创新可持续性建筑的消防安全设计

<正>引言"侨福芳草地"(Parkview Green)出于创新可持续性的设计构思,设有一个特殊的玻璃金字塔环保罩,内包含了四座高层建筑,使之既不同于普通的大空间建筑,也不同于一般的建筑群,一旦共享空间发生火灾,烟气可能在环保罩下聚集,给消防设计带来巨大挑战。除环保罩外,与其它建筑不同还有,"芳草地"的首层不是位于街面高度,而是在地下二层,在建筑周围区域形成一个露天的两层下沉广场。而其下沉广场的独     

Developmental Urbanism,City Image Branding and the “Right to the City” in Transitional China

From the 1980s, urban-led economic pursuits, city image building, and residency control of rural migrants have been three key elements which are complementary yet conflicting in China’s development path. Whilst the two former are pro-growth oriented, the “low-image” and “potential risk to slum formation” of rural migrants are found by the state to be incompatible with the modernist urbanism sought after. Under the state’s ambitious city branding and intensive-cum-high value operations, the paper revisits Henri Lefebvre and David Harvey’s notions on the “right to the city”. It highlights the social injustice issue of differentiated citizenship in terms of inequity of access to services and inequality between urban and rural origins. City-branding efforts have indeed contributed towards economic efficiency and land use rationalization but are characterized by an asymmetrical power and spatial redistribution process filled with inequalities against migrant workers and deprivation of rights. Recent developments have shown that the state has compromised and become more people-oriented and inclusive in its approach towards rural migrants.     

Polycyclic aromatic hydrocarbons (PAHs) in urban surface dust of Guangzhou, China: Status, sources and human health risk assessment

Ninety-six urban surface dust samples collected from Guangzhou, a typical urban center in South China, were analyzed for 16 PAHs (2-6 rings). ∑ PAHs concentrations in the urban surface dust ranged from 0.84 to 12.3 μg/g with a mean of 4.80 μg/g. High molecular weight compounds (4-6 rings) contributed to 62 to 94% of ∑ PAHs mass in the surface dust samples. Four hotspots with highest ∑ PAHs were identified via kriging prediction mapping, representing the highly-urbanized regions: central downtown, highway and industrial area. Two major origins of PAHs inputs to urban surface dust were identified as vehicle emissions (51.9%) and coal combustion (26.8%). The 95% UCL of Incremental Lifetime Cancer Risk (ILCR) due to human exposure to urban surface dust PAHs in central South China was 3.03 × 10⁻⁶ for children and 2.92 × 10⁻⁶ for adults.     

A combined distribution and assignment model for continuous facility location problem

Consider a general, heterogeneous geographical space with a set of competitive facilities, where the customers' demand locations from each of the facilities are continuously dispersed over the area. The total demand generated from a particular location in the space is fixed, but the demands from this location to the set of competitive facilities are subject to a distribution function with respect to the relative transportation costs to these facilities. Furthermore, we take into account congested transportation cost in characterizing customer choices. Congestion effect is explicitly built into our model by using a flow-dependent and location-dependent transportation cost function. The routing behavior of customers over the space and the user equilibrium choices of facilities are modeled by constructing a spatial user equilibrium flow pattern. The problem is formulated as a combined distribution and assignment model. An iterative algorithm between the distribution function for the choice of facilities and a mixed finite element method for route choices is proposed to solve the resulting continuous facility location problem. A numerical example is given to demonstrate the effectiveness of the proposed methodology. Received: May 1999/Accepted: May 2000     

Direct laser sintering of a copper-based alloy for creating three-dimensional metal parts

Direct laser sintering of metal, as one of the important developments in rapid prototyping technologies, is discussed in this paper. A special copper-based alloy is used for this rapid prototyping process. Experiments on the sintering conditions of this material had been conducted in a self-developed high temperature metal sintering machine. The mechanism of laser sintering for this kind of material was disclosed by SEM analysis of microstructures of sintered parts. The density, surface roughness and mechanical properties of the laser sintering parts due to variation of process parameters were measured and analysed. The effect of process parameters to the accuracy of sintered parts was also investigated. Thus, optimum parameters were obtained for direct laser sintering of three-dimensional metal parts.     

Investigation of micro-EDM material removal characteristics using single RC-pulse discharges

Similar to EDM, in micro-EDM, intense heat is generated between the workpiece and tool electrode by the discharge through a dielectric medium to result in the formation of a microcrater that is much smaller in size. In this study, a single-spark generator has been developed to study the erosion characteristics from the microcrater size. Using a simple heat transfer model, the efficiency at different discharge condition is also deduced. It is found that at lower-energy (<50 μJ) discharges, the energy required to remove the unit volume of material, defined as the specific energy, is found to be much less than that at higher-energy discharges. Additionally, the ratio of the standard deviation to the measured microcrater size is found to be lower at lower discharge energy, indicating greater consistency in shape and size when the discharge occurs at lower energy. The fundamental erosion mechanism of material is discussed by considering melting and evaporation phenomena using theoretical modeling. The average efficiency of erosion, when estimated to be due primarily to melting or evaporation alone, is found to be up to an order of magnitude higher at lower-energy discharges than that at higher-energy discharges.     

Micromechanics of compressive failure and spatial evolution of anisotropic damage in Darley Dale sandstone

The micromechanics of compressive failure in Darley Dale sandstone (with initial porosity of 13%) was investigated by characterizing quantitatively the spatial evolution of anisotropic damage under the optical and scanning electron microscopes. Two series of triaxial compression experiments were conducted at the fixed pore pressure of 10 MPa and confining pressures of 20 and 210 MPa, respectively. For each series, three samples deformed to different stages were studied. Failure in the first series was by brittle faulting. In contrast, failure in the second series was ductile, involving shear-enhanced compaction and distributed cataclastic flow. In the ductile series, crack density and acoustic emission activity both increased with the development of strain hardening. The stress-induced cracking was relatively isotropic. In the brittle series, crack density increased with the progressive development of dilatancy, with spatial distributions indicative of clustering of damage at the peak stress and shear localization in the strain softening stage. Dilatancy was associated with significant anisotropy in stress-induced cracking, that was primarily due to intragranular and intergranular cracking with a preferred orientation parallel to the maximum principal stress. Compared with published data for Westerly granite and San Marcos gabbro (with porosities of the order of 1%) and for Berea sandstone (with porosity of 21%), there is an overall trend for the stress-induced anisotropy (in a sample deformed to near the peak stress) to decrease with increasing porosity. The sliding wing crack model was adopted to analyze the evolution of anisotropic damage, using a friction coefficient and fracture toughness inferred from stress states at the onset of dilatancy. Significant discrepancy exists between the model prediction and microstructural data on stress-induced anisotropy, which is possibly due to limitations intrinsic to the microscopy technique as well as the sliding wing crack model.     

蓝牙技术与无线火灾自动报警系统

针对现阶段有线火灾自动报警系统的缺陷 ,通过对“蓝牙”技术的性能描述及其与红外无线技术的分析比较 ,提出了运用蓝牙技术将火灾自动报警系统连接组建成固定网络的远距离特别连接设备群 ,使火警信号在两个或多个电子设备之间通过无线传输进行信息交换和交叉操作的设想     

Environmental risk management for a cross interchange subway station construction in China

Ground surface settlement induced by urban subway construction using shallow tunnelling method is inevitable and it may cause a series of negative impact to existing nearby structures and utilities. In order to guarantee environmental safety, a risk management methodology which aims at process control for ground settlement and existing nearby structures is proposed. It includes 5-stage technology-based steps: survey of existing conditions, designing control standards for key risk factors, analyzing environmental response under tunnel construction and designing process control standards, monitoring and taking proper process control measures during construction, and risk reassessment after construction. This methodology was put into practice in the Huangzhuang subway station construction which is the largest cross interchange subway station construction using shallow tunnelling method in China. According to site survey, nearby pipelines and existing buildings were determined to be the key risk factors. The risk control standards for nearby pipelines and existing buildings were made according to available standards in China and related literatures. Design of process control standards for ground surface settlement was assisted by numerical simulation, which aimed at controlling the key risk factors. During construction, monitoring was adopted for the nearby pipelines, existing buildings and ground surface. After the four drifts excavation of the double-deck part of Line 4, a series of risk control measures, which included treatment of the unfavorable geological bodies, installation of roof pipes, compensation grouting, full-face grouting and some other control measures, were taken. Due to these risk control measures, ground surface settlements, except at two measuring points of Line 4, were successfully controlled under the given process control standards for both Line 4 and Line 10. All the pipelines and buildings were under their normal service state during tunnel construction. The maximum deflection for the 6 pipelines above the station was controlled to be within 2 mm/m and the maximum settlement of all the monitoring points for the pipelines was less than 30 mm. For the four important existing buildings in close vicinity, the maximum deflection was less than 1 mm/m; the maximum settlement value was 6.8 mm and the maximum uplift value was 3.0 mm. The risk control system was shown to be effective in ensuring environment safety, structure safety and construction safety. These safety control methods, the methodology of designing these control standards and the measures taken in the construction can serve as a practical reference for other similar projects.