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At least 73 records · Page 4Linked to original sources
PubMed2004

Investigation on wind energy-compressed air power system.

Wind energy is a pollution free and renewable resource widely distributed over China. Aimed at protecting the environment and enlarging application of wind energy, a new approach to application of wind energy by using compressed air power to some extent instead of electricity put forward. This includes: explaining the working principles and characteristics of the wind energy-compressed air power system; discussing the compatibility of wind energy and compressor capacity; presenting the theoretical model and computational simulation of the system. The obtained compressor capacity vs wind power relationship in certain wind velocity range can be helpful in the designing of the wind power-compressed air system. Results of investigations on the application of high-pressure compressed air for pressure reduction led to conclusion that pressure reduction with expander is better than the throttle regulator in energy saving.

Air↗
PubMed2002

Influences of wind flow on stopover decisions: the case of the reed warbler Acrocephalus scirpaceus in the Western Mediterranean.

Wind directions measured at two different heights (850 hPa and 700 hPa) and at different hours of the night were analysed during the spring migration passage at a bird stopover site located in the western Mediterranean, in order to evaluate the importance of wind components for a stopover decision. From a huge ringing campaign of bird migration in north-east Spain, data from the reed warbler Acrocephalus scirpaceus have been used for the analysis. From a total of 2,478 reed warblers captured between 1993 and 1997 data recording significant days, with a high number of captures, and decrease days, with few captures, have been selected to develop an analysis of wind direction in relation to stopover and flight resumption. On days with a high capture the winds had mainly a fourth-quadrant flow (from the north, north-west and west), these being mainly head winds. Winds with westerly component (from the north-west, west and south-west), which enhance the flight, account for the majority of the days when there was a low capture of reed warblers. Wind direction therefore appears to be a determining factor for stopover decisions and resumption of flight for the reed warblers at an intermediate stage of their spring migration where topographical characteristics govern the winds.

Animals↗
PubMed2006

Righting response of artificially inclined maritime pine (Pinus pinaster) saplings to wind loading.

To determine if trees respond to dynamic and static loading in the same manner, 2-year-old maritime pine (Pinus pinaster Ait.) trees were subjected to different types of mechanical loading in the field. One block of trees (the control) were kept in pots and planted in the field at an angle of 0 or 45 degrees to the vertical. A similar block of leaning potted trees was planted nearby and subjected to frequent, unilateral wind loading for a period of 1 s every 2 min. Half the leaning trees were oriented toward the direction of wind loading and half were oriented along the axis of wind loading. The stem profile was measured three times during the growing season to quantify the rate of stem straightening. Compression wood formation and stem shape were measured in all plants. No differences in mean height or diameter were observed between blocks and all leaning trees straightened, but not at the same rate. Although no difference in the rate of apical straightening occurred between control and wind-treated trees, the righting response of the basal part of the stem of leaning trees subjected to wind was four times greater than that of leaning trees without wind. No differences in the righting response were observed between leaning trees growing toward and trees growing away from the source of wind. No significant differences in compression wood formation were found between control trees and wind-treated trees, indicating that other factors must determine the reorientation rate of leaning trees. Results are discussed with reference to the quality of compression wood in conifers and the mechanotransductive pathway in plants.

Pinus↗
PubMed2000

Chinook winds and migraine headache.

OBJECTIVE: To determine the effects of chinook weather conditions on probability of migraine headache onset. BACKGROUND: Many migraineurs believe weather to be a trigger factor for their headaches; however, there is little supportive evidence in the literature. Migraineurs in the southern part of the Canadian province of Alberta frequently report that chinooks, warm westerly winds specific to the region, trigger their headaches. METHOD: Weather data from Environment Canada were used to designate each calendar day during the study period as a chinook, prechinook, or nonchinook day. Headache data were collected from 75 patient diaries from the University of Calgary Headache Research Clinic. Individual and multiple logistic regression models were used to determine if the weather conditions affected the probability of migraine onset. RESULTS: The probability of migraine onset was increased on both prechinook days (odds ratio 1.24; 95% CI 1.08 to 1.42) and on days with chinook winds (1.19; 1.02 to 1.39) compared with nonchinook days. Analysis of chinook wind velocities revealed that for chinook days, the relative risk of migraine onset was increased only on high-wind chinook days (velocity > 38 km/h) (odds ratio 1.41; 95% CI 1.06 to 1.88). A subset of individuals was sensitive to high-wind chinook days, and another subset was only sensitive to prechinook days. Only two patients were sensitive to both weather conditions, and the majority of patients was not sensitive to either. Neither weather condition had a protective effect. Increasing age was associated with high-wind chinook sensitivity (p = 0.009) but not prechinook sensitivity (p = 0.389). CONCLUSIONS: Both prechinook and high-wind chinook days increase the probability of migraine onset in a subset of migraineurs. Because few subjects were found to be sensitive to both weather types, the mechanisms for these weather effects may be independent. This is supported by the presence of an age interaction for high-wind chinook days but not for prechinooks day.

Adult↗
PubMed2005

[Experimental research on the anti-wind erosion of typical grasslands].

Wind erosion is one of the most important factors influencing the stability and functions of typical grassland ecosystem and one of the main reasons causing grassland degradation. In order to understand the effects of the human disturbances to the ability of anti-wind erosion of the typical grasslands, a wind tunnel experiment was made and the wind erosion rates (WER) and wind erosion amount (WEA) were selected to illustrate the effects. From the experiment, it can be found that banned-grazing reduced the WEA and the WER markedly. At the same wind speed, the longer the banned-grazing period, the less the WEA and the WER; the WEA and the WER in the grassland cultivation are more than those of the natural grasslands and the differences increase with wind speed. There exists a linear relationship between WER and the disturbance intensity. The results show that grazing and cultivation can weaken the ability of anti-wind erosion of typical grassland ecosystem, and banned-grazing can strengthen the ability. Therefore, in typical grassland areas, taking the active banned-grazing measures is the most effective approach to stop the degradation and trigger the rehabilitation of typical grassland ecosystem.

Conservation of Natural Resources↗
PubMed1982

The effect of single giant interneuron lesions on wind-evoked motor responses in the cockroach, Periplaneta americana.

In order to determine the contribution of individual giant interneurons (GIs) to wind-evoked motor outputs, responses were recorded from depressor and levator motor neurons in the cockroach Periplaneta americana to wind puffs of different directions. The depressor response was generally stronger to wind from the ipsilateral rear than to wind from the contralateral rear. The levator response was more variable but was more often stronger to wind from the contralateral rear than to wind from the ipsilateral rear. These results are as expected based on behavioral responses to wind puffs. (Camhi and Tom, 1978). The depressor response was nearly or totally abolished by severing the ipsilateral connective of the nerve cord but was little affected by severing the contralateral connective. The levator response was greatly reduced for some angles by severing the ipsilateral connective and for other angles by severing the contralateral connective. Blocking conduction in the ipsilateral GI 5 nearly or completely abolished the depressor response to wind from the ipsilateral rear. This is the first time that a GI has been shown to be necessary, not just sufficient, for a given motor output.

Animals↗
PubMedDate not supplied

Enhancement of wind-up by the combined administration of adenosine A1 receptor ligands on spinalized rats with carrageenan-induced inflammation.

The adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) is very effective in reducing wind-up in intact but not in spinalized adult rats with carrageenan-induced inflammation, suggesting an adenosine-mediated supraspinal modulation. Since wind-up is a spinal cord mediated phenomenon but highly influenced by descending modulatory systems, especially in situations of sensitization, we assessed the possible involvement of adenosine in the modulation of wind-up. We studied the effect of the adenosine A(1) receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT) in the presence and in the absence of the adenosine A(1) receptor agonist CPA. The experiments were carried out in spinalized male Wistar rats under alpha-chloralose anaesthesia. Withdrawal reflexes, studied as single motor units, were activated by noxious mechanical and high-intensity repetitive electrical stimulation (wind-up). While CPA and CPT were not able to induce any change on wind-up when injected alone, the combination of the two drugs, in any order, lead to an important enhancement of wind-up. This enhancement not always paralleled an increase of responses to noxious mechanical stimulation, indicating that the effect is mainly located in the spinal cord. In addition, the enhancement of wind-up was not further increased by the administration of the opioid receptor antagonist naloxone. We conclude that the depression of the wind-up phenomenon observed in spinalized animals is, at least in part, dependent of adenosine systems and can be relieved by the combined administration of CPA and CPT.

Adenosine↗
PubMed1998

A survey of wind speeds in indoor workplaces.

The applicability of the inhalable convention for sampling aerosols relies on its being a valid model for typical sampling environments. The current convention is based on measurements carried out in external wind speeds between 1 and 4 m.s-1. However these measurements show a degree of wind speed dependence, and it is uncertain at present how valid the convention is for describing human aspiration efficiency outside these wind speed limits. Following concerns that wind speeds in many indoor workplaces may be significantly below this range, measurements have been made in 55 work areas covering a wide range of workplaces. Measurements have concentrated on 'background' wind speeds where the influence of specific air movement sources is minimised. The pooled wind speed measurements show a highly skewed distribution with an arithmetic mean of approximately 0.3 m.s-1. Approximately 85% of all individual measurements were below this mean value. No obvious correlation was found between wind speed distribution parameters and industry type, room size or ventilation type. A limited number of comparisons were made between static anemometers and devices mounted on workers. It was found that modal wind speeds experience by workers were typically 0.05 m.s-1 higher than those measured using a static anemometer. These measurements agreed well with previously published data for similar workplaces as well as houses.

Air Movements↗
PubMed2003

Reduced drag coefficient for high wind speeds in tropical cyclones.

The transfer of momentum between the atmosphere and the ocean is described in terms of the variation of wind speed with height and a drag coefficient that increases with sea surface roughness and wind speed. But direct measurements have only been available for weak winds; momentum transfer under extreme wind conditions has therefore been extrapolated from these field measurements. Global Positioning System sondes have been used since 1997 to measure the profiles of the strong winds in the marine boundary layer associated with tropical cyclones. Here we present an analysis of these data, which show a logarithmic increase in mean wind speed with height in the lowest 200 m, maximum wind speed at 500 m and a gradual weakening up to a height of 3 km. By determining surface stress, roughness length and neutral stability drag coefficient, we find that surface momentum flux levels off as the wind speeds increase above hurricane force. This behaviour is contrary to surface flux parameterizations that are currently used in a variety of modelling applications, including hurricane risk assessment and prediction of storm motion, intensity, waves and storm surges.

Journal Article↗
PubMed2003

Infrasonic wind-noise reduction by barriers and spatial filters.

This paper reports experimental observations of wind speed and infrasonic noise reduction inside a wind barrier. The barrier is compared with "rosette" spatial filters and with a reference site that uses no noise reduction system. The barrier is investigated for use at International Monitoring System (IMS) infrasound array sites where spatially extensive noise-reducing systems cannot be used because of a shortage of suitable land. Wind speed inside a 2-m-high 50%-porous hexagonal barrier coated with a fine wire mesh is reduced from ambient levels by 90%. If the infrasound wind-noise level reductions are all plotted versus the reduced frequency given by f*L/v, where L is the characteristic size of the array or barrier, f is the frequency, and v is the wind speed, the reductions at different wind speeds are observed to collapse into a single curve for each wind-noise reduction method. The reductions are minimal below a reduced frequency of 0.3 to 1, depending on the device, then spatial averaging over the turbulence structure leads to increased reduction. Above the reduced corner frequency, the barrier reduces infrasonic noise by up to 20 to 25 dB. Below the corner frequency the barrier displays a small reduction of about 4 dB. The rosettes display no reduction below the corner frequency. One other advantage of the wind barrier over rosette spatial filters is that the signal recorded inside the barrier enters the microbarometer from free air and is not integrated, possibly out of phase, after propagation through a system of narrow pipes.

Journal Article↗
PubMed1999

Wind pollination and reproductive assurance in Linanthus parviflorus (Polemoniaceae), a self-incompatible annual.

Wind pollination was experimentally demonstrated in Linanthus parviflorus (Polemoniaceae), a predominantly beefly-pollinated, self-incompatible annual. Seed set in plants enclosed in mesh tents that excluded pollinators but allowed airborne pollen flow provided evidence for wind pollination, and the extent of seed set due to wind pollination was compared to that in open-pollinated controls and pollen-supplemented treatments. Additional controls were included to test for possible confounding effects of the mesh tent. Mean seed number in open-pollinated plants was 72.8-81.1% of that in pollen-supplemented plants, while wind pollination alone produced 49.5-52.2%, a smaller but substantial proportion of seed set with pollen supplementation. Further evidence for wind pollination was found in a comparison of sites differing in the extent of wind exposure in two populations of L. parviflorus. Airborne pollen counts were higher in exposed sites than in protected sites, and the difference was marginally significant. Seed set was significantly pollen limited in protected sites, but not in exposed sites. Taken together, the data suggest that wind pollination provides some reproductive assurance in this obligately outcrossing species. Wind pollination is hypothesized to represent an alternative to selfing as an evolutionary solution to the problem of temporal or spatial variation in pollination visitation.

Journal Article↗
PubMed1995

Solar heat gain in a desert rodent: unexpected increases with wind speed and implications for estimating the heat balance of free-living animals.

We quantified metabolic power consumption as a function of wind speed in the presence and absence of simulated solar radiation in rock squirrels, Spermophilus variegatus, a diurnal rodent inhabiting arid regions of Mexico and the western United States. In the absence of solar radiation, metabolic rate increased 2.2-fold as wind speed increased from 0.25 to 4.0m.s-1. Whole-body thermal resistance declined 56% as wind speed increased over this range, indicating that body insulation in this species is much more sensitive to wind disruption than in other mammals. In the presence of 950W.m-2 simulated solar radiation, metabolic rate increased 2.3-fold as wind speed was elevated from 0.25 to 4.0m.s-1. Solar heat gain, calculated as the reduction in metabolic heat production associated with the addition of solar radiation, increased with wind speed from 1.26mW.g-1 at 0.25m.s-1 to 2.92mW.g-1 at 4.0m.s-1. This increase is opposite to theoretical expectations. Both the unexpected increase in solar heat gain at elevated wind speeds and the large-scale reduction of coat insulation suggests that assumptions often used in heat-transfer analyses of animals can produce important errors.

Animals↗
PubMed2006

A parametric study of wind chill equivalent temperatures by a dimensionless steady-state analysis.

A first order analytical approximation of steady-state heat conduction in a hollow cylinder exchanging heat at its external surface by convection with a cold and windy environment is presented. The model depicts the thermal behavior of certain body elements, e.g., head/face, when exposed to such environments. The results are presented by dimensionless parameters and facilitate the estimation of wind chill equivalent temperatures (WCETs). The effects of several variables on determining WCETs were studied using specific examples, leading to the following generalizations: (1) the conditions assumed for "calm" wind speed appear to be a dominant factor in determining WCET; (2) the effects, on both (skin) surface temperature and on WCET, of a 1 degrees C change in environmental temperature appear to be more pronounced than those of a 1 m/s change in wind speed; (3) similarly, predicted WCETs are more sensitive to the geometrical dimensions assumed for the modeled entity than they are to wind speeds; and (4) tissue thermal conductivity, the angle at which the convective heat transfer coefficient is measured relative to wind direction, and the factor used to establish "effective" wind speeds in the domain occupied by humans relative to reported values, all seem to have relatively small effects on the determination of WCET. These conclusions strongly suggest, among other things, that for any given combination of environmental conditions, wind chill indices may best be presented as ranges rather than as single values. This seems to apply even when worst-case scenarios are considered. Also emphasized is the need for careful and realistic selection of all the parameter values used in the determination of WCETs.

Body Temperature Regulation↗
PubMed2006

Morphological characterization of suspended particles under wind-induced disturbance in Taihu Lake, China.

Sediments are disturbed by wind frequently, especially in the shallow lakes. The characteristics of resuspended sediment particles in Taihu Lake were studied under different wind velocities. It showed that sediment particles suspended obviously and particle number in overlying water increased directly under high wind-induced disturbance. Suspended solid (SS) concentration was less than 50 mg/l when the wind velocity was below 3.0 m/s, however, it increased to more than 300 mg/l when the wind velocity was 10.0 m/s. Two methods were used to measure the fractal characteristics of particles. One was light scattering and the other was image analysis. The three-dimensional fractal dimensions of suspended particles, measured by light scattering, were between 2.26 and 2.44; correspondingly, the two-dimensional fractal dimensions, calculated by image analysis, were between 1.44 and 1.77. Moreover, the three-dimensional fractal dimensions were directly proportional to two-dimensional fractal dimensions. The characteristic length of particles was calculated by image analysis. The minimum characteristic length was close to 8.5 microm when the wind velocity was 1.5 m/s at 50 cm beneath lake surface, while, the maximum characteristic length was approximate to 24 microm when the wind velocity was 10 m/s at the depth of 150 cm.

China↗
PubMed2002

Estimating the frequency distributions of PM10 and PM2.5 by the statistics of wind speed at Sha-Lu, Taiwan.

The frequency distribution of air pollutant concentration varies with the meteorological conditions and pollutant emission level. There exists a simple relation between the frequency distribution of wind speed and frequency distribution of air pollutant concentration. The concentration of air pollutant, C, at cumulative probability, p, is inversely proportional to the wind speeds, u, at probability of (100 - p) when the distributional types and shape factors of both data are the same. The relationship is shown as K=Cp u(100 - p), where K is constant. In this study, three theoretical distributions (log-normal, Weibull and type V Pearson distributions) are selected to fit the measured data of PM10, PM2.5 and wind speed. The frequency distributions of air pollutants can be estimated from the simple relationship of air pollutant concentration and wind speed. The results show that the log-normal distribution is the best one to represent the data of PM10, PM2.5 and wind speed. The K values of PM10 and PM2.5 are nearly constant from the 30-80th percentiles. It was also found that the distributions of PM10 and PM2.5 can be successfully estimated from the distribution of wind speed. The Kolmogorov-Smirnov (K-S) test shows that there is no significant discrepancy between the estimated and measured distribution of PM10 and PM2.5 at the 95% confidence level. Therefore, the distribution of air pollutants is easily estimated when the wind speed data are known.

Air Pollutants↗
PubMed2000

A comparison of wind noise in four hearing instruments.

Wind noise was measured in four behind-the-ear hearing instruments with different microphone openings. A silent airflow of 7 m/s was directed toward the ear of a Kemar head and the resulting wind noise was measured. The amplification was set to an insertion gain of 35 dB at 1.6 kHz. The wind noise amplitude at the position of the drum ranged from 84 to 97 dB(A). The hearing instrument with a partially covered microphone entrance proved best, whereas one with an open microphone entrance had the poorest performance. A reduction in wind noise of 6-17 dB could be achieved in all hearing instruments by using a simple windscreen made of Styrofoam. The windscreen affected the frequency response by less than 2 dB. By subtracting the insertion gain from the wind noise, an equivalent wind noise could be presented as a function of frequency. A considerable difference was found between the wind noise sensitivity in different hearing instruments. All could be improved by a windscreen without adversely affecting the frequency response.

Acoustic Stimulation↗
PubMed2005

Wind-dispersed seed deposition patterns and seedling recruitment of Artemisia halodendron in a moving sandy land.

BACKGROUND AND AIMS: Artemisia halodendron is a native sub-shrub that occurs mainly in moving and semi-fixed sandy lands in Inner Mongolia, China. Information on the spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron inhabiting moving sandy lands is very limited. The aim of this study was to examine wind-dispersed seed deposition patterns and post-dispersal recruitment of A. halodendron seedlings. * METHODS: The spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron were examined by investigating the numbers of deposited seeds, emerged and surviving seedlings using sampling points at a range of distances from the parent plant in eight compass directions for two consecutive growing seasons. * KEY RESULTS: Wind-dispersed seed deposition showed considerable variation between directions and years. Wind transported A. halodendron seeds only a few meters away from the parent plant in all eight directions. Seedling emergence and establishment also showed between-direction and between-year variability, but the spatial pattern of seedling distribution differed from that of seed deposition. Only a very small fraction (<1 %) of the deposited seeds emerged in the field and survived for long enough to be included in our seedling censuses at the end of the growing season. * CONCLUSIONS: The spatial variation in wind speed and frequency strongly affects the pattern of seed deposition, although the variation in seed deposition does not determine the spatial pattern of seedling recruitment. Seeds of A. halodendron are not dispersed very well by wind. The low probability of recruitment success for A. halodendron seedlings suggests that this species does not rely on seedling recruitment for its persistence and maintenance of population.

Artemisia↗
PubMed2002

Luminescence intensity in coral skeletons from Mona Island in the Caribbean Sea and its link to precipitation and wind speed.

This study investigates the potential of using changes of interannual luminescence intensity in hermatypic Montastraea coral skeletons in the northeastern Caribbean as a proxy of precipitation and (trade) wind speed. In order to find wavelength pairs that are well suited to detect variations in the concentration of incorporated terrestrial humic substances in coral skeletons, and thus to reconstruct past run-off and rainfall, three-dimensional excitation-emission matrix fluorescence spectra of seawater samples were investigated on their relationships to local precipitation. Three prominent excitation-emission peaks at 310/430, 425/480 and 390/530 nm were identified. The fluorescence intensities of the wavelength pair 310/430 nm showed a weak relationship, while the wavelength pairs at 425/480 and 390/530 nm showed strong relationships with local precipitation. Variations in luminescence intensities from scans on the coral surface along the growth axis using the wavelengths identified were then compared with instrumental records of regional precipitation and wind speed. In the coral skeleton as well, the wavelength pairs at 425/480 and 390/530 nm were more strongly correlated with regional precipitation and wind speed. This indicates that these two wavelength pairs are well suited to reconstruct past precipitation and wind speed. In order to evaluate the use as a proxy of trade wind variability in the Caribbean, tropical Atlantic region, variations in luminescence intensity were compared with a record of trade wind variability from the southern Caribbean. The two records are strongly correlated, which suggests that luminescence intensity in coral skeletons, at least from Mona Island, can be used as proxy of trade wind variability and precipitation.

Anthozoa↗