$$\mathcal{D}$$-optimal Minimum Support Mixture Designs in Blocks

An easy method to construct efficient blocked mixture experiments in the presence of fixed and/or random blocks is presented. The method can be used when qualitative variables are involved in a mixture experiment as well. The resulting designs are -optimal in the class of minimum support designs. It is illustrated that the minimum support designs are more efficient than orthogonally blocked mixture experiments presented in the literature and only slightly less efficient than -optimal designs.     

一种基于信干比门限反馈的MIMO下行系统自适应传输策略

以降低系统反馈为目标,提出一种在多天线下行系统基于信干比门限反馈的自适应传 输策略。基于正交随机波束成形,提出仅当用户最大信干比超过门限时才将最大信干比和对 应的波束序号反馈给基站,并给出了系统平均总速率与该信干比门限的关系表达式。仿真结 果表明,通过选取有效的信干比门限,可在几乎不降低总速率的情况下,系统反馈极大降低 。     

收益波动与随机冲击的非对称性影响：中国与美国股票市场的对比

通过讨论股票收益与随机;中击之间的关系,对中国股票市场和美国股票市场进行了对比研究。研究中使用了中国上海和深圳股票市场1990年12月31日至2005年12月30日的两市A股算术平均周指,以及美国股票市场1973年1月2日至2004年月12月30日的标准普尔500周指。在进行经验研究的过程中,分别使用了线性GARCH模型和GJR—GARCH模型计量股票收益的条件波动——即模型中的条件方差。研究发现,中国股票市场自1990年——1995年波动剧烈,之后波动趋于平缓,而美国股票市场在研究期间内收益波动一直处于一定范围内。同时还发现,美国股票市场的随机冲击对股票收益产生非对称性影响,即负冲击使股票收益产生的波动大于正冲击。而在中国股票市场却找不到相似的证据。鉴于对中国股票市场收益波动的研究结果,在剔除1996年以前的数据之后又进行了扩展研究,但是似然比率检验结果表明,正冲击对股票收益的影响还要略强于负冲击。     

农业信贷对我国农业经济增长贡献的实证分析

文章利用面板数据基础上的随机效果模型对2000￣2003年间我国农业信贷对农业经济增长的贡献作出实证分析。研究结果表明,我国农业信贷与农业经济增长之间存在正相关关系,增加农业信贷投入,可以提高农业产出水平。因此应不断改善农业信贷环境,增加农业信贷供给,以促进农业产出的增加。     

面向新闻领域的中文实体关系抽取

随着互联网技术的快速发展,人们能够及时地获取大量的新闻文本信息,如何从新闻中自动获取关键信息,把新闻中具有价值的信息转化为结构化数据,从而快速有效地获取有用的知识已是迫切需求。实体关系抽取是获取关键信息的方法之一,但目前关于中文的实体关系抽取工作较少。针对基于长短时记忆网络的中文实体识别模型难于提取长距离的依存关系特征和句法特征问题,提出利用双向树形长短时记忆神经网络提取依存句法树的结构特征。在提取的特征的基础上,使用条件随机场判断实体的类别和边界,并在实体识别模型中加入注意力机制提高模型的性能。在《人民日报》数据集和ACE 2005语料库上训练模型,验证了模型的有效性。     

Willingness to Pay for Rural Landscape Improvements: Combining Mixed Logit and Random‐Effects Models

This paper reports the findings from a discrete‐choice experiment designed to estimate the economic benefits associated with rural landscape improvements in Ireland. Using a mixed logit model, the panel nature of the dataset is exploited to retrieve willingness‐to‐pay values for every individual in the sample. This departs from customary approaches in which the willingness‐to‐pay estimates are normally expressed as measures of central tendency of an a priori distribution. Random‐effects models for panel data are subsequently used to identify the determinants of the individual‐specific willingness‐to‐pay estimates. In comparison with the standard methods used to incorporate individual‐specific variables into the analysis of discrete‐choice experiments, the analytical approach outlined in this paper is shown to add considerable explanatory power to the welfare estimates.     

基于随机森林算法的洪水灾害风险评估研究

根据流域灾害系统理论,在考虑致灾因子、孕灾环境和承灾体的基础上,选取9个风险评价指标,运用样本数据进行人工识别风险并得到训练样本,采用随机森林算法构建基于随机森林的洪水灾害风险评估模型。然后采用随机森林自评估工具,分析建立的洪水灾害风险评估模型的误差和指标,同时构建支持向量机模型作为对比方案,并采用五折交叉验证方法对基于随机森林算法的洪水灾害风险评估模型和支持向量机模型进行验证。最后以海河流域邱庄段为研究对象,分别运用基于随机森林算法的洪水灾害风险评估模型和基于支持向量机模型对相同的数据集进行评估和对比,结果显示,12 h内降雨总量、洪水持续时间和土壤含水量是引发洪水的主要因素,而基于随机森林算法的洪水灾害风险评估的训练精度及测试精度均高于支持向量机模型。     

构建基于VBA的PowerPoint随机指派系统

课堂提问是教学过程重要一环,通过师生问答互动,教师可以了解学生的接受程度,同时也鼓励学生积极思考。但现状是,教师经常面对学生遇见提问就低头的尴尬境地。针对在大学课堂教学过程中教师提问所面临的学生“集体沉默”这个普遍现象,文中利用VBA在PowerPoint中实现了一个随机指派系统,通过该系统随机指定回答问题的学生,提高了学生思考问题的积极性,活跃了课堂气氛。     

分形图及图案设计

本文讨论了各种分形图及在图案设计中的应用 ,并提出了利用这些分形图生成图案的一些方法。     

Assessing cost‐effectiveness when environmental benefits are bundled: agricultural water management in Great Barrier Reef catchments

Using economic analysis to prioritise improvements in environmental conditions is particularly difficult when multiple benefits are involved. This includes ‘bundling’ issues in agricultural pollution management, where a change in management action or farming systems generates multiple improvements, such as reductions in more than one pollutant. In this study, we conceptualise and compare two different approaches to analysing cost‐effectiveness when varying bundles of benefits are generated for a single project investment. Each approach requires data to be transformed in some way to allow the analysis to proceed. The index approach requires the transformation on the benefits side so that the effects of multiple pollutant changes can be combined into a measure for each project which can then be compared to costs. By comparison, the disaggregation approach requires the transformation on the costs side where costs for each project have to be apportioned across the different pollutants involved. The paper provides novel insights with an application to agricultural water quality improvements into the Great Barrier Reef in Australia, demonstrating that while both approaches are effective in prioritising projects by cost‐effectiveness, the disaggregation approach provides more insightful results and values that may be relevant for use as upper value guidelines in future project selection.