铸造Al—Si—Mg合金的时效特性及形变机制

研究了ＡｌＳｉＭｇ系Ａ３５７合金在不同时效状态下的显微组织、力学性能及形变特性。结果表明，时效条件不同，合金的强塑性配合不同，１６５℃短时时效，强塑性搭配较好；１５５℃，４ｈ预时效，再经１７５℃，１２ｈ最终时效，进一步提高合金强度的同时，保证了塑性。不同温度下短时时效，析出物均为ＧＰ区，形变以位错切过的方式进行；长时时效，析出物均为β相，形变以位错绕过的方式进行。双级过时效处理，改善了β相的析出形态，使得滑移位错均匀分布     

Study on a new kind of combined machining technology of ultrasonic machining and electrical discharge machining

An analysis on the mechanisms of ultrasonic machining and electrical discharge machining has been carried out, and a technology, which combines the advantages of both of them, has been proposed in this paper. It can be used to machine all conductive hard and brittle materials with high efficiency and surface integrity. The mechanism of this combined technology has been studied by the authors. The experimental results show that the efficiency of it is over three times greater than that of ultrasonic machining, and the surface integrity is not significantly different.     

为重要工程的要害区域提供高可靠的保障——浅析数据中心火灾自动报警系统的设置

本文介绍了某数据中心火灾自动报警系统的设计,结合设计过程中的体会,着重阐述了为数据机房等重点区域全方位设置火灾探测系统的重要性和必要性。     

The Military as an Economic Agent in Local Economic Development: The Case of South Africa

Military bases can be important agents for local and regional economic development. This article examines the role of military spending in local economic development in South Africa, a country which, under apartheid, had high levels of military spending. The local economic impacts are analyzed of three operational military bases at Potchefstroom, Louis Trichardt’ and Heidelberg. It is argued that the military assumes a significant role in local economies and should be used by localities as a basis for competitive advantage in planning for local economic development.     

Reanimating a Comatose Goddess’: Reconfiguring Central Cape Town

Central Cape Town is no longer a tawdry, unsafe provincial enclave of day-time office workers, commuter shoppers and public administrators. After the decline since the 1980s due to suburban flight, a private–public partnership has improved the downtown’s state and image. Capitalising on spectacular heritage and location, property developers have been transforming work, residential and leisure spaces. Massive private investment in new and converted buildings, and in public space, is reconfiguring the old central business district (CBD) into a post-modern space of high-end production, service and consumption that is aestheticised, commoditised and historicised. Investors, young professionals, day visitors and tourists benefit more than the peripheral metropolitan majority. Despite inclusive rhetoric, the Africanisation of post-apartheid central Cape Town is less evident than its ‘glocalisation’.     

A multi-scale analysis of urban form and commuting change in a small metropolitan area (1990–2000)

Issues of growth, especially the spatial nature of recent urban development and its implications for travel patterns, have received a great deal of attention. In particular, questions persist as to how the spatial distribution of workers and jobs influences commute patterns. This paper investigates changes in commuting and land use patterns using measures of jobs–housing balance, commuting efficiency and other statistics. A smaller urban area is chosen for study (Tallahassee, FL, USA)and data on its workers, jobs, and commute patterns are obtained from the Census Transportation Planning Package for 1990 and 2000. The key research questions investigated probe whether there were substantial changes in urban form and commuting over the period. A two-tiered approach is taken where change is explored at the regional and local scales using GIS, optimization procedures, and inferential statistical techniques. The results reveal the extent of the spatial changes in the study area between 1990 and 2000. Major findings included stability in urban structure over the time period, as well as a persistent strong relationship between land use and commute patterns. These results are discussed in light of their implications for other cities and for future work.     

The future of Dutch housing associations

This paper discusses the future of the social rented sector in the Netherlands. There are several reasons why the position of this sector is currently under close scrutiny. Whereas attention to social rented housing had lapsed by the start of this century, the growing housing shortage and stagnation in the restructuring of older urban areas brought this sector back into the political spotlight. Also the European Commission is having a major impact on the future position of the sector. The Commission has ordered the Dutch Government to establish a level playing field by abolishing the privileges of the housing associations. Against this background, this paper discusses the possible tasks and proper functioning of the Dutch housing associations.     

What types of neighbourhoods are redlined?

This paper presents a case study of lending behaviour in the city of Rotterdam, the Netherlands. It shows what types of neighbourhoods are redlined by analyzing redlining data of the two largest suppliers of mortgage loans and comparing it to social-demographic and housing market data at the neighbourhood level. Although this approach cannot explain redlining, it can show which factors are related to lending behaviour. Low income, unemployment and ethnicity are strongly positively correlated to redlining. A discriminant analysis shows that the interaction between low income, unemployment or ethnicity on the one hand, and the average value of sold units on the other hand can best approximate redlining. Lastly, this paper also highlights the importance of scale. Manuel B. Aalbers formerly at: Amsterdam institute for Metropolitan and International Development Studies (AMIDSt), University of Amsterdam, Nieuwe Prinsengracht 130, 1018 VZ Amsterdam, The Netherlands     

Fire Emissions of Organics into the Atmosphere

The mass of dioxins, PAH (polycyclic aromatic hydrocarbons) and VOC (volatile organic compounds) emitted from fires to the atmosphere in Sweden per year has been estimated. The estimate is based on the number of fires in buildings, vehicles, waste and forest fires in Sweden in 1999. It is estimated that the total emission of dioxins from fires is in the range 0.5–1.4 g TEQ. The total emissions of PAH and VOC are in the ranges 2–12 ton and 13–200 ton, respectively. The estimated emission of dioxins from fires approximately corresponds to the total emission from traffic or half the emissions from municipal waste combustion (Swedish data from 1993). The fire statistics show that the mass of material combusted in building fires during a year is approximately 7500 ton, while that from forest fires is 2600 ton. Additionally, 2000–3000 tons are combusted in vehicle fires, fires in containers, etc. In addition to the more common types of fires during a year, individual large incidents may contribute significantly to the total emission. Such incidents include fires in municipal landfills or specific waste storage facilities (such as those for used tyres). An assessment of the consequences of such incidents has been made. This assessment implies that a large contribution to the emission of dioxins could be expected from fires in landfills and from fires in waste plastics (PVC) and tyres. Fires in deposits of wood chips and tyres are also significant potential sources of PAH and VOC.