Effects of anchoring tensile stresses in axially loaded plates and sections

Thin-walled compression members are commonly designed on the assumption that the loaded edges remain straight. Under this assumption, tensile stresses develop in the most flexible parts of the component plates at advanced local buckling deformation, and thus are assumed to be ‘anchored’ at the ends. However, current design rules for plate elements, such as the Winter formulae, are partly based on tests in which the load was applied by use of rigid platens that did not permit tensile stresses to develop. There exists an apparent inconsistency between the assumption of straight loaded edges and the use of a design curve calibrated from tests in which the loaded edges of component plates may not have remained straight.This paper addresses this apparent inconsistency by comparing finite element solutions for the conditions of straight loaded edges and loading by use of a contact surface between the plate edge and a non-deformable rigid body end platen, where there is no constraint for the plate edge to remain in contact with the rigid body. Solutions are provided for a single half-wavelength of unstiffened and stiffened plate elements simply supported along three and four edges, respectively. The effect of multiple half-wavelengths is also investigated, as is the effect of interaction between elements in practical sections comprising stiffened and unstiffened elements.     

Model for oxygen transfer in rotating biological contactor

Rotating biological contactor is being widely used for wastewater treatment but there is an apparent lack of knowledge about the rate at which oxygen transfer occurs, in physical and biological system. In this study the transfer of oxygen from air to water by a rotating disc air-liquid contactor in physical system is investigated. The oxygen transfer model suggested by Kim and Molof, Water Sci. Technol. 14 (1982) 569, was modified and the developed model is termed as modified Kim and Molof model. The model was calibrated by using available data in literature and validated by experiments conducted in this study. The effect of significant physical parameters was integrated into a single term and is termed as volume renewal number. The modified Kim and Molof model was compared with the other available models. The coefficient of determination (R(2)) for the modified Kim and Molof model obtained is 0.95 which is much higher than in the other available models. Thereby the model is expected to estimate oxygen transfer more accurately. Further, a simplified linear model between K(L)a and the volume renewal number is proposed. Both modified Kim and Molof and linear model estimate the overall oxygen transfer coefficient (K(L)a) accurately.     

A field comparison of four fungal aerosol sampling instruments: inter-sampler calibrations and caveats

Four bioaerosol samplers (Reuter Centrifugal, Andersen N6 Single Stage, Surface Air System Super 90, and Air-o-Cell) were used to take c. 300 side-by-side measurements at 75 public building sites. Regression models were developed to examine the relationships between each method pair. The models demonstrate that measurements from these instruments are not directly comparable, requiring inter-instrument calibration. Sampling location (indoor vs. outdoor) was a confounder in all the pairwise comparisons between samplers. In addition, the slopes of the relationships between all method pairs except one differed in indoor vs. outdoor locations. These results emphasize that direct comparisons between methods should not be undergone without prior calibration. Where measurement circumstances are similar to those of this study, the regression models might serve as a basis to convert measurements made with one instrument to those made with another. However, the robustness and generalizability of the models in different measurement settings needs to be assessed. PRACTICAL IMPLICATIONS: Many different bioaerosol sampling devices are in common use for indoor air quality studies. If data from research studies are to be compared, an approximation of the relationships between the equipment would be useful. A comparison of three culturable sampling devices (Andersen N6, SAS 90, RCS) and one particulate sampling device (Air-o-Cell) collecting simultaneous samples under field conditions showed high linear correlations between methods. However, while direct comparisons between sampling data were not possible, the regression models reported here explained 60-85% of the variance in fungal concentrations, and underscored the importance of the effect of environment on measurement.     

Moisture buffering and effect of ventilation rate and volume rate of hygrothermal materials in a single room under steady state exterior conditions

In this paper, experiments and simulations investigating the moisture buffering of the gypsum boards are described. A test chamber was used for the experiments. The gypsum board was installed on the interior surface in the test chamber. This chamber was located in a climate chamber. The ambient condition of the chamber was controlled at constant temperature and humidity. In the experiment three cases of ventilation rate, no ventilation, 1.0 air change per hour and 5.0 air changes per hour, were investigated. In the experiment the relationship between moisture buffering and volume rate of the materials, various area and locations of the gypsum boards on the surrounding walls were investigated.     

A fire safety study of Hong Kong refuge floor building wall layout design

Since 1996, refuge floors have been an indispensable passive building element of the fire protection plan for Hong Kong high-rise buildings. These floors must be designed to comply with the relevant requirements of the Building Codes of Hong Kong. Hence, 50% of the floor area must be deployed for refuge purposes. And they must have at least two fully open building side walls so that a desired wind effect is assumed so that any smoke that enters will be purged from the safe area. Therefore wind-induced natural cross-ventilation is of prime importance for the protection of the refuge floor in fire safety. If this wind effect is not achieved, entering smoke will accumulate and cause the safety system to fail. Therefore fundamental studies of this flow phenomenon are very important and needed. This paper studies the wind-induced flow behaviour of Hong Kong's refuge floors. Different building wall layout designs are addressed. By way of this study, the author suggests that a refuge floor shall be designed to have two opposite building side walls open instead of the present Building Codes that require at least any two of them.     

Global warming potential of wheat production in Western Australia: a life cycle assessment

This study presents a greenhouse gas (GHG) life cycle assessment of 1 tonne of wheat transported to port in south-western Australia, including emissions from prefarm, onfarm and postfarm stages. The prefarm stage included GHG emissions from agricultural machinery, fertiliser and pesticide production. The onfarm stage included GHG emissions from diesel use, liming and nitrous oxide (N₂O) emissions from N fertiliser applications. The postfarm stage included grain storage and transportation to the port. GHG emissions decreased from 487 to 304 kg carbon dioxide (CO₂) equivalents when we used regional-specific data for N₂O emissions instead of the IPCC default value for the application of synthetic N fertilisers to land (1.0%). Fertiliser production in the prefarm stage contributed significantly (35%) to GHG, followed by onfarm CO₂ emissions (27%) and emissions from transportation of inputs and wheat (12%). N₂O emissions from paddock represented 9% of the total GHGs emitted. We recommend utilising regionally specific data for soil N₂O emissions, rather than international default values, when assessing GHG for agricultural production systems.     

Mehrzweckspielplatz; Fl?chenwidmung "Wohngebiet"; Grünland-Sonderwidmung für bestimmte Spiel- und Sportarten

Die Errichtung eines (hier: über 500 m² gro?en) Mehrzweckspielplatzes ist baubewilligungspflichtig. Ein solcher Mehrzweckspielplatz (hier: mit der projektierten Nutzung für verschiedene Ballspiele, wie zB Tennis) ist im "Wohngebiet" nicht zul?ssig, sondern erfordert die Widmung "Grünland" (Sonderwidmung für bestimmte Spiel- und Sportarten).     

Parteistellung der Nachbarn; 50 m Entfernung

Der für die Nachbarparteistellung ma?gebliche Abstand von h?chstens 50 m ist vom "zu bebauenden Grundstück" zu bemessen. Beim "zu bebauenden Grundstück" kann es sich auch um mehrere grundbuchsrechtliche Grundstücke handeln.     

基于非线性静态分析和软件的公路桥抗震评估

受地震扰动时,可以通过一系列方法对桥的响应进行评估。传统的方法是采用线性静态或动态分析结合适当的修正来说明非弹性响应,而现行的实践着重强调非线性静态分析方法。本研究采用线性动态分析程序,对两跨公路桥的初步地震响应进行分析以确定潜在的非弹性响应。按照两个非线性静态分析方法对桥进行分析,评估了两种方法所预测的全部响应的差别以及采用各种软件进行非线性静态分析的效率。结果显示:所采用的两种不同非线性响应预测的非线性静态分析方法,由于存在大量的简化,都不能获得正确的结果。此外,研究还揭示在综合分析和提供破坏过程图方面,一些软件更适合进行非线性静态分析(如塑性铰的性能)。     

Improved coverage of fungal diversity in polluted groundwaters by semi-nested PCR

Traditional methods used for studying communities of aquatic hyphomycetes are based on the detection and identification of their asexual spores under a microscope. These techniques limit detection to aquatic fungi present in sufficient quantity and capable of sporulating under laboratory conditions. Our objective was to develop a molecular approach to detect and monitor all types of fungi (i.e. strictly or facultatively aquatic) in harsh habitats (i.e. groundwater wells and heavily polluted surface water) where fungal biomass may become limited. We developed a semi-nested PCR protocol for fungal 18S ribosomal RNA genes coupled to subsequent analysis of the PCR products by Temperature Gradient Gel Electrophoresis (TGGE) to monitor the fungal community structure in aquatic habitats characterized by a pollution gradient. Our TGGE-protocol was compared with the traditional morphological approach and revealed a higher diversity in groundwaters and in some polluted surface waters. Thus, PCR-TGGE is a promising alternative in particular in habitats with low fungal biomass. The dynamics of fungal biomass and sporulation rates during the first weeks of leaf colonization showed that habitats with adverse ecological conditions allow only reduced fungal growth, which might subsequently impact upper trophic levels and thus interfere with key ecological processes of leaf decomposition.