The model presented in this paper relies on financial constraints and transactions costs to operationalize model of behavior akin to safety rules. The decision maker is taken to maximize long term (40 period) expected...
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The model presented in this paper relies on financial constraints and transactions costs to operationalize model of behavior akin to safety rules. The decision maker is taken to maximize long term (40 period) expected wealth in the presence of financial transactions costs. The model allows exploration of the implications of these constraints and transactions costs for measurable choice patterns over risk. The optimization analysis demonstrates very rich behavior despite the restrictive assumption of risk neutral preferences. The optimal decisions show instances of "risk aversion" with willingness to pay less than a risky option's expected value, and of "risk preference" or plunging with willingness to pay greater than a risky option's expected value. These varied behavioral patterns in the presence of risk depend on the individual's financial standing, the magnitude of the random outcomes, the underlying distribution, and the farm policy environment. (C) 2002 Elsevier Science Ltd. All rights reserved.
This article presents the analysis, comparison, and application of two alternative models to the optimal long-term operation planning of an hydro-thermal power system under conditions of uncertainty. The electrical sy...
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In this paper, we consider optimal market timing, strategies under transaction costs. We assume that the asset's return follows an auto-regressive model and use long-term investment growth as the objective of a ma...
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In this paper, we consider optimal market timing, strategies under transaction costs. We assume that the asset's return follows an auto-regressive model and use long-term investment growth as the objective of a market timing strategy which entails the shifting of funds between a risky asset and a riskless asset. We give the optimal trading strategy for a finite investment horizon, and analyze its limiting behavior. For a finite horizon, the optimal decision in each step depends on two threshold values. If the return today is between the two values, nothing needs to be done, otherwise funds will be shifted from one asset to another, depending on which threshold value is being exceeded. When investment horizon tends to infinity, the optimal strategy converges to a stationary policy, which is shown to be closely related to a well-known technical trading rule, called Momentum Index trading rule. An integral equation of them two threshold values is given. Numerical results for the limiting stationary strategy are presented. The results confirm the obvious guess that the no-transaction region increases as the transaction cost increase. Finally, the limiting stationary strategy is applied to data in the Hang Seng Index Futures market in Hong Kong. The out-of-sample performance of the limiting stationary strategy is found to be better than the simple strategy sed in literature, which is based on an 1-step ahead forecast of return. (C) 2002 Elsevier Science Ltd. All rights reserved.
Optimal control theory is finding increased application in both theoretical and applied ecology, and it is a central element of adaptive resource management. One of the steps in an adaptive management process is to de...
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Optimal control theory is finding increased application in both theoretical and applied ecology, and it is a central element of adaptive resource management. One of the steps in an adaptive management process is to develop alternative models of system dynamics, models that are all reasonable in light of available data, but that differ substantially in their implications for optimal control of the resource. We explored how the form of the recruitment and survival functions in a general population model for ducks affected the patterns in the optimal harvest strategy, using a combination of analytical, numerical, and simulation techniques. We compared three relationships between recruitment and population density (linear, exponential, and hyperbolic) and three relationships between survival during the nonharvest season and population density (constant, logistic, and one related to the compensatory harvest mortality hypothesis). We found that the form of the component functions had a dramatic influence on the optimal harvest strategy and the ultimate equilibrium state of the system. For instance, while it is commonly assumed that a compensatory hypothesis leads to higher optimal harvest rates than an additive hypothesis, we found this to depend on the form of the recruitment function, in part because of differences in the optimal steady-state population density. This work has strong direct consequences for those developing alternative models to describe harvested systems, but it is relevant to a larger class of problems applying optimal control at the population level. Often, different functional forms will not be statistically distinguishable in the range of the data. Nevertheless, differences between the functions outside the range of the data can have an important impact on the optimal harvest strategy. Thus, development of alternative models by identifying a single functional form, then choosing different parameter combinations from extremes on the likelihood profil
In this paper, we consider stochastic linear-quadratic discrete-time Nash games in which two players have access only to noise-corrupted output measurements. We assume that each player is constrained to use a linear K...
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In this paper, we consider stochastic linear-quadratic discrete-time Nash games in which two players have access only to noise-corrupted output measurements. We assume that each player is constrained to use a linear Kalman filter-like state estimator to implement his optimal strategies. Two information structures available to the players in their state estimators are investigated. The first has access to one-step delayed output and a one-step delayed control input of the player. The second has access to the current output and a one-step delayed control input of the player. In both cases, statistics of the process and statistics of the measurements of each player are known to both players. A simple example of a two-zone energy trading system is considered to illustrate the developed Nash strategies. In this example, the Nash strategies are calculated for the two cases of unlimited and limited transmission capacity constraints.
We consider general feed-forward networks of queues with deterministic service times and arbitrary arrival processes. There are holding costs at each queue, idling may or may not be permitted, and servers may fail. We...
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We consider general feed-forward networks of queues with deterministic service times and arbitrary arrival processes. There are holding costs at each queue, idling may or may not be permitted, and servers may fail. We partially characterize the optimal policy and give conditions under which lower priority should be given to jobs that would be delayed later in the network if they were processed now.
Consider a Hidden Markov model (HMM) where a single Markov chain is observed by a number of noisy sensors. Due to computational or communication constraints, at each time instant, one can select only one of the noisy ...
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Consider a Hidden Markov model (HMM) where a single Markov chain is observed by a number of noisy sensors. Due to computational or communication constraints, at each time instant, one can select only one of the noisy sensors. The sensor scheduling problem involves designing algorithms for choosing dynamically at each time instant which sensor to select to provide the next measurement. Each measurement has an associated measurement cost. The problem is to select an optimal measurement scheduling policy to minimize a cost function of estimation errors and measurement costs. The optimal measurement policy is solved via stochastic dynamic programming. Sensor management issues and suboptimal scheduling algorithms are also presented. A numerical example that deals with the aircraft identification problem is presented.
When software reliability demonstration of safety-critical systems by statistical testing is treated as a Test, Analyse and Fix (TAAF) process, an optimal testing policy can be found, which maximises the probability o...
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When software reliability demonstration of safety-critical systems by statistical testing is treated as a Test, Analyse and Fix (TAAF) process, an optimal testing policy can be found, which maximises the probability of p success of the whole process, over a pre-determined period of time. The optimisation problem is formulated, solved by stochastic dynamic programming, and demonstrated by two numerical examples. (C) 2002 Elsevier Science B.V. All rights reserved.
The Samanalawewa and Udawalawe reservoirs were built to harness the hydro-energy and irrigation potentials of the Walawe river in Sri Lanka. The recently completed Samanalawewa reservoir primarily generates hydropower...
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The Samanalawewa and Udawalawe reservoirs were built to harness the hydro-energy and irrigation potentials of the Walawe river in Sri Lanka. The recently completed Samanalawewa reservoir primarily generates hydropower while the Udawalawe reservoir, which was built in the 1960s, supplies water mainly for irrigation. With the addition of the Samanalawewa reservoir, located upstream of the Udawalawe reservoir, the Government of Sri Lanka is planning to increase the irrigated area of the Udawalawe reservoir. The Samanalawewa reservoir is expected to act as an additional storage for irrigation water supply. A study was carried out to investigate the operational behavior of these two reservoirs. The model used in the study is based on stochastic dynamic programming (SDP) and simulation techniques. Since, the direct application of SDP for two reservoirs is limited by the dimensionality of the problem, a sequential decomposition method is employed in the model. The algorithm employed breaks down the system into single-reservoir subsystems and subsequently, each subsystem's operation is individually optimized using a SDP based optimization model and then simulated using a reservoir operation simulation model. The results indicate the usefulness of optimization techniques in planning reservoirs and deriving operational policies for them. The inclusion of the Samanalawewa reservoir reduces the irrigation water supply deficits at the Udawalawe reservoir. (C) 2002 Elsevier Science B.V. All rights reserved.
The California red scale Aonidiella aurantii (Maskell) (Homoptera: Diaspididae) is a major pest of California citrus, with infestations causing growers significant financial losses. It has recently developed resistanc...
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The California red scale Aonidiella aurantii (Maskell) (Homoptera: Diaspididae) is a major pest of California citrus, with infestations causing growers significant financial losses. It has recently developed resistance to traditional insecticide sprays. An alternative suppression tactic is the release of a biological control agent, Aphytis melinus DeBach (Aphelinidae: Hymenoptera) that feeds on red scale. Although many aspects of the red scale-Aphytis interaction are now understood, it is difficult to differentiate the effects of temperature and population fluctuations in the field. To investigate such complex interactions, we propose a new stochastic modeling technique, based on event-driven competing risks, that incorporates details of life histories as well as the host-parasitoid interaction. Our continuous-time, individual-oriented modeling approach quantifies relationships among individuals and describes the resulting coupling between the interacting populations. The event-structured simulation drives time in contrast to the usual time-driven stochastic dynamic programming. Our system, developed in the public domain using the R statistical package, allows for different biological clocks, since both red scale and Aphytis development respond to temperature (degree-days) while searching female Aphytis follow a diurnal time schedule, contingent upon temperature-dependent egg maturation. (C) 2002 Elsevier Science B.V. All rights reserved.
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