石砌深窄沟长期排水对冷浸田土壤 C、N、P化学计量及酶活性的影响

通过连续30a的冷浸田开沟排水定位平台,研究石砌深窄沟改造冷浸田不同离沟距离的土壤 C、N、P生态化学计量学特征及土壤酶活性。结果表明,离沟5、15、25m 位点土壤,与典型冷浸田位点（离沟75m 位点,CK）相比,土壤全 C、全 P含量均呈下降趋势。离沟5、15、25m 位点土壤 C／N 值分别较 CK 降低2．56、1．03、0．91个单位,差异均显著。过氧化氢酶、转化酶活性变化趋势与 C／N 值一致,5～25m 位点二者分别较CK 降低0．3％～10．0％、36．6％～62．5％;而脲酶、酸性磷酸酶、硝酸还原酶活性与 CK 相比均呈上升趋势,且过氧化氢酶、转化酶活性随着离沟距离的增加而提高,酸性磷酸酶、硝酸还原酶则随离沟距离的增加而降低。土壤 C、N、P含量间存在显著相关性,但三者与土壤酶无显著相关,而土壤 C／N 值与脲酶、磷酸酶及硝酸还原酶呈显著相关。上述说明,C／N 值较单一的有机碳与全 N 指标更能体现土壤酶间的关系,土壤 C／N 值可作为冷浸田改造效果评价的一个参考指标。     

漳河灌区农田地表排水中磷素流失特征分析

:为了揭示农田面源污染的机理及其成因,该文选取湖北省漳河灌区的典型试验田作为试验对象,在田间试验结果进行分析的基础上,研究了水稻和玉米2种作物在不同处理方式下农田排水磷素流失的影响因子及其规律。试验结果表明,降雨强度、作物类型、农业耕作管理方式（包括灌溉施肥方式等）是农田磷素流失的主要影响因素;另外,土壤物理化学特性和地形地势等也在一定程度上影响农田磷素的流失。     

刘坪-姚店输油管道大落差工艺管径优化设计

在刘坪-姚店输油管道设计中,根据陕北黄土高原地区管道走向落差较大的特点,在设计中充分利用最高点与末站的650 m落差位能,克服高点至末站沿程长约104 km的摩阻损失,采用变径管的方式解决末站进站压力高的问题,达到了"一泵到底"的目的.同时,由于减少了中间增压泵站,降低了能耗,节约了工程投资,减少了操作岗位,输油管道系统的安全可靠性大大提高.     

基于叶片载荷的涡轮发电机叶片反问题优化设计研究

针对传统水力设计难以满足井下涡轮发电机的性能要求,提出了一种以叶片载荷为设计变量,输出功率为目标函数的反问题优化设计方法。基于井下涡轮发电机叶片载荷分布规律,采用“三段式”对其进行参数化,依据初始模型叶片载荷分布形式,对NC处载荷进行线性增减,每次变化为0.2倍,设计6种不同叶片载荷分布方案,采用反问题方法设计叶轮模型,计算6种方案的输出功率,得出最高输出功率为方案Ⅱ,值为118.867 W,初始模型输出功率为93.279 6 W,最低为方案Ⅳ,输出功率为80.77 W;其中方案Ⅱ的前加载点处载荷相较于初始模型增加0.2倍;对叶片载荷进行分析,得出了井下涡轮发电机输出功率随前加载点处载荷先增加后减小。基于叶片载荷与性能之间的关系以及本文所设计的叶片优化模型,经过不断计算迭代得到了适用于井下涡轮发电机高性能的目标叶片载荷分布方案,目标叶片载荷前加载点处的载荷相较于初始模型增加0.28倍;依据该方案进行反问题设计,对目标叶片载荷与模拟载荷进行比较,二者较为接近;经过数值计算得到同等条件下,经过叶片载荷分布反问题设计模型的输出功率为129.8 W,相较于前6种方案中最高输出功率增长10.93...     

土地整治项目中的输排水工程设计

输排水工程是土地整治项目中的重要内容。该文以南昌县向塘镇高田村土地整治项目为例,探讨了农田水利给排水工程方案的设计。通过对沟渠流量计算及纵横断面设计结果表明:设计灌水率是确定渠道设计流量的依据,排涝模数是确定排水沟设计流量的重要依据,而沟渠设计流量是确定纵横断面的主要依据。因此,在输排水工程中,合理确定设计灌水率及排涝模数尤为重要。     

强渗水大型河流管道开挖穿越降水系统的构建

在强渗水大型河流管道大开挖穿越施工中,降水控水是确保安全顺利施工的关键。以水源地沙河大开挖穿越工程为例,科学、合理地构建了一种改进的降水系统,其主要由发电系统、电气控制系统、水泵组系统及附件系统组成。发电系统采用冗余硬件配置,利用N模冗余系统模型构建,提高了降水系统的可靠度;电气控制系统中的自耦降压启动方式,可以通过分阶段启动降低电机的启动电压,进而减小启动电流;水泵组系统及附件系统可以有效辅助大型深水位的降水。该降水系统应用于西气东输二线水源地沙河大开挖穿越工程,取得了良好的降水效果,可为其他大型类似工程降水系统的构建提供参考。     

Simulation of movement of pesticides towards drains with a preferential flow version of PEARL

BACKGROUND: As part of the Dutch authorisation procedure for pesticides, an assessment of the effects on aquatic organisms in surface waters adjacent to agricultural fields is required. The peak concentration is considered to be the most important exposure endpoint for the ecotoxicological effect assessment. Macropore flow is an important driver for the peak concentration, so the leaching model PEARL was extended with a macropore module. The new model has two macropore domains: a bypass domain and an internal catchment domain. The model was tested against data from a field leaching study on a cracking clay soil in the Netherlands. RESULTS: Most parameters of the model could be obtained from site‐specific measurements, pedotransfer functions and general soil structural knowledge; only three macropore‐flow‐related parameters needed calibration. The flow‐related macropore parameters could not be calibrated without using the concentration in drain water. Sequential calibration strategies, in which firstly the water flow model and then the pesticide fate model are calibrated, may therefore be less suitable for preferential flow models. CONCLUSION: After calibration, PEARL could simulate well the observed rapid movement towards drains of two pesticides with contrasting sorption and degradation rate properties. The calibrated value for the fraction of the internal catchment domain was high (90%). This means that a large fraction of water entering the macropores infiltrates into the soil matrix, thus reducing the fraction of rapid flow. Copyright © 2011 Society of Chemical Industry     

黑熊自体胆囊引流道与空肠引流道的对比分析

对胆囊引流道与空肠引流道,从解剖、生理、病理角度;理论与实践角度;血管分布;抗菌、抗炎、抗异物免疫功能;再生能力;引流道狭窄;胆囊脱出;再次手术率;引流系数;手术的难易程度等诸方面做了比较,结果胆囊引流道手术除简便易行之外均不如空肠引流道.     

Long-Term Reuse of Drainage Waters of Varying Salinities for Crop Irrigation in a Cotton-Safflower Rotation System in the San Joaquin Valley of California—A Nine Year Study: II. Safflower (Carthamus tinctorius L.)

Summary

This paper reports the results on safflower crops grown in a nine-year study, conducted on a 8 ha site, to determine the feasibility of using drainage water for irrigation in a 2-year cotton/1-year safflow-er rotation system. The cotton crops were irrigated with waters of 400, 1,500, 3,000, 4,500, 6,000, and 9,000 ppm total dissolved salts, and safflower was grown only with a preplant irrigation with nonsaline water. The use of drainage water for crop irrigation may be a means of decreasing its volume. Even though safflower was never irrigated with saline drainage water directly, the residual effect of using saline water for cotton irrigation adversely impacted safflower growth and development. Safflower seed yields were reduced in plots previously irrigated with waters of 4,500 ppm or higher salinity and even more severe effects on crop growth were seen as the numbers of years of irrigation with the saline water increased. After irrigating six cotton crops, the safflower seed yield in plots irrigated with 9,000 ppm waters was reduced to only 14% of the control. The safflower oil content and quality were not affected. Impacts on plant density, shoot height, shoot biomass, and leaf ionic content also are discussed.     

高压喷射注浆法在帷幕施工中的应用

高压喷射注浆法是把注浆管钻入土层后,利用高压喷射流冲切破坏地基土,使注入的浆液与冲下的土以半置换的方式混合凝结成固体,达到改造土体的一种化学加固的方式。本文主要介绍了此法在帷幕施工中的应用。