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1

Advanced leading edge thermal-structure concept. Direct bond reusable surface insulation to a composite structure  

NASA Technical Reports Server (NTRS)

An advanced leading-edge concept was analyzed using the space shuttle leading edge system as a reference model. The comparison indicates that a direct-bond system utilizing a high temperature (2700 F) fibrous refractory composite insulation tile bonded to a high temperature (PI/graphite) composite structure can result in a weight savings of up to 800 lb. The concern that tile damage or loss during ascent would result in adverse entry aerodynamics if a leading edge tile system were used is addressed. It was found from experiment that missing tiles (as many as 22) on the leading edge would not significantly affect the basic force-and-moment aerodynamic coefficients. Additionally, this concept affords a degree of redundancy to a thermal protection system in that the base structure (being a composite material) ablates and neither melts nor burns through when subjected to entry heating in the event tiles are actually lost or damaged during ascent.

Riccitiello, S. R.; Figueroa, H.; Coe, C. F.; Kuo, C. P.

1984-01-01

2

Mechanical Properties and Microstructural Characterization of Particulate Reinforced Diboride Composites for High Temperature Leading Edge Applications  

NASA Technical Reports Server (NTRS)

Previous work on refractory diboride composites has shown that these systems have the potential for use in high temperature leading edge applications for reusable reentry vehicles. Experiments in reentry environments have shown that these materials have multiple use temperatures greater than 1900 C. The work to be discussed focuses on three compositions: HfB2/SiC, ZrB2/SiC, and ZrB2/C/SiC. These composites have been hot pressed and their mechanical properties measured at room and elevated temperatures. Extensive microstructural characterization has been conducted on polished cross sections and the fracture surfaces have been examined to determine their failure origins.

Ellerby, Donald T.; Bull, J. D.; Johnson, S. M.; Stackpoole, M. M.; Gusman, M.; Stuffle, K.; Cull, A. D.; Causey, S. J.; Arnold, Jim (Technical Monitor)

2001-01-01

3

Arc Jet Results on Candidate High Temperature Coatings for NASA's NGLT Refractory Composite Leading Edge Task  

NASA Technical Reports Server (NTRS)

In 2000, arc jet testing was conducted on thirteen material systems for possible use on the nose leading edge of the Hyper-X program s X-43A Mach 10 vehicle. Six material systems survived 3, 130- second cycles. To support NASA s Next Generation Launch Technology Programs (NGLT) need for passive refractory composite leading edges with multiple reuse capability at temperatures up to 3600 F, these six materials were subjected to an expanded arc jet test program. This expanded arc jet test program included three phases. The purpose of the first phase was to generate emissivity data as a function of temperature. The purpose of the second phase was to determine if the material systems had any thermal cycling durability, and the third phase was to determine whether the materials could survive an arc jet test of one hour duration. Some of the coating systems were found to have very low emissivities, suggesting that they would not be good candidates for leading edges coating. Other coating systems survived both the second and third phases of the test program and showed potential for use as an oxidation protection coating for leading edges. This presentation summarizes the test program results.

Ohlhorst, C. W.; Vaughn, W. L.; Lewis, R. K.; Milhoan, J. D.

2004-01-01

4

Supersonic Leading Edge Receptivity  

NASA Technical Reports Server (NTRS)

This paper describes experimental studies of leading edge boundary layer receptivity for imposed stream disturbances. Studies were conducted in the supersonic T-325 facility at ITAM and include data for both sharp and blunt leading edges. The data are in agreement with existing theory and should provide guidance for the development of more complete theories and numerical computations of this phenomena.

Maslov, Anatoly A.

1998-01-01

5

Fabrication of a graphite/epoxy composite leading edge for laminar flow control  

NASA Technical Reports Server (NTRS)

Lockheed, under NASA contract, has recently completed the first phase of a program to evaluate laminar flow control concepts for transport aircraft. Achievement of laminar flow over a wing surface requires a system of slots, metering holes, ducts and pumps to be used to remove the turbulent air adjacent to the surface. This requirement poses severe restrictions on conventional metallic structure. Graphite/epoxy composite with its unique properties appears to be the material that might solve the very complex structural problems associated with a laminar flow control aircraft. A six-foot span graphite/epoxy test article incorporating provisions for leading edge cleaning, deicing and laminar flow control was designed, fabricated and tested.

Beall, R. T.

1980-01-01

6

A Search for Compositional Differences in Slow Solar Wind at the Leading and Trailing Edges of Stream Interfaces  

NASA Astrophysics Data System (ADS)

The elemental and ionic composition of the slow (~400 km/s) solar wind (SW) differs from that of the fast (>600 km/s) SW streams. In particular, the first ionization potential (FIP) effect and the O7/O6 ratios are higher in the slow SW than in the fast SW. While this fundamental difference between fast and slow SW has long been appreciated, there has been no reason to expect or effort to search for systematic variations within given fast or slow SW streams. If present, however, such systematic variations could be diagnostic of the solar processes at the sources of the SW. We suggest two reasons to expect compositional differences between leading and trailing edges of slow SW streams. After selecting two long-lived fast SW streams from 2005 and 2006 and determining their slow-fast (SF) and fast-slow (FS) stream interfaces (SIs), ACE SWICS (version 3) compositional data were obtained for the 1-day periods of the preceding SF and following FS slow SW streams. The statistics were limited, but no compositional differences between the preceding and following slow SW regions were found for either stream sequence.

Kahler, Stephen

2010-03-01

7

Wing Leading Edge Debris Analysis  

NASA Technical Reports Server (NTRS)

This is a slide presentation showing the Left Wing Leading Edge (WLE) heat damage observations: Heavy "slag" deposits on select RCC panels. Eroded and knife-edged RCC rib sections. Excessive overheating and slumping of carrier panel tiles. Missing or molten attachment bolts but intact bushing. Deposit mainly on "inside" RCC panel. Deposit on some fractured RCC surface

Shah, Sandeep; Jerman, Gregory

2004-01-01

8

Icing tunnel tests of a composite porous leading edge for use with a liquid anti-ice system. [Lewis icing research tunnel  

NASA Technical Reports Server (NTRS)

The efficacy of liquid ice protection systems which distribute a glycol-water solution onto leading edge surfaces through a porous skin was demonstrated in tests conducted in the NASA Lewis icing research tunnel using a composite porous leading edge panels. The data obtained were compared with the performance of previously tested stainless steel leading edge with the same geometry. Results show: (1) anti-ice protection of a composite leading edge is possible for all the simulated conditions tested; (2) the glycol flow rates required to achieve anti-ice protection were generally much higher than those required for a stainless steel panel; (3) the low reservoir pressures of the glycol during test runs indicates that more uniform distribution of glycol, and therefore lower glycol flow rates, can probably be achieved by decreasing the porosity of the panel; and (4) significant weight savings can be achieved in fluid ice protection systems with composite porous leading edges. The resistance of composite panels to abrasion and erosion must yet be determined before they can be incorporated in production systems.

Kohlman, D. L.

1981-01-01

9

Leading Edge Cellular Decision Making  

E-print Network

Leading Edge Review Cellular Decision Making and Biological Noise: From Microbes to Mammals Ga´ bor.cell.2011.01.030 Cellular decision making is the process whereby cells assume different, functionally stressful environment. Here, we review several examples of cellular decision making from viruses, bacteria

van Oudenaarden, Alexander

10

Aerothermal/FEM Analysis of Hypersonic Sharp Leading Edges  

NASA Technical Reports Server (NTRS)

Advanced hypersonic vehicles, like wave riders, will have sharp leading edges to minimize drag. These designs require accurate finite element modeling (FEM) of the thermal-structural behavior of a diboride ceramic matrix composite sharp leading edge. By coupling the FEM solver to an engineering model of the aerothermodynamic heating environment the impact of non catalytic surfaces, rarefied flow effects, and multidimensional conduction on the performance envelopes of sharp leading edges can be examined.

Kolodziej, Paul; Bull, Jeffrey D.; Kowalski, Thomas R.; Rasky, Daniel J. (Technical Monitor)

1995-01-01

11

Wing Leading Edge Concepts for Noise Reduction  

NASA Technical Reports Server (NTRS)

This study focuses on the development of wing leading edge concepts for noise reduction during high-lift operations, without compromising landing stall speeds, stall characteristics or cruise performance. High-lift geometries, which can be obtained by conventional mechanical systems or morphing structures have been considered. A systematic aerodynamic analysis procedure was used to arrive at several promising configurations. The aerodynamic design of new wing leading edge shapes is obtained from a robust Computational Fluid Dynamics procedure. Acoustic benefits are qualitatively established through the evaluation of the computed flow fields.

Shmilovich, Arvin; Yadlin, Yoram; Pitera, David M.

2010-01-01

12

A fast leading-edge pulse generator  

Microsoft Academic Search

The pulse generator consists of ECL semiconductor integrated circuits, high speed transistors and step restorer diodes, among others; its circuitry is simple. The leading edge of the output pulse is less than 100 ps, and the output impedance is 50 ohms. An ECL four-wire receiver connected as a closed loop circut is used in the oscillator section of the set.

R. Wang

1986-01-01

13

Leading Edge Uncovering a Tumor Suppressor  

E-print Network

Leading Edge Previews Uncovering a Tumor Suppressor for Triple-Negative Breast Cancers John G *Correspondence: joan_brugge@hms.harvard.edu DOI 10.1016/j.cell.2011.02.030 ``Triple-negative'' breast cancers ``triple-negative'' breast cancers, these cells lack detectable expression of the three key molecular

Albeck, John

14

Leading Edge Stem Cell Trafficking in Tissue  

E-print Network

that achieving targeted trafficking of stem cells will be critical for effective tissue regeneration fromLeading Edge Review Stem Cell Trafficking in Tissue Development, Growth, and Disease Diana J. Laird, USA 4Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA 5

von Andrian, Ulrich H.

15

Leading Edge The Microbial Opsin Family  

E-print Network

Leading Edge Primer The Microbial Opsin Family of Optogenetic Tools Feng Zhang,1,2,9,* Johannes advances in understanding microbial opsins have been driven by molecular engineering for optogenetics on these and other light-sensitive proteins has resulted in a technology called optogenetics (Deisseroth, 2011

Schnitzer, Mark

16

Leading Edge Noncoding RNAs and Cancer  

E-print Network

into cells outside of the liver, which is critical for treating dissemi- nated cancer. Attractive approachesLeading Edge Voices Noncoding RNAs and Cancer Knockout Punch for Cancer Judy Lieberman Boston down genes in the liver. The biggest chal- lenge to RNA-based cancer therapeutics remains delivery

Lieberman, Judy

17

Leading Edge Democracy Derived? New Trajectories  

E-print Network

Leading Edge Commentary Democracy Derived? New Trajectories in Pluripotent Stem Cell Research of stem cell research? Here, coauthorship networks of stem cell research articles and analysis of cell lines used in stem cell research indicate that hiPSCs are not replacing human embryonic stem cells

18

Leading Edge Bacterial Genomics and Pathogen Evolution  

E-print Network

utilized to identify genes that are es- sential for bacterial growth or pathogenesis. There are two generalLeading Edge Review Bacterial Genomics and Pathogen Evolution David M. Raskin,1 Rekha Seshadri,2.02.002 The availability of hundreds of bacterial genome sequences has altered the study of bacte- rial pathogenesis

Mekalanos, John

19

Cascade with subsonic leading-edge locus  

NASA Technical Reports Server (NTRS)

The paper investigates a two-dimensional oscillating cascade with a subsonic leading edge locus in a supersonic flow. The blades are assumed to be of small thickness and camber, and are undergoing small amplitude-harmonic oscillations. The problem is reduced to the solution of a functional integral equation, and an expression is given for the kernel function.

Goldstein, M. E.

1975-01-01

20

SPH – Lagrangian study of bird impact on leading edge wing  

Microsoft Academic Search

Experimental bird-strike tests were conducted using a dead chicken of 8lb with a speed of 250kts that hit on leading edge bay in composite material made with aluminium alloy 2024-T3, core panel of honeycomb and GLARE cover plates. A validated simulation methodology has been developed in order to use a reference in further bird test certification procedure on the fin

M. Guida; F. Marulo; M. Meo; A. Grimaldi; G. Olivares

2011-01-01

21

Experimental investigation of leading-edge thrust at supersonic speeds  

NASA Technical Reports Server (NTRS)

Wings, designed for leading edge thrust at supersonic speeds, were investigated in the Unitary Plan Wind Tunnel at Mach numbers of 1.60, 1.80, 2.00, 2.16, and 2.36. Experimental data were obtained on a uncambered wing which had three interchangeable leading edges that varied from sharp to blunt. The leading edge thrust concept was evaluated. Results from the investigation showed that leading edge flow separation characteristics of all wings tested agree well with theoretical predictions. The experimental data showed that significant changes in wing leading edge bluntness did not affect the zero lift drag of the uncambered wings.

Wood, R. M.; Miller, D. S.

1983-01-01

22

Development of X-43A Mach 10 Leading Edges  

NASA Technical Reports Server (NTRS)

The nose leading edge of the Hyper-X Mach 10 vehicle was orginally anticipated to reach temperatures near 4000 F at the leading-edge stagnation line. A SiC coated carbon/carbon (C/C) leading-edge material will not survive that extreme temperature for even a short duration single flight. To identify a suitable leading edge for the Mach 10 vehicle, arc-jet testing was performed on thirteen leading-edge segments fabricated from different material systems to evaluate their performance in a simulated flight environment. Hf, Zr, Si, and Ir based materials, in most cases as a coating on C/C, were included in the evaluation. Afterwards, MER, Tucson, AZ was selected as the supplier of the flight vehicle leading edges. The nose and the vertical and horizontal tail leading edges were fabricated out of a 3:1 biased high thermal conductivity C/C. The leading edges were coated with a three layer coating comprised of a SiC conversion of the top surface of the C/C, followed by a chemical vapor deposited layer of SiC, followed by a thin chemical vapor deposited layer of HfC. This paper will describe the fabrication of the Mach 10 C/C leading edges and the testing performed to validate performance.

Ohlhorst, Craig W.; Glass, David E.; Bruce, Walter E., III; Lindell, Michael C.; Vaughn, Wallace L.; Dirling, R. B., Jr.; Hogenson, P. A.; Nichols, J. M.; Risner, N. W.; Thompson, D. R.

2005-01-01

23

Laminar Flow Control Leading Edge Systems in Simulated Airline Service  

NASA Technical Reports Server (NTRS)

Achieving laminar flow on the wings of a commercial transport involves difficult problems associated with the wing leading edge. The NASA Leading Edge Flight Test Program has made major progress toward the solution of these problems. The effectiveness and practicality of candidate laminar flow leading edge systems were proven under representative airline service conditions. This was accomplished in a series of simulated airline service flights by modifying a JetStar aircraft with laminar flow leading edge systems and operating it out of three commercial airports in the United States. The aircraft was operated as an airliner would under actual air traffic conditions, in bad weather, and in insect infested environments.

Wagner, R. D.; Maddalon, D. V.; Fisher, D. F.

1988-01-01

24

Leading and trailing edge noise of an airfoil  

Microsoft Academic Search

Theoretical and experimental predictions of the noise produced when a rigid surface, e.g., an airfoil, with a sharp edge is introduced into a turbulent flow are compared. For an airfoil in rectilinear motion agreement is good. It is better for leading edge than for trailing edge noise because of lack of knowledge of boundary layer surface pressure. For a rotating

R. K. Amiet

1981-01-01

25

Numerical study of delta wing leading edge blowing  

NASA Technical Reports Server (NTRS)

Spanwise and tangential leading edge blowing as a means of controlling the position and strength of the leading edge vortices are studied by numerical solution of the three-dimensional Navier-Stokes equations. The leading edge jet is simulated by defining a permeable boundary, corresponding to the jet slot, where suitable boundary conditions are implemented. Numerical results are shown to compare favorably with experimental measurements. It is found that the use of spanwise leading edge blowing at moderate angle of attack magnifies the size and strength of the leading edge vortices, and moves the vortex cores outboard and upward. The increase in lift primarily comes from the greater nonlinear vortex lift. However, spanwise blowing causes earlier vortex breakdown, thus decreasing the stall angle. The effects of tangential blowing at low to moderate angles of attack tend to reduce the pressure peaks associated with leading edge vortices and to increase the suction peak around the leading edge, so that the integrated value of the surface pressure remains about the same. Tangential leading edge blowing in post-stall conditions is shown to re-establish vortical flow and delay vortex bursting, thus increasing C sub L sub max and stall angle.

Yeh, David; Tavella, Domingo; Roberts, Leonard

1988-01-01

26

METHOD IMPROVEMENTS IN THERMAL ANALYSIS OF MACH 10 LEADING EDGES  

Microsoft Academic Search

Several improvements have recently been made in the thermal analysis methods for leading edges of a hypersonic vehicle. The leading edges of this vehicle undergo exceptionally high heat loads that incorporate extreme spatial gradients as well as severe transients. Due to the varying flight conditions, complex geometry, and need for thermal loads at many points along the trajectory, full computational

Ruth M. Amundsen

1999-01-01

27

Analytical study on plate edge noise (Noise generation from tandemly situated trailing and leading edges)  

Microsoft Academic Search

The problem of noise generation due to the interaction between flows and plate edges is treated analytically. In uniform flow containing vorticity waves, two semiinfinite flat plates are placed with the trailing edge of one plate and leading edge of the other being tandemly situated a finite distance apart. This flow is considered to be a simplified model for self-excited

Koji Takahashi; Shojiro Kaji

1993-01-01

28

Timing discriminator using leading-edge extrapolation  

DOEpatents

A discriminator circuit to recover timing information from slow-rising pulses by means of an output trailing edge, a fixed time after the starting corner of the input pulse, which is nearly independent of risetime and threshold setting is described. This apparatus comprises means for comparing pulses with a threshold voltage; a capacitor to be charged at a certain rate when the input signal is one-third threshold voltage, and at a lower rate when the input signal is two-thirds threshold voltage; current-generating means for charging the capacitor; means for comparing voltage capacitor with a bias voltage; a flip-flop to be set when the input pulse reaches threshold voltage and reset when capacitor voltage reaches the bias voltage; and a clamping means for discharging the capacitor when the input signal returns below one-third threshold voltage.

Gottschalk, B.

1981-07-30

29

Shock Interaction Control for Scramjet Cowl Leading Edges  

NASA Technical Reports Server (NTRS)

An experimental study was conducted to qualitatively determine the effectiveness of stagnation-region gas injection in protecting a scramjet cowl leading edge from the intense heating produced by Type III and Type IV shock interactions. The model consisted of a two-dimensional leading edge, representative of that of a scramjet cowl. Tests were conducted at a nominal freestream Mach number of 6. Gaseous nitrogen was supersonically injected through the leading-edge nozzles at various mass flux ratios and with the model pitched at angles of 0deg and -20deg relative to the freestream flow. Qualitative data, in the form of focusing and conventional schlieren images, were obtained of the shock interaction patterns. Results indicate that large shock displacements can be achieved and both the Type III and IV interactions can be altered such that the interaction does not impinge on the leading edge surface.

Albertson, Cindy W.; Venkat, Venki, S.

2005-01-01

30

Leading Edge Spinning the Web of Cell Fate  

E-print Network

Leading Edge Minireview Spinning the Web of Cell Fate Kevin Van Bortle1 and Victor G. Corces1,* 1 involved in spinning the web of cell fate. Chromatin at the Nuclear Lamina The nuclear lamina is a thin

Corces, Victor G.

31

Dynamic Stall Characteristics of Drooped Leading Edge Airfoils  

NASA Technical Reports Server (NTRS)

Helicopters in high-speed forward flight usually experience large regions of dynamic stall over the retreating side of the rotor disk. The rapid variations in the lift and pitching moments associated with the stall process can result in vibratory loads, and can cause fatigue and failure of pitch links. In some instances, the large time lag between the aerodynamic forces and the blade motion can trigger stall flutter. A number of techniques for the alleviation of dynamic stall have been proposed and studied by researchers. Passive and active control techniques have both been explored. Passive techniques include the use of high solidity rotors that reduce the lift coefficients of individual blades, leading edge slots and leading edge slats. Active control techniques include steady and unsteady blowing, and dynamically deformable leading edge (DDLE) airfoils. Considerable amount of experimental and numerical data has been collected on the effectiveness of these concepts. One concept that has not received as much attention is the drooped-leading edge airfoil idea. It has been observed in wind tunnel studies and flight tests that drooped leading edge airfoils can have a milder dynamic stall, with a significantly milder load hysteresis. Drooped leading edge airfoils may not, however, be suitable at other conditions, e.g. in hover, or in transonic flow. Work needs to be done on the analysis and design of drooped leading edge airfoils for efficient operation in a variety of flight regimes (hover, dynamic stall, and transonic flow). One concept that is worthy of investigation is the dynamically drooping airfoil, where the leading edge shape is changed roughly once-per-rev to mitigate the dynamic stall.

Sankar, Lakshmi N.; Sahin, Mehmet; Gopal, Naveen

2000-01-01

32

Effect of Leading Edge Tubercles on Swept Humpback Whale Flipper  

NASA Astrophysics Data System (ADS)

The effect of leading edge tubercles on the performance of idealized humpback whale flipper models at sweep angles of 15 and 30 degrees is analyzed. We present the experimental results based on precision wind tunnel testing, comparing the data obtained on idealized model sets with and without leading edge tubercles. We have found a significant difference in the lift and drag coefficients over a large range of angle of attack.

Murray, Mark; Miklosovic, David; Fish, Frank; Howle, Laurens

2004-11-01

33

Stall Delay by Leading Edge Tubercles on Humpback Whale Flipper  

NASA Astrophysics Data System (ADS)

The effect of leading edge tubercles on the performance of idealized humpback whale flipper models is analyzed. We present the experimental results based on precision wind tunnel testing, comparing the data obtained on idealized model sets with and without leading edge tubercles. We have found a significant increase in the angle of attack required for stall on the flipper with tubercles and a smaller drag coefficient at these higher angles of attack.

Murray, Mark; Miklosovic, David; Fish, Frank; Howle, Laurens

2003-11-01

34

Supersonic wings with significant leading-edge thrust at cruise  

NASA Technical Reports Server (NTRS)

Experimental/theoretical correlations are presented which show that significant levels of leading-edge thrust are possible at supersonic speeds for certain planforms having the geometry to support the theoretical thrust-distribution potential. The new analytical process employed provides not only the level of leading-edge thrust attainable but also the spanwise distribution of both it and that component of full theoretical thrust which acts as vortex lift. Significantly improved aerodynamic performance in the moderate supersonic speed regime is indicated.

Robins, A. W.; Carlson, H. W.; Mack, R. J.

1980-01-01

35

Symmetric airfoil geometry effects on leading edge noise.  

PubMed

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

Gill, James; Zhang, X; Joseph, P

2013-10-01

36

Design and Analysis of UHTC Leading Edge Attachment  

NASA Technical Reports Server (NTRS)

NASA Glenn Research Center was contacted to provide technical support to NASA Ames Research Center in the design and analysis of an ultra high temperature ceramic (UHTC) leading edge. UHTC materials are being considered for reusable launch vehicles because their high temperature capability may allow for un-cooled sharp leading edge designs. While ceramic materials have the design benefit of allowing subcomponents to run hot, they also provide a design challenge in that they invariably must be in contact with cooler subcomponents elsewhere in the structure. NASA Glenn Research Center proposed a modification to an existing attachment design. Thermal and structural analyses of the leading edge assembly were carried out using ABAQUS finite element software. Final results showed that the proposed modifications aided in thermally isolating hot and cold subcomponents and reducing bearing stresses at the attachment location.

Thomas, David J.; Nemeth, Noel N. (Technical Monitor)

2002-01-01

37

Fluid-thermal-structural study of aerodynamically heated leading edges  

NASA Technical Reports Server (NTRS)

A finite element approach for integrated fluid-thermal-structural analysis of aerodynamically heated leading edges is presented. The Navier-Stokes equations for high speed compressible flow, the energy equation, and the quasi-static equilibrium equations for the leading edge are solved using a single finite element approach in one integrated, vectorized computer program called LIFTS. The fluid-thermal-structural coupling is studied for Mach 6.47 flow over a 3-in diam cylinder for which the flow behavior and the aerothermal loads are calibrated by experimental data. Issues of the thermal-structural response are studied for hydrogen-cooled, super thermal conducting leading edges subjected to intense aerodynamic heating.

Deuchamphai, Pramote; Thornton, Earl A.; Wieting, Allan R.

1988-01-01

38

Space Shuttle Orbiter leading edge structural subsystem thermal performance  

NASA Technical Reports Server (NTRS)

An extensive qualification test program and the STS-1 flight of the Space Shuttle Orbiter have provided the data necessary to verify the performance of the Orbiter thermal protection system. The reinforced carbon-carbon leading edge structural subsystem is used on areas of the orbiter where temperatures exceed 2300 F. The subsystem consists of the ROC nose cap and wing leading edge panels, metallic attachments, internal insulation, and interface tiles. Thermal response data from the qualification tests and the STS-1 flight, postflight inspection, and analytical predictions support the conclusion that the thermal performance of the subsystem verified the design.

Curry, D. M.; Cunningham, J. A.; Frahm, J. R.

1982-01-01

39

Wake of forced flow around elliptical leading edge plates  

NASA Astrophysics Data System (ADS)

Previous investigations have shown that flows around rectangular plates with transverse forcing involve interactions between vortices shed from the leading and trailing edges and vortex merging in the wakes. The Strouhal number of vortex shedding at which peak base drag occurs varies with chord-to-thickness ratio in a stepwise fashion, similar to the self-sustained oscillations at low Reynolds number for unforced flows. In the present study, the leading edge flow separation and vortex shedding is eliminated by using plates with elliptical leading edges, and the trailing edge flow is examined through particle image velocimetry. In particular, the response of the trailing-edge vortex shedding and the base pressure coefficient to applied transverse oscillations of different Strouhal number and amplitude is measured. Substantial variation in the base pressure coefficient is found, with peaks appearing at the natural shedding frequency and at a harmonic. The effect of the forcing on the wake dimension and the strength of the wake vortices is quantified using particle image velocimetry. Three-dimensional structures in addition to the two-dimensional Kármán vortices in the wake are also visualized.

Mills, R.; Sheridan, J.; Hourigan, K.

2005-02-01

40

SiC/SiC Leading Edge Turbine Airfoil Tested Under Simulated Gas Turbine Conditions  

NASA Technical Reports Server (NTRS)

Silicon-based ceramics have been proposed as component materials for use in gas turbine engine hot-sections. A high pressure burner rig was used to expose both a baseline metal airfoil and ceramic matrix composite leading edge airfoil to typical gas turbine conditions to comparatively evaluate the material response at high temperatures. To eliminate many of the concerns related to an entirely ceramic, rotating airfoil, this study has focused on equipping a stationary metal airfoil with a ceramic leading edge insert to demonstrate the feasibility and benefits of such a configuration. Here, the idea was to allow the SiC/SiC composite to be integrated as the airfoil's leading edge, operating in a "free-floating" or unrestrained manner. and provide temperature relief to the metal blade underneath. The test included cycling the airfoils between simulated idle, lift, and cruise flight conditions. In addition, the airfoils were air-cooled, uniquely instrumented, and exposed to the same internal and external conditions, which included gas temperatures in excess of 1370 C (2500 F). Results show the leading edge insert remained structurally intact after 200 simulated flight cycles with only a slightly oxidized surface. The instrumentation clearly suggested a significant reduction (approximately 600 F) in internal metal temperatures as a result of the ceramic leading edge. The object of this testing was to validate the design and analysis done by Materials Research and Design of Rosemont, PA and to determine the feasibility of this design for the intended application.

Robinson, R. Craig; Hatton, Kenneth S.

1999-01-01

41

Laminar flow control leading edge glove flight test article development  

NASA Technical Reports Server (NTRS)

A laminar flow control (LFC) flight test article was designed and fabricated to fit into the right leading edge of a JetStar aircraft. The article was designed to attach to the front spar and fill in approx. 70 inches of the leading edge that are normally occupied by the large slipper fuel tank. The outer contour of the test article was constrained to align with an external fairing aft of the front spar which provided a surface pressure distribution over the test region representative of an LFC airfoil. LFC is achieved by applying suction through a finely perforated surface, which removes a small fraction of the boundary layer. The LFC test article has a retractable high lift shield to protect the laminar surface from contamination by airborne debris during takeoff and low altitude operation. The shield is designed to intercept insects and other particles that could otherwise impact the leading edge. Because the shield will intercept freezing rain and ice, a oozing glycol ice protection system is installed on the shield leading edge. In addition to the shield, a liquid freezing point depressant can be sprayed on the back of the shield.

Pearce, W. E.; Mcnay, D. E.; Thelander, J. A.

1984-01-01

42

Leading Edge The Human Condition--A Molecular Approach  

E-print Network

), but for the longest time after that, human ancestors continued doing pretty much what their ape-like ancestors did. Only some 2.6 million years ago did human ancestors start making stone tools that can be recog- nizedLeading Edge Review The Human Condition--A Molecular Approach Svante Pa¨ a¨ bo1,* 1Department

Pääbo, Svante

43

The Flow Field on Hydrofoils with Leading Edge Protuberances  

NASA Astrophysics Data System (ADS)

The agility of the humpback whale has been attributed to the use of its pectoral flippers, on which protuberances are present along the leading edge. The forces and moments on hydrofoils with leading edge protuberances were measured in a water tunnel and were compared to a baseline NACA 63(4)-021 hydrofoil revealing significant performance differences. Three protuberance amplitudes and two spanwise wavelengths, closely resembling the morphology found in nature, were examined. Qualitative flow visualization techniques were used to examine flow patterns surrounding the hydrofoils, and Particle Image Velocimetry (PIV) was used to quantify these patterns. Flow visualizations have revealed counter-rotating vortices stemming from the shoulders of the protuberances. These streamwise vortices are a result of the spanwise pressure gradient brought about by the varying leading edge curvature. PIV was used to quantify the strength of these vortices as a function of angle of attack and leading edge geometry. At low angles of attack, these vortices are symmetric with respect to the protuberances; however, the symmetry is lost at high angles of attack. The loss of symmetry can be correlated with the separation point location on the hydrofoil.

Custodio, Derrick; Henoch, Charles; Johari, Hamid

2008-11-01

44

Stability of the Leading Edge Vortex on Insect Wings  

Microsoft Academic Search

A defining characteristic of the flowfield associated with insect flight is a stable leading edge vortex that persists over a majority of the flapping stroke. While it is known that spanwise flow, coupled with the effect of wing rotation and interaction with the tip vortex can result in stability, the specific mechanisms by which this stability is achieved have not

B. Bush; K. Duraisamy; J. Baeder

2007-01-01

45

Rotational accelerations stabilize leading edge vortices on revolving fly wings  

Microsoft Academic Search

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

D. Lentink; M. H. Dickinson

2009-01-01

46

Detail view of the leading and top edge of the ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail view of the leading and top edge of the vertical stabilizer of the Orbiter Discovery showing the thermal protection system components with the white Advanced Flexible Reusable Surface Insulation (AFRSI) blanket and the black High-temperature Reusable Surface Insulation (HRSI) tiles along the outer edges. The marks seen on the HRSI tiles are injection point marks and holes for the application of waterproofing material. This view was taken from a service platform in the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

47

The fish tail motion forms an attached leading edge vortex.  

PubMed

The tail (caudal fin) is one of the most prominent characteristics of fishes, and the analysis of the flow pattern it creates is fundamental to understanding how its motion generates locomotor forces. A mechanism that is known to greatly enhance locomotor forces in insect and bird flight is the leading edge vortex (LEV) reattachment, i.e. a vortex (separation bubble) that stays attached at the leading edge of a wing. However, this mechanism has not been reported in fish-like swimming probably owing to the overemphasis on the trailing wake, and the fact that the flow does not separate along the body of undulating swimmers. We provide, to our knowledge, the first evidence of the vortex reattachment at the leading edge of the fish tail using three-dimensional high-resolution numerical simulations of self-propelled virtual swimmers with different tail shapes. We show that at Strouhal numbers (a measure of lateral velocity to the axial velocity) at which most fish swim in nature (approx. 0.25) an attached LEV is formed, whereas at a higher Strouhal number of approximately 0.6 the LEV does not reattach. We show that the evolution of the LEV drastically alters the pressure distribution on the tail and the force it generates. We also show that the tail's delta shape is not necessary for the LEV reattachment and fish-like kinematics is capable of stabilising the LEV. Our results suggest the need for a paradigm shift in fish-like swimming research to turn the focus from the trailing edge to the leading edge of the tail. PMID:23407826

Borazjani, Iman; Daghooghi, Mohsen

2013-04-01

48

The fish tail motion forms an attached leading edge vortex  

PubMed Central

The tail (caudal fin) is one of the most prominent characteristics of fishes, and the analysis of the flow pattern it creates is fundamental to understanding how its motion generates locomotor forces. A mechanism that is known to greatly enhance locomotor forces in insect and bird flight is the leading edge vortex (LEV) reattachment, i.e. a vortex (separation bubble) that stays attached at the leading edge of a wing. However, this mechanism has not been reported in fish-like swimming probably owing to the overemphasis on the trailing wake, and the fact that the flow does not separate along the body of undulating swimmers. We provide, to our knowledge, the first evidence of the vortex reattachment at the leading edge of the fish tail using three-dimensional high-resolution numerical simulations of self-propelled virtual swimmers with different tail shapes. We show that at Strouhal numbers (a measure of lateral velocity to the axial velocity) at which most fish swim in nature (approx. 0.25) an attached LEV is formed, whereas at a higher Strouhal number of approximately 0.6 the LEV does not reattach. We show that the evolution of the LEV drastically alters the pressure distribution on the tail and the force it generates. We also show that the tail's delta shape is not necessary for the LEV reattachment and fish-like kinematics is capable of stabilising the LEV. Our results suggest the need for a paradigm shift in fish-like swimming research to turn the focus from the trailing edge to the leading edge of the tail. PMID:23407826

Borazjani, Iman; Daghooghi, Mohsen

2013-01-01

49

Fabrication and Testing of a Leading-Edge-Shaped Heat Pipe  

NASA Technical Reports Server (NTRS)

The development of a refractory-composite/heat-pipe-cooled leading edge has evolved from the design stage to the fabrication and testing of a full size, leading-edge-shaped heat pipe. The heat pipe had a 'D-shaped' cross section and was fabricated from arc cast Mo-4lRe. An artery was included in the wick. Several issues were resolved with the fabrication of the sharp leading edge radius heat pipe. The heat pipe was tested in a vacuum chamber at Los Alamos National Laboratory using induction heating and was started up from the frozen state several times. However, design temperatures and heat fluxes were not obtained due to premature failure of the heat pipe resulting from electrical discharge between the induction heating apparatus and the heat pipe. Though a testing anomaly caused premature failure of the heat pipe, successful startup and operation of the heat pipe was demonstrated.

Glass, David E.; Merrigan, Michael A.; Sena, J. Tom; Reid, Robert S.

1998-01-01

50

Closed Form Equations for the Preliminary Design of a Heat-Pipe-Cooled Leading Edge  

NASA Technical Reports Server (NTRS)

A set of closed form equations for the preliminary evaluation and design of a heat-pipe-cooled leading edge is presented. The set of equations can provide a leading-edge designer with a quick evaluation of the feasibility of using heat-pipe cooling. The heat pipes can be embedded in a metallic or composite structure. The maximum heat flux, total integrated heat load, and thermal properties of the structure and heat-pipe container are required input. The heat-pipe operating temperature, maximum surface temperature, heat-pipe length, and heat pipe-spacing can be estimated. Results using the design equations compared well with those from a 3-D finite element analysis for both a large and small radius leading edge.

Glass, David E.

1998-01-01

51

Turbine Airfoil With CMC Leading-Edge Concept Tested Under Simulated Gas Turbine Conditions  

NASA Technical Reports Server (NTRS)

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 metal vane was tested for a total of 150 cycles. Both the leading edge and trailing edge of the blade exhibited fatigue cracking and burn-through similar to the failures experienced in service by the F402 engine. Next, an airfoil, fitted with the ceramic leading edge insert, was exposed for 200 cycles. The temperature response of those HPBR cycles indicated a reduced internal metal temperature, by as much as 600 F at the midspan location for the same surface temperature (2100 F). After testing, the composite insert appeared intact, with no signs of failure on either the vane s leading or trailing edge. Only a slight oxide scale, as would be expected, was noted on the insert. Overall, the CMC insert performed similarly to a thick thermal barrier coating. With a small air gap between the metal and the SiC/SiC leading edge, heat transfer from the CMC to the metal alloy was low, effectively lowering the temperatures. The insert's performance has proven that an uncooled CMC can be engineered and designed to withstand the thermal up-shock experienced during the severe lift conditions in the Pegasus engine. The design of the leading-edge insert, which minimized thermal stresses in the SiC/SiC CMC, showed that the CMC/metal assembly can be engineered to be a functioning component.

Robinson, R. Craig; Hatton, Kenneth S.

2000-01-01

52

Nondestructive Evaluation for the Space Shuttle's Wing Leading Edge  

NASA Technical Reports Server (NTRS)

The loss of the Space Shuttle Columbia highlighted concerns about the integrity of the Shuttle's thermal protection system, which includes Reinforced Carbon-Carbon (RCC) on the leading edge. This led NASA to investigate nondestructive evaluation (NDE) methods for certifying the integrity of the Shuttle's wing leading edge. That investigation was performed simultaneously with a large study conducted to understand the impact damage caused by errant debris. Among the many advanced NDE methods investigated for applicability to the RCC material, advanced digital radiography, high resolution computed tomography, thermography, ultrasound, acoustic emission and eddy current systems have demonstrated the maturity and success for application to the Shuttle RCC panels. For the purposes of evaluating the RCC panels while they are installed on the orbiters, thermographic detection incorporating principal component analysis (PCA) and eddy current array scanning systems demonstrated the ability to measure the RCC panels from one side only and to detect several flaw types of concern. These systems were field tested at Kennedy Space Center (KSC) and at several locations where impact testing was being conducted. Another advanced method that NASA has been investigating is an automated acoustic based detection system. Such a system would be based in part on methods developed over the years for acoustic emission testing. Impact sensing has been demonstrated through numerous impact tests on both reinforced carbon-carbon (RCC) leading edge materials as well as Shuttle tile materials on representative aluminum wing structures. A variety of impact materials and conditions have been evaluated including foam, ice, and ablator materials at ascent velocities as well as simulated hypervelocity micrometeoroid and orbital debris impacts. These tests have successfully demonstrated the capability to detect and localize impact events on Shuttle's wing structures. A first generation impact sensing system has been designed for the next Shuttle flight and is undergoing final evaluation for deployment on the Shuttle's first return to flight. This system will employ wireless accelerometer sensors that were qualified for other applications on previous Shuttle flights. These sensors will be deployed on the wing's leading edge to detect impacts on the RCC leading edge panels. The application of these methods will help to insure the continued integrity of the Shuttle wing's leading edge system as the Shuttle flights resume and until their retirement.

Madaras, Eric I.; Winfree, William P.; Prosser, William H.; Wincheski, Russell A.; Cramer, K. Elliot

2005-01-01

53

Probabilistic Structural Health Monitoring of the Orbiter Wing Leading Edge  

NASA Technical Reports Server (NTRS)

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.

Yap, Keng C.; Macias, Jesus; Kaouk, Mohamed; Gafka, Tammy L.; Kerr, Justin H.

2011-01-01

54

The Flow Field on Hydrofoils with Leading Edge Protuberances  

NASA Astrophysics Data System (ADS)

The exceptional mobility of the humpback whale has been linked to the use of its unique pectoral flippers. Biologists speculate that the flippers leading edge protuberances are a form of passive flow control. Force measurements on 2D hydrofoils with spanwise uniform leading edge protuberances, resembling those seen on the humpback whale flipper, were taken in a water tunnel and have revealed performance modifications when compared to a baseline NACA 63(4)-021 hydrofoil model. Qualitative flow visualization techniques and Particle Image Velocimetry (PIV) flow field measurements on the modified hydrofoils have shown that streamwise vortices originating from the shoulders of the protuberances are the likely cause of performance changes. Varying levels of interaction among adjacent streamwise vortices have been observed as a function of angle of attack and chord location. The circulation of these vortices as a function of angle of attack and spatial location was measured and an analysis of the vortex interactions will be presented.

Custodio, Derrick; Henoch, Charles; Johari, Hamid

2009-11-01

55

Heat pipes for wing leading edges of hypersonic vehicles  

NASA Technical Reports Server (NTRS)

Wing leading edge heat pipes were conceptually designed for three types of vehicle: an entry research vehicle, aero-space plane, and advanced shuttle. A full scale, internally instrumented sodium/Hastelloy X heat pipe was successfully designed and fabricated for the advanced shuttle application. The 69.4 inch long heat pipe reduces peak leading edge temperatures from 3500 F to 1800 F. It is internally instrumented with thermocouples and pressure transducers to measure sodium vapor qualities. Large thermal gradients and consequently large thermal stresses, which have the potential of limiting heat pipe life, were predicted to occur during startup. A test stand and test plan were developed for subsequent testing of this heat pipe. Heat pipe manufacturing technology was advanced during this program, including the development of an innovative technique for wick installation.

Boman, B. L.; Citrin, K. M.; Garner, E. C.; Stone, J. E.

1990-01-01

56

Dual leading-edge vortices on flapping wings.  

PubMed

An experimental investigation was performed with two aims: (1) to clarify the existence of the dual leading-edge vortices (i.e. two vortices with the same sense of rotation located close to the leading edge above the leeward wing surface) observed on flapping wings in previous studies; (2) to study systematically the influences of kinematic and geometric parameters on such a vortical structure. Based on a scaled-up electromechanical model flapping in a water tank, the leading-edge vortex (LEV) cores were visualized via dye flow visualization, and the detailed sub-structures of LEV were revealed through digital particle image velocimetry (DPIV) with high spatial resolution. Five wing aspect ratios (AR) (1.3, 3.5, 5.8, 7.5 and 10), eight mid-stroke angles of attack (alpha(m)) (10-80 degrees), and six Reynolds numbers (Re) (160-3200) were examined. In addition, the well-studied case of the fruit fly Drosophila was re-examined. The results confirm for the first time the existence of dual LEVs on flapping wings. The sectional flow structure resembles the dual-vortex observed on non-slender delta wings. Insensitive to AR, a dual LEV system such as this could be created when alpha(m) and Re reached certain high levels. The primary vortex was attached to the wing, while at the outer wing the minor vortex shed, generating a same-sense vortex behind. PMID:17142689

Lu, Yuan; Shen, Gong Xin; Lai, Guo Jun

2006-12-01

57

Flexible Plug Repair for Shuttle Wing Leading Edge  

NASA Technical Reports Server (NTRS)

In response to the Columbia Accident Investigation Board report, a plug repair kit has been developed to enable astronauts to repair the space shuttle's wing leading edge (WLE) during orbit. The plug repair kit consists of several 17.78- cm-diameter carbon/silicon carbide (C/SiC) cover plates of various curvatures that can be attached to the refractory carbon-carbon WLE panels using a TZM refractory metal attach mechanism. The attach mechanism is inserted through the damage in the WLE panel and, as it is tightened, the cover plate flexes to conform to the curvature of the WLE panel within 0.050 mm. An astronaut installs the repair during an extravehicular activity (EVA). After installing the plug repair, edge gaps are checked and the perimeter of the repair is sealed using a proprietary material, developed to fill cracks and small holes in the WLE.

Camarda, Charles J.; Sikora, Joseph; Smith, Russel; Rivers, H.; Scotti, Stephen J.; Fuller, Alan M.; Klacka, Robert; Reinders, Martin; Schwind, Francis; Sullivan, Brian; Lester, Dean

2012-01-01

58

An Aeroacoustic Study of a Leading Edge Slat Configuration  

NASA Technical Reports Server (NTRS)

Aeroacoustic evaluations of high-lift devices have been carried out in the Quiet Flow Facility of the NASA Langley Research Center. The present paper describes detailed flow and acoustic measurements that have been made in order to better understand the noise generated from airflow over a wing leading edge slat configuration, and to possibly predict and reduce this noise source. The acoustic database is obtained by a moveable Small Aperture Directional Array of microphones designed to electronically steer to different portions of models under study. The slat is shown to be a uniform distributed noise source. The data was processed such that spectra and directivity were determined with respect to a one-foot span of slat. The spectra are normalized in various fashions to demonstrate slat noise character. In order to equate portions of the spectra to different slat noise components, trailing edge noise predictions using measured slat boundary layer parameters as inputs are compared to the measured slat noise spectra.

Mendoza, J. M.; Brooks, T. F.; Humphreys, W. M., Jr.

2002-01-01

59

ISOTOPIC COMPOSITION OF LEAD FROM TEKTITES  

Microsoft Academic Search

The isotopic composition of lead in three tektites and Libyan Desert ; glass is compared with that in knowa terrestrial and extra-terrestrial sources. ; The lead contained in the glasses is similar to modern terrestrial lead, ; particularly lead frozen modern oceanic sediments. The uranium, thorium, and ; lead concentrations were determined for one of the glasses, an australia. ;

G TILTON

1958-01-01

60

Method Improvements in Thermal Analysis of Mach 10 Leading Edges  

NASA Technical Reports Server (NTRS)

Several improvements have recently been made in the thermal analysis methods for leading edges of a hypersonic vehicle. The leading edges of this vehicle undergo exceptionally high heat loads that incorporate extreme spatial gradients as well as severe transients. Due to the varying flight conditions, complex geometry, and need for thermal loads at many points along the trajectory, full computational fluid dynamics (CFD) analysis of the aeroheating; loads is not feasible. Thus, engineering methods must be used to determine the aeroheating on the vehicle surfaces, and that must be utilized in the thermal analysis. Over the last year, the thermal analysis of a hypersonic vehicle has been enhanced in several ways. Two different engineering codes are used to predict aeroheating loads: one over the curve near the stagnation point, and the other on flat surfaces downstream of the leading edge. These two are matched together at the intersection point using a method that allows closer approximation of CFD results. User-developed FORTRAN, which is part of the thermal solver PATRAN Thermal, is used to accomplish this. The customizable FORTRAN code also allows use of many different time- and space-dependent factors, interpolation of the heat load in time and space, and inclusion of both highly swept and unswept grid structures. This FORTRAN is available to other PATRAN users who may want to accomplish a similar objective in analysis. Flux, rather than convective coefficient, is used to define heat loads, which allows more accurate analysis as well as better application of margins. Improvements have also been made in more efficient utilization of imported CAD geometry, by creating faces on solids to facilitate load application.

Amundsen, Ruth M.

2001-01-01

61

Thermostructural applications of heat pipes for cooling leading edges of high-speed aerospace vehicles  

NASA Technical Reports Server (NTRS)

Heat pipes have been considered for use on wing leading edge for over 20 years. Early concepts envisioned metal heat pipes cooling a metallic leading edge. Several superalloy/sodium heat pipes were fabricated and successfully tested for wing leading edge cooling. Results of radiant heat and aerothermal testing indicate the feasibility of using heat pipes to cool the stagnation region of shuttle-type space transportation systems. The test model withstood a total seven radiant heating tests, eight aerothermal tests, and twenty-seven supplemental radiant heating tests. Cold-wall heating rates ranged from 21 to 57 Btu/sq ft-s and maximum operating temperatures ranged from 1090 to 1520 F. Follow-on studies investigated the application of heat pipes to cool the stagnation regions of single-stage-to-orbit and advanced shuttle vehicles. Results of those studies indicate that a 'D-shaped' structural design can reduce the mass of the heat-pipe concept by over 44 percent compared to a circular heat-pipe geometry. Simple analytical models for heat-pipe startup from the frozen state (working fluid initially frozen) were adequate to approximate transient, startup, and steady-state heat-pipe performance. Improvement in analysis methods has resulted in the development of a finite-element analysis technique to predict heat-pipe startup from the frozen state. However, current requirements of light-weight design and reliability suggest that metallic heat pipes embedded in a refractory composite material should be used. This concept is the concept presently being evaluated for NASP. A refractory-composite/heat-pipe-cooled wing leading edge is currently being considered for the National Aero-Space Plane (NASP). This concept uses high-temperature refractory-metal/lithium heat pipes embedded within a refractory-composite structure and is significantly lighter than an actively cooled wing leading edge because it eliminates the need for active cooling during ascent and descent. Since the NASP vehicle uses cryogenic hydrogen to cool structural components and then burns this fuel in the combustor, hydrogen necessary for descent cooling only, when the vehicle is unpowered, is considered to be a weight penalty. Details of the design of the refractory-composite/heat-pipe-cooled wing leading edge are currently being investigated. Issues such as thermal contact resistance and thermal stress are also being investigated.

Camarda, Charles J.; Glass, David E.

1992-01-01

62

Separation Control on a Hydrofoil Using Leading Edge Protuberances  

NASA Astrophysics Data System (ADS)

The humpback whale's maneuvarability has been attributed to their use of pectoral flippers, on which protuberances are present along the leading edge. To examine the effects of protuberances on hydrofoil performance, the lift, drag, and pitching moments of two-dimensional hydrofoils with leading edge sinusoidal protuberances were measured in a water tunnel and compared to those of a baseline NACA 63(4)-021 hydrofoil. The amplitude and spanwise wavelengths of the protuberances ranged from 2.5% to 12% and 25% to 50% of the mean chord length respectively. Flow visualizations using tufts and dye, as well as Laser Doppler Velocimetry (LDV) measurements were performed to examine the flow patterns surrounding the hydrofoils. At angles of attack lower than the stall angle of the baseline, the modified foils revealed lower lift and increased drag. However, above this angle the lift generated by the modified foils was up to 50% greater than the baseline foil with little or no drag penalty. The amplitude of the protuberances has a large effect on the performance of the hydrofoils whereas the wavelength has little. Flow topology on the protuberances will be discussed by means of the visualization and measured velocities.

Custodio, Derrick; Henoch, Charles; Johari, Hamid

2007-11-01

63

Stability of the Leading Edge Vortex on Insect Wings  

NASA Astrophysics Data System (ADS)

A defining characteristic of the flowfield associated with insect flight is a stable leading edge vortex that persists over a majority of the flapping stroke. While it is known that spanwise flow, coupled with the effect of wing rotation and interaction with the tip vortex can result in stability, the specific mechanisms by which this stability is achieved have not been clearly identified. Towards a clarification of this issue, two idealized cases are computationally simulated. First, computations of the flow over a rectangular plate in linear translation are compared with experimental data to provide both code validation and a basis for comparison with the rotational cases. Secondly, a model wing, similar in planform to a fruit fly (Drosophila), is simulated both in steady translation and in an impulsively started steady rotation at a constant angle of attack. The stability of the resulting vortex system is compared against the translational cases at various Reynolds numbers and angles of attack to better understand the role that rotation and planform shape play in the leading edge vortex development and stability.

Bush, B.; Duraisamy, K.; Baeder, J.

2007-11-01

64

Leading-edge tubercles delay stall on humpback whale ,,Megaptera novaeangliae... flippers  

E-print Network

Leading-edge tubercles delay stall on humpback whale ,,Megaptera novaeangliae... flippers D. S, that the addition of leading-edge tubercles to a scale model of an idealized humpback whale flipper delays the stall

Fish, Frank

65

Control of leading-edge vortices on a delta wing  

NASA Technical Reports Server (NTRS)

The unsteady flow structure of leading-edge vortices on a delta wing has been investigated using new types of experimental techniques, in order to provide insight into the consequences of various forms of active control. These investigations involve global control of the entire wing and local control applied at crucial locations on or adjacent to the wing. Transient control having long and short time-scales, relative to the convective time-scale C/U(sub infinity), allows substantial modification of the unsteady and time-mean flow structure. Global control at long time-scale involves pitching the wing at rates an order of magnitude lower than the convective time-scale C/U(sub infinity), but at large amplitudes. The functional form of the pitching maneuver exerts a predominant influence on the trajectory of the feeding sheet, the instantaneous vorticity distribution, and the instantaneous location of vortex breakdown. Global control at short time-scales of the order of the inherent frequency of the shear layer separating from the leading-edge and the natural frequency of vortex breakdown shows that 'resonant' response of the excited shear layer-vortex breakdown system is attainable. The spectral content of the induced disturbance is preserved not only across the entire core of the vortex, but also along the axis of the vortex into the region of vortex breakdown. This unsteady modification results in time-mean alteration of the axial and swirl velocity fields and the location of vortex breakdown. Localized control at long and short time-scales involves application of various transient forms of suction and blowing using small probes upstream and downstream of the location of vortex breakdown, as well as distributed suction and blowing along the leading-edge of the wing applied in a direction tangential to the feeding sheet. These local control techniques can result in substantial alteration of the location of vortex breakdown; in some cases, it is possible to accomplish this without net mass addition to the flow field.

Magness, C.; Robinson, O.; Rockwell, D.

1992-01-01

66

Seven hole probe measurement of leading edge vortex flows  

NASA Technical Reports Server (NTRS)

This paper discusses the use of a seven-hole probe on measurements of leading edge vortices of highly sweep delta wing planforms. Intrusive probe data taken with the pressure probe were compared with nonintrusive measurements made with laser Doppler anemometry system. In addition to probe size, the natural position of breakdown and the sweep angle of the wing are also factors in determining sensitivity of the flow to probe interference. At low angles of attach vortex breakdown does not occur in the vicinity of the model and the seven hole probe was found to yield reasonably accurate measurements. When the angle of attack of the model was increased so that vortex breakdown was near the trailing edge, introducing the probe over the wing would cause the breakdown position to move ahead of the probe. However, when breakdown naturally occurred ahead of the mid-chord of the wing the vortices were found to be less sensitive to a probe placed behind the breakdown point. Vortex breakdown on a lower swept wing is found to be more sensitive to interference. Near the breakdown region, seven hole probe measurement is less accurate due to a combination of probe interference and flow reversal.

Payne, F. M.; Ng, T. T.; Nelson, R. C.

1989-01-01

67

Particle rebound characteristics of turbomachinery cascade leading edge geometry  

NASA Astrophysics Data System (ADS)

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 impact velocity was used as input to the DYNA3-D numerical simulation instead of a deterministic impact velocity. From these random simulations, mean values, for rebound velocity and velocity restitution ratio, were obtained. These results are compared with the results obtained from deterministic model. Von-Mises effective stress and shear stress for multi-particle impacts are studied in detail. A DYNA3-D impact model in which several silica sand particles impact the cylindrical target was developed. The impacts were simulated in such way that the sand particles impact the cylindrical target in phase, out of phase, in the same longitudinal plane & different longitudinal plane. Maxima of effective stress (v-m) & shear stress with respect to time are plotted. Particle rebound characteristics on leading edge geometry were obtained using two-dimensional LDV measurements and high-speed photography. A Wollensax Fastax camera was used to film the particulate flow. In the current investigation a camera speed of 2500 frames/sec was used. The developed film from high-speed photography was digitized. The data were processed using x-v image processing software. The restitution ratios of the particle collisions on pressure and suction surface of the blade leading edge are obtained for different impact angles at the two different impact velocities (15 m/s & 30 m/s). A simple mechanical model was also developed to study inter-particle collisions. Results obtained from the model are compared with the results obtained from high-speed photography and DYNA3-D. Blade surface erosion rate was calculated using an empirical model and is compared against the values obtained from cold tunnel experiments.

Siravuri, Sastri

68

Experimental and Numerical Study of CMC Leading Edges in Hypersonic Flows  

NASA Astrophysics Data System (ADS)

Future transportation concepts aim at high supersonic or hypersonic speeds, where the formerly sharp boundaries between aeronautic and aerospace applications become blurred. One of the major issues involved to high speed flight are extremely high aerothermal loads, which especially appear at the leading edges of the plane's wings and at sharp edged air intake components of the propulsion system. As classical materials like metals or simple ceramics would thermally and structurally fail here, new materials have to be applied. In this context, lightweight ceramic matrix composites (CMC) seem to be prospective candidates as they are high-temperature resistant and offer low thermal expansion along with high specific strength at elevated temperature levels. A generic leading edge model with a ceramic wing assembly with a sweep back angle of 53° was designed, which allowed for easy leading edge sample integration of different CMC materials. The samples consisted of the materials C/C-SiC (non-oxide), OXIPOL and WHIPOX (both oxide) with a nose radius of 2 mm. In addition, a sharp edged C/C-SiC sample was prepared to investigate the nose radius influence. Overall, 13 thermocouples were installed inside the entire model to measure the temperature evolution at specific locations, whereby 5 thermocouples were placed inside the leading edge sample itself. In addition, non-intrusive techniques were applied for surface temperature measurements: An infrared camera was used to measure the surface temperature distribution and at specific spots, the surface temperature was also measured by pyrometers. Following, the model was investigated in DLR's arc-heated facility L3K at a total enthalpy of 8.5 MJ/kg, Mach number of 7.8, different angles of attack and varying wing inclination angles. These experiments provide a sound basis for the simulation of aerothermally loaded CMC leading edge structures. Such fluid-structure coupled approaches have been performed by FOI, basing on a modal approach for the conduction model. Results show, that the temperature profiles are correctly depicted dependent on the model's angle of attack.

Kuhn, M.; Esser, B.; Gülhan, A.; Dalenbring, M.; Cavagna, L.

2011-08-01

69

Rotational accelerations stabilize leading edge vortices on revolving fly wings.  

PubMed

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 (100leading edge) vortices could represent a convergent solution for the generation of high fluid forces over a quite large range in size. PMID:19648415

Lentink, David; Dickinson, Michael H

2009-08-01

70

ISOTOPIC COMPOSITION OF LEAD IN PEGMATITIC FELDSPARS  

Microsoft Academic Search

An ion-exchange method was developed for extracting microgram quantities ; of lead from pegmatitic feldspars. The isotopie composition of lead in feldspars ; ranging from 350 to 2750 million years (m.y.) in age was determined. Model ages ; were calculated and were generally found to be in good agreement with independent ; age determinations. The results are compatible with a

E. J. Catanzaro; P. W. Gast

1960-01-01

71

Leading edge vortex in a slow-flying passerine  

PubMed Central

Most hovering animals, such as insects and hummingbirds, enhance lift by producing leading edge vortices (LEVs) and by using both the downstroke and upstroke for lift production. By contrast, most hovering passerine birds primarily use the downstroke to generate lift. To compensate for the nearly inactive upstroke, weight support during the downstroke needs to be relatively higher in passerines when compared with, e.g. hummingbirds. Here we show, by capturing the airflow around the wing of a freely flying pied flycatcher, that passerines may use LEVs during the downstroke to increase lift. The LEV contributes up to 49 per cent to weight support, which is three times higher than in hummingbirds, suggesting that avian hoverers compensate for the nearly inactive upstroke by generating stronger LEVs. Contrary to other animals, the LEV strength in the flycatcher is lowest near the wing tip, instead of highest. This is correlated with a spanwise reduction of the wing's angle-of-attack, partly owing to upward bending of primary feathers. We suggest that this helps to delay bursting and shedding of the particularly strong LEV in passerines. PMID:22417792

Muijres, Florian T.; Johansson, L. Christoffer; Hedenström, Anders

2012-01-01

72

Nondestructive Evaluation Tests Performed on Space Shuttle Leading- Edge Materials Subjected to Impact  

NASA Technical Reports Server (NTRS)

In support of the space shuttle Return To Flight efforts at the NASA Glenn Research Center, a series of nondestructive evaluation (NDE) tests were performed on reinforced carbon/carbon (RCC) composite panels subjected to ballistic foam impact. The impact tests were conducted to refine and verify analytical models of an external tank foam strike on the space shuttle leading edge. The NDE tests were conducted to quantify the size and location of the resulting damage zone as well as to identify hidden damage.

Roth, Don J.; Martin, Richard E.; Bodis, James R.

2005-01-01

73

The Columbia River--on the Leading Edge  

NASA Astrophysics Data System (ADS)

On the leading edge of the North American plate, the Columbia River is the largest of the world's 40 or so rivers with drainage areas greater than 500,000 square kilometers to drain toward a convergent plate boundary. This unique setting results in a unique continental river basin; marked by episodic and cataclysmic geologic disturbance, but also famously fecund with perhaps 10 to 16 million salmon historically spawning in its waters each year. Now transformed by dams, transportation infrastructure, dikes and diversions, the Columbia River presents an expensive conundrum for management of its many values. Inclusion of river ecology and geomorphology in discussions of river management is generally limited to observations of the last 200 years-a time period of little natural disturbance and low sediment transport. However, consideration of longer timescales provides additional perspective of historical ecologic and geomorphic conditions. Only 230 km from its mouth, the Columbia River bisects the volcanic arc of the Cascade Range, forming the Columbia River Gorge. Cenozoic lava flows have blocked the river, forcing diversions and new canyon cutting. Holocene eruptions of Mount Mazama (Crater Lake), Mount Hood, Mount St. Helens, and Mount Rainier have shed immense quantities of sediment into the lower Columbia River, forming a large percentage of the Holocene sediment transported through the lower river. Quaternary landslides, perhaps triggered by great earthquakes, have descended from the 1000-m-high gorge walls, also blocking and diverting the river, one as recently as 550 years ago. These geologic disturbances, mostly outside the realm of historical observation and operating at timescales of 100s to 1000s of years in the gorge and elsewhere, have clearly affected basin geomorphology, riverine ecology, and past and present cultural utilization of river resources. The historic productivity of the river, however, hints at extraordinary resilience (and perhaps dependence) of the Columbia River system to such disturbances, many of which are similar to engineered disturbances of the last 200 years.

O'Connor, J. E.

2005-05-01

74

Preparation and Support of a Tap Test on the Leading Edge Surfaces of the Space Shuttle  

NASA Technical Reports Server (NTRS)

This slide presentation reports on a Tap test for the leading edge surfaces of the Space Shuttle. A description of the Wing Leading Edge Impact Detection System (WLEIDS) flight system is given, and the rationale and approach for improving the WLEIDS system. The three phases of the strategy of the test project amd the results of the tests are reviewed.

Bohr, Jerry

2009-01-01

75

Case Studies of Leading Edge Small Urban High Schools. Relevance Strategic Designs: 6. Perspectives Charter School  

ERIC Educational Resources Information Center

This report is one of nine detailed case studies of small urban high schools that served as the foundation for the Education Resource Strategies (ERS) report "Strategic Designs: Lessons from Leading Edge Small Urban High Schools." These nine schools were dubbed "Leading Edge Schools" because they stand apart from other high schools across the…

Shields, Regis Anne; Ireland, Nicole; City, Elizabeth; Derderian, Julie; Miles, Karen Hawley

2008-01-01

76

A method for computing the leading-edge suction in a higher-order panel method  

NASA Technical Reports Server (NTRS)

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.

Ehlers, F. E.; Manro, M. E.

1984-01-01

77

SIMS chemical analysis of extended impacts on the leading and trailing edges of LDEF experiment AO187-2  

NASA Technical Reports Server (NTRS)

Numerous 'extended impacts' found in both leading and trailing edge capture cells were successfully analyzed for the chemical composition of projectile residues by secondary ion mass spectrometry (SIMS). Most data were obtained from the trailing edge cells where 45 of 58 impacts were classified as 'probably natural' and the remainder as 'possibly man-made debris.' This is in striking contrast to leading edge cells where 9 of 11 impacts so far measured are definitely classified as orbital debris. Although all the leading edge cells had lost their plastic entrance foils during flight, the rate of foil failure was similar to that of the trailing edge cells, 10 percent of which were recovered intact. Ultraviolet embrittlement is suspected as the major cause of failure on both leading and trailing edges. The major impediment to the accurate determination of projectile chemistry is the fractionation of volatile and refractory elements in the hypervelocity impact and redeposition processes. This effect had been noted in a simulation experiment but is more pronounced in the LDEF capture cells, probably due to the higher average velocities of the space impacts. Surface contamination of the pure Ge surfaces with a substance rich in Si, but also containing Mg and Al, provides an additional problem for the accurate determination of impactor chemistry. The effect is variable, being much larger on surfaces that were exposed to space than in those cells that remained intact. Future work will concentrate on the analyses of more leading edge impacts and the development of new SIMS techniques for the measurement of elemental abundances in extended impacts.

Amari, S.; Foote, J.; Swan, P.; Walker, R. M.; Zinner, E.; Lange, G.

1993-01-01

78

Dynamic Impact Tolerance of Shuttle RCC Leading Edge Panels using LS-DYNA  

NASA Technical Reports Server (NTRS)

This paper describes a research program conducted to enable accurate prediction of the impact tolerance of the shuttle Orbiter leading-edge wing panels using 'physics-based- codes such as LS-DYNA, a nonlinear, explicit transient dynamic finite element code. The shuttle leading-edge panels are constructed of Reinforced-Carbon-Carbon (RCC) composite material, which issued because of its thermal properties to protect the shuttle during re-entry into the Earth's atmosphere. Accurate predictions of impact damage from insulating foam and other debris strikes that occur during launch required materials characterization of expected debris, including strain-rate effects. First, analytical models of individual foam and RCC materials were validated. Next, analytical models of individual foam cylinders impacting 6-in. x 6-in. RCC flat plates were developed and validated. LS-DYNA pre-test models of the RCC flat plate specimens established the impact velocity of the test for three damage levels: no-detectable damage, non-destructive evaluation (NDE) detectable damage, or visible damage such as a through crack or hole. Finally, the threshold of impact damage for RCC on representative Orbiter wing panels was predicted for both a small through crack and for NDE-detectable damage.

Fasanella, Edwin; Jackson, Karen E.; Lyle, Karen H.; Jones, Lisa E.; Hardy, Robin C.; Spellman, Regina L.; Carney, Kelly S.; Melis, Matthew E.; Stockwell, Alan E.

2008-01-01

79

Dynamics Impact Tolerance of Shuttle RCC Leading Edge Panels Using LS-DYNA  

NASA Technical Reports Server (NTRS)

This paper describes a research program conducted to enable accurate prediction of the impact tolerance of the shuttle Orbiter leading-edge wing panels using physics-based codes such as LS-DYNA, a nonlinear, explicit transient dynamic finite element code. The shuttle leading-edge panels are constructed of Reinforced-Carbon-Carbon (RCC) composite material, which is used because of its thermal properties to protect the shuttle during reentry into the Earth's atmosphere. Accurate predictions of impact damage from insulating foam and other debris strikes that occur during launch required materials characterization of expected debris, including strain-rate effects. First, analytical models of individual foam and RCC materials were validated. Next, analytical models of foam cylinders impacting 6- in. x 6-in. RCC flat plates were developed and validated. LS-DYNA pre-test models of the RCC flat plate specimens established the impact velocity of the test for three damage levels: no-detectable damage, non-destructive evaluation (NDE) detectable damage, or visible damage such as a through crack or hole. Finally, the threshold of impact damage for RCC on representative Orbiter wing panels was predicted for both a small through crack and for NDE-detectable damage.

Fasanella, Edwin L.; Jackson, Karen E.; Lyle, Karen H.; Jones, Lisa E.; Hardy, Robin C.; Spellman, Regina L.; Carney, Kelly S.; Melis, Matthew E.; Stockwell, Alan E.

2005-01-01

80

Study of supersonic wings employing the attainable leading-edge thrust concept  

NASA Technical Reports Server (NTRS)

A theoretical study was made of supersonic wing geometries at Mach 1.8, using the attainable leading-edge thrust concept. The attainable thrust method offers a powerful means to improve overall aerodynamic efficiency by identifying wing leading-edge geometries that promote attached flow and by defining a local angle-of-attack range over which attached flow may be obtained. The concept applies to flat and to cambered wings, which leads to the consideration of drooped-wing leading edges for attached flow at high lift coefficients.

Middleton, W. D.

1982-01-01

81

SIMS chemical analysis of extended impacts on the leading and trailing edges of LDEF experiment AO187-2  

NASA Astrophysics Data System (ADS)

The Long Duration Exposure Facility (LDEF) Experiment AO187-2 consisted of 237 capture cells, 120 on the leading edge and 117 on the trailing edge. Each cell was made of polished Ge plates covered with 2.5 micron thick mylar foil at 200 microns from the Ge. Although all leading edge cells and 105 trailing edge cells had lost their plastic covers during flight, optical and electron microscope examination revealed extended impacts in bare cells from either edge that apparently were produced by high velocity projectiles while the plastic foils were still in place. Detailed optical scanning yielded 53 extended impacts on 100 bare cells from the trailing edge that were selected for SIMS chemical analysis. Lateral multi-element ion probe profiles were obtained on 40 of these impacts. Material that can be attributed to the incoming projectiles was found in all analyzed extended compact features and most seem to be associated with cosmic dust particles. However, LDEF deposits are systematically enriched in the refractory elements Al, Ca, and Ti relative to Mg and Fe when compared to IDP's collected in the stratosphere and to chondritic compositions. These differences are most likely due to elemental fractionation effects during the high velocity impact but real differences between interplanetary particles captured on LDEF and stratospheric IDP's cannot be excluded. Recently we extended our studies to cells from the leading edge and the covered cells from the trailing edge. The 12 covered cells contain 20 extended impact candidates. Ion probe analysis of 3 yielded results similar to those obtained for impacts on the bare cells from the trailing edge. Optical scanning of the bare leading edge cell also reveals many extended impacts (42 on 22 cells scanned to date), demonstrating that the cover foils remained intact at least for some time. However, SIMS analysis showed elements that can reasonably be attributed to micrometeoroids in only 2 out of 11 impacts. Eight impacts have residues dominated by Al and one dominated by Ti, indicating a preponderance of orbital debris in leading edge impacts.

Amari, S.; Foote, J.; Simon, Charles G.; Swan, P.; Walker, R. M.; Zinner, E.; Jessberger, E. K.; Lange, G.; Stadermann, F.

1992-06-01

82

Forensic significance of bullet lead compositions.  

PubMed

The concentrations of seven elements in projectile lead specimens received as evidence were used to assess the frequency of the occurrence of two unrelated samples having indistinguishable compositions. A set of data from 1837 samples was selected for this study from a sampling of 23,054 lead bullets and shot pellets received as evidence in the FBI Laboratory over the period 1989 through 2002. The method used for selection of samples from case submissions ensured that no two samples of the same general type from the same case were included and that no bias was introduced concerning representation of manufacturers or production sources. A total of 1,686,366 pairwise lead sample comparisons were made using the concentrations of the elements Sb, Cu, As, Ag, Bi, Sn, and Cd using a match criterion of two times the sum of the standard deviations of the paired samples. Of the 1837 samples, 1397 samples, or 76%, are distinguishable from every other sample in this study. The total number of indistinguishable sample pairs is 674, for a frequency of 1 out of every 2502 comparisons. The frequency of occurrence of matching samples decreases as the number of measured elements is increased and as the precision of the measurements improves. For bullets in which all seven elements were determined, the match frequency is 1 in 7284. Compositional comparison of bullet lead provides a reliable, highly significant point of evidentiary comparison of potential sources of crime-related bullets. PMID:15813545

Koons, Robert D; Buscaglia, JoAnn

2005-03-01

83

Performance of hydrofoils with humpback whale-like leading edge protuberances.  

NASA Astrophysics Data System (ADS)

The humpback whale (Megaptera novaeangliae) is extremely maneuverable, compared to other whale species, despite its large size and rigid body. Turning maneuvers are especially evident during pursuit of prey. The agility of humpback whale has been attributed to their use of pectoral flippers. The thick flippers have large aspect ratios, and large scale protuberances are present on the leading edge. The flippers do not flap during turning maneuvers. The cross-section of the flipper has a profile similar to a NACA 634-021 airfoil. The amplitude of leading edge protuberances ranges from 2.5 to 12% of the chord, with a spanwise extent of 10 to 50% the chord depending on the location along the span. It has been hypothesized that the `bumpy' leading edge is used for flow control. To examine the effects of protuberances on the leading edge of hydrofoils, a series of rectangular foils with bumpy leading edges were manufactured. The leading edge is sinusoidal in the spanwise direction with amplitudes and wavelengths comparable to that of humpback whale's flippers. The forces and moments on these bumpy foils were measured in a water tunnel and compared with a smooth leading edge foil.

Levshin, Alexandra; Henoch, Charles; Johari, Hamid

2005-11-01

84

Analysis of edge impact stresses in composite plates  

NASA Technical Reports Server (NTRS)

The in-plane edge impact of composite plates, with or without a protection strip, is investigated. A computational analysis based on the Fast Fourier Transform technique is presented. The particular application of the present method is in the understanding of the foreign object damage problem of composite fan blades. The method is completely general and may be applied to the study of other stress wave propagation problems in a half space. Results indicate that for the protective strip to be effective in reducing impact stresses in the composite the thickness must be equal or greater than the impact contact dimension. Large interface shear stresses at the strip - composite boundary can be induced under impact.

Moon, F. C.; Kang, C. K.

1974-01-01

85

Generation of instability waves at a leading edge  

NASA Technical Reports Server (NTRS)

Two cases are considered. The first is concerned with mean flows of the Blasius type wherein the instabilities are represented by Tollmien-Schlichting waves. It is shown that the latter are generated fairly far downstream of the edge and are the result of a wave length reduction process that tunes the free stream disturbances to the Tollmien-Schlichting wave length. The other case is concerned with inflectional, uni-directional, transversely sheared mean flows. Such idealized flows provide a fairly good local representation to the nearly parallel flows in jets. They can support inviscid instabilities of the Kelvin-Helmholtz type. The various mathematically permissible mechanisms that can couple these instabilities to the upstream disturbances are discussed.

Goldstein, M. E.

1982-01-01

86

Heat transfer characteristics of hypersonic waveriders with an emphasis on the leading edge effects. M.S. Thesis, 1991  

NASA Technical Reports Server (NTRS)

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.

Vanmol, Denis O.; Anderson, John D., Jr.

1992-01-01

87

Spanwise visualization of the flow around a three-dimensional foil with leading edge protuberances  

NASA Astrophysics Data System (ADS)

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.

Stanway, M. J.; Techet, A. H.

2006-11-01

88

Industrial cooling tower fan blade having abrasion resistant leading edge  

Microsoft Academic Search

This patent describes a glass fiber reinforced, synthetic resin fan blade for large diameter industrial water cooling tower fans, wherein the outer body portion of the blade is constructed of a thermoset resin and has upper and lower surfaces of which a part thereof define an elongated leading which would be subject to abrasion deterioration during use of the blade.

L. F. Burdick; S. E. Mayes

1992-01-01

89

Hydrodynamic effects of leading-edge tubercles on control surfaces and in flapping foil propulsion  

E-print Network

This thesis investigates the hydrodynamic effects of biologically-inspired leading-edge tubercles. Two complementary studies examine the performance of three-dimensional hydrofoils based on the pectoral flippers of the ...

Stanway, Michael Jordan

2008-01-01

90

Photographer; NACA North American F-100A NASA-200 Super Sabre airplane - wing leading edge deflected  

NASA Technical Reports Server (NTRS)

Photographer; NACA North American F-100A NASA-200 Super Sabre airplane - wing leading edge deflected 60 degrees for increased lift with boundary=layer control; takeoff preformance was improved 10% (mar 1960)

1958-01-01

91

Computational simulation of flows about hypersonic geometries with sharp leading edges  

NASA Technical Reports Server (NTRS)

Hypersonic waverider design has become an important concern in the aerospace industry. As one part of an inverse design effort for waveriders, work has been done to apply existing Euler and Navier-Stokies flow solvers to hypersonic geometries with sharp leading edges. Previously, calculations were done on bodies with rounded leading edges or with conical solutions for the nose initial conditions. In this paper, solutions are computed about waveriders and conical shapes with sharp leading edges without resorting to either shortrcut. All solutions show attached shocks with fully supersonic flows at the nose and along the leading edges. Flows about several waverider shapes are shown, as well as a preliminary cone with inlet calculation to study the shock/inlet interaction.

Jones, Kevin D.; Dougherty, F. Carroll

1990-01-01

92

Manipulation of upstream rotor leading edge vortex and its effects on counter rotating propeller noise  

NASA Technical Reports Server (NTRS)

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.

Squires, Becky

1993-01-01

93

Design and fabrication of a high temperature leading edge heating array, phase 1  

NASA Technical Reports Server (NTRS)

Progress during a Phase 1 program to design a high temperature heating array is reported for environmentally testing full-scale shuttle leading edges (30 inch span, 6 to 15 inch radius) at flight heating rates and pressures. Heat transfer analyses of the heating array, individual modules, and the shuttle leading edge were performed, which influenced the array design, and the design, fabrication, and testing of a prototype heater module.

1972-01-01

94

Reduction of wing rock amplitudes using leading-edge vortex manipulations  

NASA Technical Reports Server (NTRS)

A mechanically operated leading edge flap system was used to perturb leading edge vortex position on a free-to-roll double-delta wing. The motion of the flaps was synchronized with the wing rolling oscillations and the effect of the phase shift between the oscillations of the wing and the flaps was investigated. Experimental results indicated that this simple approach was effective in reducing the amplitude of the unintended rolling motion and its implementation to actual airplane configurations is rather simple.

Walton, James; Katz, Joseph

1992-01-01

95

Edge crack growth of thermally aged graphite/polyimide composites  

NASA Technical Reports Server (NTRS)

Laminates of Celion 6000/LARC-160 and Celion 6000/PMR-15 graphite/polyimide composite materials were aged in air at temperatures of 202, 232, 260 and 288 C for various times up to 15,000 hours. Three unidirectional specimen types were studied: short beam shear (SBS), flexure, and 153 mm square panels. The interior region of the square panels exhibited little or no property degradation, whereas both laminate materials degraded and cracked preferentially at the specimen edge perpendicular to the fibers. Using a dye penetrant, the specimens were X-rayed and the crack depth measured as a function of time and temperature. A time temperature superposition of the crack data was successfully performed using an Arrhenius form for the shift factor. A direct correlation was found for edge crack depth and SBS strength for the LARC-160 laminates but the correlation for PMR-15 laminates was more complex.

Nelson, J. B.

1984-01-01

96

Vortex structures for flow over a delta wing with sinusoidal leading edge  

NASA Astrophysics Data System (ADS)

The idea of using sinusoidal leading edge as a kind of passive flow control method was inspired by observing the flipper movement of the humpback whale. It was believed that the protuberances along the whale's pectoral fin could delay stall, thus would enhance the maneuverability of the whale. It has also been shown that when equipped with sinusoidal leading edges, the stall of a delta wing could be delayed. In this paper, stereoscopic particle image velocimetry was adopted to study the vortex structures for the flow over a 52° swept delta wing with sinusoidal leading edges. A direct comparison with the flow over a baseline delta wing was made to illustrate the different vortex structures of these two kinds of models. Results have shown that the flow over the baseline delta wing was dominated by dual leading-edge vortices (LEVs), a structure that only existed for flow over nonslender delta wing at certain Reynolds number. On the other hand, the flow over the one with sinusoidal leading edge showed a very different pattern. It has been found in this paper that there were several pairs of LEVs existed on the leeward side of the wing, which might explain the stall-delaying effect of the delta wing with sinusoidal leading edges.

Chen, Huang; Wang, Jin-Jun

2014-06-01

97

An experimental investigation of leading-edge vortex augmentation by blowing  

NASA Technical Reports Server (NTRS)

A wind tunnel test was conducted to determine the effects of over-the-wing blowing as a means of augmenting the leading-edge vortex flow of several pointed-tip, sharp-edged planforms. Arrow, delta, and diamond wings with leading-edge sweeps of 30 and 45 degrees were mounted on a body-of-revolution fuselage and tested in a low-speed wind tunnel at a Mach number of 0.2. Nozzle location data, pitch data, and flow-visualization pictures were obtained for a range of blowing rates. Results show pronounced increases in vortex lift due to the blowing.

Bradley, R. G.; Wray, W. O.; Smith, C. W.

1974-01-01

98

Shuttle Wing Leading Edge Root Cause NDE Team Findings and Implementation of Quantitative Flash Infrared Thermography  

NASA Technical Reports Server (NTRS)

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.

Burke, Eric R.

2009-01-01

99

Numerical prediction of vortex cores of the leading and trailing edges of delta wings  

NASA Technical Reports Server (NTRS)

The purpose of the present paper is to predict the roll-up of the vortex sheets emanating from the leading- and trailing-edges of delta wings with emphasis on the interaction of vortex cores beyond the trailing edge. The motivation behind the present work is the recent experimental data published by Hummel. The Nonlinear Discrete-Vortex method (NDV-method) is modified and extended to predict the leading- and trailing-vortex cores beyond the trailing edge. The present model alleviates the problems previously encountered in predicting satisfactory pressure distributions. This is accomplished by lumping the free-vortex lines during the iteration procedure. The leading- and trailing-edge cores and their feeding sheets are obtained as parts of the solution. The numerical results show that the NDV-method is successful in confirming the formation of a trailing-edge core with opposite circulation and opposite roll-up to those of the leading-edge core. This work is a breakthrough in the high angle of attack aerodynamics and moreover, it is the first numerical prediction done on this problem

Kandil, O. A.

1980-01-01

100

Extension of leading-edge-suction analogy to wings with separated flow around the side edges at subsonic speeds  

NASA Technical Reports Server (NTRS)

A method for determining the lift, drag, and pitching moment for wings which have separated flow at the leading and side edges with subsequently reattached flow downstream and inboard is presented. Limiting values of the contribution to lift of the side-edge reattached flow are determined for rectangular wings. The general behavior of this contribution is computed for rectangular, cropped-delta, cropped-diamond, and cropped-arrow wings. Comparisons of the results of the method and experiment indicate reasonably good correlation of the lift, drag, and pitching moment for a wide planform range. The agreement of the method with experiment was as good as, or better than, that obtained by other methods. The procedure is computerized and is available from COSMIC as NASA Langley computer program A0313.

Lamar, J. E.

1974-01-01

101

The three-dimensional leading-edge vortex of a 'hovering' model hawkmoth  

PubMed Central

Recent flow visualisation experiments with the hawkmoth, Manduca sexta, revealed small but clear leading-edge vortex and a pronounced three-dimensional flow. Details of this flow pattern were studied with a scaled-up, robotic insect ('the flapper') that accurately mimicked the wing movements of a hovering hawkmoth. Smoke released from the leading edge of the flapper wing confirmed the existence of a small, strong and stable leading-edge vortex, increasing in size from wingbase to wingtip. Between 25 and 75 per cent of the wing length, its diameter increased approximately from 10 to 50 per cent of the wing chord. The leading-edge vortex had a strong axial flow veolocity, which stabilized it and reduced its diamater. The vortex separated from the wing at approximately 75 per cent of the wing length and thus fed vorticity into a large, tangled tip vortex. If the circulation of the leading-edge vortex were fully used for lift generation, it could support up to two-thirds of the hawkmoth's weight during the downstroke. The growth of this circulation with time and spanwise position clearly identify dynamic stall as the unsteady aerodynamic mechanism responsible for high lift production by hovering hawkmoths and possibly also by many other insect species.

Berg, C. van den; Ellington, C.P.

1997-01-01

102

The Performance of Finite-span Hydrofoils with Humpback Whale-like Leading Edge Protuberances  

NASA Astrophysics Data System (ADS)

The effects of leading edge protuberances on the lift and drag performance of finite-span hydrofoils were examined in a series of water tunnel experiments. The leading edge protuberances are analogous to the tubercles on humpback whale pectoral flippers. The hydrofoils have a rectangular planform and an aspect ratio of 4. The hydrofoil section profile is based on NACA 63(4)-021, and the leading edge has a sinusoidal geometry with constant amplitude and wavelength. The hydrofoil angle of attack was varied up to 30 , and the freestream velocity ranged from 1.8 to 5.4 m/s. Results indicate that the hydrofoils with leading edge protuberances do not stall in the traditional manner. Below 12 lift increased linearly with angle of attack. Beyond this angle, the lift either attained a nearly constant value or increased slowly up to 30 depending on the Reynolds number. Drag increased continuously with the angle of attack, and was not dependent on the Reynolds number. These observations are consistent with our previous infinite span hydrofoil data, and may be explained in terms of the flow modifications created by the leading edge protuberances.

Custodio, Derrick; Henoch, Charles; Johari, Hamid

2010-11-01

103

Acoustic Receptivity of Mach 4.5 Boundary Layer with Leading- Edge Bluntness  

NASA Technical Reports Server (NTRS)

Boundary layer receptivity to two-dimensional slow and fast acoustic waves is investigated by solving Navier-Stokes equations for Mach 4.5 flow over a flat plate with a finite-thickness leading edge. Higher order spatial and temporal schemes are employed to obtain the solution whereby the flat-plate leading edge region is resolved by providing a sufficiently refined grid. The results show that the instability waves are generated in the leading edge region and that the boundary-layer is much more receptive to slow acoustic waves (by almost a factor of 20) as compared to the fast waves. Hence, this leading-edge receptivity mechanism is expected to be more relevant in the transition process for high Mach number flows where second mode instability is dominant. Computations are performed to investigate the effect of leading-edge thickness and it is found that bluntness tends to stabilize the boundary layer. Furthermore, the relative significance of fast acoustic waves is enhanced in the presence of bluntness. The effect of acoustic wave incidence angle is also studied and it is found that the receptivity of the boundary layer on the windward side (with respect to the acoustic forcing) decreases by more than a factor of 4 when the incidence angle is increased from 0 to 45 deg. However, the receptivity coefficient for the leeward side is found to vary relatively weakly with the incidence angle.

Malik, Mujeeb R.; Balakumar, Ponnampalam

2007-01-01

104

Modeling Creep-Induced Stress Relaxation at the Leading Edge of SiC/SiC Airfoils  

NASA Technical Reports Server (NTRS)

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-thickness Sylramic-iBN fiber reinforcement and a typical EBC coating has the potential of offering a maximum long-term steady-state operating temperature of approx.3100 F at the surface of the EBC.

Lang, Jerry; DiCarlo, James A.

2007-01-01

105

Experimental investigation of boundary layer transition on a flat plate with C4 leading edge  

NASA Astrophysics Data System (ADS)

This paper considers the effects of freestream turbulence intensity on the boundary layer transition over a range of Reynolds numbers. Bypass mode of transition has been considered using a flat plate with a C4 leading edge, designed to avoid laminar separation. This configuration provides the opportunity to study the effect of a realistic turbomachinery leading edge shape on transition. Hot wire investigations of the boundary layer have been undertaken in order to acquire detailed information about the effect of the freestream conditions on the structure of the boundary layer. This paper concludes with some global observations and comparisons with theoretical predictions and with experimental observations on a more conventional flat plate with a sharp leading edge.

Kalfas, A. I.; Elder, R. L.

106

Effect of leading-edge porosity on blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

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.

Lee, Soogab

1993-01-01

107

Influence of blade angle distribution along leading edge on cavitation performance of a centrifugal pump  

NASA Astrophysics Data System (ADS)

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.

Xu, Y.; Tan, L.; Cao, S. L.; Wang, Y. C.; Meng, G.; Qu, W. S.

2015-01-01

108

Test and Analysis Correlation of Form Impact onto Space Shuttle Wing Leading Edge RCC Panel 8  

NASA Technical Reports Server (NTRS)

Soon after the Columbia Accident Investigation Board (CAIB) began their study of the space shuttle Columbia accident, "physics-based" analyses using LS-DYNA were applied to characterize the expected damage to the Reinforced Carbon-Carbon (RCC) leading edge from high-speed foam impacts. Forensic evidence quickly led CAIB investigators to concentrate on the left wing leading edge RCC panels. This paper will concentrate on the test of the left-wing RCC panel 8 conducted at Southwest Research Institute (SwRI) and the correlation with an LS-DYNA analysis. The successful correlation of the LS-DYNA model has resulted in the use of LS-DYNA as a predictive tool for characterizing the threshold of damage for impacts of various debris such as foam, ice, and ablators onto the RCC leading edge for shuttle return-to-flight.

Fasanella, Edwin L.; Lyle, Karen H.; Gabrys, Jonathan; Melis, Matthew; Carney, Kelly

2004-01-01

109

A flight test of laminar flow control leading-edge systems  

NASA Technical Reports Server (NTRS)

NASA's program for development of a laminar flow technology base for application to commercial transports has made significant progress since its inception in 1976. Current efforts are focused on development of practical reliable systems for the leading-edge region where the most difficult problems in applying laminar flow exist. Practical solutions to these problems will remove many concerns about the ultimate practicality of laminar flow. To address these issues, two contractors performed studies, conducted development tests, and designed and fabricated fully functional leading-edge test articles for installation on the NASA JetStar aircraft. Systems evaluation and performance testing will be conducted to thoroughly evaluate all system capabilities and characteristics. A simulated airline service flight test program will be performed to obtain the operational sensitivity, maintenance, and reliability data needed to establish that practical solutions exist for the difficult leading-edge area of a future commercial transport employing laminar flow control.

Fischer, M. C.; Wright, A. S., Jr.; Wagner, R. D.

1983-01-01

110

The contribution of the leading edge vortex for the total lift in small insect flight  

NASA Astrophysics Data System (ADS)

The existence of a leading edge vortex in small insect flight is studied, and its importance for the generation of lift is investigated. A 2D approximation of small insect flight is calculated with a high-order, immersed boundary, incompressible Navier-Stokes flow solver. The simulated motion of the model wing is a simplification of the flight of Drosophila melanogaster, and was done in line with previous numerical simulations. This study uses results from the time-periodic steady state regime. Above the critical Reynolds number for which flapping flight is possible, vortices are alternately shed during wing translation. Before the leading edge vortex is shed, it remains close to the leading edge region for a considerable part of the wing translation. This attachment can be a significant mechanism for the augmentation of lift in 2D flapping flight.

Ferreira de Sousa, Paulo; Allen, James

2007-03-01

111

Transonic Reynolds Number and Leading-Edge Bluntness Effects on a 65 deg Delta Wing  

NASA Technical Reports Server (NTRS)

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 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.

Luckring, J. M.

2003-01-01

112

Leading-edge tubercles delay stall on humpback whale (Megaptera novaeangliae) flippers  

NASA Astrophysics Data System (ADS)

The humpback whale (Megaptera novaeangliae) is exceptional among the baleen whales in its ability to undertake acrobatic underwater maneuvers to catch prey. In order to execute these banking and turning maneuvers, humpback whales utilize extremely mobile flippers. The humpback whale flipper is unique because of the presence of large protuberances or tubercles located on the leading edge which gives this surface a scalloped appearance. We show, through wind tunnel measurements, that the addition of leading-edge tubercles to a scale model of an idealized humpback whale flipper delays the stall angle by approximately 40%, while increasing lift and decreasing drag.

Miklosovic, D. S.; Murray, M. M.; Howle, L. E.; Fish, F. E.

2004-05-01

113

Experimental study of delta wing leading-edge devices for drag reduction at high lift  

NASA Technical Reports Server (NTRS)

The drag reduction devices selected for evaluation were the fence, slot, pylon-type vortex generator, and sharp leading-edge extension. These devices were tested on a 60 degree flatplate delta (with blunt leading edges) in the Langley Research Center 7- by 10-foot high-speed tunnel at low speed and to angles of attack of 28 degrees. Balance and static pressure measurements were taken. The results indicate that all the devices had significant drag reduction capability and improved longitudinal stability while a slight loss of lift and increased cruise drag occurred.

Johnson, T. D., Jr.; Rao, D. M.

1982-01-01

114

Summary of past experience in natural laminar flow and experimental program for resilient leading edge  

NASA Technical Reports Server (NTRS)

The potential of natural laminar flow for significant drag reduction and improved efficiency for aircraft is assessed. Past experience with natural laminar flow as reported in published and unpublished data and personal observations of various researchers is summarized. Aspects discussed include surface contour, waviness, and smoothness requirements; noise and vibration effects on boundary layer transition, boundary layer stability criteria; flight experience with natural laminar flow and suction stabilized boundary layers; and propeller slipstream, rain, frost, ice and insect contamination effects on boundary layer transition. The resilient leading edge appears to be a very promising method to prevent leading edge insect contamination.

Carmichael, B. H.

1979-01-01

115

The effects of a jet on vortex breakdown over a sharp leading-edge delta wing  

E-print Network

THE EFFECTS OF A JET ON VORTEX BREAKDOWN OVER A SHARP LEADING-EDGE DELTA WING A Thesis Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1985... Major Subject: Aerospace Engineering THE EFFECTS OF A JET ON VORTEX BREAKDOWN OVER A SHARP LEADING-EDGE DELTA WING A Thesis by IAN KENNETH MAYNARD Approved as to style and content by: Cyrus Ostowar (Chairman of Committee) Stan J Miley (M er...

Maynard, Ian Kenneth

2012-06-07

116

CARMIL leading edge localization depends on a non-canonical PH domain and dimerization  

PubMed Central

CARMIL is a ~1370 amino acid cytoskeletal scaffold that plays crucial roles in cell motility and tissue development through interactions with cytoskeletal effectors and regulation of capping protein at the leading edge. However, the mechanism of CARMIL leading edge localization is unknown. Here we show that CARMIL interacts directly with the plasma membrane through its N-terminal region. The crystal structure of CARMIL1-668 reveals that this region harbors a non-canonical pleckstrin homology (PH) domain connected to a 16 leucine-rich repeat domain. Lipid binding is mediated by the PH domain, but is further enhanced by a central helical domain. Small angle x-ray scattering reveals that the helical domain mediates antiparallel dimerization, properly positioning the PH domains for simultaneous membrane interaction. In cells, deletion of the PH domain impairs leading edge localization. The results support a direct membrane binding mechanism for CARMIL localization at the leading edge, where it regulates cytoskeletal effectors and motility. PMID:24071777

Zwolak, Adam; Yang, Changsong; Feeser, Elizabeth A.; Ostap, E. Michael; Svitkina, Tatyana; Dominguez, Roberto

2013-01-01

117

Exact Numerical Treatment of Finite Quantum Systems using Leading-Edge Supercomputers  

E-print Network

Exact Numerical Treatment of Finite Quantum Systems using Leading-Edge Supercomputers G. Hager 1 of the Peierls-insulator Mott- insulator transition is presented. Program implementation on modern supercomput problems this will become possible only by the use of modern high-performance supercomput- ers

Fehske, Holger

118

Leading edge slot blowing on an open cavity in supersonic flow  

NASA Astrophysics Data System (ADS)

Supersonic flow over an open cavity can create intense pressure loads on the surfaces within the cavity. In order to combat these loads, the development of a control scheme to reduce them is becoming increasingly important for many engineering applications. The present study implements steady leading edge blowing through various configurations of spanwise-aligned rectangular leading edge slots. The effects of this control on the flow field were examined to determine the suppression mechanisms exploited by the leading edge blowing. The cavity studied here had a length-to-depth ratio of 6 and was placed in a freestream flow with a Mach number of 1.4. Actuators with one continuous slot and three and five segmented slots spanning the width of the cavity were installed at the leading edge. Surface pressure reductions of nearly 45% were achieved on the aft wall of the cavity using the 5-slot configuration. Velocity field measurements acquired through 2-component (streamwise-aligned measurement plane) and 3-component stereoscopic (cross-stream-aligned measurement plane) particle image velocimetry revealed the presence of streamwise-aligned vortices created by the segmented slots. These act to significantly alter the shear layer formed at the mouth of the cavity creating highly three-dimensional flow field features.

Lusk, Taylor; Cattafesta, Louis; Ukeiley, Lawrence

2012-07-01

119

The Leading Edge: A Career Development Workshop Series for Young Adults. Facilitator Guide.  

ERIC Educational Resources Information Center

This booklet is designed to be used by facilitators of the Canadian Career Development Foundation's "The Leading Edge: A Career Development Workshop Series for Young Adults." The guide provides information, including objectives of the workshops and lists of required materials, needed in order to facilitate an introductory session as well as the…

Canadian Career Development Foundation, Ottawa (Ontario).

120

Spanwise gradients in flow speed help stabilize leading-edge vortices on revolving wings  

NASA Astrophysics Data System (ADS)

While a leading-edge vortex on an infinite translating wing is shed after a short distance of travel, its counterpart on a finite span revolving insect wing or maple seed membrane exhibits robust attachment. The latter explains the aerodynamic lift generated by such biological species. Here we analyze the mechanisms responsible for leading-edge vortex attachment. We compute the Navier-Stokes solution of the flow past a finite span wing (i) embedded in a uniform oncoming flow, (ii) embedded in a spanwise varying oncoming flow, and (iii) revolving about its root. We show that over flapping amplitudes typical of insect flight (? =120?), the spanwise gradient of the local wing speed may suffice in maintaining leading-edge vortex attachment. We correlate this result with the development of spanwise flow, driven by the spanwise gradient of pressure, and we evaluate the sensitivity of such a mechanism to the Reynolds number. It is noted, however, that leading-edge vortex attachment through the spanwise gradient of the local wing speed does not promote large lift, which ultimately arises from centrifugal and Coriolis effects.

Jardin, T.; David, L.

2014-07-01

121

Performance of hydrofoils with humpback whale-like leading edge protuberances  

Microsoft Academic Search

The humpback whale (Megaptera novaeangliae) is extremely maneuverable, compared to other whale species, despite its large size and rigid body. Turning maneuvers are especially evident during pursuit of prey. The agility of humpback whale has been attributed to their use of pectoral flippers. The thick flippers have large aspect ratios, and large scale protuberances are present on the leading edge.

Alexandra Levshin; Charles Henoch; Hamid Johari

2005-01-01

122

Design, analysis, and tests of a shuttle-type heat-pipe-cooled leading edge  

NASA Technical Reports Server (NTRS)

A one-half scale heat-pipe-cooled leading edge model was designed and fabricated to verify feasibility and performance of a full-scale Phase B shuttle orbiter design. Model performance was investigated experimentally by radiant heating and aerothermal tests and analytically by using a simple technique which predicts heat pipe start-up from the frozen state and also predicts transient and steady-state thermal behavior. Analytical results agree well with experimental results for start-up and steady-state heat pipe operation. The results indicate that variations in angle of attack and roll orientation had a negligible effect on heat pipe performance. The heat pipes effectively isothermalized the leading edge, and reduced peak temperatures to levels compatible with the use temperatures of superalloys. Results of these tests demonstrated the durability of the heat-pipe-cooled leading edge in withstanding earth-entry thermal and mechanical loads and indicate that the use of heat pipes in leading edge structures is a reliable concept for fully reusable hypersonic cruise and space transportation systems.

Camarda, C. J.; Masek, R. V.

1979-01-01

123

Project 2000-3 Leading Edge Enterprise: Insights into Employment and Training Practices. Working Paper.  

ERIC Educational Resources Information Center

Leading-edge firms (LEFs)--at the forefront of their industry in terms of growth or market share--may influence skill development through diffusion of technology, products, or practices and use of market power to set standards or change customer businesses. Study of LEFs can identify the type and mix of skills needed in the industry. LEFs are…

Long, Michael; Fischer, John

124

Leading Edge Cell 125, May 19, 2006 2006 Elsevier Inc. 655  

E-print Network

Leading Edge Review Cell 125, May 19, 2006 ©2006 Elsevier Inc. 655 Introduction Plants undergo The Timing of Developmental Transitions in Plants Isabel Bäurle1 and Caroline Dean1, * 1 Department of Cell as endogenous signals transmitted by plant hormones. Cold temperature and stress affect germination

Howard, Martin

125

Leading Edge Cell 125, June 30, 2006 2006 Elsevier Inc. 1241  

E-print Network

Leading Edge Review Cell 125, June 30, 2006 ©2006 Elsevier Inc. 1241 Mitochondria evolved from) are encoded by the nuclear genome and imported into the mitochondria, mitochondria neverthe- less maintain a genome that is essential for their respira- tory function (Wallace, 2005). The 16 kilobase circular

Chan, David

126

Finite element analysis of large wavelength antenna radome problems for leading edge and radar phased arrays  

Microsoft Academic Search

A method for determining the RF performance from antenna radome configurations based on a frequency-domain finite-element method is presented. The application of this analysis on the design of antenna arrays in aircraft leading edges and radar radomes is discussed. The modeled antenna array elements can be driven with arbitrary amplitude and phase weighting for sidelobe tapering and phased steering of

Mark J. Povinelli; John D'Angelo

1991-01-01

127

Leading Edge Flow Structure of a Dynamically Pitching NACA 0012 Airfoil  

E-print Network

The leading edge flow structure of the NACA 0012 airfoil is experimentally investigated under dynamic stall conditions (M = 0.1; ? = 16.7?, 22.4?; Rec = 1× 10^6) using planar particle image velocimetry. The airfoil was dynamically pitched about...

Pruski, Brandon

2012-11-27

128

1340 The Leading Edge October 2008 SAGE celebrates 25 years of learning geophysics by  

E-print Network

1340 The Leading Edge October 2008 SAGE celebrates 25 years of learning geophysics by doing geophysics The increasing world demand and record-high costs for energy and mineral resources, along and educators we must seriously ask if our geophysics pipeline can adequately address this crisis. One program

129

A leading edge heating array and a flat surface heating array - operation, maintenance and repair manual  

NASA Technical Reports Server (NTRS)

A general description of the leading edge/flat surface heating array is presented along with its components, assembly instructions, installation instructions, operation procedures, maintenance instructions, repair procedures, schematics, spare parts lists, engineering drawings of the array, and functional acceptance test log sheets. The proper replacement of components, correct torque values, step-by-step maintenance instructions, and pretest checkouts are described.

1975-01-01

130

Alumina ''Fiber FP'' reinforced pure lead composites for battery electrodes  

Microsoft Academic Search

A discussion is given on high-purity lead composites reinforced with alumina made by vacuum-assisted casting by using conventional cast iron molds. The objective is to demonstrate the fabrication of technically sound Fiber FP\\/lead composite grids with the potential to extend wet stand and cycle life and to increase volumetric specific energy density in lead-acid batteries. Mechanical properties of these composites

Hans S. Hartmann; R. A. Sutula

1982-01-01

131

Zinc halogen battery electrolyte composition with lead additive  

DOEpatents

This disclosure relates to a zinc halogen battery electrolyte composition containing an additive providing improved zinc-on-zinc recyclability. The improved electrolyte composition involves the use of a lead additive to inhibit undesirable irregular plating and reduce nodular or dendritic growth on the electrode surface. The lead-containing electrolyte composition of the present invention appears to influence not only the morphology of the base plate zinc, but also the morphology of the zinc-on-zinc replate. In addition, such lead-containing electrolyte compositions appear to reduce hydrogen formation.

Henriksen, Gary L. (Troy, MI)

1981-01-01

132

Aerothermal Performance Constraints for Hypervelocity Small Radius Unswept Leading Edges and Nosetips  

NASA Technical Reports Server (NTRS)

Small radius leading edges and nosetips were utilized to minimize wave drag in early hypervelocity vehicle concepts until further analysis demonstrated that extreme aerothermodynamic heating would cause severe ablation or blunting of the available thermal protection system materials. Recent studies indicate that ultrahigh temperature ceramic (UHTC) materials are shape stable at temperatures approaching 3033 K and will be available for use as sharp UHTC leading edge components in the near future. Aerothermal performance constraints for sharp components made from these materials are presented in this work to demonstrate the effects of convective blocking, surface catalycity, surface emissivity, and rarefied flow effects on steady state operation at altitudes from sea level to 90 km. These components are capable of steady state operation at velocities up to 7.9 km/s at attitudes near 90 km.

Kolodziej, Paul

1997-01-01

133

Wind-tunnel studies of advanced cargo aircraft concepts. [leading edge vortex flaps for drag reduction  

NASA Technical Reports Server (NTRS)

Accomplishments in vortex flap research are summarized. A singular feature of the vortex flap is that, throughout the range of angle of attack range, the flow type remains qualitatively unchanged. Accordingly, no large or sudden change in the aerodynamic characteristics, as happens when forcibly maintained attached flow suddenly reverts to separation, will occur with the vortex flap. Typical wind tunnel test data are presented which show the drag reduction potential of the vortex flap concept applied to a supersonic cruise airplane configuration. The new technology offers a means of aerodynamically augmenting roll-control effectiveness on slender wings at higher angles of attack by manipulating the vortex flow generated from leading edge separation. The proposed manipulator takes the form of a flap hinged at or close to the leading edge, normally retracted flush with the wing upper surface to conform to the airfoil shape.

Rao, D. M.; Goglia, G. L.

1981-01-01

134

Visualization of leading edge vortices on a series of flat plate delta wings  

NASA Technical Reports Server (NTRS)

A summary of flow visualization data obtained as part of NASA Grant NAG2-258 is presented. During the course of this study, many still and high speed motion pictures were taken of the leading edge vortices on a series of flat plate delta wings at varying angles of attack. The purpose is to present a systematic collection of photographs showing the state of vortices as a function of the angle of attack for the four models tested.

Payne, Francis M.; Ng, T. Terry; Nelson, Robert C.

1991-01-01

135

Effects of Nose Radius and Aerodynamic Loading on Leading Edge Receptivity  

NASA Technical Reports Server (NTRS)

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.

Hammerton, P. W.; Kerschen, E. J.

1998-01-01

136

Leading edge vortex-flap experiments on a 74 deg delta wing  

NASA Technical Reports Server (NTRS)

Exploratory wind tunnel tests are reported on a 74 deg. delta wing model. The potential of a vortex flap concept in reducing the subsonic lift dependent drag of highly swept, slender wings is examined. The suction effect of coiled vortices generated through controlled separation over leading edge flap surfaces to produce a thrust component is discussed. A series of vortex-flap configurations were investigated to explore the effect of some primary geometric variables.

Rao, D. M.

1979-01-01

137

Experimental unsteady pressures on an oscillating cascade with supersonic leading edge locus  

NASA Technical Reports Server (NTRS)

The first experimental data for an oscillating cascade with a supersonic leading edge locus (SLEL) at zero stagger angle is presented which were obtained in the NASA/OSU supersonic oscillating cascade facility. Reduced frequencies from .093 to .146, based on half chord were investigated. An influence coefficient technique for a linear oscillating cascade with constant interblade phase angle has been extended to a cascade with a SLEL.

Erwin, Daniel; Gregorek, G. M.; Ramsey, John

1992-01-01

138

A Reynolds Number Study of Wing Leading-Edge Effects on a Supersonic Transport Model at Mach 0.3  

NASA Technical Reports Server (NTRS)

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).

Williams, M. Susan; Owens, Lewis R., Jr.; Chu, Julio

1999-01-01

139

Case Studies of Leading Edge Small Urban High Schools. Relevance Strategic Designs: 7. TechBoston Academy  

ERIC Educational Resources Information Center

This report is one of nine detailed case studies of small urban high schools that served as the foundation for the Education Resource Strategies (ERS) report "Strategic Designs: Lessons from Leading Edge Small Urban High Schools." These nine schools were dubbed "Leading Edge Schools" because they stand apart from other high schools across the…

Shields, Regis Anne; Ireland, Nicole; City, Elizabeth; Derderian, Julie; Miles, Karen Hawley

2008-01-01

140

Material Modeling of Space Shuttle Leading Edge and External Tank Materials For Use in the Columbia Accident Investigation  

Microsoft Academic Search

Upon the commencement of the analytical effort to characterize the impact dynamics and damage of the Space Shuttle Columbia leading edge due to External Tank insulating foam, the necessity of creating analytical descriptions of these materials became evident. To that end, material models were developed of the leading edge thermal protection system, Reinforced Carbon Carbon (RCC), and a low density

Kelly Carney; Matthew Melis; Edwin L. Fasanella; Karen H. Lyle; Jonathan Gabrys

141

Numerical investigation of rarefaction effects in the vicinity of a sharp leading edge  

NASA Astrophysics Data System (ADS)

This paper presents a study of rarefaction effect on hypersonic flow over a sharp leading edge. Both continuum approach and kinetic method: a widely spread commercial Computational Fluid Dynamics-Navior-Stokes-Fourier (CFD-NSF) software - Fluent together with a direct simulation Monte Carlo (DSMC) code developed by the authors are employed for simulation of transition regime with Knudsen number ranging from 0.005 to 0.2. It is found that Fluent can predict the wall fluxes in the case of hypersonic argon flow over the sharp leading edge for the lowest Kn case (Kn = 0.005) in current paper while for other cases it also has a good agreement with DSMC except at the location near the sharp leading edge. Among all of the wall fluxes, it is found that coefficient of pressure is the most sensitive to rarefaction while heat transfer is the least one. A parameter based on translational nonequilibrium and a cut-off value of 0.34 is proposed for continuum breakdown in this paper. The structure of entropy and velocity profile in boundary layer is analyzed. Also, it is found that the ratio of heat transfer coefficient to skin friction coefficient remains uniform along the surface for the four cases in this paper.

Pan, Shaowu; Gao, Zhenxun; Lee, Chunhian

2014-12-01

142

Controlled vortical flow on delta wings through unsteady leading edge blowing  

NASA Technical Reports Server (NTRS)

The vortical flow over a delta wing contributes an important part of the lift - the so called nonlinear lift. Controlling this vortical flow with its favorable influence would enhance aircraft maneuverability at high angle of attack. Several previous studies have shown that control of the vortical flow field is possible through the use of blowing jets. The present experimental research studies vortical flow control by applying a new blowing scheme to the rounded leading edge of a delta wing; this blowing scheme is called Tangential Leading Edge Blowing (TLEB). Vortical flow response both to steady blowing and to unsteady blowing is investigated. It is found that TLEB can redevelop stable, strong vortices even in the post-stall angle of attack regime. Analysis of the steady data shows that the effect of leading edge blowing can be interpreted as an effective change in angle of attack. The examination of the fundamental time scales for vortical flow re-organization after the application of blowing for different initial states of the flow field is studied. Different time scales for flow re-organization are shown to depend upon the effective angle of attack. A faster response time can be achieved at angles of attack beyond stall by a suitable choice of the initial blowing momentum strength. Consequently, TLEB shows the potential of controlling the vortical flow over a wide range of angles of attack; i.e., in both for pre-stall and post-stall conditions.

Lee, K. T.; Roberts, Leonard

1990-01-01

143

Material Modeling of Space Shuttle Leading Edge and External Tank Materials For Use in the Columbia Accident Investigation  

NASA Technical Reports Server (NTRS)

Upon the commencement of the analytical effort to characterize the impact dynamics and damage of the Space Shuttle Columbia leading edge due to External Tank insulating foam, the necessity of creating analytical descriptions of these materials became evident. To that end, material models were developed of the leading edge thermal protection system, Reinforced Carbon Carbon (RCC), and a low density polyurethane foam, BX-250. Challenges in modeling the RCC include its extreme brittleness, the differing behavior in compression and tension, and the anisotropic fabric layup. These effects were successfully included in LS-DYNA Material Model 58, *MAT_LAMINATED_ COMPOSITE_ FABRIC. The differing compression and tension behavior was modeled using the available damage parameters. Each fabric layer was given an integration point in the shell element, and was allowed to fail independently. Comparisons were made to static test data and coupon ballistic impact tests before being utilized in the full scale analysis. The foam's properties were typical of elastic automotive foams; and LS-DYNA Material Model 83, *MAT_FU_CHANG_FOAM, was successfully used to model its behavior. Material parameters defined included strain rate dependent stress-strain curves for both loading and un-loading, and for both compression and tension. This model was formulated with static test data and strain rate dependent test data, and was compared to ballistic impact tests on load-cell instrumented aluminum plates. These models were subsequently utilized in analysis of the Shuttle leading edge full scale ballistic impact tests, and are currently being used in the Return to Flight Space Shuttle re-certification effort.

Carney, Kelly; Melis, Matthew; Fasanella, Edwin L.; Lyle, Karen H.; Gabrys, Jonathan

2004-01-01

144

The influence of leading-edge geometry on profile and secondary losses in turbine cascades  

NASA Astrophysics Data System (ADS)

This thesis presents detailed experimental results of the midspan and secondary flows from two large-scale, low-speed linear turbine cascades. The airfoils for the two cascades differ mainly in their leading-edge geometries. Detailed flow field measurements were made upstream and downstream of the cascades using three- and seven-hole pressure probes and static pressure distributions were measured on the airfoil surfaces. The data were supplemented with extensive surface oil flow visualization. Measurements were made at three different values of incidence: 0, +10 and +20 degrees. For the off-design profile losses, significant discrepancies were observed between the present measurements and the predictions from the most recent available correlation (Moustapha et al., 1990). Based on data from the present experiment and cases from the open literature, a revised off-design profile loss correlation has been developed that is significantly more successful than the existing correlations. The new correlation includes leading-edge wedge angle as an influential and additional correlating parameter. The results from the secondary flow measurements at the design incidence suggest that the leading-geometry has only a minor influence on the secondary losses, whereas, the loading on the forward part of the airfoil appears to be of primary importance. At off-design incidence, the most recent off-design secondary loss correlation (Moustapha et al., 1990) includes leading-edge diameter as an influential correlating parameter. The correlation predicts that the secondary losses for the airfoil with the larger leading-edge diameter are lower at off-design incidence; however, the opposite is observed experimentally. The loss results at high positive incidence have also highlighted some serious shortcomings with the conventional method of loss decomposition. An empirical prediction method for secondary losses has been developed to replace the conventional one. In addition to the experimental study, a computational investigation was conducted using a CFD code that is currently widely used in turbomachinery design. The objective was to determine the degree to which the code is capable of predicting off design profile losses. For cases at moderate values of incidence, the correct loss trend was predicted; however, the code did not predict the trailing-edge separation that occurred at high incidence.

Benner, Michael William

145

Composition of White Lead and Paints.  

E-print Network

of manganese, with linseed oil or resin, and dissolving the melt in turpentine or benzine or both. Dryers are carriers of oxygen, cau linseed oil to 'oxidize and harden. ;ed mass sing the MATERIALS DISPUTED VALUE AND ADULTERANTS. The materials described... we shall see in the following pages, "white lead" sometimes consists en- tirely of barytes. This is a fraud, pure and simple. Linseed Oil flubstitutes.-Linseed oil, as we have stated, is the best oil for use in mixing paints. Resin oils and other...

Fraps, G. S. (George Stronach)

1908-01-01

146

Modeling the Nonlinear, Strain Rate Dependent Deformation of Shuttle Leading Edge Materials with Hydrostatic Stress Effects Included  

NASA Technical Reports Server (NTRS)

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.

Goldberg, Robert K.; Carney, Kelly S.

2004-01-01

147

The effects of leading-edge serrations on reducing flow unsteadiness about airfoils.  

NASA Technical Reports Server (NTRS)

High frequency surface pressure measurements were obtained from wind-tunnel tests over the Reynolds number range 1.2 x 1,000,000 to 6.2 x 1,000,000 on a rectangular wing of NACA 63-009 airfoil section. A wide selection of leading-edge serrations were also 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 peak in rms pressure, 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 mathematically to the airfoil trailing-edge and boundary-layer thicknesses.

Schwind, R. G.; Allen, H. J.

1973-01-01

148

Leading- and trailing-edge effects on the aeromechanics of membrane aerofoils  

NASA Astrophysics Data System (ADS)

This study explores the effect that geometry of silver steel supports have on the aeromechanic performance of membrane aerofoils. Tests are performed at low Reynolds numbers, Re=9×104, and incidences of 2°-25° High-speed photogrammetry as well as force measurements are carried out to explore the effects of four different leading-edge (LE) and trailing-edge (TE) designs on the performance of membrane aerofoils. Results indicate that the mean camber as well as membrane vibrations (both mode shape and frequency) change with geometry and size of the LE and TE supports. The LE/TE supports with a rectangular cross-section consistently provide higher lift forces and higher mean camber deformations compared to the support with circular cross-section. The membrane vibrations are also found to be higher for aerofoils with LE/TE supports with rectangular cross-section. Moreover, it is shown that the LE/TE supports deflect under aerodynamic loading and consequently alter the performance of the aerofoil. Furthermore, some of the supports are found to vibrate at their resonance frequency. In all, this study quantifies the impact of the leading- and trailing-edge support on the membrane and provides guidelines for geometry selection for future studies.

Arbós-Torrent, Sara; Ganapathisubramani, Bharathram; Palacios, Rafael

2013-04-01

149

Thermal Degradation of Lead Monoxide Filled Polymer Composite Radiation Shields  

NASA Astrophysics Data System (ADS)

Lead monoxide filled Isophthalate resin particulate polymer composites were prepared with different filler concentrations and investigated for physical, thermal, mechanical and gamma radiation shielding characteristics. This paper discusses about the thermo gravimetric analysis of the composites done to understand their thermal properties especially the effect of filler concentration on the thermal stability & degradation rate of composites. Pristine polymer exhibits single stage degradation whereas filled composites exhibit two stage degradation processes. Further, the IDT values as well as degradation rates decrease with the increased filler content in the composite.

Harish, V.; Nagaiah, N.

2011-07-01

150

How differential deflection of the inboard and outboard leading-edge flaps affected the handling qua  

NASA Technical Reports Server (NTRS)

How differential deflection of the inboard and outboard leading-edge flaps affected the handling qualities of this modified F/A-18A was evaluated during the first check flight in the Active Aeroelastic Wing program at NASA's Dryden Flight Research Center. The Active Aeroelastic Wing program at NASA's Dryden Flight Research Center seeks to determine the advantages of twisting flexible wings for primary maneuvering roll control at transonic and supersonic speeds, with traditional control surfaces such as ailerons and leading-edge flaps used to aerodynamically induce the twist. From flight test and simulation data, the program intends to develop structural modeling techniques and tools to help design lighter, more flexible high aspect-ratio wings for future high-performance aircraft, which could translate to more economical operation or greater payload capability. AAW flight tests began in November, 2002 with checkout and parameter-identification flights. Based on data obtained during the first flight series, new flight control software will be developed and a second series of research flights will then evaluate the AAW concept in a real-world environment. The program uses wings that were modified to the flexibility of the original pre-production F-18 wing. Other modifications include a new actuator to operate the outboard leading edge flap over a greater range and rate, and a research flight control system to host the aeroelastic wing control laws. The Active Aeroelastic Wing Program is jointly funded and managed by the Air Force Research Laboratory and NASA Dryden Flight Research Center, with Boeing's Phantom Works as prime contractor for wing modifications and flight control software development. The F/A-18A aircraft was provided by the Naval Aviation Systems Test Team and modified for its research role by NASA Dryden technicians.

2002-01-01

151

Subsonic balance and pressure investigation of a 60-deg delta wing with leading-edge devices (data report)  

NASA Technical Reports Server (NTRS)

The drag reduction potential of leading edge devices on a 60 degree delta wing at high lift was examined. Geometric variations of fences, chordwise slots, pylon type vortex generators, leading edge vortex flaps, and sharp leading edge extensions were tested individually and in specific combinations to improve high-alpha drag performance with a minimum of low-alpha drag penalty. The force, moment, and surface static pressure data for angles of attack up to 23 degrees, at Mach and Reynolds numbers of 0.16 and 3.85 x 10 to the 6th power per meter are documented.

Rao, D. M.; Tingas, S. A.

1981-01-01

152

Composite polymer: Glass edge cladding for laser disks  

DOEpatents

Large neodymium glass laser disks for disk amplifiers such as those used in the Nova laser require an edge cladding which absorbs at 1 micrometer. This cladding prevents edge reflections from causing parasitic oscillations which would otherwise deplete the gain. Nova now utilizes volume-absorbing monolithic-glass claddings which are fused at high temperature to the disks. These perform quite well but are expensive to produce. Absorbing glass strips are adhesively bonded to the edges of polygonal disks using a bonding agent whose index of refraction matches that of both the laser and absorbing glass. Optical finishing occurs after the strips are attached. Laser disks constructed with such claddings have shown identical gain performance to the previous Nova disks and have been tested for hundreds of shots without significant degradation. 18 figs.

Powell, H.T.; Wolfe, C.A.; Campbell, J.H.; Murray, J.E.; Riley, M.O.; Lyon, R.E.; Jessop, E.S.

1987-11-02

153

Composite polymer-glass edge cladding for laser disks  

DOEpatents

Large neodymium glass laser disks for disk amplifiers such as those used in the Nova laser require an edge cladding which absorbs at 1 micrometer. This cladding prevents edge reflections from causing parasitic oscillations which would otherwise deplete the gain. Nova now utilizes volume-absorbing monolithic-glass claddings which are fused at high temperature to the disks. These perform quite well but are expensive to produce. Absorbing glass strips are adhesively bonded to the edges of polygonal disks using a bonding agent whose index of refraction matches that of both the laser and absorbing glass. Optical finishing occurs after the strips are attached. Laser disks constructed with such claddings have shown identical gain performance to the previous Nova disks and have been tested for hundreds of shots without significant degradation.

Powell, Howard T. (Livermore, CA); Riley, Michael O. (San Ramon, CA); Wolfe, Charles R. (Palo Alto, CA); Lyon, Richard E. (Livermore, CA); Campbell, John H. (Livermore, CA); Jessop, Edward S. (Tracy, CA); Murray, James E. (Livermore, CA)

1989-01-01

154

Influence of a heated leading edge on boundary layer growth, stability and transition  

NASA Astrophysics Data System (ADS)

This paper presents the results of a combined theoretical and experimental study of the influence of a heated leading edge on the growth, stability, and transition of a two-dimensional boundary layer. The findings are directly applicable to aircraft wings and nacelles that use surface heating for anti-icing protection. The potential effects of the non-adiabatic condition are particularly important for laminar-flow sections where even small perturbations can result in significantly degraded aerodynamic performance. The results of the study give new insight to the fundamental coupling between streamwise pressure gradient and surface heat flux in laminar and transitional boundary layers.

Landrum, D. B.; Macha, J. M.

1987-04-01

155

Influence of a heated leading edge on boundary layer growth, stability, and transition  

NASA Astrophysics Data System (ADS)

This paper presents the results of a combined theoretical and experimental study of the influence of a heated leading edge on the growth, stability, and transition of a two-dimensional boundary layer. The findings are directly applicable to aircraft wings and nacelles that use surface heating for anti-icing protection. The potential effects of the non-adiabatic condition are particularly important for laminar-flow sections where even small perturbations can result in significantly degraded aerodynamic performance. The results of the study give new insight to the fundamental coupling between streamwise pressure gradient and surface heat flux in laminar and transitional boundary layers.

Landrum, D. B.; Macha, J. M.

1987-06-01

156

Initial development of an ablative leading edge for the space shuttle orbiter  

NASA Technical Reports Server (NTRS)

A state-of-the-art preliminary design for typical wing areas is developed. Seven medium-density ablators (with/without honeycomb, flown on Apollo, Prime, X15A2) are evaluated. The screening tests include: (1) leading-edge models sequentially subjected to ascent heating, cold soak, entry heating, post-entry pressure fluctuations, and touchdown shock, and (2) virgin/charred models subjected to bondline strains. Two honeycomb reinforced 30 pcf elastomeric ablators were selected. Roughness/recession degradation of low speed aerodynamics appears acceptable. The design, including attachments, substructure and joints, is presented.

Daforno, G.; Rose, L.; Graham, J.; Roy, P.

1974-01-01

157

Compilation of Information on the Transonic Attachment of Flows at the Leading Edges of Airfoils  

NASA Technical Reports Server (NTRS)

Schlieren photographs have been compiled of the two-dimensional flow at transonic speeds past 37 airfoils. These airfoils have variously shaped profiles, and some are related in thickness and camber. The data for these airfoils were analyzed to provide basic information on the flow changes involved and to determine factors affecting transonic-flow attachment, which is a transition from separated to unseparated flow at the leading edges of two-dimensional airfoils at fixed angles as the subsonic Mach number is increased.

Lindsey, Walter F; Landrum, Emma Jean

1958-01-01

158

Dynamic Stall Measurements and Computations for a VR-12 Airfoil with a Variable Droop Leading Edge  

NASA Technical Reports Server (NTRS)

High density-altitude operations of helicopters with advanced performance and maneuver capabilities have lead to fundamental research on active high-lift system concepts for rotor blades. The requirement for this type of system was to improve the sectional lift-to-drag ratio by alleviating dynamic stall on the retreating blade while simultaneously reducing the transonic drag rise of the advancing blade. Both measured and computational results showed that a Variable Droop Leading Edge (VDLE) airfoil is a viable concept for application to a rotor high-lift system. Results are presented for a series of 2D compressible dynamic stall wind tunnel tests with supporting CFD results for selected test cases. These measurements and computations show a dramatic decrease in the drag and pitching moment associated with severe dynamic stall when the VDLE concept is applied to the Boeing VR-12 airfoil. Test results also show an elimination of the negative pitch damping observed in the baseline moment hysteresis curves.

Martin, P. B.; McAlister, K. W.; Chandrasekhara, M. S.; Geissler, W.

2003-01-01

159

Leading edge vortex dynamics on a pitching delta wing. M.S. Thesis  

NASA Technical Reports Server (NTRS)

The leading edge flow structure was investigated on a 70 deg flat plate delta wing which was pitched about its 1/2 chord position, to increase understanding of the high angle of attack aerodynamics on an unsteady delta wing. The wing was sinusoidally pitched at reduced frequencies ranging from k being identical with 2pi fc/u = 0.05 to 0.30 at chord Reynolds numbers between 90,000 and 350,000, for angle of attack ranges of alpha = 29 to 39 deg and alpha = 0 to 45 deg. The wing was also impulsively pitched at an approximate rate of 0.7 rad/s. During these dynamic motions, visualization of the leading edge vorticies was obtained by entraining titanium tetrachloride into the flow at the model apex. The location of vortex breakdown was recorded using 16mm high speed motion picture photography. When the wing was sinusoidally pitched, a hysteresis was observed in the location of breakdown position. This hysteresis increased with reduced frequency. The velocity of breakdown propagation along the wing, and the phase lag between model motion and breakdown location were also determined. When the wing was impulsively pitched, several convective times were required for the vortex flow to reach a steady state. Detailed information was also obtained on the oscillation of breakdown position in both static and dynamic cases.

Lemay, Scott P.

1988-01-01

160

Experimental investigation of the transonic flow around the leading edge of an eroded fan airfoil  

NASA Astrophysics Data System (ADS)

The influence of leading edge modification on the time-averaged and instantaneous flow around a fan airfoil is investigated by particle image velocimetry (PIV), schlieren imaging and high-speed shock shadowgraphs in a transonic cascade windtunnel. In addition to a global characterization of the time-averaged flow using PIV, the instantaneous passage shock position was extracted from single-shot PIV measurements by matching the tracer velocity across the normal shock with an exponential fit. The instantaneous shock positions are assigned to a probability density distribution in order to obtain the average position and the range of fluctuations of the eroded and reference leading edge. The profiles are used to estimate the response time of the particles to the normal shock which was found to be in the sub-microsecond range. Averaged PIV measurements and the probability density of shock position from both geometries are obtained at near stall and choked conditions. In order to extract the frequency range of the shock motion, the shadow of the shock wave was tracked using high-speed shadowgraphy. The paper also provides details on the experimental implementation such as a specifically designed light-sheet probe.

Klinner, Joachim; Hergt, Alexander; Willert, Christian

2014-09-01

161

The effects of leading edge and downstream film cooling on turbine vane heat transfer  

NASA Technical Reports Server (NTRS)

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.

Hylton, L. D.; Nirmalan, V.; Sultanian, B. K.; Kaufman, R. M.

1988-01-01

162

Flow Field Characteristics of Finite-span Hydrofoils with Leading Edge Protuberances  

NASA Astrophysics Data System (ADS)

Past work has shown that humpback whale-like leading edge protuberances can significantly alter the load characteristics of both 2D and finite-span hydrofoils. To understand the mechanisms responsible for observed performance changes, the flow field characteristics of a baseline hydrofoil and models with leading edge protuberances were examined using the Stereo Particle Image Velocimetry (SPIV) technique. The near surface flow field on the hydrofoils was measured along with the tip vortex flow field on finite-span hydrofoils. Angles of attack ranging from 6 to 24 degrees were examined at freestream velocities of 1.8 m/s and 4.5 m/s, corresponding to Reynolds numbers of 180 and 450 thousand, respectively. While Reynolds number does not play a major role in establishing the flow field trends, both the protuberance geometry and spatial proximity to protuberances affect the velocity and vorticity characteristics near the foil surface, and in the wake and tip vortex. Near surface measurements reveal counter-rotating vortices on protuberance shoulders, while tip vortex measurements show that streamwise vorticity can be strongly affected by the presence of protuberances. The observed flow field characteristics will be presented.

Custodio, Derrick; Henoch, Charles; Johari, Hamid

2011-11-01

163

Analytical impact models and experimental test validation for the Columbia shuttle wing leading edge panels.  

SciTech Connect

This paper describes the analyses and the experimental mechanics program to support the National Aeronautics and Space Administration (NASA) investigation of the Shuttle Columbia accident. A synergism of the analysis and experimental effort is required to insure that the final analysis is valid - the experimental program provides both the material behavior and a basis for validation, while the analysis is required to insure the experimental effort provides behavior in the correct loading regime. Preliminary scoping calculations of foam impact onto the Shuttle Columbia's wing leading edge determined if enough energy was available to damage the leading edge panel. These analyses also determined the strain-rate regimes for various materials to provide the material test conditions. Experimental testing of the reinforced carbon-carbon wing panels then proceeded to provide the material behavior in a variety of configurations and strain-rates for flown or conditioned samples of the material. After determination of the important failure mechanisms of the material, validation experiments were designed to provide a basis of comparison for the analytical effort. Using this basis, the final analyses were used for test configuration, instrumentation location, and calibration definition in support of full-scale testing of the panels in June 2003. These tests subsequently confirmed the accident cause.

Lu, Wei-Yang; Metzinger, Kurt Evan; Gwinn, Kenneth West; Antoun, Bonnie R.; Korellis, John S.

2004-10-01

164

Analytical observations on the aerodynamics of a delta wing with leading edge flaps  

NASA Technical Reports Server (NTRS)

The effect of a leading edge flap on the aerodynamics of a low aspect ratio delta wing is studied analytically. The separated flow field about the wing is represented by a simple vortex model composed of a conical straight vortex sheet and a concentrated vortex. The analysis is carried out in the cross flow plane by mapping the wing trace, by means of the Schwarz-Christoffel transformation into the real axis of the transformed plane. Particular attention is given to the influence of the angle of attack and flap deflection angle on lift and drag forces. Both lift and drag decrease with flap deflection, while the lift-to-drag ratioe increases. A simple coordinate transformation is used to obtain a closed form expression for the lift-to-drag ratio as a function of flap deflection. The main effect of leading edge flap deflection is a partial suppression of the separated flow on the leeside of the wing. Qualitative comparison with experiments is presented, showing agreement in the general trends.

Oh, S.; Tavella, D.

1986-01-01

165

The effect of undulating leading-edge modifications on NACA 0021 airfoil characteristics  

NASA Astrophysics Data System (ADS)

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.

Rostamzadeh, N.; Kelso, R. M.; Dally, B. B.; Hansen, K. L.

2013-11-01

166

Navier-Stokes analysis of airfoils with leading edge ice accretions  

NASA Technical Reports Server (NTRS)

A numerical analysis of the flowfield characteristics and the performance degradation of an airfoil with leading edge ice accretions was performed. The important fluid dynamic processes were identified and calculated. Among these were the leading edge separation bubble at low angles of attack, complete separation on the low pressure surface resulting in premature shell, drag rise due to the ice shape, and the effects of angle of attack on the separated flow field. Comparisons to experimental results were conducted to confirm these calculations. A computer code which solves the Navier-Stokes equations in two dimensions, ARC2D, was used to perform the calculations. A Modified Mixing Length turbulence model was developed to produce grids for several ice shape and airfoil combinations. Results indicate that the ability to predict overall performance characteristics, such as lift and drag, at low angles of attack is excellent. Transition location is important for accurately determining separation bubble shape. Details of the flowfield in and downstream of the separated regions requires some modifications. Calculations for the stalled airfoil indicate periodic shedding of vorticity that was generated aft of the ice accretion. Time averaged pressure values produce results which compare favorably with experimental information. A turbulence model which accounts for the history effects in the flow may be justified.

Potapczuk, Mark G.

1993-01-01

167

Influence of Large Positive Dihedral on Heat Transfer to Leading Edges of Highly Swept Wings at Very High Mach Numbers  

NASA Technical Reports Server (NTRS)

A geometric study has been made of some of the effects of dihedral on the heat transfer to swept delta wings. The results of this study show that the incorporation of large positive dihedral on highly swept wings can shift, even at moderately low angles of attack, the stagnation-line heat-transfer problem from the leading edges to the axis of symmetry (ridge line). An order-of-magnitude analysis (assuming laminar flow) indicates conditions for which it may be possible to reduce the heating at the ridge line (except in the vicinity of the wing apex) to a small fraction of the leading-edge heat transfer of a flat wing at the same lift. Furthermore, conditions are indicated where dihedral reduces the leading-edge heat transfer for angles of attack less than those required to shift the stagnation line from the leading edge to the ridge line.

Cooper, Morton; Stainback, P. Calvin

1959-01-01

168

A computer program for calculating aerodynamic characteristics of low aspect-ratio wings with partial leading-edge separation  

NASA Technical Reports Server (NTRS)

The necessary information for using a computer program to predict distributed and total aerodynamic characteristics for low aspect ratio wings with partial leading-edge separation is presented. The flow is assumed to be steady and inviscid. The wing boundary condition is formulated by the Quasi-Vortex-Lattice method. The leading edge separated vortices are represented by discrete free vortex elements which are aligned with the local velocity vector at midpoints to satisfy the force free condition. The wake behind the trailing edge is also force free. The flow tangency boundary condition is satisfied on the wing, including the leading and trailing edges. The program is restricted to delta wings with zero thickness and no camber. It is written in FORTRAN language and runs on CDC 6600 computer.

Mehrotra, S. C.; Lan, C. E.

1978-01-01

169

Aerodynamic Forces and Loadings on Symmetrical Circular-Arc Airfoils with Plain Leading-Edge and Plain Trailing-Edge Flaps  

NASA Technical Reports Server (NTRS)

An investigation has been made in the Langley two-dimensional low-turbulence tunnel and in the Langley two-dimensional low-pressure tunnel of 6- and 10-percent-thick symmetrical circular-arc airfoil sections at low Mach numbers and several Reynolds numbers. The airfoils were equipped with 0.15-chord plain leading-edge flaps and 0.20-chord plan trailing-edge flaps. The section lift and pitching-moment characteristics were determined for both airfoils with the flaps deflected individually and in combination. The section drag characteristics were obtained for the 6-percent-thick airfoil with the flaps partly deflected as low-drag-control flaps and for airfoils with the flaps neutral. Surface pressures were measured on the 6-percent-thick airfoil section with the flaps deflected either individually or in appropriate combination to furnish flap load and hinge-moment data applicable to the structural design of the airfoil. A generalized method is developed that permits the determination of the chordwise pressure distribution over sharp-edge airfoils with plain leading-edge flaps and plain trailing-edge flaps of arbitrary size and deflection.

Cahill, Jones F; Underwood, William J; Nuber, Robert J; Cheesman, Gail A

1953-01-01

170

Application of superplastically formed and diffusion bonded aluminum to a laminar flow control leading edge  

NASA Technical Reports Server (NTRS)

NASA sponsored the Aircraft Energy Efficiency (ACEE) program in 1976 to develop technologies to improve fuel efficiency. Laminar flow control was one such technology. Two approaches for achieving laminar flow were designed and manufactured under NASA sponsored programs: the perforated skin concept used at McDonnell Douglas and the slotted design used at Lockheed-Georgia. Both achieved laminar flow, with the slotted design to a lesser degree (JetStar flight test program). The latter design had several fabrication problems concerning springback and adhesive flow clogging the air flow passages. The Lockheed-Georgia Company accomplishments is documented in designing and fabricating a small section of a leading edge article addressing a simpler fabrication method to overcome the previous program's manufacturing problems, i.e., design and fabrication using advanced technologies such as diffusion bonding of aluminum, which has not been used on aerospace structures to date, and the superplastic forming of aluminum.

Goodyear, M. D.

1987-01-01

171

Multiple leading edge vortices of unexpected strength in freely flying hawkmoth  

NASA Astrophysics Data System (ADS)

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 wing there is a single, attached LEV, while at mid wing there are multiple LEVs, and towards the wingtip flow separates. At mid wing the LEV circulation is ~40% higher than in the wake, implying that the circulation unrelated to the LEV may reduce lift. The strong and complex LEV suggests relatively high flight power in hawmoths. The variable LEV structure may result in variable force production, influencing flight control in the animals.

Johansson, L. Christoffer; Engel, Sophia; Kelber, Almut; Heerenbrink, Marco Klein; Hedenström, Anders

2013-11-01

172

Multiple leading edge vortices of unexpected strength in freely flying hawkmoth.  

PubMed

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 wing there is a single, attached LEV, while at mid wing there are multiple LEVs, and towards the wingtip flow separates. At mid wing the LEV circulation is ~40% higher than in the wake, implying that the circulation unrelated to the LEV may reduce lift. The strong and complex LEV suggests relatively high flight power in hawmoths. The variable LEV structure may result in variable force production, influencing flight control in the animals. PMID:24253180

Johansson, L Christoffer; Engel, Sophia; Kelber, Almut; Heerenbrink, Marco Klein; Hedenström, Anders

2013-01-01

173

Numerical analysis of a NACA0012 airfoil with leading edge ice accretions  

NASA Technical Reports Server (NTRS)

Analysis of a NACA0012 airfoil with leading edge ice has been performed using a Navier-Stokes code coupled with a grid generation code. The computed results were compared to experimental information obtained for an airfoil with a well defined artificial ice shape. The computations were performed at angles of attack ranging from zero to ten degrees. This range is sufficient to show the development of the separation bubble aft of the ice shape on both the upper and lower surfaces. Velocity profile plots in the separation bubble are examined in order to determine if recirculation patterns are predicted properly and if separation and reattachment points are found within the resolution of the experimental information. Also, the massive separation near the point of stall is examined in order to more accurately evaluate the lift coefficient curve in that region. Lift, drag, and moment coefficients are computed and compared to experiment.

Potapczuk, Mark G.

1987-01-01

174

Cavitation on a semicircular leading-edge plate and NACA0015 hydrofoil: Visualization and velocity measurement  

NASA Astrophysics Data System (ADS)

Using high-speed visualization and particle image velocimetry (PIV), cavitating flows near a plane plate with a rounded leading edge and NACA0015 hydrofoil at angles of attack from 0° to 9° are studied. In the experiments, several known types of cavitation, as well as some differences, were detected with variation of the cavitation number. In particular, at small angles of attack (up to 3°), cavitation on the plate appears in the form of a streak array; on the hydrofoil, it appears in the form of individual bubbles. For the NACA0015 hydrofoil, isolated and intermittent streaks are divided and grow in regimes with developed cavitation; then, however, they merge in bubble clouds and form an extremely regular cellular structure. With an increase in the angle of attack to 9°, the structure of the cavitation cavity on the hydrofoil is changed by the streak structure, like in the case with the plate. In this work, it is shown that PIV permits one to measure the velocity in cavitating flows, in particular, within the gas-vapor phase. It was established from the analysis of distributions of the average flow velocity and moments of velocity fluctuations that the cavitation generation is caused by the development of the carrier fluid flow near the leading edge of the hydrofoil. Down the stream, however, the flow structure strongly depends on the cavitation regime, which is seen from the comparison of the distributions with the case of a single-phase flow. The presented measurements qualitatively verify general trends and show some quantitative distinctions for the two considered flowpast bodies.

Kravtsova, A. Yu.; Markovich, D. M.; Pervunin, K. S.; Timoshevskii, M. V.; Hanjali?, K.

2014-12-01

175

Insect Residue Contamination on Wing Leading Edge Surfaces: A Materials Investigation for Mitigation  

NASA Technical Reports Server (NTRS)

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.

Lorenzi, Tyler M.; Wohl, Christopher J.; Penner, Ronald K.; Smith, Joseph G.; Siochi, Emilie J.

2011-01-01

176

Vibration and sound of an elastic wing actuated at its leading edge  

NASA Astrophysics Data System (ADS)

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 ?res 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 ?res, the near-resonance motion results in the generation of high sound levels; however, at frequencies far from ?res, 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 ?res, 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.

Manela, A.

2012-01-01

177

Control of the separated flow around an airfoil using a wavy leading edge inspired by humpback whale flippers  

NASA Astrophysics Data System (ADS)

The influence of spanwise geometrical undulations of the leading edge of an infinite wing is investigated numerically at low Reynolds number, in the context of passive separation control and focusing on the physical mechanisms involved. Inspired by the tubercles of the humpback whale flippers, the wavy leading edge is modeled using a spanwise sinusoidal function whose amplitude and wavelength constitute the parameters of control. A direct numerical simulation is performed on a NACA0020 wing profile in a deep stall configuration ( ?=20°), with and without the presence of the leading edge waviness. The complex solid boundaries obtained by varying the sinusoidal shape of the leading edge are modeled using an immersed boundary method (IBM) recently developed by the authors [Pinelli et al., J. Comput. Phys. 229 (2010) 9073-9091]. A particular set of wave parameters is found to change drastically the topology of the separated zone, which becomes dominated by streamwise vortices generated from the sides of the leading edge bumps. A physical analysis is carried out to explain the mechanism leading to the generation of these coherent vortical structures. The role they play in the control of boundary layer separation is also investigated, in the context of the modifications of the hydrodynamic performances which have been put forward in the literature in the last decade.

Favier, Julien; Pinelli, Alfredo; Piomelli, Ugo

2012-01-01

178

Effect of leading- and trailing-edge flaps on clipped delta wings with and without wing camber at supersonic speeds  

NASA Technical Reports Server (NTRS)

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.

Hernandez, Gloria; Wood, Richard M.; Covell, Peter F.

1994-01-01

179

Computational studies of a fluid spike as a leading edge protection device for shock-shock interference heating  

NASA Technical Reports Server (NTRS)

The effectiveness of a fluid spike as a device to protect leading edges of hypersonic atmospheric flight vehicles from high aerothermal loads produced by complex shock-shock interference is studied. The two-dimensional Navier-Stokes equations are solved using an unstructured cell-centered, fully implicit, flux-difference split algorithm. Adaptively generated unstructured meshes are employed. A type IV shock-shock interference for Mach 8 flow on a cylindrical leading edge with and without a small contraflow supersonic jet (fluid spike) placed at two different locations on the body is solved. A typical flow past a blunt body with a type IV shock-shock interference produces very high pressures and heat fluxes on the leading edge. Present results indicate that a fluid spike displaces the bow shock further in front of the body and modifies the shock-shock interference pattern. This leads to reduced peak pressures and heat fluxes on the body.

Prabhu, Ramadas K.; Thareja, Rajiv R.; Wieting, Allan R.

1991-01-01

180

A Three-Dimensional Solution of Flows over Wings with Leading-Edge Vortex Separation. Part 1: Engineering Document  

NASA Technical Reports Server (NTRS)

A method of predicting forces, moments, and detailed surface pressures on thin, sharp-edged wings with leading-edge vortex separation in incompressible flow is presented. The method employs an inviscid flow model in which the wing and the rolled-up vortex sheets are represented by piecewise, continuous quadratic doublet sheet distributions. The Kutta condition is imposed on all wing edges. Computed results are compared with experimental data and with the predictions of the leading-edge suction analogy for a selected number of wing planforms over a wide range of angle of attack. These comparisons show the method to be very promising, capable of producing not only force predictions, but also accurate predictions of detailed surface pressure distributions, loads, and moments.

Brune, G. W.; Weber, J. A.; Johnson, F. T.; Lu, P.; Rubbert, P. E.

1975-01-01

181

Pressure distributions from subsonic tests of an advanced laminar-flow-control wing with leading- and trailing-edge flaps  

NASA Technical Reports Server (NTRS)

An unswept, semispan wing model equipped with full-span leading- and trailing-edge flaps was tested in the Langley 14- by 22-Foot Subsonic Tunnel to determine the effect of high-lift components on the aerodynamics of an advanced laminar-flow-control (LFC) airfoil section. Chordwise pressure distributions near the midsemispan were measured for four configurations: cruise, trailing-edge flap only, and trailing-edge flap with a leading edge Kreuger flap of either 0.10 or 0.12 chord. Part 1 of this report presents a representative sample of the plotted pressure distribution data for each configuration tested. Part 2 (under separate cover) presents the entire set of plotted and tabulated pressure distribution data. The data are presented without analysis.

Applin, Zachary T.; Gentry, Garl L., Jr.

1988-01-01

182

A Mesh Refinement Study on the Impact Response of a Shuttle Leading-Edge Panel Finite Element Simulation  

NASA Technical Reports Server (NTRS)

A study was performed to examine the influence of varying mesh density on an LS-DYNA simulation of a rectangular-shaped foam projectile impacting the space shuttle leading edge Panel 6. The shuttle leading-edge panels are fabricated of reinforced carbon-carbon (RCC) material. During the study, nine cases were executed with all possible combinations of coarse, baseline, and fine meshes of the foam and panel. For each simulation, the same material properties and impact conditions were specified and only the mesh density was varied. In the baseline model, the shell elements representing the RCC panel are approximately 0.2-in. on edge, whereas the foam elements are about 0.5-in. on edge. The element nominal edge-length for the baseline panel was halved to create a fine panel (0.1-in. edge length) mesh and doubled to create a coarse panel (0.4-in. edge length) mesh. In addition, the element nominal edge-length of the baseline foam projectile was halved (0.25-in. edge length) to create a fine foam mesh and doubled (1.0-in. edge length) to create a coarse foam mesh. The initial impact velocity of the foam was 775 ft/s. The simulations were executed in LS-DYNA for 6 ms of simulation time. Contour plots of resultant panel displacement and effective stress in the foam were compared at four discrete time intervals. Also, time-history responses of internal and kinetic energy of the panel, kinetic and hourglass energy of the foam, and resultant contact force were plotted to determine the influence of mesh density.

Fasanella, Edwin L.; Jackson, Karen E.; Lyle, Karen H.; Spellman, Regina L.

2006-01-01

183

Growth Cone Collapse through Coincident Loss of Actin Bundles and Leading Edge Actin without Actin Depolymerization  

PubMed Central

Repulsive guidance cues can either collapse the whole growth cone to arrest neurite outgrowth or cause asymmetric collapse leading to growth cone turning. How signals from repulsive cues are translated by growth cones into this morphological change through rearranging the cytoskeleton is unclear. We examined three factors that are able to induce the collapse of extending Helisoma growth cones in conditioned medium, including serotonin, myosin light chain kinase inhibitor, and phorbol ester. To study the cytoskeletal events contributing to collapse, we cultured Helisoma growth cones on polylysine in which lamellipodial collapse was prevented by substrate adhesion. We found that all three factors that induced collapse of extending growth cones also caused actin bundle loss in polylysine-attached growth cones without loss of actin meshwork. In addition, actin bundle loss correlated with specific filamentous actin redistribution away from the leading edge that is characteristic of repulsive factors. Finally, we provide direct evidence using time-lapse studies of extending growth cones that actin bundle loss paralleled collapse. Taken together, these results suggest that actin bundles could be a common cytoskeletal target of various collapsing factors, which may use different signaling pathways that converge to induce growth cone collapse. PMID:11381091

Zhou, Feng-quan; Cohan, Christopher S.

2001-01-01

184

Repeatable On-the-Machine Cutting-Edge-Forming Technology Applying Composite Electroplating and Anodic Electrolysis  

Microsoft Academic Search

If a cutting tool could be repeatedly formed without removal from a machine utilized in a cutting process, it would be highly beneficial in that it could reduce not only any positioning error due to a tool exchange, but also the consumption of scarce tool materials and energy. Composite electroplating to build up the cutting edge and anodic electrolysis to

K. Kurahashi; K. Yanagihara; Y. Tani; H. Sato

2004-01-01

185

Thermostructural Evaluation of Joggle Region on the Shuttle Orbiter's Wing Leading Edge  

NASA Technical Reports Server (NTRS)

An investigation was initiated to determine the cause of coating spallation occurring on the Shuttle Orbiter's wing leading edge panels in the slip-side joggle region. The coating spallation events were observed, post flight, on differing panels on different missions. As part of the investigation, the high re-entry heating occurring on the joggles was considered here as a possible cause. Thus, a thermostructural evaluation was conducted to determine the detailed state-of-stress in the joggle region during re-entry and the feasibility of a laboratory test on a local joggle specimen to replicate this state-of-stress. A detailed three-dimensional finite element model of a panel slip-side joggle region was developed. Parametric and sensitivity studies revealed significant stresses occur in the joggle during peak heating. A critical interlaminar normal stress concentration was predicted in the substrate at the coating interface and was confined to the curved joggle region. Specifically, the high interlaminar normal stress is identified to be the cause for the occurrence of failure in the form of local subsurface material separation occurring in the slip-side joggle. The predicted critical stresses are coincident with material separations that had been observed with microscopy in joggle specimens obtained from flight panels.

Walker, Sandra P.; Warren, Jerry E.

2012-01-01

186

Fracture Mechanics Analyses of Reinforced Carbon-Carbon Wing-Leading-Edge Panels  

NASA Technical Reports Server (NTRS)

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.

Raju, Ivatury S.; Phillips, Dawn R.; Knight, Norman F., Jr.; Song, Kyongchan

2010-01-01

187

The structure of separated flow regions occurring near the leading edge of airfoils, including transition  

NASA Technical Reports Server (NTRS)

Data was obtained for the NACA 663-018 airfoil in order to assess the advantages of tripping the boundary layer very near the leading edge for chord Reynolds numbers between 40,000 and 200,000. Single element trips were made from tape 2.5 mm wide and 0.15 mm thick. The unmodified tape trip in five thicknesses was placed across the span at 1.1% chord and the results of lift and drag measurements compared with the smooth airfoil case. Saw tooth geometry trips were also cut from tape and studied using five thicknesses. The saw tooth trips were placed across the span with the sharp points facing upstream at 1.1% chord and with the valley of the teeth at the 2.5% chord position. A large number of bumps and wiggles were produced in the lift coefficient versus angle of attack curves with various combinations of Reynolds number, thickness, and type of trips. The main result in the drag coefficient was an increase in C sub d min with increase in trip thickness.

Mueller, T. J.

1983-01-01

188

Turbulent Wing-Leading-Edge Correlation Assessment for the Shuttle Orbiter  

NASA Technical Reports Server (NTRS)

This study was conducted in support of the Orbiter damage assessment activity that takes place for each Shuttle mission since STS-107 (STS - Space Transportation System). As part of the damage assessment activity, the state of boundary layer (laminar or turbulent) during reentry needs to be estimated in order to define the aerothermal environment on the Orbiter. Premature turbulence on the wing leading edge (WLE) is possible if a surface irregularity promotes early transition and the resulting turbulent wedge flow contaminates the WLE flow. The objective of this analysis is to develop a criterion to determine if and when the flow along the WLE experiences turbulent heating given an incoming turbulent boundary layer that contaminates the attachment line. The data to be analyzed were all obtained as part of the MH-13 Space Shuttle Orbiter Aerothermodynamic Test conducted on a 1.8%-scale Orbiter model at Calspan/University of Buffalo Research Center in the Large Energy National Shock Tunnels facility. A rational framework was used to develop a means to assess the state of the WLE flow on the Orbiter during reentry given a contaminated attachment-line flow. Evidence of turbulent flow on the WLE has been recently documented for a few STS missions during the Orbiter s flight history, albeit late in the reentry trajectory. The criterion developed herein will be compared to these flight results.

King, Rudolph A.; Vaughan, Matthew P.

2009-01-01

189

Mechanism of Water Droplet Breakup near the Leading Edge of an Airfoil  

NASA Technical Reports Server (NTRS)

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 T cnica 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 micrometers, and airfoil velocities of 70 and 90 meters/second.

Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida Garcia

2012-01-01

190

Mechanism of Water Droplet Breakup Near the Leading Edge of an Airfoil  

NASA Technical Reports Server (NTRS)

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.

Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida, Garcia

2012-01-01

191

Augmentation of Fighter-Aircraft Performance by Spanwise Blowing over the Wing Leading Edge  

NASA Technical Reports Server (NTRS)

Spanwise blowing over the wing and canard of a 1:35 model of a close-coupled-canard fighter airplane configuration (similar to the Kfir-C2) was investigated experimentally in low-speed flow. Tests were conducted at airspeeds of 30 m/sec (Reynolds number of 1.8 x 10 to the 5th power based on mean aerodynamic chord) with angle-of-attack sweeps from -8 to 60 deg, and yaw-angle sweeps from -8 to 36 deg at fixed angles of attack 0, 10, 20, 25, 30, and 35 deg. Significant improvement in lift-curve slope, maximum lift, drag polar and lateral/directional stability was found, enlarging the flight envelope beyond its previous low-speed/maximum-lift limit. In spite of the highly swept (60 deg) leading edge, the efficiency of the lift augmentation by blowing was relatively high and was found to increase with increasing blowing momentum on the close-coupled-canard configuration. Interesting possibilities of obtaining much higher efficiencies with swirling jets were indicated.

Seginer, A.; Salomon, M.

1983-01-01

192

Prediction and Assessment of Reynolds Number Sensitivities Associated with Wing Leading-Edge Radius Variations  

NASA Technical Reports Server (NTRS)

The primary objectives of this study were to expand the data base showing the effects of LE radius distribution and corresponding sensitivity to Rn at subsonic and transonic conditions, and to assess the predictive capability of CFD for these effects. Several key elements led to the initiation of this project: 1) the necessity of meeting multipoint design requirements to enable a viable HSCT, 2) the demonstration that blunt supersonic leading-edges can be associated with performance gain at supersonic speeds , and 3) limited data. A test of a modified Reference H model with the TCA planform and 2 LE radius distributions was performed in the NTF, in addition to Navier-Stokes analysis for an additional 3 LE radius distributions. Results indicate that there is a tremendous potential to improve high-lift performance through the use of a blunt LE across the span given an integrated, fully optimized design, and that low Rn data alone is probably not sufficient to demonstrate the benefit.

Wahls, Richard A.; Rivers, Melissa B.; Owens, Lewis R., Jr.

1999-01-01

193

Wing Leading Edge RCC Rapid Response Damage Prediction Tool (IMPACT2)  

NASA Technical Reports Server (NTRS)

This rapid response computer program predicts Orbiter Wing Leading Edge (WLE) damage caused by ice or foam impact during a Space Shuttle launch (Program "IMPACT2"). The program was developed after the Columbia accident in order to assess quickly WLE damage due to ice, foam, or metal impact (if any) during a Shuttle launch. IMPACT2 simulates an impact event in a few minutes for foam impactors, and in seconds for ice and metal impactors. The damage criterion is derived from results obtained from one sophisticated commercial program, which requires hours to carry out simulations of the same impact events. The program was designed to run much faster than the commercial program with prediction of projectile threshold velocities within 10 to 15% of commercial-program values. The mathematical model involves coupling of Orbiter wing normal modes of vibration to nonlinear or linear springmass models. IMPACT2 solves nonlinear or linear impact problems using classical normal modes of vibration of a target, and nonlinear/ linear time-domain equations for the projectile. Impact loads and stresses developed in the target are computed as functions of time. This model is novel because of its speed of execution. A typical model of foam, or other projectile characterized by material nonlinearities, impacting an RCC panel is executed in minutes instead of hours needed by the commercial programs. Target damage due to impact can be assessed quickly, provided that target vibration modes and allowable stress are known.

Clark, Robert; Cottter, Paul; Michalopoulos, Constantine

2013-01-01

194

Numerical evaluations of the effect of leading-edge protuberances on the static and dynamic stall characteristics of an airfoil  

NASA Astrophysics Data System (ADS)

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.

Cai, C.; Zuo, Z. G.; Liu, S. H.; Wu, Y. L.; Wang, F. B.

2013-12-01

195

Electrostriction of lead zirconate titanate/polyurethane composites  

SciTech Connect

Electrostriction of a ferroelectric inclusion/nonferroelectric matrix composite system was studied. The samples were prepared by blending the lead zirconate titanate (PZT) particles with the thermoplastic polyurethane through extrusion and subsequently by hot pressing. Quasistatic cyclic electric fields were applied across the samples while strains and currents were monitored simultaneously. It was found that the electrostriction of the composites depended on the applied electric field in a hysteretic manner. In particular at the high-field regime, the samples exhibited a reversal in the electrostrictive strain. This switching effect occurred at a critical field which was inversely proportional to the PZT content. An associated increase in the displacement current with the critical field was also observed. It indicates that the switching in strain of the composites was mainly due to the flipping of the PZT dipoles in the nonferroelectric polymer matrix. A model was developed for describing the electrostriction behavior of this composite system and the calculated results are comparable to the experimental curves. The success of this theoretical model encourages its application further to the ferroelectric-ferroelectric composite systems.

Lam, K.S.; Zhou, Y.; Wong, Y.W.; Shin, F.G. [Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Hong Kong (China)

2005-05-15

196

Subsonic Investigation of a Leading-Edge Boundary Layer Control Suction System on a High-Speed Civil Transport Configuration  

NASA Technical Reports Server (NTRS)

A wind tunnel investigation of a leading edge boundary layer control system was conducted on a High Speed Civil Transport (HSCT) configuration in the Langley 14- by 22-Foot Subsonic Tunnel. Data were obtained over a Mach number range of 0.08 to 0.27, with corresponding chord Reynolds numbers of 1.79 x 10(exp 6) to 5.76 x 10(exp 6). Variations in the amount of suction, as well as the size and location of the suction area, were tested with outboard leading edge flaps deflected 0 and 30 deg and trailing-edge flaps deflected 0 and 20 deg. The longitudinal and lateral aerodynamic data are presented without analysis. A complete tabulated data listing is also presented herein.

Campbell, Bryan A.; Applin, Zachary T.; Kemmerly, Guy T.; Coe, Paul L., Jr.; Owens, D. Bruce; Gile, Brenda E.; Parikh, Pradip G.; Smith, Don

1999-01-01

197

Theoretical lift and damping in roll at supersonic speeds of thin sweptback tapered wings with streamwise tips, subsonic leading edges, and supersonic trailing edges  

NASA Technical Reports Server (NTRS)

On the basis of linearized supersonic-flow theory, generalized equations were derived and calculations made for the lift and damping in roll of a limited series of thin sweptback tapered wings. Results are applicable to wings with streamwise tips and for a range of supersonic speeds for which the wing is wholly contained between the Mach cones springing from the wing apex and from the trailing edge of the root section. A further limitation is that the tip Mach lines may not intersect on the wing. For the portion of the wing external to the Mach cones springing from the leading edge of the wing tips, the pressure distributions for lift and roll previously obtained for the triangular wing are valid. For the portion of the wing contained within the wing-tip Mach cones a satisfactory approximation to the exact pressure distribution was obtained by application of a point-source-distribution method developed in NACA-TN-1382. A series of design curves are presented which permit rapid estimation of the lift-curve slope and damping-in-roll derivative for given values of aspect ratio, taper ratio, Mach number, and leading-edge sweep. (author)

Malvestuto, Frank S , Jr; Margolis, Kenneth; Ribner, Herbert S

1950-01-01

198

On the stability of attachment-line boundary layers. Part 2. The effect of leading-edge curvature  

NASA Astrophysics Data System (ADS)

The stability of the incompressible attachment-line boundary layer has been studied by Hall, Malik & Poll (1984) and more recently by Lin & Malik (1996). These studies, however, ignored the effect of leading-edge curvature. In this paper, we investigate this effect. The second-order boundary-layer theory is used to account for the curvature effects on the mean flow and then a two-dimensional eigenvalue approach is applied to solve the linear stability equations which fully account for the effects of non-parallelism and leading-edge curvature. The results show that the leading-edge curvature has a stabilizing influence on the attachment-line boundary layer and that the inclusion of curvature in both the mean-flow and stability equations contributes to this stabilizing effect. The effect of curvature can be characterized by the Reynolds number Ra (based on the leading-edge radius). For Ra = 104, the critical Reynolds number R (based on the attachment-line boundary-layer length scale, see §2.2) for the onset of instability is about 637; however, when Ra increases to about 106 the critical Reynolds number approaches the value obtained earlier without curvature effect.

Lin, Ray-Sing; Malik, Mujeeb R.

1997-02-01

199

Heat transfer and material temperature conditions in the leading edge area of impingement-cooled turbine vanes  

NASA Astrophysics Data System (ADS)

The resultant effects on the cooling effectiveness at the leading edge area of an impingement-cooled turbine vane by varying certain geometrical parameters is described with reference to local internal heat transfer coefficients determined from experiment and temperature calculations. The local heat transfer on the cooling-air side is determined experimentally with the aid of the analogy between heat- and mass transfer. The impingement cooling is provided from an inserted sheet-metal containing a single row of holes. The Reynolds Number and several of the cooling geometry parameters were varied. The results demonstrate the high local resolution of the method of measurement, which allows improved analytical treatment of the leading-edge cooling configuration. These experiments also point to the necessity of not always performing model tests under idealized conditions. This becomes very clear in the case of the tests performed on an application-oriented impingement-cooling configuration like that often encountered in engine manufacture. In conclusion, as an example, temperature calculations are employed to demonstrate the effect on the cooling effectiveness of varying the distances between insert and inner surface of the leading edge. It shows how the effectiveness of the leading edge cooling can be increased by simple geometrical measures, which results in a considerable improvement in service life.

Berg, H. P.; Pfaff, K.; Hennecke, D. K.

200

"Partners in Science": A Model Cooperative Program Introducing High School Teachers and Students to Leading-Edge Pharmaceutical Science  

ERIC Educational Resources Information Center

"Partners in Science" is a cooperative program between Boehringer Ingelheim Pharmaceuticals, Inc. and area high schools in the community surrounding our Connecticut campus. It is a two-phase program that introduces high school students and teachers to the world of drug discovery and leading-edge pharmaceutical research. Phase 1 involves a series…

Woska, Joseph R., Jr.; Collins, Danielle M.; Canney, Brian J.; Arcario, Erin L.; Reilly, Patricia L.

2005-01-01

201

Preliminary thermal/structural analysis of a carbon-carbon/refractory-metal heat-pipe-cooled wing leading edge  

NASA Technical Reports Server (NTRS)

This study presents preliminary thermal/structural analyses of a carbon-carbon/refractory-metal heat-pipe-cooled wing leading edge concept designed for an air breathing single-stage-to-orbit hypersonic vehicle. The concept features chordwise (i.e., normal to the leading edge) and spanwise (i.e., parallel to the leading edge) refractory-metal heat pipes which are completely embedded within a carbon-carbon primary structure. Studies of the leading edge were performed using nonlinear thermal and linear structural three-dimensional finite element analyses. The concept was shown to be thermally feasible within the limits of the assumptions made in the analyses when internal radiative cooling is present during ascent, and a three-dimensional carbon-carbon architecture is used. In addition, internal radiative cooling was found not to be necessary during descent. The linear stress analysis indicated excessively large thermal stresses in the rafractory metal walls of the heat pipes even though a soft layer of carbon was included between the heat pipe and the carbon-carbon structure in an attempt to reduce the thermal stresses. A nonlinear structural analysis may be necessary to properly model the response of the refractory-metal heat pipes.

Glass, David E.; Camarda, Charles J.

1990-01-01

202

The Video Wall Project Video Technology at the Leading Edge in Education Stephen Giles and David Abramson,  

E-print Network

into the application of high­speed networks (Internet2, Next Generation Internet) in higher education and there haveThe Video Wall Project ­ Video Technology at the Leading Edge in Education Stephen Giles and David Abramson, School of Computer Science and Software Engineering, Faculty of Information Technology, Monash

Abramson, David

203

Turbulent Vortex-Flow Simulation Over a 65 deg Sharp and Blunt Leading-Edge Delta Wing at Subsonic Speeds  

NASA Technical Reports Server (NTRS)

Turbulent thin-layer, Reynolds-Averaged Navier-Stokes solutions, based on a multi-block structured grid, are presented for a 65 deg delta wing having either a sharp leading edge (SLE) or blunt leading edge (BLE) geometry. The primary objective of the study is to assess the prediction capability of the method for simulating the leading-edge flow separation and the ensuing vortex flow characteristics. Computational results are obtained for two angles of attack of approximately 13 and 20 deg, at free-stream Mach number of 0.40 and Reynolds number of 6 million based on the wing mean aerodynamic chord. The effects of two turbulence models of Baldwin-Lomax with Degani-Schiff (BL/DS) and the Spalart-Allmaras (SA) on the numerical results are also discussed. The computations also explore the effects of two numerical flux-splitting schemes, i.e., flux difference splitting (fds) and flux vector splitting (fvs), on the solution development and convergence characteristics. The resulting trends in solution sensitivity to grid resolution for the selected leading-edge geometries, angles of attack, turbulence models and flux splitting schemes are also presented. The validity of the numerical results is evaluated against a unique set of experimental wind-tunnel data that was obtained in the National Transonic Facility at the NASA Langley Research Center.

Ghaffari, Farhad

2005-01-01

204

Pb 2+ environment in lead silicate glasses probed by Pb-L III edge XAFS and 207Pb NMR  

Microsoft Academic Search

The local structural environment of lead (Pb) atoms in lead silicate glasses has been studied by two complementary spectroscopic techniques: Pb-LIII edge X-ray absorption fine structure (XAFS) and 207Pb solid state nuclear magnetic resonance (NMR). XAFS results have been obtained with two kinds of experimental devices: a synchrotron radiation source and a laboratory spectrometer. The weak photon flux is then

F. Fayon; C Landron; K Sakurai; C Bessada; D Massiot

1999-01-01

205

Characterization of multifunctional skin-material for morphing leading-edge applications  

NASA Astrophysics Data System (ADS)

Former research on morphing droop-nose applications revealed great economical and social ecological advantages in terms of providing gapless surfaces for long areas of laminar flow. Furthermore a droop-nose for laminar flow applications provides a low noise exposing high-lift system at the leading-edge. Various kinematic concepts for the active deployment of such devices are already published but the major challenge is still an open issue: a skin material which meets the compromise of needed stiffness and flexibility. Moreover additional functions have to be added to keep up with standard systems. As a result of several national and European projects the DLR developed a gapless 3D smart droop-nose concept, which was successfully analyzed in a low speed wind tunnel test under relevant loads to prove the functionality and efficiency. The main structure of this concept is made of commercial available glass fiber reinforced plastics (GRFP). This paper presents elementary tests to characterize material lay-ups and their integrity by applying different loads under extreme thermal conditions using aged specimens. On the one hand the presented work is focused on the integrity of material-interfaces and on the other hand the efficiency and feasibility of embedded functions. It can be concluded that different preparations, different adhesives and used materials have their significant influence to the interface stability and mechanical property of the whole lay-up. Especially the laminate design can be optimized due to the e. g. mechanical exploitation of the added systems beyond their main function in order to reduce structural mass.

Geier, Sebastian; Kintscher, Markus; Mahrholz, Thorsten; Wierach, Peter; Monner, Hans-Peter; Wiedemann, Martin

2013-04-01

206

Measuring forces at the leading edge: a force assay for cell motility.  

PubMed

Cancer cells become mobile by remodelling their cytoskeleton to form migratory structures. This transformation is dominated by actin assembly and disassembly (polymerisation and depolymerisation) in the cytoplasm. Synthesis of filamentous actin produces a force at the leading edge that pushes the plasma membrane forward. We describe an assay to measure the restoring force of the membrane in response to forces generated within the cytoplasm adjacent to the membrane. A laser trap is used to form a long membrane nanotube from a living cell and to measure the axial membrane force at the end of the tube. When the tube, resembling a filopodium, is formed and in a relaxed state the axial membrane force exhibits a positive stationary value. This value reflects the influence of the cytoskeleton that acts to pull the tube back to the cell. A dynamic sawtooth force that rides upon the stationary value is also observed. This force is sensitive to a toxin that affects actin assembly and disassembly, but not affected by agents that influence microtubules and myosin light chain kinase. We deduce from the magnitude and characteristics of dynamic force measurements that it originates from depolymerisation and polymerisation of F-actin. The on- and off-rates, the number of working filaments, and the force per filament (2.5 pN) are determined. We suggest the force-dependent transitions are thermodynamically uncoupled as both the on- and off-rates decrease exponentially with a compressive load. We propose kinetic schemes that require attachment of actin filaments to the membrane during depolymerisation. This demonstrates that actin kinetics can be monitored in a living cell by measuring force at the membrane, and used to probe the mobility of cells including cancer cells. PMID:23080534

Farrell, Brenda; Qian, Feng; Kolomeisky, Anatoly; Anvari, Bahman; Brownell, William E

2013-01-01

207

Mixed-mode strain-energy-release rate effects on edge delamination of composites  

NASA Technical Reports Server (NTRS)

Unnotched graphite/epoxy laminates, designed to delaminate at the edges under static and cyclic tensile loads, were tested and analyzed. The specimen stacking sequences were chosen so that the total strain-energy-release rate, G, for edge delamination was identical for all three layups. However, each layup had different percentages of crack-opening and shear-mode strain-energy-release rates, G sub 1 and G sub 2, respectively. Results with composites made from T300 graphite fibers and 5208 epoxy, a brittle resin, indicated that only G sub 1 contributed to delamination onset under static loading. However, results with composites made from C6000 fibers and H205 epoxy, a tougher resin, indicated that the total F governed the onset of edge delaminations under cyclic loads. In addition, for both materials, the threshold level of G for delamination onset in fatigue was significantly less than the critical G sub c measured in static tests. Futhermore, although the C6000/H205 material had a much higher static G sub c than T300/5208, its fatigue resistance was only slightly better. A series of mixed-mode tests, like the ones in this study, may be needed to evaluate toughened-resin composites developed for highly strained composite structures subjected to cyclic loads.

Obrien, T. K.

1983-01-01

208

Free edge strain concentrations in real composite laminates Experimental-theoretical correlation  

NASA Technical Reports Server (NTRS)

The magnitude of the maximum shear strain at the free edge of axially loaded theta (2)/theta(2)(s) and (+ or - theta(2) (s) composite laminates was investigated experimentally and numerically to ascertain the actual value of strain concentration in resin matrix laminates and to determine the accuracy of finite element results. Experimental results using moire interferometry show large, but finite, shear strain concentrations at the free edge of graphite-epoxy and graphite-polyimide laminates. Comparison of the experimental results with those obtained using several different finite element representations showed that a four node isoparametric finite element provided the best and most trouble free numerical results. The results indicate that the ratio of maximum shear strain at the free edge to applied axial strain varies with fiber orientation and does not exceed nine for the most critical angle which is 15 deg.

Herakovich, C. T.; Post, D.; Buczek, M. B.; Czarnek, R.

1985-01-01

209

Reduction of Free Edge Peeling Stress of Laminated Composites Using Active Piezoelectric Layers  

PubMed Central

An analytical approach is proposed in the reduction of free edge peeling stresses of laminated composites using active piezoelectric layers. The approach is the extended Kantorovich method which is an iterative method. Multiterms of trial function are employed and governing equations are derived by taking the principle of complementary virtual work. The solutions are obtained by solving a generalized eigenvalue problem. By this approach, the stresses automatically satisfy not only the traction-free boundary conditions, but also the free edge boundary conditions. Through the iteration processes, the free edge stresses converge very quickly. It is found that the peeling stresses generated by mechanical loadings are significantly reduced by applying a proper electric field to the piezoelectric actuators. PMID:25025088

Huang, Bin; Kim, Heung Soo

2014-01-01

210

Exploratory study of the effects of wing-leading-edge modifications on the stall/spin behavior of a light general aviation airplane  

NASA Technical Reports Server (NTRS)

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.

1979-01-01

211

Penetration of carbon-fabric-reinforced composites by edge cracks during thermal aging  

NASA Technical Reports Server (NTRS)

Thermo-oxidative stability (TOS) test results are significantly influenced by the formation and growth or presence of interlaminar and interlaminar cracks in the cut edges of all carbon-fiber-crosslinked high-temperature polymer matrix composites(exp 1-5) (i.e., unidirectional, crossplied, angle-plied, and fabric composites). The thermo-oxidative degradation of these composites is heavily dependent on the surface area that is exposed to the harmful environment and on the surface-to-volume ratio of the structure under study. Since the growth of cracks and voids on the composite surfaces significantly increases the exposed surface areas, it is imperative that the interaction between the aging process and the formation of new surface area as the aging time progresses be understood.

Bowles, Kenneth J.; Kamvouris, John E.

1994-01-01

212

Influence of airfoil geometry on delta wing leading-edge vortices and vortex-induced aerodynamics at supersonic speeds  

NASA Technical Reports Server (NTRS)

An assessment of the influence of airfoil geometry on delta wing leading edge vortex flow and vortex induced aerodynamics at supersonic speeds is discussed. A series of delta wing wind tunnel models were tested over a Mach number range from 1.7 to 2.0. The model geometric variables included leading edge sweep and airfoil shape. Surface pressure data, vapor screen, and oil flow photograph data were taken to evaluate the complex structure of the vortices and shocks on the family of wings tested. The data show that airfoil shape has a significant impact on the wing upper surface flow structure and pressure distribution, but has a minimal impact on the integrated upper surface pressure increments.

Wood, Richard M.; Byrd, James E.; Wesselmann, Gary F.

1992-01-01

213

Calculation of the 3-D viscous flow at the endwall leading edge region of an axial annular turbine cascade  

NASA Technical Reports Server (NTRS)

A three-dimensional viscous computer code (VANS/MD) was employed to calculate the turbulent flow field at the end wall leading edge region of a 20 inch axial annular turbine cascade. The initial boundary layer roll-up and formation of the end wall vortices were computed at the vane leading edge. The calculated flow field was found to be periodic with a frequency of approximately 1600 Hz. The calculated size of the separation region for the hub endwall vortex compared favorably with measured endwall oil traces. In an effort to determine the effects of the turbulence model on the calculated unsteadiness, a laminar calculation was made. The periodic nature of the calculated flow field persisted with the frequency essentially unchanged.

Walitt, L.

1984-01-01

214

Two and three-dimensional shock-shock interactions on the blunt leading edges of the hypersonic inlets  

NASA Technical Reports Server (NTRS)

The effect of shock impingement on the blunt leading edges of the top and sidewall compression type inlet of a scramjet engine is studied numerically. The impinging shock is caused by the vehicle forebody. The interaction of this forebody shock with the inlet leading edge shock results in a very complex flowfield containing local regions of high pressure and intense heating. This complex flowfield in calculated by solving the Navier-Stokes equations using a finite volume flux splitting technique due to van Leer. To resolve the finer details of the flow structure as well as to predict the surface heat transfer accurately, adaptive grid technique is used in the analysis. Results of the present numerical study are compared with available experimental results.

Singh, D. J.; Kumar, Ajay; Tiwari, S. N.

1991-01-01

215

Alignment of leading-edge and peak-picking time of arrival methods to obtain accurate source locations  

SciTech Connect

The location of a radiating source can be determined by time-tagging the arrival of the radiated signal at a network of spatially distributed sensors. The accuracy of this approach depends strongly on the particular time-tagging algorithm employed at each of the sensors. If different techniques are used across the network, then the time tags must be referenced to a common fiducial for maximum location accuracy. In this report we derive the time corrections needed to temporally align leading-edge, time-tagging techniques with peak-picking algorithms. We focus on broadband radio frequency (RF) sources, an ionospheric propagation channel, and narrowband receivers, but the final results can be generalized to apply to any source, propagation environment, and sensor. Our analytic results are checked against numerical simulations for a number of representative cases and agree with the specific leading-edge algorithm studied independently by Kim and Eng (1995) and Pongratz (2005 and 2007).

Roussel-Dupre, R.; Symbalisty, E.; Fox, C.; and Vanderlinde, O.

2009-08-01

216

Experimental and theoretical investigation of boundary-layer instability mechanisms on a swept leading edge at Mach 3.5  

NASA Technical Reports Server (NTRS)

A brief outline of the experimental and theoretical investigation of boundary layer instability mechanisms on a swept leading edge at Mach 3.5 is presented. Transition is affected by wind tunnel noise only when roughness is present. Local bar-R sub * Reynolds number and k/eta sub * are useful correlation parameters for a wide range of free stream Mach numbers. Stability theory is in good agreement with the experimental cross flow vortex wavelength. These conclusions are briefly discussed.

Creel, Theodore R., Jr.; Malik, Mujeeb R.; Beckwith, Ivan E.

1987-01-01

217

A New Method for Measuring Edge Tensions and Stability of Lipid Bilayers: Effect of Membrane Composition  

PubMed Central

We report a novel and facile method for measuring edge tensions of lipid membranes. The approach is based on electroporation of giant unilamellar vesicles and analysis of the pore closure dynamics. We applied this method to evaluate the edge tension in membranes with four different compositions: egg phosphatidylcholine (eggPC), dioleoylphosphatidylcholine (DOPC), and mixtures of DOPC with cholesterol and dioleoylphosphatidylethanolamine. Our data confirm previous results for eggPC and DOPC. The addition of 17 mol % cholesterol to the DOPC membrane causes an increase in the membrane edge tension. On the contrary, when the same fraction of dioleoylphosphatidylethanolamine is added to the membrane, a decrease in the edge tension is observed, which is an unexpected result considering the inverted-cone shape geometry of the molecule. It is presumed that interlipid hydrogen bonding is the origin of this behavior. Furthermore, cholesterol was found to lower the lysis tension of DOPC bilayers. This behavior differs from that observed on bilayers made of stearoyloleoylphosphatidylcholine, suggesting that cholesterol influences the membrane mechanical stability in a lipid-specific manner. PMID:21081074

Portet, Thomas; Dimova, Rumiana

2010-01-01

218

Low-Speed Aerodynamic Data for an 0.18-Scale Model of an F-16XL with Various Leading-Edge Modifications  

NASA Technical Reports Server (NTRS)

Using the F-16XL as a test-bed, two strategies for improving the low-speed flying characteristics that had minimal impact on high-speed performance were evaluated. In addition to the basic F-16XL configuration several modifications to the baseline configuration were tested in the Langley 30- X 60-Foot Tunnel: 1) the notched area at the wing leading edge and fuselage juncture was removed resulting in a continuous 70 deg leading-edge sweep on the inboard portion of the wing; 2) an integral attached-flow leading-edge flap concept was added to the continuous leading edge; and 3) a deployable vortex flap concept was added to the continuous leading edge. The purpose of this report is simply to document the test configurations, test conditions, and data obtained in this investigation for future reference and analysis. No analysis is presented herein and the data only appear in tabulated format.

Hahne, Daniel E.

1999-01-01

219

Asian anthropogenic lead contamination in the North Pacific Ocean as evidenced by stable lead isotopic compositions  

NASA Astrophysics Data System (ADS)

This dissertation work determined the changing scope of lead (Pb) contamination in the North Pacific Ocean since the phase-out of leaded gasoline in most of the world. Chapters 1 and 2 consisted of validating our method for determining Pb concentrations and isotopic compositions in seawater. Chapter 3 established a baseline of Pb isotopic compositions (PbICs) in the western and central North Pacific in 2002. This was an ideal time to establish such a baseline because China had recently (mid-2000) ceased their use of leaded gasoline and simultaneously began consuming increasingly large amounts of coal, known to have relatively high Pb concentrations. We found subsurface waters were contaminated with Asian industrial Pb, predominantly Chinese coal emissions. In contrast, the abyssal waters were a mix of Asian industrial Pb and background (i.e., natural) Pb. Chapter 4 revisited the western and central North Pacific in 2009 -- 2011 to determine what, if any, changes had occurred in this short time period. We found that Pb in subsurface and abyssal waters of the western North Pacific were similar to Chinese aerosols. Such a large change in the PbICs of abyssal water in 9 years was unanticipated and attributed to the relatively large flux of particle-bound Pb from the euphotic zone to the deep ocean, which was in isotopic equilibrium with the reservoir of dissolved Pb. In contrast, the central North Pacific abyssal water PbICs were similar to values previously reported because of the relatively lower particulate export. Based on comparisons to baseline PbIC data, we determined that abyssal waters in the western and central North Pacific would be isotopically indistinguishable from surface waters in the next three decades. Sources of Pb to coastal California waters were reevaluated in Chapter 5. Prior studies had found that surface waters of the California Current System (CCS) were isotopically consistent with both Asian industrial Pb and US leaded gasoline, still in use at that point in time. In 2010 and 2011, we found that surface and subsurface waters of the CCS were isotopically similar to Asian industrial emissions. However, remobilized US gasoline Pb from sediments in the San Francisco Bay, California, were accumulating in the "mud belt" on the continental shelf and changing the isotopic composition of overlying waters. During periods of intense upwelling, this historic Pb was brought to the surface of the water. However, the much larger quantity of Pb from Asian industrial emissions made the isotopic composition of Pb from historic US gasoline unidentifiable in off-shore waters. A secondary research focus of this dissertation was to improve my own teaching abilities. Chapter 6 explored the intersection of system thinking and aquatic toxicology in undergraduate education. Among a wealth of information, I found that group concept mapping was no more useful to student learning than the same activity done individually. This was due to poor implementation of team learning strategies by me and inadequate time for students to adjust to non-traditional instruction methodologies.

Zurbrick, Cheryl M.

220

EDG1 Receptor Stimulation Leads to Cardiac Hypertrophy in Rat Neonatal Myocytes  

Microsoft Academic Search

Sphingosine 1 phosphate (S1P), an aminophospholipid, acts extracellularly as a ligand via the specific G protein-coupled receptors of the endothelial differentiation gene (EDG) 1, 3, 5, 6 and 8 receptors family and intracellularly as a second messenger in various cellular types. The aim of this work was to investigate biological activity of S1P in cardiomyocytes with respect to related sphingolipids.

Philippe Robert; Ping Tsui; Marie Paule Laville; George P. Livi; Henry M. Sarau; Antoine Bril; Isabelle Berrebi-Bertrand

2001-01-01

221

Numerical Simulation of Fluctuations Leading to Noise in a Flap-Edge Flowfield  

NASA Technical Reports Server (NTRS)

In this paper we develop an approximate computational framework for simulation of the fluctuating flowfield associated with the complex vortex system seen at the side edge of a flap in a multi-element high-lift airfoil system. The eventual goal of these simulations is to provide an estimate of the spectral content of these fluctuations, in order that the spectrum of the noise generated by such flowfields may be estimated. Results from simulations utilizing this computational framework are shown.

Streett, C. L.

1998-01-01

222

The effects of leading-edge serrations on reducing flow unsteadiness about airfoils, an experimental and analytical investigation  

NASA Technical Reports Server (NTRS)

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.

Schwind, R. G.; Allen, H. J.

1973-01-01

223

Lift augmentation on a delta wing via leading edge fences and the Gurney flap. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Wind tunnel tests were conducted on two devices for the purpose of lift augmentation on a 60 deg delta wing at low speed. Lift, drag, pitching moment, and surface pressures were measured. Detailed flow visualization was also obtained. Both the leading edge fence and the Gurney flap are shown to increase lift. The fences and flap shift the lift curve as much as 5 deg and 10 deg, respectively. The fences aid in trapping vortices on the upper surface, thereby increasing suction. The Gurney flap improves circulation at the trailing edge. The individual influences of both devices are roughly additive, creating high lift gain. However, the lower lift to drag ratio and the precipitation of vortex burst caused by the fences, and the nose down pitching moment created by the flap are also significant factors.

Buchholz, Mark D.

1992-01-01

224

Experimental study of flow separation control on a low- Re airfoil using leading-edge protuberance method  

NASA Astrophysics Data System (ADS)

An experimental study of flow separation control on a low- Re c airfoil was presently investigated using a newly developed leading-edge protuberance method, motivated by the improvement in the hydrodynamics of the giant humpback whale through its pectoral flippers. Deploying this method, the control effectiveness of the airfoil aerodynamics was fully evaluated using a three-component force balance, leading to an effectively impaired stall phenomenon and great improvement in the performances within the wide post-stall angle range (22°-80°). To understand the flow physics behind, the vorticity field, velocity field and boundary layer flow field over the airfoil suction side were examined using a particle image velocimetry and an oil-flow surface visualization system. It was found that the leading-edge protuberance method, more like low-profile vortex generator, effectively modified the flow pattern of the airfoil boundary layer through the chordwise and spanwise evolutions of the interacting streamwise vortices generated by protuberances, where the separation of the turbulent boundary layer dominated within the stall region and the rather strong attachment of the laminar boundary layer still existed within the post-stall region. The characteristics to manipulate the flow separation mode of the original airfoil indicated the possibility to further optimize the control performance by reasonably designing the layout of the protuberances.

Zhang, M. M.; Wang, G. F.; Xu, J. Z.

2014-04-01

225

Effects of Wing Leading Edge Penetration with Venting and Exhaust Flow from Wheel Well at Mach 24 in Flight  

NASA Technical Reports Server (NTRS)

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.

Gnoffo, Peter A.

2003-01-01

226

A Survey of Factors Affecting Blunt Leading-Edge Separation for Swept and Semi-Slender Wings  

NASA Technical Reports Server (NTRS)

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.

Luckring, James M.

2010-01-01

227

Buckling and postbuckling of composite panels with cutouts subjected to combined edge shear and temperature change  

NASA Technical Reports Server (NTRS)

The results of a detailed study of the buckling and postbuckling responses of composite panels with central circular cutouts are presented. The panels are subjected to combined edge shear and temperature change. The panels are discretized by using a two-field degenerate solid element with each of the displacement components having a linear variation throughout the thickness of the panel. The fundamental unknowns consist of the average mechanical strains through the thickness and the displacement components. The effects of geometric nonlinearities and laminated anisotropic material behavior are included. The stability boundary, postbuckling response and the hierarchical sensitivity coefficients are evaluated. The hierarchical sensitivity coefficients measure the sensitivity of the buckling and postbuckling responses to variations in the panel stiffnesses, and the material properties of both the individual layers and the constituents (fibers and matrix). Numerical results are presented for composite panels with central circular cutouts subjected to combined edge shear and temperature change, showing the effects of variations in the hole diameter, laminate stacking sequence and fiber orientation, on the stability boundary and postbuckling response and their sensitivity to changes in the various panel parameters.

Noor, Ahmed K.; Kim, Yong H.

1995-01-01

228

Studies Conducted of Sodium Carbonate Contaminant Found on the Wing Leading Edge and the Nose Cap of the Space Shuttle Orbiter  

NASA Technical Reports Server (NTRS)

In early 2001, three of the space shuttle orbiters were found to have a sodium carbonate contaminant on the wing leading edge and nose cap. These parts are made of a reinforced carbon/carbon material protected by silicon carbide (SiC) and a glass coating. The glass coating is known as Type A and is primarily sodium silicate with particles of SiC. NASA Glenn Research Center's Environmental Durability Branch was asked to determine the chemistry of this deposit formation and assess any possible detrimental effects. At low temperatures, the reverse reaction is favorable. Previous studies of the corrosion of glass show that carbon dioxide in the presence of water does form sodium carbonate on sodium silicate glass (ref. 1). It is quite likely that a similar scenario exists for the orbiter wing leading edge. All three orbiters that formed sodium carbonate were exposed to rain. This formation of sodium carbonate was duplicated in the laboratory. The Type A glass, which coats the wing leading edge and nose cap, was made in a freestanding form and exposed to water in two separate experiments. In one set of experiments, the coating was placed in a petri dish filled with water. As the water evaporated, sodium carbonate formed. In another case, water was slowly dripped on the coating and sodium carbonate formed. The sodium carbonate was detected by chemical analysis and, in some cases, xray diffraction showed a hydrated sodium carbonate. The next step was to examine possible detrimental effects of this sodium carbonate. There are three likely scenarios for the sodium carbonate deposit: (1) it may be removed with a simple rinse, (2) it may remain and flow back into the Type A glass after heating during reentry, or (3) it may remain and flow onto unprotected SiC and/or other parts after heating during reentry. The effect of case 1 is to remove the Na2O constituent from the Type A glass, thus decreasing its effectiveness as a sealant. Even so, overall, it is probably the best approach and was used by the NASA Kennedy Space Center when the deposits were first observed. The effect of case 2 is minimal and would actually restore the the Type A glass to its composition before carbonate formation. However, the problem with allowing the carbonate to remain leads to the third scenario, the deposit flowing onto other parts. A series of tests were conducted on unprotected SiC, and minimal effects were found in the short-term, but other ceramic and metal parts could be damaged by the molten sodium carbonate and would require close monitoring.

Jacobson, Nathan S.; Palou, Jaime J.

2003-01-01

229

NONAXISYMMETRIC ENDWALL CONTOURING AND LEADING EDGE MODIFICATIONS ON TURBINE NOZZLE GUIDE VANES  

E-print Network

to the endwall surface. These LE fillets improve the aerodynamics of the flow and the heat transfer effectiveness aerodynamic improvements can be counted as the axisymmetric/nonaxisymmetric endwall contouring, blade leading be counteracted by nonaxisymmetric endwall contouring. Additionally, the aerodynamic losses related

Guiltinan, Mark

230

Clathrin-independent carriers form a high capacity endocytic sorting system at the leading edge of migrating cells.  

PubMed

Although the importance of clathrin- and caveolin-independent endocytic pathways has recently emerged, key aspects of these routes remain unknown. Using quantitative ultrastructural approaches, we show that clathrin-independent carriers (CLICs) account for approximately three times the volume internalized by the clathrin-mediated endocytic pathway, forming the major pathway involved in uptake of fluid and bulk membrane in fibroblasts. Electron tomographic analysis of the 3D morphology of the earliest carriers shows that they are multidomain organelles that form a complex sorting station as they mature. Proteomic analysis provides direct links between CLICs, cellular adhesion turnover, and migration. Consistent with this, CLIC-mediated endocytosis of key cargo proteins, CD44 and Thy-1, is polarized at the leading edge of migrating fibroblasts, while transient ablation of CLICs impairs their ability to migrate. These studies provide the first quantitative ultrastructural analysis and molecular characterization of the major endocytic pathway in fibroblasts, a pathway that provides rapid membrane turnover at the leading edge of migrating cells. PMID:20713605

Howes, Mark T; Kirkham, Matthew; Riches, James; Cortese, Katia; Walser, Piers J; Simpson, Fiona; Hill, Michelle M; Jones, Alun; Lundmark, Richard; Lindsay, Margaret R; Hernandez-Deviez, Delia J; Hadzic, Gordana; McCluskey, Adam; Bashir, Rumasia; Liu, Libin; Pilch, Paul; McMahon, Harvey; Robinson, Phillip J; Hancock, John F; Mayor, Satyajit; Parton, Robert G

2010-08-23

231

Clathrin-independent carriers form a high capacity endocytic sorting system at the leading edge of migrating cells  

PubMed Central

Although the importance of clathrin- and caveolin-independent endocytic pathways has recently emerged, key aspects of these routes remain unknown. Using quantitative ultrastructural approaches, we show that clathrin-independent carriers (CLICs) account for approximately three times the volume internalized by the clathrin-mediated endocytic pathway, forming the major pathway involved in uptake of fluid and bulk membrane in fibroblasts. Electron tomographic analysis of the 3D morphology of the earliest carriers shows that they are multidomain organelles that form a complex sorting station as they mature. Proteomic analysis provides direct links between CLICs, cellular adhesion turnover, and migration. Consistent with this, CLIC-mediated endocytosis of key cargo proteins, CD44 and Thy-1, is polarized at the leading edge of migrating fibroblasts, while transient ablation of CLICs impairs their ability to migrate. These studies provide the first quantitative ultrastructural analysis and molecular characterization of the major endocytic pathway in fibroblasts, a pathway that provides rapid membrane turnover at the leading edge of migrating cells. PMID:20713605

Howes, Mark T.; Kirkham, Matthew; Riches, James; Cortese, Katia; Walser, Piers J.; Simpson, Fiona; Hill, Michelle M.; Jones, Alun; Lundmark, Richard; Lindsay, Margaret R.; Hernandez-Deviez, Delia J.; Hadzic, Gordana; McCluskey, Adam; Bashir, Rumasia; Liu, Libin; Pilch, Paul; McMahon, Harvey; Robinson, Phillip J.; Hancock, John F.; Mayor, Satyajit

2010-01-01

232

A leading edge heating array and a flat surface heating array: Final design. [for testing the thermal protection system of the space shuttle  

NASA Technical Reports Server (NTRS)

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.

1975-01-01

233

Application of an aerodynamic analysis method including attainable thrust estimates to low speed leading-edge flap design for supersonic cruise vehicles  

NASA Technical Reports Server (NTRS)

A study of low speed leading-edge flap design for supersonic cruise vehicle was conducted. Wings with flaps were analyzed with the aid of a newly developed subsonic wing program which provides estimates of attainable leading-edge thrust. Results indicate that the thrust actually attainable can have a significant influence on the design and that the resultant flaps can be smaller and simpler than those resulting from more conventional approaches.

Carlson, H. W.

1982-01-01

234

Leading Edge Flame Detachment: Effect on Burning Rate of Ammonium Perchlorate Propellants  

NASA Technical Reports Server (NTRS)

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.

Price, E. W.; Chakravarthy, S. R.; Sambamurthi, J. K.; Sigman, R. K.

1997-01-01

235

Space Shuttle Orbiter - Leading edge structural design/analysis and material allowables  

NASA Technical Reports Server (NTRS)

Reinforced Carbon-Carbon (RCC), a structural composite whose development was targeted for the high temperature reentry environments of reusable space vehicles, has successfully demonstrated that capability on the Space Shuttle Orbiter. Unique mechanical properties, particularly at elevated temperatures up to 3000 F, make this material ideally suited for the 'hot' regions of multimission space vehicles. Design allowable characterization testing, full-scale development and qualification testing, and structural analysis techniques will be presented herein that briefly chart the history of the RCC material from infancy to eventual multimission certification for the Orbiter. Included are discussions pertaining to the development of the design allowable data base, manipulation of the test data into usable forms, and the analytical verification process.

Johnson, D. W.; Curry, D. M.; Kelly, R. E.

1986-01-01

236

Numerical investigations of free edge effects in integrally stiffened layered composite panels  

NASA Astrophysics Data System (ADS)

A linear finite element analysis is conducted to examine the free edge stresses and the displacement behavior of an integrally stiffened layered composite panel loaded under uniform inplane tension. Symmetric (+Phi, -Phi, 0, -Phi, +Phi) graphite-epoxy laminates with various fiber orientations in the off-axis plies are considered. The quadratic stress criterion, the Tsai-Wu criterion and the Mises equivalent stresses are used to determine a risk parameter for onset of delamination, first ply failure and matrix cracking in the neat resin. The results of the analysis show that the interlaminar stresses at the +Phi/-Phi and -Phi/0 interfaces increase rapidly in the skin-stringer transition. This behavior is observed at the free edge as well as at some distance from it. The magnitude of the interlaminar stresses in the skin-stringer transition is strongly influenced by the fiber orientations of the off-axis plies. In addition, the overall displacements depend on the magnitude of the off-axis ply angle. It is found that for Phi less than 30 deg the deformations of the stiffener section are dominated by bending, whereas for Phi in the range of 45 to 75 deg the deformations are dominated by torsion. The failure analysis shows that ply and matrix failure tend to occur prior to delamination for the considered configurations.

Skrna-Jakl, I.; Rammerstorfer, F. G.

237

Effects of wing-leading-edge modifications on a full-scale, low-wing general aviation airplane: Wind-tunnel investigation of high-angle-of-attack aerodynamic characteristics. [conducted in Langley 30- by 60-foot tunnel  

NASA Technical Reports Server (NTRS)

Wing-leading-edge modifications included leading-edge droop and slat configurations having full-span, partial-span, or segmented arrangements. Other devices included wing-chord extensions, fences, and leading-edge stall strips. Good correlation was apparent between the results of wind-tunnel data and the results of flight tests, on the basis of autorotational stability criterion, for a wide range of wing-leading-edge modifications.

Newsom, W. A., Jr.; Satran, D. R.; Johnson, J. L., Jr.

1982-01-01

238

X-ray absorption near edge structure spectrometry study of nickel and lead speciation in coals and coal combustion products  

SciTech Connect

The fate and environmental impacts of trace elements from coal fired power stations are a significant concern because of the large quantities of coal used as an energy source. The ultimate environmental fate and health impact of some of these trace elements is dependent on their various forms and oxidation states. Nickel and lead are two of the trace elements classified as 'priority pollutants' by the National Pollutant Inventory (NPI) in Australia. This study attempts to understand speciation of nickel and lead in coal and coal combustion products from five coal fired power stations in Australia where bituminous rank coals are utilized. Non-destructive X-ray Absorption Near Edge Structure Spectrometry (XANES) was used to determine speciation of these metals. Semiquantitative speciation of nickel and lead was calculated using a linear combination fit of XANES spectra obtained for selected pure reference compounds. In all fly ash samples, 28-80% of nickel was present as nickel in NiSO{sub 4} form, which is a more toxic and more bioavailable form of nickel. Less toxic NiO was detected in fly ash samples in the range of 0-15%. Speciation of lead revealed that 65-70% is present as PbS in the feed coals. In all fly ash samples analyzed, lead comprised different proportions of PbCl{sub 2}, PbO, and PbSO{sub 4}. PbCl{sub 2} and PbSO{sub 4} contents varied between 30-70% and 30-60%, respectively. Chemical reactions resulting in nickel and lead transformation that are likely to have occurred in the post-combustion environment are discussed. 22 refs., 7 figs., 7 tabs.

Pushan Shah; Vladimir Strezov; Peter F. Nelson [Macquarie University, Sydney, NSW (Australia). CRC for Coal in Sustainable Development

2009-03-15

239

Use of Truncated Flapped Airfoils for Impingement and Icing Tests of Full-Scale Leading-Edge Sections  

NASA Technical Reports Server (NTRS)

In an effort to increase the operational range of existing small icing tunnels, the use of truncated airfoil sections has been suggested. With truncated airfoils, large-scale or even full-scale wing-icing-protection systems could be evaluated. Therefore, experimental studies were conducted in the NACA Lewis laboratory icing 'tunnel with an NACA 651-212 airfoil section to determine the effect of truncating the airfoil chord on velocity distribution and impingement characteristics. A 6-foot-chord airfoil was cut successively at the 50- and 30-percent-chord stations to produce the truncated airfoil sections, which were equipped with trailing-edge flaps that were used to alter the flow field about the truncated sections. The study was conducted at geometric angles of attack of 00 and 40, an airspeed of about 156 knots, and volume-median droplet sizes of 11.5 and 18.6 microns. A dye-tracer technique was used in the impingement studies. With the trailing-edge flap on the truncated airfoil deflected so that the local velocity distribution in the impingement region was substantially the same as that for the full-chord airfoil, the local impingement rates and the limits of impingement for the truncated and full-chord airfoils were the same. In general, truncating the airfoils with flaps undeflected resulted in a subs'tantially altered velocity distribution and local impingement rates compared with those of the full-chord airfoil. The use of flapped truncated airfoils may permit impingement and icing studies to be conducted with full-scale leading-edge sections, ranging in size from tip to root sections.

vonGlahn, Uwe H.

1956-01-01

240

An improved panel method for the solution of three-dimensional leading-edge vortex flows. Volume 1: Theory document  

NASA Technical Reports Server (NTRS)

An improved panel method for the solution of three dimensional flow and wing and wing-body combinations with leading edge vortex separation is presented. The method employs a three dimensional inviscid flow model in which the configuration, the rolled-up vortex sheets, and the wake are represented by quadratic doublet distributions. The strength of the singularity distribution as well as shape and position of the vortex spirals are computed in an iterative fashion starting with an assumed initial sheet geometry. The method calculates forces and moments as well as detail surface pressure distributions. Improvements include the implementation of improved panel numerics for the purpose of elimination the highly nonlinear effects of ring vortices around double panel edges, and the development of a least squares procedure for damping vortex sheet geometry update instabilities. A complete description of the method is included. A variety of cases generated by the computer program implementing the method are presented which verify the mathematical assumptions of the method and which compare computed results with experimental data to verify the underlying physical assumptions made by the method.

Johnson, F. T.; Lu, P.; Tinoco, E. N.

1980-01-01

241

AMELIA CESTOL Test: Acoustic Characteristics of Circulation Control Wing with Leading-and Trailing-Edge Slot Blowing  

NASA Technical Reports Server (NTRS)

Aeroacoustic measurements of the 11 % scale full-span AMELIA CESTOL model with leading- and trailing-edge slot blowing circulation control (CCW) wing were obtained during a recent test in the Arnold Engineering Development Center 40- by 80-Ft. Wind Tunnel at NASA Ames Research Center, Sound levels and spectra were acquired with seven in-flow microphones and a 48-element phased microphone array for a variety of vehicle configurations, CCW slot flow rates, and forward speeds, Corrections to the measurements and processing are in progress, however the data from selected configurations presented in this report confirm good measurement quality and dynamic range over the test conditions, Array beamform maps at 40 kts tunnel speed show that the trailing edge flap source is dominant for most frequencies at flap angles of 0deg and 60deg, The overall sound level for the 60deg flap was similar to the 0deg flap for most slot blowing rates forward of 90deg incidence, but was louder by up to 6 dB for downstream angles, At 100 kts, the in-flow microphone levels were louder than the sensor self-noise for the higher blowing rates, while passive and active background noise suppression methods for the microphone array revealed source levels as much as 20 dB lower than observed with the in-flow microphones,

Horne, Clifton; Burnside, Nathan J.

2013-01-01

242

CFD Analysis of the Aerodynamics of a Business-Jet Airfoil with Leading-Edge Ice Accretion  

NASA Technical Reports Server (NTRS)

For rime ice - where the ice buildup has only rough and jagged surfaces but no protruding horns - this study shows two dimensional CFD analysis based on the one-equation Spalart-Almaras (S-A) turbulence model to predict accurately the lift, drag, and pressure coefficients up to near the stall angle. For glaze ice - where the ice buildup has two or more protruding horns near the airfoil's leading edge - CFD predictions were much less satisfactory because of the large separated region produced by the horns even at zero angle of attack. This CFD study, based on the WIND and the Fluent codes, assesses the following turbulence models by comparing predictions with available experimental data: S-A, standard k-epsilon, shear-stress transport, v(exp 2)-f, and differential Reynolds stress.

Chi, X.; Zhu, B.; Shih, T. I.-P.; Addy, H. E.; Choo, Y. K.

2004-01-01

243

Test-Analysis Correlation for Space Shuttle External Tank Foam Impacting RCC Wing Leading Edge Component Panels  

NASA Technical Reports Server (NTRS)

The Space Shuttle Columbia Accident Investigation Board recommended that NASA develop, validate, and maintain a modeling tool capable of predicting the damage threshold for debris impacts on the Space Shuttle Reinforced Carbon-Carbon (RCC) wing leading edge and nosecap assembly. The results presented in this paper are one part of a multi-level approach that supported the development of the predictive tool used to recertify the shuttle for flight following the Columbia Accident. The assessment of predictive capability was largely based on test analysis comparisons for simpler component structures. This paper provides comparisons of finite element simulations with test data for external tank foam debris impacts onto 6-in. square RCC flat panels. Both quantitative displacement and qualitative damage assessment correlations are provided. The comparisons show good agreement and provided the Space Shuttle Program with confidence in the predictive tool.

Lyle, Karen H.

2008-01-01

244

An Experimental Investigation of NACA Submerged Inlets at High Subsonic Speeds I: Inlets Forward of the Wing Leading Edge  

NASA Technical Reports Server (NTRS)

This report covers the first part of an experimental investigation of NACA submerged inlets at four locations on the fuselage of a fighter airplane model for Mach numbers from 0.30 to 0.875. Data are presented showing the characteristics of the model without inlets and with inlets 16.7 percent of the root chord forward of the wing-root leading edge and equipped with small boundary-layer deflectors. The data show that variations in the mass of air entering the inlet had a large effect on the ram-recovery ratio. Representative values of ram-recovery ratio were 0.50 with zero flow, 0.90 with 0.6 mass-flow coefficient, and 0.95 with 1.00 mass-flow coefficient. Variations in Mach number and angle of attack, in general, caused less than a 0.03 variation in the ram-recovery ratio.

Hall, Charles F; Barclay, F Dorn

1948-01-01

245

Icing tunnel tests of a glycol-exuding porous leading edge ice protection system on a general aviation airfoil  

NASA Technical Reports Server (NTRS)

A glycol-exuding porous leading edge ice protection system was tested. Results show that the system is very effective in preventing ice accretion (anti-ice mode) or removing ice from an airfoil. Minimum glycol flow rates required for anti-icing are a function of velocity, liquid water content in the air, ambient temperature, and droplet size. Large ice caps were removed in only a few minutes using anti-ice flow rates. It was found that the shed time is a function of the type of ice, size of the ice cap, angle of attack, and glycol flow rate. Wake survey measurements show that there is no significant drag penalty for the installation or operation of the system tested.

Kohlman, D. L.; Schweikhard, W. G.; Albright, A. E.; Evanich, P.

1981-01-01

246

Comparison of Theoretical and Experimental Unsteady Aerodynamics of Linear Oscillating Cascade With Supersonic Leading-Edge Locus  

NASA Technical Reports Server (NTRS)

An experimental influence coefficient technique was used to obtain unsteady aerodynamic influence coefficients and, consequently, unsteady pressures for a cascade of symmetric airfoils oscillating in pitch about mid-chord. Stagger angles of 0 deg and 10 deg were investigated for a cascade with a gap-to-chord ratio of 0.417 operating at an axial Mach number of 1.9, resulting in a supersonic leading-edge locus. Reduced frequencies ranged from 0.056 to 0.2. The influence coefficients obtained determine the unsteady pressures for any interblade phase angle. The unsteady pressures were compared with those predicted by several algorithms for interblade phase angles of 0 deg and 180 deg.

Ramsey, John K.; Erwin, Dan

2004-01-01

247

Rate and topography of peptidoglycan synthesis during cell division in Escherichia coli: Concept of a leading edge  

SciTech Connect

The rate at which the peptidoglycan of Escherichia coli is synthesized during the division cycle was studied with two methods. One method involved synchronization of E. coli MC4100 lysA cultures by centrifugal elutriation and subsequent pulse-labeling of the synchronously growing cultures with (meso-{sup 3}H)diaminopimelic acid (({sup 3}H)Dap). The second method was autoradiography of cells pulse-labeled with ({sup 3}H)Dap. It was found that the peptidoglycan is synthesized at a more or less exponentially increasing rate during the division cycle with a slight acceleration in this rate as the cells start to constrict. Apparently, polar cap formation requires synthesis of extra surface components, presumably to accommodate for a change in the surface-to-volume ratio. Furthermore, it was found that the pool size of Dap was constant during the division cycle. Close analysis of the topography of ({sup 3}H)Dap incorporation at the constriction site revealed that constriction proceeded by synthesis of peptidoglycan at the leading edge of the invaginating cell envelope. During constriction, no reallocation of incorporation occurred, i.e., the incorporation at the leading edge remained high throughout the process of constriction. Impairment of penicillin-binding protein 3 by mutation or by the specific {beta}-lactam antibiotic furazlocillin did not affect ({sup 3}H)Dap incorporation during initiation of constriction. However, the incorporation at the constriction site was inhibited in later stages of the constriction process. It is concluded that during division at least two peptidoglycan-synthesizing systems are operating sequentially.

Wientjes, F.B.; Nanninga, N. (Univ. of Amsterdam (Netherlands))

1989-06-01

248

Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect.  

PubMed

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. PMID:23851351

Van Truong, Tien; Byun, Doyoung; Kim, Min Jun; Yoon, Kwang Joon; Park, Hoon Cheol

2013-09-01

249

An experimental analysis of critical factors involved in the breakdown process of leading edge vortex flows. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

Experimental crosswire measurements of the flowfield above a 70 and 75 degree flat plate delta wing were performed at a Reynolds number of 250,000. Survey grids were taken normal to the platform at a series of chordwise locations for angles of attack of 20 and 30 degrees. Axial and azimuthal vorticity distributions were derived from the velocity fields. The dependence of circulation on distance from the vortex core as well as on chordwise location was examined. The effects of nondimensionalization in comparison with other experimental data was made. The circulation distribution scales with the local semispan and grows approximately linearly in the chordwise direction. For regions of the flow outside of the vortex subcore, the circulation at any chordwise station was observed to vary logarithmically with distance from the vortex axis. The circulation was also found to increase linearly with angle of incidence at a given chordwise station. A reduction in the local circulation about the vortex axis occurred at breakdown. The spanwise distribution of axial vorticity was severely altered through the breakdown region and the spanwise distribution of axial vorticity present appeared to reach a maximum immediately preceding breakdown. The local concentration of axial vorticity about the vortex axis was reduced while the magnitude of the azimuthal vorticity decreased throughout the breakdown zone. The axial vorticity components with a negative sense, found in the secondary vortex, remained unaffected by changes in wing sweep or angle of attack, in direct contrast to the positive components. The inclusion of the local wing geometry into a previously derived correlation parameter indicated that the circulation of growing leading edge vortex flows were similar at corresponding radii from the vortex axis. It was concluded that the flow over a delta wing, upstream of the breakdown regions and away from the apex and trailing edge regions, is conical. In addition, the dominating factors leading to the onset of breakdown are felt to be the local circulation of the vortex and the accompanying pressure field.

Visser, Kenneth D.

1991-01-01

250

Ca2+ influx is an essential component of the positive-feedback loop that maintains leading-edge structure and activity in macrophages  

PubMed Central

In migrating eukaryotic cells, phosphatidylinositol 3-kinase (PI3K), filamentous actin (F-actin), and monomeric Rho GTPases are key components of a complex positive-feedback system that maintains and amplifies a phosphatidylinositol-3,4,5-trisphosphate signal at the leading edge of the cell. This lipid signal is required for cell polarization and movement. In leukocytes and Dictyostelium, activation or inhibition of any one of these components leads to the activation or inhibition, respectively, of the others via undefined feedback interactions. The role of Ca2+ signals in migrating leukocytes is controversial, and there has been no indication that Ca2+ participates in positive feedback. Here, we demonstrate that an extracellular Ca2+ influx is required for positive feedback at the leading edge of spontaneously polarized macrophages. Inhibition of extracellular Ca2+ influx leads to loss of leading-edge PI3K activity, disassembly of F-actin, cessation of ruffling, and decay of chemoattractant signals. Conversely, increasing cytosolic Ca2+ enhances membrane ruffling, PI3K activity, and F-actin accumulation. Overall, these findings demonstrate that an extracellular Ca2+ influx is an essential component, together with PI3K and F-actin, of the positive-feedback cycle that maintains leading-edge structure and ruffling activity and that supports the chemoattractant response. Strikingly, the Ca2+-sensitive enzyme protein kinase C? (PKC?) is enriched at the leading edge, and its enrichment is sensitive to blockade of Ca2+ influx, to inhibition of PI3K activity, and to F-actin depolymerization. These findings support the working hypothesis that a local, leading-edge Ca2+ signal recruits PKC? as a central player in the positive-feedback loop. PMID:17911247

Evans, John H.; Falke, Joseph J.

2007-01-01

251

Lead content and isotopic composition in submound and recent soils of the Volga Upland  

NASA Astrophysics Data System (ADS)

Literature data on the historical reconstructions of the atmospheric lead deposition in Europe and the isotopic composition of the ores that are potential sources of the anthropogenic lead in the atmospheric deposition in the lower Volga steppes during different time periods have been compiled. The effect of the increasing anthropogenic lead deposition recorded since the Bronze Age on the level of soil contamination has been investigated. For the first time paleosol buried under a burial mound of the Bronze Age has been used as a reference point to assess of the current contamination level. The contents and isotopic compositions of the mobile and total lead have been determined in submound paleosols of different ages and their recent remote and roadside analogues. An increase in the content and fraction of the mobile lead and a shift of its isotopic composition toward less radiogenic values (typical for lead from the recent anthropogenic sources) has been revealed when going from a Bronze-Age paleosol to a recent soil. In the Bronze-Age soil, the isotopic composition of the mobile lead is inherited from the parent rock to a greater extent than in the modern soils, where the lead is enriched with the less radiogenic component. The effect of the anthropogenic component is traced in the analysis of the mobile lead, but it is barely visible for the total lead. An exception is provided by the recent roadside soils characterized by increased contents and the significantly less radiogenic isotopic composition of the mobile and total lead.

Pampura, T. V.; Probst, A.; Ladonin, D. V.; Demkin, V. A.

2013-11-01

252

Planform curvature effects on flutter characteristics of a wing with 56 deg leading-edge sweep and panel aspect ratio of 1.14  

NASA Technical Reports Server (NTRS)

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.

Keller, Donald F.; Sandford, Maynard C.; Pinkerton, Theresa L.

1991-01-01

253

Leading Edge Book Review  

E-print Network

in humans, to wing patterns in butterflies, to sex determination in turtles. Yet, despite the broad scope reading for regulators at the U.S. Environmental Protection Agency, chemical company CEOs, and any- one

Monteiro, Antónia

254

Thermal and mechanical properties of styrene-butadiene rubber\\/lead oxide composites as gamma-radiation shields  

Microsoft Academic Search

Styrene-butadiene rubber\\/lead oxide composites were prepared as ?-radiation shields. The composites were prepared with three different types of lead oxide, namely lead mono-oxide (PbO), lead dioxide (PbO2) and red lead oxide (Pb3O4). Concentrations of about 87–88 wt% for the three lead oxides were used. The assessment of the linear attenuation coefficient of the SBR\\/lead oxide composites for ?-rays from different

M. M. Abdel-Aziz; S. E. Gwaily

1997-01-01

255

Experimental Surface Pressure Data Obtained on 65 deg Delta Wing Across Reynolds Number and Mach Number Ranges. Vol. 4: Large-radius leading edge  

NASA Technical Reports Server (NTRS)

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.

Chu, Julio; Luckring, James M.

1996-01-01

256

Experimental Surface Pressure Data Obtained on 65 deg Delta Wing Across Reynolds Number and Mach Number Ranges. Vol. 3: Medium-radius leading edge  

NASA Technical Reports Server (NTRS)

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), 60 x 10(exp 6), and 120 x 10(exp 6). Normal-force and pitching-moment coefficient plots for these Reynolds number and Mach number ranges are also presented.

Chu, Julio; Luckring, James M.

1996-01-01

257

Experimental Surface Pressure Data Obtained on 65 deg Delta Wing Across Reynolds Number and Mach Number Ranges. Volume 2; Small-Radius Leading Edge  

NASA Technical Reports Server (NTRS)

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 84 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.

Chu, Julio; Luckring, James M.

1996-01-01

258

Subsonic Investigation of Leading-Edge Flaps Designed for Vortex- and Attached-Flow on a High-Speed Civil Transport Configuration  

NASA Technical Reports Server (NTRS)

A wind tunnel investigation of two separate leading-edge flaps, designed for vortex and attached-flow, respectively, were conducted on a High Speed Civil Transport (HSCT) configuration in the Langley 14- by 22-Foot Subsonic Tunnel. Data were obtained over a Mach number range of 0.12 to 0.27, with corresponding chord Reynolds numbers of 2.50 x 10 (sup 6) to 5.50 x 10 (sup 6). Variations of the leading-edge flap deflection angle were tested with outboard leading-edge flaps deflected 0 deg. and 26.4 deg. Trailing-edge flaps were deflected 0 deg., 10 deg., 12.9 deg., and 20 deg. The longitudinal and lateral aerodynamic data are presented without analysis. A complete tabulated data listing is also presented herein. The data associated with each deflected leading-edge flap indicate L/D improvements over the undeflected configuration. These improvements may be instrumental in providing the necessary lift augmentation required by an actual HSCT during the climb-out and landing phases of the flight envelope. However, further tests will have to be done to assess their full potential.

Campbell, Bryan A.; Kemmerly, Guy T.; Kjerstad, Kevin J.; Lessard, Victor R.

1999-01-01

259

Effects of wing leading-edge deflection on the low-speed aerodynamic characteristics of a low-aspect-ratio highly swept arrow-wing configuration  

NASA Technical Reports Server (NTRS)

Wing leading-edge deflection effects on the low-speed aerodynamic characteristics of a low-aspect-ratio highly swept arrow-wing configuration were determined. Static force tests were conducted in a V/STOL tunnel at a Reynolds number of about 2.5 x 1 million for an angle-of-attack range from -10 deg to 17 deg and an angle-of-sideslip range from -5 deg to 5 deg. Limited flow visualization studies were also conducted in order to provide a qualitative assessment of leading-edge upwash characteristics.

Coe, P. L., Jr.; Weston, R. P.

1978-01-01

260

Aeroelastic loads prediction for an arrow wing. Task 3: Evaluation of the Boeing three-dimensional leading-edge vortex code  

NASA Technical Reports Server (NTRS)

Two separated flow computer programs and a semiempirical method for incorporating the experimentally measured separated flow effects into a linear aeroelastic analysis were evaluated. The three dimensional leading edge vortex (LEV) code is evaluated. This code is an improved panel method for three dimensional inviscid flow over a wing with leading edge vortex separation. The governing equations are the linear flow differential equation with nonlinear boundary conditions. The solution is iterative; the position as well as the strength of the vortex is determined. Cases for both full and partial span vortices were executed. The predicted pressures are good and adequately reflect changes in configuration.

Manro, M. E.

1983-01-01

261

Experimental Observations on the Deformation and Breakup of Water Droplets Near the Leading Edge of an Airfoil  

NASA Technical Reports Server (NTRS)

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

Vargas, Mario; Feo, Alex

2011-01-01

262

A leading-edge hardware family for diagnostics applications and low-level RF in CERN's ELENA ring  

E-print Network

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...

Angoletta, M E; Jaussi, M; Leiononen, P; Levens, T E; Molendijk, J C; Sanchez-Quesada, J; Simonin, J

2013-01-01

263

Feature detection and Proper Orthogonal Decomposition of time resolved velocity data for flow separation over an elliptical leading edge.  

NASA Astrophysics Data System (ADS)

In this study the flow characteristics over a fixed surface, flat, low aspect ratio thin wing are investigated. Of interest is the dynamic separation process for a range of angle of attacks, and chord Reynolds numbers, particularly the time dependent nature of the vortex development, convection and interactions. Angle of attack is varied from 14 to 20 . The Reynolds number based on chord length ranges from 14,700 to 66,700; this corresponds to a velocity range between 1.75 and 5.0 m/s. Time Resolved Particle Image Velocimetry (TRPIV) is used to obtained time resolved velocity information near the leading edge. Using discrete vortex detection schemes coupled with a high pass filtering and Proper Orthogonal Decompostion (POD) analysis, the time dependent characteristics of this flow is elucidated. Methods of vortex detection include the ?2 method proposed by Jeong and Hussain [1995] and Large Eddy Simulation (LES) filtering. The POD reveals a low number of high energy, dominant modes of velocity variation for most cases.

Morse, Daniel; Liburdy, James

2007-11-01

264

Gene expression profiling of the leading edge of cutaneous squamous cell carcinoma (SCC): IL-24 driven MMP-7  

PubMed Central

The precise mechanisms governing invasion at the leading edge of SCC and its subsequent metastasis are not fully understood. We aimed to define the cancer related molecular changes that distinguish non-invasive tumor from invasive SCC. To this end, we combined laser capture microdissection with cDNA microarray analysis. We defined invasion-associated genes as those differentially regulated only in invasive SCC nests, but not in actinic keratosis or in situ SCC, compared to normal epidermis. There were 383 up- and 354 down-regulated genes in the “invasion set.” SCC invasion was characterized by aberrant expression of various proteolytic molecules. We noted increased expression of MMP7 and IL-24 in invasive SCC. IL-24 induced the expression of MMP7 in SCC cells in culture. In addition, blocking of MMP7 by a specific antibody significantly delayed the migration of SCC cells in culture. These results suggest a possible contribution of IL-24 to SCC invasion via enhancing focal expression of MMP7, though IL-24 has been suggested to have anti-tumor growth effects in other cancer types. Identification of regional molecular changes that regulate cancer invasion may facilitate the development of new targeted treatments for aggressive cancer. PMID:24270662

Mitsui, Hiroshi; Suárez-Fariñas, Mayte; Gulati, Nicholas; Shah, Kejal R.; Cannizzaro, Maria Vittoria; Coats, Israel; Felsen, Diane; Krueger, James G.; Carucci, John A.

2014-01-01

265

Three-dimensional flow structures and evolution of the leading-edge vortices on a flapping wing.  

PubMed

Following the identification and confirmation of the substructures of the leading-edge vortex (LEV) system on flapping wings, it is apparent that the actual LEV structures could be more complex than had been estimated in previous investigations. In this experimental study, we reveal for the first time the detailed three-dimensional (3-D) flow structures and evolution of the LEVs on a flapping wing in the hovering condition at high Reynolds number (Re=1624). This was accomplished by utilizing an electromechanical model dragonfly wing flapping in a water tank (mid-stroke angle of attack=60 degrees) and applying phase-lock based multi-slice digital stereoscopic particle image velocimetry (DSPIV) to measure the target flow fields at three typical stroke phases: at 0.125 T (T=stroke period), when the wing was accelerating; at 0.25 T, when the wing had maximum speed; and at 0.375 T, when the wing was decelerating. The result shows that the LEV system is a collection of four vortical elements: one primary vortex and three minor vortices, instead of a single conical or tube-like vortex as reported or hypothesized in previous studies. These vortical elements are highly time-dependent in structure and show distinct ;stay properties' at different spanwise sections. The spanwise flows are also time-dependent, not only in the velocity magnitude but also in direction. PMID:18375846

Lu, Yuan; Shen, Gong Xin

2008-04-01

266

The Vercors and Chartreuse Massifs at the leading edge of the alpine thrust belt: Tetonic history and petroleum assessment  

SciTech Connect

The Vercors and Chartreuse Massifs are located at the leading edge of the Western Alps Thrust Belt. They developed in late Miocene-Pliocene times above a major decollement hosted in late Triassic evaporites and/or Liassic marls. The uplift of both massifs led to the oblique and partial inversion of the previous Mesozoic margin of the Southeastern Basin, the thickest onshore sedimentary basin in France. Both massifs are unexplored. The regional geology of eastern France and the results of ten wells located in the near foreland suggest that source rocks are present in late Paleozoic and late Liassic strata, and that fractured sandstones and/or limestones of Triassic/Jurassic age could act as reservoirs. A nonexclusive seismic survey has been shot in 1991 by CGG allowing the first well constrained balanced sections to be drawn across both massifs. They have been used inturn to model the forward kinematics of thrust propagation, and the source rock maturation history, using the {open_quotes}Thrustpack{close_quotes} software developed by IFP and partners.

Deville, E.; Mascle, A.; Philippe, Y. [Institut Francais du Petrole, Rueil-Malmaison (France)] [and others

1995-08-01

267

Central Composite experimental design applied to removal of lead and nickel from sand  

Microsoft Academic Search

The aim of this study was to apply Central Composite experimental design in the removal of lead and nickel ions from sand by electrokinetic remediation. Sand was used for an initial study since it is inert, thus making it possible to analyze the parameters influencing the process. Central Composite Design was used to create an experimental program to provide data

V. V. Guaracho; N. M. S. Kaminari; M. J. J. S. Ponte; H. A. Ponte

2009-01-01

268

Low-Speed Wind-Tunnel Investigation of Blowing Boundary-Layer Control on Leading- and Trailing-Edge Flaps of a Large-Scale, Low-Aspect-Ratio, 45 Swept-wing Airplane Configuration  

NASA Technical Reports Server (NTRS)

Blowing boundary-layer control was applied to the leading- and trailing-edge flaps of a 45 deg sweptback-wing complete model in a full-scale low-speed wind-tunnel study. The principal purpose of the study was to determine the effects of leading-edge flap deflection and boundary-layer control on maximum lift and longitudinal stability. Leading-edge flap deflection alone was sufficient to maintain static longitudinal stability without trailing-edge flaps. However, leading-edge flap blowing was required to maintain longitudinal stability by delaying leading-edge flow separation when trailing-edge flaps were deflected either with or without blowing. Partial-span leading-edge flaps deflected 60 deg with moderate blowing gave the major increase in maximum lift, although higher deflection and additional blowing gave some further increase. Inboard of 0.4 semispan leading-edge flap deflection could be reduced to 40 deg and/or blowing could be omitted with only small loss in maximum lift. Trailing-edge flap lift increments were increased by boundary-layer control for deflections greater than 45 deg. Maximum lift was not increased with deflected trailing-edge flaps with blowing.

Maki, Ralph L.

1959-01-01

269

Cutting edge rounding: An innovative tool wear criterion in drilling CFRP composite laminates  

Microsoft Academic Search

An evenly and smoothly distributed abrasion wear, observed along the entire cutting edge of an uncoated carbide drill bit in drilling CFRPs, is due to the highly abrasive nature of the carbon fibres. A very few researchers have only quoted this wear mode as being responsible for giving rise to the rounding of the cutting edge, or its bluntness. However,

Ali Faraz; Dirk Biermann; Klaus Weinert

2009-01-01

270

New leading/trailing edge modulation strategies for two-stage AC/DC PFC adapters to reduce DC-link capacitor ripple current  

E-print Network

-link capacitor is one of the largest because it should keep the output voltage with low ripple. Also, the size of this capacitor is penalized due to the universal line voltage application. Synchronization through employing leading edge modulation for the first...

Sun, Jing

2007-09-17

271

A method of predicting flow rates required to achieve anti-icing performance with a porous leading edge ice protection system  

NASA Technical Reports Server (NTRS)

A proposed method of analytically predicting the minimum fluid flow rate required to provide anti-ice protection with a porous leading edge system on a wing under a given set of flight conditions is presented. Results of the proposed method are compared with the actual results of an icing test of a real wing section in the NASA Lewis Icing Research Tunnel.

Kohlman, D. L.

1983-01-01

272

A method of predicting flow rates required to achieve anti-icing performance with a porous leading edge ice protection system  

NASA Technical Reports Server (NTRS)

An analytical method was developed for predicting minimum flow rates required to provide anti-ice protection with a porous leading edge fluid ice protection system. The predicted flow rates compare with an average error of less than 10 percent to six experimentally determined flow rates from tests in the NASA Icing Research Tunnel on a general aviation wing section.

Kohlman, D. L.; Albright, A. E.

1983-01-01

273

An improved panel method for the solution of three-dimensional leading edge vortex flows Volume 2: User's guide and programmer's document  

NASA Technical Reports Server (NTRS)

A computer program developed for solving the subsonic, three dimensional flow over wing-body configurations with leading edge vortex separation is presented. Instructions are given for the proper set up and input of a problem into the computer code. Program input formats and output are described, as well as the overlay structure of the program. The program is written in FORTRAN.

Tinoco, E. N.; Lu, P.; Johnson, F. T.

1980-01-01

274

Experimental study of pressure and heating rate on a swept cylindrical leading edge resulting from swept shock wave interference. M.S. Thesis  

NASA Technical Reports Server (NTRS)

The effects of cylindrical leading edge sweep on surface pressure and heat transfer rate for swept shock wave interference were investigated. Experimental tests were conducted in the Calspan 48-inch Hypersonic Shock Tunnel at a nominal Mach number of 8, nominal unit Reynolds number of 1.5 x 10 to the 6th power per foot, leading edge and incident shock generator sweep angles of 0, 15, and 30 deg, and incident shock generator angle-of-attack fixed at 12.5 deg. Detailed surface pressure and heat transfer rate on the cylindircal leading edge of a swept shock wave interference model were measured at the region of the maximum surface pressure and heat transfer rate. Results show that pressure and heat transfer rate on the cylindrical leading edge of the shock wave interference model were reduced as the sweep was increased over the range of tested parameters. 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 and 30 deg swept results with the 0 deg swept results showed 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.

Glass, Christopher E.

1989-01-01

275

Preliminary Investigation in the NACA Low-Turbulence Tunnel of Low-drag Airfoil Sections Suitable for Admitting Air at the Leading Edge  

NASA Technical Reports Server (NTRS)

An investigation was carried out in the NACA low-turbulence tunnel to develop low-drag airfoil sections suitable for admitting air at the leading edge. A thickness distribution having the desired type of pressure distribution was found from tests of a flexible model. Other airfoil shapes were derived from this original shape by varying the thickness, the camper, the leading-edge radius, and the size of the leading-edge opening. Data are presented giving the characteristics of the airfoil shapes in the range of lift coefficients for high-speed and cruising flight. Shapes have been developed which show no substantial increases in drag over that of the same position along the chord. Many of these shapes appear to have higher critical compressibility speeds than plain airfoils of the same thickness. Low-drag airfoil sections have been developed with openings in the leading edge as large as 41.5 percent of the maximum thickness. The range of lift coefficients for low drag in several cases is nearly as large as that of the corresponding plain airfoil sections. Preliminary measurements of maximum lift characteristics indicate that nose-opening sections of the type herein considered may not produce any marked effects on the maximum lift coefficient.

von Doenhoff, Albert E.; Horton, Elmer A.

1942-01-01

276

Compatibility of SiC and SiC Composites with Molten Lead  

SciTech Connect

The choice of structural material candidates to contain Lead at 1000 C are limited in number. Silicon carbide composites comprise one choice of possible containment materials. Short term screening studies (120 hours) were undertaken to study the behavior of Silicon Carbide, Silicon Nitride, elemental Silicon and various Silicon Carbide fiber composites focusing mainly on melt infiltrated composites. Isothermal experiments at 1000 C utilized graphite fixtures to contain the Lead and material specimens under a low oxygen partial pressure environment. The corrosion weight loss values (grams/cm{sup 2} Hr) obtained for each of the pure materials showed SiC (monolithic CVD or Hexoloy) to have the best materials compatibility with Lead at this temperature. Increased weight loss values were observed for pure Silicon Nitride and elemental Silicon. For the SiC fiber composite samples those prepared using a SiC matrix material performed better than Si{sub 3}N{sub 4} as a matrix material. Composites prepared using a silicon melt infiltration process showed larger corrosion weight loss values due to the solubility of silicon in lead at these temperatures. When excess silicon was removed from these composite samples the corrosion performance for these material improved. These screening studies were used to guide future long term exposure (both isothermal and non-isothermal) experiments and Silicon Carbide composite fabrication work.

H Tunison

2006-03-07

277

Prediction of STS-107 Hypervelocity Flow Fields about the Shuttle Orbiter with Various Wing Leading Edge Damage  

NASA Technical Reports Server (NTRS)

Computations were performed for damaged configurations of the Shuttle Orbiter in support of the STS-107 Columbia accident investigation. Two configurations with missing wing leading-edge reinforced carbon-carbon (RCC) panels were evaluated at conditions just prior to the peak heating trajectory point. The initial configuration modeled the Orbiter with an approximate missing RCC panel 6 to determine whether this damage could result in anomalous temperatures measured during the STS-107 reentry. This missing RCC panel 6 computation was found to produce heating augmentation factors of 5 times the nominal heating rates on the side fuselage with lesser heat increases on the front of the OMS pod. This is consistent with the thermocouple and resistance temperature detector sensors from the STS-107 re-entry which observed off nominal high early in the re-entry trajectory. A second damaged configuration modeled the Orbiter with missing RCC panel 9 and included ingestion of the flow into the outboard RCC channel. This computation lowered the level (only 2 times nominal) and moved the location of the heating augmentation on the leeside fuselage relative to the missing RCC panel 6 configuration. The lesser heating augmentation for missing RCC panel 9 was confined near the wing fuselage juncture. Near nominal heating was predicted on the remainder of the side fuselage with some lower than nominal heating on the front surface of the OMS pod. These results for missing RCC panel 9 are consistent with data from the STS-107 re-entry where the heating augmentation was observed to move off the side fuselage and OMS pod sensors at later times in the trajectory. As this solution requires supersonic mass ingestion into the RCC channel, it is probably not an appropriate model prior to penetration of the flow through the spar into the wing structure. It may, however, be representative of the conditions at later times and could account for the movement of the heating signature on the side fuselage.

Pulsonetti, Maria V.; Thompson, Richard A.; Alter, Stephen J.

2004-01-01

278

Strain partitioning in the Helvetic thrust belt of eastern Switzerland from the leading edge to the internal zone  

NASA Astrophysics Data System (ADS)

The strain and strain partitioning in the Helvetic thrust belt are analysed in order to determine their variation across the belt from the external, thin-skinned portion to the internal, thick-skinned portion, and in order to begin the detailed mechanical analysis of the entire fold-and-thrust belt. Coarse-grained limestones of Jurassic and Cretaceous age were chosen for analysis because they can be traced from the external to the internal zones. The strain within a bed is partitioned into three components: transgranular (pressure solution, microfaults, veins), twinning, granular and intragranular, exclusive of twinning (crystal-plasticity, associated with recrystallization). Transgranular strain was very important in the early history of the Helvetic nappes giving way to twinning at a later stage under tectonic burial. Twinning strain was early in the Infrahelvetic complex, giving way to intracrystalline deformation at the later stage of burial. The transition from transgranular- to intragranular-dominated strain occurred at a vitrinite reflectance value of 3.5%, significantly below the greenschist grade of metamorphism. In a large-scale fold at the leading edge of the Helvetic nappes, transgranular strains were associated with the buckling stage of the fold and twinning occurred during fold-tightening. In more internal parts of the Helvetic nappes twinning strains are also late with regard to transgranular strains, but here their pattern corresponds to the regional finite strain pattern. In the internal zone, the Infrahelvetic complex, twinning seems to have been an early event and records an initial layer-parallel shortening, followed by regional internal deformation with intragranular strains.

Groshong, Richard H.; Pfiffner, O. Adrian; Pringle, Laurel R.

279

Lead  

MedlinePLUS

LEAD CAS # 7439-92-1 Division of Toxicology and Environmental Medicine ToxFAQs TM August 2007 This fact sheet answers the most frequently asked health questions (FAQs) about lead. For more information, ...

280

Aerodynamic Characteristics of a Large-Scale Unswept Wing-Body-Tail Configuration with Blowing Applied Over the Flap and Wind Leading Edge  

NASA Technical Reports Server (NTRS)

An investigation has been conducted in the Langley full-scale tunnel to determine the effects of a blowing boundary-layer-control lift-augmentation system on the aerodynamic characteristics of a large-scale model of a fighter-type airplane. The wing was unswept at the 70-percent- chord station, had an aspect ratio of 2.86, a taper ratio of 0.40, and 4-percent-thick biconvex airfoil sections parallel to the plane of symmetry. The tests were conducted over a range of angles of attack from approximately -4 deg to 23 deg for a Reynolds number of approximately 5.2 x 10(exp 6) which corresponds to a Mach number of 0.08. Blowing rates were normally restricted to values just sufficient to control air-flow separation. The results of this investigation showed that wing leading-edge blowing in combination with large values of wing leading-edge-flap deflection was a very effective leading-edge flow-control device for wings having highly loaded trailing-edge flaps. With leading-edge blowing there was no hysteresis of the lift, drag, and pitching-moment characteristics upon recovery from stall. End plates were found to improve the lift and drag characteristics of the test configuration in the moderate angle-of-attack range, and blockage to one-quarter of the blowing-slot area was not detrimental to the aerodynamic characteristics. Blowing boundary-layer control resulted in a considerably reduced landing speed and reduced landing and take-off distances. The ailerons were very effective lateral-control devices when used with blowing flaps.

McLemore, H. Clyde; Peterson, John B., Jr.

1960-01-01

281

Influence of blade leading edge geometry and upstream blowing on the heat/mass transfer in a turbine cascade  

NASA Astrophysics Data System (ADS)

The effect of secondary flows on mass transfer from a simulated gas turbine blade and hubwall is investigated. Measurements performed using naphthalene sublimation provide non-dimensional mass transfer coefficients, in the form of Sherwood numbers, that can be converted to heat transfer coefficients through the use of an analogy. Tests are conducted in a linear cascade composed of five blades having the profile of a first stage rotor blade of a high-pressure turbine aircraft engine. Detailed mass transfer maps on the airfoil and endwall surfaces allow the identification of significant flow features that are in good agreement with existing secondary flow models. These results are well-suited for validation of numerical codes, as they are obtained with an accurate technique that does not suffer from conduction or radiation errors and allows the imposition of precise boundary conditions. The performance of a RANS (Reynolds Averaged Navier-Stokes) numerical code that simulates the flow and heat/mass transfer in the cascade using the SST (Shear Stress Transport) k-o model is evaluated through a comparison with the experimental results. Tests performed with a modified blade leading edge show that the introduction of a fillet at the junction with the endwall reduces the effects of the horseshoe vortex in the first part of the passage, while no measurable changes in mass transfer are observed further downstream. Air injected through a slot located upstream of the cascade simulates the engine wheelspace coolant injection between the stator and the rotor. Local mass transfer data obtained injecting naphthalene-free and naphthalene-saturated air are reduced to derive maps of cooling effectiveness on the blade and endwall. Oil dot tests show the surface flow on the endwall. The surface downstream of the gap is coplanar to the upstream surface in the baseline configuration and is shifted to form a forward and backward facing step to investigate the effects of component misalignments. Sufficiently high injection rates alter the structure of the secondary flows and significantly improve the cooling performance.

Papa, Marco

282

Suppression of Chemotaxis by SSeCKS via Scaffolding of Phosphoinositol Phosphates and the Recruitment of the Cdc42 GEF, Frabin, to the Leading Edge  

PubMed Central

Chemotaxis is controlled by interactions between receptors, Rho-family GTPases, phosphatidylinositol 3-kinases, and cytoskeleton remodeling proteins. We investigated how the metastasis suppressor, SSeCKS, attenuates chemotaxis. Chemotaxis activity inversely correlated with SSeCKS levels in mouse embryo fibroblasts (MEF), DU145 and MDA-MB-231 cancer cells. SSeCKS loss induced chemotactic velocity and linear directionality, correlating with replacement of leading edge lamellipodia with fascin-enriched filopodia-like extensions, the formation of thickened longitudinal F-actin stress fibers reaching to filopodial tips, relative enrichments at the leading edge of phosphatidylinositol (3,4,5)P3 (PIP3), Akt, PKC-?, Cdc42-GTP and active Src (SrcpoY416), and a loss of Rac1. Leading edge lamellipodia and chemotaxis inhibition in SSeCKS-null MEF could be restored by full-length SSeCKS or SSeCKS deleted of its Src-binding domain (?Src), but not by SSeCKS deleted of its three MARCKS (myristylated alanine-rich C kinase substrate) polybasic domains (?PBD), which bind PIP2 and PIP3. The enrichment of activated Cdc42 in SSeCKS-null leading edge filopodia correlated with recruitment of the Cdc42-specific guanine nucleotide exchange factor, Frabin, likely recruited via multiple PIP2/3-binding domains. Frabin knockdown in SSeCKS-null MEF restores leading edge lamellipodia and chemotaxis inhibition. However, SSeCKS failed to co-immunoprecipitate with Rac1, Cdc42 or Frabin. Consistent with the notion that chemotaxis is controlled by SSeCKS-PIP (vs. -Src) scaffolding activity, constitutively-active phosphatidylinositol 3-kinase could override the ability of the Src inhibitor, SKI-606, to suppress chemotaxis and filopodial enrichment of Frabin in SSeCKS-null MEF. Our data suggest a role for SSeCKS in controlling Rac1 vs. Cdc42-induced cellular dynamics at the leading chemotactic edge through the scaffolding of phospholipids and signal mediators, and through the reorganization of the actin cytoskeleton controlling directional movement. PMID:25356636

Ko, Hyun-Kyung; Guo, Li-wu; Su, Bing; Gao, Lingqiu; Gelman, Irwin H.

2014-01-01

283

Natural fibre high-density polyethylene and lead oxide composites for radiation shielding  

Microsoft Academic Search

Study has been made of the radiation shielding provided by recycled agricultural fibre and industrial plastic wastes produced as composite materials. Fast neutron and gamma-ray spectra behind composites of fibre–plastic (?=1.373gcm?3) and fibre–plastic–lead (?=2.756gcm?3) have been measured using a collimated reactor beam and neutron–gamma spectrometer with a stilbene scintillator. The pulse shape discriminating technique based on the zero-cross-over method was

A El-Sayed Abdo; M. A. M Ali; M. R Ismail

2003-01-01

284

Dielectric Properties of Lead Monoxide Filled Unsaturated Polyester Based Polymer Composites  

NASA Astrophysics Data System (ADS)

Lead monoxide filled isophthalate resin particulate polymer composites were prepared with different filler concentrations and investigated for physical, thermal, mechanical and gamma radiation shielding characteristics. This paper discusses about the dielectric properties of the composites. The present study showed that the dielectric constant (?'), dielectric loss (??) and ac conductivity (?ac) of isopthalate based unsaturated polyester resin increases with the increase in wt% PbO filler in polymer matrix.

Harish, V.; Kumar, H. G. Harish; Nagaiah, N.

2011-07-01

285

Dielectric and pyroelectric properties of lead zirconate titanate/polyurethane composites  

SciTech Connect

0-3 composite ranging between 0 and 3, of ferroelectric ceramic lead zirconate titanate (PZT) and thermoplastic elastomer polyurethane (PU) were fabricated. The pyroelectric and dielectric properties of the hot-pressed thin film samples of various PZT volume fractions were measured. The experimental dielectric permittivities and losses agreed reasonably well with the Bruggeman model. The room temperature pyroelectric coefficients of the composites were found to increase linearly with PZT volume fraction and substantially larger than expected. For example, for a composite with 30% PZT, its pyroelectric coefficient is about 90 {mu}C/m{sup 2}K at room temperature, which is more than tenfold of a PZT/PVDF composite of the same ceramic volume fraction. We propose a model in which the electrical conductivity of the composite system is taken into consideration to explain the linear relationship and the extraordinarily large pyroelectric coefficients obtained.

Lam, K.S.; Wong, Y.W.; Tai, L.S.; Poon, Y.M.; Shin, F.G. [Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong (China)

2004-10-01

286

Isotopic composition of lead and strontium from Ascension and Gough Islands  

USGS Publications Warehouse

Isotopic composition of lead and strontium has been determined in a series of rock samples from two islands on the Mid-Atlantic Ridge. Both inter-and intra-island variations exist in the abundance of radiogenic isotopes of both elements. Lead from basalt of Ascension Island has a Pb206-Pb 204 ratio of 19.5, while the corresponding ratio at Gough Island is only 18.4. The Pb208-Pb204 ratios from the two islands do not differ. Conversely, strontium from basalt of Ascension Island is less radiogenic than that from Gough Island basalts. The trachytes of both islands have lead and strontium that is more radiogenic than that found in the basalts. The inter-island differences indicate the existence of regional variations in the uranium-lead and rubidium-strontium ratios of the upper mantle source of these rocks and show that isotope compositions are a means for investigating chemical heterogeneities in the mantle.

Gast, P.W.; Tilton, G.R.; Hedge, C.

1964-01-01

287

Hypersonic boundary layer in the vicinity of a point of inflection of leading edge on a flat wing in the regime of strong viscous interaction  

NASA Astrophysics Data System (ADS)

The flow in a spatial hypersonic laminar boundary layer on a planar wing with a point of inflection in the leading edge is considered in the regime of strong viscous-inviscid interaction. The boundary problems are formulated for two cases: self-similar flow near the point of inflection of the leading edge and full three-dimensional (3D) boundary layer on a wing with variable sweep angle. The numerical solution is obtained using the finite-difference method. The results of parametric calculations of influence of a wing shape and the temperature factor on flow characteristics in the boundary layer are presented. The possibility of formation of local regions with high shear stress and heat flux is shown.

Dudin, G. N.; Ledovskiy, A. V.

2013-06-01

288

Applicability of linearized-theory attached-flow methods to design and analysis of flap systems at low speeds for thin swept wings with sharp leading edges  

NASA Technical Reports Server (NTRS)

Low-speed experimental force and data on a series of thin swept wings with sharp leading edges and leading and trailing-edge flaps are compared with predictions made using a linearized-theory method which includes estimates of vortex forces. These comparisons were made to assess the effectiveness of linearized-theory methods for use in the design and analysis of flap systems in subsonic flow. Results demonstrate that linearized-theory, attached-flow methods (with approximate representation of vortex forces) can form the basis of a rational system for flap design and analysis. Even attached-flow methods that do not take vortex forces into account can be used for the selection of optimized flap-system geometry, but design-point performance levels tend to be underestimated unless vortex forces are included. Illustrative examples of the use of these methods in the design of efficient low-speed flap systems are included.

Carlson, Harry W.; Darden, Christine M.

1987-01-01

289

Heat transfer in leading and trailing edge cooling channels of the gas turbine blade under high rotation numbers  

E-print Network

edge of the gas turbine blade. Three different rib configurations (45°, inverted 45°, and 90°) were tested at four different Reynolds numbers (10000-40000), each with five different rotational speeds (0-400 rpm). By varying the Reynolds numbers (10000...

Liu, Yao-Hsien

2009-05-15

290

Results of an experimental and numerical study of the aerodynamic heating of the undersurface of delta wings with sharp leading edges at mach numbers M ? =6.1 and 8  

Microsoft Academic Search

The heat transfer between a supersonic flow and the undersurface of delta wings with leading-edge sweep angles x=65 and 70° is investigated in a shock tunnel at angles of attacka = 15°. The supersonic inviscid flow over these wings in regimes in which the bow shock is attached to the sharp leading edges is calculated numerically. The compressible boundary layer

N. A. Kovaleva; N. P. Kolina; A. P. Kosykh; A. Ya. Yushin

1991-01-01

291

Heat-requirements for Ice Protection of a Cyclically Gas-heated, 36 Degree Swept Airfoil with Partial-span Leading-edge Slat  

NASA Technical Reports Server (NTRS)

Heating requirements for satisfactory cyclic de-icing over a wide range of icing and operating conditions have been determined for a gas-heated, 36deg swept airfoil of 6.9-foot chord with a partial-span leading-edge slat. Comparisons of heating requirements and effectiveness were made between the slatted and unslatted portions of the airfoil. Studies were also made comparing cyclic de-icing with continuous anti-icing, and cycll.cde-icing systems with and without leading-edge ice-free parting strips. De-icing heat requirements were approximately the same with either heated or unheated parting strips because of the aerodynamic effects of the 36deg sweep angle and the spanwise saw-tooth profile of leading-edge glaze-ice deposits. Cyclic de-icing heat-source requirements were found to be one-fourth or less of the heat requirements for complete anti-icing. The primary factors that affected the performance of the cyclic de-icing heating system were ambient air temperature, heat distribution, and thermal lag.

Gray, Vernon H; vonGlahn, Uwe H

1956-01-01

292

Influence of optimized leading-edge deflection and geometric anhedral on the low-speed aerodynamic characteristics of a low-aspect-ratio highly swept arrow-wing configuration. [langley 7 by 10 foot tunnel  

NASA Technical Reports Server (NTRS)

An investigation conducted in the Langley 7 by 10 foot tunnel to determine the influence of an optimized leading-edge deflection on the low speed aerodynamic performance of a configuration with a low aspect ratio, highly swept wing. The sensitivity of the lateral stability derivative to geometric anhedral was also studied. The optimized leading edge deflection was developed by aligning the leading edge with the incoming flow along the entire span. Owing to spanwise variation of unwash, the resulting optimized leading edge was a smooth, continuously warped surface for which the deflection varied from 16 deg at the side of body to 50 deg at the wing tip. For the particular configuration studied, levels of leading-edge suction on the order of 90 percent were achieved. The results of tests conducted to determine the sensitivity of the lateral stability derivative to geometric anhedral indicate values which are in reasonable agreement with estimates provided by simple vortex-lattice theories.

Coe, P. L., Jr.; Huffman, J. K.

1979-01-01

293

Lead effects on body composition and organ size of wintering canvasbacks Aythya valisineria in Louisiana  

USGS Publications Warehouse

We tested whether lead exposure, as evidenced by liver lead concentration, affected body composition and organ sizes of canvasback ducks Aythya valisineria in Louisiana during winter 1987-88. After adjusting for body size, sex, age, and site and month of collection, we found decreases in ingesta-free body mass; breast, leg, and body protein; body fat; intestine length; and liver and gizzard masses associated with increased liver lead concentrations. There were no apparent associations between liver lead concentrations and testes and body ash masses, or caecal length. We used the concentration of 26.7 ppm of liver lead on a dry matter (dm) basis as indicative of lead toxicosis. We predicted that a canvasback with 26.7 ppm dm liver lead would weigh 209 g less and have 105 g less fat than an unexposed individual. Whereas many lead exposed canvasbacks may survive through winter, their subsequent survival, ability to reproduce and perform other annual cycle events may be compromised. We recommend management to make lead unavailable to waterfowl at major concentration areas and periodic monitoring of lead contamination in waterfowl populations.

Pace, R.M.; Hohman, W.L.; Custer, T.W.

1999-01-01

294

Robustness leads close to the edge of chaos in coupled map networks: toward the understanding of biological networks  

NASA Astrophysics Data System (ADS)

Dynamics in biological networks are, in general, robust against several perturbations. We investigate a coupled map network as a model motivated by gene regulatory networks and design systems that are robust against phenotypic perturbations (perturbations in dynamics), as well as systems that are robust against mutation (perturbations in network structure). To achieve such a design, we apply a multicanonical Monte Carlo method. Analysis based on the maximum Lyapunov exponent and parameter sensitivity shows that systems with marginal stability, which are regarded as systems at the edge of chaos, emerge when robustness against network perturbations is required. This emergence of the edge of chaos is a self-organization phenomenon and does not need a fine tuning of parameters.

Saito, Nen; Kikuchi, Macoto

2013-05-01

295

The isotopic composition of silver and lead in two iron meteorites - Cape York and Grant  

NASA Astrophysics Data System (ADS)

Anomalies in silver isotope composition in the metal phases of the Cape York (IIIA) and Grant (IIIB) iron meteorites are studied together with the lead isotopic composition of both the metal and sulfide phases of Cape York. Following extensive surface cleaning, the Ag-107/Ag-109 ratio in the metal phases of the meteorites is found to be in excess of the terrestrial ratio, and of that found in the sulfide phases. A definite correlation between the Ag-107/Ag-109 and Pd-108/Ag-109 ratios is observed for these meteorites, indicating the in situ decay of Pd-107 and supporting the widespread presence of Pd in the early universe. Lead, determined after cleaning and with chemical separations using low blank levels, is found to exist in variable proportions in the metal and sulfide phases. The sulfides appear to be dominated by radiogenic modern lead, which may be explained by terrestrial contamination or by late metamorphism in the meteorite parent body.

Chen, J. H.; Wasserburg, G. J.

1983-10-01

296

Movement responses of caribou to human-induced habitat edges lead to their aggregation near anthropogenic features.  

PubMed

The assessment of disturbance effects on wildlife and resulting mitigation efforts are founded on edge-effect theory. According to the classical view, the abundance of animals affected by human disturbance should increase monotonically with distance from disturbed areas to reach a maximum at remote locations. Here we show that distance-dependent movement taxis can skew abundance distributions toward disturbed areas. We develop an advection-diffusion model based on basic movement behavior commonly observed in animal populations and parameterize the model from observations on radio-collared caribou in a boreal ecosystem. The model predicts maximum abundance at 3.7 km from cutovers and roads. Consistently, aerial surveys conducted over 161,920 km(2) showed that the relative probability of caribou occurrence displays nonmonotonic changes with the distance to anthropogenic features, with a peak occurring at 4.5 km away from these features. This aggregation near disturbed areas thus provides the predators of this top-down-controlled, threatened herbivore species with specific locations to concentrate their search. The edge-effect theory developed here thus predicts that human activities should alter animal distribution and food web properties differently than anticipated from the current paradigm. Consideration of such nonmonotonic response to habitat edges may become essential to successful wildlife conservation. PMID:23669544

Fortin, Daniel; Buono, Pietro-Luciano; Fortin, André; Courbin, Nicolas; Tye Gingras, Christian; Moorcroft, Paul R; Courtois, Réhaume; Dussault, Claude

2013-06-01

297

KNN/BNT Composite Lead-Free Films for High-Frequency Ultrasonic Transducer Applications  

PubMed Central

Lead-free K0.5Na0.5NbO3/Bi0.5Na0.5TiO3 (KNN/BNT) films have been fabricated by a composite sol-gel technique. Crystalline KNN fine powder was dispersed in the BNT precursor solution to form a composite slurry which was then spin-coated onto a platinum-buffered Si substrate. Repeated layering and vacuum infiltration were applied to produce 5-?m-thick dense composite film. By optimizing the sintering temperature, the films exhibited good dielectric and ferroelectric properties comparable to PZT films. A 193-MHz high-frequency ultrasonic transducer fabricated from this composite film showed a ?6-dB bandwidth of approximately 34%. A tungsten wire phantom was imaged to demonstrate the capability of the transducer. PMID:21244994

Lau, Sien Ting; Ji, Hong Fen; Li, Xiang; Ren, Wei; Zhou, Qifa; Shung, K. Kirk

2011-01-01

298

Stress Intensity Factor Solutions for Multiple Edge Cracks in Ceramic Matrix Composites  

NASA Technical Reports Server (NTRS)

NASA Lewis Research Center conducted a study to determine the stress intensity factor solutions for periodic arrays of bridged cracks for various crack spacings and crack lengths. Initially, the stress intensity factor of an array of unbridged multiple edge cracks was determined under constant global displacement as well as at a point load along the crack wake. These solutions are expected to contribute toward the development of a damage-based life-prediction methodology for CMC engine components.

Ghosn, Louis

1997-01-01

299

Compression-Loaded Composite Panels With Elastic Edge Restraints and Initial Prestress  

NASA Technical Reports Server (NTRS)

A parametric study of the effects of test-fixture-induced initial prestress and elastic edge restraints on the prebuckling and buckling responses of a compression-loaded, quasi-isotropic curved panel is presented. The numerical results were obtained by using a geometrically nonlinear finite element analysis code with high-fidelity models. The results presented show that a wide range of prebuckling and buckling behavior can be obtained by varying parameters that represent circumferential loaded-edge restraint and rotational unloaded-edge restraint provided by a test fixture and that represent the mismatch in specimen and test-fixture radii of curvature. For a certain range of parameters, the panels exhibit substantial nonlinear prebuckling deformations that yield buckling loads nearly twice the corresponding buckling load predicted by a traditional linear bifurcation buckling analysis for shallow curved panels. In contrast, the results show another range of parameters exist for which the nonlinear prebuckling deformations either do not exist or are relatively benign, and the panels exhibit buckling loads that are nearly equal to the corresponding linear bifurcation buckling load. Overall, the results should be of particular interest to scientists, engineers, and designers involved in simulating flight-hardware boundary conditions in structural verification and certification tests, involved in validating structural analysis tools, and interested in tailoring buckling performance.

Hilburger, Mark W.; Nemeth, Michael P.; Riddick, Jaret C.; Thornburgh, Robert P.

2005-01-01

300

Piezoelectric and pyroelectric properties of lead titanate-polyethylene oxide composites  

NASA Astrophysics Data System (ADS)

Polymer-ceramic composites with pyroelectric sensitivity are presented as promising candidates for infrared detection. Selection of the appropriate ceramic filler and the polymer matrix is one of the key parameters in the development of optimized materials for specific applications. In this work lead-titanate (PT) ceramic is incorporated into a flexible polymer matrix, polyethylene oxide (PEO) with relatively high electrical conductivity to develop sensitive and at the same time flexible composites. PT particles are dispersed in PEO at varying volume fractions, and composite materials cast in the form of films for the measurements. The dielectric, piezoelectric and pyroelectric properties are measured. From these data the piezoelectric voltage coefficients as well as pyroelctric figures of merit of the composite films have been determined and values were compared with that of PT-epoxy composites in order to determine the effect of electrical conductivity of the polymer matrix on the poling efficiency and the final properties. It is found that, in general, both the piezoelectric and the pyroelectric figures of merit increase with concentration of PT; however, it is at the expense of mechanical flexibility of the material. Moreover PT-PEO composites show superior pyroelectric sensitivity compared to PT-Epoxy composites. Improving the electrical conductivity of the polymer phase enhances the poling process significantly.

Khanbareh, H.; van der Zwaag, S.; Groen, W. A.

2014-11-01

301

Influence of restorative technique, Bevelling and aging on composite bonding to sectioned incisal edges: A comparative in vitro study  

PubMed Central

Aim: To evaluate the effect of direct and indirect technique, bevel placement, and aging on the fracture resistance of composite restorations bonded to sectioned incisal edges. Materials and Methods: Incisal thirds of 80 human maxillary incisors were sectioned. Four treatment groups of 20 teeth each were formed as follows: Direct composite with bevel and without bevel (Adper single bond 2/Filtek Z350); indirect composite with bevel and without bevel (prepolymerized Filtek Z350 cemented with Adper single bond 2/Relay × ARC). Ten teeth from each group were stored in distilled water for 24 h. The remaining ten teeth were stored in distilled water for 180 days with two thermocycling treatments. The specimens were subjected to shear testing using universal testing machine. Fractured specimens were examined with a stereomicroscope at ×10 magnification to evaluate the failure patterns. The obtained data were statistically analyzed by using ANOVA, Bonferroni test, and Student's t-test. Results: Beveled restorations exhibited higher fracture resistance values than nonbeveled restorations. Long-term water storage decreased the fracture resistance. Conclusion: The use of bevels resulted in improved fracture resistance of composite restorations and reduced the impact of aging. PMID:23349572

Poojary, Pradeep K; Bhandary, Shreetha; Srinivasan, Raghu; Nasreen, Farhat; Pramod, J; Mahesh, MC

2013-01-01

302

A low speed wind tunnel investigation of Reynolds number effects on a 60-deg swept wing configuration with leading and trailing edge flaps  

NASA Technical Reports Server (NTRS)

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.

Rao, Dhanvada M.; Hoffler, Keith D.

1988-01-01

303

Fracture analysis of transverse crack-tip and free-edge delamination in laminated composites  

NASA Technical Reports Server (NTRS)

A shear deformation model including hygrothermal effects is developed for the analysis of local delaminations originating from transverse cracks in 90-deg plies located in and around the laminate midplane. A sublaminate approach is used and the model is applied to (+/- 25/90n)s T300/934 graphite/epoxy laminates for n values between 0.5 and 8, along with previously developed edge-delamination shear-deformation models. Critical loads and delamination modes are identified and compared with experimental results. Hygrothermal effects are included in all the models to make the comparisons realistic.

Armanios, Erian A.; Sriram, P.; Badir, Ashraf M.

1991-01-01

304

[Effects of highway on the vegetation species composition along a distance gradient from road edge in southeastern margin of Tengeer Desert].  

PubMed

Aimed to examine the effects of highway on the vegetation species composition in arid desert area, forty-eight transects perpendicular to the provincial highway 201 from Shapotou to Jing-tai in the southeastern margin of Tengger Desert were installed, with the vegetation species distribution along a distance gradient from the road edge investigated. The results showed that with increasing distance from the road edge, the species number, coverage, biomass, and alpha-diversity of herbaceous plants declined, but had no significant differences with the control beyond 5 m. Within 0-6 m to the road edge, the herbaceous plant height was greater than that of the control, but their density had less change. Within 0-2 m to the road edge, the species turnover rate of herbaceous plants was lower; at 2-5m, this rate was the highest; while beyond 10 m, the species composition of herbaceous plants was similar to that of the control. The herbaceous plant community at the road edge was dominated by gramineous plants, with the disturbance-tolerant species Pennisetum centrasiaticum, Chloris virgata, and Agropyron cristatum accounting for 68.6% of the total. C. virgata beyond 1 m to the road edge had a rapid decrease in its individual number and presence frequency, P. centrasiaticum and A. cristatum beyond 2 m also showed a similar trend, while the composite plants Artemisia capillaris and A. frigida beyond 2 m from the road edge had a rapid increase in its individual number, accounting for 70% of the herbaceous plants. At the road edge, the coverage and density of shrubs were significantly lower than those of the control, but the species composition had no significant difference. PMID:21812282

Feng, Li; Li, Xin-Rong; Guo, Qun; Zhang, Jing-Guang; Zhang, Zhi-Shan

2011-05-01

305

Effect of compositional variations in the lead lanthanum zirconate stannate titanate system on electrical properties  

Microsoft Academic Search

The purpose of this work was to evaluate the effect of compositional modifications on the electrical properties of lead lanthanum zirconate stannate titanate (PLZST) ceramics, as well as to examine their electrically induced phase-change behavior. Variations in the Ti:Sn ratio were evaluated. Increased Ti{sup 4+} content produced the following: decreased switching field, related to an increased antiferroelectric-ferroelectric (AFE-FE) transition temperature;

Kelley Markowski; Seung-Eek Park; Shoko Yoshikawa; L. Eric Cross

1996-01-01

306

Wind tunnel tests of a full-scale model of a light twin-engine airplane with fixed auxiliary airfoil or leading-edge slot  

NASA Technical Reports Server (NTRS)

An investigation has been conducted by means of wind-tunnel tests of a full-scale mockup of a light twin-engine airplane configuration to determine the effects of outboard partial-span slots and of auxiliary airfoils ahead of the leading edge of the wing in improving aerodynamic characteristics at high angles of attack. Both of the stall-control devices gave considerable improvement in high angle-of-attack characteristics with the auxiliary airfoil giving the more favorable results, but neither device performed as well as might have been expected.

Fink, M. P.; Shivers, J. P.; White, L. C.

1974-01-01

307

Large-Scale Wind-Tunnel Tests and Evaluation of the Low-Speed Performance of a 35 deg Sweptback Wing Jet Transport Model Equipped with a Blowing Boundary-Layer-Control Flap and Leading-Edge Slat  

NASA Technical Reports Server (NTRS)

A wind-tunnel investigation was conducted to determine the effect of trailing-edge flaps with blowing-type boundary-layer control and leading-edge slats on the low-speed performance of a large-scale jet transport model with four engines and a 35 deg. sweptback wing of aspect ratio 7. Two spanwise extents and several deflections of the trailing-edge flap were tested. Results were obtained with a normal leading-edge and with full-span leading-edge slats. Three-component longitudinal force and moment data and boundary-layer-control flow requirements are presented. The test results are analyzed in terms of possible improvements in low-speed performance. The effect on performance of the source of boundary-layer-control air flow is considered in the analysis.

Hickey, David H.; Aoyagi, Kiyoshi

1960-01-01

308

Surface-Pressure and Flow-Visualization Data at Mach Number of 1.60 for Three 65 deg Delta Wings Varying in Leading-Edge Radius and Camber  

NASA Technical Reports Server (NTRS)

An experimental investigation of the effect of leading-edge radius, camber, Reynolds number, and boundary-layer state on the incipient separation of a delta wing at supersonic speeds was conducted at the Langley Unitary Plan Wind Tunnel at Mach number of 1.60 over a free-stream Reynolds number range of 1 x 106 to 5 x 106 ft-1. The three delta wing models examined had a 65 deg swept leading edge and varied in cross-sectional shape: a sharp wedge, a 20:1 ellipse, and a 20:1 ellipse with a -9.750 circular camber imposed across the span. The wings were tested with and without transition grit applied. Surface-pressure coefficient data and flow-visualization data indicated that by rounding the wing leading edge or cambering the wing in the spanwise direction, the onset of leading-edge separation on a delta wing can be raised to a higher angle of attack than that observed on a sharp-edged delta wing. The data also showed that the onset of leading-edge separation can be raised to a higher angle of attack by forcing boundary-layer transition to occur closer to the wing leading edge by the application of grit or the increase in free-stream Reynolds number.

McMillin, S. Naomi; Bryd, James E.; Parmar, Devendra S.; Bezos-OConnor, Gaudy M.; Forrest, Dana K.; Bowen, Susan

1996-01-01

309

A comparison of finite-difference and finite-element methods for calculating free edge stresses in composites  

NASA Technical Reports Server (NTRS)

It is pointed out that edge delamination is a serious failure mechanism for laminated composite materials. Various numerical methods have been utilized in attempts to calculate the interlaminar stress components which precede delamination in a laminate. There are, however, discrepancies regarding the results provided by different methods, taking into account a finite-difference procedure, a perturbation procedure, and finite element approaches. The present investigation has the objective to assess the capacity of a finite difference method to predict the character and magnitude of the interlaminar stress distributions near an interface corner. A second purpose of the investigation is to determine if predictions by finite element method in-plane, interlaminar stress components near an interface corner represent actual laminate behavior.

Bauld, N. R., Jr.; Goree, J. G.; Tzeng, L.-S.

1985-01-01

310

Composite materials with metal oxide attached to lead chalcogenide nanocrystal quantum dots with linkers  

DOEpatents

Composite materials useful for devices such as photoelectrochemical solar cells include a substrate, a metal oxide film on the substrate, nanocrystalline quantum dots (NQDs) of lead sulfide, lead selenide, and lead telluride, and linkers that attach the NQDs to the metal oxide film. Suitable linkers preserve the 1s absorption peak of the NQDs. A suitable linker has a general structure A-B-C where A is a chemical group adapted for binding to a MO.sub.x and C is a chemical group adapted for binding to a NQD and B is a divalent, rigid, or semi-rigid organic spacer moiety. Other linkers that preserve the 1s absorption peak may also be used.

Fuke, Nobuhiro; Koposov, Alexey Y; Sykora, Milan; Hoch, Laura

2014-12-16

311

Evaluation of the Edge Crack Torsion (ECT) Test for Mode 3 Interlaminar Fracture Toughness of Laminated Composites  

NASA Technical Reports Server (NTRS)

An analytical and experimental investigation was carried out on G40-800/R6376 graphite epoxy laminates to evaluate the Edge Crack Torsion (ECT) test as a candidate for a standard Mode 3 interlaminar fracture toughness test for laminated composites. The ECT test consists of a (90/(+/- 45)(sub 3)/(+/- 45)(sub 3)/90))(sub s) laminate with a delamination introduced by a non-adhesive film at the mid-plane along one edge and loaded in a special fixture to create torsion along the length of the laminate. Dye penetrate enhanced X-radiograph of failed specimens revealed that the delamination initiated at the middle of the specimen length and propagated in a self similar manner along the laminate mid-plane. A three-dimensional finite element analysis was performed that indicated that a pure Mode 3 delamination exists at the middle of specimen length away from both ends. At the ends near the loading point a small Mode 2 component exists. However, the magnitude of this Mode 2 strain energy release rate at the loading point is small compared to the magnitude of Mode 3 component in the mid-section of the specimen. Hence, the ECT test yielded the desired Mode 3 delamination. The Mode 3 fracture toughness was obtained from a compliance calibration method and was in good agreement with the finite element results. Mode 2 End-Notched Flexure (ENF) tests and Mode 1 Double Cantilever Beam (DCB) tests were also performed for the same composite material. The Mode 1 fracture toughness was much smaller than both the Mode 2 and Mode 3 fracture toughness. The Mode 2 fracture toughness was found to be 75% of the Mode 3 fracture toughness.

Li, Jian; Lee, Edward W.; OBrien, T. Kevin; Lee, Shaw Ming

1996-01-01

312

Electrochemical Evaluation of Lead Base Composite Anodes Fabricated by Accumulative Roll Bonding Technique  

NASA Astrophysics Data System (ADS)

Accumulative roll bonding is used for the first time in lead systems to fabricate advanced lead base composite anodes. For this purpose, Ag as the most common and effective additive, Co as the best metallic immiscible substitution for Ag, and MnO2 as the ceramic and electrocatalytic agent have been used as additives to produce anodes. The accumulative roll bonding processed sheets have been fabricated under determined conditions. The electrochemical properties of the prepared samples are investigated by Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, Polarization tests, electrowinning tests, and Scanning Electron Microscopy. The results indicate that the ARB-processed composite lead sheets can be perfectly used as novel developed anodes. The advantages include 5.51 times increase of current density, in the Pb-pct0.5Ag 9-pass sample compared to pure lead anode, decreased charge transfer resistance from 56.31 (? cm2) in pure lead anode to 17.5 (? cm2) in the Pb-pct2MnO2 8-pass sample (72 pct lower), and decreased oxygen evolution potential from 1.95 (V/SHE) in pure lead anode to 1.77 (V/SHE) in the Pb-pct2MnO2 8-pass sample (0.18 (V/SHE) lower). Electrowinning tests results reveal Pb-2 pctMnO2 8-pass showed best anodic performance withsignificant lower compared corrosion rate (75 pct), product and electrolyte contamination, slime formation, energy consumption and higher Zn deposit and energy conservation (to 294 kWh/t-Zn). Finest Zn deposit morphology (effective reduced grain size corresponding to smoothness and compaction) has been supplied by Pb-2 pctMnO2 8-pass sample resulted from enhanced growth rate of Zn in lack of Pb contaminations that could act as suitable nucleation sites.

Karbasi, Maryam; Keshavarz Alamdari, Eskandar

2014-12-01

313

Design, fabrication, testing, and delivery of shuttle heat pipe leading edge test modules. Volume 2: Technical report  

NASA Technical Reports Server (NTRS)

Development in the design of leading heat pipes for the space shuttle are reported. The analysis, design, and integration of the heat pipes into the module structure are described along with the recommended tests. Results indicate the design goals were meet.

1973-01-01

314

Bidirectional coupling between integrin-mediated signaling and actomyosin mechanics explains matrix-dependent intermittency of leading-edge motility  

PubMed Central

Animal cell migration is a complex process characterized by the coupling of adhesion, cytoskeletal, and signaling dynamics. Here we model local protrusion of the cell edge as a function of the load-bearing properties of integrin-based adhesions, actin polymerization fostered by adhesion-mediated signaling, and mechanosensitive activation of RhoA that promotes myosin II–generated stress on the lamellipodial F-actin network. Analysis of stochastic model simulations illustrates how these pleiotropic functions of nascent adhesions may be integrated to govern temporal persistence and frequency of protrusions. The simulations give mechanistic insight into the documented effects of extracellular matrix density and myosin abundance, and they show characteristic, nonnormal distributions of protrusion duration times that are similar to those extracted from live-cell imaging experiments. Analysis of the model further predicts relationships between measurable quantities that reflect the partitioning of stress between tension on F-actin–bound adhesions, which act as a molecular clutch, and dissipation by retrograde F-actin flow. PMID:24152734

Welf, Erik S.; Johnson, Heath E.; Haugh, Jason M.

2013-01-01

315

Bidirectional coupling between integrin-mediated signaling and actomyosin mechanics explains matrix-dependent intermittency of leading-edge motility.  

PubMed

Animal cell migration is a complex process characterized by the coupling of adhesion, cytoskeletal, and signaling dynamics. Here we model local protrusion of the cell edge as a function of the load-bearing properties of integrin-based adhesions, actin polymerization fostered by adhesion-mediated signaling, and mechanosensitive activation of RhoA that promotes myosin II-generated stress on the lamellipodial F-actin network. Analysis of stochastic model simulations illustrates how these pleiotropic functions of nascent adhesions may be integrated to govern temporal persistence and frequency of protrusions. The simulations give mechanistic insight into the documented effects of extracellular matrix density and myosin abundance, and they show characteristic, nonnormal distributions of protrusion duration times that are similar to those extracted from live-cell imaging experiments. Analysis of the model further predicts relationships between measurable quantities that reflect the partitioning of stress between tension on F-actin-bound adhesions, which act as a molecular clutch, and dissipation by retrograde F-actin flow. PMID:24152734

Welf, Erik S; Johnson, Heath E; Haugh, Jason M

2013-12-01

316

Development of porous clay-based composites for the sorption of lead from water.  

PubMed

Lead contamination of water is a major health hazard, as illustrated by the fact that exposure to this metal has been associated with death and disease in humans, birds, and animals. The present research was aimed at the development of a porous, solid-phase sorbent that can be used in the remediation of lead-contaminated water. A suitable sorbent was identified by screening various clays and other materials for their ability to effectively bind lead. The clay was adhered to a solid support using an aqueous solution of carboxymethyl cellulose. The binary composite was then tested for its ability to bind lead from solution, while providing void volume, increased surface area, and considerably enhanced hydraulic conductivity. The results suggested that a combination of sodium montmorillonite clay and carbon exhibited enhanced sorption of lead compared to carbon alone, and also supported the potential application of various combinations of sorbent materials. This value-added combination of clay, solid support, and adhesive will allow for the construction of column filtration systems that are multifunctional and capable of purifying large volumes of contaminated water. PMID:11482800

Ake, C L; Mayura, K; Huebner, H; Bratton, G R; Phillips, T D

2001-07-20

317

Composite uranium carbide targets at TRIUMF: Development and characterization with SEM, XRD, XRF and L-edge densitometry  

NASA Astrophysics Data System (ADS)

The production of radioactive ion beams (RIB) from spallation targets by irradiation with a continuous 500 MeV proton beam, has been routine at TRIUMF for several years. Based on the experience with composite refractory carbide targets a procedure for the fabrication of UC2/C targets was developed. It includes the preparation of UC2 by carbothermal reduction of UO2, the slip-casting of fine-grained UC2/C slurry on graphite foil under inert gas atmosphere and the cutting of composite target discs which are stacked up to a lamellar structure. The thermal properties of such an arrangement are adequate to withstand the high power deposition of an intense, continuous proton beam and also beneficial for the fast release of short-lived radioactive isotopes. Molecular structure, particle size and the impact of sintering of the target discs were investigated via XRD and SEM. Thickness and mass distribution were measured with position-sensitive LIII-edge densitometry. The results confirm that the properties of the UC2/C target material are well suited for RIB production at TRIUMF while there is still room for improvement with regard to uniformity of mass distribution in target disc thickness.

Kunz, Peter; Bricault, Pierre; Dombsky, Marik; Erdmann, Nicole; Hanemaayer, Vicky; Wong, John; Lützenkirchen, Klaus

2013-09-01

318

Reaction of YBa2Cu3O(7-beta) with Gold, Silver, Bismuth and Lead: Substitution Chemistry and Composite Fabrication  

NASA Technical Reports Server (NTRS)

The reaction of YBa2Cu3O(7-beta) with Au, Ag, Bi, and Ph ions or metal is described. Three types of materials were produced: a well-defined series of homogeneous superconductors was obtained for Au ion substitution with little effect on T(sub c); attempted Ag and Bi ion substitution resulted in multi-phase samples with slightly enhanced T(sub c); finally, attempts to produce superconducting metal/superconducting ceramic composites with Pb and Bi powders resulted in multi-phase samples with drastically diminished superconducting properties. For Au- substituted superconductors, YBa2(Cu(l-x)Au(x))3O(7-beta), a substitution series (x = 0 - 0.1) has been synthesized. For x = 0.1 there was no change in the a and b lattice parameters (a = 3.826 A and b = 3.889 A) but a 0.06 A c axis expansion to 11.75 A was observed. The valence of Cu and Au in YBa2Au(0.3)Cu(2.7)O(7-beta) was investigated using X-ray Absorption Near-Edge Structure (XANES). X-ray studies indicate that Au goes into the Cu(l) site and Cu K edge XANES shows that this has little effect on the oxidation state of the remaining copper. A small effect on T(sub c) is observed (T(sub c) = 89 K for x = 0.10). Ag and Bi addition results in a rise in T(sub c) and a decrease in (delta)T(sub c) at low levels (x = 0.10 Ag, T(sub c) = 94 K and (delta)T(sub c) = 0.5 K; x = 0.02 Bi, T(sub c) = 94 K and (delta)T(sub c) = 1K) relative to typical values for YBa2Cu3O(7-beta) (T(sub c) = 91 K, (delta)T(sub c) = 2 K). Attempts at fabrication of Pb- and Pb(1-x)Bi(x)-superconductor composites are described. Cold pressing followed by low temperature (200 C) sintering resulted in a composite which excluded flux below 90 K but did not show zero electrical resistance until the metal (alloy) superconducting transition. X-ray diffraction showed the presence of pervoskite and metal. Processing at moderate (450 C) or high (950 C) temperatures resulted in oxygen-depleted pervoskite and/or metal oxides. These materials displayed greatly degraded superconducting properties. Processing at 800 C resulted in high T(sub c) only for composites containing greater than 90% weight fraction ceramic. Reaction of metal with YBa2Cu3O(7-beta) formed superconducting lead/bismuth-based oxides and other binary oxides.

Hepp, Aloysius F.; Gaier, James R.

1993-01-01

319

Composite lead for conducting an electrical current between 75--80K and 4. 5K temperatures  

DOEpatents

A composite lead is provided which electrically links and conducts a current between about 75-80K and liquid helium temperature of about 4.5K. The composite lead may be employed singly or in multiples concurrently to provide conduction of electrical current from normal conductors and semi-conductors at room temperature to superconductors operating at 4.5K. In addition, a variety of organizational arrangements and assemblies are provided by which the mechanical strength and electrical reliability of the composite lead is maintained. 12 figures.

Negm, Y.; Zimmerman, G.O.; Powers, R.E. Jr.; McConeghy, R.J.; Kaplan, A.

1994-12-27

320

Low-Speed Investigation of Upper-Surface Leading-Edge Blowing on a High-Speed Civil Transport Configuration  

NASA Technical Reports Server (NTRS)

The paper identifies speed, agility, human interface, generation of sensitivity information, task decomposition, and data transmission (including storage) as important attributes for a computer environment to have in order to support engineering design effectively. It is argued that when examined in terms of these attributes the presently available environment can be shown to be inadequate. A radical improvement is needed, and it may be achieved by combining new methods that have recently emerged from multidisciplinary design optimisation (MDO) with massively parallel processing computer technology. The caveat is that, for successful use of that technology in engineering computing, new paradigms for computing will have to be developed - specifically, innovative algorithms that are intrinsically parallel so that their performance scales up linearly with the number of processors. It may be speculated that the idea of simulating a complex behaviour by interaction of a large number of very simple models may be an inspiration for the above algorithms; the cellular automata are an example. Because of the long lead time needed to develop and mature new paradigms, development should begin now, even though the widespread availability of massively parallel processing is still a few years away.

Banks, Daniel W.; Laflin, Brenda E. Gile; Kemmerly, Guy T.; Campbell, Bryan A.

1999-01-01

321

Quasi-Static 3-Point Reinforced Carbon-Carbon Bend Test and Analysis for Shuttle Orbiter Wing Leading Edge Impact Damage Thresholds  

NASA Technical Reports Server (NTRS)

Static 3-point bend tests of Reinforced Carbon-Carbon (RCC) were conducted to failure to provide data for additional validation of an LS-DYNA RCC model suitable for predicting the threshold of impact damage to shuttle orbiter wing leading edges. LS-DYNA predictions correlated well with the average RCC failure load, and were good in matching the load vs. deflection. However, correlating the detectable damage using NDE methods with the cumulative damage parameter in LS-DYNA material model 58 was not readily achievable. The difficulty of finding internal RCC damage with NDE and the high sensitivity of the mat58 damage parameter to the load near failure made the task very challenging. In addition, damage mechanisms for RCC due to dynamic impact of debris such as foam and ice and damage mechanisms due to a static loading were, as expected, not equivalent.

Fasanella, Edwin L.; Sotiris, Kellas

2006-01-01

322

Basanite-nephelinite suite from early Kilauea: Carbonated melts of phlogopite-garnet peridotite at Hawaii's leading magmatic edge  

USGS Publications Warehouse

A basanite-nephelinite glass suite from early submarine Kilauea defines a continuous compositional array marked by increasing concentrations of incompatible components with decreasing SiO2, MgO, and Al2O3. Like peripheral and post-shield strongly alkalic Hawaiian localities (Clague et al. in J Volcanol Geotherm Res 151:279-307, 2006; Dixon et al. in J Pet 38:911-939, 1997), the early Kilauea basanite-nephelinite glasses are interpreted as olivine fractionation products from primary magnesian alkalic liquids. For early Kilauea, these were saturated with a garnet-phlogopite-sulfide peridotite assemblage, with elevated dissolved CO2 contents responsible for the liquids' distinctly low-SiO2 concentrations. Reconstructed primitive liquids for early Kilauea and other Hawaiian strongly alkalic localities are similar to experimental 3 GPa low-degree melts of moderately carbonated garnet lherzolite, and estimated parent magma temperatures of 1,350-1,400??C (olivine-liquid geothermometry) match the ambient upper mantle geotherm shortly beneath the base of the lithosphere. The ???3 GPa source regions were too hot for stable crystalline carbonate and may have consisted of ambient upper mantle peridotite containing interstitial carbonate-silicate or carbonatitic liquid, possibly (Dixon et al. in Geochem Geophys Geosyst 9(9):Q09005, 2008), although not necessarily, from the Hawaiian mantle plume. Carbonate-enriched domains were particularly susceptible to further melting upon modest decompression during upward lithospheric flexure beneath the advancing Hawaiian Arch, or by conductive heating or upward drag by the Hawaiian mantle plume. The early Kilauea basanite-nephelinite suite has a HIMU-influenced isotopic character unlike other Hawaiian magmas (Shimizu et al. in EOS Tran Amer Geophys Union 82(47): abstr V12B-0962, 2001; Shimizu et al. in Geochim Cosmochim Acta 66(15A):710, 2002) but consistent with oceanic carbonatite involvement (Hoernle et al. in Contrib Mineral Petrol 142:520-542, 2002). It may represent the melting products of a fertile domain in the ambient upper mantle impinged upon and perturbed by the sustained plume source that feeds later shield-stage magmatism. ?? US Government 2009.

Sisson, T.W.; Kimura, J.-I.; Coombs, M.L.

2009-01-01

323

Actin Filaments at the Leading Edge of Cancer Cells Are Characterized by a High Mobile Fraction and Turnover Regulation by Profilin I  

PubMed Central

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. PMID:24465723

Lorente, Gisela; Syriani, Emilio; Morales, Miguel

2014-01-01

324

The design of a functionally graded composite for service in high temperature lead and lead-bismuth cooled nuclear reactors  

E-print Network

A material that resists lead-bismuth eutectic (LBE) attack and retains its strength at 700°C would be an enabling technology for LBE-cooled reactors. No single alloy currently exists that can economically meet the required ...

Short, Michael Philip

2010-01-01

325

Lead concentration and isotopic composition in five peridotite inclusions of probable mantle origin  

USGS Publications Warehouse

The lead content of five whole-rock peridotite inclusions (four lherzolites and one harzburgite) in alkali basalt ranges from 82 to 570 ppb (parts per billion). Approximately 30-60 ppb of this amount can be accounted for by analyzed major silicate minerals (olivine ??? 10 ppb; enstatite 5-28 ppb; chrome diopside ???400 ppb). Through a series of acid leaching experiments, the remainder of the lead is shown to be quite labile and to reside in either glassy or microcrystalline veinlets or accessory mineral phases, such as apatite and mica. The lead isotopic composition of the peridotites (206Pb/204Pb = 18.01-18.90; 207Pb/204Pb = 15.52-15.61; 208Pb/204Pb = 37.80-38.86) lies within the range of values defined by many modern volcanic rocks and, in particular, is essentially coextensive with the abyssal tholeiite field. In all but one instance, isotopic differences were found between the peridotite and its host alkali basalt. Two of the peridotites clearly demonstrated internal isotopic heterogeneity between leachable and residual fractions that could not simply be due to contamination by the host basalt. However, there is no evidence that these ultramafic rocks form some layer in the mantle with isotopic characteristics fundamentally different from those of the magma sources of volcanic rocks. ?? 1973.

Zartman, R.E.; Tera, F.

1973-01-01

326

Modified Lead Titanate/polymer 1-3 Composite Transducers for Structural Health Monitoring  

NASA Astrophysics Data System (ADS)

Lamb wave techniques provide an effective means for inspecting large areas of thin structures. Defects arising from corrosion, cracking, adhesive debonding etc. can be monitored continuously by permanently embedding sensors on the structure. However, with the permanently embedded sensors, multiple wave modes are normally generated making the received signals complex to analyze. Interdigital transducers (IDT's) can be used to achieve mode control, giving the capability to excite individual modes. This significantly enhances the ability to extract meaningful information from the received signals. PVDF is commonly used with appropriate electrodes to excite the desired wave mode in the structure. However, due to its low electromechanical coupling coefficient, performance on structures like multi-layered plates and carbon fiber composites is very poor. 1-3 piezocomposites with high electromechanical coupling and bandwidth are designed to overcome the limitations of PVDF. Transducers designed with modified lead titanate are tested on a multi-layered structure to detect delamination at the metal-epoxy interface.

Koduru, Jaya Prakash; Rose, Joseph L.

2010-02-01

327

Composite lead for conducting an electric current between 75--80 K and 4. 5 K temperatures  

Microsoft Academic Search

This technology can be used to manufacture an article which allows the user to bridge and join electrical circuits which are functional at room temperatures (300K) or helium temperatures (4.5 K). The composite lead article provides multiple electrical leads and is capable of conducting 100 amperes or more of electrical current between the different temperature regions, it minimizes the heat

R. J. McConeghy; Y. Negm; O. Zimmerman; R. E. Powers; A. Kaplan

1992-01-01

328

Nonlinear absorption of laser radiation by zinc and lead phthalocyanines and zinc porphyrin in a nanoporous-glass/polymer composite  

NASA Astrophysics Data System (ADS)

We have studied the nonlinear absorption of nanosecond 532-nm laser pulses by zinc phthalocyanine (PcZn), lead phthalocyanine (PcPb) and zinc porphyrin (PrZn) incorporated into a nanoporous-glass/polymer composite and determined the basic nonlinear absorption characteristics of these compounds in the composite host. The composite is shown to be suitable for designing nonlinear optical elements activated with organic compounds. The correlation between the characteristics of the three compounds in the composite host and liquid solvents is analysed.

Dolotov, S. M.; Koldunov, L. M.; Koldunov, M. F.; Petukhov, A. V.; Sizyukhin, A. V.

2012-01-01

329

The Use of Pristine and Intercalated Graphite Fiber Composites as Buss Bars in Lead-Acid Batteries  

NASA Technical Reports Server (NTRS)

This study was conducted as a part of the Firefly Energy Space Act Agreement project to investigate the possible use of composite materials in lead acid batteries. Specifically, it examined the use of intercalated graphite composites as buss bars. Currently, buss bars of these batteries are made of lead, a material that is problematic for several reasons. Over time, the lead is subject to both corrosion at the positive plate and sulfation at the negative plate, resulting in decreased battery life. In addition, the weight and size of the lead buss bars make for a heavy and cumbersome battery that is undesirable. Functionality and practicality of lead buss bars is adequate at best; consequently, investigation of more efficient composite materials would be advantageous. Practically speaking, graphite composites have a low density that is nearly one fourth that of its lead counterpart. A battery made of less dense materials would be more attractive to the consumer and the producer because it would be light and convenient. More importantly, low weight would be especially beneficial because it would result in greater overall power density of the battery. In addition to power density, use of graphite composite materials can also increase the life of the battery. From a functional standpoint, corrosion and sulfation at the positive and negative plates are major obstacles when considering how to extend battery life. Neither of these reactions are a factor when graphite composites replace lead parts because graphite is chemically non-reactive with the electrolyte within the battery. Without the problem of corrosion or sulfation, battery life expectancy can be almost doubled. The replacement of lead battery parts with composite materials is also more environmentally favorable because of easy disposal of organic materials. For this study, both pristine and bromine intercalated single-ply graphite fiber composites were created. The composites were fabricated in such a way as to facilitate their use in a 3" x 1/2" buss bar test cell. The prime objective of this investigation was to examine the effectiveness of a variety of graphite composite materials to act as buss bars and carry the current to and from the positive and negative battery plates. This energy transfer can be maximized by use of materials with high conductivity to minimize the buss resistance. Electrical conductivity of composites was measured using both a contactless eddy current probe and a four point measurement. In addition, the stability of these materials at battery-use conditions was characterized.

Opaluch, Amanda M.

2004-01-01

330

Leading Edge Network Medicine Strikes  

E-print Network

vulnerable to a second, later hit with DNA-damaging drugs, demonstrating that time- and order-dependent drug (TNBC) cells in vitro and in vivo is a time- and order-dependent combination of drugs (Figure 1: janine.erler@bric.ku.dk (J.T.E.), linding@cbs.dtu.dk (R.L.) DOI 10.1016/j.cell.2012.04.014 Drug

331

Leading Edge Slicing across Kingdoms  

E-print Network

1,* and Alejandro Sa´ nchez Alvarado2,* 1Department of Biology, Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA 2Howard Hughes Medical Institute, University of Utah that regeneration was widely dispersed among the metazoans, including earthworms, snails, and salamanders

Alvarado, Alejandro Sánchez

332

Leading Edge In This Issue  

E-print Network

that is responsible for resistance to VEGFRIs, nor does it cause or enhance VEGFRI- related side effects. The efficacy into the mechanism of immune evasion by Plasmodium and have implications for future drug and vaccine development

Rohs, Remo

333

Experimental Surface Pressure Data Obtained on 65 deg Delta Wing Across Reynolds Number and Mach Number Ranges. Volume 1; Sharp Leading Edge; [conducted in the Langley National Transonic Facility (NTF)  

NASA Technical Reports Server (NTRS)

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 36 x 10(exp 6) at a Mach number of 0.85 and across a Mach number range of 0.4 to 0.9 at a Reynolds number of 6 x 10(exp 6). Normal-force and pitching-moment coefficient plots for these Reynolds number and Mach number ranges are also presented.

Chu, Julio; Luckring, James M.

1996-01-01

334

Lithospheric structure at the leading edge of the North American craton: Imaging the Shield-Cordillera transition in western Canada by teleseismic Rayleigh-wave analysis  

NASA Astrophysics Data System (ADS)

The tectonics of southwestern Canada is characterized by a transition from the Mesozoic-Cenozoic Cordilleran orogen to the Archean-Proterozoic craton, making this region an excellent natural laboratory to study episodic growth of continents. Here, we explore regional lithospheric structure using fundamental Rayleigh waves recorded by broadband seismometers from CNSN and various temporary networks (ATSN, CRANE, USArray) from 2006 to the present. Using a two-station cross-correlation technique, we extract phase velocities at periods ranging from 20 s to more than 200 s. Phase velocities for the region west of the deformation front are significantly lower than those of the region to the east, especially at periods of 30-200 s, reflecting strong lateral variations in lithosphere structure due to thermal and compositional differences. Our analysis is particularly focused on characterizing the lithosphere-asthenosphere boundary (LAB) across the transition, and identifying small-scale convection associated with the edge of the craton. Detailed 3-D lithospheric structural models developed in the near feature will shed more new lights on the transition from backarc to craton lithosphere and their geodynamical interactions.

Bao, X.; Eaton, D. W.

2013-12-01

335

Thermo-Active Behavior of Ethylene-Vinyl Acetate | Multiwall Carbon Nanotube Composites Examined by in Situ near-Edge X-ray Absorption Fine-Structure Spectroscopy  

PubMed Central

NEXAFS spectroscopy was used to investigate the temperature dependence of thermally active ethylene-vinyl acetate | multiwall carbon nanotube (EVA|MWCNT) films. The data shows systematic variations of intensities with increasing temperature. Molecular orbital assignment of interplaying intensities identified the 1s ? ?*C=C and 1s ? ?*C=O transitions as the main actors during temperature variation. Furthermore, enhanced near-edge interplay was observed in prestrained composites. Because macroscopic observations confirmed enhanced thermal-mechanical actuation in prestrained composites, our findings suggest that the interplay of C=C and C=O ? orbitals may be instrumental to actuation. PMID:24803975

2015-01-01

336

The isotopic composition of uranium and lead in Allende inclusions and meteoritic phosphates  

NASA Technical Reports Server (NTRS)

The isotopic compositions of uranium and lead in Ca-Al-rich inclusions from the Allende chondrite and in whitlockite from the St. Severin chondrite and the Angra dos Reis achondrite are reported. Isoptopic analysis of acid soluble fractions of the Allende inclusions and the meteoritic whitlockite, which show isotopic anomalies in other elements, reveals U-235/U-238 ratios from 1/137.6 to 1/138.3, within 20 per mil of normal terrestrial U abundances. The Pb isotopic compositions of five coarse-grained Allende inclusions give a mean Pb-207/Pb-206 model age of 4.559 + or - 0.015 AE, in agreement with the U results. Pb isotope ratios of two fine-grained inclusions and a coarse-grained inclusion with strong mass fractionation and some nonlinear isotopic anomalies indicate that the U-Pb systems of these inclusions have evolved differently from the rest of Allende. Th/U abundance ratios in the Allende inclusions and meteoritic phosphate are found to range from 3.8 to 96, presumably indicating an optimal case for Cm/U fractionation, although the normal U concentrations do not support claims of abundant live Cm-247 or Cm-247/U-238 fractionation at the time of meteorite formation, in contrast to previous results. A limiting Cm-247/U-235 ratio of 0.004 at the time of meteorite formation is calculated which implies that the last major r process contribution at the protosolar nebula was approximately 100 million years prior to Al-26 formation and injection.

Chen, J. H.; Wasserburg, G. J.

1981-01-01

337

Leading-Edge Votex-System Details Obtained on F-106B Aircraft Using a Rotating Vapor Screen and Surface Techniques  

NASA Technical Reports Server (NTRS)

A flight research program to study the flow structure and separated-flow origins over an F-106B aircraft wing is described. The flight parameters presented include Mach numbers from 0.26 to 0.81, angles of attack from 8.5 deg to 22.5 deg, Reynolds numbers from 22.6 x 10(exp 6) to 57.3 x 10(exp 6) and load factors from 0.9 to 3.9 times the acceleration due to gravity. Techniques for vapor screens, image enhancement, photogrammetry, and computer graphics are integrated to analyze vortex-flow systems. Emphasis is placed on the development and application of the techniques. The spatial location of vortex cores and their tracks over the wing are derived from the analysis. Multiple vortices are observed and are likely attributed to small surface distortions in the wing leading-edge region. A major thrust is to correlate locations of reattachment lines obtained from the off-surface (vapor-screen) observations with those obtained from on-surface oil-flow patterns and pressure-port data. Applying vapor-screen image data to approximate reattachment lines is experimental, but depending on the angle of attack, the agreement with oil-flow results is generally good. Although surface pressure-port data are limited, the vapor-screen data indicate reattachment point occurrences consistent with the available data.

Lamar, John E.; Brandon, Jay; Stacy, Kathryn; Johnson, Thomas D., Jr.; Severance, Kurt; Childers, Brooks A.

1993-01-01

338

In-flight leading-edge extension vortex flow-field survey measurements on a F-18 aircraft at high angle of attack  

NASA Technical Reports Server (NTRS)

Flow-field measurements on the leading-edge extension (LEX) of the F-18 High Alpha Research Vehicle (HARV) were obtained using a rotating rake with 16 hemispherical-tipped five-hole probes. Detailed pressure, velocity, and flow direction data were obtained through the LEX vortex core. Data were gathered during 1-g quasi-stabilized flight conditions at angles of attack alpha from 10 degrees to 52 degrees and at Reynolds numbers based on mean aerodynamic cord up to 16 x 10(exp 6). Normalized dynamic pressures and crossflow velocities clearly showed the primary vortex above the LEX and formation of a secondary vortex at higher angles of attack. The vortex was characterized by a ring of high dynamic pressure surrounding a region of low dynamic pressure at the vortex core center. The vortex core, subcore diameter, and vertical location of the core above the LEX increased with angle of attack. Minimum values for static pressure were obtained in the vortex subcore and decreased nearly linearly with increasing angle of attack until vortex breakdown. Rake-measured static pressures were consistent with previously documented surface pressures and showed good agreement with flow visualization flight test results. Comparison of the LEX vortex flight test data to computational solutions at alpha approximately equals 19 degrees and 30 degrees showed fair correlation.

Richwine, David M.; Fisher, David F.

1992-01-01

339

New type of piezo-damping epoxy-matrix composites with multi-walled carbon nanotubes and lead zirconate titanate  

Microsoft Academic Search

A new type of rigid piezo-damping epoxy-matrix composites containing multi-walled carbon nanotubes (CNT) and piezoelectric lead zirconate titanate (PZT) was prepared, and the electrical and the damping properties were investigated. Dynamic mechanical thermal analysis reveals that the loss factors of the composites were improved by incorporation of PZT and CNT under the concentration above a critical electrical percolation. Based on

Sheng Tian; Fangjin Cui; Xiaodong Wang

2008-01-01

340

Composite lead for conducting an electric current between 75--80 K and 4. 5 K temperatures  

SciTech Connect

This technology can be used to manufacture an article which allows the user to bridge and join electrical circuits which are functional at room temperatures (300K) or helium temperatures (4.5 K). The composite lead article provides multiple electrical leads and is capable of conducting 100 amperes or more of electrical current between the different temperature regions, it minimizes the heat conduction and reduces heating in the electrically conductive leads. The composite lead spaced co-axially from one another, each element being composed of at least one high transition temperature superconductor. The co-axially spaced superconductive elements are encapsulated by an electrically non-conductive filler material covering. This filler material is resistant to the effects of temperature differences from about 75--80 K to about 4.5 K.

McConeghy, R.J.; Negm, Y.; Zimmerman, O.; Powers, R.E.; Kaplan, A.

1992-01-01

341

Isotopic composition of lead in moss and soil of the European Arctic  

NASA Astrophysics Data System (ADS)

Moss, O and C horizons of podzols, mainly forming complementary sample triplets, as well as filter residues of molten snow from northern Norway, northern Finland and NW Russia have been analyzed by TIMS for their Pb isotopic composition in order to study the impacts of local geogenic/anthropogenic sources and long range atmospheric transport on the Pb balance in the European Arctic. Samples were taken along two N-S transects covering an area of ˜188.000 km 2, including both pristine environments in the W and certain regions towards the E severely contaminated by heavy metal emissions originating from large nickel smelters and processing plants in NW Russia. The lead in moss and O horizon samples clearly reflects atmospheric deposition, as it displays overall uniform isotope ratios and is decoupled from the geogenic background, i.e. the underlying mineral soils in the C horizon. Moss and O horizon samples from the eastern N-S transect are isotopically indistinguishable from those taken along the western transect but their Pb concentrations tend to be ˜2 times higher. This points to considerable contamination originating from the nearby Russian industrial and urban centers. However, isotopic signals of emissions from individual industrial point sources cannot be unambiguously identified because they lack characteristic isotope signatures. Pb derived from gasoline additives is swamped by Pb from other sources and can also be excluded as a major contributor to the environmental Pb in the European Arctic. Overall, the Pb isotopic signatures of moss and O horizon overlap values recorded in atmospheric lead all over central and southern Europe, more than 2000 km south of the study area. This may be taken as indicating continent-wide mixing of Pb derived from similar sources in the atmosphere or as reflecting economic globalization, or both. O horizon samples, which accumulate lead over 20-30 yr, conform to a distinct Pb isotope reference line in 207Pb/ 206Pb vs. 208Pb/ 206Pb space ("European Standard Pollution," ESP) defined by atmospheric Pb considered to be representative for the technical civilization in Europe. Conversely, the Arctic moss samples with a lifetime of <3 yr display a deviating linear trend reflecting a recent change of atmospheric input towards significantly more radiogenic Pb derived from Mississippi Valley-type ores in the U.S., fully compatible with signatures found in epiphytic lichens from Canada, but also in Pb from urban waste incinerators in central Europe. Considering the elevated Pb concentrations in moss collected along the eastern N-S transect, this congruence indicates that the Pb in moss of the European Arctic most probably originates from the nearby Russian centers of urbanization and not from transatlantic transport. We therefore suspect imported industrial goods and their subsequent attrition to be a more plausible explanation for the appearance of MVT lead in Europe.

Haack, U.; Kienholz, B.; Reimann, C.; Schneider, J.; Stumpfl, E. F.

2004-06-01

342

Detection of Subsurface Material Separation in Shuttle Orbiter Slip-Side Joggle Region of the Wing Leading Edge using Infrared Imaging Data from Arc Jet Tests  

NASA Technical Reports Server (NTRS)

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.

Daryabeigi, Kamran; Walker, Sandra P.

2009-01-01

343

Kinematic Coupling in the Miocene at the leading edge of the Alpine-Carpathian wedge (Waschberg-Zdanice Unit, Austria-Czech Republic)  

NASA Astrophysics Data System (ADS)

Previous studies conducted in the framework of the project KARPATIAN TECTONICS on the front of the Alpine-Carpathian wedge based on industrial 2D and 3D seismic datasets, borehole and outcrop data have confirmed and characterized the complex deformation of both the autochthonous European foreland and the thrust nappes at the transition zone between the Eastern Alps and the Carpathians. The focus on the timing and exact sequence of thrusting within the nappe pile is further refined by detailed mapping of tectonic elements in 3D seismic volumes. Interpretation focuses on the central part of the Waschberg-Zdanice Unit in Lower Austria near the border to the Czech Republic. The timing of Lower Miocene fault activation is accurately constrained by a high stratigraphic resolution within the time between the Eggenburgian (20.5 Ma) and Lower Badenian stage (~ 16.0 Ma). We identify several distinct phases of in-sequence thrusting at the leading edge of the orogen, as well as cross-cutting relationships indicating out-of sequence thrusting in the hinterland. This sequence of deformations is related to stress coupling across the floor thrust of the wedge, and deformation within the allochthon. As a first stage the European foreland is deformed in front of the Waschberg-Zdanice fold-thrust units, including sinistral reactivation Variscan strike-slip faults such as the Diendorf fault system concurrent with thrusting in the Molasse Unit. There, extensional basins form at releasing bends of such faults during the Eggenburgian (~ 20 Ma). Thin-skinned thrusting in the frontal parts of the Alpine-Carpathian nappes occur in at least two distinct stages dated by Eggenburgian-Ottnangian (~ 18 Ma) and Karpatian (~17 Ma) growth strata. Ottnangian (~ 18 Ma) blind thrusting is dated by growth strata overlying a growth trishear fold. Out-of-sequence thrusts of surface-breaking faults cutting the growth strata panel in the backlimb of the growth trishear fold are active in the early Badenian. Such thrusts occur in both, the Waschberg-Zdanice Unit and the allochthonous Alpine-Carpathian units (Penninic Flysch nappes and Northern Calcareous Alps) in the area of the present Vienna Basin. Directions of thrusting and fault kinematics are very well constrained by 3D seismic mapping and visualization as well as by outcrop data. Part of the Lower Miocene thrusts are reactivated as normal faults leading to the formation of half-grabens and listric normal faults bounding Neogene basins with Badenian to Pannonian fill. Thus, the termination of thrusting is dated by subsequent extension starting in the Badenian to Pannonian as dated by growth strata (Middle to Upper Miocene, ~ 16.0 to 10 Ma).

Zámolyi, A.; Beidinger, A.; Decker, K.; Hölzel, M.; Hoprich, M.; Strauss, P.; Wagreich, M.

2009-04-01

344

Isotopic composition of lead in oceanic basalt and its implication to mantle evolution  

Microsoft Academic Search

New data are given in this report for (1) Pb isotopic compositions and U, Th, and Pb concentrations of basalts from the island of Hawaii; (2) redetermined Pb isotopic compositions of some abyssal tholeiites; and (3) U, Th, and Pb concentrations of altered and fresh abyssal basalts, and basalt genesis and mantle evolution are discussed. The Th\\/U ratios of abyssal

Mitsunobu Tatsumoto

1978-01-01

345

The lead susceptibility of fuels and its dependence on the chemical composition  

NASA Technical Reports Server (NTRS)

The fact that by the use of tetraethyl lead a number of otherwise unsuitable fuels could be made to meet engine requirements was not sufficiently appreciated. While use of tetraethyl lead is limited, the addition of special leaded fuels that increase the octane number is a requirement for many fuels. In this connection, the extent to which the action of tetraethyl lead through the addition of knock-resistant hydrocarbons to the base gasoline is influenced, is quite important. To the elucidation of this problem and of the storage stability of leaded fuels, the present report is dedicated.

Widmaier, O

1940-01-01

346

High-strain actuation of lead-free perovskites : compositional effects, phenomenology and mechanism  

E-print Network

An experimental study was carried out to map the compositional dependence of electromechanical behavior and ferroelectric phase stability in the barium, zirconium-codoped sodium bismuth titanate (BNBZT) system for barium ...

Soukhojak, Andrey N. (Andrey Nestorovich), 1972-

2002-01-01

347

Tailoring of unipolar strain in lead-free piezoelectrics using the ceramic/ceramic composite approach  

SciTech Connect

The electric-field-induced strain response mechanism in a polycrystalline ceramic/ceramic composite of relaxor and ferroelectric materials has been studied using in situ high-energy x-ray diffraction. The addition of ferroelectric phase material in the relaxor matrix has produced a system where a small volume fraction behaves independently of the bulk under an applied electric field. Inter- and intra-grain models of the strain mechanism in the composite material consistent with the diffraction data have been proposed. The results show that such ceramic/ceramic composite microstructure has the potential for tailoring properties of future piezoelectric materials over a wider range than is possible in uniform compositions.

Khansur, Neamul H.; Daniels, John E. [School of Materials Science and Engineering, University of New South Wales, NSW 2052 (Australia); Groh, Claudia; Jo, Wook; Webber, Kyle G. [Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Reinhard, Christina [Diamond Light Source, Beamline I12 JEEP, Didcot, Oxfordshire OX11 0DE (United Kingdom); Kimpton, Justin A. [The Australian Synchrotron, Clayton, Victoria 3168 (Australia)

2014-03-28

348

Determination of the age of the earth from the isotopic composition of meteoritic lead  

Microsoft Academic Search

Summary  Under the assumption thata) the isotopic constitution of lead at the time of the formation of the lithosphére is represented by the figures found for\\u000a lead from the troilite phase of the Cafion-Diablo meteorite [Pat 53] andb) the majority of tertiary lead ores analysed for isotopic constitution has been formed according to the simple model of primary\\u000a origin (equ. 3),

F. G. Houtermans

1953-01-01

349

Effects of Elastic Edge Restraints and Initial Prestress on the Buckling Response of Compression-Loaded Composite Panels  

NASA Technical Reports Server (NTRS)

A parametric study of the effects of test-fixture-induced initial prestress and elastic edge restraints on the prebuckling and buckling responses of a compression-loaded, quasi-isotropic curved panel is presented. The numerical results were obtained by using a geometrically nonlinear finite element analysis code with high-fidelity models. The results presented show that a wide range of prebuckling and buckling behavior can be obtained by varying parameters that represent circumferential loaded-edge restraint and rotational unloaded-edge restraint provided by a test fixture and that represent the mismatch in specimen and test-fixture radii of curvature. For a certain range of parameters, the panels exhibit substantial nonlinear prebuckling deformations that yield buckling loads nearly twice the corresponding buckling load predicted by a traditional linear bifurcation buckling analysis for shallow curved panels. In contrast, the results show another range of parameters exist for which the nonlinear prebuckling deformations either do not exist or are relatively benign, and the panels exhibit buckling loads that are nearly equal to the corresponding linear bifurcation buckling load. Overall, the results should also be of particular interest to scientists, engineers, and designers involved in simulating flight-hardware boundary conditions in structural verification and certification tests, involved in validating structural analysis tools, and interested in tailoring buckling performance.

Hilburger, Mark W.; Nemeth, Michael P.; Riddick, Jaret C.; Thornburgh, Robert P.

2004-01-01

350

Wind-tunnel investigation of effects of wing-leading-edge modifications on the high angle-of-attack characteristics of a T-tail low-wing general-aviation aircraft  

NASA Technical Reports Server (NTRS)

Exploratory tests have been conducted in the NASA-Langley Research Center's 12-Foot Low-Speed wind Tunnel to evaluate the application of wing-leading-edge devices on the stall-departure and spin resistance characteristics of a 1/6-scale model of a T-tail general-aviation aircraft. The model was force tested with an internal strain-gauge balance to obtain aerodynamic data on the complete configuration and with a separate wing balance to obtain aerodynamic data on the outer portion of the wing. The addition of the outboard leading-edge droop eliminated the abrupt stall of the windtip and maintained or increased the resultant-force coefficient up to about alpha = 32 degrees. This change in slope of the resultant-force coefficient curve with angle of attack has been shown to be important for eliminating autorotation and for providing spin resistance.

White, E. R.

1982-01-01

351

Investigation of the Stability and Control Characteristics of a 1/20-Scale Model of the Consolidated Vultee XB-53 Airplane with a Full-Span Leading-Edge Slat in the Langley Free-Flight Tunnel  

NASA Technical Reports Server (NTRS)

An investigation of the low-speed; power-off stability and control characteristics of a 1/20-scale model of the Consolidated Vultee XB-53 airplane equipped with full-span leading-edge slats has been conducted in the Langley free-flight tunnel. In this investigation it was found that the-full-span leading-edge slat gave about the same maximum lift coefficient as was obtained with the outboard single slotted flap and inboard slat. The stability and control characteristics were greatly improved except near the stall where the characteristics with the full-span slat were considered unsatisfactory because of a loss of directional stability and a slight nosing-up tendency.

Bennett, Charles V.

1947-01-01

352

Mechanical and dielectric characterization of lead zirconate titanate(PZT)/polyurethane(PU) thin film composite for energy harvesting  

NASA Astrophysics Data System (ADS)

The Lead Zirconate titanate (PZT) ceramic is known by its piezoelectric feature, but also by its stiffness, the use of a composite based on a polyurethane (PU) matrix charged by a piezoelectric material, enable to generate a large deformation of the material, therefore harvesting more energy. This new material will provide a competitive alternative and low cost manufacturing technology of autonomous systems (smart clothes, car seat, boat sail, flag ...). A thin film of the PZT/PU composite was prepared using up to 80 vol. % of ceramic. Due to the dielectric nature of the PZT, inclusions of this one in a PU matrix raises the permittivity of the composite, on other hand this latter seems to decline at high frequencies.

Aboubakr, S.; Rguiti, M.; Hajjaji, A.; Eddiai, A.; Courtois, C.; d'Astorg, S.

2014-04-01

353

Synthesis of Current-Voltage Characteristics of 670 GHz Gyrotron Magnetron Injection Gun and Calculation of the Helical Electron Beam Parameters at the Leading Edge of a High-Voltage Pulse  

NASA Astrophysics Data System (ADS)

A method of synthesis of current-voltage characteristics (CVC) and calculation of the parameters of a helical electron beam (HEB) at the leading edge of the accelerating voltage pulse for gyrotron electron guns is proposed. These data can be used for a study of the gyrotron startup scenario with the mode competition taken into account. As an example, the results of calculations for a pulsed gyrotron with a frequency of 670 GHz are presented.

Manuilov, V. N.; Glyavin, M. Yu.

2013-02-01

354

Glass formation and crystallization of high lead content PbO-B2O3 compositions  

NASA Technical Reports Server (NTRS)

The glass-forming and undercooling ability of PbO-B2O3 melts in the 2PbO.B2O3 to 4PbO.B2O3 composition range were studied. The glass formation propensities were investigated as a function of cooling rate and sample mass. A qualitative investigation of the crystallization process(es) preventing glass formation was made, and it was concluded that under normal circumstances heterogeneous nucleation was the common occurrence. Hence, it was concluded that such compositions are prime candidates for containerless experiments aboard the Space Shuttle.

Weinberg, Michael C.; Smith, Gary L.; Neilson, George F.

1986-01-01

355

Asymptotic expressions for turbulent burning velocity at the leading edge of a premixed flame brush and their validation by published measurement data  

NASA Astrophysics Data System (ADS)

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/?f at low turbulence, with both normalized by those of the reference cases. ?f 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 burning velocity is shown to increase as the flamelet thickness, ?f, decreases at a high pressure, for an equivalence ratio slightly rich or close to stoichiometric and for mixture of a high H2 fraction. Two constants involved are C to scale turbulent diffusivity as a product of turbulent intensity and characteristic length scale and Cs to relate ?f with the mean effective Lm. L m = (D m u / SL u 0) is the scale of exponential decay at the LE of an unstretched laminar flame. The combined constant, KC/Cs, is adjusted to match measured turbulent burning velocities at low turbulence in each of the eight different experimental setups. All measured S T / SL u 0 values follow the line, KDtu/Dmu + 1, at low turbulent intensities and show bending below the line due to positive mean curvature and broadened flamelet thickness at high turbulent intensities. Further work is required to determine the constants, Cs and K, and the factor, (L m / Lm * - L m (? ? n) f), that is responsible for bending in different conditions of laminar flamelet and incoming turbulence.

Lee, Jaeseo; Lee, Gwang G.; Huh, Kang Y.

2014-12-01

356

Effect of sulfur isotopic composition of zinc and lead sulfides on the E. M. F. of electrochemical cells  

SciTech Connect

A new effect is reported in which unexpectedly large voltages are produced by electrochemical cells containing sulfides at natural isotopic abundance levels. Room temperature experiments were undertaken to determine whether electrochemical cells employing silver bromide and silver beta alumina as solid electrolytes would be sufficiently sensitive to detect small variations in sulfur isotopic composition for zinc and lead sulfides. Voltages obtained for silver bromide cells tended to increase progressively over at least 20 days, and increased in a regular fashion with increasing differences in isotopic composition between charges. Voltages exceeding 150 mV were obtained for /sup delta/S/sup 3,4/ differences up to 85 per mil for zinc sulfide, but reached only about 20 mV for lead sulfide. Silver beta alumina cells with opposing zinc and lead sulfide charges yielded larger voltages and E.M.F. minimum corresponding to a +8(/plus minus/2) per mil difference. This value shows reasonable agreement with interpolated 20/degrees/C equilibrium values of between +7.5 to +9.8 obtained from the literature. Matured silver bromide cells with opposed zinc and lead sulfide charges behaved similarly but yielded lower voltages. Silver concentration cells of the opposed type are thus able to detect isotopic equilibrium and this will permit calibration of sulfur isotope thermometers down to unexpectedly low temperatures.

Lusk, J.; Krouse, H.R.; Batts, B.D.

1988-03-01

357

Lead Isotopic Compositions of the Endeavour Sulfides, Juan de Fuca Ridge  

Microsoft Academic Search

32 sulfide samples from the main structures of the Endeavour vent field, Juan de Fuca Ridge, were analyzed for their Pb isotope composition. The samples were collected from 6 main vent fields between 1985 and 2005 and encompass a strike length of more than 15 km along the ridge crest. The sulfides are typical of black smoker deposits on sediment-starved

F. Labonte; M. D. Hannington; B. L. Cousens; J. Blenkinsop; J. B. Gill; D. S. Kelley; M. D. Lilley; J. R. Delaney

2006-01-01

358

Synthesis and Thermoelectric Properties of Compositional-Modulated Lead Telluride-Bismuth Telluride Nanowire  

E-print Network

of the nanowire hetero- structures has been investigated in hot pressed nanocomposite pellets. Measurements for waste heat recovery1,2 and solid-state cooling3,4 with improved stability and reliability.5 The thermo of composition (ratio between PbTe and Bi2Te3) has been investigated in hot pressed nanocomposite pellets

Ruan, Xiulin

359

SPM investigations of phase distribution in lead phthalocyanine-perylene derivative composite films  

Microsoft Academic Search

During last years organic semiconductors found practical application in organic solar cells and organic LEDs (1). One possible way to advance the electronic properties of organic semiconductor materials is a doping by another organic or inorganic material (2). The arrangement of one material in matrix of another one is important characteristic that significantly influence on electronic properties of composite. In

B. A. Gribkov; V. L. Mironov; S. V. Gaponov; A. V. Misevich; N. Novgorod

360

Alternative Processing Method Leads to Stronger Sapphire-Reinforced Alumina Composites  

NASA Technical Reports Server (NTRS)

The development of advanced engines for aerospace applications depends on the availability of strong, tough materials that can withstand increasingly higher temperatures under oxidizing conditions. The need for such materials led to the study of an oxide-based composite composed of an alumina matrix reinforced with zirconia-coated sapphire fibers. Because the nonbrittle behavior of this system depends on the interface and its ability to prevent fiber-to-matrix bonding and reduce interfacial shear stress, the microstructure of the zirconia must be carefully controlled during both coating application and composite processing. When it was both porous and unstabilized, zirconia (which does not react easily with alumina) was found to be the most effective material tested in reducing interfacial shear strength between the fiber and matrix.

Jaskowiak, Martha H.

1997-01-01

361

Lead Isotopic Compositions of the Endeavour Sulfides, Juan de Fuca Ridge  

NASA Astrophysics Data System (ADS)

32 sulfide samples from the main structures of the Endeavour vent field, Juan de Fuca Ridge, were analyzed for their Pb isotope composition. The samples were collected from 6 main vent fields between 1985 and 2005 and encompass a strike length of more than 15 km along the ridge crest. The sulfides are typical of black smoker deposits on sediment-starved mid-ocean ridges. Pb isotope compositions of the massive sulfides within the six hydrothermal fields vary within narrow ranges, with 206Pb/204Pb = 18.58 18.75, 207Pb/204Pb = 15.45 15.53 and 208Pb/204Pb = 37.84 38.10. A geographic trend is observed, with the lower Pb ratios restricted mostly to the northern part of the segment (Salty Dawg, Sasquatch and High Rise fields), and the higher Pb ratios restricted mostly to the southern part of the segment (Main Endeavour, Clam Bed and Mothra fields). Variations within individual fields are much smaller than those between fields, and variation within individual sulfide structures is within the uncertainty of the measurements. Therefore, it is unlikely that the ranges of Pb isotope compositions along the length of the segment reflect remobilization, replacement, and recrystallization of sulfides, as suggested for the observed Pb isotope variability in some large seafloor sulfide deposits. Instead, the differences in isotopic compositions from north to south are interpreted to reflect differences in the source rocks exposed to hydrothermal circulation of fluids below the seafloor. Possible sources of the somewhat more radiogenic Pb may be small amounts of buried sediment, either from turbidites or from hemipelagic sediment. This possibility is supported by high concentrations of CH4 and NHC4 found in the high-temperature vent fluids at the Main Endeavour Field, which are interpreted to reflect subseafloor interaction between hydrothermal fluids and organic material in buried sediments. However, the majority of the samples fall below and are approximately parallel to the reference line for the northern hemisphere mantle reservoirs in plots of 206Pb/204Pb versus 207Pb/204Pb and 208Pb/204Pb, suggesting relatively little contribution from buried sediment compared to deposits at sedimented ridges. Alternatively, systematic differences in the Pb isotope compositions of sulfides along the length of the ridge segment could be attributed to variable leaching of previously altered basaltic crust or interaction between hydrothermal fluids and enriched Mid-Ocean Ridge Basalts (MORB) sources.

Labonte, F.; Hannington, M. D.; Cousens, B. L.; Blenkinsop, J.; Gill, J. B.; Kelley, D. S.; Lilley, M. D.; Delaney, J. R.

2006-12-01

362

Isotopic composition of epiphytic lichens as a tracer of the sources of atmospheric lead emissions in southern Quebec, Canada  

SciTech Connect

Lead isotopic data are reported for epiphytic lichens, vegetation samples, and lacustrine sediments collected in the boreal forest of Quebec between 47{degrees} and 55{degrees}N, and along the St. Lawrence Valley between 45{degrees} to 48{degrees}N. Lichens located up to 500 km north of Noranda (48{degrees}N) record a significant input is not apparent beyond 53{degrees}N where only the isotopic signal typical of Canadian aerosols is recorded. Lichens along the St. Lawrence Valley show evidences for a dominant input from U.S. sources. The lead isotopic composition of lichens allow quantitative monitoring of the sources of atmospheric Pb. However, their slow metabolism and their unknown age detract from recording the Pb signal on short and precise timescales. Spruce needles have isotopic compositions undistinguishable from that of lichens; this reflects integration of the atmospheric Pb signal over a comparable time span, a result confirmed by the lead isotopic record in lacustrine sediments. Vegetation samples such as spruce bark, spruce wood, and decidous tree leaves are more radiogenic than lichens from the same site. This may reflect mixing of radiogenic Pb metabolized from soil solutions through the root system with atmospheric Pb. 37 refs., 4 figs.

Carignan, J.; Gariepy, C. [Universite du Quebec, Montreal (Canada)] [Universite du Quebec, Montreal (Canada)

1995-11-01

363

A state space finite element for laminated composites with free edges and subjected to transverse and in-plane loads  

E-print Network

, China c School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, Sydney, NSW transfer 1. Introduction The rapid increase of the industrial use of structures made of advanced composite that the prediction of their behavior, including the behavior of material interfaces, should be based on a three

Qin, Qinghua

364

Near-Edge X-ray Absorption Fine Structure Studies of Electrospun Poly(dimethylsiloxane)/Poly (methyl methacrylate)/Multiwall Carbon Nanotube Composites  

PubMed Central

This work describes the near conduction band edge structure of electrospun mats of MWCNT-PDMS-PMMA by near edge X-Ray absorption fine structure (NEXAFS) spectroscopy. Effects of adding nanofillers of different sizes were addressed. Despite observed morphological variations and inhomogeneous carbon nanotube distribution, spun mats appeared homogeneous under NEXAFS analysis. Spectra revealed differences in emissions from glancing and normal spectra; which may evidence phase separation within the bulk of the micron-size fibers. Further, dichroic ratios show polymer chains did not align, even in the presence of nanofillers. Addition of nanofillers affected emissions in the C-H, C=O and C-C regimes, suggesting their involvement in interfacial matrix-carbon nanotube bonding. Spectral differences at glancing angles between pristine and composite mats suggest that geometric conformational configurations are taking place between polymeric chains and carbon nanotubes. These differences appear to be carbon nanotube-dimension dependent, and are promoted upon room temperature mixing and shear flow during electrospinning. CH-? bonding between polymer chains and graphitic walls, as well as H-bonds between impurities in the as-grown CNTs and polymer pendant groups are proposed bonding mechanisms promoting matrix conformation. PMID:24308286

Winter, A. Douglas; Larios, Eduardo; Alamgir, Faisal M.; Jaye, Cherno; Fischer, Daniel; Campo, Eva M.

2014-01-01

365

Helium, argon and lead isotopic composition of volcanics from Santo Antão and Fogo, Cape Verde Islands  

Microsoft Academic Search

Helium, argon and lead isotopic ratios have been determined for volcanics from two of the youngest Cape Verde Islands, Santo Antão and Fogo. Helium isotopic ratios range from radiogenic 4He\\/3He values of 224,000 (3.2 R\\/Ra) to more primitive values of 52,000 (13.8 R\\/Ra), which suggest a contribution from different reservoirs to the magmatism at the Cape Verde Islands. 40Ar\\/36Ar isotopic

Birgitte Printz Christensen; Paul Martin Holm; Albert Jambon; J. Richard Wilson

2001-01-01

366

Enhancing the electrical and thermal stability of metallic fiber-filled polymer composites by adding tin–lead alloy  

Microsoft Academic Search

This article presents a novel way of greatly enhancing the electrical and thermal stability of copper fiber (CuF)-filled acrylonitrile–butadiene–styrene\\u000a (ABS) composites via the incorporation of small amount of tin–lead (Sn–Pb) alloy. It was observed that many fibers are soldered\\u000a together by Sn–Pb, and a continuous CuF\\/Sn–Pb network is formed throughout the ABS matrix. As a result, the percolation concentration\\u000a of

Guozhang Wu; Bingpeng Li; Jiakun Song

367

Optical design of LED edge-lit backlight based on molecular dynamics method using a random/regular composite distribution  

NASA Astrophysics Data System (ADS)

A dot generation scheme for random/regular composite distribution is developed based on the molecular dynamics (MD) method for application in light guide design. This is done by introducing random r-cut values in the force field acting between dots. The results indicated that the developed scheme can effectively randomize a regular distribution by increasing the random component of the r-cut value. In addition, for a composite distribution, in order to obtain a smooth distribution across the random/regular distribution interface, there cannot be a large difference between the expected r-cut value for these two distributions; otherwise, a distinct linear strip will occur. Finally, two practical examples are presented. One randomizes an already optimized dot distribution in a regular arrangement. The other uses a composite distribution generated by the present scheme which is substituted into the optical software to perform the optical optimization. These two examples prove the validity of the present scheme and its efficient application in the optical design of light guides.

Chang, Jee-Gong; Ju, Shin-Pon; Lee, Shin-Chin; Hsieh, Jin-Yuan

2009-12-01

368

Isotopic compositions of bismuth, lead, thallium, and mercury from mini r-processing  

NASA Technical Reports Server (NTRS)

The yields of stable isotopes of Bi, Pb, Tl and Hg as well as yields of Pb-205 are calculated with a parametrized model for 'mini r-processing' in the Ne, O, C-rich zones of explosive burning in massive stars. The Pb isotopic compositions stand out by their comparatively low Pb-207 yields and by the fact that this r-process variant yields Pb-204 quite abundantly. The average Pb-205/Pb-204 yield ratio of 6.1 is the same order of magnitude as yield ratios deduced for s-processing. The Hg from this mini r-process looks like normal solar-system mercury, but with Hg-196 missing and the light s-isotopes A = 198, 199, 200 and 201 depleted (especially the odd-A species).

Heymann, D.; Liffman, K.

1986-01-01

369

Spatial and temporal variation in isotopic composition of atmospheric lead in Norwegian moss  

SciTech Connect

Earlier studies using moss as a biomonitor of pollution have shown that long-range transport is a major source of pollution in Norway. Until now, the origin of these pollutants has been inferred from concentration measurements of various elements in moss and the climatology at each sampling site. Lead isotopes provide an opportunity to identify the sources and to quantify the contribution of each. This preliminary study reports measurements of lead isotopes in moss from selected sites along the full extent of Norway that reveal significant spatial and temporal variations. There are significant north-south trends that differ at coastal and inland sites and differ between sampling periods (1974--1994). These variations reflect the changing contributions from the different source regions as the regulation of pollution from automobiles and industry takes effect. Identifiable sources are the U.K. and possibly France, which is noticeable at coastal sites; western Europe at the southern end; and eastern Europe and Russia influencing the inland and northernmost sites.

Rosman, K.J.R.; Ly, C. [Curtin Univ. of Technology, Perth, Western Australia (Australia). Dept. of Applied Physics] [Curtin Univ. of Technology, Perth, Western Australia (Australia). Dept. of Applied Physics; Steinnes, E. [Norwegian Univ. of Science and Technology, Trondheim (Norway). Dept. of Chemistry] [Norwegian Univ. of Science and Technology, Trondheim (Norway). Dept. of Chemistry

1998-09-01

370

Entrepreneurial Edge  

NSDL National Science Digital Library

Published by the Edward Lowe Foundation, Entrepreneurial Edge Online is the electronic counterpart to the small business training magazine by the same name. Site features beyond selected Entrepreneurial Edge articles include the self-training modules--Business Builders, an Interactive Toolbox of budget, balance sheet, and cash flow calculators, and a list of discussion forums entitled Virtual Network.

371

An experimental investigation of lead zirconate titanate--epoxy-multi-walled carbon nanotube bulk and flexible thick film composites  

NASA Astrophysics Data System (ADS)

Piezoelectric sensors and actuators are needed for a wide range of applications from physiological measurement to industrial monitoring systems. Sensors that can be easily integrated with the host, while maintaining high sensitivity and reliability over a wide range of frequencies are not readily feasible and economical with homogenous piezoelectric materials. It is well known that two-phase piezoelectric-epoxy composites offer several benefits over their single phase counterparts, as the properties of the constituent phases combine to improve the range of applicability. However, the piezoelectric properties of these materials suffer from the electrically insulating properties of the epoxy matrix. The electrical properties of the matrix may be enhanced by including electrically conducting inclusions however, less is known about the mechanisms that drive the changes in these properties. Hence, this experimental investigation of sensor materials builds on the previous work in two-phase piezoelectric composites, where the aims are to understand the roles that specific fabrication parameters and inclusion composition play in determining the piezoelectric and dielectric performance the aforementioned composites. The materials under investigation will be comprised of Lead Zirconate Titanate, Epofix Cold-Setting Embedding Resin and multi-walled carbon nanotubes, i.e. the piezoelectric, epoxy and electrical inclusions respectively. Our work suggests that inclusion of MWCNTs enhances the piezoelectric and dielectric properties with increasing volume fraction below the percolation threshold. This work seeks to understand how the processing parameters: poling temperature, poling type and particle distribution influence the contact resistance, space charge double layer at the piezoelectric and conductor interfaces and electric field intensity at the piezoelectric boundary, which all ultimately dictate the piezoelectric and dielectric performance of the composite materials. Conventional solid oxide mixing, spin coating and deposition techniques will be used to fabricate the bulk and thick films. The piezoelectric and dielectric performance will be determined from the measurement of the piezoelectric strain coefficients, d33 and d31, dielectric constant, impedance and dielectric spectrum, dielectric loss tangent, and capacitance. These measurements will be correlated with inclusion size, shape, distribution, and surface morphology observations obtained from the scanning electron microscope (SEM) and transmission electron microscope (TEM).

Banerjee, Sankha

372

Effect of an iodine-containing additive on the composition, structure, and morphology of chemically deposited lead selenide films  

NASA Astrophysics Data System (ADS)

The effect of an ammonium iodide additive on the elemental and phase compositions, structural parameters, and surface morphology of lead selenide films synthesized by chemical deposition from aqueous solutions has been studied using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis. It has been established that the obtained PbSe films have a multiphase structure. The iodine content of the films is directly proportional to the NH4I concentration in the reaction mixture and increases linearly with an increase in this concentration to 0.25 mol/L. No individual iodine-containing phases have been detected in the film structure. However, the introduction of iodine leads to an increase in the PbSe phase lattice parameter from ˜6.11 to ˜6.16 Å and to a decrease in the crystal grain size to ˜ 20 nm. It has been found that there is a correlation between the grain size, lattice parameter, and ammonium iodide concentration in the reaction mixture, which can be explained by changes in the film growth mechanism at the initial growth steps.

Smirnova, Z. I.; Bakanov, V. M.; Maskaeva, L. N.; Markov, V. F.; Voronin, V. I.

2014-12-01

373

Phosphorus K-edge XANES Spectroscopy of Mineral Standards  

SciTech Connect

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.

E Ingall; J Brandes; J Diaz; M de Jonge; D Paterson; I McNulty; C Elliott; P Northrup

2011-12-31

374

Heat-Transfer Measurements at a Mach Number of 4.95 on Two 60 deg Swept Delta Wings with Blunt Leading Edges and Dihedral Angles of 0 deg and 45 deg  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted to evaluate the heat-transfer characteristics of two 60 deg swept delta wings with cylindrical leading edges of 0.25-inch radii and dihedral angles of 0 deg and 45 deg. The tests were conducted at a Mach number of 4.95 and a stagnation temperature of 400 F. The The test-section unit Reynolds number was varied from 1.95 x 10(exp 6) to 12.24 x 10(exp 6) per foot. The results of the investigation indicated that, in a plane normal to the leading edge, the laminar-flow heat-transfer distribution was in good agreement with two-dimensional blunt-body theory. The stagnation-line heat-transfer level could be predicted from two-dimensional blunt-body theory provided the stagnation-line heat-transfer coefficient was assumed to vary as the cosine of the effective sweep. A comparison of the heating rates to the 0 deg dihedral wing (planform sweep of 60 deg) and the 45 deg dihedral wing (planform sweep of 69.3 deg) with equal panel sweep and panel area indicated that the stagnation-line heat-transfer coefficient for the 45 deg dihedral wing could be as much as 40 percent less than the stagnation-line heat-transfer coefficient for the 0 deg dihedral wing at both equal angles of attack and equal lifts. The laminar-flow heat-transfer rate to both wings outside the vicinity of the stagnation line was essentially equal.

Stainback, P. Calvin

1961-01-01

375

The effects of agriculture and the availability of edge habitat on populations of Helmeted Guineafowl Numida meleagris and on the diversity and composition of associated bird assemblages in KwaZulu-Natal province, South Africa  

Microsoft Academic Search

We investigated the effects of agriculture and the availability of edge habitat on populations of Helmeted Guineafowl Numida meleagris and associated avian diversity and species composition in woodland and grassland biomes in the Midlands of KwaZulu-Natal province, South Africa. Study sites within woodland biome had greater species diversity than those in grassland, whereas adjacent, high-quality, protected habitat in grassland sites,

C. S. Ratcliffe; T. M. Crowe

2001-01-01

376

Study of growth kinetics and depth resolved composition of a-SiNx:H thin films by resonant soft X-ray reflectivity at the Si L2,3-edge  

NASA Astrophysics Data System (ADS)

Angle dependent resonant soft X-ray reflectivity (R-SoXR) measurements in the energy range (82.67-206.7 eV) were performed on PECVD grown amorphous hydrogenated silicon nitride (a-SiNx:H) thin films of different compositions near the Si-L2,3 edge (?100 eV). The compositional difference is reflected in the optical density (?) of the two films. It is demonstrated that R-SoXR can non-destructively distinguish between the compositional variations through the depth of a given thin film, whereby it becomes possible to differentiate between the growth kinetics of the films prepared under different conditions. The compositions determined from R-SoXR, are in qualitative agreement with those determined from Rutherford back scattering (RBS) and elastic recoil detection analysis (ERDA).

Bommali, R. K.; Modi, M. H.; Zhou, S.; Ghosh, S.; Srivastava, P.

2014-06-01

377

Leading Edge Regulatory RNAs in Bacteria  

E-print Network

expression in cis, small RNAs that bind to proteins or base pair with target RNAs, and CRISPR RNAs, a recently discovered group of RNA regulators, known as the CRISPR (clustered regularly interspaced short palindromic repeats) RNAs, contains short regions of homology to bacteriophage and plasmid sequences. CRISPR

Storz, Gisela

378

Leading Edge Measuring and Modeling Apoptosis  

E-print Network

) or ionizing radiation, oncogene activation, toxin exposure, etc. (Kaufmann and Earnshaw, 2000). Extrinsic.03.002 Cell death plays an essential role in the development of tissues and organisms, the etiology of disease- vival and prodeath signals to control the fates of normal and diseased cells remain poorly understood

Gauthier, Eric

379

Leading Edge Timescales of Genetic and Epigenetic  

E-print Network

Divinity Avenue, Cambridge, MA 02138, USA 3 Department of Molecular and Microbial Systems, K that are independent of selective pressure. However, recent findings suggest that organisms have evolved mechanisms of a given phenotype to match the variability of the acting selective pressure. Although these observations

380

Women Principals Leading Learning at "Poverty's Edge"  

ERIC Educational Resources Information Center

The author profiles two women principals of color who have successfully enhanced student learning in high-poverty schools. In their leadership narratives, the principals address how the complexity of poverty affects their work, how they affirm the worth and dignity of all, how they influence beliefs and attitudes of staff, why they think their…

Lyman, Linda L.

2008-01-01

381

The Leading Edge: Enduring a Campus Crisis  

ERIC Educational Resources Information Center

On June 2003, the University of North Carolina at Chapel Hill (UNC) faced a frightening crisis when an employee was diagnosed with Severe Acute Respiratory Syndrome (SARS). In this article, the author looks back and identifies four factors that enabled the university to navigate this crisis. These factors were: (1) leadership at every level; (2)…

Moeser, James

2003-01-01

382

Leading Edge Pluripotency and Cellular Reprogramming  

E-print Network

reprogramming of somatic cells to induced pluripotent stem cells by ectopic expression of defined transcription at various embryonic and postnatal stages, stem cells are characterized by self-renewal and the capacity explanted in tissue culture, the teratocarcinoma cells generated embryonal carcinoma cells, demonstrating

Saha, Krishanu

383

Leading Edge The Molecular and Systems  

E-print Network

) that the brain has two major types of memory: explicit (declarative) memory, for facts and events, people, places--implicit memory does not require conscious awareness and relies mostly on other brain systems: namely. We will then consider briefly the mechanisms of implicit memory in the mammalian brain. From there

Dudai, Yadin

384

CELL BIOLOGY: Smurfing at the Leading Edge  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. Cell biologists are only now beginning to unravel how cells maintain their polarity and how this polarity contributes to cell migration. In their Perspective, Jaffe and Hall discuss new research (Wang et al.) describing how ubiquitination and degradation of Rho GTPase (which is an important regulator of the actin cytoskeleton) results in spatial restriction of Rho at the rear of the cell, an essential step in cellular migration.

Aron B. Jaffe (University College London; MRC Laboratory for Molecular Cell Biology and Cell Biology Unit)

2003-12-05

385

Composites  

NSDL National Science Digital Library

In this activity, learners explore how composites work by creating and testing their own composite for an imaginary company. This activity shows learners that composites are simply materials that are made up of two or more visibly distinct substances. Use this activity to talk about how composites are everywhere in our lives.

Research, Cornell C.

2003-01-01

386

Sol-gel composite coatings as anti-corrosion barrier for structural materials of lead-bismuth eutectic cooled fast reactor  

NASA Astrophysics Data System (ADS)

In order to protect the structural components of lead-bismuth eutectic (LBE) cooled fast breeder reactors (FBRs) from liquid metal corrosion, advanced aluminum-yttrium nano- and micro-composite coatings were developed using an improved sol-gel process, which includes dipping specimens in a Y-added sol-gel solution dispersed with ultrafine ?-Al2O3 powders prepared by mechanical milling. Scanning electron microscopy (SEM) and field emission electron probe microprobe analyzer (FE-EPMA) analyses revealed that the coatings are composed of alumina with high density. Accelerated corrosion tests were conducted on coated specimens in liquid LBE at 650 °C under dynamic conditions. After the corrosion tests, no cracking, spallation, erosion and liquid metal (e.g., lead) penetration occurred to the coatings, indicating that the coatings possess an enhanced dynamic LBE corrosion resistance. The superior LBE corrosion resistance is due to the presence of the nano-structured composite particles integrated into the coatings and the addition of trace amount of yttrium. Severe erosion and penetration of liquid Pb occurred to the Al2O3 nano- and micro-composite coatings. After the corrosion tests, no cracking, spallation, erosion and liquid metal (e.g., lead) penetration occurred to the newly-developed aluminum-yttrium nano- and micro-composite coatings, indicating that the coatings possess an enhanced dynamic LBE corrosion resistance. Therefore we can conclude that the coatings possess an enhanced dynamic LBE corrosion resistance under the experimental conditions chosen here. It is a way to protect the structural materials of LBE cooled FBRs from liquid metal corrosion. The much improved corrosion resistance of aluminum-yttrium nano- and micro-composite coatings, relative to Al2O3 nano- and micro-composite coatings, is due to the much higher density and the significantly superior high temperature strength resulting from using of finer Al2O3 seeding particles and adding trace amount of yttrium.

Kasada, Ryuta; Dou, Peng

2013-09-01

387

Property and Microstructural Characterization of Diboride Composites for High Temperature Aerospace Applications  

NASA Technical Reports Server (NTRS)

Previous work on refractory diboride composites has shown these systems to have potential for use in high temperature leading edge applications for reusable reentry vehicles. These composites, based on compositions of HfB2 or ZrB2 with SiC particulate reinforcements, have shown good oxidation resistance in reentry environments. In this work we are investigating the effects of composition and microstructure on properties. Preliminary studies of composite mechanical properties and oxidation behavior will be discussed.

Gusman, Michael I.; Stackpoole, Mairead; Ellerby, Donald T.; Johnson, Sylvia M.; Arnold, Jim (Technical Monitor)

2001-01-01

388

Materials testing and development of functionally graded composite fuel cladding and piping for the Lead-Bismuth cooled nuclear reactor  

E-print Network

This study has extended the development of an exciting technology which promises to enable the Pb-Bi eutectic cooled reactors to operate at temperatures up to 650-700°C. This new technology is a functionally graded composite ...

Fray, Elliott Shepard

2013-01-01

389

Discovery's Edge  

NSDL National Science Digital Library

The Mayo Clinic is one of the most well-respected medical facilities in the world, so it makes sense for them to have a great online publication to celebrate their work. Designed as a general interest publication, Discovery's Edge offers "insight into the process and progress of medical science in support of the world's largest group medical practice." Visitors can explore the user-friendly site by clicking through recent stories such as, "Putting the hurt on tobacco addiction" and "Genomics: The dawn of a new medical era.� In the Features Archive users can browse through some recent triumphs, including reports on asthma triggers and the future of biomechanics. Visitors can also browse the complete online archive or sign up to receive each new edition via email or RSS feed.

390

Application of Polypyrrole Multi-Walled Carbon Nanotube Composite Layer for Detection of Mercury, Lead and Iron Ions Using Surface Plasmon Resonance Technique  

PubMed Central

Polypyrrole multi-walled carbon nanotube composite layers were used to modify the gold layer to measure heavy metal ions using the surface plasmon resonance technique. The new sensor was fabricated to detect trace amounts of mercury (Hg), lead (Pb), and iron (Fe) ions. In the present research, the sensitivity of a polypyrrole multi-walled carbon nanotube composite layer and a polypyrrole layer were compared. The application of polypyrrole multi-walled carbon nanotubes enhanced the sensitivity and accuracy of the sensor for detecting ions in an aqueous solution due to the binding of mercury, lead, and iron ions to the sensing layer. The Hg ion bonded to the sensing layer more strongly than did the Pb and Fe ions. The limitation of the sensor was calculated to be about 0.1 ppm, which produced an angle shift in the region of 0.3° to 0.6°. PMID:24733263

Sadrolhosseini, Amir Reza; Noor, A. S. M.; Bahrami, Afarin; Lim, H. N.; Talib, Zainal Abidin; Mahdi, Mohd. Adzir

2014-01-01

391

Application of polypyrrole multi-walled carbon nanotube composite layer for detection of mercury, lead and iron ions using surface plasmon resonance technique.  

PubMed

Polypyrrole multi-walled carbon nanotube composite layers were used to modify the gold layer to measure heavy metal ions using the surface plasmon resonance technique. The new sensor was fabricated to detect trace amounts of mercury (Hg), lead (Pb), and iron (Fe) ions. In the present research, the sensitivity of a polypyrrole multi-walled carbon nanotube composite layer and a polypyrrole layer were compared. The application of polypyrrole multi-walled carbon nanotubes enhanced the sensitivity and accuracy of the sensor for detecting ions in an aqueous solution due to the binding of mercury, lead, and iron ions to the sensing layer. The Hg ion bonded to the sensing layer more strongly than did the Pb and Fe ions. The limitation of the sensor was calculated to be about 0.1 ppm, which produced an angle shift in the region of 0.3° to 0.6°. PMID:24733263

Sadrolhosseini, Amir Reza; Noor, A S M; Bahrami, Afarin; Lim, H N; Talib, Zainal Abidin; Mahdi, Mohd Adzir

2014-01-01

392

Lead isotope compositions of Late Cretaceous and early Tertiary igneous rocks and sulfide minerals in Arizona: Implications for the sources of plutons and metals in porphyry copper deposits  

USGS Publications Warehouse

Porphyry copper deposits in Arizona are genetically associated with Late Cretaceous and early Tertiary igneous complexes that consist of older intermediate volcanic rocks and younger intermediate to felsic intrusions. The igneous complexes and their associated porphyry copper deposits were emplaced into an Early Proterozoic basement characterized by different rocks, geologic histories, and isotopic compositions. Lead isotope compositions of the Proterozoic basement rocks define, from northwest to southeast, the Mojave, central Arizona, and southeastern Arizona provinces. Porphyry copper deposits are present in each Pb isotope province. Lead isotope compositions of Late Cretaceous and early Tertiary plutons, together with those of sulfide minerals in porphyry copper deposits and of Proterozoic country rocks, place important constraints on genesis of the magmatic suites and the porphyry copper deposits themselves. The range of age-corrected Pb isotope compositions of plutons in 12 Late Cretaceous and early Tertiary igneous complexes is 206Pb/204Pb = 17.34 to 22.66, 207Pb/204Pb = 15.43 to 15.96, and 208Pb/204Pb = 37.19 to 40.33. These Pb isotope compositions and calculated model Th/U are similar to those of the Proterozoic rocks in which the plutons were emplaced, thereby indicating that Pb in the younger rocks and ore deposits was inherited from the basement rocks and their sources. No Pb isotope differences distinguish Late Cretaceous and early Tertiary igneous complexes that contain large economic porphyry copper deposits from less rich or smaller deposits that have not been considered economic for mining. Lead isotope compositions of Late Cretaceous and early Tertiary plutons and sulfide minerals from 30 metallic mineral districts, furthermore, require that the southeastern Arizona Pb province be divided into two subprovinces. The northern subprovince has generally lower 206Pb/204Pb and higher model Th/U, and the southern subprovince has higher 206Pb/204Pb and lower model Th/U. These Pb isotope differences are inferred to result from differences in their respective post-1.7 Ga magmatic histories. Throughout Arizona, Pb isotope compositions of Late Cretaceous and early Tertiary plutons and associated sulfide minerals are distinct from those of Jurassic plutons and also middle Tertiary igneous rocks and sulfide minerals. These differences most likely reflect changes in tectonic setting and magmatic sources. Within Late Cretaceous and early Tertiary igneous complexes that host economic porphyry copper deposits, there is commonly a decrease in Pb isotope composition from older to younger plutons. This decrease in Pb isotope values with time suggests an increasing involvement of crust with lower U/Pb than average crust in the source(s) of Late Cretaceous and early Tertiary magmas. Lead isotope compositions of the youngest porphyries in the igneous complexes are similar to those in most sulfide minerals within the associated porphyry copper deposit. This Pb isotope similarity argues for a genetic link between them. However, not all Pb in the sulfide minerals in porphyry copper deposits is magmatically derived. Some sulfide minerals, particularly those that are late stage, or distal to the main orebody, or in Proterozoic or Paleozoic rocks, have elevated Pb isotope compositions displaced toward the gross average Pb isotope composition of the local country rocks. The more radiogenic isotopic compositions argue for a contribution of Pb from those rocks at the site of ore deposition. Combining the Pb isotope data with available geochemical, isotopic, and petrologic data suggests derivation of the young porphyry copper-related plutons, most of their Pb, and other metals from a hybridized lower continental crustal source. Because of the likely involvement of subduction-related mantle-derived basaltic magma in the hybridized lower crustal source, an indiscernible mantle contribution is probable in the porphyry magmas. Clearly, in addition

Bouse, R.M.; Ruiz, J.; Titley, S.R.; Tosdal, R.M.; Wooden, J.L.

1999-01-01

393

Different Short-Term Mild Exercise Modalities Lead to Differential Effects on Body Composition in Healthy Prepubertal Male Rats  

PubMed Central

Physical activity has a vital role in regulating and improving bone strength. Responsiveness of bone mass to exercise is age dependent with the prepubertal period suggested to be the most effective stage for interventions. There is a paucity of data on the effects of exercise on bone architecture and body composition when studied within the prepubertal period. We examined the effect of two forms of low-impact exercise on prepubertal changes in body composition and bone architecture. Weanling male rats were assigned to control (CON), bipedal stance (BPS), or wheel exercise (WEX) groups for 15 days until the onset of puberty. Distance travelled via WEX was recorded, food intake measured, and body composition quantified. Trabecular and cortical microarchitecture of the femur were determined by microcomputed tomography. WEX led to a higher lean mass and reduced fat mass compared to CON. WEX animals had greater femoral cortical cross-sectional thickness and closed porosity compared to CON. The different exercise modalities had no effect on body weight or food intake, but WEX significantly altered body composition and femoral microarchitecture. These data suggest that short-term mild voluntary exercise in normal prepubertal rats can alter body composition dependent upon the exercise modality.

Sontam, D. M.; Vickers, M. H.; O'Sullivan, J. M.; Watson, M.; Firth, E. C.

2015-01-01

394

Cu(In,Ga)Se2 alloys are the leading choice for absorber layers in high-efficiency thin film solar cells due to their direct gap, high absorption  

E-print Network

to local composition variations (which lead to band edge fluctuations) and high defect density (perhaps. However, intrinsic defect chemistry and the origin of band edge fluctuations are not understood Cu(In,Ga)Se2 are used to interpret PL results. ·No evidence of band-to-band transitions (rare in CIGS

Rockett, Angus

395

Fractional and group composition of zinc and lead compounds as an indicator of the environmental status of soils  

NASA Astrophysics Data System (ADS)

An ordinary chernozem artificially contaminated with Zn and Pb salts and reclaimed by the addition of chalk and glauconite under pot experimental conditions has been analyzed. The fractional and group composition of the metal compounds in the soil extracts have been determined according to an original combined fractionation procedure. Coefficients characterizing the changes in the environmental status of the metals under the reclamation conditions have been proposed for describing the formation tendencies of the metal composition in the soils. These are the mobility coefficients (MCs) of the heavy metals (HMs) in the soils and the stability coefficients (SCs) of the soils for the HMs. They are calculated from the analysis of the fractional and group composition of the metal compounds. The MC characterizes the environmental vulnerability of soils to the impact of HMs; the SC characterizes the environmental sustainability of soils concerning the contamination with HMs. The obtained experimental data characterize the behavior features of Zn and Pb in the studied soils. An increase in the environmental hazard has been revealed at the contamination of soils with HMs, as well as its decrease at the application of the tested ameliorants. The participation of both strongly and loosely fixed HM fractions in the development of the HM mobility in the soils and the sustainability of the soils to their impact has been shown.

Mandzhieva, S. S.; Minkina, T. M.; Motuzova, G. V.; Golovatyi, S. E.; Miroshnichenko, N. N.; Lukashenko, N. K.; Fateev, A. I.

2014-05-01

396

In-situ One-step Hydrothermal Synthesis of a Lead Germanate-Graphene Composite as a Novel Anode Material for Lithium-Ion Batteries  

NASA Astrophysics Data System (ADS)

Lead germanate-graphene nanosheets (PbGeO3-GNS) composites have been prepared by an efficient one-step, in-situ hydrothermal method and were used as anode materials for Li-ion batteries (LIBs). The PbGeO3 nanowires, around 100-200 nm in diameter, are highly encapsulated in a graphene matrix. The lithiation and de-lithiation reaction mechanisms of the PbGeO3 anode during the charge-discharge processes have been investigated by X-ray diffraction and electrochemical characterization. Compared with pure PbGeO3 anode, dramatic improvements in the electrochemical performance of the composite anodes have been obtained. In the voltage window of 0.01-1.50 V, the composite anode with 20 wt.% GNS delivers a discharge capacity of 607 mAh g-1 at 100 mA g-1 after 50 cycles. Even at a high current density of 1600 mA g-1, a capacity of 406 mAh g-1 can be achieved. Therefore, the PbGeO3-GNS composite can be considered as a potential anode material for lithium ion batteries.

Wang, Jun; Feng, Chuan-Qi; Sun, Zi-Qi; Chou, Shu-Lei; Liu, Hua-Kun; Wang, Jia-Zhao

2014-11-01

397

Glass composition and excitation wavelength dependence of the luminescence of Eu{sup 3+} doped lead borate glass  

SciTech Connect

This work explores the relationship between the bandwidth of luminescence spectral features and their relative intensities, using glasses doped with europium, Eu{sup 3+}, over a wide composition range. Glasses of composition (B{sub 2}O{sub 3}){sub 70}(PbO){sub 29}(0.5Eu{sub 2}O{sub 3}){sub 1} and (B{sub 2}O{sub 3}){sub z}(PbO){sub 99.6-z}(0.5Eu{sub 2}O{sub 3}){sub 0.4}, (z = 20, 30, 40, 60, 70), were prepared by the melting-quenching technique. Variable-wavelength measurements by the prism-coupling method enabled interpolation of refractive index at selected wavelengths. Diffuse reflectance spectra confirmed the incorporation of Eu{sup 3+} into the glass, and scanning electron microscopy displayed that this was in a homogeneous manner. Vibrational spectra showed a change in boron coordination from BO{sub 3} to BO{sub 4} units with increase of PbO content in the glass. Multi-wavelength excited luminescence spectra were recorded for the glasses at temperatures down to 10 K and qualitative interpretations of spectral differences with change of B{sub 2}O{sub 3} content are given. The quantitative analysis of {sup 5}D{sub 0} luminescence intensity-bandwidth relations showed that although samples with higher boron content closely exhibit a simple proportional relationship with band intensity ratios, as expected from theory, the expression needs to be slightly modified for those with low boron content. The Judd-Ofelt intensity analysis of the {sup 5}D{sub 0} emission spectra under laser excitations at low temperature gives {Omega}{sub 2} values within the range from (3.9-6.5) x 10{sup -20} cm{sup 2}, and {Omega}{sub 4} in the range from (4.1-7.0) x 10{sup -20} cm{sup 2}, for different values of z. However, no clear monotonic relation was found between the parameter values and composition. The Judd-Ofelt parameters are compared with those from other systems doped with Eu{sup 3+} and are found to lie in the normal ranges for Eu{sup 3+}-doped glasses. The comparison of parameter values derived from the 10 K spectra with those from room temperature spectra for our glasses, which are fairly constant for different compositions, shows that site selection occurs at low temperature.

Wen Hongli; Duan, Chang-Kui; Jia Guohua; Tanner, Peter A. [Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Brik, Mikhail G. [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia)

2011-08-01

398

Edge: Third Culture  

NSDL National Science Digital Library

This stimulating online journal is the main publication of Edge Foundation, a nonprofit organization whose mandate is "to promote inquiry into and discussion of intellectual, philosophical, artistic, and literary issues, as well as to work for the intellectual and social achievement of society." To that end, the journal brings together speculative articles on contemporary issues by leading scholars and practitioners in the sciences and humanities as well as interviews with these same luminaries. The latest issue, published last week, includes, among other items, an open letter by Richard Dawkins to Prince Charles criticizing his recent call for science to be tempered with a sense of the spiritual, Freeman Dyson's thoughts on spirituality and physics entitled "Progress in Religion," and a medical doctor's argument that the large number of stock market players on psychoactive drugs like Prozac may be in part responsible for the current long-term economic boom. But the most interesting article is probably V.S. Ramachandran's "Mirror Neurons And Imitation Learning As The Driving Force Behind 'The Great Leap Forward' In Human Evolution," which argues that recent discoveries concerning the frontal lobes of monkeys are likely to lead to an unprecedented unified theory for human psychology. A searchable archive of past issues is available, reaching back to the first biweekly issue in December of 1996. An annual feature of Edge is its "What is the most important unreported story?" giving scientists and thinkers the chance to suggest where they believe the next revolution in knowledge will be coming from.

399

Changes in the lead isotopic composition of blood, diet and air in Australia over a decade: Globalization and implications for future isotopic studies  

SciTech Connect

Source apportionment in biological or environmental samples using the lead isotope method, where there are diverse sources of lead, relies on a significant difference between the isotopic composition in the target media and the sources. Because of the unique isotopic composition of Australian lead, source apportionment has been relatively successful in the past. Over the period of a decade, the {sup 206}Pb/{sup 204}Pb ratio for Australian (mainly female) adults has shown an increase from a geometric mean of 16.8-17.3. Associated with this increase, there has been a decrease in mean blood lead concentration from 4.7 to 2.3 {mu}g/dL, or about 5% per year, similar to that observed in other countries. Lead in air, which up until 2000 was derived largely from the continued use of leaded gasoline, showed an overall increase in the {sup 206}Pb/{sup 204}Pb ratio during 1993-2000 from 16.5 to 17.2. Since 1998 the levels of lead in air were less than 0.2 {mu}g/m{sup 3} and would contribute negligibly to blood lead. Over the 10-year period, the {sup 206}Pb/{sup 204}Pb ratio in diet, based mainly on quarterly 6-day duplicate diets, increased from 16.9 to 18.3. The lead concentration in diet showed a small decrease from 8.7 to 6.4 {mu}g Pb/kg although the daily intake increased markedly from 7.4 to 13.9 {mu}g Pb/day during the latter part of the decade probably reflecting differences in demographics. The changes in blood lead from sources such as lead in bone or soil or dust is not dominant because of the low {sup 206}Pb/{sup 204}Pb ratios in these media. Unless there are other sources not identified and analysed for these adults, it would appear that in spite of our earlier conclusions to the contrary, diet does make an overall contribution to blood lead, and this is certainly the case for specific individuals. Certain population groups from south Asia, south-east Asia, the Middle East and Europe (e.g. UK) are unsuitable for some studies as their isotopic ratios in blood are converging towards the increasing Australian values. The increases in blood {sup 206}Pb/{sup 204}Pb ratio combined with globalization, which has resulted in the increases in {sup 206}Pb/{sup 204}Pb ratio for diet, means that isotopic studies undertaken with a high degree of certainty of outcomes over a decade ago, are now considerably more difficult, not only in Australia but also in other countries where the isotopic differences are even less than in Australia.

Gulson, Brian [Graduate School of Environment, Macquarie University, Sydney, NSW 2109 (Australia) and CSIRO Exploration and Mining, North Ryde, Sydney, NSW 1609 (Australia)]. E-mail: bgulson@gse.mq.edu.au; Mizon, Karen [Graduate School of Environment, Macquarie University, Sydney, NSW 2109 (Australia); Korsch, Michael [CSIRO Exploration and Mining, North Ryde, Sydney, NSW 1609 (Australia); Taylor, Alan [Department of Psychology, Macquarie University, Sydney, NSW 2109 (Australia)

2006-01-15

400

Durability Evaluation of a Thin Film Sensor System With Enhanced Lead Wire Attachments on SiC/SiC Ceramic Matrix Composites  

NASA Technical Reports Server (NTRS)

An advanced thin film sensor system instrumented on silicon carbide (SiC) fiber reinforced SiC matrix ceramic matrix composites (SiC/SiC CMCs), was evaluated in a Mach 0.3 burner rig in order to determine its durability to monitor material/component surface temperature in harsh environments. The sensor system included thermocouples in a thin film form (5 microns thick), fine lead wires (75 microns diameter), and the bonds between these wires and the thin films. Other critical components of the overall system were the heavy, swaged lead wire cable (500 microns diameter) that contained the fine lead wires and was connected to the temperature readout, and ceramic attachments which were bonded onto the CMCs for the purpose of securing the lead wire cables, The newly developed ceramic attachment features a combination of hoops made of monolithic SiC or SiC/SiC CMC (which are joined to the test article) and high temperature ceramic cement. Two instrumented CMC panels were tested in a burner rig for a total of 40 cycles to 1150 C (2100 F). A cycle consisted of rapid heating to 1150 C (2100 F), a 5 minute hold at 1150 C (2100 F), and then cooling down to room temperature in 2 minutes. The thin film sensor systems provided repeatable temperature measurements for a maximum of 25 thermal cycles. Two of the monolithic SiC hoops debonded during the sensor fabrication process and two of the SiC/SiC CMC hoops failed during testing. The hoops filled with ceramic cement, however, showed no sign of detachment after 40 thermal cycle test. The primary failure mechanism of this sensor system was the loss of the fine lead wire-to-thin film connection, which either due to detachment of the fine lead wires from the thin film thermocouples or breakage of the fine wire.

Lei, Jih-Fen; Kiser, J. Douglas; Singh, Mrityunjay; Cuy, Mike; Blaha, Charles A.; Androjna, Drago

2000-01-01

401

Relation of fatty acid composition in lead-exposed mallards to fat mobilization, lipid peroxidation and alkaline phosphatase activity  

USGS Publications Warehouse

The increase of n-6 polyunsaturated fatty acids (PUFA) in animal tissues has been proposed as a mechanism of Pb poisoning through lipid peroxidation or altered eicosanoids metabolism. We have studied fatty acid (FA) composition in liver and brain of mallards (Anas platyrhynchos) feeding for three weeks on diets containing combinations of low or high levels of vitamin E (20 or 200 UI/kg) and Pb (0 or 2 g/kg). Saturated FA, n-6 PUFA and total concentrations of FA were higher in livers of Pb-exposed mallards, but not in their brains. The percentage of n-6 PUFA in liver and brain was slightly higher in Pb-exposed mallards. The increase of n-6 PUFA in liver was associated with increased triglycerides and cholesterol in plasma, thus could be in part attributed to feed refusal and fat mobilization. The hepatic ratios between adrenic acid (22:4 n-6) and arachidonic acid (20:4 n-6) or between adrenic acid and linoleic acid (18:2 n-6) were higher in Pb exposed birds, supporting the existing hypothesis of increased fatty acid elongation by Pb. Among the possible consequences of increased n-6 PUFA concentration in tissues, we found increased lipid peroxidation in liver without important histopathological changes, and decreased plasma alkaline phosphatase activity that may reflect altered bone metabolism in birds.

Mateo, R.; Beyer, W.N.; Spann, J.W.; Hoffman, D.J.

2003-01-01

402

Surface analyses of composites exposed to the space environment on LDEF  

NASA Technical Reports Server (NTRS)

A series of surface analyses on carbon fiber/poly(arylacetylene) (PAA) matrix composites that were exposed to the space environment on the Long Duration Exposure Facility (LDEF) satellite were conducted. These composite panels were arranged in pairs on both the leading edge and trailing edge of LDEF. None of the composites were catastrophically damaged by nearly six years of exposure to the space environment. Composites on the leading edge exhibited from 25 to 125 microns of surface erosion, but trailing edge panels exhibited no physical appearance changes due to exposure. Scanning electron microscopy (SEM) was used to show that the erosion morphology on the leading edge samples was dominated by crevasses parallel to the fibers with triangular cross sections 10 to 100 microns in depth. The edges of the crevasses were well defined and penetrated through both matrix and fiber. The data suggest that the carbon fibers are playing an important role in crevasse initiation and/or enlargement, and in the overall erosion rate of the composite. X-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectroscopy (EDS) results showed contamination from in-flight sources of silicone.

Mallon, Joseph J.; Uht, Joseph C.; Hemminger, Carol S.

1993-01-01

403

Longitudinally Jointed Edge-Wise Compression HoneyComb Composite Sandwich Coupon Testing And Fe Analysis: Three Methods of Strain Measurement, And Comparison  

NASA Technical Reports Server (NTRS)

Three distinct strain measurement methods (i.e., foil resistance strain gages, fiber optic strain sensors, and a three-dimensional digital image photogrammetry that gives full field strain and displacement measurements) were implemented to measure strains on the back and front surfaces of a longitudinally jointed curved test article subjected to edge-wise compression testing, at NASA Goddard Space Flight Center, according to ASTM C364. The pre-test finite element analysis (FEA) was conducted to assess ultimate failure load and predict strain distribution pattern throughout the test coupon. The predicted strain pattern contours were then utilized as guidelines for installing the strain measurement instrumentations. The foil resistance strain gages and fiber optic strain sensors were bonded on the specimen at locations with nearly the same analytically predicted strain values, and as close as possible to each other, so that, comparisons between the measured strains by strain gages and fiber optic sensors, as well as the three-dimensional digital image photogrammetric system are relevant. The test article was loaded to failure (at 167 kN), at the compressive strain value of 10,000 micro epsilon. As a part of this study, the validity of the measured strains by fiber optic sensors is examined against the foil resistance strain gages and the three-dimensional digital image photogrammetric data, and comprehensive comparisons are made with FEA predictions.

Farrokh, Babak; Rahim, Nur Aida Abul; Segal, Ken; Fan, Terry; Jones, Justin; Hodges, Ken; Mashni, Noah; Garg, Naman; Sang, Alex

2013-01-01

404

Environmental effects on FOD resistance of composite fan blade  

NASA Technical Reports Server (NTRS)

The sensitivity of the impact characteristics of typical polymeric composite fan blade materials to potential limiting combinations of moisture, temperature level and temperature transients was established. The following four technical tasks are reported: (1) evaluation and characterization of constituent blade materials; (2) ballistic impact tests; (3) leading edge impact protection systems; and (4) simulated blade spin impact tests.

Murphy, G. C.; Selemme, C. T.

1981-01-01

405

Image precision silhouette edges  

Microsoft Academic Search

Finding and displaying silhouette edges is important in applications ranging from computer vision to nonphotorealistic rendering. To render visible silhouette edges of a polygonal object in a scene from a given viewpoint, we must first find all silhouette edges, i.e. boundaries between adjacent front facing and back-facing surfaces. This is followed by solving the partial visibility problem so that only

Ramesh Raskar; Michael F. Cohen

1999-01-01

406

Composites  

NASA Astrophysics Data System (ADS)

It is commonly known that the properties of sintered materials are strongly related to technological conditions of the densification process. This paper shows the sintering behavior of a NiAl-Al2O3 composite, and its individual components sintered separately. Each kind of material was processed via the powder metallurgy route (hot pressing). The progress of sintering at different stages of the process was tested. Changes in the microstructure were examined using scanning and transmission electron microscopy. Metal-ceramics interface was clean and no additional phases were detected. Correlation between the microstructure, density, and mechanical properties of the sintered materials was analyzed. The values of elastic constants of NiAl/Al2O3 were close to intermetallic ones due to the volume content of the NiAl phase particularly at low densities, where small alumina particles had no impact on the composite's stiffness. The influence of the external pressure of 30 MPa seemed crucial for obtaining satisfactory stiffness for three kinds of the studied materials which were characterized by a high dense microstructure with a low number of isolated spherical pores.

Chmielewski, M.; Nosewicz, S.; Pietrzak, K.; Rojek, J.; Strojny-N?dza, A.; Mackiewicz, S.; Dutkiewicz, J.

2014-11-01

407

Impact resistance of hybrid composite fan blade materials  

NASA Technical Reports Server (NTRS)

Improved resistance to foreign object damage was demonstrated for hybrid composite simulated blade specimens. Transply metallic reinforcement offered additional improvement in resistance to gelatin projectile impacts. Metallic leading edge protection permitted equivalent-to-titanium performance of the hybrid composite simulated blade specimen for impacts with 1.27 cm and 2.54 cm (0.50 and 1.00 inch) diameter gelatin spheres.

Friedrich, L. A.

1974-01-01

408

Results from analysis of Boeing composite specimens flown on LDEF experiment M0003  

NASA Technical Reports Server (NTRS)

Specimens of three organic matrix/graphite fiber reinforced composites were flown at both the leading and trailing edge locations on the Long Duration Exposure Facility (LDEF). Selected specimens flown at the trailing edge position were held under tension, compression, and flexure loads for the duration of the flight. Also, two epoxy adhesives with composite and metallic adherends were flown at the trailing edge position. These specimens experienced 5.8 years of exposure to the low earth orbit (LEO) environment where they were subjected to atomic oxygen (AO), thermal cycling, ultraviolet (UV) light, and particulate radiation. Post flight mechanical, chemical, optical, and physical tests were performed and the results were compared to preflight and published values. AO erosion of the leading edge specimens resulted in a significant reduction of mechanical properties and a change in optical properties. Chemical changes occurred only on the surface.

George, Pete E.; Hill, Sylvester G.

1992-01-01

409

Neural Edge Enhancer for Supervised Edge Enhancement from Noisy Images  

Microsoft Academic Search

We propose a new edge enhancer based on a modified multilayer neural network, which is called a neural edge enhancer (NEE), for enhancing the desired edges clearly from noisy images. The NEE is a supervised edge enhancer: Through training with a set of input noisy images and teaching edges, the NEE acquires the function of a desired edge enhancer. The

Kenji Suzuki; Isao Horiba; Noboru Sugie

2003-01-01

410

[Needles stable carbon isotope composition and traits of Pinus sylvestris var. mongolica in sparse wood grassland in south edge of Keerqin Sandy Land under the conditions of different precipitation].  

PubMed

A comparative study was conducted on the needles stable carbon isotope composition (delta13 C), specific leaf area (SLA), and dry matter content (DMC) of 19-year-old Pinus sylvestris var. mongolica trees in a sparse wood grassland in the south edge of Keerqin Sandy Land under the conditions of extreme drought and extreme wetness, aimed to understand the water use of Pinus sylvestris under the conditions of extreme precipitation. The soil water content and groundwater level were also measured. In the dry year (2009), the soil water content in the grassland was significantly lower than that in the wet year (2010), but the delta13C values of the current year-old needles had no significant difference between the two years and between the same months of the two years. The SLA of the current year-old needles was significantly lower in the dry year than in the wet year, but the DMC had no significant difference between the two years. Under the conditions of the two extreme precipitations, the water use efficiency of the trees did not vary remarkably, and the trees could change their needles SLA to adapt the variations of precipitation. For the test ecosystem with a groundwater level more than 3.0 m, extreme drought could have no serious impact on the growth and survival of the trees. PMID:22937627

Song, Li-Ning; Zhu, Jiao-Jun; Li, Ming-Cai; Yan, Tao; Zhang, Jin-Xin

2012-06-01

411

LDEF fiber-composite materials characterization  

NASA Technical Reports Server (NTRS)

Degradation of a number of fiber/polymer composites located on the leading and trailing surfaces of LDEF where the atomic oxygen (AO) fluences ranged from 10(exp 22) to 10(exp 4) atoms/cm(sup 2), respectively, was observed and compared. While matrices of the composites on the leading edge generally exhibited considerable degradation and erosion-induced fragmentation, this 'asking' process was confined to the near surface regions because these degraded structures acted as a 'protective blanket' for deeper-lying regions. This finding leads to the conclusion that simple surface coatings can significantly retard AO and other combinations of degrading phenomena in low-Earth orbit. Micrometeoroid and debris particle impacts were not a prominent feature on the fiber composites studied and apparently do not contribute in a significant way to their degradation or alteration in low-Earth orbit.

Miglionico, C. J.; Stein, C.; Roybal, R. E.; Murr, L. E.

1993-01-01

412

The Edge, Fall 1999.  

ERIC Educational Resources Information Center

"The Edge" is a Canadian publication for youth. The mandate of the Edge is to support and celebrate all career journeys embraced by youth. This issue contains career profile articles covering three jobs: crane operator, indoor climbing instructor, and product certification tester. Career trends and the state of today's workplace are also…

Edge, 1999

1999-01-01

413

Muzzle-loading weapons discharging spherical lead bullets: two case studies and experimental simulation using a skin-soap composite model.  

PubMed

In current forensic practice, fatal injuries from black powder guns are rare events. In contact and close-range shots, the intensity of GSR deposition (soot, powder particles) is much greater than that in shots with smokeless powder ammunition. The same applies to any burning effects from the combustion gases. Besides, a wad of felt interposed between the propellant and the lead bullet may enter the wound channel. Apart from these findings seen in close-range shots, another characteristic feature results from the mostly spherical shape of the missiles causing maximum tissue damage at the entrance site. Two fatal injuries inflicted with muzzle-loading weapons are reported. In the first case, suicide was committed with a cal. 11.6 mm miniature cannon by firing a contact shot to the back of the neck. In test shots using black powder (1 and 2 g) as propellant, the mean bullet velocity measured 1 m away from the weapon was 87.11 and 146.85 m/s, respectively, corresponding to a kinetic energy of 32.49 and 92.95 J, respectively. Contact test shots to composite models consisting of ballistic soap covered by pig skin at the entrance site were evaluated by CT and revealed cone-like cavitations along the bullet path as known from spherical missiles and penetration depths up to 25 cm. The second case presented deals with a homicidal close-range shot discharged from a muzzle-loading percussion pistol cal. .44. The skin around the entrance site (root of the nose) was densely covered with blackish soot and powder particles, whereas the eyebrows and eyelashes showed singeing of the hairs. The flattened bullet and the wad had got stuck under the scalp of the occipital region. In both cases, there was a disproportionally large zone of tissue destruction in the initial parts of the wound tracks. PMID:23250385

Große Perdekamp, Markus; Braunwarth, Roland; Kromeier, Jan; Nadjem, Hadi; Pollak, Stefan; Thierauf, Annette

2013-07-01

414

Boundary Detection -Edges Edge Detection is a local (for now)  

E-print Network

everywhere. · Must smooth before taking derivative. Implementing1D Edge Detection 1. Filter out noise the scale of edges we locate. · Matlab 2D Edge Detection: Canny 1. Filter out noise ­ Use a 2D Gaussian · Eliminates noise edges. · Makes edges smoother. · Removes fine detail. · Matlab #12;11 Finding the Peak 1

Jacobs, David

415

Observation of magnetoelectric coupling and local piezoresponse in modified (Na0.5Bi0.5)TiO3-BaTiO3-CoFe2O4 lead-free composites.  

PubMed

Lead-free particulate multiferroic composites of [0.94(Na0.5Bi0.5)TiO3-0.06 BaTiO3]:(Co0.6Zn0.4)(Fe1.7Mn0.3)O4 were synthesized and magnetoelectric (ME) properties were studied. X-ray diffraction and microstructural studies indicated the formation of a two-phase composite system without any impurities. The shift of Raman modes corresponding to ferroelectric and ferrite phases was assigned to the induced strain amid the formation of a two-phase system, in relation to the fraction of each phase in the samples. A strong local piezoresponse and hysteresis loops observed for composites established the ferroelectric properties at a nanoscale. Magnetostriction measurements revealed values of ?11 = -10.4 and ?12 = 5.3 ppm and piezomagnetic coefficient d?11/dH = -0.0087 ppm Oe(-1) at 0.45 kOe for a composite with a ferrite concentration of 35 mol%. A maximum change of 18.5% in magnetization after electrical poling indicates a strong magnetoelectric response of the present composites followed by a direct ME coefficient of 8.2 mV cm(-1) Oe(-1). Our studies point to the fact that the present multiferroic composites having strong ME coupling are useful for lead-free electronic applications. PMID:24849499

Ramana, E Venkata; Figueiras, F; Graça, M P F; Valente, M A

2014-07-14

416

Exact Algorithms for Edge Domination  

Microsoft Academic Search

Abstract An edge dominating set in a graph G = (V, E) is a subset of the edges D ? E such that every edge in E is adjacent or equal to some edge in D. The problem of finding an edge dominating set of minimum,cardinality is NP-hard. We present a faster exact exponential time algorithm for this problem. Our

Johan M. M. Van Rooij; Hans L. Bodlaender

2008-01-01

417

Nonequilibrium spectroscopy of topological edge liquids  

NASA Astrophysics Data System (ADS)

We develop a theory for energy and spatially resolved tunneling spectroscopy of topological quantum spin Hall helical states driven out of equilibrium. When a helical liquid is constrained between two superconducting reservoirs transport at the edge is governed by multiple Andreev reflections. The resulting quasiparticle distribution functions of the edge channels exhibit multiple discontinuities at subgap energies with the periodicity of an applied voltage. The combined effect of interactions, disorder, and normal scattering off the superconducting interface leads to the inelastic processes mixing different helicity modes, thus causing smearing of these singularities. If equilibration is strong, then the distribution functions of the edge channels tend to collapse into a Fermi-like function with an effective temperature determined by the superconducting gap, applied voltage, and intraedge interaction parameter. We conclude that mapping out nonequilibrium distribution functions may help to quantify the relative importance of various relevant perturbations that spoil ideally ballistic edge transport.

Apostolov, Stanislav S.; Levchenko, Alex

2014-05-01

418

Edge energies and shapes of nanoprecipitates.  

SciTech Connect

In this report we present a model to explain the size-dependent shapes of lead nano-precipitates in aluminum. Size-dependent shape transitions, frequently observed at nanolength scales, are commonly attributed to edge energy effects. This report resolves an ambiguity in the definition and calculation of edge energies and presents an atomistic calculation of edge energies for free clusters. We also present a theory for size-dependent shapes of Pb nanoprecipitates in Al, introducing the concept of ''magic-shapes'' defined as precipitate shapes having near zero elastic strains when inserted into similarly shaped voids in the Al matrix. An algorithm for constructing a complete set of magic-shapes is presented. The experimental observations are explained by elastic strain energies and interfacial energies; edge energies play a negligible role. We replicate the experimental observations by selecting precipitates having magic-shapes and interfacial energies less than a cutoff value.

Hamilton, John C.

2006-01-01

419

Lead Poisoning  

MedlinePLUS

... be exposed to lead by Eating food or drinking water that contains lead. Water pipes in older homes ... herbs or foods that contain lead Breathing air, drinking water, eating food, or swallowing or touching dirt that ...

420

Lead isotope composition of tree rings as bio-geochemical tracers of heavy metal pollution: a reconnaissance study from Firenze, Italy  

Microsoft Academic Search

Pb isotope composition of tree rings (Celtis Australis) and urban aerosols have been determined to assess whether arboreal species can be used as bio-geochemical tracers of the evolution of heavy metal pollution to the environment. Particular care was paid to setting up a high quality analytical technique to work with arboreal species with low Pb content. The Pb isotope composition

Simone Tommasini; Gareth R Davies; Tim Elliott

2000-01-01

421

Edge-on Galaxy  

NASA Technical Reports Server (NTRS)

NASA's Hubble Space Telescope has imaged an unusual edge-on galaxy, revealing remarkable details of its warped dusty disc and showing how colliding galaxies trigger the birth of new stars.

The image, taken by Hubble's Wide Field and Planetary Camera 2 (WFPC2), is online at http://heritage.stsci.edu and http://www.jpl.nasa.gov/images/wfpc. The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. During observations of the galaxy, the camera passed a milestone, taking its 100,000th image since shuttle astronauts installed it in Hubble in 1993.

The dust and spiral arms of normal spiral galaxies, like our Milky Way, look flat when seen edge- on. The new image of the galaxy ESO 510-G13 shows an unusual twisted disc structure, first seen in ground-based photographs taken at the European Southern Observatory in Chile. ESO 510-G13 lies in the southern constellation Hydra, some 150 million light-years from Earth. Details of the galaxy's structure are visible because interstellar dust clouds that trace its disc are silhouetted from behind by light from the galaxy's bright, smooth central bulge.

The strong warping of the disc indicates that ESO 510-G13 has recently collided with a nearby galaxy and is in the process of swallowing it. Gravitational forces distort galaxies as their stars, gas, and dust merge over millions of years. When the disturbances die out, ESO 510-G13 will be a single galaxy.

The galaxy's outer regions, especially on the right side of the image, show dark dust and bright clouds of blue stars. This indicates that hot, young stars are forming in the twisted disc. Astronomers believe star formation may be triggered when galaxies collide and their interstellar clouds are compressed.

The Hubble Heritage Team used WFPC2 to observe ESO 510-G13 in April 2001. Pictures obtained through blue, green, and red filters were combined to make this color-composite image, which emphasizes the contrast between the dusty spiral arms, the bright bulge, and the blue star-forming regions. Additional information about the Hubble Space Telescope is online at http://www.stsci.edu. More information about the Wide Field and Planetary Camera 2 is at http://wfpc2.jpl.nasa.gov.

The Space Telescope Science Institute, Baltimore, Md., manages space operations for Hubble for NASA's Office of Space Science, Washington, D.C. The institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract with the Goddard Space Flight Center, Greenbelt, Md. Hubble is a project of international cooperation between NASA and the European Space Agency. JPL is a division of the California Institute of Technology in Pasadena.

1999-01-01

422

Edges and linearization  

E-print Network

This thesis is concerned with how grammar determines the phonological consequence of syntactic dislocation. It centers on a hypothesis regarding the linearization of movement chains - the Edge Condition on Copy Deletion, ...

Trinh, Tue H. (Tue Huu)

2011-01-01

423

Visualization of a ferromagnetic metallic edge state in manganite strips.  

PubMed

Recently, broken symmetry effect induced edge states in two-dimensional electronic systems have attracted great attention. However, whether edge states may exist in strongly correlated oxides is not yet known. In this work, using perovskite manganites as prototype systems, we demonstrate that edge states do exist in strongly correlated oxides. Distinct appearance of ferromagnetic metallic phase is observed along the edge of manganite strips by magnetic force microscopy. The edge states have strong influence on the transport properties of the strips, leading to higher metal-insulator transition temperatures and lower resistivity in narrower strips. Model calculations show that the edge states are associated with the broken symmetry effect of the antiferromagnetic charge-ordered states in manganites. Besides providing a new understanding of the broken symmetry effect in complex oxides, our discoveries indicate that novel edge state physics may exist in strongly correlated oxides beyond the current two-dimensional electronic systems. PMID:25649750

Du, Kai; Zhang, Kai; Dong, Shuai; Wei, Wengang; Shao, Jian; Niu, Jiebin; Chen, Jinjie; Zhu, Yinyan; Lin, Hanxuan; Yin, Xiaolu; Liou, Sy-Hwang; Yin, Lifeng; Shen, Jian

2015-01-01

424

Edge element formulations of eddy current problems  

Microsoft Academic Search

Various formulations of eddy current problems in terms of scalar and vector potentials are reviewed in the paper. The vector potentials are approximated by edge finite elements and the scalar potentials by nodal ones. The formulations are ungauged, leading, in most cases, to singular finite element equations systems. Special attention is paid to ensuring that the right-hand sides of the

Oszkár Bíró

1999-01-01

425

The Edge supersonic transport  

NASA Technical Reports Server (NTRS)

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