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Combined System (combined + system)
Selected AbstractsPost-treatment of anaerobically treated medium-age landfill leachateENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2010Ebru Akkaya Abstract This study focused on the removal of COD and NH4+ from medium-age leachate. Experiments were performed in a laboratory-scale upflow anaerobic sludge blanket (UASB), a membrane bioreactor (MBR), and using magnesium ammonium phosphate (MAP) precipitation. MBR and MAP were used for the post-treatment steps for anaerobically treated leachate to increase the removal of organics and ammonium. The UASB reactor removed nearly all biodegradable organics and supplied constant effluent COD for all concentration ranges of influent leachate. Ammonium removal efficiency in the UASB reactor was relatively low and the average value was ,7.9%. Integration of MBR to the effluent of UASB reactor increased the average COD removal efficiency from 51.8 to 65.6% and maximum removal efficiency increased to 74.3%. MAP precipitation was applied as a final step to decrease the ammonium concentration in the effluent of UASB+MBR reactors. The effect of pH and the molar ratio of MAP constituents on the removal of ammonium were evaluated. At optimal conditions (pH: 9.0 and Mg/NH4/PO4: 1/1.2/1.2), 96.6% of ammonium was removed and MAP provided additional COD and turbidity treatment. Consequently, the combined system of MBR and MAP precipitation could be used as an appropriate post treatment option for the anaerobically treated medium-age landfill leachate. © 2009 American Institute of Chemical Engineers Environ Prog, 2010 [source] Simulating Seepage into Mine Shafts and Tunnels with MODFLOWGROUND WATER, Issue 3 2010Jacob Zaidel In cases when an equivalent porous medium assumption is suitable for simulating groundwater flow in bedrock aquifers, estimation of seepage into underground mine workings (UMWs) can be achieved by specifying MODFLOW drain nodes at the contact between water bearing rock and dewatered mine openings. However, this approach results in significant numerical problems when applied to simulate seepage into an extensive network of UMWs, which often exist at the mine sites. Numerical simulations conducted for individual UMWs, such as a vertical shaft or a horizontal drift, showed that accurate prediction of seepage rates can be achieved by either applying grid spacing that is much finer than the diameter/width of the simulated openings (explicit modeling) or using coarser grid with cell sizes exceeding the characteristic width of shafts or drifts by a factor of 3. Theoretical insight into this phenomenon is presented, based on the so-called well-index theory. It is demonstrated that applying this theory allows to minimize numerical errors associated with MODFLOW simulation of seepage into UMWs on a relatively coarse Cartesian grid. Presented examples include simulated steady-state groundwater flow from homogeneous, heterogeneous, and/or anisotropic rock into a vertical shaft, a horizontal drift/cross-cut, a ramp, two parallel drifts, and a combined system of a vertical shaft connected to a horizontal drift. [source] Numerical stability of unsteady stream-function vorticity calculationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 6 2003E. Sousa Abstract The stability of a numerical solution of the Navier,Stokes equations is usually approached by con- sidering the numerical stability of a discretized advection,diffusion equation for either a velocity component, or in the case of two-dimensional flow, the vorticity. Stability restrictions for discretized advection,diffusion equations are a very serious constraint, particularly when a mesh is refined in an explicit scheme, so an accurate understanding of the numerical stability of a discretization procedure is often of equal or greater practical importance than concerns with accuracy. The stream-function vorticity formulation provides two equations, one an advection,diffusion equation for vorticity and the other a Poisson equation between the vorticity and the stream-function. These two equations are usually not coupled when considering numerical stability. The relation between the stream-function and the vorticity is linear and so has, in principle, an exact inverse. This allows an algebraic method to link the interior and the boundary vorticity into a single iteration scheme. In this work, we derive a global time-iteration matrix for the combined system. When applied to a model problem, this matrix formulation shows differences between the numerical stability of the full system equations and that of the discretized advection,diffusion equation alone. It also gives an indication of how the wall vorticity discretization affects stability. Despite the added algebraic complexity, it is straightforward to use MATLAB to carry out all the matrix operations. Copyright © 2003 John Wiley & Sons, Ltd. [source] Thermal performance of a packed bed reactor for a high-temperature chemical heat pumpINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2001Yukitaka Kato Abstract The thermal performance of a chemical heat pump that uses the reaction system of calcium oxide/lead oxide/carbon dioxide, which is developed for utilization of high-temperature heat above 800°C, is studied experimentally. The thermal performance of a packed-bed reactor of a calcium oxide/carbon dioxide reaction system, which stores and transforms a high-temperature heat source in the heat pump operation, is examined under various heat pump operation conditions. The energy analysis based on the experiment shows that it is possible to utilize high-temperature heat with this heat pump. This heat pump can store heat above 850°C and then transform it into a heat above 900°C under an approximate atmospheric pressure. An applied system that combines the heat pump and a high-temperature process is proposed for high-efficiency heat utilization. The scale of the heat pump in the combined system is estimated from the experimental results. Copyright © 2001 John Wiley & Sons, Ltd. [source] Thermodynamic and thermoeconomic analyses of an irreversible combined Carnot heat engine systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2001Jincan Chen Abstract A combined cycle model which includes the irreversibilities of finite-rate heat transfer in heat-exchange processes and heat leak loss of the heat source is used to analyse the performance of a multi-stage Carnot heat engine system. The efficiency, power output, ecological function and profit of operating the combined system are optimized. The optimally operating region of the combined system is determined. The optimal combined conditions between two adjacent cycles in the combined system are obtained. Moreover, the cycle model is generalized to include the internal irreversibilities of the working fluids so that the results obtained here become more general. Copyright © 2001 John Wiley & Sons, Ltd. [source] Performance of the hydrolyzation film bed and biological aerated filter (HFB,BAF) combined system for the treatment of low-concentration domestic sewage in south ChinaJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2006Xiao Ling Abstract The performance of the hydrolyzation film bed and biological aerated filter (HFB,BAF) combined system in pilot scale (with a daily treatment quantity of 600,1300 m3 d,1), operated for 234 days, for low-strength domestic sewage was assessed using different amounts of aeration, reflux ratios and hydraulic loading rates (HLR). In steady state it was found that the average removal efficiency of chemical oxygen demand (COD) and biological oxygen demand at 5 days (BOD5) were 82.0% and 82.2% and the average effluent concentrations were 15.8 mg L,1 and 9.4 mg L,1 respectively as the HFB was running at an HLR of 1.25,1.77 m3 m,2 h,1 and the BAF was running at an HLR of 1.56,2.21 m3 m,2 h,1. In general, the removal efficiency of total nitrogen (TN) fluctuated with the HLR, gas,water ratio and reflux ratio, so the ratio of gas to water should be controlled from 2:1 to 3:1 and the reflux ratio should be as high as possible. The effluent concentration of TN was 10.4 mg L,1 and the TN removal averaged 34.3% when the gas,water ratio was greater than 3:1 and the reflux ratio was 0.5. The effluent concentration and removal efficiency of NH4+ -N averaged respectively 2.3 mg L,1 and 78.5%. The overall reduction of total phosphorus (TP) was 30% and the average effluent concentration was 0.95 mg L,1. The removal efficiency of linear alkylbenzene sulfonates (LAS) reached 83.8% and the average effluent concentration was almost 0.9 mg L,1. The effluent concentration and removal efficiency of polychlorinated biphenyls (PCBs) were 0.0654 µ g L,1 and 37.05% respectively when the influent concentration was 0.1039 µ g L,1. The excess sludge containing water (volume 15 m3) was discharged once every 3 months. The power consumption of aeration was 0.06,0.09 kWh of sewage treated. The results show that the HFB,BAF combined technology is suitable for the treatment of low-concentration municipal sewage in south China. Copyright © 2005 Society of Chemical Industry [source] Low-temperature scanning system for near- and far-field optical investigationsJOURNAL OF MICROSCOPY, Issue 3 2003D. V. Kazantsev Summary A combined system for far- and near-field optical spectroscopy consisting of a compact scanning near-field optical microscope and a dedicated spectrometer was realized. The set-up allows the optical investigation of samples at temperatures from 10 to 300 K. The sample positioning range is as large as 5 × 5 × 5 mm3 and the spatial resolution is in the range of 1.5 µm in the far-field optical microscopy mode at low temperatures. In the scanning near-field optical microscope mode the resolution is defined by the microfabricated cantilever probe, which is placed in the focus of a double-mirror objective. The tip-to-sample distance in the scanning near-field optical microscope is controlled by a beam deflection system in dynamic scanning force microscopy mode. After a description of the apparatus, scanning force topography images of self-assembled InAs quantum dots on a GaAs substrate with a density of less than one dot per square micrometre are shown, followed by the first spectroscopic investigations of such a sample. The presented results demonstrate the potential of the system. [source] Low-frequency dielectric spectroscopy as a tool for studying the compatibility between pharmaceutical gels and mucous tissueJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2003Helene HäGerström Abstract This interdisciplinary work demonstrates how low-frequency dielectric spectroscopy, a technique that is frequently used within physics, can be used to assess the possibilities of intimate surface contact between a polymer gel and mucous tissue, which is generally considered to be the first step in the mucoadhesion process. The dielectric responses of five different gels, of freshly excised porcine nasal mucosa and of systems made by combining the two were measured. All spectra were modeled by a Randles electric circuit containing a diffusion element, a barrier resistance in parallel with a capacitance, and a high-frequency resistance. The results were used to create a measure of the compatibility between the gel and the mucus, which we have named the compatibility factor. Thus, the compatibility factor provides us with a measure of the ease with which a charged species passes the interface between a gel and the mucus layer. The compatibility factor is calculated from the high frequency (kHz region) response of the gel, of the mucosa, and of the combined system. The two highest compatibility factors in this study were obtained for gels based on crosslinked poly(acrylic acid) and chitosan, which was in agreement with the results from mucoadhesion measurements that were performed using a tensile strength method. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1869,1881, 2003 [source] Efficient electrically small loop antenna using SRR structure on the ground planeMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2009Joong-Kwan Kim Abstract In this article, an electrically small loop antenna using capacitive loading is proposed. The loop antenna acts as an inductive element and the gap between two lines of SRR in the ground plane acts as a capacitive element; hence the combined system with these two elements is operated as a LC resonator. The equivalent circuit model of the antenna structure is applied to analyze and qualify the design correctness. Although the proposed antenna has a very small size, it shows a good performance. The measured maximum gain and radiation efficiency of the fabricated antenna at the frequency of 2.04 GHz are 3.6 dBi and 81.02%, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 201,204, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24016 [source] Combined PIV/PTV-Measurements for the Analysis of Bubble Interactions and Coalescence in a Turbulent FlowTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003Dirk Bröder Abstract In order to allow more reliable modeling of coalescence processes in turbulent bubbly flows, detailed experiments in a double loop reactor were performed. Narrow and essentially monomodal bubble size distributions in the range of 2 to 4 mm were created. For simultaneous measurements of bubble size, bubble velocity and liquid velocity a combined system of PIV and PTV was developed and applied. It was possible to determine bubble size distributions and mean, as well as fluctuating velocities for both phases. The spatial changes of the bubble size distribution, due to the influence of bubble coalescence, was analyzed and coalescence rates were calculated. Afin d'améliorer la fiabilité de la modélisation des procédés de coalescence dans les écoulements bouillonnants turbulents, des expériences poussées ont été menées dans un réacteur à double boucle. Des distributions de taille des bulles étroites, essentiellement monodisperses, dans la gamme de 2 à 4 mm, ont été créées. Pour les mesures simultanées de la taille des bulles, de la vitesse des bulles et de la vitesse du liquide, on a mis au point et appliqué un système combiné de PIV et PTV. Il a été possible de déterminer les distributions de taille des bulles et la moyenne mais également les vitesses fluctuantes pour les deux phases. Les changements spatiaux de la distribution de la taille des bulles dus à l'influence de la coalescence des bulles ont été analysés et les vitesses de coalescence ont été calculées. [source] Assessment of the impact of key terrestrial observing systems using DMI-HIRLAMTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 633 2008Bjarne Amstrup Abstract Following a EUCOS decision to make an assessment of the impact on NWP forecasts of different components of the current observing systems in various combinations, a number of OSEs (Observing System Experiments) have been made by a number of NWP centres, with some running global models and some limited-area models. The Danish Meteorological Institute (DMI) carried out OSEs with the limited-area model HIRLAM. The following runs were made by DMI (two periods, one month each): (1) A baseline system (BL); (2) BL + all aircraft wind and temperature data; (3) BL + non-GUAN radiosonde winds; (4) BL + non-GUAN radiosonde temperature and wind; (5) BL + wind profiler; (6) as (4) + aircraft wind and temperature; (7) as (4) + non-GUAN radiosonde humidity; (8) as BL + all in situ data (full combined system); and (9) BL + E-AMDAR only (no ACARS and no traditional AIREPs). The lateral boundaries for these OSEs were provided by runs made by ECMWF, which was one of the centres to make OSEs with a global model. The main conclusions are that the radiosonde data are the most important data, closely followed by the aircraft data, and that aircraft data and radiosonde data are complementary and not redundant data. Furthermore the results show that it is important to have both wind and temperature profile data; wind data alone produce much poorer impact. Copyright © 2008 Royal Meteorological Society [source] Assessment of Finger Forces and Wrist Torques for Functional Grasp Using New Multichannel Textile NeuroprosthesesARTIFICIAL ORGANS, Issue 8 2008Marc Lawrence Abstract:, New multichannel textile neuroprotheses were developed, which comprise multiple sets of transcutaneous electrode arrays and connecting wires embroidered into a fabric layer. The electrode arrays were placed on the forearm above the extrinsic finger flexors and extensors. Activation regions for selective finger flexion and wrist extension were configured by switching a subset of the array elements between cathode, anode, and off states. We present a new isometric measurement system for the assessment of finger forces and wrist torques generated using the new neuroprostheses. Finger forces (from the middle phalanxes) were recorded using five load cells mounted on a "grasp handle" that can be arbitrarily positioned in space. The hand and the grasp handle were rigidly mounted to a 6-degree of freedom load cell, and the forces and torques about the wrist were recorded. A vacuum cushion was used to comfortably fixate the forearm. The position and orientation of the forearm, wrist, fingers, and handle were recorded using a new three-dimensional position measurement system (accuracy <±1 mm). The measurement system was integrated into the real-time multichannel transcutaneous electrode environment, which is able to control the spatiotemporal position of multiple activation regions. Using the combined system and textile neuroprosthesis, we were able to optimize the activation regions to produce selective finger and wrist articulation, enabling improved functional grasp. [source] Efficiency of permeable pavement systems for the removal of urban runoff pollutants under varying environmental conditionsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2010Kiran Tota-Maharaj Abstract Urban surface water runoff typically contains a high but variable number of pathogens, nutrients, and sediments that require removal before reuse. Permeable pavements can improve the water quality through interception, filtration, sedimentation, nutrient transformation, and microbial removal. There is currently insufficient scientific information available on the treatment efficiencies of permeable pavements combined with earth energy systems with regards to the removal of storm water pollutants such as nutrients, sediments, and microbial pollutants. This study evaluates the efficiency of 12 tanked combined systems during a medium-term study. The research assessed weekly the removal of the microbial indicators total coliforms, Escherichia coli, and fecal Streptococci, as well as the key nutrients ammonia-nitrogen, nitrate-nitrogen, and ortho-phosphate-phosphorus, and physical variables such as suspended solids and turbidity. Total coliforms, E. coli, and fecal Streptococci were removed by 98,99%. The ammonia-nitrogen and ortho-phosphate-phosphorus removal efficiencies were 84.6% and 77.5%, respectively. An analysis of variance indicated that the presence or absence of a geotextile did result in a very highly statistically significant difference (P < 0.001) with respect to the removal of both ammonia-nitrogen and ortho-phosphate-phosphorus. Suspended solids, turbidity, and biochemical oxygen demand were reduced by 91%, 82%, and 88%, respectively. These results indicate the potential of the proposed novel system in urban runoff pollutant removal and subsequent reuse of the treated water. © 2010 American Institute of Chemical Engineers Environ Prog, 2010 [source] | ||||||||||||||||