托辊轴承系列产品塑料保持架的改进

托辊轴承应用于煤矿带式输送机和农业带式输送机中,其轴承工作环境恶劣,灰尘大,在煤泥水和其他有害的气体环境中运转。因此,托辊轴承对旋转阻力、防卡寿命具有一定的要求。为满足托辊轴承性能要求,首先在保持架的材料选取及保持架结构设计上进行了改进。保持架的材质采用了性能优良的工程塑料,并在保持架的结构上进行了改进-增加了叶片。因此,提高了轴承的寿命及动态性能。     

石膏板吊顶石膏板隔墙的施工

为防止石膏板吊顶及石膏板隔墙裂缝的出现,简述在其制作工艺中应注意的事项。     

光射线在光纤中的传输

对光射线在光纤中的传输原理、光纤的导光原理以及光波在光纤中的传输损耗进行了理论探讨。     

Neighbourhood attachment in deprived areas: evidence from the north of England

Those living in deprived areas may have a greater reliance on the neighbourhood as a setting for social activity. However, the reduced quality of deprived neighbourhoods may make attachment in such places less likely. Other factors, like high turnover and social mix, may also act to reduce an individual’s attachment in these neighbourhoods. Using qualitative methods, this study examines both emotional and functional attachment to deprived neighbourhoods, specifically considering the impact of high turnover and of social mix. Social mix is broadly defined, including but not limited to ethnic and tenure mix. Many respondents reported strong emotional attachments to their communities, with the presence of strong social networks and a sense of security the most important contributing factors. Functional attachments and attachments to the physical environment were weak or absent. High turnover in deprived areas was found to reduce place attachment by undermining social networks, lowering social interaction, and eroding trust and feelings of security. There was little evidence that social mix in any dimension reduced attachment significantly. However, high residential turnover and a rapidly changing (ethnic) mix in one area had led to increased anxieties and reduced attachments. The research shows that rather than systemic factors being dominant, place attachment in deprived areas is very context dependent (e.g. in terms of where the neighbourhood is located in relation to others). For an individual, also experiential, historical and personal factors are strong determinants of attachment.     

Does living in a poor neighbourhood result in network poverty? A study on local networks,locality-based relationships and neighbourhood settings

This paper examines whether and how living in a poor neighbourhood results in “network poverty”. Through a detailed analysis of the formation of personal networks of people living in a poor neighbourhood and those living in an affluent neighbourhood in Rotterdam, I examine the role of the neighbourhood in the formation of personal networks. I address three issues. First, whether resource-poor people who live in a poor neighbourhood form relationships with fellow-residents to compensate for their otherwise small network. I find that they do not and that their small network is primarily caused by non-participation in settings such as study, work, leisure and associations. Second, I distinguish locally maintained relationships that have originated in other settings from locality-based relationships that originated in the neighbourhood. The study shows that high network localness is more a matter of maintaining relationships in the neighbourhood than forming many new locality-based relationships with fellow-residents. Third, I examine how the neighbourhood facilitates relationship formation and conclude that this happens not in “the neighbourhood” but in neighbourhood settings, which attract a particular segment of a neighbourhood population. I conclude that the problem of network poverty is not in the first place spatial but rather lies in lack of participation in certain settings. Furthermore, social mixing policies can only be successful if they are accompanied by initiatives to draw a mixed population to neighbourhood settings and facilitate routine encounters between resource-rich and resource-poor people.     

African Urbanization as Flight? Some Policy Implications of Geography

The mystery of the lack of a positive relationship between growth and urbanization in sub-Saharan Africa has been raised in a number of studies. A recent paper by Barrios et al. (Journal of Urban Economics 60:357–371, 2006) provides a compelling explanation for why this occurs. Exploiting a new data source, they show how climate change, specifically the reduction in rainfall, has driven people from the increasingly impoverished countryside to the city. They also show that while this is an important factor explaining urbanization in sub-Saharan African countries it does not affect urbanization elsewhere. Their explanation for this important difference is differences in the patterns of rainfall, as well as the composition of soil in most sub-Saharan countries. In a word, geographical factors have dominated the unusual pattern observed in the world’s most rapidly urbanizing continent. In this paper, we extend the work done by Barrios et al. to include more observations and more detailed geographic variables. We first replicate their results and extend the number of observations to more recent periods. Then we consider the effects of a range of specific country geographical characteristics, relying on data developed by other researchers. After discussing our results, we focus on the implications of our findings for policy formulation, particularly for sub-Saharan African countries. The results indicate that geographical circumstances place significantly more important constraints on maximization processes. In other words, urbanization in these countries takes place in a profoundly “second-best” world. We consider what this kind of context implies for the sequencing and implementation of economic reforms which would allow for an urbanization process that would be more conducive to economic growth.