基于不同行为时间的奶牛健康状况评价   总被引：3，自引：2，他引：1  

郑国生  施正香  滕光辉 《农业工程学报》2019,35(19):238-244

如何高效准确地监测和管理好奶牛是当前规模化奶牛场发展的关键。该文通过对17头奶牛休息时间、反刍时间和采食时间的连续61d监测和行为记录,利用SPSS23.0软件,结合Logistics回归分析法对试验数据进行统计分析,并构建了奶牛健康状况评价模型。研究结果表明:1)与正常行为期间相比,奶牛非正常行为期间的平均休息时间增加25.7%,反刍时间和采食时间分别平均减少12.7%和2.3%。2)荷斯坦泌乳奶牛正常行为时间呈正态分布,每天(24 h)平均休息时间为300～600 min,反刍时间为400～700 min,采食时间为200～400 min。非正常行为时间呈离散状分布,无明显分布规律。3)休息时间和采食时间是预测模型的主要影响因素,其中采食时间对模型预测概率的影响力较休息时间大,在其他条件不变的情况下,采食时间水平每增加1个单位,奶牛非正常行为预测概率变化扩大4.2倍。奶牛非正常行为预测模型预测结果与人工目视观察结果比较,模型预测准确率为91%。该研究可为现代规模化奶牛场科学、精准化管理提供参考。  相似文献   

生物质炭催化玉米秸秆热解气重整提质研究     

王敬茹  姚宗路  丛宏斌  赵立欣  马腾  霍丽丽  袁艳文 《农业工程学报》2019,35(16):258-264

为研究生物炭作催化剂消减焦油提高热解气品质的效果,以玉米秸秆为原料,以焦油转化率、热解气产率和热解气热值为评价指标,研究重整温度、停留时间和生物炭特性对热解气提质的影响,并分析生物炭作为催化剂重整前后比表面积的变化。研究结果表明,与石英砂(高温裂解)相比,生物炭具有较好的催化特性,且稻壳炭、木屑炭和玉米秸秆炭对焦油的转化率分别为79.8%、78.6%、72.6%,热解气产率分别为39.7%、38.6%、37.9%。随着重整温度和停留时间的增加,热解气产率和焦油转化率增加,而热解气热值仅随着温度升高而增加,当温度为800℃时,热解气热值为17.6 MJ/m~3。800℃催化重整后生物炭比表面积为79.81 m~2/g,高于550℃热解生物炭比表面积37.96 m~2/g,生物炭作催化剂时不但可以提高热解气品质,而且生物炭比表面积也有所增加。  相似文献   

施氮和覆膜对陕北地区玉米生长及氮素转运的影响     

密菲瑶  张腾  李卓远  邢英英  王秀康 《中国农业大学学报》2023,28(8):65-79

为探究覆膜与施氮量对陕北地区玉米生长特性及氮素转运的影响,以‘郑单958’玉米为供试材料,共设置11个处理,种植模式分为露地种植(M₀)和覆膜(M₁),施氮量分别为80(N₁)、120(N₂)、160(N₃)、200(N₄)、240(N₅)kg/hm²,以露地种植下不施氮作为对照组,测定玉米生长、产量、氮素转运及氮肥利用效率。结果表明,覆膜与施氮量对大田玉米株高、茎粗、叶面积指数有显著影响,且随着生育期推进,玉米各生长指标均呈快速升高直至平缓的趋势,二者互作效应对株高具有极显著影响;覆膜和施氮对玉米产量具有极显著影响,覆膜显著提高玉米产量,随着施氮量的增加,玉米产量呈现先增后降的趋势,M₀和M₁模式分别在N₃和N₂水平下达到高产,为12 469.02和13 181.66 kg/hm²。随施氮量增加,各营养器官氮素积累量均表现出先增后减的趋势,成熟期各器官氮素积累由高到低为籽粒>叶>茎;玉米营养器官氮素转运量呈先降后增的趋势,施氮量和覆膜均显著影响玉米氮素转运效率,氮素吸收效率呈显著下降趋势;覆膜显著提高氮肥利用率、氮肥偏生产力及氮肥农学利用率,随着施氮量的增加,氮肥利用率、氮肥偏生产力及氮肥农学利用率均显著降低,而肥料产量贡献率先增后降。通过主成分综合评价,M₁N₃处理得分最高,因此推荐覆膜条件下施氮量160 kg/hm²作为陕北地区玉米较优的栽培模式。  相似文献   

四川部分晾晒烟种质遗传关系的SRAP分析   总被引：5，自引：0，他引：5  

龙腾  刘雷  黄玉碧 《作物学报》2009,35(1):173-178

对25份四川地方性晾晒烟材料、1份黄花烟和1份普通烤烟材料进行了SRAP分析。共检测到3 368条扩增带, 其中特异性条带为998条, 平均多态检出率为29.6%。27个应试材料间遗传相似系数在0.26~0.97间, 平均为0.62, 表现出明显的遗传差异;其中黄花烟、烤烟和晾晒烟3个栽培类型间遗传相似系数为0.38~0.78;在25份晾晒烟品种间遗传相似性较高为0.75~0.97, 显示出种内的遗传基础相对比较狭窄, 但苍龙毛烟与其他供试材料有较大的遗传差异。经聚类分析, 可将黄花烟、烤烟和晾晒烟品种划分为3个栽培类别, 反映出栽培类型间的遗传差异;进一步将25份晾晒烟材料分为3个亚类和2个单一品种的个类;但按传统方法命名的多个毛烟品种和柳烟品种未被明显地分别聚为两类。SRAP标记技术能高效揭示亲缘关系很近的晾晒烟种质资源的遗传背景和亲缘关系。  相似文献   

Infiltration characteristics of water in forest soils in the Simian mountains, Chongqing City, southwestern China     

Wei Wang  Hongjiang Zhang  Meng Li  Jinhua Cheng  Bo Wang  Weili Lu 《Frontiers of Forestry in China》2009,4(3):338-343

Spearman rank-correlation analysis and grey relational grade analysis were used to study infiltration characteristics of water in different forest soils in the Simian mountains, Chongqing City. The results indicate that the soil bulk density, contents of coarse sand, and porosity of macropores were significantly correlated with saturated hydraulic conductivity. Porosity of macropores and contents of coarse sand were positively correlated with soil saturated hydraulic conductivity and soil bulk density negatively. Based on the initial infiltration rate, the stable infiltration rate, time required for infiltration to reach a stable state, and cumulative infiltration, all of which are crucial parameters determining soil infiltration capacity, the results of grey relational grade analysis showed that the grey relational grades of the different forest soils were listed from high to low as broad-leaved forest (0.8031) > Phyllostachys pubescens forest (0.7869) > mixed conifer-broadleaf forest (0.4454) > coniferous forest (0.4039). Broadleaf forest had the best ability to be infiltrated among the four soils studied. The square roots of the coefficients of determination obtained from fitting the Horton infiltration equation, simulated in our study of forest soils, were higher than 0.950.We conclude that soils of broad-leaved forests were the best suited for infiltration processes of forestry in the Simian mountains. __________ Translated from Journal of Soil and Water Conservation, 2008, 22(4): 95–99 [译自: 水土保持学报]  相似文献   

Numerical simulation of dynamic response and radiation noise of gearbox     

LIN Teng jiao  LIAO Yong jun  LI Run fang  LIU Wen 《保鲜与加工》2009,(8):892-896

Considering the internal dynamic excitation produced by stiffness excitation, error excitation and mesh impact excitation, a dynamic finite element model of transmission system and structure system of gearbox is established. The normal mode and the dynamic responses of gearbox under the internal dynamic excitation are calculated by using the numerical simulation software ANSYS. Based on the result of dynamic responses, the boundary excitation condition is determined, and then the acoustic boundary element model is built. With the software of SYSNOISE, the surface acoustic pressure of gearbox and the radiation noise of field points are solved by the direct boundary element method. The test of airborne noise is carried out. The computational results obtained are in a good agreement with the data of experimental test.  相似文献   

影响牛黄形成的环境因素的探讨     

滕建军 《家畜生态》1992,(1)

许多环境因素都会影响牛黄的形成。牛经常采食含胆碱类成分高的牧草,会使牛黄的形成量降低;在干旱地区,牛的饮水受到限制,牛黄产量较高;水中含钠多时,牛黄产量少;红壤地区牛黄多,沙壤地区较少;应激反应可以促进牛黄的形成。  相似文献   

Simulation of the barley leaf rust epidemic: Structure and validation of BARSIM—I     

P.S. Teng  M.J. Blackie  R.C. Close 《Agricultural Systems》1980,5(2):85-103

This paper, the second in a series outlining development of a management information system for barley leaf rust in New Zealand, describes the structure and biological logic of the skeleton model BARSIM—I. Validation of biological system models is discussed and results of two statistical tests with BARSIM—I presented. Using a parametric (regression) technique, nine out of fifteen simulated epidemics were found to agree with field observations. With a non-parametric (Smirnov) test, model output was found in all instances to agree with field data. The relationship of simulation modelling to mathematical modelling of plant diseases is discussed.  相似文献   

移动模架在50m跨径现浇箱梁中的应用   总被引：1，自引：0，他引：1  

宫旭黎  滕海生 《森林工程》2007,23(2):67-68

根据移动模架在温州某桥50m跨径现浇箱梁施工中的应用情况，详细介绍了移动模架的构造、工作原理和现浇箱梁的施工工艺；通过利用移动模架进行跨径50m现浇箱梁施工的经验总结，指出了其在大跨径现浇箱梁施工过程中的经济性和施工质量及工期等方面的优越性；针对移动模架的技术要求，指出了其在中大跨径现浇箱梁中的应用前景。  相似文献   

珍稀濒危树种资源的保护与管理刍议   总被引：1，自引：0，他引：1  

徐小静  汪传佳  方腾  钱孝炎  李海波 《浙江林业科技》2003,23(2):45-48

对浙皖赣闽山地珍稀濒危树种具有的直接利用价值、生态价值、学术研究意义和其它价值、珍稀植物保护所需要的研究、珍稀濒危树种资源管理等进行了阐述，提出了珍稀濒危树种资源管理流程图和珍稀濒危树种保护方案。  相似文献