玉米种子力学特性的有限元分析

在建立玉米种子几何模型与有限元计算模型的基础上，通过有限元分析方法对玉米种子在压载作用下不同作用部位的应力分布进行了分析，获得了玉米种子在不同施力部位压载作用下的微观力学性质，从而为深入研究玉米种子的力学性质、损伤机理、优化脱粒机械提供理论依据。经模型计算和试验结果相比较，得出种子的宏观破裂位置和破裂方向与模拟结果相吻合，种子的宏观破裂是由内部裂纹引起。     

玉米种子脱粒过程高速摄影观察分析

为优化差速式玉米种子脱粒机脱粒系统的有关参数,进而降低玉米种子在脱粒过程中的损伤,采用高速摄影方法对单个玉米果穗喂入与脱粒过程进行了观察分析.分析结果表明:果穗在开始喂入阶段,籽粒破碎大;在脱粒起始阶段,果穗撞击强烈,越到后段,撞击越弱;果穗在正常脱粒情况下,脱下籽粒多,籽粒运动轨迹可近似为沿直辊与果穗接触点的切线方向;而果穗非正常脱粒情况下,脱下籽粒少,籽粒运动规律呈杂乱状态,没有一定飞行方向;螺旋辊的转速偏大造成果穗的非正常脱粒加大,果穗的非正常脱粒会影响果穗的脱粒质量和脱粒效率.     

含水率对种子玉米脱粒性能的影响机理

为深入探明含水率对玉米种子脱粒的影响机理,以铁丹Ⅰ代一号等3个品种种子玉米为研究对象,进行了不同含水率下玉米种子籽粒破损强度、果柄强度和脱粒作用力等试验.试验结果表明,含水率对玉米种子脱粒的影响主要体现在籽粒破损强度和脱粒作用力两个方面:随着含水率的下降,玉米种子籽粒破损强度显著提高,因而脱粒时不容易破碎;脱粒作用力随...     

玉米种子内部机械裂纹检测与机理研究

为深入研究因脱粒造成的玉米种子内部机械裂纹机理及其对发芽与出苗的影响,构建玉米种子内部机械损伤计算机识别系统,改进玉米种子脱粒原理和脱粒部件参数,研究了盛单216等3个品种玉米种子的籽粒外观特征,并借助体视显微技术分析了内部机械裂纹损伤特征、分布状况与形成规律等,探讨了玉米种子内部机械裂纹的成因。研究结果表明：玉米种子籽粒外形和内部机械裂纹状况差异显著;3种玉米种子普遍存在内部机械裂纹,长裂纹损伤率平均为39.8%;果穗喂入时籽粒冠部受到脱粒部件的冲击是裂纹形成的主要原因,在玉米籽粒冠部形成冲击区并产生裂纹,裂纹向胚部扩展;内部裂纹信息应从籽粒冠部和背面提取。     

玉米种子的机械损伤对其发芽率的影响

玉米种子质量是决定玉米产量的重要因素.目前,由于我国没有生产专用种子玉米脱粒机,玉米种子的脱粒只能采用打击原理设计的普通脱粒机,对玉米籽粒伤害较大,从而影响了种子在田间的出苗率以及植株整个生长发育过程.为此,针对不同部位有机械损伤的玉米种子对其发芽率的影响进行了分析,进而为新型低损伤玉米种子脱粒机的研制提供作用部位与作用方向的参考.     

种子玉米机械脱粒最佳施力方式试验

为深入研究种子玉米脱粒特性和脱粒损伤机理,改进玉米脱粒机,降低脱粒损伤,提高脱粒效率,以隆迪401玉米种子为对象,应用LDS微机控制电子拉压试验机等进行了脱粒试验,研究了玉米种子品种、含水率、作用部位及不同约束性质下的种子玉米脱粒力学特性.结果表明:在同样试验条件下,玉米穗大端籽粒脱粒较容易,小端次之,中部较难;纵向弯曲力小于侧向弯曲力,侧向弯曲力小于压力;种子玉米脱粒时的最佳施力方式为纵向弯曲力.     

玉米种子差速脱粒的单因素分析

为优化差速式玉米种子脱粒机脱粒系统的有关参数,进而降低玉米种子在脱粒过程中的损伤,以籽粒破碎率与未脱净率为主要性能指标,选取直辊转速、喂入量和籽粒含水率为试验因素,对差速式玉米种子脱粒机进行了单因素试验.分析结果表明:不同玉米品种的变化总趋势相似,都随直辊转速的增加而籽粒破碎率增加;直辊转速的增加在一定范围内对未脱净率有利;喂入量的增加会使脱粒效果变差,未脱净率增加; 籽粒含水率对破碎率的影响呈一元二次函数关系,籽粒含水率太大或太小对籽粒破碎率的影响都很大;随籽粒含水率的增加.籽粒未脱净率增加.研究成果为玉米种子差速脱粒的多因素综合试验提供了考察依据.     

玉米种子脱粒装置的结构技术剖析

玉米种子脱粒装置的结构技术一直是农机工作者关心的问题。玉米种子脱粒比普通玉米脱粒要求破碎率更严格,籽粒内部不能有暗伤,否则影响种子的发芽率,而且要求生产率和功率适中,并可脱多种水分的玉米种子。为此,对国内外玉米种子脱粒装置的主要类型进行了结构技术剖析,进而为新型低损伤玉米种子脱粒机的研制提供了参考。     

玉米种子抗压特性及裂纹生成规律

为降低玉米种子脱粒过程中的机械损伤,掌握玉米种子抗压特性及其裂纹生成规律,在LDS微机控制电子拉压试验机上,对不同品种的玉米种子进行了静态压缩试验.试验结果表明:最大破裂力随含水率的增加而降低;同一品种在相同含水率下,平放时最大破裂力最大,立放时最小,侧放时居中;同一放置方式时,不同品种玉米种子承载压力的能力不同;不同放置方式时,不同受压面生成裂纹的形状、部位和规律不同.     

玉米种子机械化脱粒及精选技术特征与发展趋势

种子的品质对于玉米栽培质量和经济效益影响很大,随着种子加工机械化逐步实现,在种子加工过程中应用了大量机械设备,能够完成玉米种子脱粒、精选、包衣、包装等处理。其中脱粒与精选作为种子机械化加工的重要工序,保持其技术先进性十分重要。介绍了近年来我国针对玉米种子脱粒和精选的部分研究成果,说明了玉米种子机械化脱粒的技术特征,总结了现阶段玉米种子加工过程的脱粒与精选关键技术,并对相关技术的发展进行了展望。     

Overland water and salt flows in a set of rice paddies

Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m⁻¹) and an infiltration rate of 5.8 mm day⁻¹. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day⁻¹), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day⁻¹ was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration.     

瓦房店市水果生产标准化发展研究

瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。     

金谷子耐旱TG118引种试种及推广应用

对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。     

对《种子法》存在问题的探讨

《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。     

Review of the Egyptian experience in implementing land drainage projects

About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered.     

和谐社会理论建设的几点哲学思考

在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。     

A European irrigation map for spatially distributed agricultural modelling

We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications.     

粉质仪和拉伸仪在面粉生产中的应用

在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。     

农村信息化服务的现状及建设措施

分析当前我国农村信息化服务的现状,提出加强农村信息化服务的新举措。     

车辆ABS控制算法的研究及探讨

对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。