带截距的非线性方程与分段建模方法对立木生物量估计的比较

针对用单一的非线性模型拟合生物量方程会导致小径阶林木的估计明显有偏的问题,以东北落叶松和南方马尾松的地上生物量数据为例,提出采用带截距的非线性方程和分段建模方法来改进对立木生物量的估计,并对二者的预估效果进行了比较。结果表明:两种方法都能有效克服小径阶林木的有偏估计问题,同时对整个模型的预估效果也有一定程度的改善;从对比分析结果看,分段拟合方程的预估效果还要略好一些。     

高含油小球藻(Chlorella sp.)培养工艺条件的研究

考察了小球藻的异养能力,并利用部分析因试验和正交试验两步试验设计优化了小球藻产油条件。实验结果表明:所选小球藻能够进行异养,在葡萄糖、半乳糖和麦芽糖中均生长良好。以葡萄糖为外加碳源时,兼养组和异养组的生长量较之自养组分别提高了3.72和2.74倍。经过部分析因试验和正交试验,筛选出影响小球藻油脂产率的显著因素为氮源浓度和温度。在氮源浓度为6.0 mmol/L,温度为25℃,pH值为6.0时,小球藻的油脂产率可达到58.49 mg/(L.d)。     

Effects of temporal aggregation in integrated strategic/tactical and strategic forest planning

Integrated approaches to forest planning lead to large models and there is a subsequent need for a reduction of the number of constraints and variables. One way of achieving this is to aggregate data, either spatially or temporally. In this paper an integrated forest planning mixed integer model that takes into account both long-term strategic and shorter-term tactical forest management decisions is utilised. The study analyses the consequences of temporal aggregation in the strategic part of the integrated model, whereas the tactical part is modelled by a fixed set of years divided into seasons. For reference, analyses are also made using a pure strategic linear programming model. Cases using both equal and variable strategic period lengths are presented, and two case study areas are used. Results indicate that integrated plans, as well as strategic plans, are not particularly affected by the number of equal length strategic periods when more than five periods, i.e. less than 20 year period length, are used. When modelling strategic and integrated problems using variable-length periods, care should be taken to ensure that harvest operations late in the planning horizon get enough timing options to be adequately described.     

临城县古鲁营岗开发现划方案的研究

采用线性规划方法，利用计算机，以水和投资限额为限制因素，从２３个方案中选出了效益较高的方案，总投资４０万元，年供水量４５．３６ｍ３，栽苹果树９６．０９ｈｍ２，梨２０ｈｍ２，山楂２７ｈｍ２，杏１７ｈｍ２，石榴７ｈｍ２，枣２．７２，柿１６．７ｈｍ２，小麦１１４．３ｈｍ２，花生５．７ｈｍ２，棉花６ｈｍ２，年总产值可达３００万元以上。     

林分择伐空间结构优化模型研究

提出了林分择伐空间结构优化的建模方法 ,突破以功能优化为目标的或称功能优化模型的建模思想局限性 ,并建立了林分择伐空间结构优化模型。该模型集成现代森林经理学理论、生物多样性保护与信息技术 ,并成功地与检查法相结合。模型属非线性多目标整数规划 ,目标函数是基于混交、竞争和空间分布格局的空间结构 ,非空间结构作为主要约束条件。MonteCarlo法是模型求解的可行方法。以吉林省汪清林业局金沟岭林场的一个固定样地为例 ,用本模型进行择伐规划 ,得到具有空间位置信息的最优采伐方案。     

Heuristic planning techniques applied to forest road profiles

Two heuristic techniques, the genetic algorithm (GA) and Tabu search (TS), both with an embedded linear programming routine for earthwork allocation, were compared to a manually designed forest road profile. The manually designed road length was 345.7m and its average gradient was 14.1%. The best costs of the profiles designed by GA and TS, without changing the placement of control points, were less than that designed manually. The best cost found by GA was almost the same as the global optimum solution. While TS could not find a better solution than GA, it usually found a good solution in less time. It was not possible to search all alternatives by changing the placement of control points and find the global optimum solution within a reasonable time. However, it can be concluded from the results that both GA and TS found good solutions within a reasonable time. Since it is not possible to manually evaluate many alternatives, road designers should find heuristic techniques helpful for design of the road profile. Moreover, the effect of the number of control points on construction costs was examined. The results indicated that increasing the number of control points reduces the construction costs. However, driving safety and comfort might be decreased.     

GIS-based decision support system for wood logistics

A wood logistics system was combined with a linear programming (LP) method utilizing GIS-based techniques on the platform of GIS soflware-ARC/INFO. The combined costs of road and off-road transport were taken as the objective function to find the least cost route and the optimal landing locations of wood transportation. Then transport costs and allowable wood volume of stands were calculated. An LP model was developed to allocate timber resources among mills in order to minimize the wood logistics costs from harvesting sites to mills. The parameters of the LP model, including the transport costs, allowable wood volume and wood orders, were written into a text file in MPS format which were then accessed by LINDO to solve the LP problem. The system is an effective tool to manage logistics, information and funds together in order to increase the speed of wood logistics and reduce the cost.The benefits and efficiency of mill cluster can be improved. The focal firm in the cluster can be competitive.     

Optimal upgrading of forest road networks: Scenario analysis vs. stochastic modelling

A two-stage stochastic model with binary choice in the first stage has been developed to optimise the upgrading of a real-world forest road network, geographically located in the middle of Sweden. We have compared the model with solutions to the same problem from deterministic scenario analysis. Upgrade policies can be achieved swiftly using both approaches, since the road network is of moderate size. However, a deterministic approach is considerably faster when larger problems are involved. The study here, furthermore, indicates that deterministic scenario analysis provides us with quick, near-optimal solutions to the stochastic model, which are of reasonable good quality. We conclude that the model used here is rather insensitive to uncertainty in critical period length, such as the length of spring thaw, at least when applied to the medium-sized problem presented here. Nevertheless, we strongly recommend the use of the stochastic model whenever possible, since the stochastic and deterministic solutions differ, due to the hedging effect in the stochastic solution.     

目标规划的分解算法

提出了一种解较复杂的目标规划问题的算法.采用已开发出来的数学软件,能够方便、快速地进行计算,具有易于掌握、不易出错,适用于较复杂的模型.