3,690 research outputs found
Survey instrument for measuring level of preparedness amongst healthcare personnel in radiation emergency
Drills and exercises are globally practiced to investigate the level of preparedness towards disaster events. However, these activities
are rarely conducted because they require substantial investment, specifically to budget and time. A self-reported survey may serve
as an alternative approach, although it may not be as effective as drills and exercises. As part of the survey development process,
this article discusses preliminary validation of a survey instrument to measure the level of preparedness towards radiation
emergency amongst healthcare personnel. Prior to this validation process, extensive literature reviews pointed out that the
instrument consists of three constructs of preparedness, namely readiness, willingness, and ability. A total of seven subject matter
experts were invited to judge the contents for verification purposes. Randolph Kappa analysis was then conducted to analyse their
judgment to allow irrelevant items to be filtered from the rest prior to any improvements. Initially, the survey instrument consisted
of 69 items; however, the analysis omitted 16 of them. The following values for each preparedness construct were: Readiness (0.77),
Willingness (0.70), and Ability (0.73). These findings indicate that contents of the instrument are valid. Further analysis should be
fulfilled to complete validation process to ensure its practicality prior to using it as an evaluation tool
Location models in the public sector
The past four decades have witnessed an explosive growth in the field of networkbased facility location modeling. This is not at all surprising since location policy is one of the most profitable areas of applied systems analysis in regional science and ample theoretical and applied challenges are offered. Location-allocation models seek the location of facilities and/or services (e.g., schools, hospitals, and warehouses) so as to optimize one or several objectives generally related to the efficiency of the system or to the allocation of resources. This paper concerns the location of facilities or services in discrete space or networks, that are related to the public sector, such as emergency services (ambulances, fire stations, and police units), school systems and postal facilities. The paper is structured as follows: first, we will focus on public facility location models that use some type of coverage criterion, with special emphasis in emergency services. The second section will examine models based on the P-Median problem and some of the issues faced by planners when implementing this formulation in real world locational decisions. Finally, the last section will examine new trends in public sector facility location modeling.Location analysis, public facilities, covering models
Hierarchical location-allocation models for congested systems
In this paper we address the issue of locating hierarchical facilities in the presence of congestion. Two hierarchical models are presented, where lower level servers attend requests first, and then, some of the served customers are referred to higher level servers. In the first model, the objective is to find the minimum number of servers and their locations that will cover a given region with a distance or time standard. The second model is cast as a Maximal Covering Location formulation. A heuristic procedure is then presented together with computational experience. Finally, some extensions of these models that address other types of spatial configurations are offered.Hierarchical location, congestion, queueing
The Application of Spreadsheet Model Based on Queuing Network to Optimize Capacity Utilization in Product Development
Modeling of a manufacturing system enables one to identify the effects of key design parameters on the system performance and as a result make the correct decision. This paper proposes a manufacturing system modeling approach using computer spreadsheet software, in which a static capacity planning model and stochastic queuing model are integrated. The model was used to optimize the existing system utilization in relation to product design. The model incorporates a few parameters such as utilization, cycle time, throughput, and batch size. It is predicted that design changes initiated as a result of analysis using the model reduced subsequent manufacturing costs significantly and also can reduce the launch program by a few years, because confidence in the model justified the commissioning of full-scale manufacturing equipment when the product was still only at the concept stage
Towards a Multimodal Charging Network: Joint Planning of Charging Stations and Battery Swapping Stations for Electrified Ride-Hailing Fleets
This paper considers a multimodal charging network in which charging stations
and battery swapping stations are built in tandem to support the electrified
ride-hailing fleet in a synergistic manner. Our central thesis is predicated on
the observation that charging stations are cost-effective, making them ideal
for scaling up electric vehicles in ride-hailing fleets in the beginning, while
battery swapping stations offer quick turnaround and can be deployed in tandem
with charging stations to improve fleet utilization and reduce operational
costs for the ride-hailing platform. To fulfill this vision, we consider a
ride-hailing platform that expands the multimodal charging network with a
multi-stage investment budget and operates a ride-hailing fleet to maximize its
profit. A multi-stage network expansion model is proposed to characterize the
coupled planning and operational decisions, which captures demand elasticity,
passenger waiting time, charging and swapping waiting times, as well as their
dependence on fleet status and charging infrastructure. The overall problem is
formulated as a nonconvex program. Instead of pursuing the globally optimal
solution, we establish a theoretical upper bound through relaxation,
reformulation, and decomposition so that the global optimality of the derived
solution to the nonconvex problem is verifiable. In the case study for
Manhattan, we find that the two facilities complement each other and play
different roles during the expansion of charging infrastructure: at the early
stage, the platform always prioritizes building charging stations to electrify
the fleet, after which it initiates the deployment of swapping stations to
enhance fleet utilization. Compared to the charging-only case, ..
A Study of Moment Recursion Models for Tactical Planning of a Job Shop: Literature Survey and Research Opportunities
The Moment Recursion (MR) models are a class of models for tactical planning of job shops or other processing networks. The MR model can be used to determine or approximate the first two moments of production quantities and queue lengths at each work station of a job shop. Knowledge of these two moments is sufficient to carry out a variety of performance evaluation, optimization and decision-support applications. This paper presents a literature survey of the Moment-Recursion models. Limitations in the existing research and possible research opportunities are also discussed. Based on the research opportunities discussed, we are in the process of building a model that attempts to fill these research gaps.Singapore-MIT Alliance (SMA
A Gradient Projection Algorithm for Side-constrained Traffic Assignment
Standard static traffic assignment models do not take into account the direct effects of capacities on network flows. Separable link performance functions cannot represent bottleneck and intersection delays, and thus might load links with traffic volumes, which far exceed their capacity. This work focuses on the side-constrained traffic assignment problem (SCTAP), which incorporates explicit capacity constraints into the traffic assignment framework to create a model that deals with capacities and queues. Assigned volumes are bounded by capacities, and queues are formed when capacity is reached. Delay values at these queues are closely related to Lagrange multipliers values, which are readily found in the solution. The equilibrium state is defined by total path travel times, which combine link travel times and delays at bottlenecks and intersections for which explicit capacity constraints have been introduced.
This paper presents a new solution procedure for the SCTAP based on the inner penalty function method combined with a path-based adaptation of the gradient projection algorithm. This procedure finds a solution at the path level as well as at the link level. All intermediate solutions produced by the algorithm are strictly feasible. The procedure used to ensure that side-constraints are not violated is efficient since it is only performed on constrained links that belong to the shortest path
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