基于两阶段优化算法的神经网络预测模型

采用基于两阶段优化算法(multi-stage optimization approach,MSOA)的GA人工神经网络,将训练集分为两部分,在前一训练集训练后获得的网络基础上使用后一训练集进行进一步的训练获得更为优化的网络结构.针对复杂系统建模输入节点难以确定的问题,提出将其与自组织数据挖掘算法相结合,利用GMDH算法获得神经网络的初始化节点,使用训练好的神经网络模型进行预测.将由此建立的预测模型应用于粮食价格的预测,并进一步探讨了MSOA算法的收敛性问题.结果表明基于GMDH和MSOA的神经网络组合预测模型能较大提高神经网络的全局收敛能力和收敛速度,提高预测精度.     

Wide Diameters of Cartesian Product Graphs and Digraphs

In graph theory and study of fault tolerance and transmission delay of networks, connectivity and diameter of a graph are two very important parameters and have been deeply studied by many authors. Wide diameter combining connectivity with diameter is a more important parameter to measure fault tolerance and efficiency of parallel processing computer networks and has received much attention in the recent years. Diameter with width k of a graph G is defined as the minimum integer d for which between any two distinct vertices in G there exist at least k internally disjoint paths of length at most d. In the present paper, the tight upper bounds of wide diameter of the Cartesian product graphs are obtained. Some known results can be deduced or improved from ours.     

遗传算法优化神经网络及信用评价研究

研究关于公司神经网络信用评估问题的现状,提出遗传算法辅助网络训练策略(优化后的网络称为进化网络),克服传统网络建模中产生的局部极小缺陷。建立了适合于我国商业企业的信用评分指标体系;然后依据该指标体系建立了基于进化神经网络的信用评估模型;最后,利用样本公司实际指标数据对该模型的评分效果进行了比较研究。     

全球替代性食物体系综述

在世界各地,农业食品领域的工业化造成了日益严重的环境、经济和社会问题,如环境污染、 大量碳排放、食品安全危机、小农边缘化和小农生计的难以维系。 为了应对这些问题,多个国家的不同 群体建立了多种多样的替代性食物体系,如社区支持农业、农夫市集、共同购买、社区菜园等。 替代性食 物体系自 2009 年进入中国至今已有十年,获得了较大发展。 然而,国内研究较少关注国际替代性食物 体系产生的背景及理念。 文章从替代食物体系的产生和发展、主要特征、国内外差异以及学术界的批判 等几个方面进行概述,全面介绍相关的关键问题和概念,为推动国内替代性食物体系研究的发展助力。     

(When) Is job-finding via personal contacts a meaningful concept for social network analysis? A comment to

Chua (2011) argues that in a meritocratic context, institutions restrict the usefulness of social networks in exerting influence on job seekers’ earnings. Regressing job-finding via personal contacts on earnings, he finds negative effects of influence via personal contacts, especially for the well-educated and individuals working in the state sector. In this comment, I argue that these results are ambiguous because (1) the analysis does not sufficiently distinguish between job ‘search’ methods and job ‘finding’ methods, (2) job-finding method indicates information flow rather than a personal contact's influence, and (3) it remains unclear whether Chua's analysis reflects the effect of network usage in job search per se or the effect of self-selection into network usage by individuals with low earning potential.     

基于自组网技术的燃气无线抄表系统研究

为解决现阶段燃气无线抄表系统数据采集中无线网络不稳定、路由协议复杂、自修复能力薄弱等问题，提出并设计了一种基于cc1101无线传送模块的树形拓扑结构无线自组网系统。系统中主要对数据采集层路由协议和硬件实现进行了研究和设计，分析了该燃气无线抄表系统与传统燃气无线抄表系统的不同之处，设计了该系统数据采集层网络传输协议和总体结构。无线节点建在穿透力强的433 MHz的频率下进行通信，保证了系统自组网的稳定快速。     

A divergence of opinion: how those involved in child and family social work are responding to the challenges of the Internet and social media

This discussion paper suggests that there is possibly a divergence of opinion taking place within the field of child and family social work and that the stated positions are influencing how practitioners identify and deal with risks and opportunities afforded by the Internet and social media. The suggested divergence is examined and the conclusion drawn is that what is taking place mirrors the fact that the introduction of any new technology inevitably brings with it division and debate. In seeking to understand the reaction to digital technology, consideration is given to a series of wider social discourses on childhood and risk, which includes the controversial notion that the profession is a harbinger of moral panic and that the management of risk has been broadened from child protection to child safety. The discussion paper concludes by calling for child and family social work practitioners to have a balanced debate that needs to be informed not only by current research but also by an open and honest discussion about personal use and an acknowledgement that there will be difficult moral and ethical questions to work through.     

The strengths of close ties: Taiwanese online entrepreneurship,gender and intersectionality

This article examines entrepreneurs who have started innovative Internet and mobile technology companies in Taiwan because they are at the forefront of industrial changes in the country. Similar to findings in Europe and the USA, education and careers in technology in Taiwan remain dominated by men. However, I argue that the gender inequality of the sector is partly the result of the fact that small new enterprises rely on family support and close social networks. Few women are able to join the sector with male friends and colleagues due to the close social ties of the founding teams (homophily). Among my female interviewees, half have started their nascent companies with their husbands and male partners (husband and wife teams). However, gender, family backgrounds and childcare responsibilities affect both men and women, and the interviewees in my study were open in discussing these personal factors in relation to being entrepreneurs. This article argues that starting an Internet company is a family decision, discussed within the household. Intersectionality, not only gender, explains the founders’ decision to start a company, and their choice of co-founders.     

Analytic strategies for longitudinal networks with missing data

Missing data are often problematic when analyzing complete longitudinal social network data. We review approaches for accommodating missing data when analyzing longitudinal network data with stochastic actor-based models. One common practice is to restrict analyses to participants observed at most or all time points, to achieve model convergence. We propose and evaluate an alternative, more inclusive approach to sub-setting and analyzing longitudinal network data, using data from a school friendship network observed at four waves (N = 694). Compared to standard practices, our approach retained more information from partially observed participants, generated a more representative analytic sample, and led to less biased model estimates for this case study. The implications and potential applications for longitudinal network analysis are discussed.     

Information geodesics for gamma models of communication clustering

Recently, Akyildiz called for further work on non-Poisson models for communication arrivals in distributed networks such as cellular phone systems. The basic ‘random’ model for stochastic events is the Poisson process; for events on a line this resuits in an exponential disiribuuon of intervals between events. Network designers and managers need too monotor and quantify call clustering in order to optimize resaurce usage; the natural reference state from which to measure departures is that arising from a Poisson, process of calls. Here we consider gamma distributions, which contain exponential distributions as a special case. The surface representing gamma models has a natural Riemannian information metric and we obtain some geodesic sprays for this metric. The exponential distributions form a 1-dimensional subspace of the 2-dimensional space of all gamma distributions, so we have an isometric embedding of the random model as a subspace of the gamma models. This geometry may provide an appropriate structure on which to represent clustering as quantifiable departures from randomness and on which to impose dynamic control algorithms to optimize traffic at receiving nodes in distributed communication networks. In practice, we may expect correlation between call arrival times and call duration, reflecting for example peaks of different users of internet services. This would give rise to a twisted product of two surfaces with the twisting controlled by the correlation. Though bivariate gamma models do exist, such as Kibble's, none has tractabie information geometry nor sufficiently general marginal gammas,but a simulation method of approach is suggested.