Farm size and production costs are varied in a six state variable stochastic dynamic programming model that quantifies monthly hedging, storage, and cash cotton sale decisions for an Alabama cotton producer. State var...
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Farm size and production costs are varied in a six state variable stochastic dynamic programming model that quantifies monthly hedging, storage, and cash cotton sale decisions for an Alabama cotton producer. State variables considered are: (1) cash cotton price; (2) basis level; (3) before-tax income level; (4) cotton holdings; (5) futures position; and (6) value of futures position. Results indicate that when farm size and production cost level differ, marketing decisions diverge the most for cash cotton sales at the end of the tax year and lower range of cash price (less than $.65/lb.), basis (less than -$.05/lb.), and before-tax income (less than $0.00) states.
The series-parallel architecture of the plug-in hybrid electric powertrain has attracted wide attentions in recent years for its flexible and highly efficient operating modes. However, despite the improvement of the v...
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The series-parallel architecture of the plug-in hybrid electric powertrain has attracted wide attentions in recent years for its flexible and highly efficient operating modes. However, despite the improvement of the vehicle fuel economy, it has been gradually facing more challenges on the design of the optimal controller due to the complex structure and the fast depletion of the battery. In this paper, a two-step optimal energy management strategy is proposed for a novel single-shaft series-parallel powertrain. In the first step, an equivalent method is adopted, in which two motors are equivalently regarded as one. After detailed analysis of the operating modes, various objective functions are established to pre-optimize the power split between engine and motor or two motors. In the second step, a stochastic dynamic programming (SDP) is adopted to optimize the power split between the engine and the equivalent motor, and the optimal combination of the operating modes. Then coupled with the pre-optimized results of the first step, the optimal power split among the engine and two motors could be obtained and then constructed as simple lookup-tables, which have great potential for practical applications. Finally, the preliminary test about the real-time performance of the optimal results is developed on the hardware-in-the-loop (HIL) system. (C) 2016 Elsevier Ltd. All rights reserved.
This article applies the methods of stochastic dynamic programming to a risk management problem, where an agent hedges her derivative position by submitting limit orders. Therefore, this model is the first, in the lit...
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This article applies the methods of stochastic dynamic programming to a risk management problem, where an agent hedges her derivative position by submitting limit orders. Therefore, this model is the first, in the literature on optimal trading with limit orders, to handle a problem of hedging options or other derivatives. A hedging strategy is developed where both the size and the limit price of each order is optimally set.
In practice, traditional stock-level dependent policies, like base-stock policies (BSP) and constant order policies (COP), are commonly used for replenishing inventories of perishable products at retailers. These poli...
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In practice, traditional stock-level dependent policies, like base-stock policies (BSP) and constant order policies (COP), are commonly used for replenishing inventories of perishable products at retailers. These policies are preferred for being easy to implement: they only require information on the total number of products in stock, but not differentiated by their age. In this paper, we analyze a number of new and existing hybrid BSP-COP policies. These policies have different complexities, but, so far, they have not been systematically compared with respect to their performance. By simulation-based optimization, the parameter values of the policies are determined. For this purpose, search ranges for the parameter values are provided. Based on an extensive set of experiments, insights are gained on when to apply which policy. The results show that two newly proposed enhancements of traditional base-stock policies, in particular, perform well and can be recommended for practical implementation. (C) 2015 Elsevier B.V. All rights reserved.
The paper presents a method based on Markov decision processes to optimally schedule energy storage devices in power distribution networks with renewable generation. The time series of renewable generation is modeled ...
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The paper presents a method based on Markov decision processes to optimally schedule energy storage devices in power distribution networks with renewable generation. The time series of renewable generation is modeled as a Markov chain which allows for the implementation of a stochastic dynamic programming algorithm. The output of this algorithm is an optimal scheduling policy for the storage device achieving the minimization of an objective function including cost of energy and network losses. Besides this, other properties, such as energy storage placement and size, can be assessed and compared in optimized systems with different layouts.
In this paper, we study a dynamic procurement problem for a retailer with fixed setup costs and sales levers (such as pricing, advertising, etc.). The retailer runs a reverse auction with a procurement contract in eac...
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In this paper, we study a dynamic procurement problem for a retailer with fixed setup costs and sales levers (such as pricing, advertising, etc.). The retailer runs a reverse auction with a procurement contract in each period. A number of potential suppliers bid for this contract, and the winner is the supplier with the highest bid and is given the decision right for the quantity produced and delivered. The demand is either realized by selling via Internet auctions and unmet demand is lost, or is a price-sensitive nonnegative random variable and all shortages are backlogged. We show the existence of the retailer's optimal procurement contract, under which the suppliers' Bayesian Nash equilibrium bidding strategy is (q(.), Q(.)), similar to the classic (s, S) policy for the retailers in dynamic inventory control problems. However, the (q(.), Q(.)) strategy here is for the suppliers and is realized through the suppliers' marginal production costs and so consists of two random variables for the retailer. (C) 2015 Elsevier Inc. All rights reserved.
Personnel retention is one of the most significant challenges faced by the US Army. Central to the problem is understanding the incentives of the stay-or-leave decision for military personnel. Using three years of dat...
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Personnel retention is one of the most significant challenges faced by the US Army. Central to the problem is understanding the incentives of the stay-or-leave decision for military personnel. Using three years of data from the US Department of Defense, we construct and estimate a Markov chain model of military personnel. Unlike traditional classification approaches, such as logistic regression models, the Markov chain model allows us to describe military personnel dynamics over time and answer a number of managerially relevant questions. Building on the Markov chain model, we construct a finite-horizon stochastic dynamic programming model to study the monetary incentives of stay-or-leave decisions. The dynamicprogramming model computes the expected pay-off of staying versus leaving at different stages of the career of military personnel, depending on employment opportunities in the civilian sector. We show that the stay-or-leave decisions from the dynamicprogramming model possess surprisingly strong predictive power, without requiring personal characteristics that are typically employed in classification approaches. Furthermore, the results of the dynamicprogramming model can be used as an input in classification methods and lead to more accurate predictions. Overall, our work presents an interesting alternative to classification methods and paves the way for further investigations on personnel retention incentives.
The blocks relocation problem is a classic combinatorial optimisation problem that occurs in daily operations for facilities that use block stacking systems. In the block stacking method, blocks can be stored on top o...
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The blocks relocation problem is a classic combinatorial optimisation problem that occurs in daily operations for facilities that use block stacking systems. In the block stacking method, blocks can be stored on top of each other in order to utilise the limited surface of a storage area. When there is a predetermined pickup order among the blocks, this stacking method inevitably leads to the reshuffling moves for blocks stored above the target block and the minimisation of such unproductive reshuffling moves is of a primary concern to industry practitioners. A container terminal is a typical place where this problem arises, thus the problem being also referred to as the container relocation problem. In this study, we consider departure time windows for containers, which are usually revealed by the truck appointment system in port container terminals. We propose a stochastic dynamic programming model to calculate the minimum expected number of reshuffles for a stack of containers which all have departure time windows. The model is solved with a search-based algorithm in a tree search space, and an abstraction heuristic is proposed to improve the time performance. To overcome the computational limitation of exact methods, we develop a heuristic called the expected reshuffling index (ERI) and evaluate its performance. (C) 2016 Elsevier B.V. All rights reserved.
In this study, the authors study transmission scheduling for a two-way relay network in time-varying fading channels, where the relay node can opportunistically use traditional one-way relay technique or network codin...
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In this study, the authors study transmission scheduling for a two-way relay network in time-varying fading channels, where the relay node can opportunistically use traditional one-way relay technique or network coding to forward traffic to the end nodes. They formulate a stochasticdynamic programme with the objective of minimising the long-run cost, defined as a function of both the transmission power and data transmission delay. An unconstrained Markov decision process model is developed and solved for the average and discounted cost problems. The optimal solution requires high computational and modelling complexity when the state space is large. For this reason, they develop heuristic solutions with lower complexity. For the discounted cost problem, a simulation-based dynamicprogramming algorithm is proposed that not only simplifies the modelling process and reduces the computational complexity, but also achieves close-to-optimum cost. For the average cost problem, a heuristic scheduling scheme is proposed, which makes transmission decisions based on estimated costs in the current and next time slots. The heuristic scheme achieves close-to-optimum cost performance while greatly reducing the computational complexity.
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