Steven E. Butt

A heuristic for the multiple tour maximum collection problem

Abstract The multiple tour maximum collection problem (MTMCP) consists of determining the m optimal time constrained tours which visit a subset of weighted nodes in a graph such that the total weight collected from the subset of nodes is maximized. In this paper, a heuristic for the MTMCP is developed. The results of computational testing reveal that the heuristic has three very attractive features. First, the heuristic will always produce a feasible solution if one exists. Second, the heuristic produces very good solutions. In most cases where the exact solution is known, it produces the optimal solution. And finally, the heuristic has the ability to handle large problems in a very short amount of computation time.

An efficient algorithm for facility location in the presence of forbidden regions

Abstract This paper investigates a constrained form of the classical Weber problem. Specifically, we consider the problem of locating a new facility in the presence of convex polygonal forbidden regions such that the sum of the weighted distances from the new facility to n existing facilities is minimized. It is assumed that a forbidden region is an area in the plane where travel and facility location are not permitted and that distance is measured using the Euclidean-distance metric. A solution procedure for this nonconvex programming problem is presented. It is shown that by iteratively solving a series of unconstrained problems, this procedure terminates at a local optimum to the original constrained problem. Numerical examples are presented.

Facility location in the presence of congested regions with the rectilinear distance metric

This paper considers the planar p-median problem in the presence of congested regions, where distances are measured with the rectilinear distance metric. We define a congested region as a convex polygonal area of the plane in which a new facility cannot be located but through which travel is permitted at an additional cost per unit distance. Based on these assumptions, we show that this constrained form of the planar P-median problem can be transformed into an equivalent unconstrained P-median problem on a network. Hence, this constrained form of the P-median problem is reduced to a combinatorial search where an optimal set of new facilities is chosen from a finite set of candidate points.

Reducing Fatality Rates of the Hispanic Workforce in the U.S. Construction Industry: Challenges and Strategies

AbstractRecent government statistics have revealed a high rate of fatalities among Hispanic workers in the U.S. construction industry. This study investigates the root causes of this issue as well as the existing attempts to manage these causes effectively. Cultural barriers are one of the root causes that have not been fully explored. This detailed investigation expands into an exploration of cultural barriers and differences, variables that are directly attributable to construction site safety. A survey instrument was designed to evaluate the existence and influence of these differences at U.S. construction sites, and data were collected from construction supervisors across the United States. The results of the survey strongly suggest the existence of two differences: high power distance and collectivism cultural dimensions. Based on the survey results and feedback from construction supervisors, recommendations for best practices in workforce development that guides construction professionals and resear...

Do users desire symmetrical lumbar supports in task seating

Abstract This research was designed to objectively investigate the desired low back (lumbar) support in a task chair; specifically by allowing a user to self-select the magnitude and location of support. An experimental chair built specifically for this study allowed the users to remotely adjust 35 diodes to achieve their desired level of support. Pressure mapping was used to measure the interface pressure at the user–seat back interface. It was determined that 73.8% of the 201 participants in this study, self-selected asymmetrical lower back support that was at least 20% greater on one side vs. the other. Additionally, 16.9% of the participants self-selected support on one side which was at least twice that of the other side. Contrary to popular practice, participants were found to prefer asymmetric support in the lower back region. It is anticipated that the culmination of this research will aid chair manufacturers in designing adaptable back rests. Practitioner Summary: Most current lumbar supports are designed to move vertically and to symmetrically increase or decrease in firmness as per a user’s adjustment. This investigation highlights that participants tended to select asymmetrical lumbar support, and as such, designers should consider providing lumbar supports that provide the desired support at appropriate locations.

Managing Cultural Diversity at U.S. Construction Sites: Hispanic Workers’ Perspectives

AbstractCommunication on construction sites is crucial for improving overall construction performance. Cultural barriers influence the clarity of communication between construction supervisors and ...

Modeling nurse-patient assignments considering patient acuity and travel distance metrics

Balancing workload among nurses on a hospital unit is important for the satisfaction and safety of nurses and patients. To balance nurse workloads, direct patient care activities, indirect patient care activities, and non-patient care activities that occur throughout a shift must be considered. The layout of a hospital unit and the location of a nurses assigned patients relative to other resources on the unit are also important factors in achieving workload balance. In most hospitals, a unit charge nurse is responsible for the shift assignment of patients to nurses based on experience and past practices. The nurse-patient assignment process is also often a manual process in which the charge nurse must sort through multiple decision criteria in a limited amount of time. In this paper, a methodology for the construction of balanced nurse-patient workload assignments is proposed. Through the illustration of this methodology new scoring metrics are developed using measures currently available on, or from, the hospital unit. It was demonstrated that the complex scheduling problem can be captured. While the methodology was illustrated for a scheduling problem commonly encountered on a hospital unit, the approach can be adapted to other workforce scheduling problems in which measures of workload are required and composed of elements imposed by the work environment, variability within the required tasks, and a measurable perception of the relative intensity of the work elements.