森林收获安排模型研究进展*

森林收获安排是森林经营规划的核心问题之一。文中主要以美国的研究为代表．介绍目前森林收获安排模型的研究进展，包括：模型建立方法、模型分类和模型求解3个方面。模型的建立尚无统一方法。模型分为URM和ARM2类。模型的求解主要采用启发武搜索方法。指出．模型的发展趋势是资源保护空间优化模型。     

利用农田水量平衡模型评价棉田不同的灌溉制度

本文以田间试验为基础，应用农田水量平衡理论和棉花对不同水分亏缺的反应，建立了一个棉花不同灌溉制度的评价模型，文中用ＦＡＯ－４６提供的Ｐｅｎｍａｎ－Ｍｏｎｔｅｉｔｈ方法计算了棉花生育期间逐日参考作物蒸散量，利用Ｉｓａｒｅｇ模型［５］计算了棉田逐日实际蒸散量。研究结果表明，利用农田水量平衡模型可对棉花灌溉进行有效管理。通过对几种灌溉方案的评价，定量化地分析了不同灌溉制度对棉花产量的影响程度和水分胁迫出现的时间；明确了在黄淮海平原棉田灌溉重点在棉花生育前期，即苗期，盛蕾－初花期；给出了该地区棉花各生育时期的需水量和每日的平均耗水强度     

THE APPLICATION OF NETWORK PROGRAMMING METHOD ON THE SHORT TERM OPTIMAL SCHEDULING FOR CASCADED HYDROPOWER STATIONS

The problem of the short term economic scheduling for cascaded hydropower stations is discussed with the network programming method. A new network model is built to dispatch the load to each unit when the unit commitment is determined. An algorithm of the minimal cost maximal flow is also discussed using the model and the algorithm to the Longxi River Cascaded Hydropower Stations, the computational result on the microcomputer VAX II shows that the model and the algorithm are correct and applicable.     

基于全过程管控的配网重要用户调度管理体系

配网重要用户的管理需解决配网风险校核、供电可靠性分析等问题,以避免配网重要用户中断供电对政治、经济和社会生活造成损失或影响.文章提出一种全过程管控的配网重要用户调度管理体系.该体系以"实时预警、多态管控、分析自愈"为核心,实现配网重要用户供电规划态、正常态、调整态全过程管控,提升配网重要用户调度管理水平.     

Minimizing driving times and greenhouse gas emissions in timber transport with a near-exact solution approach

Abstract

Efficient transport of timber for supplying industrial conversion and biomass power plants is a crucial factor for competitiveness in the forest industry. Throughout the recent years minimizing driving times has been the main focus of optimizations in this field. In addition to this aim the objective of reducing environmental impacts, represented by carbon dioxide equivalent (CO₂ e) emissions, is discussed. The underlying problem is formulated as a multi-depot vehicle routing problem with pickup and delivery and time windows (MDVRPPDTW) and a new iterative solution method is proposed. For the numerical studies, real-life data are used to generate test instances of different scales concerning the supply chain of biomass power plants. Small ones are taken to validate the optimality of the new approach. Medium and large test instances are solved with respect to minimizing driving times and fuel consumptions separately. This study shows that the selection of the objective of minimizing fuel consumption leads to a significant reduction of CO₂ e emissions compared to a minimization of driving times.     

水利工程调度方式的调整及优化方案讨论

对水利工程的调度方式中存在的问题进行分析,并提出相应的调整及优化方案。     

南疆膜下滴灌棉花耗水规律以及灌溉制度研究

2004年在南疆尉犁县进行了棉花膜下滴灌耗水规律以及灌溉制度的研究,通过设置三个灌水处理:345 mm、420 mm、505 mm,并连续监测每次灌前棉花全生育期土壤含水量变化,得出以下结论:在花期(7月4日)滴灌定额45 mm,灌水只能影响到土壤0~40 cm,灌后第一天,土壤水分损失可达到20 mm;灌后四天,0~40 cm含水量已降至60%以下,棉花已受到水分胁迫。在南疆,在充分满足棉花对水分需求的条件下,膜下滴灌棉花耗水量为625 mm,505 mm的灌溉量可满足棉花对水分的需求。根据实验的灌水安排以及棉花各生育阶段的耗水率,南疆膜下滴灌棉花的灌溉制度为:蕾期每次灌水定额35 mm,每5天灌一次;花铃期每次灌水定额为50 mm,7天灌一次,盛铃期后,灌水定额逐渐降低至35 mm。     

土水势的初步测试与应用

新疆是严重干旱缺水地区，灌溉农业，农业用水占总用水量８０５以上，由于灌溉技术落后，浪费十分严重，因此，节约农业用水是缓解新疆干旱和水资源紧缺矛盾的有效途径。本文通过用负压计测定土壤水势，了解土壤水分动态变化，并对冬麦进行适时适量灌溉预报，达到显著的节水增产效果、是一项投资少，操作简单，节水增产幅度大的节水技术，为干旱地区的节水农业开辟了一条新途径。     

Yield and quality response of drip irrigated broccoli (Brassica oleracea L. var. italica) under different irrigation regimes, nitrogen applications and cultivation periods

The experiment aimed at evaluating the yield and quality response of broccoli (Brassica oleracea L. var. italica) to applied irrigation water and nitrogen by drip irrigation method during the spring and autumn cultivation periods of 2007. Irrigation water was applied based on a ratio of Class A pan evaporation (k_cp = 0.50, 0.75, 1.00 and 1.25) with 7 days interval. Also, the effect of four nitrogen levels (0 kg ha⁻¹, 150 kg ha⁻¹, 200 kg ha⁻¹ and 250 kg ha⁻¹) was compared with each treatment. The seasonal evapotranspiration in the treatments varied from 233 mm to 328 mm during the spring period and from 276 mm to 344 mm during the autumn period. The highest broccoli yield was obtained in the spring period as 11.02 t ha⁻¹ and in the autumn period as 4.55 t ha⁻¹. In general, there were statistical differences along nitrogen does with respect to yield and yield components while there were no statistically significant differences in the yield and yield components among irrigation regimes. Both yield and yield parameters in the spring period were found to be higher than that of the autumn period due to the low temperature and high rainy days in autumn. Irrigation water use efficiency (IWUE) ranged from 3.78 kg m⁻³ to 14.61 kg m⁻³ during the spring period and from 1.89 kg m⁻³ to 5.93 kg m⁻³ during the autumn period. On the other hand, nitrogen use efficiency (NUE) changed as 37.32-73.13% and 13.08-22.46% for spring and autumn season, respectively.     

Response of soybean genotypes to different irrigation regimes in a humid region of the southeastern USA

Studies on irrigation scheduling for soybean have demonstrated that avoiding irrigation during the vegetative growth stages could result in yields as high as those obtained if the crop was fully irrigated during the entire growing season. This could ultimately also lead to an improvement of the irrigation water use efficiency. The objective of this study was to determine the effect of different irrigation regimes (IRs) on growth and yield of four soybean genotypes and to determine their irrigation water use efficiency. A field experiment consisting of three IR using a lateral move sprinkler system and four soybean genotypes was conducted at the Bledsoe Research Farm of The University of Georgia, USA. The irrigation treatments consisted of full season irrigated (FSI), start irrigation at flowering (SIF), and rainfed (RFD); the soybean genotypes represented maturity groups (MGs) V, VI, VII, and VIII. A completely randomized block design in a split-plot array with four replicates was used with IR as the main treatment and the soybean MGs as the sub-treatment. Weather variables and soil moisture were recorded with an automatic weather station located nearby, while rainfall and irrigation amounts were recorded with rain gauges located in the experimental field. Samplings for growth analysis of the plant and its components as well as leaf area index (LAI) and canopy height were obtained every 12 days. The irrigation water use efficiency (I_WUE) or ratio of the difference between irrigated and rainfed yield to the amount of irrigation water applied was estimated. The results showed significant differences (P < 0.05) between IR for dry matter of the plant and its components, canopy height, and maximum leaf area index as well as significant differences (P < 0.05) between MGs due to IR. Differences for the interaction between IR and MG were significant (P < 0.05) only for dry matter of pods and seed yield. In general, seed yield increased at a rate of 7.20 kg for each mm of total water received (rainfall + irrigation) by the crop. Within IR, significant differences (P < 0.05) on I_WUE were found between maturity groups with values as low as 0.55 kg m⁻³ for MG V and as high as 1.14 kg m⁻³ for MG VI for the FSI treatment and values as low as 0.48 kg m⁻³ for maturity group V and as high as 1.02 kg m⁻³ for maturity group VI for the SIF treatment. We also found that there were genotypic differences with respect to their efficiency to use water, stressing the importance of cultivar selection as a key strategy for achieving optimum yields with reduced use of water in supplemental irrigation.