堆场疏浚泥颗粒分选特性初步量化方法

为了准确评估堆场存储能力和合理选择疏浚泥处理工艺,以泥沙运动学为理论基础,将疏浚泥颗粒分为d0.005 mm、0.005 mm≤d≤0.01 mm和d0.01 mm 3个粒组,分析了各粒组相对含量的沿程变化规律,明确了堆场疏浚泥分选的主要原因是d0.01 mm粒组与0.005 mm≤d≤0.01 mm粒组的相对运动;以分选系数量化堆场疏浚泥分选的显著程度,以偏离系数量化原泥颗粒组成对堆场疏浚泥分选的影响,分析了分选系数、偏离系数分布与堆场疏浚泥土性分布的关系,提出了堆场疏浚泥分选特性的初步量化方法。研究结果表明:随着离吹填口距离的增大,分选系数沿程减小,呈幂函数分布,堆场疏浚泥分选性沿程减弱,吹填口附近分选系数最大,颗粒分选显著,粒度差异大,退水口附近分选系数趋近于零,分选不明显,颗粒分布均匀;偏离系数沿程先减小后增大,呈勺形分布,反映堆场前、后段疏浚泥土性与原泥相差较大,而堆场中段疏浚泥土性与原泥接近;分选系数、偏离系数的沿程分布与堆场疏浚泥土性分区具有良好的相关性。     

海河流域典型河流沉积物粒度特征及分布规律

为了解海河流域典型河流沉积物粒度参数空间分布规律,对海河典型河流的表层沉积物进行采集并利用Mstersize2000激光粒度仪进行粒度分析。结果表明,海河典型河流沉积物平均粒径差异显著,分选状况总体较差;山区水系与平原水系相比,沉积物平均粒径减小,呈集中分布,水动力减弱;山区自北向南变化明显,水系沉积物平均粒径减小,分布集中化,分选状况变差,由极正偏-正偏,向对称方向变化,峰度向平坦方向趋近,水动力减弱,符合粒径自然变化规律;平原区水系沉积物粒径参数表明南北变化不明显,因受较多支流、河流-湖泊-洼淀湿地等复杂系统和人为干扰强烈的影响,南北无显著变化规律。总的来说,海河流域河流受人为干扰强度较大,河流沉积物源较为复杂,栖息地物理完整性差。     

Influence of modified forms of urea and nitrogen levels on weed growth and grain yield of lowland rice

The growth of weeds and their subsequent reduction of rice yield as affected by N source neem cake coated urea (NCU), dicyandiamide coated urea (DCU), rock phosphate coated urea (RPCU), urea supergranules (USG) and prilled urea (PU) was studied on a clay loam soil at Coimbatore, India. Experiments were conducted in northeast monsoon (NEM) 1981, summer 1982, and southwest monsoon (SWM) 1982 seasons.The crop was associated with eleven weed species, and the dominant weeds wereEchinochloa crus-galli, Cyperus difformis andMarsilea quadrifolia. The weed flora varied between seasons. Deep placement of USG reduced the dry weight of weeds in NEM and summer seasons at 60, 90 and 120 Kg N ha^–1 whereas it increased the dry weight at 60 and 90 but not 120 Kg N ha^–1 in SWM season. The dry weight of weeds decreased with increased N rates for all N sources during NEM and summer seasons. In SWM season, dry weight of weeds increased with increased N rates for all N sources except USG. The grain yield of rice was drastically reduced with the deep placement of USG at 60 but not 120 Kg N ha^–1 in SWM season. The differential effect of the N sources between seasons was due to the change of the weed flora. Dominance ofE. crus-galli during SWM season had greater influence on weed dry weight and grain yield of rice.Nitrogen uptake by weeds was frequently greater in unfertilized plots, particularly in NEM and summer seasons. In SWM season, the apparent fertilizer N recovery by weeds was high for USG. It decreased from 53% for 60 Kg USG-N ha^–1 to 4% for 120 Kg USG-N ha^–1.Contribution from the part of Ph.D. work of the first author at Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India.     

ZnO压敏电阻器的性能及发展

简要回顾了ZnO压敏电阻器的历史，阐述了ZnO压敏电阻器的性能以及当前基础性研究的现状，并对其发展进行了展望。研究了Bi2O3和TiO2的掺杂对低压ZnO压敏电阻性能和微观结构的影响规律，从理论上分析了Bi2O3和TiO2添加剂的作用机理。为ZnO压敏电阻的低压化提供了理论依据和方法。     

Bi:YIG纳米薄膜的磁光特性

用射频磁控溅射和快速退火方法制备了纳米量级的Bi:YIG薄膜,研究了薄膜的磁光特性.当晶粒尺寸从150 nm降到80 nm时,透射率和Faraday角的值分别从75%和3.6°变成了80%和4.0°.结果表明:高的透射率和大Faraday角可以在晶粒尺寸为纳米量级的薄膜中共存.     

高强箍筋混凝土简支梁抗剪承载力试验研究

通过对14根500 MPa细晶粒钢筋、1根400 MPa及1根600 MPa钢筋做箍筋的混凝土简支梁在集中荷载作用下的试验,观测了不同混凝土强度、不同剪跨比、不同箍筋强度、不同配箍率、不同截面尺寸条件下试件的裂缝、挠度、承载力及破坏形态;并将实测值与有关公式的计算值进行了比较.试验结果表明,构件的斜截面承载力仍可按现行《混凝土结构设计规范》的相关公式进行计算,并有足够的安全储备.     

传统吉祥纹样在现代平面设计思维中的运用

基于“民族风”在现代平面设计中的兴起,传统纹样在平面设计中的运用已成为现代平面设计中的一种常用思维方法,如提取并运用传统纹样中的吉祥寓意、在传统纹样中加入新文化的元素或在现代平面设计中融入传统文化,由此建立起传统纹样与现代平面设计一种协调共融的联系,从而使现代平面设计与时代、社会文化共同发展．