In this paper, the ports of origin and destination and transportation of the LNG supply chain are focused, and a model is presented to minimize the cost of sending natural gas from the primary port to the destination ...
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In this paper, the ports of origin and destination and transportation of the LNG supply chain are focused, and a model is presented to minimize the cost of sending natural gas from the primary port to the destination port, taking into account product diversity. Therefore the main research questions are as follows: What is the allocation of a loading port to the group of unloading ports? What are the optimal transportation costs for liquefied natural gas ships? This research holds innovation in two aspects, one is considering the product variety and the way of presenting the constraint (which differs from other studies in the field of liquefied natural gas), and the other is applying the actual events in the simulation-optimization model. To solve the proposed model, the branch and bound method is used and then different scenarios are designed and implemented for it with the help of simulation. The results show that the proposed solutions are appropriate and reduce transportation costs by about 11%. To clarify the computational capability and operating conditions of the model, the gas platforms of Iran and London were studied. This study shows that if the ships capacity increases and the product variation decreases, the number of times the ship leaves port are 30, the transportation cost is reduced by $ 221,661.50 at the same time, the power of responding to demands will increase.
Before medical school graduates can practice independently, they must spend a minimum of three years in a residency program, where each year is divided into different clinical assignments called blocks. In this study,...
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This article presents a new model for constructing monthly clinic schedules for interns and residents (i.e., housestaff) training in Internal Medicine. Clinical experiences during the three years of residency occur in...
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This article presents a new model for constructing monthly clinic schedules for interns and residents (i.e., housestaff) training in Internal Medicine. Clinical experiences during the three years of residency occur in inpatient and outpatient settings, and on generalist and specialist clinical services. These experiences include spending time in a primary care setting caring for an assigned group of patients over time. Housestaff rotate through different clinical experiences monthly, with their primary care clinic time overlaid longitudinally on these other clinical services. The exact amount of primary care time spent varies between clinical rotations. In fact, it is the variable clinic hour requirements that drive the scheduling process, and is what distinguishes our problem from most personnel scheduling problems. Typically, staff schedules are driven by shift or hourly demand and are designed to minimize some measure of cost. The objective in our work is to both maximize clinic utilization and minimize the number of violations of a prioritized set of goals while ensuring that certain clinic-level and individual constraints are satisfied. The corresponding problem is formulated as an integer goal program in which several of the hard constraints are temporarily allowed to be violated to avoid infeasibility. To find solutions, a three-phase methodology is proposed. In the first phase (pre-processing step), clinic assignments for a subset of the housestaff are either fixed or excluded each month in light of restrictions imposed by their current rotation. In the second phase, tentative solutions are obtained with a commercial solver. In the final phase (post-processing step), all violations of the relaxed hard constraints are removed and an attempt is made to lexicographically reduce violations of the major goals. The effectiveness of the methodology is demonstrated by analyzing eight monthly rosters provided by the Internal Medicine Residency Program at the Universi
To satisfy public demands for environmental values, forest companies are facing the prospect of a reduction in wood supply and increases in costs. Some Canadian provincial governments have proposed intensifying silvic...
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Conventionally, price discounts are offered to enhance demand, for example, to get rid of excess inventory. This paper, however, studies the possibility of using discounts in situations when total demand is non-sensit...
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With the significant growth of world economy and container transportation, large seaports are under the pressure of higher requirements for handling efficiency and often involved in recurrent congestion. For those lar...
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With the significant growth of world economy and container transportation, large seaports are under the pressure of higher requirements for handling efficiency and often involved in recurrent congestion. For those large seaports, shuttle vessels are usually run between terminals in order to fulfill container inter-terminal transshipment demand as well as to alleviate seaports' congestion effectively. This paper focuses on planning the shuttle vessel routing and scheduling, in which shuttle vessels connect a main terminal and neighboring terminals for container pickup. Two mixed-integer programming formulations are developed. The first model aims to minimize the total operational cost and the second further takes into account the time window requirement. A two-phase heuristic algorithm is devised to find a near-optimal solution within the short computational time for large-scale problems. According to the computational results, the first model shows high searching efficiency if cargo owners do not have time requirement. The two-phase heuristic algorithm shows both efficiency and effectiveness in searching near-optimal solution of the second model for large-scale instances considering time windows. The routing analysis indicates that terminal operators focus on time or no-load rate, respectively, when the waiting penalty shift from low to high.
While passenger-only ferries can be an effective instrument in mitigating road congestion in urban areas, they are among the most polluting modes of transportation. This paper studies technical and economic feasibilit...
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While passenger-only ferries can be an effective instrument in mitigating road congestion in urban areas, they are among the most polluting modes of transportation. This paper studies technical and economic feasibilities of a battery-powered high-speed ferry service in Oslo, Norway. An urban ferry planner problem that minimizes ferry operator and passenger costs and external costs of road transport subject to strategic (fleet selection and infrastructure location), tactical (service frequency) and operational (vessel speed) decisions is proposed. While the results show that zero emission technologies can pass the cost-benefit test for a short-range service, competitiveness hinges on energy costs and capacities and on the performance of the existing service. Counterfactual scenarios show substantial cost reductions from altering the current ferry route. Anticipated increase in external costs of road transport from closing the ferry service is also much smaller than the system costs of maintaining the urban ferry connection.
Effective inventory management is fundamental to order fulfillment excellence and supply chain success. In this paper, we develop a strategic inventory management decision tool that integrates inventory classification...
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Effective inventory management is fundamental to order fulfillment excellence and supply chain success. In this paper, we develop a strategic inventory management decision tool that integrates inventory classification and inventory control policy decisions for maximizing order fulfillment performance, while accounting for a constraint on inventory budget and the profit expectation of a firm. This inventory solution tool provides critical enhancements to current inventory planning software, which is developed upon the traditional inventory classification scheme and where practitioners have to balance service levels and safety stock decisions through trial-and-error. The model allows firms to assess whether the current inventory performance is Pareto optimal, quantify the trade-offs between various performance measures, and identify the right inventory level according to the firms' strategic goals. In computational results, we demonstrate the trade-off and positive relationships between key item- and order-based inventory performance measures and short-term profitability under different levels of inventory budget in a multi-item finished goods inventory system.
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