Design and scheduling of periodic review kanban systems

Ankara : Department of Industrial Engineering and Institute of Engineering and Sciences, Bilkent Univ., 1997.Thesis (Master's) -- Bilkent University, 1997.Includes bibliographical references leaves 107-112In the last years, the term just in-time (JIT) has become a common term in repretitive manufacturing systems. It can be defined as the ideal of having the necessary amount of material available where it is needed and when it is needed. One of the major elements of JIT philosophy and pull mechanism is the Kanban system. This system is the information processing and hence shop floor control system of JIT philosophy. In this study, we propose an algorithm to determine the withdrawal cycle length, kanban size and number of kanbans simultancously in a periodic review Kanban system under multi-item, multi-stage, multi period modified flowline production setting. The proposed algorithm considers the impact of operating characteristics such a.s scheduling and actual lead times on design parameters.Erhun, FeryalM.S

The NGO's Dilemma: How to Influence Firms to Replace a Potentially Hazardous Substance

We study a nongovernmental organization's (NGO's) decisions when it attempts to remove a potentially hazardous substance from commercial use in a market with competing firms. Specifically, we determine under what market and regulatory conditions an NGO should target the industry versus the regulatory body to influence firms to replace the substance. We examine how the NGO's strategy changes as the NGO's pragmatism (i.e., the extent to which the NGO incorporates firms' profits into its decision making) increases. Our results demonstrate that when the NGO is less pragmatic, it should examine the existing market structure to determine whether to target the industry or the regulatory body. However, as the pragmatism of the NGO increases, the NGO should increasingly leverage the competition between firms to ensure that a replacement is available to consumers. We examine multiple extensions including varying the competition dynamics, the NGO targeting both the industry and the regulatory body, the time discounting of replacement costs, and a firm potentially lobbying to counteract an NGO's activism. We show that the potential for a firm to lobby can benefit consumers by motivating the NGO to exert more effort and increase the market sensitivity to a substance, thereby forcing the firm to replace.National Science Foundation (U.S.) (Grant NSF/CAREER-0547021

Aortic stenosis post-COVID-19: a mathematical model on waiting lists and mortality

Objectives To provide estimates for how different treatment pathways for the management of severe aortic stenosis (AS) may affect National Health Service (NHS) England waiting list duration and associated mortality. Design We constructed a mathematical model of the excess waiting list and found the closed-form analytic solution to that model. From published data, we calculated estimates for how the strategies listed under Interventions may affect the time to clear the backlog of patients waiting for treatment and the associated waiting list mortality. Setting The NHS in England. Participants Estimated patients with AS in England. Interventions (1) Increasing the capacity for the treatment of severe AS, (2) converting proportions of cases from surgery to transcatheter aortic valve implantation and (3) a combination of these two. Results In a capacitated system, clearing the backlog by returning to pre-COVID-19 capacity is not possible. A conversion rate of 50% would clear the backlog within 666 (533–848) days with 1419 (597–2189) deaths while waiting during this time. A 20% capacity increase would require 535 (434–666) days, with an associated mortality of 1172 (466–1859). A combination of converting 40% cases and increasing capacity by 20% would clear the backlog within a year (343 (281–410) days) with 784 (292–1324) deaths while awaiting treatment. Conclusion A strategy change to the management of severe AS is required to reduce the NHS backlog and waiting list deaths during the post-COVID-19 ‘recovery’ period. However, plausible adaptations will still incur a substantial wait to treatment and many hundreds dying while waiting

Quality and entry deterrence

We analyze the role of quality, which we define as an attribute of a product that increases consumers' willingness to buy, as a competitive tool in a quality-price setting. We consider an incumbent's entry-deterrence strategies using quality as a deterrent when faced by a potential entrant. We investigate settings motivating the incumbent to blockade the entrant (i.e., prevent entry without extra effort), deter the entrant (i.e., prevent entry with extra effort), or accommodate the entrant (i.e., allow the entry to take place). We identify conditions under which the incumbent may actually over-invest in quality to deter entrance. More interestingly, we also identify conditions under which the incumbent may decrease his quality investment to make it easier for the entrant to penetrate the market. Our model sheds light on entry scenarios of particular platform product markets such as the entry of Xbox to the video game console market

Healthcare Supply Chains

In his widely recognized and cited book, Christopher (2016) defines a supply chain (SC) (Refer to Table 1 for a complete list of acronyms used in the chapter) as a “network of organizations that are involved, through upstream and downstream linkages, in the different processes and activities that produce value in the form of products and services in the hands of the ultimate consumer” (p.13). The author defines supply chain management (SCM) as the “management of upstream and downstream relationships with suppliers and customers in order to deliver superior customer value at less cost to the supply chain as a whole” (p.3). It is clear from these definitions that every SC is a system of organizations, materials, resources (including human capital), activities, information, and finances that help move a product or service from suppliers to end customers/ consumers while optimizing end-to-end efficiency and effectiveness. As a result, to match customer requirements with supply constraints, SCM as a management strategy is characterized by a systems approach (i.e., considers the organizations in the SC as an end-to-end, integrated entity), a strategic orientation (i.e., aligns the intra- and inter-firm goals and capabilities with those of the SC), and a customer focus (i.e., focuses on customer value as the key driver of the SC’s activities) (Mentzer et al. 2001)

Quantity Discounts Under Demand Uncertainty

To motivate buyers to increase their order quantity, suppliers often rely on a well-established and widely used approach--they offer quantity discounts. This practice is in large part driven to obtain improved economies in transportation through higher truckload utilization. Recently, transportation rates, which are increasing faster than other costs, have become a larger portion of total net landed cost, placing the traditional quantity-discount practices under scrutiny. Many suppliers are left perplexed as to why their approach is not effective anymore, and some are even concerned that their overall profits may have actually decreased due to their discount parameters. In this paper, we study a multiperiod model, with a buyer facing stochastic end-item demand and a supplier offering an all-units quantity discount to him, to understand better the dynamics of such systems. We provide guidelines and insights on how to set effective discount parameters, and when not to expect much from them. We derive the optimal policy of the buyer, develop insights as to why the policy is complex, study the supplier's profit as a function of her offered quantity-discount scheme (accommodating the buyer's optimal policy), and discover a new phenomenon that is distinct and structurally different from the well-known bullwhip effect.all-unit quantity discounts, inventory management, stochastic demand, periodic review policies, minimum-order quantity

Applying Systems Thinking to Inform Decentralized Clinical Trial Planning and Deployment.

Recently, there has been a growing interest in understanding how decentralized clinical trial (DCT) solutions can mitigate existing challenges in clinical development, particularly participant burden and access, and the collection, management, and quality of clinical data. This paper examines DCT deployments, emphasizing how they are integrated and how they may impact clinical trial oversight, management, and execution. We propose a conceptual framework that employs systems thinking to evaluate the impact on key stakeholders through a reiterative assessment of pain points. We conclude that decentralized solutions should be customized to meet patient needs and preferences and the unique requirements of each clinical trial. We discuss how DCT elements introduce new demands and pressures within the existing system and reflect on enablers that can overcome DCT implementation challenges. As stakeholders look for ways to make clinical research more relevant and accessible to a larger and more diverse patient population, further robust and granular research is needed to quantify the impact of DCTs empirically