浅谈培育和发展烤烟大户

该文论述了培育和发展烤烟大户在现代烟草农业建设中作用：其一是实现农用土地流转的重要形式;其二是实现现代烟草农业规模化生产的必由之路;其三是实现现代烟草农业专业化生产的桥梁。     

黑龙江省小反刍兽疫控制与消灭实践探索

2015年我国提出力争于2020年实现小反刍兽疫非免疫无疫。为此,黑龙江省制定了《黑龙江省消灭小反刍兽疫实施方案（2016—2019年）》,并于2017年1月1日起全省全面退出小反刍兽疫强制免疫,在体制、机制、条件、组织等多方面的保障下,通过监测预警、信息管理、人工屏障、应急管理等多方面工作,控制和消灭了小反刍兽疫,取得了显著的经济效益和社会效益,为我国退出小反刍兽疫免疫探索出了一套可操作、可复制的经验。     

我国青藏高原地区牦牛草地放牧系统管理及优化

基于牦牛所处地理环境,即青藏高原的特殊性,以及牦牛放牧这一生产方式在该地区第一产业中的重要地位,国内外学者从牦牛放牧系统的管理出发,对该系统中各因子之间的相互响应进行了研究,主要包括当放牧制度不同时,系统中的初级生产力和次级生产力的表现特征。从不同放牧制度中草地和家畜的特征表现,再到人为管理对这两种生产力的影响,研究者通过对比和试验进行了系统优化方法的探索。笔者通过对现阶段已有的研究成果进行整理和分析,概括在不同的放牧管理方式下草地放牧系统中的牦牛在生产力水平方面的差异,以及草地对不同放牧强度的响应,探究青藏高原地区牦牛放牧方式如何影响草畜之间的互作关系。在此基础上,分析其在实际生产活动中存在的问题,以及如何通过改进管理制度优化生产的办法,并对牦牛放牧系统发展进行了展望。     

Beneficial effects of n-3HUFA enriched Artemia as food for larval palmetto bass (Morone saxatilis × M. chrysops)

The beneficial effects of feeding n−3 highly unsaturated fatty acids (HUFA ≥ 20 carbon fatty acids with three or more double bonds) to palmetto bass (striped bass × white bass) larvae, 4–30 days of age, were studied using Artemia diets enriched with six n-3HUFA levels. Dietary n-3HUFA concentrations were < 0.03% (control diet), 0.33%, 0.63%, 0.87%, 1.26%, and 2.27% of dry-wt Artemia. Larval n-3HUFA contents were reduced at a faster rate with decreasing dietary n-3HUFA intake, and were significantly different by 30 days posthatch (4–20 mg g⁻¹ dry-wt fish). Starved larvae selectively conserved endogenous n-3HUFA reserves, indicating an essential role of n-3HUFA in larval development. Mass mortality in the control and 0.33% n-3HUFA diets occurred at metamorphosis (26–28 days posthatch). At harvest, all fish, except those fed the two highest n-3HUFA diets, suffered from handling stress (shock syndrome) with increasing severity (25 to 100%) at decreasing dietary n-3HUFA intake. Recovery from shock syndrome was 100% at the 0.63% and 0.87% n-3HUFA diets, 63% at the 0.33% n-3HUFA diet and 0% at the control diet. Post-harvest survival was similar among the four highest dietary n-3HUFA groups (64–73%), whereas the two lowest n-3HUFA groups differed significantly (0 and 37%). Growth promotion was evident with increased dietary n-3HUFA intake as fish fed the highest n-3HUFA diet were twice the size of those fed the control diet (99 vs 52 mg wet-wt). Final fish sizes at the three highest n-3HUFA diets were similar. Given similar culture conditions, a minimum dietary n-3HUFA intake of 1.26% of dry-wt Artermia is recommended to avoid handling stress and promote growth in larval palmetto bass.     

种子加工厂经济规模探讨

以种子到达最终农户的总成本费用为基础,分析了运输费用对加工厂生产规模的影响机制,通过建立数学模型推导出了运输费用的计算公式,利用对总成本费用求极值方法确定加工厂的经济规模和最佳服务半径,推导出种子需求密度、加工厂的固定成本以及单位运输费用是影响加工厂经济规模的主要因素,并得出了经济规模与各因素之间的变化关系,为今后确定加工项目的经济规模提供了理论依据。     

The improvement of growth,digestive enzyme activity and disease resistance of white shrimp by the dietary citric acid

A 45-day feeding trial was conducted to evaluate the effects of dietary citric acid on growth, digestive enzyme and disease resistance of white shrimp, Litopenaeus vannamei. Shrimp with initial body weight of 5.57 ± 0.21 g were fed with basal diet supplemented with 0.0 g kg^?1 (control), 1.0, 2.0, 3.0, 4.0 and 5.0 g kg^?1 citric acid. Results showed that weight gain was increased by 15.9 % and feed conversion ratio was decreased by 0.17 by 2.0 g kg^?1 dietary citric acid compared with control group (P < 0.05). Intestinal protease activity of shrimp fed 2.0 g kg^?1 citric acid was significantly higher (P < 0.05) than that of control group. No significant difference was found in intestinal amylase activity among treatments (P > 0.05). The activities of serum phenoloxidase, superoxide dismutase and lysozyme in 2.0 and 3.0 g kg^?1 citric acid group were significantly higher, and accumulative mortalities of the two groups on the fourth day after injection of Vibrio alginolyticus were significantly lower than those of control group (P < 0.05). Results above demonstrated that dietary citric acid could improve growth performance, immunity and resistance against V. alginolyticus. The supplementation level of citric acid in diet was suggested to be 2.0–3.0 g kg^?1 for white shrimp.     

联合收割机割台总成的虚拟装配

研究了基于虚拟现实技术的联合收割机割台总成的虚拟装配.根据产品的装配结构模型,生成了联合收割机割台总成的装配结构树;采用UG建立了割台总成零部件的三维数字模型,导入到数字制造仿真软件,建立了总成各零部件的约束及装配关系,对割台总成进行了虚拟装配.     

高速部分流泵CFD计算和优化设计

为研究高速部分流泵中流量系数、扬程系数和比转速三者之间的关系,对该泵主要参数进行了优化设计.在水泵性能试验的基础上,采用Matlab软件对试验数据进行数值拟合,推导出三者的函数关系式,并对主要性能参数进行了精确计算.将优化后的参数应用于Pro/E建模,运用ANSYS-CFX进行了数值计算和外特性试验.结果表明,中间截面静压呈环状梯度由轮毂向轮缘逐渐递增,出口静压满足优化要求;流线云图中虽然存在漩涡,但隔舌处的回流和涡流得到了明显的改善;从扬程-流量试验曲线也可以看到,在从小流量到设计工况点间运行非常平稳.该结果为实际工程应用提供了一定参考.     

基于自适应全局阈值融合标记的遥感图像建筑群分割

针对分割遥感图像建筑群时,标记不完全所产生的过分割和欠分割并存问题,提出一种基于自适应全局阈值融合标记的图像分割算法.该算法根据建筑群的分布和纹理特点,利用小波变换提取图像梯度,通过形态学重构对梯度图像进行滤波;采用局部极小值法提取背景标记,并应用自适应全局阈值法提取建筑群标记.采用逻辑运算进行标记融合,用融合后的标记修改加权像素的Sobel梯度图实现精准分割.实验结果表明,该算法能够弥补形态学滤波梯度图的局部极值标记不足问题,抑制了建筑群的过分割和欠分割,准确地将建筑群从背景中提取出来,分割正确率达到90.7％.     

贵州长坡岭林场马尾松毛虫工程治理技术设计

森林病虫害工程治理是一种新的病虫害管理方式，技术设计应严格按工程治理有关规定进行，要体现依靠科学技术和“预防为主，综合防治”的原则，明确治理目标、任务和效果，注意长、中、短期措施相结合，并将各项工程治理措施落实到各实施年度、小班。