Risk mitigation measures for pesticide runoff: How effective are they?     

Michael Klein  Judith Klein  Jens Flade  Dietlinde Großmann  Dominique Türkowsky  Isabel O'Connor  Simon Spycher  Stefan Reichenberger  Stephan Sittig  Sebastian Multsch  Kai Thomas 《Pest management science》2023,79(12):4897-4905

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Research on a Novel Inverter of VSC     

PENG Rong  ZHOU Luo-wei  DU Xiong 《保鲜与加工》2005,(3):16-21

In order to improve waveform performance of light HVDC system, a lot of switches which operate in high frequency are used, which causes large switching losses and results high cost. A new Buck type voltage source converter(BVSC) is proposed. The new BVSC comprises a dual-buck converter and a three-phase inverter operating in grid frequency. Only two high frequency switches are used, which results good output waveform performance. In order to reduce the high frequency switching losses, a novel improved double-frequency Buck type voltage source converter(DBVSC) is also proposed. An additional dual-Buck converter is added to the BVSC, the added dual-Buck converter deals with the fundamental power that operates in low frequency, and BVSC only deals with harmonic power that operates in high frequency. The output waveform is enhanced and the switching losses are reduced in DBVSC, and the power rating is also increased. The DBVSC is very suitable for large power rating application. The one cycle control theory is adopted to control the proposed DBVSC with analog circuit, which is very simple. The proposed DBVSC and control method are verified by simulation.  相似文献   

A Thermodynamic Criteria for Evaluation of Heat Exchanger Performance     

Li Yourong Jin Mingcong Tang Jingwen 《保鲜与加工》1993,(6):46-50

The concept of loss rate of available energy was introduced for evaluating heat exchanger performance. At the same time, the general expression of loss rate of available energy was obtained for heat exchangers of several typical. And NL criteria was recommended for evaluation of the loss rate of available energy of heat exchanger. Then. the influences of inlet temperatures ratio, heat capacity ratio of fluids, the number of heat transfer units and flow patterns of heat exchanger on ,VL criteria were also discussed.  相似文献   

Detecting System of the Dielectric Loss in Capacitive Equipment Based on Virtual Instruments     

TANG Ju  LIU Ming-jun  ZHANG Xiao-xing  DU Lin  PENG Li 《保鲜与加工》2007,(3):26-30

A digital detecting system of the dielectric loss in the capacitive equipment is introduced based on virtual instruments.This system can real-time collect,analyze,process and storage electrical signals with National Instruments' program LabVIEW and ADLINK,s DAQ board.Through the simulation test in lab and the real test in electric substation,it is shown that this system has high accuracy on testing the dielectric loss in the capacitive equipment,the real test data is stable and the relative error of real dielectric loss is less than 5%.It is to say that this system can meet the requirement of the real on-line monitoring.  相似文献   

玉米穗腐病导致产量损失的品种和气候因素分析   总被引：3，自引：0，他引：3  

潘惠康  张兰新 《华北农学报》1992,7(4):99-103

1986～1990年的研究结果发现,在玉米穗腐病流行年份,抗病和感病玉米自交系的严量损失分别比常年高21％和35％。在气候因素中,日照时数对发病和产量损失影响较大。同一气候条件下感病系比抗病系产量损失大52％～82％。感病品种因穗腐病造成的玉水产量损失比不利的气候因素更为严重。  相似文献   

简单屋顶绿化的滞蓄特性   总被引：2，自引：0，他引：2  

张华  李茂  张沣  曹金露  袁密 《保鲜与加工》2015,(4):135-141

设计了模拟降雨与数据采集系统,研究了短时强降雨下简单屋顶绿化基质(配比：陶粒57.0%、草炭41.5%、保水剂1.5%)的降雨产流过程,基于37次模拟降雨实验,归纳了降雨产流的一般过程、规律和特性,分析了降雨强度、基质厚度和基质初始含水率对简单屋顶绿化滞流蓄水特性的影响。结果表明：基质厚度和基质初始含水率对简单屋顶绿化的蓄水特性有显著影响,基质初始含水率越低、基质厚度越厚时蓄水特性越佳。建立了产流时间数学模型,简单屋顶绿化降雨产流时间与降雨强度呈负相关,同时也受初始含水量和基质厚度影响。随着干湿循环次数增加,基质的厚度总体呈现下降趋势,储水性能逐渐下降,延迟产流时间逐渐缩短。  相似文献   

节水灌溉对水稻钾素营养的影响   总被引：6，自引：0，他引：6  

吕国安  李远华  沙宗尧  李顺江  王建章 《中国农村水利水电》2001,(2):24-26

研究了节水灌溉条件下、不同施肥制度水稻植树对钾的吸收状况。结果表明：灌溉方式和施肥制度对水稻钾的吸收状况均不会造成极显著的影响。节水灌溉能显著提高水稻植株含钾量。  相似文献   

基于小波分析的年最大径流预测方     

刘晓安 《中国农村水利水电》2006,(7):10-11

径流序列可以看成是各种不同成分线性叠加构成的时间序列。利用小波变换良好的局部化时频分析能力，将年最大径流序列进行分解，使其趋势项、周期项和随机项得以分离。各子序列分别代表不同的时间尺度，反映了各种物理因素对径流过程的影响。然后根据各子序列的特性分别建立幂函数、周期函数或ARMA模型并进行预测。最后将各子序列的预测值合成，得到年最大径流序列的预测值。对宜昌站1991年至2002年最大径流量的预测结果表明，该方法是切实可行的。并指出小波包变换在分析中、高频信息方面优于小波变换，有助于进一步提高预测的精度。  相似文献   

小型梳穗收获机收获损失的分析与试验   总被引：2，自引：0，他引：2  

乔西铭 《农机化研究》2007,(8):103-105

小型梳穗收获机运用梳穗收获原理,一次完成田间站秆谷物梳脱、粒穗分离、复脱、清选和装袋等工序.梳穗收获中,谷物损失率是衡量小型梳穗收获机性能的重要指标.为此,对影响其损失率大小的因素进行了分析,进行了一系列室内外单因子性能试验和正交试验,找出了最佳的结构参数.  相似文献   

快速环路分解遗传算法在配电网络重构中的应用     

周青山  向铁元  罗亚  钱卫东  邹荣盛 《中国农村水利水电》2004,(7):98-100

为了有效提高配电网络的收敛速度，避免不成熟收敛，在传统遗传算法的基础上，提出了一种快速环路分解遗传算法。提出用支路的开关状态(0或1)作为控制参数，避免繁琐的编码方法，缩短了染色体的长度，同时对交叉位置的选取和变异提出了独特的方案，并用于网络重构中，极大地提高了计算效率。  相似文献