Data Driven Modelling of the Dynamic Wake Between Two Wind Turbines

DEFF Research Database (Denmark)

Knudsen, Torben; Bak, Thomas

2012-01-01

turbine. This paper establishes flow models relating the wind speeds at turbines in a farm. So far, research in this area has been mainly based on first principles static models and the data driven modelling done has not included the loading of the upwind turbine and its impact on the wind speed downwind......Wind turbines in a wind farm, influence each other through the wind flow. Downwind turbines are in the wake of upwind turbines and the wind speed experienced at downwind turbines is hence a function of the wind speeds at upwind turbines but also the momentum extracted from the wind by the upwind....... This paper is the first where modern commercial mega watt turbines are used for data driven modelling including the upwind turbine loading by changing power reference. Obtaining the necessary data is difficult and data is therefore limited. A simple dynamic extension to the Jensen wake model is tested...

Dynamic Performance of the Standalone Wind Power Driven Heat Pump

OpenAIRE

H. Li; P.E. Campana; S. Berretta; Y. Tan; J. Yan

2016-01-01

Reducing energy consumption and increasing use of renewable energyin the building sector arecrucial to the mitigation of climate change. Wind power driven heat pumps have been considered as a sustainable measure to supply heat for detached houses, especially those that even don’t have access to the grid. This work is to investigate the dynamic performance of a heat pump system directly driven by a wind turbine. The heat demand of a detached single family house was simulated in details. Accord...

γ-irradiation induces radioresistant DNA synthesis in HeLa cells

International Nuclear Information System (INIS)

Synzynys, B.I.; Aminev, A.G.; Konstantinova, S.A.; Saenko, A.S.

1987-01-01

Cells of suspension HeLa culture at the logarithmic phase of growth were exposed to 60 Co-γ-rays (5 Gy), incubated in the nutritious medium, and in 4 h subjected to repeated irradiation: the dose-response function and the dynamics of DNA synthesis inhibition were determined. It was shown that DNA synthesis was inhibited to a lesser extent after preirradiation, in other words, DNA synthesis was radioresistant. A correlation between this synthesis and reproductive cell death is discussed

An Overview of Wind-Driven Rovers for Planetary Exploration

Science.gov (United States)

Hajos, Gregory A.; Jones, Jack A.; Behar, Alberto; Dodd, Micheal

2005-01-01

The use of in-situ propulsion is considered enabling technology for long duration planetary surface missions. Most studies have focused on stored energy from chemicals extracted from the soil or the use of soil chemicals to produce photovoltaic arrays. An older form of in-situ propulsion is the use of wind power. Recent studies have shown potential for wind driven craft for exploration of Mars, Titan and Venus. The power of the wind, used for centuries to power wind mills and sailing ships, is now being applied to modern land craft. Efforts are now underway to use the wind to push exploration vehicles on other planets and moons in extended survey missions. Tumbleweed rovers are emerging as a new type of wind-driven science platform concept. Recent investigations by the National Aeronautics and Space Administration (NASA) and Jet Propulsion Laboratory (JPL) indicate that these light-weight, mostly spherical or quasi-spherical devices have potential for long distance surface exploration missions. As a power boat has unique capabilities, but relies on stored energy (fuel) to move the vessel, the Tumbleweed, like the sailing ships of the early explorers on earth, uses an unlimited resource the wind to move around the surface of Mars. This has the potential to reduce the major mass drivers of robotic rovers as well as the power generation and storage systems. Jacques Blamont of JPL and the University of Paris conceived the first documented Mars wind-blown ball in 1977, shortly after the Viking landers discovered that Mars has a thin CO2 atmosphere with relatively strong winds. In 1995, Jack Jones, et al, of JPL conceived of a large wind-blown inflated ball for Mars that could also be driven and steered by means of a motorized mass hanging beneath the rolling axis of the ball. A team at NASA Langley Research Center started a biomimetic Tumbleweed design study in 1998. Wind tunnel and CFD analysis were applied to a variety of concepts to optimize the aerodynamic

Galactic Winds Driven by Supernovae and Radiation Pressure: Theory and Simulations

Science.gov (United States)

Zhang, Dong; Davis, Shane

2018-01-01

Galactic winds are ubiquitous in most rapidly star-forming galaxies. They are crucial to the process of galaxy formation and evolution, regulating star formation, shaping the stellar mass function and the mass-metallicity relation, and enriching the intergalactic medium with metals. Although important, the physics of galactic winds is still unclear. Winds may be driven by many mechanisms including overlapping supernovae explosions, radiation pressure of starlight on dust grains, and cosmic rays. However, the growing observations of multiphase structure in galactic winds in a large number of galaxies have not been well explained by any models. In this talk I will focus on the models of supernova- and radiation-pressure-driven winds. Using the state-of-the-art numerical simulations, I will assess the relative merits of these driving mechanisms for accelerating cold and warm clouds to observed velocities, and momentum flux boost during wind propagation.

Theory of radiatively driven stellar winds. I. A physical interpretation

International Nuclear Information System (INIS)

Abbott, D.C.

1980-01-01

This series of papers extends the line-driven wind theory of Castor, Abbott, and Klein (CAK). The present paper develops a physical interpretation of line-driven flows using analytic methods. Numerical results will follow in two subsequent papers

Wind-driven stand-alone DFIG with battery and pumped hydro ...

Indian Academy of Sciences (India)

Renewable energy electric conversion system; induction generators; wind power generation; energy storage; power converters. ... converter, (ii) wide speed operation of wind-driven DFIG, (iii) reduced battery capacity, (iv) high energy storage using PHSP and (v) availability of continuous power to the isolated loads.

Solar wind contribution to the average population of energetic He+ and He++ ions in the Earth's magnetosphere

Directory of Open Access Journals (Sweden)

G. Kremser

Full Text Available Measurements with the ion charge-energy-mass spectrometer CHEM on the AMPTE/CCE spacecraft were used to investigate the origin of energetic He⁺ and He⁺⁺ ions observed in the equatorial plane at 3 ≤ L ≤ 9. Special emphasis was laid on the dependence of long-term average distributions on magnetic local time (MLT and the geomagnetic activity index K_p. The observations are described in terms of the phase space densities f₁ (for He⁺ and f₂ (for He⁺⁺. They confirm preliminary results from a previous study: f₁ is independent of MLT, whereas f₂ is much larger on the nightside than on the dayside. They show, furthermore, that f₁ increases slightly with K_p on intermediate drift shells, but decreases on high drift shells (L ≥ 7. f₂ increases with K_p on all drift shells outside the premidnight sector. Within this sector a decrease is observed on high drift shells. A simple ion tracing code was developed to determine how and from where the ions move into the region of observations. It provides ion trajectories as a function of the ion charge, the magnetic moment and K_p. The ion tracing enables a distinction between regions of closed drift orbits (ring current and open convection trajectories (plasma sheet. It also indicates how the outer part of the observation region is connected to different parts of the more distant plasma sheet. Observations and tracing show that He⁺⁺ ions are effectively transported from the plasma sheet on convection trajectories. Their distribution in the observation region corresponds to the distribution of solar wind ions in the plasma sheet. Thus, energetic He⁺⁺ ions most likely originate in the solar wind. On the other hand, the plasma sheet is not an

Wind-driven Water Bodies : a new paradigm for lake geology

Science.gov (United States)

Nutz, A.; Schuster, M.; Ghienne, J. F.; Roquin, C.; Bouchette, F. A.

2015-12-01

In this contribution we emphasize the importance in some lakes of wind-related hydrodynamic processes (fair weather waves, storm waves, and longshore, cross-shore and bottom currents) as a first order forcing for clastics remobilization and basin infill. This alternative view contrasts with more classical depositional models for lakes where fluvial-driven sedimentation and settling dominates. Here we consider three large lakes/paleo-lakes that are located in different climatic and geodynamic settings: Megalake Chad (north-central Africa), Lake Saint-Jean (Québec, Canada), and Lake Turkana (Kenya, East African Rift System). All of these three lake systems exhibit well developed modern and ancient high-energy littoral morphosedimentary structures which directly derive from wind-related hydrodynamics. The extensive paleo-shorelines of Megalake Chad are composed of beach-foredune ridges, spits, wave-dominated deltas, barriers, and wave-ravinment surface. For Lake Saint-Jean the influence of wind is also identified below the wave-base at lake bottom from erosional surfaces, and sediment drifts. In the Lake Turkana Basin, littoral landforms and deposits are identified for three different time intervals (today, Holocene, Plio-Pleistocene) evidencing that wind-driven hydrodynamics can be preserved in the geological record. Moreover, a preliminary global survey suggests that numerous modern lakes (remote sensing) and paleo-lakes (bibliographic review) behave as such. We thus coin the term "Wind-driven Water Bodies" (WWB) to refer to those lake systems where sedimentation (erosion, transport, deposition) is dominated by wind-induced hydrodynamics at any depth, as it is the case in the marine realm for shallow seas. Integrating wind forcing in lake models has strong implications for basin analysis (paleoenvironments and paleoclimates restitutions, resources exploration), but also for coastal engineering, wildlife and reservoirs management, or leisure activities.

A review on wind-driven rain research in building science

NARCIS (Netherlands)

Blocken, B.J.E.; Carmeliet, J.E.

2004-01-01

Wind-driven rain (WDR) or driving rain is rain that is given a horizontal velocity component by the wind. WDR research is of importance in a number of research areas including earth sciences, meteorology and building science. Research methods and results are exchangeable between these domains but no

Majority of Solar Wind Intervals Support Ion-Driven Instabilities

Science.gov (United States)

Klein, K. G.; Alterman, B. L.; Stevens, M. L.; Vech, D.; Kasper, J. C.

2018-05-01

We perform a statistical assessment of solar wind stability at 1 AU against ion sources of free energy using Nyquist's instability criterion. In contrast to typically employed threshold models which consider a single free-energy source, this method includes the effects of proton and He2 + temperature anisotropy with respect to the background magnetic field as well as relative drifts between the proton core, proton beam, and He2 + components on stability. Of 309 randomly selected spectra from the Wind spacecraft, 53.7% are unstable when the ion components are modeled as drifting bi-Maxwellians; only 4.5% of the spectra are unstable to long-wavelength instabilities. A majority of the instabilities occur for spectra where a proton beam is resolved. Nearly all observed instabilities have growth rates γ slower than instrumental and ion-kinetic-scale timescales. Unstable spectra are associated with relatively large He2 + drift speeds and/or a departure of the core proton temperature from isotropy; other parametric dependencies of unstable spectra are also identified.

Dynamics of Line-Driven Winds from Disks in Cataclysmic Variables. I. Solution Topology and Wind Geometry

OpenAIRE

Feldmeier, Achim; Shlosman, Isaac

1999-01-01

We analyze the dynamics of 2-D stationary, line-driven winds from accretion disks in cataclysmic variable stars. The driving force is that of line radiation pressure, in the formalism developed by Castor, Abbott & Klein for O stars. Our main assumption is that wind helical streamlines lie on straight cones. We find that the Euler equation for the disk wind has two eigenvalues, the mass loss rate and the flow tilt angle with the disk. Both are calculated self-consistently. The wind is characte...

Laser-sheet imaging of HE-driven interfaces

International Nuclear Information System (INIS)

Benjamin, R.F.; Rightley, P.M.; Kinkead, S.; Martin, R.A.; Critchfield, R.; Sandoval, D.L.; Holmes, R.; Gorman, T.

1998-01-01

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors made substantial progress in developing the MILSI (Multiple Imaging of Laser-Sheet Illumination) technique for high explosive (HE)-driven fluid interfaces. They observed the instability, but have not yet measured the instability growth rate. They developed suitable sample containers and optical systems for studying the Rightmyer-Meshkov instability of perturbed water/bromoform interfaces and they successfully fielded the new MILSI diagnostic at two firing-site facilities. The problem continues to be of central importance to the inertial confinement fusion (ICF) and weapons physics communities

Radiatively driven relativistic spherical winds under relativistic radiative transfer

Science.gov (United States)

Fukue, J.

2018-05-01

We numerically investigate radiatively driven relativistic spherical winds from the central luminous object with mass M and luminosity L* under Newtonian gravity, special relativity, and relativistic radiative transfer. We solve both the relativistic radiative transfer equation and the relativistic hydrodynamical equations for spherically symmetric flows under the double-iteration processes, to obtain the intensity and velocity fields simultaneously. We found that the momentum-driven winds with scattering are quickly accelerated near the central object to reach the terminal speed. The results of numerical solutions are roughly fitted by a relation of \\dot{m}=0.7(Γ _*-1)\\tau _* β _* β _out^{-2.6}, where \\dot{m} is the mass-loss rate normalized by the critical one, Γ* the central luminosity normalized by the critical one, τ* the typical optical depth, β* the initial flow speed at the central core of radius R*, and βout the terminal speed normalized by the speed of light. This relation is close to the non-relativistic analytical solution, \\dot{m} = 2(Γ _*-1)\\tau _* β _* β _out^{-2}, which can be re-expressed as β _out^2/2 = (Γ _*-1)GM/c^2 R_*. That is, the present solution with small optical depth is similar to that of the radiatively driven free outflow. Furthermore, we found that the normalized luminosity (Eddington parameter) must be larger than unity for the relativistic spherical wind to blow off with intermediate or small optical depth, i.e. Γ _* ≳ \\sqrt{(1+β _out)^3/(1-β _out)}. We briefly investigate and discuss an isothermal wind.

Numerical model for wind-driven circulation in the Bay of Bengal

Digital Repository Service at National Institute of Oceanography (India)

Bahulayan, N.; Varadachari, V.V.R.

Wind-driven circulation in the Bay of Bengal, generated by a southwest wind of constant speed (10 m.sec -1) and direction (225 degrees TN), is presented. A non-linear hydrodynamic model is used for the simulation of circulation. Numerical...

Wind driven saltation: a hitherto overlooked challenge for life on Mars

Science.gov (United States)

Bak, Ebbe; Goul, Michael; Rasmussen, Martin; Moeller, Ralf; Nørnberg, Per; Knak Jensen, Svend; Finster, Kai

2017-04-01

The Martian surface is a hostile environment characterized by low water availability, low atmospheric pressure and high UV and ionizing radiation. Furthermore, wind-driven saltation leads to abrasion of silicates with a production of reactive surface sites and, through triboelectric charging, a release of electrical discharges with a concomitant production of reactive oxygen species. While the effects of low water availability, low pressure and radiation have been extensively studied in relation to the habitability of the Martian surface and the preservation of organic biosignatures, the effects of wind-driven saltation have hitherto been ignored. In this study, we have investigated the effect of exposing bacteria to wind-abraded silicates and directly to wind-driven saltation on Mars in controlled laboratory simulation experiments. Wind-driven saltation was simulated by tumbling mineral samples in a Mars-like atmosphere in sealed quartz ampoules. The effects on bacterial survival and structure were evaluated by colony forming unit counts in combination with scanning electron microscopy, quantitative polymerase chain reaction and life/dead-staining with flow cytometry. The viability of vegetative cells of P. putida, B. subtilis and D. radiodurans in aqueous suspensions was reduced by more than 99% by exposure to abraded basalt, while the viability of B. subtilis endospores was unaffected. B. subtilis mutants lacking different spore components were likewise highly resistant to the exposure to abraded basalt, which indicates that the resistance of spores is not associated with any specific spore component. We found a significant but reduced effect of abraded quartz and we suggest that the stress effect of abraded silicates is induced by a production of reactive oxygen species and hydroxyl radicals produced by Fenton-like reactions in the presence of transition metals. Direct exposure to simulated saltation had a dramatic effect on both D. radiodurans cells and B

The Stability Analysis and New Torque Control Strategy of Direct-Driven PMSG Wind Turbines

OpenAIRE

Jun Liu; Feihang Zhou; Gungyi Wang

2016-01-01

This paper expounds on the direct-driven PMSG wind power system control strategy, and analyses the stability conditions of the system. The direct-driven PMSG wind power system may generate the intense mechanical vibration, when wind speed changes dramatically. This paper proposes a new type of torque control strategy, which increases the system damping effectively, mitigates mechanical vibration of the system, and enhances the stability conditions of the system. The simulation results verify ...

Wind-Driven Wireless Networked System of Mobile Sensors for Mars Exploration

Science.gov (United States)

Davoodi, Faranak; Murphy, Neil

2013-01-01

A revolutionary way is proposed of studying the surface of Mars using a wind-driven network of mobile sensors: GOWON. GOWON would be a scalable, self-powered and autonomous distributed system that could allow in situ mapping of a wide range of environmental phenomena in a much larger portion of the surface of Mars compared to earlier missions. It could improve the possibility of finding rare phenomena such as "blueberries' or bio-signatures and mapping their occurrence, through random wind-driven search. It would explore difficult terrains that were beyond the reach of previous missions, such as regions with very steep slopes and cluttered surfaces. GOWON has a potentially long life span, as individual elements can be added to the array periodically. It could potentially provide a cost-effective solution for mapping wide areas of Martian terrain, enabling leaving a long-lasting sensing and searching infrastructure on the surface of Mars. The system proposed here addresses this opportunity using technology advances in a distributed system of wind-driven sensors, referred to as Moballs.

Analysis of wind driven self-excited induction generator supplying isolated DC loads

Directory of Open Access Journals (Sweden)

Khaled S. Sakkoury

2017-05-01

Full Text Available This paper presents the analysis, modelling and simulation of wind-driven self-excited induction generator (SEIG. The three-phase SEIG is driven by a variable-speed prime mover to represent a wind turbine. Also, the paper investigates the dynamic performance of the SEIG during start-up, increasing or decreasing the load or rotor speed. The value of the excitation capacitance required for the SEIG is calculated to give suitable saturation level to assure self-excitation and to avoid heavy saturation levels. Matching of the maximum power available from the wind turbine is performed through varying the load value. The effect of AC–DC power conversion on the generator is investigated. The system simulation is carried out using MATLAB/SIMULINK toolbox program.

Assisted stellar suicide: the wind-driven evolution of the recurrent nova T Pyxidis

Science.gov (United States)

Knigge, Ch.; King, A. R.; Patterson, J.

2000-12-01

We show that the extremely high luminosity of the short-period recurrent nova T Pyx in quiescence can be understood if this system is a wind-driven supersoft x-ray source (SSS). In this scenario, a strong, radiation-induced wind is excited from the secondary star and accelerates the binary evolution. The accretion rate is therefore much higher than in an ordinary cataclysmic binary at the same orbital period, as is the luminosity of the white dwarf primary. In the steady state, the enhanced luminosity is just sufficient to maintain the wind from the secondary. The accretion rate and luminosity predicted by the wind-driven model for T Pyx are in good agreement with the observational evidence. X-ray observations with Chandra or XMM may be able to confirm T Pyx's status as a SSS. T Pyx's lifetime in the wind-driven state is on the order of a million years. Its ultimate fate is not certain, but the system may very well end up destroying itself, either via the complete evaporation of the secondary star, or in a Type Ia supernova if the white dwarf reaches the Chandrasekhar limit. Thus either the primary, the secondary, or both may currently be committing assisted stellar suicide.

Power quality issues of 3MW direct-driven PMSG wind turbine

OpenAIRE

Ahmed, IA; Zobaa, AF; Taylor, GA

2015-01-01

This paper presents power quality issues of a grid connected wind generation system with a MW-class direct-driven permanent magnet synchronous generator (PMSG). A variable speed wind turbine model was simulated and developed with the simulation tool of PSCAD/EMTDC. The model includes a wind turbine with one mass-model drive train model, a PMSG model and a full-scale voltage source back to back PWM converter. The converter controller model is employed in the dq-synchronous rotating reference f...

Wind turbines, is it just wind?

International Nuclear Information System (INIS)

Boiteux, M.

2012-01-01

The author first outlines that wind energy is not only random, but almost absent in extreme situations when it would be needed (for example and notably, very cold weather without wind). He suggests the association of a gas turbine to each wind turbine, so that the gas turbine will replace non operating wind turbines. He notices that wind turbines are not proximity energy as they were said to be, and that profitability in fact requires tens of grouped giant wind turbines. He also outlines the high cost of construction of grids for the connection of these wind turbines. Thus, he states that wind energy is far from being profitable in the present conditions of electricity tariffs in France

Modeling and evaluation of HE driven shock effects in copper with the MTS model

International Nuclear Information System (INIS)

Murphy, M.J.; Lassila, D.F.

1997-01-01

Many experimental studies have investigated the effect of shock pressure on the post-shock mechanical properties of OFHC copper. These studies have shown that significant hardening occurs during shock loading due to dislocation processes and twinning. It has been demonstrated that when an appropriate initial value of the Mechanical Threshold Stress (MTS) is specified, the post-shock flow stress of OFE copper is well described by relationships derived independently for unshocked materials. In this study we consider the evolution of the MTS during HE driven shock loading processes and the effect on the subsequent flow stress of the copper. An increased post shock flow stress results in a higher material temperature due to an increase in the plastic work. An increase in temperature leads to thermal softening which reduces the flow stress. These coupled effects will determine if there is melting in a shaped charge jet or a necking instability in an EFP Ww. 'Me critical factor is the evolution path followed combined with the 'current' temperature, plastic strain, and strain rate. Preliminary studies indicate that in simulations of HE driven shock with very high resolution zoning, the MTS saturates because of the rate dependence in the evolution law. On going studies are addressing this and other issues with the goal of developing a version of the MT'S model that treats HE driven, shock loading, temperature, strain, and rate effects apriori

The dependence of cosmic ray-driven galactic winds on halo mass

Science.gov (United States)

Jacob, Svenja; Pakmor, Rüdiger; Simpson, Christine M.; Springel, Volker; Pfrommer, Christoph

2018-03-01

Galactic winds regulate star formation in disc galaxies and help to enrich the circum-galactic medium. They are therefore crucial for galaxy formation, but their driving mechanism is still poorly understood. Recent studies have demonstrated that cosmic rays (CRs) can drive outflows if active CR transport is taken into account. Using hydrodynamical simulations of isolated galaxies with virial masses between 1010 and 1013 M⊙, we study how the properties of CR-driven winds depend on halo mass. CRs are treated in a two-fluid approximation and their transport is modelled through isotropic or anisotropic diffusion. We find that CRs are only able to drive mass-loaded winds beyond the virial radius in haloes with masses below 1012 M⊙. For our lowest examined halo mass, the wind is roughly spherical and has velocities of ˜20 km s-1. With increasing halo mass, the wind becomes biconical and can reach 10 times higher velocities. The mass loading factor drops rapidly with virial mass, a dependence that approximately follows a power law with a slope between -1 and -2. This scaling is slightly steeper than observational inferences, and also steeper than commonly used prescriptions for wind feedback in cosmological simulations. The slope is quite robust to variations of the CR injection efficiency or the CR diffusion coefficient. In contrast to the mass loading, the energy loading shows no significant dependence on halo mass. While these scalings are close to successful heuristic models of wind feedback, the CR-driven winds in our present models are not yet powerful enough to fully account for the required feedback strength.

New Solutions to Line-Driven Winds of Hot Massive Stars

Science.gov (United States)

Gormaz-Matamala, Alex C.; Curé, Michel; Cidale, Lydia; Venero, Roberto

2017-11-01

In the frame of radiation driven wind theory (Castor et al.1975), we present self-consistent hydrodynamical solutions to the line-force parameters (k, α, δ) under LTE conditions. Hydrodynamic models are provided by HydWind (Curé 2004). We evaluate these results with those ones previously found in literature, focusing in different regions of the optical depth to be used to perform the calculations. The values for mass-loss rate and terminal velocity obtained from our calculations are also presented. We also examine the line-force parameters for the case when large changes in ionization throughout the wind occurs (δ-slow solutions, Curé et al.2011).

Studies on battery storage requirement of PV fed wind-driven induction generators

International Nuclear Information System (INIS)

Rajan Singaravel, M.M.; Arul Daniel, S.

2013-01-01

Highlights: ► Sizing of battery storage for PV fed wind-driven IG system is taken up. ► Battery storage is also used to supply reactive power for wind-driven IG. ► Computation of LPSP by incorporating uncertainties of irradiation and wind speed. ► Sizing of hybrid power system components to ensure zero LPSP. ► Calculated storage size satisfied the constraints and improves battery life. - Abstract: Hybrid stand-alone renewable energy systems based on wind–solar resources are considered to be economically better and reliable than stand-alone systems with a single source. An isolated hybrid wind–solar system has been considered in this work, where the storage (battery bank) is necessary to supply the required reactive power for a wind-driven induction generator (IG) during the absence of power from a photovoltaic (PV) array. In such a scheme, to ensure zero Loss of Power Supply Probability (LPSP) and to improve battery bank life, a sizing procedure has been proposed with the incorporation of uncertainties in wind-speed and solar-irradiation level at the site of erection of the plant. Based on the proposed procedure, the size of hybrid power system components and storage capacity are determined. Storage capacity has been calculated for two different requirements. The first requirement of storage capacity is common to any hybrid scheme, which is; to supply both real and reactive power in the absence of wind and solar sources. The second requirement is to supply reactive power alone for the IG during the absence of photovoltaic power, which is unique to the hybrid scheme considered in this work. Storage capacity calculations for different conditions using the proposed approach, satisfies the constraints of maintaining zero LPSP and also improved cycle life of the battery bank

Predicting when precipitation-driven synthesis is feasible : application to biocatalysis

NARCIS (Netherlands)

Ulijn, R.V.; Janssen, A.E.M.; Moore, B.D.; Halling, P.J.

2001-01-01

Precipitation-driven synthesis offers the possibility of obtaining high reaction yields using very low volume reactors and is finding increasing applications in biocatalysis. Here, a model that allows straightforward prediction of when such a precipitation-driven reaction will be thermodynamically

Effects of DNA polymerase inhibitors on replicative and repair DNA synthesis in ultraviolet-irradiated HeLa cells

International Nuclear Information System (INIS)

Morita, T.; Nakamura, H.; Tsutsui, Y.; Nishiyama, Y.; Yoshida, S.

1982-01-01

Aphidicolin specifically inhibits eukaryotic DNA polymerase α, while 2',3'-dideoxythymidine 5'-triphosphate (d 2 TTP) inhibits DNA polymerase ν and ν but not α. 1-ν-D-Arabinofuranosylcytosine 5'-triphosphate (araCTP) inhibits both DNA polymerase α and ν although to a different extent. Here we measured the effects of these inhibitors on repair DNA synthesis of U.V.-irradiated HeLa cells by two different methods. Firstly, aphidicolin, 1-ν-D-arabinofuranosylcytosine (araC, a precursor of araCTP) and 2',3'-dideoxythimidine (d 2 Thd, a precursor of d 2 TTP) were added directly to the culture medium. In this case, aphidicolin and araC strongly inhibited replicative DNA synthesis of HeLa cells, and they also inhibited repair synthesis after U.V.-irradiation but to a much lesser extent. In contrast, high concentrations of d 2 Thd inhibited repair DNA synthesis to a higher extent than replicative DNA synthesis. Secondly, the active form of inhibitor, d 2 TTP, was microinjected directly into cytoplasm or nuclei or U.V.-irradiated HeLa cells. Microinjection of d 2 TTP effectively inhibited repair synthesis. The microinjection of d 2 TTP, into either cytoplasm or nucleus, strongly inhibited replicative synthesis. These results might indicate that multiple DNA polymerases are involved in repair synthesis as well as in replicative synthesis

Kinetic instabilities in the solar wind driven by temperature anisotropies

Science.gov (United States)

Yoon, Peter H.

2017-12-01

The present paper comprises a review of kinetic instabilities that may be operative in the solar wind, and how they influence the dynamics thereof. The review is limited to collective plasma instabilities driven by the temperature anisotropies. To limit the scope even further, the discussion is restricted to the temperature anisotropy-driven instabilities within the model of bi-Maxwellian plasma velocity distribution function. The effects of multiple particle species or the influence of field-aligned drift will not be included. The field-aligned drift or beam is particularly prominent for the solar wind electrons, and thus ignoring its effect leaves out a vast portion of important physics. Nevertheless, for the sake of limiting the scope, this effect will not be discussed. The exposition is within the context of linear and quasilinear Vlasov kinetic theories. The discussion does not cover either computer simulations or data analyses of observations, in any systematic manner, although references will be made to published works pertaining to these methods. The scientific rationale for the present analysis is that the anisotropic temperatures associated with charged particles are pervasively detected in the solar wind, and it is one of the key contemporary scientific research topics to correctly characterize how such anisotropies are generated, maintained, and regulated in the solar wind. The present article aims to provide an up-to-date theoretical development on this research topic, largely based on the author's own work.

Winds from accretion disks driven by the radiation and magnetocentrifugal force

OpenAIRE

Proga, D.

2000-01-01

We study the 2-D, time-dependent hydrodynamics of radiation-driven winds from luminous accretion disks threaded by a strong, large-scale, ordered magnetic field. The radiation force is due to spectral lines and is calculated using a generalized multidimensional formulation of the Sobolev approximation. The effects of the magnetic field are approximated by adding a force that emulates a magnetocentrifugal force. Our approach allows us to calculate disk winds when the magnetic field controls th...

WIND-DRIVEN ACCRETION IN TRANSITIONAL PROTOSTELLAR DISKS

Energy Technology Data Exchange (ETDEWEB)

Wang, Lile; Goodman, Jeremy J. [Princeton University Observatory, Princeton, NJ 08544 (United States)

2017-01-20

Transitional protostellar disks have inner cavities that are heavily depleted in dust and gas, yet most of them show signs of ongoing accretion, often at rates comparable to full disks. We show that recent constraints on the gas surface density in a few well-studied disk cavities suggest that the accretion speed is at least transsonic. We propose that this is the natural result of accretion driven by magnetized winds. Typical physical conditions of the gas inside these cavities are estimated for plausible X-ray and FUV radiation fields. The gas near the midplane is molecular and predominantly neutral, with a dimensionless ambipolar parameter in the right general range for wind solutions of the type developed by Königl, Wardle, and others. That is to say, the density of ions and electrons is sufficient for moderately good coupling to the magnetic field, but it is not so good that the magnetic flux needs to be dragged inward by the accreting neutrals.

Instabilities of line-driven stellar winds. V. Effect of an optically thick continuum

International Nuclear Information System (INIS)

Owocki, S.P.; Rybicki, G.B.

1991-01-01

Earlier analyses of the linear instability of line-driven stellar winds are extended to the case, relevant to Wolf-Rayet stars, in which the continuum remains optically thick well above the sonic point. It is found that an optically thick flow driven by pure scattering lines is stabilized by the drag effect of the diffuse, scattered radiation. However, even a relatively small photon destruction probability can cause a flow with continuum optical thickness much greater than 1 to remain unstable, with a given growth rate. The implications of these results for the variability characteristics of winds from Wolf-Rayet stars are briefly discussed. 16 refs

Antimicrobial actions of the human epididymis 2 (HE2 protein isoforms, HE2alpha, HE2beta1 and HE2beta2

Directory of Open Access Journals (Sweden)

French Frank S

2004-08-01

Full Text Available Abstract Background The HE2 gene encodes a group of isoforms with similarities to the antimicrobial beta-defensins. We demonstrated earlier that the antimicrobial activity of HE2 proteins and peptides is salt resistant and structure dependent and involves permeabilization of bacterial membranes. In this study, we further characterize the antimicrobial properties of HE2 peptides in terms of the structural changes induced in E. coli and the inhibition of macromolecular synthesis. Methods E. coli treated with 50 micro g/ml of HE2alpha, HE2beta1 or HE2beta2 peptides for 30 and 60 min were visualized using transmission and scanning electron microscopy to investigate the impact of these peptides on bacterial internal and external structure. The effects of HE2alpha, HE2beta1 and HE2beta2 on E. coli macromolecular synthesis was assayed by incubating the bacteria with 2, 10 and 25 micro g/ml of the individual peptides for 0–60 min and measuring the incorporation of the radioactive precursors [methyl-3H]thymidine, [5-3H]uridine and L-[4,5-3H(N]leucine into DNA, RNA and protein. Statistical analyses using Student's t-test were performed using Sigma Plot software. Values shown are Mean ± S.D. Results E. coli treated with HE2alpha, HE2beta1 and HE2beta2 peptides as visualized by transmission electron microscopy showed extensive damage characterized by membrane blebbing, thickening of the membrane, highly granulated cytoplasm and appearance of vacuoles in contrast to the smooth and continuous membrane structure of the untreated bacteria. Similarly, bacteria observed by scanning electron microscopy after treating with HE2alpha, HE2beta1 or HE2beta2 peptides exhibited membrane blebbing and wrinkling, leakage of cellular contents, especially at the dividing septa, and external accumulation of fibrous materials. In addition, HE2alpha, HE2beta1 and HE2beta2 peptides inhibited E. coli DNA, RNA and protein synthesis. Conclusions The morphological changes observed

Wind-driven angular momentum loss in binary systems. I - Ballistic case

Science.gov (United States)

Brookshaw, Leigh; Tavani, Marco

1993-01-01

We study numerically the average loss of specific angular momentum from binary systems due to mass outflow from one of the two stars for a variety of initial injection geometries and wind velocities. We present results of ballistic calculations in three dimensions for initial mass ratios q of the mass-losing star to primary star in the range q between 10 exp -5 and 10. We consider injection surfaces close to the Roche lobe equipotential surface of the mass-losing star, and also cases with the mass-losing star underfilling its Roche lobe. We obtain that the orbital period is expected to have a negative time derivative for wind-driven secular evolution of binaries with q greater than about 3 and with the mass-losing star near filling its Roche lobe. We also study the effect of the presence of an absorbing surface approximating an accretion disk on the average final value of the specific angular momentum loss. We find that the effect of an accretion disk is to increase the wind-driven angular momentum loss. Our results are relevant for evolutionary models of high-mass binaries and low-mass X-ray binaries.

The thermal structure of a wind-driven Reynolds ridge

Energy Technology Data Exchange (ETDEWEB)

Phongikaroon, Supathorn; Peter Judd, K.; Smith, Geoffrey B.; Handler, Robert A. [Remote Sensing Division, Naval Research Laboratory, 20375, Washington, DC (United States)

2004-08-01

In this study, we investigate the nature of a Reynolds ridge formed by wind shear. We have simultaneously imaged the water surface, with a deposit of a monolayer of the surfactant, oleyl alcohol, subject to different wind shears, by using a high-resolution infrared (IR) detector and a high-speed (HS) digital camera. The results reveal that the regions around the wind-driven Reynolds ridge, which have subtle manifestations in visual imagery, possess surprisingly complex hydrodynamical and thermal structures when observed in the infrared. The IR measurements reveal a warm, clean region upstream of the ridge, which is composed of the so called fishscale structures observed in earlier investigations. The region downstream of the ridge is composed of colder fluid which forms two counter-rotating cells. A region of intermediate temperature, which we call the mixing (wake) region, forms immediately downstream of the ridge near the channel centerline. By measuring the velocity of the advected fishscales, we have determined a surface drift speed of about 2% of the wind speed. The spanwise length-scale of the structures has also been used to estimate the wind shear. In addition, a comparison of IR and visual imagery shows that the thermal field is a very sensitive indicator of the exact position of the ridge itself. (orig.)

Wind driven erosion and the effects of particulate electrification

Science.gov (United States)

Merrison, J. P.; Bak, E.; Finster, K.; Gunnlaugsson, H. P.; Holstein-Rathlou, C.; Knak Jensen, S.; Nørnberg, P.; Rasmussen, K. R.

2012-09-01

Several related aspects of Aeolian activity are presently being studied in the laboratory, the most recent advances in this field will be presented. These include simulating wind driven erosion in the laboratory, quantifying erosion rates and the study of mineral change due to mechanical activation. Also advances in our understanding of the electrification of sand/dust particles is being made and how this phenomenon affects their behavior.

Conventional and novel control designs for direct driven PMSG wind turbines

Energy Technology Data Exchange (ETDEWEB)

Li, Shuhui; Haskew, Timothy A.; Xu, Ling [Department of Electrical and Computer Engineering, The University of Alabama, 317 Houser Hall, Tuscaloosa, AL 35487 (United States)

2010-03-15

With the advance of power electronic technology, direct driven permanent magnet synchronous generators (PMSG) have increasingly drawn interests to wind turbine manufactures. This paper studies and compares conventional and a novel control designs for a direct driven PMSG wind turbine. The paper presents transient and steady-state models of a PMSG system in a d-q reference frame. Then, general PMSG characteristics are investigated in the rotor-flux-oriented frame. A shortage of conventional control mechanisms is studied analytically and through computer simulation. A novel direct-current based d-q vector control technique is proposed by integrating fuzzy, adaptive and traditional PID control technologies in an optimal control configuration. Comparison study demonstrates that the proposed control approach, having superior performance in various aspects, is effective not only in achieving desired PMSG control objectives but also in improving the optimal performance of the overall system. (author)

Converting Wind Energy to Ammonia at Lower Pressure

International Nuclear Information System (INIS)

Malmali, Mahdi; Reese, Michael; McCormick, Alon V.; Cussler, E. L.

2017-01-01

Renewable wind energy can be used to make ammonia. However, wind-generated ammonia costs about twice that made from a traditional fossil-fuel driven process. To reduce the production cost, we replace the conventional ammonia condensation with a selective absorber containing metal halides, e.g., calcium chloride, operating at near synthesis temperatures. With this reaction-absorption process, ammonia can be synthesized at 20 bar from air, water, and wind-generated electricity, with rates comparable to the conventional process running at 150–300 bar. In our reaction-absorption process, the rate of ammonia synthesis is now controlled not by the chemical reaction but largely by the pump used to recycle the unreacted gases. The results suggest an alternative route to distributed ammonia manufacture which can locally supply nitrogen fertilizer and also a method to capture stranded wind energy as a carbon-neutral liquid fuel.

Deterministic and Advanced Statistical Modeling of Wind-Driven Sea

Science.gov (United States)

2015-07-06

It gives a ground for use an asymptotic approach for wind-driven seas in a spirit of our previous works [R16,R17]. Then we use simple...b𔃼)-—{b’’— b2 ) 1 - --r 2 b-k{\\b’\\2)--{b’k{\\b\\2)) ox *-(6’ 2) -. dx dx dx This equation has localized breather-type solution b{x,t) = B{x

Investigating Wind-Driven Rain Intrusion in Walls with the CARWASh

Science.gov (United States)

C.R. Boardman; Samuel V. Glass

2013-01-01

Wind-driven rain provides the primary external moisture load for exterior walls.Water absorption by the cladding, runoff, and penetration through the cladding or at details determine how a wall system performs. In this paper we describe a new laboratory facility that can create controlled outdoor and indoor conditions and use it to investigate the water...

Shifts in wind energy potential following land-use driven vegetation dynamics in complex terrain.

Science.gov (United States)

Fang, Jiannong; Peringer, Alexander; Stupariu, Mihai-Sorin; Pǎtru-Stupariu, Ileana; Buttler, Alexandre; Golay, Francois; Porté-Agel, Fernando

2018-10-15

Many mountainous regions with high wind energy potential are characterized by multi-scale variabilities of vegetation in both spatial and time dimensions, which strongly affect the spatial distribution of wind resource and its time evolution. To this end, we developed a coupled interdisciplinary modeling framework capable of assessing the shifts in wind energy potential following land-use driven vegetation dynamics in complex mountain terrain. It was applied to a case study area in the Romanian Carpathians. The results show that the overall shifts in wind energy potential following the changes of vegetation pattern due to different land-use policies can be dramatic. This suggests that the planning of wind energy project should be integrated with the land-use planning at a specific site to ensure that the expected energy production of the planned wind farm can be reached over its entire lifetime. Moreover, the changes in the spatial distribution of wind and turbulence under different scenarios of land-use are complex, and they must be taken into account in the micro-siting of wind turbines to maximize wind energy production and minimize fatigue loads (and associated maintenance costs). The proposed new modeling framework offers, for the first time, a powerful tool for assessing long-term variability in local wind energy potential that emerges from land-use change driven vegetation dynamics over complex terrain. Following a previously unexplored pathway of cause-effect relationships, it demonstrates a new linkage of agro- and forest policies in landscape development with an ultimate trade-off between renewable energy production and biodiversity targets. Moreover, it can be extended to study the potential effects of micro-climatic changes associated with wind farms on vegetation development (growth and patterning), which could in turn have a long-term feedback effect on wind resource distribution in mountainous regions. Copyright © 2018 Elsevier B.V. All rights

Beyond Tree Throw: Wind, Water, Rock and the Mechanics of Tree-Driven Bedrock Physical Weathering

Science.gov (United States)

Marshall, J. A.; Anderson, R. S.; Dawson, T. E.; Dietrich, W. E.; Minear, J. T.

2017-12-01

Tree throw is often invoked as the dominant process in converting bedrock to soil and thus helping to build the Critical Zone (CZ). In addition, observations of tree roots lifting sidewalk slabs, occupying cracks, and prying slabs of rock from cliff faces have led to a general belief in the power of plant growth forces. These common observations have led to conceptual models with trees at the center of the soil genesis process. This is despite the observation that tree throw is rare in many forested settings, and a dearth of field measurements that quantify the magnitude of growth forces. While few trees blow down, every tree grows roots, inserting many tens of percent of its mass below ground. Yet we lack data quantifying the role of trees in both damaging bedrock and detaching it (and thus producing soil). By combing force measurements at the tree-bedrock interface with precipitation, solar radiation, wind speed, and wind-driven tree sway data we quantified the magnitude and frequency of tree-driven soil-production mechanisms from two contrasting climatic and lithologic regimes (Boulder and Eel Creek CZ Observatories). Preliminary data suggests that in settings with relatively thin soils, trees can damage and detach rock due to diurnal fluctuations, wind response and rainfall events. Surprisingly, our data suggests that forces from roots and trunks growing against bedrock are insufficient to pry rock apart or damage bedrock although much more work is needed in this area. The frequency, magnitude and style of wind-driven tree forces at the bedrock interface varies considerably from one to another species. This suggests that tree properties such as mass, elasticity, stiffness and branch structure determine whether trees respond to gusts big or small, move at the same frequency as large wind gusts, or are able to self-dampen near-ground sway response to extended wind forces. Our measurements of precipitation-driven and daily fluctuations in root pressures exerted on

Spin-driven structural effects in alkali doped (4)He clusters from quantum calculations.

Science.gov (United States)

Bovino, S; Coccia, E; Bodo, E; Lopez-Durán, D; Gianturco, F A

2009-06-14

In this paper, we carry out variational Monte Carlo and diffusion Monte Carlo (DMC) calculations for Li(2)((1)Sigma(g) (+))((4)He)(N) and Li(2)((3)Sigma(u) (+))((4)He)(N) with N up to 30 and discuss in detail the results of our computations. After a comparison between our DMC energies with the "exact" discrete variable representation values for the species with one (4)He, in order to test the quality of our computations at 0 K, we analyze the structural features of the whole range of doped clusters. We find that both species reside on the droplet surface, but that their orientation is spin driven, i.e., the singlet molecule is perpendicular and the triplet one is parallel to the droplet's surface. We have also computed quantum vibrational relaxation rates for both dimers in collision with a single (4)He and we find them to differ by orders of magnitude at the estimated surface temperature. Our results therefore confirm the findings from a great number of experimental data present in the current literature and provide one of the first attempts at giving an accurate, fully quantum picture for the nanoscopic properties of alkali dimers in (4)He clusters.

Treatment Wetland Aeration without Electricity? Lessons Learned from the First Experiment Using a Wind-Driven Air Pump

Directory of Open Access Journals (Sweden)

Johannes Boog

2016-11-01

Full Text Available Aerated treatment wetlands have become an increasingly recognized technology for treating wastewaters from domestic and various industrial origins. To date, treatment wetland aeration is provided by air pumps which require access to the energy grid. The requirement for electricity increases the ecological footprint of an aerated wetland and limits the application of this technology to areas with centralized electrical infrastructure. Wind power offers another possibility as a driver for wetland aeration, but its use for this purpose has not yet been investigated. This paper reports the first experimental trial using a simple wind-driven air pump to replace the conventional electric air blowers of an aerated horizontal subsurface flow wetland. The wind-driven air pump was connected to a two-year old horizontal flow aerated wetland which had been in continuous (24 h aeration since startup. The wind-driven aeration system functioned, however it was not specifically adapted to wetland aeration. As a result, treatment performance decreased compared to prior continuous aeration. Inconsistent wind speed at the site may have resulted in insufficient pressure within the aeration manifold, resulting in insufficient air supply to the wetland. This paper discusses the lessons learned during the experiment.

Effects of El Niño-driven changes in wind patterns on North Pacific albatrosses.

Science.gov (United States)

Thorne, L H; Conners, M G; Hazen, E L; Bograd, S J; Antolos, M; Costa, D P; Shaffer, S A

2016-06-01

Changes to patterns of wind and ocean currents are tightly linked to climate change and have important implications for cost of travel and energy budgets in marine vertebrates. We evaluated how El Niño-Southern Oscillation (ENSO)-driven wind patterns affected breeding Laysan and black-footed albatross across a decade of study. Owing to latitudinal variation in wind patterns, wind speed differed between habitat used during incubation and brooding; during La Niña conditions, wind speeds were lower in incubating Laysan (though not black-footed) albatross habitat, but higher in habitats used by brooding albatrosses. Incubating Laysan albatrosses benefited from increased wind speeds during El Niño conditions, showing increased travel speeds and mass gained during foraging trips. However, brooding albatrosses did not benefit from stronger winds during La Niña conditions, instead experiencing stronger cumulative headwinds and a smaller proportion of trips in tailwinds. Increased travel costs during brooding may contribute to the lower reproductive success observed in La Niña conditions. Furthermore, benefits of stronger winds in incubating habitat may explain the higher reproductive success of Laysan albatross during El Niño conditions. Our findings highlight the importance of considering habitat accessibility and cost of travel when evaluating the impacts of climate-driven habitat change on marine predators. © 2016 The Author(s).

Line-driven disk winds in active galactic nuclei: The critical importance of ionization and radiative transfer

Energy Technology Data Exchange (ETDEWEB)

Higginbottom, Nick; Knigge, Christian; Matthews, James H. [School of Physics and Astronomy, University of Southampton, Highfield, Southampton, SO17 1BJ (United Kingdom); Proga, Daniel [Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4002 (United States); Long, Knox S. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Sim, Stuart A., E-mail: nick_higginbottom@fastmail.fm [School of Mathematics and Physics, Queens University Belfast, University Road, Belfast, BT7 1NN (United Kingdom)

2014-07-01

Accretion disk winds are thought to produce many of the characteristic features seen in the spectra of active galactic nuclei (AGNs) and quasi-stellar objects (QSOs). These outflows also represent a natural form of feedback between the central supermassive black hole and its host galaxy. The mechanism for driving this mass loss remains unknown, although radiation pressure mediated by spectral lines is a leading candidate. Here, we calculate the ionization state of, and emergent spectra for, the hydrodynamic simulation of a line-driven disk wind previously presented by Proga and Kallman. To achieve this, we carry out a comprehensive Monte Carlo simulation of the radiative transfer through, and energy exchange within, the predicted outflow. We find that the wind is much more ionized than originally estimated. This is in part because it is much more difficult to shield any wind regions effectively when the outflow itself is allowed to reprocess and redirect ionizing photons. As a result, the calculated spectrum that would be observed from this particular outflow solution would not contain the ultraviolet spectral lines that are observed in many AGN/QSOs. Furthermore, the wind is so highly ionized that line driving would not actually be efficient. This does not necessarily mean that line-driven winds are not viable. However, our work does illustrate that in order to arrive at a self-consistent model of line-driven disk winds in AGN/QSO, it will be critical to include a more detailed treatment of radiative transfer and ionization in the next generation of hydrodynamic simulations.

Using product driven process synthesis in the biorefinery

NARCIS (Netherlands)

Kiskini, A.; Zondervan, E.; Wierenga, P.A.; Poiesz, E.; Gruppen, H.

2015-01-01

In this work, we propose the use of the product-driven process synthesis (PDPS) methodology for the product and process design stage in biorefinery. The aim of the biorefinery is to optimize the total use of the whole feedstock – with focus being on various products simultaneously – rather than to

Multi-criteria decision making in product-driven process synthesis

NARCIS (Netherlands)

Ridder, de K.; Almeida-Rivera, C.; Bongers, P.M.M.; Bruin, S.; Flapper, S.D.P.; Braunschweig, B.; Joulia, X.

2008-01-01

Current efforts in the development of a Product-driven Process Synthesis methodology have been focusing on broadening the design scope to consumer preferences, product attributes, process variables and supply chain considerations. The methodology embraces a decision making activity to be performed

Time-resolved PIV measurements of the atmospheric boundary layer over wind-driven surface waves

Science.gov (United States)

Markfort, Corey; Stegmeir, Matt

2017-11-01

Complex interactions at the air-water interface result in two-way coupling between wind-driven surface waves and the atmospheric boundary layer (ABL). Turbulence generated at the surface plays an important role in aquatic ecology and biogeochemistry, exchange of gases such as oxygen and carbon dioxide, and it is important for the transfer of energy and controlling evaporation. Energy transferred from the ABL promotes the generation and maintenance of waves. A fraction of the energy is transferred to the surface mixed layer through the generation of turbulence. Energy is also transferred back to the ABL by waves. There is a need to quantify the details of the coupled boundary layers of the air-water system to better understand how turbulence plays a role in the interactions. We employ time-resolved PIV to measure the detailed structure of the air and water boundary layers under varying wind and wave conditions in the newly developed IIHR Boundary-Layer Wind-Wave Tunnel. The facility combines a 30-m long recirculating water channel with an open-return boundary layer wind tunnel. A thick turbulent boundary layer is developed in the 1 m high air channel, over the water surface, allowing for the study of boundary layer turbulence interacting with a wind-driven wave field.

Wind power demonstration and siting problems. [for recharging electrically driven automobiles

Science.gov (United States)

Bergey, K. H.

1973-01-01

Technical and economic feasibility studies on a small windmill to provide overnight charging for an electrically driven car are reported. The auxiliary generator provides power for heating and cooling the vehicle which runs for 25 miles on battery power alone, and for 50 miles with the onboard charger operating. The blades for this windmill have a diameter of 12 feet and are coupled through to a conventional automobile alternator so that they are able to completely recharge car batteries in 8 hours. Optimization of a windmill/storage system requires detailed wind velocity information which permits rational sitting of wind power system stations.

Experimental Study of Wind-Opposed Buoyancy-Driven Natural Ventilation

OpenAIRE

Andersen, A.; Bjerre, M.; Chen, Z. D.; Heiselberg, Per; Li, Y.

2000-01-01

Natural ventilation driven by natural forces, i.e. wind and thermal buoyancy, is an environmentally friendly system for buildings and has been increasingly used around the world in recent years to mitigate the impact on the global environment due to the significant energy consumption by heating, ventilation and air-conditioning (HV AC). There is a need for the understanding and development of theories and tools related to the design, operation and control of natural ventilation systems.

Experimental Study of Wind-Opposed Buoyancy-Driven Natural Ventilation

DEFF Research Database (Denmark)

Andersen, A.; Bjerre, M.; Chen, Z. D.

Natural ventilation driven by natural forces, i.e. wind and thermal buoyancy, is an environmentally friendly system for buildings and has been increasingly used around the world in recent years to mitigate the impact on the global environment due to the significant energy consumption by heating......, ventilation and air-conditioning (HV AC). There is a need for the understanding and development of theories and tools related to the design, operation and control of natural ventilation systems....

Modelling and Analysis of Radial Flux Surface Mounted Direct-Driven PMSG in Small Scale Wind Turbine

Directory of Open Access Journals (Sweden)

Theint Zar Htet

2017-11-01

Full Text Available This paper presents the modelling and analysis of permanent magnet synchronous generator (PMSG which are used in direct driven small scale wind turbines. The 3 kW PM generator which is driven directly without gear system is analyzed by Ansoft Maxwell 2D RMxprt. The performance analysis of generator includes the cogging torque in two teeth, induced coil voltages under load, winding current under load, airgap flux density distribution and so on. The modelling analysis is based on the 2D finite element techniques. In an electrical machine, an accurate determination of the geometry parameters is a vital role. The proper performance results of 3kW PMSG in small scale wind turbine can be seen in this paper.

Spectrum Analysis of Inertial and Subinertial Motions Based on Analyzed Winds and Wind-Driven Currents from a Primitive Equation General Ocean Circulation Model.

Science.gov (United States)

1982-12-01

1Muter.Te Motions Based on Ana lyzed Winds and wind-driven December 1982 Currents from. a Primitive Squat ion General a.OW -love"*..* Oean Circulation...mew se"$ (comeS.... do oISN..u am ae~ 00do OWaor NUN Fourier and Rotary Spc , Analysis Modeled Inertial and Subinrtial Motion 4 Primitive Equation

TURBULENCE IN THE SUB-ALFVENIC SOLAR WIND DRIVEN BY REFLECTION OF LOW-FREQUENCY ALFVEN WAVES

International Nuclear Information System (INIS)

Verdini, A.; Velli, M.; Buchlin, E.

2009-01-01

We study the formation and evolution of a turbulent spectrum of Alfven waves driven by reflection off the solar wind density gradients, starting from the coronal base up to 17 solar radii, well beyond the Alfvenic critical point. The background solar wind is assigned and two-dimensional shell models are used to describe nonlinear interactions. We find that the turbulent spectra are influenced by the nature of the reflected waves. Close to the base, these give rise to a flatter and steeper spectrum for the outgoing and reflected waves, respectively. At higher heliocentric distance both spectra evolve toward an asymptotic Kolmogorov spectrum. The turbulent dissipation is found to account for at least half of the heating required to sustain the background imposed solar wind and its shape is found to be determined by the reflection-determined turbulent heating below 1.5 solar radii. Therefore, reflection and reflection-driven turbulence are shown to play a key role in the acceleration of the fast solar wind and origin of the turbulent spectrum found at 0.3 AU in the heliosphere.

Implementation, Comparison and Application of an Average Simulation Model of a Wind Turbine Driven Doubly Fed Induction Generator

Directory of Open Access Journals (Sweden)

Lidula N. Widanagama Arachchige

2017-10-01

Full Text Available Wind turbine driven doubly-fed induction generators (DFIGs are widely used in the wind power industry. With the increasing penetration of wind farms, analysis of their effect on power systems has become a critical requirement. This paper presents the modeling of wind turbine driven DFIGs using the conventional vector controls in a detailed model of a DFIG that represents power electronics (PE converters with device level models and proposes an average model eliminating the PE converters. The PSCAD/EMTDC™ (4.6 electromagnetic transient simulation software is used to develop the detailed and the proposing average model of a DFIG. The comparison of the two models reveals that the designed average DFIG model is adequate for simulating and analyzing most of the transient conditions.

Evaluation of Discharge Coefficients for Window Openings in Wind Driven Natural Ventilation

DEFF Research Database (Denmark)

Heiselberg, Per; Sandberg, Mats

2006-01-01

This paper describes the classical approach for calculation of wind driven airflow through large openings in buildings and discusses the fulfilment of the limiting assumptions. It is demonstrated that the limiting assumptions are not fulfilled for large openings in buildings for cross ventilation...... cannot be regarded as a constant and it is very difficult to estimate correct values resulting in less accuracy of prediction of natural ventilation.......This paper describes the classical approach for calculation of wind driven airflow through large openings in buildings and discusses the fulfilment of the limiting assumptions. It is demonstrated that the limiting assumptions are not fulfilled for large openings in buildings for cross ventilation......, and therefore, the classical approach is not appropriate for prediction of airflow through large openings in buildings in the cross ventilation case. Using the approach for real openings and estimating the discharge coefficient for window openings has also not been very successful. The discharge coefficient...

Controller synthesis for negative imaginary systems: a data driven approach

KAUST Repository

Mabrok, Mohamed; Petersen, Ian R.

2016-01-01

-driven controller synthesis methodology for NI systems is presented. In this approach, measured frequency response data of the plant is used to construct the controller frequency response at every frequency by minimising a cost function. Then, this controller

Coastal upwelling by wind-driven forcing in Jervis Bay, New South Wales: A numerical study for 2011

Science.gov (United States)

Sun, Youn-Jong; Jalón-Rojas, Isabel; Wang, Xiao Hua; Jiang, Donghui

2018-06-01

The Princeton Ocean Model (POM) was used to investigate an upwelling event in Jervis Bay, New South Wales (SE Australia), with varying wind directions and strengths. The POM was adopted with a downscaling approach for the regional ocean model one-way nested to a global ocean model. The upwelling event was detected from the observed wind data and satellite sea surface temperature images. The validated model reproduced the upwelling event showing the input of bottom cold water driven by wind to the bay, its subsequent deflection to the south, and its outcropping to the surface along the west and south coasts. Nevertheless, the behavior of the bottom water that intruded into the bay varied with different wind directions and strengths. Upwelling-favorable wind directions for flushing efficiency within the bay were ranked in the following order: N (0°; northerly) > NNE (30°; northeasterly) > NW (315°; northwesterly) > NE (45°; northeasterly) > ENE (60°; northeasterly). Increasing wind strengths also enhance cold water penetration and water exchange. It was determined that wind-driven downwelling within the bay, which occurred with NNE, NE and ENE winds, played a key role in blocking the intrusion of the cold water upwelled through the bay entrance. A northerly wind stress higher than 0.3 N m-2 was required for the cold water to reach the northern innermost bay.

Rayleigh-Taylor and wind-driven instabilities of the nighttime equatorial ionosphere

International Nuclear Information System (INIS)

Chiu, Y.T.; Straus, J.M.

1979-01-01

We have made a thorough re-examination of the Rayleigh-Taylor instability in the nighttime equatorial ionosphere from approx.100 km to the bottomside F region. We have taken into account explicitly the following effects which have been ignored by other workers in various combinations: (1) The eastward drift of the ionosphere caused by the nighttime polarization electric field, (2) the eastward nighttime neutral wind, and (3) recombination in the F and E regions. We found that, well below the bottomside F region, the Rayleigh-Taylor mode can be unstable and is driven by an eastward neutral wind rather than by gravitational drift. Formation of ionospheric bubbles below the bottomside F region is consistent with the observation of lower ionospheric ions in F region ionospheric holes; furthermore, seasonal and shorter term variations in spread-F occurrence may be associated with variations in the neutral wind and polarization electric field

Data-driven wind plant control

NARCIS (Netherlands)

Gebraad, P.M.O.

2014-01-01

Each wind turbine in a cluster of wind turbines (a wind power plant) can influence the performance of other turbines through the wake that forms downstream of its rotor. The wake has a reduced wind velocity, since the turbine extracts energy from the flow, and the obstruction by the wind turbine

WIND-DRIVEN ACCRETION IN PROTOPLANETARY DISKS. II. RADIAL DEPENDENCE AND GLOBAL PICTURE

Energy Technology Data Exchange (ETDEWEB)

Bai Xuening, E-mail: xbai@cfa.harvard.edu [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States)

2013-08-01

Non-ideal magnetohydrodynamical effects play a crucial role in determining the mechanism and efficiency of angular momentum transport as well as the level of turbulence in protoplanetary disks (PPDs), which are the key to understanding PPD evolution and planet formation. It was shown in our previous work that at 1 AU, the magnetorotational instability (MRI) is completely suppressed when both ohmic resistivity and ambipolar diffusion (AD) are taken into account, resulting in a laminar flow with accretion driven by magnetocentrifugal wind. In this work, we study the radial dependence of the laminar wind solution using local shearing-box simulations. The scaling relation on the angular momentum transport for the laminar wind is obtained, and we find that the wind-driven accretion rate can be approximated as M-dot approx. 0.91 x 10{sup -8}R{sub AU}{sup 1.21}(B{sub p}/10 mG){sup 0.93} M{sub Sun} yr{sup -1}, where B{sub p} is the strength of the large-scale poloidal magnetic field threading the disk. The result is independent of disk surface density. Four criteria are outlined for the existence of the laminar wind solution: (1) ohmic resistivity dominated the midplane region, (2) the AD-dominated disk upper layer, (3) the presence of a (not too weak) net vertical magnetic flux, and (4) sufficiently well-ionized gas beyond the disk surface. All these criteria are likely to be met in the inner region of the disk from {approx}0.3 AU to about 5-10 AU for typical PPD accretion rates. Beyond this radius, the angular momentum transport is likely to proceed due to a combination of the MRI and disk wind, and eventually completely dominated by the MRI (in the presence of strong AD) in the outer disk. Our simulation results provide key ingredients for a new paradigm on the accretion processes in PPDs.

Origins of wind-driven intraseasonal sea level variations in the North Indian Ocean coastal waveguide

Digital Repository Service at National Institute of Oceanography (India)

Suresh, I.; Vialard, J.; Lengaigne, M.; Han, W.; Mc; Durand, F.; Muraleedharan, P.M.

version: Geophys. Res. Lett., vol.40(21); 2013; 5740-5744 Origins of wind-driven intraseasonal sea level variations in the North Indian Ocean coastal waveguide I. Suresh1, J. Vialard2, M. Lengaigne2, W. Han3, J. McCreary4, F. Durand5, P.M. Muraleedharan1... reversing winds. These wind variations drive seasonal equatorial Kelvin and Rossby wave responses. The seasonal equatorial Kelvin waves propagate into the North Indian Ocean (hereafter NIO) as coastal Kelvin waves [McCreary et al., 1993]. As a result...

Spectral decomposition of regulatory thresholds for climate-driven fluctuations in hydro- and wind power availability

Science.gov (United States)

Wörman, A.; Bottacin-Busolin, A.; Zmijewski, N.; Riml, J.

2017-08-01

Climate-driven fluctuations in the runoff and potential energy of surface water are generally large in comparison to the capacity of hydropower regulation, particularly when hydropower is used to balance the electricity production from covarying renewable energy sources such as wind power. To define the bounds of reservoir storage capacity, we introduce a dedicated reservoir volume that aggregates the storage capacity of several reservoirs to handle runoff from specific watersheds. We show how the storage bounds can be related to a spectrum of the climate-driven modes of variability in water availability and to the covariation between water and wind availability. A regional case study of the entire hydropower system in Sweden indicates that the longest regulation period possible to consider spans from a few days of individual subwatersheds up to several years, with an average limit of a couple of months. Watershed damping of the runoff substantially increases the longest considered regulation period and capacity. The high covariance found between the potential energy of the surface water and wind energy significantly reduces the longest considered regulation period when hydropower is used to balance the fluctuating wind power.

The effects of wind power on marine life - A Synthesis

Energy Technology Data Exchange (ETDEWEB)

Bergstroem, Lena; Kautsky, Lena; Malm, Torleif; Ohlsson, Hans; Wahlberg, Magnus; Rosenberg, Rutger; Aastrand Capetillo, Nastassja

2012-10-15

As in many other countries, an expansion of wind power is expected in Sweden during the coming decades. The expansion is driven by rising prices on electricity and the need for an increased production of renewable energy. Since wind conditions at sea are good and relatively constant, several offshore wind farms are planned in Swedish waters. Offshore wind power with a total effect of about 2500 MW has been granted permission and an additional 5500 MW are being planned for. Examples of granted projects are Storgrundet with an effect of 265 MW, Stora Middelgrund with an effect of 860 MW and Kaarehamn with an effect of 48 MW. The largest offshore wind farm in Sweden today is Lillgrund in Oeresund, with its 48 turbines with an installed effect of 110 MW. Prior to this expected expansion, it is important to investigate the environmental impact of offshore wind power, and how possible negative effects can be minimized. This synopsis about the impact of wind power on the marine life in Swedish waters is based on more than 600 studies, most of which are scientific articles, but also reports by companies and authorities.

Radiatively-driven winds: model improvements, ionization balance and the infared spectrum

International Nuclear Information System (INIS)

Castor, J.I.

1979-01-01

Recent improvements to theoretical stellar wind models and the results of empirical modelling of the ionization balance and the infrared continuum are discussed. The model of a wind driven by radiation pressure in spectral lines is improved by accounting for overlap of the driving lines, dependence of ionization balance on density, and stellar rotation. These effects produce a softer velocity law than that given by Castor, Abbott and Klein (1975). The ionization balance in zeta Puppis is shown to agree with that estimated for an optically thick wind at a gas temperature of 60,000 K. The ionization model is not unique. The infrared continuum of zeta Pup measured by Barlow and Cohen is fitted to a cool model with a linear rise of velocity with radius; this fit is also not unique. It is concluded that one should try to find a model that fits several kinds of evidence simultaneously. (Auth.)

The steady state solutions of radiatively driven stellar winds for a non-Sobolev, pure absorption model

International Nuclear Information System (INIS)

Poe, C.H.; Owocki, S.P.; Castor, J.I.

1990-01-01

The steady state solution topology for absorption line-driven flows is investigated for the condition that the Sobolev approximation is not used to compute the line force. The solution topology near the sonic point is of the nodal type with two positive slope solutions. The shallower of these slopes applies to reasonable lower boundary conditions and realistic ion thermal speed v(th) and to the Sobolev limit of zero of the usual Castor, Abbott, and Klein model. At finite v(th), this solution consists of a family of very similar solutions converging on the sonic point. It is concluded that a non-Sobolev, absorption line-driven flow with a realistic values of v(th) has no uniquely defined steady state. To the extent that a pure absorption model of the outflow of stellar winds is applicable, radiatively driven winds should be intrinsically variable. 34 refs

Wind-driven marine phytoplank blooms: Satellite observation and analysis

Science.gov (United States)

Tang, DanLing

2016-07-01

Algal bloom is defined as a rapid increase or accumulation in biomass in an aquatic system. It not only can increase the primary production but also could result in negative ecological consequence, e.g.,Harmful Algal Blooms (HABs). According to the classic theory for the formation of algal blooms "critical depth" and "eutrophication", oligotrophic sea area is usually difficult to form a large area of algal blooms, and actuallythe traditional observation is only sporadic capture to the existence of algal blooms.Taking full advantage of multiple data of satellite remote sensing , this study introduces "Wind-driven algal blooms in open oceans: observation and mechanisms" It explained except classic coastal Ekman transport, the wind through a variety of mechanisms affecting the formation of algal blooms. Proposed a conceptual model of "Strong wind -upwelling-nutrient-phytoplankton blooms" in Western South China Sea (SCS) to assess role of wind-induced advection transport in phytoplankton bloom formation. It illustrates the nutrient resources that support long-term offshore phytoplankton blooms in the western SCS; (2)Proposal of the theory that "typhoons cause vertical mixing, induce phytoplankton blooms", and quantify their important contribution to marine primary production; Proposal a new ecological index for typhoon. Proposed remote sensing inversion models. (3)Finding of the spatial and temporaldistributions pattern of harmful algal bloom (HAB)and species variations of HAB in the South Yellow Sea and East China Sea, and in the Pearl River estuary, and their oceanic dynamic mechanisms related with monsoon; The project developed new techniques and generated new knowledge, which significantly improved understanding of the formation mechanisms of algal blooms. The proposed "wind-pump" mechanism integrates theoretical system combined "ocean dynamics, development of algal blooms, and impact on primary production", which will benefit fisheries management. These

Standard test method to determine the performance of tiled roofs to wind-driven rain

Directory of Open Access Journals (Sweden)

Sánchez de Rojas, M. I.

2008-09-01

Full Text Available The extent to which roof coverings can resist water penetration from the combination of wind and rain, commonly referred to as wind driven rain, is important for the design of roofs. A new project of European Standard prEN 15601 (1 specifies a method of test to determine the performance of the roof covering against wind driven rain. The combined action of wind and rain varies considerably with geographical location of a building and the associated differences in the rain and wind climate. Three windrain conditions and one deluge condition covering Northern Europe Coastal, Central Europe and Southern Europe are specified in the project standard, each subdivided into four wind-speeds and rainfall rates to be applied to the test. The project does not contain information on the level of acceptable performance.Para el diseño de los tejados es importante determinar el punto hasta el cual éstos pueden resistirse a la penetración de agua causada por la combinación de viento y lluvia. Un nuevo proyecto de Norma Europeo prEN 15601 (1 especifica un método de ensayo para determinar el comportamiento del tejado frente a la combinación de viento y lluvia. La acción combinada de viento y lluvia varía considerablemente con la situación geográfica de un edificio y las diferencias asociadas al clima de la lluvia y del viento. El proyecto de norma especifica las condiciones de viento y lluvia y una condición de diluvio para cada una de las tres zonas de Europa: Europa del Norte y Costera, Europa Central y Europa del Sur, cada una subdividida en cuatro condiciones de velocidades de viento y caudal de lluvia para ser aplicadas en los ensayos. El proyecto no contiene la información sobre condiciones aceptables.

Applicability of product-driven process synthesis to separation processes in food

NARCIS (Netherlands)

Jankowiak, L.; Goot, van der A.J.; Trifunovic, O.; Bongers, P.; Boom, R.M.

2012-01-01

The demand for more sustainable processing in the food industry is rising but requires structured methodologies to support the fast implementation of new economic and sustainable processes. Product-driven process synthesis (PDPS) is a recently established methodology facilitating the rapid

Tidal flushing and wind driven circulation of Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia) from in situ observations and numerical modelling

International Nuclear Information System (INIS)

Dumas, F.; Le Gendre, R.; Thomas, Y.; Andréfouët, S.

2012-01-01

Hydrodynamic functioning and water circulation of the semi-closed deep lagoon of Ahe atoll (Tuamotu Archipelago, French Polynesia) were investigated using 1 year of field data and a 3D hydrodynamical model. Tidal amplitude averaged less than 30 cm, but tide generated very strong currents (2 m s −1 ) in the pass, creating a jet-like circulation that partitioned the lagoon into three residual circulation cells. The pass entirely flushed excess water brought by waves-induced radiation stress. Circulation patterns were computed for climatological meteorological conditions and summarized with stream function and flushing time. Lagoon hydrodynamics and general overturning circulation was driven by wind. Renewal time was 250 days, whereas the e-flushing time yielded a lagoon-wide 80-days average. Tide-driven flush through the pass and wind-driven overturning circulation designate Ahe as a wind-driven, tidally and weakly wave-flushed deep lagoon. The 3D model allows studying pearl oyster larvae dispersal in both realistic and climatological conditions for aquaculture applications.

Reversal of subtidal dune asymmetries caused by seasonally reversing wind-driven currents in Torres Strait, northeastern Australia

Science.gov (United States)

Harris, Peter T.

1991-07-01

Large subtidal sand dunes (sandwaves) located in Adolphus Channel, Torres Strait, have been observed to reverse their asymmetric orientation between September-February. This has been attributed to a reversal in wind-driven currents, which flow westward during the SE trade season (April-November) and eastwards during the NW monsoon season [December-March: HARRIS (1989) Continental Shelf Research, 9, 981-1002]. Observations in September 1988 and February 1989 from another area of dunes in Torres Strait corroborate this asymmetry reversal pattern. The results indicate that such reversals may be common in Torres Strait and in other areas where subtidal bedforms are subject to modification by superimposed, seasonally reversing, wind-driven currents.

Modeling X-ray Absorbers in AGNs with MHD-Driven Accretion-Disk Winds

Science.gov (United States)

Fukumura, Keigo; Kazanas, D.; Shrader, C. R.; Tombesi, F.; Contopoulos, J.; Behar, E.

2013-04-01

We have proposed a systematic view of the observed X-ray absorbers, namely warm absorbers (WAs) in soft X-ray and highly-ionized ultra-fast outflows (UFOs), in the context of magnetically-driven accretion-disk wind models. While potentially complicated by variability and thermal instability in these energetic outflows, in this simplistic model we have calculated 2D kinematic field as well as density and ionization structure of the wind with density profile of 1/r corresponding to a constant column distribution per decade of ionization parameter. In particular we show semi-analytically that the inner layer of the disk-wind manifests itself as the strongly-ionized fast outflows while the outer layer is identified as the moderately-ionized absorbers. The computed characteristics of these two apparently distinct absorbers are consistent with X-ray data (i.e. a factor of ~100 difference in column and ionization parameters as well as low wind velocity vs. near-relativistic flow). With the predicted contour curves for these wind parameters one can constrain allowed regions for the presence of WAs and UFOs.The model further implies that the UFO's gas pressure is comparable to that of the observed radio jet in 3C111 suggesting that the magnetized disk-wind with density profile of 1/r is a viable agent to help sustain such a self-collimated jet at small radii.

Imperfections of the North-Atlantic wind-driven ocean circulation: continental geometry and windstress shape

NARCIS (Netherlands)

Dijkstra, H.A.; Molemaker, M.J.

1998-01-01

Multiple equilibria of the wind-driven gyres have been found in idealized quasi- geostrophic and shallow water models.In this paper we demonstrate that multiple equilibria persist within a reduced gravity shallow water model under quite realis- tic continental geometry and windstress orcing for

Ergosphere-driven winds

International Nuclear Information System (INIS)

Punsly, B.; Coroniti, F.V.

1990-01-01

This paper is a discussion of a physical mechanism that allows large-scale magnetic fields to torque rapidly rotating black holes in an astrophysical context. The physics which is involved is that plasma in the ergosphere must rotate. Thus, if ergospheric plasma gets frozen onto large-scale magnetic field lines, then it can drive a magnetic wind to infinity, as is conjectured to occur in field-aligned pulsars. Included in this paper is a discussion of ingoing magnetic winds that accrete either toward the event horizon or to the equatorial plane in the ergosphere. 31 refs

Generation of electricity by wind power

Energy Technology Data Exchange (ETDEWEB)

Golding, E W

1976-01-01

Information on wind power is presented concerning the history of windmills; estimation of the energy obtainable from the wind; wind characteristics and distribution; wind power sites; wind surveys; wind flow over hills; measurement of wind velocity; wind structure and its determination; wind data and energy estimation; testing of wind driven ac generators; wind-driven machines; propeller type windmills; plants for isolated premises and small communities; economy of wind power generation; construction costs for large wind-driven generators; relationship of wind power to other power sources; research and development; and international cooperation.

Analysis of Dynamic Behavior of Multiple-Stage Planetary Gear Train Used in Wind Driven Generator

Directory of Open Access Journals (Sweden)

Jungang Wang

2014-01-01

Full Text Available A dynamic model of multiple-stage planetary gear train composed of a two-stage planetary gear train and a one-stage parallel axis gear is proposed to be used in wind driven generator to analyze the influence of revolution speed and mesh error on dynamic load sharing characteristic based on the lumped parameter theory. Dynamic equation of the model is solved using numerical method to analyze the uniform load distribution of the system. It is shown that the load sharing property of the system is significantly affected by mesh error and rotational speed; load sharing coefficient and change rate of internal and external meshing of the system are of obvious difference from each other. The study provides useful theoretical guideline for the design of the multiple-stage planetary gear train of wind driven generator.

Data driven fault detection and isolation: a wind turbine scenario

Directory of Open Access Journals (Sweden)

Rubén Francisco Manrique Piramanrique

2015-04-01

Full Text Available One of the greatest drawbacks in wind energy generation is the high maintenance cost associated to mechanical faults. This problem becomes more evident in utility scale wind turbines, where the increased size and nominal capacity comes with additional problems associated with structural vibrations and aeroelastic effects in the blades. Due to the increased operation capability, it is imperative to detect system degradation and faults in an efficient manner, maintaining system integrity, reliability and reducing operation costs. This paper presents a comprehensive comparison of four different Fault Detection and Isolation (FDI filters based on “Data Driven” (DD techniques. In order to enhance FDI performance, a multi-level strategy is used where:  the first level detects the occurrence of any given fault (detection, while  the second identifies the source of the fault (isolation. Four different DD classification techniques (namely Support Vector Machines, Artificial Neural Networks, K Nearest Neighbors and Gaussian Mixture Models were studied and compared for each of the proposed classification levels. The best strategy at each level could be selected to build the final data driven FDI system. The performance of the proposed scheme is evaluated on a benchmark model of a commercial wind turbine. 

Electric field measurements in a kHz-driven He jet - The influence of the gas flow speed

NARCIS (Netherlands)

Sobota, A.; Guaitella, O.; Sretenović, G.B.; Krstić, I.B.; Kovačević, V.V.; Obrusník, A.; Nguyen, Y.N.; Zajíčková, L.; Obradović, B.M.; Kuraica, M.M.

2016-01-01

This report focuses on the dependence of electric field strength in the effluent of a vertically downwards-operated plasma jet freely expanding into room air as a function of the gas flow speed. A 30 kHz AC-driven He jet was used in a coaxial geometry, with an amplitude of 2 kV and gas flow between

Wind-driven export of Weddell Sea slope water

Science.gov (United States)

Meijers, A. J. S.; Meredith, M. P.; Abrahamsen, E. P.; Morales Maqueda, M. A.; Jones, D. C.; Naveira Garabato, A. C.

2016-10-01

The export of waters from the Weddell Gyre to lower latitudes is an integral component of the southern subpolar contribution to the three-dimensional oceanic circulation. Here we use more than 20 years of repeat hydrographic data on the continental slope on the northern tip of the Antarctic Peninsula and 5 years of bottom lander data on the slope at 1000 m to show the intermittent presence of a relatively cold, fresh, westward flowing current. This is often bottom-intensified between 600 and 2000 dbar with velocities of over 20 cm s-1, transporting an average of 1.5 ± 1.5 Sv. By comparison with hydrography on the continental slope within the Weddell Sea and modeled tracer release experiments we show that this slope current is an extension of the Antarctic Slope Current that has crossed the South Scotia Ridge west of Orkney Plateau. On monthly to interannual time scales the density of the slope current is negatively correlated (r > 0.6 with a significance of over 95%) with eastward wind stress over the northern Weddell Sea, but lagging it by 6-13 months. This relationship holds in both the high temporal resolution bottom lander time series and the 20+ year annual hydrographic occupations and agrees with Weddell Sea export variability observed further east. We compare several alternative hypotheses for this wind stress/export relationship and find that it is most consistent with wind-driven acceleration of the gyre boundary current, possibly modulated by eddy dynamics, and represents a mechanism by which climatic perturbations can be rapidly transmitted as fluctuations in the supply of intermediate-level waters to lower latitudes.

Wind-embedded shocks in FASTWIND: X-ray emission and K-shell absorption

Science.gov (United States)

Carneiro, L. P.; Puls, J.; Sundqvist, J. O.; Hoffmann, T. L.

2017-11-01

EUV and X-ray radiation emitted from wind-embedded shocks can affect the ionization balance in the outer atmospheres of massive stars, and can also be the mechanism responsible for producing highly ionized atoms detected in the wind UV spectra. To investigate these processes, we implemented the emission from wind-embedded shocks and related physics into our atmosphere/spectrum synthesis code FASTWIND. We also account for the high energy absorption of the cool wind, by adding important K-shell opacities. Various tests justfying our approach have been described by Carneiro+(2016, A&A 590, A88). In particular, we studied the impact of X-ray emission on the ionization balance of important elements. In almost all the cases, the lower ionization stages (O iv, N iv, P v) are depleted and the higher stages (N v, O v, O vi) become enhanced. Moreover, also He lines (in particular He ii 1640 and He ii 4686) can be affected as well. Finally, we carried out an extensive discussion of the high-energy mass absorption coefficient, κν, regarding its spatial variation and dependence on T eff. We found that (i) the approximation of a radially constant κν can be justified for r >= 1.2R * and λ <= 18 Å, and also for many models at longer wavelengths. (ii) In order to estimate the actual value of this quantity, however, the He ii background needs to be considered from detailed modeling.

A correlative study of simultaneously measured He(++) fluxes in the solar wind and in the magnetosphere utilizing Imp-1 and 1971-089A satellite data

Science.gov (United States)

Shelley, E. G.

1975-01-01

Simultaneously measured He(++) fluxes in the solar wind and in the magnetosphere were studied using data from the plasma spectrometer on the Imp I satellite and the energetic ion mass spectrometer on the low altitude polar orbiting satellite 1971-89A. A detailed comparison of the He(++) energy spectra measured simultaneously in the solar wind and in the low altitude dayside polar cusp on March 7, 1972 was made. The energy-per-unit-charge range of the energetic ion mass spectrometer on board the polar orbiting satellite was 700 eV to 12 keV. Within this range there was a clear maximum in the He(++) energy spectrum at approximately 1.5 keV/nucleon. There was not a clearly defined maximum in the H(+) spectrum, but the data were consistent with a peak between 0.7 and 1.0 keV/nucleon. Both spectra could be reasonably well fit with a convecting Maxwellian plus a high energy tail; however, the mean velocity for He(++) distribution was significantly greater than that for the H(+) distribution. The simultaneous solar wind measurements showed the mean velocities for both ion species to be approximately 600 km/sec. The discrepancies between the relative velocity distributions in the low altitude cusp and those in the solar wind are consistent with a potential difference of approximately 1.4 kV along their flow direction between the two points of observation.

Wind-driven roof turbines: a novel way to improve ventilation for TB infection control in health facilities.

Directory of Open Access Journals (Sweden)

Helen Cox

Full Text Available OBJECTIVE: Tuberculosis transmission in healthcare facilities contributes significantly to the TB epidemic, particularly in high HIV settings. Although improving ventilation may reduce transmission, there is a lack of evidence to support low-cost practical interventions. We assessed the efficacy of wind-driven roof turbines to achieve recommended ventilation rates, compared to current recommended practices for natural ventilation (opening windows, in primary care clinic rooms in Khayelitsha, South Africa. METHODS: Room ventilation was assessed (CO₂ gas tracer technique in 4 rooms where roof turbines and air-intake grates were installed, across three scenarios: turbine, grate and window closed, only window open, and only turbine and grate open, with concurrent wind speed measurement. 332 measurements were conducted over 24 months. FINDINGS: For all 4 rooms combined, median air changes per hour (ACH increased with wind speed quartiles across all scenarios. Higher median ACH were recorded with open roof turbines and grates, compared to open windows across all wind speed quartiles. Ventilation with open turbine and grate exceeded WHO-recommended levels (60 Litres/second/patient for 95% or more of measurements in 3 of the 4 rooms; 47% in the remaining room, where wind speeds were lower and a smaller diameter turbine was installed. CONCLUSION: High room ventilation rates, meeting recommended thresholds, may be achieved using wind-driven roof turbines and grates, even at low wind speeds. Roof turbines and air-intake grates are not easily closed by staff, allowing continued ventilation through colder periods. This simple, low-cost technology represents an important addition to our tools for TB infection control.

Wind-driven roof turbines: a novel way to improve ventilation for TB infection control in health facilities.

Science.gov (United States)

Cox, Helen; Escombe, Rod; McDermid, Cheryl; Mtshemla, Yolanda; Spelman, Tim; Azevedo, Virginia; London, Leslie

2012-01-01

Tuberculosis transmission in healthcare facilities contributes significantly to the TB epidemic, particularly in high HIV settings. Although improving ventilation may reduce transmission, there is a lack of evidence to support low-cost practical interventions. We assessed the efficacy of wind-driven roof turbines to achieve recommended ventilation rates, compared to current recommended practices for natural ventilation (opening windows), in primary care clinic rooms in Khayelitsha, South Africa. Room ventilation was assessed (CO₂ gas tracer technique) in 4 rooms where roof turbines and air-intake grates were installed, across three scenarios: turbine, grate and window closed, only window open, and only turbine and grate open, with concurrent wind speed measurement. 332 measurements were conducted over 24 months. For all 4 rooms combined, median air changes per hour (ACH) increased with wind speed quartiles across all scenarios. Higher median ACH were recorded with open roof turbines and grates, compared to open windows across all wind speed quartiles. Ventilation with open turbine and grate exceeded WHO-recommended levels (60 Litres/second/patient) for 95% or more of measurements in 3 of the 4 rooms; 47% in the remaining room, where wind speeds were lower and a smaller diameter turbine was installed. High room ventilation rates, meeting recommended thresholds, may be achieved using wind-driven roof turbines and grates, even at low wind speeds. Roof turbines and air-intake grates are not easily closed by staff, allowing continued ventilation through colder periods. This simple, low-cost technology represents an important addition to our tools for TB infection control.

Steady-state analysis of a conceptual offshore wind turbine driven electricity and thermocline energy extraction plant

OpenAIRE

Buhagiar, Daniel; Sant, Tonio

2014-01-01

A system for using offshore wind energy to generate electricity and simultaneously extract thermal energy is proposed. This concept is based on an offshore wind turbine driven hydraulic pump supplying deep seawater under high pressure to a land based plant consisting of a hydroelectric power generation unit and heat exchanger. A steady-state system model is developed using empirical formulae. The mathematical model comprises the fundamental system sub-models that are categoris...

Wind-driven rain as a boundary condition for HAM simulations: analysis of simplified modelling approaches

DEFF Research Database (Denmark)

Janssen, Hans; Blocken, Bert; Roels, Staf

2007-01-01

While the numerical simulation of moisture transfer inside building components is currently undergoing standardisation, the modelling of the atmospheric boundary conditions has received far less attention. This article analyses the modelling of the wind-driven-rain load on building facades...... though: the full variability with the perpendicular wind speed and horizontal rain intensity should be preserved, where feasible, for improved estimations of the moisture transfer in building components. In the concluding section, it is moreover shown that the dependence of the surface moisture transfer...

VLTI-AMBER Velocity-Resolved Aperture-Synthesis Imaging of Eta Carinae with a Spectral Resolution of 12 000: Studies of the Primary Star Wind and Innermost Wind-Wind Collision Zone

Science.gov (United States)

Weigelt, G.; Hofmann, K.-H.; Schertl, D.; Clementel, N.; Corcoran, M. F.; Damineli, A.; de Wit, W.-J.; Grellmann, R.; Groh, J.; Guieu, S.;

Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

Directory of Open Access Journals (Sweden)

Judit Lecina-Diaz

Full Text Available Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1 determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together and (2 ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires. The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn

Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

Science.gov (United States)

Lecina-Diaz, Judit; Alvarez, Albert; Retana, Javier

2014-01-01

Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR) from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1) determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together) and (2) ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires). The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires) showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn as extreme

Impact of neutrino flavor oscillations on the neutrino-driven wind nucleosynthesis of an electron-capture supernova

NARCIS (Netherlands)

Pllumbi, E.; Tamborra, I.; Wanajo, S.; Janka, H.-T.; Hüdepohl, L.

2015-01-01

Neutrino oscillations, especially to light sterile states, can affect nucleosynthesis yields because of their possible feedback effect on the electron fraction (Ye). For the first time, we perform nucleosynthesis calculations for neutrino-driven wind trajectories from the neutrino-cooling phase of

Development of a Wind Plant Large-Eddy Simulation with Measurement-Driven Atmospheric Inflow

Energy Technology Data Exchange (ETDEWEB)

Quon, Eliot W.; Churchfield, Matthew J.; Cheung, Lawrence; Kern, Stefan

2017-01-09

This paper details the development of an aeroelastic wind plant model with large-eddy simulation (LES). The chosen LES solver is the Simulator for Wind Farm Applications (SOWFA) based on the OpenFOAM framework, coupled to NREL's comprehensive aeroelastic analysis tool, FAST. An atmospheric boundary layer (ABL) precursor simulation was constructed based on assessments of meteorological tower, lidar, and radar data over a 3-hour window. This precursor was tuned to the specific atmospheric conditions that occurred both prior to and during the measurement campaign, enabling capture of a night-to-day transition in the turbulent ABL. In the absence of height-varying temperature measurements, spatially averaged radar data were sufficient to characterize the atmospheric stability of the wind plant in terms of the shear profile, and near-ground temperature sensors provided a reasonable estimate of the ground heating rate describing the morning transition. A full aeroelastic simulation was then performed for a subset of turbines within the wind plant, driven by the precursor. Analysis of two turbines within the array, one directly waked by the other, demonstrated good agreement with measured time-averaged loads.

Wind influence on a coastal buoyant outflow

Science.gov (United States)

Whitney, Michael M.; Garvine, Richard W.

2005-03-01

This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (∣Ws∣ Wind events, however, overwhelm the buoyancy-driven flow (∣Ws∣ > 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.

Enhanced Control for a Direct-driven Permanent Synchronous Generator Wind-power Generation System with Flywheel Energy Storage Unit Under Unbalanced Grid Fault

DEFF Research Database (Denmark)

Yao, Jun; Zhou, Te; Hu, Weihao

2015-01-01

This article presents an enhanced control strategy for a direct-driven permanent synchronous generator based wind-power generation system with a flywheel energy storage unit. The behaviors of the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit under......, the DC-link voltage oscillations can be effectively suppressed during the unbalanced grid fault by controlling the flywheel energy storage unit. Furthermore, a proportional–integral-resonant controller is designed for the flywheel motor to eliminate the oscillations in the DC-link voltage. Finally......, the proposed coordinated control strategy for the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit has been validated by the simulation results of a 1-MW direct-driven permanent magnet synchronous generator wind power generation system with a flywheel energy...

Effects of Wind Velocity Driven by Alfven Waves on the Line Profiles for 32 CYG

Directory of Open Access Journals (Sweden)

Kyung-Mee Kim

1996-06-01

Full Text Available We calculate the theoretical line profiles for 32 Cyg in order to investigate the influence of various velocity fields. Line profiles are calculated with wind accelerations driven by Alfven waves and described by velocity parameters. The results for Alfvenic wave model show weakened line profiles. For the orbital phases ¥÷=0.78 and ¥÷=0.06 the Alfvenic models show strong absorption part due to very low densities at the surface of the supergiant. Hence, we conclude the velocity gradient of the wind near the supergiant could influence on the theoretical line formation.

Efficient 3He/4He separation in a nanoporous graphenylene membrane.

Science.gov (United States)

Qu, Yuanyuan; Li, Feng; Zhao, Mingwen

2017-08-16

Helium-3 is a precious noble gas, which is essential in many advanced technologies such as cryogenics, isotope labeling and nuclear weapons. The current imbalance of 3 He demand and supply shortage leads to the search for an efficient membrane with high performance for 3 He separation. In this study, based on first-principles calculations, we demonstrated that highly efficient 3 He harvesting can be achieved in a nanoporous graphenylene membrane with industrially-acceptable selectivity and permeance. The quantum tunneling effect leads to 3 He harvesting with high efficiency via kinetic sieving. Both the quantum tunneling effect and zero-point energy (ZPE) determine the 3 He/ 4 He separation via thermally-driven equilibrium sieving, where the ZPE effect dominates efficient 3 He/ 4 He separation between two reservoirs. The quantum effects revealed in this work suggest that the nanoporous graphenylene membrane is promising for efficient 3 He harvesting that can be exploited for industrial applications.

Bats and wind energy: a literature synthesis and annotated bibliography

Science.gov (United States)

Ellison, Laura E.

2012-01-01

Turbines have been used to harness energy from wind for hundreds of years. However, with growing concerns about climate change, wind energy has only recently entered the mainstream of global electricity production. Since early on in the development of wind-energy production, concerns have arisen about the potential impacts of turbines to wildlife; these concerns have especially focused on the mortality of birds. Despite recent improvements to turbines that have resulted in reduced mortality of birds, there is clear evidence that bat mortality at wind turbines is of far greater conservation concern. Bats of certain species are dying by the thousands at turbines across North America, and the species consistently affected tend to be those that rely on trees as roosts and most migrate long distances. Turbine-related bat mortalities are now affecting nearly a quarter of all bat species occurring in the United States and Canada. Most documented bat mortality at wind-energy facilities has occurred in late summer and early fall and has involved tree bats, with hoary bats (Lasiurus cinereus) being the most prevalent among fatalities. This literature synthesis and annotated bibliography focuses on refereed journal publications and theses about bats and wind-energy development in North America (United States and Canada). Thirty-six publications and eight theses were found, and their key findings were summarized. These publications date from 1996 through 2011, with the bulk of publications appearing from 2007 to present, reflecting the relatively recent conservation concerns about bats and wind energy. The idea for this Open-File Report formed while organizing a joint U.S. Fish and Wildlife Service/U.S. Geological Survey "Bats and Wind Energy Workshop," on January 25-26, 2012. The purposes of the workshop were to develop a list of research priorities to support decision making concerning bats with respect to siting and operations of wind-energy facilities across the United

Can Winds Driven by Active Galactic Nuclei Account for the Extragalactic Gamma-Ray and Neutrino Backgrounds?

Science.gov (United States)

Liu, Ruo-Yu; Murase, Kohta; Inoue, Susumu; Ge, Chong; Wang, Xiang-Yu

2018-05-01

Various observations are revealing the widespread occurrence of fast and powerful winds in active galactic nuclei (AGNs) that are distinct from relativistic jets, likely launched from accretion disks and interacting strongly with the gas of their host galaxies. During the interaction, strong shocks are expected to form that can accelerate nonthermal particles to high energies. Such winds have been suggested to be responsible for a large fraction of the observed extragalactic gamma-ray background (EGB) and the diffuse neutrino background, via the decay of neutral and charged pions generated in inelastic pp collisions between protons accelerated by the forward shock and the ambient gas. However, previous studies did not properly account for processes such as adiabatic losses that may reduce the gamma-ray and neutrino fluxes significantly. We evaluate the production of gamma rays and neutrinos by AGN-driven winds in detail by modeling their hydrodynamic and thermal evolution, including the effects of their two-temperature structure. We find that they can only account for less than ∼30% of the EGB flux, as otherwise the model would violate the independent upper limit derived from the diffuse isotropic gamma-ray background. If the neutrino spectral index is steep with Γ ≳ 2.2, a severe tension with the isotropic gamma-ray background would arise as long as the winds contribute more than 20% of the IceCube neutrino flux in the 10–100 TeV range. At energies ≳ 100 TeV, we find that the IceCube neutrino flux may still be accountable by AGN-driven winds if the spectral index is as small as Γ ∼ 2.0–2.1.

Spectroscopy of FO Aquarii - Evidence for reprocessing in a hot wind

International Nuclear Information System (INIS)

Martell, P.J.; Kaitchuck, R.H.

1991-01-01

Results are presented on spectroscopic observations of FO Aqr, carried out on the nights of September 4-7, 1986 with the 1.8-m Perkins Telescope at Lowell Observatory. It is shown that the observed 21-min modulation of the He II 4686-A line is driven by two emission components which vary in flux and have large negative radial velocities. Arguments are presented to the effect that the modulated portion of the He II 4686-A emission originates from the reprocessing of X-rays in hot winds at these two sites. It is suggested that all other 21-min modulations are due to reprocessing. 32 refs

Relational Constraint Driven Test Case Synthesis for Web Applications

Directory of Open Access Journals (Sweden)

Xiang Fu

2010-09-01

Full Text Available This paper proposes a relational constraint driven technique that synthesizes test cases automatically for web applications. Using a static analysis, servlets can be modeled as relational transducers, which manipulate backend databases. We present a synthesis algorithm that generates a sequence of HTTP requests for simulating a user session. The algorithm relies on backward symbolic image computation for reaching a certain database state, given a code coverage objective. With a slight adaptation, the technique can be used for discovering workflow attacks on web applications.

Data-Driven Method for Wind Turbine Yaw Angle Sensor Zero-Point Shifting Fault Detection

Directory of Open Access Journals (Sweden)

Yan Pei

2018-03-01

Full Text Available Wind turbine yaw control plays an important role in increasing the wind turbine production and also in protecting the wind turbine. Accurate measurement of yaw angle is the basis of an effective wind turbine yaw controller. The accuracy of yaw angle measurement is affected significantly by the problem of zero-point shifting. Hence, it is essential to evaluate the zero-point shifting error on wind turbines on-line in order to improve the reliability of yaw angle measurement in real time. Particularly, qualitative evaluation of the zero-point shifting error could be useful for wind farm operators to realize prompt and cost-effective maintenance on yaw angle sensors. In the aim of qualitatively evaluating the zero-point shifting error, the yaw angle sensor zero-point shifting fault is firstly defined in this paper. A data-driven method is then proposed to detect the zero-point shifting fault based on Supervisory Control and Data Acquisition (SCADA data. The zero-point shifting fault is detected in the proposed method by analyzing the power performance under different yaw angles. The SCADA data are partitioned into different bins according to both wind speed and yaw angle in order to deeply evaluate the power performance. An indicator is proposed in this method for power performance evaluation under each yaw angle. The yaw angle with the largest indicator is considered as the yaw angle measurement error in our work. A zero-point shifting fault would trigger an alarm if the error is larger than a predefined threshold. Case studies from several actual wind farms proved the effectiveness of the proposed method in detecting zero-point shifting fault and also in improving the wind turbine performance. Results of the proposed method could be useful for wind farm operators to realize prompt adjustment if there exists a large error of yaw angle measurement.

A Hybrid Genetic Wind Driven Heuristic Optimization Algorithm for Demand Side Management in Smart Grid

Directory of Open Access Journals (Sweden)

Nadeem Javaid

2017-03-01

Full Text Available In recent years, demand side management (DSM techniques have been designed for residential, industrial and commercial sectors. These techniques are very effective in flattening the load profile of customers in grid area networks. In this paper, a heuristic algorithms-based energy management controller is designed for a residential area in a smart grid. In essence, five heuristic algorithms (the genetic algorithm (GA, the binary particle swarm optimization (BPSO algorithm, the bacterial foraging optimization algorithm (BFOA, the wind-driven optimization (WDO algorithm and our proposed hybrid genetic wind-driven (GWD algorithm are evaluated. These algorithms are used for scheduling residential loads between peak hours (PHs and off-peak hours (OPHs in a real-time pricing (RTP environment while maximizing user comfort (UC and minimizing both electricity cost and the peak to average ratio (PAR. Moreover, these algorithms are tested in two scenarios: (i scheduling the load of a single home and (ii scheduling the load of multiple homes. Simulation results show that our proposed hybrid GWD algorithm performs better than the other heuristic algorithms in terms of the selected performance metrics.

DNA synthesis in HeLa cells and isolated nuclei after treatment with an inhibitor of spermidine synthesis, methyl glyoxal bis(guanylhydrazone).

Science.gov (United States)

Krokan, H; Eriksen, A

1977-02-01

Addition of methyl glyoxal bis(guanylhydrazone) to HeLa S3 suspension cultures resulted in increased putrescine levels and decreased spermidine and spermine levels preceding a drop in incorporation of [3H]thymidine, [3H]uridine and [14C]leucine into macromolecules. When putrescine, spermidine, spermine or cadaverine was added simultaneously with methyl glyoxal bis(guanylhydrazone), the drug had no detectable effect on the synthesis of macromolecules. In nuclei isolated from cells treated with methyl glyoxal bis(guanylhydrazone) the reduction in the rate of DNA synthesis was equal to the reduction of [3H]thymidine incorporation in the corresponding whole cells. The capability of the nuclei to synthesize DNA could not be restored by adding spermidine or spermine to the system in vitro. The rate of DNA chain elongation was only reduced slightly by methyl glyoxal bis(guanylhydrazone) indicating that decreased levels of spermidine and spermine lead to a decrease in the number of replication units active in DNA synthesis within each cell.

Star Formation-Driven Winds in the Early Universe

Science.gov (United States)

Peek, Matthew; Lundgren, Britt; Brammer, Gabriel

2018-01-01

Measuring the extent of star formation-driven winds from galaxies in the early universe is crucial for understanding of how galaxies evolve over cosmic time. Using WFC3/IR grism data from the Hubble Space Telescope (HST), we have measured the star formation rates and star formation rate surface densities of several hundred galaxies at redshift (z) = 1, when the universe was roughly half its present age. The galaxies we examine are also probed by background quasars, whose spectra provide information about the extent of metal-enriched gas in their halos. We use a computational pipeline to measure the density of the star formation in each galaxy and correlate these measurements with detections of Mg II absorption in nearby quasar spectra from the Sloan Digital Sky Survey. Our preliminary results support a model in which galaxies with high SFR surface densities drive metal-enriched gas out of the disk and into these galaxies’ extended halos, where that gas is detected in the spectra of more distant quasars.

Development of a Wind Plant Large-Eddy Simulation with Measurement-Driven Atmospheric Inflow: Preprint

Energy Technology Data Exchange (ETDEWEB)

Quon, Eliot; Churchfield, Matthew; Cheung, Lawrence; Kern, Stefan

2017-02-01

This paper details the development of an aeroelastic wind plant model with large-eddy simulation (LES). The chosen LES solver is the Simulator for Wind Farm Applications (SOWFA) based on the OpenFOAM framework, coupled to NREL's comprehensive aeroelastic analysis tool, FAST. An atmospheric boundary layer (ABL) precursor simulation was constructed based on assessments of meteorological tower, lidar, and radar data over a 3-hour window. This precursor was tuned to the specific atmospheric conditions that occurred both prior to and during the measurement campaign, enabling capture of a night-to-day transition in the turbulent ABL. In the absence of height-varying temperature measurements, spatially averaged radar data were sufficient to characterize the atmospheric stability of the wind plant in terms of the shear profile, and near-ground temperature sensors provided a reasonable estimate of the ground heating rate describing the morning transition. A full aeroelastic simulation was then performed for a subset of turbines within the wind plant, driven by the precursor. Analysis of two turbines within the array, one directly waked by the other, demonstrated good agreement with measured time-averaged loads.

Design optimization of offshore wind farms with multiple types of wind turbines

DEFF Research Database (Denmark)

Feng, Ju; Shen, Wen Zhong

2017-01-01

Most studies on offshore wind farm design assume a uniform wind farm, which consists of an identical type of wind turbines. In order to further reduce the cost of energy, we investigate the design of non-uniform offshore wind farms, i.e., wind farms with multiple types of wind turbines and hub-he...

RECONNECTION-DRIVEN CORONAL-HOLE JETS WITH GRAVITY AND SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

Karpen, J. T.; DeVore, C. R.; Antiochos, S. K. [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt MD 20771 (United States); Pariat, E. [LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, F-92195 Meudon (France)

2017-01-01

Coronal-hole jets occur ubiquitously in the Sun's coronal holes, at EUV and X-ray bright points associated with intrusions of minority magnetic polarity. The embedded-bipole model for these jets posits that they are driven by explosive, fast reconnection between the stressed closed field of the embedded bipole and the open field of the surrounding coronal hole. Previous numerical studies in Cartesian geometry, assuming uniform ambient magnetic field and plasma while neglecting gravity and solar wind, demonstrated that the model is robust and can produce jet-like events in simple configurations. We have extended these investigations by including spherical geometry, gravity, and solar wind in a nonuniform, coronal hole-like ambient atmosphere. Our simulations confirm that the jet is initiated by the onset of a kink-like instability of the internal closed field, which induces a burst of reconnection between the closed and external open field, launching a helical jet. Our new results demonstrate that the jet propagation is sustained through the outer corona, in the form of a traveling nonlinear Alfvén wave front trailed by slower-moving plasma density enhancements that are compressed and accelerated by the wave. This finding agrees well with observations of white-light coronal-hole jets, and can explain microstreams and torsional Alfvén waves detected in situ in the solar wind. We also use our numerical results to deduce scaling relationships between properties of the coronal source region and the characteristics of the resulting jet, which can be tested against observations.

Influence of input data on airflow network accuracy in residential buildings with natural wind- and stack-driven ventilation

Institute of Scientific and Technical Information of China (English)

Krzysztof Arendt; Marek Krzaczek; Jacek Tejchman

2017-01-01

The airflow network (AFN) modeling approach provides an attractive balance between the accuracy and computational demand for naturally ventilated buildings. Its accuracy depends on input parameters such as wind pressure and opening discharge coefficients. In most cases, these parameters are obtained from secondary sources which are solely representative for very simplified buildings, i.e. for buildings without facade details. Although studies comparing wind pressure coefficients or discharge coefficients from different sources exist, the knowledge regarding the effect of input data on AFN is still poor. In this paper, the influence of wind pressure data on the accuracy of a coupled AFN-BES model for a real building with natural wind- and stack-driven ventilation was analyzed. The results of 8 computation cases with different wind pressure data from secondary sources were compared with the measured data. Both the indoor temperatures and the airflow were taken into account. The outcomes indicated that the source of wind pressure data had a significant influence on the model performance.

Simulation of barotropic wind-driven circulation in the upper layers of Bay of Bengal and Andaman Sea during the southwest and northeast monsoon seasons using observed winds

Digital Repository Service at National Institute of Oceanography (India)

Bahulayan, N.; Unnikrishnan, A.S.

A two-dimensional, nonlinear, vertically integrated model was used to simulate depth-mean wind-driven circulation in the upper Ekman layers of the Bay of Bengal and Andaman Sea. The model resolution was one third of a degree in the latitude...

Wind Turbine Technologies

DEFF Research Database (Denmark)

Hansen, Anca Daniela

2017-01-01

, and with or without gearboxes, using the latest in power electronics, aerodynamics, and mechanical drive train designs [4]. The main differences between all wind turbine concepts developed over the years, concern their electrical design and control. Today, the wind turbines on the market mix and match a variety......, the design of wind turbines has changed from being convention driven to being optimized driven within the operating regime and market environment. Wind turbine designs have progressed from fixed speed, passive controlled and with drive trains with gearboxes, to become variable speed, active controlled......,6] and to implement modern control system strategies....

Scaling Relations of Starburst-driven Galactic Winds

International Nuclear Information System (INIS)

Tanner, Ryan; Cecil, Gerald; Heitsch, Fabian

2017-01-01

Using synthetic absorption lines generated from 3D hydrodynamical simulations, we explore how the velocity of a starburst-driven galactic wind correlates with the star formation rate (SFR) and SFR density. We find strong correlations for neutral and low ionized gas, but no correlation for highly ionized gas. The correlations for neutral and low ionized gas only hold for SFRs below a critical limit set by the mass loading of the starburst, above which point the scaling relations flatten abruptly. Below this point the scaling relations depend on the temperature regime being probed by the absorption line, not on the mass loading. The exact scaling relation depends on whether the maximum or mean velocity of the absorption line is used. We find that the outflow velocity of neutral gas can be up to five times lower than the average velocity of ionized gas, with the velocity difference increasing for higher ionization states. Furthermore, the velocity difference depends on both the SFR and mass loading of the starburst. Thus, absorption lines of neutral or low ionized gas cannot easily be used as a proxy for the outflow velocity of the hot gas.

Scaling Relations of Starburst-driven Galactic Winds

Energy Technology Data Exchange (ETDEWEB)

Tanner, Ryan [Department of Chemistry and Physics, Augusta University, Augusta, GA 30912 (United States); Cecil, Gerald; Heitsch, Fabian, E-mail: rytanner@augusta.edu [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255 (United States)

2017-07-10

Using synthetic absorption lines generated from 3D hydrodynamical simulations, we explore how the velocity of a starburst-driven galactic wind correlates with the star formation rate (SFR) and SFR density. We find strong correlations for neutral and low ionized gas, but no correlation for highly ionized gas. The correlations for neutral and low ionized gas only hold for SFRs below a critical limit set by the mass loading of the starburst, above which point the scaling relations flatten abruptly. Below this point the scaling relations depend on the temperature regime being probed by the absorption line, not on the mass loading. The exact scaling relation depends on whether the maximum or mean velocity of the absorption line is used. We find that the outflow velocity of neutral gas can be up to five times lower than the average velocity of ionized gas, with the velocity difference increasing for higher ionization states. Furthermore, the velocity difference depends on both the SFR and mass loading of the starburst. Thus, absorption lines of neutral or low ionized gas cannot easily be used as a proxy for the outflow velocity of the hot gas.

A Semi-analytical Model for Wind-fed Black Hole High-mass X-Ray Binaries: State Transition Triggered by Magnetic Fields from the Companion Star

Energy Technology Data Exchange (ETDEWEB)

Yaji, Kentaro; Yamada, Shinya; Masai, Kuniaki [Department of Physics, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji, Tokyo 192-0397 (Japan)

2017-10-01

We propose a mechanism of state transition in wind-fed black hole (BH) binaries (high-mass X-ray binaries) such as Cyg X-1 and LMC X-1. Modeling a line-driven stellar wind from the companion by two-dimensional hydrodynamical calculations, we investigate the processes of wind capture by, and accretion onto, the BH. We assume that the wind acceleration is terminated at the He ii ionization front because ions responsible for line-driven acceleration are ionized within the front, i.e., the He iii region. It is found that the mass accretion rate inferred from the luminosity is remarkably smaller than the capture rate. Considering the difference, we construct a model for the state transition based on the accretion flow being controlled by magnetorotational instability. The outer flow is torus-like, and plays an important role to trigger the transition. The model can explain why state transition does occur in Cyg X-1, while not in LMC X-1. Cyg X-1 exhibits a relatively low luminosity, and then the He ii ionization front is located and can move between the companion and BH, depending on its ionizing photon flux. On the other hand, LMC X-1 exhibits too high luminosity for the front to move considerably; the front is too close to the companion atmosphere. The model also predicts that each state of high-soft or low-hard would last fairly long because the luminosity depends weakly on the wind velocity. In the context of the model, the state transition is triggered by a fluctuation of the magnetic field when its amplitude becomes comparable to the field strength in the torus-like outer flow.

Formation of intrathermocline eddies at ocean fronts by wind-driven destruction of potential vorticity

Science.gov (United States)

Thomas, Leif N.

2008-08-01

A mechanism for the generation of intrathermocline eddies (ITEs) at wind-forced fronts is examined using a high resolution numerical simulation. Favorable conditions for ITE formation result at fronts forced by "down-front" winds, i.e. winds blowing in the direction of the frontal jet. Down-front winds exert frictional forces that reduce the potential vorticity (PV) within the surface boundary in the frontal outcrop, providing a source for the low-PV water that is the materia prima of ITEs. Meandering of the front drives vertical motions that subduct the low-PV water into the pycnocline, pooling it into the coherent anticyclonic vortex of a submesoscale ITE. As the fluid is subducted along the outcropping frontal isopycnal, the low-PV water, which at the surface is associated with strongly baroclinic flow, re-expresses itself as water with nearly zero absolute vorticity. This generation of strong anticyclonic vorticity results from the tilting of the horizontal vorticity of the frontal jet, not from vortex squashing. During the formation of the ITE, high-PV water from the pycnocline is upwelled alongside the subducting low-PV surface water. The positive correlation between the ITE's velocity and PV fields results in an upward, along-isopycnal eddy PV flux that scales with the surface frictional PV flux driven by the wind. The relationship between the eddy and wind-induced frictional PV flux is nonlocal in time, as the eddy PV flux persists long after the wind forcing is shut off. The ITE's PV flux affects the large-scale flow by driving an eddy-induced transport or bolus velocity down the outcropping isopycnal layer with a magnitude that scales with the Ekman velocity.

Recent Successes of Wave/Turbulence Driven Models of Solar Wind Acceleration

Science.gov (United States)

Cranmer, S. R.; Hollweg, J. V.; Chandran, B. D.; van Ballegooijen, A. A.

2010-12-01

A key obstacle in the way of producing realistic simulations of the Sun-heliosphere system is the lack of a first-principles understanding of coronal heating. Also, it is still unknown whether the solar wind is "fed" through flux tubes that remain open (and are energized by footpoint-driven wavelike fluctuations) or if mass and energy are input intermittently from closed loops into the open-field regions. In this presentation, we discuss self-consistent models that assume the energy comes from solar Alfven waves that are partially reflected, and then dissipated, by magnetohydrodynamic turbulence. These models have been found to reproduce many of the observed features of the fast and slow solar wind without the need for artificial "coronal heating functions" used by earlier models. For example, the models predict a variation with wind speed in commonly measured ratios of charge states and elemental abundances that agrees with observed trends. This contradicts a commonly held assertion that these ratios can only be produced by the injection of plasma from closed-field regions on the Sun. This presentation also reviews two recent comparisons between the models and empirical measurements: (1) The models successfully predict the amplitude and radial dependence of Faraday rotation fluctuations (FRFs) measured by the Helios probes for heliocentric distances between 2 and 15 solar radii. The FRFs are a particularly sensitive test of turbulence models because they depend not only on the plasma density and Alfven wave amplitude in the corona, but also on the turbulent correlation length. (2) The models predict the correct sense and magnitude of changes seen in the polar high-speed solar wind by Ulysses from the previous solar minimum (1996-1997) to the more recent peculiar minimum (2008-2009). By changing only the magnetic field along the polar magnetic flux tube, consistent with solar and heliospheric observations at the two epochs, the model correctly predicts that the

Loss evaluation and design optimisation for direct driven permanent magnet synchronous generators for wind power

Energy Technology Data Exchange (ETDEWEB)

Eriksson, Sandra; Bernhoff, Hans [Swedish Centre for Renewable Electric Energy Conversion, Division for Electricity, Department of Engineering Sciences, Uppsala University, Box 534, 751 21 Uppsala (Sweden)

2011-01-15

When designing a generator for a wind turbine it is important to adapt the generator to the source, i.e. the wind conditions at the specific site. Furthermore, the variable speed operation of the generator needs to be considered. In this paper, electromagnetic losses in direct driven permanent magnet synchronous generators are evaluated through simulations. Six different generators are compared to each other. The simulations are performed by using an electromagnetic model, solved in a finite element environment and a control model developed in MATLAB. It is shown that when designing a generator it is important to consider the statistical wind distribution, control system, and aerodynamic efficiency in order to evaluate the performance properly. In this paper, generators with high overload capability are studied since they are of interest for this specific application. It is shown that a generator optimised for a minimum of losses will have a high overload capability. (author)

COS-burst: Observations of the Impact of Starburst-driven Winds on the Properties of the Circum-galactic Medium

Energy Technology Data Exchange (ETDEWEB)

Heckman, Timothy; Borthakur, Sanchayeeta [Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Wild, Vivienne [School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9AJ (United Kingdom); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Bordoloi, Rongmon, E-mail: theckma1@jhu.edu [MIT-Kavli Center for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

2017-09-10

We report on observations made with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope ( HST ) using background quasi-stellar objects to probe the circum-galactic medium (CGM) around 17 low-redshift galaxies that are undergoing or have recently undergone a strong starburst (the COS-Burst program). The sightlines extend out to roughly the virial radius of the galaxy halo. We construct control samples of normal star-forming low-redshift galaxies from the COS/ HST archive that match the starbursts in terms of galaxy stellar mass and impact parameter. We find clear evidence that the CGM around the starbursts differs systematically compared to the control galaxies. The Ly α , Si iii, C iv, and possibly O vi absorption lines are stronger as a function of impact parameter, and the ratios of the equivalent widths of C iv/Ly α and Si iii/Ly α are both higher than in normal star-forming galaxies. We also find that the widths and the velocity offsets (relative to v {sub sys}) of the Ly α absorption lines are significantly larger in the CGM of the starbursts, implying velocities of the absorbing material that are roughly twice the halo virial velocity. We show that these properties can be understood as a consequence of the interaction between a starburst-driven wind and the preexisting CGM. These results underscore the importance of winds driven from intensely star-forming galaxies in helping drive the evolution of galaxies and the intergalactic medium. They also offer a new probe of the properties of starburst-driven winds and of the CGM itself.

Thermal and Driven Stochastic Growth of Langmuir Waves in the Solar Wind and Earth's Foreshock

Science.gov (United States)

Cairns, Iver H.; Robinson, P. A.; Anderson, R. R.

2000-01-01

Statistical distributions of Langmuir wave fields in the solar wind and the edge of Earth's foreshock are analyzed and compared with predictions for stochastic growth theory (SGT). SGT quantitatively explains the solar wind, edge, and deep foreshock data as pure thermal waves, driven thermal waves subject to net linear growth and stochastic effects, and as waves in a pure SGT state, respectively, plus radiation near the plasma frequency f(sub p). These changes are interpreted in terms of spatial variations in the beam instability's growth rate and evolution toward a pure SGT state. SGT analyses of field distributions are shown to provide a viable alternative to thermal noise spectroscopy for wave instruments with coarse frequency resolution, and to separate f(sub p) radiation from Langmuir waves.

Controller synthesis for negative imaginary systems: a data driven approach

KAUST Repository

Mabrok, Mohamed

2016-02-17

The negative imaginary (NI) property occurs in many important applications. For instance, flexible structure systems with collocated force actuators and position sensors can be modelled as negative imaginary systems. In this study, a data-driven controller synthesis methodology for NI systems is presented. In this approach, measured frequency response data of the plant is used to construct the controller frequency response at every frequency by minimising a cost function. Then, this controller response is used to identify the controller transfer function using system identification methods. © The Institution of Engineering and Technology 2016.

Nonspherical Radiation Driven Wind Models Applied to Be Stars

Science.gov (United States)

Arauxo, F. X.

1990-11-01

ABSTRACT. In this work we present a model for the structure of a radiatively driven wind in the meridional plane of a hot star. Rotation effects and simulation of viscous forces were included in the motion equations. The line radiation force is considered with the inclusion of the finite disk correction in self-consistent computations which also contain gravity darkening as well as distortion of the star by rotation. An application to a typical BlV star leads to mass-flux ratios between equator and pole of the order of 10 and mass loss rates in the range 5.l0 to Mo/yr. Our envelope models are flattened towards the equator and the wind terminal velocities in that region are rather high (1000 Km/s). However, in the region near the star the equatorial velocity field is dominated by rotation. RESUMEN. Se presenta un modelo de la estructura de un viento empujado radiativamente en el plano meridional de una estrella caliente. Se incluyeron en las ecuaciones de movimiento los efectos de rotaci6n y la simulaci6n de fuerzas viscosas. Se consider6 la fuerza de las lineas de radiaci6n incluyendo la correcci6n de disco finito en calculos autoconsistentes los cuales incluyen oscurecimiento gravitacional asi como distorsi6n de la estrella por rotaci6n. La aplicaci6n a una estrella tipica BlV lleva a cocientes de flujo de masa entre el ecuador y el polo del orden de 10 de perdida de masa en el intervalo 5.l0 a 10 Mo/ano. Nuestros modelos de envolvente estan achatados hacia el ecuador y las velocidads terminales del viento en esa regi6n son bastante altas (1000 Km/s). Sin embargo, en la regi6n cercana a la estrella el campo de velocidad ecuatorial esta dominado por la rotaci6n. Key words: STARS-BE -- STARS-WINDS

Simulation of barotropic wind-driven circulation in tbe Bay of Bengal and Andaman Sea during premonsoon and postmonsoon seasons

Digital Repository Service at National Institute of Oceanography (India)

Unnikrishnan, A.S.; Bahulayan, N.

Two-dimensional vertically integrated model has been used to simulate depth-mean wind-driven circulation during premonsoon and postmonsoon seasons in the upper layers of the Bay of Bengal and Andaman Sea. The model is integrated for 365 d, forcEd...

Action of caffeine on x-irradiated HeLa cells. I. Delayed inhibition of DNA synthesis

International Nuclear Information System (INIS)

Tolmach, L.J.; Jones, R.W.; Busse, P.M.

1977-01-01

Treatment of HeLa S3 cells with 1 mM caffeine delays progression through G1 by 1.5 hours but causes no other detectable inhibition of cell progression; it sometimes results in a large stimulation of thymidine incorporation. When this concentration is applied to cells that have been irradiated with 1-krad doses of 220-kV x rays, there is a marked suppression of both the inhibition of DNA synthesis and G2 arrest induced by the radiation. Larger doses require higher concentrations of caffeine to suppress the inhibition of DNA synthesis. Delaying addition until the rate of synthesis is at its minimum (1.5 hours after irradiation with 1 krad) results in a slightly accelerated recovery of the rate. Treatment before or during irradiation is without effect on the inhibition. Removal of the caffeine as late as 6 hours after its addition at the time of irradiation results in a prompt inhibition in DNA synthesis that mimics that observed immediately after irradiation in the absence of caffeine. These findings raise the possibility that the depression in rate of DNA systhesis might not result from radiation damage introduced into the replicon initiation system, but rather may be an indirect consequence of damage residing elsewhere in the irradiated cell

A Component Mode Synthesis Algorithm for Multibody Dynamics of Wind Turbines

DEFF Research Database (Denmark)

Holm-Jørgensen, Kristian; Nielsen, Søren R.K.

2009-01-01

A system reduction scheme related to a multibody formulation of wind turbine dynamics is devised. Each substructure is described in its own frame of reference, which is moving freely in the vicinity of the moving substructure, in principle without any constraints to the rigid body part of the mot......A system reduction scheme related to a multibody formulation of wind turbine dynamics is devised. Each substructure is described in its own frame of reference, which is moving freely in the vicinity of the moving substructure, in principle without any constraints to the rigid body part...... of the motion of the substructure. The system reduction is based on a component mode synthesis method, where the response of the internal degrees of freedom of the substructure is described as the quasi-static response induced by the boundary degrees of freedom via the constraint modes superimposed...

Red Geyser: A New Class of Galaxy with Large-scale AGN-driven Winds

Science.gov (United States)

Roy, Namrata; Bundy, Kevin; Cheung, Edmond; MaNGA Team

2018-01-01

A new class of quiescent (non-star-forming) galaxies harboring possible AGN-driven winds have been discovered using the spatially resolved optical spectroscopy from the ongoing SDSS-IV MaNGA (Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory) survey. These galaxies named "red geysers" constitute 5%-10% of the local quiescent galaxy population and are characterized by narrow bisymmetric ionized gas emission patterns. These enhanced patterns are seen in equivalent width maps of Hα, [OIII] and other strong emission lines. They are co-aligned with the ionized gas velocity gradients but significantly misaligned with stellar velocity gradients. They also show very high gas velocity dispersions (~200 km/s). Considering these observations in light of models of the gravitational potential, Cheung et al. argued that red geysers host large-scale AGN-driven winds of ionized gas that may play a role in suppressing star formation at late times. In this work, we test the hypothesis that AGN activity is ultimately responsible for the red geyser phenomenon. We compare the nuclear radio activity of the red geysers to a matched control sample of galaxies of similar stellar mass, redshift, rest frame NUV–r color and axis ratio. and additionally, control for the presence of ionized gas. We have used 1.4 GHz radio continuum data from the VLA FIRST Survey to stack the radio flux from the red geyser sample and control sample. We find that the red geysers have a higher average radio flux than the control galaxies at > 3σ significance. Our sample is restricted to rest-frame NUV–r color > 5, thus ruling out possible radio emission due to star formation activity. We conclude that red geysers are associated with more active AGN, supporting a feedback picture in which episodic AGN activity drives large-scale but relatively weak ionized winds in many in many early-type galaxies.

Atomic Physics of Shocked Plasma in Winds of Massive Stars

Science.gov (United States)

Leutenegger, Maurice A.; Cohen, David H.; Owocki, Stanley P.

2012-01-01

High resolution diffraction grating spectra of X-ray emission from massive stars obtained with Chandra and XMM-Newton have revolutionized our understanding of their powerful, radiation-driven winds. Emission line shapes and line ratios provide diagnostics on a number of key wind parameters. Modeling of resolved emission line velocity profiles allows us to derive independent constraints on stellar mass-loss rates, leading to downward revisions of a factor of a few from previous measurements. Line ratios in He-like ions strongly constrain the spatial distribution of Xray emitting plasma, confirming the expectations of radiation hydrodynamic simulations that X-ray emission begins moderately close to the stellar surface and extends throughout the wind. Some outstanding questions remain, including the possibility of large optical depths in resonance lines, which is hinted at by differences in line shapes of resonance and intercombination lines from the same ion. Resonance scattering leads to nontrivial radiative transfer effects, and modeling it allows us to place constraints on shock size, density, and velocity structure

Comparison of driven and simulated "free" stall flutter in a wind tunnel

Science.gov (United States)

Culler, Ethan; Farnsworth, John; Fagley, Casey; Seidel, Jurgen

2016-11-01

Stall flutter and dynamic stall have received a significant amount of attention over the years. To experimentally study this problem, the body undergoing stall flutter is typically driven at a characteristic, single frequency sinusoid with a prescribed pitching amplitude and mean angle of attack offset. This approach allows for testing with repeatable kinematics, however it effectively decouples the structural motion from the aerodynamic forcing. Recent results suggest that this driven approach could misrepresent the forcing observed in a "free" stall flutter scenario. Specifically, a dynamically pitched rigid NACA 0018 wing section was tested in the wind tunnel under two modes of operation: (1) Cyber-Physical where "free" stall flutter was physically simulated through a custom motor-control system modeling a torsional spring and (2) Direct Motor-Driven Dynamic Pitch at a single frequency sinusoid representative of the cyber-physical motion. The time-resolved pitch angle and moment were directly measured and compared for each case. It was found that small deviations in the pitch angle trajectory between these two operational cases generate significantly different aerodynamic pitching moments on the wing section, with the pitching moments nearly 180o out of phase in some cases. This work is supported by the Air Force Office of Scientific Research through the Flow Interactions and Control Program and by the National Defense Science and Engineering Graduate Fellowship Program.

Direct Driven Permanent Magnet Synchronous Generators with Diode Rectifiers for Use in Offshore Wind Turbines

OpenAIRE

Reigstad, Tor Inge

2007-01-01

This work is focused on direct-driven permanent magnets synchronous generators (PMSG) with diode rectifiers for use in offshore wind turbines. Reactive compensation of the generator, power losses and control of the generator are studied. Configurations for power transmission to onshore point of common connection are also considered. Costs, power losses, reliability and interface with the PMSG are discussed. The purpose of the laboratory tests and simulations are to learn how a PMSG with dio...

Non-axisymmetric line-driven disc winds - I. Disc perturbations

Science.gov (United States)

Dyda, Sergei; Proga, Daniel

2018-04-01

We study mass outflows driven from accretion discs by radiation pressure due to spectral lines. To investigate non-axisymmetric effects, we use the ATHENA++ code and develop a new module to account for radiation pressure driving. In 2D, our new simulations are consistent with previous 2D axisymmetric solutions by Proga et al., who used the ZEUS 2D code. Specifically, we find that the disc winds are time dependent, characterized by a dense stream confined to ˜45° relative to the disc mid-plane and bounded on the polar side by a less dense, fast stream. In 3D, we introduce a vertical, ϕ-dependent, subsonic velocity perturbation in the disc mid-plane. The perturbation does not change the overall character of the solution but global outflow properties such as the mass, momentum, and kinetic energy fluxes are altered by up to 100 per cent. Non-axisymmetric density structures develop and persist mainly at the base of the wind. They are relatively small, and their densities can be a few times higher than the azimuthal average. The structure of the non-axisymmetric and axisymmetric solutions differ also in other ways. Perhaps most importantly from the observational point of view are the differences in the so-called clumping factors, that serve as a proxy for emissivity due to two body processes. In particular, the spatially averaged clumping factor over the entire fast stream, while it is of a comparable value in both solutions, it varies about 10 times faster in the non-axisymmetric case.

Wind data for wind driven plant. [site selection for optimal performance

Science.gov (United States)

Stodhart, A. H.

1973-01-01

Simple, averaged wind velocity data provide information on energy availability, facilitate generator site selection and enable appropriate operating ranges to be established for windpowered plants. They also provide a basis for the prediction of extreme wind speeds.

A data-driven multi-model methodology with deep feature selection for short-term wind forecasting

International Nuclear Information System (INIS)

Feng, Cong; Cui, Mingjian; Hodge, Bri-Mathias; Zhang, Jie

2017-01-01

Highlights: • An ensemble model is developed to produce both deterministic and probabilistic wind forecasts. • A deep feature selection framework is developed to optimally determine the inputs to the forecasting methodology. • The developed ensemble methodology has improved the forecasting accuracy by up to 30%. - Abstract: With the growing wind penetration into the power system worldwide, improving wind power forecasting accuracy is becoming increasingly important to ensure continued economic and reliable power system operations. In this paper, a data-driven multi-model wind forecasting methodology is developed with a two-layer ensemble machine learning technique. The first layer is composed of multiple machine learning models that generate individual forecasts. A deep feature selection framework is developed to determine the most suitable inputs to the first layer machine learning models. Then, a blending algorithm is applied in the second layer to create an ensemble of the forecasts produced by first layer models and generate both deterministic and probabilistic forecasts. This two-layer model seeks to utilize the statistically different characteristics of each machine learning algorithm. A number of machine learning algorithms are selected and compared in both layers. This developed multi-model wind forecasting methodology is compared to several benchmarks. The effectiveness of the proposed methodology is evaluated to provide 1-hour-ahead wind speed forecasting at seven locations of the Surface Radiation network. Numerical results show that comparing to the single-algorithm models, the developed multi-model framework with deep feature selection procedure has improved the forecasting accuracy by up to 30%.

ISOTOPIC MASS FRACTIONATION OF SOLAR WIND: EVIDENCE FROM FAST AND SLOW SOLAR WIND COLLECTED BY THE GENESIS MISSION

International Nuclear Information System (INIS)

Heber, Veronika S.; Baur, Heinrich; Wieler, Rainer; Bochsler, Peter; McKeegan, Kevin D.; Neugebauer, Marcia; Reisenfeld, Daniel B.; Wiens, Roger C.

2012-01-01

NASA's Genesis space mission returned samples of solar wind collected over ∼2.3 years. We present elemental and isotopic compositions of He, Ne, and Ar analyzed in diamond-like carbon targets from the slow and fast solar wind collectors to investigate isotopic fractionation processes during solar wind formation. The solar wind provides information on the isotopic composition for most volatile elements for the solar atmosphere, the bulk Sun and hence, on the solar nebula from which it formed 4.6 Ga ago. Our data reveal a heavy isotope depletion in the slow solar wind compared to the fast wind composition by 63.1 ± 2.1 per mille for He, 4.2 ± 0.5 per mille amu –1 for Ne and 2.6 ± 0.5 per mille amu –1 for Ar. The three Ne isotopes suggest that isotopic fractionation processes between fast and slow solar wind are mass dependent. The He/H ratios of the collected slow and fast solar wind samples are 0.0344 and 0.0406, respectively. The inefficient Coulomb drag model reproduces the measured isotopic fractionation between fast and slow wind. Therefore, we apply this model to infer the photospheric isotopic composition of He, Ne, and Ar from our solar wind data. We also compare the isotopic composition of oxygen and nitrogen measured in the solar wind with values of early solar system condensates, probably representing solar nebula composition. We interpret the differences between these samples as being due to isotopic fractionation during solar wind formation. For both elements, the magnitude and sign of the observed differences are in good agreement with the values predicted by the inefficient Coulomb drag model.

ISOTOPIC MASS FRACTIONATION OF SOLAR WIND: EVIDENCE FROM FAST AND SLOW SOLAR WIND COLLECTED BY THE GENESIS MISSION

Energy Technology Data Exchange (ETDEWEB)

Heber, Veronika S.; Baur, Heinrich; Wieler, Rainer [Institute for Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, CH-8092 Zurich (Switzerland); Bochsler, Peter [Physikalisches Institut, Universitaet Bern, Sidlerstasse 5, CH-3012 Bern (Switzerland); McKeegan, Kevin D. [Department of Earth and Space Sciences, University of California Los Angeles, 595 Charles Young Drive East, Box 951567, Los Angeles, CA 90095-1567 (United States); Neugebauer, Marcia [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721-0092 (United States); Reisenfeld, Daniel B. [Department of Physics and Astronomy, University of Montana, Missoula, MT 59812 (United States); Wiens, Roger C., E-mail: heber@ess.ucla.edu [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2012-11-10

NASA's Genesis space mission returned samples of solar wind collected over {approx}2.3 years. We present elemental and isotopic compositions of He, Ne, and Ar analyzed in diamond-like carbon targets from the slow and fast solar wind collectors to investigate isotopic fractionation processes during solar wind formation. The solar wind provides information on the isotopic composition for most volatile elements for the solar atmosphere, the bulk Sun and hence, on the solar nebula from which it formed 4.6 Ga ago. Our data reveal a heavy isotope depletion in the slow solar wind compared to the fast wind composition by 63.1 {+-} 2.1 per mille for He, 4.2 {+-} 0.5 per mille amu{sup -1} for Ne and 2.6 {+-} 0.5 per mille amu{sup -1} for Ar. The three Ne isotopes suggest that isotopic fractionation processes between fast and slow solar wind are mass dependent. The He/H ratios of the collected slow and fast solar wind samples are 0.0344 and 0.0406, respectively. The inefficient Coulomb drag model reproduces the measured isotopic fractionation between fast and slow wind. Therefore, we apply this model to infer the photospheric isotopic composition of He, Ne, and Ar from our solar wind data. We also compare the isotopic composition of oxygen and nitrogen measured in the solar wind with values of early solar system condensates, probably representing solar nebula composition. We interpret the differences between these samples as being due to isotopic fractionation during solar wind formation. For both elements, the magnitude and sign of the observed differences are in good agreement with the values predicted by the inefficient Coulomb drag model.

EVOLUTION OF SUPER STAR CLUSTER WINDS WITH STRONG COOLING

International Nuclear Information System (INIS)

Wuensch, Richard; Palous, Jan; Silich, Sergiy; Tenorio-Tagle, Guillermo; Munoz-Tunon, Casiana

2011-01-01

We study the evolution of super star cluster winds driven by stellar winds and supernova explosions. Time-dependent rates at which mass and energy are deposited into the cluster volume, as well as the time-dependent chemical composition of the re-inserted gas, are obtained from the population synthesis code Starburst99. These results are used as input for a semi-analytic code which determines the hydrodynamic properties of the cluster wind as a function of cluster age. Two types of winds are detected in the calculations. For the quasi-adiabatic solution, all of the inserted gas leaves the cluster in the form of a stationary wind. For the bimodal solution, some of the inserted gas becomes thermally unstable and forms dense warm clumps which accumulate inside the cluster. We calculate the evolution of the wind velocity and energy flux and integrate the amount of accumulated mass for clusters of different mass, radius, and initial metallicity. We also consider conditions with low heating efficiency of the re-inserted gas or mass loading of the hot thermalized plasma with the gas left over from star formation. We find that the bimodal regime and the related mass accumulation occur if at least one of the two conditions above is fulfilled.

Capillary electrophoresis-driven synthesis of water-soluble CdTe quantum dots in nanoliter scale

Science.gov (United States)

Nejdl, Lukas; Hynek, David; Adam, Vojtech; Vaculovicova, Marketa

2018-04-01

‘Green nanotechnology’ is a term used for the design of nanomaterials and processes that reduce or eliminate the use and/or generation of hazardous substances. In this paper, a capillary electrophoresis (CE)-driven synthesis of CdTe quantum dots (QDs) and their subsequent conjugation with a metal-binding protein metallothionein (isofom MT1) is reported. Even though the toxic materials (cadmium and potassium borohydride) were used for synthesis, the proposed method can be labeled as ‘environmentally friendly’ because the whole process (synthesis of QDs and MT1 conjugation) was carried out under mild conditions: ultra-low volume (nanoliter scale), relatively low temperature (50 °C), atmospheric pressure, and completed in a short time (under 90 s). Prepared QDs were also characterized by classical fluorescence spectroscopy and transmission electron microscopy. This study opens up new possibilities for the utilization of classical CE in the synthesis of nanoparticles and on-line labeling of biomolecules in the nanoliter scale in short period of time.

High-efficiency wind turbine

Science.gov (United States)

Hein, L. A.; Myers, W. N.

1980-01-01

Vertical axis wind turbine incorporates several unique features to extract more energy from wind increasing efficiency 20% over conventional propeller driven units. System also features devices that utilize solar energy or chimney effluents during periods of no wind.

Study of the French wind sector: assessment, prospective, and strategy. Final report + Synthesis

International Nuclear Information System (INIS)

Bellini, Robert; Berrou, Yolene; Blot, Jean-Francois; Bodiguel, Aude; Callonnec, Gael; Cals, Guilain; Eyang Mbeng, Rudy; Fiol, Jack; Galiano, Mila; Gerard, Rolland; Gerson, Raphael; Guenard, Vincent; Guillot, Frederic; Guyet, Samy; Khebchache, Bouzid; Marchal, David; Parrouffe, Jean-Michel; Puygrenier, Samuel; Roger, Christophe; Furois, Timothee; Lejzerzon, Victoire; Mouhamad, Sakina; Orta, Louis; Glita, Marc; Meteyer, Herve; Plante, Ludovic; Duclos, Paul; Lettry, Marion; Mathieu, Mathilde; Langlois, Pierre-Albert; Lioret, Sonia; Monnier, Matthieu; Robin-Chevallier, Lucas; Bourdier, Pierre; Duffes, Thomas; Nocodie, Serge; Neveux, Guillaume; Paulou, Julien; Vermeulen, Valentin; Hajjar, Ali; Bouchet, Alexandre; Clicquot De Mentque, Juliette; Jan, Etienne; Pinel, Julie; Haeusler, Laurence; Moro-Goubely, Anne-Gaelle; Berthoin, Guillaume

2017-09-01

This huge document comprises several reports, and first proposes an executive summary which gives a synthetic overview of the present status of wind energy in France and abroad, of an assessment of 15 years of a policy of support to wind energy, of perspectives of development on the medium term, of economic spin-off on the long term, and of the ADEME's role in a national strategy for wind energy. These issues are then addressed in a more detailed way with notably a presentation of complete wind energy costs in France, a synthesis of an international benchmark, a detailed analysis of the support policy (in terms of efficiency, usefulness, costs-benefits), a characterisation of market evolutions, a discussion of constraint evolutions and of development strategies. A synthetic version of this report is then provided. More detailed reports are proposed on the various issues: first, analysis of the chain value, status of the sector in France and international benchmark; secondly, an assessment of the support policy through an assessment, a prospective and strategy, and then a detailed discussion of macro-economic spin-off and of jobs in the sector on the long term in association with wind energy development. A third part proposes a presentation of ADEME's strategy and action plan in favour of wind energy. Finally, a set of appendices contains presentations of survey questionnaires and of survey result processing, presentations of results regarding actors and countries, and presentation of modelling methodologies

Initiation of poliovirus plus-strand RNA synthesis in a membrane complex of infected HeLa cells

International Nuclear Information System (INIS)

Takeda, N.; Kuhn, R.J.; Yang, C.F.; Takegami, T.; Wimmer, E.

1986-01-01

An in vitro poliovirus RNA-synthesizing system derived from a crude membrance fraction of infected HeLa cells was used to analyze the mechanism of initiation of poliovirus plus-strand RNA synthesis. This system contains an activity that synthesizes the nucleotidyl proteins VPg-pU and VPg-pUpU. These molecules represent the 5'-terminal structure of nascent RNA molecules and of virion RNA. The membranous replication complex is also capable of synthesizing mucleotidyl proteins containing nine or more of the poliovirus 5'-proximal nucleotides as assayed by the formation of the RNase T 1 -resistant oligonucleotide VPg-pUUAAAACAGp or by fingerprint analysis of the in vitro-synthesized 32 P-RNA. Incubation of preformed VPg-pUpU with unlabeled nucleoside triphosphates resulted in the formation of VPg-pUUAAAACAGp. This reaction, which appeared to be an elongation of VPg-pUpU, was stimulated by the addition of a soluble fraction (S-10) obtained from uninfected HeLa cells. Preformed VPg-pU could be chased into VPg-pUpU in the presence of UTP. The data are consistent with a model that VPg-pU can function as a primer for poliovirus plus-strand RNA synthesis in the membranous replication complex and that the elongation reaction may be stimulated by a host cellular factor

Impact, runoff and drying of wind-driven rain on a window glass surface: numerical modelling based on experimental validation

NARCIS (Netherlands)

Blocken, B.J.E.; Carmeliet, J.E.

2015-01-01

This paper presents a combination of two models to study both the impingement and the contact and surface phenomena of rainwater on a glass window surface: a Computational Fluid Dynamics (CFD) model for the calculation of the distribution of the wind-driven rain (WDR) across the building facade and

Natural Ventilation Driven by Wind and Temperature Difference

DEFF Research Database (Denmark)

Larsen, Tine Steen

Natural ventilation is a commonly used principle when buildings are being ventilated. It can be controlled by openings in the building envelope, which open or close depending on the need of air inside the building. It can also be the simple action of just opening a door or a window to let the fresh...... driving forces are still wind pressure and temperature differences as with cross-ventilation, but here the turbulence in the wind and the pulsating flow near the opening also affect the flow through the opening. From earlier work, some design expressions already exist, but none of these include...... the incidence angle of the wind, which is an important parameter in this type of ventilation. Several wind tunnel experiments are made and from the results of these, a new design expression is made which includes the wind pressure, temperature difference, incidence angle of the wind and the fluctuations...

Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow

Energy Technology Data Exchange (ETDEWEB)

Hu, L.H., E-mail: hlh@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230026 (China); Huo, R.; Yang, D. [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2009-07-15

The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons-a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow.

Science.gov (United States)

Hu, L H; Huo, R; Yang, D

2009-07-15

The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons--a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow

International Nuclear Information System (INIS)

Hu, L.H.; Huo, R.; Yang, D.

2009-01-01

The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons-a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

Example-Based Automatic Music-Driven Conventional Dance Motion Synthesis

Energy Technology Data Exchange (ETDEWEB)

Xu, Songhua [ORNL; Fan, Rukun [University of North Carolina, Chapel Hill; Geng, Weidong [Zhejiang University

2011-04-21

We introduce a novel method for synthesizing dance motions that follow the emotions and contents of a piece of music. Our method employs a learning-based approach to model the music to motion mapping relationship embodied in example dance motions along with those motions' accompanying background music. A key step in our method is to train a music to motion matching quality rating function through learning the music to motion mapping relationship exhibited in synchronized music and dance motion data, which were captured from professional human dance performance. To generate an optimal sequence of dance motion segments to match with a piece of music, we introduce a constraint-based dynamic programming procedure. This procedure considers both music to motion matching quality and visual smoothness of a resultant dance motion sequence. We also introduce a two-way evaluation strategy, coupled with a GPU-based implementation, through which we can execute the dynamic programming process in parallel, resulting in significant speedup. To evaluate the effectiveness of our method, we quantitatively compare the dance motions synthesized by our method with motion synthesis results by several peer methods using the motions captured from professional human dancers' performance as the gold standard. We also conducted several medium-scale user studies to explore how perceptually our dance motion synthesis method can outperform existing methods in synthesizing dance motions to match with a piece of music. These user studies produced very positive results on our music-driven dance motion synthesis experiments for several Asian dance genres, confirming the advantages of our method.

Example-based automatic music-driven conventional dance motion synthesis.

Science.gov (United States)

Fan, Rukun; Xu, Songhua; Geng, Weidong

2012-03-01

We introduce a novel method for synthesizing dance motions that follow the emotions and contents of a piece of music. Our method employs a learning-based approach to model the music to motion mapping relationship embodied in example dance motions along with those motions' accompanying background music. A key step in our method is to train a music to motion matching quality rating function through learning the music to motion mapping relationship exhibited in synchronized music and dance motion data, which were captured from professional human dance performance. To generate an optimal sequence of dance motion segments to match with a piece of music, we introduce a constraint-based dynamic programming procedure. This procedure considers both music to motion matching quality and visual smoothness of a resultant dance motion sequence. We also introduce a two-way evaluation strategy, coupled with a GPU-based implementation, through which we can execute the dynamic programming process in parallel, resulting in significant speedup. To evaluate the effectiveness of our method, we quantitatively compare the dance motions synthesized by our method with motion synthesis results by several peer methods using the motions captured from professional human dancers' performance as the gold standard. We also conducted several medium-scale user studies to explore how perceptually our dance motion synthesis method can outperform existing methods in synthesizing dance motions to match with a piece of music. These user studies produced very positive results on our music-driven dance motion synthesis experiments for several Asian dance genres, confirming the advantages of our method.

Wind-Driven Waves in Tampa Bay, Florida

Science.gov (United States)

Gilbert, S. A.; Meyers, S. D.; Luther, M. E.

2002-12-01

Turbidity and nutrient flux due to sediment resuspension by waves and currents are important factors controlling water quality in Tampa Bay. During December 2001 and January 2002, four Sea Bird Electronics SeaGauge wave and tide recorders were deployed in Tampa Bay in each major bay segment. Since May 2002, a SeaGauge has been continuously deployed at a site in middle Tampa Bay as a component of the Bay Regional Atmospheric Chemistry Experiment (BRACE). Initial results for the summer 2002 data indicate that significant wave height is linearly dependent on wind speed and direction over a range of 1 to 12 m/s. The data were divided into four groups according to wind direction. Wave height dependence on wind speed was examined for each group. Both northeasterly and southwesterly winds force significant wave heights that are about 30% larger than those for northwesterly and southeasterly winds. This difference is explained by variations in fetch due to basin shape. Comparisons are made between these observations and the results of a SWAN-based model of Tampa Bay. The SWAN wave model is coupled to a three-dimensional circulation model and computes wave spectra at each model grid cell under observed wind conditions and modeled water velocity. When SWAN is run without dissipation, the model results are generally similar in wave period but about 25%-50% higher in significant wave height than the observations. The impact of various dissipation mechanisms such as bottom drag and whitecapping on the wave state is being investigated. Preliminary analyses on winter data give similar results.

Wind Regimes in Complex Terrain of the Great Valley of Eastern Tennessee

Energy Technology Data Exchange (ETDEWEB)

Birdwell, Kevin R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2011-05-01

This research was designed to provide an understanding of physical wind mechanisms within the complex terrain of the Great Valley of Eastern Tennessee to assess the impacts of regional air flow with regard to synoptic and mesoscale weather changes, wind direction shifts, and air quality. Meteorological data from 2008 2009 were analyzed from 13 meteorological sites along with associated upper level data. Up to 15 ancillary sites were used for reference. Two-step complete linkage and K-means cluster analyses, synoptic weather studies, and ambient meteorological comparisons were performed to generate hourly wind classifications. These wind regimes revealed seasonal variations of underlying physical wind mechanisms (forced channeled, vertically coupled, pressure-driven, and thermally-driven winds). Synoptic and ambient meteorological analysis (mixing depth, pressure gradient, pressure gradient ratio, atmospheric and surface stability) suggested up to 93% accuracy for the clustered results. Probabilistic prediction schemes of wind flow and wind class change were developed through characterization of flow change data and wind class succession. Data analysis revealed that wind flow in the Great Valley was dominated by forced channeled winds (45 67%) and vertically coupled flow (22 38%). Down-valley pressure-driven and thermally-driven winds also played significant roles (0 17% and 2 20%, respectively), usually accompanied by convergent wind patterns (15 20%) and large wind direction shifts, especially in the Central/Upper Great Valley. The behavior of most wind regimes was associated with detectable pressure differences between the Lower and Upper Great Valley. Mixing depth and synoptic pressure gradients were significant contributors to wind pattern behavior. Up to 15 wind classes and 10 sub-classes were identified in the Central Great Valley with 67 joined classes for the Great Valley at-large. Two-thirds of Great Valley at-large flow was defined by 12 classes. Winds

Further development in theory/data closure of the photoelectron-driven polar wind and day-night transition of the outflow

Directory of Open Access Journals (Sweden)

S. W. Y. Tam

Full Text Available Recent in situ observations have revealed novel features in the polar wind. Measurements between 5000 and 9000 km altitude by the Akebono satellite indicate that both H⁺ and O⁺ ions can have remarkably higher outflow velocities in the sunlit region than on the nightside. Electrons also display an asymmetric behavior: the dayside difference in energy spread, greater for upward-moving than downward-moving electrons, is absent on the nightside. Here, we discuss the further development of a theory by Tam et al. that can explain most of these observed peculiar properties by properly taking into account the global, kinetic, collisional effects of the sunlit photoelectrons, on the background polar wind and the electric field. Quantitative comparisons of the calculated results with actual data will be described. In addition, transition from the daytime photoelectron-driven polar wind to the night-time polar wind will be discussed.

Two-parameter study of the quasiperiodic route to chaos in convecting 3He--superfluid-4He mixtures

International Nuclear Information System (INIS)

Mainieri, R.; Sullivan, T.S.; Ecke, R.E.

1989-01-01

We study the frequency lockings of two intrinsic hydrodynamic modes of a convecting 3 He-superfluid- 4 He mixture by independently varying the Rayleigh and Prandtl numbers. We establish points on the critical line in this parameter space using a transient technique to locate the spiral-node transition in the interior of three resonance horns. Universal scaling is demonstrated at winding numbers with golden mean tails by computing the f(α) singularity spectrum

Observed vulnerability of Filchner-Ronne Ice Shelf to wind-driven inflow of warm deep water

Science.gov (United States)

Darelius, E.; Fer, I.; Nicholls, K. W.

2016-01-01

The average rate of melting at the base of the large Filchner-Ronne Ice Shelf in the southern Weddell Sea is currently low, but projected to increase dramatically within the next century. In a model study, melt rates increase as changing ice conditions cause a redirection of a coastal current, bringing warm water of open ocean origin through the Filchner Depression and into the Filchner Ice Shelf cavity. Here we present observations from near Filchner Ice Shelf and from the Filchner Depression, which show that pulses of warm water already arrive as far south as the ice front. This southward heat transport follows the eastern flank of the Filchner Depression and is found to be directly linked to the strength of a wind-driven coastal current. Our observations emphasize the potential sensitivity of Filchner-Ronne Ice Shelf melt rates to changes in wind forcing. PMID:27481659

Estimated solar wind-implanted helium-3 distribution on the Moon

Science.gov (United States)

Johnson, J. R.; Swindle, T.D.; Lucey, P.G.

1999-01-01

Among the solar wind-implanted volatiles present in the lunar regolith, 3 He is possibly the most valuable resource because of its potential as a fusion fuel. The abundance of 3 He in the lunar regolith at a given location depends on surface maturity, the amount of solar wind fluence, and titanium content, because ilmenite (FeTiO3) retains helium much better than other major lunar minerals. Surface maturity and TiO2 maps from Clementine multispectral data sets are combined here with a solar wind fluence model to produce a 3He abundance map of the Moon. Comparison of the predicted 3He values to landing site observations shows good correlation. The highest 3He abundances occur in the farside maria (due to greater solar wind fluence received) and in higher TiO2 nearside mare regions.

A comparison of the performance of three types of passive fog gauges under conditions of wind-driven fog and precipitation

NARCIS (Netherlands)

Frumau, K.F.A.; Burkard, R.; Schmid, S.; Bruijnzeel, L.A.; Tobón, C.; Calvo-Alvado\\, J.C.

2011-01-01

Understanding of the 'typical' amounts of fog intercepted by different types of cloud forests is hampered by a lack of comparative information on local fog climatology. Usually some kind of 'fog gauge' is used to characterize fog occurrence and amounts. Moreover, wind-driven fog and precipitation

Process design for isolation of soybean oil bodies by applying the product-driven process synthesis methodology

NARCIS (Netherlands)

Zderic, A.; Taraksci, T.; Hooshyar, N.; Zondervan, E.; Meuldijk, J.

2014-01-01

The present work describes the product driven process synthesis (PDPS) methodology for the conceptual design of extraction of intact oil bodies from soybeans. First, in this approach consumer needs are taken into account and based on these needs application of the final product (oil bodies) is

Proactive monitoring of a wind turbine array with lidar measurements, SCADA data and a data-driven RANS solver

Science.gov (United States)

Iungo, G.; Said, E. A.; Santhanagopalan, V.; Zhan, L.

2016-12-01

Power production of a wind farm and durability of wind turbines are strongly dependent on non-linear wake interactions occurring within a turbine array. Wake dynamics are highly affected by the specific site conditions, such as topography and local atmospheric conditions. Furthermore, contingencies through the life of a wind farm, such as turbine ageing and off-design operations, make prediction of wake interactions and power performance a great challenge in wind energy. In this work, operations of an onshore wind turbine array were monitored through lidar measurements, SCADA and met-tower data. The atmospheric wind field investing the wind farm was estimated by using synergistically the available data through five different methods, which are characterized by different confidence levels. By combining SCADA data and the lidar measurements, it was possible to estimate power losses connected with wake interactions. For this specific array, power losses were estimated to be 4% and 2% of the total power production for stable and convective atmospheric regimes, respectively. The entire dataset was then leveraged for the calibration of a data-driven RANS (DDRANS) solver for prediction of wind turbine wakes and power production. The DDRANS is based on a parabolic formulation of the Navier-Stokes equations with axisymmetry and boundary layer approximations, which allow achieving very low computational costs. Accuracy in prediction of wind turbine wakes and power production is achieved through an optimal tuning of the turbulence closure model. The latter is based on a mixing length model, which was developed based on previous wind turbine wake studies carried out through large eddy simulations and wind tunnel experiments. Several operative conditions of the wind farm under examination were reproduced through DDRANS for different stability regimes, wind directions and wind velocity. The results show that DDRANS is capable of achieving a good level of accuracy in prediction

MAGNETICALLY DRIVEN ACCRETION DISK WINDS AND ULTRA-FAST OUTFLOWS IN PG 1211+143

International Nuclear Information System (INIS)

Fukumura, Keigo; Tombesi, Francesco; Kazanas, Demosthenes; Shrader, Chris; Behar, Ehud; Contopoulos, Ioannis

2015-01-01

We present a study of X-ray ionization of MHD accretion-disk winds in an effort to constrain the physics underlying the highly ionized ultra-fast outflows (UFOs) inferred by X-ray absorbers often detected in various sub classes of Seyfert active galactic nuclei (AGNs). Our primary focus is to show that magnetically driven outflows are indeed physically plausible candidates for the observed outflows accounting for the AGN absorption properties of the present X-ray spectroscopic observations. Employing a stratified MHD wind launched across the entire AGN accretion disk, we calculate its X-ray ionization and the ensuing X-ray absorption-line spectra. Assuming an appropriate ionizing AGN spectrum, we apply our MHD winds to model the absorption features in an XMM-Newton/EPIC spectrum of the narrow-line Seyfert, PG 1211+143. We find, through identifying the detected features with Fe Kα transitions, that the absorber has a characteristic ionization parameter of log (ξ c [erg cm s −1 ]) ≃ 5–6 and a column density on the order of N H ≃ 10 23 cm −2 outflowing at a characteristic velocity of v c /c ≃ 0.1–0.2 (where c is the speed of light). The best-fit model favors its radial location at r c ≃ 200 R o (R o is the black hole’s innermost stable circular orbit), with an inner wind truncation radius at R t ≃ 30 R o . The overall K-shell feature in the data is suggested to be dominated by Fe xxv with very little contribution from Fe xxvi and weakly ionized iron, which is in good agreement with a series of earlier analyses of the UFOs in various AGNs, including PG 1211+143

Rotor Speed Control of a Direct-Driven Permanent Magnet Synchronous Generator-Based Wind Turbine Using Phase-Lag Compensators to Optimize Wind Power Extraction

Directory of Open Access Journals (Sweden)

Ester Hamatwi

2017-01-01

Full Text Available Due to the intermittent nature of wind, the wind power output tends to be inconsistent, and hence maximum power point tracking (MPPT is usually employed to optimize the power extracted from the wind resource at a wide range of wind speeds. This paper deals with the rotor speed control of a 2 MW direct-driven permanent magnet synchronous generator (PMSG to achieve MPPT. The proportional-integral (PI, proportional-derivative (PD, and proportional-integral-derivative (PID controllers have widely been employed in MPPT studies owing to their simple structure and simple design procedure. However, there are a number of shortcomings associated with these controllers; the trial-and-error design procedure used to determine the P, I, and D gains presents a possibility for poorly tuned controller gains, which reduces the accuracy and the dynamic performance of the entire control system. Moreover, these controllers’ linear nature, constricted operating range, and their sensitivity to changes in machine parameters make them ineffective when applied to nonlinear and uncertain systems. On the other hand, phase-lag compensators are associated with a design procedure that is well defined from fundamental principles as opposed to the aforementioned trial-and-error design procedure. This makes the latter controller type more accurate, although it is not well developed yet, and hence it is the focus of this paper. The simulation results demonstrated the effectiveness of the proposed MPPT controller.

Solar-wind minor ions: recent observations

International Nuclear Information System (INIS)

Bame, S.J.

1982-01-01

During the years following the Solar Wind Four Conference at Burghausen our knowledge of the solar wind ion composition and dynamics has grown. There have been some surprises, and our understanding of the evolution of the solar wind has been improved. Systematic studies have shown that the minor ions generally travel with a common bulk speed and have temperatures roughly proportional to their masses. It has been determined that the 3 He ++ content varies greatly; 3 He ++ / 4 He ++ ranges from as high as 10 2 values to below 2 x 10 - 4 . In some solar wind flows which can be related to energetic coronal events, the minor ions are found in unusual ionization states containing Fe 16 + as a prominent ion, showing that the states were formed at unusually high temperatures. Unexpectedly, in a few flows substantial quantities of 4 He + have been detected, sometimes with ions identifiable as O 2 + and O 3 + . Surprisingly, in some of these examples the ionization state is mixed showing that part of the plasma escaped the corona without attaining the usual million-degree temperatures while other parts were heated more nearly in the normal manner. Additionally, detailed studies of the minor ions have increased our understanding of the coronal expansion. For example, such studies have contributed to identifying near equatorial coronal streamers as the source of solar wind flows between high speed streams

Configuration Synthesis for Fully Restrained 7-Cable-Driven Manipulators

Directory of Open Access Journals (Sweden)

Xiaoqiang Tang

2012-10-01

Full Text Available Cable distribution plays a vital role in Cable Driven Parallel Manipulators (CDPMs regarding tension and workspace quality, especially in fully restrained CDPMs. This paper focuses on three typical configurations of fully restrained CDPMs with 7 cables in order to introduce an approach for configuration synthesis. Firstly, the kinematic models of three types of CDPMs with 7 cables are set up. Then, in order to evaluate workspace quality, two new indices are proposed by using tensions along each cable, which are the All Cable Tension Distribution Index (ACTDI and Global Tension Distribution Index (GTDI. Next, the three types of CDPMs with 7 cables are analysed with the two indices. At the end, according to different performance requirements, the configurations of cable distribution are discussed and selected.

design of a small scale wind generator for low wind speed areas

African Journals Online (AJOL)

USER

Most small scale level wind turbine generators are directly driven system, variable speed, and partially ... the best solutions for small-scale wind power plants. Low-speed multi-pole PM generators ..... Designs of the Same Magnet Structure for.

Wind Power Utilization Guide.

Science.gov (United States)

1981-09-01

The expres- sions for the rotor torque for a Darrieus machine can be found in Reference 4.16. The Darrieus wind turbine offers the following... turbine generators, wind -driven turbines , power conditioning, wind power, energy conservation, windmills, economic ana \\sis. 20 ABS 1"ACT (Conti,on... turbines , power conditioning requirements, siting requirements, and the economics of wind power under different conditions. Three examples are given to

Forecasting wind-driven wildfires using an inverse modelling approach

Directory of Open Access Journals (Sweden)

O. Rios

2014-06-01

Full Text Available A technology able to rapidly forecast wildfire dynamics would lead to a paradigm shift in the response to emergencies, providing the Fire Service with essential information about the ongoing fire. This paper presents and explores a novel methodology to forecast wildfire dynamics in wind-driven conditions, using real-time data assimilation and inverse modelling. The forecasting algorithm combines Rothermel's rate of spread theory with a perimeter expansion model based on Huygens principle and solves the optimisation problem with a tangent linear approach and forward automatic differentiation. Its potential is investigated using synthetic data and evaluated in different wildfire scenarios. The results show the capacity of the method to quickly predict the location of the fire front with a positive lead time (ahead of the event in the order of 10 min for a spatial scale of 100 m. The greatest strengths of our method are lightness, speed and flexibility. We specifically tailor the forecast to be efficient and computationally cheap so it can be used in mobile systems for field deployment and operativeness. Thus, we put emphasis on producing a positive lead time and the means to maximise it.

On Using Wind Speed Preview to Reduce Wind Turbine Tower Oscillations

DEFF Research Database (Denmark)

Kristalny, Maxim; Madjidian, Daria; Knudsen, Torben

2013-01-01

We investigate the potential of using previewed wind speed measurements for damping wind turbine fore-aft tower oscillations. Using recent results on continuous-time H 2 preview control, we develop a numerically efficient framework for the feedforward controller synthesis. One of the major benefits...... characteristics on the achievable performance and on the required length of preview. We demonstrate the importance of accounting for the distortion in the controller synthesis and quantify the potential benefits of using previewed information by means of simulations based on real-world turbine data....

Momentum-driven Winds from Radiatively Efficient Black Hole Accretion and Their Impact on Galaxies

Science.gov (United States)

Brennan, Ryan; Choi, Ena; Somerville, Rachel S.; Hirschmann, Michaela; Naab, Thorsten; Ostriker, Jeremiah P.

2018-06-01

We explore the effect of momentum-driven winds representing radiation-pressure-driven outflows from accretion onto supermassive black holes in a set of numerical hydrodynamical simulations. We explore two matched sets of cosmological zoom-in runs of 24 halos with masses ∼1012.0–1013.4 M ⊙ run with two different feedback models. Our “NoAGN” model includes stellar feedback via UV heating, stellar winds and supernovae, photoelectric heating, and cosmic X-ray background heating from a metagalactic background. Our fiducial “MrAGN” model is identical except that it also includes a model for black hole seeding and accretion, as well as heating and momentum injection associated with the radiation from black hole accretion. Our MrAGN model launches galactic outflows, which result in both “ejective” feedback—the outflows themselves that drive gas out of galaxies—and “preventative” feedback, which suppresses the inflow of new and recycling gas. As much as 80% of outflowing galactic gas can be expelled, and accretion can be suppressed by as much as a factor of 30 in the MrAGN runs when compared with the NoAGN runs. The histories of NoAGN galaxies are recycling dominated, with ∼70% of material that leaves the galaxy eventually returning, and the majority of outflowing gas reaccretes on 1 Gyr timescales without AGN feedback. Outflowing gas in the MrAGN runs has a higher characteristic velocity (500–1000 km s‑1 versus 100–300 km s‑1 for outflowing NoAGN gas) and travels as far as a few megaparsecs. Only ∼10% of ejected material is reaccreted in the MrAGN galaxies.

Theories for the winds from Wolf Rayet stars

International Nuclear Information System (INIS)

Cassinelli, J.P.

1982-01-01

The massive and fast winds of Wolf Rayet stars present a serious momentum problem for the line-driven wind theories that are commonly used to explain the fast winds of early type stars. It is perhaps possible for the winds to be driven by lines, if multiple scattering occurs and if there are a sufficient number of lines in the spectrum so that large fraction of the continuum is blocked by line opacity in the winds. Several other mechanisms are discussed, in particular two that rely on strong magnetic fields: a) Alfven wave driven wind models like those recently developed by Hartmann and MacGregor for late type supergiants and b) the ''Fast Magnetic Rotator'' model that was developed by Belcher and MacGregor for the winds from pre-main sequence stars. In either model, large magnetic fields (approximately equal to 10 4 gauss) are required to drive the massive and fast winds of Wolf Rayet stars. Smaller fields might be possible if the multiple scattering line radiation force can be relied on to provide a final acceleration to terminal velocity. (Auth.)

INTERPLANETARY SUPRATHERMAL He+ AND He++ OBSERVATIONS DURING QUIET PERIODS FROM 1 TO 9 AU AND IMPLICATIONS FOR PARTICLE ACCELERATION

International Nuclear Information System (INIS)

Hill, M. E.; Schwadron, N. A.; Hamilton, D. C.; DiFabio, R. D.; Squier, R. K.

2009-01-01

We measured quiet-time differential intensities of ∼2-60 keV nucleon -1 He + and He ++ during the 1999-2004, 1-9 AU portion of Cassini's interplanetary cruise to Saturn and found that the He + /He ++ composition ratio grows as the distance from the Sun r increases. An increase in the ratio is expected from the theoretical pickup ion and solar wind intensities, but the absolute He + intensity, counter to the predicted falling r -1 dependence of the density, is actually slightly increasing, and He ++ falls off much more slowly than the r -2 dependence one might expect from a population with a solar source. With an approximately r 2.2 radial dependence, our rigorous numerical transport and acceleration model (with stochastic acceleration) matches the higher-energy (>13 keV nucleon -1 ) measured He + /He ++ composition profiles well, as does our analytical theory. Two acceleration processes are likely needed: the composition ratios are explainable by stochastic acceleration while a velocity-dependent mechanism that acts beyond 1 AU equally on He + and He ++ is required to explain the spatial intensity profiles.

Wind erosion processes and control

Science.gov (United States)

Wind erosion continues to threaten the sustainability of our nations' soil, air, and water resources. To effectively apply conservation systems to prevent wind driven soil loss, an understanding of the fundamental processes of wind erosion is necessary so that land managers can better recognize the ...

Wind-Driven Ecological Flow Regimes Downstream from Hydropower Dams

Science.gov (United States)

Kern, J.; Characklis, G. W.

2012-12-01

Conventional hydropower can be turned on and off quicker and less expensively than thermal generation (coal, nuclear, or natural gas). These advantages enable hydropower utilities to respond to rapid fluctuations in energy supply and demand. More recently, a growing renewable energy sector has underlined the need for flexible generation capacity that can complement intermittent renewable resources such as wind power. While wind power entails lower variable costs than other types of generation, incorporating it into electric power systems can be problematic. Due to variable and unpredictable wind speeds, wind power is difficult to schedule and must be used when available. As a result, integrating large amounts of wind power into the grid may result in atypical, swiftly changing demand patterns for other forms of generation, placing a premium on sources that can be rapidly ramped up and down. Moreover, uncertainty in wind power forecasts will stipulate increased levels of 'reserve' generation capacity that can respond quickly if real-time wind supply is less than expected. These changes could create new hourly price dynamics for energy and reserves, altering the short-term financial signals that hydroelectric dam operators use to schedule water releases. Traditionally, hourly stream flow patterns below hydropower dams have corresponded in a very predictable manner to electricity demand, whose primary factors are weather (hourly temperature) and economic activity (workday hours). Wind power integration has the potential to yield more variable, less predictable flows at hydro dams, flows that at times could resemble reciprocal wind patterns. An existing body of research explores the impacts of standard, demand-following hydroelectric dams on downstream ecological flows; but weighing the benefits of increased reliance on wind power against further impacts to ecological flows may be a novel challenge for the environmental community. As a preliminary step in meeting this

Electronic Power Transformer Control Strategy in Wind Energy Conversion Systems for Low Voltage Ride-through Capability Enhancement of Directly Driven Wind Turbines with Permanent Magnet Synchronous Generators (D-PMSGs

Directory of Open Access Journals (Sweden)

Hui Huang

2014-11-01

Full Text Available This paper investigates the use of an Electronic Power Transformer (EPT incorporated with an energy storage system to smooth the wind power fluctuations and enhance the low voltage ride-through (LVRT capability of directly driven wind turbines with permanent magnet synchronous generators (D-PMSGs. The decoupled control schemes of the system, including the grid side converter control scheme, generator side converter control scheme and the control scheme of the energy storage system, are presented in detail. Under normal operating conditions, the energy storage system absorbs the high frequency component of the D-PMSG output power to smooth the wind power fluctuations. Under grid fault conditions, the energy storage system absorbs the redundant power, which could not be transferred to the grid by the EPT, to help the D-PMSG to ride through low voltage conditions. This coordinated control strategy is validated by simulation studies using MATLAB/Simulink. With the proposed control strategy, the output wind power quality is improved and the D-PMSG can ride through severe grid fault conditions.

Wind power's effects on marine life. A synthesis report; Vindkraftens effekter paa marint liv. En syntesrapport

Energy Technology Data Exchange (ETDEWEB)

Bergstroem, Lena (Aquatic Resources, Swedish Univ. of Agricultural Sciences, Oeregrund (Sweden)); Kautsky, Lena (Dept. on Botany, Stockholm Univ. (Sweden); Stockholm Univ. Marine Research Centre (Sweden)); Malm, Torleif; Aastrand Capetillo, Nastassja (Stockholms Univ. Marine Research Centre (Sweden)); Ohlsson, Hans (wpd Offshore Stockholm AB (Sweden)); Wahlberg, Magnus (Fjord and Baelt (Denmark)); Rosenberg, Rutger (Dept. of Biological and Environmental Sciences, Goeteborg Univ. (Sweden); Marine Monitoring AB, Lysekil (Sweden))

2012-03-15

As in many other countries, an expansion of wind power is expected in Sweden during the coming decades. The expansion is driven by rising prices on electricity and the need for an increased production of renewable energy. Since wind conditions at sea are good and relatively constant, several offshore wind farms are planned in Swedish waters. Offshore wind power with a total effect of about 2500 MW has been granted permission and additionally 5500 MW are being planned for in Sweden. Examples of granted projects are Storgrundet with an effect of 265 MW, Stora Middelgrund with an effect of 860 MW and Kaarehamn with an effect of 48 MW. Today Sweden's largest offshore wind farm is Lillgrund in Oeresund with its 48 turbines with an installed effect of 110 MW. Prior to this expected expansion, it is important to investigate the environmental impact of offshore wind power, and how possible negative effects can be minimized. This synopsis about the impact of wind power on the marine life in Swedish waters, is based on more than 600 studies, most of which are scientific articles, but also reports by companies and authorities

The combined effect of wind and rain on interrill erosion processes

International Nuclear Information System (INIS)

Erpul, G.; Gabriels, D.; Norton, L.D.

2004-01-01

Wind-driven rain is described as raindrops falling through a wind field at an angle from vertical under the effects of both gravitational and drag forces. Wind-driven raindrops gain some degree of horizontal velocity and strike the soil surface with an angle deviated from vertical. Additionally, the distribution and intensity of rainfall on sloping surfaces differs depending on wind direction and velocity. The changes in raindrop trajectory and frequency with wind velocity and direction can have significant effects on rain splash detachment process. The resultant impact velocity, impact angle, and impact frequency of raindrops determine the magnitude of rain splash detachment by wind-driven rain. This differs from the detachment process by windless rain, in which a straight-line trajectory of raindrops and accordingly greatest rainfall intensity for a given rain are implicitly assumed. Wind, as well as slope and overland flow, is another possible factor capable of transporting detached particles by raindrop impact. Once soil particles are entrained in the splash droplets that have risen into the air by raindrop impact, wind velocity gradient will transport these particles. Obviously, in addition to its role in the rain splash detachment process, the wind accompanying rain is an important consideration in the rain splash transport process, which can cause a net transportation in wind direction. In wind-driven rains, wind velocity and direction is expected to affect not only rain splash detachment and transport processes but also shallow flow sediment transport induced by raindrop impacts with an angle on flow and the rain splash trajectories of soil particles within flow. Under wind-driven rain, the interrill transport process is a combined work of both rain splash sediment transport and raindrop-impacted shallow flow sediment transport. The rain splash process acts alone until runoff occurs, and net soil transport is caused by wind. As soon as runoff starts, the

INJECTION OF PLASMA INTO THE NASCENT SOLAR WIND VIA RECONNECTION DRIVEN BY SUPERGRANULAR ADVECTION

International Nuclear Information System (INIS)

Yang Liping; He Jiansen; Tu Chuanyi; Chen Wenlei; Zhang Lei; Wang Linghua; Yan Limei; Peter, Hardi; Marsch, Eckart; Feng, Xueshang

2013-01-01

To understand the origin of the solar wind is one of the key research topics in modern solar and heliospheric physics. Previous solar wind models assumed that plasma flows outward along a steady magnetic flux tube that reaches continuously from the photosphere through the chromosphere into the corona. Inspired by more recent comprehensive observations, Tu et al. suggested a new scenario for the origin of the solar wind, in which it flows out in a magnetically open coronal funnel and mass is provided to the funnel by small-scale side loops. Thus mass is supplied by means of magnetic reconnection that is driven by supergranular convection. To validate this scenario and simulate the processes involved, a 2.5 dimensional (2.5D) numerical MHD model is established in the present paper. In our simulation a closed loop moves toward an open funnel, which has opposite polarity and is located at the edge of a supergranulation cell, and magnetic reconnection is triggered and continues while gradually opening up one half of the closed loop. Its other half connects with the root of the open funnel and forms a new closed loop which is submerged by a reconnection plasma stream flowing downward. Thus we find that the outflowing plasma in the newly reconnected funnel originates not only from the upward reconnection flow but also from the high-pressure leg of the originally closed loop. This implies an efficient supply of mass from the dense loop to the dilute funnel. The mass flux of the outflow released from the funnel considered in our study is calculated to be appropriate for providing the mass flux at the coronal base of the solar wind, though additional heating and acceleration mechanisms are necessary to keep the velocity at the higher location. Our numerical model demonstrates that in the funnel the mass for the solar wind may be supplied from adjacent closed loops via magnetic reconnection as well as directly from the footpoints of open funnels.

Design of large permanent magnetized synchronous electric machines: Low speed, high torque machines - generator for direct driven wind turbine - motor for rim driven thruster

Energy Technology Data Exchange (ETDEWEB)

Kroevel, Oeystein

2011-02-15

This work presents the design of two prototype permanent magnetized electric machines for two different applications where large permanent magnet machines might be used. Existing technology have been used as the fundament for new design and adapted to new applications, contributing, hopefully, to the development of better and more environmental friendly energy conversion. The first application presented is represented with a prototype made in cooperation with the industry in which a PM-motor is integrated into a propeller unit. Both because of the industrial connection, and the integration between the PM-motor and the propeller, the choices made for the PM-motor are conservative trying to reduce the risk. The direct rim driven thruster prototype includes a surface mounted radial flux permanent magnet machine (SM RFPM) with fractional slot winding with a q around 1. Other engineering features were introduced to make the integration of propeller and motor feasible, but without the PM-machine the thruster would not have reached the performance demand. An important part of the project was to show that the SM RFPM enables this solution, providing high performance with a large air gap. The prototype has been tested in sea, under harsh conditions, and even though the magnets have been exposed directly to sea water and been visible corroded, the electric motor still performs well within the specifications. The second application is represented with a prototype PM-generator for wind turbines. This is an example of a new, very low speed high torque machine. The generator is built to test phenomena regarding concentrated coils, and as opposed to the first application, being a pure academic university project, its success is not connected to its performance, but with the prototype's ability to expose the phenomena in question. The prototype, or laboratory model, of the generator for direct driven wind turbines features SM RFPM with concentrated coils (CC). An opportunity

Black-hole driven winds

International Nuclear Information System (INIS)

Punsly, B.M.

1988-01-01

This dissertation is a study of the physical mechanism that allows a large scale magnetic field to torque a rapidly rotating, supermassive black hole. This is an interesting problem as it has been conjectured that rapidly rotating black holes are the central engines that power the observed extragalactic double radio sources. Axisymmetric solutions of the curved space-time version of Maxwell's equations in the vacuum do not torque black holes. Plasma must be introduced for the hole to mechanically couple to the field. The dynamical aspect of rotating black holes that couples the magnetic field to the hole is the following. A rotating black hole forces the external geometry of space-time to rotate (the dragging of inertial frames). Inside of the stationary limit surface, the ergosphere, all physical particle trajectories must appear to rotate in the same direction as the black hole as viewed by the stationary observers at asymptotic infinity. In the text, it is demonstrated how plasma that is created on field lines that thread both the ergosphere and the equatorial plane will be pulled by gravity toward the equator. By the aforementioned properties of the ergosphere, the disk must rotate. Consequently, the disk acts like a unipolar generator. It drives a global current system that supports the toroidal magnetic field in an outgoing, magnetically dominated wind. This wind carries energy (mainly in the form of Poynting flux) and angular momentum towards infinity. The spin down of the black hole is the ultimate source of this energy and angular momentum flux

Maximum power extraction under different vector-control schemes and grid-synchronization strategy of a wind-driven Brushless Doubly-Fed Reluctance Generator.

Science.gov (United States)

Mousa, Mohamed G; Allam, S M; Rashad, Essam M

2018-01-01

This paper proposes an advanced strategy to synchronize the wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG) to the grid-side terminals. The proposed strategy depends mainly upon determining the electrical angle of the grid voltage, θ v and using the same transformation matrix of both the power winding and grid sides to ensure that the generated power-winding voltage has the same phase-sequence of the grid-side voltage. On the other hand, the paper proposes a vector-control (power-winding flux orientation) technique for maximum wind-power extraction under two schemes summarized as; unity power-factor operation and minimum converter-current. Moreover, a soft-starting method is suggested to avoid the employed converter over-current. The first control scheme is achieved by adjusting the command power-winding reactive power at zero for a unity power-factor operation. However, the second scheme depends on setting the command d-axis control-winding current at zero to maximize the ratio of the generator electromagnetic-torque per the converter current. This enables the system to get a certain command torque under minimum converter current. A sample of the obtained simulation and experimental results is presented to check the effectiveness of the proposed control strategies. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

The differences between storms driven by helmet streamer CIRs and storms driven by pseudostreamer CIRs

OpenAIRE

Borovsky, Joseph E.; Denton, Michael

2013-01-01

A corotating interaction region (CIR) is formed when fast coronal hole origin solar wind overtakes slow solar wind and forms a region of compressed plasma and magnetic field. The slow wind upstream of the coronal hole fast wind can be either of helmet streamer origin or pseudostreamer origin. For a collection of 125 CIR-driven geomagnetic storms, the slow wind ahead of each CIR is examined; for those storm not containing ejecta, each CIR is categorized as a helmet streamer CIR (74 of the 125 ...

Synthesis and methylation of ribosomal RNA in HeLa cells infected with the herpes virus pseudorabies virus

International Nuclear Information System (INIS)

Furlong, J.C.; Kyriakidis, S.; Stevely, W.S.

1982-01-01

The effects of infection with the herpes virus pseudorabies virus on the metabolism of HeLa cell ribosomal RNA were examined. There is a decline both in the synthesis of nucleolar 45S ribosomal precursor RNA and in its processing to mature cytoplasmic RNA. The methylated oligonucleotides in the ribosomal RNA species were studied. The methylation of cytoplasmic ribosomal RNA was essentially unchanged. However there was some undermethylation of the nucleolar precursor. If undermethylated RNA does not mature then this may partly explain the reduced processing in the infected cells. (Author)

Half century of wind power generation memoir. Part 1; Furyoku hatsuden hanseiki sono omoide. 1

Energy Technology Data Exchange (ETDEWEB)

Nakata, H.

1995-12-01

This article may be deemed an autobiography of an individual on his development of wind power generation devices. The author began to be interested in electricity while he was a pupil of primary school and during his time of middle school student, when he walked against the strong wind on an embankment, he got an idea to utilize the wind power and succeeded to generate electricity with his handmade wind power generator using a bicycle generator. Afterwards he kept interested in devices utilizing the wind power, in 1973, energy saving was widely promoted due to the oil crises, and taking that opportunity, he established single-handedly a laboratory for development of utilization of the breeze power. Since his retirement from teaching profession in the spring of 1980, he has coped with earnestly the development of wind power generators. He acquired and installed various machine tools for metal works for generators and various machines for wood works for making propellers. In this article, wind power generators using bicycle generators (direct connection type and speed increasing type), small D.C. motors (motors for driving tape recorder, motors for automobile radiator and windshield wiper, etc.) and automobile generators (D.C. generators and alternators) are explained. 11 figs.

TRANSPORT OF SOLAR WIND H{sup +} AND He{sup ++} IONS ACROSS EARTH’S BOW SHOCK

Energy Technology Data Exchange (ETDEWEB)

Parks, G. K.; Lin, N. [Space Sciences Laboratory, University of California, Berkeley, CA (United States); Lee, E. [School of Space Research and Institute of Natural Sciences, Kyung Hee University, Yongin (Korea, Republic of); Fu, S. Y.; Ma, Y. Q. [Institute of Space Science, Peking University, Beijing (China); Kim, H. E.; Hong, J. [School of Space Research, Kyung Hee University, Yongin (Korea, Republic of); Yang, Z. W.; Liu, Y. [Key Laboratory for Space Weather, Chinese Academy of Sciences, Beijing (China); Canu, P. [Plasma Physics Laboratory, Ecole Polytechnique, Paris (France); Dandouras, I.; Rème, H. [IRAP, Paul Sabatier University and CNRS, Toulouse (France); Goldstein, M. L., E-mail: parks@ssl.berkeley.edu [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

2016-07-10

We have investigated the dependence of mass, energy, and charge of solar wind (SW) transport across Earth’s bow shock. An examination of 111 crossings during quiet SW in both quasi-perpendicular and quasi-parallel shock regions shows that 64 crossings had various degrees of heating and thermalization of SW. We found 22 crossings where the SW speed was <400 km s{sup −1}. The shock potential of a typical supercritical quasi-perpendicular shock estimated from deceleration of the SW and cutoff energy of electron flat top distribution is ∼50 Volts. We find that the temperatures of H{sup +} and He{sup ++} beams that penetrate the shock can sometimes be nearly the same in the upstream and downstream regions, indicating little or no heating had occurred crossing the bow shock. None of the models predict that the SW can cross the bow shock without heating. Our observations are important constraints for new models of collisionless shocks.

Performance Analysis of a Wind Turbine Driven Swash Plate Pump for Large Scale Offshore Applications

International Nuclear Information System (INIS)

Buhagiar, D; Sant, T

2014-01-01

This paper deals with the performance modelling and analysis of offshore wind turbine-driven hydraulic pumps. The concept consists of an open loop hydraulic system with the rotor main shaft directly coupled to a swash plate pump to supply pressurised sea water. A mathematical model is derived to cater for the steady state behaviour of entire system. A simplified model for the pump is implemented together with different control scheme options for regulating the rotor shaft power. A new control scheme is investigated, based on the combined use of hydraulic pressure and pitch control. Using a steady-state analysis, the study shows how the adoption of alternative control schemes in a the wind turbine-hydraulic pump system may result in higher energy yields than those from a conventional system with an electrical generator and standard pitch control for power regulation. This is in particular the case with the new control scheme investigated in this study that is based on the combined use of pressure and rotor blade pitch control

Data-Driven and Expectation-Driven Discovery of Empirical Laws.

Science.gov (United States)

1982-10-10

occurred in small integer proportions to each other. In 1809, Joseph Gay- Lussac found evidence for his law of combining volumes, which stated that a...of Empirical Laws Patrick W. Langley Gary L. Bradshaw Herbert A. Simon T1he Robotics Institute Carnegie-Mellon University Pittsburgh, Pennsylvania...Subtitle) S. TYPE OF REPORT & PERIOD COVERED Data-Driven and Expectation-Driven Discovery Interim Report 2/82-10/82 of Empirical Laws S. PERFORMING ORG

Ocean Wave Simulation Based on Wind Field.

Directory of Open Access Journals (Sweden)

Zhongyi Li

Full Text Available Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates.

Wind Extraction for Natural Ventilation

Science.gov (United States)

Fagundes, Tadeu; Yaghoobian, Neda; Kumar, Rajan; Ordonez, Juan

2017-11-01

Due to the depletion of energy resources and the environmental impact of pollution and unsustainable energy resources, energy consumption has become one of the main concerns in our rapidly growing world. Natural ventilation, a traditional method to remove anthropogenic and solar heat gains, proved to be a cost-effective, alternative method to mechanical ventilation. However, while natural ventilation is simple in theory, its detailed design can be a challenge, particularly for wind-driven ventilation, which its performance highly involves the buildings' form, surrounding topography, turbulent flow characteristics, and climate. One of the main challenges with wind-driven natural ventilation schemes is due to the turbulent and unpredictable nature of the wind around the building that impose complex pressure loads on the structure. In practice, these challenges have resulted in founding the natural ventilation mainly on buoyancy (rather than the wind), as the primary force. This study is the initial step for investigating the physical principals of wind extraction over building walls and investigating strategies to reduce the dependence of the wind extraction on the incoming flow characteristics and the target building form.

Effects of Topography-driven Micro-climatology on Evaporation

Science.gov (United States)

Adams, D. D.; Boll, J.; Wagenbrenner, N. S.

2017-12-01

The effects of spatial-temporal variation of climatic conditions on evaporation in micro-climates are not well defined. Current spatially-based remote sensing and modeling for evaporation is limited for high resolutions and complex topographies. We investigated the effect of topography-driven micro-climatology on evaporation supported by field measurements and modeling. Fourteen anemometers and thermometers were installed in intersecting transects over the complex topography of the Cook Agronomy Farm, Pullman, WA. WindNinja was used to create 2-D vector maps based on recorded observations for wind. Spatial analysis of vector maps using ArcGIS was performed for analysis of wind patterns and variation. Based on field measurements, wind speed and direction show consequential variability based on hill-slope location in this complex topography. Wind speed and wind direction varied up to threefold and more than 45 degrees, respectively for a given time interval. The use of existing wind models enables prediction of wind variability over the landscape and subsequently topography-driven evaporation patterns relative to wind. The magnitude of the spatial-temporal variability of wind therefore resulted in variable evaporation rates over the landscape. These variations may contribute to uneven crop development patterns observed during the late growth stages of the agricultural crops at the study location. Use of hill-slope location indexes and appropriate methods for estimating actual evaporation support development of methodologies to better define topography-driven heterogeneity in evaporation. The cumulative effects of spatially-variable climatic factors on evaporation are important to quantify the localized water balance and inform precision farming practices.

Depletion of cellular poly (A) binding protein prevents protein synthesis and leads to apoptosis in HeLa cells

Energy Technology Data Exchange (ETDEWEB)

Thangima Zannat, Mst.; Bhattacharjee, Rumpa B. [Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G2W1 (Canada); Bag, Jnanankur, E-mail: jbag@uoguelph.ca [Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G2W1 (Canada)

2011-05-13

Highlights: {yields} Depletion of cellular PABP level arrests mRNA translation in HeLa cells. {yields} PABP knock down leads to apoptotic cell death. {yields} PABP depletion does not affect transcription. {yields} PABP depletion does not lead to nuclear accumulation of mRNA. -- Abstract: The cytoplasmic poly (A) binding protein (PABP) is important in mRNA translation and stability. In yeast, depletion of PABP leads to translation arrest. Similarly, the PABP gene in Drosophila is important for proper development. It is however uncertain, whether mammalian PABP is essential for mRNA translation. Here we showed the effect of PABP depletion on mRNA metabolism in HeLa cells by using a small interfering RNA. Our results suggest that depletion of PABP prevents protein synthesis and consequently leads to cell death through apoptosis. Interestingly, no detectable effect of PABP depletion on transcription, transport and stability of mRNA was observed.

Depletion of cellular poly (A) binding protein prevents protein synthesis and leads to apoptosis in HeLa cells

International Nuclear Information System (INIS)

Thangima Zannat, Mst.; Bhattacharjee, Rumpa B.; Bag, Jnanankur

2011-01-01

Highlights: → Depletion of cellular PABP level arrests mRNA translation in HeLa cells. → PABP knock down leads to apoptotic cell death. → PABP depletion does not affect transcription. → PABP depletion does not lead to nuclear accumulation of mRNA. -- Abstract: The cytoplasmic poly (A) binding protein (PABP) is important in mRNA translation and stability. In yeast, depletion of PABP leads to translation arrest. Similarly, the PABP gene in Drosophila is important for proper development. It is however uncertain, whether mammalian PABP is essential for mRNA translation. Here we showed the effect of PABP depletion on mRNA metabolism in HeLa cells by using a small interfering RNA. Our results suggest that depletion of PABP prevents protein synthesis and consequently leads to cell death through apoptosis. Interestingly, no detectable effect of PABP depletion on transcription, transport and stability of mRNA was observed.

Remote Sensing Marine Ecology: Wind-driven algal blooms in the open oceans and their ecological impacts

Science.gov (United States)

Tang, DanLing

2016-07-01

Algal bloom not only can increase the primary production but also could result in negative ecological consequence, e.g., Harmful Algal Blooms (HABs). According to the classic theory for the formation of algal blooms "critical depth" and "eutrophication", oligotrophic sea area is usually difficult to form a large area of algal blooms, and actually the traditional observation is only sporadic capture to the existence of algal blooms. Taking full advantage of multiple data of satellite remote sensing, this study: 1), introduces "Wind-driven algal blooms in open oceans: observation and mechanisms" It explained except classic coastal Ekman transport, the wind through a variety of mechanisms affecting the formation of algal blooms. Proposed a conceptual model of "Strong wind -upwelling-nutrient-phytoplankton blooms" in Western South China Sea (SCS) to assess role of wind-induced advection transport in phytoplankton bloom formation. It illustrates the nutrient resources that support long-term offshore phytoplankton blooms in the western SCS; 2), Proposal of the theory that "typhoons cause vertical mixing, induce phytoplankton blooms", and quantify their important contribution to marine primary production; Proposal a new ecological index for typhoon. Proposed remote sensing inversion models. 3), Finding of the spatial and temporaldistributions pattern of harmful algal bloom (HAB)and species variations of HAB in the South Yellow Sea and East China Sea, and in the Pearl River estuary, and their oceanic dynamic mechanisms related with monsoon; The project developed new techniques and generated new knowledge, which significantly improved understanding of the formation mechanisms of algal blooms. 1), It proposed "wind-pump" mechanism integrates theoretical system combing "ocean dynamics, development of algal blooms, and impact on primary production", which will benefit fisheries management. 2), A new interdisciplinary subject "Remote Sensing Marine Ecology"(RSME) has been

The potentialities of the wind driven engines with Magnus effect

International Nuclear Information System (INIS)

Bychkov, N.M.; Gorelov, V.P.; Gorelov, S.V.; Kachanov, A.N.

1999-01-01

Possibilities of wind engine realizing of Magnus effect like of untraditional kind energy source is shown in the article. In this engine instead of traditional propellers the rotatable cylinders are installed. According interaction of the cylinders with wind the Magnus force arises. Magnus force exceeds propellers rise force in 5-10 times and maintain very large turning moment of wind wheel and most effective operation of engine, especially at low wind rates. Advantage of the engine consists in that it switch on under wind rate 1 m/c, when for propeller one requires 4-5 m/c

On the energy gain enhancement of DT+D3He fuel configuration in nuclear fusion reactor driven by heavy ion beams

Directory of Open Access Journals (Sweden)

S Khoshbinfar

2016-09-01

Full Text Available It is expected that advanced fuels be employed in the second generation of nuclear fusion reactors. Theoretical calculations show that in such a fuel, a high plasma temperature about 100 keV is a requisite for reaction rate improvement of nuclear fusion. However, creating such a temporal condition requires a more powerful driver than we have today. Here, introducing an optimal fuel configuration consisting of DT and D-3He layers, suitable for inertial fusion reactors and driven by heavy ion beams, the optimal energy gain conditions have been simulated and derived for 1.3 MJ system. It was found that, in this new fuel configuration, the ideal energy gain, is 22 percent more comparing with energy gain in corresponding single DT fuel layer. Moreover, the inner DT fuel layer contributed as an ignition trigger, while the outer D3He fuel acts as particle and radiation shielding as well as fuel layer.

Galactic evolution of D and 3He including stellar production of 3He

International Nuclear Information System (INIS)

Dearborn, D.S.; Steigman, G.; Tosi, M.

1996-01-01

New stellar models which track the production and destruction of 3 He (and D) have been evolved for a range of stellar masses (0.65≤M/M circle-dot ≤100), metallicities (0.01≤Z/Z circle-dot ≤1), and initial (main-sequence) 3 He mass fractions (10 -5 ≤X 3,MS ≤10 -3 ). Armed with the 3 He yields from these stellar models we have followed the evolution of D and 3 He using a variety of chemical evolution models with and without infall of primordial or processed material. Production of new 3 He by the lower mass stars overwhelms any reasonable primordial contributions and leads to predicted abundances in the presolar nebula and/or the present interstellar medium in excess of the observationally inferred values. This result, which obtains even for zero primordial D and 3 He, and was anticipated by Rood, Steigman, ampersand Tinsley is insensitive to the choice of chemical evolution model; it is driven by the large 3 He yields from low-mass stars. In an attempt to ameliorate this problem we have considered a number of nonstandard models in which the yields from low-mass stars have been modified. Although several of these nonstandard models may be consistent with the 3 He data, they may be inconsistent with observations of 12 C/ 13 C, 18 O, and, most seriously the super- 3 He rich planetary nebulae. Even using the most extreme of these nonstandard models we obtain a generous upper bound to pregalactic 3 He:X 3P ≤3.2x10 -5 which, nonetheless, leads to a stringent lower bound to the universal density of nucleons. copyright 1996 The American Astronomical Society

Atmospheric NLTE models for the spectroscopic analysis of blue stars with winds. III. X-ray emission from wind-embedded shocks

Science.gov (United States)

Carneiro, L. P.; Puls, J.; Sundqvist, J. O.; Hoffmann, T. L.

2016-05-01

Context. Extreme ultraviolet (EUV) and X-ray radiation emitted from wind-embedded shocks in hot, massive stars can affect the ionization balance in their outer atmospheres and can be the mechanism responsible for producing highly ionized atomic species detected in stellar wind UV spectra. Aims: To allow for these processes in the context of spectral analysis, we have implemented the emission from wind-embedded shocks and related physics into our unified, NLTE model atmosphere/spectrum synthesis code FASTWIND. Methods: The shock structure and corresponding emission is calculated as a function of user-supplied parameters (volume filling factor, radial stratification of shock strength, and radial onset of emission). We account for a temperature and density stratification inside the postshock cooling zones, calculated for radiative and adiabatic cooling in the inner and outer wind, respectively. The high-energy absorption of the cool wind is considered by adding important K-shell opacities, and corresponding Auger ionization rates have been included in the NLTE network. To test our implementation and to check the resulting effects, we calculated a comprehensive model grid with a variety of X-ray emission parameters. Results: We tested and verified our implementation carefully against corresponding results from various alternative model atmosphere codes, and studied the effects from shock emission for important ions from He, C, N, O, Si, and P. Surprisingly, dielectronic recombination turned out to play an essential role for the ionization balance of O iv/O v (particularly in dwarfs with Teff~ 45 000 K). Finally, we investigated the frequency dependence and radial behavior of the mass absorption coefficient, κν(r), which is important in the context of X-ray line formation in massive star winds. Conclusions: In almost all of the cases considered, direct ionization is of major influence because of the enhanced EUV radiation field, and Auger ionization only affects N vi

Iterative data-driven load control for flexible wind turbine rotors

OpenAIRE

Navalkar, S.T.

2016-01-01

Wind energy has reached a high degree ofmaturity: for wind-rich onshore locations, it is already competitive with conventional energy sources. However, for low-wind, remote and offshore regions, research efforts are still required to enhance its economic viability. While it is possible to reduce the cost of energy by upscaling wind turbines, it is believed that we may be approaching a plateau in turbine size. Beyond this plateau, the material costs associated with the high dynamic turbine loa...

Sliding mode direct power control of RSC for DFIGs driven by variable speed wind turbines

Directory of Open Access Journals (Sweden)

E.G. Shehata

2015-12-01

Full Text Available In spite of its several advantages, a classic direct power control (DPC of doubly fed induction generators (DFIGs driven by variable speed wind turbines has some drawbacks. In this paper, a simple and robust total sliding mode controller (TSMC is designed to improve the classical DPC performance without complicating the overall scheme. The TSMC is designed to regulate the DFIG stator active and reactive powers. Two integral switching functions are selected for describing the switching surfaces of the active and reactive powers. Reaching phase stability problem of the classical sliding mode controller is avoided in the proposed TSMC. Neither current control loops nor accurate values of machine parameters are required in the proposed scheme. In addition, axes transformation of the stator voltage and current are eliminated. The grid side converter is controlled based on DPC principle to regulate both DC-link voltage and total reactive power. The feasibility of the proposed DPC scheme is validated through simulation studies on a 1.5 MW wind power generation system. The performance of the proposed and conventional DPC schemes is compared under different operating conditions.

A review of 3He resources and acquisition for use as fusion fuel

International Nuclear Information System (INIS)

Wittenberg, L.J.; Camerson, E.N.; Kulcinski, G.L.; Ott, S.H.; Santarius, J.F.; Sviatoslavsky, G.I.; Sviatoslavsky, I.N.; Thompson, H.E.

1992-01-01

This paper reports that a combination of man-made and natural resources on earth could provide sufficient 3 He fuel for the technological development of D- 3 He fusion reactors. Helium exists in natural gas wells; however, at the current rate of natural gas usage, this resource would provide 3 He. The radioactive decay of 3 H produced in fission production reactors could yield 110 kg of 3 He by the year 2000 if it were retained. Apparently, a large amount of 3 He exists within the earth's mantle, but it is inaccessible. A significant quantity of 3 He, which could be imported to supply a fusion power industry on earth for hundreds of years, exists on the moon. The solar wind has deposited >1 million tonnes of 3 He in the fine regolith that covers the surface of the moon. The presence of this solar wind gas was confirmed by analyses of the lunar regolith samples brought to earth. A strong correlation is noted between the helium retained and the TiO 2 content of the regolith; consequently, remote-sensing data showing high-titanium-bearing soils in the lunar maria areas have been used to locate potentially rich sites for helium extraction. Surface photographs of Mare Tranquillitatis have shown that nearly 50% of this mare may be minable and capable of supplying ∼7100 tonnes of 3 He. A mobile mining vehicle is proposed for use in the excavation of the soil and the release of the helium and other solar wind gases. The evolved gases would be purified by a combination of permeators and cryogenic techniques to provide a rich resource of H 2 , helium, CO 2 , H 2 O, and N 2 , followed by helium isotopic separation systems

Metal-enhanced galactic winds. I

International Nuclear Information System (INIS)

Vader, J.P.

1986-01-01

Supernova-driven gas loss during the early evolution of elliptical galaxies is considered as a possible explanation for the correlations among the observed chemical and structural properties of these systems. Mass loss from systems with a chemically homogeneous interstellar medium does not work. It is pointed out that supernova-driven winds are in fact metal-enhanced with respect to the star-forming gas because the metal production of any supernova that drives the wind is directly flushed out of the galaxy. The fraction of the total metal production lost in the wind is thus at least as large as the fraction epsilon(z) of supernovae that power the wind, independent of the total mass loss. As a corollary, the yield of heavy elements that are recycled in the galaxy is reduced by a factor 1 - epsilon(z). Metal-enhanced galactic winds, which can carry away a large fraction of the metal production in spite of a moderate total mass loss, offer a promising explanation for the low metallicities of dwarf elliptical galaxies. 62 references

Iterative data-driven load control for flexible wind turbine rotors

NARCIS (Netherlands)

Navalkar, S.T.

2016-01-01

Wind energy has reached a high degree ofmaturity: for wind-rich onshore locations, it is already competitive with conventional energy sources. However, for low-wind, remote and offshore regions, research efforts are still required to enhance its economic viability. While it is possible to reduce the

An Improved Adaptive-Torque-Gain MPPT Control for Direct-Driven PMSG Wind Turbines Considering Wind Farm Turbulences

Directory of Open Access Journals (Sweden)

Xiaolian Zhang

2016-11-01

Full Text Available Maximum power point tracking (MPPT plays an important role in increasing the efficiency of a wind energy conversion system (WECS. In this paper, three conventional MPPT methods are reviewed: power signal feedback (PSF control, decreased torque gain (DTG control, and adaptive torque gain (ATG control, and their potential challenges are investigated. It is found out that the conventional MPPT method ignores the effect of wind turbine inertia and wind speed fluctuations, which lowers WECS efficiency. Accordingly, an improved adaptive torque gain (IATG method is proposed, which customizes adaptive torque gains and enhances MPPT performances. Specifically, the IATG control considers wind farm turbulences and works out the relationship between the optimal torque gains and the wind speed characteristics, which has not been reported in the literature. The IATG control is promising, especially under the ongoing trend of building wind farms with large-scale wind turbines and at low and medium wind speed sites.

WIND VARIABILITY IN BZ CAMELOPARDALIS

International Nuclear Information System (INIS)

Honeycutt, R. K.; Kafka, S.; Robertson, J. W.

2013-01-01

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 wind activity known to occur frequently in this star. We confirm the results of Ringwald and Naylor that the P-Cygni absorption components of the lines mostly evolve from higher expansion velocity to lower velocity as an episode progresses. We also commonly find blueshifted emission components in the Hα line profile, whose velocities and durations strongly suggest that they are also due to the wind. Curiously, Ringwald and Naylor reported common occurrences of redshifted Hα emission components in their BZ Cam spectra. We have attributed these emission components in Hα to occasions when gas concentrations in the bipolar wind (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 velocities is due to the higher velocity portions of a wind 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 velocity of the core of the He I λ5876 line, finding P = 0.15353(4). Using this period, the wind episodes in BZ Cam are found to be concentrated near the inferior conjunction of the emission line source. This result helps confirm that the winds in nova-like CVs are often phase dependent, in spite of the puzzling implication that such winds lack axisymmetry. We argue that the radiation-driven wind 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 wind events, as well as leading to an orbital modulation of the wind due to the non

Solar cycle variations of the energetic H/He intensity ratio at high heliolatitudes and in the ecliptic plane

Directory of Open Access Journals (Sweden)

D. Lario

Full Text Available We study the variability of the heliospheric energetic proton-to-helium abundance ratios during different phases of the solar cycle. We use energetic particle, solar wind, and magnetic field data from the Ulysses, ACE and IMP-8 spacecraft to compare the H/He intensity ratio at high heliographic latitudes and in the ecliptic plane. During the first out-of-ecliptic excursion of Ulysses (1992–1996, the HI-SCALE instrument measured corotating energetic particle intensity enhancements characterized by low values (< 10 of the 0.5–1.0 MeV nucleon^-1 H/He intensity ratio. During the second out-of-ecliptic excursion of Ulysses (1999–2002, the more frequent occurrence of solar energetic particle events resulted in almost continuously high (< 20 values of the H/He ratio, even at the highest heliolatitudes reached by Ulysses. Comparison with in-ecliptic measurements from an identical instrument on the ACE spacecraft showed similar H/He values at ACE and Ulysses, suggesting a remarkable uniformity of energetic particle intensities in the solar maximum heliosphere at high heliolatitudes and in the ecliptic plane. In-ecliptic observations of the H/He intensity ratio from the IMP-8 spacecraft show variations between solar maximum and solar minimum similar to those observed by Ulysses at high heliographic latitudes. We suggest that the variation of the H/He intensity ratio throughout the solar cycle is due to the different level of transient solar activity, as well as the different structure and duration that corotating solar wind structures have under solar maximum and solar minimum conditions. During solar minimum, the interactions between the two different types of solar wind streams (slow vs. fast are strong and long-lasting, allowing for a continuous and efficient acceleration of interstellar pickup He +. During solar maximum, transient events of solar origin (characterized by high values of the H/He ratio are able to globally

Radiation Belt Transport Driven by Solar Wind Dynamic Pressure Fluctuations

Science.gov (United States)

Kress, B. T.; Hudson, M. K.; Ukhorskiy, A. Y.; Mueller, H.

2012-12-01

The creation of the Earth's outer zone radiation belts is attributed to earthward transport and adiabatic acceleration of electrons by drift-resonant interactions with electromagnetic fluctuations in the magnetosphere. Three types of radial transport driven by solar wind dynamic pressure fluctuations that have been identified are: (1) radial diffusion [Falthammer, 1965], (2) significant changes in the phase space density radial profile due to a single or few ULF drift-resonant interactions [Ukhorskiy et al., 2006; Degeling et al., 2008], and (3) shock associated injections of radiation belt electrons occurring in less than a drift period [Li et al., 1993]. A progress report will be given on work to fully characterize different forms of radial transport and their effect on the Earth's radiation belts. The work is being carried out by computing test-particle trajectories in electric and magnetic fields from a simple analytic ULF field model and from global MHD simulations of the magnetosphere. Degeling, A. W., L. G. Ozeke, R. Rankin, I. R. Mann, and K. Kabin (2008), Drift resonant generation of peaked relativistic electron distributions by Pc 5 ULF waves, textit{J. Geophys. Res., 113}, A02208, doi:10.1029/2007JA012411. Fälthammar, C.-G. (1965), Effects of Time-Dependent Electric Fields on Geomagnetically Trapped Radiation, J. Geophys. Res., 70(11), 2503-2516, doi:10.1029/JZ070i011p02503. Li, X., I. Roth, M. Temerin, J. R. Wygant, M. K. Hudson, and J. B. Blake (1993), Simulation of the prompt energization and transport of radiation belt particles during the March 24, 1991 SSC, textit{Geophys. Res. Lett., 20}(22), 2423-2426, doi:10.1029/93GL02701. Ukhorskiy, A. Y., B. J. Anderson, K. Takahashi, and N. A. Tsyganenko (2006), Impact of ULF oscillations in solar wind dynamic pressure on the outer radiation belt electrons, textit{Geophys. Res. Lett., 33}(6), L06111, doi:10.1029/2005GL024380.

Thermal loading of wind power converter considering dynamics of wind speed

DEFF Research Database (Denmark)

Baygildina, Elvira; Peltoniemi, Pasi; Pyrhönen, Olli

2013-01-01

The thermal loading of power semiconductors is a crucial performance related to the reliability and cost of the wind power converter. However, the thermal loading impacts by the variation of wind speeds have not yet been clarified, especially when considering the aerodynamic behavior of the wind...... turbines. In this paper, the junction temperatures in the wind power converter are studied under not only steady state, but also turbulent wind speed conditions. The study is based on a 1.5 MW direct-driven turbine system with aerodynamic model described by Unsteady Blade Element Momentum Method (BEMM......), and the thermal stress of power devices is investigated from the frequency spectrum point of view of wind speed. It is concluded that because of the strong inertia effects by the aerodynamic behavior of wind turbines, thermal stress of the semiconductors is relatively more stable and only influenced by the low...

Preliminary Dynamic Feasibility and Analysis of a Spherical, Wind-Driven (Tumbleweed), Martian Rover

Science.gov (United States)

Flick, John J.; Toniolo, Matthew D.

2005-01-01

The process and findings are presented from a preliminary feasibility study examining the dynamics characteristics of a spherical wind-driven (or Tumbleweed) rover, which is intended for exploration of the Martian surface. The results of an initial feasibility study involving several worst-case mobility situations that a Tumbleweed rover might encounter on the surface of Mars are discussed. Additional topics include the evaluation of several commercially available analysis software packages that were examined as possible platforms for the development of a Monte Carlo Tumbleweed mission simulation tool. This evaluation lead to the development of the Mars Tumbleweed Monte Carlo Simulator (or Tumbleweed Simulator) using the Vortex physics software package from CM-Labs, Inc. Discussions regarding the development and evaluation of the Tumbleweed Simulator, as well as the results of a preliminary analysis using the tool are also presented. Finally, a brief conclusions section is presented.

Predicting Migratory Corridors of White Storks, Ciconia ciconia, to Enhance Sustainable Wind Energy Planning: A Data-Driven Agent-Based Model

Directory of Open Access Journals (Sweden)

Francis Oloo

2018-05-01

Full Text Available White storks (Ciconia ciconia are birds that make annual long-distance migration flights from their breeding grounds in the Northern Hemisphere to the south of Africa. These trips take place in the winter season, when the temperatures in the North fall and food supply drops. White storks, because of their large size, depend on the wind, thermals, and orographic characteristics of the environment in order to minimize their energy expenditure during flight. In particular, the birds adopt a soaring behavior in landscapes where the thermal uplift and orographic updrafts are conducive. By attaining suitable soaring heights, the birds then use the wind characteristics to glide for hundreds of kilometers. It is therefore expected that white storks would prefer landscapes that are characterized by suitable wind and thermal characteristics, which promote the soaring and gliding behaviors. However, these same landscapes are also potential sites for large-scale wind energy generation. In this study, we used the observed data of the white stork movement trajectories to specify a data-driven agent-based model, which simulates flight behavior of the white storks in a dynamic environment. The data on the wind characteristics and thermal uplift are dynamically changed on a daily basis so as to mimic the scenarios that the observed birds experienced during flight. The flight corridors that emerge from the simulated flights are then combined with the predicted surface on the wind energy potential, in order to highlight the potential risk of collision between the migratory white storks and hypothetical wind farms in the locations that are suitable for wind energy developments. This work provides methods that can be adopted to assess the overlap between wind energy potential and migratory corridors of the migration of birds. This can contribute to achieving sustainable trade-offs between wind energy development and conservation of wildlife and, hence, handling the

2016 Wind Technologies Market Report

Energy Technology Data Exchange (ETDEWEB)

Wiser, Ryan [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bolinger, Mark [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2017-08-08

Wind power capacity in the United States experienced strong growth in 2016. Recent and projected near-term growth is supported by the industry’s primary federal incentive—the production tax credit (PTC)—as well as a myriad of state-level policies. Wind additions have also been driven by improvements in the cost and performance of wind power technologies, yielding low power sales prices for utility, corporate, and other purchasers.

Probing HeII Reionization at z>3.5 with Resolved HeII Lyman Alpha Forest Spectra

Science.gov (United States)

Worseck, Gabor

2017-08-01

The advent of GALEX and COS have revolutionized our view of HeII reionization, the final major phase transition of the intergalactic medium. COS spectra of the HeII Lyman alpha forest have confirmed with high confidence the high HeII transmission that signifies the completion of HeII reionization at z 2.7. However, the handful of z>3.5 quasars observed to date show a set of HeII transmission 'spikes' and larger regions with non-zero transmission that suggest HeII reionization was well underway by z=4. This is in striking conflict with predictions from state-of-the-art radiative transfer simulations of a HeII reionization driven by bright quasars. Explaining these measurements may require either faint quasars or more exotic sources of hard photons at z>4, with concomitant implications for HI reionization. However, many of the observed spikes are unresolved in G140L spectra and are significantly impacted by Poisson noise. Current data cannot reliably probe the ionization state of helium at z>3.5.We request 41 orbits to obtain science-grade G130M spectra of the two UV-brightest HeII-transmitting QSOs at z>3.5 to confirm and resolve their HeII transmission spikes as an unequivocal test of early HeII reionization. These spectra are complemented by recently obtained data from 8m telescopes: (1) Echelle spectra of the coeval HI Lya forest to map the underlying density field that modulates the HeII absorption, and (2) Our dedicated survey for foreground QSOs that may source the HeII transmission. Our recent HST programs revealed the only two viable targets to resolve the z>3.5 HeII Lyman alpha forest, and to conclusively solve this riddle.

Wind Generators

Science.gov (United States)

1989-01-01

When Enerpro, Inc. president, Frank J. Bourbeau, attempted to file a patent on a system for synchronizing a wind generator to the electric utility grid, he discovered Marshall Space Flight Center's Frank Nola's power factor controller. Bourbeau advanced the technology and received a NASA license and a patent for his Auto Synchronous Controller (ASC). The ASC reduces generator "inrush current," which occurs when large generators are abruptly brought on line. It controls voltage so the generator is smoothly connected to the utility grid when it reaches its synchronous speed, protecting the components from inrush current damage. Generator efficiency is also increased in light winds by applying lower than rated voltage. Wind energy is utilized to drive turbines to generate electricity for utility companies.

System Efficiency of a Tap Transformer Based Grid Connection Topology Applied on a Direct Driven Generator for Wind Power

Directory of Open Access Journals (Sweden)

Senad Apelfröjd

2014-01-01

Full Text Available Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed.

System efficiency of a tap transformer based grid connection topology applied on a direct driven generator for wind power.

Science.gov (United States)

Apelfröjd, Senad; Eriksson, Sandra

2014-01-01

Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed.

System Efficiency of a Tap Transformer Based Grid Connection Topology Applied on a Direct Driven Generator for Wind Power

Science.gov (United States)

2014-01-01

Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed. PMID:25258733

Energy from the wind. [For United Kingdom

Energy Technology Data Exchange (ETDEWEB)

Musgrove, P J

1977-01-01

An assessment is made of the amount of power/energy in the wind with emphasis on calculations for the United Kingdom. Windmills must be deployed over a given area in a pattern that takes account of the distribution of directions from which the wind can be expected. In the U.K., one such array can be provided in the Western Isles. The author recommends deploying such an array in the shallow waters of the southern North Sea. He concludes that deploying such an array in the shallow offshore region would have the potential for providing a very significant part of the total electricity requirements. He also concludes that such a wind-power system appears competitive with nuclear power systems. 8 references. (MCW)

Wind resource characterization in the Arabian Peninsula

KAUST Repository

Yip, Chak Man Andrew; Gunturu, Udaya; Stenchikov, Georgiy L.

2015-01-01

Wind energy is expected to contribute to alleviating the rise in energy demand in the Middle East that is driven by population growth and industrial development. However, variability and intermittency in the wind resource present significant

Single-sided natural ventilation driven by wind pressure and temperature difference

DEFF Research Database (Denmark)

Larsen, Tine Steen; Heiselberg, Per

2008-01-01

-scale wind tunnel experiments have been made with the aim of making a new expression for calculation of the airflow rate in single-sided natural ventilation. During the wind tunnel experiments it was found that the dominating driving force differs between wind speed and temperature difference depending......Even though opening a window for ventilation of a room seems very simple, the flow that occurs in this situation is rather complicated. The amount of air going through the window opening will depend on the wind speed near the building, the temperatures inside and outside the room, the wind...

Design Optimization and Evaluation of Different Wind Generator Systems

DEFF Research Database (Denmark)

Chen, Zhe; Li, Hui

2008-01-01

. In this paper, seven variable speed constant frequency (VSCF) wind generator systems are investigated, namely permanent magnet synchronous generators with the direct-driven (PMSG_DD), the single-stage gearbox (PMSG_1G) and three-stage gearbox (PMSG_3G) concepts, doubly fed induction generators with the three......With rapid development of wind power technologies and significant growth of wind power capacity installed worldwide, various wind generator systems have been developed and built. The objective of this paper is to evaluate various wind generator systems by optimization designs and comparisons......-stage gearbox (DFIG_3G) and with the single-stage gearbox (DFIG_1G), the electricity excited synchronous generator with the direct-driven (EESG_DD), and the VSCF squirrel cage induction generator with the three-stage gearbox (SCIG_3G). Firstly, the design models of wind turbines, three/single stage gearbox...

Organizational forms promoting wind power development. Organizational and legal evaluation, energy- and environmental analysis and socio-economic analysis of wind turbine location along railways

International Nuclear Information System (INIS)

1997-12-01

Modernization of the train material and transition from diesel-driven to el-driven trains result in reduced air pollution in Denmark. The purpose of this study is to define, concretize and compare organizational forms for use of wind power as the 'green' electric power for train operation. An investment into an wind turbine array with 500 kW wind turbines in roughness class 2 would be repaid in 7.9 year period. Air pollution abatement together with improved socio-economic structure due to growing employment would be achieved. Several models of 'green' electrification of the national railways are given, both for state- and privately owned wind power plants. (EG)

D-3He fuel cycles for neutron lean reactors

International Nuclear Information System (INIS)

Kernbichler, W.; Miley, G.H.; Heindler, M.

1989-01-01

The intrinsic potential of D-3He as a reactor fuel is investigated for a large range of 3He to D density ratios. A steady-state zero-dimensional reactor model is developed in which much care is attributed to a proper treatment of fast fusion products. Useful ranges of reactor parameters as well as temperature-density windows for driven and ignited operation are identified. Various figures of merit are calculated, such as power densities, net power production, neutron production, tritium load and radiative power. These results suggest several optimistic conclusions about the performance of D-3He as a reactor fuel

Detection of /sup 4/He in stratospheric particles gives evidence of extraterrestrial origin

Energy Technology Data Exchange (ETDEWEB)

Rajan, R S [Carnegie Institution of Washington, D.C. (USA). Dept. of Terrestrial Magnetism; Brownlee, D E; Tomandl, D; Hodge, P W; Farrar, H; Britten, R A

1977-05-12

The detection of large concentrations of /sup 4/He in some ..mu..m size stratospheric particles collected during the past 2 years is here reported. The final /sup 4/He concentrations ranged from 0.002 to 0.25 cc/gm. Such high concentrations confirm that the particles were extraterrestrial and that some of them were exposed to solar wind for at least 10 to 100 years; also, since solar wind ions are implanted only to depths of approximately 500 A, the measurements also indicate that the particles existed as small particles in space and were not produced in the atmosphere by fragmentation of larger meteoroids. The possibility that the observed He could have been the product of decaying U appears remote. Since micrometeorites probably have cometary origin, they are potentially a valuable source of primitive Solar System matter.

Field Tests of Wind Turbine Unit with Tandem Wind Rotors and Double Rotational Armatures

Science.gov (United States)

Galal, Ahmed Mohamed; Kanemoto, Toshiaki

This paper discusses the field tests of the wind turbine unit, in which the front and the rear wind rotors drive the inner and the outer armatures of the synchronous generator. The wind rotors were designed conveniently by the traditional procedure for the single wind rotor, where the diameters of the front and the rear wind rotors are 2 m and 1.33 m. The tests were done on a pick-up type truck driven straightly at constant speed. The rotational torque of the unit is directly proportional to the induced electric current irrespective of the rotational speeds of the wind rotors, while the induced voltage is proportional to the relative rotational speed. The performance of the unit is significantly affected not only by the wind velocity, but also by the blade setting angles of both wind rotors and the applied load especially at lower wind velocity.

Age-dependence of the x-ray-induced deficiency in DNA synthesis in HeLa S3 cells during generation 1

International Nuclear Information System (INIS)

Griffiths, T.D.; Tolmach, L.J.

1975-01-01

The radiation-induced deficiency in DNA synthesis in Generation 1 was studied as a function of the age of HeLa S3 cells at the time of exposure to 220 kV x rays in the previous generation (Generation 0). The amount of DNA synthesized is dependent on the stage in the generation cycle at which cells are irradiated. The smallest deficiency (20 to 35 percent after a dose of 500 rad) is observed in cells irradiated in early G1 or early G2, while the greatest deficiency (55 to 70 percent after 500 rad) is found in cells irradiated at mitosis or at the G1/S transition. The high sensitivity of cells at G1/S is also manifested by a steeper dose-response curve. Cells irradiated in late G2, past the point where their progression is temporarily blocked by x rays, synthesize a normal amount of DNA in Generation 1, while cells that are held up in the G2 block exhibit deficient synthesis in the next generation. The extent of the deficiency in early G1 cells can be enhanced by treatment with 1 mM hydroxyurea for several hours immediately following irradiation. The possibility that deficient DNA synthesis is related to cell killing, and the relation between the G2 block and deficient synthesis, are discussed

Observable Signatures of Wind-driven Chemistry with a Fully Consistent Three-dimensional Radiative Hydrodynamics Model of HD 209458b

Science.gov (United States)

Drummond, B.; Mayne, N. J.; Manners, J.; Carter, A. L.; Boutle, I. A.; Baraffe, I.; Hébrard, É.; Tremblin, P.; Sing, D. K.; Amundsen, D. S.; Acreman, D.

2018-03-01

We present a study of the effect of wind-driven advection on the chemical composition of hot-Jupiter atmospheres using a fully consistent 3D hydrodynamics, chemistry, and radiative transfer code, the Met Office Unified Model (UM). Chemical modeling of exoplanet atmospheres has primarily been restricted to 1D models that cannot account for 3D dynamical processes. In this work, we couple a chemical relaxation scheme to the UM to account for the chemical interconversion of methane and carbon monoxide. This is done consistently with the radiative transfer meaning that departures from chemical equilibrium are included in the heating rates (and emission) and hence complete the feedback between the dynamics, thermal structure, and chemical composition. In this Letter, we simulate the well studied atmosphere of HD 209458b. We find that the combined effect of horizontal and vertical advection leads to an increase in the methane abundance by several orders of magnitude, which is directly opposite to the trend found in previous works. Our results demonstrate the need to include 3D effects when considering the chemistry of hot-Jupiter atmospheres. We calculate transmission and emission spectra, as well as the emission phase curve, from our simulations. We conclude that gas-phase nonequilibrium chemistry is unlikely to explain the model–observation discrepancy in the 4.5 μm Spitzer/IRAC channel. However, we highlight other spectral regions, observable with the James Webb Space Telescope, where signatures of wind-driven chemistry are more prominant.

EVOLUTION OF THE RELATIONSHIPS BETWEEN HELIUM ABUNDANCE, MINOR ION CHARGE STATE, AND SOLAR WIND SPEED OVER THE SOLAR CYCLE

International Nuclear Information System (INIS)

Kasper, J. C.; Stevens, M. L.; Korreck, K. E.; Maruca, B. A.; Kiefer, K. K.; Schwadron, N. A.; Lepri, S. T.

2012-01-01

The changing relationships between solar wind speed, helium abundance, and minor ion charge state are examined over solar cycle 23. Observations of the abundance of helium relative to hydrogen (A He ≡ 100 × n He /n H ) by the Wind spacecraft are used to examine the dependence of A He on solar wind speed and solar activity between 1994 and 2010. This work updates an earlier study of A He from 1994 to 2004 to include the recent extreme solar minimum and broadly confirms our previous result that A He in slow wind is strongly correlated with sunspot number, reaching its lowest values in each solar minima. During the last minimum, as sunspot numbers reached their lowest levels in recent history, A He continued to decrease, falling to half the levels observed in slow wind during the previous minimum and, for the first time observed, decreasing even in the fastest solar wind. We have also extended our previous analysis by adding measurements of the mean carbon and oxygen charge states observed with the Advanced Composition Explorer spacecraft since 1998. We find that as solar activity decreased, the mean charge states of oxygen and carbon for solar wind of a given speed also fell, implying that the wind was formed in cooler regions in the corona during the recent solar minimum. The physical processes in the coronal responsible for establishing the mean charge state and speed of the solar wind have evolved with solar activity and time.

Data-driven online monitoring of wind turbines

NARCIS (Netherlands)

Kenbeek, T.; Kapodistria, S.; Di Bucchianico, A.

2017-01-01

Condition based maintenance is a modern approach to maintenance which has been successfully used in several industrial sectors. In this paper we present a concrete statistical approach to condition based maintenance for wind turbine by applying ideas from statistical process control. A specific

Advanced control of direct-driven PMSG generator in wind turbine system

Directory of Open Access Journals (Sweden)

Gajewski Piotr

2016-12-01

Full Text Available The paper presents the advanced control system of the wind energy conversion with a variable speed wind turbine. The considered system consists of a wind turbine with the permanent magnet synchronous generator (PMSG, machine side converter (MSC, grid side converter (GSC and control circuits. The mathematical models of a wind turbine system, the PMSG generator and converters have been described. The control algorithms of the converter systems based on the methods of vector control have been applied. In the advanced control system of the machine side converter the optimal MPPT control method has been used. Additionally the pitch control scheme is included in order to achieve the limitation of maximum power and to prevent mechanical damage of the wind turbine. In the control system of the grid side converter the control of active and reactive power has been applied with the application of Voltage Oriented Control (VOC. The performance of the considered wind energy system has been studied by digital simulation. The results of simulation studies confirmed the good effectiveness of the considered wind turbine system and very good performance of the proposed methods of vector control and control systems.

Direct Drive Synchronous Machine Models for Stability Assessment of Wind Farms

Energy Technology Data Exchange (ETDEWEB)

Poeller, Markus; Achilles, Sebastian [DIgSILENT GmbH, Gomaringen (Germany)

2003-11-01

The increasing size of wind farms requires power system stability analysis including dynamic wind generator models. For turbines above 1MW doubly-fed induction machines are the most widely used concept. However, especially in Germany, direct-drive wind generators based on converter-driven synchronous generator concepts have reached considerable market penetration. This paper presents converter driven synchronous generator models of various order that can be used for simulating transients and dynamics in a very wide time range.

Structure and Dynamics of the Accretion Process and Wind in TW Hya

Science.gov (United States)

Dupree, A. K.; Brickhouse, N. S.; Cranmer, S. R.; Berlind, P.; Strader, Jay; Smith, Graeme H.

2014-07-01

Time-domain spectroscopy of the classical accreting T Tauri star, TW Hya, covering a decade and spanning the far UV to the near-infrared spectral regions can identify the radiation sources, the atmospheric structure produced by accretion, and properties of the stellar wind. On timescales from days to years, substantial changes occur in emission line profiles and line strengths. Our extensive time-domain spectroscopy suggests that the broad near-IR, optical, and far-uv emission lines, centered on the star, originate in a turbulent post-shock region and can undergo scattering by the overlying stellar wind as well as some absorption from infalling material. Stable absorption features appear in Hα, apparently caused by an accreting column silhouetted in the stellar wind. Inflow of material onto the star is revealed by the near-IR He I 10830 Å line, and its free-fall velocity correlates inversely with the strength of the post-shock emission, consistent with a dipole accretion model. However, the predictions of hydrogen line profiles based on accretion stream models are not well-matched by these observations. Evidence of an accelerating warm to hot stellar wind is shown by the near-IR He I line, and emission profiles of C II, C III, C IV, N V, and O VI. The outflow of material changes substantially in both speed and opacity in the yearly sampling of the near-IR He I line over a decade. Terminal outflow velocities that range from 200 km s-1 to almost 400 km s-1 in He I appear to be directly related to the amount of post-shock emission, giving evidence for an accretion-driven stellar wind. Calculations of the emission from realistic post-shock regions are needed. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support

DUST DYNAMICS IN PROTOPLANETARY DISK WINDS DRIVEN BY MAGNETOROTATIONAL TURBULENCE: A MECHANISM FOR FLOATING DUST GRAINS WITH CHARACTERISTIC SIZES

Energy Technology Data Exchange (ETDEWEB)

Miyake, Tomoya; Suzuki, Takeru K.; Inutsuka, Shu-ichiro, E-mail: miyake.tomoya@e.mbox.nagoya-u.ac.jp, E-mail: stakeru@nagoya-u.jp [Department of Physics, Nagoya University, Nagoya, Aichi 464-8602 (Japan)

2016-04-10

We investigate the dynamics of dust grains of various sizes in protoplanetary disk winds driven by magnetorotational turbulence, by simulating the time evolution of the dust grain distribution in the vertical direction. Small dust grains, which are well-coupled to the gas, are dragged upward with the upflowing gas, while large grains remain near the midplane of a disk. Intermediate-size grains float near the sonic point of the disk wind located at several scale heights from the midplane, where the grains are loosely coupled to the background gas. For the minimum mass solar nebula at 1 au, dust grains with size of 25–45 μm float around 4 scale heights from the midplane. Considering the dependence on the distance from the central star, smaller-size grains remain only in an outer region of the disk, while larger-size grains are distributed in a broader region. We also discuss the implications of our result for observations of dusty material around young stellar objects.

Technic and economic viability study on exploitation of lunar 3He resource

International Nuclear Information System (INIS)

Deng Baiquan

1995-01-01

From the energetics point of view, the technic and economic viability study on exploitation of lunar 3 He for fuelling the fusion reactor burning D- 3 He has been carried out. This study is divided into the following sections: analysis of solar wind parameters and estimation of potential quantity 3 He in the lunar regolith, the cost evaluation of mining He of lunar soil; the energy cost calculation of He extraction by vacuum heating degassing during lunar day, the cost calculation of cryogenic isotopic separation 3 He/ 4 He during the lunar night, the energy cost for earth/moon transportation of liquid 3 He, the energy payback calculation of fusion power burning 3 He based lunar source, and finally the comparison of the energy multiplication with that for 235 U production of nuclear fuel and for coal mining. The comparisons of cost of electricity between D- 3 He and D-T fuel cycle for different reactor types have been discussed

Ammonia Synthesis at Low Pressure.

Science.gov (United States)

Cussler, Edward; McCormick, Alon; Reese, Michael; Malmali, Mahdi

2017-08-23

Ammonia can be synthesized at low pressure by the use of an ammonia selective absorbent. The process can be driven with wind energy, available locally in areas requiring ammonia for synthetic fertilizer. Such wind energy is often called "stranded," because it is only available far from population centers where it can be directly used. In the proposed low pressure process, nitrogen is made from air using pressure swing absorption, and hydrogen is produced by electrolysis of water. While these gases can react at approximately 400 °C in the presence of a promoted conventional catalyst, the conversion is often limited by the reverse reaction, which makes this reaction only feasible at high pressures. This limitation can be removed by absorption on an ammine-like calcium or magnesium chloride. Such alkaline metal halides can effectively remove ammonia, thus suppressing the equilibrium constraints of the reaction. In the proposed absorption-enhanced ammonia synthesis process, the rate of reaction may then be controlled not by the chemical kinetics nor the absorption rates, but by the rate of the recycle of unreacted gases. The results compare favorably with ammonia made from a conventional small scale Haber-Bosch process.

Renewable energy in pakistan part 1: wind energy

International Nuclear Information System (INIS)

Maher, M.J.

2005-01-01

Energy plays a very enhanced role in mans struggle with the capricious act of nature than merely sustaining life. And according to Cipolla the more successfully man can use his own energy-output to control and put to use other forms of energy, t he more he acquires control over his environment and achieves goals other than those strictly related to animal existence . He then adds what is certainly obvious -but does not suffer from repetition -that fundamental to the utilization of nonmuscular energy is the problem of transforming it into the needed form at a selected time; place and at convenient cost. In the present article an attempt is being made to encompass different sources of renewable energy, with special reference to wind energy and its role in sustaining the development process Wind-data generated through measurements by the meteorological department have their limitations. Therefore, for accurate analysis, a dedicated wind-monitoring system will have to be used for properly exploiting this form of energy. In practice, a mean annual wind speed (at 20 m above ground) of 12 mph is considered as the minimum requirement for economic power-generation. With this criterion, only a bare minimum area of the country, comprising the coastal areas of Sind and Baluchistan, desert parts of Cholistan and Thar regions are considered to possess adequate resource. Bulk of this wind potential is derived from the wind energy, which blows from southwest system during the major parts of the year. Daily and monthly variations of wind speed at potential locations need to be determined in order to bring out the highly seasonal behaviour of the wind resources. The significance of wind-power density is another important parameter to assess the wind potential. The capacity-factor, which is the ratio of the actual power-output to the rated output of typical wind machine to be used, has to be worked out using the frequency-distribution of hourly wind-speeds at the potential site. The

Transient analysis of a grid connected wind driven induction generator using a real-time simulation platform

Energy Technology Data Exchange (ETDEWEB)

Ouhrouche, Mohand [Department of Applied Sciences, University of Quebec at Chicoutimi, Quebec, G7H2B1 (Canada)

2009-03-15

Due to its simple construction, ruggedness and low cost, the induction generator driven by a wind turbine and feeding power to the grid appears to be an attractive solution to the problem of growing energy demand in the context of environmental issues. This paper investigates the integration of such a system into the main utility using RT-Lab trademark (Trademark of Opal-RT Technologies) software package running on a simple off-the-shelf PC. This real-time simulation platform is now adopted by many high-tech industries as a real-time laboratory package for rapid control prototyping and for Hardware-in-the-Loop applications. Real-time digital simulation results obtained during contingencies, such as islanding and unbalanced faults are presented and analysed. (author)

On the rejection of internal and external disturbances in a wind energy conversion system with direct-driven PMSG.

Science.gov (United States)

Li, Shengquan; Zhang, Kezhao; Li, Juan; Liu, Chao

2016-03-01

This paper deals with the critical issue in a wind energy conversion system (WECS) based on a direct-driven permanent magnet synchronous generator (PMSG): the rejection of lumped disturbance, including the system uncertainties in the internal dynamics and unknown external forces. To simultaneously track the motor speed in real time and capture the maximum power, a maximum power point tracking strategy is proposed based on active disturbance rejection control (ADRC) theory. In real application, system inertia, drive torque and some other parameters change in a wide range with the variations of disturbances and wind speeds, which substantially degrade the performance of WECS. The ADRC design must incorporate the available model information into an extended state observer (ESO) to compensate the lumped disturbance efficiently. Based on this principle, a model-compensation ADRC is proposed in this paper. Simulation study is conducted to evaluate the performance of the proposed control strategy. It is shown that the effect of lumped disturbance is compensated in a more effective way compared with the traditional ADRC approach. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Forest trees filter chronic wind-signals to acclimate to high winds.

Science.gov (United States)

Bonnesoeur, Vivien; Constant, Thiéry; Moulia, Bruno; Fournier, Meriem

2016-05-01

Controlled experiments have shown that trees acclimate thigmomorphogenetically to wind-loads by sensing their deformation (strain). However, the strain regime in nature is exposed to a full spectrum of winds. We hypothesized that trees avoid overreacting by responding only to winds which bring information on local climate and/or wind exposure. Additionally, competition for light dependent on tree social status also likely affects thigmomorphogenesis. We monitored and manipulated quantitatively the strain regimes of 15 pairs of beech (Fagus sylvatica) trees of contrasting social status in an acclimated stand, and quantified the effects of these regimes on the radial growth over a vegetative season. Trees exposed to artificial bending, the intensity of which corresponds to the strongest wind-induced strains, enhanced their secondary growth by at least 80%. Surprisingly, this reaction was even greater - relatively - for suppressed trees than for dominant ones. Acclimated trees did not sense the different types of wind events in the same way. Daily wind speed peaks due to thermal winds were filtered out. Thigmomorphogenesis was therefore driven by intense storms. Thigmomorphogenesis is also likely to be involved in determining social status. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Adaptive Controller for Drive System PMSG in Wind Turbine

Directory of Open Access Journals (Sweden)

Gnanambal

2014-07-01

Full Text Available This paper proposes adaptive Maximum Power Point Tracking (MPPT controller for Permanent Magnet Synchronous Generator (PMSG wind turbine and direct power control for grid side inverter for transformer less integration of wind energy. PMSG wind turbine with two back to back voltage source converters are considered more efficient, used to make real and reactive power control. The optimal control strategy has introduced for integrated control of PMSG Maximum Power Extraction, DC link voltage control and grid voltage support controls. Simulation model using MATLAB Simulink has developed to investigate the performance of proposed control techniques for PMSG wind turbine steady and variable wind conditions. This paper shows that the direct driven grid connected PMSG system has excellent performances and confirms the feasibility of the proposed techniques. While the wind turbine market continues to be dominated by conventional gear-driven wind turbine systems, the direct drive is attracting attention. PM machines are more attractive and superior with higher efficiency and energy yield, higher reliability, and power-to-weight ratio compared with electricity-excited machines.

Stratified magnetically driven accretion-disk winds and their relations to jets

International Nuclear Information System (INIS)

Fukumura, Keigo; Tombesi, Francesco; Kazanas, Demosthenes; Shrader, Chris; Behar, Ehud; Contopoulos, Ioannis

2014-01-01

We explore the poloidal structure of two-dimensional magnetohydrodynamic (MHD) winds in relation to their potential association with the X-ray warm absorbers (WAs) and the highly ionized ultra-fast outflows (UFOs) in active galactic nuclei (AGNs), in a single unifying approach. We present the density n(r, θ), ionization parameter ξ(r, θ), and velocity structure v(r, θ) of such ionized winds for typical values of their fluid-to-magnetic flux ratio, F, and specific angular momentum, H, for which wind solutions become super-Alfvénic. We explore the geometrical shape of winds for different values of these parameters and delineate the values that produce the widest and narrowest opening angles of these winds, quantities necessary in the determination of the statistics of AGN obscuration. We find that winds with smaller H show a poloidal geometry of narrower opening angles with their Alfvén surface at lower inclination angles and therefore they produce the highest line of sight (LoS) velocities for observers at higher latitudes with the respect to the disk plane. We further note a physical and spatial correlation between the X-ray WAs and UFOs that form along the same LoS to the observer but at different radii, r, and distinct values of n, ξ, and v consistent with the latest spectroscopic data of radio-quiet Seyfert galaxies. We also show that, at least in the case of 3C 111, the winds' pressure is sufficient to contain the relativistic plasma responsible for its radio emission. Stratified MHD disk winds could therefore serve as a unique means to understand and unify the diverse AGN outflows.

The effect of broad-band Alfven-cyclotron waves spectra on the preferential heating and differential acceleration of He{sup ++} ions in the solar wind

Energy Technology Data Exchange (ETDEWEB)

Maneva, Y. G. [Department of Physics, Catholic University of America, Washington DC, 20064 (United States) and Heliophysics Science Devision, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Ofman, L. [Department of Physics, Catholic University of America, Washington, DC 20064 (United States) and Heliophysics Science Devision, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Vinas, A. F. [Heliophysics Science Devision, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2013-06-13

In anticipation of results from inner heliospheric missions such as the Solar Orbiter and the Solar Probe we present the results from 1.5D hybrid simulations to study the role of magnetic fluctuations for the heating and differential acceleration of He{sup ++} ions in the solar wind. We consider the effects of nonlinear Alfven-cyclotron waves at different frequency regimes. Monochromatic nonlinear Alfven-alpha-cyclotron waves are known to preferentially heat and accelerate He{sup ++} ions in collisionless low beta plasma. In this study we demonstrate that these effects are preserved when higherfrequency monochromatic and broad-band spectra of Alfven-proton-cyclotron waves are considered. Comparison between several nonlinear monochromatic waves shows that the ion temperatures, anisotropies and relative drift are quantitatively affected by the shift in frequency. Including a broad-band wave-spectrum results in a significant reduction of both the parallel and the perpendicular temperature components for the He{sup ++} ions, whereas the proton heating is barely influenced, with the parallel proton temperature only slightly enhanced. The differential streaming is strongly affected by the available wave power in the resonant daughter ion-acoustic waves. Therefore for the same initial wave energy, the relative drift is significantly reduced in the case of initial wave-spectra in comparison to the simulations with monochromatic waves.

Evaluation of the Influence of Wind-Driven Rain on Moisture in Cellular Concrete Wall Boards

Directory of Open Access Journals (Sweden)

Alsabry A.

2017-08-01

Full Text Available The non-stationary moisture level of a cellular concrete wall board in a heated utility building located in the northern part of the town of Brest (Belarus, depending on the climatic influence, was assessed in this work. The results were obtained both in a calculation experiment and a physical test. It was observed that the main reason for the high moisture levels in cellular concrete is wind-driven rain intensifying the process of free capillary moisture transfer. A comparative analysis of the results of the physical test and the calculation experiment showed that the THSS software elaborated by the authors was able to predict the actual moisture levels of the shielding structure under study accurately enough when precise data concerning the thermal and physical characteristics of the materials as well as the occurring climatic influences were submitted.

Evaluation of the Influence of Wind-Driven Rain on Moisture in Cellular Concrete Wall Boards

Science.gov (United States)

Alsabry, A.; Nikitsin, V. I.; Kofanov, V. A.; Backiel-Brzozowska, B.

2017-08-01

The non-stationary moisture level of a cellular concrete wall board in a heated utility building located in the northern part of the town of Brest (Belarus), depending on the climatic influence, was assessed in this work. The results were obtained both in a calculation experiment and a physical test. It was observed that the main reason for the high moisture levels in cellular concrete is wind-driven rain intensifying the process of free capillary moisture transfer. A comparative analysis of the results of the physical test and the calculation experiment showed that the THSS software elaborated by the authors was able to predict the actual moisture levels of the shielding structure under study accurately enough when precise data concerning the thermal and physical characteristics of the materials as well as the occurring climatic influences were submitted.

DO HYDROGEN-DEFICIENT CARBON STARS HAVE WINDS?

International Nuclear Information System (INIS)

Geballe, T. R.; Rao, N. Kameswara; Clayton, Geoffrey C.

2009-01-01

We present high resolution spectra of the five known hydrogen-deficient carbon (HdC) stars in the vicinity of the 10830 A line of neutral helium. In R Coronae Borealis (RCB) stars the He I line is known to be strong and broad, often with a P Cygni profile, and must be formed in the powerful winds of those stars. RCB stars have similar chemical abundances as HdC stars and also share greatly enhanced 18 O abundances with them, indicating a common origin for these two classes of stars, which has been suggested to be white dwarf mergers. A narrow He I absorption line may be present in the hotter HdC stars, but no line is seen in the cooler stars, and no evidence for a wind is found in any of them. The presence of wind lines in the RCB stars is strongly correlated with dust formation episodes so the absence of wind lines in the HdC stars, which do not make dust, is as expected.

Innovation paths in wind power

DEFF Research Database (Denmark)

Lema, Rasmus; Nordensvärd, Johan; Urban, Frauke

Denmark and Germany both make substantial investments in low carbon innovation, not least in the wind power sector. These investments in wind energy are driven by the twin objectives of reducing carbon emissions and building up international competitive advantage. Support for wind power dates back....... The ‘Danish Design’ remains the global standard. The direct drive design, while uncommon in Denmark, dominates the German installation base. Direct drive technology has thus emerged as a distinctly German design and sub-trajectory within the overall technological innovation path. When it comes to organising...... global interconnectedness of wind technology markets and the role of emerging new players, such as China and India....

Impact of Neutrino Flavor Oscillations on the Neutrino-driven Wind Nucleosynthesis of an Electron-capture Supernova

Science.gov (United States)

Pllumbi, Else; Tamborra, Irene; Wanajo, Shinya; Janka, Hans-Thomas; Hüdepohl, Lorenz

2015-08-01

Neutrino oscillations, especially to light sterile states, can affect nucleosynthesis yields because of their possible feedback effect on the electron fraction (Ye). For the first time, we perform nucleosynthesis calculations for neutrino-driven wind trajectories from the neutrino-cooling phase of an 8.8 {M}⊙ electron-capture supernova (SN), whose hydrodynamic evolution was computed in spherical symmetry with sophisticated neutrino transport and whose Ye evolution was post-processed by including neutrino oscillations between both active and active-sterile flavors. We also take into account the α-effect as well as weak magnetism and recoil corrections in the neutrino absorption and emission processes. We observe effects on the Ye evolution that depend in a subtle way on the relative radial positions of the sterile Mikheyev-Smirnov-Wolfenstein resonances, on collective flavor transformations, and on the formation of α particles. For the adopted SN progenitor, we find that neutrino oscillations, also to a sterile state with eV mass, do not significantly affect the element formation and in particular cannot make the post-explosion wind outflow neutron-rich enough to activate a strong r-process. Our conclusions become even more robust when, in order to mimic equation-of-state-dependent corrections due to nucleon potential effects in the dense-medium neutrino opacities, six cases with reduced Ye in the wind are considered. In these cases, despite the conversion of active neutrinos to sterile neutrinos, Ye increases or is not significantly lowered compared to the values obtained without oscillations and active flavor transformations. This is a consequence of a complicated interplay between sterile-neutrino production, neutrino-neutrino interactions, and α-effect.

Using data-driven approach for wind power prediction: A comparative study

International Nuclear Information System (INIS)

Taslimi Renani, Ehsan; Elias, Mohamad Fathi Mohamad; Rahim, Nasrudin Abd.

2016-01-01

Highlights: • Double exponential smoothing is the most accurate model in wind speed prediction. • A two-stage feature selection method is proposed to select most important inputs. • Direct prediction illustrates better accuracy than indirect prediction. • Adaptive neuro fuzzy inference system outperforms data mining algorithms. • Random forest performs the worst compared to other data mining algorithm. - Abstract: Although wind energy is intermittent and stochastic in nature, it is increasingly important in the power generation due to its sustainability and pollution-free. Increased utilization of wind energy sources calls for more robust and efficient prediction models to mitigate uncertainties associated with wind power. This research compares two different approaches in wind power forecasting which are indirect and direct prediction methods. In indirect method, several times series are applied to forecast the wind speed, whereas the logistic function with five parameters is then used to forecast the wind power. In this study, backtracking search algorithm with novel crossover and mutation operators is employed to find the best parameters of five-parameter logistic function. A new feature selection technique, combining the mutual information and neural network is proposed in this paper to extract the most informative features with a maximum relevancy and minimum redundancy. From the comparative study, the results demonstrate that, in the direct prediction approach where the historical weather data are used to predict the wind power generation directly, adaptive neuro fuzzy inference system outperforms five data mining algorithms namely, random forest, M5Rules, k-nearest neighbor, support vector machine and multilayer perceptron. Moreover, it is also found that the mean absolute percentage error of the direct prediction method using adaptive neuro fuzzy inference system is 1.47% which is approximately less than half of the error obtained with the

Multi-scale wind erosion monitoring and assessment for US rangelands

Science.gov (United States)

Wind erosion is a major resource concern for rangeland managers. Although wind erosion is a naturally occurring process in many drylands, land use activities, and land management in particular, can accelerate wind-driven soil loss – impacting ecosystem dynamics and agricultural production, air quali...

Substorm Occurrence and Intensity Associated With Three Types of Solar Wind Structure

Science.gov (United States)

Liou, Kan; Sotirelis, Thomas; Richardson, Ian

2018-01-01

This paper presents the results of a study of the characteristics of substorms that occurred during three distinct types of solar wind: coronal mass ejection (CME) associated, high-speed streams (HSS), and slow solar wind (SSW). A total number of 53,468 geomagnetic substorm onsets from 1983 to 2009 is used and sorted by the three solar wind types. It is found that the probability density function (PDF) of the intersubstorm time can be fitted by the combination of a dominant power law with an exponential cutoff component and a minor lognormal component, implying that substorms are associated with two distinctly different dynamical processes corresponding, perhaps, to the "externally driven" and "internally driven" processes, respectively. We compare substorm frequency and intensity associated with the three types of solar wind. It is found that the intersubstorm time is the longest during SSW and shortest during CME intervals. The averaged intersubstorm time for the internally driven substorms is 3.13, 3.15, and 7.96 h for CME, HSS, and SSW, respectively. The substorm intensity PDFs, as represented by the peak value of |SML| (the generalization of AL), can be fitted by two lognormal distribution functions. The averaged substorm intensity for either component is largest for CME (292 and 674 nT) and smallest for SSW (265 and 434 nT). We argue that the externally driven substorms are more intense than those driven internally. We conclude that the dynamical process of substorms is controlled mainly by the direct solar wind-magnetosphere coupling, whereas the internally driven process only plays a very modest minor role.

Smooth Particle Hydrodynamics-based Wind Representation

Energy Technology Data Exchange (ETDEWEB)

Prescott, Steven [Idaho National Lab. (INL), Idaho Falls, ID (United States); Smith, Curtis [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hess, Stephen [Idaho National Lab. (INL), Idaho Falls, ID (United States); Lin, Linyu [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sampath, Ram [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-12-01

As a result of the 2011 accident at the Fukushima Dai-ichi NPP and other operational NPP experience, there is an identified need to better characterize and evaluate the potential impacts of externally generated hazards on NPP safety. Due to the ubiquitous occurrence of high winds around the world and the possible extreme magnitude of the hazard that has been observed, the assessment of the impact of the high-winds hazard has been identified as an important activity by both NPP owner-operators and regulatory authorities. However, recent experience obtained from the conduct of high-winds risk assessments indicates that such activities have been both labor-intensive and expensive to perform. Additionally, the existing suite of methods and tools to conduct such assessments (which were developed decades ago) do not make use of modern computational architectures (e.g., parallel processing, object-oriented programming techniques, or simple user interfaces) or methods (e.g., efficient and robust numerical-solution schemes). As a result, the current suite of methods and tools will rapidly become obsolete. Physics-based 3D simulation methods can provide information to assist in the RISMC PRA methodology. This research is intended to determine what benefits SPH methods could bring to high-winds simulations for the purposes of assessing their potential impact on NPP safety. The initial investigation has determined that SPH can simulate key areas of high-wind events with reasonable accuracy, compared to other methods. Some problems, such as simulation voids, need to be addressed, but possible solutions have been identified and will be tested with continued work. This work also demonstrated that SPH simulations can provide a means for simulating debris movement; however, further investigations into the capability to determine the impact of high winds and the impacts of wind-driven debris that lead to SSC failures need to be done. SPH simulations alone would be limited in size

Flow-driven simulation on variation diameter of counter rotating wind turbines rotor

Directory of Open Access Journals (Sweden)

Littik Y. Fredrika

2018-01-01

Full Text Available Wind turbines model in this paper developed from horizontal axis wind turbine propeller with single rotor (HAWT. This research aims to investigating the influence of front rotor diameter variation (D1 with rear rotor (D2 to the angular velocity optimal (ω and tip speed ratio (TSR on counter rotating wind turbines (CRWT. The method used transient 3D simulation with computational fluid dynamics (CFD to perform the aerodynamics characteristic of rotor wind turbines. The counter rotating wind turbines (CRWT is designed with front rotor diameter of 0.23 m and rear rotor diameter of 0.40 m. In this research, the wind velocity is 4.2 m/s and variation ratio between front rotor and rear rotor (D1/D2 are 0.65; 0.80; 1.20; 1.40; and 1.60 with axial distance (Z/D2 0.20 m. The result of this research indicated that the variation diameter on front rotor influence the aerodynamics performance of counter rotating wind turbines.

The social acceptability of wind turbines: some resident are ready to pay to keep their wind turbines

International Nuclear Information System (INIS)

2009-04-01

The author proposes a synthesis of a survey performed on four wind farms located in different French regions. It appears that only 5 % of residents feel that wind turbines are disturbing, that a dismantling would be detrimental to the resident well-being, that site expansions are well perceived in terms of social well-being, that residents do not really prefer small wind farms. The author outlines that the obtained results cannot be applied to other sites

Solar wind power electric plant on Vis (Croatia)

International Nuclear Information System (INIS)

1998-01-01

A project of a solar photovoltaic electric power plant presented by the Republic of Croatia at the meeting of the E.P.I.A. Mission for photovoltaic technology of the Mediterranean countries, aroused a great interest of the representatives of the invited countries. However, the interest within Croatia in the project has disappeared although E.P.I.A. offered a financing of two thirds of costs. There are attempts to construct 1800 kw wind-driven generators at the same location not taking into consideration a possibility of building a hybrid solar-wind-power electric plant. The chance that the solar part is completely of domestic origin is not accepted but the preference is given to the building of imported wind-driven generators. (orig.)

Spatial dependence in wind and optimal wind power allocation: A copula-based analysis

International Nuclear Information System (INIS)

Grothe, Oliver; Schnieders, Julius

2011-01-01

The investment decision on the placement of wind turbines is, neglecting legal formalities, mainly driven by the aim to maximize the expected annual energy production of single turbines. The result is a concentration of wind farms at locations with high average wind speed. While this strategy may be optimal for single investors maximizing their own return on investment, the resulting overall allocation of wind turbines may be unfavorable for energy suppliers and the economy because of large fluctuations in the overall wind power output. This paper investigates to what extent optimal allocation of wind farms in Germany can reduce these fluctuations. We analyze stochastic dependencies of wind speed for a large data set of German on- and offshore weather stations and find that these dependencies turn out to be highly nonlinear but constant over time. Using copula theory we determine the value at risk of energy production for given allocation sets of wind farms and derive optimal allocation plans. We find that the optimized allocation of wind farms may substantially stabilize the overall wind energy supply on daily as well as hourly frequency. - Highlights: → Spatial modeling of wind forces in Germany. → A novel way to assess nonlinear dependencies of wind forces by copulas. → Wind turbine allocation by maximizing lower quantiles of energy production. → Optimal results show major increase in reliable part of wind energy.

Panorama 2013 - Offshore wind power

International Nuclear Information System (INIS)

Vinot, Simon

2012-10-01

While onshore wind power is already a well-developed global industry, offshore wind power is still in the consolidation and globalization phase. The most mature of marine renewable energies is beginning to venture off the European coast and even to other continents, driven by public policies and the ever increasing number of players joining this promising market, which should evolve into deeper waters thanks to floating structures. (author)

Self-starting aerodynamics analysis of vertical axis wind turbine

OpenAIRE

Jianyang Zhu; Hailin Huang; Hao Shen

2015-01-01

Vertical axis wind turbine is a special type of wind-force electric generator which is capable of working in the complicated wind environment. The self-starting aerodynamics is one of the most important considerations for this kind of turbine. This article aims at providing a systematic synthesis on the self-starting aerodynamic characteristics of vertical axis wind turbine based on the numerical analysis approach. First, the physical model of vertical axis wind turbine and its parameter defi...

Nucleosynthesis in neutrino-driven winds: Influence of the nuclear physics input

International Nuclear Information System (INIS)

Arcones, Almudena; Martinez-Pinedo, Gabriel

2010-01-01

We have performed hydrodynamical simulations of the long-time evolution of proto-neutron stars to study the nucleosynthesis using the resulting wind trajectories. Although the conditions found in the present wind models are not favourable for the production of heavy elements, a small enhancement of the entropy results in the production of r-process elements with A ∼ 195. This allows us to explore the sensitivity of their production to the hydrodynamical evolution (wind termination shock) and nuclear physics input used.

Impact of wind on the spatial distribution of rain over micro-scale topography : numerical modelling and experimental verification

NARCIS (Netherlands)

Blocken, B.J.E.; Poesen, J.; Carmeliet, J.

2006-01-01

The wind-driven-rain effect refers to the redistribution of rainfall over micro-scale topography due to the existence of local perturbed wind-flow patterns. Rainfall measurements reported in the literature point to the fact that the wind-driven-rain distribution can show large variations over

Wind hazard assessment for Point Lepreau Generating Station

International Nuclear Information System (INIS)

Mullin, D.; Moland, M.; Sciaudone, J.C.; Twisdale, L.A.; Vickery, P.J.; Mizzen, D.R.

2015-01-01

In response to the CNSC Fukushima Action Plan, NB Power has embarked on a wind hazard assessment for the Point Lepreau Generating Station site that incorporates the latest up to date wind information and modeling. The objective was to provide characterization of the wind hazard from all potential sources and estimate wind-driven missile fragilities and wind pressure fragilities for various structures, systems and components that would provide input to a possible high wind Probabilistic Safety Assessment. The paper will discuss the overall methodology used to assess hazards related to tornadoes, hurricanes and straight-line winds, and site walk-down and hazard/fragility results. (author)

AGN feedback through UFO and galaxy-wide winds in the early Universe

Science.gov (United States)

Feruglio, C.; Piconcelli, E.; Bischetti, M.; Zappacosta, L.; Fiore, F.

2017-10-01

AGN feedback through massive molecular winds is today routinely observed in local AGN host galaxies, but not as such in the early universe. I will present the first evidence for a massive, AGN-driven molecular wind in the z 4 QSO APM08279, which also hosts the most well studied and persistent nuclear semi-raltivistic wind (UFO). This observation directly probes the expansion mechanism of a nuclear wind into the ISM on galaxy wide scales, that so far was constrained by a couple of other objects only (Feruglio et al. 2015, Tombesi et al. 2015). This result also opens the path toward the exploration of molecular AGN-driven winds at early epochs, close after the end of the Epoch of Reionisation (EoR).

Attractive well of He--He from 3He--4He differential elastic scattering measurements

International Nuclear Information System (INIS)

Burgmans, A.L.J.; Farrar, J.M.; Lee, Y.T.

1976-01-01

The elastic differential cross section for 3 He-- 4 He was measured at a relative collision energy of 0.799x10 -14 erg, approximately five times the well depth. The data are fitted to a multiparameter potential form with epsilon/k=10.57 degreeK and r/subm/=2.97 A. Comparisons with recent experimental and theoretical helium potentials are made. No evidence for a significant isotope effect in the 3 He-- 4 He and 4 He-- 4 He interactomic potentials is found in this work

Use of Three-Level Power Converters in Wind-Driven Permanent-Magnet Synchronous Generators with Unbalanced Loads

Directory of Open Access Journals (Sweden)

Ming-Hung Chen

2015-06-01

Full Text Available This paper describes the design and implementation of three-level power converters for wind-driven permanent-magnet synchronous generators with unbalanced loads. To increase voltage stress and reduce current harmonics in the electrical power generated by a wind generator, a three-phase, three-level rectifier is used. Because a synchronous rotating frame is used on the AC-input side, the use of a neutral-point-clamped controller is proposed to increase the power factor to unity and reduce current harmonics. Furthermore, a novel six-leg inverter is proposed for transferring energy from the DC voltage to a three-phase, four-wire AC source with a constant voltage and a constant frequency. The power converters also contain output transformers and filters for power buffering and filtering, respectively. All three output phase voltages are fed back to control the inverter output during load variations. A digital signal processor is used as the core control device for implementing a 1.5 kV, 75 kW drive system. Experimental data show that the power factor is successfully increased to unity and the total current harmonic distortion is 3.2% on the AC-input side. The entire system can attain an efficiency of 91%, and the voltage error between the upper and lower capacitors is approximately zero. Experimental results that confirm the high performance of the proposed system are presented.

On the solar wind - magnetosphere - ionosphere coupling: AMPTE/CCE particle data and the AE indices

International Nuclear Information System (INIS)

Daglis, I.A.; Wilken, B.; Sarris, E.T.; Kremser, G.

1992-01-01

We present a statistical study of the substorm particle energization in terms of the energy density of the major magnetospheric ions (H + , O + , He ++ , He + ). The correlation between energy density during substorm expansion phase and the auroral indices (AE, AU, Al) is examined and interpreted. Most distinct result is that the ionospheric origin O + energy density correlate remarkable well with the AE index, while the solar wind origin He ++ energy density does not correlate at all with AE. Mixed origin H + and He + ions exhibit an intermediate behavior. Furthermore, the O + energy density correlates very well with the pre-onset AU index level, while there is no correlation with the pre-onset AL index. The results are interpreted as a result of solar wind. The results are interpreted as a result of solar wind - magnetosphere - ionosphere coupling through the internal magnetospheric dynamo: the ionosphere responds to the increased activity of the internal dynamo (which is due to the high solar wind input) and influences substorm dynamics by feeding the near-Earth magnetotail with energetic ionospheric ions during late growth phase and expansion phase

Wind gust measurements using pulsed Doppler wind-lidar: comparison of direct and indirect techniques

DEFF Research Database (Denmark)

The measurements of wind gusts, defined as short duration wind speed maxima, have traditionally been limited by the height that can be reached by weather masts. Doppler lidars can potentially provide information from levels above this and thereby fill this gap in our knowledge. To measure the 3D...... is 3.9 s) which can provide high resolution turbulent measurements, both in the vertical direction, and potentially in the horizontal direction. In this study we explore different strategies of wind lidar measurements to measure the wind speed maxima. We use a novel stochastic turbulence reconstruction...... model, driven by the Doppler lidar measurements, which uses a non-linear particle filter to estimate the small-scale turbulent fluctuations. The first results show that the reconstruction method can reproduce the wind speed maxima measured by the sonic anemometer if a low-pass filter with a cut...

Dimerization of 3He in 3He-4He mixture films

International Nuclear Information System (INIS)

Bashkin, E.

1994-01-01

3 He atoms dissolved in superfluid 4 He may form dimers ( 3 He) 2 in two-dimensional geometries. Dimer formation is studied in films of dilute 3 He- 4 He mixture. After designing a schematic 3 He- 3 He interaction potential, the dimer binding energy is calculated for various substrates. It is shown that 3 He impurity states localized near the substrate give rise to the highest magnitudes of the binding energy. (author). 32 refs., 6 figs.,; 1 tab

Operation and Control of a Direct-Driven PMSG-Based Wind Turbine System with an Auxiliary Parallel Grid-Side Converter

Directory of Open Access Journals (Sweden)

Jiawei Chu

2013-07-01

Full Text Available In this paper, based on the similarity, in structure and principle, between a grid-connected converter for a direct-driven permanent magnet synchronous generator (D-PMSG and an active power filter (APF, a new D-PMSG-based wind turbine (WT system configuration that includes not only an auxiliary converter in parallel with the grid-side converter, but also a coordinated control strategy, is proposed to enhance the low voltage ride through (LVRT capability and improve power quality. During normal operation, the main grid-side converter maintains the DC-link voltage constant, whereas the auxiliary grid-side converter functions as an APF with harmonic suppression and reactive power compensation to improve the power quality. During grid faults, a hierarchical coordinated control scheme for the generator-side converter, main grid-side converter and auxiliary grid-side converter, depending on the grid voltage sags, is presented to enhance the LVRT capability of the direct-driven PMSG WT. The feasibility and the effectiveness of the proposed system’s topology and hierarchical coordinated control strategy were verified using MATLAB/Simulink simulations.

MMS Observation of Shock-Reflected He++ at Earth's Quasi-Perpendicular Bow Shock

Science.gov (United States)

Broll, Jeffrey Michael; Fuselier, S. A.; Trattner, K. J.; Schwartz, S. J.; Burch, J. L.; Giles, B. L.; Anderson, B. J.

2018-01-01

Specular reflection of protons at Earth's supercritical quasi-perpendicular bow shock has long been known to lead to the thermalization of solar wind particles by velocity-space dispersion. The same process has been proposed for He++ but could not be confirmed previously due to insufficient time resolution for velocity distribution measurements. We present observations and simulations of a bow shock crossing by the Magnetospheric Multiscale (MMS) mission on 20 November 2015 indicating that a very similar reflection process for He++ is possible, and further that the part of the incoming distribution with the highest probability of reflecting is the same for H+ and He++. However, the reflection process for He++ is accomplished by deeper penetration into the downstream magnetic fields.

Financing wind projects

International Nuclear Information System (INIS)

Manson, J.

2006-01-01

This presentation reviewed some of the partnership opportunities available from GE Energy. GE Energy's ecomagination commitment has promised to double research investment, make customers true partners and reduce greenhouse gases (GHGs). GE Energy's renewable energy team provides a broad range of financial products, and has recently funded 30 wind farms and 2 large solar projects. The company has a diverse portfolio of technology providers and wind regimes, and is increasing their investment in technology. GE Energy recognizes that the wind industry is growing rapidly and has received increased regulatory support that is backed by strong policy and public support. It is expected that Canada will have 3006 wind projects either planned or under construction by 2007. According to GE Energy, successful wind financing is dependent on the location of the site and its wind resources, as well as on the wind developer's power sales agreement. The success of a wind project is also determined by clear financing goals. Site-specific data is needed to determine the quality of wind resource, and off-site data can also be used to provide validation. Proximity to load centres will help to minimize capital costs. Power sales agreements should be based on the project's realistic net capacity factor as well as on the cost of the turbines. The economics of many wind farms is driven by the size of the turbines used. Public consultations are also needed to ensure the success of wind power projects. It was concluded that a good partner will have staying power in the wind power industry, and will understand the time-lines and needs that are peculiar to wind energy developers. refs., tabs., figs

The construction of a Pomeranchuk cell driven by a 4He-circulating dilution refrigerator and some related experiments

International Nuclear Information System (INIS)

Brandt, B. van den.

1981-01-01

This thesis deals with some investigations at very low temperatures in which a 4 He-circulating 3 He- 4 He dilution refrigerator and a Pomeranchuk cooling device are used. The main theme is the design and construction of a special device, a Pomeranchuk cell that is precooled and pressurized with a 4 He-circulating 3 He- 4 He dilution refrigerator, that can be used to obtain a lowest temperature of the order of 1.1 mK. Furthermore, some details of the working of such a dilution refrigerator and some properties of 3 He- 4 He mixtures at high pressures were investigated. (Auth.)

Wind driven nutrient and subsurface chlorophyll-a enhancement in the Bay of La Paz, Gulf of California

Science.gov (United States)

Coria-Monter, Erik; Monreal-Gómez, María Adela; Salas de León, David Alberto; Durán-Campos, Elizabeth; Merino-Ibarra, Martín

2017-09-01

Nutrient and chlorophyll-a distributions in the Bay of La Paz, Gulf of California, Mexico were analyzed during the late spring of 2004 to assess their relations to hydrography and circulation patterns. The results show the presence of both Gulf of California Water and Subtropical Subsurface Water. Water circulation was dominated by wind stress driven cyclonic circulation along f / H contours (f is planetary vorticity and H is depth), and upwelling resulting from the divergence shows a vertical velocity of ∼0.4 m d-1. Nutrient concentrations were higher in the center of the cyclonic pattern, where a rise in the nutricline contributed nutrients to the euphotic layer as a result of Ekman pumping. The vertical section showed the presence of a chlorophyll-a maximum at the thermocline shoaling to a depth of only 12 m. Along the surface, two peaks of chlorophyll-a were observed, one at Boca Grande and another off San Juan de la Costa, associated with upwelling and mixing derived from current interactions with abrupt topographies. The chlorophyll-a maximum increased from 0.8 mg m-3 in the external part of the cyclonic pattern to 2.0 mg m-3 in its center. The vertically integrated chlorophyll-a concentrations followed a similar pattern, rising from 10 to 20 mg m-2 and reaching their highest values in the center of the cyclonic circulation pattern. A schematic model was developed to describe processes that occur in late spring: the wind stress driven cyclonic structure promotes upward nutrient flux, which in turn drives an enhancement of chlorophyll-a. Upwelling was found to be the main mechanism of fertilization responsible for the enhancement of productivity levels by means of nutrient transport into the euphotic zone during spring. Other chlorophyll enhancement areas point to the occurrence of additional fertilization processes that may derive from interactions between cyclonic circulation patterns and the topography off of San Juan de la Costa, where phosphate mining

Technology library modeling for information-driven circuit synthesis

NARCIS (Netherlands)

Jozwiak, L.; Bieganski, S.J.

2008-01-01

Due to weaknesses in circuit synthesis methods used in todaypsilas CAD tools, the opportunities created by modern microelectronic technology cannot effectively be exploited. This paper considers major issues and requirements of circuit synthesis for the nano CMOS technologies, and discusses our new

Highly reliable wind-rolling triboelectric nanogenerator operating in a wide wind speed range

Science.gov (United States)

Yong, Hyungseok; Chung, Jihoon; Choi, Dukhyun; Jung, Daewoong; Cho, Minhaeng; Lee, Sangmin

2016-01-01

Triboelectric nanogenerators are aspiring energy harvesting methods that generate electricity from the triboelectric effect and electrostatic induction. This study demonstrates the harvesting of wind energy by a wind-rolling triboelectric nanogenerator (WR-TENG). The WR-TENG generates electricity from wind as a lightweight dielectric sphere rotates along the vortex whistle substrate. Increasing the kinetic energy of a dielectric converted from the wind energy is a key factor in fabricating an efficient WR-TENG. Computation fluid dynamics (CFD) analysis is introduced to estimate the precise movements of wind flow and to create a vortex flow by adjusting the parameters of the vortex whistle shape to optimize the design parameters to increase the kinetic energy conversion rate. WR-TENG can be utilized as both a self-powered wind velocity sensor and a wind energy harvester. A single unit of WR-TENG produces open-circuit voltage of 11.2 V and closed-circuit current of 1.86 μA. Additionally, findings reveal that the electrical power is enhanced through multiple electrode patterns in a single device and by increasing the number of dielectric spheres inside WR-TENG. The wind-rolling TENG is a novel approach for a sustainable wind-driven TENG that is sensitive and reliable to wind flows to harvest wasted wind energy in the near future. PMID:27653976

Magnetically driven jets and winds

Science.gov (United States)

Lovelace, R. V. E.; Berk, H. L.; Contopoulos, J.

1991-01-01

Four equations for the origin and propagation of nonrelativistic jets and winds are derived from the basic conservation laws of ideal MHD. The axial current density is negative in the vicinity of the axis and positive at larger radii; there is no net current because this is energetically favored. The magnetic field is essential for the jet solutions in that the zz-component of the magnetic stress acts, in opposition to gravity, to drive matter through the slow magnetosonic critical point. For a representative self-consistent disk/jet solution relevant to a protostellar system, the reaction of the accreted mass expelled in the jets is 0.1, the ratio of the power carried by the jets to the disk luminosity is 0.66, and the ratio of the boundary layer to disk luminosities is less than about 0.13. The star's rotation rate decreases with time even for rotation rates much less than the breakup rate.

Infrared spectra of 4HeH+, 4HeD+, 3HeH+, and 3HeD+

International Nuclear Information System (INIS)

Crofton, M.W.; Altman, R.S.; Haese, N.N.; Oka, T.

1989-01-01

Isotopic species of the HeH + molecular ion provide an excellent testing ground for studying isotopic dependence of vibration--rotation constants because of the small masses of He and H isotopes. We have observed infrared spectra of the hot band v=2 left-arrow 1 of HeH + and fundamental bands of isotopic species HeD + , 3 HeH + , and 3 HeD + , and obtained the Dunham coefficients Y kl , and the isotopically independent parameters U kl , Δ He kl , and Δ H kl

Wind power for the world international reviews and developments

CERN Document Server

Maegaard, Preben; Palz, Wolfgang

2013-01-01

Introduction, Preben MaegaardAccelerated Global Expansion of the Renewable Energy Sector: the Example of Wind Energy, Preben MaegaardWind Power Development in the European Union, Wolfgang PalzWind Energy to the rescue of mankind from the menace of the Fossil Fuel burning hazards, Anil KaneBlack or Green Wind Power, Frede HvelplundWind Energy Development in China, He DexinNon-grid-connected Wind Power and Offshore "Three Georges of Wind Power" in China, Gu WeidongWind Power in Japan: Past, Present, and Future Prospect, Izumi UshiyamaWind Power Development in India, Jami HossainChallenges and Opportunities for Energy Paradigm Shifting in Ontario, Canada, Jose EtcheverryWind Power in Cuba's Energy Revolution, Conrado Moreno FigueredoWind Power in Argentina, Erico SpinadelThe Emergence of Wind Power in Brazil, Everaldo FeitosaWind Energy in Chile, Arturo KunstmannWind Power in Austria, Wolfgang HeinThe History of Wind Power in France, Jean-Louis BalHistory, State-of-the Art and Future of Wind Energy in France, Ma...

Simulating Wind Driven Waves in the Strait of Hormuz using MIKE21 (Simulasi Gelombang Angin di Selat Hormuz Menggunakan MIKE21

Directory of Open Access Journals (Sweden)

Faeghe Eslami Mehdiabadi

2015-03-01

Full Text Available Daerah pesisir di bumi adalah salah satu zona paling dinamis yang dipengaruhi oleh berbagai parameter seperti gelombang, arus, dan badai. Untuk mengelola serta mengkontrol zona tersebut adalah penting untuk mempelajari hidrodinamika daerah. Penelitian ini menggunakan MIKE 21/3 coupled Model FM untuk melihat gelombang (wind driven waves di sekitar Pulau Larak di Selat Hormuz. Untuk mensimulasikan pola gelombang di wilayah tersebut digunakan irregular triangular grid.  Pola arus di sekitar pulau dipelajari untuk jangka waktu satu tahun. Ditemukan bahwa gelombang yang ditimbulkan karena arus di sekitar pantai utara pulau relatif lemah. Terlihat pula bahwa gelombang yang ada di daerah tersebut terutama ke arah timur laut. Tinggi gelombang rata-rata di surfzone adalah sekitar 0,5 m., Dengan kecepatan arus sekitar 0,2 m.s-1. Mengingat angin menang dan arah gelombang, disimpulkan bahwa pantai utara Pulau Larak tempat yang cocok untuk konstruksi pelabuhan dan kegiatan memancing. Kata kunci: gelombang, arus, MIKE, Pulau Larak Coastal areas on earth are among the most dynamic zones which affected by different parameters such as waves, currents, and storms. To manage and control such a zone it is essential to study the hydrodynamic of the area. MIKE 21/3 Coupled Model FM was used to investigate the wind driven waves around Larak Island located in the Strait of Hormuz. To simulate the pattern of the wave in the area irregular triangular grid was applied. The pattern of current around the Island was studied for a one year period of simulation. It was found that the current induced wave break around the Northern coast of the Island is relatively weak. It was also observed that the prevailed wave in the area is mainly toward the Northeast. The averaged wave height in the surfzone is about 0.5 m., with the current velocity of about 0.2 m.s-1. Considering the prevailed wind and wave direction, it was concluded that the northern coasts of the Larak Island are

Stellar winds in binary X-ray systems

Science.gov (United States)

Macgregor, K. B.; Vitello, P. A. J.

1982-01-01

It is thought that accretion from a strong stellar wind by a compact object may be responsible for the X-ray emission from binary systems containing a massive early-type primary. To investigate the effect of X-ray heating and ionization on the mass transfer process in systems of this type, an idealized model is constructed for the flow of a radiation-driven wind in the presence of an X-ray source of specified luminosity, L sub x. It is noted that for low values of L sub x, X-ray photoionization gives rise to additional ions having spectral lines with wavelengths situated near the peak of the primary continuum flux distribution. As a consequence, the radiation force acting on the gas increases in relation to its value in the absence of X-rays, and the wind is accelerated to higher velocities. As L sub x is increased, the degree of ionization of the wind increases, and the magnitude of the radiation force is diminished in comparison with the case in which L sub x = 0. This reduction leads at first to a decrease in the wind velocity and ultimately (for L sub x sufficiently large) to the termination of radiatively driven mass loss.

Coordinated control strategy for hybrid wind farms with DFIG-based and PMSG-based wind farms during network unbalance

DEFF Research Database (Denmark)

Yao, Jun; Liu, Ruikuo; Zhou, Te

2017-01-01

This paper investigates the coordinated control strategy for a hybrid wind farm with doubly fed induction generator (DFIG)-based and direct-driven permanent-magnet synchronous generator (PMSG)-based wind farms during network unbalance. The negative-sequence current output capabilities of DFIG...... to the controllable operating regions, a targets selection scheme for each control unit is proposed to improve the stability of the hybrid wind farms containing both DFIG-based and PMSG-based wind farms during network unbalance, especially to avoid DFIG-based wind farm tripping from connected power grid under severe...... grid voltage unbalance conditions. Finally, the proposed coordinated control strategy is validated by the simulation results of a 30-MW-DFIG-based wind farm and a 30-MW-PMSG-based wind farm under different operation conditions and experimental results on a laboratory-scale experimental rig under severe...

Bound states of 3He in 3He-4He mixture films

International Nuclear Information System (INIS)

Bashkin, E.; Pavloff, N.; Treiner, J.

1995-01-01

3 He atoms dissolved in superfluid 4 He may form dimers ( 3 He) 2 in two-dimensional (2D) geometries. We study dimer formation in films of dilute 3 He- 4 He mixture. After designing a schematic 3 He- 4 He interaction potential we calculate the dimer binding energy for various substrates. It is shown that 3 He impurity states localized near the substrate give rise to the largest magnitudes of the binding energies

Optimum path planning of mobile robot in unknown static and dynamic environments using Fuzzy-Wind Driven Optimization algorithm

Directory of Open Access Journals (Sweden)

Anish Pandey

2017-02-01

Full Text Available This article introduces a singleton type-1 fuzzy logic system (T1-SFLS controller and Fuzzy-WDO hybrid for the autonomous mobile robot navigation and collision avoidance in an unknown static and dynamic environment. The WDO (Wind Driven Optimization algorithm is used to optimize and tune the input/output membership function parameters of the fuzzy controller. The WDO algorithm is working based on the atmospheric motion of infinitesimal small air parcels navigates over an N-dimensional search domain. The performance of this proposed technique has compared through many computer simulations and real-time experiments by using Khepera-III mobile robot. As compared to the T1-SFLS controller the Fuzzy-WDO algorithm is found good agreement for mobile robot navigation.

Wind energy basics a guide to home- and community-scale wind energy systems

CERN Document Server

Gipe, Paul

2009-01-01

The availability of clean, renewable power is without question going to be the defining challenge and goal of the 21st century, and wind will lead the way. Internationally acclaimed wind energy expert Paul Gipe is as soberly critical of past energy mistakes as he is convincingly optimistic about the future. The overwhelming challenge of transforming our world from one of fossil carbon to one of clean power seems daunting at best-and paralyzingly impractical at worst. "Wind Energy Basics" offers a solution. Wind power can realistically not only replace the lion's share of oil-, coal-, and natural gasndash; fired electrical plants in the U.S., but also can add enough extra power capacity to allow for most of the cars in the nation to run on electricity. Gipe explains why such a startlingly straightforward solution is eminently doable and can be accomplished much sooner than previously thought-and will have the capacity to resuscitate small and regional economies. "Wind Energy Basics" offers a how-to for home-ba...

Simulation of Lightning Overvoltage Distribution on Stator Windings of Wind Turbine Generators

Institute of Scientific and Technical Information of China (English)

LIU Rong; LIU Xue-zhong; WANG Ying; LI Dan-dan

2011-01-01

This paper analyzes lightning surge on the stator windings of wind turbine generators. The path of lightning in the wind turbines was analyzed. An equivalent circuit model for megawatt direct-driven wind turbine system was developed, in which high-frequency distributed parameters of the blade conducts, tower, power cables and stator windings of generator were calculated based on finite element method, and the models of converter, grounding, loads, surge protection devices and power grid were established. The voltage distribution along stator windings, when struck by lightning with 10/350 ~ts wave form and different amplitude current between 50 kA and 200 kA, was simulated u- sing electro-magnetic transient analysis method. The simulated results show that the highest coil-to-core voltage peak appears on the last coil or near the neutral of stator windings, and the voltage distribution along the windings is non- uniform initially. The voltage drops of each coil fall from first to last coil, and the highest voltage drop appears on the first coil. The insulation damage may occur on the windings under lightning overvoltage. The surge arresters can re- strain the lightning surge in effect and protect the insulation. The coil-to-core voltage in the end of windings is nearly 19.5 kV under the 200 kA lightning current without surge arresters on the terminal of generator, but is only 2.7 kV with arresters.

Fatigue-Damage Estimation and Control for Wind Turbines

DEFF Research Database (Denmark)

Barradas Berglind, Jose de Jesus

How can fatigue-damage for control of wind turbines be represented? Fatigue-damage is indeed a crucial factor in structures such as wind turbines that are exposed to turbulent and rapidly changing wind flow conditions. This is relevant both in their design stage and during the control......, the inclusion of fatigue-damage within feedback control loops is of special interest. Four strategies in total are proposed in this work: three for the wind turbine level and one for the wind farm level. On one hand, the three strategies in the turbine level are based on hysteresis operators and strive......-damage estimation in wind turbine components, to the mixed objective operation of wind energy conversion systems, and to the synthesis of control strategies that include hysteresis operators....

Project "Convective Wind Gusts" (ConWinG)

Science.gov (United States)

Mohr, Susanna; Richter, Alexandra; Kunz, Michael; Ruck, Bodo

2017-04-01

Convectively-driven strong winds usually associated with thunderstorms frequently cause substantial damage to buildings and other structures in many parts of the world. Decisive for the high damage potential are the short-term wind speed maxima with duration of a few seconds, termed as gusts. Several studies have shown that convectively-driven gusts can reach even higher wind speeds compared to turbulent gusts associated with synoptic-scale weather systems. Due to the small-scale and non-stationary nature of convective wind gusts, there is a considerable lack of knowledge regarding their characteristics and statistics. Furthermore, their interaction with urban structures and their influence on buildings is not yet fully understood. For these two reasons, convective wind events are not included in the present wind load standards of buildings and structures, which so far have been based solely on the characteristics of synoptically-driven wind gusts in the near-surface boundary layer (e. g., DIN EN 1991-1-4:2010-12; ASCE7). However, convective and turbulent gusts differ considerably, e.g. concerning vertical wind-speed profiles, gust factors (i.e., maximum to mean wind speed), or exceedance probability curves. In an effort to remedy this situation, the overarching objective of the DFG-project "Convective Wind Gusts" (ConWinG) is to investigate the characteristics and statistics of convective gusts as well as their interaction with urban structures. Based on a set of 110 climate stations of the German Weather Service (DWD) between 1992 and 2014, we analyzed the temporal and spatial distribution, intensity, and occurrence probability of convective gusts. Similar to thunderstorm activity, the frequency of convective gusts decreases gradually from South to North Germany. A relation between gust intensity/probability to orography or climate conditions cannot be identified. Rather, high wind speeds, e.g., above 30 m/s, can be expected everywhere in Germany with almost

Winds of Massive Magnetic Stars: Interacting Fields and Flow

Science.gov (United States)

Daley-Yates, S.; Stevens, I. R.

2018-01-01

We present results of 3D numerical simulations of magnetically confined, radiatively driven stellar winds of massive stars, conducted using the astrophysical MHD code Pluto, with a focus on understanding the rotational variability of radio and sub-mm emission. Radiative driving is implemented according to the Castor, Abbott and Klein theory of radiatively driven winds. Many magnetic massive stars posses a magnetic axis which is inclined with respect to the rotational axis. This misalignment leads to a complex wind structure as magnetic confinement, centrifugal acceleration and radiative driving act to channel the circumstellar plasma into a warped disk whose observable properties should be apparent in multiple wavelengths. This structure is analysed to calculate free-free thermal radio emission and determine the characteristic intensity maps and radio light curves.

The North Sea offshore wind park network and the role of SMEs in project benefit management across actors

DEFF Research Database (Denmark)

Brink, Tove

routes for SMEs to enhance Project Benefit Management. It is especially difficult to move to the partner-driven approach. Here the intermediary roles of either demand-driven or supplier-driven SME approach are needed before the partner-driven approach is likely to be achieved. A contribution is hereby......The research in this paper reveals how Small and Medium-sized Enterprises (SMEs) can contribute to project benefit management for offshore wind energy to be competitive. The research is based on a longitudinal qualitative study starting in 2011 with 10 SME wind park suppliers. The research...... continued with a focus group interview and individual interviews with 20 larger enterprises and SMEs within operation and maintenance in wind parks with follow up in a seminar May 2015. The findings reveal opportunities and challenges for SMEs to contribute to project benefit management in wind parks. Four...

Suprathermal He2+ in the Earth's foreshock region

International Nuclear Information System (INIS)

Fuselier, S.A.; Thomsen, M.F.; Ipavich, F.M.; Schmidt, W.K.H.

1995-01-01

ISEE 1 and 2 H + and He 2+ observations upstream from the Earth's bow shock are used to investigate the origin of energetic (or diffuse) ion distributions. Diffuse ion distributions have energies from a few keV/e to > 100 keV/e and have near solar wind concentrations (i.e., an average of about 4% He 2+ ). These distributions may evolve from suprathermal ion distributions that have energies between 1 and a few keV/e. Upstream intervals were selected from the ISEE data to determine which suprathermal distributions have He 2+ concentrations similar to those of diffuse ion distributions. The type of distribution and the location in the foreshock were similar in all events studied. Two intervals that represent the results from this study are discussed in detail. The results suggest that diffuse ion distributions evolve from suprathermal distributions in the region upstream from the quasi-parallel bow shock. For He 2+ , the suprathermal distribution is a nongyrotropic partial ring beam and has characteristics consistent with specular reflection off the quasi-parallel bow shock. The suprathermal proton distributions associated with these He 2+ distributions are nongyrotropic partial ring beams or nearly gyrotropic ring beams also approximately consistent with specular reflection. The location in the quasi-parallel foreshock and the similarity of the suprathermal He 2+ and H + distributions suggest that these are the seed population for diffuse distributions in the foreshock region. 30 refs., 5 figs., 1 tab

Wind generation systems for remote communities: market assessment and guidelines for wind turbines selection

International Nuclear Information System (INIS)

Brothers, C.

1993-06-01

Wind technology and its market potential in remote communities of the Canadian North were discussed. These communities, unserviced by the main utility electricity grid, generate their own electricity using high quality, expensive diesel fuel to power diesel driven generators. The logistics of delivering fuel to these remote communities is an expensive operation. Wind resource in many of these communities is substantial and wind energy is seen as a prime candidate for supplying electricity to many potential sites in the Arctic and also areas in Quebec and Newfoundland. However, the severe service (i.e., cold climate, remote locations with limited facilities) requires special considerations to ensure that equipment installed performs reliably. This report described some demonstration projects in northern Canada over the last ten years, where an understanding of the special needs of wind turbines in remote areas has been developed. A guide which assessed the suitability of wind turbines for Arctic applications was included to assist organisations in preparing requirements to be used in acquiring wind turbines for use in cold regions. Refs., tabs., figs

Determining the impact of wind on system costs via the temporal patterns of load and wind generation

International Nuclear Information System (INIS)

Davis, Clay D.; Gotham, Douglas J.; Preckel, Paul V.; Liu, Andrew L.

2013-01-01

Ambitious targets have been set for expanding electricity generation from renewable sources, including wind. Expanding wind power impacts needs for other electricity generating resources. As states plan for increasing levels of wind generation in their portfolio of generation resources it is important to consider how this intermittent resource impacts the need for other generation resources. A case study for Indiana estimates the value of wind capacity and demonstrates how to optimize its level and the levels of other generation resources. Changes are driven by temporal patterns of wind power output and load. System wide impacts are calculated for energy, capacity, and costs under multiple wind expansion scenarios which highlight the geographic characteristics of a systems portfolio of wind generation. The impacts of carbon prices, as proposed in the Bingaman Bill, are considered. Finally, calculations showing the effect increasing levels of wind generation will have on end use Indiana retail rates are included. - Highlights: • We estimate the value of wind capacity. • We determine wind generation's impact on the optimal mix of non-wind generation. • Optimal levels of wind and non-wind generation are determined. • We consider the impact of a carbon price on the optimal mix of resources. • The impact of additional wind capacity on Indiana residential rates is calculated

A proposed national wind power R and D program. [offshore wind power system for electric energy supplies

Science.gov (United States)

Heronemus, W.

1973-01-01

An offshore wind power system is described that consists of wind driven electrical dc generators mounted on floating towers in offshore waters. The output from the generators supplies underwater electrolyzer stations in which water is converted into hydrogen and oxygen. The hydrogen is piped to shore for conversion to electricity in fuel cell stations. It is estimated that this system can produce 159 x 10 to the ninth power kilowatt-hours per year. It is concluded that solar energy - and that includes wind energy - is the only way out of the US energy dilemma in the not too distant future.

Strongly-sheared wind-forced currents in the nearshore regions of the central Southern California Bight

Science.gov (United States)

Noble, Marlene A.; Rosenberger, Kurt; Robertson, George L.

2015-01-01

Contrary to many previous reports, winds do drive currents along the shelf in the central portion of the Southern California Bight (SCB). Winds off Huntington Beach CA are the dominant forcing for currents over the nearshore region of the shelf (water depths less than 20 m). Winds control about 50–70% of the energy in nearshore alongshelf surface currents. The wind-driven current amplitudes are also anomalously high. For a relatively weak 1 dyne/cm2 wind stress, the alongshelf surface current amplitudes in this region can reach 80 cm/s or more. Mid-depth current amplitudes for the same wind stress are around 30–40 cm/s. These wind-driven surface current amplitudes are much larger than previously measured over other nearshore shelf regions, perhaps because this program is one of the few that measured currents within a meter of the surface. The near-bed cross-shelf currents over the nearshore region of the Huntington Beach shelf have an Ekman response to winds in that they upwell (downwell) for down (up) coast winds. This response disappears further offshore. Hence, there is upwelling in the SCB, but it does not occur across the entire shelf. Subthermocline water in the nearshore region that may contain nutrients and plankton move onshore when winds are southeastward, but subthermocline water over the shelf break is not transported to the beach. The currents over the outer shelf are not predominately controlled by winds, consistent with previous reports. Instead, they are mainly driven by cross-shelf pressure gradients that are independent of local wind stress.

Wind power barometer

International Nuclear Information System (INIS)

Anon.

2012-01-01

Despite the economic crisis affecting most of the globe's major economies, wind energy continues to gain supporters around the world. Global wind power capacity increased by 40.5 GW between 2010 and 2011 compared to a 39 GW rise between 2009 and 2010, after deduction of decommissioned capacity. By the end of 2011 global installed wind turbine capacity should stand at around 238.5 GW, and much of the world's growth is being driven by capacity build-up in the emerging markets (China, India...). In 2011 Asia was the world's biggest market (52%) ahead of Europe (24.5%) and North-America (19.7%). Europe has still the largest wind power capacity in the world with 40.6% of total in 2011. 2011 was another tough year for Vestas company while Gamesa company has managed to maintain positive profit growth by gaining market shares abroad. Siemens keeps its lead in the offshore market. The Chinese market is now suffering form excess capacity and Chinese companies fell prey to domestic competition

Wind Power: How Much, How Soon, and At What Cost?

Energy Technology Data Exchange (ETDEWEB)

Wiser, Ryan H; Hand, Maureen

2010-01-01

The global wind power market has been growing at a phenomenal pace, driven by favorable policies towards renewable energy and the improving economics of wind projects. On a going forward basis, utility-scale wind power offers the potential for significant reductions in the carbon footprint of the electricity sector. Specifically, the global wind resource is vast and, though accessing this potential is not costless or lacking in barriers, wind power can be developed at scale in the near to medium term at what promises to be an acceptable cost.

Wind-driven SEIG supplying DC microgrid through a single-stage power converter

Directory of Open Access Journals (Sweden)

Vellapatchi Nayanar

2016-09-01

Full Text Available Nowadays, there is an increased emphasis on utilizing the renewable energy sources and selection of suitable power converters for supplying dc microgrid. Among the various renewable energy sources, wind energy stands first in terms of installed capacity. So, an attempt is made in this paper for supplying dc microgrid utilizing wind energy. A self-excited induction generator has been used in the proposed wind energy conversion system (WECS. A single-stage power converter, namely, semi-converter is connected between the SEIG and dc grid terminals for closed-loop control of the proposed system. A perturb and observe (P&O based maximum power point tracking (MPPT algorithm has been developed and implemented using a dsPIC30F4011 digital controller. In this MPPT algorithm, the firing angle of the converter is adjusted by continuously monitoring the dc grid current for a given wind velocity. For analyzing the proposed system, a MATLAB/Simulink model has been developed by selecting the various components starting from wind-turbine model to the power converter supplying dc microgrid. Successful working of the proposed WECS has also been shown through experimental results obtained on a prototype model developed in the laboratory.

Structure of the 8He exotic nucleus by the direct reactions 8He(p, p')8He, 8He(p,d)7He and 8He(p,t)6He

International Nuclear Information System (INIS)

Skaza, Flore

2004-01-01

The elastic and inelastic scattering of an 8 He beam on a proton target have been measured at GANIL. The first 8 He beam produced by the SPIRAL facility at an energy of 15.6 A.MeV impinged on a proton target. The experimental setup was composed by the eight telescopes MUST array dedicated to the measure of the light charged particles, by a scintillator plastic wall for the detection of heavy projectile, and by two beam tracking detectors CATS for the measure event by event of the incident position and angle of the beam on the target. This setup allowed also to measure the one and two neutron transfer reactions 8 He(p,d) 7 He and 8 He(p,t) 6 He. The excitation energy spectrum for 6,7,8 He and the angular distributions associated to each reaction have been measured. The observed excited states are in agreement with the data of the literature. We indicate the presence of a first excited state for 7 He at 0.9 MeV and we give for the first time the position of a second excited state in 8 He at 5.4 MeV; the presence of such state was just suggested in a previous experiment. CCBA calculations allowed to extract a spectroscopic factor of 4.4 ± 1.4 for the pick-up of one neutron from 8 He to 7 He. This value is in agreement with a closed p3/2 sub-shell for 8 He. To analyse the angular distributions for elastic and inelastic scattering, it was necessary to take into account in the formalism used to describe the reactions, via coupled channels reactions calculations, the couplings to the one neutron transfer reaction. (author) [fr

Producing Turbulent Wind Tunnel Inflows Relevant to Wind Turbines using an Active Grid

Science.gov (United States)

Rumple, Christopher; Welch, Matthew; Naughton, Jonathan

2017-11-01

The rise of industries like wind energy have provided motivation for generating realistic turbulent inflows in wind tunnels. Facilities with the ability to produce such inflows can study the interaction between the inflow turbulence and the flow of interest such as a wind turbine wake. An active grid - a system of actively driven elements - has gained increasing acceptance in turbulence research over the last 20 years. The ability to tailor the inflow turbulence quantities (e.g. turbulence intensities, integral length scale, and turbulence spectrum) is a driving reason for the growing use of active grids. An active grid with 40 independent axes located within the forward contraction of a low speed wind tunnel is used to explore the range of turbulent inflows possible using hot-wire anemometry to characterize the turbulence. Motor control algorithms (i.e. user waveform inputs) used to produce various turbulent inflows will be presented. Wind data available from meteorological towers are used to develop relevant inflows for wind turbines to demonstrate the usefulness of the active grid. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award # DE-SC0012671.

Factors associated with bat mortality at wind energy facilities in the United States

Science.gov (United States)

Hundreds of thousands of bats are killed annually by colliding with wind turbines in the U.S., yet little is known about factors causing variation in mortality across wind energy facilities. We conducted a quantitative synthesis of bat collision mortality with wind turbines by re...

Agglomeration of a comprehensive model for the wind-driven sand transport at the Belgian Coast

Science.gov (United States)

Strypsteen, Glenn; Rauwoens, Pieter

2016-04-01

Although a lot of research has been done in the area of Aeolian transport, it is only during the last years that attention has been drawn to Aeolian transport in coastal areas. In these areas, the physical processes are more complex, due to a large number of transport limiting parameters. In this PhD-project, which is now in its early stage, a model will be developed which relates the wind-driven sand transport at the Belgian coast with physical parameters such as the wind speed, humidity and grain size of the sand, and the slope of beach and dune surface. For the first time, the interaction between beach and dune dynamics is studied at the Belgian coast. The Belgian coastline is only 67km long, but densely populated and therefore subject to coastal protection and safety. The coast mostly consists of sandy beaches and dikes. Although, still 33km of dunes exist, whose dynamics are far less understood. The overall research approach consists of three pathways: (i) field measurements, (ii) physical model tests, and (iii) numerical simulations. Firstly and most importantly, several field campaigns will provide accurate data of meteo-marine conditions, morphology, and sand transport events on a wide beach at the Belgian Coastline. The experimental set-up consists of a monitoring station, which will provide time series of vegetation cover, shoreline position, fetch distances, surficial moisture content, wind speed and direction and transport processes. The horizontal and vertical variability of the event scale Aeolian sand transport is analyzed with 8 MWAC sand traps. Two saltiphones register the intensity and variations of grain impacts over time. Two meteo-masts, each with four anemometers and one wind vane, provide quantitative measurements of the wind flow at different locations on the beach. Surficial moisture is measured with a moisture sensor. The topography measurements are typically done with laser techniques. To start, two sites are selected for measurement

Linear wind generator

International Nuclear Information System (INIS)

Kozarov, A.; Petrov, O.; Antonov, J.; Sotirova, S.; Petrova, B.

2006-01-01

The purpose of the linear wind-power generator described in this article is to decrease the following disadvantages of the common wind-powered turbine: 1) large bending and twisting moments to the blades and the shaft, especially when strong winds and turbulence exist; 2) significant values of the natural oscillation period of the construction result in the possibility of occurrence of destroying resonance oscillations; 3) high velocity of the peripheral parts of the rotor creating a danger for birds; 4) difficulties, connected with the installation and the operation on the mountain ridges and passages where the wind energy potential is the largest. The working surfaces of the generator in questions driven by the wind are not connected with a joint shaft but each moves along a railway track with few oscillations. So the sizes of each component are small and their number can be rather large. The mechanical trajectory is not a circle but a closed outline in a vertical plain, which consists of two rectilinear sectors, one above the other, connected in their ends by semi-circumferences. The mechanical energy of each component turns into electrical on the principle of the linear electrical generator. A regulation is provided when the direction of the wind is perpendicular to the route. A possibility of effectiveness is shown through aiming of additional quantities of air to the movable components by static barriers

Flaking and blistering on He and Ne bombardments

International Nuclear Information System (INIS)

Kamada, K.; Naramoto, H.

1979-01-01

Large scale exfoliation formed by 300 keV He + bombardment of niobium without any preceding blistering is investigated, in comparison with the blistering due to 450 and 850 keV Ne + bombardments. In-situ observations of the erosion processes were performed in a scanning electron microscope connected to the Van de Graaff. Critical doses of 7.2 x 10 17 He + /cm 2 , 2.4 x 10 17 Ne + /cm 2 and 4.0 x 10 17 Ne + /cm 2 were obtained for the 300 keV He flaking, 450 keV Ne blistering and 850 keV Ne blistering, respectively. The He flaking was presumed to be due to brittle fashion peeling-off of the surface layer by the bending moment driven by the internal gas pressure. The blistering, on the other hand, was presumed to be the result of the ductile fashion spreading of the lenticular bubble in the sub-surface layer. The necessary pressure for the peeling-off of the cover was calculated, and was speculated to be able to work as the driving force for the flaking from its unexpectedly low values. Fractographies under the exfoliations were discussed for both flaking and blistering. (author)

A VERSATILE FAMILY OF GALACTIC WIND MODELS

Energy Technology Data Exchange (ETDEWEB)

Bustard, Chad; Zweibel, Ellen G. [Physics Department, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706 (United States); D’Onghia, Elena, E-mail: bustard@wisc.edu [Department of Astronomy, University of Wisconsin-Madison, 2535 Sterling Hall, 475 N. Charter Street, Madison, WI 53706 (United States)

2016-03-01

We present a versatile family of model galactic outflows including non-uniform mass and energy source distributions, a gravitational potential from an extended mass source, and radiative losses. The model easily produces steady-state wind solutions for a range of mass-loading factors, energy-loading factors, galaxy mass, and galaxy radius. We find that, with radiative losses included, highly mass-loaded winds must be driven at high central temperatures, whereas low mass-loaded winds can be driven at low temperatures just above the peak of the cooling curve, meaning radiative losses can drastically affect the wind solution even for low mass-loading factors. By including radiative losses, we are able to show that subsonic flows can be ignored as a possible mechanism for expelling mass and energy from a galaxy compared to the more efficient transonic solutions. Specifically, the transonic solutions with low mass loading and high energy loading are the most efficient. Our model also produces low-temperature, high-velocity winds that could explain the prevalence of low-temperature material in observed outflows. Finally, we show that our model, unlike the well-known Chevalier and Clegg model, can reproduce the observed linear relationship between wind X-ray luminosity and star formation rate (SFR) over a large range of SFR from 1–1000 M{sub ⊙} yr{sup −1} assuming the wind mass-loading factor is higher for low-mass, and hence, low-SFR galaxies. We also constrain the allowed mass-loading factors that can fit the observed X-ray luminosity versus SFR trend, further suggesting an inverse relationship between mass loading and SFR as explored in advanced numerical simulations.

Forecast of icing events at a wind farm in Sweden

DEFF Research Database (Denmark)

Davis, Neil; Hahmann, Andrea N.; Clausen, Niels-Erik

2014-01-01

This paper introduces a method for identifying icing events using a physical icing model, driven by atmospheric data from the Weather Research and Forecasting (WRF) model, and applies it to a wind park in Sweden. Observed wind park icing events were identified by deviation from an idealized power...

Ring Current He Ion Control by Bounce Resonant ULF Waves

Science.gov (United States)

Kim, Hyomin; Gerrard, Andrew J.; Lanzerotti, Louis J.; Soto-Chavez, Rualdo; Cohen, Ross J.; Manweiler, Jerry W.

2017-12-01

Ring current energy He ion (˜65 keV to ˜520 keV) differential flux data from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft show considerable variability during quiet solar wind and geomagnetic time periods. Such variability is apparent from orbit to orbit (˜9 h) of the spacecraft and is observed to be ˜50-100% of the nominal flux. Using data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument, also aboard the Van Allen Probes spacecraft, we identify that a dominant source of this variability is from ULF waveforms with periods of tens of seconds. These periods correspond to the bounce resonant timescales of the ring current He ions being measured by RBSPICE. A statistical survey using the particle and field data for one full spacecraft precession period (approximately 2 years) shows that the wave and He ion flux variations are generally anticorrelated, suggesting the bounce resonant pitch angle scattering process as a major component in the scattering of He ions.

Parametric decay of current-driven Langmuir waves in plateau plasmas: Relevance to solar wind and foreshock events

Science.gov (United States)

Sauer, Konrad; Malaspina, David M.; Pulupa, Marc; Salem, Chadi S.

2017-07-01

Langmuir amplitude modulation in association with type III radio bursts is a well-known phenomenon since the beginning of space observations. It is commonly attributed to the superposition of beam-excited Langmuir waves and their backscattered counterparts as a result of parametric decay. The dilemma, however, is the discrepancy between fast beam relaxation and long-lasting Langmuir wave activity. Instead of starting with an unstable electron beam, our focus in this paper is on the nonlinear response of Langmuir oscillations that are driven after beam stabilization by the still persisting current of the (stable) two-electron plasma. The velocity distribution function of the second population forms a plateau (index h) with a point at which ∂fh/∂v ˜0 associated with weak damping over a more or less extended wave number range k. As shown by particle-in-cell simulations, this so-called plateau plasma drives primarily Langmuir oscillations at the plasma frequency (ωe) with k = 0 over long times without remarkable change of the distribution function. These Langmuir oscillations act as a pump wave for parametric decay by which an electron-acoustic wave slightly below ωe and a counterstreaming ion-acoustic wave are generated. Both high-frequency waves have nearly the same amplitude, which is given by the product of plateau density and velocity. Beating of these two wave types leads to pronounced Langmuir amplitude modulation, in reasonable agreement with solar wind and terrestrial foreshock observations made by the Wind spacecraft.

Application of the three-body model to the reactions 6Li(3He,t 3He)3He and 6Li(3He,3He3He)3H

International Nuclear Information System (INIS)

Haftel, M.I.; Allas, R.G.; Beach, L.A.; Bondelid, R.O.; Petersen, E.L.; Slaus, I.; Lambert, J.M.; Treado, P.A.

1977-01-01

Experimental and theoretical cross sections are presented for the 6 Li( 3 He, 3 He 3 He) 3 H and 6 Li( 3 He,t 3 He) 3 He reactions for the symmetric angle pairs 20 0 -20 0 , 28.3 0 -28.3 0 , and 35 0 -35 0 . The theoretical cross sections are calculated in a three-body model where the trions (i.e., mass-3 nuclei) are treated as elementary particles with 6 Li being a 3 He- 3 H bound state. The trion-trion interaction is represented by S wave separable potentials with the breakup cross sections calculated with the tree-body Haftel-Ebenhoeh code. the Coulomb interaction is taken into account by fitting the separable potential parameters to the trion-trion scattering data and is included approximately in the breakup code. The experimental cross sections are compared with both the plane-wave impulse approximation and the three-body model predictions. The plane-wave impulse approximation predicts both the shapes and magnitudes poorly (10 to 20 times experiment). Without Coulomb corrections the three-body model gives good agreement with experiment for the shapes of the spectra with the magnitudes generally being about 40% of experiment for 6 Li( 3 He, 3 He 3 He) 3 H and about 80% for 6 Li( 3 He,t 3 He) 3 He. The Coulomb corrections improve the magnitudes predicted by the three-body model but not the shapes. It is observed that for these reactions S wave separable potentials describe the breakup data much better than they do the two-body trion-trion scattering data. This result should encourage further three-body treatment of these and similar reactions

Power control for direct-driven permanent magnet wind generator system with battery storage.

Science.gov (United States)

Guang, Chu Xiao; Ying, Kong

2014-01-01

The objective of this paper is to construct a wind generator system (WGS) loss model that addresses the loss of the wind turbine and the generator. It aims to optimize the maximum effective output power and turbine speed. Given that the wind generator system has inertia and is nonlinear, the dynamic model of the wind generator system takes the advantage of the duty of the Buck converter and employs feedback linearization to design the optimized turbine speed tracking controller and the load power controller. According to that, this paper proposes a dual-mode dynamic coordination strategy based on the auxiliary load to reduce the influence of mode conversion on the lifetime of the battery. Optimized speed and power rapid tracking as well as the reduction of redundant power during mode conversion have gone through the test based on a 5 kW wind generator system test platform. The generator output power as the capture target has also been proved to be efficient.

Power Control for Direct-Driven Permanent Magnet Wind Generator System with Battery Storage

Directory of Open Access Journals (Sweden)

Chu Xiao Guang

2014-01-01

Full Text Available The objective of this paper is to construct a wind generator system (WGS loss model that addresses the loss of the wind turbine and the generator. It aims to optimize the maximum effective output power and turbine speed. Given that the wind generator system has inertia and is nonlinear, the dynamic model of the wind generator system takes the advantage of the duty of the Buck converter and employs feedback linearization to design the optimized turbine speed tracking controller and the load power controller. According to that, this paper proposes a dual-mode dynamic coordination strategy based on the auxiliary load to reduce the influence of mode conversion on the lifetime of the battery. Optimized speed and power rapid tracking as well as the reduction of redundant power during mode conversion have gone through the test based on a 5 kW wind generator system test platform. The generator output power as the capture target has also been proved to be efficient.

WIND-DRIVEN ACCRETION IN PROTOPLANETARY DISKS. I. SUPPRESSION OF THE MAGNETOROTATIONAL INSTABILITY AND LAUNCHING OF THE MAGNETOCENTRIFUGAL WIND

International Nuclear Information System (INIS)

Bai Xuening; Stone, James M.

2013-01-01

We perform local, vertically stratified shearing-box MHD simulations of protoplanetary disks (PPDs) at a fiducial radius of 1 AU that take into account the effects of both Ohmic resistivity and ambipolar diffusion (AD). The magnetic diffusion coefficients are evaluated self-consistently from a look-up table based on equilibrium chemistry. We first show that the inclusion of AD dramatically changes the conventional picture of layered accretion. Without net vertical magnetic field, the system evolves into a toroidal field dominated configuration with extremely weak turbulence in the far-UV ionization layer that is far too inefficient to drive rapid accretion. In the presence of a weak net vertical field (plasma β ∼ 10 5 at midplane), we find that the magnetorotational instability (MRI) is completely suppressed, resulting in a fully laminar flow throughout the vertical extent of the disk. A strong magnetocentrifugal wind is launched that efficiently carries away disk angular momentum and easily accounts for the observed accretion rate in PPDs. Moreover, under a physical disk wind geometry, all the accretion flow proceeds through a strong current layer with a thickness of ∼0.3H that is offset from disk midplane with radial velocity of up to 0.4 times the sound speed. Both Ohmic resistivity and AD are essential for the suppression of the MRI and wind launching. The efficiency of wind transport increases with increasing net vertical magnetic flux and the penetration depth of the FUV ionization. Our laminar wind solution has important implications on planet formation and global evolution of PPDs.

SOLAR SOURCES OF 3He-RICH SOLAR ENERGETIC PARTICLE EVENTS IN SOLAR CYCLE 24

International Nuclear Information System (INIS)

Nitta, Nariaki V.; Mason, Glenn M.; Wang, Linghua; Cohen, Christina M. S.; Wiedenbeck, Mark E.

2015-01-01

Using high-cadence EUV images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we investigate the solar sources of 26 3 He-rich solar energetic particle events at ≲1 MeV nucleon −1 that were well-observed by the Advanced Composition Explorer during solar cycle 24. Identification of the solar sources is based on the association of 3 He-rich events with type III radio bursts and electron events as observed by Wind. The source locations are further verified in EUV images from the Solar and Terrestrial Relations Observatory, which provides information on solar activities in the regions not visible from the Earth. Based on AIA observations, 3 He-rich events are not only associated with coronal jets as emphasized in solar cycle 23 studies, but also with more spatially extended eruptions. The properties of the 3 He-rich events do not appear to be strongly correlated with those of the source regions. As in the previous studies, the magnetic connection between the source region and the observer is not always reproduced adequately by the simple potential field source surface model combined with the Parker spiral. Instead, we find a broad longitudinal distribution of the source regions extending well beyond the west limb, with the longitude deviating significantly from that expected from the observed solar wind speed

Backup Mechanical Brake System of the Wind Turbine

Science.gov (United States)

Sirotkin, E. A.; Solomin, E. V.; Gandzha, S. A.; Kirpichnikova, I. M.

2018-01-01

Paper clarifies the necessity of the emergency mechanical brake systems usage for wind turbines. We made a deep analysis of the wind turbine braking methods available on the market, identifying their strengths and weaknesses. The electromechanical braking appeared the most technically reasonable and economically attractive. We described the developed combined electromechanical brake system for vertical axis wind turbine driven from electric drive with variable torque enough to brake over the turbine even on the storm wind speed up to 45 m/s. The progress was made due to the development of specific kinematic brake system diagram and intelligent control system managed by special operation algorithm.

Probing the clumpy winds of giant stars with high mass X-ray binaries

Science.gov (United States)

Grinberg, Victoria; Hell, Natalie; Hirsch, Maria; Garcia, Javier; Huenemoerder, David; Leutenegger, Maurice A.; Nowak, Michael; Pottschmidt, Katja; Schulz, Norbert S.; Sundqvists, Jon O.; Townsend, Richard D.; Wilms, Joern

2016-04-01

Line-driven winds from early type stars are structured, with small, overdense clumps embedded in tenuous hot gas. High mass X-ray binaries (HMXBs), systems where a neutron star or a black hole accretes from the line-driven stellar wind of an O/B-type companion, are ideal for studying such winds: the wind drives the accretion onto the compact object and thus the X-ray production. The radiation from close to the compact object is quasi-pointlike and effectively X-rays the wind.We used RXTE and Chandra-HETG observations of two of the brightest HMXBs, Cyg X-1 and Vela X-1, to decipher their wind structure. In Cyg X-1, we show that the orbital variability of absorption can be only explained by a clumpy wind model and constrain the porosity of the wind as well as the onion-like structure of the clumps. In Vela X-1 we show, using the newest reference energies for low ionization Si-lines obtained with LLNL’s EBIT-I, that the ionized phase of the circumstellar medium and the cold clumps have different velocities.

Wind tunnel simulation of Martian sand storms

Science.gov (United States)

Greeley, R.

1980-01-01

The physics and geological relationships of particles driven by the wind under near Martian conditions were examined in the Martian Surface Wind Tunnel. Emphasis was placed on aeolian activity as a planetary process. Threshold speeds, rates of erosion, trajectories of windblown particles, and flow fields over various landforms were among the factors considered. Results of experiments on particles thresholds, rates of erosion, and the effects of electrostatics on particles in the aeolian environment are presented.

Turbulence-driven coronal heating and improvements to empirical forecasting of the solar wind

International Nuclear Information System (INIS)

Woolsey, Lauren N.; Cranmer, Steven R.

2014-01-01

Forecasting models of the solar wind often rely on simple parameterizations of the magnetic field that ignore the effects of the full magnetic field geometry. In this paper, we present the results of two solar wind prediction models that consider the full magnetic field profile and include the effects of Alfvén waves on coronal heating and wind acceleration. The one-dimensional magnetohydrodynamic code ZEPHYR self-consistently finds solar wind solutions without the need for empirical heating functions. Another one-dimensional code, introduced in this paper (The Efficient Modified-Parker-Equation-Solving Tool, TEMPEST), can act as a smaller, stand-alone code for use in forecasting pipelines. TEMPEST is written in Python and will become a publicly available library of functions that is easy to adapt and expand. We discuss important relations between the magnetic field profile and properties of the solar wind that can be used to independently validate prediction models. ZEPHYR provides the foundation and calibration for TEMPEST, and ultimately we will use these models to predict observations and explain space weather created by the bulk solar wind. We are able to reproduce with both models the general anticorrelation seen in comparisons of observed wind speed at 1 AU and the flux tube expansion factor. There is significantly less spread than comparing the results of the two models than between ZEPHYR and a traditional flux tube expansion relation. We suggest that the new code, TEMPEST, will become a valuable tool in the forecasting of space weather.

Turbulence-driven coronal heating and improvements to empirical forecasting of the solar wind

Energy Technology Data Exchange (ETDEWEB)

Woolsey, Lauren N.; Cranmer, Steven R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2014-06-01

Forecasting models of the solar wind often rely on simple parameterizations of the magnetic field that ignore the effects of the full magnetic field geometry. In this paper, we present the results of two solar wind prediction models that consider the full magnetic field profile and include the effects of Alfvén waves on coronal heating and wind acceleration. The one-dimensional magnetohydrodynamic code ZEPHYR self-consistently finds solar wind solutions without the need for empirical heating functions. Another one-dimensional code, introduced in this paper (The Efficient Modified-Parker-Equation-Solving Tool, TEMPEST), can act as a smaller, stand-alone code for use in forecasting pipelines. TEMPEST is written in Python and will become a publicly available library of functions that is easy to adapt and expand. We discuss important relations between the magnetic field profile and properties of the solar wind that can be used to independently validate prediction models. ZEPHYR provides the foundation and calibration for TEMPEST, and ultimately we will use these models to predict observations and explain space weather created by the bulk solar wind. We are able to reproduce with both models the general anticorrelation seen in comparisons of observed wind speed at 1 AU and the flux tube expansion factor. There is significantly less spread than comparing the results of the two models than between ZEPHYR and a traditional flux tube expansion relation. We suggest that the new code, TEMPEST, will become a valuable tool in the forecasting of space weather.

A line driven Rayleigh-Taylor-type instability in hot stars

International Nuclear Information System (INIS)

Nelson, G.D.; Hearn, A.G.

1978-01-01

The existence of a Rayleigh-Taylor-type instability in the atmosphere of hot stars, driven by the radiative force associated with impurity ion resonance lines, is demonstrated. In a hot star with an effective temperature of 50 000 K, the instability will grow exponentially with a time scale of approximately 50 s in the layers where the stellar wind velocity is 5% of the thermal velocity of the ion. As a result, radially symmetric stellar winds driven by resonance line radiative forces will break up in small horizontal scale lengths. The energy fed into the instability provides a possible source of mechanical heating in the atmosphere for a chromosphere or corona. (orig.) [de

Combined He3 cryostats and He3-He4 dilution refrigerators

International Nuclear Information System (INIS)

Kovac, L.; Balla, J.

1974-07-01

A modular set of equipment was designed, which consists of a 4 He Dewar vessel with a very low evaporation rate, having a pumped 4 He bath in which either a 3 He cryostat or a dilution refrigerator within removable inserts can be placed. Any of them can be simply and rapidly connected to the versatile Dewar, auxiliary 4 He-, vacuum; and 3 He- 4 He systems. Two such sets have already been completed and can be used at temperatures from 1.5K to 0.05K for thermodynamic and neutron diffraction measurements. The performance of all inserts was stable and reliable, differences between the cryostats and runs were small - nearly all within the accuracy of temperature determination. The construction of a lot of parts is identical, allowing rapid manufacture. Assembling and repairs are simple, all parts are easily accessible. (K.A.)

Wind energy barometer - EurObserv'ER - February 2012

International Nuclear Information System (INIS)

2012-02-01

Notwithstanding the economic crisis affecting most of the globe's major economies, wind energy continues to gain supporters around the world. Global wind power capacity increased by 40.5 GW between 2010 and 2011 compared to a 39 GW rise between 2009 and 2010, after deduction of decommissioned capacity. By the end of 2011 global installed wind turbine capacity should stand at around 238.5 GW, and much of the world's growth is being driven by capacity build-up in the emerging markets. In contrast some of the key wind energy markets may be showing fault lines

Conversion of piston-driven shocks from powerful solar flares to blast wave shocks in the solar wind

International Nuclear Information System (INIS)

Pinter, S.

1990-01-01

It was suggested by Smart and Shea (1985) that the time of arrival of solar-flare-generated shock waves at any point in space may be predicted by assuming that they are first driven from the Sun after which they decay into blast shocks. Their study was extended by using the duration of the Type IV radio emission as a phenomenological symptom of the piston-driven phase of these shocks. Using a sample of 39 cases of combined Type II/Type IV observations from 1972 to 1982 solar flares, it was found that the average predicted times-of-arrival of these shocks to Earth (and elsewhere) deviate from the actual times by 1.40 hr with a standard deviation of 1.25 hr. On the average, a representative shock from this sample is emitted from a powerful flare with a velocity of 1,560 km sec -1 ; moves at a constant inertial velocity to a distance of 0.12 AU after which it begins to decelerate as a classical (Sedov-type) blast shock that is convected by the ambient solar wind as suggested by Smart and Shea; and arrives to Earth 45.8 hr after its initiation in the Sun. Shocks that appear to deviate from this phenomenological scenario by virtue of lack of detection on Earth are assumed to decay into fast mode MHD waves. (author). 7 figs., 1 tab., 53 refs

Structured Linear Parameter Varying Control of Wind Turbines

DEFF Research Database (Denmark)

Adegas, Fabiano Daher; Sloth, Christoffer; Stoustrup, Jakob

2012-01-01

High performance and reliability are required for wind turbines to be competitive within the energy market. To capture their nonlinear behavior, wind turbines are often modeled using parameter-varying models. In this chapter, a framework for modelling and controller design of wind turbines is pre...... in the controller synthesis are solved by an iterative LMI-based algorithm. The resulting controllers can also be easily implemented in practice due to low data storage and simple math operations. The performance of the LPV controllers is assessed by nonlinear simulations results....

Recombination of H+3 ions in the afterglow of a He-Ar-H2 plasma

International Nuclear Information System (INIS)

Glosik, J; Korolov, I; Plasil, R; Novotny, O; Kotrik, T; Hlavenka, P; Varju, J; Mikhailov, I A; Kokoouline, V; Greene, Chris H

2008-01-01

Recombination of H + 3 with electrons is studied in a low-temperature plasma containing He, H 2 and Ar at different He and H 2 densities. The effective plasma recombination rate is driven by binary, H + 3 + e - , and ternary, H + 3 + e - + He, processes with the rate coefficients 7.5 x 10 -8 cm 3 s -1 and 2.8 x 10 -25 cm 6 s -1 respectively at 260 K. We suggest that the ternary recombination involves formation of neutral highly excited Rydberg H 3 followed by an l-changing collision with He. The difference between recombination of para- and ortho-H + 3 is discussed. (fast track communication)

Wind effect on currents in a thin surface layer of coastal waters faced open-sea

International Nuclear Information System (INIS)

Nakano, Masanao; Isozaki, Hisaaki; Isozaki, Tokuju; Nemoto, Masashi; Hasunuma, Keiichi; Kitamura, Takashi

2009-01-01

Two-years of continuous observation of wind and current were carried out to investigate the relationship between them in the coastal waters off Tokai-mura, Ibaraki prefecture. Three instruments to measure the current were set in a thin surface layer of 3 m above the strong pycnocline, which is a common feature in coastal waters. Both of the power spectra of wind and currents showed very similar features, an outstanding high peak at 24-hour period and a range of high peaks longer than several-days period. The long term variation of the wind field always contained north-wind component, which contributed to forming the southward current along the shore throughout the year. A high correlation coefficient (0.64) was obtained between the wind and the current at a depth of 0.5 m on the basis of the two-year observation. Harmonic analysis revealed that an outstanding current with 24-hour period was the S 1 component (meteorological tide), and was driven by land and sea breezes. These breezes also contained solar tidal components such as K 1 , P 1 and S 2 . These wind components added their own wind driven currents on the original tidal currents. This meant that land and sea breezes generated wind driven currents with solar tidal periods which behaved like astronomical tidal currents. As result, coastal currents contained pseudo tidal currents which behaved like astronomical tidal currents. (author)

Listen, wind energy costs nothing

International Nuclear Information System (INIS)

Poizat, F.

2008-09-01

The author discusses the affirmation of the ADEME and the Environmental and sustainable development Ministry: the french wind park will costs in 2008 0,5 euro year for each household. He criticizes strongly this calculi, bringing many data on energy real cost today and in the next 10 years. Many references are provided. (A.L.B.)

Carbon price instead of support schemes: wind power investments by the electricity market

International Nuclear Information System (INIS)

Petitet, Marie; Finon, Dominique; Janssen, Tanguy

2014-10-01

In this paper we study the development of wind power by the electricity market without any usual support scheme which is aimed at subsidizing non mature renewables, with the sole incentive of a significant carbon price. Long term electricity market and investment decisions simulation by system dynamics modelling is used to trace the electricity generation mix evolution over a 20-year period in a pure thermal system. A range of stable carbon price, as a tax could be, is tested in order to determine the value above which wind power development by market forces becomes economically possible. Not only economic competitiveness in terms of cost price, but also profitability against traditional fossil fuel technologies are necessary for a market-driven development of wind power. Results stress that wind power is really profitable for investors only if the carbon price is very significantly higher than the price required for making wind power MWh's cost price competitive with CCGT and coal-fired plants on the simplistic basis of levelized costs. In this context, the market-driven development of wind power seems only possible if there is a strong commitment to climate policy, reflected by the preference for a stable and high carbon price rather than a fuzzy price of an emission trading scheme. Besides, results show that market-driven development of wind power would require a sky-rocketing carbon price if the initial technology mix includes a share of nuclear plants even with a moratorium on new nuclear development. (authors)

Analytical W–He and H–He interatomic potentials for a W–H–He system

International Nuclear Information System (INIS)

Li Xiaochun; Shu Xiaolin; Liu Yinan; Yu Yi; Gao, F.; Lu Guanghong

2012-01-01

We have constructed W–He and H–He analytical bond-order potentials for a W–H–He system. In combination with the previously self-developed W–H potential [X.-C. Li, X. Shu, Y.-N. Liu, F. Gao, G.-H. Lu, J. Nucl. Mater. 408 (2011) 12] and the Hartree–Fock-dispersion pair potential (Aziz-potential) for He−He interactions, we demonstrate that such potentials behave well for reproducing various properties of the W–H–He system such as defect formation energies, structural properties, and diffusion barriers. Such potentials can be employed to model both the He behaviours and the H–He synergetic effects in the W–H–He system.

2014 Wind Technologies Market Report

Energy Technology Data Exchange (ETDEWEB)

Wiser, Ryan [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bolinger, Mark [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Barbose, Galen [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Daghouth, Naim [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Hoen, Ben [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Mills, Andrew [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Hamachi LaCommare, Kristina [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Millstein, Dev [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Hansen, Dana [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Porter, Kevin [Exeter Associates, Columbia, MD (United States); Widiss, Rebecca [Exeter Associates, Columbia, MD (United States); Buckley, Michael [Exeter Associates, Columbia, MD (United States); Oteri, Frank [National Renewable Energy Lab. (NREL), Golden, CO (United States); Smith, Aaron [National Renewable Energy Lab. (NREL), Golden, CO (United States); Tegen, Suzanne [National Renewable Energy Lab. (NREL), Golden, CO (United States)

2015-08-06

Wind power capacity additions in the United States rebounded in 2014, and continued growth through 2016 is anticipated. Recent and projected near-term growth is supported by the industry’s primary federal incentive—the production tax credit (PTC)—which is available for projects that began construction by the end of 2014. Wind additions are also being driven by recent improvements in the cost and performance of wind power technologies, which have resulted in the lowest power sales prices ever seen in the U.S. wind sector. Growing corporate demand for wind energy and state-level policies play important roles as well. Expectations for continued technological advancements and cost reductions may further boost future growth. At the same time, the prospects for growth beyond 2016 are uncertain. The PTC has expired, and its renewal remains in question. Continued low natural gas prices, modest electricity demand growth, and limited near-term demand from state renewables portfolio standards (RPS) have also put a damper on growth expectations. These trends, in combination with increasingly global supply chains, have limited the growth of domestic manufacturing of wind equipment. What they mean for wind power additions through the end of the decade and beyond will be dictated in part by future natural gas prices, fossil plant retirements, and policy decisions.

Unconventional wind machine

International Nuclear Information System (INIS)

Sheff, J.R.

1979-01-01

It is the purpose of this paper to introduce an unconventional wind machine which has economics comparable with nuclear power and is already available in the public market place. Specifically, up to about 17 MWE could be saved for other uses such as sale in most 1000 MWE plants of any type - nuclear, oil, gas, peat, or wood - which use conventional electrically driven fans in their cooling towers. 10 refs

Kinetic energy of He atoms in liquid 4He-3He mixtures

International Nuclear Information System (INIS)

Senesi, R.; Andreani, C.; Fielding, A.L.; Mayers, J.; Stirling, W.G.

2003-01-01

Deep inelastic neutron scattering measurements on liquid 3 He- 4 He mixtures in the normal phase have been performed on the VESUVIO spectrometer at the ISIS pulsed neutron source at exchanged wave vectors of about q≅120.0 A -1 . The neutron Compton profiles J(y) of the mixtures were measured along the T=1.96 K isotherm for 3 He concentrations, x, ranging from 0.1 to 1.0 at saturated vapor pressures. Values of kinetic energies of 3 He and 4 He atoms as a function of x, (x), were extracted from the second moment of J(y). The present determinations of (x) confirm previous experimental findings for both isotopes and, in the case of 3 He, a substantial disagreement with theory is found. In particular (x) for the 3 He atoms is found to be independent of concentration yielding a value 3 (x=0.1)≅12 K, much lower than the value suggested by the most recent theoretical estimates of approximately 19 K

Gearless wind power generator

Energy Technology Data Exchange (ETDEWEB)

Soederlund, L.; Ridanpaeae, P.; Vihriaelae, H.; Peraelae, R. [Tampere Univ. of Technology (Finland). Lab. of Electricity and Magnetism

1998-10-01

In the project a 100 kW axial flux permanent magnet wind power generator has been designed. The toroidal stator with air gap winding is placed between two rotating discs with permanent magnets. The magnet material is NdBFe due to its excellent magnetic properties compared to other materials. This type of topology enables a very large number of poles compared to conventional machine of the same size. A large number of poles is required to achieve a low rotational speed and consequently a direct driven system. The stator winding is formed by rectangular coils. The end winding is very short leading to small resistive losses. On the other hand, the absence of iron teeth causes eddy current losses in the conductors. These can be restricted to an acceptable level by keeping the wire diameter and flux density small. This means that the number of phases should be large. Several independent three phase systems may be used. The toothless stator also means that the iron losses are small and there exists no cogging torque

Shear Driven Synthesis of Polymeric Micro- and Nanomaterials

Science.gov (United States)

Tian, Tian

Polymeric micro- and nanomaterials play a significant role in various current and emerging technologies. A liquid shear based method was developed to fabricate a wide range of polymeric materials, which include fibers, sheets, ribbons, rods and spheres in a scalable, cost-effective and simple way. During the process, droplet shearing, droplet deformation, droplet breaking up and polymer precipitation occur simultaneously. The size and morphology of the resultant structures are determined by the dominating process which is further controlled by the experimental parameters including polymer concentration, polymer molecular weight and antisolvent concentration. Among all of these structures, nanofibers have attracted the latest research interest due to the unique properties. Current leading fiber production approaches in the market possess certain drawbacks. For example, the throughput of electrospinning is limited to around 2.5 kg/hr and the diameter of fiber produced by wet spinning cannot be below micrometer while melt spinning is only applicable to melt-processable polymers. The breakthrough of our liquid shear driven technique for fiber synthesis is that it produces fibers with diameter from 200 nm to several micrometers from a wide range of liquid- processable polymers with high commercial yield (up to 12 kg/hr). Thus in Chapter 2, the optimum parameters range for fiber formation is established and the effects of those parameters on fiber size are investigated. In the original liquid shear method, medium with high viscosity is needed to exert strong shear stress on the droplet and to stretch the droplets to long strand. However, the viscous medium complicates the post sample washing procedure and introduces the potential slippery danger in the working area. Thus a non-viscous medium shearing method is developed in Chapter 3 and it is the first time proposed that the synthesis of PLA or PS nanofibers can be completed in the aqueous ethanol medium. Colloid science

Metallic Winds in Dwarf Galaxies

International Nuclear Information System (INIS)

Robles-Valdez, F.; Rodríguez-González, A.; Hernández-Martínez, L.; Esquivel, A.

2017-01-01

We present results from models of galactic winds driven by energy injected from nuclear (at the galactic center) and non-nuclear starbursts. The total energy of the starburst is provided by very massive young stellar clusters, which can push the galactic interstellar medium and produce an important outflow. Such outflow can be a well or partially mixed wind, or a highly metallic wind. We have performed adiabatic 3D N -Body/Smooth Particle Hydrodynamics simulations of galactic winds using the gadget-2 code. The numerical models cover a wide range of parameters, varying the galaxy concentration index, gas fraction of the galactic disk, and radial distance of the starburst. We show that an off-center starburst in dwarf galaxies is the most effective mechanism to produce a significant loss of metals (material from the starburst itself). At the same time, a non-nuclear starburst produces a high efficiency of metal loss, in spite of having a moderate to low mass loss rate.

BRITE-Constellation high-precision time-dependent photometry of the early O-type supergiant ζ Puppis unveils the photospheric drivers of its small- and large-scale wind structures

Science.gov (United States)

Ramiaramanantsoa, Tahina; Moffat, Anthony F. J.; Harmon, Robert; Ignace, Richard; St-Louis, Nicole; Vanbeveren, Dany; Shenar, Tomer; Pablo, Herbert; Richardson, Noel D.; Howarth, Ian D.; Stevens, Ian R.; Piaulet, Caroline; St-Jean, Lucas; Eversberg, Thomas; Pigulski, Andrzej; Popowicz, Adam; Kuschnig, Rainer; Zocłońska, Elżbieta; Buysschaert, Bram; Handler, Gerald; Weiss, Werner W.; Wade, Gregg A.; Rucinski, Slavek M.; Zwintz, Konstanze; Luckas, Paul; Heathcote, Bernard; Cacella, Paulo; Powles, Jonathan; Locke, Malcolm; Bohlsen, Terry; Chené, André-Nicolas; Miszalski, Brent; Waldron, Wayne L.; Kotze, Marissa M.; Kotze, Enrico J.; Böhm, Torsten

2018-02-01

From 5.5 months of dual-band optical photometric monitoring at the 1 mmag level, BRITE-Constellation has revealed two simultaneous types of variability in the O4I(n)fp star ζ Puppis: one single periodic non-sinusoidal component superimposed on a stochastic component. The monoperiodic component is the 1.78-d signal previously detected by Coriolis/Solar Mass Ejection Imager, but this time along with a prominent first harmonic. The shape of this signal changes over time, a behaviour that is incompatible with stellar oscillations but consistent with rotational modulation arising from evolving bright surface inhomogeneities. By means of a constrained non-linear light-curve inversion algorithm, we mapped the locations of the bright surface spots and traced their evolution. Our simultaneous ground-based multisite spectroscopic monitoring of the star unveiled cyclical modulation of its He II λ4686 wind emission line with the 1.78-d rotation period, showing signatures of corotating interaction regions that turn out to be driven by the bright photospheric spots observed by BRITE. Traces of wind clumps are also observed in the He II λ4686 line and are correlated with the amplitudes of the stochastic component of the light variations probed by BRITE at the photosphere, suggesting that the BRITE observations additionally unveiled the photospheric drivers of wind clumps in ζ Pup and that the clumping phenomenon starts at the very base of the wind. The origins of both the bright surface inhomogeneities and the stochastic light variations remain unknown, but a subsurface convective zone might play an important role in the generation of these two types of photospheric variability.

Superfluid 3He dynamcs in 3He - 4He solutions

International Nuclear Information System (INIS)

Mejerovich, A.Eh.

1984-01-01

The dynamics of a 3 He- 4 He superfluid solution with two condensates ( 3 He and 4 He) is investigated. Despite the fact that the hydrodynamics of the system is a three-velocity one (two superfluid and one normal velocity), all the thermo- and hydrodynamic functions are determined by the value of only a single linear combination of the velocities. 0n the basis of an analogy between a moving solution and a BCS system with coupling with a non-zero momentum, the dependence of the thermodynamic quantities on the velocities and critical velocities can easily be calculated for both homogeneous and inhomogeneous phases of the solution. In a magnetic field the temperature oscillations (analogue of second sound for a superfluid solution) are accompanied by oscillations of the magnetic moment. The velocity and damping of the spin-temperature waves are determined. The orienting action of a current on the inhomogeneous phases of the solution is discussed. It is shown that the energy and size of the vortexes in a superfluid solution are, due to drag effects, oscillating functions of the effective mass of the 3 He quasirartictes (pressure). At a pressure of the order of 10 atm a first order transition should take place in the vortex line which is accompanied by an abrupt change of the circulations of superfluid velocity of 3 He for a fixed circulation of the 4 He velocity

Statement on Wind Power

Energy Technology Data Exchange (ETDEWEB)

2010-01-15

Wind power will grow in importance in future electricity supply. In the next few decades it will to some degree replace fossil power but it will, at the same time also depend on fossil-b beyond, when wind power is expected to have a substantial share of the electricity market, CO{sub 2} emission-free electricity plants that are well suited for balancing the wind intermittency will be required. Predictions of the future penetration of wind power into the electricity market are critically dependent on a number of policy measures and will be especially influenced by climate driven energy policies. Very large investments will also be necessary as is shown by the lEA's Blue Map Scenario which includes 5,000 TWh wind electricity by 2050 at a cost of USD 700 billion. This implies an average 8% increase of wind electricity per year energy system, i.e. an energy system so large that it affects the entire world. The Energy Committee's scenario for electricity production in the year 2050 includes 5,000 TWh wind electricity out of a total of 45,000 TWh. Wind electricity thus has a within presently reached penetration of wind energy in a single country and within the calculated future projections of its penetration. Future large continental and intercontinental power grids may enable higher penetrations of wind energy since contributions of wind power from a larger area will tend to reduce its intermittency. Also, large-scale storage systems (thermal storage as is intermittent power systems. These alternatives have been discussed from a technical point of view [3] but for the required large-scale systems, further studies on the social, environmental and economical implications are needed

Wind resource characterization in the Arabian Peninsula

KAUST Repository

Yip, Chak Man Andrew

2015-12-28

Wind energy is expected to contribute to alleviating the rise in energy demand in the Middle East that is driven by population growth and industrial development. However, variability and intermittency in the wind resource present significant challenges to grid integration of wind energy systems. These issues are rarely addressed in the literature of wind resource assessment in the Middle East due to sparse meteorological observations with varying record lengths. In this study, the wind field with consistent space–time resolution for over three decades at three hub heights (50m, 80m, 140m) over the whole Arabian Peninsula is constructed using the Modern Era Retrospective-Analysis for Research and Applications (MERRA) dataset. The wind resource is assessed at a higher spatial resolution with metrics of temporal variations in the wind than in prior studies. Previously unrecognized locations of interest with high wind abundance and low variability and intermittency have been identified in this study and confirmed by recent on-site observations. In particular, the western mountains of Saudi Arabia experience more abundant wind resource than most Red Sea coastal areas. The wind resource is more variable in coastal areas along the Arabian Gulf than their Red Sea counterparts at a similar latitude. Persistent wind is found along the coast of the Arabian Gulf.

EWEA 2012: conference on the legal framework of wind energy

International Nuclear Information System (INIS)

Froeding, Veronique; Iuga, Dorina; Lintker, Stephanus; Edlich, Sophie

2012-01-01

At the occasion of 2012 Europe Wind energy event (EWEA), the French-German office for Renewable energies (OFAEnR) organised a conference on the legal framework of wind energy. In the framework of this French-German exchange of experience, participants exchanged views on the French and German respective regulations and administrative procedures for wind energy projects. This document brings together the available presentations (slides) made during this event: 1 - Synthesis note of the wind turbines French regulation (Veronique Froeding); 2 - Wind Barriers Presentation - Administrative and Grid access barriers (Dorina Iuga); 3 - Wind energy in France - Legal framework: what's new? (Veronique Froeding); 4 - North Rhine-Westphalia and the Wind energy Decree from July 2011: NRW Pioneer in Wind energy in Germany (Stephanus Lintker); 5 - Duration and development costs of wind energy projects in France and in Germany (Sophie Edlich)

Synthesis - Renewable energies (January 2013 - January 2014)

International Nuclear Information System (INIS)

Deharbe, David; Gandet, Stephanie

2014-01-01

This article proposes a detailed overview of the evolution of the legal context of renewable energies. The author first addresses wind energy: official critics and new uncertainties, suppression of wind energy development areas, suppression of the 'five-mast rule', purchasing obligation in the energy code, the legal framework as an obstacle to wind energy development, issue of purchase tariff and State support, jurisprudence regarding urban planning, public inquiry, radars. He then addresses sun energy: issue of self-production, anti-dumping struggle by the European Commission, continuous decrease of purchase tariffs, taxing issues for solar stations, jurisprudence on compensations and location possibilities. The next topic is biogas: current status of biogas installations, new definition of biomass, financial guarantees. He also addresses the case of hydroelectricity (longer duration and renewal of hydroelectric concessions, estate rights) and that of geothermal energy (planned reform of the applicable law)

Wind-powered aqueduct systems

Energy Technology Data Exchange (ETDEWEB)

Eldridge, F R; Ljungstroem, O [ed.

1976-01-01

The MITRE Corporation is proposing to develop a preliminarydesign for a system that would use large-scale wind-driven units to provide power for the pumping of water from the main reservoir to auxiliary reservoirs in other parts of an aqueduct system. The study would include a comparison of the cost and effectiveness of alternative methods of performing such operations.

Evidence for Pulsation-Driven Mass Loss from δ Cephei

Science.gov (United States)

Marengo, M.; Evans, N. R.; Matthews, L. D.; Bono, G.; Barmby, P.; Welch, D. L.; Romaniello, M.; Su, K. Y. L.; Fazio, G. G.; Huelsman, D.

We found the first direct evidence that the Cepheid class namesake, δ Cephei, is currently losing mass. These observations are based on data obtained with the Spitzer Space Telescope in the infrared, and with the Very Large Array in the radio. We found that δ Cephei is associated with a vast circumstellar structure, reminiscent of a bow shock. This structure is created as the wind from the star interacts with the local interstellar medium. We measure an outflow velocity of ≈ 35. 5 km s- 1 and a mass loss rate of ≈ 10- 7-10- 6 M ⊙ year- 1. The very low dust content of the outflow suggests that the wind is possibly pulsation-driven, rather than dust-driven as common for other classes of evolved stars.

The role of meridional density differences for a wind-driven overturning circulation

Energy Technology Data Exchange (ETDEWEB)

Schewe, J.; Levermann, A. [Potsdam Institute for Climate Impact Research, Earth System Analysis, Potsdam (Germany); Potsdam University, Physics Institute, Potsdam (Germany)

2010-03-15

Experiments with the coupled climate model CLIMBER-3{alpha}, which contains an oceanic general circulation model, show deep upwelling in the Southern Ocean to be proportional to the surface wind stress in the latitudinal band of Drake Passage. At the same time, the distribution of the Southern Ocean upwelling onto the oceanic basins is controlled by buoyancy distribution; the inflow into each basin being proportional to the respective meridional density difference. We observe approximately the same constant of proportionality for all basins, and demonstrate that it can be directly related to the flow geometry. For increased wind stress in the Southern Ocean, the overturning increases both in the Atlantic and the Indo-Pacific basin. For strongly reduced wind stress, the circulation enters a regime where Atlantic overturning is maintained through Pacific upwelling, in order to satisfy the transports set by the density differences. Previous results on surface buoyancy and wind stress forcing, obtained with different models, are reproduced within one model in order to distill a consistent picture. We propose that both Southern Ocean upwelling and meridional density differences set up a system of conditions that determine the global meridional overturning circulation. (orig.)

Experimental and analytical research on the aerodynamics of wind driven turbines. Final report

Energy Technology Data Exchange (ETDEWEB)

Rohrbach, C.; Wainauski, H.; Worobel, R.

1977-12-01

The successful development of reliable, cost competitive horizontal axis, propeller-type wind energy conversion systems (WECS) is strongly dependent on the availability of advanced technology for each of the system components. This aerodynamic research program was aimed at providing a reliable, comprehensive data base on a series of wind turbine models covering a broad range of the prime aerodynamic and geometric variables. Such data obtained under controlled laboratory conditions on turbines designed by the same method, of the same size, and tested in the same wind tunnel had not been available in the literature. Moreover, this research program was further aimed at providing a basis for evaluating the adequacy of existing wind turbine aerodynamic design and performance methodology, for assessing the potential of recent advanced theories and for providing a basis for further method development and refinement.

Energy Ontologies: Wind, Biomass, and Fossil Transportation

Directory of Open Access Journals (Sweden)

Heidi Scott

2016-06-01

Full Text Available This article uses literary sources to draw ontological distinctions among three distinct energy sources: wind power, biomass, and fossil fuels. The primary aim is to demonstrate how radically our fossil fuel regime has changed human ontology in the last two centuries during which we have entered the Anthropocene. Because this radical transformation contains myriad elements, this article will focus on transportation: the speed, quality, and quantity of travel permitted by successive energy sources. To consider the comparative literatures of energy as they relate to transportation, we will begin with wind, then consider muscle-driven biomass giving way to coal locomotion, and conclude with the highest octane fuel, petroleum. The central interest is in how the fuel depicted in literature illuminates historical moments in which the interfaces between self, society, and nature are configured by specific energy regimes. By using literature as a source text, we may arrive at an emotionally and philosophically more robust synthesis of energy history than the social and natural sciences, relying upon objective accounts and statistics, are able to provide. By re-reading literature through the lens of the Anthropocene, we gain perspective on how earlier insights into the relationship between energy and experience can inform our explorations of today’s ontological reality. Energy literature instructs us out of the fossil fuel mindset of world domination and back to a physical realm in which we are small actors in a world guided by capricious forces. Such a reality requires hard muscular work and emotional immersion to restore an ethic of care and sustainability.

X-ray-induced thinning of 3He and 3He/4He mixture films

International Nuclear Information System (INIS)

Penanen, Konstantin; Fukuto, Masafumi; Silvera, Isaac F.; Pershan, Peter

2000-01-01

Films of isotopic mixtures of helium have been studied using x-ray specular reflectivity techniques. In contrast with superfluid 4 He films, x-ray exposure causes a reduction in the thickness of 4 He films above the superfluid transition as well as films of pure 3 He and 3 He/ 4 He mixtures. One proposed model that could account for this effect is a charging model, in which thinning is caused by electrostatic pressure of free charges that accumulate on the helium surface. Unfortunately, this model is not fully consistent with all of the experimental observations. A localized heating model, in which indirect heating of the film causes it to thin would explain the data if there were dissipative film flow in the 3 He/ 4 He mixtures at temperatures where the bulk is superfluid. We argue that various published experimental results suggest such an effect. In this model, film thinning data for dilute 3 He/ 4 He films indicates dissipation that is linear in 3 He content of the film over two orders of magnitude

Evidence for a connection between photospheric and wind structure in HD 64760

Science.gov (United States)

Kaufer, A.; Prinja, R. K.; Stahl, O.

2002-02-01

We report on the results of an extended optical spectroscopic monitoring campaign on the early-type B supergiant HD 64760 (B0.5 Ib). The study is based on high-resolution echelle spectra obtained with the Landessternwarte Heidelberg's HEROS instrument at ESO La Silla. Ninety-nine spectra were collected over 103 nights between January 19 and May 1, 1996. The Hα line shows a characteristic profile with a central photospheric absorption superimposed by symmetrically blue- and red-shifted wind-emission humps. The time-averaged line profile is well described by a differentially rotating and expanding radiation-driven wind: the redistribution of the wind emission flux into a double peak profile is interpreted in terms of the resonance zone effect in rotating winds as first described by Petrenz & Puls (\\cite{Pet96}). Detailed time-series analyses of the line profile variations across the Hα profile reveal for the first time in an optical data set of HD 64760 a periodic 2.4-day modulation of the inner and outer flanks of the Hα emission humps. The stronger modulations of the inner flanks of the emission humps at photospheric velocities are due to complex width variations of the underlying photospheric Hα profile. The weaker variations of the outer flanks are in phase and reflect variations at the base of the stellar wind. The detected 2.4-day modulation period together with a second period of 1.2 days (in the red emission hump only) is in excellent agreement with the outer-wind modulation periods as reported by Fullerton et al. (\\cite{Ful97}) from intensive IUE UV time-series observations in 1993 and 1995. The 2.4-day period is further detected in the photospheric He I lambda4026 line as prograde traveling (pseudo-)absorption and emission features. The observed variability pattern is indicative for low-order non-radial pulsations in the photosphere of HD 64760. The non-radial pulsations are identified as the source of persistent, regularly spaced stellar surface

NMR and superfluidity of 3He in 3He-4He solutions

International Nuclear Information System (INIS)

Ivanova, K.D.; Mejerovich, A.Eh.

1986-01-01

Two possibilities of determining the superfluid transition temperature for 3 He in a 3 He- 4 He solution by the NMR technique are discussed. One of the methods consists in measuring the spin diffusion coefficient in weak magnetic fields at ultralow temperatures, and the other in measuring the ratio of the spin diffusion coefficient to the spin wave absorption coefficient at not very low temperatures. The transition temperature is estimated on the basis of the available experimental data. The effect of the superfluid transition in a system of 3 He quasiparticles on the propagation of transverse spin waves and longitudinal spin-sound oscillations in 3 He- 4 He solutions is studied. It is shown that there is a range of weak magnetic field intensities restricted from both sides in which the propagation of weakly damped spin-sound waves is possible

Influence of orographically steered winds on Mutsu Bay surface currents

Science.gov (United States)

Yamaguchi, Satoshi; Kawamura, Hiroshi

2005-09-01

Effects of spatially dependent sea surface wind field on currents in Mutsu Bay, which is located at the northern end of Japanese Honshu Island, are investigated using winds derived from synthetic aperture radar (SAR) images and a numerical model. A characteristic wind pattern over the bay was evidenced from analysis of 118 SAR images and coincided with in situ observations. Wind is topographically steered with easterly winds entering the bay through the terrestrial gap and stronger wind blowing over the central water toward its mouth. Nearshore winds are weaker due to terrestrial blockages. Using the Princeton Ocean Model, we investigated currents forced by the observed spatially dependent wind field. The predicted current pattern agrees well with available observations. For a uniform wind field of equal magnitude and average direction, the circulation pattern departs from observations demonstrating that vorticity input due to spatially dependent wind stress is essential in generation of the wind-driven current in Mutsu Bay.

Observation of the Rotational Spectra of 4HeH+, 4HeD+, 3HeH+, and 3HeD+

International Nuclear Information System (INIS)

Matsushima, F.; Oka, T.; Takagi, K.

1997-01-01

Low J rotational transitions of 4 HeH + , 4 HeD + , 3 HeH + , and 3 HeD + were observed in the 2 endash 5THz region with a high-precision far-infrared spectrometer. Dunham coefficients Y kl and isotopically independent parameters U kl , Δ He kl , and Δ H kl were determined. In particular, Δ parameters with k=0 and l=1,2 were determined with unprecedented accuracy, and provide important information for breakdown of the Born-Oppenheimer approximation. The lowest J=1 left-arrow 0 transition of 4 HeH + observed at 2010.1839(2)GHz will be an important future probe for detecting this species in space. copyright 1997 The American Physical Society

Assessment of research needs for wind turbine rotor materials technology

Energy Technology Data Exchange (ETDEWEB)

1991-01-01

Wind-driven power systems is a renewable energy technology that is still in the early stages of development. Wind power plants installed in early 1980s suffered structural failures chiefly because of incomplete understanding of wind forces (turbulent), in some cases because of poor product quality. Failures of rotor blades are now somewhat better understood. This committee has examined the experience base accumulated by wind turbines and the R and D programs sponsored by DOE. It is concluded that a wind energy system such as is described is within the capability of engineering practice; however because of certain gaps in knowledge, and the presence of only one major integrated manufacturer of wind power machines in the USA, a DOE R and D investment is still required.

COUNTERROTATION IN MAGNETOCENTRIFUGALLY DRIVEN JETS AND OTHER WINDS

Energy Technology Data Exchange (ETDEWEB)

Sauty, C.; Cayatte, V. [Laboratoire Univers et Theories, Observatoire de Paris, UMR 8102 du CNRS, Universite Paris Diderot, F-92190 Meudon (France); Lima, J. J. G. [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Matsakos, T. [CEA, IRAMIS, Service Photons, Atomes et Molecules, F-91191 Gif-sur-Yvette (France); Tsinganos, K., E-mail: christophe.sauty@obspm.fr [IASA and Section of Astrophysics, Astronomy and Mechanics, Department of Physics, University of Athens, Panepistimiopolis GR-157 84, Zografos (Greece)

2012-11-01

Rotation measurement in jets from T Tauri stars is a rather difficult task. Some jets seem to be rotating in a direction opposite to that of the underlying disk, although it is not yet clear if this affects the totality or part of the outflows. On the other hand, Ulysses data also suggest that the solar wind may rotate in two opposite ways between the northern and southern hemispheres. We show that this result is not as surprising as it may seem and that it emerges naturally from the ideal MHD equations. Specifically, counterrotating jets neither contradict the magnetocentrifugal driving of the flow nor prevent extraction of angular momentum from the disk. The demonstration of this result is shown by combining the ideal MHD equations for steady axisymmetric flows. Provided that the jet is decelerated below some given threshold beyond the Alfven surface, the flow will change its direction of rotation locally or globally. Counterrotation is also possible for only some layers of the outflow at specific altitudes along the jet axis. We conclude that the counterrotation of winds or jets with respect to the source, star or disk, is not in contradiction with the magnetocentrifugal driving paradigm. This phenomenon may affect part of the outflow, either in one hemisphere, or only in some of the outflow layers. From a time-dependent simulation, we illustrate this effect and show that it may not be permanent.

Subcooled He II heat transport in the channel with abrupt contractions/enlargements

International Nuclear Information System (INIS)

Maekawa, R.; Iwamoto, A.; Hamaguchi, S.; Mito, T.

2002-01-01

Heat transport mechanisms for subcooled He II in the channel with abrupt contractions and/or enlargements have been investigated under steady state conditions. The channel, made of G-10, contains various contraction geometries to simulate the cooling channel of a superconducting magnet. In other words, contractions are periodically placed along the channel to simulate the spacers within the magnet winding. A copper block heater inputs the heat to the channel from one end, while the other end is open to the He II bath. Temperature profiles were measured with temperature sensors embedded in the channel as a function of heat input. Calculations were performed using a simple one-dimensional turbulent heat transport equation and with geometric factor consideration. The effects on heat transport mechanisms in He II caused by abrupt change of channel geometry and size are discussed

The unbound isotopes He-9,He-10

CERN Document Server

Jonson, B; Cortina-Gil, D; Simon, H; Emling, H; Nyman, G; Nilsson, T; Johansson, H T; Borge, M J G; Paschalis, S; Muenzenberg, G; Zhukov, M V; Weick, H; Pramanik, U Datta; LeBleis, T; Meister, M; Reifarth, R; Chulkov, L V; Lantz, M; Riisager, K; Mahata, K; Suemmerer, K; Langer, C; Chatillon, A; Richter, A; Kulessa, R; Palit, R; Aksyutina, Yu; Geissel, H; Aumann, T; Prokopowicz, W; Forssen, C; Ickert, G; Fynbo, H O U; Tengblad, O; Boretzky, K

2010-01-01

The unbound nuclei He-9 and He-10 have been produced in proton-knockout reactions from a 280 MeV/u Li-11 beam impinging on a liquid hydrogen target at the ALADIN-LAND setup at GSI. Information on their nuclear structure has been obtained from the relative-energy spectra, He-8 + n and He-8 + 2n, employing reaction models incorporating the structure of Li-11. The (8H)e + n relative-energy spectrum is dominated by a strong peak-like structure at low energy, which may be interpreted within the effective-range approximation as the result of an s-wave interaction with a neutron scattering length of -3.17(66) fm. This spectrum also shows evidence for resonance states at 1.33(8) MeV and at 2.4 MeV above the He-8 + n threshold. It is argued that the s-state might not be the He-9 ground state. For He-8 + n + n, the analysis of the relative-energy spectrum gives two alternative possibilities for an interpretation: either a narrow resonance at 1.42(10) MeV (Gamma = 1.11(76) MeV) superimposed on a correlated background, o...

Transfer of the cytochrome P450-dependent dhurrin pathway from Sorghum bicolor into Nicotiana tabacum chloroplasts for light-driven synthesis

DEFF Research Database (Denmark)

Gnanasekaran, Thiyagarajan; Karcher, Daniel; Nielsen, Agnieszka Janina Zygadlo

2016-01-01

. For this purpose, we stably engineered the dhurrin pathway from Sorghum bicolor into the chloroplasts of Nicotiana tabacum (tobacco). Dhurrin is a cyanogenic glucoside and its synthesis from the amino acid tyrosine is catalysed by two membrane-bound cytochrome P450 enzymes (CYP79A1 and CYP71E1) and a soluble...... glucosyltransferase (UGT85B1), and is dependent on electron transfer from a P450 oxidoreductase. The entire pathway was introduced into the chloroplast by integrating CYP79A1, CYP71E1, and UGT85B1 into a neutral site of the N. tabacum chloroplast genome. The two P450s and the UGT85B1 were functional when expressed...... compared to 6% in sorghum. The results obtained pave the way for plant P450s involved in the synthesis of economically important compounds to be engineered into the thylakoid membrane of chloroplasts, and demonstrate that their full catalytic cycle can be driven directly by photosynthesis-derived electrons....

Financial analysis of wind power projects

International Nuclear Information System (INIS)

Juanico, Luis E.; Bergallo, Juan E.

1999-01-01

In this work a financial assessment of the economic competitiveness of wind power projects in Argentina compared with other no CO 2 emission sources, such as nuclear, was developed. Argentina has a market driven electrical grid system, and no greenhouse gas emissions penalty taxes, together with a very low natural gas cost and a sustained nuclear development program. For the financial analysis an average wind velocity source of 8 m/s, on several wind farms (from 2 machines to 60) built with new technology wind generators (750 kilowatts power, 900 dollar/kilowatt cost) operating over 20 years, was considered. The leveled cost obtained is decreasing while the number of machines is increasing, from 0,130 dollar/kilowatt-hour to 0,090 dollar/kilowatts-hour. This poor performance can be partially explained considering the higher interest rates in the argentine financial market (15%) than the ones in developed countries

Representativeness of wind measurements in moderately complex terrain

Science.gov (United States)

van den Bossche, Michael; De Wekker, Stephan F. J.

2018-02-01

We investigated the representativeness of 10-m wind measurements in a 4 km × 2 km area of modest relief by comparing observations at a central site with those at four satellite sites located in the same area. Using a combination of established and new methods to quantify and visualize representativeness, we found significant differences in wind speed and direction between the four satellite sites and the central site. The representativeness of the central site wind measurements depended strongly on surface wind speed and direction, and atmospheric stability. Through closer inspection of the observations at one of the satellite sites, we concluded that terrain-forced flows combined with thermally driven downslope winds caused large biases in wind direction and speed. We used these biases to generate a basic model, showing that terrain-related differences in wind observations can to a large extent be predicted. Such a model is a cost-effective way to enhance an area's wind field determination and to improve the outcome of pollutant dispersion and weather forecasting models.

Hall-effect-controlled gas dynamics in protoplanetary disks. I. Wind solutions at the inner disk

International Nuclear Information System (INIS)

Bai, Xue-Ning

2014-01-01

The gas dynamics of protoplanetary disks (PPDs) is largely controlled by non-ideal magnetohydrodynamic (MHD) effects including Ohmic resistivity, the Hall effect, and ambipolar diffusion. Among these the role of the Hall effect is the least explored and most poorly understood. In this series, we have included, for the first time, all three non-ideal MHD effects in a self-consistent manner to investigate the role of the Hall effect on PPD gas dynamics using local shearing-box simulations. In this first paper, we focus on the inner region of PPDs, where previous studies (Bai and Stone 2013; Bai 2013) excluding the Hall effect have revealed that the inner disk up to ∼10 AU is largely laminar, with accretion driven by a magnetocentrifugal wind. We confirm this basic picture and show that the Hall effect modifies the wind solutions depending on the polarity of the large-scale poloidal magnetic field B 0 threading the disk. When B 0 ⋅Ω>0, the horizontal magnetic field is strongly amplified toward the disk interior, leading to a stronger disk wind (by ∼50% or less in terms of the wind-driven accretion rate). The enhanced horizontal field also leads to much stronger large-scale Maxwell stress (magnetic braking) that contributes to a considerable fraction of the wind-driven accretion rate. When B 0 ⋅Ω<0, the horizontal magnetic field is reduced, leading to a weaker disk wind (by ≲ 20%) and negligible magnetic braking. Under fiducial parameters, we find that when B 0 ⋅Ω>0, the laminar region extends farther to ∼10-15 AU before the magnetorotational instability sets in, while for B 0 ⋅Ω<0, the laminar region extends only to ∼3-5 AU for a typical accretion rate of ∼10 –8 to10 –7 M ☉ yr –1 . Scaling relations for the wind properties, especially the wind-driven accretion rate, are provided for aligned and anti-aligned field geometries.

Hall-effect-controlled gas dynamics in protoplanetary disks. I. Wind solutions at the inner disk

Energy Technology Data Exchange (ETDEWEB)

Bai, Xue-Ning, E-mail: xbai@cfa.harvard.edu [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States)

2014-08-20

The gas dynamics of protoplanetary disks (PPDs) is largely controlled by non-ideal magnetohydrodynamic (MHD) effects including Ohmic resistivity, the Hall effect, and ambipolar diffusion. Among these the role of the Hall effect is the least explored and most poorly understood. In this series, we have included, for the first time, all three non-ideal MHD effects in a self-consistent manner to investigate the role of the Hall effect on PPD gas dynamics using local shearing-box simulations. In this first paper, we focus on the inner region of PPDs, where previous studies (Bai and Stone 2013; Bai 2013) excluding the Hall effect have revealed that the inner disk up to ∼10 AU is largely laminar, with accretion driven by a magnetocentrifugal wind. We confirm this basic picture and show that the Hall effect modifies the wind solutions depending on the polarity of the large-scale poloidal magnetic field B{sub 0} threading the disk. When B{sub 0}⋅Ω>0, the horizontal magnetic field is strongly amplified toward the disk interior, leading to a stronger disk wind (by ∼50% or less in terms of the wind-driven accretion rate). The enhanced horizontal field also leads to much stronger large-scale Maxwell stress (magnetic braking) that contributes to a considerable fraction of the wind-driven accretion rate. When B{sub 0}⋅Ω<0, the horizontal magnetic field is reduced, leading to a weaker disk wind (by ≲ 20%) and negligible magnetic braking. Under fiducial parameters, we find that when B{sub 0}⋅Ω>0, the laminar region extends farther to ∼10-15 AU before the magnetorotational instability sets in, while for B{sub 0}⋅Ω<0, the laminar region extends only to ∼3-5 AU for a typical accretion rate of ∼10{sup –8} to10{sup –7} M {sub ☉} yr{sup –1}. Scaling relations for the wind properties, especially the wind-driven accretion rate, are provided for aligned and anti-aligned field geometries.

Influence of He ions irradiation on the deuterium permeation and retention behavior in the CLF-1 steel

International Nuclear Information System (INIS)

Xu, Yu-Ping; Lu, Tao; Li, Xiao-Chun; Liu, Feng; Liu, Hao-Dong; Wang, Jing; An, Zhong-Qing; Ding, Fang; Hong, Suk-Ho; Zhou, Hai-Shan; Luo, Guang-Nan

2016-01-01

To evaluate the influence of He ions irradiation on the deuterium permeation and retention behavior in RAFM steels, samples made of the CLF-1 steel was irradiated with 3.5 MeV He ions. Gas driven permeation experiments were performed, and the permeability of virgin sample and pre-irradiated sample were obtained and compared. In order to characterize the effect of He ions irradiation on the deuterium retention behavior, deuterium gas exposure was carried out at 623 K, followed by thermal desorption spectra experiments. The total deuterium retention of the CLF-1 steel increased owing to He ions implantation, which could be attributed to the increase in trapping site for deuterium by the He pre-irradiation.

Quasimolecular autoionization in the collisions He+ - He, H2

International Nuclear Information System (INIS)

Ogurtsov, G.N.; Krupyshev, A.G.; Gordeev, Yu.S.

1993-01-01

Data on the autoionization transition level width dependence Γ(R) for He + - He, He + - H 2 pairs are obtained. Data on the probability of autoionization transition in a three-atom quasimolecule are obtained for the first time. It is shown that Γ(R) values for He + - He 2 quasimolecule exceed notably the similar values for isoelectron He + - He quasimolecule and may reach ∼ 1 eV. 6 refs., 2 figs

A Deeper Understanding of Stability in the Solar Wind: Applying Nyquist's Instability Criterion to Wind Faraday Cup Data

Science.gov (United States)

Alterman, B. L.; Klein, K. G.; Verscharen, D.; Stevens, M. L.; Kasper, J. C.

2017-12-01

Long duration, in situ data sets enable large-scale statistical analysis of free-energy-driven instabilities in the solar wind. The plasma beta and temperature anisotropy plane provides a well-defined parameter space in which a single-fluid plasma's stability can be represented. Because this reduced parameter space can only represent instability thresholds due to the free energy of one ion species - typically the bulk protons - the true impact of instabilities on the solar wind is under estimated. Nyquist's instability criterion allows us to systematically account for other sources of free energy including beams, drifts, and additional temperature anisotropies. Utilizing over 20 years of Wind Faraday cup and magnetic field observations, we have resolved the bulk parameters for three ion populations: the bulk protons, beam protons, and alpha particles. Applying Nyquist's criterion, we calculate the number of linearly growing modes supported by each spectrum and provide a more nuanced consideration of solar wind stability. Using collisional age measurements, we predict the stability of the solar wind close to the sun. Accounting for the free-energy from the three most common ion populations in the solar wind, our approach provides a more complete characterization of solar wind stability.

Fault ride-through and voltage support of permanent magnet synchronous generator wind turbines

Energy Technology Data Exchange (ETDEWEB)

Michalke, G.; Hartkopf, T. [Darmstadt Technical Univ., Dept. of Renewable Energies (Germany); Hansen, A.D. [Risoe National Lab., DTU, Wind Energy Dept. (Denmark)

2007-11-15

This paper presents a control strategy of direct driven multipole PMSG wind turbines, which enhances the fault ride-through and voltage support capability of such wind turbines during grid faults. A dynamic simulation model of the turbine is implemented in the simulation software DIgSILENT. Simulation results approve the effectiveness of the developed control strategy. It is shown that PMSG wind turbines equipped with such control even enable nearby connected conventional wind turbines to ride-through grid faults. (au)

Experimental and analytical research on the aerodynamics of wind driven turbines. Final report

Energy Technology Data Exchange (ETDEWEB)

Rohrbach, C.; Wainauski, H.; Worobel, R.

1977-12-01

This aerodynamic research program was aimed at providing a reliable, comprehensive data base on a series of wind turbine models covering a broad range of the prime aerodynamic and geometric variables. Such data obtained under controlled laboratory conditions on turbines designed by the same method, of the same size, and tested in the same wind tunnel had not been available in the literature. Moreover, this research program was further aimed at providing a basis for evaluating the adequacy of existing wind turbine aerodynamic design and performance methodology, for assessing the potential of recent advanced theories and for providing a basis for further method development and refinement.

Using He I λ10830 to Diagnose Mass Flows Around Herbig Ae/Be Stars

Science.gov (United States)

Cauley, Paul W.; Johns-Krull, Christopher M.

2015-01-01

The pre-main sequence Herbig Ae/Be stars (HAEBES) are the intermediate mass cousins of the low mass T Tauri stars (TTSs). However, it is not clear that the same accretion and mass outflow mechanisms operate identically in both mass regimes. Classical TTSs (CTTSs) accrete material from their disks along stellar magnetic field lines in a scenario called magnetospheric accretion. Magnetospheric accretion requires a strong stellar dipole field in order to truncate the inner gas disk. These fields are either absent or very weak on a large majority of HAEBES, challenging the view that magnetospheric accretion is the dominant accretion mechanism. If magnetospheric accretion does not operate similarly around HAEBES as it does around CTTSs, then strong magnetocentrifugal outflows, which are directly linked to accretion and are ubiquitous around CTTSs, may be driven less efficiently from HAEBE systems. Here we present high resolution spectroscopic observations of the He I λ10830 line in a sample of 48 HAEBES. He I λ10830 is an excellent tracer of both mass infall and outflow which is directly manifested as red and blue-shifted absorption in the profile morphologies. These features, among others, are common in our sample. The occurrence of both red and blue-shifted absorption profiles is less frequent, however, than is found in CTTSs. Statistical contingency tests confirm this difference at a significant level. In addition, we find strong evidence for smaller disk truncation radii in the objects displaying red-shifted absorption profiles. This is expected for HAEBES experiencing magnetospheric accretion based on their large rotation rates and weak magnetic field strengths. Finally, the low incidence of blue-shifted absorption in our sample compared to CTTSs and the complete lack of simultaneous red and blue-shifted absorption features suggests that magnetospheric accretion in HAEBES is less efficient at driving strong outflows. The stellar wind-like outflows that are

The dynamics of İzmir Bay under the effects of wind and thermohaline forces

Science.gov (United States)

Sayın, Erdem; Eronat, Canan

2018-04-01

The dominant circulation pattern of İzmir Bay on the Aegean Sea coast of Turkey is studied taking into consideration the influence of wind and thermohaline forces. İzmir Bay is discussed by subdividing the bay into outer, middle and inner areas. Wind is the most important driving force in the İzmir coastal area. There are also thermohaline forces due to the existence of water types of different physical properties in the bay. In contrast to the two-layer stratification during summer, a homogeneous water column exists in winter. The free surface version of the Princeton model (Killworth's 3-D general circulation model) is applied, with the input data obtained through the measurements made by the research vessel K. Piri Reis. As a result of the simulations with artificial wind, the strong consistent wind generates circulation patterns independent of the seasonal stratification in the bay. Wind-driven circulation causes cyclonic or anticyclonic movements in the middle bay where the distinct İzmir Bay Water (IBW) forms. Cyclonic movement takes place under the influence of southerly and westerly winds. On the other hand, northerly and easterly winds cause an anticyclonic movement in the middle bay. The outer and inner bay also have the wind-driven recirculation patterns expected.

ON THE ORIGIN OF THE SLOW SPEED SOLAR WIND: HELIUM ABUNDANCE VARIATIONS

Energy Technology Data Exchange (ETDEWEB)

Rakowski, Cara E.; Laming, J. Martin [Space Science Division, Naval Research Laboratory Code 7674L, Washington, DC 20375 (United States)

2012-07-20

The first ionization potential (FIP) effect is the by now well-known enhancement in abundance over photospheric values of Fe and other elements with FIP below about 10 eV observed in the solar corona and slow speed solar wind. In our model, this fractionation is achieved by means of the ponderomotive force, arising as Alfven waves propagate through or reflect from steep density gradients in the solar chromosphere. This is also the region where low FIP elements are ionized, and high FIP elements are largely neutral leading to the fractionation as ions interact with the waves but neutrals do not. Helium, the element with the highest FIP and consequently the last to remain neutral as one moves upward, can be depleted in such models. Here, we investigate this depletion for varying loop lengths and magnetic field strengths. Variations in this depletion arise as the concentration of the ponderomotive force at the top of the chromosphere varies in response to Alfven wave frequency with respect to the resonant frequency of the overlying coronal loop, the magnetic field, and possibly also the loop length. We find that stronger depletions of He are obtained for weaker magnetic field, at frequencies close to or just above the loop resonance. These results may have relevance to observed variations of the slow wind solar He abundance with wind speed, with slower slow speed solar wind having a stronger depletion of He.

风速波动下变速机组风电场的单机等值建模方法%Single machine equivalent modeling method of wind farms with variable speed wind turbines under wind speed fluctuations

Institute of Scientific and Technical Information of China (English)

苏勋文; 秦浩宇; 杨荣峰; 岳红轩

2017-01-01

由于风电机组的输出功率滞后于风速波动,等值风计算不能反映实际工况,采用DIg-SILENT/Powerfactory搭建变速机组风电场详细模型和单机等值模型,研究风速波动下双馈机组和直驱永磁机组风电场模型的并网点输出特性.研究表明:对于双馈机组风电场,与详细模型相比,单机等值模型会出现一定误差;对于直驱永磁机组风电场,使用等值风的优于使用平均风的等值模型.利用单机表征法建立的风电场等值模型与详细模型的动态响应基本一致.该研究验证了单机等值方法的有效性和适用性.%This paper seeks to explore an efficient and simple wind farm equivalent modeling meth-od. The exploration involves the following process:providing the calculation method of the equivalent pa-rameters and equivalent wind in the single machine equivalent model; developing a detailed model of wind farm and a single machine equivalent model using the simulation software DIgSILENT/Powerfactory;investigating dynamic response at point of interconnection of wind farm with doubly fed induction genera-tor wind turbines and directly driven permanent magnet wind turbines under wind speed fluctuation. The results demonstrate that, in the case of wind farm with doubly fed induction generator wind turbines, where wind turbine operates at the output power lagging behind the wind speed fluctuation, equivalent wind calculation fails to reflect the actual operating conditions; there occurs a certain error in the single machine equivalent model compared;equivalent wind is better than the average wind for wind farm with directly driven permanent magnet wind turbines;and the dynamic response is basically same between the equivalent model of wind farm based on the single machine representation method and the detailed model of wind farm. The research verifies the validity and applicability of the single machine equivalent method.

Dependence of the rate of DNA synthesis in x-irradiated HeLa S3 cells on dose and time after exposure

International Nuclear Information System (INIS)

Tolmach, L.J.; Jones, R.W.

1977-01-01

After irradiation of randomly dividing cultures of HeLa S3 cells with 220-kV x rays, the rate of DNA synthesis, measured by pulsed incorporation of labeled thymidine, falls nearly exponentially with time (t/sub 1/2/ approximately 1.3 hr), in a dose-independent fashion. The fall is less rapid than that observed after addition of inhibitors of protein synthesis. With doses up to 8 krad, the rate reaches a minimum and begins to increase after 1-3 hr, the minima occurring at lower values and at slightly later times with increasing dose. The increase appears to be roughly linear for about 6 hr, with the slope an inverse function of dose in the range 1-8 krad. About 7-9 hr after the completion of irradiation, the rate again falls, although no more than 10 percent of the cells die sooner than 14 hr after irradiation with 8 krad (and later with smaller doses). Fluorodeoxyuridine-mediated delay in expression of the depression, described previously for doses up to 1 krad, occurs also at higher doses. During the period when the rate per culture rises, the rate in the individual cells, measured autoradiographically, appears to increase also, i.e., the rise presumably does not merely reflect populational shifts. The initial descending portion of the rate curve can be at least partially separated from the ascending portion by administering the total dose in suitably spaced fractions. If interpreted in terms of the model that attributes the initial depression in rate of synthesis to a temporary absence of replicon initiation, the results indicate that initiation is halted by an x-ray dose smaller than 1 krad; that it begins again after a dose-dependent delay amounting to about 0.7 hr after 1 krad and 1.5 hr after 7 krad; and that once begun, the rate of synthesis increases in a dose-dependent fashion. The second depression might derive from synchronization and/or from the imminence of cell death

A Collapsar Model with Disk Wind: Implications for Supernovae Associated with Gamma-Ray Bursts

Science.gov (United States)

Hayakawa, Tomoyasu; Maeda, Keiichi

2018-02-01

We construct a simple but self-consistent collapsar model for gamma-ray bursts (GRBs) and SNe associated with GRBs (GRB-SNe). Our model includes a black hole, an accretion disk, and the envelope surrounding the central system. The evolutions of the different components are connected by the transfer of the mass and angular momentum. To address properties of the jet and the wind-driven SNe, we consider competition of the ram pressure from the infalling envelope and those from the jet and wind. The expected properties of the GRB jet and the wind-driven SN are investigated as a function of the progenitor mass and angular momentum. We find two conditions that should be satisfied if the wind-driven explosion is to explain the properties of the observed GRB-SNe: (1) the wind should be collimated at its base, and (2) it should not prevent further accretion even after the launch of the SN explosion. Under these conditions, some relations seen in the properties of the GRB-SNe could be reproduced by a sequence of different angular momentum in the progenitors. Only the model with the largest angular momentum could explain the observed (energetic) GRB-SNe, and we expect that the collapsar model can result in a wide variety of observational counterparts, mainly depending on the angular momentum of the progenitor star.

Note: Coincidence measurements of 3He and neutrons from a compact D-D neutron generator

Science.gov (United States)

Ji, Q.; Lin, C.-J.; Tindall, C.; Garcia-Sciveres, M.; Schenkel, T.; Ludewigt, B. A.

2017-05-01

Tagging of neutrons (2.45 MeV) with their associated 3He particles from deuterium-deuterium (D-D) fusion reactions has been demonstrated in a compact neutron generator setup enabled by a high brightness, microwave-driven ion source with a high fraction of deuterons. Energy spectra with well separated peaks of the D-D fusion reaction products, 3He, tritons, and protons, were measured with a silicon PIN diode. The neutrons were detected using a liquid scintillator detector with pulse shape discrimination. By correlating the 3He detection events with the neutron detection in time, we demonstrated the tagging of emitted neutrons with 3He particles detected with a Si PIN diode detector mounted inside the neutron generator vacuum vessel.

Wind-driven circulation in the subarctic north Pacific using altimeter ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

of the wind stress curl are also related to the variation of the subarctic gyre. Though the correlation .... mum in spring, accounting for 41% of all the vari- ance. This estimate ..... plays an important role as a western boundary and it is also located ...

On the Weak-Wind Problem in Massive Stars: X-Ray Spectra Reveal a Massive Hot Wind in mu Columbae

Science.gov (United States)

Huenemoerder, David P.; Oskinova, Lidia M.; Ignace, Richard; Waldron, Wayne L.; Todt, Helge; Hamaguchi, Kenji; Kitamoto, Shunji

2012-01-01

Mu Columbae is a prototypical weak-wind O star for which we have obtained a high-resolution X-ray spectrum with the Chandra LETG/ACIS instrument and a low-resolution spectrum with Suzaku. This allows us, for the first time, to investigate the role of X-rays on the wind structure in a bona fide weak-wind system and to determine whether there actually is a massive hot wind. The X-ray emission measure indicates that the outflow is an order of magnitude greater than that derived from UV lines and is commensurate with the nominal wind-luminosity relationship for O stars. Therefore, the "weak-wind problem"--identified from cool wind UV/optical spectra--is largely resolved by accounting for the hot wind seen in X-rays. From X-ray line profiles, Doppler shifts, and relative strengths, we find that this weak-wind star is typical of other late O dwarfs. The X-ray spectra do not suggest a magnetically confined plasma-the spectrum is soft and lines are broadened; Suzaku spectra confirm the lack of emission above 2 keV. Nor do the relative line shifts and widths suggest any wind decoupling by ions. The He-like triplets indicate that the bulk of the X-ray emission is formed rather close to the star, within five stellar radii. Our results challenge the idea that some OB stars are "weak-wind" stars that deviate from the standard wind-luminosity relationship. The wind is not weak, but it is hot and its bulk is only detectable in X-rays.

The WD+He star binaries as the progenitors of type Ia supernovae

Directory of Open Access Journals (Sweden)

Wang Bo

2017-12-01

Full Text Available Employing the MESA stellar evolution code, we computed He accretion onto carbon-oxygen white dwarfs (CO WDs.We found two possible outcomes for models in which the WD steadily grows in mass towards the Chandrasekhar limit. For relatively low He-accretion rates carbon ignition occurs in the center, leading to a type Ia supernova (SN Ia explosion, whereas for relatively high accretion rates carbon is ignited off-center, probably leading to collapse. Thus the parameter space producing SNe Ia is reduced compared to what was assumed in earlier papers, in which the possibility of off-center ignition was ignored. We then applied these results in binary population synthesis modelling, finding a modest reduction in the expected birthrate of SNe Ia resulting from the WD+He star channel.

Efficient cold outflows driven by cosmic rays in high-redshift galaxies and their global effects on the IGM

Science.gov (United States)

Samui, Saumyadip; Subramanian, Kandaswamy; Srianand, Raghunathan

2018-05-01

We present semi-analytical models of galactic outflows in high-redshift galaxies driven by both hot thermal gas and non-thermal cosmic rays. Thermal pressure alone may not sustain a large-scale outflow in low-mass galaxies (i.e. M ˜ 108 M⊙), in the presence of supernovae feedback with large mass loading. We show that inclusion of cosmic ray pressure allows outflow solutions even in these galaxies. In massive galaxies for the same energy efficiency, cosmic ray-driven winds can propagate to larger distances compared to pure thermally driven winds. On an average gas in the cosmic ray-driven winds has a lower temperature which could aid detecting it through absorption lines in the spectra of background sources. Using our constrained semi-analytical models of galaxy formation (that explains the observed ultraviolet luminosity functions of galaxies), we study the influence of cosmic ray-driven winds on the properties of the intergalactic medium (IGM) at different redshifts. In particular, we study the volume filling factor, average metallicity, cosmic ray and magnetic field energy densities for models invoking atomic cooled and molecular cooled haloes. We show that the cosmic rays in the IGM could have enough energy that can be transferred to the thermal gas in presence of magnetic fields to influence the thermal history of the IGM. The significant volume filling and resulting strength of IGM magnetic fields can also account for recent γ-ray observations of blazars.

Schedulability-Driven Communication Synthesis for Time Triggered Embedded Systems

DEFF Research Database (Denmark)

Pop, Paul; Eles, Petru; Peng, Zebo

2006-01-01

We present an approach to static priority preemptive process scheduling for the synthesis of hard real-time distributed embedded systems where communication plays an important role. The communication model is based on a time-triggered protocol. We have developed an analysis for the communication...... delays proposing four different message scheduling policies over a time-triggered communication channel. Optimization strategies for the synthesis of communication are developed, and the four approaches to message scheduling are compared using extensive experiments...

Schedulability-Driven Communication Synthesis for Time Triggered Embedded Systems

DEFF Research Database (Denmark)

Pop, Paul; Eles, Petru; Peng, Zebo

1999-01-01

We present an approach to static priority preemptive process scheduling for the synthesis of hard real-time distributed embedded systems where communication plays an important role. The communication model is based on a time-triggered protocol. We have developed an analysis for the communication...... delays proposing four different message scheduling policies over a time-triggered communication channel. Optimization strategies for the synthesis of communication are developed, and the four approaches to message scheduling are compared using extensive experiments....

Schedulability-Driven Communication Synthesis for Time Triggered Embedded Systems

DEFF Research Database (Denmark)

Pop, Paul; Eles, Petru; Peng, Zebo

2004-01-01

We present an approach to static priority preemptive process scheduling for the synthesis of hard real-time distributed embedded systems where communication plays an important role. The communication model is based on a time-triggered protocol. We have developed an analysis for the communication...... delays with four different message scheduling policies over a time-triggered communication channel. Optimization strategies for the synthesis of communication are developed, and the four approaches to message scheduling are compared using extensive experiments....

Stellar and wind parameters of massive stars from spectral analysis

Science.gov (United States)

Araya, Ignacio; Curé, Michel

2017-11-01

The only way to deduce information from stars is to decode the radiation it emits in an appropriate way. Spectroscopy can solve this and derive many properties of stars. In this work we seek to derive simultaneously the stellar and wind characteristics of a wide range of massive stars. Our stellar properties encompass the effective temperature, the surface gravity, the stellar radius, the micro-turbulence velocity, the rotational velocity and the Si abundance. For wind properties we consider the mass-loss rate, the terminal velocity and the line-force parameters α, k and δ (from the line-driven wind theory). To model the data we use the radiative transport code Fastwind considering the newest hydrodynamical solutions derived with Hydwind code, which needs stellar and line-force parameters to obtain a wind solution. A grid of spectral models of massive stars is created and together with the observed spectra their physical properties are determined through spectral line fittings. These fittings provide an estimation about the line-force parameters, whose theoretical calculations are extremely complex. Furthermore, we expect to confirm that the hydrodynamical solutions obtained with a value of δ slightly larger than ~ 0.25, called δ-slow solutions, describe quite reliable the radiation line-driven winds of A and late B supergiant stars and at the same time explain disagreements between observational data and theoretical models for the Wind-Momentum Luminosity Relationship (WLR).

Analysis of the potential for wind energy production in northwestern Ontario

Energy Technology Data Exchange (ETDEWEB)

Brown, C K; Warne, D F

1975-11-01

A study of the feasibility of generating electric power from wind generators at remote sites in Northwestern Ontario has been carried out on behalf of the Ontario Ministry of Energy, with project management from Ontario Hydro. The work included (1) a survey of commercially available wind driven electric plant, both currently available and planned for production, (2) an analysis of existing wind data and preparation of an isovent map for Ontario showing annual mean wind speeds, (3) the selection of suitable sites for a demonstration unit and a prototype system, (4) the matching of available plant to the wind regimes to predict annual energy production, and (5) a systems analysis of pure diesel, hybrid wind/diesel and pure wind electric plants to determine the cost of power from the various alternatives.

Direct monitoring of wind-induced pressure-pumping on gas transport in soil

Science.gov (United States)

Laemmel, Thomas; Mohr, Manuel; Schindler, Dirk; Schack-Kirchner, Helmer; Maier, Martin

2017-04-01

Gas exchange between soil and atmosphere is important for the biogeochemistry of soils and is commonly assumed to be governed by molecular diffusion. Yet a few previous field studies identified other gas transport processes such as wind-induced pressure-pumping to enhance soil-atmosphere fluxes significantly. However, since these wind-induced non-diffusive gas transport processes in soil often occur intermittently, the quantification of their contribution to soil gas emissions is challenging. To quantify the effects of wind-induced pressure-pumping on soil gas transport, we developed a method for in situ monitoring of soil gas transport. The method includes the use of Helium (He) as a tracer gas which was continuously injected into the soil. The resulting He steady-state concentration profile was monitored. Gas transport parameters of the soil were inversely modelled. We used our method during a field campaign in a well-aerated forest soil over three months. During periods of low wind speed, soil gas transport was modelled assuming diffusion as transport process. During periods of high wind speed, the previously steady diffusive He concentration profile showed temporary concentration decreases in the topsoil, indicating an increase of the effective gas transport rate in the topsoil up to 30%. The enhancement of effective topsoil soil gas diffusivity resulted from wind-induced air pressure fluctuations which are referred to as pressure-pumping. These air pressure fluctuations had frequencies between 0.1 and 0.01 Hz and amplitudes up to 10 Pa and occurred at above-canopy wind speeds greater than 5 m s-1. We could show the importance of the enhancement of the gas transport rate in relation with the wind intensity and corresponding air pressure fluctuations characteristics. We directly detected and quantified the pressure-pumping effect on gas transport in soil in a field study for the first time, and could thus validate and underpin the importance of this non

Variation of Magnetic Field (By , Bz Polarity and Statistical Analysis of Solar Wind Parameters during the Magnetic Storm Period

Directory of Open Access Journals (Sweden)

Ga-Hee Moon

2011-06-01

Full Text Available It is generally believed that the occurrence of a magnetic storm depends upon the solar wind conditions, particularly the southward interplanetary magnetic field (IMF component. To understand the relationship between solar wind parameters and magnetic storms, variations in magnetic field polarity and solar wind parameters during magnetic storms are examined. A total of 156 storms during the period of 1997~2003 are used. According to the interplanetary driver, magnetic storms are divided into three types, which are coronal mass ejection (CME-driven storms, co-rotating interaction region (CIR-driven storms, and complicated type storms. Complicated types were not included in this study. For this purpose, the manner in which the direction change of IMF By and Bz components (in geocentric solar magnetospheric coordinate system coordinate during the main phase is related with the development of the storm is examined. The time-integrated solar wind parameters are compared with the time-integrated disturbance storm time (Dst index during the main phase of each magnetic storm. The time lag with the storm size is also investigated. Some results are worth noting: CME-driven storms, under steady conditions of Bz < 0, represent more than half of the storms in number. That is, it is found that the average number of storms for negative sign of IMF Bz (T1~T4 is high, at 56.4%, 53.0%, and 63.7% in each storm category, respectively. However, for the CIR-driven storms, the percentage of moderate storms is only 29.2%, while the number of intense storms is more than half (60.0% under the Bz < 0 condition. It is found that the correlation is highest between the time-integrated IMF Bz and the time-integrated Dst index for the CME-driven storms. On the other hand, for the CIR-driven storms, a high correlation is found, with the correlation coefficient being 0.93, between time-integrated Dst index and time-integrated solar wind speed, while a low correlation, 0.51, is

A turn for the better? Innovative concepts for wind turbines

International Nuclear Information System (INIS)

De Vries, Eize

2001-01-01

This paper focuses on successful innovation in wind technology and describes the approach of Danish developers using a rigid, non-integrated, gear-driven transmission layout with 3 blades which is often viewed as the basis of the modern wind industry. Recent developments reviewed cover multi-rotor designs, hybrid designs, direct drive technology, variable speed operation, modular systems, high voltage systems, discoidal technology, and the diffuser augmented turbine

IDENTIFICATION OF WIND LOAD APPLIED TO THREE-DIMENSIONAL STRUCTURES BY VIRTUE OF ITS SIMULATION IN THE WIND TUNNEL

Directory of Open Access Journals (Sweden)

Doroshenko Sergey Aleksandrovich

2012-10-01

Full Text Available The authors discuss wind loads applied to a set of two buildings. The wind load is simulated with the help of the wind tunnel. In the Russian Federation, special attention is driven to the aerodynamics of high-rise buildings and structures. According to the Russian norms, identification of aerodynamic coefficients for high-rise buildings, as well as the influence of adjacent buildings and structures, is performed on the basis of models of structures exposed to wind impacts simulated in the wind tunnel. This article deals with the results of the wind tunnel test of buildings. The simulation was carried out with the involvement of a model of two twenty-three storied buildings. The experiment was held in a wind tunnel of the closed type at in the Institute of Mechanics of Moscow State University. Data were compared at the zero speed before and after the experiment. LabView software was used to process the output data. Graphs and tables were developed in the Microsoft Excel package. GoogleSketchUp software was used as a visualization tool. The three-dimensional flow formed in the wind tunnel can't be adequately described by solving the two-dimensional problem. The aerodynamic experiment technique is used to analyze the results for eighteen angles of the wind attack.

AGN Obscuration Through Dusty Infrared Dominated Flows. 1; Radiation-Hydrodynamics Solution for the Wind

Science.gov (United States)

Dorodnitsyn, A.; Bisnovatyi-Kogan. G. S.; Kallman, T.

2011-01-01

We construct a radiation-hydrodynamics model for the obscuring toroidal structure in active galactic nuclei. In this model the obscuration is produced at parsec scale by a dense, dusty wind which is supported by infrared radiation pressure on dust grains. To find the distribution of radiation pressure, we numerically solve the 2D radiation transfer problem in a flux limited diffusion approximation. We iteratively couple the solution with calculations of stationary 1D models for the wind, and obtain the z-component of the velocity. Our results demonstrate that for AGN luminosities greater than 0.1 L(sub edd) external illumination can support a geometrically thick obscuration via outflows driven by infrared radiation pressure. The terminal velocity of marginally Compton-thin models (0.2 infrared-driven winds is a viable option for the AGN torus problem and AGN unification models. Such winds can also provide an important channel for AGN feedback.

The sup(40,44,48)Ca(3He, 3He) and (3He, 4He) reactions at 50 MeV

International Nuclear Information System (INIS)

Griffiths, R.J.; Duggan, F.; Clarke, N.M.

1981-01-01

Measurements have been made of the ( 3 He, 3 He) and ( 3 He, 4 He) reactions on the isotopes of calcium 40 Ca, 44 Ca and 48 Ca at an energy of 50.4 MeV. The results have been analysed with conventional optical potentials and DWBA. The adequacy of the former and inadequacy of the latter for reactions with composite particles is discussed. (author)

Suprathermal He{sup 2+} in the Earth`s foreshock region

Energy Technology Data Exchange (ETDEWEB)

Fuselier, S.A. [Lockheed Palo Alto Research Lab., CA (United States); Thomsen, M.F. [Los Alamos National Lab., NM (United States); Ipavich, F.M. [Univ. of Maryland, College Park, MD (United States); Schmidt, W.K.H. [Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany)

1995-09-01

ISEE 1 and 2 H{sup +} and He{sup 2+} observations upstream from the Earth`s bow shock are used to investigate the origin of energetic (or diffuse) ion distributions. Diffuse ion distributions have energies from a few keV/e to > 100 keV/e and have near solar wind concentrations (i.e., an average of about 4% He{sup 2+}). These distributions may evolve from suprathermal ion distributions that have energies between 1 and a few keV/e. Upstream intervals were selected from the ISEE data to determine which suprathermal distributions have He{sup 2+} concentrations similar to those of diffuse ion distributions. The type of distribution and the location in the foreshock were similar in all events studied. Two intervals that represent the results from this study are discussed in detail. The results suggest that diffuse ion distributions evolve from suprathermal distributions in the region upstream from the quasi-parallel bow shock. For He{sup 2+}, the suprathermal distribution is a nongyrotropic partial ring beam and has characteristics consistent with specular reflection off the quasi-parallel bow shock. The suprathermal proton distributions associated with these He{sup 2+} distributions are nongyrotropic partial ring beams or nearly gyrotropic ring beams also approximately consistent with specular reflection. The location in the quasi-parallel foreshock and the similarity of the suprathermal He{sup 2+} and H{sup +} distributions suggest that these are the seed population for diffuse distributions in the foreshock region. 30 refs., 5 figs., 1 tab.

Role of the Coronal Alfvén Speed in Modulating the Solar-wind Helium Abundance

Science.gov (United States)

Wang, Y.-M.

2016-12-01

The helium abundance He/H in the solar wind is relatively constant at ˜0.04 in high-speed streams, but varies in phase with the sunspot number in slow wind, from ˜0.01 at solar minimum to ˜0.04 at maximum. Suggested mechanisms for helium fractionation have included frictional coupling to protons and resonant interactions with high-frequency Alfvénic fluctuations. We compare He/H measurements during 1995-2015 with coronal parameters derived from source-surface extrapolations of photospheric field maps. We find that the near-Earth helium abundance is an increasing function of the magnetic field strength and Alfvén speed v A in the outer corona, while being only weakly correlated with the proton flux density. Throughout the solar cycle, fast wind is associated with short-term increases in v A near the source surface; resonance with Alfvén waves, with v A and the relative speed of α-particles and protons decreasing with increasing heliocentric distance, may then lead to enhanced He/H at 1 au. The modulation of helium in slow wind reflects the tendency for the associated coronal Alfvén speeds to rise steeply from sunspot minimum, when this wind is concentrated around the source-surface neutral line, to sunspot maximum, when the source-surface field attains its peak strengths. The helium abundance near the source surface may represent a balance between collisional decoupling from protons and Alfvén wave acceleration.

Large-space cluster model calculations for the 3He(3He,2p)4He and 3H(3H,2n)4He reactions

International Nuclear Information System (INIS)

Csoto, Attila; Langanke, Karlheinz

1999-01-01

The 3 He( 3 He, 2p) 4 He and 3 H( 3 H, 2n) 4 He reactions are studied in a microscopic cluster model. We search for resonances in the 3 He+ 3 He and 4 He + p + p channels using methods that treat the two- and three-body resonance asymptotics correctly. Our results show that the existence of a low-energy resonance or virtual state, which could influence the 7 Be and 8 B solar neutrino fluxes, is rather unlikely. Our calculated 3 He( 3 He, 2p) 4 He and 3 H( 3 H, 2n) 4 He cross sections are in a good general agreement with the experimental data

Superfluidity of a dilute 3He-4He solution

International Nuclear Information System (INIS)

Soda, Toshio

1993-01-01

The interaction between two 3 He atoms is calculated by taking into account the backflow effect of 3 He by the 4 He in the 3 He- 4 He mixture. The effect contributes solely to the P wave part of the interaction. The repulsive S wave part of the contact interaction contributes to the exchange interaction between the 3 He atoms, while the direct one phonon exchange interaction contributes both to the S and P wave attractive interactions. The overall contribution to the attractive interaction is dominated by the P wave part and the superfluidity in the P wave is more predominant than in the S wave for the 5 % dilute 3 He- 4 He solution, and vice versa for the 1.3 % solution. (author)

Differential sensitivity to aphidicolin of replicative DNA synthesis and ultraviolet-induced unscheduled DNA synthesis in vivo in mammalian cells

International Nuclear Information System (INIS)

Seki, Shuji; Hosogi, Nobuo; Oda, Takuzo

1984-01-01

In vivo in mammalian cells, ultraviolet-induced unscheduled DNA synthesis was less sensitive to aphidicolin than was replicative DNA synthesis. Replicative DNA synthesis in HeLa, HEp-2, WI-38 VA-13 and CV-1 cells was inhibited more than 97 % by aphidicolin at 10 μg/ml, whereas aphidicolin inhibition of DNA synthesis in ultraviolet-irradiated cells varied between 30 % and 90 % depending on cell types and assay conditions. Aphidicolin inhibition of unscheduled DNA synthesis (UDS) in HeLa cells increased gradually with increasing aphidicolin concentration and reached approximately 90 % at 100 μg/ml aphidicolin. A significant fraction of UDS in ultraviolet-irradiated HEp-2 cells was resistant to aphidicolin even at 300 μg/ml. Considered along with related information reported previously, the present results suggest that both aphidicolin-sensitive and insensitive DNA polymerases, DNA polymerase α and a non-α DNA polymerase (possibly DNA polymerase β), are involved in in situ UDS in these ultraviolet-irradiated cells. Comparison of staphylococcal nuclease sensitivity between DNAs repaired in the presence and in the absence of aphidicolin in HEp-2 cells suggested that the involvement of DNA polymerase α in UDS favored DNA synthesis in the intranucleosomal region. (author)

Large scale wind power penetration in Denmark

DEFF Research Database (Denmark)

Karnøe, Peter

2013-01-01

he Danish electricity generating system prepared to adopt nuclear power in the 1970s, yet has become the world's front runner in wind power with a national plan for 50% wind power penetration by 2020. This paper deploys a sociotechnical perspective to explain the historical transformation...... of "networks of power" via the interactions of politics, the techno-physics of electrons, and the market setting. The Danish case is about how an assemblage of new agencies has reorganized and reshaped society by building a new sociotechnical network. This has rendered developments highly unpredictable...... and highly experimental. The transformation process can be followed through the way successive technical engineering reports have represented the challenges associated with the penetration of wind power. The iteration shows how novel technical phenomena emerge and are assimilated, and how new engineering...

Assessment of wind energy potential in China

Institute of Scientific and Technical Information of China (English)

Zhu Rong; Zhang De; Wang Yuedong; Xing Xuhuang; Li Zechun

2009-01-01

China wind atlas was made by numerical simulation and the wind energy potential in China was calculated. The model system for wind energy resource assessment was set up based on Canadian Wind Energy Simulating Toolkit (WEST) and the simulating method was as follows. First, the weather classes were obtained depend on meteorological data of 30 years. Then, driven by the initial meteorological field produced by each weather class, the meso-scale model ran for the distribution of wind energy resources according each weather class condition one by one. Finally, averaging all the modeling output weighted by the occurrence frequency of each weather class, the annual mean distribution of wind energy resources was worked out. Compared the simulated wind energy potential with other results from several ac-tivities and studies for wind energy resource assessment, it is found that the simulated wind energy potential in mainland of China is 3 times that from the second and the third investigations for wind energy resources by CMA, and is similar to the wind energy potential obtained by NREL in Solar and Wind Energy Resource Assessment (SWERA) project. The simulated offshore wind energy potential of China seems smaller than the true value. According to the simulated results of CMA and considering lots of limited factors to wind energy development, the final conclusion can be obtained that the wind energy availability in China is 700～1 200 GW, in which 600～1 000 GW is in mainland and 100～200 GW is on offshore, and wind power will become the important part of energy composition in future.

ROLE OF THE CORONAL ALFVÉN SPEED IN MODULATING THE SOLAR-WIND HELIUM ABUNDANCE

Energy Technology Data Exchange (ETDEWEB)

Wang, Y.-M., E-mail: yi.wang@nrl.navy.mil [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)

2016-12-20

The helium abundance He/H in the solar wind is relatively constant at ∼0.04 in high-speed streams, but varies in phase with the sunspot number in slow wind, from ∼0.01 at solar minimum to ∼0.04 at maximum. Suggested mechanisms for helium fractionation have included frictional coupling to protons and resonant interactions with high-frequency Alfvénic fluctuations. We compare He/H measurements during 1995–2015 with coronal parameters derived from source-surface extrapolations of photospheric field maps. We find that the near-Earth helium abundance is an increasing function of the magnetic field strength and Alfvén speed v {sub A} in the outer corona, while being only weakly correlated with the proton flux density. Throughout the solar cycle, fast wind is associated with short-term increases in v {sub A} near the source surface; resonance with Alfvén waves, with v {sub A} and the relative speed of α -particles and protons decreasing with increasing heliocentric distance, may then lead to enhanced He/H at 1 au. The modulation of helium in slow wind reflects the tendency for the associated coronal Alfvén speeds to rise steeply from sunspot minimum, when this wind is concentrated around the source-surface neutral line, to sunspot maximum, when the source-surface field attains its peak strengths. The helium abundance near the source surface may represent a balance between collisional decoupling from protons and Alfvén wave acceleration.

Wind pumps for agriculture: Cost and environmental benefits (comparisons with electric and combustion engine driven pumps)

International Nuclear Information System (INIS)

Piccoli, F.

1991-01-01

After describing initial and running costs of a group of wind-pumps, the author calculates and compares, as far as agricultural and zootechnical purposes are concerned, the costs for each cubic meter of water extracted through wind-powered, electric and internal-combustion engines. The comparisons clearly show, under adequate wind conditions, that wind-pumps are economically more suitable than electric and motor pumps with similar delivery heads

Development of a proof of concept low temperature 4He Superfluid Magnetic Pump

Science.gov (United States)

Jahromi, Amir E.; Miller, Franklin K.

2017-03-01

We describe the development and experimental results of a proof of concept Superfluid Magnetic Pump in this work. This novel low temperature, no moving part pump can replace the existing bellows-piston driven 4He or 3He-4He mixture compressor/circulators used in various sub Kelvin refrigeration systems such as dilution, Superfluid pulse tube, Stirling, or active magnetic regenerative refrigerators. Due to the superior thermal transport properties of sub-Lambda 4He this pump can also be used as a simple circulator to distribute cooling over large surface areas. Our pump was experimentally shown to produce a maximum flow rate of 440 mg/s (averaged over cycle), 665 mg/s (peak) and produced a maximum pressure difference of 2323 Pa using only the more common isotope of helium, 4He. This pump worked in an ;ideal; thermodynamic state: The experimental results matched with the theoretical values predicted by a computer model. Pump curves were developed to map the performance of this pump. This successful demonstration will enable this novel pump to be implemented in suitable sub Kelvin refrigeration systems.

Interspecies Ion Diffusion Studies using DT, DT(3He), and DT(H) Implosions

Science.gov (United States)

Kim, Y.; Herrmann, H. W.; Schmitt, M. J.; Kagan, G.; McEvoy, A. M.; Hoffman, N. M.; Gales, S.; Leatherland, A.; Gatu Johnson, M.; Frenje, J.; Glevov, V. Yu; Forrest, C.

2015-11-01

Anomalous ICF yield degradation has been observed from gas fills containing mixtures (i.e., D(3He), DT(3He), D(Ar), and even DT). Interspecies ion diffusion theory has been suggested as a possible cause resulting from gradient-driven diffusion (i.e., pressure, electric potential, and temperature) which forces lower mass ions away from core and higher mass ions toward core. The theory predicts hydrogen addition to deuterium or tritium should result in increased yield compared to expected yield, which is opposite to 3He addition. At Omega laser facility, we have tested hydro-equivalent fills of DT, DT(3He), and DT(H) with the assumption that same fuel mass and particle pressure will provide identical convergence. Preliminary results verify a factor of 2 yield reduction relative to scaling when 3He added to DT. At DT(H) case, however, no significant yield degradation or a slight yield enhancement was observed which agrees with the interspecies ion diffusion theory. Detailed experiment results and simulation are needed to confirm the initial observation.

Large wind ripples on Mars: A record of atmospheric evolution

Science.gov (United States)

Lapotre, M G; Ewing, R C; Lamb, M P; Fischer, W W; Grotzinger, J P; Rubin, D M; Lewis, K W; Ballard, M; Day, Mitch D.; Gupta, S.; Banham, S G; Bridges, N T; Des Marais, D J; Fraeman, A A; Grant, J A; Herkenhoff, Kenneth E.; Ming, D W; Mischna, M A; Rice, M S; Sumner, D A; Vasavada, A R; Yingst, R A

2016-01-01

Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter– to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere.

Large wind ripples on Mars: A record of atmospheric evolution

Science.gov (United States)

Lapotre, M. G. A.; Ewing, R. C.; Lamb, M. P.; Fischer, W. W.; Grotzinger, J. P.; Rubin, D. M.; Lewis, K. W.; Ballard, M. J.; Day, M.; Gupta, S.; Banham, S. G.; Bridges, N. T.; Des Marais, D. J.; Fraeman, A. A.; Grant, J. A.; Herkenhoff, K. E.; Ming, D. W.; Mischna, M. A.; Rice, M. S.; Sumner, D. A.; Vasavada, A. R.; Yingst, R. A.

2016-07-01

Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter- to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere.

Wind and waves: becoming serious Australian industries

International Nuclear Information System (INIS)

Anon

1999-01-01

Renewable energy is emerging as a critical policy issue in Australia following the Federal Government's 2% target for renewable energy. Adding to the potential for renewable energy in Victoria, Primergy in conjunction with its newly acquired subsidiary Renewable Energy Australia Pacific (REAP) Wind Pty Ltd has secured the exclusive license for the construction, operation and sale of, an advanced technology wind turbine throughout Australia and regional markets. Primergy believes that the potential market for wind generation in Australia could be between 500 to 800 MW or 700 to 1200 wind turbines. The company has also entered into a joint venture with Energetech and is funding 50% of the total cost to build the first wave machine which would be completed at Port Kembla, near Wollongong, by the end of 2000. The wave generator uses an innovative new concept incorporating an highly efficient air driven turbine

Wind wave source functions in opposing seas

KAUST Repository

Langodan, Sabique

2015-08-26

The Red Sea is a challenge for wave modeling because of its unique two opposed wave systems, forced by opposite winds and converging at its center. We investigate the different physical aspects of wave evolution and propagation in the convergence zone. The two opposing wave systems have similar amplitude and frequency, each driven by the action of its own wind. Wave patterns at the centre of the Red Sea, as derived from extensive tests and intercomparison between model and measured data, suggest that the currently available wave model source functions may not properly represent the evolution of the local fields that appear to be characterized by a less effective wind input and an enhanced white-capping. We propose and test a possible simple solution to improve the wave-model simulation under opposing winds and waves condition. This article is protected by copyright. All rights reserved.

Wind energy and spatial planning procedures; La programmation spatiale des projects eoliens

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-07-01

Wind turbines projects have been increasing, but some are very conflicted. May be it is a reason why some local authorities have to deal with different point of view, above the only energy question and including local specificity. To give local authorities the possibility to be implicated and to be in control of wind projects in their territory, wind spatial planning should permit to choose suitable areas and to optimize wind power development. In this context this synthesis presents the wind spatial planning in Finistere (France), the french regulation, some international experiences (Danish, Flemish, Walloon region, Dutch) and the different approaches of spatial planning. (A.L.B.)

Coordination of wind and water power. Better utilization of network and room for more wind power; Samkoeyring av vind- og vasskraft. Betre utnytting av nett og plass til meir vindkraft

Energy Technology Data Exchange (ETDEWEB)

Stensby, Kjell Erik; Hamnaberg, Haavard (eds.)

2011-01-15

The report describes the results of the simulation of coordination of wind power with Guolas hydro power plants in Troms. The simulations have been carried out by SINTEF Energy Research, and the purpose has been to consider to what degree it is possible to make room for more wind power in grid if the hydroelectric plant was driven with regard to wind power production. The results show that it is possible to make room for more wind power if it is granted 'priority' in the power grid. (AG)

SOLAR WIND PROTONS AT 1 AU: TRENDS AND BOUNDS, CONSTRAINTS AND CORRELATIONS

Energy Technology Data Exchange (ETDEWEB)

Hellinger, Petr; Trávníček, Pavel M., E-mail: petr.hellinger@asu.cas.cz [Astronomical Institute, AS CR, Bocni II/1401,CZ-14100 Prague (Czech Republic)

2014-03-20

The proton temperature anisotropy in the solar wind exhibits apparent bounds which are compatible with the theoretical constraints imposed by temperature-anisotropy-driven kinetic instabilities. Recent statistical analyses based on conditional averaging indicate that near these theoretical constraints the solar wind protons typically have enhanced temperatures and a weaker collisionality. Here we carefully analyze the solar wind data and show that these results are a consequence of superposition of multiple correlations in the solar wind, namely, they mostly result from the correlation between the proton temperature and the solar wind velocity and from the superimposed anti-correlation between the proton temperature anisotropy and the proton parallel beta in the fast solar wind. Colder and more collisional data are distributed around temperature isotropy whereas hotter and less collisional data have a wider range of the temperature anisotropy anti-correlated with the proton parallel beta with signatures of constraints owing to the temperature-anisotropy-driven instabilities. However, most of the hot and weakly collisional data, including the hottest and least collisional ones, lies far from the marginal stability regions. Consequently, we conclude that there is no clear relation between the enhanced temperatures and instability constraints and that the conditional averaging used for these analyses must be used carefully and need to be well tested.

Study of charge symmetry in 4He by simultaneous 4He(e,e'p)3H and 4He(e,e'n)3He measurements

International Nuclear Information System (INIS)

Spahn, M.; Kihm, T.; Knopfle, K.T.; Friedrich, J.; Voegler, N.; Schmitt, C.; Walther, V.H.; Unkelbach, M.; Hofmann, H.M.

1989-01-01

We have measured the ( 3 H+p) and ( 3 He+n) breakup of 4 He by 4 He(e,e'c) coincidence experiments at low momentum transfer (q∼0.39 fm -1 ) in the excitation energy region 22≤E x ≤36 MeV. Both channels were studied simultaneously by detecting the charged fragments c=p, 3 H, and 3 He in the same detector system. The measured 4 He(e,e'p) 3 H and 4 He(e,e'n) 3 He angular correlations as well as the deduced total 4 He(e,e'p) 3 H and 4 He(e,e'n) 3 He cross sections are reproduced by microscopic model calculations with a charge-symmetric nuclear Hamiltonian

Wind-Driven Erosion and Exposure Potential at Mars 2020 Rover Candidate-Landing Sites

Science.gov (United States)

Chojnacki, Matthew; Banks, Maria; Urso, Anna

2018-01-01

Aeolian processes have likely been the predominant geomorphic agent for most of Mars’ history and have the potential to produce relatively young exposure ages for geologic units. Thus, identifying local evidence for aeolian erosion is highly relevant to the selection of landing sites for future missions, such as the Mars 2020 Rover mission that aims to explore astrobiologically relevant ancient environments. Here we investigate wind-driven activity at eight Mars 2020 candidate-landing sites to constrain erosion potential at these locations. To demonstrate our methods, we found that contemporary dune-derived abrasion rates were in agreement with rover-derived exhumation rates at Gale crater and could be employed elsewhere. The Holden crater candidate site was interpreted to have low contemporary erosion rates, based on the presence of a thick sand coverage of static ripples. Active ripples at the Eberswalde and southwest Melas sites may account for local erosion and the dearth of small craters. Moderate-flux regional dunes near Mawrth Vallis were deemed unrepresentative of the candidate site, which is interpreted to currently be experiencing low levels of erosion. The Nili Fossae site displayed the most unambiguous evidence for local sand transport and erosion, likely yielding relatively young exposure ages. The downselected Jezero crater and northeast Syrtis sites had high-flux neighboring dunes and exhibited substantial evidence for sediment pathways across their ellipses. Both sites had relatively high estimated abrasion rates, which would yield young exposure ages. The downselected Columbia Hills site lacked evidence for sand movement, and contemporary local erosion rates are estimated to be relatively low. PMID:29568719

Wind-Driven Erosion and Exposure Potential at Mars 2020 Rover Candidate-Landing Sites

Science.gov (United States)

Chojnacki, Matthew; Banks, Maria; Urso, Anna

2018-02-01

Aeolian processes have likely been the predominant geomorphic agent for most of Mars' history and have the potential to produce relatively young exposure ages for geologic units. Thus, identifying local evidence for aeolian erosion is highly relevant to the selection of landing sites for future missions, such as the Mars 2020 Rover mission that aims to explore astrobiologically relevant ancient environments. Here we investigate wind-driven activity at eight Mars 2020 candidate-landing sites to constrain erosion potential at these locations. To demonstrate our methods, we found that contemporary dune-derived abrasion rates were in agreement with rover-derived exhumation rates at Gale crater and could be employed elsewhere. The Holden crater candidate site was interpreted to have low contemporary erosion rates, based on the presence of a thick sand coverage of static ripples. Active ripples at the Eberswalde and southwest Melas sites may account for local erosion and the dearth of small craters. Moderate-flux regional dunes near Mawrth Vallis were deemed unrepresentative of the candidate site, which is interpreted to currently be experiencing low levels of erosion. The Nili Fossae site displayed the most unambiguous evidence for local sand transport and erosion, likely yielding relatively young exposure ages. The downselected Jezero crater and northeast Syrtis sites had high-flux neighboring dunes and exhibited substantial evidence for sediment pathways across their ellipses. Both sites had relatively high estimated abrasion rates, which would yield young exposure ages. The downselected Columbia Hills site lacked evidence for sand movement, and contemporary local erosion rates are estimated to be relatively low.

Fundamental parameters of He-weak and He-strong stars

Science.gov (United States)

Cidale, L. S.; Arias, M. L.; Torres, A. F.; Zorec, J.; Frémat, Y.; Cruzado, A.

2007-06-01

Context: He-weak and He-strong stars are chemically peculiar AB objects whose He lines are anomalously weak or strong for their MK spectral type. The determination of fundamental parameters for these stars is often more complex than for normal stars due to their abundance anomalies. Aims: We discuss the determination of fundamental parameters: effective temperature, surface gravity, and visual and bolometric absolute magnitudes of He-weak and He-strong stars. We compare our values with those derived independently from methods based on photometry and model fitting. Methods: We carried out low resolution spectroscopic observations in the wavelength range 3400-4700 Å of 20 He-weak and 8 He-strong stars to determine their fundamental parameters by means of the Divan-Chalonge-Barbier (BCD) spectrophotometric system. This system is based on the measurement of the continuum energy distribution around the Balmer discontinuity (BD). For a few He-weak stars we also estimate the effective temperatures and the angular diameters by integrating absolute fluxes observed over a wide spectral range. Non-LTE model calculations are carried out to study the influence of the He/H abundance ratio on the emergent radiation of He-strong stars and on their T_eff determination. Results: We find that the effective temperatures, surface gravities and bolometric absolute magnitudes of He-weak stars estimated with the BCD system and the integrated flux method are in good agreement between each other, and they also agree with previous determinations based on several different methods. The mean discrepancy between the visual absolute magnitudes derived using the hipparcos parallaxes and the BCD values is on average ±0.3 mag for He-weak stars, while it is ±0.5 mag for He-strong stars. For He-strong stars, we note that the BCD calibration, based on stars in the solar environment, leads to overestimated values of T_eff. By means of model atmosphere calculations with enhanced He/H abundance ratios

Spectrum and light curve of a supernova shock breakout through a thick Wolf-Rayet wind

Energy Technology Data Exchange (ETDEWEB)

Svirski, Gilad; Nakar, Ehud, E-mail: swirskig@post.tau.ac.il [Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)

2014-06-20

Wolf-Rayet stars are known to eject winds. Thus, when a Wolf-Rayet star explodes as a supernova, a fast (≳ 40, 000 km s{sup –1}) shock is expected to be driven through a wind. We study the signal expected from a fast supernova shock propagating through an optically thick wind and find that the electrons behind the shock driven into the wind are efficiently cooled by inverse Compton over soft photons that were deposited by the radiation-mediated shock that crossed the star. Therefore, the bolometric luminosity is comparable to the kinetic energy flux through the shock, and the spectrum is found to be a power law, whose slope and frequency range depend on the number flux of soft photons available for cooling. Wolf-Rayet supernovae that explode through a thick wind have a high flux of soft photons, producing a flat spectrum, νF {sub ν} = Const, in the X-ray range of 0.1 ≲ T ≲ 50 keV. As the shock expands into an optically thin wind, the soft photons are no longer able to cool the shock that plows through the wind, and the bulk of the emission takes the form of a standard core-collapse supernova (without a wind). However, a small fraction of the soft photons is upscattered by the shocked wind and produces a transient unique X-ray signature.

Spectrum and light curve of a supernova shock breakout through a thick Wolf-Rayet wind

International Nuclear Information System (INIS)

Svirski, Gilad; Nakar, Ehud

2014-01-01

Wolf-Rayet stars are known to eject winds. Thus, when a Wolf-Rayet star explodes as a supernova, a fast (≳ 40, 000 km s –1 ) shock is expected to be driven through a wind. We study the signal expected from a fast supernova shock propagating through an optically thick wind and find that the electrons behind the shock driven into the wind are efficiently cooled by inverse Compton over soft photons that were deposited by the radiation-mediated shock that crossed the star. Therefore, the bolometric luminosity is comparable to the kinetic energy flux through the shock, and the spectrum is found to be a power law, whose slope and frequency range depend on the number flux of soft photons available for cooling. Wolf-Rayet supernovae that explode through a thick wind have a high flux of soft photons, producing a flat spectrum, νF ν = Const, in the X-ray range of 0.1 ≲ T ≲ 50 keV. As the shock expands into an optically thin wind, the soft photons are no longer able to cool the shock that plows through the wind, and the bulk of the emission takes the form of a standard core-collapse supernova (without a wind). However, a small fraction of the soft photons is upscattered by the shocked wind and produces a transient unique X-ray signature.

FAST TRACK COMMUNICATION: Recombination of H+3 ions in the afterglow of a He Ar H2 plasma

Science.gov (United States)

Glosik, J.; Korolov, I.; Plasil, R.; Novotny, O.; Kotrik, T.; Hlavenka, P.; Varju, J.; Mikhailov, I. A.; Kokoouline, V.; Greene, Chris H.

2008-10-01

Recombination of H+3 with electrons is studied in a low-temperature plasma containing He, H2 and Ar at different He and H2 densities. The effective plasma recombination rate is driven by binary, H+3 + e-, and ternary, H+3 + e-+ He, processes with the rate coefficients 7.5 × 10-8 cm3 s-1 and 2.8 × 10-25 cm6 s-1 respectively at 260 K. We suggest that the ternary recombination involves formation of neutral highly excited Rydberg H3 followed by an l-changing collision with He. The difference between recombination of para- and ortho-H+3 is discussed.

Ab initio study of He-He interactions in homogeneous electron gas

Energy Technology Data Exchange (ETDEWEB)

Wang, Jinlong; Niu, Liang-Liang; Zhang, Ying, E-mail: zhyi@buaa.edu.cn

2017-02-15

Highlights: • Helium atoms interact via the He induced Friedel oscillations of electron densities. • He-He global binding energy minimum of ∼−0.09 eV is reached at an optimal electron density of 0.04 e/Å{sup 3}, corresponding to an optimal He-He separation of ∼1.7 Å. • The present results can qualitatively interpret the well-known He self-trapping behavior in metals. - Abstract: We have investigated the immersion energy of a single He and the He-He interactions in homogeneous electron gas using ab initio calculations. It is found that He dislikes electrons and He-He interact via the He induced Friedel oscillations of electron densities. A critical electron density at which the global binding energy extremum shifts from the first minimum to the second one is identified. We also discover that the He-He global binding energy minimum of ∼−0.09 eV is reached at an optimal electron density of 0.04 e/Å{sup 3}, corresponding to an optimal He-He separation of ∼1.7 Å. Further, the He atoms are found to gain a trivial amount of 2s and 2p states from the free electrons, inducing a hybridization between the He s- and p-states. The present results can qualitatively interpret the well-known He self-trapping behavior in metals.

The Accretion Disk Wind in the Black Hole GRS 1915 + 105

Science.gov (United States)

Miller, J.M.; Raymond, J.; Fabian, A. C.; Gallo, E.; Kaastra, J.; Kallman, T.; King, A. L.; Proga, D.; Reynolds, C. S.; Zoghbi, A.

2016-01-01

We report on a 120 kiloseconds Chandra/HETG spectrum of the black hole GRS 1915+105. The observation was made during an extended and bright soft state in 2015 June. An extremely rich disk wind absorption spectrum is detected, similar to that observed at lower sensitivity in 2007. The very high resolution of the third-order spectrum reveals four components to the disk wind in the Fe K band alone; the fastest has a blueshift of v = 0.03 c (velocity equals 0.03 the speed of light). Broadened reemission from the wind is also detected in the first-order spectrum, giving rise to clear accretion disk P Cygni profiles. Dynamical modeling of the re-emission spectrum gives wind launching radii of r approximately equal to 10 (sup 2-4) GM (Gravitational constant times Mass) divided by c (sup 2) (the speed of light squared). Wind density values of n approximately equal to 10 (sup 13-16) per cubic centimeter are then required by the ionization parameter formalism. The small launching radii, high density values, and inferred high mass outflow rates signal a role for magnetic driving. With simple, reasonable assumptions, the wind properties constrain the magnitude of the emergent magnetic field to be B approximately equal to 10 (sup 3-4) G (Gravitational constant) if the wind is driven via magnetohydrodynamic (MHD) pressure from within the disk and B approximately equal to 10 (sup 4-5) G (Gravitational constant) if the wind is driven by magnetocentrifugal acceleration. The MHD estimates are below upper limits predicted by the canonical alpha-disk model. We discuss these results in terms of fundamental disk physics and black hole accretion modes.

The 3' untranslated region of the cyclin B mRNA is not sufficient to enhance the synthesis of cyclin B during a mitotic block in human cells.

Directory of Open Access Journals (Sweden)

Dominik Schnerch

Full Text Available Antimitotic agents are frequently used to treat solid tumors and hematologic malignancies. However, one major limitation of antimitotic approaches is mitotic slippage, which is driven by slow degradation of cyclin B during a mitotic block. The extent to which cyclin B levels decline is proposed to be governed by an equilibrium between cyclin B synthesis and degradation. It was recently shown that the 3' untranslated region (UTR of the murine cyclin B mRNA contributes to the synthesis of cyclin B during mitosis in murine cells. Using a novel live-cell imaging-based technique allowing us to study synthesis and degradation of cyclin B simultaneously at the single cell level, we tested here the role of the human cyclin B 3'UTR in regulating cyclin B synthesis during mitosis in human cells. We observed that the cyclin B 3'UTR was not sufficient to enhance cyclin B synthesis in human U2Os, HeLa or hTERT RPE-1 cells. A better understanding of how the equilibrium of cyclin B is regulated in mitosis may contribute to the development of improved therapeutic approaches to prevent mitotic slippage in cancer cells treated with antimitotic agents.

Wind, Sun and Water: Complexities of Alternative Energy Development in Rural Northern Peru

Science.gov (United States)

Love, Thomas; Garwood, Anna

2011-01-01

Drawing on recent research with NGO-driven projects in rural Cajamarca, Peru, we examine the paradoxes of relying on wind, solar and micro-hydro generation of electricity for rural community development. In spite of cost, vagaries of these energy resources and limited material benefits, especially with wind and solar systems, villagers are eagerly…

The Physics of Wind-Fed Accretion

International Nuclear Information System (INIS)

Mauche, Christopher W.; Liedahl, Duane A.; Akiyama, Shizuka; Plewa, Tomasz

2008-01-01

We provide a brief review of the physical processes behind the radiative driving of the winds of OB stars and the Bondi-Hoyle-Lyttleton capture and accretion of a fraction of the stellar wind by a compact object, typically a neutron star, in detached high-mass X-ray binaries (HMXBs). In addition, we describe a program to develop global models of the radiatively-driven photoionized winds and accretion flows of HMXBs, with particular attention to the prototypical system Vela X-l. The models combine XSTAR photoionization calculations, HULLAC emission models appropriate to X-ray photoionized plasmas, improved models of the radiative driving of photoionized winds, FLASH time-dependent adaptive-mesh hydrodynamics calculations, and Monte Carlo radiation transport. We present two- and three-dimensional maps of the density, temperature, velocity, ionization parameter, and emissivity distributions of representative X-ray emission lines, as well as synthetic global Monte Carlo X-ray spectra. Such models help to better constrain the properties of the winds of HMXBs, which bear on such fundamental questions as the long-term evolution of these binaries and the chemical enrichment of the interstellar medium.

Stochastic model for joint wave and wind loads on offshore structures

DEFF Research Database (Denmark)

Ditlevsen, Ove Dalager

2002-01-01

_s,T_z)$ from the North Sea a well fitting joint distribution of $(H_s,T_z)$ is obtained as a so-called Nataf model. Since the wave field is wind driven, there is a correlation between the time averaged wind velocity pressure $Q$ and the characteristic wave height in the stationary situation. Using the Poisson...... process model to concentrate on those load events that are of importance for the evaluation of the safety of the structure, that is, events with $Q$ larger than some threshold $q_0$, available information about the wind velocity pressure distributionin high wind situations can be used to formulate a Nataf...

The cosmological density of baryons from observations of 3He+ in the Milky Way.

Science.gov (United States)

Bania, T M; Rood, Robert T; Balser, Dana S

2002-01-03

Primordial nucleosynthesis after the Big Bang can be constrained by the abundances of the light elements and isotopes 2H, 3He, 4He and 7Li (ref. 1). The standard theory of stellar evolution predicts that 3He is also produced by solar-type stars, so its abundance is of interest not only for cosmology, but also for understanding stellar evolution and the chemical evolution of the Galaxy. The 3He abundance in star-forming (H II) regions agrees with the present value for the local interstellar medium, but seems to be incompatible with the stellar production rates inferred from observations of planetary nebulae, which provide a direct test of stellar evolution theory. Here we develop our earlier observations, which, when combined with recent theoretical developments in our understanding of light-element synthesis and destruction in stars, allow us to determine an upper limit for the primordial abundance of 3He relative to hydrogen: 3He/H = (1.1 +/- 0.2) x 10(-5). The primordial density of all baryons determined from the 3He data is in excellent agreement with the densities calculated from other cosmological probes. The previous conflict is resolved because most solar-mass stars do not produce enough 3He to enrich the interstellar medium significantly.