消费者对蓝莓产品的购买意愿及其影响因素的实证研究 ——基于吉林省消费者调查

 【目的】考察消费者购买蓝莓产品的意愿及其影响因素。【方法】采用Logistic计量模型,设计变量,对消费者购买蓝莓产品的意愿及其影响因素进行分析。【结果】多种因素影响消费者购买蓝莓产品,其中消费者性别、家庭月收入、蓝莓产品口感、品牌形象、时尚宣传对消费者购买意愿有正向影响;而消费者婚姻状况、比较购买行为、对礼品、包装和保健品关注程度对消费者购买意愿有负向影响。【结论】选择性别、档次、功能作为标准进行市场细分,打造中、高端市场,进而加强消费者对于蓝莓产品的认知,拉动需求。     

生鲜农产品物流安全质量动态监测体系构建

近年来,我国食品安全问题频频出现,给社会带来了极大恐慌。本文在分析研究我国生鲜农产品物流现状的前提下,指出要确保生鲜农产品物流全过程的安全首先应具备一定的条件基础,并且在这个基础上从生鲜农产品物流结构和物流信息网络两方面来构建农产品物流安全质量动态检测体系。     

Detection of cows with insemination problems using selected classification models

In the present study, the detection of cows with artificial insemination (AI) difficulties using selected statistical and machine learning methods is presented. Cows were divided into two classes: those that conceived after one or two services (“GOOD”) and those that required more than two services per conception (“POOR”). The best performance was exhibited by one of the artificial neural networks (ANN) and the multivariate adaptive regression spline (MARS) method (AIC, BIC, RMS and accuracy); whereas logistic regression (LR) and classification functions (CF) were of somewhat lower quality. The detection of cows with AI difficulties, performed on the basis of the test set comprising new instances, showed that the ANN and MARS were more precise in comparison with the statistical methods. Sensitivity and specificity were over 85% for the perceptron with two hidden layers (MLP2) and MARS and approximately 80% or lower for LR and CF. From among variables determining the AI category, the average calving interval and cow body condition index were the most important. Other significant variables were lactation number, pregnancy length, sex of calf from previous calving and cow age. The prognoses obtained using ANN and MARS can be used for the appropriate preparation of cows for AI.     

重庆市璧山县农户农地流转意愿研究

农地流转是解决农村土地利用细碎化、撂荒及闲置的有效途径,对于优化土地资源配置,提高土地利用率有重要的现实意义.作为农地流转的供给者,农户农地流转意愿对农地使用权流转有着根本性的影响.文章以重庆市璧山县为例,通过对5个镇156户农户的随机抽样调研,采用Logistic回归模型定量分析了影响农户农地流转意愿的因素,以期为加快农地流转和培育农地流转市场提供量化的依据和支持.     

Growth analysis of the competition–density effect in non-self-thinning Populus deltoides and Populus?×?euramericana plantations

The competition–density (C–D) effect for non-self-thinning Populus deltoides and Populus × euramericana plantations from 3 to 9 years was analyzed using the reciprocal equation of the C–D effect. The C–D effect was well described by the reciprocal equation, and with the progress of time the C–D curve, on logarithmic coordinates, of the P. × euramericana plantations shifted upward faster than that of the P. deltoides plantations. With increasing physical time t, the biological time τ, i.e. the integral from zero to t of the coefficient of growth λ(t) in the general logistic curve with respect to t, increased rapidly during early growth stages and the increases in τ gradually became slow during later growth stages. This trend was more evident in the P. deltoides plantations than in the P. × euramericana plantations. The coefficients A and B included in the reciprocal equation were calculated at each growth stage. With increasing τ, the coefficient A, the reciprocal of which means the asymptote of yield (=wρ) at a given growth stage, increased abruptly to a maximum value and then tended to decrease gradually to a constant level. On the other hand, the coefficient B, the reciprocal of which means the asymptote of mean stem volume at a given growth stage, decreased exponentially and tended to be close to zero with increasing τ. The λ(t) decreased with increasing stand age, whereas the final yield Y(t) defined as W(t) ρ, where W(t) is the asymptote of w in the general logistic growth curve, increased gradually with increasing stand age. The differences in coefficients A, B, and λ(t) between the two species were reported.     

严重水分失衡状态下四照花蒸腾表面的削减

应用RGB图像分析的方法,研究了日本山口市街区生长的四照花（Comus kousa Buerg.）对2007年夏季干热多风的环境的响应。结果表明,许多四照花叶尖叶缘出现焦枯,清晰的暗棕色防护带显示在焦枯的叶片上。这些防护带逐渐从叶尖向叶基退缩直到成功控制焦枯为止,且留下许多不成功的防卫痕迹。焦枯的叶片呈现鲜明的逻辑斯蒂函数式变化趋势。依据气象数据分析,四照花叶片退缩型焦枯几乎与干燥峰值期同步。这表明在干燥度突然升高期间,极端的水分亏缺诱发了四照花的防卫反应,从而保护其余部分免于进一步的失水。像素分析结果表明,截止到2007年8月底四照花样树通过局部叶片退缩型焦枯减少了40.2%的叶面积。相比之下,鉴于上半年雨量充足,2008年,相同的样树只有13.2%叶面积减少。不管怎样,四照花的确削减了蒸腾表面积,并且表现出一种独特的蒸腾表面减少方式。既不同于落叶也不同于地上部枯死。依据脱水过程的分析,四照花在突然的干热胁迫下叶尖始发的干缩和叶片防卫反应的共同作用被认为是其蒸腾表面削减的关键所在。     

基于AHP法的物流园区选址模糊综合评判

为了给芜湖市物流园区布局提供规划依据,探讨最佳布局方案,通过分析物流园区选址的各种影响因素,引入层次分析法,建立了芜湖市物流园区选址的综合评价指标体系。最后用模糊综合评判法对方案进行综合评价,最后得出最优的物流园区布局方案。     

黄土丘陵区柠条灌木林合理平茬期的研究

本文根据柠条(Caragana korshinskii)生长的特点,即生长速率随灌木林龄的变化呈近似正态分布的特征曲线,根据曲线的几何特征,提出以柠条生长速率与峰值和右拐点连线的斜率相等的点为平茬始点,以几何曲线的右拐点为平茬终点的平茬方案。长期观测结果表明,柠条生长指标符合Logistic方程,本文以Logistic生长函数为例,说明了柠条灌木林平茬时间确定方法的具体推导过程。最后结合柠条生长指标(株高、分枝和生物量),对不同立地条件下柠条灌木林的合理平茬时间进行了探讨,结果表明,不同立地条件下柠条的合理平茬时间存在一定的差异,这种现象是由不同立地条件下水热环境的差异造成的。     

绿衣枳实生长规律模型模拟及其应用

建立了绿衣枳实生长量与时间的logistic模型和横径与单果重的动态分形模型,用以精确描述绿衣枳实生长过程和横径、平均单果重之间的动态分形关系,并能通过此模型预测采摘日期.结合日期与药效成分含量的关系间接地判断其质量优劣,从生产栽培和商品药材流通方面对绿衣枳实的质量进行控制.     

圭亚那柱花草抗寒性初步鉴定

以11个圭亚那柱花草种质为试材,热研2号柱花草为对照,用电解质渗透法作为指标,比较其抗寒性.结果表明,圭亚那柱花草半致死温度(LT_(50))范围在-0.17～-2.33℃之间,圭亚那柱花草种内抗寒性差异较小.CIAT11362、USF873004、GC1528、Mineirao和GC1576的半致死温度(LT_(50))低于热研2号柱花草.其它种质的LT_(50)高于热研2号柱花草.