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Articles 1 - 29 of 29
Full-Text Articles in Operational Research
Trauma Network Design Considering Patient Safety And Cost., Lin Lin
Trauma Network Design Considering Patient Safety And Cost., Lin Lin
Electronic Theses and Dissertations
Trauma, as the leading cause of mortality and morbidity for those under the age of 45 in the US, incurs trillions in annual economic costs. The time-sensitive nature of trauma treatment necessitates an effective, coordinated regional trauma system to optimize patient safety. However, the financial burden associated with trauma care, especially due to low-insured population, presents a significant challenge to the financial health of trauma centers (TCs). To address critical challenges in this domain and provide much-needed insights to trauma decision-makers regarding their trauma system cost, network design, and subsidy policy, this dissertation proposes 3 contributions. First, we introduce an …
The Food Truck: A Multi-Product Newsvendor With Trans-Shipment Cost, Samuel Ajibola
The Food Truck: A Multi-Product Newsvendor With Trans-Shipment Cost, Samuel Ajibola
Electronic Theses and Dissertations
The Newsvendor Problem is a key model in supply chain management that focuses on determining the optimal order quantity to minimize costs under uncertain demand. This thesis introduces the Food Truck Problem, an extension of the Newsvendor model that incorporates nonlinear transshipment costs for inventory transportation. In this context, a Food Truck must determine the optimal stock levels for multiple products while minimizing costs related to stock shortages, excess inventory, and transportation. Unlike traditional Newsvendor models, our approach explicitly considers a quadratic transshipment cost, which necessitates the use of Lagrangian duality and Karush-Kuhn-Tucker (KKT) conditions for analysis. Moreover, we apply …
Visibility Based Hospital Inpatient Unit Design., Uttam Karki
Visibility Based Hospital Inpatient Unit Design., Uttam Karki
Electronic Theses and Dissertations
Patient fall is one of the adverse events in an inpatient unit of a hospital that can lead to disability and/or mortality. Healthcare literature suggests that increased visibility of patients by unit nurses is essential to improve patient monitoring and, in turn, reduce falls. However, such research has been descriptive in nature and does not provide an understanding of the characteristics of an optimal inpatient unit layout from a visibility-standpoint. This dissertation fills significant voids in this domain and adds much-needed realism to develop insights that hospital decision-makers can use to design their inpatient unit layout. Our first contribution (Chapter …
Simulating The Impact Of Emissions Control On Economic Productivity Using Particle Systems And Puff Dispersion Model, Najam Khan
Electronic Theses and Dissertations
A simulation platform is developed for quantifying the change in productivity of an economy under passive and active emission control mechanisms. The program uses object-oriented programming to code a collection of objects resembling typical stakeholders in an economy. These objects include firms, markets, transportation hubs, and boids which are distributed over a 2D surface. Firms are connected using a modified Prim’s Minimum spanning tree algorithm, followed by implementation of an all-pair shortest path Floyd Warshall algorithm for navigation purposes. Firms use a non-linear production function for transformation of land, labor, and capital inputs to finished product. A GA-Vehicle Routing Problem …
Models And Algorithms For Trauma Network Design., Sagarkumar Dhirubhai Hirpara
Models And Algorithms For Trauma Network Design., Sagarkumar Dhirubhai Hirpara
Electronic Theses and Dissertations
Trauma continues to be the leading cause of death and disability in the US for people aged 44 and under, making it a major public health problem. The geographical maldistribution of Trauma Centers (TCs), and the resulting higher access time to the nearest TC, has been shown to impact trauma patient safety and increase disability or mortality. State governments often design a trauma network to provide prompt and definitive care to their citizens. However, this process is mainly manual and experience-based and often leads to a suboptimal network in terms of patient safety and resource utilization. This dissertation fills important …
Forecasting Hypotension By Learning From Multivariate Mixed Responses.., Jodie Ritter
Forecasting Hypotension By Learning From Multivariate Mixed Responses.., Jodie Ritter
Electronic Theses and Dissertations
Blood Pressure is the main determinant of blood flow to organs. Hypotension is defined as a systolic blood pressure less than 90 mmHg or a diastolic blood pressure less than 50 mmHg. The severity and duration of hypotension is associated with low blood flow to organs often result in organ damage and a high mortality rate. Predicting hypotension prior to surgery and during the surgery can reduce the incidence and duration resulting in better patient outcomes. This thesis uses preoperative bloodwork and vital signs as well as perioperative vital signs in 5-minute increments as inputs to forecast hypotension. Hypotension can …
Efficient Numerical Optimization For Parallel Dynamic Optimal Power Flow Simulation Using Network Geometry, Rylee Sundermann
Efficient Numerical Optimization For Parallel Dynamic Optimal Power Flow Simulation Using Network Geometry, Rylee Sundermann
Electronic Theses and Dissertations
In this work, we present a parallel method for accelerating the multi-period dynamic optimal power flow (DOPF). Our approach involves a distributed-memory parallelization of DOPF time-steps, use of a newly developed parallel primal-dual interior point method, and an iterative Krylov subspace linear solver with a block-Jacobi preconditioning scheme. The parallel primal-dual interior point method has been implemented and distributed in the open-source PETSc library and is currently available. We present the formulation of the DOPF problem, the developed primal dual interior point method solver, the parallel implementation, and results on various multi-core machines. We demonstrate the effectiveness our proposed block-Jacobi …
Drone Location And Scheduling Problems In Humanitarian Logistics., Zabih Ghelichi
Drone Location And Scheduling Problems In Humanitarian Logistics., Zabih Ghelichi
Electronic Theses and Dissertations
Unmanned Aerial Vehicles (UAVs), commonly referred to as drones, are a promising technology for the last-mile delivery of medical and aid items in humanitarian logistics. In emergency scenarios, like disasters, where transportation networks are destroyed and people are stranded, drones can accelerate the delivery of urgently needed items, e.g., food and water, insulin shots and blood pressure pills, to those trapped in the disaster-affected areas. Drones can also provide logistics services in many non-emergency situations by delivering medical items, e.g., vaccine shots and lab specimens, to remote communities and hard-to-access locations. The contribution of using UAVs goes beyond merely having …
High-Density Parking For Autonomous Vehicles., Parag J. Siddique
High-Density Parking For Autonomous Vehicles., Parag J. Siddique
Electronic Theses and Dissertations
In a common parking lot, much of the space is devoted to lanes. Lanes must not be blocked for one simple reason: a blocked car might need to leave before the car that blocks it. However, the advent of autonomous vehicles gives us an opportunity to overcome this constraint, and to achieve a higher storage capacity of cars. Taking advantage of self-parking and intelligent communication systems of autonomous vehicles, we propose puzzle-based parking, a high-density design for a parking lot. We introduce a novel method of vehicle parking, which leads to maximum parking density. We then propose a heuristic method …
Optimization With Interval Data: New Problems, Algorithms, And Applications., Mohsen Mohammadi Dehcheshmeh
Optimization With Interval Data: New Problems, Algorithms, And Applications., Mohsen Mohammadi Dehcheshmeh
Electronic Theses and Dissertations
The parameters of real-world optimization problems are often uncertain due to the failure of exact estimation of data entries. Throughout the years, several approaches have been developed to cope with uncertainty in the input parameters of optimization problems, such as robust optimization, stochastic optimization, fuzzy programming, parametric programming, and interval optimization. Each of these approaches tackles the uncertainty in the input data with different assumptions on the source of uncertainty and imposes different requirements on the returned solutions. In this dissertation, the approach we take is that of interval optimization, and more specifically, interval linear programming. The two main problems …
Mathematical Models And Analysis For Demand Side Management In Residential Electricity Distribution Networks., Arnab Roy
Electronic Theses and Dissertations
Development of smart grids along with communication technologies have led to the increased attention and adoption of demand side management (DSM) in the residential sector. Among various DSM schemes, demand response (DR) is a market- based mechanism to shave peak electricity consumption at the system level. In the past decade, the academia has seen a growing literature studying load management methodologies for residential consumers. A typical demand response program has three important facets: the energy cost, comfort of the consumers and overall system efficiency. In this dissertation, we investigate and develop models for effective load control to minimize energy cost …
Joint Location And Inventory Models And Algorithms For Deployment Of Hybrid Electric Vehicle Charging Stations., Jie Zhang
Electronic Theses and Dissertations
This thesis describes a study of a novel concept of hybrid electric vehicle charging stations in which two types of services are offered: battery swapping and fast level-3 DC charging. The battery swapping and fast-charging service are modeled by using the M/G/s/s model and the M/G/s/$\infty$ model, respectively. In particular, we focus on the operations of joint battery swapping and fast charging services, develop four joint locations and inventory models: two for the deployment of battery swapping service, two for the deployment of hybrid electric vehicle charging service. The first model for each deployment system considers a service-level constraint for …
Optimization And Simulation Models To Improve Access To Organ Transplantation In The United States., Fatemeh Karami
Optimization And Simulation Models To Improve Access To Organ Transplantation In The United States., Fatemeh Karami
Electronic Theses and Dissertations
Organ allocation in the U.S. is administrated by the United Network of Organ Sharing (UNOS). UNOS’s mission is to ensure fair and equitable allocation of organs as stated in the Code of Federal Regulations, which reads "neither place of residence nor place of listing shall be a major determinant of access to transplant". Despite the regulations, there has been endless controversy surrounding the disparity in access to organ transplants. In this context, the primary research goal in this dissertation was to reduce geographic disparity in access to transplants in the U.S., with a focus on heart and kidney transplants. To …
A Two-Stage Approach To Ridesharing Assignment And Auction In A Crowdsourcing Collaborative Transportation Platform., Peiyu Luo
Electronic Theses and Dissertations
Collaborative transportation platforms have emerged as an innovative way for firms and individuals to meet their transportation needs through using services from external profit-seeking drivers. A number of collaborative transportation platforms (such as Uber, Lyft, and MyDHL) arise to facilitate such delivery requests in recent years. A particular collaborative transportation platform usually provides a two sided marketplace with one set of members (service seekers or passengers) posting tasks, and the another set of members (service providers or drivers) accepting on these tasks and providing services. As the collaborative transportation platform attracts more service seekers and providers, the number of open …
Solving School Bus Routing And Student Assignment Problems With Heuristic And Column Generation Approach., Di Zhang
Electronic Theses and Dissertations
In this dissertation, we solve a school bus routing problem of transporting students including special education (handicapped) students and assigning them in Oldham county education district. The main contribution of this research is that we consider special education students (Type-2) along with other students (Type-1) and design a comprehensive school bus schedule to transport both kinds of students at the same time. Also, a student assignment mathematical model is presented to optimize the number of bus stops in use as well as one important measure of service quality, the total student walking distance. Comparing to the classic clustering methods, heuristic …
Developing Optimization Techniques For Logistical Tendering Using Reverse Combinatorial Auctions, Jennifer Kiser
Developing Optimization Techniques For Logistical Tendering Using Reverse Combinatorial Auctions, Jennifer Kiser
Electronic Theses and Dissertations
In business-to-business logistical sourcing events, companies regularly use a bidding process known as tendering in the procurement of transportation services from third-party providers. Usually in the form of an auction involving a single buyer and one or more sellers, the buyer must make decisions regarding with which suppliers to partner and how to distribute the transportation lanes and volume among its suppliers; this is equivalent to solving the optimization problem commonly referred to as the Winner Determination Problem. In order to take into account the complexities inherent to the procurement problem, such as considering a supplier’s network, economies of scope, …
Location Optimization Of A Coal Power Plant To Balance Coal Supply And Electric Transmission Costs Against Plant’S Emission Exposure, Najam Khan
Electronic Theses and Dissertations
This research is focused on developing a location analysis methodology that can minimize the pollutant exposure to the public while ensuring that the combined costs of electric transmission losses and coal logistics are minimized. Coal power plants will provide a critical contribution towards meeting electricity demands for various nations in the foreseeable future. The site selection for a new coal power plant is extremely important from an investment point of view. The operational costs for running a coal power plant can be minimized by a combined emphasis on placing a coal power plant near coal mines as well as customers. …
A Multi-Period Facility Location Model For Service Organizations Operating In A Competitive Environment., Sven W. Brose
A Multi-Period Facility Location Model For Service Organizations Operating In A Competitive Environment., Sven W. Brose
Electronic Theses and Dissertations
This thesis develops a multi-period, mathematical programming location model for facilities operating in a competitive environment. The objective is to maximize the profit in a variable demand environment. The solution of the problem can either be done in a robust or in a dynamic manner. A robust solution methodology forecasts the demand for all the periods in the planning horizon and provides a robust solution that may be suboptimal for any given period, but optimal when all the periods are taken into consideration. A problem with this approach is that it requires accurate forecast of demand for multiple periods into …
Order Picking Strategies For Healthcare Warehouses., Ehsan Khodabandeh
Order Picking Strategies For Healthcare Warehouses., Ehsan Khodabandeh
Electronic Theses and Dissertations
Order picking is the process of collecting goods and items in specified quantities from storage locations, in response to customer orders. Since many labor resources are involved in this process, finding ways to make it more efficient have been a primary goal for researchers and practitioners. Determining a better allocation of products to the storage areas, finding the best route and sequence to pick multiple products, and choosing the best picking policies to minimize congestion in the aisles are just a few of many objectives regarding order picking process. Due to regulatory compliances and the chance of product spoilage, additional …
Optimization Models And Algorithms For Demand Response In Smart Grid., Guangyang Xu
Optimization Models And Algorithms For Demand Response In Smart Grid., Guangyang Xu
Electronic Theses and Dissertations
For demand response in smart grid, a utility company wants to minimize total electricity cost and end users want to maximize their own utility. The latter is considered to consist of two parts in this research: electricity cost and convenience/comfort. We first develop a system optimal (SO) model and a user equilibrium (UE) model for the utility company and end users, respectively and compare the difference of the two. We consider users' possible preference on convenience over cost-saving under the real-time pricing in smart grid, and each user is assumed to have a preferred time window for using a particular …
Simulation Modeling For Energy Consumption Of Residential Consumers In Response To Demand Side Management., Prajwal Khadgi
Simulation Modeling For Energy Consumption Of Residential Consumers In Response To Demand Side Management., Prajwal Khadgi
Electronic Theses and Dissertations
Energy efficiency in the electricity distribution system continues to gain importance as demand for electricity keeps rising and resources keep diminishing. Achieving higher energy efficiency by implementing control strategies and demand response (DR) programs has always been a topic of interest in the electric utility industry. The advent of smart grids with enhanced data communication capabilities propels DR to be an essential part of the next generation power distribution system. Fundamentally, DR has the ability to charge a customer the true price of electricity at the time of use, and the general perception is that consumers would shift their load …
Production And Inventory Control In Complex Production Systems Using Approximate Dynamic Programming., Han Wu
Electronic Theses and Dissertations
Production systems focus not only on providing enough product to supply the market, but also on delivering the right product at the right price, while lowering the cost during the production process. The dynamics and uncertainties of modern production systems and the requirements of fast response often make its design and operation very complex. Thus, analytical models, such as those involving the use of dynamic programming, may fail to generate an optimal control policy for modern production systems. Modern production systems are often in possession of the features that allow them to produce various types of product through multiple working …
Green Logistic Network Design : Intermodal Transportation Planning And Vehicle Routing Problems., Xiaoren Duan
Green Logistic Network Design : Intermodal Transportation Planning And Vehicle Routing Problems., Xiaoren Duan
Electronic Theses and Dissertations
Due to earth's climate change and global warming, environmental consideration in the design of logistic systems is accelerating in recent years. In this research we aim to design an efficient and environmentally friendly logistical system to satisfy both government and carriers. In particular, we considered three problems in this dissertation: intermodal network design, deterministic green vehicle routing problem and stochastic green vehicle routing problem. The first problem aims to design an economic and efficient intermodal network including three transportation modes: railway, highway and inland waterway. The intent of this problem is to increase the utilization percentage of waterway system in …
Operational Decision Making For Medical Clinics Through The Use Of Simulation And Multi-Attribute Utility Theory., Bo Sun
Electronic Theses and Dissertations
Currently, health care is a large industry that concerns everyone. Outpatient health care is an important part of the American health care system and is one of the strongest growth areas in the health care system. Many people pay attention to how to keep basic health care available to as many people as possible. A large health care system is usually evaluated by many performance measures. For example, the managers of a medical clinic are concerned about increasing staff utilization; both managers and patients are concerned about patient waiting time. In this dissertation, we study decision making for clinics in …
Spare Parts On Demand Using Additive Manufacturing : A Simulation Model For Cost Evaluation., Stefan Jedeck
Spare Parts On Demand Using Additive Manufacturing : A Simulation Model For Cost Evaluation., Stefan Jedeck
Electronic Theses and Dissertations
Little is known about the impact of additive manufacturing in the spare part supply chain. A few studies are available, but they focus on specific parts and their applications only. A general model, which can be adapted to different applications, is nonexistent. This dissertation proposes a decision making framework that enables an interested practitioner/manager to decide whether using additive manufacturing to make spare parts on demand is economical when compared to conventional warehousing strategy. The framework consists of two major components: a general discrete event simulation model and a process of designing a wide range of simulation scenarios. The goal …
Xqx Based Modeling For General Integer Programming Problems, Vijay P. Ramalingam
Xqx Based Modeling For General Integer Programming Problems, Vijay P. Ramalingam
Electronic Theses and Dissertations
We present a new way to model general integer programming (IP) problems with in- equality and equality constraints using XQX. We begin with the definition of IP problems folloby their practical applications, and then present the existing XQX based models to handle such problems. We then present our XQX model for general IP problems (including binary IP) with equality and inequality constraints, and also show how this model can be applied to problems with just inequality constraints. We then present the local optima based solution procedure for our XQX model. We also present new theorems and their proofs for our …
Relaxation Adaptive Memory Programming For The Resource Constrained Project Scheduling Problem, Robert Christopher-Lee Riley
Relaxation Adaptive Memory Programming For The Resource Constrained Project Scheduling Problem, Robert Christopher-Lee Riley
Electronic Theses and Dissertations
The resource constrained project scheduling problem (RCPSP) is one of the most intractable problems in operations research; it is NP-hard in the strong sense. Due to the hardness of the problem, exact solution methods can only tackle instances of relatively small size. For larger instances commonly found in real applications heuristic solution methods are necessary to find near-optimal solutions within acceptable computation time limits. In this study algorithms based on the relaxation adaptive memory programming (RAMP) method (Rego, 2005) are developed for the purpose of solving the RCPSP. The RAMP algorithms developed here combine mathematical relaxation, including Lagrangian relaxation and …
An Investigation Of The Impact Of Requirements Engineering Skills On Project Success, Cynthia Atkins
An Investigation Of The Impact Of Requirements Engineering Skills On Project Success, Cynthia Atkins
Electronic Theses and Dissertations
A survey of project managers and requirements engineers was conducted to determine what skills, qualifications, and experiences were associated with project success. Survey results indicated that projects using Joint Application Development (JAD) sessions, use cases, and prototypes to engineer requirements were most successful. Other indicators of project success, according to participants, included an adequate allotment of time for requirements engineering—at least 15% of a project's time—and the use of project managers and requirements engineers with professional work experience. In particular, data indicated that Project Managers with at least five years of experience in Information Technology resulted in more successful projects.
An Active Study Of A Roller Coaster Project In Asia., Robert Leamon Bridges
An Active Study Of A Roller Coaster Project In Asia., Robert Leamon Bridges
Electronic Theses and Dissertations
A roller coaster manufacturer became aware that improperly heat treated track couplings were sent to a construction site for assembly. Concerns were that suspect couplings might not meet the engineering specifications and could be vulnerable to sudden failure. A testing company in Oak Ridge, TN that specializes in in-situ and laboratory mechanical testing was contacted by the manufacturer for help in this endeavor. The construction company elected to enlist a local testing firm to perform field tests on the components instead of the company in Oak Ridge. The test methods used are incapable of providing quantitative results that could be …