气流辅助式喷雾工况参数对雾滴飘移特性的影响

采用三维流场的多相流计算流体力学模型,研究雾滴在自然风影响、辅助气流胁迫和自身重力作用下在连续相和雾滴粒子群离散相耦合的交互作用,并分析了不同工况参数对雾滴漂移特性的影响.结果表明:增大风筒气流出口速度,可以胁迫雾滴向靶标运动,减少雾滴飘失率.当喷嘴流量较小时,雾滴飘失率变小的趋势最为明显.然而喷嘴流量过大时,雾滴整体抗飘失能力显著下降.辅助气流的喷雾角对减少雾滴飘失相对于自然风速、辅助气流风速没有显著的影响.     

自由活塞内燃发电机能量转换与传递过程研究

根据能量守恒定律,建立自由活塞内燃发电机运行过程周期能量模型.通过计算获得一个周期内的能量转换规律,并分析相邻周期的能量传递过程,得到不同压缩比下的能量变化情况及其对性能的影响.分析结果表明,自由活塞内燃发电机能量转换有效效率的理论值可达40％.燃烧、扫气及散热等为能量损失的主要部分.连续运行过程中,一侧气缸作功行程后期的部分能量作为压缩能传递给另一侧,直接影响下一周期燃烧.压缩比变化对各能量及有效效率有不同影响,保持压缩能稳定对运行控制至关重要.     

风水光互补发电系统多目标优化设计

为了贯彻国家大力发展小水电的政策,满足偏远地区的农村用电需求,可以利用当地的新能源建立风水光互补发电系统,就地发电.为此,在充分考虑互补系统环境价值的基础上,采用了多目标优化策略的模式和模糊线形加权的算法,以确定户用风水光发电系统优化设计的方法,建立互补系统设计的数学模型,并对某村的具体情况进行计算,得出符合实际情况的最优配置.     

糙米二次加湿调质工艺优化与试验

为解决干燥后储藏的低含水率稻谷碾米加工时存在整精米率低且能耗高以及单次加湿又无法满足加湿目标的问题,以糙米(含水率12%)为原料,研究二次加湿调质工艺中单次加湿量、润糙温度及润糙间隔时间对整精米率的影响规律.在单因素试验的基础上,采用二次旋转组合设计方法,用SAS软件处理试验数据,并进行验证试验.结果表明,在单次加湿量为1.56%、润糙温度为29.6℃、润糙间隔时间为64.6 min的条件下,整精米率提高15.42%,碾米能耗降低26.86%.     

基因工程及花色素合成途径在花色改良中的研究进展

随着经济的发展,转基因技术在花卉中的应用也越来越关键,通过基因工程使花色发生变化已经在商业中运用。生物碱类、胡萝卜素和类黄酮化合物等一类活性物质共同作用使植物的花色更具观赏性,目前,在花色改良上应用较多的是类黄酮色素,其研究机理也较为清楚。本文主要介绍了F3＇5＇H（类黄酮-3＇,5＇-羟基化酶）和F3＇H（类黄酮-3＇-羟基化酶）的生物合成途径,阐述了基因工程技术对花色修改的作用,综述了目前花卉转基因工程的研究现状和花色素合成的主要途径及影响因素,同时简单介绍了目前改良花色的几种策略和就其存在的问题、发展前景做出了讨论。     

Evolution of soil chemical properties in the past 50 years in the Tai Lake Region, China

The Tai Lake Region (TLR) is traditionally an ecologically sustainable agricultural area due to the intensive application of traditional organic fertilizer. However in the past 50 years, agricultural management practices such as fertilizer usage and cropping systems changed this situation. In order to investigate how these changes affected soil chemical properties and ultimately the sustainability of agriculture production, a case study was conducted in Taicang County in the TLR. It was found that soil organic carbon (SOC) content significantly decreased from 22.8 g kg⁻¹ in 1959 to 12.9 g kg⁻¹ in 1981 while soil total nitrogen (TN) increased significantly from 1.2 g kg⁻¹ in 1959 to 1.6 g kg⁻¹ in 1981 due to the application of mineral fertilizer especially N fertilizer nearly entirely replacing of traditional organic fertilizer, and then both slightly increased to 14.0 g kg⁻¹ and 1.7 g kg⁻¹, respectively in 2004. Soil total phosphorus (TP), total potassium (TK), and available K (AK) contents showed little changes from 1981 to 2004 but soil available P (AP) content increased significantly from 7 mg kg⁻¹ in 1981 to 26 mg kg⁻¹ in 2004. The changes of soil properties from 1959 to 1981 were attributed to the changes of fertilizer usage and the changes of soil properties from 1981 to 2004 were attributed to the changes of cropping systems and fertilizer application, particularly vegetable production which resulted in the significant changes of fertilizer usage.     

热压凝胶法制备营养质构米及其营养性质研究

为弥补食用精白米导致营养不良的状况,以大米加工过程中产生的碎米作为原料和载体,产生的米糠作为天然营养强化剂,采取热压凝胶法制备营养质构米。在预试验的基础上,采用响应面法考察热压凝胶过程条件包括喂料含水率,螺杆转速,5个加热区机筒温度对营养质构米的质构和营养特性的影响,得出制备最佳工艺条件:当喂料转速为30r/min,米糠添加量为4%,物料含水率为30%,螺杆转速为17.7r/min,5个区机筒温度分别为50,65,85,100,95～97℃。在此条件下制备的营养质构米含有质量分数总膳食纤维11.44%,蛋白质11.62%,脂肪6.49%,而维生素为B12.07μg/g,维生素B20.31μg/g和γ-谷维素12.04mg/100g。相比于天然精白米,质构特性相近,但维生素B1,维生素B2,γ-谷维素分别增加了1.17,0.06,5.83μg/g,为营养质构米工业化生产提供参考。     

气候变化情景下未来赣北第四纪红壤坡面土壤侵蚀的预估

为评估未来气候条件下的土壤侵蚀变化的响应,该研究利用IPCC AR4中17个全球大气环流模式在SRES B1(低排放)、A1B(中排放)和A2(高排放)这3种典型排放情景下的未来降水预测,结合坡面土壤侵蚀WEPP模型,在对模型验证效果良好的基础上,参照集合预报方法,对未来至21世纪末赣北地区典型第四纪红壤坡面的土壤侵蚀进行预估。研究结果表明,虽不同大气环流模式的预估表现各异,但与基准期相比,确定未来降雨量增加,径流量很可能增加,坡面侵蚀也可能增加。未来降雨和侵蚀出现递增趋势,并延续至本世纪末。3种情景下预估的坡面土壤侵蚀平均水平均高于基准期,其中温室气体浓度最高的A2情景增幅最大。随降雨、径流及土壤侵蚀递增趋势的持续,至本世纪中后期(2051-2099年)红壤坡面的土壤侵蚀到达峰值。     

Spatial pattern and heterogeneity of soil properties in sand dunes under grazing and restoration in Horqin Sandy Land, Northern China

Applying a combination of classical and geostatistical methods, we identified soil properties and their spatial variation in a 5-year grazed sand dune (GSD5) and a 20-year recovered sand dune (RSD20) in Horqin Sandy Land, northern China. The paper assesses the effect of grazing, topography and vegetation restoration on spatial heterogeneity of soil properties. The results showed that soil organic carbon, total nitrogen, very fine sand (0.1–0.05 mm) content and their coefficients of variation were lower in GSD5 than in RSD20, while soil water contents (0–20 cm and 20–40 cm depths) were higher in GSD5 than in RSD20. Geostatistical analysis revealed that the spatial structured variance accounted for the largest proportion of total sample variance in soil properties at the measured scale under grazing and restoration. The spatial autocorrelation ranges were 66.30 m for soil organic carbon and 50.80 m for total nitrogen in GSD5 less than those in RSD20 (70.00 m and 76.10 m, respectively), while the spatial autocorrelation ranges of soil particle size fractions and soil water contents in RSD20 were less than those in GSD5. Kriging-interpolated maps also showed that the heterogeneity of soil organic carbon and total nitrogen and their degree of patch fragmentation were higher in GSD5 than in RSD20. These results suggested that continuous grazing resulted in an increase in spatial variability of soil nutrient and a decrease in spatial variability of soil particle size fractions and soil water content. Soil organic carbon and total nitrogen of sand dunes are associated closely with soil particle size fractions, relative height of sampling site and vegetation cover. Spatial patterns of soil properties are most strongly related to grazing, topography and plant-induced heterogeneity in sand dune ecosystems prone to wind erosion.     

不同风沙土含水量因子的抗风蚀性

土地荒漠化是当今世界环境、社会和经济所面临的一个最大问题。它是以风沙活动为主要标志，包括土壤风蚀、风沙流、风沙沉积和沙丘前移的一系列过程，其中土壤风蚀是导致土地沙漠化的主要原因和首要环节。我国是世界上受沙漠化影响最严重的国家之一。全国沙漠、戈壁和沙漠化土地约为165．3万km^2，分布在干旱、半干旱地区以及部分半湿润地区。