Much research has been reported on the possibilities of using various heuristic priority rules to sequence batches through a job shop. The SPT (Shortest Priority Time) heuristic, or modifications to it, has been proved useful in many studies. This paper reports on the results obtained when simulating the work flow through a real machine shop. The simulation model has been used to test the effect on well known priority rules of releasing batches into the shop in order of decreasing expected throughput time. The important effect of this “phased release” of batches was to increase the percentage of batches delivered in finished parts stores on time, particularly in the case where priority rules were in use which might otherwise have resulted in poor delivery. This has important repercussions for management because it implies that by “phased” release of batches in the manner discussed, a large proportion of batches will be delivered on time whatever priority rule is in operation in the shop.
Several prior studies have investigated the strategy of concurrently deploying different priority rules at different processing stages of a manufacturing system. The…
Several prior studies have investigated the strategy of concurrently deploying different priority rules at different processing stages of a manufacturing system. The purpose of this paper is to investigate the advantage of using such a strategy over that of using priority rules in their pure forms.
Three priority rules were combined in all possible ways in a simulated, three‐stage, flow‐dominated manufacturing system. The performances of these combinations, along with three other simple priority rules in their pure forms, were compared using both mean and variability in waiting, earliness, tardiness, and total costs under two shop load levels and several tardiness to earliness cost ratios.
The results indicate that the combinations between SIX and shortest processing time (SPT) rules perform well in reducing both mean and variability of waiting cost but do poorly on tardiness cost. On the other hand, the due date rule in its pure form or in conjunction with SIX or SPT is effective in reducing both mean and variability of both earliness and tardiness costs. While tardiness cost appears to dominate the total cost data, the shop load level registered little impact on the performance of the combination schemes.
The results of the paper have useful practical implications for textile and ceramic industries. However, the conclusions are limited to the cost structure used, although a wide range of cost ratios is included.
The paper offers insights into whether throughput and due date‐related costs can be reduced by using a job sequencing strategy that simultaneously deploys different priority rules at different processing stages of a manufacturing environment.
Traffic signal control is one of the oldest application areas of fuzzy sets in transportation. In general, fuzzy control is found to be superior in complex problems with…
Traffic signal control is one of the oldest application areas of fuzzy sets in transportation. In general, fuzzy control is found to be superior in complex problems with multi-objective decisions. In traffic signal control, several traffic flows compete for the same time and space, and different priorities are often set to different traffic flows or vehicle groups
The public transport priorities are a very important part of the effective traffic signal control. Normally, the public transport priorities are programmed by using special algorithms, which are tailor-made for each intersection. The experiences have proved that this kind of algorithms can be very effective if some compensation algorithms and the traffic-actuated control mode are used. We believe that using the fuzzified public transport priority algorithms, the measures of effectiveness of traffic signal control can be even better. In this paper, our fuzzy control algorithm of the public transport priorities will be presented.
Constructing an effective production control policy is the most important issue in wafer fabrication factories. Most of researches focus on the input regulations of wafer…
Constructing an effective production control policy is the most important issue in wafer fabrication factories. Most of researches focus on the input regulations of wafer fabrication. Although many of these policies have been proven to be effective for wafer fabrication manufacturing, in practical, there is a need to help operators decide which lots should be pulled in the right time and to develop a systematic way to alleviate the long queues at the bottleneck workstation. The purpose of this study is to construct a photolithography workstation dispatching rule (PADR). This dispatching rule considers several characteristics of wafer fabrication and influential factors. Then utilize the weights and threshold values to design a hierarchical priority rule. A simulation model is also constructed to demonstrate the effect of the PADR dispatching rule. The PADR performs better in throughput, yield rate, and mean cycle time than FIFO (First‐In‐First‐Out) and SPT (Shortest Process Time).
Discusses the twofold purpose of this study, first to introduce a number of measures devised to be used in comparing and evaluating two schedules for the same project, second to present and evaluate a heuristic procedure developed in this research for solving the resource constrained project scheduling problem. Posits that the new procedure is based on the notion that a project can be partitioned into a number of sections and there is no obligation to use a single policy all the way through all the sections of project. Shows that this research is also an attempt to bridge the gap between the theory and practice by eliminating the question of which priority rule to use for which project. Develops a new model showing that selecting from a number of priority rules is not required and, using the measures of performance introduced, decides on a suitable schedule from the schedules produced under varied assumptions is shown to be much easier. Concludes with suggestions for further research.
Deals with the dynamic scheduling problems and solutions of jobshop comprising six work centres and n components. Concerns thebehaviour of the system, with the arrival of…
Deals with the dynamic scheduling problems and solutions of job shop comprising six work centres and n components. Concerns the behaviour of the system, with the arrival of urgent orders and normal orders. In a typical manufacturing system, urgent orders are scheduled for processing based on their urgency and given priority over normal orders. Describes an analysis of urgent order processing on the basis of non pre‐emptive priority and pre‐emptive resume priority over normal orders. Enumerates manufacturing system performances which had been analysed for the two most popular scheduling rules – first in first out (FIFO) and shortest processing time (SPT) – through a system simulation program. Concludes by asserting that the simulation program can be used to schedule the manufacturing system dynamically by choosing the appropriate scheduling rule to measure optimal system performance leading to higher productivity.
Reports development and simulation of real‐time dispatchingprocedures, for flexible manufacturing cells (FMCs) in constantproduction circumstances, where a fixed set of…
Reports development and simulation of real‐time dispatching procedures, for flexible manufacturing cells (FMCs) in constant production circumstances, where a fixed set of part types is processed continuously while maintaining constant ratios between quantities needed of each part type. Five different procedures were tested: the first based on a simple rule, called the largest relative advantage (LRA) rule; two procedures linear programming based (named FMLPP and ALPP); a pull‐type procedure; and the last based on SPT rule. As expected, one of the linear programming based procedures achieved the best results. However, the much simpler LRA based procedure produced similar results, especially in the presence of machine failures. It was shown that, for high processing flexibility, good performance may be achieved by a dispatching procedure using the cell processing flexibility. In contrast to this, in low processing flexibility situations, there is no significant difference between the various scheduling procedures.
The purpose of this paper is to find out whether, which and how international corporations use their codes of conduct to guide employees double‐bound by contradicting…
The purpose of this paper is to find out whether, which and how international corporations use their codes of conduct to guide employees double‐bound by contradicting cultural norms.
The paper draws on integrative social contracts theory to content‐analyse the codes of conduct of the “Fortune Global 500” and the “UNCTAD 100”.
The vast majority of international corporations' codes either does not acknowledge contradictions between equally binding norms, or lacks priority rules for employees to resolve them. Nonetheless, several codes of conduct describe how norms might contradict, give clear priority to one set of norms (local or corporate) and provide specific examples to employees of when and how to apply a priority rule.
The paper identifies the 33 codes of conduct which can serve as best practices for international corporations' employee and corporate communication.
Contradictions between cultural norms are unacknowledged or unresolved in communication practice and little explored in corporate communication research. This paper assesses the scope of this caveat in communication practice and offers solutions in the form of an existing normative theory and of newly identified best practices.
Scheduling of production in a wire rope factory is complicated byseveral features: (a) the simultaneous requirement for two types oflimited resource, machines and bobbins;…
Scheduling of production in a wire rope factory is complicated by several features: (a) the simultaneous requirement for two types of limited resource, machines and bobbins; (b) multi‐stage production with normally two or three stranding and one or two closing operations; (c) queuing at the closing machines; the typical job splits into sub‐batches when passing from the stranding to the closing operation; these sub‐batches usually queue at the closing operations which, being faster than stranding operations, generally receive work from several queues; (d) alternative choices in the selection of machines and bobbin sizes for any given stranding or closing operation; (e) the presence of random elements in the timing of machine breakdowns and repairs. In this case study factory in a developing country, the existing control of production flows was ad hoc rather than according to a specified method. The management needed to know whether a scientific scheduling approach could significantly improve the low utilisation of machines. As a first attempt a strategy was synthesised based on well‐known concepts from the theory of scheduling in static and dynamic environments, taking into consideration certain effects of the complicating factors mentioned above. Simulation revealed that a significant improvement was possible.
The importance of mobile services in our everyday life is growing while at the same time new interoperability issues arise due to hardware and software heterogeneity…
The importance of mobile services in our everyday life is growing while at the same time new interoperability issues arise due to hardware and software heterogeneity. Therefore, new architectural paradigms and models are needed to enhance software engineering methodologies with regard to platform independence and interoperability. This paper describes an UML pattern based approach for developing reconfigurable autonomous mobile services. Through the analysis of an mcommerce project, the relevance of our proposed architecture will be explained. Our focus lays on a generic reconfiguration mechanism based on profile matching from software modules. This profiling part will be further described and discussed. Finally, the applicability of our approach is investigated within a project about reconfigurable indoor navigation computers and a project about robot assisted sensor networks.