Junwen Wang

Modeling and analysis of the emergency department at University of Kentucky Chandler Hospital using simulations.

INTRODUCTION In this article, we present a simulation study conducted in the emergency department at the University of Kentucky Chandler Hospital. METHODS Based on analysis of process and flow data, a simulation model of patient throughput in the emergency department has been developed. RESULTS What-if analyses have been proposed to identify bottlenecks and investigate the optimal numbers of human and equipment resources (eg, nurses, physicians, and radiology technology). The simulation results suggest that 3 additional nurses are needed to ensure desired clinical outcomes. Diagnostic testing, the computed tomography scan in particular, is found to be a bottleneck. As a result, acquisition of an additional computed tomography scanner is recommended. Hospital management has accepted the recommendations, and implementation is in progress. DISCUSSION Such a model provides a quantitative tool for continuous improvement and process control in the emergency department and also is applicable to other departments in the hospital.

Reducing Length of Stay in Emergency Department: A Simulation Study at a Community Hospital

In this paper, a simulation model of an emergency department (ED) at a large community hospital, Central Baptist Hospital in Lexington, KY, is developed. Using such a model, we can accurately emulate the patient flow in the ED and carry out sensitivity analysis to determine the most critical process for improvement in quality of care (in terms of patient length of stay). In addition, a what-if analysis is performed to investigate the potential change in operation policies and its impact. Floating nurse, combining registration with triage, mandatory requirement of physicians visit within 30 min, and simultaneous reduction of operation times of some most sensitive procedures can all result in substantial improvement. These recommendations have been submitted to the hospital leadership, and implementations are in progress.

Modeling and analysis of work flow and staffing level in a computed tomography division of University of Wisconsin Medical Foundation.

In this paper, a Markov chain model is developed to model the work flow in a computed tomography (CT) imaging department at University of Wisconsin Medical Foundation. Using this model, we estimate the patient length of stay and investigate different configurations of radiology specialists for potential efficiency improvement to reduce flow time and cost. What-if analysis is carried out to investigate the impact of various staffing levels and sensitivity study is used to identify the bottleneck operation, i.e., the most impeding one whose improvement can lead to the highest productivity increase.

Modeling and Analysis of Care Delivery Services Within Patient Rooms: A System-Theoretic Approach

Care services within the patient rooms are the most critical and time consuming processes in patient care deliveries in emergency department, clinics, and other healthcare facilities. In this paper, we introduce a Markov chain model to study such processes. A closed, parallel, and reentrant network with limited resources is used to model the process. Formulas to evaluate the patient length of stay and staff utilizations are developed. System-theoretic properties are discussed. The extension to non-Markovian scenarios is also investigated. Such a model provides a quantitative tool for healthcare professionals to study and improve patient flow in care deliveries.

Indicators for quality improvability and bottleneck sequence in flexible manufacturing systems with batch production

In this paper we study product quality in flexible manufacturing systems with batch production using a Markov chain model. To improve the quality performance in such systems, the notions of quality improvability and bottleneck sequence are introduced. Indicators for identifying the quality improvability and bottleneck sequence, based on data measured on the factory floor rather than complicated calculations, are developed. A case study of improving quality at an automotive paint shop is introduced.

A system model of work flow in the patient room of hospital emergency department.

Modeling and analysis of patient flow in hospital emergency department (ED) is of significant importance. In a hospital ED, the patients spend most of their time in the patient room and most of the care delivery services are carried out during this time period. In this paper, we propose a system model to study patient (or work) flow in the patient room of an ED when the resources are partially available. A closed and re-entrant process model is developed to characterize the care service activities in the patient room with limited resources of doctors, nurses, and diagnosis tests. Analytical calculation of patient’s length of stay in the patient room is derived, and monotonic properties with respect to care service parameters are investigated.

Quality bottleneck transitions in flexible manufacturing systems with batch productions

A Markov chain model to analyze quality in flexible manufacturing systems with batch productions is developed in this article. The cycles when good quality and defective parts are produced are defined as the good and defective states, respectively, and transition probabilities are introduced to characterize the changes between these states. The product quality is presented as a function of these transition probabilities, and the transition that has the largest impact on quality is referred to as the quality bottleneck transition (BN-t). Analytical expressions to quantify the sensitivity of quality with respect to transition probabilities are derived, and indicators to identify the BN-t based on data collected on the factory floor are developed. Through extensive numerical experiments, it is shown that such indicators have a high accuracy in identifying the correct bottlenecks and can be used as an effective tool in quality improvement efforts. Finally, a case study at an automotive paint shop is presented to illustrate the applicability of the method.

Optimal vehicle batching and sequencing to reduce energy consumption and atmospheric emissions in automotive paint shops

Reducing energy consumption and carbon emissions is an important issue to achieve sustainable manufacturing. In automotive assembly plants, the largest amount of energy consumption and atmospheric emissions is in paint shop. Optimising the energy usage to pursue maximum energy savings, and reducing carbon dioxide equivalent emissions are of significant importance in automotive paint shops. Instead of inventing new chemicals, new painting processes or new control systems in painting booths and ovens, our research focuses on developing an optimal batch and scheduling procedure of vehicles to achieve the goal of energy and emission reduction. Specifically, by selecting appropriate batch and sequence policies, the paint quality can be improved and repaints can be reduced so that fewer material and energy will be consumed, and less atmospheric emissions will be generated. It is shown that such scheduling and control method can lead to significant energy savings and emission reduction with no extra investment, nor changes to existing painting processes.

Quality Analysis in Flexible Manufacturing Systems With Batch Productions: Performance Evaluation and Nonmonotonic Properties

In this paper, we present an analytical method to evaluate the quality performance of flexible manufacturing systems with batch operations. Many flexible manufacturing systems implement batch production to shorten changeover time, reduce cost, and improve quality. In such systems, different types of products are process in batches where all products in each batch have the same type. The change of product type only occurs after the last job in a batch is processed. A closed formula to quantify the probability of producing a good part is derived and structural properties to address the appropriate sequence of products are presented.

Product Sequencing With Respect to Quality in Flexible Manufacturing Systems With Batch Operations

In many flexible manufacturing systems, batch production is often adopted to improve product quality. For example, in automotive paint shops, vehicles with same colors are typically grouped into small batches to reduce quality degradation and purge cost due to color change. In this paper, we present an analytical method to evaluate the quality performance of flexible manufacturing systems with batch operations. In addition, we investigate the impact of product sequencing and batch policies on product quality and present some insights to achieve better quality using these policies.