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Improving the Quality of Scheduling Decisions for the Engineering FunctionGrabenstetter, Douglas H 15 December 2012 (has links)
The Engineer to Order (ETO) model is used by a significant number of manufacturers across multiple sectors. Indeed, ETO firms comprise approximately one fourth of all North American manufacturing and are growing at a rate of twenty percent (Cutler [10]). In the ETO environment, the engineering process is the largest controllable consumer of lead-time in ETO firms. Since one half of the total lead-time is typically consumed by the engineering process, it is a critical task to accurately set the due date and later sequence the jobs in queue. However, unlike other manufacturing models such as Make to Stock or Make to Order, the product for each order is unique. Hence the resulting design is not realized until after the engineering process has been completed an the only information available is limited to information which has been gathered during the quoting stage of the order fulfillment process. These facts drive uncertainty into the front-end process. Therefore, the question becomes how does one predict the job difficulty let alone the due date in a complex transactional process when the job has not even been designed yet? In regard to the state of the art for the topic of design complexity, due date setting and sequencing, there is an abundance of research. Unfortunately little of it is aimed at the ETO environment. Additionally, there is not an agreed upon way in the literature to define complexity nor is there one overarching methodology for assessing complexity. Therefore, this research investigates the topics of job complexity, due date setting and job sequencing in the context of the Engineer to Order model. Analytical research is conducted with in conjunction with multiple ETO firms and several common factors are identified which drive complexity in the ETO engineering environment. These complexity factors are can be used is as an input to the accurate prediction of flow times for the ETO engineering process as well as sequencing. The research results in new innovative approaches for complexity assessment, due date setting and sequencing which outperform existing approaches.
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A computer simulation analysis of a flow shopWalters, Robert H. January 1984 (has links)
No description available.
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GETTING TO 40 WEEKS: CONSTRUCTING THE UNCERTAINTY OF DUE DATESVos, Sarah Cornelia 01 January 2012 (has links)
In the United States as many as 15% of births occur before 39 weeks because of elective inductions or cesarean sections. This qualitative study employs a grounded theory approach to understand the decisions women make of how and when to give birth. Thirty-three women who were pregnant or had given birth within the past two years participated in key informant or small group interviews. The women’s birth narratives and reflections reveal how they construct the uncertainty of their due dates and how this construction influences their birth decisions. Problematic integration theory is used to analyze this construction and identify points of influence. The results suggest that women construct the uncertainty of due dates as a reason to wait on birth and as a reason to start the process early. The results suggest that information about a baby’s brain development in the final weeks of pregnancy may persuade women to remain pregnant longer. The results demonstrate the utility of using problematic integration theory to understand a medical situation that is the result of epistemological and ontological uncertainty. The analysis suggests the existence of a third type of uncertainty, axiological uncertainty. Axiological uncertainty is rooted in the values and ethics of outcomes.
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Maximization of Delivery-Based Customer Satisfaction Considering Customer-Job Relationships in a Multi-Period EnvironmentArinsoy, Aslican January 2013 (has links)
No description available.
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Cell Loading and Family Scheduling for Jobs with Individual Due Dates in a Shoe Manufacturing CompanyMese, Emre M. 21 September 2009 (has links)
No description available.
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Determining the Optimal Transportation Method in Due-Date Driven Manufacturing EnvironmentsÇelikbilek, Can 03 October 2011 (has links)
No description available.
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Perishable Inventory Management Solutions and Challenges of Kosovo FFRs : Avoiding Product Expiration at Retails ShelvesRexhaj, Betim January 2019 (has links)
Title: Perishable Inventory Management Solutions and Challenges of Kosovo FFRs. Avoiding Product Expiration at Retails ShelvesPurpose: In this thesis perishable inventory management solutions and challenges at Kosovo FFRs have been studied and identified. Hence, after identifying PIM solutions and challenges the research suggests ideas that will contribute to avoid the expiration of perishable products if selling them takes more time than their actual shelf life. This contributes to minimizing food waste in food supply chains and fresh food retailers. Methodology: Thesis consist of qualitative methods where multiple case studies in cooperation with Kosovo FFRs have been performed. Data collection methods included semi structured interviews, site visits and some financial data accessed from annual and government reports. Theory: Theoretical chapter has been developed from preexisting theory on perishable inventory management. Five phases of fresh food retailing inventory management have been developed and used as the basis for practical research. Moreover, part two of the theoretical chapter talks about the perishable inventory management challenges and is the basis for the second research question. Findings: The findings have shown that Kosovo FFRs use a mixture of PIM solutions with a focus on shelf life and replenishment solutions. The study also revealed that Kosovo FFRs are outdated regarding to product identification and software solutions, however, manage to perform somehow satisfactorily. Consequently, because of the lack of contemporary identification technologies Kosovo FFRs PIM challenges where found to be related to data accuracy and real time data access.
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Batch Processsor Scheduling - A Class Of Problems In Steel Casting FoundriesRamasubramaniam, M 06 1900 (has links)
Modern manufacturing systems need new types of scheduling methods. While traditional scheduling methods are primarily concerned with sequencing of jobs, modern manufacturing environments provide the additional possibility to process jobs in batches. This adds to the complexity of scheduling. There are two types of batching namely: (i) serial batching (jobs may be batched if they share the same setup on a machine and one job is processed at a time. The machine which processes jobs in this manner is called as discrete processor) and (ii) parallel batching (several jobs can be processed simultaneously on a machine at a time. The machine which processes jobs in this manner is called as batch processor or batch processing machine).
Parallel batching environments have attracted wide attention of the researchers working in the field of scheduling. Particularly, taking inspiration from studies of scheduling batch processors in semiconductor manufacturing [Mathirajan and Sivakumar (2006b) and Venkataramana (2006)] and in steel casting industries [Krishnaswamy et al. (1998), Shekar (1998) and Mathirajan (2002)] in the Management Studies Department of Indian Institute of Science, this thesis addresses a special problem on scheduling batch processor, observed in the steel casting manufacturing.
A fundamental feature of the steel casting industry is its extreme flexibility, enabling castings to be produced with almost unlimited freedom in design over an extremely wide range of sizes, quantities and materials suited to practically every environment and application. Furthermore, the steel casting industry is capital intensive and highly competitive.
From the viewpoint of throughput and utilization of the important and costly resources in the foundry manufacturing, it was felt that the process-controlled furnace operations for the melting and pouring operations as well as the heat-treatment furnace operations are critical for meeting the overall production schedules. The two furnace operations are batch processes that have distinctive constraints on job-mixes in addition to the usual capacity and technical constraints associated with any industrial processes. The benefits of effective scheduling of these batch processes include higher machine utilization, lower work-in-process (WIP) inventory, shorter cycle time and greater customer satisfaction [Pinedo (1995)].
Very few studies address the production planning and scheduling models for a steel foundry, considering the melting furnace of the pre-casting stage as the core foundry operation [Voorhis et al. (2001), Krishnaswamy et al. (1998) and Shekar (1998)]. Even though the melting and pouring operations may be considered as the core of foundry operations and their scheduling is of central importance, the scheduling of heat-treatment furnaces is also of considerable importance. This is because the processing time required at the heat treatment furnace is often longer compared to other operations in the steel-casting foundry and therefore considerably affects the scheduling, overall flow time and WIP inventory.
Further, the heat-treatment operation is critical because it determines the final properties that enable components to perform under demanding service conditions such as large mechanical load, high temperature and anti-corrosive processing. It is also important to note that the heat-treatment operation is the only predominantly long process in the entire steel casting manufacturing process, taking up a large part of total processing time (taking up to a few days as against other processes that typically take only a few hours). Because of these, the heat-treatment operation is a major bottleneck operation in the entire steel casting process.
The jobs in the WIP inventory in front of heat-treatment furnace vary widely in sizes (few grams to a ton) and dimensions (from 10 mm to 2000 mm). Furthermore, castings are primarily classified into a number of job families based on the alloy type, such as low alloy castings and high alloy castings. These job families are incompatible as the temperature requirement for low alloy and high alloy vary for similar type of heat-treatment operation required. These job families are further classified into various sub-families based on the type of heat treatment operations they undergo. These sub-families are also incompatible as each of these sub-families requires a different combination of heat-treatment operation. The widely varying job sizes, job dimensions and multiple incompatible job family characteristic introduce a high degree of complexity into scheduling heat-treatment furnace.
Scheduling of heat-treatment furnace with multiple incompatible job families can have profound effect on the overall production rate as the processing time at heat-treatment operation is very much longer. Considering the complexity of the process and time consumed by the heat treatment operation, it is imperative that efficient scheduling of this operation is required in order to maximize throughput and to enhance productivity of the entire steel casting manufacturing process. This is of importance to the firm. The concerns of the management in increasing the throughput of the bottleneck machine, thereby increasing productivity, motivated us to adopt the scheduling objective of makespan.
In a recent observation of heat-treatment operations in a couple of steel casting industries and the research studies reported in the literature, we noticed that the real-life problem of dynamic scheduling of heat-treatment furnace with multiple incompatible job families, non-identical job sizes, non-identical job dimensions, non-agreeable release times and due dates to maximize the throughput, higher utilization and minimize the work-in-process inventory is not at all addressed. However, there are very few studies [Mathirajan et al. (2001, 2002, 2004a, 2007)] which have addressed the problem of scheduling of heat-treatment furnace with incompatible job families and non-identical job sizes to maximize the utilization of the furnace. Due to the difference between the real-life situation on dynamic scheduling of heat-treatment furnace of the steel casting manufacturing and the research reported on the same problem, we identified three new class of batch processor problems, which are applicable to a real-life situation based on the type of heat-treatment operation(s) being carried out and the type of steel casting industry (small, medium and large scale steel casting industry) and this thesis addresses these new class of research problems on scheduling of batch processor.
The first part of the thesis addresses our new Research Problem (called Research Problem 1) of minimizing makespan (Cmax) on a batch processor (BP) with single job family (SJF), non-identical job sizes (NIJS), and non-identical job dimensions (NIJD). This problem is of interest to small scale steel casting industries performing only one type of heat treatment operation such as surface hardening. Generally, there would be only a few steel casting industries which offer such type of special heat-treatment operation and thus the customer is willing to accept delay in the completion of his orders. So, the due date issues are not important for these types of industries.
We formulate the problem as Mixed Integer Linear Programming (MILP) model and validate the proposed MILP model through a numerical example. In order to understand the computational intractability issue, we carry out a small computational experiment. The results of this experiment indicate that the computational time required, as a function of problem size, for solving the MILP model is non-deterministic and non-polynomial.
Due to the computational intractability of the proposed MILP model, we propose five variants of a greedy heuristic algorithm and a genetic algorithm for addressing the Research Problem 1. We carry out computational experiments to obtain the performance of heuristic algorithms based on two perspectives: (i) comparison with optimal solution on small scale instances and (ii) comparison with lower bound for large scale instances. We choose five important problem parameters for the computational experiment and propose a suitable experimental design to generate pseudo problem instances.
As there is no lower bound (LB) procedure for the Research Problem1, in this thesis, we develop an LB procedure that provides LB on makespan by considering both NIJS and NIJD characteristics together. Before using the proposed LB procedure for evaluating heuristic algorithms, we conduct a computational experiment to obtain the quality of the LB on makespan in comparison with optimal makespan on number of small scale instances. The results of this experiment indicate that the proposed LB procedure is efficient and could be used to obtain LB on makespan for any large scale problem.
In the first perspective of the evaluation of the performance of the heuristic algorithms proposed for Research Problem 1, the proposed heuristic algorithms are run through small scale problem instances and we record the makespan values. We solve the MILP model to obtain optimal solutions for these small scale instances. For comparing the proposed heuristic algorithms we use the performance measures: (a) number of times the proposed heuristic algorithm solution equal to optimal solution and (b) average loss with respect to optimal solution in percentage.
In the second perspective of the evaluation of the performance of the heuristic algorithms, the proposed heuristic algorithms are run through large scale problem instances and we record the makespan values. The LB procedure is also run through these problem instances to obtain LB on makespan. For comparing the performance of heuristic algorithms with respect to LB on makespan, we use the performance measures: (a) number of times the proposed heuristic algorithm solution equal to LB on makespan (b) average loss with respect to LB on makespan in percentage, (c) average relative percentage deviation and (d) maximum relative percentage deviation.
We extend the Research Problem 1 by including additional job characteristics: job arrival time to WIP inventory area of heat-treatment furnace, due date and additional constraint on non-agreeable release time and due date (NARD). Due date considerations and the constraint on non-agreeable release times and due date (called Research Problem 2) are imperative to small scale steel casting foundries performing traditional but only one type of heat treatment operation such as annealing where due date compliance is important as many steel casting industries offer such type of heat treatment operations. The mathematical model, LB procedure, greedy heuristic algorithm and genetic algorithm proposed for Research Problem 1, including the computational experiments, are appropriately modified and\or extended for addressing Research Problem 2.
Finally, we extend the Research Problem 2 is by including an additional real life dimension: multiple incompatible job families (MIJF). This new Research Problem (called Research Problem 3) is more relevant to medium and large scale steel casting foundries performing more than one type of heat treatment operations such as homogenizing and tempering, normalizing and tempering. The solution methodologies, the LB procedure and the computational experiments proposed for Research Problem 2 are further modified and enriched to address the Research Problem 3.
From the detailed computational experiments conducted for each of the research problems defined in this study, we observe that: (a) the problem parameters considered in this study have influence on the performance of the heuristic algorithms, (b) the proposed LB procedure is found to be efficient, (c) the proposed genetic algorithm outperforms among the proposed heuristic algorithms (but the computational time required for genetic algorithm increases as problem size keeps increasing), and (d) in case the decision maker wants to choose an heuristic algorithm which is computationally most efficient algorithm among the proposed algorithms, the variants of greedy heuristic algorithms : SWB, SWB(NARD), SWB(NARD&MIJF) is relatively the best algorithm for Research Problem 1, Research Problem 2 and Research Problem 3 respectively.
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Rekalkulace splátek leasingové smlouvy / Recalculations of Leasing Contract PaymentsKračmarová, Monika January 2007 (has links)
This Diploma Work focuses on re-calculation of payments of leasing contracts concluded by D.S.Leasing, a.s. The data gained as an output of a thorough analysis are processed in MS Excel, creating a new re-calculation tool able to bring practical solution to individual modification of payments of a leasing contract.
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