A PRACTICAL PWM CONTROL METHOD OF CURRENT SOURCE GTR INVERTER

According to the principle that the orbit of stator current vector in complerplane should be as close to a circle as possible, the PWM control pattern is derived and determined. The control method is realized by using a micro-computer.     

谈施工企业定额的建立

根据建筑市场的改革发展 ,提出了施工企业应根据自身的条件和特点来建立施工企业定额 ,分析了编制企业定额的原则、方法和步骤以及成立企业定额管理机构的原则。     

兵团农机产业化的若干思考

农机产业化是社会分工细化、生产专业化深化的必然产物，其实质是传统农业转变为现代产业的过程。日前，兵团农机产业化进程中存在着一些问题。为此，结合兵团实际，提出了推进农机产业化发展的基本思路。     

泵站优化运行算法

通过对动态规划法、线性规划法、非线性规划法及遗传算法等泵站优化运行算法的综述，对泵站运行优化方法的发展提出新的看法。     

旱地玉米双相覆盖技术在太原地区的增产效果与机理

玉米双相覆盖技术在太原生态区增产率为１４．４８％。具有苗期适宜增温促发、中期保墒促长的土壤环境效应。增产机理是：玉米地上部和地下部协调增长，叶面积大，茎秆还原糖贮量多，干物质积累也多；具持续高强度灌浆特性，加快了物质运转速度     

The Rht13 dwarfing gene reduces peduncle length and plant height to increase grain number and yield of wheat

The green-revolution Rht-B1b and Rht-D1b dwarfing alleles are usually associated with increased wheat yields but are linked to reduced early growth and poor emergence if sowing conditions are unfavourable. Other dwarfing genes are available but not used in commercial breeding. The Rht13 bread wheat donor, Magnif M1, produces uniquely short peduncle and penultimate internodes to reduce plant height. A set of near-isogenic (NILs) and recombinant inbred (RILs) lines varying for height were developed from the cross of Magnif M1 and the Rht8c-containing Chuan-mai 18, and evaluated for a range of agronomic characteristics across favourable environments. Reductions in plant height were associated with increased grain number (r² = 0.35**) and harvest index (r² = 0.62**) in the NILs. Reduced-height RILs containing the Rht13-linked, Xgwm577_M microsatellite marker were significantly shorter, produced greater biomass, yield and harvest index, and increased spike and grain number than lines without the marker. Approximately 74 and 7% of the total phenotypic variance in plant height was accounted for by allelic differences in Xgwm577 and Rht8 loci, respectively. The peduncle and penultimate peduncle internodes of Rht13-containing lines were proportionately shorter than Rht8c-containing sibs and lines containing the Rht-B1b dwarfing allele. The unique height-reducing phenotype, increased grain number and yield associated with Rht13 indicate considerable potential for use of this dwarfing allele for improving wheat performance.     

基于光束法空中三角测量理论的树高测量方法研究

在总结了传统树高测量方法的基础上,提出了根据光束法空中三角测量理论对树高进行测量的方法,并对影响树高测量精度的外方位元素误差进行了检验,结果表明,外方位元素在一定的误差范围内,利用光束法空中三角测量理论测量树高,精度较高。     

民国时期方志中的苜蓿考

方志是记载一个地区自然和社会各个方面历史和现状的综合性著作,苜蓿作为民国时期的重要物产资源被许多方志记录在册。本研究试图以植物考据学原理与方法,对华东、华北和西北等地诸省的56个方志中的苜蓿进行考查。结果表明,民国时期我国华东、华北和西北都有苜蓿种植,主要分布在安徽、江苏、山东、察哈尔、河北、山西、陕西、宁夏、甘肃、青海和新疆;许多方志还对苜蓿植物生态学特征进行了描述,对苜蓿种分的较为清晰,在民国时期河北种有紫花苜蓿(Medicago sativa)和黄花苜蓿(M. falcata),而山东既种有紫花苜蓿与黄花苜蓿,还种有南苜蓿(M.hispida);苜蓿常常被种于碱地进行肥田;苜蓿不仅是饲喂牛马的重要牧草资源,而且也是重要的蔬菜资源,还是很好的蜜源植物。     

西南地区农田主要种植草种及种植模式探讨

利用南方农区丰富的农田资源,大力发展草地畜牧业,引草入田,是发挥草业优势,突破农村发展瓶颈,增加农民收入的一项重要措施。探讨了西南地区农田的主要种植草种以及适宜西南地区的种植利用模式。     

从精神分析角度看《流动推销员之死》和《绿色的帷幕》中的死亡主题

死亡主题一直以来都受到作家的青睐,尤多拉·韦尔蒂也钟情于死亡主题,她通过对各种死亡的描述,来引发人们对生活的思考。文中运用弗洛伊德的精神分析,以《流动推销员之死》和《绿色的帷幕》为例来分析韦尔蒂作品中人物死亡的原因,以及死亡给人造成的影响,并探讨死亡主题背后的深刻意义。