Production networks, geography and firm performance

This paper examines the importance of buyer-supplier relationships, geography and the structure of the production network in firm performance. We develop a simple model where firms can outsource tasks and search for suppliers in different locations. Low search and outsourcing costs lead firms to search more and find better suppliers. This in turn drives down the firm’s marginal production costs. We test the theory by exploiting the opening of a high-speed (Shinkansen) train line in Japan which lowered the cost of passenger travel but left shipping costs unchanged. Using an exhaustive dataset on firms’ buyer-seller linkages, we find significant improvements in firm performance as well as creation of new buyer-seller links, consistent with the model

Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks

无线传感器网络，作为全球未来十大技术之一，集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术，可实时感知、采集、处理、传输网络分布区域内的各种信息数据，在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议，并针对大规模的无线传感器网络设计了一种树状路由协议，它根据节点地址信息来形成路由，从而简化了复杂繁冗的路由表查找和维护，节省了不必要的开销，提高了路由效率，实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR（AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位：工学硕士院系专业：信息科学与技术学院通信工程系_通信与信息系统学号：2332007115216

Production Networks, Geography and Firm Performance *

Abstract This paper examines the importance of buyer-supplier relationships, geography and the structure of the production network in firm performance. We develop a simple model where firms can outsource tasks and search for suppliers in different locations. Firms located in close proximity to other markets, and firms that face low search costs, will search more and find better suppliers. This in turn drives down the firm's marginal production costs. We test the theory by exploiting the opening of a high-speed (Shinkansen) train line in Japan which lowered the cost of passenger travel but left shipping costs unchanged. Using an exhaustive dataset on firms' buyer-seller linkages, we find significant improvements in firm performance as well as creation of new buyer-seller links, consistent with the model