混凝土拉压强度尺寸效应的细观非均质机理

为了从材料细观非均质角度揭示混凝土强度尺寸效应机理,建立了混凝土细观单元等效非均质力学模型,开展了立方体抗拉、抗压强度尺寸效应细观数值模拟研究。研究结果表明：混凝土强度尺寸效应根源于材料细观非均质性,随着模型尺寸的增加,混凝土材料细观单元弹性模量变异系数增大,材料细观非均质性增强,大尺寸模型内部存在更多的低强度单元或缺陷,导致混凝土立方体抗拉、抗压强度降低,极限应变减小,脆性增大;混凝土损伤破坏由少量集中区域,发散扩展形成多条非贯通的裂纹带;数值模拟结果与尺寸效应实验数据相吻合。     

台湾食品工业发展经验及借鉴

通过对台湾食品工业发展历程及主要经验的分析,提出加快大陆农产品加工业发展必须在建立“五个体系”方面有所突破。     

高产棉花品种泗棉3号的遗传机制研究Ⅰ.产量及其产量构成因素的遗传分析

利用泗棉3号和CARMEN构建的RIL及其F₂、B₁、B₂、P₁、P₂、F₁两套群体,同时在3个环境中,采用各自的联合世代分析方法,研究了我国长江流域棉区广泛种植的优良品种泗棉3号高产性状的遗传规律。遗传模型分析揭示泗棉3号×Carmen组合的产量及其产量构成因素的最适遗传模型符合主基因+多基因混合遗传模型,说明存在控制这些性状的主基因。所有性状在不同环境中的遗传模型不同。同时,各性状在不同环境中的主基因遗传率变化较大,而多基因遗传率在不同环境中变化相对较小,表明环境对数量性状主基因的表达影响大,对多基因的表达也存在影响。对环境间差异较大性状的研究和选育,要在多个特定的环境中进行,才能提高效率。     

Modelling Biomass Accumulation and Partitioning in Chickpea (Cicer arietinum L.)

Quantitative information regarding biomass accumulation and partitioning in chickpea (Cicer arietinum L.) is limited or inconclusive. The objective of this study was to obtain baseline values for extinction coefficient (K_S), radiation use efficiency (RUE, g MJ^?1) and biomass partitioning coefficients of chickpea crops grown under well‐watered conditions. The stability of these parameters during the crop life cycle and under different environmental and growth conditions, caused by season and sowing date and density, were also evaluated. Two field experiments, each with three sowing dates and four plant densities, were conducted during 2002–2004. Crop leaf area index, light interception and crop biomass were measured between emergence and maturity. A K_S value of 0.5 was obtained. An average RUE of 1 g MJ^?1 was obtained. Plant density had no effect on RUE, but some effects of temperature were detected. There was no effect of solar radiation or vapour pressure deficit on RUE when RUE values were corrected for the effect of temperature. RUE was constant during the whole crop cycle. A biphasic pattern was found for biomass partitioning between leaves and stems before first‐seed stage. At lower levels of total dry matter, 54 % of biomass produced was allocated to leaves, but at higher levels of total dry matter, i.e. under favourable and prolonged conditions for vegetative growth, this portion decreased to 28 %. During the period from first‐pod to first‐seed, 60 % of biomass produced went to stems, 27 % to pods and 13 % to leaves. During the period from first‐seed to maturity, 83 % of biomass was partitioned to pods. It was concluded that using fixed partitioning coefficients after first‐seed are not as effective as they are before this stage. Environmental conditions (temperature and solar radiation) and plant density did not affect partitioning of biomass.     

Nonlinear Finite Element Analysis of RC Deep Flexural Simply Supported Beams Using Disturbed Stress Field Model

A nonlinear finite element analysis of 4 RC deep flexural simply supported beams with the program VT2 is presented. Crack development and failure modes , longitudinal reinforcement strain distributions and load -deflection curves were compared as a result in order to evaluate the validity of the disturbed stress field model to analyse such deep simply supported beam.     

基于株型的水稻光合生产模拟研究进展

株型是反映水稻(Oryza sativa L.)冠层结构与群体光合态势的综合性状,理想株型塑造与籼粳亚种间杂种优势利用相结合是提高水稻单位面积产量的关键。利用计算机可视化技术和三维数字化技术可实现对不同株型水稻的单株及群体冠层三维结构的可视化模拟,克服了G函数应用复杂与繁琐的缺点。通过调控栽培管理措施可构建高光效的水稻冠层结构,提高水稻冠层的光能截获量和单位面积产量。利用辐射度和光线跟踪技术可在三维空间上实现不同株型水稻冠层内光合有效辐射分布的精确模拟,弥补了指数模型应用假设的不足。基于生理生态过程的水稻光分布与光合作用模拟研究得到了快速广泛的发展,为数字农业技术的发展提供了强有力的模型化和定量化支撑。水稻株型的差异明显改变了光在水稻冠层内的分布和利用,进而影响冠层光合作用和物质积累,因而系统分析水稻株型与冠层内光分布及冠层光合作用间的定量关系,有利于提高水稻群体光能利用率与产量。     

乳酸菌产酸动态测定及小鼠乳酸耐量初探

摘要：乳酸是乳酸菌分泌的主要有机酸之一。该试验测定嗜酸乳杆菌分泌乳酸的最大浓度,再利用浓度为12.89ul/ml、30ul/ml、60ul/ml、90ul/ml的乳酸灌服小鼠。结果发现灌服90ul/ml组小鼠2-3h出现死亡。24h后,通过体温、临床症状及剖检观察、生化检测以及病理组织切片得到结果,灌服浓度60ul/ml乳酸血清变化微小,小鼠的小肠没有损伤,从而建立小鼠肠道中乳酸模型。     

陆地棉黄萎病抗性的遗传分析

本研究采用MINQUE(1)的统计方法,用ADM模型、ADAA模型、AD模型［1］,估算陆地棉8个杂交亲本和F1、F2代各28个组合的黄萎病抗性遗传效应。结果表明,陆地棉黄萎病抗性的遗传不存在母体效应和上位性效应,因而采用AD模型分析,加性效应占52.43,显性效应为9.01,均达极显著水平;广义遗传率为83.04%,狭义遗传率为70.87%。     

中国粮食生产核心区现代农业发展的研究进展

粮食生产核心区是中国现代农业发展重点区域,通过归纳国内外有关粮食生产区域、现代农业发展研究的相关文献,总结出粮食生产核心区现代农业发展过程中表现出的特征和存在的问题,发现粮食生产核心区现代农业发展还存在着许多研究角度,在分析了粮食生产核心区和现代农业发展内涵、模式和评价的基础上,认为粮食生产核心区现代农业采用何种发展模式、如何进行评价等问题值得进一步研究,为实现不同区域粮食生产核心区现代农业均衡发展提供理论指导。     

玉米渍水模拟模型研究及验证

作物模拟模型是研究作物生态生理过程的新工具,尽管还不完善,但是具有广泛的应用前景.本研究在试验的基础上,根据MACROS模型和文献资料组建了玉米水分模拟模型,加强了模型在渍水方面的功能.经验证,模型能较好地反应我国南方地区玉米的生长发育过程和土壤水分运动,可以用于渍害易发地区的玉米生产研究.并以杭州市为例,应用模型