模态振型相关性分析

对某轿车车身进行了有限元与试验模态分析,计算出各自的振动频率和振型,并基于内积相关度理论,对两者振型相关度进行了计算,结果表明内积相关度不仅能够进行相关性研究,而且能够发现有限元与试验过程中模态的丢失;验证了计算模型的正确,并为进一步的车身设计提供了依据。     

车身模态分析与振型相关性研究

对某车辆车身进行了计算模态分析，得到其计算振频以及相应的振型，并通过试验得到试验模态频率及振型，对计算模态和试验模态进行振型相关性分析，将有限元的动态分析与试验数据有机地结合起来，验证了车身有限元模型，为车身结构设计提供了依据。     

基于声学传递向量的某型客车车内噪声分析

以某型客车为研究对象,建立客车车身有限元模型,并在此模型基础上建立了该客车室内声腔有限元模型。基于模态分析理论,获得了该客车白车身前十阶模态频率及振型,通过与模态试验结果进行对比,验证了模型的正确性。运用Radioss进行车身的模态频率响应分析,以此分析结果为边界条件,基于声学传递向量计算车内声场及板块贡献量,为车身的优化设计提供依据。     

运动轿车白车身试验模态分析

首先设计了白车身试验悬挂系统,然后运用试验模态分析方法,测得了结构的频响函数,通过对频响函数的分析,确定了车身的模态特征。试验结果表明,测试系统组建满足精度要求,参数辨识结果有效可靠;文章还对出现共振和局部振动的结构进行了分析,为设计人员改进结构设计提供了依据。     

混合动力车GR417Z车身建模及其模态分析

简述了有限元模态分析基本理论,采用Catia软件建立了混合动力车GR417Z各个零件的三维模型,并且对其进行了装配,将装配好的车身三维模型导入到Workbench软件,然后运用Workbench软件对三维模型进行前处理生成了有限元模型,并对该有限元模型进行了自由模态求解,得到了车身的前20阶模态频率和模态特性。对模态分析结果与汽车内外部的激励源频率特性进行了较为详细的分析,得出车身刚度不足区域,为下一步继续改进设计该车的动态特性、进行噪声场分析提供了参考依据。     

基于ANSYS的客车车身骨架模态分析

详细讨论了客车车身骨架采用有限元方法进行模态分析过程中的一些关键问题,并对某客车进行了模态分析。获得车身骨架的模态参数之后,探讨了该车身骨架的动态性能,为其设计的动态性能改善提供参考依据。     

承载式车身模态性能优化

以某承载式车身为研究对象,优化车身模态分布。使用有限元方法对车身的模态性能进行分析,得到需要优化的模态频率及振型。在灵敏度分析的基础上,结合模态匹配的相关原则,并采用基于试验设计的多目标优化流程,对车身第一阶扭转模态频率和第一阶弯曲模态频率进行优化。最后,对优化后的车身进行模态仿真,验证了优化结果的正确性,优化后的车身模态分布更加合理。     

基于灵敏度分析的微客尾门模态优化

针对客车尾门的一阶模态频率和车身的固有频率相近,容易产生共振的问题,对某微型客车尾门进行模态优化和结构优化。首先采用CATIA建立几何模型,再导入HyperMesh,经过优化后得到尾门的有限元模型。通过NX Nastran求解器进行自由模态分析,基于Hyperview获得尾门的模态振型和固有频率。分析结果显示尾门的一阶模态频率和白车身的固有频率邻近,容易产生共振和车身的损坏,因此需要对尾门进行模态优化。选用灵敏度分析方法来快速获得影响尾门模态的关键部件,提出优化目标和方案。最终使尾门的各阶频率避开白车身频率,提升了尾门的模态性能。     

两种车身模态试验与分析

通过车身模态试验,得到了带与不带风窗两种车身的固有频率和振型,建立了两种车身有限元模型,并进行了模型修正。研究表明,应用综合分析技术能够较好地解决车身结构变化所带来的动态特性变化问题。提出了车身综合分析与试验及评价策略,为车身动力学设计及分析建立了基础。     

客车车身结构的模态分析

汽车结构模态参数反映汽车车身固有振动特性,而构成汽车车身大部分的板件的局部模态对汽车的车内噪声有重要影响。本文研究了客车骨架模型和车身结构模型的建模技巧和建模过程、建模单元特性、及有限元模型的创建技巧,计算了客车车身结构有限元模型的模态,最后对所计算的模态数据进行了分析,并对车身结构性能做出评价。     

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。