两种除草剂对空心莲子草的防除效果比较

空心莲子草是世界性恶性杂草。研究用使它隆乳油2g/L和Round up 15mL/L喷施空心莲子草进行防除效果比较试验。结果表明:喷药后7d,空心莲子草受害的形态和防除快速效果看,Round up防除效果优于使它隆乳油的,药后30天,从根系生理指标测定看,除Round up处理的根系硝酸还原酶活性明显高于使它隆乳油处理的外,二者对根系其他生理指标的影响无明显差异;从第二年空心莲子草复发情况看,Round up处理的区域空心莲子草无复发,而使它隆乳油处理的杂草有3%～5%左右的复发。Round up防除空心莲子草的效果优于使它隆乳油。     

筒形件拉深孔成形工艺数值模拟分析

提出了一种能提高板料成形性能的拉深孔成形工艺,该工艺是通过减小拉深时凹模圆角处对板料的压应力,实现对板料成形性能的优化。以带凸缘的圆筒形件为研究对象,对采用该工艺进行拉深有限元模拟,从拉深后拉深件的危险断面处厚度减薄率和成形极限图方面得到了很好验证,同时分析了该工艺的成形机理和力学特征,并阐明了该工艺是提高板料成形性能的技术关键。     

赣南客家围屋建筑的特点和文化探析

介绍了赣南客家围屋的基本概括及其分布情况,以口字型、国字围、套围3种类型概括了客家围屋的建筑样式,解析了客家围屋的建筑特点,突出了整个赣南客家围屋丰富多彩的建筑样式和其所具有的不同一般的防御、居住功能.解读了客家围屋所彰显的构造艺术和宗族文化,指出这支具有独特的客家方言、独特的文化民俗和情感心态的汉族支系是赣南文化的缩影,强调了承栽者千百年历史的赣南客家文化需要得到社会各界的关注和保护.     

拉伸膜裹包青贮技术研究进展

拉伸膜裹包青贮是指将收割好的新鲜牧草经捆包机高密度打捆,然后采用专业的拉伸膜进行缠绕裹包,在发酵所需的厌氧环境下形成的优质草料,是一种先进的青贮调制工艺。本文对裹包青贮在国内外的研究进展进行了综述,总结了影响裹包青贮的主要因素,分析了其在我国的应用和推广前景,并对裹包青贮研究中存在的问题提出了建议,以期为我国拉伸膜裹包青贮的进一步发展提供借鉴和参考。     

The role of spatial mixing in the spread of foot-and-mouth disease

A model of epidemic dispersal (based on the assumption that susceptible cattle were homogeneously mixed over space, or non-spatial model) was compared to a partially spatially explicit and discrete model (the spatial model), which was composed of differential equations and used geo-coded data (Euclidean distances between county centroids). While the spatial model accounted for intra- and inter-county epidemic spread, the non-spatial model did not assess regional differences. A geo-coded dataset that resembled conditions favouring homogeneous mixing assumptions (based on the 2001 Uruguayan foot-and-mouth disease epidemic), was used for testing. Significant differences between models were observed in the average transmission rate between farms, both before and after a control policy (animal movement ban) was imposed. They also differed in terms of daily number of infected farms: the non-spatial model revealed a single epidemic peak (at, approximately, 25 epidemic days); while the spatial model revealed two epidemic peaks (at, approximately, 12 and 28 days, respectively). While the spatial model fitted well with the observed cumulative number of infected farms, the non-spatial model did not (P<0.01). In addition, the spatial model: (a) indicated an early intra-county reproductive number R of approximately 87 (falling to <1 within 25 days), and an inter-county R<1; (b) predicted that, if animal movement restrictions had begun 3 days before/after the estimated initiation of such policy, cases would have decreased/increased by 23 or 26%, respectively. Spatial factors (such as inter-farm distance and coverage of vaccination campaigns, absent in non-spatial models) may explain why partially explicit spatial models describe epidemic spread more accurately than non-spatial models even at early epidemic phases. Integration of geo-coded data into mathematical models is recommended.     

乌拉圭农药进口情况分析与展望

本文介绍了乌拉圭农药进口的总体情况,分别分析了原药和制剂的进口特点,并展望了未来的发展趋势。     

圆草捆自动缠网装置设计与试验

设计了一种圆草捆自动缠网装置,该装置采用凸轮机构作为传动和控制机构,使用摆动连杆机构作为凸轮从动件,对引网作业机构、缠网计数机构和切网作业机构进行控制,实现了对圆草捆缠网、记录缠网圈数和切网的自动作业。性能试验结果表明:该装置可对宽度为80～120 cm的干草捆或宽度为80～100 cm的青贮圆草捆进行自动作业,装置对1.2 m宽干草捆缠网3圈、对1.0 m宽青贮玉米圆捆缠网4圈时,作业性价比最高。     

圆竹家具设计探究

圆竹家具在我国有着悠久的历史,具有丰富的人文内蕴,然而由于圆竹自身特性,造型和生产等方面受到限制,使圆竹家具难以适应现代人多样化的审美需求和工业化生产要求。笔者结合现代设计理念,对圆竹家具的特点和构造形式进行了深入分析,提出现代圆竹设计可以在生产过程上借鉴现代家具标准化统一生产,在外观造型上脱离传统的家具结构,精简家具构件,并且充分利用竹材韧性好等性能优势,突出造型美和材质美以满足现代审美需求;在连接结构上参考新材料或其他材料家具结构,在设计内涵上突出民族文化,引起情感共鸣。旨在为圆竹家具设计与制造提供理论指导,使圆竹家具设计符合现代生产和制造要求,满足消费者对家具外观造型的审美,达到消费者对圆竹家具情感的追求。     

乌拉圭林业的经验与启示

近 10多年来乌拉圭林业迅速崛起,成为潜在的世界木材主要出口国。意识到国际市场上木材需求量不断增长、价格稳定,1987年调整林业发展方向,重点发展出口导向型商业人工林。借鉴新西兰和智利的经验,通过补贴造林、减免税收、软贷款等优惠政策和刺激措施,加上地势平坦、气候土壤条件优越、人力资源素质高、社会经济秩序稳定以及交通便利,吸引了众多国内外投资者对人工林的大量投资,投资的年内部收益率大约是14%～27%。但是,大量采用桉树和松树等外来树种营建速生丰产林,会面临地力衰退和生物多样性丧失的危险。     

简析农产品特殊保障机制对WTO多哈谈判的影响

通过对农产品特殊保障机制与WTO项下其他与农产品有关的保障措施的比较分析,探究2008年WTO多哈谈判失败的原因及对我国的影响。