Science.gov

Sample records for air velocity effects

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  2. Effect of High Air Velocities on the Distribution and Penetration of a Fuel Spray

    NASA Technical Reports Server (NTRS)

    Rothrock, A M

    1931-01-01

    By means of the NACA Spray Photography Equipment high speed moving pictures were taken of the formation and development of fuel sprays from an automatic injection valve. The sprays were injected normal to and counter to air at velocities from 0 to 800 feet per second. The air was at atmosphere temperature and pressure. The results show that high air velocities are an effective means of mixing the fuel spray with the air during injection.

  3. Effects of air velocity on laying hen production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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. Methane flux across the air-water interface - Air velocity effects

    NASA Technical Reports Server (NTRS)

    Sebacher, D. I.; Harriss, R. C.; Bartlett, K. B.

    1983-01-01

    Methane loss to the atmosphere from flooded wetlands is influenced by the degree of supersaturation and wind stress at the water surface. Measurements in freshwater ponds in the St. Marks Wildlife Refuge, Florida, demonstrated that for the combined variability of CH4 concentrations in surface water and air velocity over the water surface, CH4 flux varied from 0.01 to 1.22 g/sq m/day. The liquid exchange coefficient for a two-layer model of the gas-liquid interface was calculated as 1.7 cm/h for CH4 at air velocity of zero and as 1.1 + 1.2 v to the 1.96th power cm/h for air velocities from 1.4 to 3.5 m/s and water temperatures of 20 C.

  5. Effect of compressibility on the rise velocity of an air bubble in porous media

    NASA Astrophysics Data System (ADS)

    Cihan, Abdullah; Corapcioglu, M. Yavuz

    2008-04-01

    The objective of this study is to develop a theoretical model to analyze the effect of air compressibility on air bubble migration in porous media. The model is obtained by combining the Newton's second law of motion and the ideal gas law assuming that the air phase in the bubble behaves as an ideal gas. Numerical and analytical solutions are presented for various cases of interest. The model results compare favorably with both experimental data and analytical solutions reported in the literature obtained for an incompressible air bubble migration. The results show that travel velocity of a compressible air bubble in porous media strongly depends on the depth of air phase injection. A bubble released from greater depths travels with a slower velocity than a bubble with an equal volume injected at shallower depths. As an air bubble rises up, it expands with decreasing bubble pressure with depth. The volume of a bubble injected at a 1-m depth increases 10% as the bubble reaches the water table. However, bubble volume increases almost twofold when it reaches to the surface from a depth of 10 m. The vertical rise velocity of a compressible bubble approaches that of an incompressible one regardless of the injection depth and volume as it reaches the water table. The compressible bubble velocity does not exceed 18.8 cm/s regardless of the injection depth and bubble volume. The results demonstrate that the effect of air compressibility on the motion of a bubble cannot be neglected except when the air is injected at very shallow depths.

  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. 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.

  8. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  10. 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.

  11. Temperature and air velocity effects on ethanol emission from corn silage with the characteristics of an exposed silo face

    NASA Astrophysics Data System (ADS)

    Montes, Felipe; Hafner, Sasha D.; Rotz, C. Alan; Mitloehner, Frank M.

    2010-05-01

    Volatile organic compounds (VOCs) from agricultural sources are believed to be an important contributor to tropospheric ozone in some locations. Recent research suggests that silage is a major source of VOCs emitted from agriculture, but only limited data exist on silage emissions. Ethanol is the most abundant VOC emitted from corn silage; therefore, ethanol was used as a representative compound to characterize the pattern of emission over time and to quantify the effect of air velocity and temperature on emission rate. Ethanol emission was measured from corn silage samples removed intact from a bunker silo. Emission rate was monitored over 12 h for a range in air velocity (0.05, 0.5, and 5 m s -1) and temperature (5, 20, and 35 °C) using a wind tunnel system. Ethanol flux ranged from 0.47 to 210 g m -2 h -1 and 12 h cumulative emission ranged from 8.5 to 260 g m -2. Ethanol flux was highly dependent on exposure time, declining rapidly over the first hour and then continuing to decline more slowly over the duration of the 12 h trials. The 12 h cumulative emission increased by a factor of three with a 30 °C increase in temperature and by a factor of nine with a 100-fold increase in air velocity. Effects of air velocity, temperature, and air-filled porosity were generally consistent with a conceptual model of VOC emission from silage. Exposure duration, temperature, and air velocity should be taken into consideration when measuring emission rates of VOCs from silage, so emission rate data obtained from studies that utilize low air flow methods are not likely representative of field conditions.

  12. 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

  13. 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.

  14. 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.

  15. Effect of temperature and air velocity on drying kinetics, antioxidant capacity, total phenolic content, colour, texture and microstructure of apple (var. Granny Smith) slices.

    PubMed

    Vega-Gálvez, Antonio; Ah-Hen, Kong; Chacana, Marcelo; Vergara, Judith; Martínez-Monzó, Javier; García-Segovia, Purificación; Lemus-Mondaca, Roberto; Di Scala, Karina

    2012-05-01

    The aim of this work was to study the effect of temperature and air velocity on the drying kinetics and quality attributes of apple (var. Granny Smith) slices during drying. Experiments were conducted at 40, 60 and 80°C, as well as at air velocities of 0.5, 1.0 and 1.5ms(-1). Effective moisture diffusivity increased with temperature and air velocity, reaching a value of 15.30×10(-9)m(2)s(-1) at maximum temperature and air velocity under study. The rehydration ratio changed with varying both air velocity and temperature indicating tissue damage due to processing. The colour difference, ΔE, showed the best results at 80°C. The DPPH-radical scavenging activity at 40°C and 0.5ms(-1) showed the highest antioxidant activity, closest to that of the fresh sample. Although ΔE decreased with temperature, antioxidant activity barely varied and even increased at high air velocities, revealing an antioxidant capacity of the browning products. The total phenolics decreased with temperature, but at high air velocity retardation of thermal degradation was observed. Firmness was also determined and explained using glass transition concept and microstructure analysis. PMID:26434262

  16. 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. PMID:11282319

  17. 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.

  18. 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.

  19. Effect of the entrained air and initial droplet velocity on the release height parameter of a Gaussian spray drift model.

    PubMed

    Stainier, C; Destain, M F; Schiffers, B; Lebeau, F

    2006-01-01

    The increased concern about environmental effect of off-target deposits of pesticides use has resulted in the development of numerous spray drift models. Statistical models based on experimental field studies are used to estimate off-target deposits for different sprayers in various environmental conditions. Random-walk and computational fluid dynamics (CFD) models have been used to predict the effect of operational parameters and were extensively validated in wind tunnel. A third group, Gaussian dispersion models have been used for several years for the environmental assessment of the pesticide spray drift, mainly for aerial application. When these models were used for the evaluation of boom sprayer spray drift, their predictions were found unreliable in the short range, were the initial release conditions of the droplets have a significant effect on the spray deposits. For longer ranges, the results were found consistent with the field measurements as the characteristics of the source have a reduced influence on the small droplets drift. Three major parameters must be taken into account in order to define realistic initial conditions of the droplets in a spray drift model: the spray pattern of the nozzle, the boom movements and the effect of entrained air and droplet velocities. To take theses parameters into account in a Gaussian model, the nozzle droplet size distribution measured with a PIV setup to divide the nozzle output into several size classes. The spray deposits of each diameter class was computed for each successive position of the nozzle combining the nozzle spray distribution with drift computed with a Gaussian tilting plume model. The summation of these footprints resulted in the global drift of the nozzle. For increasing droplet size, the release height used in the Gaussian model was decreased from nozzle height to ground level using an experimental law to take into account the effect of entrained air and droplet initial velocity. The experimental

  20. Influence of Wind Velocity Fluctuation on Air Temperature Difference between the Fan and Ground Levels and the Effect of Frost Protective Fan Operation

    NASA Astrophysics Data System (ADS)

    Araki, Takuya; Matsuo, Kiyoshi; Miyama, Daisuke; Sumikawa, Osamu; Araki, Shinsuke

    We invested the influence of wind velocity fluctuation on air temperature difference between the fan (4.8 m) and ground levels (0.5 m) and the effect of frost protective fan operation in order to develop a new method to reduce electricity consumption due to frost protective fan operation. The results of the investigations are summarized as follows: (1) Air temperature difference between the fan (4.8 m) and ground levels (0.5 m) was decreased following an increase in wind velocity, and the difference was less than 1°C for a wind velocity more than 3.0 m/s at a height of 6.5 m. (2) When the wind velocity was more than 2-3 m/s, there was hardly any increase in the temperature of the leaves. In contrast, when the wind velocity was less than 2-3 m/s, an increase in the temperature of the leaves was observed. Based on these results, it is possible that when the wind velocity is greater than 2-3 m, it prevents thermal inversion. Therefore, there would be no warmer air for the frost protective fan to return to the tea plants and the air turbulence produced by the frost protective fan would not reach the plants under the windy condition.

  1. 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.

  2. The effect of air temperature, velocity and visual lean (VL) composition on the tempering times of frozen boneless beef blocks.

    PubMed

    Brown, Tim; James, Stephen J

    2006-08-01

    Beef blocks of two compositions, 100% and 50% visual lean (VL), in standard commercial packaging with nominal dimensions of 510×390×150mm were tempered from -18°C to -3°C using air at temperatures from 3°C to -3°C and velocities of 0.5 and 5ms(-1). These conditions were then modelled using a finite difference mathematical model and the accuracy of the model assessed by comparison with the experimental results. An extended range of conditions (including an intermediate air velocity of 2ms(-1) and an intermediate composition of 75% VL) was then modelled to produce data that can be used to design tempering processes. The results show that single stage air tempering of even single blocks within their cartons needs to be a long process. In air at 3°C and 5ms(-1), blocks of 50% VL rose to deep temperatures of -10°C and -3°C after 4.0 and 22.5h, respectively, while with 100% VL 4.6 and 27.3h were required. Under these conditions, the surface layers of the meat would have spent many hours in a thawed condition that would be detrimental to both drip and optimal processing. Using lower temperatures avoids thawing and at the same time produces an optimum temperature difference for subsequent processing. However, tempering times are substantially extended. For example, times to the above temperatures using air at -1°C and 5ms(-1) were 4.8 and 37.5h for 50% VL and 5.1 and 44.5h for 100% VL.

  3. Air velocity distribution in a commercial broiler house

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  4. 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

  5. 30 CFR 75.326 - Mean entry air velocity.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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. In exhausting face ventilation systems, the mean entry air velocity shall be at least 60 feet per...

  6. 30 CFR 75.326 - Mean entry air velocity.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 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. In exhausting face ventilation systems, the mean entry air velocity shall be at least 60 feet per...

  7. 30 CFR 75.326 - Mean entry air velocity.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 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. In exhausting face ventilation systems, the mean entry air velocity shall be at least 60 feet per...

  8. 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...

  9. 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...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. Measurement of vertical velocity using clear-air Doppler radars

    NASA Technical Reports Server (NTRS)

    Vanzandt, T. E.; Green, J. L.; Nastrom, G. D.; Gage, K. S.; Clark, W. L.; Warnock, J. M.

    1989-01-01

    A new clear air Doppler radar was constructed, called the Flatland radar, in very flat terrain near Champaign-Urbana, Illinois. The radar wavelength is 6.02 m. The radar has been measuring vertical velocity every 153 s with a range resolution of 750 m almost continuously since March 2, 1987. The variance of vertical velocity at Flatland is usually quite small, comparable to the variance at radars located near rough terrain during periods of small background wind. The absence of orographic effects over very flat terrain suggests that clear air Doppler radars can be used to study vertical velocities due to other processes, including synoptic scale motions and propagating gravity waves. For example, near rough terrain the shape of frequency spectra changes drastically as the background wind increases. But at Flatland the shape at periods shorter than a few hours changes only slowly, consistent with the changes predicted by Doppler shifting of gravity wave spectra. Thus it appears that the short period fluctuations of vertical velocity at Flatland are alsmost entirely due to the propagating gravity waves.

  16. Derivation of vertical air velocity from conventional Radiosonde ascents

    NASA Astrophysics Data System (ADS)

    Manguttathil Gopalakrishnan, Manoj; Mohanakumar, Kesavapillai; Samson, Titu; Kottayil, Ajil; Varadarajan, Rakesh; Rebello, Rejoy

    2016-07-01

    In this work, we devise a method to estimate air vertical velocity from ascending radiosondes similar to that described in published results, but with certain differences in deriving the balloon parameters and the drag coefficient, while not considering explicitly the heat exchange between the balloon and the environment. We basically decompose the observed balloon ascent rate into vertical velocity in still air due to buoyancy force and that due to vertical air motion. The first part is computed from basic hydrodynamical principles and the vertical velocity is derived as the difference between observed ascent rate and the estimated still air vertical velocity. The derived values agree reasonably well (r=0.66) with vertical velocities observed with a collocated wind profiler radar, and the sources of uncertainties are discussed. Since vertical velocity is a difficult quantity to measure directly without expensive methods, derivation of the same from the conventional radiosonde ascents could be of great importance to the meteorological communities.

  17. 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.

  18. 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.

  19. Minimum detectable air velocity by thermal flow sensors.

    PubMed

    Issa, Safir; Lang, Walter

    2013-08-19

    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.

  20. 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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 a variable-rate air-assisted sprayer for tree applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  4. Study on the effect of the side secondary air velocity on the aerodynamic field in a tangentially fired furnace with HBC-SSA Burner

    NASA Astrophysics Data System (ADS)

    Zhu, Tong; Sun, Shaozeng; Wu, Shaohua; Qin, Yukun

    1999-12-01

    The present paper has compared a group of furnace aerodynamic fields at different velocities of side secondary air (SSA) in a test model of 420t/h utility boiler, applying Horizontal Bias Combustion Pulverized Coal Burner with Side Secondary Air (HBC-SSA Burner). Experimental results show that, when the ram pressure ratio of side secondary air (SSA) to primary air (PA) (ρ2sv 2s /2 /ρ1v 1 2 ) is between 1.0 2.4, the furnace aerodynamic field only varies slightly. The relative rotational diameters (φ/L) in the burner domain are moderate and the furnace is in good fullness. When ρ2sv 2s /2 /ρ1v 1 2 is beyond 4, φ/L is so large that the stream sweeps water-cooled wall and rotates strongly in the furnace. Therefore, slagging and high temperature corrosion of tube metal will be formed on the water-cooled wall in actual operation. This investigation provides the basis for the application of this new type burner. In addition, numerical simulations are conducted, and some defects in the numerical simulation are also pointed out and analyzed in this paper.

  5. Fume hood performance: Face velocity variability inconsistent air volume systems

    SciTech Connect

    Volin, C.E.; Joao, R.V.; Gershey, E.L.; Reiman, J.S.; Party, E.

    1998-09-01

    A 3-year survey of 366 bench-type fume hoods in working laboratories in conventional, constant air volume settings showed that face velocities varied greatly from unit to unit and over time. Fume hoods with bypasses performed better than those without; however, even newly fabricated bypass hoods exhibited large variations. These variations were due to several factors; however, face velocities at 100 {+-} 10 ft/min at working sash heights in the range of 20 to 40 cm (8 to 16 inches) were attainable. The use of smoke showed poor containment, especially at face velocities below 85 ft/min (0.425 m/s) or above 130 ft/min (0.65 m/s) and when the hoods were obstructed by large items placed on the work surface. Auxiliary/supplemental air created unstable face velocities and poor smoke patterns. The analysis of 3 years of fume hood monitoring showed clearly the need for and importance of a maintenance program where the fume hood lower slots are cleaned and fans, ducts, dampers, and hoods are checked periodically.

  6. Relationship among shock-wave velocity, particle velocity, and adiabatic exponent for dry air

    NASA Astrophysics Data System (ADS)

    Kim, In H.; Hong, Sang H.; Jhung, Kyu S.; Oh, Ki-Hwan; Yoon, Yo K.

    1991-07-01

    Using the results of the detailed numerical calculations, it is shown that the relationship between the shock-wave velocity U sub s and the particle velocity U sub p for shock-compressed dry air can be represented accurately by the linear relation U sub s = a(P0) + b(P0)U sub p in a wide range of U sub p (U sub p = 2 to 9 ) km/s and initial pressure P0 = 10 to the -6th to 1 atm, where a and b are given by the cubic polynomials of log10P0. Based on the linear U sub s - U sub p relation, an analytic expression has been obtained for the adiabatic exponent gamma as a function of particle velocity.

  7. 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%.

  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. 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.

  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. 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.

  12. 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; minimum requirements. 84.140 Section 84.140 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and...

  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; minimum requirements. 84.140 Section 84.140 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and...

  14. 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; minimum requirements. 84.140 Section 84.140 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and...

  15. 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; minimum requirements. 84.140 Section 84.140 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and...

  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; minimum requirements. 84.140 Section 84.140 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Supplied-Air Respirators § 84.140 Air velocity and noise levels; hoods and...

  17. 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

  18. 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.

  19. 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.

  20. 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 ...

  1. 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; minimum requirements. 84.1139 Section 84.1139 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and...

  2. 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; minimum requirements. 84.202 Section 84.202 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and...

  3. 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; minimum requirements. 84.1139 Section 84.1139 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and...

  4. 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; minimum requirements. 84.202 Section 84.202 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and...

  5. 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; minimum requirements. 84.1139 Section 84.1139 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and...

  6. 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; minimum requirements. 84.1139 Section 84.1139 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and...

  7. 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; minimum requirements. 84.202 Section 84.202 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and...

  8. 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; minimum requirements. 84.1139 Section 84.1139 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH... Efficiency Respirators and Combination Gas Masks § 84.1139 Air velocity and noise levels; hoods and...

  9. 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; minimum requirements. 84.202 Section 84.202 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and...

  10. 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; minimum requirements. 84.202 Section 84.202 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND... PROTECTIVE DEVICES Chemical Cartridge Respirators § 84.202 Air velocity and noise levels; hoods and...

  11. 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

  12. 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

  13. 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.

  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. PMID:11538791

  15. 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.

  16. The effectiveness of a heated air curtain

    NASA Astrophysics Data System (ADS)

    Frank, Daria

    2014-11-01

    Air curtains are high-velocity plane turbulent jets which are installed in the doorway in order to reduce the heat and the mass exchange between two environments. The air curtain effectiveness E is defined as the fraction of the exchange flow prevented by the air curtain compared to the open-door situation. In the present study, we investigate the effects of an opposing buoyancy force on the air curtain effectiveness. Such an opposing buoyancy force arises for example if a downwards blowing air curtain is heated. We conducted small-scale experiments using water as the working fluid with density differences created by salt and sugar. The effectiveness of a downwards blowing air curtain was measured for situations in which the initial density of the air curtain was less than both the indoor and the outdoor fluid density, which corresponds to the case of a heated air curtain. We compare the effectiveness of the heated air curtain to the case of the neutrally buoyant air curtain. It is found that the effectiveness starts to decrease if the air curtain is heated beyond a critical temperature. Furthermore, we propose a theoretical model to describe the dynamics of the buoyant air curtain. Numerical results obtained from solving this model corroborate our experimental findings.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Toxic effects of air freshener emissions.

    PubMed

    Anderson, R C; Anderson, J H

    1997-01-01

    To evaluate whether emissions of a commercial air freshener produced acute toxic effects in a mammalian species, the authors allowed male Swiss-Webster mice to breathe the emissions of one commercial-brand solid air freshener for 1 h. Sensory irritation and pulmonary irritation were evaluated with the ASTM-E-981 test. A computerized version of this test measured the duration of the break at the end of inspiration and the duration of the pause at the end of expiration--two parameters subject to alteration via respiratory effects of airborne toxins. Measurements of expiratory flow velocity indicated changes in airflow limitation. The authors then subjected mice to a functional observational battery, the purpose of which was to probe for changes in nervous system function. Emissions of this air freshener at several concentrations (including concentrations to which many individuals are actually exposed) caused increases in sensory and pulmonary irritation, decreases in airflow velocity, and abnormalities of behavior measured by the functional observational battery score. The test atmosphere was subjected to gas chromatography/mass spectroscopy, and the authors noted the presence of chemicals with known irritant and neurotoxic properties. The Material Safety Data Sheet for the air freshener indicated that there was a potential for toxic effects in humans. The air freshener used in the study did not diminish the effect of other pollutants tested in combination. The results demonstrated that the air freshener may have actually exacerbated indoor air pollution via addition of toxic chemicals to the atmosphere.

  3. Cosmology with Peculiar Velocities: Observational Effects

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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 ΛCDM 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.

  4. Penetration of Liquid Jets into a High-velocity Air Stream

    NASA Technical Reports Server (NTRS)

    Chelko, Louis J

    1950-01-01

    Data are presented showing the penetration characteristics of liquid jets directed approximately perpendicular to a high-velocity air stream for jet-nozzle-throat diameters from 0.0135 to 0.0625 inch, air stream densities from 0.0805 to 0.1365 pound per cubic foot, liquid jet velocities from 168.1 to 229.0 feet per second and a liquid jet density of approximately 62 pounds per cubic foot. The data were analyzed and a correlation was developed that permitted the determination of the penetration length of the liquid jet for any operation condition within the range of variables investigated.

  5. Using eddy covariance to estimate air-sea gas transfer velocity for oxygen

    NASA Astrophysics Data System (ADS)

    Andersson, Andreas; Rutgersson, Anna; Sahlée, Erik

    2016-07-01

    Air-sea gas transfer velocity for O2 is calculated using directly measured fluxes with the eddy covariance technique. It is a direct method and is frequently used to determine fluxes of heat, humidity, and CO2, but has not previously been used to estimate transfer velocities for O2, using atmospheric eddy covariance data. The measured O2 fluxes are upward directed, in agreement with the measured air-sea gradient of the O2 concentration, and opposite to the direction of the simultaneously measured CO2 fluxes. The transfer velocities estimated from measurements are compared with prominent wind speed parameterizations of the transfer velocity for CO2 and O2, previously established from various measurement techniques. Our result indicates stronger wind speed dependence for the transfer velocity of O2 compared to CO2 starting at intermediate wind speeds. This stronger wind speed dependence appears to coincide with the onset of whitecap formation in the flux footprint and the strong curvature of a cubic wind-dependent function for the transfer velocity provides the best fit to the data. Additional data using the measured O2 flux and an indirect method (based on the Photosynthetic Quotient) to estimate oxygen concentration in water, support the stronger wind dependence for the transfer velocity of O2 compared to CO2.

  6. 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.

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

    PubMed

    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.

  8. 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.

  9. [Time lag effect between poplar' s sap flow velocity and microclimate factors in agroforestry system in West Liaoning Province].

    PubMed

    Di, Sun; Guan, De-xin; Yuan, Feng-hui; Wang, An-zhi; Wu, Jia-bing

    2010-11-01

    By using Granier's thermal dissipation probe, the sap flow velocity of the poplars in agroforestry system in west Liaoning was continuously measured, and the microclimate factors were measured synchronously. Dislocation contrast method was applied to analyze the sap flow velocity and corresponding air temperature, air humidity, net radiation, and vapor pressure deficit to discuss the time lag effect between poplar' s sap flow velocity and microclimate factors on sunny days. It was found that the poplar's sap flow velocity advanced of air temperature, air humidity, and vapor pressure deficit, and lagged behind net radiation. The sap flow velocity in June, July, August, and September was advanced of 70, 30, 50, and 90 min to air temperature, of 80, 30, 40, and 90 min to air humidity, and of 90, 50, 70, and 120 min to vapor pressure deficit, but lagged behind 10, 10, 40, and 40 min to net radiation, respectively. The time lag time of net radiation was shorter than that of air temperature, air humidity, and vapor pressure. The regression analysis showed that in the cases the time lag effect was contained and not, the determination coefficients between comprehensive microclimate factor and poplar's sap flow velocity were 0.903 and 0.855, respectively, indicating that when the time lag effect was contained, the determination coefficient was ascended by 2.04%, and thus, the simulation accuracy of poplar's sap flow velocity was improved. PMID:21360994

  10. [Time lag effect between poplar' s sap flow velocity and microclimate factors in agroforestry system in West Liaoning Province].

    PubMed

    Di, Sun; Guan, De-xin; Yuan, Feng-hui; Wang, An-zhi; Wu, Jia-bing

    2010-11-01

    By using Granier's thermal dissipation probe, the sap flow velocity of the poplars in agroforestry system in west Liaoning was continuously measured, and the microclimate factors were measured synchronously. Dislocation contrast method was applied to analyze the sap flow velocity and corresponding air temperature, air humidity, net radiation, and vapor pressure deficit to discuss the time lag effect between poplar' s sap flow velocity and microclimate factors on sunny days. It was found that the poplar's sap flow velocity advanced of air temperature, air humidity, and vapor pressure deficit, and lagged behind net radiation. The sap flow velocity in June, July, August, and September was advanced of 70, 30, 50, and 90 min to air temperature, of 80, 30, 40, and 90 min to air humidity, and of 90, 50, 70, and 120 min to vapor pressure deficit, but lagged behind 10, 10, 40, and 40 min to net radiation, respectively. The time lag time of net radiation was shorter than that of air temperature, air humidity, and vapor pressure. The regression analysis showed that in the cases the time lag effect was contained and not, the determination coefficients between comprehensive microclimate factor and poplar's sap flow velocity were 0.903 and 0.855, respectively, indicating that when the time lag effect was contained, the determination coefficient was ascended by 2.04%, and thus, the simulation accuracy of poplar's sap flow velocity was improved.

  11. A velocity dependent effective angle method for calibration of X-probes at low velocities

    NASA Astrophysics Data System (ADS)

    Bakken, Ole Martin; Krogstad, Per-Åge

    A velocity dependent effective angle (VDEA) method for the calibration of yaw response of hot-wire X-probes at low flow velocities (0.5-6 m/s) is presented. Comparisons with a full velocity vs. yaw-angle method (Österlund 1999) in a smooth wall channel flow indicate that there is only moderate advantage in using the latter method, which is considerably more laborious. Comparisons with direct numerical simulations (DNS) (Moser et al. 1999) and the more common fixed effective angle method (FEA) show that the VDEA method significantly improves estimates of Reynolds stresses compared to the FEA method.

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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)

  17. 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.

  18. 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.

  19. 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

  20. 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)

  1. Selection effects and binary galaxy velocity differences

    NASA Technical Reports Server (NTRS)

    Schneider, Stephen E.; Salpeter, Edwin E.

    1990-01-01

    Measurements of the velocity differences (delta v's) in pairs of galaxies from large statistical samples have often been used to estimate the average masses of binary galaxies. A basic prediction of these models is that the delta v distribution ought to decline monotonically. However, some peculiar aspects of the kinematics have been uncovered, with an anomalous preference for delta v approx. equal to 72 km s(sup-1) appearing to be present in the data. The authors examine a large sample of binary galaxies with accurate redshift measurements and confirm that the distribution of delta v's appears to be non-monotonic with peaks at 0 and approx. 72 km s (exp -1). The authors suggest that the non-zero peak results from the isolation criteria employed in defining samples of binaries and that it indicates there are two populations of binary orbits contributing to the observed delta v distribution.

  2. The effect of temperature and velocity on superlubricity.

    PubMed

    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. PMID:23037889

  3. 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.

  4. Numerical modeling of probe velocity effects for electromagnetic NDE methods

    NASA Astrophysics Data System (ADS)

    Shin, Y. K.; Lord, W.

    The present discussion of magnetic flux (MLF) leakage inspection introduces the behavior of motion-induced currents. The results obtained indicate that velocity effects exist at even low probe speeds for magnetic materials, compelling the inclusion of velocity effects in MLF testing of oil pipelines, where the excitation level and pig speed are much higher than those used in the present work. Probe velocity effect studies should influence probe design, defining suitable probe speed limits and establishing training guidelines for defect-characterization schemes.

  5. Primacy and frequency effects in absolute judgments of visual velocity.

    PubMed

    Sokolov, A; Pavlova, M; Ehrenstein, W H

    2000-07-01

    In absolute judgment tasks, identical stimuli are rated higher (or lower) when presented in a series of more frequent small (or large) stimuli. Using visual stimuli differing in velocity, we show that this conventional frequency effect is largely modulated by the primacy effect--that is, by the stimuli occurring on the early trials of a run. In Experiment 1, a frequency-like primacy effect was obtained with equal-frequent velocities. Identical velocities were rated faster when mainly slow rather than fast ones occurred on initial trials. In Experiment 2, we contrasted the frequency effect and the primacy effect: In runs with frequent slow velocities, mainly fast ones occurred earlier, whereas in runs with infrequent slow velocities, mainly slow ones did so. Lack of differences of ratings in the two conditions suggests that the two effects canceled each other. In Experiment 3, when mainly frequent velocities occurred earlier, the conventional frequency effect was obtained. We conclude that the conventional frequency effect represents a combination of the primacy effect and the pure frequency effect.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Influence of speckle effect on doppler velocity measurement

    NASA Astrophysics Data System (ADS)

    Zheng, Zheng; Changming, Zhao; Haiyang, Zhang; Suhui, Yang; Dehua, Zhang; Xingyuan, Zheng; Hongzhi, Yang

    2016-06-01

    In a coherent Lidar system, velocity measurement of a target is achieved by measuring Doppler frequency shift between the echo and local oscillator (LO) signals. The measurement accuracy is proportional to the spectrum width of Doppler signal. Actually, the speckle effect caused by the scattering of laser from a target will broaden the Doppler signal's spectrum and bring uncertainty to the velocity measurement. In this paper, a theoretical model is proposed to predict the broadening of Doppler spectrum with respect to different target's surface and motion parameters. The velocity measurement uncertainty caused by the broadening of spectrum is analyzed. Based on the analysis, we design a coherent Lidar system to measure the velocity of the targets with different surface roughness and transverse velocities. The experimental results are in good agreement with theoretical analysis. It is found that the target's surface roughness and transverse velocity can significantly affect the spectrum width of Doppler signal. With the increase of surface roughness and transverse velocity, the measurement accuracy becomes worse. However, the influence of surface roughness becomes weaker when the spot size of laser beam on the target is smaller.

  13. 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…

  14. Ultrasound imaging velocimetry: effect of beam sweeping on velocity estimation.

    PubMed

    Zhou, Bin; Fraser, Katharine H; Poelma, Christian; Mari, Jean-Martial; Eckersley, Robert J; Weinberg, Peter D; Tang, Meng-Xing

    2013-09-01

    As an emerging flow-mapping tool that can penetrate deep into optically opaque media such as human tissue, ultrasound imaging velocimetry has promise in various clinical applications. Previous studies have shown that errors occur in velocity estimation, but the causes have not been well characterised. In this study, the error in velocity estimation resulting from ultrasound beam sweeping in image acquisition is quantitatively investigated. The effects on velocity estimation of the speed and direction of beam sweeping relative to those of the flow are studied through simulation and experiment. The results indicate that a relative error in velocity estimation of up to 20% can be expected. Correction methods to reduce the errors under steady flow conditions are proposed and evaluated. Errors in flow estimation under unsteady flow are discussed.

  15. Displacement velocity effects on rock fracture shear strengths

    NASA Astrophysics Data System (ADS)

    Kleepmek, M.; Khamrat, S.; Thongprapha, T.; Fuenkajorn, K.

    2016-09-01

    Triaxial shear tests are performed to assess the effects of displacement velocity and confining pressure on shear strengths and dilations of tension-induced fractures and smooth saw-cut surfaces prepared in granite, sandstone and marl specimens. A polyaxial load frame is used to apply confining pressures between 1 and 18 MPa with displacement velocities ranging from 1.15 × 10-5 to 1.15 × 10-2 mm/s. The results indicate that the shearing resistances of smooth saw-cut surfaces tend to be independent of the displacement velocity and confining pressure. Under each confinement the peak and residual shear strengths and dilation rates of rough fractures increase with displacement velocities. The sheared-off areas increase when the confining pressure increases, and the displacement rate decreases. The velocity-dependent shear strengths tend to act more under high confining pressures for the rough fractures in strong rock (granite) than for the smoother fractures in weaker rocks (sandstone and marl). An empirical criterion that explicitly incorporates the effects of shear velocity is proposed to describe the peak and residual shear strengths. The criterion fits well to the test results for the three tested rocks.

  16. 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.

  17. 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.

  18. Effects of velocity and weight support on ground reaction forces and metabolic power during running.

    PubMed

    Grabowski, Alena M; Kram, Rodger

    2008-08-01

    The biomechanical and metabolic demands of human running are distinctly affected by velocity and body weight. As runners increase velocity, ground reaction forces (GRF) increase, which may increase the risk of an overuse injury, and more metabolic power is required to produce greater rates of muscular force generation. Running with weight support attenuates GRFs, but demands less metabolic power than normal weight running. We used a recently developed device (G-trainer) that uses positive air pressure around the lower body to support body weight during treadmill running. Our scientific goal was to quantify the separate and combined effects of running velocity and weight support on GRFs and metabolic power. After obtaining this basic data set, we identified velocity and weight support combinations that resulted in different peak GRFs, yet demanded the same metabolic power. Ideal combinations of velocity and weight could potentially reduce biomechanical risks by attenuating peak GRFs while maintaining aerobic and neuromuscular benefits. Indeed, we found many combinations that decreased peak vertical GRFs yet demanded the same metabolic power as running slower at normal weight. This approach of manipulating velocity and weight during running may prove effective as a training and/or rehabilitation strategy.

  19. Methods of Measurement of High Air Velocities by the Hot-wire Method

    NASA Technical Reports Server (NTRS)

    Weske, John R.

    1943-01-01

    Investigations of strengths of hot wires at high velocities were conducted with platinum, nickel, and tungsten at approximately 200 Degrees Celcius hot-wire temperature. The results appear to disqualify platinum for velocities approaching the sonic range; whereas nickel withstands sound velocity, and tungsten may be used for supersonic velocities under standard atmospheric conditions. Hot wires must be supported by rigid prolongs at high velocities to avoid wire breakage. Resting current measurements for constant temperature show agreement with King's relation.

  20. General relativistic effects in galactic rotation velocity profiles

    NASA Astrophysics Data System (ADS)

    Cisneros, Sophia

    2008-10-01

    The anomalously high galactic rotation velocities deduced from spectroscopic observations have motivated the conjecture of additional Dark Matter. Here we investigate to what extent this picture may be impacted by general relativistic effects. Previous work involving General Relativity has used linearized field equations to arrive at estimates of wavelength shifts arising from spin induced curvature. We show here that, using the fully contravariant 3+1 dimensional wave equation (the D'Alembertian for a Kerr Metric), non-trivial results for observed velocities can be obtained. These velocities are much higher than those obtained from the linearized equations. The Kerr rotation curve is derived from first principles. The wavelength shifts are then weighted by an empirical factor which accounts for difference in curvature of the originating galaxy and the Milky Way. The resulting apparent radial dependence of the velocity is much flatter than obtained in the Keplerian case, which opens the possibility that, for our test galaxy(M33), we have correct estimates of (luminous) matter on the exterior edges, but have only underestimated the mass at the center. This result suggests that general relativistic effects mitigate, or may possibly even obviate the need to invoke the presence of Dark Matter in order to explain the observed apparent velocity profiles. All rotation curves presented are computed with data graciously provided by E.Corbelli and R.Walterbos for M33, taken in the wavelength band of H/alpha.

  1. 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.

  2. 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,...

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  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 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.

  11. Anomalous Skin Effect for Anisotropic Electron Velocity Distribution Function

    SciTech Connect

    Igor Kaganovich; Edward Startsev; Gennady Shvets

    2004-02-19

    The anomalous skin effect in a plasma with a highly anisotropic electron velocity distribution function (EVDF) is very different from skin effect in a plasma with the isotropic EVDF. An analytical solution was derived for the electric field penetrated into plasma with the EVDF described as a Maxwellian with two temperatures Tx >> Tz, where x is the direction along the plasma boundary and z is the direction perpendicular to the plasma boundary. The skin layer was found to consist of two distinctive regions of width of order nTx/w and nTz/w, where nTx,z/w = (Tx,z/m)1/2 is the thermal electron velocity and w is the incident wave frequency.

  12. Detailed Comparison of Blast Effects in Air and Vacuum

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    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 (˜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, ˜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 better understand the time-dependent coupling of shock energy that plastically deforms the plates.

  13. 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.

  14. 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).

  15. 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.

  16. 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.

  17. 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.

  18. The relationship between ocean surface turbulence and air-sea gas transfer velocity: An in-situ evaluation

    NASA Astrophysics Data System (ADS)

    Esters, L.; Landwehr, S.; Sutherland, G.; Bell, T. G.; Saltzman, E. S.; Christensen, K. H.; Miller, S. D.; Ward, B.

    2016-05-01

    Although the air-sea gas transfer velocity k is usually parameterized with wind speed, the so-called small-eddy model suggests a relationship between k and ocean surface dissipation of turbulent kinetic energy ɛ. Laboratory and field measurements of k and ɛ have shown that this model holds in various ecosystems. Here, field observations are presented supporting the theoretical model in the open ocean. These observations are based on measurements from the Air-Sea Interaction Profiler and eddy covariance CO2 and DMS air-sea flux data collected during the Knorr11 cruise. We show that the model results can be improved when applying a variable Schmidt number exponent compared to a commonly used constant value of 1/2. Scaling ɛ to the viscous sublayer allows us to investigate the model at different depths and to expand its applicability for more extensive data sets.

  19. 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.

  20. Effect of temperature on ultrasonic velocity in steel

    SciTech Connect

    Biagiotti, S.F. Jr.

    1997-12-01

    The increased mechanical integrity requirements imposed by process safety management regulations (OSHA 29 CFR 1910.119) are forcing more operators to conduct on-stream corrosion monitoring inspections. These inspections rely predominantly on the results of ultrasonic thickness (UT) measurements, which in turn are managed by using commercial software databases. UT equipment vendors such as Krautkramer Branson recommend correcting measured thickness values {minus}0.5% per 100 F, whereas ASTM E797 recommends a {minus}1% per 100 F correction for carbon steel materials. However, little technical literature exists on the topic of UT correction factors as a function of temperature. The consequence of over-correcting a UT measurement may cause premature retirement of a piece of equipment, resulting in an unnecessary outage or material outlay. Therefore, having the appropriate UT temperature correction factors available will increase the reliability of thickness data and ultimately save operators time and money. To identify the effect of temperature on straight beam (0{degree}) ultrasonic thickness values (i.e., changes in the sound velocity), experiments were conducted using carbon steel, two low-alloy steels, and 316 stainless steel materials at temperatures ranging from 70 F to 650 F. Statistical analysis of the data revealed an inverse relationship between temperature and ultrasonic velocity over the test range with a better than 97% confidence level. The change in ultrasonic velocity with temperature also varied depending on the composition of the material. Low alloy steels (i.e., AISI 4130, 4340) were less dependent on temperature than plain carbon steels, while the 316 stainless steel had a greater temperature dependence. A series of graphs, linear regression results, and correction factors are presented for plain carbon steel (C-Mn), AISI 4130 (1Cr-1/4Mo), AISI 4340 (2Ni-1Cr-1/4Mo) and 316 stainless steel (18Cr-12Ni-3Mo).

  1. Airborne nanoparticle exposures while using constant-flow, constant-velocity, and air-curtain-isolated fume hoods.

    PubMed

    Tsai, Su-Jung Candace; Huang, Rong Fung; Ellenbecker, Michael J

    2010-01-01

    Tsai et al. (Airborne nanoparticle exposures associated with the manual handling of nanoalumina and nanosilver in fume hoods. J Nanopart Res 2009; 11: 147-61) found that the handling of dry nanoalumina and nanosilver inside laboratory fume hoods can cause a significant release of airborne nanoparticles from the hood. Hood design affects the magnitude of release. With traditionally designed fume hoods, the airflow moves horizontally toward the hood cupboard; the turbulent airflow formed in the worker wake region interacts with the vortex in the constant-flow fume hood and this can cause nanoparticles to be carried out with the circulating airflow. Airborne particle concentrations were measured for three hood designs (constant-flow, constant-velocity, and air-curtain hoods) using manual handling of nanoalumina particles. The hood operator's airborne nanoparticle breathing zone exposure was measured over the size range from 5 nm to 20 mum. Experiments showed that the exposure magnitude for a constant-flow hood had high variability. The results for the constant-velocity hood varied by operating conditions, but were usually very low. The performance of the air-curtain hood, a new design with significantly different airflow pattern from traditional hoods, was consistent under all operating conditions and release was barely detected. Fog tests showed more intense turbulent airflow in traditional hoods and that the downward airflow from the double-layered sash to the suction slot of the air-curtain hood did not cause turbulence seen in other hoods. PMID:19933309

  2. After-effects of using a weighted bat on subsequent swing velocity and batters' perceptions of swing velocity and heaviness.

    PubMed

    Otsuji, Tamiki; Abe, Masafu; Kinoshita, Hiroshita

    2002-02-01

    In baseball and softball, warm-up swings with a weighted bat have been believed to increase swing velocity when an ordinary bat is used in the subsequent competitive situation. The purpose of this study was to investigate the after-effects of using a weighted bat on subsequent swing velocity and batters' perceptions of swing velocity and heaviness. Eight men in varsity softball and baseball hit a ball suspended from the ceiling 45 times (3 sets of 15 trials). For each set, the initial 5 trials were done using an ordinary 920-g wooden bat (Control condition), and the following 5 trials by a bat with an 800-g bat ring (Weighted condition), and the final 5 trials again by the ordinary bat (post-Weighted condition). Analysis of variance showed a significant decrease of 3.3% in the measured linear velocity of the bat prior to impact with the ball for the first swing of the post-Weighted condition compared with the Control condition. From the second swing the velocity returned to the level of the Control condition. Subjective judgment of the heaviness and velocity of swings for the Weighted and post-Weighted conditions by each participant showed that the ordinary bat felt lighter and swing speed felt faster for the post-Weighted condition. The advantage of the warm-up with a weighted bat was thus psychological and not biomechanical. PMID:11883550

  3. After-effects of using a weighted bat on subsequent swing velocity and batters' perceptions of swing velocity and heaviness.

    PubMed

    Otsuji, Tamiki; Abe, Masafu; Kinoshita, Hiroshita

    2002-02-01

    In baseball and softball, warm-up swings with a weighted bat have been believed to increase swing velocity when an ordinary bat is used in the subsequent competitive situation. The purpose of this study was to investigate the after-effects of using a weighted bat on subsequent swing velocity and batters' perceptions of swing velocity and heaviness. Eight men in varsity softball and baseball hit a ball suspended from the ceiling 45 times (3 sets of 15 trials). For each set, the initial 5 trials were done using an ordinary 920-g wooden bat (Control condition), and the following 5 trials by a bat with an 800-g bat ring (Weighted condition), and the final 5 trials again by the ordinary bat (post-Weighted condition). Analysis of variance showed a significant decrease of 3.3% in the measured linear velocity of the bat prior to impact with the ball for the first swing of the post-Weighted condition compared with the Control condition. From the second swing the velocity returned to the level of the Control condition. Subjective judgment of the heaviness and velocity of swings for the Weighted and post-Weighted conditions by each participant showed that the ordinary bat felt lighter and swing speed felt faster for the post-Weighted condition. The advantage of the warm-up with a weighted bat was thus psychological and not biomechanical.

  4. 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.

  5. 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.

  6. Density and compressibility effects in turbulent subsonic jets part 1: mean velocity field

    NASA Astrophysics Data System (ADS)

    Wang, Zhexuan; Andreopoulos, Yiannis

    2010-02-01

    The behavior of compressible jets originated from initially turbulent pipe flows issuing in still air has been investigated at three different subsonic Mach numbers, 0.3, 0.6 and 0.9. Helium, nitrogen and krypton gases were used to generate the jet flows and investigate the additional effects of density on the flow structure. Particle image velocimetry, high-frequency response pressure transducers and thermocouples were used to obtain velocity, Mach number and total temperature measurements inside the flow field. The jets were formed at the exit of an adiabatic compressible frictional turbulent pipe flow, which was developing toward its corresponding sonic conditions inside the pipe, and continued to expand within the first four diameters distance after it exited the pipe. Theoretical considerations based on flow self-similarity were used to obtain the decay of Mach number along the centerline of the jets for the first time. It was found that this decay depends on two contributions, one from the velocity field which is inversely proportional to the distance from the exit and one from the thermal field which is proportional to this distance. As a result, a small non-linearity in the variation of the inverse Mach number with downstream distance was found. The decay of the Mach number at the centerline of the axisymmetric jets increases by increasing the initial Mach number at the exit of the flow for all jets. The decay of mean velocity at the centerline of the jets is also higher at higher exit Mach numbers. However, the velocity non-dimensionalized by the exit velocity seems to decrease faster at low exit Mach numbers, suggesting a reduced mixing with increasing exit flow Mach numbers. Helium jets were found to have the largest spreading rate among the three different gas jets used in the present investigation, while krypton jets had the lowest spreading rate. The spreading rate of each gas decreases with increasing its kinetic energy relatively to its internal

  7. 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.

  8. EFFECTS OF HIGH SEDIMENT CONCENTRATIONS ON VELOCITY AND SEDIMENT DISTRIBUTIONS.

    USGS Publications Warehouse

    McCutcheon, Steve C.; Bradley, Jeffrey B.; ,

    1984-01-01

    Several classifications are required to describe sediment-transporting flow. The flow may be turbulent or laminar, Newtonian or non-Newtonian, and may also have a uniform or nonuniform concentration profile. As sediment concentration or transport increases, the character of flow changes. Generally, fall velocity and effective fall diameter decrease. The viscosity of the mixture increases. The flow becomes non-Newtonian when particle interaction becomes dominant. In the lowest concentration ranges, flows are Newtonian, generally nonuniform by concentration, and almost exclusively turbulent. Mudflows are non-Newtonian and usually laminar flows of a nearly uniform concentration. In the interim ranges are found transitions to non-Newtonian and laminar flows and uniform concentration profiles.

  9. 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

  10. Effect of water depth and water velocity upon the surfacing frequency of the bimodally respiring freshwater turtle, Rheodytes leukops.

    PubMed

    Gordos, Matthew A; Franklin, Craig E; Limpus, Colin J

    2004-08-01

    This study examines the effect of increasing water depth and water velocity upon the surfacing behaviour of the bimodally respiring turtle, Rheodytes leukops. Surfacing frequency was recorded for R. leukops at varying water depths (50, 100, 150 cm) and water velocities (5, 15, 30 cm s(-1)) during independent trials to provide an indirect cost-benefit analysis of aquatic versus pulmonary respiration. With increasing water velocity, R. leukops decreased its surfacing frequency twentyfold, thus suggesting a heightened reliance upon aquatic gas exchange. An elevated reliance upon aquatic respiration, which presumably translates into a decreased air-breathing frequency, may be metabolically more efficient for R. leukops compared to the expenditure (i.e. time and energy) associated with air-breathing within fast-flowing riffle zones. Additionally, R. leukops at higher water velocities preferentially selected low-velocity microhabitats, presumably to avoid the metabolic expenditure associated with high water flow. Alternatively, increasing water depth had no effect upon the surfacing frequency of R. leukops, suggesting little to no change in the respiratory partitioning of the species across treatment settings. Routinely long dives (>90 min) recorded for R. leukops indicate a high reliance upon aquatic O2 uptake regardless of water depth. Moreover, metabolic and temporal costs attributed to pulmonary gas exchange within a pool-like environment were likely minimal for R. leukops, irrespective of water depth. PMID:15277564

  11. The effects of forced air flow and oxygen concentration on flammability, smoke density, and pyrolytic toxicity

    NASA Technical Reports Server (NTRS)

    Sauers, D. G.

    1976-01-01

    The question is posed whether forced air flow should be incorporated into flammability tests as a relevant variable. A test apparatus is described which permits tests to be conducted on small test specimens in a forced flow which is (continuously) variable over flow velocities from zero to 300 feet per minute (1.52 m/s). The effects of air-flow rate and oxygen concentration on flame propagation rate, maximum smoke density, and pyrolytic product toxicity were measured for a single material and were statistically evaluated. Regression analysis was used to graph the resulting relationships. It is concluded that air velocity is an important variable for laboratory flammability testing.

  12. 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. PMID:20681430

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Effect of atomization air on droplet dynamics of spray flames

    SciTech Connect

    Presser, C.; Semerjian, H.G. . Center for Chemical Technology); Gupta, A.K. . Dept. of Mechanical Engineering)

    1988-01-01

    Fuel spray combustions is an important part of a wide variety of propulsion and power systems such as furnaces and gas turbine combustors, afterburners, fuel-injection internal combustion engines, liquid rocket engines, etc. Recent studies using air-assist nozzles have shown that the design and fabrication of these nozzles can directly influence spray circumferential uniformity, i.e., the presence of asymmetrical fuel flux profiles in combustors. The practical implications of these fuel flux nonuniformities are that they seriously alter the spray structure, which subsequently affects droplet/air interactions, local fuel/air mixing, overall flame characteristics and combustor performance, and pollutant emission levels. In addition, the effect of aerodynamic factors on spray characteristics has been investigated. This paper discusses the effect of atomization air on the droplet dynamics of spray flames formed by an air-assist nozzle. Presented are spatial distributions of mean droplet velocity and their probability distributions, which provide quantitative information for examination of the observed spray flame features.

  18. 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.

  19. Adverse health effects of outdoor air pollutants.

    PubMed

    Curtis, Luke; Rea, William; Smith-Willis, Patricia; Fenyves, Ervin; Pan, Yaqin

    2006-08-01

    Much research on the health effects of outdoor air pollution has been published in the last decade. The goal of this review is to concisely summarize a wide range of the recent research on health effects of many types of outdoor air pollution. A review of the health effects of major outdoor air pollutants including particulates, carbon monoxide, sulfur and nitrogen oxides, acid gases, metals, volatile organics, solvents, pesticides, radiation and bioaerosols is presented. Numerous studies have linked atmospheric pollutants to many types of health problems of many body systems including the respiratory, cardiovascular, immunological, hematological, neurological and reproductive/ developmental systems. Some studies have found increases in respiratory and cardiovascular problems at outdoor pollutant levels well below standards set by such agencies as the US EPA and WHO. Air pollution is associated with large increases in medical expenses, morbidity and is estimated to cause about 800,000 annual premature deaths worldwide [Cohen, A.J., Ross Alexander, H., Ostro, B., Pandey, K.D., Kryzanowski, M., Kunzail, N., et al., 2005. The global burden of disease due to outdoor air pollution. J Toxicol Environ Health A. 68: 1-7.]. Further research on the health effects of air pollution and air pollutant abatement methods should be very helpful to physicians, public health officials, industrialists, politicians and the general public. PMID:16730796

  20. Air damping effect on the air-based CMUT operation

    NASA Astrophysics Data System (ADS)

    Cha, Bu-Sang; Kanashima, Takeshi; Lee, Seung-Mok; Okuyama, Masanori

    2015-08-01

    The vibration amplitude, damping ratio and viscous damping force in capacitive micromachinedultrasonic transducers (CMUTs) with a perforated membrane have been calculated theoretically and compared with the experimental data on its vibration behavior. The electrical bias of the DC and the AC voltages and the operation frequency conditions influence the damping effect because leads to variations in the gap height and the vibration velocity of the membrane. We propose a new estimation method to determine the damping ratio by the decay rate of the vibration amplitudes of the perforated membrane plate are measured using a laser vibrometer at each frequency, and the damping ratios were calculated from those results. The influences of the vibration frequency and the electrostatic force on the damping effect under the various operation conditions have been studied.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Effect of bubble flow velocity on drag-force and shear stress working on submerged hollow fibre membrane.

    PubMed

    Nagaoka, H; Kurosaka, M; Shibata, N; Kobayashi, M

    2006-01-01

    This study is aimed at elucidating the mechanism by which rising air bubbles induce shear stress on hollow fibre membrane surfaces. Shear stress on hollow fibre membrane surfaces (laterally-set and vertically-set) caused by aeration was measured directly using a two-direction load sensor. In the laterally-set hollow fibre module, time-averaged upward-direction shear stress on the membrane surface was compared to theoretical shear stress values considering the effect of water flow on membrane surface. Measured time-average shear stress values were almost 200 times larger than theoretical values implying strong interactions between bubbles and solid surface. In the vertically-set membrane module, velocity measurement of bubble flow using laser Doppler velocimeter revealed that drag force working on membrane surface was closely related to upward-direction water velocity. Also fluctuation of drag force and shear force on membrane surface was found to be related to velocity fluctuation (turbulence).

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Air-driven Brazil nut effect

    NASA Astrophysics Data System (ADS)

    Naylor, M.; Swift, Michael; King, P.

    2003-07-01

    A large heavy object may rise to the top of a bed of smaller particles under the influence of vertical vibration, the “Brazil nut effect.” Recently it has been noted that interstitial air can influence the Brazil nut rise time. Here we report that the air movement induced by vertical vibration produces a very strong Brazil nut effect for fine granular beds. We use a porous-bottomed box to investigate the mechanism responsible for this effect and to demonstrate that it is related to the piling of fine beds, first reported by Chladni and studied by Faraday. Both effects are due to the strong interaction of the fine particles with the air, as it is forced through the bed by the vibration.

  13. 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.

  14. Forward velocity effects on jet noise with dominant internal noise source

    NASA Technical Reports Server (NTRS)

    Vonglahn, U. H.; Goodykoontz, J. H.

    1973-01-01

    Acoustic data, with and without forward velocity, were obtained with a circular nozzle using a quiet flow system and one dominated by a low frequency internal noise source (analogous to combustion noise). Forward velocity effects were obtained by installing the test nozzle in a free jet. Farfield noise data were obtained at jet pressure ratios from 1.3 to 1.7 and forward velocities up to 260 ft/sec. With a quiet flow system, jet noise is reduced by forward velocity. With a dominant low frequency core noise source, the portion of the noise spectra dominated by this source was not appreciably affected by forward velocity.

  15. 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.

  16. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  18. 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.

  19. Effects of air emissions on wildlife resources. Air pollution and acid rain report No. 1

    SciTech Connect

    Newman, J.R.

    1980-05-01

    This publication describes in general the pathways of contamination, direct and indirect effects of air emissions on wildlife resources, and the potential use of wildlife as biological indicators of air quality degradation. Also included in the report are summaries of air pollution incidents involving wildlife, responses of wildlife to air pollution, major target systems of selected air pollutants, and information on the capacity of some air pollutants to accumulate in body tissues.

  20. Asteroid collisions: Target size effects and resultant velocity distributions

    NASA Astrophysics Data System (ADS)

    Ryan, Eileen V.

    1993-03-01

    To study the dynamic fragmentation of rock to simulate asteroid collisions, we use a 2-D, continuum damage numerical hydrocode which models two-body impacts. This hydrocode monitors stress wave propagation and interaction within the target body, and includes a physical model for the formation and growth of cracks in rock. With this algorithm we have successfully reproduced fragment size distributions and mean ejecta speeds from laboratory impact experiments using basalt, and weak and strong mortar as target materials. Using the hydrocode, we have determined that the energy needed to fracture a body has a much stronger dependence on target size than predicted from most scaling theories. In addition, velocity distributions obtained indicate that mean ejecta speeds resulting from large-body collisions do not exceed escape velocities.

  1. [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. PMID:25115476

  2. [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.

  3. 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.

  4. 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.

  5. Effects of walk-by and sash movement on contaminant leakage of air curtain-isolated fume hood.

    PubMed

    Huang, Rong Fung; Chen, Hong Da; Hung, Chien-Hsiung

    2007-12-01

    The effects of the walk-by motion and sash movement on the containment leakage of an air curtain-isolated fume hood were evaluated and compared with the results of a corresponding conventional fume hood. The air curtain was generated by a narrow planar jet issued from the double-layered sash and a suction slot-flow arranged on the floor of the hood just behind the doorsill. The conventional fume hood used for comparison had the major dimensions identical to the air-curtain hood. SF tracer-gas concentrations were released and measured following the prEN 14175-3:2003 protocol to examine the contaminant leakage levels. Experimental results showed that operating the air-curtain hood at the suction velocity above about 6 m/s and jet velocity about 1 m/s could provide drastically high containment performance when compared with the corresponding conventional fume hood operated at the face velocity of 0.5 m/s. The total air flow required for the air-curtain hood operated at 6 m/s suction velocity and 1 m/s jet velocity was about 20% less than that exhausted by the conventional fume hood. If the suction velocity of the air-curtain hood was increased above 8 m/s, the containment leakage during dynamic motions could be reduced to ignorable level (about 10(3) ppm). PMID:18212476

  6. The effect of cortical endplates on ultrasound velocity through the calcaneus: an in vitro study.

    PubMed

    Njeh, C F; Langton, C M

    1997-05-01

    Ultrasound velocity has been reported as a good predictor of bone strength measured in vitro using standard mechanical testing techniques. Such mechanical investigation of bone strength cannot be carried out in vivo, because of the invasive nature of the testing. Therefore to be able to extrapolate the in vitro findings to the clinical situation, the effect of cortex on ultrasound transmission velocity through the calcaneus is required. This was investigated in vitro by measuring ultrasound velocity through samples of different modification using a CUBAResearch ultrasound machine. The different sample modifications were: "whole" (soft tissue removed), "core" (cylindrical sample), "can" (cancellous sample without the cortex) and "def" (defatted cancellous sample). Ultrasound transmission velocity for the various sample modification were highly correlated with each other (r = 0.80-0.97). Coring resulted in a 0.77% increase in the mean velocity. Substituting bone marrow (defatting) with water at room temperature had no measurable effect on the ultrasound velocity. The velocity in the whole samples and the cancellous samples were statistically different with the cortex introducing only a 2% increase in the ultrasound velocity. Therefore the in vivo ultrasound velocity measured at the calcaneus is determined mainly by the cancellous bone component which is more sensitive to osteoporotic changes. Hence the reported ability of ultrasound velocity in vitro to predict bone strength could be expected in vivo.

  7. 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.

  8. Respiratory effects of indoor air pollution

    SciTech Connect

    Samet, J.M.; Marbury, M.C.; Spengler, J.D.

    1987-05-01

    Since the early 1970s, the health effects of indoor air pollution have been investigated with increasing intensity. A large body of literature is now available on diverse aspects of indoor air pollution: sources, concentrations, health effects, engineering, and policy. This article provides a selective summary of this new information with an emphasis on health effects relevant to health care practitioners concerned primarily with immunologically mediated respiratory diseases. We address exposures associated with acute and chronic respiratory effects: tobacco smoke, nitrogen dioxide, wood smoke, and formaldehyde. The article also describes the diverse health problems experienced by workers in newer sealed office buildings. The importance of indoor concentrations in determining personal exposures to pollutants is emphasized.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. Static and dynamic characteristics of angular velocity and acceleration transducers based on optical tunneling effect

    NASA Astrophysics Data System (ADS)

    Busurin, V. I.; Korobkov, V. V.; Htoo Lwin, Naing; Tuan, Phan Anh

    2016-08-01

    Theoretical and experimental analysis of quasi-linear conversion function of angular velocity and acceleration microoptoelectromechnical (MOEM) transducers based on optical tunneling effect (OTE) are conducted. Equivalent oscillating circuit is developed and dynamic characteristics of angular velocity and acceleration MOEM-transducers are investigated.

  16. 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…

  17. 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.

  18. 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

  19. 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. PMID:27167064

  20. Human health effects of air pollution.

    PubMed

    Kampa, Marilena; Castanas, Elias

    2008-01-01

    Hazardous chemicals escape to the environment by a number of natural and/or anthropogenic activities and may cause adverse effects on human health and the environment. Increased combustion of fossil fuels in the last century is responsible for the progressive change in the atmospheric composition. Air pollutants, such as carbon monoxide (CO), sulfur dioxide (SO(2)), nitrogen oxides (NOx), volatile organic compounds (VOCs), ozone (O(3)), heavy metals, and respirable particulate matter (PM2.5 and PM10), differ in their chemical composition, reaction properties, emission, time of disintegration and ability to diffuse in long or short distances. Air pollution has both acute and chronic effects on human health, affecting a number of different systems and organs. It ranges from minor upper respiratory irritation to chronic respiratory and heart disease, lung cancer, acute respiratory infections in children and chronic bronchitis in adults, aggravating pre-existing heart and lung disease, or asthmatic attacks. In addition, short- and long-term exposures have also been linked with premature mortality and reduced life expectancy. These effects of air pollutants on human health and their mechanism of action are briefly discussed.

  1. 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.

  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. 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. PMID:18074287

  4. 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 ...

  5. Investigation of the impact of imposed air inlet velocity oscillations on the formation and oxidation of soot using simultaneous 2-Colour-TIRE-LII

    NASA Astrophysics Data System (ADS)

    Aleksandrov, A.; Suntz, R.; Bockhorn, H.

    2015-05-01

    The response of non-premixed swirling flames to acoustic perturbations at various frequencies (0-350 Hz) and the impact of imposed air inlet velocity oscillations on the formation and oxidation of soot are investigated. The results obtained from these flames are of special interest for "rich-quenched-lean" (RQL) combustion concepts applied in modern gas turbines. In RQL combustion, the fuel is initially oxidized by air under fuel-rich conditions in a first stage followed by a fuel-lean combustion step in a second stage. To mimic soot formation and oxidation in RQL combustion, soot particle measurements in highly turbulent, non-premixed swirling natural gas/ethylene-confined flames at imposed air inlet velocity oscillations are performed using simultaneous 2-Colour-Time-Resolved-Laser-Induced Incandescence (simultaneous 2-Colour-TIRE-LII). The latter technique is combined with line-of-sight averaged OH*-chemiluminescence imaging, measurements of the velocity field by high-speed particle imaging velocimetry under reactive combustion conditions and measurements of the mean temperature field obtained by a thermocouple. A natural gas/ethylene mixture (Φ = 1.56, 42 % C2H4, 58 % natural gas, P th = 17.6 kW at atmospheric pressure) is used as a fuel, which is oxidized by air under fuel-rich conditions in the first combustion chamber.

  6. Acute effects of various weighted bat warm-up protocols on bat velocity.

    PubMed

    Reyes, G Francis; Dolny, Dennis

    2009-10-01

    Although research has provided evidence of increased muscular performance following a facilitation set of resistance exercise, this has not been established for use prior to measuring baseball bat velocity. The purpose of this study was to determine the effectiveness of selected weighted bat warm-up protocols to enhance bat velocity in collegiate baseball players. Nineteen collegiate baseball players (age = 20.15 +/- 1.46 years) were tested for upper-body strength by a 3-repetition maximum (RM) bench press (mean = 97.98 +/- 14.54 kg) and mean bat velocity. Nine weighted bat warm-up protocols, utilizing 3 weighted bats (light = 794 g; standard = 850 g; heavy = 1,531 g) were swung in 3 sets of 6 repetitions in different orders. A control trial involved the warm-up protocol utilizing only the standard bat. Pearson product correlation revealed a significant relationship between 3RM strength and pretest bat velocity (r = 0.51, p = 0.01). Repeated measures analysis of variance (ANOVA) revealed no significant treatment effects of warm-up protocol on bat velocity. However, the order of standard, light, heavy bat sequence resulted in the greatest increase in bat velocity (+6.03%). These results suggest that upper-body muscle strength influences bat velocity. It appears that the standard, light, heavy warm-up order may provide the greatest benefit to increase subsequent bat velocity and may warrant use in game situations. PMID:19855339

  7. Acute effects of various weighted bat warm-up protocols on bat velocity.

    PubMed

    Reyes, G Francis; Dolny, Dennis

    2009-10-01

    Although research has provided evidence of increased muscular performance following a facilitation set of resistance exercise, this has not been established for use prior to measuring baseball bat velocity. The purpose of this study was to determine the effectiveness of selected weighted bat warm-up protocols to enhance bat velocity in collegiate baseball players. Nineteen collegiate baseball players (age = 20.15 +/- 1.46 years) were tested for upper-body strength by a 3-repetition maximum (RM) bench press (mean = 97.98 +/- 14.54 kg) and mean bat velocity. Nine weighted bat warm-up protocols, utilizing 3 weighted bats (light = 794 g; standard = 850 g; heavy = 1,531 g) were swung in 3 sets of 6 repetitions in different orders. A control trial involved the warm-up protocol utilizing only the standard bat. Pearson product correlation revealed a significant relationship between 3RM strength and pretest bat velocity (r = 0.51, p = 0.01). Repeated measures analysis of variance (ANOVA) revealed no significant treatment effects of warm-up protocol on bat velocity. However, the order of standard, light, heavy bat sequence resulted in the greatest increase in bat velocity (+6.03%). These results suggest that upper-body muscle strength influences bat velocity. It appears that the standard, light, heavy warm-up order may provide the greatest benefit to increase subsequent bat velocity and may warrant use in game situations.

  8. Effects of particulate air pollution on asthmatics

    SciTech Connect

    Perry, G.B.; Chai, H.; Dickey, D.W.; Jones, R.H.; Kinsman, R.A.; Morrill, C.G.; Spector, S.L.; Weiser, P.C.

    1983-01-01

    Twenty-four asthmatic subjects in Denver were followed from January through March 1979, a three-month period in which Denver air pollution levels are generally high and variable. Dichotomous, virtual impactor samplers provided daily measurements (micrograms/m3) of inhaled particulate matter (total mass, sulfates, and nitrates) for coarse (2.5--15 micrograms in aerodynamic diameter) and fine fractions (less than 2.5 micrometers). Carbon monoxide, sulfur dioxide, ozone, temperature, and barometric pressure were also measured. Twice daily measurements of each subject's peak expiratory flow rates, use of as-needed aerosolized bronchodilators, and report of airways obstruction symptoms characteristic of asthma were tested for relationships to air pollutants using a random effects model across subjects. During the time actually observed, there were very few days in which high levels of suspended particulates were recorded. Of the environmental variables studied, only fine nitrates were associated with increased symptom reports and increased aerosolized bronchodilator usage.

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

    PubMed Central

    Williams, Michael; Harveson, Lanisa; 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

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

    PubMed

    Williams, Michael; Harveson, Lanisa; 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

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

    PubMed

    Williams, Michael; Harveson, Lanisa; 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. The effect of non-zero radial velocity on the impulse and circulation of starting jets

    NASA Astrophysics Data System (ADS)

    Krieg, Michael; Mohseni, Kamran

    2011-11-01

    Vortex ring formation dynamics are generally studied using two basic types of vortex generators. Piston cylinder vortex generators eject fluid through a long tube which ensures a purely axial jet; whereas, vortex ring generators which expel fluid through a flat plate with a circular orifice produce 2-D jets (non-zero radial velocity). At the nozzle exit plane of the orifice type vortex generator the radial component of velocity is linearly proportional to the radial distance from the axis of symmetry, reaching a maximum at the edge of the orifice with a magnitude around 10 % of the piston velocity (the ratio of the volume flux and the nozzle area). As the jet advances downstream the radial velocity quickly dissipates, and becomes purely axial less than a diameter away from the nozzle exit plane. The radial velocity gradient in the axial direction plays a key role in the rate at which circulation and impulse are ejected from the vortex generator. Though the radial component of velocity is small compared to the axial velocity, it has a significant effect on both the circulation and impulse of the starting jet because of this gradient. The extent of circulation and impulse enhancement is investigated through experimental DPIV data showing that the orifice device produces nearly double both circulation and energy (with identical piston velocity and stroke ratios).

  18. Chronic Effects of Air Pollution are Probably Overestimated.

    PubMed

    Boffetta, Paolo; La Vecchia, Carlo; Moolgavkar, Suresh

    2015-05-01

    Inappropriate measures of exposure, including inadequate consideration of latency in the analysis of chronic effects of air pollution, may lead to overestimation of the impact of air pollution on health effects. A relatively simple way to check the plausibility of results on chronic effects of air pollution would be to report in parallel the smoking-associated risks.

  19. 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

  20. 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

  1. The effect of unburned gas axial velocity on the characteristics of rotational flame during flashback

    NASA Astrophysics Data System (ADS)

    Bufares, Ahmed M.; Wahid, M. A.

    2012-06-01

    The qualitative study has been carried out to investigate the effect of axial velocity of unburned gases on the flame characteristics during flame flashback in rotating burner. Our focus of study mainly on the flame shape and its behavior during flashback. It is found that the flame shape has been affected by the unburned gases axial velocity. Two flame shapes have been noticed the plate shape with cusp flame "fish flame" and upset dome flame. The cases that have been studied are flames at rotating speed 1200 rpm and 1620 rpm and several unburned gases axial velocity. Double concentric Bunsen rotating burner has been used in the study.

  2. 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.

  3. Optimum dimple diameter for friction reduction with laser surface texturing: the effect of velocity gradient

    NASA Astrophysics Data System (ADS)

    Greiner, Christian; Merz, Tobias; Braun, Daniel; Codrignani, Andrea; Magagnato, Franco

    2015-12-01

    The morphological texturing of surfaces has demonstrated high potential to reduce friction and wear. In order to understand the effect of different velocity gradients over the textured area on the optimum dimple diameter, we textured brass pins with round dimples having diameters between 20 and 200 μm. The dimple depth and packing density were kept constant. The samples were tested in a pin-on-disc fashion against sapphire discs and experiments were conducted under mixed lubrication and for two different sliding radii. Our results show that larger velocity gradients favor smaller dimples, whereas for the smaller velocity gradients, larger dimple diameters were beneficial. The effect of there being an influence of the velocity gradient was also found in computational fluid dynamics (CFD) simulations. Experimentally, friction forces could be reduced by up to 80%, demonstrating the tremendous potential of laser surface texturing (LST) to lower friction forces and reduce CO2 emissions.

  4. 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.

  5. Effect of Strip Velocity on Pickling Rate of Hot-Rolled Steel in Hydrochloric Acid

    NASA Astrophysics Data System (ADS)

    Hudson, R. M.; Warning, C. J.

    1982-02-01

    The combined effect of strip velocity with other parameters on pickling rate of hot-rolled low-carbon steel in hydrochloric acid (HCl) solutions was determined. At temperatures from 150 to200°F(66 to 93°), the time required for pickling decreased substantially as strip velocity was increased from 0 to about 250 fpm (76 mpm); no further decrease in time resulted when velocities were increased to 800 fpm (244 mpm). Other pickling variables were studied with a velocity of 400 fpm (122 mpm). Pickling times decrease with increases in HCl concentrations, CHCl, and temperature, TF, according to prediction equations of the form log t = A + B log CHCl + D(459 + TF)-1. At 200°F, temper-mill scalebreaking decreased pickling times by about 5 sec; at lower temperatures, a larger magnitude effect was noted for one steel in the group tested.

  6. 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

  7. 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.

  8. 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. PMID:19894128

  9. 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.

  10. 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.

  11. The effect of spiral and bar structure on the Milky Way velocity distribution

    NASA Astrophysics Data System (ADS)

    Minchev, Ivan

    2008-06-01

    Using particle integrations of more than a million particles we explore the effect of spiral arms and the Galactic bar on the velocity distribution in the Milky Way disk. In this thesis we explore four topics: (1) Heating due to multiple spiral patterns: We find that stochastic heating (increased random motions with time) is induced by interactions between two steady state spiral density waves moving at different pattern speeds. We examine a range of spiral strengths and spiral speeds and show that stars in this time dependent gravitational field can be heated. This is a new mechanism for increasing the stellar velocity dispersion in galactic disks. If multiple spiral patterns are present in the Galaxy we predict that there should be large variations in the stellar velocity dispersion as a function of radius. (2) The effect of spiral structure perturbations on Oort constant measurements: We find that a two-armed spiral density wave affects measurements of the Oort constants introducing systematic errors in A and B of order 5 km s -1 kpc -1 . Oort's | C |, on average, is larger for lower stellar velocity dispersions, contrary to recent measurements (Olling & Dehnen 2003). We conclude that spiral structure alone cannot account for this observation. This discrepancy is resolved by considering the effect of the Galactic bar on the local stellar velocity distribution (see (3)). (3) The effect of the Galactic bar on Oort's C -value: Previous work has related the Galactic bar to structure in the local stellar velocity distribution. We show that the bar also influences the spatial gradients of the velocity vector via the Oort constants. By numerical integration of test- particles we simulate measurements of the Oort C -value in a gravitational potential including the Galactic bar. We account for the observed trend that C is increasingly negative for stars with higher velocity dispersion. By comparing measurements of C with our simulations we improve on previous models of

  12. [The direct health effects of air pollution in Vratsa in 1991].

    PubMed

    Tabakova, S; Koleva, Ts; Petrov, P; Simeonov, G

    1993-01-01

    The effect of air pollution in the town of Vratsa on the daily morbidity of the population has been studied during the first half of 1991. Studies are performed on the correlation between the daily dynamics in the pollution according to specific for the town indices ammonia, hydrogen sulfide, sulphur dioxide, nitric oxides, dust, meteorological parameters temperature of the air, relative humidity, air velocity, barometric pressure and some respiratory and allergic diseases among the population. It is already established that the level of the air pollution in the town of Vratsa, among which dominate ammonia and hydrogen sulfide, have a direct effect on the acute respiratory morbidity, more expressed among the children. This influence is traced both in episodes of increased pollution, and in the course of several days afterwards and is conductive by the combination of unfavourable meteorological conditions, hindering the dispersion of the atmospheric pollutants.

  13. Effects of a 4-week youth baseball conditioning program on throwing velocity.

    PubMed

    Escamilla, Rafael F; Fleisig, Glenn S; Yamashiro, Kyle; Mikla, Tony; Dunning, Russell; Paulos, Lonnie; Andrews, James R

    2010-12-01

    Effects of a 4-week youth baseball conditioning program on throwing velocity. This study examined the effects of a 4-week youth baseball conditioning program on maximum throwing velocity. Thirty-four youth baseball players (11-15 years of age) were randomly and equally divided into control and training groups. The training group performed 3 sessions (each 75 minutes) weekly for 4 weeks, which comprised a sport specific warm-up, resistance training with elastic tubing, a throwing program, and stretching. Throwing velocity was assessed initially and at the end of the 4-week conditioning program for both control and training groups. The level of significance used was p < 0.05. After the 4-week conditioning program, throwing velocity increased significantly (from 25.1 ± 2.8 to 26.1 ± 2.8 m·s) in the training group but did not significantly increase in the control group (from 24.2 ± 3.6 to 24.0 ± 3.9 m·s). These results demonstrate that the short-term 4-week baseball conditioning program was effective in increasing throwing velocity in youth baseball players. Increased throwing velocity may be helpful for pitchers (less time for hitters to swing) and position players (decreased time for a runner to advance to the next base). PMID:21068687

  14. Effects of a 4-week youth baseball conditioning program on throwing velocity.

    PubMed

    Escamilla, Rafael F; Fleisig, Glenn S; Yamashiro, Kyle; Mikla, Tony; Dunning, Russell; Paulos, Lonnie; Andrews, James R

    2010-12-01

    Effects of a 4-week youth baseball conditioning program on throwing velocity. This study examined the effects of a 4-week youth baseball conditioning program on maximum throwing velocity. Thirty-four youth baseball players (11-15 years of age) were randomly and equally divided into control and training groups. The training group performed 3 sessions (each 75 minutes) weekly for 4 weeks, which comprised a sport specific warm-up, resistance training with elastic tubing, a throwing program, and stretching. Throwing velocity was assessed initially and at the end of the 4-week conditioning program for both control and training groups. The level of significance used was p < 0.05. After the 4-week conditioning program, throwing velocity increased significantly (from 25.1 ± 2.8 to 26.1 ± 2.8 m·s) in the training group but did not significantly increase in the control group (from 24.2 ± 3.6 to 24.0 ± 3.9 m·s). These results demonstrate that the short-term 4-week baseball conditioning program was effective in increasing throwing velocity in youth baseball players. Increased throwing velocity may be helpful for pitchers (less time for hitters to swing) and position players (decreased time for a runner to advance to the next base).

  15. 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.

  16. 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.

  17. Modeling of an air-backed diaphragm in dynamic pressure sensors: Effects of the air cavity

    NASA Astrophysics Data System (ADS)

    Liu, Haijun; Olson, Douglas A.; Yu, Miao

    2014-12-01

    As the key structure of most dynamic pressure sensors, a diaphragm backed by an air cavity plays a critical role in the determination of sensor performance metrics. In this paper, we investigate the influence of air cavity length on the sensitivity and bandwidth. A continuum mechanics model neglecting the air viscous effect is first developed to capture the structural-acoustic coupling between a clamped circular diaphragm and a cylindrical backing air cavity. To facilitate sensor design, close-form approximations are obtained to calculate the static sensitivity and the fundamental natural frequency of the air-backed diaphragm. Parametric studies based on this analytical model show that the air cavity can change both the effective mass and the effective stiffness of the diaphragm. One new finding is that the natural frequency of the air-backed diaphragm behaves differently in three different cavity length ranges. In particular, due to the mass effect of the air cavity being dominant, it is shown for the first time that the natural frequency decreases when the cavity length decreases below a critical value in the short cavity range. Furthermore, a finite element method (FEM) model is developed to validate the continuum mechanics model and to study the damping effect of the air cavity. These results provide important design guidelines for dynamic pressure sensors with air-backed diaphragms.

  18. 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

  19. 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.

  20. Effects of tangential velocity distribution on flow stability in a draft tube

    NASA Astrophysics Data System (ADS)

    Dou, Huashu; Niu, Lin; Cao, Shuliang

    2014-10-01

    Numerical simulations of the flow in the draft tube of a Francis turbine are carried out in order to elucidate the effects of tangential velocity on flow stability. Influence of the location of the maximum tangential velocity is explored considering the equality of the total energy at the inlet of the draft tube. It is found that the amplitude of the pressure fluctuation decreases when the location of the maximum of the tangential velocity moves from the centre to the wall on the cross section. Thus, the stability of the flow in the draft tube increases with the moving of the location of the maximum tangential velocity. However, the relative hydraulic loss increases and the recovery coefficient of the draft tube decreases slightly.

  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. Effect of different training programs on the velocity of overarm throwing: a brief review.

    PubMed

    van den Tillaar, Roland

    2004-05-01

    Throwing velocity in overarm throwing is of major importance in sports like baseball, team handball, javelin, and water polo. The purpose of this literature review was to give an overview of the effect of different training programs on the throwing velocity in overarm throwing, provide a theoretical framework that explains findings, and give some practical applications based on these findings. The training studies were divided into 4 categories: (a) specific resistance training with an overload of velocity, (b) specific resistance training with an overload of force, (c) specific resistance training with a combination of overload of force and velocity, and (d) general resistance training according to the overload of force. Each category is presented and discussed.

  4. Experimental study of Markstein number effects on laminar flamelet velocity in turbulent premixed flames

    SciTech Connect

    Weiss, M.; Zarzalis, N.; Suntz, R.

    2008-09-15

    Effects of turbulent flame stretch on mean local laminar burning velocity of flamelets, u{sub n}, were investigated experimentally in an explosion vessel at normal temperature and pressure. In this context, the wrinkling, A{sub t}/A{sub l}, and the burning velocity, u{sub t}, of turbulent flames were measured simultaneously. With the flamelet assumption the mean local laminar burning velocity of flamelets, u{sub n}=u{sub t} x (A{sub t}/A{sub l}){sup -1}, was calculated for different turbulence intensities. The results were compared to the influence of stretch on spherically expanding laminar flames. For spherically expanding laminar flames the stretched laminar burning velocity, u{sub n}, varied linearly with the Karlovitz stretch factor, yielding Markstein numbers that depend on the mixture composition. Six different mixtures with positive and negative Markstein numbers were investigated. The measurements of the mean local laminar burning velocity of turbulent flamelets were used to derive an efficiency parameter, I, which reflects the impact of the Markstein number and turbulent flame stretch - expressed by the turbulent Karlovitz stretch factor - on the local laminar burning velocity of flamelets. The results showed that the efficiency is reduced with increasing turbulence intensity and the reduction can be correlated to unsteady effects. (author)

  5. Amorphous silicon under mechanical shear deformations: Shear velocity and temperature effects

    NASA Astrophysics Data System (ADS)

    Kerrache, Ali; Mousseau, Normand; Lewis, Laurent J.

    2011-04-01

    Mechanical shear deformations lead, in some cases, to effects similar to those resulting from ion irradiation. Here we characterize the effects of shear velocity and temperature on amorphous silicon (a-Si) modeled using classical molecular-dynamics simulations based on the empirical environment-dependent interatomic potential (EDIP). With increasing shear velocity at low temperature, we find a systematic increase in the internal strain leading to the rapid appearance of structural defects (fivefold-coordinated atoms). The impacts of externally applied strain can be almost fully compensated by increasing the temperature, allowing the system to respond more rapidly to the deformation. In particular, we find opposite power-law relations between the temperature and the shear velocity and the deformation energy. The spatial distribution of defects is also found to depend strongly on temperature and strain velocity. For low temperature or high shear velocity, defects are concentrated in a few atomic layers near the center of the cell, while with increasing temperature or decreasing shear velocity, they spread slowly throughout the full simulation cell. This complex behavior can be related to the structure of the energy landscape and the existence of a continuous energy-barrier distribution.

  6. Influence of the inlet velocity profiles on the prediction of velocity distribution inside an electrostatic precipitator

    SciTech Connect

    Haque, Shah M.E.; Deev, A.V.; Subaschandar, N.; Rasul, M.G.; Khan, M.M.K.

    2009-01-15

    The influence of the velocity profile at the inlet boundary on the simulation of air velocity distribution inside an electrostatic precipitator is presented in this study. Measurements and simulations were performed in a duct and an electrostatic precipitator (ESP). A four-hole cobra probe was used for the measurement of velocity distribution. The flow simulation was performed by using the computational fluid dynamics (CFD) code FLUENT. Numerical calculations for the air flow were carried out by solving the Reynolds-averaged Navier-Stokes equations coupled with the realizable k-{epsilon} turbulence model equations. Simulations were performed with two different velocity profiles at the inlet boundary - one with a uniform (ideal) velocity profile and the other with a non-uniform (real) velocity profile to demonstrate the effect of velocity inlet boundary condition on the flow simulation results inside an ESP. The real velocity profile was obtained from the velocity measured at different points of the inlet boundary whereas the ideal velocity profile was obtained by calculating the mean value of the measured data. Simulation with the real velocity profile at the inlet boundary was found to predict better the velocity distribution inside the ESP suggesting that an experimentally measured velocity profile could be used as velocity inlet boundary condition for an accurate numerical simulation of the ESP. (author)

  7. Long-term carbide development in high-velocity oxygen fuel/high-velocity air fuel Cr3C2-NiCr coatings heat treated at 900 °C

    NASA Astrophysics Data System (ADS)

    Matthews, S.; Hyland, M.; James, B.

    2004-12-01

    During the deposition of Cr3C2-NiCr coatings, compositional degradation occurs, primarily through the dissolution of the carbide phase into the matrix. Exposure at an elevated temperature leads to transformations in the compositional distribution and microstructure. While these have been investigated in short-term trials, no systematic investigations of the long-term microstructural development have been presented for high-velocity sprayed coatings. In this work, high-velocity air fuel (HVAF) and high-velocity oxygen fuel (HVOF) coatings were treated at 900 °C for up to 60 days. Rapid refinement of the supersaturated matrix phase occurred, with the degree of matrix phase alloying continuing to decrease over the following 20 to 40 days. Carbide nucleation in the HVAF coatings occurred preferentially on the retained carbide grains, while that in the HVOF coatings developed in the regions of greatest carbide dissolution. This difference resulted in a variation in carbide morphologies. Preferential horizontal growth was evident in both coatings over the first 20 to 30 days of exposure, beyond which spheroidization of the microstructure occurred. After 30 days, the carbide morphology of both coatings was comparable, tending toward an expansive structure of coalesced carbide grains. The development of the carbide phase played a significant role in the microhardness variation of these coatings with time.

  8. Ambient air quality and the effects of air pollutants on otolaryngology in Beijing.

    PubMed

    Zhang, Fengying; Xu, Jin; Zhang, Ziying; Meng, Haiying; Wang, Li; Lu, Jinmei; Wang, Wuyi; Krafft, Thomas

    2015-08-01

    To investigate temporal patterns, pollution concentrations and the health effects of air pollutants in Beijing we carried out time-series analyses on daily concentrations of ambient air pollutants and daily numbers of outpatient visits for otolaryngology over 2 years (2011-2012) to identify possible health effects of air pollutants. The results showed that PM10 was the major air pollutant in Beijing and that air quality was slightly better in 2012 than in 2011. Seasonal differences were apparent for SO2 and NO2. Both the background and urban areas of Beijing experienced particulate matter pollution in 2011. In addition to local air pollution, Beijing was also affected by pollutants transported from other regions, especially during heavy air pollution episodes. PM10, NO2, and SO2 concentrations showed positive associations with numbers of outpatient visits for otolaryngology during winter. NO2 and SO2 also had adverse ear, nose, and throat health effects outside of winter. The ear, nose, and throat health risks caused by air pollutants were higher during the winter than during the summer. NO2 had stronger influence on increased the likelihood of outpatient visits than SO2. The findings provide additional information about air quality and health effects of air pollution in Beijing.

  9. Seismic velocities in unconsolidated sands: Measurements of pressure, sorting, and compaction effects

    NASA Astrophysics Data System (ADS)

    Zimmer, Michael Andrew

    This dissertation presents measurements of compressional- and shear-wave velocities made on unconsolidated sand and glass-bead samples over a pressure range from 100 kPa to 20 MPa. These measurements demonstrate that the shear-wave velocity varies with the fourth root of the effective pressure over the entire pressure range, while the compressional-wave velocity demonstrates a slightly lower pressure dependence. These pressure dependences show no systematic variation with the porosity for porosities from 25 to 44%. The porosity-velocity trend at a given pressure is described by the isostress average between the moduli of the highest porosity sample and the moduli of quartz. The significant porosity dependence of the water-saturated, compressional-wave velocities, as modeled with Gassmann fluid substitution, is mostly contained in the zero-pressure bulk modulus. Preconsolidation produces only a slight increase in the velocities and a slight reduction in the pressure dependence. A comparison of the velocities measured at 150 kHz in water-saturated samples of four natural sands to velocities predicted by Biot and Mavko-Jizba models demonstrates that the squirt mechanism is the primary dispersion mechanism active in these sands at this frequency. The dispersion in the velocities demonstrates no significant change with compaction. The static bulk modulus calculated from the volumetric strains observed in the dry samples of these four natural sands and one glass bead sample is shown to be from 2 to 10 times lower than the dynamic bulk modulus for the normally consolidated samples, and drops from being equal to the dynamic modulus on the first unloading step to being approximately 3 times lower on complete unloading. A Preisach-Mayergoyz space analysis adapted to include plastic-strain effects demonstrates that both the strain-magnitude dependence of elastic strains and the occurrence of plastic strain contribute to these differences between the static and dynamic moduli

  10. 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.

  11. 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. PMID:25996964

  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. 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.

  14. Air pollution effects on ventricular repolarization.

    PubMed

    Lux, Robert L; Pope, C Arden

    2009-05-01

    We conducted a retrospective study of a set of previously published electrocardiographic data to investigate the possible direct association between levels of particulate air pollution and changes in ventricular repolarization -- the cardiac electrophysiologic process that manifests itself as the T wave* of the electrocardiogram (ECG) and that is definitively linked to and responsible for increased arrhythmogenesis. The published findings from this data set demonstrated a clear cardiac effect, namely, a reduction in heart rate variability (HRV) parameter values with increased levels of particulate air pollution (Pope et al. 2004), suggesting possible arrhythmogenic effects. Given this positive finding and the well-established sensitivity of cardiac repolarization to physiologic, pharmacologic, and neurologic interventions, and in light of emerging novel tools for assessing repolarization, we hypothesized that high levels of particulate air pollution would alter repolarization independent of changes in heart rate and, consequently, would increase arrhythmogenic risk. The likely mechanism of any deleterious effects on repolarization would be alteration of sodium, calcium, and potassium channels. The channel's structure, function, and kinetics are responsible for generating the cellular action potentials, which, when summed over the entire heart, result in the waves recorded by the ECG. A positive finding would provide evidence that increased levels of air pollution may be directly linked to increases in arrhythmogenic risk and, potentially, sudden cardiac death. The study population consisted of 88 nonsmoking, elderly subjects in whom multiple, continuous, 24-hour, 2-channel ECG recordings were collected, along with blood samples to evaluate inflammatory mechanisms (not pursued in the current study). The concentration of fine particulate matter (PM2.5, particulate matter with an aerodynamic diameter < or = 2.5 microm) in daily samples was measured or estimated and

  15. 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

  16. 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.

  17. Group velocity of extraordinary waves in superdense magnetized quantum plasma with spin-1/2 effects

    NASA Astrophysics Data System (ADS)

    Li, Chunhua; Wu, Zhengwei; Ren, Haijun; Yang, Weihong; Chu, Paul K.

    2012-12-01

    Based on the one component plasma model, a new dispersion relation and group velocity of elliptically polarized extraordinary electromagnetic waves in a superdense quantum magnetoplasma are derived. The group velocity of the extraordinary wave is modified due to the quantum forces and magnetization effects within a certain range of wave numbers. It means that the quantum spin-1/2 effects can reduce the transport of energy in such quantum plasma systems. Our work should be of relevance for the dense astrophysical environments and the condensed matter physics.

  18. Group velocity of extraordinary waves in superdense magnetized quantum plasma with spin-1/2 effects

    SciTech Connect

    Li Chunhua; Ren Haijun; Yang Weihong; Wu Zhengwei; Chu, Paul K.

    2012-12-15

    Based on the one component plasma model, a new dispersion relation and group velocity of elliptically polarized extraordinary electromagnetic waves in a superdense quantum magnetoplasma are derived. The group velocity of the extraordinary wave is modified due to the quantum forces and magnetization effects within a certain range of wave numbers. It means that the quantum spin-1/2 effects can reduce the transport of energy in such quantum plasma systems. Our work should be of relevance for the dense astrophysical environments and the condensed matter physics.

  19. 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. PMID:19593220

  20. 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.

  1. Shallow velocity structure and seismic site effects at Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Mora, Mauricio M.; Lesage, Philippe; Valette, Bernard; Alvarado, Guillermo E.; Leandro, Carlos; Métaxian, Jean-Philippe; Dorel, Jacques

    2006-04-01

    We use the spatial autocorrelation (SPAC) method with improved inversion algorithms to estimate the Love and Rayleigh dispersion curves at two sites at the West and Northeast flanks of Arenal volcano, Costa Rica. At the West flank site, the Rayleigh waves phase velocities vary from 765 m s - 1 at 1 Hz to 300 m s - 1 at 12 Hz and those of Love waves between 780 and 295 m s - 1 in the same frequency band. At the Northeast flank site, the Rayleigh wave velocities range from 1386 to 300 m s - 1 and those of Love from 1983 to 315 m s - 1 . From dispersion curves we derive shallow (< 400 m) P and S waves velocity models. 2D velocity models down to a depth of 150 m are also obtained by seismic refraction surveys along two radial profiles on the tephra apron at West and East flanks. They present strong vertical and lateral variations in the velocity and thickness of the layers. Strong variations in amplitude of the spectral peaks are observed for the seismic events along two radial arrays. These site effects are analysed using the H/V spectral ratio method and S-wave theoretical transfer functions. Results show that the wave amplifications are related to resonance effects of shallow structure (< 150 m) and occur only where impedance contrast with the deeper layers is strong enough. In contrast, almost no site effect are detected at the Masaya shield volcano, Nicaragua, where the structure is more homogeneous and mainly composed of lava flows. When a resonance of the shallow layers occurs, the correlation coefficients between close stations increase at the corresponding frequency. The site effects may thus produce spurious results with the SPAC method. The H/V spectral ratio, used in complement of the SPAC method, can help detecting the site effects and testing the plane layer hypothesis. Furthermore, the theoretical transfer functions calculated for the estimated velocity models is also useful to validate the models.

  2. Effect of fuel/air nonuniformity on nitric oxide emissions

    NASA Technical Reports Server (NTRS)

    Lyons, V. J.

    1979-01-01

    A flame tube combustor holding jet A fuel was used in experiments performed at a pressure of .3 Mpa and a reference velocity of 25 meters/second for three inlet air temperatures of 600, 700, and 800 K. The gas sample measurements were taken at locations 18 cm and 48 cm downstream of the perforated plate flameholder. Nonuniform fuel/air profiles were produced using a fuel injector by separately fueling the inner five fuel tubes and the outer ring of twelve fuel tubes. Six fuel/air profiles were produced for nominal overall equivalence ratios of .5 and .6. An example of three of three of these profiles and their resultant nitric oxide NOx emissions are presented. The uniform fuel/air profile cases produced uniform and relatively low profile levels. When the profiles were either center-peaked or edge-peaked, the overall mass-weighted nitric oxide levels increased.

  3. 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.

  4. 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.

  5. Effect of ion velocity on SHI-induced mixing in Ti/Bi system

    NASA Astrophysics Data System (ADS)

    Bansal, Nisha; Kumar, Sarvesh; Khan, Saif Ahmad; Chauhan, R. S.

    2016-03-01

    Energetic ion beams are proving to be versatile tools for modification and depth profiling of materials. The energy and ion species are the deciding factor in the ion-beam-induced materials modification. Among the various parameters such as electronic energy loss, fluence and heat of mixing, velocity of the ions used for irradiation plays an important role in mixing at the interface. The present study is carried out to find the effect of the velocity of swift heavy ions on interface mixing of a Ti/Bi bilayer system. Ti/Bi/C was deposited on Si substrate at room temperature by an electron gun in a high-vacuum deposition system. Carbon layer is deposited on top to avoid oxidation of the samples. Eighty mega electron volts Au ions and 100 MeV Ag ions with same value of Se for Ti are used for the irradiation of samples at the fluences 1 × 1013-1 × 1014 ions/cm2. Different techniques like Rutherford backscattering spectroscopy, atomic force microscopy and grazing incidence X-ray diffraction were used to characterize the pristine and irradiated samples. The mixing effect is explained in the framework of the thermal spike model. It has been found that the mixing rate is higher for low-velocity Au ions in comparison to high-velocity Ag ions. The result could be explained as due to less energy deposition in thermal spike by high-velocity ions.

  6. Gas-rich and gas-poor structures through the stream velocity effect

    NASA Astrophysics Data System (ADS)

    Popa, Cristina; Naoz, Smadar; Marinacci, Federico; Vogelsberger, Mark

    2016-08-01

    Using adiabatic high-resolution numerical simulations, we quantify the effect of the streaming motion of baryons with respect to dark matter at the time of recombination on structure formation and evolution. Formally a second-order effect, the baryonic stream velocity has proven to have significant impact on dark matter halo abundance, as well as on the gas content and morphology of small galaxy clusters. In this work, we study the impact of stream velocity on the formation and gas content of haloes with masses up to 109 M⊙, an order of magnitude larger than previous studies. We find that the non-zero stream velocity has a sizable impact on the number density of haloes with masses ≲ few × 107 M⊙ up to z = 10, the final redshift of our simulations. Furthermore, the gas stream velocity induces a suppression of the gas fraction in haloes, which at z = 10 is ˜10 per cent for objects with M ˜ 107 M⊙, as well as a flattening of the gas density profiles in the inner regions of haloes. We further identify and study the formation, in the context of a non-zero stream velocity, of moderately long lived gas-dominated structures at intermediate redshifts 10 < z < 20, which Naoz and Narayan have recently proposed as potential progenitors of globular clusters.

  7. 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

  8. 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)

  9. 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.

  10. 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.

  11. Effect of dynamic cardiomyoplasty on phasic coronary arterial flow velocity in canine hearts.

    PubMed

    Tsukube, T; Okada, M; Mukai, T; Kashem, M A; Ota, T

    1994-10-01

    The usefulness of dynamic cardiomyoplasty has been demonstrated repeatedly, both experimentally and clinically. Although clinical applications of dynamic cardiomyoplasty to ischemic heart disease have been reported, its effect on the coronary blood flow has never been discussed. Therefore, we tested the hypothesis that dynamic cardiomyoplasty might adversely affect coronary arterial blood flow through compression of the coronary arteries during systolic skeletal muscular contraction and incomplete relaxation of the skeletal muscle flap during diastole. Dynamic cardiomyoplasty was performed in seven mongrel dogs with the use of a left latissimus dorsi-muscle flap, paced synchronously with the R wave of the electrocardiogram. A 3F Doppler catheter was placed in the left main trunk of the coronary artery to assess the instantaneous changes of coronary flow velocity by fast Fourier transformation analysis, We compared systolic and diastolic properties during assisted versus unassisted cardiac cycles by calculating the peak velocity and the time-velocity integral. During assisted cardiac cycles, a significant enhancement of coronary arterial blood flow velocity was demonstrated by significant increases in both systolic and diastolic peak velocity (26.9% +/- 6.5%, p < 0.005; 4.0% +/- 1.6%, p < 0.05, respectively) and time-velocity integral (20.9% +/- 4.8%, p < 0.05; 10.0% +/- 4.6%, p < 0.05, respectively). Enhancement of coronary arterial blood flow velocity was associated with an increase in mean aortic pressure (16.4% +/- 1.3%, p < 0.005) and descending aortic flow (67.5% +/- 5.3%, p < 0.005). Also, the improved systolic coronary arterial blood flow velocity was consistent with an increase in systolic aortic pressure (15.8% +/- 1.5%, p < 0.005), and enhancement of diastolic coronary arterial blood flow velocity was associated with an increase in diastolic aortic pressure (8.6% +/- 2.3%, p < 0.01). We concluded that coronary arterial blood flow velocity was increased by

  12. 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

  13. Health effects of particulate air pollution: time for reassessment?

    PubMed

    Pope, C A; Bates, D V; Raizenne, M E

    1995-05-01

    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.

  14. 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

  15. 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.

  16. 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…

  17. 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.

  18. Friction-Induced Parametric Resonances in Discs: Effect of a Negative FRICTION-VELOCITY Relationship

    NASA Astrophysics Data System (ADS)

    Ouyang, H.; Mottershead, J. E.; Cartmell, M. P.; Friswell, M. I.

    1998-01-01

    Parametric resonances are studied which occur when an elastic system is rotated around an annular disc with friction having a negative slope with velocity. The elastic system consists of two spring-dashpots, in the transverse and in-plane (circumferential) directions, and a common point mass. The complete arrangement is driven around the disc through the in-plane stiffness and damper. It is demonstrated that the effect of the in-plane system (including the negative friction-velocity relationship) is (i) to introduce additional parametric resonances which are destabilised by the transverse damper, and (ii) to reduce the regions of instability of the other resonances.

  19. Core size effect on the dry and saturated ultrasonic pulse velocity of limestone samples.

    PubMed

    Ercikdi, Bayram; Karaman, Kadir; Cihangir, Ferdi; Yılmaz, Tekin; Aliyazıcıoğlu, Şener; Kesimal, Ayhan

    2016-12-01

    This study presents the effect of core length on the saturated (UPVsat) and dry (UPVdry) P-wave velocities of four different biomicritic limestone samples, namely light grey (BL-LG), dark grey (BL-DG), reddish (BL-R) and yellow (BL-Y), using core samples having different lengths (25-125mm) at a constant diameter (54.7mm). The saturated P-wave velocity (UPVsat) of all core samples generally decreased with increasing the sample length. However, the dry P-wave velocity (UPVdry) of samples obtained from BL-LG and BL-Y limestones increased with increasing the sample length. In contrast to the literature, the dry P-wave velocity (UPVdry) values of core samples having a length of 75, 100 and 125mm were consistently higher (2.8-46.2%) than those of saturated (UPVsat). Chemical and mineralogical analyses have shown that the P wave velocity is very sensitive to the calcite and clay minerals potentially leading to the weakening/disintegration of rock samples in the presence of water. Severe fluctuations in UPV values were observed to occur between 25 and 75mm sample lengths, thereafter, a trend of stabilization was observed. The maximum variation of UPV values between the sample length of 75mm and 125mm was only 7.3%. Therefore, the threshold core sample length was interpreted as 75mm for UPV measurement in biomicritic limestone samples used in this study.

  20. 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.

  1. Core size effect on the dry and saturated ultrasonic pulse velocity of limestone samples.

    PubMed

    Ercikdi, Bayram; Karaman, Kadir; Cihangir, Ferdi; Yılmaz, Tekin; Aliyazıcıoğlu, Şener; Kesimal, Ayhan

    2016-12-01

    This study presents the effect of core length on the saturated (UPVsat) and dry (UPVdry) P-wave velocities of four different biomicritic limestone samples, namely light grey (BL-LG), dark grey (BL-DG), reddish (BL-R) and yellow (BL-Y), using core samples having different lengths (25-125mm) at a constant diameter (54.7mm). The saturated P-wave velocity (UPVsat) of all core samples generally decreased with increasing the sample length. However, the dry P-wave velocity (UPVdry) of samples obtained from BL-LG and BL-Y limestones increased with increasing the sample length. In contrast to the literature, the dry P-wave velocity (UPVdry) values of core samples having a length of 75, 100 and 125mm were consistently higher (2.8-46.2%) than those of saturated (UPVsat). Chemical and mineralogical analyses have shown that the P wave velocity is very sensitive to the calcite and clay minerals potentially leading to the weakening/disintegration of rock samples in the presence of water. Severe fluctuations in UPV values were observed to occur between 25 and 75mm sample lengths, thereafter, a trend of stabilization was observed. The maximum variation of UPV values between the sample length of 75mm and 125mm was only 7.3%. Therefore, the threshold core sample length was interpreted as 75mm for UPV measurement in biomicritic limestone samples used in this study. PMID:27529138

  2. 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.

  3. 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.

  4. 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.

  5. Effect of electric charging on the velocity of water flow in CNT.

    PubMed

    Abbasi, Hossein Reza; Karimian, S M Hossein

    2016-09-01

    The role of electrical charge in controlling the velocity of water molecules in a finite single-walled carbon nanotube (CNT) was studied in detail using molecular dynamics simulation. Different test cases were examined to determine the parameters affecting the control of water-flow velocity in CNT upon electrically charging the surface of a CNT. The results showed that charge magnitude and volume, as well as the charging scenario, are the parameters having greatest effect. The implementation of electric charge on the surface of a CNT was demonstrated to decrease the resistance of CNT to incoming water flow at the entrance, but to increase friction-type resistance to flow along the CNT. Therefore, through controlling the magnitude of electric charge, water flow through the CNT may be accelerated, or decelerated. The results show that the velocity of molecular flow in the CNT increases to a maximum value, and then decreases with electric charge regardless of its sign. In the case studied here, this maximum velocity occurs at electric charging of ±0.25e/atom. It was also shown that, to reach similar flow velocities in a CNT, it is not sufficient to merely implement equal volumes of electric charge, where the volume of electric charging is defined as charge magnitude × charging time. In fact , both magnitude of charging and volume of electric charging must be equal to each other. These findings, together with options to implement scenarios with alternative charging, provide the means to effectively adjust desired velocities in a CNT. PMID:27488104

  6. Effect of electric charging on the velocity of water flow in CNT.

    PubMed

    Abbasi, Hossein Reza; Karimian, S M Hossein

    2016-09-01

    The role of electrical charge in controlling the velocity of water molecules in a finite single-walled carbon nanotube (CNT) was studied in detail using molecular dynamics simulation. Different test cases were examined to determine the parameters affecting the control of water-flow velocity in CNT upon electrically charging the surface of a CNT. The results showed that charge magnitude and volume, as well as the charging scenario, are the parameters having greatest effect. The implementation of electric charge on the surface of a CNT was demonstrated to decrease the resistance of CNT to incoming water flow at the entrance, but to increase friction-type resistance to flow along the CNT. Therefore, through controlling the magnitude of electric charge, water flow through the CNT may be accelerated, or decelerated. The results show that the velocity of molecular flow in the CNT increases to a maximum value, and then decreases with electric charge regardless of its sign. In the case studied here, this maximum velocity occurs at electric charging of ±0.25e/atom. It was also shown that, to reach similar flow velocities in a CNT, it is not sufficient to merely implement equal volumes of electric charge, where the volume of electric charging is defined as charge magnitude × charging time. In fact , both magnitude of charging and volume of electric charging must be equal to each other. These findings, together with options to implement scenarios with alternative charging, provide the means to effectively adjust desired velocities in a CNT.

  7. The Effect of Charge Reactive Metal Cases on Air Blast

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Wilson, William H.

    2009-12-01

    Experiments were conducted in a 23 m3 closed chamber using a charge encased in a cylindrical reactive metal case to study the effect on air blast from the case fragments. Parameters varied included case/charge mass ratio, charge diameter and charge type (i.e., detonation energy and pressure). The pressure histories measured on the chamber wall showed a double-shock front structure with an accelerating precursor shock followed by the primary shock, suggesting the early-time reaction of small case fragments. During the early reflections on the chamber wall, significant pressure rises versus the steel-cased and bare charges indicated combustion of a large amount of small case particles generated by secondary fragmentation. The analysis of explosion pressures and recovered fragments and solid products gave an expression for burnt casing mass as a function of Gurney velocity and charge diameter. The equivalent bare charge mass that yields the same explosion pressure as the cased charge increased with case/charge mass ratio and reached 2.5 times charge mass at the ratio of 1.75.

  8. 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

  9. 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.

  10. 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. PMID:26354370

  11. Air sparging effectiveness: laboratory characterization of air-channel mass transfer zone for VOC volatilization.

    PubMed

    Braida, W J; Ong, S K

    2001-10-12

    Air sparging in conjunction with soil vapor extraction is one of many technologies currently being applied for the remediation of groundwater contaminated with volatile organic compounds (VOCs). Mass transfer at the air-water interface during air sparging is affected by various soil and VOC properties. In this study with a single air-channel apparatus, mass transfer of VOCs was shown to occur within a thin layer of saturated porous media next to the air channel. In this zone, the VOCs were found to rapidly deplete during air sparging resulting in a steep concentration gradient while the VOC concentration outside the zone remained fairly constant. The sizes of the mass transfer zone were found to range from 17 to 41 mm or 70d(50) and 215d(50) (d(50)=mean particle size) for low organic carbon content media (<0.01% OC). The size of the mass transfer zone was found to be proportional to the square root of the aqueous diffusivity of the VOC, and was affected by the mean particle size, and the uniformity coefficient. Effects of the volatility of the VOCs as represented by the Henry's law constants and the airflow rates on the mass transfer zone were found to be negligible but VOC mass transfer from air-water interface to bulk air phase seems to play a role. A general correlation for predicting the size of the mass transfer zone was developed. The model was developed using data from nine different VOCs and verified by two other VOCs. The existence of the mass transfer zone provides an explanation for the tailing effect of the air phase concentration under prolonged air sparging and the rebound in the VOC air phase concentration after the sparging system is turned off.

  12. 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 ...

  13. 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.

  14. 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.

  15. 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.

  16. 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).

  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. Effect of group-velocity dispersion on the stability of quantum-cascade lasers

    NASA Astrophysics Data System (ADS)

    Bai, Jing; Zhou, Debao

    2013-01-01

    As the effect of group-velocity dispersion (GVD) on the stability of midinfrared quantum-cascade lasers (QCLs) has not been explored so far, both amplitude and phase instabilities of QCLs were analyzed in the presence of a background saturable absorber in the lasing medium. The investigation was carried out through the linearization of the Maxwell-Bloch formalism for the lasing medium by including second-order dispersion of group velocity and intensity-dependent loss accounting for the saturable absorber. The effect of the GVD on laser instability was found to be strongly related to the strength of the saturable absorber and pumping. The effect of the GVD is more significant at lower pumping levels and with weaker saturable absorbers.

  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. Respiratory effects of air pollution on children.

    PubMed

    Goldizen, Fiona C; Sly, Peter D; Knibbs, Luke D

    2016-01-01

    A substantial proportion of the global burden of disease is directly or indirectly attributable to exposure to air pollution. Exposures occurring during the periods of organogenesis and rapid lung growth during fetal development and early post-natal life are especially damaging. In this State of the Art review, we discuss air toxicants impacting on children's respiratory health, routes of exposure with an emphasis on unique pathways relevant to young children, methods of exposure assessment and their limitations and the adverse health consequences of exposures. Finally, we point out gaps in knowledge and research needs in this area. A greater understanding of the adverse health consequences of exposure to air pollution in early life is required to encourage policy makers to reduce such exposures and improve human health.

  1. Dynamic effects on containment of air-curtain fume hood operated with heat source.

    PubMed

    Chen, Jia-Kun; Huang, Rong Fung; Hsin, Pei-Yi

    2012-01-01

    This study focused on the leakage characteristics of the air-curtain fume hood that are subject to the influences of sash movement and walk-by motion while a high temperature heat source was operated in the hood. The flow visualization and trace gas test method were used to investigate the performance of the air-curtain fume hood. An electric heater was placed in the hood to simulate the heat source. The temperature of the heat source installed inside the air-curtain fume hood varied between 180°C and 300°C. Trace gas tests following the dynamic test methods of EN-14175 protocol were employed to measure the spillages of sulfur hexafluoride gas that were released in the hood. When subject to the influence of sash movement at a heat source temperature lower than 260°C, the leakage level was high at the suction velocity V(s) < 8 m/sec but was negligibly small at V(s) > 10 m/sec. When subject to the influence of people walk-by, the leakage level was relatively low at the suction velocity larger than 8 m/sec at sash height H = 50 cm. The height of the sash opening was a crucial parameter for the containment of the air-curtain fume hood. At the sash opening lower than about 25 cm, suction velocity less than or equal to 6 m/sec was enough to make the sulfur hexafluoride leakage less than the threshold value, 0.65 ppm, suggested by the BG Chemie. The air-curtain fume hood presented a great performance to resist the effect of drafts even though there was a high temperature heat source working in the hood. PMID:23009207

  2. Gut blood flow velocities in the newborn: effects of patent ductus arteriosus and parenteral indomethacin.

    PubMed Central

    Coombs, R C; Morgan, M E; Durbin, G M; Booth, I W; McNeish, A S

    1990-01-01

    The effects on gut blood flow velocities of parenteral indomethacin (0.2 mg/kg) given either quickly as a bolus or slowly as an infusion were compared in consecutive studies of two groups of infants with symptomatic patent ductus arteriosus. In the presence of patent ductus arteriosus the range of velocities in the superior mesenteric artery before indomethacin was given was characterised by pronounced abnormalities including absent--or in some cases even retrograde--diastolic flow. In eight subjects the first rapidly given bolus dose of indomethacin (duration 20 seconds or less) caused a pronounced and sustained fall in the velocity of the superior mesenteric artery blood flow (mean peak systolic velocity (cm/second): before 74; after 38; median time to maximum fall 7.4 minutes; median time to recovery 50 minutes). A further 10 subjects received their first dose of indomethacin by slow infusion (duration 30-35 min) and the percentage fall in peak systolic velocity was both substantially less (22% compared with 47%) and later (median time to maximum fall 37.3 minutes) than after rapid infusion. Qualitatively similar but smaller changes were seen in the coeliac axis. Return of antegrade end diastolic flow in the superior mesenteric artery within one hour of the first dose of indomethacin was a good predictor of subsequent closure of the ductus. These data suggest that there is a profound disturbance in mid gut perfusion in infants with patent ductus, which is exacerbated by indomethacin given rapidly by intravenous bolus. They may also provide a rational explanation for the well recognised association between necrotising enterocolitis and both patent ductus arteriosus and indomethacin administration. The unwanted effects of the indomethacin are abrogated by slow infusion, without loss of efficacy in closure of the ductus. Images Figure 1 PMID:2241229

  3. 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.

  4. Health effects of air pollution and the Japanese compensation law

    SciTech Connect

    Namekata, T.; Duv Florey, C.

    1987-01-01

    The contents of this book are: Part 1. Individual Presentations: I. Gas Cooking and Respiratory Disease in Children, II. Health Effects of Fossil Fuel Combustion Compared With Effects of Energy Shortages, III. Daily Symptoms of Lung Function in Relation to Air Pollution: A Study in West Berlin 1982/83, IV. Studies of the Acute Effects of London Smog, and Their Relevance to Present-Day Conditions, V. Epidemiological Issues on Air Pollution in the Japanese Pollution-Related Health Damage Compensation Law. Part 2. Panel Discussion: Epidemiological Issues on Air Pollution in the Japanese Pollution-Related Health Damage Compensation Law; Problems in Air Pollution Epidemiology; Exposure Criteria for Compensation; Problems in the Use of Respiratory Symptoms Questionnaires; Legal and Policy Issues in the Japanes Compensation Law. Part 3. Background Information: I. Legal and Policy Issues in the Japanese Compensation Law. II. Reappraisal of Air Pollution/Health Effects Studies in Japan.

  5. 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.

  6. 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.

  7. On the velocity in the Effective Field Theory of Large Scale Structures

    NASA Astrophysics Data System (ADS)

    Mercolli, Lorenzo; Pajer, Enrico

    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 k4. 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.

  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. Effects of alpha-proton drift velocity on alpha particle firehose instability

    NASA Astrophysics Data System (ADS)

    Seough, Jungjoon; Nariyuki, Yasuhiro

    2016-08-01

    In situ measurements have shown that the less-abundant alpha particles are characterized by temperature anisotropy which could drive the anisotropy-driven kinetic instabilities in the solar wind. In the collisionless plasma, the differential alpha-proton flow velocity V d = V α - V p usually has a non-zero value of the order of the local Alfvén velocity. The presence of such differential flow may affect the properties of dispersion relations for anisotropy-driven instabilities. Based upon linear Vlasov dispersion theory in a homogeneous plasma, the present study investigates the effects of the alpha-proton drift velocity on the parallel and oblique firehose instabilities driven by an excessive parallel temperature anisotropy of alpha particles, where the parallel and oblique represent directions of fluctuation propagation relative to the background magnetic field. It is found that for oblique firehose mode as well as parallel mode, the dispersion properties are affected by the presence of the alpha-proton drift velocity, which in turn results in the increase of the maximum growth rates as Vd increases and consequently leads to the modification of the marginal stability conditions in the parameter space ( β ∥ α , T ⊥ α / T ∥ α ) . We discuss the relevance of our results to the measured temperature anisotropy of alpha particles in the solar wind context.

  10. 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.

  11. Velocity effects on fullerene and oxide nanoparticle deposition in porous media.

    PubMed

    Lecoanet, Hélène F; Wiesner, Mark R

    2004-08-15

    Products of nanochemistry have been proposed in a number of applications ranging from soil stabilization and cosmetics to groundwater remediation. A fundamental understanding of the transport properties of these materials is essential to assess their efficacy and environmental impact in such applications. In this work, we consider the effect of flow on nanoparticle transport and deposition in porous media. The transport of three aqueous suspensions of fullerenes in a well-characterized porous medium is compared with that of two oxide nanomaterials at two flow rates. Despite significant differences in surface chemistry and size, the fullerenes exhibited an unexpected and similar breakthrough behavior at the higher flow rate. A striking characteristic of the fullerene breakthrough curves obtained at the higher Darcy velocity was an initial enhancement in nanoparticle deposition shortly after the passage of the first pore volume of suspension, followed by an increase in passage. This velocity-sensitive "affinity transition" in the initial deposition of nanoparticles in the porous medium was observed for fullerene-based materials only at the higher velocity and was in no case observed for silica or titania nanoparticles. The removal of fullerene-based nanoparticles was observed to converge to a level that was independent of flow velocity, suggesting that under these conditions time scales for attachment or reorganization on the surface are greater than the time scale for transport to collector surfaces.

  12. 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

  13. 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.

  14. A turbulence-driven air fumigation facility for studying air pollution effects on vegetation

    SciTech Connect

    Lipfert, F.; Lewin, K.; Hendrey, G.; Nagy, J. ); Alexander, Y. . Applied Mathematics Dept.)

    1990-10-01

    Studying the effects of atmospheric perturbations on plant growth has usually involved compromises between realism and convenience. Isolating the effects of specific parameters, such as air pollution, elevated CO{sub 2} concentration, or water stress, requires a manipulated rather than a completely natural environment. Attempts to develop large free-air controlled exposure systems date back several years, primarily for experimental exposures to elevated levels of air pollutants such as SO{sub 2} or ozone. These early systems suffered from two types of problems: imprecise control of the exposure gas concentrations; substantial spatial variability within the exposed plots. The Free-Air CO{sub 2} Enrichment (FACE) open-air fumigation system, developed at Brookhaven National Laboratory (BNL), has addressed both of these problem areas. This system differs from other free-air exposure systems in that the injection gas is pre-diluted in ambient air to an average 3--4% by volume, and the injection gas mass flow is adjusted each second by the micoprocessor-driven controller. This document discusses the design and performance of this facility. 3 refs., 4 figs., 1 tab.

  15. AIR POLLUTION EFFECTS ON SEMEN QUALITY

    EPA Science Inventory

    The potential impact of exposure to periods of high air pollution on male reproductive health was examined within the framework of an international project conducted in the Czech Republic. Semen quality was evaluated in young men (age 18) living in the Teplice District who are ex...

  16. Effect of superficial velocity on vaporization pressure drop with propane in horizontal circular tube

    NASA Astrophysics Data System (ADS)

    Novianto, S.; Pamitran, A. S.; Nasruddin, Alhamid, M. I.

    2016-06-01

    Due to its friendly effect on the environment, natural refrigerants could be the best alternative refrigerant to replace conventional refrigerants. The present study was devoted to the effect of superficial velocity on vaporization pressure drop with propane in a horizontal circular tube with an inner diameter of 7.6 mm. The experiments were conditioned with 4 to 10 °C for saturation temperature, 9 to 20 kW/m2 for heat flux, and 250 to 380 kg/m2s for mass flux. It is shown here that increased heat flux may result in increasing vapor superficial velocity, and then increasing pressure drop. The present experimental results were evaluated with some existing correlations of pressure drop. The best prediction was evaluated by Lockhart-Martinelli (1949) with MARD 25.7%. In order to observe the experimental flow pattern, the present results were also mapped on the Wang flow pattern map.

  17. Effect of the Dzyaloshinskii-Moriya interaction on the propagation velocity of the entanglement

    NASA Astrophysics Data System (ADS)

    Mahmoudi, M.; Mahdavifar, S.; Soltani, M. R.

    2016-08-01

    It is known that the spin chains can be used to propagate pairwise entanglement. In particular, the time evolution of initial maximally entangled states was shown that the pairwise entanglement propagates with a velocity proportional to the exchange interaction in the spin-1/2 XX chains. Here, we add the Dzyaloshinskii-Moriya interaction in the spin-1/2 XX chain model and study the dynamics of the concurrence between nearest-neighbor spins. We show that the Dzyaloshinskii-Moriya interaction has a significant increasing effect on the velocity of propagation. In addition, extremum in derivative of the concurrence between two NN spins, exactly happen at times where each of these two spins will be entangled with NN of themselves. The effect of a phase factor is also investigated and the existence of an "optimal" value is confirmed.

  18. Phase velocity and attenuation predictions of waves in cancellous bone using an iterative effective medium approximation.

    PubMed

    Potsika, Vassiliki T; Protopappas, Vasilios C; Vavva, Maria G; Polyzos, Demosthenes; Fotiadis, Dimitrios I

    2013-01-01

    The quantitative determination of wave dispersion and attenuation in bone is an open research area as the factors responsible for ultrasound absorption and scattering in composite biological tissues have not been completely explained. In this study, we use the iterative effective medium approximation (IEMA) proposed in [1] so as to calculate phase velocity and attenuation in media with properties similar to those of cancellous bones. Calculations are performed for a frequency range of 0.4-0.8 MHz and for different inclusions' volume concentrations and sizes. Our numerical results are compared with previous experimental findings so as to assess the effectiveness of IEMA. It was made clear that attenuation and phase velocity estimations could provide supplementary information for cancellous bone characterization. PMID:24111396

  19. 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.

  20. Effects of vehicle impact velocity and front-end structure on dynamic responses of child pedestrians.

    PubMed

    Liu, Xuejun; Yang, Jikuang

    2003-12-01

    To investigate the effects of vehicle impact velocity and front-end structure on the dynamic responses of child pedestrians, an extensive parametric study was carried out using two child mathematical models at 6 and 15 years old. The effect of the vehicle impact velocity was studied at 30, 40, and 50 km/h in terms of the head linear velocity, impact angle, and head angular velocity as well as various injury parameters concerning the head, chest, pelvis, and lower extremities. The variation of vehicle front-end shape was determined according to the shape corridors of modern vehicles, while the stiffness characteristics of the bumper, hood edge, and hood were varied within stiffness corridors obtained from dynamic component tests. The simulation results show that the vehicle impact speed is of great importance on the kinematics and resulting injury severity of child pedestrians. A significant reduction in all injury parameters can be achieved as the vehicle impact speed decreases to 30 km/h. The head and lower extremities of children are at higher injury risks than other body regions. Older children are exposed to higher injury risks to the head and lower leg, whereas younger ones sustain more severe impact loads to the pelvis and upper leg. The results from factorial analysis indicate that the hood-edge height has a significant effect on the kinematics and head impact responses of children. A higher hood edge could reduce the severity of head impact for younger children, but aggravate the risks of head injury for older ones. A significant interaction exists between the bumper height and the hood-edge height on the head impact responses of younger child. Nevertheless, improving the energy absorption performance of the hood seems effective for mitigating the severity of head injuries for children.

  1. Effects of air temperature, humidity, and air movement on thermal comfort under hot and humid conditions

    SciTech Connect

    Tanabe, Shinichi; Kimura, Kenichi

    1994-12-31

    The purpose of this paper is to review and summarize the effects of air temperature, humidity, and air movement on thermal comfort under hot and humid conditions with a view toward energy conservation. Recently, ASHRAE published a new comfort envelope in Standard 55-1992. In that standard, the upper limit of relative humidity (RH) was wet at 60%. In hot and humid regions, humidity levels higher than 60% may often be observed. This upper limit of humidity is discussed based on their subjective data. In addition, the results show that under hot and humid conditions, air movement may be one of the least expensive methods of providing thermal comfort. The effect of air movement is also described in this paper.

  2. 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

  3. 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.

  4. 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. PMID:24444224

  5. 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.

  6. 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. PMID:25412161

  7. 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. PMID:24983852

  8. 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.

  9. 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.

  10. Modelling of air pressure effects in casting moulds

    NASA Astrophysics Data System (ADS)

    Attar, E.; Homayonifar, P.; Babaei, R.; Asgari, K.; Davami, P.

    2005-09-01

    In the casting process, as a mould is filled with molten metal, air escapes through the vents. Air pressure in the mould cavity has serious effects upon the filling behaviour such as surface profile of the molten metal and filling time. In this project a computational model was developed for calculation of air pressure during the mould filling. A 3D single phase code based on the SOLA-VOF algorithm was used for the prediction of the fluid flow. The ideal gas assumption, conservation of mass equation and Bernoulli law were used for the calculation of air pressure. A new algorithm was developed to interpolate air pressure on the surface cells. The creation of air pressure was correlated with the sizes of the vents and their locations. An experimental test was designed to verify the modelling results. Comparison between the experimental data and simulation results has shown a good agreement.

  11. Air exchange effectiveness in office buildings: Measurement techniques and results

    SciTech Connect

    Fisk, W.J.; Faulkner, D.

    1992-07-01

    We define two air exchange effectiveness parameters which indicate the extent of short circuiting, mixing, or displacement air flow in an entire building, the air diffusion effectiveness which indicates the air flow pattern locally, and the normalized local age of air. After describing two tracer gas procedures for measuring these parameters, we discuss assumptions inherent in the data analysis that are often violated in large office buildings. To obtain valuable data, careful selection of buildings for measurements and assessments to determine if operating conditions are reasonably consistent with the assumptions are necessary. Multiple factors, in addition to the air flow pattern in the occupied space, can affect measurement results, consequently, the interpretation of measurements is not straightforward. We summarize the results of measurements in several office buildings and in a research laboratory. Almost all measurements indicate that the extent of both short circuiting and displacement flow is small. A moderate amount of short circuiting is evident from a few measurements in rooms with heated supply air. Ages of air and their reciprocals (local ventilation rates) often vary substantially between rooms, probably because of room-to-room variation in the rate of air supply. For future research, we suggest assessments of measurement accuracy, development of measurement approaches that may be practically applied for a broader range of buildings, and a greater focus on pollutant removal efficiencies.

  12. Effect of the Trendelenburg position on the distribution of arterial air emboli in dogs

    NASA Technical Reports Server (NTRS)

    Butler, Bruce D.; Laine, Glen A.; Leiman, Basil C.; Warters, Dave; Kurusz, Mark

    1988-01-01

    The effect of Trendelenburg position (TP) on the distribution of arterial air emboli in dogs was examined in a two-part investigation. In the first part, the effects of the bubble size and the vessel angle on the bubble velocity and the direction of flow were investigated in vitro, using a simulated carotid artery preparation. It was found that larger bubbles increased in velocity in the same direction as the blood flow at 0-, 10-, and 30-deg vessel angles, and decreased when the vessel was positioned at 90 deg. Smaller bubbles did not change velocity from 0 to 30 deg, but acted to increase the velocity, in the same direction as the flood flow, at 90 deg. The second series of experiments examined the effect of 0 to 30 deg TP on carotid-artery distribution of gas bubbles injected into the left ventricle or ascending aorta of anesthetized dogs. It was found that, regardless of the degree of the TP, the bubbles passed into the carotid artery simultaneously with the passage into the abdominal aorta. It is concluded that the TP does not prevent arterial bubbles from reaching the brain.

  13. 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.

  14. 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.

  15. Membrane air-stripping: Effects of pretreatment

    SciTech Connect

    Castro, K. ); Zander, A.K. . Dept. of Civil and Environmental Engineering)

    1995-03-01

    As a result of the Safe Drinking Water Act and its 1986 amendments, the number of regulated volatile organic chemicals (VOCs) has increased substantially. The discovery of drinking water supply sources contaminated by VOCs is also increasing. These factors have led to the development of alternative treatment methods for control of VOCs. Microporous polypropylene hollow-fiber membranes offer significant advantages over packed-tower aeration for removing volatile organic chemicals. A laboratory study assessed the performance of membrane air-stripping in continuous operation, while exposed to various pretreatments. Results indicate that membrane air-stripping is compatible with low-pH or low-chlorine waters but not with waters of high pH or high-chlorine concentration or those that are ozonated.

  16. Cardiovascular Effects of Nickel in Ambient Air

    PubMed Central

    Lippmann, Morton; Ito, Kazuhiko; Hwang, Jing-Shiang; Maciejczyk, Polina; Chen, Lung-Chi

    2006-01-01

    Background Fine particulate matter (FPM) in ambient air causes premature mortality due to cardiac disease in susceptible populations. Objective Our objective in this study was to determine the most influential FPM components. Methods A mouse model of atherosclerosis (ApoE−/−) was exposed to either filtered air or concentrated FPM (CAPs) in Tuxedo, New York (85 μg/m3 average, 6 hr/day, 5 days/week, for 6 months), and the FPM elemental composition was determined for each day. We also examined associations between PM components and mortality for two population studies: National Mortality and Morbidity Air Pollution Study (NMMAPS) and Hong Kong. Results For the CAPs-exposed mice, the average of nickel was 43 ng/m3, but on 14 days, there were Ni peaks at ~ 175 ng/m3 and unusually low FPM and vanadium. For those days, back-trajectory analyses identified a remote Ni point source. Electrocardiographic measurements on CAPs-exposed and sham-exposed mice showed Ni to be significantly associated with acute changes in heart rate and its variability. In NMMAPS, daily mortality rates in the 60 cities with recent speciation data were significantly associated with average Ni and V, but not with other measured species. Also, the Hong Kong sulfur intervention produced sharp drops in sulfur dioxide, Ni, and V, but not other components, corresponding to the intervention-related reduction in cardiovascular and pulmonary mortality. Conclusions Known biological mechanisms cannot account for the significant associations between Ni with the acute cardiac function changes in the mice or with cardiovascular mortality in people at low ambient air concentrations; therefore, further research is needed. PMID:17107850

  17. 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.

  18. Effects of strength training on throwing velocity and shoulder muscle performance in teenage baseball players.

    PubMed

    Wooden, M J; Greenfield, B; Johanson, M; Litzelman, L; Mundrane, M; Donatelli, R A

    1992-01-01

    Exercise protocols designed to improve muscle function and athletic performance are continually developed and revised, often without published research supporting their efficacy. This study compared the effects of isokinetic (IKN) and accommodative isotonic training in the individualized, dynamic, variable resistance (IDVR) mode. Twenty-seven teenage baseball players were tested isokinetically for dominant shoulder rotational peak torque and power and for throwing velocity. They were then randomly assigned to 5 weeks of IKN training, IDVR training, or a control group of no training. Following the training period, pretest protocols were repeated. Analysis of variance of differences in means and Newman-Keuls post hoc tests showed statistically significant increases in throwing velocity and external rotator torque in the IDVR group but not the IKN group. External rotator power improved in both groups. Internal rotator torque and power were not improved in either group. Results suggest that IDVR may be more effective than IKN training in improving throwing velocity and external rotator torque production. Clinicians should consider using IDVR protocols in improving shoulder muscle function and throwing performance. J Orthop Sports Phys Ther 1992;15(5):223-228.

  19. 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.

  20. 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.

  1. Effect of the degree of hill slope on acute downhill running velocity and acceleration.

    PubMed

    Ebben, William P; Davies, Joseph A; Clewien, Rustin W

    2008-05-01

    This study analyzes the effects of hill slope on acute overspeed running. This study considers both acceleration and supramaximal velocity. Forty-four athletes ran 40-yard sprints, on 5 different hill slopes, ranging from 2.1 degrees to 6.9 degrees . Forty-yard sprint times and 10-yard split times were recorded using the Brower Timing System Speedtrap II. Analysis reveals that 40-yard and 10-yard sprints performed on hill slopes of approximately 5.8 degrees were optimal compared to flatland running and the other slopes assessed. Sprinting on a 5.8 degrees slope increased the subjects' maximal speed by 7.09% +/- 3.66% and increased the subjects' acceleration by 6.54% +/- 1.56%. Strength and conditioning professionals who train athletes for speed should develop and use overspeed hills or platforms with slopes of approximately 5.8 degrees in order to maximize acute sprinting velocity and acceleration.

  2. The effect of undissolved air on isochoric freezing.

    PubMed

    Perez, Pedro A; Preciado, Jessica; Carlson, Gary; DeLonzor, Russ; Rubinsky, Boris

    2016-06-01

    This study evaluates the effect of undissolved air on isochoric freezing of aqueous solutions. Isochoric freezing is concerned with freezing in a constant volume thermodynamic system. A possible advantage of the process is that it substantially reduces the percentage of ice in the system at every subzero temperature, relative to atmospheric freezing. At the pressures generated by isochoric freezing, or high pressure isobaric freezing, air cannot be considered an incompressible substance and the presence of undissolved air substantially increases the amount of ice that forms at any subfreezing temperature. This effect is measurable at air volumes as low as 1%. Therefore eliminating the undissolved air, or any separate gaseous phase, from the system is essential for retaining the properties of isochoric freezing. PMID:27074589

  3. Which ornamental plant species effectively remove benzene from indoor air?

    NASA Astrophysics Data System (ADS)

    Liu, Yan-Ju; Mu, Yu-Jing; Zhu, Yong-Guan; Ding, Hui; Crystal Arens, Nan

    Phytoremediation—using plants to remove toxins—is an attractive and cost effective way to improve indoor air quality. This study screened ornamental plants for their ability to remove volatile organic compounds from air by fumigating 73 plant species with 150 ppb benzene, an important indoor air pollutant that poses a risk to human health. The 10 species found to be most effective at removing benzene from air were fumigated for two more days (8 h per day) to quantify their benzene removal capacity. Crassula portulacea, Hydrangea macrophylla, Cymbidium Golden Elf., Ficus microcarpa var. fuyuensis, Dendranthema morifolium, Citrus medica var. sarcodactylis, Dieffenbachia amoena cv. Tropic Snow; Spathiphyllum Supreme; Nephrolepis exaltata cv. Bostoniensis; Dracaena deremensis cv. Variegata emerged as the species with the greatest capacity to remove benzene from indoor air.

  4. The effect of undissolved air on isochoric freezing.

    PubMed

    Perez, Pedro A; Preciado, Jessica; Carlson, Gary; DeLonzor, Russ; Rubinsky, Boris

    2016-06-01

    This study evaluates the effect of undissolved air on isochoric freezing of aqueous solutions. Isochoric freezing is concerned with freezing in a constant volume thermodynamic system. A possible advantage of the process is that it substantially reduces the percentage of ice in the system at every subzero temperature, relative to atmospheric freezing. At the pressures generated by isochoric freezing, or high pressure isobaric freezing, air cannot be considered an incompressible substance and the presence of undissolved air substantially increases the amount of ice that forms at any subfreezing temperature. This effect is measurable at air volumes as low as 1%. Therefore eliminating the undissolved air, or any separate gaseous phase, from the system is essential for retaining the properties of isochoric freezing.

  5. Effect of Initial Mixture Temperature on Flame Speed of Methane-Air, Propane-Air, and Ethylene-Air Mixtures

    NASA Technical Reports Server (NTRS)

    Dugger, Gordon L

    1952-01-01

    Flame speeds based on the outer edge of the shadow cast by the laminar Bunsen cone were determined as functions of composition for methane-air mixtures at initial mixture temperatures ranging from -132 degrees to 342 degrees c and for propane-air and ethylene-air mixtures at initial mixture temperatures ranging from -73 degrees to 344 degrees c. The data showed that maximum flame speed increased with temperature at an increasing rate. The percentage change in flame speed with change in initial temperature for the three fuels followed the decreasing order, methane, propane, and ethylene. Empirical equations were determined for maximum flame speed as a function of initial temperature over the temperature range covered for each fuel. The observed effect of temperature on flame speed for each of the fuels was reasonably well predicted by either the thermal theory as presented by Semenov or the square-root law of Tanford and Pease.

  6. 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) PMID:2709983

  7. 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)

  8. "Air pollution in Delhi: Its Magnitude and Effects on Health".

    PubMed

    Rizwan, Sa; Nongkynrih, Baridalyne; Gupta, Sanjeev Kumar

    2013-01-01

    Air pollution is responsible for many health problems in the urban areas. Of late, the air pollution status in Delhi has undergone many changes in terms of the levels of pollutants and the control measures taken to reduce them. This paper provides an evidence-based insight into the status of air pollution in Delhi and its effects on health and control measures instituted. The urban air database released by the World Health Organization in September 2011 reported that Delhi has exceeded the maximum PM10 limit by almost 10-times at 198 μg/m3. Vehicular emissions and industrial activities were found to be associated with indoor as well as outdoor air pollution in Delhi. Studies on air pollution and mortality from Delhi found that all-natural-cause mortality and morbidity increased with increased air pollution. Delhi has taken several steps to reduce the level of air pollution in the city during the last 10 years. However, more still needs to be done to further reduce the levels of air pollution.

  9. 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.

  10. Pile-Driving Pressure and Particle Velocity at the Seabed: Quantifying Effects on Crustaceans and Groundfish.

    PubMed

    Miller, James H; Potty, Gopu R; Kim, Hui-Kwan

    2016-01-01

    We modeled the effects of pile driving on crustaceans, groundfish, and other animals near the seafloor. Three different waves were investigated, including the compressional wave, shear wave, and interface wave. A finite element (FE) technique was employed in and around the pile, whereas a parabolic equation (PE) code was used to predict propagation at long ranges from the pile. Pressure, particle displacement, and particle velocity are presented as a function of range at the seafloor for a shallow-water environment near Rhode Island. We discuss the potential effects on animals near the seafloor.

  11. The effect of atmospheric drag on position and velocity errors of orbiting spacecraft

    NASA Technical Reports Server (NTRS)

    Russell, R. Kent

    1987-01-01

    A model, in closed form, of position and velocity changes due to atmospheric drag of a spacecraft in orbit about a planetary body is presented, considering primarily the effects of a two-body force field. Calculations for both elliptical and circular geometries indicate that the simplifying assumptions in the analysis make the theory more accurate (to less than 1 percent error) for lengthier mappings, when the drag effect becomes quite significant. The downtrack error demonstrates a quadratic growth, while the radial error demonstrates a linear growth.

  12. Flight velocity effects on the jet noise of several variations of a 104-tube suppressor nozzle

    NASA Technical Reports Server (NTRS)

    Burley, R. R.

    1974-01-01

    At the relatively high takeoff speeds of supersonic transport aircraft, an important question concerns whether the flight speed affects the noise of suppressor nozzles. To answer this question, flyover and static tests using a modified F-106B aircraft were conducted on a 104-tube suppressor nozzle. Comparison of adjusted flyover and static spectra indicated that flight velocity had a small adverse effect on the suppression of the 104-tube suppressor. The adverse effect was larger with the acoustic shroud installed than without it.

  13. Adverse respiratory effects of outdoor air pollution in the elderly.

    PubMed

    Bentayeb, M; Simoni, M; Baiz, N; Norback, D; Baldacci, S; Maio, S; Viegi, G; Annesi-Maesano, I

    2012-09-01

    Compared to the rest of the population, the elderly are potentially highly susceptible to the effects of outdoor air pollution due to normal and pathological ageing. The purpose of the present review was to gather data on the effects on respiratory health of outdoor air pollution in the elderly, on whom data are scarce. These show statistically significant short-term and chronic adverse effects of various outdoor air pollutants on cardiopulmonary morbidity and mortality in the elderly. When exposed to air pollution, the elderly experience more hospital admissions for asthma and chronic obstructive pulmonary disease (COPD) and higher COPD mortality than others. Previous studies also indicate that research on the health effects of air pollution in the elderly has been affected by methodological problems in terms of exposure and health effect assessments. Few pollutants have been considered, and exposure assessment has been based mostly on background air pollution and more rarely on objective measurements and modelling. Significant progress needs to be made through the development of 'hybrid' models utilising the strengths of information on exposure in various environments to several air pollutants, coupled with daily activity exposure patterns. Investigations of chronic effects of air pollution and of multi-pollutant mixtures are needed to better understand the role of air pollution in the elderly. Lastly, smoking, occupation, comorbidities, treatment and the neighbourhood context should be considered as confounders or modifiers of such a role. In this context, the underlying biological, physiological and toxicological mechanisms need to be explored to better understand the phenomenon through a multidisciplinary approach. PMID:22871325

  14. Optical Tomography of a Sunspot. III. Velocity Stratification and the Evershed Effect

    NASA Astrophysics Data System (ADS)

    Westendorp Plaza, C.; del Toro Iniesta, J. C.; Ruiz Cobo, B.; Martínez Pillet, V.

    2001-02-01

    The stratification with optical depth of the line-of-sight (LOS) velocity of a simple, isolated, round sunspot observed with the Advanced Stokes Polarimeter (ASP; Elmore et al.) presented here completes this series of papers that investigates the stratification in optical depths of such a typical sunspot. These results have been obtained through the use of the SIR technique (Stokes Inversion based on Response functions of Ruiz Cobo & del Toro Iniesta). From these data we have confirmed that there are strong downflowing velocities at logτ5=0 that coincide spatially with the places where the magnetic field points downward (Westendorp Plaza et al.). Further confirmation is obtained by the application of the same method on a different sunspot, already analyzed with the Milne-Eddington inversion technique (Stanchfield, Thomas, & Lites). These downflows reconcile observations that have detected Evershed velocities outside sunspots together with suggestions of the possible return of the flow within the penumbra. The Evershed flow seems to be concentrated in elevated channels not thicker than 1 or 2 scale heights that are mostly located in the space between magnetic spines, i.e., in places where the magnetic field is more inclined, weaker in the inner-middle penumbra, and stronger in the outer penumbra and beyond the visible limits of the sunspot. This conclusion is based upon the tight correlation found between LOS velocities and the (reported in the second paper of this series) magnetic field strength and zenith angle. The upstreaming material is seen in the inner penumbra and the downstreaming in the outer penumbra. A strong increase with optical depth has been obtained for the LOS velocities that provides indications of the superposition of Evershed channels along the LOS. The differential opacity effect between the center-side and the limb-side penumbra, already reported in the second paper in this series, is also seen in the velocity maps and has suggested the

  15. 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

  16. Investigating the Effects of Traffic on Air Pollution.

    ERIC Educational Resources Information Center

    Taylor, Sharon

    2001-01-01

    Discusses the benefits of bringing scientists into the classroom to collaborate with children on environmental research projects. Describes one collaborative project that focused on the effects of traffic on air pollution. (DDR)

  17. An Air Quality Data Analysis System for Interrelating Effects, Standards and Needed Source Reductions

    ERIC Educational Resources Information Center

    Larsen, Ralph I.

    1973-01-01

    Makes recommendations for a single air quality data system (using average time) for interrelating air pollution effects, air quality standards, air quality monitoring, diffusion calculations, source-reduction calculations, and emission standards. (JR)

  18. The effect of rotor motion on the induced velocity in predicting the response of rotorcraft

    NASA Astrophysics Data System (ADS)

    Keller, Jeffrey David

    The prediction of the dynamic response is a fundamental objective in rotorcraft flight mechanics, having relevance to flight simulation, handling qualities assessment and control system design. Unlike conventional fixed-wing aircraft, helicopter flight dynamics models must account for the coupling between the fuselage, rotor, and inflow degrees of freedom, resulting in highly complex systems whose predictive capability is limited by aerodynamic modeling assumptions. Quasi-steady aerodynamic models based on low-order finite-state approximations of the rotor induced velocity are commonplace due to their compact form; however, these models are unable to predict all aspects of the response, in particular the off-axis response due to cyclic control inputs, due to the lack of all effects of rotor motion on the induced velocity. This dissertation investigates the relationship between the induced velocity of a maneuvering rotor and the dynamic response due to control inputs. It is shown that rotor pitch and roll motion causes a significant induced velocity variation due to the distorted wake structure. These effects are included parametrically in an extended inflow model, suitable for flight dynamics applications, where the inflow parameters are estimated using an infinite-blade numerical vortex model and are influenced by rotor trim condition as well as the assumed wake geometry. This extended inflow model is used to demonstrate the importance of inflow variations resulting explicitly from angular motion on critical dynamic characteristics including the off-axis flap to steady angular rate, the damping of flapwise-stiff rotors, and the response to cyclic control inputs. The induced velocity model, with parameters derived from simple vortex theory, is validated against flight test data for a UH-60 helicopter in hover. Improvements in the initial off-axis acceleration are demonstrated, and system identification methods are subsequently used to adjust the inflow model

  19. Effect of ion excape velocity and conversion surface material on H- production

    SciTech Connect

    Johnson, Kenneth F; Tarvainen, Olli A; Geros, E.; Stelzer, J.; Rouleau, G.; Kalvas, T.; Komppula, J.; Carmichael, J.

    2010-10-05

    According to generally accepted models surface production of negative ions depends on ion escape velocity and work function of the surface. We have conducted an experimental study addressing the role of the ion escape velocity on H{sup -} production. A converter-type ion source at Los Alamos Neutron Science Center was employed for the experiment. The ion escape velocity was changed by varying the bias voltage of the converter electrode. It was observed that due to enhanced stripping of H{sup -} no direct gain of extracted beam current can be achieved by increasing the converter voltage. At the same time the conversion efficiency of H{sup -} was observed to vary with converter voltage and follow the existing theories in qualitative manner. We discuss the role of surface material on H{sup -} formation probability and present calculations predicting relative H{sup -} yields from different cesiated surfaces. These calculations are compared with experimental observations from different types of H{sup -} ion sources. The effects caused by varying cesium coverage are also discussed. Finally, we present a novel idea of utilizing materials exhibiting so-called negative electron affinity in H{sup -}/D{sup -} production under UV-light exposure.

  20. Hydrogen emissivity in realistic nebulae - The effects of velocity fields and internal dust

    NASA Astrophysics Data System (ADS)

    Cota, S. A.; Ferland, G. J.

    1988-03-01

    The paper presents calculations of the H-beta emissivity expected from nebulae with velocity gradients or internal dust. As has been found by Capriotti, Cox, and Mathews, Lyman line escape and destruction can prevent the 100 percent conversion of high-n Lyman lines into Ly-alpha and Balmer lines. For dusty environments such as the Orion Nebula or the general interstellar medium, the H-beta emissivity can be reduced by less than about 15 percent. Lyman line escape may cause still larger deviations in environments such as nova shells where the expansion velocities are large and velocity gradients likely. Although the partial conversion of Lyman lines only lowers the H-beta emissivity by typically less than about 10 percent under most circumstances, this introduces a systematic error in abundance measurements; the abundance of other elements relative to hydrogen will be overestimated by this amount. This effect must be considered in detail if very accurate abundance measurements are to be made. The present predictions of the deviation from case B emissivity are presented in a way in which they can be easily used by observers or incorporated into photoionization or shock codes.

  1. Edge mode velocities in the quantum Hall effect from a dc measurement

    NASA Astrophysics Data System (ADS)

    Zucker, Philip; Feldman, D. E.

    Because of the bulk gap, low energy physics in the quantum Hall effect is confined to the edges of the 2D electron liquid. The velocities of edge modes are key parameters of edge physics. They were determined in several quantum Hall systems from time-resolved measurements and high-frequency ac transport. We propose a way to extract edge velocities from dc transport in a point contact geometry defined by narrow gates. The width of the gates assumes two different sizes at small and large distances from the point contact. The Coulomb interaction across the gates depends on the gate width and affects the conductance of the contact. The conductance exhibits two different temperature dependencies at high and low temperatures. The transition between the two regimes is determined by the edge velocity. An interesting feature of the low-temperature I - V curve is current oscillations as a function of the voltage. The oscillations emerge due to charge reflection from the interface of the regions defined by the narrow and wide sections of the gates. This work is available at arXiv:1510.01725 This work was supported by the NSF under Grant No. DMR-1205715.

  2. Collisional Processing of Comet and Asteroid Surfaces: Velocity Effects on Absorption Spectra

    NASA Technical Reports Server (NTRS)

    Lederer, S. M.; Jensen, E. A.; Wooden, D. H.; Lindsay, S. S.; Smith, D. C.; Nakamura-Messenger, K.; Keller, L. P.; Cintala, M. J.; Zolensky, M. E.

    2012-01-01

    A new paradigm has emerged where 3.9 Gyr ago, a violent reshuffling reshaped the placement of small bodies in the solar system (the Nice model). Surface properties of these objects may have been affected by collisions caused by this event, and by collisions with other small bodies since their emplacement. These impacts affect the spectrographic observations of these bodies today. Shock effects (e.g., planar dislocations) manifest in minerals allowing astronomers to better understand geophysical impact processing that has occurred on small bodies. At the Experimental Impact Laboratory at NASA Johnson Space Center, we have impacted forsterite and enstatite across a range of velocities. We find that the amount of spectral variation, absorption wavelength, and full width half maximum of the absorbance peaks vary non-linearly with the velocity of the impact. We also find that the spectral variation increases with decreasing crystal size (single solid rock versus granular). Future analyses include quantification of the spectral changes with different impactor densities, temperature, and additional impact velocities. Results on diopside, fayalite, and magnesite can be found in Lederer et al., this meeting.

  3. Visual image quality assessment with sensor motion: effect of recording and presentation velocity.

    PubMed

    Bijl, Piet

    2010-01-20

    To assess the effect of motion on observer performance with an undersampled uncooled thermal imager, moving imagery from a static scene was recorded at nine different angular velocities ranging from 0 (static) to 1 pixel/frame by use of a tilted rotating mirror. The scene contained a thermal acuity test chart with triangular test patterns based on the triangle orientation discrimination test method. Visual acuity with the sensor was determined in two playback modes: normal speed and slow motion. In both playback conditions, a slow angular velocity of the test pattern over the sensor focal plane (up to 0.25 pixel/frame) results in a large acuity increase (+50%) in comparison with the static condition because the observer is able to utilize more phases of the same test pattern. At higher sensor velocities the benefit rapidly decreases due to sensor smear, and above 0.50 pixel/frame the difference with the static condition is marginal. Up to 0.75 pixel/frame, the results for the two playback conditions are similar, indicating that temporal display characteristics and human dynamic acuity are not responsible for the reduction. The results obtained with this laboratory test method correspond well with earlier perception studies on real targets for low and medium camera motion. PMID:20090798

  4. Effects of movement distance, duration, velocity, and type on action prediction in 12-month-olds.

    PubMed

    Daum, Moritz M; Gampe, Anja; Wronski, Caroline; Attig, Manja

    2016-05-01

    The goal of the present study was to test the influence of the spatial and temporal dynamics of observed manual actions on infants' action prediction. Twelve-month-old infants were presented with reach-and-transport actions performed by a human agent. Movement distance, duration, and - resulting from the two - movement velocity were systematically varied. Action prediction was measured via the latency of gaze arrival at target in relation to agent's hand. The results showed a general effect of all parameters on the infants' perception of goal-directed actions: Infants were more likely to predict the action goal the longer the movement distance was, the longer the movement duration was, and the slower the movement velocity was. In addition, they were more likely to predict the goal of a reaching than a transport action. The present findings extent previous findings by showing that infants are not only sensitive to differences in distances, durations, and velocities at early age but that these factors have a strong impact on the prediction of the goal of observed actions.

  5. High-velocity intermittent running: effects of beta-alanine supplementation.

    PubMed

    Smith-Ryan, Abbie E; Fukuda, David H; Stout, Jeffrey R; Kendall, Kristina L

    2012-10-01

    The use of β-alanine in sport is widespread. However, the effects across all sport activities are inconclusive. The purpose of this study was to evaluate the effects of β-alanine supplementation on high-intensity running performance and critical velocity (CV) and anaerobic running capacity (ARC). Fifty recreationally trained men were randomly assigned, in a double-blind fashion, to a β-alanine group (BA, 2 × 800 mg tablets, 3 times daily; CarnoSyn; n = 26) or placebo group (PL, 2 × 800 mg maltodextrin tablets, 3 times daily; n = 24). A graded exercise test (GXT) was performed to establish peak velocity (PV). Three high-speed runs to exhaustion were performed at 110, 100, and 90% of PV, with 15 minutes of rest between bouts. The distances achieved were plotted over the time to exhaustion (TTE). Linear regression was used to determine the slope (CV) and y-intercept (ARC) of these relationships to assess aerobic and anaerobic performances, respectively. There were no significant treatment effects (p > 0.05) on CV or ARC for either men or women. Additionally, no TTE effects were evident for bouts at 90-110%PV lasting 1.95-5.06 minutes. There seems to be no ergogenic effect of β-alanine supplementation on CV, ARC, or high-intensity running lasting approximately 2-5 minutes in either men or women in the current study.

  6. Analysis of the effect of the fluid-structure interface on elastic wave velocity in cornea-like structures by OCE and FEM

    NASA Astrophysics Data System (ADS)

    Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Vantipalli, Srilatha; Aglyamov, Salavat R.; Wu, Chen; Liu, Chih-hao; Raghunathan, Raksha; Twa, Michael D.; Larin, Kirill V.

    2016-03-01

    Air-pulse optical coherence elastography (OCE) is a promising technique for quantifying biomechanical properties of the cornea. This technique typically involves imaging and analysis of the propagation of the air-pulse induced elastic waves to reconstruct corneal biomechanical properties using an analytical model. However, the effect of the fluid-structure interface (FSI) at the corneal posterior surface on the elastic wave velocity is not accounted for in many models. In this study, we examined the effect of the FSI with OCE experiments on contact lenses with and without fluid in the posterior gap. Finite element models (FEM), also with and without the FSI, were constructed to simulate the elastic wave propagation based on the OCE measurements. The FEM and OCE results were in good agreement demonstrating the feasibility of the method. To further investigate the effect of the FSI, OCE experiments and subsequent FEM simulations were conducted on in situ rabbit corneas before and after rose bengal/green light corneal collagen cross-linking (RGX). Both the OCE experiments and the FE simulations demonstrated that the FSI significantly reduced the group velocity of the elastic wave, and thus, should be considered when determining corneal biomechanical properties from an appropriate mechanical model. By matching the FEM-calculated velocity to the OCE-measured velocity, the corneal elasticity was quantified. The Young’s modulus of the rabbit cornea before RGX was E  =  65  ±  10 kPa at a controlled intraocular pressure (IOP) of 15 mmHg. After RGX, the Young’s modulus increased to E  =  102  ±  7 kPa at the same IOP.

  7. Orientation and related buoyancy effects in low-velocity flow boiling.

    PubMed

    Merte, Herman; Schultz, William W; Liu, Quanyi; Keller, Robert B

    2009-04-01

    This work is an extension of experimental results reported previously, which might provide design guidance for approximating certain aspects of the flow boiling process in microgravity but taking place in Earth gravity. In that research the buoyancy effects on the bubble dynamics were minimized by the imposition of a liquid velocity parallel to a flat heater surface in the inverted horizontal position, or nearly horizontal (within +/-5 degrees ), thus holding the heated liquid and vapor formed close to the heater surface. For the fluid used, liquid velocities in the range U= 5-10 cm/s were judged to be critical for changes in the behavior of the flow boiling process. Using the hydraulic diameter of the rectangular duct used, with the heater surface embedded in one side, this velocity range gives rise to flow Reynolds numbers on the order of 4400-8800. It was subsequently judged to be of interest to extend the range of orientation of the flat heater surface relative to gravity to the full circular range of 0-360 degrees, in increments of 45 degrees, and the results of this work are presented here. A solid massive copper heater with a gold-plated boiling heat transfer surface 19 x 38 mm in size, previously used for critical heat flux measurements with boiling, provided a near-uniform surface temperature. Only steady measurements of heat flux and surface temperature were possible with the copper heater. R-113 was the fluid used; the velocity was varied over the interval of 4-28 cm/s; bulk liquid subcooling was varied over 5-11 degrees C; and heat flux varied over 0-10 w/cm(2).

  8. Walk-through survey report: HVLV (high velocity low volume) control technology for aircraft bonded wing and radome maintenance at Air Force Logistics Command, McClellan Air Force Base, Sacramento, California

    SciTech Connect

    Hollett, B.A.

    1983-08-01

    A walk through survey was conducted at the Sacramento Air Logistics Center, McClellan Air Force Base, California, on June 13, 1983, to evaluate the use of High Velocity Low Volume (HVLV) technology in the aircraft-maintenance industry. The HVLV system consisted of 65 ceiling drops in the bonded honeycomb shop where grinding and sanding operations created glass fiber and resin dusts. Preemployment and periodic physical examinations were required. Workers were required to wear disposable coveralls, and disposable dust masks were available. Workers walked through decontamination air jet showers before leaving the area to change clothes. Environmental monitoring revealed no significant dust exposures when the HVLV system was in use. Performance of the exhaust system on the eight-inch-diameter nose cone sanding operation was good, but the three-inch-diameter tools were too large and the shrouds too cumbersome for use on many hand-finishing tasks. The author concludes that the HVLV system is partially successful but requires additional shroud design. Further development of small tool shrouds is recommended.

  9. Effects of successive air and nitrox dives on human vascular function.

    PubMed

    Marinovic, Jasna; Ljubkovic, Marko; Breskovic, Toni; Gunjaca, Grgo; Obad, Ante; Modun, Darko; Bilopavlovic, Nada; Tsikas, Dimitrios; Dujic, Zeljko

    2012-06-01

    SCUBA diving is regularly associated with asymptomatic changes in cardiac, pulmonary and vascular function. The aim of this study was to evaluate the changes in vascular/endothelial function following SCUBA diving and to assess the potential difference between two breathing gases: air and nitrox 36 (36% oxygen and 64% nitrogen). Ten divers performed two 3-day diving series (no-decompression dive to 18 m with 47 min bottom time with air and nitrox, respectively), with 2 weeks pause in between. Arterial/endothelial function was assessed using SphygmoCor and flow-mediated dilation measurements, and concentration of nitrite before and after diving was determined in venous blood. Production of nitrogen bubbles post-dive was assessed by ultrasonic determination of venous gas bubble grade. Significantly higher bubbling was found after all air dives as compared to nitrox dives. Pulse wave velocity increased slightly (~6%), significantly after both air and nitrox diving, indicating an increase in arterial stiffness. However, augmentation index became significantly more negative after diving indicating smaller wave reflection. There was a trend for post-dive reduction of FMD after air dives; however, only nitrox diving significantly reduced FMD. No significant differences in blood nitrite before and after the dives were found. We found that nitrox diving affects systemic/vascular function more profoundly than air diving by reducing FMD response, most likely due to higher oxygen load. Both air and nitrox dives increased arterial stiffness, but decreased wave reflection suggesting a decrease in peripheral resistance due to exercise during diving. These effects of nitrox and air diving were not followed by changes in plasma nitrite.

  10. The Adverse Effects of Air Pollution on the Nervous System

    PubMed Central

    Genc, Sermin; Zadeoglulari, Zeynep; Fuss, Stefan H.; Genc, Kursad

    2012-01-01

    Exposure to ambient air pollution is a serious and common public health concern associated with growing morbidity and mortality worldwide. In the last decades, the adverse effects of air pollution on the pulmonary and cardiovascular systems have been well established in a series of major epidemiological and observational studies. In the recent past, air pollution has also been associated with diseases of the central nervous system (CNS), including stroke, Alzheimer's disease, Parkinson's disease, and neurodevelopmental disorders. It has been demonstrated that various components of air pollution, such as nanosized particles, can easily translocate to the CNS where they can activate innate immune responses. Furthermore, systemic inflammation arising from the pulmonary or cardiovascular system can affect CNS health. Despite intense studies on the health effects of ambient air pollution, the underlying molecular mechanisms of susceptibility and disease remain largely elusive. However, emerging evidence suggests that air pollution-induced neuroinflammation, oxidative stress, microglial activation, cerebrovascular dysfunction, and alterations in the blood-brain barrier contribute to CNS pathology. A better understanding of the mediators and mechanisms will enable the development of new strategies to protect individuals at risk and to reduce detrimental effects of air pollution on the nervous system and mental health. PMID:22523490

  11. Ventilation System Effectiveness and Tested Indoor Air Quality Impacts

    SciTech Connect

    Rudd, Armin; Bergey, Daniel

    2014-02-01

    In this project, Building America research team Building Science Corporation tested the effectiveness of ventilation systems at two unoccupied, single-family, detached lab homes at the University of Texas - Tyler. Five ventilation system tests were conducted with various whole-building ventilation systems. Multizone fan pressurization testing characterized building and zone enclosure leakage. PFT testing showed multizone air change rates and interzonal airflow. Cumulative particle counts for six particle sizes, and formaldehyde and other Top 20 VOC concentrations were measured in multiple zones. The testing showed that single-point exhaust ventilation was inferior as a whole-house ventilation strategy. This was because the source of outside air was not direct from outside, the ventilation air was not distributed, and no provision existed for air filtration. Indoor air recirculation by a central air distribution system can help improve the exhaust ventilation system by way of air mixing and filtration. In contrast, the supply and balanced ventilation systems showed that there is a significant benefit to drawing outside air from a known outside location, and filtering and distributing that air. Compared to the exhaust systems, the CFIS and ERV systems showed better ventilation air distribution and lower concentrations of particulates, formaldehyde and other VOCs. System improvement percentages were estimated based on four system factor categories: balance, distribution, outside air source, and recirculation filtration. Recommended system factors could be applied to reduce ventilation fan airflow rates relative to ASHRAE Standard 62.2 to save energy and reduce moisture control risk in humid climates. HVAC energy savings were predicted to be 8-10%, or $50-$75/year.

  12. Ventilation System Effectiveness and Tested Indoor Air Quality Impacts

    SciTech Connect

    Rudd, A.; Bergey, D.

    2014-02-01

    Ventilation system effectiveness testing was conducted at two unoccupied, single-family, detached lab homes at the University of Texas - Tyler. Five ventilation system tests were conducted with various whole-building ventilation systems. Multizone fan pressurization testing characterized building and zone enclosure leakage. PFT testing showed multizone air change rates and interzonal airflow. Cumulative particle counts for six particle sizes, and formaldehyde and other Top 20 VOC concentrations were measured in multiple zones. The testing showed that single-point exhaust ventilation was inferior as a whole-house ventilation strategy. It was inferior because the source of outside air was not direct from outside, the ventilation air was not distributed, and no provision existed for air filtration. Indoor air recirculation by a central air distribution system can help improve the exhaust ventilation system by way of air mixing and filtration. In contrast, the supply and balanced ventilation systems showed that there is a significant benefit to drawing outside air from a known outside location, and filtering and distributing that air. Compared to the Exhaust systems, the CFIS and ERV systems showed better ventilation air distribution and lower concentrations of particulates, formaldehyde and other VOCs. System improvement percentages were estimated based on four System Factor Categories: Balance, Distribution, Outside Air Source, and Recirculation Filtration. Recommended System Factors could be applied to reduce ventilation fan airflow rates relative to ASHRAE Standard 62.2 to save energy and reduce moisture control risk in humid climates. HVAC energy savings were predicted to be 8-10%, or $50-$75/year.

  13. Suppression of slip and rupture velocity increased by thermal pressurization: Effect of dilatancy

    NASA Astrophysics Data System (ADS)

    Urata, Yumi; Kuge, Keiko; Kase, Yuko

    2013-11-01

    investigated the effect of dilatancy on dynamic rupture propagation on a fault where thermal pressurization (TP) is in effect, taking into account permeability varying with porosity; the study is based on three-dimensional (3-D) numerical simulations of spontaneous ruptures obeying a slip-weakening friction law and Coulomb failure criterion. The effects of dilatancy on dynamic ruptures interacting with TP have been often investigated in one- or two-dimensional numerical simulations. The sole 3-D numerical simulation gave attention only to the behavior at a single point on a fault. Moreover, with the sole exception based on a single-degree-freedom spring-slider model, the previous simulations including dilatancy and TP have not considered changes in hydraulic diffusivity. However, the hydraulic diffusivity, which strongly affects TP, can vary as a power of porosity. In this study, we apply a power law relationship between permeability and porosity. We consider both reversible and irreversible changes in porosity, assuming that the irreversible change is proportional to the slip rate and dilatancy coefficient ɛ. Our numerical simulations suggest that the effects of dilatancy can suppress slip and rupture velocity increased by TP. The results reveal that the amount of slip on the fault decreases with increasing ɛ or exponent of the power law, and the rupture velocity is predominantly suppressed by ɛ. This was observed regardless of whether the applied stresses were high or low. The deficit of the final slip in relation to ɛ can be smaller as the fault size is larger.

  14. Effects of droplet velocity, diameter, and film height on heat removal during cryogen spray cooling.

    PubMed

    Pikkula, Brian M; Tunnell, James W; Chang, David W; Anvari, Bahman

    2004-08-01

    Cryogen spray cooling (CSC) is an effective method to reduce or eliminate epidermal damage during laser treatment of various dermatoses. This study sought to determine the effects of specific cryogen properties on heat removal. Heat removal was quantified using an algorithm that solved an inverse heat conduction problem from internal temperature measurements made within a skin phantom. A nondimensional parameter, the Weber number, characterized the combined effects of droplet velocity, diameter, and surface tension. CSC experiments with laser irradiation were conducted on ex vivo human skin samples to assess the effect of Weber number on epidermal protection. An empirical relationship between heat removal and the difference in droplet temperature and the substrate, droplet velocity, and diameter was obtained. Histological sections of irradiated ex vivo human skin demonstrated that sprays with higher Weber numbers increased epidermal protection. Results indicate that the cryogen film acts as an impediment to heat transfer between the impinging droplets and the substrate. This study offers the importance of Weber number in heat removal and epidermal protection. PMID:15446509

  15. Groundwater air stripping: Effect on water toxicity

    SciTech Connect

    Eldridge, R.B.; Simpson, C.W.; Elliott, D.J.

    1995-02-01

    An air stripping unit was designed to reduce groundwater hydrocarbon content and biotoxicity to acceptable levels. A pilot plant study was conducted to determine the water treatability and to optimize the commercial unit design conditions. A measurement of the pilot plant effluent toxicity was obtained from {open_quotes}Microtox{close_quotes} analysis and rigorous bio-assays. These results indicated that reduction of the water hydrocarbon content to permitted discharge limits was accompanied by the elimination of water toxicity. The Onda mass transfer model was used to prepare the commercial unit design. A post-installation evaluation indicated that the model gave a good representation of the commercial unit performance. Toxicity reductions observed in the pilot plant were also observed in the commercial unit. 3 refs., 5 figs., 3 tabs.

  16. Air pollution effects on the structure of Citrus aurantium leaves

    SciTech Connect

    Psaras, G.K.; Christodoulakis, N.S.

    1987-09-01

    Individual air pollutants cause acute and chronic plant injury, act on stomata and affect carbon dioxide exchange as well as plant growth and development. Inhibition of photosynthesis by several air pollutants has been reported repeatedly. Besides, structural modifications of cell organelles have been reported after fumigation by SO/sub 2/. Although chlorosis and subsequent necrosis are common phenomena caused by artificial treatment with pollutants, fine structural leaf characteristics of plants exposed to long-term air pollution in natural conditions are little explored. Light microscope examination of air pollution affected leaves of plants common in natural ecosystems of Athens' metropolitan area revealed chlorosis phenomena. Electron microscope examination of the leaves of a common subshrub of greek phryganic formations grown in a heavily air polluted natural ecosystem of Athens metropolitan area revealed pronounced ultrastructural anomalies of chloroplasts, mitochondria and microbodies of the mesophyll cells. This organelle destruction of the photosynthesizing tissue as well as the minimization of the ecosystem primary productivity are attributed to the compound action of several toxic air pollutants of the photochemical smog of Athens. This work describes the long-term air pollution effects on the structural features of the leaves of Citrus aurantium, a decorative species planted throughout the heavily air polluted city of Athens.

  17. Effect of flow velocity on phytoplankton biomass and composition in a freshwater lake.

    PubMed

    Li, Feipeng; Zhang, Haiping; Zhu, Yiping; Xiao, Yihua; Chen, Ling

    2013-03-01

    Water flow has been widely accepted as a target to suppress algae blooms. However, the effectiveness of the flow regulation is unclear due to lack of hard evidences to illuminate the direct cause-effect relationship between hydrodynamic forces and algae growth. In this study, a field observation at a freshwater lake was conducted weekly or biweekly from July 2007 to December 2009. Phytoplankton biomass and composition were investigated at flow velocities of 0.03m/s, 0.06m/s, 0.10m/s, 0.15m/s and 0.30m/s in field enclosure experiments. The results from the field observation indicated that phytoplankton biomass and spatial distribution largely depend on the flow condition. A strong negative correlation (R(2)=-0.618, n=222, P<0.001) was found between Chl-a concentration and flow velocity. The results of enclosure experiments showed that turbulent flow has the inhibition effect on phytoplankton biomass, but less impact on composition. The average Chl-a concentrations in the flowing enclosures were 20.3%-37.5% lower than that in their corresponding still water enclosures during the entire experiment period. Shear stress within pumps might have caused up to 10% of cell damage. The present study highlights that a universal critical velocity for suppressing algae growth probably does not exist in freshwater bodies, for each has its unique physical, chemical and ecological characteristics. It is therefore suggested that sufficient experiments should be conducted for each water body before a critical flow condition is applied to reduce the algae bloom occurrence.

  18. Reactions of Microsolvated Organic Compounds at Ambient Surfaces: Droplet Velocity, Charge State, and Solvent Effects

    NASA Astrophysics Data System (ADS)

    Badu-Tawiah, Abraham K.; Campbell, Dahlia I.; Cooks, R. Graham

    2012-06-01

    The exposure of charged microdroplets containing organic ions to solid-phase reagents at ambient surfaces results in heterogeneous ion/surface reactions. The electrosprayed droplets were driven pneumatically in ambient air and then electrically directed onto a surface coated with reagent. Using this reactive soft landing approach, acid-catalyzed Girard condensation was achieved at an ambient surface by directing droplets containing Girard T ions onto a dry keto-steroid. The charged droplet/surface reaction was much more efficient than the corresponding bulk solution-phase reaction performed on the same scale. The increase in product yield is ascribed to solvent evaporation, which causes moderate pH values in the starting droplet to reach extreme values and increases reagent concentrations. Comparisons are made with an experiment in which the droplets were pneumatically accelerated onto the ambient surface (reactive desorption electrospray ionization, DESI). The same reaction products were observed but differences in spatial distribution were seen associated with the "splash" of the high velocity DESI droplets. In a third type of experiment, the reactions of charged droplets with vapor phase reagents were examined by allowing electrosprayed droplets containing a reagent to intercept the headspace vapor of an analyte. Deposition onto a collector surface and mass analysis showed that samples in the vapor phase were captured by the electrospray droplets, and that instantaneous derivatization of the captured sample is possible in the open air. The systems examined under this condition included the derivatization of cortisone vapor with Girard T and that of 4-phenylpyridine N-oxide and 2-phenylacetophenone vapors with ethanolamine.

  19. A new model for investigating the mortality effects of multiple air pollutants in air pollution mortality time-series studies.

    PubMed

    Roberts, Steven

    2006-03-01

    Because the U.S. Environmental Protection Agency regulates air pollutants independently, the majority of time-series studies on air pollution and mortality have focused on estimating the adverse health effects of a single pollutant. However, due to the sometimes high correlation between air pollutants, the results from studies that focus on a single air pollutant can be difficult to interpret. In addition, the high correlation between air pollutants can produce problems of interpretation for the standard method of investigating the adverse health effects due to multiple air pollutants. The standard method involves simultaneously including the multiple air pollutants in a single statistical model. Because of this, the development of new models to concurrently estimate the adverse health effects of multiple air pollutants has recently been identified as an important area of future research. In this article, a new model for disentangling the joint effects of multiple air pollutants in air pollution mortality time-series studies is introduced. This new model uses the time-series data to assign each air pollutant a weight that indicates the pollutant's contribution to the air pollution mixture that affects mortality and to estimate the effect of this air pollution mixture on mortality. This model offers an improvement in statistical estimation precision over the standard method. It also avoids problems of interpretation that can occur if the standard method is used. This new model is then illustrated by applying it to time-series data from two U.S. counties.

  20. The Effect of Rain on Air-Water Gas Exchange

    NASA Technical Reports Server (NTRS)

    Ho, David T.; Bliven, Larry F.; Wanninkhof, Rik; Schlosser, Peter

    1997-01-01

    The relationship between gas transfer velocity and rain rate was investigated at NASA's Rain-Sea Interaction Facility (RSIF) using several SF, evasion experiments. During each experiment, a water tank below the rain simulator was supersaturated with SF6, a synthetic gas, and the gas transfer velocities were calculated from the measured decrease in SF6 concentration with time. The results from experiments with IS different rain rates (7 to 10 mm/h) and 1 of 2 drop sizes (2.8 or 4.2 mm diameter) confirm a significant and systematic enhancement of air-water gas exchange by rainfall. The gas transfer velocities derived from our experiment were related to the kinetic energy flux calculated from the rain rate and drop size. The relationship obtained for mono-dropsize rain at the RSIF was extrapolated to natural rain using the kinetic energy flux of natural rain calculated from the Marshall-Palmer raindrop size distribution. Results of laboratory experiments at RSIF were compared to field observations made during a tropical rainstorm in Miami, Florida and show good agreement between laboratory and field data.

  1. Effect of mean velocity shear on the dissipation rate of turbulent kinetic energy

    NASA Technical Reports Server (NTRS)

    Yoshizawa, Akira; Liou, Meng-Sing

    1992-01-01

    The dissipation rate of turbulent kinetic energy in incompressible turbulence is investigated using a two-scale DIA. The dissipation rate is shown to consist of two parts; one corresponds to the dissipation rate used in the current turbulence models of eddy-viscosity type, and another comes from the viscous effect that is closely connected with mean velocity shear. This result can elucidate the physical meaning of the dissipation rate used in the current turbulence models and explain part of the discrepancy in the near-wall dissipation rates between the current turbulence models and direct numerical simulation of the Navier-Stokes equation.

  2. Effect of velocity and temperature distribution at the hole exit on film cooling of turbine blades

    NASA Technical Reports Server (NTRS)

    Garg, Vijay K.; Gaugler, Raymond E.

    1995-01-01

    An existing three-dimensional Navier-Stokes code, modified to include film cooling considerations, has been used to study the effect of coolant velocity and temperature distribution at the hole exit on the heat transfer coefficient on three-film-cooled turbine blades, namely, the C3X vane, the VKI rotor, and the ACE rotor. Results are also compared with the experimental data for all the blades. Moreover, Mayle's transition criterion, Forest's model for augmentation of leading edge heat transfer due to freestream turbulence, and Crawford's model for augmentation of eddy viscosity due to film cooling are used. Use of Mayle's and Forest's models is relevant only for the ACE rotor due to the absence of showerhead cooling on this rotor. It is found that, in some cases, the effect of distribution of coolant velocity and temperature at the hole exit can be as much as 60% on the heat transfer coefficient at the blade suction surface, and 50% at the pressure surface. Also, different effects are observed on the pressure and suction surface depending upon the blade as well as upon the hole shape, conical or cylindrical.

  3. Ocular surface adverse effects of ambient levels of air pollution.

    PubMed

    Torricelli, André Augusto Miranda; Novaes, Priscila; Matsuda, Monique; Alves, Milton Ruiz; Monteiro, Mário Luiz Ribeiro

    2011-01-01

    It is widely recognized today that outdoor air pollution can affect human health. Various chemical components that are present in ambient pollution may have an irritant effect on the mucous membranes of the body, particularly those of the respiratory tract. Much less attention has been focused on the adverse effect on the ocular surface, despite the fact that this structure is even more exposed to air pollution than the respiratory mucosa since only a very thin tear film separates the corneal and conjunctival epithelia from the air pollutants. So far, clinical data are the more widespread tools used by ophthalmologists for assessing possible aggression to the ocular surface; however, clinical findings alone appears not to correlate properly with the complaints presented by the patients pointing out the need for further clinical and laboratory studies on the subject. The purpose of this study is to review signs and symptoms associated with chronic long-term exposure to environmental air pollutants on the ocular structures currently defined as the ocular surface and to review clinical and laboratory tests used to investigate the adverse effects of air pollutants on such structures. We also review previous studies that investigated the adverse effects of air pollution on the ocular surface and discuss the need for further investigation on the subject.

  4. Health effects of air quality regulations in Delhi, India

    NASA Astrophysics Data System (ADS)

    Foster, Andrew; Kumar, Naresh

    2011-03-01

    This, the first systematic study, quantifies the health effects of air quality regulations in Delhi, which adopted radical measures to improve air quality, including, for example, the conversion of all commercial vehicles to compressed natural gas (CNG), and the closure of polluting industries in residential areas from 2000 to 2002. Air pollution data, collected at 113 sites (spread across Delhi and its neighboring areas) from July-December 2003, were used to compute exposure at the place of residence of 3989 subjects. A socio-economic and respiratory health survey was administered in 1576 households. This survey collected time-use, residence histories, demographic information, and direct measurements of lung function with subjects. The optimal interpolation methods were used to link air pollution and respiratory health data at the place of their residence. Resident histories, in combination with secondary data, were used to impute cumulative exposure prior to the air-quality interventions, and the effects of recent air quality measures on lung function were then evaluated. Three important findings emerge from the analysis. First, the interventions were associated with a significant improvement in respiratory health. Second, the effect of these interventions varied significantly by gender and income. Third, consistent with a causal interpretation of these results, effects were the strongest among those individuals who spend a disproportionate share of their time out-of-doors.

  5. Health Effects of Air Quality Regulations in Delhi, India

    PubMed Central

    Foster, Andrew; Kumar, Naresh

    2011-01-01

    This, the first systematic study, quantifies the health effects of air quality regulations in Delhi, which adopted radical measures to improve air quality, including, for example, the conversion of all commercial vehicles to compressed natural gas (CNG), and the closure of polluting industries in residential areas from 2000 to 2002. Air pollution data, collected at 113 sites (spread across Delhi and its neighboring areas) from July-December 2003, were used to compute exposure at the place of residence of 3,989 subjects. A socio-economic and respiratory health survey was administered in 1,576 households. This survey collected time-use, residence histories, demographic information, and direct measurements of lung function with subjects. The optimal interpolation methods were used to link air pollution and respiratory health data at the place of their residence. Resident histories, in combination with secondary data, were used to impute cumulative exposure prior to the air-quality interventions, and the effects of recent air quality measures on lung function were then evaluated. Three important findings emerge from the analysis. First, the interventions were associated with a significant improvement in respiratory health. Second, the effect of these interventions varied significantly by gender and income. Third, consistent with a causal interpretation of these results, effects were the strongest among those individuals who spend a disproportionate share of their time out-of-doors. PMID:21461142

  6. The Effect of Velocity on the Extinction Behavior of a Diffusion Flame during Transient Depressurization

    NASA Technical Reports Server (NTRS)

    Goldmeer, Jeffrey S.; Urban, David L.; Tien, James

    1999-01-01

    Current fire suppression plans for the International Space Station include the use of venting (depressurization) as a method for extinguishing a fire. Until recently this process had only been examined as part of a material flammability experiment performed on Skylab in the early 1970's. Due to the low initial pressure (0.35 Atm) and high oxygen concentration (65%), the Skylab experimental results are not applicable for understanding the effects of venting on a fire in a space station environment (21%O2, 1 Atm). Recent research examined the extinction behavior of a diffusion flame over a polymethyl methacrylate (PMMA) cylinder during a transient depressurization in low-gravity. The numerical model was used to examine extinction limits as a function of depressurization rate, forced flow velocity, and initial solid phase temperature. The experimental and numerically predicted extinction data indicated that as the solid phase temperature increased the pressure required to extinguish the flame decreased. The numerical model was also used to examine conditions not obtainable in the low-gravity experiments. From these simulations, a series of extinction boundaries were generated that showed a region of increased flammability existed at a forced flow of 10 cm/s. Analysis of these extinction boundaries indicated that they were quasi-steady in nature, and that the final extinction conditions were independent of the transient process. The velocity range in the previous study was limited and thus the results did not examine the effects of velocities less than 1 cm/s or greater than 20 cm/s. This study utilized low-gravity experiments performed on NASA's Reduced-gravity Research Aircraft Laboratory and numerical simulations to examine conditions applicable to the Space Station environment. This paper extends the analysis of the previous study to a comprehensive examination of the effect of increased velocity on extinction behavior and extinction limits during a transient

  7. Effects of the curvature of a lava channel on velocity and stress fields

    NASA Astrophysics Data System (ADS)

    Valerio, Antonella; Tallarico, Andrea; Dragoni, Michele

    2010-05-01

    Bends in lava flows due to local variations in topography are commonly observed in volcanic fields. The curvature of a channel affects the flow surface morphology, as described in literature by Greeley (1971) and Peterson (1994). Where channels make an especially sharp bend, crust plates break and are incorporated within the flow by remelting. In some places, they jam together welding to the sides of the channel and forming a stable roof. We propose a model to explain the effects of the curvature of a channel on velocity, shear stress and formation of solid crust at the surface. Lava is described as a Newtonian, homogeneous, isotropic and incompressible fluid. The steady-state solution of the Navier-Stokes equation is found for a unidirectional flow, in cylindrical polar coordinates, neglecting the gradient of pressure and assuming a dependence of velocity on the radial coordinate only. The flow levees are described as arcs of concentric circumferences, with their centres in the origin of the reference frame. The equation is solved using non-slip boundary conditions at the levees. From the constitutive equation of a Newtonian incompressible fluid we obtain the nonvanishing component of the shear stress. As a consequence of the curvature of the channel, velocity and shear stress show an asymmetric behaviour in respect to the centre of the channel. The gradient of velocity and the shear stress reach larger values close to the levee with the higher curvature. Heat radiation and convection into the atmosphere are considered as the main cooling processes. Solid platforms form at the flow surface during cooling. Crust plates are laterally confined by the shear regions with high stress values. The model analyses the effects of the curvature of a channel on the development and shape of surface solid plates. The dimension and shape of plates are controlled by the competition between the shear stress and crust yield strength, and the degree of crust coverage of the channel

  8. PIC Simulations of the Effect of Velocity Space Instabilities on Electron Viscosity and Thermal Conduction

    NASA Astrophysics Data System (ADS)

    Riquelme, Mario A.; Quataert, Eliot; Verscharen, Daniel

    2016-06-01

    In low-collisionality plasmas, velocity-space instabilities are a key mechanism providing an effective collisionality for the plasma. We use particle-in-cell (PIC) simulations to study the interplay between electron- and ion-scale velocity-space instabilities and their effect on electron pressure anisotropy, viscous heating, and thermal conduction. The adiabatic invariance of the magnetic moment in low-collisionality plasmas leads to pressure anisotropy, {{Δ }}{p}j\\equiv {p}\\perp ,j-{p}\\parallel ,j\\gt 0, if the magnetic field {\\boldsymbol{B}} is amplified ({p}\\perp ,j and {p}\\parallel ,j denote the pressure of species j (electron, ion) perpendicular and parallel to {\\boldsymbol{B}}). If the resulting anisotropy is large enough, it can in turn trigger small-scale plasma instabilities. Our PIC simulations explore the nonlinear regime of the mirror, IC, and electron whistler instabilities, through continuous amplification of the magnetic field | {\\boldsymbol{B}}| by an imposed shear in the plasma. In the regime 1≲ {β }j≲ 20 ({β }j\\equiv 8π {p}j/| {\\boldsymbol{B}}{| }2), the saturated electron pressure anisotropy, {{Δ }}{p}{{e}}/{p}\\parallel ,{{e}}, is determined mainly by the (electron-lengthscale) whistler marginal stability condition, with a modest factor of ˜1.5-2 decrease due to the trapping of electrons into ion-lengthscale mirrors. We explicitly calculate the mean free path of the electrons and ions along the mean magnetic field and provide a simple physical prescription for the mean free path and thermal conductivity in low-collisionality β j ≳ 1 plasmas. Our results imply that velocity-space instabilities likely decrease the thermal conductivity of plasma in the outer parts of massive, hot, galaxy clusters. We also discuss the implications of our results for electron heating and thermal conduction in low-collisionality accretion flows onto black holes, including Sgr A* in the Galactic Center.

  9. The effect of gait approach velocity on the broken escalator phenomenon.

    PubMed

    Tang, K-S; Kaski, D; Allum, J H J; Bronstein, A M

    2013-05-01

    Walking onto a stationary surface previously experienced as moving generates an after-effect commonly known as the "broken escalator" after-effect (AE). This AE represents an inappropriate expression of the locomotor adaptation necessary to step onto the moving platform (or escalator). It is characterised by two main biomechanical components, an increased gait approach velocity (GAV) and a forward trunk overshoot on gait termination. We investigated whether the trunk overshoot and other biomechanical measures are the direct inertial consequence of the increased GAV or whether these are the result of an independent adaptive mechanism. Forty-eight healthy young adults walked onto a movable sled. They performed 5 trials with the sled stationary at their preferred walking velocity (BEFORE trials), 5 with the sled moving (MOVING or adaptation trials), and 5 with the sled stationary again (AFTER trials). For the AFTER trials, subjects were divided into four groups. One group was instructed to walk slowly ("slower"), another with cueing at the BEFORE pace ("metronome"). The third group walked without cueing at the BEFORE pace ("normal"), and the fourth, fast ("faster"). We measured trunk pitch angle, trunk linear horizontal displacement, left shank pitch angular velocity and surface EMG from lower leg and trunk muscles. In the AFTER trials, an AE was observed in these biomechanical measures for all gait speeds, but these were not strongly dependent on GAV. An AE was present even when GAV was not different from that of BEFORE trials. Therefore, we conclude that, although contributary, the trunk overshoot is not the direct consequence of the increased GAV. Instead, it appears to be generated by anticipatory motor activity "just in case" the sled moves, herewith termed a "pre-emptive" postural adjustment. PMID:23468158

  10. Buoyancy effects on the integral lengthscales and mean velocity profile in atmospheric surface layer flows

    NASA Astrophysics Data System (ADS)

    Salesky, Scott T.; Katul, Gabriel G.; Chamecki, Marcelo

    2013-10-01

    Within the diabatic atmospheric surface layer (ASL) under quasi-stationary and horizontal homogeneous conditions, the mean velocity profile deviates from its conventional logarithmic shape by a height-dependent universal stability correction function ϕm(ζ) that varies with the stability parameter ζ. The ζ parameter measures the relative importance of mechanical to buoyant production or destruction of turbulent kinetic energy (TKE) within the ASL. A link between ϕm(ζ) and the spectrum of turbulence in the ASL was recently proposed by Katul et al. ["Mean velocity profile in a sheared and thermally stratified atmospheric boundary layer," Phys. Rev. Lett. 107, 268502 (2011)]. By accounting for the stability-dependence of TKE production, Katul et al. were able to recover scalings for ϕm with the anticipated power-law exponents for free convective, slightly unstable, and stable conditions. To obtain coefficients for the ϕm(ζ) curve in good agreement with empirical formulas, they introduced a correction for the variation of the integral lengthscale of vertical velocity with ζ estimated from the Kansas experiment. In the current work, the link between the coefficients in empirical curves for ϕm(ζ) and stability-dependent properties of turbulence in the ASL, including the variation with ζ of the integral lengthscale and the anisotropy of momentum transporting eddies is investigated using data from the Advection Horizontal Array Turbulence Study. The theoretical framework presented by Katul et al. is revised to account explicitly for these effects. It is found that the coefficients in the ϕm(ζ) curve for unstable and near-neutral conditions can be explained by accounting for the stability-dependence of the integral lengthscale and anisotropy of momentum-transporting eddies; however, an explanation for the observed ϕm(ζ) curve for stable conditions remains elusive. The effect of buoyancy on the horizontal and vertical integral lengthscales is also analyzed in

  11. Rectilinear-motion space inversion-based detection approach for infrared dim air targets with variable velocities

    NASA Astrophysics Data System (ADS)

    Ma, Tianlei; Shi, Zelin; Yin, Jian; Liu, Yunpeng; Xu, Baoshu; Zhang, Chengshuo

    2016-03-01

    Dim targets are extremely difficult to detect using methods based on single-frame detection. Radiation accumulation is one of the effective methods to improve signal-to-noise ratio (SNR). A detection approach based on radiation accumulation is proposed. First, a location space and a motion space are established. Radiation accumulation operation, controlled by vectors from the motion space, is applied to the original image space. Then, a new image space is acquired where some images have an improved SNR. Second, quasitargets in the new image space are obtained by constant false-alarm ratio judging, and location vectors and motion vectors of quasitargets are also acquired simultaneously. Third, the location vectors and motion vectors are mapped into the two spaces, respectively. Volume density function is defined in the motion space. Location extremum of the location space and volume density extremum of motion space will confirm the true target. Finally, actual location of the true target in the original image space is obtained by space inversion. The approach is also applicable to detect multiple dim targets. Experimental results show the effectiveness of the proposed approach and demonstrate the approach is superior to compared approaches on detection probability and false alarm probability.

  12. On the impact of entrapped air in infiltration under ponding conditions. Part a: Preferential air flow path effects on infiltration

    NASA Astrophysics Data System (ADS)

    Mizrahi, Guy; Weisbrod, Noam; Furman, Alex

    2015-04-01

    Entrapped air effects on infiltration under ponding conditions could be important for massive infiltration of managed aquifer recharge (MAR) or soil aquifer treatment (SAT) of treated wastewater. Earlier studies found that under ponding conditions, air is being entrapped and compressed until it reaches a pressure which will enable the air to escape (unstable air flow). They also found that entrapped air could reduce infiltration by 70-90%. Most studies have dealt with entrapped air effects when soil surface topography is flat. The objective of this study is to investigate, under ponding conditions, the effects of: (1) irregular surface topography on preferential air flow path development (stable air flow); (2) preferential air flow path on infiltration; and (3) hydraulic head on infiltration when air is trapped. Column experiments were used to investigate these particular effects. A 140 cm deep and 30 cm wide column packed with silica sand was used under two boundary conditions: in the first, air can only escape vertically upward through the soil surface; in the second, air is free to escape through 20 ports installed along the column perimeter. The surface was flooded with 13 liters of water, with ponding depth decreasing with time. Two soil surface conditions were tested: flat surface and irregular surface (high and low surface zones). Additionally, Helle-show experiments were conducted in order to obtain a visual observation of preferential air flow path development. The measurements were carried out using a tension meter, air pressure transducers, TDR and video cameras. It was found that in irregular surfaces, stable air flow through preferential paths was developed in the high altitude zones. Flat surface topography caused unstable air flow through random paths. Comparison between irregular and flat surface topography showed that the entrapped air pressure was lower and the infiltration rate was about 40% higher in the irregular surface topography than in the

  13. Hematological and hemorheological effects of air pollution

    SciTech Connect

    Baskurt, O.K.; Levi, E.; Caglayan, S.; Dikmenoglu, N.; Kutman, M.N. )

    1990-07-01

    Selected hematological parameters and erythrocyte deformability indexes for 16 young male military students were compared before and after a period of exposure to heavy pollution. These students lived in Ankara, which has a serious air pollution problem. The mean sulfur dioxide levels measured at a station proximal to the campus where the students lived were 188 micrograms/m3 and 201 micrograms/m3 during first and second measurements, respectively. During the period between the two measurements, the mean sulfur dioxide level was 292 micrograms/m3. Significant erythropoiesis was indicated by increased erythrocyte counts and hemoglobin and hematocrit levels. Methemoglobin percentage was increased to 2.37 +/- 0.49% (mean +/- standard error) from 0.51 +/- 0.23%. Sulfhemoglobinemia was present in six subjects after the period of pollution, but it was not present in any student prior to this period. Significant increases in erythrocyte deformability indexes were observed after the period of pollution, i.e., from 1.13 +/- 0.01 to 1.21 +/0 0.02, implying that erythrocytes were less flexible, which might impair tissue perfusion.

  14. Effect of Kinesiotape Applications on Ball Velocity and Accuracy in Amateur Soccer and Handball

    PubMed Central

    Müller, Carsten; Brandes, Mirko

    2015-01-01

    Evidence supporting performance enhancing effects of kinesiotape in sports is missing. The aims of this study were to evaluate effects of kinesiotape applications with regard to shooting and throwing performance in 26 amateur soccer and 32 handball players, and to further investigate if these effects were influenced by the players’ level of performance. Ball speed as the primary outcome and accuracy of soccer kicks and handball throws were analyzed with and without kinesiotape by means of radar units and video recordings. The application of kinesiotapes significantly increased ball speed in soccer by 1.4 km/h (p=0.047) and accuracy with a lesser distance from the target by −6.9 cm (p=0.039). Ball velocity in handball throws also significantly increased by 1.2 km/h (p=0.013), while accuracy was deteriorated with a greater distance from the target by 3.4 cm (p=0.005). Larger effects with respect to ball speed were found in players with a lower performance level in kicking (1.7 km/h, p=0.028) and throwing (1.8 km/h, p=0.001) compared with higher level soccer and handball players (1.2 km/h, p=0.346 and 0.5 km/h, p=0.511, respectively). In conclusion, the applications of kinesiotape used in this study might have beneficial effects on performance in amateur soccer, but the gain in ball speed in handball is counteracted by a significant deterioration of accuracy. Subgroup analyses indicate that kinesiotape may yield larger effects on ball velocity in athletes with lower kicking and throwing skills. PMID:26839612

  15. Effect of Kinesiotape Applications on Ball Velocity and Accuracy in Amateur Soccer and Handball.

    PubMed

    Müller, Carsten; Brandes, Mirko

    2015-12-22

    Evidence supporting performance enhancing effects of kinesiotape in sports is missing. The aims of this study were to evaluate effects of kinesiotape applications with regard to shooting and throwing performance in 26 amateur soccer and 32 handball players, and to further investigate if these effects were influenced by the players' level of performance. Ball speed as the primary outcome and accuracy of soccer kicks and handball throws were analyzed with and without kinesiotape by means of radar units and video recordings. The application of kinesiotapes significantly increased ball speed in soccer by 1.4 km/h (p=0.047) and accuracy with a lesser distance from the target by -6.9 cm (p=0.039). Ball velocity in handball throws also significantly increased by 1.2 km/h (p=0.013), while accuracy was deteriorated with a greater distance from the target by 3.4 cm (p=0.005). Larger effects with respect to ball speed were found in players with a lower performance level in kicking (1.7 km/h, p=0.028) and throwing (1.8 km/h, p=0.001) compared with higher level soccer and handball players (1.2 km/h, p=0.346 and 0.5 km/h, p=0.511, respectively). In conclusion, the applications of kinesiotape used in this study might have beneficial effects on performance in amateur soccer, but the gain in ball speed in handball is counteracted by a significant deterioration of accuracy. Subgroup analyses indicate that kinesiotape may yield larger effects on ball velocity in athletes with lower kicking and throwing skills. PMID:26839612

  16. The Effects of Very Light Jet Air Taxi Operations on Commercial Air Traffic

    NASA Technical Reports Server (NTRS)

    Smith, Jeremy C.; Dollyhigh, Samuel M.

    2006-01-01

    This study investigates the potential effects of Very Light Jet (VLJ) air taxi operations adding to delays experienced by commercial passenger air transportation in the year 2025. The affordable cost relative to existing business jets and ability to use many of the existing small, minimally equipped, but conveniently located airports is projected to stimulate a large demand for the aircraft. The resulting increase in air traffic operations will mainly be at smaller airports, but this study indicates that VLJs have the potential to increase further the pressure of demand at some medium and large airports, some of which are already operating at or near capacity at peak times. The additional delays to commercial passenger air transportation due to VLJ air taxi operations are obtained from simulation results using the Airspace Concepts Evaluation System (ACES) simulator. The direct increase in operating cost due to additional delays is estimated. VLJs will also cause an increase in traffic density, and this study shows increased potential for conflicts due to VLJ operations.

  17. Rate effects on timing, key velocity, and finger kinematics in piano performance.

    PubMed

    Bella, Simone Dalla; Palmer, Caroline

    2011-01-01

    We examined the effect of rate on finger kinematics in goal-directed actions of pianists. In addition, we evaluated whether movement kinematics can be treated as an indicator of personal identity. Pianists' finger movements were recorded with a motion capture system while they performed melodies from memory at different rates. Pianists' peak finger heights above the keys preceding keystrokes increased as tempo increased, and were attained about one tone before keypress. These rate effects were not simply due to a strategy to increase key velocity (associated with tone intensity) of the corresponding keystroke. Greater finger heights may compensate via greater tactile feedback for a speed-accuracy tradeoff that underlies the tendency toward larger temporal variability at faster tempi. This would allow pianists to maintain high temporal accuracy when playing at fast rates. In addition, finger velocity and accelerations as pianists' fingers approached keys were sufficiently unique to allow pianists' identification with a neural-network classifier. Classification success was higher in pianists with more extensive musical training. Pianists' movement "signatures" may reflect unique goal-directed movement kinematic patterns, leading to individualistic sound. PMID:21731615

  18. Rate Effects on Timing, Key Velocity, and Finger Kinematics in Piano Performance

    PubMed Central

    Dalla Bella, Simone; Palmer, Caroline

    2011-01-01

    We examined the effect of rate on finger kinematics in goal-directed actions of pianists. In addition, we evaluated whether movement kinematics can be treated as an indicator of personal identity. Pianists' finger movements were recorded with a motion capture system while they performed melodies from memory at different rates. Pianists' peak finger heights above the keys preceding keystrokes increased as tempo increased, and were attained about one tone before keypress. These rate effects were not simply due to a strategy to increase key velocity (associated with tone intensity) of the corresponding keystroke. Greater finger heights may compensate via greater tactile feedback for a speed-accuracy tradeoff that underlies the tendency toward larger temporal variability at faster tempi. This would allow pianists to maintain high temporal accuracy when playing at fast rates. In addition, finger velocity and accelerations as pianists' fingers approached keys were sufficiently unique to allow pianists' identification with a neural-network classifier. Classification success was higher in pianists with more extensive musical training. Pianists' movement “signatures” may reflect unique goal-directed movement kinematic patterns, leading to individualistic sound. PMID:21731615

  19. Effect of remote voluntary contractions on knee extensor torque and rate of velocity development.

    PubMed

    Cherry, Emily A; Brown, Lee E; Coburn, Jared W; Noffal, Guillermo J

    2010-09-01

    Remote voluntary contractions (RVCs) are described as a muscle action of the prime mover while performing a simultaneous muscle action with another part of the body. Previous studies have shown that RVCs may elicit augmented performance of the prime mover. The purpose of this study was to evaluate the effect of RVCs on knee extensor rate of velocity development (RVD) and peak torque. Fourteen men and 16 women who were regularly active and free of any knee pathology for the past year took part in this study. Subjects performed 3 maximal dynamic knee extensions at 3 velocities with and without an RVC condition. The RVC condition consisted of holding hand dynamometers in each hand and maximally gripping while performing a maximal knee extension movement. The NO-RVC condition was the same only without gripping. Men produced greater peak torque and RVD than did women across speeds and conditions. Analysis demonstrated that RVC had no effect on knee extension peak torque, but RVD decreased in the RVC condition (NO-RVC 2,012.07 [46.52] degrees xs-1xs-1; RVC 1,882.61 [51.84] degrees xs-1xs-1). Grip strength of the left hand at 180 degrees xs-1decreased from 42.03 (14.40) to 38.83 (14.65) kg in the RVC condition. In conclusion, RVC should not be used when attempting to maximize RVD, because it may hinder results when performing a single joint movement.

  20. Temperature dependence of the inhibitory effects of orthovanadate on shortening velocity in fast skeletal muscle.

    PubMed Central

    Pate, E; Wilson, G J; Bhimani, M; Cooke, R

    1994-01-01

    We have investigated the effects of the orthophosphate (P(i)) analog orthovanadate (Vi) on maximum shortening velocity (Vmax) in activated, chemically skinned, vertebrate skeletal muscle fibers. Using new "temperature-jump" protocols, reproducible data can be obtained from activated fibers at high temperatures, and we have examined the effect of increased [Vi] on Vmax for temperatures in the range 5-30 degrees C. We find that for temperatures < or = 20 degrees C, increasing [Vi] inhibits Vmax; for temperatures > or = 25 degrees C, increasing [Vi] does not inhibit Vmax. Attached cross-bridges bound to Vi are thought to be an analog of the weakly bound actin-myosin.ADP-P(i) state. The data suggest that the weakly bound Vi state can inhibit velocity at low temperature, but not at high temperature, with the transition occurring over a narrow temperature range of < 5 degrees C. This suggests a highly cooperative interaction. The data also define a Q10 for Vmax of 2.1 for chemically skinned rabbit psoas fibers over the temperature range of 5-30 degrees C. Images FIGURE 3 PMID:8061204

  1. Effects of Instability Versus Traditional Resistance Training on Strength, Power and Velocity in Untrained Men

    PubMed Central

    Maté-Muñoz, José Luis; Monroy, Antonio J. Antón; Jodra Jiménez, Pablo; Garnacho-Castaño, Manuel V.

    2014-01-01

    The purpose of this study was compare the effects of a traditional and an instability resistance circuit training program on upper and lower limb strength, power, movement velocity and jumping ability. Thirty-six healthy untrained men were assigned to two experimental groups and a control group. Subjects in the experimental groups performed a resistance circuit training program consisting of traditional exercises (TRT, n = 10) or exercises executed in conditions of instability (using BOSU® and TRX®) (IRT, n = 12). Both programs involved three days per week of training for a total of seven weeks. The following variables were determined before and after training: maximal strength (1RM), average (AV) and peak velocity (PV), average (AP) and peak power (PP), all during bench press (BP) and back squat (BS) exercises, along with squat jump (SJ) height and counter movement jump (CMJ) height. All variables were found to significantly improve (p <0.05) in response to both training programs. Major improvements were observed in SJ height (IRT = 22.1%, TRT = 20.1%), CMJ height (IRT = 17.7%, TRT = 15.2%), 1RM in BS (IRT = 13.03%, TRT = 12.6%), 1RM in BP (IRT = 4.7%, TRT = 4.4%), AP in BS (IRT = 10.5%, TRT = 9.3%), AP in BP (IRT = 2.4%, TRT = 8.1%), PP in BS (IRT=19.42%, TRT = 22.3%), PP in BP (IRT = 7.6%, TRT = 11.5%), AV in BS (IRT = 10.5%, TRT = 9.4%), and PV in BS (IRT = 8.6%, TRT = 4.5%). Despite such improvements no significant differences were detected in the posttraining variables recorded for the two experimental groups. These data indicate that a circuit training program using two instability training devices is as effective in untrained men as a program executed under stable conditions for improving strength (1RM), power, movement velocity and jumping ability. Key Points Similar adaptations in terms of gains in strength, power, movement velocity and jumping ability were produced in response to both training programs. Both the stability and instability approaches

  2. Effective Stack Design in Air Pollution Control.

    ERIC Educational Resources Information Center

    Clarke, John H.

    1968-01-01

    Stack design problems fall into two general caterories--(1) those of building re-entry, and (2) those of general area pollution. Extensive research has developed adequate information, available in the literature, to permit effective stack design. A major roadblock to effective design has been the strong belief by architects and engineers that high…

  3. Effects of volcanic tremor on noise-based measurements of temporal velocity changes at Hawaiian volcanoes

    NASA Astrophysics Data System (ADS)

    Ballmer, S.; Wolfe, C. J.; Okubo, P.; Haney, M. M.; Thurber, C. H.

    2011-12-01

    Green's functions calculated with ambient seismic noise may aid in volcano research and monitoring. The continuous character of ambient seismic noise and hence of the reconstructed Green's functions has enabled measurements of short-term (~days) temporal perturbations in seismic velocities. Very small but clear velocity decreases prior to some volcanic eruptions have been documented and motivate our present study. We apply this method to Hawaiian volcanoes using data from the USGS Hawaiian Volcano Observatory (HVO) seismic network. In order to obtain geologically relevant and reliable results, stable Green's functions need to be recovered from the ambient noise. Station timing problems, changes in noise source directivity, as well as changes in the source's spectral content are known biases that critically affect the Green's functions' stability and hence need to be considered. Here we show that volcanic tremor is a potential additional bias. During the time period of our study (2007-present), we find that volcanic tremor is a common feature in the HVO seismic data. Pu'u O'o tremor is continuously present before a dike intrusion into Kilauea's east rift zone in June 2007 and Halema'uma'u tremor occurs before and during resumed Kilauea summit activity from early 2008 and onward. For the frequency band considered (0.1-0.9 Hz), we find that these active tremor sources can drastically modify the recovered Green's functions for station pairs on the entire island at higher (> 0.5 Hz) frequencies, although the effect of tremor appears diminished at lower frequencies. In this presentation, we perform measurements of temporal velocity changes using ambient noise Green's functions and explore how volcanic tremor affects the results. Careful quality assessment of reconstructed Green's functions appears to be essential for the desired high precision measurements.

  4. The effect of low- and high-velocity tendon excursion on the mechanical properties of human cadaver subsynovial connective tissue.

    PubMed

    Filius, Anika; Thoreson, Andrew R; Yang, Tai-Hua; Vanhees, Matthias; An, Kai-Nan; Zhao, Chunfeng; Amadio, Peter C

    2014-01-01

    Fibrosis of the subsynovial connective tissue (SSCT) in the carpal tunnel is the most common histological finding in carpal tunnel syndrome (CTS). Fibrosis may result from damaged SSCT. Previous studies found that with low-velocity (2 mm/s), tendon excursions can irreversibly damage the SSCT. We investigated the effect of tendon excursion velocity in the generation of SSCT damage. Nine human cadaver wrists were used. Three repeated cycles of ramp-stretch testing were performed simulating 40%, 60%, 90%, and 120% of the middle finger flexor tendon superficialis physiological excursion with an excursion velocity of 60 mm/s. Energy and force were calculated and normalized by values obtained in the first cycle for each excursion level. Data were compared with low-velocity excursion data. For high-velocity excursions, a significant drop in the excursion energy ratio was first observed at an excursion level of 60% physiological excursion (p < 0.024) and that for low-velocity excursions was first observed at 90% physiological excursion (p < 0.038). Furthermore, the energy ratio was lower at 60% for high velocities (p ≤ 0.039). Increasing velocity lowers the SSCT damage threshold. This finding may be relevant for understanding the pathogenesis of SSCT fibrosis, such as that accompanying CTS, and a relationship with occupational factors.

  5. Hydrodynamic effects of air sparging on hollow fiber membranes in a bubble column reactor.

    PubMed

    Xia, Lijun; Law, Adrian Wing-Keung; Fane, Anthony G

    2013-07-01

    Air sparging is now a standard approach to reduce concentration polarization and fouling of membrane modules in membrane bioreactors (MBRs). The hydrodynamic shear stresses, bubble-induced turbulence and cross flows scour the membrane surfaces and help reduce the deposit of foulants onto the membrane surface. However, the detailed quantitative knowledge on the effect of air sparging remains lacking in the literature due to the complex hydrodynamics generated by the gas-liquid flows. To date, there is no valid model that describes the relationship between the membrane fouling performance and the flow hydrodynamics. The present study aims to examine the impact of hydrodynamics induced by air sparging on the membrane fouling mitigation in a quantitative manner. A modelled hollow fiber module was placed in a cylindrical bubble column reactor at different axial heights with the trans-membrane pressure (TMP) monitored under constant flux conditions. The configuration of bubble column without the membrane module immersed was identical to that studied by Gan et al. (2011) using Phase Doppler Anemometry (PDA), to ensure a good quantitative understanding of turbulent flow conditions along the column height. The experimental results showed that the meandering flow regime which exhibits high flow instability at the 0.3 m is more beneficial to fouling alleviation compared with the steady flow circulation regime at the 0.6 m. The filtration tests also confirmed the existence of an optimal superficial air velocity beyond which a further increase is of no significant benefit on the membrane fouling reduction. In addition, the alternate aeration provided by two air stones mounted at the opposite end of the diameter of the bubble column was also studied to investigate the associated flow dynamics and its influence on the membrane filtration performance. It was found that with a proper switching interval and membrane module orientation, the membrane fouling can be effectively

  6. Hydrodynamic effects of air sparging on hollow fiber membranes in a bubble column reactor.

    PubMed

    Xia, Lijun; Law, Adrian Wing-Keung; Fane, Anthony G

    2013-07-01

    Air sparging is now a standard approach to reduce concentration polarization and fouling of membrane modules in membrane bioreactors (MBRs). The hydrodynamic shear stresses, bubble-induced turbulence and cross flows scour the membrane surfaces and help reduce the deposit of foulants onto the membrane surface. However, the detailed quantitative knowledge on the effect of air sparging remains lacking in the literature due to the complex hydrodynamics generated by the gas-liquid flows. To date, there is no valid model that describes the relationship between the membrane fouling performance and the flow hydrodynamics. The present study aims to examine the impact of hydrodynamics induced by air sparging on the membrane fouling mitigation in a quantitative manner. A modelled hollow fiber module was placed in a cylindrical bubble column reactor at different axial heights with the trans-membrane pressure (TMP) monitored under constant flux conditions. The configuration of bubble column without the membrane module immersed was identical to that studied by Gan et al. (2011) using Phase Doppler Anemometry (PDA), to ensure a good quantitative understanding of turbulent flow conditions along the column height. The experimental results showed that the meandering flow regime which exhibits high flow instability at the 0.3 m is more beneficial to fouling alleviation compared with the steady flow circulation regime at the 0.6 m. The filtration tests also confirmed the existence of an optimal superficial air velocity beyond which a further increase is of no significant benefit on the membrane fouling reduction. In addition, the alternate aeration provided by two air stones mounted at the opposite end of the diameter of the bubble column was also studied to investigate the associated flow dynamics and its influence on the membrane filtration performance. It was found that with a proper switching interval and membrane module orientation, the membrane fouling can be effectively

  7. The Air Force Academy Instructor Workstation (IWS): II. Effectiveness.

    ERIC Educational Resources Information Center

    Gist, Thomas E.; And Others

    1989-01-01

    Discusses the results of measuring the in-class effectiveness of a computer-controlled instructor workstation (IWS) that was developed at the Air Force Academy. Treatments for the experimental and control groups in an introductory physics course are described, and effects on student performance, student attitudes, and instructor attitudes are…

  8. Effects of a 6-week junior tennis conditioning program on service velocity.

    PubMed

    Fernandez-Fernandez, Jaime; Ellenbecker, Todd; Sanz-Rivas, David; Ulbricht, Alexander; Ferrautia, Alexander

    2013-01-01

    This study examined the effects of a 6-week strength-training program on serve velocity in youth tennis players. Thirty competitive healthy and nationally ranked male junior tennis players (13 years of age) were randomly and equally divided into control and training groups. The training group performed 3 sessions (60-70 min) weekly for 6 weeks, comprising core strength, elastic resistance and medicine ball exercises. Both groups (control and training) also performed a supervised stretching routine at the end of each training session, during the 6 week intervention. Service velocity, service accuracy and shoulder internal/external rotation were assessed initially and at the end of the 6-week conditioning program for both, control and training groups. There was a significant improvement in the serve velocity for the training group (p = 0. 0001) after the intervention, whereas in the control group there were no differences between pre and post-tests (p = 0.29). Serve accuracy was not affected in the training group (p = 0.10), nor in the control group (p = 0.15). Shoulder internal/external rotation ROM significantly improved in both groups, training (p = 0.001) and control (p = 0.0001). The present results showed that a short- term training program for young tennis players, using minimum equipment and effort, can result in improved tennis performance (i.e., serve velocity) and a reduction in the risk of a possible overuse injury, reflected by an improvement in shoulder external/internal range of motion. Key PointsA short-term training program for young tennis players, using minimum equipment and effort, can result in improved tennis performance and a reduction in the risk of a possible overuse injury, reflected by an improvement in shoulder external/internal range of motionA combination of core stabilization, elastic resistance exercises, and upper body plyometric exercises (i.e., medicine ball throws), focussing on the primary muscle groups and stabilizers involved in

  9. Effects of A 6-Week Junior Tennis Conditioning Program on Service Velocity

    PubMed Central

    Fernandez-Fernandez, Jaime; Ellenbecker, Todd; Sanz-Rivas, david; Ulbricht, Alexander; Ferrautia, lexander

    2013-01-01

    This study examined the effects of a 6-week strength-training program on serve velocity in youth tennis players. Thirty competitive healthy and nationally ranked male junior tennis players (13 years of age) were randomly and equally divided into control and training groups. The training group performed 3 sessions (60-70 min) weekly for 6 weeks, comprising core strength, elastic resistance and medicine ball exercises. Both groups (control and training) also performed a supervised stretching routine at the end of each training session, during the 6 week intervention. Service velocity, service accuracy and shoulder internal/external rotation were assessed initially and at the end of the 6-week conditioning program for both, control and training groups. There was a significant improvement in the serve velocity for the training group (p = 0. 0001) after the intervention, whereas in the control group there were no differences between pre and post-tests (p = 0.29). Serve accuracy was not affected in the training group (p = 0.10), nor in the control group (p = 0.15). Shoulder internal/external rotation ROM significantly improved in both groups, training (p = 0.001) and control (p = 0.0001). The present results showed that a short- term training program for young tennis players, using minimum equipment and effort, can result in improved tennis performance (i.e., serve velocity) and a reduction in the risk of a possible overuse injury, reflected by an improvement in shoulder external/internal range of motion. Key Points A short-term training program for young tennis players, using minimum equipment and effort, can result in improved tennis performance and a reduction in the risk of a possible overuse injury, reflected by an improvement in shoulder external/internal range of motion A combination of core stabilization, elastic resistance exercises, and upper body plyometric exercises (i.e., medicine ball throws), focussing on the primary muscle groups and stabilizers involved

  10. Effects of H2O, CO2, and N2 air contaminants on critical airside strain rates for extinction of hydrogen-air counterflow diffusion flames

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Dish-shaped counterflow diffusion flames centered by opposing laminar jets of H2 and clean and contaminant O2/N2 mixtures in an argon bath at 1 atm were used to study the effects of contaminants on critical airside strain. The jet velocities for both flame extinction and restoration are found for a wide range of contaminant and O2 concentrations in the air jet. The tests are also conducted for a variety of input H2 concentrations. The results are compared with those from several other studies.

  11. Physical modelling of the effect of fractures on compressional and shear wave velocities

    NASA Astrophysics Data System (ADS)

    Gurevich, Boris; Lebedev, Maxim; Glubokovskikh, Stanislav; Dyskin, Arcady; Pasternak, Elena; Vialle, Stephanie

    2016-04-01

    Ultrasonic measurements were performed on a sample of polyester resin permeated by multiple fractures. The samples were prepared by mixing high doses of catalyst, about 7-10 % with the liquid resin base. The mix was then heated in an oven at 60° C for a period of 1 hour. This operation produced many shrinkage cracks varying in size from 8 mm to 20 mm (Sahouryeh et al., 2002). The produced samples were parallelepiped 50 mm x 50 mm in cross-section with height of 100 mm. Micro-CT scanning of the sample reveals many open fractures with apertures 0.2 - 0.4 mm. Elastic properties of the fractured samples were derived from ultrasonic measurements using piezo-electric transducers. These measurements give compressional (Vp) and shear (Vs) wave velocities of 2450 and 1190 m/s, respectively, giving Vp/Vs = 2.04. At the same time the velocities in the intact resin are Vp=2460 and Vs=1504 m/s, respectively, with Vp/Vs = 1.63. Thus we see that the fractures have a negligible effect on the Vp (within the measurement error) but a dramatic effect on Vs (about 20%). This contradicts the common understanding that the effects of dry fractures on Vp and Vs are similar in magnitude. Indeed, assuming very roughly that the distribution of fractures is isotropic, we can estimate the cumulative normal fracture compliance from the difference between shear moduli of the intact and fractured resin to be 0.30 GPa-1 and fracture density of 0.41. This value can be used to estimate the effective bulk modulus of the fractured material. The corresponding p-wave velocity, Vp = 1860 m/s, is significantly lower that the observed value. The results suggest that an equivalent medium approximation is not applicable in this case, probably due to the fact that the long-wave approximation is inadequate. Indeed the fractures are larger than the wavelength that corresponds to the peak frequencies of the power spectrum of the signal. This suggests a strong influence of diffraction. Furthermore, the

  12. Physical modelling of the effect of fractures on compressional and shear wave velocities

    NASA Astrophysics Data System (ADS)

    Gurevich, Boris; Lebedev, Maxim; Glubokovskikh, Stanislav; Dyskin, Arcady; Pasternak, Elena; Vialle, Stephanie

    2016-04-01

    Ultrasonic measurements were performed on a sample of polyester resin permeated by multiple fractures. The samples were prepared by mixing high doses of catalyst, about 7-10 % with the liquid resin base. The mix was then heated in an oven at 60° C for a period of 1 hour. This operation produced many shrinkage cracks varying in size from 8 mm to 20 mm (Sahouryeh et al., 2002). The produced samples were parallelepiped 50 mm x 50 mm in cross-section with height of 100 mm. Micro-CT scanning of the sample reveals many open fractures with apertures 0.2 - 0.4 mm. Elastic properties of the fractured samples were derived from ultrasonic measurements using piezo-electric transducers. These measurements give compressional (Vp) and shear (Vs) wave velocities of 2450 and 1190 m/s, respectively, giving Vp/Vs = 2.04. At the same time the velocities in the intact resin are Vp=2460 and Vs=1504 m/s, respectively, with Vp/Vs = 1.63. Thus we see that the fractures have a negligible effect on the Vp (within the measurement error) but a dramatic effect on Vs (about 20%). This contradicts the common understanding that the effects of dry fractures on Vp and Vs are similar in magnitude. Indeed, assuming very roughly that the distribution of fractures is isotropic, we can estimate the cumulative normal fracture compliance from the difference between shear moduli of the intact and fractured resin to be 0.30 GPa‑1 and fracture density of 0.41. This value can be used to estimate the effective bulk modulus of the fractured material. The corresponding p-wave velocity, Vp = 1860 m/s, is significantly lower that the observed value. The results suggest that an equivalent medium approximation is not applicable in this case, probably due to the fact that the long-wave approximation is inadequate. Indeed the fractures are larger than the wavelength that corresponds to the peak frequencies of the power spectrum of the signal. This suggests a strong influence of diffraction. Furthermore, the

  13. Force-velocity profile: imbalance determination and effect on lower limb ballistic performance.

    PubMed

    Samozino, P; Edouard, P; Sangnier, S; Brughelli, M; Gimenez, P; Morin, J-B

    2014-06-01

    This study sought to lend experimental support to the theoretical influence of force-velocity (F-v) mechanical profile on jumping performance independently from the effect of maximal power output (P max ). 48 high-level athletes (soccer players, sprinters, rugby players) performed maximal squat jumps with additional loads from 0 to 100% of body mass. During each jump, mean force, velocity and power output were obtained using a simple computation method based on flight time, and then used to determine individual linear F-v relationships and P max values. Actual and optimal F-v profiles were computed for each subject to quantify mechanical F-v imbalance. A multiple regression analysis showed, with a high-adjustment quality (r²=0.931, P<0.001, SEE=0.015 m), significant contributions of P max , F-v imbalance and lower limb extension range (h PO ) to explain interindividual differences in jumping performance (P<0.001) with positive regression coefficients for P max and h PO and a negative one for F-v imbalance. This experimentally supports that ballistic performance depends, in addition to P max , on the F-v profile of lower limbs. This adds support to the actual existence of an individual optimal F-v profile that maximizes jumping performance, a F-v imbalance being associated to a lower performance. These results have potential strong applications in the field of strength and conditioning.

  14. Near-surface wave velocity structure of Faial (Azores - Portugal) Island for site effect studies

    NASA Astrophysics Data System (ADS)

    Borges, José; Neves, Samuel; Caldeira, Bento; Bezzeghoud, Mourad; Carvalho, João; Carvalho, Alexandra

    2015-04-01

    Throughout history, the life of the Azorean people has been marked by earthquakes that have had different effects depending on their proximity and magnitude. This seismic activity, which may have volcanic or tectonic origins, has affected the population of these islands by destroying infrastructure and claiming lives. The social and economic impacts of these phenomena are enormous. The last significant event affecting the Azores (Portugal) was the July 1998 Mw=6.2 earthquake causing major destruction affecting more than 5000 people, causing 8 deaths, 150 persons injured and 1500 homeless. Ground motion simulations are mainly based on source characteristics and are heavily dependent on the medium, which is still poorly understood. Subsurface soil condition can amplify the seismic waves, so, for seismic response analysis, it is necessary to know the shallow soil properties and its spatial variability. For this purpose, we applied P and S-wave refraction, Multichannel Analysis of Surface Waves (MASW) to characterize shear wave velocity at different sites in the Faial Island, in particular, in sites where already occurred amplification. Ambient vibrations can also be used to estimate physical properties of the shallower geological formations. With this goal, the obtained velocity models were confirmed by comparison between real H/V curves with synthetic ones. We concluded that the anomalous intensities observed in some sites are strongly related to thick layers of soft sediments of pyroclastic deposits produced by old volcanic eruptions occurred in the Faial Island.

  15. Effects of Jet Opening Angle and Velocity Structure on Blazar Parameters

    NASA Astrophysics Data System (ADS)

    Wiita, P. J.; Gopal-Krishna; Dhurde, S.; Sircar, P.

    2008-06-01

    We had earlier shown that for a constant velocity jet the discrepancy between the low speeds (β) indicated by VLBI knot motions and the high Doppler factors (δ) inferred from emission of TeV photons could be reconciled if ultrarelativistic jets possessed modest opening angles. Here we evaluate the (flux-weighted) viewing angles of the jet and the apparent β and δ values of the radio knots on parsec scales. The influence of the jet opening angle on these radio knot parameters are found for the usually considered types of relativistic nuclear jets: those with uniform bulk speeds and those where the bulk Lorentz factor of the flow decreases with distance from the jet axis, known as ``spine--sheath'' flows. For both types of jet velocity structures the expectation value of the jet orientation angle at first falls dramatically with increases in the (central) jet Lorentz factor, but for extremely relativistic jets it levels off at a fraction of the opening angle. The effective values of the apparent speeds and Doppler factors of the knots always decline substantially with increasing jet opening angle. The rarity of highly superluminal parsec-scale radio components in TeV blazars can be understood if their jets are both highly relativistic and intrinsically weaker, so probably less well collimated, than the jets in ordinary blazars.

  16. P wave velocity structure below India and Tibet incorporating anisotropic delay time effects

    NASA Astrophysics Data System (ADS)

    Mohanty, Debasis D.; Singh, Arun; O'Driscoll, Leland J.; Ravi Kumar, M.; Srinagesh, D.; Humphreys, Eugene D.

    2016-03-01

    We incorporate the effects of anisotropy to refine the continental-scale 3-D isotropic velocity model previously produced for India and Tibet by inverting 52,050 teleseismic P wave residuals. We have exploited a total of 1648 individual SKS splitting parameters to calculate the P wave travel time corrections due to azimuthal anisotropy. Our results suggest that anisotropy affects the P wave delays significantly (-0.3 to +0.5 s). Integration of these corrections into the 3-D modeling is achieved in two ways: (a) a priori adjustment to the delay time vector and (b) inverting only for anisotropic delays by introducing strong damping above 80 km and below 360 km depths and then subtracting the obtained anisotropic artifact image from the isotropic image, to get the corrected image. Under the assumption of azimuthal anisotropy resulting from lattice preferred orientation (LPO) alignment due to horizontal flow, the bias in isotropic P wave tomographic images is clear. The anisotropy corrected velocity perturbations are in the range of ±1.2% at depths of around 150 km and reduced further at deeper levels. Although the bias due to anisotropy does not affect the gross features, it does introduce certain artifacts at deeper levels.

  17. The effects of gait velocity on the gait characteristics of hemiplegic patients.

    PubMed

    You, Young Youl; Chung, Sin Ho

    2015-03-01

    [Purpose] The present study investigated the effects of gait speed on temporal and spatial gait characteristics of hemiplegic stroke patients. [Subjects and Methods] Twenty post-stroke hemiplegic patients participated in the present study. To enhance the reliability of the analysis of the gait characteristics, the assessments were conducted three days per week at the same time every day. Each subject walked maintaining a comfortable speed for the first minute, and measurement was conducted for 30 seconds at a treadmill speed of 1 km/hour thereafter. Then, the subjects walked at a treadmill speed of 2 km/hour for 30 seconds after a 30-minute rest. The differences in the measurements were tested for significance using the paired t-test. [Results] The measures of foot rotation, step width, load response, mid stance, pre-swing, swing phase, and double stance phase showed significant difference between the gait velocities. [Conclusion] The present study provides basic data for gait velocity changes for hemiplegic patients.

  18. Trapping effect on the sound velocity of a multilayer Fermi gas

    NASA Astrophysics Data System (ADS)

    Salas, Patricia; Solís, M. A.

    2015-03-01

    We present the trapping effect on the behavior of the isothermal compressibility and sound velocity for an interactionless Fermi gas immersed in a periodic interconnected multilayer structure created by an external Dirac comb potential which can vary both in spacing and in the intensity that controls the impenetrability of the layer edge (the wall). At T = 0 , for a given layer width and respect to the free ideal Fermi gas values, the isothermal compressibility as a function of the impenetrability starts in one and then monotonically increases to reach a larger constant value which is width dependent. The sound velocity as a function of impenetrability starts in one and for a range of impenetrabilities shows a bump which suggests that the presence of the structure increases the speed. For a finite temperature, given a separation between the walls and several values of their impenetrabilities, both properties start their evolution in temperature from the ideal Fermi gas value, unfold at temperatures near and under TF, and then recover the behavior of a classical gas at higher temperatures. We acknowledge partial support from PAPIIT IN111613 and CONACyT 221030.

  19. Effective filtering and interpolation of 2D discrete velocity fields with Navier-Stokes equations

    NASA Astrophysics Data System (ADS)

    Saumier, Louis-Philippe; Khouider, Boualem; Agueh, Martial

    2016-11-01

    We introduce a new variational technique to interpolate and filter a two-dimensional velocity vector field which is discretely sampled in a region of {{{R}}}2 and sampled only once at a time, on a small time-interval [0,{{Δ }}t]. The main idea is to find a solution of the Navier-Stokes equations that is closest to a prescribed field in the sense that it minimizes the l 2 norm of the difference between this solution and the target field. The minimization is performed on the initial vorticity by expanding it into radial basis functions of Gaussian type, with a fixed size expressed by a parameter ɛ. In addition, a penalty term with parameter k e is added to the minimizing functional in order to select a solution with a small kinetic energy. This additional term makes the minimizing functional strongly convex, and therefore ensures that the minimization problem is well-posed. The interplay between the parameters k e and ɛ effectively contributes to smoothing the discrete velocity field, as demonstrated by the numerical experiments on synthetic and real data.

  20. Concerning the flow about ring-shaped cowlings Part IX : the influence of oblique oncoming flow on the incremental velocities and air forces at the front part of circular cowls

    NASA Technical Reports Server (NTRS)

    Kuchemann, Dietrich; Weber, Johanna

    1952-01-01

    The dependence of the maximum incremental velocities and air forces on a circular cowling on the mass flow and the angle of attack of the oblique flow is determined with the aid of pressure-distribution measurements. The particular cowling tested had been partially investigated in NACA TM 1327.

  1. Effect of Diffuser Design, Diffuser-exit Velocity Profile and Fuel Distribution on Altitude Performance of Several Afterburner Configurations

    NASA Technical Reports Server (NTRS)

    Conrad, E William; Schultz, Frederick W; Usow, Karl H

    1953-01-01

    An investigation was conducted in the NACA Lewis altitude wind tunnel to improve the altitude performance and operational characteristics of an afterburner primarily by modifying the diffuser-exit velocity profile by changes in diffuser design and by changing the fuel distribution and the flame holder. Twenty configurations, consisting of combinations of six diffuser geometries, six flame-holder types, and twelve fuel systems, were investigated. Data were obtained over a range of afterburner fuel-air ratios at diffuser-inlet total pressures from 2750 to 620 pounds per square foot. Changes in fuel distribution affected the fuel-air ratio at which peak combustion efficiency occurred as well as the efficiency level. Screeching combustion, which was most prevalent at low altitudes and medium-to-high fuel-air ratios, imposed a restriction on the operable range of a number of configurations.

  2. The effect of air density on atmospheric electric fields required for lightning initiation from a long airborne object

    NASA Astrophysics Data System (ADS)

    Bazelyan, E. M.; Aleksandrov, N. L.; Raizer, Yu. P.; Konchakov, A. M.

    2007-11-01

    The purpose of the work was to determine minimum atmospheric electric fields required for lightning initiation from an airborne vehicle at various altitudes up to 10 km. The problem was reduced to the determination of a condition for initiation of a viable positive leader from a conductive object in an ambient electric field. It was shown that, depending on air density and shape and dimensions of the object, critical atmospheric fields are governed by the condition for leader viability or that for corona onset. To establish quantitative criteria for reduced air densities, available observations of spark discharges in long laboratory gaps were analyzed, the effect of air density on leader velocity was discussed and evolution in time of the properties of plasma in the leader channel was numerically simulated. The results obtained were used to evaluate the effect of pressure on the quantitative relationships between the potential difference near the leader tip, leader current and its velocity; based on these relationships, criteria for steady development of a leader were determined for various air pressures. Atmospheric electric fields required for lightning initiation from rods and ellipsoidal objects of various dimensions were calculated at different air densities. It was shown that there is no simple way to extend critical ambient fields obtained for some given objects and pressures to other objects and pressures.

  3. The Effect of Air Density on Atmospheric Electric Fields Required for Lightning Initiation from a Long Airborne Object

    NASA Technical Reports Server (NTRS)

    Bazelyan, E. M.; Aleksandrov, N. L.; Raizer, Yu. Pl.; Konchankov, A. M.

    2006-01-01

    The purpose of the work was to determine minimum atmospheric electric fields required for lightning initiation from an airborne vehicle at various altitudes up to 10 km. The problem was reduced to the determination of a condition for initiation of a viable positive leader from a conductive object in an ambient electric field. It was shown that, depending on air density and shape and dimensions of the object, critical atmospheric fields are governed by the condition for leader viability or that for corona onset. To establish quantitative criteria for reduced air densities, available observations of spark discharges in long laboratory gaps were analyzed, the effect of air density on leader velocity was discussed and evolution in time of the properties of plasma in the leader channel was numerically simulated. The results obtained were used to evaluate the effect of pressure on the quantitative relationships between the potential difference near the leader tip, leader current and its velocity; based on these relationships, criteria for steady development of a leader were determined for various air pressures. Atmospheric electric fields required for lightning initiation from rods and ellipsoidal objects of various dimensions were calculated at different air densities. It was shown that there is no simple way to extend critical ambient fields obtained for some given objects and pressures to other objects and pressures.

  4. Effect of local velocity on diffusion-induced stress in large-deformation electrodes of lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Li, Yong; Zhang, Kai; Zheng, Bailin; Yang, Fuqian

    2016-07-01

    In this work, the contribution of local velocity to the resultant flux of lithium in lithium-ion battery is introduced into the diffusion equation to describe the migration of lithium in the active material of electrodes. The effect of the local velocity on the stress evolution in a spherical electrode made of silicon is analyzed, using the derived diffusion equation and nonlinear theory of elasticity. Two boundary conditions at the surface of the electrode, which represent two extreme conditions of real electrode materials, are used in the stress analysis: one is stress-free, and the other is immobile. The numerical results with the stress-free boundary condition suggest that the effect of the local velocity on the distribution of radial stress and hoop stress increases with the increase of time and the effect of the local velocity on the distribution of lithium is relatively small. In comparison with the results without the effect of the local velocity, the effect of the local velocity is negligible for the immobile boundary condition. The numerical result shows that the use of the immobile boundary condition leads to the decrease of von-Mises stress, which likely will retard the mechanical degradation of electrode and improve the electrochemical performance of lithium-ion battery.

  5. Effect of air velocity on laying hen performance and egg quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increasing convective cooling can improve performance and thermal comfort of commercial poultry when weather or system design limit cooling through other means such as evaporative cooling. Previous work in young hens showed increased egg production rate as feed intake is maintained under heat stres...

  6. Transport of Tank 241-SY-101 Waste Slurry: Effects of Dilution and Temperature on Critical Pipeline Velocity

    SciTech Connect

    KP Recknagle; Y Onishi

    1999-06-15

    This report presents the methods and results of calculations performed to predict the critical velocity and pressure drop required for the two-inch pipeline transfer of solid/liquid waste slurry from underground waste storage Tank 241-SY-101 to Tank 241-SY- 102 at the Hanford Site. The effects of temperature and dilution on the critical velocity were included in the analysis. These analyses show that Tank 241-SY-101 slurry should be diluted with water prior to delivery to Tank 241-SY-102. A dilution ratio of 1:1 is desirable and would allow the waste to be delivered at a critical velocity of 1.5 ft/sec. The system will be operated at a flow velocity of 6 ft/sec or greater therefore, this velocity will be sufficient to maintain a stable slurry delivery through the pipeline. The effect of temperature on the critical velocity is not a limiting factor when the slurry is diluted 1:1 with water. Pressure drop at the critical velocity would be approximately two feet for a 125-ft pipeline (or 250-ft equivalent straight pipeline). At 6 ft/sec, the pressure drop would be 20 feet over a 250-ft equivalent straight pipeline.

  7. Effects of neutral interactions on velocity-shear-driven plasma waves

    SciTech Connect

    Enloe, C. L.; Tejero, E. M.; Amatucci, W. E.; Crabtree, C.; Ganguli, G.; Sotnikov, V.

    2014-06-15

    In a laboratory experiment, we demonstrate the substantial effects that collisions between charged and neutral particles have on low-frequency (Ω{sub i} ≪ ω ≪ Ω{sub e}) shear-driven electrostatic lower hybrid waves in a plasma. We establish a strong (up to 2.5 kV/m) highly localized electric field with a length scale shorter than the ion gyroradius, so that the ions in the plasma, unlike the electrons, do not develop the full E × B drift velocity. The resulting shear in the particle velocities initiates the electron-ion hybrid (EIH) instability, and we observe the formation of strong waves in the vicinity of the shear with variations in plasma densities of 10% or greater. Our experimental configuration allows us to vary the neutral background density by more than a factor of two while holding the charged particle density effectively constant. Not surprisingly, increasing the neutral density decreases the growth rate/saturation amplitude of the waves and increases the threshold electric field necessary for wave formation, but the presence of neutrals affects the dominant wave frequency as well. We show that a 50% increase in the neutral density decreases the wave frequency by 20% while also suppressing the electric field dependence of the frequency that is observed when fewer neutrals are present. The majority of these effects, as well as the values of the frequencies we observe, closely match the predictions of previously developed linear EIH instability theory, for which we present the results of a numerical solution.

  8. Electron Transport Coefficients and Effective Ionization Coefficients in SF6-O2 and SF6-Air Mixtures Using Boltzmann Analysis

    NASA Astrophysics Data System (ADS)

    Wei, Linsheng; Xu, Min; Yuan, Dingkun; Zhang, Yafang; Hu, Zhaoji; Tan, Zhihong

    2014-10-01

    The electron drift velocity, electron energy distribution function (EEDF), density-normalized effective ionization coefficient and density-normalized longitudinal diffusion velocity are calculated in SF6-O2 and SF6-Air mixtures. The experimental results from a pulsed Townsend discharge are plotted for comparison with the numerical results. The reduced field strength varies from 40 Td to 500 Td (1 Townsend=10-17 V·cm2) and the SF6 concentration ranges from 10% to 100%. A Boltzmann equation associated with the two-term spherical harmonic expansion approximation is utilized to gain the swarm parameters in steady-state Townsend. Results show that the accuracy of the Boltzmann solution with a two-term expansion in calculating the electron drift velocity, electron energy distribution function, and density-normalized effective ionization coefficient is acceptable. The effective ionization coefficient presents a distinct relationship with the SF6 content in the mixtures. Moreover, the E/Ncr values in SF6-Air mixtures are higher than those in SF6-O2 mixtures and the calculated value E/Ncr in SF6-O2 and SF6-Air mixtures is lower than the measured value in SF6-N2. Parametric studies conducted on these parameters using the Boltzmann analysis offer substantial insight into the plasma physics, as well as a basis to explore the ozone generation process.

  9. Respiratory effects of air pollution on allergic disease

    SciTech Connect

    Pierson, W.E.; Koenig, J.Q. )

    1992-10-01

    Allergic patients have an increased susceptibility to the adverse effects of both natural and man-made air pollutants. This goes for both indoor and outdoor air pollutants and manifests itself with biochemical, cellular, and pathophysiologic expressions of adverse health effects in allergic individuals. Also occupationally induced allergic diseases will remain very important. This area has been reviewed recently by Cullen et al. Since allergic patients comprise somewhere between 15% and 20% of the population, this increased susceptibility is of crucial importance not only for medical care and research but for legislative and regulatory consideration to protect these vulnerable individuals.108 references.

  10. Effects of the concentration of emulsion of oil-in-water on the propagation velocity and attenuation

    NASA Astrophysics Data System (ADS)

    Silva, L. S. F.; Bibiano, D. S.; Figueiredo, M. K. K.; Costa-Félix, R. P. B.

    2015-01-01

    Soybean oil is an important feedstock for production of biodiesel that generates about 20 % of oily effluents. This paper studied the effect of concentration of soybean oil-inwater emulsions, in the range from 6 000 to 14 000 ppm, on the propagation velocity and ultrasonic attenuation. The Emission-Reception method has shown that the propagation velocity depends linearly on the concentration. The behavior of attenuation is similar to the velocity. Thus, both parameters can be used to measure oils and greases content in water.

  11. Effective velocity distribution in an atom gravimeter: Effect of the convolution with the response of the detection

    NASA Astrophysics Data System (ADS)

    Farah, T.; Gillot, P.; Cheng, B.; Landragin, A.; Merlet, S.; Pereira Dos Santos, F.

    2014-08-01

    We present here a detailed study of the influence of the transverse motion of the atoms in a free-fall gravimeter. By implementing Raman selection in the horizontal directions at the beginning of the atoms' free fall, we characterize the effective velocity distribution, i.e., the velocity distribution of the detected atom, as a function of the laser cooling and trapping parameters. In particular, we show that the response of the detection induces a pronounced asymmetry of this effective velocity distribution that depends not only on the imbalance between molasses beams but also on the initial position of the displaced atomic sample. This convolution with the detection has a strong influence on the averaging of the bias due to Coriolis acceleration. The present study allows a fairly good understanding of results previously published in [New J. Phys. 13, 065025 (2011), 10.1088/1367-2630/13/6/065025], where the mean phase shift due to Coriolis acceleration was found to have a sign different from that expected.

  12. Effect of sea sprays on air-sea momentum exchange at severe wind conditions

    NASA Astrophysics Data System (ADS)

    Troitskaya, Yu.; Ezhova, E.; Semenova, A.; Soustova, I.

    2012-04-01

    Wind-wave interaction at extreme wind speed is of special interest now in connection with the problem of explanation of the sea surface drag saturation at the wind speed exceeding 30 m/s. The idea on saturation (and even reduction) of the coefficient of aerodynamic resistance of the sea surface at hurricane wind speed was first suggested in [1] on the basis of theoretical analysis of sensitivity of maximum wind speed in a hurricane to the ratio of the enthalpy and momentum exchange coefficients. Both field [2-4] and laboratory [5] experiments confirmed that at hurricane wind speed the sea surface drag coefficient is significantly reduced in comparison with the parameterization obtained at moderate to strong wind conditions. Two groups of possible theoretical mechanisms for explanation of the effect of the sea surface drag reduction can be specified. In the first group of models developed in [6,7], the sea surface drag reduction is explained by peculiarities of the air flow over breaking waves. Another approach more appropriate for the conditions of developed sea exploits the effect of sea drops and sprays on the wind-wave momentum exchange. Papers[8,9] focused on the effect of the sea drops on stratification of the air-sea boundary layer similar to the model of turbulent boundary layer with the suspended particles [10], while papers [11-13] estimated the momentum exchange of sea drops and air-flow. A mandatory element of the spray induced momentum flux is a parameterization of the momentum exchange between droplets and air flow, which determines the "source function" in the momentum balance equation. In this paper a model describing the motion of a spume droplet, the wind tear away from the crest of a steep surface wave, and then falling into the water. We consider two models for the injection of droplets into the air flow. The first one assumes that the drop starts from the surface at the orbital velocity of the wave. In the second model we consider droplets from

  13. Effect of hindlimb unweighting on single soleus fiber maximal shortening velocity and ATPase activity

    NASA Technical Reports Server (NTRS)

    Mcdonald, K. S.; Fitts, R. H.

    1993-01-01

    The effect of hindlimb unweighting (HU) for 1 to 3 wks on the shortening velocity of a soleus fiber, its ATPase content, and the relative contents of the slow and fast myosin was investigated by measuring fiber force, V(0), ATPase activity, and myosin content in SDS protein profiles of a single rat soleus fiber suspended between a motor arm and a transducer. It was found that HU induces a progressive increase in fiber V(0) that is likely caused, at least in part, by an increase in the fiber's myofibrillar ATPase activity. The HU-induced increases in V(0) and ATPase were associated with the presence of a greater percentage of fast type IIa fibers. However, a large population of fibers after 1, 2, and 3 wks of HU showed increases in V(0) and ATPase but displayed the same myosin protein profile on SDS gels as control fibers.

  14. The Lyman alpha bulge of Jupiter - Effects of non-thermal velocity field

    NASA Technical Reports Server (NTRS)

    Ben Jaffel, Lotfi; Clarke, John T.; Prange, Renee; Gladstone, G. R.; Vidal-Madjar, Alfred

    1993-01-01

    We outline for the first time the effect of such nonthermal line broadening processes as turbulence, random waves, convection, etc., on the shape and intensity of the H Ly-alpha line resonance scattered from the atmosphere of Jupiter. We show how a nonthermal velocity field confined to the bulge region, in the upper atmosphere of Jupiter, may account for most of the H Ly-alpha bulge features. Both the shape and the brightness of the Ly-alpha line from the bulge region as reported by the IUE instrument and the Voyager UV Spectrometer can be recovered assuming resonant scattering with a total atomic hydrogen of about 4 x 10 exp 17/sq cm, and a nonthermal component H of about 2 x 10 exp 15/sq cm above the thermopause.

  15. Wind tunnel investigation of the effect of high relative velocities on the structural integrity of birds

    NASA Technical Reports Server (NTRS)

    Bresnahan, D. L.

    1972-01-01

    An experimental investigation was conducted in a supersonic wind tunnel to determine the effect a sudden high velocity headwind had on the physical deformation and structural breakup characteristics of birds. Several sizes of recently killed birds were dropped into the test section at free-stream Mach numbers ranging from 0.2 to 0.8 and photographed with high-speed motion-picture cameras. These conditions simulated flow conditions encountered when birds are ingested into the inlets of high speed aircraft, thereby constituting a safety hazard to the aircraft and its occupants. The investigation shows that, over the range of headwind conditions tested, the birds remained structurally intact and did not suffer any appreciable deformation or structural breakup.

  16. Physical effects of negative air ions in a wet sauna

    NASA Astrophysics Data System (ADS)

    Watanabe, I.; Noro, Hiroshi; Ohtsuka, Yoshinori; Mano, Yukio; Agishi, Yuko

    The physical effects of negative air ions on humans were determined in an experimental sauna room equipped with an ionizer. Thirteen healthy persons took a wet sauna bath (dry bulb temperature 42° C, relative humidity 100%, 10 min exposure) with or without negative air ions. The subjects were not told when they were being exposed to negative air ions. There were no differences in the moods of these persons or changes in their blood pressures between the two saunas. The surface temperatures of the foreheads, hands, and legs in the sauna with negative ions were significantly higher than those in the sauna without ions. The pulse rates and sweat produced in the sauna with ions were singificantly higher than those in the sauna without ions. The results suggest that negative ions may amplify the effects on humans of the sauna.

  17. The Effect of Micrite on Velocity, Its Sensitivity to Pressure, and Dissolution of Carbonates

    NASA Astrophysics Data System (ADS)

    El Husseiny, A.; Vanorio, T.

    2014-12-01

    This study investigates the effect of micrite on the acoustic properties of well-controlled microstructures created in the laboratory to closely mimic carbonate rocks. In particular, we examine the effect of micrite content on the elastic stiffness rock, its sensitivity to pressure, and induced dissolution upon saturation with a reactive fluid. We followed Dunham's classification and fabricated the samples by mixing coarse (sand size) and very fine (micrite size) calcite grains in different ratios, with the addition of cement and then cold-compressing the mixture. The acoustic velocities were measured under bench-top conditions and as functions of confining pressure before and after the injection of a CO2aqueous solution. Our bench-top measurements indicated that micrite makes the frame of the carbonate samples stiffer. Since the sensitivity of the elastic stiffness to pressure decreases as the content of micrite increases (see figure 1), we hypothesize a stiffer pore structure (i.e., rounder pores) in micrite-richer fabrics. Furthermore, the presence of micrite makes the carbonate sample more reactive upon dissolution. The concentration of Ca+2 cations in the fluid measured at the outlet after the injection of the CO2 aqueous solution shows larger dissolution in the micrite-rich samples likely due to the higher surface area of the micrite aggregates. The content of micrite also seems to affect the evolution of stiffness as dissolution proceeds. As the content of micrite increases, the enhanced dissolution translates into a marked softening of the rock frame. We conclude that the content of micrite can play an important role in the complex rock-fluid interaction of carbonates as well as when comparing Gassmann's predictions to velocity measurements of saturated carbonates.

  18. Effect of glow discharge air plasma on grain crops seed

    SciTech Connect

    Dubinov, A.E.; Lazarenko, E.M.; Selemir, V.D.

    2000-02-01

    Oat and barley seeds have been exposed to both continuous and pulsed glow discharge plasmas in air to investigate the effects on germination and sprout growth. Statistical analysis was used to evaluate the effect of plasma exposure on the percentage germination and length of sprout growth. A stimulating effect of plasma exposure was found together with a strong dependence on whether continuous or pulsed discharges were used.

  19. The Effects of Air Pollution and Temperature on COPD

    PubMed Central

    Hansel, Nadia N.; McCormack, Meredith C.; Kim, Victor

    2016-01-01

    Chronic Obstructive Pulmonary Disease (COPD) affects 12–16 million people in the United States and is the third-leading cause of death. In developed countries, smoking is the greatest risk factor for the development of COPD, but other exposures also contribute to the development and progression of the disease. Several studies suggest, though are not definitive, that outdoor air pollution exposure is linked to the prevalence and incidence of COPD. Among individuals with COPD, outdoor air pollutants are associated with loss of lung function and increased respiratory symptoms. In addition, outdoor air pollutants are also associated with COPD exacerbations and mortality. There is much less evidence for the impact of indoor air on COPD, especially in developed countries in residences without biomass exposure. The limited existing data suggests that indoor particulate matter and nitrogen dioxide concentrations are linked to increased respiratory symptoms among patients with COPD. In addition, with the projected increases in temperature and extreme weather events in the context of climate change there has been increased attention to the effects of heat exposure. Extremes of temperature—both heat and cold—have been associated with increased respiratory morbidity in COPD. Some studies also suggest that temperature may modify the effect of pollution exposure and though results are not conclusive, understanding factors that may modify susceptibility to air pollution in patients with COPD is of utmost importance. PMID:26683097

  20. Feasibility of cooling emplacement drifts by ventilation air and effects of pre-cooling intake air by refrigeration

    SciTech Connect

    Yang, Hang; Bhattacharyya, K.K.

    1995-12-01

    This study evaluates effects of applying refrigerated air to cool emplacement drifts and provides a preliminary basis for future design analyses. Evaluations include impacts of airflow rates, intake air temperature, ventilation systems capability, and effectiveness of pre-cooling. Representative results provided from this study include the heat removal capability of ventilation air, effects of refrigerating intake air on continuous cooling, and effects of refrigerating intake air on rapid (blast cooling). It is possible to cool emplacement drifts within a reasonable time period, using airflow at ambient temperature is reasonable quantity. Refrigerating intake air can significantly reduce required cooling time or airflow rate, but it is inefficient as far as power consumption is concerned.

  1. Effects of general, special, and specific resistance training on throwing velocity in baseball: a brief review.

    PubMed

    Derenne, C; Ho, K W; Murphy, J C

    2001-02-01

    Throwing velocity is a necessary requirement for success in baseball. All position players, including pitchers, may increase their defensive performance if their throwing velocity is improved. A review of the literature suggests that throwing velocity can be increased by resistance training and/or biomechanical improvement of the throwing motion. This paper reviews the 3 broad categories of resistance-training methods by which throwing velocity is increased. The results of research using general, special, and specific throwing resistance-training exercises are presented. The role and applications of these different exercises for baseball players of different ages are discussed.

  2. The effects of skiing velocity on mechanical aspects of diagonal cross-country skiing.

    PubMed

    Andersson, Erik; Pellegrini, Barbara; Sandbakk, Oyvind; Stüggl, Thomas; Holmberg, Hans-Christer

    2014-09-01

    Cycle and force characteristics were examined in 11 elite male cross-country skiers using the diagonal stride technique while skiing uphill (7.5°) on snow at moderate (3.5 ± 0.3 m/s), high (4.5 ± 0.4 m/s), and maximal (5.6 ± 0.6 m/s) velocities. Video analysis (50 Hz) was combined with plantar (leg) force (100 Hz), pole force (1,500 Hz), and photocell measurements. Both cycle rate and cycle length increased from moderate to high velocity, while cycle rate increased and cycle length decreased at maximal compared to high velocity. The kick time decreased 26% from moderate to maximal velocity, reaching 0.14 s at maximal. The relative kick and gliding times were only altered at maximal velocity, where these were longer and shorter, respectively. The rate of force development increased with higher velocity. At maximal velocity, sprint-specialists were 14% faster than distance-specialists due to greater cycle rate, peak leg force, and rate of leg force development. In conclusion, large peak leg forces were applied rapidly across all velocities and the shorter relative gliding and longer relative kick phases at maximal velocity allow maintenance of kick duration for force generation. These results emphasise the importance of rapid leg force generation in diagonal skiing.

  3. Clearing the air: a review of the effects of particulate matter air pollution on human health.

    PubMed

    Anderson, Jonathan O; Thundiyil, Josef G; Stolbach, Andrew

    2012-06-01

    The World Health Organization estimates that particulate matter (PM) air pollution contributes to approximately 800,000 premature deaths each year, ranking it the 13th leading cause of mortality worldwide. However, many studies show that the relationship is deeper and far more complicated than originally thought. PM is a portion of air pollution that is made up of extremely small particles and liquid droplets containing acids, organic chemicals, metals, and soil or dust particles. PM is categorized by size and continues to be the fraction of air pollution that is most reliably associated with human disease. PM is thought to contribute to cardiovascular and cerebrovascular disease by the mechanisms of systemic inflammation, direct and indirect coagulation activation, and direct translocation into systemic circulation. The data demonstrating PM's effect on the cardiovascular system are strong. Populations subjected to long-term exposure to PM have a significantly higher cardiovascular incident and mortality rate. Short-term acute exposures subtly increase the rate of cardiovascular events within days of a pollution spike. The data are not as strong for PM's effects on cerebrovascular disease, though some data and similar mechanisms suggest a lesser result with smaller amplitude. Respiratory diseases are also exacerbated by exposure to PM. PM causes respiratory morbidity and mortality by creating oxidative stress and inflammation that leads to pulmonary anatomic and physiologic remodeling. The literature shows PM causes worsening respiratory symptoms, more frequent medication use, decreased lung function, recurrent health care utilization, and increased mortality. PM exposure has been shown to have a small but significant adverse effect on cardiovascular, respiratory, and to a lesser extent, cerebrovascular disease. These consistent results are shown by multiple studies with varying populations, protocols, and regions. The data demonstrate a dose

  4. The Effect of Intermittent Arm and Shoulder Cooling on Baseball Pitching Velocity.

    PubMed

    Bishop, Stacy H; Herron, Robert L; Ryan, Gregory A; Katica, Charles P; Bishop, Phillip A

    2016-04-01

    The throwing arm of a baseball pitcher is subjected to high stress as a result of the repetitive activity of pitching. Intermittent cryotherapy may facilitate recovery from this repeated high stress, but few researchers have investigated cryotherapy's efficacy in an ecologically valid setting. This study investigated the effects of intermittent cryotherapy on pitching velocity and subjective measures of recovery and exertion in a simulated baseball game. Trained college-aged male baseball pitchers (n = 8) threw 12 pitches (1 pitch every 20 seconds) per inning for 5 total innings during a simulated pitching start. Between each inning, pitchers received shoulder and arm cooling (AC) or, on a separate occasion, no cooling (NC). All sessions took place in a temperate environment (18.3 ± 2.8° C; 49 ± 4% relative humidity). Pitch speeds were averaged for each participant each inning and overall for 5 innings. Perceived exertion (rating of perceived exertion [RPE]) was recorded at the end of each simulated inning. Perceived recovery (perceived recovery scale [PRS]) was recorded after treatment between each inning. Mean pitching velocity for all-innings combined was higher (p = 0.04) for shoulder and elbow cooling (AC) (31.2 ± 2.1 m·s) than for no cooling (NC) (30.6 ± 2.1 m·s). Average pitch speed was significantly higher in the fourth (p = <0.01) and fifth (p = 0.02) innings in AC trial (31.3 ± 2 m·s for both innings) compared with NC trial (30.0 ± 2.22 m·s and 30.4 ± 1.99 m·s, for the fourth and fifth innings, respectively. AC resulted in a significantly lower RPE (p ≤ 0.01) and improved PRS (p ≤ 0.01) compared with NC. Intermittent cryotherapy attenuated velocity loss in baseball pitching, decreased RPE, and facilitated subjective recovery during a 5-inning simulated game. PMID:24077378

  5. The Effect of Intermittent Arm and Shoulder Cooling on Baseball Pitching Velocity.

    PubMed

    Bishop, Stacy H; Herron, Robert L; Ryan, Gregory A; Katica, Charles P; Bishop, Phillip A

    2016-04-01

    The throwing arm of a baseball pitcher is subjected to high stress as a result of the repetitive activity of pitching. Intermittent cryotherapy may facilitate recovery from this repeated high stress, but few researchers have investigated cryotherapy's efficacy in an ecologically valid setting. This study investigated the effects of intermittent cryotherapy on pitching velocity and subjective measures of recovery and exertion in a simulated baseball game. Trained college-aged male baseball pitchers (n = 8) threw 12 pitches (1 pitch every 20 seconds) per inning for 5 total innings during a simulated pitching start. Between each inning, pitchers received shoulder and arm cooling (AC) or, on a separate occasion, no cooling (NC). All sessions took place in a temperate environment (18.3 ± 2.8° C; 49 ± 4% relative humidity). Pitch speeds were averaged for each participant each inning and overall for 5 innings. Perceived exertion (rating of perceived exertion [RPE]) was recorded at the end of each simulated inning. Perceived recovery (perceived recovery scale [PRS]) was recorded after treatment between each inning. Mean pitching velocity for all-innings combined was higher (p = 0.04) for shoulder and elbow cooling (AC) (31.2 ± 2.1 m·s) than for no cooling (NC) (30.6 ± 2.1 m·s). Average pitch speed was significantly higher in the fourth (p = <0.01) and fifth (p = 0.02) innings in AC trial (31.3 ± 2 m·s for both innings) compared with NC trial (30.0 ± 2.22 m·s and 30.4 ± 1.99 m·s, for the fourth and fifth innings, respectively. AC resulted in a significantly lower RPE (p ≤ 0.01) and improved PRS (p ≤ 0.01) compared with NC. Intermittent cryotherapy attenuated velocity loss in baseball pitching, decreased RPE, and facilitated subjective recovery during a 5-inning simulated game.

  6. A Study of the Effects of Air Pollution on Children

    ERIC Educational Resources Information Center

    Bury, Irene B.

    1970-01-01

    An investigation of the possible effects of air pollution on the absenteeism of elementary school children showed that a greater percent of absences occurred in the test group than in a comparable group. There is little question as to the importance that such information should have for educators, informed parents, and other adults in community…

  7. The Effects of a Blizzard on Urban Air Pollution.

    ERIC Educational Resources Information Center

    da Silva, Armando; Bein, Frederick L.

    1981-01-01

    The chronology and effects of a 1978 blizzard on Indianapolis' air pollution levels (ozone, sulfur dioxide, carbon monoxide) are used as a case study for geography classes. Photographs, graphs, and maps are provided as examples of meteorological data collection and interpretation. (AM)

  8. CARDIAC MOLECULAR EFFECTS INDUCED BY AIR POLLUTION PARTICLES

    EPA Science Inventory

    Abstract Submitted to the American Thoracic Society 98th International Conference, May 17 - 22, 2002, Atlanta, GA

    CARDIAC MOLECULAR EFFECTS INDUCED BY AIR POLLUTION PARTICLES
    K. Dreher1, R. Jaskot1, J. Richards1, and T. Knuckles2. 1U. S. Environmental Protection Agency,...

  9. Effect of various warm-up devices on bat velocity of intercollegiate baseball players.

    PubMed

    Szymanski, David J; Beiser, Erik J; Bassett, Kylie E; Till, Megan E; Medlin, Greg L; Beam, Jason R; DeRenne, Coop

    2011-02-01

    A variety of warm-up devices are available to baseball players to use before their game at-bat. Past baseball research evaluating warm-up devices indicates that implements that are ±12% of standard game bat weight produce the greatest bat velocities for high school and intercollegiate players. The purpose of this study was to examine the effect of various warm-up devices on bat velocity (BV) of intercollegiate baseball players. Twenty-two Division I intercollegiate baseball players (age = 20.0 ± 1.5 years, height = 182.6 ± 8.3 cm, body mass = 91.4 ± 11.4 kg, lean body mass = 78.8 ± 8.9 kg, % body fat = 13.6 ± 3.8) participated in a warm-up with 1 of 10 weighted devices on separate days. Each of the 10 testing sessions consisted of a standardized warm-up, 3 dry swings as hard as possible with the assigned warm-up device, 2 comfortable dry swings with a standard game baseball bat followed by 3 game swings (20-second rest between swings) while hitting a baseball off of a batting tee with the same standard game baseball bat. Results indicated that there were no statistically significant differences in BV after using any of the 10 warm-up devices. For male intercollegiate baseball players, results indicate that warm-up devices varying from 623.7 to 2,721.5 g (22-96 oz.) did not change mean BV of a standard game baseball bat, suggesting that intercollegiate players can use any of the 10 warm-up devices in the on-deck circle and maintain their BV. Therefore, personal preference as to which warm-up implement to use in the on-deck circle is advised. PMID:21240027

  10. Effect of various warm-up devices on bat velocity of intercollegiate baseball players.

    PubMed

    Szymanski, David J; Beiser, Erik J; Bassett, Kylie E; Till, Megan E; Medlin, Greg L; Beam, Jason R; DeRenne, Coop

    2011-02-01

    A variety of warm-up devices are available to baseball players to use before their game at-bat. Past baseball research evaluating warm-up devices indicates that implements that are ±12% of standard game bat weight produce the greatest bat velocities for high school and intercollegiate players. The purpose of this study was to examine the effect of various warm-up devices on bat velocity (BV) of intercollegiate baseball players. Twenty-two Division I intercollegiate baseball players (age = 20.0 ± 1.5 years, height = 182.6 ± 8.3 cm, body mass = 91.4 ± 11.4 kg, lean body mass = 78.8 ± 8.9 kg, % body fat = 13.6 ± 3.8) participated in a warm-up with 1 of 10 weighted devices on separate days. Each of the 10 testing sessions consisted of a standardized warm-up, 3 dry swings as hard as possible with the assigned warm-up device, 2 comfortable dry swings with a standard game baseball bat followed by 3 game swings (20-second rest between swings) while hitting a baseball off of a batting tee with the same standard game baseball bat. Results indicated that there were no statistically significant differences in BV after using any of the 10 warm-up devices. For male intercollegiate baseball players, results indicate that warm-up devices varying from 623.7 to 2,721.5 g (22-96 oz.) did not change mean BV of a standard game baseball bat, suggesting that intercollegiate players can use any of the 10 warm-up devices in the on-deck circle and maintain their BV. Therefore, personal preference as to which warm-up implement to use in the on-deck circle is advised.

  11. Nitric Oxide and Oxygen Air-Contamination Effects on Extinction Limits of Non-Premixed Hydrocarbon-Air Flames for a HIFiRE Scramjet

    NASA Technical Reports Server (NTRS)

    Pellett, Gerald L.; Dawson, Lucy C.; Vaden, Sarah N.; Wilson, Lloyd G.

    2009-01-01

    Unique nitric oxide (NO) and oxygen air-contamination effects on the extinction Flame Strength (FS) of non-premixed hydrocarbon (HC) vs. air flames are characterized for 7 gaseous HCs, using a new idealized 9.3 mm straight-tube Opposed Jet Burner (OJB) at 1 atm. FS represents a laminar strain-induced extinction limit based on cross-section-average air jet velocity, Uair, that sustains combustion of a counter jet of gaseous fuel just before extinction. Besides ethane, propane, butane, and propylene, the HCs include ethylene, methane, and a 64 mole-% ethylene / 36 % methane mixture, the writer s previously recommended gaseous surrogate fuel for HIFiRE scramjet tests. The HC vs. clean air part of the work is an extension of a May 2008 JANNAF paper that characterized surrogates for the HIFiRE project that should mimic the flameholding of reformed (thermally- or catalytically-cracked) endothermic JP-like fuels. The new FS data for 7 HCs vs. clean air are thus consolidated with the previously validated data, normalized to absolute (local) axial-input strain rates, and co-plotted on a dual kinetically dominated reactivity scale. Excellent agreement with the prior data is obtained for all 7 fuels. Detailed comparisons are also made with recently published (Univ. Va) numerical results for ethylene extinction. A 2009-revised ethylene kinetic model (Univ. Southern Cal) led to predicted limits within approx. 5 % (compared to 45 %, earlier) of this writer s 2008 (and present) ethylene FSs, and also with recent independent data (Univ. Va) obtained on a new OJB system. These +/- 5 % agreements, and a hoped-for "near-identically-performing" reduced kinetics model, would greatly enhance the capability for accurate numerical simulations of surrogate HC flameholding in scramjets. The measured air-contamination effects on normalized FS extinction limits are projected to assess ongoing Arc-Heater-induced "facility test effects" of NO production (e.g., 3 mole-%) and resultant oxygen

  12. The free jet as a simulator of forward velocity effects on jet noise

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Tester, B. J.; Tanna, H. K.

    1978-01-01

    A thorough theoretical and experimental study of the effects of the free-jet shear layer on the transmission of sound from a model jet placed within the free jet to the far-field receiver located outside the free-jet flow was conducted. The validity and accuracy of the free-jet flight simulation technique for forward velocity effects on jet noise was evaluated. Transformation charts and a systematic computational procedure for converting measurements from a free-jet simulation to the corresponding results from a wind-tunnel simulation, and, finally, to the flight case were provided. The effects of simulated forward flight on jet mixing noise, internal noise and shock-associated noise from model-scale unheated and heated jets were established experimentally in a free-jet facility. It was illustrated that the existing anomalies between full-scale flight data and model-scale flight simulation data projected to the flight case, could well be due to the contamination of flight data by engine internal noise.

  13. Polyurethane foam (PUF) disks passive air samplers: wind effect on sampling rates.

    PubMed

    Tuduri, Ludovic; Harner, Tom; Hung, Hayley

    2006-11-01

    Different passive sampler housings were evaluated for their wind dampening ability and how this might translate to variability in sampler uptake rates. Polyurethane foam (PUF) disk samplers were used as the sampling medium and were exposed to a PCB-contaminated atmosphere in a wind tunnel. The effect of outside wind speed on PUF disk sampling rates was evaluated by exposing polyurethane foam (PUF) disks to a PCB-contaminated air stream in a wind tunnel over air velocities in the range 0 to 1.75 m s-1. PUF disk sampling rates increased gradually over the range 0-0.9 m s-1 at approximately 4.5-14.6 m3 d-1 and then increased sharply to approximately 42 m3 d-1 at approximately 1.75 m s-1 (sum of PCBs). The results indicate that for most field deployments the conventional 'flying saucer' housing adequately dampens the wind effect and will yield approximately time-weighted air concentrations.

  14. Air pollution "holiday effect" resulting from the Chinese New Year

    NASA Astrophysics Data System (ADS)

    Tan, Pei-Hua; Chou, Chia; Liang, Jing-Yi; Chou, Charles C.-K.; Shiu, Chein-Jung

    Our 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. This holiday effect can be applied to other countries with similar national or cultural holidays. Hourly and daily surface measurements of six major air pollutants from thirteen air quality monitoring stations of the Taiwan Environmental Protection Administration during the Chinese New Year (CNY) and non-Chinese New Year (NCNY) periods were used. We documented evidence of a "holiday effect", where air pollutant concentrations were significantly different between holidays (CNY) and non-holidays (NCNY), in the Taipei metropolitan area over the past thirteen years (1994-2006). The concentrations of NO x, CO, NMHC, SO 2 and PM 10 were lower in the CNY than in the NCNY period, while the variation in the concentration of O 3 was reversed, which was mainly due to the NO titration effect. Similar differences in these six air pollutants between the CNY and NCNY periods were also found in the diurnal cycle and in the interannual variation. For the diurnal cycle, a common traffic-related double-peak variation was observed in the NCNY period, but not in the CNY period. Impacts of dust storms were also observed, especially on SO 2 and PM 10 in the CNY period. In the 13-year period of 1994-2006, decreasing trends of NO x and CO in the NCNY period implied a possible reduction of local emissions. Increasing trends of SO 2 and PM 10 in the CNY period, on the other hand, indicated a possible enhancement of long-range transport. These two mechanisms weakened the holiday effect.

  15. Effects of exciting frequencies, grain sizes, and damage upon P-wave velocity for ultrasonic NDT of concrete

    NASA Astrophysics Data System (ADS)

    Ju, Jiann W.; Weng, Lisheng

    2000-05-01

    This paper focuses on the experimental study of the effects of exciting frequencies, grain (aggregate) sizes, and damage upon the ultrasonic P-wave velocity when performing the ultrasonic nondestructive testing (NDT) for concrete specimens. Two batches of concrete and mortar specimens were prepared in the laboratory for the investigation of the effects from the stated factors upon the P-wave velocity. Damage here mostly refers to microcracks and microvoids in concrete. Five different aggregate sizes, 0' (mortar), 3/8', 1/2', 3/4', and 1', were selected to demonstrate the grain (aggregate) size effect. Exciting frequencies of the ultrasonic wave were set to range from 100 kHz to 1,000 kHz, with increment of 50 kHz, to demonstrate the frequency effect. Styrofoam particles were mixed into the comparison concrete and mortar specimens to simulate the distributed microvoids (damage). Different volume fractions of styrofoam particles were mixed into the mortar specimens in order to study the effect of different porosities (damage) upon the P-wave velocity. The experimental observations show that, for mortar and concrete specimens with aggregate sizes from 0 to 1 inch, the P-wave velocity would not be affected significantly within the tested frequency range (100 - 1000 kHz). The normalized P-wave velocity exhibits almost identical pattern upon the exciting frequencies for all specimens.

  16. Effect of Air Ions on Submicron T1 Bacteriophage Aerosols

    PubMed Central

    Happ, John W.; Harstad, J. Bruce; Buchanan, Lee M.

    1966-01-01

    The effect of a high concentration of ionized air molecules on sampling T1 phage aerosols of submicron particle size was evaluated by comparing the phage recoveries of all-glass impingers (AGI-4) and type 6 filter papers. Sampler recoveries of all ionized aerosols were less than the recoveries of nonionized control aerosols. These reductions in recovery were greater with positive ions than with negative ions or ions of mixed polarity. The AGI-4 allowed considerable slippage, which was not affected by the air ions. Type 6 filter paper recoveries were less than AGI-4 recoveries. The air ions did not appear to affect the aerosol particle size as determined by an electron microscope. Images Fig. 1 Fig. 3 PMID:16349691

  17. On the impact of entrapped air in infiltration under ponding conditions: Part a: Preferential air flow path effects on infiltration

    NASA Astrophysics Data System (ADS)

    Weisbord, N.; Mizrahi, G.; Furman, A.

    2015-12-01

    Entrapped air effects on infiltration under ponding conditions could be important for massive infiltration of managed aquifer recharge or soil aquifer treatment. Earlier studies found that under ponding conditions air could reduce infiltration by 70-90%. Most studies have dealt with entrapped air effects when soil surface topography is flat. The objective of this study is to investigate the effects of: (1) irregular surface topography on preferential air flow path development; (2) preferential air flow path on infiltration; and (3) hydraulic head on infiltration when air is trapped. Column experiments were used to investigate these particular effects. A 140 cm deep and 30 cm wide column packed with silica sand was used under two boundary conditions: in the first, air can only escape vertically upward through the soil surface; in the second, air is free to escape. The surface was flooded with 13 liters of water, with ponding depth decreasing with time. Two soil surface conditions were tested: flat surface and irregular. It was found that in irregular surfaces, stable air flow through preferential paths was developed in the high altitude zones. Flat surface topography caused unstable air flow through random paths. Comparison between irregular and flat surface topography showed that the entrapped air pressure was lower and the infiltration rate was about 40% higher in the irregular surface topography than in the flat surface topography. No difference of infiltration rate between flat and irregular surface topography was observed when air was free to escape along the infiltration path. It was also found that at the first stage of infiltration, higher hydraulic heads caused higher entrapped air pressures and lower infiltration rates. In contrast, higher hydraulic head results in higher infiltration rate, when air was free to escape. Our results suggest that during ponding conditions: (1) preferential air flow paths develop at high surface zones of irregular topography

  18. Effect of cattle temperament as determined by exit velocity on lung respiratory lesions and liver disease

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this trial was to use exit velocity as a means of determining temperament of cattle to evaluate the impact of temperament on animal health. At the time of processing, exit velocity and body weight were recorded on 20 pens of cattle (2,877 head) at a commercial feedlot. Infrared sens...

  19. The effects of pressure, temperature, and pore water on velocities in Westerly granite. [for seismic wave propagation

    NASA Technical Reports Server (NTRS)

    Spencer, J. W., Jr.; Nur, A. M.

    1976-01-01

    A description is presented of an experimental assembly which has been developed to conduct concurrent measurements of compressional and shear wave velocities in rocks at high temperatures and confining pressures and with independent control of the pore pressure. The apparatus was used in studies of the joint effects of temperature, external confining pressure, and internal pore water on sonic velocities in Westerly granite. It was found that at a given temperature, confining pressure has a larger accelerating effect on compressional waves in dry rock, whereas at a given confining pressure, temperature has a larger retarding effect on shear waves.

  20. Effects of cosmic string velocities and the origin of globular clusters

    SciTech Connect

    Lin, Ling; Yamanouchi, Shoma; Brandenberger, Robert E-mail: shoma.yamanouchi@mail.mcgill.ca

    2015-12-01

    With the hypothesis that cosmic string loops act as seeds for globular clusters in mind, we study the role that velocities of these strings will play in determining the mass distribution of globular clusters. Loops with high enough velocities will not form compact and roughly spherical objects and can hence not be the seeds for globular clusters. We compute the expected number density and mass function of globular clusters as a function of both the string tension and the peak loop velocity, and compare the results with the observational data on the mass distribution of globular clusters in our Milky Way. We determine the critical peak string loop velocity above which the agreement between the string loop model for the origin of globular clusters (neglecting loop velocities) and observational data is lost.

  1. The effect of inlet air vitiation on combustion efficiency

    SciTech Connect

    Zuomin, F.; Yijun, J.

    1985-01-01

    Experimental results of the effect of inlet air vitiation produced by a vitiating preheater on combustion efficiency of a turbojet combustor and a model ramjet combustor are presented in this paper. An empirical correlation and a calculation method based on stirred reactor theory are derived to correct the vitiation effect. Results obtained by means of these two methods are in good agreement with test data.

  2. Grain size evolution in the mantle and its effect on geodynamics, seismic velocities and attenuation

    NASA Astrophysics Data System (ADS)

    Dannberg, Juliane; Eilon, Zach; Gassmoeller, Rene; Moulik, Pritwiraj; Myhill, Robert; Faul, Ulrich; Asimow, Paul

    2015-04-01

    Dynamic models of Earth's convecting mantle usually implement flow laws with constant grain size, stress-independent viscosity and a limited treatment of variations associated with changes in mineral assemblage. These simplifications greatly reduce computational requirements but preclude effects such as shear localisation and transient changes in rheology associated with phase transitions, which have the potential to fundamentally change flow patterns in the mantle. Here we use the finite-element code ASPECT (Bangerth et al., 2013) to model grain size evolution and the interplay between grain size, stress and strain rate in the convecting mantle. We include the simultaneous and competing effects of dynamic recrystallisation resulting from work done by dislocation creep, grain growth in multiphase assemblages and recrystallisation at phase transitions. Grain size variations also affect seismic properties of mantle materials. We use several published formulations to relate intrinsic variables (P, T, and grain size) from our numerical models to seismic velocity (Vs) and attenuation (Q). Our calculations use thermodynamically self-consistent anharmonic elastic moduli determined for the mineral assemblages in the mantle using HeFESTo (Stixrude and Lithgow-Bertelloni, 2013). We investigate the effect of realistically heterogeneous grain sizes by computing body wave travel times, ray paths, and attenuation (t*) at different frequencies. We highlight the frequency-dependent sensitivity of seismic waves to grain size, which is important when interpreting Vs and Q observations in terms of mineral assemblage and temperature. Our models show that rapid metamorphic reactions in mantle upwellings and downwellings lead to high lateral viscosity contrasts, as a result of gradual grain size evolution. Positive feedback between grain size reduction and viscosity reduction results in shear localisation. As a result, the edges of thermal plumes have smaller grain sizes and lower

  3. Applying policy and health effects of air pollution in South Korea: focus on ambient air quality standards

    PubMed Central

    Ha, Jongsik

    2014-01-01

    Objectives South Korea’s air quality standards are insufficient in terms of establishing a procedure for their management. The current system lacks a proper decision-making process and prior evidence is not considered. The purpose of this study is to propose a measure for establishing atmospheric environmental standards in South Korea that will take into consideration the health of its residents. Methods In this paper, the National Ambient Air Quality Standards (NAAQS) of the US was examined in order to suggest ways, which consider health effects, to establish air quality standards in South Korea. Up-to-date research on the health effects of air pollution was then reviewed, and tools were proposed to utilize the key results. This was done in an effort to ensure the reliability of the standards with regard to public health. Results This study showed that scientific research on the health effects of air pollution and the methodology used in the research have contributed significantly to establishing air quality standards. However, as the standards are legally binding, the procedure should take into account the effects on other sectors. Realistically speaking, it is impossible to establish standards that protect an entire population from air pollution. Instead, it is necessary to find a balance between what should be done and what can be done. Conclusions Therefore, establishing air quality standards should be done as part of an evidence-based policy that identifies the health effects of air pollution and takes into consideration political, economic, and social contexts. PMID:25300297

  4. Gas exchange in wetlands with emergent vegetation: The effects of wind and thermal convection at the air-water interface

    NASA Astrophysics Data System (ADS)

    Poindexter, Cristina M.; Variano, Evan A.

    2013-07-01

    Methane, carbon dioxide, and oxygen are exchanged between wetlands and the atmosphere through multiple pathways. One of these pathways, the hydrodynamic transport of dissolved gas through the surface water, is often underestimated in importance. We constructed a model wetland in the laboratory with artificial emergent plants to investigate the mechanisms and magnitude of this transport. We measured gas transfer velocities, which characterize the near-surface stirring driving air-water gas transfer, while varying two stirring processes important to gas exchange in other aquatic environments: wind and thermal convection. To isolate the effects of thermal convection, we identified a semiempirical model for the gas transfer velocity as a function of surface heat loss. The laboratory results indicate that thermal convection will be the dominant mechanism of air-water gas exchange in marshes with emergent vegetation. Thermal convection yielded peak gas transfer velocities of 1 cm h-1. Because of the sheltering of the water surface by emergent vegetation, gas transfer velocities for wind-driven stirring alone are likely to exceed this value only in extreme cases.

  5. Effect of grip strength and grip strengthening exercises on instantaneous bat velocity of collegiate baseball players.

    PubMed

    Hughes, Shawn S; Lyons, Brian C; Mayo, Jerry J

    2004-05-01

    Bat velocity is considered to be an important factor for successful hitting. The relationship between grip strength and bat velocity has not been conclusively established. The purposes of this study were to determine the relationship of grip strength to bat velocity and to ascertain whether the performance of resistance training exercises designed to specifically target the forearms and grip would significantly alter bat velocity. The subjects for this study were 23 male members (mean +/- SD, age = 19.7 +/- 1.3 years, height = 182.5 +/- 5.9 cm, weight = 85.4 +/- 15.5 kg, experience = 14.4 +/- 1.7 years) of a varsity baseball team at a National Collegiate Athletic Association Division II school. The Jamar hand dynamometer was used to test grip strength, and the SETPRO Rookie was used to measure instantaneous bat velocity at the point of contact with the ball. Subjects were randomly divided into an experimental group and a control group. For 6 weeks, both groups participated in their usual baseball practice sessions, but the experimental group also performed extra forearm and grip strengthening exercises, whereas the control group did not. Pretest and posttest correlations between grip strength and bat velocity revealed no significant relationship between grip strength and bat velocity (pretest r = 0.054, p = 0.807; posttest r = 0.315, p = 0.145). A dependent t-test performed on all subjects revealed that a significant (p = 0.001) increase in bat velocity did occur over the course of the study. A covariate analysis, employing pretest bat velocity as the covariate, revealed no significant difference (p = 0.795) in posttest bat velocity scores between the experimental and control groups. Thus, increases in bat velocity occurred, but the differences were similar for both the experimental and control groups. The findings of this study suggest that grip strength and bat velocity are not significantly related, and that the allocation of time and energy for added training

  6. Effect of grip strength and grip strengthening exercises on instantaneous bat velocity of collegiate baseball players.

    PubMed

    Hughes, Shawn S; Lyons, Brian C; Mayo, Jerry J

    2004-05-01

    Bat velocity is considered to be an important factor for successful hitting. The relationship between grip strength and bat velocity has not been conclusively established. The purposes of this study were to determine the relationship of grip strength to bat velocity and to ascertain whether the performance of resistance training exercises designed to specifically target the forearms and grip would significantly alter bat velocity. The subjects for this study were 23 male members (mean +/- SD, age = 19.7 +/- 1.3 years, height = 182.5 +/- 5.9 cm, weight = 85.4 +/- 15.5 kg, experience = 14.4 +/- 1.7 years) of a varsity baseball team at a National Collegiate Athletic Association Division II school. The Jamar hand dynamometer was used to test grip strength, and the SETPRO Rookie was used to measure instantaneous bat velocity at the point of contact with the ball. Subjects were randomly divided into an experimental group and a control group. For 6 weeks, both groups participated in their usual baseball practice sessions, but the experimental group also performed extra forearm and grip strengthening exercises, whereas the control group did not. Pretest and posttest correlations between grip strength and bat velocity revealed no significant relationship between grip strength and bat velocity (pretest r = 0.054, p = 0.807; posttest r = 0.315, p = 0.145). A dependent t-test performed on all subjects revealed that a significant (p = 0.001) increase in bat velocity did occur over the course of the study. A covariate analysis, employing pretest bat velocity as the covariate, revealed no significant difference (p = 0.795) in posttest bat velocity scores between the experimental and control groups. Thus, increases in bat velocity occurred, but the differences were similar for both the experimental and control groups. The findings of this study suggest that grip strength and bat velocity are not significantly related, and that the allocation of time and energy for added training

  7. Comparison of effectiveness of convection-, transpiration-, and film-cooling methods with air as coolant

    NASA Technical Reports Server (NTRS)

    Eckert, E R G; Livingood, N B

    1954-01-01

    Various parts of aircraft propulsion engines that are in contact with hot gases often require cooling. Transpiration and film cooling, new methods that supposedly utilize cooling air more effectively than conventional convection cooling, have already been proposed. This report presents material necessary for a comparison of the cooling requirements of these three methods. Correlations that are regarded by the authors as the most reliable today are employed in evaluating each of the cooling processes. Calculations for the special case in which the gas velocity is constant along the cooled wall (flat plate) are presented. The calculations reveal that a comparison of the three cooling processes can be made on quite a general basis. The superiority of transpiration cooling is clearly shown for both laminar and turbulent flow. This superiority is reduced when the effects of radiation are included; for gas-turbine blades, however, there is evidence indicating that radiation may be neglected.

  8. Health effects of SRS non-radiological air emissions

    SciTech Connect

    Stewart, J.

    1997-06-16

    This report examines the potential health effects of non radiological emissions to the air resulting from operations at the Savannah River Site (SRS). The scope of this study was limited to the 55 air contaminants for which the US Environmental Protection Agency (EPA) has quantified risk by determining unit risk factors (excess cancer risks) and/or reference concentrations (deleterious non cancer risks). Potential health impacts have been assessed in relation to the maximally exposed individual. This is a hypothetical person who resides for a lifetime at the SRS boundary. The most recent (1994) quality assured SRS emissions data available were used. Estimated maximum site boundary concentrations of the air contaminants were calculated using air dispersion modeling and 24-hour and annual averaging times. For the emissions studied, the excess cancer risk was found to be less than the generally accepted risk level of 1 in 100,000 and, in most cases, was less than 1 in 1,000,000. Deleterious non cancer effects were also found to be very unlikely.

  9. Air pollutant effects on fetal and early postnatal development.

    PubMed

    Wang, Lei; Pinkerton, Kent E

    2007-09-01

    Numerical research on the health effects of air pollution has been published in the last decade. Epidemiological studies have shown that children's exposure to air pollutants during fetal development and early postnatal life is associated with many types of health problems including abnormal development (low birth weight [LBW], very low birth weight [VLBW], preterm birth [PTB], intrauterine growth restriction [IUGR], congenital defects, and intrauterine and infant mortality), decreased lung growth, increased rates of respiratory tract infections, childhood asthma, behavioral problems, and neurocognitive decrements. This review focuses on the health effects of major outdoor air pollutants including particulates, carbon monoxide (CO), sulfur and nitrogen oxides (SO(2), NOx), ozone, and one common indoor air pollutant, environmental tobacco smoke (ETS). Animal data is presented that demonstrate perinatal windows of susceptibility to sidestream smoke, a surrogate for ETS, resulting in altered airway sensitivity and cell type frequency. A study of neonatal monkeys exposed to sidestream smoke during the perinatal period and/or early postnatal period that resulted in an altered balance of Th1-/Th2-cytokine secretion, skewing the immune response toward the allergy-associated Th2 cytokine phenotype, is also discussed. PMID:17963272

  10. Measured Air Distribution Effectiveness for Residential Mechanical Ventilation Systems

    SciTech Connect

    Sherman, Max; Sherman, Max H.; Walker, Iain S.

    2008-05-01

    The purpose of ventilation is dilute or remove indoor contaminants that an occupant is exposed to. In a multi-zone environment such as a house, there will be different dilution rates and different source strengths in every zone. Most US homes have central HVAC systems, which tend to mix the air thus the indoor conditions between zones. Different types of ventilation systems will provide different amounts of exposure depending on the effectiveness of their air distribution systems and the location of sources and occupants. This paper will report on field measurements using a unique multi-tracer measurement system that has the capacity to measure not only the flow of outdoor air to each zone, but zone-to-zone transport. The paper will derive seven different metrics for the evaluation of air distribution. Measured data from two homes with different levels of natural infiltration will be used to evaluate these metrics for three different ASHRAE Standard 62.2 compliant ventilation systems. Such information can be used to determine the effectiveness of different systems so that appropriate adjustments can be made in residential ventilation standards such as ASHRAE Standard 62.2.

  11. Effect of source parameters on forward-directivity velocity pulse for vertical strike slip fault in half space

    NASA Astrophysics Data System (ADS)

    Liu, Qifang; Yuan, Yifan; Jin, Xing

    2006-06-01

    It has been found that the large velocity pulse is one of the most important characteristics of near-fault strong ground motions. Some statistical relationships between pulse period and the moment magnitude for near-fault strong ground motions have been established by Somerville (1998); Alavi and Krawinkler (2000); and Mavroeidis and Papageorgiou (2003), where no variety of rupture velocity, fault depth, and fault distance, etc. were considered. Since near-fault ground motions are significantly influenced by the rupture process and source parameters, the effects of some source parameters on the amplitude and the period of a forward-directivity velocity pulse in a half space are analyzed by the finite difference method combined with the kinematic source model in this paper. The study shows that the rupture velocity, fault depth, position of the initial rupture point and distribution of asperities are the most important parameters to the velocity pulse. Generally, the pulse period decreases and the pulse amplitude increases as the rupture velocity increases for shallow crustal earthquakes. In a definite region besides the fault trace, the pulse period increases as the fault depth increases. For a uniform strike slip fault, rupture initiating from one end of a fault and propagating to the other always generates a higher pulse amplitude and longer pulse period than in other cases.

  12. Position-dependent velocity of an effective temperature point for the estimation of the thermal diffusivity of solids

    NASA Astrophysics Data System (ADS)

    Balachandar, Settu; Shivaprakash, N. C.; Kameswara Rao, L.

    2016-01-01

    A new approach is proposed to estimate the thermal diffusivity of optically transparent solids at ambient temperature based on the velocity of an effective temperature point (ETP), and by using a two-beam interferometer the proposed concept is corroborated. 1D unsteady heat flow via step-temperature excitation is interpreted as a ‘micro-scale rectilinear translatory motion’ of an ETP. The velocity dependent function is extracted by revisiting the Fourier heat diffusion equation. The relationship between the velocity of the ETP with thermal diffusivity is modeled using a standard solution. Under optimized thermal excitation, the product of the ‘velocity of the ETP’ and the distance is a new constitutive equation for the thermal diffusivity of the solid. The experimental approach involves the establishment of a 1D unsteady heat flow inside the sample through step-temperature excitation. In the moving isothermal surfaces, the ETP is identified using a two-beam interferometer. The arrival-time of the ETP to reach a fixed distance away from heat source is measured, and its velocity is calculated. The velocity of the ETP and a given distance is sufficient to estimate the thermal diffusivity of a solid. The proposed method is experimentally verified for BK7 glass samples and the measured results are found to match closely with the reported value.

  13. Effects of Current Velocity, Particle Size, and Substrate Heterogeneity on Crayfish (Orconectes propinquus) Activity

    NASA Astrophysics Data System (ADS)

    Clark, J. M.; Kershner, M. W.

    2005-05-01

    The use of flow refugia (e.g., substrate) by lotic invertebrates often increases their likelihood of survival during flood events. Movement to potential refugia becomes risky as velocities increase, and the range of velocities that benthic invertebrates can withstand is variable. In this study, activity time and slip velocities of small [carapace length (CL)=10-20 mm] and large (CL=20-30 mm) Orconectes propinquus were measured in an artificial flume across ranges of current velocity and substrate heterogeneity. Particle sizes included small pebbles (16-32 mm), large pebbles (32-64 mm), and small cobble (64-128 mm). Water velocity was increased by 0.1 m/s increments from 0.1-1.5 m/s at 5-minute intervals or until the crayfish was dislodged from the substrate. As current velocity increased, the probability of slipping increased for all crayfish. Regardless of the degree of substrate heterogeneity, small crayfish held their position at higher velocities than large crayfish and were also less active. Slip rates were generally lower for both sizes as substrate heterogeneity increased. Essentially, the availability and probability of finding refugia increased with increased habitat heterogeneity and allowed crayfish to avoid being swept into the drift.

  14. Lattice models for granular-like velocity fields: finite-size effects

    NASA Astrophysics Data System (ADS)

    Plata, C. A.; Manacorda, A.; Lasanta, A.; Puglisi, A.; Prados, A.

    2016-09-01

    Long-range spatial correlations in the velocity and energy fields of a granular fluid are discussed in the framework of a 1d lattice model. The dynamics of the velocity field occurs through nearest-neighbour inelastic collisions that conserve momentum but dissipate energy. A set of equations for the fluctuating hydrodynamics of the velocity and energy mesoscopic fields give a first approximation for (i) the velocity structure factor and (ii) the finite-size correction to the Haff law, both in the homogeneous cooling regime. At a more refined level, we have derived the equations for the two-site velocity correlations and the total energy fluctuations. First, we seek a perturbative solution thereof, in powers of the inverse of system size. On the one hand, when scaled with the granular temperature, the velocity correlations tend to a stationary value in the long time limit. On the other hand, the scaled standard deviation of the total energy diverges, that is, the system shows multiscaling. Second, we find an exact solution for the velocity correlations in terms of the spectrum of eigenvalues of a certain matrix. The results of numerical simulations of the microscopic model confirm our theoretical results, including the above described multiscaling phenomenon.

  15. The effect of prolonged exposure to 750 C air on the tribological performance of PM212

    NASA Technical Reports Server (NTRS)

    Bemis, Kirk; Bogdanski, Michael S.; Dellacorte, Christopher; Sliney, Harold E.

    1994-01-01

    The effect of prolonged exposure to 750 C air on the tribological performance and dimensional stability of PM212, a high temperature, self-lubricating composite, is studied. PM212, by weight, contains 70 percent metal-bonded Cr3C2, 15 percent BaF2/CaF2 eutectic, and 15 percent silver. Rub blocks were fabricated from PM212 by cold isostatic pressing followed by sintering. Prior to tribo-testing, the rub blocks were exposed to 750 C air for periods ranging from 100 to 1000 hours. Then, the rub blocks were slid against nickel-based superalloy disks in a double-rub-block tribometer in air under a 66 N load at temperatures from 25 to 750 C with a sliding velocity of 0.36 m/s. Unexposed rub blocks were tested for baseline comparison. Friction coefficients ranged from 0.24 to 0.37 for the unexposed rub blocks and from 0.32 to 0.56 for the exposed ones. Wear for both the composite blocks and superalloy disks was typically in the moderate to low range of 10(exp -5) to 10(exp -6) mm(exp 3)/N-m. Friction and wear data were similar for the rub blocks exposed for 100, 500, and 1000 hours. Prolonged exposure to 750 C air increased friction and wear of the PM212 rub blocks at room temperature, but their triboperformance remained unaffected at higher temperatures, probably due to the formation of lubricious metal oxides. Dimensional stability of the composite was studied by exposing specimens of varying thicknesses for 500 hours in air at 750 C. Block thicknesses were found to increase with increased exposure time until steady state was reached after 100 hours of exposure, probably due to oxidation.

  16. Effect of Intake Air Filter Condition on Vehicle Fuel Economy

    SciTech Connect

    Norman, Kevin M; Huff, Shean P; West, Brian H

    2009-02-01

    The U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy and the U.S. Environmental Protection Agency (EPA) jointly maintain a fuel economy website (www.fueleconomy.gov), which helps fulfill their responsibility under the Energy Policy Act of 1992 to provide accurate fuel economy information [in miles per gallon (mpg)] to consumers. The site provides information on EPA fuel economy ratings for passenger cars and light trucks from 1985 to the present and other relevant information related to energy use such as alternative fuels and driving and vehicle maintenance tips. In recent years, fluctuations in the price of crude oil and corresponding fluctuations in the price of gasoline and diesel fuels have renewed interest in vehicle fuel economy in the United States. (User sessions on the fuel economy website exceeded 20 million in 2008 compared to less than 5 million in 2004 and less than 1 million in 2001.) As a result of this renewed interest and the age of some of the references cited in the tips section of the website, DOE authorized the Oak Ridge National Laboratory (ORNL) Fuels, Engines, and Emissions Research Center (FEERC) to initiate studies to validate and improve these tips. This report documents a study aimed specifically at the effect of engine air filter condition on fuel economy. The goal of this study was to explore the effects of a clogged air filter on the fuel economy of vehicles operating over prescribed test cycles. Three newer vehicles (a 2007 Buick Lucerne, a 2006 Dodge Charger, and a 2003 Toyota Camry) and an older carbureted vehicle were tested. Results show that clogging the air filter has no significant effect on the fuel economy of the newer vehicles (all fuel injected with closed-loop control and one equipped with MDS). The engine control systems were able to maintain the desired AFR regardless of intake restrictions, and therefore fuel consumption was not increased. The carbureted engine did show a decrease in

  17. LOW VELOCITY ZONE AND TOPOGRAPHY AS A SOURCE OF SITE AMPLIFICATION EFFECT ON TARZANA HILL, CALIFORNIA

    NASA Astrophysics Data System (ADS)

    Graizer, V.

    2009-12-01

    Significantly amplified ground accelerations at the Tarzana Hill station were recorded during the 1987 Mw 5.9 Whittier Narrows, the 1994 Mw 6.7 Northridge and the 1999 Mw 7.1 Hector Mine earthquakes. Peak horizontal ground acceleration at the Tarzana station during the Northridge earthquake reached 1.93 g and is considered to be one of the largest ever recorded acceleration. Explanations of the strong-site amplification effect vary significantly from directional topographic effect and unusual Poisson’s ratio to the resonant sliding block. Despite all these efforts none of the above-mentioned studies came up with completely conclusive explanation of the source of the site amplification that produces unusually large motions at Tarzana. Tarzana station is located in the foothills of the Santa Monica Mountains in California near the crest of a low (< 20 m) natural hill with gentle slopes. The hill is about 500 m in length by 130 m in width and is formed of extremely weathered shale at the surface to fresh at depth. Average S-wave velocity is about 250 m/sec in the top 17-18 m, and S- and P-wave velocities significantly increase below this depth. According to the NEHRP classification based on Vs30 ~ 300 m/sec it is a site class D. Strong-motion instrumentation at Tarzana consisted of an accelerograph at the top of the hill, a downhole instrument at 60 m depth, and an accelerograph at the base of the hill. More than twenty earthquakes were recorded by at least three instruments at Tarzana from 1998 till 2003. Comparisons of recordings and Fourier spectra indicate strong directional resonance in a direction perpendicular to the strike of the hill. The dominant peaks in ground motion amplification on the top of the hill relative to the base are at frequencies ~ 3.6 Hz and 8-9 Hz for the horizontal components. Our hypothesis is that the hill acts like a wave trap. This results in an amplification at predominant frequencies f = V/4h (h is layer’s thickness) at f ~ 3.6 Hz

  18. Effects of Bed Rest on Conduction Velocity of the Triceps Surae Stretch Reflex and Postural Control

    NASA Technical Reports Server (NTRS)

    Reschke, M. F.; Wood, S. J.; Cerisano, J. M.; Kofman, I. S.; Fisher, E. A.; Esteves, J. T.; Taylor, L. C.; DeDios, Y. E.; Harm, D. L.

    2011-01-01

    Despite rigorous exercise and nutritional management during space missions, astronauts returning from microgravity exhibit neuromuscular deficits and a significant loss in muscle mass in the postural muscles of the lower leg. Similar changes in the postural muscles occur in subjects participating in long-duration bed rest studies. These adaptive muscle changes manifest as a reduction in reflex conduction velocity during head-down bed rest. Because the stretch reflex encompasses both the peripheral (muscle spindle and nerve axon) and central (spinal synapse) components involved in adaptation to calf muscle unloading, it may be used to provide feedback on the general condition of neuromuscular function, and might be used to evaluate the effectiveness of countermeasures aimed at preserving muscle mass and function during periods of unloading. Stretch reflexes were measured on 18 control subjects who spent 60 to 90 days in continuous 6 deg head-down bed rest. Using a motorized system capable of rotating the foot around the ankle joint (dorsiflexion) through an angle of 10 degrees at a peak velocity of about 250 deg/sec, a stretch reflex was recorded from the subject's left triceps surae muscle group. Using surface electromyography, about 300 reflex responses were obtained and ensemble-averaged on 3 separate days before bed rest, 3 to 4 times in bed, and 3 times after bed rest. The averaged responses for each test day were examined for reflex latency and conduction velocity (CV) across gender. Computerized posturography was also conducted on these same subjects before and after bed rest as part of the standard measures. Peak-to-peak sway was measured during Sensory Organization Tests (SOTs) to evaluate changes in the ability to effectively use or suppress visual, vestibular, and proprioceptive information for postural control. Although no gender differences were found, a significant increase in reflex latency and a significant decrease in CV were observed during the bed

  19. Plasma screening effects on the energies of hydrogen atom under the influence of velocity-dependent potential

    SciTech Connect

    Bahar, M. K.

    2014-07-15

    In order to examine the plasma screening and velocity-dependent potential effects on the hydrogen atom, the Schrödinger equation including a more general exponential cosine screened Coulomb and velocity-dependent potential is solved numerically in the framework asymptotic iteration method. The more general exponential cosine screened Coulomb potential is used to model Debye and quantum plasma for the specific values of the parameters in its structure. However, in order to examine effects of velocity-dependent potential on energy values of hydrogen atom in Debye and quantum plasma, the isotropic form factor of velocity-dependent potential is given as harmonic oscillator type, ρ(r)=ρ{sub o}r{sup 2}. Then, the energies of s and p states are calculated numerically without any approximation. In order to investigate thoroughly plasma screening effects and contribution of velocity-dependent potential on energy values of hydrogen atom, the corresponding calculations are carried out by using different values of parameters of more general exponential cosine screened Coulomb potential and isotropic dependence, results of which are discussed.

  20. Modeling the effect of varying swim speeds on fish passage through velocity barriers

    USGS Publications Warehouse

    Castro-Santos, T.

    2006-01-01

    The distance fish can swim through zones of high-velocity flow is an important factor limiting the distribution and conservation of riverine and diadromous fishes. Often, these barriers are characterized by nonuniform flow conditions, and it is likely that fish will swim at varying speeds to traverse them. Existing models used to predict passage success, however, typically include the unrealistic assumption that fish swim at a constant speed regardless of the speed of flow. This paper demonstrates how the maximum distance of ascent through velocity barriers can be estimated from the swim speed-fatigue time relationship, allowing for variation in both swim speed and water velocity.

  1. Carbonate pore system evaluation using the velocity-porosity-pressure relationship, digital image analysis, and differential effective medium theory

    NASA Astrophysics Data System (ADS)

    Lima Neto, Irineu A.; Misságia, Roseane M.; Ceia, Marco A.; Archilha, Nathaly L.; Oliveira, Lucas C.

    2014-11-01

    Carbonate reservoirs exhibit heterogeneous pore systems and a wide variety of grain types, which affect the rock's elastic properties and the reservoir parameter relationships. To study the Albian carbonates in the Campos Basin, a methodology is proposed to predict the amount of microporosity and the representative aspect ratio of these inclusions. The method assumes three pore-space scales in two representative inclusion scenarios: 1) a macro-mesopore median aspect ratio from the thin-section digital image analysis (DIA) and 2) a microporosity aspect ratio predicted based on the measured P-wave velocities. Through a laboratory analysis of 10 grainstone core samples of the Albian age, the P- and S-wave velocities (Vp and Vs) are evaluated at effective pressures of 0-10 MPa. The analytical theories in the proposed methodology are functions of the aspect ratios from the differential effective medium (DEM) theory, the macro-mesopore system recognized from the DIA, the amount of microporosity determined by the difference between the porosities estimated from laboratorial helium-gas and the thin-section petrographic images, and the P-wave velocities under dry effective pressure conditions. The DIA procedure is applied to estimate the local and global parameters, and the textural implications concerning ultrasonic velocities and image resolution. The macro-mesopore inclusions contribute to stiffer rocks and higher velocities, whereas the microporosity inclusions contribute to softer rocks and lower velocities. We observe a high potential for this methodology, which uses the microporosity aspect ratio inverted from Vp to predict Vs with a good agreement. The results acceptably characterize the Albian grainstones. The representative macro-mesopore aspect ratio is 0.5, and the inverted microporosity aspect ratio ranges from 0.01 to 0.07. The effective pressure induced an effect of slight porosity reduction during the triaxial tests, mainly in the microporosity inclusions

  2. Effect of air pollution on athlete health and performance.

    PubMed

    Rundell, Kenneth William

    2012-05-01

    Unfavourable effects on the respiratory and the cardiovascular systems from short-term and long-term inhalation of air pollution are well documented. Exposure to freshly generated mixed combustion emissions such as those observed in proximity to roadways with high volumes of traffic and those from ice-resurfacing equipment are of particular concern. This is because there is a greater toxicity from freshly generated whole exhaust than from its component parts. The particles released from emissions are considered to cause oxidative damage and inflammation in the airways and the vascular system, and may be related to decreased exercise performance. However, few studies have examined this aspect. Several papers describe deleterious effects on health from chronic and acute air pollution exposure. However, there has been no research into the effects of long-term exposure to air pollution on athletic performance and a paucity of studies that describe the effects of acute exposure on exercise performance. The current knowledge of exercising in the high-pollution environment and the consequences that it may have on athlete performance are reviewed.

  3. The effect of wind velocity on transpiration in a mixed broadleaved deciduous forest

    NASA Astrophysics Data System (ADS)

    Kim, D.; Oren, R.; Oishi, A. C.; Hsieh, C.; Phillips, N. G.; Novick, K. A.; Stoy, P. C.

    2013-12-01

    Wind velocity (U) within and above forest canopies can alter the coupling between the vapor-saturated sub-stomatal airspace and the drier atmosphere aloft, thereby influencing transpiration rates. In practice, however, the actual increase in transpiration with increasing U depends on the aerodynamic resistance (RA) to vapor transfer compared to canopy resistance to water vapor flux out of leaves (RC, dominated by stomatal resistance, Rstom), and the rate at which RA decreases with increasing U. We investigated the effect of U on transpiration at the canopy scale using filtered meteorological data and sap flux measurements gathered from six diverse species of a mature broadleaved deciduous forest. Only under high light conditions, stand transpiration (EC) increased slightly (6.5%) with increasing U ranging from ~0.7 to ~4.7 m s-1. Under other conditions, sap flux density (Js) and EC responded weakly or did not change with U. RA, estimated from Monin-Obukhov similarity theory, decreased with increasing U, but this decline was offset by increasing RC, estimated from a rearranged Penman-Monteith equation, due to a concurrent increase in vapor pressure deficit (D). The increase of RC with D over the observed range of U was consistent with increased Rstom by ~40% based on hydraulic theory. Except for very rare half-hourly values, the proportion of RA to total resistance (RT) remained < 15% over the observed range of conditions. These results suggest that in similar forests and conditions, accounting for the effects of U-D relationship on Rstom would reduce the uncertainty of modeling canopy gas exchange more than accounting for the direct effect of U on RA.

  4. Effect of Axial Velocity Density Ratio on the Performance of a Controlled Diffusion Airfoil Compressor Cascade

    NASA Astrophysics Data System (ADS)

    Senthil Kumaran, R.; Kamble, Sachin; Swamy, K. M. M.; Nagpurwala, Q. H.; Bhat, Ananthesha

    2015-12-01

    Axial Velocity Density Ratio (AVDR) is an important parameter to check the two-dimensionality of cascade flows. It can have significant influence on the cascade performance and the secondary flow structure. In the present study, the effect of AVDR has been investigated on a highly loaded Controlled Diffusion airfoil compressor cascade. Detailed 3D Computational Fluid Dynamics (CFD) studies were carried out with the cascade at five different AVDRs. Key aerodynamic performance parameters and flow structure through the cascade were analyzed in detail. CFD results of one AVDR were validated with the experimental cascade test data and were seen to be in good agreement. Loss characteristics of the cascade varied significantly with change in AVDR. Increase in AVDR postponed the point of separation on the suction surface, produced thinner boundary layers and caused substantial drop in the pressure loss coefficient. Strong end wall vortices were noticed at AVDR of 1.177. At higher AVDRs, the flow was well guided even close to the end wall and the secondary flows diminished. The loading initially improved with increase in AVDR. Beyond a certain limit, further increase in AVDR offered no improvements to the loading but rather resulted in drop in diffusion and deviation.

  5. Effect of velocity ratio on coherent-structure dynamics in turbulent free shear layers

    NASA Astrophysics Data System (ADS)

    Suryanarayanan, Saikishan; Narasimha, Roddam

    2014-11-01

    The relevance of the vortex-gas model to the large scale dynamics of temporally evolving turbulent free shear layers has been established by extensive simulations (Phys. Rev. E 89, 013009 (2014)). The effects of velocity ratio (r =U2 /U1) on shear layer dynamics are revealed by spatially evolving vortex-gas shear-layer simulations using a computational model based on Basu et al. (Appl. Math. Modelling 19, (1995)), but with a crucial improvement that ensures conservation of global circulation. The simulations show that the initial conditions and downstream boundaries can significantly affect the flow over substantial part of the domain, but the equilibrium spread rate is a universal function of r, and is within the experimental scatter. The spread in the r = 0 limit is higher than Galilean-transformed temporal value. The present 2D simulations at r = 0 show continuous growth of structures, while merger-dominated evolution is observed for r = 0 . 23 (and higher). These two mechanisms were observed across the same two values of r in the experiments of D'Ovidio & Coats (J. Fluid Mech. 737, 2013), but the continuous growth was instead attributed to mixing-transition and 3D. The 2D mechanisms responsible for the observed continuous growth of structures are analyzed in detail. Supported in part by RN/Intel/4288 and RN/DRDO/4124.

  6. Potential effects of the spin crossover transition in ferropericlase on mantle velocities

    NASA Astrophysics Data System (ADS)

    da Silva, C.; Wentzcovitch, R.; Wu, Z.; Justo, J.

    2008-12-01

    The thermoelastic properties of ferropericlase Mg1-xFexO (x = 0.1875) throughout the iron spin crossover have been investigated by first principles at Earth's lower mantle conditions. The transition has important consequences for the elasticity such as a substantial bulk modulus reduction. At room temperature the transition is quite sharp in pressure but broadens with increasing temperature. Along a typical geotherm the transition should occur across most of the lower mantle with a more significant bulk modulus reduction around 1400-1600 km depth. This crossover transition is yet another ingredient, in addition to changes in temperature, chemical composition, and mineralogy that can introduce velocity heterogeneities in the mantle. We compare predictions of the effect of this spin transition alone on the elastic properties of homogeneous aggregates with the elastic properties of the lower mantle extracted from seismic tomography and PREM. Research supported by NSF/EAR 0635990, and NSF/ITR 0428774 (VLab). Computations were performed at the Minnesota Supercomputing Institute.

  7. Quantitative Evaluation of Ground Sensing Based Cloud Velocity Derivation Methods and Their Effects on Solar Irradiance Forecast

    NASA Astrophysics Data System (ADS)

    Chu, Y.; Coimbra, C. F.

    2013-12-01

    Clouds play a key role in the radiative balance of Earth's atmosphere and cause variability of the solar energy resource, which is one of the critical obstacles for achieving higher solar penetration into the power grid. To mitigate the effects of solar resource uncertainty, short-term forecast models based on local sensing are developed. Cloud movement vectors, which are obtained by analyzing consecutive image frames, are essential inputs to these forecast models. However, the accuracy of the cloud velocity detection algorithms and its effects on the fidelity of the solar forecast system have not been investigated in depth. The performance of several commonly used cloud velocity derivation methods and their impact on direct normal irradiance (DNI) forecasts are quantitatively studied in this work. The main methods under study include the cross-correlation method, particle image velocimetry, optical flow methods, SIFT key points method, and a square sector method developed by our group. Sequences of whole sky images taken from the ground for sixteen selected days are used for performance assessment. These are captured over one minute intervals by a fish-eye network camera at one of our observatories in Folsom, CA. Cloud velocities are assessed by comparing algorithm-derived velocity with velocities identified manually from the images. The cloud velocity detection methods is integrated with a grid-cloud-fraction method to produce DNI forecasts for ten-minute horizons. Imaging and irradiance measurements for a period of one month are used to analyze statistically the impact of cloud velocity determination on the accuracy of DNI forecasts, which is quantified in terms of mean bias, root mean square error, and forecasting skill over persistence.

  8. Climate Change and Air Pollution: Effects on Respiratory Allergy.

    PubMed

    D'Amato, Gennaro; Pawankar, Ruby; Vitale, Carolina; Lanza, Maurizia; Molino, Antonio; Stanziola, Anna; Sanduzzi, Alessandro; Vatrella, Alessandro; D'Amato, Maria

    2016-09-01

    A body of evidence suggests that major changes involving the atmosphere and the climate, including global warming induced by anthropogenic factors, have impact on the biosphere and human environment. Studies on the effects of climate change on respiratory allergy are still lacking and current knowledge is provided by epidemiological and experimental studies on the relationship between allergic respiratory diseases, asthma and environmental factors, such as meteorological variables, airborne allergens, and air pollution. Urbanization with its high levels of vehicle emissions, and a westernized lifestyle are linked to the rising frequency of respiratory allergic diseases and bronchial asthma observed over recent decades in most industrialized countries. However, it is not easy to evaluate the impact of climate changes and air pollution on the prevalence of asthma in the general population and on the timing of asthma exacerbations, although the global rise in asthma prevalence and severity could also be an effect of air pollution and climate change. Since airborne allergens and air pollutants are frequently increased contemporaneously in the atmosphere, an enhanced IgE-mediated response to aeroallergens and enhanced airway inflammation could account for the increasing frequency of respiratory allergy and asthma in atopic subjects in the last 5 decades. Pollen allergy is frequently used to study the relationship between air pollution and respiratory allergic diseases, such as rhinitis and bronchial asthma. Epidemiologic studies have demonstrated that urbanization, high levels of vehicle emissions, and westernized lifestyle are correlated with an increased frequency of respiratory allergy prevalently in people who live in urban areas in comparison with people living in rural areas. Climatic factors (temperature, wind speed, humidity, thunderstorms, etc.) can affect both components (biological and chemical) of this interaction.

  9. Climate Change and Air Pollution: Effects on Respiratory Allergy.

    PubMed

    D'Amato, Gennaro; Pawankar, Ruby; Vitale, Carolina; Lanza, Maurizia; Molino, Antonio; Stanziola, Anna; Sanduzzi, Alessandro; Vatrella, Alessandro; D'Amato, Maria

    2016-09-01

    A body of evidence suggests that major changes involving the atmosphere and the climate, including global warming induced by anthropogenic factors, have impact on the biosphere and human environment. Studies on the effects of climate change on respiratory allergy are still lacking and current knowledge is provided by epidemiological and experimental studies on the relationship between allergic respiratory diseases, asthma and environmental factors, such as meteorological variables, airborne allergens, and air pollution. Urbanization with its high levels of vehicle emissions, and a westernized lifestyle are linked to the rising frequency of respiratory allergic diseases and bronchial asthma observed over recent decades in most industrialized countries. However, it is not easy to evaluate the impact of climate changes and air pollution on the prevalence of asthma in the general population and on the timing of asthma exacerbations, although the global rise in asthma prevalence and severity could also be an effect of air pollution and climate change. Since airborne allergens and air pollutants are frequently increased contemporaneously in the atmosphere, an enhanced IgE-mediated response to aeroallergens and enhanced airway inflammation could account for the increasing frequency of respiratory allergy and asthma in atopic subjects in the last 5 decades. Pollen allergy is frequently used to study the relationship between air pollution and respiratory allergic diseases, such as rhinitis and bronchial asthma. Epidemiologic studies have demonstrated that urbanization, high levels of vehicle emissions, and westernized lifestyle are correlated with an increased frequency of respiratory allergy prevalently in people who live in urban areas in comparison with people living in rural areas. Climatic factors (temperature, wind speed, humidity, thunderstorms, etc.) can affect both components (biological and chemical) of this interaction. PMID:27334776

  10. Climate Change and Air Pollution: Effects on Respiratory Allergy

    PubMed Central

    Pawankar, Ruby; Vitale, Carolina; Lanza, Maurizia; Molino, Antonio; Stanziola, Anna; Sanduzzi, Alessandro; Vatrella, Alessandro; D'Amato, Maria

    2016-01-01

    A body of evidence suggests that major changes involving the atmosphere and the climate, including global warming induced by anthropogenic factors, have impact on the biosphere and human environment. Studies on the effects of climate change on respiratory allergy are still lacking and current knowledge is provided by epidemiological and experimental studies on the relationship between allergic respiratory diseases, asthma and environmental factors, such as meteorological variables, airborne allergens, and air pollution. Urbanization with its high levels of vehicle emissions, and a westernized lifestyle are linked to the rising frequency of respiratory allergic diseases and bronchial asthma observed over recent decades in most industrialized countries. However, it is not easy to evaluate the impact of climate changes and air pollution on the prevalence of asthma in the general population and on the timing of asthma exacerbations, although the global rise in asthma prevalence and severity could also be an effect of air pollution and climate change. Since airborne allergens and air pollutants are frequently increased contemporaneously in the atmosphere, an enhanced IgE-mediated response to aeroallergens and enhanced airway inflammation could account for the increasing frequency of respiratory allergy and asthma in atopic subjects in the last 5 decades. Pollen allergy is frequently used to study the relationship between air pollution and respiratory allergic diseases, such as rhinitis and bronchial asthma. Epidemiologic studies have demonstrated that urbanization, high levels of vehicle emissions, and westernized lifestyle are correlated with an increased frequency of respiratory allergy prevalently in people who live in urban areas in comparison with people living in rural areas. Climatic factors (temperature, wind speed, humidity, thunderstorms, etc.) can affect both components (biological and chemical) of this interaction. PMID:27334776

  11. Stabilization effect of multiple drivers' desired velocities in car-following theory

    NASA Astrophysics Data System (ADS)

    Zhang, Geng; Zhao, Min; Sun, Di-Hua; Liu, Wei-Ning; Li, Hua-Min

    2016-01-01

    In order to reveal the influence of driver's individual behavior on traffic flow more accurately, a new car-following model is proposed with consideration of multiple drives' desired velocities. The stability criterion of the new model is derived through linear stability theory and the results show that the current driver's desired velocity can stabilize traffic flow but the preceding driver's desired velocity can damage traffic stability. Through nonlinear analysis, the traffic jamming transition characteristics near the critical point can be described by the kink-antikink soliton of the mKdV equation. Numerical simulation confirms the analytical results, which shows that the multiple drivers' desired velocities play an important role in traffic evolution.

  12. Analysis of wind velocity and release angle effects on discus throw using computational fluid dynamics.

    PubMed

    Rouboa, Abel I; Reis, Victor M; Mantha, Vishveshwar R; Marinho, Daniel A; Silva, António J

    2013-01-01

    The aim of this paper is to study the aerodynamics of discus throw. A comparison of numerical and experimental performance of discus throw with and without rotation was carried out using the analysis of lift and drag coefficients. Initial velocity corresponding to variation angle of around 35.5° was simulated. Boundary condition, on the top and bottom boundary edges of computational domain, was imposed in order to eliminate external influences on the discus; a wind resistance was calculated for the velocity values of 25 and 27 m/s. The results indicate that the flight distance (D) was strongly affected by the drag coefficient, the initial velocity, the release angle and the direction of wind velocity. It was observed that these variables change as a function of discus rotation. In this study, results indicate a good agreement of D between experimental values and numerical results.

  13. Effect of surface thickness on the wetting front velocity during jet impingement surface cooling

    NASA Astrophysics Data System (ADS)

    Agrawal, Chitranjan; Gotherwal, Deepesh; Singh, Chandradeep; Singh, Charan

    2016-06-01

    A hot stainless steel (SS-304) surface of 450 ± 10 °C initial temperature is cooled with a normally impinging round water jet. The experiments have been performed for the surface of different thickness e.g. 1, 2, 3 mm and jet Reynolds number in the range of Re = 26,500-48,000. The cooling performance of the hot test surface is evaluated on the basis of wetting front velocity. The wetting front velocity is determined for 10-40 mm downstream spatial locations away from the stagnation point. It has been observed that the wetting front velocity increase with the rise in jet flow rate, however, diminishes towards the downstream spatial location and with the rise in surface thickness. The proposed correlation for the dimensionless wetting front velocity predicts the experimental data well within the error band of ±30 %, whereas, 75 % of experimental data lies within the range of ±20 %.

  14. Effectiveness of national air pollution control policies on the air quality in metropolitan areas of China.

    PubMed

    Wang, Shuxiao; Xing, Jia; Zhao, Bin; Jang, Carey; Hao, Jiming

    2014-01-01

    Understanding the effectiveness of national air pollution controls is important for control policy design to improve the future air quality in China. This study evaluated the effectiveness of major national control policies implemented recently in China through a modeling analysis. The sulfur dioxide (SO2) control policy during the 11th Five Year Plan period (2006-2010) had succeeded in reducing the national SO2 emission in 2010 by 14% from its 2005 level, which correspondingly reduced ambient SO2 and sulfate (SO4(2-)) concentrations by 13%-15% and 8%-10% respectively over east China. The nitrogen oxides (NO(x)) control policy during the 12th Five Year Plan period (2011-2015) targets the reduction of the national NO(x) emission in 2015 by 10% on the basis of 2010. The simulation results suggest that such a reduction in NO(x) emission will reduce the ambient nitrogen dioxide (NO2), nitrate (NO3(-)), 1-hr maxima ozone (O3) concentrations and total nitrogen deposition by 8%, 3%-14%, 2% and 2%-4%, respectively over east China. The application of new emission standards for power plants will further reduce the NO2, NO3(-), 1-hr maxima O(3 concentrations and total nitrogen deposition by 2%-4%, 1%-6%, 0-2% and 1%-2%, respectively. Sensitivity analysis was conducted to evaluate the inter-provincial impacts of emission reduction in Beijing-Tianjin-Hebei and the Yangtze River Delta, which indicated the need to implement joint regional air pollution control.

  15. Effectiveness of national air pollution control policies on the air quality in metropolitan areas of China.

    PubMed

    Wang, Shuxiao; Xing, Jia; Zhao, Bin; Jang, Carey; Hao, Jiming

    2014-01-01

    Understanding the effectiveness of national air pollution controls is important for control policy design to improve the future air quality in China. This study evaluated the effectiveness of major national control policies implemented recently in China through a modeling analysis. The sulfur dioxide (SO2) control policy during the 11th Five Year Plan period (2006-2010) had succeeded in reducing the national SO2 emission in 2010 by 14% from its 2005 level, which correspondingly reduced ambient SO2 and sulfate (SO4(2-)) concentrations by 13%-15% and 8%-10% respectively over east China. The nitrogen oxides (NO(x)) control policy during the 12th Five Year Plan period (2011-2015) targets the reduction of the national NO(x) emission in 2015 by 10% on the basis of 2010. The simulation results suggest that such a reduction in NO(x) emission will reduce the ambient nitrogen dioxide (NO2), nitrate (NO3(-)), 1-hr maxima ozone (O3) concentrations and total nitrogen deposition by 8%, 3%-14%, 2% and 2%-4%, respectively over east China. The application of new emission standards for power plants will further reduce the NO2, NO3(-), 1-hr maxima O(3 concentrations and total nitrogen deposition by 2%-4%, 1%-6%, 0-2% and 1%-2%, respectively. Sensitivity analysis was conducted to evaluate the inter-provincial impacts of emission reduction in Beijing-Tianjin-Hebei and the Yangtze River Delta, which indicated the need to implement joint regional air pollution control. PMID:24649687

  16. Measurements of Shaped Charge Jet Velocity

    NASA Astrophysics Data System (ADS)

    Huang, Hongfa

    2013-06-01

    Penetration depth is an important requirement in oil/gas well perforating jobs. The depth determines how far the wellbore can directly communicate with reservoir fluids. Deep perforation charges are widely used in oilfield industry and most of those are powder metal liner charge for no carrot-like slug left as solid liner does. Comprehensive measurements for the powder metal liner shaped charge jet characteristics, namely, the jet density and velocity, are needed to predict the shaped charge performance and to plan the perforating job. This paper focuses on an experimental work of jet velocity measurements. A medium size of powder metal liner charges (27 grams HMX) is used in the tests. The powder jet shoots through a stack of limestone blocks with shorting switch set in between. Half inch air-gap between two blocks is design to provide space for jet traveling in air to record free fly velocity, meanwhile the jet penetration velocity in the limestone is measured. Aluminum foil switches are used to record the jet Time of Arrival (TOA). The charged switch shorted by the metal jet when it arrives. The shorting signal is recorded. The two velocities can be used to estimate the jet penetration effectiveness. A series of TOA tests show that jet velocity along its length linearly decreases from jet tip to tail until the stagnation points referring to which jet material moves in opposite direction.

  17. EFFECT OF SURFACE TREATMENTS ON THE SPREADING VELOCITY OF SIMPLIFIED ADHESIVE SYSTEMS

    PubMed Central

    Pazinatto, Flávia B.; Lopes, Fernanda A.; Marquezini, Luiz; de Castro, Fabrício L. A.; Atta, Maria Teresa

    2006-01-01

    Objectives: To determine the roughness of glass surfaces submitted to different treatments and to correlate it with the spreading velocity of two adhesive systems. Materials and Methods: Glass slides were used as substrates to evaluate the spreading velocity of Single Bond and Prime & Bond NT adhesive systems. Six different surface treatments were compared: 1) no treatment; 2) silanization (SL); 3) sandblasting (SB); 4) SB + SL; 5) 10% hydrofluoric acid treatment (HF); 6) HF + SL. Before and after treatments, surface roughness was measured by a profilometer (Ra, μm). Drop volumes (10 μl) of the adhesive systems were deposited onto substrates with a micropipette to observe materials spreading during 30s. Data were expressed in mm/s as spreading velocity. Statistical significances among groups were analyzed using one-way and two-way-ANOVA designs and the SNK test. Results: Significant differences in spreading velocity were found between materials (p < 0.001) and among treatments (p < 0.001). Silanization decreased the spreading velocity for both adhesives in comparison to groups where it was not performed (p < 0.05). Differences in roughness were found only for SB surfaces that were rougher than the others (p < 0.05). Silanization decreased the roughness of SB surfaces (p < 0.05). Linear regression did not indicate any correlation between spreading velocity and roughness (R = 0.173). Conclusions: Although surface treatments yielded different roughness, they did not provide differences in the spreading velocity of the simplified bonding systems studied. Silanization decreased bonding systems' spreading velocities. PMID:19089237

  18. Effect of low emission sources on air quality in Cracow

    SciTech Connect

    Nedoma, J.

    1995-12-31

    The paper presents calculation of power engineering low emission and results of stimulation of the effect of this emission on air quality in Cracow, Poland. It has been stated that the segment of low emission in central areas of the town makes up ca. 40% of the observed concentration of sulfur dioxide. Furthermore it has been stated that the capital investment must be concentrated in the central part of the town in order to reach noticeable improvement of air quality in Cracow. Neither the output of a separate power source nor the emission level and its individual harmful effect, but the location of the source and especially packing density of the sources must decide the priority of upgrading actions.

  19. The Effects of Air Pollution on Ischemic Stroke Admission Rate

    PubMed Central

    Alimohammadi, Hossein; Fakhri, Sara; Derakhshanfar, Hojjat; Hosseini-Zijoud, Seyed-Mostafa; Safari, Saeed

    2016-01-01

    The present study aimed to determine the relationship between the level of air pollutants and the rate of ischemic stroke (IS) admissions to hospitals. In this retrospective cross-sectional study, stroke admissions (January-March 2012 and 2013) to an emergency department and air pollution and meteorological data were gathered. The relationship between air pollutant levels and hospital admission rates were evaluated using the generalize additive model. In all 379 patients with IS were referred to the hospital (52.5% male; mean age 68.2±13.3 years). Both transient (p<0.001) and long-term (p<0.001) rises in CO level increases the risk of IS. Increased weekly (p<0.001) and monthly (p<0.001) average O3 levels amplifies this risk, while a transient increase in NO2 (p<0.001) and SO2 (p<0.001) levels has the same effect. Long-term changes in PM10 (p<0.001) and PM2.5 (p<0.001) also increase the risk of IS. The findings showed that the level of air pollutants directly correlates with the number of stroke admissions to the emergency department. PMID:26866000

  20. Effect of Limb Lengthening on Internodal Length and Conduction Velocity of Peripheral Nerve

    PubMed Central

    Gillingwater, Thomas H.; Anderson, Heather; Cottrell, David; Sherman, Diane L.; Ribchester, Richard R.; Brophy, Peter J.

    2013-01-01

    The influences of axon diameter, myelin thickness, and internodal length on the velocity of conduction of peripheral nerve action potentials are unclear. Previous studies have demonstrated a strong dependence of conduction velocity on internodal length. However, a theoretical analysis has suggested that this relationship may be lost above a nodal separation of ∼0.6 mm. Here we measured nerve conduction velocities in a rabbit model of limb lengthening that produced compensatory increases in peripheral nerve growth. Divided tibial bones in one hindlimb were gradually lengthened at 0.7 mm per day using an external frame attached to the bone. This was associated with a significant increase (33%) of internodal length (0.95–1.3 mm) in axons of the tibial nerve that varied in proportion to the mechanical strain in the nerve of the lengthened limb. Axonal diameter, myelin thickness, and g-ratios were not significantly altered by limb lengthening. Despite the substantial increase in internodal length, no significant change was detected in conduction velocity (∼43 m/s) measured either in vivo or in isolated tibial nerves. The results demonstrate that the internode remains plastic in the adult but that increases in internodal length of myelinated adult nerve axons do not result in either deficiency or proportionate increases in their conduction velocity and support the view that the internodal lengths of nerves reach a plateau beyond which their conduction velocities are no longer sensitive to increases in internodal length. PMID:23467369