Rachel T. Johnson

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OBJECTIVE Hospital hyperglycemia, in individuals with and without diabetes, has been identified as a marker of poor clinical outcome in cardiac surgery patients. However, the impact of perioperative hyperglycemia on clinical outcome in general and noncardiac surgery patients is not known. RESEARCH DESIGN AND METHODS This was an observational study with(More)
Cycle Time -- Throughput curves (CT-TH), which plot the average cycle time versus start rate for a given product mix, are often used to support decisions made in manufacturing settings, such as the impact of proposed changes in start rate on mean cycle time. Discrete event simulation is often used to generate estimations of cycle time at a significant(More)
1 OBJECTIVE — To determine the effect of total parenteral nutrition (TPN)-induced hyper-glycemia on hospital outcome. RESEARCH DESIGN AND METHODS — The study determined whether blood glucose values before, within 24 h, and during days 2–10 of TPN are predictive of hospital complications and mortality. RESULTS — Subjects included a total of 276 patients(More)
This paper illustrates an example of the use of a metamodeling approach to simulation through an example of two real world semiconductor manufacturing systems. The meta-model used was from Yang <i>et al.</i> (2004) and has similarities to Cheng and Kleijnen (1999). The approach aims at reducing the amount of simulation work necessary to generate high(More)
This paper describes the use of the design and analysis of experiments to calibrate an agent-based simulation model of a peace-keeping mission. The situation depicted is a refugee camp scenario in which de-escalation of enraged civilians is required by military personnel. Calibration was determined by ensuring that the military actions in the simulation(More)
The use of simulation as a modeling and analysis tool is wide spread. Simulation is an enabling tool for experimenting virtually on a validated computer environment. Often the underlying function for the results of a computer simulation experiment has too much curvature to be adequately modeled by a low order polynomial. In such cases finding an appropriate(More)
In the analysis of a manufacturing system, the analyst is often interested in the change in mean cycle time as a function of different throughput (start rate) levels. Since the variance of the mean cycle time generally increases as the start rate increases, an equal allocation of simulation effort at each simulated throughput level will result in confidence(More)
Response surface methodology is widely used for process development and optimisation, product design, and as part of the modern framework for robust parameter design. For normally distributed responses, the standard second-order designs such as the central composite design and the Box-Behnken design have relatively high D and G efficiencies. In situations(More)
i ABSTRACT This dissertation explores different methodologies for combining two popular design paradigms in the field of computer experiments. Space-filling designs are commonly used in order to ensure that there is good coverage of the design space, but they may not result in good properties when it comes to model fitting. Optimal designs traditionally(More)