This research seeks to explain the determinants of reverse mortgage product choice. Reverse mortgages can potentially be a great benefit to an aging population, but it is important that products be structured to meet ...
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作者：
Weber, TPEns, BJHouston, AIUniv Oxford
Dept Zool Ecol & Behav Grp BBSRCNERC Oxford OX1 3PS England DLO
IBN Inst Forestry & Nat Res NL-1790 AD Den Burg Texel Netherlands Univ Bristol
Sch Biol Sci Bristol BS8 1UG Avon England
Birds migrating between widely separated wintering and breeding grounds may choose among a number of potential stopover sites by using different itineraries. Our aim is to predict the optimal migration schedule in ter...
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Birds migrating between widely separated wintering and breeding grounds may choose among a number of potential stopover sites by using different itineraries. Our aim is to predict the optimal migration schedule in terms of (1) rates of fuel deposition, (2) departure fuel loads and (3) stopover site use, when only a handful of such sites are available. We assume that reproductive success depends on the date and fuel load at arrival on the breeding grounds. On migration, the birds face a trade-off between gaining fuel and avoiding predation. To allow the optimal decision at any given moment to depend on the fuel load and the location of the bird, as well as on unpredictability in conditions, we employed stochastic dynamic programming. This technique assumes that the birds know the probability distribution of conditions in all sites, but not the particular realization they will encounter. We examined the consequences of varying aspects of the model, like (1) the shape of the relationship between arrival date and fitness, (2) the presence of stochasticity in fuel deposition rates and wind conditions, and (3) the nature of predation (i.e. whether predation risk depends on the fuel load of the birds or their feeding intensity). Optimal fuel deposition rates are predicted to be constant if there are either only predation risks of maintaining stores or only risks of acquiring fuel stores. If only fuel acquisition is risky, fuel deposition rates can be below maximum, especially if there also is an intermediate best arrival time at the breeding ground. The fuel deposition rate at a site then depends not just on the site's quality but on the qualities of all visited sites. In contrast, rates of fuel deposition are not constant if both the acquisition and the maintenance of fuel stores carry risk. Optimal departure fuel loads are just enough to reach the next site if the environment is deterministic and are simply set by the energetic cost of covering the distance. As with time
Due to rapid change in timber prices in the Japanese market most likely affected by imported timber from countries such as the U.S., Canada, and the Nordic countries, the domestic forest managers have been facing a la...
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Due to rapid change in timber prices in the Japanese market most likely affected by imported timber from countries such as the U.S., Canada, and the Nordic countries, the domestic forest managers have been facing a large degree of future price uncertainty. Because of this, it becomes necessary to take the future price uncertainty into account within the forest management framework. In this paper, the continuous time stochastic process, i.e., the geometric Brownian motion, has been used to model the log price process. The binomial option pricing approximation was then applied to value the Sugi (Cryptomeria japonica) and Hinoki (Chamaecyparis obtusa) forested land under stochastic log prices in order to search for an optimal rotation age. Our experiments with the proposed two state stochastic dynamic programming model showed that when the current log price is high enough to cover all costs, an optimal rotation age from the stochastic price and deterministic price models coincides, although the total expected present net value from management activities differs. Also it was shown that as the current log price decreases, an optimal rotation age derived from the stochastic price model becomes longer than that from the deterministic price model. If the current log price further decreases, then forest management will be abandoned, and the forest stand will be converted into alternative uses. (C) 1998 Elsevier Science B.V.
This paper is concerned with the problem of production planning in a flexible manufacturing system consisting of a single or parallel failure-prone machines producing a number of different products. The objective is t...
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This paper is concerned with the problem of production planning in a flexible manufacturing system consisting of a single or parallel failure-prone machines producing a number of different products. The objective is to choose the rates of production of the various products over time in order to meet their demands at the minimum long-run average cost of production and surplus. The analysis proceeds with a study of the corresponding problem with a discounted cost. It is shown using the vanishing discount approach for the average cost problem that the Hamilton-Jacobi-Bellman equation in terms of directional derivatives has a solution consisting of the minimal average cost and the so-called potential function. The result helps in establishing a verification theorem, and in specifying an optimal control policy in terms of the potential function. The results settle a hitherto open problem as well as generalize known results.
Previous analyses of the timber rotation problem under price uncertainty find that timber owners can increase the expected values of their stands by using a reservation price policy that exploits stochastic variations...
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Previous analyses of the timber rotation problem under price uncertainty find that timber owners can increase the expected values of their stands by using a reservation price policy that exploits stochastic variations in prices. This result is found when the process governing prices is stationary and with nonstationary prices when there are fixed costs. This paper highlights the role of option values in influencing the optimal timing of harvests. In this context, the option value is a premium over the expected net present value of a timber stand reflecting the opportunity cost of harvesting now and foregoing the option to delay harvest until information on future stand values is revealed. With stationary prices, option values arise from two sources of forthcoming information: the level of the stumpage price relative to the long-term mean and the stand value relative to fixed costs. With nonstationary prices, option values are associated only with the latter information. This paper demonstrates analytically that reservation price policies act as a mechanism for incorporating the option value into the calculus of the optimal rotation length, Numerical simulations provide further insights into the effects of option values on rotation lengths, expected stand values, and reservation prices.
We consider the problem of deciding the beat action time when observations are made sequentially. Specifically we address a special type of optimal stopping problem where observations are made from state-contingent di...
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We consider the problem of deciding the beat action time when observations are made sequentially. Specifically we address a special type of optimal stopping problem where observations are made from state-contingent distributions and there exists uncertainty on the state. In this paper, the decision-maker's belief on state is revised sequentially based on the previous observations. By using the independence property of the observations from a given distribution, the sequential Bayesian belief revision process is represented as a simple recursive form. The methodology developed in this paper provides a new theoretical framework for addressing the uncertainty on state in the action-timing problem context. By conducting a simulation analysis, we demonstrate the value of applying Bayesian strategy which uses sequential belief revision process. In addition, we evaluate the value of perfect information to gain more insight on the effects of using Bayesian strategy in the problem. (C) 1998 Elsevier Science B.V.
The accelerated pace of technological change has led to rapid obsolescence of productive capacity in electronics and other industries. Managers must consider the impact of future technologies while making acquisition ...
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The accelerated pace of technological change has led to rapid obsolescence of productive capacity in electronics and other industries. Managers must consider the impact of future technologies while making acquisition and replacement decisions in such environments. We consider a problem where a sequence of technological breakthroughs are anticipated but their magnitude and timing are uncertain. A firm, operating in such an environment, must decide how much capacity of the current technology to acquire to meet future demand growth. It must also determine whether to upgrade any of the older vintages. We formulate this problem and present some structural results. Using these results, we then develop a highly efficient regeneration point-based dynamicprogramming algorithm. The effectiveness of the proposed algorithm is illustrated through a computational study. The sensitivity of the first period decision to various parameters is also explored.
Our ability to model spatial distributions of fish populations is reviewed by describing the available modelling tools. Ultimate models of the individual‘s motivation for behavioural decisions are derived from evolut...
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Our ability to model spatial distributions of fish populations is reviewed by describing the available modelling tools. Ultimate models of the individual‘s motivation for behavioural decisions are derived from evolutionary ecology. Mechanistic models for how fish sense and may respond to their surroundings are presented for vision, olfaction, hearing, the lateral line and other sensory organs. Models for learning and memory are presented, based both upon evolutionary optimization premises and upon neurological information processing and decision making. Functional tools for modelling behaviour and life histories can be categorized as belonging to an optimization or an adaptation approach. Among optimization tools, optimal foraging theory, life history theory, ideal free distribution, game theory and stochastic dynamic programming are presented. Among adaptation tools, genetic algorithms and the combination with artificial neural networks are described. The review advocates the combination of evolutionary and neurological approaches to modelling spatial dynamics of fish.
This paper considers the problem of precautionary savings for an expected utility specification with finite horizon. The exact solution is known for only a few cases. Numerical methods have limited applications becaus...
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This paper considers the problem of precautionary savings for an expected utility specification with finite horizon. The exact solution is known for only a few cases. Numerical methods have limited applications because of Bellman's 'curse of dimensionality'. This paper derives a simple analytical approximate solution for a general specification of the felicity function which is linear in the variance of the innovations on human wealth. Numerically, the approximation is very accurate for realistic values of the parameters of the problem. (C) 1998 Elsevier Science B.V. All rights reserved.
We consider the optimal wagers to be made by a gambler who starts with a given initial wealth. The gambler faces a sequence of two‐outcome games, i.e., “win” vs. “lose,” and wishes to maximize the expected value ...
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