A SEQUENTIAL APPROACH TO DERIVATION OF STAND TREATMENT AND FOREST-WIDE HARVEST PRESCRIPTION OR SUPPLY

Current methods for optimization of stand treatment and forest-wide harvest scheduling use mathematical programming that presumes perfect information on production, costs, and revenues over long planning periods. These approaches simultaneously optimize harvest for all periods in the planning horizon. In contrast, the method presented here assumes that stand-level planning and harvest scheduling proceed sequentially rather than simultaneously over every period. A backward-recursion dynamic program is used to determine the discounted net value of a wide range of current harvest strategies for each stand class in the forest inventory on the basis of a projected set of optimal treatments for future harvest and regeneration of each stand. The most highly valued strategy is selected if there are no volume constraints. Otherwise, suboptimal harvest alternatives are ranked in order of increasing opportunity cost for increasing or decreasing harvest; constraints met only up to a maximum opportunity cost is also demonstrated.     

LONG-RUN TIMBER SUPPLY: PRICE ELASTICITY,INVENTORY ELASTICITY,AND THE USE OF CAPITAL IN TIMBER PRODUCTION

Timber production requires substantially more capital per unit output than does virtually any other economic enterprise. The quantity of capital deployed depends primarily on the rotation length and the output price for timber. In a long-run timber supply model this gives rise to a “backward bending” supply curve. This paper summarizes a long-run model of timber supply, and computes the associated price and inventory elasticities. The role of capital in timber production is explored through a continuous-time formulation of the usual Faustmann point-input/point-output model. The theoretical results are illustrated through an example based on loblolly pine yields for the U.S. South.     

THE ECONOMICS OF TIMBER SUPPLY: AN ANALYTICAL SYNTHESIS OF MODELING APPROACHES

The joint supply of timber and other services from forest environments plays a central role in most forest land debates. This paper defines a general conceptual model of timber supply that provides the context for discussing both individual harvest choice and aggregate supply models. While the structure and breadth of these models has developed considerably over the last twenty years, unresolved issues remain. Supply formulations that account for the quality and vintage distribution of forest capital will be necessary for improving medium- and long-run forecasts. This will be especially important for examining the potential impacts of structural changes in forest production and timber markets. In addition, consistent aggregation of individual owners to total supply will be required to address changing forest land ownership patterns.     

不等式约束优化问题的精确罚函数法

1引言 在约束最优化的研究中，罚函数法有很高的理论及应用价值，为求约束优化问题的最优解x，很多方法是通过求解一系列优化问题来实现，人们称之为SUMT方法~[1].     

VALUING A TIMBER HARVEST CONTRACT AS A HIGH‐DIMENSIONAL AMERICAN CALL OPTION VIA LEAST‐SQUARES MONTE CARLO SIMULATION

Abstract Industrial timberland ownership in the United States has shifted substantially in the last 20 years. Having sold their fee‐owned timberlands, forest products companies relied heavily on the open market for raw timber. To reduce their exposure to market risks, however, forest products companies have been using a number of supply chain instruments, such as timber harvest contracts. As these vehicles become increasingly important to the forest industry, it is necessary and important to determine their economic values. In this study, we treated a 3‐year timber harvest contract on a 30‐year‐old loblolly pine plantation as a high‐dimensional American call option and calculated its value by the least‐squares Monte Carlo simulation technique. The estimated values of such a contract ranged from $1,693/ac to $1,984/ac under two timber price assumptions. With reasonable starting timber prices and strike price in the simulation, random timber prices led to higher contract values. Results from this study can help private landowners, timber brokers, and forest products companies better manage their business risks.     

AN ITERATIVE MULTILEVEL APPROACH TO NATURAL RESOURCE OPTIMIZATION: A TEST CASE

Forest planners face a dilemma. On the one hand, they desire more detail than they currently have in their planning optimization models, and on the other hand, these models are already extremely large and complex. This sort of problem is common in other natural resource management situations as well. This paper investigates an iterative multilevel approach that would allow districts within the forest to have models approaching the size and complexity of current forest models, but still approximate a forest-level optimum. A specific procedure based on equating shadow prices across districts is developed and tested with a case example where a global optimum is determinable as a standard of comparison. The procedure shows promise, but difficulties in recognizing optimality are indicated.     

DISRUPTION MANAGEMENT FOR SUPPLY CHAIN COORDINATION WITH EXPONENTIAL DEMAND FUNCTION

The coordination problem of a supply chain comprising one supplier and one retailer under market demand disruption is studied in this article. A novel exponential demand function is adopted, and the penalty cost is introduced explicitly to capture the deviation production cost caused by the market demand disruption. The optimal strategies are obtained for different disruption scale under the centralized mode. For the decentralized mode, it is proved that the supply chain can be fully coordinated by adjusting the price discount policy appropriately when disruption occurs. Furthermore, the authors point out that similar results can be established for more general demand functions that represent different market circumstances if certain assumptions are satisfied.     

不等式约束最优化的非光滑精确罚函数的一个光滑近似

为不等式约束最优化问题提出一个连续可微近似罚函数并研究它的性质.在此基础上,提出了两个罚函数方法并证明这两个方法是全局收敛的.     

CONTROLLED POLLUTION BUFFER ZONE – AN APPROACH TO WASTE MANAGEMENT

We consider pollution that arises from the leakage of a container into a contiguous water region. It is shown that if one considers this to be an “effective diffusion” process, the creation of a “Controlled Pollution Buffer Zone” significantly decreases the degradation of the water quality in the adjacent region.     

STOCHASTIC OPTIMIZATION FOR MULTISPECIES FISHERIES IN THE BARENTS SEA

We present a multispecies stochastic model that suggests optimal fishing policy for two species in a three‐species predator–prey ecosystem in the Barents Sea. We employ stochastic dynamic programming to solve a three‐dimensional model, in which the catch is optimized by using a multispecies feedback strategy. Applying the model to the cod, capelin, and herring ecosystem in the Barents Sea shows that the optimal catch for the stochastic interaction model is more conservative than that implied by the deterministic model. We also find that stochasticity has a stronger effect on the optimal exploitation policy for prey (capelin) than for predator (cod).     

AN ENCOMPASSING APPROACH TO MODELING FISHERY DYNAMICS: MODELING DYNAMIC NONLINEAR SYSTEMS

Uncertainty about the nature and significance of nonlinearities and the manner in which dynamics affect future realizations makes model specification the most difficult aspect of modeling dynamic systems. By interpreting several popular fishery models as subcases of a nesting dynamic Taylor series approximation, we isolate the specification differences between these models in a way that accounts for commonalities. On the argument that the differences due to alternative nonlinear forms are likely to be small compared to more mundane considerations such as delay difference and general dynamic lag specification, we propose an alternative model that uses the terms from the first order approximation common to all models combined with a data-based determination of the appropriate lags using the methods of state space time series analysis. Finally, the success of the alternative models is judged in an application to Pacific halibut data.     

SECOND-ORDER CONVERGENCE PROPERTIES OF TRUST-REGION METHODS USING INCOMPLETE CURVATURE INFORMATION, WITH AN APPLICATION TO MULTIGRID OPTIMIZATION

Convergence properties of trust-region methods for unconstrained nonconvex optimiza-tion is considered in the case where information on the objective function's local curvatureis incomplete,in the sense that it may be restricted to a fixed set of "test directions"and may not be available at every iteration.It is shown that convergence to local "weak"minimizers can still be obtained under some additional but algorithmically realistic condi-tions.These theoretical results are then applied to recursive multigrid trust-region meth-ods,which suggests a new class of algorithms with guaranteed second-order convergenceproperties.     

分布式配送系统在运输时间均匀分布条件下的性能分析

本文在运输时间不确定的前提下，对分布式配送系统在两个部件和最终产品早到无限制的情形下建立了随机优化模型。我们在极小化库存费用的同时以满足定时送货要求为目标，讨论了如何确定运输提前期，并给出了敏感性分析结果。