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This thesis uses data from a real-world distributed system to develop a model for realistic load tests, and analyzes the results of several different workload scenarios on a test deployment. The research focused on characterizing the workload of the real-world Pretio system using logs captured from the production deployment, modelling a workload from those logs, and analyzing the impact on a test deployment of the system of a series of scenarios providing different parameters to the model. The results were evaluated by testing the response time distributions across multiple test runs for statistical similarity. / Graduate

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Purpose – The purpose is to: Improve the efficiency of warehouses operations as well as reduce its workload imbalances by altering the warehouse layout and work zones at a storage area. This was done by answering the following research questions: What is the current state of the sites efficiency and workload imbalances? How can the warehouse layout be designed to increase the efficiency? How can warehouse work zones be altered to reduce workload imbalances? Method – The purpose was achieved through a case study at a vehicle manufacturing facility. By studying established methods of efficiency, layout designs and workload imbalances, ways of improving the operations was discovered. The effects of these methods were then tested through the case.   Findings –There are two categories improving efficiency, namely increasing output or decreasing input. The study also provides examples of ways to do both, and verifies them at the case company. The focus of both methods is a decrease in travel distance which proved to be a reliable way of increasing efficiency. Workload imbalances can be decreased by sharing workload between the resources. The case shows the result of two different resources with unequal workload and discusses the trade-off between efficiency and workload equality. Implications – The practical implications of the study is guidelines for how efficiency can be increased and how workload imbalances can be decreased. The academic implications are verifications of the used theories. Limitations – This study focuses on a restricted part of the storage process, namely traveling. There are more processes which could be included to further benefit the overall efficiency, these have however been excluded to limit the scope. The study also uses a heuristic approach based on prior research which means that the optimal solution might still be unknown. Keywords – Efficiency, workload imbalances, storage management, family grouping

Thesis advisor: Patricia Tabloski / Fatigue is a factor in human error particularly on tasks requiring sustained attention (Dinges, 1995). Work-hour studies of staff nurses have demonstrated that the risks of making an error increased when nurses worked longer shifts (Rogers, Hwang, Scott, Aiken, and Dinges, 2004. Workload in anesthesia care can vary widely with diverse cognitive and physical demands (Gaba and Lee, 1990; Weinger, Herndon, Zornow, Paulus, Gaba, and Dallen, 1994; Weinger, Reddy, and Slagle, 2004; Weinger and Slagle 2001). The purpose of the study was to examine the influence of work hours and workload on fatigue in certified registered nurse anesthetists (CRNAs). A predictive, correlational design was employed and utilized an electronic survey of 10,000 active certified and active recertified CRNAs. A total of 928 CRNAs completed the survey which included a self-report of work hours. Workload was measured by the NASA Task Load Index and fatigue by the Checklist Individual Strength (CIS-20). Hierarchical multiple regression analysis was applied to the data to test the hypotheses that 1) after controlling for demographic variables, the number of work hours and workload will positively influence post-shift fatigue in nurse anesthetists and 2) after controlling for demographic variables, there will be an interaction between work hours and workload in nurse anesthetists. Work hours and workload explained 19 % of the variance in fatigue in nurse anesthetists with the greatest contribution being from the number of work hours and the workload dimension of performance satisfaction. The study findings suggest that increasing hours of anesthesia time and increasing workload, particularly dissatisfaction with meeting the goals of the anesthetic (performance dimension) increase fatigue in nurse anesthetists. The implications for practice, policy, and research are discussed. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Connell School of Nursing. / Discipline: Nursing.

In this thesis, we investigate methods by which discrete event network diffusion simulators may execute without the restriction of lockstep or near lockstep synchronicity. We develop a discrete event simulator that allows free clock drift between threads, develop a differential equations model to approximate communication cost of such a simulator, and propose an algorithm by which we leverage information gathered in the natural course of simulation to redistribute agents to parallel threads such that the burden of communication is lowered during future replicates.

Within any manufacturing environment, the selection of the production or assembly machines is part of the day to day responsibilities of management. This is especially true when there are multiple types of machines that can be used to perform each assembly or manufacturing process. As a result, it is critical to find the optimal way to select machines when there are multiple related assembly machines available. The objective of this research is to develop and present a model that can provide guidance to management when making machine selection decisions of parallel, non-identical, related electronics assembly machines. A model driven Decision Support System (DSS) is used to solve the problem with the emphasis in optimizing available resources, minimizing production disruption, thus minimizing cost. The variables that affect electronics product costs are considered in detail. The first part of the Decision Support System was developed using Microsoft Excel as an interactive tool. The second part was developed through mathematical modeling with AMPL9 mathematical programming language and the solver CPLEX90 as the optimization tools. The mathematical model minimizes total cost of all products using a similar logic as the shortest processing time (SPT) scheduling rule. This model balances machine workload up to an allowed imbalance factor. The model also considers the impact on the product cost when expediting production. Different scenarios were studied during the sensitivity analysis, including varying the amount of assembled products, the quantity of machines at each assembly process, the imbalance factor, and the coefficient of variation (CV) of the assembly processes. The results show that the higher the CV, the total cost of all products assembled increased due to the complexity of balancing machine workload for a large number of products. Also, when the number of machines increased, given a constant number of products, the total cost of all products assembled increased because it is more difficult to keep the machines balanced. Similar results were obtained when a tighter imbalance factor was used.

Electronic commerce servers have a significant presence in today's Internet. Corporations want to maintain high availability, sufficient capacity, and satisfactory performance for their E-commerce Web systems, and want to provide satisfactory services to customers. Workload characterization and the analysis of customers' interactions with Web sites are the bases upon which to analyze server performance, plan system capacity, manage system resources, and personalize services at the Web site. To date, little empirical evidence has been discovered that identifies the characteristics for Web workloads of E-commerce systems and the behaviours of customers. This thesis analyzes the Web access logs at public Web sites for three organizations: a car rental company, an IT company, and the Computer Science department of the University of Saskatchewan. In these case studies, the characteristics of Web workloads are explored at the request level, functionlevel, resource level, and session level; customers' interactions with Web sites are analyzed by identifying and characterizing session groups. The main E-commerce Web workload characteristics and performance implications are: i) The requests for dynamic Web objects are an important part of the workload. These requests should be characterized separately since the system processes them differently; ii) Some popular image files, which are embedded in the same Web page, are always requested together. If these files are requested and sent in a bundle, a system will greatly reduce the overheads in processing requests for these files; iii) The percentage of requests for each Web page category tends to be stable in the workload when the time scale is large enough. This observation is helpful in forecasting workload composition; iv) the Secure Socket Layer protocol (SSL) is heavily used and most Web objects are either requested primarily through SSL or primarily not through SSL; and v) Session groups of different characteristics are identified for all logs. The analysis of session groups may be helpful in improving system performance, maximizing revenue throughput of the system, providing better services to customers, and managing and planning system resources. A hybrid clustering algorithm, which is a combination of the minimum spanning tree method and k-means clustering algorithm, is proposed to identify session clusters. Session clusters obtained using the three session representations Pages Requested, Navigation Pattern, and Resource Usage are similar enough so that it is possible to use different session representations interchangeably to produce similar groupings. The grouping based on one session representation is believed to be sufficient to answer questions in server performance, resource management, capacity planning and Web site personalization, which previously would have required multiple different groupings. Grouping by Pages Requested is recommended since it is the simplest and data on Web pages requested is relatively easy to obtain in HTTP logs.

Tidigare forskning har visat att kvinnor uppsöker professionell hjälp oftare än män, detta sägs bero på att kvinnor har lättare att erkänna sig själva som svaga. Syftet var att undersöka om det fanns någon skillnad i hur män och kvinnor bedömde en kollegas arbetsrelaterade stress samt om kollegans kön påverkade bedömningen. Ett urval på 108 yrkesarbetande män och kvinnor från två sektorer valdes ut, deltagarna läste tre vinjetter om en stressad man eller kvinna vars hälsa gradvis försämras på grund av ökad arbetsbelastning. En flervägs mixed ANOVA gjordes med bedömningen av målpersonens arbetsbörda, ohälsa och hjälpbehov som beroendevariabler. Resultaten visade att män uppfattade en kvinnlig kollegas ohälsa och hjälpbehov som större än en manlig kollegas. Kvinnor gjorde ingen skillnad på manliga eller kvinnliga kollegor. Män och kvinnor uppfattade det motsatta könets arbetsbörda som större än det egna. Kvinnliga eller manliga kollegor kan vara avgörande för när individen blir erbjuden hjälp.

Electronic commerce servers have a significant presence in today's Internet. Corporations want to maintain high availability, sufficient capacity, and satisfactory performance for their E-commerce Web systems, and want to provide satisfactory services to customers. Workload characterization and the analysis of customers' interactions with Web sites are the bases upon which to analyze server performance, plan system capacity, manage system resources, and personalize services at the Web site. To date, little empirical evidence has been discovered that identifies the characteristics for Web workloads of E-commerce systems and the behaviours of customers. This thesis analyzes the Web access logs at public Web sites for three organizations: a car rental company, an IT company, and the Computer Science department of the University of Saskatchewan. In these case studies, the characteristics of Web workloads are explored at the request level, functionlevel, resource level, and session level; customers' interactions with Web sites are analyzed by identifying and characterizing session groups. The main E-commerce Web workload characteristics and performance implications are: i) The requests for dynamic Web objects are an important part of the workload. These requests should be characterized separately since the system processes them differently; ii) Some popular image files, which are embedded in the same Web page, are always requested together. If these files are requested and sent in a bundle, a system will greatly reduce the overheads in processing requests for these files; iii) The percentage of requests for each Web page category tends to be stable in the workload when the time scale is large enough. This observation is helpful in forecasting workload composition; iv) the Secure Socket Layer protocol (SSL) is heavily used and most Web objects are either requested primarily through SSL or primarily not through SSL; and v) Session groups of different characteristics are identified for all logs. The analysis of session groups may be helpful in improving system performance, maximizing revenue throughput of the system, providing better services to customers, and managing and planning system resources. A hybrid clustering algorithm, which is a combination of the minimum spanning tree method and k-means clustering algorithm, is proposed to identify session clusters. Session clusters obtained using the three session representations Pages Requested, Navigation Pattern, and Resource Usage are similar enough so that it is possible to use different session representations interchangeably to produce similar groupings. The grouping based on one session representation is believed to be sufficient to answer questions in server performance, resource management, capacity planning and Web site personalization, which previously would have required multiple different groupings. Grouping by Pages Requested is recommended since it is the simplest and data on Web pages requested is relatively easy to obtain in HTTP logs.