基于Probit模型的果农技术采用行为研究

对农户技术采用行为影响因素的研究可以为技术扩散过程的优化与调控提供科学依据。选择两个果业种植专业村,对影响农户技术采用行为的因素进行了实际调查,并利用Probit模型进行了验证和确认。综合分析认为,农户科技文化素质、政府推广部门职能的发挥程度、空间距离、区域自然条件、中介组织的发育程度、技术本身的属性等是影响农户技术采用行为的主要因素,并提出了相关的政策建议。     

风险投资灵活性价值探索

本文从西方经济学生产要素理论出发,深入挖掘了风险投资项目灵活性价值的源泉,并引入二叉树期权定价模型进一步给出了一种风险投资项目灵活性价值的定量评估方法,最后通过案例应用,有效解决了风险投资项目灵活性价值评估问题。     

CEV模型下有离散红利支付的几何平均亚式期权的定价

首先阐述了标准几何亚式期权的涵义及其定价模型,介绍了CEV的涵义,然后借助PhelimP.Boyle和Yisong Tian为CEV模型下回望期权和障碍期权的定价技巧,利用二叉树逼近方法得到服从CEV过程且有离散红利支付的几何平均亚式期权的定价。     

从丧葬习俗看藏族地方社会的历史及文化——以四川甘孜藏族自治州山岩树葬为例

丧葬是一种文化现象,是文化人类学关注的重要议题之一。通过丧葬现象来解析地方文化也是人类学、民族学的一种研究视角,是人类学整体观的灵活应用。通过对山岩树葬文化的调查与分析,希望能有助于学界更好地解读当地的历史及文化现象。     

共和国知识分子的颂歌——评《大树西迁》

<大树西迁>是陕西省戏曲研究院精心打造的秦腔现代戏,她以苏毅、孟冰茜一家三代西迁50年的奋斗历程为线索,再现了西安交大50年的风云变幻,讴歌了共和国知识分子"哪里有事业哪里有爱,哪里就是家"的生存理念,展示了知识分子对祖国、对人民、对事业及对亲人的至深情感.剧作构思精巧,舞台效果美轮美奂.     

基于神经网络和决策树相结合的信用风险评估模型研究

文章提出了一种将神经网络和决策树相结合的信用风险评估模型NN-DT。该方法依据属性重要性将贷款企业的财务指标进行排序,然后通过RBF神经网络进行属性裁减生成决策树,从而得出企业是否违约的分类。最后以判别分析以及C4.5 算法为参照方法进行了实证研究,结果表明,NN-DT模型显著地提高了预测精度。     

用关系数据库实现层次模型数据库的方法探讨

结合数据结构与数据库系统理论 ,利用 FOXPRO系统实现层次模型数据库的存储、检索、遍历、插入和删除等基本算法     

论古典诗词中的"梧桐"意象

意象是古代文学作品中的一个基本范畴,特别是中国古典诗词,可以说是由无数意象构建成的艺术殿堂.梧桐,在现代日常生活中是一种普通的树木,但从意象初创时期的<诗经>一直到清词,"梧桐"意象频繁出现在古代文学作品中,并具有富贵、祥瑞、爱情、愁苦等审美意蕴.在反复使用和沿袭不衰的过程中,文人们用情感的链条,将它与其他意象组合,形成了丰富多彩的复合意象群,用来烘染氛围,营造意境,表达了不同的抒情主题.     

Bayes linear analysis for graphical models: The geometric approach to local computation and interpretive graphics

This paper concerns the geometric treatment of graphical models using Bayes linear methods. We introduce Bayes linear separation as a second order generalised conditional independence relation, and Bayes linear graphical models are constructed using this property. A system of interpretive and diagnostic shadings are given, which summarise the analysis over the associated moral graph. Principles of local computation are outlined for the graphical models, and an algorithm for implementing such computation over the junction tree is described. The approach is illustrated with two examples. The first concerns sales forecasting using a multivariate dynamic linear model. The second concerns inference for the error variance matrices of the model for sales, and illustrates the generality of our geometric approach by treating the matrices directly as random objects. The examples are implemented using a freely available set of object-oriented programming tools for Bayes linear local computation and graphical diagnostic display.     

Preference in flower visits and partitioning in pollen diets of stingless bees in an Asian tropical rain forest

Floral resource partitioning among stingless bees (Trigona, Meliponini, Apidae) in a lowland rain forest in Sarawak, Malaysia, was investigated using tree towers and walkways in a 4-year study that included a general flowering period. We obtained 100 collections of insect visitors to flowers of varying floral location and shape representing 81 plant species. The tendency of 11 species of stingless bees to visit specific flowers with a particular floral location and shape was analyzed by logistic regression analysis. This analysis showed that the proportion of flower visitor collections containing Trigona fuscobalteata and T. melanocephala differed according to floral location. The former was frequently collected at canopy and gap flowers, whereas the latter was most often collected at understory flowers. The analysis also suggested that T. erythrogastra was more rarely collected at shallow flowers than at deep flowers. Analysis of the pollen diets of T. collina, T. fuscobalteata, T. melanocephala, and T. melina revealed that similarity of pollen sources differed among the six permutated pairs of the four species. The lowest mean rank of similarity found was between T. fuscobalteata and T. melanocephala. This result supports the hypothesis that preference in visiting flowers in different locations leads to pollen resource partitioning. Received: May 14, 1997 / Accepted: April 23, 1999