Measuring Flow Rate in Crystalline Bedrock Wells Using the Dissolved Oxygen Alteration Method.

PubMed

Vitale, Sarah A; Robbins, Gary A

2017-07-01

Determination of vertical flow rates in a fractured bedrock well can aid in planning and implementing hydraulic tests, water quality sampling, and improving interpretations of water quality data. Although flowmeters are highly accurate in flow rate measurement, the high cost and logistics may be limiting. In this study the dissolved oxygen alteration method (DOAM) is expanded upon as a low-cost alternative to determine vertical flow rates in crystalline bedrock wells. The method entails altering the dissolved oxygen content in the wellbore through bubbler aeration, and monitoring the vertical advective movement of the dissolved oxygen over time. Measurements were taken for upward and downward flows, and under ambient and pumping conditions. Vertical flow rates from 0.06 to 2.30 Lpm were measured. To validate the method, flow rates determined with the DOAM were compared to pump discharge rates and found to be in agreement within 2.5%. © 2017, National Ground Water Association.

Experimental Investigation of Heat Transfer Characteristics of Automobile Radiator using TiO2-Nanofluid Coolant

NASA Astrophysics Data System (ADS)

Salamon, V.; Senthil kumar, D.; Thirumalini, S.

2017-08-01

The use of nanoparticle dispersed coolants in automobile radiators improves the heat transfer rate and facilitates overall reduction in size of the radiators. In this study, the heat transfer characteristics of water/propylene glycol based TiO2 nanofluid was analyzed experimentally and compared with pure water and water/propylene glycol mixture. Two different concentrations of nanofluids were prepared by adding 0.1 vol. % and 0.3 vol. % of TiO2 nanoparticles into water/propylene glycol mixture (70:30). The experiments were conducted by varying the coolant flow rate between 3 to 6 lit/min for various coolant temperatures (50°C, 60°C, 70°C, and 80°C) to understand the effect of coolant flow rate on heat transfer. The results showed that the Nusselt number of the nanofluid coolant increases with increase in flow rate. At low inlet coolant temperature the water/propylene glycol mixture showed higher heat transfer rate when compared with nanofluid coolant. However at higher operating temperature and higher coolant flow rate, 0.3 vol. % of TiO2 nanofluid enhances the heat transfer rate by 8.5% when compared to base fluids.

Comparative in vitro flow study of 3 different Ex-PRESS miniature glaucoma device models.

PubMed

Estermann, Stephan; Yuttitham, Kanokwan; Chen, Julie A; Lee, On-Tat; Stamper, Robert L

2013-03-01

To determine the flow characteristics of the 3 different models of the Ex-PRESS miniature glaucoma device in a controlled laboratory study. The 3 different Ex-PRESS models (P-50, R-50, and P-200; Optonol Ltd; now Alcon Lab) were tested using a gravity-driven flow test. Three samples of each of the 3 Ex-PRESS models were subjected to a constant gravitational force of fluid at 5 different pressure levels (5 to 25 mm Hg). Four measurements per sample were taken at each pressure level. The main outcome measure was flow rate (Q) (µL/min). Resistance (R) was calculated by dividing pressure (P) by the measured flow (Q). The flow rate was primarily pressure dependent. The P-200 model (internal diameter 200 µm) showed a statistically significant higher flow rate and lower resistance compared with both the P-50 and R-50 models (internal diameter 50 µm) (P<0.0001). The P-50 and R-50 models demonstrated similar flow rates (P=0.08) despite their difference in tube length (2.64 vs. 2.94 mm). The 3 models of the Ex-PRESS mini shunt behaved in vitro as simple flow resistors by creating a relatively constant resistance to flow. Tube diameter was the only parameter with significant impact on flow and resistance. All models demonstrated flow rates per unit of pressure much higher than the outflow facility of a healthy human eye.

Flow and wall shear stress characterization after endovascular aneurysm repair and endovascular aneurysm sealing in an infrarenal aneurysm model.

PubMed

Boersen, Johannes T; Groot Jebbink, Erik; Versluis, Michel; Slump, Cornelis H; Ku, David N; de Vries, Jean-Paul P M; Reijnen, Michel M P J

2017-12-01

Endovascular aneurysm repair (EVAR) with a modular endograft has become the preferred treatment for abdominal aortic aneurysms. A novel concept is endovascular aneurysm sealing (EVAS), consisting of dual endoframes surrounded by polymer-filled endobags. This dual-lumen configuration is different from a bifurcation with a tapered trajectory of the flow lumen into the two limbs and may induce unfavorable flow conditions. These include low and oscillatory wall shear stress (WSS), linked to atherosclerosis, and high shear rates that may result in thrombosis. An in vitro study was performed to assess the impact of EVAR and EVAS on flow patterns and WSS. Four abdominal aortic aneurysm phantoms were constructed, including three stented models, to study the influence of the flow divider on flow (Endurant [Medtronic, Minneapolis, Minn], AFX [Endologix, Irvine, Calif], and Nellix [Endologix]). Experimental models were tested under physiologic resting conditions, and flow was visualized with laser particle imaging velocimetry, quantified by shear rate, WSS, and oscillatory shear index (OSI) in the suprarenal aorta, renal artery (RA), and common iliac artery. WSS and OSI were comparable for all models in the suprarenal aorta. The RA flow profile in the EVAR models was comparable to the control, but a region of lower WSS was observed on the caudal wall compared with the control. The EVAS model showed a stronger jet flow with a higher shear rate in some regions compared with the other models. Small regions of low WSS and high OSI were found near the distal end of all stents in the common iliac artery compared with the control. Maximum shear rates in each region of interest were well below the pathologic threshold for acute thrombosis. The different stent designs do not influence suprarenal flow. Lower WSS is observed in the caudal wall of the RA after EVAR and a higher shear rate after EVAS. All stented models have a small region of low WSS and high OSI near the distal outflow of the stents. Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Performance of a new carbon dioxide absorbent, Yabashi lime® as compared to conventional carbon dioxide absorbent during sevoflurane anesthesia in dogs.

PubMed

Kondoh, Kei; Atiba, Ayman; Nagase, Kiyoshi; Ogawa, Shizuko; Miwa, Takashi; Katsumata, Teruya; Ueno, Hiroshi; Uzuka, Yuji

2015-08-01

In the present study, we compare a new carbon dioxide (CO2) absorbent, Yabashi lime(®) with a conventional CO2 absorbent, Sodasorb(®) as a control CO2 absorbent for Compound A (CA) and Carbon monoxide (CO) productions. Four dogs were anesthetized with sevoflurane. Each dog was anesthetized with four preparations, Yabashi lime(®) with high or low-flow rate of oxygen and control CO2 absorbent with high or low-flow rate. CA and CO concentrations in the anesthetic circuit, canister temperature and carbooxyhemoglobin (COHb) concentration in the blood were measured. Yabashi lime(®) did not produce CA. Control CO2 absorbent generated CA, and its concentration was significantly higher in low-flow rate than a high-flow rate. CO was generated only in low-flow rate groups, but there was no significance between Yabashi lime(®) groups and control CO2 absorbent groups. However, the CO concentration in the circuit could not be detected (≤5ppm), and no change was found in COHb level. Canister temperature was significantly higher in low-flow rate groups than high-flow rate groups. Furthermore, in low-flow rate groups, the lower layer of canister temperature in control CO2 absorbent group was significantly higher than Yabashi lime(®) group. CA and CO productions are thought to be related to the composition of CO2 absorbent, flow rate and canister temperature. Though CO concentration is equal, it might be safer to use Yabashi lime(®) with sevoflurane anesthesia in dogs than conventional CO2 absorbent at the point of CA production.

Salivary protein concentration, flow rate, buffer capacity and pH estimation: A comparative study among young and elderly subjects, both normal and with gingivitis and periodontitis.

PubMed

Shaila, Mulki; Pai, G Prakash; Shetty, Pushparaj

2013-01-01

To evaluate the salivary protein concentration in gingivitis and periodontitis patients and compare the parameters like salivary total protein, salivary albumin, salivary flow rate, pH, buffer capacity and flow rate in both young and elderly patients with simple methods. One hundred and twenty subjects were grouped based on their age as young and elderly. Each group was subgrouped (20 subjects) as controls, gingivitis and periodontitis. Unstimulated whole saliva was collected from patients and flow rate was noted down during collection of the sample. Salivary protein estimation was done using the Biuret method and salivary albumin was assessed using the Bromocresol green method. pH was estimated with a pHmeter and buffering capacity was analyzed with the titration method. Student's t-test, Fisher's test (ANOVA) and Tukey HSD (ANOVA) tests were used for statistical analysis. A very highly significant rise in the salivary total protein and albumin concentration was noted in gingivitis and periodontitis subjects of both young and elderly. An overall decrease in salivary flow rate was observed among the elderly, and also the salivary flow rate of women was significantly lower than that of men. Significant associations between salivary total protein and albumin in gingivitis and periodontitis were found with simple biochemical tests. A decrease in salivary flow rate among elderly and among women was noted.

A comparison of the flow of iodine 125 through three different intestinal anastomoses: standard, Gambee, and stapler

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wheeless, C.R. Jr.; Smith, J.J.

1983-10-01

Angiogenesis determines blood supply, and it is postulated that after surgery, the healing of a wound is directly related to the blood supplied to the surrounding tissues. As a first step in evaluating the process of flow through different surgical anastomoses, the flow rate of /sup 125/I through three different types of anastomoses in the intestines of dogs was determined. When the results were compared, the flow rate through the stapler anastomosis was significantly higher than the flow rate through the standard and Gambee anastomoses.

Differences in the Density of Fungiform Papillae and Composition of Saliva in Patients With Taste Disorders Compared to Healthy Controls.

PubMed

Walliczek-Dworschak, Ute; Schöps, Franz; Feron, Gilles; Brignot, Helene; Hähner, Antje; Hummel, Thomas

2017-10-01

This study investigated the relation of the fungiform taste papillae density and saliva composition with the taste perception of patients suffering from diagnosed taste disorders. For this purpose, 81 patients and 40 healthy subjects were included. Taste was measured by means of regional and whole mouth chemosensory tests, and electrogustometry. Olfaction was assessed using the Sniffin Sticks. Fungiform papillae were quantified using the "Denver Papillae Protocol for Objective Analysis of Fungiform Papillae". In addition, salivary parameters [flow rate, total proteins, catalase, total anti-oxidative capacity (TAC), carbonic anhydrase VI (caVI), and pH] were determined and the Beck Depression Inventory was administered. Patients showed less taste papillae compared to healthy subjects. The number of papillae correlated with total taste strip score and salivary flow rate. Regarding salivary parameters, the flow rate, protein concentration, and TAC of patients were higher compared to controls. In addition, salivary flow rate, protease, caVI, and catalase values correlated with the summed taste strip score. Regarding various taste disorders, salty-dysgeusia patients showed the lowest taste test scores compared to those with bitter or metal-dysgeusia. Olfactory function of patients was significantly worse compared to healthy controls. This difference was most pronounced for ageusia patients. Compared to controls, patients also exhibited higher depressive symptoms. The density of fungiform papillae seemed to be positively associated with taste perception. Furthermore, patients exhibited changes in saliva composition (higher salivary flow rate, increased protein concentration, proteolysis, and TAC) compared to controls indicating that assessment of saliva may be critical for the diagnostic procedure in taste disorders. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

In vivo study of flow-rate accuracy of the MedStream Programmable Infusion System.

PubMed

Venugopalan, Ramakrishna; Ginggen, Alec; Bork, Toralf; Anderson, William; Buffen, Elaine

2011-01-01

  Flow-rate accuracy and precision are important parameters to optimizing the efficacy of programmable intrathecal (IT) infusion pump delivery systems. Current programmable IT pumps are accurate within ±14.5% of their programmed infusion rate when assessed under ideal environmental conditions and specific flow-rate settings in vitro. We assessed the flow-rate accuracy of a novel programmable pump system across its entire flow-rate range under typical conditions in sheep (in vivo) and nominal conditions in vitro.   The flow-rate accuracy of the MedStream Programmable Pump was assessed in both the in vivo and in vitro settings. In vivo flow-rate accuracy was assessed in 16 sheep at various flow-rates (producing 90 flow intervals) more than 90 ± 3 days. Pumps were then explanted, re-sterilized and in vitro flow-rate accuracy was assessed at 37°C and 1013 mBar (80 flow intervals).   In vivo (sheep body temperatures 38.1°C-39.8°C), mean ± SD flow-rate error was 9.32% ± 9.27% and mean ± SD leak-rate was 0.028 ± 0.08 mL/day. Following explantation, mean in vitro flow-rate error and leak-rate were -1.05% ± 2.55% and 0.003 ± 0.004 mL/day (37°C, 1013 mBar), respectively.   The MedStream Programmable Pump demonstrated high flow-rate accuracy when tested in vivo and in vitro at normal body temperature and environmental pressure as well as when tested in vivo at variable sheep body temperature. The flow-rate accuracy of the MedStream Programmable Pump across its flow-rate range, compares favorably to the accuracy of current clinically utilized programmable IT infusion pumps reported at specific flow-rate settings and conditions. © 2011 International Neuromodulation Society.

Unstimulated salivary flow rate, pH and buffer capacity of saliva in healthy volunteers.

PubMed

Fenoll-Palomares, C; Muñoz Montagud, J V; Sanchiz, V; Herreros, B; Hernández, V; Mínguez, M; Benages, A

2004-11-01

To assess the salivary flow rate, pH, and buffer capacity of healthy volunteers, and their relationships with age, gender, obesity, smoking, and alcohol consumption, and to establish the lower-end value of normal salivary flow (oligosialia). A prospective study was conducted in 159 healthy volunteers (age > 18 years, absence of medical conditions that could decrease salivary flow). Unstimulated whole saliva was collected during ten minutes, and salivary flow rate (ml/min), pH, and bicarbonate concentration (mmol/l) were measured using a Radiometer ABL 520. The 5 percentile of salivary flow rate and bicarbonate concentration was considered the lower limit of normality. Median salivary flow rate was 0.48 ml/min (range: 0.1-2 ml/min). Age younger than 44 years was associated with higher flow rates (OR 2.10). Compared with women, men presented a higher flow rate (OR 3.19) and buffer capacity (OR 2.81). Bicarbonate concentration correlated with salivary flow rate. The lower-end values of normal flow rate and bicarbonate concentration were 0.15 ml/min and 1.800 mmol/l, respectively. The presence of obesity, smoking, and alcohol consumption did not influence salivary parameters. In healthy volunteers, salivary flow rate depends on age and gender, and correlates with buffer capacity. Obesity, smoking, and alcohol use do not influence salivary secretion.

Performance of a restrictive flow device and an electronic syringe driver for continuous subcutaneous infusion.

PubMed

Capes, D; Martin, K; Underwood, R

1997-10-01

The aim of this study was to investigate the flow performance of the mechanical Springfusor 30 short model and the electronic Graseby MS16A. Flow rate was measured gravimetrically in a temperature-controlled cabinet. There was no statistically significant difference between the Graseby and Springfusor syringe drivers in the flow rate error at 25 degrees C. The percentage of flow rates within +/-20% accuracy during a 35-min periods at 25 degrees C was significantly less with the Graseby, being 91.9% compared with 100% for the Springfusor. Only 58.2% of flow rates with the Graseby were within the manufacturer claimed accuracy of +/-5%. The flow rate of the Springfusor was affected by temperature; at 30 degrees C the mean flow rate was 10.8% greater than at 25 degrees C. These results indicate that the Springfusor 30 had less flow rate variation than the Graseby MS16A. However, this would not be expected to cause noticeable clinical effects when used for opioid infusion in palliative care.

A clinical study to compare between resting and stimulated whole salivary flow rate and pH before and after complete denture placement in different age groups

PubMed Central

Muddugangadhar, B. C.; Sangur, Rajashekar; Rudraprasad, I. V.; Nandeeshwar, D. B.; Kumar, B. H. Dhanya

2015-01-01

Purpose: This study compared the flow rate and pH of resting (unstimulated) and stimulated whole saliva before and after complete denture placement in different age groups. Materials and Methods: Fifty healthy, non-medicated edentulous individuals of different age groups requiring complete denture prostheses were selected from the outpatient department. The resting (unstimulated) and stimulated whole saliva and pH were measured at three stages i.e., i)Before complete denture placement;ii)Immediately after complete denture placement; andiii)After 2 to 3 months of complete denture placement. Saliva production was stimulated by chewing paraffin wax. pH was determined by using a digital pH meter. Results: Statistically significant differences were seen in resting(unstimulated) and stimulated whole salivary flow rate and pH obtained before, immediately after, and after 2 to 3 months of complete denture placement. No statistically significant differences were found between the different age groups in resting (unstimulated) as well as stimulated whole salivary flow rate and pH. Conclusion: Stimulated whole salivary flow rates and pH were significantly higher than resting (unstimulated) whole salivary flow rates and pH obtained before, immediately after, and after 2 to 3 months of complete denture placement. No age related variations in whole salivary flow rate and pH were observed in healthy, non-medicated individuals. Clinical Implications: The assessment of salivary flow rate, pH in different age groups is of prognostic value, which is an important aspect to be considered in the practice of removable prosthodontics. PMID:26929540

A clinical study to compare between resting and stimulated whole salivary flow rate and pH before and after complete denture placement in different age groups.

PubMed

Muddugangadhar, B C; Sangur, Rajashekar; Rudraprasad, I V; Nandeeshwar, D B; Kumar, B H Dhanya

2015-01-01

This study compared the flow rate and pH of resting (unstimulated) and stimulated whole saliva before and after complete denture placement in different age groups. Fifty healthy, non-medicated edentulous individuals of different age groups requiring complete denture prostheses were selected from the outpatient department. The resting (unstimulated) and stimulated whole saliva and pH were measured at three stages i.e., i)Before complete denture placement;ii)Immediately after complete denture placement; andiii)After 2 to 3 months of complete denture placement. Saliva production was stimulated by chewing paraffin wax. pH was determined by using a digital pH meter. Statistically significant differences were seen in resting(unstimulated) and stimulated whole salivary flow rate and pH obtained before, immediately after, and after 2 to 3 months of complete denture placement. No statistically significant differences were found between the different age groups in resting (unstimulated) as well as stimulated whole salivary flow rate and pH. Stimulated whole salivary flow rates and pH were significantly higher than resting (unstimulated) whole salivary flow rates and pH obtained before, immediately after, and after 2 to 3 months of complete denture placement. No age related variations in whole salivary flow rate and pH were observed in healthy, non-medicated individuals. The assessment of salivary flow rate, pH in different age groups is of prognostic value, which is an important aspect to be considered in the practice of removable prosthodontics.

Milk Flow Rates from bottle nipples used after hospital discharge.

PubMed

Pados, Britt Frisk; Park, Jinhee; Thoyre, Suzanne M; Estrem, Hayley; Nix, W Brant

To test the milk flow rates and variability in flow rates of bottle nipples used after hospital discharge. Twenty-six nipple types that represented 15 common brands as well as variety in price per nipple and store location sold (e.g., Babies R' Us, Walmart, Dollar Store) were chosen for testing. Ten of each nipple type (n = 260 total) were tested by measuring the amount of infant formula expressed in 1 minute using a breast pump. Mean milk flow rate (mL/min) and coefficient of variation (CV) were calculated. Flow rates of nipples within brand were compared statistically. Milk flow rates varied from 1.68 mL/min for the Avent Natural Newborn Flow to 85.34 mL/min for the Dr. Brown's Standard Y-cut. Variability between nipple types also varied widely, from .03 for the Dr. Brown's Standard Level 3 to .37 for MAM Nipple 1 Slow Flow. The extreme range of milk flow rates found may be significant for medically fragile infants being discharged home who are continuing to develop oral feeding skills. The name of the nipple does not provide clear information about the flow rate to guide parents in decision making. Variability in flow rates within nipples of the same type may complicate oral feeding for the medically fragile infant who may not be able to adapt easily to change in flow rates. Both flow rate and variability should be considered when guiding parents to a nipple choice.

Computational simulations of vocal fold vibration: Bernoulli versus Navier-Stokes.

PubMed

Decker, Gifford Z; Thomson, Scott L

2007-05-01

The use of the mechanical energy (ME) equation for fluid flow, an extension of the Bernoulli equation, to predict the aerodynamic loading on a two-dimensional finite element vocal fold model is examined. Three steady, one-dimensional ME flow models, incorporating different methods of flow separation point prediction, were compared. For two models, determination of the flow separation point was based on fixed ratios of the glottal area at separation to the minimum glottal area; for the third model, the separation point determination was based on fluid mechanics boundary layer theory. Results of flow rate, separation point, and intraglottal pressure distribution were compared with those of an unsteady, two-dimensional, finite element Navier-Stokes model. Cases were considered with a rigid glottal profile as well as with a vibrating vocal fold. For small glottal widths, the three ME flow models yielded good predictions of flow rate and intraglottal pressure distribution, but poor predictions of separation location. For larger orifice widths, the ME models were poor predictors of flow rate and intraglottal pressure, but they satisfactorily predicted separation location. For the vibrating vocal fold case, all models resulted in similar predictions of mean intraglottal pressure, maximum orifice area, and vibration frequency, but vastly different predictions of separation location and maximum flow rate.

Effect of beta-adrenergic blockade with timolol on myocardial blood flow during exercise after myocardial infarction in the dog.

PubMed

Herzog, C A; Aeppli, D P; Bache, R J

1984-12-01

The effect of beta-adrenergic blockade with timolol (40 micrograms/kg) on myocardial blood flow during rest and graded treadmill exercise was assessed in 12 chronically instrumented dogs 10 to 14 days after myocardial infarction was produced by acute left circumflex coronary artery occlusion. During exercise at comparable external work loads, the heart rate-systolic blood pressure product was significantly decreased after timilol, with concomitant reductions of myocardial blood flow in normal, border and central ischemic areas (p less than 0.001) and increases in subendocardial/subepicardial blood flow ratios (p less than 0.05). In addition to the blunted chronotropic response to exercise, timolol exerted an effect on myocardial blood flow that was not explained by changes in heart rate or blood pressure. At comparable rate-pressure products during exercise, total myocardial blood flow was 24% lower after timolol (p less than 0.02) and flow was redistributed from subepicardium to subendocardium in all myocardial regions. Thus, timolol altered myocardial blood flow during exercise by two separate mechanisms: a negative chronotropic effect, and a significant selective reduction of subepicardial perfusion independent of changes in heart rate or blood pressure with transmural redistribution of flow toward the subendocardium.

Comparative evaluation of the effects of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and xylitol-containing chewing gum on salivary flow rate, pH and buffering capacity in children: An in vivo study.

PubMed

Hegde, Rahul J; Thakkar, Janhavi B

2017-01-01

This study aimed to compare and evaluate the changes in the salivary flow rate, pH, and buffering capacity before and after chewing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and xylitol-containing chewing gums in children. Sixty children aged between 8 and 12 years were selected for the study. They were randomly divided into Group 1 (CPP-ACP chewing gum) and Group 2 (xylitol-containing chewing gum) comprising thirty children each. Unstimulated and stimulated saliva samples at 15 and 30 min interval were collected from all children. All the saliva samples were estimated for salivary flow rate, pH, and buffering capacity. Significant increase in salivary flow rate, pH, and buffering capacity from baseline to immediately after spitting the chewing gum was found in both the study groups. No significant difference was found between the two study groups with respect to salivary flow rate and pH. Intergroup comparison indicated a significant increase in salivary buffer capacity in Group 1 when compared to Group 2. Chewing gums containing CPP-ACP and xylitol can significantly increase the physiochemical properties of saliva. These physiochemical properties of saliva have a definite relation with caries activity in children.

Handpiece coolant flow rates and dental cutting.

PubMed

von Fraunhofer, J A; Siegel, S C; Feldman, S

2000-01-01

High-speed handpieces incorporate water coolant sprays to remove cutting debris and minimize thermal insult to the pulp. Little data exists on optimal coolant flow rates during clinical procedures. This study compared the effect of different coolant flow rates on diamond stone cutting efficiency. Cutting studies were performed on Macor machinable ceramic using a previously developed test regimen--a KaVo high-speed handpiece at a cutting force of 91.5 g (0.9 N). Cutting was performed with round end tapered medium grit diamond stones under cooling water flow rates of 15, 20, 25, 30 and 44 ml/min, with cutting rates determined as the time to transect the 13 mm square cross-section of the Macor bar. Each bur was used for five cuts, with six burs used for each flow rate, for a total of 150 measurements. The data were analyzed by one-way ANOVA with a post hoc Scheffé test. The cutting studies indicated that diamond stone cutting rates increased with higher coolant flow rates over the range of 15-44 ml/min. The data suggest that higher coolant flow rates promote cutting efficiency.

Performance of high flow rate samplers for respirable particle collection.

PubMed

Lee, Taekhee; Kim, Seung Won; Chisholm, William P; Slaven, James; Harper, Martin

2010-08-01

The American Conference of Governmental Industrial hygienists (ACGIH) lowered the threshold limit value (TLV) for respirable crystalline silica (RCS) exposure from 0.05 to 0.025 mg m(-3) in 2006. For a working environment with an airborne dust concentration near this lowered TLV, the sample collected with current standard respirable aerosol samplers might not provide enough RCS for quantitative analysis. Adopting high flow rate sampling devices for respirable dust containing silica may provide a sufficient amount of RCS to be above the limit of quantification even for samples collected for less than full shift. The performances of three high flow rate respirable samplers (CIP10-R, GK2.69, and FSP10) have been evaluated in this study. Eleven different sizes of monodisperse aerosols of ammonium fluorescein were generated with a vibrating orifice aerosol generator in a calm air chamber in order to determine the sampling efficiency of each sampler. Aluminum oxide particles generated by a fluidized bed aerosol generator were used to test (i) the uniformity of a modified calm air chamber, (ii) the effect of loading on the sampling efficiency, and (iii) the performance of dust collection compared to lower flow rate cyclones in common use in the USA (10-mm nylon and Higgins-Dewell cyclones). The coefficient of variation for eight simultaneous samples in the modified calm air chamber ranged from 1.9 to 6.1% for triplicate measures of three different aerosols. The 50% cutoff size ((50)d(ae)) of the high flow rate samplers operated at the flow rates recommended by manufacturers were determined as 4.7, 4.1, and 4.8 microm for CIP10-R, GK2.69, and FSP10, respectively. The mass concentration ratio of the high flow rate samplers to the low flow rate cyclones decreased with decreasing mass median aerodynamic diameter (MMAD) and high flow rate samplers collected more dust than low flow rate samplers by a range of 2-11 times based on gravimetric analysis. Dust loading inside the high flow rate samplers does not appear to affect the particle separation in either FSP10 or GK2.69. The high flow rate samplers overestimated compared to the International Standards Organization/Comité Européen de Normalisation/ACGIH respirable convention [up to 40% at large MMAD (27.5 microm)] and could provide overestimated exposure data with the current flow rates. However, both cyclones appeared to be able to provide relatively unbiased assessments of RCS when their flow rates were adjusted.

Performance of High Flow Rate Samplers for Respirable Particle Collection

PubMed Central

Lee, Taekhee; Kim, Seung Won; Chisholm, William P.; Slaven, James; Harper, Martin

2010-01-01

The American Conference of Governmental Industrial hygienists (ACGIH) lowered the threshold limit value (TLV) for respirable crystalline silica (RCS) exposure from 0.05 to 0.025 mg m−3 in 2006. For a working environment with an airborne dust concentration near this lowered TLV, the sample collected with current standard respirable aerosol samplers might not provide enough RCS for quantitative analysis. Adopting high flow rate sampling devices for respirable dust containing silica may provide a sufficient amount of RCS to be above the limit of quantification even for samples collected for less than full shift. The performances of three high flow rate respirable samplers (CIP10-R, GK2.69, and FSP10) have been evaluated in this study. Eleven different sizes of monodisperse aerosols of ammonium fluorescein were generated with a vibrating orifice aerosol generator in a calm air chamber in order to determine the sampling efficiency of each sampler. Aluminum oxide particles generated by a fluidized bed aerosol generator were used to test (i) the uniformity of a modified calm air chamber, (ii) the effect of loading on the sampling efficiency, and (iii) the performance of dust collection compared to lower flow rate cyclones in common use in the USA (10-mm nylon and Higgins–Dewell cyclones). The coefficient of variation for eight simultaneous samples in the modified calm air chamber ranged from 1.9 to 6.1% for triplicate measures of three different aerosols. The 50% cutoff size (50dae) of the high flow rate samplers operated at the flow rates recommended by manufacturers were determined as 4.7, 4.1, and 4.8 μm for CIP10-R, GK2.69, and FSP10, respectively. The mass concentration ratio of the high flow rate samplers to the low flow rate cyclones decreased with decreasing mass median aerodynamic diameter (MMAD) and high flow rate samplers collected more dust than low flow rate samplers by a range of 2–11 times based on gravimetric analysis. Dust loading inside the high flow rate samplers does not appear to affect the particle separation in either FSP10 or GK2.69. The high flow rate samplers overestimated compared to the International Standards Organization/Comité Européen de Normalisation/ACGIH respirable convention [up to 40% at large MMAD (27.5 μm)] and could provide overestimated exposure data with the current flow rates. However, both cyclones appeared to be able to provide relatively unbiased assessments of RCS when their flow rates were adjusted. PMID:20660144

The Relationship between High Flow Nasal Cannula Flow Rate and Effort of Breathing in Children.

PubMed

Weiler, Thomas; Kamerkar, Asavari; Hotz, Justin; Ross, Patrick A; Newth, Christopher J L; Khemani, Robinder G

2017-10-01

To use an objective metric of effort of breathing to determine optimal high flow nasal cannula (HFNC) flow rates in children <3 years of age. Single-center prospective trial in a 24-bed pediatric intensive care unit of children <3 years of age on HFNC. We measured the percent change in pressure∙rate product (PRP) (an objective measure of effort of breathing) as a function of weight-indexed flow rates of 0.5, 1.0, 1.5, and 2.0 L/kg/minute. For a subgroup of patients, 2 different HFNC delivery systems (Fisher & Paykel [Auckland, New Zealand] and Vapotherm [Exeter, New Hampshire]) were compared. Twenty-one patients (49 titration episodes) were studied. The most common diagnoses were bronchiolitis and pneumonia. Overall, there was a significant difference in the percent change in PRP from baseline (of 0.5 L/kg/minute) with increasing flow rates for the entire cohort (P < .001) with largest change at 2.0 L/kg/min (-21%). Subgroup analyses showed no significant difference in percent change in PRP from baseline when comparing the 2 different HFNC delivery systems (P = .12). Patients ≤8 kg experienced a larger percent change in PRP as HFNC flow rates were increased (P = .001) than patients >8 kg. The optimal HFNC flow rate to reduce effort of breathing in infants and young children is approximately 1.5-2.0 L/kg/minute with more benefit seen in children ≤8 kg. Copyright © 2017 Elsevier Inc. All rights reserved.

Milk flow rates from bottle nipples used after hospital discharge

PubMed Central

Pados, Britt Frisk; Park, Jinhee; Thoyre, Suzanne M.; Estrem, Hayley; Nix, W. Brant

2016-01-01

Purpose To test the milk flow rates and variability in flow rates of bottle nipples used after hospital discharge. Study Design and Methods Twenty-six nipple types that represented 15 common brands as well as variety in price per nipple and store location sold (e.g., Babies R’ Us, Walmart, Dollar Store) were chosen for testing. Ten of each nipple type (n=260 total) were tested by measuring the amount of infant formula expressed in one minute using a breast pump. Mean milk flow rate (mL/min) and coefficient of variation (CV) were calculated. Flow rates of nipples within brand were compared statistically. Results Milk flow rates varied from 1.68 mL/min for the Avent Natural Newborn Flow to 85.34 mL/min for the Dr. Brown’s Standard Y-cut. Variability between nipple types also varied widely, from .03 for the Dr. Brown’s Standard Level 3 to .37 for MAM Nipple 1 Slow Flow. Clinical Implications The extreme range of milk flow rates found may be significant for medically fragile infants being discharged home who are continuing to develop oral feeding skills. The name of the nipple does not provide clear information about the flow rate to guide parents in decision-making. Variability in flow rates within nipples of the same type may complicate oral feeding for the medically fragile infant who may not be able to adapt easily to change in flow rates. Both flow rate and variability should be considered when guiding parents to a nipple choice. PMID:27008466

An alternative arrangement of metered dosing fluid using centrifugal pump

NASA Astrophysics Data System (ADS)

Islam, Md. Arafat; Ehsan, Md.

2017-06-01

Positive displacement dosing pumps are extensively used in various types of process industries. They are widely used for metering small flow rates of a dosing fluid into a main flow. High head and low controllable flow rates make these pumps suitable for industrial flow metering applications. However their pulsating flow is not very suitable for proper mixing of fluids and they are relatively more expensive to buy and maintain. Considering such problems, alternative techniques to control the fluid flow from a low cost centrifugal pump is practiced. These include - throttling, variable speed drive, impeller geometry control and bypass control. Variable speed drive and impeller geometry control are comparatively costly and the flow control by throttling is not an energy efficient process. In this study an arrangement of metered dosing flow was developed using a typical low cost centrifugal pump using bypass flow technique. Using bypass flow control technique a wide range of metered dosing flows under a range of heads were attained using fixed pump geometry and drive speed. The bulk flow returning from the system into the main tank ensures better mixing which may eliminate the need of separate agitators. Comparative performance study was made between the bypass flow control arrangement of centrifugal pump and a diaphragm type dosing pump. Similar heads and flow rates were attainable using the bypass control system compared to the diaphragm dosing pump, but using relatively more energy. Geometrical optimization of the centrifugal pump impeller was further carried out to make the bypass flow arrangement more energy efficient. Although both the systems run at low overall efficiencies but the capital cost could be reduced by about 87% compared to the dosing pump. The savings in capital investment and lower maintenance cost very significantly exceeds the relatively higher energy cost of the bypass system. This technique can be used as a cost effective solution for industries in Bangladesh and have been implemented in two salt iodization plants at Narayangang.

Flow rate and temperature characteristics in steady state condition on FASSIP-01 loop during commissioning

NASA Astrophysics Data System (ADS)

Juarsa, M.; Giarno; Rohman, A. N.; Heru K., G. B.; Witoko, J. P.; Sony Tjahyani, D. T.

2018-02-01

The need for large-scale experimental facilities to investigate the phenomenon of natural circulation flow rate becomes a necessity in the development of nuclear reactor safety management. The FASSIP-01 loop has been built to determine the natural circulation flow rate performance in the large-scale media and aimed to reduce errors in the results for its application in the design of new generation reactors. The commissioning needs to be done to define the capability of the FASSIP-01 loop and to prescribe the experiment limitations. On this commissioning, two scenarios experimental method has been used. The first scenario is a static condition test which was conducted to verify measurement system response during 24 hours without electrical load in heater and cooler, there is water and no water inside the rectangular loop. Second scenario is a dynamics condition that aims to understand the flow rate, a dynamic test was conducted using heater power of 5627 watts and coolant flow rate in the HSS loop of 9.35 LPM. The result of this test shows that the temperature characterization on static test provide a recommendation, that the experiments should be done at night because has a better environmental temperature stability compared to afternoon, with stable temperature around 1°C - 3°C. While on the dynamic test, the water temperature difference between the inlet-outlets in the heater area is quite large, about 7 times the temperature difference in the cooler area. The magnitude of the natural circulation flow rate calculated is much larger at about 300 times compared to the measured flow rate with different flow rate profiles.

The Effects of Tooth Brushing on Whole Salivary Flow Rate in Older Adults

PubMed Central

Trottier, K.; Garrick, R.; Mascarenhas, T.; Jang, Y.

2018-01-01

Objectives (1) To determine whether manual (MTB), or electric, tooth brushing (ETB) modulates whole salivary flow rate in older adults who are free of systemic disease. (2) To determine the duration of the brushing-related modulation of salivary flow rate. (3) To compare salivary flow rate modulation associated with MTB and ETB. Method Twenty-one adults aged 60 years and older participated in two experimental sessions during which they used a manual, or electric, toothbrush to brush their teeth, tongue, and palate. Whole salivary flow rates were determined using the draining method before, during, and after brushing. Differences in salivary flow rates across time periods, and between conditions, were examined using paired samples t-tests applying a Holm-Bonferroni sequential procedure (pcorr < 0.0045). The relationship between tooth brushing and age with respect to maximum salivary flow rate increase was examined using Pearson's correlation coefficient (p < 0.05). Results/Conclusion Whole salivary flow rates increased during, and for up to 5 minutes following, tooth brushing in adults aged 60 years and older who were free of systemic disease. The salivary effects of MTB and ETB were not significantly different. A moderate, positive correlation was observed between tooth-brushing-related maximum salivary flow rate increase and age. PMID:29682540

4D spiral imaging of flows in stenotic phantoms and subjects with aortic stenosis.

PubMed

Negahdar, M J; Kadbi, Mo; Kendrick, Michael; Stoddard, Marcus F; Amini, Amir A

2016-03-01

The utility of four-dimensional (4D) spiral flow in imaging of stenotic flows in both phantoms and human subjects with aortic stenosis is investigated. The method performs 4D flow acquisitions through a stack of interleaved spiral k-space readouts. Relative to conventional 4D flow, which performs Cartesian readout, the method has reduced echo time. Thus, reduced flow artifacts are observed when imaging high-speed stenotic flows. Four-dimensional spiral flow also provides significant savings in scan times relative to conventional 4D flow. In vitro experiments were performed under both steady and pulsatile flows in a phantom model of severe stenosis (one inch diameter at the inlet, with 87% area reduction at the throat of the stenosis) while imaging a 6-cm axial extent of the phantom, which included the Gaussian-shaped stenotic narrowing. In all cases, gradient strength and slew rate for standard clinical acquisitions, and identical field of view and resolution were used. For low steady flow rates, quantitative and qualitative results showed a similar level of accuracy between 4D spiral flow (echo time [TE] = 2 ms, scan time = 40 s) and conventional 4D flow (TE = 3.6 ms, scan time = 1:01 min). However, in the case of high steady flow rates, 4D spiral flow (TE = 1.57 ms, scan time = 38 s) showed better visualization and accuracy as compared to conventional 4D flow (TE = 3.2 ms, scan time = 51 s). At low pulsatile flow rates, a good agreement was observed between 4D spiral flow (TE = 2 ms, scan time = 10:26 min) and conventional 4D flow (TE = 3.6 ms, scan time = 14:20 min). However, in the case of high flow-rate pulsatile flows, 4D spiral flow (TE = 1.57 ms, scan time = 10:26 min) demonstrated better visualization as compared to conventional 4D flow (TE = 3.2 ms, scan time = 14:20 min). The feasibility of 4D spiral flow was also investigated in five normal volunteers and four subjects with mild-to-moderate aortic stenosis. The approach achieved TE = 1.68 ms and scan time = 3:44 min. The conventional sequence achieved TE = 2.9 ms and scan time = 5:23 min. In subjects with aortic stenosis, we also compared both MRI methods with Doppler ultrasound (US) in the measurement of peak velocity, time to peak systolic velocity, and eject time. Bland-Altman analysis revealed that, when comparing peak velocities, the discrepancy between Doppler US and 4D spiral flow was significantly less than the discrepancy between Doppler and 4D Cartesian flow (2.75 cm/s vs. 10.25 cm/s), whereas the two MR methods were comparable (-5.75 s vs. -6 s) for time to peak. However, for the estimation of eject time, relative to Doppler US, the discrepancy for 4D conventional flow was smaller than that of 4D spiral flow (-16.25 s vs. -20 s). Relative to conventional 4D flow, 4D spiral flow achieves substantial reductions in both the TE and scan times; therefore, utility for it should be sought in a variety of in vivo and complex flow imaging applications. © 2015 Wiley Periodicals, Inc.

Method and system for gas flow mitigation of molecular contamination of optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delgado, Gildardo; Johnson, Terry; Arienti, Marco

A computer-implemented method for determining an optimized purge gas flow in a semi-conductor inspection metrology or lithography apparatus, comprising receiving a permissible contaminant mole fraction, a contaminant outgassing flow rate associated with a contaminant, a contaminant mass diffusivity, an outgassing surface length, a pressure, a temperature, a channel height, and a molecular weight of a purge gas, calculating a flow factor based on the permissible contaminant mole fraction, the contaminant outgassing flow rate, the channel height, and the outgassing surface length, comparing the flow factor to a predefined maximum flow factor value, calculating a minimum purge gas velocity and amore » purge gas mass flow rate from the flow factor, the contaminant mass diffusivity, the pressure, the temperature, and the molecular weight of the purge gas, and introducing the purge gas into the semi-conductor inspection metrology or lithography apparatus with the minimum purge gas velocity and the purge gas flow rate.« less

Simulation of blood flow in a small-diameter vascular graft model with a swirl (spiral) flow guider.

PubMed

Zhang, ZhiGuo; Fan, YuBo; Deng, XiaoYan; Wang, GuiXue; Zhang, He; Guidoin, Robert

2008-10-01

Small-diameter vascular grafts are in large demand for coronary and peripheral bypass procedures, but present products still fail in long-term clinical application. In the present communication, a new type of small-diameter graft with a swirl flow guider was proposed to improve graft patency rate. Flow pattern in the graft was simulated numerically and compared with that in a conventional graft. The numerical results revealed that the swirl flow guider could indeed make the blood flow rotate in the new graft. The swirling flow distal to the flow guider significantly altered the flow pattern in the new graft and the velocity profiles were re-distributed. Due to the swirling flow, the blood velocity near the vessel wall and wall shear rate were greatly enhanced. We believe that the increased blood velocity near the wall and the wall shear rate can impede the occurrence of acute thrombus formation and intimal hyperplasia, hence can improve the graft patency rate for long-term clinical use.

Modeling the hydrodynamic and electrochemical efficiency of semi-solid flow batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunini, VE; Chiang, YM; Carter, WC

2012-05-01

A mathematical model of flow cell operation incorporating hydrodynamic and electrochemical effects in three dimensions is developed. The model and resulting simulations apply to recently demonstrated high energy-density semi-solid flow cells. In particular, state of charge gradients that develop during low flow rate operation and their effects on the spatial non-uniformity of current density within flow cells are quantified. A one-dimensional scaling model is also developed and compared to the full three-dimensional simulation. The models are used to demonstrate the impact of the choice of electrochemical couple on flow cell performance. For semi-solid flow electrodes, which can use solid activemore » materials with a wide variety of voltage-capacity responses, we find that cell efficiency is maximized for electrochemical couples that have a relatively flat voltage vs. capacity curve, operated under slow flow conditions. For example, in flow electrodes limited by macroscopic charge transport, an LiFePO4-based system requires one-third the polarization to reach the same cycling rate as an LiCoO2-based system, all else being equal. Our conclusions are generally applicable to high energy density flow battery systems, in which flow rates can be comparatively low for a given required power. (C) 2012 Elsevier Ltd. All rights reserved.« less

Continuum modeling of rate-dependent granular flows in SPH

DOE PAGES

Hurley, Ryan C.; Andrade, José E.

2016-09-13

In this paper, we discuss a constitutive law for modeling rate-dependent granular flows that has been implemented in smoothed particle hydrodynamics (SPH). We model granular materials using a viscoplastic constitutive law that produces a Drucker–Prager-like yield condition in the limit of vanishing flow. A friction law for non-steady flows, incorporating rate-dependence and dilation, is derived and implemented within the constitutive law. We compare our SPH simulations with experimental data, demonstrating that they can capture both steady and non-steady dynamic flow behavior, notably including transient column collapse profiles. In conclusion, this technique may therefore be attractive for modeling the time-dependent evolutionmore » of natural and industrial flows.« less

Salivary flow and composition in diabetic and non-diabetic subjects.

PubMed

Lasisi, T J; Fasanmade, A A

2012-06-07

The study investigated the effects of type 2 diabetes mellitus on salivary flow and composition in humans compared to healthy sex and age matched controls. Forty adult human subjects divided into 20 diabetic and 20 non-diabetic healthy subjects were included. Saliva samples were collected and analysed for glucose, total protein, calcium, sodium, potassium, chloride and bicarbonate. Salivary flow rate was also determined. The results showed that salivary glucose and potassium levels were significantly higher (p = 0.01 and 0.002 respectively) in diabetic patients compared with non-diabetic participants. It was also found that the diabetic patients had significant reduction in salivary flow rate when compared with non-diabetic individuals. In contrast, there was no significant difference in levels of total protein, Na+, Ca++, Cl- and HCO3- between the two groups. These results suggest that some oral diseases associated with diabetes mellitus may be due to altered levels of salivary glucose, potassium and flow.

Oil field management system

DOEpatents

Fincke, James R.

2003-09-23

Oil field management systems and methods for managing operation of one or more wells producing a high void fraction multiphase flow. The system includes a differential pressure flow meter which samples pressure readings at various points of interest throughout the system and uses pressure differentials derived from the pressure readings to determine gas and liquid phase mass flow rates of the high void fraction multiphase flow. One or both of the gas and liquid phase mass flow rates are then compared with predetermined criteria. In the event such mass flow rates satisfy the predetermined criteria, a well control system implements a correlating adjustment action respecting the multiphase flow. In this way, various parameters regarding the high void fraction multiphase flow are used as control inputs to the well control system and thus facilitate management of well operations.

Premixed Edge-Flames in Spatially-Varying Straining Flows

NASA Technical Reports Server (NTRS)

Liu, Jian-Bang; Ronney, Paul D.

1999-01-01

Flames subject to temporally and spatially uniform hydrodynamic strain are frequently used to model the local interactions of flame fronts with turbulent flow fields (Williams, 1985; Peters, 1986; Bradley, 1992). The applicability of laminar flamelet models in strongly turbulent flows have been questioned recently (Shay and Ronney, 1998) because in turbulent flows the strain rate (sigma) changes at rates comparable to sigma itself and the scale over which the flame front curvature and sigma changes is comparable to the curvature scale itself. Therefore quasi-static, local models of turbulent strain and curvature effects on laminar flamelets may not be accurate under conditions where the strain and curvature effects are most significant. The purpose of this study is to examine flames in spatially-varying strain and compare their properties to those of uniformly strained flames.

Effect of Flow Rate Controller on Liquid Steel Flow in Continuous Casting Mold using Numerical Modeling

NASA Astrophysics Data System (ADS)

Gursoy, Kadir Ali; Yavuz, Mehmet Metin

2014-11-01

In continuous casting operation of steel, the flow through tundish to the mold can be controlled by different flow rate control systems including stopper rod and slide-gate. Ladle changes in continuous casting machines result in liquid steel level changes in tundishes. During this transient event of production, the flow rate controller opening is increased to reduce the pressure drop across the opening which helps to keep the mass flow rate at the desired level for the reduced liquid steel level in tundish. In the present study, computational fluid dynamic (CFD) models are developed to investigate the effect of flow rate controller on mold flow structure, and particularly to understand the effect of flow controller opening on meniscus flow. First, a detailed validation of the CFD models is conducted using available experimental data and the performances of different turbulence models are compared. Then, the constant throughput casting operations for different flow rate controller openings are simulated to quantify the opening effect on meniscus region. The results indicate that the meniscus velocities are significantly affected by the flow rate controller and its opening level. The steady state operations, specified as constant throughput casting, do not provide the same mold flow if the controller opening is altered. Thus, for quality and castability purposes, adjusting the flow controller opening to obtain the fixed mold flow structure is proposed. Supported by Middle East Technical University (METU) BAP (Scientific Research Projects) Coordination.

SALIVA SPECIFIC GRAVITY.

DTIC Science & Technology

Four experiments were carried out to investigate the effect of flow rate on parotid fluid specific gravity at different levels of stimulation and to...compare parotid fluid to submaxillo-sublingual fluid in this regard. A strong positive correlation was found between parotid flow rate and specific

Salivary flow rate and periodontal infection - a study among subjects aged 75 years or older.

PubMed

Syrjälä, A-M H; Raatikainen, L; Komulainen, K; Knuuttila, M; Ruoppi, P; Hartikainen, S; Sulkava, R; Ylöstalo, P

2011-05-01

To analyse the relation of stimulated and unstimulated salivary flow rates to periodontal infection in home-dwelling elderly people aged 75 years or older. This study was based on a subpopulation of 157 (111 women, 46 men) home-dwelling, dentate, non-smoking elderly people (mean age 79.8, SD 3.6 years) from the Geriatric Multidisciplinary Strategy for the Good Care of the Elderly Study). The data were collected by interview and oral clinical examination. Persons with very low (< 0.7 ml min⁻¹) and low stimulated salivary flow rates (0.7- < 1.0 ml min⁻¹) had a decreased likelihood of having teeth with deepened (≥ 4 mm) periodontal pockets, RR: 0.7, CI: 0.5-0.9 and RR: 0.7, CI: 0.5-0.9, respectively, when compared with those with normal stimulated salivary flow. Persons with a very low unstimulated salivary flow rate (< 0.1 ml min⁻¹) had a decreased likelihood of having teeth with deepened (≥ 4 mm) periodontal pockets, RR 0.8, CI: 0.6-1.0, when compared with subjects with low/normal unstimulated salivary flow. In a population of dentate, home-dwelling non-smokers, aged 75 years or older, low stimulated and unstimulated salivary flow rates were weakly associated with a decreased likelihood of having teeth with deep periodontal pockets. © 2010 John Wiley & Sons A/S.

The effect of prolapse repair on urinary flow rates and the relationship to changes in the ultrasound appearance of the bladder neck.

PubMed

Duckett, Jonathan; Chakani, Dorothy

2013-12-01

To assess whether specific changes in bladder neck morphology, caused by an anterior repair operation, are associated with resolution of overactive bladder and improved urinary flow rates. Sixty-four women with urgency documented on the urgency perception scale (UPS) underwent an anterior repair. Their preoperative flow studies were compared to those 8 weeks postoperatively. Flow rates were compared in those women who reported improved or cured urgency to those who reported no effect. Resolution of urgency was correlated with the change in bladder neck angulation (posterior urethrovesical angle-PUA). 55% (35/64) women reported no urgency after the anterior repair. A further 19% (12/64) were improved and 26% (17/64) were no better. Patients who were cured or improved showed a significant increase in their flow rates after surgery (mean flow=15 before and 17.6 ml/s after) (Mann-Whitney p=0.04). There was a significant change (increase in the PUA angle/straightening of the angle between the bladder and urethra) from a mean value of 123 degrees (SD 49.3) preoperatively to a mean value of 146.8 (SD 29.2) post operatively (p<0.001). Despite an increase in PUA, this was not correlated with an increase in the maximum flow rate centile (p=0.45, r=0.10). An anterior repair results in increased maximum urinary flow rates but this does not correlate to changes in the appearance of the bladder neck. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

[Effect of citric acid stimulation on salivary alpha-amylase, total protein, salivary flow rate and pH value in Pi deficiency children].

PubMed

Yang, Ze-min; Chen, Long-hui; Lin, Jing; Zhang, Min; Yang, Xiao-rong; Chen, Wei-wen

2015-02-01

To compare the effect of citric acid stimulation on salivary alpha-amylase (sAA), total protein (TP), salivary flow rate, and pH value between Pi deficiency (PD) children and healthy children, thereby providing evidence for Pi controlling saliva theory. Twenty PD children were recruited, and 29 healthy children were also recruited at the same time. Saliva samples from all subjects were collected before and after citric acid stimulation. The sAA activity and amount, TP contents, salivary flow rate, and pH value were determined and compared. (1) Citric acid stimulation was able to significantly increase salivary flow rate, pH value, sAA activities, sAA specific activity and sAA amount (including glycosylated and non-glycosylated sAA amount) in healthy children (P<0.05), while it could markedly increase salivary flow rate, pH value, and glycosylated sAA levels in PD children (P<0.05); (2) Although there was no statistical difference in determined salivary indices between the two groups (P>0.05), salivary indices except salivary flow rate and glycosylated sAA levels decreased more in PD children. There was statistical difference in sAA activity ratio, sAA specific activity ratio, and the ratio of glycosylated sAA levels between PD children and healthy children (P<0.05). PD children had decreased response to citric acid stimulation.

Studies on the prevalence of reduced salivary flow rate in relation to general health and dental caries, and effect of iron supplementation.

PubMed

Flink, Håkan

2007-01-01

Reduced salivary flow is a condition that affects oral health. Its prevalence is unknown in young and middle-aged adults and there is no known treatment that permanently increases the salivary flow rate. Reduced salivary flow is related to dental caries, the most common oral disease. Reduced salivary flow is often found in individuals with insufficient food intake and thereby insufficient nutrition to the salivary glands. One nutrition related factor that has been proposed to effect salivary flow rate is iron deficiency. The aims of the thesis were to investigate i) the prevalence of reduced salivary flow rate in different age groups of adults, ii) the relationship between reduced salivary flow rate, general health and dental caries, iii) the influence of time of measurement on reduced salivary flow rate, and iv) if reduced salivary flow rates could be increased by iron supplementation. In Study I saliva was collected from 1427 individuals aged 20-69 years. A questionnaire was answered regarding subjective oral dryness, general diseases, use of drugs, BMI (Body Mass Index) and use of tobacco. In Study II saliva was collected from 48 patients with active caries and 48 caries-inactive patients. A blood sample was analysed for serum ferritin. In Study III the unstimulated salivary flow rate was tested at 7:30 and 11:30 a.m. in 108 individuals, age 15-46 years. The participants were allocated to one of three groups (very low < 0.1 mL/min, low 0.1-0.2 mL/min and normal > 0.2 mL/min) based on the the unstimulated salivary flow rate at 7:30 a.m. Different aspects of the perception of oral dryness were rated using Visual Analogue Scales. In Study IV a double-blind, randomized controlled trial was carried out on 50 individuals with a low unstimulated whole salivary flow rate and low serum ferritin. Half the individuals received 60 mg of iron orally twice a day for 3 months, while the other half received placebo. In Study I it was found that the prevalence of very low (< 0.1 mL/min) and low (0.10-0.19 mL/min) unstimulated salivary flow rate were similar for different age groups up to 50 years, ranging between 10.9-17.8% and 17.3-22.7%, respectively. Multiple logistic regression revealed that above age 50, female gender, 'having fewer than 20 teeth', and taking xerogenic drugs significantly increased the risk of very low unstimulated salivary flow rate. In Study II 32 individuals (67%) in the caries active group had low unstimulated salivary flow rate compared with 13 individuals (27%) in the caries inactive group. There was no difference in serum ferritin levels between the two groups. Study III showed for all groups a statistically significant increase in unstimulated salivary flow rate at 11:30 a.m. compared with 7:30 a.m., all of similar magnitude (0.08-0.09 mL/min). In the group with very low salivary flow rate, 70% at 11:30 a.m. exceeded the 0.1 mL/min limit. There were significant difference in perception of oral dryness between the normal group and both the low and the very low groups. In Study IV no statistically significant difference was found between the groups after treatment for the unstimulated flow rate and in the subjective assessments of oral dryness. The prevalence of reduced salivary flow rates is consistent and prevalent in younger and middle-aged adults (< 50 years). Very low salivary flow rates are related to high Body Mass Index (BMI) and diagnosed diseases in younger adults, but to medication in older adults. Reduced salivary flow rate in young adult women is related to caries. The time of measurement of salivary flow rates influences diagnosis of hyposalivation. Iron supplementation does not enhance salivary flow.

The Influence of Insulin Dependent Diabetes Mellitus on Dental Caries and Salivary Flow

PubMed Central

Gupta, V. K.; Malhotra, Seema; Sharma, Vasuda; Hiremath, S. S.

2014-01-01

Objective. To assess whether or not there was any change in the dental caries and rate of salivary flow of patients with Insulin Dependent Diabetes Mellitus (IDDM) and the contribution of salivary flow to caries risk in IDDM. Setting. Department of Endocrinology, MS Ramaiah Hospital, Bangalore, India. Design. A comparative cross-sectional descriptive type. Materials and Methods. The sample consisted of two groups: 140 diabetic group (mean age 14.8 yr) and 140 nondiabetic group (mean age 13.7 yr). Dental caries by dmf(t) and dmf(s) indices for primary dentition and DMF(T) and DMF(S) indices was used in permanent dentition to assess the dental caries experience. Both stimulated and unstimulated salivary flow rate were assessed after collection of saliva. Results. In diabetic group 76% had carious lesion and in nondiabetic group 85.3% had carious lesion. Diabetics have lower mean DMFT, DMFS, dmft, and dmfs compared to the nondiabetic group. Diminished unstimulated and stimulated salivary flow rate in diabetic than nondiabetic group. Conclusions. The findings obtained conclude that even though there was reduced salivary flow rate in diabetic group the caries prevalence was low. PMID:26464864

The Influence of Insulin Dependent Diabetes Mellitus on Dental Caries and Salivary Flow.

PubMed

Gupta, V K; Malhotra, Seema; Sharma, Vasuda; Hiremath, S S

2014-01-01

Objective. To assess whether or not there was any change in the dental caries and rate of salivary flow of patients with Insulin Dependent Diabetes Mellitus (IDDM) and the contribution of salivary flow to caries risk in IDDM. Setting. Department of Endocrinology, MS Ramaiah Hospital, Bangalore, India. Design. A comparative cross-sectional descriptive type. Materials and Methods. The sample consisted of two groups: 140 diabetic group (mean age 14.8 yr) and 140 nondiabetic group (mean age 13.7 yr). Dental caries by dmf(t) and dmf(s) indices for primary dentition and DMF(T) and DMF(S) indices was used in permanent dentition to assess the dental caries experience. Both stimulated and unstimulated salivary flow rate were assessed after collection of saliva. Results. In diabetic group 76% had carious lesion and in nondiabetic group 85.3% had carious lesion. Diabetics have lower mean DMFT, DMFS, dmft, and dmfs compared to the nondiabetic group. Diminished unstimulated and stimulated salivary flow rate in diabetic than nondiabetic group. Conclusions. The findings obtained conclude that even though there was reduced salivary flow rate in diabetic group the caries prevalence was low.

Impacts of changing hydrology on permanent gully growth: experimental results

NASA Astrophysics Data System (ADS)

Day, Stephanie S.; Gran, Karen B.; Paola, Chris

2018-06-01

Permanent gullies grow through head cut propagation in response to overland flow coupled with incision and widening in the channel bottom leading to hillslope failures. Altered hydrology can impact the rate at which permanent gullies grow by changing head cut propagation, channel incision, and channel widening rates. Using a set of small physical experiments, we tested how changing overland flow rates and flow volumes alter the total volume of erosion and resulting gully morphology. Permanent gullies were modeled as both detachment-limited and transport-limited systems, using two different substrates with varying cohesion. In both cases, the erosion rate varied linearly with water discharge, such that the volume of sediment eroded was a function not of flow rate, but of total water volume. This implies that efforts to reduce peak flow rates alone without addressing flow volumes entering gully systems may not reduce erosion. The documented response in these experiments is not typical when compared to larger preexisting channels where higher flow rates result in greater erosion through nonlinear relationships between water discharge and sediment discharge. Permanent gullies do not respond like preexisting channels because channel slope remains a free parameter and can adjust relatively quickly in response to changing flows.

Optical spectral sweep comb liquid flow rate sensor.

PubMed

Shen, Changyu; Lian, Xiaokang; Kavungal, Vishnu; Zhong, Chuan; Liu, Dejun; Semenova, Yuliya; Farrell, Gerald; Albert, Jacques; Donegan, John F

2018-02-15

In microfluidic chip applications, the flow rate plays an important role. Here we propose a simple liquid flow rate sensor by using a tilted fiber Bragg grating (TFBG) as the sensing element. As the water flows in the vicinity of the TFBG along the fiber axis direction, the TFBG's spectrum changes due to its contact with water. By comparing the time-swept spectra of the TFBG in water to that of the TFBG with water flowing over it, a spectral sweep comb was formed, and the flow rate can be detected by selecting a suitable sweeping frequency. The proposed sensor has a high Q-value of over 17,000 for the lower rate and a large detectable range from 0.0058 mm/s to 3.2 mm/s. And the calculated corresponding lower detectable flow rate of 0.03 nL/s is 3 orders magnitude better than that of the current fiber flowmeter. Meanwhile, the proposed sensor has the temperature self-compensation function for the variation of the external temperature. We believe that this simple configuration will open a research direction of the TFBG-deriving theory and configuration for lower flow rate measurements for microfluidic chip applications.

Association of salivary calcium, phosphate, pH and flow rate on oral health: A study on 90 subjects.

PubMed

Fiyaz, Mohamed; Ramesh, Amitha; Ramalingam, Karthikeyan; Thomas, Biju; Shetty, Sucheta; Prakash, Prashanth

2013-07-01

This study was designed to compare inorganic salivary calcium, phosphate, flow rate and pH of un-stimulated saliva and oral hygiene of healthy subjects, patients with periodontitis and dental caries and to correlate salivary calcium level with the number of intact teeth. The present study consisted of 90 patients aged between 18 and 55 years and were divided into three groups, periodontitis, dental caries and controls. Oral hygiene index-simplified, probing pocket depth, clinical attachment level and number of teeth present, teeth with active carious lesions were recorded. Salivary flow rate and pH was recorded and subjected to biochemical investigation. Estimation of inorganic calcium and phosphate was performed by colorimetric method. Results showed statistically significant increase in salivary inorganic calcium and phosphate levels, poor oral hygiene status, pH and salivary flow rate in patients with periodontitis when compared with dental caries group and controls. Individuals who have increased salivary inorganic calcium, phosphate, pH, flow rate and maintain poor oral hygiene could be at a higher risk for developing periodontitis and may have less dental caries and more number of intact teeth.

Association of salivary calcium, phosphate, pH and flow rate on oral health: A study on 90 subjects

PubMed Central

Fiyaz, Mohamed; Ramesh, Amitha; Ramalingam, Karthikeyan; Thomas, Biju; Shetty, Sucheta; Prakash, Prashanth

2013-01-01

Background and Objectives: This study was designed to compare inorganic salivary calcium, phosphate, flow rate and pH of un-stimulated saliva and oral hygiene of healthy subjects, patients with periodontitis and dental caries and to correlate salivary calcium level with the number of intact teeth. Materials and Methods: The present study consisted of 90 patients aged between 18 and 55 years and were divided into three groups, periodontitis, dental caries and controls. Oral hygiene index-simplified, probing pocket depth, clinical attachment level and number of teeth present, teeth with active carious lesions were recorded. Salivary flow rate and pH was recorded and subjected to biochemical investigation. Estimation of inorganic calcium and phosphate was performed by colorimetric method. Results: Results showed statistically significant increase in salivary inorganic calcium and phosphate levels, poor oral hygiene status, pH and salivary flow rate in patients with periodontitis when compared with dental caries group and controls. Interpretation and Conclusion: Individuals who have increased salivary inorganic calcium, phosphate, pH, flow rate and maintain poor oral hygiene could be at a higher risk for developing periodontitis and may have less dental caries and more number of intact teeth. PMID:24174724

Gas-Liquid Packed Bed Reactors in Microgravity

NASA Technical Reports Server (NTRS)

Balakotaiah, Vemuri; Motil, Brian J.; McCready, Mark J.; Kamotani, Yasuhiro

2004-01-01

Flow regime and pressure drop data was obtained and analyzed. Pulse flow exists at lower liquid flow rates in 0-g compared to 1-g. 1-g flow regime maps do not apply in microgravity. Pressure drop is higher in microgravity (enhanced interfacial effects).

Numerical investigation and thermodynamic analysis of the effect of electrolyte flow rate on performance of all vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Khazaeli, Ali; Vatani, Ali; Tahouni, Nassim; Panjeshahi, Mohammad Hassan

2015-10-01

In flow batteries, electrolyte flow rate plays a crucial role on the minimizing mass transfer polarization which is at the compensation of higher pressure drop. In this work, a two-dimensional numerical method is applied to investigate the effect of electrolyte flow rate on cell voltage, maximum depth of discharge and pressure drop a six-cell stack of VRFB. The results show that during the discharge process, increasing electrolyte flow rate can raise the voltage of each cell up to 50 mV on average. Moreover, the maximum depth of discharge dramatically increases with electrolyte flow rate. On the other hand, the pressure drop also positively correlates with electrolyte flow rate. In order to investigate all these effects simultaneously, average energy and exergy efficiencies are introduced in this study for the transient process of VRFB. These efficiencies give insight into choosing an appropriate strategy for the electrolyte flow rate. Finally, the energy efficiency of electricity storage using VRFB is investigated and compared with other energy storage systems. The results illustrate that this kind of battery has at least 61% storage efficiency based on the second law of thermodynamics, which is considerably higher than that of their counterparts.

Study of the buffering capacity, pH and salivary flow rate in type 2 well-controlled and poorly controlled diabetic patients.

PubMed

Bernardi, Maria José; Reis, Alessandra; Loguercio, Alessandro Dourado; Kehrig, Ruth; Leite, Mariana Ferreira; Nicolau, José

2007-01-01

This study measured the flow rate, pH and buffering capacity of saliva from well- and poorly metabolically controlled Type 2 diabetic patients in three cities of the southern part of Brazil, compared with healthy individuals from the same cities. Whole saliva was collected by mechanical stimulation and buffering capacity and glucose level were measured. Blood was collected after 12 hours fasting and glucose and glycosylated haemoglobin concentrations were determined. The data were analysed by one-way ANOVA and Student-Newman-Keuls (alpha= 0.05). The flow rate was lower in the Type 2 diabetic patients, regardless of whether they were well or poorly metabolically controlled, compared with healthy individuals (p < 0.05). Salivary glucose concentration was higher in both diabetic patient groups, i.e. well and poorly metabolically controlled, than in the control (p < 0.05). The metabolic control of hyperglycaemia was not sufficient to improve the salivary flow rate or the salivary glucose concentration.

Unraveling the relationship between arterial flow and intra-aneurysmal hemodynamics.

PubMed

Morales, Hernán G; Bonnefous, Odile

2015-02-26

Arterial flow rate affects intra-aneurysmal hemodynamics but it is not clear how their relationship is. This uncertainty hinders the comparison among studies, including clinical evaluations, like a pre- and post-treatment status, since arterial flow rates may differ at each time acquisition. The purposes of this work are as follows: (1) To study how intra-aneurysmal hemodynamics changes within the full physiological range of arterial flow rates. (2) To provide characteristic curves of intra-aneurysmal velocity, wall shear stress (WSS) and pressure as functions of the arterial flow rate. Fifteen image-based aneurysm models were studied using computational fluid dynamics (CFD) simulations. The full range of physiological arterial flow rates reported in the literature was covered by 11 pulsatile simulations. For each aneurysm, the spatiotemporal-averaged blood flow velocity, WSS and pressure were calculated. Spatiotemporal-averaged velocity inside the aneurysm linearly increases as a function of the mean arterial flow (minimum R(2)>0.963). Spatiotemporal-averaged WSS and pressure at the aneurysm wall can be represented by quadratic functions of the arterial flow rate (minimum R(2)>0.996). Quantitative characterizations of spatiotemporal-averaged velocity, WSS and pressure inside cerebral aneurysms can be obtained with respect to the arterial flow rate. These characteristic curves provide more information of the relationship between arterial flow and aneurysm hemodynamics since the full range of arterial flow rates is considered. Having these curves, it is possible to compare experimental studies and clinical evaluations when different flow conditions are used. Copyright © 2015 Elsevier Ltd. All rights reserved.

Simulation of 2D Granular Hopper Flow

NASA Astrophysics Data System (ADS)

Li, Zhusong; Shattuck, Mark

2012-02-01

Jamming and intermittent granular flow are big problems in industry, and the vertical hopper is a canonical example of these difficulties. We simulate gravity driven flow and jamming of 2D disks in a vertical hopper and compare with identical companion experiments presented in this session. We measure and compare the flow rate and probability for jamming as a function of particle properties and geometry. We evaluate the ability of standard Hertz-Mindlin contact mode to quantitatively predict the experimental flow.

Observations of reduced electron Gyroscale fluctuations in national spherical torus experiment H-mode plasmas with large ExB flow shear.

PubMed

Smith, D R; Kaye, S M; Lee, W; Mazzucato, E; Park, H K; Bell, R E; Domier, C W; Leblanc, B P; Levinton, F M; Luhmann, N C; Menard, J E; Yuh, H

2009-06-05

Electron gyroscale fluctuation measurements in National Spherical Torus Experiment H-mode plasmas with large toroidal rotation reveal fluctuations consistent with electron temperature gradient (ETG) turbulence. Large toroidal rotation in National Spherical Torus Experiment plasmas with neutral beam injection generates ExB flow shear rates comparable to ETG linear growth rates. Enhanced fluctuations occur when the electron temperature gradient is marginally stable with respect to the ETG linear critical gradient. Fluctuation amplitudes decrease when the ExB flow shear rate exceeds ETG linear growth rates. The observations indicate that ExB flow shear can be an effective suppression mechanism for ETG turbulence.

Nitrate Removal Rates in Denitrifying Bioreactors During Storm Flows

NASA Astrophysics Data System (ADS)

Pluer, W.; Walter, T.

2017-12-01

Field denitrifying bioreactors are designed to reduce excess nitrate (NO3-) pollution in runoff from agricultural fields. Field bioreactors saturate organic matter to create conditions that facilitate microbial denitrification. Prior studies using steady flow in lab-scale bioreactors showed that a hydraulic retention time (HRT) between 4 and 10 hours was optimal for reducing NO3- loads. However, during storm-induced events, flow rate and actual HRT fluctuate. These fluctuations have the potential to disrupt the system in significant ways that are not captured by the idealized steady-flow HRT models. The goal of this study was to investigate removal rate during dynamic storm flows of variable rates and durations. Our results indicate that storm peak flow and duration were not significant controlling variables. Instead, we found high correlations (p=0.004) in average removal rates between bioreactors displaying a predominantly uniform flow pattern compared with bioreactors that exhibited preferential flow (24.4 and 21.4 g N m-3 d-1, respectively). This suggests that the internal flow patterns are a more significant driver of removal rate than external factors of the storm hydrograph. Designing for flow patterns in addition to theoretical HRT will facilitate complete mixing within the bioreactors. This will help maximize excess NO3- removal during large storm-induced runoff events.

Choked flow of fluid nitrogen with emphasis on the thermodynamic critical region

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Simoneau, R. J.; Ehlers, R. C.

1972-01-01

Experimental measurements of critical flow rate and pressure ratio for nitrogen flowing through a nozzle are presented. Data for selected stagnation isotherms from 87.5 to 234 K with pressures to 9.3 MN/m2 are compared to an equilibrium model with real fluid properties and also a nonequilibrium model. Critical flow pressure ratio along an isotherm tends to peak while the flow rate indicates an inflection. The point is closely associated with the transposed critical temperature and represents a change in the fluid structure.

Effect of Gravity Level on the Particle Shape and Size During Zeolite Crystal Growth

NASA Technical Reports Server (NTRS)

Song, Hong-Wei; Ilebusi, Olusegun J.; Sacco, Albert, Jr.

2003-01-01

A microscopic diffusion model is developed to represent solute transport in the boundary layer of a growing zeolite crystal. This model is used to describe the effect of gravity on particle shape and solute distribution. Particle dynamics and crystal growth kinetics serve as the boundary conditions of flow and convection-diffusion equations. A statistical rate theory is used to obtain the rate of solute transport across the growing interface, which is expressed in terms of concentration and velocity of solute species. Microgravity can significantly decrease the solute velocity across the growing interface compared to its earth-based counterpart. The extent of this reduction highly depends on solute diffusion constant in solution. Under gravity, the flow towards the crystal enhances solute transport rate across the growing interface while the flow away from crystals reduces this rate, suggesting a non-uniform growth rate and thus an elliptic final shape. However, microgravity can significantly reduce the influence of flow and obtain a final product with perfect spherical shape. The model predictions compare favorably with the data of space experiment of zeolites grown in space.

Drainage characteristics of the 3F MicroStent using a novel film occlusion anchoring mechanism.

PubMed

Lange, Dirk; Hoag, Nathan A; Poh, Beow Kiong; Chew, Ben H

2011-06-01

To determine whether the overall ureteral flow through an obstructed ureter using the 3F MicroStent™ that uses a novel film occlusion anchoring mechanism is comparable to the flow using a conventional 3F and 4.7F Double-J stent. An in vitro silicone ureter model and an ex vivo porcine urinary model (kidney and ureter) were used to measure the overall flow through obstructed and unobstructed ureters with either a 3F Double-J stent (Cook), 3F MicroStent (PercSys), or 4.7F Double-J stent (Cook). Mean flow rates were compared with descriptive statistics. Mean flow rates through the obstructed silicone ureter (12-mm stone) for the 3F MicroStent, 3F Double-J stent, and 4.7F Double-J stent were 326.7±13.3  mL/min, 283.3±19.2  mL/min, and 356.7±14.1  mL/min, respectively. In the obstructed ex vivo porcine ureter model, the flow as a percentage of free flow was 60%, 53%, and 50 %, respectively. In both ureteral models, flow rates of the 3F MicroStent and 4.7F Double-J stents were not statistically different. The 3F MicroStent demonstrated drainage equivalent to a 4.7F Double-J stent, in both in vitro silicone and ex vivo porcine obstructed urinary models. We have demonstrated the crucial first step that this 3F stent, using a novel film occlusion anchoring mechanism, has equivalent, if not slightly improved, drainage rates when compared with its larger counterpart.

Identifying High-Rate Flows Based on Sequential Sampling

NASA Astrophysics Data System (ADS)

Zhang, Yu; Fang, Binxing; Luo, Hao

We consider the problem of fast identification of high-rate flows in backbone links with possibly millions of flows. Accurate identification of high-rate flows is important for active queue management, traffic measurement and network security such as detection of distributed denial of service attacks. It is difficult to directly identify high-rate flows in backbone links because tracking the possible millions of flows needs correspondingly large high speed memories. To reduce the measurement overhead, the deterministic 1-out-of-k sampling technique is adopted which is also implemented in Cisco routers (NetFlow). Ideally, a high-rate flow identification method should have short identification time, low memory cost and processing cost. Most importantly, it should be able to specify the identification accuracy. We develop two such methods. The first method is based on fixed sample size test (FSST) which is able to identify high-rate flows with user-specified identification accuracy. However, since FSST has to record every sampled flow during the measurement period, it is not memory efficient. Therefore the second novel method based on truncated sequential probability ratio test (TSPRT) is proposed. Through sequential sampling, TSPRT is able to remove the low-rate flows and identify the high-rate flows at the early stage which can reduce the memory cost and identification time respectively. According to the way to determine the parameters in TSPRT, two versions of TSPRT are proposed: TSPRT-M which is suitable when low memory cost is preferred and TSPRT-T which is suitable when short identification time is preferred. The experimental results show that TSPRT requires less memory and identification time in identifying high-rate flows while satisfying the accuracy requirement as compared to previously proposed methods.

Flow rate-pressure drop relation for deformable shallow microfluidic channels

NASA Astrophysics Data System (ADS)

Christov, Ivan C.; Cognet, Vincent; Shidhore, Tanmay C.; Stone, Howard A.

2018-04-01

Laminar flow in devices fabricated from soft materials causes deformation of the passage geometry, which affects the flow rate--pressure drop relation. For a given pressure drop, in channels with narrow rectangular cross-section, the flow rate varies as the cube of the channel height, so deformation can produce significant quantitative effects, including nonlinear dependence on the pressure drop [{Gervais, T., El-Ali, J., G\\"unther, A. \\& Jensen, K.\\ F.}\\ 2006 Flow-induced deformation of shallow microfluidic channels.\\ \\textit{Lab Chip} \\textbf{6}, 500--507]. Gervais et. al. proposed a successful model of the deformation-induced change in the flow rate by heuristically coupling a Hookean elastic response with the lubrication approximation for Stokes flow. However, their model contains a fitting parameter that must be found for each channel shape by performing an experiment. We present a perturbation approach for the flow rate--pressure drop relation in a shallow deformable microchannel using the theory of isotropic quasi-static plate bending and the Stokes equations under a lubrication approximation (specifically, the ratio of the channel's height to its width and of the channel's height to its length are both assumed small). Our result contains no free parameters and confirms Gervais et. al.'s observation that the flow rate is a quartic polynomial of the pressure drop. The derived flow rate--pressure drop relation compares favorably with experimental measurements.

Control methods and systems for indirect evaporative coolers

DOEpatents

Woods, Jason; Kozubal, Erik

2015-09-22

A control method for operating an indirect evaporative cooler to control temperature and humidity. The method includes operating an airflow control device to provide supply air at a flow rate to a liquid desiccant dehumidifier. The supply air flows through the dehumidifier and an indirect evaporative cooler prior to exiting an outlet into a space. The method includes operating a pump to provide liquid desiccant to the liquid desiccant dehumidifier and sensing a temperature of an airstream at the outlet of the indirect evaporative cooler. The method includes comparing the temperature of the airstream at the outlet to a setpoint temperature at the outlet and controlling the pump to set the flow rate of the liquid desiccant. The method includes sensing space temperature, comparing the space temperature with a setpoint temperature, and controlling the airflow control device to set the flow rate of the supply air based on the comparison.

The two-stroke poppet valve engine. Part 2: Numerical investigations of intake and exhaust flow behaviour

NASA Astrophysics Data System (ADS)

Kamili Zahidi, M.; Razali Hanipah, M.

2017-10-01

A two-stroke poppet valve engine is developed to overcome the common problems in conventional two-stroke engine designs. However, replacing piston control port with poppet valve will resulted different flow behaviour. This paper presents the model and simulation result of three-dimensional (3D) port flow investigation of a two-stroke poppet valve engine. The objective of the investigation is to conduct a numerical investigation on port flow performance of two-stroke poppet valve engine and compare the results obtained from the experimental investigation. The model is to be used for the future numerical study of the engine. The volume flow rate results have been compared with the results obtained experimentally as presented in first part of this paper. The model has shown good agreement in terms of the flow rate at initial and final valve lifts but reduced by about 50% during half-lift region.

Effort of breathing in children receiving high-flow nasal cannula.

PubMed

Rubin, Sarah; Ghuman, Anoopindar; Deakers, Timothy; Khemani, Robinder; Ross, Patrick; Newth, Christopher J

2014-01-01

High-flow humidified nasal cannula is often used to provide noninvasive respiratory support in children. The effect of high-flow humidified nasal cannula on effort of breathing in children has not been objectively studied, and the mechanism by which respiratory support is provided remains unclear. This study uses an objective measure of effort of breathing (Pressure. Rate Product) to evaluate high-flow humidified nasal cannula in critically ill children. Prospective cohort study. Quaternary care free-standing academic children's hospital. ICU patients younger than 18 years receiving high-flow humidified nasal cannula or whom the medical team planned to extubate to high-flow humidified nasal cannula within 72 hours of enrollment. An esophageal pressure monitoring catheter was placed to measure pleural pressures via a Bicore CP-100 pulmonary mechanics monitor. Change in pleural pressure (ΔPes) and respiratory rate were measured on high-flow humidified nasal cannula at 2, 5, and 8 L/min. ΔPes and respiratory rate were multiplied to generate the Pressure.Rate Product, a well-established objective measure of effort of breathing. Baseline Pes, defined as pleural pressure at end exhalation during tidal breathing, reflected the positive pressure generated on each level of respiratory support. Twenty-five patients had measurements on high-flow humidified nasal cannula. Median age was 6.5 months (interquartile range, 1.3-15.5 mo). Median Pressure,Rate Product was lower on high-flow humidified nasal cannula 8 L/min (median, 329 cm H2O·min; interquartile range, 195-402) compared with high-flow humidified nasal cannula 5 L/min (median, 341; interquartile range, 232-475; p = 0.007) or high-flow humidified nasal cannula 2 L/min (median, 421; interquartile range, 233-621; p < 0.0001) and was lower on high-flow humidified nasal cannula 5 L/min compared with high-flow humidified nasal cannula 2 L/min (p = 0.01). Baseline Pes was higher on high-flow humidified nasal cannula 8 L/min than on high-flow humidified nasal cannula 2 L/min (p = 0.03). Increasing flow rates of high-flow humidified nasal cannula decreased effort of breathing in children, with the most significant impact seen from high-flow humidified nasal cannula 2 to 8 L/min. There are likely multiple mechanisms for this clinical effect, including generation of positive pressure and washout of airway dead space.

Performance of three systems for warming intravenous fluids at different flow rates.

PubMed

Satoh, J; Yamakage, M; Wasaki, S I; Namiki, A

2006-02-01

This study compared the intravenous fluid warming capabilities of three systems at different flow rates. The devices studied were a water-bath warmer, a dry-heat plate warmer, and an intravenous fluid tube warmer Ambient temperature was controlled at 22 degrees to 24 degrees C. Normal saline (0.9% NaCl) at either room temperature (21 degrees to 23 degrees C) or at ice-cold temperature (3 degrees to 5 degrees C) was administered through each device at a range of flow rates (2 to 100 ml/min). To mimic clinical conditions, the temperature of the fluid was measured with thermocouples at the end of a one metre tube connected to the outflow of the warmer for the first two devices and at the end of the 1.2 m warming tubing for the intravenous fluid tube warmer The temperature of fluid delivered by the water bath warmer increased as the flow rate was increased up to 15 to 20 ml/min but decreased with greater flow rates. The temperature of the fluid delivered by the dry-heat plate warmer significantly increased as the flow rate was increased within the range tested (due to decreased cooling after leaving the device at higher flow rates). The temperature of fluid delivered by the intravenous fluid tube warmer did not depend on the flow rate up to 20 ml/min but significantly and fluid temperature-dependently decreased at higher flow rates (>30 ml/min). Under the conditions of our testing, the dry heat plate warmer delivered the highest temperature fluid at high flow rates.

Maximum Plant Uptakes for Water, Nutrients, and Oxygen Are Not Always Met by Irrigation Rate and Distribution in Water-based Cultivation Systems.

PubMed

Blok, Chris; Jackson, Brian E; Guo, Xianfeng; de Visser, Pieter H B; Marcelis, Leo F M

2017-01-01

Growing on rooting media other than soils in situ -i.e., substrate-based growing- allows for higher yields than soil-based growing as transport rates of water, nutrients, and oxygen in substrate surpass those in soil. Possibly water-based growing allows for even higher yields as transport rates of water and nutrients in water surpass those in substrate, even though the transport of oxygen may be more complex. Transport rates can only limit growth when they are below a rate corresponding to maximum plant uptake. Our first objective was to compare Chrysanthemum growth performance for three water-based growing systems with different irrigation. We compared; multi-point irrigation into a pond (DeepFlow); one-point irrigation resulting in a thin film of running water (NutrientFlow) and multi-point irrigation as droplets through air (Aeroponic). Second objective was to compare press pots as propagation medium with nutrient solution as propagation medium. The comparison included DeepFlow water-rooted cuttings with either the stem 1 cm into the nutrient solution or with the stem 1 cm above the nutrient solution. Measurements included fresh weight, dry weight, length, water supply, nutrient supply, and oxygen levels. To account for differences in radiation sum received, crop performance was evaluated with Radiation Use Efficiency (RUE) expressed as dry weight over sum of Photosynthetically Active Radiation. The reference, DeepFlow with substrate-based propagation, showed the highest RUE, even while the oxygen supply provided by irrigation was potentially growth limiting. DeepFlow with water-based propagation showed 15-17% lower RUEs than the reference. NutrientFlow showed 8% lower RUE than the reference, in combination with potentially limiting irrigation supply of nutrients and oxygen. Aeroponic showed RUE levels similar to the reference and Aeroponic had non-limiting irrigation supply of water, nutrients, and oxygen. Water-based propagation affected the subsequent cultivation in the DeepFlow negatively compared to substrate-based propagation. Water-based propagation resulted in frequent transient discolorations after transplanting in all cultivation systems, indicating a factor, other than irrigation supply of water, nutrients, and oxygen, influencing plant uptake. Plant uptake rates for water, nutrients, and oxygen are offered as a more fundamental way to compare and improve growing systems.

Maximum Plant Uptakes for Water, Nutrients, and Oxygen Are Not Always Met by Irrigation Rate and Distribution in Water-based Cultivation Systems

PubMed Central

Blok, Chris; Jackson, Brian E.; Guo, Xianfeng; de Visser, Pieter H. B.; Marcelis, Leo F. M.

2017-01-01

Growing on rooting media other than soils in situ -i.e., substrate-based growing- allows for higher yields than soil-based growing as transport rates of water, nutrients, and oxygen in substrate surpass those in soil. Possibly water-based growing allows for even higher yields as transport rates of water and nutrients in water surpass those in substrate, even though the transport of oxygen may be more complex. Transport rates can only limit growth when they are below a rate corresponding to maximum plant uptake. Our first objective was to compare Chrysanthemum growth performance for three water-based growing systems with different irrigation. We compared; multi-point irrigation into a pond (DeepFlow); one-point irrigation resulting in a thin film of running water (NutrientFlow) and multi-point irrigation as droplets through air (Aeroponic). Second objective was to compare press pots as propagation medium with nutrient solution as propagation medium. The comparison included DeepFlow water-rooted cuttings with either the stem 1 cm into the nutrient solution or with the stem 1 cm above the nutrient solution. Measurements included fresh weight, dry weight, length, water supply, nutrient supply, and oxygen levels. To account for differences in radiation sum received, crop performance was evaluated with Radiation Use Efficiency (RUE) expressed as dry weight over sum of Photosynthetically Active Radiation. The reference, DeepFlow with substrate-based propagation, showed the highest RUE, even while the oxygen supply provided by irrigation was potentially growth limiting. DeepFlow with water-based propagation showed 15–17% lower RUEs than the reference. NutrientFlow showed 8% lower RUE than the reference, in combination with potentially limiting irrigation supply of nutrients and oxygen. Aeroponic showed RUE levels similar to the reference and Aeroponic had non-limiting irrigation supply of water, nutrients, and oxygen. Water-based propagation affected the subsequent cultivation in the DeepFlow negatively compared to substrate-based propagation. Water-based propagation resulted in frequent transient discolorations after transplanting in all cultivation systems, indicating a factor, other than irrigation supply of water, nutrients, and oxygen, influencing plant uptake. Plant uptake rates for water, nutrients, and oxygen are offered as a more fundamental way to compare and improve growing systems. PMID:28443129

A radial flow microfluidic device for ultra-high-throughput affinity-based isolation of circulating tumor cells.

PubMed

Murlidhar, Vasudha; Zeinali, Mina; Grabauskiene, Svetlana; Ghannad-Rezaie, Mostafa; Wicha, Max S; Simeone, Diane M; Ramnath, Nithya; Reddy, Rishindra M; Nagrath, Sunitha

2014-12-10

Circulating tumor cells (CTCs) are believed to play an important role in metastasis, a process responsible for the majority of cancer-related deaths. But their rarity in the bloodstream makes microfluidic isolation complex and time-consuming. Additionally the low processing speeds can be a hindrance to obtaining higher yields of CTCs, limiting their potential use as biomarkers for early diagnosis. Here, a high throughput microfluidic technology, the OncoBean Chip, is reported. It employs radial flow that introduces a varying shear profile across the device, enabling efficient cell capture by affinity at high flow rates. The recovery from whole blood is validated with cancer cell lines H1650 and MCF7, achieving a mean efficiency >80% at a throughput of 10 mL h(-1) in contrast to a flow rate of 1 mL h(-1) standardly reported with other microfluidic devices. Cells are recovered with a viability rate of 93% at these high speeds, increasing the ability to use captured CTCs for downstream analysis. Broad clinical application is demonstrated using comparable flow rates from blood specimens obtained from breast, pancreatic, and lung cancer patients. Comparable CTC numbers are recovered in all the samples at the two flow rates, demonstrating the ability of the technology to perform at high throughputs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of the effect of wall friction on the flow rate in 2D and 3D Granular Flow

NASA Astrophysics Data System (ADS)

Carballo-Ramirez, Brenda; Pleau, Mollie; Easwar, Nalini; Birwa, Sumit; Shah, Neil; Tewari, Shubha

We have measured the mass flow rate of spherical steel spheres under gravity in vertical, straight-walled 2 and 3-dimensional hoppers, where the flow velocity is controlled by the opening size. Our measurements focus on the role of friction and its placement along the walls of the hopper. In the 2D case, an increase in the coefficient of static friction from μ = 0.2 to 0.6 is seen to decrease the flow rate significantly. We have changed the placement of frictional boundaries/regions from the front and back walls of the 2D hopper to the side walls and floor to investigate the relative importance of the different regions in determining the flow rate. Fits to the Beverloo equation show significant departure from the expected exponent of 1.5 in the case of 2D flow. In contrast, 3D flow rates do not show much dependence on wall friction and its placement. We compare the experimental data to numerical simulations of gravity driven hopper granular flow with varying frictional walls constructed using LAMMPS*. *http://lammps.sandia.gov Supported by NSF MRSEC DMR 0820506.

Glottal volume velocity waveform characteristics in subjects with and without vocal training, related to gender, sound intensity, fundamental frequency, and age.

PubMed

Sulter, A M; Wit, H P

1996-11-01

Glottal volume velocity waveform characteristics of 224 subjects, categorized in four groups according to gender and vocal training, were determined, and their relations to sound-pressure level, fundamental frequency, intra-oral pressure, and age were analyzed. Subjects phonated at three intensity conditions. The glottal volume velocity waveforms were obtained by inverse filtering the oral flow. Glottal volume velocity waveforms were parameterized with flow-based (minimum flow, ac flow, average flow, maximum flow declination rate) and time-based parameters (closed quotient, closing quotient, speed quotient), as well as with derived parameters (vocal efficiency and glottal resistance). Higher sound-pressure levels, intra-oral pressures, and flow-parameter values (ac flow, maximum flow declination rate) were observed, when compared with previous investigations. These higher values might be the result of the specific phonation tasks (stressed /ae/ vowel in a word and a sentence) or filtering processes. Few statistically significant (p < 0.01) differences in parameters were found between untrained and trained subjects [the maximum flow declination rate and the closing quotient were higher in trained women (p < 0.001), and the speed quotient was higher in trained men (p < 0.005)]. Several statistically significant parameter differences were found between men and women [minimum flow, ac flow, average flow, maximum flow declination rate, closing quotient, glottal resistance (p < 0.001), and closed quotient (p < 0.005)]. Significant effects of intensity condition were observed on ac flow, maximum flow declination rate, closing quotient, and vocal efficiency in women (p < 0.005), and on minimum flow, ac flow, average flow, maximum flow declination rate, closed quotient, and vocal efficiency in men (p < 0.01).

Variations from morning to afternoon of middle cerebral and umbilical artery blood flow, and fetal heart rate variability, and fetal characteristics in the normally developing fetus.

PubMed

Avitan, Tehila; Sanders, Ari; Brain, Ursula; Rurak, Dan; Oberlander, Tim F; Lim, Ken

2018-05-01

To determine if there are changes in maternal uterine blood flow, fetal brain blood flow, fetal heart rate variability, and umbilical blood flow between morning (AM) and afternoon (PM) in healthy, uncomplicated pregnancies. In this prospective study, 68 uncomplicated singleton pregnancies (mean 35 + 0.7 weeks gestation) underwent a standard observational protocol at both 08:00 (AM) and 13:30 (PM) of the same day. This protocol included Doppler measurements of uterine, umbilical, and fetal middle cerebral artery (MCA) volume flow parameters (flow, HR, peak systolic velocity [PSV], PI, and RI) followed by computerized cardiotocography. Standard descriptive statistics, χ 2 and t tests were used where appropriate. P < .05 was considered significant. A significant increase in MCA flow and MCA PSV was observed in the PM compared to the AM. This was accompanied by a fall in MCA resistance. Higher umbilical artery resistance indices were also observed in the PM compared to AM. In contrast, fetal heart rate characteristics, maternal uterine artery Doppler flow and resistance indices did not vary significantly between the AM and PM. In normal pregnancies, variations in fetal cerebral and umbilical blood flow parameters were observed between AM and PM independent of other fetal movements or baseline fetal heart rate. In contrast, uterine flow parameters remained stable across the day. These findings may have implications for the use of serial Doppler parameters used to guide clinical management in high-risk pregnancies. © 2017 Wiley Periodicals, Inc.

Comparison between uroflowmetry and sonouroflowmetry in recording of urinary flow in healthy men.

PubMed

Krhut, Jan; Gärtner, Marcel; Sýkora, Radek; Hurtík, Petr; Burda, Michal; Luňáček, Libor; Zvarová, Katarína; Zvara, Peter

2015-08-01

To evaluate the accuracy of sonouroflowmetry in recording urinary flow parameters and voided volume. A total of 25 healthy male volunteers (age 18-63 years) were included in the study. All participants were asked to carry out uroflowmetry synchronous with recording of the sound generated by the urine stream hitting the water level in the urine collection receptacle, using a dedicated cell phone. From 188 recordings, 34 were excluded, because of voided volume <150 mL or technical problems during recording. Sonouroflowmetry recording was visualized in a form of a trace, representing sound intensity over time. Subsequently, the matching datasets of uroflowmetry and sonouroflowmetry were compared with respect to flow time, voided volume, maximum flow rate and average flow rate. Pearson's correlation coefficient was used to compare parameters recorded by uroflowmetry with those calculated based on sonouroflowmetry recordings. The flow pattern recorded by sonouroflowmetry showed a good correlation with the uroflowmetry trace. A strong correlation (Pearson's correlation coefficient 0.87) was documented between uroflowmetry-recorded flow time and duration of the sound signal recorded with sonouroflowmetry. A moderate correlation was observed in voided volume (Pearson's correlation coefficient 0.68) and average flow rate (Pearson's correlation coefficient 0.57). A weak correlation (Pearson's correlation coefficient 0.38) between maximum flow rate recorded using uroflowmetry and sonouroflowmetry-recorded peak sound intensity was documented. The present study shows that the basic concept utilizing sound analysis for estimation of urinary flow parameters and voided volume is valid. However, further development of this technology and standardization of recording algorithm are required. © 2015 The Japanese Urological Association.

Simulation of a hydrocarbon fueled scramjet exhaust

NASA Technical Reports Server (NTRS)

Leng, J.

1982-01-01

Exhaust nozzle flow fields for a fully integrated, hydrocarbon burning scramjet were calculated for flight conditions of M (undisturbed free stream) = 4 at 6.1 km altitude and M (undisturbed free stream) = 6 at 30.5 km altitude. Equilibrium flow, frozen flow, and finite rate chemistry effects are considered. All flow fields were calculated by method of characteristics. Finite rate chemistry results were evaluated by a one dimensional code (Bittker) using streamtube area distributions extracted from the equilibrium flow field, and compared to very slow artificial rate cases for the same streamtube area distribution. Several candidate substitute gas mixtures, designed to simulate the gas dynamics of the real engine exhaust flow, were examined. Two mixtures are found to give excellent simulations of the specified exhaust flow fields when evaluated by the same method of characteristics computer code.

Eruption mass estimation using infrasound waveform inversion and ash and gas measurements: Evaluation at Sakurajima Volcano, Japan

NASA Astrophysics Data System (ADS)

Fee, David; Izbekov, Pavel; Kim, Keehoon; Yokoo, Akihiko; Lopez, Taryn; Prata, Fred; Kazahaya, Ryunosuke; Nakamichi, Haruhisa; Iguchi, Masato

2017-12-01

Eruption mass and mass flow rate are critical parameters for determining the aerial extent and hazard of volcanic emissions. Infrasound waveform inversion is a promising technique to quantify volcanic emissions. Although topography may substantially alter the infrasound waveform as it propagates, advances in wave propagation modeling and station coverage permit robust inversion of infrasound data from volcanic explosions. The inversion can estimate eruption mass flow rate and total eruption mass if the flow density is known. However, infrasound-based eruption flow rates and mass estimates have yet to be validated against independent measurements, and numerical modeling has only recently been applied to the inversion technique. Here we present a robust full-waveform acoustic inversion method, and use it to calculate eruption flow rates and masses from 49 explosions from Sakurajima Volcano, Japan. Six infrasound stations deployed from 12-20 February 2015 recorded the explosions. We compute numerical Green's functions using 3-D Finite Difference Time Domain modeling and a high-resolution digital elevation model. The inversion, assuming a simple acoustic monopole source, provides realistic eruption masses and excellent fit to the data for the majority of the explosions. The inversion results are compared to independent eruption masses derived from ground-based ash collection and volcanic gas measurements. Assuming realistic flow densities, our infrasound-derived eruption masses for ash-rich eruptions compare favorably to the ground-based estimates, with agreement ranging from within a factor of two to one order of magnitude. Uncertainties in the time-dependent flow density and acoustic propagation likely contribute to the mismatch between the methods. Our results suggest that realistic and accurate infrasound-based eruption mass and mass flow rate estimates can be computed using the method employed here. If accurate volcanic flow parameters are known, application of this technique could be broadly applied to enable near real-time calculation of eruption mass flow rates and total masses. These critical input parameters for volcanic eruption modeling and monitoring are not currently available.

The measurements of water flow rates in the straight microchannel based on the scanning micro-PIV technique

NASA Astrophysics Data System (ADS)

Wang, H. L.; Han, W.; Xu, M.

2011-12-01

Measurement of the water flow rate in microchannel has been one of the hottest points in the applications of microfluidics, medical, biological, chemical analyses and so on. In this study, the scanning microscale particle image velocimetry (scanning micro-PIV) technique is used for the measurements of water flow rates in a straight microchannel of 200μm width and 60μm depth under the standard flow rates ranging from 2.481μL/min to 8.269μL/min. The main effort of this measurement technique is to obtain three-dimensional velocity distribution on the cross sections of microchannel by measuring velocities of the different fluid layers along the out-of-plane direction in the microchannel, so the water flow rates can be evaluated from the discrete surface integral of velocities on the cross section. At the same time, the three-dimensional velocity fields in the measured microchannel are simulated numerically using the FLUENT software in order to verify the velocity accuracy of measurement results. The results show that the experimental values of flow rates are well consistent to the standard flow rates input by the syringe pump and the compared results between numerical simulation and experiment are consistent fundamentally. This study indicates that the micro-flow rate evaluated from three-dimensional velocity by the scanning micro-PIV technique is a promising method for the micro-flow rate research.

Understanding the impact of flow rate and recycle on the conversion of a complex biorefinery stream using a flow-through microbial electrolysis cell

DOE PAGES

Lewis, Alex J.; Borole, Abhijeet P.

2016-06-16

We investigated the effect of flow rate and recycle on the conversion of a biomass-derived pyrolysis aqueous phase in amicrobial electrolysis cell (MEC) to demonstrate production of renewable hydrogen in biorefinery. A continuous MEC operation was investigated under one-pass and recycle conditions usingthe complex, biomass-derived, fermentable, mixed substrate feed at a constant concentration of 0.026 g/L,while testing flow rates ranging from 0.19 to 3.6 mL/min. This corresponds to an organic loading rate (OLR) of 0.54₋10 g/L-day. Mass transfer issues observed at low flow rates were alleviated using high flow rates.Increasing the flow rate to 3.6 mL/min (3.7 min HRT) duringmore » one-pass operation increased the hydrogen productivity 3-fold, but anode conversion efficiency (ACE) decreased from 57.9% to 9.9%. Recycle of the anode liquid helped to alleviate kinetic limitations and the ACE increased by 1.8-fold and the hydrogen productivity by 1.2-fold compared to the one-pass condition at the flow rate of 3.6 mL/min (10 g/L-d OLR). High COD removal was also achieved under recycle conditions, reaching 74.2 1.1%, with hydrogen production rate of 2.92 ± 0.51 L/L-day. This study demonstrates the advantages of combining faster flow rates with a recycle process to improve rate of hydrogen production from a switchgrass-derived stream in the biorefinery.« less

IMPROVED BIOSAND FILTERS BY ENHANCED MONITORING AND DATA COLLECTION METHODS

EPA Science Inventory

The result of this project will be the development of a sensor that will automatically and accurately record BSF use, flow rate, and volume of water poured in. The quantitative volume and flow rate data output will be used to compare actual BSF frequency and usage patterns ...

Cough-Associated Changes in CSF Flow in Chiari I Malformation Evaluated by Real-Time MRI.

PubMed

Bhadelia, R A; Patz, S; Heilman, C; Khatami, D; Kasper, E; Zhao, Y; Madan, N

2016-05-01

Invasive pressure studies have suggested that CSF flow across the foramen magnum may transiently decrease after coughing in patients with symptomatic Chiari I malformation. The purpose of this exploratory study was to demonstrate this phenomenon noninvasively by assessing CSF flow response to coughing in symptomatic patients with Chiari I malformation by using MR pencil beam imaging and to compare the response with that in healthy participants. Eight symptomatic patients with Chiari I malformation and 6 healthy participants were studied by using MR pencil beam imaging with a temporal resolution of ∼50 ms. Patients and healthy participants were scanned for 90 seconds (without cardiac gating) to continuously record cardiac cycle-related CSF flow waveforms in real-time during resting, coughing, and postcoughing periods. CSF flow waveform amplitude, CSF stroke volume, and CSF flow rate (CSF Flow Rate = CSF Stroke Volume × Heart Rate) in the resting and immediate postcoughing periods were determined and compared between patients and healthy participants. There was no significant difference in CSF flow waveform amplitude, CSF stroke volume, and the CSF flow rate between patients with Chiari I malformation and healthy participants during rest. However, immediately after coughing, a significant decrease in CSF flow waveform amplitude (P < .001), CSF stroke volume (P = .001), and CSF flow rate (P = .001) was observed in patients with Chiari I malformation but not in the healthy participants. Real-time MR imaging noninvasively showed a transient decrease in CSF flow across the foramen magnum after coughing in symptomatic patients with Chiari I malformation, a phenomenon not seen in healthy participants. Our results provide preliminary evidence that the physiology-based imaging method used here has the potential to be an objective clinical test to differentiate symptomatic from asymptomatic patients with Chiari I malformation. © 2016 by American Journal of Neuroradiology.

Xerostomia, Hyposalivation, and Salivary Flow in Diabetes Patients

PubMed Central

Casañas, Elisabeth; Ramírez, Lucía; de Arriba, Lorenzo; Hernández, Gonzalo

2016-01-01

The presence of xerostomia and hyposalivation is frequent among diabetes mellitus (DM) patients. It is not clear if the presence of xerostomia and hyposalivation is greater in DM than non-DM patients. The aims of this systematic review are (1) to compare the prevalence rates of xerostomia, (2) to evaluate the salivary flow rate, and (3) to compare the prevalence rates of hyposalivation in DM versus non-DM population. This systematic review was conducted according to the PRISMA group guidelines by performing systematic literature searches in biomedical databases from 1970 until January 18th, 2016. All studies showed higher prevalence of xerostomia in DM patients in relation to non-DM population, 12.5%–53.5% versus 0–30%. Studies that analyzed the quantity of saliva in DM population in relation to non-DM patients reported higher flow rates in non-DM than in DM patients. The variation flow rate among different studies in each group (DM/CG) is very large. Only one existing study showed higher hyposalivation prevalence in DM than non-DM patients (45% versus 2.5%). In addition, quality assessment showed the low quality of the existing studies. We recommend new studies that use more precise and current definitions concerning the determination and diagnosis of DM patients and salivary flow collection. PMID:27478847

Dental caries in diabetes mellitus: role of salivary flow rate and minerals.

PubMed

Jawed, Muhammad; Shahid, Syed M; Qader, Shah A; Azhar, Abid

2011-01-01

This study was designed to evaluate the possible protective role of salivary factors like salivary flow rate and adequate level of calcium, phosphate, and fluoride in diabetes mellitus type 2 patients with dental caries. A total of 398 diabetes mellitus type 2 patients with dental caries and 395 age- and sex-matched non-diabetic subjects with dental caries were included as controls, all of whom gave informed consent. All subjects were divided into four groups according to their age. Decayed, missed, and filled teeth (DMFT) were scored to indicate the severity of dental caries. Saliva was collected, flow rate was noted, and calcium, phosphate, and fluoride were analyzed. The blood glucose, HbA1c, and DMFT indices were found to be significantly high in diabetic patients as compared to controls. The salivary flow rate, calcium, phosphate, and fluoride were found to be significantly low whereas no significant difference was found in salivary magnesium in patients as compared to controls. Optimum salivary flow rate is responsible for establishing protective environment against dental caries. Adequate level of salivary calcium, phosphate, and fluoride is also involved in significant deposition of these minerals in plaque, which greatly reduces the development of caries in the adjacent enamel of teeth. Copyright © 2011 Elsevier Inc. All rights reserved.

Xerostomia, Hyposalivation, and Salivary Flow in Diabetes Patients.

PubMed

López-Pintor, Rosa María; Casañas, Elisabeth; González-Serrano, José; Serrano, Julia; Ramírez, Lucía; de Arriba, Lorenzo; Hernández, Gonzalo

2016-01-01

The presence of xerostomia and hyposalivation is frequent among diabetes mellitus (DM) patients. It is not clear if the presence of xerostomia and hyposalivation is greater in DM than non-DM patients. The aims of this systematic review are (1) to compare the prevalence rates of xerostomia, (2) to evaluate the salivary flow rate, and (3) to compare the prevalence rates of hyposalivation in DM versus non-DM population. This systematic review was conducted according to the PRISMA group guidelines by performing systematic literature searches in biomedical databases from 1970 until January 18th, 2016. All studies showed higher prevalence of xerostomia in DM patients in relation to non-DM population, 12.5%-53.5% versus 0-30%. Studies that analyzed the quantity of saliva in DM population in relation to non-DM patients reported higher flow rates in non-DM than in DM patients. The variation flow rate among different studies in each group (DM/CG) is very large. Only one existing study showed higher hyposalivation prevalence in DM than non-DM patients (45% versus 2.5%). In addition, quality assessment showed the low quality of the existing studies. We recommend new studies that use more precise and current definitions concerning the determination and diagnosis of DM patients and salivary flow collection.

Liquid Acquisition Device Design Sensitivity Study

NASA Technical Reports Server (NTRS)

VanDyke, M. K.; Hastings, L. J.

2012-01-01

In-space propulsion often necessitates the use of a capillary liquid acquisition device (LAD) to assure that gas-free liquid propellant is available to support engine restarts in microgravity. If a capillary screen-channel device is chosen, then the designer must determine the appropriate combination screen mesh and channel geometry. A screen mesh selection which results in the smallest LAD width when compared to any other screen candidate (for a constant length) is desirable; however, no best screen exists for all LAD design requirements. Flow rate, percent fill, and acceleration are the most influential drivers for determining screen widths. Increased flow rates and reduced percent fills increase the through-the-screen flow pressure losses, which drive the LAD to increased widths regardless of screen choice. Similarly, increased acceleration levels and corresponding liquid head pressures drive the screen mesh selection toward a higher bubble point (liquid retention capability). After ruling out some screens on the basis of acceleration requirements alone, candidates can be identified by examining screens with small flow-loss-to-bubble point ratios for a given condition (i.e., comparing screens at certain flow rates and fill levels). Within the same flow rate and fill level, the screen constants inertia resistance coefficient, void fraction, screen pore or opening diameter, and bubble point can become the driving forces in identifying the smaller flow-loss-to-bubble point ratios.

The effects of aortic coarctation on cerebral hemodynamics and its importance in the etiopathogenesis of intracranial aneurysms.

PubMed

Singh, Pankaj K; Marzo, Alberto; Staicu, Cristina; William, Matt G; Wilkinson, Iain; Lawford, Patricia V; Rufenacht, Daniel A; Bijlenga, Philippe; Frangi, Alejandro F; Hose, Rodney; Patel, Umang J; Coley, Stuart C

2010-01-01

Hemodynamic changes in the cerebral circulation in presence of coarctation of aorta (CoA) and their significance in the increased intracranial aneurysms (IAs) formation in these patients remain unclear. In the present study, we measured the flow-rate waveforms in the cerebral arteries of a patient with CoA, followed by an analysis of different hemodynamic indices in a coexisting IA. Phase-contrast Magnetic Resonance (pc-MR) volumetric flow-rate (VFR) measurements were performed in cerebral arteries of a 51 years old woman with coexisting CoA, and five healthy volunteers. Numerical predictions of a number of relevant hemodynamic indices were performed in an IA located in sub-clinoid part of left internal carotid artery (ICA) of the patient. Computations were performed using Ansys(®)-CFX(™) solver using the VFR values measured in the patient as boundary conditions (BCs). A second analysis was performed using the average VFR values measured in healthy volunteers. The VFR waveforms measured in the patient and healthy volunteers were compared followed by a comparison of the hemodynamic indices obtained using both approaches. The results are discussed in the background of relevant literature. Mean flow-rates were increased by 27.1% to 54.9% (2.66-5.44 ml/sec) in the cerebral circulation of patients with CoA as compared to healthy volunteers (1.2-3.95 ml/sec). Velocities were increased inside the IA by 35-45%. An exponential rise of 650% was observed in the area affected by high wall shear stress (WSS>15Pa) when flow-rates specific to CoA were used as compared to population average flow-rates. Absolute values of space and time averaged WSS were increased by 65%. Whereas values of maximum pressure on the IA wall were increased by 15% the area of elevated pressure was actually decreased by 50%, reflecting a more focalized jet impingement within the IA of the CoA patient. IAs can develop in patients with CoA several years after the surgical repair. Cerebral flow-rates in CoA patients are significantly higher as compared to average flow-rates in healthy population. The increased supra-physiological WSS (>15Pa), OSI (>0.2) and focalized pressure may play an important role in the etiopathogenesis of IAs in patients with CoA.

The Effects of Aortic Coarctation on Cerebral Hemodynamics and its Importance in the Etiopathogenesis of Intracranial Aneurysms

PubMed Central

Singh, Pankaj K; Marzo, Alberto; Staicu, Cristina; William, Matt G; Wilkinson, Iain; Lawford, Patricia V; Rufenacht, Daniel A; Bijlenga, Philippe; Frangi, Alejandro F; Hose, Rodney; Patel, Umang J; Coley, Stuart C

2010-01-01

Objectives: Hemodynamic changes in the cerebral circulation in presence of coarctation of aorta (CoA) and their significance in the increased intracranial aneurysms (IAs) formation in these patients remain unclear. In the present study, we measured the flow-rate waveforms in the cerebral arteries of a patient with CoA, followed by an analysis of different hemodynamic indices in a coexisting IA. Materials and Methods: Phase-contrast Magnetic Resonance (pc-MR) volumetric flow-rate (VFR) measurements were performed in cerebral arteries of a 51 years old woman with coexisting CoA, and five healthy volunteers. Numerical predictions of a number of relevant hemodynamic indices were performed in an IA located in sub-clinoid part of left internal carotid artery (ICA) of the patient. Computations were performed using Ansys®-CFX™ solver using the VFR values measured in the patient as boundary conditions (BCs). A second analysis was performed using the average VFR values measured in healthy volunteers. The VFR waveforms measured in the patient and healthy volunteers were compared followed by a comparison of the hemodynamic indices obtained using both approaches. The results are discussed in the background of relevant literature. Results: Mean flow-rates were increased by 27.1% to 54.9% (2.66–5.44 ml/sec) in the cerebral circulation of patients with CoA as compared to healthy volunteers (1.2–3.95 ml/sec). Velocities were increased inside the IA by 35–45%. An exponential rise of 650% was observed in the area affected by high wall shear stress (WSS>15Pa) when flow-rates specific to CoA were used as compared to population average flow-rates. Absolute values of space and time averaged WSS were increased by 65%. Whereas values of maximum pressure on the IA wall were increased by 15% the area of elevated pressure was actually decreased by 50%, reflecting a more focalized jet impingement within the IA of the CoA patient. Conclusions: IAs can develop in patients with CoA several years after the surgical repair. Cerebral flow-rates in CoA patients are significantly higher as compared to average flow-rates in healthy population. The increased supra-physiological WSS (>15Pa), OSI (>0.2) and focalized pressure may play an important role in the etiopathogenesis of IAs in patients with CoA. PMID:22518256

Effect of groundwater flow on remediation of dissolved-phase VOC contamination using air sparging.

PubMed

Reddy, K R; Adams, J A

2000-02-25

This paper presents two-dimensional laboratory experiments performed to study how groundwater flow may affect the injected air zone of influence and remedial performance, and how injected air may alter subsurface groundwater flow and contaminant migration during in situ air sparging. Tests were performed by subjecting uniform sand profiles contaminated with dissolved-phase benzene to a hydraulic gradient and two different air flow rates. The results of the tests were compared to a test subjected to a similar air flow rate but a static groundwater condition. The test results revealed that the size and shape of the zone of influence were negligibly affected by groundwater flow, and as a result, similar rates of contaminant removal were realized within the zone of influence with and without groundwater flow. The air flow, however, reduced the hydraulic conductivity within the zone of influence, reducing groundwater flow and subsequent downgradient contaminant migration. The use of a higher air flow rate further reduced the hydraulic conductivity and decreased groundwater flow and contaminant migration. Overall, this study demonstrated that air sparging may be effectively implemented to intercept and treat a migrating contaminant plume.

Salivary flow rate and biochemical composition analysis in stimulated whole saliva of children with cystic fibrosis.

PubMed

da Silva Modesto, Karine Barros; de Godói Simões, Jéssica Bueno; de Souza, Amanda Ferreira; Damaceno, Neiva; Duarte, Danilo Antonio; Leite, Mariana Ferreira; de Almeida, Eliete Rodrigues

2015-11-01

It is recognized that cystic fibrosis (CF) patients present a risk for oral diseases, since it affects exocrine glands, and the treatment consists of a carbohydrate-rich diet. Recognizing the protective function of saliva on maintaining oral health, the aim of the study was to evaluate salivary parameters in stimulated whole saliva from children with CF. A case-control study was conducted comparing stimulated whole saliva of healthy (n=28; control group) and CF children (n=21; experimental group). Salivary flow rate, initial pH, buffer capacity (total and in each range of pH), total protein and sialic acid (total, free, and conjugated) concentration, α-amylase and salivary peroxidase activities were evaluated. Data were compared by two-tailed Student t test (95% CI; p ≤ 0.05). CF patients presented a significant reduction in salivary parameters compared with the control group (p ≤ 0.05): salivary flow rate (36%), buffer capacity (pH range from 6.9 to 6.0), sialic acid concentration (total 75%, free 61%, and conjugated 83%); α-amylase and salivary peroxidase activities (55%). Additionally, a significant increase in total protein concentration (180%) of stimulated whole saliva from CF patients was verified compared with the control group (p ≤ 0.05). Children with CF presented significant changes in salivary composition, including salivary flow rate, buffering capacity and protective proteins of the oral cavity, compared with children without CF. Copyright © 2015 Elsevier Ltd. All rights reserved.

The effect of chewing gum's flavor on salivary flow rate and pH.

PubMed

Karami-Nogourani, Maryam; Kowsari-Isfahan, Raha; Hosseini-Beheshti, Mozhgan

2011-12-01

Chewing sugar-free gums is a convenient way to increase salivary flow. Salivary flow increases in response to both gustatory (taste) and mechanical (chewing) stimuli, and chewing gum can provide both of these stimuli. The aim of this study was to compare the effect of five different flavors of sugar-free chewing gum on the salivary flow rate (SFR) and pH. Fifteen dental students volunteered at the same time on six consecutive days, to collect one minute unstimulated saliva. After five minutes, while some volunteers continued to collect only unstimulated saliva, the others asked to start chewing one of the five flavored gums randomly. The flavors were spearmint, cinnamon, watermelon, strawberry, and apple. The whole saliva was collected over time periods of 0 - 1, 1 - 3, and 3 - 6 minutes, and the SFR and pH were also measured. The data were subjected to pair t-test, repeated-measures analysis of variance, and Duncan tests. Compared to the unstimulated rate, all five different flavored gums significantly increased the SFR within six minutes. Although the flow rate peaked during the first minute of stimulation with all five products, it reduced gradually, but still remained above the unstimulated saliva, after six minutes. In the first minute, the strawberry-flavored gums showed the highest weight, yet, it only induced a significantly higher SFR compared to the cinnamon-flavored gums. During one to three minutes, strawberry and apple-flavored gums showed significantly higher SFR, respectively, compared to cinnamon-flavored gums. There were no significant differences in the flow rates elicited by each flavored gum through the three-to-six minute interval, although the spearmint-flavored gums induced slightly higher SFR. Only the spearmint and cinnamon-flavored gum significantly increased the salivary pH. Gum flavor can affect the SFR and special flavors may be advised for different individuals according to their oral conditions.

Differential effect of T-type voltage-gated Ca2+ channel disruption on renal plasma flow and glomerular filtration rate in vivo.

PubMed

Thuesen, Anne D; Andersen, Henrik; Cardel, Majken; Toft, Anja; Walter, Steen; Marcussen, Niels; Jensen, Boye L; Bie, Peter; Hansen, Pernille B L

2014-08-15

Voltage-gated Ca(2+) (Cav) channels play an essential role in the regulation of renal blood flow and glomerular filtration rate (GFR). Because T-type Cav channels are differentially expressed in pre- and postglomerular vessels, it was hypothesized that they impact renal blood flow and GFR differentially. The question was addressed with the use of two T-type Cav knockout (Cav3.1(-/-) and Cav3.2(-/-)) mouse strains. Continuous recordings of blood pressure and heart rate, para-aminohippurate clearance (renal plasma flow), and inulin clearance (GFR) were performed in conscious, chronically catheterized, wild-type (WT) and Cav3.1(-/-) and Cav3.2(-/-) mice. The contractility of afferent and efferent arterioles was determined in isolated perfused blood vessels. Efferent arterioles from Cav3.2(-/-) mice constricted significantly more in response to a depolarization compared with WT mice. GFR was increased in Cav3.2(-/-) mice with no significant changes in renal plasma flow, heart rate, and blood pressure. Cav3.1(-/-) mice had a higher renal plasma flow compared with WT mice, whereas GFR was indistinguishable from WT mice. No difference in the concentration response to K(+) was observed in isolated afferent and efferent arterioles from Cav3.1(-/-) mice compared with WT mice. Heart rate was significantly lower in Cav3.1(-/-) mice compared with WT mice with no difference in blood pressure. T-type antagonists significantly inhibited the constriction of human intrarenal arteries in response to a small depolarization. In conclusion, Cav3.2 channels support dilatation of efferent arterioles and affect GFR, whereas Cav3.1 channels in vivo contribute to renal vascular resistance. It is suggested that endothelial and nerve localization of Cav3.2 and Cav3.1, respectively, may account for the observed effects. Copyright © 2014 the American Physiological Society.

Gravity flow rate of solids through orifices and pipes

NASA Technical Reports Server (NTRS)

Gardner, J. F.; Smith, J. E.; Hobday, J. M.

1977-01-01

Lock-hopper systems are the most common means for feeding solids to and from coal conversion reactor vessels. The rate at which crushed solids flow by gravity through the vertical pipes and valves in lock-hopper systems affects the size of pipes and valves needed to meet the solids-handling requirements of the coal conversion process. Methods used to predict flow rates are described and compared with experimental data. Preliminary indications are that solids-handling systems for coal conversion processes are over-designed by a factor of 2 or 3.

Hopper Flow: Experiments and Simulation

NASA Astrophysics Data System (ADS)

Li, Zhusong; Shattuck, Mark

2013-03-01

Jamming and intermittent granular flow are important problems in industry, and the vertical hopper is a canonical example. Clogging of granular hoppers account for significant losses across many industries. We use realistic DEM simulations of gravity driven flow in a hopper to examine flow and jamming of 2D disks and compare with identical companion experiments. We use experimental data to validate simulation parameters and the form of the inter particle force law. We measure and compare flow rate, emptying times, jamming statistics, and flow fields as a function of opening angle and opening size in both experiment and simulations. Suppored by: NSF-CBET-0968013

Dialysate Flow Rate and Delivered Kt/Vurea for Dialyzers with Enhanced Dialysate Flow Distribution

PubMed Central

Idoux, John W.; Hamdan, Hiba; Ouseph, Rosemary; Depner, Thomas A.; Golper, Thomas A.

2011-01-01

Summary Background and objectives Previous in vitro and clinical studies showed that the urea mass transfer-area coefficient (KoA) increased with increasing dialysate flow rate. This observation led to increased dialysate flow rates in an attempt to maximize the delivered dose of dialysis (Kt/Vurea). Recently, we showed that urea KoA was independent of dialysate flow rate in the range 500 to 800 ml/min for dialyzers incorporating features to enhance dialysate flow distribution, suggesting that increasing the dialysate flow rate with such dialyzers would not significantly increase delivered Kt/Vurea. Design, setting, participants, & measurements We performed a multi-center randomized clinical trial to compare delivered Kt/Vurea at dialysate flow rates of 600 and 800 ml/min in 42 patients. All other aspects of the dialysis prescription, including treatment time, blood flow rate, and dialyzer, were kept constant for a given patient. Delivered single-pool and equilibrated Kt/Vurea were calculated from pre- and postdialysis plasma urea concentrations, and ionic Kt/V was determined from serial measurements of ionic dialysance made throughout each treatment. Results Delivered Kt/Vurea differed between centers; however, the difference in Kt/Vurea between dialysate flow rates of 800 and 600 ml/min was NS by any measure (95% confidence intervals of −0.064 to 0.024 for single-pool Kt/Vurea, −0.051 to 0.023 for equilibrated Kt/Vurea, and −0.029 to 0.099 for ionic Kt/V). Conclusions These data suggest that increasing the dialysate flow rate beyond 600 ml/min for these dialyzers offers no benefit in terms of delivered Kt/Vurea. PMID:21799145

Multi-Velocity Encoding Four-Dimensional Flow Magnetic Resonance Imaging in the Assessment of Chronic Aortic Dissection

PubMed Central

Sherrah, Andrew G.; Callaghan, Fraser M.; Puranik, Rajesh; Jeremy, Richmond W.; Bannon, Paul G.; Vallely, Michael P.; Grieve, Stuart M.

2017-01-01

Background Chronic descending thoracic aortic dissection (CDTAD) following surgical repair of ascending aortic dissection requires long-term imaging surveillance. We investigated four-dimensional (4D)-flow magnetic resonance imaging (MRI) with a novel multi-velocity encoding (multi-VENC) technique as an emerging clinical method enabling the dynamic quantification of blood volume and velocity throughout the cardiac cycle. Methods Patients with CDTAD (n = 10; mean age, 55.1 years; standard deviation (SD) 10.8) and healthy volunteers (n = 9; mean age, 37.1 years; SD 11.4; p < 0.01) underwent 3T MRI, and standard views and 4D-flow data were obtained. Flow measurements were made in selected regions of interest within the ascending and descending thoracic aorta. Results The overall flow profile at peak systole was reduced in the false lumen (FL) compared with the true lumen (TL) and normal aortas (p < 0.05 for velocity < 0.4 m/s). Peak systolic flow rate per aortic lumen area (mL/s/cm2) was lower in the FL than in the TL (p < 0.05), and both rates were lower than that of control aortas (p < 0.05). Blood flow reversal was higher in the FL than in the TL throughout the descending aorta in CDTAD patients (p < 0.05). A derived pulsatility index was elevated in the TL compared with that in the FL in CDTAD patients. Generated pathline images demonstrated flow patterns in detail, including sites of communication between the true and FL. Conclusions 4D-flow MRI revealed FL blood flow and reduced blood flow velocity and flow rate in the TL of CDTAD patients compared with normal aortas of healthy participants. Thus, multi-VENC 4D-flow MRI could serve as an adjunct in the long-term assessment of CDTAD following surgical repair of ascending aortic dissection. PMID:29675440

A pilot study of change in cerebral activity during personality rating by questionnaire and personal computer.

PubMed

Sato, Emi; Matsuda, Kouhei

2018-06-11

The purpose of this study was to examine cerebral blood flow in the frontal cortex area during personality self-rating tasks. Our two hypotheses were (1) cerebral blood flow varies based on personality rating condition and (2) cerebral blood flow varies based on the personality traits. This experiment measured cerebral blood flow under 3 personal computer rating conditions and 2 questionnaire conditions. Comparing the rating conditions, the results of the t-test indicated that cerebral blood flow was higher in the questionnaire condition than it was in the personal computer condition. With respect to the Big Five, the result of the correlation coefficient, that is, cerebral blood flow during a personality rating task, changed according to the trait for agreeableness. The results of the analysis of the 5-cluster on individual differences indicated that certain personality traits were related to the factors that increased or decreased cerebral blood flow. An analysis of variance indicated that openness to experience and Behavioural Activation System-drive was significant given that participants with high intellectual curiosity were motivated in this experiment, thus, their cerebral blood flow may have increased. The significance of this experiment was that by employing certain performance measures we could examine differences in physical changes based on personality traits. © 2018 International Union of Psychological Science.

A simple analytical model of coupled single flow channel over porous electrode in vanadium redox flow battery with serpentine flow channel

NASA Astrophysics Data System (ADS)

Ke, Xinyou; Alexander, J. Iwan D.; Prahl, Joseph M.; Savinell, Robert F.

2015-08-01

A simple analytical model of a layered system comprised of a single passage of a serpentine flow channel and a parallel underlying porous electrode (or porous layer) is proposed. This analytical model is derived from Navier-Stokes motion in the flow channel and Darcy-Brinkman model in the porous layer. The continuities of flow velocity and normal stress are applied at the interface between the flow channel and the porous layer. The effects of the inlet volumetric flow rate, thickness of the flow channel and thickness of a typical carbon fiber paper porous layer on the volumetric flow rate within this porous layer are studied. The maximum current density based on the electrolyte volumetric flow rate is predicted, and found to be consistent with reported numerical simulation. It is found that, for a mean inlet flow velocity of 33.3 cm s-1, the analytical maximum current density is estimated to be 377 mA cm-2, which compares favorably with experimental result reported by others of ∼400 mA cm-2.

Effect of Outflow Graft Size on Flow in the Aortic Arch and Cerebral Blood Flow in Continuous Flow Pumps: Possible Relevance to Strokes.

PubMed

Bhat, Sindhoor; Mathew, Jayakala; Balakrishnan, Komrakshi R; Krishna Kumar, Ramarathnam

One of the most devastating complications of continuous flow left ventricular devices (CFLVADS) is stroke, with a higher incidence in HeartWare Ventricular Assist Device (HVAD) as compared with HEARTMATE II. The reason for the observed difference in stroke rates is unclear. Because outflow graft diameters are different, we hypothesized that this could contribute to the difference in stroke rates. A computational fluid-structure interaction model was created from the computed tomography (CT) scan of a patient. Pressures were used as the boundary condition and the flow through the cerebral vessels was derived as outputs. Flow into the innominate artery was very sensitive to the anastomosis angle for a 10 mm as compared with a 14 mm graft, with the net innominate flow severely compromised with a 10 mm graft at 45° angle. Aortic insufficiency seems to affect cerebral blood flow nonlinearly with an 80% decrease at certain angles of outflow graft anastomosis. Arterial return in to the arch through a narrow graft has important jet effects and results in significant flow perturbations in the aortic arch and cerebral vessels and stasis. A 10 mm graft is more sensitive to angle of insertion than a 14 mm graft. Under some conditions, serious hypoperfusion of the innominate artery is possible. Aortic incompetence results in significant decrease of cerebral blood flow. No stasis was found in the pulsatile flow compared with LVAD flow.

Numerical study of Tallinn storm-water system flooding conditions using CFD simulations of multi-phase flow in a large-scale inverted siphon

NASA Astrophysics Data System (ADS)

Kaur, K.; Laanearu, J.; Annus, I.

2017-10-01

The numerical experiments are carried out for qualitative and quantitative interpretation of a multi-phase flow processes associated with malfunctioning of the Tallinn storm-water system during rain storms. The investigations are focused on the single-line inverted siphon, which is used as under-road connection of pipes of the storm-water system under interest. A multi-phase flow solver of Computational Fluid Dynamics software OpenFOAM is used for simulating the three-phase flow dynamics in the hydraulic system. The CFD simulations are performed with different inflow rates under same initial conditions. The computational results are compared essentially in two cases 1) design flow rate and 2) larger flow rate, for emptying the initially filled inverted siphon from a slurry-fluid. The larger flow-rate situations are under particular interest to detected possible flooding. In this regard, it is anticipated that the CFD solutions provide an important insight to functioning of inverted siphon under a restricted water-flow conditions at simultaneous presence of air and slurry-fluid.

Evaluating Use of Environmental Flows to Aerate Streams by Modelling the Counterfactual Case.

PubMed

Stewardson, Michael J; Skinner, Dominic

2018-03-01

This paper evaluates an experimental environmental flow manipulation by modeling the counterfactual case that no environmental flow was applied. This is an alternate approach to evaluating the effect of an environmental flow intervention when a before-after or control-impact comparison is not possible. In this case, the flow manipulation is a minimum flow designed to prevent hypoxia in a weir on the low-gradient Broken Creek in south-eastern Australia. At low flows, low reaeration rates and high respiration rates associated with elevated organic matter loading in the weir pool can lead to a decline in dissolved oxygen concentrations with adverse consequences both for water chemistry and aquatic biota. Using a one dimensional oxygen balance model fitted to field measurements, this paper demonstrates that increased flow leads to increases in reaeration rates, presumably because of enhanced turbulence and hence mixing in the surface layers. By comparing the observed dissolved oxygen levels with the modeled counterfactual case, we show that the environmental flow was effective in preventing hypoxia.

Evaluating Use of Environmental Flows to Aerate Streams by Modelling the Counterfactual Case

NASA Astrophysics Data System (ADS)

Stewardson, Michael J.; Skinner, Dominic

2018-03-01

This paper evaluates an experimental environmental flow manipulation by modeling the counterfactual case that no environmental flow was applied. This is an alternate approach to evaluating the effect of an environmental flow intervention when a before-after or control-impact comparison is not possible. In this case, the flow manipulation is a minimum flow designed to prevent hypoxia in a weir on the low-gradient Broken Creek in south-eastern Australia. At low flows, low reaeration rates and high respiration rates associated with elevated organic matter loading in the weir pool can lead to a decline in dissolved oxygen concentrations with adverse consequences both for water chemistry and aquatic biota. Using a one dimensional oxygen balance model fitted to field measurements, this paper demonstrates that increased flow leads to increases in reaeration rates, presumably because of enhanced turbulence and hence mixing in the surface layers. By comparing the observed dissolved oxygen levels with the modeled counterfactual case, we show that the environmental flow was effective in preventing hypoxia.

Hemodynamic effects of spiral ePTFE prosthesis compared with standard arteriovenous graft in a carotid to jugular vein porcine model.

PubMed

Jahrome, Ommid K; Hoefer, Imo; Houston, Graeme J; Stonebridge, Peter A; Blankestijn, Peter J; Moll, Frans L; de Borst, Gert J

2011-01-01

The primary patency rate of arteriovenous (AV) grafts is limited by distal venous anastomosis stenosis or occlusion due to intimal hyperplasia associated with distal graft turbulence. The normal blood flow in native arteries is spiral laminar flow. Standard vascular grafts do not produce spiral laminar flow at the distal anastomosis. Vascular grafts which induce a spiral laminar flow distally result in lower turbulence, particularly near the vessel wall. This initial study compares the hemodynamic effects of a spiral flow-inducing graft and a standard graft in a new AV carotid to jugular vein crossover graft porcine model. Four spiral flow grafts and 4 control grafts were implanted from the carotid artery to the contralateral jugular vein in 4 pigs. Two animals were terminated after 48 hours and 2 at 14 days. Graft patency was assessed by selective catheter digital angiography, and the flow pattern was assessed by intraoperative flow probe and color Doppler ultrasound (CDU) measurements. The spiral grafts were also assessed at enhanced flow rates using an external roller pump to simulate increased flow rates that may occur during dialysis using a standard dialysis needle cannulation. The method increased the flow rate through the graft by 660 ml/min. The graft distal anastomotic appearances were evaluated by explant histopathology. All grafts were patent at explantation with no complications. All anastomoses were found to be wide open and showed no significant angiographic stenosis at the distal anastomosis in both spiral and control grafts. CDU examinations showed a spiral flow pattern in the spiral graft and double helix pattern in the control graft. No gross histopathological effects were seen in either spiral or control grafts. This porcine model is robust and allows hemodynamic flow assessment up to 14 days postimplantation. The spiral flow-inducing grafts produced and maintained spiral flow at baseline and enhanced flow rates during dialysis needle cannulation, whereas control grafts did not produce spiral flow through the distal anastomosis. There was no deleterious effect of the spiral flow-inducing graft on macroscopic and histological examination. The reducing effect of spiral flow on intima hyperplasia formation will be the subject of further study using the same AV graft model at a longer period of implantation.

Assessment of salivary calcium, phosphate, magnesium, pH, and flow rate in healthy subjects, periodontitis, and dental caries.

PubMed

Rajesh, K S; Zareena; Hegde, Shashikanth; Arun Kumar, M S

2015-01-01

This study was conducted to estimate and compare inorganic salivary calcium, phosphate, magnesium, salivary flow rate, and pH of unstimulated saliva and oral hygiene status of healthy subjects, subjects with periodontitis and dental caries, and to correlate salivary calcium level with number of intact teeth. The study population consisted of 48 systemically healthy subjects in the age group of 18-55 years, which was further divided into three groups: healthy, periodontitis, and dental caries. Oral hygiene index-simplified, probing pocket depth, clinical attachment level, the number of intact teeth, and active carious lesions were recorded. Estimation of inorganic salivary calcium, phosphate, and magnesium was performed spectrophotometrically using Vitros 5.1 FS. Statistical analysis was performed using the one-way analysis of variance test at 5% significance level. There was a statistically significant increase in inorganic salivary calcium, phosphate, pH, flow rate, and poor oral hygiene status in periodontitis group compared to dental caries and healthy group. Subjects with increased inorganic salivary calcium, phosphate, pH, flow rate, and poor oral hygiene are at a higher risk of developing periodontitis. Since there is increased remineralization potential, these subjects have more number of intact teeth compared to the dental caries group.

Assessment of salivary calcium, phosphate, magnesium, pH, and flow rate in healthy subjects, periodontitis, and dental caries

PubMed Central

Rajesh, K. S.; Zareena; Hegde, Shashikanth; Arun Kumar, M. S.

2015-01-01

Aim: This study was conducted to estimate and compare inorganic salivary calcium, phosphate, magnesium, salivary flow rate, and pH of unstimulated saliva and oral hygiene status of healthy subjects, subjects with periodontitis and dental caries, and to correlate salivary calcium level with number of intact teeth. Materials and Methods: The study population consisted of 48 systemically healthy subjects in the age group of 18-55 years, which was further divided into three groups: healthy, periodontitis, and dental caries. Oral hygiene index-simplified, probing pocket depth, clinical attachment level, the number of intact teeth, and active carious lesions were recorded. Estimation of inorganic salivary calcium, phosphate, and magnesium was performed spectrophotometrically using Vitros 5.1 FS. Statistical analysis was performed using the one-way analysis of variance test at 5% significance level. Results: There was a statistically significant increase in inorganic salivary calcium, phosphate, pH, flow rate, and poor oral hygiene status in periodontitis group compared to dental caries and healthy group. Conclusion: Subjects with increased inorganic salivary calcium, phosphate, pH, flow rate, and poor oral hygiene are at a higher risk of developing periodontitis. Since there is increased remineralization potential, these subjects have more number of intact teeth compared to the dental caries group. PMID:26681848

Experimental study of cassava sun drying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Njie, D.N.; Rumsey, T.R.

1997-03-01

Sun drying experiments were performed to compare drying of cassava chips in sheet-metal trays with drying on mesh wire trays. In the sheet-metal trays, there was air flow across the top of the bed chips, while the mesh wire trays permitted air to flow through the bed. Drying rate was faster and more uniform in the trays with through-flow air circulation. Higher temperatures were reached by chips in the sheet-metal trays than those in the mesh trays because of contact heating, but the drying rate was lower because of the reduced air flow.

Characteristics of the Shuttle Orbiter Leeside Flow During A Reentry Condition

NASA Technical Reports Server (NTRS)

Kleb, William L.; Weilmuenster, K. James

1992-01-01

A study of the leeside flow characteristics of the Shuttle Orbiter is presented for a reentry flight condition. The flow is computed using a point-implicit, finite-volume scheme known as the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA). LAURA is a second-order accurate, laminar Navier-Stokes solver, incorporating finite-rate chemistry with a radiative equilibrium wall temperature distribution and finite-rate wall catalysis. The resulting computational solution is analyzed in terms of salient flow features and the surface quantities are compared with flight data.

Cooling Panel Optimization for the Active Cooling System of a Hypersonic Aircraft

NASA Technical Reports Server (NTRS)

Youn, B.; Mills, A. F.

1995-01-01

Optimization of cooling panels for an active cooling system of a hypersonic aircraft is explored. The flow passages are of rectangular cross section with one wall heated. An analytical fin-type model for incompressible flow in smooth-wall rectangular ducts with coupled wall conduction is proposed. Based on this model, the a flow rate of coolant to each design minimum mass flow rate or coolant for a single cooling panel is obtained by satisfying hydrodynamic, thermal, and Mach number constraints. Also, the sensitivity of the optimal mass flow rate of coolant to each design variable is investigated. In addition, numerical solutions for constant property flow in rectangular ducts, with one side rib-roughened and coupled wall conduction, are obtained using a k-epsilon and wall function turbulence model, these results are compared with predictions of the analytical model.

[Analysis of hydrodynamics parameters of runoff erosion and sediment-yielding on unpaved road].

PubMed

Huang, Peng-Fei; Wang, Wen-Long; Luo, Ting; Wang, Zhen; Wang, Zheng-Li; Li, Ren

2013-02-01

By the method of field runoff washout experiment, a simulation study was conducted on the relationships between the soil detachment rate and the hydrodynamic parameters on unpaved road, and the related quantitative formulas were established. Under the conditions of different flow discharges and road gradients, the averaged soil detachment rate increased with increasing flow discharge and road gradient, and the relationships between them could be described by a power function. As compared with road gradient, flow discharge had greater effects on the soil detachment rate. The soil detachment rate had a power relation with water flow velocity and runoff kinetic energy, and the runoff kinetic energy was of importance to the soil detachment rate. The soil detachment rate was linearly correlated with the unit runoff kinetic energy. The averaged soil erodibility was 0.120 g m-1.J-F-1, and the averaged critical unit runoff kinetic energy was 2.875 g.m-1.J-1. Flow discharge, road gradient, and unit runoff kinetic energy could be used to accurately describe the soil erosion process and calculate the soil erosion rate on unpaved road.

Flow Rates Measurement and Uncertainty Analysis in Multiple-Zone Water-Injection Wells from Fluid Temperature Profiles

PubMed Central

Reges, José E. O.; Salazar, A. O.; Maitelli, Carla W. S. P.; Carvalho, Lucas G.; Britto, Ursula J. B.

2016-01-01

This work is a contribution to the development of flow sensors in the oil and gas industry. It presents a methodology to measure the flow rates into multiple-zone water-injection wells from fluid temperature profiles and estimate the measurement uncertainty. First, a method to iteratively calculate the zonal flow rates using the Ramey (exponential) model was described. Next, this model was linearized to perform an uncertainty analysis. Then, a computer program to calculate the injected flow rates from experimental temperature profiles was developed. In the experimental part, a fluid temperature profile from a dual-zone water-injection well located in the Northeast Brazilian region was collected. Thus, calculated and measured flow rates were compared. The results proved that linearization error is negligible for practical purposes and the relative uncertainty increases as the flow rate decreases. The calculated values from both the Ramey and linear models were very close to the measured flow rates, presenting a difference of only 4.58 m³/d and 2.38 m³/d, respectively. Finally, the measurement uncertainties from the Ramey and linear models were equal to 1.22% and 1.40% (for injection zone 1); 10.47% and 9.88% (for injection zone 2). Therefore, the methodology was successfully validated and all objectives of this work were achieved. PMID:27420068

Effects of Change in Tongue Pressure and Salivary Flow Rate on Swallow Efficiency Following Chemoradiation Treatment for Head and Neck Cancer

PubMed Central

Rogus-Pulia, Nicole M.; Larson, Charles; Mittal, Bharat B; Pierce, Marge; Zecker, Steven; Kennelty, Korey; Kind, Amy; Connor, Nadine P.

2016-01-01

Purpose Patients treated with chemoradiation for head and neck cancer frequently develop dysphagia. Tissue damage to the oral tongue causing weakness and decreases in saliva production may contribute to dysphagia. Yet, effects of these variables on swallowing-related measures are unclear. The purpose of this study was (1) to determine effects of chemoradiation on tongue pressures, as a surrogate for strength, and salivary flow rates and (2) to elucidate relationships among tongue pressures, saliva production, and swallowing efficiency by bolus type. Methods and Materials 21 patients with head and neck cancer treated with chemoradiation were assessed before and after treatment and matched with 21 healthy control participants who did not receive chemoradiation. Each participant was given a questionnaire to rate dysphagia symptoms. Videofluoroscopic evaluation of swallowing was used to determine swallowing efficiency; the Saxon test measured salivary flow rate; and the Iowa Oral Performance Instrument (IOPI) was used for oral tongue maximum and endurance measures. Results Results revealed significantly lower tongue endurance measures for patients post-treatment as compared to controls (p=.012). Salivary flow rates also were lower compared to pre-treatment (p=.000) and controls (p=.000). Simple linear regression analyses showed that change in salivary flow rate was predictive of change in swallow efficiency measures from pre- to post-treatment for 1mL thin liquid (p=.017), 3mL nectar-thick liquid (p=.026), and 3mL standard barium pudding (p=.011) boluses. Conclusions Based on these findings, it appears that chemoradiation treatment affects tongue endurance and salivary flow rate and these changes may impact swallow efficiency. These factors should be considered when planning treatment for dysphagia. PMID:27492408

Numerical Modeling of Flow Control in a Boundary-Layer-Ingesting Offset Inlet Diffuser at Transonic Mach Numbers

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Owens, Lewis R.

2006-01-01

This paper will investigate the validation of the NASA developed, Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, for a boundary-layer-ingesting (BLI) offset (S-shaped) inlet in transonic flow with passive and active flow control devices as well as a baseline case. Numerical simulations are compared to wind tunnel results of a BLI inlet experiment conducted at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. Comparisons of inlet flow distortion, pressure recovery, and inlet wall pressures are performed. The numerical simulations are compared to the BLI inlet data at a free-stream Mach number of 0.85 and a Reynolds number of approximately 2 million based on the fanface diameter. The numerical simulations with and without tunnel walls are performed, quantifying tunnel wall effects on the BLI inlet flow. A comparison is made between the numerical simulations and the BLI inlet experiment for the baseline and VG vane cases at various inlet mass flow rates. A comparison is also made to a BLI inlet jet configuration for varying actuator mass flow rates at a fixed inlet mass flow rate. Overall, the numerical simulations were able to predict the baseline circumferential flow distortion, DPCP avg, very well within the designed operating range of the BLI inlet. A comparison of the average total pressure recovery showed that the simulations were able to predict the trends but had a negative 0.01 offset when compared to the experimental levels. Numerical simulations of the baseline inlet flow also showed good agreement with the experimental inlet centerline surface pressures. The vane case showed that the CFD predicted the correct trends in the circumferential distortion levels for varying inlet mass flow but had a distortion level that was nearly twice as large as the experiment. Comparison to circumferential distortion measurements for a 15 deg clocked 40 probe rake indicated that the circumferential distortion levels are very sensitive to the symmetry of the flow and that a misalignment of the vanes in the experiment could have resulted in this difference. The numerical simulations of the BLI inlet with jets showed good agreement with the circumferential inlet distortion levels for a range of jet actuator mass flow ratios at a fixed inlet mass flow rate. The CFD simulations for the jet case also predicted an average total pressure recovery offset that was 0.01 lower than the experiment as was seen in the baseline. Comparisons of the flow features for the jet cases revealed that the CFD predicted a much larger vortex at the engine fan-face when compare to the experiment.

Generation of zonal flows by electrostatic drift waves in electron-positron-ion plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaladze, T. D.; I. Vekua Institute of Applied Mathematics, Tbilisi State University, 2 University Str., 0186 Tbilisi; Shad, M.

2010-02-15

Generation of large-scale zonal flows by comparatively small-scale electrostatic drift waves in electron-positron-ion plasmas is considered. The generation mechanism is based on the parametric excitation of convective cells by finite amplitude drift waves having arbitrary wavelengths (as compared with the ion Larmor radius of plasma ions at the plasma electron temperature). Temperature inhomogeneity of electrons and positrons is taken into account assuming ions to be cold. To describe the generation of zonal flow generalized Hasegawa-Mima equation containing both vector and two scalar (of different nature) nonlinearities is used. A set of coupled equations describing the nonlinear interaction of drift wavesmore » and zonal flows is deduced. Explicit expressions for the maximum growth rate as well as for the optimal spatial dimensions of the zonal flows are obtained. Enriched possibilities of zonal flow generation with different growth rates are revealed. The present theory can be used for interpretations of drift wave observations in laboratory and astrophysical plasmas.« less

Membrane water-flow rate in electrolyzer cells with a solid polymer electrolyte (SPE)

NASA Astrophysics Data System (ADS)

Li, Xiaojin; Qu, Shuguo; Yu, Hongmei; Hou, Ming; Shao, Zhigang; Yi, Baolian

Water-flow rate across Nafion membrane in SPE electrolyzer cells was measured and modelled. From the analysis of water transport mechanisms in SPE water electrolysis, the water-flow rate through membrane can be described by the electro-osmotic drag. The calculated electro-osmotic drag coefficients, n d, for the membrane in SPE electrolysis cells at different temperatures were compared with literature and in good agreement with those of Ge et al. and Ise et al. To describe the water-flow rate through membrane more accurately, a linear fit of n d as a function of temperature for the membrane in SPE water electrolysis was proposed in this paper. This paper studied the membrane water-flow rate experimentally and mathematically, which is of importance in the designing and optimization of the process of SPE water electrolysis. This paper also provided a novel method for measuring the electro-osmotic drag coefficient of Nafion membrane in contact with liquid water, acid and methanol solutions, etc.

Flow Mode Dependent Partitioning Processes of Preferential Flow Dynamics in Unsaturated Fractures - Findings From Analogue Percolation Experiments

NASA Astrophysics Data System (ADS)

Kordilla, J.; Noffz, T.; Dentz, M.; Sauter, M.

2017-12-01

To assess the vulnerability of an aquifer system it is of utmost importance to recognize the high potential for a rapid mass transport offered by ow through unsaturated fracture networks. Numerical models have to reproduce complex effects of gravity-driven flow dynamics to generate accurate predictions of flow and transport. However, the non-linear characteristics of free surface flow dynamics and partitioning behaviour at unsaturated fracture intersections often exceed the capacity of classical volume-effective modelling approaches. Laboratory experiments that manage to isolate single aspects of the mass partitioning process can enhance the understanding of underlying dynamics, which ultimately influence travel time distributions on multiple scales. Our analogue fracture network consists of synthetic cubes with dimensions of 20 x 20 x 20 cm creating simple geometries of a single or a cascade of consecutive horizontal fractures. Gravity-driven free surface flow (droplets; rivulets) is established via a high precision multichannel dispenser at flow rates ranging from 1.5 to 4.5 ml/min. Single-inlet experiments show the influence of variable flow rate, atmospheric pressure and temperature on the stability of flow modes and allow to delineate a droplet and rivulet regime. The transition between these regimes exhibits mixed flow characteristics. In addition, multi-inlet setups with constant total infow rates decrease the variance induced by erratic free-surface flow dynamics. We investigate the impacts of variable aperture widths, horizontal offsets of vertical fracture surfaces, and alternating injection methods for both flow regimes. Normalized fracture inflow rates allow to demonstrate and compare the effects of variable geometric features. Firstly, the fracture filling can be described by plug flow. At later stages it transitions into a Washburn-type flow, which we compare to an analytical solution for the case of rivulet flow. Observations show a considerably higher bypass effciency of droplet flow. This behaviour may not be recovered by plug flow but also transitions into a Washburn stage. Furthermore, we study the effect of additional cubes, i.e. increasing amount of horizontal fractures, on the bulk arrival times and associated importance of flow mode dependent partitioning processes.

Separation Dynamics of Controlled Internal Flow in an Adverse Pressure Gradient

NASA Astrophysics Data System (ADS)

Peterson, C. J.; Vukasinovic, B.; Glezer, A.

2017-11-01

The effects of fluidic actuation on the dynamic evolution of aggressive internal flow separation is investigated at speeds up to M = 0.4 within a constant-width diffuser branching off of a primary flow duct. It is shown that a spanwise array of fluidic actuators upstream of the separation actively controls the flow constriction (and losses) within the diffuser and consequently the local pressure gradient at its entrance. The effectiveness of the actuation, as may be measured by the increased flow rate that is diverted through the diffuser, scales with its flow rate coefficient. In the presence of actuation (0.7% mass fraction), the mass flow rate in the primary duct increases by 10% while the fraction of the diverted mass flow rate in the diffuser increases by more than 45%. The flow dynamics near separation in the absence and presence of actuation are characterized using high speed particle image velocimetry and analyzed using proper orthogonal and spectral decompositions. In particular, the spectral contents of the incipient boundary layer separation are compared in the absence and presence of actuation with emphasis on the changes in local dynamics near separation as the characteristic cross stream scale of the boundary layer increases with separation delay.

Very high pressure liquid chromatography using core-shell particles: quantitative analysis of fast gradient separations without post-run times.

PubMed

Stankovich, Joseph J; Gritti, Fabrice; Stevenson, Paul G; Beaver, Lois A; Guiochon, Georges

2014-01-17

Five methods for controlling the mobile phase flow rate for gradient elution analyses using very high pressure liquid chromatography (VHPLC) were tested to determine thermal stability of the column during rapid gradient separations. To obtain rapid separations, instruments are operated at high flow rates and high inlet pressure leading to uneven thermal effects across columns and additional time needed to restore thermal equilibrium between successive analyses. The purpose of this study is to investigate means to minimize thermal instability and obtain reliable results by measuring the reproducibility of the results of six replicate gradient separations of a nine component RPLC standard mixture under various experimental conditions with no post-run times. Gradient separations under different conditions were performed: constant flow rates, two sets of constant pressure operation, programmed flow constant pressure operation, and conditions which theoretically should yield a constant net heat loss at the column's wall. The results show that using constant flow rates, programmed flow constant pressures, and constant heat loss at the column's wall all provide reproducible separations. However, performing separations using a high constant pressure with programmed flow reduces the analysis time by 16% compared to constant flow rate methods. For the constant flow rate, programmed flow constant pressure, and constant wall heat experiments no equilibration time (post-run time) was required to obtain highly reproducible data. Copyright © 2013 Elsevier B.V. All rights reserved.

Characterization and Prediction of Flow Behavior in High-Manganese Twinning Induced Plasticity Steels: Part II. Jerky Flow and Instantaneous Strain Rate

NASA Astrophysics Data System (ADS)

Saeed-Akbari, A.; Mishra, A. K.; Mayer, J.; Bleck, W.

2012-05-01

The jerky and smooth flow curves in high-manganese twinning induced plasticity (TWIP) steels were investigated by comparing Fe-Mn-C and Fe-Mn-Al-C systems. The pronounced serrations on the flow curves of Fe-Mn-C TWIP steel, produced during tensile testing at 300 K (27 °C) and 373 K (100 °C), were shown to be the result of localized high-temperature Portevin Le-Chatelier (PLC) bands moving across the gage length throughout the deformation. The speed of the PLC bands and their temperature effects were found to be strongly dependent on the applied strain rate, which was controlled by adjusting the cross-head speed of the tensile testing machine. The localized temperature-dependent stacking fault energy (SFE) variations resulting from the PLC effect and adiabatic heating were analyzed and compared for both slow and fast deformation rates. The instabilities in the measured logarithmic strain values caused by jerky flow could cause the local strain rate to deviate systematically from the targeted (applied) strain rate. These instabilities are better observed by calculating the instantaneous strain rate (ISR) values for each instant of deformation along the entire gage length. Finally, a new type of diagram was developed by plotting the true stress against the ISR values. From the diagram, the onset of different mechanisms, such as deformation twinning, nonpronounced, and pronounced serrations, could be marked precisely.

Evaluation of In Vitro and In Vivo Flow Rate Dependency of Budesonide/Formoterol Easyhaler®

PubMed Central

Malmberg, L. Pekka; Everard, Mark L.; Haikarainen, Jussi

2014-01-01

Abstract Background: The Easyhaler® (EH) device-metered dry powder inhaler containing budesonide and formoterol is being developed for asthma and chronic obstructive pulmonary disease (COPD). As a part of product optimization, a series of in vitro and in vivo studies on flow rate dependency were carried out. Methods: Inspiratory flow parameters via EH and Symbicort® Turbuhaler® (TH) inhalers were evaluated in 187 patients with asthma and COPD. The 10th, 50th, and 90th percentile flow rates achieved by patients were utilized to study in vitro flow rate dependency of budesonide/formoterol EH and Symbicort TH. In addition, an exploratory pharmacokinetic study on pulmonary deposition of active substances for budesonide/formoterol EH in healthy volunteers was performed. Results: Mean inspiratory flow rates through EH were 64 and 56 L/min in asthmatics and COPD patients, and through TH 79 and 72 L/min, respectively. Children with asthma had marginally lower PIF values than the adults. The inspiratory volumes were similar in all groups between the inhalers. Using weighted 10th, 50th, and 90th percentile flows the in vitro delivered doses (DDs) and fine particle doses (FPDs) for EH were rather independent of flow as 98% of the median flow DDs and 89%–93% of FPDs were delivered already at 10th percentile air flow. Using±15% limits, EH and TH had similar flow rate dependency profiles between 10th and 90th percentile flows. The pharmacokinetic study with budesonide/formoterol EH in healthy subjects (n=16) revealed a trend for a flow-dependent increase in lung deposition for both budesonide and formoterol. Conclusions: Comparable in vitro flow rate dependency between budesonide/formoterol EH and Symbicort TH was found using the range of clinically relevant flow rates. The results of the pharmacokinetic study were in accordance with the in vitro results showing only a trend of flow rate-dependant increase in lung deposition of active substances with EH. PMID:24978441

Flow experience and the mobilization of attentional resources.

PubMed

de Sampaio Barros, Marcelo Felipe; Araújo-Moreira, Fernando M; Trevelin, Luis Carlos; Radel, Rémi

2018-05-07

The present study attempts to better identify the neurophysiological changes occurring during flow experience and how this can be related to the mobilization of attentional resources. Self-reports of flow (using a flow feelings scale) and attention (using thought probes), autonomic activity (heart rate, heart rate variability, and breathing rate), and cerebral oxygenation (using near-infrared spectroscopy) in two regions of the frontoparietal attention network (right lateral frontal cortex and right inferior parietal lobe) were measured during the practice of two simple video games (Tetris and Pong) played at different difficulty conditions (easy, optimal, hard, or self-selected). Our results indicated that an optimal level of difficulty, compared with an easy or hard level of difficulty led to greater flow feelings and a higher concentration of oxygenated hemoglobin in the regions of the frontoparietal network. The self-selected, named autonomy condition did not lead to more flow feelings than the optimal condition; however, the autonomy condition led to greater sympathetic activity (reduced heart rate variability and greater breathing rate) and higher activation of the frontoparietal regions. Our study suggests that flow feelings are highly connected to the mobilization of attentional resources, and all the more in a condition that promotes individuals' choice and autonomy.

Accuracy improvement of the ice flow rate measurements on Antarctic ice sheet by DInSAR method

NASA Astrophysics Data System (ADS)

Shiramizu, Kaoru; Doi, Koichiro; Aoyama, Yuichi

2015-04-01

DInSAR (Differential Interferometric Synthetic Aperture Radar) is an effective tool to measure the flow rate of slow flowing ice streams on Antarctic ice sheet with high resolution. In the flow rate measurement by DInSAR method, we use Digital Elevation Model (DEM) at two times in the estimating process. At first, we use it to remove topographic fringes from InSAR images. And then, it is used to project obtained displacements along Line-Of-Sight (LOS) direction to the actual flow direction. ASTER-GDEM widely-used for InSAR prosessing of the data of polar region has a lot of errors especially in the inland ice sheet area. Thus the errors yield irregular flow rates and directions. Therefore, quality of DEM has a substantial influence on the ice flow rate measurement. In this study, we created a new DEM (resolution 10m; hereinafter referred to as PRISM-DEM) based on ALOS/PRISM images, and compared PRISM-DEM and ASTER-GDEM. The study area is around Skallen, 90km south from Syowa Station, in the southern part of Sôya Coast, East Antarctica. For making DInSAR images, we used ALOS/PALSAR data of 13 pairs (Path633, Row 571-572), observed during the period from November 23, 2007 through January 16, 2011. PRISM-DEM covering the PALSAR scene was created from nadir and backward view images of ALOS/PRISM (Observation date: 2009/1/18) by applying stereo processing with a digital mapping equipment, and then the automatically created a primary DEM was corrected manually to make a final DEM. The number of irregular values of actual ice flow rate was reduced by applying PRISM-DEM compared with that by applying ASTER-GDEM. Additionally, an averaged displacement of approximately 0.5cm was obtained by applying PRISM-DEM over outcrop area, where no crustal displacement considered to occur during the recurrence period of ALOS/PALSAR (46days), while an averaged displacement of approximately 1.65 cm was observed by applying ASTER-GDEM. Since displacements over outcrop area are considered to be apparent ones, the average could be a measure of flow rate estimation accuracy by DInSAR. Therefore, it is concluded that the accuracy of the ice flow rate measurement can be improved by using PRISM-DEM. In this presentation, we will show the results of the estimated flow rate of ice streams in the region of interest, and discuss the additional accuracy improvement of this method.

A Soft-Start Circuit for Arcjet Ignition

NASA Technical Reports Server (NTRS)

Hamley, John A.; Sankovic, John M.

1993-01-01

The reduced propellant flow rates associated with high performance arcjets have placed new emphasis on electrode erosion, especially at startup. A soft-start current profile was defined which limited current overshoot during the initial 30 to 50 ms of operation, and maintained significantly lower than the nominal arc current for the first eight seconds of operation. A 2-5 kW arcjet PPU was modified to provide this current profile, and a 500 cycle test using simulated fully decomposed hydrazine was conducted to determine the electrode erosion during startup. Electrode geometry and mass flow rates were selected based on requirements for a 600 second specific impulse mission average arcjet system. The flow rate was varied throughout the test to simulate the blow down of a flight propellant system. Electrode damage was negligible at flow rates above 33 mg/s, and minor chamfering of the constrictor occurred at flow rates of 33 to 30 mg/s, corresponding to flow rates expected in the last 40 percent of the mission. Constrictor diameter remained unchanged and the thruster remained operable at the completion of the test. The soft-start current profile significantly reduced electrode damage when compared to state of the art starting techniques.

Steady flow rate to a partially penetrating well with seepage face in an unconfined aquifer

NASA Astrophysics Data System (ADS)

Behrooz-Koohenjani, Siavash; Samani, Nozar; Kompani-Zare, Mazda

2011-06-01

The flow rate to fully screened, partially penetrating wells in an unconfined aquifer is numerically simulated using MODFLOW 2000, taking into account the flow from the seepage face and decrease in saturated thickness of the aquifer towards the well. A simple three-step method is developed to find the top of the seepage face and hence the seepage-face length. The method is verified by comparing it with the results of previous predictive methods. The results show that the component of flow through the seepage face can supply a major portion of the total pumping rate. Variations in flow rate as a function of the penetration degree, elevation of the water level in the well and the distance to the far constant head boundary are investigated and expressed in terms of dimensionless curves and equations. These curves and equations can be used to design the degree of penetration for which the allowable steady pumping rate is attained for a given elevation of water level in the well. The designed degree of penetration or flow rate will assure the sustainability of the aquifer storage, and can be used as a management criterion for issuing drilling well permits by groundwater protection authorities.

Comparative evaluation of thermal decomposition behavior and thermal stability of powdered ammonium nitrate under different atmosphere conditions.

PubMed

Yang, Man; Chen, Xianfeng; Wang, Yujie; Yuan, Bihe; Niu, Yi; Zhang, Ying; Liao, Ruoyu; Zhang, Zumin

2017-09-05

In order to analyze the thermal decomposition characteristics of ammonium nitrate (AN), its thermal behavior and stability under different conditions are studied, including different atmospheres, heating rates and gas flow rates. The evolved decomposition gases of AN in air and nitrogen are analyzed with a quadrupole mass spectrometer. Thermal stability of AN at different heating rates and gas flow rates are studied by differential scanning calorimetry, thermogravimetric analysis, paired comparison method and safety parameter evaluation. Experimental results show that the major evolved decomposition gases in air are H 2 O, NH 3 , N 2 O, NO, NO 2 and HNO 3 , while in nitrogen, H 2 O, NH 3 , NO and HNO 3 are major components. Compared with nitrogen atmosphere, lower initial and end temperatures, higher heat flux and broader reaction temperature range are obtained in air. Meanwhile, higher air gas flow rate tends to achieve lower reaction temperature and to reduce thermal stability of AN. Self-accelerating decomposition temperature of AN in air is much lower than that in nitrogen. It is considered that thermostability of AN is influenced by atmosphere, heating rate and gas flow rate, thus changes of boundary conditions will influence its thermostability, which is helpful to its safe production, storage, transportation and utilization. Copyright © 2017 Elsevier B.V. All rights reserved.

Nitrous oxide from aerated dairy manure slurries: Effects of aeration rates and oxic/anoxic phasing.

PubMed

Molodovskaya, Marina; Singurindy, Olga; Richards, Brian K; Steenhuis, Tammo S

2008-12-01

Small-scale laboratory research was conducted to compare the effects of different aeration rates and oxic/anoxic phasing on nitrous oxide (N(2)O) formation from dairy manure slurries. Manure slurry samples were incubated in triplicate for three-weeks under a range of continuous sweep gas flows (0.01-0.23L min(-1)kg(-1) slurry) with and without oxygen (air and dinitrogen gas). The net release of N(2)O-N was affected by both aeration rates and oxic/anoxic conditions, whereas ammonia volatilization depended mainly on gas flow rates. Maximum N(2)O-N losses after three-weeks incubation were 4.2% of total slurry N. Major N losses (up to 50% of total slurry N) were caused by ammonia volatilization that increased with increasing gas flow rates. The lowest nitrous oxide and ammonia production was observed from low flow phased oxic/anoxic treatment.

Salivary flow rate and xerostomia in patients with type I and II diabetes mellitus

PubMed Central

Hoseini, Amineh; Mirzapour, Ali; Bijani, Ali; Shirzad, Atena

2017-01-01

Background Diabetes mellitus is one of the most prevalent metabolic diseases, with complications such as decreased salivary flow rate and xerostomia. Objective This study aimed to determine the salivary flow rate and xerostomia in type I and II diabetic patients in comparison with healthy controls. Methods This case-control study was performed on diabetic patients of a private office in Babol, Iran, between May 2015 and October 2016. This study involved two study groups (type I and II diabetes, with 40 in each group) and two control groups (control I and II, with 35 in each group) which were age- and sex-matched with the related study groups. They were all selected through simple sampling. Unstimulated whole saliva was collected through Navazesh method and the salivary flow rate was measured (ml/min). Xerostomia was evaluated via Fox’s test. Moreover, the patients’ data were recorded including age, sex, disease duration, type of diabetes, fasting blood glucose (FBG) and HbA1C. The obtained data were statistically analyzed by using SPSS version 17. Independent-samples t-test, Chi-square, Pearson correlation and multiple comparison post-hoc tests were employed as appropriated. p<0.05 was considered significant. Results The mean salivary flow rate in type I diabetics (0.35±0.11 ml/min) was lower than that in control I (0.50±0.07 ml/min) (p=0.01). The same difference was observed between type II diabetics (0.37±0.13 ml/min) and control II groups (0.47±0.11 ml/min) (p=0.01). No significant difference was observed in the salivary flow rate between type I and II diabetics (p=0.345). Furthermore, xerostomia was higher in type I (2.70±2.50, 1.17±1.60) and II (2.65±2.20–1.62±1.50) diabetics compared with the related control groups (p=0.01), (p=0.02). Conclusion Type I, II diabetic patients revealed lower salivary flow rate and higher xerostomia compared with healthy controls. The salivary flow rate and xerostomia had inverse correlation. PMID:29038704

Salivary flow rate and xerostomia in patients with type I and II diabetes mellitus.

PubMed

Hoseini, Amineh; Mirzapour, Ali; Bijani, Ali; Shirzad, Atena

2017-09-01

Diabetes mellitus is one of the most prevalent metabolic diseases, with complications such as decreased salivary flow rate and xerostomia. This study aimed to determine the salivary flow rate and xerostomia in type I and II diabetic patients in comparison with healthy controls. This case-control study was performed on diabetic patients of a private office in Babol, Iran, between May 2015 and October 2016. This study involved two study groups (type I and II diabetes, with 40 in each group) and two control groups (control I and II, with 35 in each group) which were age- and sex-matched with the related study groups. They were all selected through simple sampling. Unstimulated whole saliva was collected through Navazesh method and the salivary flow rate was measured (ml/min). Xerostomia was evaluated via Fox's test. Moreover, the patients' data were recorded including age, sex, disease duration, type of diabetes, fasting blood glucose (FBG) and HbA1C. The obtained data were statistically analyzed by using SPSS version 17. Independent-samples t-test, Chi-square, Pearson correlation and multiple comparison post-hoc tests were employed as appropriated. p<0.05 was considered significant. The mean salivary flow rate in type I diabetics (0.35±0.11 ml/min) was lower than that in control I (0.50±0.07 ml/min) (p=0.01). The same difference was observed between type II diabetics (0.37±0.13 ml/min) and control II groups (0.47±0.11 ml/min) (p=0.01). No significant difference was observed in the salivary flow rate between type I and II diabetics (p=0.345). Furthermore, xerostomia was higher in type I (2.70±2.50, 1.17±1.60) and II (2.65±2.20-1.62±1.50) diabetics compared with the related control groups (p=0.01), (p=0.02). Type I, II diabetic patients revealed lower salivary flow rate and higher xerostomia compared with healthy controls. The salivary flow rate and xerostomia had inverse correlation.

Extension of the Helmholtz-Smoluchowski velocity to the hydrophobic microchannels with velocity slip.

PubMed

Park, H M; Kim, T W

2009-01-21

Electrokinetic flows through hydrophobic microchannels experience velocity slip at the microchannel wall, which affects volumetric flow rate and solute retention time. The usual method of predicting the volumetric flow rate and velocity profile for hydrophobic microchannels is to solve the Navier-Stokes equation and the Poisson-Boltzmann equation for the electric potential with the boundary condition of velocity slip expressed by the Navier slip coefficient, which is computationally demanding and defies analytic solutions. In the present investigation, we have devised a simple method of predicting the velocity profiles and volumetric flow rates of electrokinetic flows by extending the concept of the Helmholtz-Smoluchowski velocity to microchannels with Navier slip. The extended Helmholtz-Smoluchowski velocity is simple to use and yields accurate results as compared to the exact solutions. Employing the extended Helmholtz-Smoluchowski velocity, the analytical expressions for volumetric flow rate and velocity profile for electrokinetic flows through rectangular microchannels with Navier slip have been obtained at high values of zeta potential. The range of validity of the extended Helmholtz-Smoluchowski velocity is also investigated.

Comparison of Tissue Heat Balance- and Thermal Dissipation-Derived Sap Flow Measurements in Ring-Porous Oaks and a Pine

PubMed Central

Renninger, Heidi J.; Schäfer, Karina V. R.

2012-01-01

Sap flow measurements have become integral in many physiological and ecological investigations. A number of methods are used to estimate sap flow rates in trees, but probably the most popular is the thermal dissipation (TD) method because of its affordability, relatively low power consumption, and ease of use. However, there have been questions about the use of this method in ring-porous species and whether individual species and site calibrations are needed. We made concurrent measurements of sap flow rates using TD sensors and the tissue heat balance (THB) method in two oak species (Quercus prinus Willd. and Quercus velutina Lam.) and one pine (Pinus echinata Mill.). We also made concurrent measurements of sap flow rates using both 1 and 2-cm long TD sensors in both oak species. We found that both the TD and THB systems tended to match well in the pine individual, but sap flow rates were underestimated by 2-cm long TD sensors in five individuals of the two ring-porous oak species. Underestimations of 20–35% occurred in Q. prinus even when a “Clearwater” correction was applied to account for the shallowness of the sapwood depth relative to the sensor length and flow rates were underestimated by up to 50% in Q. velutina. Two centimeter long TD sensors also underestimated flow rates compared with 1-cm long sensors in Q. prinus, but only at large flow rates. When 2-cm long sensor data in Q. prinus were scaled using the regression with 1-cm long data, daily flow rates matched well with the rates measured by the THB system. Daily plot level transpiration estimated using TD sap flow rates and scaled 1 cm sensor data averaged about 15% lower than those estimated by the THB method. Therefore, these results suggest that 1-cm long sensors are appropriate in species with shallow sapwood, however more corrections may be necessary in ring-porous species. PMID:22661978

Effects of forcing time scale on the simulated turbulent flows and turbulent collision statistics of inertial particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosa, B., E-mail: bogdan.rosa@imgw.pl; Parishani, H.; Department of Earth System Science, University of California, Irvine, California 92697-3100

2015-01-15

In this paper, we study systematically the effects of forcing time scale in the large-scale stochastic forcing scheme of Eswaran and Pope [“An examination of forcing in direct numerical simulations of turbulence,” Comput. Fluids 16, 257 (1988)] on the simulated flow structures and statistics of forced turbulence. Using direct numerical simulations, we find that the forcing time scale affects the flow dissipation rate and flow Reynolds number. Other flow statistics can be predicted using the altered flow dissipation rate and flow Reynolds number, except when the forcing time scale is made unrealistically large to yield a Taylor microscale flow Reynoldsmore » number of 30 and less. We then study the effects of forcing time scale on the kinematic collision statistics of inertial particles. We show that the radial distribution function and the radial relative velocity may depend on the forcing time scale when it becomes comparable to the eddy turnover time. This dependence, however, can be largely explained in terms of altered flow Reynolds number and the changing range of flow length scales present in the turbulent flow. We argue that removing this dependence is important when studying the Reynolds number dependence of the turbulent collision statistics. The results are also compared to those based on a deterministic forcing scheme to better understand the role of large-scale forcing, relative to that of the small-scale turbulence, on turbulent collision of inertial particles. To further elucidate the correlation between the altered flow structures and dynamics of inertial particles, a conditional analysis has been performed, showing that the regions of higher collision rate of inertial particles are well correlated with the regions of lower vorticity. Regions of higher concentration of pairs at contact are found to be highly correlated with the region of high energy dissipation rate.« less

Experimental analysis of flow structure in contra-rotating axial flow pump designed with different rotational speed concept

NASA Astrophysics Data System (ADS)

Cao, Linlin; Watanabe, Satoshi; Imanishi, Toshiki; Yoshimura, Hiroaki; Furukawa, Akinori

2013-08-01

As a high specific speed pump, the contra-rotating axial flow pump distinguishes itself in a rear rotor rotating in the opposite direction of the front rotor, which remarkably contributes to the energy conversion, the reduction of the pump size, better hydraulic and cavitation performances. However, with two rotors rotating reversely, the significant interaction between blade rows was observed in our prototype contra-rotating rotors, which highly affected the pump performance compared with the conventional axial flow pumps. Consequently, a new type of rear rotor was designed by the rotational speed optimization methodology with some additional considerations, aiming at better cavitation performance, the reduction of blade rows interaction and the secondary flow suppression. The new rear rotor showed a satisfactory performance at the design flow rate but an unfavorable positive slope of the head — flow rate curve in the partial flow rate range less than 40% of the design flow rate, which should be avoided for the reliability of pump-pipe systems. In the present research, to understand the internal flow field of new rear rotor and its relation to the performances at the partial flow rates, the velocity distributions at the inlets and outlets of the rotors are firstly investigated. Then, the boundary layer flows on rotor surfaces, which clearly reflect the secondary flow inside the rotors, are analyzed through the limiting streamline observations using the multi-color oil-film method. Finally, the unsteady numerical simulations are carried out to understand the complicated internal flow structures in the rotors.

Assessment of a miniature four-roll mill and a cross-slot microchannel for high-strain-rate stagnation point flows

NASA Astrophysics Data System (ADS)

Akbaridoust, Farzan; Philip, Jimmy; Marusic, Ivan

2018-04-01

Stagnation point flows have been widely used to study the deformation and break-up of objects in two-dimensional pure straining flows. Here, we report a systematic study of the characterisation of stagnation point flows in two devices, a miniature Taylor’s four-roll mill and a cross-slot microchannel. The aim of the study is to find the best platform suitable for investigating the effect of strain rate on the mechanical properties of waterborne microorganisms. Using micro-PIV, the velocity field and the strain rates in both devices were measured at different flow rates and compared with an ideal hyperbolic stagnation point flow. The cross-slot microchannel was found to be a better experimental device than the miniature four-roll mill for the purpose of confining micron-sized objects in a controlled stagnation point flow. This is mainly due to the difficulty of maintaining a fixed location for the stagnation point within one micron in the miniature four-roll mill and achieving high strain rates beyond 10 s-1 . However, with no moving parts, the cross-slot microchannel was found to maintain a steady flow, with the stagnation point varying less than one micron at a cross-junction of 400× 400~μm2 , and was able to reach uniform strain rates up to 140 s-1 .

Using Computational Fluid Dynamics to Compare Shear Rate and Turbulence in the TIM-Automated Gastric Compartment With USP Apparatus II.

PubMed

Hopgood, Matthew; Reynolds, Gavin; Barker, Richard

2018-03-30

We use computational fluid dynamics to compare the shear rate and turbulence in an advanced in vitro gastric model (TIMagc) during its simulation of fasted state Migrating Motor Complex phases I and II, with the United States Pharmacopeia paddle dissolution apparatus II (USPII). A specific focus is placed on how shear rate in these apparatus affects erosion-based solid oral dosage forms. The study finds that tablet surface shear rates in TIMagc are strongly time dependant and fluctuate between 0.001 and 360 s -1 . In USPII, tablet surface shear rates are approximately constant for a given paddle speed and increase linearly from 9 s -1 to 36 s -1 as the paddle speed is increased from 25 to 100 rpm. A strong linear relationship is observed between tablet surface shear rate and tablet erosion rate in USPII, whereas TIMagc shows highly variable behavior. The flow regimes present in each apparatus are compared to in vivo predictions using Reynolds number analysis. Reynolds numbers for flow in TIMagc lie predominantly within the predicted in vivo bounds (0.01-30), whereas Reynolds numbers for flow in USPII lie above the predicted upper bound when operating with paddle speeds as low as 25 rpm (33). Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Blood flow in hemodialysis catheters: a numerical simulation and microscopic analysis of in vivo-formed fibrin.

PubMed

Lucas, Thabata Coaglio; Tessarolo, Francesco; Jakitsch, Victor; Caola, Iole; Brunori, Giuliano; Nollo, Giandomenico; Huebner, Rudolf

2014-07-01

Although catheters with side holes allow high flow rate during hemodialysis, they also induce flow disturbances and create a critical hemodynamic environment that can favor fibrin deposition and thrombus formation. This study compared the blood flow and analyzed the influence of shear stress and shear rate in fibrin deposition and thrombus formation in nontunneled hemodialysis catheters with unobstructed side holes (unobstructed device) or with some side holes obstructed by blood thrombi (obstructed device). Computational fluid dynamics (CFD) was performed to simulate realistic blood flow under laminar and turbulent conditions. The results from the numerical simulations were compared with the fibrin distribution and thrombus architecture data obtained from scanning electron microscopy (SEM) and two photons laser scanning microscopy (TPLSM) on human thrombus formed in catheters removed from patients. CFD showed that regions of flow eddies and separation were mainly found in the venous holes region. TPLSM characterization of thrombi and fibrin structure in patient samples showed fibrin formations in accordance with simulated flux dynamics. Under laminar flow conditions, the wall shear stress close to border holes increased from 87.3±0.2 Pa in the unobstructed device to 176.2±0.5 Pa in the obstructed one. Under turbulent flow conditions, the shear stress increased by 47% when comparing the obstructed to the unobstructed catheter. The shear rates were generally higher than 5000/s and therefore sufficient to induce fibrin deposition. This findings were supported by SEM data documenting a preferential fibrin arrangement on side hole walls. Copyright © 2013 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Bathyphotometer bioluminescence potential measurements: A framework for characterizing flow agitators and predicting flow-stimulated bioluminescence intensity

NASA Astrophysics Data System (ADS)

Latz, Michael I.; Rohr, Jim

2013-07-01

Bathyphotometer measurements of bioluminescence are used as a proxy for the abundance of luminescent organisms for studying population dynamics; the interaction of luminescent organisms with physical, chemical, and biological oceanographic processes; and spatial complexity especially in coastal areas. However, the usefulness of bioluminescence measurements has been limited by the inability to compare results from different bathyphotometer designs, or even the same bathyphotometer operating at different volume flow rates. The primary objective of this study was to compare measurements of stimulated bioluminescence of four species of cultured dinoflagellates, the most common source of bioluminescence in coastal waters, using two different bathyphotometer flow agitators as a function of bathyphotometer volume flow rate and dinoflagellate concentration. For both the NOSC and BIOLITE flow agitators and each species of dinoflagellate tested, there was a critical volume flow rate, above which average bioluminescence intensity, designated as bathyphotometer bioluminescence potential (BBP), remained relatively constant and scaled directly with dinoflagellate cell concentration. At supra-critical volume flow rates, the ratio of BIOLITE to NOSC BBP was nearly constant for the same species studied, but varied between species. The spatial pattern and residence time of flash trajectories within the NOSC flow agitator indicated the presence of dominant secondary recirculating flows, where most of the bioluminescence was detected. A secondary objective (appearing in the Appendix) was to study the feasibility of using NOSC BBP to scale flow-stimulated bioluminescence intensity across similar flow fields, where the contributing composition of luminescent species remained the same. Fully developed turbulent pipe flow was chosen because it is hydrodynamically well characterized. Average bioluminescence intensity in a 2.54-cm i.d. pipe was highly correlated with wall shear stress and BBP. This correlation, when further scaled by pipe diameter, effectively predicted bioluminescence intensity in fully developed turbulent flow in a 0.83-cm i.d. pipe. Determining similar correlations between other bathyphotometer flow agitators and flow fields will allow bioluminescence potential measurements to become a more powerful tool for the oceanographic community.

Performance Comparison of High-Speed Dual-Pneumatic Vitrectomy Cutters during Simulated Vitrectomy with Balanced Salt Solution.

PubMed

Abulon, Dina Joy K; Buboltz, David C

2015-02-01

To measure flow rate of balanced salt solution and IOP during simulated vitrectomy using two sets of high-speed dual-pneumatic probes. A closed-model eye system measured IOP and flow rate of a balanced salt solution through infusion cannula. The Constellation Vision System was tested with two sets of high-speed dual-pneumatic probes (UltraVit 23-gauge and enhanced 25+-gauge 5000-cpm probes; UltraVit 23-gauge and enhanced 25+-gauge 7500-cpm probes; n = 6 each) under different vacuum levels and cut rates in three duty cycle modes. In both probe sets, flow rates were dependent on cut rate with the biased open and biased closed duty cycles. Flow rates were highest with the biased open duty cycle, lower with the 50/50 duty cycle, and lowest with the biased closed duty cycle. IOP, as expected, was inversely associated with flow rate using both probe sets. The 7500-cpm probes offer greater control and customization compared with 5000-cpm probes under certain experimental conditions. At maximum cut rates, performance of 7500-cpm probes was similar to that of 5000-cpm probes, suggesting that 7500-cpm probes may be used without sacrifice of flow rate and IOP stability. Customization of vitrectomy parameters allows greater surgeon control during vitrectomy and may expand the usefulness of vitrectomy probes.

Flow Characteristics and Robustness of an Inclined Quad-vortex Range Hood

PubMed Central

CHEN, Jia-Kun; HUANG, Rong Fung

2014-01-01

A novel design of range hood, which was termed the inclined quad-vortex (IQV) range hood, was examined for its flow and containment leakage characteristics under the influence of a plate sweeping across the hood face. A flow visualization technique was used to unveil the flow behavior. Three characteristic flow modes were observed: convex, straight, and concave modes. A tracer gas detection method using sulfur hexafluoride (SF6) was employed to measure the containment leakage levels. The results were compared with the test data reported previously in the literature for a conventional range hood and an inclined air curtain (IAC) range hood. The leakage SF6 concentration of the IQV range hood under the influence of the plate sweeping was 0.039 ppm at a suction flow rate of 9.4 m3/min. The leakage concentration of the conventional range hood was 0.768 ppm at a suction flow rate of 15.0 m3/min. For the IAC range hood, the leakage concentration was 0.326 ppm at a suction flow rate of 10.9 m3/min. The IQV range hood presented a significantly lower leakage level at a smaller suction flow rate than the conventional and IAC range hoods due to its aerodynamic design for flow behavior. PMID:24583513

Molecular simulation of flow-enhanced nucleation in n-eicosane melts under steady shear and uniaxial extension.

PubMed

Nicholson, David A; Rutledge, Gregory C

2016-12-28

Non-equilibrium molecular dynamics is used to study crystal nucleation of n-eicosane under planar shear and, for the first time, uniaxial extension. A method of analysis based on the mean first-passage time is applied to the simulation results in order to determine the effect of the applied flow field type and strain rate on the steady-state nucleation rate and a characteristic growth rate, as well as the effects on kinetic parameters associated with nucleation: the free energy barrier, critical nucleus size, and monomer attachment pre-factor. The onset of flow-enhanced nucleation (FEN) occurs at a smaller critical strain rate in extension as compared to shear. For strain rates larger than the critical rate, a rapid increase in the nucleation rate is accompanied by decreases in the free energy barrier and critical nucleus size, as well as an increase in chain extension. These observations accord with a mechanism in which FEN is caused by an increase in the driving force for crystallization due to flow-induced entropy reduction. At high applied strain rates, the free energy barrier, critical nucleus size, and degree of stretching saturate, while the monomer attachment pre-factor and degree of orientational order increase steadily. This trend is indicative of a significant diffusive contribution to the nucleation rate under intense flows that is correlated with the degree of global orientational order in a nucleating system. Both flow fields give similar results for all kinetic quantities with respect to the reduced strain rate, which we define as the ratio of the applied strain rate to the critical rate. The characteristic growth rate increases with increasing strain rate, and shows a correspondence with the nucleation rate that does not depend on the type of flow field applied. Additionally, a structural analysis of the crystalline clusters indicates that the flow field suppresses the compaction and crystalline ordering of clusters, leading to the formation of large articulated clusters under strong flow fields, and compact well-ordered clusters under weak flow fields.

Transient response of sap flow to wind speed.

PubMed

Chu, Chia R; Hsieh, Cheng-I; Wu, Shen-Yuang; Phillips, Nathan G

2009-01-01

Transient responses of sap flow to step changes in wind speed were experimentally investigated in a wind tunnel. A Granier-type sap flow sensor was calibrated and tested in a cylindrical tube for analysis of its transient time response. Then the sensor was used to measure the transient response of a well-watered Pachira macrocarpa plant to wind speed variations. The transient response of sap flow was described using the resistance-capacitance model. The steady sap flow rate increased as the wind speed increased at low wind speeds. Once the wind speed exceeded 8.0 m s(-1), the steady sap flow rate did not increase further. The transpiration rate, measured gravimetrically, showed a similar trend. The response of nocturnal sap flow to wind speed variation was also measured and compared with the results in the daytime. Under the same wind speed, the steady sap flow rate was smaller than that in the daytime, indicating differences between diurnal and nocturnal hydraulic function, and incomplete stomatal closure at night. In addition, it was found that the temporal response of the Granier sensor is fast enough to resolve the transient behaviour of water flux in plant tissue.

Mass transfer in thin films under counter-current gas: experiments and numerical study

NASA Astrophysics Data System (ADS)

Lucquiaud, Mathieu; Lavalle, Gianluca; Schmidt, Patrick; Ausner, Ilja; Wehrli, Marc; O Naraigh, Lennon; Valluri, Prashant

2016-11-01

Mass transfer in liquid-gas stratified flows is strongly affected by the waviness of the interface. For reactive flows, the chemical reactions occurring at the liquid-gas interface also influence the mass transfer rate. This is encountered in several technological applications, such as absorption units for carbon capture. We investigate the absorption rate of carbon dioxide in a liquid solution. The experimental set-up consists of a vertical channel where a falling film is sheared by a counter-current gas flow. We measure the absorption occurring at different flow conditions, by changing the liquid solution, the liquid flow rate and the gas composition. With the aim to support the experimental results with numerical simulations, we implement in our level-set flow solver a novel module for mass transfer taking into account a variant of the ghost-fluid formalism. We firstly validate the pure mass transfer case with and without hydrodynamics by comparing the species concentration in the bulk flow to the analytical solution. In a final stage, we analyse the absorption rate in reactive flows, and try to reproduce the experimental results by means of numerical simulations to explore the active role of the waves at the interface.

Simulation Study of Nano Aqueous Flow Sensor Based on Amperometric Measurement

PubMed Central

Wu, Jian; Zhou, Qingli; Liu, Jun; Lou, Zhengguo

2006-01-01

In this paper, a novel nano aqueous flow sensor which consists of two closely spaced amperometric sensors is investigated by digital simulation. The simulation results indicate that the ratio of the responses of two closely spaced amperometric sensors is only related to flow rates in the channel, insensitive to the analyte concentration in the solution. By comparing the output of two amperometric sensors, the flow rate in the channel can be deduced. It is not necessary to determine the analyte concentration in advance. The simulation results show it is able to detect flow rate by in the range of several nano-liters per minute when the distance between the working electrodes of two amperometric sensors is 200 nm and the cross-section of the channel is 1 μm × 1 μm.

The 'upstream wake' of swimming and flying animals and its correlation with propulsive efficiency.

PubMed

Peng, Jifeng; Dabiri, John O

2008-08-01

The interaction between swimming and flying animals and their fluid environments generates downstream wake structures such as vortices. In most studies, the upstream flow in front of the animal is neglected. In this study, we demonstrate the existence of upstream fluid structures even though the upstream flow is quiescent or possesses a uniform incoming velocity. Using a computational model, the flow generated by a swimmer (an oscillating flexible plate) is simulated and a new fluid mechanical analysis is applied to the flow to identify the upstream fluid structures. These upstream structures show the exact portion of fluid that is going to interact with the swimmer. A mass flow rate is then defined based on the upstream structures, and a metric for propulsive efficiency is established using the mass flow rate and the kinematics of the swimmer. We propose that the unsteady mass flow rate defined by the upstream fluid structures can be used as a metric to measure and objectively compare the efficiency of locomotion in water and air.

Paper recycling framework, the "Wheel of Fiber".

PubMed

Ervasti, Ilpo; Miranda, Ruben; Kauranen, Ilkka

2016-06-01

At present, there is no reliable method in use that unequivocally describes paper industry material flows and makes it possible to compare geographical regions with each other. A functioning paper industry Material Flow Account (MFA) that uses uniform terminology and standard definitions for terms and structures is necessary. Many of the presently used general level MFAs, which are called frameworks in this article, stress the importance of input and output flows but do not provide a uniform picture of material recycling. Paper industry is an example of a field in which recycling plays a key role. Additionally, terms related to paper industry recycling, such as collection rate, recycling rate, and utilization rate, are not defined uniformly across regions and time. Thus, reliably comparing material recycling activity between geographical regions or calculating any regional summaries is difficult or even impossible. The objective of this study is to give a partial solution to the problem of not having a reliable method in use that unequivocally describes paper industry material flows. This is done by introducing a new material flow framework for paper industry in which the flow and stage structure supports the use of uniform definitions for terms related to paper recycling. This new framework is termed the Detailed Wheel of Fiber. Copyright © 2016 Elsevier Ltd. All rights reserved.

Can hydraulic-modelled rating curves reduce uncertainty in high flow data?

NASA Astrophysics Data System (ADS)

Westerberg, Ida; Lam, Norris; Lyon, Steve W.

2017-04-01

Flood risk assessments rely on accurate discharge data records. Establishing a reliable rating curve for calculating discharge from stage at a gauging station normally takes years of data collection efforts. Estimation of high flows is particularly difficult as high flows occur rarely and are often practically difficult to gauge. Hydraulically-modelled rating curves can be derived based on as few as two concurrent stage-discharge and water-surface slope measurements at different flow conditions. This means that a reliable rating curve can, potentially, be derived much faster than a traditional rating curve based on numerous stage-discharge gaugings. In this study we compared the uncertainty in discharge data that resulted from these two rating curve modelling approaches. We applied both methods to a Swedish catchment, accounting for uncertainties in the stage-discharge gauging and water-surface slope data for the hydraulic model and in the stage-discharge gauging data and rating-curve parameters for the traditional method. We focused our analyses on high-flow uncertainty and the factors that could reduce this uncertainty. In particular, we investigated which data uncertainties were most important, and at what flow conditions the gaugings should preferably be taken. First results show that the hydraulically-modelled rating curves were more sensitive to uncertainties in the calibration measurements of discharge than water surface slope. The uncertainty of the hydraulically-modelled rating curves were lowest within the range of the three calibration stage-discharge gaugings (i.e. between median and two-times median flow) whereas uncertainties were higher outside of this range. For instance, at the highest observed stage of the 24-year stage record, the 90% uncertainty band was -15% to +40% of the official rating curve. Additional gaugings at high flows (i.e. four to five times median flow) would likely substantially reduce those uncertainties. These first results show the potential of the hydraulically-modelled curves, particularly where the calibration gaugings are of high quality and cover a wide range of flow conditions.

Effects of xylitol chewing gum on salivary flow rate, pH, buffering capacity and presence of Streptococcus mutans in saliva.

PubMed

Ribelles Llop, M; Guinot Jimeno, F; Mayné Acién, R; Bellet Dalmau, L J

2010-03-01

The first studies on the use of chewing gum in dentistry were done in the 1970s. The Turku Sugar Studies, carried out between 1970 and 1973, showed the excellent anticaries properties of xylitol chewing gums. Since then, many dentists, particularly in Scandinavian countries, have studied the role of chewing xylitol-sweetened chewing gums as another preventive strategy in the control of dental caries. To compare variations in salivary flow rate, pH, buffering capacity, and levels of Streptococcus mutans in baseline conditions and after chewing paraffin pellets or xylitol chewing gum in children between the ages of 6 and 12 years who eat lunch in a school canteen. The study sample consisted of 90 children divided into 2 study groups, and a control group. The children ate lunch at the canteen of the Escultor Ortells state school in the town of Vila-real (Castellón, Spain). The baseline data recorded in the first phase of the study were compared with the data recorded in the second phase, after 15 minutes of chewing xylitol- sweetened chewing gums or paraffin pellets, depending on the study group. Salivary flow rate was measured by collecting the stimulated saliva in a graduated beaker. Levels of pH were measured using a Cyberscan pH 110 pH meter (Eutech Instruments). CRT buffer strips and the CRT bacteria test (Ivoclar-Vivadent) were used to measure buffering capacity and levels of S. mutans, respectively. The data obtained after sample collection were compared by means of a 1-way analysis of variance using the StatGraphics Plus statistical software package, version 5.0. Statistically significant differences were found (p<.05) when pH, buffering capacity and levels of S. mutans were compared between the 3 groups. Comparison of salivary flow rates revealed no statistically significant differences (p>.05), though salivary flow rates were higher in the groups where gum was chewed. The effect of chewing is essential to the stimulation of salivary flow and the resulting recovery of pH levels and reduction of levels of S. mutans in saliva.

Numerical prediction of micro-channel LD heat sink operated with antifreeze based on CFD method

NASA Astrophysics Data System (ADS)

Liu, Gang; Liu, Yang; Wang, Chao; Wang, Wentao; Wang, Gang; Tang, Xiaojun

2014-12-01

To theoretically study the feasibility of antifreeze coolants applied as cooling fluids for high power LD heat sink, detailed Computational Fluid Dynamics (CFD) analysis of liquid cooled micro-channels heat sinks is presented. The performance operated with antifreeze coolant (ethylene glycol aqueous solution) compared with pure water are numerical calculated for the heat sinks with the same micro-channels structures. The maximum thermal resistance, total pressure loss (flow resistance), thermal resistance vs. flow-rate, and pressure loss vs. flow-rate etc. characteristics are numerical calculated. The results indicate that the type and temperature of coolants plays an important role on the performance of heat sinks. The whole thermal resistance and pressure loss of heat sinks increase significantly with antifreeze coolants compared with pure water mainly due to its relatively lower thermal conductivity and higher fluid viscosity. The thermal resistance and pressure loss are functions of the flow rate and operation temperature. Increasing of the coolant flow rate can reduce the thermal resistance of heat sinks; meanwhile increase the pressure loss significantly. The thermal resistance tends to a limit with increasing flow rate, while the pressure loss tends to increase exponentially with increasing flow rate. Low operation temperature chiefly increases the pressure loss rather than thermal resistance due to the remarkable increasing of fluid viscosity. The actual working point of the cooling circulation system can be determined on the basis of the pressure drop vs. flow rate curve for the micro-channel heat sink and that for the circulation system. In the same system, if the type or/and temperature of the coolant is changed, the working point is accordingly influenced, that is, working flow rate and pressure is changed simultaneously, due to which the heat sink performance is influenced. According to the numerical simulation results, if ethylene glycol aqueous solution is applied instead of pure water as the coolant under the same or a higher working temperature, the available output of optical power will decrease due to the worse heat sink performance; if applied under a lower working temperature(0 °C, －20 °C), although the heat sink performance become worse, however the temperature difference of heat transfer rises more significantly, the available output of optical power will increase on the contrary.

Fabrication and evaluation of a graphene oxide-based cantilever-type flow-meter for subsonic gas flow rate measurement

NASA Astrophysics Data System (ADS)

Hamdollahi, Hassan; Rahbar-Shahrouzi, Javad

2018-05-01

In this paper, a cantilever-type flow meter was fabricated to measure the rate of air flow in turbulent subsonic regimes such as purged gases. In the fabrication process, a piezoresistive material was coated on an interdigitated electric board as a substrate. The piezoresistive layer was a blend of latex as the polymeric matrix and graphene oxide as the sensing nanomaterial agent, which was reduced by solvothermal reduction method. The piezoresistive blend was dip-coated on a substrate with dotted pattern and was then reduced at 240 °C for 1 h in every coating step. When an air flow passed over the surface of the cantilever beam, the beam was bent in the downward direction, resulting in small variations in the resistance of the piezoresistive layer and a change in the bending angle of the cantilever which were measured simultaneously. The air flow rate was acquired via calibrating electrical resistance changes by Arduino and Wheatstone bridge circuit. The blending angle of the substrate caused by the interaction between the airflow and the cantilever and recorded by the camera and image processing was ultimately compared with the simulation results. The flow meter accuracy as a percentage of full scale (% FS) was calculated to be  ±5.8%, and mean deviation was equal to 2.1 (% FS) with the appropriate response time of 0.70 s at the air flow range of 100‑240 m s‑1. Highlights • A cantilever-type flow meter was fabricated to measure the high-speed air flow rate. • The sensitive piezoresistive material was composed of GO and latex. • The dip-coating method was used to deposit the piezoresistive layer on the fiberglass substrate. • The impact of effective parameters on the performance of the flow meter was investigated. • A simulation study was performed and the results were compared with the experimental data.

Effects of dose, flow rate, and bile acid on diclofenac disposition in the perfused rat liver.

PubMed

Uraki, Misato; Kawase, Atsushi; Matsushima, Yuka; Iwaki, Masahiro

2016-06-01

An in situ perfused rat liver system is useful for studying the hepatic disposition of drugs and their metabolites. However, the effects of the perfusion conditions on drug disposition are unclear. We examined the effects of conditions such as flow rate (13 or 26 mL/min) and bile acid on disposition of diclofenac (DF) as a model drug and DF metabolites [diclofenac-1-O-acyl glucuronide (DF-Glu) or 4'-hydroxydiclofenac (DF-4'OH)] in the absence of albumin. DF, DF-Glu, and DF-4'OH concentrations in the perfusate and cumulative amounts of DF-Glu excreted in bile were measured using high-performance liquid chromatography methods. DF in the perfusate was rapidly eliminated as the perfusate flow rate increased. The area under the plasma concentration-time curve from 0 to 60 min (AUC0-60) for DF-Glu and DF-4'OH in a perfusate containing bile acid was lower at a flow rate of 26 and 13 mL/min, respectively. The bile flow rate at 26 mL/min with 24 μM of bile acid in the perfusate was significantly higher (ca. 3.5 times) compared with that at 13 mL/min without bile acid. Cumulative biliary DF-Glu excretion was also dramatically affected by the flow rate and addition of bile acid. This study indicated that the flow rate and bile acid in the perfused rat liver were key factors for bile flow rate and DF, DF-Glu, and DF-4'OH disposition in the absence of albumin.

Relationship between aquaporin-5 expression and saliva flow in streptozotocin-induced diabetic mice?

PubMed

Soyfoo, M S; Bolaky, N; Depoortere, I; Delporte, C

2012-07-01

To investigate the expression and distribution of AQP5 in submandibular acinar cells from sham- and streptozotocin (STZ)-treated mice in relation to the salivary flow. Mice were sham or STZ injected. Distribution of AQP5 subcellular expression in submandibular glands was determined by immunohistochemistry. AQP5 labelling indices (LI), reflecting AQP5 subcellular distribution, were determined in acinar cells. Western blotting was performed to determine the expression of AQP5 in submandibular glands. Blood glycaemia and osmolality and saliva flow rates were also determined. AQP5 immunoreactivity was primarily located at the apical and apical-basolateral membranes of submandibular gland acinar cells from sham- and STZ-treated mice. No significant differences in AQP5 protein levels were observed between sham- and STZ-treated mice. Compared to sham-treated mice, STZ-treated mice had significant increased glycaemia, while no significant differences in blood osmolality were observed. Saliva flow rate was significantly decreased in STZ-treated mice as compared to sham-treated mice. In STZ-treated mice, significant reduction in salivary flow rate was observed without any concomitant modification in AQP5 expression and localization. © 2011 John Wiley & Sons A/S.

Effect of flow field on the performance of an all-vanadium redox flow battery

NASA Astrophysics Data System (ADS)

Kumar, S.; Jayanti, S.

2016-03-01

A comparative study of the electrochemical energy conversion performance of a single-cell all-vanadium redox flow battery (VRFB) fitted with three flow fields has been carried out experimentally. The charge-discharge, polarization curve, Coulombic, voltage and round-trip efficiencies of a 100 cm2 active area VRFB fitted with serpentine, interdigitated and conventional flow fields have been obtained under nearly identical experimental conditions. The effect of electrolyte circulation rate has also been investigated for each flow field. Stable performance has been obtained for each flow field for at least 40 charge/discharge cycles. Ex-situ measurements of pressure drop have been carried out using water over a range of Reynolds numbers. Together, the results show that the cell fitted with the serpentine flow field gives the highest energy efficiency, primarily due to high voltaic efficiency and also the lowest pressure drop. The electrolyte flow rate is seen to have considerable effect on the performance; a high round-trip energy efficiency of about 80% has been obtained at the highest flow rate with the serpentine flow field. The data offer interesting insights into the effect of electrolyte circulation on the performance of VRFB.

Flow processes in electric discharge drivers

NASA Technical Reports Server (NTRS)

Baganoff, D.

1975-01-01

The performance of an electric discharge shock tube is discussed from the point of view that the conditions at the sonic station are the primary controlling variables (likewise in comparing designs), and that the analysis of the flow on either side of the sonic station should be done separately. The importance of considering mass-flow rate in matching a given driver design to the downstream flow required for a particular shock-wave speed is stressed. It is shown that a driver based on the principle of liquid injection (of H2) is superior to one based on the Ludwieg tube, because of the greater mass-flow rate and the absence of a massive diaphragm.

Geometry of thin liquid sheet flows

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Calfo, Frederick D.; Mcconley, Marc W.; Mcmaster, Matthew S.; Afjeh, Abdollah A.

1994-01-01

Incompresible, thin sheet flows have been of research interest for many years. Those studies were mainly concerned with the stability of the flow in a surrounding gas. Squire was the first to carry out a linear, invicid stability analysis of sheet flow in air and compare the results with experiment. Dombrowski and Fraser did an experimental study of the disintegration of sheet flows using several viscous liquids. They also detected the formulation of holes in their sheet flows. Hagerty and Shea carried out an inviscid stability analysis and calculated growth rates with experimental values. They compared their calculated growth rates with experimental values. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. Brown experimentally investigated thin liquid sheet flows as a method of application of thin films. Clark and Dumbrowski carried out second-order stability analysis for invicid sheet flows. Lin introduced viscosity into the linear stability analysis of thin sheet flows in a vacuum. Mansour and Chigier conducted an experimental study of the breakup of a sheet flow surrounded by high-speed air. Lin et al. did a linear stability analysis that included viscosity and a surrounding gas. Rangel and Sirignano carried out both a linear and nonlinear invisid stability analysis that applies for any density ratio between the sheet liquid and the surrounding gas. Now there is renewed interest in sheet flows because of their possible application as low mass radiating surfaces. The objective of this study is to investigate the fluid dynamics of sheet flows that are of interest for a space radiator system. Analytical expressions that govern the sheet geometry are compared with experimental results. Since a space radiator will operate in a vacuum, the analysis does not include any drag force on the sheet flow.

Role of a Streambed's Benthic Biolayer in Enhancing Chemical Reactions in Hyporheic Flow

NASA Astrophysics Data System (ADS)

Harvey, J. W.

2016-12-01

Chemical processing of metals, nutrients, and organic compounds occurs throughout natural waters, however the rate of reactions often is greater at the streambed interface compared with surface water or deeper groundwater. Hydrologic exchange across the sediment interface brings reactive solutes and fine particulate organic matter from surface waters into contact with the streambed biolayer, a zone with algae and other living microflora and fauna, microbial communities, and reactive geochemical coatings on granular sediments. Compared with surface water or deeper hyporheic sediments, the intrinsic rate of reactions may be stimulated in biolayers because of higher rates of metabolic processing and associated redox reactions. Also, hydrologic transport may enhance reaction rates by relieving potential transport limitations through the re-supply of reactive substrates from surface water. As a result the chemical processing that occurs in the biolayer may far exceed processing that occurs in deeper hyporheic flow. Here I highlight new understanding of enhancement of reaction rates and their hydrologic and biogeochemical controls in streambed biolayers compared with hyporheic flow as a whole. The approach distinguishes and quantifies reaction limitation and transport limitation both at the centimeter-scale within the hyporheic zone and at the river network scale where the effect of streambed reactions accumulates and influences downstream water quality.

Particle size reduction in debris flows: Laboratory experiments compared with field data from Inyo Creek, California

NASA Astrophysics Data System (ADS)

Arabnia, O.; Sklar, L. S.; Mclaughlin, M. K.

2014-12-01

Rock particles in debris flows are reduced in size through abrasion and fracture. Wear of coarse sediments results in production of finer particles, which alter the bulk material rheology and influence flow dynamics and runout distance. Particle wear also affects the size distribution of coarse particles, transforming the initial sediment size distribution produced on hillslopes into that delivered to the fluvial channel network. A better understanding of the controls on particle wear in debris flows would aid in the inferring flow conditions from debris flow deposits, in estimating the initial size of sediments entrained in the flow, and in modeling debris flow dynamics and mapping hazards. The rate of particle size reduction with distance traveled should depend on the intensity of particle interactions with other particles and the flow boundary, and on rock resistance to wear. We seek a geomorphic transport law to predict rate of particle wear with debris flow travel distance as a function of particle size distribution, flow depth, channel slope, fluid composition and rock strength. Here we use four rotating drums to create laboratory debris flows across a range of scales. Drum diameters range from 0.2 to 4.0 m, with the largest drum able to accommodate up to 2 Mg of material, including boulders. Each drum has vanes along the boundary to prevent sliding. Initial experiments use angular clasts of durable granodiorite; later experiments will use less resistant rock types. Shear rate is varied by changing drum rotational velocity. We begin experiments with well-sorted coarse particle size distributions, which are allowed to evolve through particle wear. The fluid is initially clear water, which rapidly acquires fine-grained wear products. After each travel increment all coarse particles (mass > 0.4 g) are weighed individually. We quantify particle wear rates using statistics of size and mass distributions, and by fitting various comminution functions to the data. Laboratory data are compared with longitudinal evolution of grain size and angularity of particles deposited by debris flows along Inyo Creek, Sierra Nevada, California. Preliminary results suggest wear rates can be scaled across drum sizes and to field conditions using non-dimensional metrics of flow dynamics including Savage, Bagnold, and Froude numbers.

Measuring peak expiratory flow in general practice: comparison of mini Wright peak flow meter and turbine spirometer.

PubMed Central

Jones, K P; Mullee, M A

1990-01-01

OBJECTIVE--To compare measurements of the peak expiratory flow rate taken by the mini Wright peak flow meter and the turbine spirometer. DESIGN--Pragmatic study with randomised order of use of recording instruments. Phase 1 compared a peak expiratory flow type expiration recorded by the mini Wright peak flow meter with an expiration to forced vital capacity recorded by the turbine spirometer. Phase 2 compared peak expiratory flow type expirations recorded by both meters. Reproducibility was assessed separately. SETTING--Routine surgeries at Aldermoor Health Centre, Southampton. SUBJECTS--212 Patients aged 4 to 78 presenting with asthma or obstructive airways disease. Each patient contributed only once to each phase (105 in phase 1, 107 in phase 2), but some entered both phases on separate occasions. Reproducibility was tested on a further 31 patients. MAIN OUTCOME MEASURE--95% Limits of agreement between measurements on the two meters. RESULTS--208 (98%) Of the readings taken by the mini Wright meter were higher than the corresponding readings taken by the turbine spirometer, but the 95% limits of agreement (mean difference (2 SD] were wide (1 to 173 l/min). Differences due to errors in reproducibility were not sufficient to predict this level of disagreement. Analysis by age, sex, order of use, and the type of expiration did not detect any significant differences. CONCLUSIONS--The two methods of measuring peak expiratory flow rate were not comparable. The mini Wright meter is likely to remain the preferred instrument in general practice. PMID:2142611

Method of measuring the mass flow rate of a substance entering a cocurrent fluid stream

DOEpatents

Cochran, Jr., Henry D.

1978-04-11

This invention relates to an improved method of monitoring the mass flow rate of a substance entering a cocurrent fluid stream. The method very basically consists of heating equal sections of the fluid stream above and below the point of entry of the substance to be monitored, and measuring and comparing the resulting change in temperature of the sections. Advantage is taken of the difference in thermal characteristics of the fluid and the substance to be measured to correlate temperature differences in the sections above and below the substance feed point for providing an indication of the mass flow rate of the substance.

Slip-Flow and Heat Transfer of a Non-Newtonian Nanofluid in a Microtube

PubMed Central

Niu, Jun; Fu, Ceji; Tan, Wenchang

2012-01-01

The slip-flow and heat transfer of a non-Newtonian nanofluid in a microtube is theoretically studied. The power-law rheology is adopted to describe the non-Newtonian characteristics of the flow, in which the fluid consistency coefficient and the flow behavior index depend on the nanoparticle volume fraction. The velocity profile, volumetric flow rate and local Nusselt number are calculated for different values of nanoparticle volume fraction and slip length. The results show that the influence of nanoparticle volume fraction on the flow of the nanofluid depends on the pressure gradient, which is quite different from that of the Newtonian nanofluid. Increase of the nanoparticle volume fraction has the effect to impede the flow at a small pressure gradient, but it changes to facilitate the flow when the pressure gradient is large enough. This remarkable phenomenon is observed when the tube radius shrinks to micrometer scale. On the other hand, we find that increase of the slip length always results in larger flow rate of the nanofluid. Furthermore, the heat transfer rate of the nanofluid in the microtube can be enhanced due to the non-Newtonian rheology and slip boundary effects. The thermally fully developed heat transfer rate under constant wall temperature and constant heat flux boundary conditions is also compared. PMID:22615961

Flow behaviour and constitutive modelling of a ferritic stainless steel at elevated temperatures

NASA Astrophysics Data System (ADS)

Zhao, Jingwei; Jiang, Zhengyi; Zu, Guoqing; Du, Wei; Zhang, Xin; Jiang, Laizhu

2016-05-01

The flow behaviour of a ferritic stainless steel (FSS) was investigated by a Gleeble 3500 thermal-mechanical test simulator over the temperature range of 900-1100 °C and strain rate range of 1-50 s-1. Empirical and phenomenological constitutive models were established, and a comparative study was made on the predictability of them. The results indicate that the flow stress decreases with increasing the temperature and decreasing the strain rate. High strain rate may cause a drop in flow stress after a peak value due to the adiabatic heating. The Zener-Hollomon parameter depends linearly on the flow stress, and decreases with raising the temperature and reducing the strain rate. Significant deviations occur in the prediction of flow stress by the Johnson-Cook (JC) model, indicating that the JC model cannot accurately track the flow behaviour of the FSS during hot deformation. Both the multiple-linear and the Arrhenius-type models can track the flow behaviour very well under the whole hot working conditions, and have much higher accuracy in predicting the flow behaviour than that of the JC model. The multiple-linear model is recommended in the current work due to its simpler structure and less time needed for solving the equations relative to the Arrhenius-type model.

Economic considerations in the use of inhaled anesthetic agents.

PubMed

Golembiewski, Julie

2010-04-15

To describe the components of and factors contributing to the costs of inhaled anesthesia, basis for quantifying and comparing these costs, and practical strategies for performing pharmacoeconomic analyses and reducing the costs of inhaled anesthetic agents. Inhaled anesthesia can be costly, and some of the variable costs, including fresh gas flow rates and vaporizer settings, are potential targets for cost savings. The use of a low fresh gas flow rate maximizes rebreathing of exhaled anesthetic gas and is less costly than a high flow rate, but it provides less control of the level of anesthesia. The minimum alveolar concentration (MAC) hour is a measure that can be used to compare the cost of inhaled anesthetic agents at various fresh gas flow rates. Anesthesia records provide a sense of patterns of inhaled anesthetic agent use, but the amount of detail can be limited. Cost savings have resulted from efforts to reduce the direct costs of inhaled anesthetic agents, but reductions in indirect costs through shortened times to patient recovery and discharge following the judicious use of these agents are more difficult to demonstrate. The patient case mix, fresh gas flow rates typically used during inhaled anesthesia, availability and location of vaporizers, and anesthesia care provider preferences and practices should be taken into consideration in pharmacoeconomic evaluations and recommendations for controlling the costs of inhaled anesthesia. Understanding factors that contribute to the costs of inhaled anesthesia and considering those factors in pharmacoeconomic analyses and recommendations for use of these agents can result in cost savings.

A peculiar segmented flow microfluidics for isoquercitrin biosynthesis based on coupling of reaction and separation.

PubMed

Gong, An; Gu, Shuang-Shuang; Wang, Jun; Sheng, Sheng; Wu, Fu-An

2015-10-01

A segmented flow containing a buffer-ionic liquid/solvent in a micro-channel reactor was applied to synthesize isoquercitrin by the hesperidinase-catalyzed selective hydrolysis of rutin, based on a novel system of reaction coupling with separation. Within the developed microchannel reactor with one T-shaped inlet and outlet, the maximum isoquercitrin yield (101.7 ± 2.6%) was achieved in 20 min at 30 °C and 4 μL/min. Compared with a continuous-flow reactor, reaction rate was increased 4-fold due to a glycine-sodium hydroxide:[Bmim][BF4]/glycerol triacetate (1:1, v/v) system that formed a slug flow in microchannel and significantly increased mass transfer rates. The mass transfer coefficient significantly increased and exhibited a linear relationship with the flow rate. Hesperidinase could be efficiently reused at least 5 times, without losing any activity. The bonding mechanism and secondary structure of hesperidinase indicated that hesperidinase had a greater affinity to rutin at a production rate of 4 μL/min in this segmented flow microreactor. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of water flow regulation on ecosystem functioning in a Mediterranean river network assessed by wood decomposition.

PubMed

Abril, Meritxell; Muñoz, Isabel; Casas-Ruiz, Joan P; Gómez-Gener, Lluís; Barceló, Milagros; Oliva, Francesc; Menéndez, Margarita

2015-06-01

Mediterranean rivers are extensively modified by flow regulation practises along their courses. An important part of the river impoundment in this area is related to the presence of small dams constructed mainly for water abstraction purposes. These projects drastically modified the ecosystem morphology, transforming lotic into lentic reaches and increasing their alternation along the river. Hydro-morphologial differences between these reaches indicate that flow regulation can trigger important changes in the ecosystem functioning. Decomposition of organic matter is an integrative process and this complexity makes it a good indicator of changes in the ecosystem. The aim of this study was to assess the effect caused by flow regulation on ecosystem functioning at the river network scale, using wood decomposition as a functional indicator. We studied the mass loss from wood sticks during three months in different lotic and lentic reaches located along a Mediterranean river basin, in both winter and summer. Additionally, we identified the environmental factors affecting decomposition rates along the river orders. The results revealed differences in decomposition rates between sites in both seasons that were principally related to the differences between stream orders. The rates were mainly related to temperature, nutrient concentrations (NO2(-), NO3(2-)) and water residence time. High-order streams with higher temperature and nutrient concentrations exhibited higher decomposition rates compared with low-order streams. The effect of the flow regulation on the decomposition rates only appeared to be significant in high orders, especially in winter, when the hydrological characteristics of lotic and lentic habitats widely varied. Lotic reaches with lower water residence time exhibited greater decomposition rates compared with lentic reaches probably due to more physical abrasion and differences in the microbial assemblages. Overall, our study revealed that in high orders the reduction of flow caused by flow regulation affects the wood decomposition indicating changes in ecosystem functioning. Copyright © 2015 Elsevier B.V. All rights reserved.

Experimental study on heat transfer performance of fin-tube exchanger and PSHE for waste heat recovery

NASA Astrophysics Data System (ADS)

Chen, Ting; Bae, Kyung Jin; Kwon, Oh Kyung

2018-02-01

In this paper, heat transfer characteristics of fin-tube heat exchanger and primary surface heat exchanger (PSHE) used in waste heat recovery were investigated experimentally. The flow in the fin-tube heat exchanger is cross flow and in PSHE counter flow. The variations of friction factor and Colburn j factor with air mass flow rate, and Nu number with Re number are presented. Various comparison methods are used to evaluate heat transfer performance, and the results show that the heat transfer rate of the PSHE is on average 17.3% larger than that of fin-tube heat exchanger when air mass flow rate is ranging from 1.24 to 3.45 kg/min. However, the PSHE causes higher pressure drop, and the fin-tube heat exchanger has a wider application range which leads to a 31.7% higher value of maximum heat transfer rate compared to that of the PSHE. Besides, under the same fan power per unit frontal surface, a higher heat transfer rate value is given in the fin-tube heat exchanger.

Avoid cruising on the uroflowmeter: evaluation of cruising artifact on spinning disc flowmeters in an experimental setup.

PubMed

Addla, Sanjai Kumar; Marri, Rajender Reddy; Daayana, Sai Lakshmi; Irwin, Paul

2010-09-01

The aim of our study was to access the variability of maximum flow rate (Q(max)), average flow rate (Q(av)) and flow pattern while varying the point of impact of flow on the flowmeter. Water was delivered through a motorised tube holder in a standardised experimental set up. Flow was directed in 4 different directions on the funnel; 1) Periphery, 2) Base, 3) Centre and, 4) in a cruising motion from the periphery of the funnel to the centre and back again. The variation in the Q(max), Q(av) and the flow pattern were studied at 4 different flow rates. The variables recorded when the flow was directed at the centre of the funnel was taken as baseline. There was a significant difference in the Q(max) and Q(av)when the point of impact was at the periphery or in a cruising motion compared to the centre. The difference was more marked with cruising motion with a characteristic flow pattern. The maximum percentage difference in Q(av) was 4.1%, whereas the difference in Q(max) was higher at 16.6% on comparing crusing motion with the values from the centre. We have demonstrated a significant variation in Q(max), Q(av) and flow pattern with change in the point of impact on the flowmeter. Though the changes in Q(av) were statistically significant, the alteration in the recorded Q(max) values was more striking. Our study emphasizes the importance of combining Q(av) and flow pattern along with Q(max) in interpretation of results of uroflowmetry. © 2010 Wiley-Liss, Inc.

Functional Changes of Diaphragm Type Shunt Valves Induced by Pressure Pulsation

NASA Astrophysics Data System (ADS)

Lee, Chong-Sun; Suh, Chang-Min; Ra, Young-Shin

Shunt valves used to treat patients with hydrocephalus were tested to investigate influence of pressure pulsation on their flow control characteristics. Our focus was on flow dynamic and functional changes of the small and thin diaphragms in the valves that serve as the main flow control mechanism and are made from silicone elastomer. Firstly, pressure-flow control curves were compared under pulsed and steady flow (without pulsation) conditions. Secondly, functional changes of the valves were tested after a long-term continuous pulsation with a peristaltic pump. Thirdly, flushing procedures selectively conducted by neurosurgeons were simulated with a fingertip pressed on the dome of the valves. As 20cc/hr of flow rate was adjusted at a constant pressure, application of 40mmH2O of pressure pulse increased flow rate through shunt valves more than 60%. As a 90cm length silicone catheter was connected to the valve outlet, increase in the flow rate was substantially reduced to 17.5%. Pressure-flow control characteristics of some valves showed significant changes after twenty-eight days of pressure pulsation at 1.0 Hz under 50.0cc/hr of flow rate. Flushing simulation resulted in temporary decrease in the pressure level. It took three hours to fully recover the normal pressure-flow control characteristics after the flushing. Our results suggest that shunt valves with a thin elastic diaphragm as the main flow control mechanism are sensitive to intracranial pressure pulsation or pressure spikes enough to change their pressure-flow control characteristics.

Flow range enhancement by secondary flow effect in low solidity circular cascade diffusers

NASA Astrophysics Data System (ADS)

Sakaguchi, Daisaku; Tun, Min Thaw; Mizokoshi, Kanata; Kishikawa, Daiki

2014-08-01

High-pressure ratio and wide operating range are highly required for compressors and blowers. The technical issue of the design is achievement of suppression of flow separation at small flow rate without deteriorating the efficiency at design flow rate. A numerical simulation is very effective in design procedure, however, cost of the numerical simulation is generally high during the practical design process, and it is difficult to confirm the optimal design which is combined with many parameters. A multi-objective optimization technique is the idea that has been proposed for solving the problem in practical design process. In this study, a Low Solidity circular cascade Diffuser (LSD) in a centrifugal blower is successfully designed by means of multi-objective optimization technique. An optimization code with a meta-model assisted evolutionary algorithm is used with a commercial CFD code ANSYS-CFX. The optimization is aiming at improving the static pressure coefficient at design point and at low flow rate condition while constraining the slope of the lift coefficient curve. Moreover, a small tip clearance of the LSD blade was applied in order to activate and to stabilize the secondary flow effect at small flow rate condition. The optimized LSD blade has an extended operating range of 114 % towards smaller flow rate as compared to the baseline design without deteriorating the diffuser pressure recovery at design point. The diffuser pressure rise and operating flow range of the optimized LSD blade are experimentally verified by overall performance test. The detailed flow in the diffuser is also confirmed by means of a Particle Image Velocimeter. Secondary flow is clearly captured by PIV and it spreads to the whole area of LSD blade pitch. It is found that the optimized LSD blade shows good improvement of the blade loading in the whole operating range, while at small flow rate the flow separation on the LSD blade has been successfully suppressed by the secondary flow effect.

Calibration and use of filter test facility orifice plates

NASA Astrophysics Data System (ADS)

Fain, D. E.; Selby, T. W.

1984-07-01

There are three official DOE filter test facilities. These test facilities are used by the DOE, and others, to test nuclear grade HEPA filters to provide Quality Assurance that the filters meet the required specifications. The filters are tested for both filter efficiency and pressure drop. In the test equipment, standard orifice plates are used to set the specified flow rates for the tests. There has existed a need to calibrate the orifice plates from the three facilities with a common calibration source to assure that the facilities have comparable tests. A project has been undertaken to calibrate these orifice plates. In addition to reporting the results of the calibrations of the orifice plates, the means for using the calibration results will be discussed. A comparison of the orifice discharge coefficients for the orifice plates used at the seven facilities will be given. The pros and cons for the use of mass flow or volume flow rates for testing will be discussed. It is recommended that volume flow rates be used as a more practical and comparable means of testing filters. The rationale for this recommendation will be discussed.

Design of Experiment Analysis of the Sulzer Metco DJ High Velocity Oxy-Fuel Coating of Hydroxyapatite for Orthopedic Applications

NASA Astrophysics Data System (ADS)

Hasan, S.; Stokes, J.

2011-01-01

High Velocity Oxy-Fuel (HVOF) has the potential to produce hydroxyapatite (HA; Bio-ceramic) coatings based on its experience with other sprayed ceramic materials. This technique should offer mechanical and biological results comparable to other thermal spraying processes, such as atmospheric plasma thermal spray, currently FDA approved for HA deposition. Deposition of HA via HVOF is a new venture especially using the Sulzer Metco Diamond Jet (DJ) process, and the aim of this article was to establish this technique's potential in providing superior HA coating results compared to the FDA-approved plasma spray technique. In this research, a Design of Experiment (DOE) model was developed to optimize the Sulzer Metco DJ HVOF process for the deposition of HA. In order to select suitable ranges for the production of HA coatings, the parameters were first investigated. Five parameters (factors) were researched over two levels namely: oxygen flow rate, propylene flow rate, air flow rate, spray distance, and powder flow rate. Coating crystallinity and purity were measured at the surface of each sample as the responses to the factors used. The research showed that propylene, air flow rate, spray distance, and powder feed rate had the largest effect on the responses, and the study aimed to find the preferred optimized settings to achieve high crystallinity and purity of percentages of up to 95%. This research found crystallinity and purity values of 93.8 and 99.8%, respectively, for a set of HVOF parameters which showed improvement compared to the crystallinity and purity values of 87.6 and 99.4%, respectively, found using the FDA-approved Sulzer Metco Atmospheric Plasma thermal spray process. Hence, a new technique for HA deposition now exists using the DJ HVOF facility; however, other mechanical and biorelated properties must also be assessed.

Renal hemodynamics and renin-angiotensin system activity in humans with multifocal renal artery fibromuscular dysplasia.

PubMed

van Twist, Daan J L; Houben, Alphons J H M; de Haan, Michiel W; de Leeuw, Peter W; Kroon, Abraham A

2016-06-01

Fibromuscular dysplasia (FMD) is the second most common cause of renovascular hypertension. Nonetheless, knowledge on the renal microvasculature and renin-angiotensin system (RAS) activity in kidneys with FMD is scarce. Given the fairly good results of revascularization, we hypothesized that the renal microvasculature and RAS are relatively spared in kidneys with FMD. In 58 hypertensive patients with multifocal renal artery FMD (off medication) and 116 matched controls with essential hypertension, we measured renal blood flow (Xenon washout method) per kidney and drew blood samples from the aorta and both renal veins to determine renin secretion and glomerular filtration rate per kidney. We found that renal blood flow and glomerular filtration rate in FMD were comparable to those in controls. Although systemic renin levels were somewhat higher in FMD, renal renin secretion was not elevated. Moreover, in patients with unilateral FMD, no differences between the affected and unaffected kidney were observed with regard to renal blood flow, glomerular filtration rate, or renin secretion. In men, renin levels and renin secretion were higher as compared with women. The renal blood flow response to RAS modulation (by intrarenal infusion of angiotensin II, angiotensin-(1-7), an angiotensin II type 1 receptor blocker, or a nitric oxide synthase blocker) was also comparable between FMD and controls. Renal blood flow, glomerular filtration, and the response to vasoactive substances in kidneys with multifocal FMD are comparable to patients with essential hypertension, suggesting that microvascular function is relatively spared. Renin secretion was not increased and the response to RAS modulation was not affected in kidneys with FMD.

UV DRIVEN EVAPORATION OF CLOSE-IN PLANETS: ENERGY-LIMITED, RECOMBINATION-LIMITED, AND PHOTON-LIMITED FLOWS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Owen, James E.; Alvarez, Marcelo A., E-mail: jowen@ias.edu

2016-01-01

We have investigated the evaporation of close-in exoplanets irradiated by ionizing photons. We find that the properties of the flow are controlled by the ratio of the recombination time to the flow timescale. When the recombination timescale is short compared to the flow timescale, the flow is in approximate local ionization equilibrium with a thin ionization front where the photon mean free path is short compared to the flow scale. In this “recombination-limited” flow the mass-loss scales roughly with the square root of the incident flux. When the recombination time is long compared to the flow timescale the ionization frontmore » becomes thick and encompasses the entire flow with the mass-loss rate scaling linearly with flux. If the planet's potential is deep, then the flow is approximately “energy-limited”; however, if the planet's potential is shallow, then we identify a new limiting mass-loss regime, which we term “photon-limited.” In this scenario, the mass-loss rate is purely limited by the incoming flux of ionizing photons. We have developed a new numerical approach that takes into account the frequency dependence of the incoming ionizing spectrum and performed a large suite of 1D simulations to characterize UV driven mass-loss around low-mass planets. We find that the flow is “recombination-limited” at high fluxes but becomes “energy-limited” at low fluxes; however, the transition is broad occurring over several orders of magnitude in flux. Finally, we point out that the transitions between the different flow types do not occur at a single flux value but depend on the planet's properties, with higher-mass planets becoming “energy-limited” at lower fluxes.« less

High-performance, low-voltage electroosmotic pumps with molecularly thin silicon nanomembranes

PubMed Central

Snyder, Jessica L.; Getpreecharsawas, Jirachai; Fang, David Z.; Gaborski, Thomas R.; Striemer, Christopher C.; Fauchet, Philippe M.; Borkholder, David A.; McGrath, James L.

2013-01-01

We have developed electroosmotic pumps (EOPs) fabricated from 15-nm-thick porous nanocrystalline silicon (pnc-Si) membranes. Ultrathin pnc-Si membranes enable high electroosmotic flow per unit voltage. We demonstrate that electroosmosis theory compares well with the observed pnc-Si flow rates. We attribute the high flow rates to high electrical fields present across the 15-nm span of the membrane. Surface modifications, such as plasma oxidation or silanization, can influence the electroosmotic flow rates through pnc-Si membranes by alteration of the zeta potential of the material. A prototype EOP that uses pnc-Si membranes and Ag/AgCl electrodes was shown to pump microliter per minute-range flow through a 0.5-mm-diameter capillary tubing with as low as 250 mV of applied voltage. This silicon-based platform enables straightforward integration of low-voltage, on-chip EOPs into portable microfluidic devices with low back pressures. PMID:24167263

Progress in turbulence modeling for complex flow fields including effects of compressibility

NASA Technical Reports Server (NTRS)

Wilcox, D. C.; Rubesin, M. W.

1980-01-01

Two second-order-closure turbulence models were devised that are suitable for predicting properties of complex turbulent flow fields in both incompressible and compressible fluids. One model is of the "two-equation" variety in which closure is accomplished by introducing an eddy viscosity which depends on both a turbulent mixing energy and a dissipation rate per unit energy, that is, a specific dissipation rate. The other model is a "Reynolds stress equation" (RSE) formulation in which all components of the Reynolds stress tensor and turbulent heat-flux vector are computed directly and are scaled by the specific dissipation rate. Computations based on these models are compared with measurements for the following flow fields: (a) low speed, high Reynolds number channel flows with plane strain or uniform shear; (b) equilibrium turbulent boundary layers with and without pressure gradients or effects of compressibility; and (c) flow over a convex surface with and without a pressure gradient.

Regulation of electron temperature gradient turbulence by zonal flows driven by trapped electron modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asahi, Y., E-mail: y.asahi@nr.titech.ac.jp; Tsutsui, H.; Tsuji-Iio, S.

2014-05-15

Turbulent transport caused by electron temperature gradient (ETG) modes was investigated by means of gyrokinetic simulations. It was found that the ETG turbulence can be regulated by meso-scale zonal flows driven by trapped electron modes (TEMs), which are excited with much smaller growth rates than those of ETG modes. The zonal flows of which radial wavelengths are in between the ion and the electron banana widths are not shielded by trapped ions nor electrons, and hence they are effectively driven by the TEMs. It was also shown that an E × B shearing rate of the TEM-driven zonal flows is larger thanmore » or comparable to the growth rates of long-wavelength ETG modes and TEMs, which make a main contribution to the turbulent transport before excitation of the zonal flows.« less

Pilocarpine disposition and salivary flow responses following intravenous administration to dogs.

PubMed

Weaver, M L; Tanzer, J M; Kramer, P A

1992-08-01

Oral doses of pilocarpine increase salivary flow rates in patients afflicted with xerostomia (dry mouth). This study examined the pharmacokinetics of and a pharmacodynamic response (salivation) to intravenous pilocarpine nitrate administration in dogs. Disposition was linear over a dose range of 225-600 micrograms/kg; plasma concentrations were 10-120 micrograms/L. Elimination was rapid and generally biphasic, with a terminal elimination half-life of approximately 1.3 hr. The systemic clearance of pilocarpine was high (2.22 +/- 0.49 L/kg/hr) and its steady-state volume of distribution (2.30 +/- 0.64 L/kg) was comparable to that of many other basic drugs. All doses of pilocarpine induced measurable submaxillary and parotid salivary flow rates which could be maintained constant over time. Cumulative submaxillary saliva flow was linearly related to total pilocarpine dose. Plasma pilocarpine concentration was linearly related to both steady-state and postinfusion submaxillary salivary flow rates.

Calibrationless rotating Lorentz-force flowmeters for low flow rate applications

NASA Astrophysics Data System (ADS)

Hvasta, M. G.; Dudt, D.; Fisher, A. E.; Kolemen, E.

2018-07-01

A ‘weighted magnetic bearing’ has been developed to improve the performance of rotating Lorentz-force flowmeters (RLFFs). Experiments have shown that the new bearing reduces frictional losses within a double-sided, disc-style RLFF to negligible levels. Operating such an RLFF under ‘frictionless’ conditions provides two major benefits. First, the steady-state velocity of the RLFF magnets matches the average velocity of the flowing liquid at low flow rates. This enables an RLFF to make accurate volumetric flow measurements without any calibration or prior knowledge of the fluid properties. Second, due to minimized frictional losses, an RLFF is able to measure low flow rates that cannot be detected when conventional, high-friction bearings are used. This paper provides a brief background on RLFFs, gives a detailed description of weighted magnetic bearings, and compares experimental RLFF data to measurements taken with a commercially available flowmeter.

Development of a flow controller for long-term sampling of gases and vapors using evacuated canisters.

PubMed

Rossner, Alan; Farant, Jean Pierre; Simon, Philippe; Wick, David P

2002-11-15

Anthropogenic activities contribute to the release of a wide variety of volatile organic compounds (VOC) into microenvironments. Developing and implementing new air sampling technologies that allow for the characterization of exposures to VOC can be useful for evaluating environmental and health concerns arising from such occurrences. A novel air sampler based on the use of a capillary flow controller connected to evacuated canisters (300 mL, 1 and 6 L) was designed and tested. The capillary tube, used to control the flow of air, is a variation on a sharp-edge orifice flow controller. It essentially controls the velocity of the fluid (air) as a function of the properties of the fluid, tube diameter and length. A model to predict flow rate in this dynamic system was developed. The mathematical model presented here was developed using the Hagen-Poiseuille equation and the ideal gas law to predict flow into the canisters used to sample for long periods of time. The Hagen-Poiseuille equation shows the relationship between flow rate, pressure gradient, capillary resistance, fluid viscosity, capillary length and diameter. The flow rates evaluated were extremely low, ranging from 0.05 to 1 mL min(-1). The model was compared with experimental results and was shown to overestimate the flow rate. Empirical equations were developed to more accurately predict flow for the 300 mL, 1 and 6 L canisters used for sampling periods ranging from several hours to one month. The theoretical and observed flow rates for different capillary geometries were evaluated. Each capillary flow controller geometry that was tested was found to generate very reproducible results, RSD < 2%. Also, the empirical formulas developed to predict flow rate given a specified diameter and capillary length were found to predict flow rate within 6% of the experimental data. The samplers were exposed to a variety of airborne vapors that allowed for comparison of the effectiveness of capillary flow controllers to sorbent samplers and to an online gas chromatograph. The capillary flow controller was found to exceed the performance of the sorbent samplers in this comparison.

Improved analysis of transient temperature data from permanent down-hole gauges (PDGs)

NASA Astrophysics Data System (ADS)

Zhang, Yiqun; Zheng, Shiyi; Wang, Qi

2017-08-01

With the installation of permanent down-hole gauges (PDGs) during oil field development, large volumes of high resolution and continuous down-hole information are obtainable. The interpretation of these real-time temperature and pressure data can optimize well performance, provide information about the reservoir and continuously calibrate the reservoir model. Although the dynamic temperature data have been interpreted in practice to predict flow profiling and provide characteristic information of the reservoir, almost all of the approaches rely on established non-isothermal models which depend on thermodynamic parameters. Another problem comes from the temperature transient analysis (TTA), which is underutilized compared with pressure transient analysis (PTA). In this study, several model-independent methods of TTA were performed. The entire set of PDG data consists of many flow events. By utilizing the wavelet transform, the exact points of flow-rate changes can be located. The flow regime changes, for example, from early time linear flow to later time pseudo-radial flow, among every transient period with constant flow-rate. For the early time region (ETR) that is caused by flow-rate change operations, the TTA, along with the PTA can greatly reduce the uncertainties in flow regime diagnosis. Then, the temperature variations during ETR were examined to infer the true reservoir temperature history, and the relationships between the wavelet detailed coefficients and the flow-rate changes were analysed. For the scenarios with constant reservoir-well parameters, the detailed flow-rate history can be generated by calculating the coefficient of relationship in advance. For later times, the flow regime changes to pseudo-radial flow. An analytical solution was introduced to describe the sand-face temperature. The formation parameters, such as permeability and skin factor, were estimated with the previously calculated flow-rate. It is necessary to analyse temperature variation to overcome data limitation problems when information from other down-hole tools (e.g. expensive but unstable flow meters) is insufficient. This study shows the success in wellbore storage regime diagnosis, flow-rate history reconstruction, and formation parameters estimation using transient temperature data.

The effect of blood cell count on coronary flow in patients with coronary slow flow phenomenon.

PubMed

Soylu, Korhan; Gulel, Okan; Yucel, Huriye; Yuksel, Serkan; Aksan, Gokhan; Soylu, Ayşegül İdil; Demircan, Sabri; Yılmaz, Ozcan; Sahin, Mahmut

2014-09-01

The coronary slow flow phenomenon (CSFP) is a coronary artery disease with a benign course, but its pathological mechanisms are not yet fully understood.The purpose of this controlled study was to investigate the cellular content of blood in patients diagnosed with CSFP and the relationship of this with coronary flow rates. Selective coronary angiographies of 3368 patients were analyzed to assess Thrombolysis in Myocardial Infarction (TIMI) frame count (TFC) values. Seventy eight of them had CSFP, and their demographic and laboratory findings were compared with 61 patients with normal coronary flow. Patients' demographic characteristics were similar in both groups. Mean corrected TFC (cTFC) values were significantly elevated in CSFP patients (p<0.001). Furthermore, hematocrit and hemoglobin values, and eosinophil and basophil counts of the CSFP patients were significantly elevated compared to the values obtained in the control group (p=0.005, p=0.047, p=0.001 and p=0.002, respectively). The increase observed in hematocrit and eosinophil levels showed significant correlations with increased TFC values (r=0.288 and r=0.217, respectively). Significant changes have been observed in the cellular composition of blood in patients diagnosed with CSFP as compared to the patients with normal coronary blood flow. The increases in hematocrit levels and in the eosinophil and basophil counts may have direct or indirect effects on the rate of coronary blood flow.

Analysis of flow in an observation well intersecting a single fracture

USGS Publications Warehouse

Lapcevic, P.A.; Novakowski, K.S.; Paillet, Frederick L.

1993-01-01

A semi-analytical model is developed to determine transmissivity and storativity from the interpretation of transient flow in an observation well due to pumping in a source well where the two wells are connected by a single fracture. Flow rate can be determined using a heat-pulse flowmeter located above the intersection of the fracture in the observation well. The results of a field experiment were interpreted using the new model and compared with drawdown data from the same test. Good agreement between the transmissivity estimates was observed whereas estimates of storativity were found to be better determined from the analysis of flow rate. ?? 1993.

Tank depletion flow controller

DOEpatents

Georgeson, Melvin A.

1976-10-26

A flow control system includes two bubbler tubes installed at different levels within a tank containing such as radioactive liquid. As the tank is depleted, a differential pressure transmitter monitors pressure differences imparted by the two bubbler tubes at a remote, shielded location during uniform time intervals. At the end of each uniform interval, balance pots containing a dense liquid are valved together to equalize the pressures. The resulting sawtooth-shaped signal generated by the differential pressure transmitter is compared with a second sawtooth signal representing the desired flow rate during each time interval. Variations in the two signals are employed by a control instrument to regulate flow rate.

Define and Quantify the Physics of Air Flow, Pressure Drop and Aerosol Collection in Nuclear Grade HEPA Filters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Murray E.

Objective: Develop a set of peer-review and verified analytical methods to adjust HEPA filter performance to different flow rates, temperatures and altitudes. Experimental testing will measure HEPA filter flow rate, pressure drop and efficiency to verify the analytical approach. Nuclear facilities utilize HEPA (High Efficiency Particulate Air) filters to purify air flow for workspace ventilation. However, the ASME AG-1 technical standard (Code on Nuclear Air and Gas Treatment) does not adequately describe air flow measurement units for HEPA filter systems. Specifically, the AG-1 standard does not differentiate between volumetric air flow in ACFM (actual cubic feet per minute)compared to massmore » flow measured in SCFM (standard cubic feet per minute). More importantly, the AG-1 standard has an overall deficiency for using HEPA filter devices at different air flow rates, temperatures, and altitudes. Technical Approach: The collection efficiency and pressure drops of 18 different HEPA filters will be measured over a range of flow rates, temperatures and altitudes. The experimental results will be compared to analytical scoping calculations. Three manufacturers have allocated six HEPA filters each for this effort. The 18 filters will be tested at two different flow rates, two different temperatures and two different altitudes. The 36 total tests will be conducted at two different facilities: the ATI Test facilities (Baltimore MD) and the Los Alamos National Laboratory (Los Alamos NM). The Radiation Protection RP-SVS group at Los Alamos has an aerosol wind tunnel that was originally designed to evaluate small air samplers. In 2010, modifications were started to convert the wind tunnel for HEPA filter testing. (Extensive changes were necessary for the required aerosol generators, HEPA test fixtures, temperature control devices and measurement capabilities.) To this date, none of these modification activities have been funded through a specific DOE or NNSA program. This is expected to require six months of time, after receipt of funding. Benefits: US DOE facilities that use HEPA filters will benefit from access to the new operational measurement methods. Uncertainty and guesswork will be removed from HEPA filter operations.« less

Numerical Modeling of Flow Control in a Boundary-Layer-Ingesting Offset Inlet Diffuser at Transonic Mach Numbers

NASA Technical Reports Server (NTRS)

Allan Brian G.; Owens, Lewis, R.

2006-01-01

This paper will investigate the validation of a NASA developed, Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, for a boundary-layer-ingesting (BLI) offset (S-shaped) inlet in transonic flow with passive and active flow control devices as well as the baseline case. Numerical simulations are compared to wind tunnel results of a BLI inlet conducted at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. Comparisons of inlet flow distortion, pressure recovery, and inlet wall pressures are performed. The numerical simulations are compared to the BLI inlet data at a freestream Mach number of 0.85 and a Reynolds number of approximately 2 million based on the length of the fan-face diameter. The numerical simulations with and without wind tunnel walls are performed, quantifying effects of the tunnel walls on the BLI inlet flow measurements. The wind tunnel test evaluated several different combinations of jet locations and mass flow rates as well as a vortex generator (VG) vane case. The numerical simulations will be performed on a single jet configuration for varying actuator mass flow rates at a fix inlet mass flow condition. Validation of the numerical simulations for the VG vane case will also be performed for varying inlet mass flow rates. Overall, the numerical simulations were able to predict the baseline circumferential flow distortion, DPCPavg, very well for comparisons made within the designed operating range of the BLI inlet. However the CFD simulations did predict a total pressure recovery that was 0.01 lower than the experiment. Numerical simulations of the baseline inlet flow also showed good agreement with the experimental inlet centerline surface pressures. The vane case showed that the CFD predicted the correct trends in the circumferential distortion for varying inlet mass flow but had a distortion level that was nearly twice as large as the experiment. Comparison to circumferential distortion measurements for a 15 deg clocked 40 probe rake indicated that the circumferential distortion levels are very sensitive to the symmetry of the flow and that a miss alignment of the vanes in the experiment could have resulted in this difference. The numerical simulations of the BLI inlet with jets showed good agreement with the circumferential inlet distortion levels for a range of jet actuator mass flow ratios at a fixed inlet mass flow rate. The CFD simulations for the jet case also predicted an average total pressure recovery that was 0.01 lower than the experiment as was seen in the baseline. Comparison of the flow features the jet case revealed that the CFD predicted a much larger vortex at the engine fan-face when compare to the experiment.

Solution of non-continuum flows using BGK-type model with enforced relaxation of moments

NASA Astrophysics Data System (ADS)

Alekseenko, Alexander; Gimelshein, Sergey; Nguyen, Truong; Vedula, Prakash

2016-11-01

A BGK-type model with velocity dependent collision frequency and enforced relaxation rates for selected moments is applied to simulation of one- and two-dimensional super sonic flows. Relaxation rates of the moments are estimated by evaluating the full Boltzmann collision integral several times during the simulation. The solutions show improvements in velocity and temperature profiles as compared to the classical ES-BGK model. However, enforcement of relaxation rates for high order moments increases stiffness of the model.

Percolation characteristics of solvent invasion in rough fractures under miscible conditions

NASA Astrophysics Data System (ADS)

Korfanta, M.; Babadagli, T.; Develi, K.

2017-10-01

Surface roughness and flow rate effects on the solvent transport under miscible conditions in a single fracture are studied. Surface replicas of seven different rocks (marble, granite, and limestone) are used to represent different surface roughness characteristics each described by different mathematical models including three fractal dimensions. Distribution of dyed solvent is investigated at various flow rate conditions to clarify the effect of roughness on convective and diffusive mixing. After a qualitative analysis using comparative images of different rocks, the area covered by solvent with respect to time is determined to conduct a semi-quantitative analysis. In this exercise, two distinct zones are identified, namely the straight lines obtained for convective (early times) and diffusive (late times) flow. The bending point between these two lines is used to point the transition between the two zones. Finally, the slopes of the straight lines and the bending points are correlated to five different roughness parameters and the rate (Peclet number). It is observed that both surface roughness and flow rate have significant effect on solvent spatial distribution. The largest area covered is obtained at moderate flow rates and hence not only the average surface roughness characteristic is important, but coessentially total fracture surface area needs to be considered when evaluating fluid distribution. It is also noted that the rate effect is critically different for the fracture samples of large grain size (marbles and granite) compared to smaller grain sizes (limestones). Variogram fractal dimension exhibits the strongest correlation with the maximum area covered by solvent, and display increasing trend at the moderate flow rates. Equations with variogram surface fractal dimension in combination with any other surface fractal parameter coupled with Peclet number can be used to predict maximum area covered by solvent in a single fracture, which in turn can be utilized to model oil recovery, waste disposal, and groundwater contamination processes in the presence of fractures.

Effect of high negative incidence on the performance of a centrifugal compressor stage with conventional vaned diffusers

NASA Astrophysics Data System (ADS)

Jaatinen, Ahti; Grönman, Aki; Turunen-Saaresti, Teemu; Backman, Jari

2011-06-01

Three vaned diffusers, designed to have high negative incidence (-8°) at the design operating point, are studied experimentally. The overall performance (efficiency and pressure ratio) are measured at three rotational speeds, and flow angles before and after the diffuser are measured at the design rotational speed and with three mass flow rates. The results are compared to corresponding results of the original vaneless diffuser design. Attention is paid to the performance at lower mass flows than the design mass flow. The results show that it is possible to improve the performance at mass flows lower than the design mass flow with a vaned diffuser designed with high negative incidence. However, with the vaned diffusers, the compressor still stalls at higher mass flow rates than with the vaneless one. The flow angle distributions after the diffuser are more uniform with the vaned diffusers.

Dilution jets in accelerated cross flows. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Lipshitz, A.; Greber, I.

1984-01-01

Results of flow visualization experiments and measurements of the temperature field produced by a single jet and a row of dilution jets issued into a reverse flow combustor are presented. The flow in such combustors is typified by transverse and longitudinal acceleration during the passage through its bending section. The flow visualization experiments are designed to examine the separate effects of longitudinal and transverse acceleration on the jet trajectory and spreading rate. A model describing a dense single jet in a lighter accelerating cross flow is developed. The model is based on integral conservation equations, including the pressure terms appropriate to accelerating flows. It uses a modified entrainment correlation obtained from previous experiments of a jet in a cross stream. The flow visualization results are compared with the model calculations in terms of trajectories and spreading rates. Each experiment is typified by a set of three parameters: momentum ratio, density ratio and the densimetric Froude number.

Effects of water-management alternatives on streamflow in the Ipswich River basin, Massachusetts

USGS Publications Warehouse

Zarriello, Philip J.

2001-01-01

Management alternatives that could help mitigate the effects of water withdrawals on streamflow in the Ipswich River Basin were evaluated by simulation with a calibrated Hydrologic Simulation Program--Fortran (HSPF) model. The effects of management alternatives on streamflow were simulated for a 35-year period (196195). Most alternatives examined increased low flows compared to the base simulation of average 1989-93 withdrawals. Only the simulation of no septic-effluent inflow, and the simulation of a 20-percent increase in withdrawals, further lowered flows or caused the river to stop flowing for longer periods of time than the simulation of average 198993 withdrawals. Simulations of reduced seasonal withdrawals by 20 percent, and by 50 percent, resulted in a modest increase in low flow in a critical habitat reach (model reach 8 near the Reading town well field); log-Pearson Type III analysis of simulated daily-mean flow indicated that under these reduced withdrawals, model reach 8 would stop flowing for a period of seven consecutive days about every other year, whereas under average 198993 withdrawals this reach would stop flowing for a seven consecutive day period almost every year. Simulations of no seasonal withdrawals, and simulations that stopped streamflow depletion when flow in model reach 19 was below 22 cubic feet per second, indicated flow would be maintained in model reach 8 at all times. Simulations indicated wastewater-return flows would augment low flow in proportion to the rate of return flow. Simulations of a 1.5 million gallons per day return flow rate indicated model reach 8 would stop flowing for a period of seven consecutive days about once every 5 years; simulated return flow rates of 1.1 million gallons per day indicated that model reach 8 would stop flowing for a period of seven consecutive days about every other year. Simulation of reduced seasonal withdrawals, combined with no septic effluent return flow, indicated only a slight increase in low flow compared to low flows simulated under average 198993 withdrawals. Simulation of reduced seasonal withdrawal, combined with 2.6 million gallons per day wastewater-return flows, provided more flow in model reach 8 than that simulated under no withdrawals.

Stability limits of unsteady open capillary channel flow

NASA Astrophysics Data System (ADS)

Grah, Aleksander; Haake, Dennis; Rosendahl, Uwe; Klatte, J.?Rg; Dreyer, Michael E.

This paper is concerned with steady and unsteady flow rate limitations in open capillary channels under low-gravity conditions. Capillary channels are widely used in Space technology for liquid transportation and positioning, e.g. in fuel tanks and life support systems. The channel observed in this work consists of two parallel plates bounded by free liquid surfaces along the open sides. The capillary forces of the free surfaces prevent leaking of the liquid and gas ingestion into the flow.In the case of steady stable flow the capillary pressure balances the differential pressure between the liquid and the surrounding constant-pressure gas phase. Increasing the flow rate in small steps causes a decrease of the liquid pressure. A maximum steady flow rate is achieved when the flow rate exceeds a certain limit leading to a collapse of the free surfaces due to the choking effect. In the case of unsteady flow additional dynamic effects take place due to flow rate transition and liquid acceleration. The maximum flow rate is smaller than in the case of steady flow. On the other hand, the choking effect does not necessarily cause surface collapse and stable temporarily choked flow is possible under certain circumstances.To determine the limiting volumetric flow rate and stable flow dynamic properties, a new stability theory for both steady and unsteady flow is introduced. Subcritical and supercritical (choked) flow regimes are defined. Stability criteria are formulated for each flow type. The steady (subcritical) criterion corresponds to the speed index defined by the limiting longitudinal small-amplitude wave speed, similar to the Mach number. The unsteady (supercritical) criterion for choked flow is defined by a new characteristic number, the dynamic index. It is based on pressure balances and reaches unity at the stability limit.The unsteady model based on the Bernoulli equation and the mass balance equation is solved numerically for perfectly wetting incompressible liquids. The unsteady model and the stability theory are verified by comparison to results of a sounding rocket experiment (TEXUS 41) on capillary channel flows launched in December 2005 from ESRANGE in north Sweden. For a clear overview of subcritical, supercritical, and unstable flow, parametric studies and stability diagrams are shown and compared to experimental observations.

Elastic instabilities in planar elongational flow of monodisperse polymer solutions

PubMed Central

Haward, Simon J.; McKinley, Gareth H.; Shen, Amy Q.

2016-01-01

We investigate purely elastic flow instabilities in the almost ideal planar stagnation point elongational flow field generated by a microfluidic optimized-shape cross-slot extensional rheometer (OSCER). We use time-resolved flow velocimetry and full-field birefringence microscopy to study the behavior of a series of well-characterized viscoelastic polymer solutions under conditions of low fluid inertia and over a wide range of imposed deformation rates. At low deformation rates the flow is steady and symmetric and appears Newtonian-like, while at high deformation rates we observe the onset of a flow asymmetry resembling the purely elastic instabilities reported in standard-shaped cross-slot devices. However, for intermediate rates, we observe a new type of elastic instability characterized by a lateral displacement and time-dependent motion of the stagnation point. At the onset of this new instability, we evaluate a well-known dimensionless criterion M that predicts the onset of elastic instabilities based on geometric and rheological scaling parameters. The criterion yields maximum values of M which compare well with critical values of M for the onset of elastic instabilities in viscometric torsional flows. We conclude that the same mechanism of tension acting along curved streamlines governs the onset of elastic instabilities in both extensional (irrotational) and torsional (rotational) viscoelastic flows. PMID:27616181

Numerical analysis of flows of rarefied gases in long channels with octagonal cross section shapes

NASA Astrophysics Data System (ADS)

Szalmas, L.

2014-12-01

Isothermal, pressure driven rarefied gas flows through long channels with octagonal cross section shapes are analyzed computationally. The capillary is between inlet and outlet reservoirs. The cross section is constant along the axial direction. The boundary condition at the solid-gas interface is assumed to be diffuse reflection. Since the channel is long, the gaseous velocity is small compared to the average molecular speed. Consequently, a linearized description can be used. The flow is described by the linearized Bhatnagar-Gross-Krook kinetic model. The solution of the problem is divided into two stages. First, the local flow field is determined by assuming the local pressure gradient. Secondly, the global flow behavior is deduced by the consideration of the conservation of the mass along the axis of the capillary. The kinetic equation is solved by the discrete velocity method on the cross section. Both spatial and velocity spaces are discretized. A body fitted rectangular grid is used for the spatial space. Near the boundary, first-order, while in the interior part of the flow domain, second-order finite-differences are applied to approximate the spatial derivatives. This combination results into an efficient and straightforward numerical treatment. The velocity space is represented by a Gauss-Legendre quadrature. The kinetic equation is solved in an iterative manner. The local dimensionless flow rate is calculated and tabulated for a wide range of the gaseous rarefaction for octagonal cross sections with various geometrical parameters. It exhibits the Knudsen minimum phenomenon. The flow rates in the octagonal channel are compared to those through capillaries with circular and square cross sections. Typical velocity profiles are also shown. The mass flow rate and the distribution of the pressure are determined and presented for global pressure driven flows.

Heat transfer in a microvascular network: the effect of heart rate on heating and cooling in reptiles (Pogona barbata and Varanus varius).

PubMed

Seebacher, F

2000-03-21

Thermally-induced changes in heart rate and blood flow in reptiles are believed to be of selective advantage by allowing animal to exert some control over rates of heating and cooling. This notion has become one of the principal paradigms in reptilian thermal physiology. However, the functional significance of changes in heart rate is unclear, because the effect of heart rate and blood flow on total animal heat transfer is not known. I used heat transfer theory to determine the importance of heat transfer by blood flow relative to conduction. I validated theoretical predictions by comparing them with field data from two species of lizard, bearded dragons (Pogona barbata) and lace monitors (Varanus varius). Heart rates measured in free-ranging lizards in the field were significantly higher during heating than during cooling, and heart rates decreased with body mass. Convective heat transfer by blood flow increased with heart rate. Rates of heat transfer by both blood flow and conduction decreased with mass, but the mass scaling exponents were different. Hence, rate of conductive heat transfer decreased more rapidly with increasing mass than did heat transfer by blood flow, so that the relative importance of blood flow in total animal heat transfer increased with mass. The functional significance of changes in heart rate and, hence, rates of heat transfer, in response to heating and cooling in lizards was quantified. For example, by increasing heart rate when entering a heating environment in the morning, and decreasing heart rate when the environment cools in the evening a Pogona can spend up to 44 min longer per day with body temperature within its preferred range. It was concluded that changes in heart rate in response to heating and cooling confer a selective advantage at least on reptiles of mass similar to that of the study animals (0. 21-5.6 kg). Copyright 2000 Academic Press.

Comparing characteristics and clinical and echocardiographic outcomes in low-flow vs normal-flow severe aortic stenosis with preserved ejection fraction in an Asian population.

PubMed

Ngiam, Jinghao Nicholas; Tan, Benjamin Yong-Qiang; Sia, Ching-Hui; Lee, Glenn K M; Kong, William K F; Chan, Yiong-Huak; Poh, Kian-Keong

2017-05-01

In severe aortic stenosis (AS), deterioration of left ventricular ejection fraction (LVEF) to <50% is an AHA/ACC class I indication for valve replacement, regardless of symptoms. Controversy surrounds prognosis of low-flow AS compared to normal-flow, and no study has examined LVEF deterioration. We compared factors associated with LVEF deterioration (to <50%) and clinical outcomes. Consecutive subjects with low-flow (stroke volume index <35 mL/m 2 , n=56) and normal-flow (n=72) severe AS (aortic valve area <1 cm 2 ) with preserved LVEF (>50%) and with paired echocardiography were studied. Univariate and multivariate analyses identified factors associated with LVEF deterioration. Clinical outcomes were determined on follow-up for more than 5 years. Significant LVEF deterioration (to <50%) was seen in 18% of low-flow (initial LVEF 63±8% to 32±9%) and 18% of normal-flow AS (61±7% to 31±12%). Independent factors in low-flow AS were hypertension (OR: 30.7, 95% CI: 2.0-467.6, P=.014) and higher end-systolic wall stress (OR: 1.086, 95% CI: 1.022-1.153, P=.008), compared to normal-flow, which were hypertension (OR: 15.9, 95% CI: 3.1-81.9, P=.001), higher septal E/E' ratio (OR: 1.16, 95% CI: 1.01-1.35, P=.043), lower septal S' velocity (OR: 0.204, 95% CI: 0.061-0.682, P=.010), and higher end-systolic wall stress (OR: 1.051, 95% CI: 1.001-1.104, P=.047). Overall, a third of the cohort experienced MACE, regardless of flow (log-rank 0.048, P=.827). However, aortic valve replacement (AVR) rates were lower in low-flow AS (20% vs 43%, P=.005). Low-flow AS despite normal LVEF appears similar to normal-flow in terms of LVEF deterioration and clinical outcomes in our Asian population. AVR rate was lower even though low-flow may not reflect less severe disease. © 2017, Wiley Periodicals, Inc.

Nonlinear pressure-flow relationships for passive microfluidic valves.

PubMed

Seker, Erkin; Leslie, Daniel C; Haj-Hariri, Hossein; Landers, James P; Utz, Marcel; Begley, Matthew R

2009-09-21

An analytical solution is presented for the nonlinear pressure-flow relationship of deformable passive valves, which are formed by bonding a deformable film over etched channels separated by a weir. A fluidic pathway connecting the channels is opened when the upstream pressure creates a tunnel along a predefined narrow strip where the film is not bonded to the weir. When the width of the strip is comparable to the inlet channel width, the predicted closed-form pressure-flow rate relationship is in excellent agreement with experiments, which determine pressures by measuring film deflections for prescribed flow rates. The validated closed-form models involve no fitting parameters, and provide the foundation to design passive diodes with specific nonlinear pressure-flow characteristics.

Accretion flows onto supermassive black holes

NASA Technical Reports Server (NTRS)

Begelman, Mitchell C.

1988-01-01

The radiative and hydrodynamic properties of an angular momentum-dominated accretion flow onto a supermassive black hole depend largely on the ratio of the accretion rate to the Eddington accretion rate. High values of this ratio favor optically thick flows which produce largely thermal radiation, while optically thin 'two-temperature' flows may be present in systems with small values of this ratio. Observations of some AGN suggest that thermal and nonthermal sources of radiation may be of comparable importance in the 'central engine'. Consideration is given to the possibilities for coexistence of different modes of accretion in a single flow. One intriguing possibility is that runaway pair production may cause an optically thick 'accretion annulus' to form at the center of a two-temperature inflow.

Peak expiratory flow rate of children working in lock factories.

PubMed

Singhal, S; Singhal, A; Singh, P N; Agarwal, D K; Gulati, R

2006-01-01

Peak expiratory flow rate (PEFR) of 106 children working in different units of lock factory was measured and compared with age and sex matched control group of same socio-economic status children. All the children worked for about ten hours per day. It was observed that there was a significant decrease in PEFR of children working in the different units of lock factories i.e. Hand press, Polishing, Lock fitting, Lock packing units as compared to control group (P>0.001). The reduction percentage of PEFR was maximum in children working in polishing unit (25.48%).

Non-isothermal crystallization of poly(etheretherketone) aromatic polymer composite

NASA Technical Reports Server (NTRS)

Cebe, Peggy

1988-01-01

The nonisothermal crystallization kinetics of PEEK APC-2 and of 450G neat resin PEEK material were compared using a differential scanning calorimeter to monitor heat flow during crystallization; the effects of cooling rate on the crystallization temperature, the degree of crystallinity, and the conversion rate were investigated. A modified Avrami (1940) analysis was used to describe nonisothermal crystallization kinetics. It was found that, compared with the 450G neat resin PEEK, the nonisothermal crystallization of the PEEK APC-2 composite is characterized by higher initiation temperature, higher heat flow maximum temperature, and greater relative conversion by primary processes.

Failure Rates of Orthodontic Fixed Lingual Retainers bonded with Two Flowable Light-cured Adhesives: A Comparative Prospective Clinical Trial.

PubMed

Talic, Nabeel F

2016-08-01

This comparative prospective randomized clinical trial examined the in vivo failure rates of fixed mandibular and maxillary lingual retainers bonded with two light-cured flowable composites over 6 months. Consecutive patients were divided into two groups on a 1:1 basis. Two hundred fixed lingual retainers were included, and their failures were followed for 6 months. One group (n = 50) received retainers bonded with a nano-hybrid composite based on nano-optimized technology (Tetric-N-Flow, Ivoclar Vivadent). Another group (n = 50) received retainers bonded with a low viscosity (LV) composite (Transbond Supreme LV, 3M Unitek). There was no significant difference between the overall failure rates of mandibular retainers bonded with Transbond (8%) and those bonded with Tetric-N-Flow (18%). However, the odds ratio for failure using Tetric-N-flow was 2.52-fold greater than that of Transbond. The failure rate of maxillary retainers bonded with Transbond was higher (14%), but not significantly different, than that of maxillary retainers bonded with Tetric-N-flow (10%). There was no significant difference in the estimated mean survival times of the maxillary and mandibular retainers bonded with the two composites. Both types of composites tested in the current study can be used to bond fixed maxillary and mandibular lingual retainers, with low failure rates.

Mechanical performance comparison between RotaFlow and CentriMag centrifugal blood pumps in an adult ECLS model.

PubMed

Yulong Guan; Xiaowei Su; McCoach, Robert; Kunselman, Allen; El-Banayosy, Aly; Undar, Akif

2010-03-01

Centrifugal blood pumps have been widely adopted in conventional adult cardiopulmonary bypass and circulatory assist procedures. Different brands of centrifugal blood pumps incorporate distinct designs which affect pump performance. In this adult extracorporeal life support (ECLS) model, the performances of two brands of centrifugal blood pump (RotaFlow blood pump and CentriMag blood pump) were compared. The simulated adult ECLS circuit used in this study included a centrifugal blood pump, Quadrox D membrane oxygenator and Sorin adult ECLS tubing package. A Sorin Cardiovascular(R) VVR(R) 4000i venous reservoir (Sorin S.p.A., Milan, Italy) with a Hoffman clamp served as a pseudo-patient. The circuit was primed with 900ml heparinized human packed red blood cells and 300ml lactated Ringer's solution (total volume 1200 ml, corrected hematocrit 40%). Trials were conducted at normothermia (36 degrees C). Performance, including circuit pressure and flow rate, was measured for every setting analyzed. The shut-off pressure of the RotaFlow was higher than the CentriMag at all measurement points given the same rotation speed (p < 0.0001). The shut-off pressure differential between the two centrifugal blood pumps was significant and increased given higher rotation speeds (p < 0.0001). The RotaFlow blood pump has higher maximal flow rate (9.08 +/- 0.01L/min) compared with the CentriMag blood pump (8.37 +/- 0.02L/min) (p < 0.0001). The blood flow rate differential between the two pumps when measured at the same revolutions per minute (RPM) ranged from 1.64L/min to 1.73L/min. The results obtained in this experiment demonstrate that the RotaFlow has a higher shut-off pressure (less retrograde flow) and maximal blood flow rate than the CentriMag blood pump. Findings support the conclusion that the RotaFlow disposable pump head has a better mechanical performance than the CentriMag. In addition, the RotaFlow disposable pump is 20-30 times less expensive than the CentriMag.

Effects of Gravity on Cocurrent Two-Phase Gas-Liquid Flows Through Packed Columns

NASA Technical Reports Server (NTRS)

Motil, Brian J.; Balakotaiah, Vemuri; Kamotani, Yasuhiro

2001-01-01

This work presents the experimental results of research on the influence of gravity on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid two-phase flow through packed columns. The flow pattern transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under reduced gravity conditions compared to normal gravity cocurrent down-flow. This is illustrated by comparing the flow regime transitions found in reduced gravity with the transitions predicted by Talmor. Next, the effect of gravity on the total pressure drop in a packed column is shown to depend on the flow regime. The difference is roughly equivalent to the liquid static head for bubbly flow but begins to decrease at the onset of pulse flow. As the spray flow regime is approached by increasing the gas to liquid ratio, the effect of gravity on pressure drop becomes negligible. Finally, gravity tends to suppress the amplitude of each pressure pulse. An example of this phenomenon is presented.

Study the effect of nitrogen flow rate on tribological properties of tantalum nitride based coatings

NASA Astrophysics Data System (ADS)

Chauhan, Dharmesh B.; Chauhan, Kamlesh V.; Sonera, Akshay L.; Makwana, Nishant S.; Dave, Divyeshkumar P.; Rawal, Sushant K.

2018-05-01

Tantalum Nitride (TaN) based coatings are well-known for their high temperature stability and chemical inertness. We have studied the effect of nitrogen flow rate variation on the structural and tribological properties of TaN based coating deposited by RF magnetron sputtering process. The nitrogen flow rate was varied from 5 to 30 sccm. X-ray diffractometer (XRD) and Atomic Force Microscopy (AFM) were used to determine structure and surface topography of coating. Pin on disc tribometer was used to determine tribological properties of coating. TaN coated brass and mild steel substrates shows higher wear resistance compared to uncoated substrates of brass and mild steel.

Numerical simulation of left ventricular assist device implantations: comparing the ascending and the descending aorta cannulations.

PubMed

Bonnemain, Jean; Malossi, A Cristiano I; Lesinigo, Matteo; Deparis, Simone; Quarteroni, Alfio; von Segesser, Ludwig K

2013-10-01

In this work we present numerical simulations of continuous flow left ventricle assist device implantation with the aim of comparing difference in flow rates and pressure patterns depending on the location of the anastomosis and the rotational speed of the device. Despite the fact that the descending aorta anastomosis approach is less invasive, since it does not require a sternotomy and a cardiopulmonary bypass, its benefits are still controversial. Moreover, the device rotational speed should be correctly chosen to avoid anomalous flow rates and pressure distribution in specific location of the cardiovascular tree. With the aim of assessing the differences between these two approaches and device rotational speed in terms of flow rate and pressure waveforms, we set up numerical simulations of network of one-dimensional models where we account for the presence of an outflow cannula anastomosed to different locations of the aorta. Then, we use the resulting network to compare the results of the two different cannulations for several stages of heart failure and different rotational speed of the device. The inflow boundary data for the heart and the cannulas are obtained from a lumped parameters model of the entire circulatory system with an assist device, which is validated with clinical data. The results show that ascending and descending aorta cannulations lead to similar waveforms and mean flow rate in all the considered cases. Moreover, regardless of the anastomosis region, the rotational speed of the device has an important impact on wave profiles; this effect is more pronounced at high RPM. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

Characterizing pressure issues due to turbulent flow in tubing, in ultra-fast chiral supercritical fluid chromatography at up to 580bar.

PubMed

Berger, Terry A

2016-12-02

It has been widely suggested that the outlet pressure be changed to maintain constant density ("isopycnic" conditions) when comparing the kinetic performance of different columns in supercritical fluid chromatography (SFC). However, at high flow rates, flow in the tubing is turbulent, causing large extra-column pressure drops that limit options for changing outlet pressure. Some of these pressure drops occur before and some after the column, obscuring the actual column inlet and outlet pressures. In this work, a 4.6×100mm, 1.8μm R,R-Whelk-O1 column was used with low dispersion LD (120μm) plumbing to generate sub-1min chiral separations. However, the optimum, or near optimum, flow rate was 5mL-min -1 , producing a system pressure of 580bar (with 40% methanol, outlet pressure 120bar). Both the flow rate and pump pressure required were near the limits of the instrument, and significantly exceeded the capability of many other SFC's. Extra-column pressure drops (ΔP ec ) were as high as 200bar, caused mostly by turbulent flow in the tubing. The ΔP ec increased by more than the square of the flow rate. Reynolds Numbers (Re) were calculated for tubing as a function of flow rate between 100 and 400bar and 5-20% methanol in CO 2 , and 40°-60°C. This represents the most extensive analysis of turbulence in tubing in the SFC literature. Flow in 120μm ID tubing was calculated to be laminar below 1.0mL-min -1 , mostly transitional up to 2.5mL-min -1 and virtually always turbulent at 3mL-min -1 and higher. Flow in 170μm tubing is turbulent at lower flows but generates half the ΔP ec due to the lower mobile phase linear velocity. The results suggest that, while sub-minute chromatograms are easily generated, 4.6mm columns are not very user friendly for use with sub-2μm packings. The high flow rates required just to reach optimum result in high ΔP ec generated by the tubing, causing uncertainty in the true column inlet, outlet, and average column pressure/density. When comparing kinetic performance of columns with different dimensions, the pressure drops in the tubing must be considered. Copyright © 2016 Elsevier B.V. All rights reserved.

Static response of deformable microchannels

NASA Astrophysics Data System (ADS)

Christov, Ivan C.; Sidhore, Tanmay C.

2017-11-01

Microfluidic channels manufactured from PDMS are a key component of lab-on-a-chip devices. Experimentally, rectangular microchannels are found to deform into a non-rectangular cross-section due to fluid-structure interactions. Deformation affects the flow profile, which results in a nonlinear relationship between the volumetric flow rate and the pressure drop. We develop a framework, within the lubrication approximation (l >> w >> h), to self-consistently derive flow rate-pressure drop relations. Emphasis is placed on handling different types of elastic response: from pure plate-bending, to half-space deformation, to membrane stretching. The ``simplest'' model (Stokes flow in a 3D rectangular channel capped with a linearly elastic Kirchhoff-Love plate) agrees well with recent experiments. We also simulate the static response of such microfluidic channels under laminar flow conditions using ANSYSWorkbench. Simulations are calibrated using experimental flow rate-pressure drop data from the literature. The simulations provide highly resolved deformation profiles, which are difficult to measure experimentally. By comparing simulations, experiments and our theoretical models, we show good agreement in many flow/deformation regimes, without any fitting parameters.

Inertial Particle Migration in the Presence of a Permeate Flow

NASA Astrophysics Data System (ADS)

Garcia, Mike; Singelton, Amanda; Pennathur, Sumita

2016-11-01

Tangential Flow Filtration (TFF) is a rapid and efficient method for the filtration and separation of suspensions of particles such as viruses, bacteria or cellular material. Enhancing the efficacy of TFF not only requires a detailed understanding of particle transport mechanisms, but also the interactions between these mechanisms and a porous wall. In this work, we numerically and experimentally explore the mechanisms of inertial particle migration in the presence of a permeate flow through the porous walls of a microchannel. Numerically, we develop a force balance model to understand the competition between permeate and inertial forces and the resultant consequences on the particle equilibrium location. Experimentally, we fabricated MEMS TFF devices to study the migration of 5, 10 and 15 µm fluorescent polystyrene beads in straight channels with perpendicular permeate flow rates up to 90% of the inlet flow rate. We find that the permeate flow directly influences the inertial focusing position of the particles, both as a function of downstream channel position and ratio of inlet to outlet flow rate. Comparing experiments to our model, we can identify inertial, viscous and a co-dominant regimes.

[TISSUE BLOOD FLOW IN THE DIGESTIVE ORGANS OF RATS WITH ACUTE PANCREATITIS AFTER CORVITIN ADMINISTRATION].

PubMed

Vovkun, T V; Yanchuk, P I; Shtanova, L Y; Shalamay, A S

2015-01-01

We have investigated the action of quercetin (in a modified form--Corvitin, BCPP, Ukraine) on the rate of blood flow in the pancreas, liver and gastric mucosa of rats with acute pancreatitis (AP) caused by administration of L-arginine. The rate of blood flow was measured by hydrogen clearance method with electrochemical his generation using Polarographs Lr-9 (Czech Republic). During the first 10 days after modelling of AP in these organs it was observed a gradual decrease compared to the intact animals in the rate of blood flow by 42% (P < 0.01) in the pancreas; by 61% (P < 0.001) in the liver and by 64% (P < 0.001) in the gastric mucosa, i.e., the most significant changes occurred in the gastric mucosa, the least--in the tissue of the pancreas. Compared with the control group of animals with modelling acute pancreatitis which during 20 days was administered only saline, application of Corvitin (5 mg/kg, 1 time per day from 11 to 20 days of experiment) in varying degrees promoted to the recovery of the rate of blood flow in all investigated organs: in the pancreas--fully, in the liver--almost entirely and in the gastric mucosa--only partially. Thus, based on obtained results Corvitin can be recommended for partial or complete correction of blood flow disturbances, which arise in the pancreas and other organs of the digestive system in AP. Corvitin can improve the functional state of these organs in the early stages of the disease and accelerate the full restoration of their functions.

Modified schirmer test--a screening tool for xerostomia among subjects on antidepressants.

PubMed

Kumar, Nerella Narendra; Panchaksharappa, Mamatha Gowda; Annigeri, Rajeshwari G

2014-08-01

The aim of the present study is to assess salivary flow rate in the subjects who were on antidepressant medications and its comparison with healthy controls and assessment of unstimulated salivary flow rate by modified Schirmer test (MST) and volumetric method (spitting method) for evaluation of xerostomia and whether any correlation exists between two methods. Thirty subjects who were on antidepressants were divided into two groups: tricyclic antidepressants (TCA) and selective sertonin reuptake inhibitors (SSRI) of 15 each, compared with 30 age and gender matched controls. Unstimulated salivary flow rate was measured by both MST and spitting method. The unstimulated salivary flow rate measured by MST at the end of 3rd minute was 13.7 ± 10.08, 19.86 ± 8.95 and 31.0 ± 5.4 mm and by spitting method was 0.12 ± 0.07, 0.19 ± 0.10 and 0.30 ± 0.75 ml/min in TCA, SSRI and controls respectively (p<0.001). The Pearson correlation coefficient of r=0.85 shows excellent correlation between the two screening tests. Sensitivity and Specificity of MST was 90.9% and 31.5%. Salivary flow rate was less in antidepressant subjects when compared to the healthy controls. Results of the present study showed an excellent correlation excellent correlation between the two screening tests which suggests that MST can be routinely used as chair-side screening tool to evaluate hyposalivation which is time saving, patient friendly and specific of salivary secretions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effects of flow field on the metabolic characteristics of Streptomyces lincolnensis in the industrial fermentation of lincomycin.

PubMed

Li, Xiao; Zhang, Jiang; Tan, Ya-Li; Li, Zhi-Hong; Yu, Xue-Feng; Xia, Jian-Ye; Chu, Ju; Ge, You-Qun

2013-01-01

In this work, the flow field in the existing fermentor with radial-flow impellers (C1) was studied using the computational fluid dynamics (CFD) software package Fluent, then the fermentor with radial-axial flow impellers (C2) was constructed and was compared with the C1 fermentor by CFD and experimental research. The simulation results revealed that the flow field in C2 fermentor had characteristics such as higher turbulent kinetic energy, gas holdup and shear rates. Metabolic variables of Streptomyces lincolnensis in the two fermentors such as carbon and nitrogen source consumption rates, specific growth rates (μ), hyphae morphologies, and lincomycin productivities were further explored. The correlation analysis between the experimental measurements and the simulation results indicated that the hyphae clustering and dry cell weight (DCW) decreasing at production stage were eliminated in C2 fermentor, which had higher gas volumetric mass transfer coefficient (K(L)a), dissolved oxygen (DO) concentration and consumption rates of nutrient materials. When C2 was employed in the fermentor, the specific growth rate of S. lincolnensis at growth stage was higher, and the maintenance metabolism together with secondary metabolism at production stage was kept at higher levels. As a result, the yield of lincomycin was achieved 7039 μg ml(-1) when the 60 m(3) industrial fermentor was equipped with C2, which was increased by 46% compared to that obtained in the C1 fermentor. Copyright © 2012 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Flow rate, pH and calcium concentration of saliva of children and adolescents with type 1 diabetes mellitus.

PubMed

Moreira, A R; Passos, I A; Sampaio, F C; Soares, M S M; Oliveira, R J

2009-08-01

Alterations in salivary parameters may increase the caries risk in diabetic children, but, contradictory data on this issue have been reported. The aims of this study were to compare salivary parameters (flow rate, pH and calcium concentration) between healthy and type 1 diabetes mellitus (T1DM) individuals. The sample consisted of 7- to 18-year-old individuals divided into two groups: 30 subjects with T1DM (group A) and 30 healthy control subjects (group B). Fasting glucose levels were determined. Unstimulated and stimulated saliva was collected. The pH of unstimulated saliva was measured with paper strips and an electrode. Calcium concentrations in stimulated saliva were determined with a selective electrode. Group A individuals had inadequate blood glucose control (HbA(1C) >9%), with means +/- SD unstimulated salivary flow rate of 0.15 +/- 0.1 mL/min compared to 0.36 +/- 0.2 mL/min for group B (P < 0.01). Stimulated salivary flow rate was similar by both groups and above 2.0 mL/min. Saliva pH was 6.0 +/- 0.8 for group A and significantly different from 7.0 +/- 0.6 for group B (P < 0.01). Salivary calcium was 14.7 +/- 8.1 mg/L for group A and significantly higher than 9.9 +/- 6.4 mg/L for group B (P < 0.01). Except for elevated calcium concentrations in saliva, salivary parameters favoring caries such as low saliva pH and unstimulated salivary flow rate were observed in T1DM individuals.

Buoyant miscible displacement flow of shear-thinning fluids: Experiments and Simulations

NASA Astrophysics Data System (ADS)

Ale Etrati Khosroshahi, Seyed Ali; Frigaard, Ian

2017-11-01

We study displacement flow of two miscible fluids with density and viscosity contrast in an inclined pipe. Our focus is mainly on displacements where transverse mixing is not significant and thus a two-layer, stratified flow develops. Our experiments are carried out in a long pipe, covering a wide range of flow-rates, inclination angles and viscosity ratios. Density and viscosity contrasts are achieved by adding Glycerol and Xanthan gum to water, respectively. At each angle, flow rate and viscosity ratio are varied and density contrast is fixed. We identify and map different flow regimes, instabilities and front dynamics based on Fr , Re / Frcosβ and viscosity ratio m. The problem is also studied numerically to get a better insight into the flow structure and shear-thinning effects. Numerical simulations are completed using OpenFOAM in both pipe and channel geometries and are compared against the experiments. Schlumberger, NSERC.

Yield-stress fluids foams: flow patterns and controlled production in T-junction and flow-focusing devices.

PubMed

Laborie, Benoit; Rouyer, Florence; Angelescu, Dan E; Lorenceau, Elise

2016-11-23

We study the formation of yield-stress fluid foams in millifluidic flow-focusing and T-junction devices. First, we provide a phase diagram for the unsteady operating regimes of bubble production when the gas pressure and the yield-stress fluid flow rate are imposed. Three regimes are identified: a co-flow of gas and yield-stress fluid, a transient production of bubble and a flow of yield-stress fluid only. Taking wall slip into account, we provide a model for the pressure at the onset of bubble formation. Then, we detail and compare two simple methods to ensure steady bubble production: regulation of the gas pressure or flow-rate. These techniques, which are easy to implement, thus open pathways for controlled production of dry yield-stress fluid foams as shown at the end of this article.

Experimental study on burning rates of square/rectangular gasoline and methanol pool fires under longitudinal air flow in a wind tunnel.

PubMed

Hu, L H; Liu, S; Peng, W; Huo, R

2009-09-30

Square pool fires with length of 5, 7.5, 10, 15, 20, 25 and 30 cm and rectangular pool fires with dimensions of 10 cm x 20 cm and 10 cm x 40 cm were burned in a wind tunnel, under a longitudinal air flow ranged from 0 to 3m/s with incremental change of about 0.5m/s. Methanol and gasoline were burned and compared, with results indicated that their burning rates showed different response to the longitudinal air flow. With the increase of the longitudinal air flow speed, the burning rates of methanol pool fires, except the 5 cm square one, first decreased and then increased, but those of the 5 cm methanol square one and the gasoline pool fires increased monotonously. The burning rate of smaller square pool fires increased more significantly than that of the larger ones, as well as the enlargement of their flame attachment length along the ground. The burning rate of a rectangular pool fire with longer rim parallel to the longitudinal flow increased faster, but the flame attachment length seemed to increase more gradually, with the increase of the longitudinal air flow speed than that perpendicular to.

A Low-Erosion Starting Technique for High-Performance Arcjets

NASA Technical Reports Server (NTRS)

Sankovic, John M.; Curran, Francis M.

1994-01-01

The NASA arcjet program is currently sponsoring development of high specific impulse thrusters for next generation geosynchronous communications satellites (2 kW-class) and low-power arcjets for power limited spacecraft (approx. 0.5 kW-class). Performance goals in both of these efforts will require up to 1000 starts at propellant mass flow rates significantly below those used in state-of-the-art arcjet thruster systems (i.e., high specific power levels). Reductions in mass flow rate can lead to damaging modes of operation, particularly at thruster ignition. During the starting sequence, the gas dynamic force due to low propellant flow is often insufficient to rapidly push the arc anode attachment to its steady-state position in the diverging section of the nozzle. This paper describes the development and demonstration of a technique which provides for non-damaging starts at low steady-state flow rates. The technique employs a brief propellant pressure pulse at ignition to increase gas dynamic forces during the critical ignition/transition phase of operation. Starting characteristics obtained using both pressure-pulsed and conventional starting techniques were compared across a wide range of propellant flow rates. The pressure-pulsed starting technique provided reliable starts at mass flow rates down to 21 mg/s, typically required for 700 s specific impulse level operation of 2 kW thrusters. Following the comparison, a 600 start test was performed across a wide flow rate range. Post-test inspection showed minimal erosion of critical arcjet anode/nozzle surfaces.

Impact of Laurel Wilt, Caused by Raffaelea lauricola, on Leaf Gas Exchange and Xylem Sap Flow in Avocado, Persea americana.

PubMed

Ploetz, Randy C; Schaffer, Bruce; Vargas, Ana I; Konkol, Joshua L; Salvatierra, Juanpablo; Wideman, Ronney

2015-04-01

Laurel wilt, caused by Raffaelea lauricola, is a destructive disease of avocado (Persea americana). The susceptibility of different cultivars and races was examined previously but more information is needed on how this host responds to the disease. In the present study, net CO2 assimilation (A), stomatal conductance of H2O (gs), transpiration (E), water use efficiency (WUE), and xylem sap flow rates were assessed in cultivars that differed in susceptibility. After artificial inoculation with R. lauricola, there was a close relationship between symptom development and reductions in A, gs, E, WUE, and mean daily sap flow in the most susceptible cultivar, 'Russell', and significantly greater disease and lower A, gs, E, WUE, and sap flow rates were usually detected after 15 days compared with the more tolerant 'Brogdon' and 'Marcus Pumpkin'. Significant differences in preinoculation A, gs, E, and WUE were generally not detected among the cultivars but preinoculation sap flow rates were greater in Russell than in Brogdon and Marcus Pumpkin. Preinoculation sap flow rates and symptom severity for individual trees were correlated at the end of an experiment (r=0.46), indicating that a plant's susceptibility to laurel wilt was related to its ability to conduct water. The potential management of this disease with clonal rootstocks that reduce sap flow rates is discussed.

Flow Diversion versus Standard Endovascular Techniques for the Treatment of Unruptured Carotid-Ophthalmic Aneurysms.

PubMed

Di Maria, F; Pistocchi, S; Clarençon, F; Bartolini, B; Blanc, R; Biondi, A; Redjem, H; Chiras, J; Sourour, N; Piotin, M

2015-12-01

Over the past few years, flow diversion has been increasingly adopted for the treatment of intracranial aneurysms, especially in the paraclinoid and paraophthalmic carotid segment. We compared clinical and angiographic outcomes and complication rates in 2 groups of patients with unruptured carotid-ophthalmic aneurysms treated for 7 years by either standard coil-based techniques or flow diversion. From February 2006 to December 2013, 162 unruptured carotid-ophthalmic aneurysms were treated endovascularly in 138 patients. Sixty-seven aneurysms were treated by coil-based techniques in 61 patients. Flow diverters were deployed in 95 unruptured aneurysms (77 patients), with additional coiling in 27 patients. Complication rates, clinical outcome, and immediate and long-term angiographic results were retrospectively analyzed. No procedure-related deaths occurred. Four procedure-related thromboembolic events (6.6%) leading to permanent morbidity in 1 case (1.6%) occurred in the coiling group. Neurologic complications were observed in 6 patients (7.8%) in the flow-diversion group, resulting in 3.9% permanent morbidity. No statistically significant difference was found between complication (P = .9) and morbidity rates (P = .6). In the coiling group (median follow-up, 31.5 ± 24.5 months), recanalization occurred at 1 year in 23/50 (54%) aneurysms and 27/55 aneurysms (50.9%) at the latest follow-up, leading to retreatment in 6 patients (9%). In the flow-diversion group (mean follow-up, 13.5 ± 10.8 months), 85.3% (35/41) of all aneurysms were occluded after 12 months, and 74.6% (50/67) on latest follow-up. The retreatment rate was 2.1%. Occlusion rates between the 2 groups differed significantly at 12 months (P < .001) and at the latest follow-up (P < .005). Our retrospective analysis shows better long-term occlusion of carotid-ophthalmic aneurysms after use of flow diverters compared with standard coil-based techniques, without significant differences in permanent morbidity. © 2015 by American Journal of Neuroradiology.

Ultrasensitive SERS Flow Detector Using Hydrodynamic Focusing

PubMed Central

Negri, Pierre; Jacobs, Kevin T.; Dada, Oluwatosin O.; Schultz, Zachary D.

2013-01-01

Label-free, chemical specific detection in flow is important for high throughput characterization of analytes in applications such as flow injection analysis, electrophoresis, and chromatography. We have developed a surface-enhanced Raman scattering (SERS) flow detector capable of ultrasensitive optical detection on the millisecond time scale. The device employs hydrodynamic focusing to improve SERS detection in a flow channel where a sheath flow confines analyte molecules eluted from a fused silica capillary over a planar SERS-active substrate. Increased analyte interactions with the SERS substrate significantly improve detection sensitivity. The performance of this flow detector was investigated using a combination of finite element simulations, fluorescence imaging, and Raman experiments. Computational fluid dynamics based on finite element analysis was used to optimize the flow conditions. The modeling indicates that a number of factors, such as the capillary dimensions and the ratio of the sheath flow to analyte flow rates, are critical for obtaining optimal results. Sample confinement resulting from the flow dynamics was confirmed using wide-field fluorescence imaging of rhodamine 6G (R6G). Raman experiments at different sheath flow rates showed increased sensitivity compared with the modeling predictions, suggesting increased adsorption. Using a 50-millisecond acquisitions, a sheath flow rate of 180 μL/min, and a sample flow rate of 5 μL/min, a linear dynamic range from nanomolar to micromolar concentrations of R6G with a LOD of 1 nM is observed. At low analyte concentrations, rapid analyte desorption is observed, enabling repeated and high-throughput SERS detection. The flow detector offers substantial advantages over conventional SERS-based assays such as minimal sample volumes and high detection efficiency. PMID:24074461

Fluidics comparison between dual pneumatic and spring return high-speed vitrectomy systems.

PubMed

Brant Fernandes, Rodrigo A; Diniz, Bruno; Falabella, Paulo; Ribeiro, Ramiro; Teixeira, Anderson G; Magalhães, Octaviano; Moraes, Nilva; Maia, Andre; Farah, Michel E; Maia, Mauricio; Humayun, Mark S

2015-01-01

To compare the water and vitreous flow rates and duty cycle (DC) between two ultrahigh-speed vitrectomy systems: pneumatic with spring return (SR) and dual pneumatic (DP) probes. The flow rate was calculated using a high-sampling precision balance that measured the mass of water and vitreous removed from a vial by a vitreous cutter. Frame-by-frame analysis of a high-speed video of the cutter was used to determine the DC. Three cutters of each gauge (20, 23, and 25 G) were tested with an SR and a DP system using the standard DC setting (biased open) at 0 (water only), 1,000, 2,000, 3,000, 4,000, and 5,000 cuts per minute (CPM) with aspiration levels of 100, 200, 300, 400, 500, and 600 mm Hg. The DC was slightly higher with the SR system using most parameters and gauges although without statistical significance. The water flow rate was somewhat higher with the SR system, except for 25 G with 4,000 and 5,000 CPM. The vitreous flow rate was similar using most parameters, with the SR system showing higher flows at lower cut rates (1,000-3,000 CPM). SR and DP systems produced similar water and vitreous flow rates. Additional studies in human eyes are necessary to confirm these findings. Copyright 2015, SLACK Incorporated.

Doppler endoscopic probe as a guide to risk stratification and definitive hemostasis of peptic ulcer bleeding.

PubMed

Jensen, Dennis M; Ohning, Gordon V; Kovacs, Thomas O G; Ghassemi, Kevin A; Jutabha, Rome; Dulai, Gareth S; Machicado, Gustavo A

2016-01-01

For more than 4 decades endoscopists have relied on ulcer stigmata for risk stratification and as a guide to hemostasis. None used arterial blood flow underneath stigmata to predict outcomes. For patients with severe peptic ulcer bleeding (PUB), we used a Doppler endoscopic probe (DEP) for (1) detection of blood flow underlying stigmata of recent hemorrhage (SRH), (2) quantitating rates of residual arterial blood flow under SRH after visually directed standard endoscopic treatment, and (3) comparing risks of rebleeding and actual 30-day rebleed rates for spurting arterial bleeding (Forrest [F] IA) and oozing bleeding (F IB). Prospective cohort study of 163 consecutive patients with severe PUB and different SRH. All blood flow detected by the DEP was arterial. Detection rates were 87.4% in major SRH-spurting arterial bleeding (F IA), non-bleeding visible vessel (F IIA), clot (F IIB)-and were significantly lower at 42.3% (P < .0001) for an intermediate group of oozing bleeding (F IB) or flat spot (F IIC). For spurting bleeding (F IA) versus oozing (F IB), baseline DEP arterial flow was 100% versus 46.7%, residual blood flow detected after endoscopic hemostasis was 35.7% versus 0%, and 30-day rebleed rates were 28.6% versus 0% (all P < .05). (1) For major SRH versus oozing or spot, the arterial blood flow detection rate by the DEP was significantly higher, indicating a higher rebleed risk. (2) Before and after endoscopic treatment, spurting (F IA) PUB had significantly higher rates of blood flow detection than oozing (F IB) PUB and a significantly higher 30-day rebleed rate. (3) The DEP is recommended as a new endoscopic guide with SRH to improve risk stratification and potentially definitive hemostasis for PUB. Published by Elsevier Inc.

Doppler Endoscopic Probe as a Guide to Risk Stratification and Definitive Hemostasis of Peptic Ulcer Bleeding

PubMed Central

Jensen, Dennis M.; Ohning, Gordon V.; Kovacs, Thomas OG; Ghassemi, Kevin A.; Jutabha, Rome; Dulai, Gareth S.; Machicado, Gustavo A.

2015-01-01

Background and Aims For more than 4 decades endoscopists have relied on ulcer stigmata for risk stratification and as a guide to hemostasis. None used arterial blood flow underneath stigmata to predict outcomes. For patients with severe peptic ulcer bleeding (PUBs), we used Doppler endoscopic probe (DEP) for: 1. detection of blood flow underlying stigmata of recent hemorrhage (SRH), 2. quantitating rates of residual arterial blood flow under SRH after visually directed standard endoscopic treatment, and 3. comparing risks of rebleeding and actual 30 day rebleed rates for spurting arterial bleeding (Forrest – FIA) and oozing bleeding (FIB). Methods Prospective cohort study of 163 consecutive patients with severe PUBs and different SRH. Results All blood flow detected by DEP was arterial. Detection rates were 87.4% in major SRH - spurting arterial bleeding (FIA), non bleeding visible vessel (FIIA), clot (FIIB) - and significantly lower at 42.3% (p<0.0001) for intermediate group of oozing bleeding (FIB) or flat spot (FIIC). For spurting bleeding (FIA) vs. oozing (FIB), baseline DEP arterial flow was 100% vs. 46.7%; residual blood flow detected after endoscopic hemostasis was 35.7% vs. 0%; and 30 day rebleed rates were 28.6% vs. 0% (all p<0.05). Conclusions 1. For major SRH vs. oozing or spot, the arterial blood flow detection rates by DEP was significantly higher, indicating a higher rebleed risk. 2. Before and after endoscopic treatment, spurting FIA PUB’s had significantly higher rates of blood flow detection than oozing FIB PUB’s and a significantly higher 30 rebleed rate. 3. DEP is recommended as a new endoscopic guide with SRH to improve risk stratification and potentially definitive hemostasis for PUBs. PMID:26318834

CFD Based Prediction of Discharge Coefficient of Sonic Nozzle with Surface Roughness

NASA Astrophysics Data System (ADS)

Bagaskara, Agastya; Agoes Moelyadi, Mochammad

2018-04-01

Due to its simplicity and accuracy, sonic nozzle is widely used in gas flow measurement, gas flow meter calibration standard, and flow control. The nozzle obtains mass flow rate by measuring temperature and pressure in the inlet during choked flow condition and calculate the flow rate using the one-dimensional isentropic flow equation multiplied by a discharge coefficient, which takes into account multiple non-isentropic effects, which causes the reduction in mass flow. Proper determination of discharge coefficient is crucial to ensure the accuracy of mass flow measurement by the nozzle. Available analytical solution for the prediction of discharge coefficient assumes that the nozzle wall is hydraulically smooth which causes disagreement with experimental results. In this paper, the discharge coefficient of sonic nozzle is determined using computational fluid dynamics method by taking into account the roughness of the wall. It is found that the result shows better agreement with the experiment data compared to the analytical result.

Renal Blood Flow, Glomerular Filtration Rate, and Renal Oxygenation in Early Clinical Septic Shock.

PubMed

Skytte Larsson, Jenny; Krumbholz, Vitus; Enskog, Anders; Bragadottir, Gudrun; Redfors, Bengt; Ricksten, Sven-Erik

2018-06-01

Data on renal hemodynamics, function, and oxygenation in early clinical septic shock are lacking. We therefore measured renal blood flow, glomerular filtration rate, renal oxygen consumption, and oxygenation in patients with early septic shock. Prospective comparative study. General and cardiothoracic ICUs. Patients with norepinephrine-dependent early septic shock (n = 8) were studied within 24 hours after arrival in the ICU and compared with postcardiac surgery patients without acute kidney injury (comparator group, n = 58). None. Data on systemic hemodynamics and renal variables were obtained during two 30-minute periods. Renal blood flow was measured by the infusion clearance of para-aminohippuric acid, corrected for renal extraction of para-aminohippuric acid. Renal filtration fraction was measured by renal extraction of chromium-51 labeled EDTA. Renal oxygenation was estimated from renal oxygen extraction. Renal oxygen delivery (-24%; p = 0.037) and the renal blood flow-to-cardiac index ratio (-21%; p = 0.018) were lower, renal vascular resistance was higher (26%; p = 0.027), whereas renal blood flow tended to be lower (-19%; p = 0.068) in the septic group. Glomerular filtration rate (-32%; p = 0.006) and renal sodium reabsorption (-29%; p = 0.014) were both lower in the septic group. Neither renal filtration fraction nor renal oxygen consumption differed significantly between groups. Renal oxygen extraction was significantly higher in the septic group (28%; p = 0.022). In the septic group, markers of tubular injury were elevated. In early clinical septic shock, renal function was lower, which was accompanied by renal vasoconstriction, a lower renal oxygen delivery, impaired renal oxygenation, and tubular sodium reabsorption at a high oxygen cost compared with controls.

Use of hollow fiber membrane filtration for the removal of DMSO from platelet concentrates.

PubMed

Arnaud, F; Kapnik, E; Meryman, H T

2003-05-01

It has been hypothesized that, in addition to freezing injury, some damage to platelets may result from the cell packing that occurs during removal of the cryoprotectant. This study examined DMSO removal by fluid exchange across hollow-fiber (HF) filters as an alternative to centrifugation. The DMSO solution with or without cell suspension was passed once through the filter. The optimum exchange during unloading of DMSO was determined by varying the flow rates in the external and internal compartments of the HF filter. Initially, buffered solutions of a 5% DMSO solution in the absence of platelets were pumped into the fibers and exchanged against PBS. The residual DMSO was determined by osmometry. The exchange of DMSO across the membrane was flow dependent and also influenced by the chemical nature of the HF fibers. No protocol using a reasonable rate flow through the fibers removed more than 95% of the DMSO in a single pass. The optimum protocol was achieved with polysynthane fibers with an internal flow rate of approximately 20 mi/min and an external flow rate of 100 ml/min. Subsequently, frozen/thawed platelet concentrates in DMSO were washed using centrifugation and compared to the HF filtration method. Platelet quality was assayed by flow cytometry, cell count, morphology and osmotic stress test. Both filtration and centrifugal washing techniques resulted in comparable morphological scores and numbers of discoid cells. When agents reducing platelet activation were added, platelet quality was improved after washing by either technique. The lower platelet osmotic response with HF filtration than with centrifugation while using activation inhibitors was attributed to the remaining amount of the inhibitors. All other parameters tested were similar. The expression of CD62P was equivalent with both techniques, and centrifugation did not activate platelets more than filtration contrary to what was originally anticipated. In conclusion, platelet quality was comparable after washing by either technique but hollow fiber filtration does remove cryoprotectant more rapidly than does centrifugation.

A longitudinal analysis of salivary flow in control subjects and older adults with type 2 diabetes.

PubMed

Chávez, E M; Borrell, L N; Taylor, G W; Ship, J A

2001-02-01

Many diabetics complain of xerostomia, a condition that can affect oral health, nutritional status, and diet selection. This study's purposes were (1) to investigate the effect on salivary flow of type 2 diabetes and change in glycemic control in a group of older adults over time and (2) to compare flow rates with subjective complaints of xerostomia. A total of 39 older adults, 24 with type 2 diabetes and 15 who were nondiabetic (controls), aged 54-90 years, participated in a 1-year follow-up study. Diabetic status was determined by means of glycosylated hemoglobin (HbA1c) levels and 2-hour glucose tolerance tests. Poor glycemic control was defined as HbA1c > 9%. Unstimulated whole, unstimulated parotid, and stimulated parotid saliva flow rates were measured for all subjects by a single examiner at baseline and 1 year later. Each subject completed a standardized xerostomia questionnaire at every visit. Age, sex, and duration of diabetes did not adversely affect salivary flow rates. Subjects with poorly controlled diabetes had significantly lower stimulated parotid saliva flow rates at both visits. There were no significant changes in flow rates over time on the basis of diabetic status or glycemic control. Subjects with diabetes reported significantly more complaints of thirst but not of xerostomia at 1 year. These results suggest that older adults with poorly controlled diabetes may have impaired salivary flow in comparison with subjects with better controlled diabetes and nondiabetic subjects, yet they may not have concomitant xerostomic complaints. There were no significant changes in salivary flow rates or glycemic control over the 1-year period.

Effects of thyroxine and dexamethasone on rat submandibular glands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sagulin, G.B.; Roomans, G.M.

1989-08-01

Glucocorticoids and thyroxine are known to have a marked effect on the flow rate and protein composition of rat parotid saliva in hormonally intact animals. In the present study, the effects of a one-week treatment of male rats with dexamethasone and thyroxine were studied by electron microscopy and x-ray micro-analysis, and by measurement of the flow rate and determination of the chemical composition of pilocarpine-induced submandibular saliva. Thyroxine had the most extensive effects on the submandibular gland. The acinar cells were enlarged and filled with mucus; the cellular calcium concentration was significantly increased. The flow rate of the submandibular salivamore » was significantly reduced compared with that in saline-injected control animals. Thyroxine caused an increase in the concentrations of protein, total calcium, and potassium in the saliva. Dexamethasone had no significant effects on gland ultrastructure or on the elemental composition of the acinar cells; flow rate was not affected, but the concentrations of protein, calcium, and potassium were significantly increased. The effects of dexamethasone and thyroxine on the flow rate and protein composition of pilocarpine-induced rat submandibular saliva differ from those reported earlier for rat parotid saliva after simultaneous stimulation with pilocarpine and isoproterenol.« less

Atmospheric Pressure Effects on Cryogenic Storage Tank Boil-Off

NASA Technical Reports Server (NTRS)

Sass, J. P.; Frontier, C. R.

2007-01-01

The Cryogenics Test Laboratory (CTL) at the Kennedy Space Center (KSC) routinely utilizes cryostat test hardware to evaluate comparative and absolute thermal conductivities of a wide array of insulation systems. The test method is based on measurement of the flow rate of gas evolved due to evaporative boil-off of a cryogenic liquid. The gas flow rate typically stabilizes after a period of a couple of hours to a couple of days, depending upon the test setup. The stable flow rate value is then used to calculate the thermal conductivity for the insulation system being tested. The latest set of identical cryostats, 1,000-L spherical tanks, exhibited different behavior. On a macro level, the flow rate did stabilize after a couple of days; however the stable flow rate was oscillatory with peak to peak amplitude of up to 25 percent of the nominal value. The period of the oscillation was consistently 12 hours. The source of the oscillation has been traced to variations in atmospheric pressure due to atmospheric tides similar to oceanic tides. This paper will present analysis of this phenomenon, including a calculation that explains why other cryostats are not affected by it.

Injection Characteristics of Non-Swirling and Swirling Annular Liquid Sheets

NASA Technical Reports Server (NTRS)

Harper, Brent (Technical Monitor); Ibrahim, E. A.; McKinney, T. R.

2004-01-01

A simplified mathematical model, based on body-fitted coordinates, is formulated to study the evolution of non-swirling and swirling liquid sheet emanated from an annular nozzle in a quiescent surrounding medium. The model provides predictions of sheet trajectory, thickness and velocity at various liquid mass flow rates and liquid-swirler angles. It is found that a non-swirling annular sheet converges toward its centerline and assumes a bell shape as it moves downstream from the nozzle. The bell radius, and length are more pronounced at higher liquid mass flow rates. The thickness of the non-swirling annular sheet increases while its stream-wise velocity decreases with an increase in mass flow rate. The introduction of swirl results in the formation of a diverging hollow-cone sheet. The hollow-cone divergence from its centerline is enhanced by an increase in liquid mass flow rate or liquid-swirler angle. The hollow- cone sheet its radius, curvature and stream-wise velocity increase while its thickness and tangential velocity decrease as a result of increasing the mass flow rate or liquid-swirler angle. The present results are compared with previous studies and conclusions are drawn.

Relationship Between the Urine Flow Rate and Risk of Contrast-Induced Nephropathy After Emergent Percutaneous Coronary Intervention

PubMed Central

Liu, Yong; Lin, Lixia; Li, Yun; Li, Hualong; Wu, Deng-Xuan; Zhao, Jian-bin; Lian, Dan; Zhou, Yingling; Liu, Yuanhui; Ye, Piao; Ran, Peng; Duan, Chongyang; Chen, Shiqun; Chen, Pingyan; Xian, Ying; Chen, Jiyan; Tan, Ning

2015-01-01

Abstract A low urine flow rate is a marker of acute kidney injury. However, it is unclear whether a high urine flow rate is associated with a reduced risk of contrast-induced nephropathy (CIN) in high-risk patients. We conducted this study to evaluate the predictive value of the urine flow rate for the risk of CIN following emergent percutaneous coronary intervention (PCI). We prospectively examined 308 patients undergoing emergent PCI who provided consent. The predictive value of the 24-hour postprocedural urine flow rate, adjusted by weight (UR/W, mL/kg/h) and divided into quartiles, for the risk of CIN was assessed using multivariate logistic regression analysis. The cumulative incidence of CIN was 24.4%. In particular, CIN was observed in 29.5%, 19.5%, 16.7%, and 32.0% of cases in the UR/W quartile (Q)-1 (≤0.94 mL/kg/h), Q2 (0.94–1.30 mL/kg/h), Q3 (1.30–1.71 mL/kg/h), and Q4 (≥1.71 mL/kg/h), respectively. Moreover, in-hospital death was noted in 7.7%, 3.9%, 5.1%, and 5.3% of patients in Q1, Q2, Q3, and Q4, respectively. After adjusting for potential confounding predictors, multivariate analysis indicated that compared with the moderate urine flow rate quartiles (Q2 + Q3), a high urine flow rate (Q4) (odds ratio [OR], 2.69; 95% confidence interval [CI], 1.27–5.68; P = 0.010) and low urine flow rate (Q1) (OR, 2.23; 95% CI, 1.03–4.82; P = 0.041) were significantly associated with an increased risk of CIN. Moreover, a moderate urine flow rate (0.94–1.71 mL/kg/h) was significantly associated with a decreased risk of mortality. Our data suggest that higher and lower urine flow rates were significantly associated with an increased risk of CIN after emergent PCI, and a moderate urine flow rate (0.94–1.71 mL/kg/h) may be associated with a decreased risk of CIN with a good long-term prognosis after emergent PCI. PMID:26683946

Relationship Between the Urine Flow Rate and Risk of Contrast-Induced Nephropathy After Emergent Percutaneous Coronary Intervention.

PubMed

Liu, Yong; Lin, Lixia; Li, Yun; Li, Hualong; Wu, Deng-Xuan; Zhao, Jian-bin; Lian, Dan; Zhou, Yingling; Liu, Yuanhui; Ye, Piao; Ran, Peng; Duan, Chongyang; Chen, Shiqun; Chen, Pingyan; Xian, Ying; Chen, Jiyan; Tan, Ning

2015-12-01

A low urine flow rate is a marker of acute kidney injury. However, it is unclear whether a high urine flow rate is associated with a reduced risk of contrast-induced nephropathy (CIN) in high-risk patients. We conducted this study to evaluate the predictive value of the urine flow rate for the risk of CIN following emergent percutaneous coronary intervention (PCI). We prospectively examined 308 patients undergoing emergent PCI who provided consent. The predictive value of the 24-hour postprocedural urine flow rate, adjusted by weight (UR/W, mL/kg/h) and divided into quartiles, for the risk of CIN was assessed using multivariate logistic regression analysis. The cumulative incidence of CIN was 24.4%. In particular, CIN was observed in 29.5%, 19.5%, 16.7%, and 32.0% of cases in the UR/W quartile (Q)-1 (≤0.94  mL/kg/h), Q2 (0.94-1.30  mL/kg/h), Q3 (1.30-1.71  mL/kg/h), and Q4 (≥1.71  mL/kg/h), respectively. Moreover, in-hospital death was noted in 7.7%, 3.9%, 5.1%, and 5.3% of patients in Q1, Q2, Q3, and Q4, respectively. After adjusting for potential confounding predictors, multivariate analysis indicated that compared with the moderate urine flow rate quartiles (Q2 + Q3), a high urine flow rate (Q4) (odds ratio [OR], 2.69; 95% confidence interval [CI], 1.27-5.68; P = 0.010) and low urine flow rate (Q1) (OR, 2.23; 95% CI, 1.03-4.82; P = 0.041) were significantly associated with an increased risk of CIN. Moreover, a moderate urine flow rate (0.94-1.71  mL/kg/h) was significantly associated with a decreased risk of mortality. Our data suggest that higher and lower urine flow rates were significantly associated with an increased risk of CIN after emergent PCI, and a moderate urine flow rate (0.94-1.71  mL/kg/h) may be associated with a decreased risk of CIN with a good long-term prognosis after emergent PCI.

Flowfield analysis for successive oblique shock wave-turbulent boundary layer interactions

NASA Technical Reports Server (NTRS)

Sun, C. C.; Childs, M. E.

1976-01-01

A computation procedure is described for predicting the flowfields which develop when successive interactions between oblique shock waves and a turbulent boundary layer occur. Such interactions may occur, for example, in engine inlets for supersonic aircraft. Computations are carried out for axisymmetric internal flows at M 3.82 and 2.82. The effect of boundary layer bleed is considered for the M 2.82 flow. A control volume analysis is used to predict changes in the flow field across the interactions. Two bleed flow models have been considered. A turbulent boundary layer program is used to compute changes in the boundary layer between the interactions. The results given are for flows with two shock wave interactions and for bleed at the second interaction site. In principle the method described may be extended to account for additional interactions. The predicted results are compared with measured results and are shown to be in good agreement when the bleed flow rate is low (on the order of 3% of the boundary layer mass flow), or when there is no bleed. As the bleed flow rate is increased, differences between the predicted and measured results become larger. Shortcomings of the bleed flow models at higher bleed flow rates are discussed.

Exhaust plume impingement of chemically reacting gas-particle flows

NASA Technical Reports Server (NTRS)

Smith, S. D.; Penny, M. M.; Greenwood, T. F.; Roberts, B. B.

1975-01-01

A series of computer codes has been developed to predict gas-particle flows and resulting impingement forces, moments and heating rates to surfaces immersed in the flow. The gas-particle flow solution is coupled via heat transfer and drag between the phases with chemical effects included in the gas phase. The flow solution and impingement calculations are discussed. Analytical results are compared with test data obtained to evaluate gas-particle effects on the Space Shuttle thermal protection system during the staging maneuver.

Characterization of a continuous agitated cell reactor for oxygen dependent biocatalysis.

PubMed

Toftgaard Pedersen, Asbjørn; de Carvalho, Teresa Melo; Sutherland, Euan; Rehn, Gustav; Ashe, Robert; Woodley, John M

2017-06-01

Biocatalytic oxidation reactions employing molecular oxygen as the electron acceptor are difficult to conduct in a continuous flow reactor because of the requirement for high oxygen transfer rates. In this paper, the oxidation of glucose to glucono-1,5-lactone by glucose oxidase was used as a model reaction to study a novel continuous agitated cell reactor (ACR). The ACR consists of ten cells interconnected by small channels. An agitator is placed in each cell, which mixes the content of the cell when the reactor body is shaken by lateral movement. Based on tracer experiments, a hydrodynamic model for the ACR was developed. The model consisted of ten tanks-in-series with back-mixing occurring within and between each cell. The back-mixing was a necessary addition to the model in order to explain the observed phenomenon that the ACR behaved as two continuous stirred tank reactors (CSTRs) at low flow rates, while it at high flow rates behaved as the expected ten CSTRs in series. The performance of the ACR was evaluated by comparing the steady state conversion at varying residence times with the conversion observed in a stirred batch reactor of comparable size. It was found that the ACR could more than double the overall reaction rate, which was solely due to an increased oxygen transfer rate in the ACR caused by the intense mixing as a result of the spring agitators. The volumetric oxygen transfer coefficient, k L a, was estimated to be 344 h -1 in the 100 mL ACR, opposed to only 104 h -1 in a batch reactor of comparable working volume. Interestingly, the large deviation from plug flow behavior seen in the tracer experiments was found to have little influence on the conversion in the ACR, since both a plug flow reactor (PFR) model and the backflow cell model described the data sufficiently well. Biotechnol. Bioeng. 2017;114: 1222-1230. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

The Study on Flow Velocity Measurement of Antarctic Krill Trawl Model Experiment in North Bay of South China Sea

NASA Astrophysics Data System (ADS)

Chen, Shuai; Wang, Lumin; Huang, Hongliang; Zhang, Xun

2017-10-01

From August 25 to 29, 2014, the project team carried out the experiment of Antarctic krill trawl in the Beihai Bay of the South China Sea. In order to understand the flow field of the network model in the course of the experiment, it is necessary to record the speed of the ship and to grasp the flow field of the ocean. Therefore, the ocean velocity is measured during the experiment. The flow rate in this experiment was measured using an acoustic Doppler flow meter (Vectoring Plus, Nortek, Norway). In order to compensate for the flow rate error caused by ship drift, the drift condition of the ship was also measured by the positioning device (Snapdragon MSM8274AB, Qualcomm, USA) used in the flow rate measurement. The results show that the actual velocity of the target sea area is in the range of 0.06-0.49 m / s and the direction is 216.17-351.70. And compared with the previous research, the influencing factors were analysed. This study proves that it is feasible to use point Doppler flow meter for velocity study in trawl model experiment.

Performance analysis of axial flow pump on gap changing between impeller and guide vane

NASA Astrophysics Data System (ADS)

Wang, W. J.; Liang, Q. H.; Wang, Y.; Yang, Y.; Yin, G.; Shi, X. X.

2013-12-01

In order to study the influence on gap changing of the static and dynamic components in axial flow pump, the axial flow pump model (TJ04-ZL-06) that used in the eastern of south-to-north water diversion project was selected. Steady turbulence field with different gaps was simulated by standard κ-ε turbulence model and double-time stepping methods. Information on the pressure distribution and velocity distribution of impeller surfaces were obtained. Then, calculated results were compared with the test results and analyzed. The results show that the performance of pump is not sensitive with the axial gap width under design conditions and the large flow rate condition. With increasing gap width, it will be improved in low flow rate condition. The attack angle of impeller inlet in small flow rate condition become small and the flow separation phenomenon can be observed in this condition. The axial velocity distribution of impeller outlet is nonlinear and to increase the axial gap is to improve the flow pattern near the hub effectively. The trend of calculating results is identical with test. It will play a guiding role to the axial pump operation and design in south-to-north water diversion project.

Faster Blood Flow Rate Does Not Improve Circuit Life in Continuous Renal Replacement Therapy: A Randomized Controlled Trial.

PubMed

Fealy, Nigel; Aitken, Leanne; du Toit, Eugene; Lo, Serigne; Baldwin, Ian

2017-10-01

To determine whether blood flow rate influences circuit life in continuous renal replacement therapy. Prospective randomized controlled trial. Single center tertiary level ICU. Critically ill adults requiring continuous renal replacement therapy. Patients were randomized to receive one of two blood flow rates: 150 or 250 mL/min. The primary outcome was circuit life measured in hours. Circuit and patient data were collected until each circuit clotted or was ceased electively for nonclotting reasons. Data for clotted circuits are presented as median (interquartile range) and compared using the Mann-Whitney U test. Survival probability for clotted circuits was compared using log-rank test. Circuit clotting data were analyzed for repeated events using hazards ratio. One hundred patients were randomized with 96 completing the study (150 mL/min, n = 49; 250 mL/min, n = 47) using 462 circuits (245 run at 150 mL/min and 217 run at 250 mL/min). Median circuit life for first circuit (clotted) was similar for both groups (150 mL/min: 9.1 hr [5.5-26 hr] vs 10 hr [4.2-17 hr]; p = 0.37). Continuous renal replacement therapy using blood flow rate set at 250 mL/min was not more likely to cause clotting compared with 150 mL/min (hazards ratio, 1.00 [0.60-1.69]; p = 0.68). Gender, body mass index, weight, vascular access type, length, site, and mode of continuous renal replacement therapy or international normalized ratio had no effect on clotting risk. Continuous renal replacement therapy without anticoagulation was more likely to cause clotting compared with use of heparin strategies (hazards ratio, 1.62; p = 0.003). Longer activated partial thromboplastin time (hazards ratio, 0.98; p = 0.002) and decreased platelet count (hazards ratio, 1.19; p = 0.03) were associated with a reduced likelihood of circuit clotting. There was no difference in circuit life whether using blood flow rates of 250 or 150 mL/min during continuous renal replacement therapy.

Stabilization of flow past a rounded cylinder

NASA Astrophysics Data System (ADS)

Samtaney, Ravi; Zhang, Wei

2016-11-01

We perform global linear stability analysis on low-Re flow past a rounded cylinder. The cylinder corners are rounded with a radius R, normalized as R+ = R / D where D is the cylinder diameter, and its effect on the flow stability characteristics is investigated. We compute the critical Reynolds number (Recr) for the onset of first instability, and quantify the perturbation growth rate for the super-critical flows. It is found that the flow can be stabilized by partially rounding the cylinder. Compared with the square and circular cylinders, the partially rounded cylinder has a higher Recr , attaining a maximum at around R+ = 0 . 30 , and the perturbation growth rate of the super-critical flows is reduced for Re <= 100 . We perform sensitivity analysis to explore the source of the stabilization. The growth rate sensitivity to base flow modification has two different spatial structures: the growth rate is sensitive to the wake backflow in a large region for square-like cylinders (R+ -> 0 . 00), while only the near-wake backflow is crucial for circular-like cylinders (R+ -> 0 . 50). The stability analysis results are also verified with those of the direct simulations and very good agreement is achieved. Supported by the KAUST Office of Competitive Research Funds under Award No. URF/1/1394-01. The supercomputer Shaheen at KAUST was utilized for the simulations.

The effect of blood cell count on coronary flow in patients with coronary slow flow phenomenon

PubMed Central

Soylu, Korhan; Gulel, Okan; Yucel, Huriye; Yuksel, Serkan; Aksan, Gokhan; Soylu, Ayşegül İdil; Demircan, Sabri; Yılmaz, Özcan; Sahin, Mahmut

2014-01-01

Background and Objective: The coronary slow flow phenomenon (CSFP) is a coronary artery disease with a benign course, but its pathological mechanisms are not yet fully understood.The purpose of this controlled study was to investigate the cellular content of blood in patients diagnosed with CSFP and the relationship of this with coronary flow rates. Methods: Selective coronary angiographies of 3368 patients were analyzed to assess Thrombolysis in Myocardial Infarction (TIMI) frame count (TFC) values. Seventy eight of them had CSFP, and their demographic and laboratory findings were compared with 61 patients with normal coronary flow. Results: Patients’ demographic characteristics were similar in both groups. Mean corrected TFC (cTFC) values were significantly elevated in CSFP patients (p<0.001). Furthermore, hematocrit and hemoglobin values, and eosinophil and basophil counts of the CSFP patients were significantly elevated compared to the values obtained in the control group (p=0.005, p=0.047, p=0.001 and p=0.002, respectively). The increase observed in hematocrit and eosinophil levels showed significant correlations with increased TFC values (r=0.288 and r=0.217, respectively). Conclusion: Significant changes have been observed in the cellular composition of blood in patients diagnosed with CSFP as compared to the patients with normal coronary blood flow. The increases in hematocrit levels and in the eosinophil and basophil counts may have direct or indirect effects on the rate of coronary blood flow. PMID:25225502

Dancing to "groovy" music enhances the experience of flow.

PubMed

Bernardi, Nicolò F; Bellemare-Pepin, Antoine; Peretz, Isabelle

2018-05-06

We investigated whether dancing influences the emotional response to music, compared to when music is listened to in the absence of movement. Forty participants without previous dance training listened to "groovy" and "nongroovy" music excerpts while either dancing or refraining from movement. Participants were also tested while imitating their own dance movements, but in the absence of music as a control condition. Emotion ratings and ratings of flow were collected following each condition. Dance movements were recorded using motion capture. We found that the state of flow was increased specifically during spontaneous dance to groovy excerpts, compared with both still listening and motor imitation. Emotions in the realms of vitality (such as joy and power) and sublimity (such as wonder and nostalgia) were evoked by music in general, whether participants moved or not. Significant correlations were found between the emotional and flow responses to music and whole-body acceleration profiles. Thus, the results highlight a distinct state of flow when dancing, which may be of use to promote well-being and to address certain clinical conditions. © 2018 New York Academy of Sciences.

Intrahepatic Flow Redistribution in Patients Treated with Radioembolization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spreafico, Carlo, E-mail: carlo.spreafico@istitutotumori.mi.it; Morosi, Carlo, E-mail: carlo.morosi@istitutotumori.mi.it; Maccauro, Marco, E-mail: marco.maccauro@istitutotumori.mi.it

2015-04-15

IntroductionIn planning Yttrium-90 ({sup 90}Y)-radioembolizations, strategy problems arise in tumours with multiple arterial supplies. We aim to demonstrate that tumours can be treated via one main feeding artery achieving flow redistribution by embolizing accessory vessels.MethodsOne hundred {sup 90}Y-radioembolizations were performed on 90 patients using glass microspheres. In 19 lesions/17 patients, accessory branches were found feeding a minor tumour portion and embolized. In all 17 patients, the assessment of the complete perfusion was obtained by angiography and single photon emission computerized tomography–computerized tomography (SPECT–CT). Dosimetry, toxicity, and tumor response rate of the patients treated after flow redistribution were compared with themore » 83 standard-treated patients. Seventeen lesions in 15 patients with flow redistribution were chosen as target lesions and evaluated according to mRECIST criteria.ResultsIn all patients, the complete tumor perfusion was assessed immediately before radioembolization by angiography in all patients and after the {sup 90}Y-infusion by SPECT–CT in 15 of 17 patients. In the 15 assessable patients, the response rate in their 17 lesions was 3 CR, 8 PR, and 6 SD. Dosimetric and toxicity data, as well tumour response rate, were comparable with the 83 patients with regular vasculature.ConclusionsAll embolization procedures were performed successfully with no complications, and the flow redistribution was obtained in all cases. Results in term of toxicity, median dose administered, and radiological response were comparable with standard radioembolizations. Our findings confirmed the intratumoral flow redistribution after embolizing the accessory arteries, which makes it possible to treat the tumour through its single main feeding artery.« less

Spray Characteristics of a Hybrid Twin-Fluid Pressure-Swirl Atomizer

NASA Technical Reports Server (NTRS)

Durham, M. J.; Sojka, P. E.; Ashmore, C. B.

2004-01-01

The spray performance of a fuel injection system applicable for use in main combustion chamber of an oxidizer-rich staged combustion (ORSC) cycles is presented. The experimental data reported here include mean drop size and drop size distribution, spray cone half-angle, and momentum rate (directly related to spray penetration). The maximum entropy formalism, MEF, method to predict drop size distribution is applied and compared to the experimental data. Geometric variables considered include the radius of the injector inlet orifice plate through which oxidizer flows (&) and the exposed length from the fuel inlet to the injector exit plane (L2). Operating conditions that were varied include the liquid mass flow rate and air mass flow rate. For orifices B and C there is a significant dependence of D3Z on both the air and liquid mass flow rates, as well as on L2. For the A orifice, the momentum rate of the air flow appears to exceed a threshold value above which a constant D32 is obtained. Using the MEF method, a semi-analytical process was developed to model the spray distribution using two input parameters (q = 0.4 and Dso). The momentum rate of the spray is directly related to the air and liquid mass flow rates. The cone half angle of the spray ranges from 25 to 17 degrees. The data resulting from this project will eventually be used to develop advanced rocket systems.

Quantitative passive soil vapor sampling for VOCs--Part 4: Flow-through cell.

PubMed

McAlary, Todd; Groenevelt, Hester; Seethapathy, Suresh; Sacco, Paolo; Crump, Derrick; Tuday, Michael; Schumacher, Brian; Hayes, Heidi; Johnson, Paul; Parker, Louise; Górecki, Tadeusz

2014-05-01

This paper presents a controlled experiment comparing several quantitative passive samplers for monitoring concentrations of volatile organic compound (VOC) vapors in soil gas using a flow-through cell. This application is simpler than conventional active sampling using adsorptive tubes because the flow rate does not need to be precisely measured and controlled, which is advantageous because the permeability of subsurface materials affects the flow rate and the permeability of geologic materials is highly variable. Using passive samplers in a flow-through cell, the flow rate may not need to be known exactly, as long as it is sufficient to purge the cell in a reasonable time and minimize any negative bias attributable to the starvation effect. An experiment was performed in a 500 mL flow-through cell using a two-factor, one-half fraction fractional factorial test design with flow rates of 80, 670 and 930 mL min(-1) and sample durations of 10, 15 and 20 minutes for each of five different passive samplers (passive Automatic Thermal Desorption Tube, Radiello®, SKC Ultra, Waterloo Membrane Sampler™ and 3M™ OVM 3500). A Summa canister was collected coincident with each passive sampler and analyzed by EPA Method TO-15 to provide a baseline for comparison of the passive sampler concentrations. The passive sampler concentrations were within a factor of 2 of the Summa canister concentrations in 32 of 35 cases. Passive samples collected at the low flow rate and short duration showed low concentrations, which is likely attributable to insufficient purging of the cell after sampler placement.

Effect of Isometric Hand Grip Exercises on Blood Flow and Placement of IV Catheters for Administration of Chemotherapy.

PubMed

Ozkaraman, Ayse; Yesilbalkan, Öznur Usta

2016-04-01

Complications may occur in the subcutaneous or subdermal tissues during IV administration of chemotherapy related to blood flow and catheter placement. Daily isometric hand grip exercises were evaluated for their effect on blood flow in the vessels of the nondominant arm before placement of IV catheters and the success rate of IV catheter placement on the first attempt. The study focused on patients with non-Hodgkin lymphoma receiving the first and second cycles of chemotherapy. The intervention group performed daily isometric hand grip exercises before chemotherapy with peripheral catheter insertion. The control group performed routine activities only. Blood flow was measured by ultrasound in the brachial artery (BA) and brachial vein (BV) of the nondominant arm before the first (T1) and second (T2) cycles of chemotherapy. Blood flow slightly increased in the intervention group at T2 compared to T1. In the control group, blood flow decreased in the BA and did not change in the BV at T2 compared to T1. The success rate for first-attempt placement of a peripheral IV catheter was the same for the intervention and control groups.

A multiple-time-scale turbulence model based on variable partitioning of turbulent kinetic energy spectrum

NASA Technical Reports Server (NTRS)

Kim, S.-W.; Chen, C.-P.

1987-01-01

A multiple-time-scale turbulence model of a single point closure and a simplified split-spectrum method is presented. In the model, the effect of the ratio of the production rate to the dissipation rate on eddy viscosity is modeled by use of the multiple-time-scales and a variable partitioning of the turbulent kinetic energy spectrum. The concept of a variable partitioning of the turbulent kinetic energy spectrum and the rest of the model details are based on the previously reported algebraic stress turbulence model. Example problems considered include: a fully developed channel flow, a plane jet exhausting into a moving stream, a wall jet flow, and a weakly coupled wake-boundary layer interaction flow. The computational results compared favorably with those obtained by using the algebraic stress turbulence model as well as experimental data. The present turbulence model, as well as the algebraic stress turbulence model, yielded significantly improved computational results for the complex turbulent boundary layer flows, such as the wall jet flow and the wake boundary layer interaction flow, compared with available computational results obtained by using the standard kappa-epsilon turbulence model.

A multiple-time-scale turbulence model based on variable partitioning of the turbulent kinetic energy spectrum

NASA Technical Reports Server (NTRS)

Kim, S.-W.; Chen, C.-P.

1989-01-01

A multiple-time-scale turbulence model of a single point closure and a simplified split-spectrum method is presented. In the model, the effect of the ratio of the production rate to the dissipation rate on eddy viscosity is modeled by use of the multiple-time-scales and a variable partitioning of the turbulent kinetic energy spectrum. The concept of a variable partitioning of the turbulent kinetic energy spectrum and the rest of the model details are based on the previously reported algebraic stress turbulence model. Example problems considered include: a fully developed channel flow, a plane jet exhausting into a moving stream, a wall jet flow, and a weakly coupled wake-boundary layer interaction flow. The computational results compared favorably with those obtained by using the algebraic stress turbulence model as well as experimental data. The present turbulence model, as well as the algebraic stress turbulence model, yielded significantly improved computational results for the complex turbulent boundary layer flows, such as the wall jet flow and the wake boundary layer interaction flow, compared with available computational results obtained by using the standard kappa-epsilon turbulence model.

Effect of surface roughness on the heating rates of large-angled hypersonic blunt cones

NASA Astrophysics Data System (ADS)

Irimpan, Kiran Joy; Menezes, Viren

2018-03-01

Surface-roughness caused by the residue of an ablative Thermal Protection System (TPS) can alter the turbulence level and surface heating rates on a hypersonic re-entry capsule. Large-scale surface-roughness that could represent an ablated TPS, was introduced over the forebody of a 120° apex angle blunt cone, in order to test for its influence on surface heating rates in a hypersonic freestream of Mach 8.8. The surface heat transfer rates measured on smooth and roughened models under the same freestream conditions were compared. The hypersonic flow-fields of the smooth and rough-surfaced models were visualized to analyse the flow physics. Qualitative numerical simulations and pressure measurements were carried out to have an insight into the high-speed flow physics. Experimental observations under moderate Reynolds numbers indicated a delayed transition and an overall reduction of 17-46% in surface heating rates on the roughened model.

Evaluation of a turbine flow meter (Ventilometer Mark 2) in the measurement of ventilation.

PubMed

Cooper, C B; Harris, N D; Howard, P

1990-01-01

We have evaluated a turbine flow meter (Ventilometer Mark 2, PK Morgan, Kent, UK) at low flow rates and levels of ventilation which are likely to be encountered during exercise in patients with chronic respiratory disease. Pulsatile flows were generated from a volume-cycled mechanical ventilator, the flow wave-form was modified by damping to simulate a human breathing pattern. Comparative measurements of ventilation were made whilst varying tidal volume (VT) from 0.22 to 1.131 and respiratory rate (fR) from 10 to 35 min-1. At lower levels of ventilation the instrument tended to underread especially with increasing fR. The calibration factor must be adjusted to match the level of ventilation if the measurement errors are to be within 5%.

Effects of surface coal mining and reclamation on the geohydrology of six small watersheds in west-central Indiana

USGS Publications Warehouse

Martin, Jeffrey D.; Duwelius, Richard F.; Crawford, Charles G.

1987-01-01

The watersheds studied include mined and reclaimed; mined and unreclaimed; and unmined, agricultural land uses, and are each < 3 sq mi in area. Surface water, groundwater, and meteorologic data for the 1981 and 1982 water years were used to describe and compare hydrologic systems of the six watersheds and to identify hydrologic effects of mining and reclamation. Peak discharges were greater at the agricultural watersheds than at the unreclaimed watersheds, primarily because of large final-cut lakes in the unreclaimed watersheds. Annual runoff was greatest at the unreclaimed watersheds, intermediate at the agricultural watersheds, and least at the reclaimed watersheds. Hydrologic effects of mining were identified by comparing the hydrologic systems at mined and unreclaimed watersheds with those at unmined, agricultural watersheds. Comparisons of the hydrologic systems of these watersheds indicate that surface coal mining without reclamation has the potential to increase annual runoff, base flow, and groundwater recharge to the bedrock; reduce peak flow rates and variation in flow; lower the water table in upland areas; change the relation between surface water and groundwater divides; and create numerous, local flow systems in the shallow groundwater. Hydrologic effects of reclamation were identified by comparing the hydrologic systems at mined and reclaimed watersheds with those at mined and unreclaimed watersheds. Reclamation has the potential to decrease annual runoff, base flow, and recharge to the bedrock; increase peak flow rates, variation in flow, and response to thunderstorms; reestablish the premining relation between surface and groundwater divides; and create fewer local flow systems in the shallow groundwater. (Lantz-PTT)

A Modified Mechanical Threshold Stress Constitutive Model for Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Prasad, K. Sajun; Gupta, Amit Kumar; Singh, Yashjeet; Singh, Swadesh Kumar

2016-12-01

This paper presents a modified mechanical threshold stress (m-MTS) constitutive model. The m-MTS model incorporates variable athermal and dynamic strain aging (DSA) Components to accurately predict the flow stress behavior of austenitic stainless steels (ASS)-316 and 304. Under strain rate variations between 0.01-0.0001 s-1, uniaxial tensile tests were conducted at temperatures ranging from 50-650 °C to evaluate the material constants of constitutive models. The test results revealed the high dependence of flow stress on strain, strain rate and temperature. In addition, it was observed that DSA occurred at elevated temperatures and very low strain rates, causing an increase in flow stress. While the original MTS model is capable of predicting the flow stress behavior for ASS, statistical parameters point out the inefficiency of the model when compared to other models such as Johnson Cook model, modified Zerilli-Armstrong (m-ZA) model, and modified Arrhenius-type equations (m-Arr). Therefore, in order to accurately model both the DSA and non-DSA regimes, the original MTS model was modified by incorporating variable athermal and DSA components. The suitability of the m-MTS model was assessed by comparing the statistical parameters. It was observed that the m-MTS model was highly accurate for the DSA regime when compared to the existing models. However, models like m-ZA and m-Arr showed better results for the non-DSA regime.

A stage-normalized function for the synthesis of stage-discharge relations for the Colorado River in Grand Canyon, Arizona

USGS Publications Warehouse

Wiele, Stephen M.; Torizzo, Margaret

2003-01-01

A method was developed to construct stage-discharge rating curves for the Colorado River in Grand Canyon, Arizona, using two stage-discharge pairs and a stage-normalized rating curve. Stage-discharge rating curves formulated with the stage-normalized curve method are compared to (1) stage-discharge rating curves for six temporary stage gages and two streamflow-gaging stations developed by combining stage records with modeled unsteady flow; (2) stage-discharge rating curves developed from stage records and discharge measurements at three streamflow-gaging stations; and (3) stages surveyed at known discharges at the Northern Arizona Sand Bar Studies sites. The stage-normalized curve method shows good agreement with field data when the discharges used in the construction of the rating curves are at least 200 cubic meters per second apart. Predictions of stage using the stage-normalized curve method are also compared to predictions of stage from a steady-flow model.

Absent end diastolic flow of umbilical artery Doppler: pregnancy outcome in 62 cases.

PubMed

Poulain, P; Palaric, J C; Milon, J; Betremieux, P; Proudhon, J F; Signorelli, D; Grall, J Y; Giraud, J R

1994-02-01

We retrospectively studied the outcome of pregnancy in 62 cases of absent end diastolic flow (AEDF) of umbilical artery Doppler flow velocity waveform. The history of pregnancies revealed that nearly all were of high risk. Many cases presented cerebral (65%) or uterine (55.5%) Doppler flow abnormalities, or both (38%). We noted 10 fetal deaths and decided 7 pregnancy terminations. Malformation and chromosomal defect rate was 16%. We noted 44 (71%) live-births, a very high rate of cesarean section (86%), prematurity (75%), small for gestational age (39%). Forty-five percent of the neonates had a 1-min Apgar score under 7, which dropped to 27% at 5 min. Neonate mortality rate was 6.9% and the total mortality rate was 34% (21/62). Morbidity was significant (7 cases with severe morbidity, 2 cases with chromosomal abnormality of poor prognosis). We compared different sub-groups with a view to looking for some prenatal factors which predict poor neonatal outcome in case of AEDF.

Evaluation of salivary glucose, IgA and flow rate in diabetic patients: a case-control study.

PubMed

Bakianian Vaziri, P; Vahedi, M; Mortazavi, H; Abdollahzadeh, Sh; Hajilooi, M

2010-01-01

An association between diabetes mellitus and alterations in the oral cavity has been noted. In this study, we evaluated differences between salivary IgA, glucose and flow rate in diabetic patients compared with healthy controls. Forty patients with type 1 diabetes, 40 patients with type 2 diabetes and 40 healthy controls were selected. Whole unstimulated saliva samples were collected by the standard method and the salivary flow rate was determined. Nephelometric and Pars method were used to measure salivary IgA and salivary glucose concentrations, respectively. Statistical analysis was performed by Chi-square and t test. There were no significant differences in salivary IgA and glucose concentrations between type 1 and type 2 diabetic patients and their matched control subjects (P>0.05). Salivary flow rate was significantly lower in diabetic patients (P<0.05). In addition, DMFT was higher in diabetic patients than the controls. Determination of salivary constituents may be useful in the description and management of oral findings in diabetic patients.

Relationship between salivary flow rates and Candida albicans counts.

PubMed

Navazesh, M; Wood, G J; Brightman, V J

1995-09-01

Seventy-one persons (48 women, 23 men; mean age, 51.76 years) were evaluated for salivary flow rates and Candida albicans counts. Each person was seen on three different occasions. Samples of unstimulated whole, chewing-stimulated whole, acid-stimulated parotid, and candy-stimulated parotid saliva were collected under standardized conditions. An oral rinse was also obtained and evaluated for Candida albicans counts. Unstimulated and chewing-stimulated whole flow rates were negatively and significantly (p < 0.001) related to the Candida counts. Unstimulated whole saliva significantly (p < 0.05) differed in persons with Candida counts of 0 versus <500 versus < or = 500. Chewing-stimulated saliva was significantly (p < 0.05) different in persons with 0 counts compared with those with a > or = 500 count. Differences in stimulated parotid flow rates were not significant among different levels of Candida counts. The results of this study reveal that whole saliva is a better predictor than parotid saliva in identification of persons with high Candida albicans counts.

The evaluation of dentinal tubule occlusion by desensitizing agents: a real-time measurement of dentinal fluid flow rate and scanning electron microscopy.

PubMed

Kim, S Y; Kim, E J; Kim, D S; Lee, I B

2013-01-01

The aims of this study were to examine changes in dentinal fluid flow (DFF) during the application of a desensitizing agent and to compare the permeability reduction levels among different types of desensitizing agents. A cervical cavity was prepared for the exposure of cervical dentin on an extracted human premolar connected to a subnanoliter fluid flow measuring device under 20 cm of water pressure. The cavity was acid-etched with 32% phosphoric acid to make dentin highly permeable. The different types of desensitizing agents that were applied on the cavity were Seal&Protect as the light-curing adhesive type, SuperSeal and BisBlock as oxalate types, Gluma Desensitizer as the protein-precipitation type, and Bi-Fluoride 12 as the fluoride type. DFF was measured from the time before the application of the desensitizing agent throughout the application procedure to five minutes after the application. The characteristics of dentinal tubule occlusion of each desensitizing agent were examined by scanning electron microscopy. The DFF rate after each desensitizing agent application was significantly reduced when compared to the initial DFF rate before application for all of the desensitizing agents (p<0.05). Seal&Protect showed a greater reduction in the DFF rate when compared to Gluma Desensitizer and Bi-Fluoride 12 (p<0.05). SuperSeal and BisBlock exhibited a greater reduction in DFF rate when compared to Bi-Fluoride 12 (p<0.05). The dentin hypersensitivity treatment effects of the employed desensitizing agents in this study were confirmed through real-time measurements of DFF changes. The light-curing adhesive and oxalate types showed greater reduction in the DFF rate than did the protein-precipitation and fluoride types.

[Characters of infiltration and preferential flow of black soil in Northeast China under different tillage patterns].

PubMed

Li, Wen-Feng; Zhang, Xiao-Ping; Liang, Ai-Zhen; Shen, Yan; Shi, Xiu-Huan; Luo, Jin-Ming; Yang, Xue-Ming

2008-07-01

By using dye tracer and double-ring infiltrometer techniques, the characters of infiltration and preferential flow of black soil under no-tillage (NT) and fall moldboard plow (MP) were compared after six years continuous management. The results showed that the infiltration rate was higher under NT than under MP. When the infiltration reached steady, the infiltration rate and accumulative infiltration capacity under NT were 1.35 and 1.44 times as high as those under MP, respectively. The penetration depth of methylene blue reached a depth of 43 cm in NT soil, being 16 cm deeper than that in MP soil. Comparing with MP soil, NT soil had better development of pore structure and more biological pores, and presented better preferential flow character, which were of importance for water infiltration and soil and water conservation.

A novel compact heat exchanger using gap flow mechanism.

PubMed

Liang, J S; Zhang, Y; Wang, D Z; Luo, T P; Ren, T Q

2015-02-01

A novel, compact gap-flow heat exchanger (GFHE) using heat-transfer fluid (HTF) was developed in this paper. The detail design of the GFHE coaxial structure which forms the annular gap passage for HTF is presented. Computational fluid dynamics simulations were introduced into the design to determine the impacts of the gap width and the HTF flow rate on the GFHE performance. A comparative study on the GFHE heating rate, with the gap widths ranged from 0.1 to 1.0 mm and the HTF flow rates ranged from 100 to 500 ml/min, was carried out. Results show that a narrower gap passage and a higher HTF flow rate can yield a higher average heating rate in GFHE. However, considering the compromise between the GFHE heating rate and the HTF pressure drop along the gap, a 0.4 mm gap width is preferred. A testing loop was also set up to experimentally evaluate the GFHE capability. The testing results show that, by using 0.4 mm gap width and 500 ml/min HTF flow rate, the maximum heating rate in the working chamber of the as-made GFHE can reach 18 °C/min, and the average temperature change rates in the heating and cooling processes of the thermal cycle test were recorded as 6.5 and 5.4 °C/min, respectively. These temperature change rates can well satisfy the standard of IEC 60068-2-14:2009 and show that the GFHE developed in this work has sufficient heat exchange capacity and can be used as an ideal compact heat exchanger in small volume desktop thermal fatigue test apparatus.

Ductile crustal flow in Europe's lithosphere

NASA Astrophysics Data System (ADS)

Tesauro, Magdala; Burov, Evgene B.; Kaban, Mikhail K.; Cloetingh, Sierd A. P. L.

2011-12-01

Potential gravity theory (PGT) predicts the presence of significant gravity-induced horizontal stresses in the lithosphere associated with lateral variations in plate thickness and composition. New high resolution crustal thickness and density data provided by the EuCRUST-07 model are used to compute the associated lateral pressure gradients (LPG), which can drive horizontal ductile flow in the crust. Incorporation of these data in channel flow models allows us to use potential gravity theory to assess horizontal mass transfer and stress transmission within the European crust. We explore implications of the channel flow concept for a possible range of crustal strength, using end-member 'hard' and 'soft' crustal rheologies to estimate strain rates at the bottom of the ductile crustal layers. The models show that the effects of channel flow superimposed on the direct effects of plate tectonic forces might result in additional significant horizontal and vertical movements associated with zones of compression or extension. To investigate relationships between crustal and mantle lithospheric movements, we compare these results with the observed directions of mantle lithospheric anisotropy and GPS velocity vectors. We identify areas whose evolution could have been significantly affected by gravity-driven ductile crustal flow. Large values of the LPG are predicted perpendicular to the axes of European mountain belts, such as the Alps, Pyrenees-Cantabrian Mountains, Dinarides-Hellenic arc and Carpathians. In general, the crustal flow is directed away from orogens towards adjacent weaker areas. Gravitational forces directed from areas of high gravitational potential energy to subsiding basin areas can strongly reduce lithospheric extension in the latter, leading to a gradual late stage inversion of the entire system. Predicted pressure and strain rate gradients suggest that gravity driven flow may play an essential role in European intraplate tectonics. In particular, in a number of regions the predicted strain rates are comparable to tectonically induced strain rates. These results are also important for quantifying the thickness of the low viscosity zones in the lowermost part of the crustal layers.

Flow distribution analysis on the cooling tube network of ITER thermal shield

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nam, Kwanwoo; Chung, Wooho; Noh, Chang Hyun

2014-01-29

Thermal shield (TS) is to be installed between the vacuum vessel or the cryostat and the magnets in ITER tokamak to reduce the thermal radiation load to the magnets operating at 4.2K. The TS is cooled by pressurized helium gas at the inlet temperature of 80K. The cooling tube is welded on the TS panel surface and the composed flow network of the TS cooling tubes is complex. The flow rate in each panel should be matched to the thermal design value for effective radiation shielding. This paper presents one dimensional analysis on the flow distribution of cooling tube networkmore » for the ITER TS. The hydraulic cooling tube network is modeled by an electrical analogy. Only the cooling tube on the TS surface and its connecting pipe from the manifold are considered in the analysis model. Considering the frictional factor and the local loss in the cooling tube, the hydraulic resistance is expressed as a linear function with respect to mass flow rate. Sub-circuits in the TS are analyzed separately because each circuit is controlled by its own control valve independently. It is found that flow rates in some panels are insufficient compared with the design values. In order to improve the flow distribution, two kinds of design modifications are proposed. The first one is to connect the tubes of the adjacent panels. This will increase the resistance of the tube on the panel where the flow rate is excessive. The other design suggestion is that an orifice is installed at the exit of tube routing where the flow rate is to be reduced. The analysis for the design suggestions shows that the flow mal-distribution is improved significantly.« less

Experimental investigation of gas flow rate and electric field effect on refractive index and electron density distribution of cold atmospheric pressure-plasma by optical method, Moiré deflectometry

NASA Astrophysics Data System (ADS)

Khanzadeh, Mohammad; Jamal, Fatemeh; Shariat, Mahdi

2018-04-01

Nowadays, cold atmospheric-pressure (CAP) helium plasma jets are widely used in material processing devices in various industries. Researchers often use indirect and spectrometric methods for measuring the plasma parameters which are very expensive. In this paper, for the first time, characterization of CAP, i.e., finding its parameters such as refractive index and electron density distribution, was carried out using an optical method, Moiré deflectometry. This method is a wave front analysis technique based on geometric optics. The advantages of this method are simplicity, high accuracy, and low cost along with the non-contact, non-destructive, and direct measurement of CAP parameters. This method demonstrates that as the helium gas flow rate decreases, the refractive index increases. Also, we must note that the refractive index is larger in the gas flow consisting of different flow rates of plasma comparing with the gas flow without the plasma.

Plasma Free Hemoglobin Generation Using the EOS PMP™ Oxygenator and the CentriMag® Blood Pump.

PubMed

Hodge, Ashley B; Deitemyer, Matthew A; Duffy, Victoria L; Tumin, Dmitry; Garbin, Dorothy A; Nicol, Kathleen K; Hayes, Don; Cismowski, Mary J; Yates, Andrew R

2018-06-01

Hemolysis is a known consequence of extracorporeal membrane oxygenation (ECMO) resulting from shear force within the different components of the extracorporeal circuit. The primary aim of this study was to evaluate the EOS PMP ™ oxygenator for generation of plasma free hemoglobin (PfHg) over 24 hours at nominal operating range flow rates. The EOS ECMO ™ (LivaNova, Inc.; formerly Sorin, Arvada, CO) is equipped with a plasma tight polymethylpentene (PMP) hollow fiber oxygenator. We hypothesized that PfHg generation would be elevated in circuits with higher flow rates, because of the significant pressure drop across the oxygenator according to manufacturer provided flow charts. Generated PfHg concentrations were compared with PfHg concentrations from blood not exposed to an ECMO circuit. The secondary aim was to evaluate circuit flow-rate-induced changes in platelet count and platelet function over 24 hours. Circuits contained a CentriMag ® (St. Jude Medical, St. Paul, MN) blood pump and an EOS ECMO PMP ™ oxygenator. Circuits in triplicate were run continuously for 24 hours at three flow rates [1, 3, and 5 liters per minute {LPM}]. PfHg was analyzed at baseline, 6, 12, 18, and 24 hours. Platelet count and function were measured at baseline and 24 hours. Concentrations of PfHg at baseline for circuits operating at 1, 3, and 5 LPM were 24.4 ± 4.0, 38.4 ± 28.6, and 26.7 ± 6.9 mg/dL, respectively. PfHg concentrations after 24 hours were statistically compared for the three flow rates using analysis of variance; PfHg concentrations at 1 LPM (181.4 ± 29.1 mg/dL), 3 LPM (145.9 ± 8.7 mg/dL), and 5 LPM (100.1 ± 111.3 mg/dL) circuits. The F -test was not statistically significant ( p = .632), indicating that PfHg generation at 24 hours was similar among the three flow rates. Excessive hemolysis using PfHg levels in the EOS PMP ™ membrane oxygenator was not observed.

CHARACTERIZATION OF FLOW-RESISTANT TUBES USED FOR SEMI-OCCLUDED VOCAL TRACT VOICE TRAINING AND THERAPY

PubMed Central

Smith, Simeon L.; Titze, Ingo R.

2016-01-01

Objectives To characterize the pressure-flow relationship of tubes used for semi-occluded vocal tract voice training/therapy, as well as to answer these major questions: (1) What is the relative importance of tube length to tube diameter? (2) What is the range of oral pressures achieved with tubes at phonation flow rates? (3) Does mouth configuration behind the tubes matter? Methods Plastic tubes of various diameters and lengths were mounted in line with an upstream pipe, and the pressure drop across each tube was measured at stepwise increments in flow rate. Basic flow theory and modified flow theory equations were used to describe the pressure-flow relationship of the tubes based on diameter and length. Additionally, the upstream pipe diameter was varied to explore how mouth shape affects tube resistance. Results The modified equation provided an excellent prediction of the pressure-flow relationship across all tube sizes (6% error compared to the experimental data). Variation in upstream pipe diameter yielded up to 10% deviation in pressure for tube sizes typically used in voice training/therapy. Conclusions Using the presented equations, resistance can be characterized for any tube based on diameter, length, and flow rate. With regard to the original questions, we found that: (1) For commonly used tubes, diameter is the critical variable for governing flow resistance; (2) For phonation flow rates, a range of tube dimensions produced pressures between 0 and 7.0 kPa; (3) The mouth pressure behind the lips will vary slightly with different mouth shapes, but this effect can be considered relatively insignificant. PMID:27133001

Computational fluid dynamics modeling of gas dispersion in multi impeller bioreactor.

PubMed

Ahmed, Syed Ubaid; Ranganathan, Panneerselvam; Pandey, Ashok; Sivaraman, Savithri

2010-06-01

In the present study, experiments have been carried out to identify various flow regimes in a dual Rushton turbines stirred bioreactor for different gas flow rates and impeller speeds. The hydrodynamic parameters like fractional gas hold-up, power consumption and mixing time have been measured. A two fluid model along with MUSIG model to handle polydispersed gas flow has been implemented to predict the various flow regimes and hydrodynamic parameters in the dual turbines stirred bioreactor. The computational model has been mapped on commercial solver ANSYS CFX. The flow regimes predicted by numerical simulations are validated with the experimental results. The present model has successfully captured the flow regimes as observed during experiments. The measured gross flow characteristics like fractional gas hold-up, and mixing time have been compared with numerical simulations. Also the effect of gas flow rate and impeller speed on gas hold-up and power consumption have been investigated. (c) 2009 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Excitation of nonlinear wave patterns in flowing complex plasmas

NASA Astrophysics Data System (ADS)

Jaiswal, S.; Bandyopadhyay, P.; Sen, A.

2018-01-01

We describe experimental observations of nonlinear wave structures excited by a supersonic mass flow of dust particles over an electrostatic potential hill in a dusty plasma medium. The experiments have been carried out in a Π- shaped experimental (DPEx) device in which micron sized Kaolin particles are embedded in a DC glow discharge Argon plasma. An equilibrium dust cloud is formed by maintaining the pumping speed and gas flow rate and the dust flow is induced either by suddenly reducing the height of a potential hill or by suddenly reducing the gas flow rate. For a supersonic flow of the dust fluid precursor solitons are seen to propagate in the upstream direction while wake structures propagate in the downstream direction. For flow speeds with a Mach number greater than 2 the dust particles flowing over the potential hill give rise to dispersive dust acoustic shock waves. The experimental results compare favorably with model theories based on forced K-dV and K-dV Burger's equations.

Numerical simulation of calcium sulfate (CaSO4) fouling in the plate heat exchanger

NASA Astrophysics Data System (ADS)

Xu, Zhiming; Zhao, Yu; Han, Zhimin; Wang, Jingtao

2018-07-01

Plate heat exchanger is a widely used apparatus in the industrial production processes. Through a numerical simulation method, this paper calculates the deposition rate of CaSO4 fouling on heat transfer surfaces of the plate heat exchanger under saturation in the bulk. The effects of CaSO4 concentration in the range 0.7 kg/m3 to 1.5 kg/m3, inlet flow velocity under turbulent flow, and the fluid's inlet temperature from 288 K to 328 K on the deposition rate, removal mass rate and fouling resistance are investigated. The simulation results are compared with the experimental results showing similar trend. The simulation results show that the concentration and the flow velocity affect significantly the fouling characteristics in the plate heat exchanger. The deposition mass rate, removal mass rate, and asymptotic value of fouling resistance all increase with the increase in CaSO4 concentration and the inlet temperature of the hot fluid, while the asymptotic value of fouling resistance decreases with the increasing of inlet flow velocity. The influence of the inlet temperature of cold fluid may be negligible.

Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on earth

NASA Technical Reports Server (NTRS)

Komar, P. D.

1979-01-01

The hydraulics of channelized water flows on Mars and the resulting sediment transport rates are calculated, and similar computations are performed for such terrestrial analogs as the Mississippi River and the catastrophic Lake Missoula floods that formed the Channeled Scabland in eastern Washington State. The morphologies of deep-sea channels formed by catastrophic turbidity currents are compared with the Martian channels, many similarities are pointed out, and the hydraulics of the various flows are compared. The results indicate that the velocities, discharges, bottom shear stresses, and sediment-transport capacity of water flows along the Martian channels would be comparable to those of the oceanic turbidity currents and the Lake Missoula floods. It is suggested that the submarine canyons from which turbidity currents originate are the terrestrial counterparts to the chaotic-terrain areas or craters that serve as sources for many of the Martian channels.

Fixed Packed Bed Reactors in Reduced Gravity

NASA Technical Reports Server (NTRS)

Motil, Brian J.; Balakotaiah, Vemuri; Kamotani, Yasuhiro; McCready, Mark J.

2004-01-01

We present experimental data on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid flow through packed columns in microgravity. The flow pattern transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under microgravity conditions compared to 1-g and the widely used Talmor map in 1-g is not applicable for predicting the transition boundaries. A new transition criterion between bubble and pulse flow in microgravity is proposed and tested using the data. Since there is no static head in microgravity, the pressure drop measured is the true frictional pressure drop. The pressure drop data, which has much smaller scatter than most reported 1-g data clearly shows that capillary effects can enhance the pressure drop (especially in the bubble flow regime) as much as 200% compared to that predicted by the single phase Ergun equation. The pressure drop data are correlated in terms of a two-phase friction factor and its dependence on the gas and liquid Reynolds numbers and the Suratman number. The influence of gravity on the pulse amplitude and frequency is also discussed and compared to that under normal gravity conditions. Experimental work is planned to determine the gas-liquid and liquid-solid mass transfer coefficients. Because of enhanced interfacial effects, we expect the gas-liquid transfer coefficients kLa and kGa (where a is the gas-liquid interfacial area) to be higher in microgravity than in normal gravity at the same flow conditions. This will be verified by gas absorption experiments, with and without reaction in the liquid phase, using oxygen, carbon dioxide, water and dilute aqueous amine solutions. The liquid-solid mass transfer coefficient will also be determined in the bubble as well as the pulse flow regimes using solid benzoic acid particles in the packing and measuring their rate of dissolution. The mass transfer coefficients in microgravity will be compared to those in normal gravity cocurrent flow to determine the mass transfer enhancement and propose new mass transfer correlations for two-phase gas-liquid flows through packed beds in microgravity.

Fixed Packed Bed Reactors in Reduced Gravity

NASA Technical Reports Server (NTRS)

Motil, Brian J.; Balakotaiah, Vemuri; Kamotani, Yasuhiro; McCready, Mark J.

2004-01-01

We present experimental data on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid flow through packed columns in microgravity. The flow pattern transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under microgravity conditions compared to 1-g and the widely used Talmor map in 1-g is not applicable for predicting the transition boundaries. A new transition criterion between bubble and pulse flow in microgravity is proposed and tested using the data. Since there is no static head in microgravity, the pressure drop measured is the true frictional pressure drop. The pressure drop data, which has much smaller scatter than most reported 1-g data clearly shows that capillary effects can enhance the pressure drop (especially in the bubble flow regime) as much as 200% compared to that predicted by the single phase Ergun equation. The pressure drop data are correlated in terms of a two-phase friction factor and its dependence on the gas and liquid Reynolds numbers and the Suratman number. The influence of gravity on the pulse amplitude and frequency is also discussed and compared to that under normal gravity conditions. Experimental work is planned to determine the gas-liquid mass transfer coefficients. Because of enhanced interfacial effects, we expect the gas-liquid transfer coefficients k(L)a and k(G)a (where a is the gas-liquid interfacial area) to be higher in microgravity than in normal gravity at the same flow conditions. This will be verified by gas absorption experiments, with and without reaction in the liquid phase, using oxygen, carbon dioxide, water and dilute aqueous amine solutions. The liquid-solid mass transfer coefficient will also be determined in the bubble as well as the pulse flow regimes using solid benzoic acid particles in the packing and measuring their rate of dissolution. The mass transfer coefficients in microgravity will be compared to those in normal gravity cocurrent flow to determine the mass transfer enhancement and propose new mass transfer correlations for two-phase gas-liquid flows through packed beds in microgravity.

A Particle Representation Model for the Deformation of Homogeneous Turbulence

NASA Technical Reports Server (NTRS)

Kassinos, S. C.; Reynolds, W. C.

1996-01-01

In simple flows, where the mean deformation rates are mild and the turbulence has time to come to equilibrium with the mean flow, the Reynolds stresses are determined by the applied strain rate. Hence in these flows, it is often adequate to use an eddy-viscosity representation. The modern family of kappa-epsilon models has been very useful in predicting near equilibrium turbulent flows, where the rms deformation rate S is small compared to the reciprocal time scale of the turbulence (epsilon/kappa). In modern engineering applications, turbulence models are quite often required to predict flows with very rapid deformations (large S kappa/epsilon). In these flows, the structure takes some time to respond and eddy viscosity models are inadequate. The response of turbulence to rapid deformations is given by rapid distortion theory (RDT). Under RDT the nonlinear effects due to turbulence-turbulence interactions are neglected in the governing equations, but even when linearized in this fashion, the governing equations are unclosed at the one-point level due to the non-locality of the pressure fluctuations.

Nuclear magnetic resonance characterization of the stationary dynamics of partially saturated media during steady-state infiltration flow

NASA Astrophysics Data System (ADS)

Rassi, Erik M.; Codd, Sarah L.; Seymour, Joseph D.

2011-01-01

Flow in porous media and the resultant hydrodynamics are important in fields including but not limited to the hydrology, chemical, medical and petroleum industries. The observation and understanding of the hydrodynamics in porous media are critical to the design and optimal utilization of porous media, such as those seen in trickle-bed reactors, medical filters, subsurface flows and carbon sequestration. Magnetic resonance (MR) provides for a non-invasive technique that can probe the hydrodynamics on pore and bulk scale lengths; many previous works have characterized fully saturated porous media, while rapid MR imaging (MRI) methods in particular have previously been applied to partially saturated flows. We present time- and ensemble-averaged MR measurements to observe the effects on a bead pack partially saturated with air under flowing water conditions. The 10 mm internal diameter bead pack was filled with 100 μm borosilicate glass beads. Air was injected into the bead pack as water flowed simultaneously through the sample at 25 ml h-1. The initial partially saturated state was characterized with MRI density maps, free induction decay (FID) experiments, propagators and velocity maps before the water flow rate was increased incrementally from 25 to 500 ml h-1. After the maximum flow rate of 500 ml h-1, the MRI density maps, FID experiments, propagators and velocity maps were repeated and compared to the data taken before the maximum flow rate. This work shows that a partially saturated single-phase flow has global flow dynamics that return to characteristic flow statistics once a steady-state high flow rate has been reached. This high flow rate pushed out a significant amount of the air in the bead pack and caused the return of a preferential flow pattern. Velocity maps indicated that local flow statistics were not the same for the before and after blow out conditions. It has been suggested and shown previously that a flow pattern can return to similar statistics if the preceding flow history is similar.

Inflated flows on Daedalia Planum (Mars)? Clues from a comparative analysis with the Payen volcanic complex (Argentina)

NASA Astrophysics Data System (ADS)

Giacomini, L.; Massironi, M.; Martellato, E.; Pasquarè, G.; Frigeri, A.; Cremonese, G.

2009-05-01

Inflation is an emplacement process of lava flows, where a thin visco-elastic layer, produced at an early stage, is later inflated by an underlying fluid core. The core remains hot and fluid for extended period of time due to the thermal-shield effect of the surface visco-elastic crust. Plentiful and widespread morphological fingerprints of inflation like tumuli and lava rises are found on the Payen volcanic complex (Argentina), where pahoehoe lava flows extend over the relatively flat surface of the Pampean foreland and reach at least 180 km in length. The morphology of the Argentinean Payen flows were compared with lava flows on Daedalia Planum (Mars), using Thermal Emission Imaging System (THEMIS), Mars Orbiter Laser Altimeter (MOLA), Mars Orbiter Camera (MOC), Mars Reconnaissance Orbiter (MRO)/High-Resolution Imaging Science Experiment (HiRISE). THEMIS images were used to map the main geological units of Daedalia Planum and determine their stratigraphic relationships. MOLA data were used to investigate the topographic surface over which the flows propagated and assess the thickness of lava flows. Finally, MOC and MRO/HIRISE images were used to identify inflations fingerprints and assess the cratering age of the Daedalia Planum' s youngest flow unit which were found to predate the caldera formation on top of the Arsia Mons. The identification of similar inflation features between the Daedalia Planum and the Payen lava fields suggests that moderate and long lasting effusion rates coupled with very efficient spreading processes could have cyclically occurred in the Arsia Mons volcano during its eruptive history. Consequently the effusion rates and rheological proprieties of Daedalia lava flows, which do not take into account the inflation process, can be overestimated. These findings raise some doubts about the effusion rates and lava rheological properties calculated on Martian flows and recommends that these should be used with caution if applied on flows not checked with high-resolution images and potentially affected by inflation. Further HiRISE data acquisition will permit additional analysis of the flow surfaces and will allow more accurate estimates of effusion rates and rheological properties of the lava flows on Mars particularly if this data is acquired under a favourable illumination.

Flow-directed loading of block copolymer micelles with hydrophobic probes in a gas-liquid microreactor.

PubMed

Wang, Chih-Wei; Bains, Aman; Sinton, David; Moffitt, Matthew G

2013-07-02

We investigate the loading efficiencies of two chemically distinct hydrophobic fluorescent probes, pyrene and naphthalene, for self-assembly and loading of polystyrene-block-poly(acrylic acid) (PS-b-PAA) micelles in gas-liquid segmented microfluidic reactors under different chemical and flow conditions. On-chip loading efficiencies are compared to values obtained via off-chip dropwise water addition to a solution of copolymer and probe. On-chip, probe loading efficiencies depend strongly on the chemical probe, initial solvent, water content, and flow rate. For pyrene and naphthalene probes, maximum on-chip loading efficiencies of 73 ± 6% and 11 ± 3%, respectively, are obtained, in both cases using the more polar solvent (DMF), an intermediate water content (2 wt % above critical), and a low flow rate (∼5 μL/min); these values are compared to 81 ± 6% and 48 ± 2%, respectively, for off-chip loading. On-chip loading shows a significant improvement over the off-chip process where shear-induced formation of smaller micelles enables increased encapsulation of probe. As well, we show that on-chip loading allows off-chip release kinetics to be controlled via flow rate: compared to vehicles produced at ∼5 μL/min, pyrene release kinetics from vehicles produced at ∼50 μL/min showed a longer initial period of burst release, followed by slow release over a longer total period. These results demonstrate the necessity to match probes, solvents, and running conditions to achieve effective loading, which is essential information for further developing these on-chip platforms for manufacturing drug delivery formulations.

Heating rate measurements over 30 deg and 40 deg (half angle) blunt cones in air and helium in the Langley expansion tube facility

NASA Technical Reports Server (NTRS)

Reddy, N. M.

1980-01-01

Convective heat transfer measurements, made on the conical portion of spherically blunted cones (30 deg and 40 deg half angle) in an expansion tube are discussed. The test gases used were helium and air; flow velocities were about 6.8 km/sec for helium and about 5.1 km/sec for air. The measured heating rates are compared with calculated results using a viscous shock layer computer code. For air, various techniques to determine flow velocity yielded identical results, but for helium, the flow velocity varied by as much as eight percent depending on which technique was used. The measured heating rates are in satisfactory agreement with calculation for helium, assuming the lower flow velocity, the measurements are significantly greater than theory and the discrepancy increased with increasing distance along the cone.

Behavioral responses of freshwater mussels to experimental dewatering

USGS Publications Warehouse

Galbraith, Heather S.; Blakeslee, Carrie J.; Lellis, William A.

2015-01-01

Understanding the effects of flow alteration on freshwater ecosystems is critical for predicting species responses and restoring appropriate flow regimes. We experimentally evaluated the effects of 3 dewatering rates on behavior of 6 freshwater mussel species in the context of water-removal rates observed in 21 Atlantic Coast rivers. Horizontal movement differed significantly among species and dewatering rates, but a significant species × dewatering interaction suggested that these factors influence movement in complex ways. Species differences in movement were evident only in controls and under slow dewatering rates, but these differences disappeared at moderate and fast dewatering rates. Burrowing behavior did not differ with respect to species identity or dewatering rate. The proportion of individuals that became stranded did not differ among species, but most individuals became stranded under low and moderate dewatering, and all individuals became stranded under fast dewatering. Mortality after stranding differed strongly among species along a gradient from 25% inPyganodon cataracta to 92% in Alasmidonta marginata. Together, these results suggest that species behavior may differ under gradual dewatering, but all species in our study are poorly adapted for rapid dewatering. Most of the 21 rivers we assessed experienced dewatering events comparable to our moderate rate, and several experienced events comparable to our fast rate. Dewatering events that exceed the movement or survival capability of most mussel species can be expected to result in assemblage-wide impacts. Consequently, the rate of water level change may be important in refining target flow conditions for restoration.

The role of varying flow on channel morphology: a flume experiment

NASA Astrophysics Data System (ADS)

Hempel, L. A.; Grant, G.; Eaton, B. C.; Hassan, M. A.; Lewis, S.

2017-12-01

Numerous studies have explored how alluvial channels develop under different sediment and flow conditions, yet we still know very little about how channels adjust and respond to changing flow conditions. One reason for this oversight is the long-held idea that channels with complex flow regimes are adjusted to a single, channel-forming discharge. But growing evidence shows that channel form reflects time-dependent processes occuring over multiple flows. To better understand how stream channels adjust to a range of flows, and identify the timescales associated with those adjustments, we conducted a series of hydrograph experiments in a freely-adjustable flume that developed a self-formed, meander pattern with pool-riffle morphology. Hydrographs had different shapes, magnitudes, and durations, but the total sediment volume fed under equilibrium conditions was kept constant among experiments. We found that hydrograph shape controlled channel morphology, the rate of channel development, and degree of regularity in the pool-riffle pattern. Hydrographs with slowly rising rates of rise and fall produced channels that were equivalent in size to channels generated from constant flow experiments, and had regularly spaced pool-riffle and meander patterns, while hydrographs with fast rates of rise and fall produced undersized channels with a chaotic bed structure and pool-riffle pattern. The latter suggests that during quickly rising hydrographs, the flow rate increases faster than the channel capacity and planform pattern adjusts. We confirmed these observations by comparing the timescales associated with pool-riffle and planform curvature development, which were identified under simple, constant flow conditions, to the total duration of the hydrograph. Hydrographs with step durations equal to or longer than the channel adjustment time produced channels with a more regular pool-riffle patterns compared to channels with step durations shorter than the adjustment time. This work points to the importance of the hydrograph as a fundamental control on channel adjustment and offers the prospect of better understanding of how changes in the flow regime, either through climate, land use, or dams, translate into morphodynamic changes.

Impact of High-flow Nasal Cannula Therapy in Quality Improvement and Clinical Outcomes in a Non-invasive Ventilation Device-free Pediatric Intensive Care Unit.

PubMed

Can, Fulva Kamit; Anil, Ayse Berna; Anil, Murat; Zengin, Neslihan; Bal, Alkan; Bicilioglu, Yuksel; Gokalp, Gamze; Durak, Fatih; Ince, Gulberat

2017-10-15

To analyze the change in quality indicators due to the use of high-flow nasal cannula therapy as a non-invasive ventilation method in children with respiratory distress/failure in a non-invasive ventilation device-free pediatric intensive care unit. Retrospective chart review of children with respiratory distress/failure admitted 1 year before (period before high-flow nasal cannula therapy) and 1 year after (period after high-flow nasal cannula therapy) the introduction of high-flow nasal cannula therapy. We compared quality indicators as rate of mechanical ventilation, total duration of mechanical ventilation, rate of re-intubation, pediatric intensive care unit length of stay, and mortality rate between these periods. Between November 2012 and November 2014, 272 patients: 141 before and 131 after high-flow nasal cannula therapy were reviewed (median age was 20.5 mo). Of the patients in the severe respiratory distress/failure subgroup, the rate of intubation was significantly lower in period after than in period before high-flow nasal cannula therapy group (58.1% vs. 76.1%; P <0.05). The median pediatric intensive care unit length of stay was significantly shorter in patients who did not require mechanical ventilation in the period after than in the period before high-flow nasal cannula therapy group (3d vs. 4d; P<0,05). Implementation of high-flow nasal cannula therapy in pediatric intensive care unit significantly improves the quality of therapy and its outcomes.

Hollow cathode, quasi-steady MPD arc

NASA Technical Reports Server (NTRS)

Parmentier, N.; Jahn, R. G.

1971-01-01

A quasi-steady MPD accelerator has been operated with four different hollow cathodes over a power range from 5 kilowatts to 5 megawatts. The absolute level of the argon mass flow, as well as the fractional division of the flow between the cathode and the six standard chamber injectors, is varied over a range of 1 to 12 grams per second. For a fixed total current, it is observed that the voltage increases monotonically with mass flow rate, compared to the usual experience with solid cathodes where the voltage decreases with mass flow rate. For a fixed percentage of flow through the cathode, each hollow cathode configuration displays a minimum impedance at a particular value of the total mass flow. It is asserted that in order to keep the discharge inside the hollow cathode the magnetic pressure and gasdynamic pressure have to match inside the cavity.

The production of premixed flame surface area in turbulent shear flow

NASA Technical Reports Server (NTRS)

Trouve, A.

1993-01-01

In the present work, we use three-dimensional Direct Numerical Simulation (DNS) of premixed flames in turbulent shear flow to characterize the effect of a mean shear motion on flame surface production. The shear is uniform in the unburnt gas, and simulations are performed for different values of the mean shear rate, S. The data base is then used to estimate and compare the different terms appearing in the Sigma-equation as a function of S. The analysis gives in particular the relative weights f the turbulent flow and mean flow components, a(sub T) and A(sub T), of the flame surface production term. This comparison indicates whether the dominant effects of a mean flow velocity gradient on flame surface area are implicit and scale with the modified turbulent flow parameters, kappa and epsilon, or explicit and scale directly with the rate of deformation.

A Capillary Flow Dynamics-Based Sensing Modality for Direct Environmental Pathogen Monitoring.

PubMed

Klug, Katherine E; Reynolds, Kelly A; Yoon, Jeong-Yeol

2018-04-20

Toward ultra-simple and field-ready biosensors, we demonstrate a novel assay transducer mechanism based on interfacial property changes and capillary flow dynamics in antibody-conjugated submicron particle suspensions. Differential capillary flow is tunable, allowing pathogen quantification as a function of flow rate through a paper-based microfluidic device. Flow models based on interfacial and rheological properties indicate a significant relationship between the flow rate and the interfacial effects caused by target-particle aggregation. This mechanism is demonstrated for assays of Escherichia coli K12 in water samples and Zika virus (ZIKV) in blood serum. These assays achieved very low limits of detection compared with other demonstrated methods (1 log CFU/mL E. coli and 20 pg/mL ZIKV whole virus) with an operating time of 30 s, showing promise for environmental and health monitoring. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neonatal piglet model of intraaortic balloon pumping: improved efficacy using echocardiographic timing.

PubMed

Minich, L L; Tani, L Y; Pantalos, G M; Bolland, B L; Knorr, B K; Hawkins, J A

1998-11-01

Pediatric intraaortic balloon pumping (IABP) has met with little success because of technical difficulty in tracking rapid heart rates. This study was designed to evaluate the efficacy of M-mode echocardiography for IABP timing in a neonatal piglet model. Two groups of piglets underwent mitral valve avulsion to create a model of shock. Group 1 (n = 8; mean weight, 7.7+/-1.8 kg) underwent IABP timed with both the ascending aortic pressure and M-mode echocardiogram. Group 2 (n = 6; mean weight, 7.5+/-1.4 kg) underwent two separate periods of IABP: one with echocardiographic timing and the second using standard timing points from the femoral arterial pressure tracing and electrocardiogram. Measurements included ascending aortic flow, left anterior descending arterial flow, ascending aortic pressure, left atrial pressure, and heart rate. Mitral valve avulsion produced a shock model with a significant decrease in mean aortic pressure and aortic flow and a significant increase in left atrial pressure and heart rate. Compared with the shock state, IABP in group 1 animals resulted in a significant increase in aortic flow (353+/-152 versus 454+/-109 mL/min; p < 0.05) and a significant decrease in left atrial pressure (23+/-6 versus 17+/-7 mm Hg; p < 0.05). Group 2 animals with echocardiogram-timed IABP had significantly increased aortic flow (365+/-106 versus 458+/-107 mL/min; p < 0.05) and mean aortic pressure (43+/-11 versus 52+/-8 mm Hg; p < 0.05). However, standard-timed IABP failed to show any improvement. In piglets with rapid heart rates, echocardiogram-timed IABP results in increased aortic flow and pressure and decreased left atrial pressure compared with standard-timed IABP.

Safety and efficacy of the Aperio thrombectomy device when compared to the Solitaire AB/FR and the Revive devices in a pulsatile flow system.

PubMed

Saleh, Mahdi; Spence, John Nathan; Nayak, Sanjeev; Pearce, Gillian; Tennuci, Christopher; Roffe, Christine

2012-01-01

There are a limited number of studies comparing the Aperio mechanical thrombectomy device to other stent-based devices. In this paper, we compared the Aperio thrombectomy device to the Solitaire AB, FR and Revive devices in a model of the middle cerebral artery (MCA) within a modified pulsatile flow system. Thrombi made of lamb's blood were placed into a pulsatile flow system perfused with Hartmann's solution at 80 bpm with a mean pressure of 90 mm Hg. 30 experiments were run with each device. Recanalization rates were similar for all three devices (90% with the Solitaire AB, FR, 80% with the Revive, and 90% with the Aperio). The mean number of attempts to retrieve the thrombus was also similar for all three devices (1.7 with the Solitaire AB, FR, 2.1 with the Revive, 1.6 with the Aperio). Clot fragmentation and embolization rates revealed no statistical significance but there was a trend towards lower embolization rates with the Aperio (23% compared to 40% with the Solitaire AB, FR and 47% with the Revive). The Aperio was the fastest to recanalize the MCA (mean of 66 seconds compared to 186 seconds for the Solitaire AB, FR and 169 seconds for the Revive). In this in vitro setting, the Aperio device seems to be an efficacious and safe device when compared to other similar clinically used mechanical thrombectomy devices. Larger clinical trials are warranted.

Cavitation enhances coagulated size during pulsed high-intensity focussed ultrasound ablation in an isolated liver perfusion system.

PubMed

Zhao, Lu-Yan; Liu, Shan; Chen, Zong-Gui; Zou, Jian-Zhong; Wu, Feng

2016-11-24

To investigate whether cavitation enhances the degree of coagulation during pulsed high-intensity focussed ultrasound (HIFU) in an isolated liver perfusion system. Isolated liver was treated by pulsed HIFU or continuous-wave HIFU with different portal vein flow rates. The cavitation emission during exposure was recorded, and real-time ultrasound images were used to observe changes in the grey scale. The coagulation size was measured and calculated. HIFU treatment led to complete coagulation necrosis and total cell destruction in the target regions. Compared to exposure at a duty cycle (DC) of 100%, the mean volumes of lesions induced by 6 s exposure at DCs of 50% and 10% were significantly larger (P < .01) but were smaller at a DC of 5%. The necrosis volume was negatively related to the perfusion rate in the pulsed HIFU at a DC of 50% for exposure durations of 4 and 6 s, while the perfusion flow rate did not affect the necrosis volume for exposure durations of 1, 2 and 3 s. For increased perfusion flow rates, there was no significant decrease in the cavitation activity for the pulsed-HIFU (P > .05). For continuous-wave HIFU exposure, there was a significant decrease in the necrosis volume and cavitation activity for exposure times of 1, 2, 3, 4, and 6 s with increasing portal perfusion rates. Perfusion flow rates negatively influence cavitation activity and coagulation volume. Ablation is significantly enhanced during pulsed HIFU exposure compared with continuous-wave HIFU.

The effects of finite rate chemical processes on high enthalpy nozzle performance - A comparison between SPARK and SEAGULL

NASA Technical Reports Server (NTRS)

Carpenter, M. H.

1988-01-01

The generalized chemistry version of the computer code SPARK is extended to include two higher-order numerical schemes, yielding fourth-order spatial accuracy for the inviscid terms. The new and old formulations are used to study the influences of finite rate chemical processes on nozzle performance. A determination is made of the computationally optimum reaction scheme for use in high-enthalpy nozzles. Finite rate calculations are compared with the frozen and equilibrium limits to assess the validity of each formulation. In addition, the finite rate SPARK results are compared with the constant ratio of specific heats (gamma) SEAGULL code, to determine its accuracy in variable gamma flow situations. Finally, the higher-order SPARK code is used to calculate nozzle flows having species stratification. Flame quenching occurs at low nozzle pressures, while for high pressures, significant burning continues in the nozzle.

Estimating pesticide sampling rates by the polar organic chemical integrative sampler (POCIS) in the presence of natural organic matter and varying hydrodynamic conditions

USGS Publications Warehouse

Charlestra, Lucner; Amirbahman, Aria; Courtemanch, David L.; Alvarez, David A.; Patterson, Howard

2012-01-01

The polar organic chemical integrative sampler (POCIS) was calibrated to monitor pesticides in water under controlled laboratory conditions. The effect of natural organic matter (NOM) on the sampling rates (Rs) was evaluated in microcosms containing -1 of total organic carbon (TOC). The effect of hydrodynamics was studied by comparing Rs values measured in stirred (SBE) and quiescent (QBE) batch experiments and a flow-through system (FTS). The level of NOM in the water used in these experiments had no effect on the magnitude of the pesticide sampling rates (p > 0.05). However, flow velocity and turbulence significantly increased the sampling rates of the pesticides in the FTS and SBE compared to the QBE (p < 0.001). The calibration data generated can be used to derive pesticide concentrations in water from POCIS deployed in stagnant and turbulent environmental systems without correction for NOM.

Flow-structure interaction simulation of voice production in a canine larynx

NASA Astrophysics Data System (ADS)

Jiang, Weili; Zheng, Xudong; Xue, Qian; Oren, Liran; Khosla, Sid

2017-11-01

Experimental measurements conducted on a hemi-larynx canine vocal fold showed that negative pressures formed in the glottis near the superior surface of the vocal fold in the closing phase even without a supra-glottal vocal tract. It was hypothesized that such negative pressures were due to intraglottal vortices caused by flow separation in a divergent vocal tract during vocal fold closing phase. This work aims to test this hypothesis from the numerical aspect. Flow-structure interaction simulations are performed in realistic canine laryngeal shapes. In the simulations, a sharp interface immersed boundary method based incompressible flow solver is utilized to model the air flow; a finite element based solid mechanics solver is utilized to model the vocal fold vibration. The geometric structure of the vocal fold and vocal tract are based on MRI scans of a mongrel canine. The vocal fold tissue is modeled as transversely isotropic nonlinear materials with a vertical stiffness gradient. Numerical indentation is first performed and compared with the experiment data to obtain the material properties. Simulation setup about the inlet and outlet pressure follows the setup in the experiment. Simulation results including the fundamental frequency, air flow rate, the divergent angle will be compared with the experimental data, providing the validation of the simulation approach. The relationship between flow separation, intra-glottal vortices, divergent angle and flow rate will be comprehensively analyzed.

A comparative study on heat and mass transfer of the Blasius and Falkner-Skan flow of a bio-convective Casson fluid past a wedge

NASA Astrophysics Data System (ADS)

Raju, C. S. K.; Sandeep, N.

2016-11-01

Nowadays, many theoretical models are available for analyzing the heat and mass transfer of flows through different geometries. Nevertheless, it is challenging for researchers to choose among these models, the most suitable for a particular geometry. In addition to this, the extrinsic magnetic field is capable to set the thermal and physical properties of magnetic fluids and regulate the flow and heat transfer characteristics. The strength of the applied magnetic field affects the thermal conductivity of the fluids and makes it anisotropic. With this incentive, we attempt to study the thermophoresis and Brownian motion effects on the magnetohydrodynamic radiative Casson fluid flow over a wedge filled with gyrotactic microorganisms by considering the Blasius and Falkner-Skan models. Numerical solutions are offered graphically as well as in tabular form with the aid of Runge-Kutta and Newton's methods. Results for Blasius and Falkner-Skan flow cases are exhibited through plots for the parameters of concern. For real life applications, we also calculated the heat and mass transfer rates. It is observed that thermal and concentration boundary layers are not uniform for Falkner-Skan and Blasius flow cases. It is also observed that the heat and mass transfer rate is high in Falkner-Skan flow when compared with Blasius flow.

Application of partial inversion pulse to ultrasonic time-domain correlation method to measure the flow rate in a pipe

NASA Astrophysics Data System (ADS)

Wada, Sanehiro; Furuichi, Noriyuki; Shimada, Takashi

2017-11-01

This paper proposes the application of a novel ultrasonic pulse, called a partial inversion pulse (PIP), to the measurement of the velocity profile and flow rate in a pipe using the ultrasound time-domain correlation (UTDC) method. In general, the measured flow rate depends on the velocity profile in the pipe; thus, on-site calibration is the only method of checking the accuracy of on-site flow rate measurements. Flow rate calculation using UTDC is based on the integration of the measured velocity profile. The advantages of this method compared with the ultrasonic pulse Doppler method include the possibility of the velocity range having no limitation and its applicability to flow fields without a sufficient amount of reflectors. However, it has been previously reported that the measurable velocity range for UTDC is limited by false detections. Considering the application of this method to on-site flow fields, the issue of velocity range is important. To reduce the effect of false detections, a PIP signal, which is an ultrasound signal that contains a partially inverted region, was developed in this study. The advantages of the PIP signal are that it requires little additional hardware cost and no additional software cost in comparison with conventional methods. The effects of inversion on the characteristics of the ultrasound transmission were estimated through numerical calculation. Then, experimental measurements were performed at a national standard calibration facility for water flow rate in Japan. The experimental results demonstrate that measurements made using a PIP signal are more accurate and yield a higher detection ratio than measurements using a normal pulse signal.

Line-Focused Optical Excitation of Parallel Acoustic Focused Sample Streams for High Volumetric and Analytical Rate Flow Cytometry.

PubMed

Kalb, Daniel M; Fencl, Frank A; Woods, Travis A; Swanson, August; Maestas, Gian C; Juárez, Jaime J; Edwards, Bruce S; Shreve, Andrew P; Graves, Steven W

2017-09-19

Flow cytometry provides highly sensitive multiparameter analysis of cells and particles but has been largely limited to the use of a single focused sample stream. This limits the analytical rate to ∼50K particles/s and the volumetric rate to ∼250 μL/min. Despite the analytical prowess of flow cytometry, there are applications where these rates are insufficient, such as rare cell analysis in high cellular backgrounds (e.g., circulating tumor cells and fetal cells in maternal blood), detection of cells/particles in large dilute samples (e.g., water quality, urine analysis), or high-throughput screening applications. Here we report a highly parallel acoustic flow cytometer that uses an acoustic standing wave to focus particles into 16 parallel analysis points across a 2.3 mm wide optical flow cell. A line-focused laser and wide-field collection optics are used to excite and collect the fluorescence emission of these parallel streams onto a high-speed camera for analysis. With this instrument format and fluorescent microsphere standards, we obtain analysis rates of 100K/s and flow rates of 10 mL/min, while maintaining optical performance comparable to that of a commercial flow cytometer. The results with our initial prototype instrument demonstrate that the integration of key parallelizable components, including the line-focused laser, particle focusing using multinode acoustic standing waves, and a spatially arrayed detector, can increase analytical and volumetric throughputs by orders of magnitude in a compact, simple, and cost-effective platform. Such instruments will be of great value to applications in need of high-throughput yet sensitive flow cytometry analysis.

Measurement of pressure and flow rates during irrigation of a root canal ex vivo with three endodontic needles.

PubMed

Boutsioukis, C; Lambrianidis, T; Kastrinakis, E; Bekiaroglou, P

2007-07-01

To monitor ex vivo intra-canal irrigation with three endodontic needles (25, 27 and 30 gauge) and compare them in terms of irrigant flow rate, intra-barrel pressure, duration of irrigation and volume of irrigant delivered. A testing system was constructed to allow measurement of selected variables with pressure and displacement transducers during ex vivo intra-canal irrigation with a syringe and three different needles (groups A, B, C) into a prepared root canal. Ten specialist endodontists performed the irrigation procedure. Each operator performed ten procedures with each needle. Data recorded by the transducers were analysed using Friedman's test, Wilcoxon Signed Rank test, Mann-Whitney U-test and Kendall's T(b) test. The level of significance was set to 95%. Significant differences were detected among the three needles for most variables. Duration of delivery and flow rates significantly decreased as the needle diameter increased, whilst pressure increased up to 400-550 kPa. Gender of the operator had a significant impact on the results. Experience of the operators (years) were negatively correlated to volume of irrigant (all groups), to the duration of delivery (groups A, B) and to the average flow rate (group A). Finer diameter needles require increased effort to deliver the irrigant and result in higher intra-barrel pressure. The syringe and needles used tolerated the pressure developed. Irrigant flow rate should be considered as a factor directly influencing flow beyond the needle. Wide variations of flow rate were observed among operators. Syringe irrigation appears difficult to standardize and control.

Search for subgrid scale parameterization by projection pursuit regression

NASA Technical Reports Server (NTRS)

Meneveau, C.; Lund, T. S.; Moin, Parviz

1992-01-01

The dependence of subgrid-scale stresses on variables of the resolved field is studied using direct numerical simulations of isotropic turbulence, homogeneous shear flow, and channel flow. The projection pursuit algorithm, a promising new regression tool for high-dimensional data, is used to systematically search through a large collection of resolved variables, such as components of the strain rate, vorticity, velocity gradients at neighboring grid points, etc. For the case of isotropic turbulence, the search algorithm recovers the linear dependence on the rate of strain (which is necessary to transfer energy to subgrid scales) but is unable to determine any other more complex relationship. For shear flows, however, new systematic relations beyond eddy viscosity are found. For the homogeneous shear flow, the results suggest that products of the mean rotation rate tensor with both the fluctuating strain rate and fluctuating rotation rate tensors are important quantities in parameterizing the subgrid-scale stresses. A model incorporating these terms is proposed. When evaluated with direct numerical simulation data, this model significantly increases the correlation between the modeled and exact stresses, as compared with the Smagorinsky model. In the case of channel flow, the stresses are found to correlate with products of the fluctuating strain and rotation rate tensors. The mean rates of rotation or strain do not appear to be important in this case, and the model determined for homogeneous shear flow does not perform well when tested with channel flow data. Many questions remain about the physical mechanisms underlying these findings, about possible Reynolds number dependence, and, given the low level of correlations, about their impact on modeling. Nevertheless, demonstration of the existence of causal relations between sgs stresses and large-scale characteristics of turbulent shear flows, in addition to those necessary for energy transfer, provides important insight into the relation between scales in turbulent flows.

Relationship between Physicochemical Properties of Saliva and Dental Caries and Periodontal Status among Female Teachers Living in Central Iran

PubMed Central

Hosseini-Yekani, Amene; Nadjarzadeh, Azadeh; Vossoughi, Mehrdad; Reza, Javad Zavvar; Golkari, Ali

2018-01-01

Objectives: There are inconsistent data about the association between saliva properties, dental caries, and periodontal status. In this study, we tried to examine the association between dental caries and periodontal status with salivary viscosity, flow rate, pH, and buffering capacity in adults. Methods: In the present cross-sectional study, 450 female teachers were randomly selected from schools located in Yazd, Iran. Oral examinations were conducted, and unstimulated saliva samples were collected. Salivary viscosity, flow rate, pH, and buffering capacity were assessed. The salivary physicochemical properties were compared among teachers with different types of oral health. Analyses were done using the Statistical Package for the Social Sciences version 16. Results: In total, 431 female teachers aged 40.45 ± 8.18 years were included in the study. Salivary flow rate, buffering capacity, pH, and viscosity, community periodontal index status were not significantly different in participants with and without tooth caries. There was a reverse linear association between salivary pH and flow rate with the decayed, missed, and filled teeth index (P < 0.05). The saliva buffering capacity was not significantly related to dental properties. Those with bleeding on probing had lower salivary pH, and buffering capacity compared to those with healthy gum. However, the salivary resting flow rate was not different in participants with bleeding on probing and healthy participants. Conclusion: Based on our results, saliva properties might be important predictors in oral health status. This means that any change in saliva combination might affect periodontal and dental diseases. Future prospective studies are recommended to confirm these results. PMID:29629329

Laryngeal Aerodynamics in Healthy Older Adults and Adults With Parkinson's Disease.

PubMed

Matheron, Deborah; Stathopoulos, Elaine T; Huber, Jessica E; Sussman, Joan E

2017-03-01

The present study compared laryngeal aerodynamic function of healthy older adults (HOA) to adults with Parkinson's disease (PD) while speaking at a comfortable and increased vocal intensity. Laryngeal aerodynamic measures (subglottal pressure, peak-to-peak flow, minimum flow, and open quotient [OQ]) were compared between HOAs and individuals with PD who had a diagnosis of hypophonia. Increased vocal intensity was elicited via monaurally presented multitalker background noise. At a comfortable speaking intensity, HOAs and individuals with PD produced comparable vocal intensity, rates of vocal fold closure, and minimum flow. HOAs used smaller OQs, higher subglottal pressure, and lower peak-to-peak flow than individuals with PD. Both groups increased speaking intensity when speaking in noise to the same degree. However, HOAs produced increased intensity with greater driving pressure, faster vocal fold closure rates, and smaller OQs than individuals with PD. Monaural background noise elicited equivalent vocal intensity increases in HOAs and individuals with PD. Although both groups used laryngeal mechanisms as expected to increase sound pressure level, they used these mechanisms to different degrees. The HOAs appeared to have better control of the laryngeal mechanism to make changes to their vocal intensity.

Prediction of induction time for methane hydrate formation in the presence or absence of THF in flow loop system by Natarajan model

NASA Astrophysics Data System (ADS)

Talaghat, Mohammad Reza; Jokar, Seyyed Mohammad

2018-03-01

The induction time is a time interval to detect the initial hydrate formation, which is counted from the moment when the stirrer is turned on until the first detection of hydrate formation. The main objective of the present work is to predict and measure the induction time of methane hydrate formation in the presence or absence of tetrahydrofuran (THF) as promoter in the flow loop system. A laboratory flow mini-loop apparatus was set up to measure the induction time of methane hydrate formation. The induction time is predicted using developed Kashchiev and Firoozabadi model and modified model of Natarajan for a flow loop system. Furthermore, the effects of volumetric flow rate of the fluid on the induction time were investigated. The results of the models were compared with experimental data. They show that the induction time of hydrate formation in the presence of THF is very short at high pressure and high volumetric flow rate of the fluid. It decreases with increasing pressure and liquid volumetric flow rate. It is also shown that the modified Natarajan model is more accurate than the Kashchiev and Firoozabadi ones in prediction of the induction time.

Experimental and Numerical Study of Spacecraft Contamination Problems Associated With Gas and Gas-Droplet Thruster Plume Flows

DTIC Science & Technology

2006-04-17

of the droplet phase are then used for validation of theoretical models of the gas-droplet plume flow. Based on experimental and numerical results...with the continuous model adequately reproduces the Arrhenius rate at high temperatures but significantly underpredicts the theoretical rate at low...continuous model and discrete model of real gas effects, and the results on the shock -wave stand-off distance were compared with the experimental data of

Effects of exercise and excitement on mesenteric and renal dynamics in conscious, unrestrained baboons

NASA Technical Reports Server (NTRS)

Vatner, S. F.

1978-01-01

Radiotelemetry was used to measure arterial pressure and mesenteric and renal blood flows from nine unrestrained, conscious baboons during periods of rest, moderate exercise, and extreme excitement. A description of the experiments hardware is presented, including artificial depressants phenylcyclidine hydrochloride, 0.5-1.0 mg/kg, and pentobarbital sodium, 15 mg/kg, and an ultrasonic telemetry flow meter. Results showed rising heart rate and arterial pressure coupled with a reduction of mesenteric and renal flows as the level of exercise was increased. These findings are compared with mesenteric and renal flows somewhat above control level, but relatively stable heart rate and arterial pressure, postprandially. Attention is given to a quantitative analysis of the experimental results.

Randomized, double-blind, placebo-controlled trial of saw palmetto in men with lower urinary tract symptoms.

PubMed

Gerber, G S; Kuznetsov, D; Johnson, B C; Burstein, J D

2001-12-01

To assess the effects of saw palmetto on urinary symptoms, sexual function, and urinary flow rate in men with lower urinary tract symptoms using a double-blind, randomized, placebo-controlled trial. The eligible patients were 45 years of age or older and had an International Prostate Symptom Score of 8 or greater. After a 1-month placebo run-in period, 85 men were randomized to receive saw palmetto or placebo for 6 months. Patients were evaluated using the International Prostate Symptom Score, a sexual function questionnaire, and by measurement of the urinary flow rate. The mean symptom score decreased from 16.7 to 12.3 in the saw palmetto group compared with 15.8 to 13.6 in the placebo group (P = 0.038). The quality-of-life score improved to a greater degree in the saw palmetto group, but this difference was not statistically significant. No change occurred in the sexual function questionnaire results in either group. The peak flow rate increased by 1.0 mL/s and 1.4 mL/s in the saw palmetto and placebo groups, respectively (P = 0.73). Saw palmetto led to a statistically significant improvement in urinary symptoms in men with lower urinary tract symptoms compared with placebo. Saw palmetto had no measurable effect on the urinary flow rates. The mechanism by which saw palmetto improves urinary symptoms remains unknown.

[Efficacy of preoxygenation using tidal volume breathing: a comparison of Mapleson A, Bain's and Circle system].

PubMed

Arora, Suman; Gupta, Priyanka; Arya, Virender Kumar; Bhatia, Nidhi

Efficacy of preoxygenation depends upon inspired oxygen concentration, its flow rate, breathing system configuration and patient characteristics. We hypothesized that in actual clinical scenario, where breathing circuit is not primed with 100% oxygen, patients may need more time to achieve EtO 2 ≥90%, and this duration may be different among various breathing systems. We thus studied the efficacy of preoxygenation using unprimed Mapleson A, Bain's and Circle system with tidal volume breathing at oxygen flow rates of 5L.min -1 and 10L.min -1 . Patients were randomly allocated into one of the six groups, wherein they were preoxygenated using either Mapleson A, Bain's or Circle system at O 2 flow rate of either 5L.min -1 or 10L.min -1 . The primary outcome measure of our study was the time taken to achieve EtO 2 ≥90% at 5 and 10L.min -1 flow rates. At oxygen flow rate of 5L.min -1 , time to reach EtO 2 ≥90% was significantly longer with Bain's system (3.7±0.67min) than Mapleson A and Circle system (2.9±0.6, 3.3±0.97min, respectively). However at oxygen flow rate of 10L.min -1 this time was significantly shorter and comparable among all the three breathing systems (2.33±0.38min with Mapleson, 2.59±0.50min with Bain's and 2.60±0.47min with Circle system). With spontaneous normal tidal volume breathing at oxygen flow rate of 5L.min -1 , Mapleson A can optimally preoxygenate patients within 3min while Bain's and Circle system require more time. However at O 2 flow rate of 10L.min -1 all the three breathing systems are capable of optimally preoxygenating the patients in less than 3min. Copyright © 2017 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. All rights reserved.

Combined Effects of Flow Diverting Strategies and Parent Artery Curvature on Aneurysmal Hemodynamics: A CFD Study

PubMed Central

Yu, Ying; Lv, Nan; Wang, Shengzhang; Karmonik, Christof; Liu, Jian-Min; Huang, Qinghai

2015-01-01

Purpose Flow diverters (FD) are increasingly being considered for treating large or giant wide-neck aneurysms. Clinical outcome is highly variable and depends on the type of aneurysm, the flow diverting device and treatment strategies. The objective of this study was to analyze the effect of different flow diverting strategies together with parent artery curvature variations on altering intra-aneurysmal hemodynamics. Methods Four ideal intracranial aneurysm models with different parent artery curvature were constructed. Computational fluid dynamics (CFD) simulations of the hemodynamics before and after applying five types of flow diverting strategies (single FD, single FD with 5% and 10% packing density of coils, two FDs with 25% and 50% overlapping rate) were performed. Changes in pressure, wall shear stress (WSS), relative residence time (RRT), inflow velocity and inflow volume rate were calculated and compared. Results Each flow diverting strategy resulted in enhancement of RRT and reduction of normalized mean WSS, inflow volume rate and inflow velocity in various levels. Among them, 50% overlapped FD induced most effective hemodynamic changes in RRT and inflow volume rate. The mean pressure only slightly decreased after treatment. Regardless of the kind of implantation of FD, the mean pressure, inflow volume rate and inflow velocity increased and the RRT decreased as the curvature of the parent artery increased. Conclusions Of all flow diverting strategies, overlapping FDs induced most favorable hemodynamic changes. Hemodynamics alterations post treatment were substantially influenced by parent artery curvature. Our results indicate the need of an individualized flow diverting strategy that is tailored for a specific aneurysm. PMID:26398847

Simple microfluidic stagnation point flow geometries

PubMed Central

Dockx, Greet; Verwijlen, Tom; Sempels, Wouter; Nagel, Mathias; Moldenaers, Paula; Hofkens, Johan; Vermant, Jan

2016-01-01

A geometrically simple flow cell is proposed to generate different types of stagnation flows, using a separation flow and small variations of the geometric parameters. Flows with high local deformation rates can be changed from purely rotational, over simple shear flow, to extensional flow in a region surrounding a stagnation point. Computational fluid dynamic calculations are used to analyse how variations of the geometrical parameters affect the flow field. These numerical calculations are compared to the experimentally obtained streamlines of different designs, which have been determined by high speed confocal microscopy. As the flow type is dictated predominantly by the geometrical parameters, such simple separating flow devices may alleviate the requirements for flow control, while offering good stability for a wide variety of flow types. PMID:27462382

Differential effects of total and partial sleep deprivation on salivary factors in Wistar rats.

PubMed

Lasisi, Dr T J; Shittu, S T; Meludu, C C; Salami, A A

2017-01-01

Aim of this study was to investigate the effects of sleep deprivation on salivary factors in rats. Animals were randomly assigned into three groups of 6 animals each as control, total sleep deprivation (TSD) and partial sleep deprivation (PSD) groups. The multiple platform method was used to induce partial and total sleep deprivation for 7days. On the 8th day, stimulated saliva samples were collected for the analysis of salivary lag time, flow rate, salivary amylase activity, immunoglobulin A secretion rate and corticosterone levels using ELISA and standard kinetic enzyme assay. Data were analyzed using ANOVA with Dunnett T3 post hoc tests. Salivary flow rate reduced significantly in the TSD group compared with the PSD group as well as the control group (p=0.01). The secretion rate of salivary IgA was significantly reduced in the TSD group compared with the control group (p=0.04). Salivary amylase activity was significantly elevated in the TSD group compared with the PSD group as well as control group (p<0.001). However, there were no significant changes in the salivary lag time and levels of corticosterone among the groups. These findings suggest that total sleep deprivation is associated with reduced salivary flow rate and secretion rate of IgA as well as elevated levels of salivary amylase activity in rats. However, sleep recovery of four hours in the PSD group produced ameliorative effects on the impaired functions of salivary glands. Copyright © 2016 Elsevier Ltd. All rights reserved.

Numerical 3D flow simulation of attached cavitation structures at ultrasonic horn tips and statistical evaluation of flow aggressiveness via load collectives

NASA Astrophysics Data System (ADS)

Mottyll, S.; Skoda, R.

2015-12-01

A compressible inviscid flow solver with barotropic cavitation model is applied to two different ultrasonic horn set-ups and compared to hydrophone, shadowgraphy as well as erosion test data. The statistical analysis of single collapse events in wall-adjacent flow regions allows the determination of the flow aggressiveness via load collectives (cumulative event rate vs collapse pressure), which show an exponential decrease in agreement to studies on hydrodynamic cavitation [1]. A post-processing projection of event rate and collapse pressure on a reference grid reduces the grid dependency significantly. In order to evaluate the erosion-sensitive areas a statistical analysis of transient wall loads is utilised. Predicted erosion sensitive areas as well as temporal pressure and vapour volume evolution are in good agreement to the experimental data.

Characterizing Strength of Chaotic Dynamics and Numerical Simulation Relevant to Modified Taylor-Couette Flow with Hourglass Geometry

NASA Astrophysics Data System (ADS)

Hou, Yu; Kowalski, Adam; Schroder, Kjell; Halmstad, Andrew; Olsen, Thomas; Wiener, Richard

2006-05-01

We characterize the strength of chaos in two different regimes of Modified Taylor-Couette flow with Hourglass Geometry: the formation of Taylor Vortices with laminar flow and with turbulent flow. We measure the strength of chaos by calculating the correlation dimension and the Kaplan-Yorke dimension based upon the Lyapunov Exponents of each system. We determine the reliability of our calculations by considering data from a chaotic electronic circuit. In order to predict the behavior of the Modified Taylor-Couette flow system, we employ simulations based upon an idealized Reaction-Diffusion model with a third order non-linearity in the reaction rate. Variation of reaction rate with length corresponds to variation of the effective Reynolds Number along the Taylor-Couette apparatus. We present preliminary results and compare to experimental data.

Decreased muscle oxygenation and increased arterial blood flow in the non-exercising limb during leg exercise.

PubMed

Shiroishi, Kiyoshi; Kime, Ryotaro; Osada, Takuya; Murase, Norio; Shimomura, Kousuke; Katsumura, Toshihito

2010-01-01

We evaluated arterial blood flow, muscle tissue oxygenation and muscle metabolism in the non-exercising limb during leg cycling exercise. Ten healthy male volunteers performed a graded leg cycling exercise at 0, 40, 80, 120 and 160 watts (W) for 5 min each. Tissue oxygenation index (TOI) of the non-exercising left forearm muscle was measured using a near-infrared spatially resolved spectroscopy (NIR(SRS)), and non-exercising forearm blood flow ((NONEX)FBF) in the brachial artery was also evaluated by a Doppler ultrasound system. We also determined O(2) consumption of the non-exercising forearm muscle (NONEXV(O)(2mus)) by the rate of decrease in O(2)Hb during arterial occlusion at each work rate. TOI was significantly decreased at 160 W (p < 0.01) compared to the baseline. The (NONEX)V(O)(2mus) at each work rate was not significantly increased. In contrast, (NONEX)FBF was significantly increased at 120 W (p < 0.05) and 160 W (p < 0.01) compared to the baseline. These results suggest that the O(2) supply to the non-exercising muscle may be reduced, even though (NONEX)FBF increases at high work rates during leg cycling exercise.

The Stability and Interfacial Motion of Multi-layer Radial Porous Media and Hele-Shaw Flows

NASA Astrophysics Data System (ADS)

Gin, Craig; Daripa, Prabir

2017-11-01

In this talk, we will discuss viscous fingering instabilities of multi-layer immiscible porous media flows within the Hele-Shaw model in a radial flow geometry. We study the motion of the interfaces for flows with both constant and variable viscosity fluids. We consider the effects of using a variable injection rate on multi-layer flows. We also present a numerical approach to simulating the interface motion within linear theory using the method of eigenfunction expansion. We compare these results with fully non-linear simulations.

Effect of Pedestrians on the Saturation Flow Rate of Right Turn Movements at Signalized Intersection - Case Study from Rasht City

NASA Astrophysics Data System (ADS)

Roshani, Mostafa; Bargegol, Iraj

2017-10-01

Saturation flow rate is one of the important items in the analysis of the capacity of signalized intersections that are affected by some factors. Pedestrian crossing on signalized intersection is one of the factors which influence the vehicles flow. In addition, the released researches determined that the greatest impact of pedestrian on the saturation flow occurred in the Conflict zone where the highest chance of the encounter of pedestrians and vehicles has in turning movements. The purpose of this paper is to estimate the saturation flow rate considering the effect of a pedestrian on right turn movements of the signalized intersections in Rasht city. For this goal, 6 signalized intersections with 90 cycles of reviews were selected for the estimation of saturation flow rate by the microscopic method and also 3 right turn lanes containing radius differences with 70 cycles of reviews were collected for the investigation of the pedestrians’ effects. Each phase of right turn lanes cycle was divided in the pieces of 10-second period which was totally 476 sample volumes of considered pedestrians and vehicles at that period. Only 101 samples of those were ranged as saturated conditions. Finally, using different regression models, the best relationship between pedestrian’s volume and right turning vehicles flow parameters was evaluated. The results indicate that there is a primarily linear relationship between pedestrian volume and right turning vehicles flow with R2=0.6261. According to this regression model with the increase in pedestrians, saturation flow rate will be reduced. In addition, by comparing the adjustment factor obtained in the present study and other studies, it was found that the effect of pedestrians on the right-turn movements in Rasht city is less than the rest of the world.

Urine flow is a novel hemodynamic monitoring tool for the detection of hypovolemia.

PubMed

Shamir, Micha Y; Kaplan, Leonid; Marans, Rachel S; Willner, Dafna; Klein, Yoram

2011-03-01

Noticeable changes in vital signs indicating hypovolemia occur only after 15% of the blood volume is lost. More sensitive variables (e.g., cardiac output, systolic pressure variation and its Δdown component) are invasive and difficult to obtain in the early phase of bleeding. Lately, a new technology for continuous optical measurements of minute-to-minute urine flow rates has become available. We performed a preliminary evaluation to determine whether urine flow can act as an early and sensitive warning of hypovolemia. Eleven patients (ASA physical status I-II) undergoing posterior spine fusion surgery were studied prospectively. Study variables included heart rate, blood pressure (systolic and diastolic), systolic pressure variation and Δdown, minute urinary flow, hemoglobin, blood and urinary sodium, and creatinine in the blood and urine. Urine flow rate was measured using URINFO 2000™ (FlowSense Medical, Misgav, Israel). After recording baseline variables, 10 mL/kg of the patient's blood was shed and a second set of variables was recorded. Subsequently, hypovolemia was reversed by infusing colloid solution (hetastarch 6%) followed by recording a third set of variables. These 3 observations were then compared. An average of 614 ± 143 mL (mean ± SD) of blood was shed. During phlebotomy, the mean urine flow rate decreased from 5.7 ± 8 mL/min to 1.07 ± 2.5 mL/min. Systolic blood pressure and hemoglobin also decreased. Δdown increased. After rehydration, urine flow, blood pressure, and Δdown values returned to baseline. The hemoglobin concentration decreased whereas other variables did not change significantly. Urine flow rate is a dynamic variable that seems to be a reliable indicator of changes in blood volume. These results justify further investigation.

Review of flow rate estimates of the Deepwater Horizon oil spill.

PubMed

McNutt, Marcia K; Camilli, Rich; Crone, Timothy J; Guthrie, George D; Hsieh, Paul A; Ryerson, Thomas B; Savas, Omer; Shaffer, Frank

2012-12-11

The unprecedented nature of the Deepwater Horizon oil spill required the application of research methods to estimate the rate at which oil was escaping from the well in the deep sea, its disposition after it entered the ocean, and total reservoir depletion. Here, we review what advances were made in scientific understanding of quantification of flow rates during deep sea oil well blowouts. We assess the degree to which a consensus was reached on the flow rate of the well by comparing in situ observations of the leaking well with a time-dependent flow rate model derived from pressure readings taken after the Macondo well was shut in for the well integrity test. Model simulations also proved valuable for predicting the effect of partial deployment of the blowout preventer rams on flow rate. Taken together, the scientific analyses support flow rates in the range of ∼50,000-70,000 barrels/d, perhaps modestly decreasing over the duration of the oil spill, for a total release of ∼5.0 million barrels of oil, not accounting for BP's collection effort. By quantifying the amount of oil at different locations (wellhead, ocean surface, and atmosphere), we conclude that just over 2 million barrels of oil (after accounting for containment) and all of the released methane remained in the deep sea. By better understanding the fate of the hydrocarbons, the total discharge can be partitioned into separate components that pose threats to deep sea vs. coastal ecosystems, allowing responders in future events to scale their actions accordingly.

Review of flow rate estimates of the Deepwater Horizon oil spill

USGS Publications Warehouse

McNutt, Marcia K.; Camilli, Rich; Crone, Timothy J.; Guthrie, George D.; Hsieh, Paul A.; Ryerson, Thomas B.; Savas, Omer; Shaffer, Frank

2012-01-01

The unprecedented nature of the Deepwater Horizon oil spill required the application of research methods to estimate the rate at which oil was escaping from the well in the deep sea, its disposition after it entered the ocean, and total reservoir depletion. Here, we review what advances were made in scientific understanding of quantification of flow rates during deep sea oil well blowouts. We assess the degree to which a consensus was reached on the flow rate of the well by comparing in situ observations of the leaking well with a time-dependent flow rate model derived from pressure readings taken after the Macondo well was shut in for the well integrity test. Model simulations also proved valuable for predicting the effect of partial deployment of the blowout preventer rams on flow rate. Taken together, the scientific analyses support flow rates in the range of ~50,000–70,000 barrels/d, perhaps modestly decreasing over the duration of the oil spill, for a total release of ~5.0 million barrels of oil, not accounting for BP's collection effort. By quantifying the amount of oil at different locations (wellhead, ocean surface, and atmosphere), we conclude that just over 2 million barrels of oil (after accounting for containment) and all of the released methane remained in the deep sea. By better understanding the fate of the hydrocarbons, the total discharge can be partitioned into separate components that pose threats to deep sea vs. coastal ecosystems, allowing responders in future events to scale their actions accordingly.

Review of flow rate estimates of the Deepwater Horizon oil spill

PubMed Central

McNutt, Marcia K.; Camilli, Rich; Crone, Timothy J.; Guthrie, George D.; Hsieh, Paul A.; Ryerson, Thomas B.; Savas, Omer; Shaffer, Frank

2012-01-01

The unprecedented nature of the Deepwater Horizon oil spill required the application of research methods to estimate the rate at which oil was escaping from the well in the deep sea, its disposition after it entered the ocean, and total reservoir depletion. Here, we review what advances were made in scientific understanding of quantification of flow rates during deep sea oil well blowouts. We assess the degree to which a consensus was reached on the flow rate of the well by comparing in situ observations of the leaking well with a time-dependent flow rate model derived from pressure readings taken after the Macondo well was shut in for the well integrity test. Model simulations also proved valuable for predicting the effect of partial deployment of the blowout preventer rams on flow rate. Taken together, the scientific analyses support flow rates in the range of ∼50,000–70,000 barrels/d, perhaps modestly decreasing over the duration of the oil spill, for a total release of ∼5.0 million barrels of oil, not accounting for BP's collection effort. By quantifying the amount of oil at different locations (wellhead, ocean surface, and atmosphere), we conclude that just over 2 million barrels of oil (after accounting for containment) and all of the released methane remained in the deep sea. By better understanding the fate of the hydrocarbons, the total discharge can be partitioned into separate components that pose threats to deep sea vs. coastal ecosystems, allowing responders in future events to scale their actions accordingly. PMID:22187459

Effect of xylan and lignin removal by batch and flowthrough pretreatment on the enzymatic digestibility of corn stover cellulose.

PubMed

Yang, Bin; Wyman, Charles E

2004-04-05

Compared with batch systems, flowthrough and countercurrent reactors have important potential advantages for pretreating cellulosic biomass, including higher hemicellulose sugar yields, enhanced cellulose digestibility, and reduced chemical additions. Unfortunately, they suffer from high water and energy use. To better understand these trade-offs, comparative data are reported on xylan and lignin removal and enzymatic digestibility of cellulose for corn stover pretreated in batch and flowthrough reactors over a range of flow rates between 160 degrees and 220 degrees C, with water only and also with 0.1 wt% sulfuric acid. Increasing flow with just water enhanced the xylan dissolution rate, more than doubled total lignin removal, and increased cellulose digestibility. Furthermore, adding dilute sulfuric acid increased the rate of xylan removal for both batch and flowthrough systems. Interestingly, adding acid also increased the lignin removal rate with flow, but less lignin was left in solution when acid was added in batch. Although the enzymatic hydrolysis of pretreated cellulose was related to xylan removal, as others have shown, the digestibility was much better for flowthrough compared with batch systems, for the same degree of xylan removal. Cellulose digestibility for flowthrough reactors was related to lignin removal as well. These results suggest that altering lignin also affects the enzymatic digestibility of corn stover. Copyright 2004 Wiley Periodicals, Inc.

AN EVALUATION OF PRIMARY DATA-COLLECTION MODES IN AN ADDRESS-BASED SAMPLING DESIGN.

PubMed

Amaya, Ashley; Leclere, Felicia; Carris, Kari; Liao, Youlian

2015-01-01

As address-based sampling becomes increasingly popular for multimode surveys, researchers continue to refine data-collection best practices. While much work has been conducted to improve efficiency within a given mode, additional research is needed on how multimode designs can be optimized across modes. Previous research has not evaluated the consequences of mode sequencing on multimode mail and phone surveys, nor has significant research been conducted to evaluate mode sequencing on a variety of indicators beyond response rates. We conducted an experiment within the Racial and Ethnic Approaches to Community Health across the U.S. Risk Factor Survey (REACH U.S.) to evaluate two multimode case-flow designs: (1) phone followed by mail (phone-first) and (2) mail followed by phone (mail-first). We compared response rates, cost, timeliness, and data quality to identify differences across case-flow design. Because surveys often differ on the rarity of the target population, we also examined whether changes in the eligibility rate altered the choice of optimal case flow. Our results suggested that, on most metrics, the mail-first design was superior to the phone-first design. Compared with phone-first, mail-first achieved a higher yield rate at a lower cost with equivalent data quality. While the phone-first design initially achieved more interviews compared to the mail-first design, over time the mail-first design surpassed it and obtained the greatest number of interviews.

Numerical analysis of urine flow through the side holes of a double J stent in a ureteral stenosis.

PubMed

Kim, Hyoung-Ho; Choi, Young Ho; Lee, Seung Bae; Baba, Yasutaka; Kim, Kyung-Wuk; Suh, Sang-Ho

2017-07-20

Ureteral stenosis presents with a narrowing in the ureter, due to an intrinsic or extrinsic ureteral disease, such as ureter cancer or retroperitoneal fibrosis. The placement of a double J stent in the upper urinary system is one of the most common treatments of ureteral stenosis, along with the insertion of a percutaneous nephrostomy tube into the renal pelvis. The effect that the side holes in a double J stent have on urine flow has been evaluated in a few studies using straight ureter models. In this study, urine flow through a double J stent's side holes was analyzed in curved ureter models, which were based on human anatomy. In ureteral stenosis, especially in severe ureteral stenosis, a stent with side holes had a positive effect on the luminal and total flow rates, compared with the rates for a stent without side holes. The more side holes a stent has, the greater the luminal and total flow rates. However, the angular positions of the side holes did not affect flow rate. In conclusion, the side holes in a double J stent had a positive effect on ureteral stenosis, and the effect became greater as the ureteral stenosis became more severe.

Static Flow Characteristics of a Mass Flow Injecting Valve

NASA Technical Reports Server (NTRS)

Mattern, Duane; Paxson, Dan

1995-01-01

A sleeve valve is under development for ground-based forced response testing of air compression systems. This valve will be used to inject air and to impart momentum to the flow inside the first stage of a multi-stage compressor. The valve was designed to deliver a maximum mass flow of 0.22 lbm/s (0.1 kg/s) with a maximum valve throat area of 0.12 sq. in (80 sq. mm), a 100 psid (689 KPA) pressure difference across the valve and a 68 F, (20 C) air supply. It was assumed that the valve mass flow rate would be proportional to the valve orifice area. A static flow calibration revealed a nonlinear valve orifice area to mass flow relationship which limits the maximum flow rate that the valve can deliver. This nonlinearity was found to be caused by multiple choking points in the flow path. A simple model was used to explain this nonlinearity and the model was compared to the static flow calibration data. Only steady flow data is presented here. In this report, the static flow characteristics of a proportionally controlled sleeve valve are modelled and validated against experimental data.

Endovascular Treatment of Posterior Cerebral Artery Aneurysms With Flow Diversion: Case Series and Systematic Review.

PubMed

Wallace, Adam N; Grossberg, Jonathan A; Almandoz, Josser E Delgado; Kamran, Mudassar; Roy, Anil K; Kayan, Yasha; Austin, Matthew J; Howard, Brian M; Moran, Christopher J; Cawley, C Michael; Cross, DeWitte T; Dion, Jacques E; Kansagra, Akash P; Osbun, Joshua W

2018-03-08

Flow diversion of posterior cerebral artery (PCA) aneurysms has not been widely reported, possibly owing to concerns regarding parent vessel size and branch vessel coverage. To examine the safety and effectiveness of PCA aneurysm flow diverter treatment. Retrospective review of PCA aneurysms treated with the Pipeline Embolization Device (PED; Medtronic Inc, Dublin, Ireland) at 3 neurovascular centers, including periprocedural complications and clinical and angiographic outcomes. Systematic review of the literature identified published reports of PCA aneurysms treated with flow diversion. Rates of aneurysm occlusion and complications were calculated, and outcomes of saccular and fusiform aneurysm treatments were compared. Ten PCA aneurysms in 9 patients were treated with the PED. There were 2 intraprocedural thromboembolic events (20%), including 1 symptomatic infarction and 1 delayed PED thrombosis. Eight of 10 patients returned to or improved from their baseline functional status. Complete aneurysm occlusion with parent vessel preservation was achieved in 75% (6/8) of cases at mean follow-up of 16.7 mo. Eleven of 12 (92%) major branch vessels covered by a PED remained patent. Including the present study, systematic review of 15 studies found a complete aneurysm occlusion rate of 88% (30/34) and complication rate of 26% (10/38), including 5 symptomatic ischemic strokes (13%; 5/38). Fusiform aneurysms more frequently completely occluded compared with saccular aneurysms (100% vs 70%; P = .03) but were associated with a higher complication rate (43% vs 9%; P = .06). The safety and effectiveness profile of flow diverter treatment of PCA aneurysms may be acceptable in select cases.

Effect of flow rate and lead/copper pipe sequence on lead release from service lines.

PubMed

Cartier, Clément; Arnold, Roger B; Triantafyllidou, Simoni; Prévost, Michèle; Edwards, Marc

2012-09-01

A pilot experiment examined lead leaching from four representative configurations of service lines including: (1) 100% lead (Pb), (2) 100% copper (Cu), (3) 50% Pb upstream of 50% Cu, and (4) 50% Pb-downstream of 50% Cu using a range of flow rates. The cumulative mass of lead release indicated that a typical partial replacement configuration (50% lead downstream of copper) did not provide a net reduction in lead when compared to 100% lead pipe (85 mg for 50% Pb-downstream versus 83 mg for 100%-Pb) due to galvanic and deposition corrosion. The partially replaced service line configuration also had a much greater likelihood of producing water with "spikes" of lead particulates at higher flow rates, while tending to produce lower levels of lead at very low flow rates. After the first 214 days the galvanic current between copper and lead was only reduced by 34%, proving that galvanic impacts can be highly persistent even in water with optimized corrosion control by dosing of zinc orthophosphate. Finally, this experiment raises concern about the low flow rates used during some prior home sampling events, which may underestimate exposure to lead during normal water use, especially when galvanic Pb:Cu connections are present. Copyright © 2012 Elsevier Ltd. All rights reserved.

Direct-Photon Spectra and Anisotropic Flow in Heavy Ion Collisions from Holography

NASA Astrophysics Data System (ADS)

Iatrakis, Ioannis; Kiritsis, Elias; Shen, Chun; Yang, Di-Lun

2017-03-01

The thermal-photon emission from strongly coupled gauge theories at finite temperature is calculated by using holographic models for QCD in the Veneziano limit (V-QCD). These emission rates are then embedded in hydrodynamic simulations combined with prompt photons from hard scattering and the thermal photons from hadron gas to analyze the spectra and anisotropic flow of direct photons at RHIC and LHC. The results from different sources responsible for the thermal photons in the quark gluon plasma (QGP) including the weakly coupled QGP (wQGP) from perturbative calculations, strongly coupled N = 4 super Yang-Mills (SYM) plasma (as a benchmark for reference), and Gubser's phenomenological model mimicking the strongly coupled QGP (sQGP) are then compared. It is found that the direct-photon spectra are enhanced in the strongly coupled scenario compared with the ones in the wQGP, especially at intermediate and high momenta, which improve the agreements with data. Moreover, by using IP-glassma initial states, both the elliptic flow and triangular flow of direct photons are amplified at high momenta (pT > 2.5 GeV) for V-QCD, while they are suppressed at low momenta compared to wQGP. The distinct results in holography stem from the blue-shift of emission rates in strong coupling. In addition, the spectra and flow in small collision systems were evaluated for future comparisons. It is found that thermal photons from the deconfined phase are substantial to reconcile the spectra and flow at high momenta.

The effect of forward skewed rotor blades on aerodynamic and aeroacoustic performance of axial-flow fan

NASA Astrophysics Data System (ADS)

Wei, Jun; Zhong, Fangyuan

Based on comparative experiment, this paper deals with using tangentially skewed rotor blades in axial-flow fan. It is seen from the comparison of the overall performance of the fan with skewed bladed rotor and radial bladed rotor that the skewed blades operate more efficiently than the radial blades, especially at low volume flows. Meanwhile, decrease in pressure rise and flow rate of axial-flow fan with skewed rotor blades is found. The rotor-stator interaction noise and broadband noise of axial-flow fan are reduced with skewed rotor blades. Forward skewed blades tend to reduce the accumulation of the blade boundary layer in the tip region resulting from the effect of centrifugal forces. The turning of streamlines from the outer radius region into inner radius region in blade passages due to the radial component of blade forces of skewed blades is the main reason for the decrease in pressure rise and flow rate.

Blood flow measurement of human skeletal muscle during various exercise intensity using diffuse correlation spectroscopy (DCS)

NASA Astrophysics Data System (ADS)

Murakami, Yuya; Ono, Yumie; Ichinose, Masashi

2017-02-01

We studied blood flow dynamics of active skeletal muscle using diffuse correlation spectroscopy (DCS), an emerging optical modality that is suitable for noninvasive quantification of microcirculation level in deep tissue. Seven healthy subjects conducted 0.5 Hz dynamic handgrip exercise for 3 minutes at intensities of 10, 20, 30, and 50 % of maximal voluntary contraction (MVC). DCS could detect the time-dependent increase of the blood flow response of the forearm muscle for continuous exercises, and the increase ratios of the mean blood flow through the exercise periods showed good correlation with the exercise intensities. We also compared blood flow responses detected from DCS with two different photon sampling rates and found that an appropriate photon sampling rates should be selected to follow the wide-ranged increase in the muscle blood flow with dynamic exercise. Our results demonstrate the possibility for utilizing DCS in a field of sports medicine to noninvasively evaluate the dynamics of blood flow in the active muscles.

Comparison of pitch rate history effects on dynamic stall

NASA Technical Reports Server (NTRS)

Chandrasekhara, M. S.; Carr, Lawrence W.; Ahmed, S.

1992-01-01

Dynamic stall of an airfoil is a classic case of forced unsteady separated flow. Flow separation is brought about by large incidences introduced by the large amplitude unsteady pitching motion of an airfoil. One of the parameters that affects the dynamic stall process is the history of the unsteady motion. In addition, the problem is complicated by the effects of compressibility that rapidly appear over the airfoil even at low Mach numbers at moderately high angles of attack. Consequently, it is of interest to know the effects of pitch rate history on the dynamic stall process. This abstract compares the results of a flow visualization study of the problem with two different pitch rate histories, namely, oscillating airfoil motion and a linear change in the angle of attack due to a transient pitching motion.

Lava effusion rate definition and measurement: a review

USGS Publications Warehouse

Calvari, Sonia; Dehn, Jonathan; Harris, A.

2007-01-01

Measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics, as well as for monitoring efforts during on-going eruptions. However, its exact definition remains a source of confusion, and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales, or measured using different approaches. Thus our aims are to: (1) define effusion rate terminology; and (2) assess the various measurement methods and their results. We first distinguish between instantaneous effusion rate, and time-averaged discharge rate. Eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began. The ultimate extension of this is mean output rate, this being the final volume of erupted lava divided by total eruption duration. Whether these values are total values, i.e. the flux feeding all flow units across the entire flow field, or local, i.e. the flux feeding a single active unit within a flow field across which many units are active, also needs to be specified. No approach is without its problems, and all can have large error (up to ∼50%). However, good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here. There are three important factors to consider and state when measuring, giving or using an effusion rate. First, the time-period over which the value was averaged; second, whether the measurement applies to the entire active flow field, or a single lava flow within that field; and third, the measurement technique and its accompanying assumptions.

Association between chewing-stimulated salivary flow under the effects of atropine and mixing ability assessed using a color-changeable chewing gum.

PubMed

Kubota, Chieko; Kanazawa, Manabu; Hama, Yohei; Komagamine, Yuriko; Minakuchi, Shunsuke

2017-10-01

To assess the time course of chewing-stimulated salivary flow after oral atropine administration, and determine the association between chewing-stimulated salivary flow and mixing ability using color-changeable chewing gum in dentate adults. Ten healthy dentate adults were administered 1mg oral atropine to induce mouth dryness. The subjects' chewing-stimulated salivary flow was assessed using the Saxon test. They were then asked to rinse their mouth with tap water for 15s, and to chew on color-changeable chewing gum for 60s at a constant rate of 60 cycles per min. This procedure was performed before, and at 10-min intervals for up to 120min after the atropine administration. The experiment was repeated after 1 week. Steel's test was used to compare the chewing-stimulated salivary flow rates at each time point after atropine administration with the baseline value. The effect of the stimulated salivary flow rates on the degree of color change was analyzed using linear mixed effects models, with the stimulated salivary flow rates as fixed factors and subjects as the random factor. Chewing-stimulated salivary flow showed a significant decrease from 50 to 120min after oral atropine administration (P<0.05) and the amount of chewing-stimulated salivary flow had a significant effect on the color change of the color-changeable chewing gum (P<0.001). We observed a decrease in stimulated salivary flow after orally administering 1mg atropine, and a positive association between mixing ability using color-changeable chewing gum and chewing-stimulated salivary flow in dentate subjects. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Interspecific variation in hypoxia tolerance, swimming performance and plasticity in cyprinids that prefer different habitats.

PubMed

Fu, Shi-Jian; Fu, Cheng; Yan, Guan-Jie; Cao, Zhen-Dong; Zhang, An-Jie; Pang, Xu

2014-02-15

This study quantified and compared hypoxia tolerance and swim performance among cyprinid fish species from rapid-, slow- and intermediate-flow habitats (four species per habitat) in China. In addition, we explored the effects of short-term acclimation on swim performance, maximum metabolic rate (M(O2,max)) and gill remodelling to detect habitat-associated patterns of plastic response to hypoxia. Indices of hypoxia tolerance included oxygen threshold for loss of equilibrium (LOE50) and aquatic surface respiration (ASR50), and critical oxygen tension for routine metabolic rate (Pcrit). Critical swimming speed (Ucrit) and M(O2,max) were measured under normoxic and hypoxic conditions after 48 h acclimation to normoxia and hypoxia, and gill remodelling was estimated after 48 h of hypoxia exposure. Both traditional ANCOVA and phylogenetically independent contrast (PDANOVA) analyses showed that fish species from rapid-flow habitats exhibited lower LOE50 compared with fish from intermediate- and slow-flow habitats. Habitat-specific differences in Pcrit and Ucrit were detected using PDANOVA but not traditional ANCOVA analyses, with fish species from rapid-flow habitats exhibiting lower Pcrit but higher Ucrit values compared with fish from intermediate- and slow-flow habitats. Fish species from rapid-flow habitats were also characterized by less plasticity in swim performance and gill morphology in response to hypoxia acclimation compared with species from slow-flow habitats, but a greater drop in swim performance in response to acute hypoxia exposure. The study detected a habitat-specific difference in hypoxia tolerance, swimming performance and its plasticity among fish from habitats with different flow conditions, possibly because of the long-term adaptation to the habitat caused by selection stress. The PDANOVA analyses were more powerful than traditional statistical analyses according to the habitat effects in both hypoxia tolerance and swimming performance in this study.

Reduced salivary flow and colonization by mutans streptococci in children with Down syndrome

PubMed Central

Areias, Cristina; Sampaio-Maia, Benedita; de Lurdes Pereira, Maria; Azevedo, Álvaro; Melo, Paulo; Andrade, Casimiro; Scully, Crispian

2012-01-01

OBJECTIVES: Although individuals with Down syndrome have considerable oral disease, the prevalence of dental caries in this group is low. The present study aimed to compare known risk factors for dental caries development in children with Down syndrome and a matched population (siblings). In both populations, the number of acidogenic microorganisms, such as mutans streptococci, lactobacilli and Candida species, and the paraffin-stimulated pH, flow rate and IgA concentration in whole saliva were evaluated and compared. METHOD: Saliva was collected, and the caries index was evaluated in 45 sibling pairs aged between 6 and 18 years old. The salivary IgA concentration was determined by immunoturbidimetry. Salivary mutans streptococci, lactobacilli and Candida species were quantified on mitis salivarius agar containing bacitracin and 20% sucrose, rogosa agar supplemented with glacial acetic acid and sabouraud agar supplemented with chloramphenicol, respectively. RESULTS: Down syndrome children had a higher caries-free rate (p<0.05) and lower salivary mutans streptococci counts (p<0.03) compared to their siblings. Similar numbers of lactobacilli and Candida species were found in both groups. Salivary flow rates were 36% lower in Down syndrome children compared to their siblings (p<0.05). The salivary pH did not differ between Down syndrome children and controls. The Down syndrome children had an IgA secretion rate 29% lower than that of their siblings, but this difference was not statistically significant. CONCLUSIONS: In conclusion, the lower number of mutans streptococci in the saliva may be one of the factors contributing to the lower caries rate observed in Down syndrome children, despite evidence of hyposalivation. PMID:23018295

Cyclic stress analysis of an air-cooled turbine vane

NASA Technical Reports Server (NTRS)

Kaufman, A.; Gauntner, D. J.; Gauntner, J. W.

1975-01-01

The effects of gas pressure level, coolant temperature, and coolant flow rate on the stress-strain history and life of an air-cooled vane were analyzed using measured and calculated transient metal temperatures and a turbine blade stress analysis program. Predicted failure locations were compared to results from cyclic tests in a static cascade and engine. The results indicate that a high gas pressure was detrimental, a high coolant flow rate somewhat beneficial, and a low coolant temperature the most beneficial to vane life.

Effective temperature dynamics of shear bands in metallic glasses

NASA Astrophysics Data System (ADS)

Daub, Eric G.; Klaumünzer, David; Löffler, Jörg F.

2014-12-01

We study the plastic deformation of bulk metallic glasses with shear transformation zone (STZ) theory, a physical model for plasticity in amorphous systems, and compare it with experimental data. In STZ theory, plastic deformation occurs when localized regions rearrange due to applied stress and the density of these regions is determined by a dynamically evolving effective disorder temperature. We compare the predictions of STZ theory to experiments that explore the low-temperature deformation of Zr-based bulk metallic glasses via shear bands at various thermal temperatures and strain rates. By following the evolution of effective temperature with time, strain rate, and temperature through a series of approximate and numerical solutions to the STZ equations, we successfully model a suite of experimentally observed phenomena, including shear-band aging as apparent from slide-hold-slide tests, a temperature-dependent steady-state flow stress, and a strain-rate- and temperature-dependent transition from stick-slip (serrated flow) to steady-sliding (nonserrated flow). We find that STZ theory quantitatively matches the observed experimental data and provides a framework for relating the experimentally measured energy scales to different types of atomic rearrangements.

Mechanisms of high-temperature, solid-state flow in minerals and ceramics and their bearing on the creep behavior of the mantle

USGS Publications Warehouse

Kirby, S.H.; Raleigh, C.B.

1973-01-01

The problem of applying laboratory silicate-flow data to the mantle, where conditions can be vastly different, is approached through a critical review of high-temperature flow mechanisms in ceramics and their relation to empirical flow laws. The intimate association of solid-state diffusion and high-temperature creep in pure metals is found to apply to ceramics as well. It is shown that in ceramics of moderate grain size, compared on the basis of self-diffusivity and elastic modulus, normalized creep rates compare remarkably well. This comparison is paralleled by the near universal occurrence of similar creep-induced structures, and it is thought that the derived empirical flow laws can be associated with dislocation creep. Creep data in fine-grained ceramics, on the other hand, are found to compare poorly with theories involving the stress-directed diffusion of point defects and have not been successfully correlated by self-diffusion rates. We conclude that these fine-grained materials creep primarily by a quasi-viscous grain-boundary sliding mechanism which is unlikely to predominate in the earth's deep interior. Creep predictions for the mantle reveal that under most conditions the empirical dislocation creep behavior predominates over the mechanisms involving the stress-directed diffusion of point defects. The probable role of polymorphic transformations in the transition zone is also discussed. ?? 1973.

Analysis of the Casson and Carreau-Yasuda non-Newtonian blood models in steady and oscillatory flows using the lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Boyd, Joshua; Buick, James M.; Green, Simon

2007-09-01

The lattice Boltzmann method is modified to allow the simulation of non-Newtonian shear-dependent viscosity models. Casson and Carreau-Yasuda non-Newtonian blood viscosity models are implemented and are used to compare two-dimensional Newtonian and non-Newtonian flows in the context of simple steady flow and oscillatory flow in straight and curved pipe geometries. It is found that compared to analogous Newtonian flows, both the Casson and Carreau-Yasuda flows exhibit significant differences in the steady flow situation. In the straight pipe oscillatory flows, both models exhibit differences in velocity and shear, with the largest differences occurring at low Reynolds and Womersley numbers. Larger differences occur for the Casson model. In the curved pipe Carreau-Yasuda model, moderate differences are observed in the velocities in the central regions of the geometries, and the largest shear rate differences are observed near the geometry walls. These differences may be important for the study of atherosclerotic progression.

PARTICLE IMAGE VELOCIMETRY MEASUREMENTS IN A REPRESENTATIVE GAS-COOLED PRISMATIC REACTOR CORE MODEL: FLOW IN THE COOLANT CHANNELS AND INTERSTITIAL BYPASS GAPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas E. Conder; Richard Skifton; Ralph Budwig

Core bypass flow is one of the key issues with the prismatic Gas Turbine-Modular Helium Reactor, and it refers to the coolant that navigates through the interstitial, non-cooling passages between the graphite fuel blocks instead of traveling through the designated coolant channels. To determine the bypass flow, a double scale representative model was manufactured and installed in the Matched Index-of-Refraction flow facility; after which, stereo Particle Image Velocimetry (PIV) was employed to measure the flow field within. PIV images were analyzed to produce vector maps, and flow rates were calculated by numerically integrating over the velocity field. It was foundmore » that the bypass flow varied between 6.9-15.8% for channel Reynolds numbers of 1,746 and 4,618. The results were compared to computational fluid dynamic (CFD) pre-test simulations. When compared to these pretest calculations, the CFD analysis appeared to under predict the flow through the gap.« less

Comparative analysis between Payen and Daedalia Planum lava fields

NASA Astrophysics Data System (ADS)

Giacomini, Lorenza; Massironi, Matteo; Pasquarè, Giorgio; Carli, Cristian; Martellato, Elena; Frigeri, Alessandro; Cremonese, Gabriele; Bistacchi, Andrea; Federico, Costanzo

The Payen volcanic complex is a large Quaternary fissural structure belonging to the back-arc extensional area of the Andes in the Mendoza Province (Argentina). From the eastern portion of this volcanic structure huge pahoehoe lava flows were emitted, extending more than 180 km from the feeding vents. These huge flows propagated over the nearly flat surface of the Pampean foreland (ca 0.3° slope). The very low viscosity of the olivine basalt lavas, coupled with the inflation process are the most probable explanation for their considerable length. In an inflation process a thin viscoelastic crust, produced at an early stage, is later inflated by the underlying fluid core, which remains hot and fluid thanks to the thermal-shield effect of the crust. The inflation shows some typical morphological fingerprints like tumuli, lava lobes, lava rises and lava ridges. In order to compare the morphology of the Argentinean Payen flows with lava flows on Mars, MOLA, THEMIS, MOC, MRO/HIRISE, and MEX/OMEGA data have been analysed, providing a multi-scale characterisation of Martian flows. Mars Global Surveyor/MOLA data were used to investigate the topographic environment over which flows propagated on Mars in order to detect very low angle slopes where possibly inflation processes could have developed. Then Mars Odyssey/THEMIS and Mars Global Surveyor's MOC data were used to detect Martian lava flows with inflation "fingerprints", whereas OMEGA data were used to obtain some inferences about their composition. Finally the MRO/HIRISE images recently acquired, can provide further details and constraints on surface morphologies and lava fronts. All these data were used to analyze Daedalia Planum lava field, at about 300 km southwest of Arsia Mons, and clear morphological similarities with the longest flows of the Payen lava fields were found. These striking morphological analogies suggest that inflation process is quite common also for the Daedalia field. This is also supported by simple calculation of effusion rates for not inflated lava flows foreseeing for the Daedalia Planum long lava flows improbable huge rates. Consequently lower effusion rates coupled with very efficient spreading process are more likely. Nonetheless the comparison of typology vs frequency and dimension of inflation related features of Payen and Daedalia Planum field suggest that even the effusion rates responsible of inflated flows on Mars are by far higher than the one on the Earth.

Combined effects of flow condition and parasitism on shoaling behaviour of female guppies Poecilia reticulata.

PubMed

Hockley, F A; Wilson, C A M E; Graham, N; Cable, J

2014-01-01

Group living in fish can provide benefits of protection from predators and some parasites, more efficient foraging for food, increased mating opportunities and enhanced energetic benefit when swimming. For riverine species, shoaling behaviour can be influenced by various environmental stressors, yet little is known how flow rate might influence the shoaling of diseased fish shoals. In view of the increasingly unpredictable flow rates in streams and rivers, this study aimed to assess the combined effect of flow condition and parasitism on the shoaling behaviour of a model fish species. Shoal size, shoal cohesion and time spent shoaling of female guppies Poecilia reticulata were compared when infected with the directly transmitted ectoparasite Gyrodactylus turnbulli under flow and static conditions. Flow condition was an important factor in influencing shoaling behaviour of guppies with the fish forming larger shoals in the absence of flow. When a shoal member was infected with G. turnbulli , shoal cohesion was reduced, but the magnitude of this effect was dependent on flow condition. In both flow and static conditions, bigger fish formed larger shoals than smaller counterparts. Future changes to stream hydrology with more frequent flooding and drought events will affect the shoaling tendency of fish. During high-flow events, diseased fish may not be able to keep up with shoal mates and therefore have a higher risk of predation. Additionally, these findings may be important for aquaria and farmed species where an increase in flow rate may reduce aggregation in fish.

Irrigation of human prepared root canal – ex vivo based computational fluid dynamics analysis

PubMed Central

Šnjarić, Damir; Čarija, Zoran; Braut, Alen; Halaji, Adelaida; Kovačević, Maja; Kuiš, Davor

2012-01-01

Aim To analyze the influence of the needle type, insertion depth, and irrigant flow rate on irrigant flow pattern, flow velocity, and apical pressure by ex-vivo based endodontic irrigation computational fluid dynamics (CFD) analysis. Methods Human upper canine root canal was prepared using rotary files. Contrast fluid was introduced in the root canal and scanned by computed tomography (CT) providing a three-dimensional object that was exported to the computer-assisted design (CAD) software. Two probe points were established in the apical portion of the root canal model for flow velocity and pressure measurement. Three different CAD models of 27G irrigation needles (closed-end side-vented, notched open-end, and bevel open-end) were created and placed at 25, 50, 75, and 95% of the working length (WL). Flow rates of 0.05, 0.1, 0.2, 0.3, and 0.4 mL/s were simulated. A total of 60 irrigation simulations were performed by CFD fluid flow solver. Results Closed-end side-vented needle required insertion depth closer to WL, regarding efficient irrigant replacement, compared to open-end irrigation needle types, which besides increased velocity produced increased irrigant apical pressure. For all irrigation needle types and needle insertion depths, the increase of flow rate was followed by an increased irrigant apical pressure. Conclusions The human root canal shape obtained by CT is applicable in the CFD analysis of endodontic irrigation. All the analyzed values –irrigant flow pattern, velocity, and pressure – were influenced by irrigation needle type, as well as needle insertion depth and irrigant flow rate. PMID:23100209

Irrigation of human prepared root canal--ex vivo based computational fluid dynamics analysis.

PubMed

Snjaric, Damir; Carija, Zoran; Braut, Alen; Halaji, Adelaida; Kovacevic, Maja; Kuis, Davor

2012-10-01

To analyze the influence of the needle type, insertion depth, and irrigant flow rate on irrigant flow pattern, flow velocity, and apical pressure by ex-vivo based endodontic irrigation computational fluid dynamics (CFD) analysis. Human upper canine root canal was prepared using rotary files. Contrast fluid was introduced in the root canal and scanned by computed tomography (CT) providing a three-dimensional object that was exported to the computer-assisted design (CAD) software. Two probe points were established in the apical portion of the root canal model for flow velocity and pressure measurement. Three different CAD models of 27G irrigation needles (closed-end side-vented, notched open-end, and bevel open-end) were created and placed at 25, 50, 75, and 95% of the working length (WL). Flow rates of 0.05, 0.1, 0.2, 0.3, and 0.4 mL/s were simulated. A total of 60 irrigation simulations were performed by CFD fluid flow solver. Closed-end side-vented needle required insertion depth closer to WL, regarding efficient irrigant replacement, compared to open-end irrigation needle types, which besides increased velocity produced increased irrigant apical pressure. For all irrigation needle types and needle insertion depths, the increase of flow rate was followed by an increased irrigant apical pressure. The human root canal shape obtained by CT is applicable in the CFD analysis of endodontic irrigation. All the analyzed values -irrigant flow pattern, velocity, and pressure - were influenced by irrigation needle type, as well as needle insertion depth and irrigant flow rate.

Flow characteristics around a deformable stenosis under pulsatile flow condition

NASA Astrophysics Data System (ADS)

Choi, Woorak; Park, Jun Hong; Byeon, Hyeokjun; Lee, Sang Joon

2018-01-01

A specific portion of a vulnerable stenosis is deformed periodically under a pulsatile blood flow condition. Detailed analysis of such deformable stenosis is important because stenotic deformation can increase the likelihood of rupture, which may lead to sudden cardiac death or stroke. Various diagnostic indices have been developed for a nondeformable stenosis by using flow characteristics and resultant pressure drop across the stenosis. However, the effects of the stenotic deformation on the flow characteristics remain poorly understood. In this study, the flows around a deformable stenosis model and two different rigid stenosis models were investigated under a pulsatile flow condition. Particle image velocimetry was employed to measure flow structures around the three stenosis models. The deformable stenosis model was deformed to achieve high geometrical slope and height when the flow rate was increased. The deformation of the stenotic shape enhanced jet deflection toward the opposite vessel wall of the stenosis. The jet deflection in the deformable model increased the rate of jet velocity and turbulent kinetic energy (TKE) production as compared with those in the rigid models. The effect of stenotic deformation on the pulsating waveform related with the pressure drop was analyzed using the TKE production rate. The deformable stenosis model exhibited a phase delay of the peak point in the waveform. These results revealed the potential use of pressure drop waveform as a diagnostic index for deformable stenosis.

Neonatal self-inflating bags: achieving titrated oxygen delivery using low flows: an experimental study.

PubMed

Sasi, Arun; Chandrakumar, Natarajan; Deorari, Ashok; Paul, Vinod K; Shankar, Jeeva; Sreenivas, Vishnubhatla; Agarwal, Ramesh

2013-08-01

To determine delivered O2 concentration (dFiO2) during manual inflations using neonatal self-inflating resuscitation bags (SIBs) at oxygen (O2) flow rates <1 L/min. This experimental study, determined dFiO2 during 216 sets of manual inflations at different O2 flow rate (L/min; 0.2, 0.4, 0.6, 0.8, 1.0 and 5.0), controlling peak inspiratory pressures (PIP; cm of H2O; 10-15, 15-20 and 20-25), inflation rates (per min; 30, 40 and 60), with and without O2 reservoir using two SIBs--the Laerdal infant resuscitator (240 mL) and Ambu Mark IV resuscitator (300 mL). A leak proof circuit connecting the SIB in series with pressure transducer, O2 analyzer and test lung was used. All possible combinations were tested four times each. The dFiO2 with each possible combination was compared using generalised estimating equation. The mean dFiO2 with SIB even without reservoirs varied with rates and PIP from 75 to 93% at O2 flow rate of 5 L/min. At 1 L/min flow itself, 65-85% O2 is delivered. The dFiO2 was reduced to approximately 40% with flow of 0.2 L/min, PIP 20-25 cmH2O and inflations 40-60 per min. During manual breaths using neonatal SIBs, the delivered O2 concentration of nearly 40% is attained at clinically used inflation pressures and rates by using lower flows. A graded increase in O2 delivery from 40 to 99% was obtained with flow varying from 0.2 to 5 L/min and addition of reservoir. However, even at such low flows, reduction in O2 concentration below 40% was unattained. © 2013 The Authors. Journal of Paediatrics and Child Health © 2013 Paediatrics and Child Health Division (Royal Australasian College of Physicians).

A comparative assessment of irrigation and drainage characteristics for commercially available urethral catheters

PubMed Central

Davis, Niall F.; McMahon, Barry P.; Walsh, Michael; McDermott, Thomas E.D.; Thornhill, John A.; Manecksha, Rustom P.

2017-01-01

Introduction We aimed to investigate irrigation and drainage characteristics of commercially available urethral catheters and determined which catheter offers the best flow characteristics. Material and methods Twelve different commercially available urethral catheters from three companies (Bard™, Rusch™ and Dover™) were investigated to compare their irrigation and drainage properties. Irrigation port, drainage port and overall cross-sectional areas for a 24Fr 3-way catheter was measured and compared. The maximum (Qmax) and average (Qavg) irrigation and drainage flow rates for each catheter was measured for 20–40 seconds using uroflowmetry. The primary endpoint was to determine which catheter offers optimal irrigation and drainage parameters. Results Overall cross-sectional area, irrigation port cross-sectional area, and drainage port cross-sectional area differed significantly for each 24Fr 3-way catheter assessed (p <0.001). The 24Fr 3-way Rusch Simplastic™ catheter consistently demonstrated the greatest maximal flow rate (Qmax: 5 ±0.3 ml/s) and average flow rate (Qavg: 4.6 ±0.2 ml/s) for irrigation. The 24Fr 3-way Dover™ catheter provided the greatest drainage properties (Qmax: 19.7 ±2 ml/s; Q avg: 15.9 ±5 ml/s). In the setting of continuous bladder irrigation, the 24Fr 3-way Rusch Simplastic™ catheter provided the highest irrigation rates (Qmax: 6.6 ±1.8 ml/s; Q avg: 4.6 ±0.9 ml/s). Conclusions Three-way catheters demonstrate significant differences in their irrigation and drainage characteristics. The type of catheter selected should be based on the appropriate prioritization of efficient bladder irrigation versus efficient bladder drainage. PMID:29410890

Achieving high convection volumes in postdilution online hemodiafiltration: a prospective multicenter study

PubMed Central

Chapdelaine, Isabelle; Nubé, Menso J; Blankestijn, Peter J; Bots, Michiel L; Konings, Constantijn J A M; Kremer Hovinga, Ton K; Molenaar, Femke M; van der Weerd, Neelke C; Grooteman, Muriel P C

2017-01-01

Abstract Background. Available evidence suggests a reduced mortality risk for patients treated with high-volume postdilution hemodiafiltration (HDF) when compared with hemodialysis (HD) patients. As the magnitude of the convection volume depends on treatment-related factors rather than patient-related characteristics, we prospectively investigated whether a high convection volume (defined as ≥22 L/session) is feasible in the majority of patients (>75%). Methods. A multicenter study was performed in adult prevalent dialysis patients. Nonparticipating eligible patients formed the control group. Using a stepwise protocol, treatment time (up to 4 hours), blood flow rate (up to 400 mL/min) and filtration fraction (up to 33%) were optimized as much as possible. The convection volume was determined at the end of this optimization phase and at 4 and 8 weeks thereafter. Results. Baseline characteristics were comparable in participants (n = 86) and controls (n = 58). At the end of the optimization and 8 weeks thereafter, 71/86 (83%) and 66/83 (80%) of the patients achieved high-volume HDF (mean 25.5 ± 3.6 and 26.0 ± 3.4 L/session, respectively). While treatment time remained unaltered, mean blood flow rate increased by 27% and filtration fraction increased by 23%. Patients with <22 L/session had a higher percentage of central venous catheters (CVCs), a shorter treatment time and lower blood flow rate when compared with patients with ≥22 L/session. Conclusions. High-volume HDF is feasible in a clear majority of dialysis patients. Since none of the patients agreed to increase treatment time, these findings indicate that high-volume HDF is feasible just by increasing blood flow rate and filtration fraction. PMID:29225810

Caries prevalence in chronic alcoholics and the relationship to salivary flow rate and pH.

PubMed

Dukić, Walter; Dobrijević, Tanja Trivanović; Katunarić, Marina; Lesić, Stjepanka

2013-03-01

The aim of this study was to investigate the dental status of alcoholics; to evaluate the relationship of unstimulated and stimulated saliva pH on their decayed/missing/filled teeth (DMFT); and to evaluate the relationship of unstimulated and stimulated salivary flow rate on their DMFT. A cross-sectional study was conducted in patients treated for alcohol dependency (n = 70; mean age 41.7 years) and a control group of non-alcoholics (n = 70; mean age 39.1 years). Examinations for dental caries were conducted using the World Health Organization (WHO) criteria and questionnaires. The correlation between nominal variables was determined using chi2 test (alpha = 0.05). The correlation between interval variables was determined using Pearson's correlation coefficient. The mean DMFT was similar in alcoholics (14.40) and the control group (13.44) (p > 0.05). There was a statistically significant correlation between alcoholism and unstimulated salivary flow rate (p < 0.05), but no relationship on DMFT was recorded. No statistically significant differences were found between alcoholics and controls in terms of stimulated salivary flow rate (p > 0.05) or stimulated salivary flow on DMFT (p > 0.05). There was a statistically significant correlation between alcoholism and the pH value of stimulated saliva (p < 0.01). There was no correlation between the amount of alcohol consumed and the number of carious lesions (p > 0.05). No major differences were found with respect to overall DMFT in alcoholics compared to the control group. Alcoholism and stimulated salivary flow rate showed no correlation. Unstimulated salivary flow rate as well as the pH values of both unstimulated and stimulated saliva, were lower in the alcoholic group.

Solute transport with time-variable flow paths during upward and downward flux in a heterogeneous unsaturated porous medium

NASA Astrophysics Data System (ADS)

Cremer, Clemens; Neuweiler, Insa; Bechtold, Michel; Vanderborght, Jan

2014-05-01

To acquire knowledge of solute transport through the unsaturated zone in the shallow subsurface is decisive to assess groundwater quality, nutrient cycling or to plan remediation strategies. The shallow subsurface is characterized by structural heterogeneity and strongly influenced by atmospheric conditions. This leads to changing flow directions, strong temporal changes in saturation and heterogeneous water fluxes during infiltration and evaporation events. Recent studies (e.g. Lehmann and Or, 2009; Bechtold et al.,2011) demonstrated the importance of lateral flow and solute transport during evaporation conditions (upward flux). The heterogeneous structure in these studies was constructed using two types of sand with strong material contrasts and arranged in parallel with a vertical orientation. Lateral transport and redistribution of solute from coarse to fine media was observed deeper in the soil column and from fine to coarse close to the soil surface. However, if boundary conditions are reversed due to precipitation, the flow field is not necessarily reversed in the same manner, resulting in entirely different transport patterns for downward and upward flow. Therefore, considering net-flow rates alone is misleading when describing transport under those conditions. In this contribution we analyze transport of a solute in the shallow subsurface to assess effects resulting from the temporal change of heterogeneous soil structures due to dynamic flow conditions. Two-dimensional numerical simulations of unsaturated flow and transport are conducted using a coupled finite volume and random walk particle tracking algorithm to quantify solute transport and leaching rates. Following previous studies (Lehmann and Or, 2009; Bechtold et al., 2011), the chosen domain is composed of two materials, coarse and fine sand, arranged in parallel with a vertical orientation. Hence, one sharp interface of strong material heterogeneity is induced. During evaporation both sands are assumed to stay under liquid-flow dominated evaporation conditions ("stage 1"). Simulations considering dynamic (infiltration-evaporation) and steady (solely infiltration) boundary conditions are carried out. The influence of dynamic boundary conditions (intensity and duration of precipitation and evaporation events) is examined in a multitude of simulations. If flow rates smaller than the saturated hydraulic conductivity of both materials are chosen to be applied as boundary condition, simulation results indicate that the flow field within the domain is exactly reversed. However, if applied flow rates exceed the saturated hydraulic conductivity of one material, the flow field is not just reversed, but different flow paths during downward and upward flow are observed. Results show the tendency of faster solute leaching under dynamic boundary conditions compared to steady infiltration conditions with the same net-infiltration rate. We use a double domain transport method as an upscaled model to reproduce vertically averaged concentration profiles with net flux only and compare the model parameters for information about flow dynamics and soil heterogeneity.

Efficiency of autothermal thermophilic aerobic digestion under two different oxygen flow rates.

PubMed

Aynur, Sebnem Koyunluoglu; Riffat, Rumana; Murthy, Sudhir

2014-01-01

The objective of this research was to understand the influence of oxygenation at two different oxygen flow rates (0.105 and 0.210 L/L/h) on autothermal thermophilic aerobic digestion (ATAD), and on the overall performance of Dual Digestion (DD). Profile experiments on an ATAD reactor showed that a significant portion of volatile fatty acids and ammonia were produced in the first 12 h period, and both followed first order kinetics. Ammonia concentrations of ATAD effluent were 1015 mg/L and 1450 mg/L, respectively, at the two oxygenation rates. Ammonia production was not complete in the ATAD reactor at the lower oxygenation rate. However, it was sufficient to maximize volatile solids reduction in the DD process. The biological heat of oxidations were 14,300 J/g Volatile Solids (VS) removed and 15,900 J/g VS removed for the two oxygen flow rates, respectively. The ATAD step provided enhanced digestion for the DD process with higher volatile solids removal and methane yield when compared to conventional digestion.

A near-wall turbulence model and its application to fully developed turbulent channel and pipe flows

NASA Technical Reports Server (NTRS)

Kim, S.-W.

1988-01-01

A near wall turbulence model and its incorporation into a multiple-time-scale turbulence model are presented. In the method, the conservation of mass, momentum, and the turbulent kinetic energy equations are integrated up to the wall; and the energy transfer rate and the dissipation rate inside the near wall layer are obtained from algebraic equations. The algebraic equations for the energy transfer rate and the dissipation rate inside the near wall layer were obtained from a k-equation turbulence model and the near wall analysis. A fully developed turbulent channel flow and fully developed turbulent pipe flows were solved using a finite element method to test the predictive capability of the turbulence model. The computational results compared favorably with experimental data. It is also shown that the present turbulence model could resolve the over shoot phenomena of the turbulent kinetic energy and the dissipation rate in the region very close to the wall.

Microparticle tracking velocimetry as a tool for microfluidic flow measurements

NASA Astrophysics Data System (ADS)

Salipante, Paul; Hudson, Steven D.; Schmidt, James W.; Wright, John D.

2017-07-01

The accurate measurement of flows in microfluidic channels is important for commercial and research applications. We compare the accuracy of flow measurement techniques over a wide range flows. Flow measurements made using holographic microparticle tracking velocimetry (µPTV) and a gravimetric flow standard over the range of 0.5-100 nL/s agree within 0.25%, well within the uncertainty of the two flow systems. Two commercial thermal flow sensors were used as the intermediaries (transfer standards) between the two flow measurement systems. The gravimetric flow standard was used to calibrate the thermal flow sensors by measuring the rate of change of the mass of liquid in a beaker on a micro-balance as it fills. The holographic µPTV flow measurements were made in a rectangular channel and the flow was seeded with 1 µm diameter polystyrene spheres. The volumetric flow was calculated using the Hagen-Pouiseille solution for a rectangular channel. The uncertainty of both flow measurement systems is given. For the gravimetric standard, relative uncertainty increased for decreasing flows due to surface tension forces between the pipette carrying the flow and the free surface of the liquid in the beaker. The uncertainty of the holographic µPTV measurements did not vary significantly over the measured flow range, and thus comparatively are especially useful at low flow velocities.

Performance investigation and comparison of different turbulator shapes in solar water heating collector system

NASA Astrophysics Data System (ADS)

Khargotra, Rohit; Dhingra, Sunil; Chauhan, Ranchan; Singh, Tej

2018-05-01

The effective use of solar energy is hindered by the intermittent nature of its availability, limiting its use and effectiveness in domestic and industrial applications especially in water heating. In the present paper, the performance of different turbulator shapes in solar water heating collector system has been studied experimentally and comparison on the output performance has been carried out. Effects of insertion of coil-spring turbulator on heat transfer rate, mass flow rate, heat gain by the fluid etc. is studied by disturbing the flow inside the absorber tubes in a solar flat plate collector. The coil-spring used as a turbulator is placed inside the absorber tube which creates a continuous swirling flow along the tube wall. The results of the heat transfer have been compared well with the available results. The heat transfer rate in the collector has been found to be increased by 18% to 70%. Solar water heater having inserts in the flow tubes perform better than the conventional plain ones. It has been observed that heat losses are reduced consequently increasing the thermal performance to about 70% over the plain water heater under same operating conditions. The coil-spring used as a turbulator is placed inside the riser tube while the twisted tape is inserted into the wire coil to create a continuous swirling flow along the tube wall. The results of the heat transfer have been compared with the available results. Solar water heater having inserts in the flow tubes perform better than the conventional plain ones.

Compression-ignition engine tests of several fuels

NASA Technical Reports Server (NTRS)

Spanogle, J A

1932-01-01

The tests reported in this paper were made to devise simple engine tests which would rate fuels as to their comparative value and their suitability for the operating conditions of the individual engine on which the tests are made. Three commercial fuels were used in two test engines having combustion chambers with and without effective air flow. Strictly comparative performance tests gave almost identical results for the three fuels. Analysis of indicator cards allowed a differentiation between fuels on a basis of rates of combustion. The same comparative ratings were obtained by determining the consistent operating range of injection advance angle for the three fuels. The difference in fuels is more pronounced in a quiescent combustion chamber than in one with high-velocity air flow. A fuel is considered suitable for the operating conditions of an engine with a quiescent combustion chamber if it permits the injection of the fuel to be advanced beyond the optimum without exceeding allowable knock or allowable maximum cylinder pressures.

A compact model for electroosmotic flows in microfluidic devices

NASA Astrophysics Data System (ADS)

Qiao, R.; Aluru, N. R.

2002-09-01

A compact model to compute flow rate and pressure in microfluidic devices is presented. The microfluidic flow can be driven by either an applied electric field or a combined electric field and pressure gradient. A step change in the ζ-potential on a channel wall is treated by a pressure source in the compact model. The pressure source is obtained from the pressure Poisson equation and conservation of mass principle. In the proposed compact model, the complex fluidic network is simplified by an electrical circuit. The compact model can predict the flow rate, pressure distribution and other basic characteristics in microfluidic channels quickly with good accuracy when compared to detailed numerical simulation. Using the compact model, fluidic mixing and dispersion control are studied in a complex microfluidic network.

Miniature FBG-based fluidic flowmeter to measure hot oil and water

NASA Astrophysics Data System (ADS)

Liu, Zhengyong; Htein, Lin; Cheng, Lun-Kai; Martina, Quincy; Jansen, Rob; Tam, Hwa-Yaw

2017-04-01

In this paper, we present a miniature fluidic flowmeter based on a packaged FBG and laser-heated fibers. The flow rates of water and hydraulic oil were measured by utilizing the proposed flowmeter. The measured results exhibited good sensitivity of 0.339 nm/(m/s) for water and 0.578 nm/(m/s) for oil flow. Experimental results showed that the sensitivity of the fluidic flow sensor is depending on the heat capacity of the fluids, where the fluid with higher heat capacity has higher sensitivity and lower detection limit at the same measurement condition. The real-time flow rates measured by the proposed sensor and a commercial flowmeter installed in the test rig were also compared, demonstrating good agreement with correlation coefficient of 0.9974.

Comparison of amphiphilic polyurethane nanoparticles to nonionic surfactants for flushing phenanthrene from soil.

PubMed

Kim, Ju-Young; Shim, Sun-Bo; Shim, Jin-Kie

2004-12-31

Amphiphilic polyurethane (APU) nanoparticles were synthesized through crosslinking polymerization of nano-aggregates of urethane acrylate nonionomer (UAN). The efficiency of in situ extraction of sorbed phenanthrene from aquifer material was tested using soil columns and compared with that of surfactants such as Triton X-100, Brij 30, and Tween 80. The extraction efficiency of those washing materials strongly depended on their concentration, flow rate, and the degree of sorption within soil column. That is, the extraction efficiency increased with the decrease of flow rate and the degree of sorption and the increase of the concentration. Even though the surfactants are superior to APU nanoparticles at solubilizing phenanthrene, at the same flow rate (0.02 mL/min) and concentration (4000 mg/L), the effectiveness of in situ soil washing of APU nanoparticles was about two times higher than those of surfactants. This is because, at the lower flow rates, the degree of sorption of APU nanoparticles was lower than that of surfactants, owing to the chemically crosslinked nature of APU nanoparticles.

Production of acids and alcohols from syngas in a two-stage continuous fermentation process.

PubMed

Abubackar, Haris Nalakath; Veiga, María C; Kennes, Christian

2018-04-01

A two-stage continuous system with two stirred tank reactors in series was utilized to perform syngas fermentation using Clostridium carboxidivorans. The first bioreactor (bioreactor 1) was maintained at pH 6 to promote acidogenesis and the second one (bioreactor 2) at pH 5 to stimulate solventogenesis. Both reactors were operated in continuous mode by feeding syngas (CO:CO 2 :H 2 :N 2 ; 30:10:20:40; vol%) at a constant flow rate while supplying a nutrient medium at different flow rates of 8.1, 15, 22 and 30 ml/h. A cell recycling unit was added to bioreactor 2 in order to recycle the cells back to the reactor, maintaining the OD 600 around 1 in bioreactor 2 throughout the experimental run. When comparing the flow rates, the best results in terms of solvent production were obtained with a flow rate of 22 ml/h, reaching the highest average outlet concentration for alcohols (1.51 g/L) and the most favorable alcohol/acid ratio of 0.32. Copyright © 2018 Elsevier Ltd. All rights reserved.

Characterization of Hot Deformation Behavior of a Fe-Cr-Ni-Mo-N Superaustenitic Stainless Steel Using Dynamic Materials Modeling

NASA Astrophysics Data System (ADS)

Pu, Enxiang; Zheng, Wenjie; Song, Zhigang; Feng, Han; Zhu, Yuliang

2017-03-01

Hot deformation behavior of a Fe-24Cr-22Ni-7Mo-0.5N superaustenitic stainless steel was investigated by hot compression tests in a wide temperature range of 950-1250 °C and strain rate range of 0.001-10 s-1. The flow curves show that the flow stress decreases as the deformation temperature increases or the strain rate decreases. The processing maps developed on the basis of the dynamic materials model and flow stress data were adopted to optimize the parameters of hot working. It was found that the strain higher than 0.2 has no significant effect on the processing maps. The optimum processing conditions were in the temperature range of 1125-1220 °C and strain rate range of 0.1-3 s-1. Comparing to other stable domains, microstructural observations in this domain revealed the complete dynamic recrystallization (DRX) with finer and more uniform grain size. Flow instability occurred in the domain of temperature lower than 1100 °C and strain rate higher than 0.1 s-1.

Numerical simulation of hypersonic inlet flows with equilibrium or finite rate chemistry

NASA Technical Reports Server (NTRS)

Yu, Sheng-Tao; Hsieh, Kwang-Chung; Shuen, Jian-Shun; Mcbride, Bonnie J.

1988-01-01

An efficient numerical program incorporated with comprehensive high temperature gas property models has been developed to simulate hypersonic inlet flows. The computer program employs an implicit lower-upper time marching scheme to solve the two-dimensional Navier-Stokes equations with variable thermodynamic and transport properties. Both finite-rate and local-equilibrium approaches are adopted in the chemical reaction model for dissociation and ionization of the inlet air. In the finite rate approach, eleven species equations coupled with fluid dynamic equations are solved simultaneously. In the local-equilibrium approach, instead of solving species equations, an efficient chemical equilibrium package has been developed and incorporated into the flow code to obtain chemical compositions directly. Gas properties for the reaction products species are calculated by methods of statistical mechanics and fit to a polynomial form for C(p). In the present study, since the chemical reaction time is comparable to the flow residence time, the local-equilibrium model underpredicts the temperature in the shock layer. Significant differences of predicted chemical compositions in shock layer between finite rate and local-equilibrium approaches have been observed.

Internal cycle modeling and environmental assessment of multiple cycle consumer products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsiliyannis, C.A., E-mail: anion@otenet.gr

2012-01-15

Highlights: Black-Right-Pointing-Pointer Dynamic flow models are presented for remanufactured, reused or recycled products. Black-Right-Pointing-Pointer Early loss and stochastic return are included for fast and slow cycling products. Black-Right-Pointing-Pointer The reuse-to-input flow ratio (Internal Cycle Factor, ICF) is determined. Black-Right-Pointing-Pointer The cycle rate, which is increasing with the ICF, monitors eco-performance. Black-Right-Pointing-Pointer Early internal cycle losses diminish the ICF, the cycle rate and performance. - Abstract: Dynamic annual flow models incorporating consumer discard and usage loss and featuring deterministic and stochastic end-of-cycle (EOC) return by the consumer are developed for reused or remanufactured products (multiple cycle products, MCPs), including fast andmore » slow cycling, short and long-lived products. It is shown that internal flows (reuse and overall consumption) increase proportionally to the dimensionless internal cycle factor (ICF) which is related to environmental impact reduction factors. The combined reuse/recycle (or cycle) rate is shown capable for shortcut, albeit effective, monitoring of environmental performance in terms of waste production, virgin material extraction and manufacturing impacts of all MCPs, a task, which physical variables (lifetime, cycling frequency, mean or total number of return trips) and conventional rates, via which environmental policy has been officially implemented (e.g. recycling rate) cannot accomplish. The cycle rate is shown to be an increasing (hyperbolic) function of ICF. The impact of the stochastic EOC return characteristics on total reuse and consumption flows, as well as on eco-performance, is assessed: symmetric EOC return has a small, positive effect on performance compared to deterministic, while early shifted EOC return is more beneficial. In order to be efficient, environmental policy should set higher minimum reuse targets for higher trippage MCPs. The results may serve for monitoring, flow accounting and comparative eco-assessment of MCPs. They may be useful in identifying reachable and efficient reuse/recycle targets for consumer products and in planning return via appropriate labelling and digital coding for enhancing environmental performance, while satisfying consumer demand.« less

Tip Design of Hemodialysis Catheters Influences Thrombotic Events and Replacement Rate.

PubMed

Petridis, C; Nitschke, M; Lehne, W; Smith, E; Goltz, J P; Lehnert, H; Meier, M

2017-02-01

Central venous tunnelled hemodialysis catheters (CVTC) are used for initial vascular access in patients with renal failure. Tip design of the CVTC may play an important role in catheter function and complication rates, influencing adequate hemodialysis treatment of these patients. This prospective, observational cohort study compared the function and complication rates of two CVTCs in patients with end stage renal disease (ESRD) within a follow-up period of 24 months. The study included patients with ESRD who received either a CVTC with a split tip (ST) or a shotgun tip (SG). All patients underwent dialysis within 24 h of intervention. Blood flow was documented initially (Qb 0 ) and was followed up after 6 (Qb 6 ), 12 (Qb 12 ), and 24 (Qb 24 ) months. Analysis of blood flow and complication rates within the follow-up period was performed by questionnaires. In total, 185 patients were included, of whom 93 received a ST CVTC and 92 a SG CVTC. Baseline parameters did not differ significantly between groups. CVTC blood flow was not significantly different between the two devices. Thrombolytic therapy with Alteplase was used significantly more often in the ST group (29%) than in the SG group (16%) (p < 0.05). The CVTC replacement rate was significantly higher in the ST group (19.3%) compared with the SG group (8.7%) (p < 0.05). The tip design of CVTC (split or shotgun) appears to be irrelevant for long-term blood flow during dialysis treatment. However, patients may benefit from SG catheters over ST catheters where replacement rates and thrombolytic treatment are concerned. Copyright © 2016 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

Studies on biogas-fuelled compression ignition engine under dual fuel mode.

PubMed

Mahla, Sunil Kumar; Singla, Varun; Sandhu, Sarbjot Singh; Dhir, Amit

2018-04-01

Experimental investigation has been carried out to utilize biogas as an alternative source of energy in compression ignition (CI) engine under dual fuel operational mode. Biogas was inducted into the inlet manifold at different flow rates along with fresh air through inlet manifold and diesel was injected as a pilot fuel to initiate combustion under dual fuel mode. The engine performance and emission characteristics of dual fuel operational mode were analyzed at different biogas flow rates and compared with baseline conventional diesel fuel. Based upon the improved performance and lower emission characteristics under the dual fuel operation, the optimum flow rate of biogas was observed to be 2.2 kg/h. The lower brake thermal efficiency (BTE) and higher brake-specific energy consumption (BSEC) were noticed with biogas-diesel fuel under dual fuel mode when compared with neat diesel operation. Test results showed reduced NO x emissions and smoke opacity level in the exhaust tailpipe emissions. However, higher hydrocarbon (HC) and carbon monoxide (CO) emissions were noticed under dual fuel mode at entire engine loads when compared with baseline fossil petro-diesel. Hence, the use of low-cost gaseous fuel such as biogas would be an economically viable proposition to address the current and future problems of energy scarcity and associated environmental concerns.

Hospital level analysis to improve patient flow.

PubMed

Khanna, Sankalp; Boyle, Justin; Good, Norm; Bugden, Simon; Scott, Mark

2013-01-01

The complexity of hospital operations ensures that one-size-fits-all solutions seldom work. As hospitals turn to evidence based strategies to redesign flow, it is critical that they tailor the strategies to suit their individual service. This paper analyses the effect of hospital occupancy on inpatient and emergency department patient flow parameters at the Caboolture hospital in Queensland, Australia, and identifies critical levels, or choke points, that result in performance decline. The effect of weekdays and weekends on patient flow is also investigated. We compare these findings to a previous study that has analysed patient flow across Queensland hospitals grouped by size, and discover several differences in the interaction between rising occupancy and patient flow parameters including rates of patient flow, length of stay, and access block. We also identify significantly higher choke points for Caboolture hospital as compared to other similarly sized Queensland hospitals, which suggest that patient flow here can be redesigned to operate at higher levels of occupancy without degrading flow performance. The findings support arguments for hospitals to analyse patient flow at a service level to deliver optimum service improvement.

Robust estimation of simulated urinary volume from camera images under bathroom illumination.

PubMed

Honda, Chizuru; Bhuiyan, Md Shoaib; Kawanaka, Haruki; Watanabe, Eiichi; Oguri, Koji

2016-08-01

General uroflowmetry method involves the risk of nosocomial infections or time and effort of the recording. Medical institutions, therefore, need to measure voided volume simply and hygienically. Multiple cylindrical model that can estimate the fluid flow rate from the photographed image using camera has been proposed in an earlier study. This study implemented a flow rate estimation by using a general-purpose camera system (Raspberry Pi Camera Module) and the multiple cylindrical model. However, large amounts of noise in extracting liquid region are generated by the variation of the illumination when performing measurements in the bathroom. So the estimation error gets very large. In other words, the specifications of the previous study's camera setup regarding the shutter type and the frame rate was too strict. In this study, we relax the specifications to achieve a flow rate estimation using a general-purpose camera. In order to determine the appropriate approximate curve, we propose a binarizing method using background subtraction at each scanning row and a curve approximation method using RANSAC. Finally, by evaluating the estimation accuracy of our experiment and by comparing it with the earlier study's results, we show the effectiveness of our proposed method for flow rate estimation.

Constitutive modeling of the mechanical behavior of high strength ferritic steels for static and dynamic applications

NASA Astrophysics Data System (ADS)

Abed, Farid H.

2010-11-01

A constitutive relation is presented in this paper to describe the plastic behavior of ferritic steel over a broad range of temperatures and strain rates. The thermo-mechanical behavior of high strength low alloy (HSLA-65) and DH-63 naval structural steels is considered in this study at strains over 40%. The temperatures and strain rates are considered in the range where dynamic strain aging is not effective. The concept of thermal activation analysis as well as the dislocation interaction mechanism is used in developing the flow model for both the isothermal and adiabatic viscoplastic deformation. The flow stresses of the two steels are very sensitive to temperature and strain rate, the yield stresses increase with decreasing temperatures and increasing strain rates. That is, the thermal flow stress is mainly captured by the yield stresses while the hardening stresses are totally pertained to the athermal component of the flow stress. The proposed constitutive model predicts results that compare very well with the measured ones at initial temperature range of 77 K to 1000 K and strain rates between 0.001 s-1 and 8500 s-1 for both steels.

IB-LBM study on cell sorting by pinched flow fractionation.

PubMed

Ma, Jingtao; Xu, Yuanqing; Tian, Fangbao; Tang, Xiaoying

2014-01-01

Separation of two categories of cells in pinched flow fractionation(PFF) device is simulated by employing IB-LBM. The separation performances at low Reynolds number (about 1) under different pinched segment widths, flow ratios, cell features, and distances between neighboring cells are studied and the results are compared with those predicted by the empirical formula. The simulation indicates that the diluent flow rate should approximate to or more than the flow rate of particle solution in order to get a relatively ideal separation performance. The discrepancy of outflow position between numerical simulation and the empirical prediction enlarges, when the cells become more flexible. Too short distance between two neighboring cells could lead to cell banding which would result in incomplete separation, and the relative position of two neighboring cells influences the banding of cells. The present study will probably provide some new applications of PFF, and make some suggestions on the design of PFF devices.

Flow rate of some pharmaceutical diluents through die-orifices relevant to mini-tableting.

PubMed

Kachrimanis, K; Petrides, M; Malamataris, S

2005-10-13

The effects of cylindrical orifice length and diameter on the flow rate of three commonly used pharmaceutical direct compression diluents (lactose, dibasic calcium phosphate dihydrate and pregelatinised starch) were investigated, besides the powder particle characteristics (particle size, aspect ratio, roundness and convexity) and the packing properties (true, bulk and tapped density). Flow rate was determined for three different sieve fractions through a series of miniature tableting dies of different orifice diameter (0.4, 0.3 and 0.2 cm) and thickness (1.5, 1.0 and 0.5 cm). It was found that flow rate decreased with the increase of the orifice length for the small diameter (0.2 cm) but for the large diameter (0.4 cm) was increased with the orifice length (die thickness). Flow rate changes with the orifice length are attributed to the flow regime (transitional arch formation) and possible alterations in the position of the free flowing zone caused by pressure gradients arising from the flow of self-entrained air, both above the entrance in the die orifice and across it. Modelling by the conventional Jones-Pilpel non-linear equation and by two machine learning algorithms (lazy learning, LL, and feed-forward back-propagation, FBP) was applied and predictive performance of the fitted models was compared. It was found that both FBP and LL algorithms have significantly higher predictive performance than the Jones-Pilpel non-linear equation, because they account both dimensions of the cylindrical die opening (diameter and length). The automatic relevance determination for FBP revealed that orifice length is the third most influential variable after the orifice diameter and particle size, followed by the bulk density, the difference between bulk and tapped densities and the particle convexity.

Evaporation of Accretion Disks around Black Holes: The Disk-Corona Transition and the Connection to the Advection-dominated Accretion Flow.

PubMed

Liu; Yuan; Meyer; Meyer-Hofmeister; Xie

1999-12-10

We apply the disk-corona evaporation model (Meyer & Meyer-Hofmeister) originally derived for dwarf novae to black hole systems. This model describes the transition of a thin cool outer disk to a hot coronal flow. The mass accretion rate determines the location of this transition. For a number of well-studied black hole binaries, we take the mass flow rates derived from a fit of the advection-dominated accretion flow (ADAF) model to the observed spectra (for a review, see Narayan, Mahadevan, & Quataert) and determine where the transition of accretion via a cool disk to a coronal flow/ADAF would be located for these rates. We compare this with the observed location of the inner disk edge, as estimated from the maximum velocity of the Halpha emission line. We find that the transition caused by evaporation agrees with this determination in stellar disks. We also show that the ADAF and the "thin outer disk + corona" are compatible in terms of the physics in the transition region.

An experimental study of the flow of LPG as refrigerant inside an adiabatic helical coiled capillary tube in vapour compression refrigeration system

NASA Astrophysics Data System (ADS)

Punia, Sanjeev Singh; Singh, Jagdev

2015-11-01

This paper presents an experimental investigation for the flow of liquefied petroleum gas (LPG) as a refrigerant inside an adiabatic helically coiled capillary tube in vapour compression refrigeration system. The effect of various geometric parameters and operating conditions like capillary tube inner diameter, length of capillary tube, coil diameter and different inlet subcoolings on the mass flow rate of LPG through the helical coiled capillary tube geometry has been investigated. It has been established that the coil diameter significantly influences the mass flow rate of LPG through the adiabatic helical capillary tube. It has been concluded that the effect of coiling of capillary tube reduces the mass flow rate by 5-12 % as compared to those of the straight capillary tube operating under similar conditions. The data obtained from the experiments are analyzed and a dimensionless correlation has been developed. The proposed correlation predicts that more than 90 % of experimental data which is in agreement with measured data in an error band of ±10 %.

Static test-stand performance of the YF-102 turbofan engine with several exhaust configurations for the Quiet Short-Haul Research Aircraft (QSRA)

NASA Technical Reports Server (NTRS)

Mcardle, J. G.; Homyak, L.; Moore, A. S.

1979-01-01

The performance of a YF-102 turbofan engine was measured in an outdoor test stand with a bellmouth inlet and seven exhaust-system configurations. The configurations consisted of three separate-flow systems of various fan and core nozzle sizes and four confluent-flow systems of various nozzle sizes and shapes. A computer program provided good estimates of the engine performance and of thrust at maximum rating for each exhaust configuration. The internal performance of two different-shaped core nozzles for confluent-flow configurations was determined to be satisfactory. Pressure and temperature surveys were made with a traversing probe in the exhaust-nozzle flow for some confluent-flow configurations. The survey data at the mixing plane, plus the measured flow rates, were used to calculate the static-pressure variation along the exhaust nozzle length. The computed pressures compared well with experimental wall static-pressure data. External-flow surveys were made, for some confluent-flow configurations, with a large fixed rake at various locations in the exhaust plume.

Separation and quantification of monoclonal-antibody aggregates by hollow-fiber-flow field-flow fractionation.

PubMed

Fukuda, Jun; Iwura, Takafumi; Yanagihara, Shigehiro; Kano, Kenji

2014-10-01

Hollow-fiber-flow field-flow fractionation (HF5) separates protein molecules on the basis of the difference in the diffusion coefficient, and can evaluate the aggregation ratio of proteins. However, HF5 is still a minor technique because information on the separation conditions is limited. We examined in detail the effect of different settings, including the main-flow rate, the cross-flow rate, the focus point, the injection amount, and the ionic strength of the mobile phase, on fractographic characteristics. On the basis of the results, we proposed optimized conditions of the HF5 method for quantification of monoclonal antibody in sample solutions. The HF5 method was qualified regarding the precision, accuracy, linearity of the main peak, and quantitation limit. In addition, the HF5 method was applied to non-heated Mab A and heat-induced-antibody-aggregate-containing samples to evaluate the aggregation ratio and the distribution extent. The separation performance was comparable with or better than that of conventional methods including analytical ultracentrifugation-sedimentation velocity and asymmetric-flow field-flow fractionation.

Safety and efficacy of the Aperio thrombectomy device when compared to the Solitaire AB/FR and the Revive devices in a pulsatile flow system

PubMed Central

Saleh, Mahdi; Spence, John Nathan; Nayak, Sanjeev; Pearce, Gillian; Tennuci, Christopher; Roffe, Christine

2012-01-01

Background and Purpose: There are a limited number of studies comparing the Aperio mechanical thrombectomy device to other stent-based devices. In this paper, we compared the Aperio thrombectomy device to the Solitaire AB, FR and Revive devices in a model of the middle cerebral artery (MCA) within a modified pulsatile flow system. Methods: Thrombi made of lamb’s blood were placed into a pulsatile flow system perfused with Hartmann’s solution at 80 bpm with a mean pressure of 90 mm Hg. 30 experiments were run with each device. Results: Recanalization rates were similar for all three devices (90% with the Solitaire AB, FR, 80% with the Revive, and 90% with the Aperio). The mean number of attempts to retrieve the thrombus was also similar for all three devices (1.7 with the Solitaire AB, FR, 2.1 with the Revive, 1.6 with the Aperio). Clot fragmentation and embolization rates revealed no statistical significance but there was a trend towards lower embolization rates with the Aperio (23% compared to 40% with the Solitaire AB, FR and 47% with the Revive). The Aperio was the fastest to recanalize the MCA (mean of 66 seconds compared to 186 seconds for the Solitaire AB, FR and 169 seconds for the Revive). Conclusions: In this in vitro setting, the Aperio device seems to be an efficacious and safe device when compared to other similar clinically used mechanical thrombectomy devices. Larger clinical trials are warranted. PMID:23173104

Effects of continuum breakdown on hypersonic aerothermodynamics for reacting flow

NASA Astrophysics Data System (ADS)

Holman, Timothy D.; Boyd, Iain D.

2011-02-01

This study investigates the effects of continuum breakdown on the surface aerothermodynamic properties (pressure, stress, and heat transfer rate) of a sphere in a Mach 25 flow of reacting air in regimes varying from continuum to a rarefied gas. Results are generated using both continuum [computational fluid dynamics (CFD)] and particle [direct simulation Monte Carlo (DSMC)] approaches. The DSMC method utilizes a chemistry model that calculates the backward rates from an equilibrium constant. A preferential dissociation model is modified in the CFD method to better compare with the vibrationally favored dissociation model that is utilized in the DSMC method. Tests of these models are performed to confirm their validity and to compare the chemistry models in both numerical methods. This study examines the effect of reacting air flow on continuum breakdown and the surface properties of the sphere. As the global Knudsen number increases, the amount of continuum breakdown in the flow and on the surface increases. This increase in continuum breakdown significantly affects the surface properties, causing an increase in the differences between CFD and DSMC. Explanations are provided for the trends observed.

Evidence for enhanced debris flow activity in the Northern Calcareous Alps since the 1980s (Plansee, Austria)

NASA Astrophysics Data System (ADS)

Dietrich, Andreas; Krautblatter, Michael

2016-04-01

From 1950 to 2011 almost 80.000 people lost their lives through the occurrence of debris flow events (Dowling and Santi, 2014). Debris flows occur in all alpine regions due to intensive rainstorms and mobilisable loose debris. Due to their susceptible lithology, the Northern Calcareous Alps are affected by a double digit number of major hazard events per year. Some authors hypothesised a relation between an increasing frequency of heavy rainstorms and an increasing occurrence of landslides in general (Beniston and Douglas, 1996) and debris flows in special (Pelfini and Santilli, 2008), but yet there is only limited evidence. The Plansee catchment in the Ammergauer Alps consists of intensely jointed Upper Triassic Hauptdolomit lithology and therefore shows extreme debris flow activity. To investigate this activity in the last decades, the temporal and spatial development of eight active debris flow fans is examined with GIS and field mapping. The annual rates since the late 1940s are inferred accurately by using aerial photos from 1947, 1952, 1971, 1979, 1987, 2000 and 2010. These rates are compared to the mean Holocene/Lateglacial debris flow volume derived from the most prominent cone. The contact with the underlying till is revealed by electrical resistivity tomography (ERT). It shows that the mean annual debris flow volume has increased there by a factor of 10 from 1947-1952 (0.23 ± 0.07 10³m³/yr) to 1987-2000 (2.41 ± 0.66 10³m³/yr). A similar trend can be seen on all eight fans: mean post-1980 rates exceed pre-1980 rates by a factor of more than three. This increasing debris flow activity coincides with an enhanced rainstorm (def. 35 mm/d) frequency recorded at the nearest meteorological station. Since 1921 the frequency of heavy rainstorms has increased there on average by 10% per decade. Recent debris flow rates are also 2-3 times higher compared to mean Holocene/Lateglacial rates. Furthermore, we state a strong correlation between the non-vegetated catchment area and the annual debris flow volume. This might indicate a decadal positive feedback between enhanced rainstorm frequency and the occurrence of debris flows. The study contributes to a better understanding of the sensitivity of alpine catchments to heavy rainfall events in the context of climate change. Beniston, M., Douglas, G.F., 1996. Impacts of climate change on mountain regions. In: Watson, R.T., Zinyowera, M.C., Moss, R.H., Dokken, D.J. (Eds.), Climate Change 1995. Impacts, Adaptations and Mitigation of Climate Change: Scientific-Technical Analysis. Cambridge Univ. Press, Cambridge, pp. 191-213. Dowling, C.A., Santi, P.M., 2014. Debris flows and their toll on human life: a global analysis of debris-flow fatalities from 1950 to 2011. Nat. Hazards 71, 203-227. doi: 10.1007/s11069-013-0907-4 Pelfini, M., Santilli, M., 2008. Frequency of debris flows and their relation with precipitation: A case study in the Central Alps, Italy. Geomorphology 101, 721-730. doi:10.1016/j.geomorph.2008.04.002

Evidence for enhanced debris-flow activity in the Northern Calcareous Alps since the 1980s (Plansee, Austria)

NASA Astrophysics Data System (ADS)

Dietrich, A.; Krautblatter, M.

2017-06-01

Debris flows are among the most important natural hazards. The Northern Calcareous Alps with their susceptible lithology are especially affected by a double digit number of major hazard events per year. It is hypothesised that debris-flow intensity has increased significantly in the last decades in the Northern Calcareous Alps coincident to increased rainstorm frequencies, but yet there is only limited evidence. The Plansee catchment exposes extreme debris-flow activity due to the intensely jointed Upper Triassic Hauptdolomit lithology, being responsible for most of the debris-flow activity in the Northern Calcareous Alps. The debris flows feed into a closed sediment system, the Plansee Lake, where Holocene/Lateglacial sedimentation rates, rates since the late 1940s and recent rates can be inferred accurately. Using aerial photos and field mapping, the temporal and spatial development of eight active debris-flow fans is reconstructed in six time intervals from 1947, 1952, 1971, 1979, 1987, 2000 and 2010 and mean annual debris-flow volumes are calculated. These are compared with mean Holocene/Lateglacial debris-flow volumes derived from the most prominent cone whose contact with the underlying till is revealed by electrical resistivity tomography (ERT). Debris-flow activity there increased by a factor of 10 from 1947-1952 (0.23 ± 0.07 · 103 m3/yr) to 1987-2000 (2.41 ± 0.66 · 103 m3/yr). Mean post-1980 rates from all eight fans exceed pre-1980 rates by a factor of more than three coinciding with enhanced rainstorm activity recorded at meteorological stations in the Northern Calcareous Alps. The frequency of rain storms (def. 35 mm/d) has increased in the study area on average by 10% per decade and has nearly doubled since 1921. Recent debris-flow activity is also 2-3 times higher than mean Holocene/Lateglacial rates. The strong correlation between the non-vegetated catchment area and the annual debris-flow volume might indicate a decadal positive feedback between enhanced rainstorm activity and debris flows. Here we investigate the temporal and spatial development of debris-flow fans to better understand the sensitivity of alpine catchments to heavy rainfall events in the context of climate change. n.m. = not measurable.

Project Hotspot: Linear accumulation rates of late Cenozoic basalt at Kimama, Idaho, and implications for crustal strain and subsidence rates of the central Snake River Plain

NASA Astrophysics Data System (ADS)

Rodgers, D. W.; Potter, K. E.; Shervais, J. W.; Champion, D. E.; Duncan, R. A.

2013-12-01

Project Hotspot's Kimama drill hole on the Snake River Plain, Idaho recovered a 1912 m thick section of basalt core that ranges in age from ~700 ka to at least 6.14 Ma, based on five 40Ar/39Ar analyses and twenty paleomagnetic age assignments. Fifty-four flow groups comprising 510 individual flows were defined, yielding an average recurrence interval of ~11,400 years between flows. Age-depth analysis indicate that, over thicknesses >150 m and age spans >500 k.y., accumulation rates were constant at 30 m/100 k.y. The existence and persistence of this linear accumulation rate for greater than 5 m.y. documents an external tectonic control on eruption dynamics. One conceptual model relates accumulation rates to horizontal crustal strain, such that far-field extension rate controls the periodicity of dikes that feed basalt flows. In this model, each of the 54 flow groups would have a deep-seated, relatively wide (1-10m) dike that branches upward into a network of narrow (10-100 cm) dikes feeding individual lava flows. Assuming an east-west lateral lava flow extent of up to 50 km, the Kimama data record a steady-state crustal strain rate of 10-9 to 10-10 y-1. This rate is comparable to modern, decadal strain rates measured with GPS in the adjacent Basin & Range province, but exceeds decadal strain rates of zero measured in the eastern Snake River Plain. Linear accumulation rates also provide insight into basalt subsidence history. In this model, the middle-upper crust subsides due to the added weight of lava flows, the added weight of mid-crustal sills/dikes, and thermal contraction in the wake of the Yellowstone hot spot. Isostatic compensation would occur in the (nearly) molten lower crust. Assuming constant surface elevation and a basalt density of 2.6 g/cm3, the lava flow weight would account for 87% of the burial through time, yielding a steady-state "tectonic" subsidence rate of 4 m/100 k.y. attributed to the driving forces of mid-crustal injection and/or thermal contraction. An even faster tectonic rate is likely, given the evidence for decreasing surface elevation through time. We propose that tectonic subsidence was a necessary condition for maintaining basalt eruption over such a long duration -- it would inhibit the growth of a topographic plateau and maintain an appropriate level of neutral buoyancy for the periodically ascending mantle-derived magma

Characterization of bedload transport in steep-slope streams

NASA Astrophysics Data System (ADS)

Mettra, F.; Heyman, J.; Ancey, C.

2012-04-01

Large fluctuations in the sediment transport rate are observed in rivers, particularly in mountain streams at intermediate flow rates. These fluctuations seem to be, to some degree, correlated to the formation and migration of bedforms. Today the central question is still how to understand and account for the strong bedload variability. Recent experimental studies shed new light on the processes. The objective of this presentation is to show some of our results. To understand the behavior and the origins of sediment transport rate fluctuations in the case of steep-slope streams, we conducted laboratory experiments in a 3-m long, 8-cm wide, transparent flume. The experimental parameters are the flume inclination, flow rate and sediment input rate. Well-sorted natural gravel (8.5 mm mean diameter) were used. We focused on two-dimensional flows and incipient bedforms (i.e., for flow rates just above the threshold of incipient motion). A technique based on accelerometers was developed to record every particle passing through the flume outlet (more specifically, we measured the vibrations of a metallic slab, which was impacted by the falling particles). Analysis of bedload transport rates was then possible on all time scales. Moreover, the bed and flow were monitored using 2 cameras. We computed bed elevation, water depth and erosion/deposition at high temporal and spatial rates from camera shots (one image per second during several hours or days). In our laboratory experiments, the fluctuations of the sediment rate were large even for steady flow conditions involving well-sorted particles. Time series exhibited fluctuations at all scales and displayed long range correlations with a Hurst exponent close to 0.8. The results were compared for different input solid discharges. The main bedforms observed in our flume were anti-dunes migrating upstream. Bedform formation and propagation showed intermittency with pulses (high activity) followed by long sequences of low activity. We tried to interpret our results (bedform behavior, bed scouring) in terms of sediment outflow rate.

Diagnostic value of the flow profile in the distal descending aorta by phase-contrast magnetic resonance for predicting severe coarctation of the aorta.

PubMed

Muzzarelli, Stefano; Ordovas, Karen Gomes; Hope, Michael D; Meadows, Jeffery J; Higgins, Charles B; Meadows, Alison Knauth

2011-06-01

To compare aortic flow profiles at the level of the proximal descending (PDAo) and distal descending aorta (DDAo) in patients investigated for coarctation of the aorta (CoA), and compare their respective diagnostic value for predicting severe CoA. Diastolic flow decay in the PDAo predicts severe CoA, but flow measurements at this level are limited by flow turbulence, aliasing, and stent-related artifacts. We studied 49 patients evaluated for CoA with phase contrast magnetic resonance imaging (PC-MRI). Parameters of diastolic flow decay in the PDAo and DDAo were compared. Their respective diagnostic value was compared with the standard reference of transcatheter peak gradient ≥20 mmHg. Flow measurement in the PDAo required repeated acquisition with adjustment of encoding velocity or location of the imaging plane in 69% of patients; measurement in the DDAo was achieved in single acquisition in all cases. Parameters of diastolic flow decay in the PDAo and DDAo, including rate-corrected (RC) deceleration time and RC flow deceleration yielded a good correlation (r = 0.78; P < 0.01, and r = 0.92; P < 0.01), and a similar diagnostic value for predicting severe CoA. The highest diagnostic accuracy was achieved by RC deceleration time at DDAo (sensitivity 85%, specificity 85%). Characterization of aortic flow profiles at the DDAo offers a quick and reliable noninvasive means of assessing hemodynamically significant CoA. Copyright © 2011 Wiley-Liss, Inc.

A novel, microscope based, non invasive Laser Doppler flowmeter for choroidal blood flow assessment

PubMed Central

Strohmaier, C; Werkmeister, RM; Bogner, B; Runge, C; Schroedl, F; Brandtner, H; Radner, W; Schmetterer, L; Kiel, JW; Grabnerand, G; Reitsamer, HA

2015-01-01

Impaired ocular blood flow is involved in the pathogenesis of numerous ocular diseases like glaucoma or AMD. The purpose of the present study was to introduce and validate a novel, microscope based, non invasive laser Doppler flowmeter (NILDF) for measurement of blood flow in the choroid. The custom made NI-LDF was compared with a commercial fiber optic based laser Doppler flowmeter (Perimed PF4000). Linearity and stability of the NI-LDF were assessed in a silastic tubing model (i.d. 0.3 mm) at different flow rates (range 0.4 – 3 ml/h). In a rabbit model continuous choroidal blood flow measurements were performed with both instruments simultaneously. During blood flow measurements ocular perfusion pressure was changed by manipulations of intraocular pressure via intravitreal saline infusions. The NILDF measurement correlated linearly to intraluminal flow rates in the perfused tubing model (r = 0.99, p<0.05) and remained stable during a 1 hour measurement at a constant flow rate. Rabbit choroidal blood flow measured by the PF4000 and the NI-LDF linearly correlated with each other over the entire measurement range (r = 0.99, y = x* 1,01 – 12,35 P.U., p < 0,001). In conclusion, the NI-LDF provides valid, semi quantitative measurements of capillary blood flow in comparison to an established LDF instrument and is suitable for measurements at the posterior pole of the eye. PMID:21443871

Effect of calcium and phosphorus, residual lactose, and salt-to-moisture ratio on the melting characteristics and hardness of cheddar cheese during ripening.

PubMed

Chevanan, N; Muthukumarappan, K

2007-05-01

Meltability, melt profile parameters, and hardness of cheddar cheese prepared with varying levels of calcium (Ca) and phosphorus (P) content, residual lactose content, and salt-to-moisture ratio were studied at 0, 1, 2, 4, 6, and 8 mo of ripening. Meltability, melt profile parameters, and hardness of cheddar cheeses measured at 0, 1, 2, 4, 6, and 8 mo of ripening showed significant interaction between the levels of Ca and P, residual lactose, salt-to-moisture ratio, and ripening time for most of the properties studied. cheddar cheese prepared with high Ca and P (0.67% Ca and 0.53% P) resulted in up to 6.2%, 4.5%, 9.6%, 5.0%, and 22.8% increase in softening time, softening temperature, melting time, melting temperature, and hardness, respectively, and 23.5%, 9.6%, and 3.2% decrease in meltability, flow rate, and extent of flow, respectively, compared to the cheddar cheese prepared with low Ca and P (0.53% Ca and 0.39% P). cheddar cheese prepared with high lactose (1.4%) content resulted in up to 7.7%, 7.0%, 4.9%, 4.2%, and 24.6% increase in softening time, softening temperature, melting time, melting temperature, and hardness, respectively, and 14.7%, 12.7%, and 2.8% decrease in meltability, flow rate, and extent of flow respectively compared to the cheddar cheese prepared with low lactose (0.78%) content. cheddar cheese prepared with high salt-to-moisture ratio (6.4%) resulted in up to 21.8%, 11.3%, 12.9%, 4.1%, and 29.4% increase in softening time, softening temperature, melting time, melting temperature, and hardness, respectively, and 13.2%, 28.6%, and 2.6% decrease in meltability, flow rate, and extent of flow, respectively, compared to the cheddar cheese prepared with low salt-to-moisture ratio (4.8%) during ripening.

Using high-resolution satellite radar to measure lava flow morphology, rheology, effusion rate and subsidence at El Reventador Volcano, Ecuador.

NASA Astrophysics Data System (ADS)

Biggs, J.; Arnold, D. W. D.; Mothes, P. A.; Anderson, K. R.; Albino, F.; Wadge, G.; Vallejo Vargas, S.; Ebmeier, S. K.

2017-12-01

There are relatively few studies of active lava flows of an andesitic rather than basaltic composition. The flow field at El Reventador volcano, Ecuador is a good example, but observations are hampered by persistent cloud cover. We use high resolution satellite radar from Radarsat-2 and TanDEM-X to map the dimensions of 43 lava flows extruded between 9 Feb 2012 and 24 Aug 2016. Flow height is measured using the width of radar shadow cast by steep sided features, or the difference in radar phase between two sensors separated in space. The cumulative volume of erupted material was 44.8M m3 dense rock equivalent with an average rate of 0.31 ± 0.02 m3s-1, similar to the long term average. The flows were mostly emplaced over durations shorter than the satellite repeat interval of 24 days and ranged in length from 0.3 to 1.7 km. We use the dimensions of the levees to estimate the flow yield strengths and compare measurements of diversions around barriers with observations from laboratory experiments. The rate of effusion, flow length and flow volume all decrease with time, and simple physics-based models can be equally well fit by a closed reservoir depressurising during the eruption with no magma recharge, or an open reservoir with a time-constant magma recharge rate of up to 0.35 ± 0.01 m3s-1. We propose that the conduit acts as magma capacitor and individual flows are volume-limited. Emplaced flows are subsiding at rates proportional to lava thickness that decay with time following a square-root relationship. Radar observations, such as those presented here, could be used to map and measure properties of evolving lava flow fields at other remote or difficult to monitor volcanoes. Physics-based models can be run into the future, but a sudden increase in flow length in 2017 seen by Sentinel illustrates that changes in magma supply can cause rapid changes in behavior, which remain challenging to forecast.

Role of hot oxygen in Venusian ionospheric ion energetics and supersonic antisunward flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knudsen, W.C.

1990-02-01

The column heating rate of the dayside Venus ionospheric ion gas resulting from transfer of energy from the hot oxygen component of the neutral atmosphere is estimated and found equal to that which, when inserted into ionospheric models at the ionopause, raises the calculated temperature to measured values. The transfer of energy is effected through resonant charge exchange between the relatively cold ionospheric O{sup +} ions and the hot oxygen neutrals. The hot oxygen density in the nightside hemisphere does not appear to play a significant role in the nightside ion energetics. The hot oxygen neutral gas flowing across themore » terminator from its dayside source to its nightside sink will exchange momentum with the antisunward flowing ionospheric gas. Although the flow rate of hot oxygen can be estimated only crudely, the estimated rate of deposition and absorption is comparable to that produced by the plasma pressure gradient and should be included in numerical studies of the terminator ionospheric wind.« less

Large Field of View PIV Measurements of Air Entrainment by SLS SMAT Water Sound Suppression System

NASA Astrophysics Data System (ADS)

Stegmeir, Matthew; Pothos, Stamatios; Bissell, Dan

2015-11-01

Water-based sound suppressions systems have been used to reduce the acoustic impact of space vehicle launches. Water flows at a high rate during launch in order to suppress Engine Generated Acoustics and other potentially damaging sources of noise. For the Space Shuttle, peak flow rates exceeded 900,000 gallons per minute. Such large water flow rates have the potential to induce substantial entrainment of the surrounding air, affecting the launch conditions and generating airflow around the launch vehicle. Validation testing is necessary to quantify this impact for future space launch systems. In this study, PIV measurements were performed to map the flow field above the SMAT sub-scale launch vehicle scaled launch stand. Air entrainment effects generated by a water-based sound suppression system were studied. Mean and fluctuating fluid velocities were mapped up to 1m above the test stand deck and compared to simulation results. Measurements performed with NASA MSFC.

Characterising Dynamic Instability in High Water-Cut Oil-Water Flows Using High-Resolution Microwave Sensor Signals

NASA Astrophysics Data System (ADS)

Liu, Weixin; Jin, Ningde; Han, Yunfeng; Ma, Jing

2018-06-01

In the present study, multi-scale entropy algorithm was used to characterise the complex flow phenomena of turbulent droplets in high water-cut oil-water two-phase flow. First, we compared multi-scale weighted permutation entropy (MWPE), multi-scale approximate entropy (MAE), multi-scale sample entropy (MSE) and multi-scale complexity measure (MCM) for typical nonlinear systems. The results show that MWPE presents satisfied variability with scale and anti-noise ability. Accordingly, we conducted an experiment of vertical upward oil-water two-phase flow with high water-cut and collected the signals of a high-resolution microwave resonant sensor, based on which two indexes, the entropy rate and mean value of MWPE, were extracted. Besides, the effects of total flow rate and water-cut on these two indexes were analysed. Our researches show that MWPE is an effective method to uncover the dynamic instability of oil-water two-phase flow with high water-cut.

The development of an erosive burning model for solid rocket motors using direct numerical simulation

NASA Astrophysics Data System (ADS)

McDonald, Brian A.

A method for developing an erosive burning model for use in solid propellant design-and-analysis interior ballistics codes is described and evaluated. Using Direct Numerical Simulation, the primary mechanisms controlling erosive burning (turbulent heat transfer, and finite rate reactions) have been studied independently through the development of models using finite rate chemistry, and infinite rate chemistry. Both approaches are calibrated to strand burn rate data by modeling the propellant burning in an environment with no cross-flow, and adjusting thermophysical properties until the predicted regression rate matches test data. Subsequent runs are conducted where the cross-flow is increased from M = 0.0 up to M = 0.8. The resulting relationship of burn rate increase versus Mach Number is used in an interior ballistics analysis to compute the chamber pressure of an existing solid rocket motor. The resulting predictions are compared to static test data. Both the infinite rate model and the finite rate model show good agreement when compared to test data. The propellant considered is an AP/HTPB with an average AP particle size of 37 microns. The finite rate model shows that as the cross-flow increases, near wall vorticity increases due to the lifting of the boundary caused by the side injection of gases from the burning propellant surface. The point of maximum vorticity corresponds to the outer edge of the APd-binder flame. As the cross-flow increases, the APd-binder flame thickness becomes thinner; however, the point of highest reaction rate moves only slightly closer to the propellant surface. As such, the net increase of heat transfer to the propellant surface due to finite rate chemistry affects is small. This leads to the conclusion that augmentation of thermal transport properties and the resulting heat transfer increase due to turbulence dominates over combustion chemistry in the erosive burning problem. This conclusion is advantageous in the development of future models that can be calibrated to heat transfer conditions without the necessity for finite rate chemistry. These results are considered applicable for propellants with small, evenly distributed AP particles where the assumption of premixed APd-binder gases is reasonable.

Miniature piezo electric vacuum inlet valve

DOEpatents

Keville, Robert F.; Dietrich, Daniel D.

1998-03-24

A miniature piezo electric vacuum inlet valve having a fast pulse rate and is battery operated with variable flow capability. The low power (<1.6 watts), high pulse rate (<2 milliseconds), variable flow inlet valve is utilized for mass spectroscopic applications or other applications where pulsed or continuous flow conditions are needed. The inlet valve also has a very minimal dead volume of less than 0.01 std/cc. The valve can utilize, for example, a 12 Vdc input/750 Vdc, 3 mA output power supply compared to conventional piezo electric valves which require preloading of the crystal drive mechanism and 120 Vac, thus the valve of the present invention is smaller by a factor of three.

A Study of Two-Equation Turbulence Models on the Elliptic Streamline Flow

NASA Technical Reports Server (NTRS)

Blaisdell, Gregory A.; Qin, Jim H.; Shariff, Karim; Rai, Man Mohan (Technical Monitor)

1995-01-01

Several two-equation turbulence models are compared to data from direct numerical simulations (DNS) of the homogeneous elliptic streamline flow, which combines rotation and strain. The models considered include standard two-equation models and models with corrections for rotational effects. Most of the rotational corrections modify the dissipation rate equation to account for the reduced dissipation rate in rotating turbulent flows, however, the DNS data shows that the production term in the turbulent kinetic energy equation is not modeled correctly by these models. Nonlinear relations for the Reynolds stresses are considered as a means of modifying the production term. Implications for the modeling of turbulent vortices will be discussed.

An improved flux-split algorithm applied to hypersonic flows in chemical equilibrium

NASA Technical Reports Server (NTRS)

Palmer, Grant

1988-01-01

An explicit, finite-difference, shock-capturing numerical algorithm is presented and applied to hypersonic flows assumed to be in thermochemical equilibrium. Real-gas chemistry is either loosely coupled to the gasdynamics by way of a Gibbs free energy minimization package or fully coupled using species mass conservation equations with finite-rate chemical reactions. A scheme is developed that maintains stability in the explicit, finite-rate formulation while allowing relatively high time steps. The codes use flux vector splitting to difference the inviscid fluxes and employ real-gas corrections to viscosity and thermal conductivity. Numerical results are compared against existing ballistic range and flight data. Flows about complex geometries are also computed.

A novel personal air sampling device for collecting volatile organic compounds: a comparison to charcoal tubes and diffusive badges.

PubMed

Rossner, Alan; Farant, Jean-Pierre

2004-02-01

Evacuated canisters have been used for many years to collect ambient air samples for gases and vapors. Recently, significant interest has arisen in using evacuated canisters for personal breathing zone sampling as an alternative to sorbent sampling. A novel flow control device was designed and built at McGill University. The flow control device was designed to provide a very low flow rate, <0.5 mL/min, to allow a sample to be collected over an extended period of time. Previous experiments run at McGill have shown agreement between the mathematical and empirical models to predict flow rate. The flow control device combined with an evacuated canister (capillary flow control-canister) was used in a series of experiments to evaluate its performance against charcoal tubes and diffusive badges. Air samples of six volatile organic compounds were simultaneously collected in a chamber using the capillary flow control-canister, charcoal tubes, and diffusive badges. Five different concentrations of the six volatile organic compounds were evaluated. The results from the three sampling devices were compared to each other and to concentration values obtained using an online gas chromatograph (GC). Eighty-four samples of each method were collected for each of the six chemicals. Results indicate that the capillary flow control-canister device compares quite favorably to the online GC and to the charcoal tubes, p > 0.05 for most of the tests. The capillary flow control-canister was found to be more accurate for the compounds evaluated, easier to use, and easier to analyze than charcoal tubes and passive dosimeter badges.

Flow and temperature fields following injection of a jet normal to a cross stream

NASA Technical Reports Server (NTRS)

Goldstein, R. J.; Ramsey, J. W.; Eriksen, V. L.

1978-01-01

The interaction of a jet entering into a freestream normal to the main flow direction has been studied with particular attention directed to visualization of the large-scale flow interactions and to measurement of the film-cooling performance. Large eddies are apparent downstream of the entering jet even at moderate blowing rate (defined as the ratio of the mass velocity of the jet to the mass velocity of the freestream). At higher blowing rate, there is only intermittent contact between the mass from the jet and the downstream wall. The film cooling downstream from a single normal jet yields a lower centerline effectiveness compared to an inclined jet through a greater lateral spreading. The greater spreading provides a more uniform effectiveness across the span of the downstream wall, in particular at large blowing rate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong Sun Lee; Yu Ryang Pyun

A food drying process in a tunnel dryer was modeled from Keey's drying model and experimental drying curve, and optimized in operating conditions consisting of inlet air temperature, air recycle ratio and air flow rate. Radish was chosen as a typical food material to be dried, because it has the typical drying characteristics of food and quality indexes of ascorbic acid destruction and browning during drying. Optimization results of cocurrent and counter current tunnel drying showed higher inlet air temperature, lower recycle ratio and higher air flow rate with shorter total drying time. Compared with cocurrent operation counter current dryingmore » used lower air temperature, lower recycle ratio and lower air flow rate, and appeared to be more efficient in energy usage. Most of consumed energy was shown to be used for sir heating and then escaped from the dryer in the form of exhaust air.« less

Performance analysis of a new hypersonic vitrector system.

PubMed

Stanga, Paulo Eduardo; Pastor-Idoate, Salvador; Zambrano, Isaac; Carlin, Paul; McLeod, David

2017-01-01

To evaluate porcine vitreous flow and water flow rates in a new prototype hypersonic vitrectomy system compared to currently available pneumatic guillotine vitrectors (GVs) systems. Two vitrectors were tested, a prototype, ultrasound-powered, hypersonic vitrector (HV) and a GV. Porcine vitreous was obtained within 12 to 24 h of sacrifice and kept at 4°C. A vial of vitreous or water was placed on a precision balance and its weight measured before and after the use of each vitrector. Test parameters included changes in aspiration levels, vitrector gauge, cut rates for GVs, % ultrasound (US) power for HVs, and port size for HVs. Data was analysed using linear regression and t-tests. There was no difference in the total average mean water flow between the 25-gauge GV and the 25-gauge HV (t-test: P = 0.363); however, 25-gauge GV was superior (t-test: P < 0.001) in vitreous flow. The 23-gauge GV was only more efficient in water and vitreous removal than 23-gauge HV needle-1 (Port 0.0055) (t-test: P < 0.001). For HV, wall thickness and gauge had no effect on flow rates. Water and vitreous flows showed a direct correlation with increasing aspiration levels and % US power (p<0.05). The HV produced consistent water and vitreous flow rates across the range of US power and aspiration levels tested. Hypersonic vitrectomy may be a promising new alternative to the currently available guillotine-based technologies.

Postural hypocapnic hyperventilation is associated with enhanced peripheral vasoconstriction in postural tachycardia syndrome with normal supine blood flow

PubMed Central

Stewart, Julian M.; Medow, Marvin S.; Cherniack, Neil S.; Natelson, Benjamin H.

2015-01-01

Previous investigations have demonstrated a subset of postural tachycardia syndrome (POTS) patients characterized by normal peripheral resistance and blood volume while supine but thoracic hypovolemia and splanchnic blood pooling while upright secondary to splanchnic hyperemia. Such “normal-flow” POTS patients often demonstrate hypocapnia during orthostatic stress. We studied 20 POTS patients (14–23 yr of age) and compared them with 10 comparably aged healthy volunteers. We measured changes in heart rate, blood pressure, heart rate and blood pressure variability, arm and leg strain-gauge occlusion plethysmography, respiratory impedance plethysmography calibrated against pneumotachography, end-tidal partial pressure of carbon dioxide (PetCO2), and impedance plethysmographic indexes of blood volume and blood flow within the thoracic, splanchnic, pelvic (upper leg), and lower leg regional circulations while supine and during upright tilt to 70°. Ten POTS patients demonstrated significant hyperventilation and hypocapnia (POTSHC) while 10 were normocapnic with minimal increase in postural ventilation, comparable to control. While relative splanchnic hypervolemia and hyperemia occurred in both POTS groups compared with controls, marked enhancement in peripheral vasoconstriction occurred only in POTSHC and was related to thoracic blood flow. Variability indexes suggested enhanced sympathetic activation in POTSHC compared with other subjects. The data suggest enhanced cardiac and peripheral sympathetic excitation in POTSHC. PMID:16565300

Flow and axial dispersion in a sinusoidal-walled tube: Effects of inertial and unsteady flows

NASA Astrophysics Data System (ADS)

Richmond, Marshall C.; Perkins, William A.; Scheibe, Timothy D.; Lambert, Adam; Wood, Brian D.

2013-12-01

In this work, we consider a sinusoidal-walled tube (a three-dimensional tube with sinusoidally-varying diameter) as a simplified conceptualization of flow in porous media. Direct numerical simulation using computational fluid dynamics (CFD) methods was used to compute velocity fields by solving the Navier-Stokes equations, and also to numerically solve the volume averaging closure problem, for a range of Reynolds numbers (Re) spanning the low-Re to inertial flow regimes, including one simulation at Re=449 for which unsteady flow was observed. The longitudinal dispersion observed for the flow was computed using a random walk particle tracking method, and this was compared to the longitudinal dispersion predicted from a volume-averaged macroscopic mass balance using the method of volume averaging; the results of the two methods were consistent. Our results are compared to experimental measurements of dispersion in porous media and to previous theoretical results for both the low-Re, Stokes flow regime and for values of Re representing the steady inertial regime. In the steady inertial regime, a power-law increase in the effective longitudinal dispersion (DL) with Re was found, and this is consistent with previous results. This rapid rate of increase is caused by trapping of solute in expansions due to flow separation (eddies). One unsteady (but non-turbulent) flow case (Re=449) was also examined. For this case, the rate of increase of DL with Re was smaller than that observed at lower Re. Velocity fluctuations in this regime lead to increased rates of solute mass transfer between the core flow and separated flow regions, thus diminishing the amount of tailing caused by solute trapping in eddies and thereby reducing longitudinal dispersion. The observed tailing was further explored through analysis of concentration skewness (third moment) and its assymptotic convergence to conventional advection-dispersion behavior (skewness = 0). The method of volume averaging was applied to develop a skewness model, and demonstrated that the skewness decreases as a function of inverse square root of time. Our particle tracking simulation results were shown to conform to this theoretical result in most of the cases considered.

Soft Sensing of Non-Newtonian Fluid Flow in Open Venturi Channel Using an Array of Ultrasonic Level Sensors—AI Models and Their Validations

PubMed Central

Viumdal, Håkon; Mylvaganam, Saba

2017-01-01

In oil and gas and geothermal installations, open channels followed by sieves for removal of drill cuttings, are used to monitor the quality and quantity of the drilling fluids. Drilling fluid flow rate is difficult to measure due to the varying flow conditions (e.g., wavy, turbulent and irregular) and the presence of drilling cuttings and gas bubbles. Inclusion of a Venturi section in the open channel and an array of ultrasonic level sensors above it at locations in the vicinity of and above the Venturi constriction gives the varying levels of the drilling fluid in the channel. The time series of the levels from this array of ultrasonic level sensors are used to estimate the drilling fluid flow rate, which is compared with Coriolis meter measurements. Fuzzy logic, neural networks and support vector regression algorithms applied to the data from temporal and spatial ultrasonic level measurements of the drilling fluid in the open channel give estimates of its flow rate with sufficient reliability, repeatability and uncertainty, providing a novel soft sensing of an important process variable. Simulations, cross-validations and experimental results show that feedforward neural networks with the Bayesian regularization learning algorithm provide the best flow rate estimates. Finally, the benefits of using this soft sensing technique combined with Venturi constriction in open channels are discussed. PMID:29072595

Stopping dynamics of a steady uniform granular flow over a rough incline

NASA Astrophysics Data System (ADS)

Deboeuf, Stéphanie; Saingier, Guillaume; Thiruvalluvar, Nitharshini; Lagrée, Pierre-Yves; Popinet, Stéphane; Staron, Lydie

2017-06-01

Granular material flowing on complex topographies are ubiquitous in industrial and geophysical situations. Even model granular flows are difficult to understand and predict. Recently, the frictional rheology μ(I) -describing the ratio of the shear stress to the normal stress as a function of the inertial number I, that compares inertial and confinement effects- allows unifying different configurations of granular flows. However it does not succeed in describing some phenomenologies, such as creep flow, deposit height, … Is it attributable to the rheology, to non-local effects, ...? Here, we consider a thin layer of grains flowing steadily and uniformly on a rough incline, when the input mass flow rate is suddenly stopped. We focus on the arrest dynamics by using both experimental and numerical approaches. We measure the height and surface velocities of the granular layer during the long-time stopping dynamics and we compare our experimental results with computations of depthaveraged equations for a fluid of rheology μ(I).

Computation of turbulent boundary layer flows with an algebraic stress turbulence model

NASA Technical Reports Server (NTRS)

Kim, Sang-Wook; Chen, Yen-Sen

1986-01-01

An algebraic stress turbulence model is presented, characterized by the following: (1) the eddy viscosity expression is derived from the Reynolds stress turbulence model; (2) the turbulent kinetic energy dissipation rate equation is improved by including a production range time scale; and (3) the diffusion coefficients for turbulence equations are adjusted so that the kinetic energy profile extends further into the free stream region found in most experimental data. The turbulent flow equations were solved using a finite element method. Examples include: fully developed channel flow, fully developed pipe flow, flat plate boundary layer flow, plane jet exhausting into a moving stream, circular jet exhausting into a moving stream, and wall jet flow. Computational results compare favorably with experimental data for most of the examples considered. Significantly improved results were obtained for the plane jet flow, the circular jet flow, and the wall jet flow; whereas the remainder are comparable to those obtained by finite difference methods using the standard kappa-epsilon turbulence model. The latter seems to be promising with further improvement of the expression for the eddy viscosity coefficient.

Star Formation Rates in Cooling Flow Clusters: A UV Pilot Study with Archival XMM-Newton Optical Monitor Data

NASA Technical Reports Server (NTRS)

Hicks, A. K.; Mushotzky, R.

2006-01-01

We have analyzed XMM-Newton Optical Monitor (OM) UV (180-400 nm) data for a sample of 33 galaxies. 30 are cluster member galaxies, and nine of these are central cluster galaxies (CCGs) in cooling flow clusters having mass deposition rates which span a range of 8 - 525 Solar Mass/yr. By comparing the ratio of UV to 2MASS J band fluxes, we find a significant UV excess in many, but not all, cooling flow CCGs, a finding consistent with the outcome of previous studies based on optical imaging data (McNamara & O'Connell 1989; Cardiel, Gorgas, & Aragon-Salamanca 1998; Crawford et al. 1999). This UV excess is a direct indication of the presence of young massive stars, and therefore recent star formation, in these galaxies. Using the Starburst99 spectral energy distribution (SED) model of continuous star formation over a 900 Myr period, we derive star formation rates of 0.2 - 219 solar Mass/yr for the cooling flow sample. For 2/3 of this sample it is possible to equate Chandra/XMM cooling flow mass deposition rates with UV inferred star formation rates, for a combination of starburst lifetime and IMF slope. This is a pilot study of the well populated XMM UV cluster archive and a more extensive follow up study is currently underway.

Xerostomia, salivary characteristics and gland volumes following intensity-modulated radiotherapy for nasopharyngeal carcinoma: a two-year follow up.

PubMed

Sim, Cpc; Soong, Y L; Pang, Epp; Lim, C; Walker, G D; Manton, D J; Reynolds, E C; Wee, Jts

2018-06-01

To evaluate changes in xerostomia status, salivary characteristics and gland volumes 2 years following radiotherapy in nasopharyngeal carcinoma patients. Xerostomia scores, salivary flow rates, pH and buffering capacity were measured at pre-radiotherapy, mid-radiotherapy, 2 weeks, 3 months and 2 years post-radiotherapy. Salivary gland volumes and their correlation with radiation dose were also assessed. Mean radiation dose to oral cavity, parotid and submandibular glands (SMG) was 44.5, 65.0 and 38.6 Gy respectively. Parotid and SMG volumes decreased 33% at 3 months post-radiotherapy; volumes at 2 years post-radiotherapy were 84% and 51% of pre-radiotherapy levels, respectively. Correlations were observed between parotid gland volume per cent reduction and its radiation dose and between resting salivary flow rate reduction and post-radiotherapy/pre-radiotherapy SMG volume ratio. Salivary flow rates and resting saliva pH remained significantly low at 2 years post-radiotherapy (both flow rates, P = 0.001; resting saliva pH, P = 0.005). Similarly, xerostomia scores remained significantly higher compared with pre-radiotherapy levels. Submandibular gland volumetric shrinkage persisted 2 years after radiotherapy. Xerostomia scores remained significantly higher, and salivary flow rates and resting saliva pH remained significantly lower, suggesting that study participants were still at risk for hyposalivation-related oral diseases. © 2018 Australian Dental Association.

Gas Flow in the Capillary of the Atmosphere-to-Vacuum Interface of Mass Spectrometers

NASA Astrophysics Data System (ADS)

Skoblin, Michael; Chudinov, Alexey; Soulimenkov, Ilia; Brusov, Vladimir; Kozlovskiy, Viacheslav

2017-10-01

Numerical simulations of a gas flow through a capillary being a part of mass spectrometer atmospheric interface were performed using a detailed laminar flow model. The simulated interface consisted of atmospheric and forevacuum volumes connected via a thin capillary. The pressure in the forevacuum volume where the gas was expanding after passing through the capillary was varied in the wide range from 10 to 900 mbar in order to study the volume flow rate as well as the other flow parameters as functions of the pressure drop between the atmospheric and forevacuum volumes. The capillary wall temperature was varied in the range from 24 to 150 °C. Numerical integration of the complete system of Navier-Stokes equations for a viscous compressible gas taking into account the heat transfer was performed using the standard gas dynamic simulation software package ANSYS CFX. The simulation results were compared with experimental measurements of gas flow parameters both performed using our experimental setup and taken from the literature. The simulated volume flow rates through the capillary differed no more than by 10% from the measured ones over the entire pressure and temperatures ranges. A conclusion was drawn that the detailed digital laminar model is able to quantitatively describe the measured gas flow rates through the capillaries under conditions considered. [Figure not available: see fulltext.

Gas Flow in the Capillary of the Atmosphere-to-Vacuum Interface of Mass Spectrometers.

PubMed

Skoblin, Michael; Chudinov, Alexey; Soulimenkov, Ilia; Brusov, Vladimir; Kozlovskiy, Viacheslav

2017-10-01

Numerical simulations of a gas flow through a capillary being a part of mass spectrometer atmospheric interface were performed using a detailed laminar flow model. The simulated interface consisted of atmospheric and forevacuum volumes connected via a thin capillary. The pressure in the forevacuum volume where the gas was expanding after passing through the capillary was varied in the wide range from 10 to 900 mbar in order to study the volume flow rate as well as the other flow parameters as functions of the pressure drop between the atmospheric and forevacuum volumes. The capillary wall temperature was varied in the range from 24 to 150 °C. Numerical integration of the complete system of Navier-Stokes equations for a viscous compressible gas taking into account the heat transfer was performed using the standard gas dynamic simulation software package ANSYS CFX. The simulation results were compared with experimental measurements of gas flow parameters both performed using our experimental setup and taken from the literature. The simulated volume flow rates through the capillary differed no more than by 10% from the measured ones over the entire pressure and temperatures ranges. A conclusion was drawn that the detailed digital laminar model is able to quantitatively describe the measured gas flow rates through the capillaries under conditions considered. Graphical Abstract ᅟ.

Subanalysis of the CONFIRM Registries: Acute Procedural Outcomes in Claudicant and Critical Limb Ischemia Patients With Varying Levels of Calcification Treated for Peripheral Arterial Disease With Orbital Atherectomy.

PubMed

Adams, George L; Das, Tony; Lee, Michael S; Beasley, Robert; Mustapha, Jihad

2015-11-01

Patients with peripheral arterial disease (PAD) can be classified into groups based upon the severity of the disease using the Rutherford classification system. This analysis compares the procedural outcomes of PAD patients treated with orbital atherectomy stratified by Rutherford class (1-3 = intermittent claudication; 4-6 = critical limb ischemia [CLI]), and acute angiographic outcomes of these patients stratified by degree of lesion calcification. The CONFIRM registry series was analyzed and included 1697 patients with intermittent claudication (Rutherford class 1-3) and 1320 patients with CLI (Rutherford class 4-6) treated with orbital atherectomy. The composite rate of dissection, perforation, slow-flow, vessel closure, spasm, embolism, and thrombus formation was compared between claudicants and CLI patients with varying degrees of lesion calcification. Patients with CLI were older and had a higher prevalence of diabetes, coronary artery disease, and renal disease (P<.001). Claudicants with moderately/severely calcified lesions had a lower rate of dissection (both non-flow limiting and flow-limiting) than claudicants with mildly/minimally calcified lesions. CLI patients with mildly/minimally calcified lesions had higher rates of embolism and thrombus than CLI patients with moderately/severely calcified lesions. Plaque modification with orbital atherectomy resulted in similar low procedural complication rates in the CLI group compared with the claudicant group. These results suggest that orbital atherectomy is safe and effective for treating calcified lesions in high-risk patients with varying severity of PAD symptoms.

Comparison between burning mouth syndrome patients with and without psychological problems.

PubMed

Kim, M-J; Kim, J; Kho, H-S

2018-07-01

The purpose of this study was to compare clinical and socio-demographic characteristics between burning mouth syndrome (BMS) patients with and without psychological problems. Of 644 patients with symptoms of oral burning, 224 with primary BMS were selected on the basis of laboratory testing, medical history, and psychometric tests: 39 with psychological problems (age 62.5±11.5years) and 185 without psychological problems (age 58.4±11.4years). Comprehensive clinical and socio-demographic characteristics, including psychological profiles and salivary flow rates, were compared between the two groups. No significant difference in sex ratio, duration and diurnal pattern of symptoms, unstimulated whole saliva flow rate, or marital status was found between the groups. The patients with psychological problems had a significantly higher mean age, reduced stimulated whole saliva flow rate, and lower level of education than those without psychological problems. The patients with psychological problems also displayed higher rates and greater severity of various types of BMS-related symptom in most parts of the oral mucosa, higher rates of stress-related symptoms, and greater difficulties in daily activities. The severity of taste disturbance was the factor most significantly correlated with the level of psychometry. In conclusion, psychological problems in BMS patients are associated with an aggravation of BMS symptoms. Copyright © 2018 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

In-line pressure within a HOTLINE® Fluid Warmer, under various flow conditions.

PubMed

Higashi, Midoriko; Yamaura, Ken; Matsubara, Yukie; Fukudome, Takuya; Hoka, Sumio

2015-04-01

Roller pump infusion devices are widely used for rapid infusion, and may be combined with separate warming devices. There may be instances however, where the pressures generated by the roller pump may not be compatible with the warming device. We assessed a commonly used roller pump in combination with a HOTLINE® Fluid Warmer, and found that it could generate pressures exceeding the HOTLINE® manufacturers specifications. This was of concern because the HOTLINE® manufacturer guideline states that not for use with pressure devices generating over 300 mmHg. Pressure greater than 300 mmHg may compromise the integrity of the HOTLINE® Fluid Warming Set. The aim of this study was to compare in-line pressure within a HOTLINE® Fluid Warmer at different infusion rates of a roller pump using various sizes of intravenous cannulae. The rapid infusion system comprised a 500 mL-normal saline bag, roller pump type infusion device, HOTLINE® Fluid Warmer (blood and fluid warmer system), and six different sizes of intravenous cannulae. In-line pressure was measured proximal to the HOTLINE® (pre-warmer) and proximal to the cannula (post-warmer), at flow rate of 50-160 mL/min. The in-line pressures increased significantly with increasing flow rate. The pre-warmer pressures exceeded 300 mmHg when the flow rate was ≥120 mL/min with 20-gauge, 48 mm length cannula, 130 with 20-gauge, 25 mm cannula, and 160 mL/min with 18-gauge, 48 mm cannula. However, they were <300 mmHg at any flow rates with 18-gauge, 30 mm cannula and 16-gauge cannulae. The post-warmer pressures exceeded 300 mmHg at the flow rate of 140 mL/min with 20-gauge, 48 mm cannula, and 160 mL/min with 20-gauge, 25 mm cannula, while they were <300 mmHg at any flow rates with 18 and 16-gauge cannulae. The in-line pressure within a HOTLINE® could exceed 300 mmHg, depending on the flow rate and size and length of cannula. It is important to pay attention to the size and length of cannulae and flow rate to keep the maximum in-line pressure<300 mmHg when a roller pump type infusion device is used.

Estimating pesticide sampling rates by the polar organic chemical integrative sampler (POCIS) in the presence of natural organic matter and varying hydrodynamic conditions.

PubMed

Charlestra, Lucner; Amirbahman, Aria; Courtemanch, David L; Alvarez, David A; Patterson, Howard

2012-10-01

The polar organic chemical integrative sampler (POCIS) was calibrated to monitor pesticides in water under controlled laboratory conditions. The effect of natural organic matter (NOM) on the sampling rates (R(s)) was evaluated in microcosms containing <0.1-5 mg L(-1) of total organic carbon (TOC). The effect of hydrodynamics was studied by comparing R(s) values measured in stirred (SBE) and quiescent (QBE) batch experiments and a flow-through system (FTS). The level of NOM in the water used in these experiments had no effect on the magnitude of the pesticide sampling rates (p > 0.05). However, flow velocity and turbulence significantly increased the sampling rates of the pesticides in the FTS and SBE compared to the QBE (p < 0.001). The calibration data generated can be used to derive pesticide concentrations in water from POCIS deployed in stagnant and turbulent environmental systems without correction for NOM. Copyright © 2012 Elsevier Ltd. All rights reserved.

Two-Year Outcomes with a Magnetically Levitated Cardiac Pump in Heart Failure.

PubMed

Mehra, Mandeep R; Goldstein, Daniel J; Uriel, Nir; Cleveland, Joseph C; Yuzefpolskaya, Melana; Salerno, Christopher; Walsh, Mary N; Milano, Carmelo A; Patel, Chetan B; Ewald, Gregory A; Itoh, Akinobu; Dean, David; Krishnamoorthy, Arun; Cotts, William G; Tatooles, Antone J; Jorde, Ulrich P; Bruckner, Brian A; Estep, Jerry D; Jeevanandam, Valluvan; Sayer, Gabriel; Horstmanshof, Douglas; Long, James W; Gulati, Sanjeev; Skipper, Eric R; O'Connell, John B; Heatley, Gerald; Sood, Poornima; Naka, Yoshifumi

2018-04-12

In an early analysis of this trial, use of a magnetically levitated centrifugal continuous-flow circulatory pump was found to improve clinical outcomes, as compared with a mechanical-bearing axial continuous-flow pump, at 6 months in patients with advanced heart failure. In a randomized noninferiority and superiority trial, we compared the centrifugal-flow pump with the axial-flow pump in patients with advanced heart failure, irrespective of the intended goal of support (bridge to transplantation or destination therapy). The composite primary end point was survival at 2 years free of disabling stroke (with disabling stroke indicated by a modified Rankin score of >3; scores range from 0 to 6, with higher scores indicating more severe disability) or survival free of reoperation to replace or remove a malfunctioning device. The noninferiority margin for the risk difference (centrifugal-flow pump group minus axial-flow pump group) was -10 percentage points. Of 366 patients, 190 were assigned to the centrifugal-flow pump group and 176 to the axial-flow pump group. In the intention-to-treat population, the primary end point occurred in 151 patients (79.5%) in the centrifugal-flow pump group, as compared with 106 (60.2%) in the axial-flow pump group (absolute difference, 19.2 percentage points; 95% lower confidence boundary, 9.8 percentage points [P<0.001 for noninferiority]; hazard ratio, 0.46; 95% confidence interval [CI], 0.31 to 0.69 [P<0.001 for superiority]). Reoperation for pump malfunction was less frequent in the centrifugal-flow pump group than in the axial-flow pump group (3 patients [1.6%] vs. 30 patients [17.0%]; hazard ratio, 0.08; 95% CI, 0.03 to 0.27; P<0.001). The rates of death and disabling stroke were similar in the two groups, but the overall rate of stroke was lower in the centrifugal-flow pump group than in the axial-flow pump group (10.1% vs. 19.2%; hazard ratio, 0.47; 95% CI, 0.27 to 0.84, P=0.02). In patients with advanced heart failure, a fully magnetically levitated centrifugal-flow pump was superior to a mechanical-bearing axial-flow pump with regard to survival free of disabling stroke or reoperation to replace or remove a malfunctioning device. (Funded by Abbott; MOMENTUM 3 ClinicalTrials.gov number, NCT02224755 .).

A Novel Uncertainty Framework for Improving Discharge Data Quality Using Hydraulic Modelling.

NASA Astrophysics Data System (ADS)

Mansanarez, V.; Westerberg, I.; Lyon, S. W.; Lam, N.

2017-12-01

Flood risk assessments rely on accurate discharge data records. Establishing a reliable stage-discharge (SD) rating curve for calculating discharge from stage at a gauging station normally takes years of data collection efforts. Estimation of high flows is particularly difficult as high flows occur rarely and are often practically difficult to gauge. Hydraulically-modelled rating curves can be derived based on as few as two concurrent stage-discharge and water-surface slope measurements at different flow conditions. This means that a reliable rating curve can, potentially, be derived much faster than a traditional rating curve based on numerous stage-discharge gaugings. We introduce an uncertainty framework using hydraulic modelling for developing SD rating curves and estimating their uncertainties. The proposed framework incorporates information from both the hydraulic configuration (bed slope, roughness, vegetation) and the information available in the stage-discharge observation data (gaugings). This method provides a direct estimation of the hydraulic configuration (slope, bed roughness and vegetation roughness). Discharge time series are estimated propagating stage records through posterior rating curve results.We applied this novel method to two Swedish hydrometric stations, accounting for uncertainties in the gaugings for the hydraulic model. Results from these applications were compared to discharge measurements and official discharge estimations.Sensitivity analysis was performed. We focused analyses on high-flow uncertainty and the factors that could reduce this uncertainty. In particular, we investigated which data uncertainties were most important, and at what flow conditions the gaugings should preferably be taken.

Carbofuran removal in continuous-photocatalytic reactor: Reactor optimization, rate-constant determination and carbofuran degradation pathway analysis.

PubMed

Vishnuganth, M A; Remya, Neelancherry; Kumar, Mathava; Selvaraju, N

2017-05-04

Carbofuran (CBF) removal in a continuous-flow photocatalytic reactor with granular activated carbon supported titanium dioxide (GAC-TiO 2 ) catalyst was investigated. The effects of feed flow rate, TiO 2 concentration and addition of supplementary oxidants on CBF removal were investigated. The central composite design (CCD) was used to design the experiments and to estimate the effects of feed flow rate and TiO 2 concentration on CBF removal. The outcome of CCD experiments demonstrated that reactor performance was influenced mainly by feed flow rate compared to TiO 2 concentration. A second-order polynomial model developed based on CCD experiments fitted the experimental data with good correlation (R 2 ∼ 0.964). The addition of 1 mL min -1 hydrogen peroxide has shown complete CBF degradation and 76% chemical oxygen demand removal under the following operating conditions of CBF ∼50 mg L -1 , TiO 2 ∼5 mg L -1 and feed flow rate ∼82.5 mL min -1 . Rate constant of the photodegradation process was also calculated by applying the kinetic data in pseudo-first-order kinetics. Four major degradation intermediates of CBF were identified using GC-MS analysis. As a whole, the reactor system and GAC-TiO 2 catalyst used could be constructive in cost-effective CBF removal with no impact to receiving environment through getaway of photocatalyst.

Development of image processing techniques for applications in flow visualization and analysis

NASA Technical Reports Server (NTRS)

Disimile, Peter J.; Shoe, Bridget; Toy, Norman; Savory, Eric; Tahouri, Bahman

1991-01-01

A comparison between two flow visualization studies of an axi-symmetric circular jet issuing into still fluid, using two different experimental techniques, is described. In the first case laser induced fluorescence is used to visualize the flow structure, whilst smoke is utilized in the second. Quantitative information was obtained from these visualized flow regimes using two different digital imaging systems. Results are presented of the rate at which the jet expands in the downstream direction and these compare favorably with the more established data.

Magnetic Rayleigh-Taylor instability in radiative flows

NASA Astrophysics Data System (ADS)

Yaghoobi, Asiyeh; Shadmehri, Mohsen

2018-06-01

We present a linear analysis of the radiative Rayleigh-Taylor (RT) instability in the presence of magnetic field for both optically thin and thick regimes. When the flow is optically thin, magnetic field not only stabilizes perturbations with short wavelengths, but also growth rate of the instability at long wavelengths is reduced compared to a non-magnetized case. Then, we extend our analysis to the optically thick flows with a conserved total specific entropy, and properties of the unstable perturbations are investigated in detail. Growth rate of the instability at short wavelengths is suppressed due to the presence of the magnetic field; however, growth rate is nearly constant at long wavelengths because of the radiation field. Since the radiative bubbles around massive protostars are subject to the RT instability, we also explore implications of our results in this context. In the non-magnetized case, the growth time-scale of the instability for a typical bubble is found to be less than 1000 yr, which is very short compared to the typical star formation time-scale. Magnetic field with a reasonable strength significantly increases the growth time-scale to more than hundreds of thousand years. The instability, furthermore, is more efficient at large wavelengths, whereas in the non-magnetized case, growth rate at short wavelengths is more significant.

Closed-Loop Control of Chemical Injection Rate for a Direct Nozzle Injection System.

PubMed

Cai, Xiang; Walgenbach, Martin; Doerpmond, Malte; Schulze Lammers, Peter; Sun, Yurui

2016-01-20

To realize site-specific and variable-rate application of agricultural pesticides, accurately metering and controlling the chemical injection rate is necessary. This study presents a prototype of a direct nozzle injection system (DNIS) by which chemical concentration transport lag was greatly reduced. In this system, a rapid-reacting solenoid valve (RRV) was utilized for injecting chemicals, driven by a pulse-width modulation (PWM) signal at 100 Hz, so with varying pulse width the chemical injection rate could be adjusted. Meanwhile, a closed-loop control strategy, proportional-integral-derivative (PID) method, was applied for metering and stabilizing the chemical injection rate. In order to measure chemical flow rates and input them into the controller as a feedback in real-time, a thermodynamic flowmeter that was independent of chemical viscosity was used. Laboratory tests were conducted to assess the performance of DNIS and PID control strategy. Due to the nonlinear input-output characteristics of the RRV, a two-phase PID control process obtained better effects as compared with single PID control strategy. Test results also indicated that the set-point chemical flow rate could be achieved within less than 4 s, and the output stability was improved compared to the case without control strategy.

Porous glass electroosmotic pumps: design and experiments.

PubMed

Yao, Shuhuai; Hertzog, David E; Zeng, Shulin; Mikkelsen, James C; Santiago, Juan G

2003-12-01

An analytical model for electroosmotic flow rate, total pump current, and thermodynamic efficiency reported in a previous paper has been applied as a design guideline to fabricate porous-structure EO pumps. We have fabricated sintered-glass EO pumps that provide maximum flow rates and pressure capacities of 33 ml/min and 1.3 atm, respectively, at applied potential 100 V. These pumps are designed to be integrated with two-phase microchannel heat exchangers with load capacities of order 100 W and greater. Experiments were conducted with pumps of various geometries and using a relevant, practical range of working electrolyte ionic concentration. Characterization of the pumping performance are discussed in the terms of porosity, tortuosity, pore size, and the dependence of zeta potential on bulk ion density of the working solution. The effects of pressure and flow rate on pump current and thermodynamic efficiency are analyzed and compared to the model prediction. In particular, we explore the important tradeoff between increasing flow rate capacity and obtaining adequate thermodynamic efficiency. This research aims to demonstrate the performance of EOF pump systems and to investigate optimal and practical pump designs. We also present a gas recombination device that makes possible the implementation of this pumping technology into a closed-flow loop where electrolytic gases are converted into water and reclaimed by the system.

Stabilization of miscible viscous fingering by a step-growth polymerization reaction

NASA Astrophysics Data System (ADS)

Bunton, Patrick; Stewart, Simone; Marin, Daniela; Tullier, Michael; Meiburg, Eckart; Pojman, John

2017-11-01

Viscous fingering is a hydrodynamic instability that occurs when a more mobile fluid displaces a fluid of lower mobility. Viscous fingering is often undesirable in industrial processes such as secondary petroleum recovery where it limits resource recovery. Linear stability analysis by Hejazi et al. (2010) has predicted that a non-monotonic viscosity profile at an otherwise unstable interface can in some instances stabilize the flow. We use step-growth polymerization at the interface between two miscible monomers as a model system. A dithiol monomer displacing a diacrylate react to form a linear polymer that behaves as a Newtonian fluid. Viscous fingering was imaged in a horizontal Hele-Shaw cell via Schlieren, which is sensitive to polymer conversion. By varying reaction rate via initiator concentration along with flow rate, we demonstrated increasing stabilization of the flow with increasing Damkohler number (ratio of the reaction rate to the flow rate). Results were compared with regions of predicted stability from the results of Hejazi et al. (2010). When the advection outran the reaction, viscous fingering occurred as usual. However, when the reaction was able to keep pace with the advection, the increased viscosity at the interface stabilized the flow. We acknowledge support from NSF CBET-1335739 and NSF CBET 1511653.

Current and temperature distributions in-situ acquired by electrode-segmentation along a microtubular solid oxide fuel cell operating with syngas

NASA Astrophysics Data System (ADS)

Aydın, Özgür; Nakajima, Hironori; Kitahara, Tatsumi

2015-10-01

Addressing the fuel distribution and endothermic cooling by the internal reforming, we have measured longitudinal current/temperature variations by ;Electrode-segmentation; in a microtubular solid oxide fuel cell operated with syngas (50% pre-reformed methane) and equivalent H2/N2 (100% conversion of syngas to H2) at three different flow rates. Regardless of the syngas flow rates, currents and temperatures show irregular fluctuations with varying amplitudes from upstream to downstream segment. Analysis of the fluctuations suggests that the methane steam reforming reaction is highly affected by the H2 partial pressure. Current-voltage curves plotted for the syngas and equivalent H2/N2 flow rates reveal that the fuel depletion is enhanced toward the downstream during the syngas operation, resulting in a larger performance degradation. All the segments exhibit temperature drops with the syngas flow compared with the equivalent H2/N2 flow due to the endothermic cooling by the methane steam reforming reaction. Despite the drops, the segment temperatures remain above the furnace temperature; besides, the maximum temperature difference along the cell diminishes. The MSR reaction rate does not consistently increase with the decreasing gas inlet velocity (increasing residence time on the catalyst); which we ascribe to the dominating impact of the local temperatures.

The Role of Salivary Gland Scintigraphy in the Evaluation of Salivary Gland Dysfunction in Uncontrolled Type II Diabetic Patients.

PubMed

Senthilkumar, B; Sathasivasubramanian, S

2013-09-01

The aim of the present study was to evaluate the salivary gland dysfunction in patients with uncontrolled type II diabetes using salivary gland scintigraphy and then to compare these ratios with quantitative whole salivary secretion rates. Using a gamma camera (siemens-diacam) equipped with a low energy all-purpose collimator, 32 uncontrolled type II diabetic patients and 30 normal healthy patients were studied by injecting a radio isotope (technetium 99m pertechnetate) about 5 mCi was injected intravenously in to anticubital vein and the activity was measured for the 1(st), 20(th) and 40(th) min. At 20 min after injection, vitamin C chewable tablet was given to stimulate the secretion and continued until the end of the study period (40 min). Before scintigraphy, salivary sampling was carried out in both diabetic and normal individuals in a quiet room, saliva was allowed to accumulate and was expectorated into the collecting vessel approximately once a minute for 15 min and the volume was recorded as Unstimulated salivary flow rate and after 5 min break vitamin C chewable tablet was given to stimulate the secretion and the patient was asked to expectorate the saliva in the collecting vessel for 5 min. The expectorated volume was recorded as stimulated salivary flow rate. The mean of the measurements of scintigraphic ratio and salivary secretion rates were compared using the paired Student's t-test. The scintigraphic mean uptake and excretory ratio (ER) and the salivary flow rates were correlated. The result shows that there was a significant correlation between salivary flow rate and scintigraphic uptake and ER. However, statistically significant result could not be derived as it may be due to smaller sample size and marginal difference in the scintigraphic values between the groups. Salivary gland scintigraphy plays a significant role in the evaluation of salivary gland dysfunction. However, its role as an independent investigative procedure in the evaluation of salivary gland dysfunction requires a study with a larger sample size, may yield a statistical significant result and it can also act as an adjunct along with salivary flow rate procedure.

Validating Whole-Airway CFD Predictions of DPI Aerosol Deposition at Multiple Flow Rates.

PubMed

Longest, P Worth; Tian, Geng; Khajeh-Hosseini-Dalasm, Navvab; Hindle, Michael

2016-12-01

The objective of this study was to compare aerosol deposition predictions of a new whole-airway CFD model with available in vivo data for a dry powder inhaler (DPI) considered across multiple inhalation waveforms, which affect both the particle size distribution (PSD) and particle deposition. The Novolizer DPI with a budesonide formulation was selected based on the availability of 2D gamma scintigraphy data in humans for three different well-defined inhalation waveforms. Initial in vitro cascade impaction experiments were conducted at multiple constant (square-wave) particle sizing flow rates to characterize PSDs. The whole-airway CFD modeling approach implemented the experimentally determined PSDs at the point of aerosol formation in the inhaler. Complete characteristic airway geometries for an adult were evaluated through the lobar bronchi, followed by stochastic individual pathway (SIP) approximations through the tracheobronchial region and new acinar moving wall models of the alveolar region. It was determined that the PSD used for each inhalation waveform should be based on a constant particle sizing flow rate equal to the average of the inhalation waveform's peak inspiratory flow rate (PIFR) and mean flow rate [i.e., AVG(PIFR, Mean)]. Using this technique, agreement with the in vivo data was acceptable with <15% relative differences averaged across the three regions considered for all inhalation waveforms. Defining a peripheral to central deposition ratio (P/C) based on alveolar and tracheobronchial compartments, respectively, large flow-rate-dependent differences were observed, which were not evident in the original 2D in vivo data. The agreement between the CFD predictions and in vivo data was dependent on accurate initial estimates of the PSD, emphasizing the need for a combination in vitro-in silico approach. Furthermore, use of the AVG(PIFR, Mean) value was identified as a potentially useful method for characterizing a DPI aerosol at a constant flow rate.

Validating Whole-Airway CFD Predictions of DPI Aerosol Deposition at Multiple Flow Rates

PubMed Central

Tian, Geng; Khajeh-Hosseini-Dalasm, Navvab; Hindle, Michael

2016-01-01

Abstract Background: The objective of this study was to compare aerosol deposition predictions of a new whole-airway CFD model with available in vivo data for a dry powder inhaler (DPI) considered across multiple inhalation waveforms, which affect both the particle size distribution (PSD) and particle deposition. Methods: The Novolizer DPI with a budesonide formulation was selected based on the availability of 2D gamma scintigraphy data in humans for three different well-defined inhalation waveforms. Initial in vitro cascade impaction experiments were conducted at multiple constant (square-wave) particle sizing flow rates to characterize PSDs. The whole-airway CFD modeling approach implemented the experimentally determined PSDs at the point of aerosol formation in the inhaler. Complete characteristic airway geometries for an adult were evaluated through the lobar bronchi, followed by stochastic individual pathway (SIP) approximations through the tracheobronchial region and new acinar moving wall models of the alveolar region. Results: It was determined that the PSD used for each inhalation waveform should be based on a constant particle sizing flow rate equal to the average of the inhalation waveform's peak inspiratory flow rate (PIFR) and mean flow rate [i.e., AVG(PIFR, Mean)]. Using this technique, agreement with the in vivo data was acceptable with <15% relative differences averaged across the three regions considered for all inhalation waveforms. Defining a peripheral to central deposition ratio (P/C) based on alveolar and tracheobronchial compartments, respectively, large flow-rate-dependent differences were observed, which were not evident in the original 2D in vivo data. Conclusions: The agreement between the CFD predictions and in vivo data was dependent on accurate initial estimates of the PSD, emphasizing the need for a combination in vitro–in silico approach. Furthermore, use of the AVG(PIFR, Mean) value was identified as a potentially useful method for characterizing a DPI aerosol at a constant flow rate. PMID:27082824

Io's Volcanism: Thermo-Physical Models of Silicate Lava Compared with Observations of Thermal Emission

NASA Technical Reports Server (NTRS)

Davies, Ashely G.

1996-01-01

Analyses of thermal infrared outbursts from the jovian satellite Io indicate that at least some of these volcanic events are due to silicate lava. Analysis of the January 9, 1990 outburst indicates that this was an active eruption consisting of a large lava flow (with mass eruption rate of order 10(exp 5) cubic m/sec) and a sustained area at silicate liquidus temperatures. This is interpreted as a series of fire fountains along a rift zone. A possible alternative scenario is that of an overflowing lava lake with extensive fire fountaining. The January 9, 1990 event is unique as multispectral observations with respect to time were obtained. In this paper, a model is presented for the thermal energy lost by active and cooling silicate lava flows and lakes on Io. The model thermal emission is compared with Earth-based observations and Voyager IRIS data. The model (a) provides an explanation of the thermal anomalies on Io's surface; (b) provides constraints on flow behavior and extent and infers some flow parameters; and (c) determines flow geometry and change in flow size with time, and the temperature of each part of the flow or lava lake surface as a function of its age. Models of heat output from active lava flows or inactive but recently emplaced lava flows or overturning lava lakes alone are unable to reproduce the observations. If the January 9, 1990 event is the emplacement of a lava flow, the equivalent of 27 such events per year would yield a volume of material sufficient, if uniformly distributed, to resurface all of Io at a rate of 1 cm/year.

Permeation of 70% isopropyl alcohol through surgical gloves: comparison of the standard methods ASTM F739 and EN 374.

PubMed

Mäkelä, Erja A; Vainiotalo, Sinikka; Peltonen, Kimmo

2003-06-01

Standard test methods ASTM F739 and EN 374 were compared by assessing the permeation of 70% isopropyl alcohol (2-propanol) through seven brands of surgical gloves. The two standards differ in the flow rates of the collection medium and in the chemical permeation rate at which the breakthrough time (BTT) is detected, the EN detection level being 10 times higher than the permeation rate used by ASTM. In a departure from the EN standard method, a 4 h testing time was used instead of 8 h. All of the tested gloves were from the same manufacturer and were made from either natural rubber (NR) (six brands) or chloroprene rubber (CR) (one brand). Two of the NR glove brands were double layered. For the thin NR gloves (0.22, 0.28 and 0.27 mm) the permeation rates were higher throughout the tests with a flow rate of 474 ml/min (EN) of the collection medium (nitrogen) compared with the permeation rates obtained with a flow rate of 52 ml/min (ASTM). These resulted in BTTs of 4.6, 6.5 and 7.6 min (EN) and 4.8, 6.5 and 9.1 min (ASTM), respectively. No statistical difference could be observed between the BTT values obtained with the two standard methods for any of the thin gloves. Thus, although the ASTM standard has a lower criterion for the detection of permeation, it does not necessarily produce shorter BTTs. For the better barriers the methods yielded more equivalent permeation rate curves and thus the EN BTTs were longer than the ASTM BTTs: the EN results were 21, 80, 122 and >240 min compared with the ASTM results of 12, 32, 38 and 103 min for glove thicknesses of 0.37 (NR), 0.22 + 0.22 (double layered NR), 0.31 + 0.29 (double layered NR) and 0.19 mm (CR), respectively.

Research on three-phase traffic flow modeling based on interaction range

NASA Astrophysics Data System (ADS)

Zeng, Jun-Wei; Yang, Xu-Gang; Qian, Yong-Sheng; Wei, Xu-Ting

2017-12-01

On the basis of the multiple velocity difference effect (MVDE) model and under short-range interaction, a new three-phase traffic flow model (S-MVDE) is proposed through careful consideration of the influence of the relationship between the speeds of the two adjacent cars on the running state of the rear car. The random slowing rule in the MVDE model is modified in order to emphasize the influence of vehicle interaction between two vehicles on the probability of vehicles’ deceleration. A single-lane model which without bottleneck structure under periodic boundary conditions is simulated, and it is proved that the traffic flow simulated by S-MVDE model will generate the synchronous flow of three-phase traffic theory. Under the open boundary, the model is expanded by adding an on-ramp, the congestion pattern caused by the bottleneck is simulated at different main road flow rates and on-ramp flow rates, which is compared with the traffic congestion pattern observed by Kerner et al. and it is found that the results are consistent with the congestion characteristics in the three-phase traffic flow theory.

Tuning-free controller to accurately regulate flow rates in a microfluidic network

NASA Astrophysics Data System (ADS)

Heo, Young Jin; Kang, Junsu; Kim, Min Jun; Chung, Wan Kyun

2016-03-01

We describe a control algorithm that can improve accuracy and stability of flow regulation in a microfluidic network that uses a conventional pressure pump system. The algorithm enables simultaneous and independent control of fluid flows in multiple micro-channels of a microfluidic network, but does not require any model parameters or tuning process. We investigate robustness and optimality of the proposed control algorithm and those are verified by simulations and experiments. In addition, the control algorithm is compared with a conventional PID controller to show that the proposed control algorithm resolves critical problems induced by the PID control. The capability of the control algorithm can be used not only in high-precision flow regulation in the presence of disturbance, but in some useful functions for lab-on-a-chip devices such as regulation of volumetric flow rate, interface position control of two laminar flows, valveless flow switching, droplet generation and particle manipulation. We demonstrate those functions and also suggest further potential biological applications which can be accomplished by the proposed control framework.

Tuning-free controller to accurately regulate flow rates in a microfluidic network

PubMed Central

Heo, Young Jin; Kang, Junsu; Kim, Min Jun; Chung, Wan Kyun

2016-01-01

We describe a control algorithm that can improve accuracy and stability of flow regulation in a microfluidic network that uses a conventional pressure pump system. The algorithm enables simultaneous and independent control of fluid flows in multiple micro-channels of a microfluidic network, but does not require any model parameters or tuning process. We investigate robustness and optimality of the proposed control algorithm and those are verified by simulations and experiments. In addition, the control algorithm is compared with a conventional PID controller to show that the proposed control algorithm resolves critical problems induced by the PID control. The capability of the control algorithm can be used not only in high-precision flow regulation in the presence of disturbance, but in some useful functions for lab-on-a-chip devices such as regulation of volumetric flow rate, interface position control of two laminar flows, valveless flow switching, droplet generation and particle manipulation. We demonstrate those functions and also suggest further potential biological applications which can be accomplished by the proposed control framework. PMID:26987587

Large-Amplitude, High-Rate Roll Oscillations of a 65 deg Delta Wing at High Incidence

NASA Technical Reports Server (NTRS)

Chaderjian, Neal M.; Schiff, Lewis B.

2000-01-01

The IAR/WL 65 deg delta wing experimental results provide both detail pressure measurements and a wide range of flow conditions covering from simple attached flow, through fully developed vortex and vortex burst flow, up to fully-stalled flow at very high incidence. Thus, the Computational Unsteady Aerodynamics researchers can use it at different level of validating the corresponding code. In this section a range of CFD results are provided for the 65 deg delta wing at selected flow conditions. The time-dependent, three-dimensional, Reynolds-averaged, Navier-Stokes (RANS) equations are used to numerically simulate the unsteady vertical flow. Two sting angles and two large- amplitude, high-rate, forced-roll motions and a damped free-to-roll motion are presented. The free-to-roll motion is computed by coupling the time-dependent RANS equations to the flight dynamic equation of motion. The computed results are compared with experimental pressures, forces, moments and roll angle time history. In addition, surface and off-surface flow particle streaks are also presented.

Intracardiac Vortex Dynamics by High-Frame-Rate Doppler Vortography-In Vivo Comparison With Vector Flow Mapping and 4-D Flow MRI.

PubMed

Faurie, Julia; Baudet, Mathilde; Assi, Kondo Claude; Auger, Dominique; Gilbert, Guillaume; Tournoux, Francois; Garcia, Damien

2017-02-01

Recent studies have suggested that intracardiac vortex flow imaging could be of clinical interest to early diagnose the diastolic heart function. Doppler vortography has been introduced as a simple color Doppler method to detect and quantify intraventricular vortices. This method is able to locate a vortex core based on the recognition of an antisymmetric pattern in the Doppler velocity field. Because the heart is a fast-moving organ, high frame rates are needed to decipher the whole blood vortex dynamics during diastole. In this paper, we adapted the vortography method to high-frame-rate echocardiography using circular waves. Time-resolved Doppler vortography was first validated in vitro in an ideal forced vortex. We observed a strong correlation between the core vorticity determined by high-frame-rate vortography and the ground-truth vorticity. Vortography was also tested in vivo in ten healthy volunteers using high-frame-rate duplex ultrasonography. The main vortex that forms during left ventricular filling was tracked during two-three successive cardiac cycles, and its core vorticity was determined at a sampling rate up to 80 duplex images per heartbeat. Three echocardiographic apical views were evaluated. Vortography-derived vorticities were compared with those returned by the 2-D vector flow mapping approach. Comparison with 4-D flow magnetic resonance imaging was also performed in four of the ten volunteers. Strong intermethod agreements were observed when determining the peak vorticity during early filling. It is concluded that high-frame-rate Doppler vortography can accurately investigate the diastolic vortex dynamics.

Maximizing the productivity of the microalgae Scenedesmus AMDD cultivated in a continuous photobioreactor using an online flow rate control.

PubMed

McGinn, Patrick J; MacQuarrie, Scott P; Choi, Jerome; Tartakovsky, Boris

2017-01-01

In this study, production of the microalga Scenedesmus AMDD in a 300 L continuous flow photobioreactor was maximized using an online flow (dilution rate) control algorithm. To enable online control, biomass concentration was estimated in real time by measuring chlorophyll-related culture fluorescence. A simple microalgae growth model was developed and used to solve the optimization problem aimed at maximizing the photobioreactor productivity. When optimally controlled, Scenedesmus AMDD culture demonstrated an average volumetric biomass productivity of 0.11 g L -1  d -1 over a 25 day cultivation period, equivalent to a 70 % performance improvement compared to the same photobioreactor operated as a turbidostat. The proposed approach for optimizing photobioreactor flow can be adapted to a broad range of microalgae cultivation systems.

Impact of laminar flow velocity of different acids on enamel calcium loss.

PubMed

Attin, T; Becker, K; Wiegand, A; Tauböck, T T; Wegehaupt, F J

2013-03-01

The aim of the study was to evaluate the impact of flow velocity under laminar flow conditions of different acidic solutions on enamel erosion. A total of 240 bovine enamel specimens were prepared and allocated to 30 groups (n = 8 each). Samples of 18 groups were superfused in a flow chamber system with laminar flow behavior using 1 ml of citric acid or hydrochloric acid (HCl) of pH 2.0, 2.6 or 3.0. Flow rates in the sample chamber were adjusted to 10, 60 or 100 μl/min. To simulate turbulent flow behavior, samples of six groups were immersed in 1 ml of the respective solution, which was vortexed (15 min, 600 rpm). For simulating non-agitated conditions, specimens of the remaining six groups were immersed in 1 ml of the respective solution without stirring. Calcium in the solutions, released from the enamel samples, was determined using Arsenazo III method. For acidic solutions of pH 2.6 and 3.0, erosive potential of citric acid was equivalent to that of HCl at a flow of 100 μl/min. The same observation was made for the samples subjected to turbulent conditions at pH 3. At all other conditions, citric acid induced a significantly higher calcium loss than HCl. It is concluded that under slow laminar flow conditions, flow rate variations lead to higher erosive impact of citric acid compared to hydrochloric acid at pH 2.0, but not at pH ≥ 2.6 and increasing laminar flow or turbulent conditions. Erosive enamel dissolution under laminar flow conditions is a complex issue influenced by flow rate and acidic substrate.

40 CFR 1065.545 - Validation of proportional flow control for batch sampling.

Code of Federal Regulations, 2010 CFR

2010-07-01

... of the estimate, SEE, of the sample flow rate versus the total flow rate. For each test interval, demonstrate that SEE was less than or equal to 3.5% of the mean sample flow rate. (b) For any pair of flow meters, use recorded sample and total flow rates, where total flow rate means the raw exhaust flow rate...

Calibration and use of continuous heat-type automated seepage meters for submarine groundwater discharge measurements

USGS Publications Warehouse

Mwashote, B.M.; Burnett, W.C.; Chanton, J.; Santos, I.R.; Dimova, N.; Swarzenski, P.W.

2010-01-01

Submarine groundwater discharge (SGD) assessments were conducted both in the laboratory and at a field site in the northeastern Gulf of Mexico, using a continuous heat-type automated seepage meter (seepmeter). The functioning of the seepmeter is based on measurements of a temperature gradient in the water between downstream and upstream positions in its flow pipe. The device has the potential of providing long-term, high-resolution measurements of SGD. Using a simple inexpensive laboratory set-up, we have shown that connecting an extension cable to the seepmeter has a negligible effect on its measuring capability. Similarly, the observed influence of very low temperature (???3 ??C) on seepmeter measurements can be accounted for by conducting calibrations at such temperatures prior to field deployments. Compared to manual volumetric measurements, calibration experiments showed that at higher water flow rates (>28 cm day-1 or cm3 cm-2 day-1) an analog flowmeter overestimated flow rates by ???7%. This was apparently due to flow resistance, turbulence and formation of air bubbles in the seepmeter water flow tubes. Salinity had no significant effect on the performance of the seepmeter. Calibration results from fresh water and sea water showed close agreement at a 95% confidence level significance between the data sets from the two media (R2 = 0.98). Comparatively, the seepmeter SGD measurements provided data that are comparable to manually-operated seepage meters, the radon geochemical tracer approach, and an electromagnetic (EM) seepage meter. ?? 2009 Elsevier Ltd.

Particle Size Reduction in Geophysical Granular Flows: The Role of Rock Fragmentation

NASA Astrophysics Data System (ADS)

Bianchi, G.; Sklar, L. S.

2016-12-01

Particle size reduction in geophysical granular flows is caused by abrasion and fragmentation, and can affect transport dynamics by altering the particle size distribution. While the Sternberg equation is commonly used to predict the mean abrasion rate in the fluvial environment, and can also be applied to geophysical granular flows, predicting the evolution of the particle size distribution requires a better understanding the controls on the rate of fragmentation and the size distribution of resulting particle fragments. To address this knowledge gap we are using single-particle free-fall experiments to test for the influence of particle size, impact velocity, and rock properties on fragmentation and abrasion rates. Rock types tested include granodiorite, basalt, and serpentinite. Initial particle masses and drop heights range from 20 to 1000 grams and 0.1 to 3.0 meters respectively. Preliminary results of free-fall experiments suggest that the probability of fragmentation varies as a power function of kinetic energy on impact. The resulting size distributions of rock fragments can be collapsed by normalizing by initial particle mass, and can be fit with a generalized Pareto distribution. We apply the free-fall results to understand the evolution of granodiorite particle-size distributions in granular flow experiments using rotating drums ranging in diameter from 0.2 to 4.0 meters. In the drums, we find that the rates of silt production by abrasion and gravel production by fragmentation scale with drum size. To compare these rates with free-fall results we estimate the particle impact frequency and velocity. We then use population balance equations to model the evolution of particle size distributions due to the combined effects of abrasion and fragmentation. Finally, we use the free-fall and drum experimental results to model particle size evolution in Inyo Creek, a steep, debris-flow dominated catchment, and compare model results to field measurements.

Inert gas clearance from tissue by co-currently and counter-currently arranged microvessels

PubMed Central

Lu, Y.; Michel, C. C.

2012-01-01

To elucidate the clearance of dissolved inert gas from tissues, we have developed numerical models of gas transport in a cylindrical block of tissue supplied by one or two capillaries. With two capillaries, attention is given to the effects of co-current and counter-current flow on tissue gas clearance. Clearance by counter-current flow is compared with clearance by a single capillary or by two co-currently arranged capillaries. Effects of the blood velocity, solubility, and diffusivity of the gas in the tissue are investigated using parameters with physiological values. It is found that under the conditions investigated, almost identical clearances are achieved by a single capillary as by a co-current pair when the total flow per tissue volume in each unit is the same (i.e., flow velocity in the single capillary is twice that in each co-current vessel). For both co-current and counter-current arrangements, approximate linear relations exist between the tissue gas clearance rate and tissue blood perfusion rate. However, the counter-current arrangement of capillaries results in less-efficient clearance of the inert gas from tissues. Furthermore, this difference in efficiency increases at higher blood flow rates. At a given blood flow, the simple conduction-capacitance model, which has been used to estimate tissue blood perfusion rate from inert gas clearance, underestimates gas clearance rates predicted by the numerical models for single vessel or for two vessels with co-current flow. This difference is accounted for in discussion, which also considers the choice of parameters and possible effects of microvascular architecture on the interpretation of tissue inert gas clearance. PMID:22604885

Comparative Investigation on the Heat Transfer Characteristics of Gaseous CO2 and Gaseous Water Flowing Through a Single Granite Fracture

NASA Astrophysics Data System (ADS)

He, Yuanyuan; Bai, Bing; Li, Xiaochun

2017-11-01

CO2 and water are two commonly employed heat transmission fluids in several fields. Their temperature and pressure determine their phase states, thus affecting the heat transfer performance of the water/CO2. The heat transfer characteristics of gaseous CO2 and gaseous water flowing through fractured hot dry rock still need a great deal of investigation, in order to understand and evaluate the heat extraction in enhanced geothermal systems. In this work, we develop a 2D numerical model to compare the heat transfer performance of gaseous CO2 and gaseous water flowing through a single fracture aperture of 0.2 mm in a φ 50 × 50 mm cylindrical granite sample with a confining temperature of 200°C under different inlet mass flow rates. Our results indicate that: (1) the final outlet temperatures of the fluid are very close to the outer surface temperature under low inlet mass flow rate, regardless of the sample length. (2) Both the temperature of the fluid (gaseous CO2/gaseous water) and inner surface temperature rise sharply at the inlet, and the inner surface temperature is always higher than the fluid temperature. However, their temperature difference becomes increasingly small. (3) Both the overall heat transfer coefficient (OHTC) and local heat transfer coefficient (LHTC) of gaseous CO2 and gaseous water increase with increasing inlet mass flow rates. (4) Both the OHTC and LHTC of gaseous CO2 are lower than those of gaseous water under the same conditions; therefore, the heat mining performance of gaseous water is superior to gaseous CO2 under high temperature and low pressure.

Flow-field characteristics of high-temperature annular buoyant jets and their development laws influenced by ventilation system.

PubMed

Wang, Yi; Huang, Yanqiu; Liu, Jiaping; Wang, Hai; Liu, Qiuhan

2013-01-01

The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and velocity field characteristics with different pressures at the exhaust hood inlet. The results showed that when the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics had significant difference compared to circular buoyant jets with the same outer diameter. For similar diameter ratios, reattachment in this paper occurred further downstream in contrast to previous study. Besides, the development laws of volumetric flow rate and cross-section diameter were given with different initial parameters. In addition, through analyzing air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system, it could be found that the position where maximum axial velocity occurred was changing gradually when the pressure at the exhaust hood inlet changed from 0 Pa to -5 Pa.

Flow-Field Characteristics of High-Temperature Annular Buoyant Jets and Their Development Laws Influenced by Ventilation System

PubMed Central

Liu, Jiaping; Wang, Hai; Liu, Qiuhan

2013-01-01

The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and velocity field characteristics with different pressures at the exhaust hood inlet. The results showed that when the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics had significant difference compared to circular buoyant jets with the same outer diameter. For similar diameter ratios, reattachment in this paper occurred further downstream in contrast to previous study. Besides, the development laws of volumetric flow rate and cross-section diameter were given with different initial parameters. In addition, through analyzing air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system, it could be found that the position where maximum axial velocity occurred was changing gradually when the pressure at the exhaust hood inlet changed from 0 Pa to −5 Pa. PMID:24000278

Comparison of Y-jet and OIL effervescent atomizers based on internal and external two-phase flow characteristics

NASA Astrophysics Data System (ADS)

Mlkvik, Marek; Zaremba, Matous; Jedelsky, Jan; Jicha, Miroslav

2016-03-01

Presented paper focuses on spraying of two viscous liquids (μ = 60 and 143 mPa·s) by two types of twinfluid atomizers with internal mixing. We compared the well-known Y-jet atomizer with the less known, "outside in liquid" (OIL), configuration of the effervescent atomizer. The required liquid viscosity was achieved by using the water-maltodextrin solutions of different concentrations. Both the liquids were sprayed at two gas inlet pressures (Δp = 0.14 and 0.28 MPa) and various gas-to-liquid ratios (GLR = 2.5%, 5%, 10% and 20%). The comparison was focused on four characteristics: liquid flow-rate (for the same working regimes, defined by Δp and GLR), internal flow regimes, Weber numbers of a liquid breakup (We) and droplet sizes. A high-speed camera and Malvern Spraytec laser diffraction system were used to obtain necessary experimental data. Comparing the results of our experiments, we can state that for both the liquids the OIL atomizer reached higher liquid flow-rates at corresponding working regimes, it was typical by annular internal flow and higher We in the near-nozzle region at all the working regimes. As a result, it produced considerably smaller droplets than the second tested atomizing device, especially for GLR < 10%.

Comparison of flowrates and voided volumes during non-instrumented uroflowmetry and pressure-flow studies in women with stress incontinence.

PubMed

Mueller, Elizabeth R; Litman, Heather; Rickey, Leslie R; Sirls, Larry; Norton, Peggy; Wilson, Tracey; Moalli, Pamela; Albo, Michael; Zimmern, Philippe

2015-08-01

The Blaivas-Groutz nomogram defines voiding obstruction in women using Qmax from the NIF and the maximum detrusor pressure (Pdetmax ) from the PFS. The aim of this study was to understand the relationship between NIF and PFS maximum flow rates in women with stress incontinence. We analyzed the UDS of 597 women with stress-dominant urinary incontinence. Each subject underwent a NIF and then a PFS. Mixed model was used to test the hypothesis that the relationship between flow rates and voided volume (VV) were similar for NIF and PFS. There were 452 subjects with both NIF and PFS studies that met the inclusion criteria and had max flow rate (Qmax ) for both NIF and PFS. The mean age was 53. Overall, higher VV were observed during PFS compared to NIF and subjects had higher Qmax with NIF compared to PFS. The relationship between Qmax and VV was significantly different between NIF and PFS (P < 0.004). At 200 ml, NIF Qmax was 14% higher than PFS Qmax and this difference increased to 30% at 700 ml. The difference between PFS Qmax and NIF Qmax increases as VV increase. As a result, values from PFS and NIF cannot be used interchangeably as has been suggested in the Blaivas-Groutz nomogram for obstruction in women. © 2014 Wiley Periodicals, Inc.

COMPARISON OF FLOWRATES AND VOIDED VOLUMES DURING NON-INSTRUMENTED UROFLOWMETRY AND PRESSURE-FLOW STUDIES IN WOMEN WITH STRESS INCONTINENCE

PubMed Central

Mueller, ER; Litman, H; Rickey, LR; Sirls, L; Norton, P; Wilson, T; Moalli, P; Albo, M; Zimmern, P

2014-01-01

Aims The Blaivas-Groutz nomogram defines voiding obstruction in women using Qmax from the NIF and the maximum detrusor pressure (Pdetmax) from the PFS. The aim of this study was to understand the relationship between NIF and PFS maximum flow rates in women with stress incontinence. Methods We analyzed the UDS of 597 women with stress-dominant urinary incontinence. Each subject underwent a NIF and then a PFS. Mixed model was used to test the hypothesis that the relationship between flow rates and voided volume were similar for NIF and PFS. Results There were 452 subjects with both NIF and PFS studies that met the inclusion criteria and had max flow rate (Qmax) for both NIF and PFS. The mean age was 53. Overall, higher voided volumes were observed during PFS compared to NIF and subjects had higher Qmax with NIF compared to PFS. The relationship between Qmax and VV was significantly different between NIF and PFS (p < 0.004). At 200 mL, NIF Qmax was 14% higher than PFS Qmax and this difference increased to 30% at 700mL. Conclusion The difference between PFS Qmax and NIF Qmax increases as voided volumes increase. As a result, values from PFS and NIF cannot be used interchangeably as has been suggested in the Blaivas-Groutz nomogram for obstruction in women. PMID:24797058

Relationship of long-term highly active antiretroviral therapy on salivary flow rate and CD4 Count among HIV-infected patients.

PubMed

Kumar, J Vijay; Baghirath, P Venkat; Naishadham, P Parameswar; Suneetha, Sujai; Suneetha, Lavanya; Sreedevi, P

2015-01-01

To determine if long-term highly active antiretroviral therapy (HAART) therapy alters salivary flow rate and also to compare its relation of CD4 count with unstimulated and stimulated whole saliva. A cross-sectional study was performed on 150 individuals divided into three groups. Group I (50 human immunodeficiency virus (HIV) seropositive patients, but not on HAART therapy), Group II (50 HIV-infected subjects and on HAART for less than 3 years called short-term HAART), Group III (50 HIV-infected subjects and on HAART for more than or equal to 3 years called long-term HAART). Spitting method proposed by Navazesh and Kumar was used for the measurement of unstimulated and stimulated salivary flow rate. Chi-square test and analysis of variance (ANOVA) were used for statistical analysis. The mean CD4 count was 424.78 ± 187.03, 497.82 ± 206.11 and 537.6 ± 264.00 in the respective groups. Majority of the patients in all the groups had a CD4 count between 401 and 600. Both unstimulated and stimulated whole salivary (UWS and SWS) flow rates in Group I was found to be significantly higher than in Group II (P < 0.05). Unstimulated salivary flow rate between Group II and III subjects were also found to be statistically significant (P < 0.05). ANOVA performed between CD4 count and unstimulated and stimulated whole saliva in each group demonstrated a statistically significant relationship in Group II (P < 0.05). There were no significant results found between CD4 count and stimulated whole saliva in each groups. The reduction in CD4 cell counts were significantly associated with salivary flow rates of HIV-infected individuals who are on long-term HAART.

Biodegradation of toluene by a lab-scale biofilter inoculated with Pseudomonas putida DK-1.

PubMed

Park, D W; Kim, S S; Haam, S; Ahn, I S; Kim, E B; Kim, W S

2002-03-01

The biodegradation of toluene by biofiltration inoculated with Pseudomonas putida DK-1 was investigated with variation of the several environmental parameters, such as temperature, bed length, gas flow rate and optimal humidity zone. The optimal temperature range to treat toluene gas was found to be 32-35 degrees C. Increasing the gas flow rate showed an inverse effect on the elimination capacity and the removal efficiency. The optimal gas flow rate was obtained at 65 ml min(-1) from the relation between the removal efficiency and the elimination capacity. The biodegradation rate of the toluene with respect to the bed lengths (3, 6, 9, 12 and 15 cm) increased up to 80 h but was then independent of the bed lengths after 80 h except for the 3 cm bed length. The elimination capacity was improved by about 70% compared with that reported in other literature and was also in agreement with theoretical models.

Numerical Simulations of the Steady and Unsteady Aerodynamic Characteristics of a Circulation Control Wing Airfoil

NASA Technical Reports Server (NTRS)

Liu, Yi; Sankar, Lakshmi N.; Englar, Robert J.; Ahuja, Krishan K.

2003-01-01

The aerodynamic characteristics of a Circulation Control Wing (CCW) airfoil have been numerically investigated, and comparisons with experimental data have been made. The configuration chosen was a supercritical airfoil with a 30 degree dual-radius CCW flap. Steady and pulsed jet calculations were performed. It was found that the use of steady jets, even at very small mass flow rates, yielded a lift coefficient that is comparable or superior to conventional high-lift systems. The attached flow over the flap also gave rise to lower drag coefficients, and high L/D ratios. Pulsed jets with a 50% duty cycle were also studied. It was found that they were effective in generating lift at lower reduced mass flow rates compared to a steady jet, provided the pulse frequency was sufficiently high. This benefit was attributable to the fact that the momentum coefficient of the pulsed jet, during the portions of the cycle when the jet was on, was typically twice as much as that of a steady jet.

Doppler flowmeter

DOEpatents

Karplus, H.H.B.; Raptis, A.C.

1981-11-13

A Doppler flowmeter impulses an ultrasonic fixed-frequency signal obliquely into a slurry flowing in a pipe and a reflected signal is detected after having been scattered off of the slurry particles, whereby the shift in frequencies between the signals is proportional to the slurry velocity and hence slurry flow rate. This flowmeter filters the Doppler frequency-shift signal, compares the filtered and unfiltered shift signals in a divider to obtain a ratio, and then further compares this ratio against a preset fractional ratio. The flowmeter utilizes a voltage-to-frequency convertor to generate a pulsed signal having a determinable rate of repetition precisely proportional to the divergence of the ratios. The pulsed signal serves as the input control for a frequency-controlled low-pass filter, which provides thereby that the cutoff frequency of the filtered signal is known. The flowmeter provides a feedback control by minimizing the divergence. With the cutoff frequency and preset fractional ratio known, the slurry velocity and hence flow will also be determinable.

Doppler flowmeter

DOEpatents

Karplus, Henry H. B.; Raptis, Apostolos C.

1983-01-01

A Doppler flowmeter impulses an ultrasonic fixed-frequency signal obliquely into a slurry flowing in a pipe and a reflected signal is detected after having been scattered off of the slurry particles, whereby the shift in frequencies between the signals is proportional to the slurry velocity and hence slurry flow rate. This flowmeter filters the Doppler frequency-shift signal, compares the filtered and unfiltered shift signals in a divider to obtain a ratio, and then further compares this ratio against a preset fractional ratio. The flowmeter utilizes a voltage-to-frequency convertor to generate a pulsed signal having a determinable rate of repetition precisely proportional to the divergence of the ratios. The pulsed signal serves as the input control for a frequency-controlled low-pass filter, which provides thereby that the cutoff frequency of the filtered signal is known. The flowmeter provides a feedback control by minimizing the divergence. With the cutoff frequency and preset fractional ratio known, the slurry velocity and hence flow will also be determinable.

A Modified Double Multiple Nonlinear Regression Constitutive Equation for Modeling and Prediction of High Temperature Flow Behavior of BFe10-1-2 Alloy

NASA Astrophysics Data System (ADS)

Cai, Jun; Wang, Kuaishe; Shi, Jiamin; Wang, Wen; Liu, Yingying

2018-01-01

Constitutive analysis for hot working of BFe10-1-2 alloy was carried out by using experimental stress-strain data from isothermal hot compression tests, in a wide range of temperature of 1,023 1,273 K, and strain rate range of 0.001 10 s-1. A constitutive equation based on modified double multiple nonlinear regression was proposed considering the independent effects of strain, strain rate, temperature and their interrelation. The predicted flow stress data calculated from the developed equation was compared with the experimental data. Correlation coefficient (R), average absolute relative error (AARE) and relative errors were introduced to verify the validity of the developed constitutive equation. Subsequently, a comparative study was made on the capability of strain-compensated Arrhenius-type constitutive model. The results showed that the developed constitutive equation based on modified double multiple nonlinear regression could predict flow stress of BFe10-1-2 alloy with good correlation and generalization.

Improving Bedload Transport Predictions by Incorporating Hysteresis

NASA Astrophysics Data System (ADS)

Crowe Curran, J.; Gaeuman, D.

2015-12-01

The importance of unsteady flow on sediment transport rates has long been recognized. However, the majority of sediment transport models were developed under steady flow conditions that did not account for changing bed morphologies and sediment transport during flood events. More recent research has used laboratory data and field data to quantify the influence of hysteresis on bedload transport and adjust transport models. In this research, these new methods are combined to improve further the accuracy of bedload transport rate quantification and prediction. The first approach defined reference shear stresses for hydrograph rising and falling limbs, and used these values to predict total and fractional transport rates during a hydrograph. From this research, a parameter for improving transport predictions during unsteady flows was developed. The second approach applied a maximum likelihood procedure to fit a bedload rating curve to measurements from a number of different coarse bed rivers. Parameters defining the rating curve were optimized for values that maximized the conditional probability of producing the measured bedload transport rate. Bedload sample magnitude was fit to a gamma distribution, and the probability of collecting N particles in a sampler during a given time step was described with a Poisson probability density function. Both approaches improved estimates of total transport during large flow events when compared to existing methods and transport models. Recognizing and accounting for the changes in transport parameters over time frames on the order of a flood or flood sequence influences the choice of method for parameter calculation in sediment transport calculations. Those methods that more tightly link the changing flow rate and bed mobility have the potential to improve bedload transport rates.

Validation of a Multimodality Flow Phantom and Its Application for Assessment of Dynamic SPECT and PET Technologies.

PubMed

Gabrani-Juma, Hanif; Clarkin, Owen J; Pourmoghaddas, Amir; Driscoll, Brandon; Wells, R Glenn; deKemp, Robert A; Klein, Ran

2017-01-01

Simple and robust techniques are lacking to assess performance of flow quantification using dynamic imaging. We therefore developed a method to qualify flow quantification technologies using a physical compartment exchange phantom and image analysis tool. We validate and demonstrate utility of this method using dynamic PET and SPECT. Dynamic image sequences were acquired on two PET/CT and a cardiac dedicated SPECT (with and without attenuation and scatter corrections) systems. A two-compartment exchange model was fit to image derived time-activity curves to quantify flow rates. Flowmeter measured flow rates (20-300 mL/min) were set prior to imaging and were used as reference truth to which image derived flow rates were compared. Both PET cameras had excellent agreement with truth ( [Formula: see text]). High-end PET had no significant bias (p > 0.05) while lower-end PET had minimal slope bias (wash-in and wash-out slopes were 1.02 and 1.01) but no significant reduction in precision relative to high-end PET (<15% vs. <14% limits of agreement, p > 0.3). SPECT (without scatter and attenuation corrections) slope biases were noted (0.85 and 1.32) and attributed to camera saturation in early time frames. Analysis of wash-out rates from non-saturated, late time frames resulted in excellent agreement with truth ( [Formula: see text], slope = 0.97). Attenuation and scatter corrections did not significantly impact SPECT performance. The proposed phantom, software and quality assurance paradigm can be used to qualify imaging instrumentation and protocols for quantification of kinetic rate parameters using dynamic imaging.

Numerical Simulation of Fluidic Actuators for Flow Control Applications

NASA Technical Reports Server (NTRS)

Vasta, Veer N.; Koklu, Mehti; Wygnanski, Israel L.; Fares, Ehab

2012-01-01

Active flow control technology is finding increasing use in aerospace applications to control flow separation and improve aerodynamic performance. In this paper we examine the characteristics of a class of fluidic actuators that are being considered for active flow control applications for a variety of practical problems. Based on recent experimental work, such actuators have been found to be more efficient for controlling flow separation in terms of mass flow requirements compared to constant blowing and suction or even synthetic jet actuators. The fluidic actuators produce spanwise oscillating jets, and therefore are also known as sweeping jets. The frequency and spanwise sweeping extent depend on the geometric parameters and mass flow rate entering the actuators through the inlet section. The flow physics associated with these actuators is quite complex and not fully understood at this time. The unsteady flow generated by such actuators is simulated using the lattice Boltzmann based solver PowerFLOW R . Computed mean and standard deviation of velocity profiles generated by a family of fluidic actuators in quiescent air are compared with experimental data. Simulated results replicate the experimentally observed trends with parametric variation of geometry and inflow conditions.

Linear bubble plume model for hypolimnetic oxygenation: Full-scale validation and sensitivity analysis

NASA Astrophysics Data System (ADS)

Singleton, V. L.; Gantzer, P.; Little, J. C.

2007-02-01

An existing linear bubble plume model was improved, and data collected from a full-scale diffuser installed in Spring Hollow Reservoir, Virginia, were used to validate the model. The depth of maximum plume rise was simulated well for two of the three diffuser tests. Temperature predictions deviated from measured profiles near the maximum plume rise height, but predicted dissolved oxygen profiles compared very well with observations. A sensitivity analysis was performed. The gas flow rate had the greatest effect on predicted plume rise height and induced water flow rate, both of which were directly proportional to gas flow rate. Oxygen transfer within the hypolimnion was independent of all parameters except initial bubble radius and was inversely proportional for radii greater than approximately 1 mm. The results of this work suggest that plume dynamics and oxygen transfer can successfully be predicted for linear bubble plumes using the discrete-bubble approach.

Recent Advances in Synthesis and Characterization of SWCNTs Produced by Laser Oven Process

NASA Technical Reports Server (NTRS)

Aepalli, Sivaram

2004-01-01

Results from the parametric study of the two-laser oven process indicated possible improvements with flow conditions and laser characteristics. Higher flow rates, lower operating pressures coupled with changes in flow tube material are found to improve the nanotube yields. The collected nanotube material is analyzed using a combination of characterization techniques including SEM, TEM, TGA, Raman and UV-VIS-NIR to estimate the purity of the samples. In-situ diagnostics of the laser oven process is now extended to include the surface temperature of the target material. Spectral emission from the target surface is compared with black body type emission to estimate the temperature. The surface temperature seemed to correlate well with the ablation rate as well as the quality of the SWCNTs. Recent changes in improving the production rate by rastering the target and using cw laser will be presented.

Recent Advances in Synthesis and Characterization of SWCNTs produced by laser oven process

NASA Technical Reports Server (NTRS)

Arepalli, Sivaram

2004-01-01

Results from the parametric study of the two-laser oven process indicated possible improvements with flow conditions and laser characteristics (ref. 1). Higher flow rates, lower operating pressures coupled with changes in flow tube material are found to improve the nanotube yields. The collected nanotube material is analyzed using a combination of characterization techniques including SEM, TEM, TGA, Raman and UV-VIS-NIR to estimate the purity of the samples. Insitu diagnostics of the laser oven process is now extended to include the surface temperature of the target material. Spectral emission from the target surface is compared with black body type emission to estimate the temperature. The surface temperature seemed to correlate well with the ablation rate as well as the quality of the SWCNTs. Recent changes in improving the production rate by rastering the target and using cw laser will be presented.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Shifeng; Wang, Shuyu; Lu, Ming

In this paper, vanadium thin films were deposited on sapphire substrates by DC magnetron sputtering and then oxidized in a tube furnace filled with oxygen under different temperatures and oxygen flow rates. The significant influence of the oxygen flow rate and oxidation temperature on the electrical and structural properties of the vanadium oxide thin films were investigated systematically. It shows the pure vanadium dioxide (VO 2) state can only be obtained in a very narrow temperature and oxygen flow rate range. The resistivity change during the metal-insulator transition varies from 0.2 to 4 orders of magnitude depending on the oxidationmore » condition. Large thermal hysteresis during the metal-insulator phase transition was observed during the transition compared to the results in literature. Proper oxidation conditions can significantly reduce the thermal hysteresis. Finally, the fabricated VO 2 thin films showed the potential to be applied in the development of electrical sensors and other smart devices.« less

Velocity of water flow along saturated loess slopes under erosion effects

NASA Astrophysics Data System (ADS)

Huang, Yuhan; Chen, Xiaoyan; Li, Fahu; Zhang, Jing; Lei, Tingwu; Li, Juan; Chen, Ping; Wang, Xuefeng

2018-06-01

Rainfall or snow-melted water recharge easily saturates loose top soils with a less permeable underlayer, such as cultivated soil slope and partially thawed top soil layer, and thus, may influence the velocity of water flow. This study suggested a methodology and device system to supply water from the bottom soil layer at the different locations of slopes. Water seeps into and saturates the soil, when the water level is controlled at the same height of the soil surface. The structures and functions of the device, the components, and the operational principles are described in detail. A series of laboratory experiments were conducted under slope gradients of 5°, 10°, 15°, and 20° and flow rates of 2, 4, and 8 L min-1 to measure the water flow velocities over eroding and non-eroded loess soil slopes, under saturated conditions by using electrolyte tracing. Results showed that flow velocities on saturated slopes were 17% to 88% greater than those on non-saturated slopes. Flow velocity increased rapidly under high flow rates and slope gradients. Saturation conditions were suitable in maintaining smooth rill geomorphology and causing fast water flow. The saturated soil slope had a lubricant effect on the soil surface to reduce the frictional force, resulting in high flow velocity. The flow velocities of eroding rills under different slope gradients and flow rates were approximately 14% to 33% lower than those of non-eroded rills on saturated loess slopes. Compared with that on a saturated loess slope, the eroding rill on a non-saturated loess slope can produce headcuts to reduce the flow velocity. This study helps understand the hydrodynamics of soil erosion and sediment transportation of saturated soil slopes.

Doppler sonographic screening of the flow in the basilar artery during head rotation reduces the risk for sudden infant death.

PubMed

Deeg, K-H; Reisig, A

2010-10-01

Position-dependent hypoperfusion of the brain stem may be a risk factor of sudden infant death. From 1998 to 2009 we performed Doppler sonographic flow measurements in the basilar artery of 18 194 newborns, 9322 boys and 8872 girls, in five different positions: the neutral position with the head in the midline and during head rotation to the left and right in a supine or prone position. The peak systolic and the time average flow velocity were measured from the flow profile. The flow velocities during head rotation were converted to % of the flow in the neutral position. A decrease in the velocities during head rotation below 50 % was thought to be abnormal. Biphasic flow, flow oscillating around the zero line or retrograde flow during rotation was considered to be pathological. Head rotations, which had caused abnormal and pathological flow, were avoided. The incidence of SIDS in our study group was evaluated and compared with the incidence in a control group of 3 519 newborns. In 17 929 newborns (98.54 %) the blood flow in the basilar artery was independent of head rotation and body position. In 204 newborns (1.12 %) we found an abnormal decrease under 50 %. Pathological flow alterations could be found in 61 patients (0.33 %). The overall incidence rate of SIDS in the study group was 0.055 ‰ (1:18 194). The incidence rate of SIDS in the control group was 1.14 ‰ (4:3519). The comparison of both groups showed a statistically significant (p < 0.0030) lower incidence rate in the study group. Hypoperfusion of the brain stem may be a significant risk factor of SIDS. © Georg Thieme Verlag KG Stuttgart · New York.

Non-Darcian flow of shear-thinning fluids through packed beads: Experiments and predictions using Forchheimer's law and Ergun's equation

NASA Astrophysics Data System (ADS)

Rodríguez de Castro, Antonio; Radilla, Giovanni

2017-02-01

The flow of shear-thinning fluids through unconsolidated porous media is present in a number of important industrial applications such as soil depollution, Enhanced Oil Recovery or filtration of polymeric liquids. Therefore, predicting the pressure drop-flow rate relationship in model porous media has been the scope of major research efforts during the last decades. Although the flow of Newtonian fluids through packs of spherical particles is well understood in most cases, much less is known regarding the flow of shear-thinning fluids as high molecular weight polymer aqueous solutions. In particular, the experimental data for the non-Darcian flow of shear-thinning fluids are scarce and so are the current approaches for their prediction. Given the relevance of non-Darcian shear-thinning flow, the scope of this work is to perform an experimental study to systematically evaluate the effects of fluid shear rheology on the flow rate-pressure drop relationships for the non-Darcian flow through different packs of glass spheres. To do so, xanthan gum aqueous solutions with different polymer concentrations are injected through four packs of glass spheres with uniform size under Darcian and inertial flow regimes. A total of 1560 experimental data are then compared with predictions coming from different methods based on the extension of widely used Ergun's equation and Forchheimer's law to the case of shear thinning fluids, determining the accuracy of these predictions. The use of a proper definition for Reynolds number and a realistic model to represent the rheology of the injected fluids results in the porous media are shown to be key aspects to successfully predict pressure drop-flow rate relationships for the inertial shear-thinning flow in packed beads.

Investigation of a liquid-fed water resistojet plume

NASA Technical Reports Server (NTRS)

Manzella, D. H.; Carney, L. M.

1989-01-01

Measurements of mass flux and flow angle were taken throughout the forward flow region of the exhaust of a liquid-fed water resistojet using a quartz crystal microbalance (QCM). The resistojet operated at a mass flow rate of 0.1 g/s with a power input of 330 Watts. Measured values were compared to theoretical predictions obtained by employing a source flow approximation. Excellent agreement between predicted and measured mass flux values was attained; however, this agreement was highly dependent on knowledge of nozzle flow conditions. Measurements of the temperature at which the exhaust condensed on the QCM were obtained as a function of incident mass flux.

Liquid Bismuth Propellant Management System for the Very High Specific Impulse Thruster with Anode Layer

NASA Technical Reports Server (NTRS)

Polzin, K. A.; Markusic, T. E.; Stanojev, B. J.

2007-01-01

Two prototype bismuth propellant feed systems were constructed and operated in conjunction with a propellant vaporizer. One system provided bismuth to a vaporizer using gas pressurization but did not include a means to measure the flow rate. The second system incorporated an electromagnetic pump to provide fine control of the hydrostatic pressure and a new type of in-line flow sensor that was developed for accurate, real-time measurement of the mass flow rate. High-temperature material compatibility was a driving design requirement for the pump and flow sensor, leading to the selection of Macor for the main body of both components. Posttest inspections of both components revealed no degradation of the material. The gas pressurization system demonstrated continuous pressure control over a range from zero to 200 torr. In separate proof-of-concept experiments, the electromagnetic pump produced a linear pressure rise as a function of current that compared favorably with theoretical pump pressure predictions, producing a pressure rise of 10 kPa at 30 A. Preliminary flow sensor operation indicated a bismuth flow rate of 6 mg/s with an uncertainty of plus or minus 6%. An electronics suite containing a real-time controller was successfully used to control the entire system, simultaneously monitoring all power supplies and performing data acquisition duties.

Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

PubMed Central

Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

2014-01-01

The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment. PMID:25319447

Effect of geometry and scale for axial and radial flow membrane chromatography-Experimental study of bovin serum albumin adsorption.

PubMed

Teepakorn, Chalore; Fiaty, Koffi; Charcosset, Catherine

2015-07-17

During the last 10 years, membrane chromatography (MC) has been increasingly reported for biomolecule purification at both small and large scales. Although, several axial and radial flow MC devices are commercialized, the effect of the device dimensions on the adsorption performance has not been fully investigated. In this study, axial and radial flow anion ion-exchange MC devices were used for bovine serum albumin (BSA) adsorption. For both axial and radial flow, three devices at different scales were compared, two having similar diameter and two similar bed height. The pressure drop and the flow distribution using acetone as a non-binding solute were measured, as well as BSA breakthrough curves at different flow rates and BSA loading concentrations. For all devices, it was observed that the flow rate had no effect on the breakthrough curve, which confirms the advantage of MC to be used at high flow rates. In addition, the BSA binding capacity increased with increasing BSA concentration, which suggests that it could be preferable to work with concentrated solutions rather than with very dilute solutions, when using buffer at high phosphate concentration. For both axial and radial flow, the bed height had a negative impact on the binding capacity, as the lowest binding capacities per membrane volume were obtained with the devices having the highest bed height. Radial flow MC has potential at large-scale applications, as a short bed thickness can be combined with a large inlet surface area. Copyright © 2015 Elsevier B.V. All rights reserved.

A novel, microscope based, non-invasive laser Doppler flowmeter for choroidal blood flow assessment.

PubMed

Strohmaier, C; Werkmeister, R M; Bogner, B; Runge, C; Schroedl, F; Brandtner, H; Radner, W; Schmetterer, L; Kiel, J W; Grabner, G; Reitsamer, H A

2011-06-01

Impaired ocular blood flow is involved in the pathogenesis of numerous ocular diseases like glaucoma or AMD. The purpose of the present study was to introduce and validate a novel, microscope based, non-invasive Laser Doppler Flowmeter (NI-LDF) for measurement of blood flow in the choroid. The custom made NI-LDF was compared with a commercial fiber optic based laser Doppler flowmeter (Perimed PF4000). Linearity and stability of the NI-LDF were assessed in a silastic tubing model (i.d. 0.3 mm) at different flow rates (range 0.4-3 ml/h). In a rabbit model continuous choroidal blood flow measurements were performed with both instruments simultaneously. During blood flow measurements ocular perfusion pressure was changed by manipulations of intraocular pressure via intravitreal saline infusions. The NI-LDF measurement correlated linearly to intraluminal flow rates in the perfused tubing model (r = 0.99, p < 0.05) and remained stable during a 1 h measurement at a constant flow rate. Rabbit choroidal blood flow measured by the PF4000 and the NI-LDF linearly correlated with each other over the entire measurement range (r = 0.99, y = x∗1.01-12.35 P.U., p < 0.001). In conclusion, the NI-LDF provides valid, semi quantitative measurements of capillary blood flow in comparison to an established LDF instrument and is suitable for measurements at the posterior pole of the eye. Copyright © 2011 Elsevier Ltd. All rights reserved.

An in vitro test bench reproducing coronary blood flow signals.

PubMed

Chodzyński, Kamil Jerzy; Boudjeltia, Karim Zouaoui; Lalmand, Jacques; Aminian, Adel; Vanhamme, Luc; de Sousa, Daniel Ribeiro; Gremmo, Simone; Bricteux, Laurent; Renotte, Christine; Courbebaisse, Guy; Coussement, Grégory

2015-08-07

It is a known fact that blood flow pattern and more specifically the pulsatile time variation of shear stress on the vascular wall play a key role in atherogenesis. The paper presents the conception, the building and the control of a new in vitro test bench that mimics the pulsatile flows behavior based on in vivo measurements. An in vitro cardiovascular simulator is alimented with in vivo constraints upstream and provided with further post-processing analysis downstream in order to mimic the pulsatile in vivo blood flow quantities. This real-time controlled system is designed to perform real pulsatile in vivo blood flow signals to study endothelial cells' behavior under near physiological environment. The system is based on an internal model controller and a proportional-integral controller that controls a linear motor with customized piston pump, two proportional-integral controllers that control the mean flow rate and temperature of the medium. This configuration enables to mimic any resulting blood flow rate patterns between 40 and 700 ml/min. In order to feed the system with reliable periodic flow quantities in vivo measurements were performed. Data from five patients (1 female, 4 males; ages 44-63) were filtered and post-processed using the Newtonian Womersley's solution. These resulting flow signals were compared with 2D axisymmetric, numerical simulation using a Carreau non-Newtonian model to validate the approximation of a Newtonian behavior. This in vitro test bench reproduces the measured flow rate time evolution and the complexity of in vivo hemodynamic signals within the accuracy of the relative error below 5%. This post-processing method is compatible with any real complex in vivo signal and demonstrates the heterogeneity of pulsatile patterns in coronary arteries among of different patients. The comparison between analytical and numerical solution demonstrate the fair quality of the Newtonian Womersley's approximation. Therefore, Womersley's solution was used to calculate input flow rate for the in vitro test bench.

Prioritizing blood flow: cardiovascular performance in response to the competing demands of locomotion and digestion for the Burmese python, Python molurus.

PubMed

Secor, Stephen M; White, Scott E

2010-01-01

Individually, the metabolic demands of digestion or movement can be fully supported by elevations in cardiovascular performance, but when occurring simultaneously, vascular perfusion may have to be prioritized to either the gut or skeletal muscles. Burmese pythons (Python molurus) experience similar increases in metabolic rate during the digestion of a meal as they do while crawling, hence each would have an equal demand for vascular supply when these two actions are combined. To determine, for the Burmese python, whether blood flow is prioritized when snakes are digesting and moving, we examined changes in cardiac performance and blood flow in response to digestion, movement, and the combination of digestion and movement. We used perivascular blood flow probes to measure blood flow through the left carotid artery, dorsal aorta, superior mesenteric artery and hepatic portal vein, and to calculate cardiac output, heart rate and stroke volume. Fasted pythons while crawling experienced a 2.7- and 3.3-fold increase, respectively, in heart rate and cardiac output, and a 66% decrease in superior mesenteric flow. During the digestion of a rodent meal equaling in mass to 24.7% of the snake's body mass, heart rate and cardiac output increased by 3.3- and 4.4-fold, respectively. Digestion also resulted in respective 11.6- and 14.1-fold increases in superior mesenteric and hepatic portal flow. When crawling while digesting, cardiac output and dorsal aorta flow increased by only 21% and 9%, respectively, a modest increase compared with that when they start to crawl on an empty stomach. Crawling did triggered a significant reduction in blood flow to the digesting gut, decreasing superior mesenteric and hepatic portal flow by 81% and 47%, respectively. When faced with the dual demands of digestion and crawling, Burmese pythons prioritize blood flow, apparently diverting visceral supply to the axial muscles.

Microgravity Flammability of PMMA Rods in Concurrent Flow

NASA Technical Reports Server (NTRS)

Olson, Sandra L.; Ferkul, Paul V.

2015-01-01

Microgravity experiments burning cast PMMA cylindrical rods in axial flow have been conducted aboard the International Space Station in the Microgravity Science Glovebox (MSG) facility using the Burning and Suppression of Solids (BASS) flow duct, as part of the BASS-II experiment. Twenty-four concurrent-flow tests were performed, focusing on finding flammability limits as a function of oxygen and flow speed. The oxygen was varied by using gaseous nitrogen to vitiate the working volume of the MSG. The speed of the flow parallel to the rod was varied using a fan at the entrance to the duct. Both blowoff and quenching limits were obtained at several oxygen concentrations. Each experiment ignited the rod at the initially hemispherical stagnation tip of the rod, and allowed the flame to develop and heat the rod at a sufficient flow to sustain burning. For blowoff limit tests, the astronaut quickly turned up the flow to obtain extinction. Complementary 5.18-second Zero Gravity Facility drop tests were conducted to compare blowoff limits in short and long duration microgravity. For quenching tests, the flow was incrementally turned down and the flame allowed to stabilize at the new flow condition for at least the solid-phase response time before changing it again. Quenching was observed when the flow became sufficiently weak that the flame could no longer provide adequate heat flux to compensate for the heat losses (conduction into the rod and radiation). A surface energy balance is presented that shows the surface radiative loss exceeds the conductive loss into the rod near the limit. The flammability boundary is shown to represent a critical Damkohler number, expressed in terms of the reaction rate divided by the stretch rate. For the blowoff branch, the boundary exhibits a linear dependence on oxygen concentration and stretch rate, indicating that the temperature at blowoff must be fairly constant. For the quenching branch, the dominance of the exponential nature of the Arrhenius kinetics reaction rate indicates that the temperature is critical.

The physics of confined flow and its application to water leaks, water permeation and water nanoflows: a review.

PubMed

Lei, Wenwen; Rigozzi, Michelle K; McKenzie, David R

2016-02-01

This review assesses the current state of understanding of the calculation of the rate of flow of gases, vapours and liquids confined in channels, in porous media and in permeable materials with an emphasis on the flow of water and its vapour. One motivation is to investigate the relation between the permeation rate of moisture and that of a noncondensable test gas such as helium, another is to assist in unifying theory and experiment across disparate fields. Available theories of single component ideal gas flows in channels of defined geometry (cylindrical, rectangular and elliptical) are described and their predictions compared with measurement over a wide range of conditions defined by the Knudsen number. Theory for two phase flows is assembled in order to understand the behaviour of four standard water leak configurations: vapour, slug, Washburn and liquid flow, distinguished by the number and location of phase boundaries (menisci). Air may or may not be present as a background gas. Slip length is an important parameter that greatly affects leak rates. Measurements of water vapour flows confirm that water vapour shows ideal gas behaviour. Results on carbon nanotubes show that smooth walls may lead to anomalously high slip lengths arising from the properties of 'confined' water. In porous media, behaviour can be matched to the four standard leaks. Traditional membrane permeation models consider that the permeant dissolves, diffuses and evaporates at the outlet side, ideas we align with those from channel flow. Recent results on graphite oxide membranes show examples where helium which does not permeate while at the same time moisture is almost unimpeded, again a result of confined water. We conclude that while there is no a priori relation between a noncondensable gas flow and a moisture flow, measurements using helium will give results within two orders of magnitude of the moisture flow rate, except in the case where there is anomalous slip or confined water, when moisture specific measurements are essential.

Salivary secretory IgA, pH, flow rates, mutans streptococci and Candida in children with rampant caries.

PubMed

Thaweboon, Sroisiri; Thaweboon, Boonyanit; Nakornchai, Siriruk; Jitmaitree, Sukritta

2008-09-01

The aim of this study was to determine the levels of secretory IgA (SIgA), pH, flow rates, mutans streptococci (MS) and Candida in saliva of children with rampant caries compared to those caries-free. Thirty children (age 62-123 months) were enrolled and divided into two groups: Group I, children with rampant caries, Group II, caries-free children. The average salivary flow rate was measured from the volume yielded within 5 minutes and the pH was determined using a pH-electrode. Measurement of SIgA was performed using an immunoassay kit. The levels of MS and Candida were determined by culture on Mitis-Salivarius Bacitracin agar and Sabouraud dextrose agar. It was found that children with rampant caries presented with significantly higher levels of salivary SIgA, MS and Candida. However, the mean values for salivary flow rates and pH were similar between the groups. The results reveal that children with rampant caries had significantly higher levels of SIgA, MS and Candida in their oral cavities. This finding tends to support the hypothesis that higher levels of salivary SIgA may reflect a past exposure of the host to cariogenic microorganisms.

Living on the edge: transfer and traffic of E. coli in a confined flow.

PubMed

Figueroa-Morales, Nuris; Leonardo Miño, Gastón; Rivera, Aramis; Caballero, Rogelio; Clément, Eric; Altshuler, Ernesto; Lindner, Anke

2015-08-21

We quantitatively study the transport of E. coli near the walls of confined microfluidic channels, and in more detail along the edges formed by the interception of two perpendicular walls. Our experiments establish the connection between bacterial motion at the flat surface and at the edges and demonstrate the robustness of the upstream motion at the edges. Upstream migration of E. coli at the edges is possible at much larger flow rates compared to motion at the flat surfaces. Interestingly, the speed of bacteria at the edges mainly results from collisions between bacteria moving along this single line. We show that upstream motion not only takes place at the edge but also in an "edge boundary layer" whose size varies with the applied flow rate. We quantify the bacterial fluxes along the bottom walls and the edges and show that they result from both the transport velocity of bacteria and the decrease of surface concentration with increasing flow rate due to erosion processes. We rationalize our findings as a function of local variations in the shear rate in the rectangular channels and hydrodynamic attractive forces between bacteria and walls.

Damping Rates of Energetic Particle Modes and Stability With Changing Equilibrium Conditions in the MST Reversed-Field Pinch

NASA Astrophysics Data System (ADS)

Sears, S. H.; Almagri, A. F.; Anderson, J. K.; Bonofiglo, P. J.; Capecchi, W.; Kim, J.

2016-10-01

The damping of Alfvenic waves is an important process, with implications varying from anomalous ion heating in laboratory and astrophysical plasmas to the stability of fusion alpha-driven modes in a burning plasma. With a 1 MW NBI on the MST, a controllable set of energetic particle modes (EPMs) and Alfvenic eigenmodes can be excited. We investigate the damping of these modes as a function of both magnetic and flow shear. Typical EPM damping rates are -104 s-1 in standard RFP discharges. Magnetic shear in the region of large energetic ion density is -2 cm-1 and can be increased up to -2.5 cm-1 by varying the boundary field. Continuum mode damping rates can be reduced up to 50%. New experiments use a bias probe to control the rotation profile. Accelerating the edge plasma relative to the rapidly rotating NBI-driven core decreases the flow shear, while decelerating the edge plasma increases the flow shear in the region of strong energetic ion population. Mode damping rates measured as a function of the local flow shear are compared to ideal MHD predictions. Work supported by US DOE.

Plume effects on the flow around a blunted cone at hypersonic speeds

NASA Technical Reports Server (NTRS)

Atcliffe, P.; Kumar, D.; Stollery, J. L.

1992-01-01

Tests at M = 8.2 show that a simulated rocket plume at the base of a blunted cone can cause large areas of separated flow, with dramatic effects on the heat transfer rate distribution. The plume was simulated by solid discs of varying sizes or by an annular jet of gas. Flow over the cone without a plume is fully laminar and attached. Using a large disc, the boundary layer is laminar at separation at the test Reynolds number. Transition occurs along the separated shear layer and the boundary layer quickly becomes turbulent. The reduction in heat transfer associated with a laminar separated region is followed by rising values as transition occurs and the heat transfer rates towards the rear of the cone substantially exceed the values obtained without a plume. With the annular jet or a small disc, separation occurs much further aft, so that heat transfer rates at the front of the cone are comparable with those found without a plume. Downstream of separation the shear layer now remains laminar and the heat transfer rates to the surface are significantly lower than the attached flow values.

Preliminary findings on the correlation of saliva pH, buffering capacity, flow rate and consistency in relation to waterpipe tobacco smoking.

PubMed

Khemiss, Mehdi; Ben Khelifa, Mohamed; Ben Saad, Helmi

2017-12-01

The aim of the present comparative study was to compare some salivary characteristics between exclusive waterpipe smokers (EWPS) and non-smokers. 72 males (36 EWPS) were recruited. The volume of stimulated saliva was determined and divided by the duration of saliva collection. The pH was measured directly using a pH meter. The buffering capacity was determined using a quantitative method which involved the addition of 10 µl HCl. Up to a total of 160 µL was titrated up to obtain a pH titration curve. At 50 µL of titrated HCl, buffering capacity was ranked into three categories: high, medium and low. EWPS and non-smoker groups had similar flow rates (1.81 ± 0.79 and 1.78 ± 1.14 mL min-1) and similar baseline pH (6.60 ± 0.37 and 6.76 ± 0.39). Statistically significant differences in the two groups' pH were observed from 30 to 160 µL of titrated up HCl. At 50 µL of titrated up HCl, the EWPS group compared to the non-smoker group had a significantly higher pH (4.79 ± 0.72 vs. 5.32 ± 0.79). To conclude, waterpipe tobacco smoking alters the buffering capacity but does not alter either salivary flow rates or the baseline pH and consistency.

Using a reactive transport model to elucidate differences between laboratory and field dissolution rates in regolith

NASA Astrophysics Data System (ADS)

Moore, Joel; Lichtner, Peter C.; White, Art F.; Brantley, Susan L.

2012-09-01

The reactive transport model FLOTRAN was used to forward-model weathering profiles developed on granitic outwash alluvium over 40-3000 ka from the Merced, California (USA) chronosequence as well as deep granitic regolith developed over 800 ka near Davis Run, Virginia (USA). Baseline model predictions that used laboratory rate constants (km), measured fluid flow velocities (v), and BET volumetric surface areas for the parent material (AB,mo) were not consistent with measured profiles of plagioclase, potassium feldspar, and quartz. Reaction fronts predicted by the baseline model are deeper and thinner than the observed, consistent with faster rates of reaction in the model. Reaction front depth in the model depended mostly upon saturated versus unsaturated hydrologic flow conditions, rate constants controlling precipitation of secondary minerals, and the average fluid flow velocity (va). Unsaturated hydrologic flow conditions (relatively open with respect to CO2(g)) resulted in the prediction of deeper reaction fronts and significant differences in the separation between plagioclase and potassium feldspar reaction fronts compared to saturated hydrologic flow (relatively closed with respect to CO2(g)). Under saturated or unsaturated flow conditions, the rate constant that controls precipitation rates of secondary minerals must be reduced relative to laboratory rate constants to match observed reaction front depths and measured pore water chemistry. Additionally, to match the observed reaction front depths, va was set lower than the measured value, v, for three of the four profiles. The reaction front gradients in mineralogy and pore fluid chemistry could only be modeled accurately by adjusting values of the product kmAB,mo. By assuming km values were constrained by laboratory data, field observations were modeled successfully with TST-like rate equations by dividing measured values of AB,mo by factors from 50 to 1700. Alternately, with sigmoidal or Al-inhibition rate models, this adjustment factor ranges from 5 to 170. Best-fit models of the wetter, hydrologically saturated Davis Run profile required a smaller adjustment to AB,mo than the drier hydrologically unsaturated Merced profiles. We attributed the need for large adjustments in va and AB,mo necessary for the Merced models to more complex hydrologic flow that decreased the reactive surface area in contact with bulk flow water, e.g., dead-end pore spaces containing fluids that are near or at chemical equilibrium. Thus, rate models from the laboratory can successfully predict weathering over millions of years, but work is needed to understand how to incorporate changes in what controls the relationship between reactive surface area and hydrologic flow.

Balanced Flow Metering and Conditioning: Technology for Fluid Systems

NASA Technical Reports Server (NTRS)

Kelley, Anthony R.

2006-01-01

Revolutionary new technology that creates balanced conditions across the face of a multi-hole orifice plate has been developed, patented and exclusively licensed for commercialization. This balanced flow technology simultaneously measures mass flow rate, volumetric flow rate, and fluid density with little or no straight pipe run requirements. Initially, the balanced plate was a drop in replacement for a traditional orifice plate, but testing revealed substantially better performance as compared to the orifice plate such as, 10 times better accuracy, 2 times faster (shorter distance) pressure recovery, 15 times less acoustic noise energy generation, and 2.5 times less permanent pressure loss. During 2004 testing at MSFC, testing revealed several configurations of the balanced flow meter that match the accuracy of Venturi meters while having only slightly more permanent pressure loss. However, the balanced meter only requires a 0.25 inch plate and has no upstream or downstream straight pipe requirements. As a fluid conditioning device, the fluid usually reaches fully developed flow within 1 pipe diameter of the balanced conditioning plate. This paper will describe the basic balanced flow metering technology, provide performance details generated by testing to date and provide implementation details along with calculations required for differing degrees of flow metering accuracy.

Retirement Wealth, Income, and Decision Making in Higher Education.

ERIC Educational Resources Information Center

Lewis, W. Cris

1996-01-01

Retirement programs for college faculty are evaluated in terms of both their wealth-creation attributes and the incentives they provide for retirement. Wealth accumulation and relative cash flow from working compared to retirement are evaluated at various ages under alternative assumptions about rates of return and contribution rates. The nature…

Fuel thermal stability effects on spray characteristics

NASA Technical Reports Server (NTRS)

Lefebvre, A. H.; Nickolaus, D.

1987-01-01

The propensity of a heated hydrocarbon fuel toward solids deposition within a fuel injector is investigated experimentally. Fuel is arranged to flow through the injector at constant temperature, pressure, and flow rate and the pressure drop across the nozzle is monitored to provide an indication of the amount of deposition. After deposits have formed, the nozzle is removed from the test rig and its spray performance is compared with its performance before deposition. The spray characteristics measured include mean drop size, drop-size distribution, and radial and circumferential fuel distribution. It is found that small amounts of deposition can produce severe distortion of the fuel spray pattern. More extensive deposition restores spray uniformity, but the nozzle flow rate is seriously curtailed.

Miniature piezo electric vacuum inlet valve

DOEpatents

Keville, R.F.; Dietrich, D.D.

1998-03-24

A miniature piezo electric vacuum inlet valve having a fast pulse rate and is battery operated with variable flow capability is disclosed. The low power (<1.6 watts), high pulse rate (<2 milliseconds), variable flow inlet valve is utilized for mass spectroscopic applications or other applications where pulsed or continuous flow conditions are needed. The inlet valve also has a very minimal dead volume of less than 0.01 std/cc. The valve can utilize, for example, a 12 Vdc input/750 Vdc, 3 mA output power supply compared to conventional piezo electric valves which require preloading of the crystal drive mechanism and 120 Vac, thus the valve of the present invention is smaller by a factor of three. 6 figs.

Decay of the 3D inviscid liquid-gas two-phase flow model

NASA Astrophysics Data System (ADS)

Zhang, Yinghui

2016-06-01

We establish the optimal {Lp-L2(1 ≤ p < 6/5)} time decay rates of the solution to the Cauchy problem for the 3D inviscid liquid-gas two-phase flow model and analyze the influences of the damping on the qualitative behaviors of solution. Compared with the viscous liquid-gas two-phase flow model (Zhang and Zhu in J Differ Equ 258:2315-2338, 2015), our results imply that the friction effect of the damping is stronger than the dissipation effect of the viscosities and enhances the decay rate of the velocity. Our proof is based on Hodge decomposition technique, the {Lp-L2} estimates for the linearized equations and an elaborate energy method.

Determination of YAV-8B Reaction Control System bleed flow usage

NASA Technical Reports Server (NTRS)

Borchers, Paul F.; Moralez, Ernesto, III; Merrick, Vernon K.; Stortz, Michael W.; Eames, David J. H.

1992-01-01

Using a calibrated Rolls-Royce Pegasus engine, total Reaction Control System (RCS) bleed flow rates have been measured on a YAV-8B Harrier during typical short takeoff, transition, hover and vertical landing maneuvers. Using existing aircraft instrumentation and pressure taps located in the RCS ducts, bleed flow rates at each RCS valve were also measured directly during flight and ground tests. These data were compared with the calibrated engine data and with the RCS part of a YAV-8B mathematical model used in piloted simulation at NASA Ames Research Center. Areas of disagreement were small, being confined to the estimation of closed RCS valve leakages and the modeling of the RCS butterfly valve pressure losses.

Fluid Dynamics of a Novel Micro-Fistula Implant for the Surgical Treatment of Glaucoma.

PubMed

Sheybani, Arsham; Reitsamer, Herbert; Ahmed, Iqbal Ike K

2015-07-01

The purpose of this study was to describe the fluidics of a novel non-valved glaucoma implant designed to prevent hypotony and compare the fluidics of this device with two commonly used non-valved glaucoma devices. The XEN 45 micro-fistula implant was designed to limit hypotony by virtue of its length and width according to the Hagen-Poiseuille equation. Flow testing was performed using a syringe pump and pressure transducer at multiple flow rates. The pressure differentials across the XEN implant, the Ex-Press implant, and 10 mm of silicone tubing from a Baerveldt implant at a physiologic flow rate (2.5 μL/min) were extrapolated. The XEN 45 achieved a steady-state pressure calculated at 7.56 mm Hg at 2.5 μL/min. At the same flow rate, the Ex-Press device and Baerveldt tubing reached steady-state pressures of 0.09 and 0.01 mm Hg, respectively. Under flow testing, the XEN micro-fistula implant was able to maintain backpressure above numerical hypotony levels without the use of complex valve systems. This is due to the XEN implant's design, derived from the principles that dictate Newtonian fluids.

DPD simulation on the dynamics of a healthy and infected red blood cell in flow through a constricted channel

NASA Astrophysics Data System (ADS)

Hoque, Sazid Zamal; Anand, D. Vijay; Patnaik, B. S. V.

2017-11-01

The state of the red blood cell (either healthy or infected RBC) will influence its deformation dynamics. Since the pathological condition related to RBC, primarily originates from a single cell infection, therefore, it is important to relate the deformation dynamics to the mechanical properties (such as, bending rigidity and membrane elasticity). In the present study, numerical simulation of a healthy and malaria infected RBC in a constricted channel is analyzed. The flow simulations are carried out using finite sized dissipative particle dynamics (FDPD) method in conjunction with a discrete model that represents the membrane of the RBC. The numerical equivalent of optical tweezers test is validated against the experimental studies. Two different types of constrictions, viz., a converging-diverging type tapered channel and a stenosed microchannel are considered for the simulation. The effect of degree of constriction and the flow rate effect on the RBC is investigated. It was observed that, as the flow rate decreases, the infected RBC completely blocks the micro vessel. The transit time for infected cell drastically increases compared to healthy RBC. Our simulations indicate that, there is a critical flow rate below which infected RBC cannot pass through the micro capillary.

Analysis of Turbulent Flow and Heat Transfer on a Flat Plate at High Mach Numbers with Variable Fluid Properties

NASA Technical Reports Server (NTRS)

Deissler, R. G.; Loeffler, A. L., Jr.

1959-01-01

A previous analysis of turbulent heat transfer and flow with variable fluid properties in smooth passages is extended to flow over a flat plate at high Mach numbers, and the results are compared with experimental data. Velocity and temperature distributions are calculated for a boundary layer with appreciative effects of frictional heating and external heat transfer. Viscosity and thermal conductivity are assumed to vary as a power or the temperature, while Prandtl number and specific heat are taken as constant. Skin-friction and heat-transfer coefficients are calculated and compared with the incompressible values. The rate of boundary-layer growth is obtained for various Mach numbers.

Advancement of atmospheric-vacuum interfaces for mass spectrometers with a focus on increasing gas throughput for improving sensitivity.

PubMed

Prasad, Satendra; Wouters, Eloy R; Dunyach, Jean-Jacques

2015-08-18

Ion sampling from an electrospray ionization (ESI) source was improved by increasing gas conductance of the MS inlet by 4.3-fold. Converting the gas throughput (Q) into sensitivity improvement was dependent on ion desolvation and handling of the gas load. Desolvation was addressed by using a novel slot shaped inlet that exhibited desolvation properties identical to the 0.58 mm i.d capillary. An assay tailored for "small molecules" at high chromatographic flow rate (500 μL/min) yielded a compound dependent 6.5 to 14-fold signal gain while analysis at nano chromatographic flow rate (300 nL/min) showed 2 to 3.5-fold improvement for doubly charged peptides. Improvement exceeding the Q (4.3-fold) at high chromatographic flow rate was explained by superior sampling of the spatially dispersed ion spray when using the slot shaped capillary. Sensitivity improvement across a wide range of chromatographic flow rate confirmed no compromise in ion desolvation with the increase in Q. Another improvement included less overflow of gas into the mass analyzer from the foreline region owing to the slot shape of the capillary. By doubling the roughing pump capacity and operating the electrodynamic ion funnel (EDIF) at ∼4 Torr, a single pumping stage was sufficient to handle the gas load. The transport of solvent clusters from the LC effluent into the mass analyzer was prevented by a "wavy shaped" transfer quadrupole and was compared with a benchmark approach that delivered ions orthogonally into a differentially pumped dual EDIF at comparable gas Q.

Saliva composition in three selected groups with normal stimulated salivary flow rates, but yet major differences in caries experience and dental erosion.

PubMed

Bardow, Allan; Lykkeaa, Joan; Qvist, Vibeke; Ekstrand, Kim; Twetman, Svante; Fiehn, Niels-Erik

2014-08-01

It was hypothesized that, by comparing matched subjects with major differences in these dental diseases, but yet normal saliva flow rates, it would be possible to obtain data on the effect of saliva composition on dental disease isolated from the effect of the flow rate. Thus, the aim of the study was to compare the major physicochemical characteristics of stimulated whole saliva in three groups of 85 subjects, each with normal saliva flow rates and at least 24 remaining teeth. A group with very little dental disease (healthy), a group with dental erosion (erosion) and a group with very high caries experience (caries) were chosen. Furthermore, the aim was to determine whether differences among groups could also be found on an individual level. Although it was not possible to retrieve three groups whose members were completely identical, the present study points in the direction that, on a group level, subjects with very little dental disease seemed to have a more favorable physicochemical saliva composition with respect to higher calcium, phosphate, bicarbonate, pH, degree of saturation with respect to hydroxyapatite and a lower critical pH (p < 0.05 or less). However, on an individual level the explanatory power for the saliva composition was only 10% for caries experience and only 11% for dental erosion (p < 0.001). The compositional analyses performed in this study on stimulated whole saliva, including major physicochemical characteristics of saliva, will most likely have little predictive value for future dental caries and erosion in single individuals.

Internal cycle modeling and environmental assessment of multiple cycle consumer products.

PubMed

Tsiliyannis, C A

2012-01-01

Dynamic annual flow models incorporating consumer discard and usage loss and featuring deterministic and stochastic end-of-cycle (EOC) return by the consumer are developed for reused or remanufactured products (multiple cycle products, MCPs), including fast and slow cycling, short and long-lived products. It is shown that internal flows (reuse and overall consumption) increase proportionally to the dimensionless internal cycle factor (ICF) which is related to environmental impact reduction factors. The combined reuse/recycle (or cycle) rate is shown capable for shortcut, albeit effective, monitoring of environmental performance in terms of waste production, virgin material extraction and manufacturing impacts of all MCPs, a task, which physical variables (lifetime, cycling frequency, mean or total number of return trips) and conventional rates, via which environmental policy has been officially implemented (e.g. recycling rate) cannot accomplish. The cycle rate is shown to be an increasing (hyperbolic) function of ICF. The impact of the stochastic EOC return characteristics on total reuse and consumption flows, as well as on eco-performance, is assessed: symmetric EOC return has a small, positive effect on performance compared to deterministic, while early shifted EOC return is more beneficial. In order to be efficient, environmental policy should set higher minimum reuse targets for higher trippage MCPs. The results may serve for monitoring, flow accounting and comparative eco-assessment of MCPs. They may be useful in identifying reachable and efficient reuse/recycle targets for consumer products and in planning return via appropriate labelling and digital coding for enhancing environmental performance, while satisfying consumer demand. Copyright © 2011 Elsevier Ltd. All rights reserved.

Heat and mass transfer analysis for paraffin/nitrous oxide burning rate in hybrid propulsion

NASA Astrophysics Data System (ADS)

Ben-Basat (Sisi), Shani; Gany, Alon

2016-03-01

This research presents a physical-mathematical model for the combustion of liquefying fuels in hybrid combustors, accounting for blowing effect on the heat transfer. A particular attention is given to a paraffin/nitrous oxide hybrid system. The use of a paraffin fuel in hybrid propulsion has been considered because of its much higher regression rate enabling significantly higher thrust compared to that of common polymeric fuels. The model predicts the overall regression rate (melting rate) of the fuel and the different mechanisms involved, including evaporation, entrainment of droplets of molten material, and mass loss due to melt flow on the condensed fuel surface. Prediction of the thickness and velocity of the liquid (melt) layer formed at the surface during combustion was done as well. Applying the model for an oxidizer mass flux of 45 kg/(s m2) as an example representing experimental range, it was found that 21% of the molten liquid undergoes evaporation, 30% enters the gas flow by the entrainment mechanism, and 49% reaches the end of the combustion chamber as a flowing liquid layer. When increasing the oxidizer mass flux in the port, the effect of entrainment increases while that of the flowing liquid layer along the surface shows a relatively lower contribution. Yet, the latter is predicted to have a significant contribution to the overall mass loss. In practical applications it may cause reduced combustion efficiency and should be taken into account in the motor design, e.g., by reinforcing the paraffin fuel with different additives. The model predictions have been compared to experimental results revealing good agreement.

Quantitative comparison between crowd models for evacuation planning and evaluation

NASA Astrophysics Data System (ADS)

Viswanathan, Vaisagh; Lee, Chong Eu; Lees, Michael Harold; Cheong, Siew Ann; Sloot, Peter M. A.

2014-02-01

Crowd simulation is rapidly becoming a standard tool for evacuation planning and evaluation. However, the many crowd models in the literature are structurally different, and few have been rigorously calibrated against real-world egress data, especially in emergency situations. In this paper we describe a procedure to quantitatively compare different crowd models or between models and real-world data. We simulated three models: (1) the lattice gas model, (2) the social force model, and (3) the RVO2 model, and obtained the distributions of six observables: (1) evacuation time, (2) zoned evacuation time, (3) passage density, (4) total distance traveled, (5) inconvenience, and (6) flow rate. We then used the DISTATIS procedure to compute the compromise matrix of statistical distances between the three models. Projecting the three models onto the first two principal components of the compromise matrix, we find the lattice gas and RVO2 models are similar in terms of the evacuation time, passage density, and flow rates, whereas the social force and RVO2 models are similar in terms of the total distance traveled. Most importantly, we find that the zoned evacuation times of the three models to be very different from each other. Thus we propose to use this variable, if it can be measured, as the key test between different models, and also between models and the real world. Finally, we compared the model flow rates against the flow rate of an emergency evacuation during the May 2008 Sichuan earthquake, and found the social force model agrees best with this real data.

Comparison of performance of shell-and-tube heat exchangers with conventional segmental baffles and continuous helical baffle

NASA Astrophysics Data System (ADS)

Ahmed, Asif; Ferdous, Imam Ul.; Saha, Sumon

2017-06-01

In the present study, three-dimensional numerical simulation of two shell-and-tube heat exchangers (STHXs) with conventional segmental baffles (STHXsSB) and continuous helical baffle (STHXsHB) is carried out and a comparative study is performed based on the simulation results. Both of the STHXs contain 37 tubes inside a 500 mm long and 200 mm diameter shell and mass flow rate of shell-side fluid is varied from 0.5 kg/s to 2 kg/s. At first, physical and mathematical models are developed and numerically simulated using finite element method (FEM). For the validation of the computational model, shell-side average nusselt number (Nus) is calculated from the simulation results and compared with the available experimental results. The comparative study shows that STHXsHB has 72-127% higher heat transfer coefficient per unit pressure drop compared to the conventional STHXsSB for the same shell-side mass flow rate. Moreover, STHXsHB has 59-63% lower shell-side pressure drop than STHXsSB.

Implicit Coupling Approach for Simulation of Charring Carbon Ablators

NASA Technical Reports Server (NTRS)

Chen, Yih-Kanq; Gokcen, Tahir

2013-01-01

This study demonstrates that coupling of a material thermal response code and a flow solver with nonequilibrium gas/surface interaction for simulation of charring carbon ablators can be performed using an implicit approach. The material thermal response code used in this study is the three-dimensional version of Fully Implicit Ablation and Thermal response program, which predicts charring material thermal response and shape change on hypersonic space vehicles. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation method. Coupling between the material response and flow codes is performed by solving the surface mass balance in flow solver and the surface energy balance in material response code. Thus, the material surface recession is predicted in flow code, and the surface temperature and pyrolysis gas injection rate are computed in material response code. It is demonstrated that the time-lagged explicit approach is sufficient for simulations at low surface heating conditions, in which the surface ablation rate is not a strong function of the surface temperature. At elevated surface heating conditions, the implicit approach has to be taken, because the carbon ablation rate becomes a stiff function of the surface temperature, and thus the explicit approach appears to be inappropriate resulting in severe numerical oscillations of predicted surface temperature. Implicit coupling for simulation of arc-jet models is performed, and the predictions are compared with measured data. Implicit coupling for trajectory based simulation of Stardust fore-body heat shield is also conducted. The predicted stagnation point total recession is compared with that predicted using the chemical equilibrium surface assumption

Pressure fluctuation generated by the interaction of blade and tongue

NASA Astrophysics Data System (ADS)

Zheng, Lulu; Dou, Hua-Shu; Chen, Xiaoping; Zhu, Zuchao; Cui, Baoling

2018-02-01

Pressure fluctuation around the tongue has large effect on the stable operation of a centrifugal pump. In this paper, the Reynolds averaged Navier-Stokes equations (RANS) and the RNG k-epsilon turbulence model is employed to simulate the flow in a pump. The flow field in the centrifugal pump is computed for a range of flow rate. The simulation results have been compared with the experimental data and good agreement has been achieved. In order to study the interaction of the tongue with the impeller, fifteen monitor probes are evenly distributed circumferentially at three radii around the tongue. Pressure distribution is investigated at various blade positions while the blade approaches to and leaves the tongue region. Results show that pressure signal fluctuates largely around the tongue, and it is more intense near the tongue surface. At design condition, standard deviation of pressure fluctuation is the minimum. At large flow rate, the increased low pressure region at the blade trailing edge results in the increases of pressure fluctuation amplitude and pressure spectra at the monitor probes. Minimum pressure is obtained when the blade is facing to the tongue. It is found that the amplitude of pressure fluctuation strongly depends on the blade positions at large flow rate, and pressure fluctuation is caused by the relative movement between blades and tongue. At small flow rate, the rule of pressure fluctuation is mainly depending on the structure of vortex flow at blade passage exit besides the influence from the relative position between the blade and the tongue.

Fodder Resource Uses and Assessment of Nitrogen Flows on Livestock Farming with Crop Production

NASA Astrophysics Data System (ADS)

Shirahase, Kyoko; Kobayashi, Hisashi

With understanding the livestock farming on cattle breeding practiced increasing of self-production of fodders by the farmland's operation as “Livestock Farming with crop production”, we investigated the utilizations of actual fodder resources and farmland for two selected different types of livestock farming systems: “Multiple Type” which practices cattle raising with fodder cultivation, and “Grazing Type” which practices grazing and fodder cultivation with similar feed self-sufficiency rates. We also prepared and compared material and nitrogen flow of both livestock farming systems. The amount of nitrogen flow is clearly different between the two types though feed self-sufficiency rates are at similar level. Moreover, we defined “Internal Nitrogen Rate (INR)” which indicates the rate of internal nitrogen use to total nitrogen use in cattle raising, “Internal Nitrogen Circulation Rate (NCR)” which indicates the ratio of nitrogen amount in internal circulation to the nitrogen amount introduced from outside, and Nitrogen Outflow Potential (Op), which is the balance of nitrogen amount between input to farmlands and uptake by plants, and analyzed the balance of the amounts of nitrogen flows in both livestock farming type. It is suggested that “Grazing type”, which had the values of relatively high NCR and absolutely low Op, was the livestock farming type with high rates of nitrogen procurement from the interregional farming and low risk of nitrogen outflow.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miyamori, I.; Yasuhara, S.; Takeda, Y.

The effects of captopril on effective renal plasma flow and glomerular filtration rate were studied using a noninvasive radioisotopic method on individual kidneys in eight patients with renovascular hypertension and 12 patients with essential hypertension with various renin levels. Four patients with renovascular hypertension had unilateral while three had bilateral renal artery stenosis. The effective renal plasma flow and glomerular filtration rate were determined by using /sup 131/I-iodohippurate sodium and /sup 99m/Tc-diethylenetriamine pentaacetic acid, respectively. Glomerular filtration rate and effective renal plasma flow were significantly reduced in the stenotic kidneys of patients with renovascular hypertension compared with values in nonstenoticmore » kidneys (p less than 0.01). Treatment with captopril, 37.5 to 75 mg/day for 1 to 48 weeks, further reduced the glomerular filtration rate only in stenotic kidneys, and effective renal plasma flow increased in both kidney types. In two of the three renal hypertensive patients with bilateral renal artery stenosis, captopril produced a reversible azotemia that was unrelated to the fall in blood pressure, as evidenced by the lack of azotemia seen after a moderate blood pressure reduction induced by other antihypertensive medications. These results indicate that endogenous angiotensin II is essential in maintaining the glomerular filtration rate in stenotic kidneys and suggest that a reduction in glomerular filtration rate during captopril administration could indicate the presence of renal artery stenosis.« less

Effects of vacuum level and pulsation rate on milk ejection and milk flow traits in Tunisian dairy camels (Camelus dromedarius).

PubMed

Atigui, Moufida; Marnet, Pierre-Guy; Barmat, Ahmed; Khorchani, Touhami; Hammadi, Mohamed

2015-01-01

This work aims to compare the effects of milking at two vacuum levels (38 and 48 kPa) and three pulsation rates (60, 90, and 120 cpm) on milk production and milk flow characteristics. Six multiparous Maghrebi camels in late lactation and once daily milked were used. The best combination of setting for camel's milking was high vacuum and low pulsation rate (48 kPa/60 cpm). Milk yield and average and peak milk flow rate were the highest, while milking time was the shortest using this combination of setting (3.05 ± 0.30 kg, 1.52 ± 0.21 kg/min, 2.52 ± 0.21 kg/min, and 3.32 ± 0.31 min, respectively). Lower vacuum level lengthened milking time by more than 100 % and was not sufficient to extract milk correctly (1.69 to 2.48 times less milk yield harvested), suggesting a negative interaction with the stimulatory effect of pulsation. Higher pulsation rates did not better stimulate the camels and induced more bimodality and lower milk flow rates. Animal characteristics and liner/claw design affect machine milking and further investigations must be carried out to verify their effects and to study long-term effect of high vacuum level on udder health and teat condition.

Salivary glucose concentration and excretion in normal and diabetic subjects.

PubMed

Jurysta, Cedric; Bulur, Nurdan; Oguzhan, Berrin; Satman, Ilhan; Yilmaz, Temel M; Malaisse, Willy J; Sener, Abdullah

2009-01-01

The present report aims mainly at a reevaluation of salivary glucose concentration and excretion in unstimulated and mechanically stimulated saliva in both normal and diabetic subjects. In normal subjects, a decrease in saliva glucose concentration, an increase in salivary flow, but an unchanged glucose excretion rate were recorded when comparing stimulated saliva to unstimulated saliva. In diabetic patients, an increase in salivary flow with unchanged salivary glucose concentration and glucose excretion rate were observed under the same experimental conditions. Salivary glucose concentration and excretion were much higher in diabetic patients than in control subjects, whether in unstimulated or stimulated saliva. No significant correlation between glycemia and either glucose concentration or glucose excretion rate was found in the diabetic patients, whether in unstimulated or stimulated saliva. In the latter patients, as compared to control subjects, the relative magnitude of the increase in saliva glucose concentration was comparable, however, to that of blood glucose concentration. The relationship between these two variables was also documented in normal subjects and diabetic patients undergoing an oral glucose tolerance test.

Comparative Analysis of Two Biological Warfare Air Samplers Using Live Surrogate Agents

DTIC Science & Technology

2012-03-01

extensively for Phosphate Buffer Saline (PBS) solution and water , and, to a very limited degree in AF evaluations, for virus preserving media, specifically...or water . Furthermore, viral studies have been conducted comparing the effectiveness of utilizing the reduced secondary flow rate on the XMX/2L...with using bioagent aerosols rated BSL-2 or higher. Male Specific Coliphage 2 (MS2), American Type Culture Collection (ATCC) 15597-B1, was selected

An Ejector Air Intake Design Method for a Novel Rocket-Based Combined-Cycle Rocket Nozzle

NASA Astrophysics Data System (ADS)

Waung, Timothy S.

Rocket-based combined-cycle (RBCC) vehicles have the potential to reduce launch costs through the use of several different air breathing engine cycles, which reduce fuel consumption. The rocket-ejector cycle, in which air is entrained into an ejector section by the rocket exhaust, is used at flight speeds below Mach 2. This thesis develops a design method for an air intake geometry around a novel RBCC rocket nozzle design for the rocket-ejector engine cycle. This design method consists of a geometry creation step in which a three-dimensional intake geometry is generated, and a simple flow analysis step which predicts the air intake mass flow rate. The air intake geometry is created using the rocket nozzle geometry and eight primary input parameters. The input parameters are selected to give the user significant control over the air intake shape. The flow analysis step uses an inviscid panel method and an integral boundary layer method to estimate the air mass flow rate through the intake geometry. Intake mass flow rate is used as a performance metric since it directly affects the amount of thrust a rocket-ejector can produce. The design method results for the air intake operating at several different points along the subsonic portion of the Ariane 4 flight profile are found to under predict mass flow rate by up to 8.6% when compared to three-dimensional computational fluid dynamics simulations for the same air intake.

Development of braided rope seals for hypersonic engine applications: Flow modeling

NASA Technical Reports Server (NTRS)

Mutharasan, Rajakkannu; Steinetz, Bruce M.; Tao, Xiaoming; Du, Guang-Wu; Ko, Frank

1992-01-01

A new type of engine seal is being developed to meet the needs of advanced hypersonic engines. A seal braided of emerging high temperature ceramic fibers comprised of a sheath-core construction was selected for study based on its low leakage rates. Flexible, low-leakage, high temperature seals are required to seal the movable engine panels of advanced ramjet-scramjet engines either preventing potentially dangerous leakage into backside engine cavities or limiting the purge coolant flow rates through the seals. To predict the leakage through these flexible, porous seal structures new analytical flow models are required. Two such models based on the Kozeny-Carman equations are developed herein and are compared to experimental leakage measurements for simulated pressure and seal gap conditions. The models developed allow prediction of the gas leakage rate as a function of fiber diameter, fiber packing density, gas properties, and pressure drop across the seal. The first model treats the seal as a homogeneous fiber bed. The second model divides the seal into two homogeneous fiber beds identified as the core and the sheath of the seal. Flow resistances of each of the main seal elements are combined to determine the total flow resistance. Comparisons between measured leakage rates and model predictions for seal structures covering a wide range of braid architectures show good agreement. Within the experimental range, the second model provides a prediction within 6 to 13 percent of the flow for many of the cases examined. Areas where future model refinements are required are identified.

Basic experiments during loss of vacuum event (LOVE) in fusion experimental reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogawa, Masuro; Kunugi, Tomoaki; Seki, Yasushi

If a loss of vacuum event (LOVE) occurs due to damage of the vacuum vessel of a nuclear fusion experimental reactor, some chemical reactions such as a graphic oxidation and a buoyancy-driven exchange flow take place after equalization of the gas pressure between the inside and outside of the vacuum vessel. The graphite oxidation would generate inflammable carbon monoxide and release tritium retained in the graphite. The exchange flow through the breaches may transport the carbon monoxide and tritium out of the vacuum vessel. To add confidence to the safety evaluations and analyses, it is important to grasp the basicmore » phenomena such as the exchange flow and the graphite oxidation. Experiments of the exchange flow and the graphite oxidation were carried out to obtain the exchange flow rate and the rate constant for the carbon monoxide combustion, respectively. These experimental results were compared with existing correlations. The authors plan a scaled-model test and a full-scale model test for the LOVE.« less

Formation of perched lava ponds on basaltic volcanoes: Interaction between cooling rate and flow geometry allows estimation of lava effusion rates

NASA Technical Reports Server (NTRS)

Wilson, L.; Parfitt, E. A.

1993-01-01

Perched lava ponds are infrequent but distinctive topographic features formed during some basaltic eruptions. Two such ponds, each approximately 150 m in diameter, formed during the 1968 eruption at Napau Crater and the 1974 eruption of Mauna Ulu, both on Kilauea Volcano, Hawaii. Each one formed where a channelized, high volume flux lava flow encountered a sharp reduction of slope: the flow spread out radially and stalled, forming a well-defined terminal levee enclosing a nearly circular lava pond. We describe a model of how cooling limits the motion of lava spreading radially into a pond and compare this with the case of a channelized flow. The difference in geometry has a major effect, such that the size of a pond is a good indicator of the volume flux of the lava forming it. Lateral spreading on distal shallow slopes is a major factor limiting the lengths of lava flows.

Summary on the depressurization from supercritical pressure conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, M.; Chen, Y.; Ammirable, L.

When a fluid discharges from a high pressure and temperature system, a 'choking' or critical condition occurs, and the flow rate becomes independent of the downstream pressure. During a postulated loss of coolant accident (LOCA) of a water reactor the break flow will be subject to this condition. An accurate estimation of the critical flow rate is important for the evaluation of the reactor safety, because this flow rate controls the loss of coolant inventory and energy from the system, and thus has a significant effect on the accident consequences[1]. In the design of safety systems for a super criticalmore » water reactor (SCWR), postulated LOCA transients are particularly important due to the lower coolant inventory compared to a typical PWR for the same power output. This lower coolant inventory would result in a faster transient response of the SCWR, and hence accurate prediction of the critical discharge is mandatory. Under potential two-phase conditions critical flow is dominated by the vapor content or quality of the vapor, which is closely related with the onset of vaporization and the interfacial interaction between phases [2]. This presents a major challenge for the estimation of the flow rate due to the lack of the knowledge of those processes, especially under the conditions of interest for the SCWR. According to the limited data of supercritical fluids, the critical flows at conditions above the pseudo-critical point seem to be fairly stable and consistent with the subcritical homogeneous equilibrium model (HEM) model predictions, while having a lower flow rate than those in the two-phase region. Thus the major difficulty in the prediction of the depressurization flow rates remains in the region where two phases co-exist at the top of the vapor dome. In this region, the flow rate is strongly affected by the nozzle geometry and tends to be unstable. Various models for this region have been developed with different assumptions, e.g. the HEM and Moody model [3], and the Henry-Fauske non-equilibrium model [4], and are currently used in subcritical pressure reactor safety design[5]. It appears that some of these models could be reasonably extended to above the thermodynamic pseudo-critical point. The more stable and lower discharge flow rates observed in conditions above the pseudo-critical point suggests that even though SCWR's have a smaller coolant inventory, the safety implications of a LOCA and the subsequent depressurization may not be as severe as expected, this however needs to be confirmed by a rigorous evaluation of the particular event and further evaluation of the critical flow rate. This paper will summarize activities on critical flow models, experimental data and numerical modeling during blowdown from supercritical pressure conditions under the International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on 'Heat Transfer Behaviour and Thermo-hydraulics Code testing for SCWRs'. (authors)« less

Dental erosion and salivary flow rate in cerebral palsy individuals with gastroesophageal reflux.

PubMed

Guaré, Renata O; Ferreira, Maria C D; Leite, Mariana F; Rodrigues, Jonas A; Lussi, Adrian; Santos, Maria T B R

2012-05-01

A high prevalence of gastroesophageal reflux (GERD) has been observed in individuals with cerebral palsy (CP). One of the main risks for dental erosion is GERD. This study aimed to evaluate the presence of GERD, variables related to dental erosion and associated with GERD (diet consumption, gastrointestinal symptoms, bruxism), and salivary flow rate, in a group of 46 non-institutionalized CP individuals aged from 3 to 13 years. Twenty CP individuals with gastroesophageal reflux (GERDG) and 26 without gastroesophageal reflux (CG) were examined according to dental erosion criteria, drinking habits, presence of bruxism, and salivary flow rate. A face-to-face detailed questionnaire with the consumption and frequency of acid drinks, gastrointestinal symptoms (regurgitation and heart burn), and the presence of bruxism were answered by the caregivers of both groups. Unstimulated whole saliva was collected under slight suction, and salivary flow rate (ml/min) was calculated. The GERDG presented higher percentages of younger quadriplegics individuals compared to CG. The presence of regurgitation, heart burn, and tooth erosion (Grade 1) was significantly more prevalent in GERDG. It was observed difference in the salivary flow rate between the studied groups. On logistic multivariate regression analysis, the unique variable independently associated with the presence of GERD was dental erosion (P = 0.012, OR 86.64). The presence of GERD contributes significantly to dental erosion in the most compromised individuals with quadriplegics cerebral palsy individuals, increasing the risk of oral disease in this population. © 2011 John Wiley & Sons A/S.

The case of the 1981 eruption of Mount Etna: An example of very fast moving lava flows

NASA Astrophysics Data System (ADS)

Coltelli, Mauro; Marsella, Maria; Proietti, Cristina; Scifoni, Silvia

2012-01-01

Mount Etna despite being an extremely active volcano which, during the last 400 years, has produced many lava flow flank eruptions has rarely threatened or damaged populated areas. The reconstruction of the temporal evolution of potentially hazardous flank eruptions represents a useful contribution to reducing the impact of future eruptions by and analyzing actions to be taken for protecting sensitive areas. In this work, we quantitatively reconstructed the evolution of the 1981 lava flow field of Mt Etna, which threatened the town of Randazzo. This reconstruction was used to evaluate the cumulated volume, the time averaged discharge rate trend and to estimate its maximum value. The analysis was conducted by comparing pre- and post-eruption topographic surfaces, extracted by processing historical photogrammetric data sets and by utilizing the eruption chronology to establish the lava flow front positions at different times. An unusually high discharge rate (for Etna) of 640 m3/s was obtained, which corresponds well with the very fast advance rate observed for the main lava flow. A comparison with other volcanoes, presenting high discharge rate, was proposed for finding a clue to unveil the 1981 Etna eruptive mechanism. A model was presented to explain the high discharge rate, which includes an additional contribution to the lava discharge caused by the interception of a shallow magma reservoir by a dike rising from depth and the subsequent emptying of the reservoir.

Sinks for photosynthetic electron flow in green petioles and pedicels of Zantedeschia aethiopica: evidence for innately high photorespiration and cyclic electron flow rates.

PubMed

Yiotis, Charilaos; Manetas, Yiannis

2010-07-01

A combination of gas exchange and various chlorophyll fluorescence measurements under varying O(2) and CO(2) partial pressures were used to characterize photosynthesis in green, stomata-bearing petioles of Zantedeschia aethiopica (calla lily) while corresponding leaves served as controls. Compared to leaves, petioles displayed considerably lower CO(2) assimilation rates, limited by both stomatal and mesophyll components. Further analysis of mesophyll limitations indicated lower carboxylating efficiencies and insufficient RuBP regeneration but almost similar rates of linear electron transport. Accordingly, higher oxygenation/carboxylation ratios were assumed for petioles and confirmed by experiments under non-photorespiratory conditions. Higher photorespiration rates in petioles were accompanied by higher cyclic electron flow around PSI, the latter being possibly linked to limitations in electron transport from intermediate electron carriers to end acceptors and low contents of PSI. Based on chlorophyll fluorescence methods, similar conclusions can be drawn for green pedicels, although gas exchange in these organs could not be applied due to their bulky size. Since our test plants were not subjected to stress we argue that higher photorespiration and cyclic electron flow rates are innate attributes of photosynthesis in stalks of calla lily. Active nitrogen metabolism may be inferred, while increased cyclic electron flow may provide the additional ATP required for the enhanced photorespiratory activity in petiole and pedicel chloroplasts and/or the decarboxylation of malate ascending from roots.

Evaluation of Granulated Lactose as a Carrier for Dry Powder Inhaler Formulations 2: Effect of Drugs and Drug Loading.

PubMed

Du, Ping; Du, Ju; Smyth, Hugh D C

2017-01-01

Previously, granulated lactose carriers were shown to improve uniformity and aerosolization of a low-dose model drug. In the present study, the blending uniformity and aerosol dispersion performance were assessed for 2 model drugs salbutamol sulfate (SS) and rifampicin (RIF), blended at high loadings (10% or 30% drug) with granulated lactose carriers. The model drug powders differed in particle size distribution, morphology, density, and surface energies. Content uniformity of RIF blends was better than that of SS. Aerosolization studies showed that all blend formulations had acceptable emitted fractions (>70%). The SS blends showed low induction-port deposition (6%-10%) compared to RIF (5%-30%). This difference was greater at high flow rates. At 90 L/min, the low induction port deposition of SS blends allowed high fine particle fraction (FPF) of 73%-81%, whereas the FPF of the RIF blends was around 43%-45% with higher induction port deposition. However, SS blends exhibited strong flow rate-dependent performance. Increasing the flow rate from 30 L/min to 90 L/min increased SS FPF from approximately 20% to 80%. Conversely, RIF blends were flow rate and drug loading independent. It was concluded that the aerosolization of high drug-loaded dry powder inhaler formulations using granulated lactose, particularly flow rate dependency, varies with active pharmaceutical ingredient properties. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Metal Flow in Friction Stir Welding

NASA Technical Reports Server (NTRS)

Nunes, Arthur C., Jr.

2006-01-01

The plastic deformation field in Friction Stir Welding (FSW) is compared to that in metal cutting. A shear surface around the FSW tool analogous to the metal cutting shear plane is identified and comprises the basis of the "rotating plug" flow field model and the "wiping" model of tool interaction with weld metal. Within the context of these models: The FSW shear rate is estimated to be comparable to metal cutting shear rates. The effect of tool geometry on the FSW shear surface is discussed and related to published torque measurements. Various FS W structural features are explained, including a difference in structure of bimetallic welds when alloys on the advancing and retreating sides of the weld seam are exchanged. The joining mechanism and critical parameters of the FSW process are made clear.

Field Measurements of the 1983 Royal Gardens Lava Flows, Kilauea Volcano, and 1984 Mauna Loa Lava Flow, Hawaii

NASA Technical Reports Server (NTRS)

Fink, J.; Zimbelman, J.

1985-01-01

Theoretical models used in the remote determination of lava flow rheology and compositions rely on estimates of such geometric and flow parameters as volume flow rates, levee heights, and channel dimensions, as well as morphologic and structural patterns on the flow surfaces. Quantitative measures of these variables are difficult to obtain, even under optimum conditions. Detailed topographic profiles across several Hawaiian lava flows that were carefully monitored by the U.S. Geological Survey during their emplacement in 1983 were surveyed in order to test various flow emplacement models. Twenty two accurate channel cross sections were constructed by combining these profiles with digitized pre-flow topographic measurements. Levee heights, shear zone widths, and flow depths could then be read directly from the cross sections and input into the models. The profiles were also compared with ones constructed for some Martian lava flows.

Flow-gated radial phase-contrast imaging in the presence of weak flow.

PubMed

Peng, Hsu-Hsia; Huang, Teng-Yi; Wang, Fu-Nien; Chung, Hsiao-Wen

2013-01-01

To implement a flow-gating method to acquire phase-contrast (PC) images of carotid arteries without use of an electrocardiography (ECG) signal to synchronize the acquisition of imaging data with pulsatile arterial flow. The flow-gating method was realized through radial scanning and sophisticated post-processing methods including downsampling, complex difference, and correlation analysis to improve the evaluation of flow-gating times in radial phase-contrast scans. Quantitatively comparable results (R = 0.92-0.96, n = 9) of flow-related parameters, including mean velocity, mean flow rate, and flow volume, with conventional ECG-gated imaging demonstrated that the proposed method is highly feasible. The radial flow-gating PC imaging method is applicable in carotid arteries. The proposed flow-gating method can potentially avoid the setting up of ECG-related equipment for brain imaging. This technique has potential use in patients with arrhythmia or weak ECG signals.

A Comparative Study on Johnson Cook, Modified Zerilli-Armstrong and Arrhenius-Type Constitutive Models to Predict High-Temperature Flow Behavior of Ti-6Al-4V Alloy in α + β Phase

NASA Astrophysics Data System (ADS)

Cai, Jun; Wang, Kuaishe; Han, Yingying

2016-03-01

True stress and true strain values obtained from isothermal compression tests over a wide temperature range from 1,073 to 1,323 K and a strain rate range from 0.001 to 1 s-1 were employed to establish the constitutive equations based on Johnson Cook, modified Zerilli-Armstrong (ZA) and strain-compensated Arrhenius-type models, respectively, to predict the high-temperature flow behavior of Ti-6Al-4V alloy in α + β phase. Furthermore, a comparative study has been made on the capability of the three models to represent the elevated temperature flow behavior of Ti-6Al-4V alloy. Suitability of the three models was evaluated by comparing both the correlation coefficient R and the average absolute relative error (AARE). The results showed that the Johnson Cook model is inadequate to provide good description of flow behavior of Ti-6Al-4V alloy in α + β phase domain, while the predicted values of modified ZA model and the strain-compensated Arrhenius-type model could agree well with the experimental values except under some deformation conditions. Meanwhile, the modified ZA model could track the deformation behavior more accurately than other model throughout the entire temperature and strain rate range.

Turbulent transport of He II in active and passive phase separators using slit devices and porous media

NASA Technical Reports Server (NTRS)

Yuan, S. W. K.; Lee, J. M.; Frederking, T. H. K.

1988-01-01

The turbulent transport mode of vapor liquid phase separators (VLPS) for He II has been investigated comparing passive porous plug separators with active phase separators (APS) using slits of variable flow paths within a common frame of reference. It is concluded that the basic transport regimes in both devices are identical. An integrated Gorter-Mellink (1949) equation, found previously to predict VLPS results of porous plugs, is employed to analyze APS data published in the literature. It is found that the Gorter-Mellink flow rate parameter for 9-micron and 14-micron APS slit widths are relatively independent of the slit width, having a rate constant of about 9 + or - 10 percent. This agrees with the early heat flow results for He II entropy transport at zero net mass flow in wide capillaries and slits.