Adaptive broadcast by fault-tolerant spanning tree switching

Adaptation is a desirable requirement in a distributed system as it helps the system to perform efficiently under different environments. For many problems, more than one protocol exists, such that one protocol performs better in one environment while the other performs better in another. In such cases, adaptive distributed systems can be designed by dynamically switching between the protocols as the environment changes. Distributed protocol switching is also important for performance enhancement, or fault-tolerance of a distributed system. In this work, we illustrate distributed protocol switching by providing a distributed algorithm for adaptive broadcast that dynamically switches from a BFS tree to a DFS tree. The proposed switching algorithm can also handle arbitrary crash failures. It ensures that switching eventually terminates in spite of failures and the desired tree (DFS tree) results as the output. We also investigate the properties that can be guaranteed on the delivery of broadcast messages under specific failure conditions. We show that under no failure, each broadcast message is eventually correctly delivered to all the nodes in spite of switching. Under arbitrary crash fault, we ensure that switching eventually terminates with the desired tree as the broadcast topology. We also investigate the specific delivery guarantees that can be provided when a single crash fault happens, both during switching and when no switching is in progress.     

Consumer perceptions on web advertisements and motivation factors to purchase in the online shopping

The principal objective of this study was to investigate the mediating and moderating effects of product involvement and trust toward websites in relation to the effects of the attributes of web advertisements on customers’ purchase intentions. We collected data consisting of a total of 264 responses from individuals with previous experience with purchasing products from online shopping mall sites, and utilized the PLS (partial least squares) method to analyze the collected data.     

Robust gossiping with an application to consensus

We study deterministic gossiping in synchronous systems with dynamic crash failures. Each processor is initialized with an input value called rumor. In the standard gossip problem, the goal of every processor is to learn all the rumors. When processors may crash, then this goal needs to be revised, since it is possible, at a point in an execution, that certain rumors are known only to processors that have already crashed. We define gossiping to be completed, for a system with crashes, when every processor knows either the rumor of processor v or that v has already crashed, for any processor v. We design gossiping algorithms that are efficient with respect to both time and communication. Let t<n be the number of failures, where n is the number of processors. If , then one of our algorithms completes gossiping in O(log²t) time and with O(npolylogn) messages. We develop an algorithm that performs gossiping with O(n^1.77) messages and in O(log²n) time, in any execution in which at least one processor remains non-faulty. We show a trade-off between time and communication in gossiping algorithms: if the number of messages is at most O(npolylogn), then the time has to be at least . By way of application, we show that if n−t=Ω(n), then consensus can be solved in O(t) time and with O(nlog²t) messages.     

和谐社会背景下土地整理农民参与机制研究

从土地整理与和谐社会的关系、农民参与土地整理对构建和谐社会重要性和必要性的研究出发,本文分析中国农民参与土地整理的现状及存在的问题,提出中国土地整理农民参与机制构建的必要性及其基本框架,为促进土地整理持续健康发展,推动农村经济社会进步,构建和谐社会提供借鉴。     

Hazard perception and driving experience among novice drivers

The crash risk of novice drivers decreases rapidly during the first few months of post-licensing driving, indicating that some important safety-relevant traffic skills are learnt during this period. The present study tested the hypothesis that the risk decrease is related to improved hazard perception skills. A video-based hazard perception/reaction test, measuring reaction times to 31 traffic scenes, was administered to three groups of drivers, having held a licence for 1, 5, and 9 months, respectively, and to a group of drivers who had held their licences for several years. Average reaction times tended to decrease with experience, but the decrease was not significant. There were some significant differences in the expected direction for individual test items, indicating a possible effect of experience. One half of the situations were presented together with a secondary task, in order to investigate effects of increased mental load on hazard perception. Male novice drivers had relatively longer reaction times with the secondary task, compared to both female novice drivers and male experienced drivers. It is concluded that hazard perception as tested here is probably only a minor factor in explaining the initial risk decrease among novice drivers.     

Distribution and characteristics of road traffic crashes in the Chaoyang District of Beijing, China

In many developing urban settings, economic growth and motorization are coupled with increasing rates of road traffic injuries (RTIs). By highlighting typical sites and circumstances at/in which car crashes occur, more specific targets for prevention can be identified. The study is based on police data for a 1-year period and covers the Chaoyang District, the biggest district of Beijing City. Focus is placed on crash patterns and their distribution by types of road and areas. Both fatal and non-fatal crashes are considered (n=754). In the main, the crashes occurred in relatively favorable driving circumstances (e.g., sunny weather, flat and straight roads, asphalted roads, and good traffic signals and road markings). They were also quite evenly distributed over time of day, day of week and season. Five crash patterns were highlighted, of which three were strongly associated with specific areas and four with specific types of road. The study supports the idea that type of road and RTI severity or pattern are closely related. It contributes to the development of context-relevant prevention measures aimed at reducing road crashes and minimizing their consequences and also supports safe planning of the road traffic environment.     

Teen driver crash risk and associations with smoking and drowsy driving

Motor vehicle crashes are the leading cause of death for young people in the United States. The goal of this study was to identify risk factor profiles of teen and young adult drivers involved in crashes. General demographic and behavioral as well as driving-related factors were considered. Analysis of a nationally representative telephone survey of U.S. young drivers ages 14 to 22 (N = 900) conducted in 2005 was restricted to 506 licensed drivers (learners excluded). Statistically significant univariate associations between factors of interest and the primary outcome, crash involvement (ever) as a driver, were identified and included within a multivariate logistic regression model, controlling for potential demographic confounders. Aside from length of licensure, only driving alone while drowsy and being a current smoker were associated with having been in a crash. Gaining a better understanding of these behaviors could enhance the development of more customized interventions for new drivers.     

Self-organization in urban development: towards a new perspective on spatial planning

To date, participatory spatial planning has produced disappointing results. We argue that one reason is that time and again participatory planning proposals remain controlled by public government, and that public government seems not to be very adaptive to initiatives that emerge from the dynamics of civil society itself. To find out why and how citizens could and would be motivated to contribute out of their own motivation to urban development, we propose turning the focus outside-in, instead of inside-out. In this article, we therefore introduce the notion of self-organization, referring to initiatives that originate in civil society itself, via autonomous community-based networks of citizens outside government control which participate in developing the ‘urban fabric’ too. We discuss some examples of self-organization and draw preliminary conclusions of the concept's usefulness for the theory and practice of spatial planning.     

Learning from the social construction of environmental indicators: From the retrospective to the pro-active use of SCOT in technology development

This article explores the challenges, advantages and limitations of the pro-active use of the social construction of technology (SCOT) to improve the methods applied in the development of technology for use by a broad range of actors. Our example is the development of environmental indicators for buildings (EIFOBs). We compare the pro-active use of SCOT with both the ‘traditional’ use of SCOT and with the ‘traditional’ way of developing EIFOBs. pro-actively applying SCOT in developing EIFOBs has the potential of bridging some of the communication gaps at the boundaries between the various professional groups in a multi-actor decision-making process. Using SCOT in a pro-active way means the research becomes action research and the researcher goes beyond the role of a mere observer and becomes an actor too. This means the researcher has to consider the criteria for valid action research when designing and carrying out the research.     

Towards a contingent approach of customer involvement in defence projects: An exploratory study

This paper reports the main results of an exploratory, multiple case study investigating customer involvement practices in system development projects in the Israeli defence industry. The study proposes and examines a theoretical contingency model regarding the effect of customer involvement modes on project success, moderated by project characteristics. It focuses specifically on the working mode of customers' representatives along the continuum between external supervision to full participation in project activities.