Towards flexible management of postharvest variation in fruit firmness of three apple cultivars

Stochastic modeling provides a useful tool in managing biological variation in the postharvest chain. In the current study, the fruit-to-fruit variability in the postharvest firmness of apples was modeled. Apples from three cultivars (‘Jonagold’, ‘Braeburn’, and ‘Kanzi’) were harvested at different levels of maturity, and stored at different temperatures and controlled atmosphere (CA) conditions. By using a kinetic model describing firmness breakdown as a function of time, temperature, controlled atmosphere conditions and endogenous ethylene concentration, the main stochastic variables were identified as the initial firmness and the rate constants for firmness breakdown and ethylene production. Treating these variables as random model parameters, the Monte Carlo method was used to simulate the propagation of the fruit-to-fruit variability in flesh firmness within a batch of apples during storage under different CA conditions and subsequent shelf-life exposure. The model was validated using independent data sets from apples picked in a different season. The model developed in this study can be used to predict the probability of having apples of certain firmness after long term storage for different scenarios of temperatures and CA conditions.     

Simulation analysis of the effect of herd immunity and age structure on infection of a cattle herd with bluetongue viruses in Queensland, Australia

A state-transition model based on Leslie matrix formulation was used to investigate the effects of herd immunity and age structure on the infection of a simulated cattle herd with bluetongue viruses under Australian climatic conditions. Increasing duration of immunity decreased the prevalence of infection. A duration of immunity of 33 months was consistent with prevalence estimates made from previous serological studies of bluetongue virus. Herd prevalence displayed slowly dampening cyclical variation over time (most pronounced when a short duration of immunity was simulated). Increasing calving and mortality risk rates in the simulated herd increased prevalence, whereas increasing age at first calving decreased prevalence. Manipulation of calving rates had the greatest effect on the predicted prevalence of infection in the herd. Simulation of a number of herd-management scenarios suggested that management systems in which cattle are bred early and where high calving rates are achieved are likely to contribute to high levels of infection with bluetongue viruses. Results confirm the importance of management factors in influencing the prevalence of infectious diseases in animal populations.     

斜纹夜蛾幼虫存活过程的神经网络模型的建立

利用BP神经网络对斜纹夜蛾幼虫的存活过程进行建模分析,给出了BP神经网络建模的Matlab算法程序。结果表明,BP神经网络能充分逼近斜纹夜蛾幼虫的存活过程曲线,使用BP神经网络可对斜纹夜蛾幼虫的存活过程进行有效的建模。利用所建立的模型,得到了关于斜纹夜蛾幼虫存活过程的模拟预测结果。不同温度下斜纹夜蛾幼虫种群的死亡过程有所不同。在20,24,36和40℃温度下,斜纹夜蛾幼虫种群的死亡高峰分别出现在卵孵化后20d左右,5～20d,5～10d及3～6d。最后,对神经网络建模的特点,以及影响BP神经网络建模效果的主要因素进行了分析讨论。     

基于特征的敏捷界面原型驱动开发过程框架

提出了一种基于特征的敏捷界面原型驱动开发过程框架(AIDD),给出了相应的形式化描述.基于该AIDD过程框架,结合项目实例,分析了如何应用该框架,实现从需求分析到有效设计的快速切换;将应用该过程的项目与其他规模相当的项目进行比对分析,结果表明:AIDD框架具备一定的理论基础并符合工程原则,解决了从需求到设计的快速切换问题,提高了以数据为中心的应用系统设计的质量和效率.     

由汉诺塔游戏想到的汉诺塔简单非递归算法

汉诺塔问题是一个古典的数学问题，也是程序设计中的经典递归问题，其递归算法由于简洁清晰，为大家所熟悉，编写出来的程序也比较简单，缺点是占用太多的内存空间。本文对汉诺塔问题进行了数学建模，并用几个简单的判断条件，对问题迅速求解，程序用C语言实现。     

时序建模及其在农药降解动态模拟中的应用

用数学方法对农药残留量进行预测预报及动态模拟，对于合理使用农药，加强环境保护具有重要意义．作者用时间序列分析的理论与方法，研制农药残留定量预测模型，给出参数估计，提出非平稳时序叠合模型，对农药降解规律进行动态模拟，并以剩余平方和作为优化标准与其他方法进行比较．实例计算结果表明：时序模型预测值与实测值拟合程度优于其他模型，简便实用     

卫星遥感估产技术的发展与展望

在简述遥感估产的基本原理、程序及研究进展的基础上，对遥感估产模型进行了评价，并介绍了面积估算方法的发展趋势。遥感信息源的分辨率越来越高，3S、建模与农业、生态、计算机应用等技术相结合，为遥感估产打下了良好基础，从而使建立集高时效性、高精度、可操作性强、易于业务化等优点于一身的优秀的遥感估产系统成为可能。     

吡虫啉对小十三星瓢虫幼虫-枸杞蚜虫的时间-剂量-死亡率模拟分析

进行了吡虫啉对小十三星瓢虫幼虫-枸杞蚜虫的综合作用研究,所获数据经时间-剂量-死亡率模型分析,结果表明,吡虫啉对枸杞蚜虫药后1 d的各致死浓度:LC50~LC99为3.0255~17.5711μg/mL,药后5 d的LC50~LC99为0.6551~3.8036μg/mL;对小十三星瓢虫幼虫药后1 d的各致死浓度:LC50~LC99为1.8655~21.9584μg/mL,药后4 d的LC50~LC99为0.4811~5.6624μg/mL;致死浓度和致死时间,两者互为函数关系;进一步研究了吡虫啉直接处理后不同时间的小十三星瓢虫幼虫对蚜虫的取食量,高剂量处理的捕食量小于低剂量处理的捕食量,且日捕食量随时间延长而减少。     

ASCM中的虚拟企业合作伙伴评价体系研究

基于现代企业敏捷供需链管理(ASCM)的需求现状，以虚拟企业的构建为研究对象，分析了现代企业管理方式的变革及其不同的市场适应性．在此基础上提出了虚拟企业建模过程中合作伙伴选择的评价体系及主要的评价方法．     

枯草芽孢杆菌新抗病基因aiiA的克隆

枯草芽孢杆菌内生亚种BS-1aiiA基因测序结果表明,该基因(GenBank登录号DQ000640)由753个碱基组成,其编码的蛋白质含有250个氨基酸残基,与10个已报道的具有减弱欧文氏菌胡萝卜亚种致病力的AiiA蛋白酶氨基酸序列总的相似性为82%.它们均含有相同的氨基酸序列保守区.Signal P分析结果显示,BS-1 AiiA没有信号肽序列,并利用Swiss-model预测、分析了BS-1 AiiA蛋白的三维结构.