A technique has been developed that allows the application of free-standing membranes of polymer adhesives used in microfabricated structures. The film is made free-standing by the application of the adhesive to a pol...
A technique has been developed that allows the application of free-standing membranes of polymer adhesives used in microfabricated structures. The film is made free-standing by the application of the adhesive to a polymer template, followed by an adhesion step to a microfabricated substrate, and the final release of the film by the removal of the polymer template. It was found that the surface treatment used to treat the Teflon template made it adhere too strongly to the adhesive film for this application. The results show that Gel-Paks make a suitable template for the transference of polymer films over holes of at least micron size.
A numerical model for simulation of the regional flow and salt-water intrustion in an integrated stream-aquifer system in coastal regions is developed, considering the dynamic interaction between the streams and the a...
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A numerical model for simulation of the regional flow and salt-water intrustion in an integrated stream-aquifer system in coastal regions is developed, considering the dynamic interaction between the streams and the aquifer, The stream-aquifer model comprised of a two-dimensional depth-average finite-element model of the aquifer system and a quasi-steady node and reach model of the river network. The applicability of the model was demonstrated, through simulation of the spatial and temporal distributions of flow and salinity in the estuaries and in the underlying aquifer of the Southwest Region of Bangladesh. The important management aspects of water transfer and additional pumping and their effects on the system were evaluated. The interactions between the streams and the aquifer significantly influenced the flow and salt-water intrusion in the aquifer and the river network. An increased abstraction of ground water in the area caused a significant increase in the estuarine salinity. The salinity intrusion in the estuaries of the area, except in the southwest corner, could be reduced significantly by diverting the available water from the Ganges through the boundary river Gorai.
Research is focused on an integrated way to simultaneously optimize the bleaching operations and subsequent wastewater treatment for pulp and paper mills. Bleach wastewaters from ClO2-bleached pulping studies at Insti...
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Research is focused on an integrated way to simultaneously optimize the bleaching operations and subsequent wastewater treatment for pulp and paper mills. Bleach wastewaters from ClO2-bleached pulping studies at Institute of Paper Science and technology (IPST) were used as the feed for batch reactors to test and rank the treatability and kinetics. The key aspect of the system is the use of sequential anaerobic/aerobic phases to enhance reductive dehalogenation of chloro-organic materials. Two continuous reactor systems, one operated in an anaerobic-aerobic mode and a second in an aerobic-aerobic mode, received bleaching wastewater obtained from a full-scale plant. Acclimated cultures from both continuous reactors were used to quantify the AOX (Adsorbable Organic Halide) and COD removal from various bleaching wastewaters. In general, the sequential anaerobic/aerobic treatment of bleach wastewater can improve both biotreatability and degradation rates. (C) 1997 IAWQ.
A monthly irrigation planning model is formulated for determining the optimal cropping pattern and the groundwater abstraction requirement in an existing groundwater development project. Two objectives, maximisation o...
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A monthly irrigation planning model is formulated for determining the optimal cropping pattern and the groundwater abstraction requirement in an existing groundwater development project. Two objectives, maximisation of net economic benefit and maximisation of irrigated area, aspired to by both the irrigation authority and the individual farmers in the Sukhothai Groundwater Development Project in Thailand are considered, To account for uncertainty in water resources availability, the model is solved for three levels of reliability of rainfall and groundwater resources (80, 50 and 20%). The effects of deficit irrigation on the net benefit and cropping intensity as well as on the yield of crops are also assessed by considering three levels (no deficit, 25% deficit and 50% deficit) of water application to the crops, To select the best alternative plan, a multi-objective analysis is carried out using the Analytic Hierarchy Process considering the preference of the decision makers, including farmers and irrigation project managers, The selected decision makers in the Sukhothai Project collectively allocate almost half of the total weight to reliability (or risk) factors, while the remaining preference is almost equally divided between the two objectives listed above. On average, they seem to prefer the planning alternative corresponding to average (hydrologic) conditions and full irrigation without any deficit.
Three aspects involving the use of thin walled cylinders for the determination of material properties of transverse isotropic rock have been studied. It has been demonstrated that for the specific specimen geometry te...
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Three aspects involving the use of thin walled cylinders for the determination of material properties of transverse isotropic rock have been studied. It has been demonstrated that for the specific specimen geometry tested, the distribution of tangential strains across the specimen is close to linear. Test results illustrate the varied development of radial strains which are noted for different rock types when subjected to identical conditions of radial compression. Finally, the development of radial strains has been shown to be directly dependent upon specimen geometry and stress dependence of the Poisson ratio within the plane of material symmetry.
Only comparatively few experimental studies have been carried out to investigate the performance of the HEC-6 river morphological model. The model was developed by the Hydrologic engineering Center of the US Army Corp...
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Only comparatively few experimental studies have been carried out to investigate the performance of the HEC-6 river morphological model. The model was developed by the Hydrologic engineering Center of the US Army Corps of Engineers. In this study, experiments were carried out in a 20m long concrete flume 0 . 6m wide with varying rectangular cross-sections. The channel bed is paved with uniform sand of D-50 = 0 . 9 mm and D-90 = 1 . 2mm within the test reach of 12m. Two types of experiments were carried out with sediment transport, one under steady uniform flow and another under steady non-uniform flow conditions. Nine steady uniform flow experiments were carried out to compare the measured equilibrium relationship of dow and sediment transport rate with two bedload formulae, namely, Du Boys and Meyer-Peter and Muller, and with three total load formulae, namely, Toffaleti, Laursen and Yang. It was found that even though the sediment transport consists of a certain portion of bedload, the total load formulae give satisfactory results and better agreement than the two bedload formulae. Five steady non-uniform flow experiments were carried out under various conditions of varying bed profile and channel width and also with sediment addition and withdrawal. The measured transient water surface and bed pro files are compared with the computed results from the HEC-6 model. It was found that the Toffaleti and Yang total load formulae used in the HEC-6 model give the most satisfactory prediction of actual bed profiles under various conditions of non-uniform flow and sediment transport. The effects of Manning's n, variations of sediment inflow, various sediment transport formulae, sediment grain size and the model numerical parameters, i.e. distance interval Delta x and numerical weighting factor, on the computed water surface and bed profiles were determined. It was found that the selection of the sediment transport formulae has the most significant effect on the computed res
作者：
Lo, IMCEnvironmental and Hydraulics Program
Department of Civil & Structural Engineering Hong Kong University of Science & Technology Clear Water Bay Kowloon Hong Kong China
The main objectives of this study were to develop a useful database for the leachate quality of Hong Kong landfills, and to compare different experimental trials for the treatment of methanogenic-stage sanitary landfi...
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The main objectives of this study were to develop a useful database for the leachate quality of Hong Kong landfills, and to compare different experimental trials for the treatment of methanogenic-stage sanitary landfill leachate, which is generally characterized by a low chemical oxygen demand (COD) of 3000 mg L(-1) or less. Extensive chemical analysis data of leachate composition generated from 10 landfills in Hong Kong were collected to identify variations in leachate quality. Variations in COD and ammonia-nitrogen (NH3-N) with time revealed that the rate at which Hong Kong landfills become 'methanogenic' is relatively fast. The transition from phase II (where leachates are characterized by high 5-day biochemical oxygen demand values) to phase III (where high organic strength leachates are converted into methane and carbon dioxide) for the landfills in Hong Kong took less than one year. Several leachate indicator parameters were utilized to assess the stabilization of the landfill. Controlled experimental studies using an aerobic biological treatment process (i.e., sequencing batch reactor) were used to examine its treatment efficiency. Retention times of 20 days and 40 days resulted in a removal efficiency of NH3-N in excess of 99%.
Salt-water encroachment in the multi-layer groundwater system underlying the Bangkok metropolitan area was simulated with a quasi-three-dimensional flow and solute-transport model. The quasi-three-dimensional model us...
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