Deformation behavior of curling strips on tearing tubes

Energy Technology Data Exchange (ETDEWEB)

Choi, Ji Won; Kwon, Tae Soo; Jung, Hyun Seung; Kim, Jin Sung [Dept. of Robotics and Virtual Engineering, Korea University of Science and Technology, Seoul (Korea, Republic of)

2015-10-15

This paper discusses the analysis of the curl deformation behavior when a dynamic force is applied to a tearing tube installed on a flat die to predict the energy absorption capacity and deformation behavior. The deformation of the tips of the curling strips was obtained when the curl tips and tube body are in contact with each other, and a formula describing the energy dissipation rate caused by the deformation of the curl tips is proposed. To improve this formula, we focused on the variation of the curl radius and the reduced thickness of the tube. A formula describing the mean curl radius is proposed and verified using the curl radius measurement data of collision test specimens. These improved formulas are added to the theoretical model previously proposed by Huang et al. and verified from the collision test results of a tearing tube.

Southern Ocean carbon-wind stress feedback

Science.gov (United States)

Bronselaer, Ben; Zanna, Laure; Munday, David R.; Lowe, Jason

2018-02-01

The Southern Ocean is the largest sink of anthropogenic carbon in the present-day climate. Here, Southern Ocean pCO2 and its dependence on wind forcing are investigated using an equilibrium mixed layer carbon budget. This budget is used to derive an expression for Southern Ocean pCO2 sensitivity to wind stress. Southern Ocean pCO2 is found to vary as the square root of area-mean wind stress, arising from the dominance of vertical mixing over other processes such as lateral Ekman transport. The expression for pCO2 is validated using idealised coarse-resolution ocean numerical experiments. Additionally, we show that increased (decreased) stratification through surface warming reduces (increases) the sensitivity of the Southern Ocean pCO2 to wind stress. The scaling is then used to estimate the wind-stress induced changes of atmospheric pCO_2 in CMIP5 models using only a handful of parameters. The scaling is further used to model the anthropogenic carbon sink, showing a long-term reversal of the Southern Ocean sink for large wind stress strength.

Non-Euclidean stress-free configuration of arteries accounting for curl of axial strips sectioned from vessels.

Science.gov (United States)

Takamizawa, Keiichi; Nakayama, Yasuhide

2013-11-01

It is well known that arteries are subject to residual stress. In earlier studies, the residual stress in the arterial ring relieved by a radial cut was considered in stress analysis. However, it has been found that axial strips sectioned from arteries also curled into arcs, showing that the axial residual stresses were relieved from the arterial walls. The combined relief of circumferential and axial residual stresses must be considered to accurately analyze stress and strain distributions under physiological loading conditions. In the present study, a mathematical model of a stress-free configuration of artery was proposed using Riemannian geometry. Stress analysis for arterial walls under unloaded and physiologically loaded conditions was performed using exponential strain energy functions for porcine and human common carotid arteries. In the porcine artery, the circumferential stress distribution under physiological loading became uniform compared with that without axial residual strain, whereas a gradient of axial stress distribution increased through the wall thickness. This behavior showed almost the same pattern that was observed in a recent study in which approximate analysis accounting for circumferential and axial residual strains was performed, whereas the circumferential and axial stresses increased from the inner surface to the outer surface under a physiological condition in the human common carotid artery of a two-layer model based on data of other recent studies. In both analyses, Riemannian geometry was appropriate to define the stress-free configurations of the arterial walls with both circumferential and axial residual strains.

Tomato yellow leaf curl virus infection mitigates the heat stress response of plants grown at high temperatures

Science.gov (United States)

Ghandi, Anfoka; Adi, Moshe; Lilia, Fridman; Linoy, Amrani; Or, Rotem; Mikhail, Kolot; Mouhammad, Zeidan; Henryk, Czosnek; Rena, Gorovits

2016-01-01

Cultured tomatoes are often exposed to a combination of extreme heat and infection with Tomato yellow leaf curl virus (TYLCV). This stress combination leads to intense disease symptoms and yield losses. The response of TYLCV-susceptible and resistant tomatoes to heat stress together with viral infection was compared. The plant heat-stress response was undermined in TYLCV infected plants. The decline correlated with the down-regulation of heat shock transcription factors (HSFs) HSFA2 and HSFB1, and consequently, of HSF-regulated genes Hsp17, Apx1, Apx2 and Hsp90. We proposed that the weakened heat stress response was due to the decreased capacity of HSFA2 to translocate into the nuclei of infected cells. All the six TYLCV proteins were able to interact with tomato HSFA2 in vitro, moreover, coat protein developed complexes with HSFA2 in nuclei. Capturing of HSFA2 by viral proteins could suppress the transcriptional activation of heat stress response genes. Application of both heat and TYLCV stresses was accompanied by the development of intracellular large protein aggregates containing TYLCV proteins and DNA. The maintenance of cellular chaperones in the aggregated state, even after recovery from heat stress, prevents the circulation of free soluble chaperones, causing an additional decrease in stress response efficiency. PMID:26792235

The sports science of curling: a practical review.

Science.gov (United States)

Bradley, John L

2009-01-01

Curling is a sport played on ice in which two teams each deliver 8 granite stones towards a target, or 'house'. It is the only sport in which the trajectory of the projectile can be influenced after it has been released by the athlete. This is achieved by sweeping the ice in front of the stone to change the stone-ice friction and thereby enable to stone to travel further, curl more or stay straight. Hard sweeping is physically demanding. Different techniques of sweeping can also have different effects on the stone. This paper will review the current research behind sweeping a curling stone, outline the physiological demands of sweeping, the associated performance effects and suggest potential strategies of sweeping that can be used by both coaches and curling teams. Key pointsSweeping a curling stone can be highly physically demanding.Effective sweeping requires a combination of downward force and brush head speed, determined by the stone velocity.Sweeping on the left or right of a stone can help the stone to remain straight or curl more depending on the rotation of the stone.This can lead to the development of sweeping and playing tactics and contribute to team selection.

Enhancement of wind stress evaluation method under storm conditions

Science.gov (United States)

Chen, Yingjian; Yu, Xiping

2016-12-01

Wind stress is an important driving force for many meteorological and oceanographical processes. However, most of the existing methods for evaluation of the wind stress, including various bulk formulas in terms of the wind speed at a given height and formulas relating the roughness height of the sea surface with wind conditions, predict an ever-increasing tendency of the wind stress coefficient as the wind speed increases, which is inconsistent with the field observations under storm conditions. The wave boundary layer model, which is based on the momentum and energy conservation, has the advantage to take into account the physical details of the air-sea interaction process, but is still invalid under storm conditions without a modification. By including the energy dissipation due to the presence of sea spray, which is speculated to be an important aspect of the air-sea interaction under storm conditions, the wave boundary layer model is improved in this study. The improved model is employed to estimate the wind stress caused by an idealized tropical cyclone motion. The computational results show that the wind stress coefficient reaches its maximal value at a wind speed of about 40 m/s and decreases as the wind speed further increases. This is in fairly good agreement with the field data.

Wind impact on the Black Sea ecosystem

Science.gov (United States)

Stanichny, Sergey; Ratner, Yuriy; Shokurov, Mike; Stanychna, Rimma; Soloviev, Dmytro; Burdyugov, Vyacheslav

2010-05-01

Combination of the recent satellite and meteorological data for the regional investigation allowed to describe new features of the processes in marine ecosystem and detect some relations with wind variability for different time scales. Next topics are highlighted in presentation: 1. Inter-annual variability of the wind stress curl over the Black Sea. Shift in the atmospheric processes after 2003 year and related variations in chlorophyll concentration and intensity of the mesoscale currents. 2. Like-tropical cyclone in September 2005 and its impact o the Black Sea upper layer. 3. Strong storm November 11, 2007 and oil pollutions of the Kerch Strait. 4. Relation of the Danube waters transport with wind fields for summer 2007 and 2008. 5. "Valley" wind in the Eastern part of the Black Sea and its impact on the Rim current formation. 6. Low wind conditions and blue -green algae bloom. NCEP, SKIRON and MHI MM5 wind data together with AVHRR, MODIS, MERIS, ETM+, QuikSCAT, ASAR (ESA) satellite data were used for investigation. Work was done with support of the SESAME FP7, "Stable Ecosystem" and Operational Oceanography NASU projects.

Swept Away: Exploring the Physics of Curling

Science.gov (United States)

Esser, Liza

2011-01-01

Studying the Olympic sport of curling is a fun and engaging way to learn about the concepts of friction, forces, momentum, and Newton's laws. Each winter, the author takes her eighth-grade physical science class on a field trip to experience curling firsthand. This field trip has become a favorite of the eighth graders at Capitol Hill Day School…

Gene expression in response to Cotton Leaf Curl Virus infection in Gossypium hirsutum under variable environmental conditions

Directory of Open Access Journals (Sweden)

Rehman Iqra

2017-01-01

Full Text Available Cotton Leaf Curl Disease (CLCuD is one of the threatening constrains of cotton production in Pakistan for which no adequate remedy is available until now. Local variety of Gossypium hirsutum (FH-142 was grown in field and infected naturally by CLCuV under variable range of temperature and humidity. Plants showed thickening of veins in lower leaf surface at 34°C and 60% relative humidity at 15days post infection (dpi and curling of leaf margins at 33°C with 58% relative humidity at 30dpi. Remarkable leaf darkening was observed with reduced boll formation at 45dpi at 26°C and 41% relative humidity. Enation developed, severe thickening and curling of leaves intensified and plants showed dwarf growth at 60dpi at 24°C with 52% relative humidity. PCR amplification of Rep associated gene confirmed the presence of CLCuD-associated begomovirus in the infected samples. Quantitative RT-PCR confirmed the amplification and differential expression of a number of pathogen stress responsive genes at different levels of temperature and humidity. This observation predicts that Cotton Leaf Curl Virus (CLCuV interacts with several host genes that are upregulated to make plants susceptible or suppress other genes to overcome host defense responses.

Curls of My Dreams.

Science.gov (United States)

Greenman, Geri

2001-01-01

Describes an art activity in which students draw ribbons (thin watercolor paper that, when torn, will stand up in a curling fashion). Explains in detail the assignment in which students used pencil rendering or charcoal pencil depending on the type of paper used for the assignment. (CMK)

Seasonal controls on surface pCO2 in the central and eastern ...

Indian Academy of Sciences (India)

, low-level atmospheric. Findlater Jet (Findlater 1969, 1974) generates strong gradients in the wind stress over the Arabian Sea. To the northwest of the jet axis, a positive wind stress curl drives divergence (open-ocean upwelling) through.

Variation of air--water gas transfer with wind stress and surface viscoelasticity

OpenAIRE

Frew, Nelson M.; Bock, Erik J.; McGillis, Wade R.; Karachintsev, Andrey V.; Hara, Tetsu; Münsterer, Thomas; Jähne, Bernd

1995-01-01

Previous parameterizations of gas transfer velocity have attempted to cast this quantity as a function of wind speed or wind-stress. This study demonstrates that the presence of a surface film is effective at reducing the gas transfer velocity at constant wind-stress. Gas exchange experiments were performed at WHOI and UH using annular wind-wave tanks of different scales. Systematic variations of wind-stress and surfactant concentration (Triton-X-100) were explored to determ...

Wind stress over the Arabian Sea from ship reports and Seasat scatterometer data

Science.gov (United States)

Perigaud, C.; Minster, J. F.; Delecluse, P.

1989-01-01

Seasat scatterometer data over the Arabian Sea are used to build wind-stress fields during July and August 1978. They are first compared with 3-day wind analyses from ship data along the Somali coast. Seasat scatterometer specifications of 2-m/s and 20-deg accuracy are fulfilled in almost all cases. The exceptions are for winds stronger than 14 m/s, which are underestimated by the scatterometer by 15 percent. Wind stress is derived from these wind data using a bulk formula with a drag coefficient depending on the wind intensity. A successive-correction objective analysis is used to build the wind-stress field over the Arabian Sea with 2 x 2-deg and 6-day resolution. The final wind-stress fields are not significantly dependent on the objective analysis because of the dense coverage of the scatterometer. The combination of scatterometer and coastal ship data gives the best coverage to resolve monsoon wind structures even close to the coast. The final wind stress fields show wind features consistent with other monthly mean wind stress field. However, a high variability is observed on the 6-day time scale.

Stress analysis of composite wind turbine blade by finite element method

Science.gov (United States)

Yeh, Meng-Kao; Wang, Chen-Hsu

2017-10-01

In this study, the finite element analysis software ANSYS was used to analyze the composite wind turbine blade. The wind turbine blade model used is adopted from the 5 MW model of US National Renewable Energy Laboratory (NREL). The wind turbine blade is a sandwich structure, comprising outermost carbon fiber cloth/epoxy composites, the inner glass fiber/vinylester layers, and PVC foam core, together with stiffeners. The wind pressure is converted into the load on the blade structure. The stress distribution and deformation of wind turbine blade were obtained by considering different pitch angles and at different angular positions. The Tsai-Hill criterion was used to determine the failure of wind turbine blade. The results show that at the 0° pitch angle, the wind turbine blade is subjected to the largest combined load and therefore the stress is the largest; with the increasing pitch angle, the load gradually decreases and the stress is also smaller. The stress and displacement are the greatest when the wind blade is located at 120° angular position from its highest vertex.

Effects of Cross-axis Wind Jet Events on the Northern Red Sea Circulation

Science.gov (United States)

Menezes, V. V.; Bower, A. S.; Farrar, J. T.

2016-12-01

Despite its small size, the Red Sea has a complex circulation. There are boundary currents in both sides of the basin, a meridional overturning circulation, water mass formation in the northern part and an intense eddy activity. This complex pattern is driven by strong air-sea interactions. The Red Sea has one of the largest evaporation rates of the global oceans (2m/yr), an intricate and seasonally varying wind pattern. The winds blowing over the Northern Rea Sea (NRS, north of 20N) are predominantly southeastward along the main axis all year round; in the southern, they reverse seasonally due to the monsoonal regime. Although the winds are mostly along-axis in the NRS, several works have shown that sometimes during the boreal winter, the winds blow in a cross-axis direction. The westward winds from Saudi Arabia bring relatively cold dry air and dust from the desert, enhancing heat loss and evaporation off the Red Sea. These wind-jet events may contribute to increased eddy activity and are a trigger for water mass formation. Despite that, our knowledge about the cross-axis winds and their effect on NRS circulation is still incipient. In the present work we analyze 10-years of Quikscat scatterometer winds and altimetric sea surface height anomalies, together with 2-yrs of mooring data, to characterize the westward wind jet events and their impacts on the circulation. We show that the cross-axis winds are, indeed, an important component of the wind regime, explaining 11% of wind variability of the NRS (well-described by a 2nd EOF mode). The westward events occur predominantly in the winter, preferentially in January (about 15 events in 10-years) and have a mean duration of 4-5 days, with a maximum of 12 days (north of 22N). There are around 6 events per year, but in 2002-2003 and 2007-2008, twice more events were detected. The westward wind events are found to strongly modify the wind stress curl, causing a distinct positive/negative curl pattern along the main axis

Classical dynamics with curl forces, and motion driven by time-dependent flux

International Nuclear Information System (INIS)

Berry, M V; Shukla, Pragya

2012-01-01

For position-dependent forces whose curl is non-zero (‘curl forces’), there is no associated scalar potential and therefore no obvious Hamiltonian or Lagrangean and, except in special cases, no obvious conserved quantities. Nevertheless, the motion is nondissipative (measure-preserving in position and velocity). In a class of planar motions, some of which are exactly solvable, the curl force is directed azimuthally with a magnitude varying with radius, and the orbits are usually spirals. If the curl is concentrated at the origin (for example, the curl force could be an electric field generated by a changing localized magnetic flux, as in the betatron), a Hamiltonian does exist but violates the rotational symmetry of the force. In this case, reminiscent of the Aharonov–Bohm effect, the spiralling is extraordinarily slow. (paper)

The Curl of a Vector Field: Beyond the Formula

Science.gov (United States)

Burch, Kimberly Jordan; Choi, Youngna

2006-01-01

It has been widely acknowledged that there is some discrepancy in the teaching of vector calculus in mathematics courses and other applied fields. The curl of a vector field is one topic many students can calculate without understanding its significance. In this paper, we explain the origin of the curl after presenting the standard mathematical…

Wind Stress Variability Observed Over Coastal Waters

Science.gov (United States)

Ortiz-Suslow, D. G.; Haus, B. K.; Laxague, N.; Williams, N. J.; Graber, H. C.

2016-02-01

The wind stress on the ocean surface generates waves, drives currents, and enhances gas exchange; and a significant amount of work has been done to characterize the air-sea momentum flux in terms of bulk oceanographic and atmospheric parameters. However, the majority of this work to develop operational algorithms has been focused on the deep ocean and the suitability of these methods in the coastal regime has not been evaluated. The findings from a two-part field campaign will be presented which highlight the divergence of nearshore wind stress observations from conventional, deep water results. The first set of data comes from a coastal region near a relatively small, natural tidal inlet. A high degree of spatial variability was observed in both the wind stress magnitude and direction, suggestive of coastal processes (e.g., depth-limited wave affects and horizontal current shear) modulating the momentum flux from the atmosphere to the ocean surface. These shallow-water processes are typically not accounted for in conventional parameterizations. Across the experimental domain and for a given wind speed, the stress magnitude was found to be nearly 2.5 times that predicted by conventional methods; also, a high propensity for stress steering off the mean azimuthal wind direction (up to ±70 degrees) was observed and linked to horizontal current gradients produced by the tidal inlet. The preliminary findings from a second data set taken in the vicinity of the macrotidal Columbia River Mouth will also be presented. Compared to the first data set, a similar degree of variability is observed here, but the processes responsible for this are present at a much larger scale. Specifically, the Columbia River Mouth observations were made in the presence of significant swell wave energy and during periods of very high estuarine discharge. The relative angle between the wind and swell direction is expected to be significant with regards to the observed momentum flux. Also, these

Suppressors of RNA silencing encoded by tomato leaf curl

Indian Academy of Sciences (India)

Whitefly-transmitted begomoviruses infecting tomato crop code for five different proteins, ORF AC4, ORF AC2 and ORF AV2 in DNA-A component, ORF BV1 in DNA-B ... In the present study suppressor function of ORF C1 of three betasatellites Tomato leaf curl Bangalore betasatellite ToLCBB-[IN:Hess:08], Cotton leaf curl ...

From monsoon to marine productivity in the Arabian Sea: insights from glacial and interglacial climates

Science.gov (United States)

Le Mézo, Priscilla; Beaufort, Luc; Bopp, Laurent; Braconnot, Pascale; Kageyama, Masa

2017-07-01

The current-climate Indian monsoon is known to boost biological productivity in the Arabian Sea. This paradigm has been extensively used to reconstruct past monsoon variability from palaeo-proxies indicative of changes in surface productivity. Here, we test this paradigm by simulating changes in marine primary productivity for eight contrasted climates from the last glacial-interglacial cycle. We show that there is no straightforward correlation between boreal summer productivity of the Arabian Sea and summer monsoon strength across the different simulated climates. Locally, productivity is fuelled by nutrient supply driven by Ekman dynamics. Upward transport of nutrients is modulated by a combination of alongshore wind stress intensity, which drives coastal upwelling, and by a positive wind stress curl to the west of the jet axis resulting in upward Ekman pumping. To the east of the jet axis there is however a strong downward Ekman pumping due to a negative wind stress curl. Consequently, changes in coastal alongshore stress and/or curl depend on both the jet intensity and position. The jet position is constrained by the Indian summer monsoon pattern, which in turn is influenced by the astronomical parameters and the ice sheet cover. The astronomical parameters are indeed shown to impact wind stress intensity in the Arabian Sea through large-scale changes in the meridional gradient of upper-tropospheric temperature. However, both the astronomical parameters and the ice sheets affect the pattern of wind stress curl through the position of the sea level depression barycentre over the monsoon region (20-150° W, 30° S-60° N). The combined changes in monsoon intensity and pattern lead to some higher glacial productivity during the summer season, in agreement with some palaeo-productivity reconstructions.

Dispersive stresses in wind farms

Science.gov (United States)

Segalini, Antonio; Braunbehrens, Robert; Hyvarinen, Ann

2017-11-01

One of the most famous models of wind farms is provided by the assumption that the farm can be approximated as a horizontally-homogeneous forest canopy with vertically-varying force intensity. By means of this approximation, the flow-motion equations become drastically simpler, as many of the three-dimensional effects are gone. However, the application of the horizontal average operator to the RANS equations leads to the appearance of new transport terms (called dispersive stresses) originating from the horizontal (small-scale) variation of the mean velocity field. Since these terms are related to the individual turbine signature, they are expected to vanish outside the roughness sublayer, providing a definition for the latter. In the present work, an assessment of the dispersive stresses is performed by means of a wake-model approach and through the linearised code ORFEUS developed at KTH. Both approaches are very fast and enable the characterization of a large number of wind-farm layouts. The dispersive stress tensor and its effect on the turbulence closure models are investigated, providing guidelines for those simulations where it is impossible to resolve the farm at a turbine scale due to grid requirements (as, for instance, mesoscale simulations).

Comparison of the ocean surface vector winds over the Nordic Seas and their application for ocean modeling

Science.gov (United States)

Dukhovskoy, Dmitry; Bourassa, Mark

2017-04-01

fields should manifest different behaviors of the isopycnals in the Nordic Seas. Time evolution of isopycnal depths in the sensitivity experiments forced by different wind fields is discussed. Results of these sensitivity experiments demonstrate a relationship between the isopycnal surfaces and the wind stress curl. The numerical experiments are also analyzed to investigate the relationship between the East Greenland Current and the wind stress curl over the Nordic Seas. The transport of the current at this location has substantial contribution from wind-driven large-scale circulation. This wind-driven part of the East Greenland Current is a western-intensified return flow of a wind-driven cyclonic gyre in the central Nordic Seas. The numerical experiments with different wind fields reveal notable sensitivity of the East Greenland Current to differences in the wind forcing.

Acceptance and stress effects of aircraft obstruction markings of wind turbines

International Nuclear Information System (INIS)

Pohl, Johannes; Hübner, Gundula; Mohs, Anja

2012-01-01

A dominant resistance factor against wind power projects seems to be their visual impact on the landscape. In addition stress effects from aircraft obstruction markings are an emerging topic related to acceptance. As the height of wind turbines increases, so does the number of mandatory obstruction markings. Recently, obstruction markings have caused a growing number of complaints from residents. Whether obstruction markings indeed cause stress or even substantial annoyance remains an open question. To analyse the stress impact of obstruction markings, we used environmental and stress psychology methodologies. Residents (N=420) with direct sight of turbines at 13 wind farms participated in a questionnaire survey. Evidence of substantial annoyance caused by obstruction markings was not found. However, residents exposed to xenon lights reported more intense and multifaceted stress responses than exposed to LED or colour markings on blades. Moreover, xenon lights negatively affected the general acceptance of wind energy. Additionally, synchronised navigation lights were found to be less annoying than non-synchronised lights under certain weather conditions. Markings with light intensity adjustment proved to be advantageous. To reduce stress and increase social acceptance of wind power, xenon lights should be abandoned, navigation lights synchronised, and light intensity adjustment applied. - Research highlights: ► Wind turbine obstruction markings influence the social acceptance of wind energy. ► Residents exposed to xenon lights reported more intense stress responses than exposed to LED or colour markings. ► Synchronised lights were found to be less annoying under certain weather conditions. ► Markings with light intensity adjustment proved to be advantageous. ► Evidence of substantial annoyance caused by obstruction markings was not found.

Soil erosion rates caused by wind and saltating sand stresses in a wind tunnel

International Nuclear Information System (INIS)

Ligotke, M.W.

1993-02-01

Wind erosion tests were performed in a wind tunnel in support of the development of long-term protective barriers to cap stabilized waste sites at the Hanford Site. Controlled wind and saltating sand erosive stresses were applied to physical models of barrier surface layers to simulate worst-case eolian erosive stresses. The goal of these tests was to provide information useful to the design and evaluation of the surface layer composition of an arid-region waste site barrier concept that incorporates a deep fine-soil reservoir. A surface layer composition is needed that will form an armor resistant to eolian erosion during periods of extreme dry climatic conditions, especially when such conditions result in the elimination or reduction of vegetation by water deprivation or wildfire. Because of the life span required of Hanford waste barriers, it is important that additional work follow these wind tunnel studies. A modeling effort is planned to aid the interpretation of test results with respect to the suitability of pea gravel to protect the finite-soil reservoir during long periods of climatic stress. It is additionally recommended that wind tunnel tests be continued and field data be obtained at prototype or actual barrier sites. Results wig contribute to barrier design efforts and provide confidence in the design of long-term waste site caps for and regions

Arctic Ice-Ocean Coupling and Gyre Equilibration Observed With Remote Sensing

Science.gov (United States)

Dewey, Sarah; Morison, James; Kwok, Ronald; Dickinson, Suzanne; Morison, David; Andersen, Roger

2018-02-01

Model and observational evidence has shown that ocean current speeds in the Beaufort Gyre have increased and recently stabilized. Because these currents rival ice drift speeds, we examine the potential for the Beaufort Gyre's shift from a system in which the wind drives the ice and the ice drives a passive ocean to one in which the ocean often, in the absence of high winds, drives the ice. The resultant stress exerted on the ocean by the ice and the resultant Ekman pumping are reversed, without any change in average wind stress curl. Through these curl reversals, the ice-ocean stress provides a key feedback in Beaufort Gyre stabilization. This manuscript constitutes one of the first observational studies of ice-ocean stress inclusive of geostrophic ocean currents, by making use of recently available remote sensing data.

Untitled

Indian Academy of Sciences (India)

away the water from the disturbance source. This is measured by the divergence of the wind stress. Subsequently, the rotational character of the wind will become more important. This is the curl of the wind stress. . . . " We may express the solution of (14) in terms of a Green's function when we consider an infinite domain. If.

Analysis of monthly variability of thermocline in the South China Sea

Science.gov (United States)

Peng, Hanbang; Pan, Aijun; Zheng, Quan'an; Hu, Jianyu

2018-03-01

This study analyzes monthly variability of thermocline and its mechanism in the South China Sea (SCS). The study is based on 51-year (1960-2010) monthly seawater temperature and surface wind stress data from Simple Ocean Data Assimilation (SODA), together with heat flux, precipitation and evaporation data from the National Centers for Environmental Prediction (NCEP), the National Oceanic and Atmospheric Administration (NOAA) and the Woods Hole Oceanographic Institution, respectively. The results reveal that the upper boundary depth ( Z up), lower boundary depth ( Z low), thickness (Δ Z) and intensity ( T z ) of thermocline in the SCS show remarkable monthly variability. Being averaged for the deep basin of SCS, Z up deepens gradually from May to the following January and then shoals from February to May, while Z low varies little throughout the whole year. Further diagnostics indicates that the monthly variability of Z up is mainly caused by the buoyancy flux and wind stress curl. Using a linear method, the impacts of the buoyancy flux and wind stress curl on Z up can be quantitatively distinguished. The results suggest that Z up tends to deepen about 4.6 m when the buoyancy flux increases by 1×10 -5 kg/(m•s 3), while it shoals about 2.5 m when the wind stress curl strengthens by 1×10 -7 N/m³.

Flange Curling in Cold Formed Profiles

DEFF Research Database (Denmark)

Jönsson, Jeppe; Ramonas, Gediminas

2012-01-01

The non-linear flange curling phenomenon in cold formed profiles is the tendency of slender flanges to deform towards the neutral axis for increasing flexural curvature. Based on Braziers work, Winter proposed a simple engineering formula for determination of the local flange deformation towards...

Blended 6-Hourly Sea Surface Wind Vectors and Wind Stress on a Global 0.25 Degree Grid (1987-2011)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Blended Global Sea Surface Winds products contain ocean surface wind vectors and wind stress on a global 0.25 degree grid, in multiple time resolutions of...

EFFECT OF THE SHOULDER POSITION ON THE BICEPS BRACHII EMG IN DIFFERENT DUMBBELL CURLS

Directory of Open Access Journals (Sweden)

Taian M.M. Vieira

2009-03-01

Full Text Available Incline Dumbbell Curl (IDC and Dumbbell Preacher Curl (DPC are two variations of the standard Dumbbell Biceps Curl (DBC, generally applied to optimize biceps brachii contribution for elbow flexion by fixing shoulder at a specific angle. The aim of this study is to identify changes in the neuromuscular activity of biceps brachii long head for IDC, DPC and DBC exercises, by taking into account the changes in load moment arm and muscle length elicited by each dumbbell curl protocol. A single cycle (concentric-eccentric of DBC, IDC and DPC, was applied to 22 subjects using a submaximal load of 40% estimated from an isometric MVC test. The neuromuscular activity of biceps brachii long head was compared by further partitioning each contraction into three phases, according to individual elbow joint range of motion. Although all protocols elicited a considerable level of activation of the biceps brachii muscle (at least 50% of maximum RMS, the contribution of this muscle for elbow flexion/extension varied among exercises. The submaximal elbow flexion (concentric elicited neuro muscular activity up to 95% of the maximum RMS value during the final phase of IDC and DBC and 80% for DPC at the beginning of the movement. All exercises showed significant less muscle activity for the elbow extension (eccentric. The Incline Dumbbell Curl and the classical Dumbbell Biceps Curl resulted in similar patterns of biceps brachii activation for the whole range of motion, whereas Dumbbell Preacher Curl elicited high muscle activation only for a short range of elbow joint angle

Swell impact on wind stress and atmospheric mixing in a regional coupled atmosphere-wave model

DEFF Research Database (Denmark)

Wu, Lichuan; Rutgersson, Anna; Sahlée, Erik

2016-01-01

Over the ocean, the atmospheric turbulence can be significantly affected by swell waves. Change in the atmospheric turbulence affects the wind stress and atmospheric mixing over swell waves. In this study, the influence of swell on atmospheric mixing and wind stress is introduced into an atmosphere-wave-coupled...... regional climate model, separately and combined. The swell influence on atmospheric mixing is introduced into the atmospheric mixing length formula by adding a swell-induced contribution to the mixing. The swell influence on the wind stress under wind-following swell, moderate-range wind, and near......-neutral and unstable stratification conditions is introduced by changing the roughness length. Five year simulation results indicate that adding the swell influence on atmospheric mixing has limited influence, only slightly increasing the near-surface wind speed; in contrast, adding the swell influence on wind stress...

A subsurface cyclonic eddy in the Bay of Bengal

Digital Repository Service at National Institute of Oceanography (India)

Babu, M.T.; PrasannaKumar, S.; Rao, D.P.

and to a larger extent from the action of wind stress curl while in the southern part the northward current is purely wind-driven. High stratification causEd. by fresh water influx prevented the eddy from being detected at the surface....

Investigation of residual stresses in thick-walled vessels with combination of autofrettage and wire-winding

International Nuclear Information System (INIS)

Sedighi, M.; Jabbari, A.H.

2013-01-01

Wire-winding and autofrettage processes can be used to introduce beneficial residual stress in the cylinder of thick-walled pressure vessels. In both techniques, internal residual compressive stress will increase internal pressure capacity, improve fatigue life and reduce fatigue crack initiation. The purpose of this paper is to analyze the effects of wire-winding on an autofrettaged thick-walled vessel. Direct method which is a modified Variable Material Properties (VMP) method has been used in order to calculate residual stresses in an autofrettaged vessel. Since wire-winding is done after autofrettage process, the tangent and/or Young's modulus could be changed. For this reason, a new wire-winding method based on Direct Method is introduced. The obtained results for wire-wound autofrettaged vessels are validated by finite element method. The results show that by using this approach, the residual hoop stresses in a wire-wound autofrettaged vessel have a more desirable distribution in the cylinder. -- Highlights: • Combination of autofrettage and wire-winding in pressure vessels has been presented. • A new method based on Direct method is presented for wire-winding process. • Residual hoop stresses are compared in vessels cylinders for different cases. • The residual hoop stress has a more desirable stress distribution. • The benefits of the combined vessel are highlighted in comparison with single cases

Apparatus and method for transfer of information by means of a curl-free magnetic vector potential field

International Nuclear Information System (INIS)

Gelinas, R.C.

1984-01-01

A system for transmission of information using a curl-free magnetic vector potential radiation field. The system includes current-carrying apparatus for generating a magnetic vector potential field with a curl-free component coupled to apparatus for modulating the current applied to the field generating apparatus. Receiving apparatus includes a detector with observable properties that vary with the application of an applied curl-free magnetic vector potential field. Analyzing apparatus for determining the information content of modulation imposed on the curl-free vector potential field can be established in materials that are not capable of transmitting more common electromagnetic radiation

WIND TURBINES CAUSE CHRONIC STRESS IN BADGERS (MELES MELES) IN GREAT BRITAIN.

Science.gov (United States)

Agnew, Roseanna C N; Smith, Valerie J; Fowkes, Robert C

2016-07-01

A paucity of data exists with which to assess the effects of wind turbines noise on terrestrial wildlife, despite growing concern about the impact of infrasound from wind farms on human health and well-being. In 2013, we assessed whether the presence of turbines in Great Britain impacted the stress levels of badgers ( Meles meles ) in nearby setts. Hair cortisol levels were used to determine if the badgers were physiologically stressed. Hair of badgers living 10 km from a wind farm. This demonstrates that affected badgers suffer from enhanced hypothalamo-pituitary-adrenal activity and are physiologically stressed. No differences were found between the cortisol levels of badgers living near wind farms operational since 2009 and 2012, indicating that the animals do not become habituated to turbine disturbance. Cortisol levels in the affected badgers did not vary in relation to the distance from turbines within 1 km, wind farm annual power output, or number of turbines. We suggest that the higher cortisol levels in affected badgers is caused by the turbines' sound and that these high levels may affect badgers' immune systems, which could result in increased risk of infection and disease in the badger population.

The relationship between the statistics of open ocean currents and the temporal correlations of the wind stress

International Nuclear Information System (INIS)

Bel, Golan; Ashkenazy, Yosef

2013-01-01

We study the statistics of wind-driven open ocean currents. Using the Ekman layer model for the integrated currents, we investigate analytically and numerically the relationship between the wind-stress distribution and its temporal correlations and the statistics of the open ocean currents. We found that temporally long-range correlated winds result in currents whose statistics is proportional to the wind-stress statistics. On the other hand, short-range correlated winds lead to Gaussian distributions of the current components, regardless of the stationary distribution of the winds, and therefore to a Rayleigh distribution of the current amplitude, if the wind stress is isotropic. We found that the second moment of the current speed exhibits a maximum as a function of the correlation time of the wind stress for a non-zero Coriolis parameter. The results were validated using an oceanic general circulation model. (paper)

Test Results of a Nb3Sn Wind/React ''Stress-Managed'' Block Dipole

International Nuclear Information System (INIS)

McInturff, A.; Bish, P.; Blackburn, R.; Diaczenko, N.; Elliott, T.; Hafalia Jr., R.; Henchel, W.; Jaisle, A.; Lau, W.; Lietzke, A.; McIntyre, P.; Noyes, P.; Nyman, M.; Sattarov, A.; Sattarov, A.

2006-01-01

A second phase of a highfield dipole technology development has been tested. A Nb3Sn block-coil model dipole was fabricated, using magnetic mirror geometry and wind/react coil technology. The primary objective of this phase was to make a first experimental test of the stress-management strategy pioneered at Texas A and M. In this strategy a high-strength support matrix is integrated with the windings to intercept Lorentz stress from the inner winding so that it does not accumulate in the outer winding. The magnet attained a field that was consistent with short sample limit on the first quench; there was no training. The decoupling of Lorentz stress between inner and outer windings was validated. In ramp rate studies the magnet exhibited a remarkable robustness in rapid ramping operation. It reached 85 percent of short sample(ss) current even while ramping 2-3 T/s. This robustness is attributed to the orientation of the Rutherford cables parallel to the field in the windings, instead of the transverse orientation that characterizes common dipole designs. Test results are presented and the next development phase plans are discussed

Biology and interactions of two distinct monopartite begomoviruses and betasatellites associated with radish leaf curl disease in India

Directory of Open Access Journals (Sweden)

Singh AK

2012-02-01

Full Text Available Abstract Background Emerging whitefly transmitted begomoviruses are major pathogens of vegetable and fibre crops throughout the world, particularly in tropical and sub-tropical regions. Mutation, pseudorecombination and recombination are driving forces for the emergence and evolution of new crop-infecting begomoviruses. Leaf curl disease of field grown radish plants was noticed in Varanasi and Pataudi region of northern India. We have identified and characterized two distinct monopartite begomoviruses and associated beta satellite DNA causing leaf curl disease of radish (Raphanus sativus in India. Results We demonstrate that RaLCD is caused by a complex of two Old World begomoviruses and their associated betasatellites. Radish leaf curl virus-Varanasi is identified as a new recombinant species, Radish leaf curl virus (RaLCV sharing maximum nucleotide identity of 87.7% with Tomato leaf curl Bangladesh virus-[Bangladesh:2] (Accession number AF188481 while the virus causing radish leaf curl disease-Pataudi is an isolate of Croton yellow vein mosaic virus-[India] (CYVMV-IN (Accession number AJ507777 sharing 95.8% nucleotide identity. Further, RDP analysis revealed that the RaLCV has a hybrid genome, a putative recombinant between Euphorbia leaf curl virus and Papaya leaf curl virus. Cloned DNA of either RaLCV or CYVMV induced mild leaf curl symptoms in radish plants. However, when these clones (RaLCV or CYVMV were individually co-inoculated with their associated cloned DNA betasatellite, symptom severity and viral DNA levels were increased in radish plants and induced typical RaLCD symptoms. To further extend these studies, we carried out an investigation of the interaction of these radish-infecting begomoviruses and their associated satellite, with two tomato infecting begomoviruses (Tomato leaf curl Gujarat virus and Tomato leaf curl New Delhi virus. Both of the tomato-infecting begomoviruses showed a contrasting and differential interaction with

MicroRNA profiling of tomato leaf curl new delhi virus (tolcndv infected tomato leaves indicates that deregulation of mir159/319 and mir172 might be linked with leaf curl disease

Directory of Open Access Journals (Sweden)

Haq Qazi MR

2010-10-01

Full Text Available Abstract Background Tomato leaf curl virus (ToLCV, a constituent of the genus Begomovirus, infects tomato and other plants with a hallmark disease symptom of upward leaf curling. Since microRNAs (miRs are known to control plants developmental processes, we evaluated the roles of miRNAs in Tomato leaf curl New Delhi virus (ToLCNDV induced leaf curling. Results Microarray analyses of miRNAs, isolated from the leaves of both healthy and ToLCNDV agroinfected tomato cv Pusa Ruby, revealed that ToLCNDV infection significantly deregulated various miRNAs representing ~13 different conserved families (e.g., miR319, miR172, etc.. The precursors of these miRNAs showed similar deregulated patterns, indicating that the transcription regulation of respective miRNA genes was perhaps the cause of deregulation. The expression levels of the miRNA-targeted genes were antagonistic with respect to the amount of corresponding miRNA. Such deregulation was tissue-specific in nature as no analogous misexpression was found in flowers. The accumulation of miR159/319 and miR172 was observed to increase with the days post inoculation (dpi of ToLCNDV agroinfection in tomato cv Pusa Ruby. Similarly, these miRs were also induced in ToLCNDV agroinfected tomato cv JK Asha and chilli plants, both exhibiting leaf curl symptoms. Our results indicate that miR159/319 and miR172 might be associated with leaf curl symptoms. This report raises the possibility of using miRNA(s as potential signature molecules for ToLCNDV infection. Conclusions The expression of several host miRNAs is affected in response to viral infection. The levels of the corresponding pre-miRs and the predicted targets were also deregulated. This change in miRNA expression levels was specific to leaf tissues and observed to be associated with disease progression. Thus, certain host miRs are likely indicator of viral infection and could be potentially employed to develop viral resistance strategies.

The off-shore Transport of China Coastal Current over Taiwan Bank in Winter

Science.gov (United States)

Liao, E.; Yan, X. H.; Oey, L. Y.; Jiang, Y.

2016-12-01

In winter, an off-shore flow of China Coastal Current can be inferred from satellite and in-situ data over the Taiwan Bank. The dynamics related to this off-shore flow have not been previously explained and are examined here using observations and model. Influenced by southward wind stress and opposing pressure gradient, currents over the Taiwan Bank can be classified into three regimes. The southward China Coastal Current flows pass the Taiwan Bank when the wind stress is stronger than a critical value which depends on the opposite pressure gradient force. The coastal current turns northward under a weak wind stress. Two opposite currents converge over the bank and a branch of the coastal current then turns into the northward warm current when these two forces are in balance. Analysis of the vorticity balance shows that the cross-isobath movement is related to a negative bottom stress curl over the Taiwan Bank. Both bottom Ekman transport and shear and curvature vorticity related to the weak bottom slope over the Taiwan Bank contribute to the bottom stress curl. Composite analyses using observations tend to support the model results.

Dynamic ocean topography from CryoSat-2: examining recent changes in ice-ocean stress and advancing a theory for Beaufort Gyre stabilization

Science.gov (United States)

Dewey, S.; Morison, J.; Kwok, R.; Dickinson, S.; Morison, D.; Andersen, R.

2017-12-01

Model and sparse observational evidence has shown the ocean current speed in the Beaufort Gyre to have increased and recently stabilized. However, full-basin altimetric observations of dynamic ocean topography (DOT) and ocean surface currents have yet to be applied to the dynamics of gyre stabilization. DOT fields from retracked CryoSat-2 retrievals in Arctic Ocean leads have enabled us to calculate 2-month average ocean geostrophic currents. These currents are crucial to accurately computing ice-ocean stress, especially because they have accelerated so that their speed rivals that of the overlying sea ice. Given these observations, we can shift our view of the Beaufort Gyre as a system in which the wind drives the ice and the ice drives a passive ocean to a system with the following feedback: After initial input of energy by wind, ice velocity decreases due to water drag and internal ice stress and the ocean drives the ice, reversing Ekman pumping and decelerating the gyre. This reversal changes the system from a persistently convergent regime to one in which freshwater is released from the gyre and doming of the gyre decreases, without any change in long-term average wind stress curl. Through these processes, the ice-ocean stress provides a key feedback in Beaufort Gyre stabilization.

Role of wind forcing and eddy activity in the intraseasonal variability of the barrier layer in the South China Sea

Science.gov (United States)

Liang, Zhanlin; Xie, Qiang; Zeng, Lili; Wang, Dongxiao

2018-03-01

In addition to widely discussed seasonal variability, the barrier layer (BL) of the South China Sea (SCS) also exhibits significant intraseasonal variability (ISV) and plays an important role in the upper heat and salt balances. The characteristics and mechanisms of spatiotemporal variations in the BL are investigated using an eddy-resolving ocean model OFES (OGCM For the Earth Simulator) ouput and related atmospheric and oceanic processes. The active intraseasonal BL variability in the SCS occurs mainly during the late summer/autumn and winter and exhibits remarkable differences between these two periods. The BL ISV in late summer/autumn occurs in the southern basin, while in winter, it is limited to the northwestern basin. To further discuss the evolution and driving thermodynamic mechanisms, we quantify the processes that control the variability of intraseasonal BL. Different mechanisms for the intraseasonal BL variability for these two active periods are investigated based on the case study and composite analysis. During late summer/autumn, the active BL in the southern basin is generated by advected and local freshwater, and then decays rapidly with the enhanced wind. In winter, anticyclonic eddy activity is associated with the evolution of the BL by affecting the thermocline and halocline variations, while wind stress and wind stress curl have no obvious influence on BL.

Seed storage protein components are associated with curled ...

African Journals Online (AJOL)

PRECIOUS

2009-11-16

Nov 16, 2009 ... analysis suggests that the two increased protein spots in mutants were ... The main objective of this work was to gain further understanding of the influence of curled cotyledon on the seed storage protein components in soybean by com- .... cotyledon formation during Arabidopsis embryogenesis: interaction.

Temporal and Spatial Variabilities of Japan Sea Surface Temperature and Atmospheric Forcings

National Research Council Canada - National Science Library

Chu, Peter C; Chen, Yuchun; Lu, Shihua

1998-01-01

...) and surface air temperature (SAT) data during 1982-1994 and the National Center for Atmospheric Research surface wind stress curl data during 1982-1989 to investigate the Japan Sea SST temporal and spatial variabilities...

Sensitivity of ocean oxygenation to variations in tropical zonal wind stress magnitude

Science.gov (United States)

Ridder, Nina N.; England, Matthew H.

2014-09-01

Ocean oxygenation has been observed to have changed over the past few decades and is projected to change further under global climate change due to an interplay of several mechanisms. In this study we isolate the effect of modified tropical surface wind stress conditions on the evolution of ocean oxygenation in a numerical climate model. We find that ocean oxygenation varies inversely with low-latitude surface wind stress. Approximately one third of this response is driven by sea surface temperature anomalies; the remaining two thirds result from changes in ocean circulation and marine biology. Global mean O2 concentration changes reach maximum values of +4 μM and -3.6 μM in the two most extreme perturbation cases of -30% and +30% wind change, respectively. Localized changes lie between +92 μM under 30% reduced winds and -56 μM for 30% increased winds. Overall, we find that the extent of the global low-oxygen volume varies with the same sign as the wind perturbation; namely, weaker winds reduce the low-oxygen volume on the global scale and vice versa for increased trade winds. We identify two regions, one in the Pacific Ocean off Chile and the other in the Indian Ocean off Somalia, that are of particular importance for the evolution of oxygen minimum zones in the global ocean.

Alignment of stress, mean wind, and vertical gradient of the velocity vector

DEFF Research Database (Denmark)

Berg, Jacob; Mann, Jakob; Patton, E.G.

2012-01-01

In many applications in the atmospheric surface layer the turbulent-viscosity hypothesis is applied, i.e. the stress vector can be described through the vertical gradient of velocity. In the atmospheric surface layer, where the Coriolis force and baroclinic effects are considered negligible......, this is supposedly a good approximation. High resolution large-eddy simulation (LES) data show that it is indeed the case. Through analysis of WindCube lidar measurements accompanied by sonic measurements we show that this is, on the other hand, rarely the case in the real atmosphere. This might indicate that large...... of atmospheric boundary layer modeling. The measurements are from the Danish wind turbine test sites at Høvsøre. With theWindCube lidar we are able to reach heights of 250 meters and hence capture the entire atmospheric surface layer both in terms of wind speed and the direction of the mean stress vector....

Reliability of Arm Curl and Chair Stand tests for assessing muscular endurance in older people

Directory of Open Access Journals (Sweden)

Boneth M

2012-05-01

Full Text Available Objective: to assess the test-retest reliability and level of agreement between measures of the 30 second (30-s Arm Curl and 30-s Chair Stand test in a sample of older adults from Bucaramanga. Materials and methods: a study of evaluation of diagnostic technology was done. Both tests were administered by the same evaluator to 111 adults older than 59 year-old (70,4 ± 7,3, on two occasions, with an interval of time between measures of 4 to 8 days. In the analysis, test-retest reliability was determined using the Intraclass Correlation Coefficient ICC= 2,1 with their confidence interval 95% (CI 95% respective. The agreement level was established by the Bland and Altman method. Results: the test-retest reproducibility of the 30-s Arm Curl test was very good ICC= 0,88 and to the Chair Stand test was good ICC= 0,78. The agreement was very good for both tests of muscle endurance. The CI 95% were between -3,8 and 3,2 stands to 30-s Chair Stand test and between -3,1 and 2,8 curls to 30-s Arm Curl test. Conclusion: the 30-s Arm Curl and 30-s Chair Stand test have good reliability and agreement to assess muscle endurance in older adults functionally independent.

Reconstruction of Local Sea Levels at South West Pacific Islands—A Multiple Linear Regression Approach (1988-2014)

Science.gov (United States)

Kumar, V.; Melet, A.; Meyssignac, B.; Ganachaud, A.; Kessler, W. S.; Singh, A.; Aucan, J.

2018-02-01

Rising sea levels are a critical concern in small island nations. The problem is especially serious in the western south Pacific, where the total sea level rise over the last 60 years has been up to 3 times the global average. In this study, we aim at reconstructing sea levels at selected sites in the region (Suva, Lautoka—Fiji, and Nouméa—New Caledonia) as a multilinear regression (MLR) of atmospheric and oceanic variables. We focus on sea level variability at interannual-to-interdecadal time scales, and trend over the 1988-2014 period. Local sea levels are first expressed as a sum of steric and mass changes. Then a dynamical approach is used based on wind stress curl as a proxy for the thermosteric component, as wind stress curl anomalies can modulate the thermocline depth and resultant sea levels via Rossby wave propagation. Statistically significant predictors among wind stress curl, halosteric sea level, zonal/meridional wind stress components, and sea surface temperature are used to construct a MLR model simulating local sea levels. Although we are focusing on the local scale, the global mean sea level needs to be adjusted for. Our reconstructions provide insights on key drivers of sea level variability at the selected sites, showing that while local dynamics and the global signal modulate sea level to a given extent, most of the variance is driven by regional factors. On average, the MLR model is able to reproduce 82% of the variance in island sea level, and could be used to derive local sea level projections via downscaling of climate models.

Characterization of a novel curled-cotyledons mutant in soybean ...

African Journals Online (AJOL)

ARL

different stages. Protein and amino acid contents in seeds of mutant are higher than those of the wild .... curled shape, from seedling to maturation phase (Figure. 1D-1F). ..... Arabidopsis seed dermination by stimulating abscisic acid synthesis.

Wind-Induced Fatigue Analysis of High-Rise Steel Structures Using Equivalent Structural Stress Method

Directory of Open Access Journals (Sweden)

Zhao Fang

2017-01-01

Full Text Available Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on the meshing styles and massive curves selected. To address this problem, in this paper, the equivalent structural stress method with advantages of mesh-insensitive quality and capability of unifying different stress-life curves (S-N curves into one is introduced to the wind-induced fatigue assessment of a large-scale complicated high-rise steel structure. The multi-scale finite element model is established and the corresponding wind loading is simulated. Fatigue life assessments using equivalent structural stress method, hot spot stress method and nominal stress method are performed, and the results are verified and comparisons are made. The mesh-insensitive quality is also verified. The results show that the lateral weld toe of the butt weld connecting the beam flange plate and the column is the location where fatigue damage most likely happens. Nominal stress method considers fatigue assessment of welds in a more global way by averaging all the stress on the weld section while in equivalent structural stress method and hot spot method local stress concentration can be taken into account more precisely.

Qualitative investigation into students' use of divergence and curl in electromagnetism

Science.gov (United States)

Bollen, Laurens; van Kampen, Paul; Baily, Charles; De Cock, Mieke

2016-12-01

Many students struggle with the use of mathematics in physics courses. Although typically well trained in rote mathematical calculation, they often lack the ability to apply their acquired skills to physical contexts. Such student difficulties are particularly apparent in undergraduate electrodynamics, which relies heavily on the use of vector calculus. To gain insight into student reasoning when solving problems involving divergence and curl, we conducted eight semistructured individual student interviews. During these interviews, students discussed the divergence and curl of electromagnetic fields using graphical representations, mathematical calculations, and the differential form of Maxwell's equations. We observed that while many students attempt to clarify the problem by making a sketch of the electromagnetic field, they struggle to interpret graphical representations of vector fields in terms of divergence and curl. In addition, some students confuse the characteristics of field line diagrams and field vector plots. By interpreting our results within the conceptual blending framework, we show how a lack of conceptual understanding of the vector operators and difficulties with graphical representations can account for an improper understanding of Maxwell's equations in differential form. Consequently, specific learning materials based on a multiple representation approach are required to clarify Maxwell's equations.

Genome wide identification of cotton (Gossypium hirsutum)-encoded microRNA targets against Cotton leaf curl Burewala virus.

Science.gov (United States)

Shweta; Akhter, Yusuf; Khan, Jawaid Ahmad

2018-01-05

Cotton leaf curl Burewala virus (CLCuBV, genus Begomovirus) causes devastating cotton leaf curl disease. Among various known virus controlling strategies, RNAi-mediated one has shown potential to protect host crop plants. Micro(mi) RNAs, are the endogenous small RNAs and play a key role in plant development and stress resistance. In the present study we have identified cotton (Gossypium hirsutum)-encoded miRNAs targeting the CLCuBV. Based on threshold free energy and maximum complementarity scores of host miRNA-viral mRNA target pairs, a number of potential miRNAs were annotated. Among them, ghr-miR168 was selected as the most potent candidate, capable of targeting several vital genes namely C1, C3, C4, V1 and V2 of CLCuBV genome. In addition, ghr-miR395a and ghr-miR395d were observed to target the overlapping transcripts of C1 and C4 genes. We have verified the efficacy of these miRNA targets against CLCuBV following suppression of RNAi-mediated virus control through translational inhibition or cleavage of viral mRNA. Copyright © 2017 Elsevier B.V. All rights reserved.

Injuries in recreational curling include head injuries and may be prevented by using proper footwear.

Science.gov (United States)

Ting, D K; Brison, R J

2015-04-01

Our study examines a recreational curling population to describe patterns of injury occurrence, estimate risk of injury and to gauge attitudes towards equipment-based prevention strategies. In a retrospective case series, we queried the Canadian Hospitals Injury Reporting and Prevention Program (CHIRPP), a national injury surveillance database, for curling injuries entered between 1993 and 2011. Kingston General Hospital and Hotel Dieu Hospital provide the two Kingston, Ontario, sites for emergency department (ED) care and participate in CHIRPP. Each retrieved entry underwent a chart review. A secondary survey was mailed to select individuals who had experienced curling injuries to solicit details on their injury and attitudes towards equipment to prevent injury. We used descriptive statistics for rates and proportions. Over 90% of acute curling injuries resulted from a fall, and 31.7% were head impacts. We found that acute injuries requiring ED presentation occur at a rate of approximately 0.17 per 1000 athlete-exposures (95% CI: 0.12-0.22). The secondary survey was completed by 54% of potential respondents. Of survey respondents, 41.3% attributed their fall to a lack of proper footwear and 73.5% of respondents agreed with mandatory sport-specific footwear as a prevention strategy, but only 8% agreed with mandatory helmet wear. Although curling injuries requiring medical care are not common, head injuries make up a large proportion. Mandated use of appropriate footwear appears to be the most effective prevention strategy, as well as the measure deemed most acceptable by players.

Impacts of the Mesoscale Ocean-Atmosphere Coupling on the Peru-Chile Ocean Dynamics: The Current-Induced Wind Stress Modulation

Science.gov (United States)

Oerder, V.; Colas, F.; Echevin, V.; Masson, S.; Lemarié, F.

2018-02-01

The ocean dynamical responses to the surface current-wind stress interaction at the oceanic mesoscale are investigated in the South-East Pacific using a high-resolution regional ocean-atmosphere coupled model. Two simulations are compared: one includes the surface current in the wind stress computation while the other does not. In the coastal region, absolute wind velocities are different between the two simulations but the wind stress remains very similar. As a consequence, the mean regional oceanic circulation is almost unchanged. On the contrary, the mesoscale activity is strongly reduced when taking into account the effect of the surface current on the wind stress. This is caused by a weakening of the eddy kinetic energy generation near the coast by the wind work and to intensified offshore eddy damping. We show that, above coherent eddies, the current-stress interaction generates eddy damping through Ekman pumping and eddy kinetic energy dissipation through wind work. This alters significantly the coherent eddy vertical structures compared with the control simulation, weakening the temperature and vorticity anomalies and increasing strongly the vertical velocity anomalies associated to eddies.

Predicting hand function in older adults: evaluations of grip strength, arm curl strength, and manual dexterity.

Science.gov (United States)

Liu, Chiung-Ju; Marie, Deana; Fredrick, Aaron; Bertram, Jessica; Utley, Kristen; Fess, Elaine Ewing

2017-08-01

Hand function is critical for independence in activities of daily living for older adults. The purpose of this study was to examine how grip strength, arm curl strength, and manual dexterous coordination contributed to time-based versus self-report assessment of hand function in community-dwelling older adults. Adults aged ≥60 years without low vision or neurological disorders were recruited. Purdue Pegboard Test, Jamar hand dynamometer, 30-second arm curl test, Jebsen-Taylor Hand Function Test, and the Late-Life Function and Disability Instrument were administered to assess manual dexterous coordination, grip strength, arm curl strength, time-based hand function, and self-report of hand function, respectively. Eighty-four adults (mean age = 72 years) completed the study. Hierarchical multiple regressions show that older adults with better arm curl strength (β = -.25, p function test. In comparison, older adults with better grip strength (β = .40, p function. The relationship between grip strength and hand function may be test-specific. Grip strength becomes a significant factor when the test requires grip strength to successfully complete the test tasks. Arm curl strength independently contributed to hand function in both time-based and self-report assessments, indicating that strength of extrinsic muscles of the hand are essential for hand function.

Computation of Surface Integrals of Curl Vector Fields

Science.gov (United States)

Hu, Chenglie

2007-01-01

This article presents a way of computing a surface integral when the vector field of the integrand is a curl field. Presented in some advanced calculus textbooks such as [1], the technique, as the author experienced, is simple and applicable. The computation is based on Stokes' theorem in 3-space calculus, and thus provides not only a means to…

Effect of morphological fin curl on the swimming performance and station-holding ability of juvenile shovelnose sturgeon

Science.gov (United States)

Deslauriers, David; Johnston, Ryan; Chipps, Steven R.

2016-01-01

We assessed the effect of fin-curl on the swimming and station-holding ability of juvenile shovelnose sturgeon Scaphirhynchus platorynchus (mean fork length = 17 cm; mean weight = 16 g; n = 21) using a critical swimming speed test performed in a small swim chamber (90 L) at 20°C. We quantified fin-curl severity using the pectoral fin index. Results showed a positive relationship between pectoral fin index and critical swimming speed indicative of reduced swimming performance displayed by fish afflicted with a pectoral fin index < 8%. Fin-curl severity, however, did not affect the station-holding ability of individual fish. Rather, fish affected with severe fin-curl were likely unable to use their pectoral fins to position their body adequately in the water column, which led to the early onset of fatigue. Results generated from this study should serve as an important consideration for future stocking practices.

Engineered disease resistance in cotton using RNA-interference to knock down cotton leaf curl kokhran virus-Burewala and cotton leaf curl Multan betasatellite

Science.gov (United States)

Cotton Leaf Curl virus Disease (CLCuD) has caused enormous losses in cotton (Gossypium hirsutum) production in Pakistan. RNA interference (RNAi) is an emerging technique that could knock out CLCuD by targeting different regions of the pathogen genome that are important for replication, transcription...

Estimation of wind stress using dual-frequency TOPEX data

Science.gov (United States)

Elfouhaily, Tanos; Vandemark, Douglas; Gourrion, Jéro‸me; Chapron, Bertrand

1998-10-01

The TOPEX/POSEIDON satellite carries the first dual-frequency radar altimeter. Monofrequency (Ku-band) algorithms are presently used to retrieve surface wind speed from the altimeter's radar cross-section measurement (σ0Ku). These algorithms work reasonably well, but it is also known that altimeter wind estimates can be contaminated by residual effects, such as sea state, embedded in the σ0Ku measurement. Investigating the potential benefit of using two frequencies for wind retrieval, it is shown that a simple evaluation of TOPEX data yields previously unavailable information, particularly for high and low wind speeds. As the wind speed increases, the dual-frequency data provides a measurement more directly linked to the short-scale surface roughness, which in turn is associated with the local surface wind stress. Using a global TOPEX σ0° data set and TOPEX's significant wave height (Hs) estimate as a surrogate for the sea state's degree of development, it is also shown that differences between the two TOPEX σ0 measurements strongly evidence nonlocal sea state signature. A composite scattering theory is used to show how the dual-frequency data can provide an improved friction velocity model, especially for winds above 7 m/s. A wind speed conversion is included using a sea state dependent drag coefficient fed with TOPEX Hs data. Two colocated TOPEX-buoy data sets (from the National Data Buoy Center (NDBC) and the Structure des Echanges Mer-Atmosphre, Proprietes des Heterogeneites Oceaniques: Recherche Expérimentale (SEMAPHORE) campaign) are employed to test the new wind speed algorithm. A measurable improvement in wind speed estimation is obtained when compared to the monofrequency Witter and Chelton [1991] model.

Injuries in recreational curling include head injuries and may be prevented by using proper footwear

Directory of Open Access Journals (Sweden)

D. K. Ting

2015-04-01

Full Text Available Introduction: Our study examines a recreational curling population to describe patterns of injury occurrence, estimate risk of injury and to gauge attitudes towards equipment-based prevention strategies. Methods: In a retrospective case series, we queried the Canadian Hospitals Injury Reporting and Prevention Program (CHIRPP, a national injury surveillance database, for curling injuries entered between 1993 and 2011. Kingston General Hospital and Hotel Dieu Hospital provide the two Kingston, Ontario, sites for emergency department (ED care and participate in CHIRPP. Each retrieved entry underwent a chart review. A secondary survey was mailed to select individuals who had experienced curling injuries to solicit details on their injury and attitudes towards equipment to prevent injury. We used descriptive statistics for rates and proportions. Results: Over 90% of acute curling injuries resulted from a fall, and 31.7% were head impacts. We found that acute injuries requiring ED presentation occur at a rate of approximately 0.17 per 1000 athlete-exposures (95% CI: 0.12–0.22. The secondary survey was completed by 54% of potential respondents. Of survey respondents, 41.3% attributed their fall to a lack of proper footwear and 73.5% of respondents agreed with mandatory sport-specific footwear as a prevention strategy, but only 8% agreed with mandatory helmet wear. Conclusions: Although curling injuries requiring medical care are not common, head injuries make up a large proportion. Mandated use of appropriate footwear appears to be the most effective prevention strategy, as well as the measure deemed most acceptable by players.

A Scott bench with ergonomic thorax stabilisation pad improves body posture during preacher arm curl exercise.

Science.gov (United States)

Biscarini, Andrea; Benvenuti, Paolo; Busti, Daniele; Zanuso, Silvano

2016-05-01

We assessed whether the use of an ergonomic thorax stabilisation pad, during the preacher arm curl exercise, could significantly reduce the excessive shoulder protraction and thoracic kyphosis induced by the standard flat pad built into the existing preacher arm curl equipment. A 3D motion capture system and inclinometers were used to measure shoulder protraction and thoracic kyphosis in 15 subjects performing preacher arm curl with a plate-loaded machine provided with the standard flat pad. The same measures were repeated after replacing the flat pad with a new ergonomic pad, specifically designed to accommodate the thorax profile and improve body posture. Pad replacement significantly (p ergonomic pad may potentially allow a more effective training, prevent musculoskeletal discomfort and reduce the risk of injury. Practitioner summary: We have designed an ergonomic thorax stabilisation pad for the preacher arm curl exercise. The new ergonomic pad improves the poor posture conditions induced by the standard flat pad and may potentially allow a more effective training, prevent musculoskeletal discomfort, improve the breathing function and reduce the risk of injury.

Northeast storms ranked by wind stress and wave-generated bottom stress observed in Massachusetts Bay, 1990-2006

Science.gov (United States)

Butman, B.; Sherwood, C.R.; Dalyander, P.S.

2008-01-01

Along the coast of the northeastern United States, strong winds blowing from the northeast are often associated with storms called northeasters, coastal storms that strongly influence weather. In addition to effects caused by wind stress, the sea floor is affected by bottom stress associated with these storms. Bottom stress caused by orbital velocities associated with surface waves integrated over the duration of a storm is a metric of storm strength at the sea floor. Near-bottom wave-orbital velocities calculated by using measurements of significant wave height and dominant wave period and the parametric spectral method described in Wiberg and Sherwood [Wiberg, P.L., Sherwood, C.R. Calculating wave-generated bottom orbital velocities from surface wave parameters. Computers in Geosciences, in press] compared well with observations in Massachusetts Bay. Integrated bottom-wave stress (called IWAVES), calculated at 30 m water depth, and a companion storm-strength metric, integrated surface wind stress at 10 m (called IWINDS), are used to provide an overview of the strength, frequency, and timing of large storms in Massachusetts Bay over a 17-year period from January 1990 through December 2006. These new metrics reflect both storm duration and intensity. Northeast storms were the major cause of large waves in Massachusetts Bay because of the long fetch to the east: of the strongest 10% of storms (n=38) ranked by IWAVES, 22 had vector-averaged wind stress from the northeast quadrant. The Blizzard of December 1992, the Perfect Storm of October 1991, and a December 2003 storm were the strongest three storms ranked by IWAVES and IWINDS, and all were northeasters. IWAVES integrated over the winter season (defined as October-May) ranged by about a factor of 11; the winters with the highest integrated IWAVES were 1992-1993 and 2004-2005 and the winter with the lowest integrated IWAVES was 2001-2002. May 2005 was the only month in the 17-year record that two of the nine

On the impact of multi-axial stress states on trailing edge bondlines in wind turbine rotor blades

Science.gov (United States)

Noever Castelos, Pablo; Balzani, Claudio

2016-09-01

For a reliable design of wind turbine systems all of their components have to be designed to withstand the loads appearing in the turbine's lifetime. When performed in an integral manner this is called systems engineering, and is exceptionally important for components that have an impact on the entire wind turbine system, such as the rotor blade. Bondlines are crucial subcomponents of rotor blades, but they are not much recognized in the wind energy research community. However, a bondline failure can lead to the loss of a rotor blade, and potentially of the entire turbine, and is extraordinarily relevant to be treated with strong emphasis when designing a wind turbine. Modern wind turbine rotor blades with lengths of 80 m and more offer a degree of flexibility that has never been seen in wind energy technology before. Large deflections result in high strains in the adhesive connections, especially at the trailing edge. The latest edition of the DNV GL guideline from end of 2015 demands a three-dimensional stress analysis of bondlines, whereas before an isolated shear stress proof was sufficient. In order to quantify the lack of safety from older certification guidelines this paper studies the influence of multi-axial stress states on the ultimate and fatigue load resistance of trailing edge adhesive bonds. For this purpose, detailed finite element simulations of the IWES IWT-7.5-164 reference wind turbine blades are performed. Different yield criteria are evaluated for the prediction of failure and lifetime. The results show that the multi-axial stress state is governed by span-wise normal stresses. Those are evidently not captured in isolated shear stress proofs, yielding non-conservative estimates of lifetime and ultimate load resistance. This finding highlights the importance to include a three-dimensional stress state in the failure analysis of adhesive bonds in modern wind turbine rotor blades, and the necessity to perform a three-dimensional characterization

Wheat streak mosaic virus coat protein is a determinant for vector transmission by the wheat curl mite

Science.gov (United States)

Wheat streak mosaic virus (WSMV; genus Tritimovirus; family Potyviridae), is transmitted by the wheat curl mite (Aceria tosichella Keifer). The requirement of coat protein (CP) for WSMV transmission by the wheat curl mite was examined using a series of viable deletion and point mutations. Mite trans...

Diversity, Mutation and Recombination Analysis of Cotton Leaf Curl Geminiviruses.

Directory of Open Access Journals (Sweden)

Huma Saleem

Full Text Available The spread of cotton leaf curl disease in China, India and Pakistan is a recent phenomenon. Analysis of available sequence data determined that there is a substantial diversity of cotton-infecting geminiviruses in Pakistan. Phylogenetic analyses indicated that recombination between two major groups of viruses, cotton leaf curl Multan virus (CLCuMuV and cotton leaf curl Kokhran virus (CLCuKoV, led to the emergence of several new viruses. Recombination detection programs and phylogenetic analyses showed that CLCuMuV and CLCuKoV are highly recombinant viruses. Indeed, CLCuKoV appeared to be a major donor virus for the coat protein (CP gene, while CLCuMuV donated the Rep gene in the majority of recombination events. Using recombination free nucleotide datasets the substitution rates for CP and Rep genes were determined. We inferred similar nucleotide substitution rates for the CLCuMuV-Rep gene (4.96X10-4 and CLCuKoV-CP gene (2.706X10-4, whereas relatively higher substitution rates were observed for CLCuMuV-CP and CLCuKoV-Rep genes. The combination of sequences with equal and relatively low substitution rates, seemed to result in the emergence of viral isolates that caused epidemics in Pakistan and India. Our findings also suggest that CLCuMuV is spreading at an alarming rate, which can potentially be a threat to cotton production in the Indian subcontinent.

Thermal and curl properties of PET/PP blend fibers compatibilized ...

Indian Academy of Sciences (India)

67

blend fibers were prepared using a melt-spinning system, and their curl properties were investigated. ... by extrusion and injection molding processes. ..... Inuwa I M, Hassan A, Samsudin S A, Kassim M H M and Jawaid M 2014. Polym.

Molecular Characterization of Tomato Yellow Leaf Curl Virus in Korea and the Construction of an Infectious Clone

Directory of Open Access Journals (Sweden)

Bong Choon Lee

2015-06-01

Full Text Available Several tomato production regions in Korea were surveyed for tomato yellow leaf curl disease (TYLCD. Tomato leaf samples showing TYLCD-like symptoms were collected from Tongyeong (To, Geoje (Gi, and Gimhae (Gh cities of the southern part of Korea. Tomato yellow leaf curl virus (TYLCV was detected and the full-length genomes of the isolates were sequenced. The TYLCV isolates found in Korea shared high sequence identity (> 99% with TYLCV-IL [JR:Omu:Ng] (AB110217. Phylogenetic relationship analysis revealed that they formed two groups (with little genetic variability, and the To, Gj, and Gh isolates belonged to the TYLCV-IL group. An infectious clone of TYLCV-To (JQ013089 was constructed and agroinoculated into Nicotiana benthamiana, Nicotiana tabacum var. Xanthi, Petunia hybrida, Capsicum annuum, and Lycopersicon esculentum cv. Hausumomotaro. Agroinfection with a dimeric infectious clone of TYLCV-To induced severe leaf curling and stunting symptoms in these plants, excluding C. annuum. Tomato plants then developed typical yellow leaf curl symptoms.

Spectral mimetic least-squares method for div-curl systems

NARCIS (Netherlands)

Gerritsma, Marc; Palha, Artur; Lirkov, I.; Margenov, S.

2018-01-01

In this paper the spectral mimetic least-squares method is applied to a two-dimensional div-curl system. A test problem is solved on orthogonal and curvilinear meshes and both h- and p-convergence results are presented. The resulting solutions will be pointwise divergence-free for these test

Transcript mapping of Cotton leaf curl Burewala virus and its cognate betasatellite, Cotton leaf curl Multan betasatellite

Directory of Open Access Journals (Sweden)

Akbar Fazal

2012-10-01

Full Text Available Abstract Background Whitefly-transmitted geminiviruses (family Geminiviridae, genus Begomovirus are major limiting factors for the production of numerous dicotyledonous crops throughout the warmer regions of the world. In the Old World a small number of begomoviruses have genomes consisting of two components whereas the majority have single-component genomes. Most of the monopartite begomoviruses associate with satellite DNA molecules, the most important of which are the betasatellites. Cotton leaf curl disease (CLCuD is one of the major problems for cotton production on the Indian sub-continent. Across Pakistan, CLCuD is currently associated with a single begomovirus (Cotton leaf curl Burewala virus [CLCuBuV] and the cotton-specific betasatellite Cotton leaf curl Multan betasatellite (CLCuMuB, both of which have recombinant origins. Surprisingly, CLCuBuV lacks C2, one of the genes present in all previously characterized begomoviruses. Virus-specific transcripts have only been mapped for few begomoviruses, including one monopartite begomovirus that does not associate with betasatellites. Similarly, the transcripts of only two betasatellites have been mapped so far. The study described has investigated whether the recombination/mutation events involved in the evolution of CLCuBuV and its associated CLCuMuB have affected their transcription strategies. Results The major transcripts of CLCuBuV and its associated betasatellite (CLCuMuB from infected Nicotiana benthamiana plants have been determined. Two complementary-sense transcripts of ~1.7 and ~0.7 kb were identified for CLCuBuV. The ~1.7 kb transcript appears similar in position and size to that of several begomoviruses and likely directs the translation of C1 and C4 proteins. Both complementary-sense transcripts can potentially direct the translation of C2 and C3 proteins. A single virion-sense transcript of ~1 kb, suitable for translation of the V1 and V2 genes was identified. A predominant

Injuries in recreational curling include head injuries and may be prevented by using proper footwear

OpenAIRE

D. K. Ting; R. J. Brison

2015-01-01

Introduction: Our study examines a recreational curling population to describe patterns of injury occurrence, estimate risk of injury and to gauge attitudes towards equipment-based prevention strategies. Methods: In a retrospective case series, we queried the Canadian Hospitals Injury Reporting and Prevention Program (CHIRPP), a national injury surveillance database, for curling injuries entered between 1993 and 2011. Kingston General Hospital and Hotel Dieu Hospital provide the two Kingston,...

Molecular characterization of two isolates of sweet potato leaf curl ...

African Journals Online (AJOL)

Jane

2011-08-17

Aug 17, 2011 ... related to that of sweet potato leaf curl virus (SPLCV) from United States with nucleotide sequence identity of ... species including Ipomoea indica, are grown orna- mentally all .... and AC4 were closely related to that of SPLCV-.

Detection of pepper leaf curl virus through PCR amplification and ...

African Journals Online (AJOL)

Administrator

2011-04-25

Apr 25, 2011 ... crop. Among the five domesticated species of the genus. Capsicum, C. annuum is the most widely cultivated all over the world ... In India, PepLCV has been an emerging ... virus-vector relationship of chilli leaf curl disease was.

Edge curling that has plagued scrolls for millenniums

Science.gov (United States)

Chou, Ming-Han; Shen, Wei-Chao; Wang, Yi-Ping; Hung, Sun-Hsin; Hong, Tzay-Ming; Department of Registration and Conservation, National Palace Museum Collaboration; Department of Physics, National Tsing Hua University Team

2014-03-01

Qi-Wa refers to the up curl on the lengths of handscrolls and hanging scrolls, which has troubled Chinese artisans and emperors for as long as the art of painting and calligraphy exists. This warp is unwelcome not only for aesthetic reasons, but its potential damage to the fiber and ink. Although it is generally treated as a part of the cockling and curling due to moisture, consistency of paste, and defects from the mounting procedures, we demonstrate that the spontaneous extrinsic curvature incurred from the storage is in fact more essential to understanding and curing Qi-Wa. In contrast to the former factors whose effects are less predictable, the plastic deformation and strain distribution on a membrane are a well-defined mechanical problem. We study this phenomenon by experiments, theoretical models, and Molecular Dynamics Simulation, and obtain consistent scaling relations for the Qi-Wa height. This knowledge enables us to propose modifications on the traditional mounting techniques, that are tested on real mounted paper to be effective at mitigating Qi-Wa. By experimenting on polymer-based films, we demonstrate possible relevance of our study to the modern development of flexible electronic paper.

TAO/TRITON, RAMA, and PIRATA Buoys, Daily, 1989-present, Wind Stress

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has daily Wind Stress data from the TAO/TRITON (Pacific Ocean, https://www.pmel.noaa.gov/gtmba/ ), RAMA (Indian Ocean,...

TAO/TRITON, RAMA, and PIRATA Buoys, Monthly, 1989-present, Wind Stress

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has monthly Wind Stress data from the TAO/TRITON (Pacific Ocean, https://www.pmel.noaa.gov/gtmba/ ), RAMA (Indian Ocean,...

Effect of Performance Speed on Trunk Movement Control During the Curl-Up Exercise

Directory of Open Access Journals (Sweden)

Barbado David

2015-06-01

Full Text Available Trunk exercise speed has significant effects on neuro-mechanical demands; however, the influence of a variety of exercise speeds on motor control of the trunk displacement remains unknown. The aim of this study was to assess the effect of performance speed on trunk motion control during the curl-up exercise by analyzing the kinematic variance about the sagittal trajectory. Seventeen subjects volunteered to perform curl-ups at different cadences controlled by a metronome. Standard deviation (SD and range (RG of shoulder girdle medial-lateral displacement (SGML and detrended fluctuation analysis (DFA of SGML were calculated to examine linear variability and long range autocorrelation of medial-lateral upper trunk displacements, respectively. In addition, SD, RG and DFA of centre of pressure medial-lateral displacement (COPML were performed to analyze the behavior of the motor system while controlling trunk displacement. Although SD and RG of COPML increased as speed increased, the curl-up cadence did not have significant effects on SD and RG of SGML. These results suggest that although high speed curl-ups challenged participants’ ability to carry out medial-lateral adjustments, an increase of performance speed did not modify the linear variability about the sagittal trajectory. Regarding DFA, the scaling exponent α of SGML and COPML was higher for the fastest movements, mainly in long term fluctuations. Therefore, to maintain the target trajectory, participants used different strategies depending on performance speed. This is to say, there were less trajectory changes when participants performed the fastest exercises.

Impacts of Wind Stress Changes on the Global Heat Transport, Baroclinic Instability, and the Thermohaline Circulation

Directory of Open Access Journals (Sweden)

Jeferson Prietsch Machado

2016-01-01

Full Text Available The wind stress is a measure of momentum transfer due to the relative motion between the atmosphere and the ocean. This study aims to investigate the anomalous pattern of atmospheric and oceanic circulations due to 50% increase in the wind stress over the equatorial region and the Southern Ocean. In this paper we use a coupled climate model of intermediate complexity (SPEEDO. The results show that the intensification of equatorial wind stress causes a decrease in sea surface temperature in the tropical region due to increased upwelling and evaporative cooling. On the other hand, the intensification of wind stress over the Southern Ocean induces a regional increase in the air and sea surface temperatures which in turn leads to a reduction in Antarctic sea ice thickness. This occurs in association with changes in the global thermohaline circulation strengthening the rate of Antarctic Bottom Water formation and a weakening of the North Atlantic Deep Water. Moreover, changes in the Southern Hemisphere thermal gradient lead to modified atmospheric and oceanic heat transports reducing the storm tracks and baroclinic activity.

The stress ulcer syndrome

NARCIS (Netherlands)

H.A. van Essen

1986-01-01

textabstractThe stress ulcer syndrome is described in this thesis. This syndrome is seen in patients admitted to intensive care departments or being treated in field hospitals, in disaster areas, or battle fields. Acute mucosal lesions associated with burns (Curling's ulcers) and central nervous

Temporal and Spatial Variabilities of Japan Sea Surface Temperature and Atmospheric Forcings

National Research Council Canada - National Science Library

Chu, Peter C; Chen, Yuchun; Lu, Shihua

1998-01-01

... and their relations to atmospheric forcing. First, we found an asymmetry in the correlation coefficients between SST and wind stress curl, which implies that the SST variability at the scales of the order of one month is largely due to atmospheric forcing...

Seasonal cycle of cross-equatorial flow in the central Indian Ocean

Science.gov (United States)

Wang, Yi; McPhaden, Michael J.

2017-05-01

This study investigates the seasonal cycle of meridional currents in the upper layers of central equatorial Indian Ocean using acoustic Doppler current profiler (ADCP) and other data over the period 2004-2013. The ADCP data set collected along 80.5°E is the most comprehensive collection of direct velocity measurements in the central Indian Ocean to date, providing new insights into the meridional circulation in this region. We find that mean volume transport is southward across the equator in the central Indian Ocean in approximate Sverdrup balance with the wind stress curl. In addition, mean westerly wind stress near the equator drives convergent Ekman flow in the surface layer and subsurface divergent geostrophic flow in the thermocline at 50-150 m depths. In response to a mean northward component of the surface wind stress, the maximum surface layer convergence is shifted off the equator to between 0.5° and 1°N. Evidence is also presented for the existence of a shallow equatorial roll consisting of a northward wind-driven surface drift overlaying the southward directed subsurface Sverdrup transport. Seasonal variations are characterized by cross-equatorial transports flowing from the summer to the winter hemisphere in quasi-steady Sverdrup balance with the wind stress curl. In addition, semiannually varying westerly monsoon transition winds lead to semiannual enhancements of surface layer Ekman convergence and geostrophic divergence in the thermocline. These results quantify expectations from ocean circulation theories for equatorial Indian Ocean meridional circulation patterns with a high degree of confidence given the length of the data records.

A Non-Linear Upscaling Approach for Wind Turbines Blades Based on Stresses

NARCIS (Netherlands)

Castillo Capponi, P.; Van Bussel, G.J.W.; Ashuri, T.; Kallesoe, B.

2011-01-01

The linear scaling laws for upscaling wind turbine blades show a linear increase of stresses due to the weight. However, the stresses should remain the same for a suitable design. Application of linear scaling laws may lead to an upscaled blade that may not be any more a feasible design. In this

Recent evolution of a novel begomovirus causing tomato leaf curl disease in the Al-Batinah region of Oman.

Science.gov (United States)

Khan, Akhtar J; Akhtar, Sohail; Singh, Achuit K; Al-Shehi, Adel A; Al-Matrushi, Abdulrahman M; Ammara, Ume; Briddon, Rob W

2014-03-01

For last two decades, begomoviruses (family Geminiviridae) have been a major constraint for tomato production in Oman, particularly in the Al-Batinah region, the major agricultural area of Oman. Farms in the Al-Batinah region were surveyed during January-March and November-December in 2012 and January-February in 2013. Leaf samples of tomato plants showing typical leaf curl disease symptoms were collected and analyzed for begomoviruses. Out of fifteen begomovirus clones sequenced, seven were shown to be tomato yellow leaf curl virus strain Oman (TYLCV-OM); three, chili leaf curl virus strain Oman (ChLCV-OM); and one, tomato leaf curl Oman virus (ToLCOMV) - viruses that have previously been shown to occur in Oman. Four sequences were shown to have relatively low percent identity values to known begomoviruses, with the highest (86 %) to isolates of pepper leaf curl Lahore virus, indicating that these should be included in a new species, for which the name "Tomato leaf curl Al Batinah virus" (ToLCABV) is proposed. Although the betasatellite tomato leaf curl betasatellite (ToLCB; 7 full-length sequences isolated) was identified with some isolates of ChLCV-OM, TYLCV-OM and ToLCOMV, it was not identified in association with any of the ToLCABV isolates. Analysis of the sequences of the TYLCV-OM and ToLCOMV isolates characterized here did not show them to differ significantly from previously characterized isolates of these viruses. The three isolates of ChLCV-OM characterized were shown to have a recombination pattern distinct from earlier characterized isolates. ToLCABV was shown to have resulted from recombination between ChLCV-OM and ToLCOMV. A clone of ToLCABV was infectious by Agrobacterium-mediated inoculation to Nicotiana benthamiana and tomato, inducing symptoms typical of those seen in tomato in the field. Additionally, ToLCABV was shown to be able to interact in planta with ToLCB, resulting in a change in symptom phenotype, although the betasatellite did not

The Role of the New Zealand Plateau in the Tasman Sea Circulation and Separation of the East Australian Current

Science.gov (United States)

Bull, Christopher Y. S.; Kiss, Andrew E.; van Sebille, Erik; Jourdain, Nicolas C.; England, Matthew H.

2018-02-01

The East Australian Current (EAC) plays a major role in regional climate, circulation, and ecosystems, but predicting future changes is hampered by limited understanding of the factors controlling EAC separation. While there has been speculation that the presence of New Zealand may be important for the EAC separation, the prevailing view is that the time-mean partial separation is set by the ocean's response to gradients in the wind stress curl. This study focuses on the role of New Zealand, and the associated adjacent bathymetry, in the partial separation of the EAC and ocean circulation in the Tasman Sea. Here utilizing an eddy-permitting ocean model (NEMO), we find that the complete removal of the New Zealand plateau leads to a smaller fraction of EAC transport heading east and more heading south, with the mean separation latitude shifting >100 km southward. To examine the underlying dynamics, we remove New Zealand with two linear models: the Sverdrup/Godfrey Island Rule and NEMO in linear mode. We find that linear processes and deep bathymetry play a major role in the mean Tasman Front position, whereas nonlinear processes are crucial for the extent of the EAC retroflection. Contrary to past work, we find that meridional gradients in the basin-wide wind stress curl are not the sole factor determining the latitude of EAC separation. We suggest that the Tasman Front location is set by either the maximum meridional gradient in the wind stress curl or the northern tip of New Zealand, whichever is furthest north.

Warm and Saline Events Embedded in the Meridional Circulation of the Northern North Atlantic

Science.gov (United States)

Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.

2011-01-01

Ocean state estimates from 1958 to 2005 from the Simple Ocean Assimilation System (SODA) system are analyzed to understand circulation between subtropical and subpolar Atlantic and their connection with atmospheric forcing. This analysis shows three periods (1960s, around 1980, and 2000s) with enhanced warm, saline waters reaching high latitudes, alternating with freshwater events originating at high latitudes. It complements surface drifter and altimetry data showing the subtropical -subpolar exchange leading to a significant temperature and salinity increase in the northeast Atlantic after 2001. The warm water limb of the Atlantic meridional overturning cell represented by SODA expanded in density/salinity space during these warm events. Tracer simulations using SODA velocities also show decadal variation of the Gulf Stream waters reaching the subpolar gyre and Nordic seas. The negative phase of the North Atlantic Oscillation index, usually invoked in such variability, fails to predict the warming and salinization in the early 2000s, with salinities not seen since the 1960s. Wind stress curl variability provided a linkage to this subtropical/subpolar gyre exchange as illustrated using an idealized two ]layer circulation model. The ocean response to the modulation of the climatological wind stress curl pattern was found to be such that the northward penetration of subtropical tracers is enhanced when amplitude of the wind stress curl is weaker than normal. In this case both the subtropical and subpolar gyres weaken and the subpolar density surfaces relax; hence, the polar front moves westward, opening an enhanced northward access of the subtropical waters in the eastern boundary current.

An Exploration of Wind Stress Calculation Techniques in Hurricane Storm Surge Modeling

Directory of Open Access Journals (Sweden)

Kyra M. Bryant

2016-09-01

Full Text Available As hurricanes continue to threaten coastal communities, accurate storm surge forecasting remains a global priority. Achieving a reliable storm surge prediction necessitates accurate hurricane intensity and wind field information. The wind field must be converted to wind stress, which represents the air-sea momentum flux component required in storm surge and other oceanic models. This conversion requires a multiplicative drag coefficient for the air density and wind speed to represent the air-sea momentum exchange at a given location. Air density is a known parameter and wind speed is a forecasted variable, whereas the drag coefficient is calculated using an empirical correlation. The correlation’s accuracy has brewed a controversy of its own for more than half a century. This review paper examines the lineage of drag coefficient correlations and their acceptance among scientists.

Electromagnetic field and mechanical stress analysis code

International Nuclear Information System (INIS)

1978-01-01

Analysis TEXMAGST is a two stage linear finite element code for the analysis of static magnetic fields in three dimensional structures and associated mechanical stresses produced by the anti J x anti B forces within these structures. The electromagnetic problem is solved in terms of magnetic vector potential A for a given current density anti J as curl 1/μ curl anti A = anti J considering the magnetic permeability as constant. The Coulombian gauge (div anti A = o) was chosen and was implemented through the use of Lagrange multipliers. The second stage of the problem - the calculation of mechanical stresses in the same three dimensional structure is solved by using the same code with few modifications - through a restart card. Body forces anti J x anti B within each element are calculated from the solution of the first stage run and represent the input to the second stage run which will give the solution for the stress problem

The merging of two dynasties--identification of an African cotton leaf curl disease-associated begomovirus with cotton in Pakistan.

Directory of Open Access Journals (Sweden)

Muhammad Nouman Tahir

Full Text Available Cotton leaf curl disease (CLCuD is a severe disease of cotton that occurs in Africa and Pakistan/northwestern India. The disease is caused by begomoviruses in association with specific betasatellites that differ between Africa and Asia. During survey of symptomatic cotton in Sindh (southern Pakistan Cotton leaf curl Gezira virus (CLCuGV, the begomovirus associated with CLCuD in Africa, was identified. However, the cognate African betasatellite (Cotton leaf curl Gezira betasatellite was not found. Instead, two Asian betasatellites, the CLCuD-associated Cotton leaf curl Multan betasatellite (CLCuMB and Chilli leaf curl betasatellite (ChLCB were identified. Inoculation of the experimental plant species Nicotiana benthamiana showed that CLCuGV was competent to maintain both CLCuMB and ChLCB. Interestingly, the enations typical of CLCuD were only induced by CLCuGV in the presence of CLCuMB. Also in infections involving both CLCuMB and ChLCB the enations typical of CLCuMB were less evident. This is the first time an African begomovirus has been identified on the Indian sub-continent, highlight the growing threat of begomoviruses and particularly the threat of CLCuD causing viruses to cotton cultivation in the rest of the world.

Alfalfa Leaf Curl Virus: an Aphid-Transmitted Geminivirus.

Science.gov (United States)

Roumagnac, Philippe; Granier, Martine; Bernardo, Pauline; Deshoux, Maëlle; Ferdinand, Romain; Galzi, Serge; Fernandez, Emmanuel; Julian, Charlotte; Abt, Isabelle; Filloux, Denis; Mesléard, François; Varsani, Arvind; Blanc, Stéphane; Martin, Darren P; Peterschmitt, Michel

2015-09-01

The family Geminiviridae comprises seven genera differentiated by genome organization, sequence similarity, and insect vector. Capulavirus, an eighth genus, has been proposed to accommodate two newly discovered highly divergent geminiviruses that presently have no known vector. Alfalfa leaf curl virus, identified here as a third capulavirus, is shown to be transmitted by Aphis craccivora. This is the first report of an aphid-transmitted geminivirus. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Further influence of the eastern boundary on the seasonal variability of the Atlantic Meridional Overturning Circulation at 26N

Science.gov (United States)

Baehr, Johanna; Schmidt, Christian

2016-04-01

The seasonal cycle of the Atlantic Meridional Overturning Circulation (AMOC) at 26.5 N has been shown to arise predominantly from sub-surface density variations at the Eastern boundary. Here, we suggest that these sub-surface density variations have their origin in the seasonal variability of the Canary Current system, in particular the Poleward Undercurrent (PUC). We use a high-resolution ocean model (STORM) for which we show that the seasonal variability resembles observations for both sub-surface density variability and meridional transports. In particular, the STORM model simulation density variations at the eastern boundary show seasonal variations reaching down to well over 1000m, a pattern that most model simulations systematically underestimate. We find that positive wind stress curl anomalies in late summer and already within one degree off the eastern boundary result -through water column stretching- in strong transport anomlies in PUC in fall, coherent down to 1000m depth. Simultaneously with a westward propagation of these transport anomalies, we find in winter a weak PUC between 200 m and 500m, and southward transports between 600m and 1300m. This variability is in agreement with the observationally-based suggestion of a seasonal reversal of the meridional transports at intermediate depths. Our findings extend earlier studies which suggested that the seasonal variability at of the meridional transports across 26N is created by changes in the basin-wide thermocline through wind-driven upwelling at the eastern boundary analyzing wind stress curl anomalies 2 degrees off the eastern boundary. Our results suggest that the investigation of AMOC variability and particular its seasonal cycle modulations require the analysis of boundary wind stress curl and the upper ocean transports within 1 degree off the eastern boundary. These findings also implicate that without high-resolution coverage of the eastern boundary, coarser model simulation might not fully

Adding insult to injury: The development of psychosocial stress in Ontario wind turbine communities.

Science.gov (United States)

Walker, Chad; Baxter, Jamie; Ouellette, Danielle

2015-05-01

Though historically dismissed as not-in-my-backyard (NIMBY) attitudes, reports of psychosocial stress linked to wind energy developments have emerged in Ontario, Canada. While the debate and rhetoric intensify concerning whether wind turbines 'actually' cause 'health' effects, less sincere attention has been given to the lived experience and mental well-being of those near turbines. Drawing on theories of environmental stress, this grounded theory, mixed-method (n = 26 interviews; n = 152 questionnaires) study of two communities in 2011 and 2012 traces how and why some wind turbine community residents suffer substantial changes to quality of life, develop negative perceptions of 'the other' and in some cases, experience intra-community conflict. Policy-related forces, along with existing community relationships may help explain much of these differences between communities. We suggest a move beyond debating simply whether or not 'annoyance' represents a 'health impact' and instead focus on ways to minimize and attenuate these feelings of threat (risk) and stress at the community level. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effects of the mutation of selected genes of cotton leaf curl Kokhran virus on infectivity, symptoms and the maintenance of cotton leaf curl Multan betasatellite

NARCIS (Netherlands)

Iqbal, Z.; Sattar, M.N.; Kvarnheden, A.; Mansoor, S.; Briddon, R.W.

2012-01-01

Cotton leaf curl Kokhran virus (CLCuKoV) is a cotton-infecting monopartite begomovirus (family Geminiviridae). The effects of mutation of the coat protein (CP), V2, C2 and C4 genes of CLCuKoV on infectivity and symptoms in Nicotiana benthamiana were investigated. Each mutation introduced a premature

TAO/TRITON, RAMA, and PIRATA Buoys, 5-Day, 1989-present, Wind Stress

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has 5-day Wind Stress data from the TAO/TRITON (Pacific Ocean, https://www.pmel.noaa.gov/gtmba/ ), RAMA (Indian Ocean,...

Land-atmosphere-ocean interactions in the southeastern Atlantic: interannual variability

Science.gov (United States)

Sun, Xiaoming; Vizy, Edward K.; Cook, Kerry H.

2018-02-01

Land-atmosphere-ocean interactions in the southeastern South Atlantic and their connections to interannual variability are examined using a regional climate model coupled with an intermediate-level ocean model. In austral summer, zonal displacements of the South Atlantic subtropical high (SASH) can induce variations of mixed-layer currents in the Benguela upwelling region through surface wind stress curl anomalies near the Namibian coast, and an eastward shifted SASH is related to the first Pacific-South American mode. When the SASH is meridionally displaced, mixed layer vertically-integrated Ekman transport anomalies are mainly a response to the change of alongshore surface wind stress. The latitudinal shift of the SASH tends to dampen the anomalous alongshore wind by modulating the land-sea thermal contrast, while opposed by oceanic diffusion. Although the position of the SASH is closely linked to the phase of El Niño-Southern Oscillation (ENSO) and the southern annular mode (SAM) in austral summer, an overall relationship between Benguela upwelling strength and ENSO or SAM is absent. During austral winter, variations of the mixed layer Ekman transport in the Benguela upwelling region are connected to the strength of the SASH through its impact on both coastal wind stress curl and alongshore surface wind stress. Compared with austral summer, low-level cloud cover change plays a more important role. Although wintertime sea surface temperature fluctuations in the equatorial Atlantic are strong and may act to influence variability over the northern Benguela area, the surface heat budget analysis suggests that local air-sea interactions dominate.

Intercomparison of the Charnock and COARE bulk wind stress formulations for coastal ocean modelling

Directory of Open Access Journals (Sweden)

J. M. Brown

2013-08-01

Full Text Available The accurate parameterisation of momentum and heat transfer across the air–sea interface is vital for realistic simulation of the atmosphere–ocean system. In most modelling applications accurate representation of the wind stress is required to numerically reproduce surge, coastal ocean circulation, surface waves, turbulence and mixing. Different formulations can be implemented and impact the accuracy of the instantaneous and long-term residual circulation, the surface mixed layer, and the generation of wave-surge conditions. This, in turn, affects predictions of storm impact, sediment pathways, and coastal resilience to climate change. The specific numerical formulation needs careful selection to ensure the accuracy of the simulation. Two wind stress parameterisations widely used in the ocean circulation and the storm surge communities respectively are studied with focus on an application to the NW region of the UK. Model–observation validation is performed at two nearshore and one estuarine ADCP (acoustic Doppler current profiler stations in Liverpool Bay, a hypertidal region of freshwater influence (ROFI with vast intertidal areas. The period of study covers both calm and extreme conditions to test the robustness of the 10 m wind stress component of the Coupled Ocean–Atmosphere Response Experiment (COARE bulk formulae and the standard Charnock relation. In this coastal application a realistic barotropic–baroclinic simulation of the circulation and surge elevation is set-up, demonstrating greater accuracy occurs when using the Charnock relation, with a constant Charnock coefficient of 0.0185, for surface wind stress during this one month period.

Water characteristics, mixing and circulation in the Bay of Bengal during southwest monsoon

Digital Repository Service at National Institute of Oceanography (India)

Murty, V.S.N.; Sarma, Y.V.B.; Rao, D.P.; Murty, C.S.

in the western, central and southeastern regions of the Bay respectively. The wind-stress-curl-induced upwelling effect is confined to depth limits of 50-100 m as is supportEd. by a band of cold (24 degrees -19 degrees C) water in the central Bay. In the southern...

Transport and potential vorticity in the Bay of Bengal during the southwest monsoon

Digital Repository Service at National Institute of Oceanography (India)

Murty, V.S.N.; Murty, C.S.; Sarma, Y.V.B.; Rao, D.P.; Sastry, J.S.; Rao, G.R.L.

Current (EBC) contributed to an influx of 3.5 x 10 sup(6 m sup(3/s water respectively. The influence of overlying less saline, fresher water at the northern Bay: Ekman suction due to the wind stress curl in the central Bay; and the east-flowing IMC...

Initialization shock in decadal hindcasts due to errors in wind stress over the tropical Pacific

Science.gov (United States)

Pohlmann, Holger; Kröger, Jürgen; Greatbatch, Richard J.; Müller, Wolfgang A.

2017-10-01

Low prediction skill in the tropical Pacific is a common problem in decadal prediction systems, especially for lead years 2-5 which, in many systems, is lower than in uninitialized experiments. On the other hand, the tropical Pacific is of almost worldwide climate relevance through its teleconnections with other tropical and extratropical regions and also of importance for global mean temperature. Understanding the causes of the reduced prediction skill is thus of major interest for decadal climate predictions. We look into the problem of reduced prediction skill by analyzing the Max Planck Institute Earth System Model (MPI-ESM) decadal hindcasts for the fifth phase of the Climate Model Intercomparison Project and performing a sensitivity experiment in which hindcasts are initialized from a model run forced only by surface wind stress. In both systems, sea surface temperature variability in the tropical Pacific is successfully initialized, but most skill is lost at lead years 2-5. Utilizing the sensitivity experiment enables us to pin down the reason for the reduced prediction skill in MPI-ESM to errors in wind stress used for the initialization. A spurious trend in the wind stress forcing displaces the equatorial thermocline in MPI-ESM unrealistically. When the climate model is then switched into its forecast mode, the recovery process triggers artificial El Niño and La Niña events at the surface. Our results demonstrate the importance of realistic wind stress products for the initialization of decadal predictions.

Molecular characterization of two isolates of sweet potato leaf curl ...

African Journals Online (AJOL)

Comparison analysis showed that DNA-A sequence of JS1 isolate was closely related to that of sweet potato leaf curl virus (SPLCV) from United States with nucleotide sequence identity of 97.0% and DNA-A of Y338 showed highest sequence identity at 97.8% with an isolate of SPLCV from China. Phylogenetic analysis ...

Wind Forcing of the Pacific Ocean Using Scatterometer Wind Data

Science.gov (United States)

Kelly, Kathryn A.

1999-01-01

The long-term objective of this research was an understanding of the wind-forced ocean circulation, particularly for the Pacific Ocean. To determine the ocean's response to the winds, we first needed to generate accurate maps of wind stress. For the ocean's response to wind stress we examined the sea surface height (SSH) both from altimeters and from numerical models for the Pacific Ocean.

Seasonal cooling and blooming in tropical oceans

Science.gov (United States)

Longhurst, Alan

1993-11-01

The relative importance of tropical pelagic algal blooms in not yet fully appreciated and the way they are induced not well understood. The tropical Atlantic supports pelagic blooms together equivalent to the North Atlantic spring bloom. These blooms are driven by thermocline tilting, curl of wind stress and eddy upwelling as the ocean responds to intensified basin-scale winds in boreal summer. The dimensions of the Pacific Ocean are such that seasonal thermocline tilting does not occur, and nutrient conditions are such that tilting might not induce bloom, in any case. Divergence at the equator is a separate process that strengthens the Atlantic bloom, is more prominent in the eastern Pacific, and in the Indian Ocean induces a bloom only in the western part of the ocean. Where western jet currents are retroflected from the coast off Somalia and Brazil, eddy upwelling induces prominent blooms. In the eastward flow of the northern equatorial countercurrents, positive wind curl stress induces Ekman pumping and the induction of algal blooms aligned with the currents. Some apparent algal bloom, such as that seen frequently in CZCS images westwards from Senegal, must be due to interference from airborne dust.

Monthly mean wind stress along the coast of the north Indian Ocean

Digital Repository Service at National Institute of Oceanography (India)

Shetye, S.R.; Shenoi, S.S.C.; Antony, M.K.; Krishnakumar, V.

Monthly-mean wind stress and its longshore and offshore components have been computed using the bulk aerodynamic method for each of a string of 36 two-degree-latitude by two-degree-longitude squares along the coast of the north Indian Ocean...

Curling Edges: A Problem that Has Plagued Scrolls for Millennia

Science.gov (United States)

Chou, Ming-Han; Shen, Wei-Chao; Wang, Yi-Ping; Hung, Sun-Hsin; Hong, Tzay-Ming

2014-01-01

Qi-Wa refers to the up curl on the lengths of hand scrolls and hanging scrolls, which has troubled Chinese artisans and emperors for as long as the art of painting and calligraphy has existed. This warp is unwelcome not only for aesthetic reasons, but its potential damage to the fiber and ink. Although it is generally treated as a part of the cockling and curling due to moisture, consistency of paste, and defects from the mounting procedures, we demonstrate that the spontaneous extrinsic curvature incurred from the storage is in fact more essential to understanding and curing Qi-Wa. In contrast to the former factors whose effects are less predictable, the plastic deformation and strain distribution on a membrane are a well-defined mechanical problem. We study this phenomenon by experiments, theoretical models, and molecular dynamics simulation, and obtain consistent scaling relations for the Qi-Wa height. This knowledge enables us to propose modifications on the traditional mounting techniques that are tested on real mounted paper to be effective at mitigating Qi-Wa. By experimenting on polymer-based films, we demonstrate the possible relevance of our study to the modern development of flexible electronic paper.

Observability of the effects of curl-free magnetic vector potential on ...

Indian Academy of Sciences (India)

We discuss here the prediction, based on a formalism by the author, on the observable effects of a curl-free magnetic vector potential on the macroscale as against the microscale of the Aharonov–Bohm effect. A new quantum concept – the 'transition amplitude wave' – postulated in the formalism has already been shown to ...

The Internal Stress Evaluation of Pultruded Blades for a Darrieus Wind Turbine

DEFF Research Database (Denmark)

Baran, Ismet; Tutum, Cem Celal; Hattel, Jesper Henri

2013-01-01

This paper investigates the integrated modeling of a pultruded NACA0018 blade profile which is a part of the FP7 EU project DeepWind. The pultrusion process simulation is combined with the preliminary subsequent in-service load scenario. In particular, the process induced residual stresses...

The Internal Stress Evaluation of Pultruded Blades for a Darrieus Wind Turbine

NARCIS (Netherlands)

Baran, Ismet; Tutum, Cem C.; Hattel, Jesper Henri

2013-01-01

This paper investigates the integrated modeling of a pultruded NACA0018 blade profile which is a part of the FP7 EU project DeepWind. The pultrusion process simulation is combined with the preliminary subsequent in-service load scenario. In particular, the process induced residual stresses and

Analysis of Mechanical Stresses Due to Voltage Dips in Fixed-Speed Wind Turbines

DEFF Research Database (Denmark)

Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

2011-01-01

stresses transients that may have a detrimental effect on the fatigue life of drivetrain system due to voltage dips. A rainflow cycle counting method for the stress history during the voltage dip event, analyses mean and amplitudes of the counted cycles, their occurrence moment and time of duration.......Voltage dips due to electrical grid faults generate transients of the generator electromagnetic torque which result in significant high stresses and noticeable vibrations for the wind turbine mechanical system. These events may also have a detrimental effect on the fatigue life of important...

Large-Deformation Curling Actuators Based on Carbon Nanotube Composite: Advanced-Structure Design and Biomimetic Application.

Science.gov (United States)

Chen, Luzhuo; Weng, Mingcen; Zhou, Zhiwei; Zhou, Yi; Zhang, Lingling; Li, Jiaxin; Huang, Zhigao; Zhang, Wei; Liu, Changhong; Fan, Shoushan

2015-12-22

In recent years, electroactive polymers have been developed as actuator materials. As an important branch of electroactive polymers, electrothermal actuators (ETAs) demonstrate potential applications in the fields of artificial muscles, biomimetic devices, robotics, and so on. Large-shape deformation, low-voltage-driven actuation, and ultrafast fabrication are critical to the development of ETA. However, a simultaneous optimization of all of these advantages has not been realized yet. Practical biomimetic applications are also rare. In this work, we introduce an ultrafast approach to fabricate a curling actuator based on a newly designed carbon nanotube and polymer composite, which completely realizes all of the above required advantages. The actuator shows an ultralarge curling actuation with a curvature greater than 1.0 cm(-1) and bending angle larger than 360°, even curling into a tubular structure. The driving voltage is down to a low voltage of 5 V. The remarkable actuation is attributed not only to the mismatch in the coefficients of thermal expansion but also to the mechanical property changes of materials during temperature change. We also construct an S-shape actuator to show the possibility of building advanced-structure actuators. A weightlifting walking robot is further designed that exhibits a fast-moving motion while lifting a sample heavier than itself, demonstrating promising biomimetic applications.

The Alignment of the Mean Wind and Stress Vectors in the Unstable Surface Layer

Science.gov (United States)

Bernardes, M.; Dias, N. L.

2010-01-01

A significant non-alignment between the mean horizontal wind vector and the stress vector was observed for turbulence measurements both above the water surface of a large lake, and over a land surface (soybean crop). Possible causes for this discrepancy such as flow distortion, averaging times and the procedure used for extracting the turbulent fluctuations (low-pass filtering and filter widths etc.), were dismissed after a detailed analysis. Minimum averaging times always less than 30 min were established by calculating ogives, and error bounds for the turbulent stresses were derived with three different approaches, based on integral time scales (first-crossing and lag-window estimates) and on a bootstrap technique. It was found that the mean absolute value of the angle between the mean wind and stress vectors is highly related to atmospheric stability, with the non-alignment increasing distinctively with increasing instability. Given a coordinate rotation that aligns the mean wind with the x direction, this behaviour can be explained by the growth of the relative error of the u- w component with instability. As a result, under more unstable conditions the u- w and the v- w components become of the same order of magnitude, and the local stress vector gives the impression of being non-aligned with the mean wind vector. The relative error of the v- w component is large enough to make it undistinguishable from zero throughout the range of stabilities. Therefore, the standard assumptions of Monin-Obukhov similarity theory hold: it is fair to assume that the v- w stress component is actually zero, and that the non-alignment is a purely statistical effect. An analysis of the dimensionless budgets of the u- w and the v- w components confirms this interpretation, with both shear and buoyant production of u- w decreasing with increasing instability. In the v- w budget, shear production is zero by definition, while buoyancy displays very low-intensity fluctuations around

Is the begomovirus, sweet potato leaf curl virus, really seed transmitted in sweetpotato?

Science.gov (United States)

Sweetpotato is one of the major root crops in the world and is also widely grown in the southern United States. Sweet potato leaf curl virus (SPLCV) is a begomovirus posing a serious threat to sweetpotato production worldwide and is primarily transmitted by whitefly (Bemisia tabaci) or through veget...

Identification of a disease complex involving a novel monopartite begomovirus with beta- and alphasatellites associated with okra leaf curl disease in Oman.

Science.gov (United States)

Akhtar, Sohail; Khan, Akhtar J; Singh, Achuit S; Briddon, Rob W

2014-05-01

Okra leaf curl disease (OLCD) is an important viral disease of okra in tropical and subtropical areas. The disease is caused by begomovirus-satellite complexes. A begomovirus and associated betasatellite and alphasatellite were identified in symptomatic okra plants from Barka, in the Al-Batinah region of Oman. Analysis of the begomovirus sequences showed them to represent a new begomovirus most closely related to cotton leaf curl Gezira virus (CLCuGeV), a begomovirus of African origin. The sequences showed less than 85 % nucleotide sequence identity to CLCuGeV isolates. The name okra leaf curl Oman virus (OLCOMV) is proposed for the new virus. Further analysis revealed that the OLCOMV is a recombinant begomovirus that evolved by the recombination of CLCuGeV isolates with tomato yellow leaf curl virus-Oman (TYLCV-OM). An alpha- and a betasatellite were also identified from the same plant sample, which were also unique when compared to sequences available in the databases. However, although the betasatellite appeared to be of African origin, the alphasatellite was most closely related to alphasatellites originating from South Asia. This is the first report of a begomovirus-satellite complex infecting okra in Oman.

Field measurement of wind pressure and wind-induced vibration of large-span spatial cable-truss system under strong wind or typhoon

Directory of Open Access Journals (Sweden)

ZHANG Zhihong

2013-10-01

Full Text Available In order to ensure wind-resistance safety of large-span pre-stressed flexible system in southeast coast area of China,and to prepare something for revising of current codes of practice or technical standards,the present paper conducts field measurement of wind pressure and wind-induced vibration of a practical and typical large-span spatial cable-truss system-lunar stadium in Yueqing city.Wind loading and wind effects on full-scale structure under strong wind or typhoon in real architectural environment can be obtained directly and effectively.Field measurement is the best way to investigate the wind loading property,wind effects,and wind-structure interactions of large-span flexible system.Measured data will be highly valuable for scientific research and practical design.On the other hand,it also provides the basis of wind-resistance safety design of this kind of tension structures.If any creative development,it would dramatically improve the research level of large-span pre-stressed flexible system in our country.

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...

Direct measurement of conformational strain energy in protofilaments curling outward from disassembling microtubule tips.

Science.gov (United States)

Driver, Jonathan W; Geyer, Elisabeth A; Bailey, Megan E; Rice, Luke M; Asbury, Charles L

2017-06-19

Disassembling microtubules can generate movement independently of motor enzymes, especially at kinetochores where they drive chromosome motility. A popular explanation is the 'conformational wave' model, in which protofilaments pull on the kinetochore as they curl outward from a disassembling tip. But whether protofilaments can work efficiently via this spring-like mechanism has been unclear. By modifying a previous assay to use recombinant tubulin and feedback-controlled laser trapping, we directly demonstrate the spring-like elasticity of curling protofilaments. Measuring their mechanical work output suggests they carry ~25% of the energy of GTP hydrolysis as bending strain, enabling them to drive movement with efficiency similar to conventional motors. Surprisingly, a β-tubulin mutant that dramatically slows disassembly has no effect on work output, indicating an uncoupling of disassembly speed from protofilament strain. These results show the wave mechanism can make a major contribution to kinetochore motility and establish a direct approach for measuring tubulin mechano-chemistry.

Diversity in Betasatellites Associated with Cotton Leaf Curl Disease During Source-To-Sink Movement Through a Resistant Host

Directory of Open Access Journals (Sweden)

Iftikhar Ali Khan

2016-02-01

Full Text Available Cotton leaf curl is devastating disease of cotton characterized by leaf curling, vein darkening and enations. The disease symptoms are induced by DNA satellite known as Cotton leaf curl Multan betasatellite (CLCuMuB, dominant betasatellite in cotton but another betasatellite known as Chili leaf curl betasatellite (ChLCB is also found associated with the disease. Grafting experiment was performed to determine if host plant resistance is determinant of dominant population of betasatellite in cotton (several distinct strains of CLCuMuB are associated with the disease. Infected scion of Gossypium hirsutum collected from field (the source was grafted on G. arboreum, a diploid cotton species, resistant to the disease. A healthy scion of G. hirsutum (sink was grafted at the top of G. arboreum to determine the movement of virus/betasatellite to upper susceptible scion of G. hirsutum. Symptoms of disease appeared in the upper scion and presence of virus/betasatellite in the upper scion was confirmed via molecular techniques, showing that virus/betasatellite was able to move to upper scion through resistant G. arboreum. However, no symptoms appeared on G. arboreum. Betasatelites were cloned and sequenced from lower scion, upper scion and G. arboreum which show that the lower scion contained both CLCuMuB and ChLCB, however only ChLCB was found in G. arboreum. The upper scion contained CLCuMuB with a deletion of 78 nucleotides (nt in the non-coding region between A-rich sequence and βC1 gene and insertion of 27 nt in the middle of βC1 ORF. This study may help in investigating molecular basis of resistance in G. arboreum.

TropFlux wind stresses over the tropical oceans: Evaluation and comparison with other products

Digital Repository Service at National Institute of Oceanography (India)

PraveenKumar, B.; Vialard, J.; Lengaigne, M.; Murty, V.S.N.; McPhaden, M.J.; Cronin, M.F.; Pinsard, F.; Reddy, K.G.

Convergence Zones. ERA-I and TropFlux display the best agreement with in situ data, with correlations more than 0.93 and rms-differences less than 0.012 Nm sup(-2). TropFlux wind stresses exhibit a small, but consistent improvement (at all timescales and most...

Turbulent Reynolds stress and quadrant event activity in wind flow over a coastal foredune

Science.gov (United States)

Chapman, Connie A.; Walker, Ian J.; Hesp, Patrick A.; Bauer, Bernard O.; Davidson-Arnott, Robin G. D.

2012-05-01

Recent research on quasi-instantaneous turbulent kinematic Reynolds stresses (RS, - u'w') and decomposed quadrant event activity (e.g., ejections and sweeps) over dunes in fluvial settings and in wind tunnels has shown that turbulent stresses at the toe of a dune often exceed time-averaged, streamwise shear stress (ρ u * 2) estimates. It is believed that semi-coherent turbulent structures are conveyed toward the bed along concave streamlines in this region and that impact of these structures cause fluctuations in local surface stresses that assist in grain entrainment. This has been hypothesized to explain how sand is supplied to the windward slope through a region of flow stagnation. Toward the crest, surface stress increases and becomes dominated by streamwise accelerations resulting from streamline compression and convexity that suppress vertical motions. High-frequency (32 Hz) measurements of turbulent wind flow from 3-D ultrasonic anemometers are analyzed for oblique onshore flow over a vegetated coastal foredune in Prince Edward Island, Canada. Reynolds stress and quadrant activity distributions varied with height (0.60 m and 1.66 m) and location over the dune. In general, quadrant 2 ejection (u' 0) and quadrant 4 sweep activity (u' > 0, w' 0, w' > 0) and quadrant 3 inward interaction (u' dune and may help to explain sand transport potential and dune maintenance. For example, areas with a high frequency of ejection and sweep activity may have higher rates of sediment entrainment and transport, whereas areas with lower ejection and sweep activity and an increase in outward and inward interactions, which contribute negatively to Reynolds stress generation, may experience a greater potential for deposition. Further research on associations between quadrant event activity and coincident sand transport is required to confirm this hypothesis and the resultant significance of the flow exuberance effect in aeolian dune morphodynamics.

Analysis of factors that influence the maximum number of repetitions in two upper-body resistance exercises: curl biceps and bench press.

Science.gov (United States)

Iglesias, Eliseo; Boullosa, Daniel A; Dopico, Xurxo; Carballeira, Eduardo

2010-06-01

The purpose of this study was to analyze the influence of exercise type, set configuration, and relative intensity load on relationship between 1 repetition maximum (1RM) and maximum number of repetitions (MNR). Thirteen male subjects, experienced in resistance training, were tested in bench press and biceps curl for 1RM, MNR at 90% of 1RM with cluster set configuration (rest of 30s between repetitions) and MNR at 70% of 1RM with traditional set configuration (no rest between repetitions). A lineal encoder was used for measuring displacement of load. Analysis of variance analysis revealed a significant effect of load (pbench press and biceps curl, respectively; pbench press and biceps curl, respectively; p>0.05). Correlation between 1RM and MNR was significant for medium-intensity in biceps curl (r=-0.574; pvelocity along set, so velocity seems to be similar at a same relative intensity for subjects with differences in maximum strength levels. From our results, we suggest the employment of MNR rather than % of 1RM for training monitoring. Furthermore, we suggest the introduction of cluster set configuration for upper-body assessment of MNR and for upper-body muscular endurance training at high-intensity loads, as it seems an efficient approach in looking for sessions with greater training volumes. This could be an interesting approach for such sports as wrestling or weightlifting.

Maintaining the Background Dust Opacity During Northern Hemisphere Summer Mars Using Wind Stress Based Dust Lifting

Science.gov (United States)

Jha, V.; Kahre, M. A.

2017-12-01

The Mars atmosphere has low levels of dust during Northern Hemisphere (NH) spring and summer (the non-dusty season) and increased levels during NH autumn and winter (the dusty season). In the absence of regional or global storms, dust devils and local storms maintain a background minimum dust loading during the non-dusty season. While observational surveys and Global Climate Model (GCM) studies suggest that dust devils are likely to be major contributors to the background haze during NH spring and summer, a complete understanding of the relative contribution of dust devils and local dust storms has not yet been achieved. We present preliminary results from an investigation that focuses on the effects of radiatively active water ice clouds on dust lifting processes during these seasons. Water ice clouds are known to affect atmospheric temperatures directly by absorption and emission of thermal infrared radiation and indirectly through dynamical feedbacks. Our goal is to understand how clouds affect the contribution by local (wind stress) dust storms to the background dust haze during NH spring and summer. The primary tool for this work is the NASA Ames Mars GCM, which contains physical parameterizations for a fully interactive dust cycle. Three simulations that included wind stress dust lifting were executed for a period of 5 Martian years: a case that included no cloud formation, a case that included radiatively inert cloud formation and a case that included radiatively active cloud (RAC) formation. Results show that when radiatively active clouds are included, the clouds in the aphelion cloud belt radiatively heat the atmosphere aloft in the tropics (Figure 1). This heating produces a stronger overturning circulation, which in turn produces an enhanced low-level flow in the Hadley cell return branch. The stronger low-level flow drives higher surface stresses and increased dust lifting in those locations. We examine how realistic these simulated results are by

A weak Galerkin least-squares finite element method for div-curl systems

Science.gov (United States)

Li, Jichun; Ye, Xiu; Zhang, Shangyou

2018-06-01

In this paper, we introduce a weak Galerkin least-squares method for solving div-curl problem. This finite element method leads to a symmetric positive definite system and has the flexibility to work with general meshes such as hybrid mesh, polytopal mesh and mesh with hanging nodes. Error estimates of the finite element solution are derived. The numerical examples demonstrate the robustness and flexibility of the proposed method.

Turbulent wind at the equatorial segment of an operating Darrieus wind turbine blade

Science.gov (United States)

Connell, J. R.; Morris, V. R.

1989-09-01

Six turbulent wind time series, measured at equally spaced equator-height locations on a circle 3 m outside a 34-m Darrieus rotor, are analyzed to approximate the wind fluctuations experienced by the rotor. The flatwise lower root-bending stress of one blade was concurrently recorded. The wind data are analyzed in three ways: wind components that are radial and tangential to the rotation of a blade were rotationally sampled; induction and wake effects of the rotor were estimated from the six Eulerian time series; and turbulence spectra of both the measured wind and the modeled wind from the PNL theory of rotationally sampled turbulence. The wind and the rotor response are related by computing the spectral response function of the flatwise lower root-bending stress. Two bands of resonant response that surround the first and second flatwise modal frequencies shift with the rotor rotation rate.

Predicting the presence of whiteflies and tomato yellow leaf curl virus in Florida tomato fields

Science.gov (United States)

Florida is one of the leading states for production of fresh market tomatoes. Production is severely affected by Tomato yellow leaf curl virus (TYLCV). The objective of this study was to identify landscape and climatic factors that drive whitefly populations and TYLCV incidence in commercial tomato ...

Wheat curl mite and dry bulb mite: untangling a taxonomic conundrum through a multidisciplinary approach

Science.gov (United States)

The taxonomy of two economically important eriophyoid species, Aceria tosichella (wheat curl mite, WCM) and A. tulipae (dry bulb mite, DBM), was confounded in the world literature until the late 20th century due to their morphological similarity and ambiguous data from plant-transfer and virus-trans...

Human cold stress of strong local-wind "Hijikawa-arashi" in Japan, based on the UTCI index and thermo-physiological responses

Science.gov (United States)

Ohashi, Yukitaka; Katsuta, Takumi; Tani, Haruka; Okabayashi, Taiki; Miyahara, Satoshi; Miyashita, Ryoji

2018-03-01

We investigated the cold stress caused by a strong local wind called "Hijikawa-arashi," through in situ vital measurements and the Universal Thermal Climate Index (UTCI). This wind is a very interesting winter phenomenon, localized in an area within 1 km of the seashore in Ozu City, Ehime Prefecture in Japan. When a strong Hijikawa-arashi (HA) occurred at 14-15 m s-1, the UTCI decreased to - 30 °C along the bridge where commuting residents are the most exposed to strong and cold winds. On the bridge, most participants in our experiment felt "very cold" or "extremely cold." The UTCI of HA can be predicted from a multiple regression equation using wind speed and air temperature. The cold HA wind is also harmful to human thermo-physiological responses. It leads to higher blood pressure and increased heart rate, both of which act as cardiovascular stress triggers. Increases of 6-10 mmHg and 3-6 bpm for every 10 °C reduction in UTCI were seen on all observational days, including HA and non-HA days. In fact, the participants' body skin temperatures decreased by approximately 1.2 to 1.7 °C for every 10 °C reduction in UTCI. Thus, the UTCI variation due to the HA outbreak corresponded well with the cold sensation and thermo-physiological responses in humans. This result suggests that daily UTCI monitoring enables the prediction of thermo-physiological responses to the HA cold stress.

The relationship between the microwave radar cross section and both wind speed and stress: Model function studies using Frontal Air-Sea Interaction Experiment data

Science.gov (United States)

Weissman, David E.; Davidson, Kenneth L.; Brown, Robert A.; Friehe, Carl A.; Li, Fuk

1994-01-01

The Frontal Air-Sea Interaction Experiment (FASINEX) provided a unique data set with coincident airborne scatterometer measurements of the ocean surface radar cross section (RCS)(at Ku band) and near-surface wind and wind stress. These data have been analyzed to study new model functions which relate wind speed and surface friction velocity (square root of the kinematic wind stress) to the radar cross section and to better understand the processes in the boundary layer that have a strong influence on the radar backscatter. Studies of data from FASINEX indicate that the RCS has a different relation to the friction velocity than to the wind speed. The difference between the RCS models using these two variables depends on the polarization and the incidence angle. The radar data have been acquired from the Jet Propulsion Laboratory airborne scatterometer. These data span 10 different flight days. Stress measurements were inferred from shipboard instruments and from aircraft flying at low altitudes, closely following the scatterometer. Wide ranges of radar incidence angles and environmental conditions needed to fully develop algorithms are available from this experiment.

Flat acoustic lens by acoustic grating with curled slits

KAUST Repository

Peng, Pai

2014-10-01

We design a flat sub-wavelength lens that can focus acoustic wave. We analytically study the transmission through an acoustic grating with curled slits, which can serve as a material with tunable impedance and refractive index for acoustic waves. The effective parameters rely on the geometry of the slits and are independent of frequency. A flat acoustic focusing lens by such acoustic grating with gradient effective refractive index is designed. The focusing effect is clearly observed in simulations and well predicted by the theory. We demonstrate that despite the large impedance mismatch between the acoustic lens and the matrix, the intensity at the focal point is still high due to Fabry-Perot resonance.

Association of an Alphasatellite with Tomato Yellow Leaf Curl Virus and Ageratum Yellow Vein Virus in Japan is Suggestive of a Recent Introduction

OpenAIRE

Shahid, Muhammad Shafiq; Ikegami, Masato; Waheed, Abdul; Briddon, Rob W.; Natsuaki, Keiko T.

2014-01-01

Samples were collected in 2011 from tomato plants exhibiting typical tomato leaf curl disease symptoms in the vicinity of Komae, Japan. PCR mediated amplification, cloning and sequencing of all begomovirus components from two plants from different fields showed the plants to be infected by Tomato yellow leaf curl virus (TYLCV) and Ageratum yellow vein virus (AYVV). Both viruses have previously been shown to be present in Japan, although this is the first identification of AYVV on mainland Jap...

Human cold stress of strong local-wind "Hijikawa-arashi" in Japan, based on the UTCI index and thermo-physiological responses.

Science.gov (United States)

Ohashi, Yukitaka; Katsuta, Takumi; Tani, Haruka; Okabayashi, Taiki; Miyahara, Satoshi; Miyashita, Ryoji

2018-03-30

We investigated the cold stress caused by a strong local wind called "Hijikawa-arashi," through in situ vital measurements and the Universal Thermal Climate Index (UTCI). This wind is a very interesting winter phenomenon, localized in an area within 1 km of the seashore in Ozu City, Ehime Prefecture in Japan. When a strong Hijikawa-arashi (HA) occurred at 14-15 m s -1 , the UTCI decreased to - 30 °C along the bridge where commuting residents are the most exposed to strong and cold winds. On the bridge, most participants in our experiment felt "very cold" or "extremely cold." The UTCI of HA can be predicted from a multiple regression equation using wind speed and air temperature. The cold HA wind is also harmful to human thermo-physiological responses. It leads to higher blood pressure and increased heart rate, both of which act as cardiovascular stress triggers. Increases of 6-10 mmHg and 3-6 bpm for every 10 °C reduction in UTCI were seen on all observational days, including HA and non-HA days. In fact, the participants' body skin temperatures decreased by approximately 1.2 to 1.7 °C for every 10 °C reduction in UTCI. Thus, the UTCI variation due to the HA outbreak corresponded well with the cold sensation and thermo-physiological responses in humans. This result suggests that daily UTCI monitoring enables the prediction of thermo-physiological responses to the HA cold stress.

Sequence characterization of cotton leaf curl virus from Rajasthan: phylogenetic relationship with other members of geminiviruses and detection of recombination.

Science.gov (United States)

Kumar, A; Kumar, J; Khan, J A

2010-04-01

Diseased cotton plants showing typical leaf curl symptoms were collected from experimental plot of Agriculture Research Station-Sriganganagar, Rajasthan. Complete DNA-A component from samples taken from two areas were amplified through rolling circle amplification (RCA) using templiphi kit (GE Healthcare) and characterized. DNA-A of one isolate consists of 2751 nucleotides and second isolate of 2759 nucleotide. Both sequences comprised six ORF's. Genome organization of DNA-A of one isolate shows high sequence similarity with other characterized local begomovirus isolates of Rajasthan, while other isolate shows high sequence similarity with CLCuV reported from Pakistan. The maximum similarity of first isolate, CLCuV-SG01, shows highest sequence identity with Cotton leaf curl Abohar (Rajasthan) virus, and second isolate, CLCuV-SG02, shows highest sequence identity with cotton leaf curl virus from Pakistan. Both isolates showed 85% similarities with each other. The sequence data revealed probable infiltration of some strains of Cotton leaf curl virus from Pakistan to India, or co-existence of different isolates under similar geographical conditions. While CLCuV-SG01 shows highest nt sequence similarity with CLCuV Rajasthan (Abohar), nt identity of V1 ORF (encoding coat protein) of SG01 shows the highest nt identity (100%) with CLCuV Multan (Bhatinda) and Abohar virus while AC1 region also showed difference. Complete nucleotide sequence of SG01 shows only 86% similarity with CLCuV Multan virus. Similarity search revealed significant difference in AV1 and AC1 regions with respect to DNA-A suggesting an evolutionary history of recombination. Computer based analysis, recombination detection Program (RDP) supports the recombination hypothesis, indicated that recombination with other begomoviruses had taken place within V1 ORF and AC1 ORF of CLCuV-SG01 and AC1 ORF of CLCuV-SG02 and also in noncoding intergenic region (IR).

Isolation and sequence characterization of DNA-A genome of a new begomovirus strain associated with severe leaf curling symptoms of Jatropha curcas L.

KAUST Repository

Chauhan, Sushma

2018-04-22

Begomoviruses belong to the family Geminiviridae are associated with several disease symptoms, such as mosaic and leaf curling in Jatropha curcas. The molecular characterization of these viral strains will help in developing management strategies to control the disease. In this study, J. curcas that was infected with begomovirus and showed acute leaf curling symptoms were identified. DNA-A segment from pathogenic viral strain was isolated and sequenced. The sequenced genome was assembled and characterized in detail. The full-length DNA-A sequence was covered by primer walking. The genome sequence showed the general organization of DNA-A from begomovirus by the distribution of ORFs in both viral and anti-viral strands. The genome size ranged from 2844 bp–2852 bp. Three strains with minor nucleotide variations were identified, and a phylogenetic analysis was performed by comparing the DNA-A segments from other reported begomovirus isolates. The maximum sequence similarity was observed with Euphorbia yellow mosaic virus (FN435995). In the phylogenetic tree, no clustering was observed with previously reported begomovirus strains isolated from J. curcas host. The strains isolated in this study belong to new begomoviral strain that elicits symptoms of leaf curling in J. curcas. The results indicate that the probable origin of the strains is from Jatropha mosaic virus infecting J. gassypifolia. The strains isolated in this study are referred as Jatropha curcas leaf curl India virus (JCLCIV) based on the major symptoms exhibited by host J. curcas.

Remote wind stress influence on mean sea level in a subtropical coastal region

Directory of Open Access Journals (Sweden)

Mabel Calim Costa

2012-09-01

Full Text Available The purpose of this study was to assess the relative influence of remote wind stress on mean sea level (MSL variations in the coastal region of Cananeia (Sao Paulo State, Southern Brazil during the period from 1/1/1955 to 12/31/1993. An optimized low-pass Thompson filter for the study area, and spectral analysis (cross spectrum, coherence and phase lag of the relationship between the MSL and both parallel (T// and perpendicular (T| wind stress components were applied. These were extracted from four grid points of the NCEP/NCAR global model. The predominance of annual oscillations as those of greatest coherence and energy, of periods of approximately 341 days (frequency of 0.00293 cpd and 410 days (frequency of 0.00244 cpd, respectively, were observed. Offshore NCEP/NCAR grid points were those with the highest coherence and energy throughout the study in relation to the observed MSL. This may be linked to the restriction of the NCEP/NCAR model as regards the inland limit. It is also concluded that remote wind stress may play an important role in several MSL time scales, including the annual ones. Based on criteria such as coherence and energy peaks, the wind stress component of greatest effect on MSL was the parallel one.O presente estudo tem por objetivo avaliar a influência relativa de tensão do vento remoto na variação do nível médio do mar (NMM para a região costeira de Cananéia (SP durante o período de 1/1/1955 a 31/12/1993. Foram aplicados um filtro de passa-baixa de Thompson (1983, otimizado para a região de Cananéia, além de análise espectral (espectro cruzado, coerência e defasagem entre o NMM e as componentes paralela (T// e perpendicular (T| da tensão do vento. Estas foram extraídas de quatro pontos de grade do modelo global NCEP/NCAR. Observou-se a predominância das oscilações anuais como aquelas de maior coerência e energia, destacando-se os períodos de aproximadamente 341 dias (frequência de 0,00293 cpd e 410

Correlation of meteorological parameters and remotely sensed normalized difference vegetation index (NDVI) with cotton leaf curl virus (CLCV) in Multan

International Nuclear Information System (INIS)

Ahmed, A; Akhtar, A; Khalid, B; Shamim, A

2013-01-01

Climate change and weather has a profound effect on the spread of Cotton Leaf Curl Virus (CLCV) which is transmitted by whitefly. Climate change is altering temperature and precipitation patterns, resulting in the shift of some insect/pest from small population to large population thus effecting crops yield. To find out the relationship between the weather conditions, outburst of CLCV and changes in Normalized Difference Vegetation Index (NDVI) values due to the outburst of CLCV, a study was carried out for tehsil Multan. Data was acquired for the months of June, July, August and September for the year 2010. Regression analysis between CLCV and meteorological conditions as well as between CLCV and NDVI was performed. Meteorological parameters included temperature, humidity, precipitation, cloud cover, wind direction, pan evaporation and sunshine hours. NDVI values were calculated from SPOT satellite imagery (1km) using ArcMap10 and WinDisp v5.1. Correlation coefficients obtained in most of the cases were acceptable however the significance F and P-value were higher than their critical value at 95% level of significance. Therefore significant correlation was found only between CLCV and temperature and between CLCV and PAN evaporation during the month of July.

Tomato yellow leaf curl virus can be acquired and transmitted by Bemisia tabaci (Gennadius) from tomato fruits

NARCIS (Netherlands)

Delatte, H.; Dalmon, A.; Rist, D.; Soustrade, I.; Wuster, G.; Lett, J.M.; Goldbach, R.W.; Peterschmitt, M.; Reynaud, B.

2003-01-01

The whitefly Bemisia tabaci is an insect pest causing worldwide economic losses, especially as a vector of geminiviruses such as Tomato yellow leaf curl virus (TYLCV). Currently, imported and exported tomato fruit are not monitored for TYLCV infection because they are not considered to represent a

Surface Buoyancy Fluxes and the Strength of the Subpolar Gyre

Science.gov (United States)

Hogg, A. M.; Gayen, B.

2017-12-01

Midlatitude ocean gyres have long been considered to be driven by the mechanical wind stress on the ocean's surface (strictly speaking, the potential vorticity input from wind stress curl). However, surface buoyancy forcing (i.e. heating/cooling or freshening/salinification) also modifies the potential vorticity at the surface. Here, we present a simple argument to demonstrate that ocean gyres may (in principle) be driven by surface buoyancy forcing. This argument is derived in two ways: A Direct Numerical Simulation, driven purely by buoyancy forcing, which generates strong nonlinear gyers in the absence of wind stress; and A series of idealised eddy-resolving numerical ocean model simulations, in which wind stress and buoyancy flux are varied independently and together, are used to understand the relative importance of these two types of forcing. In these simulations, basin-scale gyres and western boundary currents with realistic magnitudes, remain even in the absence of mechanical forcing by surface wind stress. These results support the notion that surface buoyancy forcing can reorganise the potential vorticity in the ocean in such a way as to drive basin-scale gyres. The role of buoyancy is stronger in the subpolar gyre than in the subtropical gyre. We infer that surface buoyancy fluxes are likely to play a contributing role in governing the strength, variability and predictability of the North Atlantic subpolar gyre.

Isolation and sequence characterization of DNA-A genome of a new begomovirus strain associated with severe leaf curling symptoms of Jatropha curcas L.

Science.gov (United States)

Chauhan, Sushma; Rahman, Hifzur; Mastan, Shaik G; Pamidimarri, D V N Sudheer; Reddy, Muppala P

2018-07-20

Begomoviruses belong to the family Geminiviridae are associated with several disease symptoms, such as mosaic and leaf curling in Jatropha curcas. The molecular characterization of these viral strains will help in developing management strategies to control the disease. In this study, J. curcas that was infected with begomovirus and showed acute leaf curling symptoms were identified. DNA-A segment from pathogenic viral strain was isolated and sequenced. The sequenced genome was assembled and characterized in detail. The full-length DNA-A sequence was covered by primer walking. The genome sequence showed the general organization of DNA-A from begomovirus by the distribution of ORFs in both viral and anti-viral strands. The genome size ranged from 2844 bp-2852 bp. Three strains with minor nucleotide variations were identified, and a phylogenetic analysis was performed by comparing the DNA-A segments from other reported begomovirus isolates. The maximum sequence similarity was observed with Euphorbia yellow mosaic virus (FN435995). In the phylogenetic tree, no clustering was observed with previously reported begomovirus strains isolated from J. curcas host. The strains isolated in this study belong to new begomoviral strain that elicits symptoms of leaf curling in J. curcas. The results indicate that the probable origin of the strains is from Jatropha mosaic virus infecting J. gassypifolia. The strains isolated in this study are referred as Jatropha curcas leaf curl India virus (JCLCIV) based on the major symptoms exhibited by host J. curcas. Copyright © 2018 Elsevier B.V. All rights reserved.

Infection of the whitefly Bemisia tabaci with Rickettsia spp. alters its interactions with Tomato yellow leaf curl virus

Science.gov (United States)

Numerous animal and plant viruses are transmitted by arthropod vectors in a persistent, circulative manner. Tomato yellow leaf curl virus (TYLCV) is transmitted by the sweet potato whitefly Bemisia tabaci. Here we report that infection with Rickettsia spp., a facultative endosymbiont of whiteflies...

The single-leg Roman chair hold is more effective than the Nordic hamstring curl in improving hamstring strength-endurance in Gaelic footballers with previous hamstring injury.

Science.gov (United States)

Macdonald, Ben; O'Neill, John; Pollock, Noel; Van Hooren, Bas

2018-03-06

Poor hamstring strength-endurance is a risk factor for hamstring injuries. This study investigated the effectiveness of the single-leg Roman hold and Nordic hamstring curl in improving hamstring strength-endurance. Twelve Gaelic footballers (mean ± standard deviation age, height and mass were 25.17 ± 3.46 years, 179.25 ± 5.88 cm, 85.75 ± 4.75 kilo) with a history of hamstring injury were randomized into 2 groups that performed 6 weeks of either Nordic hamstring curl, or single-leg Roman chair hold training. The single-leg hamstring bridge (SLHB) was measured pre- and post- intervention. The Roman chair group showed a very likely moderate magnitude improvement on SLHB performance for both legs (23.7% for the previously injured leg [90% confidence interval 9.6% to 39.6%] and 16.9% for the non-injured leg [6.2% to 28.8%]). The Nordic curl group showed a likely trivial change in SLHB performance for the non-injured leg (-2.1% [-6.7% to 2.6%]) and an unclear, but possibly trivial change for the previously injured leg (0.3% [-5.6% to 6.6%]). The Roman chair group improved very likely more with a moderate magnitude in both the non-injured (19.5% [8.0% to 32.2%]) and the previously injured leg (23.3% [8.5% to 40.0%]) compared to the Nordic curl group. This study demonstrated that 6-weeks single-leg Roman chair training substantially improved SLHB performance, suggesting that it may be an efficacious strategy to mitigate hamstring (re-) injury risk. Conversely, 6-weeks Nordic curl training did not substantially improve SLHB performance, suggesting this may not be the intervention of choice for modifying this risk factor.

Genetic diversity and distribution of a distinct strain of Chili leaf curl virus and associated betasatellite infecting tomato and pepper in Oman.

Science.gov (United States)

Khan, Akhtar J; Akhtar, Sohail; Al-Zaidi, Amal M; Singh, Achuit K; Briddon, Rob W

2013-10-01

Tomato and pepper are widely grown in Oman for local consumption. A countrywide survey was conducted during 2010-2011 to collect samples and assess the diversity of begomoviruses associated with leaf curl disease of tomato and pepper. A virus previously only identified on the Indian subcontinent, chili leaf curl virus (ChLCV), was found associated with tomato and pepper diseases in all vegetable grown areas of Oman. Some of the infected plant samples were also found to contain a betasatellite. A total of 19 potentially full-length begomovirus and eight betasatellite clones were sequenced. The begomovirus clones showed >96% nucleotide sequence identity, showing them to represent a single species. Comparisons to sequences available in the databases showed the highest levels of nucleotide sequence identity (88.0-91.1%) to isolates of the "Pakistan" strain of ChLCV (ChLCV-PK), indicating the virus from Oman to be a distinct strain, for which the name Oman strain (ChLCV-OM) is proposed. An analysis for recombination showed ChLCV-OM likely to have originated by recombination between ChLCV-PK (the major parent), pepper leaf curl Lahore virus and a third strain of ChLCV. The betasatellite sequences obtained were shown to have high levels of identity to isolates of tomato leaf curl betasatellite (ToLCB) previous shown to be present in Oman. For the disease in tomato Koch's postulates were satisfied by Agrobacterium-mediated inoculation of virus and betasatellites clones. This showed the symptoms induced by the virus in the presence of the betasatellite to be enhanced, although viral DNA levels were not affected. ChLCV-OM is the fourth begomovirus identified in tomato in Oman and the first in Capsicum. The significance of these findings is discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

Geometric classification of scalp hair for valid drug testing, 6 more reliable than 8 hair curl groups.

Directory of Open Access Journals (Sweden)

K Mkentane

Full Text Available Curly hair is reported to contain higher lipid content than straight hair, which may influence incorporation of lipid soluble drugs. The use of race to describe hair curl variation (Asian, Caucasian and African is unscientific yet common in medical literature (including reports of drug levels in hair. This study investigated the reliability of a geometric classification of hair (based on 3 measurements: the curve diameter, curl index and number of waves.After ethical approval and informed consent, proximal virgin (6cm hair sampled from the vertex of scalp in 48 healthy volunteers were evaluated. Three raters each scored hairs from 48 volunteers at two occasions each for the 8 and 6-group classifications. One rater applied the 6-group classification to 80 additional volunteers in order to further confirm the reliability of this system. The Kappa statistic was used to assess intra and inter rater agreement.Each rater classified 480 hairs on each occasion. No rater classified any volunteer's 10 hairs into the same group; the most frequently occurring group was used for analysis. The inter-rater agreement was poor for the 8-groups (k = 0.418 but improved for the 6-groups (k = 0.671. The intra-rater agreement also improved (k = 0.444 to 0.648 versus 0.599 to 0.836 for 6-groups; that for the one evaluator for all volunteers was good (k = 0.754.Although small, this is the first study to test the reliability of a geometric classification. The 6-group method is more reliable. However, a digital classification system is likely to reduce operator error. A reliable objective classification of human hair curl is long overdue, particularly with the increasing use of hair as a testing substrate for treatment compliance in Medicine.

Aphid transmission of Lettuce necrotic leaf curl virus, a member of atentative new subgroup within the genus Torradovirus

NARCIS (Netherlands)

Verbeek, M.; Dullemans, A.M.; Vlugt, van der R.A.A.

2017-01-01

Lettuce necrotic leaf curl virus (LNLCV) was described as the first non-tomato-infecting member of the genus Torradovirus. Until today, the virus was found only in The Netherlands in two different areas in open field crops of lettuce. In 2015, LNLCV was accepted by the ICTV as a new member of the

A randomised clinical trial of the efficacy of drop squats or leg extension/leg curl exercises to treat clinically diagnosed jumper's knee in athletes: pilot study

Science.gov (United States)

Cannell, L; Taunton, J; Clement, D; Smith, C; Khan, K

2001-01-01

Objectives—To compare the therapeutic effect of two different exercise protocols in athletes with jumper's knee. Methods—Randomised clinical trial comparing a 12 week programme of either drop squat exercises or leg extension/leg curl exercises. Measurement was performed at baseline and after six and 12 weeks. Primary outcome measures were pain (visual analogue scale 1–10) and return to sport. Secondary outcome measures included quadriceps and hamstring moment of force using a Cybex II isokinetic dynamometer at 30°/second. Differences in pain response between the drop squat and leg extension/curl treatment groups were assessed by 2 (group) x 3 (time) analysis of variance. Two by two contingency tables were used to test differences in rates of return to sport. Analysis of variance (2 (injured versus non-injured leg) x 2 (group) x 3 (time)) was also used to determine differences for secondary outcome measures. Results—Over the 12 week intervention, pain diminished by 2.3 points (36%) in the leg extension/curl group and 3.2 points (57%) in the squat group. There was a significant main effect of both exercise protocols on pain (psquat group returned to sporting activity by 12 weeks, but five of those subjects still had low level pain. Six of nine of the leg extension/curl group returned to sporting activity by 12 weeks and four patients had low level pain. There was no significant difference between groups in numbers returning to sporting activity. There were no differences in the change in quadriceps or hamstring muscle moment of force between groups. Conclusions—Progressive drop squats and leg extension/curl exercises can reduce the pain of jumper's knee in a 12 week period and permit a high proportion of patients to return to sport. Not all patients, however, return to sport by that time. Key Words: knee; patellar tendon; tendinopathy; tendinosis; eccentric strengthening; strength training PMID:11157465

Variations of Sea Surface Temperature, Wind Stress, and Rainfall over the Tropical Atlantic and South America.

Science.gov (United States)

Nobre, Paulo; Srukla, J.

1996-10-01

Empirical orthogonal functions (E0Fs) and composite analyses are used to investigate the development of sea surface temperature (SST) anomaly patterns over the tropical Atlantic. The evolution of large-scale rainfall anomaly patterns over the equatorial Atlantic and South America are also investigated. 71e EOF analyses revealed that a pattern of anomalous SST and wind stress asymmetric relative to the equator is the dominant mode of interannual and longer variability over the tropical Atlantic. The most important findings of this study are as follows.Atmospheric circulation anomalies precede the development of basinwide anomalous SST patterns over the tropical Atlantic. Anomalous SST originate off the African coast simultaneously with atmospheric circulation anomalies and expand westward afterward. The time lag between wind stress relaxation (strengthening) and maximum SST warming (cooling) is about two months.Anomalous atmospheric circulation patterns over northern tropical Atlantic are phase locked to the seasonal cycle. Composite fields of SLP and wind stress over northern tropical Atlantic can be distinguished from random only within a few months preceding the March-May (MAM) season. Observational evidence is presented to show that the El Niño-Southern Oscillation phenomenon in the Pacific influences atmospheric circulation and SST anomalies over northern tropical Atlantic through atmospheric teleconnection patterns into higher latitudes of the Northern Hemisphere.The well-known droughts over northeastern Brazil (Nordeste) are a local manifestation of a much larger-scale rainfall anomaly pattern encompassing the whole equatorial Atlantic and Amazon region. Negative rainfall anomalies to the south of the equator during MAM, which is the rainy season for the Nordeste region, are related to an early withdrawal of the intertropical convergence zone toward the warm SST anomalies over the northern tropical Atlantic. Also, it is shown that precipitation anomalies

Genome organization of Tobacco leaf curl Zimbabwe virus, a new, distinct monopartite begomovirus associated with subgenomic defective DNA molecules.

Science.gov (United States)

Paximadis, M; Rey, M E

2001-12-01

The complete DNA A of the begomovirus Tobacco leaf curl Zimbabwe virus (TbLCZWV) was sequenced: it comprises 2767 nucleotides with six major open reading frames encoding proteins with molecular masses greater than 9 kDa. Full-length TbLCZWV DNA A tandem dimers, cloned in binary vectors (pBin19 and pBI121) and transformed into Agrobacterium tumefaciens, were systemically infectious upon agroinoculation of tobacco and tomato. Efforts to identify a DNA B component were unsuccessful. These findings suggest that TbLCZWV is a new member of the monopartite group of begomoviruses. Phylogenetic analysis identified TbLCZWV as a distinct begomovirus with its closest relative being Chayote mosaic virus. Abutting primer PCR amplified ca. 1300 bp molecules, and cloning and sequencing of two of these molecules revealed them to be subgenomic defective DNA molecules originating from TbLCZWV DNA A. Variable symptom severity associated with tobacco leaf curl disease and TbLCZWV is discussed.

Analytical solutions of the electrostatically actuated curled beam problem

KAUST Repository

Younis, Mohammad I.

2014-07-24

This works presents analytical expressions of the electrostatically actuated initially deformed cantilever beam problem. The formulation is based on the continuous Euler-Bernoulli beam model combined with a single-mode Galerkin approximation. We derive simple analytical expressions for two commonly observed deformed beams configurations: the curled and tilted configurations. The derived analytical formulas are validated by comparing their results to experimental data and numerical results of a multi-mode reduced order model. The derived expressions do not involve any complicated integrals or complex terms and can be conveniently used by designers for quick, yet accurate, estimations. The formulas are found to yield accurate results for most commonly encountered microbeams of initial tip deflections of few microns. For largely deformed beams, we found that these formulas yield less accurate results due to the limitations of the single-mode approximation. In such cases, multi-mode reduced order models are shown to yield accurate results. © 2014 Springer-Verlag Berlin Heidelberg.

Association of an alphasatellite with tomato yellow leaf curl virus and ageratum yellow vein virus in Japan is suggestive of a recent introduction.

Science.gov (United States)

Shahid, Muhammad Shafiq; Ikegami, Masato; Waheed, Abdul; Briddon, Rob W; Natsuaki, Keiko T

2014-01-14

Samples were collected in 2011 from tomato plants exhibiting typical tomato leaf curl disease symptoms in the vicinity of Komae, Japan. PCR mediated amplification, cloning and sequencing of all begomovirus components from two plants from different fields showed the plants to be infected by Tomato yellow leaf curl virus (TYLCV) and Ageratum yellow vein virus (AYVV). Both viruses have previously been shown to be present in Japan, although this is the first identification of AYVV on mainland Japan; the virus previously having been shown to be present on the Okinawa Islands. The plant harboring AYVV was also shown to contain the betasatellite Tomato leaf curl Java betasatellite (ToLCJaB), a satellite not previously shown to be present in Japan. No betasatellite was associated with the TYLCV infected tomato plants analyzed here, consistent with earlier findings for this virus in Japan. Surprisingly both plants were also found to harbor an alphasatellite; no alphasatellites having previously been reported from Japan. The alphasatellite associated with both viruses was shown to be Sida yellow vein China alphasatellite which has previously only been identified in the Yunnan Province of China and Nepal. The results suggest that further begomoviruses, and their associated satellites, are being introduced to Japan. The significance of these findings is discussed.

Association of an Alphasatellite with Tomato Yellow Leaf Curl Virus and Ageratum Yellow Vein Virus in Japan Is Suggestive of a Recent Introduction

Directory of Open Access Journals (Sweden)

Muhammad Shafiq Shahid

2014-01-01

Full Text Available Samples were collected in 2011 from tomato plants exhibiting typical tomato leaf curl disease symptoms in the vicinity of Komae, Japan. PCR mediated amplification, cloning and sequencing of all begomovirus components from two plants from different fields showed the plants to be infected by Tomato yellow leaf curl virus (TYLCV and Ageratum yellow vein virus (AYVV. Both viruses have previously been shown to be present in Japan, although this is the first identification of AYVV on mainland Japan; the virus previously having been shown to be present on the Okinawa Islands. The plant harboring AYVV was also shown to contain the betasatellite Tomato leaf curl Java betasatellite (ToLCJaB, a satellite not previously shown to be present in Japan. No betasatellite was associated with the TYLCV infected tomato plants analyzed here, consistent with earlier findings for this virus in Japan. Surprisingly both plants were also found to harbor an alphasatellite; no alphasatellites having previously been reported from Japan. The alphasatellite associated with both viruses was shown to be Sida yellow vein China alphasatellite which has previously only been identified in the Yunnan Province of China and Nepal. The results suggest that further begomoviruses, and their associated satellites, are being introduced to Japan. The significance of these findings is discussed.

Wind-Induced Reconfigurations in Flexible Branched Trees

Science.gov (United States)

Ojo, Oluwafemi; Shoele, Kourosh

2017-11-01

Wind induced stresses are the major mechanical cause of failure in trees. We know that the branching mechanism has an important effect on the stress distribution and stability of a tree in the wind. Eloy in PRL 2011, showed that Leonardo da Vinci's original observation which states the total cross section of branches is conserved across branching nodes is the best configuration for resisting wind-induced fracture in rigid trees. However, prediction of the fracture risk and pattern of a tree is also a function of their reconfiguration capabilities and how they mitigate large wind-induced stresses. In this studies through developing an efficient numerical simulation of flexible branched trees, we explore the role of the tree flexibility on the optimal branching. Our results show that the probability of a tree breaking at any point depends on both the cross-section changes in the branching nodes and the level of tree flexibility. It is found that the branching mechanism based on Leonardo da Vinci's original observation leads to a uniform stress distribution over a wide range of flexibilities but the pattern changes for more flexible systems.

Comparison of residual stresses in sand- and chill casting of ductile cast iron wind turbine main shafts

International Nuclear Information System (INIS)

Sonne, M R; Hattel, J H; Frandsen, J O

2015-01-01

In this work, simulations of pouring, solidification and cooling, and residual stress evolution of sand and chill cast wind turbine main shafts is performed. The models are made in the commercial software MAGMAsoft. As expected, the cooling rate of the sand casting is shown to be much lower than for the chill casting, resulting in a very course microstructure. From the simulations the nodule count is found to be 17 nodules per mm 2 and 159 nodules per mm 2 for the sand and chill casting, respectively, in the critical region of the main bearing seat. This is verified from nodule counts performed on the real cast main shafts. Residual stress evaluations show an overall increase of the maximum principal stress field for the chill casting, which is expected. However, the stresses are found to be in compression on the surface of the chill cast main shaft, which is unforeseen. (paper)

Dependence of Wave-Breaking Statistics on Wind Stress and Wave Development

Science.gov (United States)

Katsaros, Kristina B.; Atakturk, Serhad S.

1992-01-01

Incidence of wave breaking for pure wind driven waves has been studied on Lake Washington at wind speeds up to 8 m/s. Video recordings were employed to identify and categorize the breaking events in terms of micro-scale, spilling and plunging breakers. These events were correlated with the magnitude of the wave spectrum measured with a resistance wire wave gauge and band pass filtered between 6 and 10 Hz. An equivalent percentage of breaking crests were found for spilling and plunging events. Wave forcing as measured by wind stress (or friction velocity, u(sub *), squared) and by inverse wave age, u(sub *)/Cp where Cp is the phase velocity of the waves at the peak of the frequency spectrum, were found to be good prerictors of percentage of breaking crests. When combined in a two parameter regression, those two variables gave small standard deviation and had a high correlation coefficient (66 percent). The combination of u(sub *)(exp 2) and u(sub *)/Cp can be understood in physical terms. Furthermore, for the larger values of u(sub *)(exp 2) the dependence of wave braking and wave age was stronger than at the low end of the values u(sub *)(exp 2) and u(sub *)/Cp. Thus, both the level of wave development as determined by inverse wave age, which we may term relative wind effectiveness for wave forcing and the wind forcing on the water surface determine the incidence of wave breaking. Substituting U(sub 10)(sup 3.75) (which is the dependence of whitecap cover found by Monahan and coworkers) an equivalent correlation was found to the prediction by u(sub *)(exp 2). Slightly better standard deviation value and higher correlation coefficient were found by using a Reynolds number as predictor. A two-parameter regression involving u(sub *)(exp 2) and a Reynold's number proposed by Toba and his colleagues which relates u(sub *)(exp 2) and peak wave frequency, improves the correlation even more but is less easy to interpret in physical terms. The equivalent percentage of

Rigid MATLAB drivetrain model of a 500 kW wind turbine for predicting maximum gear tooth stresses in a planetary gearbox using multibody gear constraints

DEFF Research Database (Denmark)

Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær

2014-01-01

multiple planetary gears are not taken into account. Finite Element Method (FEM) calculations show that when the wind turbine runs close to the maximum wind speed, the maximum gear tooth stress is in the range of 500–700 MPa, which is considered to be realistic using a “worst-case” method. The presented...... for not only transferring torque but also for calculating the gear tooth and internal body reaction forces. The method is appropriate for predicting gear tooth stresses without considering all the complexity of gear tooth geometries. This means that, e.g. gear tooth load-sharing and load-distribution among...

Anisotropy of the Reynolds stress tensor in the wakes of wind turbine arrays in Cartesian arrangements with counter-rotating rotors

Science.gov (United States)

Hamilton, Nicholas; Cal, Raúl Bayoán

2015-01-01

A 4 × 3 wind turbine array in a Cartesian arrangement was constructed in a wind tunnel setting with four configurations based on the rotational sense of the rotor blades. The fourth row of devices is considered to be in the fully developed turbine canopy for a Cartesian arrangement. Measurements of the flow field were made with stereo particle-image velocimetry immediately upstream and downstream of the selected model turbines. Rotational sense of the turbine blades is evident in the mean spanwise velocity W and the Reynolds shear stress - v w ¯ . The flux of kinetic energy is shown to be of greater magnitude following turbines in arrays where direction of rotation of the blades varies. Invariants of the normalized Reynolds stress anisotropy tensor (η and ξ) are plotted in the Lumley triangle and indicate that distinct characters of turbulence exist in regions of the wake following the nacelle and the rotor blade tips. Eigendecomposition of the tensor yields principle components and corresponding coordinate system transformations. Characteristic spheroids representing the balance of components in the normalized anisotropy tensor are composed with the eigenvalues yielding shapes predicted by the Lumley triangle. Rotation of the coordinate system defined by the eigenvectors demonstrates trends in the streamwise coordinate following the rotors, especially trailing the top-tip of the rotor and below the hub. Direction of rotation of rotor blades is shown by the orientation of characteristic spheroids according to principle axes. In the inflows of exit row turbines, the normalized Reynolds stress anisotropy tensor shows cumulative effects of the upstream turbines, tending toward prolate shapes for uniform rotational sense, oblate spheroids for streamwise organization of rotational senses, and a mixture of characteristic shapes when the rotation varies by row. Comparison between the invariants of the Reynolds stress anisotropy tensor and terms from the mean

Isolation and sequence characterization of DNA-A genome of a new begomovirus strain associated with severe leaf curling symptoms of Jatropha curcas L.

KAUST Repository

Chauhan, Sushma; Rahman, Hifzur; Mastan, Shaik G.; Sudheer, Pamidimarri D.V.N.; Reddy, Muppala P.

2018-01-01

Begomoviruses belong to the family Geminiviridae are associated with several disease symptoms, such as mosaic and leaf curling in Jatropha curcas. The molecular characterization of these viral strains will help in developing management strategies

Wind forces and related saltation transport

NARCIS (Netherlands)

Leenders, J.K.; van Boxel, J.H.; Sterk, G.

2005-01-01

The effect of several wind characteristics on sand transport was studied in three experiments in north Burkina Faso, West Africa. The first experiment is used to analyse the relation between wind speed and shear stress fluctuations across height. The second experiment is used to study the relation

A Technique for Mitigating Thermal Stress and Extending Life Cycle of Power Electronic Converters Used for Wind Turbines

Directory of Open Access Journals (Sweden)

Canras Batunlu

2015-11-01

Full Text Available Over the last two decades, various models have been developed to assess and improve the reliability of power electronic conversion systems (PECs with a focus on those used for wind turbines. However, only few studies have dealt with mitigating the PECs thermo-mechanical effects on their reliability taking into account variations in wind characteristics. This work critically investigates this issue and attempts to offer a mitigating technique by, first, developing realistic full scale (FS and partial scale (PS induction generator models combined with two level back-to-back PECs. Subsequently, deriving a driving algorithm, which reduces PEC’s operating temperature by controlling its switching patterns. The developed switching procedure ensures minimum temperature fluctuations by adapting the variable DC link and system’s frequency of operation. It was found for both FS and PS topologies, that the generator side converters have higher mean junction temperatures where the grid side ones have more fluctuations on their thermal profile. The FS and PS cycling temperatures were reduced by 12 °C and 5 °C, respectively. Moreover, this led to a significant improvement in stress; approximately 27 MPa stress reduction for the FS induction generator PEC.

Within-host dynamics of the emergence of Tomato yellow leaf curl virus recombinants.

Directory of Open Access Journals (Sweden)

Cica Urbino

Full Text Available Tomato yellow leaf curl virus (TYLCV is a highly damaging begomovirus native to the Middle East. TYLCV has recently spread worldwide, recombining with other begomoviruses. Recent analysis of mixed infections between TYLCV and Tomato leaf curl Comoros begomovirus (ToLCKMV has shown that, although natural selection preserves certain co-evolved intra-genomic interactions, numerous and diverse recombinants are produced at 120 days post-inoculation (dpi, and recombinant populations from different tomato plants are very divergent. Here, we investigate the population dynamics that lead to such patterns in tomato plants co-infected with TYLCV and ToLCKMV either by agro-inoculation or using the natural whitefly vector Bemisia tabaci. We monitored the frequency of parental and recombinant genotypes independently in 35 plants between 18 and 330 dpi and identified 177 recombinants isolated at different times. Recombinants were detected from 18 dpi and their frequency increased over time to reach about 50% at 150 dpi regardless of the inoculation method. The distribution of breakpoints detected on 96 fully sequenced recombinants was consistent with a continuous generation of new recombinants as well as random and deterministic effects in their maintenance. A severe population bottleneck of around 10 genomes was estimated during early systemic infection-a phenomenon that could account partially for the heterogeneity in recombinant patterns observed among plants. The detection of the same recombinant genome in six of the thirteen plants analysed beyond 30 dpi supported the influence of selection on observed recombination patterns. Moreover, a highly virulent recombinant genotype dominating virus populations within one plant has, apparently, the potential to be maintained in the natural population according to its infectivity, within-host accumulation, and transmission efficiency - all of which were similar or intermediate to those of the parent genotypes. Our

Comparison of residual stresses in sand- and chill casting of ductile cast iron wind turbine main shafts

DEFF Research Database (Denmark)

Sonne, Mads Rostgaard; Frandsen, J. O.; Hattel, Jesper Henri

2015-01-01

In this work, simulations of pouring, solidification and cooling, and residual stress evolution of sand and chill cast wind turbine main shafts is performed. The models are made in the commercial software MAGMAsoft. As expected, the cooling rate of the sand casting is shown to be much lower than...... for the chill casting, resulting in a very course microstructure.From the simulations the nodule count is found to be 17 nodules per mm2 and 159 nodules permm2 for the sand and chill casting, respectively, in the critical region of the main bearing seat.This is verified from nodule counts performed on the real...... cast main shafts. Residual stressevaluations show an overall increase of the maximum principal stress field for the chill casting,which is expected. However, the stresses are found to be in compression on the surface of thechill cast main shaft, which is unforeseen....

Wind effect in turbulence parametrization

Science.gov (United States)

Colombini, M.; Stocchino, A.

2005-09-01

The action of wind blowing over a closed basin ultimately results in a steady shear-induced circulation pattern and in a leeward rising of the free surface—and a corresponding windward lowering—known as wind set-up. If the horizontal dimensions of the basin are large with respect to the average flow depth, the occurrence of local quasi-equilibrium conditions can be expected, i.e. the flow can be assumed to be locally driven only by the wind stress and by the opposing free surface gradient due to set-up. This wind-induced flow configuration shows a strong similarity with turbulent Couette-Poiseuille flow, the one dimensional flow between parallel plates generated by the simultaneous action of a constant pressure gradient and of the shear induced by the relative motion of the plates. A two-equation turbulence closure is then employed to perform a numerical study of turbulent Couette-Poiseuille flows for different values of the ratio of the shear stresses at the two walls. The resulting eddy viscosity vertical distributions are analyzed in order to devise analytical profiles of eddy viscosity that account for the effect of wind. The results of this study, beside allowing for a physical insight on the turbulence process of this class of flows, will allow for a more accurate description of the wind effect to be included in the formulation of quasi-3D and 3D models of lagoon hydrodynamics.

Wind Effects on Retention Time in Highway Ponds

DEFF Research Database (Denmark)

Bentzen, Thomas Ruby; Larsen, Torben; Rasmussen, Michael R.

2007-01-01

is to evaluate the quality of long term simulations based on historical rain series of the pollutant discharges from roads and highways. The idea of this paper is to evaluate the effects of wind on the retention time and compare the retention time for the situation of a spatial uniform wind shear stress...... with the situation of a "real" spatial non-uniform shear stress distribution on the surface of the pond. The result of this paper shows that wind plays a dominant role for the retention time and flow pattern. Furthermore, the results shows that the differences in retention time between the use of uniform and non...

Wind Effects on Retention Time in Highway Ponds

DEFF Research Database (Denmark)

Bentzen, Thomas Ruby; Larsen, Torben; Rasmussen, Michael R.

2008-01-01

is to evaluate the quality of long term simulations based on historical rain series of the pollutant discharges from roads and highways. The idea of this paper is to evaluate the effects of wind on the retention time and compare the retention time for the situation of a spatial uniform wind shear stress...... with the situation of a "real" spatial non-uniform shear stress distribution on the surface of the pond. The result of this paper shows that wind plays a dominant role for the retention time and flow pattern. Furthermore, the results shows that the differences in retention time between the use of uniform and non...

Global surface wind and flux fields from model assimilation of Seasat data

Science.gov (United States)

Atlas, R.; Busalacchi, A. J.; Kalnay, E.; Bloom, S.; Ghil, M.

1986-01-01

Procedures for dealiasing Seasat data and developing global surface wind and latent and sensible heat flux fields are discussed. Seasat data from September 20, 1978 was dealiased using the Goddard Laboratory for Atmospheres (GLA) analysis/forecast system. The wind data obtained with the objective GLA forecast model are compared to the data subjectively dealiased by Peteherych et al. (1984) and Hoffman (1982, 1984). The GLA procedure is also verified using simulated Seasat data. The areas of high and low heat fluxes and cyclonic and anticyclonic wind stresses detected in the generated fields are analyzed and compared to climatological fields. It is observed that there is good correlation between the time-averaged analyses of wind stress obtained subjectively and objectively, and the monthly mean wind stress and latent fluxes agree with climatological fields and atmospheric and oceanic features.

Adhesive Joints in Wind Turbine Blades

DEFF Research Database (Denmark)

Jørgensen, Jeppe Bjørn

to be determined in several different ways. The accuracy of different ways of measuring residual stresses in the adhesive was tested by applying five different methods on a single sandwich test specimen (laminate/adhesive/laminate) that was instrumented with strain gauges and fiber Bragg gratings. Quasi...... of the project is to develop new- and to improve the existing design rules for adhesive joints in wind turbine blades. The first scientific studies of adhesive joints were based on stress analysis, which requires that the bond-line is free of defects, but this is rarely the case for a wind turbine blade. Instead...... curing and test temperatures) on the formation of transverse cracks in the adhesive were tested experimentally. It was assumed that the transverse cracks evolved due to a combination of mechanical- and residual stresses in the adhesive. A new approach was developed that allows the residual stress...

Cotton Leaf Curl Multan Betasatellite DNA as a Tool to Deliver and Express the Human B-Cell Lymphoma 2 (Bcl-2) Gene in Plants.

Science.gov (United States)

Kharazmi, Sara; Ataie Kachoie, Elham; Behjatnia, Seyed Ali Akbar

2016-05-01

The betasatellite DNA associated with Cotton leaf curl Multan virus (CLCuMB) contains a single complementary-sense ORF, βC1, which is a pathogenicity determinant. CLCuMB was able to replicate in plants in the presence of diverse helper geminiviruses, including Tomato leaf curl virus-Australia (TLCV-Au), Iranian isolate of Tomato yellow leaf curl virus (TYLCV-[Ab]), and Beet curly top virus (BCTV-Svr), and can be used as a plant gene delivery vector. To test the hypothesis that CLCuMB has the potential to act as an animal gene delivery vector, a specific insertion construct was produced by the introduction of a human B-cell lymphoma 2 (Bcl-2) cDNA into a mutant DNA of CLCuMB in which the βC1 was deleted (β∆C1). The recombinant βΔC1-Bcl-2 construct was successfully replicated in tomato and tobacco plants in the presence of TLCV-Au, BCTV-Svr and TYLCV-[Ab]. Real-time PCR and Western blot analyses of plants containing the replicative forms of recombinant βΔC1-Bcl-2 DNA showed that Bcl-2 gene was expressed in an acceptable level in these plants, indicating that β∆C1 can be used as a tool to deliver and express animal genes in plants. This CLCuMB-based system, having its own promoter activity, offers the possibility of production of animal recombinant proteins in plants.

Aeroelastic analysis of an offshore wind turbine: Design and Fatigue Performance of Large Utility-Scale Wind Turbine Blades

OpenAIRE

Fossum, Peter Kalsaas

2012-01-01

Aeroelastic design and fatigue analysis of large utility-scale wind turbine blades are performed. The applied fatigue model is based on established methods and is incorporated in an iterative numerical design tool for realistic wind turbine blades. All aerodynamic and structural design properties are available in literature. The software tool FAST is used for advanced aero-servo-elastic load calculations and stress-histories are calculated with elementary beam theory.According to wind energy ...

Simultaneous bilateral distal biceps tendon rupture during a preacher curl exercise: a case report.

Science.gov (United States)

Rokito, Andrew S; lofin, Ilya

2008-01-01

Complete rupture of the distal biceps tendon is a rare injury, the overwhelming majority occurring in the dominant arm of males during the fourth to sixth decades of life. Simultaneous bilateral rupture of the distal biceps tendon is an extremely rare occurrence, with only three cases reported in the literature. This unusual injury occurred in a recreational weightlifter during a preacher curl exercise. In this particular case, a 6-week delay in presentation necessitated a staged procedure in which a primary repair was feasible in one elbow, while reconstruction using allograft tissue was required in the contralateral elbow. Satisfactory results for both elbows were achieved, with return to weightlifting by one year following surgery.

Role of sea surface wind stress forcing on transport between Tropical Pacific and Indian Ocean

Science.gov (United States)

Zhao, Q.

Using an Indian-Pacific Ocean Circulation Model (IPOM) a simulation study on the Transports of between Tropical Pacific and Indian Ocean such as Indonesian Through flow (ITF) has been done. IPOM covered the area 25°E-70°W, 35°S-60°N. There are 31 levels in the vertical with 22 levels upper 400m in it. The horizontal resolution is 1/3° lat x 1.5° lon between 10°S and 10°N. The coastline and ocean topography of IPOM is prepared from Scripps topography data on 1x1°grid. Forcing IPOM with monthly observational wind stress in 1990-1999 the interannual variation of sea temperature has been reproduced well, not only on El Nino in the Pacific but also on Indian Ocean Dipole (IOD). Therefore, the oceanic circulations in the tropical ocean are reasonable. The analyses of the oceanic circulations from the simulations suggest that the transport southward through Makassar Strait is the primary route of thermocline water masses from the North Pacific to the Indonesian sea. The transport westward through Bali-Western Australian Transect (BWAT, at 117.5E) can be thought as the final output of ITF through the archipelago to Indian Ocean. The transport westward through BWAT is in 8-12S above 150m, its core centered near surface 10S, which looks like a jet. The westward velocity is more than 50 cm/s. The transport shows significant seasonal and interannual variations. The maximum is in Jul-Oct, minimum in Jan-Mar. These results are consistent with some observation basically. The correlation analyses indict that the variations of transport westward is related with the southeasterly anomaly in the east tropical Indian ocean. The transport variation lags wind anomaly about 3 months. The correlation coefficient is more than 0.6. The transport is strong during IOD, for example in 1994 and 1997. The variations are also related with the northwesterly anomaly in the center equatorial Pacific and the easterly in the eastern equatorial Pacific. The transport is strong in most ENSO

Development and application of triple antibody sandwich enzyme-linked immunosorbent assays for begomovirus detection using monoclonal antibodies against Tomato yellow leaf curl Thailand virus.

Science.gov (United States)

Seepiban, Channarong; Charoenvilaisiri, Saengsoon; Warin, Nuchnard; Bhunchoth, Anjana; Phironrit, Namthip; Phuangrat, Bencharong; Chatchawankanphanich, Orawan; Attathom, Supat; Gajanandana, Oraprapai

2017-05-30

Tomato yellow leaf curl Thailand virus, TYLCTHV, is a begomovirus that causes severe losses of tomato crops in Thailand as well as several countries in Southeast and East Asia. The development of monoclonal antibodies (MAbs) and serological methods for detecting TYLCTHV is essential for epidemiological studies and screening for virus-resistant cultivars. The recombinant coat protein (CP) of TYLCTHV was expressed in Escherichia coli and used to generate MAbs against TYLCTHV through hybridoma technology. The MAbs were characterized and optimized to develop triple antibody sandwich enzyme-linked immunosorbent assays (TAS-ELISAs) for begomovirus detection. The efficiency of TAS-ELISAs for begomovirus detection was evaluated with tomato, pepper, eggplant, okra and cucurbit plants collected from several provinces in Thailand. Molecular identification of begomoviruses in these samples was also performed through PCR and DNA sequence analysis of the CP gene. Two MAbs (M1 and D2) were generated and used to develop TAS-ELISAs for begomovirus detection. The results of begomovirus detection in 147 field samples indicated that MAb M1 reacted with 2 begomovirus species, TYLCTHV and Tobacco leaf curl Yunnan virus (TbLCYnV), whereas MAb D2 reacted with 4 begomovirus species, TYLCTHV, TbLCYnV, Tomato leaf curl New Delhi virus (ToLCNDV) and Squash leaf curl China virus (SLCCNV). Phylogenetic analyses of CP amino acid sequences from these begomoviruses revealed that the CP sequences of begomoviruses recognized by the narrow-spectrum MAb M1 were highly conserved, sharing 93% identity with each other but only 72-81% identity with MAb M1-negative begomoviruses. The CP sequences of begomoviruses recognized by the broad-spectrum MAb D2 demonstrated a wider range of amino acid sequence identity, sharing 78-96% identity with each other and 72-91% identity with those that were not detected by MAb D2. TAS-ELISAs using the narrow-specificity MAb M1 proved highly efficient for the detection of

Thermal niches of two invasive genotypes of the wheat curl mite Aceria tosichella (Acari: Eriophyidae): congruence between physiological and geographical distribution data

Science.gov (United States)

The wheat curl mite (WCM; Aceria tosichella) is a major pest of cereals worldwide. It is also a complex of well-defined genetic lineages with divergent physiological traits, which has not been accounted for in applied contexts. The aims of the study were to model the thermal niches of the two most p...

Metric of the 2–6 day sea-surface temperature response to wind stress in the Tropical Pacific and its sensitivity to the K-Profile Parameterization of vertical mixing

KAUST Repository

Wagman, Benjamin M.

2014-05-04

Uncertainty in wind forcing has long hampered direct tests of ocean model output against observations for the purpose of refining the boundary layer K-Profile Parameterization (KPP) of oceanic vertical mixing. Considered here is a short-term metric that could be sensitive to the ways in which the KPP directly affects the adjustment of sea surface temperatures for a given change in wind stress. In particular a metric is developed based on the lagged correlation between the 2–6 day filtered wind stress and sea surface temperature. The metric is normalized by estimated observational and model uncertainties such that the significance of differences may be assessed. For this purpose multiple wind reanalysis products and their blended combinations were used to represent the range of forcing uncertainty, while perturbed KPP parameter model runs explore the sensitivity of the metric to the parameterization of vertical mixing. The correlation metric is sensitive to perturbations to most KPP parameters, in ways that accord with expectations, although only a few parameters show a sensitivity on the same order as the sensitivity to switching between wind products. This suggests that uncertainties in wind forcing continue to be a significant limitation for applying direct observational tests of KPP physics. Moreover, model correlations are biased high, suggesting that the model lacks or does not resolve sources of variability on the 2–6 day time scale.

Metric of the 2–6 day sea-surface temperature response to wind stress in the Tropical Pacific and its sensitivity to the K-Profile Parameterization of vertical mixing

KAUST Repository

Wagman, Benjamin M.; Jackson, Charles S.; Yao, Fengchao; Zedler, Sarah; Hoteit, Ibrahim

2014-01-01

Uncertainty in wind forcing has long hampered direct tests of ocean model output against observations for the purpose of refining the boundary layer K-Profile Parameterization (KPP) of oceanic vertical mixing. Considered here is a short-term metric that could be sensitive to the ways in which the KPP directly affects the adjustment of sea surface temperatures for a given change in wind stress. In particular a metric is developed based on the lagged correlation between the 2–6 day filtered wind stress and sea surface temperature. The metric is normalized by estimated observational and model uncertainties such that the significance of differences may be assessed. For this purpose multiple wind reanalysis products and their blended combinations were used to represent the range of forcing uncertainty, while perturbed KPP parameter model runs explore the sensitivity of the metric to the parameterization of vertical mixing. The correlation metric is sensitive to perturbations to most KPP parameters, in ways that accord with expectations, although only a few parameters show a sensitivity on the same order as the sensitivity to switching between wind products. This suggests that uncertainties in wind forcing continue to be a significant limitation for applying direct observational tests of KPP physics. Moreover, model correlations are biased high, suggesting that the model lacks or does not resolve sources of variability on the 2–6 day time scale.

Currents and upwelling along the Latium coasts in the Central Tyrrhenian Sea (western Mediterranean

Directory of Open Access Journals (Sweden)

V. Rossi

1995-04-01

Full Text Available In this study, springtime coastal currents along the Latium coast and their relation to external forcings, mainly wind stress curl and atmospheric pressure, are analysed. As a main result, we find that hydrographical measurements reveal currents parallel to the bottom isobaths, but with isopycnal sloping upwards towards the coast, suggesting the importance of upwellings in determining the coastal currents. This is confirmed by thermal satellite data showing the presence of a ~10-km-wide patch of cold water east of Mount Argentario, i.e. a cyclonic vortex. The current meter data give rather small values of the time-averaged alongshore velocities (~2 cm s–1 for most current meters and ~3 cm s–1 for the current meter placed immediately off the Argentario and also smaller values for the offshore velocities. The correlation between these two types of currents is rather poor; this is also due to the variability characteristic of a wind-induced upwelling. Finally, we obtain a value of 0.74 for the correlation between the alongshore current (first mode of Empirical Orthogonal Functions decomposition and the wind stress if a 23-h time lag is assumed.

Energy efficiency guide for ice arenas and curling rinks

Energy Technology Data Exchange (ETDEWEB)

NONE

2007-07-01

This document presented a set of guidelines which were designed to help operators of Manitoba's rinks and arenas by presenting practical ideas for saving money on energy in ice arenas, curling rinks, and similar recreational complexes. They cover a broad range of topics, from funding projects to details of specific components, and apply to new facilities, renovations, and day-to-day maintenance. These guidelines were based on a manual produced by the Saskatchewan Parks and Recreation Association in cooperation with the Saskatchewan Recreation Facility Association and sponsored by SaskPower. They represent an update of the 1991 manual to reflect improvements in technology, Manitoba Hydro's utility rates, and the requirements of Manitoba operators. The document presented guidelines and tips for understanding electrical and natural gas rates and structures; energy estimating methods; making a financial analysis; the building envelope; heating and ventilation; refrigeration; lighting; and heating effects of electrical equipment. Other guidelines presented came under the topics of operation and maintenance and project planning. Several appendices were also included, such as a glossary of terms; reference publications; energy calculations; power factor correction; heat pumps for rinks and arenas; and power smart programs for commercial buildings. refs., tabs., figs.

Wind Turbines Make Waves: Why Some Residents near Wind Turbines Become Ill

Science.gov (United States)

Havas, Magda; Colling, David

2011-01-01

People who live near wind turbines complain of symptoms that include some combination of the following: difficulty sleeping, fatigue, depression, irritability, aggressiveness, cognitive dysfunction, chest pain/pressure, headaches, joint pain, skin irritations, nausea, dizziness, tinnitus, and stress. These symptoms have been attributed to the…

The influence of Seychelles Dome on the large scale Tropical Variability

Science.gov (United States)

Manola, Iris; Selten, Frank; Hazeleger, Wilco

2013-04-01

The Seychelles Dome (SD) is the thermocline ridge just South of the equator in the Western Indian Ocean basin. It is characterized by strong atmospheric convection and a shallow thermocline and is associated with large intraseasonal convection and SST variability (Harrison and Vecchi 2001). The SD is influenced by surface and subsurface processes, such as air-sea fluxes, Ekman upwelling from wind stress curl, ocean dynamics (vertical mixing) and oceanic Rossby waves from southeastern Indian Ocean. The favoring season for a strong SD is the boreal winter, where the thermocline is most shallow. Then the southeasterly trade winds converge with the northwesterly monsoonal winds over the intertropical convergence zone and cause cyclonic wind stress curl that drives Ekman divergence and a ridging of the thermocline. It is found that the subseasonal and interranual variability of the SD is influenced by large scale events, such as the Indian Ocean Dipole (IOD), the ENSO and the Madden-Julian Oscillation (MJO) (Tozuka et al., 2010, Lloyd and Vecchi, 2010). The SD is enhanced by cooling events in the Western Indian Ocean and easterly winds that raise the thermocline and increase the upwelling. This can be associated with a strong Walker circulation, like negative IOD conditions or La Nina-like conditions. So far the studies focus on the origins of the SD variability, but the influence of the SD itself on regional or large scale climate is largely unknown. In this study we focus on the influence of the SD variations on the large scale tropical circulation. We analyze the covariance of the SD variations and the tropical circulation in a 200 year control imulation of the climate model EC-EARTH and perform idealized SST forced simulations to study the character of the atmospheric response and its relation to ENSO, IOD and MJO. References -Harrison, D. E. and G. A. Vecchi, 2001: January 1999 Indian Ocean cooling event. Geophys. Res. Lett., 28, 3717-3720. -Lloyd, I. D., and G. A

Is the pull-out force of the Meniscus Arrow in bone affected by the inward curling of the barbs during biodegradation? An in vitro study

NARCIS (Netherlands)

Wouters, Diederick B.; Burgerhof, Johannes G. M.; de Hosson, Jeff T. M.; Bos, Rudolf R. M.

Background: Inward curling of the barbs of Meniscus Arrows during degradation was observed in a previous study, in which swelling, distention, and water uptake by Meniscus Arrows was evaluated. This change of configuration could have consequences with respect to anchorage capacity in bone.

Mechanism of seasonal eddy kinetic energy variability in the eastern equatorial Pacific Ocean

Science.gov (United States)

Wang, Minyang; Du, Yan; Qiu, Bo; Cheng, Xuhua; Luo, Yiyong; Chen, Xiao; Feng, Ming

2017-04-01

Enhanced mesoscale eddy activities or tropical instability waves (TIWs) exist along the northern front of the cold tongue in the eastern equatorial Pacific Ocean. In this study, we investigate seasonal variability of eddy kinetic energy (EKE) over this region and its associated dynamic mechanism using a global, eddy-resolving ocean general circulation model (OGCM) simulation, the equatorial mooring data, and satellite altimeter observations. The seasonal-varying enhanced EKE signals are found to expand westward from 100°W in June to 180°W in December between 0°N and 6°N. This westward expansion in EKE is closely connected to the barotropically-baroclinically unstable zonal flows that are in thermal-wind balance with the seasonal-varying thermocline trough along 4°N. By adopting an 1½-layer reduced-gravity model, we confirm that the seasonal perturbation of the thermocline trough is dominated by the anticyclonic wind stress curl forcing, which develops due to southerly winds along 4°N from June to December.

Aspects of the determination of winds by means of scatterometry and of the utilization of vector wind data for meteorological forecasts

Science.gov (United States)

Pierson, W. J., Jr.; Sylvester, W. B.; Donelan, M. A.

1986-01-01

The present paper provides a description of four aspects of scatterometer winds and their uses. The theory of wave generation by the wind is considered along with an analysis of the properties of superobservations, and studies of intermittent versus continuous data assimilation methods for numerical weather predictions which use remotely sensed data. A comparison of the sum of squares versus the maximum likelihood method for recovering the vector winds is also conducted. Questions regarding wind speed, friction velocity, or normal stress are discussed and synoptic scale fields from Seasat-SASS data are examined.

Molecular and Biochemical Characterization of Cotton Epicuticular Wax in Defense Against Cotton Leaf Curl Disease.

Science.gov (United States)

Khan, Muhammad Azmat Ullah; Shahid, Ahmad Ali; Rao, Abdul Qayyum; Bajwa, Kamran Shehzad; Samiullah, Tahir Rehman; Muzaffar, Adnan; Nasir, Idrees Ahmad; Husnain, Tayyab

2015-12-01

Gossypium arboreumis resistant to Cotton leaf curl Burewala virus and its cognate Cotton leaf curl Multan beta satellite ( CLCuBuV and CLCuMB ). However, the G. arboreum wax deficient mutant (GaWM3) is susceptible to CLCuV . Therefore, epicuticular wax was characterized both quantitatively and qualitatively for its role as physical barrier against whitefly mediated viral transmission and co-related with the titer of each viral component (DNA-A, alphasatellite and betasatellite) in plants. The hypothesis was the CLCuV titer in cotton is dependent on the amount of wax laid down on plant surface and the wax composition. Analysis of the presence of viral genes, namely alphasatellite, betasatellite and DNA-A, via real-time PCR in cotton species indicated that these genes are detectable in G. hirsutum , G. harknessii and GaWM3, whereas no particle was detected in G. arboreum . Quantitative wax analysis revealed that G. arboreum contained 183 μg.cm -2 as compared to GaWM3 with only 95 μg.cm -2 . G. hirsutum and G. harknessii had 130 μg.cm -2 and 146 μg.cm -2 , respectively. The GCMS results depicted that Lanceol, cis was 45% in G. harknessii . Heptadecanoic acid was dominant in G. arboreum with 25.6%. GaWM3 had 18% 1,2,-Benenedicarboxylic acid. G. hirsutum contained 25% diisooctyl ester. The whitefly feeding assay with Nile Blue dye showed no color in whiteflies gut fed on G. arboreum . In contrast, color was observed in the rest of whiteflies. From results, it was concluded that reduced quantity as well as absence of (1) 3-trifluoroacetoxytetradecane, (2) 2-piperidinone,n-|4-bromo-n-butyl|, (3) 4-heptafluorobutyroxypentadecane, (4) Silane, trichlorodocosyl-, (5) 6- Octadecenoic acid, methyl ester, and (6) Heptadecanoicacid,16-methyl-,methyl ester in wax could make plants susceptible to CLCuV , infested by whiteflies.

Worldwide potential of wind energy

Energy Technology Data Exchange (ETDEWEB)

Flavin, C

1982-01-01

A well-documented discussion is presented dealing with the worldwide potential of wind energy as a source of electrical and mechanical power. It is pointed out that 2% of the solar insolation is converted to wind kinetic energy; it is constantly renewed and nondepletable. Efficiency of windmills are discussed (20 to 40%) and payback periods of less than 5 years are cited. Effects of wind velocity and site location are described. Wind pumps are reviewed and the need for wind pumps, particularly in the developing countries is stressed. The generation of electricity by windmills using small turbines is reviewed and appears promising in areas with wind velocities greater than 12 mi/hr. The development of large windmills and groups of windmills (windfarms) for large scale electrical power is discussed, illustrated, and reviewed (offshore sites included). Environmental and safety problems are considered as well as the role of electrical utilities, government support and research activities. It is concluded that the potential contribution of wind energy is immense and that mechanical windmills may become one of the most important renewable technologies. Electrical generating potential is estimated at 20 to 30% of electrical needs. International programs are discussed briefly. 57 references. (MJJ)

Calculating wind profiles above a pine forest

International Nuclear Information System (INIS)

Murphy, C.E.; Dexter, A.H.

1978-01-01

A major part of the environmental transport work at the Savannah River Laboratory (SRL) involves the dispersion of airborne pollutants (aerosols and gases). A major part of the Savannah River Plant (SRP) site is covered with pine forests. Because forests are ''rough'' surfaces which increase turbulence and surface shear stress and, hence, alter the dispersion patterns, the nature of the wind profiles above the forests is being investigated. Two methods for determining the surface shear caused by the atmospheric wind field over a pine plantation were compared. Friction velocity [the square root of the ratio of shearing stress over the density of air; U/sub */ = (stress/density)1/2] calculated by eddy correlation was compared with friction velocity calculated from wind profiles. Data from the first five meters above the pine forest were compared. The data indicated that there was no significant difference in the mean friction velocity measured by each method. However, there were large differences in individual values calculated by the two methods for many of the measurement periods. An attempt was made to reconcile the differences in the measured values, but no satisfactory method was found

Coupled wave and surge modelling for the eastern Irish Sea and implications for model wind-stress

Science.gov (United States)

Brown, Jennifer M.; Wolf, Judith

2009-05-01

We revisit the surge of November 1977, a storm event which caused damage on the Sefton coast in NW England. A hindcast has been made with a coupled surge-tide-wave model, to investigate whether a wave-dependent surface drag is necessary for accurate surge prediction, and also if this can be represented by an optimised Charnock parameter. The Proudman Oceanographic Laboratory Coastal Modelling System-Wave Model (POLCOMS-WAM) has been used to model combined tides, surges, waves and wave-current interaction in the Irish Sea on a 1.85 km grid. This period has been previously thoroughly studied, e.g. Jones and Davies [Jones, J.E., Davies, A.M., 1998. Storm surge computations for the Irish Sea using a three-dimensional numerical model including wave-current interaction. Continental Shelf Research 18(2), 201-251] and we build upon this previous work to validate the POLCOMS-WAM model to test the accuracy of surge elevation predictions in the study area. A one-way nested approach has been set up from larger scale models to the Irish Sea model. It was demonstrated that (as expected) swell from the North Atlantic does not have a significant impact in the eastern Irish Sea. To capture the external surge generated outside of the Irish Sea a (1/9° by 1/6°) model extending beyond the continental shelf edge was run using the POLCOMS model for tide and surge. The model results were compared with tide gauge observations around the eastern Irish Sea. The model was tested with different wind-stress formulations including Smith and Banke [Smith, S.D., Banke, E.G., 1975. Variation of the surface drag coefficient with wind speed. Quarterly Journal of the Royal Meteorology Society, 101(429), 665-673] and Charnock [Charnock, H., 1955. Wind-stress on a water surface. Quarterly Journal of the Royal Meteorological Society, 81(350), 639-640]. In order to get a single parameterisation that works with wave-coupling, the wave-derived surface roughness length has been imposed in the surge model

Social barriers in wind power implementation in The Netherlands: Perceptions of wind power entrepreneurs and local civil servants of institutional and social conditions in realizing wind power projects

International Nuclear Information System (INIS)

Agterbosch, Susanne; Glasbergen, Pieter; Vermeulen, Walter J.V.

2007-01-01

The primary social factors for the implementation of wind energy projects in a liberalized market are entrepreneurs willing to invest. Understanding conditions that trigger entrepreneurs to invest in these projects, and understanding conditions that determine the chance of success for entrepreneurs to implement and exploit their projects, is vital for setting up effective policies to stimulate wind electricity generation. This paper analyses the way in which wind power entrepreneurs and local civil servants experience social and institutional conditions in the operational process of realizing wind power projects, and their perceptions of policy implications. A groups support system in an electronic board room was used to analyze the perceptions. From the analysis it was concluded that wind power entrepreneurs and civil servants share the opinion that the institutionally embedded power position of local politicians, and the sensitiveness of the local political debate for the popular opinion are most critical for project realization. With regard to the proposed solutions, both groups differ in their approach. Entrepreneurs stress procedural solutions, such as limiting the possibilities to appeal, reducing the complexity of the formal authorization trajectory and using a top down planning approach. Civil servants stress more strategic solutions, such as providing more public information on the necessity of wind power for local politicians and citizens, and community involvement in planning processes. Finally, the analysis explains that steering strategies that have been developed at the national level to solve the planning problems at the operational level do not address the right problems. (author)

Assessment of the genetic diversity of tomato yellow leaf curl virus.

Science.gov (United States)

Wan, H J; Yuan, W; Wang, R Q; Ye, Q J; Ruan, M Y; Li, Z M; Zhou, G Z; Yao, Z P; Yang, Y J

2015-01-26

The objective of the present study was to analyze the genetic diversity of tomato yellow leaf curl virus (TYLCV). Representative TYLCV sequences were searched in the National Center for Biotechnology Information database. Comprehensive analysis of TYLCV was performed using bioinformatics by examining gene structure, sequence alignments, phylogeny, GC content, and homology. Forty-eight representative TYLCV sequences were selected from 48 regions in 29 countries. The results showed that all TYLCV sequences were 2752-2794 nucleotides in length, which encoded 6 open reading frames (AV1, AV2, AC1, AC2, AC3, and AC4). GC content ranged from 0.41-0.42. Sequence alignment showed a number of insertions and deletions within these TYLCV sequences. Phylogenetic tree results revealed that the sequences were divided into 10 classes; homology of the sequences ranged from 72.8 to 98.6%. All 48 sequences contained the typical structure of TYLCV, including open reading frames and intergenic regions. These results provide a theoretical basis for the identification and evolution of the virus in the future.

An Integrated Structural Strength Analysis Method for Spar Type Floating Wind Turbine

Institute of Scientific and Technical Information of China (English)

胡志强; 刘毅; 王晋

2016-01-01

An integrated structural strength analysis method for a Spar type floating wind turbine is proposed in this paper, and technical issues related to turbine structure modeling and stress combination are also addressed. The NREL-5MW “Hywind” Spar type wind turbine is adopted as study object. Time-domain dynamic coupled simulations are performed by a fully-coupled aero-hydro-servo-elastic tool, FAST, on the purpose of obtaining the dynamic characteristics of the floating wind turbine, and determining parameters for design load cases of finite element calculation. Then design load cases are identified, and finite element analyses are performed for these design load cases. The structural stresses due to wave-induced loads and wind-induced loads are calculated, and then combined to assess the structural strength of the floating wind turbine. The feasibility of the proposed structural strength analysis method for floating wind turbines is then validated.

Simple and Accurate Analytical Solutions of the Electrostatically Actuated Curled Beam Problem

KAUST Repository

Younis, Mohammad I.

2014-08-17

We present analytical solutions of the electrostatically actuated initially deformed cantilever beam problem. We use a continuous Euler-Bernoulli beam model combined with a single-mode Galerkin approximation. We derive simple analytical expressions for two commonly observed deformed beams configurations: the curled and tilted configurations. The derived analytical formulas are validated by comparing their results to experimental data in the literature and numerical results of a multi-mode reduced order model. The derived expressions do not involve any complicated integrals or complex terms and can be conveniently used by designers for quick, yet accurate, estimations. The formulas are found to yield accurate results for most commonly encountered microbeams of initial tip deflections of few microns. For largely deformed beams, we found that these formulas yield less accurate results due to the limitations of the single-mode approximations they are based on. In such cases, multi-mode reduced order models need to be utilized.

Transformer sound level caused by core magnetostriction and winding stress displacement variation

Directory of Open Access Journals (Sweden)

Chang-Hung Hsu

2017-05-01

Full Text Available Magnetostriction caused by the exciting variation of the magnetic core and the current conducted by the winding wired to the core has a significant result impact on a power transformer. This paper presents the sound of a factory transformer before on-site delivery for no-load tests. This paper also discusses the winding characteristics from the transformer full-load tests. The simulation and the measurement for several transformers with capacities ranging from 15 to 60 MVA and high voltage 132kV to low voltage 33 kV are performed. This study compares the sound levels for transformers by no-load test (core/magnetostriction and full-load test (winding/displacement ε. The difference between the simulated and the measured sound levels is about 3dB. The results show that the sound level depends on several parameters, including winding displacement, capacity, mass of the core and windings. Comparative results of magnetic induction of cores and the electromagnetic force of windings for no-load and full-load conditions are examined.

Structural optimization procedure of a composite wind turbine blade for reducing both material cost and blade weight

Science.gov (United States)

Hu, Weifei; Park, Dohyun; Choi, DongHoon

2013-12-01

A composite blade structure for a 2 MW horizontal axis wind turbine is optimally designed. Design requirements are simultaneously minimizing material cost and blade weight while satisfying the constraints on stress ratio, tip deflection, fatigue life and laminate layup requirements. The stress ratio and tip deflection under extreme gust loads and the fatigue life under a stochastic normal wind load are evaluated. A blade element wind load model is proposed to explain the wind pressure difference due to blade height change during rotor rotation. For fatigue life evaluation, the stress result of an implicit nonlinear dynamic analysis under a time-varying fluctuating wind is converted to the histograms of mean and amplitude of maximum stress ratio using the rainflow counting algorithm Miner's rule is employed to predict the fatigue life. After integrating and automating the whole analysis procedure an evolutionary algorithm is used to solve the discrete optimization problem.

Application of Failure Mode and Effect Analysis (FMEA), cause and effect analysis, and Pareto diagram in conjunction with HACCP to a corn curl manufacturing plant.

Science.gov (United States)

Varzakas, Theodoros H; Arvanitoyannis, Ioannis S

2007-01-01

The Failure Mode and Effect Analysis (FMEA) model has been applied for the risk assessment of corn curl manufacturing. A tentative approach of FMEA application to the snacks industry was attempted in an effort to exclude the presence of GMOs in the final product. This is of crucial importance both from the ethics and the legislation (Regulations EC 1829/2003; EC 1830/2003; Directive EC 18/2001) point of view. The Preliminary Hazard Analysis and the Fault Tree Analysis were used to analyze and predict the occurring failure modes in a food chain system (corn curls processing plant), based on the functions, characteristics, and/or interactions of the ingredients or the processes, upon which the system depends. Critical Control points have been identified and implemented in the cause and effect diagram (also known as Ishikawa, tree diagram, and the fishbone diagram). Finally, Pareto diagrams were employed towards the optimization of GMOs detection potential of FMEA.

Amplicon based RNA interference targeting V2 gene of cotton leaf curl Kokhran virus-Burewala strain can provide resistance in transgenic cotton plants

Science.gov (United States)

An RNAi based gene construct designated “C2” was used to target the V2 region of the cotton leaf curl virus (CLCuV) genome which is responsible for virus movement. The construct was transformed into two elite cotton varieties MNH-786 and VH-289. A shoot apex method of plant transformation using Agr...

Impacts of pre-existing ocean cyclonic circulation on sea surface chlorophyll-a concentrations off northeastern Taiwan following episodic typhoon passages

Science.gov (United States)

Xu, Fanghua; Yao, Yuan; Oey, Leo; Lin, Yanluan

2017-08-01

Off northeastern Taiwan, enhancement of sea surface chlorophyll-a (Chl-a) concentration is frequently found after typhoon passages. From 1998 to 2013, 46 typhoon events are analyzed to examine the variations in Chl-a concentration from satellite ocean color data. On average, Chl-a concentration increased by 38% after a typhoon passage. Noticeably, four remarkable Chl-a increases after typhoons coincide with pre-existing oceanic cyclones in the study area. The Chl-a increase is significantly anticorrelated (p typhoons, we conduct a series of numerical experiments to simulate the oceanic response to Typhoon Kaemi (2006) with or without a pre-existing oceanic cyclone, and with or without strong typhoon winds. The results show that the experiment with a pre-existing oceanic cyclone produces the largest upwelling due to cyclone intensification, mainly induced by the positive wind stress curl dipole northeast of Taiwan.

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

1998-12-31

During the wind power generator project a design algorithm for a gearless permanent magnet generator with an axially orientated magnetic flux was developed and a 10 kW model machine was constructed. Utilising the test results a variable wind speed system of 100 kW was designed that incorporates a permanent magnet generator, a frequency converter and a fuzzy controller. This system produces about 5-15% more energy than existing types and stresses to the blades are minimised. The type of generator designed in the project represents in general a gearless solution for slow-speed electrical drives. (orig.)

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.)

'Wind turbine syndrome': fact or fiction?

Science.gov (United States)

Farboud, A; Crunkhorn, R; Trinidade, A

2013-03-01

Symptoms, including tinnitus, ear pain and vertigo, have been reported following exposure to wind turbine noise. This review addresses the effects of infrasound and low frequency noise and questions the existence of 'wind turbine syndrome'. This review is based on a search for articles published within the last 10 years, conducted using the PubMed database and Google Scholar search engine, which included in their title or abstract the terms 'wind turbine', 'infrasound' or 'low frequency noise'. There is evidence that infrasound has a physiological effect on the ear. Until this effect is fully understood, it is impossible to conclude that wind turbine noise does not cause any of the symptoms described. However, many believe that these symptoms are related largely to the stress caused by unwanted noise exposure. There is some evidence of symptoms in patients exposed to wind turbine noise. The effects of infrasound require further investigation.

Wind/seismic comparison for upgrading existing structures

International Nuclear Information System (INIS)

Giller, R.A.

1989-01-01

This paper depicts the analysis procedures and methods used to evaluate three existing building structures for extreme wind loads. The three structures involved in this evaluation are located at the US Department of Energy's Hanford Site near Richland, Washington. This site is characterized by open flat grassland with few surrounding obstructions and has extreme winds in lieu of tornados as a design basis accident condition. This group of buildings represents a variety of construction types, including a concrete stack, a concrete load-bearing wall structure, and a rigid steel-frame building. The three structures included in this group have recently been evaluated for response to the design basis earthquake that included non-linear time history effects. The resulting loads and stresses from the wind analyses were compared to the loads and stresses resulting from seismic analyses. This approach eliminated the need to prepare additional capacity calculations that were already contained in the seismic evaluations

Voltage sag influence on fatigue life of the drivetrain of fixed speed wind turbines

DEFF Research Database (Denmark)

Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

2011-01-01

Occurrence of voltage sags due to electrical grid faults and other network disturbances generate transients of the generator electromagnetic torque which result in significant high stresses and noticeable vibrations for the wind turbine mechanical system and may also have a detrimental effect...... on the fatigue life of important drivetrain components. The high penetration of wind energy in the electrical grids demands new requirements for the operation of wind energy conversion systems. Although fixed speed wind turbine technology is nowadays replaced by variable speed wind turbines. In some countries...... by the stator flux oscillations which cause high transients of the generator electromagnetic torque. This paper focuses in estimating the resulting significant stresses transients due to the electromagnetic torque transients, which transmits to the wind turbine mechanical system that may have a detrimental...

Wind - Prototypes on the landscape

Science.gov (United States)

Smith, M. L.

1981-12-01

Large wind turbines are shown to be attractive to utilities because of the potential for decreasing gas and oil consumption, the relatively low costs for entry into the field, and the wide distribution of wind energy. The total generating capacity can be increased in incremental steps, experience in construction and operation of large turbines have been gained from the NASA Mod O, OA, 1, and 2 models, and advances in manufacturing processes will make the large turbines competitive as replacement power for oil and gas burning utility generators. The 300 ft rotor Mod 2 machines are described, along with designs for the Mod 5A and Mod 5B wind turbines, with 400 and 422 ft, 6.2 and 7.2 MW rotors and outputs, respectively. Current plans for multi-MW windfarms are reviewed, and the option of using the land around large wind turbines for other purposes is stressed.

Wind Tunnel Tests of Parabolic Trough Solar Collectors: March 2001--August 2003

Energy Technology Data Exchange (ETDEWEB)

Hosoya, N.; Peterka, J. A.; Gee, R. C.; Kearney, D.

2008-05-01

Conducted extensive wind-tunnel tests on parabolic trough solar collectors to determine practical wind loads applicable to structural design for stress and deformation, and local component design for concentrator reflectors.

Thermal analysis of two-level wind power converter under symmetrical grid fault

DEFF Research Database (Denmark)

Zhou, Dao; Blaabjerg, Frede

2013-01-01

In this paper, the case of symmetrical grid fault when using the multi-MW wind turbine of partial-scale and full-scale two-level power converter are designed and investigated. Firstly, the different operation behaviors of the relevant power converters under the voltage dip will be described......) condition as well as the junction temperature. For the full-scale wind turbine system, the most thermal stressed power device in the grid-side converter will appear at the grid voltage below 0.5 pu, and for the partial-scale wind turbine system, the most thermal stressed power device in the rotor...

Role of multiaxial stress state in the hydrogen-assisted rolling-contact fatigue in bearings for wind turbines

Directory of Open Access Journals (Sweden)

J. Toribio

2015-07-01

Full Text Available Offshore wind turbines often involve important engineering challenges such as the improvement of hydrogen embrittlement resistance of the turbine bearings. These elements frequently suffer the so-called phenomenon of hydrogen-assisted rolling-contact fatigue (HA-RCF as a consequence of the synergic action of the surrounding harsh environment (the lubricant supplying hydrogen to the material and the cyclic multiaxial stress state caused by in-service mechanical loading. Thus the complex phenomenon could be classified as hydrogen-assisted rolling-contact multiaxial fatigue (HA-RC-MF. This paper analyses, from the mechanical and the chemical points of view, the so-called ball-on-rod test, widely used to evaluate the hydrogen embrittlement susceptibility of turbine bearings. Both the stress-strain states and the steady-state hydrogen concentration distribution are studied, so that a better elucidation can be obtained of the potential fracture places where the hydrogen could be more harmful and, consequently, where the turbine bearings could fail during their life in service.

Early stages of wind wave and drift current generation under non-stationary wind conditions.

Science.gov (United States)

Robles-Diaz, Lucia; Ocampo-Torres, Francisco J.; Branger, Hubert

2016-04-01

waves by turbulent wind." Journal of Fluid Mechanics, 2: 417-445. • Smith, Stuart D. 1980. "Wind Stress and Heat Flux over the Ocean in Gale Force Winds." Journal of Physical Oceanography 10: 709-26. • Yelland, Margaret, and Peter K. Taylor. 1996. "Wind Stress Measurements from the Open Ocean." Journal of Physical Oceanography 26: 541-58.

The most intense electric currents in turbulent high speed solar wind

Science.gov (United States)

Podesta, J. J.

2017-12-01

Theory and simulations suggest that dissipation of turbulent energy in collisionless astrophysical plasmas occurs most rapidly in spatial regions where the current density is most intense. To advance understanding of plasma heating by turbulent dissipation in the solar corona and solar wind, it is of interest to characterize the properties of plasma regions where the current density takes exceptionally large values and to identify the operative dissipation processes. In the solar wind, the curl of the magnetic field cannot be measured using data from a single spacecraft, however, a suitable proxy for this quantity can be constructed from the spatial derivative of the magnetic field along the flow direction of the plasma. This new approach is used to study the properties of the most intense current carrying structures in a high speed solar wind stream near 1 AU. In this study, based on 11 Hz magnetometer data from the WIND spacecraft, the spatial resolution of the proxy technique is approximately equal to the proton inertial length. Intense current sheets or current carrying structures were identified as events where the magnitude of the current density exceeds μ+5σ, where μ and σ are the mean and standard deviation of the magnitude of the current density (or its proxy), respectively. Statistical studies show (1) the average size of these 5σ events is close to the smallest resolvable scale in the data set, the proton inertial length; (2) the linear distance between neighboring events follows a power law distribution; and (3) the average peak current density of 5σ events is around 1 pA/cm2. The analysis techniques used in these studies have been validated using simulated spacecraft data from three dimensional hybrid simulations which show that results based on the analysis of the proxy are qualitatively and quantitatively similar to results based on the analysis of the true current density.

Phylogenetic analysis of Melon chlorotic leaf curl virus from Guatemala: Another emergent species in the Squash leaf curl virus clade

KAUST Repository

Brown, J.K.

2011-06-01

The genome of a new bipartite begomovirus Melon chlorotic leaf curl virus from Guatemala (MCLCuV-GT) was cloned and the genome sequence was determined. The virus causes distinct symptoms on melons that were not previously observed in melon crops in Guatemala or elsewhere. Phylogenetic analysis of MCLCuV-GT and begomoviruses infecting cucurbits and other host plant species indicated that its closest relative was MCLCuV from Costa Rica (MCLCuV-CR). The DNA-A components of two isolates shared 88.8% nucleotide identity, making them strains of the same species. Further, both MCLCuV-GT and MCLCuV-CR grouped with other Western Hemisphere cucurbit-infecting species in the SLCV-clade making them the most southerly cucurbit-infecting members of the clade to date. Although the common region of the cognate components of MCLCuV-GT and MCLCuV-CR, shared similar to 96.3% nucleotide identity. While DNA-A and DNA-B components of MCLCuV-GT were less than 86% nucleotide identity with the respective DNAA and DNA-B common regions of MCLCuV-CR. The late viral genes of the two strains shared the least nt identity (<88%) while their early genes shared the highest nt identity (>90%). The collective evidence suggests that these two strains of MCLCuV are evolutionarily divergent owing in part to recombination, but also due to the accumulation of a substantial number of mutations. In addition they are differentially host-adapted, as has been documented for other cucurbit-infecting, bean-adapted, species in the SLCV clade. (C) 2011 Elsevier B.V. All rights reserved.

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.

Effect of load eccentricity and stress level on monopile support for offshore wind turbines

DEFF Research Database (Denmark)

Klinkvort, Rasmus Tofte; Hededal, Ole

2014-01-01

on which load is applied with a large eccentricity. With centrifuge tests as the basis, this paper investigates the behaviour of a rigid pile loaded with a high eccentricity. A test series was carried out to simulate idealized monotonic load cases for monopiles supporting an offshore wind turbine....... Centrifuge tests were performed on model monopiles subjected to stress distributions equal to prototype monopiles with pile diameters ranging from 1–5 m and eccentricities ranging from 8.25–17.75 pile diameters. It was possible to identify a unified response of all of these tests by using dimensional...... analysis and Rankine’s passive earth pressure coefficient as a normalization parameter. The normalized ultimate soil resistance was unaffected by acceleration level and load eccentricity, indicating that the failure mechanism was the same for all tests. Based on the centrifuge tests, a reformulation...

DISTRIBUTED EXTERNAL SURFACE HARDENING OF CAR DESIGN BY WINDING

Directory of Open Access Journals (Sweden)

O. V. Fomin

2017-04-01

Full Text Available Purpose. The paper involves coverage of features and results of the research conducted by the authors to determine the feasibility and establishment of pre-stressed-strained state of freight cars by winding in order to improve their strength characteristics. It is also necessary to present the theoretical justification for the effectiveness of the application of this method for car designs and an appropriate example for the tank-car. Methodology. The conducted study is based on an analysis of known works on the subject, mathematical justification and computer modeling. At the calculations of rolling stock components contemporary conventional techniques were used. Findings. Authors found that the winding method for pre-stressed-strained state is effective and appropriate for use in the construction of railway rolling stock and, in particular freight cars. Freight car designs with the pre-stressed-strained state are characterized by a number of strength advantages, among which there is an improvement of the work on the perception of operational loads and resource conservation. Originality. For the first time it is proposed the improvement of bearing capacity of freight car constructions through the creation of its component in the directed stress-strained state. It is also for the first time proposed the use of distributed external surface hardening by the method of winding to create a pre-stress-strained state of structural components of freight cars. The methods for winding designs of freight cars and their implementation were considered. Practical value. The studies developed a number of technical solutions for improving the design of freight cars and tank-container, which has been patented. Corresponding solutions for the tank-car are partially presented. Practical implementation of such solutions will significantly improve the technical, economic and operational performances of car designs.

Como diferenciar uma marca num mercado pouco heterogéneo: inovação da Rip Curl

OpenAIRE

Real, Isabel Corte

2011-01-01

Mestrado em Marketing A partir de uma paixão pessoal que é o surf, e um interesse cada vez maior pelas novas tecnologias e como elas estão a mudar tudo à nossa volta, surgiu a ideia de criar um projecto para uma marca de surf que tem investido muito em Portugal, percebendo o potencial que o nosso país tem com tantos quilómetros de costa. As conclusões retiradas do quadro teórico e de toda a envolvente externa e interna à Rip Curl permitem apresentar um plano inovador para a criação de u...

Leaf curl diseases of two solanaceous species in Southwest Arabia are caused by a monopartite begomovirus evolutionarily most closely related to a species from the Nile Basin and unique suite of betasatellites

KAUST Repository

Idris, Ali

2012-10-01

The complete genome of 2780 bases was amplified using rolling circle amplification, and cloned, and sequenced for two distinct strains of the monopartite begomovirus Tomato leaf curl Sudan virus (ToLCSDV). The two strains shared 86-91% identity with the previously described ToLCSDV from the Nile Basin, and 90-91% identity with one another. One strain was cloned from symptomatic tomato plants from Tihamah (ToLCSDV-YE[YE:Tih:05]) while the other was cloned from symptomatic tobacco plants collected from Wadi Hadramaut (ToLCSDV-YE[YE:Had:89]). A distinct full-length betasatellite molecule (1352 bases) was cloned from the respective field-infected tomato and tobacco plants. Agro-inoculation of tomato and Nicotiana benthamiana plants with cloned partial tandem repeats of ToLCSDV-YE[YE:Tih11:05]) and the associated betasatellite, Tomato leaf curl Yemen betasatellite (ToLCYEB-[Tih:tom:137:05]), resulted in the reproduction of leaf curl disease symptoms in test plants like those observed in the field-infected plants. The betasatellite contributed to symptom severity in N. benthamiana test plants when it was co-inoculated with ToLCSDV-YE, compared to the milder symptoms that were observed in tobacco plants infected with the helper virus alone. © 2012 Elsevier B.V.

Leaf curl diseases of two solanaceous species in Southwest Arabia are caused by a monopartite begomovirus evolutionarily most closely related to a species from the Nile Basin and unique suite of betasatellites

KAUST Repository

Idris, Ali; Abdullah, N.; Brown, Judith K.

2012-01-01

The complete genome of 2780 bases was amplified using rolling circle amplification, and cloned, and sequenced for two distinct strains of the monopartite begomovirus Tomato leaf curl Sudan virus (ToLCSDV). The two strains shared 86-91% identity with the previously described ToLCSDV from the Nile Basin, and 90-91% identity with one another. One strain was cloned from symptomatic tomato plants from Tihamah (ToLCSDV-YE[YE:Tih:05]) while the other was cloned from symptomatic tobacco plants collected from Wadi Hadramaut (ToLCSDV-YE[YE:Had:89]). A distinct full-length betasatellite molecule (1352 bases) was cloned from the respective field-infected tomato and tobacco plants. Agro-inoculation of tomato and Nicotiana benthamiana plants with cloned partial tandem repeats of ToLCSDV-YE[YE:Tih11:05]) and the associated betasatellite, Tomato leaf curl Yemen betasatellite (ToLCYEB-[Tih:tom:137:05]), resulted in the reproduction of leaf curl disease symptoms in test plants like those observed in the field-infected plants. The betasatellite contributed to symptom severity in N. benthamiana test plants when it was co-inoculated with ToLCSDV-YE, compared to the milder symptoms that were observed in tobacco plants infected with the helper virus alone. © 2012 Elsevier B.V.

Siting wind farms in and around forests

Energy Technology Data Exchange (ETDEWEB)

Douglas, N. [Natural Power Consultants, Vancouver, BC (Canada)

2010-07-01

This PowerPoint presentation discussed methods of assessing the impact of trees on wind resources. Turbulence is generated and also absorbed by trees. Disturbances generated at tree level are then transported upwards and down-wind by the wind. The turbulence induced by trees can be felt kilometers downwind of forests at wind turbine hub heights. Wind speeds can be less than predicted, and significant over-estimations can occur with modelled results. The effects of high shear and high turbulence can also have an impact on power curve performance and lead to higher levels of mechanical stress. A SCADA analysis was used to demonstrate the impact of forests on power curves. Wind power predictions near forests can be optimized by using a full year of data capture at hub height, full rotor measurements, and a consideration of seasonal variations. Accurate tree maps are needed to determine the effects of trees on wind shear. Various forestry scenarios were modelled to demonstrate the effects of forestry management over time. tabs., figs.

High-order Div- and Quasi Curl-Conforming Basis Functions for Calderón Multiplicative Preconditioning of the EFIE

KAUST Repository

Valdes, Felipe; Andriulli, Francesco P.; Cools, Kristof; Michielssen, Eric

2011-01-01

A new high-order Calderón multiplicative preconditioner (HO-CMP) for the electric field integral equation (EFIE) is presented. In contrast to previous CMPs, the proposed preconditioner allows for high-order surface representations and current expansions by using a novel set of high-order quasi curl-conforming basis functions. Like its predecessors, the HO-CMP can be seamlessly integrated into existing EFIE codes. Numerical results demonstrate that the linear systems of equations obtained using the proposed HO-CMP converge rapidly, regardless of the mesh density and of the order of the current expansion. © 2006 IEEE.

High-order Div- and Quasi Curl-Conforming Basis Functions for Calderón Multiplicative Preconditioning of the EFIE

KAUST Repository

Valdes, Felipe

2011-04-01

A new high-order Calderón multiplicative preconditioner (HO-CMP) for the electric field integral equation (EFIE) is presented. In contrast to previous CMPs, the proposed preconditioner allows for high-order surface representations and current expansions by using a novel set of high-order quasi curl-conforming basis functions. Like its predecessors, the HO-CMP can be seamlessly integrated into existing EFIE codes. Numerical results demonstrate that the linear systems of equations obtained using the proposed HO-CMP converge rapidly, regardless of the mesh density and of the order of the current expansion. © 2006 IEEE.

Monitoring of wind load and response for cable-supported bridges in Hong Kong

Science.gov (United States)

Wong, Kai-yuen; Chan, Wai-Yee K.; Man, King-Leung

2001-08-01

Structural health monitoring for the three cable-supported bridges located in the West of Hong Kong or the Tsing Ma Control Area has been carried out since the opening of these bridges to public traffic. The three cable-supported bridges are referred to as the Tsing Ma (suspension) Bridge, the Kap Shui Mun (cable-stayed) Bridge and the Ting Kau (cable-stayed) Bridge. The structural health monitoring works involved are classified as six monitoring categories, namely, wind load and response, temperature load and response, traffic load and response, geometrical configuration monitoring, strains and stresses/forces monitoring and global dynamic characteristics monitoring. As wind loads and responses had been a major concern in the design and construction stages, this paper therefore outlines the work of wind load and response monitoring on Tsing Ma, Kap Shui Mun and Ting Kau Bridges. The paper starts with a brief description of the sensory systems. The description includes the layout and performance requirements of sensory systems for wind load and responses monitoring. Typical results of wind load and response monitoring in graphical forms are then presented. These graphical forms include the plots of wind rose diagrams, wind incidences vs wind speeds, wind turbulence intensities, wind power spectra, gust wind factors, coefficient of terrain roughness, extreme wind analyses, deck deflections/rotations vs wind speeds, acceleration spectra, acceleration/displacement contours, and stress demand ratios. Finally conclusions on wind load and response monitoring on the three cable-supported bridges are drawn.

Suppression of cotton leaf curl disease symptoms in Gossypium hirsutum through over expression of host-encoded miRNAs.

Science.gov (United States)

Akmal, Mohd; Baig, Mirza S; Khan, Jawaid A

2017-12-10

Cotton leaf curl disease (CLCuD), a major factor resulting in the enormous yield losses in cotton crop, is caused by a distinct monopartite begomovirus in association with Cotton leaf curl Multan betasatellite (CLCuMB). Micro(mi)RNAs are known to regulate gene expression in eukaryotes, including antiviral defense in plants. In a previous study, we had computationally identified a set of cotton miRNAs, which were shown to have potential targets in the genomes of Cotton leaf curl Multan virus (CLCuMuV) and CLCuMB at multiple loci. In the current study, effect of Gossypium arboreum-encoded miRNAs on the genome of CLCuMuV and CLCuMB was investigated in planta. Two computationally predicted cotton-encoded miRNAs (miR398 and miR2950) that showed potential to bind multiple Open Reading Frames (ORFs; C1, C4, V1, and non- coding intergenic region) of CLCuMuV, and (βC1) of CLCuMB were selected. Functional validation of miR398 and miR2950 was done by overexpression approach in G. hirsutum var. HS6. A total of ten in vitro cotton plants were generated from independent events and subjected to biological and molecular analyses. Presence of the respective Precursor (pre)-miRNA was confirmed through PCR and Southern blotting, and their expression level was assessed by semi quantitative RT-PCR, Real Time quantitative PCR and northern hybridization in the PCR-positive lines. Southern hybridization revealed 2-4 copy integration of T-DNA in the genome of the transformed lines. Remarkably, expression of pre-miRNAs was shown up to 5.8-fold higher in the transgenic (T 0 ) lines as revealed by Real Time PCR. The virus resistance was monitored following inoculation of the transgenic cotton lines with viruliferous whitefly (Bemisia tabaci) insect vector. After inoculation, four of the transgenic lines remained apparently symptom free. While a very low titre of viral DNA could be detected by Rolling circle amplification, betasatellite responsible for symptom induction could not be detected

Genetic diversity in upland cotton for cotton leaf curl virus disease, earliness and fiber quality

International Nuclear Information System (INIS)

Saeed, F.; Farooq, J.; Mahmood, A.; Hussain, T.

2014-01-01

In Pakistan during last two decades the major factor limiting cotton production is cotton leaf curl virus disease (CLCuD). For estimation of genetic diversity regarding CLCuD tolerance, fiber quality and some yield contributing traits, 101 cotton genotypes imported from USA were evaluated. Different statistical procedures like cluster, principle components (PC) and correlation analysis were employed to identify the suitable genotypes that can be further exploited in breeding programme. Significant associations were found between yield contributing trait, boll weight and fiber related trait, staple length. Earliness related traits, like days taken to 1 square and days taken to 1 flower had positive correlation with each other and both these traits also showed their positive association with ginning out turn. The negative significant correlation of CLCuD was obtained with monopodial branches, sympodial branches and plant height. Principal component (PC) analysis showed first five PCs having eigen value >1 explaining 67.8% of the total variation with days to st 1 square and flowering along with plant height and sympodia plant which were being the most important characters in PC1. Cluster analysis classified 101 accessions into five divergent groups. The genotypes in st cluster 1 only showed reasonable values for days to 1 square and flower, sympodia per plant, ginning out turn, staple length and fiber fineness and the genotypes in cluster 5 showed promising values for the traits like cotton leaf curl virus, ginning out turn and fiber fineness. The genotypes in cluster 1 and 5 may be combined to obtain desirable traits related to earliness and better disease tolerance. Scatter plot and tree diagrams demonstrated sufficient diversity among the cotton accessions for various traits and some extent of association between various clusters. It is concluded that diversity among the genotypes could be utilized for the development of CLCuD resistant lines with increased seed

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.

Bubbles generated from wind-steepened breaking waves: 1. Bubble plume bubbles

NARCIS (Netherlands)

Leifer, I.; Leeuw, G. de

2006-01-01

Measurements of bubble plumes from paddle-amplified, wind stress breaking waves were made in a large wind-wave channel during the LUMINY experiment in fresh (but not clean) water. Bubble plumes exhibited considerable variability with respect to dynamics, bubble size distribution, and physical

Causes of the large warm bias in the Angola-Benguela Frontal Zone in the Norwegian Earth System Model

Science.gov (United States)

Koseki, Shunya; Keenlyside, Noel; Demissie, Teferi; Toniazzo, Thomas; Counillon, Francois; Bethke, Ingo; Ilicak, Mehmet; Shen, Mao-Lin

2018-06-01

We have investigated the causes of the sea surface temperature (SST) bias in the Angola-Benguela Frontal Zone (ABFZ) of the southeastern Atlantic Ocean simulated by the Norwegian Earth System Model (NorESM). Similar to other coupled-models, NorESM has a warm SST bias in the ABFZ of up to 8 °C in the annual mean. Our analysis of NorESM reveals that a cyclonic surface wind bias over the ABFZ drives a locally excessively strong southward (0.05 m/s (relative to observation)) Angola Current displacing the ABFZ southward. A series of uncoupled stand-alone atmosphere and ocean model simulations are performed to investigate the cause of the coupled model bias. The stand-alone atmosphere model driven with observed SST exhibits a similar cyclonic surface circulation bias; while the stand-alone ocean model forced with the reanalysis data produces a warm SST in the ABFZ with a magnitude approximately half of that in the coupled NorESM simulation. An additional uncoupled sensitivity experiment shows that the atmospheric model's local negative surface wind curl generates anomalously strong Angola Current at the ocean surface. Consequently, this contributes to the warm SST bias in the ABFZ by 2 °C (compared to the reanalysis forced simulation). There is no evidence that local air-sea feedbacks among wind stress curl, SST, and sea level pressure (SLP) affect the ABFZ SST bias. Turbulent surface heat flux differences between coupled and uncoupled experiments explain the remaining 2 °C warm SST bias in NorESM. Ocean circulation, upwelling and turbulent heat flux errors all modulate the intensity and the seasonality of the ABFZ errors.

Causes of the large warm bias in the Angola-Benguela Frontal Zone in the Norwegian Earth System Model

Science.gov (United States)

Koseki, Shunya; Keenlyside, Noel; Demissie, Teferi; Toniazzo, Thomas; Counillon, Francois; Bethke, Ingo; Ilicak, Mehmet; Shen, Mao-Lin

2017-09-01

We have investigated the causes of the sea surface temperature (SST) bias in the Angola-Benguela Frontal Zone (ABFZ) of the southeastern Atlantic Ocean simulated by the Norwegian Earth System Model (NorESM). Similar to other coupled-models, NorESM has a warm SST bias in the ABFZ of up to 8 °C in the annual mean. Our analysis of NorESM reveals that a cyclonic surface wind bias over the ABFZ drives a locally excessively strong southward (0.05 m/s (relative to observation)) Angola Current displacing the ABFZ southward. A series of uncoupled stand-alone atmosphere and ocean model simulations are performed to investigate the cause of the coupled model bias. The stand-alone atmosphere model driven with observed SST exhibits a similar cyclonic surface circulation bias; while the stand-alone ocean model forced with the reanalysis data produces a warm SST in the ABFZ with a magnitude approximately half of that in the coupled NorESM simulation. An additional uncoupled sensitivity experiment shows that the atmospheric model's local negative surface wind curl generates anomalously strong Angola Current at the ocean surface. Consequently, this contributes to the warm SST bias in the ABFZ by 2 °C (compared to the reanalysis forced simulation). There is no evidence that local air-sea feedbacks among wind stress curl, SST, and sea level pressure (SLP) affect the ABFZ SST bias. Turbulent surface heat flux differences between coupled and uncoupled experiments explain the remaining 2 °C warm SST bias in NorESM. Ocean circulation, upwelling and turbulent heat flux errors all modulate the intensity and the seasonality of the ABFZ errors.

Field measurements in the wake of a model wind turbine

International Nuclear Information System (INIS)

Pol, Suhas; Taylor, Amelia; Doostalab, Ali; Novoa, Santiago; Castillo, Luciano; Bilbao, Argenis; Sheng, Jian; Giesselmann, Michael; Westergaard, Carsten; Hussain, Fazle; Ren, Beibei; Glauser, Mark

2014-01-01

As a first step to study the dynamics of a wind farm' we experimentally explored the flow field behind a single wind turbine of diameter 1.17 m at a hub height of 6.25 m. A 10 m tower upstream of the wind farm characterizes the atmospheric conditions and its influence on the wake evolution. A vertical rake of sonic anemometers is clustered around the hub height on a second tower' 6D downstream of the turbine. We present preliminary observations from a 1- hour block of data recorded in near-neutral atmospheric conditions. The ratio of the standard deviation of power to the inflow velocity is greater than three' revealing adverse effects of inflow turbulence on the power and load fluctuations. Furthermore' the wake defect and Reynolds stress and its gradient are pronounced at 6D. The flux of energy due to Reynolds stresses is similar to that reported in wind tunnel studies. The swirl and mixing produces a constant temperature wake which results in a density jump across the wake interface. Further field measurements will explore the dynamics of a model wind farm' including the effects of atmospheric variability

Industrial wind turbines and adverse health effects.

Science.gov (United States)

Jeffery, Roy D; Krogh, Carmen M E; Horner, Brett

2014-01-01

Some people living in the environs of industrial wind turbines (IWTs) report experiencing adverse health and socioeconomic effects. This review considers the hypothesis that annoyance from audible IWTs is the cause of these adverse health effects. We searched PubMed and Google Scholar for articles published since 2000 that included the terms "wind turbine health," "wind turbine infrasound," "wind turbine annoyance," "noise annoyance" or "low frequency noise" in the title or abstract. Industrial wind turbines produce sound that is perceived to be more annoying than other sources of sound. Reported effects from exposure to IWTs are consistent with well-known stress effects from persistent unwanted sound. If placed too close to residents, IWTs can negatively affect the physical, mental and social well-being of people. There is sufficient evidence to support the conclusion that noise from audible IWTs is a potential cause of health effects. Inaudible low-frequency noise and infrasound from IWTs cannot be ruled out as plausible causes of health effects.

Wind Turbine Contingency Control Through Generator De-Rating

Science.gov (United States)

Frost, Susan; Goebel, Kai; Balas, Mark

2013-01-01

Maximizing turbine up-time and reducing maintenance costs are key technology drivers for wind turbine operators. Components within wind turbines are subject to considerable stresses due to unpredictable environmental conditions resulting from rapidly changing local dynamics. In that context, systems health management has the aim to assess the state-of-health of components within a wind turbine, to estimate remaining life, and to aid in autonomous decision-making to minimize damage to the turbine. Advanced contingency control is one way to enable autonomous decision-making by providing the mechanism to enable safe and efficient turbine operation. The work reported herein explores the integration of condition monitoring of wind turbines with contingency control to balance the trade-offs between maintaining system health and energy capture. The contingency control involves de-rating the generator operating point to achieve reduced loads on the wind turbine. Results are demonstrated using a high fidelity simulator of a utility-scale wind turbine.

Indo-Pacific sea level variability during recent decades

Science.gov (United States)

Yamanaka, G.; Tsujino, H.; Nakano, H.; Urakawa, S. L.; Sakamoto, K.

2016-12-01

Decadal variability of sea level in the Indo-Pacific region is investigated using a historical OGCM simulation. The OGCM driven by the atmospheric forcing removing long-term trends clearly exhibits decadal sea level variability in the Pacific Ocean, which is associated with eastern tropical Pacific thermal anomalies. During the period of 1977-1987, the sea level anomalies are positive in the eastern equatorial Pacific and show deviations from a north-south symmetric distribution, with strongly negative anomalies in the western tropical South Pacific. During the period of 1996-2006, in contrast, the sea level anomalies are negative in the eastern equatorial Pacific and show a nearly north-south symmetric pattern, with positive anomalies in both hemispheres. Concurrently, sea level anomalies in the south-eastern Indian Ocean vary with those in the western tropical Pacific. These sea level variations are closely related to large-scale wind fields. Indo-Pacific sea level distributions are basically determined by wind anomalies over the equatorial region as well as wind stress curl anomalies over the off-equatorial region.

Wake Effects on Lifetime Distribution in DFIG-based Wind Farms

DEFF Research Database (Denmark)

Tian, Jie; Zhou, Dao; Su, Chi

2017-01-01

With the increasing size of the wind farms, the impact of the wake effect on the energy yields and lifetime consumption of wind turbine can no longer be neglected. In this paper, the affecting factors like the wind speed and wind direction are investigated in terms of the single wake and multiple...... wakes. As the power converter is the most fragile component among the turbine system, its lifetime estimation can be calculated seen from the thermal stress of the power semiconductor. On the basis of the relationship of the power converter in a 5 MW Doubly-Fed Induction Generator (DFIG) wind turbine...... system and the wind speed, the lifetime consumption of the individual turbine in a 10-turbine and an 80-turbine wind farms can be calculated by considering the real distributions of the wind speed and direction. It can be seen that there is significant lifetime difference among individual turbines...

The Offshore New European Wind Atlas

Science.gov (United States)

Karagali, I.; Hahmann, A. N.; Badger, M.; Hasager, C.; Mann, J.

2017-12-01

The New European Wind Atlas (NEWA) is a joint effort of research agencies from eight European countries, co-funded under the ERANET Plus Program. The project is structured around two areas of work: development of dynamical downscaling methodologies and measurement campaigns to validate these methodologies, leading to the creation and publication of a European wind atlas in electronic form. This atlas will contain an offshore component extending 100 km from the European coasts. To achieve this, mesoscale models along with various observational datasets are utilised. Scanning lidars located at the coastline were used to compare the coastal wind gradient reproduced by the meso-scale model. Currently, an experimental campaign is occurring in the Baltic Sea, with a lidar located in a commercial ship sailing from Germany to Lithuania, thus covering the entire span of the south Baltic basin. In addition, satellite wind retrievals from scatterometers and Synthetic Aperture Radar (SAR) instruments were used to generate mean wind field maps and validate offshore modelled wind fields and identify the optimal model set-up parameters.The aim of this study is to compare the initial outputs from the offshore wind atlas produced by the Weather & Research Forecasting (WRF) model, still in pre-operational phase, and the METOP-A/B Advanced Scatterometer (ASCAT) wind fields, reprocessed to stress equivalent winds at 10m. Different experiments were set-up to evaluate the model sensitivity for the various domains covered by the NEWA offshore atlas. ASCAT winds were utilised to assess the performance of the WRF offshore atlases. In addition, ASCAT winds were used to create an offshore atlas covering the years 2007 to 2016, capturing the signature of various spatial wind features, such as channelling and lee effects from complex coastal topographical elements.

A compact high-voltage pulse generator based on pulse transformer with closed magnetic core.

Science.gov (United States)

Zhang, Yu; Liu, Jinliang; Cheng, Xinbing; Bai, Guoqiang; Zhang, Hongbo; Feng, Jiahuai; Liang, Bo

2010-03-01

A compact high-voltage nanosecond pulse generator, based on a pulse transformer with a closed magnetic core, is presented in this paper. The pulse generator consists of a miniaturized pulse transformer, a curled parallel strip pulse forming line (PFL), a spark gap, and a matched load. The innovative design is characterized by the compact structure of the transformer and the curled strip PFL. A new structure of transformer windings was designed to keep good insulation and decrease distributed capacitance between turns of windings. A three-copper-strip structure was adopted to avoid asymmetric coupling of the curled strip PFL. When the 31 microF primary capacitor is charged to 2 kV, the pulse transformer can charge the PFL to 165 kV, and the 3.5 ohm matched load can deliver a high-voltage pulse with a duration of 9 ns, amplitude of 84 kV, and rise time of 5.1 ns. When the load is changed to 50 ohms, the output peak voltage of the generator can be 165 kV, the full width at half maximum is 68 ns, and the rise time is 6.5 ns.

Local inertial oscillations in the surface ocean generated by time-varying winds

Science.gov (United States)

Chen, Shengli; Polton, Jeff A.; Hu, Jianyu; Xing, Jiuxing

2015-12-01

A new relationship is presented to give a review study on the evolution of inertial oscillations in the surface ocean locally generated by time-varying wind stress. The inertial oscillation is expressed as the superposition of a previous oscillation and a newly generated oscillation, which depends upon the time-varying wind stress. This relationship is employed to investigate some idealized wind change events. For a wind series varying temporally with different rates, the induced inertial oscillation is dominated by the wind with the greatest variation. The resonant wind, which rotates anti-cyclonically at the local inertial frequency with time, produces maximal amplitude of inertial oscillations, which grows monotonically. For the wind rotating at non-inertial frequencies, the responses vary periodically, with wind injecting inertial energy when it is in phase with the currents, but removing inertial energy when it is out of phase. The wind rotating anti-cyclonically with time is much more favorable to generate inertial oscillations than the cyclonic rotating wind. The wind with a frequency closer to the inertial frequency generates stronger inertial oscillations. For a diurnal wind, the induced inertial oscillation is dependent on latitude and is most significant at 30 °. This relationship is also applied to examine idealized moving cyclones. The inertial oscillation is much stronger on the right-hand side of the cyclone path than on the left-hand side (in the northern hemisphere). This is due to the wind being anti-cyclonic with time on the right-hand side, but cyclonic on the other side. The inertial oscillation varies with the cyclone translation speed. The optimal translation speed generating the greatest inertial oscillations is 2 m/s at the latitude of 10 ° and gradually increases to 6 m/s at the latitude of 30 °.

Combining ability estimates for earliness in cotton leaf curl virus resistant inbred parents

International Nuclear Information System (INIS)

Baloch, M.J.; Baloch, Q.B.

2005-01-01

Four female cotton leaf curl virus-resistant resistant (cclv) parents consisting of advance strains and commercial varieties (VH-137, FH-901, CRIS-467 and Cyto-51) and four male parents, all clcv resistant Punjab varieties (FH-945, CIM-707, CIM-473 and FH-1000) were mated in a cross classification Design-II fashion. The results show that genetic variances due to additive genes were higher than the dominant variances, yet both types of variances were substantial, implying that significant improvement could reliably be made from segregating populations. The general combining ability (gca) estimates by and large suggested that for improvement in the appearance of first white flower and 1st sympodial branch node number, parents FH-945 and VH-137 whereas for 1st effective boll setting, parents FH-1000 and FH-901 and for percent of open bolls at 120 days after planting, parents CIM-707 and CRIS-467 may be given preference. However, for hybrid cotton development regarding earliness, hybrids CRIS-467 x CIM-707, VH-137 x FH-945 and Cyto-51 x FH-1000 may be chosen. (author)

Fatigue Life of Wind Turbine Blades

DEFF Research Database (Denmark)

Thoft-Christensen, Palle

2010-01-01

The present paper analyses the possibility of reducing the expected damage accumulation during tower passage by modifying the wind turbine tower design from a traditional mono-tower to a tripod. Due to a narrow stagnation zone the stress reversals and hence the damage accumulation in the blades...

Modelling the effect of coating on the stresses and microstructure evolution in chill casting of wind turbine main shafts

DEFF Research Database (Denmark)

Sonne, Mads Rostgaard; Thorborg, J.; Hattel, Jesper Henri

2017-01-01

The purpose of the present work is to quantify the effect of the inside coating on chills for casting of large wind turbine main shafts with respect to the evolution of internal stresses. These are known to affect the lifetime of the chills, and this is a major cost for the foundries today. Simul......, it is concluded that the material quality obtained from casting the main shafts in chills (and hence the performance of the part) is still much better than for sand casting, even though a very thick layer of coating is applied. Copyright © 2017 John Wiley & Sons, Ltd....... in the simulations. The outcome is validated by comparisons with samples taken out from a critical region of main shafts cast in sand and in chills. The results reveal minor reductions in the maximum principal stresses on the inner and outer surfaces of the chill of 3.1% and 18.5%, respectively, from changing...

Computational aerodynamics and aeroacoustics for wind turbines

Energy Technology Data Exchange (ETDEWEB)

Shen, W.Z.

2009-10-15

The present thesis consists of 19 selected papers dealing with the development and use of CFD methods for studying the aerodynamics and aero-acoustics of wind turbines. The papers are written in the period from 1997 to 2008 and numbered according to the list in page v. The work consists of two parts: an aerodynamic part based on Computational Fluid Dynamics and an aero-acoustic part based on Computational Aero Acoustics for wind turbines. The main objective of the research was to develop new computational tools and techniques for analysing flows about wind turbines. A few papers deal with applications of Blade Element Momentum (BEM) theory to wind turbines. In most cases the incompressible Navier-Stokes equations in primitive variables (velocity-pressure formulation) are employed as the basic governing equations. However, since fluid mechanical problems essentially are governed by vortex dynamics, it is sometimes advantageous to use the concept of vorticity (defined as the curl of velocity). In vorticity form the Navier-Stokes equations may be formulated in different ways, using a vorticity-stream function formulation, a vorticity-velocity formulation or a vorticity-potential-stream function formulation. In [1] - [3] two different vorticity formulations were developed for 2D and 3D wind turbine flows. In [4] and [5] numerical techniques for avoiding pressure oscillations were developed when solving the velocity-pressure coupling system in the in-house EllipSys2D/3D code. In [6] - [8] different actuator disc techniques combined with CFD are presented. This includes actuator disc, actuator line and actuator surface techniques, which were developed to simulate flows past one or more wind turbines. In [9] and [10] a tip loss correction method that improves the conventional models was developed for use in combination with BEM or actuator/Navier-Stokes computations. A simple and efficient technique for determining the angle of attack for flow past a wind turbine rotor

Dynamics of wind setdown at Suez and the Eastern Nile Delta.

Directory of Open Access Journals (Sweden)

Carl Drews

Full Text Available BACKGROUND: Wind setdown is the drop in water level caused by wind stress acting on the surface of a body of water for an extended period of time. As the wind blows, water recedes from the upwind shore and exposes terrain that was formerly underwater. Previous researchers have suggested wind setdown as a possible hydrodynamic explanation for Moses crossing the Red Sea, as described in Exodus 14. METHODOLOGY/PRINCIPAL FINDINGS: This study analyzes the hydrodynamic mechanism proposed by earlier studies, focusing on the time needed to reach a steady-state solution. In addition, the authors investigate a site in the eastern Nile delta, where the ancient Pelusiac branch of the Nile once flowed into a coastal lagoon then known as the Lake of Tanis. We conduct a satellite and modeling survey to analyze this location, using geological evidence of the ancient bathymetry and a historical description of a strong wind event in 1882. A suite of model experiments are performed to demonstrate a new hydrodynamic mechanism that can cause an angular body of water to divide under wind stress, and to test the behavior of our study location and reconstructed topography. CONCLUSIONS/SIGNIFICANCE: Under a uniform 28 m/s easterly wind forcing in the reconstructed model basin, the ocean model produces an area of exposed mud flats where the river mouth opens into the lake. This land bridge is 3-4 km long and 5 km wide, and it remains open for 4 hours. Model results indicate that navigation in shallow-water harbors can be significantly curtailed by wind setdown when strong winds blow offshore.

Comparative Analyses of Tomato yellow leaf curl virus C4 Protein-Interacting Host Proteins in Healthy and Infected Tomato Tissues

Directory of Open Access Journals (Sweden)

Namgyu Kim

2016-10-01

Full Text Available Tomato yellow leaf curl virus (TYLCV, a member of the genus Begomovirus, is one of the most important viruses of cultivated tomatoes worldwide, mainly causing yellowing and curling of leaves with stunting in plants. TYLCV causes severe problems in sub-tropical and tropical countries, as well as in Korea. However, the mechanism of TYLCV infection remains unclear, although the function of each viral component has been identified. TYLCV C4 codes for a small protein involved in various cellular functions, including symptom determination, gene silencing, viral movement, and induction of the plant defense response. In this study, through yeast-two hybrid screenings, we identified TYLCV C4-interacting host proteins from both healthy and symptom-exhibiting tomato tissues, to determine the role of TYLCV C4 proteins in the infection processes. Comparative analyses of 28 proteins from healthy tissues and 36 from infected tissues showing interactions with TYLCV C4 indicated that TYLCV C4 mainly interacts with host proteins involved in translation, ubiquitination, and plant defense, and most interacting proteins differed between the two tissues but belong to similar molecular functional categories. Four proteins—two ribosomal proteins, S-adenosyl-L-homocysteine hydrolase, and 14-3-3 family protein—were detected in both tissues. Furthermore, the identified proteins in symptom-exhibiting tissues showed greater involvement in plant defenses. Some are key regulators, such as receptor-like kinases and pathogenesis-related proteins, of plant defenses. Thus, TYLCV C4 may contribute to the suppression of host defense during TYLCV infection and be involved in ubiquitination for viral infection.

Extreme winds in the Western North Pacific

DEFF Research Database (Denmark)

Ott, Søren

2006-01-01

satellite images is discussed with emphasis on the empirical basis, which, unfortunately, is not very strong. This is stressed by the fact that Japanese and US agencies arrive at markedly different estimates. Onthe other hand, best track data records cover a long period of time and if not perfect......A statistical model for extreme winds in the western North Pacific is developed, the region on the Planet where tropical cyclones are most common. The model is based on best track data derived mostly from satellite images of tropical cyclones. The methodsused to estimate surface wind speeds from...... they are at least coherent over time in their imperfections. Applying the the Holland model to the best track data, wind profiles can be assigned along the tracks. Fromthis annual wind speed maxima at any particular point in the region can be derived. The annual maxima, in turn, are fitted to a Gumbel distribution...

Final Report for Project: Impacts of stratification and non-equilibrium winds and waves on hub-height winds

Energy Technology Data Exchange (ETDEWEB)

Patton, Edward G. [Univ. Corporation for Atmospheric Research, Boulder, CO (United States)

2015-07-14

wind plant scale. Overall project conclusions include; In the presence of fast-moving swell (significant wave height Hs = 6.4 m, and phase speed cp = 18 ms^-1), the atmospheric boundary layer grows more rapidly when waves propagate opposite to the winds compared to when winds and waves are aligned. Pressure drag increases by nearly a factor of 2 relative to the turbulent stress for the extreme case where waves propagate at 180° compared to the pressure gradient forcing. Net wind speed reduces by nearly 15% at hub-height for the 180°-case compared to the 0°-case, and turbulence intensities increase by nearly a factor of 2. These impacts diminish with decreasing wave age; Stratification increases hub height wind speeds and increases the vertical shear of the mean wind across the rotor plane. Fortuitously, this stability-induced enhanced shear does not influence turbulence intensity at hub height, but does increase (decrease) turbulence intensity below (above) hub height. Increased stability also increases the wave-induced pressure stress by ~ 10%; Off the East Coast of the United States during Coupled Boundary Layers Air-Sea Transfer - Low Wind (CBLAST-Low), cases with short fetch include thin stable boundary layers with depths of only a few tens of meters. In the coastal zone, the relationship between the mean wind and the surface fiction velocity (u*(V )) is significantly related to wind direction for weak winds but is not systematically related to the air sea difference of virtual potential temperature, δθv; since waves generally propagate from the south at the Air-Sea Interaction Tower (ASIT) tower, these results suggest that under weak wind conditions waves likely influence surface stress more than stratification does; and Winds and waves are frequently misaligned in the coastal zone. Stability conditions persist for long duration. Over a four year period, the Forschungsplattformen in Nord- und Ostsee Nr. 1 (FINO1) tower (a site with long fetch

Wind energy applications for municipal water services: Opportunities, situational analyses, and case studies

Energy Technology Data Exchange (ETDEWEB)

Flowers, L. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Miner-Nordstrom, L. [U.S. Dept. of Energy, Washington, D.C. (United States)

2006-01-01

As communities grow, greater demands are placed on water supplies, wastewater services, and the electricity needed to power the growing water services infrastructure. Water is also a critical resource for thermoelectric power plants. Future population growth in the United States is therefore expected to heighten competition for water resources. Especially in arid U.S. regions, communities may soon face hard choices with respect to water and electric power. Many parts of the United States with increasing water stresses also have significant wind energy resources. Wind power is the fastest-growing electric generation source in the United States and is decreasing in cost to be competitive with thermoelectric generation. Wind energy can potentially offer communities in water-stressed areas the option of economically meeting increasing energy needs without increasing demands on valuable water resources. Wind energy can also provide targeted energy production to serve critical local water-system needs. The U.S. Department of Energy (DOE) Wind Energy Technologies Program has been exploring the potential for wind power to meet growing challenges for water supply and treatment. The DOE is currently characterizing the U.S. regions that are most likely to benefit from wind-water applications and is also exploring the associated technical and policy issues associated with bringing wind energy to bear on water resource challenges.

Lidar-Observed Stress Vectors and Veer in the Atmospheric Boundary Layer

DEFF Research Database (Denmark)

Berg, Jacob; Mann, Jakob; Patton, Edward G.

2013-01-01

This study demonstrates that a pulsed wind lidar is a reliable instrument for measuring angles between horizontal vectors of significance in the atmospheric boundary layer. Three different angles are considered: the wind turning, the angle between the stress vector and the mean wind direction......, and the angle between the stress vector and the vertical gradient of the mean velocity vector. The latter is assumed to be zero by the often applied turbulent-viscosity hypothesis, so that the stress vector can be described through the vertical gradient of velocity. In the atmospheric surface layer, where...... the Coriolis force is negligible, this is supposedly a good approximation. High-resolution large-eddy simulation data show that this is indeed the case even beyond the surface layer. In contrast, through analysis of WindCube lidar measurements supported by sonic measurements, the study shows that it is only...

Uncovering a New Current: The Southwest MAdagascar Coastal Current

Science.gov (United States)

Ramanantsoa, Juliano D.; Penven, P.; Krug, M.; Gula, J.; Rouault, M.

2018-02-01

Cruise data sets, satellite remote sensing observations, and model data analyses are combined to highlight the existence of a coastal surface poleward flow in the southwest of Madagascar: the Southwest MAdagascar Coastal Current (SMACC). The SMACC is a relatively shallow (water surface signature of the SMACC extends from 22°S (upstream) to 26.4°S (downstream). The SMACC exhibits a seasonal variability: more intense in summer and reduced in winter. The average volume transport of its core is about 1.3 Sv with a mean summer maximum of 2.1 Sv. It is forced by a strong cyclonic wind stress curl associated with the bending of the trade winds along the southern tip of Madagascar. The SMACC directly influences the coastal upwelling regions south of Madagascar. Its existence is likely to influence local fisheries and larval transport patterns, as well as the connectivity with the Agulhas Current, affecting the returning branch of the global overturning circulation.

Nonlinear internal gravity waves and their interaction with the mean wind

International Nuclear Information System (INIS)

Grimshaw, R.

1975-01-01

The interaction of a wave packet of internal gravity waves with the mean wind is investigated, for the case when there is a region of wind shear and hence a critical level. The principal equations are the Doppler-shifted dispersion relation, the equation for conservation of wave action and the mean momentum equation, in which the mean wind is accelerated by a 'radiation stress' tensor, due to the waves. These equations are integrated numerically to study the behaviour of a wave packet approaching a critical level, where the horizontal phase speed matches the mean wind. The results demonstrate the exchange of energy from the waves to the mean wind in the vicinity of the critical level. The interaction between the waves and the mean wind is also studied in the absence of any initial wind shear. (author)

Simulation of a flexible wind turbine response to a grid fault

DEFF Research Database (Denmark)

Hansen, Anca Daniela; Cutululis, Nicolaos Antonio; Sørensen, Poul Ejnar

2007-01-01

The purpose of this work is to illustrate the impact of a grid fault on the mechanical loads of a wind turbine. Grid faults generate transients in the generator electromagnetic torque, which are propagated in the wind turbine, stressing its mechanical components. Grid faults are normally simulated...... in power system simulation tools applying simplified mechanical models of the drive train. This paper presents simulations of the wind turbine load response to grid faults with an advanced aeroelastic computer code (HAWC2). The core of this code is an advanced model for the flexible structure of the wind...... turbines, taking the flexibility of the tower, blades and other components of the wind turbines into account. The effect of a grid fault on the wind turbine flexible structure is assessed for a typical fixed speed wind turbine, equipped with an induction generator....

Interannual variability of Danube waters propagation in summer period of 1992-2015 and its influence on the Black Sea ecosystem

Science.gov (United States)

Kubryakov, A. A.; Stanichny, S. V.; Zatsepin, A. G.

2018-03-01

The propagation of the Danube River plume has strong interannual variability that impacts the local balance of nutrients and the thermohaline structure in the western Black Sea. In the present study, we use a particle-tracking model based on satellite altimetry measurements and wind reanalysis data, as well as satellite measurements (SeaWiFS, MODIS), to investigate the interannual variability in the Danube plume pathways during the summer from 1993 to 2015. The wind conditions largely define the variability in the Danube water propagation. Relatively low-frequency variability (on periods of a week to months) in the wind stress curl modulates the intensity of the geostrophic Rim Current and related mesoscale eddy dynamics. High-frequency offshore wind-drift currents transport the plume across isobaths and provide an important transport link between shelf and offshore circulation. Inherent plume dynamics play an additional role in the near-mouth transport of the plume and its connection with offshore circulation. During the years with prevailing northeast winds ( 30% of studied cases), which are usually accompanied by increased wind curl over the Black Sea and higher Danube discharge, an alongshore southward current at the NorthWestern Shelf (NWS) is formed near the western Black Sea coast. Advected southward, the Danube waters are entrained in the Rim Current jet, which transports them along the west coast of the basin. The strong Rim Current, fewer eddies and downwelling winds substantially decrease the cross-shelf exchange of nutrients. During the years with prevailing southeastern winds ( 40%), the Rim Current is less intense. Mesoscale eddies effectively trap the Danube waters, transporting them to the deep western part of the basin. The low- and high-frequency southeastern wind-drift currents contribute significantly to cross-isobath plume transport and its connection with offshore circulation. During several years ( 15%), the Danube waters moved eastward to

The Whitefly Bemisia tabaci Knottin-1 Gene Is Implicated in Regulating the Quantity of Tomato Yellow Leaf Curl Virus Ingested and Transmitted by the Insect

Directory of Open Access Journals (Sweden)

Aliza Hariton Shalev

2016-07-01

Full Text Available The whitefly Bemisia tabaci is a major pest to agricultural crops. It transmits begomoviruses, such as Tomato yellow leaf curl virus (TYLCV, in a circular, persistent fashion. Transcriptome analyses revealed that B. tabaci knottin genes were responsive to various stresses. Upon ingestion of tomato begomoviruses, two of the four knottin genes were upregulated, knot-1 (with the highest expression and knot-3. In this study, we examined the involvement of B. tabaci knottin genes in relation to TYLCV circulative transmission. Knottins were silenced by feeding whiteflies with knottin dsRNA via detached tomato leaves. Large amounts of knot-1 transcripts were present in the abdomen of whiteflies, an obligatory transit site of begomoviruses in their circulative transmission pathway; knot-1 silencing significantly depleted the abdomen from knot-1 transcripts. Knot-1 silencing led to an increase in the amounts of TYLCV ingested by the insects and transmitted to tomato test plants by several orders of magnitude. This effect was not observed following knot-3 silencing. Hence, knot-1 plays a role in restricting the quantity of virions an insect may acquire and transmit. We suggest that knot-1 protects B. tabaci against deleterious effects caused by TYLCV by limiting the amount of virus associated with the whitefly vector.

Detection and molecular characterization of tomato yellow leaf curl virus naturally infecting Lycopersicon esculentum in Egypt.

Science.gov (United States)

Rabie, M; Ratti, C; Abdel Aleem, E; Fattouh, F

Tomato yellow leaf curl virus (TYLCV) infections of tomato crops in Egypt were widely spread in 2014. Infected symptomatic tomato plants from different governorates were sampled. TYLCV strains Israel and Mild (TYLCV-IL, TYLCV-Mild) were identified by multiplex and real-time PCR. In addition, nucleotide sequence analysis of the V1 and V2 protein genes, revealed ten TYLCV Egyptian isolates (TYLCV from TY1 to 10). Phylogenetic analysis showed their high degree of relatedness with TYLCV-IL Jordan isolate (98%). Here we have showed the complete nucleotide sequence of the TYLCV Egyptian isolate TY10, sampled from El Beheira. A high degree of similarity to other previously reported Egyptian isolates and isolates from Jordan and Japan reflect the importance of phylogenetic analysis in monitoring virus genetic diversity and possibilities for divergence of more virulent strains or genotypes.

Power Electronics for the Next Generation Wind Turbine System

DEFF Research Database (Denmark)

Ma, Ke

generation unit, are becoming crucial in the wind turbine system. The objective of this project is to study the power electronics technology used for the next generation wind turbines. Some emerging challenges as well as potentials like the cost of energy and reliability are going to be addressed. First...... conversion is pushed to multi-MW level with high power density requirement. It has also been revealed that thermal stress in the power semiconductors is closely related to many determining factors in the wind power application like the reliability, cost, power density, etc. therefore it is an important......The wind power generation has been steadily growing both for the total installed capacity and for the individual turbine size. Due to much more significant impacts to the power grid, the power electronics, which can change the behavior of wind turbines from an unregulated power source to an active...

Mechanical properties of timber from wind damaged Norway spruce

DEFF Research Database (Denmark)

Hoffmeyer, Preben

2003-01-01

A storm may subject a tree to such bending stresses that extensive compression damage develops in the lee side. The tree may survive the wind load or it may be thrown. However, the damage is inherent and it may be of a magnitude to influence the mechanical properties of boards sawn from the stem....... The paper reports on a investigation of the relation between degree of damage and mechanical proper-ties of sawn timber from wind damaged Norway spruce. The project included about 250 bolts from wind damaged trees. The majority of bolts were cut to deliver a full-diameter plank containing the pith...

Resonant vibration control of wind turbine blades

DEFF Research Database (Denmark)

Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker

2010-01-01

. The efficiency of the resonant controller is demonstrated for a representative turbine blade exposed to turbulent wind loading. It is found that the present explicit tuning procedure yields close to optimal tuning, with very limited modal spill-over and effective reduction of the vibration amplitudes.......The paper deals with introduction of damping to specific vibration modes of wind turbine blades, using a resonant controller with acceleration feedback. The wind turbine blade is represented by three-dimensional, two-node finite elements in a local, rotating frame of reference. The element...... formulation accounts for arbitrary mass density distributions, general elastic crosssection properties and geometric stiffness effects due to internal stresses. A compact, linear formulation for aerodynamic forces with associated stiffness and damping terms is established and added to the structural model...

75 FR 23263 - Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC...

Science.gov (United States)

2010-05-03

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL10-62-000] Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC; Alta Wind VI, LLC; Alta Wind VII, LLC; Alta Wind VIII, LLC; Alta Windpower Development, LLC; TGP Development Company, LLC...

77 FR 29633 - Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC...

Science.gov (United States)

2012-05-18

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL12-68-000] Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC, Alta Wind XIII, LLC, Alta Wind XIV, LLC, Alta Wind XV, LLC, Alta Windpower Development, LLC, TGP Development Company, LLC...

Plasma turbulence resulting from the interaction between the solar wind and the earth's magnetic field

International Nuclear Information System (INIS)

Roux, A.

1989-01-01

The interaction between the supersonic and super-Alfvenic solar wind plasma and the Earth's magnetic field leads to the formation of critical layers, such as the bow shock, the magnetopause, the polar cusp, and the inner and outer edge of the plasmasheet. The mean free path between binary colisions being much larger than the transverse scale of these layers, plasma turbulence must ensure the thermalization, the magnetic diffusion, the dissipation within these critical layers. We suggest the existence of small scale, presumably 2D structures, developing within these thin layers. The unambiguous characterization of these small-scale structures is, however, beyond the capabilities of existing spacecraft, which cannot spatially resolve them, nor disentangle spatial/temporal variations. We present a new mission concept: a cluster of four relatively simple spacecraft, which will make it possible (i) to disentangle spatial from temporal variations, (ii) to evaluate, by finite differences between spacecraft measurements, the gradients, divergences, curls of MHD parameters, and )iii) to characterize small-scale structures, via inter-spacecraft correlations. (author). 10 refs.; 10 figs

Study on Determination Method of Fatigue Testing Load for Wind Turbine Blade

Science.gov (United States)

Liao, Gaohua; Wu, Jianzhong

2017-07-01

In this paper, the load calculation method of the fatigue test was studied for the wind turbine blade under uniaxial loading. The characteristics of wind load and blade equivalent load were analyzed. The fatigue property and damage theory of blade material were studied. The fatigue load for 2MW blade was calculated by Bladed, and the stress calculated by ANSYS. Goodman modified exponential function S-N curve and linear cumulative damage rule were used to calculate the fatigue load of wind turbine blades. It lays the foundation for the design and experiment of wind turbine blade fatigue loading system.

Engineering cotton (Gossypium hirsutum L.) for resistance to cotton leaf curl disease using viral truncated AC1 DNA sequences.

Science.gov (United States)

Hashmi, Jamil A; Zafar, Yusuf; Arshad, Muhammad; Mansoor, Shahid; Asad, Shaheen

2011-04-01

Several important biological processes are performed by distinct functional domains found on replication-associated protein (Rep) encoded by AC1 of geminiviruses. Two truncated forms of replicase (tAC1) gene, capable of expressing only the N-terminal 669 bp (5'AC1) and C-terminal 783 bp (3'AC1) nucleotides cloned under transcriptional control of the CaMV35S were introduced into cotton (Gossypium hirsutum L.) using LBA4404 strain of Agrobacterium tumefaciens to make use of an interference strategy for impairing cotton leaf curl virus (CLCuV) infection in transgenic cotton. Compared with nontransformed control, we observed that transgenic cotton plants overexpressing either N-terminal (5'AC1) or C-terminal (3'AC1) sequences confer resistance to CLCuV by inhibiting replication of viral genomic and β satellite DNA components. Molecular analysis by Northern blot hybridization revealed high transgene expression in early and late growth stages associated with inhibition of CLCuV replication. Of the eight T(1) transgenic lines tested, six had delayed and minor symptoms as compared to nontransformed control lines which developed disease symptoms after 2-3 weeks of whitefly-mediated viral delivery. Virus biological assay and growth of T(2) plants proved that transgenic cotton plants overexpressing 5'- and 3'AC1 displayed high resistance level up to 72, 81%, respectively, as compared to non-transformed control plants following inoculation with viruliferous whiteflies giving significantly high cotton seed yield. Progeny analysis of these plants by polymerase chain reaction (PCR), Southern blotting and virus biological assay showed stable transgene, integration, inheritance and cotton leaf curl disease (CLCuD) resistance in two of the eight transgenic lines having single or two transgene insertions. Transgenic cotton expressing partial AC1 gene of CLCuV can be used as virus resistance source in cotton breeding programs aiming to improve virus resistance in cotton crop.

Design of power converter in DFIG wind turbine with enhanced system-level reliability

DEFF Research Database (Denmark)

Zhou, Dao; Zhang, Guanguan; Blaabjerg, Frede

2017-01-01

With the increasing penetration of wind power, reliable and cost-effective wind energy production are of more and more importance. As one of the promising configurations, the doubly-fed induction generator based partial-scale wind power converter is still dominating in the existing wind farms...... margin. It can be seen that the B1 lifetime of the grid-side converter and the rotor-side converter deviates a lot by considering the electrical stresses, while they become more balanced by using an optimized reliable design. The system-level lifetime significantly increases with an appropriate design...

Structural Optimization of an Innovative 10 MW Wind Turbine Nacelle

DEFF Research Database (Denmark)

Dabrowski, Dariusz; Natarajan, Anand; Stehouwer, Ewoud

2015-01-01

For large wind turbine configurations of 10 MW and higher capacities, direct-drives present a more compact solution over conventional geared drivetrains. Further, if the generator is placed in front of the wind turbine rotor, a compact “king-pin” drive is designed, that allows the generator...... to be directly coupled to the hub. In presented study, the structural re-design of the innovative 10 MW nacelle was made using extreme loads obtained from a 10 MW reference wind turbine. On the basis of extreme loads the ultimate stresses on critical nacelle components were determined to ensure integrity...

Integrating Structural Health Management with Contingency Control for Wind Turbines

Directory of Open Access Journals (Sweden)

Kai Goebel

2013-01-01

Full Text Available Maximizing turbine up-time and reducing maintenance costs are key technology drivers for wind turbine operators. Components within wind turbines are subject to considerable stresses due to unpredictable environmental conditions resulting from rapidly changing local dynamics. In that context, systems health management has the aim to assess the state-of-health of components within a wind turbine, to estimate remaining life, and to aid in autonomous decision-making to minimize damage to the turbine. Advanced contingency control is one way to enable autonomous decision-making by providing the mechanism to enable safe and efficient turbine operation. The work reported herein explores the integration of condition monitoring of wind turbine blades with contingency control to balance the trade-offs between maintaining system health and energy capture. Results are demonstrated using a high fidelity simulator of a utility-scale wind turbine.

Reliability Evaluation of Power Capacitors in a Wind Turbine System

DEFF Research Database (Denmark)

Zhou, Dao; Blaabjerg, Frede

2018-01-01

With the increasing penetration of wind power, reliable and cost-effective wind energy production is of more and more importance. The doubly-fed induction generator based partial-scale wind power converter is still dominating in the existing wind farms. In this paper, the reliability assessment...... block diagram is used to bridge the gap between the Weibull distribution based component-level individual capacitor and the capacitor bank. A case study of a 2 MW wind power converter shows that the lifetime is significantly reduced from the individual capacitor to the capacitor bank. Besides, the dc...... of power capacitors is studied considering the annual mission profile. According to an electro-thermal stress evaluation, the time-to-failure distribution of both the dc-link capacitor and ac-side filter capacitor is detailed investigated. Aiming for the systemlevel reliability analysis, a reliability...

Barotropic Eulerian residual circulation in the Gulf of California due to the M{sub 2} tide and wind stress

Energy Technology Data Exchange (ETDEWEB)

Argote, M. L.; Lavin, M. F.; Amador, A. [Departamento de Oceanografia Fisica, CICESE, Ensenada, Baja California (Mexico)

1998-07-01

A vertically integrated, non-linear numerical model in finite differences is used to analyze two forcing mechanisms of the mean barotropic circulation in the Gulf of California: topographic rectification due to tidal currents (M{sub 2}) and wind stress. Under tidal forcing the nonlinearities of the momentum equations induce unorganized strong tidal induced residual currents (u{sub e} > 5 cm s{sup -}1) in the channels between the islands, and along-isobath anticyclonic circulation in the Northern Gulf, with speeds u{sub 3} < 2.5 cm s{sup -}1 over the edge of Delfin Basin. These numerical results are in agreement with analytical results, which indicate that the tidal-induced currents are mostly due to the advective terms, and that continuity and the Coriolis term (but regulated by bottom friction) are responsible for the along-isobath flow. The quadratic bottom friction plays a role in generating mean currents only in the very shallow area off the Colorado River Delta. The effect of wind stress was modeled by imposing upon the running M{sub 2} model a constant surface stress ( r = 0.016 Pa), from the NW for winter conditions and from the SE for summer conditions. The wind-induced circulation was obtained by averaging over a tidal cycle and then subtracting the tidal residuals. The two wind directions produce almost identical circulation patterns, but with opposite directions. For the NW wind stress, the main features of the predicted circulation are: (a) In the Northern Gulf an anticyclonic circulation pattern, with the strongest currents (up to {approx} 10 cm s-1) following the bathymetry of the rim of Delfin Basin, Wagner Basin and the mainland coast off Bahia Adair and Bahia San Jorge. There is also a southward flow along the peninsula coast, from the Colorado River to Bahia San Luis Gonzaga. (b) In the Southern Gulf, there is a strong flow ({approx} 10 to 15 cm s{sup -}1) to the SE over the continental shelf along the mainland coast. A somewhat less well

Impact of the interfaces for wind and wave modeling - interpretation using COAWST, SAR and point measurements

DEFF Research Database (Denmark)

Air and sea interacts, where winds generate waves and waves affect the winds. This topic is ever relevant for offshore functions such as shipping, portal routines, wind farm operation and maintenance. In a coupled modeling system, the atmospheric modeling and the wave modeling interfere with each...... use the stress directly, thus avoiding the uncertainties caused by parameterizations. This study examines the efficiency of the wave impact transfer to the atmospheric modeling through the two types of interfaces, roughness length and stress, through the coupled......-ocean-atmosphere-wave-sediment-transport (COAWST) modeling system. The roughness length has been calculated using seven schemes (Charnock, Fan, Oost, Drennen, Liu, Andreas, Taylor-Yelland). The stress approach is applied through a wave boundary layer model in SWAN. The experiments are done to a case where the Synthetic Aperture Radar (SAR) image...

Structural analysis of wind turbine rotors for NSF-NASA Mod-0 wind power system

Science.gov (United States)

Spera, D. A.

1976-01-01

Preliminary estimates are presented of vibratory loads and stresses in hingeless and teetering rotors for the proposed NSF-NASA Mod-0 wind power system. Preliminary blade design utilizes a tapered tubular aluminum spar which supports nonstructural aluminum ribs and skin and is joined to the rotor hub by a steel shank tube. Stresses in the shank of the blade are calculated for static, rated, and overload operating conditions. Blade vibrations were limited to the fundamental flapping modes, which were elastic cantilever bending for hingeless rotor blades and rigid-body rotation for teetering rotor blades. The MOSTAB-C computer code was used to calculate aerodynamic and mechanical loads. The teetering rotor has substantial advantages over the hingeless rotor with respect to shank stresses, fatigue life, and tower loading. The hingeless rotor analyzed does not appear to be structurally stable during overloads.

Numerical simulation analysis as a tool to identify areas of weakness in a turbine wind-blade and solutions for their reinforcement

OpenAIRE

RAMAN, Venkadesh; DRISSI-HABTI, Monssef; GUILLAUMAT, Laurent; KHADHOUR, Aghihad

2016-01-01

Offshore wind energy is one of the main sources of renewable energy that can benefit from new generation materials that exhibit good oxidation resistance and mechanical reliability. Composite materials are the best consideration for harsh environment and deep sea wind turbine manufacturing. In this study, a numerical simulation was implemented to predict the stress distribution over a wind turbineblade and to determine areas with high stress concentration. Finite Element Analysis (FEA) was us...

Method of eliminating the training effect in superconducting coils by post-wind preload

International Nuclear Information System (INIS)

Heim, J.R.

1976-01-01

The training effect in superconducting coils is eliminated by winding the coil with a composite material that includes both a superconductor and a normal material. Stresses are applied to the wound coil in the direction that electromagnetic stresses will be applied to the coil during normal use. The applied stresses are greater than the calculated magnitude of the greatest electromagnetic stresses to be applied to the coil

A green energy for a blue growth: offshore wind energy. Proposals by France Energie Eolienne for the development of a competitive and job-creating offshore wind energy sector

International Nuclear Information System (INIS)

2013-06-01

This report outlines the significant and efficient contribution of wind energy to the energy mix, highlights the high potential of offshore wind energy for France, and stresses the need of an ambitious programme as a sine qua non condition for the development of this sector. It also makes ten proposals for this development. It describes how to specify ambitious objectives for offshore wind turbines (grounded or floating) in compliance with the French potential and the European market. It analyses means to reach an ambitious objective of 15 GW of grounded offshore wind energy and 6 GW of floating offshore wind energy by 2030. It discusses how benefits can be drawn from such a development for the community and future generations

High-frequency and meso-scale winter sea-ice variability in the Southern Ocean in a high-resolution global ocean model

Science.gov (United States)

Stössel, Achim; von Storch, Jin-Song; Notz, Dirk; Haak, Helmuth; Gerdes, Rüdiger

2018-03-01

This study is on high-frequency temporal variability (HFV) and meso-scale spatial variability (MSV) of winter sea-ice drift in the Southern Ocean simulated with a global high-resolution (0.1°) sea ice-ocean model. Hourly model output is used to distinguish MSV characteristics via patterns of mean kinetic energy (MKE) and turbulent kinetic energy (TKE) of ice drift, surface currents, and wind stress, and HFV characteristics via time series of raw variables and correlations. We find that (1) along the ice edge, the MSV of ice drift coincides with that of surface currents, in particular such due to ocean eddies; (2) along the coast, the MKE of ice drift is substantially larger than its TKE and coincides with the MKE of wind stress; (3) in the interior of the ice pack, the TKE of ice drift is larger than its MKE, mostly following the TKE pattern of wind stress; (4) the HFV of ice drift is dominated by weather events, and, in the absence of tidal currents, locally and to a much smaller degree by inertial oscillations; (5) along the ice edge, the curl of the ice drift is highly correlated with that of surface currents, mostly reflecting the impact of ocean eddies. Where ocean eddies occur and the ice is relatively thin, ice velocity is characterized by enhanced relative vorticity, largely matching that of surface currents. Along the ice edge, ocean eddies produce distinct ice filaments, the realism of which is largely confirmed by high-resolution satellite passive-microwave data.

Novel screening techniques for wind turbine power converters

DEFF Research Database (Denmark)

Jørgensen, Asger Bjørn; Sønderskov, Simon Dyhr; Christensen, Nicklas

2016-01-01

Power converters represent one of the highest failure rates in the wind turbine. Therefore converter manufacturers perform burn-in tests to prevent shipping of faulty converters. Recent developments in junction temperature estimation, based on accurate online IGBT collector-emitter voltage...... measurements, allow for thermal stress estimation of the IGBT modules. This is utilized to detect infant mortalities in power converters, by comparing thermal responses of IGBTs for faulty and non-faulty converters. The method proves to be a time and cost efficient candidate to replace burn-in tests of power...... converters for wind turbines applications....

Equivalent models of wind farms by using aggregated wind turbines and equivalent winds

International Nuclear Information System (INIS)

Fernandez, L.M.; Garcia, C.A.; Saenz, J.R.; Jurado, F.

2009-01-01

As a result of the increasing wind farms penetration on power systems, the wind farms begin to influence power system, and therefore the modeling of wind farms has become an interesting research topic. In this paper, new equivalent models of wind farms equipped with wind turbines based on squirrel-cage induction generators and doubly-fed induction generators are proposed to represent the collective behavior on large power systems simulations, instead of using a complete model of wind farms where all the wind turbines are modeled. The models proposed here are based on aggregating wind turbines into an equivalent wind turbine which receives an equivalent wind of the ones incident on the aggregated wind turbines. The equivalent wind turbine presents re-scaled power capacity and the same complete model as the individual wind turbines, which supposes the main feature of the present equivalent models. Two equivalent winds are evaluated in this work: (1) the average wind from the ones incident on the aggregated wind turbines with similar winds, and (2) an equivalent incoming wind derived from the power curve and the wind incident on each wind turbine. The effectiveness of the equivalent models to represent the collective response of the wind farm at the point of common coupling to grid is demonstrated by comparison with the wind farm response obtained from the detailed model during power system dynamic simulations, such as wind fluctuations and a grid disturbance. The present models can be used for grid integration studies of large power system with an important reduction of the model order and the computation time

78 FR 29364 - Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4...

Science.gov (United States)

2013-05-20

...-005, QF07-55-005, QF07-56-005, QF07-257-004] Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4, LLC, Exelon Wind 5, LLC, Exelon Wind 6, LLC, Exelon Wind 7, LLC, Exelon Wind 8, LLC, Exelon Wind 9, LLC, Exelon Wind 10, LLC, Exelon Wind 11, LLC, High Plains...

SAT-WIND project. Final report[Winds from satellites for offshore and coastal wind energy mapping and wind-indexing

Energy Technology Data Exchange (ETDEWEB)

Hasager, C.B.; Astrup, P.; Nielsen, M. (and others)

2007-04-15

The SAT-WIND project 'Winds from satellites for offshore and coastal wind energy mapping and wind-indexing' was a research project funded by STVF/DSF in the years 2003 to 2006 (Sagsnr. 2058-03-0006). The goal of the project was to verify the applicability of satellite wind maps derived from passive microwave, altimeter, scatterometer and imaging Synthetic Aperture Radar (SAR) technologies for wind energy tools for wind resources and wind-indexing. The study area was the Danish Seas including the North Sea, interior seas and the Baltic Sea. The report describes technical details on the satellite data sources including: 1) passive microwave (SSM/I, AMSR-E), 2) passive microwave polarimetric (WindSat), 3) scatterometer (ERS, QuikSCAT, Midori-2 and NSCAT), 4) altimeter (ERS, Topex, Poseidon, GFO-1, Jason-1), 5) SAR (ERS, Envisat). The SAR wind maps were treated in S-WAsP developed by Risoe National Laboratory in cooperation with GRAS A/S in the innovative project SAT-WIND-SMV (Sagsnr. 2104-05-0084) in the years 2005 and 2006 in parallel with SAT-WIND. The results from the SAT-WIND project are presented. These include ocean wind statistics, offshore wind resource estimates and comparison results for wind-indexing. (au)

SAT-WIND project. Final report[Winds from satellites for offshore and coastal wind energy mapping and wind-indexing

Energy Technology Data Exchange (ETDEWEB)

Hasager, C B; Astrup, P; Nielsen, M [and others

2007-04-15

The SAT-WIND project 'Winds from satellites for offshore and coastal wind energy mapping and wind-indexing' was a research project funded by STVF/DSF in the years 2003 to 2006 (Sagsnr. 2058-03-0006). The goal of the project was to verify the applicability of satellite wind maps derived from passive microwave, altimeter, scatterometer and imaging Synthetic Aperture Radar (SAR) technologies for wind energy tools for wind resources and wind-indexing. The study area was the Danish Seas including the North Sea, interior seas and the Baltic Sea. The report describes technical details on the satellite data sources including: 1) passive microwave (SSM/I, AMSR-E), 2) passive microwave polarimetric (WindSat), 3) scatterometer (ERS, QuikSCAT, Midori-2 and NSCAT), 4) altimeter (ERS, Topex, Poseidon, GFO-1, Jason-1), 5) SAR (ERS, Envisat). The SAR wind maps were treated in S-WAsP developed by Risoe National Laboratory in cooperation with GRAS A/S in the innovative project SAT-WIND-SMV (Sagsnr. 2104-05-0084) in the years 2005 and 2006 in parallel with SAT-WIND. The results from the SAT-WIND project are presented. These include ocean wind statistics, offshore wind resource estimates and comparison results for wind-indexing. (au)

The influence of ENSO on an oceanic eddy pair in the South China Sea

Science.gov (United States)

Chu, Xiaoqing; Dong, Changming; Qi, Yiquan

2017-03-01

An eddy pair off the Vietnam coast is one of the most important features of the summertime South China Sea circulation. Its variability is of interest due to its profound impact on regional climate, ecosystems, biological processes, and fisheries. This study examines the influence of the El Niño-Southern Oscillation (ENSO), a basin-scale climatic mode, on the interannual variability of this regional eddy pair using satellite observational data and historical hydrographic measurements. Over the last three decades, the eddy pair strengthened in 1994 and 2002, and weakened in 2006, 2007, and 2008. It was absent in 1988, 1995, 1998, and 2010, coinciding with strong El Nino-to-La Nina transitions. Composite analyses showed that the strong transition events of ENSO led to radical changes in the summer monsoon, through the forcing of a unique sea surface temperature anomaly structure over the tropical Indo-Pacific basin. With weaker zonal wind, a more northward wind direction, and the disappearance of a pair of positive and negative wind stress curls, the eastward current jet turns northward along the Vietnam coast and the eddy pair disappears.

The role of streamline curvature in sand dune dynamics: evidence from field and wind tunnel measurements

Science.gov (United States)

Wiggs, Giles F. S.; Livingstone, Ian; Warren, Andrew

1996-09-01

Field measurements on an unvegetated, 10 m high barchan dune in Oman are compared with measurements over a 1:200 scale fixed model in a wind tunnel. Both the field and wind tunnel data demonstrate similar patterns of wind and shear velocity over the dune, confirming significant flow deceleration upwind of and at the toe of the dune, acceleration of flow up the windward slope, and deceleration between the crest and brink. This pattern, including the widely reported upwind reduction in shear velocity, reflects observations of previous studies. Such a reduction in shear velocity upwind of the dune should result in a reduction in sand transport and subsequent sand deposition. This is not observed in the field. Wind tunnel modelling using a near-surface pulse-wire probe suggests that the field method of shear velocity derivation is inadequate. The wind tunnel results exhibit no reduction in shear velocity upwind of or at the toe of the dune. Evidence provided by Reynolds stress profiles and turbulence intensities measured in the wind tunnel suggest that this maintenance of upwind shear stress may be a result of concave (unstable) streamline curvature. These additional surface stresses are not recorded by the techniques used in the field measurements. Using the occurrence of streamline curvature as a starting point, a new 2-D model of dune dynamics is deduced. This model relies on the establishment of an equilibrium between windward slope morphology, surface stresses induced by streamline curvature, and streamwise acceleration. Adopting the criteria that concave streamline curvature and streamwise acceleration both increase surface shear stress, whereas convex streamline curvature and deceleration have the opposite effect, the relationships between form and process are investigated in each of three morphologically distinct zones: the upwind interdune and concave toe region of the dune, the convex portion of the windward slope, and the crest-brink region. The

Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

OpenAIRE

Ju Feng; Wen Zhong Shen

2015-01-01

Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distributions of wind speed and wind direction, which is based on the parameters of sector-wise Weibull distributions and interpolations between direction sectors. It is applied to the wind measurement data a...

Influence of glacial ice sheets on the Atlantic meridional overturning circulation through surface wind change

Science.gov (United States)

Sherriff-Tadano, Sam; Abe-Ouchi, Ayako; Yoshimori, Masakazu; Oka, Akira; Chan, Wing-Le

2018-04-01

Coupled modeling studies have recently shown that the existence of the glacial ice sheets intensifies the Atlantic meridional overturning circulation (AMOC). However, most models show a strong AMOC in their simulations of the Last Glacial Maximum (LGM), which is biased compared to reconstructions that indicate both a weaker and stronger AMOC during the LGM. Therefore, a detailed investigation of the mechanism behind this intensification of the AMOC is important for a better understanding of the glacial climate and the LGM AMOC. Here, various numerical simulations are conducted to focus on the effect of wind changes due to glacial ice sheets on the AMOC and the crucial region where the wind modifies the AMOC. First, from atmospheric general circulation model experiments, the effect of glacial ice sheets on the surface wind is evaluated. Second, from ocean general circulation model experiments, the influence of the wind stress change on the AMOC is evaluated by applying wind stress anomalies regionally or at different magnitudes as a boundary condition. These experiments demonstrate that glacial ice sheets intensify the AMOC through an increase in the wind stress at the North Atlantic mid-latitudes, which is induced by the North American ice sheet. This intensification of the AMOC is caused by the increased oceanic horizontal and vertical transport of salt, while the change in sea ice transport has an opposite, though minor, effect. Experiments further show that the Eurasian ice sheet intensifies the AMOC by directly affecting the deep-water formation in the Norwegian Sea.

Structural experiment of wind turbine blades; Fushayo blade no zairyo rikigakuteki jikken kenkyu

Energy Technology Data Exchange (ETDEWEB)

Seki, K; Shimizu, Y; Kuroyanagi, H [Tokai University, Tokyo (Japan)

1997-11-25

Aluminum, GFRP and composite of aluminum coated with carbon as structural materials for wind turbine blades were bending-tested, to improve blade bending stiffness, understand stress conditions at each position, and clarify structural dynamic strength by the bending-failure test. It is possible to estimate stress conditions at each position from the test results of displacement and strain at each load. The test results with GFRP are well explained qualitatively by the boundary theory, known as a theory for composite materials. The test gives reasonable material strength data, useful for designing wind turbines of high functions and safety. The results of the blade bending-failure test are in good agreement with the calculated structural blade strength. It is also found that GFRP is a good material of high structural strength for wind turbines. 8 refs., 6 tabs.

The Effect of High-Intensity Interval Cycling Sprints Subsequent to Arm-Curl Exercise on Upper-Body Muscle Strength and Hypertrophy.

Science.gov (United States)

Kikuchi, Naoki; Yoshida, Shou; Okuyama, Mizuki; Nakazato, Koichi

2016-08-01

Kikuchi, N, Yoshida, S, Okuyama, M, and Nakazato, K. The effect of high-intensity interval cycling sprints subsequent to arm-curl exercise on upper-body muscle strength and hypertrophy. J Strength Cond Res 30(8): 2318-2323, 2016-The purpose of this study was to examine whether lower limb sprint interval training (SIT) after arm resistance training (RT) influences training response of arm muscle strength and hypertrophy. Twenty men participated in this study. We divided subjects into RT group (n = 6) and concurrent training group (CT, n = 6). The RT program was designed to induce muscular hypertrophy (3 sets × 10 repetitions [reps] at 80% 1 repetition maximum [1RM] of arm-curl exercise) and was performed in an 8-week training schedule performed 3 times per week on nonconsecutive days. Subjects assigned to the CT group performed identical protocols as strength training and modified SIT (4 sets of 30-s maximal effort, separated in 4 m 30-s rest intervals) on the same day. Pretest and posttest maximal oxygen consumption (V[Combining Dot Above]O2max), muscle cross-sectional area (CSA), and 1RM were measured. Significant increase in V[Combining Dot Above]O2max from pretest to posttest was observed in the CT group (p = 0.010, effect size [ES] = 1.84) but not in the RT group (p = 0.559, ES = 0.35). Significant increase in CSA from pretest to posttest was observed in the RT group (p = 0.030, ES = 1.49) but not in the CT group (p = 0.110, ES = 1.01). Significant increase in 1RM from pretest to posttest was observed in the RT group (p = 0.021, ES = 1.57) but not in the CT group (p = 0.065, ES = 1.19). In conclusion, our data indicate that concurrent lower limb SIT interferes with arm muscle hypertrophy and strength.

Experimental study of the wake characteristics of a two-blade horizontal axis wind turbine by time-resolved PIV

Institute of Scientific and Technical Information of China (English)

ZHANG LiRu; CEN KeFa; XING JiangKuan; WANG JianWen; YUAN RenYu; DONG XueQing; MA JianLong; LUO Kun; QIU KunZan; NI MingJiang

2017-01-01

Wind tunnel experiments of the wake characteristics of a two-blade wind turbine,in the downstream region of 0＜x/R＜ 10,have been carried out.With the help of the time resolved particle image velocimetry (TRPIV),flow properties such as the vortex structure,average velocity,fluctuations velocities and Reynolds stresses are obtained at different tip speed ratios (TSR).It is found that the wind turbine wake flow can be divided into velocity deficit region,velocity remained region and velocity increased region,with generally higher velocity deficit compared with a three-blade wind turbine wake.Once a blade rotates to the reference 0° plane,the tip vortices generate,shed and move downstream with the intensity gradually decreased.The leapfrogging phenomenon of tip vortices caused by the force interaction of adjacent vortices is found and more apparent in the far wake region.The axial fluctuation velocity is larger than radial fluctuation velocity at the blade root region,and the turbulent kinetic energy shares the similar trend as the axial fluctuation velocity.The axial normalized Reynolds normal stress is much larger than the radial normalized Reynolds normal stress and Reynolds shear stress at the blade root region.As the TSR increases,the radial location where the peak axial normalized Reynolds normal stress u u / U2 and axial fluctuation velocity appear descends in the radial direction.

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

A large-eddy simulation based power estimation capability for wind farms over complex terrain

Science.gov (United States)

Senocak, I.; Sandusky, M.; Deleon, R.

2017-12-01

There has been an increasing interest in predicting wind fields over complex terrain at the micro-scale for resource assessment, turbine siting, and power forecasting. These capabilities are made possible by advancements in computational speed from a new generation of computing hardware, numerical methods and physics modelling. The micro-scale wind prediction model presented in this work is based on the large-eddy simulation paradigm with surface-stress parameterization. The complex terrain is represented using an immersed-boundary method that takes into account the parameterization of the surface stresses. Governing equations of incompressible fluid flow are solved using a projection method with second-order accurate schemes in space and time. We use actuator disk models with rotation to simulate the influence of turbines on the wind field. Data regarding power production from individual turbines are mostly restricted because of proprietary nature of the wind energy business. Most studies report percentage drop of power relative to power from the first row. There have been different approaches to predict power production. Some studies simply report available wind power in the upstream, some studies estimate power production using power curves available from turbine manufacturers, and some studies estimate power as torque multiplied by rotational speed. In the present work, we propose a black-box approach that considers a control volume around a turbine and estimate the power extracted from the turbine based on the conservation of energy principle. We applied our wind power prediction capability to wind farms over flat terrain such as the wind farm over Mower County, Minnesota and the Horns Rev offshore wind farm in Denmark. The results from these simulations are in good agreement with published data. We also estimate power production from a hypothetical wind farm in complex terrain region and identify potential zones suitable for wind power production.

Pollen, water, and wind: Chaotic mixing in a puddle of water

DEFF Research Database (Denmark)

Jensen, Kaare Hartvig

2016-01-01

and nutrient distribution in puddles and small ponds.The flow patterns are generated by wind blowing across the puddle surface. This causes a shear stress at the atmospheric interface, which drives a flow in the liquid below. Chaotic mixing can occur if the wind direction changes over time. A fluid patch......This paper talks about how pine pollen grains dispersedin an approximately 1 m wide and 1 cm deep water puddle. The pollen has mixed due to wind blowing across the liquid surface, revealing a strikingly complex flow pattern. The flows revealed by nature’s tracer particles may influence circulation...

Ocean's response to Hurricane Frances and its implications for drag coefficient parameterization at high wind speeds

KAUST Repository

Zedler, S. E.; Niiler, P. P.; Stammer, D.; Terrill, E.; Morzel, J.

2009-01-01

with realistic stratification and forcing fields representing Hurricane Frances, which in early September 2004 passed east of the Caribbean Leeward Island chain. The model was forced with a NOAA-HWIND wind speed product after converting it to wind stress using

Wind: new wind markets

International Nuclear Information System (INIS)

Cameron, A.

2005-01-01

The June 2005 edition of 'Wind Force 12' suggests that wind could generate 12% of global electricity requirements by 2020. But what moves a potential market into an emerging one? Geographical factors include a good wind resource, plenty of open space and the ability to get the generated electricity to end-users. A country's political framework is equally important, with fixed price systems, renewable quota systems and political will all playing a part. Some potential wind markets around the world are thought to have the conditions necessary to become key players in the wind industry. The emerging markets in countries such as Australia, Brazil, Canada, France, Japan and the Philippines are highlighted as examples

Resistance to Wheat Curl Mite in Arthropod-Resistant Rye-Wheat Translocation Lines

Directory of Open Access Journals (Sweden)

Lina Maria Aguirre-Rojas

2017-11-01

Full Text Available The wheat curl mite, Aceria toschiella (Keifer, and a complex of viruses vectored by A. toschiella substantially reduce wheat yields in every wheat-producing continent in the world. The development of A. toschiella-resistant wheat cultivars is a proven economically and ecologically viable method of controlling this pest. This study assessed A. toschiella resistance in wheat genotypes containing the H13, H21, H25, H26, H18 and Hdic genes for resistance to the Hessian fly, Mayetiola destructor (Say and in 94M370 wheat, which contains the Dn7 gene for resistance to the Russian wheat aphid, Diuraphis noxia (Kurdjumov. A. toschiella populations produced on plants containing Dn7 and H21 were significantly lower than those on plants of the susceptible control and no different than those on the resistant control. Dn7 resistance to D. noxia and H21 resistance to M. destructor resulted from translocations of chromatin from rye into wheat (H21—2BS/2RL, Dn7—1BL/1RS. These results provide new wheat pest management information, indicating that Dn7 and H21 constitute resources that can be used to reduce yield losses caused by A. toschiella, M. destructor, D. noxia, and wheat streak mosaic virus infection by transferring multi-pest resistance to single sources of germplasm.

Engineering resistance against Tomato yellow leaf curl virus via the CRISPR/Cas9 system in tomato

KAUST Repository

Mahfouz, Magdy M.

2017-12-22

CRISPR/Cas systems confer molecular immunity against phages and conjugative plasmids in prokaryotes. Recently, CRISPR/Cas9 systems have been used to confer interference against eukaryotic viruses. Here, we engineered Nicotiana benthamiana and tomato (Solanum lycopersicum) plants with the CRISPR/Cas9 system to confer immunity against the Tomato yellow leaf curl virus (TYLCV). Targeting the TYLCV genome with Cas9-single guide RNA at the sequences encoding the coat protein (CP) or replicase (Rep) resulted in efficient virus interference, as evidenced by low accumulation of the TYLCV DNA genome in the transgenic plants. The CRISPR/Cas9-based immunity remained active across multiple generations in the N. benthamiana and tomato plants. Together, our results confirmed the efficiency of the CRISPR/Cas9 system for stable engineering of TYLCV resistance in N. benthamiana and tomato, and opens the possibilities of engineering virus resistance against single and multiple infectious viruses in other crops.

Finite element modeling of the filament winding process using ABAQUS

OpenAIRE

Miltenberger, Louis C.

1992-01-01

A comprehensive stress model of the filament winding fabrication process, previously implemented in the finite element program, WACSAFE, was implemented using the ABAQUS finite element software package. This new implementation, referred to as the ABWACSAFE procedure, consists of the ABAQUS software and a pre/postprocessing routine that was developed to prepare necessary ABAQUS input files and process ABAQUS displacement results for stress and strain computation. The ABWACSAF...

Partial Safety Factors for Fatigue Design of Wind Turbine Blades

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

2010-01-01

In the present paper calibration of partial safety factors for fatigue design of wind turbine blades is considered. The stochastic models for the physical uncertainties on the material properties are based on constant amplitude fatigue tests and the uncertainty on Miners rule for linear damage...... accumulation is determined from variable amplitude fatigue tests with the Wisper and Wisperx spectra. The statistical uncertainty for the assessment of the fatigue loads is also investigated. The partial safety factors are calibrated for design load case 1.2 in IEC 61400-1. The fatigue loads are determined...... from rainflow-counting of simulated time series for a 5MW reference wind turbine [1]. A possible influence of a complex stress state in the blade is not taken into account and only longitudinal stresses are considered....

Grid Integration of Offshore Wind | Wind | NREL

Science.gov (United States)

Grid Integration of Offshore Wind Grid Integration of Offshore Wind Much can be learned from the existing land-based integration research for handling the variability and uncertainty of the wind resource Arklow Bank offshore wind park consists of seven GE Wind 3.6-MW wind turbines. Integration and

Modelling, simulation and measurements of fast transients in transformer windings with consideration of frequency-dependent losses

NARCIS (Netherlands)

Popov, M.; Sluis, van der L.; Smeets, R.P.P.; Lopez Roldan, J.; Terzija, V.V.

2007-01-01

For the specification of winding insulation of transformers, it is important to know the electrical stresses to which the winding can be exposed during fast transient oscillations. These oscillations occur during switching operations performed by circuit breakers, or when gas-insulated substations

Electromagnetic and mechanical design of RFX Magnetizing Winding

International Nuclear Information System (INIS)

Guarnieri, M.; Modena, C.; Schrefler, B.A.; Stella, A.

1985-01-01

This paper presents the RFX Magnetizing Winding design and describes its most significant features. Two numerical codes have been used for the magnetic design and a number of solutions, complying with the design specifications, have been obtained. The most attractive of them have been studied in detail from the electromagnetic point of view and a comparison is given here together with an analysis of the stress states. The finite element procedure used is discussed in the paper and the results of the comparison indicated above are presented together with the main electromagnetic parameters and winding features

Characteristics for wind energy and wind turbines by considering vertical wind shear

Institute of Scientific and Technical Information of China (English)

郑玉巧; 赵荣珍

2015-01-01

The probability distributions of wind speeds and the availability of wind turbines were investigated by considering the vertical wind shear. Based on the wind speed data at the standard height observed at a wind farm, the power-law process was used to simulate the wind speeds at a hub height of 60 m. The Weibull and Rayleigh distributions were chosen to express the wind speeds at two different heights. The parameters in the model were estimated via the least square (LS) method and the maximum likelihood estimation (MLE) method, respectively. An adjusted MLE approach was also presented for parameter estimation. The main indices of wind energy characteristics were calculated based on observational wind speed data. A case study based on the data of Hexi area, Gansu Province of China was given. The results show that MLE method generally outperforms LS method for parameter estimation, and Weibull distribution is more appropriate to describe the wind speed at the hub height.

Potential of Partially Superconducting Generators for Large Direct-Drive Wind Turbines

DEFF Research Database (Denmark)

Liu, Dong; Polinder, Henk; Abrahamsen, Asger Bech

2017-01-01

This paper aims at assessing the potential of partially superconducting generators for 10 MW direct-drive wind turbines by investigating their performance for a very wide range of excitation currents. Performance indicators such as shear stress and efficiency and other generator characteristics...... are compared for 12 different generator topologies. To be sufficiently attractive, superconducting generators must have significant advantages over permanent magnet direct-drive generators, which typically have shear stresses of the order of 53 kPa and efficiencies of 96%. Therefore, we investigate what...... they achieve this performance. By examining the maximum magnetic flux density at the location of the superconducting field winding, feasible superconductors can be chosen according to their engineering current density capabilities. It is found that high- and low-temperature superconductors can meet...

Wind turbines and human health

Directory of Open Access Journals (Sweden)

Loren eKnopper

2014-06-01

Full Text Available The association between wind turbines and health effects is highly debated. Some argue that reported health effects are related to wind turbine operation (electromagnetic fields (EMF, shadow flicker, audible noise, low frequency noise, infrasound. Others suggest that when turbines are sited correctly, effects are more likely attributable to a number of subjective variables that result in an annoyed/stressed state. In this review we provide a bibliographic-like summary and analysis of the science around this issue specifically in terms of noise (including audible, low frequency noise and infrasound, EMF and shadow flicker. Now there are roughly 60 scientific peer-reviewed articles on this issue. The available scientific evidence suggests that EMF, shadow flicker, low frequency noise and infrasound from wind turbines are not likely to affect human health; some studies have found that audible noise from wind turbines can be annoying to some. Annoyance may be associated with some self-reported health effects (e.g., sleep disturbance especially at sound pressure levels >40 dB(A. Because environmental noise above certain levels is a recognized factor in a number of health issues, siting restrictions have been implemented in many jurisdictions to limit noise exposure. These setbacks should help alleviate annoyance from noise. Subjective variables (attitudes and expectations are also linked to annoyance and have the potential to facilitate other health complaints via the nocebo effect. Therefore, it is possible that a segment of the population may remain annoyed (or report other health impacts even when noise limits are enforced. Based on the findings and scientific merit of the available studies, the weight of evidence suggests that when sited properly, wind turbines are not related to adverse health. Stemming from this review, we provide a number of recommended best practices for wind turbine development in the context of human health.

Wind turbines and human health.

Science.gov (United States)

Knopper, Loren D; Ollson, Christopher A; McCallum, Lindsay C; Whitfield Aslund, Melissa L; Berger, Robert G; Souweine, Kathleen; McDaniel, Mary

2014-01-01

The association between wind turbines and health effects is highly debated. Some argue that reported health effects are related to wind turbine operation [electromagnetic fields (EMF), shadow flicker, audible noise, low-frequency noise, infrasound]. Others suggest that when turbines are sited correctly, effects are more likely attributable to a number of subjective variables that result in an annoyed/stressed state. In this review, we provide a bibliographic-like summary and analysis of the science around this issue specifically in terms of noise (including audible, low-frequency noise, and infrasound), EMF, and shadow flicker. Now there are roughly 60 scientific peer-reviewed articles on this issue. The available scientific evidence suggests that EMF, shadow flicker, low-frequency noise, and infrasound from wind turbines are not likely to affect human health; some studies have found that audible noise from wind turbines can be annoying to some. Annoyance may be associated with some self-reported health effects (e.g., sleep disturbance) especially at sound pressure levels >40 dB(A). Because environmental noise above certain levels is a recognized factor in a number of health issues, siting restrictions have been implemented in many jurisdictions to limit noise exposure. These setbacks should help alleviate annoyance from noise. Subjective variables (attitudes and expectations) are also linked to annoyance and have the potential to facilitate other health complaints via the nocebo effect. Therefore, it is possible that a segment of the population may remain annoyed (or report other health impacts) even when noise limits are enforced. Based on the findings and scientific merit of the available studies, the weight of evidence suggests that when sited properly, wind turbines are not related to adverse health. Stemming from this review, we provide a number of recommended best practices for wind turbine development in the context of human health.

Wind Turbines and Human Health

Science.gov (United States)

Knopper, Loren D.; Ollson, Christopher A.; McCallum, Lindsay C.; Whitfield Aslund, Melissa L.; Berger, Robert G.; Souweine, Kathleen; McDaniel, Mary

2014-01-01

The association between wind turbines and health effects is highly debated. Some argue that reported health effects are related to wind turbine operation [electromagnetic fields (EMF), shadow flicker, audible noise, low-frequency noise, infrasound]. Others suggest that when turbines are sited correctly, effects are more likely attributable to a number of subjective variables that result in an annoyed/stressed state. In this review, we provide a bibliographic-like summary and analysis of the science around this issue specifically in terms of noise (including audible, low-frequency noise, and infrasound), EMF, and shadow flicker. Now there are roughly 60 scientific peer-reviewed articles on this issue. The available scientific evidence suggests that EMF, shadow flicker, low-frequency noise, and infrasound from wind turbines are not likely to affect human health; some studies have found that audible noise from wind turbines can be annoying to some. Annoyance may be associated with some self-reported health effects (e.g., sleep disturbance) especially at sound pressure levels >40 dB(A). Because environmental noise above certain levels is a recognized factor in a number of health issues, siting restrictions have been implemented in many jurisdictions to limit noise exposure. These setbacks should help alleviate annoyance from noise. Subjective variables (attitudes and expectations) are also linked to annoyance and have the potential to facilitate other health complaints via the nocebo effect. Therefore, it is possible that a segment of the population may remain annoyed (or report other health impacts) even when noise limits are enforced. Based on the findings and scientific merit of the available studies, the weight of evidence suggests that when sited properly, wind turbines are not related to adverse health. Stemming from this review, we provide a number of recommended best practices for wind turbine development in the context of human health. PMID:24995266

Wind Energy Applications for Municipal Water Services: Opportunities, Situation Analyses, and Case Studies; Preprint

Energy Technology Data Exchange (ETDEWEB)

Flowers, L.; Miner-Nordstrom, L.

2006-01-01

As communities grow, greater demands are placed on water supplies, wastewater services, and the electricity needed to power the growing water services infrastructure. Water is also a critical resource for thermoelectric power plants. Future population growth in the United States is therefore expected to heighten competition for water resources. Many parts of the United States with increasing water stresses also have significant wind energy resources. Wind power is the fastest-growing electric generation source in the United States and is decreasing in cost to be competitive with thermoelectric generation. Wind energy can offer communities in water-stressed areas the option of economically meeting increasing energy needs without increasing demands on valuable water resources. Wind energy can also provide targeted energy production to serve critical local water-system needs. The research presented in this report describes a systematic assessment of the potential for wind power to support water utility operation, with the objective to identify promising technical applications and water utility case study opportunities. The first section describes the current situation that municipal providers face with respect to energy and water. The second section describes the progress that wind technologies have made in recent years to become a cost-effective electricity source. The third section describes the analysis employed to assess potential for wind power in support of water service providers, as well as two case studies. The report concludes with results and recommendations.

Integrating Systems Health Management with Adaptive Controls for a Utility-Scale Wind Turbine

Science.gov (United States)

Frost, Susan A.; Goebel, Kai; Trinh, Khanh V.; Balas, Mark J.; Frost, Alan M.

2011-01-01

Increasing turbine up-time and reducing maintenance costs are key technology drivers for wind turbine operators. Components within wind turbines are subject to considerable stresses due to unpredictable environmental conditions resulting from rapidly changing local dynamics. Systems health management has the aim to assess the state-of-health of components within a wind turbine, to estimate remaining life, and to aid in autonomous decision-making to minimize damage. Advanced adaptive controls can provide the mechanism to enable optimized operations that also provide the enabling technology for Systems Health Management goals. The work reported herein explores the integration of condition monitoring of wind turbine blades with contingency management and adaptive controls. Results are demonstrated using a high fidelity simulator of a utility-scale wind turbine.

Seychelles Dome variability in a high resolution ocean model

Science.gov (United States)

Nyadjro, E. S.; Jensen, T.; Richman, J. G.; Shriver, J. F.

2016-02-01

The Seychelles-Chagos Thermocline Ridge (SCTR; 5ºS-10ºS, 50ºE-80ºE) in the tropical Southwest Indian Ocean (SWIO) has been recognized as a region of prominence with regards to climate variability in the Indian Ocean. Convective activities in this region have regional consequences as it affect socio-economic livelihood of the people especially in the countries along the Indian Ocean rim. The SCTR is characterized by a quasi-permanent upwelling that is often associated with thermocline shoaling. This upwelling affects sea surface temperature (SST) variability. We present results on the variability and dynamics of the SCTR as simulated by the 1/12º high resolution HYbrid Coordinate Ocean Model (HYCOM). It is observed that locally, wind stress affects SST via Ekman pumping of cooler subsurface waters, mixing and anomalous zonal advection. Remotely, wind stress curl in the eastern equatorial Indian Ocean generates westward-propagating Rossby waves that impacts the depth of the thermocline which in turn impacts SST variability in the SCTR region. The variability of the contributions of these processes, especially with regard to the Indian Ocean Dipole (IOD) are further examined. In a typical positive IOD (PIOD) year, the net vertical velocity in the SCTR is negative year-round as easterlies along the region are intensified leading to a strong positive curl. This vertical velocity is caused mainly by anomalous local Ekman downwelling (with peak during September-November), a direct opposite to the climatology scenario when local Ekman pumping is positive (upwelling favorable) year-round. The anomalous remote contribution to the vertical velocity changes is minimal especially during the developing and peak stages of PIOD events. In a typical negative IOD (NIOD) year, anomalous vertical velocity is positive almost year-round with peaks in May and October. The remote contribution is positive, in contrast to the climatology and most of the PIOD years.

Siemens Wind Power 3.6 MW wind turbines for large offshore wind farms

Energy Technology Data Exchange (ETDEWEB)

Akhmatov, Vladislav; Nygaard Nielsen, Joergen; Thisted, Jan; Groendahl, Erik; Egedal, Per; Noertoft Frydensbjerg, Michael; Jensen, Kim Hoej [Siemens Wind Power A/S, Brande (Denmark)

2008-07-01

Siemens Wind power A/S is the key player on the offshore wind power market. The Siemens Wind Power 3.6 MW variable-speed wind turbine is among the word's largest, most advanced and competitive wind turbines with a solid portfolio of large offshore wind farms. Transmission system operators and developers require dynamic wind turbine models for evaluation of fault-ride-through capability and investigations of power system stability. The even larger size of the on- and offshore wind farms has entailed that the grid impact of the voltage and frequency control capability of the wind farm can be appropriated modelled and evaluated. Siemens Wind Power has developed a dynamic model of the 3.6 MW variable-speed wind turbine with the fault-ride-through sequences and models of the voltage and frequency controllers to be applied for large offshore wind farms. The dynamic models have been implemented in the commercially available simulation tools such as DIgSILENT PowerFactory and Siemens PTI PSS/E and successfully validated from measurements. (orig.)

A study on the strength of leg extention and leg curl exercise measured with the "Tremax System" and the "ADR" (Aero Dynamic Resistance System)

OpenAIRE

安藤, 勝英

1995-01-01

This is a study on the nature of the extensor and flexor muscles by the leg extention and leg curl exercise. The strength of the static muscles were measured with the "Tremax system" and for the strength of the dynamic muscles the "ADR" was used. Measuring the strength of the extensor muscles at bar no.1 to 4 of the Tremax System，it comes to a maximum at bar no.2 (extention 60°) but it declines radically when approaching extention 0°. Compared to the extensor muscles, the flexor muscules show...

Wind conditions for wind turbine design

Energy Technology Data Exchange (ETDEWEB)

Maribo Pedersen, B.

1999-04-01

Delegates from Europe and USA attended the meeting and discussed general aspects of wind conditions for wind turbine design. The subjects and the presented papers covered a very broad range of aspects of wind conditions and related influence on the wind turbine. (EHS)

Decadal Variations of the Western Subarctic Gyre and Main Pycnocline Depth due to Wind Stress Change in the Northern North Pacific

Science.gov (United States)

Nagano, A.; Wakita, M.

2017-12-01

From the late 1990s to the early 2000s, the western subarctic gyre of the North Pacific, a cyclonic circulation in the western subarctic region, shrank northward associated with a decadal increase of sea surface height (SSH). This gyre change displaced the main pycnocline (halocline) downward and is expected to contribute to the deepening of the overlying temperature minimum layer. This is considered to affect the biogeochemical conditions in the western subarctic region, where is known as substantially slow ocean acidification region. In this study, on the basis of wind stress field data in the subpolar region (40˚N—54˚N, 160˚E—135˚W) during 1979—2014 provided by U.S. National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis, we estimated the variation in SSH, solving the vorticity gradient equation on the beta plane. Decadal increase in SSH at Station K2 (47˚N, 160˚E), representative point of the western subarctic region, was well produced by the calculation, and the correlation coefficient with altimetric SSH exceeds 0.6. The calculated SSH variation consists of the variations due to the barotropic and baroclinic Rossby wave modes. The gyre shrinkage is found to be caused primarily by the barotropic response to the wind change in the whole subpolar region and secondary by the first baroclinic response. Meanwhile, the decadal deepening of the main pycnocline at K2 is attributed to the baroclinic responses of the higher (second, third, and fourth) vertical modes to the local wind change.

Physiological characteristics under the influence of heat stress working in the hot environment, (4)

International Nuclear Information System (INIS)

Nagasaka, Akihiko; Yoshino, Kenji; Takano, Ken-ichi

1987-01-01

There is a possibility that physical and mental stress appears under hot environmental condition for the cause of wearing protection suits on reactor maintenance work. It is important to reduce heat stress rapidly and effectively. This paper mentioned following about the results of static state and simulation work done by testees with or without protection suits under 25 kinds of temperatures and wind velocities in a artificial climate chamber. (1) the correlation between ambient temperatures or wind velocities and subjective symptoms without protection suits. (2) the correlation between ambient temperatures or wind velocities and skin temperatures without protection suits. (3) investigation of the parts of body affecting subjective symptoms. (4) the correlation between ambient temperatures or wind velocities and skin temperatures at working with protection suits. (5) working out countermeasures of recovery from heat stress with the index of skin temperatures and subjective symptoms. (author)

CCSM3 simulation of pacific multi-decadal climate variability: the role of subpolar North Pacific Ocean

International Nuclear Information System (INIS)

Zhong, Y; Liu, Z

2008-01-01

Previous analyses of the CCSM3 standard integration have revealed pronounced multidecadal variability in the Pacific climate system. The purpose of the present work is to investigate the physical mechanism underlying the Pacific multidecadal variability (PMV) using specifically designed sensitivity experiments. A novel mechanism is advanced, characterized by a crucial role of the subpolar North Pacific Ocean. The multidecadal signal in ocean temperature and salinity fields is found to originate from the subsurface of the subpolar North Pacific, as result of the wave adjustment to the preceding basin-scale wind curl forcing. The multidecadal signal then ascends to the surface and is amplified through local temperature/salinity convective feedback. Along the southward Oyashio current, the anomaly travels to the Kuroshio Extension (KOE) region and is further intensified through a similar convective feedback in addition to the wind-evaporation-sea surface temperature feedback. The temperature anomaly in the KOE is able to feed back to the large-scale atmospheric circulation, inducing wind curl anomaly over the subpolar region, which in turn generates anomalous oceanic circulation and causes temperature/salinty variability in the subpolar subsurface. Thereby, a closed loop of PMV is established, in the form of a subpolar delayed oscillator

Anisotropy of turbulence in wind turbine wakes

Energy Technology Data Exchange (ETDEWEB)

Gomez-Elvira, Rafael [Comision Nacional de Energia (Spain); Crespo, Antonio; Migoya, Emilio; Manuel, Fernando [Departamento de Ingenieria Energetica y Fluidomecanica, Escuela Tecnica Superior de Ingenieros Industriales, Universidad Politecnica de Madrid, Jose Gutierrez Abascal, 2. 28006 Madrid (Spain); Hernandez, Julio [Departamento de Mecanica, ETSII, Universidad Nacional de Educacion a Distancia, Ciudad Universitaria, 28040 Madrid (Spain)

2005-10-01

This work is mainly dedicated to the study of non-isotropic characteristics of turbulence in wind turbine wakes, specifically the shear layer of the near wake. A calculation method based on an explicit algebraic model for the components of the turbulent stress tensor is proposed, and the results are found to be in acceptable agreement with experimental results. Analytical expressions for the estimation of an upper limit of the global turbulence kinetic energy, k, and the individual contributions of each diagonal term in the turbulent stress tensor are proposed. Their predictions are compared with experimental results.

Solar wind acceleration in coronal holes

International Nuclear Information System (INIS)

Kopp, R.A.

1978-01-01

Past attempts to explain the large solar wind velocities in high speed streams by theoretical models of the expansion have invoked either extended nonthermal heating of the corona, heat flux inhibition, or direct addition of momentum to the expanding coronal plasma. Several workers have shown that inhibiting the heat flux at low coronal densities is probably not adequate to explain quantitatively the observed plasma velocities in high speed streams. It stressed that, in order to account for both these large plasma velocities and the low densities found in coronal holes (from which most high speed streams are believed to emanate), extended heating by itself will not suffice. One needs a nonthermal mechanism to provide the bulk acceleration of the high wind plasma close to the sun, and the most likely candidate at present is direct addition of the momentum carried by outward-propagating waves to the expanding corona. Some form of momentum addition appears to be absolutely necessary if one hopes to build quantitatively self-consistent models of coronal holes and high speed solar wind streams

Variability of the western Pacific warm pool structure associated with El Niño

Science.gov (United States)

Hu, Shijian; Hu, Dunxin; Guan, Cong; Xing, Nan; Li, Jianping; Feng, Junqiao

2017-10-01

Sea surface temperature (SST) structure inside the western Pacific warm pool (WPWP) is usually overlooked because of its distinct homogeneity, but in fact it possesses a clear meridional high-low-high pattern. Here we show that the SST low in the WPWP is significantly intensified in July-October of El Niño years (especially extreme El Niño years) and splits the 28.5 °C-isotherm-defined WPWP (WPWP split for simplification). Composite analysis and heat budget analysis indicate that the enhanced upwelling due to positive wind stress curl anomaly and western propagating upwelling Rossby waves account for the WPWP split. Zonal advection at the eastern edge of split region plays a secondary role in the formation of the WPWP split. Composite analysis and results from a Matsuno-Gill model with an asymmetric cooling forcing imply that the WPWP split seems to give rise to significant anomalous westerly winds and intensify the following El Niño event. Lead-lag correlation shows that the WPWP split slightly leads the Niño 3.4 index.

Wind resource estimation and siting of wind turbines

DEFF Research Database (Denmark)

Lundtang Petersen, Erik; Mortensen, N.G.; Landberg, L.

1994-01-01

Detailed knowledge of the characteristics of the natural wind is necessary for the design, planning and operational aspect of wind energy systems. Here, we shall only be concerned with those meteorological aspects of wind energy planning that are termed wind resource estimation. The estimation...... of the wind resource ranges from the overall estimation of the mean energy content of the wind over a large area - called regional assessment - to the prediction of the average yearly energy production of a specific wind turbine at a specific location - called siting. A regional assessment will most often...... lead to a so-called wind atlas. A precise prediction of the wind speed at a given site is essential because for aerodynamic reasons the power output of a wind turbine is proportional to the third power of the wind speed, hence even small errors in prediction of wind speed may result in large deviations...

Wind power production: from the characterisation of the wind resource to wind turbine technologies

International Nuclear Information System (INIS)

Beslin, Guy; Multon, Bernard

2016-01-01

Illustrated by graphs and tables, this article first describes the various factors and means related to the assessment of wind resource in the World, in Europe, and the factors which characterize a local wind resource. In this last respect, the authors indicate how local topography is taken into account to calculate wind speed, how time variations are taken into account (at the yearly, seasonal or daily level), the different methods used to model a local wind resource, how to assess the power recoverable by a wind turbine with horizontal axis (notion of Betz limit). In the second part, the authors present the different wind turbines, their benefits and drawbacks: vertical axis, horizontal axis (examples of a Danish-type wind turbine, of wind turbines designed for extreme conditions). Then, they address the technology of big wind turbines: evolution of technology and of commercial offer, aerodynamic characteristics of wind turbine and benefit of a varying speed (technological solutions, importance of the electric generator). They describe how to choose a wind turbine, how product lines are organised, how the power curve and energy capacity are determined. The issue of integration of wind energy into the power system is then addressed. The next part addressed the economy of wind energy production (annualized production cost, order of magnitude of wind electric power production cost). Future trends are discussed and offshore wind energy production is briefly addressed

Extreme winds and waves for offshore turbines: Coupling atmosphere and wave modeling for design and operation in coastal zones

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo; Bolanos, Rodolfo; Du, Jianting

modeling for oshore wind farms. This modeling system consists of the atmospheric Weather Research and Forecasting (WRF) model, the wave model SWAN and an interface the Wave Boundary Layer Model WBLM, within the framework of coupled-ocean-atmosphere-wave-sediment transport modeling system COAWST...... (Hereinafter the WRF-WBLM-SWAN model). WBLM is implemented in SWAN, and it calculates stress and kinetic energy budgets in the lowest atmospheric layer where the wave-induced stress is introduced to the atmospheric modeling. WBLM ensures consistent calculation of stress for both the atmospheric and wave......, which can aect the choice of the off-shore wind turbine type. X-WiWa examined various methodologies for wave modeling. The offline coupling system using atmospheric data such as WRF or global reanalysis wind field to the MIKE 21 SW model has been improved with considerations of stability, air density...

The impact of high penetration of wind energy on the vulnerability of power systems

Energy Technology Data Exchange (ETDEWEB)

EL-Arroudi, K.; Joos, G.; McGillis, D. [McGill Univ., Montreal, PQ (Canada). Dept. of Electrical and Computer Engineering

2006-07-01

This paper examined the impact of higher penetrations of wind energy installations on the vulnerability of power systems. Vulnerability was defined in terms of migration of system states based on the contingencies that might occur. It was noted that both the penetration levels and physical locations of wind energy installations in power systems have a strong influence on system vulnerability. A methodology was proposed to analyze the impacts of wind energy on power system vulnerability through the construction of a decision-tree classification model at the point of common coupling (PCC) bus. The aim of the model was to determine planning criteria for wind power interconnection and to ensure that design concepts are adequate and secure. The model was built by simulating a pre-specified range of system contingencies to generate patterns at the PCC bus. Actual measurements were then compared against known patterns, from which the stress levels of disturbances were estimated. Stress levels were defined in terms of the performance level measures delineated by National Electricity Reliability Council (NERC) planning standards. The methodology is a non-parametric learning technique able to produce classifiers about given problems in order to deduce information from new, unobserved cases. A case study consisting of a 4-machine system with a total generation of 2295 MW was presented where wind-based generation accounted for 450 MW. The decision-tree classifier was constructed by simulating 120 events generated by combinations of contingencies; seasonal wind patterns and different wind production levels per season. Results showed that with a knowledge of the total penetration level and location of wind power installations, it is possible to estimate the effect of wind energy on the vulnerability of a power system. 12 refs., 6 figs.

Structural Reliability Methods for Wind Power Converter System Component Reliability Assessment

DEFF Research Database (Denmark)

Kostandyan, Erik; Sørensen, John Dalsgaard

2012-01-01

Wind power converter systems are essential subsystems in both off-shore and on-shore wind turbines. It is the main interface between generator and grid connection. This system is affected by numerous stresses where the main contributors might be defined as vibration and temperature loadings....... The temperature variations induce time-varying stresses and thereby fatigue loads. A probabilistic model is used to model fatigue failure for an electrical component in the power converter system. This model is based on a linear damage accumulation and physics of failure approaches, where a failure criterion...... is defined by the threshold model. The attention is focused on crack propagation in solder joints of electrical components due to the temperature loadings. Structural Reliability approaches are used to incorporate model, physical and statistical uncertainties. Reliability estimation by means of structural...

Large fog collectors: New strategies for collection efficiency and structural response to wind pressure

Science.gov (United States)

Holmes, Robert; Rivera, Juan de Dios; de la Jara, Emilio

2015-01-01

Most studies of large fog collectors (LFC) have focused on the collection efficiency, the amount of water collected, or economic and social aspects, but have not addressed the effects of strong winds on the system. Wind pressure is directly related to fog water collection efficiency but on the other hand may cause serious damage on the structure of LFCs. This study focuses in the effects of wind pressure on the components of the LFC as an integral system, and the ways to face strong winds with no significant damage. For this purpose we analysed cases of mechanical failure of LFCs both in our experimental station at Peña Blanca in Chile and elsewhere. The effects of wind pressure can be described as a sequence of physical processes, starting with the mesh deformation as a way of adapting to the induced stresses. For a big enough pressure, local stress concentrations generate a progressive rupture of the mesh. In cases where the mesh is sufficiently strong the wind force causes the partial or total collapse of the structure. Usually the weakest part is the mesh, especially close to where it is attached to the structure. The way the mesh is attached to the frame or cable of the structure is particularly important since it can induce significant stress concentrations. Mesh failure before the structure failure may be considered as a mechanical fuse, since it is cheaper to repair. However, more practical mechanical fuses can be conceived. In relation to structural performance and water collection efficiency, we propose a new design strategy that considers a three-dimensional spatial display of the collection screen, oblique incidence angle of wind on mesh and small mesh area between the supporting frame. The proposed design strategies consider both the wind pressure on mesh and structure and the collection efficiency as an integral solution for the LFC. These new design strategies are the final output of this research. Applying these strategies a multi-funnel LFC is

Application of the transfer function to recognition of resonance overvoltages in transformer windings

International Nuclear Information System (INIS)

Florkowski, Marek; Furgał, Jakub

2010-01-01

Power transformer insulation systems are subjected to many stresses during normal operation due to lightning and switching. If the spectrum of incoming surge voltage matches the winding one, a corresponding resonance will be excited. Therefore external transients occurring in power systems might trigger internal overvoltages of a large maximum value in transformer windings. Overvoltages having such a character have been the main cause of many power transformer failures. This paper presents a novel approach to the identification of sensitive zones in the transformer windings based on measurements of overvoltages inside the windings and the frequency dependences of admittance of the power transformer. The frequency characteristics of the transformer winding may determine those regions in the frequency spectrum. The presented methodology might be used both for design optimization and diagnostics of power transformers

WINDING METHOD SELECTION FOR TECHNICAL IMPLEMENTATION OF FIBER OPTIC COMMUNICATION LINE FOR HIGH-SPEED OBJECT

Directory of Open Access Journals (Sweden)

Vyacheslav A. Loparev

2017-07-01

Full Text Available The paper deals with fiber-optical cable winding methods for realization of fiber-optic communication line with high-speed object. We consider possible options of coils for optical cable winding providing mobility of one of the cable ends on an object. It is shown that the choice of a winding process is caused by the need of ensuring the minimum deformation of fiber-optical micro cable in case of separation from a winding body. It is revealed that the minimum tension value and its unevenness are observed when reeling from coils with a rocket form. Design ratios for determination of winding parameters are given. It is shown that reduction of tension unevenness reduces the jumps of internal tension and probability of break and emergence of optical signal local attenuation. Decrease in internal stresses occurs due to the absence of overlapping of the coils of the underlying layers with the overlying ones. To confirm the operability and the possibility of constructive implementation of the selected winding scheme, experiments were carried out to perform rocket and other types of winding with the use of a specially designed machine model. It is shown that the application of line rocket winding enables to achieve stability when reeling a cable during the movement and excludes breaks. Attenuation of optical signal decreases due to the increase in the bend minimum radius. This phenomenon is explained by reduction of the internal stresses causing optical signal attenuation in the place of cable separation from the coil.

Wind farm project economics : value of wind

Energy Technology Data Exchange (ETDEWEB)

Bills-Everett, T. [Mainstream Renewable Power, Toronto, ON (Canada)

2010-07-01

This PowerPoint presentation discussed methods of increasing the value of wind power projects. Appropriate turbine selection and layout is needed to ensure that wind resources are fully developed. Construction costs have a significant impact on project costs. The world turbine price index has not significantly fluctuated since 2006. Operating costs, and the value of wind power projects, are linked with OPEX fluctuations. Wind power projects can significantly reduce greenhouse gas (GHG) emissions. An increase in wind power capacity will reduce the overall cost of energy produced from wind power. Countries can use wind power as part of a renewable energy portfolio designed to reduce risks related to diminishing petroleum supplies. Wind power will help to ensure a global transition to renewable energy use. tabs., figs.

A CFD code comparison of wind turbine wakes

DEFF Research Database (Denmark)

Laan, van der, Paul Maarten; Storey, R. C.; Sørensen, Niels N.

2014-01-01

A comparison is made between the EllipSys3D and SnS CFD codes. Both codes are used to perform Large-Eddy Simulations (LES) of single wind turbine wakes, using the actuator disk method. The comparison shows that both LES models predict similar velocity deficits and stream-wise Reynolds-stresses fo...

Wind Power Today: Wind Energy Program Highlights 2001

Energy Technology Data Exchange (ETDEWEB)

2002-05-01

Wind Power Today is an annual publication that provides an overview of the U.S. Department of Energy's Wind Energy Program accomplishments for the previous year. The purpose of Wind Power Today is to show how DOE's Wind Energy Program supports wind turbine research and deployment in hopes of furthering the advancement of wind technologies that produce clean, low-cost, reliable energy. Content objectives include: educate readers about the advantages and potential for widespread deployment of wind energy; explain the program's objectives and goals; describe the program's accomplishments in research and application; examine the barriers to widespread deployment; describe the benefits of continued research and development; facilitate technology transfer; and attract cooperative wind energy projects with industry. This 2001 edition of Wind Power Today also includes discussions about wind industry growth in 2001, how DOE is taking advantage of low wind speed regions through advancing technology, and distributed applications for small wind turbines.

Proceedings of the Canadian Wind Energy Association's 2009 wind matters conference : wind and power systems

International Nuclear Information System (INIS)

2009-01-01

This conference provided a forum for wind energy and electric power industry experts to discuss issues related to wind and power systems. An overview of wind integration studies and activities in Canada and the United States was provided. New tools and technologies for facilitating the integration of wind and improve market conditions for wind energy developers were presented. Methods of increasing wind penetration were evaluated, and technical issues related to wind interconnections throughout North America were reviewed. The conference was divided into the following 5 sessions: (1) experiences with wind integration, and lessons learned, (2) update on ongoing wind integration initiatives in Canada and the United States, (3) initiatives and tools to facilitate wind integration and market access, (4) developments in wind interconnection and grid codes, (5) wind energy and cold weather considerations, and (6) challenges to achieving the 20 per cent WindVision goal in Canada. The conference featured 21 presentations, of which 13 have been catalogued separately for inclusion in this database. refs., tabs., figs

Wind power today: 1999 Wind Energy program highlights

Energy Technology Data Exchange (ETDEWEB)

Weis-Taylor, Pat

2000-04-06

Wind Power Today is an annual publication that provides an overview for the Department of Energy's Wind Energy Program. The purpose of Wind Power Today is to show how DOE's Wind Energy Program supports wind turbine research and deployment in hopes of furthering the advancement of wind technologies that produce clean, low-cost, reliable energy for the 21st century. Content objectives include: Educate readers about the advantages and potential for widespread deployment of wind energy; explain DOE wind energy program objectives and goals; describe program accomplishments in research and application; examine the barriers to widespread deployment; describe benefits of continued research and development; facilitate technology transfer; attract cooperative wind energy projects with industry.

Extreme winds in the Western North Pacific

Energy Technology Data Exchange (ETDEWEB)

Ott, S.

2006-11-15

A statistical model for extreme winds in the western North Pacific is developed, the region on the Planet where tropical cyclones are most common. The model is based on best track data derived mostly from satellite images of tropical cyclones. The methods used to estimate surface wind speeds from satellite images is discussed with emphasis on the empirical basis, which, unfortunately, is not very strong. This is stressed by the fact that Japanese and US agencies arrive at markedly different estimates. On the other hand, best track data records cover a long period of time and if not perfect they are at least coherent over time in their imperfections. Applying the the Holland model to the best track data, wind profiles can be assigned along the tracks. From this annual wind speed maxima at any particular point in the region can be derived. The annual maxima, in turn, are fitted to a Gumbel distribution using a generalization Abild's method that allows for data wind collected from multiple positions. The choice of this method is justified by a Monte Carlo simulation comparing it to two other methods. The principle output is a map showing fifty year winds in the region. The method is tested against observed winds from Philippine synoptic stations and fair agreement is found for observed and predicted 48 year maxima. However, the almost biasfree performance of the model could be fortuitous, since precise definitions of 'windspeed' in terms averaging time, height above ground and assumed surface roughness are not available, neither for best tracks nor for the synoptic data. The work has been carried out under Danish Research Agency grant 2104-04-0005 'Offshore wind power' and it also covers the findings and analysis carried out in connection with task 1.6 of the project 'Feasibility Assessment and Capacity Building for Wind Energy Development in Cambodia, The Philippines and Vietnam' during 2005-06 under contract 125-2004 with EU

Wind energy. To produce electricity with the wind

International Nuclear Information System (INIS)

Bareau, Helene

2015-11-01

This guide addresses the different aspects of wind-based power generation. It outlines the role of wind energy to meet objectives related to the share of renewable energies in the French energy mix, that wind energy is actually replacing fossil energies, that it is based on local resources within higher safety and less wastage, that current advances are made to integrate wind energy production into the grid, and that it is a solution to diversify energy production. Some figures are presented and commented, regarding onshore wind energy production in France, the location of wind farms, and wind energy production in comparison with other renewable sources. The operation of a wind turbine is described and the different types of wind turbines are evoked. The issue of wind farm planning with citizen participation is addressed: regional planning, studies of pre-feasibility for location selection, procedure, and content of the impact study (radars, fauna and flora, landscapes, safety, health). Other features are outlined: a planned dismantling, and a globally favourable perception. The next part addresses offshore wind energy: the interesting potential of stronger and more reliable wind at sea (European situation, French opportunities, elements comprised in an offshore wind farm), impacts (on marine ecosystems, on neighbouring localities, and interests for visitors). Economic aspects are then addressed: cost and profitability, economic spin-offs, and perspectives. The last part concerns individuals and the possibilities to participate to wind farm projects or to invest in small wind turbines with some prerequisites (constant and steady winds, installation assessment, required expertise, indispensable preliminary steps, costs, aids and profitability)

Wind power integration : From individual wind turbine to wind park as a power plant

NARCIS (Netherlands)

Zhou, Y.

2009-01-01

As power capacities of single wind turbine, single wind park and total wind power installation are continuously increasing, the wind power begins to challenge the safety operation of the power system. This thesis focuses on the grid integration aspects such as the dynamic behaviours of wind power

An evaluation of the WindEye wind lidar

DEFF Research Database (Denmark)

Dellwik, Ebba; Sjöholm, Mikael; Mann, Jakob

Prevision of the wind field by remote sensing wind lidars has the potential to improve the performance of wind turbines. The functionality of a WindEye lidar developed by Windar Photonics A/S (Denmark) for the wind energy market was tested in a two months long field experiment. The WindEye sensor...... with a high accuracy during the whole campaign....

Wind Structure and Wind Loading

DEFF Research Database (Denmark)

Brorsen, Michael

The purpose of this note is to provide a short description of wind, i.e. of the flow in the atmosphere of the Earth and the loading caused by wind on structures. The description comprises: causes to the generation of windhe interaction between wind and the surface of the Earthhe stochastic nature...

An Appropriate Wind Model for Wind Integrated Power Systems Reliability Evaluation Considering Wind Speed Correlations

Directory of Open Access Journals (Sweden)

Rajesh Karki

2013-02-01

Full Text Available Adverse environmental impacts of carbon emissions are causing increasing concerns to the general public throughout the world. Electric energy generation from conventional energy sources is considered to be a major contributor to these harmful emissions. High emphasis is therefore being given to green alternatives of energy, such as wind and solar. Wind energy is being perceived as a promising alternative. This source of energy technology and its applications have undergone significant research and development over the past decade. As a result, many modern power systems include a significant portion of power generation from wind energy sources. The impact of wind generation on the overall system performance increases substantially as wind penetration in power systems continues to increase to relatively high levels. It becomes increasingly important to accurately model the wind behavior, the interaction with other wind sources and conventional sources, and incorporate the characteristics of the energy demand in order to carry out a realistic evaluation of system reliability. Power systems with high wind penetrations are often connected to multiple wind farms at different geographic locations. Wind speed correlations between the different wind farms largely affect the total wind power generation characteristics of such systems, and therefore should be an important parameter in the wind modeling process. This paper evaluates the effect of the correlation between multiple wind farms on the adequacy indices of wind-integrated systems. The paper also proposes a simple and appropriate probabilistic analytical model that incorporates wind correlations, and can be used for adequacy evaluation of multiple wind-integrated systems.

Wind energy

International Nuclear Information System (INIS)

Anon.

1992-01-01

This chapter discusses the role wind energy may have in the energy future of the US. The topics discussed in the chapter include historical aspects of wind energy use, the wind energy resource, wind energy technology including intermediate-size and small wind turbines and intermittency of wind power, public attitudes toward wind power, and environmental, siting and land use issues

Detection and Host Range Study of Virus Associated with Pepper Yellow Leaf Curl Disease

Directory of Open Access Journals (Sweden)

SRI SULANDARI

2006-03-01

Full Text Available High incidence of Pepper yellow leaf curl virus (PepYLCV was observed in Indonesia since early 2000. Disease incidence in Yogyakarta, Central and West Java reached 100% on Capsicum frutescens, but only 10-35% on C. annuum. As an exception, the disease incidence on C. annuum cv. TM 999 was in the range of 70-100%. The causal agent of the disease, PepYLCV, was detected by polymerase chain reaction. Viral specific DNA fragment of the size ~1600 bp and ~550 bp was amplified from infected plants using two pairs of geminivirus universal primers pAL1v1978/pAL1c715, and pAv494/pAc1048, respectively. The PepYLCV has an intermediate host range including plants belonging to the family of Solanaceae, Leguminosae, and Compositae. The species belonging to the families of Cucurbitaceae, Malvaceae, Chenopodiaceae, and Amaranthaceae were resistant to the virus. Physalis floridana, is very prospective as a propagation host for the geminivirus infecting pepper. Nicotiana spp., cucumber, watermelon, cotton, and Sida sp. could be used as a differential host. Besides, Capsicum frutescens cv. Cakra, tomato, N. benthamiana, N. glutinosa, and Ageratum conyzoides could be used as indicator plants for the geminivirus infecting pepper.

Tomato Leaf Curl New Delhi Virus: An Emerging Virus Complex Threatening Vegetable and Fiber Crops

Directory of Open Access Journals (Sweden)

Enrique Moriones

2017-09-01

Full Text Available The tomato leaf curl New Delhi virus (ToLCNDV (genus Begomovirus, family Geminiviridae represents an important constraint to tomato production, as it causes the most predominant and economically important disease affecting tomato in the Indian sub-continent. However, in recent years, ToLCNDV has been fast extending its host range and spreading to new geographical regions, including the Middle East and the western Mediterranean Basin. Extensive research on the genome structure, protein functions, molecular biology, and plant–virus interactions of ToLCNDV has been conducted in the last decade. Special emphasis has been given to gene silencing suppression ability in order to counteract host plant defense responses. The importance of the interaction with DNA alphasatellites and betasatellites in the biology of the virus has been demonstrated. ToLCNDV genetic variability has been analyzed, providing new insights into the taxonomy, host adaptation, and evolution of this virus. Recombination and pseudorecombination have been shown as motors of diversification and adaptive evolution. Important progress has also been made in control strategies to reduce disease damage. This review highlights these various achievements in the context of the previous knowledge of begomoviruses and their interactions with plants.

The analysis of dynamic characteristics and wind-induced displacement response of space Beam String Structure

Directory of Open Access Journals (Sweden)

Chen Yong Jian

2018-01-01

Full Text Available The Beam String Structure structural system, also called BSS, has the advantages of lighter dead weight and greater flexibility. The wind load is the main design control factor. The dynamic characteristics and wind-induced displacement response of BSS are studied by the finite element method. The roof structure of the stadium roof of the Fuzhou Olympic Sports Center is the engineering background. 1The numerical model was built by ANSYS, by shape finding, determine the initial stress state of structural members such as external cables; 2From the analysis of dynamic characteristics, the main mode of vibration is the vibration of cables; 3The wind speed spectrum of MATLAB generation structure is obtained by AR method, the structural response of the structure under static wind load and fluctuating wind load is calculated. From the analysis result, considering the equivalent static wind load of BSS , the design of adverse wind is not safe, and the fluctuating wind load should be taken into account.

Comparative transcriptome profiling of a resistant vs. susceptible tomato (Solanum lycopersicum cultivar in response to infection by tomato yellow leaf curl virus.

Directory of Open Access Journals (Sweden)

Tianzi Chen

Full Text Available Tomato yellow leaf curl virus (TYLCV threatens tomato production worldwide by causing leaf yellowing, leaf curling, plant stunting and flower abscission. The current understanding of the host plant defense response to this virus is very limited. Using whole transcriptome sequencing, we analyzed the differential gene expression in response to TYLCV infection in the TYLCV-resistant tomato breeding line CLN2777A (R and TYLCV-susceptible tomato breeding line TMXA48-4-0 (S. The mixed inoculated samples from 3, 5 and 7 day post inoculation (dpi were compared to non-inoculated samples at 0 dpi. Of the total of 34831 mapped transcripts, 209 and 809 genes were differentially expressed in the R and S tomato line, respectively. The proportion of up-regulated differentially expressed genes (DEGs in the R tomato line (58.37% was higher than that in the S line (9.17%. Gene ontology (GO analyses revealed that similar GO terms existed in both DEGs of R and S lines; however, some sets of defense related genes and their expression levels were not similar between the two tomato lines. Genes encoding for WRKY transcriptional factors, R genes, protein kinases and receptor (-like kinases which were identified as down-regulated DEGs in the S line were up-regulated or not differentially expressed in the R line. The up-regulated DEGs in the R tomato line revealed the defense response of tomato to TYLCV infection was characterized by the induction and regulation of a series of genes involved in cell wall reorganization, transcriptional regulation, defense response, ubiquitination, metabolite synthesis and so on. The present study provides insights into various reactions underlining the successful establishment of resistance to TYLCV in the R tomato line, and helps in the identification of important defense-related genes in tomato for TYLCV disease management.

Strategic wind power trading considering rival wind power production

DEFF Research Database (Denmark)

Exizidis, Lazaros; Kazempour, Jalal; Pinson, Pierre

2016-01-01

In an electricity market with high share of wind power, it is expected that wind power producers may exercise market power. However, wind producers have to cope with wind’s uncertain nature in order to optimally offer their generation, whereas in a market with more than one wind producers, uncert...... depending on the rival’s wind generation, given that its own expected generation is not high. Finally, as anticipated, expected system cost is higher when both wind power producers are expected to have low wind power generation......In an electricity market with high share of wind power, it is expected that wind power producers may exercise market power. However, wind producers have to cope with wind’s uncertain nature in order to optimally offer their generation, whereas in a market with more than one wind producers......, uncertainty of rival wind power generation should also be considered. Under this context, this paper addresses the impact of rival wind producers on the offering strategy and profits of a pricemaker wind producer. A stochastic day-ahead market setup is considered, which optimizes the day-ahead schedules...

Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

DEFF Research Database (Denmark)

Feng, Ju; Shen, Wen Zhong

2015-01-01

Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distribu...

A zero torsional stiffness twist morphing blade as a wind turbine load alleviation device

Science.gov (United States)

Lachenal, X.; Daynes, S.; Weaver, P. M.

2013-06-01

This paper presents the design, analysis and realization of a zero stiffness twist morphing wind turbine blade. The morphing blade is designed to actively twist as a means of alleviating the gust loads which reduce the fatigue life of wind turbine blades. The morphing structure exploits an elastic strain energy balance within the blade to enable large twisting deformations with modest actuation requirements. While twist is introduced using the warping of the blade skin, internal pre-stressed members ensure that a constant strain energy balance is achieved throughout the deformation, resulting in a zero torsional stiffness structure. The torsional stability of the morphing blade is characterized by analysing the elastic strain energy in the device. Analytical models of the skin, the pre-stressed components and the complete blade are compared to their respective finite element models as well as experimental results. The load alleviation potential of the adaptive structure is quantified using a two-dimensional steady flow aerodynamic model which is experimentally validated with wind tunnel measurements.

LIDAR Wind Speed Measurements of Evolving Wind Fields

Energy Technology Data Exchange (ETDEWEB)

Simley, E.; Pao, L. Y.

2012-07-01

Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. Past studies have assumed Taylor's frozen turbulence hypothesis, which implies that turbulence remains unchanged as it advects downwind at the mean wind speed. With Taylor's hypothesis applied, the only source of wind speed measurement error is distortion caused by the LIDAR. This study introduces wind evolution, characterized by the longitudinal coherence of the wind, to LIDAR measurement simulations to create a more realistic measurement model. A simple model of wind evolution is applied to a frozen wind field used in previous studies to investigate the effects of varying the intensity of wind evolution. LIDAR measurements are also evaluated with a large eddy simulation of a stable boundary layer provided by the National Center for Atmospheric Research. Simulation results show the combined effects of LIDAR errors and wind evolution for realistic turbine-mounted LIDAR measurement scenarios.

Wind Energy

International Nuclear Information System (INIS)

Rodriguez D, J.M.

1998-01-01

The general theory of the wind energy conversion systems is presented. The availability of the wind resource in Colombia and the ranges of the speed of the wind in those which is possible economically to use the wind turbines are described. It is continued with a description of the principal technological characteristics of the wind turbines and are split into wind power and wind-powered pumps; and its use in large quantities grouped in wind farms or in autonomous systems. Finally, its costs and its environmental impact are presented

Evaluation of wind farm efficiency and wind turbine wakes at the Nysted offshore wind farm

DEFF Research Database (Denmark)

Barthelmie, Rebecca Jane; Jensen, L.E.

2010-01-01

Here, we quantify relationships between wind farm efficiency and wind speed, direction, turbulence and atmospheric stability using power output from the large offshore wind farm at Nysted in Denmark. Wake losses are, as expected, most strongly related to wind speed variations through the turbine...... thrust coefficient; with direction, atmospheric stability and turbulence as important second order effects. While the wind farm efficiency is highly dependent on the distribution of wind speeds and wind direction, it is shown that the impact of turbine spacing on wake losses and turbine efficiency can...... be quantified, albeit with relatively large uncertainty due to stochastic effects in the data. There is evidence of the ‘deep array effect’ in that wake losses in the centre of the wind farm are under-estimated by the wind farm model WAsP, although overall efficiency of the wind farm is well predicted due...

Fatigue impact on Mod-1 wind turbine design

Science.gov (United States)

Stahle, C. V., Jr.

1978-01-01

Fatigue is a key consideration in the design of a long-life Wind Turbine Generator (WTG) system. This paper discusses the fatigue aspects of the large Mod-1 horizontal-axis WTG design starting with the characterization of the environment and proceeding through the design. Major sources of fatigue loading are discussed and methods of limiting fatigue loading are described. NASTRAN finite element models are used to determine dynamic loading and internal cyclic stresses. Recent developments in determining the allowable fatigue stress consistent with present construction codes are discussed relative to their application to WTG structural design.

Wind Power Today: 2000 Wind Energy Program Highlights

Energy Technology Data Exchange (ETDEWEB)

Weis-Taylor, W.

2001-05-08

Wind Power Today is an annual publication that provides an overview of the U.S. Department of Energy's Wind Energy Program. The purpose of Wind Power Today is to show how DOE's Wind Energy Program supports wind turbine research and deployment in hopes of furthering the advancement of wind technologies that produce clean, low-cost, reliable energy. Content objectives include: educate readers about the advantages and potential for widespread deployment of wind energy; explain the program's objectives and goals; describe the program's accomplishments in research and application; examine the barriers to widespread deployment; describe the benefits of continued research and development; facilitate technology transfer; and attract cooperative wind energy projects with industry.

A comparative calculation of the wind turbines capacities on the basis of the L-{sigma} criterion

Energy Technology Data Exchange (ETDEWEB)

Menet, Jean-Luc; Valdes, Laurent-Charles; Menart, Bruno [Universite de Valenciennes et du Hainaut-Cambresis, Groupe de Recherche Energies et Environnement, Valenciennes, 59 (France)

2001-04-01

Usually, wind sites are equipped with fast-running Horizontal Axis Wind Turbines of the airscrew type, which has a high efficiency. In this article, the argument is put forward that the choice of a wind turbine must not be based only on high efficiency. We propose a comparative criterion adapted to the comparison of a horizontal axis wind turbine with a vertical axis wind turbine: the L-{sigma} criterion. This criterion consists in comparing wind turbines which intercept the same front width of wind, by allocating them a same reference value of the maximal mechanical stress on the blades or the paddles. On the basis of this criterion, a quantitative comparison points to a clear advantage of the Savonius rotors, because of their lower angular velocity, and provides some elements for the improvement of their rotor. (Author)

Thermal analysis of multi-MW two-level wind power converter

DEFF Research Database (Denmark)

Zhou, Dao; Blaabjerg, Frede; Mogens, Lau

2012-01-01

In this paper, the multi-MW wind turbine of partial-scale and full-scale two-level power converter with DFIG and direct-drive PMSG are designed and compared in terms of their thermal performance. Simulations of different configurations regarding loss distribution and junction temperature...... in the power device in the whole range of wind speed are presented and analyzed. It is concluded that in both partial-scale and full-scale power converter the most thermal stressed power device in the generator-side converter will have higher mean junction temperature and larger junction temperature...... fluctuation compared to grid-side converter at the rated wind speed. Moreover, the thermal performance of the generator-side converter in the partial-scale power converter becomes crucial around the synchronous operating point and should be considered carefully....

Advancements in Wind Integration Study Data Modeling: The Wind Integration National Dataset (WIND) Toolkit; Preprint

Energy Technology Data Exchange (ETDEWEB)

Draxl, C.; Hodge, B. M.; Orwig, K.; Jones, W.; Searight, K.; Getman, D.; Harrold, S.; McCaa, J.; Cline, J.; Clark, C.

2013-10-01

Regional wind integration studies in the United States require detailed wind power output data at many locations to perform simulations of how the power system will operate under high-penetration scenarios. The wind data sets that serve as inputs into the study must realistically reflect the ramping characteristics, spatial and temporal correlations, and capacity factors of the simulated wind plants, as well as be time synchronized with available load profiles. The Wind Integration National Dataset (WIND) Toolkit described in this paper fulfills these requirements. A wind resource dataset, wind power production time series, and simulated forecasts from a numerical weather prediction model run on a nationwide 2-km grid at 5-min resolution will be made publicly available for more than 110,000 onshore and offshore wind power production sites.

The triple helix frame for Small and Medium-sized Enterprises for innovation and development of offshore wind energy

DEFF Research Database (Denmark)

Brink, Tove; Madsen, Svend Ole

2016-01-01

innovation for the reduction of the LCOE in the wind farm industry. This knowledge space also provides important insight and understanding for the governmental and university helices for active contribution to offshore wind energy. The governmental policy impact stresses the need for a more strategic long...

Wind Climate Parameters for Wind Turbine Fatigue Load Assessment

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Svenningsen, Lasse; Moser, Wolfgang

2016-01-01

Site-specific assessment of wind turbine design requires verification that the individual wind turbine components can survive the site-specific wind climate. The wind turbine design standard, IEC 61400-1 (third edition), describes how this should be done using a simplified, equivalent wind climate...... climate required by the current design standard by comparing damage equivalent fatigue loads estimated based on wind climate parameters for each 10 min time-series with fatigue loads estimated based on the equivalent wind climate parameters. Wind measurements from Boulder, CO, in the United States...

European Wind Atlas and Wind Resource Research in Denmark

DEFF Research Database (Denmark)

Mortensen, Niels Gylling

to estimate the actual wind climate at any specific site and height within this region. The Danish and European Wind Atlases are examples of how the wind atlas methodology can be employed to estimate the wind resource potential for a country or a sub-continent. Recently, the methodology has also been used...... - from wind measurements at prospective sites to wind tunnel simulations and advanced flow modelling. Among these approaches, the wind atlas methodology - developed at Ris0 National Laboratory over the last 25 years - has gained widespread recognition and is presently considered by many as the industry......-standard tool for wind resource assessment and siting of wind turbines. The PC-implementation of the methodology, the Wind Atlas Analysis and Application Program (WAsP), has been applied in more than 70 countries and territories world-wide. The wind atlas methodology is based on physical descriptions and models...

When real life wind speed exceeds design wind assumptions

Energy Technology Data Exchange (ETDEWEB)

Winther-Jensen, M; Joergensen, E R [Risoe National Lab., Roskilde (Denmark)

1999-03-01

Most modern wind turbines are designed according to a standard or a set of standards to withstand the design loads with a defined survival probability. Mainly the loads are given by the wind conditions on the site defining the `design wind speeds`, normally including extreme wind speeds given as an average and a peak value. The extreme wind speeds are normally (e.g. in the upcoming IEC standard for wind turbine safety) defined as having a 50-year recurrence period. But what happens when the 100 or 10,000 year wind situation hits a wind turbine? Results on wind turbines of wind speeds higher than the extreme design wind speeds are presented based on experiences especially from the State of Gujarat in India. A description of the normal approach of designing wind turbines in accordance with the standards in briefly given in this paper with special focus on limitations and built-in safety levels. Based on that, other possibilities than just accepting damages on wind turbines exposed for higher than design wind speeds are mentioned and discussed. The presentation does not intend to give the final answer to this problem but is meant as an input to further investigations and discussions. (au)

Crater Mound Formation by Wind Erosion on Mars

Science.gov (United States)

Steele, L. J.; Kite, E. S.; Michaels, T. I.

2018-01-01

Most of Mars' ancient sedimentary rocks by volume are in wind-eroded sedimentary mounds within impact craters and canyons, but the connections between mound form and wind erosion are unclear. We perform mesoscale simulations of different crater and mound morphologies to understand the formation of sedimentary mounds. As crater depth increases, slope winds produce increased erosion near the base of the crater wall, forming mounds. Peak erosion rates occur when the crater depth is ˜2 km. Mound evolution depends on the size of the host crater. In smaller craters mounds preferentially erode at the top, becoming more squat, while in larger craters mounds become steeper sided. This agrees with observations where smaller craters tend to have proportionally shorter mounds and larger craters have mounds encircled by moats. If a large-scale sedimentary layer blankets a crater, then as the layer recedes across the crater it will erode more toward the edges of the crater, resulting in a crescent-shaped moat. When a 160 km diameter mound-hosting crater is subject to a prevailing wind, the surface wind stress is stronger on the leeward side than on the windward side. This results in the center of the mound appearing to "march upwind" over time and forming a "bat-wing" shape, as is observed for Mount Sharp in Gale crater.

Wind Turbine Gearbox Oil Filtration and Condition Monitoring

Energy Technology Data Exchange (ETDEWEB)

Sheng, Shuangwen

2015-10-25

This is an invited presentation for a pre-conference workshop, titled advances and opportunities in lubrication: wind turbine, at the 2015 Society of Tribologists and Lubrication Engineers (STLE) Tribology Frontiers Conference held in Denver, CO. It gives a brief overview of wind turbine gearbox oil filtration and condition monitoring by highlighting typical industry practices and challenges. The presentation starts with an introduction by covering recent growth of global wind industry, reliability challenges, benefits of oil filtration and condition monitoring, and financial incentives to conduct wind operation and maintenance research, which includes gearbox oil filtration and condition monitoring work presented herein. Then, the presentation moves on to oil filtration by stressing the benefits of filtration, discussing typical main- and offline-loop practices, highlighting important factors considered when specifying a filtration system, and illustrating real-world application challenges through a cold-start example. In the next section on oil condition monitoring, a discussion on oil sample analysis, oil debris monitoring, oil cleanliness measurements and filter analysis is given based on testing results mostly obtained by and at NREL, and by pointing out a few challenges with oil sample analysis. The presentation concludes with a brief touch on future research and development (R and D) opportunities. It is hoping that the information presented can inform the STLE community to start or redirect their R and D work to help the wind industry advance.

3D WindScanner lidar measurements of wind and turbulence around wind turbines, buildings and bridges

Science.gov (United States)

Mikkelsen, T.; Sjöholm, M.; Angelou, N.; Mann, J.

2017-12-01

WindScanner is a distributed research infrastructure developed at DTU with the participation of a number of European countries. The research infrastructure consists of a mobile technically advanced facility for remote measurement of wind and turbulence in 3D. The WindScanners provide coordinated measurements of the entire wind and turbulence fields, of all three wind components scanned in 3D space. Although primarily developed for research related to on- and offshore wind turbines and wind farms, the facility is also well suited for scanning turbulent wind fields around buildings, bridges, aviation structures and of flow in urban environments. The mobile WindScanner facility enables 3D scanning of wind and turbulence fields in full scale within the atmospheric boundary layer at ranges from 10 meters to 5 (10) kilometers. Measurements of turbulent coherent structures are applied for investigation of flow pattern and dynamical loads from turbines, building structures and bridges and in relation to optimization of the location of, for example, wind farms and suspension bridges. This paper presents our achievements to date and reviews briefly the state-of-the-art of the WindScanner measurement technology with examples of uses for wind engineering applications.

Damage detection in wind turbine blades using acoustic techniques

Energy Technology Data Exchange (ETDEWEB)

Juengert, A., E-mail: anne.juengert@mpa.uni-stuttgart.de [Univ. of Stuttgart, Materialpruefungsanstalt Stuttgart, Stuttgart (Germany)

2013-05-15

Facing climate change, the use of renewable energy gains importance. The wind energy sector grows very fast. Bigger and more powerful wind turbines will be built in the coming decades and the safety and reliability of the turbines will become more important. Wind turbine blades have to be inspected at regular intervals, because they are highly stressed during operation and a blade breakdown can cause big economic damages. The turbine blades consist of fiber reinforced plastics (GFRP/CFRP) and sandwich areas containing wood or plastic foam. The blades are manufactured as two halves and glued together afterwards. Typical damages are delaminations within the GFRP or the sandwich and missing adhesive or deficient bond at the bonding surfaces. The regular inspections of wind turbine blades are performed manually by experts and are limited to visual appraisals and simple tapping tests. To improve the inspections of wind turbine blades non-destructive testing techniques using acoustic waves are being developed. To detect delaminations within the laminates of the turbine blade, a local resonance spectroscopy was used. To detect missing bond areas from the outside of the blade the impulse-echo-technique was applied. This paper is an updated reprint of an article published on ndt.net in 2008. (author)

Current R and D needs in wind energy technology

International Nuclear Information System (INIS)

Maribo Pedersen, B.

1995-01-01

The meeting, hosted by NOVEM, the Netherlands Agency for Energy and the Environment, was attended by 22 people. The purpose of the meeting was to get an impression of how far the efforts spent until now on worldwide research and development have brought the general understanding of, and possibly solutions to, the various problems within wind energy technology - thereby providing some guidance as to where to go from now. In 1994 it was estimated that more than 100 million U.S. dollars was spent on R, D and D by those OECD countries which have a wind energy program, and that since 1974 at least 1000 mil. U.S. dollars must have been spent. The necessity of continued basic research within certain areas was recognized, and it was emphasized that the size of the research teams should always be greater than 'the critical mass'. There seemed to be consensus among all participants that the areas for continued research were the following: aerodynamics, aeroelasticity and load calculations, aeroacoustics (verification of fatigue calculation procedures for 3D stress distribution, establishing a data base of material properties), lightning protection measures, offshore installations (combined wind/wave loading, dynamics of support structures, wind and turbulence over the open sea), power conversion and wind turbine - grid interaction. (EG)

Damage detection in wind turbine blades using acoustic techniques

International Nuclear Information System (INIS)

Juengert, A.

2013-01-01

Facing climate change, the use of renewable energy gains importance. The wind energy sector grows very fast. Bigger and more powerful wind turbines will be built in the coming decades and the safety and reliability of the turbines will become more important. Wind turbine blades have to be inspected at regular intervals, because they are highly stressed during operation and a blade breakdown can cause big economic damages. The turbine blades consist of fiber reinforced plastics (GFRP/CFRP) and sandwich areas containing wood or plastic foam. The blades are manufactured as two halves and glued together afterwards. Typical damages are delaminations within the GFRP or the sandwich and missing adhesive or deficient bond at the bonding surfaces. The regular inspections of wind turbine blades are performed manually by experts and are limited to visual appraisals and simple tapping tests. To improve the inspections of wind turbine blades non-destructive testing techniques using acoustic waves are being developed. To detect delaminations within the laminates of the turbine blade, a local resonance spectroscopy was used. To detect missing bond areas from the outside of the blade the impulse-echo-technique was applied. This paper is an updated reprint of an article published on ndt.net in 2008. (author)

Wind Turbine Converter Control Interaction with Complex Wind Farm Systems

DEFF Research Database (Denmark)

Kocewiak, Lukasz Hubert; Hjerrild, Jesper; Bak, Claus Leth

2013-01-01

. The same wind turbine converter control strategy is evaluated in two different wind farms. It is emphasised that the grid-side converter controller should be characterised by sufficient harmonic/noise rejection and adjusted depending on wind farms to which it is connected. Various stability indices......This study presents wind turbine converter stability analysis of wind farms in frequency domain. The interaction between the wind turbine control system and the wind farm structure in wind farms is deeply investigated. Two wind farms (i.e. Horns Rev II and Karnice) are taken into consideration...... in this study. It is shown that wind farm components, such as long high-voltage alternating current cables and park transformers, can introduce significant low-frequency series resonances seen from the wind turbine terminals that can affect wind turbine control system operation and overall wind farm stability...

The Wind Integration National Dataset (WIND) toolkit (Presentation)

Energy Technology Data Exchange (ETDEWEB)

Caroline Draxl: NREL

2014-01-01

Regional wind integration studies require detailed wind power output data at many locations to perform simulations of how the power system will operate under high penetration scenarios. The wind datasets that serve as inputs into the study must realistically reflect the ramping characteristics, spatial and temporal correlations, and capacity factors of the simulated wind plants, as well as being time synchronized with available load profiles.As described in this presentation, the WIND Toolkit fulfills these requirements by providing a state-of-the-art national (US) wind resource, power production and forecast dataset.

Characterization of a New World Monopartite Begomovirus Causing Leaf Curl Disease of Tomato in Ecuador and Peru Reveals a New Direction in Geminivirus Evolution

Science.gov (United States)

Melgarejo, Tomas A.; Kon, Tatsuya; Rojas, Maria R.; Paz-Carrasco, Lenin; Zerbini, F. Murilo

2013-01-01

All characterized whitefly-transmitted geminiviruses (begomoviruses) with origins in the New World (NW) have bipartite genomes composed of a DNA-A and DNA-B component. Recently, an NW begomovirus lacking a DNA-B component was associated with tomato leaf curl disease (ToLCD) in Peru, and it was named Tomato leaf deformation virus (ToLDeV). Here, we show that isolates of ToLDeV associated with ToLCD in Ecuador and Peru have a single, genetically diverse genomic DNA that is most closely related to DNA-A components of NW bipartite begomoviruses. Agroinoculation of multimeric clones of the genomic DNA of three ToLDeV genotypes (two variants and a strain) resulted in the development of tomato leaf curl symptoms indistinguishable from those of ToLCD in Ecuador and Peru. Biological properties of these ToLDeV genotypes were similar to those of Old World (OW) monopartite tomato-infecting begomoviruses, including lack of sap transmissibility, phloem limitation, a resistance phenotype in tomato germplasm with the Ty-1 gene, and functional properties of the V1 (capsid protein) and C4 genes. Differences in symptom phenotypes induced by the ToLDeV genotypes in tomato and Nicotiana benthamiana plants were associated with a highly divergent left intergenic region and C4 gene. Together, these results establish that ToLDeV is an emergent NW monopartite begomovirus that is causing ToLCD in Ecuador and Peru. This is the first report of an indigenous NW monopartite begomovirus, and evidence is presented that it emerged from the DNA-A component of a NW bipartite progenitor via convergent evolution and recombination. PMID:23468482

Wind power

International Nuclear Information System (INIS)

Gipe, P.

2007-01-01

This book is a translation of the edition published in the USA under the title of ''wind power: renewable energy for home, farm and business''. In the wake of mass blackouts and energy crises, wind power remains a largely untapped resource of renewable energy. It is a booming worldwide industry whose technology, under the collective wing of aficionados like author Paul Gipe, is coming of age. Wind Power guides us through the emergent, sometimes daunting discourse on wind technology, giving frank explanations of how to use wind technology wisely and sound advice on how to avoid common mistakes. Since the mid-1970's, Paul Gipe has played a part in nearly every aspect of wind energy development from installing small turbines to promoting wind energy worldwide. As an American proponent of renewable energy, Gipe has earned the acclaim and respect of European energy specialists for years, but his arguments have often fallen on deaf ears at home. Today, the topic of wind power is cropping up everywhere from the beaches of Cape Cod to the Oregon-Washington border, and one wind turbine is capable of producing enough electricity per year to run 200 average American households. Now, Paul Gipe is back to shed light on this increasingly important energy source with a revised edition of Wind Power. Over the course of his career, Paul Gipe has been a proponent, participant, observer, and critic of the wind industry. His experience with wind has given rise to two previous books on the subject, Wind Energy Basics and Wind Power for Home and Business, which have sold over 50,000 copies. Wind Power for Home and Business has become a staple for both homeowners and professionals interested in the subject, and now, with energy prices soaring, interest in wind power is hitting an all-time high. With chapters on output and economics, Wind Power discloses how much you can expect from each method of wind technology, both in terms of energy and financial savings. The book updated models

Assessing spacing impact on coherent features in a wind turbine array boundary layer

Directory of Open Access Journals (Sweden)

N. Ali

2018-02-01

Full Text Available As wind farms become larger, the spacing between turbines becomes a significant design consideration that can impose serious economic constraints. To investigate the turbulent flow structures in a 4 × 3 Cartesian wind turbine array boundary layer (WTABL, a wind tunnel experiment was carried out parameterizing the streamwise and spanwise wind turbine spacing. Four cases are chosen spacing turbines by 6 or 3D in the streamwise direction, and 3 or 1.5D in the spanwise direction, where D = 12 cm is the rotor diameter. Data are obtained experimentally using stereo particle image velocimetry. Mean streamwise velocity showed maximum values upstream of the turbine with the spacing of 6 and 3D in the streamwise and spanwise direction, respectively. Fixing the spanwise turbine spacing to 3D, variations in the streamwise spacing influence the turbulent flow structure and the power available to following wind turbines. Quantitative comparisons are made through spatial averaging, shifting measurement data and interpolating to account for the full range between devices to obtain data independent of array spacing. The largest averaged Reynolds stress is seen in cases with spacing of 3D × 3D. Snapshot proper orthogonal decomposition (POD was employed to identify the flow structures based on the turbulence kinetic energy content. The maximum turbulence kinetic energy content in the first POD mode is seen for turbine spacing of 6D × 1.5D. The flow upstream of each wind turbine converges faster than the flow downstream according to accumulation of turbulence kinetic energy by POD modes, regardless of spacing. The streamwise-averaged profile of the Reynolds stress is reconstructed using a specific number of modes for each case; the case of 6D × 1.5D spacing shows the fastest reconstruction to compare the rate of reconstruction of statistical profiles. Intermediate modes are also used to reconstruct the averaged profile and show that the

Marine wind data presentation using wind transition matrix

Digital Repository Service at National Institute of Oceanography (India)

Mascarenhas, A.J.; Gouveia, A.D.; Desai, R.G.P.

One of the methods to simulate the random wind behaviour through time is to use historical wind data presented in the form of wind transition matrix. Here it is assumed that, the probability that the wind will shift from one direction to another...

An introduction to reactive power compensation for wind farms

Energy Technology Data Exchange (ETDEWEB)

Nigim, K.A. [Waterloo Univ., Ont. (Canada). Dept. of Electrical and Computer Engineering; Cairo Univ., Giza (Egypt). Faculty of Engineering; Zobaa, A.F.; El Amin, I. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia). Dept. of Electrical Engineering

2005-07-01

The paper summarises the refereed contributions of seven articles reviewed for publication in the IJETP - Special Issue on 'Reactive compensation for wind farms'. The main goal of the special issue is to provide a forum to exchange information on the reactive power compensation requirements for wind farms and introducing possible price mechanisms for today's deregulated power industry. Uncompensated reactive power causes stress on the hosting utility grid as well as added expenses, which create in difficulties for power purchasing agreements from independent wind energy producers. Wind power producers need to comply with the hosting utility grid interconnection standards, e.g., voltage and frequency, as well as to provide controllable active and reactive sources of power. Active power supply is mainly dependent on the potential of wind power produced and the turbine design. Reactive power demand on the other hand depends on the conversion devices and the recovered power quantity fed to the grid. Static Var Compensators (SVC), Unified Power Quality Conditioners (UPQC), Unified Power Flow Controllers (UPFC), and the Distributed Static Synchronous Compensators (DSTATCOM) are all new emerging devices aimed at regulating the reactive power requirements. The excellent controllability of these devices has paved the way to flexible and dynamic controllers that are capable of regulating the flow of active and reactive power components. These devices are now suggested for the control of the reactive power requirement of wind generators. Studies have demonstrated acceptable voltage stabilisation results. This has increased the penetration level of wind power into existing distribution networks in many countries. (Author)

An introduction to reactive power compensation for wind farms

International Nuclear Information System (INIS)

Nigim, K.A.; Cairo Univ., Giza; Zobaa, A.F.; El Amin, I.

2005-01-01

The paper summarises the refereed contributions of seven articles reviewed for publication in the IJETP - Special Issue on 'Reactive compensation for wind farms'. The main goal of the special issue is to provide a forum to exchange information on the reactive power compensation requirements for wind farms and introducing possible price mechanisms for today's deregulated power industry. Uncompensated reactive power causes stress on the hosting utility grid as well as added expenses, which create in difficulties for power purchasing agreements from independent wind energy producers. Wind power producers need to comply with the hosting utility grid interconnection standards, e.g., voltage and frequency, as well as to provide controllable active and reactive sources of power. Active power supply is mainly dependent on the potential of wind power produced and the turbine design. Reactive power demand on the other hand depends on the conversion devices and the recovered power quantity fed to the grid. Static Var Compensators (SVC), Unified Power Quality Conditioners (UPQC), Unified Power Flow Controllers (UPFC), and the Distributed Static Synchronous Compensators (DSTATCOM) are all new emerging devices aimed at regulating the reactive power requirements. The excellent controllability of these devices has paved the way to flexible and dynamic controllers that are capable of regulating the flow of active and reactive power components. These devices are now suggested for the control of the reactive power requirement of wind generators. Studies have demonstrated acceptable voltage stabilisation results. This has increased the penetration level of wind power into existing distribution networks in many countries. (Author)

Wind power forecast error smoothing within a wind farm

International Nuclear Information System (INIS)

Saleck, Nadja; Bremen, Lueder von

2007-01-01

Smoothing of wind power forecast errors is well-known for large areas. Comparable effects within a wind farm are investigated in this paper. A Neural Network was taken to predict the power output of a wind farm in north-western Germany comprising 17 turbines. A comparison was done between an algorithm that fits mean wind and mean power data of the wind farm and a second algorithm that fits wind and power data individually for each turbine. The evaluation of root mean square errors (RMSE) shows that relative small smoothing effects occur. However, it can be shown for this wind farm that individual calculations have the advantage that only a few turbines are needed to give better results than the use of mean data. Furthermore different results occurred if predicted wind speeds are directly fitted to observed wind power or if predicted wind speeds are first fitted to observed wind speeds and then applied to a power curve. The first approach gives slightly better RMSE values, the bias improves considerably

FUNCTIONAL AND NEUROMUSCULAR CHANGES IN THE HAMSTRINGS AFTER DROP JUMPS AND LEG CURLS

Directory of Open Access Journals (Sweden)

Nejc Sarabon

2013-09-01

Full Text Available The purpose of this study was to use a holistic approach to investigate changes in jumping performance, kinaesthesia, static balance, isometric strength and fast stepping on spot during a 5-day recovery period, following an acute bout of damaging exercise consisted of drop jumps and leg curls, where specific emphasis was given on the hamstring muscles. Eleven young healthy subjects completed a series of highly intensive damaging exercises for their hamstring muscles. Prior to the exercise, and during the 5-day recovery period, the subjects were tested for biochemical markers (creatine kinase, aspartate aminotransferase, and lactate dehydrogenase, perceived pain sensation, physical performance (squat jump, counter movement jump, maximal frequency leg stamping, maximal isometric torque production and maximally explosive isometric torque production, kinaesthesia (active torque tracking and static balance. We observed significant decreases in maximal isometric knee flexion torque production, the rate of torque production, and majority of the parameters for vertical jump performance. No alterations were found in kinaesthesia, static balance and fast stepping on spot. The highest drop in performance and increase in perceived pain sensation generally occurred 24 or 48 hours after the exercise. Damaging exercise substantially alters the neuromuscular functions of the hamstring muscles, which is specifically relevant for sports and rehabilitation experts, as the hamstrings are often stretched to significant lengths, in particular when the knee is extended and hip flexed. These findings are practically important for recovery after high-intensity trainings for hamstring muscles

Wind Power Today: 1998 Wind Energy Program Highlights

Energy Technology Data Exchange (ETDEWEB)

Tromly, K.

1999-06-17

The US Department of Energy's Office of Energy Efficiency and Renewable Energy manages the Federal Wind Energy Program. The mission of the program is to help the US wind industry to complete the research, testing, and field verification needed to fully develop advanced wind technologies that will lead the world in cost-effectiveness and reliability. This publication, printed annually, provides a summary of significant achievements in wind energy made during the previous calendar year. Articles include wind energy in the Midwest, an Alaskan wind energy project, the US certification program, structural testing, and the federal program in review.

Wind energy: Overcoming inadequate wind and modeling uncertainties

Energy Technology Data Exchange (ETDEWEB)

Kane, Vivek

2010-09-15

'Green Energy' is the call of the day, and significance of Wind Energy can never be overemphasized. But the key question here is - What if the wind resources are inadequate? Studies reveal that the probability of finding favorable wind at a given place on land is only 15%. Moreover, there are inherent uncertainties associated with wind business. Can we overcome inadequate wind resources? Can we scientifically quantify uncertainty and model it to make business sense? This paper proposes a solution, by way of break-through Wind Technologies, combined with advanced tools for Financial Modeling, enabling vital business decisions.

Structural Dynamic Behavior of Wind Turbines

Science.gov (United States)

Thresher, Robert W.; Mirandy, Louis P.; Carne, Thomas G.; Lobitz, Donald W.; James, George H. III

2009-01-01

The structural dynamicist s areas of responsibility require interaction with most other members of the wind turbine project team. These responsibilities are to predict structural loads and deflections that will occur over the lifetime of the machine, ensure favorable dynamic responses through appropriate design and operational procedures, evaluate potential design improvements for their impact on dynamic loads and stability, and correlate load and control test data with design predictions. Load prediction has been a major concern in wind turbine designs to date, and it is perhaps the single most important task faced by the structural dynamics engineer. However, even if we were able to predict all loads perfectly, this in itself would not lead to an economic system. Reduction of dynamic loads, not merely a "design to loads" policy, is required to achieve a cost-effective design. The two processes of load prediction and structural design are highly interactive: loads and deflections must be known before designers and stress analysts can perform structural sizing, which in turn influences the loads through changes in stiffness and mass. Structural design identifies "hot spots" (local areas of high stress) that would benefit most from dynamic load alleviation. Convergence of this cycle leads to a turbine structure that is neither under-designed (which may result in structural failure), nor over-designed (which will lead to excessive weight and cost).

SMES for wind energy systems

Science.gov (United States)

Paul Antony, Anish

copper oxide (BSCCO), Yttrium barium copper oxide (YBCO) and Magnesium diboride (MgB 2)] is carried out. The assessed attributes include superconducting transition temperature (Tc), critical current density (Jc ), the irreversibility field (H*) and the superconducting critical field (Hc). Chapter 4 presents the design of a solenoid shaped 1MJ MgB2 SMES. This SMES is used to mitigate the problem of momentary interruptions on a wind turbine. The total length of superconducting wire required for a 1MJ solenoid is calculated to be 21km. The maximum wire lengths currently available are 6km thus we hypothesize that either wire lengths have to be increased or work has to be done on MgB2 superconducting splice technology for multifilament wire. Another design consisting of 8 solenoids storing 120 kJ each is presented. The stress analysis on the proposed coil is performed using finite element analysis exhibiting the safety of the proposed design. Chapter 5 presents the design of a toroid shaped 20MJ MgB2 SMES. This is used to mitigate the problem of sustained interruptions on a wind turbine. The toroid coil is chosen since the magnetic field could be completely contained within the coil, thus reducing stray magnetic fields. A combination of genetic algorithm and nonlinear programming is used in determining the design. In Chapter 6, the different methods of operation of the SMES are examined. The Voltage Source Convertor (VSC) based SMES topology was chosen based on its ease of switching. The VSC switching strategy is based on a sinusoidal pulse width modulation technique. EMTDC/PSCAD software was used to demonstrate the efficacy of the VSC based SMES coupled to a wind turbine. The wind generator was modeled as an induction machine feeding into a load. The simulation results established that SMES connected to wind turbines improved output quality. Although the efficacy of SMES for wind energy has been stated previously in other work, this chapter specifically demonstrates through

Operation Design of Wind Turbines in Strong Wind Conditions

DEFF Research Database (Denmark)

Shen, Wen Zhong; Montes, Melissa Barroso; Odgaard, Peter Fogh

2012-01-01

and variable speed pitch regulated wind turbines. The variable speed design is more suitable for wind turbines to run at very high wind speeds which can help the turbine braking system to stop the turbine at the new "cut-out" wind speed. Reference power, rotational speed and pitch angle have been designed...... optimally. In order to reduce the possible increased loading, fatigue due to the wind gusts, control strategies have been considered for both constant sped and variable speed pitch regulated wind turbines. The control study shows that the designed controllers can reduce the standard deviations efficiently......In order to reduce the impact on the electrical grid from the shutdown of MW wind turbines at wind speeds higher than the cut-out wind speed of 25 m/s, we propose in this paper to run the turbines at high wind speeds up to 40 m/s. Two different operation designs are made for both constant speed...

Turbulent oscillating channel flow subjected to a free-surface stress.

NARCIS (Netherlands)

Kramer, W.; Clercx, H.J.H.; Armenio, V.

2010-01-01

The channel flow subjected to a wind stress at the free surface and an oscillating pressure gradient is investigated using large-eddy simulations. The orientation of the surface stress is parallel with the oscillating pressure gradient and a purely pulsating mean flow develops. The Reynolds number

Endurance Wind Power : practical insights into small wind

International Nuclear Information System (INIS)

Hicks, D.

2008-01-01

This presentation discussed practical issues related to purchasing and installing small wind turbines in Canada. Wind power capacity can be estimated by looking at provincial wind maps as well as by seeking wind data at local airports. Wind resources are typically measured at heights of between 20 meters and 50 m. The height of a wind turbine tower can significantly increase the turbine's wind generating capacity. Turbine rotors should always be placed 30 feet higher than obstacles within 500 feet. Many provinces have now mandated utilities to accept renewable energy resources from grid-connected wind energy plants. Net billing systems are used to determine the billing relationship between power-producing consumers and the utilities who will buy the excess power and sell it to other consumers. Utilities are not yet mandated to purchase excess power, and it is likely that federal and provincial legislation will be needed to ensure that net billing systems continue to grow. Many Canadian municipalities have no ordinances related to wind turbine placements. Consumers interested in purchasing small wind turbines should ensure that the turbine has been certified by an accredited test facility and has an adequate safety system. The noise of the turbine as well as its power performance in relation to the purchaser's needs must also be considered. It was concluded that small wind turbines can provide a means for electricity consumers to reduce their carbon footprint and hedge against the inflationary costs of fossil-fuelled energy resources. tabs., figs

Operation and control of large wind turbines and wind farms

Energy Technology Data Exchange (ETDEWEB)

Soerensen, Poul; Hansen, Anca D.; Thomsen, Kenneth (and others)

2005-09-01

This report is the final report of a Danish research project 'Operation and control of large wind turbines and wind farms'. The objective of the project has been to analyse and assess operational strategies and possibilities for control of different types of wind turbines and different wind farm concepts. The potentials of optimising the lifetime/energy production ratio by means of using revised operational strategies for the individual wind turbines are investigated. Different strategies have been simulated, where the power production is decreased to an optimum when taking loads and actual price of produced electricity into account. Dynamic models and control strategies for the wind farms have also been developed, with the aim to optimise the operation of the wind farms considering participation in power system control of power (frequency) and reactive power (voltage), maximise power production, keep good power quality and limit mechanical loads and life time consumption. The project developed models for 3 different concepts for wind farms. Two of the concepts use active stall controlled wind turbines, one with AC connection and one with modern HVDC/VSC connection of the wind farm. The third concept is based on pitch controlled wind turbines using doubly fed induction generators. The models were applied to simulate the behaviour of the wind farm control when they were connected to a strong grid, and some initial simulations were performed to study the behaviour of the wind farms when it was isolated from the main grid on a local grid. Also the possibility to use the available information from the wind turbine controllers to predict the wind speed has been investigated. The main idea has been to predict the wind speed at a wind turbine using up-wind measurements of the wind speed in another wind turbine. (au)

VisibleWind: wind profile measurements at low altitude

Science.gov (United States)

Wilkerson, Tom; Bradford, Bill; Marchant, Alan; Apedaile, Tom; Wright, Cordell

2009-09-01

VisibleWindTM is developing an inexpensive rapid response system, for accurately characterizing wind shear and small scale wind phenomena in the boundary layer and for prospecting suitable locations for wind power turbines. The ValidWind system can also collect reliable "ground truth" for other remote wind sensors. The system employs small (0.25 m dia.) lightweight balloons and a tracker consisting of an Impulse 200 XL laser rangefinder coupled to a PC for automated data recording. Experiments on balloon trajectories demonstrate that the laser detection of range (+/- 0.5 m), together with measured azimuth and altitude, is an inexpensive, convenient, and capable alternative to other wind tracking methods. The maximum detection range has been increased to 2200 meters using micro-corner-cube retroreflector tape on balloons. Low power LEDs enable nighttime tracking. To avoid large balloon gyrations about the mean trajectory, we use balloons having low ascent rates and subcritical Reynolds numbers. Trajectory points are typically recorded every 4 - 7 seconds. Atmospheric features observed under conditions of inversions or "light and variable winds" include abrupt onsets of shear at altitudes of 100-250 m, velocity changes of order 1-3 m/s within layers of 10-20 m thickness, and veering of the wind direction by 180 degrees or more as altitude increases from 300 to 500 m. We have previously reported comparisons of balloon-based wind profiles with the output of a co-located sodar. Even with the Impulse rangefinder, our system still requires a "man in the loop" to track the balloon. A future system enhancement will automate balloon tracking, so that laser returns are obtained automatically at 1 Hz. While balloon measurements of large-scale, high altitude wind profiles are well known, this novel measurement system provides high-resolution, real-time characterization of the fluctuating local wind fields at the bottom of the boundary layer where wind power turbines and other

On the impact of multi-axial stress states on trailing edge bondlines in wind turbine rotor blades

OpenAIRE

Castelos, Pablo Noever; Balzani, Claudio

2016-01-01

For a reliable design of wind turbine systems all of their components have to be designed to withstand the loads appearing in the turbine's lifetime. When performed in an integral manner this is called systems engineering, and is exceptionally important for components that have an impact on the entire wind turbine system, such as the rotor blade. Bondlines are crucial subcomponents of rotor blades, but they are not much recognized in the wind energy research community. However, a bondline fai...

Full-scale investigation of wind-induced vibrations of mast-arm traffic signal structures.

Science.gov (United States)

2014-08-01

Because of their inherent : fl : exibility and low damping ratios, cantilevered mast : - : arm : tra : ffi : c signal structures are suscepti : b : le to : wind : - : induced vibrations. : These vibrations : cause stru : ctural stresses and strains t...

Wind Power Meteorology

DEFF Research Database (Denmark)

Lundtang Petersen, Erik; Mortensen, Niels Gylling; Landberg, Lars

Wind power meteorology has evolved as an applied science, firmly founded on boundary-layer meteorology, but with strong links to climatology and geography. It concerns itself with three main areas: siting of wind turbines, regional wind resource assessment, and short-term prediction of the wind...... resource. The history, status and perspectives of wind power meteorology are presented, with emphasis on physical considerations and on its practical application. Following a global view of the wind resource, the elements of boundary layer meteorology which are most important for wind energy are reviewed......: wind profiles and shear, turbulence and gust, and extreme winds. The data used in wind power meteorology stem mainly from three sources: onsite wind measurements, the synoptic networks, and the re-analysis projects. Wind climate analysis, wind resource estimation and siting further require a detailed...

On the Decrease of the Oceanic Drag Coefficient in High Winds

Science.gov (United States)

Donelan, Mark A.

2018-02-01

The sheltering coefficient - prefixing Jeffreys' concept of the exponential wave growth rate at a gas-liquid interface - is shown to be Reynolds number dependent from laboratory measurements of waves and Reynolds stresses. There are two turbulent flow regimes: wind speed range of 2.5 to 30 m/s where the drag coefficients increase with wind speed, and wind speed range of 30 to 50 m/s where sheltering/drag coefficients decrease/saturate with wind speed. By comparing model calculations of drag coefficients - using a fixed sheltering coefficient - with ocean observations over a wind speed range of 1 to 50 m/s a similar Reynolds number dependence of the oceanic sheltering coefficient is revealed. In consequence the drag coefficient is a function of Reynolds number and wave age, and not just wind speed as frequently assumed. The resulting decreasing drag coefficient above 30 m/s is shown to be critical in explaining the rapid intensification so prominent in the climatology of Atlantic hurricanes. The Reynolds number dependence of the sheltering coefficient, when employed in coupled models, should lead to significant improvements in the prediction of intensification and decay of tropical cyclones. A calculation of curvature at the wave crest suggests that at wind speeds above 56.15 m/s all waves-breaking or not-induce steady flow separation leading to a minimum in the drag coefficient. This is further evidence of the veracity of the observations of the oceanic drag coefficient at high winds.

Remote Sensing Wind and Wind Shear System.

Science.gov (United States)

Contents: Remote sensing of wind shear and the theory and development of acoustic doppler; Wind studies; A comparison of methods for the remote detection of winds in the airport environment; Acoustic doppler system development; System calibration; Airport operational tests.

Wind for Schools: A Wind Powering America Project

Science.gov (United States)

US Department of Energy, 2007

2007-01-01

The U.S. Department of Energy's (DOE's) Wind Powering America program (based at the National Renewable Energy Laboratory) sponsors the Wind for Schools Project to raise awareness in rural America about the benefits of wind energy while simultaneously educating college seniors regarding wind energy applications. The three primary project goals of…

Load alleviation on wind turbine blades using variable airfoil geometry

Energy Technology Data Exchange (ETDEWEB)

Basualdo, S.

2005-03-01

A two-dimensional theoretical study of the aeroelastic behaviour of an airfoil has been performed, whose geometry can be altered using a rear-mounted flap. This device is governed by a controller, whose objective is to reduce the airfoil displacements and, therefore, the stresses present in a real blade. The aerodynamic problem was solved numerically by a panel method using the potential theory, suitable for modelling attached flows. It is therefore mostly applicable for Pitch Regulated Variable Speed (PRVS) wind turbines, which mainly operate under this flow condition. The results show evident reductions in the airfoil displacements by using simple control strategies having the airfoil position and its first and second derivatives as input, especially at the system's eigenfrequency. The use of variable airfoil geometry is an effective means of reducing the vibration magnitudes of an airfoil that represents a section of a wind turbine blade, when subject to stochastic wind signals. The results of this investigation encourage further investigations with 3D aeroelastic models to predict the reduction in loads in real wind turbines. (author)

A simulation environment for assisting system design of coherent laser doppler wind sensor for active wind turbine pitch control

Science.gov (United States)

Shinohara, Leilei; Pham Tran, Tuan Anh; Beuth, Thorsten; Umesh Babu, Harsha; Heussner, Nico; Bogatscher, Siegwart; Danilova, Svetlana; Stork, Wilhelm

2013-05-01

In order to assist a system design of laser coherent Doppler wind sensor for active pitch control of wind turbine systems (WTS), we developed a numerical simulation environment for modeling and simulation of the sensor system. In this paper we present this simulation concept. In previous works, we have shown the general idea and the possibility of using a low cost coherent laser Doppler wind sensing system for an active pitch control of WTS in order to achieve a reduced mechanical stress, increase the WTS lifetime and therefore reduce the electricity price from wind energy. Such a system is based on a 1.55μm Continuous-Wave (CW) laser plus an erbium-doped fiber amplifier (EDFA) with an output power of 1W. Within this system, an optical coherent detection method is chosen for the Doppler frequency measurement in megahertz range. A comparatively low cost short coherent length laser with a fiber delay line is used for achieving a multiple range measurement. In this paper, we show the current results on the improvement of our simulation by applying a Monte Carlo random generation method for positioning the random particles in atmosphere and extend the simulation to the entire beam penetrated space by introducing a cylindrical co-ordinate concept and meshing the entire volume into small elements in order to achieve a faster calculation and gain more realistic simulation result. In addition, by applying different atmospheric parameters, such as particle sizes and distributions, we can simulate different weather and wind situations.

A zero torsional stiffness twist morphing blade as a wind turbine load alleviation device

International Nuclear Information System (INIS)

Lachenal, X; Daynes, S; Weaver, P M

2013-01-01

This paper presents the design, analysis and realization of a zero stiffness twist morphing wind turbine blade. The morphing blade is designed to actively twist as a means of alleviating the gust loads which reduce the fatigue life of wind turbine blades. The morphing structure exploits an elastic strain energy balance within the blade to enable large twisting deformations with modest actuation requirements. While twist is introduced using the warping of the blade skin, internal pre-stressed members ensure that a constant strain energy balance is achieved throughout the deformation, resulting in a zero torsional stiffness structure. The torsional stability of the morphing blade is characterized by analysing the elastic strain energy in the device. Analytical models of the skin, the pre-stressed components and the complete blade are compared to their respective finite element models as well as experimental results. The load alleviation potential of the adaptive structure is quantified using a two-dimensional steady flow aerodynamic model which is experimentally validated with wind tunnel measurements. (paper)

Wind induced fatigue of slender light weight structures in structural dynamics

NARCIS (Netherlands)

Staalduinen, P.C. van; Courage, W.M.G.

1996-01-01

The paper presents a simplified analytical method for calculating the stress ranges in light weight slender structures due to wind loading. The background and assumptions of the method have been explained as well as the derivation of the relevant formula. The application of the simplified method on

An advanced structural trailing edge modelling method for wind turbine blades

DEFF Research Database (Denmark)

Haselbach, Philipp Ulrich

2017-01-01

to ultimate loads. The prediction accuracy of the numerical simulations was compared to a certification load case and a full-scale ultimate limit state test of a 34 m wind turbine rotor blade. The displacements, stresses and strains show reasonably good agreement and demonstrate the capabilities...

Control Strategies for Smoothing of Output Power of Wind Energy Conversion Systems

Science.gov (United States)

Pratap, Alok; Urasaki, Naomitsu; Senju, Tomonobu

2013-10-01

This article presents a control method for output power smoothing of a wind energy conversion system (WECS) with a permanent magnet synchronous generator (PMSG) using the inertia of wind turbine and the pitch control. The WECS used in this article adopts an AC-DC-AC converter system. The generator-side converter controls the torque of the PMSG, while the grid-side inverter controls the DC-link and grid voltages. For the generator-side converter, the torque command is determined by using the fuzzy logic. The inputs of the fuzzy logic are the operating point of the rotational speed of the PMSG and the difference between the wind turbine torque and the generator torque. By means of the proposed method, the generator torque is smoothed, and the kinetic energy stored by the inertia of the wind turbine can be utilized to smooth the output power fluctuations of the PMSG. In addition, the wind turbines shaft stress is mitigated compared to a conventional maximum power point tracking control. Effectiveness of the proposed method is verified by the numerical simulations.

Study on Unified Chaotic System-Based Wind Turbine Blade Fault Diagnostic System

Science.gov (United States)

Kuo, Ying-Che; Hsieh, Chin-Tsung; Yau, Her-Terng; Li, Yu-Chung

At present, vibration signals are processed and analyzed mostly in the frequency domain. The spectrum clearly shows the signal structure and the specific characteristic frequency band is analyzed, but the number of calculations required is huge, resulting in delays. Therefore, this study uses the characteristics of a nonlinear system to load the complete vibration signal to the unified chaotic system, applying the dynamic error to analyze the wind turbine vibration signal, and adopting extenics theory for artificial intelligent fault diagnosis of the analysis signal. Hence, a fault diagnostor has been developed for wind turbine rotating blades. This study simulates three wind turbine blade states, namely stress rupture, screw loosening and blade loss, and validates the methods. The experimental results prove that the unified chaotic system used in this paper has a significant effect on vibration signal analysis. Thus, the operating conditions of wind turbines can be quickly known from this fault diagnostic system, and the maintenance schedule can be arranged before the faults worsen, making the management and implementation of wind turbines smoother, so as to reduce many unnecessary costs.

Wind generator with electronic variable-speed drives

Energy Technology Data Exchange (ETDEWEB)

David, A.; Buchheit, N.; Jakobsen, H.

1996-12-31

Variable speed drives have been inserted between the network and the generator on certain recent wind power facilities. They have the following advantages: the drive allows the wind generator to operate at low speed with a significant reduction in acoustic noise, an important point if the facilities are sited near populated areas; the drive optimizes energy transfer, providing a gain of 4 to 10 %; the drive can possibly replace certain mechanical parts (the starting system and it in some cases, the reduction gear); the drive not only provides better transient management in relation to the network for less mechanical stress on the wind generator, it is also able to control reactive power. One commercial drive design sold by several manufacturers has already been installed on several wind generators with outputs of between 150 and 600 kw. In addition, such a solution is extremely well suited to mixed renewable energy systems. This design uses two inverse rectifier type converters and can therefore exchange energy in both directions. The equivalent drive with a single IGBT converter on the motor side and a diode converter on the network side is the solution most widely adopted throughout industry (with more than 50, 000 units installed in France per year). It still remains to be seen whether such a solution could be profitable in wind generator application (since the cost of the drive is quite high). This technical analysis is more destined for the converter-machine assembly specialists and is presented in this document, paying particular attention as it does to the modelling of the `wind energy - generator - drive - network` assembly, the associated drive command and control strategies and the simulations obtained during various transients. A 7.5 kW test bed has been installed in the Laboratoire d`Electronique de Puissance de Clamart, enabling tests to be carried out which emulate the operation of a wind generator.

Microplastics in a wind farm area: A case study at the Rudong Offshore Wind Farm, Yellow Sea, China.

Science.gov (United States)

Wang, Teng; Zou, Xinqing; Li, Baojie; Yao, Yulong; Li, Jiasheng; Hui, Hejiu; Yu, Wenwen; Wang, Chenglong

2018-03-01

Despite the rapid construction of offshore wind farms, the available information regarding the risks of this type of development in terms of emerging pollutants, particularly microplastics, is scarce. In this study, we quantified the level of microplastic pollution at an offshore wind farm in the Yellow Sea, China, in 2016. The abundance of microplastics was 0.330 ± 0.278 items/m 3 in the surface water and 2.58 ± 1.14 items/g (dry) in the sediment. To the best of our knowledge, the level of microplastic pollution in our study area was slightly higher than that in coastal areas around the world. The microplastics detected in the surface waters and sediments were mainly fibrous (75.3% and 68.7%, respectively) and consisted of some granules and films. The microplastics in the samples might originate from garments or ropes via wastewater discharge. The abundance of plastic in the water and sediment samples collected from the wind farm area was lower than that in the samples collected from outside the wind farm area. The anthropogenic hydrodynamic effect was the main factor affecting the local distribution of microplastics. The presence of a wind farm could increase the bed shear stress during ebb tide, disturbing the bed sediment, facilitating its initiation and transport, and ultimately increasing the ease of washing away the microplastics adhered to the sediment. This study will serve as a reference for further studies of the distribution and migration of microplastics in coastal zones subjected to similar marine utilization. Copyright © 2018 Elsevier Ltd. All rights reserved.

Offshore wind resource estimation for wind energy

DEFF Research Database (Denmark)

Hasager, Charlotte Bay; Badger, Merete; Mouche, A.

2010-01-01

Satellite remote sensing from active and passive microwave instruments is used to estimate the offshore wind resource in the Northern European Seas in the EU-Norsewind project. The satellite data include 8 years of Envisat ASAR, 10 years of QuikSCAT, and 23 years of SSM/I. The satellite observati......Satellite remote sensing from active and passive microwave instruments is used to estimate the offshore wind resource in the Northern European Seas in the EU-Norsewind project. The satellite data include 8 years of Envisat ASAR, 10 years of QuikSCAT, and 23 years of SSM/I. The satellite...... observations are compared to selected offshore meteorological masts in the Baltic Sea and North Sea. The overall aim of the Norsewind project is a state-of-the-art wind atlas at 100 m height. The satellite winds are all valid at 10 m above sea level. Extrapolation to higher heights is a challenge. Mesoscale...... modeling of the winds at hub height will be compared to data from wind lidars observing at 100 m above sea level. Plans are also to compare mesoscale model results and satellite-based estimates of the offshore wind resource....

Wind Observatory 2017. Analysis of the wind power market, wind jobs and future of the wind industry in France

International Nuclear Information System (INIS)

2017-09-01

Two years after the enactment of the Energy Transition for Green Growth Act, wind power capacity continues to grow in France, exceeding 12 GWatt the end of 2016 and soon to account for 5% of France's electric power consumption. This vitality, which is set to continue in 2017, will help France achieve its objectives of an installed capacity of 15,000 MW in onshore wind by 2018 and 21,800 to 26,000 MW by 2023. The current pace will nevertheless have to be accelerated in order to reach the realistic objective of 26 GW by 2023 mentioned in the multi-annual energy plan (PPE). With 1,400 jobs created in one year and more than 3,300 over the last two years, the relevance of wind power as a driving force of sustainable job creation throughout the country is unequivocally confirmed: the increase in wind power capacity continues to contribute to the growth in employment in the country. Prepared in collaboration with the consulting firm BearingPoint, the 2017 edition of the Observatory aims to give the reader an overview of employment in the wind industry and the wind power market over the period under consideration. Any changes from the three previous editions are highlighted. It is based on a comprehensive census of all market participants on three themes: employment, the market and the future of wind power. The Observatory gives an accurate picture of how the wind energy industry is structured, thereby presenting a precise overview of the wind energy industry and all its components

Extreme wind estimate for Hornsea wind farm

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo

The purpose of this study is to provide estimation of the 50-year winds of 10 min and 1-s gust value at hub height of 100 m, as well as the design parameter shear exponent for the Hornsea offshore wind farm. The turbulence intensity required for estimating the gust value is estimated using two...... approaches. One is through the measurements from the wind Doppler lidar, WindCube, which implies serious uncertainty, and the other one is through similarity theory for the atmospheric surface layer where the hub height is likely to belong to during strong storms. The turbulence intensity for storm wind...... strength is taken as 0.1. The shear exponents at several heights were calculated from the measurements. The values at 100 m are less than the limit given by IEC standard for all sectors. The 50-year winds have been calculated from various global reanalysis and analysis products as well as mesoscale models...

Molecular evidence for the occurrence of tomato leaf curl New Delhi virus on chayote (Sechium edule) in southern India.

Science.gov (United States)

Nagendran, K; Mohankumar, S; Mohammed Faisal, P; Bagewadi, B; Karthikeyan, G

2017-12-01

During 2012-2014, mosaic disease on chayote in the farmers field of Kodaikanal region (high altitude zone) of Tamil Nadu was observed. The disease was characterized with severe mosaic, cupping and enation on leaves with reduced fruit size. Disease was found to causes an yield loss of more than 60% with the maximum disease incidence of 100% for the past 5 years consecutively. Preliminary serological and molecular screening indicated the association of begomovirus with the disease. Complete nucleotide sequence and phylogenetic analysis of DNA A revealed the identity of the virus as tomato leaf curl New Delhi virus (ToLCNDV). In recombination analysis study, the major parent was identified as ToLCNDV from Pakistan infecting tomato. Thus the present finding confirms expansion of new geographical region and host for ToLCNDV causing mosaic disease on chayote from Tamil Nadu. To our knowledge this is the first confirmed report for the occurrence of ToLCNDV on chayote in southern India.

Optimization design of spar cap layup for wind turbine blade

Institute of Scientific and Technical Information of China (English)

2012-01-01

Based on the aerodynamic shape and structural form of the blade are fixed,a mathematical model of optimization design for wind turbine blade is established.The model is pursued with respect to minimum the blade mass to reduce the cost of wind turbine production.The material layup numbers of the spar cap are chosen as the design variables;while the demands of strength,stiffness and stability of the blade are employed as the constraint conditions.The optimization design for a 1.5 MW wind turbine blade is carried out by combing above objective and constraint conditions at the action of ultimate flapwise loads with the finite element software ANSYS.Compared with the original design,the optimization design result achieves a reduction of 7.2% of the blade mass,the stress and strain distribution of the blade is more reasonable,and there is no occurrence of resonance,therefore its effectiveness is verified.

Evaluation model of wind energy resources and utilization efficiency of wind farm

Science.gov (United States)

Ma, Jie

2018-04-01

Due to the large amount of abandoned winds in wind farms, the establishment of a wind farm evaluation model is particularly important for the future development of wind farms In this essay, consider the wind farm's wind energy situation, Wind Energy Resource Model (WERM) and Wind Energy Utilization Efficiency Model(WEUEM) are established to conduct a comprehensive assessment of the wind farm. Wind Energy Resource Model (WERM) contains average wind speed, average wind power density and turbulence intensity, which assessed wind energy resources together. Based on our model, combined with the actual measurement data of a wind farm, calculate the indicators using the model, and the results are in line with the actual situation. We can plan the future development of the wind farm based on this result. Thus, the proposed establishment approach of wind farm assessment model has application value.

Wind Turbines Adaptation to the Variability of the Wind Field

Science.gov (United States)

Ulianov, Yuriy; Martynenko, Gennadii; Misaylov, Vitaliy; Soliannikova, Iuliia

2010-05-01

WIND TURBINES ADAPTATION TO THE VARIABILITY OF THE WIND FIELD The subject of our scientific research is wind power turbines (WPT) with the horizontal axis which were now common in the world. Efficient wind turbines work is largely determined by non-stationarity of the wind field, expressed in its gustiness, the presence of vertical and horizontal shifts of wind speed and direction. At critical values of the wind parameters WPT has aerodynamic and mechanical overload, leading to breakdowns, premature wear and reduce the life of the wind turbine. To prevent accidents at the peak values of wind speed it is used the regulatory system of windwheels. WPT control systems provide a process orientation of the wind turbine rotor axis in the line of the mean wind. Wind turbines are also equipped with braking device used to protect against breakdowns when a significant increase in the wind. In general, all these methods of regulation are not always effective. Thus, in practice there may be situations when the wind speed is many times greater than the stated limit. For example, if there are microbursts in the atmospheric boundary layer, low-level wind shears caused by its gust front, storms, etc. It is required for a wind power turbine adaptation to intensive short-term wind impulses and considerable vertical wind shifts that the data about them shall be obtained ahead of time. To do this it is necessary to have the information on the real structure of the wind field in the area of the blade sweep for the minimum range against the wind that is determined by the mean speed and the system action time. The implementation of acoustic and laser traditional wind sounding systems is limited by ambient acoustic noise, by heavy rain, snowfall and by fog. There are free of these disadvantages the inclined radioacoustic sounding (IRASS) technique which works for a system of remote detection and control of wind gusts. IRASS technique is realized as low-potential Doppler pulse radar

Evolution and Reduction of Scour around Offshore Wind Turbines

Science.gov (United States)

McGovern, David; Ilic, Suzana

2010-05-01

Evolution and Reduction of Scour around Offshore Wind Turbines In response to growing socio-economic and environmental demands, electricity generation through offshore wind turbine farms is a fast growing sector of the renewable energy market. Considerable numbers of offshore wind farms exist in the shallow continental shelf seas of the North-West Europe, with many more in the planning stages. Wind energy is harnessed by large rotating blades that drive an electricity generating turbine placed on top of a long cylindrical monopile that are driven into the sea-bed, well into the bed rock below the sediment. Offshore wind turbines are popular due to consistently higher wind speeds and lower visual impact than their onshore counter parts, but their construction and maintenance is not without its difficulties. The alteration of flow by the presence of the wind turbine monopile results in changes in sedimentary processes and morphology at its base. The increase in flow velocity and turbulence causes an amplification of bed shear stress and this can result in the creation of a large scour hole at the monopile base. Such a scour hole can adversely affect the structural integrity and hence longevity of the monopile. Changes to the sea bed caused by this may also locally affect the benthic habitat. We conducted an extensive series of rigid and mobile bed experiments to examine the process of scour under tidal currents. We also test the effectiveness of a flow-altering collared monopile in reducing scour. Firstly, we used Particle Image Velocimetry (PIV) and Acoustic Doppler Velocimetry (ADV) to visualise and analyse the flow and turbulence properties in the local flow around the monopile and collared monopile over a smooth rigid bed under tidal flow. The measured flow, turbulence and shear stress properties are related to mobile bed tests where a Seatek 5 MHz Ultrasonic Ranging system is used to identify the evolution of scour under reversing tidal currents. The tidal

Wear Resistance Performance of Conventional and Non-Conventional Wind Turbine Blades with TiN Nano-Coating

Directory of Open Access Journals (Sweden)

Muhammad Hasibul Hasan

2017-09-01

Full Text Available Efficiency and durability are critical issues that affect widely-adopted aerofoil-power generator as a sustainable source of electrical power. Even though high wind power density can be achieved; installing wind turbines in desert condition has difficulties including thermal variation, high turbulence and sand storms. Sand blasting on turbine blade surface at high velocities causes erosion resulting turbine efficiency drop. Damage-induced erosion phenomena and aeroelastic performance of the blades needed to be investigated. Suitable coating may prevent erosion to a great extent. A numerical investigation of erosion on NACA 4412 wind turbine blade has been performed using commercial computational fluid dynamics software ANSYS FLUENT 14.5 release. Discrete phase model (DPM has been used for modelling multi-phase flow of air and sand particles over the turbine blade. Governing equations have been solved by finite volume method (FVM. Conventional 30-70% glass fibre resin and non-conventional jute fibre composite have been used as turbine blade material. Sand particles of  diameter have been injected from 20, 30, 45, 60 and 90 degree angles at 500C temperature. Erosion rate, wall shear stress and strain rate have been calculated for different wind velocities and impingement angles. Simulation results for higher velocities deviate from the results observed at lower wind velocities. In simulation, erosion rate is highest for impingement angle at low wind velocities, which has been validated by experiment with a mean absolute error (MAE of 5.56%. Erosion rate and wall shear stress are higher on jute composite fibre than glass fibre resin. Developed shear stress on wind turbine blade surface is highest for  impingement angle at all velocities. On the other hand, exerted pressure on turbine blade surface is found highest for 9  angle of attack. Experimental results, with or without Titanium nitride(TiN nano-coating, also revealed that surface roughness

Investigation of Wind Turbine Rotor Concepts for Offshore Wind Farms

International Nuclear Information System (INIS)

Ceyhan, Özlem; Grasso, Francesco

2014-01-01

Current plans in offshore wind energy developments call for further reduction of cost of energy. In order to contribute to this goal, several wind turbine rotor concepts have been investigated. Assuming the future offshore wind turbines will operate only in the offshore wind farms, the rotor concepts are not only evaluated for their stand-alone performances and their potential in reducing the loads, but also for their performance in an offshore wind farm. In order to do that, the 10MW reference wind turbine designed in Innwind.EU project is chosen as baseline. Several rotor parameters have been modified and their influences are investigated for offshore wind turbine design purposes. This investigation is carried out as a conceptual parametrical study. All concepts are evaluated numerically with BOT (Blade optimisation tool) software in wind turbine level and with Farmflow software in wind farm level for two wind farm layouts. At the end, all these concepts are compared with each other in terms of their advantages and disadvantages

An improved excitation control technique of three-phase induction machine operating as dual winding generator for micro-wind domestic application

International Nuclear Information System (INIS)

Chatterjee, Arunava; Chatterjee, Debashis

2015-01-01

Highlights: • A three-phase induction machine working as single phase generator is studied. • The generator is assisted by an inverter and photovoltaic panel for excitation. • Proposed control involves operating the machine as balanced two-phase generator. • Torque pulsations associated with unbalanced phase currents are minimized. • The generator can be used for grid-isolated micro-wind power generation. - Abstract: Single-phase generation schemes are widely utilized for harnessing wind power in remote and grid secluded applications. This paper presents a novel control methodology for a three-phase induction machine working as a single-phase dual winding induction generator. Three-phase induction machines providing single-phase output with proper control strategy can be beneficial in grid secluded micro-wind energy conversion systems compared to single-phase induction generators. Three-phase induction machines operating in single-phase mode are mostly excited asymmetrically to provide single-phase power leading to unbalanced current flow in the stator windings causing heating and insulation breakdown. The asymmetrical excitation also initiates torque pulsations which results in additional stress and vibration at the machine shaft and bearings degrading the machine performance. The proposed control is chiefly aimed to minimize this unbalance. The variable excitation required for the proposed generator is provided through a single-phase inverter with photovoltaic panels. The suitability for such a generator along with its control is tested with appropriate simulations and experimental results. The induction generator with the proposed control strategy is expected to be useful in remote and grid isolated households as a standalone source of single-phase electrical power

Development of an Integrated Water and Wind Erosion Model

Science.gov (United States)

Flanagan, D. C.; Ascough, J. C.; Wagner, L. E.; Geter, W. F.

2006-12-01

Prediction technologies for soil erosion by the forces of wind or water have largely been developed independently from one another, especially within the United States. Much of this has been due to the initial creation of equations and models which were empirical in nature (i.e., Universal Soil Loss Equation, Wind Erosion Equation) and based upon separate water erosion or wind erosion plot and field measurements. Additionally, institutional organizations in place typically divided research efforts and funding to unique wind or water erosion research and modeling projects. However, during the past 20 years computer technologies and erosion modeling have progressed to the point where it is now possible to merge physical process-based computer simulation models into an integrated water and wind erosion prediction system. In a physically- based model, many of the processes which must be simulated for wind and water erosion computations are the same, e.g., climate, water balance, runoff, plant growth, etc. Model components which specifically deal with the wind or water detachment, transport and deposition processes are those that must differ, as well as any necessary parameterization of input variables (e.g., adjusted soil erodibilities, critical shear stresses, etc.) for those components. This presentation describes current efforts towards development of a combined wind and water erosion model, based in part upon technologies present in the Water Erosion Prediction Project (WEPP) and the Wind Erosion Prediction System (WEPS) models. Initial efforts during the past two years have resulted in modular modeling components that allow for prediction of infiltration, surface runoff, and water erosion at a hillslope scale within an Object Modeling System. Additional components currently in development include wind detachment at a single field point, continuous water balance, and unified plant growth. Challenges in this project are many, and include adequate field

Wind of opportunity

International Nuclear Information System (INIS)

Jamieson, Peter

1999-01-01

This article traces the move towards the offshore exploitation of wind energy in Europe, and presents information on existing offshore wind energy projects and proposed wind turbine prototypes for offshore operation. The building of the first major offshore wind project at Vindeby, the use of rock socketed monopile foundations for pile drilling and erection of the wind turbines from a mobile jack-up barge, the costs of wind turbines, the fatigue loads on the support structures due to the wind loading, and the offshore wind market in the UK and Europe are discussed. (UK)

Wind Atlas of Bay of Bengal with Satellite Wind Measurement

DEFF Research Database (Denmark)

Nadi, Navila Rahman

footstep towards offshore wind energy analysis for this region. Generally, it is difficult to find offshore wind data relative to the wind turbine hub heights, therefore a starting point is necessary to identify the possible wind power density of the region. In such scenario, Synthetic aperture radars (SAR......The objective of this study is to obtain appropriate offshore location in the Bay of Bengal, Bangladesh for further development of wind energy. Through analyzing the previous published works, no offshore wind energy estimation has been found here. That is why, this study can be claimed as the first......) have proven useful. In this study, SAR based dataset- ENVISAT ASAR has been used for Wind Atlas generation. Furthermore, a comparative study has been performed with Global Wind Atlas (GWA) to determine a potential offshore wind farm. Additionally, the annual energy production of that offshore windfarm...

Connection between wind turbine noise and health effects. Prepared for the National Board of Health, Denmark; Sammenhaeng mellem vindmoellestoej og helbredseffekter. Udfoert for Sundhedsstyrelsen

Energy Technology Data Exchange (ETDEWEB)

Holm Pedersen, T.

2011-03-15

The purpose of this report is, through a limited literature study, to elucidate the direct and probable indirect health effects due to wind turbine noise / vibrations / shadow effect. It is shown that the wind turbine noise's character is not substantially different from many other sources of noise in our daily lives. The sound levels are rather low, seen in relation to the sound impacts that we normally are exposed to, and that also includes low-frequency noise. Audible infrasound does not occur. Noise annoyance is the most significant effect of noise from wind turbines. The noise annoyance from wind turbines is greater than from road traffic at the same level of noise. At the noise limit of 39 dB for noise-sensitive land use one must expect that for wind turbines about 10% is highly annoying. Sleep disorders can occur. There is a sharp increase in the percentage of sleep disorders just above the noise limits. There was not found a direct correlation between stress and noise. By contrast, significant correlations between stress symptoms and noise nuisance are found. Existing studies show no significant correlations to chronic diseases, diabetes, high blood pressure and cardiovascular diseases. The literature reports on phenomenon called vibro-acoustic diseases and wind turbine syndrome, without, however, a proven causal dose-response relationship or without conducted studies where it is compared to control groups. These phenomena are not considered real for wind turbines. On the present basis, there are no demonstrated direct health effects due to wind turbine noise, though there are observed correlation between noise and stress symptoms Shadows from the rotating blades are annoying, but cannot induce epileptic attacks. (LN)

Connection between wind turbine noise and health effects. Prepared for the National Board of Health, Denmark; Sammenhaeng mellem vindmoellestoej og helbredseffekter. Udfoert for Sundhedsstyrelsen

Energy Technology Data Exchange (ETDEWEB)

Holm Pedersen, T

2011-03-15

The purpose of this report is, through a limited literature study, to elucidate the direct and probable indirect health effects due to wind turbine noise / vibrations / shadow effect. It is shown that the wind turbine noise's character is not substantially different from many other sources of noise in our daily lives. The sound levels are rather low, seen in relation to the sound impacts that we normally are exposed to, and that also includes low-frequency noise. Audible infrasound does not occur. Noise annoyance is the most significant effect of noise from wind turbines. The noise annoyance from wind turbines is greater than from road traffic at the same level of noise. At the noise limit of 39 dB for noise-sensitive land use one must expect that for wind turbines about 10% is highly annoying. Sleep disorders can occur. There is a sharp increase in the percentage of sleep disorders just above the noise limits. There was not found a direct correlation between stress and noise. By contrast, significant correlations between stress symptoms and noise nuisance are found. Existing studies show no significant correlations to chronic diseases, diabetes, high blood pressure and cardiovascular diseases. The literature reports on phenomenon called vibro-acoustic diseases and wind turbine syndrome, without, however, a proven causal dose-response relationship or without conducted studies where it is compared to control groups. These phenomena are not considered real for wind turbines. On the present basis, there are no demonstrated direct health effects due to wind turbine noise, though there are observed correlation between noise and stress symptoms Shadows from the rotating blades are annoying, but cannot induce epileptic attacks. (LN)

Effects of Slip Planes on Stresses in MICE Coupling Solenoid Coil Assembly

International Nuclear Information System (INIS)

Wang, Li; Pan, Heng; Wu, Hong; Guo, XingLong; Cheng, Y.; Green, Michael A.

2010-01-01

The MICE superconducting coupling solenoid magnet is made from copper matrix Nb-Ti conductors with inner radius of 750 mm, length of 285 mm and thickness of 110.4 mm at room temperature. The coil is to be wound on a mandrel made of aluminum. The peak magnetic field on the conductor is about 7.3 T when fully charged at 210 A. High magnetic field and large size make the stress inside the coupling coil assembly relatively high during cool down and full energizing. The shear stress between coil winding and aluminum casing may cause premature quench. To avoid quench potential induced by stress, slip planes were designed for the coil assembly. In this paper, FE models with and without slip planes for it have been developed to simulate the stresses during the process including winding, cooling down and charging. The stress distribution in the coil assembly with and without slip planes was investigated. The results show that slip planes with low friction coefficients can improve the stress condition in the coil, especially reduce the shear stress largely so that improve the stability.

Modulation Methods for Neutral-Point-Clamped Wind Power Converter Achieving Loss and Thermal Redistribution Under Low-Voltage Ride-Through

DEFF Research Database (Denmark)

Ma, Ke; Blaabjerg, Frede

2014-01-01

The three-level neutral-point (NP)-clamped (3L-NPC) converter is a promising multilevel topology in the application of megawatt wind power generation systems. However, the growing requirements by grid codes may impose high stress and even give reliability problem to this converter topology......, with the proposed modulation methods, the thermal distribution in the 3L-NPC wind power inverter undergoing LVRT becomes more equal, and the junction temperature of the most stressed devices can be also relieved. Also, the control ability of the dc-bus NP potential, which is one of the crucial considerations...

Predictions of Resuspension of Highway Detention Pond Deposits in Interrain Event Periods due to Wind-Induced Currents and Waves

DEFF Research Database (Denmark)

Bentzen, Thomas Ruby; Larsen, Torben; Rasmussen, Michael R.

2009-01-01

-shear stress induced by the return flow near the bed and waves both generated by the wind. Wind statistics for 30 years have been applied for prediction of the annual discharged bulk of suspended solids and associated pollutants; fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo......(a,h)anthracene and indeno(1,2,3-cd)pyrene (PAHs) and the heavy metals of cadmium, chromium, copper, lead, nickel, and zinc. The current and wave-generated bed-shear stresses entail a discharged bulk of pollutants corresponding to approximately 10% of the annual accumulation of pollutants in the present pond due...

Atmospheric Wind Relaxations and the Oceanic Response in the California Current Large Marine Ecosystem

Science.gov (United States)

Fewings, M. R.; Dorman, C. E.; Washburn, L.; Liu, W.

2010-12-01

On the West Coast of North America in summer, episodic relaxation of the upwelling-favorable winds causes warm water to propagate northward from southern to central California, against the prevailing currents [Harms and Winant 1998, Winant et al. 2003, Melton et al. 2009]. Similar wind relaxations are an important characteristic of coastal upwelling ecosystems worldwide. Although these wind relaxations have an important influence on coastal ocean dynamics, no description exists of the regional atmospheric patterns that lead to wind relaxations in southern California, or of the regional ocean response. We use QuikSCAT wind stress, North American Regional Reanalysis atmospheric pressure products, water temperature and velocity from coastal ocean moorings, surface ocean currents from high-frequency radars, and MODIS satellite sea-surface temperature and ocean color images to analyze wind relaxation events and the ocean response. We identify the events based on an empirical index calculated from NDBC buoy winds [Melton et al. 2009]. We describe the regional evolution of the atmosphere from the Gulf of Alaska to Baja California over the few days leading up to wind relaxations, and the coastal ocean temperature, color, and current response off southern and central California. We analyze ~100 wind relaxation events in June-September during the QuikSCAT mission, 1999-2009. Our results indicate south-central California wind relaxations in summer are tied to mid-level atmospheric low-pressure systems that form in the Gulf of Alaska and propagate southeastward over 3-5 days. As the low-pressure systems reach southern California, the atmospheric pressure gradient along the coast weakens, causing the surface wind stress to relax to near zero. The weak wind signal appears first at San Diego and propagates northward. QuikSCAT data indicate the relaxed winds extend over the entire Southern California Bight and up to 200 km offshore of central California. Atmospheric dynamics in

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.

Healthy offshore workforce? A qualitative study on offshore wind employees' occupational strain, health, and coping.

Science.gov (United States)

Mette, Janika; Velasco Garrido, Marcial; Harth, Volker; Preisser, Alexandra M; Mache, Stefanie

2018-01-23

Offshore work has been described as demanding and stressful. Despite this, evidence regarding the occupational strain, health, and coping behaviors of workers in the growing offshore wind industry in Germany is still limited. The purpose of our study was to explore offshore wind employees' perceptions of occupational strain and health, and to investigate their strategies for dealing with the demands of offshore work. We conducted 21 semi-structured telephone interviews with employees in the German offshore wind industry. The interviews were transcribed and analyzed in a deductive-inductive approach following Mayring's qualitative content analysis. Workers generally reported good mental and physical health. However, they also stated perceptions of stress at work, fatigue, difficulties detaching from work, and sleeping problems, all to varying extents. In addition, physical health impairment in relation to offshore work, e.g. musculoskeletal and gastrointestinal complaints, was documented. Employees described different strategies for coping with their job demands. The strategies comprised of both problem and emotion-focused approaches, and were classified as either work-related, health-related, or related to seeking social support. Our study is the first to investigate the occupational strain, health, and coping of workers in the expanding German offshore wind industry. The results offer new insights that can be utilized for future research in this field. In terms of practical implications, the findings suggest that measures should be carried out aimed at reducing occupational strain and health impairment among offshore wind workers. In addition, interventions should be initiated that foster offshore wind workers' health and empower them to further expand on effective coping strategies at their workplace.

Wind variability and sheltering effects on measurements and modeling of air-water exchange for a small lake

Science.gov (United States)

Markfort, Corey D.; Resseger, Emily; Porté-Agel, Fernando; Stefan, Heinz

2014-05-01

Lakes with a surface area of less than 10 km2 account for over 50% of the global cumulative lake surface water area, and make up more than 99% of the total number of global lakes, ponds, and wetlands. Within the boreal regions as well as some temperate and tropical areas, a significant proportion of land cover is characterized by lakes or wetlands, which can have a dramatic effect on land-atmosphere fluxes as well as the local and regional energy budget. Many of these small water bodies are surrounded by complex terrain and forest, which cause the wind blowing over a small lake or wetland to be highly variable. Wind mixing of the lake surface layer affects thermal stratification, surface temperature and air-water gas transfer, e.g. O2, CO2, and CH4. As the wind blows from the land to the lake, wake turbulence behind trees and other shoreline obstacles leads to a recirculation zone and enhanced turbulence. This wake flow results in the delay of the development of wind shear stress on the lake surface, and the fetch required for surface shear stress to fully develop may be ~O(1 km). Interpretation of wind measurements made on the lake is hampered by the unknown effect of wake turbulence. We present field measurements designed to quantify wind variability over a sheltered lake. The wind data and water column temperature profiles are used to evaluate a new method to quantify wind sheltering of lakes that takes into account lake size, shape and the surrounding landscape features. The model is validated against field data for 36 Minnesota lakes. Effects of non-uniform sheltering and lake shape are also demonstrated. The effects of wind sheltering must be included in lake models to determine the effect of wind-derived energy inputs on lake stratification, surface gas transfer, lake water quality, and fish habitat. These effects are also important for correctly modeling momentum, heat, moisture and trace gas flux to the atmosphere.

Wind Tunnel Tests for Wind Pressure Distribution on Gable Roof Buildings

Science.gov (United States)

2013-01-01

Gable roof buildings are widely used in industrial buildings. Based on wind tunnel tests with rigid models, wind pressure distributions on gable roof buildings with different aspect ratios were measured simultaneously. Some characteristics of the measured wind pressure field on the surfaces of the models were analyzed, including mean wind pressure, fluctuating wind pressure, peak negative wind pressure, and characteristics of proper orthogonal decomposition results of the measured wind pressure field. The results show that extremely high local suctions often occur in the leading edges of longitudinal wall and windward roof, roof corner, and roof ridge which are the severe damaged locations under strong wind. The aspect ratio of building has a certain effect on the mean wind pressure coefficients, and the effect relates to wind attack angle. Compared with experimental results, the region division of roof corner and roof ridge from AIJ2004 is more reasonable than those from CECS102:2002 and MBMA2006.The contributions of the first several eigenvectors to the overall wind pressure distributions become much bigger. The investigation can offer some basic understanding for estimating wind load distribution on gable roof buildings and facilitate wind-resistant design of cladding components and their connections considering wind load path. PMID:24082851

Current and turbulence measurements at the FINO1 offshore wind energy site: analysis using 5-beam ADCPs

Science.gov (United States)

Bakhoday-Paskyabi, Mostafa; Fer, Ilker; Reuder, Joachim

2018-01-01

We report concurrent measurements of ocean currents and turbulence at two sites in the North Sea, one site at upwind of the FINO1 platform and the other 200-m downwind of the Alpha Ventus wind farm. At each site, mean currents, Reynolds stresses, turbulence intensity and production of turbulent kinetic energy are obtained from two bottom-mounted 5-beam Nortek Signature1000s, high-frequency Doppler current profiler, at a water depth of approximately 30 m. Measurements from the two sites are compared to statistically identify the effects of wind farm and waves on ocean current variability and the turbulent structure in the water column. Profiles of Reynolds stresses are found to be sensible to both environmental forcing and the wind farm wake-induced distortions in both boundary layers near the surface and the seabed. Production of turbulent kinetic energy and turbulence intensity exhibit approximately similar, but less pronounced, patterns in the presence of farm wake effects.

Wind Loads on Structures

DEFF Research Database (Denmark)

Dyrbye, Claes; Hansen, Svend Ole

Wind loads have to be taken into account when designing civil engineering structures. The wind load on structures can be systematised by means of the wind load chain: wind climate (global), terrain (wind at low height), aerodynamic response (wind load to pressure), mechanical response (wind...... pressure to structural response) and design criteria. Starting with an introduction of the wind load chain, the book moves on to meteorological considerations, atmospheric boundary layer, static wind load, dynamic wind load and scaling laws used in wind-tunnel tests. The dynamic wind load covers vibrations...... induced by wind turbulence, vortex shedding, flutter and galloping. The book gives a comprehensive treatment of wind effects on structures and it will be useful for consulting engineers designing wind-sensitive structures. It will also be valuable for students of civil engineering as textbook...

Nature of global large-scale sea level variability in relation to atmospheric forcing: A modeling study

Science.gov (United States)

Fukumori, Ichiro; Raghunath, Ramanujam; Fu, Lee-Lueng

1998-03-01

The relation between large-scale sea level variability and ocean circulation is studied using a numerical model. A global primitive equation model of the ocean is forced by daily winds and climatological heat fluxes corresponding to the period from January 1992 to January 1994. The physical nature of sea level's temporal variability from periods of days to a year is examined on the basis of spectral analyses of model results and comparisons with satellite altimetry and tide gauge measurements. The study elucidates and diagnoses the inhomogeneous physics of sea level change in space and frequency domain. At midlatitudes, large-scale sea level variability is primarily due to steric changes associated with the seasonal heating and cooling cycle of the surface layer. In comparison, changes in the tropics and high latitudes are mainly wind driven. Wind-driven variability exhibits a strong latitudinal dependence in itself. Wind-driven changes are largely baroclinic in the tropics but barotropic at higher latitudes. Baroclinic changes are dominated by the annual harmonic of the first baroclinic mode and is largest off the equator; variabilities associated with equatorial waves are smaller in comparison. Wind-driven barotropic changes exhibit a notable enhancement over several abyssal plains in the Southern Ocean, which is likely due to resonant planetary wave modes in basins semienclosed by discontinuities in potential vorticity. Otherwise, barotropic sea level changes are typically dominated by high frequencies with as much as half the total variance in periods shorter than 20 days, reflecting the frequency spectra of wind stress curl. Implications of the findings with regards to analyzing observations and data assimilation are discussed.

A simple method to downscale daily wind statistics to hourly wind data

OpenAIRE

Guo, Zhongling

2013-01-01

Wind is the principal driver in the wind erosion models. The hourly wind speed data were generally required for precisely wind erosion modeling. In this study, a simple method to generate hourly wind speed data from daily wind statistics (daily average and maximum wind speeds together or daily average wind speed only) was established. A typical windy location with 3285 days (9 years) measured hourly wind speed data were used to validate the downscaling method. The results showed that the over...

A Record-High Ocean Bottom Pressure in the South Pacific Observed by GRACE

Science.gov (United States)

Boening, Carmen; Lee, Tong; Zlotnicki, Victor

2011-01-01

In late 2009 to early 2010, the Gravity Recovery and Climate Experiment (GRACE) satellite pair observed a record increase in ocean bottom pressure (OBP) over a large mid-latitude region of the South East Pacific. Its magnitude is substantially larger than other oceanic events in the Southern Hemisphere found in the entire GRACE data records (2003-2010) on multi-month time scales. The OBP data help to understand the nature of a similar signal in sea surface height (SSH) anomaly observed by altimetry: the SSH increase is mainly due to mass convergence. Analysis of the barotropic vorticity equation using scatterometer data, atmospheric reanalysis product, and GRACE and altimeter an atmospheric reanalysis product observations suggests that the observed OBP/SSH signal was primarily caused by wind stress curl associated with a strong and persistent anticyclone in late 2009 in combination with effects of planetary vorticity gradient, bottom topography, and friction

Performance of cotton leaf curl virus resistant intrahirsutum f/sub 1/ hybrids

International Nuclear Information System (INIS)

Baloch, M.J.

2004-01-01

The first and foremost effort to combat the devastating cotton leaf curl virus (clcv) disease would be to utilize those clcv resistant germplasm in a hybridization programme which can enhance the possibilities of selecting desirable progenies from segregating populations. In this connection, 16 clcv intrahirsutum F1 hybrids were developed and evaluated for their performance. The hybrids, on an average gave an increase of 26.02 % in seed cotton yield; 11.52 % in bolls per plant; 14.23 % in boll weight; 4.28 % in lint; 3.89 % in fibre length and 8.21 % in earliness against the average of parents. However, among the hybrids, the top three scoring for yield were, BH.121 x Cyto.9/91, Cyto.9/91 x CRIS-226 and VH-137 x CRIS-226. The number of bolls per plant was found to be a major contributing factor for increased yield because the hybrids which set higher bolls correspondingly gave higher yields. Boll weight was not regarded as an important attribute to increase yield because hybrids with moderate boll sizes were among the top three high yielders. For lint %, the hybrids CRIS-129 x LRA-5166 and FH-901 x VH-137 were first for fibre length, whereas CRIS-121 x Cyto.51 and BH-124 x CIM-448 were among the top two rankers. Regarding earliness, the hybrids CRIS-121 x Cyto. 51 gave the highest boll opening percent and next in order was the hybrid VH-137 x DNH-49. Our results thus generally suggest that although the best three hybrids were desirable for other traits, the choice of the hybrids may be made on the priority for characters to be bred. (author)

Cost optimization of wind turbines for large-scale offshore wind farms

International Nuclear Information System (INIS)

Fuglsang, P.; Thomsen, K.