647 research outputs found

    Optimal Cycle Service Level for Continuous Stocked Items with Limited Storage Capacity

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    This paper involves determining an optimal cycle service level for continuously stocked items that explicitly considers storage space capacity. Inventory management is under a continuous review policy. The total inventory management cost consisting of ordering cost, inventory holding cost, shortage cost, and over-capacity cost. Shortage items are assumed to be backlogged. A numerical example is provided to demonstrate the method. Keywords: Continuous Review; Cycle Service Level; Storage Space Capacity; Over-Capacity Cos

    Big Data for Urban Sustainability: Integrating Personal Mobility Dynamics in Environmental Assessments.

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    To alleviate fossil fuel use, reduce air emissions, and mitigate climate change, “new mobility” systems start to emerge with technologies such as electric vehicles, multi-modal transportation enabled by information and communications technology, and car/ride sharing. Current literature on the environmental implications of these emerging systems is often limited by using aggregated travel pattern data to characterize personal mobility dynamics, neglecting the individual heterogeneity. Individual travel patterns affect several key factors that determine potential environmental impacts, including charging behaviors, connection needs between different transportation modes, and car/ride sharing potentials. Therefore, to better understand these systems and inform decision making, travel patterns at the individual level need to be considered. Using vehicle trajectory data of over 10,000 taxis in Beijing, this research demonstrates the benefits of integrating individual travel patterns into environmental assessments through three case studies (vehicle electrification, charging station siting, and ride sharing) focusing on two emerging systems: electric vehicles and ride sharing. Results from the vehicle electrification study indicate that individual travel patterns can impact the environmental performance of fleet electrification. When battery cost exceeds 200/kWh,vehicleswithgreaterbatteryrangecannotcontinuouslyimprovetravelelectrificationandcanreduceelectrificationrate.Atthecurrentbatterycostof200/kWh, vehicles with greater battery range cannot continuously improve travel electrification and can reduce electrification rate. At the current battery cost of 400/kWh, targeting subsidies to vehicles with battery range around 90 miles can achieve higher electrification rate. The public charging station siting case demonstrates that individual travel patterns can better estimate charging demand and guide charging infrastructure development. Charging stations sited according to individual travel patterns can increase electrification rate by 59% to 88% compared to existing sites. Lastly, the ride sharing case shows that trip details extracted from vehicle trajectory data enable dynamic ride sharing modeling. Shared taxi rides in Beijing can reduce total travel distance and air emissions by 33% with 10-minute travel time deviation tolerance. Only minimal tolerance to travel time change (4 minutes) is needed from the riders to enable significant ride sharing (sharing 60% of the trips and saving 20% of travel distance). In summary, vehicle trajectory data can be integrated into environmental assessments to capture individual travel patterns and improve our understanding of the emerging transportation systems.PhDNatural Resources and Environment and Environmental EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113510/1/caih_1.pd

    Recent advances in industrial wireless sensor networks towards efficient management in IoT

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    With the accelerated development of Internet-of- Things (IoT), wireless sensor networks (WSN) are gaining importance in the continued advancement of information and communication technologies, and have been connected and integrated with Internet in vast industrial applications. However, given the fact that most wireless sensor devices are resource constrained and operate on batteries, the communication overhead and power consumption are therefore important issues for wireless sensor networks design. In order to efficiently manage these wireless sensor devices in a unified manner, the industrial authorities should be able to provide a network infrastructure supporting various WSN applications and services that facilitate the management of sensor-equipped real-world entities. This paper presents an overview of industrial ecosystem, technical architecture, industrial device management standards and our latest research activity in developing a WSN management system. The key approach to enable efficient and reliable management of WSN within such an infrastructure is a cross layer design of lightweight and cloud-based RESTful web service

    Mesoscale mapping of sediment source hotspots for dam sediment management in data-sparse semi-arid catchments

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    Land degradation and water availability in semi-arid regions are interdependent challenges for management that are influenced by climatic and anthropogenic changes. Erosion and high sediment loads in rivers cause reservoir siltation and decrease storage capacity, which pose risk on water security for citizens, agriculture, and industry. In regions where resources for management are limited, identifying spatial-temporal variability of sediment sources is crucial to decrease siltation. Despite widespread availability of rigorous methods, approaches simplifying spatial and temporal variability of erosion are often inappropriately applied to very data sparse semi-arid regions. In this work, we review existing approaches for mapping erosional hotspots, and provide an example of spatial-temporal mapping approach in two case study regions. The barriers limiting data availability and their effects on erosion mapping methods, their validation, and resulting prioritization of leverage management areas are discussed.BMBF, 02WGR1421A-I, GROW - Verbundprojekt SaWaM: Saisonales Wasserressourcen-Management in Trockenregionen: Praxistransfer regionalisierter globaler Informationen, Teilprojekt 1DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

    Optimal inventory policies with an exact cost function under large demand uncertainty

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    In this paper we investigate the minimization process of the exact cost function for a continuous review (Q,R) inventory model with non-negative reorder point and fixed lead-time. Backorders are allowed and the unit shortage cost is used to determine the expected annual shortage cost. Provided that the lead-time demand has J-shaped or unimodal distribution satisfying specific assumptions we derive the general condition when the minimum cost is attained at a positive reorder point or at a reorder point equal to zero. Based on this condition a general algorithm is developed. Some numerical experimentation based on this algorithm using parameter values from the relevant literature indicates that with large demand uncertainty measured by the coefficient of variation the optimal inventory policies lead to excessively large orders and zero reorder points

    Shared Modular Course Development: A Feasibility Study

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    This project evaluated the viability of shared course development (SCD) and identified the necessary baseline mechanisms, principles, policies, and procedures for future joint course development collaborations. Although collaborative course design is still relatively new in Ontario, our institutionally-based project teams identified and researched a number of successful examples from Australia, Canada, Europe, New Zealand, the United Kingdom, and the United States. These successful models demonstrated the transformative possibilities of blended learning, expanded course variety, maintained or enhanced the breadth of course offerings, and reduced institution-specific development costs while maintaining delivery autonomy. They also focused on enhancing student learning and produced momentum for instructional improvement and course re-design among collaborating institutions. This report concludes that there is considerable value to the development of collaborative institutional cultures in and of itself, and that collaborative capacity will become an increasingly important core competency in the more differentiated and change-oriented university sector that is emerginghttps://scholar.uwindsor.ca/ctlreports/1000/thumbnail.jp

    A Query-Centered Perspective on Context Awareness in Mobile Ad Hoc Networks

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    The wide-spread use of mobile computing devices has ledto an increased demand for applications that operate de-pendably in opportunistically formed networks. A promis-ing approach to supporting software development for suchdynamic settings is to rely on the context-aware computingparadigm, in which an application views the state of the sur-rounding ad hoc network as a valuable source of contextualinformation that can be used to adapt its behavior. Col-lecting context information distributed across a constantlychanging network remains a significant technical challenge.With this in mind, we propose a query-centered approach tosimplifying context interactions in mobile ad hoc networks.With our approach, an application programmer views thesurrounding world as a single data repository over whichdescriptive queries can be issued. Queries may be tran-sient, or may be more durable persistent queries that reactto changes in data or the network. Processing such queriesentails the creation and maintenance of a distributed over-lay data structure whose size needs to be under applicationcontrol. A high level of flexibility is achieved by judicioususage of mobile code fragments. In this paper, we presentthe design and implementation of our query service for adhoc networks
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