基于流固耦合的离心泵蜗壳振动特性优化

针对具有超厚叶片的离心泵叶轮与蜗壳匹配问题,采用双向耦合方法对3种蜗壳结构产生的振动位移和振动速度进行了数值模拟。计算结果表明,由于叶轮与隔舌之间的流场动静干涉作用,蜗壳受到交替的激振力作用,在不同时刻振动位移和振动速度分布呈周期性变化;蜗壳基圆直径与叶轮直径的比值D3/D2对蜗壳振动有明显的影响,当D3/D2≤1.013时,超厚叶片出口压力诱导蜗壳振动强烈;当D3/D2逐渐增大时,蜗壳振动明显减弱。在设计工况下,方案A（D3/D2=1.013）振动位移最大值为4.288×10-6m,振动速度最大值为8.547×10-4m/s;方案C（D3/D2=1.19）振动位移最大值为2.923×10-6m,振动速度最大值为5.253×10-4m/s;优选方案B（D3/D2=1.13）的振动最小,其位移和速度最大值分别为2.56×10-6m和4.823×10-4m/s,仅约为方案A的60%。该结果也验证了径向力的作用规律与蜗壳振动特性的直接关联性。     

淀粉颗粒外壳分离方法与其性质表征研究

以薯类（红薯、木薯）、豆类（豌豆、绿豆）和谷类（玉米、小麦）淀粉为研究对象,在淀粉糊化温度测定的基础上,通过降低温度和pH值,研究了不同淀粉颗粒外壳的分离方法。结果表明,将最高处理温度与淀粉糊化温度差值设置为-16~15℃,在乙酸溶液（pH值1.5、浓度7.1mol/L）中对淀粉颗粒进行处理,糊化程度为19%~56%时,可以得到不同淀粉的颗粒外壳,厚度为50~470nm。除绿豆淀粉外,其他淀粉颗粒外壳的分子量（4.3×107~5.2×107g/mol）均大于原淀粉的分子量（3.8×107~4.7×107g/mol）。不同淀粉外壳的厚度与其粒径、直链淀粉质量分数以及相对结晶度没有明显的相关性。玉米淀粉的颗粒外壳结构相对完整,可作为生物大分子缓释自组装包膜材料。     

风干板栗太阳能-热泵联合干燥特性与数学模型研究

为研究风干板栗太阳能-热泵联合干燥特性,以新鲜板栗为原料,探讨干燥温度、干燥风速、装载量对风干板栗干燥速率和干基含水率的影响,在不同干燥温度、干燥风速、装载量条件下分别对新鲜板栗进行干燥,并比较了6种数学模型在风干板栗太阳能-热泵联合干燥的适用性,同时以Fick第二扩散定律为依据,确定风干板栗不同干燥条件下的有效水分扩散系数。结果表明：风干板栗干燥过程由调整阶段和降速干燥阶段控制,主要表现为降速干燥;干燥温度越高、干燥风速越高以及装载量越小,干燥至目标含水率所用时间越短,干燥速率越大;干燥过程中,有效水分扩散系数随干燥温度及干燥风速的升高、装载量的降低呈现增大的趋势,干燥温度从15℃升高到35℃,其有效水分扩散系数由3.00124×10-10m2/s增大到8.42115×10-10m2/s,干燥风速由1.0m/s升高到5.0m/s,其有效水分扩散系数由4.54717×10-10m2/s增大到9.13767×10-10m2/s;装载量从0.6kg升高至5.4kg,其有效水分扩散系数由1.14753×10-9m2/s降至3.20443×10-10m2/s;通过比较决定系数（R2）、残差平方和及卡方（χ2）得出,Page模型为描述风干板栗太阳能-热泵联合干燥的最优模型,验证发现试验值与模型预测值拟合度较高,Pearson相关系数为0.998,二者显著相关（P＜0.05）,说明Page模型能够较好地反映风干板栗干燥过程中水分变化规律。     

激素在瓜菜上的应用

在瓜菜生产中,适时正确地使用植物激素,可起到早熟增产的作用。 (一)防止徒长,培养壮苗。对有徒长趋势的瓜菜幼苗,用浓度为50×10~(-6)～100×10~(-6)的矮壮素溶液,或200×10~(-60～4000×10~(-6)的B_9溶液,或300×10~(-6)的多效唑溶液,在苗期全株喷施,可     

小麦粉特性与面条品质关系及对挂面行业展望

本文综述了小麦粉中淀粉和蛋白质特性与面条品质关系的国内外相关研究。蛋白质含量和质量都会影响面条品质,适宜的蛋白质含量和谷蛋白/醇溶蛋白比率能够赋予面条较好的加工特性和口感;淀粉能够填充面筋网络,使口感更加饱满,适宜的淀粉总量和直链淀粉/支链淀粉比率,较高的淀粉糊化峰值黏度也是影响面条品质的重要决定因素之一。本文也探讨了面条行业对研发新的要求和挑战,并对挂面行业发展趋势进行了预测和展望。     

风筛式谷物清选模拟研究及参数讨论

为研究风筛式谷物清选装置工作原理及寻找最佳工作参数,采用EDEM软件与Fluent软件耦合的方法,对稻米与茎秆在风筛装置中的运动行为进行仿真,并通过统计稻米含杂率和损失率来衡量不同参数下风筛装置工作性能的好坏。结果表明:所设计的风筛装置可以完成稻米与茎秆的分离。通过对风速8、10、12 m/s的讨论,可以得出增大风速能减小含杂率,但会增大损失率;通过对筛面倾角0°、2°、4°的讨论,可以得出增大筛面倾角会导致含杂率和损失率均增大;通过对筛孔形状的讨论,可以得出选用方孔筛时清选效果更佳。综合考虑,风速为10m/s、方孔筛筛面倾角为0°时,得到稻米含杂率为0.33%,损失率为0.38%,为最佳工作参数。研究可为谷物清选装置参数优化提供一定参考。     

无线电波

1　波长与频率因为无线电波在真空中的波长 (λ)、频率 (f )和光速 (c)有如下关系 :λ· f=c=3× 10 3 m/ s所以 λ=cf=3× 10 8f其中　波长 λ的单位是 m;频率 f 的单位是Hz;光速 c的单位是 m/ s。无线电波的频率从 3× 10 3 Hz至 3× 10 11Hz,对应的波长为 10 km至 0 .1mm。2　长波 (LW)长波 (包括超长波 )是指频率为 30 0 k Hz以下的无线电波。由于大气层中的电离层对长波有强烈的吸收作用 ,长波主要靠沿着地球表面的地波传播 ,其传播损耗小 ,绕射能力强。频率低于 30 k Hz的超长波 ,能绕地球作环球传播。长波传播时 ,具有传播稳定 ,…     

油茶籽热风干燥动力学研究

为研究油茶籽热风干燥特性,探讨热风温度、初始干基含水率对油茶籽干燥速率的影响,在不同初始干基含水率、不同热风温度条件下分别对油茶籽进行干燥,并比较了9种数学模型在油茶籽热风干燥中的适用性。结果表明,油茶籽热风干燥过程并没有出现恒速干燥段,干燥主要发生在降速干燥阶段。物料初始干基含水率、温度是影响干燥的主要因素,初始干基含水率越低、干燥温度越高,干燥到目标含水率所用时间越短。干燥过程中,有效水分扩散系数随温度升高而增大,热风温度从50℃升高到80℃,其有效水分扩散系数由1.3132×10-9m2/s增大到3.9223×10-9m2/s,油茶籽的干燥活化能为33.6193kJ/mol;通过比较决定系数R2、均方根误差eRMSE以及卡方检验值χ2得出,Lewis模型为描述油茶籽热风薄层干燥的最优模型,预测值与试验值的均方误差为1.36%,最大相对误差小于4%,表明模型预测的干燥曲线和试验干燥曲线一致性较好。     

交联酯化作用对木薯淀粉流变特性的影响研究

利用数显黏度计研究了木薯淀粉(NS)、交联淀粉(CS)、辛烯基琥珀酸淀粉酯(OSAS)和交联辛烯基琥珀酸淀粉酯(COSAS)糊的流变特性,考察了淀粉浓度和NaCl对这4种淀粉糊流变性能的影响。结果表明:随NS、CS和COSAS浓度增大,这3种淀粉糊均具有增强的触变性,但OSAS基本上没有触变性;NS、CS、OSAS和COSAS糊均呈非牛顿流体特征,不同浓度下这4种淀粉糊表观黏度随剪切速率的变化可用Ostwald-Dewaele方程描述。随着外加NaCl浓度增加,NS糊黏度迅速降低,表现出聚电解质溶液的通性,CS糊黏度总体上呈上升趋势,表现为具有一定耐盐能力;NaCl浓度在0.5%~3.0%范围内,OSAS糊黏度先降后升,COSAS糊呈上升趋势,具有明显的盐增稠现象,说明交联酯化作用改善了木薯淀粉的黏盐特性。     

人类活动条件下民勤绿洲地下水动态模拟研究

以石羊河流域下游民勤绿洲区域地下水为研究对象,运用地下水位动态ANN-FEFLOW模型模拟了不同情景下(现状条件、灌溉面积减少、节水灌溉实施、地表来水增加及综合工程措施等)地下水动态变化。结果表明,民勤绿洲现状条件下地下水将持续下降;灌溉面积减少可以明显缓解地下水位下降速度,节水灌溉对地下水的影响并不明显。地表来水为2.51×108 m3/a时,湖区地下水将出现正均衡;综合工程措施情景下,湖区和泉坝区地表来水分别为1.45×108 m3/a和2.51×108 m3/a时,地下水位回升。     

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。