奶牛体型线性鉴定应用的探讨     

邹木兰  金尔光 《华中农业大学学报》1992,11(3):268-275

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基于激光雷达数据的东北林区航空林分材积表编制     

曾伟生  孙乡楠  王六如  王威  蒲莹 《林业资源管理》2021,(1):147-155

利用东北林区云冷杉林、落叶松林、樟子松林、红松林、栎树林、桦树林、杨树林、榆树林、椴树林和水胡黄林10种森林类型的1947个样地的激光雷达数据和地面实测蓄积量数据,首先通过多元线性回归和非线性回归方法,分别建立基于机载激光雷达数据的森林蓄积量回归估计模型,并通过对比分析,确定统一形式的基础回归模型;然后利用哑变量建模方法,建立基于不同森林类型参数和相同激光雷达变量的蓄积量模型。结果表明,研究建立的10种森林类型的线性蓄积量回归模型的解释变量个数在2~7之间,确定系数在0.460~0.858之间;非线性蓄积量回归模型的解释变量个数在2~4之间,确定系数在0.461~0.846之间。基于点云平均高度和平均强度建立的10种森林类型的二元蓄积量模型(研究称之为标准模型),其确定系数在0.440~0.815之间,平均预估误差在2.88%~4.42%之间,平均百分标准误差在16.76%~25.52%之间,预估精度基本达到森林资源规划设计调查技术规定要求。依据研究建立的10种森林类型的蓄积量模型,可以编制基于激光雷达数据的航空林分材积表,在森林资源调查实践中推广应用。  相似文献   

模糊向量空间的不变子空间     

郑千里  邢灵博  吴炎  王鸿绪 《河北北方学院学报(自然科学版)》2006,22(2):11-15

引进模糊向量空间的不变子空间的定义,研究了在模糊变换下的模糊向量空间的不变子空间的性质.  相似文献   

农业分区框架下Hargreaves-Samani公式的逐月回归修正     

夏兴生  潘耀忠  朱秀芳  张锦水 《农业机械学报》2020,51(3):258-267

为验证中国农业综合分区框架下Hargreaves-Samani(HS)公式线性回归修正方案的适用性,利用中国气象数据网发布的124个站点1957—2016年的逐月有效日平均气压、平均最低气温、平均最高气温、平均风速、平均水汽压、月总太阳辐射数据及站点经纬度数据,首先,分别基于Penman-Monteith(PM)公式和HS公式计算了各站点多年逐月的参考作物需水量ET_(0-PM)和ET_(0-HS)。然后,以ET_(0-PM)为真值,基于1957—2010年的逐月ET_(0-PM)和ET_(0-HS),利用线性回归分析方法获取了中国38个农业管理子区的HS公式校正系数a、b,并以2011—2016年为验证年份,通过比较ET_(0-HS)校正前后的相对误差变化,验证了HS公式线性回归校正方法在中国农业区的适用性,并结合验证年份的具体误差结果,确定了各农业区HS公式校正系数a、b的逐月最优取值。结果表明:大部分农业区的大部分月份ET_(0-PM)与ET_(0-HS)的相关系数超过0. 6,可以进行ET_(0-HS)的回归校正;回归校正得到的系数a存在显著的季节变化规律,系数b则表现较为平稳;系数a、b的大小及变化说明了ET_(0-PM)和ET_(0-HS)彼此之间存在差异,且季节性明显;校正前后的ET_(0-HS)均存在不同程度的相对误差,但校正后的ET_(0-HS)的误差范围已经显著缩小;在具体的验证应用中,校正后的ET_(0-HS)并不完全是最优结果,实践中系数a、b的优选使用才是最佳方案。本研究验证的HS公式线性回归校正方法是实践中简便、可行的方案,对大尺度区域快速获得较高精度的参考作物需水量具有实际意义和推广价值。  相似文献   

基于光合有效辐射瞬时值估算日均值的方法     

张璟  谢亚楠  汪鸣泉  王茂华 《干旱区研究》2019,36(1):220-227

光合有效辐射是太阳辐射的一部分,是植被进行光合作用和陆地生态系统碳循环的核心因素,对估算植被生产力具有重要影响。本文基于SURFRAD多年观测数据,建立了一个线性回归模型,由上午、下午瞬时光合有效辐射值估算日均值。该模型模拟效果较好,单个观测站的均方误差低于9 W·m^-2,判定系数不低于0.96,并适用于不同经纬度、气候条件和海拔高度下的区域,总的均方误差为8.863 1 W·m^-2,判定系数R2为0.977,表明该模型和方法有较好的可行性和可靠性。  相似文献   

Catch per unit effort standardization of the eastern Bering Sea walleye pollock (Theragra chalcogramma) fleet     

Brian C. Battaile  Terrance J. Quinn II   《Fisheries Research》2004,70(2-3):161-177

A general linear model (GLM) was used to standardize catch per unit effort (CPUE) data for Alaska walleye pollock (Theragra chalcogramma) from the Bering Sea fleet for the years 1995–1999. Data were stratified temporally by year and season and spatially by area using either Alaska Department of Fish and Game (ADF&G) or National Marine Fisheries Service (NMFS) reporting areas. Four factors were used: vessel identification (ID) number, vessel speed, percentage of pollock by weight in the haul (a measure of targeting), and whether most of the haul took place before or after sunset. At least 29 combinations of main effects, quadratic covariates, and interactions were tested for each year/area/season stratum. GLM models explained from 31 to 48% of the total sums of squares. Vessel identification number was included in all models and explained the most variability. Of the remaining factors, the square of the percentage of pollock in the haul was included in most models, following an F-test to determine parsimony. Analysis of the vessel identification number coefficients indicated that larger vessels tended to have higher CPUEs; and that this relationship differed between dedicated catcher vessels and offshore catcher processors. Coefficient estimates and response surfaces generally indicated increased CPUEs with the percentage of pollock in the haul and showed mixed results with vessel speed. The vessel identification number incorporated most vessel characteristics, leaving vessel speed primarily as a fitting variable with less biological meaning. The year/area/season stratification procedure was found to be necessary due to the unbalanced design, which otherwise would have factor levels with no data in a large combined model. In addition, the stratification procedure reduced the variability in CPUE substantially.  相似文献   

基于线性混合模型的蓝点马鲛叉长和体重关系的月间及性别差异     

瞿俊跃  方舟  陈新军 《中国水产科学》2020,27(8):953-960

为了研究蓝点马鲛（）生活史特征的异质性,根据2018年10月至2019年3月在东海外海渔场的拖网调查采样数据,对其叉长和体重关系的月间及性别差异进行了研究。依据收集的367尾蓝点马鲛样本,求得其叉长和体重关系（b的估计均值为2.794。本研究构建了广义线性模型和9个线性混合模型,用于研究蓝点马鲛的叉长和体重关系（）在时间及性别上的差异。贝叶斯信息准则（BIC）值和均方根误差值均表明,最复杂的线性混合模型（即月份和性别对两个参数P<0.01）。在最优模型中,a值则与此相反。本研究表明,月份和性别对蓝点马鲛叉长和体重关系具有显著的影响,线性混合模型能把月份和性别的异质性通过随机效应在单个模型中更准确、快速地体现,从而进一步证实了此模型在数据来源异质性研究中的优势。  相似文献   

Predicting the age of fish using general and generalized linear models of biometric data: A case study of two estuarine finfish from New South Wales, Australia     

Faith A. Ochwada  James P. Scandol  Charles A. Gray 《Fisheries Research》2008,90(1-3):187-197

Direct ageing of fish can be a laborious and expensive task when age estimates from a large population are required, and often involves a degree of subjectivity. This study examined the application of general and generalized linear models that predict the age of fish from a range of efficiently and objectively measured covariates. The data sampled were from yellowfin bream (Acanthopagrus australis (Sparidae) (Owen, 1853)) and sand whiting (Sillago ciliata (Sillaginidae) Cuvier, 1829) populations from New South Wales, Australia. The covariates evaluated in the models were fish length, otolith weight, sex and location (the estuary from which the fish were sampled). Akaike Information Criteria were used for model selection and residual plots of the final models revealed a satisfactory fit to the observations. The best fitting model for each species included all covariates. An additional investigation considered whether general and generalized linear models that predict age from two different categories of biometric information outperform age-length keys with respect to subsequent estimates of total mortality from catch-curve analysis. The two categories of biometric information differed in the ease and cost with which the information could be collected. The first category only included fish length and location as covariates, whilst the second category also included otolith weight and sex. It was found that traditional age-length keys outperformed the predictive models that estimated age from only fish length and location, because the results from the models were prone to significant bias. However, when otolith weight and sex were added as covariates to the predictive models, some of them, including a generalized linear model with a Poisson-distributed response variable, performed similarly to the age-length key. Given that otolith weight and the sex of fish are cheaper to quantify than age from a sectioned otolith in many situations, general or generalized linear models may represent a cheaper and faster method of estimating mortality compared to age-length keys. Such models can also easily incorporate the influence of spatial, temporal and demographic variation.  相似文献   

Application of the Tweedie distribution to zero-catch data in CPUE analysis   总被引：2，自引：0，他引：2  

Hiroshi Shono   《Fisheries Research》2008,93(1-2):154-162

We focus on the zero-catch problem of CPUE (catch per unit effort) standardization. Because the traditional CPUE model with a log-normal error structure cannot be applied in this case, three methods have often been utilized as follows:

(1) Ad hoc method adds a small constant value to all response variables.

(2) Catch model with a Poisson or negative-binomial (NB) error structure.

(3) Delta-type two-step method such as the delta-normal model (after estimating the ratio of zero-catch using a logit or probit model, a model such as CPUE log-normal or Catch-Poisson is applied to CPUE without zero-data).

However, there are some statistical problems with each of these methods.In this paper, we carried out the CPUE standardization mainly using the Tweedie distribution model based on the actual by-catch data (silky shark, Carcharhimus falciformis, in the North Pacific Ocean caught by Japanese training vessels) including many observations with zero-catch (>2/3rd) and tuna fishery data as a target (yellowfin tuna, Thunnus albacares, in the Indian Ocean caught by Japanese commercial vessels) where the ratio of zero-catch is not so high (<1/3rd). The Tweedie model is an extension of compound Poisson model derived from the stochastic process where the weight of the counted objects (i.e., number of fish) has a gamma distribution and has an advantage of handling the zero-catch data in a unified way.We also compared four candidate models, the Catch-NB model, ad hoc method, Delta-lognormal model (delta-type two-step method) and Tweedie distribution, through CPUE analyses of actual fishery data in terms of the statistical performance. Square error and Pearson's correlation coefficient were calculated based on the observed CPUE and the corresponding predicted CPUE using the n-fold cross-validation.As a result, the differences in the trend of CPUE between years and model performance between the ad hoc method and Tweedie model were found to be not so large in the example of yellowfin tuna (target species). However, the statistical performance of Tweedie distribution is rather better than Delta-lognormal model, the Catch-NB distribution and ad hoc method in the example of silky shark (by-catch species). Standardized CPUE year trend of ad hoc method was found to be quite different from that of the Tweedie distribution and other two models. Model performance of the Tweedie distribution is good judging from the 5-fold cross-validation using the fishery data if including many zero-catch data such as by-catch species.  相似文献   

一类二元正态分布随机变量的线性函数相互独立的充要条件     

金秀岩 《河北北方学院学报(自然科学版)》2007,23(2):10-12

根据随机变量相互独立的条件,推导了二元正态分布随机变量的线性函数1η=pξ1 q2ξ与2η=m1ξ n2ξ相互独立的充要条件是nqσ22 rσ12σ(np mq) mp21σ=0(其中m、n、p、q为非零实数,且np-mq≠0),并做了详细证明.在此基础上说明了随机变量1ξ 2ξ与1ξ-2ξ以及1ξcosα 2ξsinα与-1ξsinα 2ξcosα相互独立的充要条件是本文的特例.  相似文献