共查询到19条相似文献,搜索用时 125 毫秒
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本文根据农业系统工程的原理,应用二次回归正交旋转组合设计的方法,将对玉米生育影响较大的主要裁培因素做为决策变量以最大的产量指标做为目标函数,通过田间试验和生产实施,对影响玉米生产的各个要素进行了模型化研究,应用微机进行了参数测辨和统计分析,建立了产量函数模型,解析了各因子的产量效应和交互作用。通过模拟寻优,优选出了本市玉米生产最优的综合农艺措施方案。 相似文献
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本文根据农业系统工程的原理,应用二次回归正交旋转组合设计的方法,将对玉米生育影响较大的主要栽培因素做为决策变量以最大的产量指标做为目标函数,通过田间试验和生产实施,对影响玉米生产的各个要素进行了模型化研究,应用微机进行了参数测辨和统计分析,建立了产量函数模型,解析了各因子的产量效应和交互作用。通过模拟寻优,优选出了本市玉米生产最优的综合农艺措施方案。 相似文献
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采用三因子五水平二次回归通用旋转组合设计试验,应用回归分析方法建立了洋芋丰产栽培技术模型,并进行了因子效应、交互效应、综合农艺措施寻优等方面的分析,获得高产优化农艺方案。 相似文献
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安徽省农业投入产出效果分析 总被引:6,自引:0,他引:6
应用回归等多种数学模型,分不同时段对安徽省农业投入产出的变动关系进行了深入细致地分析,得出了积极有益的结论,为农业可持续发展战略提供了理论依据 相似文献
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针对新疆北部地区在玉米生产过程中存在的水肥利用率低下问题,提出一种基于麻雀搜索算法和广义回归神经网络模型的玉米产量预测方法,以探索水肥因素与玉米产量间的非线性关系,可为优化新疆北部地区春播玉米灌溉制度及水肥配饰方略提供理论指导.该方法采用36组既有玉米生产数据,通过广义回归神经网络技术建立模型,使用麻雀搜索算法对关键参数进行优化,降低了人为因素对模型超参数选择的影响.该模型用于新疆灌溉中心试验站的玉米产量预测仿真实验,证明该模型预测性能良好,相较于传统模型,在学习速度、预测精度及鲁棒性上具有优势,可有效预测新疆北部地区春播玉米产量. 相似文献
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回归设计在作物间作技术研究中的应用 总被引:16,自引:0,他引:16
本研究采用回归正交组合设计的方法,选择春玉米间作春大豆的畦幅、春玉米密度、春大豆密度三个农艺因子,布置田间参数试验,通过对试验结果的分析,建立了春玉米间作春大豆的总产、春玉米产量、春大豆产量及净产值的三元二次回归模型。根据建立的模型,进行了因子效应分析,并结合计算机模拟寻优,对春玉米间作春大豆的畦幅及其复合群体结构进行了优化。 相似文献
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《数学的实践与认识》2017,(24)
通过建立船舶-货物的亚洲区域化学品船航运市场动态预测模型,对区域内船舶营运情况作了分析.并运用市场变量相关航运市场景气程度的回归关系,应用系统动力学模拟的结果加入到回归模型中对实际船舶运营期租水平进行解释,对回归方程进行敏感性分析,优化模型,得到亚洲市场化学品船期租水平与各市场变量的系数关系,首次提出化学品船期租水平运价指数,并为亚洲航线化学品船远期期租水平指数的交易、与相关产品的价格对冲、套期保值等操作的可能性提出理论基础. 相似文献
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Copula函数具有可以准确刻画变量间的相依结构、精准描述金融时间序列"尖峰厚尾"分布特点的良好统计性质.针对传统计量模型在计算套期保值比率时存在的局限性,利用Copula函数描述变量的尾部相关性,并结合ECM-GARCH模型,对大豆、小麦、玉米三种国内农产品期货进行套期保值研究,分别计算最优的套期保值比率及其绩效,并与OLS、B-VAR、ECM和ECM-GARCH模型进行比较.结果表明,对于大豆来说,运用Copula-ECM-GARCH模型计算得到的套期保值比率进行对冲操作,可以最大化降低现货市场的价格风险,为投资者提供了一种可以更好规避价格风险的工具选择. 相似文献
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中国玉米期货市场价格发现功能的实证分析 总被引:4,自引:0,他引:4
利用相关系数、协整检验、格兰杰因果检验以及GS模型等方法对大连期货交易所玉米期货市场的发现价格功能进行了实证分析.结果表明:玉米期货价格与现货价格之间存在协整关系,期货价格具有良好的发现价格功能;存在期货价格和现货价格的双向格兰杰引导关系;玉米期货市场的发现价格功能中期货价格起着决定性的作用. 相似文献
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运用灰色系统理论的灰色关联分析方法,分别对西藏林芝地区玉米地膜与露地栽培主要性状与产量之间的关系进行了探讨.分析结果表明,两种种植方式都表现为果穗粒重对产量影响最大.在玉米地膜栽培条件下,果穗重、单株绿叶面积对其产量影响较大,株高、秃顶长对其产量影响较小;在玉米露天栽培条件下,百粒重、果穗重对其产量影响较大,秃顶长、单株绿叶面积对其产量影响较小. 相似文献
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由于GrangerN果关系检验的局限性,使农产品价格上涨与通胀之间因果关系的传导方向一直存在争议.为此,本文用似无关回归模型(SUR)和广义脉冲响应函数(GIRF)相结合的组合研究模式对农产品价格上涨和通胀之间的因果关系进行了实证研究.首先,利用似无关回归模型构造统计量检验各种传导机制的存在性;其次,在农产品价格上涨与通胀之间双向传导机制都存在的情况下,利用广义脉冲响应函数方法对各种传导机制的显著性进行了对比.结论认为,农产品价格上涨导致通胀的因果关系更显著. 相似文献
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The variational relation problems have been introduced in 2008, by Dinh The Luc, as general models for a large class of problems in nonlinear analysis and applied mathematics. Since this manner of approach proved to be a powerful tool for studying a wide class of problems in nonlinear analysis and applied mathematics, several types of variational relation problems or systems of variational relation problems have been investigated in many recent papers. The present paper fits into this interesting group of works, establishing existence criteria for the solutions of two very general types of variational relation problems. 相似文献
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The supply chain of agricultural products has received a great deal of attention lately due to issues related to public health. Something that has become apparent is that in the near future the design and operation of agricultural supply chains will be subject to more stringent regulations and closer monitoring, in particular those for products destined for human consumption (agri-foods). This implies that the traditional supply chain practices may be subject to revision and change. One of the aspects that may be the subject of considerable scrutiny is the planning activities performed along the supply chains of agricultural products. In this paper, we review the main contributions in the field of production and distribution planning for agri-foods based on agricultural crops. We focus particularly on those models that have been successfully implemented. The models are classified according to relevant features, such as the optimization approaches used, the type of crops modeled and the scope of the plans, among many others. Through our analysis of the current state of the research, we diagnose some of the future requirements for modeling the supply chain of agri-foods. 相似文献
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Songsak Sriboonchitta Hung T. Nguyen Aree Wiboonpongse Jianxu Liu 《International Journal of Approximate Reasoning》2013,54(6):793-808
Volatility and dependence structure are two main sources of uncertainty in many economic issues, such as exchange rates, future prices and agricultural product prices etc. who fully embody uncertainty among relationship and variation. This paper aims at estimating the dependency between the percentage changes of the agricultural price and agricultural production indices of Thailand and also their conditional volatilities using copula-based GARCH models. The motivation of this paper is twofold. First, the strategic department of agriculture of Thailand would like to have reliable empirical models for the dependency and volatilities for use in policy strategy. Second, this paper provides less restrictive models for dependency and the conditional volatility GARCH. The copula-based multivariate analysis used in this paper nested the traditional multivariate as a special case (Tae-Hwy and Xiangdong, 2009) [13]. Appropriate marginal distributions for both, the percentage changes of the agricultural price and agricultural production indices were selected for their estimation. Static as well as time varying copulas were estimated. The empirical results were found that the suitable margins were skew t distribution and the time varying copula i.e., the time varying rotate Joe copula (270°) was the choice for the policy makers to follow. The one-period ahead forecasted-growth rate of agricultural price index conditional on growth rate of agricultural production index was also provided as an example of forecasting it using the resulted margins and time-varying copula based GARCH model. 相似文献