超磁致伸缩执行器全耦合非线性动态有限元模型

超磁致伸缩执行器在高频率下工作时,能量损失不仅包括磁滞损失、Terfenol-D棒涡流损失,还包括执行器导磁回路的附加涡流损失,同时执行器上存在磁场、电场、温度场及机械应力场四场之间的耦合.本文考虑超磁致伸缩执行器Terfenol-D棒质量、预压应力、偏置磁场、磁滞和涡流损失,从电场、磁场和机械应力场三场耦合角度,建立超磁致伸缩执行器三维非线性动态有限元模型.超磁致伸缩材料磁滞特性由Berqvist和Engdahl磁滞模型来描述.应用FEMLAB建模分析并与实验结果对比,发现模型与实验结果吻合较好,验证了所建立三维动态FEM模型的正确性.     

超磁致伸缩微致动器结构优化与静态特性试验

采用超磁致伸缩材料作为微致动器的主要材料,详细阐述了超磁致伸缩微致动器的结构及性能。通过建立超磁致伸缩微致动器的2D轴对称模型,利用有限元方法对微致动器的电磁结构进行优化。试验结果表明超磁致伸缩致动器在合适的偏置磁场及预压力作用下,能达到较佳的输出电流-位移及电流-输出力响应特性。     

考虑附加涡流损失的Galfenol合金动态滞后建模与实验

在Galfenol合金能量平均静态滞后模型基础上,考虑铁磁材料在动态磁场作用下的涡流损耗和附加损耗,建立了Galfenol合金动态滞后磁化强度模型和应变模型。利用Galfenol合金磁特性测试系统进行了应变和磁场静态特性测试,测试结果与模型计算结果吻合较好。利用该测试系统测试了〈100〉取向多晶Fe83Ga17合金在动态磁场频率分别为1、10、20、40、60、100、200、300 Hz作用下的应变和磁场的关系。实验结果和模型计算结果对比表明,在磁场频率为200 Hz以下时,模型能准确反映应变与磁场的关系,频率为200 Hz以上时,计算结果与实验结果出现偏差。该模型能用于Galfenol合金的器件设计与应用。     

基于虚功原理的Galfenol悬臂梁建模与带载特性研究

研究了带载条件下Galfenol驱动器的磁机耦合建模方法,利用离散型能量均分模型(Discrete energy-averaged model)对Galfenol的磁滞非线性和饱和非线性进行建模,可以同时描述合金对于磁场和应力的依赖性。采用虚功原理将能量均分模型与驱动器的结构模型进行动力学耦合,研究了带载条件下驱动器的输出特性,并对不同Galfenol覆盖比时驱动器的驱动能力进行了研究,将计算结果与稀土超磁致伸缩材料(Terfenol-D)和压电陶瓷进行了对比。研究结果表明,驱动器的带载能力随着Galfenol悬臂梁材料覆盖比的增加而增加,材料内部承受的张力也随之增大;Galfenol合金良好的机械性能可以克服负载增加时所承受的张力的变化,解决其他智能材料易产生的失效问题。     

强偏置超磁致伸缩致动器准静态位移建模与试验

为满足电控喷油器球阀开闭的要求,设计了强偏置超磁致伸缩致动器。阐述了强偏置超磁致伸缩致动器的工作原理,基于其偏置特征分析了致动器适用的正弦波信号。根据磁阻理论、J-A模型、二次畴转模型和线性系统理论建立了强偏置致动器的准静态位移模型,计算了此模型致动器方波输入时位移幅值和电流幅值的关系,正弦波输入时位移-电流滞环曲线,幅值为3 A的方波电流输入时的致动器位移输出。设计了强偏置致动器的试验系统,通过同幅值反向的方波信号辨别输入方向,并进行了致动器的方波和正弦波测试。结果表明:模型计算得到的方波位移幅值特性以及谐波位移-电流滞环与试验结果吻合,由此验证了模型的准确性;强偏置致动器在3 A方波电流输入时位移超过30μm,响应时间约为10μs,超调量为零,具有较好的驱动性能。     

柱棒式超磁致伸缩振动能量收集装置建模与实验

针对目前超磁致伸缩式振动能量收集在理论研究上的不足,根据超磁致伸缩材料的材料特性,设计了一种柱棒式超磁致伸缩能量收集装置(GMEHD),并对其工作原理进行了阐述。结合GMEHD的结构特点,建立了装置的输入输出模型,推导了输出电压计算公式,对系统在正弦激励下的响应进行了求解;根据线圈结构,通过电路分析,对线圈匝数进行了优化。利用仿真软件COMSOL Multiphysics,建立了GMEHD有限元模型,得到其仿真结果。在上述基础上制作了GMEHD样机,搭建了实验测试系统,得到了不同频率正弦力作用下GMEHD输出电动势曲线,并与模型计算值和仿真结果进行了对比。结果表明:在1、10、50 Hz单位正弦激励下,GMEHD输出电动势幅值分别为2、15、75 m V,相位超前于输入力π/2。实验与模型计算和仿真分析结果基本吻合,验证了模型的准确性,为GMEHD优化设计提供了参考依据。     

基于稀土超磁致伸缩材料的微致动器设计

选择Terfenol-D作为微致动器主要材料，采用弹簧对GMM棒施加一定的预压力以获得较大的磁致伸缩应变，采用偏置磁场消除GMM棒的倍频现象并使之工作在线性段，对磁路进行了分析和优化设计。针对电磁线圈工作发热及涡流损耗引起的GMM棒温升，采取了强制水冷方法并专门设计了一个恒温冷却系统用以消除材料的热变形对致动精度的影响。     

超磁致伸缩材料高频磁能损耗特性测试与分析

为进一步研究超磁致伸缩材料磁能损耗特性,将棒状Terfenol-D材料沿着不同磁化方向进行切片,制成多个方形环状薄片样品,对比分析了材料磁化方向以及样品尺寸对磁能损耗的影响。在不同驱动磁场频率和磁密幅值下,对磁能损耗进行测试,分析损耗实测数值变化趋势。基于损耗分离法,结合实测数据,考虑了材料内部涡流集肤效应及动态磁滞特性等影响,对高频磁能损耗进行了数值模拟,研究各项损耗系数变化规律。结果表明,Terfenol-D材料高频磁能损耗随着频率及磁密幅值增加,整体呈数值增大、增速加快趋势。在高频下,损耗系数为随着频率和磁密幅值变化的变量。当频率大于5 k Hz、磁密幅值大于0. 05 T时,数值模拟方法所得计算值与实测值的平均误差为3%。     

喷油器用超磁致伸缩致动器设计方法和驱动波形研究

将超磁致伸缩材料的输出特点和喷油器的驱动需求相结合,设计并驱动适用于电控喷油器的超磁致伸缩致动器。针对常闭式电控喷油器仅需要单向和缩短位移的特点,结合超磁致伸缩材料在不同偏置磁场强度输出特性,提出了2种不同偏置磁场的致动器结构并分析了各自适用的电流输入方向;借助实验系统测试了2种致动器的稳态位移和响应时间,并分析了二者输出性能。针对传统直流方波驱动时致动器响应过慢的问题,借鉴电磁铁大电压快速开启的方法,设计了喷油器用超磁致伸缩致动器的驱动波形,并测试了该设计波形对强偏置致动器的驱动性能。研究结果表明,采用所设计的驱动电压,可将超磁致伸缩致动器的响应时间由4 ms降至1 ms,极大地提升了致动器的瞬态响应速度,同时,超磁致伸缩致动器可输出12~33μm的连续稳态位移,提供了更多的驱动效果。     

超磁致伸缩材料与自传感执行器

分别综述了超磁致伸缩材料和自传感执行器的发展、特性以及应用状况,剖析了自传感执行器的物理基础和关键技术,并分析探讨了一种新颖的基于Joule效应和Villari效应的自传感超磁致伸缩执行器。     

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。