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1

??????????????????????????????? Maximum Velocity of a Racing Car  

Microsoft Academic Search

The purpose of this paper is to analysis optimum maximum velocity of a racing car along the given path by using the minimum time optimization method. The simple mathematical model are the equations of motion with geometrical path constraints, also total driving and braking forces are upper and lower bounds, respectively. The usefulness of this paper is to predict optimum

Tawiwat Veeraklaew; Yotsak Saisanit

2

Maximum Possible Transverse Velocity in Special Relativity.  

ERIC Educational Resources Information Center

Using a physical picture, an expression for the maximum possible transverse velocity and orientation required for that by a linear emitter in special theory of relativity has been derived. A differential calculus method is also used to derive the expression. (Author/KR)

Medhekar, Sarang

1991-01-01

3

Modeling maximum astrophysical gravitational recoil velocities  

SciTech Connect

We measure the recoil velocity as a function of spin for equal-mass, highly spinning black-hole binaries, with spins in the orbital plane, equal in magnitude, and opposite in direction. We confirm that the leading-order effect is linear in the spin and the cosine of angle between the spin direction and the infall direction at the merger. We find higher-order corrections that are proportional to the odd powers in both the spin and cosine of this angle. Taking these corrections into account, we predict that the maximum recoil will be 3680{+-}130 km s{sup -1}.

Lousto, Carlos O.; Zlochower, Yosef [Center for Computational Relativity and Gravitation, School of Mathematical Sciences, Rochester Institute of Technology, 78 Lomb Memorial Drive, Rochester, New York 14623 (United States)

2011-01-15

4

Solar-wind velocity decreases  

NASA Astrophysics Data System (ADS)

A model is developed to account for the solar wind electron and proton temperature decreases observed following the passage of an interplanetary shock wave and during the velocity decrease of a solar wind stream. The equations of mass and energy conservation are solved for a fully ionized, electrically neutral plasma expanding radially and spherically symmetrically, taking into account the heat flux from the solor corona to the plasma along the open magnetic field lines, and the electron thermal conductivity. An analytical relationship between the temperature and the velocity of the solar wind plasma is obtained which is found to be in agreement with experimental measurements made by the Vela 5 and 6 and IMP 6 satellites from August 1969-May 1974. It is thus proposed that the observed low plasma temperatures are due to the fact that the temperature decrease of the expanding plasma exceeds the heat gain due to thermal conduction from the corona.

Geranios, A.

1980-08-01

5

14 CFR 25.237 - Wind velocities.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Wind velocities. 25.237 Section 25.237 Aeronautics...Handling Characteristics § 25.237 Wind velocities. (a) For land planes and amphibians...A 90-degree cross component of wind velocity, demonstrated to be safe for...

2010-01-01

6

14 CFR 25.237 - Wind velocities.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Wind velocities. 25.237 Section 25.237 Aeronautics...Handling Characteristics § 25.237 Wind velocities. (a) For land planes and amphibians...A 90-degree cross component of wind velocity, demonstrated to be safe for...

2009-01-01

7

14 CFR 25.237 - Wind velocities.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Wind velocities. 25.237 Section 25...Handling Characteristics § 25.237 Wind velocities. (a) For land planes and... (1) A 90-degree cross component of wind velocity, demonstrated to be safe...

2013-01-01

8

Estimating the Wind Driven Velocity Structure of the California Current  

NASA Astrophysics Data System (ADS)

We investigate the wind driven velocity structure of the California Current (CC) using a 12-year time series of ageostrophic velocities, ocean surface winds, and two regression models of the system. The ageostrophic current is estimated by removing geostrophic velocities, which are determined by the combination of CTD (conductivity, temperature, depth) and altimetry data from total flow velocity observations. Total current (i.e. ageostrophic and geostrophic) observations are derived from satellite-tracked drifting buoys, the maximum cross-correlation (MCC) technique applied to satellite thermal imagery, and shipboard acoustic Doppler current profiler (ADCP) data. Residual ageostrophic observations demonstrate magnitude and phase decay, with increasing depth, which is consistent with Ekman theory. Regression models, driven by wind velocities from scatterometry and ageostrophic current estimates, are used to characterize the response of the ocean to wind forcing. The first model is run on each ageostrophic data set independently (MCC, drifters, ADCP at different depths) to characterize the vertical wind-driven response of the ocean current. Strong linear magnitude decay with depth is found. The second model run takes into account the depth of ageostrophic observations and is used to characterize the horizontal response of the ocean to wind forcing. Parameters estimated show parallel, jet-like regions of increased response to wind forcing offshore of coastal promontories. These jet-like features are ~200 km wide and are tilted at an angle of 20 to the parallel.

Matthews, D. K.; Emery, W.

2008-12-01

9

Methodology for predicting maximum velocity and shear stress in a ...  

Treesearch

Title: Methodology for predicting maximum velocity and shear stress in a sinuous ... patterns, or quite unpredictable, such as major flooding events or tectonic activity. ... and often times can produce catastrophic changes to natural ecosystems.

10

Distribution of Maximum Velocities in Avalanches Near the Depinning Transition  

NASA Astrophysics Data System (ADS)

We report exact predictions for universal scaling exponents and scaling functions associated with the distribution of the maximum collective avalanche propagation velocities vm in the mean field theory of the interface depinning transition. We derive the extreme value distribution P(vm|T) for the maximum velocities in avalanches of fixed duration T and verify the results by numerical simulation near the critical point. We find that the tail of the distribution of maximum velocity for an arbitrary avalanche duration, vm, scales as P(vm)vm-2 for large vm. These results account for the observed power-law distribution of the maximum amplitudes in acoustic emission experiments of crystal plasticity and are also broadly applicable to other systems in the mean-field interface depinning universality class, ranging from magnets to earthquakes.

LeBlanc, Michael; Angheluta, Luiza; Dahmen, Karin; Goldenfeld, Nigel

2012-09-01

11

A Novel Scheme for Rapid Tracking of Maximum Power Point in Wind Energy Generation Systems  

Microsoft Academic Search

This paper presents a novel maximum power point (MPP) tracking (MPPT) algorithm for grid-connected wind energy generation systems (WEGS). This is a rapid tracking algorithm that uses the fact that the value of ????,?? an intermediate variable, especially defined for the purpose, remains constant ( =??MPP ) for a given WEGS at the MPP irrespective of the wind velocity. The

Vivek Agarwal; Rakesh K. Aggarwal; Pravin Patidar; Chetan Patki

2010-01-01

12

Maximum wind speed changes over China  

NASA Astrophysics Data System (ADS)

In this study, the maximum wind speed (WSmax) changes across China from 1956 to 2004 were analyzed based on observed station data, and the changes of WSmax for 2046-2065 and 2080-2099 are projected using three global climate models (GFDL_CM2_0, CCCMA_CGCM3, and MRI_CGCM2) that have participated in the IPCC Fourth Assessment Report (AR4). The observed annual and seasonal WSmax and the frequency of gale days showed obvious declining trends. The annual WSmax decreased by approximately 1.46 m s-1 per decade, and the number of gale days decreased by 3.0 days per decade from 1956 to 2004. The amplitudes of the annual and seasonal WSmax decreases are larger than those of the annual and seasonal average wind speeds (WSavg). The weakening of the East Asian winter and summer monsoons is the cause for the distinct decreases of both WSmax and WSavg over the whole China. The decrease of WSmax in the southeast coastal areas of China is related to the reduced intensity of cold waves in China and the decreasing number (and decreasing intensity) of land-falling typhoons originated in the Northwest Pacific Ocean. The global climate models GFDL_CM2_0, MRI_CGCM2, and EBGCM (the ensemble of above mentioned three global climate models) consistently suggest that the annual and seasonal WSmax values will decrease during 2046-2065 and 2080-2099 relative to 1981-2000. The models also suggest that decreases in WSmax for whole China during 2046-2065 and 2080-2099 are related to both the reduced intensity of cold waves and the reduced intensity of the winter monsoon, and the decrease in WSmax in the southeast coastal areas of China is corresponding to the decreasing number of tropical cyclones over the Northwest Pacific Ocean in the summer during the same periods.

Jiang, Ying; Luo, Yong; Zhao, Zongci

2013-02-01

13

Maximum wind energy extraction strategies using power electronic converters  

Microsoft Academic Search

This thesis focuses on maximum wind energy extraction strategies for achieving the highest energy output of variable speed wind turbine power generation systems. Power electronic converters and controls provide the basic platform to accomplish the research of this thesis in both hardware and software aspects. In order to send wind energy to a utility grid, a variable speed wind turbine

Quincy Qing Wang

2003-01-01

14

Estimating maximum global wind power availability and associated climatic consequences  

Microsoft Academic Search

Estimating maximum global wind power availability and associated climatic consequences Wind speed reflects the continuous generation of kinetic energy and its dissipation, primarily in the atmospheric boundary layer. When wind turbines extract kinetic wind energy, less kinetic energy remains in the atmosphere in the mean state. While this effect does not play a significant role for a single turbine, it

Lee Miller; Fabian Gans; Axel Kleidon

2010-01-01

15

Latitudinal Variation of Solar Wind Velocity  

NASA Astrophysics Data System (ADS)

Single station solar wind velocity measurements using the Ooty Radio Telescope (ORT) in India (operating at 327 MHz) are reported for the period August 1992 to August 1993. Interplanetary scintillation (IPS) observations on a large number of compact radio sources covering a latitudinal range of 80 were used to derive solar wind velocities using the method of fitting a power law model to the observed IPS spectra. The data shows a velocity versus heliographic latitude pattern which is similar to that reported by Rickett and Coles (1991) for the 1981 1982 period. However, the average of the measured equatorial velocities are higher, being about 470 km s-1 compared to their value of 400 km s-1. The distribution of electron density variations (?N e ) between 50R? and 90R? was also determined and it was found that ?N e was about 30% less at the poles as compared to the equator.

Ananthakrishnan, S.; Balasubramanian, V.; Janardhan, P.

1995-04-01

16

Differential turbulence and wind velocity meters  

Microsoft Academic Search

Here we are presenting the basic theoretical consideration to measurement of turbulence characteristics from observations of the onboard a flying aircraft. The method allows to record the integral turbulence intensity and two components of wind velocity along the optical path. The variance of the jitter of astronomic images is a measured characteristic. This paper presents the basic theoretical equations, needed

V. P. Lukin; V. V. Lavrinov; N. N. Botugina; O. N. Emaleev; V. V. Nosov

2007-01-01

17

An approximate, maximum-terminal-velocity descent to a point  

Microsoft Academic Search

A neighboring extremal control problem is formulated for a hypersonic glider to execute a maximum-terminal-velocity descent to a stationary target in a vertical plane. The resulting two-part, feedback control scheme initially solves a nonlinear algebraic problem to generate a nominal trajectory to the target altitude. Secondly, quadrature about the nominal provides the lift perturbation necessary to achieve the target downrange.

G. Richard Eisler; David G. Hull

1988-01-01

18

Maximum wind speeds and US hurricane losses  

NASA Astrophysics Data System (ADS)

There is academic, commercial, and public interest in estimating loss from hurricanes striking land and understanding how loss might change as a result of future variations in climate. Here we show that the relationship between wind speed and loss is exponential and that loss increases with wind speed at a rate of 5% per m s-1. The relationship is derived using quantile regression and a data set comprising wind speeds of hurricanes hitting the United States and normalized economic losses. We suggest that the centercepts for the different quantiles account for exposure-related factors such as population density, precipitation, and surface roughness, and that once these effects are accounted for, the increase in loss with wind speed is consistent across quantiles. An out-of-sample test of this relationship correctly predicts economic losses from Hurricane Irene in 2011. The exponential relationship suggests that increased wind speeds will produce significantly higher losses; however, increases in exposed property and population are expected to be a more important factor for near future losses.

Murnane, R. J.; Elsner, J. B.

2012-08-01

19

Velocity shear generation of solar wind turbulence  

Microsoft Academic Search

A two-dimensional incompressible MHD spectral code is used to show that shear-driven turbulence is a possible means for producing many observed properties of the evolution of the magnetic and velocity fluctuations in the solar wind and, in particular, the evolution of the cross helicity ('Alfvenicity') at small scales. It is shown that large-scale shear can nonlinearly produce a cascade to

D. A. Roberts; Melvyn L. Goldstein; William H. Matthaeus; Sanjoy Ghosh

1992-01-01

20

Velocity shear generation of solar wind turbulence  

Microsoft Academic Search

The authors use a two-dimensional, incompressible MHD spectral code to establish that shear-driven turbulence is a possible means for producing many observed properties of the evolution of the magnetic and velocity fluctuations in the solar wind and, in particular, the evolution of the cross helicity ({open_quotes}Alfvenicity{close_quotes}) at small scales. They find that large-scale shear can nonlinearly produce a cascade to

D. Aaron Roberts; Melvyn L. Goldstein; S. Ghosh; W. H. Matthaeus

1992-01-01

21

Maximum wind energy extraction strategies using power electronic converters  

NASA Astrophysics Data System (ADS)

This thesis focuses on maximum wind energy extraction strategies for achieving the highest energy output of variable speed wind turbine power generation systems. Power electronic converters and controls provide the basic platform to accomplish the research of this thesis in both hardware and software aspects. In order to send wind energy to a utility grid, a variable speed wind turbine requires a power electronic converter to convert a variable voltage variable frequency source into a fixed voltage fixed frequency supply. Generic single-phase and three-phase converter topologies, converter control methods for wind power generation, as well as the developed direct drive generator, are introduced in the thesis for establishing variable-speed wind energy conversion systems. Variable speed wind power generation system modeling and simulation are essential methods both for understanding the system behavior and for developing advanced system control strategies. Wind generation system components, including wind turbine, 1-phase IGBT inverter, 3-phase IGBT inverter, synchronous generator, and rectifier, are modeled in this thesis using MATLAB/SIMULINK. The simulation results have been verified by a commercial simulation software package, PSIM, and confirmed by field test results. Since the dynamic time constants for these individual models are much different, a creative approach has also been developed in this thesis to combine these models for entire wind power generation system simulation. An advanced maximum wind energy extraction strategy relies not only on proper system hardware design, but also on sophisticated software control algorithms. Based on literature review and computer simulation on wind turbine control algorithms, an intelligent maximum wind energy extraction control algorithm is proposed in this thesis. This algorithm has a unique on-line adaptation and optimization capability, which is able to achieve maximum wind energy conversion efficiency through continuously improving the performance of wind power generation systems. This algorithm is independent of wind power generation system characteristics, and does not need wind speed and turbine speed measurements. Therefore, it can be easily implemented into various wind energy generation systems with different turbine inertia and diverse system hardware environments. In addition to the detailed description of the proposed algorithm, computer simulation results are presented in the thesis to demonstrate the advantage of this algorithm. As a final confirmation of the algorithm feasibility, the algorithm has been implemented inside a single-phase IGBT inverter, and tested with a wind simulator system in research laboratory. Test results were found consistent with the simulation results. (Abstract shortened by UMI.)

Wang, Quincy Qing

2003-10-01

22

Embankment wind velocity field and traffic safety under the influence of sudden cross-wind  

Microsoft Academic Search

In order to analyze the influence of embankment on wind velocity field and vehicle dynamic responses under the influence of sudden cross-wind, Finite element models of different height embankments are built to analyze wind velocity field, and wind velocity on different height of left travel lane is computed. Then two degree of freedom vehicle model is established to analyze vehicle

Peng Hu; Xiaodong Pan

2010-01-01

23

Three-Dimensional Winds: a Maximum Cross-Correlation Application to Elastic LIDAR Data.  

NASA Astrophysics Data System (ADS)

Maximum cross-correlation techniques have been used with satellite data to estimate winds and sea surface velocities for several years. Los Alamos National Laboratory (LANL) is currently using a variation of the basic maximum cross-correlation technique, coupled with a deterministic application of a vector median filter, to measure transverse winds as a function of range and altitude from incoherent elastic back-scatter lidar (light detection and ranging) data taken throughout large volumes within the atmospheric boundary layer. Hourly representations of three-dimensional wind fields, derived from elastic lidar data taken during an air-quality study performed in a region of complex terrain near Sunland Park, New Mexico, are presented and compared with results from an Environmental Protection Agency (EPA) approved laser doppler velocimeter. The wind fields showed persistent large scale eddies as well as general terrain -following winds in the Rio Grande valley.

Buttler, William Tillman

24

Estimating maximum global wind power availability and associated climatic consequences  

NASA Astrophysics Data System (ADS)

Estimating maximum global wind power availability and associated climatic consequences Wind speed reflects the continuous generation of kinetic energy and its dissipation, primarily in the atmospheric boundary layer. When wind turbines extract kinetic wind energy, less kinetic energy remains in the atmosphere in the mean state. While this effect does not play a significant role for a single turbine, it becomes a critical factor for the estimation of large-scale wind power availability. This extraction of kinetic energy by turbines also competes with the natural processes of kinetic energy dissipation, thus setting fundamental limits on extractability that are not considered in previous large-scale studies [1,2,3]. Our simple momentum balance model using ECMWF climate data illustrates a fundamental limit to global wind power extractability and thereby electricity potential (93TW). This is independent of engineering advances in turbine design and wind farm layout. These results are supported by similar results using a global climate model of intermediate complexity. Varying the surface drag coefficient with different simulations allows us to directly relate changes in atmospheric and boundary layer dissipation with resulting climate indices and wind power potential. These new estimates of the maximum power generation by wind turbines are well above the currently installed capacity. Hence, present day installations are unlikely to have a global impact. However, when compared to the current human energy demand of 17TW combined with plans by the US and EU to drastically increase onshore and offshore wind turbine installations [4,5,6], understanding the climatic response and ultimate limitations of wind power as a large-scale renewable energy source is critical. [1] Archer, C., and M.Z. Jacobson, (2005) Evaluation of global wind power, J. Geophys. Res. 110:D12110. [2] Lu, X., M.B. McElroy, and J. Kiviluoma, (2009) Global potential for wind-generated electricity, Proc Natl Acad Sci, 106. [3] Liu, W.T., W. Tang, and X. Xie, (2008) Wind power distribution over the ocean, Geophys. Res. Lett., 35 L13808. [4] IPCC, (2008) IPCC scoping meeting on renewable energy sources - proceedings, Intergovernmental Panel on Climate Change [5] U.S. Department of Energy, (2008) 20% wind energy by 2030: increasing wind energy's contribution to U.S. electricity supply, U.S. Dept. of Energy - Energy Information Administration. [6] EEA, (2009) Europe's onshore and offshore wind energy potential, European Environment Agency, ISSN 1725-2237.

Miller, Lee; Gans, Fabian; Kleidon, Axel

2010-05-01

25

Velocity of the Solar Wind at Low Heliographic Latitudes.  

National Technical Information Service (NTIS)

Data from comet tail deflection observations were used to analyze the relationship between the solar-wind aberrational velocity and the heliographic latitude in the near-equatorial region. The aberrational velocities are found to vary with heliographic la...

V. P. Tarashchuk

1976-01-01

26

Instantaneous torque ripple control and maximum power extraction in a permanent magnet reluctance generator driven wind energy conversion system  

Microsoft Academic Search

A usual wind energy conversion system (WECS) suffers from significant amount of torque ripples even if the wind velocity remains constant. These torque ripples propagate mechanical stress in the turbine-generator drive train and may eventually lead to the failure of its various components. This research paper presents a unified control strategy which yields maximum power from WECS while minimizing the

Erkan Sunan; Kazmi Syed Muhammad Raza; Hiroki Goto; Hai-Jiao Guo; O. Ichinokur

2010-01-01

27

A Two-Dimensional Study of the Maximum Power That Can Be Obtained from a Wind Turbine in a Wind Shear Layer.  

National Technical Information Service (NTIS)

In 1926 Albert Betz derived a one-dimensional stream tube theory for the maximum power that can be obtained from a wind turbine in a uniform flow. However, for modern large wind turbines there is a considerable velocity gradient in the approaching flow, s...

B. C. A. Johansson

1981-01-01

28

Velocity shear generation of solar wind turbulence  

SciTech Connect

The authors use a two-dimensional, incompressible MHD spectral code to establish that shear-driven turbulence is a possible means for producing many observed properties of the evolution of the magnetic and velocity fluctuations in the solar wind and, in particular, the evolution of the cross helicity ({open_quotes}Alfvenicity{close_quotes}) at small scales. They find that large-scale shear can nonlinearly produce a cascade to smaller scale fluctuations even when the linear Kelvin-Helmholtz mode is stable and that a roughly power law inertial range is established by this process. While the fluctuations thus produced are not Alfvenic, they are nearly equipartitioned between magnetic and kinetic energy. The authors report simulations with Alfvenic fluctuations at high wave numbers, both with and without shear layers and find that it is the low cross helicity at low wave numbers that is critical to the cross helicity evolution, rather than the geometry of the flow or the dominance of kinetic energy at large scales. The fluctuations produced by shear effects are shown to evolve similarly but more slowly in the presence of a larger mean field and to be anisotropic with a preferred direction of spectral transfer perpendicular to the mean field. The evolution found is similar to that seen in some other simulations of HMD turbulence, and thus seems in many respects to be an instance of a more generic turbulent evolution rather than due to specific conditions in the solar wind. 75 refs., 18 figs.

Roberts, D.A.; Goldstein, M.L.; Ghosh, S. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Matthaeus, W.H. [Univ. of Delaware, Newark, DE (United States)

1992-11-01

29

Wind velocity effects on sampling rate of NO2 badge  

SciTech Connect

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

Lee, K.; Yanagisawa, Y.; Spengler, J.D.; Billick, I.H. (Harvard School of Public Health, Department of Environmental Health, Boston, MA (United States))

1992-04-01

30

Analytical expressions for maximum wind turbine average power in a Rayleigh wind regime  

SciTech Connect

Average or expectation values for annual power of a wind turbine in a Rayleigh wind regime are calculated and plotted as a function of cut-out wind speed. This wind speed is expressed in multiples of the annual average wind speed at the turbine installation site. To provide a common basis for comparison of all real and imagined turbines, the Rayleigh-Betz wind machine is postulated. This machine is an ideal wind machine operating with the ideal Betz power coefficient of 0.593 in a Rayleigh probability wind regime. All other average annual powers are expressed in fractions of that power. Cases considered include: (1) an ideal machine with finite power and finite cutout speed, (2) real machines operating in variable speed mode at their maximum power coefficient, and (3) real machines operating at constant speed.

Carlin, P.W.

1996-12-01

31

A two-dimensional study of the maximum power that can be obtained from a wind turbine in a wind shear layer  

SciTech Connect

In 1926 Albert Betz derived a one-dimensional stream tube theory for the maximum power that can be obtained from a wind turbine in a uniform flow. However, for modern large wind turbines there is a considerable velocity gradient in the approaching flow, since the wind flow field above the ground normally is a shear layer with a velocity profile reminding of that of a boundary layer of a wing or a flat plate. The present study extends Betz' theory to a two-dimensional case, where the undisturbed velocity field is given and allowed to vary arbitrarily vertically, and the location of the wind turbine is given. The maximum power is calculated by the method of calculus of variations. It is found that for common wind velocity profiles the maximum power is only slightly larger than the power, which is obtained by a constant relative wind speed retardation, equal to Betz' retardation, while for a linear velocity profile there is a considerable difference.

Johansson, B.C.A.

1981-04-01

32

Influence of sand grain diameter and wind velocity on lift-off velocities of sand particles.  

PubMed

In this paper, the velocities of sand particles near the sand bed in the saltation cloud were measured in a wind tunnel through an improved experimental scheme of the Particle Image Velocimetry (PIV) system. The influences of the diameter of sand particles in the saltation cloud and wind velocity on the probability distribution function (PDF) of lift-off velocities of sand particles were investigated. Results demonstrate that for the sand particles saltating above the sand bed with the mean grain diameter (d m = 0.3 mm), smaller and larger ones have the same velocity distribution, and wind velocity has no obvious influence on the distribution shape of the lift-off velocities, i.e., the PDFs of the horizontal and vertical lift-off velocities both follow a lognormal distribution, but the diameter of sand particles in the saltation cloud and wind velocity have an influence on the parameters of the PDF of horizontal and vertical lift-off velocities. Eventually, we present formulas to describe the PDF of lift-off velocities of sand particles with regard to the influence of wind velocity and the diameter of sand particles in the saltation cloud above the sand bed with d m = 0.3 mm. PMID:23695368

Bo, Tian-Li; Zheng, Xiao-Jing; Duan, Shao-Zhen; Liang, Yi-Rui

2013-05-24

33

Novel Maximum Power Point Tracking Controller for Wind Turbine Driven Permanent Magnet Generator  

Microsoft Academic Search

This paper presents Maximum Power Point Control for variable speed wind turbine driven permanent-magnet generator. The wind turbine generator is operated such that the rotor speed varies according to wind speed to adjust the duty cycle of power converter and maximizes Wind Energy Conversion System (WECS) efficiency. The maximum power point for each speed value is traced using Maximum Power

R. Bharanikumar; A. C. Yazhini; A. N. Kumar

2008-01-01

34

Maximum flight velocity of blood drops in analysing blood traces.  

PubMed

When analysing blood spatters, traces often occur which regarding the collision angle, cannot be allocated to any supposed centre of origin. Drops following highly curved (ballistic) trajectories usually form these types of traces. The reconstruction of such trajectories requires knowledge of the mass, the diameter (of which approximations are known) and the velocity of the blood drops. This article provides an upper range of the velocity in relation to the diameter of the blood drops based on physical laws. This is very helpful in analysing ballistic trajectories. PMID:22277155

Kneubuehl, Beat P

2012-01-23

35

Wind Velocity Neural Estimator for Small Autonomous Surface Vehicles  

Microsoft Academic Search

Surface aquatic vehicles present a complex dynamic behavior since they operate between two different fluids, air and water, each one with a different density and viscosity. Wind and surface currents affect vehicle motion in different manners. This paper shows the development of an estimator based on an artificial neural network which is used for wind velocity estimation in autonomous surface

J. R. B. A. Monteiro; M. Suetake; G. T. Paula; T. E. P. Almeida; M. P. Santana; G. B. Romero; J. C. Faracco; F. J. Monaco; R. S. Pinto

2012-01-01

36

Association of Maximum Pitch Velocity and Elbow Injury in Professional Baseball Pitchers  

Microsoft Academic Search

Background: Recent literature has explored the association of upper extremity injury in baseball players with various aspects of the pitching motion. To our knowledge, no study has directly evaluated the connection between maximum pitch velocity and elbow injury in professional baseball pitchers.Hypothesis: Professional pitchers throwing at higher maximum ball velocity will have a higher risk of elbow injury.Study Design: Cohort

Brandon D. Bushnell; Adam W. Anz; Thomas J. Noonan; Michael R. Torry; Richard J. Hawkins

2010-01-01

37

High-velocity tails on the velocity distribution of solar wind ions  

SciTech Connect

Recent observations of the solar wind using the SWICS instrument on the Ulysses spacecraft have shown the presence of high-velocity [open quotes]tails[close quotes] on the velocity distribution of protons. Similar features have also been observed on the velocity distributions of helium and oxygen ions. Of the order of 1% of the solar wind density is involved in these tails, which are approximately exponential in shape and persist to V = V[sub B] + 10V[sub th] or beyond, where V[sub B] is the bulk velocity and V[sub th] the thermal velocity of the solar wind. This paper contains a preliminary description of the phenomenon. It is clear that it is ultimately connected with the passage of interplanetary shocks past the spacecraft and that particle acceleration at oblique shocks is involved. 21 refs., 6 figs., 2 tabs.

Ogilvie, K.W. (Goddard Space Flight Center, Greenbelt, MD (United States)); Geiss, J. (Univ. of Bern (Swaziland)); Gloeckler, G. (Univ. of Maryland, College Park (United States)); Berdichevsky, D. (Highes-STX, Lanham, MD (United States)); Wilken, B. (Max-Plank-Institut fuer Aeronomie Katlenburg-Lindau (Germany))

1993-03-01

38

Maximum electrical energy production of a variable speed Wind Energy Conversion System  

Microsoft Academic Search

This paper proposes a control strategy for Wind Energy Conversion Systems (WECSs) aiming in both maximum power harvesting from the wind turbine and minimum power loss of the electrical generator. Thus, maximum efficiency along the whole wind energy conversion process is achieved and additionally expansion of the exploitable wind speed region towards the lower-speed range is accomplished. A squirrel cage

A. Mesemanolis; C. Mademlis; I. Kioskeridis

2012-01-01

39

A review of maximum power point tracking algorithms for wind energy systems  

Microsoft Academic Search

This paper reviews state of the art maximum power point tracking (MPPT) algorithms for wind energy systems. Due to the instantaneous changing nature of the wind, it is desirable to determine the one optimal generator speed that ensures maximum energy yield. Therefore, it is essential to include a controller that can track the maximum peak regardless of wind speed. The

M. A. Abdullah; A. H. M. Yatim; C. W. Tan; R. Saidur

2012-01-01

40

An intelligent maximum power extraction algorithm for inverter-based variable speed wind turbine systems  

Microsoft Academic Search

This paper focuses on the development of maximum wind power extraction algorithms for inverter-based variable speed wind power generation systems. A review of existing maximum wind power extraction algorithms is presented in this paper, based on which an intelligent maximum power extraction algorithm is developed by the authors to improve the system performance and to facilitate the control implementation. As

Quincy Wang; Liuchen Chang

2004-01-01

41

Simultaneous Thermospheric Neutral Winds and Plasma Velocities  

Microsoft Academic Search

Simultaneous Fabry-Perot spectrometer, FPS, data from Davis (gg 68.6 S 78.0 E, magnetic 74.3 S 101.5 E) and Mawson (gg 67.6 S 62.9 E, magnetic 70.2 S 91.7 E) have been obtained on a number of occasions since 1997. Data from the two instruments can be combined to provide an average wind field in the region spanning approximately 10 degrees

P. A. Greet; P. L. Dyson; Y. Murata; N. Sato

42

High-Speed Vortex Wind Velocity Imaging by Acoustic Tomography  

Microsoft Academic Search

\\u000a A technique for monitoring strong vortex wind fields is highly desired due to the rapid development of global warming. Vortex\\u000a wind velocity imaging using an acoustic travel time tomography technique was developed to meet this need. The method can be\\u000a implemented with a small number of parallel facing pairs of acoustic transmitters\\/receivers from just a single illumination\\u000a view direction, so

H. Li; T. Ueki; K. Hayashi; A. Yamada

43

Determination of the envelope function (maximum velocity curve) in Doppler ultrasound flow velocity diagrams  

NASA Astrophysics Data System (ADS)

This paper presents a new approach for the evaluation of Doppler flow velocity diagrams, obtained during brachial artery flow mediated dilatation (FMD) studies. The velocity diagrams are stored as image sequences on VCR tape. For this reason standard signal processing methods can not be used. A method for determination of blood velocity envelopes from image data is reported that uses Doppler-data specific heuristic to achieve high accuracy and robustness. The approach was tested in 40 Doppler blood flow images. Comparisons with manually defined independent standards demonstrated a very good correlation in determined peak velocity values (r equals 0.993) and flow envelope areas (r equals 0.996). The method is currently tested in a large volume clinical study.

Tschirren, Juerg; Lauer, Ronald M.; Sonka, Milan

2000-06-01

44

Helium and hydrogen velocity differences in the solar wind  

Microsoft Academic Search

Scalar and vector velocity differences between helium and hydrogen ions in the solar wind measured with the Los Alamos plasma analyzers on Imp 6 and 7 are presented and interpreted. From the bulk speeds and azimuthal components of flow direction for both types of ions the ecliptic projection of the helium to hydrogen velocity difference vector v\\/subo\\/\\/subp\\/ is determined. Short-term

J. R. Asbridge; S. J. Bame; W. C. Feldman; M. D. Montgomery

1976-01-01

45

On the Variation of Maximum Wind Gusts with Height  

Microsoft Academic Search

The effects of time-averaging and length of record on the variance of horizontal wind speed are considered through power spectral techniques. These effects are applied to a height profile of intensity of turbulence (ratio of the standard deviation of horizontal wind speed to mean wind speed) derived from data published by Deacon. For stationary strong-wind regimes dominated by `mechanical turbulence,'

R. R. Brook; K. T. Spillane

1970-01-01

46

New Forecasting Factor for Solar Wind Velocity From EIT Observations  

NASA Astrophysics Data System (ADS)

Various solar wind velocity forecasting methods at 1AU have been developed during the last decade, such as Wang-sheeley model and Hakamada-Akasofu-Fry Version 2 (HAFv2) model. Some authors have found that Coronal hole(CH) areas can be used to forecast the solar wind velocity with better results in low CME activity periods(e.g. Vrnak et.al.). The property of the solar surface is a good indication of the following interplanetary and geomagnetic activities. We analyzed all EIT284 images in almost the whole solar cycle 23 and developed a new forecasting factor(Pch) from the brightness of the solar Extreme Ultraviolet Images. and a good relationship was found between the Pch and solar wind velocity V three days later probed by ACE spacecraft. A simple method of forecasting the solar wind speed near earth in low CME activity periods is presented. For Pch and solar wind velocity, the linear correlation coefficients is R = 0.89 from 21 September until 26 December. For comparison we also analysed the same period data as Vrnak(2007) who using the coronal hole areas AM as input parameters for predicting solar wind velocity. The linear least-squares fit of Pch with the 3-day lag solar wind velocity showed a correlation coefficient R = 0.70, which is better than the result using AM(R = 0.62). The solar wind speed could be expressed as V (km s-1) = 337 + 0.00868 Pch. The average of relative difference between the calculated and the observed values amounts to |?| ? 12.15%. Furthermore, for the ten peaks during the analysis period, AM and V just showed a correlation coefficient R = 0.32, much worse than using Pch factor which showed R = 0.75. Moreover, the Pch factor exterminated personal bias in the forecasting process, which existed in the method using AM as input parameters because the coronal hole boundary can not be easily determined since no quantitative criteria can be used to precisely locate coronal holes from observation. Finally, the expression of V by Pch is analysed, which showed the variation of background solar wind speed during the whole solar cycle 23.

Luo, B.; Liu, S.; Zhong, Q.; Gong, J.

2007-12-01

47

Does the scatterometer see wind speed or friction velocity?  

Microsoft Academic Search

Studies of radar backscatter from the sea surface are referred either to the wind speed, U, or friction velocity, u(sub *). Bragg scattering theory suggests that these variations in backscatter are directly related to the height of the capillary-gravity waves modulated by the larger waves in tilt and by straining of the short wave field. The question then arises as

M. A. Donelan; W. J. Pierson Jr.

1984-01-01

48

Measurement of turbulent wind velocities using a rotating boom apparatus  

SciTech Connect

The present report covers both the development of a rotating-boom facility and the evaluation of the spectral energy of the turbulence measured relative to the rotating boom. The rotating boom is composed of a helicopter blade driven through a pulley speed reducer by a variable speed motor. The boom is mounted on a semiportable tower that can be raised to provide various ratios of hub height to rotor diameter. The boom can be mounted to rotate in either the vertical or horizontal plane. Probes that measure the three components of turbulence can be mounted at any location along the radius of the boom. Special hot-film sensors measured two components of the turbulence at a point directly in front of the rotating blade. By using the probe rotated 90/sup 0/ about its axis, the third turbulent velocity component was measured. Evaluation of the spectral energy distributions for the three components of velocity indicates a large concentration of energy at the rotational frequency. At frequencies slightly below the rotational frequency, the spectral energy is greatly reduced over that measured for the nonrotating case measurements. Peaks in the energy at frequencies that are multiples of the rotation frequency were also observed. We conclude that the rotating boom apparatus is suitable and ready to be used in experiments for developing and testing sensors for rotational measurement of wind velocity from wind turbine rotors. It also can be used to accurately measure turbulent wind for testing theories of rotationally sampled wind velocity.

Sandborn, V.A.; Connell, J.R.

1984-04-01

49

ALADIN: an atmosphere laser doppler wind lidar instrument for wind velocity measurements from space  

Microsoft Academic Search

AEROSPATIALE, leading a European team, has just conducted a successful study, under ESA contract, to demonstrate the feasibility of a spaceborne Doppler wind lidar instrument meeting the scientific requirements of wind velocity measurements from space with high spatial resolution. A first parametric investigation, based upon the initial set of mission requirements, and supported by dedicated models and detailed trade-off studies,

Rodolphe Krawczyk; Jean-Bernard Ghibaudo; Jean-Yves Labandibar; David V. Willetts; M. Vaughan; G. Pearson; M. R. Harris; Pierre H. Flamant; P. Salamitou; Alain Dabas; R. Charasse; Thierri Midavaine; Michel Royer; H. Heimel

1995-01-01

50

Electronic frequency modulation for the increase of maximum measurable velocity in a heterodyne laser interferometer  

SciTech Connect

A Zeeman-type He-Ne laser is frequently used as a heterodyne laser due to the simple construction and the small loss of a light. However, the low beat frequency of the Zeeman-type laser limits the maximum measurable velocity. In this article, an electronic frequency modulation algorithm is proposed to overcome the drawback of the low velocity measurement capability by increasing the beat frequency electronically. The brief analysis, the measurement scheme of the proposed algorithm, and the experimental results are presented. It is demonstrated that the proposed algorithm is proven to enhance the maximum measurable velocity.

Choi, Hyunseung; La, Jongpil; Park, Kyihwan [Intelligent Manufacturing Group, LG Production Engineering Research Institute, 19-1 Cheongho-Ri, Jinwuy-myun, Pyungtaik, Kyunggi-Do 451-713 (Korea, Republic of); Compressor Development Group, Samsung Gwangju Electronic Company, 1119 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); Department of Mechatronics, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of)

2006-10-15

51

A critical examination of the maximum velocity of shortening used in simulation models of human movement  

Microsoft Academic Search

The maximum velocity of shortening of a muscle is an important parameter in musculoskeletal models. The most commonly used values are derived from animal studies; however, these values are well above the values that have been reported for human muscle. The purpose of this study was to examine the sensitivity of simulations of maximum vertical jumping performance to the parameters

Zachary J. Domire; John H. Challis

2010-01-01

52

A double-gaussian, percentile-based method for estimating maximum blood flow velocity.  

PubMed

Objectives- Transcranial Doppler sonography allows for the estimation of blood flow velocity, whose maximum value, especially at systole, is often of clinical interest. Given that observed values of flow velocity are subject to noise, a useful notion of "maximum" requires a criterion for separating the signal from the noise. All commonly used criteria produce a point estimate (ie, a single value) of maximum flow velocity at any time and therefore convey no information on the distribution or uncertainty of flow velocity. This limitation has clinical consequences especially for patients in vasospasm, whose largest flow velocities can be difficult to measure. Therefore, a method for estimating flow velocity and its uncertainty is desirable. Methods- A gaussian mixture model is used to separate the noise from the signal distribution. The time series of a given percentile of the latter, then, provides a flow velocity envelope. This means of estimating the flow velocity envelope naturally allows for displaying several percentiles (eg, 95th and 99th), thereby conveying uncertainty in the highest flow velocity. Results- Such envelopes were computed for 59 patients and were shown to provide reasonable and useful estimates of the largest flow velocities compared to a standard algorithm. Moreover, we found that the commonly used envelope was generally consistent with the 90th percentile of the signal distribution derived via the gaussian mixture model. Conclusions- Separating the observed distribution of flow velocity into a noise component and a signal component, using a double-gaussian mixture model, allows for the percentiles of the latter to provide meaningful measures of the largest flow velocities and their uncertainty. PMID:24154894

Marzban, Caren; Illian, Paul R; Morison, David; Mourad, Pierre D

2013-11-01

53

Examining the wind forced velocity structure of the California Current system using observations derived from satellite remote sensing  

NASA Astrophysics Data System (ADS)

Methodology is derived to observe mesoscale time-dependent wind-driven ocean velocities. The procedure involves the removal of a geostrophic component from "total flow" velocity observations. Total flow measuring data sets are investigated by statistical analysis, searching for theoretical characteristic signals of wind-driven flow. These signals are found in drifting buoy data, acoustic Doppler current profiler data (ADCP) data, and velocity data extracted from satellite imagery using the maximum cross-correlation technique (MCC), demonstrating that these products observe both the geostrophic and the wind-driven components of the ocean flow. Initial tests, used altimeter mean absolute dynamic topography (MADT) data as the geostrophic signal removed. This resulted in residual velocities that were dominated by vertical geostrophic shear. Methodology was then developed to combine CTD (conductivity, depth, temperature) data, which provides estimates of the geostrophic current relative to the surface, with the MADT product, to produce geostrophic velocity estimates at depth. For MCC derived observations to be used in this analysis, the depth of this product required consideration. Statistical comparison with coincident ADPC and drifter velocity observations suggest that the MCC derived velocities are characteristics of ocean currents at 30 m depth. This characteristic is hypothesized to be a result of the inherent average velocity observations produced by the MCC method and the nature of the variability of the ocean currents. A 12-year time series of wind-driven velocity observations is then produced using this methodology applied to the satellite and in situ data sets. Observations generated demonstrate characteristics consistent with Ekman theory. Strong temporal agreement was found in the fluctuations wind velocity observations derived from satellite scatterometry and the wind-driven observations. Regression models, driven by the wind and the wind-driven current observations, are then used to characterize the response of the ocean to wind-forcing. The vertical response demonstrated strong linear magnitude decay with depth. The horizontal response shows complex structure that demonstrates little connection to the spatial patterns of wind velocity. To attempt to understand these patterns of wind-influence EOF and principal axis analysis are used. The results suggest that the spatial variation of frictional wind influence is strongly modulated by the shape of the coastline. Further analysis suggests that these regions of increased wind influence are driving a significant portion of the variability of the California Current. Future work will involve generating coastal altimetry observations to increase the spatial coverage of this wind-driven velocity product.

Matthews, Dax Kristopher

54

An experimental study of a plasma actuator in absence of free airflow: Ionic wind velocity profile  

NASA Astrophysics Data System (ADS)

In this study, we are interested in the direct current electrical corona discharge created between two wire electrodes. The experimental results are related to some electroaerodynamic actuators based on the direct current corona discharge at the surface of a dielectric material. Several geometrical forms are selected for the dielectric surface, such as a plate, a cylinder, and a NACA 0015 aircraft wing. The current density-electric field characteristics are presented for different cases in order to determine the discharge regimes. The corona discharge produces nonthermal plasma, so it is called plasma discharge. Plasma discharge creates a tangential ionic wind above the surface at the vicinity of the wall. The ionic wind induced by the corona discharge is measured in absence of free external airflow. The ionic wind velocity profiles and the maximum induced tangential force are given for different surface forms, so it is possible to compare the actuators effect based on the span of the ionic wind velocity and thrust values. The higher ionic wind velocity is obtained with the NACA profile, which shows the effectiveness of this actuator for the airflow control.

Mestiri, R.; Hadaji, R.; Ben Nasrallah, S.

2010-08-01

55

An experimental study of a plasma actuator in absence of free airflow: Ionic wind velocity profile  

SciTech Connect

In this study, we are interested in the direct current electrical corona discharge created between two wire electrodes. The experimental results are related to some electroaerodynamic actuators based on the direct current corona discharge at the surface of a dielectric material. Several geometrical forms are selected for the dielectric surface, such as a plate, a cylinder, and a NACA 0015 aircraft wing. The current density-electric field characteristics are presented for different cases in order to determine the discharge regimes. The corona discharge produces nonthermal plasma, so it is called plasma discharge. Plasma discharge creates a tangential ionic wind above the surface at the vicinity of the wall. The ionic wind induced by the corona discharge is measured in absence of free external airflow. The ionic wind velocity profiles and the maximum induced tangential force are given for different surface forms, so it is possible to compare the actuators effect based on the span of the ionic wind velocity and thrust values. The higher ionic wind velocity is obtained with the NACA profile, which shows the effectiveness of this actuator for the airflow control.

Mestiri, R.; Hadaji, R.; Ben Nasrallah, S. [Ecole Nationale d'Ingenieurs de Monastir, Monastir 5019 (Tunisia)

2010-08-15

56

Solar wind bulk velocity fluctuations acting as velocity space diffusion on comoving ions  

NASA Astrophysics Data System (ADS)

From most in-situ plasma observations made in the outer heliosphere it became evident that above the injection border of pick-up ions (?1 keV), an extended suprathermal ion tail is found which in most cases can be fitted by a power law with velocity power indices of (-6) ? ?v ? (-4). As has been shown by theory such energetic ion tails cannot be explained by Fermi-2 type velocity diffusion, since in the outer heliosphere both Alfvenic and magnetoacoustic turbulences become too weak. Here we come to a new solution of this unsolved problem by studying the action of solar wind bulk velocity fluctuations on ions co-moving with the wind. As we show the passage of such fluctuations results in energization of each individual ion and systematic evolution of the ion distribution function towards suprathermal tails. From the basic knowledge that we can obtain on this process we can calculate the velocity divergence of the ion phasespace flow and thus can derive a velocity diffusion operator. As we can show here this operator leads to a velocity diffusion coefficient proportional to the square of the ion velocity and, when employed in the phasespace transport equation, together with terms for convective changes, cooling processes and pick-up ion injection, interestingly enough, permits to find solutions for suprathermal power law tails with power indices of ?v ? -5 as very often observed.

Fahr, H.-J.; Chashei, I. V.; Siewert, M.

2012-01-01

57

Solar wind velocity distribution on the heliospheric current sheet during Carrington rotations 1787-1795  

NASA Astrophysics Data System (ADS)

The solar wind velocity distribution in the heliosphere is best represented using a v-map, where velocity contours are plotted in heliographic latitude-longitude coordinates. It has already been established that low-speed regions of the solar wind on the source surface correspond to the maximum bright regions of the K-corona and the neutral line of the coronal magnetic field. In this analysis, v-maps on the source surface for Carrington rotations (CRs) 1787-1795, during 1987, have been prepared using the interplanetary scintillation measurements at Research Institute of Atmospherics (RIA), Nagoya Univ., Japan. These v-maps were then used to study the time evolution of the low-speed (leq450 km s-1) belt of the solar wind and to deduce the distribution of solar wind velocity on the heliospheric current sheet. The low-speed belt of the solar wind on the source surface was found to change from one CR to the next, implying a time evolution. Instead of a slow and systematic evolution, the pattern of distribution of solar wind changed dramatically at one particular solar rotation (CR 1792) and the distributions for the succeeding rotations were similar to this pattern. The low-speed region, in most cases, was found to be close to the solar equator and almost parallel to it. However, during some solar rotations, they were found to be organised in certain longitudes, leaving regions with longitudinal width greater than 30 free of low-speed solar wind, i.e. these regions were occupied by solar wind with velocities greater than 450 km s-1. It is also noted from this study that the low-speed belt, in general, followed the neutral line of the coronal magnetic field, except in certain cases. The solar wind velocity on the heliospheric current sheet (HCS) varied in the range 300-585 km s-1 during the period of study, and the pattern of velocity distribution varied from rotation to rotation.

Bala, B.; Prabhakaran Nayar, S. R.

1995-08-01

58

Wind velocities on venus: vector determination by radio interferometry.  

PubMed

To determine the wind directions and speeds on Venus, as each Pioneer probe fell to the surface we tracked its motion in three dimensions using a combination of Doppler and long-baseline radio interferometric methods. Preliminary results from this tracking, coupled with results from test observations of other spacecraft, enable us to estimate the uncertainties of our eventual determinations of the velocity vectors of the probes with respect to Venus. For altitudes below about 65 kilometers and with time-averaging over 100-second intervals, all three components of the velocity should have errors of the order of 0.3 meter per second or less. PMID:17833005

Counselman, C C; Gourevitch, S A; King, R W; Pettengill, G H; Prinn, R G; Shapiro, I I; Miller, R B; Smith, J R; Ramos, R; Liebrecht, P

1979-02-23

59

A critical examination of the maximum velocity of shortening used in simulation models of human movement.  

PubMed

The maximum velocity of shortening of a muscle is an important parameter in musculoskeletal models. The most commonly used values are derived from animal studies; however, these values are well above the values that have been reported for human muscle. The purpose of this study was to examine the sensitivity of simulations of maximum vertical jumping performance to the parameters describing the force-velocity properties of muscle. Simulations performed with parameters derived from animal studies were similar to measured jump heights from previous experimental studies. While simulations performed with parameters derived from human muscle were much lower than previously measured jump heights. If current measurements of maximum shortening velocity in human muscle are correct, a compensating error must exist. Of the possible compensating errors that could produce this discrepancy, it was concluded that reduced muscle fibre excursion is the most likely candidate. PMID:20162474

Domire, Zachary J; Challis, John H

2010-12-01

60

Maximum Power Point Tracking of a Microprocessor - Controlled Wind Turbine.  

National Technical Information Service (NTIS)

A wind turbine adaptative control has been designed and optimized. The horizontal axis wind turbine and its mechanical regulation device is first described. An impedance matching is shown to be necessary and is obtained with a direct-direct static convert...

C. Kraif

1984-01-01

61

A method for measuring mean wind velocities in a canyon with tracer balloons  

Microsoft Academic Search

A method using balloons as tracers for measuring mean wind velocity in street canyons or mountain valleys has been developed. Tests of the method with numerical experiments showed that the method reproduced an assumed wind field quite well provided that the buoyancy component of the balloon velocity was larger than the downward velocity component of the wind. Tests of the

C. M. Sheih; B. J. Billman; F. T. Depaul

1985-01-01

62

Comet flares and velocity waves in the solar wind  

SciTech Connect

The flare activity of comets and the structure of the solar wind fluxes are compared with data of measurements of Pioneer-10, -11, Vela-3, IPM-7, and -8 at a heliocentric distance of r approx. = 1-6 AU. It is shown that velocity waves of the solar wind, which evolve into corotating shock waves beyond the orbit of the earth, may be responsible for the flare activity of comets. The work notes a correspondence between the variations of flare activity of comets as a function of heliocentric distance and the behavior of velocity waves in the solar wind, the closeness of the characteristic times of velocity waves (about 7-8 days at r = 1 AU) and the duration of comet flares, and the increase of this characteristic time with increasing r in both cases. The observed distribution of the parameters of comet flare activity in the 11-yr cycle also corresponds well to the distribution of the area of coronal holes and the rate of variation of the area of sunspots ..delta..Sp over the phase of the solar cycle.

Ptitsyna, N.G.; Breus, T.K.; Rikhter, A.K.

1986-05-01

63

Mechanical sensorless maximum power tracking control for direct-drive PMSG wind turbines  

Microsoft Academic Search

Wind turbine generators (WTGs) are usually equipped with mechanical sensors to measure wind speed and rotor position for system control, monitoring, and protection. The use of mechanical sensors increases the cost and hardware complexity and reduces the reliability of the WTG systems. This paper proposes a mechanical sensorless maximum power tracking control for wind turbines directly driving permanent magnetic synchronous

Xu Yang; Xiang Gong; Wei Qiao

2010-01-01

64

Statistical errors in the determination of wind velocities by the spaced antenna technique  

NASA Astrophysics Data System (ADS)

This paper is concerned with the statistical errors which are presented when wind velocities in the atmosphere are determined by the radar method known as the spaced antenna technique. It is assumed that the (complex) data are processed by the method known as full correlation analysis (FCA). A theory is first developed to give the error in the determination of the position of the maximum of a cross-correlation function and the value of lag such that the autocorrelation falls to a value equal to that of the cross-correlation at zero lag. These are the basic quantities needed for the application of FCA. These error estimates are tested with a variety of numerically simulated data and shown to be realistic. The results are applied to real data and, using the standard techniques for the propagation of errors, they lead to estimates of the errors in the derived wind velocities. In order to test these estimates, an experiment was carried out in which two independent wind determinations were made simultaneously. The differences were used to obtain experimental estimates of the errors. It was found that the theory overestimates the error in the wind velocities by about 50 percent. Possible reasons for this are discussed.

May, P. T.

1988-01-01

65

Dependence of the Maximum Static Pressure in the Inner Magnetosphere on the Solar Wind Dynamic Pressure and Different Coupling Functions  

NASA Astrophysics Data System (ADS)

Knowledge about distribution of plasma pressure is crucial for the evaluation of the stability of any plasma configuration. Nevertheless, this distribution should be affected by the solar wind-magnetosphere interaction, generally expressed as a series of coupling functions of Dungey, Akasofu, Newell, among others, as well as different characteristics of the solar wind like velocity, interplanetary magnetic field and dynamic pressure. In this study we used the precipitating particles flux data obtained by Aureol-3 satellite to reconstruct the radial plasma pressure profiles in the night-side inner magnetosphere with high space and time resolution. The instantaneous radial profiles of plasma pressure have been obtained using the THEMIS mission satellites. The dynamics of these profiles has been compared with the main parameters of the solar wind, inferred from the NSSDC date base. In particular, it was found that the maximum value of static pressure in the night-side inner magnetosphere correlates with the value of dynamic pressure of the solar wind. The position of the maximum is also affected by the solar wind dynamic pressure, being closer to the Earth in case of high dynamic pressure. The fact that the inner pressure in the magnetosphere and the relation with the dynamic pressure of the solar wind is important for understanding the dynamics of geomagnetic substorms and storms. Finally we compare these results with the analysis of THEMIS data.

Gallardo-Lacourt, B. I.; Stepanova, M. V.; Antonova, E. E.

2009-12-01

66

Design and performance evaluation of a low cost wind velocity meter  

Microsoft Academic Search

This paper depicts design and performance assessment of a wind velocity meter. Actually this is a mechatronics project. Since, both electrical and mechanical conceptions are used to execute this project. The mechanical system consists of two physical subsections wind vane and anemometer. Here wind van is used to detect wind direction and anemometer for wind speed measurement. Its hardware

Muhammad Asad Rahman; Mokarrom Hossain

2012-01-01

67

Solar wind collimation of the Jupiter high velocity dust streams  

NASA Astrophysics Data System (ADS)

The dust bursts discovered by the Ulysses dust sensor when approaching Jupiter in 1992 were later confirmed as collimated streams of high velocity (~200 km/s) charged (~5V) dust grains escaping from Jupiter and dominated by the interplanetary Magnetic field (IMF). With Cassini, a similar phenomenon was observed in Saturn. It was demonstrated that the Jovian dust streams are closely related to the solar wind compressed regions, either Corotating interaction regions (CIRs) or Coronal mass ejections (CMEs) Cto a minor extent-. Actually the dust streams seem ultimately to be generated by such events. This can be explained considering that dust grains are accelerated as they gain substantial energy while compressed at the forward and reverse shocks that bound or precede these solar wind regions.

Flandes, A.; Krueger, H.

2006-12-01

68

Multifractal two-scale Cantor set model for slow solar wind turbulence in the outer heliosphere during solar maximum  

NASA Astrophysics Data System (ADS)

To quantify solar wind turbulence, we consider a generalized two-scale weighted Cantor set with two different scales describing nonuniform distribution of the kinetic energy flux between cascading eddies of various sizes. We examine generalized dimensions and the corresponding multifractal singularity spectrum depending on one probability measure parameter and two rescaling parameters. In particular, we analyse time series of velocities of the slow speed streams of the solar wind measured in situ by Voyager 2 spacecraft in the outer heliosphere during solar maximum at various distances from the Sun: 10, 30, and 65 AU. This allows us to look at the evolution of multifractal intermittent scaling of the solar wind in the distant heliosphere. Namely, it appears that while the degree of multifractality for the solar wind during solar maximum is only weakly correlated with the heliospheric distance, but the multifractal spectrum could substantially be asymmetric in a very distant heliosphere beyond the planetary orbits. Therefore, one could expect that this scaling near the frontiers of the heliosphere should rather be asymmetric. It is worth noting that for the model with two different scaling parameters a better agreement with the solar wind data is obtained, especially for the negative index of the generalized dimensions. Therefore we argue that there is a need to use a two-scale cascade model. Hence we propose this model as a useful tool for analysis of intermittent turbulence in various environments and we hope that our general asymmetric multifractal model could shed more light on the nature of turbulence.

Macek, W. M.; Wawrzaszek, A.

2011-05-01

69

On the relationship between relativistic electron flux and solar wind velocity: Paulikas and Blake revisited  

NASA Astrophysics Data System (ADS)

Thirty years ago Paulikas and Blake (1979) showed a remarkable correlation between geosynchronous relativistic electron fluxes and solar wind speed (Vsw). This seminal result has been a foundation of radiation belt studies, space weather forecasting, and current understanding of solar wind radiation belt coupling. We have repeated their analysis with a considerably longer-running data set (1989-2010) from the Los Alamos National Laboratory energetic particle instruments with several surprising results. Rather than the roughly linear correlation between Vsw and log (flux), our results show a triangle-shaped distribution in which fluxes have a distinct velocity-dependent lower limit but a velocity-independent upper limit. The highest-electron fluxes can occur for any value of Vsw with no indication of a Vsw threshold. We also find a distinct solar cycle dependence with the triangle-shaped distribution evident in 2 declining phase years dominated by high-speed streams but essentially no correlation in 2 solar maximum years. For time periods that do show a triangle-shaped distribution we consider whether it can be explained by scatter due to other parameters. We examine the role of time dependence and time lag in producing the observed distribution. We also look at the same statistical relationship but at energies $\\ll$1 MeV. We conclude that the relationship between radiation belt electron fluxes and solar wind velocity is substantially more complex than suggested by previous statistical studies. We find that there are important ways in which the conventional wisdom stating that high-velocity wind drives high-MeV electron fluxes is, in general, either misleading or unsupported.

Reeves, Geoffrey D.; Morley, Steven K.; Friedel, Reiner H. W.; Henderson, Michael G.; Cayton, Thomas E.; Cunningham, Gregory; Blake, J. Bernard; Christensen, Rod A.; Thomsen, Davis

2011-02-01

70

The relationship between consistency of propulsive cycles and maximum angular velocity during wheelchair racing.  

PubMed

The purposes of this study were to examine the consistency of wheelchair athletes' upper-limb kinematics in consecutive propulsive cycles and to investigate the relationship between the maximum angular velocities of the upper arm and forearm and the consistency of the upper-limb kinematical pattern. Eleven elite international wheelchair racers propelled their own chairs on a roller while performing maximum speeds during wheelchair propulsion. A Qualisys motion analysis system was used to film the wheelchair propulsive cycles. Six reflective markers placed on the right shoulder, elbow, wrist joints, metacarpal, wheel axis, and wheel were automatically digitized. The deviations in cycle time, upper-arm and forearm angles, and angular velocities among these propulsive cycles were analyzed. The results demonstrated that in the consecutive cycles of wheelchair propulsion the increased maximum angular velocity may lead to increased variability in the upper-limb angular kinematics. It is speculated that this increased variability may be important for the distribution of load on different upper-extremity muscles to avoid the fatigue during wheelchair racing. PMID:18843158

Wang, Yong Tai; Vrongistinos, Konstantinos Dino; Xu, Dali

2008-08-01

71

Correlation of interplanetary medium parameters in transition region of high-velocity solar wind streams  

NASA Astrophysics Data System (ADS)

Investigations of variations in the intensity of galactic cosmic rays (GCR) during presence of the Earth in high velocity streams (HVS) of the solar wind which are associated with coronal holes have shown that the structure of HVS and characteristics of the medium exert a considerable influence on the distribution of cosmic rays in the interplanetary medium. The transition region between the quiet solar wind and HVS, where a significant anisotropy of cosmic rays arises, is of considerable importance. These phenomena were studied using data from the King catalogue for the period 1973-1974 (declining solar activity) when there was a great number of HVS, of which 62 with a velocity 500-800 km/sec were selected for analysis. This made it possible to obtain a number of relationships between the parameters of the streams. It was discovered that there is a close correlation between the transverse dimensions of the HVS and the maximum velocity of plasma in the stream. This agrees well with the known correlation between the dimensions of coronal holes and the velocity of HVS if it is assumed that the size of the coronal hole and the width of the HVS are closely correlated.

Mymrina, N. V.; Dorman, L. I.; Kaminer, N. S.; Kuzmicheva, A. Y.

1985-02-01

72

A novel algorithm for fast and efficient maximum power point tracking of wind energy conversion systems  

Microsoft Academic Search

This research paper proposes a novel solution to the problems that exists in the normal hill climb searching (HCS) maximum power point tracking (MPPT) algorithm for wind energy conversion systems (WECS). The solution presented not only solves the tracking speed vs. efficiency tradeoff problem of HCS but also makes sure that the changing wind conditions shouldn't lead HCS in the

Kazmi Syed Muhammad Raza; Hiroki Goto; Hai-Jiao Guo; Osamu Ichinokura

2008-01-01

73

Doubly Fed Induction Generator Maximum Wind Power Extraction Study Through Integrated Steady-state and Close-loop Control Evaluation  

Microsoft Academic Search

A doubly fed induction generator wind turbine is a variable-speed wind turbine widely used in the modern wind power industry. Unlike a fixed-speed wind turbine, the maximum power extraction of the turbine is affected by (1) electrical characteristics of the generator, (2) aerodynamic characteristics of the turbine blades, and (3) maximum power extraction control strategies. This article presents a doubly

Shuhui Li; Timothy A. Haskew; Eduard Muljadi

2010-01-01

74

Laser Doppler Anemometer (LDA) wind velocity measurements: Possibilities for measurements on windpower units  

Microsoft Academic Search

The utilization of laser Doppler anemometers for wind velocity measurements over distances of several hundred meters is described. Systems which allow the measurement of wind fields make it possible to determine quantitatively the flow field of windpowered units.

F. Durst

1984-01-01

75

The effect of wind velocity on the amplitude scintillations of millimetre radio waves  

Microsoft Academic Search

The effect of transverse wind velocity on the amplitude scintillations of millimeter radio waves is studied. Scintillation data obtained on two line-of-sight microwave links at 36 GHz and 110 GHz on a common 4.1 km path are used to estimate the wind velocity perpendicular to the propagation path. The estimated wind velocity is within 20% of the value obtained from

K. L. Ho; R. S. Cole; N. D. Mavrokoukoulakis

1978-01-01

76

A Theory for the Determination of Wind and Precipitation Velocities with Doppler Radars.  

National Technical Information Service (NTIS)

The feasibility of determining components of wind velocity and precipitation particle terminal fall speeds from the equation of continuity for air and precipitation velocity data collected by Doppler radars is investigated. The investigation is carried ou...

L. Armijo

1967-01-01

77

The wind potential impact on the maximum wind energy penetration in autonomous electrical grids  

Microsoft Academic Search

According to long-term wind speed measurements the Aegean Archipelago possesses excellent wind potential, hence properly designed wind energy applications can substantially contribute to fulfill the energy requirements of the island societies. On top of this, in most islands the electricity production cost is extremely high, while significant insufficient power supply problems are often encountered, especially during the summer. Unfortunately, the

J. K. Kaldellis

2008-01-01

78

Loop Current variability due to wind stress and reduced sea level during the Last Glacial Maximum  

NASA Astrophysics Data System (ADS)

One of the most prominent features of the circulation in the Gulf of Mexico is the Loop Current (LC). It is of special interest as it influences not only the climate in the Gulf of Mexico. Although causation is not well understood yet, dynamical relationships between LC retraction and extension, seasonal migrations of the Intertropical Convergence Zone (ITCZ) and the related wind stress curl over the subtropical North Atlantic, and changes in the thermohaline circulation are indicated by model simulations. A characteristic feature of the LC is the shedding of anticyclonic eddies. These eddies can have depth signatures of up to 1000 m and are of special interest as they supply heat and moisture into the western and northern Gulf. The eddies are generated aperiodically every 3 to 21 months, with an average shedding time of 9.5 months. Eddy shedding appears to be related to a suite of oceanographic forcing fields such as the Yucatan Channel throughflow, the Florida Current and North Brazil Current variability, as well as synoptic meteorological forcing variability. By combining state-of-the-art paleoceanographic and meso-scale eddy-resolving numerical modeling techniques, we examined the Loop Current dynamics and hydrographic changes in the Gulf going back in time up to ~21,000 years. To assess the impact of Last Glacial Maximum (LGM) wind stress and reduced sea level we have re-configured an existing hierarchy of models of the North Atlantic Ocean (FLAME) with a horizontal grid resolution of ca. 30 km (wind stress was taken from the PMIP-II database). The sea level was lowered compared to the CONTROL run by 110 m and 67 m. These sea level changes have been chosen according to the cold-deglacial periods Heinrich I and Younger Dryas. The result of our model simulations is a continuous increase in eddy shedding from the LGM to the Holocene. This increase is predominantly controlled by the continuous deglacial sea level rise. Changes in wind stress curl related to the southward displacement of the ITCZ tend to produce larger Yucatan and Florida Strait throughflow but do not play a dominant role in controlling the eddy shedding, and appear thus of minor importance for the regional climate in the Gulf of Mexico. Comparing our results to observations we found that mean sortable silt values from Florida Strait depict an increase in bottom current velocities during cold climatic periods and times of lowered sea level, too. This is in contrast to recent hydrographic estimates pointing to reduced transports through the Florida Straits.

Mildner, T. C.; Eden, C.; Nuernberg, D.; Schoenfeld, J.

2011-12-01

79

Flexible Grid-connection Technique and Novel Maximum Wind Power Tracking Algorithm for Doubly-Fed Wind Power Generator  

Microsoft Academic Search

The connection between the doubly-fed wind power generators (WPGs) and the grid affects the security of the grid and generator. The maximum. wind power tracking (MWPT) affects the efficiency of the generators connected to the grid. This paper deals with two problems above. Based on a no-load model of doubly-fed induction generator (DFIG), and by applying a vector control technique

Yu Fang; Liu Qi-hui; Zhang Jian-hua

2007-01-01

80

A new control method of permanent magnet generator for maximum power tracking in wind turbine application  

Microsoft Academic Search

This paper discusses a new and simple control method for maximum power tracking in a variable speed wind turbine by using a step-up dc-dc converter. The output voltage of permanent magnet generator is connected to a fixed dc-link through a three-phase rectifier and the dc-dc converter. A maximum power-tracking algorithm calculates the speed command that corresponds to maximum power output

R. Esmaili; L. Xu; D. K. Nichols

2005-01-01

81

Observations of the velocity distribution of solar wind ions  

SciTech Connect

Measurements made by the Isee 3 ion composition experiment have been used to determine the kinetic temperatures of /sup 3/He/sup + +/, /sup 4/He/sup + +/, /sup 16/O/sup 6 +/, and /sup 16/O/sup 7 +/ in the solar wind. It is found that these temperatures generally obey the relation that T/sub i//m/sub i/=const, but fluctuations, some of which are caused by dynamical effects in the flow, are observed. Whether this relation applies to ions with masses greater than 16 requires more analysis to determine. The temperature of oxygen sometimes rises above 10/sup 6/ /sup 0/K, which is very strong evidence for heating outside the collisional region of the corona. The tendency toward equal temperatures per nucleon occurs everywhere where collisions are unimportant, suggesting that the temperatures are set up close to the sun rather than elsewhere in the interplanetary medium. The velocity distribution function of helium is observed to be non-Maxwellian, with a pronounced high velocity tail. As this is one condition for heating by wave dissipation, this mechanism must still be considered as a heating mechanism.

Ogilvie, K.W.; Bochsler, P.; Geiss, J.; Coplan, M.A.

1980-11-01

82

Scaling of maximum probability density functions of velocity and temperature increments in turbulent systems  

NASA Astrophysics Data System (ADS)

In this paper, we introduce a new way to estimate the scaling parameter of a self-similar process by considering the maximum probability density function (pdf) of its increments. We prove this for H-self-similar processes in general and experimentally investigate it for turbulent velocity and temperature increments. We consider turbulent velocity database from an experimental homogeneous and nearly isotropic turbulent channel flow, and temperature data set obtained near the sidewall of a Rayleigh-Bnard convection cell, where the turbulent flow is driven by buoyancy. For the former database, it is found that the maximum value of increment pdf pmax(?) is in a good agreement with lognormal distribution. We also obtain a scaling exponent ?~=0.37, which is consistent with the scaling exponent for the first-order structure function reported in other studies. For the latter one, we obtain a scaling exponent ??~=0.33. This index value is consistent with the Kolmogorov-Obukhov-Corrsin scaling for passive scalar turbulence but different from the scaling exponent of the first-order structure function that is found to be ??(1)~=0.19, which is in favor of Bolgiano-Obukhov scaling. A possible explanation for these results is also given.

Huang, Y. X.; Schmitt, F. G.; Zhou, Q.; Qiu, X.; Shang, X. D.; Lu, Z. M.; Liu, Y. L.

2011-12-01

83

Role of wind stress in causing maximum transport through the Korea Strait in autumn  

NASA Astrophysics Data System (ADS)

Observations show that the maximum transport for the Tsushima Current (TC) through the Korea Strait occurs in autumn. For the TC, variation in transport changes the physical properties of the water as well as the distribution of nutrients, plankton, and other materials in the Japan/East Sea. Despite the importance of the TC, research is yet to unravel the cause of the maximum transport for the TC in autumn. In this study, observational data and numerical modeling data were analyzed in an effort to explore this phenomenon. The maximum transport through the Korea Strait was determined to be the result of the maximum onshore transport crossing the shelf break in the East China Sea (ECS); this transport is driven by strong northeasterly wind stress. Ekman transport driven by wind in the ECS is the primary cause of the maximum transport for the TC through the Korea Strait in autumn.

Cho, Yang-Ki; Seo, Gwang-Ho; Kim, Chang-Sin; Choi, Byoung-Ju; Shaha, Dinesh Chandra

2013-04-01

84

Estimating random transverse velocities in the fast solar wind from EISCAT Interplanetary Scintillation measurements  

Microsoft Academic Search

Interplanetary scintillation measurements can yield estimates of a large number of solar wind parameters, including bulk flow speed, variation in bulk velocity along the observing path through the solar wind and random variation in transverse velocity. This last parameter is of particular interest, as it can indicate the flux of low-frequency Alfvn waves, and the dissipation of these waves has

A. Canals; A. R. Breen; L. Ofman; P. J. Moran; R. A. Fallows

2002-01-01

85

Deposition velocities for full-scale corn and soybean canopies: a wind tunnel simulation  

Microsoft Academic Search

Deposition velocities have been determined for corn and soybeans in the first 4 to 6 weeks of growth in a full-scale study of canopy flow in a wind tunnel. Particles of 1, 5, 10 and 15 ..mu..m aerodynamic diameter made of sodium fluorescein were injected into the Environmental Wind Tunnel Facility at Colorado State University. Deposition velocities were determined as

J. B. Wedding; M. E. Montgomery

1980-01-01

86

Intelligent inverse control to maximum power point tracking control strategy of wind energy conversion system  

Microsoft Academic Search

When the wind speed is below the rated value, the rbf neural network inverse controller is designed to achieve maximum power point tracking (MPPT) for wind energy conversion system,the simulation model is built based on the Matlab \\/ Simulink.The results show that power coefficient and tip speed ratio has high accuracy of tracking the optimal power value,what's more,the neural network

Tai Li; Z. C Ji

2011-01-01

87

Gas transfer velocities measured at low wind speed over a lake  

USGS Publications Warehouse

The relationship between gas transfer velocity and wind speed was evaluated at low wind speeds by quantifying the rate of evasion of the deliberate tracer, SF6, from a small oligotrophic lake. Several possible relationships between gas transfer velocity and low wind speed were evaluated by using 1-min-averaged wind speeds as a measure of the instantaneous wind speed values. Gas transfer velocities in this data set can be estimated virtually equally well by assuming any of three widely used relationships between k600 and winds referenced to 10-m height, U10: (1) a bilinear dependence with a break in the slope at ???3.7 m s-1, which resulted in the best fit; (2) a power dependence; and (3) a constant transfer velocity for U10 3.7 m s-1 which, coupled with the typical variability in instantaneous wind speeds observed in the field, leads to average transfer velocity estimates that are higher than those predicted for steady wind trends. The transfer velocities predicted by the bilinear steady wind relationship for U10 < ???3.7 m s-1 are virtually identical to the theoretical predictions for transfer across a smooth surface.

Crusius, J.; Wanninkhof, R.

2003-01-01

88

A maximum likelihood algorithm for the reconstruction of velocity profile with nano-PIV  

NASA Astrophysics Data System (ADS)

At nano-scale, images of particle flows near a channel wall are obtained combining standard PIV techniques with evanescent wave illumination [R. Sadr et al., J. Fluid Mech. 506, 357-367 (2004)]. Assuming a Langevin description with experimentally known diffusion tensor and a fluid velocity profile directed in one-in-plane direction, we simulate linear, parabolic and electro-osmotic flow with a Milstein scheme of both strong- and weak- order 1. We develop a maximum likelihood algorithm to reconstruct the dependence of the in-plane velocity profile from the out-ot-plane direction. We use PIV simulated particle images and assume an uniform out-of-plane distribution. We further compare the results obtained with two different forms of the probability density function for the in-plane displacement. Next we discuss the validity of the model and of the reconstruction in light of the comparison with true experimental data, in particular the difficulties encountered when assuming a non-uniform out-of-plane distribution. Finally we identify the values of the physical parameters guarantying the validity of the reconstruction algorithm.

Hohenegger, Christel

2005-11-01

89

On the relationship between relativistic electron flux and solar wind velocity: Paulikas and Blake Revisited  

NASA Astrophysics Data System (ADS)

Thirty years ago Paulikas and Blake, [1979] showed a remarkable correlation between geosynchronous relativistic electron fluxes and the speed of the solar wind (Vsw). This seminal result has been a foundation of radiation belt studies, space weather forecasting, and our current picture of how the solar wind couples energy into the inner magnetosphere. We have repeated their analysis with the considerably longer-running data sets (1989 through 2009) from the LANL geosynchronous energetic particle instruments. While our results do not contradict those of Paulikas and Blake, the more complete data set points to several surprising differences in interpretation. While we do find a strong relationship between relativistic electron flux and Vsw we show that the relationship is distinctly non-linear. In fact the scatter plot shows a rather distinct triangle-shaped plot. The distribution has a distinct velocity-dependent lower limit on fluxes rather than a velocity-dependent upper limit that one might expect. There is also a sharp upper limit on electron fluxes that is roughly independent of Vsw. High electron fluxes can be observed for any value of Vsw with no indication of a Vsw threshold. We also find a distinct solar cycle dependence with the triangle-shaped distribution most evident in two declining phase years but weak or no correlation in the conditions found during two solar maximum years. We examine and test a number of possible explanations for the shape of the distribution. We examine the role of time dependence and time lag. We also look at the same relationship but at much lower energies than considered previously. We find that the relationship between Vsw and flux at 62 keV show roughly the same features as the triangle distribution seen at MeV energies suggesting that Vsw likely controls the source population, the source of free energy for acceleration, or both. We conclude that the relationship between radiation belt electron fluxes and solar wind velocity is substantially more complex than suggested by previous statistical studies. We find that there are important ways in which the conventional wisdom stating that high velocity wind drives high MeV electron fluxes is, in general, either misleading or overly simplistic.

Reeves, G. D.; Morley, S.; Friedel, R. H.; Henderson, M. G.; Cayton, T. E.; Blake, J.; Thomsen, D.

2010-12-01

90

Electron velocity distribution functions from the solar wind to the corona  

Microsoft Academic Search

Typical electron velocity distribution functions observed at 1 AU from the Sun by the instrument 3DP aboard of WIND are used as boundary conditions to determine the electron velocity distribution function at 4 solar radii in the corona. The velocity distribution functions (VDF) at low altitude are obtained by solving the Fokker-Planck equation, using two different sets of boundary conditions.

M. Maksimovic; V. Pierrard; J. Lemaire; D. Larson

1999-01-01

91

Effects of a tip vane on velocity distribution around wind turbine blade  

Microsoft Academic Search

It is proved that a tip vane can improve the wind turbine's efficiency by the test and CFD. In this paper, the performance of horizontal axis wind turbine and horizontal axis wind turbine with a tip vane by CFD were simulated. After comparing the velocity distribution around wind turbine blade with the tip vane-V(8.88) and without the tip vane and

Jia Rui-Bo; Wang Jian-Wen

2010-01-01

92

Two-Dimensional Study of the Maximum Power That Can Be Obtained from a Wind Turbine in a Wind Shear Layer.  

National Technical Information Service (NTIS)

For modern large wind turbines there is a considerable velocity gradient in the approaching flow, since the wind flow field above the ground normally is a shear layer with a velocity profile reminding of that of a boundary layer of a wing or a flat plate....

B. C. A. Johansson

1981-01-01

93

Estimate of Maximum Wind Speeds of Tornadoes in Three Northwestern States.  

National Technical Information Service (NTIS)

In an attempt to estimate the maximum wind speeds of potential tornadoes expected in three Northwestern states, all tornadoes and funnel clouds reported in Storm Data during a 20 year period, 1950 through 1969 were examined. Each storm was reevaluated usi...

T. T. Fujita

1970-01-01

94

Maximum Power Point Tracking of Wind Energy Conversion Systems Based on Sliding Mode Extremum Seeking Control  

Microsoft Academic Search

This paper presents a novel maximum power point tracking (MPPT) control method for variable-speed constant-frequency wind energy conversion systems (WECS). The proposed tracking method combines the ideas of sliding mode (SM) control and extremum seeking control (ESC). The only input needed in this method is the output active power of the generator. It avoids some difficult problems in traditional tracking

Tinglong Pan; Zhicheng Ji; Zhenhua Jiang

2008-01-01

95

Sensorless Maximum Power Point Tracking of Wind by DFIG Using Rotor Position Phase Lock Loop (PLL)  

Microsoft Academic Search

This paper presents an invention, the rotor position phase lock loop (PLL), which enables maximum power point (MPPT) tracking of wind by doubly-fed induction generators without needing a tachometer, an absolute position encoder, or an anemometer. The rotor position PLL is parameter variation insensitive, requiring only an estimate of the magnetization inductance for it to operate. It is also insensitive

Baike Shen; Bakari Mwinyiwiwa; Yongzheng Zhang; Boon-Teck Ooi

2009-01-01

96

Measurements of Wind Velocity and Direction Using Acoustic Reflection against Wall  

NASA Astrophysics Data System (ADS)

The measurements of wind velocity and direction using an acoustic reflection against a wall are described. We aim to measure the spatial mean wind velocity and direction to be used for an air-conditioning system. The proposed anemometer consists of a single wall and two pairs of loudspeakers (SP) and microphones (MIC) that form a triangular shape. Two sound paths of direct and reflected waves are available. One is that of the direct wave and the other is that of the wave reflected on the wall. The times of flights (TOFs) of the direct and reflected waves can be measured using a single MIC because there is a difference in the TOF between direct and reflected waves. By using these TOFs, wind velocity and direction can be calculated. In the experiments, the wind velocities and directions were measured in a wind tunnel by changing the wind velocity. The wind direction was examined by changing the setup of the transducers. The measured values using the proposed and conventional anemometers agreed with each other. By using the wave reflected against a wall, wind velocities and directions can be measured using only two pairs of transducers, while four pairs are required in the case of conventional anemometers.

Saito, Ikumi; Wakatsuki, Naoto; Mizutani, Koichi; Ishii, Masahisa; Okushima, Limi; Sase, Sadanori

2008-05-01

97

Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison  

NASA Astrophysics Data System (ADS)

The Southern Hemisphere (SH) westerly winds are thought to be critical to global ocean circulation, productivity, and carbon storage. For example, an equatorward shift in the winds, though its affect on the Southern Ocean circulation, has been suggested as the leading cause for the reduction in atmospheric CO2 during the Last Glacial period. Despite the importance of the winds, it is currently not clear, from observations or model results, how they behave during the Last Glacial. Here, an atmospheric modelling study is performed to help determine likely changes in the SH westerly winds during the Last Glacial Maximum (LGM). Using LGM boundary conditions, the maximum in SH westerlies is strengthened by +1 m s-1 and moved southward by 2 at the 850 hPa pressure level. Boundary layer stabilisation effects over equatorward extended LGM sea-ice can lead to a small apparent equatorward shift in the wind band at the surface. Further sensitivity analysis with individual boundary condition changes indicate that changes in sea surface temperatures are the strongest factor behind the wind change. The HadAM3 atmospheric simulations, along with published PMIP2 coupled climate model simulations, are then assessed against the newly synthesised database of moisture observations for the LGM. Although the moisture data is the most commonly cited evidence in support of a large equatorward shift in the SH winds during the LGM, none of the models that produce realistic LGM precipitation changes show such a large equatorward shift. In fact, the model which best simulates the moisture proxy data is the HadAM3 LGM simulation which shows a small poleward wind shift. While we cannot prove here that a large equatorward shift would not be able to reproduce the moisture data as well, we show that the moisture proxies do not provide an observational evidence base for it.

Sime, Louise C.; Kohfeld, Karen E.; Le Qur, Corinne; Wolff, Eric W.; de Boer, Agatha M.; Graham, Robert M.; Bopp, Laurent

2013-03-01

98

Research on Capture the Maximum Wind Energy of Wind Generation with DFIG  

Microsoft Academic Search

Take do uble2fed induction generato r ( DFI G) as example , to make use of wind energy for t he high limit and increase generating capacit y , t he system st ruct ure and part s of mat hematical model of DFI G were int roduced ,t he p rinciple and p rocess of capt ure t he

XIE Hua

2008-01-01

99

Dependence of the equatorial anomaly and of equatorial spread F on the maximum prereversal E B drift velocity measured at solar maximum  

NASA Astrophysics Data System (ADS)

The relation of equatorial bubbles to the equatorial anomaly is important because scintillation that is most disruptive to transionospheric RF propagation occurs when it passes through the intersection of the two. However, measurement of the relation between the two and of the electric field from which both arise is difficult because of large separations in space and time. This first attempt to perform these measurements employs a latitudinal array of ionospheric sounders spanning 0 to 40 dip latitude (DLAT) in the Western American sector. Measured on each day of a solar maximum year are the following: (1) the maximum electron density of the postsunset equatorial anomaly, Ne, at 16 and at 20.3 DLAT at 2100 LT, the time when the anomaly crest is at its maximum latitude; (2) equatorial spread F (ESF), detected by the occurrence of macroscopic bubbles and of bottomside spread F (BSSF), the latter recorded at levels of none, weak and strong; (3) Kp averaged over the 6 hours before sunset. Ne and ESF are considered functions of the maximum prereversal F layer drift E B drift velocity measured by the Jicamarca incoherent scatter radar also during solar maximum and at the same longitude. Parameters are averaged over two levels of Kp for the three seasons, the E months (March, April, September, and October), D months (November-February), and J months (May-August) to yield the following results: (1) Ne measured at 16, at 20.3 DLAT or at the anomaly crest are linearly dependent on maximum E B drift velocity. (2) Occurrence of each level of ESF increases with Ne approximately linearly during the E and J months but not during the D months. (3) ESF occurrence is dependent on and increases approximately linearly with maximum E B drift velocity during the E and J months. During the D months this dependence is absent. Except for the D months, these results indicate that scintillation increases with maximum prereversal E B drift velocity: at L-band at the bubble-anomaly intersection because bubble occurrence increases, Ne increases, and the latitudinal extent of the anomaly increases; and at VHF/UHF near the equator because the occurrence of strong BSSF increases.

Whalen, J. A.

2003-05-01

100

Remote sensing of atmospheric wind velocities using solid-state and CO2 coherent laser systems  

Microsoft Academic Search

Coherent lidar\\/laser radar systems have been used for the remote measurement of atmospheric wind velocity since 1966. Both CW and pulsed coherent lidars have been developed and applied to a variety of ground-based and airborne applications. In recent years, most efforts have concentrated on pulsed CO2 and solid-state Doppler lidars for the remote measurement of atmospheric wind velocities. Issues associated

R. MILTON HUFFAKER; R. MICHAEL HARDESTY

1996-01-01

101

Southern Hemisphere Westerly Wind Changes during the Last Glacial Maximum: Model-Data Comparison  

NASA Astrophysics Data System (ADS)

The Southern Hemisphere (SH) westerly winds are thought to be critical to both past and future global ocean circulation, productivity, and carbon storage. For example, an equatorward shift in the winds has been suggested as the leading cause for the reduction in atmospheric CO2 during the Last Glacial Maximum (LGM), through its affect on the Southern Ocean circulation. Despite the importance of the SH westerlies, paleo-records and modelling studies still disagree on how they behaved during the LGM. Here, a joint model-data evaluation study is performed to determine likely changes in the SH westerly winds during the LGM. HadAM3 atmospheric simulations, along with published PMIP2 coupled climate model simulations, are assessed against our newly synthesised database of moisture records for the LGM (Kohfeld et al., accepted, QSR). While moisture data are the most commonly cited evidence in support of a large equatorward shift in the SH winds during the LGM, none of the models that produce realistic LGM precipitation patterns show a large equatorward shift. In fact, the model which best simulates the moisture proxy data, our HadAM3 LGM simulation, shows a small poleward wind shift. Thus, moisture proxies do not provide a robust observational evidence base for equatorward shifted winds during the LGM (Sime et al, in press, QSR). Sensitivity simulations, featuring individual boundary condition changes, suggest that changes in sea surface temperatures are the strongest factor behind LGM wind changes, compared with sea ice and land ice effects. If the SH westerly winds were not shifted equatorward at the LGM, this raises intriguing questions regarding past and future carbon storage in the Southern Ocean.

Sime, Louise; Kohfeld, Karen; Le Quere, Corinne; Wolff, Eric; de Boer, Agatha; Graham, Robert; Bopp, Laurent

2013-04-01

102

Artificial neural network-based maximum power point tracking control for variable speed wind energy conversion systems  

Microsoft Academic Search

A new maximum power point tracking (MPPT) controller using artificial neural networks (ANN) for variable speed wind energy conversion system (WECS) is proposed. The algorithm uses Jordan recurrent ANN and is trained online using back propagation. The inputs to the networks are the instantaneous output power, maximum output power, rotor speed and wind speed, and the output is the rotor

J. S. Thongam; P. Bouchard; H. Ezzaidi; M. Ouhrouche

2009-01-01

103

Turbulence velocity spectra dependence on the mean wind at the bottom of a valley  

Microsoft Academic Search

A spectral analysis of the surface boundary layer turbulence at the bottom of a valley is presented. The spectra were classified according to wind speed, wind direction with respect to the valley axis and stability condition. The results reveal that the vertical velocity spectra have a well defined peak in all cases. The average spectra are better defined for mean

Roberto Magnago; Osvaldo Moraes; Otvio Acevedo

2009-01-01

104

New results on equatorial thermospheric winds and the midnight temperature maximum  

NASA Astrophysics Data System (ADS)

Optical observations of thermospheric winds and temperatures determined with high resolution measurements of Doppler shifts and Doppler widths of the OI 630-nm equatorial nightglow emission have been made with improved accuracy at Arequipa, Peru (16.4 S, 71.4 W) with an imaging Fabry-Perot interferometer. An observing procedure previously used at Arecibo Observatory was applied to achieve increased spatial and temporal sampling of the thermospheric wind and temperature with the selection of eight azimuthal directions, equally spaced from 0 to 360, at a zenith angle of 60. By assuming the equivalence of longitude and local time, the data obtained using this technique is analyzed to determine the mean neutral wind speeds and mean horizontal gradients of the wind field in the zonal and meridional directions. The new temperature measurements obtained with the improved instrumental accuracy clearly show the midnight temperature maximum (MTM) peak with amplitudes of 25 to 200 K in all directions observed for most nights. The horizontal wind field maps calculated from the mean winds and gradients show the MTM peak is always preceded by an equatorward wind surge lasting 1-2 h. The results also show for winter events a meridional wind abatement seen after the MTM peak. On one occasion, near the September equinox, a reversal was observed during the poleward transit of the MTM over Arequipa. Analysis inferring vertical winds from the observed convergence yielded inconsistent results, calling into question the validity of this calculation for the MTM structure at equatorial latitudes during solar minimum. Comparison of the observations with the predictions of the NCAR general circulation model indicates that the model fails to reproduce the observed amplitude by a factor of 5 or more. This is attributed in part to the lack of adequate spatial resolution in the model as the MTM phenomenon takes place within a scale of 300-500 km and ~45 min in local time. The model shortcoming is also attributed in part to the need for the model to include a hydrodynamical mechanism to describe the merging of the zonal wind with the meridional tidal winds that converge onto the geographical equator. Finally, a conclusion of this work is that the MTM compressional heating takes place along the perimeter of the pressure bulge rather than within the bulge, an issue previously not appreciated.

Meriwether, J.; Faivre, M.; Fesen, C.; Sherwood, P.; Veliz, O.

2008-03-01

105

Maximum-power-point tracking with reduced mechanical stress applied to wind-energy-conversion-systems  

Microsoft Academic Search

This paper presents an improved maximum-power-point tracking algorithm for wind-energy-conversion-systems. The proposed method significantly reduces the turbine mechanical stress with regard to conventional techniques, so that both the maintenance needs and the medium time between failures are expected to be improved. To achieve these objectives, a sensorless speed control loop receives its reference signal from a modified Perturb&Observe algorithm, in

L. G. Gonzlez; E. Figueres; G. Garcer; O. Carranza

2010-01-01

106

Southern Hemisphere Westerly Wind Changes during the Last Glacial Maximum: Paleo-data Synthesis  

NASA Astrophysics Data System (ADS)

Changes in the strength and position of Southern Hemisphere westerly winds during the last glacial cycle have been invoked to explain glacial-interglacial climate fluctuations. However, neither paleo models nor paleodata agree on the magnitude, or even the sign, of the change in wind strength and latitude during the Last Glacial Maximum (LGM), compared to the recent past. This study synthesizes paleo-environmental data that have been used to infer changes in winds during the LGM compared with the late Holocene. These compilations include changes in terrestrial moisture, dust deposition, and ocean productivity, along with summaries of previously published information on sea surface temperatures (SSTs) and ocean dynamics in the Southern Hemisphere. Our compilations of terrestrial moisture from 94 sites and dust deposition from 87 sites show generally drier conditions for the LGM between 0 and 40S, with wetter conditions along the west coasts and drying along the east coasts of continents. LGM dust deposition rates ranged from 2 to 4.5 times higher over the Southern Ocean and about 13 times higher over the Antarctic continent. For the oceans, reconstructed changes in SSTs show maximum cooling (>4C) in the modern-day Subantarctic Zone, coincident with a region of enhanced export production during the LGM compared with today. We find that any hypothesis of LGM wind and climate change needs to provide a plausible explanation for increased moisture on the west coast of continents, cooler temperatures and higher productivity in the Subantarctic Zone, and reductions in Agulhas leakage around southern Africa. Our comparison suggests that an overall strengthening, an equatorward displacement, or no change at all in winds could all be interpreted as consistent with observations. If a single cause related to the southern westerlies is sought for all the evidence presented, then an equatorward displacement or strengthening of the winds would be consistent with the largest proportion of the data evidence. However, other processes, such as weakening or poleward shifts in winds, a weakened hydrological cycle, extended sea-ice cover, and changed buoyancy fluxes, cannot be ruled out as potential explanations of observed changes in moisture, surface temperature, and productivity. We contend that resolving the position and strength of westerly winds during the LGM remains elusive based on data reconstructions alone. However, we believe that these data reconstructions of environmental conditions can be used in conjunction with model simulations to identify which processes best represent westerly wind conditions during the LGM.

Kohfeld, Karen; Graham, Robert; De Boer, Agatha; Sime, Louise; Wolff, Eric; Le Qur, Corinne; Bopp, Laurent

2013-04-01

107

New results on equatorial thermospheric winds and the midnight temperature maximum  

NASA Astrophysics Data System (ADS)

Fabry-Perot interferometer measurements of Doppler shift and Doppler broadening of the Oi 630-nm nightglow at Arequipa, Peru (16.2 S, 71.5 W) have been made with a new observing strategy that is designed to determine the divergence and vorticity of the neutral wind field. These results were obtained with a CCD detector that increased the Fabry-Perot sensitivity by 15 times. Observations were made with the new imaging Fabry-Perot instrument during 2005 and 2006. These results have been analyzed to produce maps of the thermospheric neutral winds and temperatures. The results show that one or two hours prior to the detection of a midnight temperature maximum (MTM) with an amplitude of 50 to 200 K, there is always seen a meridional northward flow of air with a speed of 50 to 75 ms-1. When the MTM amplitude is weak, the meridional wind component is also weak and generally nil. These results are interpreted to indicate that thermospheric tidal winds contribute to the formation of the MTM. Modeling calculations using the NCAR general circulation model were performed to reproduce the MTM peak but with unsuccessful results. It is proposed that these calculations need to include the terdiurnal tidal mode as part of the lower boundary tidal specifications. It is also proposed that the observed variability of the MTM peak amplitude is a direct consequence of the variability of the tidal wind forcing.

Meriwether, John

108

A Theory for the Determination of Wind and Precipitation Velocities with Doppler Radars  

Microsoft Academic Search

The feasibility of determining components of wind velocity and precipitation particle terminal fallspeeds from the equation of continuity for air and precipitation velocity data collected by Doppler radars is investigated. The investigation is carded out for a system which utilizes two Doppler radars as well as for a system which utilizes three Doppler radars. When only two Doppler radars are

L. Armijo

1969-01-01

109

Wind tunnel studies of a ship model using vortex generators to improve wake velocities  

Microsoft Academic Search

Severe vibration during trials of a 13,000 ton displacement cargo ship was attributed to the propeller working in a strongly non-uniform velocity field. This report gives the results of a series of wind tunnel experiments performed on a reflex model fitted with vortex generators which substantially improved the wake velocity distribution. It was recommended that these generators be geometrically scaled

N. Matheson

1974-01-01

110

Influence of wind velocity on pollen concentration in urban canopy layer  

NASA Astrophysics Data System (ADS)

POLLEN RELEASE Temperature is the basic parameter for prediction of the beginning of the pollen season and identification days with good potential for pollen release. Different approaches are used for determination of the start of the pollen season: i) the sum of daily pollen counts = ?x criterion (Arnold 2002), ii) the mean temperature method during pre-defined period (Sparks, 2000), iii) the temperature sum method (Jones 1992). Another parameters influencing pollen release are: day light length, morning temperature gradient, relative humidity. The mentioned parameters enable to create the "statistical model for determination of timing of pollen potential release. But, the correct determination of pollen release timing is only the first step to correct prediction of pollen concentration in air. The above mentioned collection of parameters isn't complete for correct pollen production prediction without inclusion of the actual wind velocity. The wind velocity directly influences the pollen release rate from mother plant and subsequently transport of pollen grains. From this reason, influence of wind conditions has to be considered as exactly as possible in complex prediction models. WIND VELOCITY AND POLLEN CONCENTRATION Results of in-situ measurements were used for carried out analysis of the relation between wind velocity and pollen concentration in an urban canopy layer. The mean daily wind velocities and the mean daily pollen concentrations were used as the input data describing the pollen season 2005 in an inner part of the city of Brno (pop. 400 000). The mean daily pollen concentrations were matched to corresponding mean daily wind velocity and depicted in graphs. This procedure was done for all locally monitored aeroallergens, namely Alnus, Ambrosia, Betula, Artemis, Corylus, Fraxinus, Poaceae and Quercus. Only days with significant pollen concentration (above 10% of maximal pollen season concentration) were considered for detail analysis. Clear evidence of the wind threshold velocity of pollination appears in the carried out graphical expression of in-situ measurement. The threshold velocity of pollination is the lowest wind velocity with significant concentration of pollen grains in the air. Wind velocity increase above the wind threshold velocity of pollination causes another increase in pollen maximal concentration until reaching the highest concentration of the pollen season. This trend reflects increase in the total pollen release rate due to increase of the air velocity in deeper layers of vegetation and branch bundles. Another increase of wind velocity causes decrease of the maximal air pollen concentration due to "dilution of the canopy layer by vast quantity of fresh air. The described "triangle" trend was confirmed for majority of considered species. The particularly determined values of the wind threshold velocity of pollination in urban area are: Alnus 0,66 m/s, Ambrosia 0,4 m/s, Betula 0,59 m/s, Artemis 0,62 m/s, Corylus 0,75 m/s, Fraxinus 0,5 m/s, Poaceae 0,45 m/s and Quercus 0,66 m/s. The wind velocities corresponding to the highest pollen concentration values are: Alnus 0,95 m/s, Ambrosia 1,01 m/s, Betula 1,1 m/s, Artemis 0,8 m/s, Corylus 0,95 m/s, Fraxinus 1,1 m/s, Poaceae 1,29 m/s and Quercus 0,96 m/s.

Pospisil, J.; Jcha, M.

2009-09-01

111

The determination by microdensitometry of the initial maximum velocity rate of rat ovarian 3 ? hydroxysteroid dehydrogenase activity  

Microsoft Academic Search

The determination of the initial maximum velocity rate of 3 hydroxysteroid dehydrogenase activity (3 HSD) of the newest generation of corpora lutea of the adult dioestrous rat ovary is described. Under conditions where the substrate and co-factor concentrations are not rate limiting (410-4 M epiandrosterone; 310-3 M NAD+ respectively) the initial maximum reaction rate was maintained for approximately 6 min.

W. R. Robertson; R. J. Earnshaw; A. Lambert

1982-01-01

112

Neotectonic Velocity Field of the Western United States: A new Maximum-likelihood Solution  

Microsoft Academic Search

New kinematic finite-element program NeoKinema solves for long-term-average velocity fields and fault slip rates in deforming lithosphere, based on three kinds of information: (1) geologic slip rates of an unlimited number of faults, with standard deviations (which may be large); (2) geodetic velocities of benchmarks, either in fixed or free-floating velocity reference frame, with covariance matrix; (3) stress-direction data. Faults

P. Bird

2002-01-01

113

Comparison of zonal neutral winds with equatorial plasma bubble and plasma drift velocities  

NASA Astrophysics Data System (ADS)

A one-year dataset spanning March 2011 to March 2012 of coincident observations of nighttime thermospheric zonal neutral winds, equatorial plasma bubble (EPB) velocities, and zonal plasma drifts is used to examine the relationship between the thermosphere and the ionosphere near the geomagnetic equator over Peru. Thermospheric neutral winds are determined by using a bistatic Fabry-Perot interferometer (FPI) experiment located at Merihill and Nazca in Peru. The ambient plasma drift velocities were obtained using the incoherent scatter radar at the Jicamarca Radio Observatory in Peru. The EPB zonal velocities were estimated utilizing images of the OI 630.0 nm emission recorded by a narrow-field optical imaging system at the Cerro Tololo Inter-American Observatory in Chile. The joint analysis of these datasets illustrates that the nighttime and night-to-night variations in the zonal neutral winds, EPB velocities, and plasma drifts are well correlated. This consistent result of the local time variations of the neutral winds with that of EPB and plasma drifts illustrates that the F-region dynamo is, in general, fully activated. However, at times, the magnitude of the EPB velocities and the plasma drifts are different from the neutral winds. It is plausible that such a difference is due either to the effect of polarization electric fields developed inside the EPB or due to the latitudinal gradient of the neutral winds and EPB velocity measurements since the EPB velocities are estimated at a higher latitude, corresponding to an apex altitude of ~400 km, than the wind estimates, which derive from an apex altitude of ~250 km.

Chapagain, Narayan P.; Fisher, Daniel J.; Meriwether, John W.; Chau, Jorge L.; Makela, Jonathan J.

2013-04-01

114

Aeolian dust deposition on photovoltaic solar cells: the effects of wind velocity and airborne dust concentration on cell performance  

Microsoft Academic Search

Wind tunnel experiments were conducted to investigate the effect of wind velocity and airborne dust concentration on the drop of photovoltaic (PV) cell performance caused by dust accumulation on such cells. Performance drop was investigated at four wind velocities and four dust concentrations. IV characteristics were determined for various intensities of cell pollution. The evolutions of the short circuit current,

Dirk Goossens; Emmanuel Van Kerschaever

1999-01-01

115

Large and small-scale structures of the local Galactic disc. A maximum entropy approach to the stellar velocity distribution  

NASA Astrophysics Data System (ADS)

An analytical model based on the maximum entropy approach is proposed to describe the eventual asymmetries of the velocity distribution, which are collected through its sample moments. If an extended set of moments is available, the current method provides a linear algorithm, associated with a Gramian system of equations, that leads to a fast and suitable estimation of the velocity distribution. In particular, it could be used to model multimodal distributions that cannot be described through Gaussian mixtures. The method is used with several samples from the HIPPARCOS and Geneva-Copenhagen survey catalogues. For the large-scale distribution, the phase density function may be obtained by fitting moments up to sixth order as a product of two exponential functions, one giving a background ellipsoidal shape of the distribution and the other accounting for the skewness and for the slight shift in the ellipsoidal isocontours in terms of the rotation velocity. The small-scale distribution can be deduced from truncated distributions, such as velocity-bounded samples with |V| ? 51 km s-1, which contain a complex mixture of early-type and young disc stars. By fitting up to ten-order moments, the maximum entropy approach gives a realistic portrait of actual asymmetries, showing a clear bimodal pattern: (i) around the Hyades-Pleiades stream, with negative radial mean velocity and (ii) around the Sirius-UMa stream, with slightly positive radial mean velocity. Among metallicity, colour, and other star properties, the eccentricity of the star's orbit behaves as a very good sampling parameter to find a more detailed structure for the disc velocity distribution, allowing distinctions between different eccentricity layers. For subsamples with eccentricities e<0.15, star velocities are approximately symmetrically distributed around the LSR in the radial direction, with a dearth of stars at the LSR. For e=0.15, the core distribution of the thin disc is supported by two major stellar groups with opposite radial velocities. Several simulations confirm that such a double-peaked distribution comes from the lognormal distribution of the velocity amplitudes. For maximum eccentricity 0.3 and maximum distance to the Galactic plane 0.5 kpc a representative thin disc sample is obtained. The U-anomaly along the radial direction is estimated straightforwardly 30-35 km s-1 from the contour plots. An explanation of the apparent vertex deviation of the disc from the swinging of those major kinematic groups around the LSR is then possible, which predicts a continuously changing orientation of the disc's pseudo ellipsoid.

Cubarsi, R.

2010-02-01

116

The validity of an assessment of maximum angular velocity of knee extension (KE) using a gyroscope.  

PubMed

Although it is more important to assess the muscular power of the lower extremities than the strength, no simplified method for doing so has been found. The aim of this study was to assess the validity of the assessment of the angular velocity of KE using a gyroscope. Participants included 105 community-dwelling older people (55 women, 50 men, age standard deviation (SD) 755.3). Pearson correlation coefficients and Spearman rank-correlation coefficients were used to examine the relationships between the angular velocity of KE and functional performance measurements, a self-efficacy scale and health-related quality of life (HRQOL). The data from the gyroscope were significantly correlated with some physical functions such as muscle strength (r=0.304, p<0.01), and walking velocity (r=0.543, p<0.001). In addition, the joint angular velocity was significantly correlated with self-efficacy (r=0.219-0.329, p<0.01-0.05) and HRQOL (r=0.207-0.359, p<0.01-0.05). The absolute value of the correlation coefficient of angular velocity tended to be greater than that of the muscle strength for mobility functions such as walking velocity and the timed-up-and-go (TUG) test. In conclusion, it was found that the assessment of the angular velocity of the knee joint using a gyroscope could be a feasible and meaningful measurement in the geriatrics field. PMID:22100108

Arai, Takeshi; Obuchi, Shuichi; Shiba, Yoshitaka; Omuro, Kazuya; Inaba, Yasuko; Kojima, Motonaga

2011-11-17

117

Maximum-likelihood fitting of the 6dFGS peculiar velocities  

NASA Astrophysics Data System (ADS)

We develop a robust Bayesian model to derive peculiar velocities and Fundamental Plane (FP) distances for a subsample of 9000 galaxies from the 6dF Galaxy Survey (6dFGS). These galaxies form the basis of 6dFGSv, the largest and most uniform galaxy peculiar-velocity sample to date. We perform a Bayesian analysis of the data set as a whole, determining cosmological parameters from the peculiar-velocity field (e.g., fitting ? and the bulk flow), by comparing to the field predicted from the redshift survey and assuming that the galaxy distribution traces the matter distribution.

Magoulas, Christina; Springob, Christopher; Colless, Matthew; Jones, D. Heath; Campbell, Lachlan; Lucey, John; Mould, Jeremy

2013-02-01

118

ACOUSTIC TOMOGRAPHY METHOD FOR MEASURING TEMPERATURE AND WIND VELOCITY  

Microsoft Academic Search

We consider the problem of reconstructing superimposed tempera- ture and wind flow fields from acoustic measurements. A new tech- nique based solely on acoustic waves propagation is presented. In contrast to the usual straight ray assumption, a bent ray model is con- sidered in order to achieve higher accuracy. Under this assumption, we propose an iterative reconstruction algorithm that allows

Ivana Jovanovi; Luciano Sbaiz; Martin Vetterli

2009-01-01

119

Long term variability in solar wind velocity and IMF intensity and the relationship between solar wind parameters & geomagnetic activity  

Microsoft Academic Search

A study is carried out on the mean monthly values of in situ observations of solar wind velocity (V) and the intensity of interplanetary magnetic field, Bto elucidate their long term variations using the technique of singular spectrum analysis. It is shown that Bexhibits a clear solar cycle signal with progressively deepening minimum and a well-defined longer period variation but

G. K. Rangarajan; L. M. Barreto

2000-01-01

120

Long term variability in solar wind velocity and IMF intensity and the relationship between solar wind parameters & geomagnetic activity  

Microsoft Academic Search

A study is carried out on the mean monthly values of in situ observations of solar wind velocity ( V ) and the intensity of interplanetary magnetic field, B to elucidate their long term variations using the technique of singular spectrum analysis. It is shown that B exhibits a clear solar cycle signal with progressively deepening minimum and a well-defined

G. K. Rangarajan; L. M. Barreto

2000-01-01

121

Remote Sensing Of Three-Dimensional Winds With Elastic Lidar: Explanation Of Maximum Cross-Correlation Method  

NASA Astrophysics Data System (ADS)

Maximum cross-correlation provides a method to remotely determine highly resolved three-dimensional fields of horizontal winds with elastic lidar throughout large volumes of the planetary boundary layer (PBL). This paper details the technique and shows comparisons between elastic lidar winds, remotely sensed laser Doppler velocimeter (LDV) wind profiles, and radiosonde winds. Radiosonde wind data were acquired at Barcelona, Spain, during the Barcelona Air-Quality Initiative (1992), and the LDV wind data were acquired at Sunland Park, New Mexico (N.M.), during the Border Area Air-Quality Study (1994). Comparisons show good agreement between the different instruments, and demonstrate the method useful for air pollution management at the local/regional scale. Elastic lidar winds could thus offer insight into aerosol and pollution transport within the PBL. Lidar wind fields might also be used to nudge or improve initialization and evaluation of atmospheric meteorological models.

Buttler, William T.; Soriano, Cecilia; Baldasano, Jose M.; et al.

122

Covariance statistics of turbulence velocity components for wind-energy-conversion system design-homogeneous, isotropic case  

Microsoft Academic Search

When designing a wind energy converison system (WECS), it may be necessary to take into account the distribution of wind across the disc of rotation. The specific engineering applications include structural strength, fatigue, and control. This wind distribution consists of two parts, namely that associated with the mean wind profile and that associated with the turbulence velocity fluctuation field. The

Fichtl

1983-01-01

123

A complementary review of maximum power point tracking methods for wind generators  

NASA Astrophysics Data System (ADS)

Maximum power point tracking (MPPT) is a very important necessity in a system of energy conversion from a renewable energy source. In this paper, is made an attempt to provide a brief review of 12 very recent publications, not analyzed in the last surveys appeared in 2010 and 2011, and to make a comparative analyze and a classification of all available MPPT algorithms, highlighting their strength and drawbacks. After addressing the reasons for use of MPPT techniques, various power optimization schemes are surveyed. The comparative analysis and a classification of the MPPT algorithms are useful for the designers of wind energy power systems.

Cr?ciunescu, Aurelian; Popescu, Claudia; Popescu, Mihai

2012-09-01

124

A Stand-Alone Hybrid Generation System Combining Solar Photovoltaic and Wind Turbine with Simple Maximum Power Point Tracking Control  

Microsoft Academic Search

This paper proposes a hybrid energy system combing solar photovoltaic and wind turbine as a small-scale alternative source of electrical energy where conventional generation is not practical. A simple and cost effective control technique has been proposed for maximum power point tracking from the photovoltaic array and wind turbine under varying climatic conditions without measuring the irradiance of the photovoltaic

Nabil A. Ahmed; Masafumi Miyatake

2006-01-01

125

Growing Neural Gas (GNG)Based Maximum Power Point Tracking for High-Performance Wind Generator With an Induction Machine  

Microsoft Academic Search

This paper presents a maximum power point track- ing (MPPT) technique for a high-performance wind generator with induction machine based on the growing neural gas (GNG) network. Here, a GNG network has been trained offline to learn the turbine characteristic surface torque versus wind speed and machine speed. It has been implemented online to perform the inversion of this function,

Maurizio Cirrincione; Marcello Pucci; Gianpaolo Vitale

2011-01-01

126

Reynolds-number-dependence of the maximum in the streamwise velocity fluctuations in wall turbulence  

NASA Astrophysics Data System (ADS)

A survey is made of the standard deviation of the streamwise velocity fluctuations in near-wall turbulence and in particular of the Reynolds-number-dependency of its peak value. The following canonical flow geometries are considered: an incompressible turbulent boundary layer under zero pressure gradient, a fully developed two-dimensional channel and a cylindrical pipe flow. Data were collected from 47 independent experimental and numerical studies, which cover a Reynolds number range of R ?= U ? ?/v=300-20,920 for the boundary layer with ? the momentum thickness and R += u *R/v=100-4,300 for the internal flows with R the pipe radius or the channel half-width. It is found that the peak value of the rms-value normalised by the friction velocity, u *, is within statistical errors independent of the Reynolds number. The most probable value for this parameter was found to be 2.710.14 and 2.700.09 for the case of a boundary layer and an internal flow, respectively. The present survey also includes some data of the streamwise velocity fluctuations measured over a riblet surface. We find no significant difference in magnitude of the normalised peak value between the riblet and smooth surfaces and this property of the normalised peak value may for instance be exploited to estimate the wall shear stress from the streamwise velocity fluctuations. We also consider the skewness of the streamwise velocity fluctuations and find its value to be close to zero at the position where the variance has its peak value. This is explained with help of the equations of the third-order moment of velocity fluctuations. These results for the peak value of the rms of the streamwise velocity fluctuations and also the coincidence of this peak with the zero value of the third moment can be interpreted as confirmation of local equilibrium in the near-wall layer, which is the basis of inner-layer scaling. Furthermore, these results can be also used as a requirement which turbulence models for the second and triple velocity correlations should satisfy.

Mochizuki, S.; Nieuwstadt, F. T. M.

1996-07-01

127

A simple method to estimate threshold friction velocity of wind erosion in the field  

Microsoft Academic Search

This study provides a fast and easy-to-apply method to estimate threshold friction velocity (TFV) of wind erosion in the field. Wind tunnel experiments and a variety of ground measurements including air gun, pocket penetrometer, torvane, and roughness chain were conducted in Moab, Utah and cross-validated in the Mojave Desert, California. Patterns between TFV and ground measurements were examined to identify

Junran Li; Gregory S. Okin; Jeffrey E. Herrick; Jayne Belnap; Seth M. Munson; Mark E. Miller

2010-01-01

128

Space weather modelling with intelligent hybrid systems: Predicting the solar wind velocity  

Microsoft Academic Search

We are developing a space weather model to predict disturbances of the Earth's magnetosphere\\/ionosphere on four different time-scales: minutes, hours, 13 days, and 27 days. The minutes to hours predictions are made from solar-wind measurements, while predictions days in advance are made from solar observations.In this work we concentrate on predictions of solar wind velocities 3 days ahead. Using daily

P. Wintoft; H. Lundstedt

1998-01-01

129

Comparison of nighttime zonal neutral winds and equatorial plasma bubble drift velocities over Brazil  

NASA Astrophysics Data System (ADS)

We present results from the first extended period of coincident observations of thermospheric zonal neutral winds and equatorial plasma bubble (EPB) zonal drift velocities over northeastern Brazil during the October to December months of 2009 and 2010. The EPB zonal drift velocities are estimated utilizing images of the O I 630.0 nm emissions recorded by a wide-angle imaging system at Cajazeiras. Thermospheric neutral wind estimates are based upon common volume observations made by a bistatic Fabry-Perot interferometer (FPI) experiment using FPIs located at Cajazeiras and Cariri in Brazil observing the Doppler shift of the O I 630.0 nm emission. The results illustrate a similar pattern of nighttime and night-to-night variations in the zonal neutral winds and EPB zonal drift velocities. In general, the geomagnetic zonal neutral winds and the EPB velocities show an excellent agreement illustrating that the F region dynamo is fully developed. However, in the early evening hours the EPB zonal speed is slower than that of the background winds on several occasions. We conclude that this indicates that during the bubble evolution period in the early evening the F region dynamo is not fully activated.

Chapagain, Narayan P.; Makela, Jonathan J.; Meriwether, John W.; Fisher, Daniel J.; Buriti, Ricardo A.; Medeiros, Amauri F.

2012-06-01

130

The use of wind probability distributions derived from the maximum entropy principle in the analysis of wind energy. A case study  

Microsoft Academic Search

This paper analyses the use of a general probability distribution obtained through application of the maximum entropy principle (MEP), constrained by the low-order statistical moments of a given set of wind speed data, in the estimation of wind energy. For this purpose, a comparison is made between the two parameter Weibull distribution and the distributions obtained through the MEP. This

Penlope Ramrez; Jos Antonio Carta

2006-01-01

131

Magnetic cloud field intensities and solar wind velocities  

NASA Astrophysics Data System (ADS)

For the sets of magnetic clouds studied in this work we have shown the existence of a relationship between their peak magnetic field strength and peak velocity values, with a clear tendency that clouds which move at higher speeds also possess higher core magnetic field strengths. This result suggests a possible intrinsic property of magnetic clouds and also implies a geophysical consequence. The relatively low field strengths at low velocities is presumably the cause of the lack of intense storms during low speed ejecta. There is also an indication that this type of behavior is peculiar for magnetic clouds, whereas other types of non cloud-driver gas events do not seem to show a similar relationship, at least for the data studied in this paper. We suggest that a field/speed relationship for magnetic clouds, as that obtained in our present study, could be associated with the cloud release and acceleration mechanism at the sun. Since for magnetic clouds the total field tyically has a substantial southward component, Bs, our results imply that the interplanetary dawn-dusk electric field, given by vBs (where v is the cloud's velocity), is enhanced by both factors. Therefore, the consequent magnetospheric energization (that is governed by this electric field) becomes more efficient for the occurrence of magnetic storms.

Gonzalez, W. D.; de Gonzalez, A. L. Cla; Dal Lago, A.; Tsurutani, B. T.; Arballo, J. K.; Lakhina, G. K.; Buti, B.; Ho, C. M.; Wu, S.-T.

132

Effective transport velocity and plume elongation in nocturnal valley wind fields  

SciTech Connect

Using three atmospheric tracers the effective transport velocity and plume elongation produced by nocturnal drainage wind in three different valleys were investigated. Tracer was released in each valley in a well defined drainage wind field and sequentially sampled at downvalley locations. The effective transport velocity (V-eff) was determined from the elapsed time from the start of the release to the time when the plume concentration reached 10% of its peak value and the distance from the release site. The plume elongation factor was determined from the ratio of the width (time) of the plume at 10% of its peak value to the duration of the release. This method was chosen as an objective analysis scheme. Mean measured winds (V) were computed from surface wind instruments along the drainage flow path with values weighted by the estimated time the plume was in the wind field best represented by a measurement. The values used were from the start of release to the time of arrival at the sampler in question. V is compred to V-eff to see how reasonable an estimate of plume transport in valleys can be made from a few surface measurements in the valley. The simple tracer technique used in the studies has proven to be a good one in accomplishing the stated objective of investigating effective transport velocity and plume elongation in nocturnal valley drainage winds.

Clements, W.E.; Barr, S.; Fowler, M.M.

1980-01-01

133

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

PubMed

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 27m/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. PMID:22148924

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

2011-12-08

134

Blowout of nonpremixed flames; Maximum coaxial air velocities achievable, with and without swirl  

Microsoft Academic Search

This paper demonstrates how to optimize parameters in order to maximize the amount of coaxial air that can be provided to a nonpremixed jet flame without causing the flame to blow out. Maximizing the coaxial air velocity is important in the effort to reduce the flame length and the oxides of nitrogen emitted from gas turbines and industrial burners, a

D. F. Feikema; R. H. Chen; J. F. Driscoll

1991-01-01

135

Climatological mean and interannual variance of United States surface wind speed, direction and velocity  

Microsoft Academic Search

Means and variances of monthly mean wind speed, direction and velocity (the mean resultant vector) are derived for the period 1961-1990 at 216 stations in the coterminous United States. Direction and velocity means and variances are calculated using a complex-arithmetic extension of the equations for scalar mean and variance. Variance is derived from the 30-year time series of monthly means.

Katherine Klink

1999-01-01

136

Intermittency of surface-layer wind velocity series in the mesoscale range  

NASA Astrophysics Data System (ADS)

We study various time series of surface-layer wind velocity at different locations and provide evidences for the intermittent nature of the wind fluctuations in mesoscale to large-scale range. By means of the magnitude covariance analysis, which is shown to be a more efficient tool to study intermittency than classical scaling analysis, we find that all wind series exhibit similar features than those observed for laboratory turbulence. Our findings suggest the existence of a universal cascade mechanism associated with the energy transfer between synoptic motions and turbulent microscales in the atmospheric boundary layer.

Muzy, Jean-Franois; Bale, Rachel; Poggi, Philippe

2010-05-01

137

Predictions for mass-loss rates and terminal wind velocities of massive O-type stars  

NASA Astrophysics Data System (ADS)

Context. Mass loss from massive stars forms an important aspect of the evolution of massive stars, as well as for the enrichment of the surrounding interstellar medium. Aims: Our goal is to predict accurate mass-loss rates and terminal wind velocities. These quantities can be compared to empirical values, thereby testing radiation-driven wind models. One specific topical issue is that of the so-called "weak-wind problem", where empirically derived mass-loss rates and (modified) wind momenta fall orders of magnitude short of predicted values. Methods: We employ an established Monte Carlo model and a recently suggested new line acceleration formalism to solve the wind dynamics more consistently. Results: We provide a new grid of mass-loss rates and terminal wind velocities of O-type stars, and compare the values to empirical results. Our models fail to provide mass-loss rates for main-sequence stars below a luminosity of log(L/L?) = 5.2, where we appear to run into a fundamental limit. At luminosities below this critical value there is insufficient momentum transferred to the wind in the region below the sonic point in order to kick-start the acceleration of the flow. This problem occurs at almost the exact location of the onset of the weak-wind problem. For O dwarfs, the boundary between being able to start a wind, and failing to do so, is at spectral type O6/O6.5. The direct cause of this failure for O6.5 stars is a combination of the lower luminosity and a lack of Fe v lines at the base of the wind. This might indicate that - in addition to radiation pressure - another mechanism is required to provide the necessary driving to initiate the wind acceleration. Conclusions: For stars more luminous than 105.2 L?, our new mass-loss rates are in excellent agreement with the mass-loss prescription by Vink et al. (2000, A&A, 362, 295) using our terminal wind velocities as input to this recipe. This implies that the main assumption entering the method of the Vink et al. prescriptions - i.e. that the momentum equation is not explicitly solved for - does not compromise the reliability of the Vink et al. results for this part of parameter space. Finally, our new models predict terminal velocities that are typically 35 and 45 percent larger than observed values. Such over-predictions are similar to those from (modified) CAK-theory.

Muijres, L. E.; Vink, Jorick S.; de Koter, A.; Mller, P. E.; Langer, N.

2012-01-01

138

Aging-Related Differences in Maximum Force, Unloaded Velocity and Power of Human Leg Multi-Joint Movement  

Microsoft Academic Search

Background: Because many of our movements of daily living are multi-joint movements and lower limb performance decreases with aging, it is important to understand the influence of aging on muscle functions of lower limb multi-joint movements. Objective: To investigate aging-related differences in the maximum force, unloaded velocity and power of muscles that control leg multi-joint movements. Methods: 285 recreationally active

Junichiro Yamauchi; Chizuko Mishima; Satoshi Nakayama; Naokata Ishii

2010-01-01

139

Reynolds-number-dependence of the maximum in the streamwise velocity fluctuations in wall turbulence  

Microsoft Academic Search

A survey is made of the standard deviation of the streamwise velocity fluctuations in near-wall turbulence and in particular\\u000a of the Reynolds-number-dependency of its peak value. The following canonical flow geometries are considered: an incompressible\\u000a turbulent boundary layer under zero pressure gradient, a fully developed two-dimensional channel and a cylindrical pipe flow.\\u000a Data were collected from 47 independent experimental and

S. Mochizuki; F. T. M. Nieuwstadt

1996-01-01

140

Pheromone-modulated optomotor response in male gypsy moths, Lymantria dispar L.: Upwind flight in a pheromone plume in different wind velocities  

Microsoft Academic Search

1.Lymantria dispar males flying in a wind tunnel, up a plume of female sex pheromone, respond to increasing wind velocity by steering a course more precisely upwind. Even though the course angles steered are distributed unimodally about zero degrees (0), the resulting track angles maintain a remarkably consistent bimodal distribution across all wind velocities tested (Fig. 4).2.As the wind velocity

Mark A. Willis; Ring T. Card

1990-01-01

141

Periodical oscillation of zonal wind velocities at the cloud top of Venus  

Microsoft Academic Search

Zonal wind velocity of Venus increases with height and reaches about 100 m s-1 at the cloud top level (~70km). The speed is approximately 60 times faster than the rotation speed of the solid body of Venus (~1.6 m s-1, at the equator) and this phenomenon is called a \\

T. Kouyama; T. Imamura; M. Nakamura; T. Satoh; Y. Futaana

2010-01-01

142

Aspiration efficiency for thin-walled nozzles facing the wind and for very high velocity ratios  

Microsoft Academic Search

The study of thin-walled aerosol sampling probes facing the wind was originally driven by practical applications (e.g., stack sampling). But more recently it has provided useful scientific insights into the performances of more complicated blunt aerosol samplers. Previous work has been carried out for a relatively narrow range of conditions, especially for R (the ratio of freestream air velocity to

Samuel Paik; James H. Vincent

2002-01-01

143

Reduction of Near-Inertial Energy by Ocean-Surface-Velocity-Dependent Wind Stress  

NASA Astrophysics Data System (ADS)

This study aims at understanding the effect of including or neglecting the surface velocity of the ocean into the wind stress parameterization for the strength and distribution of near-inertial oscillations. Wind-generated near-inertial oscillations are an important source of energy for surface mixed layer deepening as well as for internal wave breaking and the associated diapycnal mixing at depth which, in turn, is thought to be important for driving the meridional overturning circulation. By using a realistic primitive equation model of the Southern Ocean at eddying resolution, we find that including ocean surface velocities into the wind stress leads to a large reduction of both wind power input into near-inertial oscillations (WPI) and near-inertial energy (NIE) in the surface mixed layer. The relative reduction of WPI can be as large as 30 percent and the relative reduction of NIE can be as large as 50 percent. Using both, the primitive equation model and a simple linear local slab-ocean model for illustration, we find that a large part of this reduction can be explained by the leading order modification to the wind stress if ocean surface velocities are included. We also find that the strength of the reduction is modulated by the inverse of the ocean surface mixed layer depth.

Rath, Willi; Greatbatch, Richard; Zhai, Xiaoming

2013-04-01

144

Reproduction of wind velocity history in a multiple fan wind tunnel  

Microsoft Academic Search

An actively controlled wind tunnel for simulating the atmospheric boundary layer is described. The air flows are generated by 99 frequency-controlled fans arranged in a 9 wide by 11 high matrix. Various fluctuating flows can be reproduced in this wind tunnel by altering the input data of the fans through computer control. In this paper the method used to reproduce

Shuyang Cao; Akira Nishi; Hironori Kikugawa; Yuji Matsuda

2002-01-01

145

Neotectonic Velocity Field of the Western United States: A new Maximum-likelihood Solution  

NASA Astrophysics Data System (ADS)

New kinematic finite-element program NeoKinema solves for long-term-average velocity fields and fault slip rates in deforming lithosphere, based on three kinds of information: (1) geologic slip rates of an unlimited number of faults, with standard deviations (which may be large); (2) geodetic velocities of benchmarks, either in fixed or free-floating velocity reference frame, with covariance matrix; (3) stress-direction data. Faults need not be explicitly represented in the finite element grid. The geodetic data are corrected for local effects of temporary fault locking by an iterative procedure. The strain rates of non-faulting finite elements are determined by a balance between (a) minimization of viscous dissipation, and (b) conformity to principal strain rate directions interpolated from the stress-direction data. NeoKinema has been applied to model neotectonics of the western United States, from the Gorda "plate" on the west, to the Gulf of California on the south, Yellowstone on the east, and Victoria on the north. Data comes from 378 active or potentially-active faults, 298 benchmarks of the WUSC002 solution [Bennett et al., 1999], and 2080 stress directions from the World Stress Map 2000 [Mueller et al., 2000]. The F-E grid has 1813 nodes and 3468 triangular elements of 30-km and 60-km dimensions. Results of this first application are very plausible, and confirm the concept of a Sierra Nevada-Great Valley plate moving ~9 mm/a NW. After a few local artifacts are investigated and eliminated (primarily by better gridding), the model will be used to compute various measures of long-term seismic hazard. It is already apparent from the map of predicted strain rates that 20th-century seismicity levels in western Oregon, the Wasatch Front area of Utah, and the Las Vegas region have been less than their long-term-average expectations.

Bird, P.

2002-12-01

146

Vertical velocities and momentum fluxes derived from wind measurements in the dusk auroral oval  

NASA Astrophysics Data System (ADS)

Results are presented on a chemical release experiment carried out on March 20, 1985 in connection with NASA's Cooperative Observations of Polar Electrodynamics I campaign. Simultaneous neutral wind measurements in E region were carried out at three separate locations over a triangular region with sides of about 150 km in the dusk auroral oval, and the three wind profiles were used to calculate values of divergence and vorticity over the area. The vertical velocity over the hight range was calculated using the mass continuity equation, and the instantaneous vertical momentum fluxes in the E region were derived using the combination of horizontal-wind measurements and calculated vertical velocities. Results show that there is strong coupling between layers in the E region and that the momentum-flux-induced accelerations are at least comparable in magnitude to the pressure gradient and Coriolis force accelerations.

Larsen, M. F.; Mikkelsen, I. S.

1990-12-01

147

The effects of lunar surface plasma absorption and solar wind temperature anisotropies on the solar wind proton velocity space distributions in the low-altitude lunar plasma wake  

NASA Astrophysics Data System (ADS)

We study the solar wind proton velocity space distribution functions on the lunar nightside at low altitudes (?100 km) above the lunar surface using a three-dimensional hybrid plasma solver, when the Moon is in the unperturbed solar wind. When the solar wind encounters a passive obstacle, such as the Moon, without any strong magnetic field and no atmosphere, solar wind protons that impact the obstacle's surface are absorbed and removed from the velocity space distribution functions. We show first that a hybrid model of plasma is applicable to study the low-altitude lunar plasma wake by comparing the simulation results with observations. Then we examine the effects of a solar wind bi-Maxwellian velocity space distribution function and the lunar surface plasma absorption on the solar wind protons' velocity space distribution functions and their entry in the direction parallel to the interplanetary magnetic field lines into the low-altitude lunar wake. We present a backward Liouville method for particle-in-cell solvers that improves velocity space resolution. The results show that the lunar surface plasma absorption and anisotropic solar wind velocity space distributions result in substantial changes in the solar wind proton distribution functions in the low-altitude lunar plasma wake, modifying proton number density, velocity, and temperature there. Additionally, a large temperature anisotropy is found at close distances to the Moon on the lunar nightside as a consequence of the lunar surface plasma absorption effect.

Fatemi, S.; Holmstrm, M.; Futaana, Y.

2012-10-01

148

Anisotropy and symmetry of fluctuations in the solar wind magnetic field and velocity  

NASA Astrophysics Data System (ADS)

The behavior of correlation tensors of fluctuations in the solar wind magnetic field and velocity is studied during different phases of a solar cycle on the basis of a 45-year measurement series of solar wind parameters. It is found that the orientation of fluctuations in the magnetic field and velocity is approximately axisymmetric relative to the direction of a local magnetic field during high solar activity. This symmetry is violated significantly during periods of low solar activity, and deviations from the symmetry are regular and oppositely directed during minima of even and odd 11-year cycles, which is probably connected with variations in the orientation of the Sun's magnetic field. The dependence of the power of fluctuations on the local magnetic field direction reveals significant deviations from local symmetry during all phases of a solar cycle, especially for velocity fluctuations.

Erofeev, D. V.

2012-12-01

149

An investigation into the contraction of the hurricane radius of maximum wind  

NASA Astrophysics Data System (ADS)

The radius of the maximum tangential wind (RMW) associated with the hurricane primary circulation has been long known to undergo continuous contraction during the hurricane development. In this study, we document some characteristic behaviors of the RMW contraction in a series of ensemble real-time simulations of Hurricane Katrina (2005) and in idealized experiments using the Rotunno and Emanuel (Mon Weather Rev 137:1770-1789, 1987) axisymmetric hurricane model. Of specific interest is that the contraction appears to slow down abruptly at the middle of the hurricane intensification, and the RMW becomes nearly stationary subsequently, despite the rapidly strengthening rotational flows. A kinematic model is then presented to examine such behaviors of the RMW in which necessary conditions for the RMW to stop contracting are examined. Further use of the Emanuel's (J Atmos Sci 43:585-605, 1986) analytical hurricane theory reveals a connection between the hurricane maximum potential intensity and the hurricane eye size, an issue that has not been considered adequately in previous studies.

Kieu, Chanh Q.

2012-01-01

150

Intelligent control based maximum power extraction strategy for wind energy conversion systems  

Microsoft Academic Search

This paper proposes a control strategy to optimize power output performance of wind energy conversion system. In order to obtain optimum power output from a wind turbine generator system, it is necessary to drive the wind turbine at an optimal rotor speed for a particular wind speed. Fuzzy logic based control algorithm is implemented with the embedded microcontroller which will

Shakil Ahamed Khan

2011-01-01

151

Autonomous dual-mode CAES systems for maximum wind energy contribution in remote island networks  

Microsoft Academic Search

Wind parks operating in autonomous island networks with limited capacity of wind energy absorption are faced with considerable energy curtailments. To encounter the existing situation, the concept of wind energy storage suggests an alternative worth investigating. On the other hand, the expansion of natural gas networks in big islands, where remarkable wind potential may be met as well, questions the

D. Zafirakis; J. K. Kaldellis

2010-01-01

152

Maximum capacity model of grid-connected multi-wind farms considering static security constraints in electrical grids  

NASA Astrophysics Data System (ADS)

An increasing interest in wind energy and the advance of related technologies have increased the connection of wind power generation into electrical grids. This paper proposes an optimization model for determining the maximum capacity of wind farms in a power system. In this model, generator power output limits, voltage limits and thermal limits of branches in the grid system were considered in order to limit the steady-state security influence of wind generators on the power system. The optimization model was solved by a nonlinear primal-dual interior-point method. An IEEE-30 bus system with two wind farms was tested through simulation studies, plus an analysis conducted to verify the effectiveness of the proposed model. The results indicated that the model is efficient and reasonable.

Zhou, W.; Qiu, G. Y.; Oodo, S. O.; He, H.

2013-03-01

153

Predicting solar and wind energy trends using cloud cover and wind velocity  

Microsoft Academic Search

Developments include: (1) a mode to predict potential and clear sky solar radiation on a horizontal surface and clear sky solar radiation on a tilted panel for any latitude, POTSOL; (2) a model to predict solar radiation on a horizontal surface for any latitude as a function of total opaque cloud cover, ESR; and (3) a program to estimate wind

Brinsfield

1981-01-01

154

Cascade-like and scaling behavior of wind velocity increments in the atmospheric surface layer  

NASA Astrophysics Data System (ADS)

By using a large amount of data collected in the atmospheric surface layer, we analyze the probability density functions (PDFs), the probability of return and the moments of wind velocity increments. Results show that the PDFs change from the non-Gaussian long-tailed distributions to Gaussian with the increase of time scales. This is similar to what has been observed and interpreted as an indication of cascade in the fully developed homogeneous and isotropic turbulence. Besides, both the probability of return and the moments are found to be scaling with time scales. We then compare above results with the truncated Lvy flights and the log-normal PDF model. It is found that although both models show the cascade-like behavior in the PDFs and the scaling behavior in the probability of return and the moments under some conditions, they are not good enough for quantitatively describing the random process of wind velocity increments.

Liu, Lei; Hu, Fei

2013-12-01

155

Electron Velocity Distribution Function in Magnetic Clouds in the Solar Wind  

Microsoft Academic Search

We present a study of the kinetic properties of the electron velocity distribution functions within magnetic clouds, since they are the dominant thermal component. The study is based on high time resolution data from the GSFC WIND\\/SWE electron spectrometer and the Berkeley 3DP electron plasma instrument. Recent studies on magnetic clouds has shown observational evidence of anti-correlation between the total

T. Nieves-Chinchil; A. F.-Vinas; S. D. Bale

2006-01-01

156

Interpretation of solar wind reconnection exhaust in terms of kinetic Alfvn wave group-velocity cones  

Microsoft Academic Search

Recent multi-satellite measurements of reconnection exhausts in the solar wind have allowed for the first time to determine the reconnection rate (R) and the exhaust wedge angle 2$\\\\theta$w. We compare such observations of R and $\\\\theta$w with the theoretical predictions based on the half-cone angles ($\\\\theta$g) of the group velocity vectors (Vg) of the kinetic Alfvn (KA) and slow MHD

Nagendra Singh

2007-01-01

157

Evaporation under cavity flow: laser speckle correlation of the wind velocity above the liquid surface  

NASA Astrophysics Data System (ADS)

One of the major accident scenarios in industrial safety deals with liquid pool evaporation consequent to a tank rupture. Numerous previous studies have been performed and several correlations are available in the literature. It appears that all of the correlations are strongly dependent on wind velocity but have nevertheless been all created under a boundary layer flow above the pool. However, industrial safety bunds do not allow such a profile because of obstacles and so cavity flows may occur. For such a configuration, is it then possible to describe the evaporation phenomena thanks to correlations in the literature? Experiments involving evaporation under this configuration have thus been performed in this work. Particular care is devoted to the wind profile measurement as the wind velocity is one of the main parameters. Digital speckle correlation insures high accuracy and good spatial resolution. We used a double pulse YAG laser (200mJ, 15Hz at 532 nm) with a high resolution double frame camera (2048 pixel x 2048 pixels, 15Hz). The experiments involve 200 liters (200L) of liquid (acetone and water) in a 58 cm diameter pool. The pool is located in the wind tunnel facility. The study presents 2 different wind velocities (2m.s-1 and 4m.s-1) and four different dike step heights (0 cm, 3 cm, 6 cm and 10 cm). Displacement vector maps are obtained after adaptative correlation and related processing. The final results are also crossed with IR measurements and open new fields of investigation that will be discussed.

Forestier, Serge; Heymes, Frdric; Slangen, Pierre; Munier, Laurent; Lapbie, Emmanuel; Dusserre, Gilles

158

Eddy and deep chlorophyl maximum response to wind-shear in the lee of Gran Canaria  

NASA Astrophysics Data System (ADS)

The physical and biological properties of the warm wake of Gran Canaria were examined during a survey carried out in June 1998. The sampling region was dominated by the presence of a warm triangular region downwind the island and an anticyclonic eddy spun off the island. Convergent and divergent frontal regions were generated by the wind shear zones extending along either side of the sheltered region of the warm wake. With increasing distance from shore, evidence of convergent/divergent frontal regions weakened, but the influence of the eddy increased. Both structures, frontal regions and the eddy, clearly altered the vertical phytoplankton biomass distribution as indicated by chlorophyll-fluorescence. Downwelling on the convergent boundary moved the 26.2 kg m -3 isopycnal and its associated deep chlorophyll maximum (DCM) below the 1% light zone. Upwelling at the divergent boundary not only elevated the DCM with its associated isopycnal but also, because of the increased light levels, allowed a shift in the DCM to higher (deeper) density surfaces (26.4 kg m -3). However, the highest integrated chlorophyll occurred in the central wake.

Basterretxea, G.; Barton, E. D.; Tett, P.; Sangr, P.; Navarro-Perez, E.; Ar?stegui, J.

2002-06-01

159

Time scales for formation and spreading of velocity shells of pickup ions in the solar wind  

SciTech Connect

The pickup of newborn ions in the solar wind by means of low-frequency, electromagnetic waves, either due to the intrinsic turbulence of the solar wind or induced turbulence due to instabilities excited by the newborn ions, is discussed. The pickup process is envisioned to occur in three stages, formation of a ring-beam distribution, rapid pitch angle scattering of this initial distribution into a thin shell, and slower velocity diffusion that spreads out the shell. The process of shell formation and evolution are studied by means of numerical simulations, first for the situation of relatively low levels of turbulence such as would occur naturally in the solar wind and then for higher levels of turbulence characteristic of those encountered near cometary bow shocks. The results of the numerical experiments are compared with theory.

Gaffey J.D. Jr.; Winske, D.; Wu, C.S.

1988-06-01

160

Empirical Determination of the Wind Velocity and Density Laws for the K Supergiant Zeta Aurigae  

NASA Astrophysics Data System (ADS)

We will derive the velocity and density laws and mass loss rate for the K4 supergiant in the eclipsing Zeta Aurigae binary system. The slow passage of the geometrically small B dwarf with its bright UV continuum behind the extended atmosphere of the K supergiant provides a splendid opportunity to probe the column densities and velocities of many absorption lines of various strengths as a function of stellar impact parameter. Our empirical determination of the wind physical parameters throughout the acceleration region will place tight constraints on the physical processes responsible for mass loss in evolved, massive stars that contribute significantly to the enrichment of the interstellar medium with chemically processed material. We request time for observations of lines of Fe I-II, Si II, Ti II, and V II at 6 orbital phases, including the terminal velocity wind, wind aceleration region, eclipse by the K star chromosphere, and total eclipse. This program is time critical but with typical tolerances of 1-7 days due to the long (972 day) orbital period.

Brown, Alexander

1992-07-01

161

A statistical comparison of solar wind sources of moderate and intense geomagnetic storms at solar minimum and maximum  

Microsoft Academic Search

Superposed epoch analyses of 549 storms are performed to make a comparison of solar wind features of geomagnetic storm events at solar minimum (July 1974 to June 1977; July 1984 to June 1987; July 1994 to June 1997) and solar maximum (January 1979 to December 1981; January 1989 to December 1991; July 1999 to June 2002). In this study, geomagnetic

Jichun Zhang; Michael W. Liemohn; Janet U. Kozyra; Michelle F. Thomsen; Heather A. Elliott; James M. Weygand

2006-01-01

162

Determination of the effect of wind velocity and direction changes on turbidity removal in rectangular sedimentation tanks.  

PubMed

In the present study, a pilot-scale sedimentation tank was used to determine the effect of wind velocity and direction on the removal efficiency of particles. For this purpose, a 1:20 scale pilot simulated according to Frude law. First, the actual efficiency of total suspended solids (TSS) removal was calculated in no wind condition. Then, the wind was blown in the same and the opposite directions of water flow. At each direction TSS removal was calculated at three different velocities from 2.5 to 7 m/s. Results showed that when the wind was in the opposite direction of water flow, TSS removal efficiency initially increased with the increase of wind velocity from 0 to 2.5 m/s, then it decreased with the increase of velocity to 5 m/s. This mainly might happen because the opposite direction of wind can increase particles' retention time in the sedimentation tank. However, higher wind velocities (i.e. 3.5 and 5.5 m/s) could not increase TSS removal efficiency. Thus, if sedimentation tanks are appropriately exposed to the wind, TSS removal efficiency increases by approximately 6%. Therefore, energy consumption will be reduced by a proper site selection for sedimentation tank unit in water and waste water treatment plants. PMID:23109603

Khezri, Seyed Mostafa; Biati, Aida; Erfani, Zeynab

2012-01-01

163

Analysis of sand particles' lift-off and incident velocities in wind-blown sand flux  

NASA Astrophysics Data System (ADS)

In the research of windblown sand movement, the lift-off and incident velocities of saltating sand particles play a significant role in bridging the spatial and temporal scales from single sand particle's motion to windblown sand flux. In this paper, we achieved wind tunnel measurements of the movement of sand particles near sand bed through improving the wind tunnel experimental scheme of particle image velocimetry (PIV) and data processing method. And then the influence of observation height on the probability distributions of lift-off and incident velocities of sand particles was analyzed. The results demonstrate that the observation height has no obvious influence on the distribution pattern of the lift-off and incident velocities of sand particles, i.e., the probability distribution of horizontal and vertical velocities of lift-off and incident sand particles follow a Gaussian distribution and a negative exponential distribution, respectively. However, it influences the center of the Gaussian distribution, the decay constant and the amplitude of the negative exponential distribution.

Bo, Tian-Li; Zheng, Xiao-Jing; Duan, Shao-Zhen; Liang, Yi-Rui

2013-04-01

164

A new apparatus for continuous measuring the falling velocity of the wind-dispersal seeds  

NASA Astrophysics Data System (ADS)

A new apparatus for continuous measuring the falling velocity of wind-dispersal seeds is presented in this paper. The key unit of this apparatus is the photo-detectors installed on the ends of a vertical tube. The photodetector is composed of a LED and a photo-sensor. The LED light goes through a horizontal slit to from a flat light plane, which be received by the photo-sensors on the opposite side. When a plant seed falls down and passes through the flat light plane, a pulse signal will be detected by the photo-sensor. The average falling velocity of the seed is calculated according to the falling time and the distance from the starting point to the testing point. By using several tubes and photo-detectors, the apparatus can continuously measure the velocity of a seed falling down to different height. This apparatus avoids the affect of the static electricity and airflow to the seeds.

Ji, Huihua; Wang, Shoubing; Chen, Huacai; Zhu, Zhouhong; Zhu, Min

2011-11-01

165

Vertical profiles of wind velocity in the Venus atmosphere according to Doppler measurements of the Venera-13 and Venera-14 probes  

Microsoft Academic Search

Vertical profiles of wind velocity in the Venus atmosphere were obtained through Doppler measurements of the velocities of the Venera-13 and Venera-14 probes. The vertical distribution of the zonal component of wind velocity is presented, and variations of the radial component of the velocity of the descent module near the lower boundary of the cloud layer are examined. The general

V. V. Kerzhanovich; N. M. Antsibor; V. D. Kustodiev; Iu. F. Makarov; I. A. Matsygorin; E. P. Molotov; V. P. Sorokin; K. G. Sukhanov; V. F. Tikhonov; V. P. Kariagin

1983-01-01

166

Measurement of motion corrected wind velocity using an aerostat lofted sonic anemometer  

NASA Astrophysics Data System (ADS)

An aerostat-lofted, sonic anemometer was used to determine instantaneous 3 dimensional wind velocities at altitudes relevant to fire plume dispersion modeling. An integrated GPS, inertial measurement unit, and attitude heading and reference system corrected the wind data for the rotational and translational motion of the anemometer and rotated wind vectors to a global North, West, Up coordinate system. Data were taken at rates of 10 and 20 Hz to adequately correct for motion of the aerostat. The method was applied during a prescribed forest burn. These data were averaged over 15 min intervals and used as inputs for subsequent dispersion modeling. The anemometer's orientation data are demonstrated to be robust for converting the wind vector from the internal anemometer reference system to the global reference system with an average bias between 5 and 7. Lofted wind data are compared with sonic anemometer data acquired at 10 m on a mast located near the tether point of the aerostat and with local meteorological data.

Stevens, W. R.; Squier, W.; Mitchell, W.; Gullett, B. K.; Pressley, C.

2013-01-01

167

Uncertainties in wind speed dependent CO 2 transfer velocities due to airflow distortion at anemometer sites on ships  

Microsoft Academic Search

Data from platforms, research vessels and mer- chant ships are used to estimate ocean CO2 uptake via param- eterisations of the gas transfer velocity (k) and measurements of the difference between the partial pressures of CO2 in the ocean (pCO2 sw) and atmosphere (pCO2 atm) and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be

F. Griessbaum; B. I. Moat; Y. Narita; M. J. Yelland; O. Klemm; M. Uematsu

2010-01-01

168

Uncertainties in wind speed dependent CO2 transfer velocities due to airflow distortion at anemometer sites on ships  

Microsoft Academic Search

Data from research vessels and merchant ships are used to estimate ocean CO2 uptake via parameterizations of the gas transfer velocity (k) and measurements of the difference between the concentration of CO2 in the ocean (pCO2sw) and atmosphere (pCO2atm) and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be in error due to air flow

F. Griessbaum; B. I. Moat; Y. Narita; M. J. Yelland; O. Klemm; M. Uematsu

2009-01-01

169

Uncertainties in wind speed dependent CO2 transfer velocities due to airflow distortion at anemometer sites on ships  

Microsoft Academic Search

Data from platforms, research vessels and merchant ships are used to estimate ocean CO2 uptake via parameterisations of the gas transfer velocity (k) and measurements of the difference between the partial pressures of CO2 in the ocean (pCO2 sw) and atmosphere (pCO2 atm) and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be in error

F. Griessbaum; B. I. Moat; Y. Narita; M. J. Yelland; O. Klemm; M. Uematsu

2010-01-01

170

Temporal Evolution of the Solar Wind Bulk Velocity at Solar Minimum by Correlating the STEREO A and B PLASTIC Measurements  

NASA Astrophysics Data System (ADS)

The two STEREO spacecraft with nearly identical instrumentation were launched near solar activity minimum and they separate by about 45 per year, providing a unique tool to study the temporal evolution of the solar wind. We analyze the solar wind bulk velocity measured by the two PLASTIC plasma instruments onboard the two STEREO spacecraft. During the first half year of our measurements (March - August 2007) we find the typical alternating slow and fast solar wind stream pattern expected at solar minimum. To evaluate the temporal evolution of the solar wind bulk velocity we exclude the spatial variations and calculate the correlation between the solar wind bulk velocity measured by the two spacecraft. We account for the different spacecraft positions in radial distance and longitude by calculating the corresponding time lag. After adjusting for this time lag we compare the solar wind bulk velocity measurements at the two spacecraft and calculate the correlation between the two time-shifted datasets. We show how this correlation decreases as the time difference between two corresponding measurements increases. As a result, the characteristic temporal changes in the solar wind bulk velocity can be inferred. The obtained correlation is 0.95 for a time lag of 0.5 days and 0.85 for 2 days.

Opitz, A.; Karrer, R.; Wurz, P.; Galvin, A. B.; Bochsler, P.; Blush, L. M.; Daoudi, H.; Ellis, L.; Farrugia, C. J.; Giammanco, C.; Kistler, L. M.; Klecker, B.; Kucharek, H.; Lee, M. A.; Mbius, E.; Popecki, M.; Sigrist, M.; Simunac, K.; Singer, K.; Thompson, B.; Wimmer-Schweingruber, R. F.

2009-05-01

171

Reduction of near-inertial energy through the dependence of wind stress on the ocean-surface velocity  

NASA Astrophysics Data System (ADS)

A realistic primitive-equation model of the Southern Ocean at eddying spatial resolution is used to examine the effect of ocean-surface-velocity dependence of the wind stress on the strength of near-inertial oscillations. Accounting for the ocean-surface-velocity dependence of the wind stress leads to a large reduction of wind-induced near-inertial energy of approximately 40% and of wind power input into the near-inertial frequency band of approximately 20%. A large part of this reduction can be explained by the leading-order modification to the wind stress if the ocean-surface velocity is included. The strength of the reduction is shown to be modulated by the inverse of the ocean-surface-mixed-layer depth. We conclude that the effect of surface-velocity dependence of the wind stress should be taken into account when estimating the wind-power input into the near-inertial frequency band and when estimating near-inertial energy levels in the ocean due to wind forcing.

Rath, Willi; Greatbatch, Richard J.; Zhai, Xiaoming

2013-06-01

172

Responses of giant interneurons of the cockroach Periplaneta americana to wind puffs of different directions and velocities  

Microsoft Academic Search

1.Controlled wind puffs of different directions and velocities were delivered to the cerci of cockroaches (Periplaneta americana), while the responses of individually identifiable giant interneurons (GI's) were recorded intracellularly.2.All fourteen histologically identified GI's (seven bilateral pairs) respond with a burst of action potentials to wind from some or all directions. The directional sensitivity of a given GI is consistent from

Joanne Westin; Jonathan J. Langberg; Jeffrey M. Camhi

1977-01-01

173

The hourly average solar wind velocity prediction based on support vector regression method  

NASA Astrophysics Data System (ADS)

A new neural network technique, support vector regression (SVR), is applied to forecast the solar wind (SW) velocity. SVR is a non-linear efficient tool for high data processing based on statistical learning theory. Its advantage is that the input only requires several periods data (about four 27-d solar-rotation periods to SW velocity prediction in this study), and the prediction is quite reliable. In our work, we deliberately choose the typical SW data covering all main space weather conditions: the SW data during the 9 yr from 1998 to 2006, which includes the periods of the SW speed variation associated with high-speed streams from coronal hole and coronal mass ejections. The performance of the SVR is measured by calculating the absolute average fractional deviation and correlation coefficient between the SVR model and observed SW velocity. We find that the predicted velocity values are over 90 per cent of the observed ones, i.e. the new approach is accurate and reliable in forecasting SW velocity. Based on the error difference, it can be concluded that the SVR technique can lend itself to future space weather forecasting models.

Liu, D. D.; Huang, C.; Lu, J. Y.; Wang, J. S.

2011-06-01

174

Dynamics of Line-driven Winds from Disks in Cataclysmic Variables. II. Mass-Loss Rates and Velocity Laws  

Microsoft Academic Search

We analyze the dynamics of two-dimensional stationary, line-driven winds from accretion disks in cataclysmic variable (CV) stars by generalizing the formalism of Castor, Abbott, and Klein (CAK) for O stars. In Paper I, we solved the wind Euler equation, derived its two eigenvalues, and addressed the solution topology and wind geometry. Here, we focus on mass-loss rates and velocity laws

Achim Feldmeier; Isaac Shlosman; Peter Vitello

1999-01-01

175

The maximum efficiency of the conversion of solar energy into wind energy  

Microsoft Academic Search

In the present paper, the Gordon and Zarmi model is applied for the conversion of solar energy into wind energy, in such a way that simple calculations lead to a universal result: The upper bound for the conversion efficiency of solar energy into wind energy equals 8.3%.

Alexis De Vos; G. Flater

1991-01-01

176

Autonomous operation of wind-battery hybrid power system with maximum power extraction capability  

Microsoft Academic Search

The hybrid operation of a remote area power system consisting of a Doubly Fed Induction Generator (DFIG) based wind turbine, a battery storage unit and a dummy load is investigated in this paper. The battery storage unit operates as a source or load, depending on the wind power output and loading conditions of the system. The battery storage is connected

Nishad Mendis; Kashem M. Muttaqi; Saad Sayeef; Sarath Perera

2010-01-01

177

Adaptive algorithm for fast maximum power point tracking in wind energy systems  

Microsoft Academic Search

Wind energy systems are being closely studied because of its benefits as an environmentally friendly and renewable source of energy. Because of its unpredictable nature, power management concepts are essential to extract as much power as possible from the wind when it becomes available. In this paper an algorithm has been developed to keep the system at its highest possible

Joanne Hui; Alireza Bakhshai

2008-01-01

178

Modeling of Wind Turbine Driving Permanent Magnet Generator with Maximum Power Point Tracking System  

Microsoft Academic Search

This paper elaborates on the analysis and simulation of 15 kW Wind Turbine Generator (WTG) driving low speed Permanent Magnet Synchronous Generator (PMSG) using PSIM computer simulation program. The system consists of wind turbine, permanent magnet generator, three-phase diode rectifier, boost converter, and voltage source inverter models. In the WTG model, the best performance coefficient has been determined according to

Ali M. Eltamaly

2007-01-01

179

An Adaptive Control Algorithm for Maximum Power Point Tracking for Wind Energy Conversion Systems  

Microsoft Academic Search

Abstract Wind energy systems are being closely studied because of its benefits as an envi- ronmentally friendly and renewable source of energy. Because of its unpredictable availability, power management concepts are essential to extract as much power as possible from the wind when it becomes available. The purpose of this thesis is to presents a new adaptive control algorithm for

Joanne Hui

2008-01-01

180

Dependence of the head injury criterion and maximum acceleration on headform mass and initial velocity in tests simulating pedestrian impacts with vehicles.  

PubMed

Impact testing of pedestrian headforms is usually conducted at one velocity and with one mass of headform, but real impacts occur at a range of velocities and masses. A method is proposed to predict the Head Injury Criterion (HIC) and similar quantities at other velocities from their values observed under test conditions. A specific assumption is made about acceleration during the impact as related to displacement, its differential (instantaneous velocity), mass of headform, and initial velocity: namely, that it is the product of a power function of displacement (representing a possibly nonlinear spring) and a term that includes a type of damping. This equation is not solved, but some properties of the solution are obtained: HIC, maximum acceleration, and maximum displacement are found to be power functions of mass of headform and initial velocity. Expressions for the exponents are obtained in terms of the nonlinearity parameter of the spring. Simple formulae are obtained for the dependence of HIC, maximum acceleration, and maximum displacement on velocity and mass. These are relevant to many types of impact. PMID:24008426

Hutchinson, T P

2013-11-01

181

Advective surface velocities derived from sequential images for rotational flow field: Limitations and applications of maximum cross-correlation method with rotational registration  

NASA Astrophysics Data System (ADS)

An objective technique is developed to calculate advective surface velocities from sequential images. A pattern matching method is used with the identification of maximum cross correlation (MCC) between a template window in the first image and search areas in the second image. We examined the limitations of the MCC method in two cases: (1) eddy size (LE) much smaller than the radius of deformation (LD), and (2) LE?LD. In the first case an eddy is regarded as a particle. Maximum detectable time period is estimated to be about 1 day. For the second case we developed the MCC method to detect a rotational motion. We compared velocity fields derived from the method with a real velocity field in a numerical analysis of tracer and quasi-geostrophic eddy fields. The optimal template size is about the eddy diameter which spans between the maximum velocity points. We also applied the MCC method to infrared images in the Kuroshio-Oyashio confluence zone.

Kamachi, M.

1989-12-01

182

Correlation length of large-scale solar wind velocity fluctuations measured tangent to the Earth's orbit: First results from Stereo  

Microsoft Academic Search

Proton velocity data from identical plasma instruments on board NASA's two Stereo spacecraft are used to investigate the correlation length of large-scale radial velocity fluctuations in the solar wind in the direction tangent to the Earth's orbit. The data cover the period from February 2007 through August 2007, near solar minimum in 2007. Estimates of the spatial correlation function are

J. J. Podesta; A. B. Galvin; C. J. Farrugia

2008-01-01

183

Remote Sensing of Three-dimensional Winds with Elastic Lidar: Explanation of Maximum Cross-correlation Method  

NASA Astrophysics Data System (ADS)

Maximum cross-correlation provides a method toremotely de-ter-mine high-lyre-solved three-dimensional fields of horizontalwinds with e-las-tic li-darthrough-out large volumes of the planetaryboundary layer (PBL). This paperdetails the technique and shows comparisonsbetween elastic lidar winds, remotelysensed laser Doppler velocimeter (LDV) windprofiles, and radiosonde winds.Radiosonde wind data were acquired at Barcelona,Spain, during the BarcelonaAir-Quality Initiative (1992), and the LDVwind data were acquired at SunlandPark, New Mexico during the 1994 Border AreaAir-Quality Study. Comparisonsshow good agreement between the differentinstruments, and demonstrate the methoduseful for air pollution management at thelocal/regional scale. Elastic lidar windscould thus offer insight into aerosol andpollution transport within the PBL. Lidarwind fields might also be used to nudge orimprove initialization and evaluation ofatmospheric meteorological models.

Buttler, Williamt.; Soriano, Cecilia; Baldasano, Josem.; et al.

184

Automatic corellation method to estimate wind velocity from UV images of Venus on VMC data  

NASA Astrophysics Data System (ADS)

The horizontal components of wind velocity vectors of the Venus upper clouds are estimated from the UV images obtained by the Venus Monitoring Camera on the Venus Express spacecraft. Two images obtained at different moments provide information about motion of cloud layer regions. The motion of each region is evaluated by means of correlations. The method includes: -creation of longitude-latitude grid -computation of intensity for every node of the grid by using a three-point interpolation -computation of correlation coefficients -analysis of the correlation function -elimination of wrong results -computation of zonal and meridional velocity -computation of averaged profiles The obtained profiles are compared with results obtained by means of a visual method.

Patsaeva, Marina; Khatuntsev, Igor; Titov, Dmitri; Markiewicz, Wojciech; Ignatiev, Nikolay

185

THE VALIATION OF WATER LEVEL AND FLOW VELOCITY IN SEMI-CLOSED WATER AERA BY WIND AND BOAT WAVE  

NASA Astrophysics Data System (ADS)

In this study, to clarify the relationship between water level variation and turbulence of flow, field observations were carried out in Omaehama beach, Nishinomiya City, Hyogo Prefecture, JAPAN. In each observation, wind speed and its direction, water level, wave height, flow velocity and its direction were measured in the vicinity of shoreline. The data of wave height was transformed to the velocity by using a liner filter theory and examined the effect of boat wave and wind one on turbulence of flow. The transferred velocity from wind wave was coincided with the turbulence of flow, however, that from boat wave was not so good. From the results of this study, we can see both boat wave and wind one are the significant factors of water level variation in urban semi-closed water area.

Uno, Kohji; Tsujimoto, Gozo; Kakinoki, Tetsuya

186

Vector velocity profiles of the solar wind within expanding magnetic clouds at 1 AU: Some surprises  

NASA Astrophysics Data System (ADS)

We investigated the average vector velocity profile of 36 carefully chosen WIND interplanetary magnetic clouds occurring over about a 7 year period since spacecraft launch, to see if a differential pattern of solar wind flow exists. Particular cases were chosen of clouds whose axes were generally within 45 degrees of the ecliptic plane and of relatively well determined characteristics obtained from cloud-parameter (cylindrically symmetric force free) fitting. This study was motivated by the desire to understand the manner in which magnetic clouds expand, a well know phenomenon revealed by most cloud speed-profiles at 1 AU. One unexpected and major result was that, even though cloud expansion was confirmed, it was primarily along the Xgse axis; i.e., neither the Ygse or Zgse velocity components reveal any noteworthy pattern. After splitting the full set of clouds into a north-passing set (spacecraft passing above the cloud, where Nn = 21) and south-passing set (Ns = 15), to study the plasma expansion of the clouds with respect to the position of the observer, it was seen that the Xgse component of velocity differs for these two sets in a rather uniform and measurable way for most of the average cloud's extent. This does not appear to be the case for the Ygse or Zgse velocity components where little measurable differences exists, and clearly no pattern, across the average cloud between the north and south positions. It is not clear why such a remarkably non-axisymmetric plasma flow pattern within the "average magnetic cloud" at 1 AU should exist. The study continues from the perspective of magnetic cloud coordinate representation. ~ ~ ~

Wu, C.; Lepping, R. P.; Berdichevsky, D.; Ferguson, T.; Lazarus, A. J.

2002-12-01

187

IMF orientation, solar wind velocity, and Pc 3--4 signals: A joint distribution  

SciTech Connect

Separate studies using the same micropulsation data base in the period range 10--150 s have shown earlier that signal levels recorded during September, October, and November 1969 at Calgary correlated positively with both solar wind alignment of the IMF and solar wind speed, but each correlation contained enough scatter to allow for influence of the other factor. In this report, joint correlations of velocity and field direction with parameters representing hourly distributions rather than minima of IMF orientation angle display the relative effect of the two agents on magnetic pulsation signal levels. The joint correlations reduce the overall scatter and show that solar wind speeds above 200--300 km/s and angles between the IMF and the sun-earth line of less than 50/sup 0/--60/sup 0/ are associated with enlarged magnetic pulsation amplitudes. These threshold effects tend to support both the bow shock origin and the Kelvin-Helmholtz amplification of daytime signal transients in the Pc 3, 4 period ranges.

Greenstadt, E.W.; Singer, H.J.; Russell, C.T.; Olson, J.V.

1979-02-01

188

Vertical velocity variance in the mixed layer from radar wind profilers  

USGS Publications Warehouse

Vertical velocity variance data were derived from remotely sensed mixed layer turbulence measurements at the Atmospheric Boundary Layer Experiments (ABLE) facility in Butler County, Kansas. These measurements and associated data were provided by a collection of instruments that included two 915 MHz wind profilers, two radio acoustic sounding systems, and two eddy correlation devices. The data from these devices were available through the Atmospheric Boundary Layer Experiment (ABLE) database operated by Argonne National Laboratory. A signal processing procedure outlined by Angevine et al. was adapted and further built upon to derive vertical velocity variance, w_pm???2, from 915 MHz wind profiler measurements in the mixed layer. The proposed procedure consisted of the application of a height-dependent signal-to-noise ratio (SNR) filter, removal of outliers plus and minus two standard deviations about the mean on the spectral width squared, and removal of the effects of beam broadening and vertical shearing of horizontal winds. The scatter associated with w_pm???2 was mainly affected by the choice of SNR filter cutoff values. Several different sets of cutoff values were considered, and the optimal one was selected which reduced the overall scatter on w_pm???2 and yet retained a sufficient number of data points to average. A similarity relationship of w_pm???2 versus height was established for the mixed layer on the basis of the available data. A strong link between the SNR and growth/decay phases of turbulence was identified. Thus, the mid to late afternoon hours, when strong surface heating occurred, were observed to produce the highest quality signals.

Eng, K.; Coulter, R. L.; Brutsaert, W.

2003-01-01

189

Analysis of trends between solar wind velocity and energetic electron fluxes at geostationary orbit using the reverse arrangement test  

NASA Astrophysics Data System (ADS)

A correlation between solar wind velocity (VSW) and energetic electron fluxes (EEF) at the geosynchronous orbit was first identified more than 30 years ago. However, recent studies have shown that the relation between VSW and EEF is considerably more complex than was previously suggested. The application of process identification technique to the evolution of electron fluxes in the range 1.8 - 3.5 MeV has also revealed peculiarities in the relation between VSW and EEF at the geosynchronous orbit. It has been revealed that for a constant solar wind density, EEF increase with VSW until a saturation velocity is reached. Beyond the saturation velocity, an increase in VSW is statistically not accompanied with EEF enhancement. The present study is devoted to the investigation of saturation velocity and its dependency upon solar wind density using the reverse arrangement test. In general, the results indicate that saturation velocity increases as solar wind density decreases. This implies that solar wind density plays an important role in defining the relationship between VSW and EEF at the geosynchronous orbit.

Aryan, Homayon; Boynton, Richard J.; Walker, Simon N.

2013-02-01

190

Effects of Errors of Velocity Modulation on Maximum Longitudinal Drift Compression of an Intense Neutralized Ion Beam  

NASA Astrophysics Data System (ADS)

Neutralized drift compression offers an effective means for particle beam focusing and current amplification with applications to heavy ion fusion. An ion beam pulse is passed through an inductive bunching module that produces a longitudinal velocity modulation. Due to applied velocity tilt the beam pulse compresses during neutralized drift. The ion beam pulse can be compressed by a factor of more than 100; however errors in the velocity modulation affect this compression in complicated ways. We have preformed an analytical and numerical study of how the longitudinal compression of the ion beam is affected by the initial errors in velocity. Higher errors generally proportionally decrease compression. However, some parts of a beam pulse with large errors in the velocity tilt compress to high values while other parts do not compress at all. Without any errors an ideal compression is limited only by the initial thermal velocity of the ion beam. Compression with an experiential velocity tilt is compared to an ideal limit.

Massidda, S.; Kaganovich, I.; Startsev, E.; Davidson, R.

2010-11-01

191

Power strategies for maximum control structure of a wind energy conversion system with a synchronous machine  

Microsoft Academic Search

The control of a wind energy conversion system can be decomposed into two parts: a local control depending on the power structure and a global control (strategy) deduced from global considerations. The local part ensures an efficient energy management of each component of the system. The local control structure can be deduced from the Energetic Macroscopic Representation, which is a

A. Bouscayrol; Ph. Delarue; X. Guillaud

2005-01-01

192

Maximum wind energy contribution in autonomous electrical grids based on thermal power stations  

Microsoft Academic Search

Greek islands cover their continuously increasing electricity demand on the basis of small autonomous thermal power stations. This electrification solution is related with increased operational cost and power insufficiency, especially during summer. On the other hand, the stochastic behaviour of the wind and the important fluctuations of daily and seasonal electricity load in almost all Greek islands pose a substantial

J. K. Kaldellis

2007-01-01

193

Duplex-Doppler ultrasonography in the assessment of portal hypertension. Utility of the measurement of maximum portal flow velocity.  

PubMed

To assess the utility of Duplex-Doppler ultrasonography (DDUS) in the evaluation of portal haemodynamics we studied 52 patients with compensated liver cirrhosis (mean age 53.9 +/- 9.2 years, males 32, females 20) diagnosed by laparoscopy and biopsy. All patients underwent laparoscopy and oesophageal-gastro-duodenoscopy (OGDS): we postulated that haemodynamically significant portal hypertension (PH) was present if varices were detected at OGDS and/or if collateral veins were revealed at laparoscopy. DDUS was performed with a strictly standardized method and maximum portal flow velocity (PFV) was measured in all patients. Max-PFV ranged between 3.5 and 33.4 cm/s. Overall, 36 patients (69%) had a max-PFV lower than 20.3 cm/s (normal max-PFV range in our laboratory is 20.3-33.3 cm/s), while 16 patients (31%) had normal max-PFV values. Five patients (9.6%) had no signs of PH at laparoscopy and/or OGDS and all five had normal max-PFV values. The other 47 patients (90.4%) had collateral circuli at laparoscopy and 29/47 (61.7%) exhibited also varices at OGDS: max-PFV was lower than 20.3 cm/s in 36/47 patients (76.6%). The measurement of max-PFV demonstrated a 76.6% sensitivity and a 100% specificity in detecting PH, with 100% positive predictive value and 31% negative predictive value. Three patients with PH and apparently normal max-PFV values exhibited a recanalization of the umbilical vein.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8223681

D'Alimonte, P; Cioni, G; Cristani, A; Ferrari, A; Ventura, E; Romagnoli, R

1993-09-01

194

CO2 Doppler lidar measurement of wind velocity and relative backscatter associated with the nocturnal boundary layer  

NASA Astrophysics Data System (ADS)

Heterodyne CO2 Doppler lidar measurements of horizontal wind velocity from the surface to 11,000 feet AGL using the Velocity Azimuth Display (VAD) method were made at Holloman AFB, NM from the end of July through mid-August 1998. These data were entered real-time into the space maneuver vehicle descent analysis program to make flight performance predictions needed for test decisions. Daily measurements encompassed the early morning time period associated with the stably-stratified nocturnal boundary layer (NBL). Measurement periods were characterized by growth the decay of wind maxima or jets at different altitudes. Strong vertical shears were often observed in conjunction with these wind maxima. Relative backscatter profiles at the lowest altitudes exhibited periodic oscillations on most mornings. Relative backscatter profiles at the lowest altitudes exhibited periodic oscillations on most mornings. The observed NBL wind profiles were poorly represented by the Ekman model.

Roadcap, John R.; McNicholl, Patrick J.; Laird, Mitchell H.; Swirbalus, Robert A.

1999-08-01

195

Retrieval of stratified atmospheric reflectivity and wind velocity using inverse methods: application to a VHF ST mini-radar  

NASA Astrophysics Data System (ADS)

The growing interest of measuring wind and turbulence in the lower atmosphere has led to the development of new radar systems. UHF radars, though being an interesting solution from a technical and logistical point of view, have some disadvantages due to their high sensitivity to Rayleigh scattering and interference from precipitations, birds and insects. The standard VHF ST radars were originally designed for high altitude investigations and are consequently not suited for low atmosphere soundings. This context makes it necessary to develop the new concept of a VHF `mini-radar'. But the simultaneous use of a small antenna in the VHF band, combined with a beam having a more grazing angle, results in an important mixing of the altitude contributions for each range, a problem which is non existent with previous ST radars. Consequently, the atmospheric reflectivity and wind velocity profiles cannot be directly obtained and have to be treated by other methods. In this context, the aim of the present work consists in the development of an appropriate inverse method. Two different classic methods are considered, the least squares method and the maximum entropy method. The `direct problem' is first addressed, resulting in an integral description of the zeroth and first moments of the Doppler spectra. In order to perform various simulations to test the validity of the two proposed inverse methods in the particular case of the VHF mini-radar, a model is built for the radar which includes a set of reference atmospheric profiles. The simulations give evidence for the validity of the inversion processes. The high robustness of the least squares method always leads to significant results. But its over-determined nature results in a poor vertical resolution for the inverted profiles. Consequently this method is not suited to retrieving strong gradients. The maximum entropy method is intrinsically much more appropriate in terms of vertical resolution and consequently leads to valuable results, but its high sensitivity to the data noise requires some additional constraints. The practical efficiency of the methods is tested with real data from the mini-radar, and the resulting retrieved profiles are compared to those obtained simultaneously using a conventional ST radar (the `Provence' radar). As a result of a poor vertical resolution, the least squares method cannot provide a valid retrieval of the atmospheric profiles under real experimental conditions. Nevertheless, a preliminary inversion using the least squares method can be used as constraint for initializing the maximum entropy inversion process. Although this processing appears to be very efficient for the reflectivity, the retrieved profiles reveal a smoothing effect which seems to be linked to a faulty radar antenna radiation model. In contrast, the retrieval of wind velocity seems to be more difficult and requires additional investigations.

Fillol, J.-M.; Broche, P.; Crochet, M.

1997-07-01

196

Effect of maximum torque according to the permanent magnet configuration of a brushless dc motor with concentrated winding  

NASA Astrophysics Data System (ADS)

A brushless dc (BLDC) motor, which has a permanent magnet (PM) component, is a potential candidate for hybrid or electric vehicle applications. Minimizing the BLDC motor size is an important requirement for application. This requirement is usually satisfied by adopting a high performance permanent magnet or improved winding methods. The PM configuration is also a critical point in design. This article presents the effect of the PM configuration on motor performance, especially the maximum torque. Four representative BLDC motor types are analytically investigated under the condition that the volume of the PM and magnetic material is constant. An embedded interior permanent magnet motor has the best torque performance the maximum torque of which is more than 1.5 times larger than that of the surface mounted permanent magnet motor. The performance of back electromotive force, instantaneous torques is also investigated.

Lee, Kab-Jae; Kim, Sol; Lee, Ju; Oh, Jae-Eung

2003-05-01

197

Maximum power point tracking control and voltage regulation of a DC grid-tied wind energy conversion system based on a novel permanent magnet reluctance generator  

Microsoft Academic Search

This research paper aims to employ a new permanent magnet reluctance generator in a variable speed wind energy conversion system (WECS) of a grid-tied distributed generation application. The grid integration of WECS is achieved through cascaded dc-dc converters ensuring maximum power extraction from the wind energy while maintaining a constant output voltage at the grid side. The surplus power is

Kazmi Syed Muhammad Raza; Hiroki Goto; Hai-Jiao Guo; Osamu Ichinokura

2007-01-01

198

A novel speed-sensorless adaptive hill climbing algorithm for fast and efficient maximum power point tracking of wind energy conversion systems  

Microsoft Academic Search

This research paper proposes a novel solution to the problems that exists in the normal hill climb searching (HCS) maximum power point tracking (MPPT) algorithm for wind energy conversion systems (WECS). The solution presented not only solves the tracking speed vs. control efficiency tradeoff problem of HCS but also makes sure that the changing wind conditions shouldnpsilat lead HCS in

Kazmi Syed Muhammad Raza; Hiroki Goto; Hai-Jiao Guo; Osamu Ichinokura

2008-01-01

199

Measurements of solar transition zone velocities and line broadening using the ultraviolet spectrometer and polarimeter on the Solar Maximum Mission  

NASA Astrophysics Data System (ADS)

The UVSP instrument on SMM is able to observe solar regions at two wavelengths in the same line with a band-pass of 0.3 A. Intensity and Doppler velocity maps are derived. It is shown that the numerical values are sensitive to the adopted Doppler width and the range of velocities is limited to within 30 km/sec. A method called Double Dopplergram Determination (DDD) is described for deriving both the Doppler width and the velocity (up to 80 km/sec), and the main sources of uncertainties are discussed. To illustrate the method, a set of C IV 1548 A observations is analyzed according to this procedure. The mean C IV Doppler width measured (0.15 A) is comparable to previous determinations. A relation is found between bright regions and down-flows. Large Doppler widths correspond to strong velocity gradients.

Simon, G.; Mein, P.; Vial, J. C.; Shine, R. A.; Woodgate, B. E.

1982-11-01

200

Field measurements of horizontal forward motion velocities of terrestrial dust devils: Towards a proxy for ambient winds on Mars and Earth  

NASA Astrophysics Data System (ADS)

Dust devils - convective vortices made visible by the dust and debris they entrain - are common in arid environments and have been observed on Earth and Mars. Martian dust devils have been identified both in images taken at the surface and in remote sensing observations from orbiting spacecraft. Observations from landing craft and orbiting instruments have allowed the dust devil translational forward motion (ground velocity) to be calculated, but it is unclear how these velocities relate to the local ambient wind conditions, for (i) only model wind speeds are generally available for Mars, and (ii) on Earth only anecdotal evidence exists that compares dust devil ground velocity with ambient wind velocity. If dust devil ground velocity can be reliably correlated to the ambient wind regime, observations of dust devils could provide a proxy for wind speed and direction measurements on Mars. Hence, dust devil ground velocities could be used to probe the circulation of the martian boundary layer and help constrain climate models or assess the safety of future landing sites. We present results from a field study of terrestrial dust devils performed in the southwest USA in which we measured dust devil horizontal velocity as a function of ambient wind velocity. We acquired stereo images of more than a 100 active dust devils and recorded multiple size and position measurements for each dust devil. We used these data to calculate dust devil translational velocity. The dust devils were within a study area bounded by 10 m high meteorology towers such that dust devil speed and direction could be correlated with the local ambient wind speed and direction measurements. Daily (10:00-16:00 local time) and 2-h averaged dust devil ground speeds correlate well with ambient wind speeds averaged over the same period. Unsurprisingly, individual measurements of dust devil ground speed match instantaneous measurements of ambient wind speed more poorly; a 20-min smoothing window applied to the ambient wind speed data improves the correlation. In general, dust devils travel 10-20% faster than ambient wind speed measured at 10 m height, suggesting that their ground speeds are representative of the boundary layer winds a few tens of meters above ground level. Dust devil ground motion direction closely matches the measured ambient wind direction. The link between ambient winds and dust devil ground velocity demonstrated here suggests that a similar one should apply on Mars. Determining the details of the martian relationship between dust devil ground velocity and ambient wind velocity might require new in situ or modelling studies but, if completed successfully, would provide a quantitative means of measuring wind velocities on Mars that would otherwise be impossible to obtain.

Balme, M. R.; Pathare, A.; Metzger, S. M.; Towner, M. C.; Lewis, S. R.; Spiga, A.; Fenton, L. K.; Renno, N. O.; Elliott, H. M.; Saca, F. A.; Michaels, T. I.; Russell, P.; Verdasca, J.

2012-11-01

201

An Explanation of the Wind Speed Underestimation Obtained from a Least Squares Type Single-Doppler Radar Velocity Retrieval Method  

Microsoft Academic Search

The errors produced by a least squares type single-Doppler velocity retrieval scheme based on variational analysis are studied. With proper simplifications of the retrieval formulation, it can be found that the strength of the retrieved radial wind is comparable to the true one. By contrast, the retrieved azimuthal component is, in most cases, underestimated. For a given radar site, this

Yu-Chieng Liou

2002-01-01

202

The algorithm and the associated errors in measuring the wind velocity component by the photon-counting correlation method  

Microsoft Academic Search

An algorithm is proposed for determining the wind velocity by a correlation lidar with photon-counting signal detection. The algorithm is based on the parabolic approximation of the least squares estimates of the correlation function. The measurement error resulting from signal and noise fluctuations in the receive channel, laser emission energy, and transparency is estimated; simple expressions for estimating the measurement

V. G. Astafurov; G. N. Glazov

1987-01-01

203

Measurement of wind velocity on the surface of Venus during operation of the Venera 9 and Venera 10 space probes  

Microsoft Academic Search

The paper reports on the first measurements of the wind velocity on the surface of Venus recorded during final phase of descent of Venera 9 and 10 and while on the surface. The cup anemometer system and some tests on earth for determining best placement of the equipment in order to eliminate any effect of the spacecraft are described. Venera-9

V. S. Avduevskii; S. L. Vishnevetskii; I. A. Golov; Iu. Ia. Karpeiskii; A. D. Lavrov; V. Ia. Likhushin; M. Ia. Marov; D. A. Melnikov; N. I. Pomogin; N. N. Pronina

1976-01-01

204

Determination of the Maximum Aerodynamic Efficiency of Wind Turbine Rotors with Winglets  

NASA Astrophysics Data System (ADS)

The present work contains theoretical considerations and computational results on the nature of using winglets on wind turbines. The theoretical results presented show that the power augmentation obtainable with winglets is due to a reduction of tip-effects, and is not, as believed up to now, caused by the downwind vorticity shift due to downwind winglets. The numerical work includes optimization of the power coefficient for a given tip speed ratio and geometry of the span using a newly developed free wake lifting line code, which takes into account also viscous effects and self induced forces. Validation of the new code with CFD results for a rotor without winglets showed very good agreement. Results from the new code with winglets indicate that downwind winglets are superior to upwind ones with respect to optimization of Cp, and that the increase in power production is less than what may be obtained by a simple extension of the wing in the radial direction. The computations also show that shorter downwind winglets (>2%) come close to the increase in Cp obtained by a radial extension of the wing. Lastly, the results from the code are used to design a rotor with a 2% downwind winglet, which is computed using the Navier-Stokes solver EllipSys3D. These computations show that further work is needed to validate the FWLL code for cases where the rotor is equipped with winglets.

Gaunaa, Mac; Johansen, Jeppe

2007-07-01

205

Aging of solar wind magnetic and velocity fluctuations from observations in the inner heliosphere  

NASA Astrophysics Data System (ADS)

The heliosphere is a natural laboratory to study several aspects of Magnetohydrodynamic (MHD) turbulence. MHD fluctuations are ubiquitous in the solar wind (SW) and 'in situ' observations of plasma properties and magnetic field are one of the keys to unveil the secrets of MHD turbulence. In the interplanetary medium, MHD scale fluctuations are usually anisotropic, and these fluctuations frequently present different properties in regions of quasi-stationary SW with different bulk plasma parameters, or in regions associated with the presence of transients (e.g., magnetic clouds). It is known that the spatial structure of magnetic and velocity correlation functions evolves in the inner heliosphere. This evolution in terms of the aging of plasma parcels, as observed by the spacecrafts Helios 1-2, is the subject of the work presented here. Particular interest is put on the evolution of anisotropies in the integral length scale. Results are consistent with driving modes with wavevectors parallel to the direction of the local mean magnetic field near Sun, and a progressive spectral transfer of energy to modes with perpendicular wavevectors. Advances made in this direction, as those presented here, will be usefull to refine models used to describe the propagation and diffusion of charged solar and galactic energetic particles in the inner heliosphere, and will contribute to understand the MHD Alfvenic wave activity for this system.

Ruiz, M. E.; Dasso, S.; Matthaeus, W. H.; Weygand, J. M.; Marsch, E.

2010-12-01

206

Duration and fetch-limited growth functions of wind-generated waves parameterized with three different scaling wind velocities  

Microsoft Academic Search

Under steady wind forcing, wave development follows the duration- and fetch-limited growth laws. These growth functions are used extensively to obtain the sea state information when only limited observations of the environmental variables are available. Validation and verification of wave models also employ numerical experiments of duration- and fetch-limited wave growth as benchmark tests. The reference wind speed reported in

Paul A. Hwang

2006-01-01

207

Reinterpretation of Slowdown of Solar Wind Mean Velocity in Nonlinear Structures Observed Upstream of Earth's Bow Shock  

NASA Astrophysics Data System (ADS)

Two of the many features associated with nonlinear upstream structures are (1) the solar wind (SW) mean flow slows down and deviates substantially and (2) the temperature of the plasma increases in the structure. In this Letter, we show that the SW beam can be present throughout the entire upstream event maintaining a nearly constant beam velocity and temperature. The decrease of the velocity is due to the appearance of new particles moving in the opposite direction that act against the SW beam and reduce the mean velocity as computed via moments. The new population, which occupies a larger velocity space, also contributes to the second moment, increasing the temperature. The new particles include the reflected SW beam at the bow shock and another population of lower energies, accelerated nearby at the shock or at the boundary of the nonlinear structures.

Parks, G. K.; Lee, E.; Lin, N.; Fu, S. Y.; McCarthy, M.; Cao, J. B.; Hong, J.; Liu, Y.; Shi, J. K.; Goldstein, M. L.; Canu, P.; Dandouras, I.; Rme, H.

2013-07-01

208

Limits imposed by solenoid damage on the maximum velocity achieved by an electromagnetic coilgun: A computational study  

NASA Astrophysics Data System (ADS)

CAD has set up an electromagnetic acceleration and impact facility for studies of material fracture and deformation at high strain rates. The target is to reach projectile velocities of 200-500 m/s. The mechanical strength of the solenoid coil and potting material is an important factor affecting coil survival during experiments. We have performed a computational study, using the materials and coil and circuit parameters typically used in experiments, and found the operating limits up to which the coil can survive without breaking.

Madhavan, S.; Sijoy, C. D.; Pahari, S.; Chaturvedi, S.

2012-06-01

209

Wind speed and velocity at three Estonian coastal stations 19691992  

Microsoft Academic Search

Wind climate, based on monthly average values of wind parameters during a 24-year period, is analysed for three data sets - two from surface recordings at meteorological stations and one from aerological measurements at 850 hPa level. Several statistically significant trends in wind properties have been detected in January, March, May and November. It is shown that the average air

Sirje Keevallik

2008-01-01

210

Global average of air-sea CO2 transfer velocity from QuikSCAT scatterometer wind speeds  

Microsoft Academic Search

The absolute calibration of the relationship between air-sea CO2 transfer velocity, k, and wind speed, U, has been a topic of debate for some time, because k global average, $\\\\langle$k$\\\\rangle$, as deduced from Geochemical Ocean Sections Study oceanic 14C inventory has differed from that deduced from experimental k-U relationships. Recently, new oceanic 14C inventories and inversions have lead to a

J. Boutin; Y. Quilfen; L. Merlivat; J. F. Piolle

2009-01-01

211

Prediction of Summer Precipitation During The Indian Monsoon Applying The Circulating Index of Wind Velocity  

NASA Astrophysics Data System (ADS)

In the MSU ECTRA model (Moscow State University empirical circulating model for the tropical atmosphere) ten action centers in the tropical atmosphere were cho- sen, which are responsible for the formation of summer monsoon rains above India. In the lower troposphere (850 hPa) the following action centers were chosen: 1 Mon- soonal depression above India. 2 Equatorial depression on the southern branch of the ITCZ (the south of the Arabian sea). 3 Equatorial depression above Indonesia. 4 Asian summer depression. 5 Subtropical anticyclone of the Southern Hemisphere. 6 North- Australian subtropical anticyclone. In the upper troposphere (200hPa) the chosen action centers are: 1 Tibet upper-level anticyclone. 2 North-African upper-level anticyclone. 3 Upper-level anticyclone above Madagascar. 4 North-Australian upper-level anticyclone. Based on NCEP/NCAR 1948-1997 reanalysis data the circulation index, i.e. the inte- gral of the wind velocity vector along contours, was calculated and the reliable con- tours' sizes and the central points were determined for each action center. In the next stage the connection between the intensity of the chosen circulating systems and sum- mer rains was assessed for five Indian regions with different precipitation regimes: 1 The coast of the Arabian Sea. 2 The southern part of India. 3 The central part of India. 4 The northern part of India. 5 The north of Bengal. The system of predictors that were found allows us to estimate the influence of each baric center in the system of summer Indian monsoon circulation and to forecast the summer rains during Indian monsoon in the future.

Sokolikhina, E.; Semenov, E.; Sokolikhina, N.

212

Armature and Field Controlled DC Motor Based Wind Turbine Emulation for Wind Energy Conversion Systems Operating over a Wide Range of Wind Velocity  

Microsoft Academic Search

A Wind Turbine Emulator (WTE), which can mimic the steady-state wind turbine characteristics, is reported. It can be used\\u000a for research and development work in the area of wind energy conversion systems, without depending on natural wind energy\\u000a resources and is especially suited for testing and experimentation work in the laboratory environment. It offers a controllable\\u000a test environment that allows

Rahul Patel; Chetan V. Patki; Vivek Agarwal

213

A Technique for Estimating Low-Level Wind Velocity from Satellite Photographs of Cellular Convection  

Microsoft Academic Search

A technique for estimating the low-level wind field from satellite photographs of cumuliform cellular cloud patterns is presented. This technique applies to areas of such patterns, which are frequently photographed behind major oceanic cyclones. The wind speed estimates are obtained by correlating the different cumuliform cellular patterns with three wind speed categories, 0-7, 8-22, and 23-37 knots. This categorization was

Charles W. C. Rogers

1965-01-01

214

Towards an expert system for estimating wind loads on building attachments using detailed local velocity data  

Microsoft Academic Search

This paper presents a new working method for predicting design wind loads on attachments projecting from the walls of buildings. In the University of Oxford environmental wind tunnel, a two-component fibre-optic laser-Doppler anemometer has been used in a systematic study of highly turbulent wind flows at various locations close to walls and roofs of buildings. This includes instantaneous vertical and

A. J. Minson; R. I. Harris; C. J. Wood

1996-01-01

215

Wind tunnel measurements of adobe abrasion by blown sand: profile characteristics in relation to wind velocity and sand flux  

Microsoft Academic Search

Blown sand causes various damages, such as extensive abrasion to crops, structural wear of facilities and buildings, and abrasion of soil clods and clayey materials generating fine particulate matter. In this study, experiments conducted in a straight-line blowing wind tunnel confirmed field observations and provided useful information for understanding abrasion profiles created by sand drift. Abrasion rates of 20 adobe

Liu Lian-You; Gao Shang-Yu; Shi Pei-Jun; Li Xiao-Yan; Dong Zhi-Bao

2003-01-01

216

IMF orientation, solar wind velocity, and Pc 3--4 signals: A joint distribution  

Microsoft Academic Search

Separate studies using the same micropulsation data base in the period range 10--150 s have shown earlier that signal levels recorded during September, October, and November 1969 at Calgary correlated positively with both solar wind alignment of the IMF and solar wind speed, but each correlation contained enough scatter to allow for influence of the other factor. In this report,

Eugene W. Greenstadt; Howard J. Singer; Christopher T. Russell; John V. Olson

1979-01-01

217

Spectral Analysis of the U Component of Wind Velocity at Three Meters  

Microsoft Academic Search

A broad-band spectral analysis has been carried out for 54 ten-minute observations of the u component of wind speed at a height three meters. The observations were made with mean wind speeds ranging from 2 to 9 m per sec and under all solar heating conditions. The data were taken on a flat grassland in Nebraska. The method of analysis

Robert P. Ely Jr.

1958-01-01

218

Threshold wind velocities for sand movement in the Mescalero Sands of southeastern New Mexico  

Technology Transfer Automated Retrieval System (TEKTRAN)

Wind erosion activity was studied at two Chihuahuan Desert sites, the Gnome site which was contaminated with radioactivity from a nuclear device in 1961 and Near Field, a reference site. Saltation activity was measured with piezoelectric sensors, and those data were used to calculate threshold wind...

219

Estimation of wind velocity over a complex terrain using the Generalized Mapping Regressor  

Microsoft Academic Search

Wind energy evaluation is an important goal in the conversion of energy systems to more environmentally friendly solutions. In this paper, we present a novel approach to wind speed spatial estimation on the isle of Sicily (Italy): an incremental self-organizing neural network (Generalized Mapping Regressor GMR) is coupled with exploratory data analysis techniques in order to obtain a map

M. Beccali; G. Cirrincione; A. Marvuglia; C. Serporta

2010-01-01

220

Review and critical analysis of the research papers published till date on maximum power point tracking in wind energy conversion system  

Microsoft Academic Search

Maximum power point tracking (MPPT) is a very important necessity in a system of energy conversion from a renewable energy source. Every year a number of publications appear in various journals and conferences claiming to offer better and faster MPPT techniques for wind energy conversion system (WECS). This research paper provides a concise yet comprehensive critical analysis of these techniques

Syed Muhammad Raza Kazmi; Hiroki Goto; Hai-Jiao Guo; Osamu Ichinokura

2010-01-01

221

Lidar Measurement of Wind Velocity Turbulence Spectra Encountered by a Rotating Turbine Blade.  

National Technical Information Service (NTIS)

A homodyne CO sub 2 lidar system beam was conically scanned around a horizontal axis to measure the wind speed and turbulence characteristics encountered by a rotating turbine blade. Turbulence spectra obtained from the scanning lidar differed considerabl...

F. F. Hall J. A. Korrell R. M. Hardesty

1982-01-01

222

Estimations of the maximum tangential velocity V ?m in the vortex core region and also the mean rotational velocity V oi near the concave wall surface in the returned flow type cyclone dust collector  

NASA Astrophysics Data System (ADS)

There are many types of cyclone dust collectors for separating the fine solid and dust particles from gases in the various industries and also in the home used purposes. For estimating the power loss and the collection efficiency, one of the most important factors is the maximum tangential velocity V ?m in the vortex core region in the cyclone body. In order to determine V ?m by the simple method, it is useful to apply the mechanical balance of the angular momentum fluxes under the assumption of Ogawa combined vortex model which is composed of the quasi-forced vortex in the vortex core region and also the quasi-free vortex surrounded the vortex core region and also under the assumption of the introduction of equivalent length Heq corresponding to the cone spaces of the cyclone body and the dust bunker. On the other hand, the mean rotational velocity V oi near the concave wall surface is also estimated by the mechanical balance of angular momentum fluxes with the moment of viscous friction force. For confirming the general applications of the obtained equations, the returned flow types cyclones changed the throat diameter D3 are designed. The material of the cyclone is the transparent acrylic resin. Therefore the inner surface of the cyclone body can be regarded as smooth surface. The comparisons of the measured velocities V ?m and V oi by a cylindrical Pitot tube are shown in good agreement with those of the proposed equations. The above stated results are described in detail.

Ogawa, Akira

2010-12-01

223

Power control of a stand-alone photovoltaic\\/ wind\\/ energy storage hybrid generation system with Maximum Power Point Tracker  

Microsoft Academic Search

In this paper, a hybrid generation system combining photovoltaic (PV), wind turbine (WT) and Electric Double Layer Capacitor (EDLC) is presented to supply stable power to residential power applications as stand-alone loads. The photovoltaic and wind systems are used as main energy sources while the EDLC is used as storage device. Three individual DC\\/DC converters are used to control the

Yukihiro Ozaki; Masafumi Miyatake; Daisuke Iwaki

2010-01-01

224

THIRD MOMENTS AND THE ROLE OF ANISOTROPY FROM VELOCITY SHEAR IN THE SOLAR WIND  

SciTech Connect

We have extended the recent analyses of magnetohydrodynamic third moments as they relate to the turbulent energy cascade in the solar wind to consider the effects of large-scale shear flows. Moments from a large set of Advanced Composition Explorer data have been taken, and chosen data intervals are characterized by the rate of change in the solar wind speed. Mean dissipation rates are obtained in accordance with the predictions of homogeneous shear-driven turbulence. Agreement with predictions is best made for rarefaction intervals where the solar wind speed is decreasing with time. For decreasing speed intervals, we find that the dissipation rates increase with increasing shear magnitude and that the shear-induced fluctuation anisotropy is consistent with a relatively small amount.

Stawarz, Joshua E.; Vasquez, Bernard J.; Smith, Charles W. [Physics Department, Space Science Center, University of New Hampshire, Durham, NH 03824 (United States); Forman, Miriam A. [Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY 11794-3800 (United States); Klewicki, Joseph, E-mail: jek32@cisunix.unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: Charles.Smith@unh.edu, E-mail: Miriam.Forman@sunysb.edu, E-mail: Joe.Klewicki@unh.edu [Mechanical Engineering Department, University of New Hampshire, Durham, NH 03824 (United States)

2011-07-20

225

The velocity distribution function of the neutral lithium cloud produced by an AMPTE solar wind release  

Microsoft Academic Search

On Sept. 20, 1984 a release of photoionizing lithium neutrals was made in the quiet solar wind by the AMPTE-IRM spacecraft. The MSSL ion instrument on board the UKS spacecraft that was positioned about 30 km from the release center enabled measurement of significant fluxes of lithium ions to be made for about 3 min after the release; that is,

S. C. Chapman; A. D. Johnstone; A. J. Coates

1987-01-01

226

Vector Wind Velocity, Speed, and Mode Summaries for the Southeastern U.S.  

National Technical Information Service (NTIS)

This report presents wind speed and direction summaries for a wide area of the Southeastern United States (including EPA Region 4) and portions of the Ohio and Mississippi River Valleys in a monthly time series format that is further broken down for eight...

2004-01-01

227

Comparison of Nighttime Zonal Neutral Winds and Plasma Bubble Drift Velocities over Brazil  

NASA Astrophysics Data System (ADS)

We present the first simultaneous measurements of equatorial thermospheric neutral wind measurements and plasma bubble (EPB) zonal speeds over northeastern Brazil during September-December 2009 and 2010. The wind data are obtained from a bi-static Fabry-Perot interferometer experiment measuring the Doppler shift of the 630.0-nm spectral emission. The FPIs are located at Cajazeiras (6.86S, 38.56W) and Cariri (7.38S, 36.53W). The EPB zonal speed, which is assumed to be equal to the drift of the background plasma, is measured using images of the 630.0-nm emission obtained from a wide-angle imaging system collocated with the FPI at Cajazeiras. In general, the simultaneous measurement of the zonal neutral wind and the EPB zonal speed show excellent agreement. However, the EPB zonal speed is slower than that of the wind motion in the early evening hours on several occasions, suggesting the F-region dynamo is not fully activated.

Chapagain, N. P.; Makela, J. J.; Meriwether, J. W.; Buriti, R. A.; Medeiros, A.

2011-12-01

228

Pulsed-Doppler Velocity Isotach Displays of Storm Winds in Real Time.  

National Technical Information Service (NTIS)

First results derived from an NSSL effort to develop a real-time Plan Position Indicator (PPI) display of Doppler isotachs are described. The mean Doppler velocity is estimated for multiple range locations by measuring the phase change of the complex echo...

D. Sirmans R. J. Doviak

1973-01-01

229

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

Microsoft Academic Search

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

Abel I. Rouboa; Victor M. Reis; Vishveshwar R. Mantha; Daniel A. Marinho; Antnio J. Silva

2011-01-01

230

Wavelet profiling of wind velocity using intensity fluctuations of laser beam propagating in the atmosphere  

Microsoft Academic Search

A method for the remote determination of the crosswind velocity profile using a wavelet analysis of fluctuations in the intensity of transmitted laser radiation is proposed. Results of an experimental investigation are presented that show how turbulent flow inhomogeneities (intensity fluctuations) localized in separate parts of the path contribute to the total distortions of the intensity distribution in a beam

A. L. Afanas'ev; V. A. Banakh; A. P. Rostov

2008-01-01

231

Wavelet profiling of wind velocity using intensity fluctuations of laser beam propagating in the atmosphere  

Microsoft Academic Search

A method for the remote determination of the crosswind velocity profile using a wavelet analysis of fluctuations in the intensity\\u000a of transmitted laser radiation is proposed. Results of an experimental investigation are presented that show how turbulent\\u000a flow inhomogeneities (intensity fluctuations) localized in separate parts of the path contribute to the total distortions\\u000a of the intensity distribution in a beam

A. L. Afanasev; V. A. Banakh; A. P. Rostov

2008-01-01

232

Mitigation of Low-velocity, Wind-induced Vibration of an Architectural Spire  

Microsoft Academic Search

\\u000a This paper presents the results of analytical and experimental studies conducted on an architectural spire, which experienced\\u000a wind-induced vibrations shortly after its construction. The circular spire is attached to the corner of a 30-story building\\u000a along the upper ten stories then cantilevers up for 21.44 m (70.33 ft) with a pipe cross-section of 0.508 m (20 in)-diameter\\u000a for the first

Omer F. Tigli; Luca Caracoglia

233

Optical fiber-based laser remote sensor for airborne measurement of wind velocity and turbulence.  

PubMed

We discuss an optical fiber-based continuous-wave coherent laser system for measuring the wind speed in undisturbed air ahead of an aircraft. The operational principles of the instrument are described, and estimates of performance are presented. The instrument is demonstrated as a single line of sight, and data from the inaugural test flight of August 2010 is presented. The system was successfully operated under various atmospheric conditions, including cloud and clear air up to 12?km (40,300?ft). PMID:21343963

Spuler, Scott M; Richter, Dirk; Spowart, Michael P; Rieken, Kathrin

2011-02-20

234

A maximum power control of wind generator system using a permanent magnet synchronous generator and a boost chopper circuit  

Microsoft Academic Search

The wind generator system using a boost chopper for generation control of permanent magnet synchronous generator is proposed. And, the theoretical analysis of characteristics of power generation is discussed. By replacing the main circuit composition of generator and boost chopper with the equivalent circuit, characteristics for generating power and DC output voltage were expressed by the function of duty ratio

Kenji Amei; Y. Takayasu; T. Ohji; M. Sakui

2002-01-01

235

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)

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 0.40.4 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 ?m polyamide particles with density 1.02 g/sm3 and inertial time 710-3 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 both method were in a good agreement. The application of PIV method enabled us measuring wind velocity profiles much closer to water surface than in the case of contact method. As a result there exists the logarithmic parts in velocity profiles, which yield turbulent momentum flux from the slope and also the equivalent 10-m wind speed and the surface drag coefficient. It was shown that similarly to [2] the surface drag coefficient tends to saturate at wind velocities exceeding 25 m/s. The decrease of the water surface drag coefficient with wind velocity increase was not observed. This work was supported by RFBR (project 11-05-12047-ofi-m, 13-05-00865-a, 12-05-33070 mol-a-ved, 12-05-31435 mol-a, 12-05-01064-a). References 1. Canny, J. A. Computational approach to edge detection/ J.A. Canny// IEEE Trans. Pattern Analysis and Machine Intelligence. - 1986. - V. 8(6). - P. 679-698.. 2. Troitskaya, Y. I., D. A. Sergeev, A. A. Kandaurov, G. A. Baidakov, M. A. Vdovin, and V. I. Kazakov Laboratory and theoretical modeling of air-sea momentum transfer under severe wind conditions J.Geophys. Res., 117, C00J21, doi:10.1029/2011JC007778.

Troitskaya, Yuliya; Kandaurov, Alexander; Sergeev, Daniil; Ermakova, Olga

2013-04-01

236

Cross-Bridge Attachment during High-Speed Active Shortening of Skinned Fibers of the Rabbit Psoas Muscle: Implications for Cross-Bridge Action during Maximum Velocity of Filament Sliding  

Microsoft Academic Search

To characterize the kinetics of cross-bridge attachment to actin during unloaded contraction (maximum velocity of filament sliding), ramp-shaped stretches with different stretch-velocities (240,000nm per half-sarcomere per s) were applied to actively contracting skinned fibers of the rabbit psoas muscle. Apparent fiber stiffness observed during such stretches was plotted versus the speed of the imposed stretch (stiffness-speed relation) to derive the

R. Stehle; B. Brenner

2000-01-01

237

Forward velocity effects on fan noise and the suppression characteristics of advanced inlets as measured in the NASA-Ames 40 by 80 foot wind tunnel  

Microsoft Academic Search

Forward velocity effects on the forward radiated fan noise and on the suppression characteristics of three advanced inlets relative to a baseline cylindrical inlet were measured in the NASA Ames Research Center 40 x 80 foot Wind Tunnel. A modified JT15D turbofan engine in a quiet nacelle was the source of fan noise; the advanced inlets were a Conventional Takeoff\\/Landing

M. T. Moore

1980-01-01

238

The effect of the wind speed velocity on the stack pressure in medium-rise buildings in cold region of China  

Microsoft Academic Search

This paper presents the numerical simulation results of the stack effect in medium-rise buildings in Harbin, a typical city in the severe cold region of China. The simulation was carried out using the multizone ventilation model COMIS. The effect of the wind speed velocity and the temperature of the stairwell on the pressure difference curves shape have been investigated. The

Maatouk Khoukhi; Hiroshi Yoshino; Jing Liu

2007-01-01

239

Forward velocity effects on fan noise and the suppression characteristics of advanced inlets as measured in the NASA Ames 40 by 80 foot wind tunnel: Acoustic data report  

Microsoft Academic Search

Forward velocity effects on the forward radiated fan noise and on the suppression characteristics of three advanced inlets relative to a baseline cylindrical inlet were measured in a wind tunnel. A modified JT15D turbofan engine in a quiet nacelle was the source of fan noise; the advanced inlets were a CTOL hybrid inlet, an STOL hybrid inlet, and a treated

M. T. Moore

1981-01-01

240

A new method for obtaining velocity and diffusivity from time-dependent distributions of a tracer via the maximum likelihood estimator for the advection-diffusion equation  

SciTech Connect

An inverse problem for the advection-diffusion equation is considered, and a method of maximum likelihood (ML) estimation is developed to derive velocity and diffusivity from time-dependent distributions of a tracer. Piterbarg and Rozovskii showed theoretically that the ML estimator for diffusivity is consistent ever in an asymptotic case of infinite number of observational spatial modes. In the present work, the ML estimator is studied based on numerical experiments with a tracer in a two-dimensional flow under the condition of a limited number of observations in space. The numerical experiments involve the direct and the inverse problems. For the former, the time evolution of a tracer is simulated using the Galerkin-type method-as a response of the conservation equation to stochastic forcing. In the inverse problem, the advection-diffusion equation is fitted to the simulated data employing the ML estimator. It is shown that the ML method allows us a method to estimate diffusion coefficient components D{sub x} and D{sub y} based on a short time series of tracer observations. The estimate of the diffusion anistropy, D{sub x}/D{sub y}, is shown to be even more robust than the estimate of the diffusivity itself. A comparison with an estimation technique based on the finite-difference approximation demonstrates advantages of the ML estimator. Finally, the ML method is employed for analysis of heat balance in the upper layer of the North Pacific in the winter. This application focuses on the heat diffusion anisotropy at the ocean mesoscale. 29 refs., 14 figs.

Ostrovskii, A.G. [Kyushu Univ., Kasuga (Japan); Piterbarg, L.I. [Univ. of Southern California, Los Angeles, CA (United States)

1997-05-15

241

Pitch angle and velocity diffusions of newborn ions by turbulence in the solar wind  

SciTech Connect

The present study is dedicated to the analysis of dynamical processes relevant to the interaction of newborn ions with turbulence in the solar wind, when the level of turbulence is moderately low so that quasi-linear theory is applicable. It is assumed that the low-frequency turbulence is at saturation level and not affected by the newborn ions. In order to follow the time evolution of the ion distribution, the quasi-linear diffusion equation is derived and numerically solved, starting from a ring-beam initial distribution. A simplified treatment of the resonance broadening effect is included in the diffusion equation, and its role in the pickup process is discussed. Two different configurations of wave polarization and direction of propagation are considered, using model turbulence spectra. The conditions that lead either to the formation of anisotropic shells as a long-duration transient state or to rapid isotropization of the ion pitch angle distribution are discussed, as well as the conditions leading to significant acceleration of the ions.

Ziebell, L.F.; Yoon, P.H. (Univ. of Maryland, College Park (USA))

1990-12-01

242

Comparing solar wind velocity measurements derived from Sun-grazing Comet Lovejoy (C/2011 W3) as observed from multiple locations  

NASA Astrophysics Data System (ADS)

Comets' plasma (type I) tails have been studied as natural probes of the solar wind since the mid-20th century. Local solar wind conditions directly control the morphology and dynamics of a comet's plasma tail. During ideal observing geometries, the orientation and structure of the plasma tail can reveal large-scale and small-scale variations in the local solar wind structure. These variations can be manifested as tail condensations, kinks, and disconnection events. The technique employed in this study was established by analysing geocentric amateur observations of comets C/2001 Q4 (NEAT) and C/2004 Q2 (Machholz). These amateur images, obtained with modern equipment and sensors, are arguably better in quality than professional images obtained only 2-3 decades ago. Multiple solar wind velocity estimates were derived from each image and the results compared to observed and modelled near-Earth solar wind data. Our unique analysis technique allows us to determine the latitudinal variations of the solar wind, heliospheric current sheet sector boundaries and the boundaries of transient features as a comet with an observable plasma tail probes the inner heliosphere. We present solar wind velocity measurements derived from multiple observing locations of comet Lovejoy (C/2011 W3) from the 14th - 19th December 2011 using recent images from the SECCHI and LASCO heliospheric imagers and coronagraphs aboard STEREO A and B, and SOHO. Comet Lovejoy was a very bright sungrazer, which plunged into the solar corona and largely survived its perihelion (1.19 solar radii) on 16th December at 00:17 UT. Lovejoy, an exception amongst sungrazers, displayed a prominent plasma tail pre-perihelion and post-perihelion, as it probed the solar atmosphere. Overlapping observation sessions from the three spacecraft provided the perfect opportunity to use comet Lovejoy as a diagnostic tool to understand solar wind variability close to the Sun. We plan to compare our observations to results of suitable simulations of plasma conditions in the corona and inner heliosphere during the time of Lovejoy's perihelion passage. The correlation of the solar wind velocity distribution from different observing locations can provide clues towards the morphology and orientation of the plasma tail. We also attempt to determine the non-radial contributions to the measured solar wind velocities via this study.

Ramanjooloo, Yudish; Jones, Geraint H.; Coates, Andrew J.; Owens, Mathew J.; Battams, Karl

2013-04-01

243

Estimation of wind friction velocity and direction at the ocean surface from physical models and space-borne radar scatterometer measurements  

NASA Astrophysics Data System (ADS)

This paper presents a new technique for estimating the wind friction velocity at the ocean surface from C-band radar scatterometer measurements. This technique uses physical models of ocean surface waves and electromagnetic backscattering from a rough surface at intermediate angles of incidence to generate predictions of the normalized radar cross section (NRCS, or ?0) of the ocean surface for a given wind friction velocity and observational geometry. The ocean spectral model used in this technique has been developed specifically for this application. It combines in situ wave measurements at low wave numbers with the Phillips [1985] equilibrium spectral model. This choice of ocean wave model is supported by a set of open ocean wave measurements summarized in this paper. A suite of models, derived from both in situ and remote measurements of the sea surface, is used to characterize the directional spreading of ocean waves relative to the wind direction. The resulting two-dimensional ocean wave spectra are used with a composite surface model to predict radar backscattering from the ocean surface at C-band. These radar cross-section predictions are combined with ERS-1 scatterometer measurements in a cost function minimization scheme to yield estimates of the friction velocity vector at the ocean surface. We present examples of this technique and compare friction velocity retrievals obtained via this scheme with buoy-based measurements under a variety of wind and wave conditions. On the basis of the analysis of a limited number of cases, this technique yielded friction velocity estimates for which the magnitude was within 22% and the direction was within 25. Given that scientific applications require magnitude estimates within 10-15% and directional estimates within 20 of in situ measurements, these preliminary results suggest that this is a promising approach to wind retrieval.

Lettvin, Ellen E.; Vesecky, John F.

2001-10-01

244

Wind  

NSDL National Science Digital Library

This document examine wind power as an energy resource. The reading will define wind and discuss topics such as (1) The history of wind machines, (2) Today's windmills, and (3) Types of wind machines. This resource is structured as an informational handout to supplement your energy activities or to generate discussion questions. Copyright 2005 International Technology Education Association

National Energy Education Development (NEED) Project

2003-01-01

245

Low-latitude thermospheric neutral winds determined from AEE measurements of the 6300-A nightglow at solar maximum  

Microsoft Academic Search

Atmosphere Explorer E (AE-E) measurements of the O(1D) 6300-A emission in the nighttime equatorial thermosphere are used to infer the height of the F2 layer peak as a function of latitude and local time. The investigation is conducted both for northern hemisphere winter solstice and for spring equinox, under solar maximum conditions. The layer heights are used to derive magnetic

M. D. Burrage; V. J. Abreu; C. G. Fesen

1990-01-01

246

Maximum rates of sustained metabolic rate in cold-exposed Djungarian hamsters ( Phodopus sungorus ): the second wind  

Microsoft Academic Search

Djungarian hamsters (Phodopus sungorus) tolerate short-term exposure to ambient temperatures (T\\u000a as) down to ?70C, but surprisingly, previously appeared to reach maximum sustainable metabolic rate (SusMR) when kept at T\\u000a as as high as ??2C. We hypothesized that SusMR in Djungarian hamsters may be affected by the degree of prior cold acclimation\\u000a and temporal patterns of T\\u000a a changes experienced

Thomas Ruf; Beatrice Grafl

2010-01-01

247

VAWT Stochastic Wind Simulator.  

National Technical Information Service (NTIS)

A stochastic wind simulation for VAWTs (VSTOC) has been developed which yields turbulent wind-velocity fluctuations for rotationally sampled points. This allows three-component wind-velocity fluctuations to be simulated at specified nodal points on the wi...

J. H. Strickland

1987-01-01

248

Coronal holes as sources of solar wind  

Microsoft Academic Search

We investigate the association of high-speed solar wind with coronal holes during the Skylab mission by: (1) direct comparison of solar wind and coronal X-ray data; (2) comparison of near-equatorial coronal hole area with maximum solar wind velocity in the associated streams; and (3) examination of the correlation between solar and interplanetary magnetic polarities. We find that all large near-equatorial

J. T. Nolte; A. S. Krieger; A. F. Timothy; R. E. Gold; E. C. Roelof; G. Vaiana; A. J. Lazarus; J. D. Sullivan; P. S. McIntosh

1976-01-01

249

The effects of the solar magnetic polarity and the solar wind velocity on Bz-component of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We have studied the effect of both solar magnetic polarity and the solar wind velocity on the Bz-component of the interplanetary magnetic field, IMFBz, for the minimum activity of the solar cycles 21, 22, 23 and 24. We made a statistical study of IMFBz in the first section which is considered as an extension of Lyatsky et al. (2003). They made a statistical study of IMFBz for two periods of minimum solar activity 22 and 23 related to 1985-1987 and 1995-1997 when the solar magnetic field had opposite polarity. Our results seem to be consistent with the results obtained by Lyatsky et al. (2003). We found that there is a dependence of IMFBz on the IMFBx and the solar magnetic polarity for the minimum periods of the selected four solar cycles. In addition, we found that there is a dependence of IMFBz on the solar wind velocity.

Youssef, M.; Mahrous, A.; Mawad, R.; Ghamry, E.; Shaltout, M.; El-Nawawy, M.; Fahim, A.

2012-04-01

250

A Novel Sensorless MPPT Controller for a High-Efficiency Microscale Wind Power Generation System  

Microsoft Academic Search

In this paper, a novel maximum power point tracking (MPPT) controller with an adaptive compensation control is first proposed for a microscale wind power generation system (WPGS). Based on the adaptive control, the dynamic response is improved and more wind energy can be captured during wind velocity variations. For cost and reliability consideration, no mechanical sensors are used in this

Ching-Tsai Pan; Yu-Ling Juan

2010-01-01

251

Orientation Cues for High-Flying Nocturnal Insect Migrants: Do Turbulence-Induced Temperature and Velocity Fluctuations Indicate the Mean Wind Flow?  

PubMed Central

Migratory insects flying at high altitude at night often show a degree of common alignment, sometimes with quite small angular dispersions around the mean. The observed orientation directions are often close to the downwind direction and this would seemingly be adaptive in that large insects could add their self-propelled speed to the wind speed, thus maximising their displacement in a given time. There are increasing indications that high-altitude orientation may be maintained by some intrinsic property of the wind rather than by visual perception of relative ground movement. Therefore, we first examined whether migrating insects could deduce the mean wind direction from the turbulent fluctuations in temperature. Within the atmospheric boundary-layer, temperature records show characteristic ramp-cliff structures, and insects flying downwind would move through these ramps whilst those flying crosswind would not. However, analysis of vertical-looking radar data on the common orientations of nocturnally migrating insects in the UK produced no evidence that the migrants actually use temperature ramps as orientation cues. This suggests that insects rely on turbulent velocity and acceleration cues, and refocuses attention on how these can be detected, especially as small-scale turbulence is usually held to be directionally invariant (isotropic). In the second part of the paper we present a theoretical analysis and simulations showing that velocity fluctuations and accelerations felt by an insect are predicted to be anisotropic even when the small-scale turbulence (measured at a fixed point or along the trajectory of a fluid-particle) is isotropic. Our results thus provide further evidence that insects do indeed use turbulent velocity and acceleration cues as indicators of the mean wind direction.

Reynolds, Andy M.; Reynolds, Don R.; Smith, Alan D.; Chapman, Jason W.

2010-01-01

252

Evolution of the solar wind structure over a solar cycle: Interplanetary scintillation velocity measurements compared with coronal observations  

Microsoft Academic Search

Sixteen years of solar wind observations via the technique of interplanetary scintillation (IPS) are presented. By an ecliptic comparison with in situ spacecraft observations, these data are shown to be valuable estimates of the large-scale slowly evolving structures in the solar wind speed, but to underestimate the speed in small-scale or rapidly evolving structures. These IPS observations allow the large

B. J. Rickett; W. A. Coles

1991-01-01

253

Rocket-based measurements of ion velocity, neutral wind, and electric field in the collisional transition region of the auroral ionosphere  

NASA Astrophysics Data System (ADS)

The JOULE-II sounding rocket salvo was launched from Poker Flat Rocket Range into weak pulsating aurora following a moderate substorm at 0345 LT on 19 January 2007. We present in situ measurements of ion flow velocity and electric and magnetic fields combined with neutral wind observations derived from ground observations of in situ chemical tracers. Measured ion drifts in the 150-198 km and 92-105 km altitude ranges are consistent with ${\\vec{E} ${\\vec{B} motion to within 16 m s-1 rms and with neutral wind velocity to within 20 m s-1, respectively. From these measurements we have calculated the ratio $\\kappa$ of the ion cyclotron and ion collision frequencies, finding $\\kappa$ = 1 at an altitude of 118 0.3 km. Using direct measurements of ion current, we calculate the Joule heating rate and Pedersen and Hall conductivity profiles for this moderately active event and find height-integrated values of 390 W km-2 and 0.59 and 2.22 S, respectively. We also find that these values would have errors of up to tens of percent without coincident neutral wind measurements, and presumably more so during more active conditions. Ion flow vectors were measured at a rate of 125 s-1 however, no significant fluctuations were observed at spatial/temporal scales below 350 m and 0.5 s. Observational limits were 5.5 m and 0.016 s.

Sangalli, L.; Knudsen, D. J.; Larsen, M. F.; Zhan, T.; Pfaff, R. F.; Rowland, D.

2009-04-01

254

Some features of the radial-velocity variations of lines of different intensity in the spectrum of HD 93521. Variability of the stellar wind  

NASA Astrophysics Data System (ADS)

CCD spectra taken with the PFES echelle spectrograph of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences are used to perform a detailed study of the variability of the profiles of Hell, H ?, and H ? lines in the spectrum of HD 93521. The pattern and nature of the variability of the Hell lines are similar to those of weak HeI lines and are due to nonradial pulsations. The period and amplitude of the radial-velocity variations are the same for the blue and red halves of the absorption profile but their phases are opposite. The behavior of the variations of H ? and H ? hydrogen lines relative to their mean profiles is the same as that of strong HeI line and is due to nonradial pulsations. The period and phase of the radial-velocity oscillations are the same for the blue and red halves of the absorption profile but their amplitude are different. The behavior of the radial-velocity variations of the absorption and emission components of the H ? line indicates that the latter also are caused by nonradial pulsations. All this is indicative of the complex structure of the stellar wind in the region of its origin. The behavior of variability and wind kinematics differ in different directions and for different regions of the atmosphere and/or envelope.

Rzaev, A. Kh.

2007-12-01

255

Growing Neural Gas (GNG) based Maximum Power Point Tracking for high performance VOC-FOC based wind generator system with an induction machine  

Microsoft Academic Search

This paper presents a MPPT technique for high performance wind generator with induction machine based on the Growing Neural Gas (GNG) network. Here a GNG network has been trained off-line to learn the turbine characteristic surface torque versus wind speed and machine speed, and implemented on-line so to perform the inversion of this function obtaining the wind free speed on

Maurizio Cirrincione; Marcello Pucci; Gianpaolo Vitale

2009-01-01

256

Equivalent wind speed model of wind generation  

Microsoft Academic Search

The time series intervals of wind speed and wind power prediction are from a few minutes to ten minutes, which are used for power system energy dispatch, and the power is a mean value in the interval. But physical parameters for wind, such as instantaneous wind speed, maximum wind speed, average wind speed, cannot describe the relationship properly between the

Jing Tian-jun; Yang Ming-hao

2010-01-01

257

Linear dependence of the postsunset equatorial anomaly electron density on solar flux and its relation to the maximum prereversal E B drift velocity through its dependence on solar flux  

NASA Astrophysics Data System (ADS)

The postsunset equatorial ionization anomaly, with maximum F layer electron density, Nemax, occurring near 2100 LT, has been found during solar maximum to be a linear function of the maximum prereversal E B drift velocity (E B drift). In order to examine this relation at all levels of solar flux, Nemax is measured during 13 years of an entire solar cycle by eight ionospheric sounders located in the anomaly in both north and south dip latitudes and in eastern Asia, the Pacific, and South America. At each location the monthly median Nemax increases linearly with the monthly average solar flux, Sa, over the range from 70 to 285 sfu. The linear function varies markedly with location and by month at each location. The relation to E B drift, which is also a linear function of Sa, is determined using measurements of Nemax versus Sa measured at Bogota in the anomaly plotted as a function of E B versus Sa measured at Jicamarca at the dip equator. The result is that Nemax is a linear function of E B, which is in agreement with that found previously during solar maximum. Accordingly, the Nemax versus E B relation is independent of Sa. The fact that Nemax is linear in Sa at each site implies Nemax is linear in E B at each but with a functional dependence that varies with latitude and longitude.

Whalen, James A.

2004-07-01

258

The derivation of the forward velocity of Martian dust devils and its comparison with wind profiles from a general circulation model  

NASA Astrophysics Data System (ADS)

The High Resolution Stereo Camera (HRSC) on Mars Express provides stereo images of the Martian surface in excellent quality and high resolution. The stereo channels can also be used to detect and investigate temporal and spatial variable surface features like dust devils. Dust devils on Mars are dust-filled vortices with diameters up to hundreds of meters and up to 8 km high. They are identified by a bright spot from the sunlight reflecting dust column and their cast shadow. Dust devils on Mars have been found by HRSC in areas quite different in character: from desert-like lowlands like Amazonis Planitia to highlands like Thaumasia Planum. In contrast to common assumptions, dust devils have been detected by HRSC in local summer and local winter of the respective hemisphere, in all cases, however, at local afternoon as expected. The forward velocity is derived for 20 dust devils from their change in position seen in the three stereo images of HRSC. Speeds of a few meters per second have been measured for dust devils with small diameters. This corresponds to expected velocities for dust devils assuming that they are travelling with the ambient wind. The speeds of the bigger and higher dust devils, however, have been determined between 15 and 27 m/s not consistent with previous assumptions of the wind velocity at the Martian surface (ca. 5 m/s). Wind profiles from the Martian Climate Database (http://www.lmd.jussieu.fr/mars.html) for the given local time, season and region of each detected dust devil are used to be compared with the derived dust devil speeds and their heights. The comparison suggests that the observed dust devil velocity (the change in position of the bright spot in HRSC images) have been measured at the "upper end" of the vortex rather than at the surface. This seems to apply for the large dust devils only. If the high speeds result from observations of the plume at higher altitudes and not directly from the surface, then the parallax error has to be taken into account because of the tilted viewing direction (18.9) of the stereo channels. But finally, the derived speeds are interpreted as near-surface values (underlined by 1 the impression of the images) after reanalysing the data including the error from the parallax. 2

Stanzel, C.; Patzold, M.; Neukum, G.; HRSC Co-Investigator Team

259

MACS for Global measurement of the Solar wind velocity and the Thermal electron temperature during the Total solar eclipse on 11 August 1999  

NASA Astrophysics Data System (ADS)

MACS for Multi-Aperture Coronal Spectrometer is a fiber-optic-based spectrograph designed and used to perform global measurement of the solar wind velocity and the thermal electron temperature of the solar corona during the total solar eclipse on 11 August 1999. The motivation for the construction of MACS was provided by the theory formulated by Cram (1976) for the formation of the K-coronal spectrum and a method for determining the radial profile of the thermal electron temperature of the solar corona. Based on this theory a subsequent application was carried out by Ichimoto et al. (1996) using a slit-based spectroscopic study during the total solar eclipse on 3 November 1994. We have modified Cram's theory to incorporate the role of the solar wind velocity in the formation of the K-corona and have identified wind and temperature sensitive intensity ratios. Instead of a slit-based spectrograph MACS consists of twenty fiber optic tips placed at the focal plane of the telescope and positioned to see different radii and latitudes of the solar corona. Another fiber is placed at the center of the frame and uses the lunar shadow for a measure of the background signal. The other ends of the fibers are vertically aligned and placed at the primary focus of the collimating lens of the spectrograph thus providing simultaneous spectra from all of the fibers. In this first paper (Paper I) we describe our instrument and the obtained coronal spectra. The final and complete results will be presented in Paper II (Reginald and Davila, 2000).

Reginald, Nelson L.; Davila, Joseph M.

2000-07-01

260

Comparison of time- and frequency-domain techniques for wind velocity estimation using multiple-receiver MF radar data  

NASA Astrophysics Data System (ADS)

Multiple-receiver MF radar returns from the mesosphere are used to investigate the relationship between spaced antenna (SA), radar interferometry (RI), and imaging Doppler interferometry (IDI) wind estimation techniques. The results show that frequency-domain (RI and IDI) and time-domain (SA) techniques yield almost identical results under high SNR conditions suitable for SA full correlation analysis.

Franke, Patricia M.; Thorsen, Denise; Champion, Mark; Franke, Steven J.; Kudeki, Erhan

1990-11-01

261

VAWT stochastic wind simulator  

Microsoft Academic Search

A stochastic wind simulation for VAWTs (VSTOC) has been developed which yields turbulent wind-velocity fluctuations for rotationally sampled points. This allows three-component wind-velocity fluctuations to be simulated at specified nodal points on the wind-turbine rotor. A first-order convection scheme is used which accounts for the decrease in streamwise velocity as the flow passes through the wind-turbine rotor. The VSTOC simulation

Strickland

1987-01-01

262

Cross-bridge attachment during high-speed active shortening of skinned fibers of the rabbit psoas muscle: implications for cross-bridge action during maximum velocity of filament sliding.  

PubMed

To characterize the kinetics of cross-bridge attachment to actin during unloaded contraction (maximum velocity of filament sliding), ramp-shaped stretches with different stretch-velocities (2-40,000 nm per half-sarcomere per s) were applied to actively contracting skinned fibers of the rabbit psoas muscle. Apparent fiber stiffness observed during such stretches was plotted versus the speed of the imposed stretch (stiffness-speed relation) to derive the rate constants for cross-bridge dissociation from actin. The stiffness-speed relation obtained for unloaded shortening conditions was shifted by about two orders of magnitude to faster stretch velocities compared to isometric conditions and was almost identical to the stiffness-speed relation observed in the presence of MgATPgammaS at high Ca(2+) concentrations, i.e., under conditions where cross-bridges are weakly attached to the fully Ca(2+) activated thin filaments. These data together with several control experiments suggest that, in contrast to previous assumptions, most of the fiber stiffness observed during high-speed shortening results from weak cross-bridge attachment to actin. The fraction of strongly attached cross-bridges during unloaded shortening appears to be as low as some 1-5% of the fraction present during isometric contraction. This is about an order of magnitude less than previous estimates in which contribution of weak cross-bridge attachment to observed fiber stiffness was not considered. Our findings imply that 1) the interaction distance of strongly attached cross-bridges during high-speed shortening is well within the range consistent with conventional cross-bridge models, i.e., that no repetitive power strokes need to be assumed, and 2) that a significant part of the negative forces that limit the maximum speed of filament sliding might originate from weak cross-bridge interactions with actin. PMID:10692331

Stehle, R; Brenner, B

2000-03-01

263

Cross-bridge attachment during high-speed active shortening of skinned fibers of the rabbit psoas muscle: implications for cross-bridge action during maximum velocity of filament sliding.  

PubMed Central

To characterize the kinetics of cross-bridge attachment to actin during unloaded contraction (maximum velocity of filament sliding), ramp-shaped stretches with different stretch-velocities (2-40,000 nm per half-sarcomere per s) were applied to actively contracting skinned fibers of the rabbit psoas muscle. Apparent fiber stiffness observed during such stretches was plotted versus the speed of the imposed stretch (stiffness-speed relation) to derive the rate constants for cross-bridge dissociation from actin. The stiffness-speed relation obtained for unloaded shortening conditions was shifted by about two orders of magnitude to faster stretch velocities compared to isometric conditions and was almost identical to the stiffness-speed relation observed in the presence of MgATPgammaS at high Ca(2+) concentrations, i.e., under conditions where cross-bridges are weakly attached to the fully Ca(2+) activated thin filaments. These data together with several control experiments suggest that, in contrast to previous assumptions, most of the fiber stiffness observed during high-speed shortening results from weak cross-bridge attachment to actin. The fraction of strongly attached cross-bridges during unloaded shortening appears to be as low as some 1-5% of the fraction present during isometric contraction. This is about an order of magnitude less than previous estimates in which contribution of weak cross-bridge attachment to observed fiber stiffness was not considered. Our findings imply that 1) the interaction distance of strongly attached cross-bridges during high-speed shortening is well within the range consistent with conventional cross-bridge models, i.e., that no repetitive power strokes need to be assumed, and 2) that a significant part of the negative forces that limit the maximum speed of filament sliding might originate from weak cross-bridge interactions with actin.

Stehle, R; Brenner, B

2000-01-01

264

The Effects of Non-stationarity on the Clustering Properties of the Boundary-layer Vertical Wind Velocity  

NASA Astrophysics Data System (ADS)

Non-stationarity is a common feature in geophysical flows, though it still remains an open question on how the non-stationarity of flow affects its statistical structure. Using the telegraph approximation (TA) method, we quantified how non-stationarity in the measured atmospheric turbulent vertical velocity time series affects its clustering propertiesone of the two main components of intermittency in turbulence. We compare different TA results between stationary and non-stationary atmospheric turbulent vertical velocity records, and find that the non-stationary data possess different cluster and intermittency exponents from stationary data. The inter-pulse period of the non-stationary records takes a near power-law distribution while the inter-pulse period of the stationary records exhibits a stretched exponential distribution. These results suggest that non-stationarity of the underlying processes can affect the statistical structure of turbulence, especially the clustering properties.

Li, Qinglei; Fu, Zuntao

2013-11-01

265

The two-stream plasma instability in a velocity shear and its role in the solar wind-Venus ionosphere interaction  

NASA Astrophysics Data System (ADS)

We study the linear development of the two-stream instability in a plasma consisting of cold ions, assumed at rest and taken to represent planetary ions, and a hot, streaming population of electrons, representing the solar wind. The stability of quasi-global perturbations is analyzed as a function of plasma density, temperature and streaming velocity, using a QR algorithm to compute the growth rate of eigenmodes of the coupled fluid equations of motion for both species. The sense of the cross-flow, viscous-like momentum transfer from the streaming plasma to ionospheric ions, is determined on the basis of an heuristic estimation following a Reynolds averaging procedure of the cross-flow momentum flux term in the equation of motion.

Reyes-Ruiz, M.; Aceves, H.; Perez De Tejada, H. A.

2011-12-01

266

Source localization corrections for airborne acoustic platforms based on a climatological assessment of temperature and wind velocity profiles  

NASA Astrophysics Data System (ADS)

Acoustic sensors are being employed on airborne platforms, such as Persistent Threat Detection System (PTDS) and Persistent Ground Surveillance System (PGSS), for source localization. Under certain atmospheric conditions, airborne sensors oer a distinct advantage over ground sensors. The performance of both ground and airborne sensors is aected by environmental factors, such as atmospheric turbulence and wind and temperature proles. For airborne sensors, the eects of refraction must be accounted for in order to determine the source coordinates. Such a method for ground-to-air applications has been developed and is further rened here. Ideally, knowledge of the exact atmospheric proles will allow for the most accurate mitigation of refractive eects. However, acoustic sensors deployed in theater are rarely supported by atmospheric sensing systems that retrieve real-time temperature and wind elds. Atmospheric conditions evolve through seasons, time of day, and are strongly location dependent. Therefore, the development of an atmospheric proles database based on a long time series climatological assessment will provide knowledge for use in physics-based bearing estimation algorithms, where otherwise no correction would have been performed. Long term atmospheric data sets from weather modeling systems are used for a climatological assessment of the refraction corrections and localization errors over selected sites.

Ostashev, Vladimir E.; Cheinet, Sylvain; Collier, Sandra L.; Reiff, Christian; Ligon, David A.; Wilson, D. Keith; Noble, John M.; Alberts, W. C. Kirkpatrick, II

2012-05-01

267

Fuzzy logic control of variable speed induction machine wind generation system  

Microsoft Academic Search

This paper presents the use of fuzzy logic control (FLC) of a variable speed induction machine wind generation system. The generation system uses three fuzzy logic controllers (FLC's), first fuzzy logic controller tracks the generator speed with wind velocity to extract maximum power. Second fuzzy logic controller programs the machine flux for light load efficiency improvement. Third fuzzy logic controller

M. K. K. Reddy; G. Sreenivasulu

2010-01-01

268

What price wind power  

Microsoft Academic Search

Basic considerations in adapting wind power systems for different uses and locations are discussed. The role of such factors as average wind velocity and wind variation in the selection of a wind system design is examined. The advantages and disadvantages of different types of wind power systems, including lift or drag types and horizontal or vertical axis types, are discussed

D. G. Shepherd

1977-01-01

269

Observations of mesospheric wind velocities. I. Gravity wave horizontal scales and phase velocities determined from spaced wind observations. II. Cross sections of power spectral density for 48-8 hours, 8-1 hours, and 1 hour to 10 min over 60-110 km for 1981  

SciTech Connect

Dual bistatic radar and the Saskatoon MF radar were used to obtain horizontal scales, phase velocities and power spectral density cross sections of upper middle atmosphere gravity waves as determined from spaced wind velocities. The wave scales averaged 60-110 km and varied from 44-210 km during the 10-100 min observation periods. The horizontal length scales varied directly with the length of the observation interval, while the phase speeds decreased as the observation interval increased. The rms velocity perturbations were about 5 m/sec. The associated vertical wavelengths were 30 and 6 km for the 10-100 min intervals. The power spectra densities obtained, when compared with similar data from previous compaigns, were found to vary on an annual basis. The spectral densities were noted to track the zero line of mean zonal velocity closely in the 10 min to 8 hr period bands. This last phenomena strongly indicates the occurrence of gravity wave mean flow interactions. 80 references.

Meek, C.E.; Reid, I.M.; Manson, A.H.

1985-12-01

270

Maalinger paa Nibe moelle A ved hoeje vindhastigheder, 12-30 m/s. (Measurements on a Nibe turbine A at high wind velocity, 12-30 m/s).  

National Technical Information Service (NTIS)

Analyses of measurements on Nibe turbine A, a stall regulated wind turbine are presented. The purpose of the measurements was to investigate whether the flap moments in the blades would grow to unacceptable levels when operating under a high velocity. It ...

B. Maribo Pedersen

1990-01-01

271

Dry deposition velocities  

SciTech Connect

Dry deposition velocities are very difficult to predict accurately. In this article, reported values of dry deposition velocities are summarized. This summary includes values from the literature on field measurements of gas and particle dry deposition velocities, and the uncertainties inherent in extrapolating field results to predict dry deposition velocities are discussed. A new method is described for predicting dry deposition velocity using a least-squares correlation of surface mass transfer resistances evaluated in wind tunnel experiments. 14 references, 4 figures, 1 table.

Sehmel, G.A.

1984-03-01

272

Relative Velocity and Vectors  

NSDL National Science Digital Library

This activity is designed to enhance student comprehension of air and wind velocity, through the use of real time flight data. Students will read about relative velocity, complete a work sheet on vectors, and then gather and analyze real world data. All of the materials, including links to sites for data collection, are provided in this learning object. After completing the activity, students will be able to define relative velocity, add and subtract vectors, and determine aircraft speed using raw data.

Weaver, David

2009-11-16

273

Maximum windmill efficiency  

NASA Astrophysics Data System (ADS)

Consideration is given to the maximum efficiency obtainable from a windmill as predicted by one-dimensional fluid flow theory. Considerations of the conservation of mass, energy and linear momentum for the one-dimensional flow of an incompressible fluid through an active windmill blade section are used to derive an expression for the windmill efficiency, or power coefficient, as a function of thrust force on the frame and mean stream velocity. It is noted that the present expression cannot be differentiated to obtain a theoretical maximum power output as was done by Betz (1927) on the basis of an incorrect statement of the energy balance.

Greet, R. J.

1980-09-01

274

Wind loads on flat plate photovoltaic array fields. Phase III, final report  

SciTech Connect

The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads.

Miller, R.D.; Zimmerman, D.K.

1981-04-01

275

Microburst Wind Structure and Evaluation of Doppler Radar for Airport Wind Shear Detection.  

NASA Astrophysics Data System (ADS)

Doppler weather radar data from the Joint Airport Weather Studies (JAWS) Project are used to determine the horizontal and vertical structure of airflow within microbursts. Typically, the associated downdraft is about 1 km wide and begins to spread horizontally at a height below 1 km. The median time from initial divergence at the surface to maximum differential wind velocity across the microburst is 5 min. The height of maximum differential velocity is 75 m. The median velocity differential is 22 m s1 over an average distance of 3.1 km. The outflow is asymmetric, averaging twice as strong along the maximum shear axis compared to the minimum axis.Doppler radar could be an effective means for identifying microbursts and warning aircraft of wind shear hazards. For microburst detection such a radar must be able to measure wind velocities in clear air as well as in heavy rain and hail. Scan update rates should be approximately every 2 min and the lowest few hundred meters of the atmosphere must be observed. Ground clutter must be considerably reduced from levels typically obtained with present Doppler radars. New antenna technology and signal processing techniques may solve this problem. Automated range and velocity unfolding is required, as well as automated identification and dissemination techniques.

Wilson, James W.; Roberts, Rita D.; Kessinger, Cathy; McCarthy, John

1984-06-01

276

Helium, hydrogen, and oxygen velocities observed on isee-3  

Microsoft Academic Search

The velocities of hydrogen, helium, and oxygen ions over a full range of solar wind conditions were recorded by the ion composition instrument and Los Alamos National Laboratory plasma instrument aboard the International Sun Earth Explorer. Interspecie velocity differences were observed frequently. For solar wind velocities between 300 and 400 km s(-1) the helium velocity exceeded the hydrogen velocity by

K. W. Ogilvie; M. A. Coplan; R. D. Zwickl

1982-01-01

277

Wind data requirements for wind turbine generator design  

Microsoft Academic Search

The statistical methods of wind modeling for the design of tall masts, buildings, towers, and bridges are shown to be effective for the analysis of wind loads on wind turbine generators (WTG). The wind velocity profile and turbulence is defined as the instantaneous deviations from the short term mean wind speed, and is capable of reducing the fatigue life of

U. Hassan

1980-01-01

278

PULSED ALFVEN WAVES IN THE SOLAR WIND  

SciTech Connect

Using 3 s plasma and magnetic field data from the Wind spacecraft located in the solar wind well upstream from Earth, we report observations of isolated, pulse-like Alfvenic disturbances in the solar wind. These isolated events are characterized by roughly plane-polarized rotations in the solar wind magnetic field and velocity vectors away from the directions of the underlying field and velocity and then back again. They pass over Wind on timescales ranging from seconds to several minutes. These isolated, pulsed Alfven waves are pervasive; we have identified 175 such events over the full range of solar wind speeds (320-550 km s{sup -1}) observed in a randomly chosen 10 day interval. The large majority of these events are propagating away from the Sun in the solar wind rest frame. Maximum field rotations in the interval studied ranged from 6 Degree-Sign to 109 Degree-Sign . Similar to most Alfvenic fluctuations in the solar wind at 1 AU, the observed changes in velocity are typically less than that predicted for pure Alfven waves (Alfvenicity ranged from 0.28 to 0.93). Most of the events are associated with small enhancements or depressions in magnetic field strength and small changes in proton number density and/or temperature. The pulse-like and roughly symmetric nature of the magnetic field and velocity rotations in these events suggests that these Alfvenic disturbances are not evolving when observed. They thus appear to be, and probably are, solitary waves. It is presently uncertain how these waves originate, although they may evolve out of Alfvenic turbulence.

Gosling, J. T. [Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303 (United States); Tian, H. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307 (United States); Phan, T. D., E-mail: jack.gosling@lasp.colorado.edu [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

2011-08-20

279

Wind tunnel investigation on wind turbine wakes and wind farms  

NASA Astrophysics Data System (ADS)

The interaction between atmospheric boundary layer and wind farms leads to flow modifications, which need to be deeply characterized in order to relate them to wind farm performance. The wake flow produced from a wind farm is the result of a strong interaction between multiple turbine wakes, so that the wind farm configuration turns out to be one of the dominant features to enhance power production. For the present work a wind tunnel investigation was carried out with hot-wire anemometry and velocity measurements performed with multi-hole pressure probes. The tested wind farms consist of miniature three-bladed wind turbine models. Preliminarily, the wake flow generated from a single wind turbine is surveyed, which is characterized by a strong velocity defect lying in proximity of the wind turbine hub height. The wake gradually recovers by moving downstream; the characteristics of the incoming boundary layer and wind turbulence intensity can strongly affect the wake recovery, and thus performance of following wind turbines. An increased turbulence level is typically detected downstream of each wind turbine for heights comparable to the wind turbine blade top-tip. These wake flow fluctuations produce increased fatigue loads on the following wind turbines within a wind farm, which could represent a significant hazard for real wind turbines. Dynamics of vorticity structures present in wind turbine wakes are also investigated; particular attention is paid to the downstream evolution of the tip helicoidal vortices and to oscillations of the hub vortex. The effect of wind farm layout on power production is deeply investigated. Particular emphasis is placed on studying how the flow adjusts as it moves inside the wind farm and can affect the power production. Aligned and staggered wind farm configurations are analysed, also with varying separation distances in the streamwise and spanwise directions. The present experimental results are being used to test and guide the development of improved parameterizations of wind turbines in high-resolution numerical models, such as large-eddy simulations (LES).

Iungo, G. V.; Coff, J.; Port-Agel, F.

2012-04-01

280

Velocity observations of the California Current derived from satellite imagery  

NASA Astrophysics Data System (ADS)

This research examines the potential of ocean velocity observations generated from the maximum cross-correlation technique (MCC) applied to thermal infrared imagery to capture the total current at a high sampling rate, especially in the nearshore region, allowing for a novel view of the California Current. Comparison of 12 years of weekly ocean velocity fields derived from the MCC method with velocity observations from drifting buoys reveals strong correspondence between the data sets. The MCC method, however, is able to produce over 10 times the number of observations. Comparison of MCC velocities with geostrophic velocities from altimetry demonstrates differences that suggest ageostrophic currents in the MCC observations that are likely wind driven. The time-averaged mean velocity field from MCC observations reveals strong offshore jet-like features that extend off of coastline promontories. Eddy statistics from the MCC velocity observations indicate dramatically different dynamics in the nearshore and offshore regions. Differences in spatial statistics derived from the MCC observations compared to previous studies of the region are attributed to wind-driven currents in the observations that can dominate the variability of the current in the nearshore region.

Matthews, D. K.; Emery, W. J.

2009-08-01

281

Aeolian sand transport: a wind tunnel model  

Microsoft Academic Search

Wind sand transport is an important geological process on earth and some other planets. Formulating the wind sand transport model has been of continuing significance. Majority of the existing models relate sand transport rate to the wind shear velocity based on dynamic analysis. However, the wind shear velocity readapted to blown sand is difficult to determine from the measured wind

Zhibao Dong; Xiaoping Liu; Hongtao Wang; Xunming Wang

2003-01-01

282

Simulating climates of the last glacial maximum and of the mid-Holocene: Wind changes, atmosphere-ocean interactions, and the tropical thermocline.  

NASA Astrophysics Data System (ADS)

Transition of the Earth's climate from the cold and windy conditions prevailing at the Last Glacial Maximum to the relatively warm and strongly seasonal conditions of the mid-Holocene produced many changes in the climate system. This study compares and contrasts the differences during these two time periods as simulated by a coupled atmosphere-ocean general circulation model. Compared to today, there is enhanced equatorward flux of easterly momentum in the northern hemisphere during both time periods, but for different reasons. During the mid-Holocene, a majority of the increase is associated with transient eddy activity in the upper troposphere at northern midlatitudes; an additional component arises from changes in the mean meridional circulation. Increased eddy activity is related to increased seasonality associated with mid-Holocene insolation. At the LGM, there are also increases in transient eddy momentum flux near the southern edge of the North American ice sheets, but a majority of the anomalous flux arises from stationary eddies that are also induced by the ice sheets. These enhanced momentum fluxes increase the strength of the surface equatorial easterlies through intensification of subtropical subsidence and modification of the lower troposphere's meridional pressure gradient. Through atmosphere-ocean interactions, this increases the spatial extent of the tropical Pacific cold tongue in both simulations. Results imply that the mean state of the tropical thermocline may be changed in a similar way either by increasing seasonal radiative forcing or by introducing strong topographic forcing.

Bush, Andrew B. G.

283

Conduction velocity costs energy  

Microsoft Academic Search

Hodgkin and Adrian's 1975 hypothesis that the squid axon is optimized for maximum conduction velocity is flawed by (i) the inaccurate value of its prediction for channel density, and (ii) the prohibitive energetic expense entailed by their prediction. Here we investigate the metabolic cost of conduction velocity. By manipulating ion channel density or by manipulating the Nernst battery voltages, we

Thomas Sangrey; William B Levy

2005-01-01

284

Conduction velocity costs energy  

Microsoft Academic Search

Hodgkin and Adrian's 1975 hypothesis that the squid axon is optimized for maximum conduction velocity is flawed by (i) the inaccurate value of its prediction for channel density, and (ii) the prohibitive energetic expense entailed by their prediction. Here we investigate the metabolic cost of conduction velocity. By manipulating ion channel density or by manipulating the Nernst battery voltages, we

Thomas Sangre; William B Levy

285

Observations of wind turbine wakes and surface roughness effects on wind flow variability  

SciTech Connect

Wind data collected at nine meteorological towers at the Goodnoe Hills MOD-2 wind turbine site were analyzed to characterize the wind flow over the site both in the absence and presence of wind turbine wakes. Free-flow characteristics examined were the variability of wind speed and turbulence intensity across the site as a function of wind direction and surface roughness. The nine towers' data revealed that scattered areas of trees upwind of the site caused pronounced variations in the wind flow over the site. Wind turbine wake characteristics analyzed included the average velocity deficits, wake turbulence, wake width, wake trajectory, vertical profile of the wake, and the stratification of wake properties as a function of the ambient wind speed and turbulence intensity. The wind turbine rotor disk spanned a height of 15 m to 107 m. The nine towers' data permitted a detailed analysis of the wake behavior at a height of 32 m at various downwind distances from 2 to 10 rotor diameters (D). The relationship between velocity deficit and downwind distance was surprisingly linear, with average maximum deficits ranging from 34% at 2 D to 7% at 10 D. Largest deficits were at low wind speeds and low turbulence intensities. Average wake widths were 2.8 D at a downwind distance of 10 D. Implications for turbine spacing are that, for a wind farm with a 10-D row separation, array losses would be significantly greater for a 2-D than a 3-D spacing because of incremental effects caused by overlapping wakes. Other interesting wake properties observed were the wake turbulence, the vertical variation of deficits, and the trajectory of the wake.

Elliott, D.L.; Barnard, J.C. (Pacific Northwest Lab., Richland, WA (USA))

1990-01-01

286

Wind power generating system  

SciTech Connect

Normally feathered propeller blades of a wind power generating system unfeather in response to the actuation of a power cylinder that responds to actuating signals. Once operational, the propellers generate power over a large range of wind velocities. A maximum power generation design point signals a feather response of the propellers so that once the design point is reached no increase in power results, but the system still generates power. At wind speeds below this maximum point, propeller speed and power output optimize to preset values. The propellers drive a positive displacement pump that in turn drives a positive displacement motor of the swash plate type. The displacement of the motor varies depending on the load on the system, with increasing displacement resulting in increasing propeller speeds, and the converse. In the event of dangerous but not clandestine problems developing in the system, a control circuit dumps hydraulic pressure from the unfeathering cylinder resulting in a predetermined, lower operating pressure produced by the pump. In the event that a problem of potentially cladestine consequence arises, the propeller unfeathering cylinder immediately unloads. Upon startup, a bypass around the motor is blocked, applying a pressure across the motor. The motor drives the generator until the generator reaches a predetermined speed whereupon the generator is placed in circuit with a utility grid and permitted to motor up to synchronous speed.

Schachle, Ch.; Schachle, E. C.; Schachle, J. R.; Schachle, P. J.

1985-03-12

287

Pigeon flight in a wind tunnel  

Microsoft Academic Search

1.An 8 part 9 m long wind tunnel, built of wooden frames and chipboards supported by an iron tube base, specially suited for bird flight investigation, is described (Fig. 1, 2). The working section measures 111.4 m and consists of smoothly fitting interchangeable walls of glass, wood or metal. Maximum velocity is 24 m s-1 (86 km h-1). In the

H.-J. Rothe; W. Nachtigall

1987-01-01

288

Measurements of the wind turbine wake parameters with a pulsed coherent lidar under various atmospheric conditions  

NASA Astrophysics Data System (ADS)

The strategy of measurements with a pulsed coherent Doppler lidar (PCDL) and the method of raw data processing to estimate the parameters of the wake formed behind a wind turbine downwind are suggested. Measurements with a 2-?m PCDL demonstrate that depending on the atmospheric conditions, the operating wind turbine generates a wake with maximum deficit of the wind velocity from 27 to 75% and longitudinal wake sizes varying from 120 to 1180 m. It is demonstrated that doubling of the turbulent energy dissipation rate causes the longitudinal size of the wake generated by the wind turbine to halve.

Smalikho, I. N.; Pitchugina, Y. L.; Banakh, V. A.; Brewer, W. A.

2013-01-01

289

Thermospheric Meridional Wind Control on Equatorial Scintillations and the Role of the Evening F-Region Height Rise, E B Drift Velocities and F2Peak Density Gradients  

Microsoft Academic Search

The possible role, on L-band scintillation activity, played by the nighttime magnetic meridional component of the thermospheric horizontal neutral winds, the post-sunset F-layer base height, the electrical field pre-reversal enhancement (PRE) and the latitudinal gradients of the F2-layer peak density is analyzed, considering different cases of scintillation occurrence (and their latitudinal extent) during August and September 2002. The meridional winds

M. T. A. H. Muella; E. R. de Paula; P. R. Fagundes; J. A. Bittencourt; Y. Sahai

2010-01-01

290

Thermospheric Meridional Wind Control on Equatorial Scintillations and the Role of the Evening F Region Height Rise, E B Drift Velocities and F 2Peak Density Gradients  

Microsoft Academic Search

The possible role, on L-band scintillation activity, played by the nighttime magnetic meridional component of the thermospheric\\u000a horizontal neutral winds, the post-sunset F-layer base height, the electrical field pre-reversal enhancement (PRE) and the latitudinal gradients of the F2-layer peak density is analyzed, considering different cases of scintillation occurrence (and their latitudinal extent) during\\u000a August and September 2002. The meridional winds

M. T. A. H. Muella; E. R. de Paula; P. R. Fagundes; J. A. Bittencourt; Y. Sahai

2010-01-01

291

Maximizing the wind power production of DFIG-based wind turbines at low wind speed operation  

Microsoft Academic Search

This paper introduces an improved strategy to increase the power production of wind turbines equipped with doubly fed induction generators (DFIGs) at low wind speed operation. The performance of DFIG-based wind turbines at low wind speeds, close to the cut in speed, is investigated. A modified control to extend the concept of maximum wind power tracking to cover the low

Ali H. Kasem; Ehab F. El-Saadany; H. H. El-Tamaly; Mohamed A. A. Wahab

2008-01-01

292

33 CFR 156.320 - Maximum operating conditions.  

Code of Federal Regulations, 2013 CFR

...wind velocity is 56 km/hr (30 knots) or more; or (2) The wave height is 3 meters (10 feet) or more. (b) Cargo transfer...The wind velocity exceeds 82 km/hr (44 knots); or (2) Wave heights exceed 5 meters (16...

2013-07-01

293

The neutral lithium velocity distribution of an AMPTE solar wind release as inferred from lithium ion measurements on the UKS spacecraft  

Microsoft Academic Search

As part of the AMPTE mission on September 20, 1984 a neutral lithium release was made in the quiet solar wind. The MSSL ion instrument on board the AMPTE-UKS spacecraft that was positioned about 30 km from the release center enabled measurements of significant fluxes of lithium ions to be made for about 3 min after the release; that is,

S. C. Chapman; S. W. H. Cowley; A. D. Johnstone

1986-01-01

294

Estimating the Structure and Geometry of Winds from Luminous Blue Variables via Fitting the Continuum Energy Distributions  

NASA Astrophysics Data System (ADS)

By combining the UV spectra from IUE with photometric data in the optical band, we present a quantitative study on the continuum energy distributions of LBVs to determine the structure and geometry of LBV winds. It is shown that the shape of continuum energy distributions around the Balmer jump is sensitive to the velocity law of LBV winds. A simple, spherically symmetric wind model including free-bound and free-free radiation is constructed to compute the continuum energy distributions of LBVs. By matching theoretical ones to the observed continuum energy distributions around the Balmer jump, we have obtained value of the exponent of the velocity law ? in both minimum and maximum state for five LBVs, i.e., AG Car, HR Car, R40, S Dor, and R127. We have found that ? is about 0.5-0.7 in the minimum state and larger than 1.5 in the maximum state. Transitions in the ionization states of metals between the minimum and maximum state of LBVs, which lead to changes in the radiative acceleration due to spectral lines, are most likely responsible for such effect on the velocity law. We have also determined the geometry of the wind and found that a spherically symmetric wind model can well reproduce the observed continuum energy distributions of the five LBVs. Based on these results we suggest that the wind of LBVs be basically quasi-spherical, maybe with some clumpy structure in the spherical wind to produce some observed aspherical features.

Guo, J. H.; Li, Y.

2007-04-01

295

Energy from the Wind  

ERIC Educational Resources Information Center

|The large-scale generation of electrical power by wind turbine fields is discussed. It is shown that the maximum power that can be extracted by a wind turbine is 16/27 of the power available in the wind. (BB)|

Pelka, David G.; And Others

1978-01-01

296

Energy from the Wind  

ERIC Educational Resources Information Center

The large-scale generation of electrical power by wind turbine fields is discussed. It is shown that the maximum power that can be extracted by a wind turbine is 16/27 of the power available in the wind. (BB)

Pelka, David G.; And Others

1978-01-01

297

Parametrization of the increase of the aeolian erosion threshold wind friction velocity due to soil moisture for arid and semi-arid areas  

Microsoft Academic Search

Large-scale simulation of the soil-derived dust emission in semi-arid regions needs to account for the influence of the soil moisture on the wind erosion threshold. Soil water retention consists of molecular adsorption on the soil grain surface and capillary forces between the grain. Interparticle capillary forces (char- acterized by the moisture tension) are the main factor responsible for the increase

F. Fecan; B. Marticorena; G. Bergametti

1999-01-01

298

Parametrization of the increase of the aeolian erosion threshold wind friction velocity due to soil moisture for arid and semi-arid areas  

Microsoft Academic Search

Large-scale simulation of the soil-derived dust emission in semi-arid regions needs to account for the influence of the soil moisture on the wind erosion threshold. Soil water retention consists of molecular adsorption on the soil grain surface and capillary forces between the grain. Interparticle capillary forces (characterized by the moisture tension) are the main factor responsible for the increase of

F. Fcan; B. Marticorena; G. Bergametti

1998-01-01

299

X-ray and UV Observations of Narrow Absorption Line Quasars with High Velocity Outflows  

NASA Astrophysics Data System (ADS)

High velocity and massive outflowing winds may be present in most quasars but only detected in those cases where our line of sight intersects the outflowing absorbing stream. We present results from Chandra, Suzaku and XMM-Newton observations of a sample of Narrow Absorption Line (NAL) quasars with high velocity outflows. In contrast to what is found in Broad Absorption Line (BAL) quasars we do not detect any significant excess intrinsic X-ray absorption in NAL quasars, however, we do find a possible correlation between the maximum outflow velocities of the UV absorbers of NAL quasars with the slope of the UV to X-ray continuum. Such a correlation, if confirmed in a larger sample, may provide constraints on the geometry and acceleration mechanism of quasar winds.

Chartas, G.; Eracleous, M.; Misawa, T.; Giustini, G.; Charlton, J.

2012-08-01

300

Solar cycle dependence of thermospheric neutral winds at Arecibo, Puerto Rico  

Microsoft Academic Search

The 12-month running averages of the meridional wind velocities obtained at Arecibo Observatory, Puerto Rico, using a Fabry-Perot interferometer, showed transitions during the night which were of different natures during sunspot cycle maximum and minimum. The meridional component at 18-21 AST (Atlantic Standard Time) shifted from large southward at sunspot maximum to small northward at sunspot minimum. The meridional and

R. P. Kane

1995-01-01

301

Oblique, Stratified Winds about a Shelter Fence. Part I: Measurements.  

NASA Astrophysics Data System (ADS)

Wind statistics were measured using cup and sonic anemometers, placed upwind and downwind from a porous plastic windbreak fence (height h = 1.25 m, length Y = 114 m, resistance coefficient kr0 = 2.4, and porosity p = 0.45) standing on otherwise uniform land (short grass with roughness length z0 1.9 cm). Intercomparison with collocated two-dimensional sonic anemometers suggested that, except in strongly stratified winds, cup anemometers (distance constant 1.5 m), subjected to a uniform overspeeding correction (here 10%), provide a reasonably accurate transect of the mean wind across the disturbed flow region. The measurements, binned with respect to mean wind direction and stratification, establish that the resistance coefficient of a windbreak of this type implies the maximum (or potential) mean wind reduction, a potential that is realized in neutral, perpendicular flow and for which a semiempirical formula is derived. Obliquity of the approaching wind reduces actual shelter effectiveness below the potential value, as was already known. However, a systematic influence of stratification could only be discriminated in winds that were not too far (say, within about 30) from perpendicular, under which conditions both stable and unstable stratification reduced shelter effectiveness. The quiet zone, in which velocity standard deviations (?u, ?) are reduced relative to the approach flow, was found to extend farther downwind for the normal velocity component (u) than for the parallel component ().


Wilson, John D.

2004-08-01

302

Multiterminal LVDC system for optimal acquisition of power in wind-farm using induction generators  

Microsoft Academic Search

Optimal wind-power acquisition requires automatic tracking of the optimum wind-turbine speed for the prevailing wind velocity. As the wind velocity keeps changing with time so the wind-turbine must keep adjusting its speed. In a wind-farm, the wind velocities depend on the locations of the wind-turbines, each of which has its optimal turbine speed at any given time. With an eye

Weixing Lu; Boon Teck Ooi

2002-01-01

303

Interferometric phase velocity measurements  

Microsoft Academic Search

Phase velocities of plasma waves near the lower hybrid frequency were measured with an interferometer composed of two spatially separated electron density probes. The plasma waves were produced in the F-region ionosphere by an argon ion beam. By calculating the normalized cross spectrum of the plasma waves a coherency of .98 was estimated along with a maximum phase difference of

P. M. Kintner; J. LaBelle; M. C. Kelley; L. J. Cahill; T. Moore; R. Arnoldy

1984-01-01

304

Interferometric phase velocity measurements  

Microsoft Academic Search

Phase velocities of plasma waves near the lower hybrid frequency were measured with an interferometer composed of two spatially separated electron density probes. The plasma waves are produced in the F-region ionosphere by an argon ion beam. By calculating the normalized cross spectrum of the plasma waves a coherency of .98 was estimated along with a maximum phase difference of

P. M. Kintner; J. LaBelle; M. C. Kelley; L. J. Cahill; T. Moore; R. Arnoldy

1984-01-01

305

VAWT stochastic wind simulator  

SciTech Connect

A stochastic wind simulation for VAWTs (VSTOC) has been developed which yields turbulent wind-velocity fluctuations for rotationally sampled points. This allows three-component wind-velocity fluctuations to be simulated at specified nodal points on the wind-turbine rotor. A first-order convection scheme is used which accounts for the decrease in streamwise velocity as the flow passes through the wind-turbine rotor. The VSTOC simulation is independent of the particular analytical technique used to predict the aerodynamic and performance characteristics of the turbine. The VSTOC subroutine may be used simply as a subroutine in a particular VAWT prediction code or it may be used as a subroutine in an independent processor. The independent processor is used to interact with a version of the VAWT prediction code which is segmented into deterministic and stochastic modules. Using VSTOC in this fashion is very efficient with regard to decreasing computer time for the overall calculation process.

Strickland, J.H.

1987-04-01

306

Simulation of Variable Speed Wind Generation System Using Boost Converter of Permanent Magnet Synchronous Generator  

Microsoft Academic Search

This paper proposes variable-speed wind generation system using the boost converter. The proposed system has three speed control modes for the wind velocity. The control mode of low wind velocity regulates the armature current of the generator with the boost converter to control the speed of wind turbine. The control mode of middle wind velocity regulates the DC link voltage

Kazuhiro Ohyama; Tsuyoshi Sakamoto; Shinji Arinaga; Yukio Yamashita

2008-01-01

307

Wind turbine  

DOEpatents

A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

Cheney, Jr., Marvin C. (Glastonbury, CT)

1982-01-01

308

Wind turbine  

SciTech Connect

A wind turbine of the type having an airfoil blade mounted on a flexible beam and a pitch governor which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

Cheney, M.C.

1982-10-05

309

The effect of subgrid velocity scale on site-specific\\/subgrid area and grid-averaged dry deposition velocities  

Microsoft Academic Search

A method for deriving the site-specific and subgrid area wind speed and friction velocity from regional model output and detailed land type information is developed. The subgrid velocity scale is introduced to account for generation of turbulent fluxes by subgrid motions. The grid vector averaged wind speed is adjusted by adding the subgrid velocity scale. This is to account for

Leiming Zhang; Jeffrey R Brook

2001-01-01

310

14 CFR Appendix J to Part 36 - Alternative Noise Certification Procedure for Helicopters Under Subpart H Having a Maximum...  

Code of Federal Regulations, 2013 CFR

...8 kiloHertz. (3) Wind velocity that does not exceed 10 knots...relative humidity, wind speed, and wind direction must...relative humidity and wind velocity may be used, if approved by...sum of blade tip rotational speed (VR ) and the...

2013-01-01

311

Critical velocity experiments in space  

NASA Astrophysics Data System (ADS)

Critical ionization velocity experiments in space are discussed. The high relative velocity of the neutral gas with respect to the ambient plasma is produced in three different ways. In one group of experiments gas jets with speeds of the order of 10 km/sec are produced by shaped charges with Ba or Sr. The second uses the high velocity of orbiting spacecraft; the third is based on the high flow velocities in the upper magnetosphere and the solar wind. The experiments show that the Townsend condition is the most critical restriction for fast gas jets and gas releases in the ionosphere while mass loading and diamagnetic effects are the main restrictions for releases in the flowing plasmas of the upper magnetosphere and the solar wind.

Moebius, E.

1983-07-01

312

Introduction of a new index for evaluating the effect of wind dynamics on the power of variable speed wind turbines  

Microsoft Academic Search

The instantaneous wind speed variations are ignored in the wind turbine power curves. Hence, the output power of the wind turbines becomes a function of only the average wind speed. In the variable-speed wind turbines, the output power is a function of wind speed as well as the wind dynamics because in order to extract the maximum amount of electrical

M. H. Zamani; G. H. Riahy; R. Z. Foroushani

2008-01-01

313

Erosion by Wind: Modeling  

Technology Transfer Automated Retrieval System (TEKTRAN)

Models of wind erosion are used to investigate fundamental processes and guide resource management. Many models are similar in that - temporal variables control soil wind erodibility; erosion begins when friction velocity exceeds a threshold; and transport capacity for saltation/creep is proportion...

314

Pulsar Velocities  

Microsoft Academic Search

Observations of proper motions of single radio pulsars enable the determination of transverse velocities and hence provide a tool for measuring the amount of asymmetry (i. e., the magnitude of the kick velocity vec{w}) in supernovae (SNe). However, single pulsars are thought to originate from both isolated early type stars which explode in a type II SN and from the

Th. M. Tauris

1999-01-01

315

Discontinuities in the solar wind  

Microsoft Academic Search

The nonuniform emission of the solar wind from the sun means that conditions are established which favor the development of discontinuities in the plasma parameters. Since the solar wind is in rapid proper motion with respect to the sun and the earth, examination of these discontinuities requires that the wind velocity be transformed away. Then it is found that they

D. S. Colburn; C. P. Sonett

1966-01-01

316

A Simple Method to Predict Threshold Shear Velocity in the Field  

Microsoft Academic Search

A very important parameter in predicting wind erosion is the threshold shear velocity, which is the minimal shear velocity required to initiate deflation of soil particles. Modeling and wind tunnel are primary methods in predicting threshold shear velocity. However, most models have limited applications in the presence of roughness elements, and running a wind tunnel in the field is labor-intensive

J. Li; G. S. Okin; J. E. Herrick; M. E. Miller; S. M. Munson; J. Belnap

2009-01-01

317

Noise measurements around the Nibe (Denmark) wind turbines and the Windane 31 wind turbine  

NASA Astrophysics Data System (ADS)

Noise around the two 640 kW wind turbines, and a 300 kW wind turbine at various distances and wind velocities was measured. The results are stated partly as the energy equivalent, A-weighted sound pressure level as a function of the wind velocity, partly as frequency analyses based on tape recordings of the A-weighted sound pressure level. A subjective evaluation of the noise emission from the wind turbines is given.

Kristensen, J.

318

Relative Velocity  

NSDL National Science Digital Library

This applet simulates a boat crossing a river. The user can set the speed at which the river flows, and the magnitude and direction of the boat's velocity. The applet then displays the path taken by the boat. It also calculates the velocity of the boat with respect to the river and the shore, as well as the time it takes for the boat to cross the river.

Duffy, Andrew

2008-07-31

319

An estimate of large-scale solar wind density and velocity profiles in a coronal hole and the coronal streamer belt  

NASA Astrophysics Data System (ADS)

With the use of the total electron content data obtained by the Ulysses Solar Corona Experiment (SCE) during the first solar conjunction in summer 1991, two data sets were selected, one associated with a coronal hole and the other associated with coronal streamer belt crossings. To determine a large-scale coronal streamer belt density profile, the electron content of the tracking passes embedded in the coronal streamer belt were corrected for the contributions from coronal hole densities. The inferred large-scale streamer belt electron density profile has a radial falloff exponent of -2.4 for distances greater than 7 Rs implying the acceleration of the slow solar wind according to v(r)~r0.4, in qualitative agreement with SOHO results. The acceleration terminates beyond 60 Rs in agreement with Helios in situ observations. All radial electron density profiles inferred from coronal radio sounding observations, particularly during times of high solar activity, are dominated by coronal streamer contributions. They are applicable to coronal streamers, confined to a limited latitude range about the heliospheric current sheet, and they are not representative of a large-scale mean coronal electron density profile. Because of a lack of data, similar analysis of the coronal hole electron content data was not unequivocally feasible. The coronal hole tracking passes corrected for contributions from coronal streamer areas display large electron content and density fluctuations inconsisting with the plume interpretation by Woo [1996]. Assuming that the lowest densities represent typical hole densities and comparing these with streamer densities at the same distance, we found the streamer-to-hole density ratio to be a factor of 10, which agrees with white light coronagraph results.

Ptzold, Martin; Tsurutani, Bruce T.; Bird, Michael K.

1997-10-01

320

Midnight reversal of ionospheric plasma bubble eastward velocity to westward velocity during geomagnetically quiettime: Climatology and its model validation  

NASA Astrophysics Data System (ADS)

In an effort to better understand the dynamics of westward velocities of the nocturnal F-region plasma, the climatology of the westward traveling plasma bubbles - WTB - occurring during quiettime is studied here. The climatology of the WTB is analyzed here based on airglow images obtained during 14 quiet days between 2001 and 2006 at the Brazilian station So Joo do Cariri (Geographic 7.45S, 36.5W, dip 20S). The frequency of occurrence of the WTB maximizes in the descending phase of the solar cycle. The WTB velocities ranged between 20 and 40 ms-1. The frequency of occurrence had a peak value of only 3.65% at 2345 LT. The maximum occurrence of the WTB was in July-September. No WTB have been observed from November until April in all years 2001-2006. We show for the first time theoretically that the WTB dominant forcing mechanisms during geomagnetically quiet days are westward thermospheric winds.

Sobral, Jos H. A.; de Castilho, Vivian M.; Abdu, M. A.; Takahashi, Hisao; Paulino, I.; Gasparelo, Ulisses A. C.; Arruda, Daniela C. S.; Mascarenhas, Matheus; Zamlutti, C. J.; Denardini, C. M.; Koga, Daiki; de Medeiros, A. F.; Buriti, R. A.

2011-07-01

321

Predicting maximum eccentric strength from surface EMG measurements  

Microsoft Academic Search

The origin of the well-documented discrepancy between maximum voluntary and in vitro tetanic eccentric strength has yet to be fully understood. This study aimed to determine whether surface EMG measurements can be used to reproduce the in vitro tetanic forcevelocity relationship from maximum voluntary contractions. Five subjects performed maximal knee extensions over a range of eccentric and concentric velocities on

Matthew T. G. Pain; Stephanie E. Forrester

2009-01-01

322

Input Turbulence Features at a Megawatt-Size Wind Turbine, Medicine Bow, Wyoming.  

National Technical Information Service (NTIS)

In response to recent observations that wind turbulence has a strong effect on wind turbine fatigue life, measurements of turbulent wind velocity profiles have been made at the Medicine Bow, Wyoming, WTS-4 wind turbine site. These measurements were taken ...

J. R. Connell V. R. Morris M. E. Hinchee

1986-01-01

323

Line formation in the inner winds of classical T Tauri stars: testing the conical-shell wind solution  

NASA Astrophysics Data System (ADS)

We present the emission-line profile models of hydrogen and helium based on the results from axisymmetric magnetohydrodynamics (MHD) simulations of the wind formed near the disc-magnetosphere boundary of classical T Tauri stars (CTTSs). We extend the previous outflow models of 'the conical-shell wind' by Romanova et al. to include a well-defined magnetospheric accretion funnel flow which is essential for modelling the optical and near-infrared hydrogen and helium lines of CTTSs. The MHD model with an intermediate mass-accretion rate shows outflows in conical-shell shape with a half opening angle 35. The flow properties such as the maximum outflow speed in the conical-shell wind, maximum inflow speed in the accretion funnel, mass accretion and mass-loss rates are comparable to those found in a typical CTTS. The density, velocity and modified temperature from the MHD simulations are used in a separate radiative transfer model to predict the line profiles and test the consistency of the MHD models with observations. The line profiles are computed with various combinations of X-ray luminosities, temperatures of X-ray-emitting plasma and inclination angles. A rich diversity of line profile morphology is found, and many of the model profiles are very similar to those found in observations. We find that the conical-shell wind may contribute to the emission in some hydrogen lines (e.g. H?, H?, Pa? and Pa?) significantly when the temperature in the wind is relatively high (e.g. 104 K); however, the wind contribution decreases rapidly when a lower wind temperature is adopted. The model well reproduces a relatively narrow and low-velocity blueshifted absorption component in He I ?10830, which are often seen in observations.

Kurosawa, Ryuichi; Romanova, M. M.

2012-11-01

324

The Vertical Mean Wind Profile Over the Ocean for Light to Moderate Winds  

Microsoft Academic Search

Analysis of 299 wind profile observations collected at the Massachusetts Institute of Technology oceano-graphic research platform provides a detailed picture of the behavior of wind profile parameters. A plot of roughness length vs velocity suggests the existence of classical hydrodynamic phenomena such as Jeffreys' minimum wind speed and the Kelvin-Helmholtz instability. The friction velocity appears to be, in general, a

Kenneth W. Ruggles

1970-01-01

325

Wind Characteristics Analyses and Determination of Appropriate Wind Turbine for AmasraBlack Sea Region, Turkey  

Microsoft Academic Search

In this study, wind characteristics of Amasra were analyzed with hourly wind data collected between 1997 and 2006. Wind characteristics such as monthly average mean speeds, power densities, turbulence intensities, maximum gust, and prevailing wind directions were identified. Weibull distribution model was used to determine energy output of thirty commercial wind turbines ranging from 335 to 3000 kW. Estimated mean

S. A. Akda?; . Gler

2010-01-01

326

Wind Speed Estimation Based Sensorless Output Maximization Control for a Wind Turbine Driving a DFIG  

Microsoft Academic Search

This paper proposes a wind speed estimation based sensorless maximum wind power tracking control for variable-speed wind turbine generators (WTGs). A specific design of the proposed control algorithm for a wind turbine equipped with a doubly fed induction generator (DFIG) is presented. The aerodynamic characteristics of the wind turbine are approximated by a Gaussian radial basis function network based nonlinear

Wei Qiao; Wei Zhou; Jos M. Aller; Ronald G. Harley

2008-01-01

327

Dynamic stall occurrence on a horizontal axis wind turbine blade  

SciTech Connect

Surface pressure data from the National Renewable Energy Laboratory`s ``Combined Experiment`` were analyzed to provide a statistical representation of dynamic stall occurrence on a downwind horizontal axis wind turbine (HAWT). Over twenty thousand blade rotational cycles were each characterized at four span locations by the maximum leading edge suction pressure and by the azimuth, velocity, and yaw at which it occurred. Peak suction values at least twice that seen in static wind tunnel tests were taken to be indicative of dynamic stall. The occurrence of dynamic stall at all but the inboard station (30% span) shows good quantitative agreement with the theoretical limits on inflow velocity and yaw that should yield dynamic stall. Two hypotheses were developed to explain the discrepancy at 30% span. Estimates are also given for the frequency of dynamic stall occurrence on upwind turbines. Operational regimes were identified which minimize the occurrence of dynamic stall events.

Shipley, D.E.; Miller, M.S.; Robinson, M.C. [Colorado Univ., Boulder, CO (United States). Dept. of Aerospace Engineering Sciences

1995-07-01

328

Terminal Velocity  

NSDL National Science Digital Library

This lab is an inquiry activity in that students have not been exposed to the idea of terminal velocity, though they are using skills that they already have to analyze the balloon's motion. The lab is both a review of graphing and translating distance ver

Horton, Michael

2009-05-30

329

On optimal velocity during cycling.  

PubMed

This paper focuses on the solution of two problems related to cycling. One is to determine the velocity as a function of distance which minimizes the cyclist's energy expenditure in covering a given distance in a set time. The other is to determine the velocity as a function of the distance which minimizes time for fixed energy expenditure. To solve these problems, an equation of motion for the cyclist riding over arbitrary terrain is written using Newton's second law. This equation is used to evaluate either energy expenditure or time, and the minimization problems are solved using an optimal control formulation in conjunction with the method of Miele [Optimization Techniques with Applications to Aerospace Systems, pp. 69-98 (1962) Academic Press, New York]. Solutions to both optimal control problems are the same. The solutions are illustrated through two examples. In one example where the relative wind velocity is zero, the optimal cruising velocity is constant regardless of terrain. In the second, where the relative wind velocity fluctuates, the optimal cruising velocity varies. PMID:8132689

Maro?ski, R

1994-02-01

330

Explicit Solution for Polytrope Solar Wind Equations.  

National Technical Information Service (NTIS)

An explicit solution for polytrope solar winds is presented, in which both the distance and the flow velocity are expressed as simple functions of the mass density. The correspondence between the velocity and the distance is explicitly exhibited through t...

T. Yeh

1970-01-01

331

A field experiment on dust emission by wind erosion in the Taklimakan Desert  

NASA Astrophysics Data System (ADS)

Dust emission by wind erosion in surface is a serious problem in many arid regions around the world, and it is harmful to the ecological environment, human health, and social economy. To monitor the characteristics of saltation activity and to calculate the threshold wind velocity and sediment discharge under field conditions have significance on the research of dust emission by wind erosion. Therefore, a field experiment was conducted over the flat sand in the hinterland of the Taklimakan Desert. One sampling system was installed on the flat sand surface at Tazhong, consisting of a meteorological tower with a height of 2 m, a piezoelectric saltation sensor (Sensit), and a Big Spring Number Eight (BSNE) sampler station. Occurrence of saltation activity was recorded every second using the Sensit. Each BSNE station consisted of five BSNE samplers with the lowest sampler at 0.05 m and the highest sampler at 1.0 m above the soil surface. Sediment was collected from the samplers every 24 h. It is found that saltation activity was detected for only 21.5% of the hours measured, and the longest period of saltation activity occurring continuously was not longer than 5 min under the field conditions. The threshold wind velocity was variable, its minimum value was 4.9 m s-1, the maximum value was 9.2 m s-1, and the average value was 7.0 m s-1. The threshold wind velocity presented a positive linear increase during the measurement period. The observation site had a sediment discharge of 82.1 kg m-1 over a period of 24 h. Based on hourly saltation counts, hourly sediment discharge was estimated. Overall, there was no obvious linear or other functional relationship between the hourly sediment discharge and wind velocity. The results show that the changes of sediment discharge do not quite depend on wind velocity.

Yang, Xinghua; He, Qing; Ali, Mamtimin; Huo, Wen; Liu, Xinchun; Strake, Miriam

2012-04-01

332

Wind driven device and method of recovering wind energy  

SciTech Connect

A wind driven device for driving an electrical generator to produce electricity having a base, an anchor pole stationarily affixed to the base, and a drive assembly support rotatably mounted around the anchor pole. A plurality of gears engage the lower portion of the drive assembly support. The device also includes an upper exterior wind column support and a lower exterior wind column support. A plurality of attachment beams are connected to the drive assembly. A plurality of wind panel support columns connect to at least one of the attachment beams and to the upper and lower exterior support. A plurality of wind panels pivotally engage the wind panel support columns and is responsive to the wind such that the force of the wind against the wind panel causes the drive assembly support and the attached gears to revolve to provide for a power take off from the revolving gears to drive the electrical generator. A mobile wind panel angle selection guide is positioned around the drive assembly support to permit operation of the wind driven device when the direction of the wind changes. A method of recovering wind energy to drive an electrical generator to produce electricity having the steps of positioning the mobile wind panel angle selection guide around the drive assembly. A plurality of wind panels is mounted to the drive assembly to be guided by the mobile wind panel angle selection guide such that the force of the wind against the guided wind panels rotates the drive assembly which in turn causes the connected gears to operate the electrical generator. The position of the mobile wind panel guide is subsequently adjusted such that the force of the wind against any particular wind panel is a maximum when the particular wind panel is in a predetermined position with respect to the mobile wind panel angle selection guide.

Lanzrath, R.A.

1984-06-19

333

Velocity spectra in the marine atmospheric boundary layer  

NASA Astrophysics Data System (ADS)

Velocity spectra in the marine atmospheric boundary layerAnn-Sofi Smedman and Ulf Hgstrm Department of Earth Sciences, Meteorology, Uppsala University Spectra of longitudinal and vertical velocity have been studied at a marine site, stergarnsholm, in the Baltic Sea during a period of six days with near neutral or slightly unstable conditions when the wave state gradually changed from pure wind sea to strong swell having approximately the same direction as the wind. During the period with pure wind sea, u- and w-spectra are shown to be in complete agreement with a new theory for the neutral atmospheric surface layer, which was earlier shown to agree very well with measurements over flat land surfaces. These spectra are used as references for the analysis of the corresponding spectra during the subsequent time period. The sensible heat flux was upward but small during the entire sequence of events. The analysis shows that the shape of both the longitudinal wind spectrum and the vertical wind spectrum start to deviate from their ideal' forms as soon as the wave age parameter co/U exceeds about 0.8. The spectral modification appears to start at a frequency around 0.2 Hz, resulting in two processes that evolve gradually as co/U increases: 1) A down-scale cascade effect, which causes the lower frequency limit of the f2/3-range to gradually move to higher values of normalized frequency, f = nz/U. This effect proceeds at a greater pace in the vertical velocity component and more slowly in the longitudinal. 2) A low-frequency modification, which lifts the entire spectral level in the normalized w-spectra below 0.2 and creates a maximum in the corresponding normalized u-spectra which gradually moves towards lower frequencies. It is argued that this low-frequency spectral behaviour is a secondary effect caused by strong reduction of the friction velocity u*, which in turn, is a result of an upward directed uw co-spectral component accomplished by swell.

Smedman, A.-S.

2009-09-01

334

Turbulent Flow Properties Around a Staggered Wind Farm  

NASA Astrophysics Data System (ADS)

The fundamental properties of turbulent flow around a perfectly staggered wind farm are investigated in a wind tunnel. The wind farm consisted of a series of 10 rows by 2-3 columns of miniature wind turbines spaced 5 and 4 rotor diameters in the streamwise and spanwise directions respectively. It was placed in a boundary-layer flow developed over a smooth surface under thermally neutral conditions. Cross-wire anemometry was used to obtain high resolution measurements of streamwise and vertical velocity components at various locations within and above the wind farm. The results show that the staggered configuration is more efficient in terms of momentum transfer from the background flow to the turbines compared to the case of an aligned wind turbine array under similar turbine separations in the streamwise and spanwise directions. This leads to improved power output of the overall wind farm. A simplified analysis suggests that the difference in power output between the two configurations is on the order of 10%. The maximum levels of turbulence intensity in the staggered wind farm were found to be very similar to that observed in the wake of a single wind turbine, differing substantially with that observed in an aligned configuration with similar spacing. The dramatic changes in momentum and turbulence characteristics in the two configurations show the importance of turbine layout in engineering design. Lateral homogenization of the turbulence statistics above the wind farm allows for the development of simple parametrizations for the adjustment of flow properties, similar to the case of a surface roughness transition. The development of an internal boundary layer was observed at the upper edge of the wind farm within which the flow statistics are affected by the superposition of the ambient flow and the flow disturbance induced by the wind turbines. The adjustment of the flow in this layer is much slower in the staggered situation (with respect to its aligned counterpart), implying a change in the momentum/power available at turbine locations. Additionally, power spectra of the streamwise and vertical velocity components indicate that the signature of each turbine-tip vortex structure persists to locations deep within the wind farm.

Chamorro, Leonardo P.; Arndt, R. E. A.; Sotiropoulos, Fotis

2011-12-01

335

Step motor control for maximum torque  

Microsoft Academic Search

The relationship between the switching angle and the output torque of a step motor is derived, and the optimal angle, which maximized the output torque, is found. The resulting maximum torque, which varies with the velocity, is an upper limit for the torque that can be generated by the step motor.

J. Tal

1976-01-01

336

Maximum Likelihood Stereo Matching  

Microsoft Academic Search

In the research literature, maximum likelihood principles were applied to stereo matching by altering the stereo pair so that the difference would have a Gaussian distribution. Here in this paper we present a novel method of applying maximum likelihood to stereo matching. In our approach, we measure the real noise distribution from a training set, and then construct a new

Nicu Sebe; Michael S. Lew

2000-01-01

337

The H_2O(+) Velocity Field in Comet Hale-Bopp, Observations and MHD Models  

NASA Astrophysics Data System (ADS)

The 3.5-meter WIYN Telescope and its Multi-Object Spectrograph (MOS)obtained simultaneous spectra at many points in the coma of Comet Hale-Bopp between 1996 October and 1997 April. The "Hydra" fiber positioner was used to sample a ring pattern of points about the nucleus with a minimum spacing of 40 arc seconds and a maximum radius of 22.5 arc minutes. A integral field device called "Densepak" was also used to sample a 7 x 13 rectangular pattern of 91, 3 arc second fibers on 4 arc second centers. The bench spectrograph was used in the echelle mode with an interference filter to isolate a single order and covered the wavelength range from 6100 Angstroms to 6400 Angstroms with resolution of approximately 15,000. This spectral region contains the emission features of H_2O(+) . From these data we have extracted the radial velocity of the H_2O(+) . We find the acceleration in the anit-sun direction to be of the order of 20 cm sec(-) (2) . The measured velocity fields have been compared to full 3D MAUS-MHD models. The models suggest that the degree ofconfinement of the coma and the velocities attained in the anti-sun direction depend sensitively upon the velocity of the ambient solar wind. The observed velocity fields are consistent with the confinement of the near coma by a relatively slow solar wind while the speeds attained at distances of the order of a million kilometers in the anti-sun direction are more like those produced by a fast solar wind. The observations were obtained at a time when Hale-Bopp was at intermediate heliocentric latitudes where the solar wind speed is known to change rapidly from slow to fast modes. This situation is under further investigation.

Anderson, C. M.; Combi, M. R.; Gombosi, T.; Hansen, K. C.

1998-09-01

338

THREE-DIMENSIONAL NUMERICAL SIMULATIONS OF MAGNETIZED WINDS OF SOLAR-LIKE STARS  

SciTech Connect

By means of self-consistent three-dimensional magnetohydrodynamics (MHD) numerical simulations, we analyze magnetized solar-like stellar winds and their dependence on the plasma-{beta} parameter (the ratio between thermal and magnetic energy densities). This is the first study to perform such analysis solving the fully ideal three-dimensional MHD equations. We adopt in our simulations a heating parameter described by {gamma}, which is responsible for the thermal acceleration of the wind. We analyze winds with polar magnetic field intensities ranging from 1 to 20 G. We show that the wind structure presents characteristics that are similar to the solar coronal wind. The steady-state magnetic field topology for all cases is similar, presenting a configuration of helmet streamer-type, with zones of closed field lines and open field lines coexisting. Higher magnetic field intensities lead to faster and hotter winds. For the maximum magnetic intensity simulated of 20 G and solar coronal base density, the wind velocity reaches values of {approx}1000 km s{sup -1} at r {approx} 20r {sub 0} and a maximum temperature of {approx}6 x 10{sup 6} K at r {approx} 6r {sub 0}. The increase of the field intensity generates a larger 'dead zone' in the wind, i.e., the closed loops that inhibit matter to escape from latitudes lower than {approx}45 deg. extend farther away from the star. The Lorentz force leads naturally to a latitude-dependent wind. We show that by increasing the density and maintaining B {sub 0} = 20 G the system recover back to slower and cooler winds. For a fixed {gamma}, we show that the key parameter in determining the wind velocity profile is the {beta}-parameter at the coronal base. Therefore, there is a group of magnetized flows that would present the same terminal velocity despite its thermal and magnetic energy densities, as long as the plasma-{beta} parameter is the same. This degeneracy, however, can be removed if we compare other physical parameters of the wind, such as the mass-loss rate. We analyze the influence of {gamma} in our results and we show that it is also important in determining the wind structure.

Vidotto, A. A.; Jatenco-Pereira, V. [University of Sao Paulo, Rua do Matao 1226, Sao Paulo, SP 05508-090 (Brazil); Opher, M. [George Mason University, 4400 University Drive, Fairfax, VA 22030-4444 (United States); Gombosi, T. I. [University of Michigan, 1517 Space Research Building, Ann Arbor, MI 48109-2143 (United States)], E-mail: aline@astro.iag.usp.br

2009-07-01

339

Maximum Power Training and Plyometrics for Cross-Country Running.  

ERIC Educational Resources Information Center

|Provides a rationale for maximum power training and plyometrics as conditioning strategies for cross-country runners, examining: an evaluation of training methods (strength training and maximum power training and plyometrics); biomechanic and velocity specificity (role in preventing injury); and practical application of maximum power training and

Ebben, William P.

2001-01-01

340

Maximum Power Training and Plyometrics for Cross-Country Running.  

ERIC Educational Resources Information Center

Provides a rationale for maximum power training and plyometrics as conditioning strategies for cross-country runners, examining: an evaluation of training methods (strength training and maximum power training and plyometrics); biomechanic and velocity specificity (role in preventing injury); and practical application of maximum power training and

Ebben, William P.

2001-01-01

341

Turbulence characteristics around a staggered wind farm configuration: A wind tunnel study  

Microsoft Academic Search

Turbulent flow around a wind farm is characterized by the coexistence and superposition of multiple wind turbine wakes. The understanding of the momentum transport and velocity fluctuations at different locations in the wind farm is essential to improve energy production and the structural stability of the different turbines. In this study, a staggered model wind farm was placed in the

Leonardo Chamorro; Roger Arndt; Fotis Sotiropoulos

2010-01-01

342

Flow properties around a staggered wind farm. A wind tunnel study  

Microsoft Academic Search

Turbulent flow around a wind farm is characterized by the coexistence and superposition of multiple wind turbine wakes. The understanding of the momentum transport and velocity fluctuations at different locations in the wind farm is essential to improve energy production and the structural stability of the different turbines. In this study, a staggered model wind farm was placed in the

L. P. Chamorro; R. Arndt; F. Sotiropoulos

2010-01-01

343

A wind tunnel investigation of wind turbine wakes: Boundary-layer turbulence and surface roughness effects  

Microsoft Academic Search

Wind turbine wakes are known to have an important effect on power generation and fatigue loads in wind energy parks. Wake characteristics are expected to depend on the incoming atmospheric boundary layer flow statistics (mean velocity and turbulence levels). Here, results are presented from a wind tunnel experiment carried out at the St. Anthony Falls Laboratory atmospheric boundary layer wind

L. Chamorro; F. Porte-Agel

2008-01-01

344

An examination of wake effects and power production for a group of large wind turbines  

NASA Astrophysics Data System (ADS)

Data from a group of three MOD-2 wind turbines and two meteorological towers at Goodnoe Hills were analyzed to evaluate turbine power output and wake effects (losses in power production due to operation of upwind turbines), and atmospheric factors influencing them. The influences of variations in the ambient wind speed, wind direction, and turbulence intensity were the primary factors evaluated. Meteorological and turbine data collected at the Goodnoe Hills site from April 1 to October 17, 1985, were examined. Wind data from the two meteorological towers were evaluated to estimate the effect of a wake from an upwind turbine on the wind flow measured at the downwind tower. Maximum velocity deficits were about 25 percent and 12 percent at downwind distances of 5.8 and 8.3 rotor diameters (D), respectively. However, the maximum deficits at 5.8 D were about 14 degrees off the centerline orientation between the turbine and the tower, indicating significant wake curvature. Velocity deficits were found to depend on the ambient wind speed, ranging from 27 percent at lower speeds (15 to 25 mph) to 20 percent at higher speeds (30 to 35 mph). Turbulence intensity increases dramatically in the wake by factors of about 2.3 and 1.5 over ambient and conditions at 5.8 D and 8.3 D, respectively. An analysis of the ambient (non-wake) power production for all three turbines showed that the MOD-2 power output depends, not only on wind speed, but also on the turbulence intensity. At wind speeds below rated, there was a dramatic difference in turbine power output between low and high turbulence intensities for the same wind speed. One of the turbines had vortex generators on the blades. This turbine produced from 10 percent to 13 percent more power than the other two turbines when speeds were from 24 to 31 mph.

Elliott, D. L.; Buck, J. W.; Barnard, J. C.

1988-04-01

345

Glacier winds and parameterisation of the related surface heat fluxes  

NASA Astrophysics Data System (ADS)

The katabatic flow over glaciers is studied with data from automatic weather stations (AWS). We analyse data from the Morteratschgletscher (Switzerland), Vatnajkull (Iceland) and West Greenland, and conclude that katabatic flow is very common over melting glacier surfaces and rarely disrupted by the large-scale flow. Over small and medium-size glaciers the height of the wind maximum is generally low (typically 10 m), and vertical temperature differences near the surface are very large (up to 15 K over 4 m). In glacier mass-balance models there is a great need for parameterisations of the surface heat flux. We develop a simple method to estimate the sensible heat flux Fh associated with the glacier wind. It is based on the classical Prandtl model for slope flows. We set the turbulent exchange coefficient proportional to the maximum wind speed (velocity scale) and the height of the wind maximum (length scale). The resulting theory shows that Fh increases quadratically with the temperature difference between the surface and the ambient atmosphere; Fh decreases with the square root of the potential temperature gradient of the ambient atmosphere; and Fh is independent of the surface slope.

Oerlemans, J.; Grisogono, B.

2002-10-01

346

Global distribution of the solar wind during solar cycle 23: ACE observations  

NASA Astrophysics Data System (ADS)

The composition of the solar wind can be used to determine its origin at the Sun; e.g., solar wind from coronal holes has demonstrably lower charge states than solar wind of other origins. The O 7+/O 6+ ratio as measured by Advanced Composition Explorer (ACE) during 1998-2008 is used to divide the solar wind into three categories: non-transient solar wind from coronal holes (hereafter referred to as CHW); non-transient solar wind that originates from outside of coronal holes (hereafter referred to as NCHW), and solar wind associated with transient interplanetary coronal mass ejections (ICMEs). The global distribution of the solar wind relative to the Heliospheric Current Sheet (HCS), as specified by a Potential-Field-Source-Surface model, is then determined. The solar wind from outside of coronal holes is found to originate from a band of about 40 in width about the HCS during solar maximum conditions, and a much smaller band of < 17 during solar minimum. These results are consistent with models for the global transport of the solar magnetic field during the solar cycle, and they are consistent with earlier global flow structure determinations based upon velocity alone.

Zhao, L.; Zurbuchen, T. H.; Fisk, L. A.

2009-07-01

347

The maximum significant wave height in the Southern North Sea  

Microsoft Academic Search

The maximum possible wave conditions along the Dutch coast, which seem to be dominated by the limited water depth, have been estimated in the present study with numerical simulations.\\u000aDiscussions with meteorologists suggest that the maximum possible sustained wind speed in North Sea conditions is between 40 and 50 m\\/s (roughly equal to the wind speed in hurricanes but under

L. H. Holthuijsen; Y. Eldeberky; N. Booij; P. Ferier

1995-01-01

348

The Vertical Mean Wind Profile over the Ocean for Light To Moderate Winds.  

National Technical Information Service (NTIS)

Analysis of 299 wind profile observations collected at the Massachusetts Institute of Technology oceanographic research platform provides a detailed picture of the behavior of wind profile parameters. A plot of roughness length vs velocity suggests the ex...

K. W. Ruggles

1970-01-01

349

Frequency spectra of vertical velocity from Flatland VHF radar data  

SciTech Connect

The vertical wind velocity over very flat terrain was observed every 153 s in the troposphere and lower stratosphere by the Flatland radar, near Champaign-Urbana, Illinois. By stratifying the spectra in various ways, the authors find the following: (1) the spectra were independent of altitude within the troposphere or lower stratosphere, but the spectra in the two regions differed in amplitude and frequency; (2) at a given altitude the spectra were independent of the wind shear d{bar u}/dz, the buoyancy frequency N, and the maximum wind speed below 16 km; (3) the change of spectral shape and amplitude with increasing background wind speed {bar u} was much less than at stations near mountains. The variance of the spectra, equal to twice the vertical kinetic energy per unit mass, roughly doubled as {bar u} increased by 10 m/s; (4) the spectra were consistent with being due to a spectrum of gravity waves, as indicated by the sharp drop in spectral amplitude near N at small {bar u} and by the fact that the observed change of shape with increasing {bar u} was quite consistent with the change of shape of model Doppler-shifted gravity wave spectra; (5) the results of comparison between the observed and model spectra are consistent with an intrinsic gravity wave spectrum that is invariant with {bar u}, d{bar u}/dz, etc., contrary to expectations from gravity wave theory; (6) the results are insensitive to the azimuthal distribution of gravity wave energy, as long as the distribution is roughly symmetrical relative to the mean flow; (7) the resulting characteristic horizontal phase velocity c{sub *} of the intrinsic frequency spectrum was about 6 m/s in both the troposphere and the stratosphere.

VanZandt, T.E.; Green, J.L. (National Oceanic and Atmospheric Administration, Boulder, CO (USA)); Nastrom G.D. (St. Cloud State Univ., MN (USA))

1991-02-20

350

Utilization of Wind Energy at High Altitude  

Microsoft Academic Search

Ground based, wind energy extraction systems have reached their maximum capability. The limitations of current designs are: wind instability, high cost of installations, and small power output of a single unit. The wind energy industry needs of revolutionary ideas to increase the capabilities of wind installations. This article suggests a revolutionary innovation which produces a dramatic increase in power per

Alexander Bolonkin

2007-01-01

351

Noise measurements around the Nibe (Denmark) wind turbines and the Windane 31 wind turbine  

Microsoft Academic Search

Noise around the two 640 kW wind turbines, and a 300 kW wind turbine at various distances and wind velocities was measured. The results are stated partly as the energy equivalent, A-weighted sound pressure level as a function of the wind velocity, partly as frequency analyses based on tape recordings of the A-weighted sound pressure level. A subjective evaluation of

J. Kristensen

1984-01-01

352

MHD wind tunnel  

Microsoft Academic Search

Preliminary results are presented from a high-velocity, turbulent MHD wind tunnel at the SSX facility. The prototype wind tunnel has dimensions L = 1 m and R = 0.08 m. Flow is measured with a cylindrical Mach probe calibrated both with magnetic time-of-flight and ion Doppler spectroscopy. Magnetic structure and turbulence are measured with arrays of magnetic probes. In a

M. R. Brown; T. Gray; X. Zhang; D. Dandurand

2010-01-01

353

Water Velocity and Suspended Solids Measurements by In-situ Instruments in Upper Klamath Lake, Oregon  

USGS Publications Warehouse

The U. S. Geological Survey conducted hydrodynamic measurements in Upper Klamath Lake during four summer seasons (approximately mid-June to mid-September) during 2003 to 2006. Measurements included water current profiles made by acoustic Doppler current profilers at a number of fixed locations in the lake during all four years as well as from a moving boat during 2005 and 2006. Measurements of size distribution of suspended material were made at four locations in the lake during 2004-2006. Raw (unfiltered) data are presented as time series of measurements. In addition, water-velocity data have been filtered to remove wind-induced variations with periods less than thirty hours from the measurements. Bar graphs of horizontal and vertical water speed and acoustic backscatter have been generated to discern diurnal variations, especially as they relate to wind patterns over the lake. Mean speeds of the horizontal currents in the lake range between about 3.5 to 15 cm/s with the higher speeds at the deep locations in the trench on the west side of the lake. Current directions generally conform to the lake's bathymetry contours and the water circulation pattern is usually in a clockwise direction around the lake as established by the prevailing north to northwesterly surface winds in the region. Diurnal patterns in horizontal currents probably relate to diurnal wind patterns with minimum wind speeds near noon and maximum wind speeds near 2100. Diurnal variations in vertical velocities do not appear to be related to wind patterns; they do appear to be related to expected patterns of vertical migration of Aphanizomenon flos aquae, (AFA) the predominant species of blue-green algae in the lake. Similarly, diurnal variations in acoustic backscatter, especially near the lake's surface, are probably related to the vertical migration of AFA.

Gartner, Jeffrey W.; Wellman, Roy E.; Wood, Tamara M.; Cheng, Ralph T.

2007-01-01

354

Hoodia Maximum Strength  

Center for Drug Evaluation (CDER)

Text Version... reviewed your web site at the Internet address http://www.life-all.com and has determined that the product Hoodia Maximum Strength is promoted ... More results from www.fda.gov/downloads/drugs/guidancecomplianceregulatoryinformation

355

Maximum</span> 255 Characters)></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://google2.fda.gov/search?client=FDAgov&site=FDAgov&lr=&proxystylesheet=FDAgov&output=xml_no_dtd&&proxycustom=%3CADVANCED/%3E">Center for Biologics Evaluation and Research (CBER)</a></p> <p class="result-summary">Text Version... shorter periods of euthymia, greater likelihood of suicide ... tolerated doses and the <span class="hlt">maximum</span> tolerable dose ... N Mean (SD) Median Min/ Max (95% CI ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">356</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010BoLMe.136..515C"> <span id="translatedtitle">Effects of Thermal Stability and Incoming Boundary-Layer Flow Characteristics on <span class="hlt">Wind</span>-Turbine Wakes: A <span class="hlt">Wind</span>-Tunnel Study</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary"><span class="hlt">Wind</span>-tunnel experiments were carried out to study turbulence statistics in the wake of a model <span class="hlt">wind</span> turbine placed in a boundary-layer flow under both neutral and stably stratified conditions. High-resolution <span class="hlt">velocity</span> and temperature measurements, obtained using a customized triple wire (cross-wire and cold wire) anemometer, were used to characterize the mean <span class="hlt">velocity</span>, turbulence intensity, turbulent fluxes, and spectra at different locations in the wake. The effect of the wake on the turbulence statistics is found to extend as far as 20 rotor diameters downwind of the turbine. The <span class="hlt">velocity</span> deficit has a nearly axisymmetric shape, which can be approximated by a Gaussian distribution and a power-law decay with distance. This decay in the near-wake region is found to be faster in the stable case. Turbulence intensity distribution is clearly non-axisymmetric due to the non-uniform distribution of the incoming <span class="hlt">velocity</span> in the boundary layer. In the neutral case, the <span class="hlt">maximum</span> turbulence intensity is located above the hub height, around the rotor tip location and at a distance of about 4-5.5 rotor diameters, which are common separations between <span class="hlt">wind</span> turbines in <span class="hlt">wind</span> farms. The enhancement of turbulence intensity is associated with strong shear and turbulent kinetic energy production in that region. In the stable case, the stronger shear in the incoming flow leads to a slightly stronger and larger region of enhanced turbulence intensity, which extends between 3 and 6 rotor diameters downwind of the turbine location. Power spectra of the streamwise and vertical <span class="hlt">velocities</span> show a strong signature of the turbine blade tip vortices at the top tip height up to a distance of about 1-2 rotor diameters. This spectral signature is stronger in the vertical <span class="hlt">velocity</span> component. At longer downwind distances, tip vortices are not evident and the von Krmn formulation agrees well with the measured <span class="hlt">velocity</span> spectra.</p> <div class="credits"> <p class="dwt_author">Chamorro, Leonardo P.; Port-Agel, Fernando</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">357</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/1455682"> <span id="translatedtitle"><span class="hlt">Maximum</span> ratio transmission</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This paper presents the concept, principles, and analysis of <span class="hlt">maximum</span> ratio transmission for wireless communications, where multiple antennas are used for both transmission and reception. The principles and analysis are applicable to general cases, including <span class="hlt">maximum</span>-ratio combining. Simulation results agree with the analysis. The analysis shows that the average overall signal-to-mise ratio (SNR) is proportional to the cross correlation between</p> <div class="credits"> <p class="dwt_author">Titus K. Y. Lo</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">358</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012Icar..218..817S"> <span id="translatedtitle">Longitudinal variation and waves in Jupiter's south equatorial <span class="hlt">wind</span> jet</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A detailed study of the chevron-shaped dark spots on the strong southern equatorial <span class="hlt">wind</span> jet near 7.5S planetographic latitude shows variations in <span class="hlt">velocity</span> with longitude and time. The presence of the large anticyclonic South Equatorial Disturbance (SED) has a profound effect on the chevron <span class="hlt">velocity</span>, causing slower <span class="hlt">velocities</span> to its east and increasing with distance from the disturbance. The chevrons move with <span class="hlt">velocities</span> near the <span class="hlt">maximum</span> <span class="hlt">wind</span> jet <span class="hlt">velocity</span> of 140 m/s, as deduced by the history of <span class="hlt">velocities</span> at this latitude and the magnitude of the symmetric <span class="hlt">wind</span> jet near 7N latitude. Their repetitive nature is consistent with a gravity-inertia wave (n = 75-100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, for the first time, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a 6.7 0.7-day period. This oscillating motion has a wavelength of 20 and a speed of 101 3 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it. All dates show chevron latitude variability, but it is unclear if this larger wave is present during other epochs, as there are no other suitable time series movies that fully delineate it. In the presence of multiple wave modes, the difference in dominant cloud appearance between 7N and 7.5S is likely due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.</p> <div class="credits"> <p class="dwt_author">Simon-Miller, Amy A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael D.; Adamoli, Gianluigi; Mettig, Hans-Joerg</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">359</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006IJGA....6.2006K"> <span id="translatedtitle">Causes of longitude-latitudinal variations in the ionospheric F2-layer <span class="hlt">maximum</span> in summer nighttime conditions}\\</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">[1] The causes of longitudinal and latitudinal variations in the F2-layer <span class="hlt">maximum</span> in the summer nighttime ionosphere at middle, subauroral, and auroral latitudes are investigated. To do this the following problems are solved in sequence. The longitudinal variations in hmF2 are studied in the belt of invariant latitudes between 40 and 65 according to the Intercosmos 19 satellite data. It is shown that the longitudinal effect in the quiet ionosphere is rather stable but differs by its character in the Southern and Northern hemispheres. Considerable discrepancies between Intercosmos 19 data and International Reference Ionosphere (IRI) model are detected at high latitudes. On the basis of the longitudinal variations in hmF2 using the servo model of the ionosphere and the Mass Spectrometer Incoherent Scatter thermosphere model, variations in the vertical drift <span class="hlt">velocity</span>, W, caused by neutral <span class="hlt">wind</span> are calculated. In terms of the Tikhonov regularization method, the approach to a solution of the inverse problem on deriving meridional and zonal components of the neutral <span class="hlt">wind</span> from the longitudinal variations in W is developed. A comparison with the Horizontal <span class="hlt">Wind</span> Model (HWM) neutral <span class="hlt">wind</span> model is performed and an attempt to correct this model for the considered conditions is made. Estimation of the contribution of the neutral <span class="hlt">wind</span>, composition and temperature into longitudinal and latitudinal variations in hmF2 is performed. The causes of the asymmetry between the Northern and Southern hemispheres are discussed.</p> <div class="credits"> <p class="dwt_author">Karpachev, A. T.; Gasilov, N. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">360</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41336998"> <span id="translatedtitle">New Measurements of the <span class="hlt">Winds</span> of Uranus</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Hubble Space Telescope imaging of Uranus in 1994, 1997, 1998, and 2000 revealed 13 cloud features, allowing the first measurements of <span class="hlt">wind</span> <span class="hlt">velocities</span> at northern latitudes not accessible to the Voyager cameras and new measurements of southern-latitude <span class="hlt">wind</span> <span class="hlt">velocities</span> determined during the 1986 Voyager encounter. Images acquired with the Keck 10-meter telescope adaptive optics system in June 2000 also showed</p> <div class="credits"> <p class="dwt_author">H. B. Hammel; K. Rages; G. W. Lockwood; E. Karkoschka; I. de Pater</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_17");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return 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href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a style="font-weight: bold;">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_20");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">361</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=AD742176"> <span id="translatedtitle">Temperature Profile of Solar <span class="hlt">Winds</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">The temperature profile of the solar <span class="hlt">wind</span> can be calculated from the energy equation by assuming that the <span class="hlt">velocity</span> profile is known. When the logarithmic expansion rate of the solar <span class="hlt">wind</span> is small, the heat-flow equation can be integrated analytically. If ...</p> <div class="credits"> <p class="dwt_author">T. Yeh</p> <p class="dwt_publisher"></p> <p class="publishDate">1971-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">362</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2002GeoRL..29.1585D"> <span id="translatedtitle"><span class="hlt">Wind</span> initiation thresholds of the moistened sands</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The widely accepted Bagnold-type function for calculating threshold <span class="hlt">wind</span> <span class="hlt">velocity</span> or shear <span class="hlt">velocity</span> was developed for dry sands, but surface moisture is an extremely important variable controlling the entrainment process of sands by <span class="hlt">wind</span> because the tensile force between the water molecules and sand grains produces cohesion. Here we report detailed <span class="hlt">wind</span> tunnel experimental results on the threshold shear <span class="hlt">velocity</span> of moistened sand of different sizes. The results show that relative threshold shear <span class="hlt">velocity</span>, which is the ratio of threshold shear <span class="hlt">velocity</span> of sand in the moistened state to that in the dry state, is better related to moisture content than threshold shear <span class="hlt">velocity</span> itself. Function, modified after the Bagnold equation has been developed to estimate the threshold shear <span class="hlt">velocities</span> of moistened sands. For a given grain size, the threshold shear <span class="hlt">velocity</span> is proportional to (1 + KM)1/2, where, M is the moisture content, and K is a coefficient depending on grain size.</p> <div class="credits"> <p class="dwt_author">Dong, Zhibao; Liu, Xiaoping; Wang, Xunming</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">363</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3790993"> <span id="translatedtitle">Coupling a Neural Network-Based forward Model and a Bayesian Inversion Approach to Retrieve <span class="hlt">Wind</span> Field from Spaceborne Polarimetric Radiometers</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">A simulation study to assess the potentiality of sea surface <span class="hlt">wind</span> vector estimation based on the approximation of the forward model through Neural Networks and on the Bayesian theory of parameter estimation is presented. A polarimetric microwave radiometer has been considered and its observations have been simulated by means of the two scale model. To perform the simulations, the atmospheric and surface parameters have been derived from ECMWF analysis fields. To retrieve <span class="hlt">wind</span> speed, Minimum Variance (MV) and <span class="hlt">Maximum</span> Posterior Probability (MAP) criteria have been used while, for <span class="hlt">wind</span> direction, a <span class="hlt">Maximum</span> Likelihood (ML) criterion has been exploited. To minimize the cost function of MAP and ML, conventional Gradient Descent method, as well as Simulated Annealing optimization technique, have been employed. Results have shown that the standard deviation of the <span class="hlt">wind</span> speed retrieval error is approximately 1.1 m/s for the best estimator. As for the <span class="hlt">wind</span> direction, the standard deviation of the estimation error is less than 13 for <span class="hlt">wind</span> speeds larger than 6 m/s. For lower <span class="hlt">wind</span> <span class="hlt">velocities</span>, the <span class="hlt">wind</span> direction signal is too weak to ensure reliable retrievals. A method to deal with the non-uniqueness of the <span class="hlt">wind</span> direction solution has been also developed. A test on a case study has yielded encouraging results.</p> <div class="credits"> <p class="dwt_author">Pulvirenti, Luca; Pierdicca, Nazzareno; Marzano, Frank S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">364</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012AtmRe.106...18C"> <span id="translatedtitle">Application of a method for the automatic detection and Ground-Based <span class="hlt">Velocity</span> Track Display (GBVTD) analysis of a tornado crossing the Hong Kong International Airport</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A weak tornado with a <span class="hlt">maximum</span> Doppler <span class="hlt">velocity</span> shear of about 40 m s - 1 moved across the Hong Kong International Airport (HKIA) during the evening of 20 May 2002. The tornado caused damage equivalent to F0 on the Fujita Scale, based on a damage survey. The Doppler <span class="hlt">velocity</span> data from the Hong Kong Terminal Doppler Weather Radar (TDWR) are studied using the Ground-Based <span class="hlt">Velocity</span> Track Display (GBVTD) method of single Doppler analysis. The GBVTD analysis is able to clearly depict the development and decay of the tornado though it appears to underestimate its magnitude. In the pre-tornadic state, the <span class="hlt">wind</span> field is characterized by inflow toward the center near the ground and upward motion near the center. When the tornado attains its <span class="hlt">maximum</span> strength, an eye-like structure with a downdraft appears to form in the center. Several minutes later the tornado begins to decay and outflow dominates at low levels. Assuming cyclostrophic balance, the pressure drop 200 m from the center of the tornado at its <span class="hlt">maximum</span> strength is calculated to be about 6 hPa. To estimate the <span class="hlt">maximum</span> ground-relative <span class="hlt">wind</span> speed of the tornado, the TDWR's Doppler <span class="hlt">velocities</span> are adjusted for the ratio of the sample-volume size of the radar and the radius of the tornado, resulting in a peak <span class="hlt">wind</span> speed of 28 m s - 1 , consistent with the readings from a nearby ground-based anemometers and the F0 damage observed. An automatic tornado detection algorithm based on Doppler <span class="hlt">velocity</span> difference (delta-V) and temporal and spatial continuity is applied to this event. The locations and the core flow radii of the tornado as determined by the automatic method and by subjective analysis agree closely.</p> <div class="credits"> <p class="dwt_author">Chan, P. W.; Wurman, J.; Shun, C. M.; Robinson, P.; Kosiba, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">365</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/1585575"> <span id="translatedtitle"><span class="hlt">Maximum</span> likelihood pitch estimation</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A method for estimating the pitch period of voiced speech sounds is developed based on a <span class="hlt">maximum</span> likelihood (ML) formulation. It is capable of resolution finer than one sampling period and is shown to perform better in the presence of noise than the cepstrum method.</p> <div class="credits"> <p class="dwt_author">J. Wise; J. Caprio; T. Parks</p> <p class="dwt_publisher"></p> <p class="publishDate">1976-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">366</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/188840"> <span id="translatedtitle"><span class="hlt">Maximum</span> Entropy Discrimination</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We present a general framework for discriminative estimation based on the <span class="hlt">maximum</span> entropyprinciple and its extensions. All calculations involve distributions over structures and\\/orparameters rather than specic settings and reduce to relative entropy projections. This holdseven when the data is not separable within the chosen parametric class, in the context of anomalydetection rather than classication, or when the labels in the</p> <div class="credits"> <p class="dwt_author">Tommi Jaakkola; Marina Meila; Tony Jebara</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">367</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/72711p13425r1253.pdf"> <span id="translatedtitle">Finding <span class="hlt">Maximum</span> Convex Polygons</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This paper considers the situation where one is given a finite set of n points in the plane each of which is labeled either positive or negative. The problem is to find a bounded convex polygon of <span class="hlt">maximum</span> area, the vertices of which are positive points and which does not contain any negative point. It is shown that this problem</p> <div class="credits"> <p class="dwt_author">Paul Fischer; Lehrstuhl Informatik II</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">368</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/27455079"> <span id="translatedtitle">Stability Simulation of <span class="hlt">Wind</span> Turbine Systems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A simulation and digital computer modeling effort is described in which a <span class="hlt">wind</span> turbine-generator system is adapted for stability evaluation using a large scale transient stability computer program. Component models of the MOD-2 <span class="hlt">wind</span> generator system are described and their digital model equations are provided. A versatile <span class="hlt">wind</span> <span class="hlt">velocity</span> model is described, which provides the capability of simulating a wide</p> <div class="credits"> <p class="dwt_author">P. M. Anderson; Anjan Bose</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">369</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/27506535"> <span id="translatedtitle"><span class="hlt">Wind</span> energy in the built environment: concentrator effects of buildings</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This thesis deals with <span class="hlt">wind</span> energy conversion in the built environment. It gives a description of the <span class="hlt">wind</span> resources in the built environment that can be converted into energy by a <span class="hlt">wind</span> turbine. With a focus on <span class="hlt">maximum</span> energy yield of the <span class="hlt">wind</span> turbine, it especially deals with the integration of <span class="hlt">wind</span> turbine and building in such a way that</p> <div class="credits"> <p class="dwt_author">Sander Mertens</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">370</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/50884659"> <span id="translatedtitle">A neural network based <span class="hlt">wind</span> speed estimator for a <span class="hlt">wind</span> turbine control</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Variable speed <span class="hlt">wind</span> generation systems are more attractive than fixed-speed systems because of the more efficient energy production improved power quality, and improved dynamic performance during grid disturbances. In this sense, to implement <span class="hlt">maximum</span> <span class="hlt">wind</span> power extraction, most controller designs of the variable-speed <span class="hlt">wind</span> turbine generators employ anemometers to measure <span class="hlt">wind</span> speed in order to derive the desired optimal shaft</p> <div class="credits"> <p class="dwt_author">Oscar Barambones; Jose Maria Gonzalez de Durana; Enrique Kremers</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">371</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/jc/jc0210/2001JC001116/2001JC001116.pdf"> <span id="translatedtitle">Continuity preserving modified <span class="hlt">maximum</span> cross-correlation technique</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The <span class="hlt">maximum</span> cross-correlation (MCC) method reconstructs the surface advective <span class="hlt">velocity</span> fields from the displacements of spatial patterns in pairs of sequential satellite (normally infrared) images. However, the performance of the conventional MCC method is not always satisfactory. One of the main reasons for this is the fact that the method can correctly estimate only the <span class="hlt">velocity</span> component parallel to the</p> <div class="credits"> <p class="dwt_author">Peter O. Zavialov; Julia V. Grigorieva; Osmar O. Mller; Andrey G. Kostianoy; Marilaure Gregoire</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">372</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2000APS..DFD.ME006J"> <span id="translatedtitle">Preliminary <span class="hlt">Velocity</span> Measurements in the Wake of a Submarine Model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Preliminary Particle Image Velocimetry (PIV) over a submarine shape has been conducted in a low speed <span class="hlt">wind</span> tunnel at Princeton University. The model is a 1/67 replica of the USS Albacore, an experimental submarine designed to achieve <span class="hlt">maximum</span> underwater performance, and based on "bodies of revolution." The model is tested with a sail, and different tail appendages. <span class="hlt">Velocity</span> vector fields and flow visualizations in the wake region are presented for Reynolds numbers based on model length up to 10^5. The experiments establish the groundwork for future investigations of submarine models in the new High Reynolds Number Test Facility (http://www.princeton.edu/ gasdyn/HRTF.html). Supported by ONR Grants N00014-97-1-0325, N00014-97-1-0340 and N00014-97-1-0618.</p> <div class="credits"> <p class="dwt_author">Jimenez, J. M.; Reynolds, R.; Smits, A. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">373</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1999JGR...104.2603V"> <span id="translatedtitle">Longitudinal and seasonal variations in nighttime plasma temperatures in the equatorial topside ionosphere during solar <span class="hlt">maximum</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Latitude profiles of the ion and electron temperatures and total ion concentration across the equatorial region near 800 km altitude are routinely obtained from Defense Meteorological Satellite Program (DMSP) spacecraft. We have examined these profiles at 2100 hours local time to discover the influences of field-aligned plasma transport induced by F region neutral <span class="hlt">winds</span>. Such dependencies are readily seen by contrasting observations at different seasons and different longitudes distinguished by different magnetic declinations. These data show strong evidence for adiabatic heating produced by interhemispheric plasma transport. This heating manifests itself as a local temperature <span class="hlt">maximum</span> that appears in the winter hemisphere during the solstices and is generally absent during equinox. A longitudinal variation in the appearance of this <span class="hlt">maximum</span> is consistent with the roles of meridional and zonal <span class="hlt">winds</span> in modulating the field-aligned plasma <span class="hlt">velocities</span>. The data also show a local temperature minimum near the dip equator. However, it is not so easy to attribute this minimum to adiabatic cooling since transport of plasma from below and the latitude variation in the flux tube content may also produce such a minimum.</p> <div class="credits"> <p class="dwt_author">Venkatraman, Sarita; Heelis, Rod</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">374</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6446292"> <span id="translatedtitle"><span class="hlt">Winds</span> in hot stars</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Models are calculated for stellar <span class="hlt">winds</span> driven by radiation pressure in spectral lines. The line transfer equation in the fluid frame is solved in order to evaluate the radiation pressure force, and the hydrodynamic structure is constructed to be consistent with this force. This technique avoids use of the Sobolev approximation, which is not applicable for low flow <span class="hlt">velocities</span>. The models either use a number of driving lines of equal strenght or several lines covering a range of opacities which are weighted to simulate a distribution of line strengths. We find acceleration near the base of the <span class="hlt">wind</span> which is considerably more gradual than in the model of Castor, Abbott, and Klein. This difference is significant even well above the point. In our model, v(r) is approximately linear out to 1.3--1.4 stellar radii, where the <span class="hlt">velocity</span> reaches one fourth the terminal <span class="hlt">velocity</span>. Observations also support slower acceleration in this region. The mass-loss rate and the <span class="hlt">wind</span> structure at large radii are in substantial agreement with earlier results. The mass-loss rate is NL/c/sup 2/, where N is the number of lines which contribute significantly to the radiation pressure force. For a reasonable line strength distribution, the terminal <span class="hlt">velocity</span> is several times the escape <span class="hlt">velocity</span>.</p> <div class="credits"> <p class="dwt_author">Weber, S.V.</p> <p class="dwt_publisher"></p> <p class="publishDate">1981-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">375</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/53170761"> <span id="translatedtitle">On the bimodal kick <span class="hlt">velocity</span> distribution</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We propose that the bimodal nature of the kick <span class="hlt">velocity</span> distribution of radio pulsars is connected with dichotomy between neutron stars and quark stars. Bimodality can appear due to two different mechanisms of explosions or two different sets of parameters mastering particular mechanism. The low <span class="hlt">velocity</span> <span class="hlt">maximum</span> (at 100 km s-1) is connected with neutron star formation. The second</p> <div class="credits"> <p class="dwt_author">S. B. Popov; I. Bombaci</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">376</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013A%26A...551A...9A"> <span id="translatedtitle"><span class="hlt">Maximum</span> likelihood estimation of local stellar kinematics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Context. Kinematical data such as the mean <span class="hlt">velocities</span> and <span class="hlt">velocity</span> dispersions of stellar samples are useful tools to study galactic structure and evolution. However, observational data are often incomplete (e.g., lacking the radial component of the motion) and may have significant observational errors. For example, the majority of faint stars observed with Gaia will not have their radial <span class="hlt">velocities</span> measured. Aims: Our aim is to formulate and test a new <span class="hlt">maximum</span> likelihood approach to estimating the kinematical parameters for a local stellar sample when only the transverse <span class="hlt">velocities</span> are known (from parallaxes and proper motions). Methods: Numerical simulations using synthetically generated data as well as real data (based on the Geneva-Copenhagen survey) are used to investigate the statistical properties (bias, precision) of the method, and to compare its performance with the much simpler "projection method" described by Dehnen & Binney (1998, MNRAS, 298, 387). Results: The <span class="hlt">maximum</span> likelihood method gives more correct estimates of the dispersion when observational errors are important, and guarantees a positive-definite dispersion matrix, which is not always obtained with the projection method. Possible extensions and improvements of the method are discussed.</p> <div class="credits"> <p class="dwt_author">Aghajani, T.; Lindegren, L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">377</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA342680"> <span id="translatedtitle">Azimuth and Range Optimization of the <span class="hlt">Velocity</span> Azimuth Display (VAD) Algorithm in the WSR-88D.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">The <span class="hlt">Velocity</span> Azimuth Display (VAD) algorithm occasionally produces inaccurate <span class="hlt">wind</span> estimates for the VAD <span class="hlt">Wind</span> Profile (VWP) product of the Weather Surveillance Radar 1988 Doppler (WSR-88D) System. Weather forecasters have observed differences between the ...</p> <div class="credits"> <p class="dwt_author">D. L. Craft</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">378</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013ACP....13.9515D"> <span id="translatedtitle">Mean <span class="hlt">winds</span> in the MLT, the SQBO and MSAO over Ascension Island (8 S, 14 W)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Mean <span class="hlt">winds</span> in the mesosphere and lower thermosphere (MLT) over Ascension Island (8 S, 14 W) have been measured at heights of approximately 80-100 km by a meteor radar. The results presented in this study are from the interval October 2001 to December 2011. In all years, the monthly-mean meridional <span class="hlt">winds</span> display a clear annual oscillation. Typically, these <span class="hlt">winds</span> are found to be southward during April-October, when they reach <span class="hlt">velocities</span> of up to about -23 m s-1, and northward throughout the rest of the year, when they reach <span class="hlt">velocities</span> up to about 16 m s-1. The monthly-mean zonal <span class="hlt">winds</span> are generally westward throughout most of the year and reach <span class="hlt">velocities</span> of up to about -46 m s-1. However, eastward <span class="hlt">winds</span> are observed in May-August and again in December at the lower heights observed. These eastward <span class="hlt">winds</span> reach a <span class="hlt">maximum</span> at heights of about 86 km with <span class="hlt">velocities</span> of up to about 36 m s-1, but decay quickly at heights above and below that level. The mesospheric semi-annual oscillation (MSAO) is clearly apparent in the observed monthly-mean zonal <span class="hlt">winds</span>. The <span class="hlt">winds</span> in first westward phase of the MSAO are observed to be much stronger than in the second phase. The westward phase of the MSAO is found to maximise at heights of about 84 km with typical first-phase <span class="hlt">wind</span> <span class="hlt">velocities</span> reaching about -35 m s-1. These meteor-radar observations have been compared to the HWM-07 empirical model. The observed meridional <span class="hlt">winds</span> are found to be generally more southward than those of the model during May-August, when at the lower heights observed the model suggests there will be only weakly southward, or even northward, <span class="hlt">winds</span>. The zonal monthly-mean <span class="hlt">winds</span> are in generally good agreement, although in the model they are somewhat less westward than those observed. Throughout the observations there were eight occasions in which the first westward phase of the MSAO was observed. Strikingly, in 2002 there was an event in which the westward <span class="hlt">winds</span> during the first phase of the MSAO were much stronger than normal and reached <span class="hlt">velocities</span> of about -75 m s-1. This event is explained in terms of a previously proposed mechanism in which the relative phasing of the stratospheric quasi-biennial oscillation (SQBO) and the MSAO allows an unusually large flux of gravity waves of large westward phase speed to reach the mesosphere. It is the dissipation of these gravity waves that then drives the MLT <span class="hlt">winds</span> to the large westward <span class="hlt">velocities</span> observed. It is demonstrated that the necessary SQBO-MSAO phase relationship did indeed exist during 2002, but not during the other years observed here. This demonstration provides strong support for the suggestion that extreme zonal-<span class="hlt">wind</span> events during the MSAO result from the modulation of gravity-wave fluxes.</p> <div class="credits"> <p class="dwt_author">Day, K. A.; Mitchell, N. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">379</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1988PhDT.......115M"> <span id="translatedtitle">High Resolution Observations of the L1551, B335 and L723 Bipolar Molecular Outflows Using <span class="hlt">Maximum</span> Entropy Image Reconstruction.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The application of <span class="hlt">maximum</span> entropy image reconstruction to maps made at millimetre wavelengths to enhance their angular resolution, is discussed. We present complete maps of the high <span class="hlt">velocity</span> ^{12} CO emission in the L1551 outflow, a map of the CS core of the L1551 molecular cloud, and a ^ {13}CO map of the entire cloud. The molecular <span class="hlt">wind</span> has been swept into a thin shell surrounding a cavity, and has broken out of the cloud at one position. Both lobes show an acceleration of high <span class="hlt">velocity</span> emission away from IRS-5, caused by true acceleration produced by a hydromagnetically driven <span class="hlt">wind</span>, or perhaps a geometric effect caused by a latitude dependent <span class="hlt">wind</span> driving the molecular gas. The blue lobe experiences an abrupt narrowing and <span class="hlt">velocity</span> decrease where it becomes recollimated. Red-shifted emission in the blue lobe and vice verse is likely due to an increased <span class="hlt">velocity</span> dispersion in these regions. The optical depth of high-<span class="hlt">velocity</span> emission is larger than expected. The outflow mass may be more than 3.5M_odot . The energy within the outflow is greater than the total energy within the cloud. The outflow has sufficient momentum to disrupt the cloud core. The CS core shows no evidence for a rotating disk. Dense clumps exhibit shearing due to the outflow. Our data are most consistent with a model in which the molecular material is swept up by a high <span class="hlt">velocity</span>, perhaps latitude dependent, <span class="hlt">wind</span> originating near IRS-5. The B335 outflow was also mapped and has structure similar to L1551. Limb brightening, and red-shifted emission in the center of the blue lobe and vice versa suggest a shell structure. The outflow is oriented ^ ~9^circ out of the sky. The energy of the outflow is greater than that of the molecular cloud core, and there is sufficient momentum to disrupt the cloud core. The L723 outflow is very narrow and highly collimated, and has not been resolved by these observations. There is no evidence for a shell structure at this resolution. The outflow appears to have two axes of symmetry nearly perpendicular to each other, perhaps indicating that the outflow axis has precessed.</p> <div class="credits"> <p class="dwt_author">Moriarty-Schieven, Gerald Henry</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">380</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/7491748"> <span id="translatedtitle"><span class="hlt">Velocity</span> matched spectrum analysis: a new method for suppressing <span class="hlt">velocity</span> ambiguity in pulsed-wave Doppler.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">A new approach to spectrum analysis, which is capable of suppressing <span class="hlt">velocity</span> ambiguity in pulsed-wave ultrasonic Doppler, is presented. By simultaneous processing of several data samples from a range in depth, the movement of the scatterers along the ultrasonic beam can be tracked from pulse to pulse for each <span class="hlt">velocity</span> component in the spectrum. In this way the correlation length of the signal component arising from a specific <span class="hlt">velocity</span> increases when that <span class="hlt">velocity</span> matches the expected <span class="hlt">velocity</span>. The resulting <span class="hlt">velocity</span>/time spectral display shows a more clearly defined spectral envelope of the <span class="hlt">maximum</span> <span class="hlt">velocity</span> than with conventional methods based on the discrete Fourier transform of the Doppler signal. This makes it possible to delineate <span class="hlt">velocity</span> waveforms with peak <span class="hlt">velocity</span> up to several times the Nyquist limit. Experimental data from human subclavian and aortic arteries are presented, where the new method is compared to conventional spectrum analysis. PMID:7491748</p> <div class="credits"> <p class="dwt_author">Torp, H; Kristoffersen, K</p> <p class="dwt_publisher"></p> <p class="publishDate">1995-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_18");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return 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<a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a style="font-weight: bold;">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_21");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">381</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/50411916"> <span id="translatedtitle">Laboratory set-up for <span class="hlt">wind</span> turbine emulation</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This paper presents a laboratory set-up to be used as <span class="hlt">wind</span> turbine emulator. The emulator can be used for research applications to drive an electrical generator in a similar way as a <span class="hlt">wind</span> turbine, by reproducing the torque developed by a <span class="hlt">wind</span> turbine for a given <span class="hlt">wind</span> <span class="hlt">velocity</span>. Also, it can be used as an educational tool to teach the</p> <div class="credits"> <p class="dwt_author">M. Chinchilla; S. Arnaltes; J. L. Rodriguez-Amenedo</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">382</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/26364623"> <span id="translatedtitle">A twisted flow <span class="hlt">wind</span> tunnel for testing yacht sails</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The paper outlines the requirements for <span class="hlt">wind</span> tunnel testing model yachts for sail aerodynamics investigations. It is shown that the apparent <span class="hlt">wind</span> onto a yacht is twisted over the mast height, due to the vector addition of the yacht and <span class="hlt">wind</span> <span class="hlt">velocities</span>. The design features of a special <span class="hlt">wind</span> tunnel built in New Zealand which can produce twisted flow in</p> <div class="credits"> <p class="dwt_author">Richard G. J. Flay</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">383</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009JAP...105j4908H"> <span id="translatedtitle"><span class="hlt">Maximum</span> windmill efficiency in finite time</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The fraction of the kinetic energy of the <span class="hlt">wind</span> impinging on the rotor-swept area that a <span class="hlt">wind</span> turbine can convert to useful power has been shown by Betz in an idealized laminar-flow model to have an upper limit of 16/27 or 59% approximately [I. H. Shames, Mechanics of Fluids, 2nd ed. (McGraw-Hill, New York, 1982), pp. A26-A31]. This figure is known as Betz number. Other studies [A. Rauh and W. Seelret, Appl. Energy 17, 15 (1984)] suggested that this figure should be considered as a guideline. In this paper, a new model is introduced and its efficiency at <span class="hlt">maximum</span> power output is derived. The derived value is shown to be a function of the Betz number B and given by the formula ?mp=1-1-B. This value is 36.2%, which agrees well with those of actually operating <span class="hlt">wind</span> turbines. As a guideline, the <span class="hlt">wind</span> turbine efficiency can be considered to be within the range of the two numbers of merit, the Betz number and ?mp.</p> <div class="credits"> <p class="dwt_author">Huleihil, Mahmoud</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">384</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003IAUS..212...56F"> <span id="translatedtitle">Overloaded and fractured stellar <span class="hlt">winds</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We discuss the connection between <span class="hlt">wind</span> overloading and discrete absorption components in P-Cygni line profiles from O-type stars. Overloading can create horizontal plateaus in the radial <span class="hlt">wind</span> speed that cause the extra absorption in the line profile. The upstream propagation speed of these <span class="hlt">velocity</span> plateaus is analyzed. The second part of the paper deals with X-ray emission from O-type stars. X-ray line profiles observed with Chandra and XMM are often symmetric, contrary to what is expected for lines from a homogeneous <span class="hlt">wind</span>. We discuss the influence on line symmetry of photon escape channels in a strongly clumped <span class="hlt">wind</span>.</p> <div class="credits"> <p class="dwt_author">Feldmeier, Achim; Oskinova, Lida M.; Hamann, Wolf-Rainer; Owocki, Stanley P.</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">385</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/19661421"> <span id="translatedtitle">The Last Glacial <span class="hlt">Maximum</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial <span class="hlt">Maximum</span> (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their <span class="hlt">maximum</span> positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level approximately 14.5 ka. PMID:19661421</p> <div class="credits"> <p class="dwt_author">Clark, Peter U; Dyke, Arthur S; Shakun, Jeremy D; Carlson, Anders E; Clark, Jorie; Wohlfarth, Barbara; Mitrovica, Jerry X; Hostetler, Steven W; McCabe, A Marshall</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">386</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://dx.doi.org/10.1126/science.1172873"> <span id="translatedtitle">The last glacial <span class="hlt">maximum</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial <span class="hlt">Maximum</span> (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their <span class="hlt">maximum</span> positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ???14.5 ka.</p> <div class="credits"> <p class="dwt_author">Clark, P. U.; Dyke, A. S.; Shakun, J. D.; Carlson, A. E.; Clark, J.; Wohlfarth, B.; Mitrovica, J. X.; Hostetler, S. W.; McCabe, A. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">387</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/51605958"> <span id="translatedtitle">Flow structure inside and above a variable <span class="hlt">wind</span> farm: A <span class="hlt">wind</span> tunnel study</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"><span class="hlt">Wind</span> turbine wakes are known to have important effects on both power generation and fatigue loads in <span class="hlt">wind</span> farms. Wake characteristics are expected to depend on the incoming atmospheric boundary layer flow statistics (e.g., mean <span class="hlt">velocity</span>, turbulence intensity and turbulent fluxes), and vertical transport, which is affected by the relative position of the turbines in the <span class="hlt">wind</span> farm. In this</p> <div class="credits"> <p class="dwt_author">Leonardo Chamorro; Fernando Porte-Agel</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">388</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AIPC.1539..410M"> <span id="translatedtitle">Kinetic and potential sputtering of lunar regolith: The contribution of the heavy (minority) solar <span class="hlt">wind</span> ions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In this paper the sputtering of lunar regolith by protons and solar <span class="hlt">wind</span> heavy ions is considered. From preliminary measurements of H+, Ar+1, Ar+6 and Ar+9 ion sputtering of JSC-1A AGGL lunar regolith simulant at solar <span class="hlt">wind</span> <span class="hlt">velocities</span>, and TRIM simulations of kinetic sputtering yields, the relative contributions of kinetic and potential sputtering contributions are estimated. An 80-fold enhancement of oxygen sputtering by Ar+ over same-<span class="hlt">velocity</span> H+, and an additional x2 increase for Ar+9 over same-<span class="hlt">velocity</span> Ar+ was measured. This enhancement persisted to the <span class="hlt">maximum</span> fluences investigated (~1016/cm2). Modeling studies including the enhanced oxygen ejection by potential sputtering due to the minority heavy ion multicharged ion solar <span class="hlt">wind</span> component, and the kinetic sputtering contribution of all solar <span class="hlt">wind</span> constituents, as determined from TRIM sputtering simulations, indicate an overall 35% reduction of near-surface oxygen abundance. XPS analyses of simulant samples exposed to singly and multicharged Ar ions show the characteristic signature of reduced (metallic) Fe, consistent with the preferential ejection of oxygen atoms that can occur in potential sputtering of some metal oxides.</p> <div class="credits"> <p class="dwt_author">Meyer, F. W.; Harris, P. R.; Meyer, H. M., III; Hijazi, H.; Barghouty, A. F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">389</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1989ApJ...337..888P"> <span id="translatedtitle">A rotating, magnetic, radiation-driven <span class="hlt">wind</span> model for Wolf-Rayet stars</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A radiation-driven <span class="hlt">wind</span> model that incorporates the effects of rotation and an open magnetic field is applied to WR stars in order to address the <span class="hlt">wind</span> momentum problem. The dependence of the mass-loss rate and terminal <span class="hlt">velocity</span> on the rotation rate and surface magnetic field is studied for the flow in the equatorial region. The transition from a purely radiatively driven <span class="hlt">wind</span> to a rotationally and magnetically driven <span class="hlt">wind</span> is investigated for the case in which the stellar luminosity is consistent with Maeder's mass-luminosity relation. An alternative picture for WR <span class="hlt">winds</span> is developed in which there is a slower but denser equatorial flow and a fast radiation-driven <span class="hlt">wind</span> at higher latitudes. <span class="hlt">Wind</span> models for several stars are presented that are consistent with interior theory. If the stars have field of about 1500 G and rotate at rates greater than about 85 percent <span class="hlt">maximum</span>, they can satisfy the radio and UV observations and explain the momentum problem, and also overcome the spindown problem.</p> <div class="credits"> <p class="dwt_author">Poe, Clint H.; Friend, David B.; Cassinelli, Joseph P.</p> <p class="dwt_publisher"></p> <p class="publishDate">1989-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">390</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001Entrp...3..191H"> <span id="translatedtitle"><span class="hlt">Maximum</span> Entropy Fundamentals</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In its modern formulation, the <span class="hlt">Maximum</span> Entropy Principle was promoted by E.T. Jaynes, starting in the mid-fifties. The principle dictates that one should look for a distribution, consistent with available information, which maximizes the entropy. However, this principle focuses only on distributions and it appears advantageous to bring information theoretical thinking more prominently into play by also focusing on the "observer" and on coding. This view was brought forward by the second named author in the late seventies and is the view we will follow-up on here. It leads to the consideration of a certain game, the Code Length Game and, via standard game theoretical thinking, to a principle of Game Theoretical Equilibrium. This principle is more basic than the <span class="hlt">Maximum</span> Entropy Principle in the sense that the search for one type of optimal strategies in the Code Length Game translates directly into the search for distributions with <span class="hlt">maximum</span> entropy. In the present paper we offer a self-contained and comprehensive treatment of fundamentals of both principles mentioned, based on a study of the Code Length Game. Though new concepts and results are presented, the reading should be instructional and accessible to a rather wide audience, at least if certain mathematical details are left aside at a rst reading. The most frequently studied instance of entropy maximization pertains to the Mean Energy Model which involves a moment constraint related to a given function, here taken to represent "energy". This type of application is very well known from the literature with hundreds of applications pertaining to several different elds and will also here serve as important illustration of the theory. But our approach reaches further, especially regarding the study of continuity properties of the entropy function, and this leads to new results which allow a discussion of models with so-called entropy loss. These results have tempted us to speculate over the development of natural languages. In fact, we are able to relate our theoretical findings to the empirically found Zipf's law which involves statistical aspects of words in a language. The apparent irregularity inherent in models with entropy loss turns out to imply desirable stability properties of languages.</p> <div class="credits"> <p class="dwt_author">Harremoes, P.; Topse, F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">391</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/59011717"> <span id="translatedtitle">Designing Drive Trains for the Next Generation of <span class="hlt">Wind</span> Turbines (FloDesign <span class="hlt">Wind</span> Turbine Corporation)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Today's <span class="hlt">wind</span> turbines have nearly reached their <span class="hlt">maximum</span> possible efficiency and are limited to sites with a narrow profile of <span class="hlt">wind</span> patterns. The patent-pending Mixer Ejector <span class="hlt">Wind</span> Turbine (MEWT) concept proposed by FloDesign promises to outperform existing <span class="hlt">wind</span> turbines by a factor of three or more in a much wider range of <span class="hlt">wind</span> resources. Olin Colleges FloDesign SCOPE team was</p> <div class="credits"> <p class="dwt_author">Mateen Abdul; Kelcy Adamec; Gavin Boggs; Matthew Crawford; Kevin Sihlanick; Russell Torres</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">392</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/26973125"> <span id="translatedtitle">The Potential of <span class="hlt">Wind</span> Energy as an Alternative Source in Turkey</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Development in <span class="hlt">wind</span> energy systems and the potential of <span class="hlt">wind</span> energy in Turkey were studied; the <span class="hlt">wind</span> energy potential of various regions was investigated in this study. A power equation was derived by a mathematical approach using the characteristics of <span class="hlt">wind</span> energy, including rotor diameter, <span class="hlt">wind</span> speed, and density of the <span class="hlt">wind</span> power. The <span class="hlt">maximum</span> power obtainable at each location</p> <div class="credits"> <p class="dwt_author">C. ?lkili; M. Nursoy</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">393</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/19964460"> <span id="translatedtitle">Electrohysterographic conduction <span class="hlt">velocity</span> estimation.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Monitoring and analysis of the fetal-heart and the uterine-muscle activity, referred to as electrohysterogram (EHG), is essential to permit timely treatment during pregnancy. While remarkable progress is reported for monitoring of the fetal cardiac activity, the EHG measurement and interpretation remains challenging, and limited knowledge is available on the underlying physiological processes. In particular, little attention has been paid to the analysis of the EHG propagation, whose characteristics might indicate the presence of coordinated uterine contractions leading to intrauterine pressure increase. Therefore, this study focuses for the first time on the noninvasive estimation of the conduction <span class="hlt">velocity</span> of EHG action potentials by means of multichannel EHG recording and surface high-density electrodes. A <span class="hlt">maximum</span> likelihood algorithm, initially proposed for skeletal-muscle electromyog-raphy, is modified for the required EHG analysis. The use of clustering and weighting is introduced to deal with poor signal similarity between different channels. The presented methods were evaluated by specific simulations, proving the combination of weighting and clustering to be the most accurate method. A preliminary EHG measurement during labor confirmed the feasibility of the method. An extensive clinical validation will however be necessary to optimize the method and assess the relevance of the EHG conduction <span class="hlt">velocity</span> for pregnancy monitoring. PMID:19964460</p> <div class="credits"> <p class="dwt_author">Mischi, M; Rabotti, C; Vosters, L J; Oei, S G; Bergmans, J M</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">394</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/34726780"> <span id="translatedtitle">Correlations between aerodynamic output, electrical activity in the indirect flight muscles and wing positions of bees flying in a servomechanically controlled <span class="hlt">wind</span> tunnel</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">1)Bees hanging on an aerodynamic two component balance were placed in front of a laminar <span class="hlt">wind</span> tunnel. They controlled the <span class="hlt">wind</span> <span class="hlt">velocity</span> in the tunnel through a servo-mechanism that held the <span class="hlt">wind</span> <span class="hlt">velocity</span> to exactly the opposite of the flight speed, thus selecting lift and thrust freely. The parameters lift, <span class="hlt">wind</span> <span class="hlt">velocity</span>, occurrence of action potentials in the indirect dorsoventral</p> <div class="credits"> <p class="dwt_author">Harald Esch; Werner Nachtigall; Stephen N. Kogge</p> <p class="dwt_publisher"></p> <p class="publishDate">1975-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">395</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AJ....145...45H"> <span id="translatedtitle"><span class="hlt">Wind</span> Variability in BZ Camelopardalis</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Sequences of spectra of the nova-like cataclysmic variable (CV) BZ Cam were acquired on nine nights in 2005-2006 in order to study the time development of episodes of <span class="hlt">wind</span> activity known to occur frequently in this star. We confirm the results of Ringwald & Naylor that the P-Cygni absorption components of the lines mostly evolve from higher expansion <span class="hlt">velocity</span> to lower <span class="hlt">velocity</span> as an episode progresses. We also commonly find blueshifted emission components in the H? line profile, whose <span class="hlt">velocities</span> and durations strongly suggest that they are also due to the <span class="hlt">wind</span>. Curiously, Ringwald & Naylor reported common occurrences of redshifted H? emission components in their BZ Cam spectra. We have attributed these emission components in H? to occasions when gas concentrations in the bipolar <span class="hlt">wind</span> (both front side and back side) become manifested as emission lines as they move beyond the disk's outer edge. We also suggest, based on changes in the P-Cygni profiles during an episode, that the progression from larger to smaller expansion <span class="hlt">velocities</span> is due to the higher <span class="hlt">velocity</span> portions of a <span class="hlt">wind</span> concentration moving beyond the edge of the continuum light of the disk first, leaving a net redward shift of the remaining absorption profile. We derive a new orbital ephemeris for BZ Cam, using the radial <span class="hlt">velocity</span> of the core of the He I ?5876 line, finding P = 0.15353(4). Using this period, the <span class="hlt">wind</span> episodes in BZ Cam are found to be concentrated near the inferior conjunction of the emission line source. This result helps confirm that the <span class="hlt">winds</span> in nova-like CVs are often phase dependent, in spite of the puzzling implication that such <span class="hlt">winds</span> lack axisymmetry. We argue that the radiation-driven <span class="hlt">wind</span> in BZ Cam receives an initial boost by acting on gas that has been lifted above the disk by the interaction of the accretion stream with the disk, thereby imposing flickering timescales onto the <span class="hlt">wind</span> events, as well as leading to an orbital modulation of the <span class="hlt">wind</span> due to the non-axisymmetric nature of the stream/disk interaction. Simultaneous photometry and spectroscopy were acquired on three nights in order to test the possible connection between flickering continuum light and the strength of the front-side <span class="hlt">wind</span>. We found strong agreement on one night, some agreement on another, and no agreement on the third. We suggest that some flickering events lead to only back-side <span class="hlt">winds</span> which will not have associated P-Cygni profiles.</p> <div class="credits"> <p class="dwt_author">Honeycutt, R. K.; Kafka, S.; Robertson, J. W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">396</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60046682"> <span id="translatedtitle">Blade pitch control of a <span class="hlt">wind</span> turbine</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A control system is described for adjusting the pitch of variable-pitch angle blades in a <span class="hlt">wind</span> turbine generating electric power and for maintaining dynamic stability under all conditions. At low <span class="hlt">wind</span> speeds the control system maintains the pitch of the blades at an angle close to the value providing <span class="hlt">maximum</span> torque, and at high <span class="hlt">wind</span> speeds the control system adjusts</p> <div class="credits"> <p class="dwt_author">Quynn</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">397</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012JGRC..117.0J05D"> <span id="translatedtitle">Direct numerical simulation of a turbulent <span class="hlt">wind</span> over a wavy water surface</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Parameterization of the <span class="hlt">wind</span>-water-waves interaction is a key problem of the air-sea system modeling. Of most importance are water waves with sufficiently large steepness, when nonlinear effects related to the boundary layer separation and vortex generation in the <span class="hlt">wind</span> flow are well pronounced. Known experimental techniques (contact methods and particle image velocimetry) are not yet able to provide a full, detailed understanding of the <span class="hlt">wind</span> flow in the viscous sublayer and the buffer region. As an alternative, we consider direct numerical simulations (DNS). In the present paper we discuss numerical algorithm and results of DNS of a turbulent <span class="hlt">wind</span> flow over a wavy water surface. Waves with <span class="hlt">maximum</span> steepness of ka = 0.2, wave age 0 < c/u* < 10, and Reynolds number Re = 15,000 are considered. Full, 3-D Navier-Stokes equations are solved in curvilinear coordinates in a reference frame moving with the wave phase speed c. DNS results show that an instantaneous <span class="hlt">velocity</span> field is characterized by the presence of well-pronounced separation zones in the vicinity of the wave crests whereas the average <span class="hlt">velocity</span> field is nonseparating. We also perform a comparison of the DNS results with the predictions of a theoretical quasi-linear model of the <span class="hlt">wind</span>-wave interaction.</p> <div class="credits"> <p class="dwt_author">Druzhinin, O. A.; Troitskaya, Y. I.; Zilitinkevich, S. S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">398</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/26366070"> <span id="translatedtitle">Reliability analysis of <span class="hlt">wind</span>-excited structures</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The structural effects induced by the <span class="hlt">wind</span> constitute a stochastic process which depends, in turn, on the <span class="hlt">wind</span>, the structure and the aerodynamic parameters. Structural verifications usually consider statistical moments of the process, such as the mean <span class="hlt">maximum</span> or standard deviation, or its <span class="hlt">maximum</span> value. Since the estimate of the parameters is uncertain, all these quantities should be treated as</p> <div class="credits"> <p class="dwt_author">Luisa Pagnini</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">399</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA069005"> <span id="translatedtitle">Projectile <span class="hlt">Velocity</span> Measurements.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">The report describes methods for measuring projectile <span class="hlt">velocity</span>. Discusses time of flight and distance measurements and equipment including muzzle <span class="hlt">velocity</span> radar, solenoid coils, <span class="hlt">velocity</span> screens, chronographs, smear camera, ultra-high-speed camera, flash ...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate">1979-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">400</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/488894"> <span id="translatedtitle">Fuzzy logic based intelligent control of a variable speed cage machine <span class="hlt">wind</span> generation system</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The paper describes a variable speed <span class="hlt">wind</span> generation system where fuzzy logic principles are used for efficiency optimization and performance enhancement control. A squirrel cage induction generator feeds the power to a double-sided pulse width modulated converter system which pumps power to a utility grid or can supply to an autonomous system. The generation system has fuzzy logic control with vector control in the inner loops. A fuzzy controller tracks the generator speed with the <span class="hlt">wind</span> <span class="hlt">velocity</span> to extract the <span class="hlt">maximum</span> power. A second fuzzy controller programs the machine flux for light load efficiency improvement, and a third fuzzy controller gives robust speed control against <span class="hlt">wind</span> gust and turbine oscillatory torque. The complete control system has been developed, analyzed, and validated by simulation study. Performances have then been evaluated in detail.</p> <div class="credits"> <p class="dwt_author">Simoes, M.G. [Univ. of Sao Paulo (Brazil); Bose, B.K. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Electrical Engineering; Spiegel, R.J. [Environmental Protection Agency, Research Triangle Park, NC (United States), Air and Energy Engineering Research Lab.</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_19");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' 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id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_20");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a onClick='return showDiv("page_5");' href="#">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a style="font-weight: bold;">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_22");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">401</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/56251397"> <span id="translatedtitle"><span class="hlt">Wind</span> power</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The fundamentals of <span class="hlt">wind</span> power utilization are described with emphasis placed on the information needed to determine the basic geometry of <span class="hlt">wind</span> power devices and to discuss the availability of <span class="hlt">wind</span> for power generation. The economics and social acceptance of <span class="hlt">wind</span> power systems at the present time are analyzed.</p> <div class="credits"> <p class="dwt_author">G. M. Bragg</p> <p class="dwt_publisher"></p> <p class="publishDate">1979-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">402</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/50259236"> <span id="translatedtitle">Steady state power system issues when planning large <span class="hlt">wind</span> farms</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Issues regarding steady state power system characteristics when planning large <span class="hlt">wind</span> farms are investigated. Studies of a specific grid have been performed. A method for finding the <span class="hlt">maximum</span> <span class="hlt">wind</span> farm size at a given site is presented. The investigations show that the <span class="hlt">maximum</span> <span class="hlt">wind</span> farm capacity is highly dependent on the electrical configuration at the individual windmills. Reactive compensation increases</p> <div class="credits"> <p class="dwt_author">J. Wiik; J. O. Gjerde; T. Gjengedal; M. Gustafsson</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">403</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010ems..confE.719H"> <span id="translatedtitle"><span class="hlt">Wind</span> tunnel simulations of <span class="hlt">wind</span> turbine wake interactions in neutral and stratified <span class="hlt">wind</span> flow.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A second programme of work is about to commence as part of a further four years of funding for the UK-EPSRC SUPERGEN-<span class="hlt">Wind</span> large-<span class="hlt">wind</span>-farm consortium. The first part of the initial programme at Surrey was to establish and set up appropriate techniques for both on- and off-shore boundary layers (though with an emphasis on the latter) at a suitable scale, and to build suitable rotating model <span class="hlt">wind</span> turbines. The EnFlo <span class="hlt">wind</span> tunnel, a UK-NCAS special facility, is capable of creating scaled neutral, stable and unstable boundary layers in its 20m long working section. The model turbines are 1/300-scale of 5MW-size, speed controlled with phase-lock measurement capability, and the blade design takes into account low Reynolds-number effects. <span class="hlt">Velocity</span> measurements are primarily made using two-component LDA, combined with a cold-wire' probe in order to measure the local turbulent heat flux. Simulation of off-shore wakes is particularly constrained because i) at <span class="hlt">wind</span> tunnel scale the inherently low surface roughness can be below that for fully rough conditions, ii) the power required to stratify the flow varies as the square of the flow speed, and could easily be impractically large, iii) low blade Reynolds number. The boundary layer simulations, set up to give near-equilibrium conditions in terms of streamwise development, and the model turbines have been designed against these constraints, but not all constraints can be always met simultaneously in practice. Most measurements so far have been made behind just one or two turbines in neutral off- and on-shore boundary layers, at stations up to 12 disk diameters downstream. These show how, for example, the wake of a turbine affects the development of the wake of a downwind turbine that is laterally off-set by say half or one diameter, and how the unaffected part from the first turbine merges with the affected wake of the second. As expected a lower level of atmospheric turbulence causes the wakes to develop and fill-in more slowly compared with the on-shore case. A turbine can also suppress the level of atmospheric turbulence below hub height. In neutral flow, the wakes grow in width and height. However, even in mild stable stratification the vertical development of the wake deficit can be completely inhibited; at least some reduction would be expected arising from the stabilizing influence on vertical fluctuations. The width in contrast develops at about the same rate. As anticipated, the wake development is slower still in the stable case because of the lower level ambient turbulence. The <span class="hlt">maximum</span> deficit is at a lower height than it is for neutral flow. Various aspects of the turbulence in the wake have been investigated. Second-phase work will examine a larger number of wake-turbine and wake-wake interactions, make a more detailed study of how turbines alter the atmospheric turbulence, and examine more cases of stratification. Work is also in hand related to turbines in or near forested regions, and it is expected that aspects of the physics will have links with the effect a large <span class="hlt">wind</span> farm will have on the ABL and on the <span class="hlt">wind</span> resource for a downwind farm. The work will produce a series of test cases to assist in the development of better wake and <span class="hlt">wind</span> resource prediction models as well as a better understanding of wake physics.</p> <div class="credits"> <p class="dwt_author">Hancock, P. E.; Pascheke, F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">404</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/6739488"> <span id="translatedtitle"><span class="hlt">Wind</span> shear climatology for large <span class="hlt">wind</span> turbine generators</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Climatological <span class="hlt">wind</span> shear analyses relevant to the design and operation of multimegawatt <span class="hlt">wind</span> turbines are provided. Insight is provided for relating the <span class="hlt">wind</span> experienced by a rotating blade in a shear flow to the analysis results. A simple analysis of the <span class="hlt">wind</span> experienced by a rotating blade for three types of <span class="hlt">wind</span> shear profiles under steady-state conditions is presented in graphical form. Comparisons of the magnitude and frequency of the variations in 1) the <span class="hlt">wind</span> sensed by a single blade element, 2) the sum, and 3) the difference of the <span class="hlt">winds</span> sensed by opposite blade elements show strong sensitivity to profile shape. These three items represent forcing functions that can be related to 1) flatwise bending moment, 2) torque on the shaft, and 3) teeter angle. A computer model was constructed to simulate rotational sampling of 10-s sampled <span class="hlt">winds</span> from a tall tower for three different types of large <span class="hlt">wind</span> turbines. Time series produced by the model indicated that the forcing functions on a rotating blade vary according to the shear profile encountered during each revolution as opposed to a profile derived from average <span class="hlt">wind</span> conditions, e.g., hourly average <span class="hlt">winds</span>. An analysis scheme was developed to establish a climatology of <span class="hlt">wind</span> shear profiles derived from 10-s sampled <span class="hlt">winds</span> and hourly average <span class="hlt">winds</span> measured over a one-year period at several levels on a tall tower. Because of the sensitivity of the forcing function variability to profile shape, the analyses performed and presented are in the form of joint frequency distributions of <span class="hlt">velocity</span> differences of the the top-to-hub versus the hub-to-bottom portion of disks of rotation for the three turbine configurations.</p> <div class="credits"> <p class="dwt_author">Elliott, D.L.; Wendell, L.L.; Heflick, S.K.</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">405</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005AGUFMSA53A1153F"> <span id="translatedtitle">Observing Equatorial Thermospheric <span class="hlt">Winds</span> and Temperatures with a New Mapping Technique</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Application of the Fabry-Perot interferometer (FPI) at Arequipa, Peru (16.4S, 71.4 W) to measure the Doppler shifts and Doppler broadenings in the equatorial O(1D) 630-nm nightglow has resulted in numerous detections of a large-scale thermospheric phenomenon called the Midnight Temperature <span class="hlt">Maximum</span> (MTM). A recent detector upgrade with a CCD camera has improved the accuracy of these measurements by a factor of 5. Temperature increases of 50 to 150K have been measured during nights in April and July, 2005, with error bars less than 10K after averaging in all directions. Moreover, the meridional <span class="hlt">wind</span> measurements show evidence for a flow reversal from equatorward to poleward near local midnight for such events. A new observing strategy based upon the pioneering work of Burnside et al.[1981] maps the equatorial <span class="hlt">wind</span> and temperature fields by observing in eight equally-spaced azimuth directions, each with a zenith angle of 60 degrees. Analysis of the data obtained with this technique gives the mean <span class="hlt">wind</span> <span class="hlt">velocities</span> in the meridional and zonal directions as well as the horizontal gradients of the <span class="hlt">wind</span> field for these directions. Significant horizontal <span class="hlt">wind</span> gradients are found for the meridional direction but not for the zonal direction. The zonal <span class="hlt">wind</span> blows eastward throughout the night with a <span class="hlt">maximum</span> speed of ~150 m/s near the middle of the night and then decreases towards zero just before dawn. In general, the fastest poleward meridional <span class="hlt">wind</span> is observed near mid-evening. By the end of the night, the meridional flow tends to be more equatorward at speeds of about 50 m/s. Using the assumption that local time and longitude are equivalent over a period of 30 minutes, a map of the horizontal <span class="hlt">wind</span> field vector field is constructed over a range of 12 degrees latitude centered at 16.5 S. Comparison between MTM nights and quiet nights (no MTM) revealed significant differences in the horizontal <span class="hlt">wind</span> fields. Using the method of Fourier decomposition of the line-of-sight <span class="hlt">winds</span>, the vertical <span class="hlt">wind</span> can be retrieved from the horizontal flow divergence with a much-improved sensitivity than that represented by direct zenith measurements. The value of the vertical <span class="hlt">wind</span> speed ranges from -5 to 5 m/s. Some nights seem to present gravity wave activity with periodic fluctuations of 1-2 hours visible in the vertical <span class="hlt">winds</span> as well as in the temperature series.</p> <div class="credits"> <p class="dwt_author">Faivre, M. W.; Meriwether, J. W.; Sherwood, P.; Veliz, O.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">406</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=turbine&pg=5&id=EJ203680"> <span id="translatedtitle">A Windmill's Theoretical <span class="hlt">Maximum</span> Extraction of Power from the <span class="hlt">Wind</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">Explains that the efficiency and the useful power available from a windmill turbine, of a laminar-flow model, will vary due to rotational kinetic energy of the downwind stream and turbulent mixing from outside the boundaries of the idealized stream. (GA)</p> <div class="credits"> <p class="dwt_author">Inglis, David Rittenhouse</p> <p class="dwt_publisher"></p> <p class="publishDate">1979-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">407</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=Laminar&pg=2&id=EJ203680"> <span id="translatedtitle">A Windmill's Theoretical <span class="hlt">Maximum</span> Extraction of Power from the <span class="hlt">Wind</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">|Explains that the efficiency and the useful power available from a windmill turbine, of a laminar-flow model, will vary due to rotational kinetic energy of the downwind stream and turbulent mixing from outside the boundaries of the idealized stream. (GA)|</p> <div class="credits"> <p class="dwt_author">Inglis, David Rittenhouse</p> <p class="dwt_publisher"></p> <p class="publishDate">1979-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">408</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/57814286"> <span id="translatedtitle"><span class="hlt">Wind</span> Speed Characteristics and Resource Assessment Using Weibull Parameters</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The study utilized <span class="hlt">wind</span> speed measurements made at three heights and the Weibull parameters to study the <span class="hlt">wind</span> speed characteristics and assess the <span class="hlt">wind</span> power potential of seven sites in Saudi Arabia. Weibull shape and scale parameters were estimated using <span class="hlt">maximum</span> likelihood method. These parameters were found to fit the actual <span class="hlt">wind</span> frequency distributions with acceptable coefficient of determination (>0.95)</p> <div class="credits"> <p class="dwt_author">S. Rehman; A. M. Mahbub; Josua P. Meyer; L. M. Al-Hadhrami</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">409</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/56843654"> <span id="translatedtitle">Molecular <span class="hlt">Velocity</span> Distribution Function Measurements in a Normal Shock Wave</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Molecular <span class="hlt">velocity</span> distribution functions have been measured throughout a normal, M = 1.59 helium shock wave that was formed in a low-density <span class="hlt">wind</span> tunnel. The measurements were obtained by using the electron beam fluorescence technique. Throughout the shock transition, distributions of random <span class="hlt">velocities</span> were observed from directions both parallel and perpendicular to the flow. Also, direct measurements were made of</p> <div class="credits"> <p class="dwt_author">E. P. Muntz; L. N. Harnett</p> <p class="dwt_publisher"></p> <p class="publishDate">1969-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">410</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/26365162"> <span id="translatedtitle">CFD analysis of <span class="hlt">wind</span> environment around a human body</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The thermal and dynamic effects of <span class="hlt">wind</span> on a human body are analyzed by means of computational fluid dynamics (CFD) technique. <span class="hlt">Wind</span> effects on a human body are examined under various <span class="hlt">wind</span> conditions. At first, the human body is placed in a stagnant <span class="hlt">wind</span> environment. Secondly, the human body is set in a weak <span class="hlt">wind</span> of <span class="hlt">velocity</span> 0.25m\\/s, with several</p> <div class="credits"> <p class="dwt_author">Shuzo Murakami; Jie Zeng; Tatsuya Hayashi</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">411</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/10169730"> <span id="translatedtitle">Analysis of <span class="hlt">maximum</span> pressure attainable by water jet impact</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The <span class="hlt">maximum</span> pressure attainable in an impacting jet has been addressed by researchers for jet-cutting technology, notably in rock-drilling operations and the minimization of turbine-blade erosion. The authors have analyzed the <span class="hlt">maximum</span> pressure attainable in a liquid jet when it impinges on a rigid surface. The CALE hydrodynamics code has been used for this purpose. The calculated <span class="hlt">maximum</span> pressure for a given jet <span class="hlt">velocity</span> is higher than the so-called water-hammer value, {rho}{sub 0}C{sub 0}V where the term {rho} denotes the liquid density, C the sound speed, V the flow <span class="hlt">velocity</span>, and the subscript o the undisturbed (upstream) region in the jet. However, the calculated results agree well with experimental data and with a well-known generalized water hammer pressure expression for high (as well as low) jet <span class="hlt">velocities</span>.</p> <div class="credits"> <p class="dwt_author">Reitter, T.A.; Kang, S.W.</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">412</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6197537"> <span id="translatedtitle">Analysis of <span class="hlt">maximum</span> pressure attainable by water jet impact</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The <span class="hlt">maximum</span> pressure attainable in an impacting jet has been addressed by researchers for jet-cutting technology, notably in rock-drilling operations and the minimization of turbine-blade erosion. The authors have analyzed the <span class="hlt">maximum</span> pressure attainable in a liquid jet when it impinges on a rigid surface. The CALE hydrodynamics code has been used for this purpose. The calculated <span class="hlt">maximum</span> pressure for a given jet <span class="hlt">velocity</span> is higher than the so-called water-hammer value, [rho][sub 0]C[sub 0]V where the term [rho] denotes the liquid density, C the sound speed, V the flow <span class="hlt">velocity</span>, and the subscript o the undisturbed (upstream) region in the jet. However, the calculated results agree well with experimental data and with a well-known generalized water hammer pressure expression for high (as well as low) jet <span class="hlt">velocities</span>.</p> <div class="credits"> <p class="dwt_author">Reitter, T.A.; Kang, S.W.</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">413</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/ja/v080/i031/JA080i031p04181/JA080i031p04181.pdf"> <span id="translatedtitle">Solar <span class="hlt">Wind</span> Electrons</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Average characteristics of solar <span class="hlt">wind</span> electron <span class="hlt">velocity</span> distributions as well as the range and nature of their variations are presented. The measured distributions are generally symmetric about the heat flux direction and are adequately parameterized by the superposition of a nearly bi-Maxwellian function which characterizes the low-energy electrons and a bi-Maxwellian function which characterizes a distinct, ubiquitous component of higher-energy</p> <div class="credits"> <p class="dwt_author">W. C. Feldman; J. R. Asbridge; S. J. Bame; M. D. Montgomery; S. P. Gary</p> <p class="dwt_publisher"></p> <p class="publishDate">1975-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">414</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5200116"> <span id="translatedtitle"><span class="hlt">Wind</span> turbine system</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">A <span class="hlt">wind</span> turbine system utilizes a bicycle wheel type turbine having airfoils mounted on various spoke pairs. The vertical yaw axis lies in the horizontal projection of the airfoils to offer better control of the system; for example, automatic stowage in the case of excessive <span class="hlt">wind</span> is provided since the superstructure of the turbine provides a torque around the vertical yaw axis which moves the wheel into a stowed position. At the same time, the wheel diameter can be made larger and thus heavier since the drive connection to the generator also helps support the weight of the wheel, since it is a rim drive. Greater electrical generation is also provided since an air scoop facing into the <span class="hlt">wind</span> allows the effective generator capacity to be increased with air <span class="hlt">velocity</span>. Lastly, the radial rate of change of the angle of the airfoils can be closely controlled.</p> <div class="credits"> <p class="dwt_author">Smith, O.J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-05-18</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">415</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ams.confex.com/ams/pdfpapers/94494.pdf"> <span id="translatedtitle">Impact of Assimilation of Doppler Radial <span class="hlt">Velocity</span> on a Variational System and on its Forecasts</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">An approach to the assimilation of Doppler radar radial <span class="hlt">winds</span> into a high resolution Numerical Weather Prediction (NWP) model is described. In this paper, we discuss the types of errors which might occur in radar radial <span class="hlt">winds</span>. A new approach to specifying the radial <span class="hlt">velocity</span> observation error is proposed based upon the radial gradient of the <span class="hlt">velocity</span> across the pulse</p> <div class="credits"> <p class="dwt_author">Fathalla A. Rihana; Chris G. Collier; Sue P. Ballard</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">416</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/6060322"> <span id="translatedtitle">Using a new characterization of turbulent <span class="hlt">wind</span> for accurate correlation of <span class="hlt">wind</span> turbine response with <span class="hlt">wind</span> speed</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The turbulence encountered by a point on a rotating <span class="hlt">wind</span> turbine blade has characteristics that in some important respects are different from those measured by a stationary anemometer. The conventional one-peaked continuous spectrum becomes, broadly, a two-peaked spectrum that in addition contains a set of narrow-band spikes of turbulence energy, one centered on the frequency of rotor rotation and the others centered on multiples of that frequency. The rotational sampling effect on <span class="hlt">wind</span> spectra is quantified using measurements of <span class="hlt">wind</span> <span class="hlt">velocity</span> by anemometers on stationary crosswind circular arrays. Characteristics of fluctuating <span class="hlt">wind</span> are compared to measured fluctuations of bending moments of the rotor blades and power output fluctuations of a horizontal-axis <span class="hlt">wind</span> turbine at the same site. The <span class="hlt">wind</span> characteristics and the correlations between <span class="hlt">wind</span> fluctuations and <span class="hlt">wind</span> turbine fluctuations provide a basis for improving turbine design, siting, and control. 6 refs., 11 figs., 1 tab.</p> <div class="credits"> <p class="dwt_author">Connell, J.R.; George, R.L.</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">417</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/656123"> <span id="translatedtitle">Validation of a UHF spaced antenna <span class="hlt">wind</span> profiler for high-resolution boundary layer observations</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">In this paper we apply a spaced antenna technique derived from the recent work of {ital Doviak} {ital et al.} and {ital Holloway} {ital et al.} to <span class="hlt">wind</span> measurement with a small UHF boundary layer profiler. We discuss the implementation of the technique, averaging and quality control strategies, and some advantages and limitations of spaced antenna methods over conventional Doppler beam swinging <span class="hlt">wind</span> profilers in the boundary layer. Such advantages include a relaxation of the assumption of a horizontally uniform <span class="hlt">wind</span> field and the possibility of high temporal resolution <span class="hlt">wind</span> profiles. In this regard we present <span class="hlt">velocity</span> measurements derived from this UHF system with time resolution of about 30 s and compare these measurements with in situ sonic anemometer data taken on a 300-m tower. Finally, we present an example of a high-resolution time-height cross section of atmospheric <span class="hlt">winds</span>. This example, collected in stratiform precipitation, shows the intriguing situation of a <span class="hlt">wind</span> speed <span class="hlt">maximum</span> (jet) which closely follows the height of the melting layer over several hours even as this height changes by several hundred meters.{copyright} 1997 American Geophysical Union</p> <div class="credits"> <p class="dwt_author">Cohn, S.A. [NCAR Atmospheric Technology Division, Boulder, Colorado (United States); Holloway, C.L. [NTIA Institute for Telecommunications Science, Boulder, Colorado (United States); Oncley, S.P. [NCAR Atmospheric Technology Division, Boulder, Colorado (United States); Doviak, R.J. [NOAA National Severe Storms Laboratory, Norman, Oklahoma (United States); Lataitis, R.J. [NOAA Environmental Technology Laboratory, Boulder, Colorado (United States)</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">418</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008A%26A...491L...1H"> <span id="translatedtitle"><span class="hlt">Winds</span> of M-type AGB stars driven by micron-sized grains</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Context: In view of the recent problem regarding the dynamical modelling of <span class="hlt">winds</span> of M-type AGB stars (insufficient radiation pressure on silicate grains), some of the basic assumptions of these models need to be re-evaluated critically. Aims: Accepting the conclusion that non-grey effects will force silicate grains to be virtually Fe-free, the viability of driving <span class="hlt">winds</span> with micron-sized Fe-free silicates, instead of small particles, is examined. Methods: Using both simple estimates and detailed dynamical atmosphere and <span class="hlt">wind</span> models, it is demonstrated that radiation pressure on Fe-free silicate grains is sufficient to drive outflows if the restriction to the small particle limit is relaxed, and prevailing thermodynamic conditions allow grains to grow to sizes in the micrometer range. Results: The predicted <span class="hlt">wind</span> properties, such as mass loss rates and outflow <span class="hlt">velocities</span>, are in good agreement with observations of M-type AGB stars. Due to a self-regulating feedback between dust condensation and <span class="hlt">wind</span> acceleration, grain growth naturally comes to a halt at particle diameters of about 1~?m. Conclusions: The most efficient grain sizes to drive <span class="hlt">winds</span> are in a rather narrow interval around 1~?m. These values are set by the wavelength range corresponding to the flux <span class="hlt">maximum</span> in typical AGB stars, and are very similar to interstellar grains.</p> <div class="credits"> <p class="dwt_author">Hfner, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">419</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5939706"> <span id="translatedtitle">Scaling <span class="hlt">wind</span> characteristics for designing small and large <span class="hlt">wind</span> turbines</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Since rotationally sampled <span class="hlt">wind</span> speed spectra are required to explain the turbulence experienced by rotating <span class="hlt">wind</span>-turbine blades, methods of estimating the shape and magnitude of the rotationally sampled <span class="hlt">wind</span>-speed spectra for different sizes of turbines have been developed. The primary model used in this paper, called STRS-2, is an empirical one that processes turbulence measurements from a single meteorologial tower at any chosen site. The secondary model used is based upon homogeneous, isotropic turbulence theory. Several examples of direct measurement of rotationally sampled <span class="hlt">wind</span> <span class="hlt">velocity</span> for small turbines are used to complement the two models. Several comparisons of the estimates of turbulence experienced by different sizes of turbines indicate that all turbines will experience previously unanticipated turublence in the higher-frequency region. Further, the character and intensity of rotational sampled <span class="hlt">wind</span> are shown to vary with the variation of turbine diameter, hub height, and rotation rate in a predictable manner.</p> <div class="credits"> <p class="dwt_author">Connell, J.R.; George, R.L.</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">420</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/50498400"> <span id="translatedtitle">DC bus control of variable speed <span class="hlt">wind</span> turbine using a buck-boost converter</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">For most of the peak power extraction methods in <span class="hlt">wind</span> turbine generation system described in the current literature, it is necessary to know the <span class="hlt">wind</span> turbine's <span class="hlt">maximum</span> power curve and the <span class="hlt">wind</span> speed measurement. These methods used the <span class="hlt">maximum</span> power curve obtained via simulations or tests for individual <span class="hlt">wind</span> turbines. This makes these methods difficult and expensive to implement in</p> <div class="credits"> <p class="dwt_author">T. Tafticht; K. Agbossou; A. Cheriti</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_20");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_21");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a onClick='return showDiv("page_5");' href="#">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">421</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..1411864R"> <span id="translatedtitle">Effect of biological soil crusts of the Sahel (Niger) on <span class="hlt">wind</span> erosion</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Biological Soil crusts (BSC) are widespread in semi arid areas like the Sahel where they are colonizing sandy soils prone to water and <span class="hlt">wind</span> erosions. This study aimed at understanding the effect of BSC on <span class="hlt">wind</span> erosion. It was performed at the ICRISAT Sahelian Center of Sadore (Niger) in an old fallow. The annual rainfall depth is around 560 mm. The experimental set up comprised five circular plots (diameter 10 m) with BSC cover varying from 5 % to 40 %. Vegetation and litter inside the experimental plots were removed without breaking the crusts during the whole experiment duration (1.5 year), while shrubs and annual grass were maintained around the plots to minimize <span class="hlt">wind</span> erosion. Both horizontal flux of <span class="hlt">wind</span>-blown sediment and <span class="hlt">wind</span> erosion threshold were measured with BSNE sand catchers and Sensit recording saltating particles impacts. Meteorological parameters such as <span class="hlt">wind</span> <span class="hlt">velocity</span> and direction and rainfall were also monitored. The measured flux followed the classical cycle of <span class="hlt">wind</span> erosion in the Sahel with a <span class="hlt">maximum</span> occurring by the beginning of the rainy season from May to July. <span class="hlt">Wind</span> erosion thresholds did not show important variation during the whole year. Moreover they are almost the same (about 13 m/s) whatever the plot, i.e. whatever the BSC cover percentage. This value is higher than that measured on cultivated field. This suggest that the threshold is likely linked to the presence of loose sand particles at the crust surface and do not represent the real threshold of BSC. In the same way, there is still not a clear relationship between the flux intensity and the BSC cover. This seems to indicate that the physical crusts colonized by BSC play also a role in the soil erodibility to <span class="hlt">wind</span> erosion as it was clearly demonstrated in the case of water erosion.</p> <div class="credits"> <p class="dwt_author">Rajot, J. L.; Paris, R.; Malam Issa, O.; Maman, A.; Abdourhamane Tour, A.; Valentin, C.; Marticorena, B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">422</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6561914"> <span id="translatedtitle">Optimum propeller <span class="hlt">wind</span> turbines</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The Prandtl-Betz-Theodorsen theory of heavily loaded airscrews has been adapted to the design of propeller windmills which are to be optimized for <span class="hlt">maximum</span> power coefficient. It is shown that the simpler, light-loading, constant-area wake assumption can generate significantly different ''optimum'' performance and geometry, and that it is therefore not appropriate to the design of propeller <span class="hlt">wind</span> turbines when operating in their normal range of high-tip-speed-to-<span class="hlt">wind</span>-speed ratio. Design curves for optimum power coefficient are presented and an example of the design of a typical two-blade optimum rotor is given.</p> <div class="credits"> <p class="dwt_author">Sanderson, R.J.; Archer, R.D.</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">423</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.6052M"> <span id="translatedtitle">Jet stream <span class="hlt">wind</span> power as a renewable energy resource: little power, big impacts</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Jet streams are regions of sustained high <span class="hlt">wind</span> speeds in the upper atmosphere and are seen by some as a substantial renewable energy resource. However, jet streams are nearly geostrophic flow, that is, they result from the balance between the pressure gradient and Coriolis force in the near absence of friction. Therefore, jet stream motion is associated with very small generation rates of kinetic energy to maintain the high <span class="hlt">wind</span> <span class="hlt">velocities</span>, and it is this generation rate that will ultimately limit the potential use of jet streams as a renewable energy resource. Here we estimate the <span class="hlt">maximum</span> limit of jet stream <span class="hlt">wind</span> power by considering extraction of kinetic energy as a term in the free energy balance of kinetic energy that describes the generation, depletion, and extraction of kinetic energy. We use this balance as the basis to quantify the <span class="hlt">maximum</span> limit of how much kinetic energy can be extracted sustainably from the jet streams of the global atmosphere as well as the potential climatic impacts of its use. We first use a simple thought experiment of geostrophic flow to demonstrate why the high <span class="hlt">wind</span> <span class="hlt">velocities</span> of the jet streams are not associated with a high potential for renewable energy generation. We then use an atmospheric general circulation model to estimate that the <span class="hlt">maximum</span> sustainable extraction from jet streams of the global atmosphere is about 7.5 TW. This estimate is about 200-times less than previous estimates and is due to the fact that the common expression for instantaneous <span class="hlt">wind</span> power 1 2?v3 merely characterizes the transport of kinetic energy by the flow, but not the generation rate of kinetic energy. We also find that when <span class="hlt">maximum</span> <span class="hlt">wind</span> power is extracted from the jet streams, it results in significant climatic impacts due to a substantial increase of heat transport across the jet streams in the upper atmosphere. This results in upper atmospheric temperature differences of >20 C, greater atmospheric stability, substantial reduction in synoptic activity, and substantial differences in surface climate. We conclude that jet stream <span class="hlt">wind</span> power does not have the potential to become a significant source of renewable energy.</p> <div class="credits"> <p class="dwt_author">Miller, L. M.; Gans, F.; Kleidon, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">424</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011ESD.....2..201M"> <span id="translatedtitle">Jet stream <span class="hlt">wind</span> power as a renewable energy resource: little power, big impacts</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Jet streams are regions of sustained high <span class="hlt">wind</span> speeds in the upper atmosphere and are seen by some as a substantial renewable energy resource. However, jet streams are nearly geostrophic flow, that is, they result from the balance between the pressure gradient and Coriolis force in the near absence of friction. Therefore, jet stream motion is associated with very small generation rates of kinetic energy to maintain the high <span class="hlt">wind</span> <span class="hlt">velocities</span>, and it is this generation rate that will ultimately limit the potential use of jet streams as a renewable energy resource. Here we estimate the <span class="hlt">maximum</span> limit of jet stream <span class="hlt">wind</span> power by considering extraction of kinetic energy as a term in the free energy balance of kinetic energy that describes the generation, depletion, and extraction of kinetic energy. We use this balance as the basis to quantify the <span class="hlt">maximum</span> limit of how much kinetic energy can be extracted sustainably from the jet streams of the global atmosphere as well as the potential climatic impacts of its use. We first use a simple thought experiment of geostrophic flow to demonstrate why the high <span class="hlt">wind</span> <span class="hlt">velocities</span> of the jet streams are not associated with a high potential for renewable energy generation. We then use an atmospheric general circulation model to estimate that the <span class="hlt">maximum</span> sustainable extraction from jet streams of the global atmosphere is about 7.5 TW. This estimate is about 200-times less than previous estimates and is due to the fact that the common expression for instantaneous <span class="hlt">wind</span> power <span style="border-bottom: 1px solid #000; vertical-align: 50%; font-size: .7em; color: #000;">1<span style="margin-left: -0.5em; margin-right: .5em; vertical-align: -15%; font-size: .7em; color: #000;">2 ?v3 merely characterizes the transport of kinetic energy by the flow, but not the generation rate of kinetic energy. We also find that when <span class="hlt">maximum</span> <span class="hlt">wind</span> power is extracted from the jet streams, it results in significant climatic impacts due to a substantial increase of heat transport across the jet streams in the upper atmosphere. This results in upper atmospheric temperature differences of >20 C, greater atmospheric stability, substantial reduction in synoptic activity, and substantial differences in surface climate. We conclude that jet stream <span class="hlt">wind</span> power does not have the potential to become a significant source of renewable energy.</p> <div class="credits"> <p class="dwt_author">Miller, L. M.; Gans, F.; Kleidon, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">425</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.A44D..08C"> <span id="translatedtitle">Flow properties around a staggered <span class="hlt">wind</span> farm. A <span class="hlt">wind</span> tunnel study</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Turbulent flow around a <span class="hlt">wind</span> farm is characterized by the coexistence and superposition of multiple <span class="hlt">wind</span> turbine wakes. The understanding of the momentum transport and <span class="hlt">velocity</span> fluctuations at different locations in the <span class="hlt">wind</span> farm is essential to improve energy production and the structural stability of the different turbines. In this study, a staggered model <span class="hlt">wind</span> farm was placed in the boundary layer <span class="hlt">wind</span> tunnel of the Saint Anthony Falls Laboratory at the University of Minnesota. The staggered <span class="hlt">wind</span> farm consisted on 10 rows in the streamwise direction by 2-3 columns. A cross-wire anemometer was used to obtain high-resolution measurements of 2 <span class="hlt">velocity</span> components (streamwise and vertical) inside and above the model staggered <span class="hlt">wind</span> farm. Full characterization of the turbulent flow was obtained at a vertical plane parallel to the flow direction through the entire <span class="hlt">wind</span> farm and at 4 spanwise vertical planes (located at 5 rotor diameter behind the 4th, 6th, 8th and the 10th row). Particle Image Velocimetry (PIV) was used at selected locations in the <span class="hlt">wind</span> turbine array to better understand transport processes. Special emphasis is placed on the description of the enhancement of the turbulence levels in the <span class="hlt">wind</span> farm as a function the number of rows of the <span class="hlt">wind</span> farm as well as the growth of the internal boundary layer induced by the <span class="hlt">wind</span> farm. The results are being used to develop new parameterizations of <span class="hlt">wind</span> turbines for high-resolution and large-scale numerical models.</p> <div class="credits"> <p class="dwt_author">Chamorro, L. P.; Arndt, R.; Sotiropoulos, F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">426</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.teachengineering.org/view_activity.php?url=collection/cub_/activities/cub_earth/cub_earth_lesson04_activity2.xml"> <span id="translatedtitle"><span class="hlt">Wind</span> Energy</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">Students learn about <span class="hlt">wind</span> energy by making a pinwheel to model a <span class="hlt">wind</span> turbine. Just like engineers, they decide where and how their turbine works best by testing it in different areas of the playground.</p> <div class="credits"> <p class="dwt_author">Integrated Teaching And Learning Program</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">427</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/52934330"> <span id="translatedtitle">Intercomparison of <span class="hlt">wind</span> measurements performed with metrockets</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Falling sphere and chaff clouds tracked by monopulse radar were compared to assess the accuracy of <span class="hlt">wind</span> measurement techniques. The accuracy of the horizontal <span class="hlt">wind</span> speed derived from the radar track of meteorological rocket payloads depends on the equilibrium fall <span class="hlt">velocity</span> of the payloads and the precision of tracking them by the radar. For inflatable passive falling spheres both effects</p> <div class="credits"> <p class="dwt_author">W. Meyer</p> <p class="dwt_publisher"></p> <p class="publishDate">1985-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">428</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.lpl.arizona.edu/%7eshowman/publications/choi-etal-2007.pdf"> <span id="translatedtitle"><span class="hlt">Velocity</span> and vorticity measurements of Jupiter's Great Red Spot using automated cloud feature tracking</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We have produced mosaics of the Great Red Spot (GRS) using images taken by the Galileo spacecraft in May 2000, and have measured the <span class="hlt">winds</span> of the GRS using an automated algorithm that does not require manual cloud tracking. Our technique yields a high-density, regular grid of <span class="hlt">wind</span> <span class="hlt">velocity</span> vectors that is advantageous over a limited number of scattered <span class="hlt">wind</span></p> <div class="credits"> <p class="dwt_author">David S. Choi; Don Banfield; Peter Gierasch; Adam P. Showman</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">429</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48757537"> <span id="translatedtitle"><span class="hlt">Wind</span> Energy</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">\\u000a The kinetic energy of <span class="hlt">wind</span> is harvested using <span class="hlt">wind</span> turbines to generate electricity. Among various renewable energy sources,\\u000a <span class="hlt">wind</span> energy is the second most technologically advanced renewable energy source; hydropower is the first. Although there is\\u000a a significant potential for converting <span class="hlt">wind</span> energy to electricity, a number of issues must be addressed before it can be used\\u000a to its full</p> <div class="credits"> <p class="dwt_author">Tushar K. Ghosh; Mark A. Prelas</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">430</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/52094892"> <span id="translatedtitle">Aeroacoustic noise measurements in <span class="hlt">wind</span> tunnel</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The paper describes the general characteristics of the lowspeed Acoustic Research <span class="hlt">Wind</span> Tunnel constructed in the Aerodynamics Laboratory of E.N.S.M.A (poitiers\\/France) and presents the results of the preliminary experiments conducted in this <span class="hlt">wind</span> tunnel. The <span class="hlt">wind</span> tunnel is of open test section, open circuit and blower type. It has a test section of 30x30 sq cm and a mean <span class="hlt">velocity</span></p> <div class="credits"> <p class="dwt_author">H. N. Alemdaroglu</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">431</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54233861"> <span id="translatedtitle"><span class="hlt">Wind</span> energy</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The 1972 Solar Energy Panel of NASA and the National Science Foundation estimated the potential <span class="hlt">wind</span> power available in the U.S. to be about 100,000 gigawatts, which is 30 times greater than the projected energy consumption for 1980. <span class="hlt">Wind</span> energy is discussed with a view of providing a practical foundation and guide to the analysis and application of <span class="hlt">wind</span> energy</p> <div class="credits"> <p class="dwt_author">B. Wolff; H. Meyer</p> <p class="dwt_publisher"></p> <p class="publishDate">1978-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">432</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..1413024O"> <span id="translatedtitle">Assessing the effects of the vegetation pattern and topography on the <span class="hlt">wind</span>-driven sediment flux by GIS and Geostatistics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The assessment of vegetation pattern is important as a physical parameter in the research of <span class="hlt">wind</span> erosion, which is one of land degradation problems in semi-arid regions. The role of vegetation shelters is to protect soils from the corrosive effects of the <span class="hlt">wind</span> and to capture the sediments transported from the neighboring land. In this study, we aimed to investigate the effects of vegetation pattern and topography on sediment flux by the <span class="hlt">wind</span> erosion process in a plot scale, using GIS and Geostatistics. The study was performed in Karapinar <span class="hlt">Wind</span> Erosion Research Station, Konya, Turkey where the <span class="hlt">wind</span> erosion is the most degrading land process. The sediment fluxes were randomly measured in the research area of 0.25 ha with the BEST sediment traps. In the measuring period, two erosive events were recorded and the amount of transported sediments was calculated. The obtained <span class="hlt">maximum</span> <span class="hlt">wind</span> <span class="hlt">velocity</span> in the events were 10.03 m s-1 (average <span class="hlt">velocity</span> is 3.64) and 8.19 m s-1 (average <span class="hlt">velocity</span> is 4.87 m s-1), respectively. First event continued one hour and 25 minutes; and the <span class="hlt">maximum</span> sediment flux was 813.96 gr m-2 (8.16 t ha-1) for the plot with intense vegetation cover. However, the sediment flux was 3633.24 gr m-2 (356.32 t ha-1) for the plot with no vegetation. The other <span class="hlt">wind</span> storm continued 8 hour and 3 min; and the <span class="hlt">maximum</span> sediment flux was 2755 gr m-2 (27.56 t ha-1) and 4677.70 gr m-2 (46.76 t ha-1) for the plots with and without vegetation, respectively. Using point measurements of the sediment fluxes, the spatial distribution of dust was also mapped by the GIS and Geostatistics technologies in each event. These results of the spatial analysis indicated that the sediment flux decreased significantly at both outside and inside of the vegetated plot depending upon the pattern of the plants. Key words: Vegetation pattern, topography, <span class="hlt">wind</span> erosion, sediment flux, Geostatistics, GIS Acknowledgement Authors gratefully acknowledge the "The Scientific and Technological Research Council of Turkey" (TUBITAK) for providing support within the frame of the project of TOVAG 110O296.</p> <div class="credits"> <p class="dwt_author">Ozcan, A. U.; Oguzhan, U.; Sayg?n Deviren, S.; Gharahassanlou, A. N.; Youssef, F.; Basaran, M.; Erpul, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">433</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60330399"> <span id="translatedtitle">Discrete time blade pitch control for <span class="hlt">wind</span> turbine torque regulation with digitally simulated random turbulence excitation</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A time domain simulation model that approximates the three-dimensional <span class="hlt">velocity</span> fluctuations of <span class="hlt">wind</span> turbulence was developed. This model is used in a discrete time control algorithm to regulate the output torque of a <span class="hlt">wind</span> turbine by changing the pitch angle of the turbine blade. The <span class="hlt">wind</span> model provides a <span class="hlt">velocity</span> field that varies randomly with time and space and gives</p> <div class="credits"> <p class="dwt_author">Sharif-Razi</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">434</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/wn7p210778474664.pdf"> <span id="translatedtitle">Impact of <span class="hlt">wind</span> direction on diurnal and seasonal changes in <span class="hlt">wind</span> profiles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We explored the relationship between directional variation (changes in direction from a reference point) in vegetation and\\u000a <span class="hlt">wind</span> profiles, and propose an empirical <span class="hlt">wind</span> profile model that may reproduce the <span class="hlt">wind</span> profile within the canopy (such as\\u000a secondary <span class="hlt">wind</span> <span class="hlt">maximum</span>) and reduce calculation loads. Based on the results of our observations in secondary broad-leaved forest,\\u000a we clarified the variation in</p> <div class="credits"> <p class="dwt_author">Kenichi Daikoku; Shigeaki Hattori; Aiko Deguchi; Yuji Fujita; Kazuho Matsumoto</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">435</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA576317"> <span id="translatedtitle">Observed Near-Surface Currents Under High <span class="hlt">Wind</span> Speeds.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">From the Surface <span class="hlt">Velocity</span> Program (SVP) drifter current and QuikSCAT <span class="hlt">wind</span> data, the relationship between the observed near-surface current vectors and surface <span class="hlt">wind</span> vectors for the northwestern Pacific Ocean under high <span class="hlt">winds</span> (20 50 m s expn -1) are obtaine...</p> <div class="credits"> <p class="dwt_author">G. Chen L. R. Centurioni P. C. Chu R. Tseng Y. Chang</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">436</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/ja/v076/i022/JA076i022p05316/JA076i022p05316.pdf"> <span id="translatedtitle">DIRECT OBSERVATIONS OF THERMOSPHERIC <span class="hlt">WINDS</span> DURING GEOMAGNETIC STORMS</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Direct measurements of thermospheric <span class="hlt">winds</span> were made during two geomagnetic storms. <span class="hlt">Winds</span> were detected (a) in the stable auroral red arc of October 31 to November 1, 1968, and (b) during the aurora .of May 14-15, 1969. In both storms the measured <span class="hlt">winds</span> were from the north and persisted throughout the night with a <span class="hlt">velocity</span> between 250 and 400 m</p> <div class="credits"> <p class="dwt_author">P. B. Hays; R. G. Roble</p> <p class="dwt_publisher"></p> <p class="publishDate">1971-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">437</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60334726"> <span id="translatedtitle"><span class="hlt">Wind</span> characteristics at the Vawt Test Facility. [New Mexico</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A limited program of field measurements was undertaken in order to define the <span class="hlt">wind</span> characteristics of the DOE\\/Sandia vertical axis <span class="hlt">wind</span> turbine test facility. Because micrometeorological conditions under which a particular <span class="hlt">wind</span> turbine is tested may have an effect on the performance of that turbine, it is important that these conditions be properly documented. The mean <span class="hlt">velocity</span> profile, longitudinal and</p> <div class="credits"> <p class="dwt_author">Akins</p> <p class="dwt_publisher"></p> <p class="publishDate">1978-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">438</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.me.iitb.ac.in/~shashisn/research/papers/suryanarayanan_acc2005.pdf"> <span id="translatedtitle">On Pitch Control of Horizontal-Axis Large <span class="hlt">Wind</span> Turbines</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"> Most commercial large <span class="hlt">wind</span> turbines use blade pitch action to mitigate structural loads in high <span class="hlt">wind</span> <span class="hlt">velocity</span> conditions. In this paper, we study the linearized dynamics of the map from blade pitch to tower top fore-aft deection in horizontal-axis <span class="hlt">wind</span> turbines. We show that the mass and stiffness distribution of the blades at certain operating conditions determine the presence</p> <div class="credits"> <p class="dwt_author">Shashikanth Suryanarayanan; Amit Dixit</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">439</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54833827"> <span id="translatedtitle">Kinetic Models of the Solar <span class="hlt">Wind</span>: Achievements and Fundamental Questions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Recent kinetic models of the solar corona and of the solar <span class="hlt">wind</span> will be presented with emphasis on the characteristics of the particle <span class="hlt">velocity</span> distribution function (VDF). ULYSSES and <span class="hlt">WIND</span> have observed that the VDF of the solar <span class="hlt">wind</span> particles deviate significantly from Maxwellians. Using exospheric collisionless models based on the solution of Vlasov equation, we show that the presence</p> <div class="credits"> <p class="dwt_author">V. Pierrard</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">440</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oceandatacenter.ucsc.edu/reprints/Kochanski_WEST_061606.pdf"> <span id="translatedtitle">1 Comparison of <span class="hlt">Wind</span> Stress Algorithms and Their Influence on <span class="hlt">Wind</span> Stress Curl Using Buoy Measurements over the Shelf off Bodega Bay, California</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The main objectives of this study were to compare three <span class="hlt">wind</span> stress algorithms of varying intricacy and estimate the extent to which each method altered computed <span class="hlt">wind</span> stress curl. The algorithms included (1) a simple bulk formula for neutral conditions that is dependent only on <span class="hlt">wind</span> <span class="hlt">velocity</span> components; (2) a formula that in addition to dependence on <span class="hlt">wind</span> components includes</p> <div class="credits"> <p class="dwt_author">Adam Kochanski; E. Dorman</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_21");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a onClick='return showDiv("page_5");' href="#">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a style="font-weight: bold;">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_23");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> </div><!-- page_22 div --> <div id="page_23" class="hiddenDiv"> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_22");' hr