Hank Grant

Real-time due-date promising by build-to-order environments

A vast amount of literature exists on scheduling to meet due dates, but very little work considers how to set these due dates before scheduling the orders. A method is described for real-time promising of order due dates that is applicable to discrete build-to-order environments facing dynamic order arrivals. When computing a due date, the method considers: (1) dynamic time-phased availability of resources required for each operation of the order, (2) individual order-specific characteristics and (3) existing commitments to orders that arrived previously. Performance of the method surpasses that of due-date assignment methods previously examined in the literature and also those commonly used in practice. The median and standard deviation of absolute flow-time estimation error and of absolute lateness are chosen as the primary performance criteria because they capture both positive and negative error in flow-time estimation of each individual order. Computational results from large-scale simulation studies of realistic systems with 20 resources and up to 100 000 orders also indicate the method is highly scalable.

Simulation modeling with artificial reality technology (SMART): an integration of virtual reality and simulation modeling

Simulation Modeling with Artificial Reality Technology (SMART) is a simulation modeling tool that provides a virtual reality interface for building graphical simulation models. The simulation models, comprised of nodes and arcs, are constructed in three dimensions. As the user builds a model, he may immerse himself in it using virtual reality hardware and software tools and take advantage of the three dimensional environment provided by SMART. Models built using SMART can be exported to AweSim, and simulated as SLAM models (Pristker et al., 1996). The virtual reality hardware includes an electronic glove and head-mounted display. The specific hardware is the 5DT Glove (Fifth Dimension Technologies, 1996) and VIO I-Glasses (Virtual I-O, 1995), respectively. By wearing the 5DT Glove, the user can navigate through virtual space and manipulate a three dimensional simulation model. The VIO I-Glasses allows the user to experience immersion in the virtual modeling world. The head-mounted device constantly responds to the motions of the users head to reflect changes in his view of the virtual world. With SMART, simulation practitioners are no longer restricted to building simulation models on a flat two dimensional space. Rather, they can now build three dimensional simulation models with high non-planar complexity through the virtual reality interface provided by SMART.

Investigation of spurious emissions from cellular phones and the possible effect on aircraft navigation equipment

The study described in this paper investigated the possible interference of spurious emissions from cellular phones on aircraft navigation and communication equipment. Six wireless phone technologies were investigated over three frequency ranges, which covered the receiving ranges of five aircraft systems. The aircraft systems examined were very-high frequency omnidirectional range (VOR), localizer (LOC), very high frequency communication (VHF), glide slope (GS), and global positioning system (GPS). Research was performed in a semi-anechoic chamber (SAC) and a reverberation chamber (RC), with the phone at a distance of 1 m from the receiving antenna. Two antenna orientations were tested in the SAC. Initial tests yielded the appropriate height from the receiving antenna above the ground plane that would produce a maximum field measurement. Keypad programming was used to simulate worst-case phone transmissions. Radiated power measurements were performed and analyzed taking into consideration path loss results from the RTCA/DO-233 study. None of the six phone technologies investigated exhibited a power level greater than a 38-dBm path loss level above the maximum sensitivity of the aircraft system antennae when tested 1 m away from the antenna. These results indicate that, for the aircraft systems tested (VOR, LOC, VHF, GS, and GPS), the antenna of these systems would not have detected the emissions of the phones used in this study (CDMA-cellular, TDMA-11 Hz, TDMA-50 Hz cellular and PCS, GSM, and DCS-1800).

Wireless EMC in the medical industry: review of research and the impact on EMI risk

This paper reviews research performed at the University of Oklahoma Center for the Study of Wireless EMC, providing a summary of the results and discussion concerning the impact of the research on industry. In addition to a review of the research, we also discuss the management of risk of EMI in conjunction with these and other electronic devices, based on the results of our research.

An application of discrete-event simulation to an outpatient healthcare clinic with batch arrivals

An application of discrete-event simulation is performed on an unique outpatient primary care clinic serving a military population at Fort Sill, OK. Access to the clinic is on an exclusively walk-in basis. Arrivals occur primarily in batches; arrival times and batch sizes are stochastic in nature. The nursing and medical staffs available each day also follow a stochastic process. The arrival process is characterized through discrete distributions. Several alternatives are modeled to examine procedural changes that may result in improved patient flow and provider utilization. A hybrid appointment/walk-in model was determined to have the best promise for improvement, but the possible benefits it may yield do not seem to justify the costs of its implementation in this setting. Possible applications of the hybrid model to other facilities such as urgent care facilities are discussed.

Using simulation to evaluate buffer adjustment methods in order promising

Much literature exists for scheduling production, but there is little work on establishing the due dates that serve as the inputs to developing a production schedule. We call this order promising. This paper explores a simulation-based approach for evaluating methods for promising the delivery of orders based on dynamic buffer adjustment coupled with various methods to forecast the amount of buffer required. The primary objective of the paper is to frame the problem and suggest methods of analysis. Preliminary computational results are also presented.

Simulation of an injector plunger production line

As part of the design of a new production system, simulation was used to evaluate four production cell design options for the manufacturer of fuel injector plungers. By simulating the proposed design options, Rochester Products was able to select the alternative that would provide the best performance. This paper describes the model used and provides details on the analysis performed.

A survey of issues in biomanufacturing research

Biotechnology has become one of the primary development areas of the 21st century. For a medical device or pharmaceutical manufacturer to remain on the competitive edge, not only is it necessary to satisfy the stringent product demands of the biotechnology markets, but those companies must also develop processes that can accelerate the time frame from research and development to manufacturing and actual marketing of the medical products. Biomanufacturing is defined as the design, development, implementation and management of systems for the production of products that are integrated into or interact with human systems. This paper identifies important research issues in this relatively new manufacturing field that is anticipated to be an important area for industrial engineering, because it involves products that are expensive, complex, contain rapidly changing technology and are difficult to manufacture on a large scale.

Naïve learning algorithms utilized for the prediction of stock prices to compare economic models of decision making

An advance in economic thought is in the area of behavioral economics where traditional models of rational decision-making are challenged by newer models of behavior such as Prospect Theory. This is coupled with a world where algorithms have abilities to learn, remember and evolve over time to make better decisions. The advances on these two fronts are forcing the world of markets to be analyzed from a different angle. This work is a look at markets to compare traditional expected utility theory of economic decision-making to the newer idea of Prospect Theory. Two learning algorithms, based on traditional expected utility and Prospect Theory, are designed and then compared under several scenarios designed to replicate various market conditions faced by investors. Deviations were analyzed to measure the effectiveness of the two algorithms and also the two models of economic decision making, where it was found that risk averseness described by Prospect Theory will lead to greater deviations in expected prices than more traditional models of economic decision making. This is for several reasons, including risk aversion can, in most situations, lead to suboptimal economic decisions.