Data relaying with constraints in hierarchical sensor networks

In this paper we present and discuss several optimisation problems that arise in the management of data flow in wireless sensor networks (WSNets). We consider a hierarchical architecture for WSNets composed of sensors, relays, and relay gateways. Sensors send data they generate at a known average bit rate to relays in one hop. The relay nodes use a multi-hop mechanism to reach a set of assigned gateways which then forward the data directly to the base station. We are concerned with finding an assignment of relay gateways to relays so that certain constraints are satisfied. We define a unified model in which constraints such as lifetime, data delay, and data flow splitting are formulated in terms of four optimisation problem in graphs.     

一种基于闭排队网络的集装箱码头设备配置优化模型

将集装箱码头龙门吊装卸工艺抽象为闭排队网络模型,采用估算均值法计算了顾客到达和服务时间分布为一般情况的闭排队网络系统性能指标.仿真结果表明,闭排队网络模型计算结果可以为集装箱码头设备配置提供一定的决策支持.     

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.     

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。     

Improving operational plant performance in international manufacturing networks: the effects of integrative capabilities and plant roles

Abstract

This study adopts the resource-based view to examine how two integrative capabilities of a plant embedded in a manufacturing network enhance operational performance: the capability to connect with other plants in its manufacturing network (a networking capability, NC), and the capability to integrate manufacturing processes with new product development processes (a new product development capability, NPDC). Our model tests the indirect effect of NC on cost, quality, flexibility and delivery through NPDC. Furthermore, we test if the relationship between NC and NPDC depends on the strategic role of the plant. Using survey data from a sample of 521 plants, we confirmed the mediating effect of NPDC. However, the moderation effect was not confirmed. Our findings reveal that plants can deploy NPDC capabilities, fostered by NC, independently from their role in the network. This study contributes to the understanding of plant capabilities and plant roles in manufacturing networks.     

非正式创新网络结构仿真研究

非正式创新网络对于组织创新能力的提高具有重要意义,特别是我国社会具有充满"人情"味的特征,研究非正式创新网络更具有重要的现实意义.在对非正式创新网络的概念和研究现状进行分析梳理的基础之上,对非正式创新网络建立计算机仿真模型.初步研究了非正式创新网络的结构特征.发现非正式创新网络同时具有小世界以及无标度特性.     

Two-level network design with intermediate facilities: An application to electrical distribution systems

We consider the two-level network design problem with intermediate facilities. This problem consists of designing a minimum cost network respecting some requirements, usually described in terms of the network topology or in terms of a desired flow of commodities between source and destination vertices. Each selected link must receive one of two types of edge facilities and the connection of different edge facilities requires a costly and capacitated vertex facility. We propose a hybrid decomposition approach which heuristically obtains tentative solutions for the vertex facilities number and location and use these solutions to limit the computational burden of a branch-and-cut algorithm. We test our method on instances of the power system secondary distribution network design problem. The results show that the method is efficient both in terms of solution quality and computational times.     

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.     

TEI@I方法论及其在外汇汇率预测中的应用

基于TE I@I方法论的理论框架,构建了一个基于TE I@I方法论的外汇汇率预测模型。在此模型中,传统的经济计量模型用于处理外汇汇率的主要趋势,人工神经网络技术用于分析外汇汇率的非线性,而文本挖掘和专家系统用于处理外汇市场中的突现性和不稳定性。最后,基于集成的思想,利用支持向量回归技术对上述3个部分进行非线性集成,从而获得一个更为精确的预测结果。通过实证方法验证了基于TE I@I方法论的外汇汇率预测模型的有效性。     

兴趣社交网络中的供需匹配研究:以豆瓣网为例

近年来兴起的兴趣社交网络中因其内在的商业价值引起了人们的注意.兴趣社交网络中涌现出大量的商品供需信息,带来的问题之一就是商品供需信息传播匹配效率低下.为解决上述问题,本文依托社会网络分析方法,探讨在具备小世界特性的兴趣社交网络中商品供需匹配的特点,研究商品传播和匹配的规律和提高匹配效率的策略.本文选取豆瓣网关注关系为实证数据,提出在兴趣社交网络中友邻信息相关度与供需信息传播匹配效率正相关的假设,并采用计算机仿真方法来验证假设.论文获取豆瓣网的社交网络数据、包括网络用户藏书数据和图书的标签数据,针对随机选取的1000个用户和200本图书作为实验样本,分别设计两套友邻信息相关度度量算法和两套兴趣社交网络中商品供需信息传播匹配算法,采用进行仿真模拟实验进行了比较.实验结果证实了人们对于商品检索的直观判断,得出在兴趣社交网络中,商品供需信息传播匹配效率与友邻信息相关度正相关的结论.