一种改进的天然气管网流动方程表示方法

针对应用关联矩阵法在描述天然气管网流动方程时未考虑压气站的自耗气,在准确描述该部分气量的模型中易产生偏差的问题,通过增加自耗气源向量的方法对此进行了改进,可以完整地描述这部分天然气,准确地对管网的结构和管网的流动方程进行描述。     

常熟市水体氮负荷对土地利用方式的响应

为研究水环境变化对土地利用方式的响应,以常熟地区为例,利用ArcGIS10.0空间分析功能和SPSS相关性分析方法,对常熟市各土地利用类型和水体总氮含量进行了分析。结果表明:1990—2010年间常熟地区耕地和水域面积在持续缩减,建设用地和林地面积在增加;各土类状态指数(Di)大小依次为:建设用地林地草地耕地水域;建设用地面积的增加主要占据的是耕地和水域,水域面积的缩减主要被耕地占用;耕地面积与水体总氮含量呈显著性负相关关系(r=–0.959*,P0.05),说明种植型污染贡献比例在下降;林草地与水体总氮含量无显著相关性;建设用地与水体总氮含量呈显著性正相关关系(r=0.929*,P0.05),说明建设用地造成了点源污染。     

Influence of Sucrose, Mucin and Xanthan Gum on Spore Germination of Ten Different Fungi

Germination of conidia, uredospores and basidiospores of ten diverse fungi were compared in sterile distilled water, 0.5% sucrose, 0.5% mucin and 0.5% xanthan gum. All three compounds generally increased spore germination on cellophane membranes compared to water, but mucin was the most effective. Mucin stimulated significantly more germination than sucrose for 7 of the 10 fungi, and only Aspergillus niger and Colletotrichum gloeosporioides showed greater spore germination in sucrose than in mucin. Sucrose had no effect on uredospore or basidiospore germination, but mucin stimulated germination of these spores. Mucin was more effective than xanthan gum in increasing spore germination for 9 of the 10 fungi. Animal mucin is chemically similar to the natural spore matrix of some fungi and may provide some of the benefits of the spore matrix without the drawback of possible germination inhibitors. Animal mucin may be a useful substitute for the spore matrix in inoculations of a variety of fungi.     

Optimal management of uneven-aged Norway spruce stands

An optimization model is specified to analyze forest management without any restrictions on the forest management system. The data on forest growth comes from unique field experiments and is used to estimate a nonlinear transition matrix or size-structured model for Norway spruce. The objective function includes detailed harvesting cost specifications and the optimization problem is solved in its most general dynamic form. In optimal uneven-aged management, stand density is shown to be dominated by limitations in natural regeneration. If the goal is volume maximization, even-aged management with artificial regeneration (and thinnings from above) is superior to uneven-aged management. After including regeneration and harvesting costs, the interest rate, and the price differential between saw timber and pulpwood, uneven-aged management becomes superior to even-aged management. However, in the short term the superiority is conditional on the initial stand state.     

黄河干流水文缺水分类模型研究

本文通过对黄河干流节点径流频率分析和超越机率分析,推求了节点水文缺水量。通过制定黄河干流水文缺水等级划分标准,用节点天然径流系列为样本,建立了节点水文缺水分类模型。应用分类模型,进一步得到了节点缺水状态转移概率矩阵。节点水文缺水分类模型和状态转移概率矩阵将会对黄河干流水资源合理配置提供决策依据。     

MMP-2、MMP-9在子宫内膜增生症和腺癌中的表达

目的 探讨基质金属蛋白酶-2(MMP-2)和MMP-9在子宫内膜腺癌发生、发展中的作用.方法 采用免疫组化法检测100例子宫内膜腺癌、30例子宫内膜增生症及30例正常子宫内膜中MMP-2、MMP-9表达.结果 MP-2、MMP-9 在正常子宫内膜增生期表达增加,而在早分泌期几乎无表达;MMP-2、MP-9在不典型增生及...     

基于RS与GIS技术的西吉县土地利用/覆盖变化分析

 以黄土高原较早实施退耕还林的宁夏西吉县为例,选择1990和2005年的2期TM遥感图像,对西吉县1990—2005年的各种土地利用类型,从土地利用结构及空间景观特征进行分析,得到退耕还林政策实施过程中的土地利用变化情况,为黄土高原地区的土地利用政策提供决策依据。     

玻璃基质缓释肥料的养分淋溶特性研究

以自制的玻璃基质缓释肥料为供试材料,采用土壤淋溶方法,研究玻璃缓释肥料在土壤中的养分释放规律。结果表明:培养28d后玻璃肥料的氮、钾累积释放率分别为普通肥料的81.34%和75.32%(P<0.01),极大的减少了养分淋溶损失。玻璃肥料在淋溶的中后期仍有一定的氮、钾释放速率和释放量,减少了养分损失率,有效地延长了氮、钾养分供应期,具有明显的缓释效果。     

层次分析法(AHP)的标度分析及其在水利工程评价中的应用

应用实例说明了1-9标度在应用时可能导致的一致性与思维一致性相脱节问题,并进一步分析了出现这种问题的原因。在此基础上,对层次分析法应用时所出现的标度进行了归纳和分析,并把评价准则的指标分为定性指标和定量指标两种情况进行讨论,提供了两种情况下构造判断矩阵的方法。对于定性指标·给出了构造两两比较判断矩阵时选用标度的建议;对于定量指标,构造了标度函数,并建立了定量准则下满足一致性要求的两两比较判断矩阵。