四自由度两模式并联机构结构综合与位置分析

为设计可实现一机多用的并联机构,提出了多模式并联机构的结构类型综合方法以及操作模式分析方法。首先利用方位特征集方法,综合得到一类(640种)具有运动分岔特性的4自由度并联机构;然后从中优选出一种机构进行操作模式分析,分析结果表明:机构处于分岔奇异点时动平台瞬时自由度为5,此时采用冗余驱动的方法可引导动平台通过分岔奇异点顺利到达三平移一转动或两平移两转动模式;最后推导了该并联机构处于上述2种操作模式时的位置正、逆解分析方程,得知位置逆解方程和三平移一转动模式时的位置正解方程均可解析求解。     

苹果氮素营养研究 Ⅴ.不同形态~(15)N的吸收、运转特性

在盆栽条件下利用~(1)N示踪物——(~(15)NH_4)_2SO_4,Ca(~(15)NO_3)_2及~(15)NH_4NO_3与NH_4~(15)NO_3研究苹果植株对不同形态氮肥的吸收、运转特性及不同季节的吸~(15)N特性。结果表明在分别施用Ca(~(15)NO_3)_2、(~(15)NH_4)_2SO_4及~(15)NH_4NO_3时,植株的吸~(15)N量除根系外,以(~(15)NH_4)_2SO_4最多。但是采用同一形态~(15)N肥标记不同离子(~(15)NH_4NO_3与NH_4~(15)NO_3)的示踪物作试验时,植株吸收的~(15)N量,不论是春季还是夏季均是~(15)NO_3—N高于~(15)NH_4—N。~(15)NH_4—N分配到枝、干与根系中的量比~(15)NO_3—N少30～40%新梢与叶片中的~(15)N量随季节的不同而不同,春季二者差异小,约少10～20%,夏季差异增大,分别少70%与40%。不同季节~(15)N的运转方向不同,但不同形态~(15)N的运转规律是一致的。春季主要运向叶片,新梢、细根等新生器官,枝、干中的~(15)N量仅占叶片的5%,夏季根系与枝、干的~(15)N量显著上升,约比春季增加100～150%,而叶片中~(15)N量显著下降,尤为中、短梢上的叶与春季相比下降85%左右。说明春追氮利于叶片、新梢等新生器官的建造,夏追氮则利于根系的第二次生长及枝、干的加粗生长与芽的分化。本文为进一步揭示NH_4—N与NO_3—N作氮源时,对苹果树生长发育过程中物质代谢与植株形态的相互作用的研究打下了基础。     

近视眼患者头发中钙、镁、锌、铜含量检测分析

用原子吸收法测定了45例近视眼患者及34例正视眼者头发中Ca、Mg、Zn、Cu元素的含量。结果表明:近视眼患者头发中Zn、Cu、Ca含量显著低于正视眼(P<0.05),Mg含量与正视眼者差异不显著。揭示人体内Zn、Cu、Ca元素含量与近视眼发病存在一定关系。     

商陆钾离子吸收特性研究

采用K+浓度分别为50、200和800 μmol/L的Hoagland营养液培养商陆和水稻,观测商陆的形态和生理指标,比较商陆和水稻的K+吸收动力学参数米氏常数(Km)、最大吸收速率(Imax)和钾离子吸收最低临界浓度值(Cmin).结果表明,各处理的商陆能正常生长,光合速率、蒸腾速率、株高和根冠比等的差异不显著;在低...     

Application of multi-dimension parallel genetic algorithm to energy-saving optimum control of trains in following operation

In order to study the energy-saving optimum control strategy of a leading train and a tracing train in following operation under a moving block system,an energy-saving control model of trains is created. The aims of the model are energy consumption and trip time error. The control variables of this model are the operating handle level and the train’s position when the operating handle level is changed. Based on the model,the static and dynamic speed restraints are put forward. The static speed restraints are defined by the line conditions and the dynamic speed restraints of the tracing train caused by the leading train for the sake of safety. This problem is solved with the help of multi-dimension parallel genetic algorithm (GA) and external punishment function. During the solving process,the crossover probability and the mutation probability are adjusted dynamically according to the GA generation to improve the efficiency of the coarse grain search and the fine grain search. Ramps divided into three parts and the real number coding are adopted to shorten the length of chromosomes and improve the speed of convergence. Its correctness and effectiveness are validated at a simulation platform of train operation.     

烟草叶片分泌物及植株挥发物释放规律研究

烟草次生物质不仅对多种害虫的定向、产卵等行为具有调控作用,还能吸引天敌进行间接防御。本研究利用溶剂漂洗法提取了烟草旺长期和成熟期的叶片分泌物,利用顶空吸附法收集了烟草旺长期植株的挥发物,并利用气相色谱(GC)/质谱(MS)联用技术测定了烟草次生物质的成分及含量。结果表明,烟草叶片分泌物中共检测出36种化合物,其中旺长期有33种,成熟期有31种。烟草旺长期植株挥发物中共检测出48种挥发物组分。其中36种组分的日周期释放规律表现为随光照加强和温度升高,释放量呈现上升趋势;11:00-15:00时段的释放量显著高于其他各个时段(P0.05)。而其中9种组分表现为在夜间的释放量显著升高。     

有机肥对大麦根系生理代谢和磷吸收的影响

通过温室砂培，室内分析，研究了有机肥，无机肥和有机无机肥配施对大麦根系活力，根系酸性磷酸酶活性，根尖吸收作用和磷吸收动力学参数的影响，结果表明，有机肥与无机肥配施可增加并较长时间保持根系有较高的活力；单施有机肥在培养初期能显著提高系活力，随培养时间增长，效果明显下降，有机肥显著增加了根系酸性磷酸酶的活性和根尖的呼吸作用，有机无机肥配施，使大麦磷吸收动力学参数发生变化，Ｖｍａｘ增加，Ｋｍ减小。单施有     

基于层次分析法的哈尔滨市现代农业发展综合评价

哈尔滨市作为农业大省黑龙江的省会城市,要实现保证国家粮食安全、建设社会主义新农村等目标,必须要加快农业现代化建设。本文通过建立现代农业发展评价的指标体系和基于层次分析法确立权重的综合评价模型,利用1995-2008年数据对哈尔滨市现代农业发展现状进行评价后认为,哈尔滨市现代农业发展始终在进步,各子系统的发展也非常均衡,特别是农业经营水平和新型农民的发展水平比较高。今后应重点加强科技投入和产业结构调整,进行产业化经营。     

Absorption of dissolved and dispersed nutrients from sea-water by Panulirus japonicus phyllosoma larvae

This study examined the capacity of Japanese spiny lobster Panulirus japonicus phyllosoma larvae to absorb nutrients directly from the surrounding water. For this purpose, 48-, 81-, 124-, 160-, and 264-day-old intermoult larvae were starved for 48 h, held for 30 min to 4 h in 0.05 g L^–1 solutions or dispersions of cholesterol, peanut oil, saccharose and horseradish peroxidase in seawater, and subsequently examined by histological and ultrastructural methods. Lipids, carbohydrate, and protein were detected in either the lumen of the midgut gland tubules, the midgut gland cells, the haemolymph or in the cells of the epidermis of all larvae examined after each experimental period, with general improvement of the cell and tissue characteristics over unfed controls. The lipids were also found in the cuticle. Thus, the results provide evidence of nutrient absorption via the digestive tract, and possibly also via the integument. Structural adaptations that may be involved in the process of absorption were tentatively identified. Our observations suggest the possibility that particulate organic matter (POM) and dissolved organic matter (DOM) can be utilized by the P. japonicus phyllosoma larvae, perhaps as supplementary sources of nutrients to macroscopic diets.     

抗虫棉杂交种中棉所39高产生育特征及其吸肥特性

关于抗虫棉生育特征和抗虫性的表达,国内外学者已有较多的研究[1～6],但有关中棉所39这一杂交种则未见报道.中棉所39系中国农业科学院棉花研究所最新培育的抗虫棉杂交种,2000年6月通过国家农作物审定委员会审定[7],1999～2003年江苏盐城地区进行引种示范,其早熟丰产性、抗虫抗病性以及纤维品质表现突出,适合江苏沿海棉区发展种植[8].