Structural optimization to include material selection

The mini-max dual method ia applied for solving the material selection structural optimization problems. A somewhat general objective function is introduced to consider structural weight and material cost simultaneously. It is expressed by the sum of scaled structural weight and material cost. The present formulation can yield minimum cost and minimum weight designs as two distinct special cases. It is shown that practically useful intermediate optimal designs can exist between the two extremes. Only truss structures are considered as a representative example. One numerical example is provided to illustrate the change in optimal material distribution when various objective functions are employed. A particular advantage in using the dual method for the material selection problem is also described.     

An approach to systematic materials selection

An approach to systematic materials selection is believed to be suitable for both manual and computer aided materials selection. The procedure is divided into two stages; the discriminating and the optimising parts. In the former, all requirements on properties which do not influence the final sizing of the component in question are considered. From this stage a number of materials survives which are used in the optimisation stage. To rank the materials, merit parameters are introduced. This is exemplified for pressurized containers. With the help of the merit parameters it is possible to decide which material is the most suitable in a given situation. A procedure is also proposed from which the influence of the design parameters on the selection can be evaluated. This is exemplified by analysing how the pressure in the containers affects the choice of optimum material.     

A fuzzy approach to process plan selection

Process planning is the systematic determination of the detailed methods by which parts can be manufactured from raw material to finished product. In a real manufacturing environment, usually several different parts need to be manufactured in a single facility sharing constrained resources. The existence of alternative process plans for each part makes the selection of process plan a very important issue in manufacturing. The objectives in process plan selection might be imprecise and conflicting. In this paper, a fuzzy approach is used to deal quantitatively with the imprecision of the process plan selection problem. Each process plan is evaluated and its contribution to shopfloor performance is calculated using fuzzy set theory. A progressive refinement approach is used to first identify the set of process plans that maximize the contributions, and then consolidate the set to reduce the manufacturing resources needed.     

A two-way approach to supply chain partner selection

All organisations face partner selection. It is the first step in establishing partnership. Over recent decades, a one-way selection approach has been dominant in the literature. It is assumed that a buyer searches for one or more suppliers from a set of suppliers. Once the best supplier is found and selected, a partnership is formed. However, in reality, not only is the selection not a one-way process as the relationship itself is bilateral, but the existence of other buyers and suppliers also needs to be taken into account. In this study, a two-way partner selection approach is proposed, where not only the buyers evaluate suppliers, but also the suppliers have the opportunity to evaluate buyers. Considering a marketplace where there are several buyers and suppliers, an integrative model is proposed in the form of an assignment model to optimally match all the buyers and suppliers. A generalised model is also formulated to take the suppliers’ capacity and buyers’ demand into account. The proposed models are illustrated using some numerical examples. Finally, conclusions and recommendations for future research are provided.     

Strategic selection: matching executives to business conditions

Each business situation requires that executives have a specific set of management skills and characteristics to make the business successful. As businesses adapt their strategies and organizational structures to a changing environment, this set of managerial characteristics must also change: a company may discover its executives are not as suited to manage under the new conditions as they were under the old. The authors contend that executive selection should be linked to strategy, and they present a framework for assessing the managerial characteristics required by various strategic business situations.     

Multiple attribute decision-making solution to material selection problem based on modified fuzzy axiomatic design-model selection interface algorithm

Material selection, one of the mostly encountered decision problems in material science literature, is still an onerous task for manufacturing organisations. Achieving accurate solution to this issue, the paper developed a model selection interface to enable analytical solutions to different problem concepts in material selection under multiple attribute decision-making (MADM) environments. Specifically, the generic framework of the fuzzy axiomatic design-model selection interface (FAD-MSI) is modified and successfully applied to the different material selection problem concepts. Consequently, the derived problem-model sets can be referred to accomplish further proposals on this era.     

Fuzzy logic approach to ic quality assurance plan selection

The problem of selection of a proper quality assurance and control programme for manufacturing of microelectronics devices is usually solved empirically by analogy with existing situations, or those experienced in the past. This problem is characterized by incomplete comprehension of influencing variables, unknown relationships among them, and their often vague definitions. This makes it an almost perfect candidate for application of methods from the theory of fuzzy sets and approximate reasoning. One such reasoning process is described here using familiar terms from the MIL-HDBK-217E, and is illustrated by an ASIC MOS device example.     

The analytic hierarchy process applied to maintenance strategy selection

This paper describes an application of the Analytic Hierarchy Process (AHP) for selecting the best maintenance strategy for an important Italian oil refinery (an Integrated Gasification and Combined Cycle plant). Five possible alternatives are considered: preventive, predictive, condition-based, corrective and opportunistic maintenance. The best maintenance policy must be selected for each facility of the plant (about 200 in total). The machines are clustered in three homogeneous groups after a criticality analysis based on internal procedures of the oil refinery. With AHP technique, several aspects, which characterise each of the above-mentioned maintenance strategies, are arranged in a hierarchic structure and evaluated using only a series of pairwise judgements. To improve the effectiveness of the methodology AHP is coupled with a sensitivity analysis.     

An integrated decision aid extension to material selection problem

Choice of an adequate material in design process is one of the critical tasks for the relevant decision-makers. At this insight, the consistency of the decisions is extremely depending on the relevance of adapted techniques to the nature of different problem cases. This paper proposed an integrated decision aid (IDEA) to match the suitable techniques with different problem cases based on the following six dimensions: (i) the type of the decision problem, (ii) the size of the problem, (iii) selection of the preference techniques by decision-makers, (iv) decision-makers’ preference structure, (v) the necessity for the use of relative importance, (vi) the nature of performance values. Furthermore, the implementation procedure of the proposed IDEA for a material selection problem is demonstrated with the previously cited applications from material science literature. Hereafter, it is expected that the IDEA provides great advantages and encouragements to researchers/practitioners in order to prevent excessive time consuming, probable misapplications, and the other challenging issues in multiple criteria analysis of material selection problems.     

Discriminator threshold selection logic to improve signal to noise ratio in photon counting

The discriminator threshold plays a vital role in photon counting technique used with low level light detection in lidars and bio-medical instruments. A low discriminator threshold gives high counts due to secondary emitted electrons and ground level (electrical) noise, while high threshold skips the photon pulses having lower amplitude. In both the cases the signal to noise ratio of photon counting system deteriorates. In this article the impact of improper selection of discriminator threshold on photon counting has been described. Here we introduce a simple technique by which the system (micro pulse lidar) selects the discriminator threshold at the set PMT voltage and assigns this value to the multi-channel scaler. The technique is applicable in diverse fields employing photon counting system.     

Iterative approach to operation selection and sequencing in process planning

This paper considers the problem of selecting and sequencing operations in process planning for the objective of minimizing the sum of operation processing costs and machine, set-up and tool change costs. The main constraint is the precedence relations among operations. To represent the precedence relations and alternative operations, a tree-structured precedence graph is suggested. Based on the graph, the entire problem is decomposed into two subproblems: operation selection and operation sequencing. Then, three iterative algorithms are suggested that solve the two subproblems iteratively until optimal and near-optimal solutions are obtained. The algorithms are illustrated using an example part, and to show the performances of the algorithms, computational experiments were done on randomly generated test problems. The results show that the algorithms suggested work well for the test problems.     

Adhesive selection

Abstract

There have been a number of attempts to develop a logical method of evaluating and assessing adhesives which would make their selection a more reliable process. The most recent, and successful, of these has been developed into a computerised process. This makes the initial selection of an adhesive type quick and simple and gives the user of the computer program a very good insight into the criteria which limit the choice. These criteria and the means in which they are displayed in the program are discussed in some detail in the present paper. This covers the geometry of the joint, its fabrication and ultimate use, the influence of adherend choice, and how the adherend and adhesive will perform under a variety of loading conditions. In addition, how differences in the material engineering characteristics – modulus and the elastic and plastic limit – of the various types of adhesive influence their practical performance and, hence, their logical selection is reviewed. Considerations such as these are of fundamental importance when designing power delivery systems and load bearing structures which involve bonded joints.

MST/827     

A hybrid approach to machine-tool selection through AHP and simulation

The selection process of a machine tool has been a critical issue for companies for years, because the improper selection of a machine tool might cause many problems having a negative effect on productivity, precision, flexibility, and a company's responsive manufacturing capabilities. Therefore, in this paper, to determine the best machine tool satisfying the needs and expectations of a manufacturing organization among a set of possible alternatives in the market, a hybrid approach is proposed, which integrates an analytic hierarchy process (AHP) with simulation techniques. The AHP as one of the most commonly used multiple criteria decision-making methods is used to narrow down all possible machine tool alternatives in the market by eliminating those whose scores (or weights) are smaller than a determined value obtained under certain circumstances. Then, a simulation generator is used first to automatically model a manufacturing organization, where the ultimate machine tool will be used, and second to try each alternative remaining from the AHP as a scenario on the generated model. Finally, the final alternative is selected by using the unit investment cost ratio, which is calculated by dividing the investment cost per year of each alternative by the additional number of produced units obtained from the simulation experiment of the relevant alternative.     

Evolutionary feature selection applied to artificial neural networks for wood-veneer classification

This paper presents the application of FeaSANNT, an evolutionary algorithm for optimization of artificial neural networks, to the training of a multi-layer perceptron for identification of defects in wood veneer. Given a fixed artificial neural network structure, FeaSANNT concurrently evolves the input feature vector and the network weights. The novelty of the method lies in the implementation of the embedded approach in an evolutionary feature selection paradigm. Experimental tests show that the proposed algorithm produces high-performing solutions with robust learning results. A significant reduction of the set of veneer features is obtained. Experimental comparisons are made with a previous method based on statistical filtering of the input features and a standard genetic wrapper algorithm. In the first case, FeaSANNT greatly reduces the feature set with no degradation of the neural network accuracy. Moreover, FeaSANNT entails lower design costs, since feature selection is fully automated. In the second case, the proposed algorithm achieves superior results in terms of identification accuracy and reduction of the feature set. FeaSANNT involves also lower computational costs than the standard evolutionary wrapper approach and eases the algorithm design effort. Limited overlapping is observed between the patterns of features selected by the three algorithms. This result suggests that the full feature set contains mainly redundant attributes.     

浅析空分设备中低温液体流量计的选型

随着空分设备自动化程度的不断提高和变负荷运行的需求不断增大,作为体现空分设备运行负荷的重要参数——低温液体流量测量的准确性显得越来越重要。提高仪表检测精度,减少测量误差,流量计的正确选型和使用是关键。比较分析空分设备低温液体流量计的测量原理,结合具体的使用案例,阐述低温液体流量计的选用原则,以及设计和安装过程中需考虑的具体因素。