区域土壤侵蚀定量评价中的坡长因子尺度变换方法

 区域土壤侵蚀研究中,坡度、坡长只能基于中低分辨率DEM提取,但提取的坡度发生衰减,坡长发生扩张。以陕西省延安市及周边地区为研究区,利用国家测绘局生产的1∶25万数字地形图和研究区内典型地区1∶5万数字地形图,在ANUDEM软件支持下,建立了研究区50m分辨率和典型地区10 m分辨率的水文地貌关系正确DEM,利用直方图匹配原理对50m分辨率DEM上提取的坡度、坡长进行变换,并对变换前后坡度、坡长对土壤侵蚀强度的影响进行了评价分析。结果表明,经变换后的坡度整体变陡,坡长整体变短,变换后坡长平均值和累积频率曲线与高分辨率(10m)坡长均较接近,且其空间格局基本保持不变。利用中国土壤流失方程计算坡度坡长均不变换、只对坡度变换、只对坡长变换和坡度坡长均变换4种情况下的土壤侵蚀强度研究结果表明,只对坡长变换时土壤侵蚀强度有所减小,而只对坡度变换和坡度、坡长均变换时土壤侵蚀强度增大,且前者增大幅度较大。说明坡度衰减比坡长扩张对土壤侵蚀评价结果的影响更大,在实际应用中有必要对坡度和坡长都进行变换,以期为土壤侵蚀定量评价提供更加准确的数据支持。     

中国粮食安全现状与应对策略

粮食是人类生存与发展的基础,粮食安全目前已经纳入国家战略,在世界贸易摩擦不断加剧的新形势下,保障国家粮食安全是长期艰巨的任务。分析了我国粮食生产现状及存在的问题,并针对粮食总量和质量上存在的问题提出了应对策略。提出了加强耕地保护与环境治理,建立粮食加工监管全程追溯系统,深化粮食科研院所改革,构建上下协同、功能互补和配置高效的粮食科技协同创新体系,持续推进粮食品种与区域结构调整,开展粮食增产模式攻关等方法,从而促进粮食安全保障能力稳步提升。      

珍稀油料树种琴叶风吹楠种子萌发习性

从西双版纳地区采集野生琴叶风吹楠(Horsfieldia pandurifolia)的种子开展萌发习性研究。结果表明:成熟的新鲜种子沙床催芽萌发率在96%以上,幼苗移栽成活率高达100%;相同植株的种子土壤播种萌发率为80.00%～86.27%,而整个果实播种萌发率仅有9.09%～33.33%;模拟野生环境下浅覆土的种子萌发率为55%～95%,不覆土的种子萌发率为20%～65%;8个月苗龄土壤播种苗11个家系平均株高为24.70～47.43cm,变异系数为21.95%～41.26%,平均地径为7.16～11.08mm,变异系数为16.62%～35.12%,家系间变异大。     

维生素C对青鱼幼鱼生长、免疫及抗氨氮胁迫能力的影响

以初始体质量为(7.27 ±0.40)g的青鱼为研究对象,采用维生素C(VC)含量分别为0(对照组)、16.3、33.9、69.1、137.8和277.5 mg/kg 6种等氮等能实验饲料,饲养青鱼8周后,选取0、69.1和277.5 mg/kg VC组进行24 h氨氮胁迫(20 mg/L),研究VC对青鱼幼鱼生长、免疫及抗氨氮胁迫能力的影响.结果显示:以特定生长率为指标,折线模型分析表明青鱼有效维生素C需要量为63.0 mg/kg.肌肉、肝脏和血清中VC积累量与饲料中VC含量呈正相关性,当VC添加量达到137.8 mg/kg时,肌肉和肝脏中VC积累量达到饱和.饲料中添加VC对血清总超氧化物歧化酶(T-SOD)活性及丙二醛(MDA)含量无显著影响,饲料中添加VC显著提高了血清谷胱甘肽过氧化物酶(GSH-px)和过氧化氢酶(CAT)活性(P＜0.05);血清中谷胱甘肽(GSH)含量和鳃丝Na+/K+-ATP酶活力(NKA)随饲料中VC添加量的增加呈升高趋势,而血清皮质醇含量(COR)呈下降趋势.氨氮胁迫有使肝脏和肌肉VC含量、血清T-SOD、CAT、GSH-px活性、GSH含量和鳃丝NKA活性降低,血清VC含量、COR和MDA含量增加趋势.其中,对照组T-SOD、CAT、NKA活性、GSH、MDA和COR胁迫前后差异显著(P＜0.05),氨氮胁迫使VC添加组青鱼肝脏VC含量显著降低(P＜0.05),而CAT、NKA活力、GSH、COR胁迫前后均无显著变化.69.1 mg/kg VC组T-SOD活性胁迫前后无显著差异,但GSH-px活性和MDA含量胁迫前后差异显著(P＜0.05),而277.5 mg/kg VC添加组GSH-px活力和MDA含量胁迫前后差异不显著,但T-SOD活性显著降低,血清VC含量显著升高(P＜0.05).研究表明,青鱼获得最好生长的饲料有效VC添加量为63.0 mg/kg,氨氮胁迫使青鱼产生免疫应激反应,而补充VC可有效增强机体免疫,缓解机体免疫应激,改善青鱼抗氨氮胁迫能力.     

Comparison of effects of high-pressure processing and heat treatment on immunoactivity of bovine milk immunoglobulin G in enriched soymilk under equivalent microbial inactivation levels

Immunoglobulin-rich foods may provide health benefits to consumers. To extend the refrigerated shelf life of functional foods enriched with bovine immunoglobulin G (IgG), nonthermal alternatives such as high-pressure processing (HPP) may offer advantages to thermal processing for microbial reduction. To evaluate the effects of HPP on the immunoactivity of bovine IgG, a soymilk product enriched with milk protein concentrates, derived from dairy cows that were hyperimmunized with 26 human pathogens, was subjected to HPP or heat treatment. To achieve a 5 log reduction in inoculated Escherichia coli 8739, the HPP or heat treatment requirements were 345 MPa for 4 min at 30 degrees C or for 20 s at 70 degrees C, respectively. To achieve a 5 log reduction in natural flora in the enriched soymilk, the HPP or heat treatments needed were 552 MPa for 4 min at 30 degrees C or for 120 s at 78.2 degrees C, respectively. At equivalent levels for a 5 log reduction in E. coli, HPP and heat treatment caused 25% and no detectable loss in bovine IgG activity, respectively. However, at equivalent levels for a 5 log reduction in natural flora, HPP and heat resulted in 65 and 85% loss of bovine IgG activity, respectively. Results of combined pressure-thermal kinetic studies of bovine milk IgG activity were provided to determine the optimal process conditions to preserve product function.     

漩涡泵内部不稳定流场数值模拟

为了研究漩涡泵内部流场对其外特性的影响,采用RNGk-ε湍流模型和结构化网格技术对漩涡泵内部非定常流动进行数值模拟计算。结果表明,漩涡泵流道内压力变化呈直线分布;流道内纵向漩涡随流量的增大而减小,径向漩涡周期性地脱离叶片被液流带走且随着时间增加而增大;设计工况下,各监测点处压力脉动变化呈周期性分布,从流道进口到出口压力脉动幅值逐步增大;不同工况下,叶片通过频率是压力脉动的主频,其对应的压力脉动幅值随流量增大而增大。     

植物文化性及其在园林景观中表达的研究

随着人类文明的不断进步,人类社会的不断发展,文化的地位越发显得举足轻重。形成了许多独特的文化体系。如茶文化、企业文化等等名词渐渐为人们所熟悉。于是,越来越多的人在越来越多的领域开始关注文化,研究文化。文化也变得流行起来,并且渗透到了园林景观的领域。植物是园林景观的重要组成部分,植物配置的水平在一定程度上决定了园林景观设计的优劣程度。在景观建设不断发展的今天,植物的文化性作为考察植物配置水平的重要因素,越来越引起景观工作者的重视。在不同的园林景观环境中,合理的利用植物文化性能够体现整体环境的文化氛围。让人们在自然环境中品味文化,达到提升审美情趣,感悟世界观、人生观和了解人文历史的目的。目前,对于植物文化性的概念还没有统一的定义。本篇论文目的在于对植物文化性的概念进行定义,并且在此基础上,创新性的提出植物文化性的分类和评价依据。最后,引入在不同地域环境中,植物文化性的实例分析,对植物文化性展开讨论。旨在使读者系统的了解植物的文化性,弘扬民族文化,使园林工作者在植物配植造景中更好的运用植物的文化性。     

水稻土CH4产生潜力及其影响因素

培养试验所用15种水稻土样品采自全国各主要稻米产区。15种水稻土产CH4潜力差异很大,厌氧培养CH4产生率显著大于好氧培养,整个培养期(132d)总CH4产生量的变化范围为1.18～1180μgg-1(厌氧培养)和0.41～136μgg-1(好氧培养)。土壤CH4产生量受与土壤有机质含量有关的有机碳和全氮含量的显著影响,而与活性铁锰含量、颗粒组成、阳离子交换量、土壤pH等其他土壤理化性质之间无显著相关性,表明土壤有机质含量是影响CH4产生的最重要土壤性质。与类似试验的结果比较说明,土壤有机质含量对CH4产生量的影响程度可能与土样代表的空间尺度有关。     

Evaluation of pea proteins and poultry protein as fish meal alternatives in the diets for juvenile black sea bream,Acanthopagrus schlegelii

The potential of three different protein resources (pea protein isolate, PPI; pea protein concentrate, PPC; enzyme treated poultry protein, ETPP) as fish meal (FM) alternative protein in diets for juvenile black sea bream, Acanthopagrus schlegelii. (initial average weight 7.90 ± 0.13 g) was evaluated. Seven isonitrogenous and isoenergetic diets were formulated to replace FM at 0% (T0, control diet), 8% (designated as T1‐T3) and 16% (designated as T4‐T6) using PPI, PPC and ETPP respectively. Each diet was randomly assigned to triplicate groups of 25 juvenile fish for 8 weeks. At the end of the feeding period, survival rate was not significantly affected by dietary treatments. Growth performance in T6 (16% ETPP) group was significantly inferior to T0 group, however, weight gain and specific growth rate in other treatments showed no significant differences (P > 0.05). Mean feed intake, feed efficiency ratio and protein efficiency ratio were also poorer in fish fed in T6 than those of fish fed with the control diet respectively. Apparent digestibility coefficients (ADCs) of dry matter and crude protein for fish fed ETPP diets were significant lower than those of fish fed with the control diet, whereas ADCs of lipid were unaffected by dietary treatments. ADC's of dietary Leu, Ile, His and Lys was also significantly influenced. There were no marked variations in proximate compositions of dorsal muscle. With regard to plasma characteristics, significant difference was observed in triacylglycerol content. Ammonia concentration in plasma tended to increase in alternative protein diets as substitution level increased. There were significant differences in aspartate aminotransferase activities among groups, but alanine aminotransferase levels were unaffected by treatments. In conclusion, the present study demonstrated that PPI and PPC were potential protein sources for using in juvenile black sea bream diet. However, the substitution level of FM by ETPP should be limited within 16%.     

基于曲面分区的多道次数控渐进成形轨迹生成

为实现含有直壁等难成形曲面的高效成形,以三角网格模型为研究对象,提出基于曲面分区的个性化多道次数控渐进成形方式和在各曲面分区内进行各道次成形加工所需轨迹生成方法.给出了基于可成形性的三角网格曲面分区算法和通过偏置来生成各曲面分区多道次螺旋线成形轨迹的方法.算法应用实例表明,该方法能够对曲面进行分区,并为相关曲面分区生成光滑连续的多道次螺旋线成形轨迹.