Evaluation of Different Predictor Models for Detailed Soil Particle-Size Distribution     

Naser DAVATGAR 《土壤圈》2018,28(1):157-164

An accurate mathematical representation of soil particle-size distribution (PSD) is required to estimate soil hydraulic properties or to compare texture measurements using different classification systems. However, many databases do not contain full PSD data, but instead contain only the clay, silt, and sand mass fractions. The objective of this study was to evaluate the abilities of four PSD models (the Skaggs model, the Fooladmand model, the modified Gray model GM (1,1), and the Fredlund model) to predict detailed PSD using limited soil textural data and to determine the effects of soil texture on the performance of the individual PSD model. The mean absolute error (MAE) and root mean square error (RMSE) were used to measure the goodness-of-fit of the models, and the Akaike''s information criterion (AIC) was used to compare the quality of model fits. The performance of all PSD models except the GM (1,1) improved with increasing clay content in soils. This result showed that the GM (1,1) was less dependent on soil texture. The Fredlund model was the best for describing the PSDs of all soil textures except in the sand textural class. However, the GM (1,1) showed better performance as the sand content increased. These results indicated that the Fredlund model showed the best performance and the least values of all evaluation criteria, and can be used using limited soil textural data for detailed PSD.  相似文献   

Role of inbreeding depression,non‐inbred dominance deviations and random year‐season effect in genetic trends for prolificacy in closed rabbit lines          下载免费PDF全文

E.N. Fernández  J.P. Sánchez  R. Martínez  A. Legarra  M. Baselga 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2017,134(6):441-452

In closed rabbit lines selected for prolificacy at the Polytechnic University of Valencia, genetic responses are predicted using BLUP. With a standard additive BLUP model and year‐season (YS) effects fitted as fixed, genetic trends were overestimated compared to responses estimated using control populations obtained from frozen embryos. In these lines, there is a confounding between genetic trend, YS effects and inbreeding, and the role of dominance is uncertain. This is a common situation in data from reproductively closed selection lines. This paper fits different genetic evaluation models to data of these lines, aiming to identify the source of these biases: dominance, inbreeding depression and/or an ill‐conditioned model due to the strong collinearity between YS, inbreeding and genetic trend. The study involved three maternal lines (A, V and H) and analysed two traits, total born (TB) and the number of kits at weaning (NW). Models fitting YS effect as fixed or random were implemented, in addition to additive genetic, permanent environment effects and non‐inbred dominance deviations effects. When YS was fitted as a fixed effect, the genetic trends were overestimated compared to control populations, inbreeding had an apparent positive effect on litter size and the environmental trends were negative. When YS was fitted as random, the genetic trends were compatible with control populations results, inbreeding had a negative effect (lower prolificacy) and environmental trends were flat. The model fitting random YS, inbreeding and non‐inbred dominance deviations yielded the following ratios of additive and dominance variances to total variance for NW: 0.06 and 0.01 for line A, 0.06 and 0.00 for line V and 0.01 and 0.08 for line H. Except for line H, dominance deviations seem to be of low relevance. When it is confounded with inbreeding as in these lines, fitting YS effect as random allows correct estimation of genetic trends.  相似文献   

Objective evaluation of analyzer performance based on a retrospective meta‐analysis of instrument validation studies: point‐of‐care hematology analyzers          下载免费PDF全文

Andrea M. Cook  Andreas Moritz  Kathleen P. Freeman  Natali Bauer 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2017,46(2):248-261

  相似文献   

Genetic analysis of the main growth traits using random regression models in Japanese flounder (Paralichthys olivaceus)          下载免费PDF全文

Jingli Zhao  Yunfeng Zhao  Zongcheng Song  Haoming Liu  Yongxin Liu  Runqing Yang 《Aquaculture Research》2018,49(4):1504-1511

For body weight (BW) and morphological traits measured repeatedly during growth in Japanese flounder, random regression models (RRMs) were constructed to genetically analyse growth curves and relative growth of morphological traits to BW or body length (BL). In the RRM of growth curves, genetic effects were optimally modelled using Legendre polynomials of two orders for six growth traits. Family and permanent environmental effects remained constant for morphological traits, whereas family effects changed linearly for BWs. During the measuring periods, the heritabilities of the traits increased with age and ranged from 0.256 to 0.843 for BW, 0.379 to 0.806 for body height, 0.338 to 0.773 for BL, 0.286 to 0.665 for head length, 0.159 to 0.708 for length of caudal fin and 0.335 to 0.774 for width of caudal peduncle. Genetic correlations for each trait decreased with increased lag in days of age. In the RRM of relative growth, all morphological traits analysed were significantly associated with BW and BL. The heritabilities for the allometries of morphological traits to BWs ranged from 0.251 to 0.755, whereas those to BLs ranged from 0.412 to 0.871. The majority of genetic correlations among these allometry scalings were negative. These estimated parameters can be utilized to not only guide the efficient selection of traits, but also to genetically regulate synchronous growth of body shape with BW in Japanese flounder.  相似文献   

气垫导轨实验中导轨弯曲的系统误差分析     

刘方  陈刚 《长江大学学报》2004,1(1):57-58

研究了气轨实验中系统误差的另一个重要来源--导轨弯曲对滑块运动的影响,给出了定量的计算,提出了避免减少导轨弯曲所引起的系统误差的方法.  相似文献   

多项式趋势曲线预测模型及软件设计   总被引：1，自引：0，他引：1  

左秀霞  王伟  张伟苇 《长江大学学报》2004,1(1):10-13

在文献[1]的基础上,讨论了多项式趋势曲线预测模型的参数估计方法,并用Turbo C语言建立相应的软件进行了趋势曲线的预测与误差分析.  相似文献   

基于自适应步长RRT的双机器人协同路径规划   总被引：1，自引：0，他引：1  

李洋  徐达  周诚 《农业机械学报》2019,50(3):358-367

针对快速随机扩展树(Rapidly exploring-random tree,RRT)方法的步长确定过分依赖于程序调试,需耗费大量时间,且固定步长存在碰撞检测失效问题,提出了自适应步长RRT方法。通过建立构型空间与工作空间的范数相容不等式,把工作空间中产生的步长约束在允许范围内,进而实现有效的碰撞检测;提出了随机树被动生长方法,实现了双机器人在各自构型空间中的协同路径规划。仿真对比结果表明,采用自适应步长RRT方法进行双机器人路径规划时,随机树的每一次生长所产生的位移不超过设定值,保证了碰撞检测的有效性,相比传统的固定步长RRT,自适应步长RRT方法无需多次调试就能确定步长,提高了机器人的路径规划速度。  相似文献   

基于多时相Sentinel-2A的县域农作物分类   总被引：1，自引：0，他引：1  

吴静  吕玉娜  李纯斌  李全红 《农业机械学报》2019,50(9):194-200

利用遥感技术精准地获取区域农作物种植结构数据,对指导农业生产、制定农业政策具有重要意义。以景泰县为研究区,以多时相Sentinel-2A遥感影像为数据源,计算时序归一化植被指数(Normalized difference vegetation index,NDVI)和红边归一化植被指数(Red edge normalized vegetation index,RENDVI)及其组合特征(NDVI+RENDVI、NDVI-RENDVI和NDVIRENDVI),分析作物特征曲线,并采用随机森林法分别以5种特征参数作为分类特征对研究区农作物进行精细分类。结果表明:根据形态特征,研究区农作物特征值曲线可划分为3种类型:高值型(玉米、水稻、胡麻和马铃薯)、低值型(洋葱、大棚作物和砂田瓜果)和开口型(春小麦、春小麦-秋油葵)。高值型和低值型可在7、8月影像中区分,开口型和前两种类型在5月和9月影像上的特征值有明显差异。3种类型内的作物可以通过不同时相影像区分,高值型的4种作物在9月影像上通过成熟期差异可以区分;低值型的3种作物的特征值差异在全年影像上都可以明显体现;开口型的两种作物利用9月影像可以明显区分。利用NDVI、RENDVI、NDVI+RENDVI、NDVI-RENDVI和NDVIRENDVI 5种特征分类的总体精度分别为82. 14%、78. 16%、81. 17%、75. 64%和86. 20%,Kappa系数分别为0. 78、0. 74、0. 77、0. 71和0. 83,总体精度和Kappa系数由大到小依次为NDVIRENDVI、NDVI、NDVI+RENDVI、RENDVI、NDVI-RENDVI,说明RENDVI辅助NDVI可以有效提高分类精度(精度较仅用NDVI提高4. 06个百分点)。选择合适的时期和分类特征,利用Sentinel-2A特有的红边波段数据及其较高的空间分辨率在县域农作物精细分类上具有较好的精度。  相似文献   

农产品介电参数在线检测装置研究     

杨万泽  鄢金山 《农业科技与装备》2019,(4):14-16,19

利用平行板式电学参数检测系统,研究一种用于农产品干燥过程检测物料介电参数的综合实验装置,配合LCR数字测量仪器实现在线检测监视、远程控制、数据存储分析功能。装置具有功能齐全、温度控制精准等优点,为实现农产品介电参数在线检测及干燥控制提供理论支持。  相似文献   

种子投入产出效率、饲料粮转化效率与粮食和营养安全     

黄泽颖  郭燕枝  孙君茂 《中国农业科技导报》2019,21(11):17-26

科技实现饲料粮供需平衡有助于保障我国粮食和营养安全。聚焦粮食种子和饲料粮转化科技,采用误差修正模型测算了我国1981—2016年种子投入产出效率与饲料粮年产量的长期均衡系数及1992—2016年畜禽饲料粮转化效率与畜禽产品年产量的长期均衡系数。结果表明:种子投入产出效率每提高1,稻谷、小麦、玉米、大豆的饲料粮年增产分别为0.91万、127.33万、9.46万、68.51万t,替代2012—2017年进口量平均需要提高447.71、2.74、39.39、108.14;饲料粮转化效率每提高1,猪肉、牛肉、羊肉、鸡肉、鸡蛋、牛奶年增产分别为748.69万、643.08万、148.30万、437.69万、606.33万、241.89万t,2020年营养纲要目标需要提高的蛋鸡和奶牛饲料粮转化效率分别是1.74和12.13;居民蛋白质、钙、锌、维生素A的摄入量需要分别提高肉牛饲料粮转化效率5.52、奶牛饲料粮转化效率89.40、肉牛饲料粮转化效率3.10、蛋鸡饲料粮转化效率14.80。  相似文献