非接触式移动电源技术研究     

欧阳红林  杨民生  朱思国  童调生 《湖南农业大学学报(自然科学版)》2006,33(1)

研究了提高非接触式移动电源系统传输效率的方法.提出了一种可以实现零电压、零电流开关的移相全桥PWM逆变器的电路拓扑结构,这种电路拓扑可以显著提高逆变器的频率,降低开关损耗.对于非接触式移动电源的能量传输装置,提出了一种新型的基于松耦合变压器构成的结构.建立了松耦合变压器的数学模型和参数计算方法,研究了原边线圈处于不同位置的松耦合变压器的传输效率.  相似文献   

无定河粗泥沙产沙量的变化及其原因          下载免费PDF全文

许炯心 《中国水土保持科学》2007,5(6):1-7

 为了解决黄河治理中迫切需要解决的粗泥沙来源和数量问题,依据大量实测资料,运用统计方法对无定河粗泥沙产沙量进行研究。结果表明:无定河流域d>0.05 mm粗泥沙产沙量呈现出减少趋势,这种减少与年降水量、年沙尘暴频率的减少和水土保持面积的增大有一定的因果关系;估算出最大30d降雨量和年沙尘暴频率的变化对d>0.05mm粗泥沙产沙量变化的贡献率分别为66.5%和33.5%,即沙尘暴特征的变化对粗泥沙产沙量变化的贡献率相当于暴雨特征的变化贡献率的1/2。建立了粗泥沙年产沙量与最大30d降雨量、年沙尘暴频率和水土保持措施面积之间的回归方程,表明粗泥沙年产沙量随最大30d降雨量、年沙尘暴频率的减小而减小,随水土保持面积的增大而减小。因此,20世纪50年代以来暴雨的减弱、沙尘暴的减弱和水土保持措施面积的增大是无定河流域粗泥沙产沙量减少的原因。  相似文献   

库水位升降作用对库岸滑坡稳定性的影响研究   总被引：5，自引：0，他引：5  

王学武  冯学钢  王维早 《水土保持研究》2006,13(5):232-234,237

利用了渗流场-应力场耦合的有限元法,对三峡库区某滑坡体在库水位升降作用下的渗流特征及稳定性变化规律进行了研究。结果发现,对于该滑坡体在库水位上升过程中其稳定性将有降低的趋势,而在水位上升过程中,滑坡的稳定性开始阶段下降而后逐渐上升。  相似文献   

Influence of Backfill Air Gap on Soil Temperature Recovery in Ground coupled Heat Pumps   总被引：2，自引：0，他引：2  

WANG Yong  JIN Yitao 《保鲜与加工》2012,(4):142-148

Air gap may easily emerge in the progress of backfill in ground heat exchange due to field operation problems. The single U tube three dimensional numerical heat transfer model is set up and there are 3 kinds of backfill air gap assumptions for computational analysis, which are the most common situations in practical projects. Different air gap situations will have considerable effects on soil heat transfer, especially the factor of soil temperature recovery performance, which is investigated in this research, and there is practical project operating data for the comparison confirmation with the theoretical calculation results in inlet and outlet water temperatures. It can be concluded that the backfill air gap will increase the soil average excess temperature in the period of recovery inside the place where the air gap is, and degrade the heat transfer performance of the ground heat exchange.  相似文献   

Semiquantitative multi‐analysis of plasma obtained from Romney lambs (Ovis aries) by inductively coupled plasma mass spectrometry,and the classification according to feed type     

Fumihito Takahashi  Mariko Mochizuki  Touko Sato  Kinya Katayama  Paul R. Kenyon  Stephen T. Morris  Peter D. Kemp  Takeyuki Ozawa  Fukiko Ueda  Hiroyuki Tazaki 《Animal Science Journal》2013,84(6):496-501

The establishment of a classification system for domestic animals on consumed feed stuff is thought to be important from both a hygiene and market point of view. We collected plasma samples of Romney lambs (Ovis aries) which were fed one of the following: a herb‐clover mix (n = 10) which included chicory, red clover, white clover and plantain; a plant‐grass mix (n = 10) which included plantain, ryegrass and white clover; or a grass mix (n = 10) which included ryegrass and white clover. A total of 20 elements in plasma samples obtained from the lambs were analyzed using inductively coupled plasma mass spectrometry. The data were then analyzed by principal component analysis. The lambs were divided into three groups on a score plot depending on the different feed conditions. Furthermore, discriminant analyses of the elements were examined, using linear discriminant analysis with forward stepwise regression. This discriminant function correctly classified the samples from each group. The accuracy of classification of each group, as shown by 10‐fold cross‐validation, proved the effectiveness of the established discriminant function. It is concluded that using linear discriminant analysis might be a useful tool for the validation of elements from plasma in lambs grown in different conditions.  相似文献   

黄土丘陵沟壑区沟道土地整治对乡村人地系统的影响   总被引：4，自引：1，他引：3  

李裕瑞  李怡  范朋灿  刘彦随 《农业工程学报》2019,35(5):241-250

深入开展土地整治对区域乡村人地系统的影响研究对于优化土地整治模式、促进乡村振兴具有积极意义。该文以延安市某典型小流域为例,结合高分影像数据、景观格局分析和人文实地调查,从土地利用、景观格局、生态安全、社会响应和综合研判等角度探讨了黄土丘陵沟壑区沟道土地整治对当地乡村人地系统的影响。研究表明:1)在土地整治工程措施的作用下,沟道底部及其两侧的台地、坡耕地、灌木林地和草地大多转变为高产稳产的坝地,部分灌木林地由于生物措施转变为生态功能更强的乡土适生林地;坝地和林地分别增加159.06 hm2和69.75 hm2,灌木林地、草地和坡耕地分别减少112.37、63.26和59.06 hm2。2)坝地平均斑块面积和凝聚度增加,生产功能提升;乔木林地和灌木林地的景观指数、斑块凝聚度指数均保持在较高水平,生态功能稳定;流域整体的景观破碎化程度降低,景观趋于多样化和均衡化发展,景观抗干扰能力和生态系统稳定性得到提升。3)从生态安全效应来看,流域植被和生态环境明显改善,土壤侵蚀显著减少,防洪能力明显提升,但局部存在生态安全隐患。4)人类活动对流域地理环境变化有所响应,土地规模化、农业机械化、就业兼业化和非农化程度提高;但仍存在农业结构单一、效益不高等问题。应着力创新"共同商议、协同推进"的乡村治理机制,进而发挥土地整治综合效能,促进流域乡村转型与振兴。  相似文献   

高温胁迫下坛紫菜中红藻糖苷及其异构体的含量变化     

赵佳丽  杨怡  赵倩  钟琪  陈娟娟  杨锐  陈海敏 《核农学报》2019,33(1):103-111

为了解热激应答下坛紫菜中红藻糖苷和异红藻糖苷含量的变化,以及两者与坛紫菜高温耐受性之间的联系,以ME-05坛紫菜为样品,采用高效液相色谱三重四级杆质谱联用技术(HPLC-MS)分析35℃高温胁迫和20℃恢复培养条件下,坛紫菜中红藻糖苷及其异构体含量的变化趋势,通过两者的含量波动,探讨其与坛紫菜耐受性之间的关系。结果表明,相同品种、相同日龄但生长地点不同的坛紫菜中,红藻糖苷含量稳定;不同生长阶段的坛紫菜经35℃高温胁迫后,红藻糖苷和异红藻糖苷含量减少,经恢复培养3 h后发现红藻糖苷和异红藻糖苷含量逐渐回升并超过对照组;红藻糖苷和异红藻糖苷的变化率为:Ⅲ组(生长期第75天)>Ⅳ组(生长期第135天)>Ⅱ组(生长期第45天)>Ⅰ组(丝状体),红藻糖苷的变化更为敏感且具有规律。综上,红藻糖苷与坛紫菜的生长状况和抗逆能力相关,可作为紫菜选育的指标物。本研究结果为进一步探讨坛紫菜在高温胁迫下的生理响应及健康养殖奠定了理论基础。  相似文献   

电感耦合等离子体质谱法测定农产品中的锗     

马海萍 《现代农业科技》2019,(16)

采用微波消解处理农产品样品,电感耦合等离子体质谱法测定Ge,简单快速,检出限低。选用103Rh为内标,采用校正方程消除质谱干扰,经国家一级标准物质验证,方法准确度和精密度均满足实际样品分析的要求,回收率达到90%～110%。  相似文献   

坛紫菜中铝的形态分析及风险性评价   总被引：2，自引：0，他引：2  

严华  黄东仁  陈火荣  张新明  杨琳 《水产学报》2011,35(6):918-924

应用化学连续萃取法结合电感耦合等离子体质谱(ICP-MS)法对紫菜中铝的存在形态进行了初步研究,并对紫菜中铝食用安全性进行了评价。所测30份紫菜样品中铝的总含量范围为74.3~1 479 mg/kg,紫菜中铝的形态存在难溶态>有机态>无机态>水溶性游离态的分布规律。约75%的铝以难溶态存在。可溶态的铝主要以有机铝的形态存在,有机铝占总可溶态铝的72%左右。无机铝主要以Al(OH)₃的形态存在,水溶性游离态铝占无机铝的18.5%。通过模拟胃肠消化环境测定紫菜中铝的溶出率,结果表明,模拟胃液可溶出的铝占总铝的1.38%～6.80%,说明大部分铝在人体消化过程中不易溶出,对人体的潜在危害并不大。  相似文献   

Connectivity of lobster (Homarus americanus) populations in the coastal Gulf of Maine: part II. Coupled biophysical dynamics     

LEWIS INCZE  HUIJIE XUE  NICHOLAS WOLFF  DANYA XU  CARL WILSON  ROBERT STENECK  RICHARD WAHLE  PETER LAWTON  NEAL PETTIGREW  YONG CHEN 《Fisheries Oceanography》2010,19(1):1-20

We used a coupled biophysical model to investigate larval transport and connectivity patterns in the Gulf of Maine lobster ( Homarus americanus ) population. Biological 'particles' were released at over 21 000 locations every 10 days over a 4-month hatching period, and were followed from hatching through late postlarval stage. In addition to circulation and dispersion, model calculations included spatial patterns of egg production, temporal patterns of hatching, temperature-dependent development, vertical distribution and mortality. We ran the model for three larval production seasons using the same hatching patterns and individual-based modeling parameters but different flow patterns in the coastal current system. Model results gave distribution and abundance patterns of competent postlarvae that closely resembled observed, alongshore patterns of lobster settlement density. We evaluated the relative contribution of all source regions to the total number of competent postlarvae in a series of medium-size zones along the coastal shelf, many of which are used in lobster management. Connectivity depended on many factors, including patterns of egg production and transport, and the location and size of the receiving zones. Self recruitment ranged from a few percent to >90% of competent postlarvae. Although it was common for postlarvae to come from many, often distant, sources, most of the competent postlarvae in a zone originated within one to two zones in the prevailing 'up-stream' direction, forming shorter connections along the coast than the energetic currents might otherwise suggest. Inshore migrations during summer hatching may contribute to these shorter patterns of connectivity. Transport in the prevailing 'upstream' direction was also indicated.  相似文献