6898048
Supporting manufacturing with simulation: model design, development, and deployment
In this paper, we identify and discuss the features we believe are key to the successful use of simulation as a manufacturing support tool. The discussion begins with three sample projects drawn from the authors' industrial and consulting experiences. Using these projects as motivation, we discuss the ideal project lifecycle model design, development, and deployment. For model design, we emphasize the importance of a clear and consistent specification, articulated in a written document. This specification should identify project customers, goals, and deliverables. We next review a range of model development options, stressing the existence of many non-simulation alternatives. We also discuss methods for model verification and validation. Finally, we consider the difficulties of model deployment, including simulation output analysis, data maintenance, and model integration. We close with several suggestions on how best to present simulation results to a management audience.
5441653
Integrating targeted cycle-time reduction into the capital planning process
This paper describes the development and application of an integrated static capacity and dynamic simulation analysis methodology for purchasing equipment capacity. The goal of the study is to address targeted cycle time objectives in a start up recording head wafer manufacturing facility at Seagate Technology, Minneapolis, MN. The short product cycle time, coupled with the competitive nature of the disc drive industry, has made cycle time reduction one of the most important objectives of production capacity planning. This paper describes an equipment procurement strategy in which static capacity analysis is used to identify an initial equipment set with a low slack capacity variable on each tool group. Simulation analysis is then used to identify the critical tool groups that contribute to cycle time delays. The Seagate Industrial Engineering team used the simulation analysis tool Factory Explorer(R) from Wright, Williams and Kelly to perform the cycle time reduction analysis. This targeted approach is compared to the traditional static capacity planning approach of globally applying reserve capacity buffers of 20% or more to achieve the same cycle time reduction goal. Overall, the targeted approach has proven to be efficient in terms of minimizing capital equipment expenditures and also effective on the factory floor.
17448440
Effective implementation of cycle time reduction strategies for semiconductor back-end manufacturing
Using discrete event simulation models, a study was conducted to evaluate the current production practices of a high volume semiconductor back-end operation. The overall goal was to find potential areas for productivity improvement that would collectively yield a 60% reduction in manufacturing cycle time. The paper presents the simulation methodology and findings pertaining to analysis of the Assembly, Burn-In, and Test operations. Many of the recommendations identified can be implemented at no additional cost to the factory. The most significant opportunities for improvement are in the Test area, the system constraint. Additionally, the model is extremely sensitive to changes in operator staffing levels, an accurate reflection of many back-end operations. The model shows that the cumulative impact of these recommendations is a 41% reduction in average cycle time, a significant contribution to the overall goal.
955470
Improved Data Retrieval Using Semantic Transformation
Semantic query optimisation uses knowledge about properties of the data, represented as a set of subset descriptor rules, to transform a query into another form that can be executed in a more efficient manner but still yields the same result as the original query. Commonly this ’semantic knowledge’ in the form of rules is generated either during the query process itself or else is constructed in advance according to defined heuristics. Over a period of time the rule set may, therefore, become very large and the number of semantically equivalent queries that may be derived rises exponentially. Each rule use creates a new equivalent query. The problem is to identify one near optimal alternative query in a time that is minimal and also short relative to the overall query execution time. In this paper we propose a method for measuring the effectiveness of each rule and present a fast algorithm which selects the most cost effective transformations to directly yield the optimal alternative query. Experiments carried out on a large publicly available dataset show worthwhile savings using the approach.
15957762
Sensor networks and grid middleware for laboratory monitoring
By combining automatic environment sensing and experimental data collection with broker based messaging middleware, a system has been produced far the real-time monitoring of experiments whilst away from the lab. Changes in the laboratory environment are encapsulated as simple messages, which are published using an MQTT compliant broker. Clients subscribe to the MQTT stream, and perform a data transform on the messages; this may be to produce a user display or to change the format of the message for republishing. For example, an MQTT client written for the Java MIDP platform can be run on a smart-phone with a GPRS Internet connection, freeing us from the constraints of the network. We present an overview of the technologies used, and how these are helping chemists make the best use of their time
6479052
Data Analysis for Query Processing
Data analysis is needed in connection with query processing, to produce data summary information in the form of rules or assertions that allow semantic query optimisation or direct query answering without consulting the data itself. The goal of an intelligent analyser in this context is to produce robust rules, stable in the presence of data changes, which allow easy rule maintenance as data changes, and provide rapid query reformulation, refutation or answering. It must also limit the rule set to rules useful for query processing.
12408680
Utilising Multiple Computers in Database Query Processing and Descriptor Rule Management
A fundamental problem to be solved in systems that derive rules from database tables to use in query optimisation is the workload involved. If the data server has to do the work it can interfere with query processing and cause slower query answering, which is the opposite of the required effect. This paper reports our investigation of the use of multiple workstations in the same local network as the data server to derive and maintain sets of rules describing data subsets. These rules are used in query optimisation. In a local area network of workstations, one computer accepts SQL queries and data manipulation commands from networked clients. This computer provides an interface to one or more database management systems located on computers in the network. It uses a collection of subset-descriptor rules for query reformulation before forwarding the semantically optimised query. It manages a set of workstations in the network, to derive and maintain the rules. The workstations are ordinary networked computers whose spare computing capacity is utilised by spawning background programs on them.
27367510
Genetic search for Golomb arrays
Genetic search with a decision level chromosome is used to search efficiently for Golomb (1982) arrays. A Golomb array A is a binary array with three values for its discrete autocorrelation function; M, the number of ones in A for no offset, 1 when there is partial overlap, and 0 otherwise. In one dimension, A is known as a Golomb ruler. The method yields improvement because the genetic search considers only feasible solutions in the most likely portion of the search space. Each chromosome bit represents a decision to place a one in an iterative construction. The representation includes all possible arrays. Since the chromosome bits represent binary decisions in the search space, genetic operations (such as crossover and mutation) always result in feasible descendent chromosomes. Experimental results include comparison to previously known search methods and several new arrays. These results indicate that the proposed search is significantly more efficient than prior methods.