Cdc42-dependent leading edge coordination is essential for interstitial dendritic cell migration
DEFF Research Database (Denmark)
Lammermann, Tim; Renkawitz, Jorg; Wu, Xunwei; Hirsch, Karin; Brakebusch, Cord; Sixt, Michael
2009-01-01
Mature dendritic cells (DCs) moving from the skin to the lymph node are a prototypic example of rapidly migrating amoeboid leukocytes. Interstitial DC migration is directionally guided by chemokines, but independent of specific adhesive interactions with the tissue as well as pericellular...
International Nuclear Information System (INIS)
localize to lipid rafts and recruit cholesterol into protrusions and away from caveolae, leading to increased phosphorylation of caveolin-1, which inhibits Cdc42-dependent endocytosis. This study provides a new insight for the role for prominins in the regulation of PM lipid organization
Energy Technology Data Exchange (ETDEWEB)
Singh, Raman Deep, E-mail: Takhter.Ramandeep@mayo.edu; Schroeder, Andreas S.; Scheffer, Luana; Holicky, Eileen L.; Wheatley, Christine L.; Marks, David L., E-mail: Marks.david@mayo.edu; Pagano, Richard E.
2013-05-10
localize to lipid rafts and recruit cholesterol into protrusions and away from caveolae, leading to increased phosphorylation of caveolin-1, which inhibits Cdc42-dependent endocytosis. This study provides a new insight for the role for prominins in the regulation of PM lipid organization.
Goodhand, Martin
2011-01-01
Compressor blades often have a small 'spike' in the surface pressure distribution at the leading edge. This may result from blade erosion, manufacture defects or compromises made in the original design process. In this thesis it is shown that these spikes will increase the loss generated by a blade only when they become large enough to initiate boundary layer transition at the leading edge through a separation bubble; this process increases profile loss by about 30%. A criterion is presen...
Leading Edge Device Aerodynamic Optimization
Directory of Open Access Journals (Sweden)
Marius Gabriel COJOCARU
2015-12-01
Full Text Available Leading edge devices are conventionally used as aerodynamic devices that enhance performances during landing and in some cases during takeoff. The need to increase the efficiency of the aircrafts has brought the idea of maintaining as much as possible a laminar flow over the wings. This is possible only when the leading edge of the wings is free from contamination, therefore using the leading edge devices with the additional role of shielding during takeoff. Such a device based on the Krueger flap design is aerodynamically analyzed and optimized. The optimization comprises three steps: first, the positioning of the flap such that the shielding criterion is kept, second, the analysis of the flap size and third, the optimization of the flap shape. The first step is subject of a gradient based optimization process of the position described by two parameters, the position along the line and the deflection angle. For the third step the Adjoint method is used to gain insight on the shape of the Krueger flap that will extend the most the stall limit. All these steps have been numerically performed using Ansys Fluent and the results are presented for the optimized shape in comparison with the baseline configuration.
Leading-Edge Flutter of Supercavitating Hydrofoils
Brennen, C.; Oey, K. T.; Babcock, C. D.
1980-01-01
This paper presents the results of experiments and analysis of the phenomenon of leading-edge flutter which has been observed to occur for supercavitating hydrofoils. The experiments confirmed the existence of such a single-degree-of-freedom flutter involving chordwise bending and indicated that for long, natural (or vapor-filled) cavities the reduced flutter speed, [formula], was in the range 0.15 to 0.23. Secondary effects observed were the variation with the angle of attack (a minimum fl...
Symmetric airfoil geometry effects on leading edge noise
Gill, James; Zhang, Xin; Joseph, Phillip F.
2013-01-01
Computational aeroacoustic methods are applied to the modeling of noise due to interactions between gusts and the leading edge of real symmetric airfoils. Single frequency harmonic gusts are interacted with various airfoil geometries at zero angle of attack. The effects of airfoil thickness and leading edge radius on noise are investigated systematically and independently for the first time, at higher frequencies than previously used in computational methods. Increases in both leading edge ra...
Turbine Airfoil Leading Edge Film Cooling Bibliography: 1972–1998
Directory of Open Access Journals (Sweden)
D. M. Kercher
2000-01-01
Full Text Available Film cooling for turbine airfoil leading edges has been a common practice for at least 35 years as turbine inlet gas temperatures and pressures have continually increased along with cooling air temperatures for higher engine cycle efficiency. With substantial engine cycle performance improvements from higher gas temperatures, it has become increasingly necessary to film cool nozzle and rotor blade leading edges since external heat transfer coefficients and thus heat load are the highest in this airfoil region. Optimum cooling air requirements in this harsh environment has prompted a significant number of film cooling investigations and analytical studies reported over the past 25 years from academia, industry and government agencies. Substantial progress has been made in understanding the complex nature of leading edge film cooling from airfoil cascades, simulated airfoil leading edges and environment. This bibliography is a report of the open-literature references available which provide information on the complex aero–thermo interaction of leading edge gaseous film cooling with mainstream flow. From much of this investigative information has come successful operational leading edge film cooling design systems capable of sustaining airfoil leading edge durability in very hostile turbine environments.
Structural Health Monitoring Analysis for the Orbiter Wing Leading Edge
Yap, Keng C.
2010-01-01
This viewgraph presentation reviews Structural Health Monitoring Analysis for the Orbiter Wing Leading Edge. The Wing Leading Edge Impact Detection System (WLE IDS) and the Impact Analysis Process are also described to monitor WLE debris threats. The contents include: 1) Risk Management via SHM; 2) Hardware Overview; 3) Instrumentation; 4) Sensor Configuration; 5) Debris Hazard Monitoring; 6) Ascent Response Summary; 7) Response Signal; 8) Distribution of Flight Indications; 9) Probabilistic Risk Analysis (PRA); 10) Model Correlation; 11) Impact Tests; 12) Wing Leading Edge Modeling; 13) Ascent Debris PRA Results; and 14) MM/OD PRA Results.
Sharp Refractory Composite Leading Edges on Hypersonic Vehicles
Walker, Sandra P.; Sullivan, Brian J.
2003-01-01
On-going research of advanced sharp refractory composite leading edges for use on hypersonic air-breathing vehicles is presented in this paper. Intense magnitudes of heating and of heating gradients on the leading edge lead to thermal stresses that challenge the survivability of current material systems. A fundamental understanding of the problem is needed to further design development. Methodology for furthering the technology along with the use of advanced fiber architectures to improve the thermal-structural response is explored in the current work. Thermal and structural finite element analyses are conducted for several advanced fiber architectures of interest. A tailored thermal shock parameter for sharp orthotropic leading edges is identified for evaluating composite material systems. The use of the tailored thermal shock parameter has the potential to eliminate the need for detailed thermal-structural finite element analyses for initial screening of material systems being considered for a leading edge component.
Leading-Edge Learning: Two Views.
Abernathy, Donna J.
1999-01-01
Peter Senge and Jack Welch share thoughts about what it means to learn and lead into the next century. Senge urges leaders to be aware of the economic and the natural environment. Welch asserts that an organization's ability to learn and translate learning into action is the ultimate competitive advantage. (JOW)
Turbine Airfoil Leading Edge Film Cooling Bibliography: 1972–1998
Kercher, D. M.
2000-01-01
Film cooling for turbine airfoil leading edges has been a common practice for at least 35 years as turbine inlet gas temperatures and pressures have continually increased along with cooling air temperatures for higher engine cycle efficiency. With substantial engine cycle performance improvements from higher gas temperatures, it has become increasingly necessary to film cool nozzle and rotor blade leading edges since external heat transfer coefficients and thus heat load are the highest in th...
Symmetric airfoil geometry effects on leading edge noise.
Gill, James; Zhang, X; Joseph, P
2013-10-01
Computational aeroacoustic methods are applied to the modeling of noise due to interactions between gusts and the leading edge of real symmetric airfoils. Single frequency harmonic gusts are interacted with various airfoil geometries at zero angle of attack. The effects of airfoil thickness and leading edge radius on noise are investigated systematically and independently for the first time, at higher frequencies than previously used in computational methods. Increases in both leading edge radius and thickness are found to reduce the predicted noise. This noise reduction effect becomes greater with increasing frequency and Mach number. The dominant noise reduction mechanism for airfoils with real geometry is found to be related to the leading edge stagnation region. It is shown that accurate leading edge noise predictions can be made when assuming an inviscid meanflow, but that it is not valid to assume a uniform meanflow. Analytic flat plate predictions are found to over-predict the noise due to a NACA 0002 airfoil by up to 3 dB at high frequencies. The accuracy of analytic flat plate solutions can be expected to decrease with increasing airfoil thickness, leading edge radius, gust frequency, and Mach number. PMID:24116405
A Thermostructural Analysis of a Diboride Composite Leading Edge
Kowalski, Tom; Buesking, Kent; Kolodziej, Paul; Bull, Jeff
1996-01-01
In an effort to support the design of zirconium diboride composite leading edges for hypersonic vehicles, a finite element model (FEM) of a prototype leading edge was created and finite element analysis (FEA) was employed to assess its thermal and structural response to aerothermal boundary conditions. Unidirectional material properties for the structural components of the leading edge, a continuous fiber reinforced diboride composite, were computed with COSTAR. These properties agree well with those experimentally measured. To verify the analytical approach taken with COSMOS/M, an independent FEA of one of the leading edge assembly components was also done with COSTAR. Good agreement was obtained between the two codes. Both showed that a unidirectional lay-up had the best margin of safety for a simple loading case. Both located the maximum stress in the same region and ply. The magnitudes agreed within 4 percent. Trajectory based aerothermal heating was then applied to the leading edge assembly FEM created with COSMOS/M to determine steady state temperature response, displacement, stresses, and contact forces due to thermal expansion and thermal strains. Results show that the leading edge stagnation line temperature reached 4700 F. The maximum computed failure index for the laminated composite components peaks at 4.2, and is located at the bolt flange in layer 2 of the side bracket. The temperature gradient in the tip causes a compressive stress of 279 ksi along its width and substantial tensile stresses within its depth.
Mitigation of biological adhesion to aircraft leading edge surfaces
Kok, Mariana
2014-01-01
Contamination caused by insects on aircraft leading edge surfaces can result in premature transition of the boundary layer, leading to an increase in skin friction drag and fuel consumption. Consequently, the use of novel low surface energy coatings to mitigate insect residue adhesion was investigated. In order to determine the effect of surface characteristics on insect residue adhesion a range of surfaces, from superhydrophobic to hydrophilic, were evaluated. Surfaces were characterized in ...
Probabilistic Structural Health Monitoring of the Orbiter Wing Leading Edge
Yap, Keng C.; Macias, Jesus; Kaouk, Mohamed; Gafka, Tammy L.; Kerr, Justin H.
2011-01-01
A structural health monitoring (SHM) system can contribute to the risk management of a structure operating under hazardous conditions. An example is the Wing Leading Edge Impact Detection System (WLEIDS) that monitors the debris hazards to the Space Shuttle Orbiter s Reinforced Carbon-Carbon (RCC) panels. Since Return-to-Flight (RTF) after the Columbia accident, WLEIDS was developed and subsequently deployed on board the Orbiter to detect ascent and on-orbit debris impacts, so as to support the assessment of wing leading edge structural integrity prior to Orbiter re-entry. As SHM is inherently an inverse problem, the analyses involved, including those performed for WLEIDS, tend to be associated with significant uncertainty. The use of probabilistic approaches to handle the uncertainty has resulted in the successful implementation of many development and application milestones.
Leading-edge vortex shedding from rotating wings
Energy Technology Data Exchange (ETDEWEB)
Kolomenskiy, Dmitry [Centre de Recherches Mathématiques (CRM), Department of Mathematics and Statistics, McGill University, 805 Sherbrooke W., Montreal, QC H3A 0B9 (Canada); Elimelech, Yossef [Faculty of Aerospace Engineering, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Schneider, Kai, E-mail: dkolom@gmail.com [M2P2–CNRS, Université d' Aix-Marseille, 39, rue Frédéric Joliot-Curie, F-13453 Marseille Cedex 13 (France)
2014-06-01
This paper presents a numerical investigation of the leading-edge vortices generated by rotating triangular wings at Reynolds number Re = 250. A series of three-dimensional numerical simulations have been carried out using a Fourier pseudo-spectral method with volume penalization. The transition from stable attachment of the leading-edge vortex to periodic vortex shedding is explored, as a function of the wing aspect ratio and the angle of attack. It is found that, in a stable configuration, the spanwise flow in the recirculation bubble past the wing is due to the centrifugal force, incompressibility and viscous stresses. For the flow outside of the bubble, an inviscid model of spanwise flow is presented. (papers)
Rotational accelerations stabilize leading edge vortices on revolving fly wings
Lentink, David; Dickinson, Michael H.
2009-01-01
The aerodynamic performance of hovering insects is largely explained by the presence of a stably attached leading edge vortex (LEV) on top of their wings. Although LEVs have been visualized on real, physically modeled, and simulated insects, the physical mechanisms responsible for their stability are poorly understood. To gain fundamental insight into LEV stability on flapping fly wings we expressed the Navier–Stokes equations in a rotating frame of reference attached to the wing's surface. U...
Synthetic turbulence methods for leading edge noise predictions
Gea-Aguilera, Fernando; Xin ZHANG; Chen, Xiaoxian; Gill, James R.; Node-Langlois, Thomas
2015-01-01
An advanced digital filter method to generate synthetic turbulence is presented for efficient two- and three-dimensional leading edge noise predictions. The technique, which is based on the Random Particle-Mesh method, produces a turbulent inflow that matches a target isotropic energy spectrum. The discretized equations for the synthetic eddies, and the input parameters needed to recover the desired turbulence statistics, are presented. Moreover, a simple and fast implementatio...
Characteristics of deformable leading edge for high performance helicopter rotor
Lee, Soogab; Mcalister, K. W.; Tung, Chee
1993-01-01
The deformable leading edge (DLE) concept to improve the blade capability in lift, drag and pitching moments has been investigated for the purpose of meeting new rotor maneuverability and susceptibility requirements. The advantages and disadvantages of this concept have been carefully examined with limited computational and experimental results. This work showed that this concept achieves a substantial improvement in lift capability and also reduces the drag and pitching moment at the same time. Effects of various parameters, such as Reynolds number, reduced frequency, mean angle of oscillation, and airfoil shape, on the performance of these airfoils were also investigated.
A high-performance, low-cost, leading edge discriminator
Indian Academy of Sciences (India)
S K Gupta; Y Hayashi; A Jain; S Karthikeyan; S Kawakami; K C Ravindran; S C Tonwar
2005-08-01
A high-performance, low-cost, leading edge discriminator has been designed with a timing performance comparable to state-of-the-art, commercially available discriminators. A timing error of 16 ps is achieved under ideal operating conditions. Under more realistic operating conditions the discriminator displays a timing error of 90 ps. It has an intrinsic double pulse resolution of 4 ns which is better than most commercial discriminators. A low-cost discriminator is an essential requirement of the GRAPES-3 experiment where a large number of discriminator channels are used.
Measurements of leading edge vortices in a supersonic stream
Milanovic, Ivana Milija
An experimental investigation of the leading edge vortices from a 75° sweptback, sharp edge delta wing has been carried out in a Mach 2.49 stream. Five-hole conical probe traverses were conducted vertically and horizontally through the primary vortices at the trailing edge and at one half chord downstream station for 7° and 12° angles of attack. The main objective was to determine the Mach number and pressure distributions in the primary vortex and to present comparisons of flow properties at different survey stations. In response to the continued interest in efficient supersonic flight vehicles, particularly in the missile arena, the motivation for this research has been to provide the quantitative details of supersonic leading edge vortices, the understanding of which up to now has been largely based on flow visualizations and presumed similarity to low speed flows. As a prerequisite to the measurement campaign, the employed five-hole conical probe was numerically calibrated using a three-dimensional Thin Layer Navier-Stokes solver in order to circumvent the traditional experimental approach vastly demanding on resources. The pressure readings at the probe orifices were computed for a range of Mach numbers and pitch angles, and subsequently verified in wind tunnel tests. The calibration phase also demonstrated the profound influence of the probe bluntness on the nearby static pressure ports, its relevance to the ultimate modeling strategy and the resulting calibration charts. Flow diagnostics of the leading edge vortices included both qualitative flow visualizations, as well as quantitative measurements. Shadowgraphs provided information regarding the trajectory and relative size of the generated vortices while assuring that no probe-induced vortex breakdown occurred. Surface oil patterns revealed the general spanwise locations of leeward vortices, and confirmed topological similarity to their low speed counterparts. The probe measurements revealed substantial
Particle rebound characteristics of turbomachinery cascade leading edge geometry
Siravuri, Sastri
The objective of this research work is to investigate and understand the complex phenomena associated with the mechanism of particle impacts on turbomachinery cascade leading edge geometry. At present, there is a need for experimental work in basic and applied research to find out the parameters that are relevant to particle rebound characteristics on turbomachinery blades. In the present work, experiments were conducted with air velocity at 15 m/s (˜50 ft/sec) and at 30 m/s (˜100 ft/sec) using high-speed photography and Laser Doppler Velocimetry (LDV). Silica sand particles of 1000--1500 micron size were used for this study. In the present investigation, particle rebound data was obtained for cylindrical targets with radius of curvature representative of leading edge geometry (cylinder diameter = 4.5mm & 6.5 mm) using LDV. The numerical simulations, which are based on non-linear dynamic analysis, were also performed using the finite element code DYNA3-D. Several different material models viz elastic-elastic, elastic-plastic, elastic-plastic with friction & isotropic-elastic-plastic with dynamic friction and particle rotation were used in the DYNA3-D numerical analysis. The computational results include a time history of the displacement, stress and strain profiles through the particle collision. Numerical results are presented for the rebound conditions of spherical silica sand particle for different pre-collision velocities. The computed particle restitution coefficients, after they reach steady rebound conditions, are compared with experimental results obtained from LDV. A probabilistic model was developed to incorporate the uncertainties in the impact velocity in the numerical model. Histograms and Cumulative Distribution Functions (CDFs) for impact velocity were obtained from experimental LDV data. Ten randomly selected probabilities for each impact angle were used to calculate the impact velocity from cumulative distribution function. This randomly selected
Flow over 50º Delta Wings with Different Leading-Edge Radii
Verhaagen, N.G.
2011-01-01
The experimental study focuses on the effects of the leading-edge radius on the flow over 50º swept delta wing models. Three models were tested, one model has a sharp leading edge and two other have a semi-circular leading edge of different radius. The vortical flow on and off the surface of the mod
Rotational accelerations stabilize leading edge vortices on revolving fly wings.
Lentink, David; Dickinson, Michael H
2009-08-01
The aerodynamic performance of hovering insects is largely explained by the presence of a stably attached leading edge vortex (LEV) on top of their wings. Although LEVs have been visualized on real, physically modeled, and simulated insects, the physical mechanisms responsible for their stability are poorly understood. To gain fundamental insight into LEV stability on flapping fly wings we expressed the Navier-Stokes equations in a rotating frame of reference attached to the wing's surface. Using these equations we show that LEV dynamics on flapping wings are governed by three terms: angular, centripetal and Coriolis acceleration. Our analysis for hovering conditions shows that angular acceleration is proportional to the inverse of dimensionless stroke amplitude, whereas Coriolis and centripetal acceleration are proportional to the inverse of the Rossby number. Using a dynamically scaled robot model of a flapping fruit fly wing to systematically vary these dimensionless numbers, we determined which of the three accelerations mediate LEV stability. Our force measurements and flow visualizations indicate that the LEV is stabilized by the ;quasi-steady' centripetal and Coriolis accelerations that are present at low Rossby number and result from the propeller-like sweep of the wing. In contrast, the unsteady angular acceleration that results from the back and forth motion of a flapping wing does not appear to play a role in the stable attachment of the LEV. Angular acceleration is, however, critical for LEV integrity as we found it can mediate LEV spiral bursting, a high Reynolds number effect. Our analysis and experiments further suggest that the mechanism responsible for LEV stability is not dependent on Reynolds number, at least over the range most relevant for insect flight (100wind turbines at much higher Reynolds numbers suggest that even large flying animals could potentially exploit LEV-based force augmentation during slow hovering flight, take-offs or landing
Multidisciplinary design optimization of adaptive wing leading edge
Institute of Scientific and Technical Information of China (English)
SUN; RuJie; CHEN; GuoPing; ZHOU; Chen; ZHOU; LanWei; JIANG; JinHui
2013-01-01
Adaptive wing can significantly enhance aircraft aerodynamic performance, which refers to aerodynamic and structural opti-mization designs. This paper introduces a two-step approach to solve the interrelated problems of the adaptive leading edge. In the first step, the procedure of airfoil optimization is carried out with an initial configuration of NACA 0006. On the basis of the combination of design of experiment (DOE), response surface method (RSM) and genetic algorithm (GA), an adaptive air-foil can be obtained whose lift-to-drag ratio is larger than the baseline airfoil’s at the given angle of attack and subsonic speed.The next step is to design a compliant structure to achieve the target airfoil shape, which is the optimization result of the previous step. In order to minimize the deviation of the deformed shape from the target shape, the load path representation topology method is presented. This method is developed by way of GA, with size and shape optimization incorporated in it simul-taneously. Finally, a comparison study with the Solid Isotropic Material with Penalization (SIMP) method in Altair OptiStruct is conducted, and the results demonstrate the validity and effectiveness of the proposed approach.
Development of Advanced High Lift Leading Edge Technology for Laminar Flow Wings
Bright, Michelle M.; Korntheuer, Andrea; Komadina, Steve; Lin, John C.
2013-01-01
This paper describes the Advanced High Lift Leading Edge (AHLLE) task performed by Northrop Grumman Systems Corporation, Aerospace Systems (NGAS) for the NASA Subsonic Fixed Wing project in an effort to develop enabling high-lift technology for laminar flow wings. Based on a known laminar cruise airfoil that incorporated an NGAS-developed integrated slot design, this effort involved using Computational Fluid Dynamics (CFD) analysis and quality function deployment (QFD) analysis on several leading edge concepts, and subsequently down-selected to two blown leading-edge concepts for testing. A 7-foot-span AHLLE airfoil model was designed and fabricated at NGAS and then tested at the NGAS 7 x 10 Low Speed Wind Tunnel in Hawthorne, CA. The model configurations tested included: baseline, deflected trailing edge, blown deflected trailing edge, blown leading edge, morphed leading edge, and blown/morphed leading edge. A successful demonstration of high lift leading edge technology was achieved, and the target goals for improved lift were exceeded by 30% with a maximum section lift coefficient (Cl) of 5.2. Maximum incremental section lift coefficients ( Cl) of 3.5 and 3.1 were achieved for a blown drooped (morphed) leading edge concept and a non-drooped leading edge blowing concept, respectively. The most effective AHLLE design yielded an estimated 94% lift improvement over the conventional high lift Krueger flap configurations while providing laminar flow capability on the cruise configuration.
Morphological Variations of Leading-Edge Serrations in Owls (Strigiformes.
Directory of Open Access Journals (Sweden)
Matthias Weger
Full Text Available Owls have developed serrations, comb-like structures, along the leading edge of their wings. Serrations were investigated from a morphological and a mechanical point of view, but were not yet quantitatively compared for different species. Such a comparative investigation of serrations from species of different sizes and activity patterns may provide new information about the function of the serrations.Serrations on complete wings and on tenth primary remiges of seven owl species were investigated. Small, middle-sized, and large owl species were investigated as well as species being more active during the day and owls being more active during the night. Serrations occurred at the outer parts of the wings, predominantly at tenth primary remiges, but also on further wing feathers in most species. Serration tips were oriented away from the feather rachis so that they faced into the air stream during flight. The serrations of nocturnal owl species were higher developed as demonstrated by a larger inclination angle (the angle between the base of the barb and the rachis, a larger tip displacement angle (the angle between the tip of the serration and the base of the serration and a longer length. Putting the measured data into a clustering algorithm yielded dendrograms that suggested a strong influence of activity pattern, but only a weak influence of size on the development of the serrations.Serrations are supposed to be involved in noise reduction during flight and also depend on the aerodynamic properties that in turn depend on body size. Since especially nocturnal owls have to rely on hearing during prey capture, the more pronounced serrations of nocturnal species lend further support to the notion that serrations have an important function in noise reduction. The differences in shape of the serrations investigated indicate that a silent flight requires well-developed serrations.
Forebody and leading edge vortex measurements using planar Doppler velocimetry
Beutner, Thomas J.; Elliott, Gregory S.; Williams, Glenn W.; Baust, Henry D.; Crafton, Jim; Carter, Campbell D.
2001-04-01
The planar Doppler velocimetry (PDV) technique has been demonstrated by employing it in a large-scale wind tunnel to record velocity fields surrounding a model of a generic fighter plane. The PDV instrument employed here included the following: (i) a frequency monitoring system for measuring the laser frequency corresponding to each set of scattering images; (ii) two detector systems (each composed of two 16-bit CCD cameras), one viewing the model from the top of the wind tunnel and the second from the side; (iii) iodine vapour cells based on the starved-cell design, which eliminated the need for separate temperature control of the iodine reservoir; iv) a vibration-isolated, injection-seeded, Q-switched Nd:YAG laser and (v) custom data acquisition software for linking the four cameras, the laser and the frequency monitor. The PDV instrument was validated by comparing the PDV-derived velocity to the known value in the empty wind tunnel. An error of about 1 m s-1 out of an 18.9 m s-1 velocity component was found; the image noise component (resulting primarily from the speckle effect) was found to be about 1 m s-1. In addition, as a result of laser-sheet impingement on the model surface, velocities near the model surfaces are biased by background scattering effects. Nonetheless, it has been shown that PDV can be used effectively to map velocity fields with high spatial resolution over complex model geometries. Frame-averaged velocity images recorded at four axial stations along the model have shown the formation of forebody and leading-edge vortices and their complex interaction in the presence of the wing flow field.
Robinson, L. M.; Hobday, A. J.; Possingham, H. P.; Richardson, A. J.
2015-03-01
There is mounting evidence to suggest that many species are shifting their ranges in concordance with the climate velocity of their preferred environmental conditions/habitat. While accelerated rates in species' range shifts have been noted in areas of intense warming, due to climate change, few studies have considered the influence that both spatial temperature gradients and rates of warming (i.e., the two components of climate velocity) could have on rates of movement in species habitats. We compared projected shifts in the core habitat of nine large pelagic fish species (five tuna, two billfish and two shark species) off the east coast of Australia at different spatial points (centre, leading and trailing edges of the core habitat), during different seasons (summer and winter), in the near-(2030) and long-term (2070), using independent species distribution models and habitat suitability models. Model projections incorporated depth integrated temperature data from 11 climate models with a focus on the IPCC SRES A2 general emission scenario. Projections showed a number of consistent patterns: southern (poleward) shifts in all species' core habitats; trailing edges shifted faster than leading edges; shifts were faster by 2070 than 2030; and there was little difference in shifts among species and between seasons. Averaging across all species and climate models, rates of habitat shifts for 2030 were 45-60 km decade-1 at the trailing edge, 40-45 km decade-1 at the centre, and 20-30 km decade-1 at the leading edge. Habitat shifts for 2070 were 60-70 km decade-1 at the trailing edge, 50-55 km decade-1 at the centre, and 30-40 km decade-1 at the leading edge. It is often assumed that the leading edge of a species range will shift faster than the trailing edge, but there are few projections or observations in large pelagic fish to validate this assumption. We found that projected shifts at the trailing edge were greater than at the centre and leading of core habitats in
A numerical model for the platelet heat-pipe-cooled leading edge of hypersonic vehicle
Liu, Hongpeng; Liu, Weiqiang
2016-01-01
A new design, the platelet heat-pipe-cooled leading edge, is discussed for the thermal management to prevent damage to hypersonic vehicle leading edge component. For calculating the steady state behavior of platelet heat-pipe-cooled leading edge, a numerical model based on the principles of evaporation, convection, and condensation of a working fluid is presented. And then its effectiveness is validated by comparing the wall and vapor temperature against experimental data for a conventional heat pipe. Further investigations indicate that alloy IN718, with sodium as the working fluid is a feasible combination for Mach 8 flight with a 15 mm leading edge radius.
Modulation of leading edge vorticity and aerodynamic forces in flexible flapping wings
Energy Technology Data Exchange (ETDEWEB)
Zhao Liang; Deng Xinyan [School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States); Sane, Sanjay P, E-mail: xdeng@purdue.edu, E-mail: sane@ncbs.res.in [National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560 065 (India)
2011-09-15
In diverse biological flight systems, the leading edge vortex has been implicated as a flow feature of key importance in the generation of flight forces. Unlike fixed wings, flapping wings can translate at higher angles of attack without stalling because their leading edge vorticity is more stable than the corresponding fixed wing case. Hence, the leading edge vorticity has often been suggested as the primary determinant of the high forces generated by flapping wings. To test this hypothesis, it is necessary to modulate the size and strength of the leading edge vorticity independently of the gross kinematics while simultaneously monitoring the forces generated by the wing. In a recent study, we observed that forces generated by wings with flexible trailing margins showed a direct dependence on the flexural stiffness of the wing. Based on that study, we hypothesized that trailing edge flexion directly influences leading edge vorticity, and thereby the magnitude of aerodynamic forces on the flexible flapping wings. To test this hypothesis, we visualized the flows on wings of varying flexural stiffness using a custom 2D digital particle image velocimetry system, while simultaneously monitoring the magnitude of the aerodynamic forces. Our data show that as flexion decreases, the magnitude of the leading edge vorticity increases and enhances aerodynamic forces, thus confirming that the leading edge vortex is indeed a key feature for aerodynamic force generation in flapping flight. The data shown here thus support the hypothesis that camber influences instantaneous aerodynamic forces through modulation of the leading edge vorticity.
Modulation of leading edge vorticity and aerodynamic forces in flexible flapping wings
International Nuclear Information System (INIS)
In diverse biological flight systems, the leading edge vortex has been implicated as a flow feature of key importance in the generation of flight forces. Unlike fixed wings, flapping wings can translate at higher angles of attack without stalling because their leading edge vorticity is more stable than the corresponding fixed wing case. Hence, the leading edge vorticity has often been suggested as the primary determinant of the high forces generated by flapping wings. To test this hypothesis, it is necessary to modulate the size and strength of the leading edge vorticity independently of the gross kinematics while simultaneously monitoring the forces generated by the wing. In a recent study, we observed that forces generated by wings with flexible trailing margins showed a direct dependence on the flexural stiffness of the wing. Based on that study, we hypothesized that trailing edge flexion directly influences leading edge vorticity, and thereby the magnitude of aerodynamic forces on the flexible flapping wings. To test this hypothesis, we visualized the flows on wings of varying flexural stiffness using a custom 2D digital particle image velocimetry system, while simultaneously monitoring the magnitude of the aerodynamic forces. Our data show that as flexion decreases, the magnitude of the leading edge vorticity increases and enhances aerodynamic forces, thus confirming that the leading edge vortex is indeed a key feature for aerodynamic force generation in flapping flight. The data shown here thus support the hypothesis that camber influences instantaneous aerodynamic forces through modulation of the leading edge vorticity.
Topology optimization of compliant adaptive wing leading edge with composite materials
Directory of Open Access Journals (Sweden)
Tong Xinxing
2014-12-01
Full Text Available An approach for designing the compliant adaptive wing leading edge with composite material is proposed based on the topology optimization. Firstly, an equivalent constitutive relationship of laminated glass fiber reinforced epoxy composite plates has been built based on the symmetric laminated plate theory. Then, an optimization objective function of compliant adaptive wing leading edge was used to minimize the least square error (LSE between deformed curve and desired aerodynamics shape. After that, the topology structures of wing leading edge of different glass fiber ply-orientations were obtained by using the solid isotropic material with penalization (SIMP model and sensitivity filtering technique. The desired aerodynamics shape of compliant adaptive wing leading edge was obtained based on the proposed approach. The topology structures of wing leading edge depend on the glass fiber ply-orientation. Finally, the corresponding morphing experiment of compliant wing leading edge with composite materials was implemented, which verified the morphing capability of topology structure and illustrated the feasibility for designing compliant wing leading edge. The present paper lays the basis of ply-orientation optimization for compliant adaptive wing leading edge in unmanned aerial vehicle (UAV field.
A method for computing the leading-edge suction in a higher-order panel method
Ehlers, F. E.; Manro, M. E.
1984-01-01
Experimental data show that the phenomenon of a separation induced leading edge vortex is influenced by the wing thickness and the shape of the leading edge. Both thickness and leading edge shape (rounded rather than point) delay the formation of a vortex. Existing computer programs used to predict the effect of a leading edge vortex do not include a procedure for determining whether or not a vortex actually exists. Studies under NASA Contract NAS1-15678 have shown that the vortex development can be predicted by using the relationship between the leading edge suction coefficient and the parabolic nose drag. The linear theory FLEXSTAB was used to calculate the leading edge suction coefficient. This report describes the development of a method for calculating leading edge suction using the capabilities of the higher order panel methods (exact boundary conditions). For a two dimensional case, numerical methods were developed using the double strength and downwash distribution along the chord. A Gaussian quadrature formula that directly incorporates the logarithmic singularity in the downwash distribution, at all panel edges, was found to be the best method.
Compressibility and Leading-Edge Bluntness Effects for a 65 Deg Delta Wing
Luckring, J. M.
2004-01-01
A 65 deg. delta wing has been tested in the National Transonic Facility (NTF) at mean aerodynamic chord Reynolds numbers from 6 million to 120 million at subsonic and transonic speeds. The configuration incorporated a systematic variation of the leading edge bluntness. The analysis for this paper is focused on the compressibility and bluntness effects primarily at a Reynolds number of 6 million from this data set. Emphasis is placed upon on the onset and progression of leading-edge vortex separation, and compressibility is shown to promote this separation. Comparisons with recent publications show that compressibility and Reynolds number have opposite effects on blunt leading edge vortex separation
Modelling Combined Heat Exchange in the Leading Edge of Perspective Aircraft Wing
Kandinsky Roman O.; Prosuntsov Pavel V.
2015-01-01
In this paper gas dynamic numerical modelling of leading edge flow is presented and thermal loading parameters are determined. Numerical modelling of combined radiative and conductive heat transfer of the wing edge is carried out, thermal state of structure is given and the results are analyzed.
Modelling Combined Heat Exchange in the Leading Edge of Perspective Aircraft Wing
Directory of Open Access Journals (Sweden)
Kandinsky Roman O.
2015-01-01
Full Text Available In this paper gas dynamic numerical modelling of leading edge flow is presented and thermal loading parameters are determined. Numerical modelling of combined radiative and conductive heat transfer of the wing edge is carried out, thermal state of structure is given and the results are analyzed.
Spanwise visualization of the flow around a three-dimensional foil with leading edge protuberances
Stanway, M. J.; Techet, A. H.
2006-11-01
Studies of model humpback whale fins have shown that leading edge protuberances, or tubercles, can lead to delayed stall and increased lift at higher angles of attack, compared to foils with geometrically smooth leading edges. Such enhanced performance characteristics could prove highly useful in underwater vehicles such as gliders or long range AUVs (autonomous underwater vehicles). In this work, Particle Imaging Velocimetry (PIV) is performed on two static wings in a water tunnel over a range of angles of attack. These three- dimensional, finite-aspect ratio wings are modeled after a humpback whale flipper and are identical in shape, tapered from root to tip, except for the leading edge. In one of the foils the leading edge is smooth, whereas in the other, regularly spaced leading edge bumps are machined to simulate the whale’s fin tubercles. Results from these PIV tests reveal distinct cells where coherent flow structures are destroyed as a result of the leading edge perturbations. Tests are performed at Reynolds numbers Re ˜ O(10^5), based on chordlength, in a recirculating water tunnel. An inline six-axis load cell is mounted to measure the forces on the foil over a range of static pitch angles. It is hypothesized that this spanwise breakup of coherent vortical structures is responsible for the delayed angle of stall. These quantitative experiments complement exiting qualitative studies with two dimensional foils.
Predictive Gust Load Alleviation Control Using Leading Edge Stagnation Point Sensor Project
National Aeronautics and Space Administration — ZONA Technology, Inc proposes an R&D effort to develop a Gust Load Alleviation (GLA) control system using a novel Leading Edge Stagnation Point (LESP) sensor...
Squires, Becky
1993-01-01
The leading edge vortex of a counter rotating propeller (CRP) model was altered by using shrouds and by turning the upstream rotors to a forward sweep configuration. Performance, flow, and acoustic data were used to determine the effect of vortex impingement on the noise signature of the CRP system. Forward sweep was found to eliminate the leading edge vortex of the upstream blades. Removal of the vortex had little effect on the tone noise at the forward and rear blade passing frequencies (BPF's) but significantly altered both the sound pressure level and directivity of the interaction tone which occurs at the sum of the two BPF's. A separate manipulation of the leading edge vortex performed by installing shrouds of various inlet length on the CRP verified that diverting the vortex path increases the noise level of the interaction tone. An unexpected link has been established between the interaction tone and the leading edge vortex-blade interaction phenomenon.
Effect of leading edge roundness on a delta wing in wing-rock motion
Ng, T. Terry; Malcolm, Gerald N.
1990-01-01
The effect of wing leading-edge roundness on wing rock was investigated using flow visualization in a water tunnel. Eighty degree delta wing models were tested on free-to-roll and forced oscillation rigs. The onset of wing rock was delayed by increasing the roundness of the leading edges. The wing rock amplitude and frequency results suggested that damping was increased at lower angles of attack but reduced at higher angles of attack. Vortex lift-off and vortex breakdown, especially during dynamic situations, were strongly affected by the leading edge roundness. Different forms of wing rock motion could be sustained by combinations of vortex breakdown and vortex lift-off. Behaviors of the wing and vortex motions were explained by the influence of leading edge roundness on the separation location, vortex trajectory, and vortex breakdown.
Rivers, S. M. B.; Wahls, R. A.; Owens, L. R.
2001-01-01
A computational study focused on leading-edge radius effects and associated Reynolds number sensitivity for a High Speed Civil Transport configuration at transonic conditions was conducted as part of NASA's High Speed Research Program. The primary purposes were to assess the capabilities of computational fluid dynamics to predict Reynolds number effects for a range of leading-edge radius distributions on a second-generation supersonic transport configuration, and to evaluate the potential performance benefits of each at the transonic cruise condition. Five leading-edge radius distributions are described, and the potential performance benefit including the Reynolds number sensitivity for each is presented. Computational results for two leading-edge radius distributions are compared with experimental results acquired in the National Transonic Facility over a broad Reynolds number range.
The effect of leading-edge sweep angle asymmetry on lateral aerodynamics
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Based on the results of force measurement experiment in a low speed wind tunnel, the effect of asymmetrical leading-edge sweep angle on aerodynamic load was investigated with the commonswift’s wing model. The wing model was divided into three segments, i.e., arm wing, hand wingin and hand wingout, and the roll moment produced by the variation of asymmetrical change of wing segment’s leading-edge sweep angle was analyzed.
Thermal protection mechanism of heat pipe in leading edge under hypersonic conditions
Peng Wengen; He Yurong; Wang Xinzhi; Zhu Jiaqi; Han Jiecai
2015-01-01
Sharp local structure, like the leading edge of hypersonic aircraft, confronts a severe aerodynamic heating environment at a Mach number greater than 5. To eliminate the danger of a material failure, a semi-active thermal protection system is proposed by integrating a metallic heat pipe into the structure of the leading edge. An analytical heat-balance model is established from traditional aerodynamic theories, and then thermal and mechanical characteristics of the structure are studied at Ma...
Topology optimization of compliant adaptive wing leading edge with composite materials
Tong Xinxing; Ge Wenjie; Sun Chao; Liu Xiaoyong
2014-01-01
An approach for designing the compliant adaptive wing leading edge with composite material is proposed based on the topology optimization. Firstly, an equivalent constitutive relationship of laminated glass fiber reinforced epoxy composite plates has been built based on the symmetric laminated plate theory. Then, an optimization objective function of compliant adaptive wing leading edge was used to minimize the least square error (LSE) between deformed curve and desired aerodynamics shape. Af...
Effects of Leading Edge Sweep on the Cavitating Characteristics of Inducer Pumps
Acosta, Allan J.; Yoshinobu Tsujimoto; Yoshiki Yoshida; Seiji Azuma; Paul Cooper
2001-01-01
It is well known that leading edge sweep has a favorable effect on the cavitation of turbomachines. However, the mechanisms of the improvement have not been made clear. It has been shown that the lift and the drag on a cavitating swept single hydrofoil can be correlated fairly well based on the velocity component normal to the leading edge. In the present paper, such correlations for swept cascades are derived and the results are examined, neglecting the full geometrical effects of the induce...
Effects of real airfoil geometry on leading edge gust interaction noise
Gill, James; Zhang, Xin; Joseph, Phillip; Node-Langlois, Thomas
2013-01-01
High-order computational aeroacoustic methods are applied to the modeling of noise due to interactions between gusts and the leading edge of real symmetric airfoils. The effects of airfoil thickness and leading edge radius on noise are investigated systematically and in-dependently for the first time, at higher frequencies than previously used in computational methods. Single frequency harmonic gusts are interacted with airfoils of varying geometry at zero angle of attack. Increases in both l...
Burke, Eric R.
2009-01-01
Comparison metrics can be established to reliably and repeatedly establish the health of the joggle region of the Orbiter Wing Leading Edge reinforced carbon carbon (RCC) panels. Using these metrics can greatly reduced the man hours needed to perform, wing leading edge scanning for service induced damage. These time savings have allowed for more thorough inspections to be preformed in the necessary areas with out affecting orbiter flow schedule. Using specialized local inspections allows for a larger margin of safety by allowing for more complete characterizations of panel defects. The presence of the t-seal during thermographic inspection can have adverse masking affects on ability properly characterize defects that exist in the joggle region of the RCC panels. This masking affect dictates the final specialized inspection should be preformed with the t-seal removed. Removal of the t-seal and use of the higher magnification optics has lead to the most effective and repeatable inspection method for characterizing and tracking defects in the wing leading edge. Through this study some inadequacies in the main health monitoring system for the orbiter wing leading edge have been identified and corrected. The use of metrics and local specialized inspection have lead to a greatly increased reliability and repeatable inspection of the shuttle wing leading edge.
Davis, Richard E.; Maddalon, Dal V.; Wagner, Richard D.; Fisher, David F.; Young, Ronald
1989-01-01
Summary evaluations of the performance of laminar-flow control (LFC) leading edge test articles on a NASA JetStar aircraft are presented. Statistics, presented for the test articles' performance in haze and cloud situations, as well as in clear air, show a significant effect of cloud particle concentrations on the extent of laminar flow. The cloud particle environment was monitored by two instruments, a cloud particle spectrometer (Knollenberg probe) and a charging patch. Both instruments are evaluated as diagnostic aids for avoiding laminar-flow detrimental particle concentrations in future LFC aircraft operations. The data base covers 19 flights in the simulated airline service phase of the NASA Leading-Edge Flight-Test (LEFT) Program.
X-Ray Absorption Near Edge Structure Spectra as a basis for the speciation of lead
International Nuclear Information System (INIS)
For this study several inorganic lead (II) compounds were measured at the Pb-L3-(13035 eV), L1- (15860 eV) and M5- (2484 eV) edge using X-Ray Absorption Near Edge Structure Spectroscopy (XANES) to determine experimentally which edge is most sensitive to the coordination environment. Each edge probes a different electronic configuration because of the selection rules and has a different resolution because of life-time broadening. Pb-L1-XANES spectra are only sensitive to the first coordination shell. Pb-M5-XANES spectra show a better energy resolution which is due to decreased lifetime broadening, but the pure lead spectra are also sensitive only to the first coordination shell. Spectra at the Pb-L3-edge show the highest sensitivity: differences in coordination out to the third shell could be distinguished. Therefore, even though Pb-L1- and M5-edges have some advantages, because of physical conditions compared to the L3-edge, these advantages do not result in increased sensitivity.
Modification of the NACA 63_{2}-415 leading edge for better aerodynamic performance
DEFF Research Database (Denmark)
Bak, C.; Fuglsang, P.
2002-01-01
region of wind turbines. A numerical optimization tool incorporating XFOIL was used with a special formulation for the airfoil leading edge shape. The EllipSys2D CFD code was used to analyze the modified airfoil. In theory and in wind tunnel tests, the modified airfoil showed smooth and stable stall......Double stall causes more than one power level when stall-regulated wind turbines operate in stall. This involves significant uncertainty on power production and loads. To avoid double stall, a new leading edge was designed for the NACA 632-415 airfoil, an airfoil that is often used in the tip...... stall and aerodynamic damping characteristics for the modified airfoil and the NACA 632-415 airfoil were the same. The modified airfoil with leading edge roughness in general had better characteristics compared with the NACA 632-415 airfoil. ©2002 ASME...
Xu, Y.; Tan, L.; Cao, S. L.; Wang, Y. C.; Meng, G.; Qu, W. S.
2015-01-01
The influence of blade angle distribution along leading edge on cavitation performance of centrifugal pumps is analysed in the present paper. Three sets of blade angle distribution along leading edge for three blade inlet angles are chosen to design nine centrifugal pump impellers. The RNG k-epsilon turbulence model and the Zwart-Gerber-Belamri cavitation model are employed to simulate the cavitation flows in centrifugal pumps with different impellers and the same volute. The numerical results are compared with the experimental data, and the comparison proves that the numerical simulation can accurately predict the cavitation performance of centrifugal pumps. On the basis of the numerical simulations, the pump head variations with pump inlet pressure, and the flow details in centrifugal pump are revealed to demonstrate the influence of blade angle distribution along leading edge on cavitation performances of centrifugal pumps.
Leading edge sweep effects in generic three-dimensional sidewall compression scramjet inlets
Cozart, Aaron B.; Holland, Scott D.; Trexler, Carl A.; Perkins, John N.
1992-01-01
A computational and experimental study of generic 3D sidewall compression inlets is conducted to examine the effects of fore and aft leading edge sweep on the internal shock structure. Inlets with leading edge sweeps of +30 deg and -30 deg with sidewall compression angles of 6 deg were tested in the NASA Langley Mach 4 air tunnel at a geometric contraction ratio of 1.87. The principal difference in performance was determined to be in the mass capture. Spillage was identified as having two components: a pressure induced component and a sweep induced component. It was found that while the direction of the leading edge sweep had a large influence on the spillage, the pressure effects were more important.
Effect of leading-edge porosity on blade-vortex interaction noise
Lee, Soogab
1993-01-01
The effect of the porous leading-edge of an airfoil on the blade-vortex interaction noise, which dominates far-field acoustic spectrum of the helicopter, is investigated. The thin-layer Navier-Stokes equations are solved with a high-order upwind-biased scheme and a multizonal grid system. The Baldwin-Lomax turbulence model is modified for considering transpiration on the surface. The amplitudes of the propagating acoustic wave in the near-field are calculated directly from the computation. The porosity effect on the surface is modeled. Results show leading-edge transpiration can suppress pressure fluctuations at the leading-edge during BVI, and consequently reduce the amplitude of propagating noise by 30 percent at maximum in the near-field. The effect of porosity factor on the noise level is also investigated.
Cervical Length & Leading Placental Edge to Internal OS Measurements - TA vs TV
DEFF Research Database (Denmark)
Westerway, Sue Campbell; Pedersen, Lars Henning; Hyett, Jon
sectional study of 374 consecutive pregnancies with gestation 12 weeks to term. The cervical length was estimated as the distance from internal to external os, and the placenta / cervix distance as the leading placental edge to internal cervical os. Bland-Altman plots were used to evaluate the two methods......Brief Description of the Purpose of the Study: To compare cervical length/leading placental edge from the internal cervical os measurements obtained by both transabdominal (TA) and transvaginal (TV) approach and to assess intra / inter-observer variation for these measurements. Methods: Cross...
Falke, Joseph J.; Ziemba, Brian P
2014-01-01
The chemotactic migration of eukaryotic ameboid cells up concentration gradients is among the most advanced forms of cellular behavior. Chemotaxis is controlled by a complex network of signaling proteins bound to specific lipids on the cytoplasmic surface of the plasma membrane at the front of the cell, or the leading edge. The central lipid players in this leading edge signaling pathway include the phosphoinositides PI(4,5)P2 (PIP2) and PI(3,4,5)P3 (PIP3), both of which play multiple roles. ...
Reynolds Number, Compressibility, and Leading-Edge Bluntness Effects on Delta-Wing Aerodynamics
Luckring, James M.
2004-01-01
An overview of Reynolds number, compressibility, and leading edge bluntness effects is presented for a 65 degree delta wing. The results of this study address both attached and vortex-flow aerodynamics and are based upon a unique data set obtained in the NASA-Langley National Transonic Facility (NTF) for i) Reynolds numbers ranging from conventional wind-tunnel to flight values, ii) Mach numbers ranging from subsonic to transonic speeds, and iii) leading-edge bluntness values that span practical slender wing applications. The data were obtained so as to isolate the subject effects and they present many challenges for Computational Fluid Dynamics (CFD) studies.
Transonic Reynolds Number and Leading-Edge Bluntness Effects on a 65 deg Delta Wing
Luckring, J. M.
2003-01-01
A 65 degree delta wing has been tested in the National Transonic Facility (NTF) at mean aerodynamic chord Reynolds numbers from 6 million to 120 million at subsonic and transonic speeds. The configuration incorporated a systematic variation of the leading edge bluntness. The analysis for this paper is focused on the Reynolds number and bluntness effects at transonic speeds (M = 0.85) from this data set. The results show significant effects of both these parameters on the onset and progression of leading edge vortex separation.
Reynolds Number and Leading-Edge Bluntness Effects on a 65 Deg Delta Wing
Luckring, J. M.
2002-01-01
A 65 deg delta wing has been tested in the National Transonic Facility (NTF) at mean aerodynamic chord Reynolds numbers from 6 million to 120 million at subsonic and transonic speeds. The configuration incorporated systematic variation of the leading edge bluntness. The analysis for this paper is focused on the Reynolds number and bluntness effects at subsonic speeds (M = 0.4) from this data set. The results show significant effects of both these parameters on the onset and progression of leading-edge vortex separation.
Turbine Airfoil With CMC Leading-Edge Concept Tested Under Simulated Gas Turbine Conditions
Robinson, R. Craig; Hatton, Kenneth S.
2000-01-01
Silicon-based ceramics have been proposed as component materials for gas turbine engine hot-sections. When the Navy s Harrier fighter experienced engine (Pegasus F402) failure because of leading-edge durability problems on the second-stage high-pressure turbine vane, the Office of Naval Research came to the NASA Glenn Research Center at Lewis Field for test support in evaluating a concept for eliminating the vane-edge degradation. The High Pressure Burner Rig (HPBR) was selected for testing since it could provide temperature, pressure, velocity, and combustion gas compositions that closely simulate the engine environment. The study focused on equipping the stationary metal airfoil (Pegasus F402) with a ceramic matrix composite (CMC) leading-edge insert and evaluating the feasibility and benefits of such a configuration. The test exposed the component, with and without the CMC insert, to the harsh engine environment in an unloaded condition, with cooling to provide temperature relief to the metal blade underneath. The insert was made using an AlliedSignal Composites, Inc., enhanced HiNicalon (Nippon Carbon Co. LTD., Yokohama, Japan) fiber-reinforced silicon carbide composite (SiC/SiC CMC) material fabricated via chemical vapor infiltration. This insert was 45-mils thick and occupied a recessed area in the leading edge and shroud of the vane. It was designed to be free floating with an end cap design. The HPBR tests provided a comparative evaluation of the temperature response and leading-edge durability and included cycling the airfoils between simulated idle, lift, and cruise flight conditions. In addition, the airfoils were aircooled, uniquely instrumented, and exposed to the exact set of internal and external conditions, which included gas temperatures in excess of 1370 C (2500 F). In addition to documenting the temperature response of the metal vane for comparison with the CMC, a demonstration of improved leading-edge durability was a primary goal. First, the
Effect of leading-edge geometry on boundary-layer receptivity to freestream sound
Lin, Nay; Reed, Helen L.; Saric, W. S.
1991-01-01
The receptivity to freestream sound of the laminar boundary layer over a semi-infinite flat plate with an elliptic leading edge is simulated numerically. The incompressible flow past the flat plate is computed by solving the full Navier-Stokes equations in general curvilinear coordinates. A finite-difference method which is second-order accurate in space and time is used. Spatial and temporal developments of the Tollmien-Schlichting wave in the boundary layer, due to small-amplitude time-harmonic oscillations of the freestream velocity that closely simulate a sound wave travelling parallel to the plate, are observed. The effect of leading-edge curvature is studied by varying the aspect ratio of the ellipse. The boundary layer over the flat plate with a sharper leading edge is found to be less receptive. The relative contribution of the discontinuity in curvature at the ellipse-flat-plate juncture to receptivity is investigated by smoothing the juncture with a polynomial. Continuous curvature leads to less receptivity. A new geometry of the leading edge, a modified super ellipse, which provides continuous curvature at the juncture with the flat plate, is used to study the effect of continuous curvature and inherent pressure gradient on receptivity.
Leading edge erosion of coated wind turbine blades: Review of coating life models
Slot, H.M.; Gelinck, E.R.M.; Rentrop, C.; Heider, E. van der
2015-01-01
Erosion of the leading edge of wind turbine blades by droplet impingement wear, reduces blade aerodynamic efficiency and power output. Eventually, it compromises the integrity of blade surfaces. Elastomeric coatings are currently used for erosion resistance, yet the life of such coatings cannot be p
Thermal protection mechanism of heat pipe in leading edge under hypersonic conditions
Directory of Open Access Journals (Sweden)
Peng Wengen
2015-02-01
Full Text Available Sharp local structure, like the leading edge of hypersonic aircraft, confronts a severe aerodynamic heating environment at a Mach number greater than 5. To eliminate the danger of a material failure, a semi-active thermal protection system is proposed by integrating a metallic heat pipe into the structure of the leading edge. An analytical heat-balance model is established from traditional aerodynamic theories, and then thermal and mechanical characteristics of the structure are studied at Mach number 6–8 for three refractory alloys, Inconel 625, C-103, and T-111. The feasibility of this simple analytical method as an initial design tool for hypersonic aircraft is assessed through numerical simulations using a finite element method. The results indicate that both the isothermal and the maximum temperatures fall but the von Mises stress increases with a longer design length of the leading edge. These two temperatures and the stress rise remarkably at a higher Mach number. Under all investigated hypersonic conditions, with a 3 mm leading edge radius and a 0.15 m design length, the maximum stress exceeds the yield strength of Inconel 625 at Mach numbers greater than 6, which means a material failure. Moreover, both C-103 and T-111 meet all requirements at Mach number 6–8.
Thermal protection mechanism of heat pipe in leading edge under hypersonic conditions
Institute of Scientific and Technical Information of China (English)
Peng Wengen; He Yurong; Wang Xinzhi; Zhu Jiaqi; Han Jiecai
2015-01-01
Sharp local structure, like the leading edge of hypersonic aircraft, confronts a severe aerodynamic heating environment at a Mach number greater than 5. To eliminate the danger of a material failure, a semi-active thermal protection system is proposed by integrating a metallic heat pipe into the structure of the leading edge. An analytical heat-balance model is established from tra-ditional aerodynamic theories, and then thermal and mechanical characteristics of the structure are studied at Mach number 6–8 for three refractory alloys, Inconel 625, C-103, and T-111. The feasi-bility of this simple analytical method as an initial design tool for hypersonic aircraft is assessed through numerical simulations using a finite element method. The results indicate that both the iso-thermal and the maximum temperatures fall but the von Mises stress increases with a longer design length of the leading edge. These two temperatures and the stress rise remarkably at a higher Mach number. Under all investigated hypersonic conditions, with a 3 mm leading edge radius and a 0.15 m design length, the maximum stress exceeds the yield strength of Inconel 625 at Mach num-bers greater than 6, which means a material failure. Moreover, both C-103 and T-111 meet all requirements at Mach number 6–8.
Effect of guide wall on jet impingement cooling in blade leading edge channel
Energy Technology Data Exchange (ETDEWEB)
Zhao, Qing-Yang; Chung, Heeyoon; Choi, Seok Min; Cho, Hyung Hee [Yonsei University, Seoul (Korea, Republic of)
2016-02-15
The characteristics of fluid flow and heat transfer, which are affected by the guide wall in a jet impinged leading edge channel, have been investigated numerically using three-dimensional Reynolds-averaged Navier-Stokes analysis via the shear stress transport turbulence model and gamma theta transitional turbulence model. A constant wall heat flux condition has been applied to the leading edge surface. The jet-to-surface distance is constant, which is three times that of the jet diameter. The arrangement of the guide wall near the jet hole is set as a variable. Results presented in this study include the Nusselt number contour, velocity vector, streamline with velocity, and local Nusselt number distribution along the central line on the leading edge surface. The average Nusselt number and average pressure loss between jet nozzle and channel exit are calculated to assess the thermal performance. The application of the guide wall is aimed at improving heat transfer uniformity on the leading edge surface. Results indicated that the streamwise guide wall ensures the vertical jet impingement flow intensity and prevents the flow after impingement to reflux into jet flow. Thus, a combined rectangular guide wall benefits the average heat transfer, thermal performance and heat transfer distribution uniformity.
Effects of Fin Leading Edge Sweep on Shock-Shock Interaction at Mach 6
Berry, Scott A.; Nowak, Robert J.
1996-01-01
The effects of fin leading edge sweep on peak heating rates due to shock-shock interaction have been experimentally examined in the Langley 20-Inch Mach 6 Tunnel. The shock interaction was produced by the intersection of a planar incident shock (16.8 deg shock angle relative to the freestream, generated by a 9 deg wedge) with the bow shock formed around a O.5-inch diameter cylindrical leading edge fin. Heating distributions along the leading edge stagnation line have been obtained using densely spaced thin film resistive-type sensors. Schlieren images were obtained to illustrate the very complex shock-shock interactions. The fin leading edge sweep angle was varied from 15-degrees swept back to 45-degrees swept forward for a freestream unit Reynolds number of 2 x 10(exp 6)/ft. Two models were utilized during the study, one with 0.025-inch spacing between gage centers, and the other 0.015-inch spacing. Gage spatial resolution on the order of 0.015-in appeared to accurately capture the narrow spike in heating. Peak heating due to shock interaction was maximized when the fin was swept forward 15 deg and 25 deg, both promoting augmentations about 7 times the baseline value. The schlieren images for these cases revealed Type 4 and Type 3 interactions, respectively.
Research on Aerodynamic Performance of an Wind Turbine Airfoil With Leading Edge Ice
Directory of Open Access Journals (Sweden)
Fu Jie
2013-12-01
Full Text Available The performance of wind turbine was influenced by the environment. Among them, airfoil with leading edge ice has a great effect on the changes of aerodynamic performance. This study calculated the performance of an wind tubine airfoil at two iced shape model by CFD simulation using LES. LES in various models has been developed to simulate turbulent flows, especially to separated flows. In this investigation, 2D LES has been used to simulate flow past a wind turbine airfoil with leading edge ice which is a classical separated flow. The results show that flow structure is more complex with abundant whirlpools signifying violent turbulence when airfoil with ice and leads to poorer performance of wind turbine.
Effects of leading and trailing edge flaps on the aerodynamics of airfoil/vortex interactions
Hassan, Ahmed A.; Sankar, L. N.; Tadghighi, H.
1994-01-01
A numerical procedure has been developed for predicting the two-dimensional parallel interaction between a free convecting vortex and a NACA 0012 airfoil having leading and trailing edge integral-type flaps. Special emphasis is placed on the unsteady flap motion effects which result in alleviating the interaction at subcritical and supercritical onset flows. The numerical procedure described here is based on the implicit finite-difference solutions to the unsteady two-dimensional full potential equation. Vortex-induced effects are computed using the Biot-Savart Law with allowance for a finite core radius. The vortex-induced velocities at the surface of the airfoil are incorporated into the potential flow model via the use of the velocity transpiration approach. Flap motion effects are also modeled using the transpiration approach. For subcritical interactions, our results indicate that trailing edge flaps can be used to alleviate the impulsive loads experienced by the airfoil. For supercritical interactions, our results demonstrate the necessity of using a leading edge flap, rather than a trailing edge flap, to alleviate the interaction. Results for various time-dependent flap motions and their effect on the predicted temporal sectional loads, differential pressures, and the free vortex trajectories are presented
Effects of leading-edge flap oscillation on unsteady delta wing flow and rock control
Kandil, Osama A.; Salman, Ahmed A.
1991-01-01
The isolated and interdisciplinary problems of unsteady fluid dynamics and rigid-body dynamics and control of delta wings with and without leading-edge flap oscillation are considered. For the fluid dynamics problem, the unsteady, compressible, thin-layer Navier-Stokes (NS) equations, which are written relative to a moving frame of reference, are solved along with the unsteady, linearized, Navier-displacement (ND) equations. The NS equations are solved for the flowfield using an implicit finite-volume scheme. The ND equations are solved for the grid deformation, if the leading-edge flaps oscillate, using an ADI scheme. For the dynamics and control problem, the Euler equation of rigid-body rolling motion for a wing and its flaps are solved interactively with the fluid dynamics equations for the wing-rock motion and subsequently for its control. A four-stage Runge-Kutta scheme is used to explicitly integrate the dynamics equation.
Unsteady vortex-dominated flow around wings with oscillating leading-edge flaps
Kandil, Osama A.; Salman, Ahmed A.
1991-01-01
Unsteady vortex-dominated flow around delta wings with oscillating leading-edge flaps represents an important classs of problems for supermaneuverability and flow control of advanced aircraft. The problem is solved using time accurate integration of the unsteady, compressible, thin-layer Navier-Stokes equations in conjunction with the unsteady, linearized, Navier-displacement equations. Starting with an initial configuration of the wing and its flaps, the Navier-Stokes equations are solved on an initial structured grid for the steady flow. The forced oscillation of the flaps is then applied, and the problem is solved accurately in time. The Navier-displacement equations are solved for the grid deformation and the Navier-Stokes equations are solved for the flowfield. Symmetric and anti-symmetric flaps oscillations are presented to study the effect of the flaps oscillation on the leading-edge vortical flow.
Investigation of film cooling on the leading edge of turbine blade based on detached eddy simulation
Institute of Scientific and Technical Information of China (English)
LIANG JunYu; KANG Shun
2012-01-01
In order to assess the influences of curved hole passage on cooling effectiveness and flow structure of turbine blade leading edge,the detached eddy simulation is applied to numerically investigate the AGTB turbine cascade under the condition of global blowing ratio M=0.7.The straight or curved cooling holes are located at either the pressure or suction side near the leading edge.The analysis and discussion focus on the local turbulence structure; influence of pressure gradient on the structure,and distribution of cooling effectiveness on the blade surface.The numerical results show that cooling hole with curved passage could bring positive impact on the increase of the local cooling effectiveness.On the suction side,the increased cooling effectiveness could be about 82％ and about 77％ on the pressure side,compared to the conventional straight hole.
Energy Technology Data Exchange (ETDEWEB)
Ames, Forrest; Bons, Jeffrey
2014-09-30
The Department of Energy has goals to move land based gas turbine systems to alternate fuels including coal derived synthetic gas and hydrogen. Coal is the most abundant energy resource in the US and in the world and it is economically advantageous to develop power systems which can use coal. Integrated gasification combined cycles are (IGCC) expected to allow the clean use of coal derived fuels while improving the ability to capture and sequester carbon dioxide. These cycles will need to maintain or increase turbine entry temperatures to develop competitive efficiencies. The use of coal derived syngas introduces a range of potential contaminants into the hot section of the gas turbine including sulfur, iron, calcium, and various alkali metals. Depending on the effectiveness of the gas clean up processes, there exists significant likelihood that the remaining materials will become molten in the combustion process and potentially deposit on downstream turbine surfaces. Past evidence suggests that deposition will be a strong function of increasing temperature. Currently, even with the best gas cleanup processes a small level of particulate matter in the syngas is expected. Consequently, particulate deposition is expected to be an important consideration in the design of turbine components. The leading edge region of first stage vanes most often have higher deposition rates than other areas due to strong fluid acceleration and streamline curvature in the vicinity of the surface. This region remains one of the most difficult areas in a turbine nozzle to cool due to high inlet temperatures and only a small pressure ratio for cooling. The leading edge of a vane often has relatively high heat transfer coefficients and is often cooled using showerhead film cooling arrays. The throat of the first stage nozzle is another area where deposition potentially has a strongly adverse effect on turbine performance as this region meters the turbine inlet flow. Based on roughness
The leading-edge stall of airfoils with various nose shapes
Kraljic, Matthew; Rusak, Zvi; Wang, Shixiao
2015-11-01
We study the inception of leading-edge stall on stationary, smooth thin airfoils with various nose shapes of the form xa (where 0 nose, that asymptotically match each other. The flow in the outer region is dominated by the classical thin airfoil theory. Scaled (magnified) coordinates and a modified (smaller) Reynolds number ReM are used to correctly account for the nonlinear behavior and extreme velocity changes in the inner region, where both the near-stagnation and high suction areas occur. The inner region problem is solved numerically to determine the inception of leading-edge stall on the nose. It is found that stall is delayed to higher angles of attack with the decrease of nose parameter a. Specifically, new airfoil shapes are proposed with increased stall angle at subsonic speeds and higher critical Mach numbers at transonic speeds.
Effect of a round airfoil nose on leading-edge suction
Lan, C. Edward; Su, Ingchung
1987-01-01
Kulfan (1979) assumed that the angle of attack for initial vortex separation on a slender wing with rounded leading edges could be obtained by equating the leading-edge suction (LES) and nose drag coefficients. In the present study, this assumption is examined and is shown to predict reasonably well the initial angle of attack at which laminar separation occurs near the airfoil nose. However, the assumption is shown to be slightly less accurate for thick or cambered airfoils. Attainable LES estimated by Kulfan's method seemed to agree well with that obtained from an airfoil aerodynamics code and experimental data on a NACA 64A009 airfoil at M = 0.4 and Re = 0.86 x 10 to the 6th.
Effect of flow obstacles with various leading and trailing edges on critical heat flux
International Nuclear Information System (INIS)
A joint investigation has been performed by the University of Ottawa and Chalk River Laboratories that examined the effect of the shape of the leading and trailing edges of the turbulence enhancing devices ('flow obstacles') on critical heat flux (CHF). The objective of this study was to gain a better overall understanding of the limit of CHF improvement for various obstacle designs and the impact of flow conditions on the improvements. (author)
Multiple leading edge vortices of unexpected strength in freely flying hawkmoth
L. Christoffer Johansson; Sophia Engel; Almut Kelber; Marco Klein Heerenbrink; Anders Hedenström
2013-01-01
The Leading Edge Vortex (LEV) is a universal mechanism enhancing lift in flying organisms. LEVs, generally illustrated as a single vortex attached to the wing throughout the downstroke, have not been studied quantitatively in freely flying insects. Previous findings are either qualitative or from flappers and tethered insects. We measure the flow above the wing of freely flying hawkmoths and find multiple simultaneous LEVs of varying strength and structure along the wingspan. At the inner win...
Fracture Mechanics Analyses of the Slip-Side Joggle Regions of Wing-Leading-Edge Panels
Raju, Ivatury S.; Knight, Norman F., Jr.; Song, Kyongchan; Phillips, Dawn R.
2011-01-01
The Space Shuttle wing-leading edge consists of panels that are made of reinforced carbon-carbon. Coating spallation was observed near the slip-side region of the panels that experience extreme heating. To understand this phenomenon, a root-cause investigation was conducted. As part of that investigation, fracture mechanics analyses of the slip-side joggle regions of the hot panels were conducted. This paper presents an overview of the fracture mechanics analyses.
Fracture mechanics analyses of the slip-side joggle regions of wing-leading-edge panels
Directory of Open Access Journals (Sweden)
Kyongchan Song
2011-01-01
Full Text Available The Space Shuttle wing-leading edge consists of panels that are made of reinforced carbon-carbon. Coating spallation was observed near the slip-side region of the panels that experience extreme heating. To understand this phenomenon, a root-cause investigation was conducted. As part of that investigation, fracture mechanics analyses of the slip-side joggle regions of the hot panels were conducted. This paper presents an overview of the fracture mechanics analyses.
Effects of Nose Radius and Aerodynamic Loading on Leading Edge Receptivity
Hammerton, P. W.; Kerschen, E. J.
1998-01-01
An analysis is presented of the effects of airfoil thickness and mean aerodynamic loading on boundary-layer receptivity in the leading-edge region. The case of acoustic free-stream disturbances, incident on a thin cambered airfoil with a parabolic leading edge in a low Mach number flow, is considered. An asymptotic analysis based on large Reynolds number is developed, supplemented by numerical results. The airfoil thickness distribution enters the theory through a Strouhal number based on the nose radius of the airfoil, S = (omega)tau(sub n)/U, where omega is the frequency of the acoustic wave and U is the mean flow speed. The influence of mean aerodynamic loading enters through an effective angle-of-attack parameter ti, related to flow around the leading edge from the lower surface to the upper. The variation of the receptivity level is analyzed as a function of S, mu, and characteristics of the free-stream acoustic wave. For an unloaded leading edge, a finite nose radius dramatically reduces the receptivity level compared to that for a flat plate, the amplitude of the instability waves in the boundary layer being decreased by an order of magnitude when S = 0.3. Modest levels of aerodynamic loading are found to further decrease the receptivity level for the upper surface of the airfoil, while an increase in receptivity level occurs for the lower surface. For larger angles of attack close to the critical angle for boundary layer separation, a local rise in the receptivity level occurs for the upper surface, while for the lower surface the receptivity decreases. The effects of aerodynamic loading are more pronounced at larger values of S. Oblique acoustic waves produce much higher receptivity levels than acoustic waves propagating downstream parallel to the airfoil chord.
Vorticity transport and the leading-edge vortex of a plunging airfoil
Eslam Panah, Azar; Akkala, James M.; Buchholz, James H. J.
2015-08-01
The three-dimensional flow field was experimentally characterized for a nominally two-dimensional flat-plate airfoil plunging at large amplitude and reduced frequencies, using three-dimensional reconstructions of planar PIV data at a chord-based Reynolds number of 10,000. Time-resolved, instantaneous PIV measurements reveal that secondary vorticity, of opposite sign to the primary vortex, is intermittently entrained into the leading-edge vortex (LEV) throughout the downstroke, with the rate of entrainment increasing toward the end of the stroke when the leading-edge shear layer weakens. A planar vorticity transport analysis around the LEV indicated that, during the downstroke, the surface vorticity flux due to the pressure gradient is consistently about half that due to the leading-edge shear layer for all parameter values investigated, demonstrating that production and entrainment of secondary vorticity is an important mechanism regulating LEV strength. A small but non-negligible vorticity source was also attributed to spanwise flow toward the end of the downstroke. Aggregate vortex tilting is notably more significant for higher plunge frequencies, suggesting that the vortex core is more three-dimensional.
Experimental investigation of the leading edge vortex on vertical axis wind turbine blades
Dunne, Reeve; McKeon, Beverley
2012-11-01
A NACA 0018 airfoil is pitched about the leading edge over a large angle of attack range (+/- ~40°) at a chord Reynolds number of 110,000 to simulate the flow over a single blade in a vertical axis wind turbine (VAWT). Particle image velocimetry (PIV) measurements are made to investigate the effects of pitching on leading edge vortex (LEV) development and separation. Time resolved experiments are performed to track vortex formation and convection over the airfoil for sinusoidal pitching motions corresponding to a VAWT trajectory as well as impulsive pitch up and pitch down motions. These results are compared to the wake of steady, post stall, high angle of attack airfoils (α =20° -30°). The characteristics of the leading edge vortex development and subsequent separation from the airfoil are discussed, with a view to characterizing its effect on power generation with VAWTs and future flow control strategies for turbine performance improvement. Funding from the Gordon and Betty Moore Foundation is gratefully acknowledged.
A Reynolds Number Study of Wing Leading-Edge Effects on a Supersonic Transport Model at Mach 0.3
Williams, M. Susan; Owens, Lewis R., Jr.; Chu, Julio
1999-01-01
A representative supersonic transport design was tested in the National Transonic Facility (NTF) in its original configuration with small-radius leading-edge flaps and also with modified large-radius inboard leading-edge flaps. Aerodynamic data were obtained over a range of Reynolds numbers at a Mach number of 0.3 and angles of attack up to 16 deg. Increasing the radius of the inboard leading-edge flap delayed nose-up pitching moment to a higher lift coefficient. Deflecting the large-radius leading-edge flap produced an overall decrease in lift coefficient and delayed nose-up pitching moment to even higher angles of attack as compared with the undeflected large- radius leading-edge flap. At angles of attack corresponding to the maximum untrimmed lift-to-drag ratio, lift and drag coefficients decreased while lift-to-drag ratio increased with increasing Reynolds number. At an angle of attack of 13.5 deg., the pitching-moment coefficient was nearly constant with increasing Reynolds number for both the small-radius leading-edge flap and the deflected large-radius leading-edge flap. However, the pitching moment coefficient increased with increasing Reynolds number for the undeflected large-radius leading-edge flap above a chord Reynolds number of about 35 x 10 (exp 6).
Precocious reproduction increases at the leading edge of a mangrove range expansion.
Dangremond, Emily M; Feller, Ilka C
2016-07-01
Climate change-driven shifts in species ranges are ongoing and expected to increase. However, life-history traits may interact with climate to influence species ranges, potentially accelerating or slowing range shifts in response to climate change. Tropical mangroves have expanded their ranges poleward in the last three decades. Here, we report on a shift at the range edge in life-history traits related to reproduction and dispersal. With a common garden experiment and field observations, we show that Rhizophora mangle individuals from northern populations reproduce at a younger age than those from southern populations. In a common garden at the northern range limit, 38% of individuals from the northernmost population were reproductive by age 2, but less than 10% of individuals from the southernmost population were reproductive by the same age, with intermediate amounts of reproduction from intermediate latitudes. Field observations show a similar pattern of younger reproductive individuals toward the northern range limit. We also demonstrate a shift toward larger propagule size in populations at the leading range edge, which may aid seedling growth. The substantial increase in precocious reproduction at the leading edge of the R. mangle range could accelerate population growth and hasten the expansion of mangroves into salt marshes. PMID:27547335
DEFF Research Database (Denmark)
Anttonen, Tommi; Kirjavainen, Anna; Belevich, Ilya;
2012-01-01
of a basolateral membrane protein in the apical domain were observed. These defects and changes in aPKCλ/ι expression suggested that apical polarization is impaired. Following a lesion at adulthood, supporting cells with Cdc42 loss-induced maturational defects collapsed and failed to remodel F...
Performance of the bio-inspired leading edge protuberances on a static wing and a pitching wing
Institute of Scientific and Technical Information of China (English)
胡文蓉; 张仕栋; 王雅赟
2014-01-01
It is shown that the leading edge protuberances on the flippers of a humpback whale can significantly improve the hydrodynamic performance. The present study numerically investigates the flow control mechanisms of the leading edge protuberances on a static wing and a pitching wing. For static wings, the performance in both laminar flow and turbulent flow are studied in the context of the flow control mechanisms. It is shown that the protuberances have slight effects on the performance of static wings in laminar flow. Also, it could be deduced that non-uniform downwash does not delay the stall occurrence in either laminar flow or turbulent flow. In turbulent flow, the leading edge protuberances act in a manner similar to vortex generators, enhancing the momentum exchange within the boundary layer. Streamwise vortices do contribute to the delay of the stall occurrence. The normal vorticity component also plays an important role in delaying the stall occurrence. However, for the pitching wing, the effect of leading edge protuberances is negligible in turbulent flow. Detailed analysis of the flow field indicates that for the wing with the leading edge protuberances, the leading edge vortices become more complex, while the thrust jet and the vortices in the wake are not changed significantly by the leading edge protuberances.
Minimum dispersion in leading edge timing with coaxial Ge(Li) detectors
International Nuclear Information System (INIS)
Time variances due to systematic walk and noise jitter are analytically performed as a function of integration time in leading-edge timing with coaxial Ge(Li) detectors for several values of the trigger fraction and the geometrical factor. This reveals the existence of a minimum in the curve which represents the total timing error vs the integration time constant. The best time resolution of a specified detector is achieved when the RC-filtered signal has a time constant (in ns) that is numerically equal to the thickness (in mm) of the detector depletion layer. (orig.)
International Nuclear Information System (INIS)
Zirconium diboride with addition of silicon carbide has been demonstrated in earlier studies to be a material with superior properties for leading edges for hypersonic atmospheric flight and re-entry vehicles. However, this material is brittle and flaw sensitive, making it unreliable in application. This paper reports on continuous fiber reinforced composites which have been prepared with zirconium diboride-silicon carbide matrix materials in a recent study to improve reliability. Composites were characterized for mechanical properties, and for oxidation and ablation response in representative re-entry conditions. Room temperature and elevated temperature flexure strengths, recession rate for oxidation at 1200 degrees C, and arc-jet ablation response are reported
Compressible Navier-Stokes equations: A study of leading edge effects
Hariharan, S. I.; Karbhari, P. R.
1987-01-01
A computational method is developed that allows numerical calculations of the time dependent compressible Navier-Stokes equations.The current results concern a study of flow past a semi-infinite flat plate.Flow develops from given inflow conditions upstream and passes over the flat plate to leave the computational domain without reflecting at the downstream boundary. Leading edge effects are included in this paper. In addition, specification of a heated region which gets convected with the flow is considered. The time history of this convection is obtained, and it exhibits a wave phenomena.
Dursch, Harry; George, Pete; Hill, Sylvester
1992-01-01
The composite electronics-module cover for the leading edge (row D9) experiment M0003-8 was fabricated from T300 graphite/934 epoxy unidirectional prepreg tape in a multi-oriented layup. This panel contained thermal control coatings in three of the four quadrants with the fourth quadrant left uncoated as a control. The composite experienced different thermal cycling extremes in each quadrant due to the differing optical properties of the coatings. Results will be presented on microcracking and other Low Earth Orbital (LEO) effects on the coated panel substrate.
Heat transfer characteristics of hypersonic waveriders with an emphasis on leading edge effects
Vanmol, Denis O.; Anderson, John D., Jr.
1992-01-01
The present analysis of the heat-transfer characteristics of a family of viscous-optimized, 60 m-long waverider hypersonic vehicles gives attention to the transition from laminar to turbulent flow, and to how the transition affects aerodynamic heating distributions over the waverider surface. Two different constant-dynamic-pressure flight trajectories are considered, at 0.2 and 1.0 freestream atmospheres. For Mach numbers below 10, it is found that passive radiative cooling of the surface is sufficient. The degree of leading-edge bluntness required by aerodynamic heating constraints does not significantly degrade the aerodynamic performance of these waveriders.
Lu, Z. B.; Halim, D.; Cheng, L.
2016-05-01
The present paper is devoted to an investigation on the flow-induced noise control downstream of bluff bodies with various leading edges using the surface perturbation technique. Four typical leading edges used in various engineering applications were studied in this work: the semi-circular, square, 30° symmetric trapezoid and 30° asymmetric trapezoid leading edges. The surface perturbation was created by piezo-ceramic actuators embedded underneath the surface of a bluff body placed in a cross flow. To suppress the flow-induced noise downstream bluff bodies with those leading edges, the surface perturbation technique was implemented. Based on the experiments, a noise reduction in the duct of more than 14.0 dB has been achieved for all leading-edge cases. These results indicated that the vortex shedding and its flow-induced noise have been successfully suppressed by the proposed control scheme. The flow structure alteration around the bluff bodies and the shear layer shift phenomenon observed on the trailing edges were then investigated for interpreting the control mechanism for this flow-induced noise suppression, which were based on the vortex shedding strength suppression and vortex shedding frequency shift phenomenon. The effective control position for various leading edges was also studied for developing optimal control strategies for practical engineering applications.
Analog filtering methods improve leading edge timing performance of multiplexed SiPMs.
Bieniosek, M F; Cates, J W; Grant, A M; Levin, C S
2016-08-21
Multiplexing many SiPMs to a single readout channel is an attractive option to reduce the readout complexity of high performance time of flight (TOF) PET systems. However, the additional dark counts and shaping from each SiPM cause significant baseline fluctuations in the output waveform, degrading timing measurements using a leading edge threshold. This work proposes the use of a simple analog filtering network to reduce the baseline fluctuations in highly multiplexed SiPM readouts. With 16 SiPMs multiplexed, the FWHM coincident timing resolution for single [Formula: see text] mm LYSO crystals was improved from 401 ± 4 ps without filtering to 248 ± 5 ps with filtering. With 4 SiPMs multiplexed, using an array of [Formula: see text] mm LFS crystals the mean time resolution was improved from 436 ± 6 ps to 249 ± 2 ps. Position information was acquired with a novel binary positioning network. All experiments were performed at room temperature with no active temperature regulation. These results show a promising technique for the construction of high performance multiplexed TOF PET readout systems using analog leading edge timing pickoff. PMID:27484131
Analog filtering methods improve leading edge timing performance of multiplexed SiPMs
Bieniosek, M. F.; Cates, J. W.; Grant, A. M.; Levin, C. S.
2016-08-01
Multiplexing many SiPMs to a single readout channel is an attractive option to reduce the readout complexity of high performance time of flight (TOF) PET systems. However, the additional dark counts and shaping from each SiPM cause significant baseline fluctuations in the output waveform, degrading timing measurements using a leading edge threshold. This work proposes the use of a simple analog filtering network to reduce the baseline fluctuations in highly multiplexed SiPM readouts. With 16 SiPMs multiplexed, the FWHM coincident timing resolution for single 3~\\text{mm}× 3~\\text{mm}× 20 mm LYSO crystals was improved from 401 ± 4 ps without filtering to 248 ± 5 ps with filtering. With 4 SiPMs multiplexed, using an array of 3~\\text{mm}× 3~\\text{mm}× 20 mm LFS crystals the mean time resolution was improved from 436 ± 6 ps to 249 ± 2 ps. Position information was acquired with a novel binary positioning network. All experiments were performed at room temperature with no active temperature regulation. These results show a promising technique for the construction of high performance multiplexed TOF PET readout systems using analog leading edge timing pickoff.
Leading-edge vortex trajectories under the influence of Coriolis acceleration
Limacher, Eric; Morton, Chris; Wood, David
2015-11-01
Leading-edge vortices (LEVs) can form and remain attached to a rotating wing indefinitely, but the mechanisms of stable attachment are not well understood. Taking for granted that such stable structures do form, a practical question arisesof where an LEV core persists in the body-fixed frame of reference. Noting that span-wise flow exists within the LEV core, it is apparent that a mean streamline aligned with the axis of the LEV must exist. The present work usesthe Navier-Stokes equations alongthis steady, axial streamline in order to consider the accelerations that act in the steamline-normal direction to affect its local curvature. With some simplifying assumptions, an ordinary differential equation is derivedthat describes the trajectory of the axial streamline through the vortex core. Usingempirical values of axial velocity in the vortex core from previous studies, it can be shown that Coriolis and centrifugal forces alone can account for the tilting of the stable LEV into the wake within several chord lengths from the root of rotationin the span-wise direction. This result supports an hypothesisthat LEVs are observed at inboard locations because Coriolis force must actover a finite distance to tilt the stable LEV away from the leading edge.
The effect of undulating leading-edge modifications on NACA 0021 airfoil characteristics
Rostamzadeh, N.; Kelso, R. M.; Dally, B. B.; Hansen, K. L.
2013-11-01
In spite of its mammoth physical size, the humpback whale's manoeuvrability in hunting has captured the attention of biologists as well as fluid mechanists. It has now been established that the protrusions on the leading-edges of the humpback's pectoral flippers, known as tubercles, account for this species' agility and manoeuvrability. In the present work, Prandtl's nonlinear lifting-line theory was employed to propose a hypothesis that the favourable traits observed in the performance of tubercled lifting bodies are not exclusive to this form of leading-edge configuration. Accordingly, a novel alternative to tubercles was introduced and incorporated into the design of four airfoils that underwent wind tunnel force and pressure measurement tests in the transitional flow regime. In addition, a Computation Fluid Dynamics study was performed using the Shear Stress Transport transitional model in the context of unsteady Reynolds-Averaged Navier-Stokes at several attack angles. The results from the numerical investigation are in reasonable agreement with those of the experiments, and suggest the presence of features that are also observed in flows over tubercled foils, most notably a distinct pair of streamwise vortices for each wavelength of the tubercle-like feature.
Fracture Mechanics Analyses of the Slip-Side Joggle Regions of Wing-Leading Edge Panels
Raju, Ivatury S.; Knight, Norman F., Jr.; Song, Kyongchan; Phillips, Dawn R.
2010-01-01
The Space Shuttle Orbiter wing comprises of 22 leading edge panels on each side of the wing. These panels are part of the thermal protection system that protects the Orbiter wings from extreme heating that take place on the reentry in to the earth atmosphere. On some panels that experience extreme heating, liberation of silicon carbon (SiC) coating was observed on the slip side regions of the panels. Global structural and local fracture mechanics analyses were performed on these panels as a part of the root cause investigation of this coating liberation anomaly. The wing-leading-edge reinforced carbon-carbon (RCC) panels, Panel 9, T-seal 10, and Panel 10, are shown in Figure 1 and the progression of the stress analysis models is presented in Figure 2. The global structural analyses showed minimal interaction between adjacent panels and the T-seal that bridges the gap between the panels. A bounding uniform temperature is applied to a representative panel and the resulting stress distribution is examined. For this loading condition, the interlaminar normal stresses showed negligible variation in the chord direction and increased values in the vicinity of the slip-side joggle shoulder. As such, a representative span wise slice on the panel can be taken and the cross section can be analyzed using plane strain analysis.
The effects of leading edge and downstream film cooling on turbine vane heat transfer
Hylton, L. D.; Nirmalan, V.; Sultanian, B. K.; Kaufman, R. M.
1988-01-01
The progress under contract NAS3-24619 toward the goal of establishing a relevant data base for use in improving the predictive design capabilities for external heat transfer to turbine vanes, including the effect of downstream film cooling with and without leading edge showerhead film cooling. Experimental measurements were made in a two-dimensional cascade previously used to obtain vane surface heat transfer distributions on nonfilm cooled airfoils under contract NAS3-22761 and leading edge showerhead film cooled airfoils under contract NAS3-23695. The principal independent parameters (Mach number, Reynolds number, turbulence, wall-to-gas temperature ratio, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio) were maintained over ranges consistent with actual engine conditions and the test matrix was structured to provide an assessment of the independent influence of parameters of interest, namely, exit Mach number, exit Reynolds number, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio. Data provide a data base for downstream film cooled turbine vanes and extends the data bases generated in the two previous studies. The vane external heat transfer obtained indicate that considerable cooling benefits can be achieved by utilizing downstream film cooling. The data obtained and presented illustrate the interaction of the variables and should provide the airfoil designer and computational analyst the information required to improve heat transfer design capabilities for film cooled turbine airfoils.
Lamar, J. E.
1976-01-01
Various subsonic configurations which develop vortex lift are examined herein. Comparisons are made with data and the combination of direct and indirect edge forces through use of the suction analogy. For most configurations, the use of the indirect or augmented vortex lift leads to improved agreement with data. The studies conducted showed that it is possible for the leading-edge vortex to exhibit bursting on a cropped wing and the wing aerodynamic characteristics not show the effect. It was further found that the distributions of leading-edge suction correlate well with the maintenance of vortex flow aerodynamic characteristics. Lastly, a method is presented for relating the initial value of circulation and axial velocity of the leading-edge shed vortex to the wing geometry.
International Nuclear Information System (INIS)
A customized leading-edge discriminator has been developed for picking up information on the position and the time for a planar-type segmented germanium detector. The discriminator consisted of three stages: a differentiating amplifier, a voltage comparator, and a mono-stable multivibrator. With the present discriminator modules, we examined spectral characteristics for the segmented germanium detector by using uncollimated 662-keV gamma rays. Anode energy spectra in coincidence with cathodes showed that better peak-to-total ratios could be obtained with increasing coincidence fold. Further, a salient feature of the exponential decay in the time difference spectrum between the anode and cathodes was observed to a fair extent
Next-generation science information network for leading-edge applications
International Nuclear Information System (INIS)
High-speed networks are definitely essential tools for leading-edge applications in many research areas, including nuclear fusion research. This paper describes a number of advanced features in the Japanese next-generation science information network, called SINET3, and gives researchers clues on the uses of advanced high-speed network for their applications. The network services have four categories, multiple layer transfer, enriched virtual private network, enhanced quality-of-service, and bandwidth on demand services, and comprise a versatile service platform. The paper also describes the network architecture and advanced networking capabilities that enable economical service accommodation and flexible network resource assignment as well as effective use of Japan's first 40-Gbps lines
Average pulse shape model for leading edge timing with Ge(Li) coaxial detector
International Nuclear Information System (INIS)
A model is presented for prompt time-response from leading-edge triggering, where calculations are rendered simpler for uniform γ-irradiation of coaxial Ge(Li) detector. Pulse shapes are formed at the timing filter amplifier output, from direct detector pulse. Average pulse-shape method is found responsible for some sort of walk compensation and by drawing time-resolution vs triggering fraction, one can predict the best FWHM with detector of RC-filtered signal. It also shows the effect of mixed filter time-constant on r.m.s. noise. Taking account of both statistical and noise effects on FWHM, the statistical contribution increases to 7% at 3 MeV of the detected energy
Computation of leading edge film cooling from a CONSOLE geometry (CONverging Slot hOLE)
Guelailia, A.; Khorsi, A.; Hamidou, M. K.
2016-01-01
The aim of this study is to investigate the effect of mass flow rate on film cooling effectiveness and heat transfer over a gas turbine rotor blade with three staggered rows of shower-head holes which are inclined at 30° to the spanwise direction, and are normal to the streamwise direction on the blade. To improve film cooling effectiveness, the standard cylindrical holes, located on the leading edge region, are replaced with the converging slot holes (console). The ANSYS CFX has been used for this computational simulation. The turbulence is approximated by a k-ɛ model. Detailed film effectiveness distributions are presented for different mass flow rate. The numerical results are compared with experimental data.
Effect of leading edge sweep on shock-shock interference at Mach 8
Glass, Christopher E.; Wieting, Allan R.; Holden, Michael S.
1989-01-01
These Mach 8 experimental results are applicable to the details of a shock-shock interference that may occur on an engine inlet of a hypersonic vehicle from a swept forebody shock interacting with a swept cowl leading edge bow shock or from a swept splitter plate shock interacting with a swept fuel injection strut bow shock. Peak surface pressure and heat transfer rate on the cylinder were about 10 and 30 times the undisturbed flow stagnation point value, respectively, for the 0 deg sweep test. A comparison of the 15 deg and 30 deg swept results with the 0 deg swept results shows that peak pressure was reduced about 13 percent and 44 percent, respectively, and peak heat transfer rate was reduced about 7 percent and 27 percent, respectively.
A mechanism for mitigation of blade-vortex interaction using leading edge blowing flow control
Weiland, Chris; Vlachos, Pavlos P.
2009-09-01
The interaction of a vortical unsteady flow with structures is often encountered in engineering applications. Such flow structure interactions (FSI) can be responsible for generating significant loads and can have many detrimental structural and acoustic side effects, such as structural fatigue, radiated noise and even catastrophic results. Amongst the different types of FSI, the parallel blade-vortex interaction (BVI) is the most common, often encountered in helicopters and propulsors. In this work, we report on the implementation of leading edge blowing (LEB) active flow control for successfully minimizing the parallel BVI. Our results show reduction of the airfoil vibrations up to 38% based on the root-mean-square of the vibration velocity amplitude. This technique is based on displacing an incident vortex using a jet issued from the leading edge of a sharp airfoil effectively increasing the stand-off distance of the vortex from the body. The effectiveness of the method was experimentally analyzed using time-resolved digital particle image velocimetry (TRDPIV) recorded at an 800 Hz rate, which is sufficient to resolve the spatio-temporal dynamics of the flow field and it was combined with simultaneous accelerometer measurements of the airfoil, which was free to oscillate in a direction perpendicular to the freestream. Analysis of the flow field spectra and a Proper Orthogonal Decomposition (POD) of the TRDPIV data of the temporally resolved planar flow fields indicate that the LEB effectively modified the flow field surrounding the airfoil and increased the convecting vortices stand-off distance for over half of the airfoil chord length. It is shown that LEB also causes a redistribution of the flow field spectral energy over a larger range of frequencies.
Vibration and sound of an elastic wing actuated at its leading edge
Manela, A.
2012-01-01
The motion and sound of a thin elastic plate, subject to uniform low-Mach flow and actuated at its leading edge, is studied. The linearized response to arbitrary small-amplitude translation and rotation is analyzed using Fourier decomposition of the forcing signal. Both periodic (sinusoidal) and non-periodic ("step-jump") actuations are investigated. When the frequency spectrum of the forcing signal contains an eigenfrequency Ωres of the unforced system, a resonance motion is excited and the plate oscillates at the corresponding eigenmode. The dynamical description is applied to formulate the acoustic problem, where the sources of sound include the plate velocity and fluid vorticity. Acoustic radiation of a dipole type is calculated and discussed in the limit where the plate is acoustically compact. In the case of sinusoidal excitation, plate elasticity has two opposite effects on sound radiation, depending on the forcing frequency: at frequencies close to Ωres, the near-resonance motion results in the generation of high sound levels; however, at frequencies far from Ωres, plate elasticity reduces the amplitude of plate deflection (compared to that of a rigid plate), leading to noise reduction. In the case of non-periodic actuation, the plate-fluid system amplifies those frequencies that are closest to Ωres, which, in turn, dominate the acoustic signature. The results identify the trailing edge noise as the main source of sound, dominating the sound generated by direct plate motion. We suggest the present theory as a preliminary tool for examining the acoustic signature of flapping flight, common in insects and flapping micro-air-vehicles.
Insect Residue Contamination on Wing Leading Edge Surfaces: A Materials Investigation for Mitigation
Lorenzi, Tyler M.; Wohl, Christopher J.; Penner, Ronald K.; Smith, Joseph G.; Siochi, Emilie J.
2011-01-01
Flight tests have shown that residue from insect strikes on aircraft wing leading edge surfaces may induce localized transition of laminar to turbulent flow. The highest density of insect populations have been observed between ground level and 153 m during light winds (2.6 -- 5.1 m/s), high humidity, and temperatures from 21 -- 29 C. At a critical residue height, dependent on the airfoil and Reynolds number, boundary layer transition from laminar to turbulent results in increased drag and fuel consumption. Although this represents a minimal increase in fuel burn for conventional transport aircraft, future aircraft designs will rely on maintaining laminar flow across a larger portion of wing surfaces to reduce fuel burn during cruise. Thus, insect residue adhesion mitigation is most critical during takeoff and initial climb to maintain laminar flow in fuel-efficient aircraft configurations. Several exterior treatments investigated to mitigate insect residue buildup (e.g., paper, scrapers, surfactants, flexible surfaces) have shown potential; however, implementation has proven to be impractical. Current research is focused on evaluation of wing leading edge surface coatings that may reduce insect residue adhesion. Initial work under NASA's Environmentally Responsible Aviation Program focused on evaluation of several commercially available products (commercial off-the-shelf, COTS), polymers, and substituted alkoxy silanes that were applied to aluminum (Al) substrates. Surface energies of these coatings were determined from contact angle data and were correlated to residual insect excrescence on coated aluminum substrates using a custom-built "bug gun." Quantification of insect excrescence surface coverage was evaluated by a series of digital photographic image processing techniques.
A mechanism for mitigation of blade-vortex interaction using leading edge blowing flow control
Energy Technology Data Exchange (ETDEWEB)
Weiland, Chris; Vlachos, Pavlos P. [Virginia Tech, Department of Mechanical Engineering, Blacksburg, VA (United States)
2009-09-15
The interaction of a vortical unsteady flow with structures is often encountered in engineering applications. Such flow structure interactions (FSI) can be responsible for generating significant loads and can have many detrimental structural and acoustic side effects, such as structural fatigue, radiated noise and even catastrophic results. Amongst the different types of FSI, the parallel blade-vortex interaction (BVI) is the most common, often encountered in helicopters and propulsors. In this work, we report on the implementation of leading edge blowing (LEB) active flow control for successfully minimizing the parallel BVI. Our results show reduction of the airfoil vibrations up to 38% based on the root-mean-square of the vibration velocity amplitude. This technique is based on displacing an incident vortex using a jet issued from the leading edge of a sharp airfoil effectively increasing the stand-off distance of the vortex from the body. The effectiveness of the method was experimentally analyzed using time-resolved digital particle image velocimetry (TRDPIV) recorded at an 800 Hz rate, which is sufficient to resolve the spatio-temporal dynamics of the flow field and it was combined with simultaneous accelerometer measurements of the airfoil, which was free to oscillate in a direction perpendicular to the freestream. Analysis of the flow field spectra and a Proper Orthogonal Decomposition (POD) of the TRDPIV data of the temporally resolved planar flow fields indicate that the LEB effectively modified the flow field surrounding the airfoil and increased the convecting vortices stand-off distance for over half of the airfoil chord length. It is shown that LEB also causes a redistribution of the flow field spectral energy over a larger range of frequencies. (orig.)
Stability Derivatives of a Delta Wing with Straight Leading Edge in the Newtonian Limit
Directory of Open Access Journals (Sweden)
Asha Crasta
2014-03-01
Full Text Available This paper presents an analytical method to predict the aerodynamic stability derivatives of oscillating delta wings with straight leading edge. It uses the Ghosh similitude and the strip theory to obtain the expressions for stability derivatives in pitch and roll in the Newtonian limit. The present theory gives a quick and approximate method to estimate the stability derivatives which is very essential at the design stage. They are applicable for wings of arbitrary plan form shape at high angles of attack provided the shock wave is attached to the leading edge of the wing. The expressions derived for stability derivatives become exact in the Newtonian limit. The stiffness derivative and damping derivative in pitch and roll are dependent on the geometric parameter of the wing. It is found that stiffness derivative linearly varies with the pivot position. In the case of damping derivative since expressions for these derivatives are non-linear and the same is reflected in the results. Roll damping derivative also varies linearly with respect to the angle of attack. When the variation of roll damping derivative was considered, it is found it also, varies linearly with angle of attack for given sweep angle, but with increase in sweep angle there is continuous decrease in the magnitude of the roll damping derivative however, the values differ for different values in sweep angle and the same is reflected in the result when it was studied with respect to sweep angle. From the results it is found that one can arrive at the optimum value of the angle of attack sweep angle which will give the best performance.
Hernandez, Gloria; Wood, Richard M.; Covell, Peter F.
1994-01-01
An experimental investigation of the aerodynamic characteristics of thin, moderately swept fighter wings has been conducted to evaluate the effect of camber and twist on the effectiveness of leading- and trailing-edge flaps at supersonic speeds in the Langley Unitary Plan Wind Tunnel. The study geometry consisted of a generic fuselage with camber typical of advanced fighter designs without inlets, canopy, or vertical tail. The model was tested with two wing configurations an uncambered (flat) wing and a cambered and twisted wing. Each wing had an identical clipped delta planform with an inboard leading edge swept back 65 deg and an outboard leading edge swept back 50 deg. The trailing edge was swept forward 25 deg. The leading-edge flaps were deflected 4 deg to 15 deg, and the trailing-edge flaps were deflected from -30 deg to 10 deg. Longitudinal force and moment data were obtained at Mach numbers of 1.60, 1.80, 2.00, and 2.16 for an angle-of-attack range 4 deg to 20 deg at a Reynolds number of 2.16 x 10(exp 6) per foot and for an angle-of-attack range 4 deg to 20 deg at a Reynolds number of 2.0 x 10(exp 6) per foot. Vapor screen, tuft, and oil flow visualization data are also included.
A comparison of experimental and calculated thin-shell leading-edge buckling due to thermal stresses
Jenkins, Jerald M.
1988-01-01
High-temperature thin-shell leading-edge buckling test data are analyzed using NASA structural analysis (NASTRAN) as a finite element tool for predicting thermal buckling characteristics. Buckling points are predicted for several combinations of edge boundary conditions. The problem of relating the appropriate plate area to the edge stress distribution and the stress gradient is addressed in terms of analysis assumptions. Local plasticity was found to occur on the specimen analyzed, and this tended to simplify the basic problem since it effectively equalized the stress gradient from loaded edge to loaded edge. The initial loading was found to be difficult to select for the buckling analysis because of the transient nature of thermal stress. Multiple initial model loadings are likely required for complicated thermal stress time histories before a pertinent finite element buckling analysis can be achieved. The basic mode shapes determined from experimentation were correctly identified from computation.
Leading edge embedded fan airfoil concept -- A new powered high lift technology
Phan, Nhan Huu
A new powered-lift airfoil concept called Leading Edge Embedded Fan (LEEF) is proposed for Extremely Short Take-Off and Landing (ESTOL) and Vertical Take-Off and Landing (VTOL) applications. The LEEF airfoil concept is a powered-lift airfoil concept capable of generating thrust and very high lift-coefficient at extreme angles-of attack (AoA). It is designed to activate only at the take-off and landing phases, similar to conventional flaps or slats, allowing the aircraft to operate efficiently at cruise in its conventional configuration. The LEEF concept consists of placing a crossflow fan (CFF) along the leading-edge (LE) of the wing, and the housing is designed to alter the airfoil shape between take-off/landing and cruise configurations with ease. The unique rectangular cross section of the crossflow fan allows for its ease of integration into a conventional subsonic wing. This technology is developed for ESTOL aircraft applications and is most effectively applied to General Aviation (GA) aircraft. Another potential area of application for LEEF is tiltrotor aircraft. Unlike existing powered high-lift systems, the LEEF airfoil uses a local high-pressure air source from cross-flow fans, does not require ducting, and is able to be deployed using distributed electric power systems throughout the wing. In addition to distributed lift augmentation, the LEEF system can provide additional thrust during takeoff and landing operation to supplement the primary cruise propulsion system. Two-dimensional (2D) and three-dimensional (3D) Computational Fluid Dynamics (CFD) simulations of a conventional airfoil/wing using the NACA 63-3-418 section, commonly used in GA, and a LEEF airfoil/wing embedded into the same airfoil section were carried out to evaluate the advantages of and the costs associated with implementing the LEEF concept. Computational results show that significant lift and augmented thrust are available during LEEF operation while requiring only moderate fan power
Drag Coefficient of Water Droplets Approaching the Leading Edge of an Airfoil
Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida Garcia
2013-01-01
This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. An airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Results are presented and discussed for drag coefficients of droplets with diameters in the range of 300 to 1800 micrometers, and airfoil velocities of 50, 70 and 90 meters/second. The effect of droplet oscillation on the drag coefficient is discussed.
Mechanism of Water Droplet Breakup Near the Leading Edge of an Airfoil
Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida, Garcia
2012-01-01
This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. The airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Droplet deformation is defined and studied against main parameters. The high speed imaging allowed observation of the actual mechanism of breakup and identification of the sequence of configurations from the initiation of the breakup to the disintegration of the droplet. Results and comparisons are presented for droplets of diameters in the range of 500 to 1800 microns, and airfoil velocities of 70 and 90 m/sec.
Hasheminejad, S. M.
2016-01-05
A series of flow visualizations were conducted to qualitatively study the development of streamwise counter-rotating vortices over a flat plate induced by triangular patterns at the leading edge of a flat plate. The experiments were carried out for a Reynolds number based on the pattern wavelength (λ) of 3080. The results depict the onset, development and breakdown of the vortical structures within the flat plate boundary layer. Moreover, the effect of one spanwise array of holes with diameter of 0.2λ (=3 mm) was examined. This investigation was done on two different flat plates with holes placed at the location x/λ = 2 downstream of the troughs and peaks. The presence of holes after troughs does not show any significant effect on the vortical structures. However, the plate with holes after peaks noticeably delays the vortex breakdown. In this case, the “mushroom-like” vortices move away from the wall and propagate downstream with stable vortical structures. The vortex growth is halted further downstream but start to tilt aside.
Koch, Stefan; Capaldo, Christopher T.; Samarin, Stanislav; Nava, Porfirio; Neumaier, Irmgard; Skerra, Arne; Sacks, David B.; Parkos, Charles A.
2009-01-01
Wnt signaling pathways regulate proliferation, motility, and survival in a variety of human cell types. Dickkopf-1 (Dkk-1) is a secreted Wnt antagonist that has been proposed to regulate tissue homeostasis in the intestine. In this report, we show that Dkk-1 is secreted by intestinal epithelial cells after wounding and that it inhibits cell migration by attenuating the directional orientation of migrating epithelial cells. Dkk-1 exposure induced mislocalized activation of Cdc42 in migrating cells, which coincided with a displacement of the polarity protein Par6 from the leading edge. Consequently, the relocation of the microtubule organizing center and the Golgi apparatus in the direction of migration was significantly and persistently inhibited in the presence of Dkk-1. Small interfering RNA-induced down-regulation of Dkk-1 confirmed that extracellular exposure to Dkk-1 was required for this effect. Together, these data demonstrate a novel role of Dkk-1 in the regulation of directional polarization of migrating intestinal epithelial cells, which contributes to the effect of Dkk-1 on wound closure in vivo. PMID:19776352
The effect of butterfly-scale inspired patterning on leading-edge vortex growth
Wilroy, Jacob; Lang, Amy
2015-11-01
Leading edge vortices (LEVs) are important for generating thrust and lift in flapping flight, and the surface patterning (scales) on butterfly wings is hypothesized to play a role in the vortex formation of the LEV. To simplify this complex flow problem, an experiment was designed to focus on the alteration of 2-D vortex development with a variation in surface patterning. Specifically, the secondary vorticity generated by the LEV interacting at the patterned surface was studied and the subsequent affect on the growth rate of the circulation in the LEV. For this experiment we used butterfly inspired grooves attached to a flat plate and compared the vortex formation to a smooth plate case as the plate moved vertically. The plate is impulsively started in quiescent water and flow fields at Re = 1500, 3000, and 6000 are examined using Digital Particle Image Velocimetry (DPIV). The vortex formation time is 3.0 and is based on the flat plate travel length and chord length. We would like to thank the National Science Foundation REU Site Award 1358991 for funding this research.
A practical study of the aerodynamic impact of wind turbine blade leading edge erosion
International Nuclear Information System (INIS)
During operation wind turbine blades are exposed to a wide variety of atmospheric and environmental conditions; inspection reports for blades that have been operating for several years show varying degrees of leading edge erosion. It is important to be able to estimate the impact of different stages of erosion on wind turbine performance, but this is very difficult even with advanced CFD models. In this study, wind tunnel testing was used to evaluate a range of complex erosion stages. Erosion patterns were transferred to thin films that were applied to 18% thick commercial wind turbine aerofoils and full lift and drag polars were measured in a wind tunnel. Tests were conducted up to a Reynolds number of 2.20 × 106 scaling based on the local roughness Reynolds number was used in combination with different film thicknesses to simulate a variety of erosion depths. The results will be very useful for conducting cost/benefit analyses of different methods of blade protection and repair, as well as for defining the appropriate timescales for these processes
Fracture Mechanics Analyses of Reinforced Carbon-Carbon Wing-Leading-Edge Panels
Raju, Ivatury S.; Phillips, Dawn R.; Knight, Norman F., Jr.; Song, Kyongchan
2010-01-01
Fracture mechanics analyses of subsurface defects within the joggle regions of the Space Shuttle wing-leading-edge RCC panels are performed. A 2D plane strain idealized joggle finite element model is developed to study the fracture behavior of the panels for three distinct loading conditions - lift-off and ascent, on-orbit, and entry. For lift-off and ascent, an estimated bounding aerodynamic pressure load is used for the analyses, while for on-orbit and entry, thermo-mechanical analyses are performed using the extreme cold and hot temperatures experienced by the panels. In addition, a best estimate for the material stress-free temperature is used in the thermo-mechanical analyses. In the finite element models, the substrate and coating are modeled separately as two distinct materials. Subsurface defects are introduced at the coating-substrate interface and within the substrate. The objective of the fracture mechanics analyses is to evaluate the defect driving forces, which are characterized by the strain energy release rates, and determine if defects can become unstable for each of the loading conditions.
The Multipoint Global Shape Optimization of Flying Configuration with Movable Leading Edges Flaps
Directory of Open Access Journals (Sweden)
Adriana NASTASE
2012-12-01
Full Text Available The aerodynamical global optimized (GO shape of flying configuration (FC, at two cruising Mach numbers, can be realized by morphing. Movable leading edge flaps are used for this purpose. The equations of the surfaces of the wing, of the fuselage and of the flaps in stretched position are approximated in form of superpositions of homogeneous polynomes in two variables with free coefficients. These coefficients together with the similarity parameters of the planform of the FC are the free parameters of the global optimization. Two enlarged variational problems with free boundaries occur. The first one consists in the determination of the GO shape of the wing-fuselageFC, with the flaps in retracted position, which must be of minimum drag, at higher cruising Mach number. The second enlarged variational problem consists in the determination of the GO shape of the flaps in stretched position in such a manner that the entire FC shall be of minimum drag at the second lower Mach number. The iterative optimum-optimorum (OO theory of the author is used for the solving of these both enlarged variational problems. The inviscid GO shape of the FC is used only in the first step of iteration and the own developed hybrid solutions for the compressible Navier-Stokes partial-differential equations (PDEs are used for the determination of the friction drag coefficient and up the second step of iteration of OO theory.
Effect of Impact Location on the Response of Shuttle Wing Leading Edge Panel 9
Lyle, Karen H.; Spellman, Regina L.; Hardy, Robin C.; Fasanella, Edwin L.; Jackson, Karen E.
2005-01-01
The objective of this paper is to compare the results of several simulations performed to determine the worst-case location for a foam impact on the Space Shuttle wing leading edge. The simulations were performed using the commercial non-linear transient dynamic finite element code, LS-DYNA. These simulations represent the first in a series of parametric studies performed to support the selection of the worst-case impact scenario. Panel 9 was selected for this study to enable comparisons with previous simulations performed during the Columbia Accident Investigation. The projectile for this study is a 5.5-in cube of typical external tank foam weighing 0.23 lb. Seven locations spanning the panel surface were impacted with the foam cube. For each of these cases, the foam was traveling at 1000 ft/s directly aft, along the orbiter X-axis. Results compared from the parametric studies included strains, contact forces, and material energies for various simulations. The results show that the worst case impact location was on the top surface, near the apex.
Tropomyosin Promotes Lamellipodial Persistence by Collaborating with Arp2/3 at the Leading Edge.
Brayford, Simon; Bryce, Nicole S; Schevzov, Galina; Haynes, Elizabeth M; Bear, James E; Hardeman, Edna C; Gunning, Peter W
2016-05-23
At the leading edge of migrating cells, protrusion of the lamellipodium is driven by Arp2/3-mediated polymerization of actin filaments [1]. This dense, branched actin network is promoted and stabilized by cortactin [2, 3]. In order to drive filament turnover, Arp2/3 networks are remodeled by proteins such as GMF, which blocks the actin-Arp2/3 interaction [4, 5], and coronin 1B, which acts by directing SSH1L to the lamellipodium where it activates the actin-severing protein cofilin [6, 7]. It has been shown in vitro that cofilin-mediated severing of Arp2/3 actin networks results in the generation of new pointed ends to which the actin-stabilizing protein tropomyosin (Tpm) can bind [8]. The presence of Tpm in lamellipodia, however, is disputed in the literature [9-19]. Here, we report that the Tpm isoforms 1.8/9 are enriched in the lamellipodium of fibroblasts as detected with a novel isoform-specific monoclonal antibody. RNAi-mediated silencing of Tpm1.8/9 led to an increase of Arp2/3 accumulation at the cell periphery and a decrease in the persistence of lamellipodia and cell motility, a phenotype consistent with cortactin- and coronin 1B-deficient cells [2, 7]. In the absence of coronin 1B or cofilin, Tpm1.8/9 protein levels are reduced while, conversely, inhibition of Arp2/3 with CK666 leads to an increase in Tpm1.8/9 protein. These findings establish a novel regulatory mechanism within the lamellipodium whereby Tpm collaborates with Arp2/3 to promote lamellipodial-based cell migration. PMID:27112294
International Nuclear Information System (INIS)
Wavy leading edge modifications of airfoils through imitating humpback whale flippers has been considered as a viable passive way to control flow separation. In this paper, flows around a baseline 634-021 airfoil and one with leading-edge sinusoidal protuberances were simulated using S-A turbulence model. When studying the static stall characteristics, it is found that the modified airfoil does not stall in the traditional manner, with increasing poststall lift coefficients. At high angles of attack, the flows past the wavy leading edge stayed attached for a distance, while the baseline foil is in a totally separated flow condition. On this basis, the simulations of pitch characteristic were carried out for both foils. At high angles of attack mild variations in lift and drag coefficients of the modified foil can be found, leading to a smaller area of hysteresis loop. The special structure of wavy leading edge can help maintain high consistency of the flow field in dynamic pitching station within a particular range of angles of attack
International Nuclear Information System (INIS)
We present a new high-performance and low-cost approach for implementing radiation detection acquisition systems. The basic elements used are charge-integrating ADCs and a set of components encapsulated in an HDL (hardware definition language) library which makes it possible to implement several acquisition tasks such as time pickoff and coincidence detection using a new and simple trigger technique that we name WMLET (width-modulated leading-edge timing). As proof of concept, a 32-channel hybrid PET/SPECT acquisition system based on these elements was developed and tested. This demonstrator consists of a master module responsible for the generation and distribution of trigger signals, 2 x 16-channel ADC cards (12-bit resolution) for data digitization and a 32-bit digital I/O PCI card for handling data transmission to a personal computer. System characteristics such as linearity, maximum transmission rates or timing resolution in coincidence mode were evaluated with test and real detector signals. Imaging capabilities of the prototype were also evaluated using different detector configurations. The performance tests showed that this implementation is able to handle data rates in excess of 600k events s-1 when acquiring simultaneously 32 channels (96-byte events). ADC channel linearity is >98.5% in energy quantification. Time resolution in PET mode for the tested configurations ranges from 3.64 ns FWHM to 7.88 ns FWHM when signals from LYSO-based detectors are used. The measured energy resolution matched the expected values for the detectors evaluated and single elements of crystal matrices can be neatly separated in the acquired flood histograms.
Energy Technology Data Exchange (ETDEWEB)
Lage, E; Tapias, G; Villena, J; Desco, M; Vaquero, J J, E-mail: desco@mce.hggm.e [Unidad de Medicina y CirugIa Experimental, Hospital General Universitario Gregorio Maranon, Madrid (Spain)
2010-08-07
We present a new high-performance and low-cost approach for implementing radiation detection acquisition systems. The basic elements used are charge-integrating ADCs and a set of components encapsulated in an HDL (hardware definition language) library which makes it possible to implement several acquisition tasks such as time pickoff and coincidence detection using a new and simple trigger technique that we name WMLET (width-modulated leading-edge timing). As proof of concept, a 32-channel hybrid PET/SPECT acquisition system based on these elements was developed and tested. This demonstrator consists of a master module responsible for the generation and distribution of trigger signals, 2 x 16-channel ADC cards (12-bit resolution) for data digitization and a 32-bit digital I/O PCI card for handling data transmission to a personal computer. System characteristics such as linearity, maximum transmission rates or timing resolution in coincidence mode were evaluated with test and real detector signals. Imaging capabilities of the prototype were also evaluated using different detector configurations. The performance tests showed that this implementation is able to handle data rates in excess of 600k events s{sup -1} when acquiring simultaneously 32 channels (96-byte events). ADC channel linearity is >98.5% in energy quantification. Time resolution in PET mode for the tested configurations ranges from 3.64 ns FWHM to 7.88 ns FWHM when signals from LYSO-based detectors are used. The measured energy resolution matched the expected values for the detectors evaluated and single elements of crystal matrices can be neatly separated in the acquired flood histograms.
Gall, Peter D.
The aircraft industry, as a whole, has been deeply concerned with improving the aerodynamic efficiency of current and future flight vehicles, particularly in the commercial and military markets. However, of particular interest to the field of aerodynamics is the elusive concept of a workable flow control mechanism. Effective flow control is a concept which if properly applied can increase aerodynamic efficiency. Various concepts and ideas to obtain successful flow control have been studied in an attempt to reap these rewards. Some examples include boundary layer blowing (steady and periodic), suction, and compliant walls for laminar flow control. The overall goal of flow control is to increase performance by increasing lift, reducing drag, and delaying or eliminating leading edge separation. The specific objectives of flow control are to (1) delay or eliminate flow separation, (2) delay boundary layer transition, and (3) and reduce skin friction drag. The purpose of this research is to investigate dynamic roughness as a novel method of flow control technology for external boundary layer flows. As opposed to standard surface roughness, dynamic roughness incorporates small time dependent perturbations to the surface of the airfoil. These surface perturbations are actual humps and/or ridges on the surface of the airfoil that are on the scale of the laminar boundary, and oscillate with an unsteady motion. Research has shown that this can provide a means to modify the instantaneous and mean velocity profile near the wall and favorably control the existing state of the boundary layer. Several flow control parameters were studied including dynamic roughness frequency, amplitude, and geometry. The results of this study have shown, both numerically and experimentally, that dynamic roughness can provide an effective means for eliminating both a short and long laminar separation bubble and possibly prove a viable alternative in effective flow control, hence reaping some of
Space environmental effects on LDEF composites: A leading edge coated graphite epoxy panel
George, Pete E.; Dursch, Harry W.; Hill, Sylvester G.
1993-01-01
The electronics module cover for the leading edge (Row D 9) experiment M0003-8 was fabricated from T300 graphite/934 epoxy unidirectional prepreg tape in a (O(sub 2), +/- 45, O(sub 2), +/- 45, 90, 0)(sub s) layup. This 11.75 in x 16.75 in panel was covered with thermal control coatings in three of the four quadrants with the fourth quadrant uncoated. The composite panel experienced different thermal cycling extremes in each quadrant due to the different optical properties of the coatings and bare composite. The panel also experienced ultraviolet (UV) and atomic oxygen (AO) attack as well as micrometeoroid and space debris impacts. An AO reactivity of 0.99 x 10(exp -24) cm(sup 3)/atom was calculated for the bare composite based on thickness loss. The white urethane thermal control coatings (A276 and BMS 1060) prevented AO attack of the composite substrate. However, the black urethane thermal control coating (Z306) was severely eroded by AO, allowing some AO attack of the composite substrate. An interesting banding pattern on the AO eroded bare composite surface was investigated and found to match the dimensions of the graphite fiber tow widths as prepregged. Also, erosion depths were greater in the darker bands. Five micrometeoroid/space debris impacts were cross sectioned to investigate possible structural damage as well as impact/AO interactions. Local crushing and delaminations were found to some extent in all of the impacts. No signs of coating undercutting were observed despite the extensive AO erosion patterns seen in the exposed composite material at the impact sites. An extensive microcrack study was performed on the panel along with modeling of the thermal environment to estimate temperature extremes and thermal shock. The white coated composite substrate displayed almost no microcracking while the black coated and bare composite showed extensive microcracking. Significant AO erosion was seen in many of the cracks in the bare composite.
Creager, Marcus O.
1959-01-01
An investigation of the effects of variation of leading-edge sweep and surface inclination on the flow over blunt flat plates was conducted at Mach numbers of 4 and 5.7 at free-stream Reynolds numbers per inch of 6,600 and 20,000, respectively. Surface pressures were measured on a flat plate blunted by a semicylindrical leading edge over a range of sweep angles from 0 deg to 60 deg and a range of surface inclinations from -10 deg to +10 deg. The surface pressures were predicted within an average error of +/- 8 percent by a combination of blast-wave and boundary-layer theory extended herein to include effects of sweep and surface inclination. This combination applied equally well to similar data of other investigations. The local Reynolds number per inch was found to be lower than the free-stream Reynolds number per inch. The reduction in local Reynolds number was mitigated by increasing the sweep of the leading edge. Boundary-layer thickness and shock-wave shape were changed little by the sweep of the leading edge.
Vanmol, Denis O.; Anderson, John D., Jr.
1992-01-01
The heat transfer characteristics in surface radiative equilibrium and the aerodynamic performance of blunted hypersonic waveriders are studied along two constant dynamic pressure trajectories for four different Mach numbers. The inviscid leading edge drag was found to be a small (4 to 8 percent) but not negligible fraction of the inviscid drag of the vehicle. Although the viscous drag at the leading edge can be neglected, the presence of the leading edge will influence the transition pattern of the upper and the lower surfaces and therefore affect the viscous drag of the entire vehicle. For an application similar to the National Aerospace Plane (NASP), the present study demonstrates that the waverider remains a valuable concept at high Mach numbers if a state-of-the-art active cooling device is used along the leading edge. At low Mach number (less than 5), the study shows the surface radiative cooling might be sufficient. In all cases, radiative cooling is sufficient for the upper and lower surfaces of the vehicle if ceramic composites are used as thermal protection.
Huffman, J. K.; Fox, C. H., Jr.
1977-01-01
A configuration which integrates a close coupled canard wing combination, spanwise blowing for enhancement of the wing leading edge vortex, an engine-over-wing concept, and a wing trailing edge coanda-effect flap is studied. The data on the configuration are presented in tabular from without discussion. The investigation was conducted in the Langley 7- by 10-foot high speed tunnel at a Mach number of 0.166 through an angle-of-attack range from -2 to 22 deg. Rectangular main engine nozzles of aspect ratio 4, 6, and 8 were tested over a momentum coefficient range from 1.0 to 1.8.
1979-01-01
Configurations with full-span and segmented leading-edge flaps and full-span and segmented leading-edge droop were tested. Studies were conducted with wind-tunnel models, with an outdoor radio-controlled model, and with a full-scale airplane. Results show that wing-leading-edge modifications can produce large effects on stall/spin characteristics, particularly on spin resistance. One outboard wing-leading-edge modification tested significantly improved lateral stability at stall, spin resistance, and developed spin characteristics.
Fujisawa, Nobumichi; Hara, Shotaro; Ohta, Yutaka
2016-02-01
The characteristics of a rotating stall of an impeller and diffuser and the evolution of a vortex generated at the diffuser leading-edge (i.e., the leading-edge vortex (LEV)) in a centrifugal compressor were investigated by experiments and numerical analysis. The results of the experiments revealed that both the impeller and diffuser rotating stalls occurred at 55 and 25 Hz during off-design flow operation. For both, stall cells existed only on the shroud side of the flow passages, which is very close to the source location of the LEV. According to the CFD results, the LEV is made up of multiple vortices. The LEV is a combination of a separated vortex near the leading- edge and a longitudinal vortex generated by the extended tip-leakage flow from the impeller. Therefore, the LEV is generated by the accumulation of vorticity caused by the velocity gradient of the impeller discharge flow. In partial-flow operation, the spanwise extent and the position of the LEV origin are temporarily transmuted. The LEV develops with a drop in the velocity in the diffuser passage and forms a significant blockage within the diffuser passage. Therefore, the LEV may be regarded as being one of the causes of a diffuser stall in a centrifugal compressor.
Miller, Sandi G.; Handschuh, Katherine; Sinnott, Matthew J.; Kohlman, Lee W.; Roberts, Gary D.; Martin, Richard E.; Ruggeri, Charles R.; Pereira, J. Michael
2015-01-01
Application of polymer matrix composite materials for jet engine fan blades is becoming attractive as an alternative to metallic blades; particularly for large engines where significant weight savings are recognized on moving to a composite structure. However, the weight benefit of the composite is offset by a reduction of aerodynamic efficiency resulting from a necessary increase in blade thickness; relative to the titanium blades. Blade dimensions are largely driven by resistance to damage on bird strike. Further development of the composite material is necessary to allow composite blade designs to approximate the dimensions of a metallic fan blade. The reduction in thickness over the state of the art composite blades is expected to translate into structural weight reduction, improved aerodynamic efficiency, and therefore reduced fuel consumption. This paper presents test article design, subcomponent blade leading edge fabrication, test method development, and initial results from ballistic impact of a gelatin projectile on the leading edge of composite fan blades. The simplified test article geometry was developed to realistically simulate a blade leading edge while decreasing fabrication complexity. Impact data is presented on baseline composite blades and toughened blades; where a considerable improvement to impact resistance was recorded.
Dicarlo, Daniel J.; Brown, Philip W.; Hallissy, James B.
1992-01-01
Flight tests of an F-106B aircraft equipped with a leading-edge vortex flap, which represented the culmination of a research effort to examine the effectiveness of the flap, were conducted at the NASA Langley Research Center. The purpose of the flight tests was to establish a data base on the use of a wing leading-edge vortex flap as a means to validate the design and analysis methods associated with the development of such a vortical flow-control concept. The overall experiment included: refinements of the design codes for vortex flaps; numerous wind tunnel entries to aid in verifying design codes and determining basic aerodynamic characteristics; design and fabrication of the flaps, structural modifications to the wing tip and leading edges of the test aircraft; development and installation of an aircraft research instrumentation system, including wing and flap surface pressure measurements and selected structural loads measurements; ground-based simulation to assess flying qualities; and finally, flight testing. This paper reviews the operational aspects associated with the flight experiment, which includes a description of modifications to the research airplane, the overall flight test procedures, and problems encountered. Selected research results are also presented to illustrate the accomplishments of the research effort.
Europe hones an edge in technology Continent leads U.S. in linking PC "grids"
Markoff, John
2003-01-01
The Swiss-based pharmaceutical company, Novartis, is using a grid to help create drugs. Although the US leads technical developments it is European organisations who have the lead on practical grid projects (2 pages)
Modeling Creep-Induced Stress Relaxation at the Leading Edge of SiC/SiC Airfoils
Lang, Jerry; DiCarlo, James A.
2007-01-01
Anticipating the implementation of advanced SiC/SiC composites into internally cooled airfoil components within the turbine section of future aero-propulsion engines, the primary objective of this study was to develop physics-based analytical and finite-element modeling tools to predict the effects of composite creep and stress relaxation at the airfoil leading edges, which will generally experience large thermal gradients at high temperatures. A second objective was to examine how some advanced NASA-developed SiC/SiC systems coated with typical EBC materials would behave as leading edge materials in terms of long-term steady-state operating temperatures. Because of the complexities introduced by mechanical stresses inherent in internally cooled airfoils, a simple cylindrical thin-walled tube model subjected to thermal stresses only is employed for the leading edge, thereby obtaining a best-case scenario for the material behavior. In addition, the SiC/SiC composite materials are assumed to behave as isotropic materials with temperature-dependent viscoelastic creep behavior as measured in-plane on thin-walled panels. Key findings include: (1) without mechanical stresses and for typical airfoil geometries, as heat flux is increased through the leading edge, life-limiting tensile crack formation will occur first in the hoop direction on the inside wall of the leading edge; (2) thermal gradients through all current SiC/SiC systems should be kept below approx.300 F at high temperatures to avoid this cracking; (3) at temperatures near the maximum operating temperatures of advanced SiC/SiC systems, thermal stresses induced by the thermal gradients will beneficially relax with time due to creep; (4) although stress relaxation occurs, the maximum gradient should still not exceed 300oF because of residual tensile stress buildup on the airfoil outer wall during cool-down; and (5) without film cooling and mechanical stresses, the NASA-developed N26 SiC/SiC system with thru
Energy Technology Data Exchange (ETDEWEB)
Lamballais, Eric, E-mail: lamballais@univ-poitiers.f [Institute PPRIME, Department of Fluid Flow, Heat Transfer and Combustion, Universite de Poitiers, ENSMA, CNRS, Teleport 2 - Bd. Marie et Pierre Curie B.P. 30179, 86962 Futuroscope Chasseneuil Cedex (France); Silvestrini, Jorge, E-mail: jorgehs@pucrs.b [Faculdade de Engenharia, Pontificia Universidade Catolica do Rio Grande do Sul, Av. Ipiranga 6681, 90619-900 Porto Alegre - RS (Brazil); Laizet, Sylvain, E-mail: s.laizet@imperial.ac.u [Institute PPRIME, Department of Fluid Flow, Heat Transfer and Combustion, Universite de Poitiers, ENSMA, CNRS, Teleport 2 - Bd. Marie et Pierre Curie B.P. 30179, 86962 Futuroscope Chasseneuil Cedex (France); Department of Aeronautics, Institute for Mathematical Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom)
2010-06-15
The separation bubble formed over a 2D half-body is studied by direct numerical simulation. The aim of this work is to consider the physical influence of the shape of the body that can be viewed as a thick half-plate with a front edge more or less rounded. The present generic body geometry is defined with a unique parameter {eta}=R/H corresponding to the ratio of the curvature radius R of the front edge over the body height H. In this paper, 18 calculations are presented depending on: (i) the value of {eta} with {eta}=0.125,0.25,0.5,1; (ii) the 2D/3D nature of the computation; (iii) the inflow perturbations used to mimic residual turbulence in the free stream velocity U{sub {infinity}.} Only one Reynolds number Re=U{sub {infinity}H}/{nu} is used for every simulation, allowing us to focus on the curvature effects over the separation bubble dynamics. The value of the Reynolds number (Re=2000) combined with the resolution demand of the front edge (close to a sharp corner for the highest curvature case) requires to simulate the flow using up to 876 million mesh nodes. The curvature effects are found to deeply influence the separation bubble dynamics, with a significant expansion of the separated region size predicted by 3D computations. This expansion is driven by the separation angle rise combined with the reinforcement of turbulence levels as the curvature is increased. These trends are associated with a change of bubble sensitivity with respect to upstream/downstream perturbations that can be interpreted in terms of convective/absolute stability.
International Nuclear Information System (INIS)
The separation bubble formed over a 2D half-body is studied by direct numerical simulation. The aim of this work is to consider the physical influence of the shape of the body that can be viewed as a thick half-plate with a front edge more or less rounded. The present generic body geometry is defined with a unique parameter η=R/H corresponding to the ratio of the curvature radius R of the front edge over the body height H. In this paper, 18 calculations are presented depending on: (i) the value of η with η=0.125,0.25,0.5,1; (ii) the 2D/3D nature of the computation; (iii) the inflow perturbations used to mimic residual turbulence in the free stream velocity U∞. Only one Reynolds number Re=U∞H/ν is used for every simulation, allowing us to focus on the curvature effects over the separation bubble dynamics. The value of the Reynolds number (Re=2000) combined with the resolution demand of the front edge (close to a sharp corner for the highest curvature case) requires to simulate the flow using up to 876 million mesh nodes. The curvature effects are found to deeply influence the separation bubble dynamics, with a significant expansion of the separated region size predicted by 3D computations. This expansion is driven by the separation angle rise combined with the reinforcement of turbulence levels as the curvature is increased. These trends are associated with a change of bubble sensitivity with respect to upstream/downstream perturbations that can be interpreted in terms of convective/absolute stability.
Schwind, R. G.; Allen, H. J.
1973-01-01
High frequency surface pressure measurements were obtained from wind-tunnel tests over the Reynolds number range 1.2 times one million to 6.2 times one million on a rectangular wing of NACA 63-009 airfoil section. Measurements were also obtained with a wide selection of leading-edge serrations added to the basic airfoil. Under a two-dimensional laminar bubble very close to the leading edge of the basic airfoil there is a large apatial peak in rms pressure. Frequency analysis of the pressure signals in this region show a large, high-frequency energy peak which is interpreted as an oscillation in size and position of the bubble. The serrations divide the bubble into segments and reduce the peak rms pressures. A low Reynolds number flow visualization test on a hydrofoil in water was also conducted. A von Karman vortex street was found trailing from the rear of the foil. Its frequency is at a much lower Strouhal number than in the high Reynolds number experiment, and is related to the trailing-edge and boundary-layer thicknesses.
Direct numerical simulation of a separation bubble on a rounded finite-width leading edge
International Nuclear Information System (INIS)
The formation of a separation bubble over a generic half-body with a rounded edge is studied by direct numerical simulation. A single Reynolds number Re=1250 (based on the body height Hs and the inflow velocity U∞) corresponding to reference experimental results is investigated. Various body geometries are considered through the change of its width L (four aspect ratios L/Hs addressed) and its front edge curvature R (two rounded shapes R/Hs addressed). The combined effects of aspect ratio and curvature are considered by focusing on the vortex dynamics associated with the breakdown of the bubble through three-dimensional processes. Qualitative and quantitative comparisons with previous experiments are presented. The main influences of curvature and aspect ratio are consistently recovered in present simulations. The structure of the separation bubble is in agreement with experiments, especially the combination of singular points associated with the surface flow on the top-boundary of the body. Behind the separated region, the examination of the mean flow reveals the presence of a pair of longitudinal counter-rotating vortices pumping fluid from the side of the body to the top of the flow. The analysis of instantaneous visualizations shows the formation of strong lambda vortices for small aspect ratios. These vortices cause ejection of the fluid through a periodic bursting process which seems to be linked to the flapping of the separation bubble. The increase of the curvature of the rounded front edge is found to increase the separation angle, in qualitative agreement with experiments, with a global growing of the size of the separation bubble. The sensitivity of the flow to upstream conditions is discussed by considering different levels of inflow fluctuations (with a root mean square from zero to 1% of U∞) while evaluating the deterministic response of the bubble dynamics with respect to cyclic inlet excitation. Strong curvature is found to reduce drastically
Direct numerical simulation of a separation bubble on a rounded finite-width leading edge
Energy Technology Data Exchange (ETDEWEB)
Lamballais, Eric [Laboratoire d' Etudes Aerodynamiques UMR 6609, Universite de Poitiers, ENSMA, CNRS, Teleport 2 - Bd. Marie et Pierre Curie B.P. 30179, 86962 Futuroscope Chasseneuil Cedex (France)], E-mail: lamballais@univ-poitiers.fr; Silvestrini, Jorge [Faculdade de Engenharia, Pontificia Universidade Catolica do Rio Grande do Sul, Av. Ipiranga 6681, 90619-900 Porto Alegre - RS (Brazil)], E-mail: jorgehs@pucrs.br; Laizet, Sylvain [Laboratoire d' Etudes Aerodynamiques UMR 6609, Universite de Poitiers, ENSMA, CNRS, Teleport 2 - Bd. Marie et Pierre Curie B.P. 30179, 86962 Futuroscope Chasseneuil Cedex (France); Department of Aeronautics, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom)], E-mail: s.laizet@imperial.ac.uk
2008-06-15
The formation of a separation bubble over a generic half-body with a rounded edge is studied by direct numerical simulation. A single Reynolds number Re=1250 (based on the body height H{sub s} and the inflow velocity U{sub {infinity}}) corresponding to reference experimental results is investigated. Various body geometries are considered through the change of its width L (four aspect ratios L/H{sub s} addressed) and its front edge curvature R (two rounded shapes R/H{sub s} addressed). The combined effects of aspect ratio and curvature are considered by focusing on the vortex dynamics associated with the breakdown of the bubble through three-dimensional processes. Qualitative and quantitative comparisons with previous experiments are presented. The main influences of curvature and aspect ratio are consistently recovered in present simulations. The structure of the separation bubble is in agreement with experiments, especially the combination of singular points associated with the surface flow on the top-boundary of the body. Behind the separated region, the examination of the mean flow reveals the presence of a pair of longitudinal counter-rotating vortices pumping fluid from the side of the body to the top of the flow. The analysis of instantaneous visualizations shows the formation of strong lambda vortices for small aspect ratios. These vortices cause ejection of the fluid through a periodic bursting process which seems to be linked to the flapping of the separation bubble. The increase of the curvature of the rounded front edge is found to increase the separation angle, in qualitative agreement with experiments, with a global growing of the size of the separation bubble. The sensitivity of the flow to upstream conditions is discussed by considering different levels of inflow fluctuations (with a root mean square from zero to 1% of U{sub {infinity}}) while evaluating the deterministic response of the bubble dynamics with respect to cyclic inlet excitation. Strong
Gnoffo, Peter A.
2003-01-01
A baseline solution for CFD Point 1 (Mach 24) in the STS-107 accident investigation was modified to include effects of: (1) holes through the leading edge into a vented cavity; and (2) a scarfed, conical nozzle directed toward the centerline of the vehicle from the forward, inboard corner of the landing gear door. The simulations were generated relatively quickly and early in the investigation because simplifications were made to the leading edge cavity geometry and an existing utility to merge scarfed nozzle grid domains with structured baseline external domains was implemented. These simplifications in the breach simulations enabled: (1) a very quick grid generation procedure; and (2) high fidelity corroboration of jet physics with internal surface impingements ensuing from a breach through the leading edge, fully coupled to the external shock layer flow at flight conditions. These simulations provided early evidence that the flow through a two-inch diameter (or larger) breach enters the cavity with significant retention of external flow directionality. A normal jet directed into the cavity was not an appropriate model for these conditions at CFD Point 1 (Mach 24). The breach diameters were of the same order or larger than the local, external boundary-layer thickness. High impingement heating and pressures on the downstream lip of the breach were computed. It is likely that hole shape would evolve as a slot cut in the direction of the external streamlines. In the case of the six-inch diameter breach the boundary layer is fully ingested. The intent of externally directed jet simulations in the second scenario was to approximately model aerodynamic effects of a relatively large internal wing pressure, fueled by combusting aluminum, which deforms the corner of the landing gear door and directs a jet across the windside surface. These jet interactions, in and of themselves, were not sufficiently large to explain observed aerodynamic behavior.
A Survey of Factors Affecting Blunt Leading-Edge Separation for Swept and Semi-Slender Wings
Luckring, James M.
2010-01-01
A survey is presented of factors affecting blunt leading-edge separation for swept and semi-slender wings. This class of separation often results in the onset and progression of separation-induced vortical flow over a slender or semi-slender wing. The term semi-slender is used to distinguish wings with moderate sweeps and aspect ratios from the more traditional highly-swept, low-aspect-ratio slender wing. Emphasis is divided between a selection of results obtained through literature survey a section of results from some recent research projects primarily being coordinated through NATO s Research and Technology Organization (RTO). An aircraft context to these studies is included.
Horne, William C.; Burnside, Nathan J.
2013-01-01
The AMELIA Cruise-Efficient Short Take-off and Landing (CESTOL) configuration concept was developed to meet future requirements of reduced field length, noise, and fuel burn by researchers at Cal Poly, San Luis Obispo and Georgia Tech Research Institute under sponsorship by the NASA Fundamental Aeronautics Program (FAP), Subsonic Fixed Wing Project. The novel configuration includes leading- and trailing-edge circulation control wing (CCW), over-wing podded turbine propulsion simulation (TPS). Extensive aerodynamic measurements of forces, surfaces pressures, and wing surface skin friction measurements were recently measured over a wide range of test conditions in the Arnold Engineering Development Center(AEDC) National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Ft Wind Tunnel. Acoustic measurements of the model were also acquired for each configuration with 7 fixed microphones on a line under the left wing, and with a 48-element, 40-inch diameter phased microphone array under the right wing. This presentation will discuss acoustic characteristics of the CCW system for a variety of tunnel speeds (0 to 120 kts), model configurations (leading edge(LE) and/or trailing-edge(TE) slot blowing, and orientations (incidence and yaw) based on acoustic measurements acquired concurrently with the aerodynamic measurements. The flow coefficient, Cmu= mVSLOT/qSW varied from 0 to 0.88 at 40 kts, and from 0 to 0.15 at 120 kts. Here m is the slot mass flow rate, VSLOT is the slot exit velocity, q is dynamic pressure, and SW is wing surface area. Directivities at selected 1/3 octave bands will be compared with comparable measurements of a 2-D wing at GTRI, as will as microphone array near-field measurements of the right wing at maximum flow rate. The presentation will include discussion of acoustic sensor calibrations as well as characterization of the wind tunnel background noise environment.
Leading Edge Flame Detachment: Effect on Burning Rate of Ammonium Perchlorate Propellants
Price, E. W.; Chakravarthy, S. R.; Sambamurthi, J. K.; Sigman, R. K.
1997-01-01
Inner details of the transition from premixed to diffusion controlled burning are examined by considering the transition at the individual particle flamelet level. These considerations lead to prediction of observable singular burning rate behavior of bimodal AP formulations. Burning rate measurements verify the predictions, supporting the view that particle flamelets become detached and retreat to more remote premixed locations at definite (particles size dependent) pressures, revealed by the burning rate tests.
Lift and Drag Control on a Lambda Wing Using Leading-Edge Slot Pulsation of Various Wave Forms
Bouras, Constantinos; Nagib, Hassan; Durst, Franz; Heim, Ulrich
2000-11-01
Direct force measurements of lift and drag for a three-dimensional wing with a lambda-shaped planform are made in the Fejer Wind Tunnel at IIT using high angles of attack with and without various unsteady forcing conditions through a leading-edge slot. In addition to changing the pulsation frequency in the range of 2--200 Hz, the waveform was varied between sinusoidal, triangular and square shapes. This was made possible by a novel device called Luftikus, designed and manufactured by Dragerwerke GmbH, Lubeck, Germany, and originally tested at the Fluid Mechanics Institute (LSTM), Erlangen University, Germany. Substantial enhancements in the lift and the lift-to-drag ratio are achieved over a wide range of forcing frequencies with an optimum improvement at a particular dimensionless frequency scaling with the freestream speed and a representative chord length. However, the variation of the shape of the waveform does not lead to significant changes.
Indian Academy of Sciences (India)
K Anand; S Sarkar
2015-05-01
Shear layer development over a thick flat plate with a semi-circular leading edge is investigated for a range of angles of attack under different pressure gradients for a Reynolds number of 2.44×105 (based on chord and free-stream velocity). The characteristics of the separated shear layer are very well documented through a combination of surface pressure measurement and smoke flow visualization. The instability of the separated layer occurs because of enhanced receptivity of perturbations leading to the development of significant unsteadiness and three-dimensional motions in the second-half of the bubble. The onset of separation, transition and the point of reattachment are identified for varying angles of attack and pressure gradients imposed by tail flap deflections. The data concerning bubble length, laminar portion and reattachment points agree well with the literature.
Rostamzadeh, Nikan; Kelso, Richard M.; Dally, Bassam
2016-05-01
Leading-edge modifications based on designs inspired by the protrusions on the pectoral flippers of the humpback whale (tubercles) have been the subject of research for the past decade primarily due to their flow control potential in ameliorating stall characteristics. Previous studies have demonstrated that, in the transitional flow regime, full-span wings with tubercled leading edges outperform unmodified wings at high attack angles. The flow mechanism associated with such enhanced loading traits is, however, still being investigated. Also, the performance of full-span tubercled wings in the turbulent regime is largely unexplored. The present study aims to investigate Reynolds number effects on the flow mechanism induced by a full-span tubercled wing with the NACA-0021 cross-sectional profile in the transitional and near-turbulent regimes using computational fluid dynamics. The analysis of the flow field suggests that, with the exception of a few different flow features, the same underlying flow mechanism, involving the presence of transverse and streamwise vorticity, is at play in both cases. With regard to lift-generation characteristics, the numerical simulation results indicate that in contrast to the transitional flow regime, where the unmodified NACA-0021 undergoes a sudden loss of lift, in the turbulent regime, the baseline foil experiences gradual stall and produces more lift than the tubercled foil. This observation highlights the importance of considerations regarding the Reynolds number effects and the stall characteristics of the baseline foil, in the industrial applications of tubercled lifting bodies.
1975-01-01
A heating array is described for testing full-scale sections of the leading edge and lower fuselage surfaces of the shuttle. The heating array was designed to provide a tool for development and acceptance testing of leading edge segments and large flat sections of the main body thermal protection system. The array was designed using a variable length module concept to meet test requirements using interchangeable components from one test configuration in another configuration. Heat generating modules and heat absorbing modules were employed to achieve the thermal gradient around the leading edge. A support was developed to hold the modules to form an envelope around a variety of leading edges; to supply coolant to each module; the support structure and to hold the modules in the flat surface heater configuration. An optical pyrometer system mounted within the array was designed to monitor specimen surface temperatures without altering the test article's surface.
Predictive process simulation of cryogenic implants for leading edge transistor design
Energy Technology Data Exchange (ETDEWEB)
Gossmann, Hans-Joachim; Zographos, Nikolas; Park, Hugh; Colombeau, Benjamin; Parrill, Thomas; Khasgiwale, Niranjan; Borges, Ricardo; Gull, Ronald; Erokhin, Yuri [Applied Materials, Inc., Varian Semiconductor Equipment Business Unit, 35 Dory Road, Gloucester, MA 01930 (United States); Synopsys Switzerland LLC, Thurgauerstrasse 40, 8050 Zuerich (Switzerland); Applied Materials, Inc., Varian Semiconductor Equipment Business Unit, 35 Dory Road, Gloucester, MA 01930 (United States); Synopsys Inc., 1101 Slater Road, Durham, NC 27703 (United States); Synopsys Switzerland LLC, Thurgauerstrasse 40, 8050 Zuerich (Switzerland); Applied Materials, Inc., Varian Semiconductor Equipment Business Unit, 35 Dory Road, Gloucester, MA 01930 (United States)
2012-11-06
Two cryogenic implant TCAD-modules have been developed: (i) A continuum-based compact model targeted towards a TCAD production environment calibrated against an extensive data-set for all common dopants. Ion-specific calibration parameters related to damage generation and dynamic annealing were used and resulted in excellent fits to the calibration data-set. (ii) A Kinetic Monte Carlo (kMC) model including the full time dependence of ion-exposure that a particular spot on the wafer experiences, as well as the resulting temperature vs. time profile of this spot. It was calibrated by adjusting damage generation and dynamic annealing parameters. The kMC simulations clearly demonstrate the importance of the time-structure of the beam for the amorphization process: Assuming an average dose-rate does not capture all of the physics and may lead to incorrect conclusions. The model enables optimization of the amorphization process through tool parameters such as scan speed or beam height.
Predictive process simulation of cryogenic implants for leading edge transistor design
International Nuclear Information System (INIS)
Two cryogenic implant TCAD-modules have been developed: (i) A continuum-based compact model targeted towards a TCAD production environment calibrated against an extensive data-set for all common dopants. Ion-specific calibration parameters related to damage generation and dynamic annealing were used and resulted in excellent fits to the calibration data-set. (ii) A Kinetic Monte Carlo (kMC) model including the full time dependence of ion-exposure that a particular spot on the wafer experiences, as well as the resulting temperature vs. time profile of this spot. It was calibrated by adjusting damage generation and dynamic annealing parameters. The kMC simulations clearly demonstrate the importance of the time-structure of the beam for the amorphization process: Assuming an average dose-rate does not capture all of the physics and may lead to incorrect conclusions. The model enables optimization of the amorphization process through tool parameters such as scan speed or beam height.
Rostamzadeh, N.; Hansen, K. L.; Kelso, R. M.; Dally, B. B.
2014-10-01
Wings with tubercles have been shown to display advantageous loading behavior at high attack angles compared to their unmodified counterparts. In an earlier study by the authors, it was shown that an undulating leading-edge configuration, including but not limited to a tubercled model, induces a cyclic variation in circulation along the span that gives rise to the formation of counter-rotating streamwise vortices. While the aerodynamic benefits of full-span tubercled wings have been associated with the presence of such vortices, their formation mechanism and influence on wing performance are still in question. In the present work, experimental and numerical tests were conducted to further investigate the effect of tubercles on the flow structure over full-span modified wings based on the NACA 0021 profile, in the transitional flow regime. It is found that a skew-induced mechanism accounts for the formation of streamwise vortices whose development is accompanied by flow separation in delta-shaped regions near the trailing edge. The presence of vortices is detrimental to the performance of full-span wings pre-stall, however renders benefits post-stall as demonstrated by wind tunnel pressure measurement tests. Finally, primary and secondary vortices are identified post-stall that produce an enhanced momentum transfer effect that reduces flow separation, thus increasing the generated amount of lift.
Szafrański, Marek; Katrusiak, Andrzej
2016-09-01
Our single-crystal X-ray diffraction study of methylammonium lead triiodide, MAPbI3, provides the first comprehensive structural information on the tetragonal phase II in the pressure range to 0.35 GPa, on the cubic phase IV stable between 0.35 and 2.5 GPa, and on the isostructural cubic phase V observed above 2.5 GPa, which undergoes a gradual amorphization. The optical absorption study confirms that up to 0.35 GPa, the absorption edge of MAPbI3 is red-shifted, allowing an extension of spectral absorption. The transitions to phases IV and V are associated with the abrupt blue shifts of the absorption edge. The strong increase of the energy gap in phase V result in a spectacular color change of the crystal from black to red around 3.5 GPa. The optical changes have been correlated with the pressure-induced strain of the MAPbI3 inorganic framework and its frustration, triggered by methylammonium cations trapped at random orientations in the squeezed voids. PMID:27538989
Henderson, W. P.
1976-01-01
An investigation was conducted in the Langley low turbulence pressure tunnel to determine the effects of wing leading edge radius and Reynolds number on the longitudinal aerodynamic characteristics of a series of highly swept wing-body configurations. The tests were conducted at Mach numbers below 0.30, angles of attack up to 16 deg, and Reynolds numbers per meter from 6.57 million to 43.27 million. The wings under study in this investigation had leading edge sweep angles of 61.7 deg, 64.61 deg, and 67.01 deg in combination with trailing edge sweep angles of 0 deg and 40.6 deg. The leading edge radii of each wing planform could be varied from sharp to nearly round.
International Nuclear Information System (INIS)
Leading-edge discriminators (LEDs) are one of the prominent discriminator technologies used in time-of-flight systems due to their simplicity, but they have large time walks such that the measured time should be corrected using amplitude information. In this article, we analyze off-line time corrections using four kinds of amplitude parameters, namely, peak values, slew rates, and signal widths, as well as charge amounts. For these corrections, we developed the front-end electronics (FEE) that can measure these amplitude parameters and performed time measurements with the developed FEE in an amplitude range of about 20 dB for various threshold conditions, which are the only adjustment in LEDs. Then, we off-line corrected the measured time using the amplitude parameters mentioned above and compared the corrected efficiencies by the used parameters and threshold conditions
International Nuclear Information System (INIS)
The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff
Van Truong, Tien; Byun, Doyoung; Kim, Min Jun; Yoon, Kwang Joon; Park, Hoon Cheol
2013-09-01
The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff
Keller, Donald F.; Sandford, Maynard C.; Pinkerton, Theresa L.
1991-01-01
An experimental and analytical investigation was initiated to determine the effects of planform curvature (curving the leading and trailing edges of a wing in the X-Y plane) on the transonic flutter characteristics of a series of three moderately swept wing models. Experimental flutter results were obtained in the Langley Transonic Dynamics Tunnel for Mach numbers from 0.60-1.00, with air as the test medium. The models were semispan cantilevered wings with a 3 percent biconvex airfoil and a panel aspect ratio of 1.14. The baseline model had straight leading and trailing edges (i.e., no planform curvature). The radii of curvature of the leading edges for these two models were 200 and 80 inches. The radii of curvature of the leading edges of the other two models were determined so that the root and tip chords were identical for all three models. Experimental results showed that flutter-speed index and flutter frequency ratio increased as planform curvature increase (radius of curvature of the leading edge was decreased) over the test range of Mach numbers. Analytical flutter results were calculated with a subsonic flutter-prediction program, and they agreed well with the experimental results.
Chu, Julio; Luckring, James M.
1996-01-01
An experimental wind tunnel test of a 65 deg delta wing model with interchangeable leading edges was conducted in the Langley National Transonic Facility (NTF). The objective was to investigate the effects of Reynolds and Mach numbers on slender-wing leading-edge vortex flows with four values of wing leading-edge bluntness. Experimentally obtained pressure data are presented without analysis in tabulated and graphical formats across a Reynolds number range of 6 x 10(exp 6) to 120 x 10(exp 6) at a Mach number of 0.85 and across a Mach number range of 0.4 to 0.9 at Reynolds numbers of 6 x 10(exp 6) and 60 x 10(exp 6). Normal-force and pitching-moment coefficient plots for these Reynolds number and Mach number ranges are also presented.
Vargas, Mario; Feo, Alex
2011-01-01
This work presents the results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. An airfoil model placed at the end of the rotating arm was moved at speeds of 50 to 90 m/sec. A monosize droplet generator was employed to produce droplets that were allowed to fall from above, perpendicular to the path of the airfoil at a given location. High speed imaging was employed to observe the interaction between the droplets and the airfoil. The high speed imaging allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. A tracking software program was used to measure from the high speed movies the horizontal and vertical displacement of the droplet against time. The velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of a given droplet from beginning of deformation to breakup and/or hitting the airfoil. Results are presented for droplets with a diameter of 490 micrometers at airfoil speeds of 50, 60, 70, 80 and 90 m/sec
Morgan, Margie Ann
2009-02-01
As hospitals become increasingly sensitive to the health and financial consequences of health care-associated infections (HAIs), a new generation of molecular-based testing technologies promises to significantly shorten the time required to identify "superbugs" and other bacterial infections. The leading-edge techniques promise to reduce costs by helping hospitals quickly determine which patients to isolate because they carry active methicillin-resistant Staphylococcus aureus (MRSA) infections, for example, or which ones to release from prophylactic isolation because they ultimately tested negative for a dangerous infection. But diagnostic speed comes at a price--the costs to perform molecular tests are significantly higher than conventional methods. This challenges hospitals to balance health care expenses with medical efficacy, says molecular testing veteran Margie Morgan, Ph.D., scientific director at Cedars-Sinai Medical Center, Los Angeles. "The rapid methods can be extreme time savers and possibly help a great deal with the isolation of patients. But some of the tests may cost five times what manual methods might be, so there is a price for seeing so much of a reduction in time," she says. PMID:19288674
A leading-edge hardware family for diagnostics applications and low-level RF in CERN's ELENA ring
Angoletta, M E; Jaussi, M; Leiononen, P; Levens, T E; Molendijk, J C; Sanchez-Quesada, J; Simonin, J
2013-01-01
The CERN Extra Low ENergy Antiproton (ELENA) Ring is a new synchrotron that will be commissioned in 2016 to further decelerate the antiprotons transferred from the CERN’s Antiproton Decelerator (AD). The requirements for the acquisition and treatment of signals for longitudinal diagnostics are very demanding, owing to the revolution frequency swing as well as to the digital signal processing required. The requirements for the Low-Level Radio-Frequency (LLRF) system are very demanding as well, especially in terms of revolution frequency swing, dynamic range and low noise required by the cavity voltage control and digital signal processing to be performed. Both sets of requirements will be satisfied by using a leading-edge hardware family, developed to cover the LLRF needs of all synchrotrons in the Meyrin site; it will be first deployed in 2014 in the CERN’s PSB and in the medical machine MedAustron. This paper gives an overview of the main building blocks of the hardware family and of th...
Leading edge vortices in lesser long-nosed bats occurring at slow but not fast flight speeds
International Nuclear Information System (INIS)
Slow and hovering animal flight creates high demands on the lift production of animal wings. Steady state aerodynamics is unable to explain the forces required and the most commonly used mechanism to enhance the lift production is a leading edge vortex (LEV). Although LEVs increase the lift, they come at the cost of high drag. Here we determine the flow above the wing of lesser long-nosed bats at slow and cruising speed using particle image velocimetry (PIV). We find that a prominent LEV is present during the downstroke at slow speed, but not at cruising speed. Comparison with previously published LEV data from a robotic flapper inspired by lesser long-nosed bats suggests that bats should be able to generate LEVs at cruising speeds, but that they avoid doing so, probably to increase flight efficiency. In addition, at slow flight speeds we find LEVs of opposite spin at the inner and outer wing during the upstroke, potentially providing a control challenge to the animal. We also note that the LEV stays attached to the wing throughout the downstoke and does not show the complex structures found in insects. This suggests that bats are able to control the development of the LEV and potential control mechanisms are discussed. (papers)
Goldberg, Robert K.; Carney, Kelly S.
2004-01-01
An analysis method based on a deformation (as opposed to damage) approach has been developed to model the strain rate dependent, nonlinear deformation of woven ceramic matrix composites, such as the Reinforced Carbon Carbon (RCC) material used on the leading edges of the Space Shuttle. In the developed model, the differences in the tension and compression deformation behaviors have also been accounted for. State variable viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the effective stress and effective inelastic strain definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear response is independent of the stiffness in the normal directions. The developed equations have been implemented into LS-DYNA through the use of user defined subroutines (UMATs). Several sample qualitative calculations have been conducted, which demonstrate the ability of the model to qualitatively capture the features of the deformation response present in woven ceramic matrix composites.
Carlson, H. W.
1994-01-01
This code was developed to aid design engineers in the selection and evaluation of aerodynamically efficient wing-canard and wing-horizontal-tail configurations that may employ simple hinged-flap systems. Rapid estimates of the longitudinal aerodynamic characteristics of conceptual airplane lifting surface arrangements are provided. The method is particularly well suited to configurations which, because of high speed flight requirements, must employ thin wings with highly swept leading edges. The code is applicable to wings with either sharp or rounded leading edges. The code provides theoretical pressure distributions over the wing, the canard or horizontal tail, and the deflected flap surfaces as well as estimates of the wing lift, drag, and pitching moments which account for attainable leading edge thrust and leading edge separation vortex forces. The wing planform information is specified by a series of leading edge and trailing edge breakpoints for a right hand wing panel. Up to 21 pairs of coordinates may be used to describe both the leading edge and the trailing edge. The code has been written to accommodate 2000 right hand panel elements, but can easily be modified to accommodate a larger or smaller number of elements depending on the capacity of the target computer platform. The code provides solutions for wing surfaces composed of all possible combinations of leading edge and trailing edge flap settings provided by the original deflection multipliers and by the flap deflection multipliers. Up to 25 pairs of leading edge and trailing edge flap deflection schedules may thus be treated simultaneously. The code also provides for an improved accounting of hinge-line singularities in determination of wing forces and moments. To determine lifting surface perturbation velocity distributions, the code provides for a maximum of 70 iterations. The program is constructed so that successive runs may be made with a given code entry. To make additional runs, it is
The effect of aspect ratio on the leading-edge vortex over an insect-like flapping wing.
Phillips, Nathan; Knowles, Kevin; Bomphrey, Richard J
2015-10-01
Insect wing shapes are diverse and a renowned source of inspiration for the new generation of autonomous flapping vehicles, yet the aerodynamic consequences of varying geometry is not well understood. One of the most defining and aerodynamically significant measures of wing shape is the aspect ratio, defined as the ratio of wing length (R) to mean wing chord (c). We investigated the impact of aspect ratio, AR, on the induced flow field around a flapping wing using a robotic device. Rigid rectangular wings ranging from AR = 1.5 to 7.5 were flapped with insect-like kinematics in air with a constant Reynolds number (Re) of 1400, and a dimensionless stroke amplitude of 6.5c (number of chords traversed by the wingtip). Pseudo-volumetric, ensemble-averaged, flow fields around the wings were captured using particle image velocimetry at 11 instances throughout simulated downstrokes. Results confirmed the presence of a high-lift, separated flow field with a leading-edge vortex (LEV), and revealed that the conical, primary LEV grows in size and strength with increasing AR. In each case, the LEV had an arch-shaped axis with its outboard end originating from a focus-sink singularity on the wing surface near the tip. LEV detachment was observed for AR > 1.5 around mid-stroke at ~70% span, and initiated sooner over higher aspect ratio wings. At AR > 3 the larger, stronger vortex persisted under the wing surface well into the next half-stroke leading to a reduction in lift. Circulatory lift attributable to the LEV increased with AR up to AR = 6. Higher aspect ratios generated proportionally less lift distally because of LEV breakdown, and also less lift closer to the wing root due to the previous LEV's continuing presence under the wing. In nature, insect wings go no higher than AR ~ 5, likely in part due to architectural and physiological constraints but also because of the reducing aerodynamic benefits of high AR wings. PMID:26451802
Grechnev, V. V.; Uralov, A. M.; Chertok, I. M.; Kuzmenko, I. V.; Afanasyev, A. N.; Meshalkina, N. S.; Kalashnikov, S. S.; Kubo, Y.
2011-01-01
We show examples of excitation of coronal waves by flare-related abrupt eruptions of magnetic rope structures. The waves presumably rapidly steepened into shocks and freely propagated afterwards like decelerating blast waves that showed up as Moreton waves and EUV waves. We propose a simple quantitative description for such shock waves to reconcile their observed propagation with drift rates of metric type II bursts and kinematics of leading edges of coronal mass ejections (CMEs). Taking acco...
Yepuri, Giridhara Babu; Talanki Puttarangasetty, Ashok Babu; Kolke, Deepak Kumar; Jesuraj, Felix
2016-06-01
Increasing the gas turbine inlet temperature is one of the key technologies in raising gas turbine engine power output. Film cooling is one of the efficient cooling techniques to cool the hot section components of a gas turbine engines in turn the turbine inlet temperature can be increased. This study aims at investigating the effect of RANS-type turbulence models on adiabatic film cooling effectiveness over a scaled up gas turbine blade leading edge surfaces. For the evaluation, five different two equation RANS-type turbulent models have been taken in consideration, which are available in the ANSYS-Fluent. For this analysis, the gas turbine blade leading edge configuration is generated using Solid Works. The meshing is done using ANSYS-Workbench Mesh and ANSYS-Fluent is used as a solver to solve the flow field. The considered gas turbine blade leading edge model is having five rows of film cooling circular holes, one at stagnation line and the two each on either side of stagnation line at 30° and 60° respectively. Each row has the five holes with the hole diameter of 4 mm, pitch of 21 mm arranged in staggered manner and has the hole injection angle of 30° in span wise direction. The experiments are carried in a subsonic cascade tunnel facility at heat transfer lab of CSIR-National Aerospace Laboratory with a Reynolds number of 1,00,000 based on leading edge diameter. From the Computational Fluid Dynamics (CFD) evaluation it is found that K-ɛ Realizable model gives more acceptable results with the experimental values, compared to the other considered turbulence models for this type of geometries. Further the CFD evaluated results, using K-ɛ Realizable model at different blowing ratios are compared with the experimental results.
Partial oxidation of step-bound water leads to anomalous pH effects on metal electrode step-edges.
Schwarz, Kathleen; Xu, Bingjun; Yan, Yushan; Sundararaman, Ravishankar
2016-06-28
The design of better heterogeneous catalysts for applications such as fuel cells and electrolyzers requires a mechanistic understanding of electrocatalytic reactions and the dependence of their activity on operating conditions such as pH. A satisfactory explanation for the unexpected pH dependence of electrochemical properties of platinum surfaces has so far remained elusive, with previous explanations resorting to complex co-adsorption of multiple species and resulting in limited predictive power. This knowledge gap suggests that the fundamental properties of these catalysts are not yet understood, limiting systematic improvement. Here, we analyze the change in charge and free energies upon adsorption using density-functional theory (DFT) to establish that water adsorbs on platinum step edges across a wide voltage range, including the double-layer region, with a loss of approximately 0.2 electrons upon adsorption. We show how this as-yet unreported change in net surface charge due to this water explains the anomalous pH variations of the hydrogen underpotential deposition (Hupd) and the potentials of zero total charge (PZTC) observed in published experimental data. This partial oxidation of water is not limited to platinum metal step edges, and we report the charge of the water on metal step edges of commonly used catalytic metals, including copper, silver, iridium, and palladium, illustrating that this partial oxidation of water broadly influences the reactivity of metal electrodes. PMID:27250359
Rao, Dhanvada M.; Hoffler, Keith D.
1988-01-01
A low-speed wind tunnel test was performed to investigate Reynolds number effects on the aerodynamic characteristics of a supersonic cruise wing concept model with a 60-deg swept wing incorporating leading-edge and trailing-edge flap deflections. The Reynolds number ranged from 0.3 to 1.6 x 10 to the 6th, and corresponding Mach numbers from .05 to 0.3. The objective was to define a threshold Reynolds number above which the flap aerodynamics basically remained unchanged, and also to generate a data base useful for validating theoretical predictions for the Reynolds number effects on flap performance. This report documents the test procedures used and the basic data acquired in the investigation.
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-12-31
This is one of a series of reports made on industrial pollutants by the Expert Panel on Air Quality Standards to advise the United Kingdom Government on air quality standards. It describes the main sources of lead exposure, including the relative contribution of lead in the air and lead in the diet, and the methods by which it is measured in air. The Panel also considers the airborne concentrations recorded to date in the United Kingdom, ways in which lead is handled in by the body, and its toxic effects on people. The dominant source of airborne lead is petrol combustion. Other source include coal combustion, the production of non-ferrous metals and waste treatment and disposal. The justification of an air quality standard for lead is set down. The Panel recommends an air quality standard for lead in the United Kingdom of 0.25 {mu}g/m{sup 3} measured as an annual average. This is intended to protect young children, the group most vulnerable to impairment of brain function. 17 refs., 3 figs., 2 tabs.
Partial oxidation of Step-Bound Water Leads to Anomalous pH Effects on Metal Electrode Step-Edges
Schwarz, Kathleen; Yan, Yushan; Sundararaman, Ravishankar
2016-01-01
The design of better heterogeneous catalysts for applications such as fuel cells and electrolyzers requires a mechanistic understanding of electrocatalytic reactions and the dependence of their activity on operating conditions such as pH. A satisfactory explanation for the unexpected pH dependence of electrochemical properties of platinum surfaces has so far remained elusive, with previous explanations resorting to complex co-adsorption of multiple species and resulting in limited predictive power. This knowledge gap suggests that the fundamental properties of these catalysts are not yet understood, limiting systematic improvement. Here, we analyze the change in charge and free energies upon adsorption using density-functional theory (DFT) to establish that water adsorbs on platinum step edges across a wide voltage range, including the double-layer region, with a loss of approximately 0.2 electrons upon adsorption. We show how the change in net surface charge due to this water explains the anomalous pH variat...
International Nuclear Information System (INIS)
Crystals of Dicalcium lead propionate (DLP) irradiated with different doses of gamma radiation were used to investigate gamma radiation effect on some optical parameters. The absorption coefficient of unirradiated and irradiated DLP crystals were calculated. Values of the allowed indirect optical energy gap (Ε) of DLP were calculated as a function of gamma-dose. decreases from 4.12 eV to 3.94 eV with increasing gamma-doses from 0 up to 10 kGy. This decrease was attributed to point defects created in DLP crystals during gamma-irradiation. The exponential dependence of the absorption coefficient as a function of the incident photon energy suggests that the Urbach rule is obeyed, and indicated the formation of a band tail. It was found that the band tail exhibits the opposite Ε behaviour
Energy Technology Data Exchange (ETDEWEB)
Meirer, Florian [Atominstitut, Vienna University of Technology, 1020 Wien (Austria); MiNALab, CMM-Irst, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Trento (Italy); Pemmer, Bernhard, E-mail: bpemmer@ati.ac.at [Atominstitut, Vienna University of Technology, 1020 Wien (Austria); Pepponi, Giancarlo [MiNALab, CMM-Irst, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Trento (Italy); Zoeger, Norbert; Wobrauschek, Peter [Atominstitut, Vienna University of Technology, 1020 Wien (Austria); Sprio, Simone; Tampieri, Anna [Istituto di Scienza e Tecnologia dei Materiali Ceramici CNR, Faenca (Italy); Goettlicher, Joerg; Steininger, Ralph; Mangold, Stefan [Institute for Synchrotron Radiation, Karlsruhe Institute of Technology, Campus South, 76344 Eggenstein-Leopoldshafen (Germany); Roschger, Paul [Ludwig Boltzmann Institute of Osteology, Hanusch Hospital of WGKK and AUVA Trauma Centre Meidling, 4th Medical Department, Hanusch Hospital, Vienna (Austria); Berzlanovich, Andrea [Department of Forensic Medicine, Medical University of Vienna, A-1090 Vienna (Austria); Hofstaetter, Jochen G. [Ludwig Boltzmann Institute of Osteology, Hanusch Hospital of WGKK and AUVA Trauma Centre Meidling, 4th Medical Department, Hanusch Hospital, Vienna (Austria); Department of Orthopaedics, Vienna General Hospital, Medical University of Vienna, A-1090 Vienna (Austria); Streli, Christina [Atominstitut, Vienna University of Technology, 1020 Wien (Austria)
2011-03-01
Lead is a toxic trace element that shows a highly specific accumulation in the transition zone between calcified and non-calcified articular cartilage, the so-called ‘tidemark’. Excellent agreement has been found between XANES spectra of synthetic Pb-doped carbonated hydroxyapatite and spectra obtained in the tidemark region and trabecular bone of normal human samples, confirming that in both tissues Pb is incorporated into the hydroxyapatite crystal structure of bone. During this study the µ-XANES set-up at the SUL-X beamline at ANKA was tested and has proven to be well suited for speciation of lead in human mineralized tissue samples. A highly specific accumulation of the toxic element lead was recently measured in the transition zone between non-calcified and calcified normal human articular cartilage. This transition zone, the so-called ‘tidemark’, is considered to be an active calcification front of great clinical importance. However, little is known about the mechanisms of accumulation and the chemical form of Pb in calcified cartilage and bone. Using spatially resolved X-ray absorption near-edge structure analysis (µ-XANES) at the Pb L{sub 3}-edge, the chemical state of Pb in the osteochondral region was investigated. The feasibility of the µ-XANES set-up at the SUL-X beamline (ANKA synchrotron light source) was tested and confirmed by comparing XANES spectra of bulk Pb-reference compounds recorded at both the XAS and the SUL-X beamline at ANKA. The µ-XANES set-up was then used to investigate the tidemark region of human bone (two patella samples and one femoral head sample). The spectra recorded at the tidemark and at the trabecular bone were found to be highly correlated with the spectra of synthetic Pb-doped carbonated hydroxyapatite, suggesting that in both of these very different tissues Pb is incorporated into the hydroxyapatite structure.
International Nuclear Information System (INIS)
Lead is a toxic trace element that shows a highly specific accumulation in the transition zone between calcified and non-calcified articular cartilage, the so-called ‘tidemark’. Excellent agreement has been found between XANES spectra of synthetic Pb-doped carbonated hydroxyapatite and spectra obtained in the tidemark region and trabecular bone of normal human samples, confirming that in both tissues Pb is incorporated into the hydroxyapatite crystal structure of bone. During this study the µ-XANES set-up at the SUL-X beamline at ANKA was tested and has proven to be well suited for speciation of lead in human mineralized tissue samples. A highly specific accumulation of the toxic element lead was recently measured in the transition zone between non-calcified and calcified normal human articular cartilage. This transition zone, the so-called ‘tidemark’, is considered to be an active calcification front of great clinical importance. However, little is known about the mechanisms of accumulation and the chemical form of Pb in calcified cartilage and bone. Using spatially resolved X-ray absorption near-edge structure analysis (µ-XANES) at the Pb L3-edge, the chemical state of Pb in the osteochondral region was investigated. The feasibility of the µ-XANES set-up at the SUL-X beamline (ANKA synchrotron light source) was tested and confirmed by comparing XANES spectra of bulk Pb-reference compounds recorded at both the XAS and the SUL-X beamline at ANKA. The µ-XANES set-up was then used to investigate the tidemark region of human bone (two patella samples and one femoral head sample). The spectra recorded at the tidemark and at the trabecular bone were found to be highly correlated with the spectra of synthetic Pb-doped carbonated hydroxyapatite, suggesting that in both of these very different tissues Pb is incorporated into the hydroxyapatite structure
Baumrind, N L; Parkinson, D; Wayne, D B; Heuser, J E; Pearlman, A L
1992-08-01
To identify cell-surface molecules that mediate interactions between neurons and their environment during neural development, we used monoclonal antibody techniques to define a developmentally regulated antigen in the central nervous system of the mouse. The antibody we produced (2A1) immunolabels cells throughout the central nervous system; we analyzed its distribution in the developing cerebral cortex, where it is expressed on cells very soon after they complete mitosis and leave the periventricular proliferative zone. Expression continues into adult life. The antibody also labels the epithelium of the choroid plexus and the renal proximal tubules, but does not label neurons of the peripheral nervous system in the dorsal root ganglia. In dissociated cell culture of embryonic cerebral cortex, 2A1 labels the surface of neurons but not glia. Immunolabeling of neurons in tissue culture is particularly prominent on the edge of growth cones, including filopodia and the leading edge of lamellipodia, when observed with either immunofluorescence or freeze-etch immunoelectron microscopy. Immunopurification with 2A1 of a CHAPS-extracted membrane preparation from brains of neonatal mice produces a broad (32-36 kD) electrophoretic band and a less prominent 70 kD band that are sensitive to N-glycosidase but not endoglycosidase H. Thus the 2A1 antibody recognizes a developmentally regulated, neuronal cell surface glycoprotein (or glycoproteins) with complex N-linked oligosaccharide side chains. We have termed the glycoprotein antigen EMA because of its prominence on the edge membrane of growth cones. EMA is similar to the M6 antigen (Lagenaur et al: J. Neurobiol. 23:71-88, 1992) in apparent molecular weight, distribution in tissue sections, and immunoreactivity on Western blots, suggesting that the two antigens are similar or identical. Expression of EMA is a very early manifestation of neuronal differentiation; its distribution on growth cones suggests a role in mediating the
International Nuclear Information System (INIS)
This contribution is aimed at analyzing the capabilities of popular two-equation turbulence models to predict features of 3D flow fields and endwall heat transfer near the blunt edge of a symmetric body mounted on a plate. The configuration studied experimentally by Praisner and Smith is considered. Results obtained with the in-house CFD code SINF and the commercial package ANSYS-CFX are presented and compared. Prediction capabilities of the low-Re Wilcox turbulence model and two versions of the Menter SST model, the original and the modified one, are analyzed in comparison with the experimental data. Special attention is paid to grid sensitivity of the numerical solutions. Advanced visualization of the vortex structures computed is performed with author's visualization tool HDVIS. It has been established that the Wilcox model is not capable of predicting the development of a multiple-vortex system observed in the experiment upstream of the body leading edge. Both versions of the MSST model produce qualitatively correct results, with a considerable superiority of the modified version when compared with the quantitative data.
Directory of Open Access Journals (Sweden)
Gisela Lorente
Full Text Available Cellular motility is the basis for cancer cell invasion and metastasis. In the case of breast cancer, the most common type of cancer among women, metastasis represents the most devastating stage of the disease. The central role of cellular motility in cancer development emphasizes the importance of understanding the specific mechanisms involved in this process. In this context, tumor development and metastasis would be the consequence of a loss or defect of the mechanisms that control cytoskeletal remodeling. Profilin I belongs to a family of small actin binding proteins that are thought to assist in actin filament elongation at the leading edge of migrating cells. Traditionally, Profilin I has been considered to be an essential control element for actin polymerization and cell migration. Expression of Profilin I is down-regulated in breast and various other cancer cells. In MDA-MB-231 cells, a breast cancer cell line, further inhibition of Profilin I expression promotes hypermotility and metastatic spread, a finding that contrasts with the proposed role of Profilin in enhancing polymerization. In this report, we have taken advantage of the fluorescence recovery after photobleaching (FRAP of GFP-actin to quantify and compare actin dynamics at the leading edge level in both cancer and non-cancer cell models. Our results suggest that (i a high level of actin dynamics (i.e., a large mobile fraction of actin filaments and a fast turnover is a common characteristic of some cancer cells; (ii actin polymerization shows a high degree of independence from the presence of extracellular growth factors; and (iii our results also corroborate the role of Profilin I in regulating actin polymerization, as raising the intracellular levels of Profilin I decreased the mobile fraction ratio of actin filaments and slowed their polymerization rate; furthermore, increased Profilin levels also led to reduced individual cell velocity and directionality.
Energy Technology Data Exchange (ETDEWEB)
Yang Zhiyin [Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough LE11 3TU (United Kingdom)], E-mail: z.yang@iboro.ac.uk; Abdalla, Ibrahim E. [School of Engineering and Technology, De Montfort University, Leicester LE1 9BH (United Kingdom)
2009-10-15
The transitional separated-reattached flow on a flat plate with a blunt leading edge under 2% free-stream turbulence (FST) is numerically simulated using the Large-eddy simulation (LES) approach. The Reynolds number based on the free-stream velocity and the plate thickness is 6500. A dynamic subgrid-scale model is employed and the LES results compare well with the available experimental data. It is well known that FST enhances shear-layer entrainment rates, reduces the mean reattachment distance, and causes early transition to turbulence leading to an early breakdown of the separated boundary layer. Many experimental studies have shown that different vortex shedding frequencies exist, specially the so called low-frequency flapping when there is a separation bubble but its mechanism is still not completely understood. The previous study by us without free-stream turbulence (NFST) did not show the existence of such a low-frequency flapping of the shear layer and it is not clear what the effects of FST will have on these shedding modes. Detailed analysis of the LES data has been presented in the present paper and the low-frequency flapping has not been detected in the current study.
Energy Technology Data Exchange (ETDEWEB)
Nishiyama, Hideya
1988-07-25
Any analytic study of a centrifugal impeller with a leading edge cavitation is concentrated only on blade or cavity characteristics. Therefore, internal flow condition, especially exit flow, has many indistinctness. Considering that, analysis of flow inside the centrifugal impeller casing and at its exit was performed by the singularity method. In the inside flow of the centrifugal impeller casing, cavitation rear end distortion, cavitation area, relative velocity distribution, pressure inside the cavity, iso-hydrostatic line distribution were examined. In the exit flow, hydrostatic distribution, flow angle distribution, slip velocity distribution, slip constant, blade efficiency, and comparison between obtained and existing slip constant values were examined. As a result, the flow inside the centrifugal impeller in front cavity is found to vary with the number or angle of blades because of the large cavitation area and different from that of no cavitation. The exit flow in the front cavity is different from that at the center of the cavity. The rate of change of slip constant and blade efficiency is large in the front cavity; it is larger when the impeller has fewer blades a lager blade angle. (13 figs, 10 refs)
Bocquet, L
2006-01-01
We show that the baking of potato wedges constitutes a crunchy example of edge effects, which are usually demonstrated in electrostatics. A simple model of the diffusive transport of water vapor around the potato wedges shows that the water vapor flux diverges at the sharp edges in analogy with its electrostatic counterpart. This increased evaporation at the edges leads to the crispy taste of these parts of the potatoes.
Healy, A M; Morgenthau, L; Zhu, X; Farber, H W; Cardoso, W V
2000-11-01
We used whole lung cultures as a model to study blood vessel formation in vitro and to examine the role that epithelial-mesenchymal interactions play during embryonic pulmonary vascular development. Mouse lungs were isolated at embryonic day 11.5 (E11.5) and cultured for up to 4 days prior to blood vessel analysis. Platelet endothelial cell adhesion molecule-1 (PECAM/CD31) and thrombomodulin (TM/CD141) immunolocalization demonstrate that vascular development occurs in lung cultures. The vascular structures identified in lung cultures first appear as a loosely associated plexus of capillary-like structures that with time surround the airways. To investigate the potential role of vascular endothelial cell growth factor (VEGF) during pulmonary neovascularization, we immunolocalized VEGF in embryonic lungs. Our data demonstrate that VEGF is uniformly present in the airway epithelium and the subepithelial matrix of E11.5 lungs. At later time points, E13.5 and E15.5, VEGF is no longer detected in the proximal airways, but is restricted to the branching tips of airways in the distal lung. RT-PCR analysis reveals that VEGF(164) is the predominant isoform expressed in lung cultures. Grafting heparin-bound VEGF(164) beads onto lung explants locally stimulates a marked neovascular response within 48 hr in culture. Semi-quantitative RT-PCR reveals an 18% increase in PECAM mRNA in VEGF(164)-treated whole lung cultures as compared with untreated cultures. The restricted temporal and spatial expression of VEGF suggests that matrix-associated VEGF links airway branching with blood vessel formation by stimulating neovascularization at the leading edge of branching airways. PMID:11066091
Daryabeigi, Kamran; Walker, Sandra P.
2009-01-01
The objective of the present study was to determine whether infrared imaging (IR) surface temperature data obtained during arc-jet tests of Space Shuttle Orbiter s reinforced carbon-carbon (RCC) wing leading edge panel slip-side joggle region could be used to detect presence of subsurface material separation, and if so, to determine when separation occurs during the simulated entry profile. Recent thermostructural studies have indicated thermally induced interlaminar normal stress concentrations at the substrate/coating interface in the curved joggle region can result in local subsurface material separation, with the separation predicted to occur during approach to peak heating during reentry. The present study was an attempt to determine experimentally when subsurface material separations occur. A simplified thermal model of a flat RCC panel with subsurface material separation was developed and used to infer general surface temperature trends due to the presence of subsurface material separation. IR data from previously conducted arc-jet tests on three test specimens were analyzed: one without subsurface material separation either pre or post test, one with pre test separation, and one with separation developing during test. The simplified thermal model trend predictions along with comparison of experimental IR data of the three test specimens were used to successfully infer material separation from the arc-jet test data. Furthermore, for the test specimen that had developed subsurface material separation during the arc-jet tests, the initiation of separation appeared to occur during the ramp up to the peak heating condition, where test specimen temperature went from 2500 to 2800 F.
Tempelmeyer, Kenneth E.; Osborne, Robert S.
1954-01-01
The effects of several wing leading-edge camber and deflected-tip modifications on the force and moment characteristics of a 1/20-scale model of the Convair F-102 airplane have been determined at Mach numbers from 0.60 t o 1.14 for angles of attack up to 14 deg. in the Langley 8-foot transonic tunnel. The effects of elevator deflections from 0 deg. to -10 deg. were also obtained for a configuration incorporating favorable leading- edge and tip modifications. Leading-edge modifications which had a small amount of constant-chord camber obtained by vertically adjusting the thickness distribution over the forward (3.9 percent of the mean aerodynamic chord) portion of the wing were ineffective in reducing the drag at lifting conditions at transonic speeds. Leading edges with relatively large cambers designed to support nearly elliptical span load distributions at lift coefficients of 0.15 and 0.22 near a Mach number of 1.0 produced substantial reductions in drag at most lift coefficients.
Lee, Jaeseo; Lee, Gwang G.; Huh, Kang Y.
2014-12-01
This paper presents validation of new analytical expressions for the turbulent burning velocity, ST, based on asymptotic behavior at the leading edge (LE) in turbulent premixed combustion. Reaction and density variation are assumed to be negligible at the LE to avoid the cold boundary difficulty in the statistically steady state. Good agreement is shown for the slopes, dST/du', with respect to Lc/δf at low turbulence, with both normalized by those of the reference cases. δf is the inverse of the maximum gradient of reaction progress variable through an unstretched laminar flame, and Lc is the characteristic length scale given as burner diameter or measured integral length scale. Comparison is made for thirty-five datasets involving different fuels, equivalence ratios, H2 fractions in fuel, pressures, and integral length scales from eight references [R. C. Aldredge et al., "Premixed-flame propagation in turbulent Taylor-Couette flow," Combust. Flame 115, 395 (1998); M. Lawes et al., "The turbulent burning velocity of iso-octane/air mixtures," Combust. Flame 159, 1949 (2012); H. Kido et al., "Influence of local flame displacement velocity on turbulent burning velocity," Proc. Combust. Inst. 29, 1855 (2002); J. Wang et al., "Correlation of turbulent burning velocity for syngas/air mixtures at high pressure up to 1.0 MPa," Exp. Therm. Fluid Sci. 50, 90 (2013); H. Kobayashi et al., "Experimental study on general correlation of turbulent burning velocity at high pressure," Proc. Combust. Inst. 27, 941 (1998); C. W. Chiu et al., "High-pressure hydrogen/carbon monoxide syngas turbulent burning velocities measured at constant turbulent Reynolds numbers," Int. J. Hydrogen Energy 37, 10935 (2012); P. Venkateswaran et al., "Pressure and fuel effects on turbulent consumption speeds of H2/CO blends," Proc. Combust. Inst. 34, 1527 (2013); M. Fairweather et al., "Turbulent burning rates of methane and methane-hydrogen mixtures," Combust. Flame 156, 780 (2009)]. The turbulent
Institute of Scientific and Technical Information of China (English)
李友军; 罗孝勇; 郭向荣
2013-01-01
Rac activation is strongly regulated spacially and temporally in migrating cells, leading to the formation of specific cell protrusion-lamellipodia in leading edge of the cells and generating the pushing force to put the cells forward, but the molecular mechanism of positive regulation of localized Rac activation remains unclear. We propose that the phosphorylation of the intracellular α4 integrin inhibits the interaction of α4 with paxillin, thus the signaling pathway paxillin-GITl -PIX-PAK would be formed, leading to localized Rac activation in leading edge of the migrating cells. In the paper, western blotting clearly showed that the interactions accurately exist between the cytoskeleton proteins GIT1 and paxillin or PIX respectively. Fluorescent colocalization confirmed that the interactions between GIT1 and paxillin or PIX occur in the leading edge of the cells. Rac activation assay elucidated that Rac is in activated state (GTP-bound) under the stimulation of ECM fibronectin, suggesting that the signaling pathway paxillin-GITl -PIX-PAK led to Rac activation. The results built the experimental basis for the study of regulation mechanism on localized Rac activation in leading edge of directed migrating cells.%提出构想:当α4胞内区域磷酸化而抑制其与paxillin结合时,paxillin、GIT1与PIX、PAK形成信号分子复合物.由于PIX为Rac的转换分子,PAK为Rac的效应分子,构成了paxillin-GIT1-PIX-PAK信号转导通路,从而促使Rac在细胞前沿持续地局部化激活,导致片状足的形成,产生细胞向前扩展推动力.研究结果表明,GIT1与paxillin、PIX在活细胞中均存在强烈的相互作用,且这种相互作用可发生在细胞前沿.由于Rac的转换因子PIX(PAK-interacting exchange factor)在活细胞中往往与PAK相伴而行,因而,在细胞前沿,必定存在paxillin-GIT1-PIX-PAK的信号转导通路.在纤粘蛋白(fibronectin)刺激下,整合素α4诱导Rac蛋白处于激活状态(GTP-bound).
Institute of Scientific and Technical Information of China (English)
罗烈; 高旭; 孙海军
2015-01-01
To deal with the problem that the aerodynamic and stealth characteristics of wing configuration are more sensitive to its airfoil shape, a leading edge parameterization method was proposed, and high ifdelity methods were used to investigate the sensitivity of leading edge parameter to the aerodynamic and stealth characteristics of the airfoil. The results show that , as the leading edge radius increases, not only the maximum lift coefifcuent, stall angle and speed for maximum lift to dray ratio have a great increase, but the average RCS also increases obviously.For this reason, a compromise should be made in airfoil design. Without affecting the structure and loading condition, the delfexion angle of the lower surface of airfoil should be as small as possible, and the modiifcation length should be 0.15c.%针对翼面部件对隐身飞机气动和隐身性能影响更为突出的问题，提出了一种翼型前缘参数化修形方法，采用高精度气动和电磁数值计算方法，进行了前缘形状对翼型气动-隐身特性的敏感性分析。研究结果表明：翼型前缘半径增加，其最大升力系数、失速迎角、最大升阻比显著增加，但其前向RCS均值也增加明显，设计时需进行综合权衡；在不影响结构和装载的情况下，下表面偏角尽量小，修形长度取0.15c，对翼型的低、高速气动和隐身特性都有利。
DEFF Research Database (Denmark)
Earon, Ofri
2013-01-01
building. The research explores and develops the architectural characteristics of correlations between the resident, the singular unit, the building and the given location at the edge zone. It approaches the edge zone of the urban house as a platform for dynamic interactions between these behaviours. The...... following text includes the first draft of the first two chapters: introduction and theory. The chapters are not written completely, and some parts are written only as headlines. These headlines and other comments are marked in red. The text is on working progress and far from being finished, but it will be...
DEFF Research Database (Denmark)
Earon, Ofri
2014-01-01
“What is an edge? We can think about an edge as having been of two sorts. In one, it is a border. In the other, it is a boundary. A border is a zone of interaction where things meet and intersect. A boundary is a place where something ends” Architects and planners normally approach domestic borders...... the involved actors at the border. By doing so, the study underlines a forgotten, yet important, role of this edge zone – being a zone of commonality between the house and city, between indoors and outdoors, between the man at home and the man at the street. The city of Copenhagen promotes porous...... borders on the ground level, but there is a lack of recognition in the significance of communicative characters as well at the higher part of the edge. The city’s planning approach is “Consider urban life before urban space. Consider urban space before buildings” This urban strategy neglects the possible...
Manro, M. E.; Manning, K. J. R.; Hallstaff, T. H.; Rogers, J. T.
1975-01-01
A wind tunnel test of an arrow-wing-body configuration consisting of flat and twisted wings, as well as a variety of leading- and trailing-edge control surface deflections, was conducted at Mach numbers from 0.4 to 1.1 to provide an experimental pressure data base for comparison with theoretical methods. Theory-to-experiment comparisons of detailed pressure distributions were made using current state-of-the-art attached and separated flow methods. The purpose of these comparisons was to delineate conditions under which these theories are valid for both flat and twisted wings and to explore the use of empirical methods to correct the theoretical methods where theory is deficient.
Stough, H. Paul, III; Dicarlo, Daniel J.; Patton, James M., Jr.
1987-01-01
Flight tests were performed to investigate the change in stall/spin characteristics due to the addition of an outboard wing-leading-edge modification to a four-place, low-wing, single-engine, T-tail, general aviation research airplane. Stalls and attempted spins were performed for various weights, center of gravity positions, power settings, flap deflections, and landing-gear positions. Both stall behavior and wind resistance were improved compared with the baseline airplane. The latter would readily spin for all combinations of power settings, flap deflections, and aileron inputs, but the modified airplane did not spin at idle power or with flaps extended. With maximum power and flaps retracted, the modified airplane did enter spins with abused loadings or for certain combinations of maneuver and control input. The modified airplane tended to spin at a higher angle of attack than the baseline airplane.
Leading Edge Aeronautics Research for NASA Project
National Aeronautics and Space Administration — The LEARN Project explores the creation of novel concepts and processes with the potential to create new capabilities in aeronautics research through awards to the...
Institute of Scientific and Technical Information of China (English)
王毅; 卢新根; 赵胜丰; 朱俊强
2011-01-01
为拓宽离心压气机稳定工作范围,以某高负荷离心压气机为研究对象,对径向扩压器叶片前缘进行盘侧开槽处理,借助数值模拟手段,探讨了开槽处理对离心压气机性能和稳定工作范围的影响,并对开槽结构进行了参数化研究,确定了主要开槽参数对离心压气机的影响.数值计算表明,径向扩压器前缘盘侧开槽能够在一定程度上提高离心压气机的稳定工作裕度,但同时伴随着压气机性能的降低.详细对比分析了开槽结构引人前后离心压气机内部流场结构,揭示了径向扩压器叶片前缘开槽提高离心压气机稳定工作裕度机理.%To extend the stable operating range of centrifugal compressor, a series of numerical simulations were performed for a highly - loaded centrifugal compressor with slotted radial diffuser blade at the bottom of leading edge, and the effects of slotted radial diffuser blade on performance and stable operating range of the centrifugal compressor were investigated in detail. In addition, parametric studies on slot depth and slot width were conducted in order to explore the key role parameters for optimum performance. The simulation results indicate that slotted radial diffuser blade at leading edge could extend the stable operating range, but slightly decrease the pressure ratio and efficiency. Detailed analysis of the flow visualization has exposed the different tip flow topologies between the cases with original radial diffuser and slotted radial diffuser, therefore led to some preliminary conclusions as to the flow physics involved in the stall margin improvements afforded by the use of slotted radial diffuser.
Edge instabilities of topological superconductors
Hofmann, Johannes S.; Assaad, Fakher F.; Schnyder, Andreas P.
2016-05-01
Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground-state degeneracy. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry-broken phases, which lift the ground-state degeneracy. We examine the instabilities of the flat-band edge states of dx y-wave superconductors by performing a mean-field analysis in the Majorana basis of the edge states. The leading instabilities are Majorana mass terms, which correspond to coherent superpositions of particle-particle and particle-hole channels in the fermionic language. We find that attractive interactions induce three different mass terms. One is a coherent superposition of imaginary s -wave pairing and current order, and another combines a charge-density-wave and finite-momentum singlet pairing. Repulsive interactions, on the other hand, lead to ferromagnetism together with spin-triplet pairing at the edge. Our quantum Monte Carlo simulations confirm these findings and demonstrate that these instabilities occur even in the presence of strong quantum fluctuations. We discuss the implications of our results for experiments on cuprate high-temperature superconductors.
Chemistry at the Edge of Graphene.
Bellunato, Amedeo; Arjmandi Tash, Hadi; Cesa, Yanina; Schneider, Grégory F
2016-03-16
The selective functionalization of graphene edges is driven by the chemical reactivity of its carbon atoms. The chemical reactivity of an edge, as an interruption of the honeycomb lattice of graphene, differs from the relative inertness of the basal plane. In fact, the unsaturation of the pz orbitals and the break of the π conjugation on an edge increase the energy of the electrons at the edge sites, leading to specific chemical reactivity and electronic properties. Given the relevance of the chemistry at the edges in many aspects of graphene, the present Review investigates the processes and mechanisms that drive the chemical functionalization of graphene at the edges. Emphasis is given to the selective chemical functionalization of graphene edges from theoretical and experimental perspectives, with a particular focus on the characterization tools available to investigate the chemistry of graphene at the edge. PMID:26693841
Wiström, Björn
2015-01-01
This thesis investigates design guidelines and management systems for the development of stationary forest edges with a graded profile in infrastructure and urban environments. The spatial restriction for the edge to move forward caused by human land use counteracts the natural dynamics and development patterns of graded forest edges. However graded forest edges with successively increasing height from the periphery to the interior of the forest edge are often seen as ideal as they supports ...
Institute of Scientific and Technical Information of China (English)
李伟光; 杨期江; 蒙启泳; 彭喆; 罗健彬; 赵伟; 骆稢行
2015-01-01
Firstly,according to the lubrication characteristics of tilting pad bearing,a novel three-pad tilting pad bearing with leading edge groove (LEG)was proposed.Secondly,in order to obtain the test parameters of the bearing,a dynamic performance test rig with the functions of automatic data acquisition and real-time data analysis was developed.Then,the temperature characteristics of flooded bearing and LEG bearing were analyzed in a com-parison way,and eight dynamic parameters of tilting pad bearing were obtained respectively via finite difference al-gorithm and frequency sweep excitation test.Finally,the effectiveness of the proposed test method was verified by a comparison between the theoretical results and the test ones.It is found that the developed bearing is of good tem-perature,stiffness and damping characteristics.%针对可倾瓦轴承润滑的特征，开发了一种新型前缘沟槽型（LEG）三瓦可倾瓦轴承；为获取该可倾瓦轴承的试验参数，研制了一套具有自动采集数据、实时分析数据等功能的可倾瓦轴承动态特性测试试验台；对比分析了浸润式滑动轴承与前缘沟槽型滑动轴承的轴瓦温度特性；采用有限差分算法理论计算了该轴承的动态特性参数，采用扫频激振方法试验研究了该轴承的8个动态特性参数，并通过对比分析理论计算与试验结果验证了试验方法的有效性。研究表明，所开发的滑动轴承具有较好的温度特性及刚度阻尼特性。
Zhang, Xiuyun; Xin, John; Ding, Feng
2013-03-01
The edge of two dimensional (2D) graphene, as the surface of a three dimensional (3D) crystal, plays a crucial role in the determination of its physical, electronic and chemical properties and thus has been extensively studied recently. In this review, we summarize the recent advances in the study of graphene edges, including edge formation energy, edge reconstruction, method of graphene edge synthesis and the recent progress on metal-passivated graphene edges and the role of edges in graphene CVD growth. We expect this review to provide a guideline for readers to gain a clear picture of graphene edges from several aspects, especially the catalyst-passivated graphene edges and their role in graphene CVD growth.
Zhang, Xiuyun; Xin, John; Ding, Feng
2013-04-01
The edge of two dimensional (2D) graphene, as the surface of a three dimensional (3D) crystal, plays a crucial role in the determination of its physical, electronic and chemical properties and thus has been extensively studied recently. In this review, we summarize the recent advances in the study of graphene edges, including edge formation energy, edge reconstruction, method of graphene edge synthesis and the recent progress on metal-passivated graphene edges and the role of edges in graphene CVD growth. We expect this review to provide a guideline for readers to gain a clear picture of graphene edges from several aspects, especially the catalyst-passivated graphene edges and their role in graphene CVD growth. PMID:23420074
Edges and Switches, Tunnels and Bridges
Eppstein, David; Mumford, Elena; Speckmann, Bettina
2007-01-01
Edge casing is a well-known method to improve the readability of drawings of non-planar graphs. A cased drawing orders the edges of each edge crossing and interrupts the lower edge in an appropriate neighborhood of the crossing. Certain orders will lead to a more readable drawing than others. We formulate several optimization criteria that try to capture the concept of a "good" cased drawing. Further, we address the algorithmic question of how to turn a given drawing into an optimal cased drawing. For many of the resulting optimization problems, we either find polynomial time algorithms or NP-hardness results.
Edges and Switches, Tunnels and Bridges
Eppstein, D; Kreveld, van, MJ Marc; Mumford, E Elena; Speckmann, B Bettina
2007-01-01
Edge casing is a well-known method to improve the readability of drawings of non-planar graphs. A cased drawing orders the edges of each edge crossing and interrupts the lower edge in an appropriate neighborhood of the crossing. Certain orders will lead to a more readable drawing than others. We formulate several optimization criteria that try to capture the concept of a "good" cased drawing. Further, we address the algorithmic question of how to turn a given drawing into an optimal cased dra...
Continued Growth on Graphene Edges
Luo, Zhengtang
Previously, we have shown that the large-size single crystal graphene can be obtained by suppressing the nucleation density during Chemical Vapor Deposition (CVD) growth. Here we demonstrate that the graphene single crystal can be amplified by a continued growth method. In this process, we used a mild oxidation step after the first-growth, which lead to the observed fromation of oxides at the vicinity of graphene edges, which allows the graphene growth at seed edges due to reduced activation energy. Consequently, we successful grown a secondary single-crystal graphene structures with the same lattice structure, orientation on the graphene edges. This amplification method would enable the production of graphene electronics with controlled properties.
Stability of edge states and edge magnetism in graphene nanoribbons
Kunstmann, Jens; Özdoğan, Cem; Quandt, Alexander; Fehske, Holger
2010-01-01
We critically discuss the stability of edge states and edge magnetism in zigzag edge graphene nanoribbons (ZGNRs). We point out that magnetic edge states might not exist in real systems, and show that there are at least three very natural mechanisms - edge reconstruction, edge passivation, and edge closure - which dramatically reduce the effect of edge states in ZGNRs or even totally eliminate them. Even if systems with magnetic edge states could be made, the intrinsic magnetism would not be ...
Institute of Scientific and Technical Information of China (English)
X.Q. Xu; C.S. Chang
2007-01-01
@@ The plasma edge includes the pedestal, scrape-off, and divertor regions. A complete edge physics should deal with the plasma, atomic, and the plasma-wall interaction phenomena. The edge provides the source of plasma through ionization of the incoming neutral particles and source of impurity through the wall sputtering. Edge plasma sets a boundary condition for the core confinement physics. Importance of the edge plasma has been elevated to the top list of the ITER physics research needs due to the necessity of the self-organized plasma pedestal and its destruction by edge localized mode activities. Extrapolation of the present tokamak data base predicts that a sufficient pedestal height is a necessary condition for the success of ITER.
Cascading Edge Failures: A Dynamic Network Process
Zhang, June
2016-01-01
This paper considers the dynamics of edges in a network. The Dynamic Bond Percolation (DBP) process models, through stochastic local rules, the dependence of an edge $(a,b)$ in a network on the states of its neighboring edges. Unlike previous models, DBP does not assume statistical independence between different edges. In applications, this means for example that failures of transmission lines in a power grid are not statistically independent, or alternatively, relationships between individuals (dyads) can lead to changes in other dyads in a social network. We consider the time evolution of the probability distribution of the network state, the collective states of all the edges (bonds), and show that it converges to a stationary distribution. We use this distribution to study the emergence of global behaviors like consensus (i.e., catastrophic failure or full recovery of the entire grid) or coexistence (i.e., some failed and some operating substructures in the grid). In particular, we show that, depending on...
Edge plasma in snowflake divertor
International Nuclear Information System (INIS)
The snowflake divertor (Ryutov 2007, Phys. Plasmas 14, 064502) uses a 2nd order null of the poloidal magnetic field instead of the 1st order null used in the standard divertor. This leads to a number of interesting geometric properties such as stronger fanning of the poloidal flux, stronger magnetic shear in the edge region, larger radiating volume, and larger connection length in the scrape-off layer. These can potentially lead to new ways for alleviating heat loads on the divertor target plates. Discussion of properties of snowflake is presented, along with results of numerical modeling. Divertor leg volume is larger in snowflake than in the standard x-point configuration, which leads to larger fraction of radiated power in the divertor. This allows the snowflake to transition to a strongly detached plasma regime more easily than for the standard x-point. Besides, stronger shearing of the magnetic field in snowflake may be beneficial for controlling magneto-hydrodynamic instabilities in the edge (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Labrecque, Joseph
2012-01-01
Adobe Edge Quickstart Guide is a practical guide on creating engaging content for the Web with Adobe's newest HTML5 tool. By taking a chapter-by-chapter look at each major aspect of Adobe Edge, the book lets you digest the available features in small, easily understandable chunks, allowing you to start using Adobe Edge for your web design needs immediately. If you are interested in creating engaging motion and interactive compositions using web standards with professional tooling, then this book is for you. Those with a background in Flash Professional wanting to get started quickly with Adobe
Losing your edge: climate change and the conservation value of range-edge populations.
Rehm, Evan M; Olivas, Paulo; Stroud, James; Feeley, Kenneth J
2015-10-01
Populations occurring at species' range edges can be locally adapted to unique environmental conditions. From a species' perspective, range-edge environments generally have higher severity and frequency of extreme climatic events relative to the range core. Under future climates, extreme climatic events are predicted to become increasingly important in defining species' distributions. Therefore, range-edge genotypes that are better adapted to extreme climates relative to core populations may be essential to species' persistence during periods of rapid climate change. We use relatively simple conceptual models to highlight the importance of locally adapted range-edge populations (leading and trailing edges) for determining the ability of species to persist under future climates. Using trees as an example, we show how locally adapted populations at species' range edges may expand under future climate change and become more common relative to range-core populations. We also highlight how large-scale habitat destruction occurring in some geographic areas where many species range edge converge, such as biome boundaries and ecotones (e.g., the arc of deforestation along the rainforest-cerrado ecotone in the southern Amazonia), can have major implications for global biodiversity. As climate changes, range-edge populations will play key roles in helping species to maintain or expand their geographic distributions. The loss of these locally adapted range-edge populations through anthropogenic disturbance is therefore hypothesized to reduce the ability of species to persist in the face of rapid future climate change. PMID:26664681
Color image retrieval using edge and edge-spatial features
Institute of Scientific and Technical Information of China (English)
Chaobing Huang; Quan Liu
2006-01-01
@@ A novel methodology to integrate edge feature and edge-spatial feature of an image is proposed. The edge feature is described by edge histogram of image, the edge-spatial feature is described by spatial distribution of pixels of identical edge value in the image. Experimental results show that the method can achieve better retrieval performance, especially for color natural images with more complex spatial layout.
Geloni, Gianluca; Saldin, Evgeni; Schneidmiller, Evgeni; Yurkov, Mikhail
2008-01-01
We formulate a complete theory of Edge Radiation based on a novel method relying on Fourier Optics techniques. Similar types of radiation like Transition Undulator Radiation are addressed in the framework of the same formalism. Special attention is payed in discussing the validity of approximations upon which the theory is built. Our study makes consistent use of both similarity techniques and comparisons with numerical results from simulation. We discuss both near and far zone. Physical understanding of many asymptotes is discussed. Based on the solution of the field equation with a tensor Green's function technique, we also discuss an analytical model to describe the presence of a vacuum chamber. In particular, explicit calculations for a circular vacuum chamber are reported. Finally, we consider the use of Edge Radiation as a tool for electron beam diagnostics. We discuss Coherent Edge Radiation, Extraction of Edge Radiation by a mirror, and other issues becoming important at high electron energy and long ...
Grover, Chris
2011-01-01
Want to use an Adobe tool to design animated web graphics that work on iPhone and iPad? You've come to the right book. Adobe Edge Preview 3: The Missing Manual shows you how to build HTML5 graphics using simple visual tools. No programming experience? No problem. Adobe Edge writes the underlying code for you. With this eBook, you'll be designing great-looking web elements in no time. Get to know the workspace. Learn how Adobe Edge Preview 3 performs its magic.Create and import graphics. Make drawings with Edge's tools, or use art you designed in other programs.Work with text. Build menus, lab
Memristive fuzzy edge detector
Merrikh-Bayat, Farnood
2011-01-01
Fuzzy inference systems always suffer from the lack of efficient structures or platforms for their hardware implementation. In this paper, we tried to overcome this problem by proposing new method for the implementation of those fuzzy inference systems which use fuzzy rule base to make inference. To achieve this goal, we have designed a multi-layer neuro-fuzzy computing system based on the memristor crossbar structure by introducing some new concepts like fuzzy minterms. Although many applications can be realized through the use of our proposed system, in this study we show how the fuzzy XOR function can be constructed and how it can be used to extract edges from grayscale images. Our memristive fuzzy edge detector (implemented in analog form) compared with other common edge detectors has this advantage that it can extract edges of any given image all at once in real-time.
Edge Effects and Huanglongbing
Luo, W.; Anco, D J; Gottwald, T. R.; Irey, M. S.
2014-01-01
Huanglongbing (HLB), spread by a psyllid vector, is globally considered a major threat to commercial and sustainable citrus production. Better understanding of the vector-mediated patterns of HLB spread is essential to inform and maximize disease management. From previous studies, edge effects are a significant characteristic of the HLB pathosystem and have been observed predominately in larger plantings. In this study, we investigated 1) the impact of different edge classes and orientations,...
LEADING WITH LEADING INDICATORS
International Nuclear Information System (INIS)
This paper documents Fluor Hanford's use of Leading Indicators, management leadership, and statistical methodology in order to improve safe performance of work. By applying these methods, Fluor Hanford achieved a significant reduction in injury rates in 2003 and 2004, and the improvement continues today. The integration of data, leadership, and teamwork pays off with improved safety performance and credibility with the customer. The use of Statistical Process Control, Pareto Charts, and Systems Thinking and their effect on management decisions and employee involvement are discussed. Included are practical examples of choosing leading indicators. A statistically based color coded dashboard presentation system methodology is provided. These tools, management theories and methods, coupled with involved leadership and employee efforts, directly led to significant improvements in worker safety and health, and environmental protection and restoration at one of the nation's largest nuclear cleanup sites
LEADING WITH LEADING INDICATORS
Energy Technology Data Exchange (ETDEWEB)
PREVETTE, S.S.
2005-01-27
This paper documents Fluor Hanford's use of Leading Indicators, management leadership, and statistical methodology in order to improve safe performance of work. By applying these methods, Fluor Hanford achieved a significant reduction in injury rates in 2003 and 2004, and the improvement continues today. The integration of data, leadership, and teamwork pays off with improved safety performance and credibility with the customer. The use of Statistical Process Control, Pareto Charts, and Systems Thinking and their effect on management decisions and employee involvement are discussed. Included are practical examples of choosing leading indicators. A statistically based color coded dashboard presentation system methodology is provided. These tools, management theories and methods, coupled with involved leadership and employee efforts, directly led to significant improvements in worker safety and health, and environmental protection and restoration at one of the nation's largest nuclear cleanup sites.
Integrated core-edge-divertor modeling studies
International Nuclear Information System (INIS)
An integrated calculation model for simulating the interaction of physics phenomena taking place in the plasma core, in the plasma edge and in the SOL and divertor of tokamaks has been developed and applied to study such interactions. The model synthesises a combination of numerical calculations (1) the power and particle balances for the core plasma, using empirical confinement scaling laws and taking into account radiation losses (2), the particle, momentum and power balances in the SOL and divertor, taking into account the effects of radiation and recycling neutrals, (3) the transport of feeling and recycling neutrals, explicitly representing divertor and pumping geometry, and (4) edge pedestal gradient scale lengths and widths, evaluation of theoretical predictions (5) confinement degradation due to thermal instabilities in the edge pedestals, (6) detachment and divertor MARFE onset, (7) core MARFE onsets leading to a H-L transition, and (8) radiative collapse leading to a disruption and evaluation of empirical fits (9) power thresholds for the L-H and H-L transitions and (10) the width of the edge pedestals. The various components of the calculation model are coupled and must be iterated to a self-consistent convergence. The model was developed over several years for the purpose of interpreting various edge phenomena observed in DIII-D experiments and thereby, to some extent, has been benchmarked against experiment. Because the model treats the interactions of various phenomena in the core, edge and divertor, yet is computationally efficient, it lends itself to the investigation of the effects of different choices of various edge plasma operating conditions on overall divertor and core plasma performance. Studies of the effect of feeling location and rate, divertor geometry, plasma shape, pumping and over 'edge parameters' on core plasma properties (line average density, confinement, density limit, etc.) have been performed for DIII-D model problems. A
Agosta, Roxana; Bilbija, Dushan; Deutsch, Marc; Gallant, David; Rose, Don; Shreve, Gene; Smario, David; Suffredini, Brian
1992-01-01
As intercontinental business and tourism volumes continue their rapid expansion, the need to reduce travel times becomes increasingly acute. The Edge Supersonic Transport Aircraft is designed to meet this demand by the year 2015. With a maximum range of 5750 nm, a payload of 294 passengers and a cruising speed of M = 2.4, The Edge will cut current international flight durations in half, while maintaining competitive first class, business class, and economy class comfort levels. Moreover, this transport will render a minimal impact upon the environment, and will meet all Federal Aviation Administration Part 36, Stage III noise requirements. The cornerstone of The Edge's superior flight performance is its aerodynamically efficient, dual-configuration design incorporating variable-geometry wingtips. This arrangement combines the benefits of a high aspect ratio wing at takeoff and low cruising speeds with the high performance of an arrow-wing in supersonic cruise. And while the structural weight concerns relating to swinging wingtips are substantial, The Edge looks to ever-advancing material technologies to further increase its viability. Heeding well the lessons of the past, The Edge design holds economic feasibility as its primary focus. Therefore, in addition to its inherently superior aerodynamic performance, The Edge uses a lightweight, largely windowless configuration, relying on a synthetic vision system for outside viewing by both pilot and passengers. Additionally, a fly-by-light flight control system is incorporated to address aircraft supersonic cruise instability. The Edge will be produced at an estimated volume of 400 aircraft and will be offered to airlines in 2015 at $167 million per transport (1992 dollars).
A New Edge-directed Subpixel Edge Localization Method
Institute of Scientific and Technical Information of China (English)
于新瑞; 徐威; 王石刚; 李倩
2004-01-01
Localization of the inspected chip image is one of the key problems with machine vision aided surface mount devices (SMD) and other micro-electronic equipments. This paper presents a new edge-directed subpixel edge localization method. The image is divided into two regions, edge and non-edge, using edge detection to emphasize the edge feature. Since the edges of the chip image are straight, they have straight-line characteristics locally and globally. First,the line segments of the straight edge are located to subpixel precision, according to their local straight properties, in a 3 × 3 neighborhood of the edge region. Second, the subpixel midpoints of the line segments are computed. Finally, the straight edge is fitted using the midpoints and the least square method, according to its global straight property in the entire edge region. In this way, the edge is located to subpixel precision. While fitting the edge, the irregular points are eliminated by the angles of the line segments to improve the precision. We can also distinguish different edges and their intersections using the angles of the line segments and distances between the edge points, then give the vectorial result of the image edge with high precision.
On finite edge-primitive and edge-quasiprimitive graphs
Giudici, Michael; Li, Cai Heng
2009-01-01
Many famous graphs are edge-primitive, for example, the Heawood graph, the Tutte--Coxeter graph and the Higman--Sims graph. In this paper we systematically analyse edge-primitive and edge-quasiprimitive graphs via the O'Nan--Scott Theorem to determine the possible edge and vertex actions of such graphs. Many interesting examples are given and we also determine all $G$-edge-primitive graphs for $G$ an almost simple group with socle $PSL(2,q)$.
Mani, Arjun; Benjamin, Colin
2016-04-01
On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin-orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible—the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case.
Spin and edge channel dependent transport through quantum dots
International Nuclear Information System (INIS)
We investigate the influence of spin polarized currents and non-equilibrated edge channels on the transport properties of a single quantum dot. Polarized currents are realized by the manual depletion of edge channels in high magnetic fields via a metallic top gate covering the source contact in the system. We observe a suppression and enhancement in the conductance of the quantum dot dependent on the edge channel configuration in the leads.
Spin and edge channel dependent transport through quantum dots
Energy Technology Data Exchange (ETDEWEB)
Ridder, T; Rogge, M C; Haug, R J [Institut fuer Festkoerperphysik, Gottfried Wilhelm Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany)], E-mail: ridder@nano.uni-hannover.de
2008-11-12
We investigate the influence of spin polarized currents and non-equilibrated edge channels on the transport properties of a single quantum dot. Polarized currents are realized by the manual depletion of edge channels in high magnetic fields via a metallic top gate covering the source contact in the system. We observe a suppression and enhancement in the conductance of the quantum dot dependent on the edge channel configuration in the leads.
Inter-Edge interaction in the Quantum Hall Effect
Oreg, Yuval; Finkel'stein, Alexander M.
1995-01-01
We consider effects of the interaction between electrons drifting along the opposite sides of a narrow sample under the conditions of the quantum Hall effect. A spatial variation of this interaction leads to backward scattering of collective excitations propagating along the edges. Experiments on propagation of the edge modes in samples with constrictions may give information about the strength of the inter-edge electron interaction in the quantum Hall regime.
Canny Edge Detection using Verilog
D Narayana Reddy*; , Mohan A R2; , Subhramanya Bhat3
2014-01-01
Edge detection is one of the key stages in image processing and objects identification. The Canny Edge Detector is one of the most widely used edge detection algorithm due to its good performance. Edge detection carries preprocessing step for many image processing algorithms such as image enhancement, image segmentation, tracking and image/video coding. Canny’s edge detection algorithm that results in significantly reduced memory requirements decreased latency and increased th...
Edge effects in magnetoplasmas
Suttorp, L G
1995-01-01
Edge effects in magnetized charged-particle systems are discussed with the help of a multiple-reflection expansion for the Green function. The profiles of the density and the electric current are determined both for the non-degenerate and the highly degenerate case. The asymptotic form of the profiles near the bulk is found to be exponentially decaying in both cases.
Superpixel edges for boundary detection
Energy Technology Data Exchange (ETDEWEB)
Moya, Mary M.; Koch, Mark W.
2016-07-12
Various embodiments presented herein relate to identifying one or more edges in a synthetic aperture radar (SAR) image comprising a plurality of superpixels. Superpixels sharing an edge (or boundary) can be identified and one or more properties of the shared superpixels can be compared to determine whether the superpixels form the same or two different features. Where the superpixels form the same feature the edge is identified as an internal edge. Where the superpixels form two different features, the edge is identified as an external edge. Based upon classification of the superpixels, the external edge can be further determined to form part of a roof, wall, etc. The superpixels can be formed from a speckle-reduced SAR image product formed from a registered stack of SAR images, which is further segmented into a plurality of superpixels. The edge identification process is applied to the SAR image comprising the superpixels and edges.
International Nuclear Information System (INIS)
Los Alamos National Laboratory has designed, built, and is currently testing a compact K-edge densitometer for use by International Atomic Energy Agency (IAEA) inspectors. The unit, which can easily be moved from one location to another within a facility, is positioned outside a glovebox with the body of the instrument inserted into the glove. A fixture inside the glovebox fits around the body and positions a sample holder. A hand-held high-purity germanium detector powered by a battery pack and a Davidson portable multichannel analyzer (MCA) is used to measure the transmission through plutonium nitrate solutions at E/sub Y/ = 121.1 and 122.2 keV. The Davidson MCA is programmed to lead the user through the measurement procedure and perform all the data analyses. The instrument is currently installed at the Safeguards Analytical Laboratory, where IAEA personnel are evaluating its accuracy, ease of operation, and safety. 5 references, 5 figures, 5 tables
Graphene edges; localized edge state and electron wave interference
Directory of Open Access Journals (Sweden)
Enoki Toshiaki
2012-03-01
Full Text Available The electronic structure of massless Dirac fermion in the graphene hexagonal bipartite is seriously modified by the presence of edges depending on the edge chirality. In the zigzag edge, strongly spin polarized nonbonding edge state is created as a consequence of broken symmetry of pseudo-spin. In the scattering at armchair edges, the K-K’ intervalley transition gives rise to electron wave interference. The presence of edge state in zigzag edges is observed in ultra-high vacuum STM/STS observations. The electron wave interference phenomenon in the armchair edge is observed in the Raman G-band and the honeycomb superlattice pattern with its fine structure in STM images.
Ilaria Vanni
2016-01-01
Critical writing about transculturation has a long history in Latin American studies, and more recently the concept has been used to analyse the effects of globalization. This article takes as its point of departure the Latin American genealogy of the idea, and brings it together with the ecological notion of ‘edge’ intended as a transition area between different systems. By bringing transculturation and edge together this paper seeks to understand transculturation as a process in which human...
Forest edges in boreal landscapes - factors affecting edge influence
Jansson, Ulrika
2009-01-01
The boreal forest in Fennoscandia has been subjected to major loss and fragmentation of natural forests due to intensive forestry. This has resulted in that forest edges are now abundant and important landscape features. Edges have documented effects on the structure, function and biodiversity in forests. Edge influence on biodiversity is complex and depends on interactions between many local and regional factors. This thesis focuses on sharp forest edges and their potential to influence biod...
Computing at the leading edge: Research in the energy sciences
International Nuclear Information System (INIS)
The purpose of this publication is to highlight selected scientific challenges that have been undertaken by the DOE Energy Research community. The high quality of the research reflected in these contributions underscores the growing importance both to the Grand Challenge scientific efforts sponsored by DOE and of the related supporting technologies that the National Energy Research Supercomputer Center (NERSC) and other facilities are able to provide. The continued improvement of the computing resources available to DOE scientists is prerequisite to ensuring their future progress in solving the Grand Challenges. Titles of articles included in this publication include: the numerical tokamak project; static and animated molecular views of a tumorigenic chemical bound to DNA; toward a high-performance climate systems model; modeling molecular processes in the environment; lattice Boltzmann models for flow in porous media; parallel algorithms for modeling superconductors; parallel computing at the Superconducting Super Collider Laboratory; the advanced combustion modeling environment; adaptive methodologies for computational fluid dynamics; lattice simulations of quantum chromodynamics; simulating high-intensity charged-particle beams for the design of high-power accelerators; electronic structure and phase stability of random alloys
Editorial "Strategic management and social media: the leading edge"
Olivas-Lujan, Miguel R.; Bondarouk, Tanya; Olivas-Lujan, M.R.; Bondarouk, T.V.
2013-01-01
This volume is a bridge made up by exemplary contributions linking strategic perspectives with the use of social media — the most recent family of technologies that are evolving rapidly and exciting businesses as well as all sectors of society. Social media, defined by Kaplan and Haenlein (2010, p.
Leading edge film cooling effects on turbine blade heat transfer
Garg, Vijay K.; Gaugler, Raymond E.
1995-01-01
An existing three dimensional Navier-Stokes code, modified to include film cooling considerations, has been used to study the effect of spanwise pitch of shower-head holes and coolant to mainstream mass flow ratio on the adiabatic effectiveness and heat transfer coefficient on a film-cooled turbine vane. The mainstream is akin to that under real engine conditions with stagnation temperature = 1900 K and stagnation pressure = 3 MPa. It is found that with the coolant to mainstream mass flow ratio fixed, reducing P, the spanwise pitch for shower-head holes, from 7.5 d to 3.0 d, where d is the hole diameter, increases the average effectiveness considerably over the blade surface. However, when P/d= 7.5, increasing the coolant mass flow increases the effectiveness on the pressure surface but reduces it on the suction surface due to coolant jet lift-off. For P/d = 4.5 or 3.0, such an anomaly does not occur within the range of coolant to mainstream mass flow ratios analyzed. In all cases, adiabatic effectiveness and heat transfer coefficient are highly three-dimensional.
Leading-edge effects on boundary-layer receptivity
Gatski, Thomas B.; Kerschen, Edward J.
1990-01-01
Numerical calculations are presented for the incompressible flow over a parabolic cylinder. The computational domain extends from a region upstream of the body downstream to the region where the Blasius boundary-layer solution holds. A steady mean flow solution is computed and the results for the scaled surface vorticity, surface pressure and displacement thickness are compared to previous studies. The unsteady problem is then formulated as a perturbation solution starting with and evolving from the mean flow. The response to irrotational time harmonic pulsation of the free-stream is examined. Results for the initial development of the velocity profile and displacement thickness are presented. These calculations will be extended to later times to investigate the initiation of instability waves within the boundary-layer.
Lead is a metal that occurs naturally in the earth's crust. Lead can be found in all parts of our ... from human activities such as mining and manufacturing. Lead used to be in paint; older houses may ...
Push-Edge and Slide-Edge: Scrolling by Pushing Against the Viewport Edge
Malacria, Sylvain; Aceituno, Jonathan; Quinn, Philip; Casiez, Géry; Cockburn, Andy; ROUSSEL, Nicolas
2015-01-01
International audience Edge-scrolling allows users to scroll a viewport while simultaneously dragging near or beyond a window’s edge. Common implementations rely on rate control, mapping the distance between the pointer and the edge of the viewport to the scrolling velocity. While ubiquitous in operating systems, edge-scrolling has received little attention, even though previous works suggest that (1) rate control may be suboptimal for isotonic pointing devices like mice and trackpads and ...
Efficient edge domination in regular graphs
Cardoso, Domingos M.; Cerdeira, J. Orestes; Delorme, Charles; Silva, Pedro C
2008-01-01
An induced matching of a graph G is a matching having no two edges joined by an edge. An efficient edge dominating set of G is an induced matching M such that every other edge of G is adjacent to some edge in M. We relate maximum induced matchings and efficient edge dominating sets, showing that efficient edge dominating sets are maximum induced matchings, and that maximum induced matchings on regular graphs with efficient edge dominating sets are efficient edge dominating sets. A ...
Topological number of edge states
Hashimoto, Koji; Kimura, Taro
2016-05-01
We show that the edge states of the four-dimensional class A system can have topological charges, which are characterized by Abelian/non-Abelian monopoles. The edge topological charges are a new feature of relations among theories with different dimensions. From this novel viewpoint, we provide a non-Abelian analog of the TKNN number as an edge topological charge, which is defined by an SU(2) 't Hooft-Polyakov BPS monopole through an equivalence to Nahm construction. Furthermore, putting a constant magnetic field yields an edge monopole in a noncommutative momentum space, where D-brane methods in string theory facilitate study of edge fermions.
Topological Number of Edge States
Hashimoto, Koji
2016-01-01
We show that the edge states of the four-dimensional class A system can have topological charges, which are characterized by Abelian/non-Abelian monopoles. The edge topological charges are a new feature of relations among theories with different dimensions. From this novel viewpoint, we provide a non-Abelian analogue of the TKNN number as an edge topological charge, which is defined by an SU(2) 't Hooft-Polyakov BPS monopole through an equivalence to Nahm construction. Furthermore, putting a constant magnetic field yields an edge monopole in a non-commutative momentum space, where D-brane methods in string theory facilitate study of edge fermions.
EDGE COVERING COLORING AND FRACTIONAL EDGE COVERING COLORING
Institute of Scientific and Technical Information of China (English)
MIAOLianying; LIUGuizhen
2002-01-01
Let G be a graph with edge set E(G).S E（G)is called an edge cover of G if every vertex of G is an end vertex of some edges in S.The edge covering chromatic number of a graph G,denoted by Xc(G),is the maximum size of a partition of E(G) into edge covers of G.It is known that for any graph G with minimum degree δ,δ-1≤Xc(G)≤δ.The fractional edge covering chromatic number of a graph G,denoted by Xcf(G),is the fractional matiching number of the edge covering hypergraph H of G whose vertices are the edges of G and whose hypereges the edge covers of G.In this paper,we study the relation between Xc(G) and δfor any graph G,and give a new simple proof of the inequalities δ-1≤Xc(G)≤δ by the technique of graph coloring.For any graph G,we give an exact formula o Xcf(G),that is,Xcf(G)=min{δ,λ(G)},where λ(G)=minCS/S/2 and the minimum is taken over all noempty subsets S of V(G) and C[S] is the set of edges that have at least one end in S.δ
EDGE COVERING COLORING AND FRACTIONAL EDGE COVERING COLORING
Institute of Scientific and Technical Information of China (English)
MIAO Lianying; LIU Guizhen
2002-01-01
Let G be a graph with edge set E(G). S _C E(G) is called an edge cover of G if every vertex of G is an end vertex of some edges in S. The edge covering chromatic number of a graph G, denoted by X'c(G) , is the maximum size of a partition of E(G) into edge covers of G. It is known that for any graph G with minimum degree δ, δ - 1 ≤ X'c(G) ≤ δ.The fractional edge covering chromatic number of a graph G, denoted by X'cf(G), is the fractional matching number of the edge covering hypergraph H of G whose vertices are the edges of G and whose hyperedges the edge covers of G. In this paper, we study the relation between X'c(G) and δ for any graph G, and give a new simple proof of the inequalities δ - 1 ≤ X'c(G) ≤ δ by the technique of graph coloring. For any graph G, we give an exact formula of X'cf(G), that is, X'cf(G)=min{δ,λ(G)}, where λ(G)=min |C[S]|/[|S|/2]and the minimum is taken over all noempty subsets S of V(G) and C[S] is the set of edges that have at least one end in S.
Edge Localized Mode Control in TCV
Rossel, Jonathan
2012-01-01
The Tokamak concept, based on magnetic confinement of a hydrogen plasma, is one of today's most promising paths to energy production by nuclear fusion. The experimental scenarios leading to the largest fusion rate are based on a high confinement plasma regime, the H-mode, in which the energy and particle confinement are enhanced by a transport barrier located at the plasma edge and forming a pedestal in the plasma pressure profile. In standard axisymm...
Power loads to misaligned edges in COMPASS
Czech Academy of Sciences Publication Activity Database
Dejarnac, Renaud; Corre, C.; Vondráček, Petr; Gardarein, J.-L.; Gauthier, E.; Gunn, J. P.; Horáček, Jan; Hron, Martin; Komm, Michael; Pánek, Radomír; Pitts, R. A.
Aix-en-Provence : Commissariat à l'Energie Atomique, 2015. [International Conference on PLASMA-FACING MATERIALS and COMPONENTS for FUSION APPLICATIONS/15./. Aix-en-Provence (FR), 18.05.2015-22.05.2015] Institutional support: RVO:61389021 Keywords : Heat loads * limiter * leading edge * IR thermography Subject RIV: BL - Plasma and Gas Discharge Physics http://irfm.cea.fr/pfmc15/index.html
... free solder, lead is still found in some modern faucets. Soil contaminated by decades of car exhaust ... NOT store wine, spirits, or vinegar-based salad dressings in lead crystal decanters for long periods of ...
... in children over time may lead to reduced IQ, slow learning, Attention Deficit Hyperactivity Disorder (ADHD), or ... avoid exposure to soil. Is there a medical test for lead exposure? • Blood samples can be tested ...
DEFF Research Database (Denmark)
Larsen, Mette Vinther; Rasmussen, Jørgen Gulddahl
2015-01-01
This first chapter presents the exploratory and curious approach to leading as relational processes – an approach that pervades the entire book. We explore leading from a perspective that emphasises the unpredictable challenges and triviality of everyday life, which we consider an interesting......, relevant and realistic way to examine leading. The chapter brings up a number of concepts and contexts as formulated by researchers within the field, and in this way seeks to construct a first understanding of relational leading....
International Nuclear Information System (INIS)
We introduce a model for a pair of nonlinear evolving networks, defined over a common set of vertices, subject to edgewise competition. Each network may grow new edges spontaneously or through triad closure. Both networks inhibit the other's growth and encourage the other's demise. These nonlinear stochastic competition equations yield to a mean field analysis resulting in a nonlinear deterministic system. There may be multiple equilibria; and bifurcations of different types are shown to occur within a reduced parameter space. This situation models competitive communication networks such as BlackBerry Messenger displacing SMS; or instant messaging displacing emails. -- Highlights: ► A model for edgewise-competing evolving network pairs is introduced. ► Defined competition equations yield to a mean field analysis. ► Multiple equilibrium states and different bifurcation types can occur. ► The system is sensitive to sparse initial conditions and near unstable equilibriums.
2007-08-01
Peering at Uranus's Rings as they Swing Edge-on to Earth for the First Time Since their Discovery in 1977 As Uranus coasts through a brief window of time when its rings are edge-on to Earth - a view of the planet we get only once every 42 years - astronomers peering at the rings with ESO's Very Large Telescope and other space or ground-based telescopes are getting an unprecedented view of the fine dust in the system, free from the glare of the bright rocky rings. They may even find a new moon or two. ESO PR Photo 37/07 ESO PR Photo 37/07 The Uranus System "ESO's VLT took data at the precise moment when the rings were edge-on to Earth," said Imke de Pater, of University of California, Berkeley who coordinated the worldwide campaign. She worked with two team members observing in Chile: Daphne Stam of the Technical University Delft in the Netherlands and Markus Hartung of ESO. The observations were done with NACO, one of the adaptive optics instruments installed at the VLT. With adaptive optics, it is possible to obtain images almost free from the blurring effect of the atmosphere. It is as if the 8.2-m telescope were observing from space. Observations were also done with the Keck telescope in Hawaii, the Hubble Space Telescope, and at the Palomar Observatory. "Using different telescopes around the world allows us to observe as much of the changes during the ring-plane crossing as possible: when Uranus sets as seen from the VLT, it can still be observed by the Keck," emphasised Stam. Uranus orbits the Sun in 84 years. Twice during a Uranian year, the rings appear edge-on to Earth for a brief period. The rings were discovered in 1977, so this is the first time for a Uranus ring-crossing to be observed from Earth. The advantage of observations at a ring-plane crossing is that it becomes possible to look at the rings from the shadowed or dark side. From that vantage point, the normally bright outer rings grow fainter because their centimetre- to metre-sized rocks obscure
Energy Technology Data Exchange (ETDEWEB)
Kamm, James R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Love, Edward [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Robinson, Allen C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Young, Joseph G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ridzal, Denis [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2013-12-01
We review the edge element formulation for describing the kinematics of hyperelastic solids. This approach is used to frame the problem of remapping the inverse deformation gradient for Arbitrary Lagrangian-Eulerian (ALE) simulations of solid dynamics. For hyperelastic materials, the stress state is completely determined by the deformation gradient, so remapping this quantity effectively updates the stress state of the material. A method, inspired by the constrained transport remap in electromagnetics, is reviewed, according to which the zero-curl constraint on the inverse deformation gradient is implicitly satisfied. Open issues related to the accuracy of this approach are identified. An optimization-based approach is implemented to enforce positivity of the determinant of the deformation gradient. The efficacy of this approach is illustrated with numerical examples.
Edge maps: Representing flow with bounded error
Bhatia, Harsh
2011-03-01
Robust analysis of vector fields has been established as an important tool for deriving insights from the complex systems these fields model. Many analysis techniques rely on computing streamlines, a task often hampered by numerical instabilities. Approaches that ignore the resulting errors can lead to inconsistencies that may produce unreliable visualizations and ultimately prevent in-depth analysis. We propose a new representation for vector fields on surfaces that replaces numerical integration through triangles with linear maps defined on its boundary. This representation, called edge maps, is equivalent to computing all possible streamlines at a user defined error threshold. In spite of this error, all the streamlines computed using edge maps will be pairwise disjoint. Furthermore, our representation stores the error explicitly, and thus can be used to produce more informative visualizations. Given a piecewise-linear interpolated vector field, a recent result [15] shows that there are only 23 possible map classes for a triangle, permitting a concise description of flow behaviors. This work describes the details of computing edge maps, provides techniques to quantify and refine edge map error, and gives qualitative and visual comparisons to more traditional techniques. © 2011 IEEE.
Edge phonons in black phosphorus.
Ribeiro, H B; Villegas, C E P; Bahamon, D A; Muraca, D; Castro Neto, A H; de Souza, E A T; Rocha, A R; Pimenta, M A; de Matos, C J S
2016-01-01
Black phosphorus has recently emerged as a new layered crystal that, due to its peculiar and anisotropic crystalline and electronic band structures, may have important applications in electronics, optoelectronics and photonics. Despite the fact that the edges of layered crystals host a range of singular properties whose characterization and exploitation are of utmost importance for device development, the edges of black phosphorus remain poorly characterized. In this work, the atomic structure and behaviour of phonons near different black phosphorus edges are experimentally and theoretically studied using Raman spectroscopy and density functional theory calculations. Polarized Raman results show the appearance of new modes at the edges of the sample, and their spectra depend on the atomic structure of the edges (zigzag or armchair). Theoretical simulations confirm that the new modes are due to edge phonon states that are forbidden in the bulk, and originated from the lattice termination rearrangements. PMID:27412813
Edge colouring by total labellings
DEFF Research Database (Denmark)
Brandt, Stephan; Rautenbach, D.; Stiebitz, M.;
2010-01-01
We introduce the concept of an edge-colouring total k-labelling. This is a labelling of the vertices and the edges of a graph G with labels 1, 2, ..., k such that the weights of the edges define a proper edge colouring of G. Here the weight of an edge is the sum of its label and the labels of its...... two endvertices. We define χ (G) to be the smallest integer k for which G has an edge-colouring total k-labelling. This parameter has natural upper and lower bounds in terms of the maximum degree Δ of G : ⌈ (Δ + 1) / 2 ⌉ ≤ χ (G) ≤ Δ + 1. We improve the upper bound by 1 for every graph and prove χ (G...
Edge-edge interactions in stacked graphene nanoplatelets
Energy Technology Data Exchange (ETDEWEB)
Cruz Silva, Eduardo [ORNL; Terrones Maldonado, Humberto [ORNL; Terrones Maldonado, Mauricio [ORNL; Jia, Xiaoting [Massachusetts Institute of Technology (MIT); Sumpter, Bobby G [ORNL; Dresselhaus, M [Massachusetts Institute of Technology (MIT); Meunier, V. [Rensselaer Polytechnic Institute (RPI)
2013-01-01
High-resolution transmission electron microscopy (HRTEM) studies show the dynamics of small graphene platelets on larger graphene layers. The platelets move nearly freely to eventually lock in at well-defined positions close to the edges of the larger underlying graphene sheet. While such movement is driven by a shallow potential energy surface described by an interplane interaction, the lock-in position occurs by via edge-edge interactions of the platelet and the graphene surface located underneath. Here we quantitatively study this behavior using van der Waals density functional calculations. Local interactions at the open edges are found to dictate stacking configurations that are different from Bernal (AB) stacking. These stacking configurations are known to be otherwise absent in edge-free two-dimensional (2D) graphene. The results explain the experimentally observed platelet dynamics and provide a detailed account of the new electronic properties of these combined systems.
Giant edge state splitting at atomically precise graphene zigzag edges
Wang, Shiyong; Talirz, Leopold; Pignedoli, Carlo A.; Feng, Xinliang; Müllen, Klaus; Fasel, Roman; Ruffieux, Pascal
2016-05-01
Zigzag edges of graphene nanostructures host localized electronic states that are predicted to be spin-polarized. However, these edge states are highly susceptible to edge roughness and interaction with a supporting substrate, complicating the study of their intrinsic electronic and magnetic structure. Here, we focus on atomically precise graphene nanoribbons whose two short zigzag edges host exactly one localized electron each. Using the tip of a scanning tunnelling microscope, the graphene nanoribbons are transferred from the metallic growth substrate onto insulating islands of NaCl in order to decouple their electronic structure from the metal. The absence of charge transfer and hybridization with the substrate is confirmed by scanning tunnelling spectroscopy, which reveals a pair of occupied/unoccupied edge states. Their large energy splitting of 1.9 eV is in accordance with ab initio many-body perturbation theory calculations and reflects the dominant role of electron-electron interactions in these localized states.
Wisps in the outer edge of the Keeler Gap
Tiscareno, Matthew S.; Arnault, Ethan G.
2015-11-01
Superposed upon the relatively smooth outer edge of the Keeler Gap are a system of "wisps," which appear to be ring material protruding inward into the gap, usually with a sharp trailing edge and a smooth gradation back to the background edge location on the leading side (Porco et al. 2005, Science). The radial amplitude of wisps is usually 0.5 to 1 km, and their azimuthal extent is approximately a degree of longitude (~2400 km). Wisps are likely caused by an interplay between Daphnis (and perhaps other moons) and embedded moonlets within the ring, though the details remain unclear.Aside from the wisps, the Keeler Gap outer edge is the only one of the five sharp edges in the outer part of Saturn's A ring that is reasonably smooth in appearance (Tiscareno et al. 2005, DPS), with occultations indicating residuals less than 1 km upon a possibly non-zero eccentricity (R.G. French, personal communication, 2014). The other four (the inner and outer edges of the Encke Gap, the inner edge of the Keeler Gap, and the outer edge of the A ring itself) are characterized by wavy structure at moderate to high spatial frequencies, with amplitudes ranging from 2 to 30 km (Tiscareno et al. 2005, DPS).We will present a catalogue of wisp detections in Cassini images. We carry out repeated gaussian fits of the radial edge location in order to characterize edge structure and visually scan those fitted edges in order to detect wisps. With extensive coverage in longitude and in time, we will report on how wisps evolve and move, both within an orbit period and on longer timescales. We will also report on the frequency and interpretation of wisps that deviate from the standard morphology. We will discuss the implications of our results for the origin and nature of wisps, and for the larger picture of how masses interact within Saturn's rings.
Helical Quantum Edge Gears in 2D Topological Insulators
Chou, Yang-Zhi; Levchenko, Alex; Foster, Matthew S.
2015-10-01
We show that two-terminal transport can measure the Luttinger liquid (LL) parameter K , in helical LLs at the edges of two-dimensional topological insulators (TIs) with Rashba spin-orbit coupling. We consider a Coulomb drag geometry with two coplanar TIs and short-ranged spin-flip interedge scattering. Current injected into one edge loop induces circulation in the second, which floats without leads. In the low-temperature (T →0 ) perfect drag regime, the conductance is (e2/h )(2 K +1 )/(K +1 ). At higher T , we predict a conductivity ˜T-4 K +3. The conductivity for a single edge is also computed.
Nonlocal edge state transport in the quantum spin Hall state
Roth, Andreas; Bruene, Christoph; Buhmann, Hartmut; Molenkamp, Laurens W.; Maciejko, Joseph; Qi, Xiao-Liang; Zhang, Shou-Cheng
2009-01-01
We present direct experimental evidence for nonlocal transport in HgTe quantum wells in the quantum spin Hall regime, in the absence of any external magnetic field. The data conclusively show that the non-dissipative quantum transport occurs through edge channels, while the contacts lead to equilibration between the counter-propagating spin states at the edge. We show that the experimental data agree quantitatively with the theory of the quantum spin Hall effect.
Electronic quantum teleportation in Hall edge channels
Buscemi, Fabrizio; Bertoni, Andrea
2011-01-01
We present a proposal for the quantum teleportation of electrons in an edge channel setup operating in the quantum Hall regime. Three qubits are used, each defined by the occupancy of a couple of edge channels connected to source and drains leads providing electrical control of initialization and readouts. Our scheme consists of two concatenated two-particle Hanbury Brown-Twiss (HBT) interferometers [Nederet al.}, Nature, 448, 333 (2007)] and, in analogy with quantum optics implementations, can be realized by means of linear quantum gates only, without relying on inter-electron Coulomb interaction. We show how the coincident detection of two carriers in couples of drains allows teleportation with a 50% success rate.
Nonlinear dynamics in the Tokamak edge
International Nuclear Information System (INIS)
The nonlinear character of the Tokamak edge results from a unique combination of parameters, leading to a wide dynamical range for most processes. The energetically consistent gyrokinetic equilibrium is emphasised. Edge turbulence computed gyrokinetically exhibits energetic contact to mesoscale MHD and does not follow linear scaling. Gyrofluid studies show self consistent profiles, currents and flows which are kicked out of equilibrium to varying degree. L-mode turbulence and ELM crash phenomenology are both examples of energetic contact between turbulence and MHD, with opposite causality. The overall equilibrium is a statistical saturation rather than a state to which the plasma dissipatively converges (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Rock Segmentation through Edge Regrouping
Burl, Michael
2008-01-01
Rockster is an algorithm that automatically identifies the locations and boundaries of rocks imaged by the rover hazard cameras (hazcams), navigation cameras (navcams), or panoramic cameras (pancams). The software uses edge detection and edge regrouping to identify closed contours that separate the rocks from the background.
Edge Detection Using Fuzzy Logic
Directory of Open Access Journals (Sweden)
B. Govinda Lakshmi
2014-09-01
Full Text Available Edge detection is still difficult task in the image processing field. In this paper we implemented fuzzy techniques for detecting edges in the image. This algorithm also works for medical images. In this paper we also explained about Fuzzy inference system, which is more robust to contrast and lighting variations.
Fission of Halving Edges Graphs
Khovanova, Tanya; Yang, Dai
2013-01-01
In this paper we discuss an operation on halving edges graph that we call fission. Fission replaces each point in a given configuration with a small cluster of k points. The operation interacts nicely with halving edges, so we examine its properties in detail.
... help if this information is not immediately available. Poison Control If someone has severe symptoms from possible ... be caused by lead poisoning, call your local poison control center. Your local poison center can be ...
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... has also been associated with juvenile delinquency and criminal behavior. In adults, lead can increase blood pressure ... and-forth manner, but rather from left to right (or vise-versa), or from the top of ...
Non-linear Heat Transport Modelling with Edge Localized Modes and Plasma Edge Control in Tokamaks
Energy Technology Data Exchange (ETDEWEB)
Becoulet, M.; Huysmans, G.; Thomas, P.; Ghendrih, P.; Grosman, A.; Monier-Garbet, P.; Garbet, X.; Zwingman, W.; Nardon, E. [Euratom-CEA, Centre d' Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Moyer, R. [California Univ., San Diego, La Jolla CA (United States); Evans, T.; Leonard, A. [General Atomics, San Diego, CA (United States)
2004-07-01
The paper presents a new approach for the modelling of the pedestal energy transport in the presence of Type I ELMs (edge localized mode) based on the linear ideal MHD code MISHKA coupled with the non-linear energy transport code TELM in a realistic tokamak geometry. The main mechanism of increased transport through the External Transport Barrier (ETB) in this model of ELMs is the increased convective flux due to the MHD velocity perturbation and an additional conductive flux due the radial perturbation of the magnetic field leading to a flattening of the pressure profile in the unstable zone. The typical Type I ELM time-cycle including the destabilization of the ballooning modes leading to the fast (200 {mu}s) collapse of the pedestal pressure followed by the edge pressure profile re-building on a diffusive time scale was reproduced numerically. The possible mechanism of Type I ELMs control using a stochastic plasma boundary created by external coils is modelled in the paper. In the stochastic layer the transverse transport is effectively increased by the magnetic field line diffusion. The modelling results for DIII-D experiment on Type I ELM suppression using the external perturbation from the I-coils demonstrated the possibility to decrease the edge pressure gradient just under the ideal ballooning limit, leading to the high confinement regime without Type I ELMs. (authors)
Reduction of airfoil trailing edge noise by trailing edge blowing
International Nuclear Information System (INIS)
The paper deals with airfoil trailing edge noise and its reduction by trailing edge blowing. A Somers S834 airfoil section which originally was designed for small wind turbines is investigated. To mimic realistic Reynolds numbers the boundary layer is tripped on pressure and suction side. The chordwise position of the blowing slot is varied. The acoustic sources, i.e. the unsteady flow quantities in the turbulent boundary layer in the vicinity of the trailing edge, are quantified for the airfoil without and with trailing edge blowing by means of a large eddy simulation and complementary measurements. Eventually the far field airfoil noise is measured by a two-microphone filtering and correlation and a 40 microphone array technique. Both, LES-prediction and measurements showed that a suitable blowing jet on the airfoil suction side is able to reduce significantly the turbulence intensity and the induced surface pressure fluctuations in the trailing edge region. As a consequence, trailing edge noise associated with a spectral hump around 500 Hz could be reduced by 3 dB. For that a jet velocity of 50% of the free field velocity was sufficient. The most favourable slot position was at 90% chord length
Recent Advances in Plasma Edge Physics Theory
Stacey, W. M.
2015-11-01
This presentation summarizes recent theory developments for interpreting plasma edge physics experiments in DIII-D. i) Radial and poloidal moment balance require that the radial particle flux be of a pinch-diffusive nature with the pinch representing the electromagnetic forces and external momentum input. Ion radial particle fluxes in experiment are found to be a smaller difference between large outward diffusion fluxes and inward pinch fluxes. When the pinch-diffusion relation is used in the continuity equation a new diffusion theory that preserves momentum balance is obtained. ii) The majority of thermalized ions and their energy cross the LCFS on ion loss orbits and are deposited in the SOL near the outboard midplane. The lost ions are predominantly ctr-current, producing a co-current intrinsic rotation of the remaining ions in the edge plasma. iii) While the contribution of the leading order parallel viscosity to toroidal momentum damping vanishes identically in axisymmetric plasmas, non-axisymmetric radial B-fields in the edge plasma enable parallel viscosity to enhance the damping of toroidal rotation. Work supported by the US DOE under DE-FG02-00ER54538, DE-FC02-04ER54698.
Fast tracking using edge histograms
Rokita, Przemyslaw
1997-04-01
This paper proposes a new algorithm for tracking objects and objects boundaries. This algorithm was developed and applied in a system used for compositing computer generated images and real world video sequences, but can be applied in general in all tracking systems where accuracy and high processing speed are required. The algorithm is based on analysis of histograms obtained by summing along chosen axles pixels of edge segmented images. Edge segmentation is done by spatial convolution using gradient operator. The advantage of such an approach is that it can be performed in real-time using available on the market hardware convolution filters. After edge extraction and histograms computation, respective positions of maximums in edge intensity histograms, in current and previous frame, are compared and matched. Obtained this way information about displacement of histograms maximums, can be directly converted into information about changes of target boundaries positions along chosen axles.
The Role of the Pattern Edge in Goldfish Visual Motion Detection
Kim, Sun-Hee; Jung, Chang-Sub
2010-01-01
To understand the function of edges in perception of moving objects, we defined four questions to answer. Is the focus point in visual motion detection of a moving object: (1) the body or the edge of the object, (2) the leading edge or trailing edge of the object, (3) different in scotopic, mesopic and photopic luminance levels, or (4) different for colored objects? We measured the Optomotor Response (OMR) and Edge Triggering Response (ETR) of goldfish. We used a square and sine wave patterns...
Flatband Engineering of Mobility Edges
Danieli, Carlo; Bodyfelt, Joshua D.; Flach, Sergej
2015-01-01
Properly modulated flatband lattices have a divergent density of states at the flatband energy. Quasiperiodic modulations are known to host a metal insulator transition already in one space dimension. Their embedding into flatband geometries consequently allows for a precise engineering and fine tuning of mobility edges. We obtain analytic expressions for singular mobility edges for two flatband lattice examples. In particular, we engineer cases with arbitrarily small energy separations of mo...
DEFF Research Database (Denmark)
Bekker-Nielsen, Tønnes
2016-01-01
Through a systematic comparison of c. 50 careers leading to the koinarchate or high priesthood of Asia, Bithynia, Galatia, Lycia, Macedonia and coastal Pontus, as described in funeral or honorary inscriptions of individual koinarchs, it is possible to identify common denominators but also...
1974-01-01
One of the 150 lead grids used in the multiwire proportional chamber g-ray detector. The 0.75 mm diameter holes are spaced 1 mm centre to centre. The grids were made by chemical cutting techniques in the Godet Workshop of the SB Physics.
... Environment Kids Health Kids Environment Kids Health Topics Environment & Health Healthy Living Pollution Reduce, Reuse, Recycle Science – How ... poisoning is still one of the most important health issues in the United States ... in housing built before 1946 have elevated blood lead levels. These ...
Curtis, Fred
2001-01-01
Existing planar map encodings neglect maps with loops. The presented scheme encodes any connected planar map in 4 bits/edge. Encoding and decoding time is O(edges). Implicit face/edge/vertex orderings and canonical encodings are discussed.
Judder-Induced Edge Flicker at Zero Spatial Contrast
Larimer, James; Feng, Christine; Gille, Jennifer; Cheung, Victor
2004-01-01
Judder is a motion artifact that degrades the quality of video imagery. Smooth motion appears jerky and can appear to flicker along the leading and trailing edge of the moving object. In a previous paper, we demonstrated that the strength of the edge flicker signal depended upon the brightness of the scene and the contrast of the moving object relative to the background. Reducing the contrast between foreground and background reduced the flicker signal. In this report, we show that the contrast signal required for judder-induced edge flicker is due to temporal contrast and not simply to spatial contrast. Bars made of random dots of the same dot density as the background exhibit edge flicker when moved at sufficient rate.
Orientation Relationships between Ferrite and Cementite by Edge-to-edge Matching Principle
Institute of Scientific and Technical Information of China (English)
Ning Zhong; Xiaodong Wang; Zhenghong Guo; Yonghua Rong
2011-01-01
The crystallographic features of pearlite were investigated by experiments and edge-to-edge matching principle. Two new orientation relationships between ferrite and cementite were determinated by selected area electron diffraction and then explained by our modified edge-to-edge matching method. The consistence of the experimental results with theoretical prediction confirms the practicability of the modified edge-to-edge matching model.
Computation of Edge-Edge-Edge Events Based on Conicoid Theory for 3-D Object Recognition
Institute of Scientific and Technical Information of China (English)
WU Chenye; MA Huimin
2009-01-01
The availability of a good viewpoint space partition is crucial in three dimensional (3-D) object rec-ognition on the approach of aspect graph. There are two important events depicted by the aspect graph ap-proach, edge-edge-edge (EEE) events and edge-vertex (EV) events. This paper presents an algorithm to compute EEE events by characteristic analysis based on conicoid theory, in contrast to current algorithms that focus too much on EV events and often overlook the importance of EEE events. Also, the paper provides a standard flowchart for the viewpoint space partitioning based on aspect graph theory that makes it suitable for perspective models. The partitioning result best demonstrates the algorithm's efficiency with more valu-able viewpoints found with the help of EEE events, which can definitely help to achieve high recognition rate for 3-D object recognition.
Improved bound on facial parity edge coloring
Lužar, Borut; Škrekovski, Riste
2013-01-01
A facial parity edge coloring of a 2-edge connected plane graph is an edge coloring where no two consecutive edges of a facial walk of any face receive the same color. Additionally, for every face f and every color c either no edge or an odd number of edges incident to f are colored by c. Czap, Jendrol', Kardo\\v{s} and Sotak showed that every 2-edge connected plane graph admits a facial parity edge coloring with at most 20 colors. We improve this bound to 16 colors.
Multi-scale edge detection with local noise estimate
Jiang, Bo; Rahman, Zia-ur
2010-08-01
The (unrealistic) assumption that noise can be modeled as independent, additive and uniform can lead to problems when edge detection methods are applied to real or natural images. The main reason for this is because filter scale and threshold for the gradient are difficult to determine at a regional or local scale when the noise estimate is on a global scale. A filter with one global scale might under-smooth areas of high noise, but over-smooth less noisy area. Similarly, a static, global threshold may not be appropriate for the entire image because different regions have different degrees of detail. Thus, some methods use more than one filter for detecting edges and discard the thresholding method in edge discrimination. Multi-scale description of the image mimics the receptive fields of neurons in the early visual cortex of animals. At the small scale, details can be reliably detected. At the larger scale, the contours or the frame get more attention. So, the image features can be fully represented by combining a range of scales. The proposed multi-scale edge detection algorithm utilizes this hierarchical organization to detect and localize edges. Furthermore, instead of using one default global threshold, local dynamic threshold is introduced to discriminate edge or non-edge. Based on a critical value function, the local dynamic threshold for each scale is determined using a novel local noise estimation (LNE) method. Additionally, the proposed algorithm performs connectivity analysis on edge map to ensure that small, disconnected edges are removed. Experiments where this method is applied to a sequence of images of the same scene but with different signal-noise-ratio (SNR), show the method to be robust to noise.
Decay patterns of edge states at reconstructed armchair graphene edges
Park, Changwon; Ihm, Jisoon; Kim, Gunn
Density functional theory calculations are used to investigate the electronic structures of localized states at reconstructed armchair graphene edges. We consider graphene nanoribbons with two different edge types and obtain the energy band structures and charge densities of the edge states. By examining the imaginary part of the wave vector in the forbidden energy region, we reveal the decay behavior of the wave functions in graphene. The complex band structures of graphene in the armchair and zigzag directions are presented in the first-principles framework. G.K. acknowledges the support of the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education (Grant No. 2013R1A1A2009131) and the Priority Research Center Program (Grant No. 2010-0020207).
On the edge: haptic discrimination of edge sharpness.
Directory of Open Access Journals (Sweden)
Andy L Skinner
Full Text Available The increasing ubiquity of haptic displays (e.g., smart phones and tablets necessitates a better understanding of the perceptual capabilities of the human haptic system. Haptic displays will soon be capable of locally deforming to create simple 3D shapes. This study investigated the sensitivity of our haptic system to a fundamental component of shapes: edges. A novel set of eight high quality shape stimuli with test edges that varied in sharpness were fabricated in a 3D printer. In a two alternative, forced choice task, blindfolded participants were presented with two of these shapes side by side (one the reference, the other selected randomly from the remaining set of seven and after actively exploring the test edge of each shape with the tip of their index finger, reported which shape had the sharper edge. We used a model selection approach to fit optimal psychometric functions to performance data, and from these obtained just noticeable differences and Weber fractions. In Experiment 1, participants performed the task with four different references. With sharpness defined as the angle at which one surface meets the horizontal plane, the four JNDs closely followed Weber's Law, giving a Weber fraction of 0.11. Comparisons to previously reported Weber fractions from other haptic manipulations (e.g. amplitude of vibration suggests we are sufficiently sensitive to changes in edge sharpness for this to be of potential utility in the design of future haptic displays. In Experiment 2, two groups of participants performed the task with a single reference but different exploration strategies; one was limited to a single touch, the other unconstrained and free to explore as they wished. As predicted, the JND in the free exploration condition was lower than that in the single touch condition, indicating exploration strategy affects sensitivity to edge sharpness.
Edge-injective and edge-surjective vertex labellings
DEFF Research Database (Denmark)
Brandt, Stephan; Rautenbach, D.; Regen, F.;
2010-01-01
For a graph G = (V, E) we consider vertex-k-labellings f : V → {1,2, ,k} for which the induced edge weighting w : E → {2, 3,., 2k} with w(uv) = f(u) + f(v) is injective or surjective or both. We study the relation between these labellings and the number theoretic notions of an additive basis and a...... recent conjecture of Ivančo and Jendroł concerning edge-irregular total labellings for graphs that are sparse enough. © 2010 Societ y for Industrial and Applied Mathematics....
Expanding population edges: theories, traits, and trade-offs.
Chuang, Angela; Peterson, Christopher R
2016-02-01
Recent patterns of global change have highlighted the importance of understanding the dynamics and mechanisms of species range shifts and expansions. Unique demographic features, spatial processes, and selective pressures can result in the accumulation and evolution of distinctive phenotypic traits at the leading edges of expansions. We review the characteristics of expanding range margins and highlight possible mechanisms for the appearance of phenotypic differences between individuals at the leading edge and core of the range. The development of life history traits that increase dispersal or reproductive ability is predicted by theory and supported with extensive empirical evidence. Many examples of rapid phenotypic change are associated with trade-offs that may influence the persistence of the trait once expansion ends. Accounting for the effects of edge phenotypes and related trade-offs could be critical for predicting the spread of invasive species and population responses to climate change. PMID:26426311
Institute of Scientific and Technical Information of China (English)
孙建伶; 罗立强
2014-01-01
Synchrotron radiation X-ray fluorescence analysis technology (SRXRF) can effectively reduce the detection limit for the determination of heavy metal elements, especially suitable for in situ nondestructive analysis of biological samples with low contents. By corn seed germination test, and combining with SRXRF technology, the effects of Pb on corn seed germination and Pb micro-distribution in the corn seed were studied. X-ray absorption near edge structure (XANES ) technique was used to analyze the Pb chemical speciation in different parts of corn seed. The above experiment was taken to understand the absorption and transformation mechanism of Pb by corn seeds. Results showed that germination rate, bud length and root length decreased with increased Pb contents. The analysis of variance showed that P-value of the germination rate, bud length and root elongation of corn seeds which were exposed to different concentration of Pb were 2. 0×10-3, 1. 4×10-4 and 2. 39×10-8, which were all less than 0. 01, therefore there were highly significant differences during these three indicators and the content of Pb. In addition, the inhibition effect on root growth was greater. SRXRF analysis results showed that Pb was mainly enriched in episperm and embryo, which would inhibit embryonic develop into bud and root. The Pb-LⅢ(13035 eV) XANES spectra of all samples include of root, shoot and the different part of seed were the same, they were the same speciation. Linear combination fitting results indicated that the lead phosphate chloride and lead stearate accounted for 74 . 3 %and 24. 2 % respectively, which suggested that the main Pb speciation of corn was lead phosphate chloride which deposited inside of corn, and a few combined with carboxylic to form the organic lead.%以受不同浓度Pb胁迫下的玉米种子萌芽试验为基础,结合SRXRF研究Pb对玉米种子萌芽的影响和Pb在玉米种子的微区分布特征,利用X射线吸收近边结构技术( XANES)对
Edges and Corners With Shearlets.
Duval-Poo, Miguel A; Odone, Francesca; De Vito, Ernesto
2015-11-01
Shearlets are a relatively new and very effective multi-scale framework for signal analysis. Contrary to the traditional wavelets, shearlets are capable to efficiently capture the anisotropic information in multivariate problem classes. Therefore, shearlets can be seen as the valid choice for multi-scale analysis and detection of directional sensitive visual features like edges and corners. In this paper, we start by reviewing the main properties of shearlets that are important for edge and corner detection. Then, we study algorithms for multi-scale edge and corner detection based on the shearlet representation. We provide an extensive experimental assessment on benchmark data sets which empirically confirms the potential of shearlets feature detection. PMID:26353351
Directory of Open Access Journals (Sweden)
John J. Lattanzio
2010-01-01
Full Text Available Problem statement: The vertex double-critical conjecture that the only vertex double-critical graph is the complete graph has remained unresolved for over forty years. The edge analogue of this conjecture has been proved. Approach: It was observed that if the chromatic number decreases by two upon the removal of a 2-matching, then the 2-matching comprises four vertices which determine an induced subgraph isomorphic to the complete graph on four vertices. This observation was generalized to t-matchings. Results: In this note, it has been shown that the only edge double-critical graph is the complete graph. Conclusion/Recommendations: An alternate proof that the only edge double-critical graph is the complete graph has been obtained. Moreover, the result has been obtained independently.
DEFF Research Database (Denmark)
Jacobsen, Kåre Wedel; Falkenberg, Jesper Toft; Papior, Nick Rübner;
2016-01-01
Using ab-initio methods we investigate the possibility of three-terminalgraphene "T-junction" devices and show that these all-graphene edge contactsare energetically feasible when the 1D interface itself is free from foreignatoms. We examine the energetics of various junction structures as a...... therange of 1-10 kΩμm which is comparable to the best contact resistance reportedfor edge-contacted graphene-metal contacts. We conclude that conductingall-carbon T-junctions should be feasible....
International Nuclear Information System (INIS)
In this paper the design for a new technology for particle track detectors is described. Using standard IC fabrication techniques, a pattern of microscopic knife edges and field-shaping electrodes can be fabricated on a silicon substrate. The knife-edge chamber uniquely offers attractive performance for the track chambers required for SSC detectors, for which no present technology is yet satisfactory. Its features include: excellent radiation hardness (10 Mrad), excellent spatial resolution (∼20 μm), short drift time (20 ns), and large pulse height (1 mV)
Geometric phase at graphene edge
Choi, Sang-Jun; Park, Sunghun; Sim, H. -S.
2014-01-01
We study the scattering phase shift of Dirac fermions at graphene edge. We find that when a plane wave of a Dirac fermion is reflected at an edge of graphene, its reflection phase is shifted by the geometric phase resulting from the change of the pseudospin of the Dirac fermion in the reflection. The geometric phase is the Pancharatnam-Berry phase that equals the half of the solid angle on Bloch sphere determined by the propagation direction of the incident wave and also by the orientation an...
Energy Technology Data Exchange (ETDEWEB)
Subbiah, Sathyan [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Melkote, Shreyes N. [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States)], E-mail: shreyes.melkote@me.gatech.edu
2008-02-15
Evidence of ductile fracture leading to material separation has been reported recently in ductile metal cutting [S. Subbiah, S.N. Melkote, ASME J. Manuf. Sci. Eng. 28(3) (2006)]. This paper investigates the effect of finite edge radius on such ductile fracture. The basic question of whether such ductile fracture occurs in the presence of a finite edge radius is explored by performing a series of experiments with inserts of different edge radii at various uncut chip thickness values ranging from 15 to 105 {mu}m. Chip-roots are obtained in these experiments using a quick-stop device and examined in a scanning electron microscope. Clear evidence of material separation is seen at the interface zone between the chip and machined surface even when the edge radius is large compared to the uncut chip thickness. Failure is seen to occur at the upper, middle, and/or the lower edges of the interface zone. Based on these observations, a hypothesis is presented for the events leading to the occurrence of this failure when cutting with an edge radius tool. Finite element simulations are performed to study the nature of stress state ahead of the tool edge with and without edge radius. Hydrostatic stress is seen to be tensile in front of the tool and hence favors the occurrence of ductile fracture leading to material separation. The stress components are, however lower than those seen with a sharp tool.
Phosphorus K-edge XANES spectroscopy of mineral standards
Energy Technology Data Exchange (ETDEWEB)
Ingall, Ellery D., E-mail: ingall@eas.gatech.edu [School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332-0340 (United States); Brandes, Jay A. [Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, Georgia 31411 (United States); Diaz, Julia M. [School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332-0340 (United States); Jonge, Martin D. de; Paterson, David [Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168 (Australia); McNulty, Ian [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States); Elliott, W. Crawford [Department of Geosciences, Georgia State University, Atlanta, GA 30302-4105 (United States); Northrup, Paul [Department of Geosciences, Stony Brook University, Stony Brook, NY 11794 (United States)
2011-03-01
Phosphorus K-edge XANES spectra are presented for a diverse set of 44 phosphate minerals. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was performed on phosphate mineral specimens including (a) twelve specimens from the apatite group covering a range of compositional variation and crystallinity; (b) six non-apatite calcium-rich phosphate minerals; (c) 15 aluminium-rich phosphate minerals; (d) ten phosphate minerals rich in either reduced iron or manganese; (e) four phosphate minerals rich in either oxidized iron or manganese; (f) eight phosphate minerals rich in either magnesium, copper, lead, zinc or rare-earth elements; and (g) four uranium phosphate minerals. The identity of all minerals examined in this study was independently confirmed using X-ray powder diffraction. Minerals were distinguished using XANES spectra with a combination of pre-edge features, edge position, peak shapes and post-edge features. Shared spectral features were observed in minerals with compositions dominated by the same specific cation. Analyses of apatite-group minerals indicate that XANES spectral patterns are not strongly affected by variations in composition and crystallinity typical of natural mineral specimens.
Edge shape and comfort of rigid lenses.
La Hood, D
1988-08-01
One of the main factors determining the comfort of a rigid contact lens is the shape of the edge. The comfort of four different contact lens edge shapes was assessed with four unadapted subjects in a randomized masked trial. Lenses with well rounded anterior edge profiles were found to be significantly more comfortable than lenses with square anterior edges. There was no significant difference in subjective comfort between a rounded and square posterior edge profile. The results suggest that the interaction of the edge with the eyelid is more important in determining comfort than edge effects on the cornea, when lenses are fitted according to a corneal alignment philosophy. PMID:3177585
Krepel, Dana; Kalikhman-Razvozov, Lena; Hod, Oded
2014-01-01
The effects of edge hydrogenation and hydroxylation on the relative stability and electronic properties of hexagonal boron nitride quantum dots (h-BNQDs) are investigated. Zigzag edge hydroxylation is found to result in considerable energetic stabilization of h-BNQDs as well as a reduction of their electronic gap with respect to their hydrogenated counterparts. The application of an external in-plane electric field leads to a monotonous decrease of the gap. When compared to their edge-hydroge...
Tungsten dust impact on ITER-like plasma edge
International Nuclear Information System (INIS)
The impact of tungsten dust originating from divertor plates on the performance of edge plasma in ITER-like discharge is evaluated using computer modeling with the coupled dust-plasma transport code DUSTT-UEDGE. Different dust injection parameters, including dust size and mass injection rates, are surveyed. It is found that tungsten dust injection with rates as low as a few mg/s can lead to dangerously high tungsten impurity concentrations in the plasma core. Dust injections with rates of a few tens of mg/s are shown to have a significant effect on edge plasma parameters and dynamics in ITER scale tokamaks. The large impact of certain phenomena, such as dust shielding by an ablation cloud and the thermal force on tungsten ions, on dust/impurity transport in edge plasma and consequently on core tungsten contamination level is demonstrated. It is also found that high-Z impurities provided by dust can induce macroscopic self-sustained plasma oscillations in plasma edge leading to large temporal variations of edge plasma parameters and heat load to divertor target plates
Design and Simulation of Canny Edge Detection
D Narayana Reddy*; Vaijanath V.Yerigeri; Harish Sanu
2014-01-01
Edge is one of the prominent features in the image processing applications. The edge detection algorithm is carried out by using different methods. Canny edge algorithm is one of the well known edge detection algorithm. In proposed design, the canny edge detection algorithm is designed in verilog and simulated using the MATLAB and Modelsim. The input image is converted to text/pixel values using MATLAB and is stored in a new text file. Verilog with test bench program is used to as...
Color Image Interpolation using Optimal Edge Detector
R. Jansi; Asnath Victy Phamila; Amutha, R.
2013-01-01
This paper proposes an efficient image interpolation algorithm using optimal edge detector. The proposed interpolation algorithm is done in two steps. In the first step, the missing pixels with diagonal neighbors are interpolated and in the second step, the missing pixels with axial neighbors are interpolated. In both the steps classification of edge and smooth pixels is performed using canny edge detector. For the pixels classified as edge pixels, the direction of the edge is found using var...
Experimental Study of Wake / Flap Interaction Noise and the Reduction of Flap Side Edge Noise
Hutcheson, Florence V.; Stead, Daniel J.; Plassman, Gerald E.
2016-01-01
The effects of the interaction of a wake with a half-span flap on radiated noise are examined. The incident wake is generated by bars of various widths and lengths or by a simplified landing gear model. Single microphone and phased array measurements are used to isolate the effects of the wake interaction on the noise radiating from the flap side edge and flap cove regions. The effects on noise of the wake generator's geometry and relative placement with respect to the flap are assessed. Placement of the wake generators upstream of the flap side edge is shown to lead to the reduction of flap side edge noise by introducing a velocity deficit and likely altering the instabilities in the flap side edge vortex system. Significant reduction in flap side edge noise is achieved with a bar positioned directly upstream of the flap side edge. The noise reduction benefit is seen to improve with increased bar width, length and proximity to the flap edge. Positioning of the landing gear model upstream of the flap side edge also leads to decreased flap side edge noise. In addition, flap cove noise levels are significantly lower than when the landing gear is positioned upstream of the flap mid-span. The impact of the local flow velocity on the noise radiating directly from the landing gear is discussed. The effects of the landing gear side-braces on flap side edge, flap cove and landing gear noise are shown.
DEFF Research Database (Denmark)
Niebuhr, Oliver
2012-01-01
The paper is concerned with the 'edge of intonation' in a twofold sense. It focuses on utterance-final F0 movements and crosses the traditional segment-prosody divide by investigating the interplay of F0 and voiceless fricatives in speech production. An experiment was performed for German with fo...
Edge classification for color constancy
A. Gijsenij; T. Gevers; J. van de Weijer
2008-01-01
The goal of color constancy is to measure image colors despite differences in the color of the light source. Traditionally, the computational method of obtaining this ability is by using pixel values only. Recently, methods using edges instead of pixel values have been proposed. However, different e
Faatz, Judith A.
1998-01-01
Describes a field study in a local ecosystem which allows high school students to investigate the edge effect, where a meadow and a forest meet. Students measure soil moisture content, soil temperature, air temperature, relative humidity, wind intensity, and illumination level. Teachers can help students apply their findings to understand problems…
Photon Counting Using Edge-Detection Algorithm
Gin, Jonathan W.; Nguyen, Danh H.; Farr, William H.
2010-01-01
New applications such as high-datarate, photon-starved, free-space optical communications require photon counting at flux rates into gigaphoton-per-second regimes coupled with subnanosecond timing accuracy. Current single-photon detectors that are capable of handling such operating conditions are designed in an array format and produce output pulses that span multiple sample times. In order to discern one pulse from another and not to overcount the number of incoming photons, a detection algorithm must be applied to the sampled detector output pulses. As flux rates increase, the ability to implement such a detection algorithm becomes difficult within a digital processor that may reside within a field-programmable gate array (FPGA). Systems have been developed and implemented to both characterize gigahertz bandwidth single-photon detectors, as well as process photon count signals at rates into gigaphotons per second in order to implement communications links at SCPPM (serial concatenated pulse position modulation) encoded data rates exceeding 100 megabits per second with efficiencies greater than two bits per detected photon. A hardware edge-detection algorithm and corresponding signal combining and deserialization hardware were developed to meet these requirements at sample rates up to 10 GHz. The photon discriminator deserializer hardware board accepts four inputs, which allows for the ability to take inputs from a quadphoton counting detector, to support requirements for optical tracking with a reduced number of hardware components. The four inputs are hardware leading-edge detected independently. After leading-edge detection, the resultant samples are ORed together prior to deserialization. The deserialization is performed to reduce the rate at which data is passed to a digital signal processor, perhaps residing within an FPGA. The hardware implements four separate analog inputs that are connected through RF connectors. Each analog input is fed to a high-speed 1
Vertices of degree k in edge-minimal, k-edge-connected graphs
Kingsford, Carl; Marçais, Guillaume
2009-01-01
Halin showed that every edge minimal, k-vertex connected graph has a vertex of degree k. In this note, we prove the analogue to Halin's theorem for edge-minimal, k-edge-connected graphs. We show there are two vertices of degree k in every edge-minimal, k-edge-connected graph.
Ecological edge effects are sensitive to landscape context. In particular, edge effects can be altered by matrix type and by the presence of other nearby edges. We experimentally altered patch configurations in an African savanna to determine how edge density and matrix type influence edge effect de...
A dynamic stall model for airfoils with deformable trailing edges
DEFF Research Database (Denmark)
Andersen, Peter Bjørn; Gaunaa, Mac; Bak, Christian; Hansen, Morten Hartvig
2009-01-01
The present work contains an extension of the Beddoes-Leishman-type dynamic stall model. In this work, a deformable trailing-edge flap has been added to the dynamic stall model. The model predicts the unsteady aerodynamic forces and moments on an airfoil section undergoing arbitrary motion in heave......, lead-lag, pitch, trailing-edge flapping. In the linear region, the model reduces to the inviscid model, which includes the aerodynamic effect of a thin airfoil with a deformable camberline in inviscid flow. Therefore, the proposed model can be considered a crossover between the work of Gaunaa for the...
3D edge energy transport in stellarator configurations
Energy Technology Data Exchange (ETDEWEB)
McTaggart, N. [Max-Planck-Institut fuer Plasmaphysik, Teilinstitut Greifswald, EURATOM Association, Wendelsteinstrasse 1, D-17491 Greifswald (Germany); Zagorski, R. [Institute of Plasma Physics and Laser Microfusion, P.O. Box 49, Warsaw (Poland)]. E-mail: zagorski@ifpilm.waw.pl; Bonnin, X. [Max-Planck-Institut fuer Plasmaphysik, Teilinstitut Greifswald, EURATOM Association, Wendelsteinstrasse 1, D-17491 Greifswald (Germany); Runov, A. [Max-Planck-Institut fuer Plasmaphysik, Teilinstitut Greifswald, EURATOM Association, Wendelsteinstrasse 1, D-17491 Greifswald (Germany); Schneider, R. [Max-Planck-Institut fuer Plasmaphysik, Teilinstitut Greifswald, EURATOM Association, Wendelsteinstrasse 1, D-17491 Greifswald (Germany); Kaiser, T. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Rognlien, T. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Umansky, M. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States)
2005-03-01
The finite difference discretization method is used to solve the electron energy transport equation in complex 3D edge geometries using an unstructured grid. This grid is generated by field-line tracing to separate the radial and parallel fluxes and minimize the numerical diffusion connected with the strong anisotropy of the system. The influence of ergodicity on the edge plasma transport in the W7-X stellarator is investigated in this paper. Results show that the combined effect of ergodicity and the radial plasma diffusion leads to the efficient smoothing of the temperature profiles in the finite-{beta} case.
Softening of edges of solids by surface tension.
Mora, Serge; Pomeau, Yves
2015-01-01
Surface tension tends to minimize the area of interfaces between pieces of matter in different thermodynamic phases, be they in the solid or the liquid state. This can be relevant for the macroscopic shape of very soft solids, and lead to a roughening of initially sharp edges. We calculate this effect for a neo-Hookean elastic solid, with assumptions corresponding to actual experiments, namely the case where an initially sharp edge is rounded by the effect of surface tension felt when the flu...
A dynamic stall model for airfoils with deformable trailing edges
DEFF Research Database (Denmark)
Andersen, Peter Bjørn; Gaunaa, Mac; Bak, Dan Christian; Hansen, Morten Hartvig
2007-01-01
airfoil section undergoing arbitrary motion in heave, lead-lag, pitch, Trailing Edge (TE) flapping. In the linear region, the model reduces to the inviscid model of Gaunaa [4], which includes the aerodynamic effect of a thin airfoil with a deformable camberline in inviscid flow. Therefore, the proposed......The present work contains an extension of the Beddoes-Leishman (B-L) type dynamic stall model, as described by Hansen et al. [7]. In this work a Deformable Trailing Edge Geometry (DTEG) has been added to the dynamic stall model. The model predicts the unsteady aerodynamic forces and moments on an...
Impurity penetration through the edge transport barrier
Energy Technology Data Exchange (ETDEWEB)
Belo, P [EURATOM/IST Fusion Association, Centro de Fusao Nuclear, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Parail, V [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Corrigan, G [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Heading, D [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Houlberg, W [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Monier-Garbet, P [Association Euratom-CEA, Cadarache 13108 Saint Paul Lez Durance (France); Ongena, J [Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association EURATOM-Belgian State, Ecole Royale Militaire-B-1000 Brussels, Koninklijke Militaire School (Belgium)
2004-08-01
The ELMs in H-mode plasmas manifest themselves as short bursts of increased edge transport, which expel energy and particles, including impurities from the plasma edge to the SOL and further towards target plates and limiters (Zohm H 1996 Plasma Phys. Control. Fusion 38 1213, Loarte A et al 2003 Plasma Phys. Control. Fusion 45 1549). ELMs are considered beneficial events with respect to impurities since they can prevent impurities from accumulating in the plasma core. JET has recently performed an experiment in which a controlled influx of noble gas impurities was successfully used in order to reduce the amplitude and frequency of type-I ELMs. An interesting correlation between the level of the main gas puffing and the radial redistribution of impurities has been found in this experiment: it was shown that impurities are contained near the separatrix in discharges with a relatively strong level of main gas puffing. Reduction of the puffing below a certain level leads to impurity accumulation in the core followed by thermal collapse. This paper describes the results of predictive modelling of impurity seeding experiments on JET using a coupling of the 1.5D core transport code JETTO (for the main ions) and 1D transport code SANCO (for impurities). Two sets of boundary conditions for the density and temperatures, which correspond to two different deuterium gas puffing rates, were used in the modelling. An explanation for the experimentally observed phenomenon is presented.
Edge detection based on directional space
Institute of Scientific and Technical Information of China (English)
YUAN Wei-qi; LI De-sheng
2006-01-01
A new method for edge detection based on directional space is proposed.The principle is that:firstly,the directional differential space is set up in which the ridge edge pixels and valley edge pixels are abstracted with the help of the method of logical judgments along the direction of differential function,forming a directional roof edge map;secondly,step edge pixels are abstracted between the neighboring directional ridge edge and directional valley edge along the direction of differential function;finally,the ridge edge map,valley edge map and step edge map gained along different directions are combined into corresponding ridge edge map,valley edge map and step edge map.This method is different from classical algorithms in which the gray differential values of the mutual vertical direction are combined into one gradient value.The experiment of edge detection is made for the images of nature scenery,human body and accumulative raw material,whose result is compared with the one of classical algorithms and showing the robustness of the proposed method.
Topological invariants of edge states for periodic two-dimensional models
Avila, Julio Cesar; Villegas-Blas, Carlos
2012-01-01
Transfer matrix methods and intersection theory are used to calculate the bands of edge states for a wide class of periodic two-dimensional tight-binding models including a sublattice and spin degree of freedom. This allows to define topological invariants by considering the associated Bott-Maslov indices which can be easily calculated numerically. For time-reversal symmetric systems in the symplectic universality class this leads to a Z_2-invariant for the edge states. It is shown that the edge state invariants are related to Chern numbers of the bulk systems and also to (spin) edge currents, in the spirit of the theory of topological insulators.
Topological Invariants of Edge States for Periodic Two-Dimensional Models
Energy Technology Data Exchange (ETDEWEB)
Avila, Julio Cesar; Schulz-Baldes, Hermann, E-mail: schuba@mi.uni-erlangen.de; Villegas-Blas, Carlos [Instituto de Matematicas, UNAM (Mexico)
2013-06-15
Transfer matrix methods and intersection theory are used to calculate the bands of edge states for a wide class of periodic two-dimensional tight-binding models including a sublattice and spin degree of freedom. This allows to define topological invariants by considering the associated Bott-Maslov indices which can be easily calculated numerically. For time-reversal symmetric systems in the symplectic universality class this leads to a Z{sub 2} -invariant for the edge states. It is shown that the edge state invariants are related to Chern numbers of the bulk systems and also to (spin) edge currents, in the spirit of the theory of topological insulators.
Finite size effects of helical edge states in HgTe/CdTe quantum wells
Zhou, Bin; Lu, Hai-Zhou; Chu, Rui-Lin; Shen, Shun-Qing; Niu, Qian
2008-01-01
The solutions for the helical edge states for an effective continuum model for the quantum spin Hall effect in HgTe/CdTe quantum wells are presented. For a sample of a large size, the solution gives the linear dispersion for the edge states. However, in a finite strip geometry, the edge states at two sides will couple with each other, which leads to a finite energy gap in the spectra. The gap decays in an exponential law of the width of sample. The magnetic field dependence of the edge states...
Kasparova, A.; Katkov, I.; Chilingarian, I.; Silchenko, O.; Moiseev, A.; Borisov, S.
2016-06-01
Although thick stellar discs are detected in nearly all edge-on disc galaxies, their formation scenarios still remain a matter of debate. Due to observational difﬁculties, there is a lack of information about their stellar populations. Using the Russian 6-m telescope BTA we collected deep spectra of thick discs in three edge-on early-type disc galaxies located in different environments: NGC4111 in a dense group, NGC4710 in the Virgo cluster, and NGC5422 in a sparse group. We see intermediate age (4 ‑ 5 Gyr) metal rich ([Fe/H] ~ ‑0.2 ‑ 0.0 dex) stellar populations in NGC4111 and NGC4710. On the other hand, NGC5422 does not harbour young stars, its only disc is thick and old (10 Gyr) and its α-element abundance suggests a long formation epoch implying its formation at high redshift. Our results prove the diversity of thick disc formation scenarios.
EDGE-ORIENTED HEXAGONAL ELEMENTS
Institute of Scientific and Technical Information of China (English)
Chao Yang; Jiachang Sun
2007-01-01
In this paper, two new nonconforming hexagonal elements are presented, which are based on the trilinear function space Q(3)1 and are edge-oriented, analogical to the case of the rotated Q1 quadrilateral element. A priori error estimates are given to show that the new elements achieve first-order accuracy in the energy norm and second-order accuracy in the L2 norm. This theoretical result is confirmed by the numerical tests.
Edge effects and delamination failures
Herakovich, C. T.
1989-01-01
The fundamental relationship between the morphology of a composite laminate and the resulting free edge effects is explored and related to delamination failures. Cross-ply, angle-ply, and quasi-isotropic laminates are discussed in detail. It is shown that the local mismatch in elastic properties of adjacent layers and the global stacking sequence of a laminate both have a significant influence on the interlaminar stresses and delamination failures.
Edge-driven microplate kinematics
Schouten, Hans; Klitgord, Kim D.; Gallo, David G.
1993-01-01
It is known from plate tectonic reconstructions that oceanic microplates undergo rapid rotation about a vertical axis and that the instantaneous rotation axes describing the microplate's motion relative to the bounding major plates are frequently located close to its margins with those plates, close to the tips of propagating rifts. We propose a class of edge-driven block models to illustrate how slip across the microplate margins, block rotation, and propagation of rifting may be related to the relative motion of the plates on either side. An important feature of these edge-driven models is that the instantaneous rotation axes are always located on the margins between block and two bounding plates. According to those models the pseudofaults or traces of disrupted seafloor resulting from the propagation of rifting between microplate and major plates may be used independently to approximately trace the continuous kinematic evolution of the microplate back in time. Pseudofault geometries and matching rotations of the Easter microplate show that for most of its 5 m.y. history, block rotation could be driven by the drag of the Nazca and Pacific plates on the microplate's edges rather than by a shear flow of mantle underneath.
Nonreference Medical Image Edge Map Measure
Directory of Open Access Journals (Sweden)
Karen Panetta
2014-01-01
Full Text Available Edge detection is a key step in medical image processing. It is widely used to extract features, perform segmentation, and further assist in diagnosis. A poor quality edge map can result in false alarms and misses in cancer detection algorithms. Therefore, it is necessary to have a reliable edge measure to assist in selecting the optimal edge map. Existing reference based edge measures require a ground truth edge map to evaluate the similarity between the generated edge map and the ground truth. However, the ground truth images are not available for medical images. Therefore, a nonreference edge measure is ideal for medical image processing applications. In this paper, a nonreference reconstruction based edge map evaluation (NREM is proposed. The theoretical basis is that a good edge map keeps the structure and details of the original image thus would yield a good reconstructed image. The NREM is based on comparing the similarity between the reconstructed image with the original image using this concept. The edge measure is used for selecting the optimal edge detection algorithm and optimal parameters for the algorithm. Experimental results show that the quantitative evaluations given by the edge measure have good correlations with human visual analysis.
Quantum spin Hall effect in graphene nanoribbons: Effect of edge geometry
Rhim, Jun-Won; Moon, Kyungsun
2011-07-01
There has been tremendous recent progress in realizing topological insulator initiated by the proposal of Kane and Mele for the graphene system. They have suggested that the odd Z2 index for the graphene manifests the spin-filtered edge states for the graphene nanoribbons, which lead to the quantum spin Hall effect (QSHE). Here, we investigate the role of the spin-orbit interaction both for the zigzag and armchair nanoribbons with special care in the edge geometry. For the pristine zigzag nanoribbons, we have shown that one of the σ edge bands located near E=0 lifts up the energy of the spin-filtered chiral edge states at the zone boundary by warping the π edge bands, and hence the QSHE does not occur. Upon increasing the carrier density above a certain critical value, the spin-filtered edge states are formed leading to the QSHE. We suggest that the hydrogen passivation on the edge can recover the original feature of the QSHE. For the armchair nanoribbon, the QSHE is shown to be stable. We have also derived the real-space effective Hamiltonian, which demonstrates that the on-site energy and the effective spin-orbit coupling strength are strongly enhanced near the ribbon edges. We have shown that the steep rise of the confinement potential thus obtained is responsible for the warping of the π edge bands.
Survey of techniques for reduction of wind turbine blade trailing edge noise.
Energy Technology Data Exchange (ETDEWEB)
Barone, Matthew Franklin
2011-08-01
Aerodynamic noise from wind turbine rotors leads to constraints in both rotor design and turbine siting. The primary source of aerodynamic noise on wind turbine rotors is the interaction of turbulent boundary layers on the blades with the blade trailing edges. This report surveys concepts that have been proposed for trailing edge noise reduction, with emphasis on concepts that have been tested at either sub-scale or full-scale. These concepts include trailing edge serrations, low-noise airfoil designs, trailing edge brushes, and porous trailing edges. The demonstrated noise reductions of these concepts are cited, along with their impacts on aerodynamic performance. An assessment is made of future research opportunities in trailing edge noise reduction for wind turbine rotors.
Reducing the Edge Chipping for Capillary End Face Grinding and Polishing
Directory of Open Access Journals (Sweden)
Hošek J.
2013-05-01
Full Text Available This paper presents results of glass capillary end face grinding and polishing by approach that reduces the edge chipping. Brittle materials have natural tendency for edge chipping what leads to beveling the sharp edges. Not beveled sharp edges on glass capillary are important for special applications like surface tension measurement of small liquid samples. We use common grinding and polishing process for capillary end face machining modified with gradual decreasing of grinding load based on the relation of the critical chipping load. Achieved surface roughness is measured using atomic force microscopy (AFM. Capillary inner edge quality is checked both with optical microscopes and electron microscope too. We achieved a non-chipped capillary inner edge with radius down to 100 nm.
Adjoint-based optimization of flapping plates hinged with a trailing-edge flap
Directory of Open Access Journals (Sweden)
Min Xu
2015-01-01
Full Text Available It is important to understand the impact of wing-morphing on aerodynamic performance in the study of flapping-wing flight of birds and insects. We use a flapping plate hinged with a trailing-edge flap as a simplified model for flexible/morphing wings in hovering. The trailing-edge flapping motion is optimized by an adjoint-based approach. The optimized configuration suggests that the trailing-edge flap can substantially enhance the overall lift. Further analysis indicates that the lift enhancement by the trailing-edge flapping is from the change of circulation in two ways: the local circulation change by the rotational motion of the flap, and the modification of vortex shedding process by the relative location between the trailing-edge flap and leading-edge main plate.
Energy Technology Data Exchange (ETDEWEB)
Sommer, F; Guenter, S; Kallenbach, A; Maraschek, M; Boom, J; Fischer, R; Hicks, N; Reiter, B; Wolfrum, E [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching, EURATOM Association (Germany); Luhmann, N C Jr [University of California at Davis, Davis, CA 95616 (United States); Park, H K [POSTECH, Pahang, Gyeongbuk 790-784 (Korea, Republic of); Wenninger, R, E-mail: fabian.sommer@ipp.mpg.de [Universitaetssternwarte der Ludwig-Maximilians-Universitaet, D-81679 Muenchen (Germany)
2011-08-15
A new magnetohydrodynamic instability called the 'Edge Snake', which was found in 2006 at the tokamak ASDEX Upgrade during type-I ELMy H-modes, is investigated. It is located within the separatrix in the region of high temperature and density gradients and has a toroidal mode number of n = 1. The Edge Snake consists of a radially and poloidally strongly localized current wire, in which the temperature and density profiles flatten. This significant reduction in pressure gradient leads to a reduction in the neoclassical Bootstrap current and can plausibly explain the drive of the instability. The experimental observations point towards a magnetic island with a defect current inside the O-point of the island. The Edge Snake is compared with similar instabilities at JET, DIII-D and ASDEX Upgrade.
Exploring the Constrained Maximum Edge-weight Connected Graph Problem
Institute of Scientific and Technical Information of China (English)
Zhen-ping Li; Shi-hua Zhang; Xiang-Sun Zhang; Luo-nan Chen
2009-01-01
Given an edge weighted graph,the maximum edge-weight connected graph (MECG) is a connected subgraph with a given number of edges and the maximal weight sum.Here we study a special case,i.e.the Constrained Maximum Edge-Weight Connected Graph problem (CMECG),which is an MECG whose candidate subgraphs must include a given set of k edges,then also called the k-CMECG.We formulate the k-CMECG into an integer linear programming model based on the network flow problem.The k-CMECG is proved to be NP-hard.For the special case 1-CMECG,we propose an exact algorithm and a heuristic algorithm respectively.We also propose a heuristic algorithm for the k-CMECG problem.Some simulations have been done to analyze the quality of these algorithms.Moreover,we show that the algorithm for 1-CMECG problem can lead to the solution of the general MECG problem.
Phosphorus K-edge XANES spectroscopy of mineral standards.
Ingall, Ellery D; Brandes, Jay A; Diaz, Julia M; de Jonge, Martin D; Paterson, David; McNulty, Ian; Elliott, W Crawford; Northrup, Paul
2011-03-01
Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was performed on phosphate mineral specimens including (a) twelve specimens from the apatite group covering a range of compositional variation and crystallinity; (b) six non-apatite calcium-rich phosphate minerals; (c) 15 aluminium-rich phosphate minerals; (d) ten phosphate minerals rich in either reduced iron or manganese; (e) four phosphate minerals rich in either oxidized iron or manganese; (f) eight phosphate minerals rich in either magnesium, copper, lead, zinc or rare-earth elements; and (g) four uranium phosphate minerals. The identity of all minerals examined in this study was independently confirmed using X-ray powder diffraction. Minerals were distinguished using XANES spectra with a combination of pre-edge features, edge position, peak shapes and post-edge features. Shared spectral features were observed in minerals with compositions dominated by the same specific cation. Analyses of apatite-group minerals indicate that XANES spectral patterns are not strongly affected by variations in composition and crystallinity typical of natural mineral specimens. PMID:21335905
Environmental Dataset Gateway (EDG) REST Interface
U.S. Environmental Protection Agency — Use the Environmental Dataset Gateway (EDG) to find and access EPA's environmental resources. Many options are available for easily reusing EDG content in other...
A Fuzzy Set Approach for Edge Detection
Directory of Open Access Journals (Sweden)
Pushpajit A. Khaire
2012-12-01
Full Text Available Image segmentation is one of the most studied problems in image analysis, computer vision, pattern recognition etc. Edge detection is a discontinuity based approach used for image segmentation. In this paper, an edge detection using fuzzy set is proposed, where an image is considered as a fuzzy set and pixels are taken as elements of fuzzy set. The fuzzy approach converts the color image to a partially segmented image; finally an edge detector is convolved over the partially segmented image to obtain an edged image. The approach is implemented using MATLAB 7.11. (R2010b. For qualitative and quantitative comparison, BSD (Berkeley Segmentation Database images are used for experimentation. Performance parameters used are PSNR (dB and Performance ratio (PR of true to false edges. It has been shown that the proposed approach performs better than Canny’s edge detection algorithm under almost all scenarios. The proposed approach reduces false edge detection and double edges.
Evaluation of edge detectors using avarage risk
Spreeuwers, L.J.; Heijden, van der F.
1992-01-01
A new method for evaluation of edge detectors, based on the average risk of a decision, is discussed. The average risk is a performance measure well-known in Bayesian decision theory. Since edge detection can be regarded as a compound decision making process, the performance of an edge detector is
Edge and coupled core-edge transport modelling in tokamaks
International Nuclear Information System (INIS)
Recent advances in the theory and modelling of tokamak edge, scrape-off-layer (SOL) and divertor plasmas are described. The effects of the poloidal ExB drift on inner/outer divertor-plate asymmetries within a 1D analysis are shown to be in good agreement with experimental trends; above a critical v ExB, the model predicts transitions to supersonic SOL flow at the inboard midplane. 2D simulations show the importance of ExB flow in the private-flux region and of ∇ B-drifts. A theory of rough plasma-facing surfaces is given, predicting modifications to the SOL plasma. The parametric dependence of detached-plasma states in slab geometry has been explored; with sufficient pumping, the location of the ionization front can be controlled; otherwise only fronts near the plate or the X-point are stable. Studies with a more accurate Monte-Carlo neutrals model and a detailed non-LTE radiation-transport code indicate various effects are important for quantitative modelling. Detailed simulations of the DIII-D core and edge are presented; impurity and plasma flow are discussed and shown to be well modelled with UEDGE. (author)
Energy Technology Data Exchange (ETDEWEB)
Sprinkle, J.K.; Hansen, W.J.
1993-02-11
In 1979, a K-edge densitometer (KED) was installed by the Safeguards Assay group from Los Alamos National Laboratory in the PNC reprocessing plant at Tokai-mura, Japan. It uses an active nondestructive assay technique, KED, to measure the plutonium concentration of the product solution. The measurement uncertainty of an assay depends on the count time chosen, but can be 0.5% or better. The computer hardware and software were upgraded in 1992. This manual describes the operation of the instrument, with an emphasis on the user interface to the software.
Instant Adobe Edge Inspect starter
Khan, Joseph
2013-01-01
Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. This easy-to-understand Starter guide will get you up to speed with Adobe Edge Inspect quickly and with little effort.This book is for frontend web developers and designers who are developing and testing web applications targeted for mobile browsers. It's assumed that you have a basic understanding of creating web applications using HTML, CSS, and JavaScript, as well as being familiar with running web pages from local HTTP servers. Readers are a
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Edge impact modeling on stiffened composite structures
Ostré, Benjamin; Bouvet, Christophe; Minot, Clément; Aboissière, Jacky
2015-01-01
Finite Element Analysis of low velocity/low energy edge impact has been carried out on carbon fiber reinforced plastic structure. Edge impact experimental results were then compared to the numerical ‘‘Discrete Ply Model’’ in order to simulate the edge impact damage. This edge impact model is inspired to out-of-plan impact model on a laminate plate with addition of new friction and crushing behaviors. From a qualitative and quantitative point of view, this edge impact model reveals a relati...
Image edge detection based on beamlet transform
Institute of Scientific and Technical Information of China (English)
Li Jing; Huang Peikang; Wang Xiaohu; Pan Xudong
2009-01-01
Combining beamlet transform with steerable filters, a new edge detection method based on line gra-dient is proposed. Compared with operators based on point local properties, the edge-detection results with this method achieve higher SNR and position accuracy, and are quite helpful for image registration, object identification, etc. Some edge-detection experiments on optical and SAR images that demonstrate the significant improvement over classical edge operators are also presented. Moreover, the template matching result based on edge information of optical reference image and SAR image also proves the validity of this method.
Topological edge states of bound photon pairs
Gorlach, Maxim A
2016-01-01
We predict the existence of interaction-driven edge states of bound two-photon quasiparticles in a dimer periodic array of nonlinear optical cavities. Energy spectrum of photon pairs is dramatically richer than in the noninteracting case or in a simple lattice, featuring collapse and revival of multiple edge and bulk modes as well as edge states in continuum. Despite the unexpected breakdown of the Zak phase technique and the edge mixing of internal and center-of-mass motion we link the edge state existence to the two-photon quantum walk graph connectivity, thus uncovering the topological nature of the many-body problem in complex lattices.
Edge states in Open Antiferromagnetic Heisenberg Chains
Qin, Shaojin; Ng, Tai-Kai; Su, Zhao-Bin
1995-01-01
In this letter we report our results in investigating edge effects of open antiferromagnetic Heisenberg spin chains with spin magnitudes $S=1/2, 1,3/2,2$ using the density-matrix renormalization group (DMRG) method initiated by White. For integer spin chains, we find that edge states with spin magnitude $S_{edge}=S/2$ exist, in agreement with Valence-Bond-Solid model picture. For half-integer spin chains, we find that no edge states exist for $S=1/2$ spin chain, but edge state exists in $S=3/...
3D modelling of edge parallel flow asymmetries
International Nuclear Information System (INIS)
The issue of parallel flows asymmetries in the edge plasma is tackled with a new first principle transport and turbulence code. TOKAM-3D is a 3D full-torus fluid code that can be used both in diffusive and turbulent regimes and covers either exclusively closed flux surfaces or both open and closed field lines in limiter geometry. Two independent mechanisms susceptible to lead to large amplitude asymmetric parallel flows are evidenced. Global ExB drifts coupled with the presence of the limiter break the poloidal symmetry and can generate large amplitude parallel flows even with poloidally uniform transport coefficients. On the other hand, turbulent transport in the edge exhibits a strong ballooning of the radial particle flux generating an up-down m = 1, n = 0 structure on the parallel velocity. The combination of both mechanisms in complete simulations leads to a poloidal and radial distribution of the parallel velocity comparable to experimental results.
Edge scour at scour protections around offshore wind turbine foundations
DEFF Research Database (Denmark)
Petersen, Thor Ugelvig; Sumer, B. Mutlu; Fredsøe, Jørgen
2014-01-01
experimental campaign to explain the edge sour process in steady current is presented. The three-dimensional flow field around the pile and scour protection is resolved by particle image velocimetry, showing a local increase in the hydrodynamic field leading to increased sediment transport and scour. The...... governing process in steady current is a pair of symmetrical counter-rotating vortices emerging in the near bed region in the wake of the pile and scour protection, causing a significant downstream scour hole....
Quantum Manifestations of Graphene Edge Stress and Edge Instability: A First-Principles Study
Huang, Bing; Liu,Miao; Su, Ninghai; Wu, Jian; Duan, Wenhui; Gu, Bing-Lin; LIU Feng
2010-01-01
We have performed first-principles calculations of graphene edge stresses, which display two interesting quantum manifestations absent from the classical interpretation: the armchair edge stress oscillates with a nanoribbon width, and the zigzag edge stress is noticeably reduced by spin polarization. Such quantum stress effects in turn manifest in mechanical edge twisting and warping instability, showing features not captured by empirical potentials or continuum theory. Edge adsorption of H a...
Understanding the edge crack phenomenon in ceramic laminates
Directory of Open Access Journals (Sweden)
O. Ševeček
2015-10-01
Full Text Available Layered ceramic materials (also referred to as “ceramic laminates” are becoming one of the most promising areas of materials technology aiming to improve the brittle behavior of bulk ceramics. The utilization of tailored compressive residual stresses acting as physical barriers to crack propagation has already succeeded in many ceramic systems. Relatively thick compressive layers located below the surface have proven very effective to enhance the fracture resistance and provide a minimum strength for the material. However, internal compressive stresses result in out-of plane stresses at the free surfaces, what can cause cracking of the compressive layer, forming the so-called edge cracks. Experimental observations have shown that edge cracking may be associated with the magnitude of the compressive stresses and with the thickness of the compressive layer. However, an understanding of the parameters related to the onset and extension of such edge cracks in the compressive layers is still lacking. In this work, a 2D parametric finite element model has been developed to predict the onset and propagation of an edge crack in ceramic laminates using a coupled stress-energy criterion. This approach states that a crack is originated when both stress and energy criteria are fulfilled simultaneously. Several designs with different residual stresses and a given thickness in the compressive layers have been computed. The results predict the existence of a lower bound, below no edge crack will be observed, and an upper bound, beyond which the onset of an edge crack would lead to the complete fracture of the layer
On-surface synthesis of graphene nanoribbons with zigzag edge topology
Ruffieux, Pascal; Wang, Shiyong; Yang, Bo; Sánchez-Sánchez, Carlos; Liu, Jia; Dienel, Thomas; Talirz, Leopold; Shinde, Prashant; Pignedoli, Carlo A.; Passerone, Daniele; Dumslaff, Tim; Feng, Xinliang; Müllen, Klaus; Fasel, Roman
2016-03-01
Graphene-based nanostructures exhibit electronic properties that are not present in extended graphene. For example, quantum confinement in carbon nanotubes and armchair graphene nanoribbons leads to the opening of substantial electronic bandgaps that are directly linked to their structural boundary conditions. Nanostructures with zigzag edges are expected to host spin-polarized electronic edge states and can thus serve as key elements for graphene-based spintronics. The edge states of zigzag graphene nanoribbons (ZGNRs) are predicted to couple ferromagnetically along the edge and antiferromagnetically between the edges, but direct observation of spin-polarized edge states for zigzag edge topologies—including ZGNRs—has not yet been achieved owing to the limited precision of current top-down approaches. Here we describe the bottom-up synthesis of ZGNRs through surface-assisted polymerization and cyclodehydrogenation of specifically designed precursor monomers to yield atomically precise zigzag edges. Using scanning tunnelling spectroscopy we show the existence of edge-localized states with large energy splittings. We expect that the availability of ZGNRs will enable the characterization of their predicted spin-related properties, such as spin confinement and filtering, and will ultimately add the spin degree of freedom to graphene-based circuitry.
2012-05-01
Education: Physics Education Networks meeting has global scale Competition: Competition seeks the next Brian Cox Experiment: New measurement of neutrino time-of-flight consistent with the speed of light Event: A day for all those who teach physics Conference: Students attend first Anglo-Japanese international science conference Celebration: Will 2015 be the 'Year of Light'? Teachers: Challenging our intuition in spectacular fashion: the fascinating world of quantum physics awaits Research: Science sharpens up sport Learning: Kittinger and Baumgartner: on a mission to the edge of space International: London International Youth Science Forum calls for leading young scientists Competition: Physics paralympian challenge needs inquisitive, analytical, artistic and eloquent pupils Forthcoming events
Predicted solar cell edge radiation effects
International Nuclear Information System (INIS)
The Advanced Solar Cell Orbital Test (ASCOT) will test six types of solar cells in a high energy proton environment. During the design of the experiment a question was raised about the effects of proton radiation incident on the edge of the solar cells and whether edge radiation shielding was required. Historical geosynchronous data indicated that edge radiation damage is not detectable over the normal end of life solar cell degradation; however because the ASCOT radiation environment has a much higher and more energetic fluence of protons, considerably more edge damage is expected. A computer analysis of the problem was made by modeling the expected radiation damage at the cell edge and using a network model of small interconnected solar cells to predict degradation in the cell's electrical output. The model indicated that the deepest penetration of edge radiation was at the top of the cell near the junction where the protons have access to the cell through the low density cell/cover adhesive layer. The network model indicated that the cells could tolerate high fluences at their edge as long as there was high electrical resistance between the edge radiated region and the contact system on top of the cell. The predicted edge radiation related loss was less than 2% of maximum power for GaAs/Ge solar cells. As a result, no edge radiation protection was used for ASCOT
Imaging edges of nanostructured graphene
DEFF Research Database (Denmark)
Kling, Jens; Cagliani, Alberto; Booth, T. J.;
Graphene, as the forefather of 2D-materials, attracts much attention due to its extraordinary properties like transparency, flexibility and outstanding high conductivity, together with a thickness of only one atom. However, graphene also possesses no band gap, which makes it unsuitable for many...... electronic applications like transistors. It has been shown theoretically that by nanostructuring pristine graphene, e.g. with regular holes, the electronic properties can be tuned and a band gap introduced. The size, distance and edge termination of these “defects” influence the adaptability....... Such nanostructuring can be done experimentally, but especially characterization at atomic level is a huge challenge. High-resolution TEM (HRTEM) is used to characterize the atomic structure of graphene. We optimized the imaging conditions used for the FEI Titan ETEM. To reduce the knock-on damage of the carbon atoms...
Composite superconducting transition edge bolometer
International Nuclear Information System (INIS)
A composite far-infrared bolometer has been constructed that uses an aluminum film at the superconducting transition temperature of 1.3 K as the temperature-sensitive element. The film is evaporated on one edge of a 4 x 4-mm sapphire substrate, which is coated on the reverse side with an absorbing film of bismuth. The best bolometer has an electrical NEP of (1.7 +- 0.1) x 10-15 W Hz-1/2 at 2 Hz, and a specific detectivity D* of (1.1 +- 0.1) x 1014 cm W-1 Hz1/2. This measured electrical NEP is within a factor 2 of the fundamental thermal noise limit
Edge localized mode physics and operational aspects in tokamaks
Energy Technology Data Exchange (ETDEWEB)
Becoulet, M [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Huysmans, G [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Sarazin, Y [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Garbet, X [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Ghendrih, Ph [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Rimini, F [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Joffrin, E [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Litaudon, X [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Monier-Garbet, P [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Ane, J-M [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Thomas, P [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Grosman, A [Association Euratom-CEA, CEA Cadarache, F-13108 St Paul-lez-Durance (France); Parail, V [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Wilson, H [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Lomas, P [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Vries, P de[Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Zastrow, K-D [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Matthews, G F [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Lonnroth, J [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom); Gerasimov, S [Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA (United Kingdom)] [and others
2003-12-01
Recent progress in experimental and theoretical studies of edge localized mode (ELM) physics is reviewed for the reactor relevant plasma regimes, namely the high confinement regimes, that is, H-modes and advanced scenarios. Theoretical approaches to ELM physics, from a linear ideal magnetohydrodynamic (MHD) stability analysis to non-linear transport models with ELMs are discussed with respect to experimental observations, in particular the fast collapse of pedestal pressure profiles, magnetic measurements and scrape-off layer transport during ELMs. High confinement regimes with different types of ELMs are addressed in this paper in the context of development of operational scenarios for ITER. The key parameters that have been identified at present to reduce the energy losses in Type I ELMs are operation at high density, high edge magnetic shear and high triangularity. However, according to the present experimental scaling for the energy losses in Type I ELMs, the extrapolation of such regimes for ITER leads to unacceptably large heat loads on the divertor target plates exceeding the material limits. High confinement H-mode scenarios at high triangularity and high density with small ELMs (Type II), mixed regimes (Type II and Type I) and combined advanced regimes at high beta{sub p} are discussed for present-day tokamaks. The optimum combination of high confinement and small MHD activity at the edge in Type II ELM scenarios is of interest to ITER. However, to date, these regimes have been achieved in a rather narrow operational window and far from ITER parameters in terms of collisionality, edge safety factor and beta{sub p}. The compatibility of the alternative internal transport barrier (ITB) scenario with edge pedestal formation and ELMs is also addressed. Edge physics issues related to the possible combination of small benign ELMs (Type III, Type II ELMs, quiescent double barrier) and high performance ITBs are discussed for present-day experiments (JET, JT-60U
Bound on m-restricted Edge Connectivity
Institute of Scientific and Technical Information of China (English)
Jian-ping Ou; Fu-ji Zhang
2003-01-01
An m-restricted edge cut is an edge cut that separates a connected graph into a disconnected one with no components having order less than m. m-restricted edge connectivity λm is the cardinality of a minimum m-restricted edge cut. Let G be a connected k-regular graph of order at least 2m that contains m-restricted edge cuts and X be a subgraph of G. Let( )(X) denote the number of edges with one end in X and the other not in X and ξm = min{( )(X): X is a connected vertex-induced subgraph of order m}. It is proved in this paper that if G has girth at least m/2 + 2, then λm ≤ξm. The upper bound of λm is sharp.
Novel wavelet synthesis for edge detection
International Nuclear Information System (INIS)
This paper presents a novel wavelet synthesis approach based on scale multiplication of concordant detail bands coefficients of dyadic wavelet transform that highlights edge structure and suppresses noise in an image. The algorithm works on default threshold values for image denoising. However, to achieve optimality of edge detection, image decomposition level through wavelet transform is not unique and depends upon image resolution along with its structural parameters. Scale controls the significance of edges to be shown. High resolution images with thick edges support high level decomposition and vice versa. The paper presents a novel edge detection paradigm in which innovative wavelet synthesis of detail bands based on nearest neighborhood interpolation and wavelet scale correlation is conceived such that the reconstructed image fabricates its edge map. (author)
Object detection using categorised 3D edges
DEFF Research Database (Denmark)
Kiforenko, Lilita; Buch, Anders Glent; Bodenhagen, Leon; Krüger, Norbert
2015-01-01
is made possible by the explicit use of edge categories in the feature descriptor. We quantitatively compare our approach with the state-of-the-art template based Linemod method, which also provides an effective way of dealing with texture-less objects, tests were performed on our own object dataset......In this paper we present an object detection method that uses edge categorisation in combination with a local multi-modal histogram descriptor, all based on RGB-D data. Our target application is robust detection and pose estimation of known objects. We propose to apply a recently introduced edge...... categorisation algorithm for describing objects in terms of its different edge types. Relying on edge information allow our system to deal with objects with little or no texture or surface variation. We show that edge categorisation improves matching performance due to the higher level of discrimination, which...
Hale, Wayne N.
2008-01-01
life is good. More often when an unbelievably difficult test fails, we are left with a very long discussion of why and what was wrong in the design or execution of the test. Make sure that the test is well defined. Even then, it is important to explain to your leaders what inherent accuracy (or error) the test conditions or equipment have and what the assumptions or initial conditions were for the test. Test results without a good understanding of the test's accuracy or the pedigree of the test assumptions are worth very little. Finally, there is flight test data. Always limited, never at the edge of the envelope, it still shows how the real hardware works in a combined environment. Flight experience is dangerous because it typically doesn't show how close to the edge of the cliff the equipment is operating, but it does demonstrate how the hardware really works. A flight test is the ultimate test, again taken with the knowledge that it is probably not the extreme but something more like the middle of the environmental and systems performance. Good understanding of a problem and its solution always relies on a combination of all these methods. Be sure to lead your leaders by using all the tools you have at your disposal. At the end of the day, decisions in space flight always come down to a risk trade. Our business is not remotely safe, not in the sense that the public, the media, or our legislators use the term. Everything we do has a risk, cost, schedule, or performance trade-off. For your leaders to make an appropriate decision, you need to educate them, lead them, talk with them, and engage them in the discussion until full understanding takes place. It's your job. *
Edge Detection for Pattern Recognition: A Survey
James, Alex Pappachen
2016-01-01
This review provides an overview of the literature on the edge detection methods for pattern recognition that inspire from the understanding of human vision. We note that edge detection is one of the most fundamental process within the low level vision and provides the basis for the higher level visual intelligence in primates. The recognition of the patterns within the images relate closely to the spatiotemporal processes of edge formations, and its implementation needs a crossdisciplanry ap...
Selective Electroless Silver Deposition on Graphene Edges
DEFF Research Database (Denmark)
Durhuus, D.; Larsen, M. V.; Andryieuski, Andrei;
2015-01-01
We demonstrate a method of electroless selective silver deposition on graphene edges or between graphene islands without covering the surface of graphene. Modifications of the deposition recipe allow for decoration of graphene edges with silver nanoparticles or filling holes in damaged graphene...... on silica substrate and thus potentially restoring electric connectivity with minimal influence on the overall graphene electrical and optical properties. The presented technique could find applications in graphene based transparent conductors as well as selective edge functionalization and can be extended...
Kononov, A.; Egorov, S. V.; Kvon, Z.D.; Mikhailov, N. N.; Dvoretsky, S. A.; Deviatov, E. V.
2014-01-01
We experimentally investigate spin-polarized electron transport between a permalloy ferromagnet and the edge of a two-dimensional electron system with band inversion, realized in a narrow, 8~nm wide HgTe quantum well. In zero magnetic field, we observe strong asymmetry of the edge potential distribution with respect to the ferromagnetic ground lead. This result indicates, that the helical edge channel, specific for the structures with band inversion, is strongly coupled to the ferromagnetic s...
Electrically tunable spin polarization of chiral edge modes in a quantum anomalous Hall insulator
Zhang, Rui-Xing; Hsu, Hsiu-Chuan; Liu, Chao-Xing
2016-06-01
In the quantum anomalous Hall effect, chiral edge modes are expected to conduct spin polarized current without dissipation and thus hold great promise for future electronics and spintronics with low energy consumption. However, spin polarization of chiral edge modes has never been established in experiments. In this work, we theoretically study spin polarization of chiral edge modes in the quantum anomalous Hall effect, based on both the effective model and more realistic tight-binding model constructed from first-principles calculations. We find that spin polarization can be manipulated by tuning either a local gate voltage or the Fermi energy. We also propose to extract spin information of chiral edge modes by contacting the quantum anomalous Hall insulator to a ferromagnetic lead. The establishment of spin polarization of chiral edge modes, as well as the manipulation and detection in a fully electrical manner, will pave the way to the applications of the quantum anomalous Hall effect in spintronics.
Edge and line detection of complicated and blurred objects
Haugsdal, Kari
2010-01-01
This report deals with edge and line detection in pictures with complicated and/or blurred objects. It explores the alternatives available, in edge detection, edge linking and object recognition. Choice of methods are the Canny edge detection and Local edge search processing combined with regional edge search processing in the form of polygon approximation.
A new fuzzy edge detection algorithm
Institute of Scientific and Technical Information of China (English)
SunWei; XiaLiangzheng
2003-01-01
Based upon the maximum entropy theorem of information theory, a novel fuzzy approach for edge detection is presented. Firsdy, a definition of fuzzy partition entropy is proposed after introducing the concepts of fuzzy probability and fuzzy partition. The relation of the probability partition and the fuzzy c-partition of the image gradient are used in the algorithm. Secondly, based on the conditional probabilities and the fuzzy partition, the optimal thresholding is searched adaptively through the maximum fuzzy entropy principle, and then the edge image is obtained. Lastly, an edge-enhancing procedure is executed on the edge image. The experimental results show that the proposed approach performs well.
An edge index for topological insulators
Prodan, Emil
2009-03-01
Topological insulators display dissipationless currents flowing at the edges of the samples. These currents are associated to chiral edge modes, whose existence is intrinsically linked to the topology of the electronic states of the bulk. The edge modes can be easily investigated when the edges are smooth and have a periodicity, but as soon as the periodicity is absent, the problem becomes un-traceable by purely theoretical means. In my talk I will exemplify the use of non-commutative calculus to explore the properties, especially the stability of the edge modes. For example, using such techniques one can give a fairly elementary proof that the edge modes in Chern insulators survive even for a rough (random) edge. Similarly, for the Spin-Hall effect, one can define an observable and its associated current whose conductance remains quantized during various deformations of the Hamiltonian system. It turns out that in all cases, the edge conductance is given by the index of a Fredholm operator, which provides a new topological invariant linked directly to the edge rather than the bulk.
IMAGE ANALYSIS BASED ON EDGE DETECTION TECHNIQUES
Institute of Scientific and Technical Information of China (English)
纳瑟; 刘重庆
2002-01-01
A method that incorporates edge detection technique, Markov Random field (MRF), watershed segmentation and merging techniques was presented for performing image segmentation and edge detection tasks. It first applies edge detection technique to obtain a Difference In Strength (DIS) map. An initial segmented result is obtained based on K-means clustering technique and the minimum distance. Then the region process is modeled by MRF to obtain an image that contains different intensity regions. The gradient values are calculated and then the watershed technique is used. DIS calculation is used for each pixel to define all the edges (weak or strong) in the image. The DIS map is obtained. This help as priority knowledge to know the possibility of the region segmentation by the next step (MRF), which gives an image that has all the edges and regions information. In MRF model,gray level l, at pixel location i, in an image X, depends on the gray levels of neighboring pixels. The segmentation results are improved by using watershed algorithm. After all pixels of the segmented regions are processed, a map of primitive region with edges is generated. The edge map is obtained using a merge process based on averaged intensity mean values. A common edge detectors that work on (MRF) segmented image are used and the results are compared. The segmentation and edge detection result is one closed boundary per actual region in the image.
Visible imaging of edge turbulence in NSTX
International Nuclear Information System (INIS)
Edge plasma turbulence in tokamaks and stellarators is believed to cause the radical heat and particle flux across the separatrix and into the scrape-off-layers of these devices. This paper describes initial measurements of 2-D space-time structure of the edge density turbulence made using a visible imaging diagnostic in the National Spherical Torus Experiment (NSTX). The structure of the edge turbulence is most clearly visible using a method of gas puff imaging to locally illuminate the edge density turbulence
A Gravitational Edge Detection for Multispectral Images
Directory of Open Access Journals (Sweden)
Genyun Sun
2013-07-01
Full Text Available Gravitational edge detection is one of the new edge detection algorithms that is based on the law of gravity. This algorithm assumes that each image pixel is a celestial body with a mass represented by its grayscale intensity and their interactions are based on the Newtonian laws of gravity. In this article, a multispectral version of the algorithm is introduced. The method uses gravitational techniques in combination with metric tensor to detect edges of multispectral images including color images. To evaluate the performances of the proposed algorithm, several experiments are performed. The experimental results confirm the efficiency of the multispectral gravitational edge detection.
Edge mode spectroscopy and imaging for film edge properties in magnetic nanostructures
McMichael, Robert
2014-03-01
Lithography is an act of violence. Often, films are almost entirely obliterated by patterning, leaving only nanostructures behind with film edges that have borne the brunt of the damage, edges that carry with them the scars of energetic ion bombardment, reactive ions, liftoff and exposure to ambient conditions. In this talk, I will present a variation on ferromagnetic resonance force microscopy that can provide insight into the magnetic properties of film edges in magnetic nanostructures. The method relies on the non-uniformity of the magnetic field in patterned-film nanostructures that are magnetized in-plane, specifically, the low-field regions that form near where the magnetization is directed normal to the edge. In these regions, localized precession forms as trapped spin wave modes, and the resonance condition of these modes serves as an indicator of the edge properties. I will present modeling and measurements on a 500 nm diameter, 25 nm thick Permalloy disk to illustrate the method. Micromagnetic modeling of this disk predicts a main mode that is nearly uniform across the sample and three localized edge modes with higher resonance fields. The spectra measured with various tip positions and mode imaging are consistent with the modeling results. In addition to a strong center mode, three distinct edge modes are observed when the tip is near the disk edge. For a symmetric disk, the modeling predicts that the edge mode resonances are identical on the two opposite edges. However, the measured edge mode resonances on opposite edges of the disk are detected at different resonance fields, suggesting inhomogeneity of the edge properties. By rotating the applied field, we control the position of the localized edge mode along the edge of the disk and confirm that the edge mode resonance field has a strong angular dependence, showing that edge mode properties can vary significantly in a nominally circular disk.
Edges and Diffractive Effects in Casimir Energies
Kabat, Daniel; Nair, V P
2010-01-01
The prototypical Casimir effect arises when a scalar field is confined between parallel Dirichlet boundaries. We study corrections to this when the boundaries themselves have apertures and edges. We consider several geometries: a single plate with a slit in it, perpendicular plates separated by a gap, and two parallel plates, one of which has a long slit of large width, related to the case of one plate being semi-infinite. We develop a general formalism for studying such problems, based on the wavefunctional for the field in the gap between the plates. This formalism leads to a lower dimensional theory defined on the open regions of the plates or boundaries. The Casimir energy is then given in terms of the determinant of the nonlocal differential operator which defines the lower dimensional theory. We develop perturbative methods for computing these determinants. Our results are in good agreement with known results based on Monte Carlo simulations. The method is well suited to isolating the diffractive contri...
Edge effects and geometric constraints: a landscape-level empirical test.
Ribeiro, Suzy E; Prevedello, Jayme A; Delciellos, Ana Cláudia; Vieira, Marcus Vinícius
2016-01-01
Edge effects are pervasive in landscapes yet their causal mechanisms are still poorly understood. Traditionally, edge effects have been attributed to differences in habitat quality along the edge-interior gradient of habitat patches, under the assumption that no edge effects would occur if habitat quality was uniform. This assumption was questioned recently after the recognition that geometric constraints tend to reduce population abundances near the edges of habitat patches, the so-called geometric edge effect (GEE). Here, we present the first empirical, landscape-level evaluation of the importance of the GEE in shaping abundance patterns in fragmented landscapes. Using a data set on the distribution of small mammals across 18 forest fragments, we assessed whether the incorporation of the GEE into the analysis changes the interpretation of edge effects and the degree to which predictions based on the GEE match observed responses. Quantitative predictions were generated for each fragment using simulations that took into account home range, density and matrix use for each species. The incorporation of the GEE into the analysis changed substantially the interpretation of overall observed edge responses at the landscape scale. Observed abundances alone would lead to the conclusion that the small mammals as a group have no consistent preference for forest edges or interiors and that the black-eared opossum Didelphis aurita (a numerically dominant species in the community) has on average a preference for forest interiors. In contrast, incorporation of the GEE suggested that the small mammal community as a whole has a preference for forest edges, whereas D. aurita has no preference for forest edges or interiors. Unexplained variance in edge responses was reduced by the incorporation of GEE, but remained large, varying greatly on a fragment-by-fragment basis. This study demonstrates how to model and incorporate the GEE in analyses of edge effects and that this
Introduction: Centering on the Edge
Directory of Open Access Journals (Sweden)
Anne Dalke
2007-01-01
Full Text Available [First two paragraphs][T]here is growing resistance to embracing interdisciplinarity, in part because we are simply tired of hearing about it and in part because, in practice, it often requires attending the meetings of more than one department. Few are willing to concede that the reason we now need it so desperately stems from the mismatch between how we structured knowledge decades ago to create departments and how we organize it today. (Tartar, 2005, p. B2 As the international academic enterprise settles into the first decade of the twenty-first century, the future of our work is in flux. Academic specializations established a century ago no longer adequately reflect the growing points of human thought, and the opening of higher education to wider populations of students has challenged the relevance of traditional disciplines for future lives and careers. In this context, teachers and scholars have been rethinking the academic enterprise and the functions it serves for their students; new centers are being organized around what was once thought to mark the edge of knowledge-making. At Bryn Mawr College in the USA, where many of the contributors of this special issue teach, the Center for Science in Society has been an important locus for such restructuring.
Yukawa Unification on the Edge
Poh, Zijie
2015-01-01
In this paper we analyze Yukawa unification in a three family SO(10) SUSY GUT. We perform a global $\\chi^2$ analysis and show that SUSY effects do not decouple even though the universal scalar mass parameter at the GUT scale, $m_{16}$, is found to lie between 15 and 30 TeV with the best fit given for $m_{16} \\approx 25$ TeV. Note, SUSY effects don't decouple since stops and bottoms have mass of order 5 TeV, due to RG running from $M_{GUT}$. The model has many testable predictions. Gauginos are the lightest sparticles and the light Higgs boson is very much Standard Model-like. The model is consistent with flavor and CP observables with the $BR(\\mu \\to e\\gamma)$ close to the experimental upper bound. With such a large value of $m_{16}$ we clearly cannot be considered "natural" SUSY nor are we "Split" SUSY. We are thus in the region in between or "SUSY on the Edge."
Blob/hole formation and zonal-flow generation in the edge plasma of the JET tokamak
DEFF Research Database (Denmark)
Xu, G.S.; Naulin, Volker; Fundamenski, W.;
2009-01-01
The first experimental evidence showing the connection between blob/hole formation and zonal-flow generation was obtained in the edge plasma of the JET tokamak. Holes as well as blobs are observed to be born in the edge shear layer, where zonal-flows shear off meso-scale coherent structures, lead...
Reduction in Edge-Ringing in Aberrated Images of Coherent Edge Objects by Multishaded Aperture
Venkanna Mekala; Karuna Sagar Dasari
2014-01-01
The images of a straight edge in coherent illumination produced by an optical system with circular aperture and apodized with multiple filters have been studied. The most common problem encountered in the coherent-imaging techniques is the edge-ringing. To minimize the edge-ringing, multishaded aperture method has been proposed. Image intensity distribution curves are drawn and edge-ringing values are evaluated. The results are compared to that of the airy case with the use of single, double ...
Edge Detection with Sub-pixel Accuracy Based on Approximation of Edge with Erf Function
M. Hagara; P. Kulla
2011-01-01
Edge detection is an often used procedure in digital image processing. For some practical applications is desirable to detect edges with sub-pixel accuracy. In this paper we present edge detection method for 1-D images based on approximation of real image function with Erf function. This method is verified by simulations and experiments for various numbers of samples of simulated and real images. Results of simulations and experiments are also used to compare proposed edge detection scheme wi...
Gravitational acceleration and edge effects in molecular clouds
Li, Guang-Xing; Megeath, Tom; Wyrowski, Friedrich
2016-01-01
Gravity plays important roles in the evolution of molecular clouds. We present an acceleration mapping method to estimate the acceleration induced by gravitational interactions in molecular clouds based on observational data. We find that the geometry of a region has a significant impact on the behavior of gravity. In the Pipe nebula which can be approximated as a gas filament, we find that gravitational acceleration can effectively compress the end of this filament, which may have triggered star formation. We identify this as the "gravitational focusing" effect proposed by Burkert & Hartman (2004). In the sheet-like IC348-B3 region, gravity can lead to collapse at its edge, while in the centrally condensed NGC1333 cluster-forming region gravity can drive accretion towards the center. In general, gravitational acceleration tends to be enhanced in the localized regions around the ends of the filaments and the edges of sheet-like structures. Neglecting magnetic fields, these "gravitational focusing" and "ed...
Theory of Double Ladder Lumped Circuits With Degenerate Band Edge
Sloan, Jeff; Capolino, Filippo
2016-01-01
Conventional periodic LC ladder circuits exhibit a regular band edge between a pass and a stop band. Here for the first time we develop the theory of simple yet unconventional double ladder circuits exhibiting a special degeneracy condition referred to as degenerate band edge (DBE). This special DBE condition is associated with four independent eigenstates of the double ladder that coalesce into a single one when the operative frequency coincides with the DBE one. In particular, we show that double ladder resonators may exhibit giant loaded quality factor near the DBE and stable resonance frequency against load variations. These two properties in the proposed circuit are superior to the analogous properties in single ladder circuits. Our proposed analysis leads to analytic expressions for all circuit quantities thus providing insight into the very complex behavior near points of degeneracy in periodic circuits; and provides a design procedure for the use of such double ladder in practical applications. Intere...
Softening of edges of solids by surface tension
International Nuclear Information System (INIS)
Surface tension tends to minimize the area of interfaces between pieces of matter in different thermodynamic phases, be they in the solid or the liquid state. This can be relevant for the macroscopic shape of very soft solids and lead to a roughening of initially sharp edges. We calculate this effect for a Neo-Hookean elastic solid, with assumptions corresponding to actual experiments, namely the case where an initially sharp edge is rounded by the effect of surface tension felt when the fluid surrounding the soft solid (and so surface tension) is changed at the solid/liquid boundary. We consider two opposite limits where the analysis can be carried to the end, the one of a shallow angle and the one of a very sharp angle. Both cases yield a discontinuity of curvature in the state with surface tension although the initial state had a discontinuous slope. (paper)
Reprint of : Time dependent electronic transport in chiral edge channels
Fève, G.; Berroir, J.-M.; Plaçais, B.
2016-08-01
We study time dependent electronic transport along the chiral edge channels of the quantum Hall regime, focusing on the role of Coulomb interaction. In the low frequency regime, the a.c. conductance can be derived from a lumped element description of the circuit. At higher frequencies, the propagation equations of the Coulomb coupled edge channels need to be solved. As a consequence of the interchannel coupling, a charge pulse emitted in a given channel fractionalized in several pulses. In particular, Coulomb interaction between channels leads to the fractionalization of a charge pulse emitted in a given channel in several pulses. We finally study how the Coulomb interaction, and in particular the fractionalization process, affects the propagation of a single electron in the circuit. All the above-mentioned topics are illustrated by experimental realizations.
Edge localized modes control: experiment and theory
Energy Technology Data Exchange (ETDEWEB)
Bedoulet, M.; Huysmans, G.; Thomas, P.; Joffrin, E.; Rimini, F.; Monier-Garbet, P.; Grosman, A.; Ghendrih, P. [Association Euratom-CEA, Centre d' Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Parail, V.; Lomas, P.; Matthews, G.; Wilson, H.; Gryaznevich, M.; Gonsell, G.; Loarte, A.; Saibene, G.; Sartori, R.; Leonard, A.; Snyder, P.; Evans, T.; Gohil, P.; Burell, H.; Moyer, R.; Kamada, Y.; Oyama, N.; Hatae, T.; Degeling, A.; Martin, Y.; Lister, J.; Rapp, J.; Perez, C.; Lang, P.; Chankin, A.; Eich, T.; Sips, A.; Stober, J.; Horton, L.; Kallenbach, A.; Suttrop, W.; Saarelma, S.; Cowley, S.; Lonnroth, J.; Kamiya, K.; Shimada, M.; Polevoi, A.; Federici, G
2004-07-01
modelling (JETTO) demonstrated that the edge plasma current increase in ramp-up phase can lead to the destabilization of peeling modes, in agreement with ideal MHD stability models. Experiments on TCV demonstrated the possibility of triggering ELMs with a frequency imposed by rapid vertical plasma displacements induced by control coils. This effect is attributed to the induction of an edge current and hence the destabilization of peeling modes. (authors)
Edge localized modes control: experiment and theory
International Nuclear Information System (INIS)
current increase in ramp-up phase can lead to the destabilization of peeling modes, in agreement with ideal MHD stability models. Experiments on TCV demonstrated the possibility of triggering ELMs with a frequency imposed by rapid vertical plasma displacements induced by control coils. This effect is attributed to the induction of an edge current and hence the destabilization of peeling modes. (authors)
[Microbes on the edge of global biosphere].
Naganuma, T
2000-12-01
The search for life on the edge of global biosphere is a frontier to bridge conventional bio/ecology and exo/astrobiology. This communication reviews the foci of microbiological studies on the inhabitants of the selected "edges", i.e., deep-sea, deep subsurface and Antarctic habitats. The deep-sea is characterized as the no-light (non-photosynthetic) habitat, and the primary production is mostly due to the chemosynthetic autotrophy at the hydrothermal vents and methane-rich seeps. Formation of the chemosynthesis-dependent animal communities in the deep leads to the idea that such communities may be found in "ocean" of the Jovian satellite, Europa. The oxygen minimal layer (OML) in mid-water provides another field of deep-sea research. Modern OML is a relatively thin layer, found between the water depth of 200 and 1000 m, but was much thicker during the periods of oceanic anoxia events (OAEs) in the past. The history of oceanic biosphere is regarded as the cycle of OAE and non-OAE periods, and the remnants of the past OAEs may be seen in the modem OML. Anoxic (no-O2) condition is also characteristic of deep subsurface biosphere. Microorganisms in deep subsurface biosphere exploit every available oxidant, or terminal electron acceptor (TEA), for anaerobic respiration. Sulfate, nitrate, iron (III) and CO2 are the representative TEAs in the deep subsurface. Subsurface of hydrothermal vents, or sub-vent biosphere, may house brine (high salt) habitats and halophilic microorganisms. Some sub-vent halophiles were phylogenetically closely similar to the ones found in the Antarctic habitats which are extremely dry by the liophilizing climate. Below the 3000-4000 m-thick glacier on Antarctica, there have been >70 lakes with liquid water located. One of such sub-glacial lakes, Lake Vostok, has been a target of "life in extreme environments" and is about to be drill-penetrated for microbiological studies. These 'microbiological platforms' will provide new knowledge about the
Manoeuvring along the edge of breathlessness
DEFF Research Database (Denmark)
Jellington, Maria Omel; Overgaard, Dorthe; Sørensen, Erik Elgaard
2016-01-01
. Third, hermeneutical principles were used as all data were interpreted from the viewpoint of each theme. Results Three themes were identified: Manoeuvring along the edge; Dyspnoea within the pattern; and Dyspnoea outside the pattern. They were encompassed by the main finding: Manoeuvring along the edge...
Annotated Bibliography of EDGE2D Use
International Nuclear Information System (INIS)
This annotated bibliography is intended to help EDGE2D users, and particularly new users, find existing published literature that has used EDGE2D. Our idea is that a person can find existing studies which may relate to his intended use, as well as gain ideas about other possible applications by scanning the attached tables
Comprehensive Infrared Image Edge detection Algorithm
Directory of Open Access Journals (Sweden)
Abhishek Gudipalli
2012-10-01
Full Text Available Edge detection is one of the most powerful image analysis tools for enhancing and detecting edges. Indeed, identifying and localizing edges are a low level task in a variety of applications such as 3-D reconstruction, shape recognition, image compression, enhancement, and restoration. This paper introduces a new algorithm for detecting edges based on color space models. In this RGB image is taken as an input image and transforming the RGB image to color models such as YUV, YCbCr and XYZ. The edges have been detected for each component in color models separately and compared with the original image of that particular model. In order to measure the quality assessment between images, SSIM (Structural Similarity Index Method and VIF (Visual Information Fidelity has been calculated. The results have shown that XYZ color model is having high SSIM value and VIF value. In the previous papers, edge detection based on RGB color model has low SSIM and VIF values. So by converting the images into different color models shows a significant improvement in detection of edges. Keywords: Edge detection, Color models, SSIM, VIF.
Breaking graph symmetries by edge colourings
Lehner, Florian
2016-01-01
The distinguishing index $D'(G)$ of a graph $G$ is the least number of colours needed in an edge colouring which is not preserved by any non-trivial automorphism. Broere and Pil\\'sniak conjectured that if every non-trivial automorphism of a countable graph $G$ moves infinitely many edges, then $D'(G) \\leq 2$. We prove this conjecture.
Annotated Bibliography of EDGE2D Use
Energy Technology Data Exchange (ETDEWEB)
J.D. Strachan and G. Corrigan
2005-06-24
This annotated bibliography is intended to help EDGE2D users, and particularly new users, find existing published literature that has used EDGE2D. Our idea is that a person can find existing studies which may relate to his intended use, as well as gain ideas about other possible applications by scanning the attached tables.
Blood lead levels ... is used to screen people at risk for lead poisoning. This may include industrial workers and children ... also used to measure how well treatment for lead poisoning is working. Lead is common in the ...
Lead Poisoning Prevention Tips
... or removed safely. How are children exposed to lead? Lead-based paint and lead contaminated dust are ... What can be done to prevent exposure to lead? It is important to determine the construction year ...
International Nuclear Information System (INIS)
Fabrication programme lead in radiation protection: lead bricks, radiation protection tables and windows, locks, lead containers, vaults and bunkers, radiation protection capsules as well as lead fillings for reactor aggregates. (RW/LH)
On edge graceful labelings of disjoint unions of $2r$-regular edge graceful graphs
Riskin, Adrian; Weidman, Georgia
2006-01-01
We prove that if $G$ is a $2r$-regular edge graceful $(p,q)$ graph with $(r,kp)=1$ then $kG$ is edge graceful for odd $k$. We also prove that for certain specific classes of $2r$-regular edge graceful graphs it is possible to drop the requirement that $(r,kp)=1$
More results on oscillating edge-flames
International Nuclear Information System (INIS)
We examine a simple model of a side-anchored non-premixed edge-flame in order to gain insights into the oscillations that are sometimes observed in microgravity candle burning, flame-spread over liquids, etc. Previous results describe the role played by the Lewis number of the fuel, and the Damkoehler number, and here we examine both the effects of an on-edge and off-edge convective flow, and the effects of a heat sink. The on-edge flow and the heat sink tend to destabilize and the off-edge flow tends to stabilize, results consistent with our hypothesis regarding the genesis of the oscillations. (c) 2000 American Institute of Physics
Magnetism of zigzag edge phosphorene nanoribbons
International Nuclear Information System (INIS)
We have investigated, by means of ab initio calculations, the electronic and magnetic structures of zigzag edge phosphorene nanoribbons (ZPNRs) with various widths. The stable magnetic state was found in pristine ZPNRs by allowing the systems to be spin-polarized. The ground state of pristine ZPNRs prefers ferromagnetic order in the same edge but antiferromagnetic order between two opposite edges. The magnetism arises from the dangling bond states as well as edge localized π-orbital states. The presence of a dangling bond is crucial to the formation of the magnetism of ZPNRs. The hydrogenated ZPNRs get nonmagnetic semiconductors with a direct band gap. While, the O-saturated ZPNRs show magnetic ground states due to the weak P-O bond in the ribbon plane between the pz-orbitals of the edge O and P atoms.
Edge exchangeable models for network data
Crane, Harry
2016-01-01
Exchangeable models for vertex labeled graphs cannot replicate the large sample behaviors of sparsity and power law degree distributions observed in many network datasets. Out of this mathematical impossibility emerges the question of how network data can be modeled in a way that reflects known empirical behaviors and respects basic statistical principles. We address this question by observing that edges, not vertices, act as the statistical units in most network datasets, making a theory of edge labeled networks more natural for most applications. Within this context we introduce the new invariance principle of {\\em edge exchangeability}, which unlike its vertex exchangeable counterpart can produce networks with sparse and/or power law structure. We characterize the class of all edge exchangeable network models and identify a particular two parameter family of models with suitable theoretical properties for statistical inference. We discuss issues of estimation from edge exchangeable models and compare our a...
A synthesis for exactly 3-edge-connected graphs
Kingsford, Carl; Marçais, Guillaume
2009-01-01
A multigraph is exactly k-edge-connected if there are exactly k edge-disjoint paths between any pair of vertices. We characterize the class of exactly 3-edge-connected graphs, giving a synthesis involving two operations by which every exactly 3-edge-connected multigraph can be generated. Slightly modified syntheses give the planar exactly 3-edge-connected graphs and the exactly 3-edge-connected graphs with the fewest possible edges.
Edge Detection with Sub-pixel Accuracy Based on Approximation of Edge with Erf Function
Directory of Open Access Journals (Sweden)
M. Hagara
2011-06-01
Full Text Available Edge detection is an often used procedure in digital image processing. For some practical applications is desirable to detect edges with sub-pixel accuracy. In this paper we present edge detection method for 1-D images based on approximation of real image function with Erf function. This method is verified by simulations and experiments for various numbers of samples of simulated and real images. Results of simulations and experiments are also used to compare proposed edge detection scheme with two often used moment-based edge detectors with sub-pixel precision.
Elastically Deformable Side-Edge Link for Trailing-Edge Flap Aeroacoustic Noise Reduction
Khorrami, Mehdi R. (Inventor); Lockard, David P. (Inventor); Moore, James B. (Inventor); Su, Ji (Inventor); Turner, Travis L. (Inventor); Lin, John C. (Inventor); Taminger, Karen M. (Inventor); Kahng, Seun K. (Inventor); Verden, Scott A. (Inventor)
2014-01-01
A system is provided for reducing aeroacoustic noise generated by an aircraft having wings equipped with trailing-edge flaps. The system includes a plurality of elastically deformable structures. Each structure is coupled to and along one of the side edges of one of the trailing-edge flaps, and is coupled to a portion of one of the wings that is adjacent to the one of the side edges. The structures elastically deform when the trailing-edge flaps are deployed away from the wings.
Edge states in a honeycomb lattice: effects of anisotropic hopping and mixed edges
Dahal, Hari P.; Hu, Zi-Xiang; Sinitsyn, N. A.; YANG Kun; Balatsky, A. V.
2009-01-01
We study the edge states in graphene in the presence of a magnetic field perpendicular to the plane of the lattice. Most of the works done so far discuss the edge states in either zigzag or armchair edge graphene considering an isotropic electron hopping. In practice, graphene can have mixture of armchair and zigzag edges and the electron hopping can be anisotropic, which is the subject of this article. We predict that the mixed edges smear the enhanced local density of states (LDOS) at E=0 o...
The Hidden K-edge Signal in K-edge Imaging
Bateman, Christopher J; de Ruiter, Niels J A; Butler, Anthony P; Butler, Philip H; Renaud, Peter F
2015-01-01
K-edge imaging is commonly used for viewing contrast pharmaceuticals in a variety of multi-energy x-ray imaging techniques, ranging from dual-energy and spectral computed tomography to fluoroscopy. When looking for the K-edge signal of a specific contrast, by taking measurements either side of the K-edge, it is found that the K-edge is not always observable for low concentrations. We have also observed that the ability to see the K-edge is unit dependent - a K-edge that is not observable in computed tomography (CT) reconstructed linear attenuation units can often be made visible by converting to Hounsfield units. This paper presents an investigation of this K-edge hiding phenomenon. We conclude that if a multi-energy x-ray measurement of any K-edge material contains a signal of any other material, then there will be a positive concentration of that K-edge material below which its K-edge cannot be observed without extracting the K-edge signal through means of basis decomposition. Mathematical descriptions of t...
Background Modelling Using Edge-Segment Distributions
Directory of Open Access Journals (Sweden)
Jaemyun Kim
2013-02-01
Full Text Available We propose an edge‐segment‐based statistical background modelling algorithm to detect the moving edges for the detection of moving objects using a static camera. Traditional pixel intensity‐based background modelling algorithms face difficulties in dynamic environments since they cannot handle sudden changes in illumination. They also bring out ghosts when a sudden change occurs in the scene. To cope with this issue, intensity and noise robust edge‐based features have emerged. However, existing edge‐pixel‐based methods suffer from scattered moving edge pixels since they cannot utilize the shape. Moreover, traditional segment‐ based methods cannot handle edge shape variations and miss moving edges when they come close to the background edges. Unlike traditional approaches, our proposed method builds the background model from ordinary training frames that may contain moving objects. Furthermore, it does not leave any ghosts behind. Moreover, our method uses an automatic threshold for every background edge distribution for matching. This makes our approach robust to illumination change, camera movement and background motion. Experiments show that our method outperforms others and can detect moving edges efficiently despite the above mentioned difficulties.
Energy Technology Data Exchange (ETDEWEB)
Good, L.; Wirdzek, P.
1999-07-01
Equipment? System? Building? Campus? Neighborhood? Community? Region? What is to be audited and what needs to be corrected? Can the energy management professional decide, or should the customer? Over the last few decades, energy professionals have been evaluating energy use in order to balance clients' expenditures with acceptable levels of service. Traditionally, professional expertise and creativity have been limited more by budget than any other single element. Today, energy and the environment are tightly intertwined. In the future, effective energy management may not be possible without considering the relationships between them. Conversely, environmental protection cannot be achieved without considering energy production, distribution, and use. To this end, two powerful federal organizations, the US Environmental Protection Agency (EPA) and the US Department of Energy (DOE), have been engaged in defining the interrelationships of these areas and fashioning national energy policies aimed at awakening Americans to these facts. Environmental demands are becoming a factor in efficiency equations. Energy management professionals should prepare a response. They will face demands for cutting-edge audits that reach further than giving utility power just a trim in the energy barber shop. Survival in the business of energy management will require a broader perspective. One need only look to current advertisements by national and international corporations which praise the environmental benefits of their products and even their places of business as cleaner than their competitors'. For the energy management professional then, energy diversity and source versus site considerations are opportunities to be identified in the audit process, in addition to replacement of inefficient equipment. The country is rich with technology choices, with documented experience, and with the knowledge to create systems that can mine deep savings. True, some have niche
DEFF Research Database (Denmark)
Tanenbaum, David M.; Dam, Henrik Friis; Rösch, R.;
2012-01-01
Fully roll-to-roll processed polymer solar cell modules were prepared, characterized, and laminated. Cell modules were cut from the roll and matched pairs were selected, one module with exposed cut edges, the other laminated again with the same materials and adhesive sealing fully around the cut...... edges. The edge sealing rim was 10 mm wide. Cell modules were characterized by periodic measurements of IV curves over extended periods in a variety of conditions, as well as by a variety of spatial imaging techniques. Data show significant stability benefits of the edge sealing process. The results...... of the imaging experiments show that the ingress of atmospheric reactants from the edges leads to degradation. In the case of edge sealed devices the same effects are observed but significantly slowed down. In particular, the fast nonlinear degradation is eliminated....
Differential Search Algorithm Based Edge Detection
Gunen, M. A.; Civicioglu, P.; Beşdok, E.
2016-06-01
In this paper, a new method has been presented for the extraction of edge information by using Differential Search Optimization Algorithm. The proposed method is based on using a new heuristic image thresholding method for edge detection. The success of the proposed method has been examined on fusion of two remote sensed images. The applicability of the proposed method on edge detection and image fusion problems have been analysed in detail and the empirical results exposed that the proposed method is useful for solving the mentioned problems.
Edge of Chaos and Genesis of Turbulence
Chian, Abraham C -L; Rempel, Erico
2013-01-01
The edge of chaos is analyzed in a spatially extended system, modeled by the regularized long-wave equation, prior to the transition to permanent spatiotemporal chaos. In the presence of coexisting attractors, a chaotic saddle is born at the basin boundary due to a smooth-fractal metamorphosis. As a control parameter is varied, the chaotic transient evolves to well-developed transient turbulence via a cascade of fractal-fractal metamorphoses. The edge state responsible for the edge of chaos and the genesis of turbulence is an unstable travelling wave in the laboratory frame, corresponding to a saddle point lying at the basin boundary in the Fourier space.
Adobe Edge Animate CC for dummies
Rohde, Michael
2013-01-01
The easy way to build HTML5 mobile and web apps using Adobe's new Edge Animate CC Edge Animate CC is an approachable WYSIWYG alternative for leveraging the power of languages like HTML5, CSS3, and JavaScript to design and develop for the web and mobile devices, even if you have no programming experience. Written by Michael Rohde, the book calls on this seasoned web developer's wealth of experience using Edge Animate CC, and a companion website includes all code from the book to help you apply what you learn as you go. Features an easy-to-use interface, with a propert
Image Edge Extraction via Fuzzy Reasoning
Dominquez, Jesus A. (Inventor); Klinko, Steve (Inventor)
2008-01-01
A computer-based technique for detecting edges in gray level digital images employs fuzzy reasoning to analyze whether each pixel in an image is likely on an edge. The image is analyzed on a pixel-by-pixel basis by analyzing gradient levels of pixels in a square window surrounding the pixel being analyzed. An edge path passing through the pixel having the greatest intensity gradient is used as input to a fuzzy membership function, which employs fuzzy singletons and inference rules to assigns a new gray level value to the pixel that is related to the pixel's edginess degree.
Edge transport barriers in magnetic fusion plasmas
International Nuclear Information System (INIS)
The present level of understanding of the physics of the formation and sustainment of edge transport barriers in magnetically confined fusion plasmas is presented. The formation of edge transport barriers is studied through evolution of mechanisms which can suppress plasma turbulence and so reduce turbulent driven transport, such as E x B flow shear stabilization of turbulence. Comparisons of theoretical studies with experimental results are described including investigations of zonal flows, which are considered important for saturation and self-regulation of turbulence and turbulence-driven transport. Processes that affect the dynamics and spatial structure of the edge barrier are described with emphasis on the width of the transport barrier. (authors)
Flat-band engineering of mobility edges
Danieli, Carlo; Bodyfelt, Joshua D.; Flach, Sergej
2015-06-01
Properly modulated flat-band lattices have a divergent density of states at the flat-band energy. Quasiperiodic modulations are known to host a metal-insulator transition already in one space dimension. Their embedding into flat-band geometries consequently allows for a precise engineering and fine tuning of mobility edges. We obtain analytic expressions for singular mobility edges for two flat-band lattice examples. In particular, we engineer cases with arbitrarily small energy separations of mobility edge, zeroes, and divergencies.
Edge-Disjoint Fibonacci Trees in Hypercube
Directory of Open Access Journals (Sweden)
Indhumathi Raman
2014-01-01
Full Text Available The Fibonacci tree is a rooted binary tree whose number of vertices admit a recursive definition similar to the Fibonacci numbers. In this paper, we prove that a hypercube of dimension h admits two edge-disjoint Fibonacci trees of height h, two edge-disjoint Fibonacci trees of height h-2, two edge-disjoint Fibonacci trees of height h-4 and so on, as subgraphs. The result shows that an algorithm with Fibonacci trees as underlying data structure can be implemented concurrently on a hypercube network with no communication latency.
Edge-Matching Problems with Rotations
DEFF Research Database (Denmark)
Ebbesen, Martin; Fischer, Paul; Witt, Carsten
2011-01-01
Edge-matching problems, also called puzzles, are abstractions of placement problems with neighborhood conditions. Pieces with colored edges have to be placed on a board such that adjacent edges have the same color. The problem has gained interest recently with the (now terminated) Eternity II...... far. We show that some problems have polynomial time algorithms while others are NP-complete. Especially we show that allowing rotations in one-row puzzles makes the problem NP-hard. We moreover show that many commonly considered puzzles can be emulated by simple puzzles with quadratic pieces, so that...
Reddy, Aravind; Braun, Charles L.
2010-01-01
Lead poisoning has been a problem since early history and continues into modern times. An appealing characteristic of lead is that many lead salts are sweet. In the absence of cane and beet sugars, early Romans used "sugar of lead" (lead acetate) to sweeten desserts, fruits, and sour wine. People most at risk would have been those who consumed the…
Profiles and fluctuations in edge and SOL turbulence
DEFF Research Database (Denmark)
Naulin, Volker; Xu, G.; Vianello, N.;
2012-01-01
propagating structures and parallel transport sets up the observed profiles and how intermittency influences edge conditions. The filamentary blob structures also transport and generate currents in the SOL, which can be investigated by means of local magnetic diagnostics. Finally, the ratio of ion to electron...... temperature in the SOL is an important measure for the influence of finite larmor radius effects on the propagation properties of blobs. Numerical investigations indicate that these effects can lead to an increased self confinement and radial reach of these structures. © 2012 WILEY-VCH Verlag GmbH & Co. KGa...
Jinde Lead lead smelting project starts construction
Institute of Scientific and Technical Information of China (English)
2008-01-01
<正>On Dec.20,the lead smelting project of Jiangxi Jinde Lead started construction in Dexin as a technical renovation project on environmental treatment of Jiangxi Metallurgical Group.The project is the one with the largest investment of Provincial Metallurgical Group in non-ferrous
Pacemaker lead design masquerading as lead fracture
Madhu Gangadhara; Charles Peebles; James Gnanapragasam
2015-01-01
Performing chest X-ray is an important annual investigation to check pacemaker lead integrity during follow-up of patients with pacemakers. Understanding lead design is vital to the correct interpretation of X-rays to prevent inappropriate interventions for patients as highlighted in this case.
Ergodic divertor impact on Tore Supra edge
International Nuclear Information System (INIS)
The present ergodic divertor experiments in Tore Supra have been devoted to benchmarking the operational regimes of the apparatus. Two major effects are reported: on the one hand, strong changes occur in the ergodized boundary layer (up to 20% of the minor radius), and on the other hand, the central plasma and especially the confinement is not directly affected, i.e. the observed modifications are induced by edge effects. The basic trends, which are recorded are a decrease of both the edge electronic temperature and the edge density gradient while the radiated power is increased at the very edge of the ergodic region. The latter feature is in agreement with the impurity line emission characterized by an increase of the peripheral lines with a strong decrease of the central lines. (orig.)
Strain imaging by Bragg edge neutron transmission
Santisteban, J R; Fitzpatrick, M E; Steuwer, A; Withers, P J; Daymond, M R; Johnson, M W; Rhodes, N; Schooneveld, E M
2002-01-01
The Bragg edges appearing in the transmitted time-of-flight spectra of polycrystalline materials have been recorded using a two-dimensional array of detectors. Subsequent analysis has enabled maps of the elastic strain to be produced.
Fast Edge-Searching and Related Problems
Yang, Boting
Given a graph G = (V,E) in which a fugitive hides on vertices or along edges, graph searching problems are usually to find the minimum number of searchers required to capture the fugitive. In this paper, we consider the problem of finding the minimum number of steps to capture the fugitive. We introduce the fast edge-searching problem in the edge search model, which is the problem of finding the minimum number of steps (called the fast edge-search time) to capture the fugitive. We establish relations between the fast edge-search time and the fast search number. While the family of graphs whose fast search number is at most k is not minor-closed for any positive integer k ≥ 2, we show that the family of graphs whose fast edge-search time is at most k is minor-closed. We establish relations between the fast (edge-)searching and the node searching. These relations allow us to transform the problem of computing node search numbers to the problem of computing fast edge-search time or fast search numbers. Using these relations, we prove that the problem of deciding, given a graph G and an integer k, whether the fast (edge-)search number of G is less than or equal to k is NP-complete; and it remains NP-complete for Eulerian graphs. We also prove that the problem of determining whether the fast (edge-)search number of G is a half of the number of odd vertices in G is NP-complete; and it remains NP-complete for planar graphs with maximum degree 4. We present a linear time approximation algorithm for the fast edge-search time that always delivers solutions of at most (1+|V|-1/|E|+1) times the optimal value. This algorithm also gives us a tight upper bound on the fast search number of the graph. We also show a lower bound on the fast search number using the minimum degree and the number of odd vertices.
Edge and core dynamics in harness
International Nuclear Information System (INIS)
Resistive kink oscillations in tokamak plasmas are usually treated as core localized events, yet there there are several mechanisms by which they may interact with the edge dynamics. This suggests that we may regulate edge oscillatory behaviour, or ELMs, by harnessing the natural or contrived sawtooth period and amplitude. In this work I investigate core-edge oscillatory entrainment through direct propagation of heat pulses, inductive coupling, and global higher order resonance effects. In the core of auxiliary heated tokamak plasmas the ineluctable rhythm of slow buildup and rapid conversion of potential energy governs electron and heat radial transport. The growth phase of the sawtooth is accompanied by significant reconnection, then during the collapse the temperature and density in the core fall dramatically. There is evidence from experiments in reversed field pinch devices that ensuing energy fluxes can affect flow shear and confinement at the edge. The basis for this study is the dynamical (BDS) model for edge plasma behavior that was derived from electrostatic resistive MHD equations. The BDS model reflects the major qualitative features of edge dynamics that have been observed, such as L-H transitions and associated ELMs, hysteresis, and spontaneous reversal of poloidal shear flow. Under poorly dissipative conditions the transient behavior of the model can exhibit period-doubling, blue-sky, homoclinic, and other exotic bifurcations. Thus we might ask questions such as: Is it possible to mode-lock the edge dynamics to the core sawteeth? Can we induce, or prevent, a change in direction of shear flow? What about MHD effects? Is core-edge communication one way or is there some feedback? In the simplest prototype for coupled core-edge dynamics I model the sawtooth crash as a periodic power input to the edge potential energy reservoir. This is effected by coupling the BDS model to the dynamical system u = u(1 - u2 - x2) - ωsx, x = x(1-u2 -x2) + ωsu, which has
Magnetic quantum dots and magnetic edge states
International Nuclear Information System (INIS)
Starting with defining the magnetic edge state in a magnetic quantum dot, which becomes quite popular nowadays conjunction with a possible candidate for a high density memory device or spintronic materials, various magnetic nano-quantum structures are reviewed in detail. We study the magnetic edge states of the two dimensional electron gas in strong perpendicular magnetic fields. We find that magnetic edge states are formed along the boundary of the magnetic dot, which is formed by a nonuniform distribution of magnetic fields. These magnetic edge states circulate either clockwise or counterclockwise, depending on the number of missing flux quanta, and exhibit quite different properties, as compared to the conventional ones which are induced by electrostatic confinements in the quantum Hall system. We also find that a close relation between the quantum mechanical eigenstates and the classical trajectories in the magnetic dot. When a magnetic dot is located inside a quantum wire, the edge-channel scattering mechanism by the magnetic quantum dot is very different from that by electrostatic dots. Here, the magnetic dot is formed by two different magnetic fields inside and outside the dot. We study the ballistic edge-channel transport and magnetic edge states in this situation. When the inner field is parallel to the outer one, the two-terminal conductance is quantized and shows the features of a transmission barrier and a resonator. On the other hand, when the inner field is reversed, the conductance is not quantized and all channels can be completely reflected in some energy ranges. The difference between the above two cases results from the distinct magnetic confinements. We also describe successfully the edge states of magnetic quantum rings and others in detail
Refining Nodes and Edges of State Machines
Hallerstede, Stefan; Snook, Colin
2011-01-01
State machines are hierarchical automata that are widely used to structure complex behavioural specifications. We develop two notions of refinement of state machines, node refinement and edge refinement. We compare the two notions by means of examples and argue that, by adopting simple conventions, they can be combined into one method of refinement. In the combined method, node refinement can be used to develop architectural aspects of a model and edge refinement to develop algorithmic aspect...
Edge direction and the structure of networks
Foster, Jacob G.; Foster, David V.; Grassberger, Peter; Paczuski, Maya
2009-01-01
Directed networks are ubiquitous and are necessary to represent complex systems with asymmetric interactions---from food webs to the World Wide Web. Despite the importance of edge direction for detecting local and community structure, it has been disregarded in studying a basic type of global diversity in networks: the tendency of nodes with similar numbers of edges to connect. This tendency, called assortativity, affects crucial structural and dynamic properties of real-world networks, such ...
Directed Percolation with a Wall or Edge
Frojdh, Per; Howard, Martin; Lauritsen, Kent B.
1997-01-01
We examine the effects of introducing a wall or edge into a directed percolation process. Scaling ansatzes are presented for the density and survival probability of a cluster in these geometries, and we make the connection to surface critical phenomena and field theory. The results of previous numerical work for a wall can thus be interpreted in terms of surface exponents satisfying scaling relations generalising those for ordinary directed percolation. New exponents for edge directed percola...
Image Edge Detection Based on Oscillation
Institute of Scientific and Technical Information of China (English)
FAN Hong; WANG Zhi-jie
2005-01-01
A new method for image edge detection based on a pulse neural network is proposed in this paper. The network is locally connected. The external input of each neuron of the network is gray value of the corresponding pixel. The synchrony of the neuron and its neighbors is detected by detection neurons. The edge of the image can be read off at minima of the total activity of the detection neurons.
The perceptual contrast of impossible shadow edges
Soranzo, Alessandro; Galmonte, Alessandra; Agostini, Tiziano
2009-01-01
Luminance ratios along shadow edges remain the same even when they cross reflectance borders. According to Gilchrist (1988, Perception & Psychophysics 43 415 ^ 424) this so-called ratio-invariance property is a crucial factor in the perception of shadows. However, Soranzo and Agostini (2004, Perception 33 1359 ^ 1368) suggested that in some conditions (named `impossible shadows'), a luminance pattern might still be perceived as a shadow even if the ratio-invariance property along its edge ...
Face analysis using curve edge maps
Deboeverie, Francis; Veelaert, Peter; Philips, Wilfried
2011-01-01
This paper proposes an automatic and real-time system for face analysis, usable in visual communication applications. In this approach, faces are represented with Curve Edge Maps, which are collections of polynomial segments with a convex region. The segments are extracted from edge pixels using an adaptive incremental linear-time fitting algorithm, which is based on constructive polynomial fitting. The face analysis system considers face tracking, face recognition and facial feature detectio...
Acoustic metamaterial for subwavelength edge detection
Molerón, Miguel; Daraio, Chiara
2015-01-01
Metamaterials have demonstrated the possibility to produce super-resolved images by restoring propagative and evanescent waves. However, for efficient information transfer, for example, in compressed sensing, it is often desirable to visualize only the fast spatial variations of the wave field (carried by evanescent waves), as the one created by edges or small details. Image processing edge detection algorithms perform such operation, but they add time and complexity to the ima...
FACIAL EXPRESSION RECOGNITION BASED ON EDGE DETECTION
Chen, Xiaoming; Cheng, Wushan
2015-01-01
Relational Over the last two decades, the advances in computer vision and pattern recognition power have opened the door to new opportunity of automatic facial expression recognition system[1]. This paper use Canny edge detection method for facial expression recognition. Image color space transformation in the first place and then to identify and locate human face .Next pick up the edge of eyes and mouth's features extraction. Last we judge the facial expressions after compared wi...
EDGE SENSING DEMOSAICING USING ADAPTIVE WEIGHTED INTERPOLATION
Directory of Open Access Journals (Sweden)
Dev R. Newlin
2013-01-01
Full Text Available Demosaicing is a process of obtaining a full color image by interpolating the missing colors of an image captured from a digital still and video cameras that use a single-sensor array.The edges are not handled properly in the existing demosaicking methods. This study provides an effective demosaicing algorithm applying an adaptive weighted-edge interpolation to handle green pixels. Due to the introduction of adaptive threshold based on the high frequency information for the classification of edges and textures, the interpolation of edges is performed excellently. Adaptive weights depending on spatial and spectral correlation are assigned for interpolation on both edges and smooth region. A refinement scheme based on enhanced effective color interpolation is used to improve the red and blue interpolation to obtain better quality image. As compared with the latest demosaicing algorithms, the proposed algorithm produces the best average demosaicing performance both objectively and subjectively. This approach handles the edges in a proper way and reconstructs the color image with best peak signal to noise ratio.
Understanding the dynamics of fractional edge states with composite fermions
Chklovskii, Dmitri B.; Halperin, Bertrand I.
1996-01-01
Fractional edge states can be viewed as integer edge states of composite fermions. We exploit this to discuss the conductance of the fractional quantized Hall states and the velocity of edge magnetoplasmons.
International Nuclear Information System (INIS)
The magnetic perturbations due to in-vessel coils, foreseen to mitigate edge-localized modes (ELMs) in ITER, could also compromise the confinement of energetic ions. We simulate the losses of fusion alpha particles and neutral beam injection-generated fast ions in ITER under the influence of the 3D perturbations caused by toroidal field coils, ferritic inserts, test blanket modules and ELM control coils (ECCs) with the ASCOT code. The ECCs are found to stochastize the magnetic field deep inside the pedestal in the 15 MA inductive reference operating scenario. Such a field is found insufficient to confine not only the fast but also the thermal ion population, leading to a strongly reduced fast ion source in the edge. Therefore, even with a stochastic edge, no high fast ion power loads are expected. However, the plasma response has not yet been included in the calculation of ITER magnetic background data, and it is probable that the perturbation is currently overestimated. (paper)
Asymmetric edge modes by staggered potential in honeycomb lattice: Spin splitter
Energy Technology Data Exchange (ETDEWEB)
Chen, Son-Hsien, E-mail: d92222006@ntu.edu.tw [Department of Applied Physics and Chemistry, University of Taipei, Taipei 10048, Taiwan (China); Sun, Shih-Jye [Department of Applied Physics, National University of Kaohsiung, Kaohsiung 81148, Taiwan (China); Su, Yu-Hsin; Chang, Ching-Ray [Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (China)
2015-05-07
In honeycomb lattice with staggered potential such as silicene nanoribbon (SN) as used for illustrations here, we show that the lack of inversion symmetry due to buckled structure can lead to asymmetric edge modes where only one edge is utilized in transport, yielding no cross-walk (due to size effect) between edges. We also find asymmetric Hall accumulations formed because of the presence of staggered potential. Applying two opposite out-of-plane electric fields to two adjacent SNs appropriately, so that cross-walk occurs between two internal edge states, the bulk states serve as a spin-splitter that splits two specious of spins (spin-up and spin-down) into those two SNs. The spin-splitter proposed here does not require any magnetic field and thus manipulates spins in a full electric manner.
Edge effects in the magnetic interference pattern of a ballistic SNS junction
Meier, Hendrik; Fal'ko, Vladimir I.; Glazman, Leonid I.
2016-05-01
We investigate the Josephson critical current Ic(Φ ) of a wide superconductor-normal metal-superconductor (SNS) junction as a function of the magnetic flux Φ threading it. Electronic trajectories reflected from the side edges alter the function Ic(Φ ) as compared to the conventional Fraunhofer-type dependence. At weak magnetic fields, B ≲Φ0/d2 , the edge effect lifts zeros in Ic(Φ ) and gradually shifts the minima of that function toward half-integer multiples of the flux quantum. At B >Φ0/d2 , the edge effect leads to an accelerated decay of the critical current Ic(Φ ) with increasing Φ . At larger fields, eventually, the system is expected to cross into a regime of "classical" mesoscopic fluctuations that is specific for wide ballistic SNS junctions with rough edges.
Lee, Yea-Lee; Park, Hee Chul; Ihm, Jisoon; Son, Young-Woo
2015-09-15
Because topological surface states of a single-crystal topological insulator can exist on all surfaces with different crystal orientations enclosing the crystal, mutual interactions among those states contiguous to each other through edges can lead to unique phenomena inconceivable in normal insulators. Here we show, based on a first-principles approach, that the difference in the work function between adjacent surfaces with different crystal-face orientations generates a built-in electric field around facet edges of a prototypical topological insulator such as Bi2Se3. Owing to the topological magnetoelectric coupling for a given broken time-reversal symmetry in the crystal, the electric field, in turn, forces effective magnetic dipoles to accumulate along the edges, realizing the facet-edge magnetic ordering. We demonstrate that the predicted magnetic ordering is in fact a manifestation of the axion electrodynamics in real solids. PMID:26324891
Edge-Fault-Tolerant Edge-Bipancyclicity of Bubble-Sort Graphs
Institute of Scientific and Technical Information of China (English)
Xin Ping XU; Min XU; Jin JING
2012-01-01
The bubble-sort graph Bn is a bipartite graph.Kikuchi and Araki [Edge-bipancyclicity and edge-fault-tolerant bipancyclicity of bubble-sort graphs.Information Processing Letters,100,52-59 (2006)] have proved that Bn is edge-bipancyclic for n ≥ 5 and Bn - F is bipancyclic when n ≥ 4and |F| ≤ n - 3.In this paper,we improve this result by showing that for any edge set F of Bn with |F| ≤ n - 3,every edge of Bn - F lies on a cycle of every even length from 6 to n! for n ≥ 5 and every edge of Bn - F lies on a cycle of every even length from 8 to n! for n =4.
A Shearlets-based Edge Identification Algorithem for Infrared Image
Rui-bin ZOU; Cai-cheng SHI
2013-01-01
A shearlets-based edge identification algorithem for infrared image is proposed. The algorithem demonstrates the performance of edge detection based on shearlets, combines with the edge hysteresis thresholding, designs steps of edge detection, which is proper to use in infrared images.Simultaneously, with the advantage of edge geometric features provided by the shearlets, infrared image were extracted the direction information of edge of Infrared image, and classified. In computer simulations...
Image edge detection based on adaptive weighted morphology
Institute of Scientific and Technical Information of China (English)
Lihui Jiang; Yanying Guo
2007-01-01
A novel morphological edge detector based on adaptive weighted morphological operators is presented. It judges image edge and direction by adaptive weighted morphological structuring elements (SEs). If the edge direction exists, a big weight factor in SE is put; if it does not exist, a small weight factor in SE is put. Thus we can achieve an intensified edge detector. Experimental results prove that the new operator's performance dominates those of classical operators for images in edge detection, and obtains superbly detail edges.
Edge State and Intrinsic Hole Doping in Bilayer Phosphorene
Osada, Toshihito
2014-01-01
Using a simple LCAO model by Harrison, we have qualitatively studied the edge state of bilayer phosphorene, which is a unit structure of the layered crystal of black phosphorus. This model successfully reproduces the isolated edge state in the bulk gap in monolayer phosphorene. In bilayer phosphorene, however, it shows that edge states are almost buried in the valence band and there is no isolated midgap edge state at the zigzag edge. Since the buried edge state works as acceptor, holes are d...
Losing your edge: climate change and the conservation value of range‐edge populations
Evan M. Rehm; Olivas, Paulo; Stroud, James; Feeley, Kenneth J.
2015-01-01
Abstract Populations occurring at species' range edges can be locally adapted to unique environmental conditions. From a species' perspective, range‐edge environments generally have higher severity and frequency of extreme climatic events relative to the range core. Under future climates, extreme climatic events are predicted to become increasingly important in defining species' distributions. Therefore, range‐edge genotypes that are better adapted to extreme climates relative to core populat...
Fabião, António; Reino, Luís; Osborne, Patrick E.; Beja, Pedro; Morgado, Rui; Rotenberry, John T
2009-01-01
Afforestation often causes direct habitat losses for farmland birds of conservation concern, but it is uncertain whether negative effects also extend significantly into adjacent open land. Information is thus required on how these species react to wooded edges, and how their responses are affected by edge and landscape characteristics. These issues were examined in Mediterranean arable farmland, using bird counts at 0, 100, 200, 300 and >300 m from oak, pine and eucalyptus edge...
Flap-edge aeroacoustic measurements and predictions
Brooks, Thomas F.; Humphreys, William M.
2003-03-01
An aeroacoustic model test has been conducted to investigate the mechanisms of sound generation on high-lift wing configurations. This paper presents an analysis of flap side-edge noise, which is often the most dominant source. A model of a main element wing section with a half-span flap was tested at low speeds of up to a Mach number of 0.17, corresponding to a wing chord Reynolds number of approximately 1.7 million. Results are presented for flat (or blunt), flanged, and round flap-edge geometries, with and without boundary-layer tripping, deployed at both moderate and high flap angles. The acoustic database is obtained from a small aperture directional array (SADA) of microphones, which was constructed to electronically steer to different regions of the model and to obtain farfield noise spectra and directivity from these regions. The basic flap-edge aerodynamics is established by static surface pressure data, as well as by computational fluid dynamics (CFD) calculations and simplified edge flow analyses. Distributions of unsteady pressure sensors over the flap allow the noise source regions to be defined and quantified via cross-spectral diagnostics using the SADA output. It is found that shear layer instability and related pressure scatter is the primary noise mechanism. For the flat edge flap, two noise prediction methods based on unsteady-surface-pressure measurements are evaluated and compared to measured noise. One is a new causality spectral approach developed here. The other is a new application of an edge-noise scatter prediction method. The good comparisons for both approaches suggest that the prediction models capture much of the physics. Areas of disagreement appear to reveal when the assumed edge noise mechanism does not fully define the noise production. For the different edge conditions, extensive spectra and directivity are presented. The complexity of the directivity results demonstrate the strong role of edge source geometry and frequency in
Plasma-materials interactions and edge-plasma physics research
International Nuclear Information System (INIS)
This report discusses the: Pisces Program; Pisces Facilities; Pisces Experiments: Materials and Surface Physics; Pisces Experiments: Edge Plasma Physics; and, Theoretical Analysis: Edge Plasma Behavior
Hopfield neural network and its applications on image edge detection
Institute of Scientific and Technical Information of China (English)
Yonghong Zhang(张永宏); Dejin Hu(胡德金); Kai Zhang(张凯); Junjie Xu(徐俊杰)
2004-01-01
A method of image edge detection using the Hopfield neural network (HNN) is proposed in this paper.The image edge parameters are introduced in detail, and the energy function of HNN is given based on the edge parameters. Tests on the image edge detection show that images detected by the proposed method have good edge closeness and true edge, at the same time it has good anti-noise performance. The image edge detection using HNN is better than that obtained by some other edge detection operators.
Disorder effects on helical edge transport in graphene under a strong tilted magnetic field
Huang, Chunli; Cazalilla, Miguel A.
2015-10-01
In a recent experiment, Young et al. [Nature (London) 505, 528 (2014), 10.1038/nature12800] observed a metal to insulator transition as well as transport through helical edge states in monolayer graphene under a strong, tilted magnetic field. Under such conditions, the bulk is a magnetic insulator which can exhibit metallic conduction through helical edges. It was found that the two-terminal conductance of the helical channels deviates from the expected quantized value (=e2/h per edge, at zero temperature). Motivated by this observation, we study the effect of disorder on the conduction through the edge channels. We show that, unlike for helical edges of topological insulators in semiconducting quantum wells, a disorder Rashba spin-orbit coupling does not lead to backscattering, at least to leading order. Instead, we find that the lack of perfect antialignment of the electron spins in the helical channels to be the most likely cause for backscattering arising from scalar (i.e., spin-independent) impurities. The intrinsic spin-orbit coupling and other time-reversal symmetry-breaking and/or sublattice parity-breaking potentials also lead to (subleading) corrections to the channel conductance.
Partnership for Edge Physics Simulation (EPSI)
Energy Technology Data Exchange (ETDEWEB)
Schroder, Peter [California Inst. of Technology, Pasadena, CA (United States)
2015-02-11
We propose to develop advanced simulation codes, based upon an extreme parallelism, first principles kinetic approach, to address the challenges associated with the edge region of magnetically confined plasmas. This work is relevant to both existing magnetic fusion facilities and essential for next-generation burning plasma experiments, such as ITER where success is critically dependent upon H-mode operation achieving an edge pedestal of sufficient height for good core plasma performance without producing deleterious large scale edge localized instabilities. The plasma edge presents a well-known set of multi-physics, multi-scale problems involving complex 3D magnetic geometry. Perhaps the greatest computational challenge is the lack of scale separation – temporal scales for drift waves, Alfven waves, ELM dynamics for example have strong overlap. Similar overlap occurs on the spatial scales for the ion poloidal gyro-radius, drift wave and pedestal width. The traditional approach of separating fusion problems into weakly interacting spatial or temporal domains clearly breaks down in the edge. A full kinetic model (full-f model) must be solved to understand and predict the edge physics including non-equilibrium thermodynamic issues arising from the magnetic topology (the open field lines producing a spatially sensitive velocity hole), plasma wall interactions, neutral and atomic physics. The plan here is to model these phenomena within a comprehensive first principles set of equations without the need for the insurmountable multiple-codes coupling issues by building on the XGC1 code developed under the SciDAC Proto-FSP Center for Plasma Edge Simulation (CPES). This proposal includes the critical participants in the XGC1 development. We propose enhancing the capability of XGC1 by including all the important turbulence physics contained in kinetic ion and electron electromagnetic dynamics, by extending the PIC technology to incorporate several positive features found
Flap Edge Aeroacoustic Measurements and Predictions
Brooks, Thomas F.; Humphreys, William M., Jr.
2000-01-01
An aeroacoustic model test has been conducted to investigate the mechanisms of sound generation on high-lift wing configurations. This paper presents an analysis of flap side-edge noise, which is often the most dominant source. A model of a main element wing section with a half-span flap was tested at low speeds of up to a Mach number of 0.17, corresponding to a wing chord Reynolds number of approximately 1.7 million. Results are presented for flat (or blunt), flanged, and round flap-edge geometries, with and without boundary-layer tripping, deployed at both moderate and high flap angles. The acoustic database is obtained from a Small Aperture Directional Array (SADA) of microphones, which was constructed to electronically steer to different regions of the model and to obtain farfield noise spectra and directivity from these regions. The basic flap-edge aerodynamics is established by static surface pressure data, as well as by Computational Fluid Dynamics (CFD) calculations and simplified edge flow analyses. Distributions of unsteady pressure sensors over the flap allow the noise source regions to be defined and quantified via cross-spectral diagnostics using the SADA output. It is found that shear layer instability and related pressure scatter is the primary noise mechanism. For the flat edge flap, two noise prediction methods based on unsteady surface pressure measurements are evaluated and compared to measured noise. One is a new causality spectral approach developed here. The other is a new application of an edge-noise scatter prediction method. The good comparisons for both approaches suggest that much of the physics is captured by the prediction models. Areas of disagreement appear to reveal when the assumed edge noise mechanism does not fully define the noise production. For the different edge conditions, extensive spectra and directivity are presented. Significantly, for each edge configuration, the spectra for different flow speeds, flap angles, and
Image enhancement based on edge boosting algorithm
Ngernplubpla, Jaturon; Chitsobhuk, Orachat
2015-12-01
In this paper, a technique for image enhancement based on proposed edge boosting algorithm to reconstruct high quality image from a single low resolution image is described. The difficulty in single-image super-resolution is that the generic image priors resided in the low resolution input image may not be sufficient to generate the effective solutions. In order to achieve a success in super-resolution reconstruction, efficient prior knowledge should be estimated. The statistics of gradient priors in terms of priority map based on separable gradient estimation, maximum likelihood edge estimation, and local variance are introduced. The proposed edge boosting algorithm takes advantages of these gradient statistics to select the appropriate enhancement weights. The larger weights are applied to the higher frequency details while the low frequency details are smoothed. From the experimental results, the significant performance improvement quantitatively and perceptually is illustrated. It can be seen that the proposed edge boosting algorithm demonstrates high quality results with fewer artifacts, sharper edges, superior texture areas, and finer detail with low noise.
Trailing edge modifications for flatback airfoils.
Energy Technology Data Exchange (ETDEWEB)
Kahn, Daniel L. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Berg, Dale E.
2008-03-01
The adoption of blunt trailing edge airfoils (also called flatback airfoils) for the inboard region of large wind turbine blades has been proposed. Blunt trailing edge airfoils would not only provide a number of structural benefits, such as increased structural volume and ease of fabrication and handling, but they have also been found to improve the lift characteristics of thick airfoils. Therefore, the incorporation of blunt trailing edge airfoils would allow blade designers to more freely address the structural demands without having to sacrifice aerodynamic performance. These airfoils do have the disadvantage of generating high levels of drag as a result of the low-pressure steady or periodic flow in the near-wake of the blunt trailing edge. Although for rotors, the drag penalty appears secondary to the lift enhancement produced by the blunt trailing edge, high drag levels are of concern in terms of the negative effect on the torque and power generated by the rotor. Hence, devices are sought that mitigate the drag of these airfoils. This report summarizes the literature on bluff body vortex shedding and bluff body drag reduction devices and proposes four devices for further study in the wind tunnel.
Edge states of zigzag bilayer graphite nanoribbons
Rhim, Jun-Won; Moon, Kyungsun
2008-09-01
The electronic structures of zigzag bilayer graphite nanoribbons (Z-BGNRs) with various ribbon widths N are studied within the tight binding approximation. Neglecting the inter-layer hopping amplitude γ4, which is an order of magnitude smaller than the other inter-layer hopping parameters, there exist two fixed Fermi points ± k* independent of the ribbon width with a peculiar energy dispersion near k* as ɛ(k)~ ± (k-k*)N. By investigating the edge states of Z-BGNRs, we notice that the trigonal warping of the bilayer graphene sheets is reflected in the edge state structure. With the inclusion of γ4, the above two Fermi points are not fixed but drift toward the vicinity of the Dirac point with increasing width N, as shown by the finite scaling method, and the peculiar dispersions change to parabolic ones. The edge magnetism of Z-BGNRs is also examined by solving the half-filled Hubbard Hamiltonian for the ribbon using the Hartree-Fock approximation. We have shown that within the same side of the edges, the edge spins are aligned ferromagnetically for the experimentally relevant set of parameters.
Edge states of zigzag bilayer graphite nanoribbons
Energy Technology Data Exchange (ETDEWEB)
Rhim, Jun-Won; Moon, Kyungsun [Department of Physics and Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of)], E-mail: kmoon@yonsei.ac.kr
2008-09-10
The electronic structures of zigzag bilayer graphite nanoribbons (Z-BGNRs) with various ribbon widths N are studied within the tight binding approximation. Neglecting the inter-layer hopping amplitude {gamma}{sub 4}, which is an order of magnitude smaller than the other inter-layer hopping parameters, there exist two fixed Fermi points {+-} k{sup *} independent of the ribbon width with a peculiar energy dispersion near k{sup *} as {epsilon}(k){approx} {+-} (k-k{sup *}){sup N}. By investigating the edge states of Z-BGNRs, we notice that the trigonal warping of the bilayer graphene sheets is reflected in the edge state structure. With the inclusion of {gamma}{sub 4}, the above two Fermi points are not fixed but drift toward the vicinity of the Dirac point with increasing width N, as shown by the finite scaling method, and the peculiar dispersions change to parabolic ones. The edge magnetism of Z-BGNRs is also examined by solving the half-filled Hubbard Hamiltonian for the ribbon using the Hartree-Fock approximation. We have shown that within the same side of the edges, the edge spins are aligned ferromagnetically for the experimentally relevant set of parameters.
International Nuclear Information System (INIS)
Ion implantation at room temperature of lead into aluminum leads to spontaneous phase separation and formation of lead precipitates growing topotactically with the matrix. Unlike the highly pressurized (∼ 1-5 GPa) solid inclusions formed after noble gas implantations, the pressure in the lead precipitates is found to be less than 0.12 GPa. Recently the authors have observed the result that the lead inclusions in aluminum exhibit both superheating and supercooling. In this paper they review and elaborate on these results. Small implantation-induced lead precipitates embedded in an aluminum matrix were studied by x-ray diffraction
Coronary Sinus Lead Extraction.
Cronin, Edmond M; Wilkoff, Bruce L
2015-12-01
Expanded indications for cardiac resynchronization therapy and the increasing incidence of cardiac implantable electronic device infection have led to an increased need for coronary sinus (CS) lead extraction. The CS presents unique anatomical obstacles to successful lead extraction. Training and facility requirements for CS lead extraction should mirror those for other leads. Here we review the indications, technique, and results of CS lead extraction. Published success rates and complications are similar to those reported for other leads, although multiple techniques may be required. Re-implantation options may be limited, which should be incorporated into pre-procedural decision making. PMID:26596810
Localized Edge Vibrations and Edge Reconstruction by Joule Heating in Graphene Nanostructures
DEFF Research Database (Denmark)
Engelund, Mads; Fürst, Joachim Alexander; Jauho, Antti-Pekka;
2010-01-01
Control of the edge topology of graphene nanostructures is critical to graphene-based electronics. A means of producing atomically smooth zigzag edges using electronic current has recently been demonstrated in experiments [Jia et al., Science 323, 1701 (2009)]. We develop a microscopic theory for...
Study of airfoil trailing edge bluntness noise
DEFF Research Database (Denmark)
Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær
This paper deals with airfoil trailing edge noise with special focus on airfoils with blunt trailing edges. Two methods are employed to calculate airfoil noise: The flow/acoustic splitting method and the semi-empirical method. The flow/acoustic splitting method is derived from compressible Navier......-Stokes equations. It provides us possibilities to study details about noise generation mechanism. The formulation of the semi-empirical model is based on acoustic analogy and then curve-fitted with experimental data. Due to its high efficiency, such empirical relation is used for purpose of low noise airfoil...... design or optimization. Calculations from both methods are compared with exist experiments. The airfoil blunt noise is found as a function of trailing edge bluntness, Reynolds number, angle of attack, etc....
Black phosphorus edges: a polarized Raman study
Ribeiro, H.; Villegas, C.; Bahamon, D.; Castro Neto, A.; de Souza, E.; Rocha, A.; Pimenta, M.; de Matos, C.
Black phosphorus (BP) has been recently exfoliated down to few-layer thicknesses revealing numerous interesting features such as a tunable direct bandgap. Ever since, demonstrations of BP electronic devices have bloomed, as well as studies of the electric, optical, mechanical and thermal properties of its bulk and few-layer forms. However, the edges of BP crystals have, so far, been poorly characterized, even though the terminations of layered crystals are known to possess a range of interesting properties. In this work, the edges of exfoliated BP flakes are characterized by polarized confocal Raman spectroscopy. We will present experimental Raman spectra at zigzag and armchair edges, as well as density functional theory calculations that explain the peculiarities of the experimental data. Fapesp, INCT/Nanocarbono, Fapemig, CNPq, MackPesquisa, Grid-Unesp, CENAPAD-SP, and NRF.
Dictionary based Approach to Edge Detection
Chandra, Nitish
2015-01-01
Edge detection is a very essential part of image processing, as quality and accuracy of detection determines the success of further processing. We have developed a new self learning technique for edge detection using dictionary comprised of eigenfilters constructed using features of the input image. The dictionary based method eliminates the need of pre or post processing of the image and accounts for noise, blurriness, class of image and variation of illumination during the detection process itself. Since, this method depends on the characteristics of the image, the new technique can detect edges more accurately and capture greater detail than existing algorithms such as Sobel, Prewitt Laplacian of Gaussian, Canny method etc which use generic filters and operators. We have demonstrated its application on various classes of images such as text, face, barcodes, traffic and cell images. An application of this technique to cell counting in a microscopic image is also presented.
Predictability of the Arctic sea ice edge
Goessling, H. F.; Tietsche, S.; Day, J. J.; Hawkins, E.; Jung, T.
2016-02-01
Skillful sea ice forecasts from days to years ahead are becoming increasingly important for the operation and planning of human activities in the Arctic. Here we analyze the potential predictability of the Arctic sea ice edge in six climate models. We introduce the integrated ice-edge error (IIEE), a user-relevant verification metric defined as the area where the forecast and the "truth" disagree on the ice concentration being above or below 15%. The IIEE lends itself to decomposition into an absolute extent error, corresponding to the common sea ice extent error, and a misplacement error. We find that the often-neglected misplacement error makes up more than half of the climatological IIEE. In idealized forecast ensembles initialized on 1 July, the IIEE grows faster than the absolute extent error. This means that the Arctic sea ice edge is less predictable than sea ice extent, particularly in September, with implications for the potential skill of end-user relevant forecasts.
Controllable edge feature sharpening for dental applications.
Fan, Ran; Jin, Xiaogang
2014-01-01
This paper presents a new approach to sharpen blurred edge features in scanned tooth preparation surfaces generated by structured-light scanners. It aims to efficiently enhance the edge features so that the embedded feature lines can be easily identified in dental CAD systems, and to avoid unnatural oversharpening geometry. We first separate the feature regions using graph-cut segmentation, which does not require a user-defined threshold. Then, we filter the face normal vectors to propagate the geometry from the smooth region to the feature region. In order to control the degree of the sharpness, we propose a feature distance measure which is based on normal tensor voting. Finally, the vertex positions are updated according to the modified face normal vectors. We have applied the approach to scanned tooth preparation models. The results show that the blurred edge features are enhanced without unnatural oversharpening geometry. PMID:24741376
Exploring topological edge states in photonic quasicrystals
Baboux, F; Lemaître, A; Gomez, C; Galopin, E; Gratiet, L Le; Sagnes, I; Amo, A; Bloch, J; Akkermans, E
2016-01-01
We experimentally investigate the topological properties of quasiperiodic chains using cavity polaritons confined in a potential following the Fibonacci sequence. Edge states forming in the gaps of a fractal energy spectrum are imaged both in real and momentum space. These edge states periodically traverse the gaps when varying a structural degree of freedom $\\phi$ of the Fibonacci sequence. The period and direction of the traverses are directly related to the Chern numbers assigned to each gap by the gap-labeling theorem. Additionally, we show that the Chern numbers determine the spatial symmetry properties of the edge states. These results highlight the potential of cavity polaritons to emulate nontrivial topological properties in a controlled environment.
Acoustic metamaterial for subwavelength edge detection
Molerón, Miguel; Daraio, Chiara
2015-08-01
Metamaterials have demonstrated the possibility to produce super-resolved images by restoring propagative and evanescent waves. However, for efficient information transfer, for example, in compressed sensing, it is often desirable to visualize only the fast spatial variations of the wave field (carried by evanescent waves), as the one created by edges or small details. Image processing edge detection algorithms perform such operation, but they add time and complexity to the imaging process. Here we present an acoustic metamaterial that transmits only components of the acoustic field that are approximately equal to or smaller than the operating wavelength. The metamaterial converts evanescent waves into propagative waves exciting trapped resonances, and it uses periodicity to attenuate the propagative components. This approach achieves resolutions ~5 times smaller than the operating wavelength and makes it possible to visualize independently edges aligned along different directions.
Mesh Simplification Using the Edge Attributes
Directory of Open Access Journals (Sweden)
Il Dong Yun
2002-10-01
Full Text Available This paper presents a novel technique for simplifying a triangulated surface at different levels of resolution. While most existing algorithms, based on iterative vertex decimation, employ the distance for error metric, the proposed algorithm utilizes an edge criterion for removing a vertex. An interior angle of a vertex is defined as the maximum value of all possible angles formed by combinations of edges connected to a vertex. Since the surface curvature examined with the interior angle provides more information for decision of vertex removal than the conventional distance measure, the proposed algorithm can approximate the surface with less computation. The height of a triangle, which is formed by the pair of edges, is also used for an additional constraint. The computational complexity can thus be greatly alleviated to logarithmic scale from the exponential scale required for the conventional algorithms, while yielding the comparable error level.
AUTOMATED EDGE DETECTION USING CONVOLUTIONAL NEURAL NETWORK
Directory of Open Access Journals (Sweden)
Mohamed A. El-Sayed
2013-11-01
Full Text Available The edge detection on the images is so important for image processing. It is used in a various fields of applications ranging from real-time video surveillance and traffic management to medical imaging applications. Currently, there is not a single edge detector that has both efficiency and reliability. Traditional differential filter-based algorithms have the advantage of theoretical strictness, but require excessive post-processing. Proposed CNN technique is used to realize edge detection task it takes the advantage of momentum features extraction, it can process any input image of any size with no more training required, the results are very promising when compared to both classical methods and other ANN based methods
Edge effects in composites by moire interferometry
Czarnek, R.; Post, D.; Herakovich, C.
1983-01-01
The very high sensitivity of moire interferometry has permitted the present edge effect experiments to be conducted at a low average stress and strain level, assuring linear and elastic behavior in the composite material samples tested. Sensitivity corresponding to 2450 line/mm moire was achieved with a 0.408 micron/fringe. Simultaneous observations of the specimen face and edge displacement fields showed good fringe definition despite the 1-mm thickness of the specimens and the high gradients, and it is noted that the use of a carrier pattern and optical filtering was effective in even these conditions. Edge effects and dramatic displacement gradients were confirmed in angle-ply composite laminates.
Free edge effects in laminated composites
Herakovich, C. T.
1989-01-01
The fundamental mechanics of free-edge effects in laminated fiber-reinforced composites is examined, reviewing the results of recent experimental and analytical investigations. The derivation of the governing equations for the basic problem is outlined, including the equilibrium and mismatch conditions and the elasticity formulation, and experimental data on axial displacement and shear strain in angle-ply laminates are summarized. Numerical predictions of free-edge deformation and interlaminar and through-thickness stress distributions are presented for cross-ply, angle-ply, and quasi-isotropic laminates, and the mechanisms of edge damage and failure in angle-ply laminates are briefly characterized. Extensive diagrams, drawings, graphs, and photographs are provided.
Finding Well-Balanced Pairs of Edge-Disjoint Trees in Edge-Weighted Graphs
DEFF Research Database (Denmark)
Bang-Jensen, Jørgen; Goncalves, Daniel; Gørtz, Inge Li
2007-01-01
the elements in Y (or equivalently, minimize the maximum of the two sums). In this paper we study the following generalization of the partition problem: given an edge-weighted graph G containing two edge-disjoint spanning trees. Find a pair of edge-disjoint spanning trees such that the maximum weight...... of these two trees is as small as possible. In the case when G is precisely the union of two trees this problem may be seen as a generalization of the partition problem in which we have added a graph structure to the numbers (through the edges) and the extra restriction that only the sets X and Y...... value of an optimal solution. We also show that the approach above may sometimes exclude all the optimal solutions. Both the partition problem and its generalization to the problem above on edge-disjoint spanning trees are special cases of the problem of finding, in a weighted matroid with two disjoint...
Electrochemistry at the edge of a single graphene layer in a nanopore
DEFF Research Database (Denmark)
Banerjee, Sutanuka; Shim, Jeong; Rivera, J.;
2013-01-01
We study the electrochemistry of single layer graphene edges using a nanopore-based structure consisting of stacked graphene and AlO dielectric layers. Nanopores, with diameters ranging from 5 to 20 nm, are formed by an electron beam sculpting process on the stacked layers. This leads to a unique...
... to Z Index Contact Us FAQs What's New Lead Health Effects Exposure and Controls General Resources Enforcement ... section of this webpage. Who is Exposed to Lead? OSHA estimates that approximately 804,000 workers in ...
... Medical Procedures In Vitro Diagnostics Lab Tests Rapid Lead Screening Test Share Tweet Linkedin Pin it More ... reducing the need for a follow-up visit. Lead Risk Links Centers for Disease Control and Prevention ( ...
... Issue Past Issues Feature: Vision Leading Causes of Blindness Past Issues / Summer 2008 Table of Contents For ... have cataracts. They are the leading cause of blindness in the world. By age 80, more than ...
International Nuclear Information System (INIS)
This report describes a system for handling and radioassay of lead, consisting of a robot, a conveyor, and a gamma spectrometer. The report also presents a cost-benefit analysis of options: radioassay and recycling lead vs. disposal as waste
Water contaminated with lead ... The Environmental Protection Agency (EPA) monitors drinking water in the United States. It requires water suppliers to produce annual water quality reports. These reports include information about lead amounts, and they ...
Water contaminated with lead ... The Environmental Protection Agency (EPA) monitors drinking water and requires water suppliers to produce annual water quality reports. These reports, which include information about lead amounts, are available to consumers. For ...
AliEn - EDG Interoperability in ALICE
Bagnasco, S.; Barbera, R.(Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Catania, Italy); Buncic, P.; Carminati, F.; Cerello, P.(Sezione INFN, Turin, Italy); Saiz, P.
2003-01-01
AliEn (ALICE Environment) is a GRID-like system for large scale job submission and distributed data management developed and used in the context of ALICE, the CERN LHC heavy-ion experiment. With the aim of exploiting upcoming Grid resources to run AliEn-managed jobs and store the produced data, the problem of AliEn-EDG interoperability was addressed and an in-terface was designed. One or more EDG (European Data Grid) User Interface machines run the AliEn software suite (Cluster Monitor, Stora...
Refining Nodes and Edges of State Machines
DEFF Research Database (Denmark)
Hallerstede, Stefan; Snook, Colin
2011-01-01
State machines are hierarchical automata that are widely used to structure complex behavioural specifications. We develop two notions of refinement of state machines, node refinement and edge refinement. We compare the two notions by means of examples and argue that, by adopting simple conventions......, they can be combined into one method of refinement. In the combined method, node refinement can be used to develop architectural aspects of a model and edge refinement to develop algorithmic aspects. The two notions of refinement are grounded in previous work. Event-B is used as the foundation for our...
Active-edge planar radiation sensors
Kenney, C. J.; Segal, J.D.; Westbrook, E.; Parker, Sherwood; Hasi, J.; Da Via, C.; Watts, S.; Morse, J
2006-01-01
Many systems in medicine, biology, high-energy physics, and astrophysics require large area radiation sensors. In most of these applications, minimizing the amount of dead area or dead material is crucial. We have developed a new type of silicon radiation sensor in which the device is active to within a few microns of the mechanical edge. Their perimeter is made by a plasma etcher rather than a diamond saw. Their edges can be defined and also passivated by growing, in an intermediate step, a ...
Edge detection techniques for iris recognition system
International Nuclear Information System (INIS)
Nowadays security and authentication are the major parts of our daily life. Iris is one of the most reliable organ or part of human body which can be used for identification and authentication purpose. To develop an iris authentication algorithm for personal identification, this paper examines two edge detection techniques for iris recognition system. Between the Sobel and the Canny edge detection techniques, the experimental result shows that the Canny's technique has better ability to detect points in a digital image where image gray level changes even at slow rate
Edge detection techniques for iris recognition system
Tania, U. T.; Motakabber, S. M. A.; Ibrahimy, M. I.
2013-12-01
Nowadays security and authentication are the major parts of our daily life. Iris is one of the most reliable organ or part of human body which can be used for identification and authentication purpose. To develop an iris authentication algorithm for personal identification, this paper examines two edge detection techniques for iris recognition system. Between the Sobel and the Canny edge detection techniques, the experimental result shows that the Canny's technique has better ability to detect points in a digital image where image gray level changes even at slow rate.
Particle Size Estimation Based on Edge Density
Institute of Scientific and Technical Information of China (English)
WANG Wei-xing
2005-01-01
Given image sequences of closely packed particles, the underlying aim is to estimate diameters without explicit segmentation. In a way, this is similar to the task of counting objects without directly counting them. Such calculations may, for example, be useful fast estimation of particle size in different application areas. The topic is that of estimating average size (=average diameter) of packed particles, from formulas involving edge density, and the edges from moment-based thresholding are used. An average shape factor is involved in the calculations, obtained for some frames from crude partial segmentation. Measurement results from about 80 frames have been analyzed.
Active-edge planar radiation sensors
International Nuclear Information System (INIS)
Many systems in medicine, biology, high-energy physics, and astrophysics require large area radiation sensors. In most of these applications, minimizing the amount of dead area or dead material is crucial. We have developed a new type of silicon radiation sensor in which the device is active to within a few microns of the mechanical edge. Their perimeter is made by a plasma etcher rather than a diamond saw. Their edges can be defined and also passivated by growing, in an intermediate step, a field oxide on the side surfaces. In this paper, the basic architecture and results from a synchrotron beam test are presented
Prodhomme, Pierre-Yves; Toulhoat, Hervé; 10.1016/j.jcat.2011.03.017
2011-01-01
We present the results of DFT calculations of free energy profiles along the reaction pathways starting from 50% coverage of MoS2 M-edge and 100% coverage of S-edge by sulfur, and leading to 37% coverage, i.e. creation of anionic vacancies, upon reduction by dihydrogen and production of H2S. Significant entropic and enthalpic corrections to electronic energies are deduced from the sets of normal modes vibration frequencies computed for all stationary and transition states. On that basis, we revisit and discuss the surface phase diagrams for M- and S- edges as a function of temperature, H2 partial pressure and H2S/H2 molar ratio, with respect to ranges of conditions relevant to industrial hydrotreating operations. We show that in such conditions, anionic vacancies on the M-edge, and surface SH groups on the M- and S- edges, may coexist at equilibrium. Moderate activation barriers connect stationary states along all paths explored.
Group edge choosability of planar graphs without adjacent short cycles
Xin ZHANG; Liu, Guizhen
2011-01-01
In this paper, we aim to introduce the group version of edge coloring and list edge coloring, and prove that all 2-degenerate graphs along with some planar graphs without adjacent short cycles is group $(\\Delta(G)+1)$-edge-choosable while some planar graphs with large girth and maximum degree is group $\\Delta(G)$-edge-choosable.
Optimization of K-edge imaging with spectral CT
He, Peng; Wei, Biao; Cong, Wenxiang; Wang, Ge
2012-01-01
Purpose: Spectral/multienergy CT has the potential to distinguish different materials by K-edge characteristics. K-edge imaging involves the two energy bins on both sides of a K-edge. The authors propose a K-edge imaging optimization model to determine these two energy bins.
Natural domains for edge-degenerate differential operators
Seiler, Jörg
2010-01-01
We study cone differential operators on the half-axis and edge-degenerate differential operators on a half-space. We construct subspaces of edge Sobolev spaces that can be considered as natural domains for edge-degenerate operators and indicate how they can be used in the study of boundary problems for edge-degenerate operators.
Tilings of the Sphere by Edge Congruent Pentagons
Cheuk, Ka Yue; Cheung, Ho Man; Yan, Min
2013-01-01
We study edge-to-edge tilings of the sphere by edge congruent pentagons, under the assumption that there are tiles with all vertices having degree 3. We develop the technique of neighborhood tilings and apply the technique to completely classify edge congruent earth map tilings.
Physics-based edge evaluation for improved color constancy
A. Gijsenij; T. Gevers; J. van de Weijer
2009-01-01
Edge-based color constancy makes use of image derivatives to estimate the illuminant. However, different edge types exist in real-world images such as shadow, geometry, material and highlight edges. These different edge types may have a distinctive influence on the performance of the illuminant esti
A Note on Edge Guards in Art Galleries
Nandakumar, R
2011-01-01
We examine the Art Gallery Problem with Edge Guards. We present a heuristic algorithm to arrange edge guards to guard only the inward side of the walls of any N-vertex simple polygonal gallery using at most roof (N/4) edge guards - a weakened version of Toussaint's conjecture on the number of edge guards that can guard an entire simple polygon
1996-01-01
This is an image of an actual lead ion collision taken from tracking detectors on the NA49 experiment, part of the heavy ion project at CERN. These collisions produce a very complicated array of hadrons as the heavy ions break up. It is hoped that one of these collisions will eventually create a new state of matter known as quark-gluon plasma.
Star formation on the leading edge of a ring-like density wave in Arp 143
Appleton, P. N.
1990-01-01
NGC 2445 is a member of the pair of interacting galaxies Arp 143 (=VV117) and has been classified as an irregular ring galaxy by deVaucouleurs et al. (1976). Although not obviously a classical ring galaxy from its optical appearance, it nevertheless shows many of the symptoms of a collisional off-center ring galaxy in the early stages of development. Optically the galaxy shows a rough ring of super-giant HII regions distributed asymmetrically with respect to the nucleus with most of the emission concentrated on the western side of the galaxy. Researchers mapped the HI emission in this system (with F. Ghigo and J. van Gorkom; NRAO) and the observations show that the disk of NGC 2445 is characterized by a large-scale banana-shaped HI wave with its peak to the west of the nucleus. Nearing-IR imaging (with E. I. Robson and A. J. Adamson; Lancs. Polytechnic, U.K.) demonstrates that, like the HI, the underlying population of old stars is very asymmetrically distributed with the bulk of the stars concentrated to the western side of the galaxy.
Energy Technology Data Exchange (ETDEWEB)
MacQueen, Duncan
2007-12-15
Avoided deforestation has re-emerged as a tool to curb climate change. But how does paying poor countries to keep their forests intact tally with poverty reduction? Doing both at the same time is a challenge, but a necessary one. Forests are not just crucial in keeping the global environment stable; they are also a lifeline for hundreds of millions of the world's poor. Fortunately, a solution to both aims is already in place. Community forest enterprises, if run sustainably and democratically, can both avoid deforestation and pull people out of poverty. Large industrial concessions, on the other hand, generally do neither. The challenge is to overcome vested interests and pave the way for greater political support.
"What Works" Reviewers Find No Learning Edge for Leading Math Texts
Viadero, Debra
2007-01-01
In the recent textbook review by the federal What Works Clearinghouse, only one out of four elementary school math programs has received even a qualified nod from evaluators for its research record. The result shows that most major commercial textbooks can not yet muster the proof that they are any better than their competitors at improving…
Boundary Layer Transition in the Leading Edge Region of a Swept Cylinder in High Speed Flow
Coleman, Colin P.
1998-01-01
Experiments were conducted on a 76 degree swept cylinder to establish the behavior of the attachment line transition process in a low-disturbance level, Mach number 1.6 flow. For a near adiabatic wall condition, the attachment-line boundary layer remained laminar up to the highest attainable Reynolds number. The attachment-line boundary layer transition under the influence of trip wires depended on wind tunnel disturbance level, and a transition onset condition for this flow is established. Internal heating raised the surface temperature of the attachment line to induce boundary layer instabilities. This was demonstrated experimentally for the first time and the frequencies of the most amplified disturbances were determined over a range of temperature settings. Results were in excellent agreement to those predicted by a linear stability code, and provide the first experimental verification of theory. Transition onset along the heated attachment line at an R-bar of 800 under quiet tunnel conditions was found to correlate with an N factor of 13.2. Increased tunnel disturbance levels caused the transition onset to occur at lower cylinder surface temperatures and was found to correlate with an approximate N factor of 1 1.9, so demonstrating that the attachment-line boundary layer is receptive to increases in the tunnel disturbance level.
A comment on the flat plate leading edge shape on laminar-turbulent transition
Czech Academy of Sciences Publication Activity Database
Antoš, Pavel; Jonáš, Pavel; Procházka, Pavel P.
Liberec: Polypress s.r.o, 2015 - (Dančová, P.; Veselý, M.), s. 32-37 [Experimental Fluid Mechanics 2015. Praha (CZ), 17.11.2015-20.11.2015] R&D Projects: GA ČR GAP101/12/1271 Institutional support: RVO:61388998 Keywords : flat plate * laminar-turbulent transition * HW anemometry Subject RIV: BK - Fluid Dynamics
Koch, Stefan; Capaldo, Christopher T.; Samarin, Stanislav; Nava, Porfirio; Neumaier, Irmgard; Skerra, Arne; Sacks, David B; Parkos, Charles A.; Nusrat, Asma
2009-01-01
Wnt signaling pathways regulate proliferation, motility, and survival in a variety of human cell types. Dickkopf-1 (Dkk-1) is a secreted Wnt antagonist that has been proposed to regulate tissue homeostasis in the intestine. In this report, we show that Dkk-1 is secreted by intestinal epithelial cells after wounding and that it inhibits cell migration by attenuating the directional orientation of migrating epithelial cells. Dkk-1 exposure induced mislocalized activation of Cdc42 in migrating c...
Use of Leading Edge Waves to Increase Lift/Drag Ratio Project
National Aeronautics and Space Administration — One of the goals of NASA's Fundamental Aeronautics "Subsonic Fixed Wing" project is to reduce fuel burn by 25% 5% by 2018. This corresponds approximately to an...
The leading edge. Data systems can provide the tools needed to meet goals.
Austin, C J
1989-10-01
Management information systems--essential for strategic planning and management in today's complex healthcare environment--must be designed in concert with goals and strategies developed at the executive or corporate level. Healthcare organizations need management information to support four major functions: strategic planning and marketing, resource allocation, performance assessment, and evaluation of products and services. Computer systems fall into three general categories--administrative, clinical, and decision support (management information systems). Management information systems are the least advanced of the three. The need for strategic planning and managerial control in the face of complexity and competition, however, will result in rapid advances. The chief executive officer must be responsible for the following areas to ensure the effective use of information systems: strategic planning, information systems planning, user-driven focus, systems integration, and monitoring of results. Many larger healthcare organizations have established the position of chief information officer (CIO) to assist in these tasks. The CIO coordinates information systems, telecommunications, management engineering, and office automation. PMID:10295574
Energy Technology Data Exchange (ETDEWEB)
Saleska, Scott [Univ. of Arizona, Tucson, AZ (United States); Rich, Virginia [The Ohio State Univ., Columbus, OH (United States); Tyson, Gene [Univ. of Queensland, St. Lucia (Australia); Chanton, Jeff [Florida State Univ., Tallahassee, FL (United States); Crill, Patrick [Stockholm Univ. (Sweden); Li, Changshen [Univ. of New Hampshire, Durham, NH (United States)
2016-02-22
This project integrates across three fields (microbiology, biogeochemistry, and modeling) to understand the mechanisms of methane cycling in thawing permafrost. We have made substantial progress in each area, and in cross-cutting interdisciplinary synthesis. Large releases of CH_{4} from thawing permafrost to the atmosphere, a strong positive feedback to global warming, are plausible but little is known about the controls on such release. Our project (“IsoGenie”) addresses the key question: What is the interplay of microbial communities and soil organic matter composition in the decomposition of organic C to CH_{4} across a permafrost thaw gradient?
John Boswell: Posting Historical Landmarks at the Leading Edge of the Culture Wars
Cisneros, Jeffrey
2013-01-01
One of the most enduring and controversial figures in the field of history is John E. Boswell. His work on homosexuality and the history of the Christian Church was published at a key time during the Stonewall Riots in the late 1960s and the removal of homosexuality from the list of diagnostic mental disorders in the mid 1970s. This social…
Discrete-vortex simulation of pulsating flow on a turbulent leading-edge separation bubble
Sung, Hyung Jin; Rhim, Jae Wook; Kiya, Masaru
1992-01-01
Studies are made of the turbulent separation bubble in a two-dimensional semi-infinite blunt plate aligned to a uniform free stream with a pulsating component. The discrete-vortex method is applied to simulate this flow situation because this approach is effective for representing the unsteady motions of the turbulent shear layer and the effect of viscosity near the solid surface. The numerical simulation provides reasonable predictions when compared with the experimental results. A particular frequency with a minimum reattachment is related to the drag reduction. The most effective frequency is dependent on the amplified shedding frequency. The turbulent flow structure is scrutinized. This includes the time-mean and fluctuations of the velocity and the surface pressure, together with correlations between the fluctuating components. A comparison between the pulsating flow and the non-pulsating flow at the particular frequency of the minimum reattachment length of the separation bubble suggests that the large-scale vortical structure is associated with the shedding frequency and the flow instabilities.
Thermal Structure Analysis of SIRCA Tile for X-34 Wing Leading Edge TPS
Milos, Frank S.; Squire, Thomas H.; Rasky, Daniel J. (Technical Monitor)
1997-01-01
This paper will describe in detail thermal/structural analyses of SIRCA tiles which were performed at NASA Ames under the The Tile Analysis Task of the X-34 Program. The analyses used the COSMOS/M finite element software to simulate the material response in arc-jet tests, mechanical deflection tests, and the performance of candidate designs for the TPS system. Purposes of the analysis were to verify thermal and structural models for the SIRCA tiles, to establish failure criteria for stressed tiles, to simulate the TPS response under flight aerothermal and mechanical load, and to confirm that adequate safety margins exist for the actual TPS design.
Open source and healthcare in Europe - time to put leading edge ideas into practice.
Murray, Peter J; Wright, Graham; Karopka, Thomas; Betts, Helen; Orel, Andrej
2009-01-01
Free/Libre and Open Source Software (FLOSS) is a process of software development, a method of licensing and a philosophy. Although FLOSS plays a significant role in several market areas, the impact in the health care arena is still limited. FLOSS is promoted as one of the most effective means for overcoming fragmentation in the health care sector and providing a basis for more efficient, timely and cost effective health care provision. The 2008 European Federation for Medical Informatics (EFMI) Special Topic Conference (STC) explored a range of current and future issues related to FLOSS in healthcare (FLOSS-HC). In particular, there was a focus on health records, ubiquitous computing, knowledge sharing, and current and future applications. Discussions resulted in a list of main barriers and challenges for use of FLOSS-HC. Based on the outputs of this event, the 2004 Open Steps events and subsequent workshops at OSEHC2009 and Med-e-Tel 2009, a four-step strategy has been proposed for FLOSS-HC: 1) a FLOSS-HC inventory; 2) a FLOSS-HC collaboration platform, use case database and knowledge base; 3) a worldwide FLOSS-HC network; and 4) FLOSS-HC dissemination activities. The workshop will further refine this strategy and elaborate avenues for FLOSS-HC from scientific, business and end-user perspectives. To gain acceptance by different stakeholders in the health care industry, different activities have to be conducted in collaboration. The workshop will focus on the scientific challenges in developing methodologies and criteria to support FLOSS-HC in becoming a viable alternative to commercial and proprietary software development and deployment. PMID:19745456
Literature in Focus - “At the Leading Edge: the ATLAS and CMS LHC experiments”
CERN Library
2010-01-01
edited by Dan Green Too often descriptions of detectors focus on the “what” and not the “why”. This volume aims to elucidate how the requirements of the physics at the Large Hadron Collider (LHC) define the detector environment. In turn, the detector choices are made to adapt to that environment. The goal of LHC physics is to explore the mechanism for electroweak symmetry breaking. Because of the minuscule cross-sections which need to be explored, 0.1 fb, the LHC needs to provide 100 fb-1/yr, or an instantaneous luminosity of 1034 / (cm2 sec). With a bunch crossing interval of 25 nsec, well-matched to detector speeds, there will be 25 events occupying each bunch crossing. Thus the physics requires fast, finely segmented, low noise and radiation-resistant detectors which provide redundant measurements of the rarely produced electrons and muons. To achieve those goals, new ground was broken in constructing the A Toroidal LHC ApparatuS (ATLAS) and Compact Muon Soleno...
CFD zonal modeling of leading-edge ice effects for a complete aircraft
Summa, J. M.; Strash, D. J.; Lednicer, D. A.
1993-01-01
A simplified, uncoupled zonal procedure was utilized to assess the capability of numerically simulating icing effects on a Boeing 727-200 aircraft. The computational approach combines potential flow, plus boundary layer simulations by VSAERO for the un-iced aircraft forces and moments, with Navier-Stokes simulations by ARC3D for the incremental forces and moments due to iced components. These are compared with wind tunnel longitudinal force and moment data. Although the computational results compared favorably with the test data in the linear angle of attack range, it is clear that for general aircraft icing calculations, a multiblock Navier-Stokes code will be required for the viscous component of this zonal method.
Analysis of the leading edge effects on the boundary layer transition
Chow, Pao-Liu
1990-01-01
A general theory of boundary layer control by surface heating is presented. Some analytical results for a simplified model, i.e., the optimal control of temperature fluctuations in a shear flow are described. The results may provide a clue to the effectiveness of the active feedback control of a boundary layer flow by wall heating. In a practical situation, the feedback control may not be feasible from the instrumentational point of view. In this case the vibrational control introduced in systems science can provide a useful alternative. This principle is briefly explained and applied to the control of an unstable wavepacket in a parallel shear flow.
... Story" 5 Things to Know About Zika & Pregnancy Lead Poisoning KidsHealth > For Parents > Lead Poisoning Print A ... Family en español La intoxicación por plomo About Lead Poisoning If you have young kids, it's important ...
Development of composite polymer-glass edge claddings for Nova Laser Disks
International Nuclear Information System (INIS)
Large Nd:glass laser disks for disk amplifiers require an edge cladding which absorbs at 1 μ m. This cladding prevents edge reflections from causing parasitic oscillations that would otherwise deplete the gain. The authors have developed a composite polymer-glass edge cladding that consists of absorbing glass strips bonded to the edges of laser glass disks using an epoxy adhesive. The edge cladding must survive a fluence of approximately 20 J/cm2 in a 0.5-ms pulse. Failure can occur either by decomposition of the polymer or by mechanical failure from thermal stresses which leads to bond delamination. An epoxy has been developed that gives the required damage resistance, refractive index match and processing characteristics. A slight tilt of the disk edges greatly reduces the threat from parasitic oscillations and a glass surface treatment is used to promote bond adhesion. Laser disks fabricated with this new cladding show identical gain performance to disks using conventional fused-glass cladding and have been tested for over 2000 shots (equivalent to about a 4-year lifetime on Nova) with out degradation
Electron and ion edges and the associated magnetic topology of the reconnecting magnetopause
Øieroset, M.; Phan, T. D.; Gosling, J. T.; Fujimoto, M.; Angelopoulos, V.
2015-11-01
Using high-resolution burst mode THEMIS data, we have examined in detail the electron and ion edges of the reconnecting magnetopause and the associated magnetic topologies of 23 high shear reconnecting magnetopause crossings. The electron edge is identified as the most earthward detection of entering magnetosheath electrons and the accompanying first loss of magnetospheric electrons. The electron edge thus marks the most earthward measurable open (reconnected) field line. The ion edge, identified as the most earthward detection of entering magnetosheath ions, was always detected either sunward of the electron edge or simultaneous with it, indicating that the entire low-latitude boundary layer (LLBL) was on open field lines. The radial separation of the electron and ion edges is due to a time-of-flight effect associated with the fact that the entering magnetosheath electrons have considerably higher speeds than the entering magnetosheath ions. Importantly, our study reveals that an examination of three-dimensional particle distributions covering the entire range of energies of the various magnetosheath and magnetospheric populations present is essential for a correct determination of the magnetic topology of the LLBL. Deducing the topology from electron pitch angle distributions covering a limited energy range can lead to incorrect deduction of the topology.
Restricted Edge Connectivity of BinaryUndirected Kautz Graphs
Institute of Scientific and Technical Information of China (English)
OUJian-ping
2004-01-01
A restricted edge cut is an edge cut of a connected graph whose removal resultsin a disconnected graph without isolated vertices. The size of a minimum restricted edge cutof a graph G is called its restricted edge connectivity, and is denoted by λ′(G). Let ξ(G) bethe minimum edge degree of graph G. It is known that λ′(G) ≤ξ(G) if G contains restrictededge cuts. Graph G is called maximal restricted edge connected if the equality holds in thethe preceding inequality. In this paper, undirected Kautz graph UK(2, n) is proved to bemaximal restricted edge connected if n ≥ 2.
Edge Cut Domination, Irredundance, and Independence in Graphs
Fenstermacher, Todd; Hedetniemi, Stephen; Laskar, Renu
2016-01-01
An edge dominating set $F$ of a graph $G=(V,E)$ is an \\textit{edge cut dominating set} if the subgraph $\\langle V,G-F \\rangle$ is disconnected. The \\textit{edge cut domination number} $\\gamma_{ct}(G)$ of $G$ is the minimum cardinality of an edge cut dominating set of $G.$ In this paper we study the edge cut domination number and investigate its relationships with other parameters of graphs. We also introduce the properties edge cut irredundance and edge cut independence.