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91.
A simplified model of a municipal water recycle system is presented and gives a clear picture of the relationship between process variables such as the intensity of the treatment, the accumulation of pollutants and the number of times the water is re-used. The model can be used to determine the necessary requirements for the treatment process in order to reach a certain desired drinking water quality. This model is extended to cover a variety of practical conditions. It is also shown that accumulation under practical conditions is limited, even if there is no treatment. The model predicts that the recycle system can utilise a low quality supplementary supply, e.g. brackish water. Although the model is derived for a recycle system for domestic water supply it can be used for any closed loop water system. 相似文献
92.
近期有几个因素影响到玻璃钢化领域,不仅钢化工艺本身是推动钢化工业的主要因素,其它因素比如钢化市场的参与者们正面临着日益上升的全球化的竞争;客户需要高质量的产品和安全装配规则,新发明的非破坏性检验方法正代替成本较高的老方法;市场上满足汽车及建筑工业要求的新产品;最后钢化设备制造商所生产的满足于新玻璃产品的热处理要求的新产品。对这些问题全面进行了讨论以便为今天的钢化技术提供一个完整的画面。同时也对使用新钢化技术使钢化工业有更辉煌的明天提出了一些建议。 相似文献
93.
This paper describes a new test to determine flexibility of beam-to-column connectors used in conventional pallet racking systems. In this study, two different ways were used to find the flexibility of a connector. The connector developed was tested using the conventional cantilever method [Bajoria, KM. Three dimensional progressive collapse of warehouse racking, PhD Thesis, University of Cambridge, UK 1986], and then also using a newly proposed double cantilever method. To verify the results obtained from both the tests, a full scale frame test was carried out. In the double cantilever test the connector is subjected to three types of forces namely moment, shear and the axial pull by the beams, thereby giving behavior close to practical usage of connectors. Non-linear finite element analysis of both the tests and also of the full scale test were carried out using ANSYS [ANSYS 7.0—User's Manual, ANSYS Inc., 2005] software. The results obtained from the double cantilever test were found to match well with the full scale frame test. The experimental results and the finite element results are compared in this paper. 相似文献
94.
95.
Thin sections cut from cast concrete cylinders have been examined in transmitted light to investigate the significance of coarse aggregate type in “primary” microfracturing. Concretes manufactured with crushed-rock aggregates and gravel aggregates were studied and, in every case, the dominant fracture type was a parting of the aggregate-matrix bond. Bond cracking was least severe with the marble aggregate where epitaxial calcite over-growth was indicated. The ability of bond cracks to maintain continuity by bridging surface irregularities, via mortar cracks, reduced the inhibiting influence of rough-surfaced aggregate on bond-crack development. 相似文献
96.
The levels of lead in city street dirt and in soil from various locations in Glasgow were investigated during spring 1976. Lead concentrations in street dirt ranged from 150–2300 ppm, mean 960 ppm, and were significantly elevated with respect to the observed “natural” level of 78 ppm. Lead derived from anti-knock compounds in petrol and introduced to the environment via automobile exhausts was clearly implicated as the main source of lead pollution in a series of soil lead measurements at the centre and periphery of eight Glasgow parks.Various chemical leaching techniques were employed and compared. Less than 5% of street dirt and soil lead was found to be associated with the organic phase. 相似文献
97.
de Vet WW Kleerebezem R van der Wielen PW Rietveld LC van Loosdrecht MC 《Water research》2011,45(13):4008-4018
In groundwater treatment for drinking water production, the causes of nitrification problems and the effectiveness of process optimization in rapid sand filters are often not clear. To assess both issues, the performance of a full-scale groundwater filter with nitrification problems and another filter with complete nitrification and pretreatment by subsurface aeration was monitored over nine months. Quantitative real-time polymerase chain reaction (qPCR) targeting the amoA gene of bacteria and archaea and activity measurements of ammonia oxidation were used to regularly evaluate water and filter sand samples. Results demonstrated that subsurface aeration stimulated the growth of ammonia-oxidizing prokaryotes (AOP) in the aquifer. Cell balances, using qPCR counts of AOP for each filter, showed that the inoculated AOP numbers from the aquifer were marginal compared with AOP numbers detected in the filter. Excessive washout of AOP was not observed and did not cause the nitrification problems. Ammonia-oxidizing archaea grew in both filters, but only in low numbers compared to bacteria. The cell-specific nitrification rate in the sand and backwash water samples was high for the subsurface aerated filter, but systematically much lower for the filter with nitrification problems. From this, we conclude that incomplete nitrification was caused by nutrient limitation. 相似文献
98.
A short- and long-term toxicity study with α-hexachlorocyclohexane (α-HCH) was carried out with freshwater organisms of different trophic levels (algae, crustaceae and fishes). In this study mortality, immobilization, growth, reproduction, histopathologic changes and enzyme activities were chosen as criteria.Furthermore accumulation and elimination processes were investigated in separate organisms as well as the uptake of α-HCH by one organism and through a food-chain.Finally a tentative method for deriving an “ecological limit” for χ-HCH in surface water is described. 相似文献
99.
This paper presents the development of a comfort index that measures adaptivity in outdoor spaces. Over a 9-month period 649 people were surveyed in three locations, in temperatures between 10 and 28 °C. An exploratory factor analysis develops a 15-item scale of comfort that includes measures of adaptivity: clothing, exposure time and seating location. The scale is regressed on physical measures: average instantaneous wind speed; maximum wind speed; mean-exposed radiant temperature; mean-shaded radiant temperature and ambient temperature. The results model the relative contributions of the microclimatic factors for the comfort in the outdoor space. Analyses suggest gustiness and wind speed are most important in determining user satisfaction. There is strong support for the theory that people actively adapt to microclimatic conditions. 相似文献
100.