustration. Based on the numerical results, we also outline a factorial design of simulation experiments for future research. [ABSTRACT FROM AUTHOR]

Choosing the optimal material and manufacturing process combination for a given engineering component application is mostly non-trivial and involves considerable design expertise and experience. This choice is not made in isolation of a lot of other conflicting design issues, technical and non-technical, as well as the need to satisfy interface requirements with adjoining components. This paper describes, through a practical case study, a systematic approach to designing engineering components, with an emphasis on selecting appropriate materials and manufacturing processes. The approach adopted exploits commercially available technologies only, avoiding more exotic materials and processes that may satisfy the technical demands but are inherently risky and prohibitively expensive. [Copyright &y& Elsevier]

Throughout the 1980s there has been a growing realisation amongst practitioners, consultants and academics of the multi-faceted nature of Advanced Manufacturing systems. At no point in the development of Advanced Manufacturing Systems has this been more keenly felt than in implementation. It seems that in the analysis and design phases of development, it is often possible to proceed on the basis, indeed the fond belief, that the major hurdles to be surmounted are technological and can be addressed solely using engineering or computing knowledge and skills. It is not the intention of this article to devalue or down grade the considerable technological challenge which Advanced Manufacturing Systems pose. It is the intention of this article to argue that a purely narrow technological perspective is insufficient, producing suboptimal implementations, and that a wider focus is needed if such problems are to be implemented effectively. This wider focus needs to encompass the business strategy and organisation design dimensions. In this sense, it is argued, integration is required with both the business and organisational context in which the technology, is to fit, as well as within the computer applications to manufacturing itself. [ABSTRACT FROM AUTHOR]