基于特定主题的社交网络影响力评估方法

针对用户在社交网络应用中的影响力评价方法，以往的研究重点关注网络结构和转发行为对用户影响力的影响，基于用户发布内容和主题的影响力评估研究较少，且未考虑主题间的交互关系.为此提出了一种半监督的主题提取方法，通过在初始化过程中引入种子词并赋予不同的权重，更好地提取目标主题.此外，为了提高用户影响力评估的效果，该文考虑了不同主题之间的交互，将主题之间的相似性叠加于用户相似性的计算.在真实数据上的实验结果验证了所提方法的有效性.     

基于非线性混合效应模型的针阔混交林地位指数研究

基于非线性混合效应模型和树种间地位指数转换方程，建立混交林中不同树种地位指数混合效应模型，为多树种混交林立地生产力评价提供科学依据。     

Function,persistence, and selection: Generalizing the selected-effect account of function adequately

The selected effect account is regarded by many as one of the most attractive accounts of function. This account assumes that the function of a trait is what it has been selected for. Recently, it has been generalized by Justin Garson to include cases in which selection is understood as a simple sorting process, i.e., a selection process between entities that do not reproduce. However, once extended, this generalized selected effect account seems to ascribe functions to entities for which it looks unintuitive to do so. For instance, the hardness of rocks on a beach being differentially eroded by waves would be ascribed the function of resisting erosion. Garson provides one central argument why, despite appearance, one should not ascribe functions in cases of such sorting processes. In this paper, I start by presenting his argument, which hinges on whether a collection of entities form a population. I find it wanting. I argue instead that some selection processes are evolutionarily more or less interesting and that when a selection process is regarded as evolutionarily uninteresting, it will yield an uninteresting form of function rather than a reason for withholding the concept of function altogether.     

基于内部控制质量的股利代理理论门槛效应研究

本文以我国沪深两市2011-2016年上市公司作为研究样本,选择内部控制质量作为门槛变量,建立面板门槛模型,研究现金股利与代理成本之间的非线性关系.结果表明,在内部控制的影响下,现金股利与代理成本存在门槛效应:当内部控制质量高于门槛值时,现金股利可以有效降低代理成本;当内部控制质量低于门槛值时,现金股利则难以降低代理成本.这说明,良好的内部控制是现金股利发挥治理功能的前提与基础.通过统计发现,高于内部控制质量门槛值的公司数量更多、股利支付公司占比更高.表明股利代理理论在我国是有效的,且正是由于该门槛效应的存在,使内部控制质量较高的公司更愿意支付现金股利.因此,本文不赞同以往内部控制与现金股利之间的"结果"或"替代"假说.     

鲁中南山区松树人工林近自然经营效果分析

近自然抚育作业于徂徕山林场、泰山林场和明光寺林场进行，采用目标树抚育作业方式，对不同林分进行间伐处理，时长分别为2、10和3年。结果表明，与对照相比，抚育处理后林分平均胸径、树高和冠幅较对照提高3.13%~12.89%、3.03%~8.91%和2.75%~25.91%；林分生长速度加快，保留木的胸径、树高和冠幅年生长量分别提高21.43%~66.67%、9.21%~26.15%和64.29%~300%；林下灌木层植物种类增多，出现侧柏、臭椿等喜光物种；油松纯林和松栎混交林中草本植物多样性改善，Simpson、Shannon-wiener和Gleason指数分别提高0.95%~1.93%、5.33%~10.43%和4.67%~18.18%，马唐、大油芒、羊胡子草等植物重要值提高；另外，抚育间伐后林下土壤pH提高0.77%~3.78%，土壤容重降低5.48%~12.68%；同时，过氧化氢酶、土壤磷酸酶、土壤蔗糖酶、土壤脲酶活性较对照分别提高6.74%~29.33%、4.79%~4.99%、2.13%~10.34%和1.25%~25.56%。近自然抚育间伐在一定程度上可以促进林分生长量积累、丰富林下植物多样性、改善林下土壤质量。     

Modeling and forecasting commodity market volatility with long-term economic and financial variables

This paper investigates the time-varying volatility patterns of some major commodities as well as the potential factors that drive their long-term volatility component. For this purpose, we make use of a recently proposed generalized autoregressive conditional heteroskedasticity–mixed data sampling approach, which typically allows us to examine the role of economic and financial variables of different frequencies. Using commodity futures for Crude Oil (WTI and Brent), Gold, Silver and Platinum, as well as a commodity index, our results show the necessity for disentangling the short-term and long-term components in modeling and forecasting commodity volatility. They also indicate that the long-term volatility of most commodity futures is significantly driven by the level of global real economic activity as well as changes in consumer sentiment, industrial production, and economic policy uncertainty. However, the forecasting results are not alike across commodity futures as no single model fits all commodities.     

上市公司现金股利政策的同伴效应研究

本文以A股上市公司为样本,从派现意愿和派现水平两个角度,对公司现金股利政策的同伴效应进行研究.结果显示,上市公司的派现意愿存在同伴效应,即公司是否派现受到同伴公司的显著影响,而且,该现象集中在高成长性且低现金流公司样本中;同时,研究并未发现上市公司的派现水平存在同伴效应.这些结果表明,在半强制分红的制度背景下,高成长性低现金流公司为了争取到再融资资格,会充分考虑同伴公司的派现决策并做出反应,但它们关注的重点在于同伴公司是否派现,而不是其派现水平.进一步研究发现,信息学习、行业竞争以及高管声誉关注是公司派现意愿同伴效应形成的主要原因.本文的研究丰富了公司财务决策同伴效应的相关文献,有助于在特殊的制度背景下理解上市公司的派现行为.     

动态空间自回归固定效应面板模型的估计与应用

文章首次探寻了在空间系统稳定以及n和T均为很大的情况下,DSAC固定效应面板模型的拟极大似然估计量的渐近性质.研究发现:运用转换法估计时,在一般情况下得到拟极大似然估计量存在O(1/T)阶的偏差,当(n-1)/T→0时,转换法得到的估计量以√(n-1)/T的速度一致地收敛于真值,当(n-1)/T→∞时,估计量以T的速度收敛至一个退化分布;用直接法估计时,在一般情况下得到的估计量会产生max(O(1/T),O(1/n))阶的偏差,当n/T→0和n/T→∞时,估计量分别以n和T的速度收敛至不同的退化分布;偏差修正估计量比拟极大似然估计量具有更好的有限样本性质:当n/T³→0时,转换法得到的偏差修正估计量以√(n-1)/T1的速度一致地收敛于真值,当n/T³和n³/T同时趋于0时,直接法得到的偏差修正估计量以√nT的速度一致地收敛于真值;直接法可以一致地估计个体效应和时间效应而转换法不能;当扰动项存在空间相关结构时DSAC固定效应面板模型的有限样本性质优于DSAR面板模型;最后用一个实证研究的例子表明了DSAC模型的应用价值.     

Robust function-on-function regression model with nonparametric random effects

Extended t-process is robust to outliers and inherits many attractive properties from the Gaussian process. In this paper, we provide a function-on-function nonparametric random-effects model using extended t-process priors in which we consider heterogeneity of individual effect, flexible mean function, nonparametric covariance function and robustness. A likelihood-based estimation procedure is constructed to estimate parameters involved in the model. Information consistency for the parameter estimation is provided. Simulation studies and a real data example are further investigated to evaluate the performance of the developed procedures.     

基于DTU模块的热网计量数据采集与监控系统研究

为了实现热网计量数据的采集与监控，基于已有的DSC模块，构建上层服务；通过与DTU的通信连接实现向流量积算仪发送指令、请求数据，最终实现对所有已连接的DTU进行数据轮询，从而获取所有已连接的流量积算仪的监控数据；通过对过往数据的处理和分析，进行实时结算和远程监督与控制，帮助供热单位实时监测热用户的用热状况。