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51.
立地条件对杉木生长过程的影响   总被引:1,自引:0,他引:1  
本文结合基层杉木材林业生产实际,提出以土壤厚度作为其划分立地类型的依据;对杉木树高、胸径和材积生长进行数学方程拟合;分析立地对其方程参数变化及各生长项目的总生长量、连年生长量、平均生长量所产生的影响,并应用D、H、及DH有序样本对杉木生长进行了生长阶段的划分.  相似文献   
52.
通过制备脂多糖(LPS)并将其作为检测抗原,建立了一种检测奶样中布鲁氏菌抗体的酶联免疫层析方法。通过对处理方法和反应条件的优化,制备出敏感性高、特异性强的布鲁氏菌抗体检测试纸条。该试纸条敏感性为98.0%,抗体滴度为1:2~1:8,特异性为96.0%,且与其他常见病原无交叉反应,批内、批间重复性良好。保存期加速试验显示,该试纸条在2~30℃下可保存12个月;符合率验证显示,该方法与标准奶样的符合率达94.9%。上述结果表明,该检测方法具有敏感性高、特异性强以及方便、快捷等优点,适用于现场大批量检测,因而可应用于奶牛场布鲁氏菌病的快速诊断。  相似文献   
53.
通过单因素和复配试验,研究糙米粉和柑橘皮粉复配对牛肉饼品质的影响。将糙米粉(0%、1%、2%和3%)和柑橘皮粉(0%、1%、2%、3%和4%)分别添加到牛肉饼中,通过产品得率、颜色(L*、a*、b*)、质构(弹性、黏聚和回复性)等指标的测定,并结合感官评价,筛选出糙米粉和柑橘皮粉的适合添加量,分别为2%和3%,在此添加量下的牛肉饼与空白对照组相比均有最大的产品得率、最佳的质构特性以及最好的感官评分(P < 0.05)。再利用复配试验优化出糙米粉和柑橘皮粉的最适复合配比,结果表明糙米粉和柑橘皮粉的最适复配比例为:糙米粉1.5%,柑橘皮粉3.5%,在此配比下加工的牛肉饼具有良好的产品得率(92.73%)和感官评分。同时低场核磁弛豫时间(T2)结果显示,此配比下的牛肉饼水分结合最牢固,保水性最好。  相似文献   
54.
The aim was to study the quality and quantity of pasture selected by sheep on various planted pastures. A further aim was to assess NDF and IVDOM as easy measurable parameters for use in equations to predict intake. Pasture samples were collected using oesophageal‐fistulated sheep and from knowledge of the in vitro digestibility of these samples and the total faeces voided as measured with faeces bags, intake was calculated. Pastures observed included ryegrass, cocksfoot, C. dactylon, Smuts finger, triticale, E. curvula, Eragrostislucerne combination, lucerne and sainfoin. Nitrogen content of oesophageal samples varied between 2,3 and 5,1%, NDF between 33 and 65% and IVDOM between 50 and 80%. Intake of grass DOM varied from 24,4 to 43,3 g/kg W0,75/day for lambs and from 29,0 to 37,4 g/kg W0,75/day for mature wethers. DOM intake on the two legumes was generally poor and varied between 13,7 and 22,9 g/kg W0,75/day. Although some of the variation in voluntary intake is accounted for by the variation in NDF and IVDOM, these two parameters are of limited value as general predictors, but may be used in selection indices.  相似文献   
55.
The method of matching samples was used to compare the costs and returns associated with broiler housing technology using Agricultural Resource Management Survey data for 2006 and 2011. Farms with housing that included tunnel ventilation and evaporative cooling cells (new technology) were compared with farms with housing that did not include this technology (old technology). Gross farm income, total variable expenses, and total fixed expenses were higher for the new technology farms for both years. New technology farms had greater income over variable expenses and net cash farm income in both years.  相似文献   
56.
【研究目的】样本总体的分布特征是影响抽样样本数量的主要因素,对于样本总体为非正态分布的情况,正态转换是降低抽样样本数量、提高抽样调查效率的有效手段。【方法】该文采用中国大陆区域2005年耕地空间分布数据,以1:10万地形图图幅框作为抽样单元,统计每个图幅框内耕地面积占比。分别采样1.5次开方、2次开方、2.5次开方、3次开方和4次开方运算的方式对原始数据进行正态转换。在此基础上对比分析了转换前后数据的峰度及偏度、抽样个数及抽样结果误差等。【结果】结果表明,基于2.5次开方运算后的分层抽样可以大大降低抽样率,由92.26%降低为22.55%,耕地面积指数平均值相对误差由7.06%降低为5.66%。利用2015年耕地面积指数进行抽样方法的精度检验,抽样平均值相对误差仅为3.27%。【结论】研究提出的抽样方法具有较高的适用性,同时也表明空间抽样中数据分布正态转换是非常必要的。本研究成果为广大学者在空间抽样调查方面的研究提供了有益的借鉴。  相似文献   
57.
Precompression stress (σp) is commonly used as an indicator for the load carrying capacity of a soil and its stress history. Several calculation methods have been proposed to determine σp, but they have proven to be not interchangeable. The aim of this study was to perform a functional evaluation of seven existing methods to test which method would be most recommended to assess soil strength in cultivated fields. This was achieved by investigating the relation of the obtained σp of undisturbed soil samples to other soil properties and stress history. Additionally, the robustness of the methods was evaluated by checking their sensitivity to perturbation of the measured strains. The two most commonly used methods, the Casagrande method and Gompertz model fit method, were found to be the least suitable to calculate σp. These methods lack robustness and do not yield a significant relation with the relevant soil properties or stress history. Better results were obtained with Intersecting linear regressions or at the inflection point of a fourth-degree polynomial.  相似文献   
58.
Preparation and characterization of wood/montmorillonite nanocomposites   总被引:2,自引:0,他引:2  
With montmorillonite (MMT) organically modified as organophilic MMT (OMMT) and water-soluble phenol formaldehyde resin (PF) as intermediate, Chinese fir (Cunninghamia lanceolata) wood/MMT nanocomposites (WMNC) were prepared via nano intercalation compounding and characterized by XRD, SEM and FTIR. Results show that: 1) the preparation of OMMT is very successful; 2) the self-made PF can effectively intercalate into MMT to increase markably its gallery distance and even exfoliate its nano silicate laminae; 3) the XRD analysis indicates that some exfoliated MMT enters the non-crystallized region of microfibrils in wood cell walls and the crystallinity degree of wood in WMNC decreases; 4) the SEM graphs show that multiform MMT exists in WMNC. Some grains block in wood cell lumen, some layers adhere to the wood surface of the inner cell wall and some exfoliated nanolaminae even insert into wood cell walls; and 5) the FTIR analysis suggests that MMT and wood in WMNC perhaps interact via certain chemical bonding.  相似文献   
59.
木材/蒙脱土(MMT)纳米插层复合材料的制备构想   总被引:11,自引:0,他引:11  
吕文华  赵广杰 《林业科学》2005,41(1):181-188
基于聚合物 蒙脱土纳米插层复合材料的研究成果 ,综述了插层复合方法的原理、工艺过程和产品性能 ,分析比较了单体插层原位聚合和聚合物直接插层等方法。从木材与蒙脱土的结构和组成特性出发 ,分析比较了木材与聚合物溶解、熔融性的不同 ,讨论了利用插层复合原理制备木材 蒙脱土纳米复合材料的基本构想 ,并进一步提出了相应的技术路线和工艺流程概念图。  相似文献   
60.
The present natural language processing (NLP) methods mainly employ bottom-up language analysis ways, which have only limited semantic analysis capabilities. Therefore it is impossible to carry out semantic processing for large amounts of real texts. This paper presents a semantic analysis approach and corresponding algorithms based on term connections. The approach has rooted in semantics based on term connections and taken a major sentence cut-in, bottom-up semantic analyzing process. The main algorithm is to find the optimal sentence tree based on the semantic meaning conformity of term connections. So far, this approach has been applied in project CAPC (Computer Aided Poetry Composing) funded by the Chinese Natural Science Foundation.  相似文献   
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