工业X-CT散射校正技术综述

在工业X-CT成像系统中,散射现象对重建图像的质量有重要的影响,一直是CT研究的热点之一。随着工业X-CT系统的最新发展,锥束CT也逐渐被广泛应用,由于成像质量要求高,散射成二维分布,及新型平板探测器的应用,对散射校正带来更大的挑战。在传统的散射校正方法基础上,近几年出现了众多新的校正方法。本文首先分析了散射干扰的形成原理,介绍了散射评估方法,同时又对目前主要的几种校正方法进行了归纳总结,并对散射校正研究的发展趋势进行了展望。     

Environmental change and human mobility in the digital age

This intervention argues for the need of research to examine how information and communication technologies (ICTs) shape human mobility in the context of environmental change. ICTs are becoming increasingly central in the daily lives of migrants and communities at risk of environmental events. There is a lack of research, however, exploring how access to and the use of ICTs influences practices and dynamics of human mobility in the face of environmental change. I will outline this research gap and highlight areas for further research. I will do so by bringing together literature from human geography and environmental studies on migration and social resilience, and from sociology on the influence of our mobile and network society. In conceptualizing the role that ICTs play, I argue that the use of ICTs shapes human mobility through its impact on social network activities and relations. In this manner, this intervention builds on a growing body of research conceptualizing social networks – and related dynamics of power, access, in/exclusion – as shaping migration trajectories and abilities to cope with environmental events.     

基于卷积反投影CT重建的一种新型实用滤波函数

在实际的CT重建中,由于受散射、射束硬化等低频干扰因素的影响,使得重建图像产生"杯状”伪像以及图像模糊降质.针对在ICT工程实践中投影数据存在诸如此类的低频污染问题,本文提出了一新型实用滤波函数取代传统的滤波函数,得到了较为满意的重建效果.     

Wireless valley, silicon wadi and digital island--Helsinki, Tel Aviv and Dublin and the ICT global production network

Hyper-capitalism in global information and communication technology (ICT) markets during the late 1990s created a new global production network, shaped by multinational corporations, international capital flows, and a flourishing of high-tech entrepreneurship. Each of the cities considered here benefited substantially from this growth, but their positions as nodes in the ICT global production network differed markedly, as did their ability to appropriate the value they generated. In Dublin, value creation was based largely on inward technology and capital flows, although indigenous Dublin-based software companies did demonstrate their ability to compete internationally. ICT development in Helsinki and Tel Aviv drew more strongly on the local knowledge base, and benefited from changes in national regulatory and political conditions. In Helsinki, public and private R&D investments supported the highly effective globalisation strategy of Nokia to create a strongly localised, vertically-integrated and strongly specialised sector. Value creation in the more diverse Israeli ICT sector was also based primarily on locally developed technology, university R&D and the commercialisation of technology developed initially for military applications. By the end of the 1990s, the resulting ICT node in Tel Aviv was grounded in the local knowledge-base, technologically diverse, strongly entrepreneurial and globally oriented.     

Formation and emergence of ICT clusters in India: the case of Bangalore and Hyderabad

Since the 1990s, information and communication technologies clusters (ICT clusters) have been created in developing countries, especially in Asia, where India is one of the most dynamic countries. Bangalore and Hyderabad are two important examples of Indian clusters. This article aims to analyze the characteristics of ICT clusters, Indian policies to develop IC technologies, the formation and emergence of the Bangalore and Hyderabad clusters and their impacts on the population, as well as to show that ICT development is a strategic issue for India but does not benefit all of its population.     

The emergence of a post-industrial music economy? Music and ICT synergies in Stockholm, Sweden

Research into the music industry has for a long time been almost exclusively dominated by a focus on the production of albums and songs. In recent years, however, cities such as Stockholm have seen the growth of a profitable and varied music services industry producing everything from remixes to music marketing strategies. Standing at the forefront of this growth industry are a large number of firms attempting to combine in innovative ways music and ICT. This can take a variety of forms, for instance: selling and distributing music over the internet; web design and computerised advertising services tailored to music products; software design focused on multimedia products and virtual instruments; high-tech post-production and mixing services; and virtual centres and communities of music industry actors. The article will examine these activities within the city in attempt to measure the direction and cohesiveness of the emerging sector. The article concludes by arguing that these type of new industrial synergies tell us much about the way industrial innovations are formed in an interindustry and inter-cluster environment, and the future competitiveness and shape of the music industry. In particular, the article argues that evidence from Stockholm points to the emergence of a post-industrial musical economy.     

信息时代高铁走廊区域居民活动空间——概念模型与研究框架

作为中国最重要的城市与区域基础设施,信息技术和高速铁路正加速影响居民的行为活动,传统的活动空间已发生转型,而以高流动性为基本特点的信息时代高铁走廊区域活动空间逐渐形成。这一背景下,活动空间研究亟需立足信息与交通技术前沿,探究新时期活动空间的基本形态与研究范式。通过构建信息时代高铁走廊区域活动空间的概念模型,分析了活动空间的构成与形成机理,并从空间性质、尺度、形态、结构等方面提炼了活动空间的新特征。在此基础上提出新时期活动空间的研究框架,即构建以流动空间为基本的理论出发点,利用多元数据融合、集成分析的创新方法探索居民行为活动与区域空间要素的相互作用、影响机制及其空间效应的研究框架。这对于活动空间研究体系的丰富和深化、实证研究的开展以及高铁走廊区域的统筹规划具有重要意义。     

Local Innovativeness and Knowledge Spillovers of Indigenous Firms on Foreign Firms: Evidence from China's ICT Industry

Literature on transboundary knowledge flows has primarily focused on foreign direct investment (FDI) spillover effects in emerging economies during the last decades. Little has been known, however, about whether or not and how foreign firms learn from local firms to enhance their innovation performance. The existing literature on clusters lays much emphasis on the variety of knowledge sources in the process of innovation, but it largely ignores the social and institutional barriers to transboundary knowledge flows. This article argues that for foreign firms operating in emerging economies, the issues about legitimacy and liability of foreignness might inhibit “outsiders” from effective knowledge sourcing; therefore, the social and institutional structure in a region plays a no less significant role than knowledge per se. Based on a large-scale firm-level database from China's information and communications technology (ICT) industry, this article reveals that local innovativeness of indigenous firms significantly stimulates and enhances innovation of foreign firms. It is interesting to find that whereas related variety of a region fails to exert positive influences, ownership diversity and a low extent of market concentration that reflect the openness of a local innovation system significantly affect innovation performance of foreign firms. It calls for more studies on local institutional and social construction of interfirm knowledge flows.     

信息技术对服务业创新影响的空间计量分析

信息技术成为服务业创新的关键因素,并受到国内外学术界的普遍关注,但鲜有从省域及市域层面探索信息技术对服务业创新影响的研究成果。以广东省地级市(域) 为例,运用因子分析、探索性空间数据分析、空间计量模型等实证研究方法,深入分析信息技术和服务业创新的空间分布特征和两者之间的关系。结果表明,服务业创新和信息技术均存在空间正相关性,形成全域空间的核心—边缘模式和局域空间的"俱乐部"模式。高值簇集聚区(珠三角) 的扩散效应只局限在局域"俱乐部"里面,而低值簇亦形成集聚区(粤北、粤东和粤西),体现出珠三角同东西两翼与粤北山区之间巨大的差距。在空间差异和扩散效应的影响下,信息技术和服务业创新在空间上均出现"俱乐部"内趋同、"俱乐部"间趋异的现象。空间计量回归表明,服务业创新在市域空间上具有相互促进作用,信息技术对服务业创新具有明显的促进作用,当信息技术水平每提高1%,服务业创新水平就将提高0.7158%,证明了信息技术是影响服务业创新的重要因素。