451 research outputs found

    Supply Chain

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    Traditionally supply chain management has meant factories, assembly lines, warehouses, transportation vehicles, and time sheets. Modern supply chain management is a highly complex, multidimensional problem set with virtually endless number of variables for optimization. An Internet enabled supply chain may have just-in-time delivery, precise inventory visibility, and up-to-the-minute distribution-tracking capabilities. Technology advances have enabled supply chains to become strategic weapons that can help avoid disasters, lower costs, and make money. From internal enterprise processes to external business transactions with suppliers, transporters, channels and end-users marks the wide range of challenges researchers have to handle. The aim of this book is at revealing and illustrating this diversity in terms of scientific and theoretical fundamentals, prevailing concepts as well as current practical applications

    Acta Cybernetica : Volume 18. Number 2.

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    Mitigating Space Industry Supply Chain Risk Thru Risk-Based Analysis

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    Using risk-based analysis to consider supply chain disruptions and uncertainty along with potential mitigation strategies in the early stages of space industry projects can be used avoid schedule delays, cost overruns, and lead to successful project outcomes. Space industry projects, especially launch vehicles, are complicated assemblies of high-technology and specialized components. Components are engineered, procured, manufactured, and assembled for specific missions or projects, unlike make-to-stock manufacturing where assemblies are produced at a mass production rate for customers to choose off the shelf or lot, like automobiles. The supply chain for a space industry project is a large, complicated web where one disruption, especially for sole-sourced components, could ripple through the project causing delays at multiple project milestones. This ripple effect can even cause the delay or cancelation of the entire project unless project managers develop and employ risk mitigations strategies against supply chain disruption and uncertainty. The unpredictability of when delays and disruptions may occur makes managing these projects extremely difficult. By using risk-based analysis, project managers can better plan for and mitigate supply chain risk and uncertainty for space industry projects to better manage project success. Space industry project supply chain risk and uncertainty can be evaluated through risk assessments at major project milestones and during the procurement process. Mitigations for identified risks can be evaluated and implemented to better manage project success. One mitigation strategy to supply chain risk and uncertainty is implementing a dual or multi-supplier sourcing procurement strategy. This research explores using a risk-based analysis to identify where this mitigation strategy can be beneficial for space industry projects and how its implementation affects project success. First a supply chain risk assessment and mitigation decision tool will be used at major project milestones to show where a multi-sourcing strategy may be beneficial. Next, updated supplier quote evaluation tools will confirm the usage of multiple suppliers for procurement. Modeling and simulation are then used to show the impact of that strategy on the project success metrics of cost and schedule

    Telecommunications Networks

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    This book guides readers through the basics of rapidly emerging networks to more advanced concepts and future expectations of Telecommunications Networks. It identifies and examines the most pressing research issues in Telecommunications and it contains chapters written by leading researchers, academics and industry professionals. Telecommunications Networks - Current Status and Future Trends covers surveys of recent publications that investigate key areas of interest such as: IMS, eTOM, 3G/4G, optimization problems, modeling, simulation, quality of service, etc. This book, that is suitable for both PhD and master students, is organized into six sections: New Generation Networks, Quality of Services, Sensor Networks, Telecommunications, Traffic Engineering and Routing

    Distributed Operation of Uncertain Dynamical Cyberphysical Systems

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    In this thesis we address challenging issues that are faced in the operation of important cyber-physical systems of great current interest. The two particular systems that we address are communication networks and the smart grid. Both systems feature distributed agents making decisions in dynamic uncertain environments. In communication networks, nodes need to decide which packets to transmit, while in the power grid individual generators and loads need to decide how much to pro-duce or consume in a dynamic uncertain environment. The goal in both systems, which also holds for other cyber-physical systems, is to develop distributed policies that perform efficiently in uncertain dynamically changing environments. This thesis proposes an approach of employing duality theory on dynamic stochastic systems in such a way as to develop such distributed operating policies for cyber-physical systems. In the first half of the thesis we examine communication networks. Many cyber-physical systems, e.g., sensor networks, mobile ad-hoc networks, or networked control systems, involve transmitting data over multiple-hops of a communication network. These networks can be unreliable, for example due to the unreliability of the wireless medium. However, real-time applications in cyber-physical systems often require that requisite amounts of data be delivered in a timely manner so that it can be utilized for safely controlling physical processes. Data packets may need to be delivered within their deadlines or at regular intervals without large gaps in packet deliveries when carrying sensor readings. How such packets with deadlines can be scheduled over networks is a major challenge for cyber-physical systems. We develop a framework for routing and scheduling such data packets in a multi-hop network. This framework employs duality theory in such a way that actions of nodes get decoupled, and results in efficient decentralized policies for routing and scheduling such multi-hop communication networks. A key feature of the scheduling policy derived in this work is that the scheduling decisions regarding packets can be made in a fully distributed fashion. A decision regarding the scheduling of an individual packet depend only on the age and location of the packet, and does not require sharing of the queue lengths at various nodes. We examine in more detail a network in which multiple clients stream video packets over shared wireless networks. We are able to derive simple policies of threshold type which maximize the combined QoE of the users. We turn to another important cyber-physical system of great current interest – the emerging smarter grid for electrical power. We address some fundamental problems that arise when attempting to increase the utilization of renewable energy sources. A major challenge is that renewable energy sources are unpredictable in their availability. Utilizing them requires adaptation of demand to their uncertain availability. We address the problem faced by the system operator of coordinating sources of power and loads to balance stochastically time varying supply and demand while maximizing the total utilities of all agents in the system. We develop policies for the system operator that is charged with coordinating such distributed entities through a notion of price. We analyze some models for such systems and employ a combination of duality theory and analysis of stochastic dynamic systems to develop policies that maximize the total utility function of all the agents. We also address the issue of how the size of energy storage facilities should scale with respect to the stochastic behavior of renewables in order to mitigate the unreliability of renewable energy sources

    Proceedings, MSVSCC 2018

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    Proceedings of the 12th Annual Modeling, Simulation & Visualization Student Capstone Conference held on April 19, 2018 at VMASC in Suffolk, Virginia. 155 pp
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