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Flow Ratio (flow + ratio)
Selected AbstractsTheoretical and experimental comparison of the performance of a single-stage heat transformer operating with water/lithium bromide and water/CarrolÔINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2002W. Rivera This paper compares under the same operating conditions, the theoretical and experimental performance of a single-stage heat transformer operating with the water/lithium bromide and the water/CarrolÔ mixtures, where CarrolÔ is a mixture of lithium bromide and ethylene glycol [(CH2OH)2] in the ratio 1:4.5 by weight patented by Carrier Corp. Flow ratios, gross temperature lifts, useful heat, and coefficients of performance are plotted for the heat transformer against temperatures and solution concentrations. Because the water/CarrolÔ mixture has higher solubility than water/lithium bromide and high experimental values were obtained for the gross temperature lift, it seems to be a better alternative mixture to be used in absorption heat transformers. Copyright © 2002 John Wiley & Sons, Ltd. [source] Vertical-type organic device using thin-film ZnO transparent electrodeELECTRICAL ENGINEERING IN JAPAN, Issue 2 2007Hiroyuki Iechi Abstract We propose a double heterojunction organic light-emitting diode (OLED) using a zinc oxide (ZnO) film, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O2 flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of the novel OLED were obtained, as high as 470 cd/m2 at 22 V and 7.6 mA/cm2. The results obtained here demonstrate that the vertical organic light-emitting transistor (OLET) using a ZnO layer as an electron injection layer is promising as a key element for flexible sheet displays. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 49,55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20151 [source] Effect of growing watershed imperviousness on hydrograph parameters and peak dischargeHYDROLOGICAL PROCESSES, Issue 13 2008Huang-jia Huang Abstract An increasing impervious area is quickly extending over the Wu-Tu watershed due to the endless demands of the people. Generally, impervious paving is a major result of urbanization and more recently has had the potential to produce more enormous flood disasters than those of the past. In this study, 40 available rainfall,runoff events were chosen to calibrate the applicable parameters of the models and to determine the relationships between the impervious surfaces and the calibrated parameters. Model inputs came from the outcomes of the block kriging method and the non-linear programming method. In the optimal process, the shuffled complex evolution method and three criteria were applied to compare the observed and simulated hydrographs. The tendencies of the variations of the parameters with their corresponding imperviousness were established through regression analysis. Ten cases were used to examine the established equations of the parameters and impervious covers. Finally, the design flood routines of various return periods were furnished through use of approaches containing a design storm, block kriging, the SCS model, and a rainfall-runoff model with established functional relationships. These simulated flood hydrographs were used to compare and understand the past, present, and future hydrological conditions of the watershed studied. In the research results, the time to peak of flood hydrographs for various storms was diminished approximately from 11 h to 6 h in different decrements, whereas peak flow increased respectively from 127 m3 s,1 to 629 m3 s,1 for different storm intensities. In addition, this study provides a design diagram for the peak flow ratio to help engineers and designers to construct hydraulic structures efficiently and prevent possible damage to human life and property. Copyright © 2007 John Wiley & Sons, Ltd. [source] Energy and exergy analysis of a double absorption heat transformer operating with water/lithium bromideINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2009H. Martínez Abstract In the present study, the first and second law of thermodynamics have been used to analyze in detail the performance of a double absorption (lift) heat transformer operating with the water,lithium bromide mixture. A mathematical model was developed to estimate the coefficient of performance (COP), the exergy coefficient of performance (ECOP), the total exergy destruction in the system (,TD) and the exergy destruction (,D) in each one of the main components, as a function of the system temperatures, the efficiency of the economizer (EFEC), the gross temperature lift and flow ratio (FR). The results showed that the generator is the component with the highest irreversibilities or exergy destruction contributing to about 40% of the total exergy destruction in the whole system, reason why this component should be carefully designed and optimized. The results also showed that the COP and ECOP increase with increase in the generator, the evaporator and the absorber,evaporator temperatures and decrease with the absorber and condenser temperatures. Finally, it was observed that the COP and ECOP are very dependent of the FR and the economizer efficiency (EFEC) values. Also the optimum operating region of the analyzed system is shown in the present study. Copyright © 2009 John Wiley & Sons, Ltd. [source] Update on desiccant wheel modelINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2004M. Beccali Abstract This short communication presents the update on the desiccant wheel models, developed earlier by the present authors. It is to be mentioned here that the psycrometric model presented earlier (Int. J. Energy Res., 2003; 27:17) is valid only for the desiccant wheel running with identical volume air-flows in supply and regeneration sides. However, when system runs with volume air flow ratio between supply and regeneration side (,), different from 1 (one), the model need further modifications. In the present work, correction factors were developed and incorporated in order to update the earlier model for predicting correctly the temperature and humidity of processed air at the outlet of desiccant wheel. The modified model were verified against the experimental results corresponding to different values of ,, obtained from the industry for three different kinds of desiccant wheels. Copyright © 2004 John Wiley & Sons, Ltd. [source] Supercritical antisolvent micronisation of synthetic all- trans -,-carotene with tetrahydrofuran as solvent and carbon dioxide as antisolventJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2009Miguel A Tavares Cardoso Abstract BACKGROUND: Supercritical antisolvent (SAS) micronisation of synthetic trans -,-carotene was studied using tetrahydrofuran (THF) as solvent and supercritical carbon dioxide (CO2) as antisolvent, with the objective of increasing its bioavailability and facilitating its dispersion in oil and emulsion formulations as a result of its smaller particle size. The micronised powder was analysed by scanning electron microscopy and high-performance liquid chromatography. Micronisation experiments were performed in order to evaluate the effects of temperature (308.15,333.15 K), pressure (6.5,13 MPa) and concentration of the liquid solution (6,9 g L,1). The effect of the supercritical CO2/THF flow ratio in the range between 4 and 44 (on a mass basis) was also analysed. Determinations of equilibrium concentrations of ,-carotene in the CO2/THF mixture were also performed. RESULTS: The particle size obtained ranged from 1 to 500 µm, with mean particle diameters around 100 µm. Three types of morphology were found in the precipitated powder: crystalline with superficial pores and leaf-like appearance; crystalline with regular shapes and blade-like edges; and crystalline without superficial pores and leaf-like apearance. The Peng,Robinson equation of state was used to calculate the density of the CO2/THF binary mixture, and the solubility of ,-carotene in this mixture was correlated with its density. CONCLUSION: The use of the SAS technique to micronise ,-carotene proved to be efficient, and the absence of degradation in the micronised powder allows the industrial application of this technique. Copyright © 2008 Society of Chemical Industry [source] Deodorization of Fish Sauce by Continuous-Flow Extraction with Microbubbles of Supercritical Carbon DioxideJOURNAL OF FOOD SCIENCE, Issue 8 2000M. Shimoda ABSTRACT: Volatiles were removed from fish sauce by continuous-flow extraction with microbubbles of supercritical carbon dioxide. The extraction was done at 35 °C and CO2/sample flow ratio of 0.14 and 0.29 under pressures of 10 to 30 MPa. After the treatment at a CO2/sample flow ratio, 0.29 at 10 MPa, remaining percentage ((the concentration in treated sample/that in untreated one) × 100) was 5.2% trimethylamine, 8.0% S-methyl ethanethioate, 30% dimethyldisulfide, 55 to 61% aliphatic aldehydes, and 25 to 42% carboxylic acids. The increase in CO2 flow rate improved the extraction efficiency significantly, but no effect of pressure was observed. The odor intensities of treated samples were between 1/4 and 1/8 of the untreated fish sauce. [source] Transcatheter Closure of Congenital Ventricular Septal Defects: Experience with Various DevicesJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 1 2003RAMESH ARORA D.M. Transcatheter closure of congenital ventricular septal defect (VSD) using various devices is gaining acceptance in selected cases of perimembranous and muscular defects, avoiding the inherent risks of cardiopulmonary bypass. The procedure was attempted in 137 patients having congenital defects using Rashkind Umbrella Device (RUD) in 29 patients, Amplatzer ventricular septal occluder (AVSO) in 107 patients, and Detachable Coil in one. All patients were selected using stringent criteria by detailed transthoracic echocardiography and/or transesophageal echocardiography. The location of VSD was perimembranous in 91 patients and was muscular trabecular in 46 patients. Seven patients had left ventricle (LV) to right atrium (RA) communication. Thirty-five patients with perimembranous and two with muscular VSD had aneurysm formation. The patients were 3 to 33 years old, and the diameter of VSD ranged from 3 to 12 mm. The pulmonary to systemic flow ratio was ,2:1 in 47 (34.3%) patients. The procedure was successful in 130 (94.8%) patients, with a success rate of 86.2% with RUD and 97.1% with AVSO. Residual shunt at 24 hours was seen in eight (32%) patients with RUD and in one patient (0.9%) with AVSO. Three (2.8%) developed transient bundle branch block, and two (1.9%) patients had complete heart block. New tricuspid stenosis and tricuspid regurgitation was observed in one patient each with AVSO. After immediate balloon dilatation, the mean pressure gradient across tricuspid valve decreased from 11 to 3 mmHg in the patient with tricuspid stenosis. On a follow-up of 1 to 66(mean 35.2 ± 10.7)months, the device was in position in all. None developed late conduction defect, aortic regurgitation, infective endocarditis, or hemolysis. At 9-month follow-up, the mean pressure gradient across the tricuspid valve was 3 mmHg in the patient with tricuspid stenosis. Complete occlusion of the shunt was achieved in 129 (99.2%) patients. One patient with RUD having persistent residual shunt underwent a second procedure with AVSO. Three out of 107 patients with AVSO had an unsuccessful procedure where the defect was perimembranous with a superior margin of defect less than 3 mm away from the aortic valve, and the specially designed perimembranous AVSO had to be retrieved because of hemodynamic compromise due to significant acute aortic regurgitation, whereas in all others, the defect was either ,3 mm away from the aortic valve or had aneurysm formation. All seven patients with LV to RA communication showed complete abolition of the shunt. Thus, in properly selected cases of perimembranous and muscular ventricular septal defects, the transcatheter closure is safe and efficacious using appropriate devices. The success rate is higher with AVSO compared with the previously used devices, as well as more successful for the muscular defects than those that are perimembranous in location. (J Interven Cardiol 2003;16:83,91) [source] Time evolution of cerebral perfusion and apparent diffusion coefficient measured by magnetic resonance imaging in a porcine stroke modelJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2002Lisbeth Røhl MD Abstract Purpose To demonstrate the feasibility of sequential diffusion-weighted (DW) and perfusion-weighted (PW) magnetic resonance imaging (MRI) of a recently developed porcine stroke model and to evaluate the evolution of cerebral perfusion and the apparent diffusion coefficient (ADC) over time. Materials and Methods In five pigs, DW imaging (DWI) and PW imaging (PWI) was carried out for 7 hours after stroke onset, starting 1 hour after middle cerebral artery occlusion (MCAO). Results The DWI lesion volume increased significantly with time, and final DWI lesion volume correlated well with lesion area on histological sections (r = 0.910). T2 changes could be recognized 3 hours after stroke onset. At 1 hour the ADC ratio (ischemic lesion/contralateral side) was reduced to 0.81 in the caudate-putamen and to 0.87 in the cortex, and the cerebral blood flow ratio was reduced to 0.40 in the caudate-putamen and 0.51 in the cortex. Conclusion The level of flow reduction in the caudate-putamen and the cortex after 1 hour is in good correlation with human thresholds of irreversible and reversible ischemic damage, and accordingly, this model might be a model for mechanisms of infarct evolution and therapeutic intervention. J. Magn. Reson. Imaging 2002;15:123,129. © 2002 Wiley-Liss, Inc. [source] Dynamic control of split flow in packed column supercritical fluid chromatography using dual resistively heated restrictorsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2009Jian Jun Li Abstract Remote control of the vent/detector split flow ratio in packed column supercritical fluid chromatography (pSFC) with flame ionization detector (FID) is demonstrated using a dual heated restrictor method. Restrictors stemming from a Tee at the separation column outlet were, respectively, fixed into an FID and a vent port, and their individual temperatures were controlled using resistively heated wires. Subsequently, both system pressure and split flow could be manipulated. For example, for applied restrictor temperatures examined up to 600°C, corresponding vent/FID split flow ratios between 2 and 7 were observed depending on the port heated. As well, column pressures around 16,23 MPa were also achievable over the same range. Conversely, isobaric altering of the split flow ratio was possible when opposing positive and negative temperature gradients were applied at the two restrictors. Under these conditions, the system pressure varied less than 1% RSD over a 10 min period. As an application, the method was used to establish stable detector operation in the analysis of n -alkanes under pSFC-FID conditions that initiated flame instability. Results indicate that this technique could be a relatively simple and inexpensive means of controlling system pressure and detector split flow ratios in pSFC-FID. [source] Long-term population isolation in the endangered tropical tree species Caesalpinia echinata Lam. revealed by chloroplast microsatellitesMOLECULAR ECOLOGY, Issue 12 2003C. F. Lira Abstract Habitat fragmentation represents the single most serious threat to the survival of tropical ecosystems. In formulating strategies to counteract the detrimental effects of fragmentation, knowledge of the levels and patterns of genetic diversity within and between natural populations is vital to the establishment of any conservation programme. We utilized polymorphic chloroplast microsatellite markers to analyse genetic diversity in populations of the endangered tropical tree Caesalpinia echinata Lam. representing the entire extant range of the species. Levels of within-population diversity were low, with only two of seven populations studied displaying any variation. The vast majority of the genetic variation was partitioned between geographical regions (36%) and between populations within regions (55%). These levels of genetic structuring, coupled with a calculated pollen-to-seed flow ratio of , 6.7:1, suggest that there has been little gene flow between the three major geographical regions over an extended period. Thus, the current tripartite distribution of the species is more consistent with the existence of separate glacial refugia, rather than reflecting any anthropogenic effects. [source] A simple method to reduce the inspiratory oxygen fraction for high pulmonary blood flow patients in an operating roomPEDIATRIC ANESTHESIA, Issue 12 2007AYAKO ASAKURA MD Summary Background:, Low inspired oxygen acutely increases pulmonary vascular resistance and decreases pulmonary-systemic blood flow ratio. We present a simple method to lower inspired oxygen fraction (FIO2 < 0.21) without supplemental nitrogen, during mechanical ventilation by an anesthesia machine. Methods:, After institutional approval, seven healthy adult volunteers and three infants (0,12 month old) scheduled for congenital heart surgery were enrolled in this study. All the infants were diagnosed with congestive heart failure because of high pulmonary blood flow and were thought to benefit from low FIO2. The volunteers performed spontaneous ventilation (fresh air flow rate = 10 l·min,1, tidal volume = 600 ml, frequency = 10 br·min,1). The infants were mechanically ventilated with air (fresh air flow rate = 6 l·min,1, tidal volume = 10 ml·kg,1, 15 < frequency < 30 br·min,1 to adjust PaCO2 between 5.8 kPa and 6.5 kPa (45,50 mmHg), after induction of general anesthesia and tracheal intubation. The fresh gas flow rates were determined by the following formula. Fresh gas flow rate = (FIO2 , FEO2) EVE/(0.21 + FIO2 , FEO2 , target FIO2). We recorded FIO2 every 5 min for 30 min. When arterial oxygen saturation decreased >15%, fresh gas flow rates were increased to adjust FIO2 to 0.21. Results:, In all of the seven volunteers and three infants target FIO2 was achieved in <10 min. FIO2 was kept at 0.18 ± 0.01 (SD) by calculated fresh air flow rates. In one infant, SpO2 decreased >15% 20 min after lowering FIO2, we had to discontinue this study, and increase fresh gas flow to ventilate the infant with FIO2 0.21. In the other two infants, FIO2 was maintained throughout the study. Conclusions:, This simple and convenient method to decrease FIO2, has a utility in clinical situations, in which pulmonary vascular resistance is to be increased to improve systemic oxygen delivery in patients with high pulmonary blood flow during cardiac surgery. [source] Transcatheter closure of patent ductus arteriosus with Nit-Occlud coilsCATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 4 2005Alpay Celiker MD Abstract The detachable coils have been successfully used for transcatheter occlusion of small- to moderate-sized patent ductus arteriosus (PDA). We report our experience regarding the use of the Nit-Occlud coils (NOCs) for transcatheter PDA and major aortopulmonary collateral (MAPCA) occlusion. Single NOCs were used to close PDA in 26 patients, and one small and two large MAPCAs in two patients. Mean age and weight of the patients were 7.7 ± 5.4 years and 20.6 ± 11.6 kg. Mean minimum duct diameter was 2.8 ± 0.8 mm; ampulla, 8.7 ± 2.4 mm; and PDA length, 9.3 ± 4.4 mm. Mean pulmonary artery pressure ranged from 9 to 51 mm Hg and pulmonary/systemic flow ratio from 1.1 to 5.8. Ductal shape was conical in 24 patients. Route of approach was venous in 23 and arterial in 3. Successful coil implantation was achieved in 24/26 (92.3%). Mean procedure and fluoroscopy time were 67.2 ± 22.1 and 14.9 ± 6.5 min. The three MAPCAs were also successfully occluded using NOC Medium and Flex. Postimplantation angiograms revealed no leak in 3, a trace or small leak in 17, and a medium leak in 4 patients. Mean follow-up was 7 ± 5 months. Complete occlusion was achieved in 17/24 (71%) at 24 hr, 19/24 (79%) by 1 month, 13/15 (87%) by 3 months, 14/15 (93%) by 6 months, and 10/11 (90%) by 12 months postprocedure. Hemolysis, late embolization, duct recanalization, and flow disturbances were not observed. Transcatheter occlusion of moderate-sized PDAs and MAPCAs using NOCs seems to offer a safe, simple, and controlled method in pediatric patients. Catheter Cardiovasc Interv 2005 © 2005 Wiley-Liss, Inc. [source] Regional cerebral blood flow during hyperventilation in patients with acute bacterial meningitisCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2000K. Møller Mechanical hyperventilation is often instituted in patients with acute bacterial meningitis when increased intracranial pressure is suspected. However, the effect on regional cerebral blood flow (CBF) is unknown. In this study, we measured regional CBF (rCBF) in patients with acute bacterial meningitis before and during short-term hyperventilation. In 17 patients with acute bacterial meningitis, absolute rCBF (in ml/100 g min,1) was measured during baseline ventilation and hyperventilation by single-photon emission computed tomography (SPECT) using intravenous 133Xe bolus injection. Intravenous 99mTc-HMPAO (hexamethylpropyleneamine oxime) was subsequently given during hyperventilation. In 12 healthy volunteers, rCBF was measured by SPECT and 99mTc-HMPAO during spontaneous ventilation. Using standard templates to identify regions of interest (ROIs), we calculated rCBF in percentage of cerebellar (99mTc-HMPAO images) or mean hemispheric (133Xe images) flow for each ROI, the degree of side-to-side asymmetry for each ROI, and the anterior-to-posterior flow ratio. On 133Xe images, absolute rCBF decreased significantly during hyperventilation compared to baseline ventilation in all regions, but the relative rCBF did not change significantly from baseline ventilation (n=14) to hyperventilation (n=12), indicating that the perfusion distribution was unchanged. On 99mTc-HMPAO images (n=12), relative rCBF and the anterior-to-posterior flow ratio were significantly lower in patients than in controls in the frontal and parietal cortex as well as in the basal ganglia. Focal perfusion abnormalities were present in 10 of 12 patients. Regional cerebral blood flow abnormalities are frequent in patients with acute bacterial meningitis. Short-term hyperventilation does not enhance these abnormalities. [source] Ampicillin micronization by supercritical assisted atomizationJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 11 2003E. Reverchon ABSTRACT The micronization technique called supercritical assisted atomization (SAA) was used to produce ampicillin microparticles with controlled particle size and particle size distribution suitable for aerosol drug delivery. The process is based on the solubilization of supercritical CO2 in a liquid solution. The ternary mixture is then sprayed through a nozzle and, as a consequence of enhanced atomization, solid microparticles are formed. Water and organic solvents were tested with ampicillin to determine the influence of the solvent on the process mechanism. SAA process parameters were studied by testing different supercritical/liquid solvent flow ratios, ampicillin concentrations in the liquid solution and nozzle diameters. The effect of these parameters on morphology, particle size and particle size distribution of microparticles was analysed. Ampicillin particles suitable for aerosol delivery in the size range 1,5 ,m were obtained using buffered water. Moreover, by varying the solute concentration, ampicillin particles in a narrower range (1,3 ,m) than that usually suggested for aerosol deliverable drugs were obtained. This is an example of particle size tailoring by SAA. [source] Flow,volume curve changes in patients with obstructive sleep apnoea and brief upper airway dysfunctionRESPIROLOGY, Issue 1 2000Alastair H Campbell Objective: Patients with obstructive sleep apnoea (OSA) and those with brief upper airway dysfunction (BUAD) have been reported to have abnormalities of maximal flow,volume curves. This study was designed to assess the ability of flow,volume curves to predict the presence of OSA or BUAD. Methodology: Four maximal flow,volume manoeuvres performed by 33 OSA patients and 16 BUAD patients were compared with those of 36 normal subjects. Flow,volume indices, their variability, saw-toothing in the curve and an algorithm based on the flow ratios and shape of the curves were assessed. Results: When the confounding factors, body mass index (BMI), age, gender and smoking status were taken into account, there was no significant difference in a variety of indices derived from the flow,volume curves between OSA and normal subjects. No BUAD patient had normal flow,volume curves as determined with the algorithm. After BMI, age, gender and smoking status were accounted for, decreased forced expiratory volume in 1 s (FEV1), and increased variability of peak expiratory flow (PEF)/peak inspiratory flow (PIF) and FEV1/PEF remained significantly associated with BUAD. Conclusions: These findings suggest that flow,volume curve indices have no value in predicting OSA. Some abnormalities are found in patients with BUAD; a normal flow,volume curve makes the diagnosis of BUAD unlikely. [source] Mass transfer during air humidification in spouted bedsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2009Andrzej Kmiec Abstract This article presents the results obtained from analysing the impacts of bed media, static bed height, and the water-to-air mass flow ratios on the mass transfer coefficient and Colburn factor. The experimental data were compared with the correlations for mass transfer and the analogy between heat and mass transfer in conical spouted beds described earlier in literature. Moreover, the aim of the article is to present some new correlations of dimensionless groups for description of mass transfer and analogy of heat and mass transfer in sprayed spouted beds, which were developed by the authors. Cet exposé présente les résultats obtenus suite à l'analyse de l'impact du médium et de la hauteur statique du lit, des rapports d'écoulement de la masse eau-air sur le coefficient de transfert de masse et le facteur de Colburn. Les données expérimentales ont été comparées aux corrélations pour le transfert de masse et à l'analogie entre le transfert de chaleur et de masse dans des lits jaillissants coniques décrits plus tôt dans la documentation. En outre, le but de l'article est de présenter quelques nouvelles corrélations de groupes adimensionnels, développées par les auteurs, en vue de décrire le transfert de masse et l'analogie du transfert de chaleur et de masse dans les lits jaillissants pulvérisés. [source] | ||||||||||||||||