高压电场中蔗糖溶液的蒸发特性

[目的]为进一步研究高压电场中蔗糖溶液的蒸发特性和机理.[方法]在高压电场中,以不同浓度蔗糖溶液为研究对象,进行电压、电极间距、电场类型等参数对蒸发速度的试验研究,同时进行在针-板电极中间放绝缘板阻挡和不放绝缘板的对比试验研究.[结果]高压电场可以提高蔗糖溶液的蒸发速度;在低浓度下,蔗糖浓度对蔗糖溶液蒸发速度的影响极小;蒸发速度与电压极距有关,极距越小,蒸发速度越大;交流电压下蔗糖溶液的蒸发速度明显高于直流电压下;在无绝缘板阻挡的条件下蒸发速度明显高于阻挡条件下的.[结论]这为探索高压电场干燥特性和机理提供新的实验理论上的线索和依据.     

Modelling long-term transpiration measurments from grassland in southern England

Observations of latent heat, sensible heat and momentum flux from eddy correlation equipment are presented, along with approximately weekly measurements of soil moisture content. The measurements were made over a pasture field in the south of England for 3 years, covering two dry years, 1995 and 1996 and a more normal year, 1997. The data show that, overall, approximately 80% of the measured net radiation was used for evaporation. During July and August of the two dry years, soil moisture deficits of over 150 mm developed within the top 1400 mm, and at these deficits the evaporation was reduced. During the summer months, overall between 71 and 76% of the net radiation was used for evaporation. During the winter months, the latent heat flux exceeded the net incoming radiation. An energy closure better than 10% suggests that the measurements were well founded. The surrounding trees may, however, have influenced the momentum exchange; the estimated roughness length of 38 mm is considerably more than the commonly accepted 10% of vegetation height.This extensive dataset provides an excellent test for the current UK Meteorological Office Surface Energy Scheme (MOSES) when applied to this site, the results of which are presented here. In its unoptimised form, the model can explain 72% of the variance of the hourly evaporative flux data, and with excellent agreement with the soil moisture measurements. Optimisation can improve the model fit, but only up to a maximum of 76%. The largest remaining errors occur during mid-summer when high temperatures, vapour pressure deficits and soil moisture deficits occur.     

基于MODIS的水文遥感信息提取——以东苕溪流域为例

分布式水文模型的发展对水文信息的范围和精度提出了更高的要求,用遥感信息获取水文要素成为重要手段.探讨使用ENVI软件对MODIS数据处理和计算的方法,并分析和讨论了此方法的优缺点.以东苕溪流域为应用实例,提取了下垫面蒸发量信息和计算土壤含水量,并用4个水文站的实测数据对遥感数据进行了验证.最后,结合土地利用情况分析两者在时间和空间上的变化.结果表明,东苕溪流域蒸散发量与实测数据符合度比较好,可以用来估算流域蒸散发量.东苕溪流域平均月蒸发量和地域分布年内变化大,土壤含水量在地域上呈东西向阶梯分布,随时间变化不大.     

干旱区稳定蒸发条件下土壤盐溶质迁移的动态预测

<正> 1.导言土壤盐碱化是世界干旱区共同性的问题,也是人类遇到的最古老的环境问题。近30年来,迫于人口压力和食物需求,许多容易开发的土地均已得到利用,人们正在将注意力转向干旱区。由于干旱区自身的特征,土地开发和盐渍化防治,在强烈蒸发条件下土壤盐溶质浓度目标C(Z,t)及迁移预测已成为近代土壤—水环境研究热点之一,成为中国北     

若尔盖地区不同下垫面对蒸发量影响的研究

地处高原平台的若尔盖地区下垫面的变化影响地气界面的热质传递。多种数据表明,若尔盖高原的水汽输送情况直接影响中国北部地区的干旱情况。本文采用多种蒸发公式计算若尔盖不同下垫面蒸发量的差异,分析了若尔盖高原盆地中下垫面的状况对蒸发量的影响,讨论了不同下垫面对若尔盖地区水汽输送、土壤沙化退化影响机制。     

Slowly odor-evaporating polyethylene film containing surface-modified celite powder

Celite powder surface-modified with cationic surfactant was used to make polyethylene (PE) specialty film that can be contrasted with ordinary film in having high odor storing capacity and long odor lasting period. Mechanical properties of the films were sacrificed as more celite particles were included, whether celite surface was modified or not. The film with CTAB-modified celite showed the best odor storing and lasting properties for five different flavors ofodor, three artificial and two natural ones, among the kinds of films developed. Comparisons among the different films are made, together with brief discussion about the reason for differences in odor lasting period and possible application to packaging industry.     

膨润土对土壤含水量及蒸发特性和燕麦产量的影响

为给长城沿线土壤改良和农业节水增产提供理论依据,于2011-2013年在清水河县采用大田与室内试验相结合的方法,通过不同膨润土施用量处理(CK:0kg·hm-2;1D:6 000kg·hm-2;2D:12 000kg·hm-2;3D:18 000kg·hm-2;4D:24 000kg·hm-2;5D:30 000kg·hm-2),研究其对农田土壤水分含量、蒸发特性及燕麦产量的影响。结果表明,膨润土可显著增加燕麦播前及苗期土壤含水量,施用的第2年3D处理含水量最高,第3年5D处理最佳。土壤水分蒸发量与播前含水量关系密切,播前0~10cm土壤含水量在5.00%左右时,0~10、20~40、60~80cm土层中5D、4D、3D处理蒸发特性为"先吸水、后失水",10~20、40~60、80~100cm土层为"持续失水";播前0~10cm土壤含水量在8.00%以上时,播前及苗期水分蒸发量随时间推移逐渐降低。各处理在不同土层中,水分蒸发量均持续降低,并于20~25d达到稳定。施用膨润土可显著提高燕麦产量,施用后第2年3D处理较CK增产10.70%,第3年5D处理较CK增产11.53%。     

多针电极高压静电场下蒸馏水蒸发的研究

在前期研究的基础上,通过与单针电极高压静电场的比较,探讨了两针、三针电极与平板接地电极形成的高压静电场对蒸馏水蒸发的影响。     

单针电极高压静电场下蒸馏水蒸发作用范围的研究

探讨了单针电极与平板接地电极形成的高压静电场对蒸馏水蒸发的作用范围。结果表明,蒸馏水的蒸发速度与以针尖正下方水面为圆心的半径呈二次曲线关系。     

东北农田黑土蒸发量与土壤水分及气象因子的关系

为准确地掌握东北农田黑土水分蒸发量的变化规律,2007年8月开始在吉林省吉林市龙潭区江密峰苗圃进行蒸发量测量试验,采用称质量法测量不同设置水分条件下农田黑土的昼夜蒸发量,并根据蒸发量与测量的气象因子建立了相应的回归方程.结果表明:土壤蒸发量与土壤含水量呈极显著正相关;土壤蒸发量在不同土壤含水量之间差异显著.通常情况下,土壤白天的蒸发量大约是夜间的12倍,全天蒸发量集中在11:00-15:00,占全天蒸发量的60%～70%.土壤蒸发量与光合有效辐射和风速呈显著的正相关,与其它气象因子相关关系不显著.