具有最优学习率的RBF神经网络及其应用

传统固定学习率的RBF神经网络在金融时间序列预测方面已经有比较成功的应用,但网络学习率的选择问题却给传统RBF神经网络的使用带来了不便.利用梯度下降法及优化方法推导出了RBF神经网络的动态最优学习率并将其应用于网络学习算法,具有最优学习率的RBF神经网络能够在保证网络稳定学习的同时兼顾网络的收敛速度.为了检验具有动态最优学习率的RBF神经网络的预测效果,对沪深300指数波动率进行了预测实验.实验结果表明,具有动态最优学习率的RBF神经网络比传统的固定学习率的RBF神经网络有着更快的收敛速度,同时也避免了人为选定学习率的不便.     

高等学校投资效益的评价体系探讨

分析高等学校的投入产出关系,建立了一套高等学校投资效益评价指标体系和权重体系,通过模糊数学中隶属度的概念,采用层次分析法针对评价体系进行单因素模糊评价和多级模糊综合评判,并采集了某所高校不同年度的数据,通过软件对评价体系进行了计算和验证,得出各年度投资效益的产出率。     

真空管太阳能集热器热风干燥试验研究

随着对食品干燥的需求变多,干燥过程往往要消耗大量能源,课题组提出把真空管太阳能集热器和干燥箱结合起来,对物料进行热风干燥。设计一个带有回风系统的干燥箱,采用控制变量法对胡萝卜热风干燥进行试验研究,分析空气流量、热风温度等因素对干燥箱干燥性能的影响。试验表明：空气流量越大,物料的干燥速率越小;当干燥箱进口的热风温度升高时,物料的热质交换更充分,因此干燥进程得以加快。提出的真空管太阳能集热器热风干燥系统可以达到节能目的并有效快速地对物料进行干燥。     

水流量对热泵热水器性能影响的实验研究

针对空气源热泵热水器运行工况多变,制热效率不稳定的特点,设计了循环加热式热泵热水器实验装置,系统由制冷剂循环和水循环两部分构成,重点研究了水流量对系统性能的影响。实验结果表明：逐时能效比随水温的升高而下降,加热前期水流量越大能效比越低,加热后期刚好相反;水流量越小系统越容易吸气带液,吸气带液会使制热量降低,能效比下降速率增大,导致系统性能变差;吸气带液时,制冷剂流量减小,换热系数增大,与换热系数相比制冷剂流量对制热量的影响更大。该结果为系统实际运行和进一步研究提供参考。     

保险公司投入要素产出贡献率研究

基于柯布-道格拉斯生产函数,构建保险公司投入要素产出贡献率计算模型,采用中国90家保险公司2008—2015年面板数据进行实证研究。结果表明：第一,资本投入对保险公司产出贡献率最高,创新次之,最后为劳动投入;第二,不同规模保险公司的投入要素产出贡献率存在明显差异。为此,在供给侧改革背景下保险公司应注重优化投入要素结构,以促进保险业的健康与稳定发展。     

人民币汇率失衡与调整问题研究

 摘　　要:目前，学术界在人民币汇率问题的研究上存在着分歧。尤其是对均衡汇率的测算，在方法上存在不足。多数模型的设计实质上是把名义汇率或实际有效汇率的平滑值当作了均衡汇率，而非真正的经济学意义上的均衡汇率。本文设计了一种“多目标两阶段估值”的方法来测算均衡汇率：在第一阶段，依据实现均衡汇率的各个目标，分别估算不同目标条件下的均衡汇率；第二阶段，以第一阶段估算的均衡汇率和实现均衡汇率的各目标建立计量模型，得到均衡汇率精算值。在深入分析汇率失衡给宏观经挤带来的后果的基础上，依据均衡汇率的计算结果，本文认为，提升汇率符合中国的长期利益和根本利益，而且在觋阶段政府还不应该放弃对汇率调整的干预     

On Rates of Convergence for Bayesian Density Estimation

Abstract.  We consider the problem of estimating a compactly supported density taking a Bayesian nonparametric approach. We define a Dirichlet mixture prior that, while selecting piecewise constant densities, has full support on the Hellinger metric space of all commonly dominated probability measures on a known bounded interval. We derive pointwise rates of convergence for the posterior expected density by studying the speed at which the posterior mass accumulates on shrinking Hellinger neighbourhoods of the sampling density. If the data are sampled from a strictly positive, α -Hölderian density, with α  ∈ ( 0,1] , then the optimal convergence rate n^{− α / (2 α +1)} is obtained up to a logarithmic factor. Smoothing histograms by polygons, a continuous piecewise linear estimator is obtained that for twice continuously differentiable, strictly positive densities satisfying boundary conditions attains a rate comparable up to a logarithmic factor to the convergence rate n ^−4/5 for integrated mean squared error of kernel type density estimators.     

我国遗产税的相关问题探讨

文章阐述了我国开征遗产税的必要性和可能性,进而在课征遗产税的方式、立法和管理等方面提出了自己的一些见解。     

The Possibility of Mixed-Mode Surveys in Sociological Studies

Abstract:  This paper explores the possibility of the mixed-mode survey in Japan in order to ensure a wider range of respondents, focusing on the specific type of mixture that is designed to make contact with a respondent by more than one mode and in which a respondent can choose an alternative mode convenient for him or her. The dataset mainly used comes from the survey Study on the Social Composition of the Urban Local Community conducted in Shinagawa Ward of Tokyo in 1999. Three other studies are introduced for additional information. As an indicator of the effectiveness of a mixed-mode design, the response rates of four studies are examined and some improvement in the response rates is observed, compared to that of a single-mode design. Another indicator is the representativeness of a sample and it is evaluated using the data of the Shinagawa survey. When the discrepancy between valid respondents and the population on some demographic characteristics is regarded as representation bias, a mixed-mode design is found to reduce the bias. An inherent problem in a mixed-mode design is "mode effect." In order to control for the mode effect in analyses, the inclusion of an additional variable indicating "mode" in the model is recommended. It is further suggested that the interaction effects between the "mode" and the respondents' traits should be checked, on the assumption that the survey mode affects respondents differently. The attempts are made and discussed in this paper using two variables drawn from the Shinagawa survey.     

On Nonparametric Maximum Likelihood Estimations of Multivariate Distribution Function Based on Interval-Censored Data

This article considers the nonparametric maximum likelihood estimator (NPMLE) of a joint distribution function when the multivariate failure times of interest are interval-censored. With different types of interval censoring mechanism, the NPMLE's of the multivariate distribution function are studied and the strong consistency for the NPMLEs is obtained in terms of a self-consistency equation. Furthermore, the convergence rate of the estimator is given, which depends on the types of interval censoring mechanism.