一种单视广义极化K-分布纹理参数的估计方法

提出了通过归一化极化联合矩对SAR（合成孔径雷达）单视广义极化K-分布纹理参数进行估计的方法,阐述了SAR各个极化通道之间的纹理相关性。在此基础上给出了单视广义极化K-分布波形因子、纹理相关系数和相干斑相关系数的算法及偏差性能分析,并进行了蒙特卡洛仿真实验论证,进一步证明了该方法的良好估计性能。     

基于幂律型分布的动态VaR模型及实证研究

针对金融资产回报时间序列的尖峰厚尾性和波动集聚性,提出了基于AR(1)-GARCH(1,1)模型与幂律型分布相结合计算VaR的方法。用GARCH模型对时间序列建模刻画波动集聚性,用基于幂律型分布的扩展形式拟合GARCH模型的残差分布尾部,刻画回报时间序列的厚尾特征,二者结合更好地描述回报时序的动态波动现象。对上证综指进行实证分析,结果表明本文提出的方法比基于正态分布的GARCH模型和静态幂律尾法更精确。     

政府补贴下制造商回收的多期闭环供应链网络均衡

为刻画闭环供应链系统运作的动态性和复杂性特点,本文在综合考虑环保约束和政府补贴等因素的基础上,建立了制造商回收模式下的多期闭环供应链网络均衡模型,其中假设市场需求在不同规划期内动态变化,渠道成员通过库存和旧产品的回收连接相邻规划期。运用变分不等式理论分别刻画了制造商层、零售商层和需求市场层的最优行为和均衡条件,进而推导整个多期闭环供应链网络均衡模型。通过投影收缩算法对数值算例进行求解和灵敏度分析,研究结果表明:再制造转化率的提高有利于各渠道成员和消费者利益的改善;尽管资源再生厂向制造商收取未再利用旧产品的处理费能够迫使其提高回收力度,但却导致零售商和闭环供应链收益的损失;政府应实施补贴机制并促进渠道成员之间的协作来改善闭环供应链网络的绩效。这些结论将为现实中闭环供应链节点企业的动态决策以及政府部门制定补贴政策提供支持。     

Family socioeconomic status and sibling correlations in upper secondary education. An empirical analysis of educational inequalities in Italy

The study examines the educational inequalities in upper secondary education in Italy, with a focus on the vertical dimension of school enrolment and the horizontal dimension of track and curriculum choice. To measure the importance of family background, we use the estimation of sibling correlations, which has seldom been used in the analysis of track choice in upper secondary education. Using data from the Italian Labor Force Survey 2005–2020 (ILFS), which includes detailed information on household characteristics such as the gender composition of siblings and parental education and occupational status, we find that around half of the variation in the probability of attending upper secondary school in Italy is related to the family of origin. We also show that comparing sibling correlations on binary outcomes should be complemented by additional statistics, such as variances at the individual and family levels and proportions of enrolled sibling pairs. For upper secondary school enrolment, advantaged families have a relatively lower sibling correlation due to minor variations at both individual and family levels. However, in terms of track choice, the sibling correlation is relatively higher for enrolment in the academic track compared to the technical and vocational tracks. Additionally, with respect to the attendance of science/technical curricula within each track, the results indicate a lower sibling correlation for the academic track than for the other two tracks, which suggests that individual characteristics have a greater impact than family background when these outcomes are considered.     

力矩电机调速系统

介绍一种力矩电机调速系统，阐述了系统原理、构成，以及为提高系统性能所采取的一系列措施，所构成的系统已经投入实际运行。     

基于委托代理关系的生态产业链均衡研究

研究生态产业链中委托代理结构和委托代理契约履约率对生态产业链的产品流量、利润和成本收益率影响等问题,指出生态产业链中的委托代理关系包括产品流通的委托代理关系和废弃物处理的委托代理关系,提出生态产业链的前导委托和后续代理关系结构。在此基础上,结合维持生态产业链运行的平衡条件,构建带有激励和委托代理契约履约率约束的生态产业链均衡的最优化模型,利用变分不等式模型解释生态产业链均衡的经济意义,并运用LINGO 9.0对鲁北生态工业园中的生态产业链进行模拟计算。结果表明,随着生态产业链中前导委托与后续代理之间履约率的增加,彼此间交易量、利润和成本收益率及整体生态产业链的利润和成本收益率都获得提升,计算结果与实际问题相符,验证了模型的有效性。     

Diffusion of innovations through social networks: Determinants and implications

Social scientists have long been interested in the diffusion of innovations—the process by which new ideas, behavior, and practices spread between persons, organizations, and even countries. While innovations can enter a community through various channels, ongoing spread of innovations through a community occurs through the medium of social networks—collections of interpersonal or digital relationships connecting actors to each other. Social networks are important for diffusion because relationships foster communication, trust, and flow of information. Diffusion outcomes are also shaped by the structural properties of social networks such as density, centrality, and strength of ties, as well as properties of the innovation and the actors involved in the process. The purpose of the article is twofold: (1) to take stock of the field and review ongoing debates on the role of social networks in the diffusion of innovations and (2) to summarize the sociological implications of the diffusion of innovations through social networks.