Science.gov

Sample records for air velocity effects

  1. The effects of high-air velocity on broiler performance.

    PubMed

    Simmons, J D; Lott, B D; Miles, D M

    2003-02-01

    Two trials using a total of 1,484 Ross male broilers were conducted to study the effect of air velocities of 180 and 120 m/min versus still air (<15 m/min) on BW gain (BWG) and feed:gain from 3 to 7 wk of age. Broilers were raised in a common environment to 3 wk of age. The experimental facility was a closed sided house containing eight wind tunnel floor pens and six floor pens. There were two wind tunnels (four pens/tunnel) used to test air velocities of 180 or 120 m/min. At 3 wk of age, 53 birds were placed in pens on litter in each of two wind tunnels (four pens/tunnel) or on litter in floor pens (six pens) in an environmentally controlled facility. All floor pens contained 3.75 square meters of floor space, one tube feeder, and one trough waterer. The temperature regimen was a diurnal cycle of 25-30-25 C with 23 C dewpoint. Air velocities of 180 and 120 m/min had no significant effect on BWG or feed:gain during the first week (3 to 4 wk) in the tunnels as compared with the still air. However, significant improvements were noted in BWG and feed:gains for increased air velocities from 4 to 5 and 5 to 6 wk of age. During the last week (6 to 7), an air velocity of 180 m/min significantly improved BWG and feed:gain, as compared with the 120 m/min or the still air.

  2. Effect of air velocity on the drying rate of single eastern white pine boards

    Treesearch

    W. T. Simpson

    1997-01-01

    The qualitative effect of air velocity on drying rate of lumber has long been known. This report provides quantification of the effects of air velocity on drying rate of individual eastern white pine boards. An empirical equation correlating moisture content with time during drying was used to aid in the analysis. The drying rate increased with air velocity for...

  3. Effect of wind tunnel air velocity on VOC flux rates from CAFO manure and wastewater

    USDA-ARS?s Scientific Manuscript database

    Wind tunnels and flux chambers are often used to estimate volatile organic compound (VOC) emissions from animal feeding operations (AFOs) without regard to air velocity or sweep air flow rates. Laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission ...

  4. Effects of air velocity on laying hen production

    USDA-ARS?s Scientific Manuscript database

    Thermal conditions play a major role in production efficiency in commercial poultry production. Mitigation of thermal stress can improve productivity, but must be achieved economically. Weather and system design can limit effectiveness of evaporative cooling and increased air movement has been sho...

  5. Effect of air velocity and direction for indirect evaporative cooling in tropical area

    NASA Astrophysics Data System (ADS)

    Ayodha Ajiwiguna, Tri; Nugraha Rismi, Fadhlin; Ramdlan Kirom, Mukhammad

    2017-06-01

    In this research, experimental study of heat absorption rate caused by indirect evaporative cooling is performed by varying the velocity and direction of air. The ambient is at average temperature and relative humidity of 28.7 °C and 78% respectively. The experiment is conducted by attaching wet medium on the top of material reference plate with the dimension of 14 x 8 cm with 5 mm thickness. To get evaporative cooling effect, the air flow is directed to the wet medium with velocity from 1.6 m/s to 3.4 m/s with the increment of 0.2 m/s. The direction of air is set 0° (parallel), 45° (inclined), and 90° (perpendicular) to the wet medium surface. While the experiment is being performed, the air temperature, top and bottom of plate temperature are measured simultaneously after steady state condition is established. Based on the measurement result, heat absorption is calculated by analysing the heat conduction on the material reference. The result shows that the heat absorption rate is increased by higher velocity. Perpendicular direction of air flow results the highest cooling capacity compared with other direction. The maximum heat absorption rate is achieved at 13.9 Watt with 3.4 m/s velocity and perpendicular direction of air.

  6. Research on inert gas narcosis and air velocity effects on metabolic performance

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The effects of air velocity on metabolic performance are studied by using high forced airflow in a closed environment as a mechanism to control the concentration of volatile animal wastes. Air velocities between 100 and 200 ft/min are without significant effects on the metabolism of rats. At velocities of 200 ft/min and above, oxygen consumption and CO2 production as well as food consumption increase. In most instances, the changes are on the order of 5-10%. At the same time, the RQ for the animals increases slightly and generally correlates well with oxygen consumption and CO2 production. Experiments on the nature of inert gas narcosis show that halothane and methoxyflurane are rather potent inhibitors of the NADH:O2 oxidoreductase system in rats. These experiments suggest that the mechanism of inert gas narcosis is not mandatorily related to a membrane surface phenomenon.

  7. Effect of air velocity on kinetics of thin layer carrot pomace drying.

    PubMed

    Kumar, N; Sarkar, B C; Sharma, H K

    2011-10-01

    Carrot pomace is a by-product obtained during carrot juice processing. Thin layer carrot pomace drying was performed in a laboratory scale hot air forced convective dryer. The drying experiments were carried out at the air velocity of 0.5, 0.7 and 1.0 m/s at air temperatures from 60 to 75 °C. It was observed that whole drying process of carrot pomace took place in a falling rate period except a very short accelerating period at the beginning. Mathematical models were tested to fit drying data of carrot pomace. The best fit model was observed on the basis of R², Chi-square and RMSE values. R² values for all the selected models were above 0.9783. The average values of effective diffusivity ranged from 2.61 × 10(-9) to 3.64 × 10(-9) m²/s.

  8. The Effect of Solid Admixtures on the Velocity of Motion of a Free Dusty Air Jet

    NASA Technical Reports Server (NTRS)

    Chernov, A. P.

    1957-01-01

    In dusty air flows occurring in industrial practice in transport by air pressure of friable materials, in the drying, annealing, and so forth, of a pulverized solid mass in suspension, and in other processes, the concentration of solid particles usually has a magnitude of the order of 1 kg per 1 kg of air. At such a concentration, the ratio of the volume of the particles to the volume of the air is small (less than one-thousandth part). However, regardless of this, the presence of a solid admixture manifests itself in the rules for the velocity distribution of the air in a dusty air flow. As a result, the rules of velocity change are different for clean and for dusty air flows. The estimation of the influence of the admixture on the velocity of the motion of the flow presents a definitive interest. One of the attempts to estimate that influence on the axial velocity of a free axially symmetrical jet with admixtures was made by Abramovich. Abramovich assumed beforehand that the fine particles of the admixture in the jet are subject to the motion of the air (that is, that the velocity of the admixture is approximately equal to the local velocity of the air); he then took as the basis of his considerations, in solving the problem, the condition that the amount of motion of the two-phase jet must be constant.

  9. The effect of humidity on ionic wind velocity in ambient air

    NASA Astrophysics Data System (ADS)

    Chen, She; Nobelen, J. C. P. Y.; Nijdam, S.

    2016-09-01

    Due to the evolution of portable electronics and LED lightning system, advances in air cooling technologies must also keep pace. Active cooling by ionic wind, which is usually generated by corona discharge, can greatly reduce the noise and lifetime issues compared to the mechanical fans. The wind is induced when a gas discharge is formed, and neutral molecules gain their energy by the momentum transfer of ion-neutral collisions. However, there is few discussion about the effect of gas composition such as humidity on the wind generation and the physical mechanism is not clear. In the experiment, a positive 5-20 kV DC voltage is applied to the needle-cylinder electrodes with separation of 20 mm. The ionic wind velocity is measured by hot wire anemometry. As the relative humidity (RH) in the ambient air increases, the velocity is found to be severely inhibited. The current is also measured between the cylinder electrode and earth. The results show that the DC component of corona current decreases when RH increases. Since both the discharge current and the ion mobility are reduced when RH increases, their combined effects determine the ionic wind velocity. This work is supported by STW project 13651.

  10. Thermal stability effects on the structure of the velocity field above an air-water interface

    NASA Technical Reports Server (NTRS)

    Papadimitrakis, Y. A.; Hsu, Y.-H. L.; Wu, J.

    1987-01-01

    Mean velocity and turbulence measurements are described for turbulent flows above laboratory water waves, under various wind and thermal stratification conditions. Experimental results, when presented in the framework of Monin-Obukhov (1954) similarity theory, support local scaling based on evaluation of stratification effects at the same nondimensional distance from the mean water surface. Such scaling allows an extension of application of the above theory to the outer region of the boundary layer. Throughout the fully turbulent region, ratios of mean velocity gradients, eddy viscosities, and turbulence intensities under nonneutral and neutral conditions correlate well with the parameter z/Lambda (Lambda being a local Obukhov length and z the vertical coordinate of the mean air flow) and show good agreement with established field correlations. The influence of stratification on the wind-stress coefficient can be estimated from an empirical relationship in terms of its value under neutral conditions and a bulk Richardson number.

  11. Effect of low air velocities on thermal homeostasis and comfort during exercise at space station operational temperature and humidity

    NASA Technical Reports Server (NTRS)

    Beumer, Ronald J.

    1989-01-01

    The effectiveness of different low air velocities in maintaining thermal comfort and homeostasis during exercise at space station operational temperature and humidity was investigated. Five male subjects exercised on a treadmill for successive ten minute periods at 60, 71, and 83 percent of maximum oxygen consumption at each of four air velocities, 30, 50, 80, and 120 ft/min, at 22 C and 62 percent relative humidity. No consistent trends or statistically significant differences between air velocities were found in body weight loss, sweat accumulation, or changes in rectal, skin, and body temperatures. Occurrence of the smallest body weight loss at 120 ft/min, the largest sweat accumulation at 30 ft/min, and the smallest rise in rectal temperature and the greatest drop in skin temperature at 120 ft/min all suggested more efficient evaporative cooling at the highest velocity. Heat storage at all velocities was evidenced by increased rectal and body temperatures; skin temperatures declined or increased only slightly. Body and rectal temperature increases corresponded with increased perception of warmth and slight thermal discomfort as exercise progressed. At all air velocities, mean thermal perception never exceeded warm and mean discomfort, greatest at 30 ft/min, was categorized at worst as uncomfortable; sensation of thermal neutrality and comfort returned rapidly after cessation of exercise. Suggestions for further elucidation of the effects of low air velocities on thermal comfort and homeostasis include larger numbers of subjects, more extensive skin temperature measurements and more rigorous analysis of the data from this study.

  12. Effect of Wind Tunnel Air Velocity on VOC Flux from Standard Solutions and CAFO Manure/Wastewater

    USDA-ARS?s Scientific Manuscript database

    Researchers and practitioners have used wind tunnels and flux chambers to quantify the flux of volatile organic compounds (VOCs), ammonia, and hydrogen sulfide and estimate emission factors from animal feeding operations (AFOs) without accounting for effects of air velocity or sweep air flow rate. L...

  13. Effect of airstream velocity on mean drop diameters of water sprays produced by pressure and air atomizing nozzles

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.

    1977-01-01

    A scanning radiometer was used to determine the effect of airstream velocity on the mean drop diameter of water sprays produced by pressure atomizing and air atomizing fuel nozzles used in previous combustion studies. Increasing airstream velocity from 23 to 53.4 meters per second reduced the Sauter mean diameter by approximately 50 percent with both types of fuel nozzles. The use of a sonic cup attached to the tip of an air assist nozzle reduced the Sauter mean diameter by approximately 40 percent. Test conditions included airstream velocities of 23 to 53.4 meters per second at 293 K and atmospheric pressure.

  14. The effects of different air velocities on heat storage and body temperature in humans cycling in a hot, humid environment.

    PubMed

    Saunders, A G; Dugas, J P; Tucker, R; Lambert, M I; Noakes, T D

    2005-03-01

    The purposes of this study were to determine (i) the effects of different facing air velocities on body temperature and heat storage during exercise in hot environmental conditions and (ii) the effects of ingesting fluids at two different rates on thermoregulation during exercise in hot conditions with higher air velocities. On five occasions nine subjects cycled for 2 h at 33.0 +/- 0.4 degrees C with a relative humidity of 59 +/- 3%. Air velocity was maintained at 0.2 km h(-1) (0 WS), 9.9 +/- 0.3 km h(-1) (10 WS), 33.3 +/-2.2 km h(-1) (100 WS) and 50.1 +/- 3.2 km h(-1) (150 WS) while subjects replaced 58.8 +/- 6.8% of sweat losses. In the fifth condition, air velocity was maintained at 33.7 +/- 2.2 km h(-1) and subjects replaced 80.0 +/- 6.8% of sweat losses (100.80 WS). Heat storage, body temperature and rating of perceived exertion were higher in 0 and 10 WS compared with all other conditions. There were no differences in any measured variable between 100 and 150 WS, or between 100 and 100.80 WS. Thus, the evaporative capacity of the environment is increased with higher air velocities, reducing heat storage and body temperature. At higher air velocities, a higher rate of fluid ingestion did not influence heat storage, body temperature or sweat rate. The finding of previous laboratory studies showing a beneficial effect of high rates of fluid ingestion on thermoregulation during exercise in hot, humid, windstill conditions cannot be extrapolated to out-of-doors exercise in which facing air velocities are seldom lower than the athlete's rate of forward progression.

  15. Experimental investigation of the effect of air velocity on a unit cooler under frosting condition: a case study

    NASA Astrophysics Data System (ADS)

    Bayrak, Ergin; Çağlayan, Akın; Konukman, Alp Er S.

    2017-10-01

    Finned tube evaporators are used in a wide range of applications such as commercial and industrial cold/freezed storage rooms with high traffic loading under frosting conditions. In this case study, an evaporator with an integrated fan was manufactured and tested under frosting conditions by only changing the air flow rate in an ambient balanced type test laboratory compared to testing in a wind tunnel with a more uniform flow distribution in order to detect the effect of air flow rate on frosting. During the test, operation was performed separately based on three different air flow rates. The parameters concerning test operation such as the changes of air temperature, air relative humidity, surface temperature, air-side pressure drop and refrigerant side capacity etc. were followed in detail for each air flow rate. At the same time, digital images were captured in front of the evaporator; thus, frost thicknesses and blockage ratios at the course of fan stall were determined by using an image-processing technique. Consequently, the test and visual results showed that the trendline of air-side pressure drop increased slowly at the first stage of test operations, then increased linearly up to a top point and then the linearity was disrupted instantly. This point speculated the beginning of defrost operation for each case. In addition, despite detecting a velocity that needs to be avoided, a test applied at minimum air velocity is superior to providing minimum capacity in terms of loss of capacity during test operations.

  16. Experimental investigation of the effect of air velocity on a unit cooler under frosting condition: a case study

    NASA Astrophysics Data System (ADS)

    Bayrak, Ergin; Çağlayan, Akın; Konukman, Alp Er S.

    2017-05-01

    Finned tube evaporators are used in a wide range of applications such as commercial and industrial cold/freezed storage rooms with high traffic loading under frosting conditions. In this case study, an evaporator with an integrated fan was manufactured and tested under frosting conditions by only changing the air flow rate in an ambient balanced type test laboratory compared to testing in a wind tunnel with a more uniform flow distribution in order to detect the effect of air flow rate on frosting. During the test, operation was performed separately based on three different air flow rates. The parameters concerning test operation such as the changes of air temperature, air relative humidity, surface temperature, air-side pressure drop and refrigerant side capacity etc. were followed in detail for each air flow rate. At the same time, digital images were captured in front of the evaporator; thus, frost thicknesses and blockage ratios at the course of fan stall were determined by using an image-processing technique. Consequently, the test and visual results showed that the trendline of air-side pressure drop increased slowly at the first stage of test operations, then increased linearly up to a top point and then the linearity was disrupted instantly. This point speculated the beginning of defrost operation for each case. In addition, despite detecting a velocity that needs to be avoided, a test applied at minimum air velocity is superior to providing minimum capacity in terms of loss of capacity during test operations.

  17. Effects of light intensity light quality and air velocity on temperature in plant reproductive organs

    NASA Astrophysics Data System (ADS)

    Kitaya, Y.; Hirai, H.

    Excess temperature increase in plant reproductive organs such as anthers and stigmata could cause fertility impediments and thus produce sterile seeds under artificial lighting conditions in closed plant growth facilities There is a possibility that the aberration was caused by an excess increase in temperatures of reproductive organs in Bioregenerative Life Support Systems under microgravity conditions in space The fundamental study was conducted to know the thermal situation of the plant reproductive organs as affected by light intensity light quality and air velocity on the earth and to estimate the excess temperature increase in the reproductive organs in closed plant growth facilities in space Thermal images of reproductive organs of rice and strawberry were captured using infrared thermography at an air temperature of 10 r C The temperatures in flowers at 300 mu mol m -2 s -1 PPFD under the lights from red LEDs white LEDs blue LEDs fluorescent lamps and incandescent lamps increased by 1 4 1 7 1 9 6 0 and 25 3 r C respectively for rice and by 2 8 3 4 4 1 7 8 and 43 4 r C respectively for strawberry The flower temperatures increased with increasing PPFD levels The temperatures in petals anthers and stigmas of strawberry at 300 mu mol m -2 s -1 PPFD under incandescent lamps increased by 32 7 29 0 and 26 6 r C respectively at 0 1 m s -1 air velocity and by 20 6 18 5 and 15 9 r C respectively at 0 8 m s -1 air velocity The temperatures of reproductive organs decreased with increasing

  18. Effects of light intensity and air velocity on air temperature, water vapor pressure, and CO2 concentration inside a plant canopy under an artificial lighting condition.

    PubMed

    Kitaya, Y; Shibuya, T; Kozai, T; Kubota, C

    1998-01-01

    In order to characterize environmental variables inside a plant canopy under artificial lighting in the CELSS, we investigated the effects of light intensity and air velocity on air temperature, water vapor pressure, and CO2 concentration inside a plant canopy. Under a PPF of 500 micromoles m-2 s-1, air temperature was 2-3 degrees C higher, water vapor pressure was 0.6 kPa higher, and CO2 concentration was 25-35 micromoles mol-1 lower at heights ranging from 0 to 30 mm below the canopy than at a height 60 mm above the canopy. Increasing the PPF increased air temperature and water vapor pressure and decreased CO2 concentration inside the canopy. The air temperature was lower and the CO2 concentration was higher inside the canopy at an air velocity of 0.3 m s-1 than at an air velocity of 0.1 m s-1. The environmental variables inside the canopy under a high light intensity were characterized by higher air temperature, higher vapor pressure, and lower CO2 concentration than those outside the canopy.

  19. Effects of air velocity on photosynthesis of plant canopies under elevated CO2 levels in a plant culture system.

    PubMed

    Kitaya, Y; Shibuya, T; Yoshida, M; Kiyota, M

    2004-01-01

    To obtain basic data for adequate air circulation for promoting plant growth in closed plant production modules in bioregenerative life support systems in space, effects of air velocities ranging from 0.1 to 0.8 m s-1 on photosynthesis in tomato seedlings canopies were investigated under atmospheric CO2 concentrations of 0.4 and 0.8 mmol mol-1. The canopy of tomato seedlings on a plug tray (0.4 x 0.4 m2) was set in a wind-tunnel-type chamber (0.6 x 0.4 x 0.3 m3) installed in a semi-closed-type assimilation chamber (0.9 x 0.5 x 0.4 m3). The net photosynthetic rate in the plant canopy was determined with the differences in CO2 concentrations between the inlet and outlet of the assimilation chamber multiplied by the volumetric air exchange rate of the chamber. Photosynthetic photon flux (PPF) on the plant canopy was kept at 0.25 mmol m-2 s-1, air temperature at 23 degrees C and relative humidity at 55%. The leaf area indices (LAIs) of the plant canopies were 0.6-2.5 and plant heights were 0.05-0.2 m. The net photosynthetic rate of the plant canopy increased with increasing air velocities inside plant canopies and saturated at 0.2 m s-1. The net photosynthetic rate at the air velocity of 0.4 m s-1 was 1.3 times that at 0.1 m s-1 under CO2 concentrations of 0.4 and 0.8 mmol mol-1. The net photosynthetic rate under CO2 concentrations of 0.8 mmol mol-1 was 1.2 times that under 0.4 mmol mol-1 at the air velocity ranging from 0.1 to 0.8 m s-1. The results confirmed the importance of controlling air movement for enhancing the canopy photosynthesis under an elevated CO2 level as well as under a normal CO2 level in the closed plant production modules. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

  20. Optimization and investigation of the effect of velocity distribution of air curtains on the performance of food refrigerated display cabinets

    NASA Astrophysics Data System (ADS)

    Wu, XueHong; Chang, ZhiJuan; Ma, QiuYang; Lu, YanLi; Yin, XueMei

    2016-08-01

    This paper focuses on improving the performance of the vertical open refrigerated display cabinets (VORDC) by optimizing the structure of deflector, which is affected by inlet velocity and velocity distribution of air curtains. The results show that the temperature of products located at the front and at the rear reduces as the increases of inlet velocity of air curtains. The increase of the inlet velocity of air curtains can strengthen the disturbance inside the VORDC, and also decrease the temperature of products inside the VORDC; the increase of the outer velocity of air curtain will exacerbate the disturbance outside the VORDC and decrease air curtain's performance. The present study can provide a theoretical foundation for the design of VORDC.

  1. Effect of flow velocity and temperature on ignition characteristics in laser ignition of natural gas and air mixtures

    NASA Astrophysics Data System (ADS)

    Griffiths, J.; Riley, M. J. W.; Borman, A.; Dowding, C.; Kirk, A.; Bickerton, R.

    2015-03-01

    Laser induced spark ignition offers the potential for greater reliability and consistency in ignition of lean air/fuel mixtures. This increased reliability is essential for the application of gas turbines as primary or secondary reserve energy sources in smart grid systems, enabling the integration of renewable energy sources whose output is prone to fluctuation over time. This work details a study into the effect of flow velocity and temperature on minimum ignition energies in laser-induced spark ignition in an atmospheric combustion test rig, representative of a sub 15 MW industrial gas turbine (Siemens Industrial Turbomachinery Ltd., Lincoln, UK). Determination of minimum ignition energies required for a range of temperatures and flow velocities is essential for establishing an operating window in which laser-induced spark ignition can operate under realistic, engine-like start conditions. Ignition of a natural gas and air mixture at atmospheric pressure was conducted using a laser ignition system utilizing a Q-switched Nd:YAG laser source operating at 532 nm wavelength and 4 ns pulse length. Analysis of the influence of flow velocity and temperature on ignition characteristics is presented in terms of required photon flux density, a useful parameter to consider during the development laser ignition systems.

  2. Effects of air velocity and clothing combination on heating efficiency of an electrically heated vest (EHV): a pilot study.

    PubMed

    Wang, Faming; Gao, Chuansi; Holmér, Ingvar

    2010-09-01

    Cold endangers the heat balance of the human body. Protective clothing is the natural and most common equipment against cold stress. However, clothing for cold protection may be bulky and heavy, affecting human performance and increasing the work load. In such cases, a heated garment with built-in heating elements may be helpful. This pilot study presents a method based on a thermal manikin to investigate the effects of air velocity and clothing combination on the heating efficiency of an electrically heated vest (EHV). An infrared thermal camera was used to detect surface temperature distributions of the EHV on the front and back. Results show that the heating efficiency of the EHV decreases with increasing air velocity. Changes in EHV sequence in the three-layer clothing combination also significantly affect the heating efficiency: it increases with the increasing number of layers on top of the EHV. The highest mean temperature on the inner surface of the EHV was 40.2 degrees C, which indicates that it is safe for the wearers. For the EHV to heat the human body effectively, we suggest that it be worn as a middle layer. Finally, the EHV is especially suitable for occupational groups whose metabolic rate is below 1.9 Mets.

  3. Drying southern pine at 240°F. -- effects of air velocity and humidity, board thickness and density

    Treesearch

    Peter Koch

    1972-01-01

    Kiln time to each 10 percent moisture content was shortened by circulating air at high velocity, but was little affected by board specific gravity. A wet-bulb depression of 80oF. provided faster drying than depressions of 40 or 115oF. At 80 depression and with air circulated at 930 f.p.m., kiln time was directly...

  4. Effects of CO2/N2 dilution on laminar burning velocity of stoichiometric DME-air mixture at elevated temperatures.

    PubMed

    Mohammed, Abdul Naseer; Juhany, Khalid A; Kumar, Sudarshan; Kishore, V Ratna; Mohammad, Akram

    2017-03-21

    The laminar burning velocity of CO2/N2 diluted stoichiometric dimethyl ether (DME) air mixtures is determined experimentally at atmospheric pressure and elevated mixture temperatures using a mesoscale high aspect-ratio diverging channel with inlet dimensions of 25mm×2mm. In this method, planar flames at different initial temperatures (Tu) were stabilized inside the channel using an external electric heater. The magnitude of burning velocities was acquired by measuring the flame position and initial temperature. The mass conservation of the mixture entering the inlet and the stationary planar flame front is applied to obtain the laminar burning velocity. Laminar burning velocity at different initial mixture temperatures is plotted with temperature ratio (Tu/Tu,o), where a reference temperature (Tu,o) of 300K is used. Enhancement in the laminar burning velocity is observed with mixture temperature for DME-air mixtures with CO2 and N2 dilutions. A significant decrease in the burning velocity and slight increase in temperature exponent of the stoichiometric DME-air mixture was observed with dilution at same temperatures. The addition of CO2 has profound influence when compared to N2 addition on both burning velocity and temperature exponent.

  5. Effects of metabolic rate on thermal responses at different air velocities in -10 degrees C.

    PubMed

    Mäkinen, T T; Gavhed, D; Holmér, I; Rintamäki, H

    2001-04-01

    The effects of exercise intensity on thermoregulatory responses in cold (-10 degrees C) in a 0.2 (still air, NoWi), 1.0 (Wi1), and 5.0 (Wi5) m x s(-1) wind were studied. Eight young and healthy men, preconditioned in thermoneutral (+20 degrees C) environment for 60 min, walked for 60 min on the treadmill at 2.8 km/h with different combinations of wind and exercise intensity. Exercise level was adjusted by changing the inclination of the treadmill between 0 degrees (lower exercise intensity, metabolic rate 124 W x m(-2), LE) and 6 degrees (higher exercise intensity, metabolic rate 195 W x m(-2), HE). Due to exercise increased heat production and circulatory adjustments, the rectal temperature (T(re)), mean skin temperature (Tsk) and mean body temperature (Tb) were significantly higher at the end of HE in comparison to LE in NoWi and Wi1, and T(re) and Tb also in Wi5. Tsk and Tb were significantly decreased by 5.0 m x s(-1) wind in comparison to NoWi and Wi1. The higher exercise intensity was intense enough to diminish peripheral vasoconstriction and consequently the finger skin temperature was significantly higher at the end of HE in comparison to LE in NoWi and Wi1. Mean heat flux from the skin was unaffected by the exercise intensity. At LE oxygen consumption (VO2) was significantly higher in Wi5 than NoWi and Wi1. Heart rate was unaffected by the wind speed. The results suggest that, with studied exercise intensities, produced without changes in walking speed, the metabolic rate is not so important that it should be taken into consideration in the calculation of wind chill index.

  6. Effect of airstream velocity on mean drop diameters of water sprays produced by pressure and air atomizing nozzles. [for combustion studies

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.

    1977-01-01

    A scanning radiometer was used to determine the effect of airstream velocity on the mean drop diameter of water sprays produced by pressure atomizing and air atomizing fuel nozzles used in previous combustion studies. Increasing airstream velocity from 23 to 53.4 meters per second reduced the Sauter mean diameter by approximately 50 percent with both types of fuel nozzles. The use of a sonic cup attached to the tip of an air assist nozzle reduced the Sauter mean diameter by approximately 40 percent. Test conditions included airstream velocities of 23 to 53.4 meters per second at 293 K and atmospheric pressure.

  7. Drying southern pine at 240°F-- effects of air velocity and humidity, board thickness and density

    Treesearch

    P. Koch

    1972-01-01

    Kiln time to reach 10 percent moisture content was shortened by circulating air at high velocity, but was little affected by board specific gravity. A wet-bulb depression of 80°F. provided faster drying than depressions of 40 or 115°F. At 80° depression and with air circulated at 930 f.p.m.. kiln time was directly proportional to board thickness. Under these optimum...

  8. Effects of fungal species, cultivation time, growth substrate, and air exposure velocity on the fluorescence properties of airborne fungal spores.

    PubMed

    Saari, S; Mensah-Attipoe, J; Reponen, T; Veijalainen, A M; Salmela, A; Pasanen, P; Keskinen, J

    2015-12-01

    Real-time bioaerosol monitoring is possible with fluorescence based instruments. This study provides information on major factors that can affect the fluorescence properties of airborne fungal spores. Two fluorescence-based bioaerosol detectors, BioScout, and ultraviolet aerodynamic particle sizer (UVAPS), were used to study fluorescent particle fractions (FPFs) of released spores of three fungal species (Aspergillus versicolor, Cladosporium cladosporioides, and Penicillium brevicompactum). Two culture media (agar and gypsum board), three ages of the culture (one week, one month, and four months), and three aerosolization air velocities (5, 15, and 27 m/s) were tested. The results showed that the FPF values for spores released from gypsum were typically lower than for those released from agar indicating that poor nutrient substrate produces spores with lower amounts of fluorescent compounds. The results also showed higher FPF values with lower air velocities in aerosolization. This indicates that easily released fully developed spores have more fluorescent compounds compared to forcibly extracted non-matured spores. The FPFs typically were lower with older samples. The FPF results between the two instruments were similar, except with four-month-old samples. The results can be utilized in field measurements of fungal spores to estimate actual concentrations and compare different instruments with fluorescence-based devices as well as in instrument calibration and testing in laboratory conditions. Fluorescence-based instruments are the only choice for real-time detection of fungal spores at the moment. In general, all fluorescence-based bioaerosol instruments are tested against known bacterial and fungal spores in laboratory conditions. This study showed that fungal species, growth substrate, age of culture, and air current exposure rate have an effect on detection efficiency of fungal spores in the fluorescence-based instruments. Therefore, these factors should be

  9. Air Velocity Mapping of Environmental Test Chambers

    DTIC Science & Technology

    1989-07-01

    variable that must be measured for the evaluations of the air diffusion performance index (ADPI), or the thermal comfort indices such as predicted mean...altered. The impact of asymmetrical airflow patterns undoubtedly affect human thermal comfort votes. The standardized 6 technique described in this...report could be easily employed prior to or along with specific studies requiring precise air velocity data, and coupled with human thermal comfort surveys

  10. Computational Fluid Dynamics Investigation of Human Aspiration in Low-Velocity Air: Orientation Effects on Mouth-Breathing Simulations

    PubMed Central

    Anthony, T. Renée

    2013-01-01

    Computational fluid dynamics was used to investigate particle aspiration efficiency in low-moving air typical of occupational settings (0.1–0.4 m s−1). Fluid flow surrounding an inhaling humanoid form and particle trajectories traveling into the mouth were simulated for seven discrete orientations relative to the oncoming wind (0°, 15°, 30°, 60°, 90°, 135° and 180°). Three continuous inhalation velocities (1.81, 4.33, and 12.11 m s−1), representing the mean inhalation velocity associated with sinusoidal at-rest, moderate, and heavy breathing (7.5, 20.8, and 50.3 l min−1, respectively) were simulated. These simulations identified a decrease in aspiration efficiency below the inhalable particulate mass (IPM) criterion of 0.5 for large particles, with no aspiration of particles 100 µm and larger for at-rest breathing and no aspiration of particles 116 µm for moderate breathing, over all freestream velocities and orientations relative to the wind. For particles smaller than 100 µm, orientation-averaged aspiration efficiency exceeded the IPM criterion, with increased aspiration efficiency as freestream velocity decreased. Variability in aspiration efficiencies between velocities was low for small (<22 µm) particles, but increased with increasing particle size over the range of conditions studied. Orientation-averaged simulation estimates of aspiration efficiency agree with the linear form of the proposed linear low-velocity inhalable convention through 100 µm, based on laboratory studies using human mannequins. PMID:23316076

  11. Computational fluid dynamics investigation of human aspiration in low-velocity air: orientation effects on mouth-breathing simulations.

    PubMed

    Anthony, T Renée; Anderson, Kimberly R

    2013-07-01

    Computational fluid dynamics was used to investigate particle aspiration efficiency in low-moving air typical of occupational settings (0.1-0.4 m s(-1)). Fluid flow surrounding an inhaling humanoid form and particle trajectories traveling into the mouth were simulated for seven discrete orientations relative to the oncoming wind (0°, 15°, 30°, 60°, 90°, 135° and 180°). Three continuous inhalation velocities (1.81, 4.33, and 12.11 m s(-1)), representing the mean inhalation velocity associated with sinusoidal at-rest, moderate, and heavy breathing (7.5, 20.8, and 50.3 l min(-1), respectively) were simulated. These simulations identified a decrease in aspiration efficiency below the inhalable particulate mass (IPM) criterion of 0.5 for large particles, with no aspiration of particles 100 µm and larger for at-rest breathing and no aspiration of particles 116 µm for moderate breathing, over all freestream velocities and orientations relative to the wind. For particles smaller than 100 µm, orientation-averaged aspiration efficiency exceeded the IPM criterion, with increased aspiration efficiency as freestream velocity decreased. Variability in aspiration efficiencies between velocities was low for small (<22 µm) particles, but increased with increasing particle size over the range of conditions studied. Orientation-averaged simulation estimates of aspiration efficiency agree with the linear form of the proposed linear low-velocity inhalable convention through 100 µm, based on laboratory studies using human mannequins.

  12. Air velocity distribution in a commercial broiler house

    USDA-ARS?s Scientific Manuscript database

    Increasing air velocity during tunnel ventilation in commercial broiler production facilities improves production efficiency, and many housing design specifications require a minimum air velocity. Air velocities are typically assessed with a hand-held velocity meter at random locations, rather than ...

  13. Effects of air velocity on convective and radiant heat transfer from domestic fowls at environmental temperatures of 20 degrees and 30 degrees C.

    PubMed

    Mitchell, M A

    1985-07-01

    The effects of air movement upon sensible heat loss from individual birds at ambient temperatures of 20 degrees and 30 degrees C were determined by partitional calorimetry using a newly developed wind tunnel calorimeter. The relationship between area specific convective heat loss (W/m2) and air velocity (in the range 0.3 to 1.05 m/s) was described by y = 56.5 + 16.9 log x at an air temperature of 20 degrees C, but at 30 degrees C convective heat loss increased linearly with air speed (y = 11.8 + 40.1 x). At 20 degrees C sensible heat exchange (W/m2) was related to air velocity by y = 70.6 exp (0.099 x) and by y = 41.4 + 25.9 x at 30 degrees C, the proportional increase with air speed being greater at the higher temperature. The differences in the effects of air movement on convective cooling and sensible heat loss at 20 degrees and 30 degrees C reflect the thermoregulatory responses of the birds, induced by the thermal demands of the environment.

  14. Computational Fluid Dynamics Investigation of Human Aspiration in Low Velocity Air: Orientation Effects on Nose-Breathing Simulations

    PubMed Central

    Anderson, Kimberly R.; Anthony, T. Renée

    2014-01-01

    An understanding of how particles are inhaled into the human nose is important for developing samplers that measure biologically relevant estimates of exposure in the workplace. While previous computational mouth-breathing investigations of particle aspiration have been conducted in slow moving air, nose breathing still required exploration. Computational fluid dynamics was used to estimate nasal aspiration efficiency for an inhaling humanoid form in low velocity wind speeds (0.1–0.4 m s−1). Breathing was simplified as continuous inhalation through the nose. Fluid flow and particle trajectories were simulated over seven discrete orientations relative to the oncoming wind (0, 15, 30, 60, 90, 135, 180°). Sensitivities of the model simplification and methods were assessed, particularly the placement of the recessed nostril surface and the size of the nose. Simulations identified higher aspiration (13% on average) when compared to published experimental wind tunnel data. Significant differences in aspiration were identified between nose geometry, with the smaller nose aspirating an average of 8.6% more than the larger nose. Differences in fluid flow solution methods accounted for 2% average differences, on the order of methodological uncertainty. Similar trends to mouth-breathing simulations were observed including increasing aspiration efficiency with decreasing freestream velocity and decreasing aspiration with increasing rotation away from the oncoming wind. These models indicate nasal aspiration in slow moving air occurs only for particles <100 µm. PMID:24665111

  15. Computational fluid dynamics investigation of human aspiration in low velocity air: orientation effects on nose-breathing simulations.

    PubMed

    Anderson, Kimberly R; Anthony, T Renée

    2014-06-01

    An understanding of how particles are inhaled into the human nose is important for developing samplers that measure biologically relevant estimates of exposure in the workplace. While previous computational mouth-breathing investigations of particle aspiration have been conducted in slow moving air, nose breathing still required exploration. Computational fluid dynamics was used to estimate nasal aspiration efficiency for an inhaling humanoid form in low velocity wind speeds (0.1-0.4 m s(-1)). Breathing was simplified as continuous inhalation through the nose. Fluid flow and particle trajectories were simulated over seven discrete orientations relative to the oncoming wind (0, 15, 30, 60, 90, 135, 180°). Sensitivities of the model simplification and methods were assessed, particularly the placement of the recessed nostril surface and the size of the nose. Simulations identified higher aspiration (13% on average) when compared to published experimental wind tunnel data. Significant differences in aspiration were identified between nose geometry, with the smaller nose aspirating an average of 8.6% more than the larger nose. Differences in fluid flow solution methods accounted for 2% average differences, on the order of methodological uncertainty. Similar trends to mouth-breathing simulations were observed including increasing aspiration efficiency with decreasing freestream velocity and decreasing aspiration with increasing rotation away from the oncoming wind. These models indicate nasal aspiration in slow moving air occurs only for particles <100 µm.

  16. The effect of wind velocity, air temperature and humidity on NH 3 and SO 2 transfer into bean leaves ( phaseolus vulgaris L.)

    NASA Astrophysics Data System (ADS)

    van Hove, L. W. A.; Vredenberg, W. J.; Adema, E. H.

    The influence of wind velocity, air temperature and vapour pressure deficit of the air (VPD) on NH 3 and SO 2 transfer into bean leaves ( Phaseolus vulgaris L.) was examined using a leaf chamber. The measurements suggested a transition in the properties of the leaf boundary layer at a wind velocity of 0.3-0.4 ms -1 which corresponds to a Recrit value of about 2000. At higher wind velocities the leaf boundary layer resistance ( rb) was 1.5-2 times lower than can be calculated from the theory. Nevertheless, the assessed relationships between rb and wind velocity appeared to be similar to the theoretical derived relationship for rb. The NH 3 flux and in particular the SO 2 flux into the leaf strongly increased at a VPD decline. The increase of the NH 3 flux could be attributed to an increase of the stomatal conductance ( gs). However, the increase of the SO 2 flux could only partly be explained by an increase of gs. An apparent additional uptake was also observed for the NH 3 uptake at a low temperature and VPD. The SO 2 flux was also influenced by air temperature which could be explained by a temperature effect on gs. The results suggest that calculation of the NH 3 and SO 2 flux using data of gs gives a serious understimation of the real flux of these gases into leaves at a low temperature and VPD.

  17. 30 CFR 75.326 - Mean entry air velocity.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Mean entry air velocity. 75.326 Section 75.326... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.326 Mean entry air velocity. In exhausting face ventilation systems, the mean entry air velocity shall be at least 60 feet per...

  18. 30 CFR 75.326 - Mean entry air velocity.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Mean entry air velocity. 75.326 Section 75.326... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.326 Mean entry air velocity. In exhausting face ventilation systems, the mean entry air velocity shall be at least 60 feet per...

  19. 30 CFR 75.326 - Mean entry air velocity.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... concentrations in accordance with the applicable levels. Mean entry air velocity shall be determined at or near... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Mean entry air velocity. 75.326 Section 75.326... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.326 Mean entry air velocity....

  20. 30 CFR 75.326 - Mean entry air velocity.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... concentrations in accordance with the applicable levels. Mean entry air velocity shall be determined at or near... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Mean entry air velocity. 75.326 Section 75.326... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.326 Mean entry air velocity....

  1. 30 CFR 75.326 - Mean entry air velocity.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... concentrations in accordance with the applicable levels. Mean entry air velocity shall be determined at or near... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Mean entry air velocity. 75.326 Section 75.326... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.326 Mean entry air velocity....

  2. Provide a suitable range to include the thermal creeping effect on slip velocity and temperature jump of an air flow in a nanochannel by lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Karimipour, Arash

    2017-01-01

    The thermal creeping effect on slip velocity of air forced convection through a nanochannel is studied for the first time by using a lattice Boltzmann method. The nanochannel side walls are kept hot while the cold inlet air streams along them. The computations are presented for the wide range of Reynolds number, Knudsen number and Eckert number while slip velocity and temperature jump effects are involved. Moreover appropriate validations are performed versus previous works concerned the micro-nanoflows. The achieved results are shown as the velocity and temperature profiles at different cross sections, streamlines and isotherms and also the values of slip velocity and temperature jump along the nanochannel walls. The ability of the lattice Boltzmann method to simulate the thermal creeping effects on hydrodynamic and thermal domains of flow is shown at this study; so that its effects should be involved at lower values of Eckert number and higher values of Reynolds number especially at entrance region where the most temperature gradient exists.

  3. Effects of air velocity on laying hen production from 24 to 27 weeks under simulated evaporatively cooled conditions

    USDA-ARS?s Scientific Manuscript database

    Thermal conditions play a major role in production efficiency in commercial poultry production. Mitigation of thermal stress can improve productivity, but must be achieved economically. Weather and system design can limit effectiveness of evaporative cooling and increased air movement has been sho...

  4. Significance of air humidity and air velocity for fungal spore release into the air

    NASA Astrophysics Data System (ADS)

    Pasanen, A.-L.; Pasanen, P.; Jantunen, M. J.; Kalliokoski, P.

    Our previous field studies have shown that the presence of molds in buildings does not necessarily mean elevated airborne spore counts. Therefore, we investigated the release of fungal spores from cultures of Aspergillus fumigatus, Penicillium sp. and Cladosporium sp. at different air velocities and air humidities. Spores of A. fumigatus and Penicillium sp. were released from conidiophores already at air velocity of 0.5 ms -1, whereas Cladosporium spores required at least a velocity of 1.0 ms -1. Airborne spore counts of A. fumigatus and Penicillium sp. were usually higher in dry than moist air, being minimal at relative humidities (r.h.) above 70%, while the effect of r.h. on the release of Cladosporium sp. was ambivalent. The geometric mean diameter of released spores increased when the r.h. exceeded a certain level which depends on fungal genus. Thus, spores of all three fungi were hygroscopic but the hygroscopicity of various spores appeared at different r.h.-ranges. This study indicates that spore release is controlled by external factors and depends on fungal genus which can be one reason for considerable variation of airborne spore counts in buildings with mold problems.

  5. Simulation of air velocity in a vertical perforated air distributor

    NASA Astrophysics Data System (ADS)

    Ngu, T. N. W.; Chu, C. M.; Janaun, J. A.

    2016-06-01

    Perforated pipes are utilized to divide a fluid flow into several smaller streams. Uniform flow distribution requirement is of great concern in engineering applications because it has significant influence on the performance of fluidic devices. For industrial applications, it is crucial to provide a uniform velocity distribution through orifices. In this research, flow distribution patterns of a closed-end multiple outlet pipe standing vertically for air delivery in the horizontal direction was simulated. Computational Fluid Dynamics (CFD), a tool of research for enhancing and understanding design was used as the simulator and the drawing software SolidWorks was used for geometry setup. The main purpose of this work is to establish the influence of size of orifices, intervals between outlets, and the length of tube in order to attain uniformity of exit flows through a multi outlet perforated tube. However, due to the gravitational effect, the compactness of paddy increases gradually from top to bottom of dryer, uniform flow pattern was aimed for top orifices and larger flow for bottom orifices.

  6. Evaluation of the effect of media velocity on filter efficiency and most penetrating particle size of nuclear grade high-efficiency particulate air filters.

    PubMed

    Alderman, Steven L; Parsons, Michael S; Hogancamp, Kristina U; Waggoner, Charles A

    2008-11-01

    High-efficiency particulate air (HEPA) filters are widely used to control particulate matter emissions from processes that involve management or treatment of radioactive materials. Section FC of the American Society of Mechanical Engineers AG-1 Code on Nuclear Air and Gas Treatment currently restricts media velocity to a maximum of 2.5 cm/sec in any application where this standard is invoked. There is some desire to eliminate or increase this media velocity limit. A concern is that increasing media velocity will result in higher emissions of ultrafine particles; thus, it is unlikely that higher media velocities will be allowed without data to demonstrate the effect of media velocity on removal of ultrafine particles. In this study, the performance of nuclear grade HEPA filters, with respect to filter efficiency and most penetrating particle size, was evaluated as a function of media velocity. Deep-pleat nuclear grade HEPA filters (31 cm x 31 cm x 29 cm) were evaluated at media velocities ranging from 2.0 to 4.5 cm/sec using a potassium chloride aerosol challenge having a particle size distribution centered near the HEPA filter most penetrating particle size. Filters were challenged under two distinct mass loading rate regimes through the use of or exclusion of a 3 microm aerodynamic diameter cut point cyclone. Filter efficiency and most penetrating particle size measurements were made throughout the duration of filter testing. Filter efficiency measured at the onset of aerosol challenge was noted to decrease with increasing media velocity, with values ranging from 99.999 to 99.977%. The filter most penetrating particle size recorded at the onset of testing was noted to decrease slightly as media velocity was increased and was typically in the range of 110-130 nm. Although additional testing is needed, these findings indicate that filters operating at media velocities up to 4.5 cm/sec will meet or exceed current filter efficiency requirements. Additionally

  7. Influence of velocity effects on the shape of N2 (and air) broadened H2O lines revisited with classical molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Ngo, N. H.; Tran, H.; Gamache, R. R.; Bermejo, D.; Domenech, J.-L.

    2012-08-01

    The modeling of the shape of H2O lines perturbed by N2 (and air) using the Keilson-Storer (KS) kernel for collision-induced velocity changes is revisited with classical molecular dynamics simulations (CMDS). The latter have been performed for a large number of molecules starting from intermolecular-potential surfaces. Contrary to the assumption made in a previous study [H. Tran, D. Bermejo, J.-L. Domenech, P. Joubert, R. R. Gamache, and J.-M. Hartmann, J. Quant. Spectrosc. Radiat. Transf. 108, 126 (2007)], 10.1016/j.jqsrt.2007.03.009, the results of these CMDS show that the velocity-orientation and -modulus changes statistically occur at the same time scale. This validates the use of a single memory parameter in the Keilson-Storer kernel to describe both the velocity-orientation and -modulus changes. The CMDS results also show that velocity- and rotational state-changing collisions are statistically partially correlated. A partially correlated speed-dependent Keilson-Storer model has thus been used to describe the line-shape. For this, the velocity changes KS kernel parameters have been directly determined from CMDS, while the speed-dependent broadening and shifting coefficients have been calculated with a semi-classical approach. Comparisons between calculated spectra and measurements of several lines of H2O broadened by N2 (and air) in the ν3 and 2ν1 + ν2 + ν3 bands for a wide range of pressure show very satisfactory agreement. The evolution of non-Voigt effects from Doppler to collisional regimes is also presented and discussed.

  8. Influence of velocity effects on the shape of N2 (and air) broadened H2O lines revisited with classical molecular dynamics simulations.

    PubMed

    Ngo, N H; Tran, H; Gamache, R R; Bermejo, D; Domenech, J-L

    2012-08-14

    The modeling of the shape of H(2)O lines perturbed by N(2) (and air) using the Keilson-Storer (KS) kernel for collision-induced velocity changes is revisited with classical molecular dynamics simulations (CMDS). The latter have been performed for a large number of molecules starting from intermolecular-potential surfaces. Contrary to the assumption made in a previous study [H. Tran, D. Bermejo, J.-L. Domenech, P. Joubert, R. R. Gamache, and J.-M. Hartmann, J. Quant. Spectrosc. Radiat. Transf. 108, 126 (2007)], the results of these CMDS show that the velocity-orientation and -modulus changes statistically occur at the same time scale. This validates the use of a single memory parameter in the Keilson-Storer kernel to describe both the velocity-orientation and -modulus changes. The CMDS results also show that velocity- and rotational state-changing collisions are statistically partially correlated. A partially correlated speed-dependent Keilson-Storer model has thus been used to describe the line-shape. For this, the velocity changes KS kernel parameters have been directly determined from CMDS, while the speed-dependent broadening and shifting coefficients have been calculated with a semi-classical approach. Comparisons between calculated spectra and measurements of several lines of H(2)O broadened by N(2) (and air) in the ν(3) and 2ν(1) + ν(2) + ν(3) bands for a wide range of pressure show very satisfactory agreement. The evolution of non-Voigt effects from Doppler to collisional regimes is also presented and discussed.

  9. A Computational and Experimental Study of Coflow Laminar Methane/Air Diffusion Flames: Effects of Fuel Dilution, Inlet Velocity, and Gravity

    NASA Technical Reports Server (NTRS)

    Cao, S.; Ma, B.; Bennett, B. A. V.; Giassi, D.; Stocker, D. P.; Takahashi, F.; Long, M. B.; Smooke, M. D.

    2014-01-01

    The influences of fuel dilution, inlet velocity, and gravity on the shape and structure of laminar coflow CH4-air diffusion flames were investigated computationally and experimentally. A series of nitrogen-diluted flames measured in the Structure and Liftoff in Combustion Experiment (SLICE) on board the International Space Station was assessed numerically under microgravity (mu g) and normal gravity (1g) conditions with CH4 mole fraction ranging from 0.4 to 1.0 and average inlet velocity ranging from 23 to 90 cm/s. Computationally, the MC-Smooth vorticity-velocity formulation was employed to describe the reactive gaseous mixture, and soot evolution was modeled by sectional aerosol equations. The governing equations and boundary conditions were discretized on a two-dimensional computational domain by finite differences, and the resulting set of fully coupled, strongly nonlinear equations was solved simultaneously at all points using a damped, modified Newton's method. Experimentally, flame shape and soot temperature were determined by flame emission images recorded by a digital color camera. Very good agreement between computation and measurement was obtained, and the conclusions were as follows. (1) Buoyant and nonbuoyant luminous flame lengths are proportional to the mass flow rate of the fuel mixture; computed and measured nonbuoyant flames are noticeably longer than their 1g counterparts; the effect of fuel dilution on flame shape (i.e., flame length and flame radius) is negligible when the flame shape is normalized by the methane flow rate. (2) Buoyancy-induced reduction of the flame radius through radially inward convection near the flame front is demonstrated. (3) Buoyant and nonbuoyant flame structure is mainly controlled by the fuel mass flow rate, and the effects from fuel dilution and inlet velocity are secondary.

  10. Flame Velocities over a Wide Composition Range for Pentane-air, Ethylene-air, and Propyne-air Flames

    NASA Technical Reports Server (NTRS)

    Simon, Dorothy M; Wong, Edgar, L

    1951-01-01

    Fundamental flame velocities are reported for pentane air, ethylene-air, and propylene-air mixtures for the concentration range 60 to 130 percent of stoichiometric. A form of the Tanford and Pease equation, which includes a small constant velocity term independent of diffusion, will predict the observed changes in flame velocity.

  11. Robonaut 2 Humanoid Robot holds instrument to measure air velocity

    NASA Image and Video Library

    2012-03-14

    ISS030-E-148268 (14 March 2012) --- Controlled by teams on the ground, Robonaut 2 humanoid robot holds an instrument to measure air velocity during another system check out in the Destiny laboratory of the International Space Station.

  12. Robonaut 2 Humanoid Robot holds instrument to measure air velocity

    NASA Image and Video Library

    2012-03-14

    ISS030-E-148257 (14 March 2012) --- Controlled by teams on the ground, Robonaut 2 humanoid robot holds an instrument to measure air velocity during another system check out in the Destiny laboratory of the International Space Station.

  13. Robonaut 2 Humanoid Robot holds instrument to measure air velocity

    NASA Image and Video Library

    2012-03-14

    ISS030-E-148260 (14 March 2012) --- Controlled by teams on the ground, Robonaut 2 humanoid robot holds an instrument to measure air velocity during another system check out in the Destiny laboratory of the International Space Station.

  14. Robonaut 2 Humanoid Robot holds instrument to measure air velocity

    NASA Image and Video Library

    2012-03-14

    ISS030-E-148273 (14 March 2012) --- Controlled by teams on the ground, Robonaut 2 humanoid robot holds an instrument to measure air velocity during another system check out in the Destiny laboratory of the International Space Station.

  15. Velocity Estimate Following Air Data System Failure

    DTIC Science & Technology

    2008-03-01

    Latt , Long, Altitude) Velocity (North, East, Down) Attitude (Roll, Pitch, Yaw) Body Accelerations (Nx, Ny, Nz) Body Rates (p, q, r...algorithm; however, this would be less of an issue with modern fighter aircraft which have state-of-the- art INS systems (something the Learjet did not have

  16. Drift Velocity of Electrons in Hot and Moist Air mixtures

    NASA Astrophysics Data System (ADS)

    Abner, Douglas

    1999-10-01

    The drift velocity of electrons in hot and moist air is presented. The apparatus consisted of a pulsed Townsend-type drift tube with an oil-free vacuum system and employed a temperature controller and heating system to regulate the temperature of the gas mixture and chamber to within 0.1 deg. C. over a range of ambient to 200 deg C. The drift tube is equipped with a movable anode allowing the anode-cathode separation to be varied from 0.8 to 7.4 cm. Water vapor concentration in the air mixture ranged from 0.7510.0Temperature was varied from ambient to 150 deg C. E/N (electric field normalized to gas density) ranged from 1.0 to 16 Td (1 Td = 10-17 V-cm2). Comparisons of data collected at elevated temperature, data collected at ambient temperature, and Boltzmann transport equation calculations show the effects of enhanced rotational and vibrational populations on the drift velocity.

  17. Air velocity distributions inside tree canopies from a variable-rate air-assisted sprayer

    USDA-ARS?s Scientific Manuscript database

    A variable-rate, air assisted, five-port sprayer had been in development to achieve variable discharge rates of both liquid and air. To verify the variable air rate capability by changing the fan inlet diameter of the sprayer, air jet velocities impeded by plant canopies were measured at various loc...

  18. A note of effects of kiln stick thickness and air velocity on drying time of southern pine 2 by 4 and 2 by 6 lumber

    Treesearch

    E.W. Price; P. Koch

    1982-01-01

    To dry to 10% moisture content, 4- and 6-inch-wide lumber 1.75 inch thick required about 13.7 h (including 4 3/4-h kiln warmup time) in 5-ft-wide loads at 260 F (wet-bulb temperature was 180 F) on 1.00-inch-thick sticks with air cross-circulated at 1,000 fpm. If air velocity is increased to 1,400 fpm or stick thickness increased to 1.5 inches, kiln time required to...

  19. Minimum Detectable Air Velocity by Thermal Flow Sensors

    PubMed Central

    Issa, Safir; Lang, Walter

    2013-01-01

    Miniaturized thermal flow sensors have opened the doors for a large variety of new applications due to their small size, high sensitivity and low power consumption. Theoretically, very small detection limits of air velocity of some micrometers per second are achievable. However, the superimposed free convection is the main obstacle which prevents reaching these expected limits. Furthermore, experimental investigations are an additional challenge since it is difficult to generate very low flows. In this paper, we introduce a physical method, capable of generating very low flow values in the mixed convection region. Additionally, we present the sensor characteristic curves at the zero flow case and in the mixed convection region. Results show that the estimated minimum detectable air velocity by the presented method is 0.8 mm/s. The equivalent air velocity to the noise level of the sensor at the zero flow case is about 0.13 mm/s. PMID:23966190

  20. Air velocity distributions from a variable-rate air-assisted sprayer for tree applications

    USDA-ARS?s Scientific Manuscript database

    A capability that implements tree structure to control liquid and air flow rates is the preferential design in the development of variable-rate orchard and nursery sprayers. Air jet velocity distributions from an air assisted, five-port sprayer which was under the development to achieve variable-rat...

  1. Unimpeded air velocity profiles of air-assisted five-port sprayer

    USDA-ARS?s Scientific Manuscript database

    A capability that relies on tree structure information to control liquid and air flow rates is the preferential design in the development of variable-rate orchard and nursery sprayers. Unimpeded air jet velocities from an air assisted, five-port sprayer in an open field were measured at four height...

  2. Air velocity distributions from air-assisted five-port sprayer

    USDA-ARS?s Scientific Manuscript database

    Capability to control both liquid and air flow rates based on tree structures would be one of the advantages of future variable-rate orchard and nursery sprayers. Air jet velocity distributions from an air assisted, five-port sprayer which was under the development to achieve variable-rate functions...

  3. Comparison of umbo velocity in air and bone conduction

    PubMed Central

    Röösli, Christof; Chhan, David; Halpin, Chris; Rosowski, John J.

    2014-01-01

    This study investigates the ossicular motion produced by bone-conducted (BC) sound in live human ears. Laser Doppler Vibrometry was used to measure air conduction (AC) and BC induced umbo velocity (Vu) in both ears of 10 subjects, 20 ears total. Sound pressure in the ear canal (PEC) was measured simultaneously. For air conduction, Vu at threshold was calculated. For BC, ΔV was defined as the difference between Vu and the tympanic ring velocity (an estimate of the skull velocity measured in the ear canal). ΔV and PEC at BC threshold were calculated and compared to the corresponding air conduction measurements. ΔV at BC threshold was significantly smaller than Vu at AC threshold between 500 Hz and 2000 Hz. Ear canal pressure at BC threshold tended to be smaller than for AC below 3000 Hz (with significant differences at 1000 Hz and 2000 Hz). Our results are most consistent with inertia of the ossicles and cochlear fluid driving BC hearing below 500 Hz, but with other mechanisms playing a significant role at higher frequencies. Sound radiated into the external ear canal might contribute to BC hearing at 3000 Hz and above. PMID:22609771

  4. Thermistor based, low velocity isothermal, air flow sensor

    NASA Astrophysics Data System (ADS)

    Cabrita, Admésio A. C. M.; Mendes, Ricardo; Quintela, Divo A.

    2016-03-01

    The semiconductor thermistor technology is applied as a flow sensor to measure low isothermal air velocities (<2 ms-1). The sensor is subjected to heating and cooling cycles controlled by a multifunctional timer. In the heating stage, the alternating current of a main AC power supply source guarantees a uniform thermistor temperature distribution. The conditioning circuit assures an adequate increase of the sensors temperature and avoids the thermal disturbance of the flow. The power supply interruption reduces the consumption from the source and extends the sensors life time. In the cooling stage, the resistance variation of the flow sensor is recorded by the measuring chain. The resistive sensor parameters proposed vary significantly and feature a high sensitivity to the flow velocity. With the aid of a computer, the data transfer, storage and analysis provides a great advantage over the traditional local anemometer readings. The data acquisition chain has a good repeatability and low standard uncertainties. The proposed method measures isothermal air mean velocities from 0.1 ms-1 to 2 ms-1 with a standard uncertainty error less than 4%.

  5. Influence of air velocity on the habit of ice crystal growth from the vapor

    NASA Technical Reports Server (NTRS)

    Keller, V. W.; Hallett, J.

    1982-01-01

    The effect of air velocity on the growth behavior of ice crystals growing from water vapor was investigated at temperatures between 0 and -35 C and at supersaturation levels ranging from 2 to 40 percent, using a laboratory chamber in which it was possible to make these variations. It was found that crystal growth was most sensitive to changes in the air velocity at temperatures near -4 C and -15 C where, near water saturation, the introduction of only a 5 cm/s air velocity induced skeletal transitions (columns to needles near -4 C and plates to dendrites near -15 C). The experiments provide conditions which simulate growth of ice crystals in the atmosphere, where crystal growth takes place at or somewhat below water saturation.

  6. Measurement of velocity of air flow in the sinus maxillaris.

    PubMed

    Müsebeck, K; Rosenberg, H

    1979-03-01

    Anemometry with the hot wire and hot film technique previously described, enables the rhinologist to record slow and rapidly changing air flow in the maxillary sinus. The advantages and disadvantages of this method are considered. Anemometry together with manometry may be designated sinumetry and used as a diagnostic procedure following sinuscopy in chronic maxillary sinus disease. The value of the function from velocity of time allows the estimation of flow-volume in the sinus. Furthermore, the method is useful to evaluate the optimal therapy to restore ventilation in the case of an obstructed ostium demonstrated before and after surgical opening in the inferior meatus.

  7. Live performance of male broilers subjected to constant or increasing air velocities at moderate temperatures with a high dew point.

    PubMed

    Dozier, W A; Lott, B D; Branton, S L

    2005-08-01

    This study examined the effects of varying air velocities vs. a constant air velocity with a cyclic temperature curve of 25-30-25 degrees C and a dew point of 23 degrees C on broilers from 28 to 49 d of age. Four replicate trials were conducted. In each trial, 742 male broilers were randomly allocated to 6 floor pens or 2 air velocity tunnels, with each tunnel consisting of 4 pens. Bird density, feeder, and waterer space were similar across all pens (53 birds/ pen; 0.07 m2/bird). The treatments were control (still air), constant air velocity of 120 m/min, and increasing air velocity (90 m/min from 28 to 35 d, 120 m/min from 36 to 42 d, and 180 m/min from 43 to 49 d). Birds grown in a still air environment gained less weight, consumed less feed, and converted feed less efficiently between 28 and 49 d than birds subjected to moving air (constant or increasing). Growth responses between the air velocity treatments were similar from 28 to 35 and 36 to 42 d of age. Increasing air velocity to 180 m/min improved (P < or = 0.02) the growth rate of broilers from 43 to 49 d of age over birds receiving an air velocity of 120 m/min, but the incidence of mortality was not affected. These results provide evidence that increasing air velocity from 120 to 180 m/min is beneficial to broilers weighing 2.5 kg or greater when exposed to moderate temperatures.

  8. Effect of gas-transfer velocity parameterization choice on air-sea CO2 fluxes in the North Atlantic Ocean and the European Arctic

    NASA Astrophysics Data System (ADS)

    Wrobel, Iwona; Piskozub, Jacek

    2016-09-01

    The oceanic sink of carbon dioxide (CO2) is an important part of the global carbon budget. Understanding uncertainties in the calculation of this net flux into the ocean is crucial for climate research. One of the sources of the uncertainty within this calculation is the parameterization chosen for the CO2 gas-transfer velocity. We used a recently developed software toolbox, called the FluxEngine (Shutler et al., 2016), to estimate the monthly air-sea CO2 fluxes for the extratropical North Atlantic Ocean, including the European Arctic, and for the global ocean using several published quadratic and cubic wind speed parameterizations of the gas-transfer velocity. The aim of the study is to constrain the uncertainty caused by the choice of parameterization in the North Atlantic Ocean. This region is a large oceanic sink of CO2, and it is also a region characterized by strong winds, especially in winter but with good in situ data coverage. We show that the uncertainty in the parameterization is smaller in the North Atlantic Ocean and the Arctic than in the global ocean. It is as little as 5 % in the North Atlantic and 4 % in the European Arctic, in comparison to 9 % for the global ocean when restricted to parameterizations with quadratic wind dependence. This uncertainty becomes 46, 44, and 65 %, respectively, when all parameterizations are considered. We suggest that this smaller uncertainty (5 and 4 %) is caused by a combination of higher than global average wind speeds in the North Atlantic (> 7 ms-1) and lack of any seasonal changes in the direction of the flux direction within most of the region. We also compare the impact of using two different in situ pCO2 data sets (Takahashi et al. (2009) and Surface Ocean CO2 Atlas (SOCAT) v1.5 and v2.0, for the flux calculation. The annual fluxes using the two data sets differ by 8 % in the North Atlantic and 19 % in the European Arctic. The seasonal fluxes in the Arctic computed from the two data sets disagree with each

  9. Preservation of cognitive performance with age during exertional heat stress under low and high air velocity.

    PubMed

    Wright Beatty, Heather E; Keillor, Jocelyn M; Hardcastle, Stephen G; Boulay, Pierre; Kenny, Glen P

    2015-01-01

    Older adults may be at greater risk for occupational injuries given their reduced capacity to dissipate heat, leading to greater thermal strain and potentially cognitive decrements. To examine the effects of age and increased air velocity, during exercise in humid heat, on information processing and attention. Nine young (24 ± 1 years) and 9 older (59 ± 1 years) males cycled 4 × 15 min (separated by 15 min rest) at a fixed rate of heat production (400 W) in humid heat (35°C, 60% relative humidity) under 0.5 (low) and 3.0 (high) m·s(-1) air velocity wearing coveralls. At rest, immediately following exercise (end exercise), and after the final recovery, participants performed an abbreviated paced auditory serial addition task (PASAT, 2 sec pace). PASAT numbers of correct responses at end exercise were similar for young (low = 49 ± 3; high = 51 ± 3) and older (low = 46 ± 5; high = 47 ± 4) males and across air velocity conditions, and when scored relative to age norms. Psychological sweating, or an increased sweat rate with the administration of the PASAT, was observed in both age groups in the high condition. No significant decrements in attention and speeded information processing were observed, with age or altered air velocity, following intermittent exercise in humid heat.

  10. Preservation of Cognitive Performance with Age during Exertional Heat Stress under Low and High Air Velocity

    PubMed Central

    Wright Beatty, Heather E.; Keillor, Jocelyn M.; Hardcastle, Stephen G.; Boulay, Pierre; Kenny, Glen P.

    2015-01-01

    Older adults may be at greater risk for occupational injuries given their reduced capacity to dissipate heat, leading to greater thermal strain and potentially cognitive decrements. Purpose. To examine the effects of age and increased air velocity, during exercise in humid heat, on information processing and attention. Methods. Nine young (24 ± 1 years) and 9 older (59 ± 1 years) males cycled 4 × 15 min (separated by 15 min rest) at a fixed rate of heat production (400 W) in humid heat (35°C, 60% relative humidity) under 0.5 (low) and 3.0 (high) m·s−1 air velocity wearing coveralls. At rest, immediately following exercise (end exercise), and after the final recovery, participants performed an abbreviated paced auditory serial addition task (PASAT, 2 sec pace). Results. PASAT numbers of correct responses at end exercise were similar for young (low = 49 ± 3; high = 51 ± 3) and older (low = 46 ± 5; high = 47 ± 4) males and across air velocity conditions, and when scored relative to age norms. Psychological sweating, or an increased sweat rate with the administration of the PASAT, was observed in both age groups in the high condition. Conclusion. No significant decrements in attention and speeded information processing were observed, with age or altered air velocity, following intermittent exercise in humid heat. PMID:25874223

  11. Egomotion estimation with optic flow and air velocity sensors.

    PubMed

    Rutkowski, Adam J; Miller, Mikel M; Quinn, Roger D; Willis, Mark A

    2011-06-01

    We develop a method that allows a flyer to estimate its own motion (egomotion), the wind velocity, ground slope, and flight height using only inputs from onboard optic flow and air velocity sensors. Our artificial algorithm demonstrates how it could be possible for flying insects to determine their absolute egomotion using their available sensors, namely their eyes and wind sensitive hairs and antennae. Although many behaviors can be performed by only knowing the direction of travel, behavioral experiments indicate that odor tracking insects are able to estimate the wind direction and control their absolute egomotion (i.e., groundspeed). The egomotion estimation method that we have developed, which we call the opto-aeronautic algorithm, is tested in a variety of wind and ground slope conditions using a video recorded flight of a moth tracking a pheromone plume. Over all test cases that we examined, the algorithm achieved a mean absolute error in height of 7% or less. Furthermore, our algorithm is suitable for the navigation of aerial vehicles in environments where signals from the Global Positioning System are unavailable.

  12. An Idea of Staged and Large Velocity Differential Secondary Air for Waterwall Erosion Protection and Oxygen Complementarity

    NASA Astrophysics Data System (ADS)

    Liu, B. Q.; Zhang, X. H.

    A successful design of circulating fluidized bed (CFB) boiler should have the highest combustion efficiency, economic operation, and optimum availability. There is a coupled phenomenon of an oxygen lean zone existing in the CFB boiler furnace which depresses combustion efficiency and particle (group) falling down faster and faster when it falls along the waterwall, abrading the tube metal effectively. A new secondary air design for the oxygen lean zone and erosion protection is conceived by using staged and large velocity differential secondary air. For example, a part of concentrate supplied secondary air has been divided into two parts: a low velocity part and a high velocity part. The low velocity part is used for rigid gas layer to reduce the particle falling velocity, and the high velocity part is used for oxygen supply. It is believed that 40˜6Om/s projecting air velocity could send new oxygen to at least half furnace depth in a short projecting lift as shown in calculation. In another view point, operational superficial gas velocity has an obvious effect on waterwall metal erosion, with a lower operation velocity having lower erosion.

  13. 42 CFR 84.140 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  14. 42 CFR 84.140 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  15. 42 CFR 84.140 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  16. 42 CFR 84.140 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  17. 42 CFR 84.140 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  18. Laminar burning velocities and flame instabilities of butanol isomers-air mixtures

    SciTech Connect

    Gu, Xiaolei; Huang, Zuohua; Wu, Si; Li, Qianqian

    2010-12-15

    Laminar burning velocities and flame instabilities of the butanol-air premixed flames and its isomers are investigated using the spherically expanding flame with central ignition at initial temperature of 428 K and initial pressures of 0.10 MPa, 0.25 MPa, 0.50 MPa and 0.75 MPa. Laminar burning velocities and sensitivity factor of n-butanol-air mixtures are computed using a newly developed kinetic mechanism. Unstretched laminar burning velocity, adiabatic temperature, Lewis number, Markstein length, critical flame radius and Peclet number are obtained over a wide range of equivalence ratios. Effect of molecular structure on laminar burning velocity of the isomers of butanol is analyzed from the aspect of C-H bond dissociation energy. Study indicates that although adiabatic flame temperatures of the isomers of butanol are the same, laminar burning velocities give an obvious difference among the isomers of butanol. This indicates that molecular structure has a large influence on laminar burning velocities of the isomers of butanol. Branching (-CH3) will decrease laminar burning velocity. Hydroxyl functional group (-OH) attaching to the terminal carbon atoms gives higher laminar burning velocity compared to that attaching to the inner carbon atoms. Calculated dissociation bond energies show that terminal C-H bonds have larger bond energies than that of inner C-H bonds. n-Butanol, no branching and with hydroxyl functional group (-OH) attaching to the terminal carbon atom, gives the largest laminar burning velocity. tert-Butanol, with highly branching and hydroxyl functional group (-OH) attaching to the inner carbon atom, gives the lowest laminar burning velocity. Laminar burning velocities of iso-butanol and sec-butanol are between those of n-butanol and tert-butanol. The instant of transition to cellularity is experimentally determined for the isomers of butanol and subsequently interpreted on the basis of hydrodynamic and diffusion-thermal instabilities. Little effect

  19. Drop size distribution and air velocity measurements in air assist swirl atomizer sprays

    NASA Technical Reports Server (NTRS)

    Mao, C.-P.; Oechsle, V.; Chigier, N.

    1987-01-01

    Detailed measurements of mean drop size (SMD) and size distribution parameters have been made using a Fraunhofer diffraction particle sizing instrument in a series of sprays generated by an air assist swirl atomizer. Thirty-six different combinations of fuel and air mass flow rates were examined with liquid flow rates up to 14 lbm/hr and atomizing air flow rates up to 10 lbm/hr. Linear relationships were found between SMD and liquid to air mass flow rate ratios. SMD increased with distance downstream along the center line and also with radial distance from the axis. Increase in obscuration with distance downstream was due to an increase in number density of particles as the result of deceleration of drops and an increase in the exposed path length of the laser beam. Velocity components of the atomizing air flow field measured by a laser anemometer show swirling jet air flow fields with solid body rotation in the core and free vortex flow in the outer regions.

  20. A Hypothetical Burning-Velocity Formula for Very Lean Hydrogen-Air Mixtures

    SciTech Connect

    Williams, Forman; Williams, Forman A; Grcar, Joseph F

    2008-06-30

    Very lean hydrogen-air mixtures experience strong diffusive-thermal types of cellular instabilities that tend to increase the laminar burning velocity above the value that applies to steady, planar laminar flames that are homogeneous in transverse directions. Flame balls constitute an extreme limit of evolution of cellular flames. To account qualitatively for the ultimate effect of diffusive-thermal instability, a model is proposed in which the flame is a steadily propagating, planar, hexagonal, close-packed array of flame balls, each burning as if it were an isolated, stationary, ideal flame ball in an infinite, quiescent atmosphere. An expression for the laminar burning velocity is derived from this model, which theoretically may provide an upper limit for the experimental burning velocity.

  1. Surface velocity divergence model of air/water interfacial gas transfer in open-channel flows

    NASA Astrophysics Data System (ADS)

    Sanjou, M.; Nezu, I.; Okamoto, T.

    2017-04-01

    Air/water interfacial gas transfer through a free surface plays a significant role in preserving and restoring water quality in creeks and rivers. However, direct measurements of the gas transfer velocity and reaeration coefficient are still difficult, and therefore a reliable prediction model needs to be developed. Varying systematically the bulk-mean velocity and water depth, laboratory flume experiments were conducted and we measured surface velocities and dissolved oxygen (DO) concentrations in open-channel flows to reveal the relationship between DO transfer velocity and surface divergence (SD). Horizontal particle image velocimetry measurements provide the time-variations of surface velocity divergence. Positive and negative regions of surface velocity divergence are transferred downstream in time, as occurs in boil phenomenon on natural river free-surfaces. The result implies that interfacial gas transfer is related to bottom-situated turbulence motion and vertical mass transfer. The original SD model focuses mainly on small-scale viscous motion, and this model strongly depends on the water depth. Therefore, we modify the SD model theoretically to accommodate the effects of the water depth on gas transfer, introducing a non-dimensional parameter that includes contributions of depth-scale large-vortex motion, such as secondary currents, to surface renewal events related to DO transport. The modified SD model proved effective and reasonable without any dependence on the bulk mean velocity and water depth, and has a larger coefficient of determination than the original SD model. Furthermore, modeling of friction velocity with the Reynolds number improves the practicality of a new formula that is expected to be used in studies of natural rivers.

  2. 42 CFR 84.202 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  3. 42 CFR 84.202 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  4. 42 CFR 84.1139 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Air velocity and noise levels; hoods and helmets... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  5. 42 CFR 84.202 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  6. 42 CFR 84.1139 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Air velocity and noise levels; hoods and helmets... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  7. 42 CFR 84.1139 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Air velocity and noise levels; hoods and helmets... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  8. 42 CFR 84.1139 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Air velocity and noise levels; hoods and helmets... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  9. 42 CFR 84.1139 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Air velocity and noise levels; hoods and helmets... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  10. 42 CFR 84.202 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  11. 42 CFR 84.202 - Air velocity and noise levels; hoods and helmets; minimum requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Air velocity and noise levels; hoods and helmets... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and helmets; minimum requirements. Noise levels generated by the respirator will be measured inside the hood or helmet...

  12. Impact of air velocity on the development and detection of small coal fires

    SciTech Connect

    Egan, M.R.

    1993-12-31

    The U.S. Bureau of Mines conducted experiments in the intermediate-scale fire tunnel to assess the influence of air velocity on the gas production and smoke characteristics during smoldering and flaming combustion of Pittsburgh seam coal and its impact on the detection of the combustion products. On-line determinations of mass and number smoke particles, light transmission, and various gas concentrations were made. From these experimental values, generation rates, heat-release rates, production constants, particle sizes, obscuration rates, and optical densities were calculated. Ventilation has a direct effect on fire detection and development. The results indicate, that in general, increased air velocity lengthened the onset of smoke and flaming ignition, increased the fire intensity, but decreased the gas and smoke concentrations. Increased air velocity also lengthened the response times of all the fire sensors tested. Rapid and reliable detector response at this most crucial stage of fire development can increase the possibility that appropriate miner response (fire suppression tactics or evacuation) can be completed before toxic smoke spreads throughout the mine. 9 refs., 3 figs., 10 tabs.

  13. Calibration of a system for measuring low air flow velocity in a wind tunnel

    NASA Astrophysics Data System (ADS)

    Krach, Andrzej; Kruczkowski, Janusz

    2016-08-01

    This article presents the calibration of a system for measuring air flow velocity in a wind tunnel with a multiple-hole orifice. The comparative method was applied for the calibration. The method consists in equalising the air flow velocity in a test section of the tunnel with that of the hot-wire anemometer probe which should then read zero value. The hot-wire anemometer probe moves reciprocally in the tunnel test section with a constant velocity, aligned and opposite to the air velocity. Air velocity in the tunnel test section is adjusted so that the minimum values of a periodic hot-wire anemometer signal displayed on an oscilloscope screen reach the lowest position (the minimum method). A sinusoidal component can be superimposed to the probe constant velocity. Then, the air flow velocity in the tunnel test section is adjusted so that, when the probe moves in the direction of air flow, only the second harmonic of the periodically variable velocity superimposed on the constant velocity (second harmonic method) remains at the output of the low-pass filter to which the hot-wire anemometer signal, displayed on the oscilloscope screen, is supplied. The velocity of the uniform motion of the hot-wire anemometer probe is measured with a magnetic linear encoder. The calibration of the system for the measurement of low air velocities in the wind tunnel was performed in the following steps: 1. Calibration of the linear encoder for the measurement of the uniform motion velocity of the hot-wire anemometer probe in the test section of the tunnel. 2. Calibration of the system for measurement of low air velocities with a multiple-hole orifice for the velocities of 0.1 and 0.25 m s-1: - (a) measurement of the probe movement velocity setting; - (b) measurement of air velocity in the tunnel test section with comparison according to the second harmonic method; - (c) measurement of air velocity in the tunnel with comparison according to the minimum method. The calibration

  14. Quantifying energy and mass transfer in crop canopies: sensors for measurement of temperature and air velocity.

    PubMed

    Bugbee, B; Monje, O; Tanner, B

    1996-01-01

    Here we report on the in situ performance of inexpensive, miniature sensors that have increased our ability to measure mass and energy fluxes from plant canopies in controlled environments: 1. Surface temperature. Canopy temperature measurements indicate changes in stomatal aperture and thus latent and sensible heat fluxes. Infrared transducers from two manufacturers (Exergen Corporation, Newton, MA; and Everest Interscience, Tucson, AZ, USA) have recently become available. Transducer accuracy matched that of a more expensive hand-held infrared thermometer. 2. Air velocity varies above and within plant canopies and is an important component in mass and energy transfer models. We tested commercially-available needle, heat-transfer anemometers (1 x 50 mm cylinder) that consist of a fine-wire thermocouple and a heater inside a hypodermic needle. The needle is heated and wind speed determined from the temperature rise above ambient. These sensors are particularly useful in measuring the low wind speeds found within plant canopies. 3. Accurate measurements of air temperature adjacent to plant leaves facilitates transport phenomena modeling. We quantified the effect of radiation and air velocity on temperature rise in thermocouples from 10 to 500 micrometers. At high radiation loads and low wind speeds, temperature errors were as large as 7 degrees C above air temperature.

  15. Quantifying energy and mass transfer in crop canopies: sensors for measurement of temperature and air velocity

    NASA Technical Reports Server (NTRS)

    Bugbee, B.; Monje, O.; Tanner, B.

    1996-01-01

    Here we report on the in situ performance of inexpensive, miniature sensors that have increased our ability to measure mass and energy fluxes from plant canopies in controlled environments: 1. Surface temperature. Canopy temperature measurements indicate changes in stomatal aperture and thus latent and sensible heat fluxes. Infrared transducers from two manufacturers (Exergen Corporation, Newton, MA; and Everest Interscience, Tucson, AZ, USA) have recently become available. Transducer accuracy matched that of a more expensive hand-held infrared thermometer. 2. Air velocity varies above and within plant canopies and is an important component in mass and energy transfer models. We tested commercially-available needle, heat-transfer anemometers (1 x 50 mm cylinder) that consist of a fine-wire thermocouple and a heater inside a hypodermic needle. The needle is heated and wind speed determined from the temperature rise above ambient. These sensors are particularly useful in measuring the low wind speeds found within plant canopies. 3. Accurate measurements of air temperature adjacent to plant leaves facilitates transport phenomena modeling. We quantified the effect of radiation and air velocity on temperature rise in thermocouples from 10 to 500 micrometers. At high radiation loads and low wind speeds, temperature errors were as large as 7 degrees C above air temperature.

  16. Quantifying energy and mass transfer in crop canopies: sensors for measurement of temperature and air velocity

    NASA Technical Reports Server (NTRS)

    Bugbee, B.; Monje, O.; Tanner, B.

    1996-01-01

    Here we report on the in situ performance of inexpensive, miniature sensors that have increased our ability to measure mass and energy fluxes from plant canopies in controlled environments: 1. Surface temperature. Canopy temperature measurements indicate changes in stomatal aperture and thus latent and sensible heat fluxes. Infrared transducers from two manufacturers (Exergen Corporation, Newton, MA; and Everest Interscience, Tucson, AZ, USA) have recently become available. Transducer accuracy matched that of a more expensive hand-held infrared thermometer. 2. Air velocity varies above and within plant canopies and is an important component in mass and energy transfer models. We tested commercially-available needle, heat-transfer anemometers (1 x 50 mm cylinder) that consist of a fine-wire thermocouple and a heater inside a hypodermic needle. The needle is heated and wind speed determined from the temperature rise above ambient. These sensors are particularly useful in measuring the low wind speeds found within plant canopies. 3. Accurate measurements of air temperature adjacent to plant leaves facilitates transport phenomena modeling. We quantified the effect of radiation and air velocity on temperature rise in thermocouples from 10 to 500 micrometers. At high radiation loads and low wind speeds, temperature errors were as large as 7 degrees C above air temperature.

  17. Health Effects of Air Pollution

    MedlinePlus

    ... Health effects of air pollution Health effects of air pollution Breathing air that is not clean can hurt ... important to know about the health effects that air pollution can have on you and others. Once you ...

  18. Velocity and temperature field characteristics of water and air during natural convection heating in cans.

    PubMed

    Erdogdu, Ferruh; Tutar, Mustafa

    2011-01-01

    Presence of headspace during canning is required since an adequate amount allows forming vacuum during the process. Sealing technology may not totally eliminate all entrapped gases, and headspace might affect heat transfer. Not much attention has been given to solve this problem in computational studies, and cans, for example, were mostly assumed to be fully filled with product. Therefore, the objective of this study was to determine velocity and temperature evolution of water and air in cans during heating to evaluate the relevance of headspace in the transport mechanism. For this purpose, canned water samples with a certain headspace were used, and required governing continuity, energy, and momentum equations were solved using a finite volume approach coupled with a volume of fluid element model. Simulation results correlated well with experimental results validating faster heating effects of headspace rather than insulation effects as reported in the literature. The organized velocity motions along the air-water interface were also shown. Practical Application: Canning is a universal and economic method for processing of food products, and presence of adequate headspace is required to form vacuum during sealing of the cans. Since sealing technology may not totally eliminate the entrapped gases, mainly air, headspace might affect heating rates in cans. This study demonstrated the increased heating rates in the presence of headspace in contrast with some studies in the literature. By applying the effect of headspace, required processing time for thermally processed foods can be reduced leading to more rapid processes and lower energy consumptions.

  19. Velocity-jump models with crowding effects

    NASA Astrophysics Data System (ADS)

    Treloar, Katrina K.; Simpson, Matthew J.; McCue, Scott W.

    2011-12-01

    Velocity-jump processes are discrete random-walk models that have many applications including the study of biological and ecological collective motion. In particular, velocity-jump models are often used to represent a type of persistent motion, known as a run and tumble, that is exhibited by some isolated bacteria cells. All previous velocity-jump processes are noninteracting, which means that crowding effects and agent-to-agent interactions are neglected. By neglecting these agent-to-agent interactions, traditional velocity-jump models are only applicable to very dilute systems. Our work is motivated by the fact that many applications in cell biology, such as wound healing, cancer invasion, and development, often involve tissues that are densely packed with cells where cell-to-cell contact and crowding effects can be important. To describe these kinds of high-cell-density problems using a velocity-jump process we introduce three different classes of crowding interactions into a one-dimensional model. Simulation data and averaging arguments lead to a suite of continuum descriptions of the interacting velocity-jump processes. We show that the resulting systems of hyperbolic partial differential equations predict the mean behavior of the stochastic simulations very well.

  20. Velocity-jump models with crowding effects.

    PubMed

    Treloar, Katrina K; Simpson, Matthew J; McCue, Scott W

    2011-12-01

    Velocity-jump processes are discrete random-walk models that have many applications including the study of biological and ecological collective motion. In particular, velocity-jump models are often used to represent a type of persistent motion, known as a run and tumble, that is exhibited by some isolated bacteria cells. All previous velocity-jump processes are noninteracting, which means that crowding effects and agent-to-agent interactions are neglected. By neglecting these agent-to-agent interactions, traditional velocity-jump models are only applicable to very dilute systems. Our work is motivated by the fact that many applications in cell biology, such as wound healing, cancer invasion, and development, often involve tissues that are densely packed with cells where cell-to-cell contact and crowding effects can be important. To describe these kinds of high-cell-density problems using a velocity-jump process we introduce three different classes of crowding interactions into a one-dimensional model. Simulation data and averaging arguments lead to a suite of continuum descriptions of the interacting velocity-jump processes. We show that the resulting systems of hyperbolic partial differential equations predict the mean behavior of the stochastic simulations very well.

  1. A model for sound velocity in a two-phase air-water bubbly flow

    SciTech Connect

    Chung, N.M.; Lin, W.K.; Pei, B.S.; Hsu, Y.Y. )

    1992-07-01

    In this paper, wave propagation in a homogeneous, low void fraction, two-phase air-water bubbly flow is analyzed through the compressibility of a single bubble to derive a P({rho}) relation; the dispersion relation is then derived by a homogeneous model. The phase velocity and attenuation calculated from the model are compared with existing data and are in good agreement. The momentum transfer effect is considered through the virtual mass term and is significant at a higher void fraction. The interfacial heat transfer between phases is significant at low frequency, while bubble scattering effects are important at high frequency (near resonance). Bubble behavior at both low and high frequency is derived based on the isothermal and the adiabatic cases, respectively. The phase velocity occurs at the limiting condition in both cases. Furthermore, resonance is present in the model, and the resonant frequency is determined.

  2. Velocity and pressure distribution behind bodies in an air current

    NASA Technical Reports Server (NTRS)

    Betz, A

    1924-01-01

    The following experiments on the air flow behind bodies were made for the purpose of assisting in the explanation of the phenomena connected with air resistance. The first two series of experiments dealt with the phenomena behind a cylinder. The third series of experiments was carried out behind a streamlined strut.

  3. Velocity Fields of Axisymmetric Hydrogen-Air Counterflow Diffusion Flames from LDV, PIV, and Numerical Computation

    NASA Technical Reports Server (NTRS)

    Pellett, Gerald L.; Wilson, Lloyd G.; Humphreys, William M., Jr.; Bartram, Scott M.; Gartrell, Luther R.; Isaac, K. M.

    1995-01-01

    Laminar fuel-air counterflow diffusion flames (CFDFs) were studied using axisymmetric convergent-nozzle and straight-tube opposed jet burners (OJBs). The subject diagnostics were used to probe a systematic set of H2/N2-air CFDFs over wide ranges of fuel input (22 to 100% Ha), and input axial strain rate (130 to 1700 Us) just upstream of the airside edge, for both plug-flow and parabolic input velocity profiles. Laser Doppler Velocimetry (LDV) was applied along the centerline of seeded air flows from a convergent nozzle OJB (7.2 mm i.d.), and Particle Imaging Velocimetry (PIV) was applied on the entire airside of both nozzle and tube OJBs (7 and 5 mm i.d.) to characterize global velocity structure. Data are compared to numerical results from a one-dimensional (1-D) CFDF code based on a stream function solution for a potential flow input boundary condition. Axial strain rate inputs at the airside edge of nozzle-OJB flows, using LDV and PIV, were consistent with 1-D impingement theory, and supported earlier diagnostic studies. The LDV results also characterized a heat-release hump. Radial strain rates in the flame substantially exceeded 1-D numerical predictions. Whereas the 1-D model closely predicted the max I min axial velocity ratio in the hot layer, it overpredicted its thickness. The results also support previously measured effects of plug-flow and parabolic input strain rates on CFDF extinction limits. Finally, the submillimeter-scale LDV and PIV diagnostics were tested under severe conditions, which reinforced their use with subcentimeter OJB tools to assess effects of aerodynamic strain, and fueVair composition, on laminar CFDF properties, including extinction.

  4. Effect of Temperature on Jet Velocity Spectra

    NASA Technical Reports Server (NTRS)

    Bridges, James E.; Wernet, Mark P.

    2007-01-01

    Statistical jet noise prediction codes that accurately predict spectral directivity for both cold and hot jets are highly sought both in industry and academia. Their formulation, whether based upon manipulations of the Navier-Stokes equations or upon heuristic arguments, require substantial experimental observation of jet turbulence statistics. Unfortunately, the statistics of most interest involve the space-time correlation of flow quantities, especially velocity. Until the last 10 years, all turbulence statistics were made with single-point probes, such as hotwires or laser Doppler anemometry. Particle image velocimetry (PIV) brought many new insights with its ability to measure velocity fields over large regions of jets simultaneously; however, it could not measure velocity at rates higher than a few fields per second, making it unsuitable for obtaining temporal spectra and correlations. The development of time-resolved PIV, herein called TR-PIV, has removed this limitation, enabling measurement of velocity fields at high resolution in both space and time. In this paper, ground-breaking results from the application of TR-PIV to single-flow hot jets are used to explore the impact of heat on turbulent statistics of interest to jet noise models. First, a brief summary of validation studies is reported, undertaken to show that the new technique produces the same trusted results as hotwire at cold, low-speed jets. Second, velocity spectra from cold and hot jets are compared to see the effect of heat on the spectra. It is seen that heated jets possess 10 percent more turbulence intensity compared to the unheated jets with the same velocity. The spectral shapes, when normalized using Strouhal scaling, are insensitive to temperature if the stream-wise location is normalized relative to the potential core length. Similarly, second order velocity correlations, of interest in modeling of jet noise sources, are also insensitive to temperature as well.

  5. Robonaut 2 Humanoid Robot measures the air velocity in the U.S. Laboratory

    NASA Image and Video Library

    2012-03-14

    ISS030-E-142876 (14 March 2012) --- Controlled by teams on the ground, Robonaut 2 humanoid robot holds an instrument to measure air velocity during another system check out in the Destiny laboratory of the International Space Station.

  6. Robonaut 2 Humanoid Robot measures the air velocity in the U.S. Laboratory

    NASA Image and Video Library

    2012-03-14

    ISS030-E-142875 (14 March 2012) --- Controlled by teams on the ground, Robonaut 2 humanoid robot holds an instrument to measure air velocity during another system check out in the Destiny laboratory of the International Space Station.

  7. Cleansing technique using high-velocity steam-air micromist jet spray.

    PubMed

    Fukuda, Koichi; Ishihara, Masayuki; Murakami, Kaoru; Nakamura, Shingo; Sato, Yoko; Kuwabara, Masahiro; Fujita, Masanori; Kiyosawa, Tomoharu; Yokoe, Hidetaka

    2017-08-29

    Application of a high-velocity steam-air micromist jet spray (HVS-AMJS; micromist average diameter: 2.4 μm) for cleansing the skin is proposed. Low-pressure steam is mixed with compressed air (pH 6.5) in a nozzle, and then sprayed at a pressure of ≦0.25 MPa and a velocity of ≧0.34 m/s on the skin or surface of material located approximately 5-10 cm from the nozzle. The temperature on the sprayed surface and water flow rate could be controlled between 42 °C and 46 °C and at approximately 50 mL/min, respectively. Compared with ultrasonic cleansing with tap water and rubbing with only tap water, the HVS-AMJS successfully removed fluorescent lotion covering pieces of wood and significantly reduced both the number of coliforms and the total viable counts on pieces of wood and gauze. Furthermore, the HVS-AMJS effectively removed oily ink from the skin of hairless rats, and temporarily elevated the skin temperature and blood flow, indicating massage effects. The striking characteristics of this cleansing technique using HVS-AMJS are not only its ability to remove microbes and residue without using any chemicals or detergents but also its massage effects.

  8. A new test chamber to measure material emissions under controlled air velocity

    SciTech Connect

    Bortoli, M. de; Ghezzi, E.; Knoeppel, H.; Vissers, H.

    1999-05-15

    A new 20-L glass chamber for the determination of VOC emissions from construction materials and consumer products under controlled air velocity and turbulence is described. Profiles of air velocity and turbulence, obtained with precisely positioned hot wire anemometric probes, show that the velocity field is homogeneous and that air velocity is tightly controlled by the fan rotation speed; this overcomes the problem of selecting representative positions to measure air velocity above a test specimen. First tests on material emissions show that the influence of air velocity on the emission rate of VOCs is negligible for sources limited by internal diffusion and strong for sources limited by evaporation. In a velocity interval from 0.15 to 0.30 m s{sup {minus}1}, an emission rate increase of 50% has been observed for pure n-decane and 1,4-dichlorobenzene and of 30% for 1,2-propanediol from a water-based paint. In contrast, no measurable influence of turbulence could be observed during vaporization of 1,4-dichlorobenzene within a 3-fold turbulence interval. Investigations still underway show that the chamber has a high recovery for the heavier VOC (TXIB), even at low concentrations.

  9. Assessment of air velocity sensors for use in animal produciton facilities

    USDA-ARS?s Scientific Manuscript database

    Ventilation is an integral part of thermal environment control in animal production facilities. Accurately measuring the air velocity distribution within these facilities is cumbersome using the traverse method and a distributed velocity measurement system would reduce the time necessary to perform ...

  10. Simultaneous Measurement of Air Temperature and Humidity Based on Sound Velocity and Attenuation Using Ultrasonic Probe

    NASA Astrophysics Data System (ADS)

    Motegi, Takahiro; Mizutani, Koichi; Wakatsuki, Naoto

    2013-07-01

    In this paper, an acoustic technique for air temperature and humidity measurement in moist air is described. The previous ultrasonic probe can enable the estimation of temperature from sound velocity in dry air by making use of the relationship between sound velocity and temperature. However, temperature measurement using the previous ultrasonic probe is not suitable in moist air because sound velocity also depends on humidity, and the temperature estimated from the sound velocity measured in moist air must be adjusted. Moreover, a method of humidity measurement by using only an ultrasonic probe has not been established. Thus, we focus on sound attenuation, which depends on temperature and humidity. Our proposed technique utilizes two parameters, sound velocity and attenuation, and can measure both temperature and humidity simultaneously. The acoustic technique for temperature and humidity measurement has the advantages that instantaneous temperature and humidity can be measured, and the measurement is not affected by thermal radiation because air itself is used as a sensing element. As an experiment, temperature and humidity are measured in a chamber, and compared with the reference values. The experimental results indicate the achievement of a practical temperature measurement accuracy of within +/-0.5 K in moist air, of which the temperature is 293-308 K and relative humidity (RH) is 50-90% RH, and the simultaneous measurement of temperature and humidity.

  11. Dynamics of Air Temperature, Velocity and Ammonia Emissions in Enclosed and Conventional Pig Housing Systems

    PubMed Central

    Song, J. I.; Park, K.-H.; Jeon, J. H.; Choi, H. L.; Barroga, A. J.

    2013-01-01

    This study aimed to compare the dynamics of air temperature and velocity under two different ventilation and housing systems during summer and winter in Korea. The NH3 concentration of both housing systems was also investigated in relation to the pig’s growth. The ventilation systems used were; negative pressure type for the enclosed pig house (EPH) and natural airflow for the conventional pig house (CPH). Against a highly fluctuating outdoor temperature, the EPH was able to maintain a stable temperature at 24.8 to 29.1°C during summer and 17.9 to 23.1°C during winter whilst the CPH had a wider temperature variance during summer at 24.7 to 32.3°C. However, the temperature fluctuation of the CPH during winter was almost the same with that of EPH at 14.5 to 18.2°C. The NH3 levels in the CPH ranged from 9.31 to 16.9 mg/L during summer and 5.1 to 19.7 mg/L during winter whilst that of the EPH pig house was 7.9 to 16.1 mg/L and 3.7 to 9.6 mg/L during summer and winter, respectively. These values were less than the critical ammonia level for pigs with the EPH maintaining a lower level than the CPH in both winter and summer. The air velocity at pig nose level in the EPH during summer was 0.23 m/s, enough to provide comfort because of the unique design of the inlet feature. However, no air movement was observed in almost all the lower portions of the CPH during winter because of the absence of an inlet feature. There was a significant improvement in weight gain and feed intake of pigs reared in the EPH compared to the CPH (p<0.05). These findings proved that despite the difference in the housing systems, a stable indoor temperature was necessary to minimize the impact of an avoidable and highly fluctuating outdoor temperature. The EPH consistently maintained an effective indoor airspeed irrespective of season; however the CPH had defective and stagnant air at pig nose level during winter. Characteristics of airflow direction and pattern were consistent relative to

  12. Dynamics of air temperature, velocity and ammonia emissions in enclosed and conventional pig housing systems.

    PubMed

    Song, J I; Park, K-H; Jeon, J H; Choi, H L; Barroga, A J

    2013-03-01

    This study aimed to compare the dynamics of air temperature and velocity under two different ventilation and housing systems during summer and winter in Korea. The NH3 concentration of both housing systems was also investigated in relation to the pig's growth. The ventilation systems used were; negative pressure type for the enclosed pig house (EPH) and natural airflow for the conventional pig house (CPH). Against a highly fluctuating outdoor temperature, the EPH was able to maintain a stable temperature at 24.8 to 29.1°C during summer and 17.9 to 23.1°C during winter whilst the CPH had a wider temperature variance during summer at 24.7 to 32.3°C. However, the temperature fluctuation of the CPH during winter was almost the same with that of EPH at 14.5 to 18.2°C. The NH3 levels in the CPH ranged from 9.31 to 16.9 mg/L during summer and 5.1 to 19.7 mg/L during winter whilst that of the EPH pig house was 7.9 to 16.1 mg/L and 3.7 to 9.6 mg/L during summer and winter, respectively. These values were less than the critical ammonia level for pigs with the EPH maintaining a lower level than the CPH in both winter and summer. The air velocity at pig nose level in the EPH during summer was 0.23 m/s, enough to provide comfort because of the unique design of the inlet feature. However, no air movement was observed in almost all the lower portions of the CPH during winter because of the absence of an inlet feature. There was a significant improvement in weight gain and feed intake of pigs reared in the EPH compared to the CPH (p<0.05). These findings proved that despite the difference in the housing systems, a stable indoor temperature was necessary to minimize the impact of an avoidable and highly fluctuating outdoor temperature. The EPH consistently maintained an effective indoor airspeed irrespective of season; however the CPH had defective and stagnant air at pig nose level during winter. Characteristics of airflow direction and pattern were consistent relative to

  13. Robonaut measures air velocity in the U.S. Laboratory

    NASA Image and Video Library

    2012-03-14

    ISS030-E-177178 (14 March 2012) --- Robonaut 2 – the first dexterous humanoid robot in space – is pictured in the Destiny laboratory of the International Space Station measuring the air flow in front of vents inside the station to ensure that none of the ventilation ductwork gets clogged or blocked.

  14. Calculation and measurement of a neutral air flow velocity impacting a high voltage capacitor with asymmetrical electrodes

    SciTech Connect

    Malík, M. Primas, J.; Kopecký, V.; Svoboda, M.

    2014-01-15

    This paper deals with the effects surrounding phenomenon of a mechanical force generated on a high voltage asymmetrical capacitor (the so called Biefeld-Brown effect). A method to measure this force is described and a formula to calculate its value is also given. Based on this the authors derive a formula characterising the neutral air flow velocity impacting an asymmetrical capacitor connected to high voltage. This air flow under normal circumstances lessens the generated force. In the following part this velocity is measured using Particle Image Velocimetry measuring technique and the results of the theoretically calculated velocity and the experimentally measured value are compared. The authors found a good agreement between the results of both approaches.

  15. Effects of horizontal velocity variations on ultrasonic velocity measurements in open channels

    USGS Publications Warehouse

    Swain, E.D.

    1992-01-01

    Use of an ultrasonic velocity meter to determine discharge in open channels involves measuring the velocity in a line between transducers in the stream and relating that velocity to the average velocity in the stream. The standard method of calculating average velocity in the channel assumes that the velocity profile in the channel can be represented by the one-dimensional von Karman universal velocity profile. However, the velocity profile can be described by a two-dimensional equation that accounts for the horizontal velocity variations induced by the channel sides. An equation to calculate average velocity accounts for the two-dimensional variations in velocity within a stream. The use of this new equation to calculate average velocity was compared to the standard method in theoretical trapezoidal cross sections and in the L-31N and Snapper Creek Extension Canals near Miami, Florida. These comparisons indicate that the two-dimensional variations have the most significant effect in narrow, deep channels. Also, the two-dimensional effects may be significant in some field situations and need to be considered when determining average velocity and discharge with an ultrasonic velocity meter.

  16. Design of passively aerated compost piles: Vertical air velocities between the pipes

    SciTech Connect

    Lynch, N.J.; Cherry, R.S.

    1996-09-01

    Passively aerated compost piles are built on a base of porous materials, such as straw or wood chips, in which perforated air supply pipes are distributed. The piles are not turned during composting, nor is forced-aeration equipment used, which significantly reduces the operating and capital expenses associated with these piles. Currently, pile configurations and materials are worked out by trial and error. Fundamentally based design procedures are difficult to develop because the natural convection air flow rate is not explicitly known, but rather is closely coupled with the pile temperature. This paper develops a mathematical model to analytically determine the maximum upward air flow velocity over an air supply pipe and the drop in vertical velocity away from the pipe. This model has one dimensionless number, dependent on the pile and base properties, which fully characterizes the velocity profile between the pipes. 9 refs., 4 figs., 1 tab.

  17. Wartime Distribution Operations: Roles of Focused Logistics, Velocity Management, Strategic Distribution Policy and Air Clearance Policy

    DTIC Science & Technology

    2004-03-19

    EFFECTIVE AND EFFICIENT ..................................................1 VELOCITY MANAGEMENT – DEFINITION AND HISTORY...achieve immediate improvements. This effort resulted in the Army adopting VM. VELOCITY MANAGEMENT – DEFINITION AND HISTORY Beginning in 1995, the Army

  18. Experimental analysis of the velocity field of the air flowing through the swirl diffusers

    NASA Astrophysics Data System (ADS)

    Jaszczur, M.; Branny, M.; Karch, M.; Borowski, M.

    2016-09-01

    The article presents the results of experimental studies of flow of air through diffusers. Presented laboratory model is a simplification of the real system and was made in a geometric scale 1:10. Simplifying refer both to the geometry of the object and conditions of air flow. The aim of the study is to determine the actual velocity fields of air flowing out of the swirl diffuser. The results obtained for the diffuser various settings are presented. We have tested various flow rates of air. Stereo Particle Image Velocimetry (SPIV) method was used to measure all velocity vector components. The experimental results allow to determine the actual penetration depth of the supply air into the room. This will allow for better definition of the conditions of ventilation in buildings.

  19. Cosmology with peculiar velocities: observational effects

    NASA Astrophysics Data System (ADS)

    Andersen, P.; Davis, T. M.; Howlett, C.

    2016-12-01

    In this paper we investigate how observational effects could possibly bias cosmological inferences from peculiar velocity measurements. Specifically, we look at how bulk flow measurements are compared with theoretical predictions. Usually bulk flow calculations try to approximate the flow that would occur in a sphere around the observer. Using the Horizon Run 2 simulation we show that the traditional methods for bulk flow estimation can overestimate the magnitude of the bulk flow for two reasons: when the survey geometry is not spherical (the data do not cover the whole sky), and when the observations undersample the velocity distributions. Our results may explain why several bulk flow measurements found bulk flow velocities that seem larger than those expected in standard Λ cold dark matter cosmologies. We recommend a different approach when comparing bulk flows to cosmological models, in which the theoretical prediction for each bulk flow measurement is calculated specifically for the geometry and sampling rate of that survey. This means that bulk flow values will not be comparable between surveys, but instead they are comparable with cosmological models, which is the more important measure.

  20. Inert gas influence on the laminar burning velocity of methane-air mixtures.

    PubMed

    Mitu, Maria; Giurcan, Venera; Razus, Domnina; Oancea, Dumitru

    2017-01-05

    Flame propagation was studied in methane-air-inert (He, Ar, N2 or CO2) mixtures with various initial pressures and compositions using pressure-time records obtained in a spherical vessel with central ignition. The laminar burning velocities of CH4-air and CH4-air-inert mixtures obtained from experimental p(t) records of the early stage of combustion were compared with literature data and with those obtained from numerical modeling of 1D flames. The overall reaction orders of methane oxidation were determined from the baric coefficients of the laminar burning velocities determined from power-law equations. For all mixtures, the adiabatic flames temperatures were computed, assuming that the chemical equilibrium is reached in the flame front. The overall activation energy for the propagation stage of the combustion process was determined from the temperature dependence of the laminar burning velocity.

  1. Spatial Characteristics of Water Spray Formed by Two Impinging Jets at Several Jet Velocities in Quiescent Air

    NASA Technical Reports Server (NTRS)

    Foster, Hampton H.; Heidmann, Marcus F.

    1960-01-01

    The spatial characteristics of a spray formed by two impinging water jets in quiescent air were studied over a range of nominal jet velocities of 30 to 74 feet per second. The total included angle between the 0.089-inch jets was 90 deg. The jet velocity, spray velocity, disappearance of the ligaments just before drop formation, mass distribution, and size and position of the largest drops were measured in a circumferential survey around the point of jet impingement. Photographic techniques were used in the evaluations. The distance from the point of jet impingement to ligament breakup into drops was about 4 inches on the spray axis and about 1.3 inches in the radial position +/-90 deg from the axis. The distance tended to increase slightly with increase in jet velocity. The spray velocity varied from about 99 to about 72 percent of the jet velocity for a change in circumferential position from the spray axis to the +/-80 deg positions. The percentages tended to increase slightly with an increase in jet velocity. Fifty percent of the mass was distributed about the spray axis in an included angle of slightly less than 40 deg. The effect of jet velocity was small. The largest observed drops (2260-micron or 0.090-in. diam.) were found on and about the spray axis. The size of the largest drops decreased for an increase in radial angular position, being about 1860 microns (0.074 in.) at the +/-90 deg positions. The largest drop sizes tended to decrease for an increase in jet velocity, although the velocity effect was small. A drop-size distribution analysis indicated a mass mean drop size equal to 54 percent of an extrapolated maximum drop size.

  2. Measurement of temperature and velocity fields in a convective fluid flow in air using schlieren images.

    PubMed

    Martínez-González, A; Moreno-Hernández, D; Guerrero-Viramontes, J A

    2013-08-01

    A convective fluid flow in air could be regulated if the physical process were better understood. Temperature and velocity measurements are required in order to obtain a proper characterization of a convective fluid flow. In this study, we show that a classical schlieren system can be used for simultaneous measurements of temperature and velocity in a convective fluid flow in air. The schlieren technique allows measurement of the average fluid temperature and velocity integrated in the direction of the test beam. Therefore, in our experiments we considered surfaces with isothermal conditions. Temperature measurements are made by relating the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the schlieren system. The same schlieren images were also used to measure the velocity of the fluid flow by using optical flow techniques. The algorithm implemented analyzes motion between consecutive schlieren frames to obtain a tracked sequence and finally velocity fields. The proposed technique was applied to measure the temperature and velocity fields in natural convection of air due to unconfined and confined heated rectangular plates.

  3. Analysis of possible improvement of acceleration of a high-velocity air-breathing flying vehicle

    NASA Astrophysics Data System (ADS)

    Goonko, Yu. P.; Mazhul, I. I.

    2008-09-01

    Results of parametric calculations of the total aeropropulsive characteristics and characteristics of acceleration of a small-scale high-velocity flying vehicle with an air-breathing engine are presented. Integral parameters of acceleration from the flight Mach number M∞ = 4 to M∞ = 7 are determined, namely, the time required fuel stock, and range. A schematic configuration of the vehicle is considered, which allows studying the basic parameters, such as the forebody shape, the angles of surfaces of compression of the stream captured by the inlet, angles of external aerodynamic surfaces of the airframe, relative planform area of the wing panels, and relative area of the nozzle cross section. A comparative estimate of the effect of these parameters shows that it is possible to improve the characteristics of acceleration of vehicles of the type considered.

  4. Multiple mechanisms generate a universal scaling with dissipation for the air-water gas transfer velocity

    NASA Astrophysics Data System (ADS)

    Katul, Gabriel; Liu, Heping

    2017-02-01

    A large corpus of field and laboratory experiments support the finding that the water side transfer velocity kL of sparingly soluble gases near air-water interfaces scales as kL˜(νɛ)1/4, where ν is the kinematic water viscosity and ɛ is the mean turbulent kinetic energy dissipation rate. Originally predicted from surface renewal theory, this scaling appears to hold for marine and coastal systems and across many environmental conditions. It is shown that multiple approaches to representing the effects of turbulence on kL lead to this expression when the Kolmogorov microscale is assumed to be the most efficient transporting eddy near the interface. The approaches considered range from simplified surface renewal schemes with distinct models for renewal durations, scaling and dimensional considerations, and a new structure function approach derived using analogies between scalar and momentum transfer. The work offers a new perspective as to why the aforementioned 1/4 scaling is robust.

  5. Experimental study of the development and structure of high-velocity liquid jets in air

    NASA Astrophysics Data System (ADS)

    Baev, V. K.; Bazhaikin, A. N.; Buzukov, A. A.; Timoshenko, B. P.; Bichenko, E. I.

    The dynamics of unsteady high-velocity liquid jets injected into air were studied by methods of high-speed cinematography, roentgenography, microphotography using pulsed lasers, and pulsed X-rays. It has been shown that in a jet with a positive longitudinal velocity gradient, a hydrodynamical instability develops, resulting in the appearance of density inhomogeneity. The concentration of liquid components along the jet differs by an order of magnitude. The compression and rarefaction waves affecting the jet structure and the flow pattern at its different sections may propagate along the jet. A cumulative type flow develops at the head of the high-velocity jet in a gaseous medium.

  6. Passive acoustic measurements of wind velocity and sound speed in air.

    PubMed

    Godin, Oleg A; Irisov, Vladimir G; Charnotskii, Mikhail I

    2014-02-01

    Random acoustic fields generated by uncorrelated sources in moving media contain information about the propagation environment, including sound speed and flow velocity. This information can be recovered by noise interferometry. Here interferometric techniques are applied to road traffic noise. Acoustic travel times and their nonreciprocity are retrieved from two-point cross-correlation functions of noise. The feasibility of passive acoustic measurements of wind velocity using diffuse noise is experimentally demonstrated for the first time. The accuracy of the interferometric measurements of sound speed and wind velocity is confirmed by comparison with in situ measurements of wind, air temperature, and humidity.

  7. Retrieval of Air Vertical Velocity in Convective Clouds over the Tibetan Plateau by Ka-band Cloud Radar

    NASA Astrophysics Data System (ADS)

    Zheng, J.; Liu, L.

    2016-12-01

    Convective clouds over the Tibetan Plateau (TP) have great influences on the weather and climate of China and East Asia. Deriving air vertical motion can help us understand the cloud dynamic and microphysical processes, and provide dynamic parameters for numerical model. Since Chinese scientists launched the 3rd Tibetan Plateau Meteorological Science Experiment in 2013, Chinese Academy of Meteorological Sciences had deployed several ground-based active remote sensing instruments at eastern TP (31°28' N, 92°03' E). As critical equipment, a vertical incident Ka-band cloud radar designed with solid-state transmitter and multiple observation modes is used to detect the overhead cloud systems. In an attempt to accurately map the time-height structure of the air vertical motion, this manuscript develops an improved method for the retrieval of air vertical velocity from cloud radar Doppler spectra based on previous scientists' work. The highlights of this paper mainly involve data quality control of Doppler spectra and retrieval algorithm design using multiple-mode measurements. Cases analysis of weak Cu, moderate Cb and light convective precipitation demonstrate that the retrievals are reliable, updrafts are beneficial to the cloud development and correlative with the increase of reflectivity factor and spectrum width. As general phenomenon on TP, updrafts in cloud are relatively weak before noon, but apparently increased in the afternoon as a result of ground thermodynamic effect. The maximum air vertical velocity could be up to 15 m/s in convective systems with a strong updraft core in the middle and two strong downdrafts on both sides. The inversion results of air vertical velocity are proved to be quite accurate with an acceptable uncertainty by using a theoretical method. Key Word Cloud radar, air vertical velocity, retrieval method

  8. Laminar Flame Velocity and Temperature Exponent of Diluted DME-Air Mixture

    NASA Astrophysics Data System (ADS)

    Naseer Mohammed, Abdul; Anwar, Muzammil; Juhany, Khalid A.; Mohammad, Akram

    2017-03-01

    In this paper, the laminar flame velocity and temperature exponent diluted dimethyl ether (DME) air mixtures are reported. Laminar premixed mixture of DME-air with volumetric dilutions of carbon dioxides (CO2) and nitrogen (N2) are considered. Experiments were conducted using a preheated mesoscale high aspect-ratio diverging channel with inlet dimensions of 25 mm × 2 mm. In this method, flame velocities are extracted from planar flames that were stabilized near adiabatic conditions inside the channel. The flame velocities are then plotted against the ratio of mixture temperature and the initial reference temperature. A non-linear power law regression is observed suitable. This regression analysis gives the laminar flame velocity at the initial reference temperature and temperature exponent. Decrease in the laminar flame velocity and increase in temperature exponent is observed for CO2 and N2 diluted mixtures. The addition of CO2 has profound influence when compared to N2 addition on both flame velocity and temperature exponent. Numerical prediction of the similar mixture using a detailed reaction mechanism is obtained. The computational mechanism predicts higher magnitudes for laminar flame velocity and smaller magnitudes of temperature exponent compared to experimental data.

  9. Step-Wise Velocity of an Air Bubble Rising in a Vertical Tube Filled with a Liquid Dispersion of Nanoparticles.

    PubMed

    Cho, Heon Ki; Nikolov, Alex D; Wasan, Darsh T

    2017-03-21

    The motion of air bubbles in tubes filled with aqueous suspensions of nanoparticles (nanofluids) is of practical interest for bubble jets, lab-on-a-chip, and transporting media. Therefore, the focus of this study is the dynamics of air bubbles rising in a tube in a nanofluid. Many authors experimentally and analytically proposed that the velocity of rising air bubbles is constant for long air bubbles suspended in a vertical tube in common liquids (e.g. an aqueous glycerol solution) when the capillary number is larger than 10(-4). For the first time, we report here a systematic study of an air bubble rising in a vertical tube in a nanofluid (e.g. an aqueous silica dioxide nanoparticle suspension, nominal particle size, 19 nm). We varied the bubble length scaled by the diameter of the tubes (L/D), the concentration of the nanofluid (10 and 12.5 v %), and the tube diameter (0.45, 0.47, and 0.50 cm). The presence of the nanoparticles creates a significant change in the bubble velocity compared with the bubble rising in the common liquid with the same bulk viscosity. We observed a novel phenomenon of a step-wise increase in the air bubble rising velocity versus bubble length for small capillary numbers less than 10(-7). This step-wise velocity increase versus the bubble length was not observed in a common fluid. The step-wise velocity increase is attributed to the nanoparticle self-layering phenomenon in the film adjacent to the tube wall. To elucidate the role of the nanoparticle film self-layering on the bubble rising velocity, the effect of the capillary number, the tube diameter (e.g. the capillary pressure), and nanofilm viscosity are investigated. We propose a model that takes into consideration the nanoparticle layering in the film confinement to explain the step-wise velocity phenomenon versus the length of the bubble. The oscillatory film interaction energy isotherm is calculated and the Frenkel approach is used to estimate the film viscosity.

  10. High contrast air-coupled acoustic imaging with zero group velocity lamb modes.

    PubMed

    Holland, Stephen D; Chimenti, D E

    2004-04-01

    The well known zero in the group velocity of the first-order symmetric (S1) plate wave mode has been exploited in air-coupled ultrasonic imaging to obtain significantly higher sensitivity than can be achieved in conventional air-coupled scanning. At the zero group velocity point at the frequency minimum of the S1 mode, a broad range of wavenumbers couple into the first-order symmetric mode at nearly a constant frequency, greatly enhancing transmission at that frequency. Coupled energy remains localized near the coupling point because the group velocity is zero. We excite the mode with a broadband, focussing, air-coupled transducer at the frequency of the zero group velocity point in the S1 mode. By exploiting the efficient coupling at the zero group velocity frequency, we have easily imaged a single layer of Scotch tape attached to a 6.4-mm thick Plexiglas plate and 3.2-mm Teflon inserts in a composite laminate.

  11. Measurement of the Group Velocity Dispersion of air using a femtosecond comb

    NASA Astrophysics Data System (ADS)

    Al salamah, Reem

    In this thesis, the Group Velocity Dispersion (GVD) of air has been measured by using a femtosecond frequency comb at 1.5 microm. By comparing the spectra from a balanced and unbalanced Mach - Zehnder interferometer, the need for vacuum tube is eliminated. The method employs the Fast Fourier Transform of both auto- and cross correlation to find the spectral and their differences. The GVD of air is then calculated from these spectral phase differences. With twenty-five independent measurements, the GVD of air was found to be 0.0120 fs2/mm, with a standard deviation of 0.0075 fs2/mm.

  12. A multi-channel, low velocity, hot film anemometry system for measuring air flows in buildings

    SciTech Connect

    Guire, J.L.

    1987-01-01

    A complete analytical and experimental development of a multichannel anemometry system is presented. The system consists of an array of low velocity sensors (0.0 m/s to 1.0 m/s), a constant current power supply, and the required data acquisition equipment. The velocity sensors can be scanned simultaneously yielding absolute air velocities and absolute ambient air temperatures at each of the probe positions in the array. One of the key results that this system can produce is the relationship between boundary layer flow and pressure driven flow through a large irregular aperture, such as a doorway, which up until now has been difficult to accomplish with regard to cost and experimental error incurred. 7 refs., 57 figs.

  13. New sensor for measurement of low air flow velocity. Phase I final report

    SciTech Connect

    Hashemian, H.M.; Hashemian, M.; Riggsbee, E.T.

    1995-08-01

    The project described here is the Phase I feasibility study of a two-phase program to integrate existing technologies to provide a system for determining air flow velocity and direction in radiation work areas. Basically, a low air flow sensor referred to as a thermocouple flow sensor has been developed. The sensor uses a thermocouple as its sensing element. The response time of the thermocouple is measured using an existing in-situ method called the Loop Current Step Response (LCSR) test. The response time results are then converted to a flow signal using a response time-versus-flow correlation. The Phase I effort has shown that a strong correlation exists between the response time of small diameter thermocouples and the ambient flow rate. As such, it has been demonstrated that thermocouple flow sensors can be used successfully to measure low air flow rates that can not be measured with conventional flow sensors. While the thermocouple flow sensor developed in this project was very successful in determining air flow velocity, determining air flow direction was beyond the scope of the Phase I project. Nevertheless, work was performed during Phase I to determine how the new flow sensor can be used to determine the direction, as well as the velocity, of ambient air movements. Basically, it is necessary to use either multiple flow sensors or move a single sensor in the monitoring area and make flow measurements at various locations sweeping the area from top to bottom and from left to right. The results can then be used with empirical or physical models, or in terms of directional vectors to estimate air flow patterns. The measurements can be made continuously or periodically to update the flow patterns as they change when people and objects are moved in the monitoring area. The potential for using multiple thermocouple flow sensors for determining air flow patterns will be examined in Phase II.

  14. Performance of a Compression-ignition Engine with a Precombustion Chamber Having High-Velocity Air Flow

    NASA Technical Reports Server (NTRS)

    Spanogle, J A; Moore, C S

    1931-01-01

    Presented here are the results of performance tests made with a single-cylinder, four stroke cycle, compression-ignition engine. These tests were made on a precombustion chamber type of cylinder head designed to have air velocity and tangential air flow in both the chamber and cylinder. The performance was investigated for variable load and engine speed, type of fuel spray, valve opening pressure, injection period and, for the spherical chamber, position of the injection spray relative to the air flow. The pressure variations between the pear-shaped precombustion chamber and the cylinder for motoring and full load conditions were determined with a Farnboro electric indicator. The combustion chamber designs tested gave good mixing of a single compact fuel spray with the air, but did not control the ensuing combustion sufficiently. Relative to each other, the velocity of air flow was too high, the spray dispersion by injection too great, and the metering effect of the cylinder head passage insufficient. The correct relation of these factors is of the utmost importance for engine performance.

  15. The influence of bubble plumes on air-seawater gas transfer velocities

    SciTech Connect

    Asher, W.E.; Karle, L.M.; Higgins, B.J.

    1995-07-01

    Air-sea gas exchange is an important process in the geochemical cycling of carbon dioxide (CO{sub 2}). The air-sea flux of CO{sub 2} is determined in part by the physical forcing functions, which are parameterized in terms of the air-sea transfer velocity, k{sub L}. Past studies have attempted to correlate k{sub L} with wind speed, U. Because strong winds occur in ocean regions thought to be important sources or sinks of CO{sub 2}, accurate knowledge of k{sub L} at high U is important in estimating the global air-sea flux of CO{sub 2}. Better understanding of the physical processes affecting gas transfer at large U will increase the accuracy in estimating k{sub L} in ocean regions with high CO{sub 2}, fluxes. Increased accuracy in estimating k{sub L} will increase the accuracy in calculating the net global air-sea CO{sub 2} flux and provide more accurate boundary and initial conditions for global ocean carbon cycle models. High wind speeds are associated with the presence of whitecaps, which can increase the gas flux by generating turbulence, disrupting surface films, and creating bubble plumes. Bubble plumes will create additional turbulence, prolong the surface disruption, and transfer gas to or from individual bubbles while they are beneath the surface. These turbulence and bubble processes very effectively promote gas transfer. Because of this, it is postulated that breaking waves, if present, will dominate non-whitecap related gas exchange. Under this assumption, k{sub L} Will increase linearly with increasing fractional area whitecap coverage, W{sub c}. In support of this, researchers found k{sub L} measured in a whitecap simulation tank (WSI) was linearly correlated with bubble plume coverage, B{sub c} (the laboratory analog of W{sub c}). However, it is not definitively known how the presence of breaking waves and bubble plumes affect the dependence of k{sub L} on Schmidt number, Sc, and aqueous-phase solubility, {alpha}.

  16. Sensory and chemical characterization of VOC emissions from building products: impact of concentration and air velocity

    NASA Astrophysics Data System (ADS)

    Knudsen, H. N.; Kjaer, U. D.; Nielsen, P. A.; Wolkoff, P.

    The emissions from five commonly used building products were studied in small-scale test chambers over a period of 50 days. The odor intensity was assessed by a sensory panel and the concentrations of selected volatile organic compounds (VOCs) of concern for the indoor air quality were measured. The building products were three floor coverings: PVC, floor varnish on beechwood parquet and nylon carpet on a latex foam backing; an acrylic sealant, and a waterborne wall paint on gypsum board. The impacts of the VOC concentration in the air and the air velocity over the building products on the odor intensity and on the emission rate of VOCs were studied. The emission from each building product was studied under two or three different area-specific ventilation rates, i.e. different ratios of ventilation rate of the test chamber and building product area in the test chamber. The air velocity over the building product samples was adjusted to different levels between 0.1 and 0.3 m s -1. The origin of the emitted VOCs was assessed in order to distinguish between primary and secondary emissions. The results show that it is reasonable after an initial period of up to 14 days to consider the emission rate of VOCs of primary origin from most building products as being independent of the concentration and of the air velocity. However, if the building product surface is sensitive to oxidative degradation, increased air velocity may result in increased secondary emissions. The odor intensity of the emissions from the building products only decayed modestly over time. Consequently, it is recommended to use building products which have a low impact on the perceived air quality from the moment they are applied. The odor indices (i.e. concentration divided by odor threshold) of primary VOCs decayed markedly faster than the corresponding odor intensities. This indicates that the secondary emissions rather than the primary emissions, are likely to affect the perceived air quality in the

  17. ADL ORVIS: An air-delay-leg, line-imaging optically recording velocity interferometer system

    NASA Astrophysics Data System (ADS)

    Trott, Wayne M.; Castañeda, Jaime N.; Cooper, Marcia A.

    2014-04-01

    An interferometry system that enables acquisition of spatially resolved velocity-time profiles with very high velocity sensitivity has been designed and applied to two diverse, instructive experimental problems: (1) measurement of low-amplitude reverberations in laser-driven flyer plates and (2) measurement of ramp-wave profiles in symmetric impact studies of fused silica. The delay leg in this version of a line-imaging optically recording velocity interferometer system (ORVIS) consists of a long air path that includes relay optics to transmit the optical signal through the interferometer cavity. Target image quality from the delay path at the image recombination plane is preserved by means of a compact and flexible optical design utilizing two parabolic reflectors (serving as the relay optics) in a folded path. With an instrument tuned to a velocity per fringe constant of 22.4 m s-1 fringe-1, differences of 1-2 m s-1 across the probe line segment can be readily distinguished. Measurements that capture small spatial variations in flyer velocity are presented and briefly discussed. In the fused silica impact experiments, the ramp-wave profile observed by this air-delay instrument compares favorably to the profile recorded simultaneously by a conventional line-imaging ORVIS.

  18. Impact of air velocity on the development and detection of small coal fires. Report of investigations/1993

    SciTech Connect

    Egan, M.R.

    1993-01-01

    The U.S. Bureau of Mines conducted experiments in the intermediate-scale fire tunnel to assess the influence of air velocity on the gas production and smoke characteristics during smoldering and flaming combustion of Pittsburgh seam coal and its impact on the detection of the combustion products. On-line determinations of mass and number of smoke particles, light transmission, and various gas concentrations were made. From these experimental values, generation rates, heat-release rates, production constants, particle sizes, obscuration rates, and optical densities were calculated. Ventilation has a direct effect on fire detection and development. The results indicate that, in general, increased air velocity lengthened the onset of smoke and flaming ignition, increased the fire intensity, but decreased the gas and smoke concentrations. Increased air velocity also lengthened the response times of all the fire sensors tested. Rapid and reliable detector response at this most crucial state of fire development can increase the possibility that appropriate miner response (fire suppression tactics or evacuation) can be completed before toxic smoke spreads throughout the mine.

  19. Increased Air Velocity Reduces Thermal and Cardiovascular Strain in Young and Older Males during Humid Exertional Heat Stress.

    PubMed

    Wright Beatty, Heather E; Hardcastle, Stephen G; Boulay, Pierre; Flouris, Andreas D; Kenny, Glen P

    2015-01-01

    Older adults have been reported to have a lower evaporative heat loss capacity than younger adults during exercise when full sweat evaporation is permitted. However, it is unclear how conditions of restricted evaporative and convective heat loss (i.e., high humidity, clothing insulation) alter heat stress. to the purpose of this study was to examine the heat stress responses of young and older males during and following exercise in a warm/humid environment under two different levels of air velocity. Ten young (YOUNG: 24±2 yr) and 10 older (OLDER: 59±3 yr) males, matched for body surface area performed 4×15-min cycling bouts (15-min rest) at a fixed rate of heat production (400 W) in warm/humid conditions (35°C, 60% relative humidity) under 0.5 (Low) and 3.0 (High) m·s(-1) air velocity while wearing work coveralls. Rectal (Tre) and mean skin (MTsk) temperatures, heart rate (HR), local sweat rate, % max skin blood flow (SkBF) (recovery only), and blood pressure (recovery only) were measured. High air velocity reduced core and skin temperatures (p < 0.05) equally in YOUNG and OLDER males (p > 0.05) but was more effective in reducing cardiovascular strain (absolute and % max HR; p < 0.05) in YOUNG males (p < 0.05). Greater increases in local dry heat loss responses (% max SkBF and cutaneous vascular conductance) were detected across time in OLDER than YOUNG males in both conditions (p < 0.05). Local dry heat loss responses and cardiovascular strain were attenuated during the High condition in YOUNG compared to OLDER (p < 0.05). High air velocity reduced the number of males surpassing the 38.0°C Tre threshold from 90% (Low) to 50% (High). Despite age-related local heat loss differences, YOUNG and OLDER males had similar levels of heat stress during intermittent exercise in warm and humid conditions while wearing work coveralls. Increased air velocity was effective in reducing heat stress equally, and cardiovascular strain to a greater extent, in YOUNG and OLDER

  20. Measurements of Flat-Flame Velocities of Diethyl Ether in Air

    PubMed Central

    Gillespie, Fiona; Metcalfe, Wayne K.; Dirrenberger, Patricia; Herbinet, Olivier; Glaude, Pierre-Alexandre; Battin-Leclerc, Frédérique; Curran, Henry J.

    2013-01-01

    This study presents new adiabatic laminar burning velocities of diethyl ether in air, measured on a flat-flame burner using the heat flux method. The experimental pressure was 1 atm and temperatures of the fresh gas mixture ranged from 298 to 398 K. Flame velocities were recorded at equivalence ratios from 0.55 to 1.60, for which stabilization of the flame was possible. The maximum laminar burning velocity was found at an equivalence ratio of 1.10 or 1.15 at different temperatures. These results are compared with experimental and computational data reported in the literature. The data reported in this study deviate significantly from previous experimental results and are well-predicted by a previously reported chemical kinetic mechanism. PMID:23710107

  1. An Empirical Model of Human Aspiration in Low-Velocity Air Using CFD Investigations

    PubMed Central

    Anthony, T. Renée; Anderson, Kimberly R.

    2016-01-01

    Computational fluid dynamics (CFD) modeling was performed to investigate the aspiration efficiency of the human head in low velocities to examine whether the current inhaled particulate mass (IPM) sampling criterion matches the aspiration efficiency of an inhaling human in airflows common to worker exposures. Data from both mouth and nose inhalation, averaged to assess omnidirectional aspiration efficiencies, were compiled and used to generate a unifying model to relate particle size to aspiration efficiency of the human head. Multiple linear regression was used to generate an empirical model to estimate human aspiration efficiency and included particle size as well as breathing and freestream velocities as dependent variables. A new set of simulated mouth and nose breathing aspiration efficiencies was generated and used to test the fit of empirical models. Further, empirical relationships between test conditions and CFD estimates of aspiration were compared to experimental data from mannequin studies, including both calm-air and ultra-low velocity experiments. While a linear relationship between particle size and aspiration is reported in calm air studies, the CFD simulations identified a more reasonable fit using the square of particle aerodynamic diameter, which better addressed the shape of the efficiency curve’s decline toward zero for large particles. The ultimate goal of this work was to develop an empirical model that incorporates real-world variations in critical factors associated with particle aspiration to inform low-velocity modifications to the inhalable particle sampling criterion. PMID:25438035

  2. An empirical model of human aspiration in low-velocity air using CFD investigations.

    PubMed

    Anthony, T Renée; Anderson, Kimberly R

    2015-01-01

    Computational fluid dynamics (CFD) modeling was performed to investigate the aspiration efficiency of the human head in low velocities to examine whether the current inhaled particulate mass (IPM) sampling criterion matches the aspiration efficiency of an inhaling human in airflows common to worker exposures. Data from both mouth and nose inhalation, averaged to assess omnidirectional aspiration efficiencies, were compiled and used to generate a unifying model to relate particle size to aspiration efficiency of the human head. Multiple linear regression was used to generate an empirical model to estimate human aspiration efficiency and included particle size as well as breathing and freestream velocities as dependent variables. A new set of simulated mouth and nose breathing aspiration efficiencies was generated and used to test the fit of empirical models. Further, empirical relationships between test conditions and CFD estimates of aspiration were compared to experimental data from mannequin studies, including both calm-air and ultra-low velocity experiments. While a linear relationship between particle size and aspiration is reported in calm air studies, the CFD simulations identified a more reasonable fit using the square of particle aerodynamic diameter, which better addressed the shape of the efficiency curve's decline toward zero for large particles. The ultimate goal of this work was to develop an empirical model that incorporates real-world variations in critical factors associated with particle aspiration to inform low-velocity modifications to the inhalable particle sampling criterion.

  3. Air speed and velocity measurements in a room with a sidewall jet.

    PubMed

    Hurnik, M; Blaszczok, M; Popiolek, Z

    2015-12-01

    In mixing ventilation systems, diffusers are often located on side walls and supply quasi-free air jets above the occupied zone. The data presented in this paper shows a new CFD 3D benchmark with two well-defined characteristic zones in the room, i.e., the quasi-free jet zone and the occupied zone. Measurement methods adequate for air velocity and speed measurement were applied: laser Doppler anemometry for the axial velocity component in the jet and low velocity thermal anemometry for the air speed in the occupied zone. Measurements were performed in a physical scale model (1:5) of the room. The kinematic similarity criterion was fulfilled by the equality of the Reynolds numbers in the model and in the prototype. To identify boundary conditions, additional measurements were carried out in the inlet region (as close as possible to the supply opening). The CFD results validation and reporting methods applicable for the benchmark data are proposed in Hurnik et al. (2015) [1].

  4. Measurements of laminar burning velocities for natural gas-hydrogen-air mixtures

    SciTech Connect

    Huang, Zuohua; Zhang, Yong; Zeng, Ke; Liu, Bing; Wang, Qian; Jiang, Deming

    2006-07-15

    Laminar flame characteristics of natural gas-hydrogen-air flames were studied in a constant-volume bomb at normal temperature and pressure. Laminar burning velocities and Markstein lengths were obtained at various ratios of hydrogen to natural gas (volume fraction from 0 to 100%) and equivalence ratios (f from 0.6 to 1.4). The influence of stretch rate on flame was also analyzed. The results show that, for lean mixture combustion, the flame radius increases with time but the increasing rate decreases with flame expansion for natural gas and for mixtures with low hydrogen fractions, while at high hydrogen fractions, there exists a linear correlation between flame radius and time. For rich mixture combustion, the flame radius shows a slowly increasing rate at early stages of flame propagation and a quickly increasing rate at late stages of flame propagation for natural gas and for mixtures with low hydrogen fractions, and there also exists a linear correlation between flame radius and time for mixtures with high hydrogen fractions. Combustion at stoichiometric mixture demonstrates the linear relationship between flame radius and time for natural gas-air, hydrogen-air, and natural gas-hydrogen-air flames. Laminar burning velocities increase exponentially with the increase of hydrogen fraction in mixtures, while the Markstein length decreases and flame instability increases with the increase of hydrogen fractions in mixture. For a fixed hydrogen fraction, the Markstein number shows an increase and flame stability increases with the increase of equivalence ratios. Based on the experimental data, a formula for calculating the laminar burning velocities of natural gas-hydrogen-air flames is proposed. (author)

  5. Tuning a physically-based model of the air-sea gas transfer velocity

    NASA Astrophysics Data System (ADS)

    Jeffery, C. D.; Robinson, I. S.; Woolf, D. K.

    Air-sea gas transfer velocities are estimated for one year using a 1-D upper-ocean model (GOTM) and a modified version of the NOAA-COARE transfer velocity parameterization. Tuning parameters are evaluated with the aim of bringing the physically based NOAA-COARE parameterization in line with current estimates, based on simple wind-speed dependent models derived from bomb-radiocarbon inventories and deliberate tracer release experiments. We suggest that A = 1.3 and B = 1.0, for the sub-layer scaling parameter and the bubble mediated exchange, respectively, are consistent with the global average CO 2 transfer velocity k. Using these parameters and a simple 2nd order polynomial approximation, with respect to wind speed, we estimate a global annual average k for CO 2 of 16.4 ± 5.6 cm h -1 when using global mean winds of 6.89 m s -1 from the NCEP/NCAR Reanalysis 1 1954-2000. The tuned model can be used to predict the transfer velocity of any gas, with appropriate treatment of the dependence on molecular properties including the strong solubility dependence of bubble-mediated transfer. For example, an initial estimate of the global average transfer velocity of DMS (a relatively soluble gas) is only 11.9 cm h -1 whilst for less soluble methane the estimate is 18.0 cm h -1.

  6. The Effect of Velocity Gradients on Cepheid Spectra: Models

    NASA Astrophysics Data System (ADS)

    Butler, R. Paul; Bell, Roger A.; Hindsley, Robert B.

    1996-04-01

    High-resolution observations of η Aql and other Cepheids have revealed differences in the radial velocity curves from the spectral lines of elements having differing ionization states and excitation energies. The effect of atmospheric velocity gradients on these differential radial velocity curves is investigated with synthetic spectra calculated from model hydrostatic stellar atmospheres appropriate for Cepheids. A number of velocity gradients have been kinematically introduced in these models. It is shown that a significant velocity gradient is needed near the phase of maximum infall velocity to account for the line profile asymmetries and velocity differences observed in the spectrum of η Aql. The effect of this velocity gradient is to reduce the amplitude of the pulsational velocity curve at optical depth τ = ⅔ by 20% and to decrease the γ velocity by 2 km s-1 relative to the standard assumption of a comoving atmosphere. The Barnes-Evans method has been used to analyze η Aql, taking this velocity gradient into account. The resulting radius and distance are reduced by about 17%, compared to the result found earlier for a comoving atmosphere, while the mean Mυ changes from -4.47 to -4.08.

  7. Studying the impact of air/brine displacement on acoustic velocities in carbonates. El Amin Mokhtar and Sandra Vega

    NASA Astrophysics Data System (ADS)

    Mokhtar, E.; Vega, D.

    2012-12-01

    The impact of air/brine displacement on acoustic velocities of carbonate rocks is not fully comprehended yet. In order to improve our understanding of this effect, we conducted laboratory measurements of porosity and acoustic velocities (Vp and Vs) under both dry and brine saturated conditions at ambient pressure and temperature. The core plug samples in this study were collected from a hydrocarbon reservoir in the Middle East. A petrographic analysis was also performed on thin sections taken from the core plugs using a microscope and a digital camera. The aim of this analysis was to study depositional facies and the extent of diagenetic overprint that caused the observed variations in rock fabrics. Cross-plots were generated to analyze the trends of behavior between acoustic velocities and porosities taking into account the influence of different rock fabrics, in both dry and brine saturated samples. Acoustic velocities of brine saturated samples were higher than velocities of dry samples, as expected. However, their differences also respond to both, total porosity and carbonate rock fabrics. This result can be attributed to the different carbonate pore structures and rock frames formed during deposition and diagenesis. Similarly, the Vp/Vs ratio cross-plots display an increase in Vp/Vs ratios for the brine saturated samples compared to the dry ones. In conclusion, differences in acoustic velocities between dry and brine saturated carbonate rocks seem to be highly effected by porosity, rock fabric, and fluid content. This information can help to better understand the differences in acoustic response between gas and brine saturated zones in well logs and seismic.

  8. Tunable diode laser absorption sensor for temperature and velocity measurements of O2 in air flows

    NASA Technical Reports Server (NTRS)

    Philippe, L. C.; Hanson, R. K.

    1991-01-01

    A fast and nonintrusive velocity and temperature diagnostic based on oxygen absorption is presented. The system uses a GaAlAs tunable diode laser, ramped and modulated in wavelength at high frequency. Detection is performed at twice the modulating frequency, leading to second harmonic absorption lineshapes. Velocity is inferred from the wavelength shift of the absorption line center due to the Doppler effect. Temperature is determined by comparing experimental and calculated lineshapes. Capabilities of the technique for studies of transient high-speed flows are demonstrated in shock tube experiments. Good agreement is obtained with predicted temperatures and velocities when pressure-induced shifts are accounted for.

  9. Effective diffusion equation in a random velocity field

    NASA Technical Reports Server (NTRS)

    Vinals, Jorge; Sekerka, Robert F.

    1992-01-01

    The effects are studied of assumed random velocity fields on diffusion in a binary fluid. Random velocity fields can result, for example, from the high-frequency components of residual accelerations onboard spacecraft (often called g-jitter). An effective diffusion equation is derived for an average concentration which includes spatial and temporal correlations induced by the fluctuating velocity fields assumed to be Gaussianly distributed. The resulting equation becomes nonlocal, and if correlations between different components of the velocity field exist, it is also anisotropic. The simple limiting case of short correlation times is discussed and an effective diffusivity is obtained which reflects the enhanced mixing caused by the velocity fields. The results obtained in the limit of short correlation times are valid even if the probability distribution of the velocity field is not Gaussian.

  10. Burning Velocity Measurements in Aluminum-Air Suspensions using Bunsen Type Dust Flames

    NASA Technical Reports Server (NTRS)

    Lee, John; Goroshin, Samuel; Kolbe, Massimiliano

    2001-01-01

    Laminar burning velocity (sometimes also referred in literature as fundamental or normal flame propagation speed) is probably the most important combustion characteristic of the premixed combustible mixture. The majority of experimental data on burning velocities in gaseous mixtures was obtained with the help of the Bunsen conical flame. The Bunsen cone method was found to be sufficiently accurate for gaseous mixtures with burning velocities higher than 10-15 cm/s at normal pressure. Hans Cassel was the first to demonstrate that suspensions of micron-size solid fuel particles in a gaseous oxidizer can also form self-sustained Bunsen flames. He was able to stabilize Bunsen flames in a number of suspensions of different nonvolatile solid fuels (aluminum, carbon, and boron). Using the Bunsen cone method he estimated burning velocities in the premixed aluminum-air mixtures (particle size less than 10 microns) to be in the range of 30-40 cm/s. Cassel also found, that the burning velocity in dust clouds is a function of the burner diameter. In our recent work, we have used the Bunsen cone method to investigate dependence of burning velocity on dust concentration in fuel-rich aluminum dust clouds. Burning velocities in stoichiometric and fuel-rich aluminum dust suspensions with average particle sizes of about 5 microns were found to be in the range of 20-25 cm/s and largely independent on dust concentration. These results raise the question to what degree burning velocities derived from Bunsen flame specifically and other dust flame configurations in general, are indeed fundamental characteristics of the mixture and to what degree are they apparatus dependent. Dust flames in comparison to gas combustion, are thicker, may be influenced by radiation heat transfer in the flame front, respond differently to heat losses, and are fundamentally influenced by the particular flow configuration due to the particles inertia. Since characteristic spatial scales of dust flames are

  11. Influence of relative air/water flow velocity on oxygen mass transfer in gravity sewers.

    PubMed

    Carrera, Lucie; Springer, Fanny; Lipeme-Kouyi, Gislain; Buffiere, Pierre

    2017-04-01

    Problems related to hydrogen sulfide may be serious for both network stakeholders and the public in terms of health, sustainability of the sewer structure and urban comfort. H2S emission models are generally theoretical and simplified in terms of environmental conditions. Although air transport characteristics in sewers must play a role in the fate of hydrogen sulfide, only a limited number of studies have investigated this issue. The aim of this study was to better understand H2S liquid to gas transfer by highlighting the link between the mass transfer coefficient and the turbulence in the air flow and the water flow. For experimental safety reasons, O2 was taken as a model compound. The oxygen mass transfer coefficients were obtained using a mass balance in plug flow. The mass transfer coefficient was not impacted by the range of the interface air-flow velocity values tested (0.55-2.28 m·s(-1)) or the water velocity values (0.06-0.55 m·s(-1)). Using the ratio between kL,O2 to kL,H2S, the H2S mass transfer behavior in a gravity pipe in the same hydraulic conditions can be predicted.

  12. Correlation of turbulent burning velocities of ethanol-air, measured in a fan-stirred bomb up to 1.2 MPa

    SciTech Connect

    Bradley, D.; Lawes, M.; Mansour, M.S.

    2011-01-15

    The turbulent burning velocity is defined by the mass rate of burning and this also requires that the associated flame surface area should be defined. Previous measurements of the radial distribution of the mean reaction progress variable in turbulent explosion flames provide a basis for definitions of such surface areas for turbulent burning velocities. These inter-relationships. in general, are different from those for burner flames. Burning velocities are presented for a spherical flame surface, at which the mass of unburned gas inside it is equal to the mass of burned gas outside it. These can readily be transformed to burning velocities based on other surfaces. The measurements of the turbulent burning velocities presented are the mean from five different explosions, all under the same conditions. These cover a wide range of equivalence ratios, pressures and rms turbulent velocities for ethanol-air mixtures. Two techniques are employed, one based on measurements of high speed schlieren images, the other on pressure transducer measurements. There is good agreement between turbulent burning velocities measured by the two techniques. All the measurement are generalised in plots of burning velocity normalised by the effective unburned gas rms velocity as a function of the Karlovitz stretch factor for different strain rate Markstein numbers. For a given value of this stretch factor a decrease in Markstein number increases the normalised burning velocity. Comparisons are made with the findings of other workers. (author)

  13. Velocity and phase distribution measurements in vertical air-water annular flows

    SciTech Connect

    Vassallo, P.

    1997-07-01

    Annular flow topology for three air-water conditions in a vertical duct is investigated through the use of a traversing double-sensor hot-film anemometry probe and differential pressure measurements. Near wall measurements of mean and fluctuating velocities, as well as local void fraction, are taken in the liquid film, with the highest turbulent fluctuations occurring for the flow condition with the largest pressure drop. A modified law-of-the-wall formulation for wall shear is presented which, using near wall values of mean velocity and kinetic energy, agrees reasonably well with the average stress obtained from direct pressure drop measurements. The linear profile using wall coordinates in the logarithmic layer is preserved in annular flow; however, the slope and intercept of the profile differ from the single-phase values for the annular flow condition which has a thicker, more turbulent, liquid film.

  14. Impact of air velocity, temperature, humidity, and air on long-term voc emissions from building products

    NASA Astrophysics Data System (ADS)

    Wolkoff, Peder

    The emissions of two volatile organic compounds (VOCs) of concern from five building products (BPs) were measured in the field and laboratory emission cell (FLEC) up to 250 d. The BPs (VOCs selected on the basis of abundance and low human odor thresholds) were: nylon carpet with latex backing (2-ethylhexanol, 4-phenylcyclohexene), PVC flooring (2-ethylhexanol, phenol), floor varnish on pretreated beechwood parquet (butyl acetate, N-methylpyrrolidone), sealant (hexane, dimethyloctanols), and waterborne wall paint on gypsum board (1,2-propandiol, Texanol). Ten different climate conditions were tested: four different air velocities from ca. 1 cm s -1 to ca. 9 cm s -1, three different temperatures (23, 35, and 60°C), two different relative humidities (0% and 50% RH), and pure nitrogen instead of clean air supply. Additionally, two sample specimen and two different batches were compared for repeatability and homogeneity. The VOCs were sampled on Tenax TA and determined by thermal desorption and gas chromatography (FID). Quantification was carried out by individual calibration of each VOC of concern. Concentration/time profiles of the selected VOCs (i.e. their concentration decay curves over time) in a standard room were used for comparison. Primary source emissions were not affected by the air velocity after a few days to any great extent. Both the temperature and relative humidity affected the emission rates, but depended strongly on the type of BP and type of VOC. Secondary (oxidative) source emissions were only observed for the PVC and for dimethyloctanols from the sealant. The time to reach a given concentration (emission rate) appears to be a good approach for future interlaboratory comparisons of BP's VOC emissions.

  15. The effect of temperature and velocity on superlubricity.

    PubMed

    van den Ende, Joost A; de Wijn, Astrid S; Fasolino, Annalisa

    2012-11-07

    We study the effects of temperature and sliding velocity on superlubricity in numerical simulations of the Frenkel-Kontorova model. We show that resonant excitations of the phonons in an incommensurate sliding body lead to an effective friction and to thermal equilibrium with energy distributed over the internal degrees of freedom. For finite temperature, the effective friction can be described well in terms of a viscous damping force, with a damping coefficient that emerges naturally from the microscopic dynamics. This damping coefficient is a non-monotonic function of the sliding velocity which peaks around resonant velocities and increases with temperature. At low velocities, it remains finite and nonzero, indicating the preservation of superlubricity in the zero-velocity limit. Finally, we propose experimental systems in which our results could be verified.

  16. The effect of temperature and velocity on superlubricity

    NASA Astrophysics Data System (ADS)

    van den Ende, Joost A.; de Wijn, Astrid S.; Fasolino, Annalisa

    2012-11-01

    We study the effects of temperature and sliding velocity on superlubricity in numerical simulations of the Frenkel-Kontorova model. We show that resonant excitations of the phonons in an incommensurate sliding body lead to an effective friction and to thermal equilibrium with energy distributed over the internal degrees of freedom. For finite temperature, the effective friction can be described well in terms of a viscous damping force, with a damping coefficient that emerges naturally from the microscopic dynamics. This damping coefficient is a non-monotonic function of the sliding velocity which peaks around resonant velocities and increases with temperature. At low velocities, it remains finite and nonzero, indicating the preservation of superlubricity in the zero-velocity limit. Finally, we propose experimental systems in which our results could be verified.

  17. Motion Prediction and the Velocity Effect in Children

    ERIC Educational Resources Information Center

    Benguigui, Nicolas; Broderick, Michael P.; Baures, Robin; Amorim, Michel-Ange

    2008-01-01

    In coincidence-timing studies, children have been shown to respond too early to slower stimuli and too late to faster stimuli. To examine this velocity effect, children aged 6, 7.5, 9, 10.5, and adults were tested with two different velocities in a prediction-motion task which consisted of judging, after the occlusion of the final part of its…

  18. Motion Prediction and the Velocity Effect in Children

    ERIC Educational Resources Information Center

    Benguigui, Nicolas; Broderick, Michael P.; Baures, Robin; Amorim, Michel-Ange

    2008-01-01

    In coincidence-timing studies, children have been shown to respond too early to slower stimuli and too late to faster stimuli. To examine this velocity effect, children aged 6, 7.5, 9, 10.5, and adults were tested with two different velocities in a prediction-motion task which consisted of judging, after the occlusion of the final part of its…

  19. Anomalous Velocity Dependence of the Friction Coefficient of an Air Supported Pulley

    NASA Astrophysics Data System (ADS)

    Crismani, Matteo; Nauenberg, Michael

    2009-11-01

    A standard undergraduate lab exercise to verify Newton's law, F = ma, is to measure the acceleration a of a glider of mass m suspended on an air track. In our experiment the glider is accelerated by a thin tape attached to the glider at one end, and to a weight of mass M at the other end. The weight hangs vertically via a pulley over which the tape is suspended by air pressure. In the absence of friction, the force pulling the glider is F = (M m/(M + m)g, where g is the acceleration of gravity. To the accuracy provided by the fast electronic timers (accurate to 1/10000 second) used in our experiment to measure the velocity and the acceleration of the glider, we verified that the friction due to the air track can be neglected. But we found that this is not the case for the friction due to the air pulley which adds a component -v/T to the force F on the glider, where T is the friction coefficient. We have measured the dependence of this coefficient on v, and found an excellent analytic fit to our data. This fit deviates considerable from the conventional assumption that 1/T is a constant and/or depends linearly on v.

  20. Velocity measurements within a shock and reshock induced air/SF6 turbulent mixing zone

    NASA Astrophysics Data System (ADS)

    Haas, Jean-Francois; Bouzgarrou, Ghazi; Bury, Yannick; Jamme, Stephane; Joly, Laurent; Shock-induced mixing Team

    2012-11-01

    A turbulent mixing zone (TMZ) is created in a shock tube (based in ISAE, DAEP) when a Mach 1.2 shock wave in air accelerates impulsively to 70 m/s an air/SF6 interface. The gases are initially separated by a 1 μm thick plastic microfilm maintained flat and parallel to the shock by two wire grids. The upper grid of square spacing 1.8 mm imposes the nonlinear initial perturbation for the Richtmyer-Meshkov instability (RMI). After interaction with a reshock and a rarefaction, the TMZ remains approximately stagnant but much more turbulent. High speed Schlieren visualizations enable the choice of abscissae for Laser Doppler Velocity (LDV) measurements. For a length of the SF6 section equal to 250 mm, the LDV abscissae are 43, 135 and 150 mm from the initial position of the interface. Because of numerous microfilm fragments in the flow and a limited number of olive oil droplets as seeding particles for the LDV, statistical convergence requires the superposition of a least 50 identical runs at each abscissa. The dependence of TMZ structure and velocity field on length of the SF6 section between 100 and 300 mm will be presented. This experimental investigation is carried out in support of modeling and multidimensional simulation efforts at CEA, DAM, DIF. Financial support from CEA is thanksfully appreciated by ISAE.

  1. Validation of a CFD model by using 3D sonic anemometers to analyse the air velocity generated by an air-assisted sprayer equipped with two axial fans.

    PubMed

    García-Ramos, F Javier; Malón, Hugo; Aguirre, A Javier; Boné, Antonio; Puyuelo, Javier; Vidal, Mariano

    2015-01-22

    A computational fluid dynamics (CFD) model of the air flow generated by an air-assisted sprayer equipped with two axial fans was developed and validated by practical experiments in the laboratory. The CFD model was developed by considering the total air flow supplied by the sprayer fan to be the main parameter, rather than the outlet air velocity. The model was developed for three air flows corresponding to three fan blade settings and assuming that the sprayer is stationary. Actual measurements of the air velocity near the sprayer were taken using 3D sonic anemometers. The workspace sprayer was divided into three sections, and the air velocity was measured in each section on both sides of the machine at a horizontal distance of 1.5, 2.5, and 3.5 m from the machine, and at heights of 1, 2, 3, and 4 m above the ground The coefficient of determination (R2) between the simulated and measured values was 0.859, which demonstrates a good correlation between the simulated and measured data. Considering the overall data, the air velocity values produced by the CFD model were not significantly different from the measured values.

  2. Validation of a CFD Model by Using 3D Sonic Anemometers to Analyse the Air Velocity Generated by an Air-Assisted Sprayer Equipped with Two Axial Fans

    PubMed Central

    García-Ramos, F. Javier; Malón, Hugo; Aguirre, A. Javier; Boné, Antonio; Puyuelo, Javier; Vidal, Mariano

    2015-01-01

    A computational fluid dynamics (CFD) model of the air flow generated by an air-assisted sprayer equipped with two axial fans was developed and validated by practical experiments in the laboratory. The CFD model was developed by considering the total air flow supplied by the sprayer fan to be the main parameter, rather than the outlet air velocity. The model was developed for three air flows corresponding to three fan blade settings and assuming that the sprayer is stationary. Actual measurements of the air velocity near the sprayer were taken using 3D sonic anemometers. The workspace sprayer was divided into three sections, and the air velocity was measured in each section on both sides of the machine at a horizontal distance of 1.5, 2.5, and 3.5 m from the machine, and at heights of 1, 2, 3, and 4 m above the ground The coefficient of determination (R2) between the simulated and measured values was 0.859, which demonstrates a good correlation between the simulated and measured data. Considering the overall data, the air velocity values produced by the CFD model were not significantly different from the measured values. PMID:25621611

  3. Strain-induced extinction of hydrogen-air counterflow diffusion flames - Effects of steam, CO2, N2, and O2 additives to air

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Northam, G. B.; Wilson, L. G.

    1992-01-01

    A fundamental study was performed using axisymmetric nozzle and tubular opposed jet burners to measure the effects of laminar plug flow and parabolic input velocity profiles on the extinction limits of H2-air counterflow diffusion flames. Extinction limits were quantified by 'flame strength', (average axial air jet velocity) at blowoff of the central flame. The effects of key air contaminants, on the extinction limits, are characterized and analyzed relative to utilization of combustion contaminated vitiated air in high enthalpy supersonic test facilities.

  4. Strain-induced extinction of hydrogen-air counterflow diffusion flames - Effects of steam, CO2, N2, and O2 additives to air

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Northam, G. B.; Wilson, L. G.

    1992-01-01

    A fundamental study was performed using axisymmetric nozzle and tubular opposed jet burners to measure the effects of laminar plug flow and parabolic input velocity profiles on the extinction limits of H2-air counterflow diffusion flames. Extinction limits were quantified by 'flame strength', (average axial air jet velocity) at blowoff of the central flame. The effects of key air contaminants, on the extinction limits, are characterized and analyzed relative to utilization of combustion contaminated vitiated air in high enthalpy supersonic test facilities.

  5. Effects of low velocity impacts on basaltoids

    NASA Astrophysics Data System (ADS)

    Oszkiewicz, Dagmara; Nowak, Monika; Kohout, Tomas; McDermott, Kathryn; Marciniak, Lukasz; Muinonen, Karri; Penttila, Antti

    2015-04-01

    basalts. We perform low velocity impacts (˜4-7 km/s) into the selected basaltoids using the two stage light gas gun facilities based at the University of Kent. We next investigate the spectra and shock iduced changes in the samples. The conclusion of this experiments may be applicable to HED meteorites and the topic of altering the surfaces of basaltoid-like planetary bodies. Acknowledgement MN was supported by Polish National Science Center, grant number NN307039740. DAO was supported by Polish National Science Center, grant number 2012/04/S/ST9/00022. References [Burbine et al., 1996] Burbine, Thomas H., Anders Meibom, and Richard P. Binzel 1996, Meteoritics & Planetary Science 31.5: 607-620. [Weiss et al., 2013] Weiss, B. P., Elkins-Tanton, L. T., Barucci, M. A., et al. 2012, Planetary and Space Science 66(1), 137-146

  6. Simultaneous measurement of temperature and velocity fields in convective air flows

    NASA Astrophysics Data System (ADS)

    Schmeling, Daniel; Bosbach, Johannes; Wagner, Claus

    2014-03-01

    Thermal convective air flows are of great relevance in fundamental studies and technical applications such as heat exchangers or indoor ventilation. Since these kinds of flow are driven by temperature gradients, simultaneous measurements of instantaneous velocity and temperature fields are highly desirable. A possible solution is the combination of particle image velocimetry (PIV) and particle image thermography (PIT) using thermochromic liquid crystals (TLCs) as tracer particles. While combined PIV and PIT is already state of the art for measurements in liquids, this is not yet the case for gas flows. In this study we address the adaptation of the measuring technique to gaseous fluids with respect to the generation of the tracer particles, the particle illumination and the image filtering process. Results of the simultaneous PIV/PIT stemming from application to a fluid system with continuous air exchange are presented. The measurements were conducted in a cuboidal convection sample with air in- and outlet at a Rayleigh number Ra ≈ 9.0 × 107. They prove the feasibility of the method by providing absolute and relative temperature accuracies of σT = 0.19 K and σΔT = 0.06 K, respectively. Further open issues that have to be addressed in order to mature the technique are identified.

  7. Effects of velocity averaging on the shapes of absorption lines

    NASA Technical Reports Server (NTRS)

    Pickett, H. M.

    1980-01-01

    The velocity averaging of collision cross sections produces non-Lorentz line shapes, even at densities where Doppler broadening is not apparent. The magnitude of the effects will be described using a model in which the collision broadening depends on a simple velocity power law. The effect of the modified profile on experimental measures of linewidth, shift and amplitude will be examined and an improved approximate line shape will be derived.

  8. Effects of running velocity on running kinetics and kinematics.

    PubMed

    Brughelli, Matt; Cronin, John; Chaouachi, Anis

    2011-04-01

    Sixteen semiprofessional Australian football players performed running bouts at incremental velocities of 40, 60, 80, and 100% of their maximum velocity on a Woodway nonmotorized force treadmill. As running velocity increased from 40 to 60%, peak vertical and peak horizontal forces increased by 14.3% (effect size [ES] = 1.0) and 34.4% (ES = 4.2), respectively. The changes in peak vertical and peak horizontal forces from 60 to 80% were 1.0% (ES = 0.05) and 21.0% (ES = 2.9), respectively. Finally, the changes in peak vertical and peak horizontal forces from 80% to maximum were 2.0% (ES = 0.1) and 24.3% (ES = 3.4). In addition, both stride frequency and stride length significantly increased with each incremental velocity (p < 0.05). Conversely, contact times and the vertical displacement of the center of mass significantly decreased with increased running velocity (p < 0.05). A significant positive correlation was found between horizontal force and maximum running velocity (r = 0.47). For the kinematic variables, only stride length was found to have a significant positive correlation with maximum running velocity (r = 0.66). It would seem that increasing maximal sprint velocity may be more dependent on horizontal force production as opposed to vertical force production.

  9. Modeling of velocity effects in eddy current applications

    NASA Astrophysics Data System (ADS)

    Ida, Nathan

    1988-04-01

    The effects of velocity on moving sources are encountered in many practical eddy current applications. In many instances these effects are ignored either because velocities are relatively low, because of our inability to quantify these effects, or for purposes of simplifying the solution. There are, however, a number of important applications in which this cannot be done and full account of velocity must be taken. Some obvious applications are magnetic recording, magnetic braking, and nondestructive testing. This work presents a finite element formulation for eddy current problems that takes into account the relative movement of sources. Results are presented indicating that velocity effects are significant at high velocities, and are important for correct signal interpretation. The effect of velocity on nondestructive testing signals is investigated and shown to display significant deviation from static behavior. Because of the form of the governing equations, spurious, nonphysical solutions may be generated. These are eliminated by two separate methods. One involves refinement of the finite element mesh and the second, upwinding of the finite elements.

  10. Coupling liquids acoustic velocity effects on elastic metallic bioglass properties

    NASA Astrophysics Data System (ADS)

    Metiri, W.; Hadjoub, F.; Doghmane, A.; Hadjoub, Z.

    2009-11-01

    The effect of surface acoustic wave, SAW, velocities of coupling liquids on acoustical properties of several bulk metallic glasses, BMG, has been investigated using simulation program based on acoustic microscopy. Thus, we determined variations of critical angles at which the excitation of longitudinal mode, θL and Rayleigh mode, θR occurs as a function of wave velocities in different coupling liquids, Vliq. Linear relations of the form θi =ai0 +βiVliq were deduced. The importance of such formula, used with Snell's law, lies in the direct determination of SAW velocities and consequently mechanical properties of BMGs.

  11. Collision and average velocity effects on the ratchet pinch

    SciTech Connect

    Vlad, M.; Benkadda, S.

    2008-03-15

    A ratchet-type average velocity V{sup R} appears for test particles moving in a stochastic potential and a magnetic field that is space dependent. This model is developed by including particle collisions and an average velocity. We show that these components of the motion can destroy the ratchet velocity but they also can produce significant increase of V{sup R}, depending on the parameters. The amplification of the ratchet pinch is a nonlinear effect that appears in the presence of trajectory eddying.

  12. Wind velocity effects on sampling rate of NO2 badge.

    PubMed

    Lee, K; Yanagisawa, Y; Spengler, J D; Billick, I H

    1992-01-01

    The effects of wind velocity on a sampling rate of a nitrogen dioxide (NO2) diffusive badge were experimentally determined using a turntable. The use of a turntable permits the collection of the large amounts of data that are needed for statistically reliable results at several wind velocities in one experiment. The regression model for the wind effect determined by these experiments was closely correlated with data previously gathered from experiments using wind tunnels. Experiments at two different relative humidities, 35% and 60%, were performed and analyzed by a simple least square regression model. A multi-regression model containing two independent variables, wind velocity and relative humidity, also was developed. The multi-regression model was useful at relative humidity between 20% and 60% and wind velocity between 0 and 7 meter per second (m/sec).

  13. Retrieving the Velocity of Motion of Air Masses from Digital Images of Clouds

    NASA Astrophysics Data System (ADS)

    Bakalova, Kalinka; Bakalov, Dimitar

    2007-04-01

    An interdisciplinary project, aimed at developing tools for the determination of physical characteristics of the atmosphere by means of ground-based digital imaging in the visible range is in progress. Determining the 3-dimensional field of velocities of motion of the air masses from digital images of clouds is among the central tasks. The approach consists in identifying patterns of the cloud structure with characteristic shape and measuring their angular displacement by tracking them in series of consecutive digital images, taken at optimal time intervals. The geometrical mapping of the cloud of an image onto the following image (including translation, rotation, dilatation and additional small irregular deformations) is parameterized, and the numerical values of the parameters are computed by minimizing the sum over pixels of the squared deviation of the brightness, weighed with factors accounting for the representativeness of the group of pixels, and with constrains on the parameters describing irregular deformations.

  14. Size-effect of explosive sensitivity under low velocity impact

    NASA Astrophysics Data System (ADS)

    Ma, Danzhu; Chen, Pengwan; Zhou, Qiang

    2013-06-01

    Low velocity impact may ignite the solid high explosives and cause undesired explosion incidents. The safety of high explosives under low velocity impact is one of the most important problems in handling, manufacture, storage, and transportation procedures. More and more evaluation tests have been developed for low velocity impact scenarios, including, but not limited to the drop hammer impact test, the Susan test, the Spigot test, and the Steven test, with a charge mass varying from tens of milligrams to several kilograms. The effects of specimen size on explosive sensitivity were found in our drop hammer impact test and Steven tests, including the threshold velocity/height and reaction violence. To further analyze the size effects on explosive sensitivity under low velocity impacts, we collected the impact sensitivity data of several PBX explosives in the drop hammer test, the Steven test, the Susan test and the Spigot test. The effective volume of explosive charge and the threshold specific mechanical energy were introduced to investigate the size-effect on the explosive ignition thresholds. The effective volumes of explosive charge in Steven test and Spigot test were obtained by numerical simulation, due to the localization of the impact. The threshold specific mechanical energy is closely related to the effective volume of explosive charge. The results show that, with the increase of effective volume, the specific mechanical energy needed for explosive ignition decreases and trends to reach a constant value. The mechanisms of size effects on explosive sensitivity are also discussed.

  15. Specimen size effect of explosive sensitivity under low velocity impact

    NASA Astrophysics Data System (ADS)

    Ma, Danzhu; Chen, Pengwan; Dai, Kaida; Zhou, Qiang

    2014-05-01

    Low velocity impact may ignite the solid high explosives and cause undesired explosion incidents. The safety of high explosives under low velocity impact is one of the most important issues in handling, manufacture, storage, and transportation procedures. Various evaluation tests have been developed for low velocity impact scenarios, including, but not limited to the drop hammer test, the Susan test, the Spigot test, and the Steven test, with a charge mass varying from tens of milligrams to several kilograms. The effects of specimen size on explosive sensitivity were found in some impact tests such as drop hammer test and Steven tests, including the threshold velocity/height and reaction violence. To analyse the specimen size effects on explosive sensitivity under low velocity impacts, we collected the impact sensitivity data of several PBX explosives in the drop hammer test, the Steven test, the Susan test and the Spigot test. The effective volume of explosive charge and the critical specific mechanical energy were introduced to investigate the size-effect on the explosive reaction thresholds. The effective volumes of explosive charge in Steven test and Spigot test were obtained by numerical simulation, due to the deformation localization of the impact loading. The critical specific mechanical energy is closely related to the effective volume of explosive charge. The results show that, with the increase of effective volume, the critical mechanical energy needed for explosive ignition decreases and tends to reach a constant value. The mechanisms of size effects on explosive sensitivity are also discussed.

  16. Blood characteristics effect on pulse wave velocity.

    PubMed

    Kim, Jong Youn; Yoon, Jihyun; Cho, Minhee; Lee, Byoung-Kwon; Karimi, Ali; Shin, Sehyun

    2013-01-01

    PWV, a surrogate marker for vascular stiffness, can be also expressed by the Bramwell-Hill equation. The effect of blood density to PWV has been ignored, because variation of blood density is assumed to be negligible. In some clinical situation, blood density could be changed, and blood density as a mechanical property of blood flow might affect to PWV. While the elastic property plays an important role in determining the wave propagation in an elastic tube, our assumption is that there might be some relation between blood flow and vascular wall, and that the characteristics of blood flow might influence PWV. This study was objected to investigate the role of mechanical and hemorheologic parameters on PWV in subjects with cardiovascular disease. We have measured and analyzed the PWV, hemorheologic parameters, and other clinical parameters in 814 patients with coronary arterial disease scheduled for coronary angiography. There is no commercial method for measuring whole blood density. So, we defined the density score, which is sum of hemoglobin and total protein. And the hemorheologic parameters were measured within 4 hours after sampling by automated microfluidic hemorheometer. And the effect of all the clinical and hemorheologic parameter on PWV was analyzed by multiple linear regression analysis. Many clinical parameters including age and blood pressure, high shear WBV and ESR as hemorheologic parameters, and density score were correlated well with ba-PWV. However, many clinical variables, high shear WBV and ESR lost the independent significance on multivariable regression analysis. Only age, SBP, and density score were independent variables (p < 0.001). In conclusion, density score as a mechanical property of blood might be suggested as an independent variable influencing PWV in addition to age and blood pressure, but hemorheologic parameters, such as RBC deformability, aggregation, and whole blood viscosity do not affect PWV independently.

  17. The effect of nitrous oxide on cerebral blood flow velocity in children anaesthetised with sevoflurane.

    PubMed

    Rowney, D A; Fairgrieve, R; Bissonnette, B

    2004-01-01

    To determine the effects of nitrous oxide on middle cerebral artery blood flow velocity (CBFV) during sevoflurane anaesthesia in children, CBFV was measured using transcranial Doppler sonography in 16 ASA I or II children. Anaesthesia consisted of 1.0 MAC sevoflurane in 30% oxygen with intermittent positive pressure ventilation maintaining FEco2 at 38 mmHg (5.0 kPa) and a caudal epidural block using 0.25% bupivacaine 1.0 ml.kg-1. The remainder of the inspired gas was varied in one of two sequences either air/nitrous oxide/air or nitrous oxide/air/nitrous oxide. The results showed that CBFV decreased when nitrous oxide was replaced by air (p = 0.03) and returned to its initial value when nitrous oxide was reintroduced. CBFV increased when air was replaced by nitrous oxide (p = 0.04) and returned to its initial value when air was reintroduced. Mean heart rate and blood pressure remained constant. We conclude that nitrous oxide increases cerebral blood flow velocity in healthy children anaesthetised with 1.0 MAC sevoflurane.

  18. The effect of transport velocity upon spin torque

    NASA Astrophysics Data System (ADS)

    Alaci, S.; Ciornei, F. C.; Amarandei, D.; Irimescu, L.; Romanu, I. C.; Rotar, M. A.

    2017-02-01

    The paper analysis the effect produced by superposition of a rotation motion from contact area on a transport translational motion, having the same value for all contact points. A theoretical model is proposed for the calculus of the total friction torque. The deduced expression shows that the friction torque has a maximum value when the translational velocity is zero and rapidly decreases with increasing the translational velocity. The diminishing is not uniform, but is more evident at the beginning, when the ratio between the transport velocity and angular velocity is comparable to the radius of contact area and, afterwards, the decline of the friction torque is slower. The last part of the paper proposes a solution for an experimental validation of the theoretical results.

  19. The effectiveness of air bags.

    PubMed

    Barry, S; Ginpil, S; O'Neill, T J

    1999-11-01

    Previous research has shown that the installation of air bags in vehicles significantly reduces crash related deaths, but these analyses have used statistical techniques which have not been capable of controlling for other major determinants of crash survival. This study analysed data from the US FARS database of fatal crashes using conditional logistic regression which is simultaneously able to estimate occupant protection effects for a range of variables. Results of the analysis provided a comparative quantification of both the effect of the air bag as well as other well known determinants of occupant crash survival (age, seat belt use, and gender). When potentially confounding variables were controlled, both the driver and passenger side air bag devices were shown to significantly reduce the probability of death in direct frontal collisions, but the effect size calculated was small compared to the effect of the seat belt. The effect size may also be very small in absolute terms depending on the severity of the crash involved. Given the limited benefit of the air bag, efforts to promote air bags seem particularly difficult to justify in countries such as the United States where the vastly superior occupant protection of the seat belt is under-utilised.

  20. Measuring OutdoorAir Intake Rates Using Electronic Velocity Sensors at Louvers and Downstream of Airflow Straighteners

    SciTech Connect

    Fisk, William; Sullivan, Douglas; Cohen, Sebastian; Han, Hwataik

    2008-10-01

    Practical and accurate technologies are needed for continuously measuring and controlling outdoor air (OA) intake rates in commercial building heating, ventilating, and air conditioning (HVAC) systems. This project evaluated two new measurement approaches. Laboratory experiments determined that OA flow rates were measurable with errors generally less than 10percent using electronic air velocity probes installed between OA intake louver blades or at the outlet face of louvers. High accuracy was maintained with OA flow rates as low as 15percent of the maximum for the louvers. Thus, with this measurement approach HVAC systems do not need separate OA intakes for minimum OA supply. System calibration parameters are required for each unique combination of louver type and velocity sensor location but calibrations are not necessary for each system installation. The research also determined that the accuracy of measuring OA flow rates with velocity probes located in the duct downstream of the intake louver was not improved by installing honeycomb airflow straighteners upstream of the probes. Errors varied with type of upstream louver, were as high as 100percent, and were often greater than 25percent. In conclusion, use of electronic air velocity probes between the blades of OA intake louvers or at the outlet face of louvers is a highly promising means of accurately measuring rates of OA flow into HVAC systems. The use of electronic velocity probes downstream of airflow straighteners is less promising, at least with the relatively small OA HVAC inlet systems employed in this research.

  1. Air Vertical Velocity Distributions of Trade Cumulus and Stratocumulus Clouds from the ARM Mobile Facility CAP-MBL Campaign

    NASA Astrophysics Data System (ADS)

    Verlinden, K. L.; de Szoeke, S. P.

    2013-12-01

    The ARM mobile facility W-band ARM Cloud Radar (WACR) was deployed as part of the Cloud, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) campaign on the north shore of Graciosa Island, Azores during the summers of 2009 and 2010. Vertical air velocities from cumulus and stratocumulus clouds over this location are retrieved using radar reflectivity and mean Doppler vertical velocity, employing the assumptions of Pinsky et al. (2010) that gravitational settling of hydrometeors is independent of vertical air motion. Cases of trade cumulus and stratocumulus clouds are identified from the CAP-MBL WACR dataset by examining hourly ceilometer-derived cloud base and cloud top heights, cloud top height variability, temporal duration of hydrometeor clusters from the WACR-derived hydrometeor mask, and precipitation type (Remillard et al. 2012). The structure of mean Doppler velocity as a function of reflectivity and cloud properties (e.g. cloud depth and distance below cloud top) are characterized for these two cloud types. Once the settling velocity has been subtracted, the distribution of air vertical velocities are examined. Vertical velocity histograms provide clues to test parameterizations of updrafts and downdrafts within clouds.

  2. Experimental investigation of the influence of the liquid drop size and velocity on the parameters of drop deformation in air

    NASA Astrophysics Data System (ADS)

    Volkov, R. S.; Vysokomornaya, O. V.; Kuznetsov, G. V.; Strizhak, P. A.

    2015-08-01

    The deformation of water, kerosene, and ethyl alcohol drops traveling a distance of up to 1 m in air with different velocities (1-5 m/s) is recorded by high-speed photography (the frame of the cross-correlation camera is less than 1 µs). It is shown that the shape of the drops varies cyclically. Several tens of "deformation cycles" are found, which have characteristic times, drop size variation amplitudes, and number of shapes. It is found that the velocity and size of the drops influence the parameters of their deformation cycles. Experiments with the drops are conducted in air at moderate Weber numbers (We < 10).

  3. Cardiovascular effects of air pollution.

    PubMed

    Bourdrel, Thomas; Bind, Marie-Abèle; Béjot, Yannick; Morel, Olivier; Argacha, Jean-François

    2017-07-20

    Air pollution is composed of particulate matter (PM) and gaseous pollutants, such as nitrogen dioxide and ozone. PM is classified according to size into coarse particles (PM10), fine particles (PM2.5) and ultrafine particles. We aim to provide an original review of the scientific evidence from epidemiological and experimental studies examining the cardiovascular effects of outdoor air pollution. Pooled epidemiological studies reported that a 10μg/m(3) increase in long-term exposure to PM2.5 was associated with an 11% increase in cardiovascular mortality. Increased cardiovascular mortality was also related to long-term and short-term exposure to nitrogen dioxide. Exposure to air pollution and road traffic was associated with an increased risk of arteriosclerosis, as shown by premature aortic and coronary calcification. Short-term increases in air pollution were associated with an increased risk of myocardial infarction, stroke and acute heart failure. The risk was increased even when pollutant concentrations were below European standards. Reinforcing the evidence from epidemiological studies, numerous experimental studies demonstrated that air pollution promotes a systemic vascular oxidative stress reaction. Radical oxygen species induce endothelial dysfunction, monocyte activation and some proatherogenic changes in lipoproteins, which initiate plaque formation. Furthermore, air pollution favours thrombus formation, because of an increase in coagulation factors and platelet activation. Experimental studies also indicate that some pollutants have more harmful cardiovascular effects, such as combustion-derived PM2.5 and ultrafine particles. Air pollution is a major contributor to cardiovascular diseases. Promotion of safer air quality appears to be a new challenge in cardiovascular disease prevention. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  4. An application of particle image velocimetry to the direct measurement of laminar burning velocity in homogeneous propane-air mixtures

    SciTech Connect

    Zhou, M.; Garner, C.P.

    1995-12-31

    An experiment is described for the direct measurement of laminar burning velocity within an optically accessed cylindrical combustion chamber. The laminar burning velocity was determined directly as the difference between the flame propagation speed and the unburned gas velocity immediately ahead of the flame front. Particle Image Velocimetry (PIV) has been applied to measure the unburned gas velocity field. The local flame speed and flame front position were determined from a pair of ionization probes in conjunction with the simultaneous PIV measurement. The laminar burning velocity of propane-air mixtures initially at atmospheric condition for different equivalence ratios ranging from 0.7--1.4 are presented. Close agreement with other measurements and predicted results was found.

  5. Effects of certain analysis procedures on solar global velocity signals

    SciTech Connect

    Gilman, P.A.; Glatzmaier, G.A.

    1980-10-15

    We examine the data reduction procedures used by Howard and colleagues to deduce global solar velocities from the orginal Mount Wilson Doppler-magnetograph record. We demonstrate that removing daily rotation ''ears,'' and zero offset signals will greatly attenuate east-west global velocities of longitudinal wavenumber m< or =5. In addition we show that, because global velocity patterns are expected on theoretical grounds to have variable phase speeds in longitude, the construction of synoptic maps can severely attenuate high wavenumbers. The combination of these two effects can easily reduce an original periodic east-west flow velocity of peak amplitude 100 m s/sup -1/ to 10 m s/sup -1/ or less for any wavenumber. We demonstrate further that a velocity spectrum, obtained from a nonlinear spherical convection model for a case in which a differential rotation similar in amplitude and profile to the Sun, is attenuated to rms residual velocities close to or within the upper limits obtained by Howard and LaBonte. However, somewhat more power than they find is retained in variations of the daily rotation rate.

  6. Effect of movement velocity during resistance training on neuromuscular performance.

    PubMed

    Pareja-Blanco, F; Rodríguez-Rosell, D; Sánchez-Medina, L; Gorostiaga, E M; González-Badillo, J J

    2014-10-01

    This study aimed to compare the effect on neuromuscular performance of 2 isoinertial resistance training programs that differed only in actual repetition velocity: maximal intended (MaxV) vs. half-maximal (HalfV) concentric velocity. 21 resistance-trained young men were randomly assigned to a MaxV (n=10) or HalfV (n=11) group and trained for 6 weeks using the full squat exercise. A complementary study (n=8) described the acute metabolic and mechanical response to the protocols used. MaxV training resulted in a likely more beneficial effect than HalfV on squat performance: maximum strength (ES: 0.94 vs. 0.54), velocity developed against all (ES: 1.76 vs. 0.88), light (ES: 1.76 vs. 0.75) and heavy (ES: 2.03 vs. 1.64) loads common to pre- and post-tests, and CMJ height (ES: 0.63 vs. 0.15). The effect on 20-m sprint was unclear, however. Both groups attained the greatest improvements in squat performance at their training velocities. Movement velocity seemed to be of greater importance than time under tension for inducing strength adaptations. Slightly higher metabolic stress (blood lactate and ammonia) and CMJ height loss were found for MaxV vs. HalfV, while metabolite levels were low to moderate for both conditions. MaxV may provide a superior stimulus for inducing adaptations directed towards improving athletic performance.

  7. Effects of Flow Velocity and Particle Size on Transport of Ultrafine Bubbles in Porous Media

    NASA Astrophysics Data System (ADS)

    Hamamoto, S.; Nihei, N.; Ueda, Y.; Nishimura, T.

    2015-12-01

    Potential applications of ultrafine bubbles (UFBs) have drawn more attention, especially in environmental engineering fields such as soil/groundwater remediation. Understanding a transport mechanism of UFBs in soils is essential to optimize remediation techniques using UFBs. In this study, column transport experiments using glass beads with different size fraction were conducted, where UFBs created by either air or oxygen were injected to the column with different flow conditions. Effects of particle size and flow velocities on transport characteristics of UFBs were investigated based on the column experiments. The results showed that attachments of UFBs were enhanced under lower water velocity condition, exhibiting more than 50% of UFBs injected were attached inside the column. The mobility of O2-UFBs which have lower zeta potential was higher than that of Air-UFBs. A convection-dispersion model including bubble attachment and detachment terms was applied to the obtained breakthrough curves for each experiment, showing good fitness against the measured data.

  8. Rich methane/air flames: Burning velocities, extinction limits, and flammability limit

    SciTech Connect

    Bui-Pham, M.N.; Miller, J.A.

    1994-12-31

    A theoretical investigation has been conducted to establish a reliable chemical kinetic mechanism that can determine the extinction limit of opposed-flow, strained, rich premixed methane-air flames. In the process of developing this kinetic representation for rich methane-air flames, we found that the heat of formation of {sup 1}CH{sub 2}=102.5 kcal/mole, which is 1 kcal/mole higher than the currently available thermochemical data, gives the best agreement with experimental data on burning velocities for equivalence ratios between 0.5 and 1.7. Employing this value for {Delta}H{sub f{sup 1}CH{sub 2}} in our calculations, the extinction stretch rate, K{sub ex}, was found to be K{sub ex}=2250 sec {sup {minus}1} for {phi}=1.0, K{sub ex}=2000 sec{sup {minus}1} for {phi}=1.1, and K{sub ex}=1400 sec{sup {minus}1} for {phi}=1.2. These results agree better with experiments than those using a lower heat of formation of singlet methylene. In comparison with previous calculations made by Kee et al., our predictions are basically the same except that our extinction stretch rate is slightly higher at {phi}=1.0 and that our location of the maximum extinction stretch rate is closer to that found in experiments. In addition, we establish the rich flammability limit using two different criteria to be approximately between {phi}=1.61 and {phi}=1.68, which agrees very well with an experimental value of {phi}=1.67.

  9. Health Effects of Air Pollution.

    ERIC Educational Resources Information Center

    Environmental Education Report and Newsletter, 1985

    1985-01-01

    Summarizes health hazards associated with air pollution, highlighting the difficulty in establishing acceptable thresholds of exposure. Respiratory disease, asthma, cancer, cardiovascular disease, and other problems are addressed. Indicates that a wide range of effects from any one chemical exists and that there are differences in sensitivity to…

  10. Health Effects of Air Pollution.

    ERIC Educational Resources Information Center

    Environmental Education Report and Newsletter, 1985

    1985-01-01

    Summarizes health hazards associated with air pollution, highlighting the difficulty in establishing acceptable thresholds of exposure. Respiratory disease, asthma, cancer, cardiovascular disease, and other problems are addressed. Indicates that a wide range of effects from any one chemical exists and that there are differences in sensitivity to…

  11. INVESTIGATING THE INFLUENCE OF RELATIVE HUMIDITY, AIR VELOCITY, AND AMPLIFICATION ON THE EMISSION RATES OF FUNGAL SPORES

    EPA Science Inventory

    The paper discusses the impact of relative humidity (RH), air velocity, and surface growth on the emission rates of fungal spores from the surface of contaminated material. Although the results show a complex interaction of factors, we have determined, for this limited data set,...

  12. INVESTIGATING THE INFLUENCE OF RELATIVE HUMIDITY, AIR VELOCITY, AND AMPLIFICATION ON THE EMISSION RATES OF FUNGAL SPORES

    EPA Science Inventory

    The paper discusses the impact of relative humidity (RH), air velocity, and surface growth on the emission rates of fungal spores from the surface of contaminated material. Although the results show a complex interaction of factors, we have determined, for this limited data set,...

  13. Growth responses of male broilers subjected to increasing air velocities at high ambient temperatures and a high dew point.

    PubMed

    Dozier, W A; Lott, B D; Branton, S L

    2005-06-01

    This study examined live performance responses of male broilers to increasing air velocity of 120 and 180 m/min reared under high cyclic temperatures (25-35-25 degrees C) with a 23 degrees C dew point from 21 to 49 d. Birds were reared in an environmental facility containing 2 wind tunnels (4 pens/tunnel) and 6 floor pens (control). At 21 d, 53 birds were placed in each pen of the wind tunnels and control group, respectively, and growth performance was determined weekly. Increasing air velocity from 120 to 180 m/min improved BW and BW gain from 29 to 35, 36 to 42, and 43 to 49 d of age leading to a cumulative advantage of 287 g in BW gain and a 10-point difference in feed conversion from 21 to 49 d of age. Subjecting birds to air velocity improved growth rate, feed consumption, and feed conversion at each weekly interval from 28 to 49 d over the control birds. These results indicate that male broilers approximating 2.0 to 3.0 kg respond to an air velocity of 180 m/min when exposed to high cyclic temperatures.

  14. Space-based retrievals of air-sea gas transfer velocities using altimeters: Calibration for dimethyl sulfide

    NASA Astrophysics Data System (ADS)

    Goddijn-Murphy, Lonneke; Woolf, David K.; Marandino, Christa

    2012-08-01

    This study is the first to directly correlate gas transfer velocity, measured at sea using the eddy-correlation (EC) technique, and satellite altimeter backscattering. During eight research cruises in different parts of the world, gas transfer velocity of dimethyl sulfide (DMS) was measured. The sample times and locations were compared with overpass times and locations of remote sensing satellites carrying Ku-band altimeters: ERS-1, ERS-2, TOPEX, POSEIDON, GEOSAT Follow-On, JASON-1, JASON-2 and ENVISAT. The result was 179 pairs of gas transfer velocity measurements and backscattering coefficients. An inter-calibration of the different altimeters significantly reduced data scatter. The inter-calibrated data was best fitted to a quadratic relation between the inverse of the backscattering coefficients and the gas transfer velocity measurements. A gas transfer parameterization based on backscattering, corresponding with sea surface roughness, might be expected to perform better than wind speed-based parameterizations. Our results, however, did not show improvement compared to direct correlation of shipboard wind speeds. The relationship of gas transfer velocity to satellite-derived backscatter, or wind speed, is useful to provide retrieval algorithms. Gas transfer velocity (cm/hr), corrected to a Schmidt number of 660, is proportional to wind speed (m/s). The measured gas transfer velocity is controlled by both the individual water-side and air-side gas transfer velocities. We calculated the latter using a numerical scheme, to derive water-side gas transfer velocity. DMS is sufficiently soluble to neglect bubble-mediated gas transfer, thus, the DMS transfer velocities could be applied to estimate water-side gas transfer velocities through the unbroken surface of any other gas.

  15. Statistics of Velocity Centroids: Effects of Correlations of Density and Velocity.

    NASA Astrophysics Data System (ADS)

    Horibe, S.; Esquivel, A.; Lazarian, A.

    2005-05-01

    Centroids of velocity from spectroscopic observations have been widely used to study the properties of the underlying turbulent field, however, it was not clear until recently how density fluctuations affect the results. In a previous work, Lazarian and Esquivel provided an analytical description of velocity centroids. In that work the structure function of centroids was decomposed into four contributions: column density, integrated velocity, ``cross-terms'', and density-velocity ``cross-correlations''. From the second term (integrated velocity) we can retrieve the spectral index of velocity. At the same time, the contribution of column density, entirely attainable from observations, can in principle be removed. In this poster, we present an in-depth analysis of the remaining terms. It is found that the ratio of the standard deviation to the mean of density correlates with the ``cross-term''. We also introduce artificial density-velocity ``cross-correlations''. And, for a reasonable level of those, it is found that when velocity centroid fails to trace velocity the ``cross-term'' contaminates the velocity statistics well before the ``cross-correlation'' term. Our results suggest that limitations of the use of centroids to study the scaling properties of velocity will arise primarily from the ``cross-terms''.

  16. Effect of kinesin velocity distribution on slow axonal transport

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Andrey

    2012-08-01

    The goal of this paper is to investigate the effect that a distribution of kinesin motor velocities could have on cytoskeletal element (CE) concentration waves in slow axonal transport. Previous models of slow axonal transport based on the stop-and-go hypothesis (P. Jung, A. Brown, Modeling the slowing of neurofilament transport along the mouse sciatic nerve, Physical Biology 6 (2009) 046002) assumed that in the anterograde running state all CEs move with one and the same velocity as they are propelled by kinesin motors. This paper extends the aforementioned theoretical approach by allowing for a distribution of kinesin motor velocities; the distribution is described by a probability density function (PDF). For a two kinetic state model (that accounts for the pausing and running populations of CEs) an analytical solution describing the propagation of the CE concentration wave is derived. Published experimental data are used to obtain an analytical expression for the PDF characterizing the kinesin velocity distribution; this analytical expression is then utilized as an input for computations. It is demonstrated that accounting for the kinesin velocity distribution increases the rate of spreading of the CE concentration waves, which is a significant improvement in the two kinetic state model.

  17. Effects of increasing tip velocity on wind turbine rotor design.

    SciTech Connect

    Resor, Brian Ray; Maniaci, David Charles; Berg, Jonathan Charles; Richards, Phillip William

    2014-05-01

    A reduction in cost of energy from wind is anticipated when maximum allowable tip velocity is allowed to increase. Rotor torque decreases as tip velocity increases and rotor size and power rating are held constant. Reduction in rotor torque yields a lighter weight gearbox, a decrease in the turbine cost, and an increase in the capacity for the turbine to deliver cost competitive electricity. The high speed rotor incurs costs attributable to rotor aero-acoustics and system loads. The increased loads of high speed rotors drive the sizing and cost of other components in the system. Rotor, drivetrain, and tower designs at 80 m/s maximum tip velocity and 100 m/s maximum tip velocity are created to quantify these effects. Component costs, annualized energy production, and cost of energy are computed for each design to quantify the change in overall cost of energy resulting from the increase in turbine tip velocity. High fidelity physics based models rather than cost and scaling models are used to perform the work. Results provide a quantitative assessment of anticipated costs and benefits for high speed rotors. Finally, important lessons regarding full system optimization of wind turbines are documented.

  18. Determination of burst initiation location and tear propagation velocity during air burst testing of latex condoms

    NASA Astrophysics Data System (ADS)

    Davidhazy, Andrew

    1991-04-01

    The stress testing of latex condoms by an air burst procedure has been slow in gaining industry acceptance because questions have been raised regarding the influence of the test apparatus on the likelihood of breakage occurring where the condom is attached to the inflation device. It was desired to locate the areas at which the condoms tend to burst and thus corroborate or disprove these claims. Several factors associated with the bursting condom demanded the use of special instrumentation to detect arid study the burst initiation process. Microsecond duration electronic flashes were used for the initial stages of the investigation. Although the absolute point of initiation of a given burst could not be photographed, these high speed studies tend to indicate that the most likely place for high quality condoms to break is not where they are attached to the inflation device but at an intermediate area between the base and the tip of the condom. In addition, tear propagation characteristics and velocities were determined with a delayed-flash technique, a double-slit strip method and a rotating drum framing camera.

  19. Effects of forward velocity on turbulent jet mixing noise

    NASA Technical Reports Server (NTRS)

    Plumblee, H. E., Jr. (Editor)

    1976-01-01

    Flight simulation experiments were conducted in an anechoic free jet facility over a broad range of model and free jet velocities. The resulting scaling laws were in close agreement with scaling laws derived from theoretical and semiempirical considerations. Additionally, measurements of the flow structure of jets were made in a wind tunnel by using a laser velocimeter. These tests were conducted to describe the effects of velocity ratio and jet exit Mach number on the development of a jet in a coflowing stream. These turbulence measurements and a simplified Lighthill radiation model were used in predicting the variation in radiated noise at 90 deg to the jet axis with velocity ratio. Finally, the influence of forward motion on flow-acoustic interactions was examined through a reinterpretation of the 'static' numerical solutions to the Lilley equation.

  20. Species and velocity visualization of unseeded heated air and combusting hydrogen jets using laser and flashlamp sources

    NASA Technical Reports Server (NTRS)

    Diskin, Glenn S.; Lempert, Walter R.; Miles, Richard B.

    1990-01-01

    Three techniques for the visualization of species and/or velocity in unseeded H2/air flames and heated air jets are described and preliminary image data are presented. The techniques described are: (1) simultaneous ArF laser imaging of H2, O2, and Rayleigh cross-section weighted density in an H2, O2, and Rayleigh cross-section weighted density in an H2/air flame; (2) ultraviolet flashlamp imaging of O2, OH, and Rayleigh cross-section weighted density in an H2/air flame; and (3) Raman Excitation plus Laser Induced Electronic Fluorescence velocimetry in heater air flows, up to static temperatures of 700 K. Application of these techniques, individually or in combination, should provide useful insight into mixing and reacting flows containing H2, O2, N2 and reaction intermediates such as OH.

  1. Species and velocity visualization of unseeded heated air and combusting hydrogen jets using laser and flashlamp sources

    NASA Technical Reports Server (NTRS)

    Diskin, Glenn S.; Lempert, Walter R.; Miles, Richard B.

    1990-01-01

    Three techniques for the visualization of species and/or velocity in unseeded H2/air flames and heated air jets are described and preliminary image data are presented. The techniques described are: (1) simultaneous ArF laser imaging of H2, O2, and Rayleigh cross-section weighted density in an H2, O2, and Rayleigh cross-section weighted density in an H2/air flame; (2) ultraviolet flashlamp imaging of O2, OH, and Rayleigh cross-section weighted density in an H2/air flame; and (3) Raman Excitation plus Laser Induced Electronic Fluorescence velocimetry in heater air flows, up to static temperatures of 700 K. Application of these techniques, individually or in combination, should provide useful insight into mixing and reacting flows containing H2, O2, N2 and reaction intermediates such as OH.

  2. THE EFFECT OF PECULIAR VELOCITIES ON SUPERNOVA COSMOLOGY

    SciTech Connect

    Davis, Tamara M.; Sinclair, Benjamin; Hui, Lam; Frieman, Joshua A.; Kessler, Richard; Haugbolle, Troels; Sollerman, Jesper; Bassett, Bruce; Marriner, John; Moertsell, Edvard; Nichol, Robert C.; Richmond, Michael W.; Sako, Masao; Schneider, Donald P.; Smith, Mathew

    2011-11-01

    We analyze the effect that peculiar velocities have on the cosmological inferences we make using luminosity distance indicators, such as Type Ia supernovae. In particular we study the corrections required to account for (1) our own motion, (2) correlations in galaxy motions, and (3) a possible local under- or overdensity. For all of these effects we present a case study showing the impact on the cosmology derived by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SN Survey). Correcting supernova (SN) redshifts for the cosmic microwave background (CMB) dipole slightly overcorrects nearby SNe that share some of our local motion. We show that while neglecting the CMB dipole would cause a shift in the derived equation of state of {Delta}w {approx} 0.04 (at fixed {Omega}{sub m}), the additional local-motion correction is currently negligible ({Delta}w {approx}< 0.01). We then demonstrate a covariance-matrix approach to statistically account for correlated peculiar velocities. This down-weights nearby SNe and effectively acts as a graduated version of the usual sharp low-redshift cut. Neglecting coherent velocities in the current sample causes a systematic shift of {Delta}w {approx} 0.02. This will therefore have to be considered carefully when future surveys aim for percent-level accuracy and we recommend our statistical approach to down-weighting peculiar velocities as a more robust option than a sharp low-redshift cut.

  3. Simultaneous measurement of temperature and velocity of air flow over 1000°C using two color phosphor thermometry

    NASA Astrophysics Data System (ADS)

    Fukuta, Masatoshi; Someya, Satoshi; Munakata, Tetsuo; LCS Team

    2016-11-01

    Thermal barrier coatings were applied to the gas turbines and the internal combustion engines for the high thermal efficiency. The evaluation and the improvement of coatings require to measure transient gaseous flow near the wall with coatings. An aim of this study is to combine a two color phosphor thermometry with the PIV to measure simultaneously temperature and velocity of the gas over 1000°C. The temperature and velocity distribution of an impinging jet of high temperature air was simultaneously visualized in experiments. The temperature was estimated from an intensity ratio of luminescent in different ranges of wavelength, 500 600 nm and 400 480 nm. Uncertainty of measured temperature was less than 10°C. Temperatures measured by the developed method and by thermocouples were agreed well. The measured velocity by the PIV with phosphor particles were also agreed well with the velocity measured by a Laser Doppler Velocimeter.

  4. Ground cloud air quality effects

    NASA Technical Reports Server (NTRS)

    Brubaker, K. L.

    1980-01-01

    The effects of the ground cloud associated with launching of a large rocket on air quality are discussed. The ground cloud consists of the exhaust emitted by the rocket during the first 15 to 25 seconds following ignition and liftoff, together with a large quantity of entrained air, cooling water, dust and other debris. Immediately after formation, the ground cloud rises in the air due to the buoyant effect of its high thermal energy content. Eventually, at an altitude typically between 0.7 and 3 km, the cloud stabilizes and is carried along by the prevailing wind at that altitude. For the use of heavy lift launch vehicles small quantities of nitrogen oxides, primarily nitric oxide and nitrogen dioxide, are expected to be produced from a molecular nitrogen impurity in the fuel or liquid oxygen, or from entrainment and heating of ambient air in the hot rocket exhaust. In addition, possible impurities such as sulfur in the fuel would give rise to a corresponding amount of oxidation products such as sulfur dioxide.

  5. Effect of velocity profile skewing on blood velocity and volume flow waveforms derived from maximum Doppler spectral velocity.

    PubMed

    Mynard, Jonathan P; Steinman, David A

    2013-05-01

    Given evidence that fully developed axisymmetric flow may be the exception rather than the rule, even in nominally straight arteries, maximum velocity (V(max)) can lie outside the Doppler sample volume (SV). The link between V(max) and derived quantities, such as volume flow (Q), may therefore be more complex than commonly thought. We performed idealized virtual Doppler ultrasound on data from image-based computational fluid dynamics (CFD) models of the normal human carotid artery and investigated how velocity profile skewing and choice of sample volume affected V(max) waveforms and derived Q variables, considering common assumptions about velocity profile shape (i.e., Poiseuille or Womersley). Severe velocity profile skewing caused substantial errors in V(max) waveforms when using a small, centered SV, although peak V(max) was reliably detected; errors with a long SV covering the vessel diameter were orientation dependent but lower overall. Cycle-averaged Q calculated from V(max) was typically within ±15%, although substantial skewing and use of a small SV caused 10%-25% underestimation. Peak Q derived from Womersley's theory was generally accurate to within ±10%. V(max) pulsatility and resistance indexes differed from Q-based values, although the Q-based resistance index could be predicted reliably. Skewing introduced significant error into V(max)-derived Q waveforms, particularly during mid-to-late systole. Our findings suggest that errors in the V(max) and Q waveforms related to velocity profile skewing and use of a small SV, or orientation-dependent errors for a long SV, could limit their use in wave analysis or for constructing characteristic or patient-specific flow boundary conditions for model studies.

  6. Curvature effects on the velocity profile in turbulent pipe flow.

    PubMed

    Grossmann, Siegfried; Lohse, Detlef

    2017-02-01

    Prandtl and von Kármán have developed the famous log-law for the mean velocity profile for turbulent flow over a plate. The log-law has also been applied to turbulent pipe flow, though the wall surface is curved (in span-wise direction) and has finite diameter. Here we discuss the theoretical framework, based on the Navier-Stokes equations, with which one can describe curvature effects and also the well-known finite-size effects in the turbulent mean-velocity profile. When comparing with experimental data we confirm that the turbulent eddy viscosity must contain both curvature and finite-size contributions and that the usual ansatz for the turbulent eddy viscosity as being linear in the wall distance is insufficient, both for small and large wall distances. We analyze the experimental velocity profile in terms of an r-dependent generalized turbulent viscosity [Formula: see text] (with [Formula: see text] being the wall distance, a pipe radius, u * shear stress velocity, and g([Formula: see text]/a) the nondimensionalized viscosity), which reflects the radially strongly varying radial eddy transport of the axial velocity. After the near wall linear viscous sublayer, which soon sees the pipe wall's curvature, a strong transport (eddy) activity steepens the profile considerably, leading to a maximum in g([Formula: see text]/a) at about half radius, then decreasing again towards the pipe center. This reflects the smaller eddy transport effect near the pipe's center, where even in strongly turbulent flow (the so-called "ultimate state") the profile remains parabolic. The turbulent viscous transport is strongest were the deviations of the profile from parabolic are strongest, and this happens in the range around half radius.

  7. The Effect of Compressibility on the Pressure Reading of a Prandtl Pitot Tube at Subsonic Flow Velocity

    NASA Technical Reports Server (NTRS)

    Walchner, O

    1939-01-01

    Errors arising from yawed flow were also determined up to 20 degrees angle of attack. In axial flow, the Prandtl pitot tube begins at w/a approx. = 0.8 to give an incorrect static pressure reading, while it records the tank pressure correctly, as anticipated, up to sonic velocity. Owing to the compressibility of the air, the Prandtl pitot tube manifests compression shocks when the air speed approaches velocity of sound. This affects the pressure reading of the instrument. Because of the increasing importance of high speed in aviation, this compressibility effect is investigated in detail.

  8. Effect of Core Training on Male Handball Players’ Throwing Velocity

    PubMed Central

    García-Ruiz, José; Cortell-Tormo, Juan Manuel; Tortosa-Martínez, Juan

    2017-01-01

    Abstract In handball, throwing velocity is considered to be one of the essential factors in achieving the ultimate aim of scoring a goal. The objective of the present study was to analyze the effect of a core training program on throwing velocity in 30 handball players (age 18.7 ± 3.4 years, body height 179.3 ± 7.0 cm, body mass 78.9 ± 7.7 kg), 16 of whom were in the junior category and 14 of whom were in the senior category. The 30 players were randomly divided into two groups, the control group (n = 15) and the experimental group (n = 15). For a period of ten weeks, both groups attended their regular handball training sessions (four per week), but in addition, the experimental group participated in a program specifically aimed at progressively strengthening the lumbo-pelvic region and consisting of seven exercises performed after the general warm-up in each regular session. Pre- and post-tests were carried out to analyze each player’s throwing velocity from different throwing positions and thus assess the effects of this specific training program. Statistically significant differences (p ≤ 0.05) in throwing velocity were observed between the experimental group, which presented a percentage improvement of 4.5%, and the control group, which did not show any improvement. The results seem to indicate that an increase in the strength and stability of the lumbo-pelvic region can contribute to an improvement in the kinetic chain of the specific movement of throwing in handball, thus, increasing throwing velocity. PMID:28469756

  9. Laminar burning velocities of lean hydrogen-air mixtures at pressures up to 1.0 MPa

    SciTech Connect

    Bradley, D.; Lawes, M.; Liu, Kexin; Woolley, R.; Verhelst, S.

    2007-04-15

    Values of laminar burning velocity, u{sub l}, and the associated strain rate Markstein number, Ma{sub sr}, of H{sub 2}-air mixtures have been obtained from measurements of flame speeds in a spherical explosion bomb with central ignition. Pressures ranged from 0.1 to 1.0 MPa, with values of equivalence ratio between 0.3 and 1.0. Many of the flames soon became unstable, with an accelerating flame speed, due to Darrieus-Landau and thermodiffusive instabilities. This effect increased with pressure. The flame wrinkling arising from the instabilities enhanced the flame speed. A method is described for allowing for this effect, based on measurements of the flame radii at which the instabilities increased the flame speed. This enabled u{sub l} and Ma{sub sr} to be obtained, devoid of the effects of instabilities. With increasing pressure, the time interval between the end of the ignition spark and the onset of flame instability, during which stable stretched flame propagation occurred, became increasingly small and very high camera speeds were necessary for accurate measurement. Eventually this time interval became so short that first Ma{sub sr} and then u{sub l} could not be measured. Such flame instabilities throw into question the utility of u{sub l} for high pressure, very unstable, flames. The measured values of u{sub l} are compared with those predicted by detailed chemical kinetic models of one-dimensional flames. (author)

  10. The effect of velocity filtering in pressure estimation

    NASA Astrophysics Data System (ADS)

    Schiavazzi, D. E.; Nemes, A.; Schmitter, S.; Coletti, F.

    2017-05-01

    Velocity field measurements allow, in principle, the evaluation of the pressure field by integrating the equations of fluid motion. Unavoidable experimental uncertainty, however, may result in unreliable estimates. In this study, we use the Poisson pressure equation to estimate the relative pressure from experimental velocities, and investigate how pre-processing with smoothing and solenoidal filters affects this estimate. For diffusion dominated laminar flow or for turbulent flow modeled through an eddy viscosity, measurement noise significantly affects the results. In this case, solenoidal filtering provides superior performance over other smoothing approaches, as it preserves the second spatial derivatives of the velocity field. For laminar flows dominated by advection or acceleration components of the pressure gradient, the choice of the filter appears to have little effect under limited noise, while smoothing produces improved relative pressure estimates for higher noise intensities. The above statements are verified using idealized flow conditions, numerical fluid dynamics simulations, and velocity fields from in-vivo and in-vitro magnetic resonance velocimetry.

  11. Effect of Observing Session Duration on Static GPS Velocity Estimation

    NASA Astrophysics Data System (ADS)

    Sanli, D. U.; Akarsu, V.; Arslan, E.

    2011-12-01

    The effect of the observing session duration on static GPS positional accuracies has previously been detected. This study further investigates this effect on the estimated velocities. This is especially important for tectonic/deformation monitoring studies that use GPS observations shorter than 24 h. A sample has been made from 13 IGS stations that cover the earth globally. GIPSY research software has been used for the processing. GPS velocities have been estimated from GPS campaigns using the time series of 15-year length on average. The sampling rate was chosen as one observation per year as still used by some of the tectonic studies today. The solutions from 24 h data were taken as the truth and the velocities estimated from the shorter sessions were assessed. We show how the coefficient of multiple determination R-squared can successfully be used to assess the accuracy of GPS velocities from campaign measurements. Results based on this assessment indicate that vertical velocities are affected most when observation sessions shorter than 24 h are used. An accuracy improvement of 12% on average on the vertical velocity is gained as the observation session is extended from 8 h to 12 h. Individual solutions show that this improvement can be as high as 32%. Similarly, the improvement in horizontal velocities is 3% on average but it could be as high as 13% for some stations. A further amount of improvement at similar levels can only be obtained when observing session duration is extended from 12 h to 18 h which is not practical when one needs to use the advantage of the day light. This suggests us that the lowest limit for the session length of GPS campaigns needs to be 12 h rather than 6-8 h which have typically been applied conventionally by many research groups up to date. Using 12 h of GPS observations, 90% of the vertical deformation pattern is recovered. The percentages for the same duration are 96 and 100 for the longitudinal and latitudinal deformations

  12. Carbon isotope evidence for the latitudinal distribution and wind speed dependence of the air-sea gas transfer velocity

    NASA Astrophysics Data System (ADS)

    Krakauer, Nir Y.; Randerson, James T.; Primeau, François W.; Gruber, Nicolas; Menemenlis, Dimitris

    2006-11-01

    The air-sea gas transfer velocity is an important determinant of the exchange of gases, including CO2, between the atmosphere and ocean, but the magnitude of the transfer velocity and what factors control it remains poorly known. Here, we use oceanic and atmospheric observations of 14C and 13C to constrain the global mean gas transfer velocity as well as the exponent of its wind speed dependence, utilizing the distinct signatures left by the air-sea exchange of 14CO2 and 13CO2. While the atmosphere and ocean inventories of 14CO2 and 13CO2 constrain the mean gas transfer velocity, the latitudinal pattern in the atmospheric and oceanic 14C and 13C distributions contain information about the wind speed dependence. We computed the uptake of bomb 14C by the ocean for different transfer velocity patterns using pulse response functions from an ocean general circulation model, and evaluated the match between the predicted bomb 14C concentrations and observationally based estimates for the 1970s-1990s. Using a wind speed climatology based on satellite measurements, we solved either for the best-fit global relationship between gas exchange and mean wind speed or for the mean gas transfer velocity over each of 11 ocean regions. We also compared the predicted consequences of different gas exchange relationships on the rate of change and interhemisphere gradient of 14C in atmospheric CO2 with tree-ring and atmospheric measurements. Our results suggest that globally, the dependence of the air-sea gas transfer velocity on wind speed is close to linear, with an exponent of 0.5 +/- 0.4, and that the global mean gas transfer velocity at a Schmidt number of 660 is 20 +/- 3 cm/hr, similar to the results of previous analyses. We find that the air-sea flux of 13C estimated from atmosphere and ocean observations also suggests a lower than quadratic dependence of gas exchange on wind speed.

  13. Detailed Comparison of Blast Effects in Air and Vacuum

    SciTech Connect

    Tringe, J W; Molitoris, J D; Garza, R G; Andreski, H G; Batteux, J D; Lauderbach, L M; Vincent, E R; Wong, B M

    2007-07-26

    Although blast mitigation is most often achieved with solid shielding, ambient gas pressure can also affect the coupling of shock waves to solid targets. In this work the role of air as an energy transfer medium was examined experimentally by subjecting identical large-area rectangular witness plates to short-range blast effects in air and vacuum ({approx}50 mtorr) at 25 C. The expanding reactant front of 3 kg C4 charges was observed by fast camera to be cylindrically symmetric in both air and vacuum. The horizontal component of the reactant cloud velocity (perpendicular to the witness plates) was constant in both cases, with values of 3.0 and 5.9 km/s for air and vacuum, respectively. As a result of the blast, witness plates were plastically deformed into a shallow dish geometry, with local maxima 30 and 20 mm deep for air and vacuum, respectively. The average plate deflection from the air blast was 11 mm, {approx}10% deeper than the average vacuum plate deflection. Shock pressure estimates were made with a simple impedance-matching model, and indicate peak values in the 30-50 MPa range are consistent with the reactant cloud density and velocity. However, more detailed analysis is necessary to definitely establish the mechanisms by which air couples shock energy to the plates.

  14. Effects of wind velocity and slope on flame properties

    Treesearch

    David R. Weise; Gregory S. Biging

    1996-01-01

    Abstract: The combined effects of wind velocity and percent slope on flame length and angle were measured in an open-topped, tilting wind tunnel by burning fuel beds composed of vertical birch sticks and aspen excelsior. Mean flame length ranged from 0.08 to 1.69 m; 0.25 m was the maximum observed flame length for most backing fires. Flame angle ranged from -46o to 50o...

  15. Effects of wind velocity and slope on fire behavior

    Treesearch

    D.R. Weise; G.S. Biging

    1994-01-01

    Effects of wind velocity and slope on fire spread rate and flame length were examined. Fuel beds of vertical sticks (13.97 cm x 0.455 cm x 0.1 10 cm) and coarse excelsior were burned in an open-topped tilting wind tunnel. Mean fuel moisture content of sticks and excelsior was 11% and 12%, respectively. Mean surface area to volume ratio was 23 cm-! Five slopes (negative...

  16. Forging of compressor blades: Temperature and ram velocity effects

    SciTech Connect

    Saigal, A.; Zhen, K.; Chan, T.S.

    1995-07-01

    Forging is one of the most widely used manufacturing process for making high-strength, structurally integrated, impact and creep-resistant Ti-6Al-4V compressor blades for jet engines. In addition, in modern metal forming technology, finite element analysis method and computer modeling are being extensively employed for initial evaluation and optimization of various processes, including forging. In this study, DEFORM, a rigid viscoplastic two-dimensional finite element code was used to study the effects of initial die temperature and initial ram velocity on the forging process. For a given billet, die temperature and ram velocity influence the strain rate, temperature distribution,and thus the flow stress of the material. The die temperature and the ram velocity were varied over the range 300 to 700 F and 15--25 in./sec, respectively, to estimate the maximum forging load and the total energy required to forge compressor blades. The ram velocity was assumed to vary linearly as a function of stroke. Based on the analysis,it was found the increasing the die temperature from 300 to 700 F decreases the forging loads by 19.9 percent and increases the average temperature of the workpiece by 43 F. Similarly, increasing the initial ram velocity from 15 to 25 in./sec decreases the forging loads by 25.2 percent and increases the average temperature of the workpiece by 36 F. The nodal temperature distribution is bimodal in each case. The forging energy required to forge the blades is approximately 18 kips *in./in.

  17. Velocity Profiles in a Rotating Drum: The Effects of Cohesion

    NASA Astrophysics Data System (ADS)

    Brewster, Robert C.; Silbert, Leonardo E.; Grest, Gary S.; Levine, Alex J.

    2007-03-01

    The dynamics of granular media in a rotating drum is important in a wide range of applications in industry associated with mixing granular materials. The rotating drum also serves as a standard experimental geometry to observe continuous avalanching in the laboratory. We study the effect of interparticle cohesion on the velocity field of the rotating drum using large scale granular dynamics simulations. Such cohesion is easily introduced in the system by a wetting fluid that forms menisci at interparticle contacts. Previously, we have examined the effect of interparticle cohesion in gravity driven chute flows, and have shown that the cohesion has a dramatic effect on the granular rheology. For strong enough cohesion, these forces generate a coherently moving plug at the free surface. In this talk, we examine the velocity profile in the rotating drum geometry in this plug-flow regime. We compare our results for angle of the pile in the continuous flow regime to the experiments of Nowak et al. [Nature Physics, 1 (2005)] and we examine the stress and velocity profile within the pile as well.

  18. A Novel Method for Saving Energy of HVAC Using Autonomous Variable Air Velocity Based On Thermal Comfort

    NASA Astrophysics Data System (ADS)

    Auttawaitkul, Yingrak; Therdyothin, Apichit; Monyakul, Veerapol

    The tower building categories used in the energy breakdown are Electric lighting, the heating, ventilating, and air conditioning (HVAC) auxiliary and Office equipment. The HVAC system has the greatest energy saving potential as it is the major energy consumer. It consumes approximately 64 percent of the total building energy. A good HVAC in buildings helps reduce energy use and maintain occupant comfort. To this end, there are many systems and equipment conditions to observe HVAC systems. This paper critically examines indoor climate control technologies to reduce the HVAC system energy. The autonomous variable air volume diffusers are interconnected to simulate the responses of the system. The constrained optimal control problem is formulated and solved for increased operative temperature. The experiment results show that by increasing the operative temperature from 25°C to 27°C, the electrical energy can be saved by 11.64 percent. The proposed method feeds back the output air to input boundary conditions of the same human thermal sensation even though the air velocity distributions in the sections are different from each other. The experiment results also show that the proposed method can maintain the PMV values in an interval of -0.5 to +0.5 at an acceptable air velocity range.

  19. A wind tunnel study of air flow in waving wheat: Two-point velocity statistics

    NASA Astrophysics Data System (ADS)

    Shaw, R. H.; Brunet, Y.; Finnigan, J. J.; Raupach, M. R.

    1995-12-01

    Two-point, space-time correlations of streamwise and vertical velocity were obtained from a wind tunnel simulation of an atmospheric surface layer with an underlying model wheat canopy constructed of flexible nylon stalks. Velocity data extend from 1/6 canopy height to several canopy heights, with in excess of 2000 three-dimensional vector separations of the two x-wire probes. Isocorrelation contours over an x, z slice show the streamwise velocity autocorrelation to be roughly circular, such that vertical velocities at the same horizontal position but different heights are closely in phase. Cross-correlations between the two velocity components reflect this difference to some extent. Lateral displacements of the probes revealed side lobes with correlations of reversed sign but we cannot positively link this pattern to particular vorticular structures. Integral length scales obtained directly from the spatial correlations match similar scales deduced from single-point time series with Taylor's hypothesis at 2 to 3 times the canopy height but greatly exceed such scales at lower levels, particularly within the wheat. We conclude that the reversed sign lateral lobes are important components of the correlation field and that an integral length scale for the lateral direction must be defined such that they are included. Convective velocities obtained from the time lag to optimally restore correlation lost by physical separation of the probes change only slowly with height and greatly exceed the mean wind velocity within and immediately above the canopy. Thus, mean wind velocity is not a suitable proxy for convective velocity in the application of Taylor's hypothesis in this situation. The ratio of vertical to longitudinal convective velocity for the streawise velocity signal yields a downwind tilt angle of about 39° which is probably a better estimate of the slope of the dominant fluid motions than the tilt of the major axis of the isocorrellation contours mentioned

  20. Influence of current velocity and wind speed on air-water gas exchange in a mangrove estuary

    NASA Astrophysics Data System (ADS)

    Ho, David T.; Coffineau, Nathalie; Hickman, Benjamin; Chow, Nicholas; Koffman, Tobias; Schlosser, Peter

    2016-04-01

    Knowledge of air-water gas transfer velocities and water residence times is necessary to study the fate of mangrove derived carbon exported into surrounding estuaries and ultimately to determine carbon balances in mangrove ecosystems. For the first time, the 3He/SF6 dual tracer technique, which has been proven to be a powerful tool to determine gas transfer velocities in the ocean, is applied to Shark River, an estuary situated in the largest contiguous mangrove forest in North America. The mean gas transfer velocity was 3.3 ± 0.2 cm h-1 during the experiment, with a water residence time of 16.5 ± 2.0 days. We propose a gas exchange parameterization that takes into account the major sources of turbulence in the estuary (i.e., bottom generated shear and wind stress).

  1. Anomalous high-velocity outbursts ejected from the surface of tungsten microdroplets in a flow of argon-air plasma

    NASA Astrophysics Data System (ADS)

    Gulyaev, I. P.; Dolmatov, A. V.; Gulyaev, P. Yu; Iordan, V. I.; Kharlamov, M. Yu; Krivtsun, I. V.

    2016-02-01

    For the first time, a phenomenon of high-velocity outbursts ejected from the surface of liquid tungsten microparticles in a flow of argon-air plasma under atmospheric pressure was observed. As tungsten particles sized 50 to 200 μm moved in a plasma flow, stratified radiating spheres up to 9 mm in diameter formed around such particles. The spheres were sources of high-velocity outbursts whose ejection direction coincided with the direction of the plasma flow. The velocity of the anomalous outbursts amounted to 3-20 km/s. In the outburst images, the distribution of glow intensity along outburst tracks exhibited a wavy decaying behavior with a wavelength of 5-15 mm. Possible physical factors that could be the cause of the phenomenon are discussed.

  2. Group-phase Velocity Difference and THz Oscillation of the Nonlinear Refractive Index in Air: Particle-like Solutions

    SciTech Connect

    Kovachev, L. M.

    2009-10-29

    We present an analytical approach to the theory of optical pulses with superbroad spectrum propagated in air. The corresponding modified amplitude envelope equation admits oscillated with terahertz frequency nonlinear term The fluctuation is due to the group and phase velocity difference. In the partial case of femtosecond pulses with power, little above the critical for self-focusing, exact (3+1)D particle-like solution is found.

  3. Spatially and Temporally Resolved Measurements of Velocity in a H2-air Combustion-Heated Supersonic Jet

    NASA Technical Reports Server (NTRS)

    Bivolaru, Daniel; Cutler, Andrew D.; Danehy, Paul M.; Gaffney, Richard L.; Baurle, Robert a.

    2009-01-01

    This paper presents simultaneous measurements at multiple points of two orthogonal components of flow velocity using a single-shot interferometric Rayleigh scattering (IRS) technique. The measurements are performed on a large-scale Mach 1.6 (Mach 5.5 enthalpy) H2-air combustion jet during the 2007 test campaign in the Direct Connect Supersonic Combustion Test facility at NASA Langley Research Center. The measurements are performed simultaneously with CARS (Coherent Anti-stokes Raman Spectroscopy) using a combined CARS-IRS instrument with a common path 9-nanosecond pulsed, injection-seeded, 532-nm Nd:YAG laser probe pulse. The paper summarizes the measurements of velocities along the core of the vitiated air flow as well as two radial profiles. The average velocity measurement near the centerline at the closest point from the nozzle exit compares favorably with the CFD calculations using the VULCAN code. Further downstream, the measured axial velocity shows overall higher values than predicted with a trend of convergence at further distances. Larger discrepancies are shown in the radial profiles.

  4. Combustion Velocity of Benzine-Benzol-Air Mixtures in High-Speed Internal-Combustion Engines

    NASA Technical Reports Server (NTRS)

    Schnauffer, Kurt

    1932-01-01

    The present paper describes a device whereby rapid flame movement within an internal-combustion engine cylinder may be recorded and determined. By the aid of a simple cylindrical contact and an oscillograph the rate of combustion within the cylinder of an airplane engine during its normal operation may be measured for gas intake velocities of from 30 to 35 m/s and for velocities within the cylinder of from 20 to 25 m/s. With it the influence of mixture ratios, of turbulence, of compression ratio and kind of fuel on combustion velocity may be determined. Besides the determination of the influence of the above factors on combustion velocity, the degree of turbulence may also be determined. As a unit of reference in estimating the degree of turbulence, the intake velocity of the charge is chosen.

  5. Pickup Ion Velocity Distributions at Titan: Effects of Spatial Gradients

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Sittler, E. C.

    2004-01-01

    The principle source of pickup ions at Titan is its neutral exosphere, extending well above the ionopause into the magnetosphere of Saturn or the solar wind, depending on the moon's orbital position. Thermal and nonthermal processes in the thermosphere generate the distribution of neutral atoms and molecules in the exosphere. The combination of these processes and the range of mass numbers, 1 to over 28, contribute to an exospheric source structure that produces pickup ions with gyroradii that are much larger or smaller than the corresponding scale heights of their neutral sources. The resulting phase space distributions are dependent on the spatial structure of the exosphere as well as that of the magnetic field and background plasma. When the pickup ion gyroradius is less than the source gas scale height, the pickup ion velocity distribution is characterized by a sharp cutoff near the maximum speed, which is twice that of the ambient plasma times the sine of the angle between the magnetic field and the flow velocity. This was the case for pickup H(sup +) ions identified during the Voyager 1 flyby. In contrast, as the gyroradius becomes much larger than the scale height, the peak of the velocity distribution in the source region recedes from the maximum speed. Iri addition, the amplitude of the distribution near the maximum speed decreases. These more beam like distributions of heavy ions were not observed from Voyager 1 , but should be observable by more sensitive instruments on future spacecraft, including Cassini. The finite gyroradius effects in the pickup ion velocity distributions are studied by including in the analysis the possible range of spatial structures in the neutral exosphere and background plasma.

  6. Pickup Ion Velocity Distributions at Titan: Effects of Spatial Gradients

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Sittler, E. C.

    2004-01-01

    The principle source of pickup ions at Titan is its neutral exosphere, extending well above the ionopause into the magnetosphere of Saturn or the solar wind, depending on the moon's orbital position. Thermal and nonthermal processes in the thermosphere generate the distribution of neutral atoms and molecules in the exosphere. The combination of these processes and the range of mass numbers, 1 to over 28, contribute to an exospheric source structure that produces pickup ions with gyroradii that are much larger or smaller than the corresponding scale heights of their neutral sources. The resulting phase space distributions are dependent on the spatial structure of the exosphere as well as that of the magnetic field and background plasma. When the pickup ion gyroradius is less than the source gas scale height, the pickup ion velocity distribution is characterized by a sharp cutoff near the maximum speed, which is twice that of the ambient plasma times the sine of the angle between the magnetic field and the flow velocity. This was the case for pickup H(sup +) ions identified during the Voyager 1 flyby. In contrast, as the gyroradius becomes much larger than the scale height, the peak of the velocity distribution in the source region recedes from the maximum speed. Iri addition, the amplitude of the distribution near the maximum speed decreases. These more beam like distributions of heavy ions were not observed from Voyager 1 , but should be observable by more sensitive instruments on future spacecraft, including Cassini. The finite gyroradius effects in the pickup ion velocity distributions are studied by including in the analysis the possible range of spatial structures in the neutral exosphere and background plasma.

  7. Measurements of the Air-flow Velocity in the Cylinder of an Airplane Engine

    NASA Technical Reports Server (NTRS)

    Wenger, Hermann

    1939-01-01

    The object of the present investigation is to determine the velocity in the BMW-VI cylinder of an externally driven single-cylinder test engine at high engine speeds using the hot-wire method of Ulsamer.

  8. A pulsed wire probe for the measurement of velocity and flow direction in slowly moving air.

    PubMed

    Olson, D E; Parker, K H; Snyder, B

    1984-02-01

    This report describes the theory and operation of a pulsed-probe anemometer designed to measure steady three-dimensional velocity fields typical of pulmonary tracheo-bronchial airflows. Local velocities are determined by measuring the transport time and orientation of a thermal pulse initiated at an upstream wire and sensed at a downstream wire. The transport time is a reproducible function of velocity and the probe wire spacing, as verified by a theoretical model of convective heat transfer. When calibrated the anemometer yields measurements of velocity accurate to +/- 5 percent and resolves flow direction to within 1 deg at airspeeds greater than or equal to 10 cm/s. Spatial resolution is +/- 0.5 mm. Measured flow patterns typical of curved circular pipes are included as examples of its application.

  9. Threshold velocities for input of soil particles into the air by desert soils

    SciTech Connect

    Gillette, D.A.; Adams, J.; Endo, A.; Smith, D.; Kihl, R.

    1980-10-20

    Desert soils mostly from the Mojave Desert were tested for threshold friction velocity (the friction velocity above which soil erosion takes place) with an open-bottomed portable wind tunnel. Several geomorphological settings were chosen to be representative of much of the surface of the Mojave Desert, for example, playas, alluvial fans, and aeolian features. Variables which increase threshold velocity are decreasing proportion of sand, increasing size of dry aggregates of the soil, and increasing fraction of the soil mass larger than 1 mm. Threshold velocity increases with different types of soil surfaces in the following order: disturbed soils (except disturbed heavy clay soils), sand dunes, alluvial and aeolian sand deposits, disturbed playa soils, skirts of playas, playa centers, and desert pavement (alluvial deposits). 21 references, 5 figures, 6 tables.

  10. Threshold velocities for input of soil particles into the air by desert soils

    NASA Astrophysics Data System (ADS)

    Gillette, Dale A.; Adams, John; Endo, Albert; Smith, Dudley; Kihl, Rolf

    1980-10-01

    Desert soils mostly from the Mojave Desert were tested for threshold friction velocity (the friction velocity above which soil erosion takes place) with an open-bottomed portable wind tunnel. Several geomorphological settings were chosen to be representative of much of the surface of the Mojave Desert, for example, playas, alluvial fans, and aeolian features. Variables which increase threshold velocity are decreasing proportion of sand, increasing size of dry aggregates of the soil, and increasing fraction of the soil mass larger than 1 mm. Threshold velocity increases with different types of soil surfaces in the following order: distrubed soils (except disturbed heavy clay soils), sand dunes, alluvial and aeolian sand deposits, disturbed playa soils, skirts of playas, playa centers, and desert pavements (alluvial deposits).

  11. Impact of seasonality and air pollutants on carotid-femoral pulse wave velocity and wave reflection in hypertensive patients

    PubMed Central

    Stea, Francesco; Massetti, Luciano; Taddei, Stefano; Ghiadoni, Lorenzo; Modesti, Pietro Amedeo

    2017-01-01

    Objective The effects of seasonality on blood pressure (BP) and cardiovascular (CV) events are well established, while the influence of seasonality and other environmental factors on arterial stiffness and wave reflection has never been analyzed. This study evaluated whether seasonality (daily number of hours of light) and acute variations in outdoor temperature and air pollutants may affect carotid-femoral pulse wave velocity (PWV) and pressure augmentation. Design and method 731 hypertensive patients (30–88 years, 417 treated) were enrolled in a cross-sectional study during a 5-year period. PWV, central BP, Augmentation Index (AIx) and Augmentation Pressure (AP) were measured in a temperature-controlled (22–24°C) room. Data of the local office of the National Climatic Data Observatory were used to estimate meteorological conditions and air pollutants (PM10, O3, CO, N2O) exposure on the same day. Results PWV (mean value 8.5±1.8 m/s) was related to age (r = 0.467, p<0.001), body mass index (r = 0.132, p<0.001), central systolic (r = 0.414, p<0.001) and diastolic BP (r = 0.093, p = 0.013), daylight hours (r = -0.176, p<0.001), mean outdoor temperature (r = -0.082, p = 0.027), O3 (r = -0.135, p<0.001), CO (r = 0.096, p = 0.012), N2O (r = 0.087, p = 0.022). In multiple linear regression analysis, adjusted for confounders, PWV remained independently associated only with daylight hours (β = -0.170; 95% CI: -0.273 to -0.067, p = 0.001). No significant correlation was found between pressure augmentation and daylight hours, mean temperature or air pollutants. The relationship was stronger in untreated patients and women. Furthermore, a positive, independent association between O3 levels and PWV emerged in untreated patients (β: 0.018; p = 0.029; CI: 0.002 to 0.034) and in women (β: 0.027; p = 0.004; CI: 0.009 to 0.045). Conclusions PWV showed a marked seasonality in hypertensive patients. Environmental O3 levels may acutely reduce arterial stiffness in

  12. The Behavior of Large Low Surface Tension Water Drops Falling at Terminal Velocity in Air.

    DTIC Science & Technology

    To study the behavior of large low surface tension drops in free fall a vertical wind tunnel was constructed. The tunnel is simple, but provides a...low turbulence (0.7%) flow which stably supports large water drops falling at terminal velocity. The influence of reduced surface tension on maximum...drop size, drop terminal velocity and drop shape was investigated. It was found that drops of low surface tension break up at a smaller size than

  13. Cup anemometer calibration: effect of flow velocity distribution

    NASA Astrophysics Data System (ADS)

    Piccato, A.; Spazzini, P. G.; Malvano, R.

    2011-10-01

    The effects of different working conditions and specifically of different velocity profiles on the output of a commercial cup anemometer were analysed experimentally. A simple mathematical model is also presented and provides results in line with the experiments. Results show that a cup anemometer with certain geometrical features can be calibrated through a rotating drag rig by correcting for the bias on the instrument output. The increase in uncertainty caused by this systematic correction was evaluated and applied to the results. The correction was validated by checking the compatibility of calibrations of a cup anemometer at the rotating rig and in a wind tunnel.

  14. Retrieval of Raindrop Size Distribution, Vertical Air Velocity and Water Vapor Attenuation Using Dual-Wavelength Doppler Radar Observations

    NASA Technical Reports Server (NTRS)

    Heymsfield, Gerald M.; Tian, Lin; Li, Lihua; Srivastava, C.

    2005-01-01

    Two techniques for retrieving the slope and intercept parameters of an assumed exponential raindrop size distribution (RSD), vertical air velocity, and attenuation by precipitation and water vapor in light stratiform rain using observations by airborne, nadir looking dual-wavelength (X-band, 3.2 cm and W-band, 3.2 mm) radars are presented. In both techniques, the slope parameter of the RSD and the vertical air velocity are retrieved using only the mean Doppler velocities at the two wavelengths. In the first method, the intercept of the RSD is estimated from the observed reflectivity at the longer wavelength assuming no attenuation at that wavelength. The attenuation of the shorter wavelength radiation by precipitation and water vapor are retrieved using the observed reflectivity at the shorter wavelength. In the second technique, it is assumed that the longer wavelength suffers attenuation only in the melting band. Then, assuming a distribution of water vapor, the melting band attenuation at both wavelengths and the rain attenuation at the shorter wavelength are retrieved. Results of the retrievals are discussed and several physically meaningful results are presented.

  15. Performance of a combined three-hole conductivity probe for void fraction and velocity measurement in air-water flows

    NASA Astrophysics Data System (ADS)

    Borges, João Eduardo; Pereira, Nuno H. C.; Matos, Jorge; Frizell, Kathleen H.

    2010-01-01

    The development of a three-hole pressure probe with back-flushing combined with a conductivity probe, used for measuring simultaneously the magnitude and direction of the velocity vector in complex air-water flows, is described in this paper. The air-water flows envisaged in the current work are typically those occurring around the rotors of impulse hydraulic turbines (like the Pelton and Cross-Flow turbines), where the flow direction is not known prior to the data acquisition. The calibration of both the conductivity and three-hole pressure components of the combined probe in a rig built for the purpose, where the probe was placed in a position similar to that adopted for the flow measurements, will be reported. After concluding the calibration procedure, the probe was utilized in the outside region of a Cross-Flow turbine rotor. The experimental results obtained in the present study illustrate the satisfactory performance of the combined probe, and are encouraging toward its use for characterizing the velocity field of other complex air-water flows.

  16. Fabry-Perot spectroscopy for kinetic temperature and velocity measurements of a high enthalpy air plasma flow

    NASA Astrophysics Data System (ADS)

    Zander, Fabian; Löhle, Stefan; Hermann, Tobias; Fulge, Hannes

    2017-08-01

    The atomic translational temperatures and velocities of a low pressure, high enthalpy air plasma are measured using Fabry-Perot spectroscopy. The measurements presented here are the first measurements using this system at this enthalpy level. The sub-picometre resolution of the unique system has allowed accurate translational temperature and velocity measurements of the atomic species in the plasma. The detection system allows the Doppler broadening of multiple atomic nitrogen and oxygen lines to be measured simultaneously. Additionally, having two optical paths, one perpendicular to the flow and one at 45 deg. allows the Doppler shift to be measured. Measurements were taken during three different plasma wind tunnel tests. Mean atomic nitrogen temperatures of 1.08+/- 0.11 × 104 K and atomic oxygen translational temperatures of 1.23+/- 0.12 ×104 K were measured. The thermal non-equilibrium determined verified earlier measurements of the same phenomena, however, the mechanism behind this has not yet been determined. The mean measured flow velocity was 3350+/- 840~m~s-1 and was consistent between the atomic species. The translational temperature and velocity contribute approximately 35% of the local enthalpy of the flow. The direct measurement of these parameters, removing previously required assumptions, increases the fidelity of the flow characterisation significantly. This allows high quality testing to be conducted in this flow field.

  17. Effects of radial and circumferential inlet velocity profile distortions on performance of a short-length double-annular ram induction combustor

    NASA Technical Reports Server (NTRS)

    Schultz, D. F.; Perkins, P. J.

    1972-01-01

    Inlet air velocity profile tests were conducted on a full-scale short-length 102-centimeter-diameter annual combustor designed for advanced gas turbine engine applications. The inlet profiles studied include radial distortions that were center peaked, and tip peaked, as well as a circumferential distortion which was center peaked for one-third of the circumference and flat for the other two-thirds. An increase in combustor pressure loss was the most significant effect of the radial air velocity distortions. With the circumferential distortion, exit temperature pattern factor doubled when compared to a flat velocity profile.

  18. Melt convection effects on the critical velocity of particle engulfment

    NASA Astrophysics Data System (ADS)

    Sen, S.; Dhindaw, B. K.; Stefanescu, D. M.; Catalina, A.; Curreri, P. A.

    1997-04-01

    Liquid convection ahead of the solidifying interface alters particle behavior in the vicinity of the interface. This effect has not been quantified to date. Relevant directional solidification experiments were conducted using samples of varying thicknesses, as well as normal and low-gravity experiments. A mixture of transparent biphenyl matrix and spherical glass particles, as well as one of succinonitrile matrix with polystyrene particles were used. Two experimental setups were used: a horizontal gradient heating facility (HGF) for horizontal solidification, and a Bridgman-type furnace (BF) for vertical solidification. The convection level during solidification in the HGF was varied by changing the distance between the glass slides containing the composite sample. The BF was used on ground and during parabolic flights, and thus the convection level was changed by alternating low-gravity and high-gravity solidified regions. It was found that the convection level and/or particle buoyancy significantly influences the critical velocity for particle engulfment. At higher natural convection during solidification the critical velocity increases by up to 40%. At very high convection levels engulfment may become impossible because particles fail to interact with the interface. A systematic analysis of some theoretical models was performed in an attempt to evaluate the present level of theoretical understanding of the problem. Methods of evaluating the surface energies required for model validation are also presented.

  19. Simultaneous measurements of air-sea gas transfer velocity and near surface turbulence at low to moderate winds (Invited)

    NASA Astrophysics Data System (ADS)

    Wang, B.; Liao, Q.; Fillingham, J. H.; Bootsma, H. A.

    2013-12-01

    Parameterization of air-sea gas transfer velocity was routinely made with wind speed. Near surface turbulent dissipation rate has been shown to have better correlation with the gas transfer velocity in a variety of aquatic environments (i.e., the small eddy model) while wind speed is low to moderate. Wind speed model may underestimate gas transfer velocity at low to moderate winds when the near surface turbulence is produced by other environmental forcing. We performed a series of field experiments to measure the CO2 transfer velocity, and the statistics of turbulence immediately below the air-water interface using a novel floating PIV and chamber system. The small eddy model was evaluated and the model coefficient was found to be a non-constant, and it varies with the local turbulent level (figure 1). Measure results also suggested an appropriate scaling of the vertical dissipation profile immediately below the interface under non-breaking conditions, which can be parameterized by the wind shear, wave height and wave age (figure 2). Figure 1. Relation between the coefficient of the small eddy model and dissipation rate. The data also include Chu & Jirka (2003) and Vachon et al. (2010). The solid regression line: α = 0.188log(ɛ)+1.158 Figure 2. Non-dimensional dissipation profiles. Symbols: measured data with the floating PIV. Solid line: regression of measured data with a -0.79 decaying rate. Dash line with -2 slope: Terray et al. (1996) relation. Dash line with two layer structure: Siddiqui & Loewen (2007) relation.

  20. Effect of gas velocity on the weakly nonlinear instability of a planar viscous sheet

    SciTech Connect

    Yang, Li-Jun Chen, Pi-Min; Wang, Chen

    2014-07-15

    A weakly nonlinear spatial instability of a two-dimensional planar viscous sheet for sinuous disturbances in a co-flowing inviscid gas stream is investigated theoretically, with an emphasis on the effect of the surrounding gas velocity. The solutions of the second-order interface disturbances are derived and the wave deformation has been computed. The results indicate that the second-order surface disturbance of the fundamental sinuous mode is varicose, which causes the thinning and the subsequent breakup of the liquid sheet. The nonlinear behaviors of the planar sheet are quite sensitive to variations in gas-to-liquid velocity ratio. The deviation of the velocity ratio from the value of unity leads to a larger growth rate, a larger second-order initial amplitude, and a shorter breakup length, and therefore enhances the instability. The growth rates predicted by the present nonlinear analysis according to the shortest breakup length are generally smaller than the linear predictions and can better conform to the experimental measures of Barreras et al. [“Linear instability analysis of the viscous longitudinal perturbation on an air-blasted liquid sheets,” Atomization Sprays 11, 139 (2001)]. Furthermore, the wave deformations of the most unstable disturbances are presented. The nonlinear instability of the planar sheet for a fixed velocity difference is performed. An equal increase of the gas and liquid velocity reduces the spatial growth rate and increases the breakup length, but generally has no influences on the second-order initial amplitude and the wavelength of the disturbance.

  1. The influence of topography on vertical velocity of air in relation to severe storms near the Southern Andes Mountains

    NASA Astrophysics Data System (ADS)

    de la Torre, A.; Pessano, H.; Hierro, R.; Santos, J. R.; Llamedo, P.; Alexander, P.

    2015-04-01

    On the basis of 180 storms which took place between 2004 and 2011 over the province of Mendoza (Argentina) near to the Andes Range at southern mid-latitudes, we consider those registered in the northern and central crop areas (oases). The regions affected by these storms are currently protected by an operational hail mitigation project. Differences with previously reported storms detected in the southern oasis are highlighted. Mendoza is a semiarid region situated roughly between 32S and 37S at the east of the highest Andes top. It forms a natural laboratory where different sources of gravity waves, mainly mountain waves, occur. In this work, we analyze the effects of flow over topography generating mountain waves and favoring deep convection. The joint occurrence of storms with hail production and mountain waves is determined from mesoscale numerical simulations, radar and radiosounding data. In particular, two case studies that properly represent diverse structures observed in the region are considered in detail. A continuous wavelet transform is applied to each variable and profile to detect the main oscillation modes present. Simulated temperature profiles are validated and compared with radiosounding data. Each first radar echo, time and location are determined. The necessary energy to lift a parcel to its level of free convection is tested from the Convective Available Potential Energy and Convection Inhibition. This last parameter is compared against the mountain waves' vertical kinetic energy. The time evolution and vertical structure of vertical velocity and equivalent potential temperature suggest in both cases that the detected mountain wave amplitudes are able to provide the necessary energy to lift the air parcel and trigger convection. A simple conceptual scheme linking the dynamical factors taking place before and during storm development is proposed.

  2. Size and Velocity Characteristics of Droplets Generated by Thin Steel Slab Continuous Casting Secondary Cooling Air-Mist Nozzles

    NASA Astrophysics Data System (ADS)

    Minchaca M, J. I.; Castillejos E, A. H.; Acosta G, F. A.

    2011-06-01

    Direct spray impingement of high temperature surfaces, 1473 K to 973 K (1200 °C to 700 °C), plays a critical role in the secondary cooling of continuously cast thin steel slabs. It is known that the spray parameters affecting the local heat flux are the water impact flux w as well as the droplet velocity and size. However, few works have been done to characterize the last two parameters in the case of dense mists ( i.e., mists with w in the range of 2 to 90 L/m2s). This makes it difficult to rationalize how the nozzle type and its operating conditions must be selected to control the cooling process. In the present study, particle/droplet image analysis was used to determine the droplet size and velocity distributions simultaneously at various locations along the major axis of the mist cross section at a distance where the steel strand would stand. The measurements were carried out at room temperature for two standard commercial air-assisted nozzles of fan-discharge type operating over a broad range of conditions of practical interest. To achieve statistically meaningful samples, at least 6000 drops were analyzed at each location. Measuring the droplet size revealed that the number and volume frequency distributions were fitted satisfactorily by the respective log-normal and Nukiyama-Tanasawa distributions. The correlation of the parameters of the distribution functions with the water- and air-nozzle pressures allowed for reasonable estimation of the mean values of the size of the droplets generated. The ensemble of measurements across the mist axis showed that the relationship between the droplet velocity and the diameter exhibited a weak positive correlation. Additionally, increasing the water flow rate at constant air pressure caused a decrease in the proportion of the water volume made of finer droplets, whereas the volume proportion of faster droplets augmented until the water flow reached a certain value, after which it decreased. Diminishing the air

  3. Effects of Angular Scattering on Ion Velocity Distribution Functions

    NASA Astrophysics Data System (ADS)

    Wang, Huihui; Sukhomlinov, Vladimir; Kaganovich, Igor; Mustafaev, Alexander

    2016-09-01

    An approximation model for total elastic and charge exchange ion-atom angular differential scattering cross sections is developed for simulations of the ion velocity distribution functions (IVDF), which is validated by the experiment data of mobility and diffusion. IVDFs are simulated using the developed model and compared with recently published experimental data. The IVDFs obtained with this model are compared to that from two other conventional models of less accurate differential cross sections. The simulation results show the necessity to take into account the accurate differential cross sections, especially for strong E/ N. The study reveals that IVDF cannot be separated into product of two independent IVDFs in the transverse and parallel to the electric field directions due to the significant effect of scattering.

  4. Air Reactions to Objects Moving at Rates Above the Velocity of Sound with Application to the Air Propeller

    NASA Technical Reports Server (NTRS)

    Reed, S Albert

    1922-01-01

    There has been a tradition general among aeronautical engineers that a critical point exists for tip speeds at or near the velocity of sound, indicating a physical limit in the use of propellers at higher tip speeds; the idea being that something would occur analogous to what is known in marine propellers as cavitation. In the examination of the physics pertaining to both propellers and projectiles moving at or above 1100 feet per second, the conclusion was reached by the author that there is no reason for the existence of such a critical point and that, if it had been noted by observers it was not inherent in the phenomena revealed, but rather due to a particular shape or proportion of the projectile and that, with properly proportioned sections, it would not exist.

  5. Experimental analysis of the air velocity and contaminant dispersion of human exhalation flows.

    PubMed

    Berlanga, F A; Olmedo, I; Ruiz de Adana, M

    2017-07-01

    Human exhalation flow is a potential source of pathogens that can constitute a cross-infection risk to people in indoor environments. Thus, it is important to investigate the characteristics of this flow, its development, area of influence, and the diffusion of the exhaled contaminants. This paper uses phase-averaged particle image velocimetry together with a tracer gas (CO2 ) to study two different exhalation flows over time: the exhalation of an average male (test M) and an average female (test F), using a life-sized thermal manikin in a supine position. The exhalation jets generated for both tests are similar in terms of symmetrical geometry, vorticity values, jet opening angles, and velocity and concentration decays. However, there is a difference in the penetration length of the two flows throughout the whole exhalation process. There is also a time difference in reaching maximum velocity between the two tests. It is also possible to see that the tracer gas dispersion depends on the momentum of the jet so the test with the highest velocity decay shows the lowest concentration decay. All these results are of interest to better understand cross-infection risk. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Predicting S-wave velocities for unconsolidated sediments at low effective pressure

    USGS Publications Warehouse

    Lee, Myung W.

    2010-01-01

    Accurate S-wave velocities for shallow sediments are important in performing a reliable elastic inversion for gas hydrate-bearing sediments and in evaluating velocity models for predicting S-wave velocities, but few S-wave velocities are measured at low effective pressure. Predicting S-wave velocities by using conventional methods based on the Biot-Gassmann theory appears to be inaccurate for laboratory-measured velocities at effective pressures less than about 4-5 megapascals (MPa). Measured laboratory and well log velocities show two distinct trends for S-wave velocities with respect to P-wave velocity: one for the S-wave velocity less than about 0.6 kilometer per second (km/s) which approximately corresponds to effective pressure of about 4-5 MPa, and the other for S-wave velocities greater than 0.6 km/s. To accurately predict S-wave velocities at low effective pressure less than about 4-5 MPa, a pressure-dependent parameter that relates the consolidation parameter to shear modulus of the sediments at low effective pressure is proposed. The proposed method in predicting S-wave velocity at low effective pressure worked well for velocities of water-saturated sands measured in the laboratory. However, this method underestimates the well-log S-wave velocities measured in the Gulf of Mexico, whereas the conventional method performs well for the well log velocities. The P-wave velocity dispersion due to fluid in the pore spaces, which is more pronounced at high frequency with low effective pressures less than about 4 MPa, is probably a cause for this discrepancy.

  7. Gas dispersion and immobile gas volume in solid and porous particle biofilter materials at low air flow velocities.

    PubMed

    Sharma, Prabhakar; Poulsen, Tjalfe G

    2010-07-01

    Gas-phase dispersion in granular biofilter materials with a wide range of particle sizes was investigated using atmospheric air and nitrogen as tracer gases. Two types of materials were used: (1) light extended clay aggregates (LECA), consisting of highly porous particles, and (2) gravel, consisting of solid particles. LECA is a commercial material that is used for insulation, as a soil conditioner, and as a carrier material in biofilters for air cleaning. These two materials were selected to have approximately the same particle shape. Column gas transport experiments were conducted for both materials using different mean particle diameters, different particle size ranges, and different gas flow velocities. Measured breakthrough curves were modeled using the advection-dispersion equation modified for mass transfer between mobile and immobile gas phases. The results showed that gas dispersivity increased with increasing mean particle diameter for LECA but was independent of mean particle diameter for gravel. Gas dispersivity also increased with increasing particle size range for both media. Dispersivities in LECA were generally higher than for gravel. The mobile gas content in both materials increased with increasing gas flow velocity but it did not show any strong dependency on mean particle diameter or particle size range. The relative fraction of mobile gas compared with total porosity was highest for gravel and lowest for LECA likely because of its high internal porosity.

  8. Numerical Simulation of Transient Development of Flame, Temperature and Velocity under Reduced Gravity in a Methane Air Diffusion Flame

    NASA Astrophysics Data System (ADS)

    Bhowal, Arup Jyoti; Mandal, Bijan Kumar

    2017-02-01

    A methane air co flow diffusion flame has been numerically simulated with the help of an in-house developed code at normal gravity, 0.5 G, and 0.0001 G (microgravity) for the study of transient behavior of the flame in terms of flame shape, temperature profile and velocity (streamlines). The study indicates that lower is the gravity level, the higher is the time of early transience. The flame developments during transience are marked by the formation of a secondary flamelet at different heights above the primary flame at all gravity levels. The development of temperature profile at microgravity takes a much longer time to stabilize than the flame development. At normal gravity and 0.5 G gravity level, streamlines, during transience, show intermediate vortices which are finally replaced by recirculation of ambient air from the exit plane. At microgravity, neither any vortex nor any recirculation at any stage is observed. Centerline temperature plots, at all gravity levels during transience, demonstrate a secondary peak at some instants as a consequence of the secondary flamelet formation. The centerline velocity at microgravity decreases gradually during transience, unlike at other two gravity levels where the fall is very sharp and is indicative of negligible buoyancy at microgravity.

  9. Experimental determination of the velocity and strain rate field in a laminar H2/Air counter-flow diffusion flame via LDA

    NASA Technical Reports Server (NTRS)

    Yeo, S. H.; Dancey, C. L.

    1991-01-01

    Measurements of the axial and radial components of velocity on the air side of stagnation in an axisymmetric H2/Air laminar counter-flow diffusion flame are reported. Results include the two-dimensional velocity field and computed velocity gradients (strain rates) along the stagnation streamline at two 'characteristic' strain rates, below the extinction limit. The measurements generally verify the modeling assumptions appropriate to the model of Kee et al. (1988). The 'traditional' potential flow model is not consistent with the measured results.

  10. Experimental determination of the velocity and strain rate field in a laminar H2/Air counter-flow diffusion flame via LDA

    NASA Technical Reports Server (NTRS)

    Yeo, S. H.; Dancey, C. L.

    1991-01-01

    Measurements of the axial and radial components of velocity on the air side of stagnation in an axisymmetric H2/Air laminar counter-flow diffusion flame are reported. Results include the two-dimensional velocity field and computed velocity gradients (strain rates) along the stagnation streamline at two 'characteristic' strain rates, below the extinction limit. The measurements generally verify the modeling assumptions appropriate to the model of Kee et al. (1988). The 'traditional' potential flow model is not consistent with the measured results.

  11. The effect of dilatancy on velocity anisotropy in Westerly granite

    NASA Technical Reports Server (NTRS)

    Soga, N.; Mizutani, H.; Spetzler, H.; Martin, R. J., III

    1978-01-01

    Jacketed samples of Westerly granite were fractured at confining pressures up to 1 kbar, and compressional and horizontally as well as vertically polarized shear velocities were measured in orthogonal directions perpendicular to the compression axis. Changes occurring with increased strain are described, and the velocity data were analyzed by application of the Anderson et al (1974) approach. Observed and calculated velocities are found to be in good agreement, and the degree of dilatancy was determined from the differences between the strains measured perpendicularly to the compression axis and the estimated elastic strains in those directions.

  12. Effect of Fermion Velocity on Phase Structure of QED3

    NASA Astrophysics Data System (ADS)

    Li, Jian-Feng; Feng, Hong-Tao; Zong, Hong-Shi

    2016-11-01

    Dynamical chiral symmetry breaking (DCSB) in thermal QED3 with fermion velocity is studied in the framework of Dyson-Schwinger equations. By adopting instantaneous approximation and neglecting the transverse component of gauge boson propagator at finite temperature, we numerically solve the fermion self-energy equation in the rainbow approximation. It is found that both DCSB and fermion chiral condensate are suppressed by fermion velocity. Moreover, the critical temperature decreases as fermion velocity increases. Supported in part by the National Natural Science Foundation of China under Grant No. 11535005 and the Natural Science Foundation of Jiangsu Province under Grant No. BK20130387

  13. Summary of forward velocity effects on fan noise

    NASA Technical Reports Server (NTRS)

    Feiler, C. E.; Groeneweg, J. F.

    1977-01-01

    Available experimental data comparing the in-flight and static behavior of fan noise are reviewed. These results are then compared with recent data obtained for a fan stage tested with forward velocity in a low speed wind tunnel. Tentative conclusions are presented about the significance and nature of the changes in noise observed when a forward velocity is imposed. Finally, the implications of the emerging picture of in-flight fan source noise for suppressor design are discussed.

  14. Air pollution: worldwide effects on mountain forests

    Treesearch

    Anne M. Rosenthal; Andrzej Featured: Bytnerowicz

    2004-01-01

    Widespread forest decline in remote areas of the Carpathian Mountains has been linked to air pollution from urban and industrial regions. Besides injuring plant tissues directly, pollutants may deposit to soils and water, drastically changing susceptible ecosystems. Researcher Andrzej Bytnerowicz has developed effective methods for assessing air quality over wildlands...

  15. Illumination Profile & Dispersion Variation Effects on Radial Velocity Measurements

    NASA Astrophysics Data System (ADS)

    Grieves, Nolan; Ge, Jian; Thomas, Neil B.; Ma, Bo; Li, Rui; SDSS-III

    2015-01-01

    The Multi-object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS) measures radial velocities using a fiber-fed dispersed fixed-delay interferometer (DFDI) with a moderate dispersion spectrograph. This setup allows a unique insight into the 2D illumination profile from the fiber on to the dispersion grating. Illumination profile investigations show large changes in the profile over time and fiber location. These profile changes are correlated with dispersion changes and long-term radial velocity offsets, a major problem within the MARVELS radial velocity data. Characterizing illumination profiles creates a method to both detect and correct radial velocity offsets, allowing for better planet detection. Here we report our early results from this study including improvement of radial velocity data points from detected giant planet candidates. We also report an illumination profile experiment conducted at the Kitt Peak National Observatory using the EXPERT instrument, which has a DFDI mode similar to MARVELS. Using profile controlling octagonal-shaped fibers, long term offsets over a 3 month time period were reduced from ~50 m/s to within the photon limit of ~4 m/s.

  16. Pulmonary Health Effects of Air Pollution

    PubMed Central

    Kurt, Ozlem Kar; Zhang, Jingjing; Pinkerton, Kent E.

    2016-01-01

    Purpose of the review Air pollution continues to be a major public health concern affecting nine out of ten individuals living in urban areas worldwide. Exposure to air pollution is the ninth leading risk factor for cardiopulmonary mortality. The aim of this review is to examine the current literature for the most recent updates on health effects of specific air pollutants and their impact on asthma, chronic obstructive pulmonary disease (COPD), lung cancer and respiratory infection. Recent findings A total of 53 publications were reviewed to establish new insights as to how air pollution is associated with pulmonary morbidity and mortality. Considerable past evidence suggests that air pollution is an important factor that enhances pulmonary disease, while also causing greater harm in susceptible populations, such as children, the elderly and those of low socio-economic status worldwide. Asthma, COPD, lung cancer and respiratory infections all seem to be exacerbated due to exposure to a variety of environmental air pollutants with the greatest effects due to particulate matter (PM), ozone and nitrogen oxides. New publications reviewed reaffirm these findings. Summary Continued vigilence will be essential to lessen the effects of air pollution on human health and pulmonary disease. Cooperation at a multi-national level will be required on the part of governments, industry, energy-based enterprises and the public working together to solve our air quality issues at the local, national and global level. PMID:26761628

  17. Pulmonary health effects of air pollution.

    PubMed

    Kurt, Ozlem Kar; Zhang, Jingjing; Pinkerton, Kent E

    2016-03-01

    Air pollution continues to be a major public health concern affecting nine out of 10 individuals living in urban areas worldwide. Exposure to air pollution is the ninth leading risk factor for cardiopulmonary mortality. The aim of this review is to examine the current literature for the most recent updates on health effects of specific air pollutants and their impact on asthma, chronic obstructive pulmonary disease, lung cancer, and respiratory infection. A total of 52 publications were reviewed to establish new insights as to how air pollution is associated with pulmonary morbidity and mortality. Considerable past evidence suggests that air pollution is an important factor that enhances pulmonary disease, while also causing greater harm in susceptible populations, such as children, the elderly, and those of low socio-economic status worldwide. Asthma, chronic obstructive pulmonary disease, lung cancer, and respiratory infections all seem to be exacerbated because of exposure to a variety of environmental air pollutants with the greatest effects because of particulate matter, ozone, and nitrogen oxides. New publications reviewed reaffirm these findings. Continued vigilance will be essential to lessen the effects of air pollution on human health and pulmonary disease. Cooperation at a multinational level will be required on the part of governments, industry, energy-based enterprises, and the public working together to solve our air quality issues at the local, national, and global level.

  18. Air bubble bursting effect of lotus leaf.

    PubMed

    Wang, Jingming; Zheng, Yongmei; Nie, Fu-Qiang; Zhai, Jin; Jiang, Lei

    2009-12-15

    In this paper, a phenomenon of air bubbles quickly bursting within several milliseconds on a "self-cleaning" lotus leaf was described. This observation prompted the synthesis of artificial surfaces similar to that of the lotus leaf. The artificial leaf surfaces, prepared by photolithography and wet etching, showed a similar air bubble bursting effect. Smooth and rough silicon surfaces with an ordered nanostructure or patterned microstructure were utilized to study the contribution of the micro/nano hierarchical structures to this phenomenon of air bubble bursting. Air bubbles were found to burst on some superhydrophobic surfaces with microstructure (within 220 ms). However, air bubbles burst much more rapidly (within 13 ms) on similar surfaces with micro/nanostructure. The height, width, and spacing of hierarchical structures could also affect air bubble bursting, and the effect of the height was more obvious. When the height of hierarchical structures was around the height found in natural lotus papillae, the width and spacing were significant for air bubble bursting. An original model was proposed to further evaluate the reason why the micro/nano hierarchical rough structures had an excellent air bubble bursting effect, and the validity of the model was theoretically demonstrated.

  19. The velocity effects of large historical earthquakes in Chinese mainland

    NASA Astrophysics Data System (ADS)

    Tan, Weijie; Dong, Danan; Wu, Bin

    2016-04-01

    Accompanying with the collision between Indian and Eurasian plates, China has experienced decadal large earthquakes over the past 100 years. These large earthquakes are mainly located along several seismic belts in Tien Shan, Tibet Plateau, and Northern China. The postseismic deformation and stress accumulation induced by the historical earthquakes is important for assess the contemporary seismic hazards. The postseismic deformation induced by historical large earthquakes also influences the observed present day velocity field. The relaxation of the viscoelastic asthenosphere is modeled on a layered spherically symmetric earth with Maxwell rheology. The layer's thickness, the density p and the P-wave velocity Vp are from PREM. The shear modulus are derived from the p and Vp. The viscosity between lower crust and upper mantle adopted in this study is 1×1019 Pa.s. Viscoelastic relaxation contributions due to 34 historical large earthquakes in China from 1900 to 2001 are calculated using VISCO1D-v3 program developed by Pollitz (1997). We calculated the model predicted velocity field in 2015 in China caused by historical big earthquakes. The pattern of predicted velocity field is consistent with the present movement of crust, with peak velocities reaching 6mm yr-1. The region of Southwestern China moves northeastwards, and also a significant rotation occurred at the edge of the Tibetan Plateau. The velocity field caused by historical large earthquakes provides a base to isolate the velocity field caused by the contemporary tectonic movement from the geodetic observations. It also provides critical information to investigate the regional stress accumulation and to assess the mid-term to long-term earthquake risk.

  20. On the coefficients of small eddy and surface divergence models for the air-water gas transfer velocity

    NASA Astrophysics Data System (ADS)

    Wang, Binbin; Liao, Qian; Fillingham, Joseph H.; Bootsma, Harvey A.

    2015-03-01

    Recent studies suggested that under low to moderate wind conditions without bubble entraining wave breaking, the air-water gas transfer velocity k+ can be mechanistically parameterized by the near-surface turbulence, following the small eddy model (SEM). Field measurements have supported this model in a variety of environmental forcing systems. Alternatively, surface divergence model (SDM) has also been shown to predict the gas transfer velocity across the air-water interface in laboratory settings. However, the empirically determined model coefficients (α in SEM and c1 in SDM) scattered over a wide range. Here we present the first field measurement of the near-surface turbulence with a novel floating PIV system on Lake Michigan, which allows us to evaluate the SEM and SDM in situ in the natural environment. k+ was derived from the CO2 flux that was measured simultaneously with a floating gas chamber. Measured results indicate that α and c1 are not universal constants. Regression analysis showed that α˜log>(ɛ>) while the near-surface turbulence dissipation rate ɛ is approximately greater than 10-6 m2 s-3 according to data measured for this study as well as from other published results measured in similar environments or in laboratory settings. It also showed that α scales linearly with the turbulent Reynolds number. Similarly, coefficient c1 in the SDM was found to linearly scale with the Reynolds number. These findings suggest that larger eddies are also important parameters, and the dissipation rate in the SEM or the surface divergence β' in the SDM alone may not be adequate to determine k+ completely.

  1. Effect of water velocity on hydroponic phytoremediation of metals.

    PubMed

    Weiss, P; Westbrook, A; Weiss, J; Gulliver, J; Biesboer, D

    2014-01-01

    The influence of flow velocity on the uptake of cadmium, copper, lead, and zinc by hydroponically grown soft stem bulrush (Scirpus validus) was investigated. The roots of the plants were exposed to a continually recycled, nutrient enriched, synthetic stormwater. Plants were divided into groups and the roots of each group exposed to different but constant water velocities. The metal concentrations in the roots and stems were compared after three weeks. Metal accumulation in roots was increased for water velocities between 1.3 and 4.0 cm s(-1). In a second experiment, the roots of all plants were exposed to a single velocity and the root and stem metal concentrations were determined as a function of time. Metal concentrations in the roots approached a constant value after three weeks. After this time, accumulation of metals depends upon root growth. The results suggest that long-term accumulation by the roots of hydroponic Scirpus validus can be increased by increasing water velocity, which implies that floating islands with movement will retain more metals from the water column.

  2. Effect of water on carbon monoxide-oxygen flame velocity

    NASA Technical Reports Server (NTRS)

    Mcdonald, Glen E

    1954-01-01

    The flame velocities were measured of 20 percent oxygen and 80 percent carbon monoxide mixtures containing either light water or heavy water. The flame velocity increased from 34.5 centimeters per second with no added water to about 104 centimeters per second for a 1.8 percent addition of light water and to 84 centimeters per second for an equal addition of heavy water. The addition of heavy water caused greater increases in flame velocity with equilibrium hydrogen-atom concentration than would be predicted by the Tanford and Pease square-root relation. The ratio of the flame velocity of a mixture containing light water to that of a mixture containing heavy water was found to be 1.4. This value is the same as the ratio of the reaction rate of hydrogen to that of deuterium and oxygen. A ratio of reaction rates of 1.4 would also be required for the square-root law to give the observed ratio of flame-velocity changes.

  3. Application of TiC reinforced Fe-based coatings by means of High Velocity Air Fuel Spraying

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.; Knoch, M. A.; Liao, X.; Sommer, J.

    2017-03-01

    In the field of hydraulic applications, different development trends can cause problems for coatings currently used as wear and corrosion protection for piston rods. Aqueous hydraulic fluids and rising raw material prices necessitate the search for alternatives to conventional coatings like galvanic hard chrome or High Velocity Oxygen Fuel (HVOF)-sprayed WC/Co coatings. In a previous study, Fe/TiC coatings sprayed by a HVOF-process, were identified to be promising coating systems for wear and corrosion protection in hydraulic systems. In this feasibility study, the novel High Velocity Air Fuel (HVAF)-process, a modification of the HVOF-process, is investigated using the same feedstock material, which means the powder is not optimized for the HVAF-process. The asserted benefits of the HVAF-process are higher particle velocities and lower process temperatures, which can result in a lower porosity and oxidation of the coating. Further benefits of the HVAF process are claimed to be lower process costs and higher deposition rates. In this study, the focus is set on to the applicability of Fe/TiC coatings by HVAF in general. The Fe/TiC HVAF coating could be produced, successfully. The HVAF- and HVOF-coatings, produced with the same powder, were investigated using micro-hardness, porosity, wear and corrosion tests. A similar wear coefficient and micro-hardness for both processes could be achieved. Furthermore the propane/hydrogen proportion of the HVAF process and its influence on the coating thickness and the porosity was investigated.

  4. Changes in speed skating velocity in relation to push-off effectiveness.

    PubMed

    Noordhof, Dionne A; Foster, Carl; Hoozemans, Marco J M; de Koning, Jos J

    2013-03-01

    Speed skating posture, or technique, is characterized by the push-off angle or effectiveness (e), determined as the angle between the push-off leg and the ice; the preextension knee angle (θ(0)); and the trunk angle (θ(1)). Together with muscle-power output and environmental conditions, skating posture, or technique, determines velocity (v). To gain insight into technical variables that are important to skate efficiently and perform well, e, θ(0), θ(1), and skating v were determined every lap during a 5000-m World Cup. Second, the authors evaluated if changes (Δ) in e, θ(0), and θ(1) are associated with Δv. One camera filmed the skaters from a frontal view, from which e was determined. Another camera filmed the skaters from a sagittal view, from which θ(0) and θ(1) were determined. Radio-frequency identification tags around the ankles of the skaters measured v. During the race, e progressively increased and v progressively decreased, while θ(0) and θ(1) showed a less consistent pattern of change. Generalized estimating equations showed that Δe is significantly associated with Δv over the midsection of the race (β = -0.10, P < .001) and that Δθ(0) and Δθ(1) are not significantly associated with Δv. The decrease in skating v over the race is not due to increases in power losses to air friction, as knee and trunk angle were not significantly associated with changes in velocity. The decrease in velocity can be partly ascribed to the decrease in effectiveness, which reflects a decrease in power production associated with fatigue.

  5. Quantifying air distribution, ventilation effectiveness and airborne pollutant transport in an aircraft cabin mockup

    NASA Astrophysics Data System (ADS)

    Wang, Aijun

    The health, safety and comfort of passengers during flight inspired this research into cabin air quality, which is closely related to its airflow distribution, ventilation effectiveness and airborne pollutant transport. The experimental facility is a full-scale aircraft cabin mockup. A volumetric particle tracking velocimetry (VPTV) technique was enhanced by incorporating a self-developed streak recognition algorithm. Two stable recirculation regions, the reverse flows above the seats and the main air jets from the air supply inlets formed the complicated airflow patterns inside the cabin mockup. The primary air flow was parallel to the passenger rows. The small velocity component in the direction of the cabin depth caused less net air exchange between the passenger rows than that parallel to the passenger rows. Different total air supply rate changed the developing behaviors of the main air jets, leading to different local air distribution patterns. Two indices, Local mean age of air and ventilation effectiveness factor (VEF), were measured at five levels of air supply rate and two levels of heating load. Local mean age of air decreased linearly with an increase in the air supply rate, while the VEF remained consistent when the air supply rate varied. The thermal buoyancy force from the thermal plume generated the upside plume flow, opposite to the main jet flow above the boundary seats and thus lowered the local net air exchange. The airborne transport dynamics depends on the distance between the source and the receptors, the relative location of pollutant source, and air supply rate. Exposure risk was significantly reduced with increased distance between source and receptors. Another possible way to decrease the exposure risk was to position the release source close to the exhaust outlets. Increasing the air supply rate could be an effective solution under some emergency situations. The large volume of data regarding the three-dimensional air velocities was

  6. Effects of Coaxial Air on Nitrogen-Diluted Hydrogen Jet Diffusion Flame Length and NOx Emission

    SciTech Connect

    Weiland, N.T.; Chen, R.-H.; Strakey, P.A.

    2007-10-01

    Turbulent nitrogen-diluted hydrogen jet diffusion flames with high velocity coaxial air flows are investigated for their NOx emission levels. This study is motivated by the DOE turbine program’s goal of achieving 2 ppm dry low NOx from turbine combustors running on nitrogen-diluted high-hydrogen fuels. In this study, effects of coaxial air velocity and momentum are varied while maintaining low overall equivalence ratios to eliminate the effects of recirculation of combustion products on flame lengths, flame temperatures, and resulting NOx emission levels. The nature of flame length and NOx emission scaling relationships are found to vary, depending on whether the combined fuel and coaxial air jet is fuel-rich or fuel-lean. In the absence of differential diffusion effects, flame lengths agree well with predicted trends, and NOx emissions levels are shown to decrease with increasing coaxial air velocity, as expected. Normalizing the NOx emission index with a flame residence time reveals some interesting trends, and indicates that a global flame strain based on the difference between the fuel and coaxial air velocities, as is traditionally used, is not a viable parameter for scaling the normalized NOx emissions of coaxial air jet diffusion flames.

  7. The Altitude Effect on Air Speed Indicators

    NASA Technical Reports Server (NTRS)

    Hersey, M D; Hunt, F L; Eaton, H N

    1921-01-01

    The object of this report is to present the results of a theoretical and experimental study of the effect, on the performance of air speed indicators, of the different atmospheric conditions experienced at various altitudes.

  8. Effects of superficial gas velocity on process dynamics in bioreactors

    NASA Astrophysics Data System (ADS)

    Devi, T. T.; Kumar, B.

    2014-06-01

    Present work analyzes the flow hydrodynamics and mass transfer mechanisms in double Rushton and CD-6 impeller on wide range (0.0075-0.25 m/s) of superficial gas velocity ( v g) in a gas-liquid phase bioreactor by employing computational fluid dynamics (CFD) technique. The volume averaged velocity magnitude and dissipation rate are found higher with increasing superficial gas velocity. Higher relative power draw ( P g/ P 0) is predicted in CD-6 than the Rushton impeller but no significant difference in volume averaged mass transfer coefficient ( k L a) observed between these two types of impeller. The ratio of power draw with mass transfer coefficient has been found higher in CD-6 impeller (25-50 %) than the Rushton impeller.

  9. Effect of Machining Velocity in Nanoscale Machining Operations

    NASA Astrophysics Data System (ADS)

    Islam, Sumaiya; Ibrahim, Raafat; Khondoker, Noman

    2015-04-01

    The aim of this study is to investigate the generated forces and deformations of single crystal Cu with (100), (110) and (111) crystallographic orientations at nanoscale machining operation. A nanoindenter equipped with nanoscratching attachment was used for machining operations and in-situ observation of a nano scale groove. As a machining parameter, the machining velocity was varied to measure the normal and cutting forces. At a fixed machining velocity, different levels of normal and cutting forces were generated due to different crystallographic orientations of the specimens. Moreover, after machining operation percentage of elastic recovery was measured and it was found that both the elastic and plastic deformations were responsible for producing a nano scale groove within the range of machining velocities from 250-1000 nm/s.

  10. Aircraft Carrier Turbulence Study for Predicting Air Flow Dynamics with Increasing Wind-Over-Deck Velocities

    DTIC Science & Technology

    1968-03-28

    Approximate Times When Initial Burble Is Encountered for Various Approaches 34 2 Minimum Safe Land’ing Angie with Different Wftd Over Deck 35 3 Liass...effect of the " burble ". This effect im primarily a dynamic updraft upon the Incoming aercraft which le foLl.owed by . dogdowndraft immedioately aft...point is 150 feet forward of the ramp). The strong burble effect is normally encountered at approximately 100 to 150 feet from the ramp. With

  11. Effect of enclosure shape on natural convection velocities

    NASA Technical Reports Server (NTRS)

    Robertson, S. J.; Nicholson, L. A.

    1982-01-01

    A numerical analysis was performed to compare natural convection velocities in two dimensional enclosures of various shape. The following shapes were investigated: circle, square, horizontal and upright 2 x 1 aspect ratio rectangles, horizontal and upright half circles, diamond. In all cases, the length scale in the various dimensionless parameters, such as Rayleigh number, is defined as the diameter of the equal area circle. Natural convection velocities were calculated for Rayleigh numbers of 1000 and 5000 with the temperature difference taken to be across (1) the maximum horizontal dimension, (2) the median horizontal line (line through centroid) and (3) the horizontal distance such that the temperature gradient is the same for shapes of equal area. For the class of shapes including the square, upright half circle and upright rectangle, the computed velocities were found to agree very closely with that of the equal area circle when the temperature difference is taken to be across the maximum horizontal dimension (condition (a)). The velocities for the horizontal rectangle and half circle were found to be approximately one half that of the equal area circle for the same condition. Better overall agreement among all shapes was obtained by setting the temperature difference across a distance such that the temperature gradients were equal for shapes of equal area.

  12. Numerical Study on the Effect of Substrate Angle on Particle Impact Velocity and Normal Velocity Component in Cold Gas Dynamic Spraying Based on CFD

    NASA Astrophysics Data System (ADS)

    Yin, Shuo; Wang, Xiao-Fang; Li, Wen-Ya; Xu, Bao-Peng

    2010-12-01

    Numerical study was conducted to investigate the effect of substrate angle on particle impact velocity and normal velocity component in cold gas dynamic spraying by using three-dimensional models based on computational fluid dynamics. It was found that the substrate angle has significant effect on particle impact velocity and normal velocity component. With increasing the substrate angle, the bow shock strength becomes increasingly weak, which results in a gradual rise in particle impact velocity. The distribution of the impact velocity presents a linearly increase along the substrate centerline due to the existence of the substrate angle and the growth rate rises gradually with increasing the substrate angle. Furthermore, the normal velocity component reduces steeply with the increase in substrate angle, which may result in a sharp decrease in deposition efficiency. In addition, the study on the influence of procedure parameters showed that gas pressure, temperature, type, and particle size also play an important role in particle acceleration.

  13. Effects of aging on maximal and rapid velocity capacities of the leg extensors.

    PubMed

    Thompson, Brennan J; Conchola, Eric C; Palmer, Ty B; Stock, Matt S

    2014-10-01

    Declines in muscle strength and power are commonly reported as a consequence of aging; however, few studies have investigated the influence of aging on maximal and rapid velocity characteristics. The objective of this study was to examine the effects of aging on maximal and rapid velocity characteristics of the leg extensor muscles. Twenty-three young (age=25±3yrs) and twenty-one old (72±4yrs) men performed three leg extension maximal voluntary contractions (MVCs) at 240°·s(-1) and at maximum unloaded velocity (Vmax). Vmax was calculated as the highest velocity attained during the unloaded MVC and RVD was the linear slope of the velocity-time curve for the 240deg·s(-1) (RVD240) and maximum unloaded velocity (RVD-Vmax) contractions. The old men exhibited lower (P<0.01) Vmax (10.1%), RVD240 (37.2%), and RVD-Vmax (26.7%) compared to the young men. These lower velocity characteristics for the old men may contribute to the increased functional limitations often observed in older adults. Interestingly, the greater age-related declines observed for RVD240 and RVD-Vmax compared to Vmax perhaps suggest an enhanced age-related impairment in the ability of the older adults' muscle to generate velocity rapidly versus the ability to generate maximal velocity. Such findings highlight the importance of time-dependent velocity measures when assessing the effects of aging on rapid velocity capacities.

  14. Health effects of outdoor air pollution

    PubMed Central

    Abelsohn, Alan; Stieb, Dave M.

    2011-01-01

    Abstract Objective To inform family physicians about the health effects of air pollution and to provide an approach to counseling vulnerable patients in order to reduce exposure. Sources of information MEDLINE was searched using terms relevant to air pollution and its adverse effects. We reviewed English-language articles published from January 2008 to December 2009. Most studies provided level II evidence. Main message Outdoor air pollution causes substantial morbidity and mortality in Canada. It can affect both the respiratory system (exacerbating asthma and chronic obstructive pulmonary disease) and the cardiovascular system (triggering arrhythmias, cardiac failure, and stroke). The Air Quality Health Index (AQHI) is a new communication tool developed by Health Canada and Environment Canada that indicates the level of health risk from air pollution on a scale of 1 to 10. The AQHI is widely reported in the media, and the tool might be of use to family physicians in counseling high-risk patients (such as those with asthma, chronic obstructive pulmonary disease, or cardiac failure) to reduce exposure to outdoor air pollution. Conclusion Family physicians can use the AQHI and its health messages to teach patients with asthma and other high-risk patients how to reduce health risks from air pollution. PMID:21841106

  15. Experimental study on copper cathode erosion rate and rotational velocity of magnetically driven arcs in a well-type cathode non-transferred plasma torch operating in air

    NASA Astrophysics Data System (ADS)

    Chau, S. W.; Hsu, K. L.; Lin, D. L.; Tzeng, C. C.

    2007-04-01

    The cathode erosion rate, arc root velocity and output power of a well-type cathode (WTC), non-transferred plasma torch operating in air are studied experimentally in this paper. An external solenoid to generate a magnetically driven arc and a circular swirler to produce a vortex flow structure are equipped in the studied torch system, which is designed to reduce the erosion rate at the cathode. A least square technique is applied to correlate the system parameters, i.e. current, axial magnetic field and mass flow rate, with the cathode erosion rate, arc root velocity and system power output. In the studied WTC torch system, the cathode erosion has a major thermal erosion component and a minor component due to the ion-bombardment effect. The cathode erosion increases with the increase of current due to the enhancement in both Joule heating and ion bombardment. The axial magnetic field can significantly reduce the cathode erosion by reducing the thermal loading of cathode materials at the arc root and improving the heat transfer to gas near the cathode. But, the rise in the mass flow rate leads to the deterioration of erosion, since the ion-bombardment effect prevails over the convective cooling at the cathode. The most dominant system parameter to influence the arc root velocity is the axial magnetic field, which is mainly contributed to the magnetic force driving the arc. The growth in current has a negative impact on increasing the arc root velocity, because the friction force acting at the spot due to a severe molten condition becomes the dominant component counteracting the magnetic force. The mass flow rate also suppresses the arc root velocity, as a result of which the arc root moves in the direction against that of the swirled working gas. All system parameters such as current, magnetic field and gas flow rate increase with the increase in the torch output power. The experimental evidences suggest that the axial magnetic field is the most important parameter

  16. Human health effects of air pollution.

    PubMed Central

    Folinsbee, L J

    1993-01-01

    Over the past three or four decades, there have been important advances in the understanding of the actions, exposure-response characteristics, and mechanisms of action of many common air pollutants. A multidisciplinary approach using epidemiology, animal toxicology, and controlled human exposure studies has contributed to the database. This review will emphasize studies of humans but will also draw on findings from the other disciplines. Air pollutants have been shown to cause responses ranging from reversible changes in respiratory symptoms and lung function, changes in airway reactivity and inflammation, structural remodeling of pulmonary airways, and impairment of pulmonary host defenses, to increased respiratory morbidity and mortality. Quantitative and qualitative understanding of the effects of a small group of air pollutants has advanced considerably, but the understanding is by no means complete, and the breadth of effects of all air pollutants is only partially understood. PMID:8354181

  17. Effects of 3D random correlated velocity perturbations on predicted ground motions

    USGS Publications Warehouse

    Hartzell, S.; Harmsen, S.; Frankel, A.

    2010-01-01

    Three-dimensional, finite-difference simulations of a realistic finite-fault rupture on the southern Hayward fault are used to evaluate the effects of random, correlated velocity perturbations on predicted ground motions. Velocity perturbations are added to a three-dimensional (3D) regional seismic velocity model of the San Francisco Bay Area using a 3D von Karman random medium. Velocity correlation lengths of 5 and 10 km and standard deviations in the velocity of 5% and 10% are considered. The results show that significant deviations in predicted ground velocities are seen in the calculated frequency range (≤1 Hz) for standard deviations in velocity of 5% to 10%. These results have implications for the practical limits on the accuracy of scenario ground-motion calculations and on retrieval of source parameters using higher-frequency, strong-motion data.

  18. Effect of air deflectors on fan performance in tunnel-ventilated broiler houses with a dropped ceiling

    USDA-ARS?s Scientific Manuscript database

    Air velocity is a critical design parameter for modern commercial broiler houses, owing to the beneficial effects of increased cooling on live performance and thermal comfort in broiler chickens. As a result, design velocities have increased over the last 15 years and broiler growers have installed ...

  19. Fluid Structure Interaction Effects on Composites Under Low Velocity Impact

    DTIC Science & Technology

    2012-06-01

    Interaction, FSI, low velocity impact, carbon fiber reinforced polymers, CFRP, carbon nanotubes, CNT, vacuum assisted resin transfer molding, VARTM . 16...Ethyl Ketone Peroxide MWCNT Multi-Walled Carbon Nanotube VARTM Vacuum-Assisted Resin Transfer Molding xiv THIS PAGE INTENTIONALLY LEFT BLANK...samples used in this research is known as vacuum assisted resin transfer molding ( VARTM ). VARTM is a very common method used in low pressure composite

  20. Doppler effects on velocity spectra observed by MST radars

    NASA Technical Reports Server (NTRS)

    Scheffler, A. O.; Liu, C. H.

    1986-01-01

    Recently, wind data from mesophere-stratosphere-troposphere (MST) radars have been used to study the spectra of gravity waves in the atmosphere (Scheffler and Liu, 1985; VanZandt et al., 1985). Since MST radar measures the line-of-sight Doppler velocities, it senses the components of the wave-associated velocities along its beam directions. These components are related through the polarization relations which depend on the frequency and wave number of the wave. Therfore, the radar-observed velocity spectrum will be different from the original gravity-wave spectrum. Their relationship depends on the frequency and wave number of the wave as well as the propagation geometry. This relation can be used to interpret the observed data. It can also be used to test the assumption of gravity-wave spectrum (Scheffler and Liu, 1985). In deriving this relation, the background atmosphere has been assumed to be motionless. Obviously, the Doppler shift due to the background wind will change the shape of the gravity-wave power spectrum as well as its relation with the radar-observed spectrum. Here, researcher's investigate these changes.

  1. Evaluating the effectiveness of air quality interventions.

    PubMed

    van Erp, Annemoon M M; O'Keefe, Robert; Cohen, Aaron J; Warren, Jane

    2008-01-01

    Evaluating the extent to which air quality regulations improve public health--sometimes referred to as accountability--is part of an emerging effort to assess the effectiveness of environmental regulatory policies. Air quality has improved substantially in the United States and Western Europe in recent decades, with far less visible pollution and decreasing concentrations of several major pollutants. In large part, these gains were achieved through increasingly stringent air quality regulations. The costs associated with compliance and, importantly, the need to ensure that the regulations are achieving the intended public health benefits underscore the importance of accountability research. To date, accountability research has emphasized measuring the effects of actions already taken to improve air quality. Such research may also contribute to estimating the burden of disease that might be avoided in the future if certain actions are taken. The Health Effects Institute (HEI) currently funds eight ongoing studies on accountability, which cover near-term interventions to improve air quality including (1) a ban on the sale of coal, (2) replacing old wood stoves with cleaner ones, (3) decreasing sulfur content in fuel, (4) measures to reduce traffic, and (5) longer term, wide-ranging actions or events (such as complex changes associated with the reunification of Germany). HEI is also funding the development of methods and research to assess regulations that are implemented incrementally over extended periods of time, such as Title IV of the 1990 Clean Air Act Amendments, which reduces sulfur dioxide emissions from power plants in the eastern United States.

  2. Measuring air-sea gas-exchange velocities in a large-scale annular wind-wave tank

    NASA Astrophysics Data System (ADS)

    Mesarchaki, E.; Kräuter, C.; Krall, K. E.; Bopp, M.; Helleis, F.; Williams, J.; Jähne, B.

    2015-01-01

    In this study we present gas-exchange measurements conducted in a large-scale wind-wave tank. Fourteen chemical species spanning a wide range of solubility (dimensionless solubility, α = 0.4 to 5470) and diffusivity (Schmidt number in water, Scw = 594 to 1194) were examined under various turbulent (u10 = 0.73 to 13.2 m s-1) conditions. Additional experiments were performed under different surfactant modulated (two different concentration levels of Triton X-100) surface states. This paper details the complete methodology, experimental procedure and instrumentation used to derive the total transfer velocity for all examined tracers. The results presented here demonstrate the efficacy of the proposed method, and the derived gas-exchange velocities are shown to be comparable to previous investigations. The gas transfer behaviour is exemplified by contrasting two species at the two solubility extremes, namely nitrous oxide (N2O) and methanol (CH3OH). Interestingly, a strong transfer velocity reduction (up to a factor of 3) was observed for the relatively insoluble N2O under a surfactant covered water surface. In contrast, the surfactant effect for CH3OH, the high solubility tracer, was significantly weaker.

  3. Air pollution holiday effect in metropolitan Kaohsiung

    NASA Astrophysics Data System (ADS)

    Tan, P.; Chen, P. Y.

    2014-12-01

    Different from Taipei, the metropolitan Kaohsiung which is a coastal and industrial city has the major pollution sources from stationary sources such as coal-fired power plants, petrochemical facilities and steel plants, rather than mobile sources. This study was an attempt to conduct a comprehensive and systematical examination of the holiday effect, defined as the difference in air pollutant concentrations between holiday and non-holiday periods, over the Kaohsiung metropolitan area. We documented evidence of a "holiday effect", where concentrations of NOx, CO, NMHC, SO2 and PM10 were significantly different between holidays and non-holidays, in the Kaohsiung metropolitan area from daily surface measurements of seven air quality monitoring stations of the Taiwan Environmental Protection Administration during the Chinese New Year (CNY) and non-Chinese New Year (NCNY) periods of 1994-2010. Concentrations of the five pollutants were lower in the CNY than in the NCNY period, however, that of O3 was higher in the CNY than in the NCNY period and had no holiday effect. The exclusion of the bad air quality day (PSI > 100) and the Lantern Festival Day showed no significant effects on the holiday effects of air pollutants. Ship transportation data of Kaohsiung Harbor Bureau showed a statistically significant difference in the CNY and NCNY period. This difference was consistent with those found in air pollutant concentrations of some industrial and general stations in coastal areas, implying the possible impact of traffic activity on the air quality of coastal areas. Holiday effects of air pollutants over the Taipei metropolitan area by Tan et al. (2009) are also compared.

  4. The Effect of Guided Practice on Overhand-Throw Ball Velocities of Kindergarten Children.

    ERIC Educational Resources Information Center

    Halverson, Lolas E.; And Others

    This report, the first of three on the effects of teaching kindergarten children the overhand throw, compares the children's final ball velocities to those of two control groups. Later reports will discuss the effect of instruction on the children's movement processes and the relationship between velocity and movement process. Forty-five children…

  5. A one-dimensional numerical model for predicting pressure and velocity oscillations of a compressed air-pocket in a vertical shaft

    NASA Astrophysics Data System (ADS)

    Choi, Y.; Leon, A.; Apte, S.

    2015-12-01

    The presence of pressurized air pockets in combined sewer systems is argued to produce geyser flows, which is an oscillating jetting of a mixture of gas-liquid flows through vertical shafts. A 1D numerical model is developed for predicting pressure and velocity oscillations of a compressed air-pocket in a vertical shaft which in turn attempts to simulate geyser like flows. The vertical shaft is closed at the bottom and open to ambient pressure at the top. Initially, the lower section of the vertical shaft is filled with compressed air and the upper section with water. The interaction between the pressurized air pocket and the water column in the vertical shaft exhibits an oscillatory motion of the water column that decays over time. The model accounts for steady and unsteady friction to estimate the energy dissipation. The model also includes the falling flow of water around the external perimeter of the pressurized air pocket by assuming that any expansion in the pressurized air pocket would result in the falling volume of water. The acceleration of air-water interface is predicted through a force balance between the pressurized air pocket and the water column combined with the Method of Characteristics that resolves pressure and velocity within the water column. The expansion and compression of the pressurized air pocket is assumed to follow either isothermal process or adiabatic process. Results for both assumptions; isothermal and adiabatic processes, are presented. The performance of the developed 1D numerical model is compared with that of a commercial 3D CFD model. Overall, a good agreement between both models is obtained for pressure and velocity oscillations. The paper will also present a sensitivity analysis of the 3D CFD model.

  6. Air-pollution effects on biodiversity

    SciTech Connect

    Barker, J.R.; Tingey, D.T.

    1992-04-01

    To address the issues of air pollution impacts on biodiversity, the U.S. Environmental Protection Agency, Environmental Research Laboratory in Corvallis, OR, the U.S. Fish and Wildlife Service National Fisheries Research Center in Leetown, and the Electric Power Research Institute convened a workshop to evaluate current knowledge, identify information gaps, provide direction to research and assess policy issues. In order to obtain the most current and authoritative information possible, air pollution and biodiversity experts were invited to participate in a workshop and author the papers that make up this report. Each paper was presented and discussed, then collected in this document. The material has been organized into four parts: an introduction, an overview of air pollution exposure and effects, the consequences of air pollution on biodiversity, and policy issues and research needs.

  7. Study on measurement of the coal powder concentration in pneumatic pipes of a boiler with relationship between air velocity and pressure drop

    SciTech Connect

    Pan, W.; Shen, F.; Lin, W.; Chen, L.; Zhang, D.; Wang, Q.; Ke, J.; Quan, W.

    1999-07-01

    According to the theoretical relationship between air velocity and pressure drop in different solid-air mass flow in vertical pipes with the condition of upward air-solid flowing, the experimental research on measuring the coal powder concentration is directed against the pneumatic pipes of a boiler's combustion system in the energy industry. Through analyzing the experimental results, a mathematical model for measuring the coal powder concentration in pneumatic pipes is obtained. Then, the error analysis is done, and the method of on-line measurement and its function are provided.

  8. Air pollutants effects on forest ecosystems

    SciTech Connect

    Not Available

    1985-01-01

    This book presents the papers given at a conference on the effects of acid rain on forests. The conference was sponsored by the National Acid Precipitation Assessment Program (NAPAP). Topics considered at the conference included the status of US research on acid deposition and its effects contributing factors to the decline of forests, evidence for effects on ecosystems, the effects of air pollutants on forest ecosystems in North America and Europe, forest management, and future scientific research programs and management approaches.

  9. The role of loading rate, backwashing, water and air velocities in an up-flow nitrifying tertiary filter.

    PubMed

    Vigne, Emmanuelle; Choubert, Jean-Marc; Canler, Jean-Pierre; Heduit, Alain; Sørensen, Kim Helleshøj; Lessard, Paul

    2011-01-01

    The vertical distribution of nitrification performances in an up-flow biological aerated filter operated at tertiary nitrification stage is evaluated in this paper. Experimental data were collected from a semi-industrial pilot-plant under various operating conditions. The actual and the maximum nitrification rates were measured at different levels inside the up-flow biofilter. A nitrogen loading rate higher than 1.0 kg NH4-Nm(-3)_mediad(-1) is necessary to obtain nitrification activity over all the height of the biofilter. The increase in water and air velocities from 6 to 10 m h(-1) and 10 to 20 m h(-1) has increased the nitrification rate by 80% and 20% respectively. Backwashing decreases the maximum nitrification rate in the media by only 3-14%. The nitrification rate measured at a level of 0.5 m above the bottom of the filter is four times higher than the applied daily average volumetric nitrogen loading rate up to 1.5 kg NH4-N m(-3)_mediad(-1). Finally, it is shown that 58% of the available nitrification activity is mobilized in steady-state conditions while up to 100% is used under inflow-rate increase. Copyright © 2010 Elsevier Ltd. All rights reserved.

  10. Computational simulation of temperature and velocity distribution in human upper respiratory airway during inhalation of hot air.

    PubMed

    Goodarzi-Ardakani, V; Taeibi-Rahni, M; Salimi, M R; Ahmadi, G

    2016-03-01

    The present study provides an accurate simulation of velocity and temperature distributions of inhalation thermal injury in a human upper airway, including vestibule, nasal cavity, paranasal sinuses, nasopharynx, oropharynx, larynx, and upper part of main bronchus. To this end, a series of CT scan images, taken from an adult woman, was used to construct a three dimensional model. The airway walls temperature was adjusted according to existing in vivo temperature measurements. Also, in order to cover all breathing activities, five different breathing flow rates (10, 15, 20, 30, and 40 l/min) and different ambient air temperatures (100, 200, 300, 400, and 500 °C) were studied. Different flow regimes, including laminar, transitional, and turbulence were considered and the simulations were validated using reliable experimental data. The results show that nostrils, vestibule, and nasal cavity are damaged more than other part of airway. Finally, In order to obtain the heat flux through the walls, correlations for Nusselt number for each individual parts of airway (vestibule, main upper airway, nasopharynx etc.,) are proposed. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. The effects of air leaks on solar air heating systems

    NASA Technical Reports Server (NTRS)

    Elkin, R.; Cash, M.

    1979-01-01

    This paper presents the results of an investigation to determine the effects of leakages in collector and duct work on the system performance of a typical single-family residence solar air heating system. Positive (leakage out) and negative (leakage in) pressure systems were examined. Collector and duct leakage rates were varied from 10 to 30 percent of the system flow rate. Within the range of leakage rates investigated, solar contribution to heated space and domestic hot water loads was found to be reduced up to 30 percent from the no-leak system contribution with duct leakage equally divided between supply and return duct; with supply duct leakage greater than return leakage a reduction of up to 35 percent was noted. The negative pressure system exhibited a reduction in solar contribution somewhat larger than the positive pressure system for the same leakage rates.

  12. Effects of spoilers and gear on B-747 wake vortex velocities

    NASA Technical Reports Server (NTRS)

    Luebs, A. B.; Bradfute, J. G.; Ciffone, D. L.

    1976-01-01

    Vortex velocities were measured in the wakes of four configurations of a 0.61-m span model of a B-747 aircraft. The wakes were generated by towing the model underwater in a ship model basin. Tangential and axial velocity profiles were obtained with a scanning laser velocimeter as the wakes aged to 35 span lengths behind the model. A 45 deg deflection of two outboard flight spoilers with the model in the landing configuration resulted in a 36 percent reduction in wake maximum tangential velocity, altered velocity profiles, and erratic vortex trajectories. Deployment of the landing gear with the inboard flaps in the landing position and outboard flaps retracted had little effect on the flap vortices to 35 spans, but caused the wing tip vortices to have: (1) more diffuse velocity profiles; (2) a 27 percent reduction in maximum tangential velocity; and (3) a more rapid merger with the flap vortices.

  13. Spatial fluctuations of pedestrian velocities in bidirectional streams: Exploring the effects of self-organization

    NASA Astrophysics Data System (ADS)

    Saberi, Meead; Aghabayk, Kayvan; Sobhani, Amir

    2015-09-01

    Individual pedestrian velocities vary over time and space depending on the crowd size, location of individuals' within the crowd, and formation of self-organized lanes. We use empirical data to explore the spatial fluctuations of pedestrian velocities in bidirectional streams. We find that, unlike ordinary fluids, the velocity profile in bidirectional pedestrian streams does not necessarily follow a hyperbolic form. Rather, the shape of the velocity profile is highly dependent on the formation of self-organized lanes. We also show that the spatial fluctuations of pedestrian velocities along and transverse to the flow direction are widely distributed and can be modeled by a sum of Gaussian distributions. Results suggest that the effect of self-organization phenomenon is strong enough that for the same crowd size, the velocity distribution does not significantly change when pedestrians are highly mixed compared to when separate lanes are formed.

  14. Turbulent burning velocities of premixed CH{sub 4}/diluent/air flames in intense isotropic turbulence with consideration of radiation losses

    SciTech Connect

    Shy, S.S.; Yang, S.I.; Lin, W.J.; Su, R.C.

    2005-10-01

    This paper presents turbulent burning velocities, S{sub T}, of several premixed CH{sub 4}/diluent/air flames at the same laminar burning velocity S{sub L}=0.1 m/s for two equivalence ratios f=0.7 and 1.4 near flammability limits with consideration of radiation heat losses from small (N{sub 2} diluted) to large (CO{sub 2} diluted). Experiments are carried out in a cruciform burner, in which the long vertical vessel is used to provide a downward propagating premixed flame and the large horizontal vessel equipped with a pair of counterrotating fans and perforated plates can be used to generate an intense isotropic turbulence in the central region between the two perforated plates. Turbulent flame speeds are measured by four different arrangements of pairs of ion-probe sensors at different positions from the top to the bottom of the central region in the burner. It is found that the effect of gas velocity on S{sub T} measured in the central region can be neglected. Simultaneous measurements using the pressure transducer and ion-probe sensors show that the pressure rise due to turbulent burning has little influence on S{sub T}. These measurements prove the accuracy of the S{sub T} data. At f=0.7, the percentage of [(S{sub T}/S{sub L}){sub CO{sub 2}}-(S{sub T}/S{sub L}){sub N{sub 2}}]/(S{sub T}/S{sub L}){sub N{sub 2}} decreases gradually from -4 to -17% when values of u{sup '}/S{sub L} increase from 4 to 46, while at f=1.4 such decrease is much more abrupt from -19 to -53% when values of u{sup '}/S{sub L} only increase from 4 to 18. The larger the radiation losses, the smaller the values of S{sub T}. This decreasing effect is augmented by increasing u{sup '}/S{sub L} and is particularly pronounced for rich CH{sub 4} flames. When u{sup '}/S{sub L}=18, lean CO{sub 2} and/or N{sub 2}-diluted CH{sub 4} flames have much higher, 3.6 and/or 1.8 times higher, values of S{sub T}/S{sub L} than rich CO{sub 2} and/or N{sub 2}-diluted CH{sub 4} flames, respectively. It is found that

  15. Effect of salinity on the swimming velocity of the water flea Daphnia magna.

    PubMed

    Baillieul, M; De Wachter, B; Blust, R

    1998-01-01

    The swimming velocity of the water flea Daphnia magna is dependent on its body size. Therefore, environmental factors that influence growth also influence swimming velocity. This study examined whether exposure to increased salinity reduces swimming velocity only through its effect on body size or whether it also reduces size-specific swimming velocity. Initially, size-specific swimming velocity decreased in a salinity-dependent way. Thereafter, swimming velocities gradually returned to their expected values in all treatments. This acclimation coincided with considerable mortality in the highest-salinity treatment, indicating that daphnids in this treatment either acclimated or died. The initial decrease in size-specific swimming velocity could not be explained by decreased uptake of food. Thus, the results indicate that salinity temporarily impaired physiology. The experiment illustrates how size effects can be accounted for in swimming-velocity analysis and how size-specific swimming-velocity analysis can be used as a non-invasive method to detect stress-induced deviations from normal physiology.

  16. [Airport related air pollution and health effects].

    PubMed

    Iavicoli, Ivo; Fontana, Luca; Ancona, Carla; Forastiere, Francesco

    2014-01-01

    Airport is an extremely complex emission source of airborne pollutants that can have a significant impact on the environment. Indeed, several airborne chemicals emitted during airport activities may significantly get worse air quality and increase exposure level of both airport workers and general population living nearby the airports. In recent years airport traffic has increased and consequently several studies investigated the association between airport-related air pollution and occurrence of adverse health effects, particularly on respiratory system, in exposed workers and general population resident nearby. In this context, we carried out a critical evaluation of the studies that investigated this correlation in order to obtain a deeper knowledge of this issue and to identify the future research needs. Results show that the evidence of association between airport-related air pollution and health effects on workers and residents is still limited.

  17. Improved technique for blood flow velocity measurement using Doppler effect

    NASA Astrophysics Data System (ADS)

    Valadares Oliveira, Eduardo J.; Nantes Button, Vera L. d. S.; Maia, Joaquim M.; Costa, Eduardo T.

    2002-04-01

    The Doppler velocimeter developed allows to determine the angle between the ultrasonic beam and the velocity vector of the flow, and to calculate the precise blood flow in a vessel. Four piezoelectric transducers constitute the Doppler velocimeter. Three of these transducers are positioned to form an equilateral triangle (base of a pyramid). When these transducers move simultaneously, backward or forward from the initial position, the emitted ultrasonic beams focalize on a position (peak of the pyramid) closer or farther from the transducers faces, according to the depth of the vessel where we intend to measure de flow. The angle between the transducers allows adjusting the height of this pyramid and the position of the focus (where the three beams meet). A forth transducer is used to determine the diameter of the vessel and monitor the position of the Doppler velocimeter relative to the vessel. Simulation results showed that with this technique is possible to accomplish precise measurement of blood flow.

  18. Effects of Movement Velocity and Maximal Concentric and Eccentric Actions on the Bilateral Deficit

    ERIC Educational Resources Information Center

    Dickin, D. Clark; Too, Danny

    2006-01-01

    This study was performed to examine the effects of movement velocity and maximal concentric and eccentric actions on the bilateral deficit. Eighteen female participants performed maximal unilateral and bilateral knee extensions concentrically and eccentrically across six movement velocities (30, 60, 90, 120, 150, and 180[degrees]/s). Repeated…

  19. Effects of Movement Velocity and Maximal Concentric and Eccentric Actions on the Bilateral Deficit

    ERIC Educational Resources Information Center

    Dickin, D. Clark; Too, Danny

    2006-01-01

    This study was performed to examine the effects of movement velocity and maximal concentric and eccentric actions on the bilateral deficit. Eighteen female participants performed maximal unilateral and bilateral knee extensions concentrically and eccentrically across six movement velocities (30, 60, 90, 120, 150, and 180[degrees]/s). Repeated…

  20. Analysis of Wave Velocity Patterns in Black Cherry Trees and its Effect on Internal Decay Detection

    Treesearch

    Guanghui Li; Xiping Wang; Jan Wiedenbeck; Robert J. Ross

    2013-01-01

    In this study, we examined stress wave velocity patterns in the cross sections of black cherry trees, developed analytical models of stress wave velocity in sound healthy trees, and then tested the effectiveness of the models as a tool for tree decay diagnosis. Acoustic tomography data of the tree cross sections were collected from 12 black cherry trees at a production...

  1. Analysis of wave velocity patterns in black cherry trees and its effect on internal decay detection

    Treesearch

    Guanghui Li; Xiping Wang; Hailin Feng; Jan Wiedenbeck; Robert J. Ross

    2014-01-01

    In this study, we examined stress wave velocity patterns in the cross sections of black cherry trees, developed analytical models of stress wave velocity in sound healthy trees, and then tested the effectiveness of the models as a tool for tree decay diagnosis. Acoustic tomography data of the tree cross sections were collected from 12 black cherry trees at a production...

  2. Effect of particle volume fraction on the settling velocity of volcanic ash particles: implications for ash dispersion models

    NASA Astrophysics Data System (ADS)

    Del Bello, E.; Taddeucci, J.; De'Michieli Vitturi, M.; Scarlato, P.; Andronico, D.; Scollo, S.; Kueppers, U.

    2015-12-01

    We present the first report of experimental measurements of the enhanced settling velocity of volcanic particles as function of particle volume fraction. In order to investigate the differences in the aerodynamic behavior of ash particles when settling individually or in mass, we performed systematic large-scale ash settling experiments using natural basaltic and phonolitic ash. By releasing ash particles at different, controlled volumetric flow rates, in an unconstrained open space and at minimal air movement, we measured their terminal velocity, size, and particle volume fraction with a high-speed camera at 2000 fps. Enhanced settling velocities of individual particles increase with increasing particle volume fraction. This suggests that particle clustering during fallout may be one reason explaining larger than theoretical depletion rates of fine particles from volcanic ash clouds. We provide a quantitative empirical model that allows to calculate, from a given particle size and density, the enhanced velocity resulting from a given particle volume fraction. The proposed model has the potential to serve as a simple tool for the prediction of the terminal velocity of ash of an hypothetical distribution of ash of known particle size and volume fraction. This is of particular importance for advection-diffusion transport model of ash where generally a one-way coupling is adopted, considering only the flow effects on particles. To better quantify the importance of the enhanced settling velocity in ash dispersal, we finally introduced the new formulation in a Lagrangian model calculating for realistic eruptive conditions the resulting ash concentration in the atmosphere and on the ground.

  3. Respiratory effects of outdoor air pollution

    SciTech Connect

    Griffith, D.E.; Levin, J.L. )

    1989-10-01

    Outdoor air pollution adversely affects human health and the quality of the environment. However, epidemiologic studies of these effects are difficult to control because of confounding variables such as age and cigarette smoking and the difficulty in estimating doses of pollutants. Drs Griffith and Levin discuss the relationship between major types of pollutants and increased morbidity and mortality from respiratory disease.35 references.

  4. Spontaneous Velocity Effect of Musical Expression on Self-Paced Walking

    PubMed Central

    Buhmann, Jeska; Desmet, Frank; Moens, Bart; Van Dyck, Edith; Leman, Marc

    2016-01-01

    The expressive features of music can influence the velocity of walking. So far, studies used instructed (and intended) synchronization. But is this velocity effect still present with non-instructed (spontaneous) synchronization? To figure that out, participants were instructed to walk in their own comfort tempo on an indoor track, first in silence and then with tempo-matched music. We compared velocities of silence and music conditions. The results show that some music has an activating influence, increasing velocity and motivation, while other music has a relaxing influence, decreasing velocity and motivation. The influence of musical expression on the velocity of self-paced walking can be predicted with a regression model using only three sonic features explaining 56% of the variance. Phase-coherence between footfall and beat did not contribute to the velocity effect, due to its implied fixed pacing. The findings suggest that the velocity effect depends on vigor entrainment that influences both stride length and pacing. Our findings are relevant for preventing injuries, for gait improvement in walking rehabilitation, and for improving performance in sports activities. PMID:27167064

  5. Spontaneous Velocity Effect of Musical Expression on Self-Paced Walking.

    PubMed

    Buhmann, Jeska; Desmet, Frank; Moens, Bart; Van Dyck, Edith; Leman, Marc

    2016-01-01

    The expressive features of music can influence the velocity of walking. So far, studies used instructed (and intended) synchronization. But is this velocity effect still present with non-instructed (spontaneous) synchronization? To figure that out, participants were instructed to walk in their own comfort tempo on an indoor track, first in silence and then with tempo-matched music. We compared velocities of silence and music conditions. The results show that some music has an activating influence, increasing velocity and motivation, while other music has a relaxing influence, decreasing velocity and motivation. The influence of musical expression on the velocity of self-paced walking can be predicted with a regression model using only three sonic features explaining 56% of the variance. Phase-coherence between footfall and beat did not contribute to the velocity effect, due to its implied fixed pacing. The findings suggest that the velocity effect depends on vigor entrainment that influences both stride length and pacing. Our findings are relevant for preventing injuries, for gait improvement in walking rehabilitation, and for improving performance in sports activities.

  6. Effects of pressure drop and superficial velocity on the bubbling fluidized bed incinerator.

    PubMed

    Wang, Feng-Jehng; Chen, Suming; Lei, Perng-Kwei; Wu, Chung-Hsing

    2007-12-01

    Since performance and operational conditions, such as superficial velocity, pressure drop, particles viodage, and terminal velocity, are difficult to measure on an incinerator, this study used computational fluid dynamics (CFD) to determine numerical solutions. The effects of pressure drop and superficial velocity on a bubbling fluidized bed incinerator (BFBI) were evaluated. Analytical results indicated that simulation models were able to effectively predict the relationship between superficial velocity and pressure drop over bed height in the BFBI. Second, the models in BFBI were simplified to simulate scale-up beds without excessive computation time. Moreover, simulation and experimental results showed that minimum fluidization velocity of the BFBI must be controlled in at 0.188-3.684 m/s and pressure drop was mainly caused by bed particles.

  7. Effect of initial tangential velocity distribution on the mean evolution of a swirling turbulent free jet

    NASA Technical Reports Server (NTRS)

    Farokhi, S.; Taghavi, R.; Rice, E. J.

    1988-01-01

    An existing cold jet facility at NASA-Lewis was modified to produce swirling flows with controllable initial tangential velocity distribution. Distinctly different swirl velocity profiles were produced, and their effects on jet mixing characteristics were measured downstream of an 11.43 cm diameter convergent nozzle. It was experimentally shown that in the near field of a swirling turbulent jet, the mean velocity field strongly depends on the initial swirl profile. Two extreme tangential velocity distributions were produced. The two jets shared approximately the same initial mass flow rate of 5.9 kg/s, mass averaged axial Mach number and swirl number. Mean centerline velocity decay characteristics of the solid body rotation jet flow exhibited classical decay features of a swirling jet with S = 0.48 reported in the literature. It is concluded that the integrated swirl effect, reflected in the swirl number, is inadequate in describing the mean swirling jet behavior in the near field.

  8. Effect of initial tangential velocity distribution on the mean evolution of a swirling turbulent free jet

    NASA Technical Reports Server (NTRS)

    Farokhi, S.; Taghavi, R.; Rice, E. J.

    1988-01-01

    An existing cold jet facility at NASA-Lewis was modified to produce swirling flows with controllable initial tangential velocity distribution. Distinctly different swirl velocity profiles were produced, and their effects on jet mixing characteristics were measured downstream of an 11.43 cm diameter convergent nozzle. It was experimentally shown that in the near field of a swirling turbulent jet, the mean velocity field strongly depends on the initial swirl profile. Two extreme tangential velocity distributions were produced. The two jets shared approximately the same initial mass flow rate of 5.9 kg/s, mass averaged axial Mach number and swirl number. Mean centerline velocity decay characteristics of the solid body rotation jet flow exhibited classical decay features of a swirling jet with S = 0.48 reported in the literature. It is concluded that the integrated swirl effect, reflected in the swirl number, is inadequate in describing the mean swirling jet behavior in the near field.

  9. Effect of transverse velocity and temperature gradients on sound attenuation in two-dimensional ducts

    NASA Technical Reports Server (NTRS)

    Nayfeh, A. H.; Sun, J.

    1974-01-01

    An investigation is described of the effect of transverse mean-velocity and temperature gradients on sound attenuation in acoustically treated two-dimensional ducts. The results show that cooling the duct walls leads to channeling the sound toward the walls for both downstream and upstream propagation. The effect of mean-temperature gradients on the attenuation rates of the lowest three modes can be as important as the effect of mean-velocity gradients.

  10. Effects of water-contaminated air on blowoff limits of opposed jet hydrogen-air diffusion flames

    NASA Technical Reports Server (NTRS)

    Pellett, Gerald L.; Jentzen, Marilyn E.; Wilson, Lloyd G.; Northam, G. Burton

    1988-01-01

    The effects of water-contaminated air on the extinction and flame restoration of the central portion of N2-diluted H2 versus air counterflow diffusion flames are investigated using a coaxial tubular opposed jet burner. The results show that the replacement of N2 contaminant in air by water on a mole for mole basis decreases the maximum sustainable H2 mass flow, just prior to extinction, of the flame. This result contrasts strongly with the analogous substitution of water for N2 in a relatively hot premixed H2-O2-N2 flame, which was shown by Koroll and Mulpuru (1986) to lead to a significant, kinetically controlled increase in laminar burning velocity.

  11. Effect of Velocity of Detonation of Explosives on Seismic Radiation

    NASA Astrophysics Data System (ADS)

    Stroujkova, A. F.; Leidig, M.; Bonner, J. L.

    2014-12-01

    We studied seismic body wave generation from four fully contained explosions of approximately the same yields (68 kg of TNT equivalent) conducted in anisotropic granite in Barre, VT. The explosions were detonated using three types of explosives with different velocities of detonation (VOD): Black Powder (BP), Ammonium Nitrate Fuel Oil/Emulsion (ANFO), and Composition B (COMP B). The main objective of the experiment was to study differences in seismic wave generation among different types of explosives, and to determine the mechanism responsible for these differences. The explosives with slow burn rate (BP) produced lower P-wave amplitude and lower corner frequency, which resulted in lower seismic efficiency (0.35%) in comparison with high burn rate explosives (2.2% for ANFO and 3% for COMP B). The seismic efficiency estimates for ANFO and COMP B agree with previous studies for nuclear explosions in granite. The body wave radiation pattern is consistent with an isotropic explosion with an added azimuthal component caused by vertical tensile fractures oriented along pre-existing micro-fracturing in the granite, although the complexities in the P- and S-wave radiation patterns suggest that more than one fracture orientation could be responsible for their generation. High S/P amplitude ratios and low P-wave amplitudes suggest that a significant fraction of the BP source mechanism can be explained by opening of the tensile fractures as a result of the slow energy release.

  12. Adverse cardiovascular effects of air pollution.

    PubMed

    Mills, Nicholas L; Donaldson, Ken; Hadoke, Paddy W; Boon, Nicholas A; MacNee, William; Cassee, Flemming R; Sandström, Thomas; Blomberg, Anders; Newby, David E

    2009-01-01

    Air pollution is increasingly recognized as an important and modifiable determinant of cardiovascular disease in urban communities. Acute exposure has been linked to a range of adverse cardiovascular events including hospital admissions with angina, myocardial infarction, and heart failure. Long-term exposure increases an individual's lifetime risk of death from coronary heart disease. The main arbiter of these adverse health effects seems to be combustion-derived nanoparticles that incorporate reactive organic and transition metal components. Inhalation of this particulate matter leads to pulmonary inflammation with secondary systemic effects or, after translocation from the lung into the circulation, to direct toxic cardiovascular effects. Through the induction of cellular oxidative stress and proinflammatory pathways, particulate matter augments the development and progression of atherosclerosis via detrimental effects on platelets, vascular tissue, and the myocardium. These effects seem to underpin the atherothrombotic consequences of acute and chronic exposure to air pollution. An increased understanding of the mediators and mechanisms of these processes is necessary if we are to develop strategies to protect individuals at risk and reduce the effect of air pollution on cardiovascular disease.

  13. The Acute Effects of Upper Extremity Stretching on Throwing Velocity in Baseball Throwers

    PubMed Central

    Melton, Jason; Delobel, Ashley; Puentedura, Emilio J.

    2013-01-01

    Purpose. To examine the effects of static and proprioceptive neuromuscular facilitation (PNF) stretching of the shoulder internal rotators on throwing velocity. Subjects. 27 male throwers (mean age = 25.1 years old, SD = 2.4) with adequate knowledge of demonstrable throwing mechanics. Study Design. Randomized crossover trial with repeated measures. Methods. Subjects warmed up, threw 10 pitches at their maximum velocity, were randomly assigned to 1 of 3 stretching protocols (static, PNF, or no stretch), and then repeated their 10 pitches. Velocities were recorded after each pitch and average and peak velocities were recorded after each session. Results. Data were analyzed using a 3 × 2 repeated measures ANOVA. No significant interaction between stretching and throwing velocity was observed. Main effects for time were not statistically significant. Main effects for the stretching groups were statistically significant. Discussion. Results suggest that stretching of the shoulder internal rotators did not significantly affect throwing velocity immediately after stretching. This may be due to the complexity of the throwing task. Conclusions. Stretching may be included in a thrower's warm-up without any effects on throwing velocity. Further research should be performed using a population with more throwing experience and skill. PMID:26464880

  14. Effects of buoyancy on lean premixed v-flames, Part II. VelocityStatistics in Normal and Microgravity

    SciTech Connect

    Cheng, R.K.; Bedat, B.; Yegian, D.T.

    1999-07-01

    The field effects of buoyancy on laminar and turbulent premixed v-flames have been studied by the use of laser Doppler velocimetry to measure the velocity statistics in +1g, -1g and {micro}g flames. The experimental conditions covered mean velocity, Uo, of 0.4 to 2 m/s, methane/air equivalence ratio, f, of 0.62 to 0.75. The Reynolds numbers, from 625 to 3130 and the Richardson number from 0.05 to 1.34. The results show that a change from favorable (+1g) to unfavorable (-1g) mean pressure gradient in the plume create stagnating flows in the far field whose influences on the mean and fluctuating velocities persist in the near field even at the highest Re we have investigated. The use of Richardson number < 0.1 as a criterion for momentum dominance is not sufficient to prescribe an upper limit for these buoyancy effects. In {micro}g, the flows within the plumes are non-accelerating and parallel. Therefore, velocity gradients and hence mean strain rates in the plumes of laboratory flames are direct consequences of buoyancy. Furthermore, the rms fluctuations in the plumes of {micro}g flames are lower and more isotropic than in the laboratory flames to show that the unstable plumes in laboratory flames also induce velocity fluctuations. The phenomena influenced by buoyancy i.e. degree of flame wrinkling, flow acceleration, flow distribution, and turbulence production, can be subtle due to their close coupling with other flame flow interaction processes. But they cannot be ignored in fundamental studies or else the conclusions and insights would be ambiguous and not very meaningful.

  15. A Model for Determining the Effect of the Wind Velocity on 100 m Sprinting Performance

    PubMed Central

    Janjic, Natasa; Kapor, Darko; Doder, Dragan; Petrovic, Aleksandar; Doder, Radoslava

    2017-01-01

    Abstract This paper introduces an equation for determining instantaneous and final velocity of a sprinter in a 100 m run completed with a wind resistance ranging from 0.1 to 4.5 m/s. The validity of the equation was verified using the data of three world class sprinters: Carl Lewis, Maurice Green, and Usain Bolt. For the given constant wind velocity with the values + 0.9 and + 1.1 m/s, the wind contribution to the change of sprinter velocity was the same for the maximum as well as for the final velocity. This study assessed how the effect of the wind velocity influenced the change of sprinting velocity. The analysis led to the conclusion that the official limit of safely neglecting the wind influence could be chosen as 1 m/s instead of 2 m/s, if the velocity were presented using three, instead of two decimal digits. This implies that wind velocity should be rounded off to two decimal places instead of the present practice of one decimal place. In particular, the results indicated that the influence of wind on the change of sprinting velocity in the range of up to 2 m/s and was of order of magnitude of 10-3 m/s. This proves that the IAAF Competition Rules correctly neglect the influence of the wind with regard to such velocities. However, for the wind velocity over 2 m/s, the wind influence is of order 10-2 m/s and cannot be neglected. PMID:28713468

  16. A Model for Determining the Effect of the Wind Velocity on 100 m Sprinting Performance.

    PubMed

    Janjic, Natasa; Kapor, Darko; Doder, Dragan; Petrovic, Aleksandar; Doder, Radoslava

    2017-06-01

    This paper introduces an equation for determining instantaneous and final velocity of a sprinter in a 100 m run completed with a wind resistance ranging from 0.1 to 4.5 m/s. The validity of the equation was verified using the data of three world class sprinters: Carl Lewis, Maurice Green, and Usain Bolt. For the given constant wind velocity with the values + 0.9 and + 1.1 m/s, the wind contribution to the change of sprinter velocity was the same for the maximum as well as for the final velocity. This study assessed how the effect of the wind velocity influenced the change of sprinting velocity. The analysis led to the conclusion that the official limit of safely neglecting the wind influence could be chosen as 1 m/s instead of 2 m/s, if the velocity were presented using three, instead of two decimal digits. This implies that wind velocity should be rounded off to two decimal places instead of the present practice of one decimal place. In particular, the results indicated that the influence of wind on the change of sprinting velocity in the range of up to 2 m/s and was of order of magnitude of 10(-3) m/s. This proves that the IAAF Competition Rules correctly neglect the influence of the wind with regard to such velocities. However, for the wind velocity over 2 m/s, the wind influence is of order 10(-2) m/s and cannot be neglected.

  17. Effects of mass flow rate and droplet velocity on surface heat flux during cryogen spray cooling.

    PubMed

    Karapetian, Emil; Aguilar, Guillermo; Kimel, Sol; Lavernia, Enrique J; Nelson, J Stuart

    2003-01-07

    Cryogen spray cooling (CSC) is used to protect the epidermis during dermatologic laser surgery. To date, the relative influence of the fundamental spray parameters on surface cooling remains incompletely understood. This study explores the effects of mass flow rate and average droplet velocity on the surface heat flux during CSC. It is shown that the effect of mass flow rate on the surface heat flux is much more important compared to that of droplet velocity. However, for fully atomized sprays with small flow rates, droplet velocity can make a substantial difference in the surface heat flux.

  18. Velocity-changing collisional effects in nonlinear atomic spectroscopy and photon echo decay in gases

    NASA Technical Reports Server (NTRS)

    Herman, R. M.

    1983-01-01

    A general theory of atomic dipole coherence under the influence of collisional phase changes, inelastic effects and optically active atom velocity changes, including those due to anisotropic interactions is presented. Velocity change effects are obtained in closed form. Line shapes appear as convolutions of standard pressure broadening contours with velocity-change contours. Width and shift parameters for the He-broadened Na D lines at 2 m bar pressure, 380 K are calculated, as are He-induced photon echo decay rates for these lines. Overall agreement with xperiment is reasonably good.

  19. Gaussian diffusion sphere model to predict deposition velocities under the combined effects of electrophoresis and thermophoresis

    NASA Astrophysics Data System (ADS)

    Kang, Soojin; Yook, Se-Jin; Lee, Kwan-Soo

    2014-03-01

    The Gaussian diffusion sphere model (GDSM) is proposed to predict the average deposition velocity of particles onto a flat plate exposed to parallel airflow after considering the combined effects of electrophoresis and thermophoresis. This model can account for convection, Brownian diffusion, gravitational settling, thermophoresis, and electrophoresis, and it provides fast calculation times and accurate predictions. Using the GDSM, the effects of the deposition surface size on the deposition velocity are analyzed. When the gravitational effect is dominant for a face-up surface or the attractive electrophoresis effect is dominant, the deposition velocity is estimated to be independent of the deposition surface size. Deposition under the influence of thermophoresis depends on the deposition surface size due to the formation of a thermal boundary layer. Deposition velocities for a 450-mm-long surface are studied under a temperature difference of 40 K and for electric field strengths ranging from 0 to 1000 V/cm.

  20. Measurement of unsteady airflow velocity at nozzle outlet

    NASA Astrophysics Data System (ADS)

    Pyszko, René; Machů, Mário

    2017-09-01

    The paper deals with a method of measuring and evaluating the cooling air flow velocity at the outlet of the flat nozzle for cooling a rolled steel product. The selected properties of the Prandtl and Pitot sensing tubes were measured and compared. A Pitot tube was used for operational measurements of unsteady dynamic pressure of the air flowing from nozzles to abtain the flow velocity. The article also discusses the effects of air temperature, pressure and relative air humidity on air density, as well as the influence of dynamic pressure filtering on the error of averaged velocity.

  1. Effects of spanwise topographic heterogeneity on amplitude and frequency modulation of streamwise velocity fluctuations

    NASA Astrophysics Data System (ADS)

    Awasthi, Ankit; Subdberg, Matthew; Anderson, William

    2016-11-01

    We present results on the effects of topographic height, and spanwise heterogeneity, on amplitude and frequency modulation of small-scale structures in the roughness sublayer due to large-scale structures in the logarithmic region of turbulent channel flows. This work follows preceding contributions on amplitude and frequency modulation in smooth wall turbulent boundary layers. We have considered three topographic cases with different characteristics from homogeneous (sandpaper), to two spanwise heterogeneous cases where the height amplitude is increased (this topographic configuration induces turbulent secondary flows, which are known to alter the outer-layer flow characteristics). Indeed, pre-multiplied energy spectra across wavelength and elevation (so-called spectrograms) illustrate how turbulent energy is redistributed with systematic modification to the underlying topography. We have determined how the large-scale (low-pass filtered) streamwise velocity modulates the amplitude and frequency response of small-scale (high-pass filtered) signal. We find that outer-layer topographic-induced perturbations completely alter the intensity of amplitude and frequency modulation. This highlights the passive-actuator-like role of roughness heterogeneity, and underpins the need to incorporate such functional dependence in the development of wall models for LES. Air Force Office of Scientific Research, Grant # FA9550-14-1-0101.

  2. Dilution rates for tailpipe emissions: effects of vehicle shape, tailpipe position, and exhaust velocity.

    PubMed

    Chang, Victor W C; Hildemann, Lynn M; Chang, Cheng-hisn

    2009-06-01

    The rate at which motor vehicle exhaust undergoes dilution with ambient air will greatly affect the size distribution characteristics of the particulate emissions. Wind tunnel experiments were conducted to investigate the impacts of vehicle shape, tailpipe orientation, and exhaust exit velocity on the dilution profiles under steady driving conditions for three model vehicles: a light-duty truck, a passenger car, and a heavy-duty tractor head. A three dimensional array of 60 sensors provided simultaneous measurements of dilution ratios for the emissions in the near- and far-wake regions downstream of the vehicle. The processes underlying the observations were investigated via nondimensionalization. Many of the trends seen substantially downstream can be well generalized using a simple nondimensionalization technique; however, this is not true in the near-wake region (within a downstream distance equivalent to a few vehicle heights). In the near-wake region, using the vehicle width and length to normalize for the vehicle shape is not enough to fully account for the variations seen. Including the exhaust flow rate in the nondimensionalization process is effective further downwind but does not adequately capture the complexity in the near-wake region. Tailpipe orientation and location are also shown to be influential factors affecting the near-wake dilution characteristics.

  3. An Analysis of Consolidation Grouting Effect of Bedrock Based on its Acoustic Velocity Increase

    NASA Astrophysics Data System (ADS)

    Chen, Ming; Lu, Wen-bo; Zhang, Wen-ju; Yan, Peng; Zhou, Chuang-bing

    2015-05-01

    Acoustic velocity is an important parameter to evaluate the mechanical properties of fractured rock masses. Based on the in situ acoustic velocity measurement data of ~20 hydropower stations in China, we assessed the acoustic velocity increase of rock masses as a result of consolidation grouting in different geological conditions, such as fault sites, weathered areas and excavation-induced damage zones. We established an empirical relationship between the acoustic velocity of rock masses before and after consolidation grouting, and examined the correlation between acoustic velocity and deformation modulus. A case study is presented about a foundation consolidation grouting project for an intake tower of Pubugou Hydropower Station. The results show that different types of rock masses possess distinct ranges for resultant acoustic velocity increase by consolidation grouting. Under a confidence interval of 95 %, the ranges of the increasing rate of acoustic velocity in a faulted zone, weathered zone, and excavation-induced damage zone are observed to be 12.7-43.1, 12.3-31.2, and 6.9-14.5 %, respectively. The acoustic velocity before grouting and its increasing rate can be used to predict the effectiveness of consolidation grouting.

  4. Effects of mechanical horseback riding velocity on spinal alignment in young adults.

    PubMed

    Lim, Jae-Heon; Cho, Woon-Su; Lee, Seong-Jin; Park, Chi-Bok; Park, Jang-Sung

    2016-06-01

    [Purpose] This study aimed to determine if the velocity of mechanical horseback-riding training can improve spinal alignment in young adults. [Subjects and Methods] Thirty-six subjects were enrolled in this study. The subjects were randomly allocated into high-, moderate-, and low-velocity mechanical horseback-riding training groups. All participants completed one 20-minute session per day, 3 days per week, for 6 weeks. The evaluation was performed before and 6 weeks after the training intervention. The spinal alignment was measured by a Formetric III device. The measurement items were kyphotic angle, lordotic angle, trunk inclination, pelvic torsion, pelvic rotation, and lateral deviation. The data were analyzed using analysis of covariance to determine the statistical significance. [Results] The kyphotic angle and trunk inclination were significantly different among the groups. The kyphotic angles of the high- and moderate-velocity groups were significantly lower than that of the low-velocity group after the intervention. The trunk inclination of the high-velocity group was significantly lower than that of the low-velocity group after intervention. [Conclusion] Higher-velocity mechanical horseback-riding training is more effective than lower-velocity mechanical horseback-riding training for improving spinal alignment.

  5. The effect of increasing strength and approach velocity on triple jump performance.

    PubMed

    Allen, Sam J; Yeadon, M R Fred; King, Mark A

    2016-12-08

    The triple jump is an athletic event comprising three phases in which the optimal phase ratio (the proportion of each phase to the total distance jumped) is unknown. This study used a planar whole body torque-driven computer simulation model of the ground contact parts of all three phases of the triple jump to investigate the effect of strength and approach velocity on optimal performance. The strength and approach velocity of the simulation model were each increased by up to 30% in 10% increments from baseline data collected from a national standard triple jumper. Increasing strength always resulted in an increased overall jump distance. Increasing approach velocity also typically resulted in an increased overall jump distance but there was a point past which increasing approach velocity without increasing strength did not lead to an increase in overall jump distance. Increasing both strength and approach velocity by 10%, 20%, and 30% led to roughly equivalent increases in overall jump distances. Distances ranged from 14.05m with baseline strength and approach velocity, up to 18.49m with 30% increases in both. Optimal phase ratios were either hop-dominated or balanced, and typically became more balanced when the strength of the model was increased by a greater percentage than its approach velocity. The range of triple jump distances that resulted from the optimisation process suggests that strength and approach velocity are of great importance for triple jump performance.

  6. Effects of mechanical horseback riding velocity on spinal alignment in young adults

    PubMed Central

    Lim, Jae-Heon; Cho, Woon-Su; Lee, Seong-Jin; Park, Chi-Bok; Park, Jang-Sung

    2016-01-01

    [Purpose] This study aimed to determine if the velocity of mechanical horseback-riding training can improve spinal alignment in young adults. [Subjects and Methods] Thirty-six subjects were enrolled in this study. The subjects were randomly allocated into high-, moderate-, and low-velocity mechanical horseback-riding training groups. All participants completed one 20-minute session per day, 3 days per week, for 6 weeks. The evaluation was performed before and 6 weeks after the training intervention. The spinal alignment was measured by a Formetric III device. The measurement items were kyphotic angle, lordotic angle, trunk inclination, pelvic torsion, pelvic rotation, and lateral deviation. The data were analyzed using analysis of covariance to determine the statistical significance. [Results] The kyphotic angle and trunk inclination were significantly different among the groups. The kyphotic angles of the high- and moderate-velocity groups were significantly lower than that of the low-velocity group after the intervention. The trunk inclination of the high-velocity group was significantly lower than that of the low-velocity group after intervention. [Conclusion] Higher-velocity mechanical horseback-riding training is more effective than lower-velocity mechanical horseback-riding training for improving spinal alignment. PMID:27390428

  7. Effects of uneven moisture distribution on the strength of and wave velocity in concrete.

    PubMed

    Popovics, Sandor

    2005-05-01

    Earlier findings showed that the effects of moisture (liquid or free water) in hardened concrete on its behavior, especially the lesser known effects ofuneven moisture distribution, can (a) be significant, and (b) vary from property to property. This distribution, for instance whether or not the surface layer is drier than the overall average moisture content, can be characterized by the difference between the velocity of the longitudinal wave (pulse velocity) measured in the standard through-thickness manner, and the velocity of the longitudinal wave propagating on the concrete surface. The summary of earlier findings on the effects of moisture distribution is followed by a recent investigation on pulse velocity in the special case, occurring frequently in practice, when the distribution is uneven because the liquid is concentrated in cracks in the concrete.

  8. Effects of friction massage of the popliteal fossa on blood flow velocity of the popliteal vein

    PubMed Central

    Iwamoto, Koji; Mizukami, Masafumi; Asakawa, Yasutsugu; Endo, Yusuke; Takata, Yuichi; Yoshikawa, Kenichi; Yoshio, Masaharu

    2017-01-01

    [Purpose] Friction massage (friction) of the popliteal fossa is provided for the purpose of relieving pain related to circulatory disorders by improving venous flow in the lower legs. The purpose of this study is to verify the effects of enhancing the venous flow based on measuring the blood flow velocity of the popliteal vein before and after providing friction to the patients. [Subjects and Methods] Fifteen healthy male university students participated in the study. The Doppler ultrasonography (DU) was used to measure the blood flow velocity of the popliteal vein, in order to verify the effects of enhancing the venous flow by comparing the measured values before and after a friction massage. [Results] The result of comparing the blood flow velocity before and after providing friction showed that there was a significant increase after friction. [Conclusion] This study proved that friction to the popliteal fossa is effectively enhances venous flow by increasing the blood flow velocity in the popliteal vein. PMID:28356643

  9. Effect of the relative velocity on the collision dipole in a pair of atoms

    SciTech Connect

    Humbert, J.; Galatry, L.

    1983-08-01

    It is shown that the dispersive collision induced dipole in a pair of atoms is dependent on the relative velocity of the partners. Two formulations taking into account this effect are successively presented. In the first one, the origin of the induced dipole lies in the energy coupling between the fluctuating instantaneous dipole of an atom and the reaction field due to the presence of the neighbor; the effect of the relative velocity is introduced through a Fourier expansion of the time dependent internuclear distance. The second method is based on the consideration of the secular equation for approximate instantaneous normal modes of the whole system. In the two cases, the vanishing velocity limit allows to find again a known result. For a nonzero relative velocity, a limited expansion is obtained and the two lowest order terms are given. Order of magnitude of the effects are estimated in a model of harmonic oscillators.

  10. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  11. The Air Toxics Health Effects Database (ATHED)

    SciTech Connect

    Woodall, George M. Smith, Roy L.

    2008-11-15

    The Air Toxics Health Effects Database (ATHED) is currently used by the EPA's Office of Air Quality Planning and Standards (OAQPS) to support risk assessments for the Residual Risk Program. An assessment of the residual risk is required to be performed at a specified time (typically 8years) following the promulgation of a technology-based Maximum Achievable Control Technologies (MACT) standard. The goal of the Residual Risk Program is to assure that the risk that remains after MACT standards are implemented (i.e., the 'residual risk') is acceptable, and if not, to propose additional regulations to mitigate those risks. ATHED maintains all available reference values for each chemical as separate data records, and includes values for all exposure durations (acute, short-term, subchronic and chronic). These values are used as benchmarks to determine acceptable exposure levels to the hazardous air pollutants (HAPs) listed in Section 112 of the Clean Air Act. ATHED also provides useful background information on the uncertainty and/or modifying factors that were applied in the derivation of each reference value, as well as the point of departure and the critical study/studies. To facilitate comparisons across durations for a specific chemical, ATHED data can be graphically presented.

  12. The Air Toxics Health Effects Database (ATHED).

    PubMed

    Woodall, George M; Smith, Roy L

    2008-11-15

    The Air Toxics Health Effects Database (ATHED) is currently used by the EPA's Office of Air Quality Planning and Standards (OAQPS) to support risk assessments for the Residual Risk Program. An assessment of the residual risk is required to be performed at a specified time (typically 8 years) following the promulgation of a technology-based Maximum Achievable Control Technologies (MACT) standard. The goal of the Residual Risk Program is to assure that the risk that remains after MACT standards are implemented (i.e., the "residual risk") is acceptable, and if not, to propose additional regulations to mitigate those risks. ATHED maintains all available reference values for each chemical as separate data records, and includes values for all exposure durations (acute, short-term, subchronic and chronic). These values are used as benchmarks to determine acceptable exposure levels to the hazardous air pollutants (HAPs) listed in Section 112 of the Clean Air Act. ATHED also provides useful background information on the uncertainty and/or modifying factors that were applied in the derivation of each reference value, as well as the point of departure and the critical study/studies. To facilitate comparisons across durations for a specific chemical, ATHED data can be graphically presented.

  13. Simultaneous determination of the ultrasound velocity and the thickness of solid plates from the analysis of thickness resonances using air-coupled ultrasound.

    PubMed

    Gómez Alvarez-Arenas, Tomás E

    2010-02-01

    A method that combines transmission of air-coupled ultrasound pulses through solid plates and amplitude and phase spectral analysis is presented. In particular, the method analyzes the first thickness resonance of the plates. The purpose is to determine, simultaneously, velocity and attenuation coefficient of the ultrasounds in the material and the thickness of the plate. This is especially useful when thickness can not be measured independently. The method is successfully applied to soft membranes, biological samples and FRP composites.

  14. Effect of Ambient Wind Velocity on the Shaping of Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Dwarkadas, V. V.; Chevalier, R. A.; Blondin, J.

    1995-05-01

    We have modelled planetary nebulae (PNe) using a 2-wind interacting-stellar-winds (ISW) model. If the two interacting winds have constant properties, the velocity of the PN shell tends towards a constant with time and the shape becomes self-similar. Additionally, if the velocity of the fast wind is much higher than the expansion velocity of the shell, the interior of the hot shocked bubble becomes isobaric. We have computed the shapes of PNe in the self-similar stage with both semi-analytic methods and numerical hydrodynamic simulations. An asymmetric density profile was assumed for the slow wind. We include the effects of the ambient wind velocity. Though the ambient velocity is often comparable to the expansion velocity of the PN, it has not received much attention since the work of Kahn & West (1985). The morphological appearance depends on the density contrast, steepness of the density profile with polar angle and velocity of the ambient medium; classification of PNe purely on the basis of the first two factors may be misleading. In particular the ambient wind velocity determines whether the PN will show a bulge or a cusp at the equator. Moderate values of the density contrast result in a cusp at the equator. Higher density contrast coupled with a low velocity for the external medium gives rise to extremely bipolar nebulae. For large density contrasts and a significant value of the slow wind velocity, the surface density maximicrons of the shell shifts away from the equator, giving rise to peanut-shaped structures with pronounced equatorial bulges. Our work shows that bipolar nebulae result when the expansion velocity of the PN is much larger than that of the external wind. An asymmetry in the external wind velocity can also lead to a bipolar shape if the equatorial velocity is sufficiently low. Our simulations indicate that all PNe may not reach the isobaric, self-similar shape. A ratio of interior sound speed to shell velocity ga 10 is found to yield nebulae

  15. Effect of old age on human skeletal muscle force-velocity and fatigue properties.

    PubMed

    Callahan, Damien M; Kent-Braun, Jane A

    2011-11-01

    It is generally accepted that the muscles of aged individuals contract with less force, have slower relaxation rates, and demonstrate a downward shift in their force-velocity relationship. The factors mediating age-related differences in skeletal muscle fatigue are less clear. The present study was designed to test the hypothesis that age-related shifts in the force-velocity relationship impact the fatigue response in a velocity-dependent manner. Three fatigue protocols, consisting of intermittent, maximum voluntary knee extension contractions performed for 4 min, were performed by 11 young (23.5 ± 0.9 yr, mean ± SE) and 10 older (68.9 ± 4.3) women. The older group fatigued less during isometric contractions than the young group (to 71.1 ± 3.7% initial torque and 59.8 ± 2.5%, respectively; P = 0.02), while the opposite was true during contractions performed at a relatively high angular velocity of 270°·s(-1) (old: 28.0 ± 3.9% initial power, young: 52.1 ± 6.9%; P < 0.01). Fatigue was not different (P = 0.74) between groups during contractions at an intermediate velocity, which was selected for each participant based on their force-velocity relationship. There was a significant association between force-velocity properties and fatigue induced by the intermediate-velocity fatigue protocol in the older (r = 0.72; P = 0.02) and young (r = 0.63; P = 0.04) groups. These results indicate that contractile velocity has a profound impact on age-related skeletal muscle fatigue resistance and suggest that changes in the force-velocity relationship partially mediate this effect.

  16. Acceleration bias in visually perceived velocity change and effects of Parkinson's bradykinesia.

    PubMed

    Beudel, Martijn; de Geus, Crista M; Leenders, Klaus L; de Jong, Bauke M

    2013-10-02

    In Parkinson's disease (PD), basal ganglia dysfunction leads to disturbed sensorimotor integration and associated timing. Previous functional MRI and behavioural PD studies on timing indicated a specific striatal contribution to assessing spatial displacement in velocity estimation. In this computation, cerebral processing time implies demarcating discrete intervals of spatial change. To quantify these putative intervals, the threshold of perceived velocity change of a moving ball was assessed in healthy volunteers and PD patients. After rebound from the upper side of a monitor screen, the ball's velocity increased or decreased with variable magnitudes while participants indicated whether they noticed this velocity change. The threshold for detecting velocity change was around 0.014 rad/s in both groups. Moreover, velocity was perceived as equal when the ball decelerated; unchanged velocity was perceived as acceleration. This shift was 0.009 rad/s for healthy volunteers and 0.007 rad/s for PD patients, and was negatively correlated with the severity of bradykinesia. As the trajectory length before and after velocity change was the same, velocity change was also expressed as a change in stimulus duration (relative to 1 s initial duration). The temporal equivalent of a threshold for perceived velocity change was around 75 ms in both groups. The perceptual 'acceleration bias' is in line with the 'flash-lag' effect: the position of a moving stimulus is projected ahead compared with a stationary landmark. Such an extrapolation over adjacent past and predicted locations enables 'real-time' visuomotor control, notwithstanding delays because of intrinsic cerebral processing time. In PD, such impaired perceptual feed-forward processing may result in slow movements.

  17. Effect of old age on human skeletal muscle force-velocity and fatigue properties

    PubMed Central

    Callahan, Damien M.

    2011-01-01

    It is generally accepted that the muscles of aged individuals contract with less force, have slower relaxation rates, and demonstrate a downward shift in their force-velocity relationship. The factors mediating age-related differences in skeletal muscle fatigue are less clear. The present study was designed to test the hypothesis that age-related shifts in the force-velocity relationship impact the fatigue response in a velocity-dependent manner. Three fatigue protocols, consisting of intermittent, maximum voluntary knee extension contractions performed for 4 min, were performed by 11 young (23.5 ± 0.9 yr, mean ± SE) and 10 older (68.9 ± 4.3) women. The older group fatigued less during isometric contractions than the young group (to 71.1 ± 3.7% initial torque and 59.8 ± 2.5%, respectively; P = 0.02), while the opposite was true during contractions performed at a relatively high angular velocity of 270°·s−1 (old: 28.0 ± 3.9% initial power, young: 52.1 ± 6.9%; P < 0.01). Fatigue was not different (P = 0.74) between groups during contractions at an intermediate velocity, which was selected for each participant based on their force-velocity relationship. There was a significant association between force-velocity properties and fatigue induced by the intermediate-velocity fatigue protocol in the older (r = 0.72; P = 0.02) and young (r = 0.63; P = 0.04) groups. These results indicate that contractile velocity has a profound impact on age-related skeletal muscle fatigue resistance and suggest that changes in the force-velocity relationship partially mediate this effect. PMID:21868683

  18. Effect of wind velocity on suction trap catches of some Florida mosquitoes.

    PubMed

    Bidlingmayer, W L; Day, J F; Evans, D G

    1995-09-01

    The correlations between wind velocity and suction trap catches of mosquitoes when taken at 15-min intervals during the night were studied at 2 locations. Although normal mosquito flight speeds are approximately 1 m/sec, trap catches were reduced about 50% by winds of 0.5 m/sec and 75% at 1.0 m/sec. Trap catches were inversely related to winds of all velocities and even the lightest winds reduced trap catches. No evidence was found for a threshold below which wind velocity had no effect.

  19. Effect of rotation and velocity shear on tearing layer stability in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    White, Ryan L.; Fitzpatrick, Richard

    2015-10-01

    Using a resistive generalization of the Frieman-Rotenberg formalism, the leading-order effects of velocity shear and rotation on linear tearing layer stability are studied for tokamak equilibria. The layer equations for resistive interchange modes are derived for arbitrary equilibrium rotation and velocity shear. The resulting layer equations do not conserve parity and are not simplified by Fourier transform. Thus, many standard numerical techniques cannot be implemented in a straightforward manner. Layer equations are also derived in the constant- Ψ limit. The constant- Ψ dispersion relation is obtained and is used to study the leading-order effects of rotation and velocity shear on the critical value of Δ' required for tearing instability. It is found that rotation and velocity shear can couple with the parallel current and the current gradient in the layer to reduce Δ'crit . If parallel currents are sufficiently weak to compete with second-order effects, velocity shear can be stabilizing, while rotation is found to have a destabilizing effect. Second-order coupling of velocity shear and rotation can have either sign, and thus can affect stability in either direction.

  20. Effect of eccentric contraction velocity on muscle damage in repeated bouts of elbow flexor exercise.

    PubMed

    Barroso, Renato; Roschel, Hamilton; Ugrinowitsch, Carlos; Araújo, Rubens; Nosaka, Kazunori; Tricoli, Valmor

    2010-08-01

    Eccentric exercise induces muscle damage, but controversy exists concerning the effect of contraction velocity on the magnitude of muscle damage, and little is known about the effect of contraction velocity on the repeated-bout effect. This study examined slow (60 degrees.s(-1)) and fast (180 degrees.s(-1)) velocity eccentric exercises for changes in indirect markers of muscle damage following 3 exercise bouts that were performed every 2 weeks. Fifteen young men were divided into 2 groups based on the velocity of eccentric exercise: 7 in the Ecc60 (60 degrees.s(-1)) group, and 8 in the Ecc180 (180 degrees.s(-1)) group. The exercise consisted of 30 maximal eccentric contractions of the elbow flexors at each velocity, in which the elbow joint was forcibly extended from 60 degrees to 180 degrees (full extension) on an isokinetic dynamometer. Changes in maximal voluntary isometric contraction strength, range of motion, muscle soreness, and plasma creatine kinase activity before and for 4 days after the exercise were compared in the 2 groups using a mixed-model analysis (groupxboutxtime). No significant differences between groups were evident for changes in any variables following exercise bouts; however, the changes were significantly smaller (p<0.05) after the second and third bouts than after the first bout. These results indicate that the contraction velocity does not influence muscle damage or the repeated-bout effect.

  1. Effect of mass-velocity on liquid jet atomization in Mach 1 gasflow

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1988-01-01

    Interacting two-phase flow in four differently sized pneumatic two-fluid atomizers was investigated to determine the effect of gas mass-velocity on the Sauter mean diameter of sprays produced by small diameter liquid jets breaking up in high velocity gas flow. Tests were conducted primarily in the acceleration-wave regime for liquid jet atomization, where it was found that the loss of droplets due to vaporization had a marked effect on drop size measurements. A scattered-light scanner, developed at NASA Lewis Research Center, was used to measure the Sauter mean diameter, D sub 32, which was correlated with nitrogen gas mass-velocity to give the following expression: D (sup -1)(sub 32) = 11.7(rho (sub n) V (sub n)) (sup 1.33). The exponent 1.33 for the gas mass-velocity is identical to that predicted by atomization theory for liquid jet breakup in the acceleration-wave regime.

  2. Effect of gravity on terminal particle settling velocity on Moon, Mars and Earth

    NASA Astrophysics Data System (ADS)

    Kuhn, Nikolaus J.

    2013-04-01

    Gravity has a non-linear effect on the settling velocity of sediment particles in liquids and gases due to the interdependence of settling velocity, drag and friction. However, StokeśLaw, the common way of estimating the terminal velocity of a particle moving in a gas of liquid assumes a linear relationship between terminal velocity and gravity. For terrestrial applications, this "error" is not relevant, but it may strongly influence the terminal velocity achieved by settling particles on Mars. False estimates of these settling velocities will, in turn, affect the interpretation of particle sizes observed in sedimentary rocks on Mars. Wrong interpretations may occur, for example, when the texture of sedimentary rocks is linked to the amount and hydraulics of runoff and thus ultimately the environmental conditions on Mars at the time of their formation. A good understanding of particle behaviour in liquids on Mars is therefore essential. In principle, the effect of lower gravity on settling velocity can also be achieved by reducing the difference in density between particle and gas or liquid. However, the use of such analogues simulating the lower gravity on Mars on Earth is creates other problems because the properties (i.e. viscosity) and interaction of the liquids and sediment (i.e. flow around the boundary layer between liquid and particle) differ from those of water and mineral particles. An alternative for measuring the actual settling velocities of particles under Martian gravity, on Earth, is offered by placing a settling tube on a reduced gravity flight and conduct settling tests within the 20 to 25 seconds of Martian gravity that can be simulated during such a flight. In this presentation we report the results of such a test conducted during a reduced gravity flight in November 2012. The results explore the strength of the non-linearity in the gravity-settling velocity relationship for terrestrial, lunar and Martian gravity.

  3. Wildland fire in ecosystems: effects of fire on air

    Treesearch

    David V. Sandberg; Roger D. Ottmar; Janice L. Peterson

    2002-01-01

    This state-of-knowledge review about the effects of fire on air quality can assist land, fire, and air resource managers with fire and smoke planning, and their efforts to explain to others the science behind fire-related program policies and practices to improve air quality. Chapter topics include air quality regulations and fire; characterization of emissions from...

  4. Velocity Averaging, Kinetic Formulations and Regularizing Effects in Quasilinear PDEs

    DTIC Science & Technology

    2005-10-31

    nonlinear conservation laws. In [LPT94a], Lions, Perthame & Tadmor have shown that entropy solutions of such laws admit a regularizing effect of a fractional...one augments (1.1) with additional conditions on the behavior of Φ(ρ) for a large enough family of entropies Φ’s. These additional entropy conditions...imply that g is in fact a positive distribution, g = m ∈ M+, measuring the entropy dissipation of the nonlinear equation. We arrive at the kinetic

  5. Coupled Effects of Pore Space Geometry, Velocity, and Solution Chemistry on Colloid Retention in Porous Media

    NASA Astrophysics Data System (ADS)

    Bradford, S. A.; Torkzaban, S.; Leij, F.; Toride, N.; Simunek, J.; van Genuchten, M.

    2008-05-01

    Colloid transport in porous media has traditionally been assumed to be controlled by chemical interactions between the colloids and the solid-water and air-water interfaces. The influence of pore space geometry, interface configuration, and system hydrodynamics in classical colloid retention models has largely been neglected. Recent experimental and theoretical work, however, has demonstrated that these factors can also play important roles in colloid retention under unfavorable attachment conditions. In particular, hydrodynamic forces can funnel weakly associated colloids to grain-grain contacts and air-water-solid triple points, as well as to hydrodynamically isolated low velocity (eddy) regions. The extent to which colloid mass transfer and retention will occur to/in these locations is a function of the balance of adhesive, diffusion, and hydrodynamic forces. One consequence of enhanced colloid retention in low velocity regions is that the colloid retention profile may not be exponential with depth. Pore- and column-scale experimental evidence that support this conceptual model for colloid retention is summarized. Furthermore, colloid transport models that account for enhanced colloid retention in low velocity regions are demonstrated and discussed.

  6. Effects of particle size and velocity on burial depth of airborne particles in glass fiber filters

    SciTech Connect

    Higby, D.P.

    1984-11-01

    Air sampling for particulate radioactive material involves collecting airborne particles on a filter and then determining the amount of radioactivity collected per unit volume of air drawn through the filter. The amount of radioactivity collected is frequently determined by directly measuring the radiation emitted from the particles collected on the filter. Counting losses caused by the particle becoming buried in the filter matrix may cause concentrations of airborne particulate radioactive materials to be underestimated by as much as 50%. Furthermore, the dose calculation for inhaled radionuclides will also be affected. The present study was designed to evaluate the extent to which particle size and sampling velocity influence burial depth in glass-fiber filters. Aerosols of high-fired /sup 239/PuO/sub 2/ were collected at various sampling velocities on glass-fiber filters. The fraction of alpha counts lost due to burial was determined as the ratio of activity detected by direct alpha count to the quantity determined by photon spectrometry. The results show that burial of airborne particles collected on glass-fiber filters appears to be a weak function of sampling velocity and particle size. Counting losses ranged from 0 to 25%. A correction that assumes losses of 10 to 15% would ensure that the concentration of airborne alpha-emitting radionuclides would not be underestimated when glass-fiber filters are used. 32 references, 21 figures, 11 tables.

  7. Analysis of of Injection-Velocity Effects on Rocket Motor Dynamics and Stability

    NASA Technical Reports Server (NTRS)

    Hurrell, Herbert G.

    1959-01-01

    A concept of combustion time lag that includes dependency on injection velocity is introduced. The concept is used in the formulation of chamber transfer functions and in an analysis of low-frequency combustion instability. Theoretical frequency responses and stability boundaries are compared with those obtained when the injection-velocity effect on the time lag to be an important consideration, in the theory of chamber dynamics and combustion instability

  8. Effect of stone content on water flow velocity over Loess slope: non-frozen soil

    NASA Astrophysics Data System (ADS)

    Ban, Yunyun; Lei, Tingwu; Gao, Yuan; Qu, Liqin

    2017-06-01

    Stony soils are commonly found worldwide and are considerably studied for their hydrological characteristics and effect on soil erosion. Water flow velocity is an important parameter in understanding the effect of stone content on hydrodynamics and soil erosion. In this study, laboratory experiments were used to measure rill flow velocity by using electrolyte tracer method under different hydraulic conditions: flow rates of 1, 2, 4, and 8 L/min, slope gradients of 5°, 10°, 15°, and 20°, and stone mass contents amounting to 0%, 10%, 20% and 50%. Nine sensors, which were 1 m apart along the 8 m long rill, were used to measure flow velocity by tracing solute transport. Measured flow velocity increased with slope gradient and flow rate. The highest increase in flow velocity was measured from 15° to 20° which were also affected by flow rate. Effects of discharge rate on flow velocity presented the largest difference when flow rate increased from 2 L/min to 8 L/min at slope gradients higher than 5°. The effects of different factors were quantified by a regression model with high accuracy of 0.99. Maximum flow velocity of water was predicted at 15.23% of stone content. Flow velocity increased with 0-15.23% of stone content but decreased at higher values. This study aims at further understanding the hydrodynamics of soil erosion and sediment transport behaviors in hillslopes with different stone contents to obtain information for quantifying soil erosion on stony slopes.

  9. Effect of extracellular potassium accumulation on muscle fiber conduction velocity: a simulation study.

    PubMed

    Fortune, Emma; Lowery, Madeleine M

    2009-10-01

    A progressive reduction in muscle fiber conduction velocity is typically observed during fatiguing muscle contraction. Although the exact causes of the conduction velocity decrease have not yet been fully established, increasing evidence suggests that changes in extracellular potassium concentration may be largely responsible. In this study, a mathematical model was developed to examine the effect of extracellular potassium concentration on the muscle fiber action potential and conduction velocity. The model was used to simulate changes in extracellular potassium concentration at a range of temperatures and extracellular potassium accumulation during repetitive stimulation of the muscle fiber at 37 degrees C. The action potential broadened, and its amplitude and conduction velocity decreased as extracellular potassium concentration increased. The potassium-induced changes in action potential shape and conduction velocity were eliminated when the inward rectifier channels were removed from the model. The results support the hypothesis that accumulation of extracellular potassium ions may be a major contributor to the reduction in muscle fiber conduction velocity and loss of membrane excitability during fatiguing contractions. They additionally suggest that inward rectifier currents play a critical role in potassium-induced membrane depolarization, leading to increased sodium inactivation and resulting in the observed reduction in conduction velocity and membrane excitability.

  10. Effect of velocity ratio on plane mixing layer development - Influence of the splitter plate wake

    NASA Technical Reports Server (NTRS)

    Mehta, R. D.

    1991-01-01

    The effect of the velocity ratio on the approach of a plane mixing layer to self-similarity was investigated experimentally. In the experiment, plane mixing layers with velocity ratios 0.5, 0.6, 0.7, 0.8, and 0.9 were generated in a mixing-layer wind tunnel consisting of two individually driven legs, in which the two streams were allowed to merge at the sharp edge of a tappered splitter plate. The leg driven by the bigger blower was operated at a free-stream velocity in the test section of 21 m/s, while the flow speed in the other leg was varied to change the velocity ratio. For each velocity ratio, the mean flow- and turbulence measurements were carried out at eight streamwise locations. Results showed that, for velocity ratios between 0.5 and 0.7, self-similarity of the mixing layer was achieved, with the asymptotic states comparable; mixing layers with higher velocity ratios failed to achieve a self-similar state within the measurement domain.

  11. Effect of pore velocity on biodegradation of cis-dichloroethene (DCE) in column experiments.

    PubMed

    Mendoza-Sanchez, Itza; Autenrieth, Robin L; McDonald, Thomas J; Cunningham, Jeffrey A

    2010-06-01

    Column experiments were conducted to evaluate the effect of pore velocity on the extent of biodegradation of cis-dichloroethene (cis-DCE) during transport in porous media. Columns were filled with homogeneous glass beads and inoculated with a culture capable of complete dechlorination of tetrachloroethene to ethene. A constant concentration of cis-DCE was maintained in the columns' influent. Three different pore velocities were tested in duplicate, subjecting each column to a constant velocity. At high flow velocity, degradation of cis-DCE to ethene was nearly complete within the residence time of the columns. However, at medium and low flow velocities, incomplete dechlorination was observed. After 7 weeks, DNA was harvested from the columns to determine differences in the microbial populations. Results suggest that Dehalococcoides sp. were present in higher quantities in the high-velocity columns, consistent with the observed dechlorination. These results suggest that, at contaminated groundwater sites, heterogeneity of groundwater velocity may be one factor that contributes to heterogeneous distribution of biological activity.

  12. Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields

    DOEpatents

    Chaffin, R.J.; Dawson, L.R.; Fritz, I.J.; Osbourn, G.C.; Zipperian, T.E.

    1984-04-19

    In a field-effect transistor comprising a semiconductor having therein a source, a drain, a channel and a gate in operational relationship, there is provided an improvement wherein said semiconductor is a superlattice comprising alternating quantum well and barrier layers, the quantum well layers comprising a first direct gap semiconductor material which in bulk form has a certain bandgap and a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, the barrier layers comprising a second semiconductor material having a bandgap wider than that of said first semiconductor material, wherein the layer thicknesses of said quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice having a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, and wherein the thicknesses of said quantum well layers are selected to provide a superlattice curve of electron velocity versus applied electric field whereby, at applied electric fields higher than that at which the maximum electron velocity occurs in said first material when in bulk form, the electron velocities are higher in said superlattice than they are in said first semiconductor material in bulk form.

  13. Water velocity at water-air interface is not zero: Comment on "Three-dimensional quantification of soil hydraulic properties using X-ray computed tomography and image-based modeling" by Saoirse R. Tracy et al.

    NASA Astrophysics Data System (ADS)

    Zhang, X. X.; Fan, X. Y.; Li, Z. Y.

    2016-07-01

    Tracy et al. (2015, doi: 10.1002/2014WR016020) assumed in their recent paper that water velocity at the water-air interface is zero in their pore-scale simulations of water flow in 3-D soil images acquired using X-ray computed tomography. We comment that such a treatment is physically wrong, and explain that it is the water-velocity gradient in the direction normal to the water-air interface, rather than the water velocity, that should be assumed to be zero at the water-air interface if one needs to decouple the water flow and the air flow. We analyze the potential errors caused by incorrectly taking water velocity at the water-air interface zero based on two simple examples, and conclude that it is not physically sound to make such a presumption because its associated errors are unpredictable.

  14. Relativistic effects of light in moving media with extremely low group velocity

    PubMed

    Leonhardt; Piwnicki

    2000-01-31

    A moving dielectric medium acts as an effective gravitational field on light. One can use media with extremely low group velocities [Lene Vestergaard Hau et al., Nature (London) 397, 594 (1999)] to create dielectric analogs of astronomical effects on Earth. In particular, a vortex flow imprints a long-ranging topological effect on incident light and can behave like an optical black hole.

  15. Investigations of the air flow velocity field structure above the wavy surface under severe wind conditions by particle image velosimetry technique.

    NASA Astrophysics Data System (ADS)

    Troitskaya, Yuliya; Kandaurov, Alexander; Sergeev, Daniil; Ermakova, Olga

    2013-04-01

    Preliminary experiments devoted to measuring characteristics of the air flow above the waved water surface for the wide range of wind speeds were performed with the application of modified Particle Image Velosimetry (PIV) technique. Experiments were carried out at the Wind - wave stratified flume of IAP RAS (length 10 °, cross section of air channel 0.4×0.4 m) for four different axial wind speeds: 8.7, 13.5, 19 and 24 m/s, corresponding to the equivalent 10-m wind speeds 15, 20, 30 40 m/s correspondingly. Intensive wave breaking with forming foam crest and droplets generations was occurred for two last wind conditions. The modified PIV-method based on the use of continuous-wave (CW) laser illumination of the airflow seeded by tiny particles and with highspeed video. Spherical 20 μm polyamide particles with density 1.02 g/sm3 and inertial time 7•10-3 s were used for seeding airflow with special injecting device. Green (532 nm) CW laser with 4 Wt output power was used as a source for light sheet. High speed digital camera Videosprint was used for taking visualized air flow images with the frame rate 2000 Hz s and exposure time 10 ms Combination including iteration Canny method [1] for obtaining curvilinear surface from the images in the laser sheet view and contact measurements of surface elevation by wire wave gauge installed near the border of working area for the surface wave profile was used. Then velocity air flow field was retrieved by PIV images processing with adaptive cross-correlation method on the curvilinear grid following surface wave profile. The mean wind velocity profiles were retrieved by averaging over obtained ensembles of wind velocity field realizations and over a wave period even for the cases of intensive wave breaking and droplets generation. To verify the PIV method additional measurements of mean velocity profiles over were carried out by the contact method using the Pitot tube. In the area of overlap, wind velocity profiles measured by

  16. High-Velocity Estimates for the Scattering Operator and Aharonov-Bohm Effect in Three Dimensions

    NASA Astrophysics Data System (ADS)

    Ballesteros, Miguel; Weder, Ricardo

    2009-01-01

    We obtain high-velocity estimates with error bounds for the scattering operator of the Schrödinger equation in three dimensions with electromagnetic potentials in the exterior of bounded obstacles that are handlebodies. A particular case is a finite number of tori. We prove our results with time-dependent methods. We consider high-velocity estimates where the direction of the velocity of the incoming electrons is kept fixed as its absolute value goes to infinity. In the case of one torus our results give a rigorous proof that quantum mechanics predicts the interference patterns observed in the fundamental experiments of Tonomura et al. that gave conclusive evidence of the existence of the Aharonov-Bohm effect using a toroidal magnet. We give a method for the reconstruction of the flux of the magnetic field over a cross-section of the torus modulo 2π. Equivalently, we determine modulo 2π the difference in phase for two electrons that travel to infinity, when one goes inside the hole and the other outside it. For this purpose we only need the high-velocity limit of the scattering operator for one direction of the velocity of the incoming electrons. When there are several tori-or more generally handlebodies-the information that we obtain in the fluxes, and on the difference of phases, depends on the relative position of the tori and on the direction of the velocities when we take the high-velocity limit of the incoming electrons. For some locations of the tori we can determine all the fluxes modulo 2π by taking the high-velocity limit in only one direction. We also give a method for the unique reconstruction of the electric potential and the magnetic field outside the handlebodies from the high-velocity limit of the scattering operator.

  17. Effect of disjoining pressure on terminal velocity of a bubble sliding along an inclined wall.

    PubMed

    Del Castillo, Lorena A; Ohnishi, Satomi; White, Lee R; Carnie, Steven L; Horn, Roger G

    2011-12-15

    The influence of salt concentration on the terminal velocities of gravity-driven single bubbles sliding along an inclined glass wall has been investigated, in an effort to establish whether surface forces acting between the wall and the bubble influence the latter's mobility. A simple sliding bubble apparatus was employed to measure the terminal velocities of air bubbles with radii ranging from 0.3 to 1.5 mm sliding along the interior wall of an inclined Pyrex glass cylinder with inclination angles between 0.6 and 40.1°. Experiments were performed in pure water, 10 mM and 100 mM KCl solutions. We compared our experimental results with a theory by Hodges et al. which considers hydrodynamic forces only, and with a theory developed by two of us which considers surface forces to play a significant role. Our experimental results demonstrate that the terminal velocity of the bubble not only varies with the angle of inclination and the bubble size but also with the salt concentration, particularly at low inclination angles of ∼1-5°, indicating that double-layer forces between the bubble and the wall influence the sliding behavior. This is the first demonstration that terminal velocities of sliding bubbles are affected by disjoining pressure. Copyright © 2011 Elsevier Inc. All rights reserved.

  18. Effect of disjoining pressure on terminal velocity of a bubble sliding along an inclined wall

    PubMed Central

    Del Castillo, Lorena A.; Ohnishi, Satomi; White, Lee R.; Carnie, Steven L.; Horn, Roger G.

    2011-01-01

    The influence of salt concentration on the terminal velocities of gravity-driven single bubbles sliding along an inclined glass wall has been investigated, in an effort to establish whether surface forces acting between the wall and the bubble influence the latter’s mobility. A simple sliding bubble apparatus was employed to measure the terminal velocities of air bubbles with radii ranging from 0.3 to 1.5 mm sliding along the interior wall of an inclined Pyrex glass cylinder with inclination angles between 0.6 and 40.1°. Experiments were performed in pure water, 10 mM and 100 mM KCl solutions. We compared our experimental results with a theory by Hodges et al. [1] which considers hydrodynamic forces only, and with a theory developed by two of us [2] which considers surface forces to play a significant role. Our experimental results demonstrate that the terminal velocity of the bubble not only varies with the angle of inclination and the bubble size but also with the salt concentration, particularly at low inclination angles of ∼1–5°, indicating that double-layer forces between the bubble and the wall influence the sliding behavior. This is the first demonstration that terminal velocities of sliding bubbles are affected by disjoining pressure. PMID:21924429

  19. Effects of moderate-velocity strength training on peak muscle power and movement velocity: do women respond differently than men?

    PubMed

    Delmonico, Matthew J; Kostek, Matthew C; Doldo, Neil A; Hand, Brian D; Bailey, Jason A; Rabon-Stith, Karma M; Conway, Joan M; Carignan, Craig R; Lang, Jesse; Hurley, Ben F

    2005-11-01

    The effects of a 10-wk unilateral knee extension strength training (ST) program on peak power (PP) and peak movement velocity (PV), at given absolute (force load) and relative (same % of 1 repetition maximum) resistances (loads), were examined in 30 older men [64 yr (7 SD)] and 32 older women [62 yr (6 SD)]. PP increased significantly in both men and women at the same absolute (P < 0.001) and relative loads (P < 0.01) with ST. Men had a significantly greater increase in relative PP than women with ST at 60% (P < 0.01) and 70% (P < 0.001) of 1 repetition maximum when covarying for baseline differences and age. However, when each subject was tested at the same absolute load and when PP was normalized for the muscle volume of the trained knee extensors (i.e., absolute muscle power quality), women increased by 9% (P < 0.05), whereas men did not change. Both men and women increased their absolute PV (P < 0.001) but decreased their relative PV significantly with ST (P < 0.05). However, when baseline values and age were covaried, women had significantly less of a decrease in relative PV quality with ST than men (P < 0.01), although the difference was small. These normalized data suggest that ST-induced increases in PP depend on muscular hypertrophy in men, but not in women, providing further support for the hypothesis developed from our previous report (Ivey FM, Tracy BL, Lemmer JT, NessAiver M, Metter EJ, Fozard JL and Hurley BF. J Gerontol A Biol Sci Med Sci 55: B152-B157, 2000) that improvements in muscle function with ST result from nonmuscle mass adaptations to a greater extent in women than men.

  20. Effect of Wind Velocity on Flame Spread in Microgravity

    NASA Technical Reports Server (NTRS)

    Prasad, Kuldeep; Olson, Sandra L.; Nakamura, Yuji; Fujita, Osamu; Nishizawa, Katsuhiro; Ito, Kenichi; Kashiwagi, Takashi; Simons, Stephen N. (Technical Monitor)

    2002-01-01

    A three-dimensional, time-dependent model is developed describing ignition and subsequent transition to flame spread over a thermally thin cellulosic sheet heated by external radiation in a microgravity environment. A low Mach number approximation to the Navier Stokes equations with global reaction rate equations describing combustion in the gas phase and the condensed phase is numerically solved. The effects of a slow external wind (1-20 cm/s) on flame transition are studied in an atmosphere of 35% oxygen concentration. The ignition is initiated at the center part of the sample by generating a line-shape flame along the width of the sample. The calculated results are compared with data obtained in the 10s drop tower. Numerical results exhibit flame quenching at a wind speed of 1.0 cm/s, two localized flames propagating upstream along the sample edges at 1.5 cm/s, a single line-shape flame front at 5.0 cm/s, three flames structure observed at 10.0 cm/s (consisting of a single line-shape flame propagating upstream and two localized flames propagating downstream along sample edges) and followed by two line-shape flames (one propagating upstream and another propagating downstream) at 20.0 cm/s. These observations qualitatively compare with experimental data. Three-dimensional visualization of the observed flame complex, fuel concentration contours, oxygen and reaction rate isosurfaces, convective and diffusive mass flux are used to obtain a detailed understanding of the controlling mechanism, Physical arguments based on lateral diffusive flux of oxygen, fuel depletion, oxygen shadow of the flame and heat release rate are constructed to explain the various observed flame shapes.

  1. Lane-changing behavior and its effect on energy dissipation using full velocity difference model

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Ding, Jian-Xun; Shi, Qin; Kühne, Reinhart D.

    2016-07-01

    In real urban traffic, roadways are usually multilane with lane-specific velocity limits. Most previous researches are derived from single-lane car-following theory which in the past years has been extensively investigated and applied. In this paper, we extend the continuous single-lane car-following model (full velocity difference model) to simulate the three-lane-changing behavior on an urban roadway which consists of three lanes. To meet incentive and security requirements, a comprehensive lane-changing rule set is constructed, taking safety distance and velocity difference into consideration and setting lane-specific speed restriction for each lane. We also investigate the effect of lane-changing behavior on distribution of cars, velocity, headway, fundamental diagram of traffic and energy dissipation. Simulation results have demonstrated asymmetric lane-changing “attraction” on changeable lane-specific speed-limited roadway, which leads to dramatically increasing energy dissipation.

  2. Effect of sliding velocity on the tribological behavior of copper and associated nanostructure development

    NASA Astrophysics Data System (ADS)

    Emge, Andrew

    The unlubricated sliding of metals is important in many mechanical devices covering a wide range of sliding velocities. However, the effect of sliding velocity on the tribological behavior of unlubricated metals has not been widely studied. Similarly, the relationship between microstructures developed at high sliding velocities and tribological behavior has not been studied in depth. Microstructures produced at low sliding velocities have been studied extensively and commonly include nanocrystalline or fine grained material near the sliding surface with heavily deformed microstructures further from the surface. The current research relates two aspects of the sliding friction of ductile metals, the effect of sliding velocity and the production of nanocrystalline tribomaterial. The project focused on the effects of sliding velocity on the frictional behavior of oxygen free high conductivity (OFHC) copper sliding against 440C stainless steel, Nitronic 40 stainless steel, and copper. Low velocity tests were performed with a pin on disk tribometer. High velocity tests were performed with a rotating barrel gas gun (RBGG) which combined impact with sliding. The RBGG provides sliding velocities as high as 5.5 m/s and impact velocities as high as 12 m/s while maintaining sliding times on the order of tens of microseconds. Changes in the coefficient of friction, microstructure, and composition were studied. Surface and subsurface microstructures of the worn samples were characterized with a range of instruments including scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), focused ion beam (FIB) milling and imaging, transmission electron microscopy (TEM) with EDS, orientation imaging microscopy (OIM), and nanoindentation. In the case of self-mated copper the sliding velocity had little effect on the coefficient of friction for both experimental apparatuses. For the case of copper sliding against 440C stainless steel on the pin on disk system

  3. Effects of non-uniform velocity profiles on dual jets in a crossflow

    NASA Technical Reports Server (NTRS)

    Moore, C. L.; Schetz, J. A.

    1985-01-01

    The interaction between engine exhaust jets and the freestream affects the aerodynamic and stability characteristics of VTOL aircraft during the transition from hover to forward flight. This interaction is often modeled as a simple uniform jet issuing from a flat plate into a subsonic crossflow. The distribution of pressures induced by the jet on the surface of the plate can be used to predict the lift loss and pitching moment for a full-scale aircraft. The uniform jet model has limitations because an actual turbofan engine generates a rather nonuniform exit velocity profile. The purpose of this work is to study the effect of a nonuniform velocity profile on the surface pressure distribution. The mutual interaction of dual jets also is investigated in side-by-side and tandem configurations. Detailed pressure distributions are presented for two jet-to-freestream velocity ratios of 2.2 and 4.0. One important finding is that a nonuniform jet with a high velocity periphery and a low velocity core has a higher effective velocity ratio than a uniform jet with the same mass flow.

  4. Effect of climate change on air quality

    NASA Astrophysics Data System (ADS)

    Jacob, Daniel J.; Winner, Darrell A.

    Air quality is strongly dependent on weather and is therefore sensitive to climate change. Recent studies have provided estimates of this climate effect through correlations of air quality with meteorological variables, perturbation analyses in chemical transport models (CTMs), and CTM simulations driven by general circulation model (GCM) simulations of 21st-century climate change. We review these different approaches and their results. The future climate is expected to be more stagnant, due to a weaker global circulation and a decreasing frequency of mid-latitude cyclones. The observed correlation between surface ozone and temperature in polluted regions points to a detrimental effect of warming. Coupled GCM-CTM studies find that climate change alone will increase summertime surface ozone in polluted regions by 1-10 ppb over the coming decades, with the largest effects in urban areas and during pollution episodes. This climate penalty means that stronger emission controls will be needed to meet a given air quality standard. Higher water vapor in the future climate is expected to decrease the ozone background, so that pollution and background ozone have opposite sensitivities to climate change. The effect of climate change on particulate matter (PM) is more complicated and uncertain than for ozone. Precipitation frequency and mixing depth are important driving factors but projections for these variables are often unreliable. GCM-CTM studies find that climate change will affect PM concentrations in polluted environments by ±0.1-1 μg m -3 over the coming decades. Wildfires fueled by climate change could become an increasingly important PM source. Major issues that should be addressed in future research include the ability of GCMs to simulate regional air pollution meteorology and its sensitivity to climate change, the response of natural emissions to climate change, and the atmospheric chemistry of isoprene. Research needs to be undertaken on the effect of climate

  5. Effect of Periodic Surface Air Temperature Variations on Subsurface Thermal Structure with Vertical Fluid flow

    NASA Astrophysics Data System (ADS)

    D, R. V.; Ravi, M.; Srivastava, K.

    2016-12-01

    The influence of climate change on near subsurface temperatures is an important research topic for global change impact assessment at the regional scale. The varying temperature of the air over the surface in long term will disturb subsurface thermal structure. Groundwater flow is another important process which perturbs the thermal distribution into the subsurface. To investigate the effect of periodic air temperature on nonisothermal subsurface, one dimensional transient heat conduction-advection equation is solved numerically using finite element method. Thermal response of subsurface for periodic variations in surface air temperature (SAT) with robin type boundary condition on the surface with vertical ground water flow are calculated and the amplitude attenuation of propagation of surface temperature information in the subsurface for different scenarios of advection and convective coefficient are discussed briefly. The results show the coupled response of trigonometric variation in air temperature with surface temperatures along with ground water velocity has significant implications for the effects of climate change.

  6. Dark matter velocity dispersion effects on CMB and matter power spectra

    SciTech Connect

    Piattella, O.F.; Casarini, L.; Fabris, J.C.; Pacheco, J.A. de Freitas E-mail: luciano.casarini@cosmo-ufes.org E-mail: pacheco@oca.eu

    2016-02-01

    Effects of velocity dispersion of dark matter particles on the CMB TT power spectrum and on the matter linear power spectrum are investigated using a modified CAMB code. Cold dark matter originated from thermal equilibrium processes does not produce appreciable effects but this is not the case if particles have a non-thermal origin. A cut-off in the matter power spectrum at small scales, similar to that produced by warm dark matter or that produced in the late forming dark matter scenario, appears as a consequence of velocity dispersion effects, which act as a pressure perturbation.

  7. Effects of Air Drag and Lunar Third-Body Perturbations on Motion Near a Reference KAM Torus

    DTIC Science & Technology

    2011-03-01

    Effects of Air Drag and Lunar Third-Body Pertubrations on Orbital Motion Near a Reference KAM Torus THESIS Luke J. Hagen, Captain, USAF AFIT/GA/ENY...to copyright protection in the United States. AFIT/GA/ENY/11-M06 Effects of Air Drag and Lunar Third-Body Pertubrations on Orbital Motion Near a...Earth orbiting satellites. Physical state variables of position and velocity are transformed into KAM Torus variables. The KAM Torus is a geometrical

  8. A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running.

    PubMed

    Samozino, P; Rabita, G; Dorel, S; Slawinski, J; Peyrot, N; Saez de Villarreal, E; Morin, J-B

    2016-06-01

    This study aimed to validate a simple field method for determining force- and power-velocity relationships and mechanical effectiveness of force application during sprint running. The proposed method, based on an inverse dynamic approach applied to the body center of mass, estimates the step-averaged ground reaction forces in runner's sagittal plane of motion during overground sprint acceleration from only anthropometric and spatiotemporal data. Force- and power-velocity relationships, the associated variables, and mechanical effectiveness were determined (a) on nine sprinters using both the proposed method and force plate measurements and (b) on six other sprinters using the proposed method during several consecutive trials to assess the inter-trial reliability. The low bias (<5%) and narrow limits of agreement between both methods for maximal horizontal force (638 ± 84 N), velocity (10.5 ± 0.74 m/s), and power output (1680 ± 280 W); for the slope of the force-velocity relationships; and for the mechanical effectiveness of force application showed high concurrent validity of the proposed method. The low standard errors of measurements between trials (<5%) highlighted the high reliability of the method. These findings support the validity of the proposed simple method, convenient for field use, to determine power, force, velocity properties, and mechanical effectiveness in sprint running.

  9. Effects of Velocity Loss During Resistance Training on Performance in Professional Soccer Players.

    PubMed

    Pareja-Blanco, Fernando; Sánchez-Medina, Luis; Suárez-Arrones, Luis; González-Badillo, Juan José

    2017-04-01

    To analyze the effects of 2 resistance-training (RT) programs that used the same relative loading but different repetition volume, using the velocity loss during the set as the independent variable: 15% (VL15) vs 30% (VL30). Sixteen professional soccer players with RT experience (age 23.8 ± 3.5 y, body mass 75.5 ± 8.6 kg) were randomly assigned to 2 groups, VL15 (n = 8) or VL30 (n = 8), that followed a 6-wk (18-session) velocity-based squat-training program. Repetition velocity was monitored in all sessions. Assessments performed before (Pre) and after training (Post) included estimated 1-repetition maximum (1RM) and change in average mean propulsive velocity (AMPV) against absolute loads common to Pre and Post tests, countermovement jump (CMJ), 30-m sprint (T30), and Yo-Yo Intermittent Recovery Test (YIRT). Null-hypothesis significance testing and magnitude-based-inference statistical analyses were performed. VL15 obtained greater gains in CMJ height than VL30 (P < .05), with no significant differences between groups for the remaining variables. VL15 showed a likely/possibly positive effect on 1RM (91/9/0%), AMPV (73/25/2%), and CMJ (87/12/1%), whereas VL30 showed possibly/unclear positive effects on 1RM (65/33/2%) and AMPV (46/36/18%) and possibly negative effects on CMJ (4/38/57%). The effects on T30 performance were unclear/unlikely for both groups, whereas both groups showed most likely/likely positive effects on YIRT. A velocity-based RT program characterized by a low degree of fatigue (15% velocity loss in each set) is effective to induce improvements in neuromuscular performance in professional soccer players with previous RT experience.

  10. The effect of gradational velocities and anisotropy on fault-zone trapped waves

    NASA Astrophysics Data System (ADS)

    Gulley, A. K.; Eccles, J. D.; Kaipio, J. P.; Malin, P. E.

    2017-08-01

    Synthetic fault-zone trapped wave (FZTW) dispersion curves and amplitude responses for FL (Love) and FR (Rayleigh) type phases are analysed in transversely isotropic 1-D elastic models. We explore the effects of velocity gradients, anisotropy, source location and mechanism. These experiments suggest: (i) A smooth exponentially decaying velocity model produces a significantly different dispersion curve to that of a three-layer model, with the main difference being that Airy phases are not produced. (ii) The FZTW dispersion and amplitude information of a waveguide with transverse-isotropy depends mostly on the Shear wave velocities in the direction parallel with the fault, particularly if the fault zone to country-rock velocity contrast is small. In this low velocity contrast situation, fully isotropic approximations to a transversely isotropic velocity model can be made. (iii) Fault-aligned fractures and/or bedding in the fault zone that cause transverse-isotropy enhance the amplitude and wave-train length of the FR type FZTW. (iv) Moving the source and/or receiver away from the fault zone removes the higher frequencies first, similar to attenuation. (v) In most physically realistic cases, the radial component of the FR type FZTW is significantly smaller in amplitude than the transverse.

  11. Effect of elastic stockings and ankle positions on the blood velocity in the common femoral vein.

    PubMed

    Toya, Kaori; Takahashi, Tetsuya; Fujimoto, Yuta; Nishimoto, Teppei; Takasoh, Tomomi; Sasano, Ken; Kusaka, Satomi

    2016-09-01

    [Purpose] The aim of this study was to identify how to effectively use elastic stockings. [Subjects and Methods] Ten young healthy men participated in this study. Time-averaged maximum flow velocity in the common femoral vein was measured for 20 seconds using a pulse Doppler method with a diagnostic ultrasound system under six conditions (three different positions and with and without stockings). Changes of blood flow velocity were compared. [Results] Elastic stockings did not affect the blood flow velocity in the common femoral vein. For both the with stockings condition and without stockings condition, the time-averaged maximum flow velocity in the head-up position was significantly lower than that in the supine and leg-up positions. Time-averaged maximum flow velocity showed no significant difference between the supine position and leg-up position. [Conclusion] Elastic stockings did not affect the blood flow velocity in the common femoral vein, but ankle positions did affect it. Further studies of patients with venous insufficiency are needed.

  12. Effect of elastic stockings and ankle positions on the blood velocity in the common femoral vein

    PubMed Central

    Toya, Kaori; Takahashi, Tetsuya; Fujimoto, Yuta; Nishimoto, Teppei; Takasoh, Tomomi; Sasano, Ken; Kusaka, Satomi

    2016-01-01

    [Purpose] The aim of this study was to identify how to effectively use elastic stockings. [Subjects and Methods] Ten young healthy men participated in this study. Time-averaged maximum flow velocity in the common femoral vein was measured for 20 seconds using a pulse Doppler method with a diagnostic ultrasound system under six conditions (three different positions and with and without stockings). Changes of blood flow velocity were compared. [Results] Elastic stockings did not affect the blood flow velocity in the common femoral vein. For both the with stockings condition and without stockings condition, the time-averaged maximum flow velocity in the head-up position was significantly lower than that in the supine and leg-up positions. Time-averaged maximum flow velocity showed no significant difference between the supine position and leg-up position. [Conclusion] Elastic stockings did not affect the blood flow velocity in the common femoral vein, but ankle positions did affect it. Further studies of patients with venous insufficiency are needed. PMID:27799704

  13. Breaking through: The effects of a velocity distribution on barriers to dust growth

    NASA Astrophysics Data System (ADS)

    Windmark, F.; Birnstiel, T.; Ormel, C. W.; Dullemond, C. P.

    2012-08-01

    Context. It is unknown how far dust growth can proceed by coagulation. Obstacles to collisional growth are the fragmentation and bouncing barriers. However, in all previous simulations of the dust-size evolution, only the mean collision velocity has been considered, neglecting that a small but possibly important fraction of the collisions will occur at both much lower and higher velocities. Aims: We study the effect of the probability distribution of impact velocities on the collisional dust growth barriers. Methods: We assume a Maxwellian velocity distribution for colliding particles to determine the fraction of sticking, bouncing, and fragmentation, and implement this in a dust-size evolution code. We also calculate the probability of growing through the barriers and the growth timescale in these regimes. Results: We find that the collisional growth barriers are not as sharp as previously thought. With the existence of low-velocity collisions, a small fraction of the particles manage to grow to masses orders of magnitude above the main population. Conclusions: A particle velocity distribution softens the fragmentation barrier and removes the bouncing barrier. It broadens the size distribution in a natural way, allowing the largest particles to become the first seeds that initiate sweep-up growth towards planetesimal sizes.

  14. Effective-medium theory for energy velocity in one-dimensional finite lossless photonic crystals.

    PubMed

    Torrese, Guido; Taylor, Jason; Hall, Trevor J; Mégret, Patrice

    2006-06-01

    The effective medium theory is a useful approach for investigating the electromagnetic wave propagation in periodic multilayer slabs. It allows accurate computation of transmission and reflection spectra as well as of phase and group velocities. In this paper we derive an exact analytical expression for the energy velocity of a one-dimensional finite photonic crystal based on the effective medium approach. It accounts for the multiple reflections within the structure which results in the characteristic oscillations of the transmission spectrum. Our analytical expression holds for an arbitrary refractive index contrast and goes beyond the limits of the standard homogenization method. In order to validate our approach, results obtained by using the all-frequency effective energy velocity have been compared to those obtained using the transfer matrix method.

  15. Effects of Age and Bolus Volume on Velocity of Hyolaryngeal Excursion in Healthy Adults.

    PubMed

    Barikroo, Ali; Carnaby, Giselle; Crary, Michael

    2015-10-01

    Reduced movement velocity has been identified as a risk marker for movement impairment in older adults. Hyolaryngeal excursion is a key movement feature of normal swallowing function which is known to change with age and other extrinsic variables such as bolus volume. However, velocity of hyolaryngeal excursion has received limited attention in the literature on normal or abnormal swallowing. This study evaluated the effects of age and bolus volume on the velocity of hyoid and laryngeal excursion during swallowing in healthy adults. Forty-four healthy volunteers were grouped into three age bands (young: 20-35 years, middle age: 36-55 years, older: 56 ≥ years). All subjects swallowed 5 and 20 mL of thin liquid during fluoroscopic recording. Fluoroscopic images were extracted for each swallow representing the onset and maximum excursion positions of the hyoid and larynx. Superior and anterior excursion distance (excursion magnitude) and the time difference between rest and maximum excursion (excursion duration) were calculated. Velocity was calculated as a ratio of distance over time. Superior hyoid excursion magnitude was significantly increased for the 20 mL volume. Anterior laryngeal excursion magnitude was also significantly increased for the 20 mL volume. No kinematic duration measure demonstrated significant change across age or bolus conditions. Superior hyoid excursion velocity was significantly faster for the 20 mL volume. Superior and anterior laryngeal excursion velocity were significantly faster for the 20 mL volume only in the older group. Results of this study indicate that magnitude and velocity of hyoid and laryngeal excursion vary with age and volume. Comprising both excursion magnitude and duration, kinematic velocity may be a more complete metric to evaluate age-related swallowing performance.

  16. Effect of Anisotropic Velocity Structure on Acoustic Emission Source Location during True-Triaxial Deformation Experiments

    NASA Astrophysics Data System (ADS)

    Ghofrani Tabari, Mehdi; Goodfellow, Sebastian; Young, R. Paul

    2016-04-01

    Although true-triaxial testing (TTT) of rocks is now more extensive worldwide, stress-induced heterogeneity due to the existence of several loading boundary effects is not usually accounted for and simplified anisotropic models are used. This study focuses on the enhanced anisotropic velocity structure to improve acoustic emission (AE) analysis for an enhanced interpretation of induced fracturing. Data from a TTT on a cubic sample of Fontainebleau sandstone is used in this study to evaluate the methodology. At different stages of the experiment the True-Triaxial Geophysical Imaging Cell (TTGIC), armed with an ultrasonic and AE monitoring system, performed several velocity surveys to image velocity structure of the sample. Going beyond a hydrostatic stress state (poro-elastic phase), the rock sample went through a non-dilatational elastic phase, a dilatational non-damaging elasto-plastic phase containing initial AE activity and finally a dilatational and damaging elasto-plastic phase up to the failure point. The experiment was divided into these phases based on the information obtained from strain, velocity and AE streaming data. Analysis of the ultrasonic velocity survey data discovered that a homogeneous anisotropic core in the center of the sample is formed with ellipsoidal symmetry under the standard polyaxial setup. Location of the transducer shots were improved by implementation of different velocity models for the sample starting from isotropic and homogeneous models going toward anisotropic and heterogeneous models. The transducer shot locations showed a major improvement after the velocity model corrections had been applied especially at the final phase of the experiment. This location improvement validated our velocity model at the final phase of the experiment consisting lower-velocity zones bearing partially saturated fractures. The ellipsoidal anisotropic velocity model was also verified at the core of the cubic rock specimen by AE event location of

  17. Indoor air pollution: Acute adverse health effects and host susceptibility

    SciTech Connect

    Zummo, S.M.; Karol, M.H.

    1996-01-01

    Increased awareness of the poor quality of indoor air compared with outdoor air has resulted in a significant amount of research on the adverse health effects and mechanisms of action of indoor air pollutants. Common indoor air agents are identified, along with resultant adverse health effects, mechanisms of action, and likely susceptible populations. Indoor air pollutants range from biological agents (such as dust mites) to chemical irritants (such as nitrogen dioxide, carbon monoxide, sulfur dioxide, formaldehyde, and isocyanates). These agents may exert their effects through allergic as well as nonallergic mechanisms. While the public does not generally perceive poor indoor air quality as a significant health risk, increasing reports of illness related to indoor air and an expanding base of knowledge on the health effects of indoor air pollution are likely to continue pushing the issue to the forefront.

  18. Effect of postural changes on 3D joint angular velocity during starting block phase.

    PubMed

    Slawinski, Jean; Dumas, Raphaël; Cheze, Laurence; Ontanon, Guy; Miller, Christian; Mazure-Bonnefoy, Alice

    2013-01-01

    Few studies have focused on the effect of posture during sprint start. The aim of this study was to measure the effect of the modification of horizontal distance between the blocks during sprint start on three dimensional (3D) joint angular velocity. Nine trained sprinters started using three different starting positions (bunched, medium and elongated). They were equipped with 63 passive reflective markers, and an opto-electronic Motion Analysis system was used to collect the 3D marker trajectories. During the pushing phase on the blocks, norm of the joint angular velocity (NJAV), 3D Euler angular velocity (EAV) and pushing time on the blocks were calculated. The results demonstrated that the decrease of the block spacing induces an opposite effect on the angular velocity of joints of the lower and the upper limbs. The NJAV of the upper limbs is greater in the bunched start, whereas the NJAV of the lower limbs is smaller. The modifications of NJAV were due to a combination of the movement of the joints in the different degrees of freedom. The medium start seems to be the best compromise because it leads, in a short pushing time, to a combination of optimal joint velocities for upper and lower segments.

  19. Ballistic Range Measurements of Stagnation-Point Heat Transfer in Air and in Carbon Dioxide at Velocities up to 18,000 Feet Per Second

    NASA Technical Reports Server (NTRS)

    Yee, Layton; Bailey, Harry E.; Woodward, Henry T.

    1961-01-01

    A new technique for measuring heat-transfer rates on free-flight models in a ballistic range is described in this report. The accuracy of the heat-transfer rates measured in this way is shown to be comparable with the accuracy obtained in shock-tube measurements. The specific results of the present experiments consist of measurements of the stagnation-point heat-transfer rates experienced by a spherical-nosed model during flight through air and through carbon dioxide at velocities up to 18,000 feet per second. For flight through air these measured heat-transfer rates agree well with both the theoretically predicted rates and the rates measured in shock tubes. the heat-transfer rates agree well with the rates measured in a shock tube. Two methods of estimating the stagnation-point heat-transfer rates in carbon dioxide are compared with the experimental measurements. At each velocity the measured stagnation-point heat-transfer rate in carbon dioxide is about the same as the measured heat-transfer rate in air.

  20. Isotope effect of mercury diffusion in air

    PubMed Central

    Koster van Groos, Paul G.; Esser, Bradley K.; Williams, Ross W.; Hunt, James R.

    2014-01-01

    Identifying and reducing impacts from mercury sources in the environment remains a considerable challenge and requires process based models to quantify mercury stocks and flows. The stable isotope composition of mercury in environmental samples can help address this challenge by serving as a tracer of specific sources and processes. Mercury isotope variations are small and result only from isotope fractionation during transport, equilibrium, and transformation processes. Because these processes occur in both industrial and environmental settings, knowledge of their associated isotope effects is required to interpret mercury isotope data. To improve the mechanistic modeling of mercury isotope effects during gas phase diffusion, an experimental program tested the applicability of kinetic gas theory. Gas-phase elemental mercury diffusion through small bore needles from finite sources demonstrated mass dependent diffusivities leading to isotope fractionation described by a Rayleigh distillation model. The measured relative atomic diffusivities among mercury isotopes in air are large and in agreement with kinetic gas theory. Mercury diffusion in air offers a reasonable explanation of recent field results reported in the literature. PMID:24364380

  1. Effect of warm-up with different weighted bats on normal baseball bat velocity.

    PubMed

    Montoya, Brian S; Brown, Lee E; Coburn, Jared W; Zinder, Steven M

    2009-08-01

    Traditionally, baseball players have used a heavy bat for warm-up before competition. Because bat velocity is an essential component to hitting a baseball, and because players warm up differently, there is a need to investigate the best way to maximize post warm-up bat velocity. The purpose of this study was to determine the effects of warm-up with different weighted bats on normal baseball bat velocity. Nineteen recreational male baseball players (age, 24.5 +/- 3.9 years; height, 181.1 +/- 8.4 cm; body mass, 87.9 +/- 18.4 kg) participated in this study. Three different randomized warm-up conditions were completed and analyzed for velocity and for their effect on post warm-up normal baseball bat velocity. Subjects were instructed to perform 5 maximal swings with each of 3 different weighted bats-light (LB = 9.6 oz), normal (NB = 31.5 oz), and heavy (HB = 55.2 oz)-followed by 30-second rest and then 5 swings of the NB. Analysis of variance revealed that warm-up velocity of the LB (63.57 +/- 3.58 mph) was significantly (p < 0.05) faster than that of NB (51.25 +/- 3.01 mph) and HB (41.79 +/- 3.01 mph), whereas warm-up velocity of NB was also significantly faster than that of HB. For post warm-up, LB (52.29 +/- 2.68 mph) and NB (50.60 +/- 3.04 mph) produced significantly faster velocity of the normal bat than the HB (48.26 +/- 2.98 mph). Warming up with 5 swings of a light or normal bat appears to increase post warm-up velocity of the normal bat when compared with warming up with a heavy bat after a rest period of 30 seconds. Within the bat weight spectrum of this study, it is suggested that when preparing to hit, 5 warm-up swings with either a light or normal bat will allow a player to achieve the greatest velocity of their normal bat.

  2. Wind-induced flow velocity effects on nutrient concentrations at Eastern Bay of Lake Taihu, China.

    PubMed

    Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Jianwei; Gao, Xiaomeng; Wang, Wencai; Acharya, Kumud

    2017-07-01

    Shallow lakes are highly sensitive to respond internal nutrient loading due to wind-induced flow velocity effects. Wind-induced flow velocity effects on nutrient suspension were investigated at a long narrow bay of large shallow Lake Taihu, the third largest freshwater lake in China. Wind-induced reverse/compensation flow and consistent flow field probabilities at vertical column of the water were measured. The probabilities between the wind field and the flow velocities provided a strong correlation at the surface (80.6%) and the bottom (65.1%) layers of water profile. Vertical flow velocity profile analysis provided the evidence of delay response time to wind field at the bottom layer of lake water. Strong wind field generated by the west (W) and west-north-west (WNW) winds produced displaced water movements in opposite directions to the prevailing flow field. An exponential correlation was observed between the current velocities of the surface and the bottom layers while considering wind speed as a control factor. A linear model was developed to correlate the wind field-induced flow velocity impacts on nutrient concentration at the surface and bottom layers. Results showed that dominant wind directions (ENE, E, and ESE) had a maximum nutrient resuspension contribution (nutrient resuspension potential) of 34.7 and 43.6% at the surface and the bottom profile layers, respectively. Total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) average concentrations were 6.38, 1.5, and 0.03 mg/L during our field experiment at Eastern Bay of Lake Taihu. Overall, wind-induced low-to-moderate hydrodynamic disturbances contributed more in nutrient resuspension at Eastern Bay of Lake Taihu. The present study can be used to understand the linkage between wind-induced flow velocities and nutrient concentrations for shallow lakes (with uniform morphology and deep margins) water quality management and to develop further models.

  3. Evaluation of Gust and Draft Velocities from Flights of P-61C Airplanes within Thunderstorms September 10, 1947 to September 15, 1947 at Clinton County Army Air Field, Ohio

    NASA Technical Reports Server (NTRS)

    Funk, Jack

    1948-01-01

    The gust and draft velocities from records of NACA instruments installed in P-61C airplanes participating in thunderstorm flights at Clinton County Army Air Field, Ohio, from September 10, 1947 to September 15, 1947, are presented.

  4. Evaluation of Gust and Draft Velocities from Flights of P-61C Airplanes within Thunderstorms August 16, 1947 to August 20, 1947 at Clinton County Army Air Field, Ohio

    NASA Technical Reports Server (NTRS)

    Funk, Jack

    1948-01-01

    The gust and draft velocities from records of NACA instruments installed in P-61C airplanes participating in thunderstorm flights at Clinton County Army Air Field, Ohio, from August 16, 1947 to August 20, 1947 are presented.

  5. Evaluation of Gust and Draft Velocities from Flights of P-61C Airplanes within Thunderstorms August 13, 1947 to August 15, 1947 at Clinton County Army Air Field, Ohio

    NASA Technical Reports Server (NTRS)

    Funk, Jack

    1948-01-01

    The gust and draft velocities from records of NACA instruments installed in P-61C airplanes participating in thunderstorm flights at Clinton County Army Air Field, Ohio, from August 13, 1947 to August 15, 1947 are presented.

  6. Effects of Ultrasonic Bonding Materials on Velocity and Attenuation of Sound in Red Lauan Wood

    NASA Astrophysics Data System (ADS)

    Kamioka, Hiroaki

    1988-02-01

    The effects of ultrasonic bonding materials between an acoustic transducer and a specimen surface on the velocity and attenuation of sound in red lauan wood were studied by using the ultrasonic pulse transmission method, since it was important to determine the acoustic coupling between the transducer and the specimen for measuring the sound velocity and attenuation in highly dissipative materials such as wood. Vaseline, grease, various kinds of machine oils, etc., were employed as an ultrasonic bonding material. The energy dissipation of sound was smallest in the case of grease. By combining the data of attenuation with that of the sound velocity, the effects of ultrasonic bonding materials on the ultrasonic behavior in red lauan wood are reported and discussed.

  7. Effects of magnetic field and Hall current to the blood velocity and LDL transfer

    NASA Astrophysics Data System (ADS)

    Abdullah, I.; Naser, N.; Talib, A. H.; Mahali, S.

    2015-09-01

    The magnetic field and Hall current effects have been considered on blood velocity and concentration of low-density lipoprotein (LDL). It is important to observe those effects to the flowing blood in a stenosed artery. The analysis from the obtained results may be useful to some clinical procedures, such as MRI, where the radiologists may have more information in the investigations before cardiac operations could be done. In this study, the uniform magnetic field and Hall current are applied to the Newtonian blood flow through an artery having a cosine-shaped stenosis. The governing equations are coupled with mass transfer and solved employing a finite difference Marker and Cell (MAC) method with an appropriate initial and boundary conditions. The graphical results of velocity profiles and LDL concentration are presented in this paper and the results show that the velocity increases and concentration decreases as Hall parameter increased.

  8. Effect of velocity-dependent friction on multiple-vehicle collisions in traffic flow

    NASA Astrophysics Data System (ADS)

    Nagatani, Takashi

    2017-01-01

    We present the dynamic model for the multiple-vehicle collisions to take into account the velocity-dependent friction force. We study the effect of the velocity-dependent friction on the chain-reaction crash on a road. In the traffic situation, drivers brake according to taillights of the forward vehicle and the friction force depends highly on the vehicular speed. The first crash may induce more collisions. We investigate whether or not the first collision induces the multiple-vehicle collisions, numerically and analytically. The dynamic transitions occur from no collisions, through a single collision and double collisions, to multiple collisions with decreasing the headway. We explore the effect of the velocity-dependent friction on the dynamic transitions and the region maps in the multiple-vehicle collisions.

  9. Wounding effects of small fragments of different shapes at different velocities on soft tissues of dogs.

    PubMed

    Liu, Y Q; Chen, X Y; Li, S G; Chen, X M; Guo, R F; Wang, D T; Fu, X B; Jiang, S P; Xu, G W

    1988-01-01

    The wounding effects of small fragments of the same weight (0.44 gm) but different shapes and at different impact velocities (708-1,560 m/s) on the soft tissues of the hind legs of 156 dogs were studied. The experiments showed that velocity was the major factor in causing wounds. For fragments of the same shape, the energy transmission, volume of wound cavity, sectional areas at entrance and exit, and amount of tissue that had to be excised increased rapidly with increasing velocity. In particular, as the velocity reached about 1,500 m/s, a shallow and wide wound tract was liable to occur, peripheral tissue lesion was relatively apparent, even extended to the whole leg, and the rate of occurrence of bone fracture was high. The wounding effect of the shape of the fragment closely related to its sectional specific weight (W) and drag coefficient (CD). Given the weight of the projectile and the density and thickness of the tissue, the energy transmission (delta E) was directly proportional to the square of the velocity and to the drag coefficient, and inversely proportional to the sectional specific weight of the fragment. Therefore, under certain conditions, reducing the sectional specific weight often increased the drag coefficient, in favour of causing a wound. In this experiment, the extent of wounds caused by the triangular, the square, and the cylindrical, and the spherical fragments decreased in that order, in agreement with their values of sectional specific weight and drag coefficient.

  10. The effects of water velocity on the Ceratomyxa shasta infectious cycle

    PubMed Central

    Bjork, Sarah J.; Bartholomew, Jerri L.

    2014-01-01

    Ceratomyxa shasta is a myxozoan parasite identified as a contributor to salmon mortality in the Klamath River, USA. The parasite has a complex life cycle involving a freshwater polychaete, Manayunkia speciosa and a salmonid. As part of ongoing research on how environmental parameters influence parasite establishment and replication, we designed a laboratory experiment to examine the effect of water flow (velocity) on completion of the C. shasta infectious cycle. The experiment tested the effect of two water velocities, 0.05 and 0.01 m/s, on survival and infection of M. speciosa as well as transmission to susceptible rainbow trout and comparatively resistant Klamath River Chinook salmon. The faster water velocity facilitated the greatest polychaete densities, but the lowest polychaete infection prevalence. Rainbow trout became infected in all treatments, but at the slower velocity had a shorter mean day to death, indicating a higher infectious dose. Infection was not detected in Chinook salmon even at a dose estimated to be as high as 80,000 actinospores per fish. The higher water velocity resulted in lower C. shasta infection prevalence in M. speciosa and decreased infection severity in fish. Another outcome of our experiment is the description of a system for maintaining and infecting M. speciosa in the laboratory. PMID:18803584

  11. Effect of the microstructure on the propagation velocity of ultrasound in magnetic powders.

    PubMed

    Botello, Francisco Ruiz; Quintanilla, Miguel A S; Castellanos, Antonio; Grekova, Elena F; Tournat, Vincent

    2017-08-01

    We analyze experimentally and theoretically the sound propagation velocity of P-waves in granular media made of micrometer-size magnetite particles under an external magnetic field. The sound velocity is measured in a coherent (long-wavelength) regime of propagation after a controlled sample preparation consisting of a fluidization and the application of a magnetic field. Several different procedures are applied and result in different but reproducible particle arrangements and preferential contact orientations affecting the measured sound velocity. Interestingly, we find that the sound velocity increases when the magnetic field is applied parallel to the sound propagation direction and decreases when the magnetic field is applied perpendicular to the sound propagation direction. The observed qualitative relationship between the changes in the particle arrangement and the sound velocity is analyzed theoretically based on an effective medium theory adapted to account for the effect of the magnetic field in the preparation procedure and its influence on the medium contact fabric. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Effect of pressurization on helical guided wave energy velocity in fluid-filled pipes.

    PubMed

    Dubuc, Brennan; Ebrahimkhanlou, Arvin; Salamone, Salvatore

    2017-03-01

    The effect of pressurization stresses on helical guided waves in a thin-walled fluid-filled pipe is studied by modeling leaky Lamb waves in a stressed plate bordered by fluid. Fluid pressurization produces hoop and longitudinal stresses in a thin-walled pipe, which corresponds to biaxial in-plane stress in a plate waveguide model. The effect of stress on guided wave propagation is accounted for through nonlinear elasticity and finite deformation theory. Emphasis is placed on the stress dependence of the energy velocity of the guided wave modes. For this purpose, an expression for the energy velocity of leaky Lamb waves in a stressed plate is derived. Theoretical results are presented for the mode, frequency, and directional dependent variations in energy velocity with respect to stress. An experimental setup is designed for measuring variations in helical wave energy velocity in a thin-walled water-filled steel pipe at different levels of pressure. Good agreement is achieved between the experimental variations in energy velocity for the helical guided waves and the theoretical leaky Lamb wave solutions. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Effects of transducer, velocity, Doppler angle, and instrument settings on the accuracy of color Doppler ultrasound.

    PubMed

    Stewart, S F

    2001-04-01

    The accuracy of a commercial color Doppler ultrasound (US) system was assessed in vitro using a rotating torus phantom. The phantom consisted of a thin rubber tube filled with a blood-mimicking fluid, joined at the ends to form a torus. The torus was mounted on a disk suspended in water, and rotated at constant speeds by a motor. The torus fluid was shown in a previous study to rotate as a solid body, so that the actual fluid velocity was dependent only on the motor speed and sample volume radius. The fluid velocity could, thus, be easily compared to the color Doppler-derived velocity. The effects of instrument settings, velocity and the Doppler angle was assessed in four transducers: a 2.0-MHz phased-array transducer designed for cardiac use, a 4.0-MHz curved-array transducer designed for general thoracic use, and two linear transducers designed for vascular use (one 4.0 MHz and one 6.0 MHz). The color Doppler accuracy was found to be significantly dependent on the transducer used, the pulse-repetition frequency and wall-filter frequency, the actual fluid velocity and the Doppler angle (p < 0.001 by analysis of variance). In particular, the phased array and curved array were observed to be significantly more accurate than the two linear arrays. The torus phantom was found to provide a sensitive measure of color Doppler accuracy. Clinicians need to be aware of these effects when performing color Doppler US exams.

  14. Adverse Health Effects of Particulate Air Pollution

    PubMed Central

    Bell, Michelle L.; Ebisu, Keita; Peng, Roger D.; Dominici, Francesca

    2011-01-01

    Background The short-term effects of particulate matter (PM) on mortality and morbidity differ by geographic location and season. Several hypotheses have been proposed for this variation, including different exposures with air conditioning (AC) versus open windows. Methods Bayesian hierarchical modeling was used to explore whether AC prevalence modified day-to-day associations between PM10 and mortality, and between PM2.5 and cardiovascular or respiratory hospitalizations, for those 65 years and older. We considered yearly, summer-only, and winter-only effect estimates and 2 types of AC (central and window units). Results Communities with higher AC prevalence had lower PM effects. Associations were observed for cardiovascular hospitalizations and central AC. Each additional 20% of households with central AC was associated with a 43% decrease in PM2.5 effects on cardiovascular hospitalization. Central AC prevalence explained 17% of between-community variability in PM2.5 effect estimates for cardiovascular hospitalizations. Conclusions Higher AC prevalence was associated with lower health effect estimates for PM. PMID:19535984

  15. A Numerical and Experimental Study of Coflow Laminar Diffusion Flames: Effects of Gravity and Inlet Velocity

    NASA Technical Reports Server (NTRS)

    Cao, S.; Bennett, B. A. V.; Ma, B.; Giassi, D.; Stocker, D. P.; Takahashi, F.; Long, M. B.; Smooke, M. D.

    2015-01-01

    In this work, the influence of gravity, fuel dilution, and inlet velocity on the structure, stabilization, and sooting behavior of laminar coflow methane-air diffusion flames was investigated both computationally and experimentally. A series of flames measured in the Structure and Liftoff in Combustion Experiment (SLICE) was assessed numerically under microgravity and normal gravity conditions with the fuel stream CH4 mole fraction ranging from 0.4 to 1.0. Computationally, the MC-Smooth vorticity-velocity formulation of the governing equations was employed to describe the reactive gaseous mixture; the soot evolution process was considered as a classical aerosol dynamics problem and was represented by the sectional aerosol equations. Since each flame is axisymmetric, a two-dimensional computational domain was employed, where the grid on the axisymmetric domain was a nonuniform tensor product mesh. The governing equations and boundary conditions were discretized on the mesh by a nine-point finite difference stencil, with the convective terms approximated by a monotonic upwind scheme and all other derivatives approximated by centered differences. The resulting set of fully coupled, strongly nonlinear equations was solved simultaneously using a damped, modified Newton's method and a nested Bi-CGSTAB linear algebra solver. Experimentally, the flame shape, size, lift-off height, and soot temperature were determined by flame emission images recorded by a digital camera, and the soot volume fraction was quantified through an absolute light calibration using a thermocouple. For a broad spectrum of flames in microgravity and normal gravity, the computed and measured flame quantities (e.g., temperature profile, flame shape, lift-off height, and soot volume fraction) were first compared to assess the accuracy of the numerical model. After its validity was established, the influence of gravity, fuel dilution, and inlet velocity on the structure, stabilization, and sooting

  16. The effects of air pollution on children.

    PubMed

    Bates, D V

    1995-09-01

    Air pollutants have been documented to be associated with a wide variety of adverse health impacts in children. These include increases in mortality in very severe episodes; an increased risk of perineonatal mortality in regions of higher pollution, and an increased general rate of mortality in children; increased acute respiratory disease morbidity; aggravation of asthma, as shown by increased hospital emergency visits or admissions as well as in longitudinal panel studies; increased prevalence of respiratory symptoms in children, and infectious episodes of longer duration; lowered lung function in children when pollutants increase; lowered lung function in more polluted regions; increased sickness rates as indicated by kindergarten and school absences; the adverse effects of inhaled lead from automobile exhaust. These impacts are especially severe when high levels of outdoor pollution (usually from uncontrolled coal burning) are combined with high levels of indoor pollution. In developed countries, where indoor pollution levels are lower, increasing traffic density and elevated NO2 levels with secondary photochemical and fine particulate pollution appear to be the main contemporary problem. By virtue of physical activity out of doors when pollution levels may be high, children may experience higher exposures than adults. Air pollution is likely to have a greater impact on asthmatic children if they are without access to routine medical care.

  17. The Effect of Periosteal Resection on Tibial Growth Velocity Measured by Microtransducer Technology in Lambs

    PubMed Central

    Sansone, Jason M.; Wilsman, Norman J.; Leiferman, Ellen M.; Noonan, Kenneth J.

    2010-01-01

    Background Disruption of the periosteum, whether traumatic or elective, has long been known to accelerate growth in the developing skeleton. However, the extent, timing, and mechanism of the resultant increase in growth velocity (if any) remain undefined. The primary research questions were: Does periosteal resection result in a change (increase) in growth velocity of a long bone at the growth plate? When after the resection does the effect start and for how long? Finally, which of several cellular mechanisms is most likely responsible for the change in growth velocity. Methods Five lambs underwent proximal tibial growth plate periosteal resection with subsequent measurement of growth velocity by implantable microtransducers or fluorochrome labeling. This former technique provided real-time growth velocity data with a resolution of about 10µm (width of a proliferative zone chondrocyte). These measurements were accurate at up to four weeks postoperative, as verified by fluorochrome labeling, and radiographic measurement. Two lambs were continued on the study for an additional three weeks. Histomorphometric and stereological assessment of chondrocytic kinetic parameters was performed on control and experimental tibiae following euthanasia. Results Periosteal resection increased growth velocity in every lamb, at every time point, and in a consistent and sustained manner. Histomorphometric correlation to this phenomenon indicated that the cellular basis of this acceleration was most likely the result of hypertrophic chondrocyte axial elongation, rather than changes in chondrocyte proliferation, magnitude of hypertrophic chondrocytic swelling, or increased matrix production. Conclusions Periosteal resection creates immediate and sustained acceleration of growth resulting from axial elongation of the hypertrophic chondrocyte. While the increase in growth velocity was consistent, the absolute magnitude of the acceleration suggests that periosteal resection be considered

  18. Orthogonal design on range hood with air curtain and its effects on kitchen environment.

    PubMed

    Liu, Xiaomin; Wang, Xing; Xi, Guang

    2014-01-01

    Conventional range hoods cannot effectively prevent the oil fumes containing cooking-induced harmful material from escaping into the kitchen Air curtains and guide plates have been used in range hoods to reduce the escape of airborne emissions and heat, thereby improving the kitchen environment and the cook's degree of comfort. In this article, numerical simulations are used to study the effects of the jet velocity of an air curtain, the jet angle of the air curtain, the width of the jet slot, the area of the guide plate, and the exhaust rate of the range hood on the perceived temperature, the perceived concentration of oil fumes, the release temperature of oil fumes, and the concentration of escaped oil fumes in a kitchen. The orthogonal experiment results show that the exhaust rate of the range hood is the main factor influencing the fumes concentration and the temperature distribution in the kitchen. For the range hood examined in the present study, the optimum values of the exhaust rate, the jet velocity of the air curtain, the jet angle of the air curtain, the width of the jet slot, and the area of the guide plate are 10.5 m(3)/min, 1.5 m/s, -5°, 4 mm, and 0.22 m(2), respectively, based on the results of the parametric study. In addition, the velocity field, temperature field, and oil fumes concentration field in the kitchen using the proposed range hood with the air curtain and guide plate are analyzed for those parameters. The study's results provide significant information needed for improving the kitchen environment.

  19. Effects of CO addition on the characteristics of laminar premixed CH{sub 4}/air opposed-jet flames

    SciTech Connect

    Wu, C.-Y.; Chao, Y.-C.; Chen, C.-P.; Ho, C.-T.; Cheng, T.S.

    2009-02-15

    The effects of CO addition on the characteristics of premixed CH{sub 4}/air opposed-jet flames are investigated experimentally and numerically. Experimental measurements and numerical simulations of the flame front position, temperature, and velocity are performed in stoichiometric CH{sub 4}/CO/air opposed-jet flames with various CO contents in the fuel. Thermocouple is used for the determination of flame temperature, velocity measurement is made using particle image velocimetry (PIV), and the flame front position is measured by direct photograph as well as with laser-induced predissociative fluorescence (LIPF) of OH imaging techniques. The laminar burning velocity is calculated using the PREMIX code of Chemkin collection 3.5. The flame structures of the premixed stoichiometric CH{sub 4}/CO/air opposed-jet flames are simulated using the OPPDIF package with GRI-Mech 3.0 chemical kinetic mechanisms and detailed transport properties. The measured flame front position, temperature, and velocity of the stoichiometric CH{sub 4}/CO/air flames are closely predicted by the numerical calculations. Detailed analysis of the calculated chemical kinetic structures reveals that as the CO content in the fuel is increased from 0% to 80%, CO oxidation (R99) increases significantly and contributes to a significant level of heat-release rate. It is also shown that the laminar burning velocity reaches a maximum value (57.5 cm/s) at the condition of 80% of CO in the fuel. Based on the results of sensitivity analysis, the chemistry of CO consumption shifts to the dry oxidation kinetics when CO content is further increased over 80%. Comparison between the results of computed laminar burning velocity, flame temperature, CO consumption rate, and sensitivity analysis reveals that the effect of CO addition on the laminar burning velocity of the stoichiometric CH{sub 4}/CO/air flames is due mostly to the transition of the dominant chemical kinetic steps. (author)

  20. Ensemble Monte Carlo Simulation of a Velocity-Modulation Field Effect Transistor (VMT)

    NASA Astrophysics Data System (ADS)

    Kizilyalli, I. C.; Hess, K.

    1987-09-01

    We present numerical simulations of velocity modulated field effect transistors as proposed by Sakaki. Using self-consistent particle-field Monte Carlo analysis, we assess possible advantages of these novel device structures with respect to switching speed and show the qualitative correctness of Sakaki’s ideas. Quantitatively, delays are introduced by the redistribution of electrons in the separated channels.

  1. Evaluation of an Imputed Pitch Velocity Model of the Auditory Kappa Effect

    ERIC Educational Resources Information Center

    Henry, Molly J.; McAuley, J. Devin

    2009-01-01

    Three experiments evaluated an imputed pitch velocity model of the auditory kappa effect. Listeners heard 3-tone sequences and judged the timing of the middle (target) tone relative to the timing of the 1st and 3rd (bounding) tones. Experiment 1 held pitch constant but varied the time (T) interval between bounding tones (T = 728, 1,000, or 1,600…

  2. Effects of oxide charge and surface recombination velocity on the excess base current of BJTs

    SciTech Connect

    Kosier, S.L.; Schrimpf, R.D.; Wei, A.; DeLaus, M.; Fleetwood, D.M.; Combs, W.E.

    1993-12-01

    The role of net positive oxide trapped charge and surface recombination velocity on excess base current in BJTs is identified. The effects of the two types of damage can be detected by plotting the excess base current versus base-emitter voltage. Differences and similarities between ionizing-radiation-induced and hot electron-induced degradation are discussed.

  3. Forward velocity effects on under-the-wing externally blown flap noise

    NASA Technical Reports Server (NTRS)

    Goodykoontz, J.; Vonglahn, U.; Dorsch, R. G.

    1975-01-01

    Noise tests were conducted with small-scale models of externally blown-flap powered-lift systems that were subjected to simulated takeoff and landing free-stream velocities by placing the nozzle-wing models in a free jet. The nozzle configurations consisted of a conical and an 8-tube mixer nozzle. The results show that the free-stream velocity attenuates the noise from the various configurations, with the amount of attenuation depending on the flap setting. More attenuation was obtained with a flap setting of 20 degrees than with a flap setting of 60 degrees. The dynamic effect on the total attenuation caused by aircraft motion is also discussed.

  4. Forward velocity effects on under-the-wing externally blown flap noise

    NASA Technical Reports Server (NTRS)

    Goodykoontz, J.; Von Glahn, U.; Dorsch, R.

    1975-01-01

    Noise tests were conducted with small-scale models of externally blown-flap powered-lift systems that were subjected to simulated takeoff and landing free-stream velocities by placing the nozzle-wing models in a free jet. The nozzle configurations consisted of a conical and an 8-tube mixer nozzle. The results showed that the free-stream velocity attenuated the noise from the various configurations with the amount of attenuation depending on the flap setting. More attenuation was obtained with a flap setting of 20 deg than with a flap setting of 60 deg. The dynamic effect on the total attenuation caused by aircraft motion is also discussed.

  5. Effect of particle velocity fluctuations on the inertia coupling in two-phase flow

    NASA Technical Reports Server (NTRS)

    Drew, Donald A.

    1989-01-01

    Consistent forms for the interfacial force, the interfacial pressure, the Reynolds stresses and the particle stress have been derived for the inviscid, irrotational incompressible flow of fluid in a dilute suspension of spheres. The particles are assumed to have a velocity distribution, giving rise to an effective pressure and stress in the particle phase. The velocity fluctuations also contribute in the fluid Reynolds stress and in the (elastic) stress field inside the spheres. The relation of these constitutive equations to the force on an individual sphere is discussed.

  6. Effect of simulated forward speed on the jet noise of inverted velocity profile coannular nozzles

    NASA Technical Reports Server (NTRS)

    Packman, A. B.; Ng, K. W.; Chen, C. Y.

    1977-01-01

    Tests were conducted of inverted velocity profile coannular nozzles and a conical nozzle in an acoustic wind tunnel facility to simulate flight effects on jet noise generation. Coannular model nozzles were tested at fan to core nozzle exit area ratios of .75 and 1.2. Fan stream jet velocity ranged up to 2000 fps at a variety of fan exhaust pressure ratios and temperatures for a core stream of 1000 fps. The wind tunnel airflow was varied from static to 425 fps. The acoustic results indicated that the noise level differences seen previously under static conditions are retained in the flight environment.

  7. Effects of current velocity on byssal thread production in the zebra mussel (Dreissena polymorpha)

    SciTech Connect

    Clarke, M.; McMahon, R.F.

    1995-06-01

    Effect of current velocity on byssal thread production by the zebra mussel (Dreissena polymorpha) was investigated. Number of threads produced by samples of 20 mussels at 25{degrees}C exposed to currents velocities of 0.1, 0.15, 0.2, 0.27 m/s were counted over 21 days. Mussels were removed from current daily and number of new threads counted over a period of 21 days after which mussels were removed and their shell length measured. Increased current velocity significantly elevated rates of byssal thread production between 0.1 m/s and 0.2 m/s. velocities of 0.27 m/s suppressed production. Suppression may be due to agitation, interfering with the mussels ability to successfully produce a byssal thread. Mean byssal thread number in a newly formed byssal complex after 21 days exposure was 52.5, 63.8, 73.3 and 60.4 at current velocities of 0.1, 0.15, 0.2 and 0.27 m/s respectively. Some of these results are consistent with observations made on the intertidal bivalve Mytilus edulis, others conflict. Results support contention that characteristics of byssal attachment may vary between freshwater and marine species.

  8. Analysis of Aircraft Evasion Strategies in Air-to-Air Missille Effectiveness Models

    DTIC Science & Technology

    1975-08-01

    AD-A015 238 ANALYSIS OF AIRCRAFT EVASION STRATEGIES IN AIR-TO-AIR MISSILE EFFECTIVENESS MObri ’ G. Carpenter, et al Grumman Aerospace Corporation ...overall tep t Es CIS*atiet d) Oft ’IsNA 1tTNG AC ?v I TV ? corpor te author) 2S. REPORT SECUNITY CLASSIrICA TION Unclassified ;rummn Aerospace... Corporation b RoU N/A I NEPOA’ I ?LE nalysis of Aircraft Evasion Strategies in Air-to-Air Missile Effectiveness Models 4 DESCRIP T IVE *40TS ’Type of repct

  9. The effect of nonleading foot placement on power and velocity in the fencing lunge.

    PubMed

    Gresham-Fiegel, Carolyn N; House, Paul D; Zupan, Michael F

    2013-01-01

    The fencing lunge is a sport-specific movement, which helps the fencer score quickly and accurately. The fencing lunge is executed from a stable guard position, with the toes of the leading foot pointing directly toward the opponent. As a result of coach or fencer preference, however, the angle of the nonleading foot may vary greatly among fencers, from acute (nonleading foot facing forward) to obtuse (nonleading foot facing slightly backward). Studies in other sports suggest that foot placement may affect the efficient use of leg muscles and influence the power produced. Twenty-five experienced fencers from the U.S. Air Force Academy fencing team executed lunges from 3 specific angles of nonleading foot placement and from the natural stance. Foot placements were measured as the angle of the nonleading foot from the line of the leading foot and were delimited to an acute angle (45°), a perpendicular angle (90°), and an obtuse angle (135°). The angle of natural stance was also determined for each participant. Velocity and power were measured with a TENDO Weightlifting Analyzer, and the data were analyzed with repeated measures analysis of variance. Two statistical groups were considered, one containing all participants (N = 25) and a second group of participants with a natural forward-deviated stance (n = 15). Significant differences appeared between the nonleading foot placements in peak power (p < 0.001), average power (p < 0.001), peak velocity (p < 0.001), and average velocity (p < 0.001) in both groups. Pairwise t-test results indicated that, for both statistical groups, a perpendicular placement of the feet produced the greatest power and velocity during lunging.

  10. Misperceptions of angular velocities influence the perception of rigidity in the kinetic depth effect

    NASA Technical Reports Server (NTRS)

    Domini, F.; Caudek, C.; Proffitt, D. R.; Kaiser, M. K. (Principal Investigator)

    1997-01-01

    Accuracy in discriminating rigid from nonrigid motion was investigated for orthographic projections of three-dimension rotating objects. In 3 experiments the hypothesis that magnitudes of angular velocity are misperceived in the kinetic depth effect was tested, and in 4 other experiments the hypothesis that misperceiving angular velocities leads to misperceiving rigidity was tested. The principal findings were (a) the magnitude of perceived angular velocity is derived heuristically as a function of a property of the first-order optic flow called deformation and (b) perceptual performance in discriminating rigid from nonrigid motion is accurate in cases when the variability of the deformations of the individual triplets of points of the stimulus displays favors this interpretation and not accurate in other cases.

  11. Effect of velocity-changing collisions on the output of a gas laser.

    NASA Technical Reports Server (NTRS)

    Borenstein, M.; Lamb, W. E., Jr.

    1972-01-01

    A theoretical model for the pressure dependence of the intensity of a gas laser is presented in which only velocity-changing collisions with foreign-gas atoms are included. This is a special case where the phase shifts are the same for the two atomic-laser levels or are so small that deflections are the dominant effect of collisions. A collision model for hard-sphere repulsive interactions is derived and the collision parameters, persistence of velocity and collision frequency, are assumed to be independent of velocity. The collision theory is applied to a third-order expansion of the polarization in powers of the cavity electric field (weak-signal theory). The resulting expression for the intensity shows strong pressure dependence. The collisions reduce the amount of saturation and the laser intensity increases with pressure in a characteristic fashion.

  12. Effect of reed stalks on the flow velocity in a rectangular open canal in arid areas

    NASA Astrophysics Data System (ADS)

    Mechri, Laid; Boutoutaou, Djamel; Saggaï, Sofiane; Saker, Mohamed Lakhdar

    2016-07-01

    The water velocity in an open canal is a critical factor in the sizing of drains intended for evacuation of excess water in agricultural soils. The study aims to examine, by experimental way, the effect of roughness that is due to the existence of reed stalks on the characteristics of the flows in a rectangular open canal intended to drain excess water. The tests have been done by varying the flow rate, the diameter of reed stalks and their density. The results of this research allowed taking out relations between the relative velocity and the relative density. These results also showed that, in an herbaceous open canal, the velocity is rather low than no herbaceous canal.

  13. Misperceptions of angular velocities influence the perception of rigidity in the kinetic depth effect

    NASA Technical Reports Server (NTRS)

    Domini, F.; Caudek, C.; Proffitt, D. R.; Kaiser, M. K. (Principal Investigator)

    1997-01-01

    Accuracy in discriminating rigid from nonrigid motion was investigated for orthographic projections of three-dimension rotating objects. In 3 experiments the hypothesis that magnitudes of angular velocity are misperceived in the kinetic depth effect was tested, and in 4 other experiments the hypothesis that misperceiving angular velocities leads to misperceiving rigidity was tested. The principal findings were (a) the magnitude of perceived angular velocity is derived heuristically as a function of a property of the first-order optic flow called deformation and (b) perceptual performance in discriminating rigid from nonrigid motion is accurate in cases when the variability of the deformations of the individual triplets of points of the stimulus displays favors this interpretation and not accurate in other cases.

  14. A new air quality perception scale for global assessment of air pollution health effects.

    PubMed

    Deguen, Séverine; Ségala, Claire; Pédrono, Gaëlle; Mesbah, Mounir

    2012-12-01

    Despite improvements in air quality in developed countries, air pollution remains a major public health issue. To fully assess the health impact, we must consider that air pollution exposure has both physical and psychological effects; this latter dimension, less documented, is more difficult to measure and subjective indicators constitute an appropriate alternative. In this context, this work presents the methodological development of a new scale to measure the perception of air quality, useful as an exposure or risk appraisal metric in public health contexts. On the basis of the responses from 2,522 subjects in eight French cities, psychometric methods are used to construct the scale from 22 items that assess risk perception (anxiety about health and quality of life) and the extent to which air pollution is a nuisance (sensorial perception and symptoms). The scale is robust, reproducible, and discriminates between subpopulations more susceptible to poor air pollution perception. The individual risk factors of poor air pollution perception are coherent with those findings in the risk perception literature. Perception of air pollution by the general public is a key issue in the development of comprehensive risk assessment studies as well as in air pollution risk management and policy. This study offers a useful new tool to measure such efforts and to help set priorities for air quality improvements in combination with air quality measurements.

  15. Experimental Evaluation of a Downsized Residential Air Distribution System: Comfort and Ventilation Effectiveness

    SciTech Connect

    Jalalzadeh-Azar, A. A.

    2007-01-01

    Good air mixing not only improves thermal comfort Human thermal comfort is the state of mind that expresses satisfaction with the surrounding environment, according to ASHRAE Standard 55. Achieving thermal comfort for most occupants of buildings or other enclosures is a goal of HVAC design engineers. but also enhances ventilation effectiveness by inducing uniform supply-air diffusion. In general, the performance of an air distribution system in terms of comfort and ventilation effectiveness is influenced by the supply air temperature, velocity, and flow rate, all of which are in part dictated by the HVAC (Heating Ventilation Air Conditioning) In the home or small office with a handful of computers, HVAC is more for human comfort than the machines. In large datacenters, a humidity-free room with a steady, cool temperature is essential for the trouble-free system as well as the thermal load attributes. Any potential deficiencies associated with these design variables can be further exacerbated by an improper proximity of the supply and return outlets with respect to the thermal and geometrical characteristics of the indoor space. For high-performance houses, the factors influencing air distribution performance take on an even greater significance because of a reduced supply-air design flow rate resulting from downsized HVAC systems.

  16. Evaluation of the effect of media velocity on HEPA filter performance

    SciTech Connect

    Alderman, Steven; Parsons, Michael; Hogancamp, Kristina; Norton, O. Perry; Waggoner, Charles

    2007-07-01

    Section FC of the ASME AG-1 Code addresses glass fiber HEPA filters and restricts the media velocity to a maximum of 2.54 cm/s (5 ft/min). Advances in filter media technology allow glass fiber HEPA filters to function at significantly higher velocities and still achieve HEPA performance. However, diffusional capture of particles < 100 nm is reduced at higher media velocities due to shorter residence times within the media matrix. Therefore, it is unlikely that higher media velocities for HEPA filters will be allowed without data to demonstrate the effect of media velocity on removal of particles in the smaller size classes. In order to address this issue, static testing has been conducted to generate performance related data and a range of dynamic testing has provided data regarding filter lifetimes, loading characteristics, changes in filter efficiency and the most penetrating particle size over time. Testing was conducted using 31 cm x 31 cm x 29 cm deep pleat HEPA filters supplied from two manufacturers. Testing was conducted at media velocities ranging from 2.0-4.5 cm/s with a solid aerosol challenge composed of potassium chloride. Two set of media velocity data were obtained for each filter type. In one set of evaluations, the maximum aerosol challenge particle size was limited to 3 {mu}m, while particles above 3 {mu}m were not constrained in the second set. This provided for considerable variability in the challenge mass mean diameter and overall mass loading rate. Results of this testing will be provided to the ASME AG-1 FC Committee for consideration in future versions of the HEPA standard. In general, the initial filter efficiency decreased with increasing media velocity. However, initial filter efficiencies were generally good in all cases. Filter efficiency values averaged over the first ten minute of the loading cycle ranged from 99.970 to 99.996 %. Additionally, the most penetrating particle size was observed to decrease with increasing media velocity

  17. Velocity overshoot decay mechanisms in compound semiconductor field-effect transistors with a submicron characteristic length

    SciTech Connect

    Jyegal, Jang

    2015-06-15

    Velocity overshoot is a critically important nonstationary effect utilized for the enhanced performance of submicron field-effect devices fabricated with high-electron-mobility compound semiconductors. However, the physical mechanisms of velocity overshoot decay dynamics in the devices are not known in detail. Therefore, a numerical analysis is conducted typically for a submicron GaAs metal-semiconductor field-effect transistor in order to elucidate the physical mechanisms. It is found that there exist three different mechanisms, depending on device bias conditions. Specifically, at large drain biases corresponding to the saturation drain current (dc) region, the velocity overshoot suddenly begins to drop very sensitively due to the onset of a rapid decrease of the momentum relaxation time, not the mobility, arising from the effect of velocity-randomizing intervalley scattering. It then continues to drop rapidly and decays completely by severe mobility reduction due to intervalley scattering. On the other hand, at small drain biases corresponding to the linear dc region, the velocity overshoot suddenly begins to drop very sensitively due to the onset of a rapid increase of thermal energy diffusion by electrons in the channel of the gate. It then continues to drop rapidly for a certain channel distance due to the increasing thermal energy diffusion effect, and later completely decays by a sharply decreasing electric field. Moreover, at drain biases close to a dc saturation voltage, the mechanism is a mixture of the above two bias conditions. It is suggested that a large secondary-valley energy separation is essential to increase the performance of submicron devices.

  18. Acute effects of deltamethrin on swimming velocity and biomarkers of the common prawn Palaemon serratus.

    PubMed

    Oliveira, Cristiana; Almeida, Joana; Guilhermino, Lúcia; Soares, Amadeu M V M; Gravato, Carlos

    2012-11-15

    The main purpose of the present study was to investigate the effects of deltamethrin on biomarkers and behavior of Palaemon serratus (common prawn), since this attempt to link different levels of biological organization will allow determining which biomarkers might be ecologically relevant and will be useful to complement the information about the effects of pesticides by using behavioral parameters. Therefore, parameters of liver antioxidant status, energy metabolism and neurotransmission were determined in different tissues of the common prawn and used to assess the effects at sub-individual level, whereas swimming velocity was used to assess the effects at the individual level. It was also investigated if the swimming velocity can be used as an endpoint in ecotoxicology bioassays and if it can be as sensitive as biomarker endpoints. Swimming velocity was significantly reduced in prawns exposed to deltamethrin, showing a lowest observed effect (LOEC) of 0.6 ng L(-1). Eye acetylcholinesterase (AChE) activity was significantly increased in prawns exposed to 0.6, 1.2 and 2.4 ng L(-1) deltamethrin, whereas muscle cholinesterase (ChE) activity was significantly increased in prawns exposed to 19 and 39 ng L(-1). On the other hand, lactate dehydrogenase (LDH) activity was significantly increased in muscle of prawns exposed to 0.6, 1.2, 2.4, 4.9 ng L(-1) deltamethrin, showing that organisms were requiring additional energy, but probably using it for detoxification processes rather than locomotion, since swimming velocity was inhibited. Glutathione S-transferase (GST) activity was significantly increased in the digestive gland of common prawn exposed to 19 and 39 ng L(-1) deltamethrin. Catalase (CAT) activity was significantly increased in digestive gland of prawn exposed to 19 ng L(-1) deltamethrin. However, CAT activity decreased in digestive gland of prawn exposed to 39 ng L(-1), suggesting an antioxidant defense system failure concomitant with high levels of lipid

  19. Effect of Cutting Velocity / Stem Size on the Efficiency of NRCRI Cassave Stem Cutting Machine

    NASA Astrophysics Data System (ADS)

    Ikejiofor, M. C.

    2012-11-01

    The developed NRCRI (National Root Crops Research Institute) cassava stem cutting machine was evaluated. The cassava stems from the variety TME 419 were used. The sizes of the stem used were 1.8, 2.0, 2.3 and 2.6cm. Also, different cutting velocities of 1.20, 1.23 and 1.32m/s were used. The stakes produced has length of 2.5cm. Analysis of variance in RCBD was used to evaluate the effect of the cutting velocity and the stem size on the efficiency of the cutting machine. The result of the analysis showed that the cutting velocity had very highly significant effect, while the stem size had no significant effect at 5% level on the efficiency of the cutting machine. The data obtained also showed that the highest and least cutting efficiencies of 99.42 and 94.71% were obtained with the machine cutting velocities of 1.2 and 1.32m/s respectively.

  20. Effects on health of air pollution: a narrative review.

    PubMed

    Mannucci, Pier Mannuccio; Harari, Sergio; Martinelli, Ida; Franchini, Massimo

    2015-09-01

    Air pollution is a complex and ubiquitous mixture of pollutants including particulate matter, chemical substances and biological materials. There is growing awareness of the adverse effects on health of air pollution following both acute and chronic exposure, with a rapidly expanding body of evidence linking air pollution with an increased risk of respiratory (e.g., asthma, chronic obstructive pulmonary disease, lung cancer) and cardiovascular disease (e.g., myocardial infarction, heart failure, cerebrovascular accidents). Elderly subjects, pregnant women, infants and people with prior diseases appear especially susceptible to the deleterious effects of ambient air pollution. The main diseases associated with exposure to air pollutants will be summarized in this narrative review.

  1. Effects of Run-Up Velocity on Performance, Kinematics, and Energy Exchanges in The Pole Vault

    PubMed Central

    Linthorne, Nicholas P.; Weetman, A. H. Gemma

    2012-01-01

    This study examined the effect of run-up velocity on the peak height achieved by the athlete in the pole vault and on the corresponding changes in the athlete's kinematics and energy exchanges. Seventeen jumps by an experienced male pole vaulter were video recorded in the sagittal plane and a wide range of run-up velocities (4.5-8.5 m/s) was obtained by setting the length of the athlete's run-up (2-16 steps). A selection of performance variables, kinematic variables, energy variables, and pole variables were calculated from the digitized video data. We found that the athlete's peak height increased linearly at a rate of 0.54 m per 1 m/s increase in run-up velocity and this increase was achieved through a combination of a greater grip height and a greater push height. At the athlete's competition run-up velocity (8.4 m/s) about one third of the rate of increase in peak height arose from an increase in grip height and about two thirds arose from an increase in push height. Across the range of run-up velocities examined here the athlete always performed the basic actions of running, planting, jumping, and inverting on the pole. However, he made minor systematic changes to his jumping kinematics, vaulting kinematics, and selection of pole characteristics as the run-up velocity increased. The increase in run-up velocity and changes in the athlete's vaulting kinematics resulted in substantial changes to the magnitudes of the energy exchanges during the vault. A faster run-up produced a greater loss of energy during the take-off, but this loss was not sufficient to negate the increase in run-up velocity and the increase in work done by the athlete during the pole support phase. The athlete therefore always had a net energy gain during the vault. However, the magnitude of this gain decreased slightly as run-up velocity increased. Key pointsIn the pole vault the optimum technique is to run-up as fast as possible.The athlete's vault height increases at a rate of about 0.5 m

  2. Effects of run-up velocity on performance, kinematics, and energy exchanges in the pole vault.

    PubMed

    Linthorne, Nicholas P; Weetman, A H Gemma

    2012-01-01

    This study examined the effect of run-up velocity on the peak height achieved by the athlete in the pole vault and on the corresponding changes in the athlete's kinematics and energy exchanges. Seventeen jumps by an experienced male pole vaulter were video recorded in the sagittal plane and a wide range of run-up velocities (4.5-8.5 m/s) was obtained by setting the length of the athlete's run-up (2-16 steps). A selection of performance variables, kinematic variables, energy variables, and pole variables were calculated from the digitized video data. We found that the athlete's peak height increased linearly at a rate of 0.54 m per 1 m/s increase in run-up velocity and this increase was achieved through a combination of a greater grip height and a greater push height. At the athlete's competition run-up velocity (8.4 m/s) about one third of the rate of increase in peak height arose from an increase in grip height and about two thirds arose from an increase in push height. Across the range of run-up velocities examined here the athlete always performed the basic actions of running, planting, jumping, and inverting on the pole. However, he made minor systematic changes to his jumping kinematics, vaulting kinematics, and selection of pole characteristics as the run-up velocity increased. The increase in run-up velocity and changes in the athlete's vaulting kinematics resulted in substantial changes to the magnitudes of the energy exchanges during the vault. A faster run-up produced a greater loss of energy during the take-off, but this loss was not sufficient to negate the increase in run-up velocity and the increase in work done by the athlete during the pole support phase. The athlete therefore always had a net energy gain during the vault. However, the magnitude of this gain decreased slightly as run-up velocity increased. Key pointsIn the pole vault the optimum technique is to run-up as fast as possible.The athlete's vault height increases at a rate of about 0.5 m

  3. The importance of vertical velocity variability for estimates of the indirect aerosol effects

    NASA Astrophysics Data System (ADS)

    West, R. E. L.; Stier, P.; Jones, A.; Johnson, C. E.; Mann, G. W.; Bellouin, N.; Partridge, D. G.; Kipling, Z.

    2014-06-01

    The activation of aerosols to form cloud droplets is dependent upon vertical velocities whose local variability is not typically resolved at the GCM grid scale. Consequently, it is necessary to represent the subgrid-scale variability of vertical velocity in the calculation of cloud droplet number concentration. This study uses the UK Chemistry and Aerosols community model (UKCA) within the Hadley Centre Global Environmental Model (HadGEM3), coupled for the first time to an explicit aerosol activation parameterisation, and hence known as UKCA-Activate. We explore the range of uncertainty in estimates of the indirect aerosol effects attributable to the choice of parameterisation of the subgrid-scale variability of vertical velocity in HadGEM-UKCA. Results of simulations demonstrate that the use of a characteristic vertical velocity cannot replicate results derived with a distribution of vertical velocities, and is to be discouraged in GCMs. This study focuses on the effect of the variance (σw2) of a Gaussian pdf (probability density function) of vertical velocity. Fixed values of σw (spanning the range measured in situ by nine flight campaigns found in the literature) and a configuration in which σw depends on turbulent kinetic energy are tested. Results from the mid-range fixed σw and TKE-based configurations both compare well with observed vertical velocity distributions and cloud droplet number concentrations. The radiative flux perturbation due to the total effects of anthropogenic aerosol is estimated at -1.9 W m-2 with σw = 0.1 m s-1, -2.1 W m-2 with σw derived from TKE, -2.25 W m-2 with σw = 0.4 m s-1, and -2.3 W m-2 with σw = 0.7 m s-1. The breadth of this range is 0.4 W m-2, which is comparable to a substantial fraction of the total diversity of current aerosol forcing estimates. Reducing the uncertainty in the parameterisation of σw would therefore be an important step towards reducing the uncertainty in estimates of the indirect aerosol effects

  4. Resolution and Smoothing Effect of Tomogram and Their Impact on Computational Velocity Estimation

    NASA Astrophysics Data System (ADS)

    Song, D.; Keehm, Y.

    2008-12-01

    Pore microstructure and pore-scale simulations have been used to understand physical properties of rocks and their interrelations. Pore microstructures are typically obtained from the X-ray tomographic technique, and we can obtain up to one micron spatial resolution from high-resolution scanning facilities. Though the accuracy of pore-scale simulations depends on grain size distribution, transport properties (permeability and electrical conductivity) can be accurately estimated with current spatial resolution and are recently used widely in many applications. However, the elastic properties can be problematic, because they are sensitive to grain contact areas, which are very difficult to resolve accurately by tomography. In this paper, we are presenting results on the effect of resolution and smoothing of tomogram on pore-scale velocity calculation. We used three different rocks: 17%-porosity sandstone from offshore Korea; 23%-porosity Aztec sandstone; and 42%-porosity beach sand. Three dimensional microstructures were obtained from different high-resolution scan facilities with different resolutions. We found that the resolution of tomogram highly affect velocity estimation from FEM elastic simulation. Two-micron spatial resolution is sometimes not enough to resolve the contact areas between 200-micron grains. Especially for high porosity sandstone, the calculated velocity was overestimated by tens of percent. In addition, smoothing effect from image processing on tomogram acquisition can cause non-negligible velocity overestimation; however, this effect is smaller than that from resolution and can be corrected by anti-smoothing filtering techniques. In conclusion, care should be taken to estimate the velocity of unconsolidated or high-porosity sandstone from pore-scale simulation and smoothing effect is also investigated more carefully.

  5. CHARACTERIZATION OF AN AQUITARD AND DIRECT DETECTION OF LNAPL AT HILL AIR FORCE BASE USING GPR AVO AND MIGRATION VELOCITY ANALYSES

    SciTech Connect

    Deeds, Jake; Bradford, John

    2002-06-01

    Large quantities of non-aqueous phase liquids (NAPL), contaminate the near surface sediments at Operable Unit 1 (OU1), Hill Air Force Base (HAFB), Utah. In October 2000, a 3D, multi-offset GPR survey was acquired at OU1 with two objectives: (1) to image the aquifer/aquitard boundary at a depth of about 30 ft, and (2) to evaluate quantitative processing and interpretation methodologies for direct detection of NAPL. Using pre-stack depth migration, we map the aquitard boundary to about {+-} 1 ft throughout the survey area. An unusual reflection is identified within the vadose zone that does not correlate with known geology. The region below this reflection has anomalously high velocity, implying low electric permittivity, and the amplitude of the anomalous reflection deviates significantly from the background AVO trend. Fitting the Fresnel equation to the AVO data, we estimate the velocity contrast at the anomaly boundary and find that it is in good agreement with the migration velocity model. We interpret the anomaly as a previously unidentified NAPL rich zone. Subsequent coring and chemical analyses verify our interpretation. This exciting result implies that these methodologies may be useful for direct detection of NAPL at other HAFB locations and at sites with similar hydrogeology.

  6. Effects of ankle exercise combined with deep breathing on blood flow velocity in the femoral vein.

    PubMed

    Kwon, Oh-Yun; Jung, Do-Young; Kim, Young; Cho, Sang-Hyun; Yi, Chung-Hwi

    2003-01-01

    Ankle exercises are commonly used to facilitate venous return in the lower extremity and to prevent deep vein thrombosis. Moreover, the respiratory cycle affects venous return. This study examined the effects of ankle exercise combined with deep breathing on the blood flow velocity in the femoral vein. Twenty healthy males (mean age 21.3 years), who had no medical history of lower extremity disease, were recruited for this study. The blood flow velocity in the femoral vein was measured while performing four exercise protocols: quiet breathing while resting (QR), deep breathing (DB), ankle exercise with quiet breathing (AQB), and ankle exercising combined with deep breathing (ADB). Using a Doppler ultrasound with an 8 MHz probe, peak blood flow velocities were collected for a 20 second period at the start of the inspiration phase in each protocol, three times. There were statistically significant differences in the peak blood flow velocity in the femoral vein with the four protocols (p lt 0.001). The mean (SD) peak blood flow velocity in the femoral vein was as follows: QR 10.1 (4.2) cm/sec, DB 15.5 (3.9) cm/sec, AQB 20.7 (6.6) cm/sec, and ADB 26.5 (9.4) cm/sec. Post hoc analyses revealed significant differences between each of the four protocols (p(adj) lt 0.01). The mean peak blood flow velocity in the femoral vein was greatest with the ADB protocol, which implies that the ADB protocol may be useful to prevent the blood stasis in patients at risk of deep vein thrombosis.

  7. Effects of Air Pollutants on Childhood Asthma

    PubMed Central

    Kim, Jeong-Hee; Kim, Ja-Kyoung; Son, Byong-Kwan; Oh, Ji-Eun; Lee, Kwan-Hee; Hong, Youn-Chol; Cho, Sung-Il

    2005-01-01

    Epidemiologic studies have suggested the association between environmental exposure to volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) and the increased risk of incurring asthma. Yet there is little data regarding the relationship between personal exposure to air pollution and the incidence of asthma in children. This study was designed to evaluate the effect of exposure to air pollution on children with asthma by using exposure biomarkers. We assessed the exposure level to VOCs by measuring urinary concentrations of hippuric acid and muconic acid, and PAHs by 1-OH pyrene and 2-naphthol in 30 children with asthma and 30 children without asthma (control). The mean level of hippuric acid was 0.158 ± 0.169 µmol/mol creatinine in the asthma group and 0.148 ± 0.249 µmol/mol creatinine in the control group, with no statistical significance noted (p=0.30). The mean concentration of muconic acid was higher in the asthma group than in the control group (7.630 ± 8.915 µmol/mol creatinine vs. 3.390 ± 4.526 µmol/mol creatinine p=0.01). The mean level of urinary 1-OHP was higher in the asthma group (0.430 ± 0.343 µmol/mol creatinine) than the control group (0.239 ± 0.175 µmol/mol creatinine), which was statistically significant (p=0.03). There was no difference in the mean concentration of 2-NAP between the two groups (9.864 ± 10.037 µmol/mol in the asthma group vs. 9.157 ± 9.640 µmol/mol in the control group, p=0.96). In conclusion, this study suggests that VOCs and PAHs have some role in asthma. PMID:15861497

  8. Thermally developing MHD peristaltic transport of nanofluids with velocity and thermal slip effects

    NASA Astrophysics Data System (ADS)

    Sher Akbar, Noreen; Bintul Huda, A.; Tripathi, D.

    2016-09-01

    We investigate the velocity slip and thermal slip effects on peristaltically driven thermal transport of nanofluids through the vertical parallel plates under the influence of transverse magnetic field. The wall surface is propagating with sinusoidal wave velocity c. The flow characteristics are governed by the mass, momentum and energy conservation principle. Low Reynolds number and large wavelength approximations are taken into consideration to simplify the non-linear terms. Analytical solutions for axial velocity, temperature field, pressure gradient and stream function are obtained under certain physical boundary conditions. Two types of nanoparticles, SiO2 and Ag, are considered for analysis with water as base fluid. This is the first article in the literature that discusses the SiO2 and Ag nanoparticles for a peristaltic flow with variable viscosity. The effects of physical parameters on velocity, temperature, pressure and trapping are discussed. A comparative study of SiO2 nanofluid, Ag nanofluid and pure water is also presented. This model is applicable in biomedical engineering to make thermal peristaltic pumps and other pumping devices like syringe pumps, etc. It is observed that pressure for pure water is maximum and pressure for Ag nanofluid is minimum.

  9. Effects of Interior Velocity Models and Scattering Structure on the Coda Decay Properties of Seismic Signals

    NASA Astrophysics Data System (ADS)

    Blanchette-guertin, J.; Johnson, C. L.; Lawrence, J. F.

    2013-12-01

    We investigate the effects of scattering on the coda rise and decay times of synthetic seismic signals using an adapted version of the seismic phonon method. We examine the amplitudes and dependence on epicentral distance of decay times for a range of interior models with 1D velocity structure as well as intrinsic attenuation that can be specified as a function of depth and frequency. Scattering is 3D, assuming longitudinal symmetry, and occurs globally within layer(s) of prescribed thickness. Scatterers within the layer(s) have random orientations, defined length-scales distributions (distance between scatterers), and random velocity and density perturbations within a prescribed range. We demonstrate that variations in the signal's coda decay attributes can be analyzed to assess the first-order structural properties of highly scattering bodies such as Earth's moon. The variation of decay time with epicentral distance is most affected by the event source depth (surface impact vs. deep event), the frequency content, the background velocity model and intrinsic attenuation. On the other hand, the magnitude of the decay times is controlled by the size-frequency distribution of scatterers, the thickness and location of the scattering layer(s) and the presence of a low velocity layer. We use this new understanding of the effects of interior scattering structure on coda decay times to examine suites of lunar interior models that produce rise and decay characteristics similar to those observed in the Apollo Passive Seismic Experiment data.

  10. Health effects of particulate air pollution: time for reassessment?

    PubMed Central

    Pope, C A; Bates, D V; Raizenne, M E

    1995-01-01

    Numerous studies have observed health effects of particulate air pollution. Compared to early studies that focused on severe air pollution episodes, recent studies are more relevant to understanding health effects of pollution at levels common to contemporary cities in the developed world. We review recent epidemiologic studies that evaluated health effects of particulate air pollution and conclude that respirable particulate air pollution is likely an important contributing factor to respiratory disease. Observed health effects include increased respiratory symptoms, decreased lung function, increased hospitalizations and other health care visits for respiratory and cardiovascular disease, increased respiratory morbidity as measured by absenteeism from work or school or other restrictions in activity, and increased cardiopulmonary disease mortality. These health effects are observed at levels common to many U.S. cities including levels below current U.S. National Ambient Air Quality Standards for particulate air pollution. Images Figure 1. PMID:7656877

  11. Error estimations of dry deposition velocities of air pollutants using bulk sea surface temperature under common assumptions

    NASA Astrophysics Data System (ADS)

    Lan, Yung-Yao; Tsuang, Ben-Jei; Keenlyside, Noel; Wang, Shu-Lun; Arthur Chen, Chen-Tung; Wang, Bin-Jye; Liu, Tsun-Hsien

    2010-07-01

    It is well known that skin sea surface temperature (SSST) is different from bulk sea surface temperature (BSST) by a few tenths of a degree Celsius. However, the extent of the error associated with dry deposition (or uptake) estimation by using BSST is not well known. This study tries to conduct such an evaluation using the on-board observation data over the South China Sea in the summers of 2004 and 2006. It was found that when a warm layer occurred, the deposition velocities using BSST were underestimated within the range of 0.8-4.3%, and the absorbed sea surface heat flux was overestimated by 21 W m -2. In contrast, under cool skin only conditions, the deposition velocities using BSST were overestimated within the range of 0.5-2.0%, varying with pollutants and the absorbed sea surface heat flux was underestimated also by 21 W m -2. Scale analysis shows that for a slightly soluble gas (e.g., NO 2, NO and CO), the error in the solubility estimation using BSST is the major source of the error in dry deposition estimation. For a highly soluble gas (e.g., SO 2), the error in the estimation of turbulent heat fluxes and, consequently, aerodynamic resistance and gas-phase film resistance using BSST is the major source of the total error. In contrast, for a medium soluble gas (e.g., O 3 and CO 2) both the errors from the estimations of the solubility and aerodynamic resistance are important. In addition, deposition estimations using various assumptions are discussed. The largest uncertainty is from the parameterizations for chemical enhancement factors. Other important areas of uncertainty include: (1) various parameterizations for gas-transfer velocity; (2) neutral-atmosphere assumption; (3) using BSST as SST, and (4) constant pH value assumption.

  12. Effects of fluid pressures to the seismic velocity of crustal rocks

    NASA Astrophysics Data System (ADS)

    Harada, Y.; Katayama, I.

    2012-12-01

    pressure of 200. These values are lower than Christensen (1996)'s experiments (Vp = 6.246 km/s, Vs = 3.669 km/s), but from the measurement of both compression and decompression process, it is confirmed that velocity variation has the reproducibility and there is an effect depending on cracks or pores closed by high confining pressure. Under wet experiments, at first, permeable time of water was measured. We found that water completely percolates into the sample around eight hours. Next, velocities of granite were measured up to confining pressure and pore pressure as high as 120 and 100 MPa (effecting pressure of 20 MPa). At confining pressure of 20 MPa before raising pore pressure, velocities were Vp = 5.414 km/s and Vs = 3.091 km/s. After confining pressure and pore pressure increased to 40 and 20 MPa, Vp was significantly increased to 5.869 km/s, while Vs was slightly changed to 3.124 km/s. Poisson's ratio was increased from 0.258 to 0.302. After the pore fluid penetrates homogeneously into the samples, both velocities were little change and became nearly constant values. These variations are similar to previous experiments (e.g., Saito, 1987). However, under high pore pressure, signal from the sample reflection is very weak and therefore these values may have large uncertainty. We try to fix this issue and hope to present the effect of pore pressure on seismic velocity in the coming AGU meeting.

  13. Constraining the relative velocity effect using the Baryon Oscillation Spectroscopic Survey

    DOE PAGES

    Beutler, Florian; Seljak, Uroš; Vlah, Zvonimir

    2017-05-16

    Here, we analyse the power spectrum of the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 to constrain the relative velocity effect, which represents a potential systematic for measurements of the baryon acoustic oscillation (BAO) scale. The relative velocity effect is sourced by the different evolution of baryon and cold dark matter perturbations before decoupling. Our power spectrum model includes all one-loop redshift-space terms corresponding to vbc parametrized by the bias parameter bmore » $$2\\atop{v}$$ . We also include the linear terms proportional to the relative density, δbc, and relative velocity dispersion, θbc, which we parametrize with the bias parameters b$$bc\\atop{δ}$$ and b$$bc\\atop{θ}$$. This data does not support a detection of the relative velocity effect in any of these parameters. Combining the low- and high-redshift bins of BOSS, we find limits of b$$2\\atop{v}$$=0.012±0.015(±0.031) , b$$bc\\atop{δ}$$=-1.0±2.5(±6.2) and b$$bc\\atop{θ}$$=-114±55(±175) with 68 percent (95 percent) confidence levels. These constraints restrict the potential systematic shift in DA(z), H(z) and fσ8, due to the relative velocity, to 1 percent, 0.8 percent and 2 percent, respectively. Given the current uncertainties on the BAO measurements of BOSS, these shifts correspond to 0.53σ, 0.5σ and 0.22σ for DA(z), H(z) and fσ8, respectively.« less

  14. Constraining the relative velocity effect using the Baryon Oscillation Spectroscopic Survey

    NASA Astrophysics Data System (ADS)

    Beutler, Florian; Seljak, Uroš; Vlah, Zvonimir

    2017-09-01

    We analyse the power spectrum of the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 to constrain the relative velocity effect, which represents a potential systematic for measurements of the baryon acoustic oscillation (BAO) scale. The relative velocity effect is sourced by the different evolution of baryon and cold dark matter perturbations before decoupling. Our power spectrum model includes all one-loop redshift-space terms corresponding to vbc parametrized by the bias parameter bv2. We also include the linear terms proportional to the relative density, δbc, and relative velocity dispersion, θbc, which we parametrize with the bias parameters b^bc_{δ } and b^bc_{θ }. Our data does not support a detection of the relative velocity effect in any of these parameters. Combining the low- and high-redshift bins of BOSS, we find limits of bv2 = 0.012 ± 0.015 (± 0.031), b^bc_{δ } = -1.0 ± 2.5 (± 6.2) and b^bc_{θ } = -114 ± 55 (± 175) with 68 per cent (95 per cent) confidence levels. These constraints restrict the potential systematic shift in DA(z), H(z) and fσ8, due to the relative velocity, to 1 per cent, 0.8 per cent and 2 per cent, respectively. Given the current uncertainties on the BAO measurements of BOSS, these shifts correspond to 0.53σ, 0.5σ and 0.22σ for DA(z), H(z) and fσ8, respectively.

  15. Effect of CO2 hydrate formation on seismic wave velocities of fine-grained sediments

    NASA Astrophysics Data System (ADS)

    Kim, Hak-Sung; Cho, Gye-Chun; Kwon, Tae-Hyuk

    2013-06-01

    study examines the effect of gas hydrate formation on seismic wave velocities of fine-grained sediments. Synthesis of gas hydrates in fine-grained sediments has proved to be challenging, and how hydrate formation would affect the seismic wave velocities and stiffness of clay-rich sediments has not yet been fully understood. In this study, CO2 hydrate was synthesized in remolded and partially water-saturated clayey silt sediments that were originally cored from a hydrate occurrence region in the Ulleung Basin, East Sea, offshore Korea. After achieving excess water conditions, compressional wave and shear wave velocities were measured for different hydrate saturations and under different vertical effective stresses. The results reveal that the compressional wave velocity VP and shear wave velocity VS increase, and the stress-dependency of VP and VS decreases as the hydrate saturation SH increases from 0% to ~60%. In particular, the VS-SH trend lies between the grain-cementing model and the load-bearing model, suggesting that gas hydrate formation in clayey silt sediments causes weak cementation from a hydrate saturation less than ~28%. The weak cementation in fine-grained sediments can be explained by the breakage of hydrate bonds that are cementing grains during sediment compression and/or the innate weakness in bonding between hydrate crystals and fine mineral grains owing to the presence of unfrozen water films on clay mineral surfaces. In addition, it is found that at low SH, the cementation effect on VP is masked by the high stiffness of pore-filling phases, but it becomes pronounced at SH greater than 47%.

  16. Laboratory measurement of saltating sand particles' angular velocities and simulation of its effect on saltation trajectory

    NASA Astrophysics Data System (ADS)

    Xie, Li; Ling, Yuquan; Zheng, Xiaojing

    2007-06-01

    This paper reports a laboratory observation of spin attitudes and angular velocities of saltating sand particles in wind-blown sand flux by using the high-speed and dynamic cinecamera and presents a numerical simulation to show the effect of spin on the saltating trajectories of sand particles. Experiment results show that a saltating sand particle has two basic spin attitudes, rolling spin (Ωx, which is perpendicularity to wind direction and parallel with sand surface) and left/right spin. The percentages of the former and the latter attitude are 5% and 95%, respectively. The left/right spin angular velocities range from 0 revolutions per second ("rev/s" henceforth) to 800 rev/s and obey a single-peaked distribution, the peak value of which lies in (150 rev/s, 250 rev/s). The rolling spin angular velocity of a saltation sand particle is variational along its entire saltating trajectory. The left/right spin vector is composed of two spin components, Ωy (called lateral spin component, rotating around the wind direction) and Ωz (called up spin component, rotating around the axis perpendicular to the sand bed). The theoretical simulation indicates that lateral and up spin components not only have effects on the trajectories' scales (i.e., heights and lengths) but also have effects on the trajectories' dimensions, especially when they are higher than 2000 rev/s and 200 rev/s, respectively. While the rolling spin angular velocities only change the trajectories' heights and lengths, especially for the rolling angular velocity higher than 300 rev/s.

  17. Extraordinary Hall effect in Kondo-type systems: Contributions from anomalous velocity

    NASA Astrophysics Data System (ADS)

    Levy, P. M.

    1988-10-01

    Kondo systems exhibit a relatively large extraordinary Hall effect which is due to asymmetric resonant scattering of conduction electrons. Theories based on the skew scattering mechanism account for data at high temperatures T>TK (the Kondo temperature) but are unable to explain the very-low-temperature variation of the Hall constant observed in heavy-fermion compounds. Aside from the ordinary Hall effect, caused by the Lorentz force and skew scattering (which makes the scattering probability antisymmetric with respect to interchange of scattering vectors), there exists an additional contribution to the Hall effect known as the anomalous-velocity contribution. This contribution is due to a change in the expression for the current operator in the presence of spin-orbit forces. We derive an expression for the anomalous velocity in terms of the T matrices describing conduction-electron scattering; it is not limited to weak spin-orbit scattering as were previous results. We use the Anderson model of local moments in metals to write this scattering in terms of the mixing interaction between local and conduction electrons, and the local state's Green's function. The transverse Hall current due to anomalous velocity is determined and evaluated in two limits. At high temperature, we use the weak-coupling form of the local state's Green's function; at T=0 K a phase-shift analysis is used, and we rely on the Friedel-Langreth sum rule to give us the phase shift at the Fermi surface. At high temperatures we find that the contribution from anomalous velocity to the Hall constant is quite small compared to that from skew scattering. On the contrary, at low temperatures the anomalous velocity makes the dominant contribution to the Hall constant in Kondo systems.

  18. Characteristics of Air Core and Surface Velocity for Water Flow in a Vortex Sediment-Extraction Chamber Measured by Using Photo Images and PTV Technique.

    NASA Astrophysics Data System (ADS)

    Yao, Hou Chang; Chyan Deng, Jan; Chao, Hsu Yu; Chih Yuan, Yang

    2017-04-01

    A vortex sediment-extraction chamber, consisted of cylindrical chamber, inflow system, bottom orifice and overflow weir, is used to separate sediment from sediment-laden water flow. A tangential inflow is introduced into a cylindrical chamber with a bottom orifice; thus, a strong vortex flow is produced there. Under actions of gravity and centrifugal force, heavier sediment particles are forced to move towards the bottom orifice, and relatively clear water flows over through the top overflow weir. The flow field in the cylindrical chamber consists of forced vortex and free vortex. When the bottom orifice is opened during the sediment-extraction process, an air core appears and changes with different settings. In this study, the air core and water surface velocity in the cylindrical chamber were measured by using a photo image process and particle tracking velocimetry (PTV), as well as numerically simulated by using a commercial software, Flow-3D.Laboratory experiments were conducted in a vortex chamber, having height of 130 cm and diameter of 48 cm. Five kinds of bottom orifice size from 1.0 cm to 3.0 cm and four kinds of inflow water discharge from 1,300cm3/s to 1,700 cm3/s were used while the inflow pipe of 3 cm in diameter was kept the same for all experiments. The characteristics of the air core and water surface velocity, and the inflow and outflow ratios under different experimental arrangements were observed and discussed so as to provide a better design and application for a vortex sediment-extraction chamber in the future.

  19. Elastic-wave velocity in marine sediments with gas hydrates: Effective medium modeling

    USGS Publications Warehouse

    Helgerud, M.B.; Dvorkin, J.; Nur, A.; Sakai, A.; Collett, T.

    1999-01-01

    We offer a first-principle-based effective medium model for elastic-wave velocity in unconsolidated, high porosity, ocean bottom sediments containing gas hydrate. The dry sediment frame elastic constants depend on porosity, elastic moduli of the solid phase, and effective pressure. Elastic moduli of saturated sediment are calculated from those of the dry frame using Gassmann's equation. To model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions: (a) hydrate modifies the pore fluid elastic properties without affecting the frame; (b) hydrate becomes a component of the solid phase, modifying the elasticity of the frame. The goal of the modeling is to predict the amount of hydrate in sediments from sonic or seismic velocity data. We apply the model to sonic and VSP data from ODP Hole 995 and obtain hydrate concentration estimates from assumption (b) consistent with estimates obtained from resistivity, chlorinity and evolved gas data. Copyright 1999 by the American Geophysical Union.

  20. The electromagnetic effect on the critical ionization velocity process. [in earth atmosphere

    NASA Technical Reports Server (NTRS)

    Machida, S.; Goertz, C. K.

    1988-01-01

    Electromagnetic effects on the critical ionization velocity (CIV) process become important when the neutral gas velocity V(n) exceeds the local Alfven speed V(A). The electron heating due to unstable lower hybrid waves necessary for CIV still occurs, but the efficiency of the electron heating is significantly reduced when the electromagnetic effect comes into play. This is verified by a series of simulation runs using two-dimensional electromagnetic particle code combined with PANIC. The significance of the electromagnetic effects for the occurrence of CIV in the comet-solar wind interaction and other space phenomena is briefly discussed. It is found that the comet environment is marginal for the excitation of CIV.

  1. Group velocity effect on resonant, long-range wake-fields in slow wave structures

    NASA Astrophysics Data System (ADS)

    Smirnov, A. V.

    2002-03-01

    Synchronous wake-fields in a dispersive waveguide are derived in a general explicit form on the basis of a rigorous electro-dynamical approach using Fourier transformations. The fundamental role of group velocity in wake-field propagation, calculation of attenuation, amplitudes, form-factors and loss-factors is analyzed for single bunch radiation. Adiabatic tapering of the waveguide and bunch density variation is taken into account analytically for the time-domain fields. Effects of field "compression/expansion" and group delays are demonstrated. The role of these effects is discussed for single bunch wake-fields, transient beam loading, BBU and HOMs. A novel waveguide structure with central rf coupling and both positive and negative velocities is proposed. It can be used effectively in both high-energy accelerators and single-section linacs.

  2. Air plasma effect on dental disinfection

    SciTech Connect

    Duarte, S.; Murata, R. M.; Saxena, D.; Kuo, S. P.; Chen, C. Y.; Huang, K. J.; Popovic, S.

    2011-07-15

    A nonthermal low temperature air plasma jet is characterized and applied to study the plasma effects on oral pathogens and biofilms. Experiments were performed on samples of six defined microorganisms' cultures, including those of gram-positive bacteria and fungi, and on a cultivating biofilm sample of Streptococcus mutans UA159. The results show that the plasma jet creates a zone of microbial growth inhibition in each treated sample; the zone increases with the plasma treatment time and expands beyond the entire region directly exposed to the plasma jet. With 30s plasma treatment twice daily during 5 days of biofilm cultivation, its formation was inhibited. The viability of S. mutans cells in the treated biofilms dropped to below the measurable level and the killed bacterial cells concentrated to local regions as manifested by the fluorescence microscopy via the environmental scanning electron microscope. The emission spectroscopy of the jet indicates that its plasma effluent carries an abundance of reactive atomic oxygen, providing catalyst for the observed plasma effect.

  3. Air plasma effect on dental disinfection

    NASA Astrophysics Data System (ADS)

    Duarte, S.; Kuo, S. P.; Murata, R. M.; Chen, C. Y.; Saxena, D.; Huang, K. J.; Popovic, S.

    2011-07-01

    A nonthermal low temperature air plasma jet is characterized and applied to study the plasma effects on oral pathogens and biofilms. Experiments were performed on samples of six defined microorganisms' cultures, including those of gram-positive bacteria and fungi, and on a cultivating biofilm sample of Streptococcus mutans UA159. The results show that the plasma jet creates a zone of microbial growth inhibition in each treated sample; the zone increases with the plasma treatment time and expands beyond the entire region directly exposed to the plasma jet. With 30s plasma treatment twice daily during 5 days of biofilm cultivation, its formation was inhibited. The viability of S. mutans cells in the treated biofilms dropped to below the measurable level and the killed bacterial cells concentrated to local regions as manifested by the fluorescence microscopy via the environmental scanning electron microscope. The emission spectroscopy of the jet indicates that its plasma effluent carries an abundance of reactive atomic oxygen, providing catalyst for the observed plasma effect.

  4. Measurement of Off-Body Velocity, Pressure, and Temperature in an Unseeded Supersonic Air Vortex by Stimulated Raman Scattering

    NASA Technical Reports Server (NTRS)

    Herring, Gregory C.

    2008-01-01

    A noninvasive optical method is used to make time-averaged (30 sec) off-body measurements in a supersonic airflow. Seeding of tracer particles is not required. One spatial component of velocity, static pressure, and static temperature are measured with stimulated Raman scattering. The three flow parameters are determined simultaneously from a common sample volume (0.3 by 0.3 by 15 mm) using concurrent measurements of the forward and backward scattered line shapes of a N2 vibrational Raman transition. The capability of this technique is illustrated with laboratory and large-scale wind tunnel testing that demonstrate 5-10% measurement uncertainties. Because the spatial resolution of the present work was improved to 1.5 cm (compared to 20 cm in previous work), it was possible to demonstrate a modest one-dimensional profiling of cross-flow velocity, pressure, and translational temperature through the low-density core of a stream-wise vortex (delta-wing model at Mach 2.8 in NASA Langley's Unitary Plan Wind Tunnel).

  5. Investigations into the Effect of Current Velocity on Amidoxime-Based Polymeric Uranium Adsorbent Performance

    SciTech Connect

    Gill, Gary A.; Kuo, Li-Jung; Strivens, Jonathan E.; Wood, Jordana R.; Schlafer, Nicholas J.; Tsouris, Costas; Ladshaw, Austin; Yiacoumi, Sotira

    2015-12-01

    The Fuel Resources Program at the U.S. Department of Energy’s (DOE), Office of Nuclear Energy (DOE-NE) is developing adsorbent technology to extract uranium from seawater. This technology is being developed to provide a sustainable and economically viable supply of uranium fuel for nuclear reactors (DOE, 2010). Among the key environmental variables to understand for adsorbent deployment in the coastal ocean is what effect flow-rates or linear velocity has on uranium adsorption capacity. The goal is to find a flow conditions that optimize uranium adsorption capacity in the shortest exposure time. Understanding these criteria will be critical in choosing a location for deployment of a marine adsorbent farm. The objective of this study was to identify at what linear velocity the adsorption kinetics for uranium extraction starts to drop off due to limitations in mass transport of uranium to the surface of the adsorbent fibers. Two independent laboratory-based experimental approaches using flow-through columns and recirculating flumes for adsorbent exposure were used to assess the effect of flow-rate (linear velocity) on the kinetic uptake of uranium on amidoxime-based polymeric adsorbent material. Time series observations over a 56 day period were conducted with flow-through columns over a 35-fold range in linear velocity from 0.29 to 10.2 cm/s, while the flume study was conducted over a narrower 11-fold range, from 0.48 to 5.52 cm/s. These ranges were specifically chosen to focus on the lower end of oceanic currents and expand above and below the linear velocity of ~ 2.5 cm/s adopted for marine testing of adsorbent material at PNNL.

  6. Effect of swim sprints on throwing accuracy and velocity in female collegiate water polo players.

    PubMed

    Stevens, Hayley B; Brown, Lee E; Coburn, Jared W; Spiering, Barry A

    2010-05-01

    Swim sprints are a central component of water polo competitions; however, a paucity of data describes the effect of repeated swim sprints on game-like performances. Therefore, the purpose of this study was to investigate the effect of repeated swim sprints on water polo throwing velocity and accuracy. Eleven female community college water polo players (age: 18.91 +/- 1.04 years, height: 165.91 +/- 4.69 cm, and mass: 70.22 +/- 15.36 kg) performed 2 conditions: control and sprint. The control condition consisted of 10 shots at the 5-m line, each with a 35-second rest period and aimed at a specific target on the goal. The sprint condition also had the same 10 shots but included a sprint between each throwing attempt. The sprints consisted of "head-down" swimming from the 2-m line to half court, then "head-up" swimming from half court to the 5-m line where the ball was shot and aimed at a specific target on the goal. Analysis was performed on ball velocity and accuracy between conditions. Ball velocity in the control condition (26.01 +/- 3.13 mph) was significantly (p < 0.05) greater than the sprint condition (25.08 +/- 2.76 mph); however, there was no significant difference in accuracy (shots made; 3.00 +/- 1.67; Sprint: 2.45 +/- 1.03). These results indicate that ball velocity decreases in female collegiate water polo players after repeated swim sprints when compared with a control condition, yet accuracy is unaffected. Therefore, coaches should incorporate "game-like" conditions during practice that include repeated sprints--while focusing on maintaining high velocity to promote goal scoring.

  7. Sediment deposit thickness and its effect on critical velocity for incipient motion.

    PubMed

    Bong, C H J; Lau, T L; Ab Ghani, A; Chan, N W

    2016-10-01

    The understanding of how the sediment deposit thickness influences the incipient motion characteristic is still lacking in the literature. Hence, the current study aims to determine the effect of sediment deposition thickness on the critical velocity for incipient motion. An incipient motion experiment was conducted in a rigid boundary rectangular flume of 0.6 m width with varying sediment deposition thickness. Findings from the experiment revealed that the densimetric Froude number has a logarithmic relationship with both the thickness ratios ts/d and ts/y0 (ts: sediment deposit thickness; d: grain size; y0: normal flow depth). Multiple linear regression analysis was performed using the data from the current study to develop a new critical velocity equation by incorporating thickness ratios into the equation. The new equation can be used to predict critical velocity for incipient motion for both loose and rigid boundary conditions. The new critical velocity equation is an attempt toward unifying the equations for both rigid and loose boundary conditions.

  8. On the velocity in the Effective Field Theory of Large Scale Structures

    SciTech Connect

    Mercolli, Lorenzo; Pajer, Enrico E-mail: enrico.pajer@gmail.com

    2014-03-01

    We compute the renormalized two-point functions of density, divergence and vorticity of the velocity in the Effective Field Theory of Large Scale Structures. Because of momentum and mass conservation, the corrections from short scales to the large-scale power spectra of density, divergence and vorticity must start at order k{sup 4}. For the vorticity this constitutes one of the two leading terms. Exact (approximated) self-similarity of an Einstein-de Sitter (ΛCDM) background fixes the time dependence so that the vorticity power spectrum at leading order is determined by the symmetries of the problem and the power spectrum around the non-linear scale. We show that to cancel all divergences in the velocity correlators one needs new counterterms. These fix the definition of velocity and do not represent new properties of the system. For an Einstein-de Sitter universe, we show that all three renormalized cross- and auto-correlation functions have the same structure but different numerical coefficients, which we compute. We elucidate the differences between using momentum and velocity.

  9. Temperature and salt effects on settling velocity in granular sludge technology.

    PubMed

    Winkler, M-K H; Bassin, J P; Kleerebezem, R; van der Lans, R G J M; van Loosdrecht, M C M

    2012-08-01

    Settling velocity is a crucial parameter in granular sludge technology. In this study the effects of temperature and salt concentrations on settling velocities of granular sludge particles were evaluated. A two-fold slower settling velocity for the same granules where observed when the temperature of water decreases from 40 °C to 5 °C. Settling velocities also decreased with increasing salt concentrations. Experiments showed that when granules were not pre-incubated in a solution with increased salt concentration, they initially floated. The time dependent increase in mass and hence in settling speed of a granule due to salt diffusion into the granule was dependent on the granule diameter. The time needed for full salt equilibrium with the bulk liquid took 1 min for small particles from the top of the sludge bed and up to 30 min for big granules from the bottom of the sludge bed. These results suggest that temperature and salt concentration are important parameters to consider in the design, start-up and operation of granular sludge reactors and monitoring of these parameters will aid in a better control of the sludge management in anaerobic and aerobic granular sludge technology. The observations also give an explanation for previous reports which were suggesting that a start-up of granular sludge reactors is more difficult at low temperatures.

  10. Temperature and salt effects on settling velocity in granular sludge technology.

    PubMed

    Winkler, M-K H; Bassin, J P; Kleerebezem, R; van der Lans, R G J M; van Loosdrecht, M C M

    2012-10-15

    Settling velocity is a crucial parameter in granular sludge technology. In this study the effects of temperature and salt concentrations on settling velocities of granular sludge particles were evaluated. A two-fold slower settling velocity for the same granules was observed when the temperature of water decreases from 40 °C to 5 °C. Settling velocities also decreased with increasing salt concentrations. Experiments showed that when granules were not pre-incubated in a solution with increased salt concentration, they initially floated. The time dependent increase in mass and hence in settling speed of a granule due to salt diffusion into the granule was dependent on the granule diameter. The time needed for full salt equilibrium with the bulk liquid took 1 min for small particles from the top of the sludge bed and up to 30 min for big granules from the bottom of the sludge bed. These results suggest that temperature and salt concentration are important parameters to consider in the design, start-up and operation of granular sludge reactors and monitoring of these parameters will aid in a better control of the sludge management in anaerobic and aerobic granular sludge technology. The observations also give an explanation for previous reports which were suggesting that a start-up of granular sludge reactors is more difficult at low temperatures.

  11. RADIAL VELOCITY ALONG THE VOYAGER 1 TRAJECTORY: THE EFFECT OF SOLAR CYCLE

    SciTech Connect

    Pogorelov, N. V.; Zank, G. P.; Borovikov, S. N.; Burlaga, L. F.; Decker, R. A.; Stone, E. C.

    2012-05-01

    As Voyager 1 and Voyager 2 are approaching the heliopause (HP)-the boundary between the solar wind (SW) and the local interstellar medium (LISM)-we expect new, unknown features of the heliospheric interface to be revealed. A seeming puzzle reported recently by Krimigis et al. concerns the unusually low, even negative, radial velocity components derived from the energetic ion distribution. Steady-state plasma models of the inner heliosheath (IHS) show that the radial velocity should not be equal to zero even at the surface of the HP. Here we demonstrate that the velocity distributions observed by Voyager 1 are consistent with time-dependent simulations of the SW-LISM interaction. In this Letter, we analyze the results from a numerical model of the large-scale heliosphere that includes solar cycle effects. Our simulations show that prolonged periods of low to negative radial velocity can exist in the IHS at substantial distances from the HP. It is also shown that Voyager 1 was more likely to observe such regions than Voyager 2.

  12. Quantifying the combined effects of attempt rate and swimming capacity on passage through velocity barriers

    USGS Publications Warehouse

    Castro-Santos, T.

    2004-01-01

    The ability of fish to migrate past velocity barriers results from both attempt rate and swimming capacity. Here, I formalize this relationship, providing equations for estimating the proportion of a population successfully passing a barrier over a range of distances and times. These equations take into account the cumulative effect of multiple attempts, the time required to stage those attempts, and both the distance traversed on each attempt and its variability. I apply these equations to models of white sucker (Catostomus commersoni) and walleye (Stizostedion vitreum) ascending a 23-m-long flume against flows ranging from 1.5 to 4.5 m??s-1. Attempt rate varied between species, attempts, and over time and was influenced by hydraulic variables (velocity of flow and discharge). Distance of ascent was primarily influenced by flow velocity. Although swimming capacity was similar, white sucker had greater attempt rates, and consequently better passage success, than walleye. Over short distances, models for both species predict greater passage success against higher velocities owing to the associated increased attempt rate. These results highlight the importance of attraction to fish passage and the need for further investigation into the hydraulic and other environmental conditions required to simultaneously optimize both attempt rate and passage success.

  13. Effect of a weak lower crustal channel in Tibet on geodetic velocities

    NASA Astrophysics Data System (ADS)

    Robinson, P.; Meade, B. J.

    2011-12-01

    Geodetic observations of deformation across the Tibetan plateau contain information about both tectonic and earthquake cycle processes. Time-dependent variations in surface velocities may occur as a result of stress relaxation in a weak lower crustal channel underneath the plateau. Earthquake cycle models with a weak lower crustal channel reveal substantially more near-fault strain than do classical two-layer models. We assess whether or not observed GPS velocity gradients across faults in Tibet are consistent with models that incorporate a weak lower crustal channel with a viscosity less than 1019 Pa s. In particular, we infer a lower bound on lower crustal viscosity beneath the Kunlun and Altyn Tagh faults. Based on these geodetically-constrained estimates of channel viscosity, we use a simple lubrication theory model in two dimensions to calculate the time-dependent evolution of the lower crustal channel thickness and the velocity within the flowing channel. The magnitudes of the shear stresses exerted by the lower crustal material on the underside of the upper crust are of particular interest; these shear stresses could have a significant effect on the observed east-west geodetic velocities on the Tibetan Plateau.

  14. The effects of sliding velocity on the frictional and physical properties of heated fault gouge

    USGS Publications Warehouse

    Moore, Diane E.; Summers, R.; Byerlee, J.D.

    1986-01-01

    The frictional properties of a crushed granite gouge and of gouges rich in montmorillonite, illite, and serpentine minerals have been investigated at temperatures as high as 600??C, confining pressures as high as 2.5 kbar, a pore pressure of 30 bar, and sliding velocities of 4.8 and 4.8??10-2 ??m/sec. The gouges showed nearly identical strength behaviors at the two sliding velocities; all four gouges, however, showed a greater tendency to stick-slip movement and somewhat higher stress drops in the experiments at 4.8??10-2 ??m/sec. Varying the sliding velocity also had an effect on the mineral assemblages and deformation textures developed in the heated gouges. The principal mineralogical difference was that at 400??C and 1 kbar confining pressure a serpentine breakdown reaction occurred in the experiments at 4.8??10-2 ??m/sec but not in those at 4.8 ??m/sec. The textures developed in the gouge layers were in part functions of the gouge type and the temperature, but changes in the sliding velocity affected, among other features, the degree of mineral deformation and the orientation of some fractures. ?? 1986 Birkha??user Verlag.

  15. Effects of vehicle impact velocity, vehicle front-end shapes on pedestrian injury risk.

    PubMed

    Han, Yong; Yang, Jikuang; Mizuno, Koji; Matsui, Yasuhiro

    2012-09-01

    This study aimed at investigating the effects of vehicle impact velocity, vehicle front-end shape, and pedestrian size on injury risk to pedestrians in collisions with passenger vehicles with various frontal shapes. A series of parametric studies was carried out using 2 total human model for safety (THUMS) pedestrian models (177 and 165 cm) and 4 vehicle finite element (FE) models with different front-end shapes (medium-size sedan, minicar, one-box vehicle, and sport utility vehicle [SUV]). The effects of the impact velocity on pedestrian injury risk were analyzed at velocities of 20, 30, 40, and 50 km/h. The dynamic response of the pedestrian was investigated, and the injury risk to the head, chest, pelvis, and lower extremities was compared in terms of the injury parameters head injury criteria (HIC), chest deflection, and von Mises stress distribution of the rib cage, pelvis force, and bending moment diagram of the lower extremities. Vehicle impact velocity has the most significant influence on injury severity for adult pedestrians. All injury parameters can be reduced in severity by decreasing vehicle impact velocities. The head and lower extremities are at greater risk of injury in medium-size sedan and SUV collisions. The chest injury risk was particularly high in one-box vehicle impacts. The fracture risk of the pelvis was also high in one-box vehicle and SUV collisions. In minicar collisions, the injury risk was the smallest if the head did not make contact with the A-pillar. The vehicle impact velocity and vehicle front-end shape are 2 dominant factors that influence the pedestrian kinematics and injury severity. A significant reduction of all injuries can be achieved for all vehicle types when the vehicle impact velocity is less than 30 km/h. Vehicle designs consisting of a short front-end and a wide windshield area can protect pedestrians from fatalities. The results also could be valuable in the design of a pedestrian-friendly vehicle front-end shape

  16. Characterization of air freshener emission: the potential health effects.

    PubMed

    Kim, Sanghwa; Hong, Seong-Ho; Bong, Choon-Keun; Cho, Myung-Haing

    2015-01-01

    Air freshener could be one of the multiple sources that release volatile organic compounds (VOCs) into the indoor environment. The use of these products may be associated with an increase in the measured level of terpene, such as xylene and other volatile air freshener components, including aldehydes, and esters. Air freshener is usually used indoors, and thus some compounds emitted from air freshener may have potentially harmful health impacts, including sensory irritation, respiratory symptoms, and dysfunction of the lungs. The constituents of air fresheners can react with ozone to produce secondary pollutants such as formaldehyde, secondary organic aerosol (SOA), oxidative product, and ultrafine particles. These pollutants then adversely affect human health, in many ways such as damage to the central nervous system, alteration of hormone levels, etc. In particular, the ultrafine particles may induce severe adverse effects on diverse organs, including the pulmonary and cardiovascular systems. Although the indoor use of air freshener is increasing, deleterious effects do not manifest for many years, making it difficult to identify air freshener-associated symptoms. In addition, risk assessment recognizes the association between air fresheners and adverse health effects, but the distinct causal relationship remains unclear. In this review, the emitted components of air freshener, including benzene, phthalate, and limonene, were described. Moreover, we focused on the health effects of these chemicals and secondary pollutants formed by the reaction with ozone. In conclusion, scientific guidelines on emission and exposure as well as risk characterization of air freshener need to be established.

  17. Effect of temperature on ultrasonic velocities of unconsolidated sandstones reservoirs during the SAGD recovery process

    NASA Astrophysics Data System (ADS)

    Doan, D.-H.; Nauroy, J.-F.; Delage, P.; Mainguy, M.

    2010-06-01

    The steam assisted gravity drainage (SAGD) is a thermal in-situ technology that has been successfully used to enhance the recovery of heavy oil and bitumen in the Western Canada and in the Eastern Venezuela basins. Pressure and temperature variations during SAGD operations induce complex changes in the mechanical and acoustic properties of the reservoir rocks as well as of the caprock. To study these changes, measurements of ultrasonic wave velocities Vp, Vs were performed on both reconstituted samples and natural samples from oil sands reservoir. Reconstituted samples were made of Fontainebleau sands with a slight cementation formed by a silicate solution. They have a high porosity (about 30 % to 40 %) and a high permeability (up to 10 D). Natural oil sands samples are unconsolidated sandstones extracted from the fluvio-estuarine McMurray Formation in Alberta (Canada). The saturating fluids were bitumen and glycerol with a strongly temperature dependent viscosity. The tests were carried out at different temperatures (in the range 40° and +86°C) and at different effective pressures (from 12 bars up to 120 bars). Experimental results firstly showed that the elastic wave propagation velocities measured are strongly dependent on temperature and pore fluid viscosity whereas little effect of effective pressure was observed. Velocities decreased with increasing temperature and increased with increasing effective pressure. These effects are mainly due to the variations of the saturating fluids properties. Finally, the tests were modelled by using Ciz and Shapiro (2007) approach and satisfactory velocities values were obtained with highly viscous fluids, a case that cannot be easily explained by using the poro-elastic theory of Biot-Gassmann.

  18. Biofilm development in a membrane-aerated biofilm reactor: effect of flow velocity on performance.

    PubMed

    Casey, E; Glennon, B; Hamer, G

    2000-02-20

    The effect of liquid flow velocity on biofilm development in a membrane-aerated biofilm reactor was investigated both by mathematical modeling and by experiment, using Vibrio natriegens as a test organism and acetate as carbon substrate. It was shown that velocity influenced mass transfer in the diffusion boundary layer, the biomass detachment rate from the biofilm, and the maximum biofilm thickness attained. Values of the overall mass transfer coefficient of a tracer through the diffusion boundary layer, the biofilm, and the membrane were shown to be identical during different experiments at the maximum biofilm thickness. Comparison of the results with published values of this parameter in membrane attached biofilms showed a similar trend. Therefore, it was postulated that this result might indicate the mechanism that determines the maximum biofilm thickness in membrane attached biofilms. In a series of experiments, where conditions were set so that the active layer of the membrane attached biofilm was located close to the membrane biofilm interface, it was shown that the most critical effect on process performance was the effect of velocity on biofilm structure. Biofilm thickness and effective diffusivity influenced reaction and diffusion in a complex manner such that the yield of biomass on acetate was highly variable. Consideration of endogenous respiration in the mathematical model was validated by direct experimental measurements of yield coefficients. Good agreement between experimental measurements of acetate and oxygen uptake rates and their prediction by the mathematical model was achieved.

  19. Air Gap Effects in LX-17

    SciTech Connect

    Souers, P C; Ault, S; Avara, R; Bahl, K L; Boat, R; Cunningham, B; Gidding, D; Janzen, J; Kuklo, D; Lee, R; Lauderbach, L; Weingart, W C; Wu, B; Winer, K

    2005-09-26

    Three experiments done over twenty years on gaps in LX-17 are reported. For the detonation front moving parallel to the gaps, jets of gas products were seen coming from the gaps at velocities greater than the detonation velocity. A case can be made that the jet velocity increased with gap thickness but the data is scattered. For the detonation front moving transverse to the gap, time delays were seen. The delays roughly increase with gap width, going from 0-70 ns at 'zero gap' to around 300 ns at 0.5-1 mm gap. Larger gaps of up to 6 mm width almost certainly stopped the detonation, but this was not proved. Real-time resolution of the parallel jets and determination of the actual re-detonation or failure in the transverse case needs to be done in future experiments.

  20. Firn air-content of Larsen C Ice Shelf, Antarctic Peninsula, from seismic velocities, borehole surveys and firn modelling

    NASA Astrophysics Data System (ADS)

    Kulessa, Bernd; Brisbourne, Alex; Booth, Adam; Kuipers Munneke, Peter; Bevan, Suzanne; Luckman, Adrian; Hubbard, Bryn; Gourmelen, Noel; Palmer, Steve; Holland, Paul; Ashmore, David; Shepherd, Andrew

    2016-04-01

    The rising surface temperature of Antarctic Peninsula ice shelves is strongly implicated in ice shelf disintegration, by exacerbating the compaction of firn layers. Firn compaction is expected to warm the ice column and, given sufficiently wet and compacted layers, to allow meltwater to penetrate into surface crevasses and thus enhance hydrofracture potential. Integrating seismic refraction surveys with borehole neutron and firn core density logging, we reveal vertical and horizontal changes in firn properties across Larsen C Ice Shelf. Patterns of firn air-content derived from seismic surveys are broadly similar to those estimated previously from airborne radar and satellite data. Specifically, these estimates show greater firn compaction in the north and landward inlets compared to the south, although spatial gradients in seismic-derived air-contents are less pronounced than those previously inferred. Firn thickness is less than 10 m in the extreme northwest of Larsen C, in Cabinet Inlet, yet exceeds 40 m in the southeast, suggesting that the inlet is a focus of firn compaction; indeed, buried layers of massive refrozen ice were observed in 200 MHz GPR data in Cabinet and Whirlwind Inlets during a field campaign in the 2014-15 austral summer. Depth profiles of firn density provide a reasonable fit with those derived from closely-located firn cores and neutron probe data. Our model of firn structure is driven by RACMO and includes a 'bucket'-type hydrological implementation, and simulates the depth-density profiles in the inlets well. Discrepancies between measured and modelled depth-density profiles become progressively greater towards the ice-shelf front. RACMO incorrectly simulates the particular leeward (sea-ice-influenced) microclimate of the shallow boundary layer, leading to excess melt and/or lack of snowfall. The spatial sampling density of our seismic observations will be augmented following a further field campaign in the 2016-17 austral summer

  1. Effects of velocity-based resistance training on young soccer players of different ages.

    PubMed

    González-Badillo, Juan J; Pareja-Blanco, Fernando; Rodríguez-Rosell, David; Abad-Herencia, José L; Del Ojo-López, Juan J; Sánchez-Medina, Luis

    2015-05-01

    This study aimed to analyze the effect of velocity-based resistance training (RT) with moderate loads and few repetitions per set combined with jumps and sprints on physical performance in young soccer players of different ages. A total of 44 elite youth soccer players belonging to 3 teams participated in this study: an under-16 team (U16, n = 17) and an under-18 team (U18, n = 16) performed maximal velocity RT program for 26 weeks in addition to typical soccer training, whereas an under-21 team (U21, n = 11) did not perform RT. Before and after the training program, all players performed 20-m running sprint (T20), countermovement jump (CMJ), a progressive isoinertial loading test in squat to determine the load that elicited a ∼ 1 m · s(-1) velocity (V1LOAD) and an incremental field test to determine maximal aerobic speed (MAS). U16 showed significantly (p = 0.000) greater gains in V1LOAD than U18 and U21 (100/0/0%). Only U16 showed significantly (p = 0.01) greater gains than U21 (99/1/0%) in CMJ height. U18 obtained a likely better effect on CMJ performance than U21 (89/10/1%). The beneficial effects on T20 between groups were unclear. U16 showed a likely better effect on MAS than U21 (80/17/3%), whereas the rest of comparisons were unclear. The changes in CMJ correlated with the changes in T20 (r = -0.49) and V1LOAD (r = 0.40). In conclusion, velocity-based RT with moderate load and few repetitions per set seems to be an adequate method to improve physical performance in young soccer players.

  2. Effects of unsteady free stream velocity and free stream turbulence on stagnation point heat transfer

    NASA Technical Reports Server (NTRS)

    Gorla, R. S. R.

    1984-01-01

    The combined effects of transient free stream velocity and free stream turbulence on heat transfer at a stagnation point over a cylinder situated in a crossflow are studied. An eddy diffusivity model was formulated and the governing momentum and energy equations are integrated by means of the steepest descent method. The numerical results for the wall shear stress and heat transfer rate are correlated by a turbulence parameter. The wall friction and heat transfer rate increase with increasing free stream turbulence intensity.

  3. Focussing effects at the edge of the Large Low Shear Velocity Provinces

    NASA Astrophysics Data System (ADS)

    Rost, S.; Nowacki, A.

    2015-12-01

    Tomographic images of the Earth's lowermost mantle are dominated by two equatorial and nearly antipodal regions of large-scale reductions in seismic S-wave velocities beneath the central Pacific and Africa. These Large Low Shear Velocity Provinces (LLSVPs) are much less constrained in tomographic P-wave models. This discrepancy, together with other geophysical data, led to the interpretation of LLSVPs as thermo-chemical piles, but models of purely thermal LLSVPs might also be able to explain the geophysical data. Data from seismic arrays and high-resolution processing techniques are able to precisely determine the slowness vector of incoming seismic energy and therefore to extract velocity and directivity information from the seismic data directly. Here we use records of P and Pdiff from the medium aperture, short-period, vertical component Yellowknife array (YKA) located in northern Canada and S/Sdiff from stations of the Canadian POLARIS network. Using seismicity from the western Pacific rim allows good sampling of the lowermost mantle in the region of the Pacific LLSVP and the northern Pacific. The slowness information extracted from the array data using the high-resolution F-statistic allows detailed mapping of the LLSVP boundary and indicates a sharp boundary and velocity reductions of several percent. The data also indicate a second region of strongly reduced seismic velocities to the north of the Pacific LLSVP beneath the Sea of Okhotsk that does not seem to be connected to the main LLSVP, and which is not consistently resolved in S-wave tomography models. We observe very strong focussing and defocussing effects along the LLSVP boundary that indicate strong and small-scale heterogeneities in the vicinity of the LLSVP boundary beyond what can be explained by LLSVP material. This detection allows further insight into the structure and dynamics of the LLSVP. Using seismic wave propagation simulations we are aiming to resolve both structure and shape of these

  4. The effects of pressure and temperature on sound velocity and density of Ni-S liquid

    NASA Astrophysics Data System (ADS)

    Terasaki, H. G.; Nishida, K.; Urakawa, S.; Uesugi, K.; Kuwabara, S.; Takubo, Y.; Shimoyama, Y.; Takeuchi, A.; Suzuki, Y.; Kono, Y.; Higo, Y.; Kondo, T.

    2013-12-01

    Sound velocity and density of the core material are indispensable properties to estimate a composition in the terrestrial core comparing with the observed seismic data. Here, we report these properties of Ni-S, which corresponds to the end-member of possible core composition Fe-Ni-S, at high pressure and temperature. These properties were measured based on simultaneous measurement of sound velocity and density combined with X-ray tomography technique. The experiments were carried out at X-ray computed micro-tomography (CT) beamlines (BL20XU, BL20B2), SPring-8 synchrotron radiation facility. Monochromatized X-ray of 51 keV passed through the sample cell and detected as a radiography image using CCD camera. X-ray radiography images from 0 to 180o were measured for CT measurement by rotating the press. An 80-ton uni-axial press was used to generate high pressure with using opposed-type cupped anvils (Urakawa et al. 2010). Density was determined by using X-ray absorption method obtained from the X-ray radiograph image. The sample thickness for the X-ray path can be directly obtained from the CT data. The sample density was also determined from the volume of the sample at high pressure and temperature. P-wave sound velocity was measured using pulse-echo overlapping ultrasonic method using LiNbO3 transducer attached backside of the anvil. We have successfully measured the sound velocity and density of Ni-S up to 1.5 GPa. Comparing with the previous results of liquid Fe-S, the effect of Ni on the sound velocity is minor but that on the density can not be negligible.

  5. Effects of nitroglycerine on coronary flow velocity before and during adenosine provocation.

    PubMed

    Wittfeldt, Ann; Jeppsson, Anders; Gan, Li-Ming

    2016-12-06

    Transthoracic echocardiography-assessed coronary flow velocity reserve (CFVR) evaluates coronary microvascular arterial function. Coronary flow velocity measurements at baseline and during hyperemia are used to calculate CFVR. Adenosine infusion induces hyperemia but it is not known if it causes a maximal response. We hypothesized that pre-treatment with nitroglycerine before adenosine provocation enhances hyperemia. Twenty-three healthy study subjects (mean age 27.5 ± 5.5, 35% women) underwent CFVR measurements before and after pretreatment with sublingual nitroglycerine (0.5 mg). Hyperemia was induced by adenosine infusion (140 μg/kg/min). In addition, the effect of nitroglycerin on left main coronary artery diameter was assessed. Pretreatment with nitroglycerine increased median CFVR from 3.6 (range 2.8-4.3) to 5.0 (4.1-6.0), p = 0.002. The increase was caused by a marked reduction in baseline coronary flow velocity 17 (15-24) vs 27 (19-31) cm/s, p < 0.0001) while hyperemic velocity remained unchanged (90 (68-116) vs 93 (75-105) cm/s, p = 0.48). Nitroglycerin significantly dilated the left main coronary artery (from median 3.1 (2.7-3.6) mm to 3.8 (3.1-4.3) mm, p = 0.018). Pretreatment with nitroglycerine dilates coronary arteries and increases coronary flow velocity reserve indicating that adenosine alone causes a submaximal hyperemia.

  6. Effects of a defender on run-up velocity and ball speed when crossing a football.

    PubMed

    Orth, Dominic; Davids, Keith; Araújo, Duarte; Renshaw, Ian; Passos, Pedro

    2014-01-01

    This study evaluated effects of defensive pressure on running velocity in footballers during the approach to kick a stationary football. Approach velocity and ball speed/accuracy data were recorded from eight football youth academy participants (15.25, SD=0.46 yrs). Participants were required to run to a football to cross it to a receiver to score against a goal-keeper. Defensive pressure was manipulated across three counterbalanced conditions: defender-absent (DA); defender-far (DF) and defender-near (DN). Pass accuracy (percentages of a total of 32 trials with 95% confidence limits in parenthesis) did not significantly reduce under changing defensive pressure: DA, 78% (55-100%); DF, 78% (61-96%); DN, 59% (40-79%). Ball speed (m · s(-1)) significantly reduced as defensive pressure was included and increased: DA, 23.10 (22.38-23.83); DF, 20.40 (19.69-21.11); DN, 19.22 (18.51-19.93). When defensive pressure was introduced, average running velocity of attackers did not change significantly: DA versus DF (m · s(-1)), 5.40 (5.30-5.51) versus 5.41 (5.34-5.48). Scaling defender starting positions closer to the start position of the attacker (DN) significantly increased average running velocity relative to the DA and DF conditions, 5.60 (5.50-5.71). In the final approach footfalls, all conditions significantly differed: DA, 5.69 (5.35-6.03); DF, 6 .22 (5.93-6.50); DN, 6.52 (6.23-6.80). Data suggested that approach velocity is constrained by both presence and initial distance of the defender during task performance. Implications are that the expression of kicking behaviour is specific to a performance context and some movement regulation features will not emerge unless a defender is present as a task constraint in practice.

  7. The effects of "grunting" on serve and forehand velocities in collegiate tennis players.

    PubMed

    OʼConnell, Dennis G; Hinman, Martha R; Hearne, Kevin F; Michael, Zach S; Nixon, Sam L

    2014-12-01

    The aim of this study was to examine the effects of grunting on velocity and force production during dynamic and static tennis strokes in collegiate tennis players. Thirty-two (16 male and 16 female) division II and III collegiate tennis athletes with a mean age of 20.2 ± 1.89 years participated as subjects. Demographic and survey data were obtained before subjects completed a 10- to 15-minute warm-up of serves and ground strokes while grunting and not grunting. The subjects performed randomized sets (3 grunting and 3 nongrunting trials) of serves and forehand strokes both dynamically and isometrically. Stroke velocities and isometric forces were measured with a calibrated radar gun and calibrated dynamometer, respectively. Electromyographic (EMG) data from subjects' dominant pectoralis major and contralateral external oblique muscles were recorded and averaged for data analysis. A repeated measures multivariate analysis of variance (RM-MANOVA) compared dynamic stroke velocity, isometric muscle force, and peak EMG activity during each breathing condition at the 0.05 alpha level. The RM-MANOVA indicated that dynamic velocity and isometric force of both serves and forehand strokes were significantly greater when the subjects grunted (F = 46.572, p < 0.001, power = 1.00). Peak muscle activity in the external oblique and pectoralis major muscles was also greater when grunting during both types of strokes (F = 3.867, p = 0.05, power = 0.950). Grunt history, gender, perceived advantages, and disadvantages of grunting, years of experience, highest level of competition, and order of testing did not significantly alter any of these results. The velocity, force, and peak muscle activity during tennis serves and forehand strokes are significantly enhanced when athletes are allowed to grunt.

  8. The Effects of "Grunting" on Serve and Forehand Velocity in Collegiate Tennis Players.

    PubMed

    O'Connell, Dennis G; Hinman, Martha; Hearne, Kevin F; Michael, Zach S; Nixon, Sam L

    2014-06-30

    To examine the effects of grunting on velocity and force production during dynamic and static tennis strokes in collegiate tennis players. Thirty-two (16 M and 16 F) Division II and III collegiate tennis athletes with a mean age of 20.2 ± 1.89 years participated as subjects. Demographic and survey data were obtained prior to subjects completing a 10-15 minute warm-up of serves and ground strokes while grunting and not grunting. Subjects performed randomized sets (3 grunting and 3 non-grunting trials) of serves and forehand strokes both dynamically and isometrically. Stroke velocities and isometric forces were measured with a calibrated radar gun and calibrated dynamometer, respectively. EMG data from subjects' dominant pectoralis major and contralateral external oblique muscles were recorded and averaged for data analysis. A repeated measures multivariate analysis of variance (RM-MANOVA) compared dynamic stroke velocity, isometric muscle force, and peak EMG activity during each breathing condition at the 0.05 alpha level. The RMANOVA indicated that dynamic velocity and isometric force of both serves and forehand strokes were significantly greater when subjects grunted (F=46.572, p<0.001, power=1.00). Peak muscle activity in the external oblique and pectoralis major muscles was also greater when grunting during both types of strokes (F=3.867, p=0.05, power=0.950). Grunt history, gender, perceived advantages and disadvantages of grunting, years of experience, highest level of competition, and order of testing did not significantly alter any of these results. The velocity, force, and peak muscle activity during tennis serves and forehand strokes are significantly enhanced when athletes are allowed to grunt.

  9. Spatio-temporal linear stability analysis of stratified planar wakes: Velocity and density asymmetry effects

    NASA Astrophysics Data System (ADS)

    Emerson, Benjamin; Jagtap, Swapnil; Quinlan, J. Mathew; Renfro, Michael W.; Cetegen, Baki M.; Lieuwen, Tim

    2016-04-01

    This paper explores the hydrodynamic stability of bluff body wakes with non-uniform mean density, asymmetric mean density, and velocity profiles. This work is motivated by experiments [S. Tuttle et al., "Lean blow off behavior of asymmetrically-fueled bluff body-stabilized flames," Combust. Flame 160, 1677 (2013)], which investigated reacting wakes with equivalence ratio stratification and, hence, asymmetry in the base flow density profiles. They showed that highly stratified cases exhibited strong, narrowband oscillations, suggestive of global hydrodynamic instability. In this paper, we present a local hydrodynamic stability analysis for non-uniform density wakes that includes base flow asymmetry. The results show that increasing the degree of base density asymmetry generally has a destabilizing effect and that increasing base velocity asymmetry tends to be stabilizing. Furthermore, we show that increasing base density asymmetry slightly decreases the absolute frequency and that increasing the base velocity asymmetry slightly increases the absolute frequency. In addition, we show that increasing the degree of base density asymmetry distorts the most absolutely unstable hydrodynamic mode from its nominally sinuous structure. This distorted mode exhibits higher amplitude pressure and velocity oscillations near the interface with the smaller density jump than near the one with the bigger density jump. This would then be anticipated to lead to strongly non-symmetric amplitudes of flame flapping, with much stronger flame flapping on the side with lower density ratio. These predictions are shown to be consistent with experimental data. These comparisons support the analytical predictions that increased base density asymmetry are destabilizing and that hydrodynamic velocity fluctuation amplitudes should be greatest at the flame with the lowest density jump.

  10. The variance of convection velocity in the turbulent boundary layer and its effect on coherence length

    NASA Astrophysics Data System (ADS)

    Palumbo, Dan

    2013-07-01

    variance in the convection velocity has a significant effect on the decay of coherent power in the wall pressure of the turbulent boundary layer.

  11. High velocity pulsed wire-arc spray

    NASA Technical Reports Server (NTRS)

    Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor); Kincaid, Russell W. (Inventor)

    1999-01-01

    Wire arc spraying using repetitively pulsed, high temperature gas jets, usually referred to as plasma jets, and generated by capillary discharges, substantially increases the velocity of atomized and entrained molten droplets. The quality of coatings produced is improved by increasing the velocity with which coating particles impact the coated surface. The effectiveness of wire-arc spraying is improved by replacing the usual atomizing air stream with a rapidly pulsed high velocity plasma jet. Pulsed power provides higher coating particle velocities leading to improved coatings. 50 micron aluminum droplets with velocities of 1500 m/s are produced. Pulsed plasma jet spraying provides the means to coat the insides of pipes, tubes, and engine block cylinders with very high velocity droplet impact.

  12. INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY An Extended Optimal Velocity Model with Consideration of Honk Effect

    NASA Astrophysics Data System (ADS)

    Tang, Tie-Qiao; Li, Chuan-Yao; Huang, Hai-Jun; Shang, Hua-Yan

    2010-12-01

    Based on the OV (optimal velocity) model, we in this paper present an extended OV model with the consideration of the honk effect. The analytical and numerical results illustrate that the honk effect can improve the velocity and flow of uniform flow but that the increments are relevant to the density.

  13. Effects of plume spacing and flowrate on destratification efficiency of air diffusers.

    PubMed

    Yum, Kyungtaek; Kim, Sung Hoon; Park, Heekyung

    2008-07-01

    This study adopts techniques of computational fluid dynamics (CFD) to analyze the combined effect of adjacent plumes of an air-diffuser system on its destratification efficiency. Lab experiments were carried out to calibrate and verify the CFD models in thermally stratified freshwater. The CFD simulation and lab experiment results were analyzed to relate destratification efficiency with four non-dimensional variables. The results indicate that destratification number, D(N), has the best relationship that includes air flowrate, stratification frequency, water depth, and bubble slip velocity. Since plume spacing and air flowrate are the major control variables of the system, especially in the field, two charts showing the relationships between destratification efficiency, plume spacing, and destratification number are developed for guiding their control in its design and operation.

  14. UNDERSTANDING THE EFFECTS OF AIR POLLUTION ON HUMAN HEALTH

    EPA Science Inventory

    Modern air pollution regulation is first and foremost motivated by concerns about the effects of air pollutants on human health and secondarily by concerns about its effects on ecosystems, cultural artifacts, and quality of life values such as visibility. This order of priority ...

  15. UNDERSTANDING THE EFFECTS OF AIR POLLUTION ON HUMAN HEALTH

    EPA Science Inventory

    Modern air pollution regulation is first and foremost motivated by concerns about the effects of air pollutants on human health and secondarily by concerns about its effects on ecosystems, cultural artifacts, and quality of life values such as visibility. This order of priority ...

  16. Some Factors Influencing Air Force Simulator Training Effectiveness. Technical Report.

    ERIC Educational Resources Information Center

    Caro, Paul W.

    A study of U.S. Air Force simulator training was conducted to identify factors that influence the effectiveness of such training and to learn how its effectiveness is being determined. The research consisted of a survey of ten representative Air Force simulator training programs and a review of the simulator training research literature. A number…

  17. The effects of velocity difference changes with memory on the dynamics characteristics and fuel economy of traffic flow

    NASA Astrophysics Data System (ADS)

    Yu, Shaowei; Zhao, Xiangmo; Xu, Zhigang; Zhang, Licheng

    2016-11-01

    To evaluate the effects of velocity difference changes with memory in the intelligent transportation environment on the dynamics and fuel consumptions of traffic flow, we first investigate the linkage between velocity difference changes with memory and car-following behaviors with the measured data in cities, and then propose an improved cooperative car-following model considering multiple velocity difference changes with memory in the cooperative adaptive cruise control strategy, finally carry out several numerical simulations under the periodic boundary condition and at signalized intersections to explore how velocity difference changes with memory affect car's velocity, velocity fluctuation, acceleration and fuel consumptions in the intelligent transportation environment. The results show that velocity difference changes with memory have obvious effects on car-following behaviors, that the improved cooperative car-following model can describe the phase transition of traffic flow and estimate the evolution of traffic congestion, that the stability and fuel economy of traffic flow simulated by the improved car-following model with velocity difference changes with memory is obviously superior to those without velocity difference changes, and that taking velocity difference changes with memory into account in designing the advanced adaptive cruise control strategy can significantly improve the stability and fuel economy of traffic flow.

  18. Anomalous effect of ion velocity on track formation in GeS

    NASA Astrophysics Data System (ADS)

    Szenes, G.; Pécz, B.

    2016-12-01

    Systematic experiments were performed for studying the effect of the projectile velocity (velocity effect, VE) in GeS which has a highly anisotropic conductivity. The prethinned specimens were irradiated by Bi, Au, W, Xe, Ag, Kr, Ni and Fe ions of about E ≈ 1 MeV/nucleon energy. Track radii were measured by transmission electron microscopy. Compared to previous experiments performed with high velocity projectile, there is a marked VE for Se > 20 keV/nm (Se - electronic stopping power). However, the VE is gradually reduced and finally disappears as Se decreases. This effect is described for the first time. The predictions according to the Analytical Thermal Spike Model are in excellent quantitative agreement with the experiments in the range Se > 20 keV/nm. The anomalous behavior of track evolution at lower values of Se is attributed to the combination of semiconducting and insulating properties. An explanation of the VE is given based on the Coulomb explosion model.

  19. 30 CFR 75.350 - Belt air course ventilation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... except as provided in paragraph (c) of this section. (2) Effective December 31, 2009, the air velocity in... manager may approve lower velocities in the ventilation plan based on specific mine conditions. Air velocities must be compatible with all fire detection systems and fire suppression systems used in the...

  20. 30 CFR 75.350 - Belt air course ventilation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... except as provided in paragraph (c) of this section. (2) Effective December 31, 2009, the air velocity in... manager may approve lower velocities in the ventilation plan based on specific mine conditions. Air velocities must be compatible with all fire detection systems and fire suppression systems used in the...

  1. 30 CFR 75.350 - Belt air course ventilation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... except as provided in paragraph (c) of this section. (2) Effective December 31, 2009, the air velocity in... manager may approve lower velocities in the ventilation plan based on specific mine conditions. Air velocities must be compatible with all fire detection systems and fire suppression systems used in the...

  2. Committee on air pollution effects research: 40 years of UK air pollution.

    PubMed

    Fowler, David; Dise, Nancy; Sheppard, Lucy

    2016-01-01

    The UK Committee on Air Pollution Effects Research (CAPER) was established 40 years ago. This special section was compiled to mark this anniversary. During this time there have been dramatic changes in the composition of the air over the UK. The four papers in this special section of Environmental Pollution represent the current air pollution effects research focus on ozone and nitrogen deposition, two related issues and are proving from a policy perspective to be quite intractable issues. The UK CAPER research community continues to advance the underpinning science and engages closely with the user community in government departments. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  3. The effect of heating and cooling on the velocity fluctuations in the ISM induced by the system of stars

    NASA Astrophysics Data System (ADS)

    Deiss, B. M.; Kegel, W. H.

    1986-06-01

    Dissipative thermal effects are taken into account in the expressions for interstellar gas velocity fluctuations (due to the gravitational interaction with stars) derived by Kegel and Volk (1983), with application to the interpretation of interstellar lines, the large scale flow of the interstellar matter, and the collapse of interstellar clouds. Results indicate a decrease in the critical wavelength for gravitational instability, which value is prevented by thermal effects from becoming zero when the relative velocity approaches the velocity of sound, in contradiction with the results of Kegel and Volk, and of Niimi (1970). The velocity fluctuations in the gas derived by Kegel and Volk are shown to be reduced considerably, though velocity fluctuations many times the velocity of sound, which increase with increasing relative motion between gas and stars, are found, principally in molecular clouds.

  4. Modeling of integrated sunlight velocity measurements: The effect of surface darkening by magnetic fields

    NASA Technical Reports Server (NTRS)

    Ulrich, R. K.; Henney, C. J.; Schimpf, S.; Fossat, E.; Gelly, B.; Grec, G.; Loudagh, S.; Schmider, F.-X; Palle, P.; Regulo, C.

    1993-01-01

    It has been known since the work by Claverie et al. (1982) that integrated-sunlight velocities measured with the resonance scattering technique show variations with time scales of weeks to months. The cause can be understood in terms of the effects of solar activity as was pointed out by Edmunds & Gough (1983) and Andersen & Maltby (1983). The latter authors included a model calculation based on sunspot areas which showed good promise of being able to quantitatively reproduce the observed velocity shifts. We discuss in this paper a new modeling effort based on daily magnetograms obtained at the 150-ft tower on Mt. Wilson. This type of database is more quantitative than sunspot area. Similar maps of magnetically sensitive quantities will be measured on a continuous time base as part of several planned helioseismology experiments (from space with the Solar Oscillations Imagery/Michelson Doppler Imager (SOI/MDI) experiment on the Solar and Heliospheric Observatory (SOHO), see Scherrer et al. (1991) or with ground-based networks, see Hill & Leibacher (1991)). We discuss the correlations between various magnetically sensitive quantities and develop a new model for the effects of magnetic field on line profiles and surface brightness. From these correlations we integrate the line profile changes over the solar surface using observed magnetic field strengths measured at lambda 5250.2. The final output is a new model for the effects of magnetic fields on integrated sunlight velocities which we compare with daily offset velocities derived from the International Research on the Interior of the Sun (IRIS)-T instrument at the Observatorio del Teide.

  5. Effect of pool length on blood lactate, heart rate, and velocity in swimming.

    PubMed

    Keskinen, O P; Keskinen, K L; Mero, A A

    2007-05-01

    Exercise testing in water has been used to follow the progression of conditioning during regular training in swimmers. The present study examined the effects of pool length in eleven male swimmers on a set of 5 x 200-m freestyle swims with increasing speed from submaximal to maximal. Mean velocity of swimming, blood lactate and heart rate were examined in both 25-m and 50-m pools. Turning benefit as a marker for turning skill was measured separately by a underwater video system (speed difference between pre- and post-turning) during short all-out swims. Maximum force during swimming was measured in tethered swimming and explosive strength of leg extensor muscles was evaluated by a counter movement jump. The significantly higher (p=0.033 - 0.000) blood lactate values for the 50-m pool as compared to the 25-m pool were found at each point of swimming velocity versus blood lactate curve. The highest post-test lactate level was 7.36 +/- 1.47 mmol x l (-1) in the short course and 8.24 +/- 1.55 mmol x l (-1) (p=0.033) in the long course. The maximum swimming velocity was significantly greater (4.5 %) in the 25-m pool swimming (1.38 +/- 0.11 m x s (-1) vs. 1.32 +/- 0.12 m x s (-1); p=0.000). The heart rate values were significantly (p=0.020 - 0.000) lower in the short course than in the long course at all points of submaximal velocity with a mean difference of 7.3 +/- 0.7 bpm. Heart rate was equal (172 +/- 14 vs. 172 +/- 14 bpm) after the maximum swims in both short and long course. The turning benefit in the short maximum swim was 0.12 +/- 0.05 m x s (-1) (8.1 +/- 3.2 %), correlating positively with the difference in maximal swimming velocity between the short and long-pool swims (r = 0.59; p = 0.029), with the maximum force during tethered swimming (r=0.75; p=0.004) and with the vertical jumping height in the counter movement jump (r=0.55; p=0.039). We conclude that the pool length has a strong effect on blood lactate concentration and heart rate with greater swimming

  6. Health Effects of Ambient Air Pollution in Developing Countries.

    PubMed

    Mannucci, Pier Mannuccio; Franchini, Massimo

    2017-09-12

    The deleterious effects of ambient air pollution on human health have been consistently documented by many epidemiologic studies worldwide, and it has been calculated that globally at least seven million deaths are annually attributable to the effects of air pollution. The major air pollutants emitted into the atmosphere by a number of natural processes and human activities include nitrogen oxides, volatile organic compounds, and particulate matter. In addition to the poor ambient air quality, there is increasing evidence that indoor air pollution also poses a serious threat to human health, especially in low-income countries that still use biomass fuels as an energy resource. This review summarizes the current knowledge on ambient air pollution in financially deprived populations.

  7. Health Effects of Ambient Air Pollution in Developing Countries

    PubMed Central

    Mannucci, Pier Mannuccio; Franchini, Massimo

    2017-01-01

    The deleterious effects of ambient air pollution on human health have been consistently documented by many epidemiologic studies worldwide, and it has been calculated that globally at least seven million deaths are annually attributable to the effects of air pollution. The major air pollutants emitted into the atmosphere by a number of natural processes and human activities include nitrogen oxides, volatile organic compounds, and particulate matter. In addition to the poor ambient air quality, there is increasing evidence that indoor air pollution also poses a serious threat to human health, especially in low-income countries that still use biomass fuels as an energy resource. This review summarizes the current knowledge on ambient air pollution in financially deprived populations. PMID:28895888

  8. Effects of Wrist Posture and Fingertip Force on Median Nerve Blood Flow Velocity

    PubMed Central

    Wilson, Katherine E.; Tat, Jimmy

    2017-01-01

    Purpose. The purpose of this study was to assess nerve hypervascularization using high resolution ultrasonography to determine the effects of wrist posture and fingertip force on median nerve blood flow at the wrist in healthy participants and those experiencing carpal tunnel syndrome (CTS) symptoms. Methods. The median nerves of nine healthy participants and nine participants experiencing symptoms of CTS were evaluated using optimized ultrasonography in five wrist postures with and without a middle digit fingertip press (0, 6 N). Results. Both wrist posture and fingertip force had significant main effects on mean peak blood flow velocity. Blood flow velocity with a neutral wrist (2.87 cm/s) was significantly lower than flexed 30° (3.37 cm/s), flexed 15° (3.27 cm/s), and extended 30° (3.29 cm/s). Similarly, median nerve blood flow velocity was lower without force (2.81 cm/s) than with force (3.56 cm/s). A significant difference was not found between groups. Discussion. Vascular changes associated with CTS may be acutely induced by nonneutral wrist postures and fingertip force. This study represents an early evaluation of intraneural blood flow as a measure of nerve hypervascularization in response to occupational risk factors and advances our understanding of the vascular phenomena associated with peripheral nerve compression. PMID:28286771

  9. Effects of Velocity on Electromyographic, Mechanomyographic, and Torque Responses to Repeated Eccentric Muscle Actions.

    PubMed

    Hill, Ethan C; Housh, Terry J; Camic, Clayton L; Smith, Cory M; Cochrane, Kristen C; Jenkins, Nathaniel D M; Cramer, Joel T; Schmidt, Richard J; Johnson, Glen O

    2016-06-01

    The purposes of this study were to examine the effects of the velocity of repeated eccentric muscle actions on the torque and neuromuscular responses during maximal isometric and eccentric muscle actions. Twelve resistance-trained men performed 30 repeated, maximal, eccentric, isokinetic muscle actions at randomly ordered velocities of 60, 120, or 180°·s on separate days. Maximal voluntary isometric contractions (MVICs) were performed before (pretest) and after (posttest) the repeated eccentric muscle actions on each day. Eccentric isokinetic peak torque (EIPT) values were the averages of the first 3 and last 3 repetitions of the 30 repeated eccentric muscle actions. During the EIPT and MVIC muscle actions, electromyographic (EMG) and mechanomyographic (MMG) amplitude (EMG AMP and MMG AMP) and mean power frequency (EMG MPF and MMG MPF) values were assessed. These results indicated that the repeated eccentric muscle actions had no effects on EIPT, or the EMG AMP, EMG MPF, or MMG MPF values assessed during the EIPT muscle actions, but decreased MMG AMP. The repeated eccentric muscle actions, however, decreased MVIC torque, and also the EMG AMP and MMG MPF values assessed during the MVIC muscle actions, but increased MMG AMP. The results indicated that the velocity of the repeated eccentric muscle actions affected the MVIC torque responses, but not EIPT or any of the neuromuscular parameters. Furthermore, there are differences in the torque and neuromuscular responses for isometric vs. eccentric muscle actions after repeated eccentric muscle actions.

  10. Effect of the q-nonextensive electron velocity distribution on a magnetized plasma sheath

    SciTech Connect

    Safa, N. Navab Ghomi, H.; Niknam, A. R.

    2014-08-15

    In this work, a sheath model has been developed to investigate the effect of the q-nonextensive electron velocity distribution on the different characteristics of a magnetized plasma. By using Segdeev potential method, a modified Bohm criterion for a magnetized plasma with the nonextensive electron velocity distribution is derived. The sheath model is then used to analyze numerically the sheath structure under different q, the parameter quantifying the nonextensivity degree of the system. The results show that as the q-parameter decreases, the floating potential becomes more negative. The sheath length increases at the lower values of the q-parameter due to the increase in the electron population at the high-energy tail of the distribution function. As q-parameter decreases, the effective temperature of the electrons increases which results in a more extended plasma sheath. The ion velocity and density profiles for the different nonextensivity degrees of the system reflect the gyro-motion of the ions in the presence of the magnetic field. Furthermore, the results coincide with those given by the Maxwellian electron distribution function, when q tends to 1.

  11. Exploration of Tactile Contact in a Haptic Display: Effects of Contact Velocity and Transient Vibrations.

    PubMed

    Gleeson, B T; Provancher, W R

    2011-01-01

    Experiments were conducted using a novel tactile contact rendering device to explore important factors of the tactile contact event. The effects of contact velocity and event-based transient vibrations were explored. Our research was motivated by a need to better understand the perception of the tactile contact event and to develop a means of rendering stiff surfaces with a nonspecialized haptic device. A passive tactile display, suitable for mounting on a Phantom robot, was developed and is capable of rendering the tactile sensation of contact on a fingertip over a range of velocities commonly experienced during everyday manipulation and tactile exploration. Experiments were conducted with this device to explore how tactile contact dynamics affect the perceived stiffness of a virtual surface. It was found that contact velocity does not have a significant effect on perceived stiffness. These results can be explained by prior research that defines perceived hardness (akin to stiffness) in terms of rate-hardness. However, in agreement with prior literature with stylus-based studies, the addition of transient vibrations to the contact event can, in some cases, increase the perceived stiffness.

  12. Particle size, magnetic field, and blood velocity effects on particle retention in magnetic drug targeting.

    PubMed

    Cherry, Erica M; Maxim, Peter G; Eaton, John K

    2010-01-01

    A physics-based model of a general magnetic drug targeting (MDT) system was developed with the goal of realizing the practical limitations of MDT when electromagnets are the source of the magnetic field. The simulation tracks magnetic particles subject to gravity, drag force, magnetic force, and hydrodynamic lift in specified flow fields and external magnetic field distributions. A model problem was analyzed to determine the effect of drug particle size, blood flow velocity, and magnetic field gradient strength on efficiency in holding particles stationary in a laminar Poiseuille flow modeling blood flow in a medium-sized artery. It was found that particle retention rate increased with increasing particle diameter and magnetic field gradient strength and decreased with increasing bulk flow velocity. The results suggest that MDT systems with electromagnets are unsuitable for use in small arteries because it is difficult to control particles smaller than about 20 microm in diameter.

  13. Interchange and Flow Velocity Shear Instabilities in the Presence of Finite Larmor Radius Effects

    NASA Astrophysics Data System (ADS)

    Sotnikov, V.; Kim, T.; Mishin, E.; Genoni, T.; Rose, D.; Mehlhorn, T.

    2014-09-01

    Ionospheric irregularities cause scintillations of electromagnetic signals that can severely affect navigation and transionospheric communication, in particular during Equatorial Plasma Bubbles (EPBs) events. However, the existing ionospheric models do not describe density irregularities with typical scales of several ion Larmor radii that affect UHF and L bands. These irregularities can be produced in the process of nonlinear evolution of interchange or flow velocity shear instabilities. The model of nonlinear development of these instabilities based on two-fluid hydrodynamic description with inclusion of finite Larmor radius effects will be presented. The derived nonlinear equations will be numerically solved by using the code Flute, which was originally developed for High Energy Density applications and modified to describe interchange and flow velocity shear instabilities in the ionosphere. The high-resolution simulations will be driven by the ambient conditions corresponding to the AFRL C/NOFS satellite low-resolution data during EPBs.

  14. Effect of anisotropy of electron velocity distribution function on dynamic characteristics of sheath in Hall thrusters

    SciTech Connect

    Zhang Fengkui; Wu Xiande; Ding Yongjie; Li Hong; Yu Daren

    2011-10-15

    In Hall thrusters, the electron velocity distribution function is not only depleted at high energies, but also strongly anisotropic. With these electrons interacting with the channel wall, the sheath will be changed in its dynamic characteristics. In the present letter, a two dimensional particle-in-cell code is used to simulate these effects in a collisionless plasma slab. The simulated results indicate that the sheath changes from steady regime to temporal oscillation regime when the electron velocity distribution function alters from isotropy to anisotropy. Moreover, the temporal oscillation sheath formed by the anisotropic electrons has a much greater oscillating amplitude and a much smaller average potential drop than that formed by the isotropic electrons has. The anisotropic electrons are also found to lower the critical value of electron temperature needed for the appearance of the spatial oscillation sheath.

  15. The effects of impact velocity on the evolution of experimental regoliths

    NASA Technical Reports Server (NTRS)

    Cintala, Mark J.; Horz, Friedrich

    1988-01-01

    Fragmental targets consisting of a coarse-grained gabbro were subjected to multiple impacts with stainless-steel spheres at 0.7, 1.4, and 1.9 km/s in order to investigate the effects of impact velocity on the generation and evolution of experimental regoliths. Although the low-velocity impactors were shown to be more efficient in terms of both mass comminution and the creating of new surfaces, the comminuted material formed by the faster projectiles possessed smaller mean grain sizes and larger proportions of fine-grained debris. The 2-4 mm material was found in all cases to exhibit a mass excess relative to the adjacent size fractions.

  16. Effects of bat composition, grip firmness, and impact location on postimpact ball velocity.

    PubMed

    Weyrich, A S; Messier, S P; Ruhmann, B S; Berry, M J

    1989-04-01

    The purpose of this investigation was to examine the effects of bat composition (aluminum and wooden), impact location [center of percussion (COP), center of gravity (COG), and end of the bat (E)], and grip firmness [tight (T) and no tension (NT)] on postimpact ball velocity. With the bats placed alternately in NT and T conditions, baseballs were delivered at a speed of 27.1 m.s-1 from a pitching machine positioned 1.5 m from the bat. High-speed photography (400 fps) was performed using a Locam camera positioned 7.54 m from and perpendicular to the principal plane of ball movement. A three-way ANCOVA revealed significant (P less than 0.01) differences in postimpact ball velocity between the three impact locations, with the COP yielding the greatest values, followed by the COG and E. Moreover, there was a significant (P less than 0.01) grip vs bat interaction. A simple-effects procedure revealed the following results: 1) the T grip produced greater (P less than 0.01) velocities than the NT grip across the aluminum (Al) bat; 2) there was no difference (P greater than 0.01) between the T and NT grips across the wooden (W) bat; 3) the W bat produced greater (P less than 0.01) velocities than the Al bat across the NT grip; and 4) there was no difference (P greater than 0.01) between the Al and W bats across the T grip.(ABSTRACT TRUNCATED AT 250 WORDS)

  17. Estimation of bubble-mediated air-sea gas exchange from concurrent DMS and CO2 transfer velocities at intermediate-high wind speeds

    NASA Astrophysics Data System (ADS)

    Bell, Thomas G.; Landwehr, Sebastian; Miller, Scott D.; de Bruyn, Warren J.; Callaghan, Adrian H.; Scanlon, Brian; Ward, Brian; Yang, Mingxi; Saltzman, Eric S.

    2017-07-01

    Simultaneous air-sea fluxes and concentration differences of dimethylsulfide (DMS) and carbon dioxide (CO2) were measured during a summertime North Atlantic cruise in 2011. This data set reveals significant differences between the gas transfer velocities of these two gases (Δkw) over a range of wind speeds up to 21 m s-1. These differences occur at and above the approximate wind speed threshold when waves begin breaking. Whitecap fraction (a proxy for bubbles) was also measured and has a positive relationship with Δkw, consistent with enhanced bubble-mediated transfer of the less soluble CO2 relative to that of the more soluble DMS. However, the correlation of Δkw with whitecap fraction is no stronger than with wind speed. Models used to estimate bubble-mediated transfer from in situ whitecap fraction underpredict the observations, particularly at intermediate wind speeds. Examining the differences between gas transfer velocities of gases with different solubilities is a useful way to detect the impact of bubble-mediated exchange. More simultaneous gas transfer measurements of different solubility gases across a wide range of oceanic conditions are needed to understand the factors controlling the magnitude and scaling of bubble-mediated gas exchange.

  18. The health effects of exercising in air pollution.

    PubMed

    Giles, Luisa V; Koehle, Michael S

    2014-02-01

    The health benefits of exercise are well known. Many of the most accessible forms of exercise, such as walking, cycling, and running often occur outdoors. This means that exercising outdoors may increase exposure to urban air pollution. Regular exercise plays a key role in improving some of the physiologic mechanisms and health outcomes that air pollution exposure may exacerbate. This problem presents an interesting challenge of balancing the beneficial effects of exercise along with the detrimental effects of air pollution upon health. This article summarizes the pulmonary, cardiovascular, cognitive, and systemic health effects of exposure to particulate matter, ozone, and carbon monoxide during exercise. It also summarizes how air pollution exposure affects maximal oxygen consumption and exercise performance. This article highlights ways in which exercisers could mitigate the adverse health effects of air pollution exposure during exercise and draws attention to the potential importance of land use planning in selecting exercise facilities.

  19. Concrete blocks` adverse effects on indoor air and recommended solutions

    SciTech Connect

    Ruppersberger, J.S.

    1995-04-01

    Air infiltration through highly permeable concrete blocks can allow entry of various serious indoor air pollutants including radon. An easy approach to avoiding these pollutants is to select a less-air-permeable concrete block. Tests show that air permeability of concrete blocks can vary by a factor greater than 50 (0.63--35 standard L/min/m{sup 2} at 3 Pa). The surface texture of the blocks correlates well with air permeability; test results of smoother, closed-surface-texture blocks were usually less air-permeable. During construction, air infiltration can be minimized by capping walls and carefully sealing around openings for utilities or other penetrations. Structures with indoor air-quality problems due to soil-gas entry can be mitigated more effectively with less coating material if the blocks have a closed surface texture. All coatings evaluated--cementaceous block filler (which has the lowest applied cost and is more than 99.5% effective), surface bonding cement, water-based epoxy, polysulfide vinyl acrylic, and latex (three coats)--were highly effective (more than 98%) in reducing air permeability when adequately applied. Coating selection should be influenced by expected service life, considering surface condition and cost.

  20. Effect of soil surface conditions on runoff velocity and sediment mean aggregate diameter

    NASA Astrophysics Data System (ADS)

    César Ramos, Júlio; Bertol, Ildegardis; Paz González, Antonio; de Souza Werner, Romeu; Marioti, Juliana; Henrique Bandeira, Douglas; Andrighetti Leolatto, Lidiane

    2013-04-01

    Soil cover and soil management are the factors that most influence soil erosion by water, because they directly affect soil surface roughness and surface cover. The main effect of soil cover by crop residues consists in dissipation of kinetic energy of raindrops and also partly kinetic energy of runoff, so that the soil disaggregation is considerably reduced but, in addition, soil cover captures detached soil particles, retains water on its surface and decreases runoff volume and velocity. In turn, soil surface roughness, influences soil surface water storage and infiltration and also runoff volume and velocity, sediment retention and subsequently water and sediment losses. Based on the above rationale, we performed a field experiment to assess the influence of soil cover and soil surface roughness on decay of runoff velocity as well as on mean diameter of transported sediments (D50 index). The following treatments were evaluated: SRR) residues of Italian ryegrass (Lolium multiflorum) on a smooth soil surfcace, SRV) residues of common vetch (Vicia sativa) on a smooth soil surface, SSR) scarification after cultivation of Italian ryegrass resulting in a rough surface, SSV) scarification after cultivation of common vetch resulting in a rough surface, and SBS) scarified bare soil with high roughness as a control. The field experiments was performed on an Inceptisol in South Brazil under simulated rainfall conditions during 2012. Experimental plots were 11 m long and 3.5 m wide with an area of 38.5 m2. Six successive simulated rainfall tests were applied using a rotating-boom rain simulator. During each test, rain intensity was 60 mmhr-1, whereas rain duration was 90 minutes. Runoff velocity showed no significant differences between cultivated treatments. However, when compared to bare soil treatment, SBS (0.178 m s-1) and irrespective of the presence of surface crop residues or scarification operations, cultivated soil treatments significantly reduced runoff velocity