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1

SHARP REFRACTORY COMPOSITE LEADING EDGES ON HYPERSONIC VEHICLES  

Microsoft Academic Search

On-going research of advanced sharp refractory composite leading edges for use on hypersonic air-breathing vehicles is presented in this paper. Intense magnitudes of heating and of heating gradients on the leading edge lead to thermal stresses that challenge the survivability of current material systems. A fundamental understanding of the problem is needed to further design development. Methodology for furthering the

Sandra P. Walker; Brian J. Sullivan

2003-01-01

2

Thermostructural Analysis of a Diboride Composite Leading Edge.  

National Technical Information Service (NTIS)

In an effort to support the design of zirconium diboride composite leading edges for hypersonic vehicles, a finite element model (FEM) of a prototype leading edge was created and finite element analysis (FEA) was employed to assess its thermal and structu...

T. Kowalski K. Buesking P. Kolodziej J. Bull

1996-01-01

3

Bird strike simulation on a novel composite leading edge design  

Microsoft Academic Search

A methodology for the numerical simulation of bird strike on a novel leading edge (LE) structure of a horizontal tail plane is presented. The innovative LE design is based on the ‘tensor skin’ concept, comprising one or more folded composite sub-laminates that unfold during the bird impact, thus providing high-energy absorption characteristics. The simulation technique is based on a non-linear

Th Kermanidis; G. Labeas; M. Sunaric; A. F. Johnson; M. Holzapfel

2006-01-01

4

Impact Behaviour Modelling of a Composite Leading Edge Structure  

Microsoft Academic Search

A methodology for the numerical simulation of bird impact on a novel Leading Edge (LE) structure of a Horizontal Tail Plane\\u000a is presented. The innovative LE design is based on a ‘tensor skin’ structure, which is an efficient impact resistant design,\\u000a comprising one or more folded composite sub-laminates, which unfold during the bird impact, providing the required high-energy\\u000a absorption efficiency.

G. Labeas; Th. Kermanidis

5

Analysis of Bird Impact on a Composite Tailplane Leading Edge  

NASA Astrophysics Data System (ADS)

One of the main structural requirements of a leading edge of a tailplane is to ensure that any significant damage caused by foreign object (i.e. birdstrike, etc...) would still allow the aircraft to land safely. In particular, leading edge must be certified for a proven level of bird impact resistance. Since the experimental tests are expensive and difficult to perform, numerical simulations can provide significant help in designing high-efficiency bird-proof structures. The aim of this research paper was to evaluate two different leading edge designs by reducing the testing costs by employing state-of-the-art numerical simulations. The material considered was a sandwich structure made up of aluminium skins and flexcore as core. Before each test was carried out, pre-test numerical analyses of birdstrike were performed adopting a lagrangian approach on a tailplane leading edge of a large scale aircraft using the MSC/Dytran solver code. The numerical and experimental correlation have shown good results both in terms of global behaviour of the test article and local evolution of some measurable parameters confirming the validity of the approach and possible guidelines for structural design including the bird impact requirements.

Guida, M.; Marulo, F.; Meo, M.; Riccio, M.

2008-11-01

6

Development and Validation of a Novel Bird Strike Resistant Composite Leading Edge Structure  

Microsoft Academic Search

A novel design of a fibre-reinforced composite Leading Edge (LE) of a Horizontal Tail Plain (HTP) is proposed. The development and validation approach of the innovative composite LE structure are described. The main design goal is the satisfactory impact resistance of the novel composite LE in the case of bird strike. The design concept is based on the absorption of

Th. Kermanidis; G. Labeas; M. Sunaric; L. Ubels

2005-01-01

7

Experimental investigation on the composite cooling of a semicylinder leading edge  

Microsoft Academic Search

Composite cooling of the leading edge region of a semicylinder simulating a turbine vane was studied experimentally. The cylinder's inner surface served as an impingement target for studying impingement cooling; the outer surface was used to study the film cooling effectiveness. The equipment for composite cooling was a sucked-wind tunnel with the test section of 140 x 200-sq m in

Ji-Rui Cheng; Hong-Hu Ji

1986-01-01

8

Icing Tunnel Tests of a Composite Porous Leading Edge for Use with a Liquid Anti-Ice System.  

National Technical Information Service (NTIS)

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 panel...

D. L. Kohlman

1981-01-01

9

Development and Validation of a Novel Bird Strike Resistant Composite Leading Edge Structure  

NASA Astrophysics Data System (ADS)

A novel design of a fibre-reinforced composite Leading Edge (LE) of a Horizontal Tail Plain (HTP) is proposed. The development and validation approach of the innovative composite LE structure are described. The main design goal is the satisfactory impact resistance of the novel composite LE in the case of bird strike. The design concept is based on the absorption of the major portion of the bird kinetic energy by the composite skins, in order to protect the ribs and the inner LE structure from damaging, thus preserving the tail plane functionality for safe landing. To this purpose, the LE skin is fabricated from specially designed composite panels, so called ‘tensor skin’ panels, comprising folded layers, which unfold under the impact load and increase the energy absorption capability of the LE. A numerical model simulating the bird strike process is developed and bird strike experimental testing is performed, in order to validate the proposed layout and prove the capability of the structure to successfully withstand the impact loading. The numerical modelling issues and the critical parameters of the simulation are discussed. The present work is part of the European Aeronautics Research Project, ‘Crashworthiness of aircraft for high velocity impact CRAHVI’ [1].

Kermanidis, Th.; Labeas, G.; Sunaric, M.; Ubels, L.

2005-11-01

10

An experimental investigation of composite cooling on the leading edge region of a turbine blade  

Microsoft Academic Search

A semicylinder with film holes is used to simulate the impingement and film cooling on the leading edge region of a turbine blade. It is found that the impingement cooling on the concave surface is enhanced in the presence of film holes, and the film cooling effectiveness is evidently increased in the presence of the laterally slant film holes.

H. Ji; J. Zheng

1986-01-01

11

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

National Technical Information Service (NTIS)

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 Tec...

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

2004-01-01

12

Southeast Directed Thrusting Associated With the Leading Edge of the Wrangellia Composite Terrane: The Chulitna Block South Central Alaska  

Microsoft Academic Search

Structural mapping of the Chulitna block in south central Alaska reveals a regional scale southeast-vergent, anticline-syncline pair and a series of related southeast-directed thrusts that record the imbrication of the leading edge of the Wrangellia Composite Terrane (WCT). The Chulitna block has been recognized as an unusual Paleozoic through Mesozoic collage of oceanic and clastic rocks that are not found

T. L. Gilman; D. Fisher

2005-01-01

13

The preparation of a composite structure for a first large scale ground test of a smart and gapless wing leading edge  

Microsoft Academic Search

At the Institute of Composite Structures and Adaptive Systems (FA, Prof. Wiedemann) of the DLR the structure of a flexible and gapless wing leading edge has been developed for testing in large scale structure-system ground tests. The absence of gaps in a flexible wing leading edge allows for a significant noise reduction and provides an additional key technology for realizing

Olaf Heintze; Sebastian Geier; Daniel Hartung; Markus Kintscher

2011-01-01

14

Advanced composites: the leading edge in high performance motor and transformer insulation  

Microsoft Academic Search

Advanced composite electrical structures, offer excellent strength, heat, and electrical properties. The author reviews their electrical performance and manufacturing advantages and reports on new designs in high-performance motors and transformers incorporating them. The applications for slot liners and coil forms outlined underscore the potential of composites for cutting costs, scaling down size, and improving the performance of various types of

M. L. Sheer

1991-01-01

15

Leading-edge receptivity by adjoint methods  

Microsoft Academic Search

The properties of adjoint operators and the method of composite expansion are used to study the generation of Tollmien Schlichting (TS) waves in the leading-edge region of an incompressible, flat-plate boundary layer. Following the classical asymptotic approach, the flow field is divided into an initial receptivity region, where the unsteady motion is governed by the linearized unsteady boundary-layer equation (LUBLE),

Flavio Giannetti; Paolo Luchini

2006-01-01

16

Structure at the Leading Edge  

NASA Astrophysics Data System (ADS)

The leading edge of a crawling cell is propelled forward by a polymerizing network of branched actin filaments. This emergent structural array seems to be rigid enough to support and push against the cell membrane within the appropriate time scales under which cell motility can be realized. We seek to understand how such a network can optimize its structure to generate the rigidity required, particularly focusing on the role of branching in the network. For isolated elastic beams, which model semiflexible polymers, the critical buckling load is enhanced when branched supports are included. Therefore, we conjecture that an optimal branching angle is found by looking at the competition between branching providing collective structural support, which results in polymerization with a component perpendicular to the direction of motion, and polymerization along the direction of motion. To partially test this conjecture, we simulate a directed, branched network in the absence of forces. Preliminary results indicate a lower bound on the optimal branching angle of approximately 40 degrees (to be compared with the observed 70 degree branching angle). Studies of a directed, branched network with forces will also be addressed.

Quint, D. A.; Schwarz, J. M.; Marchetti, M. C.

2009-03-01

17

Edge Delamination of Composite Laminates.  

National Technical Information Service (NTIS)

A review of the literature and the research performed at the Institute for Aerospace Research on the subject of delamination in composite laminates are presented. Delamination is known to initiate at free edges where the influence of interlaminar stresses...

C. Poon N. C. Bellinger Y. Xiong R. W. Gould

1992-01-01

18

Leading-edge receptivity by adjoint methods  

NASA Astrophysics Data System (ADS)

The properties of adjoint operators and the method of composite expansion are used to study the generation of Tollmien Schlichting (TS) waves in the leading-edge region of an incompressible, flat-plate boundary layer. Following the classical asymptotic approach, the flow field is divided into an initial receptivity region, where the unsteady motion is governed by the linearized unsteady boundary-layer equation (LUBLE), and a downstream linear amplification area, where the evolution of the unstable mode is described by the classical Orr Sommerfeld equation (OSE). The large bar{x} behaviour of the LUBLE is analysed using a multiple-scale expansion which leads to a set of composite differential equations uniformly valid in the wall-normal direction. These are solved numerically as an eigenvalue problem to determine the local properties of the Lam and Rott eigensolutions. The receptivity coefficient for an impinging acoustic wave is extracted by projecting the numerical solution of the LUBLE onto the adjoint of the Lam and Rott eigenfunction which, further downstream, turns into an unstable TS wave. In the linear amplification region, the main characteristics of the instability are recovered by using a multiple-scale expansion of the Navier Stokes equations and solving numerically the derived eigenvalue problems. A new matching procedure, based on the properties of the adjoint Orr Sommerfeld operator, is then used to check the existence and the extent of an overlapping domain between the two asymptotic regions. Results for different frequencies are discussed.

Giannetti, Flavio; Luchini, Paolo

19

Fiber optic damage detection for an aircraft leading edge  

Microsoft Academic Search

First test results of a multilayered fiber optic impact damage detection system fabricated within an aircraft wing composite leading edge are reported. The graphically presented results indicate that embedded optical fiber will track the growth of a delamination region. These results strongly support the concept of structurally integrated fiber optic damage assessment system for composites.

Raymond M. Measures; M. Leblanc; D. Hogg; K. McEwen

1990-01-01

20

Fiber optic damage detection for an aircraft leading edge  

NASA Astrophysics Data System (ADS)

First test results of a multilayered fiber optic impact damage detection system fabricated within an aircraft wing composite leading edge are reported. The graphically presented results indicate that embedded optical fiber will track the growth of a delamination region. These results strongly support the concept of structurally integrated fiber optic damage assessment system for composites.

Measures, Raymond M.; Leblanc, M.; Hogg, D.; McEwen, K.; Park, B.

21

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

Microsoft Academic Search

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

Stephen Kahler

2010-01-01

22

Leading edge flutter of supercavitating hydrofoils  

Microsoft Academic Search

This document represents the results of experiments and analysis of the phenomenon of leading edge flutter which has been observed to occur for supercavitating hydrofoils. The experiments confirmed the existence of such a single degree of freedom flutter involving chordwise bending and indicated that for long, natural (or vapor-filled) cavities the reduced flutter speed U sub F\\/omega sub FC was

C. Brennen; K. T. Oey; C. D. Babcock

1979-01-01

23

Dynamic stall alleviation using leading edge deformation  

NASA Astrophysics Data System (ADS)

Dynamic stall on a two dimensional oscillating airfoil is alleviated through the use of a dynamically deforming leading edge. The airfoil undergoes three motions: pitching, plunging, and simultaneous pitching and plunging. Numerical investigation of dynamic stall prevention using a thin layer, Navier-Stokes flow solver is presented. Dynamic stall prevention, postponement, and alleviation is shown for high angles of attack, primarily 20° effective angle of attack. An investigation of the combined aerodynamic interactions of the local components of the flow field is presented for understanding and alleviating dynamic stall. The effects of the deflection schedule are explained by examining the flowfield about the airfoil as it undergoes each particular motion. Dynamic stall resulting from pitching motions is fundamentally different from dynamic stall resulting from plunging motion, and therefore the ability of leading edge deformation to prevent dynamic stall becomes dependent on airfoil motion. Performance results for steady airfoils with a constant deformation angle, pitching or plunging airfoils with a constant deformation angle, and steady airfoils with a deforming leading edge are given to explain why a leading edge deformation scheme either fails or succeeds with dynamic stall alleviation. Two control systems are developed to alleviate dynamic stall. The first method is a heuristic prescribed deformation schedule based on results from a sample of different deformation schedules. The second method is a controlled deformation schedule based on the resulting flow field about the surface of the airfoil while oscillating. The second control system is developed to keep the peak suction coefficient of pressure value below a specified limit. The increase in peak coefficient of pressure values creates a more favorable pressure gradient at the leading edge, which reduces the tendency for the flow to separate. This control system is based on understanding the individual effects of leading edge deformation angle and leading edge deformation pitch rate on the value of the peak coefficient of pressure. The prescribed deformation schedule and the developed controlled deformation schedule is tested for each of the three airfoil motions. Results from the deflection schedules are compared at Mach numbers, Reynolds numbers, and reduced frequencies typical of rotorcraft environments.

Reuster, James Gavin

24

Leading edge effects in bypass transition  

NASA Astrophysics Data System (ADS)

In the presence of free-stream disturbances, the boundary layer over a flat plate circumvents the process of transition through growth of Tollmien-Schlichting waves. Instead, transition occurs at lower Reynolds numbers, through processes that are yet to be fully explored. Recent studies have shed more light on the pre-transitional boundary layer, which contains streamwise velocity streaks that attain very large amplitudes. However, the actual transition process, and the relevance of the so-called Klebanoff modes, remain unexplained. Additional effects, such as that of a finite leading-edge, pressure gradients, and surface curvature have not received much attention. Numerical simulations provide a unique complement to theory and experiments. However, large-eddy-simulation of compressible flows has remained a difficult task. In this work, a robust high-order method based on a staggered variable arrangement is developed with the aim of studying transitional and turbulent flows in a compressible medium. The present method is demonstrated to be more robust than those based on collocated grids. It has been extended to curvilinear coordinates and combined with multi-zonal implicit-explicit time marching to allow efficient simulations in the presence of solid walls. The numerical method developed is applied to boundary layer transition on a flat plate with a blunt leading edge. Five simulations, conducted within a parameter space defined by the leading-edge geometry and free-stream intensity and length scales, confirm observed effects of various parameters. For the case of a sharp leading edge, with low levels of free-stream turbulence, transition occurs through instabilities on backward jets, as observed in earlier studies. The leading-edge enhances the transition process when it is blunt, or when the free-stream turbulence is intense. Transition is brought about by wave-packet-like spot precursors that are induced at the leading-edge by interaction with strong free-stream vortices. These wave-packets contain frequencies higher than those in the unstable Tollmien-Schlichting range and move at around 50% of the free stream speed. They grow in amplitude with downstream distance and eventually break down to form a turbulent spot. Qualitative and quantitative characterization of these precursors show that they inhabit the lower half of the boundary layer and contain frequencies higher than the unstable range of Tollmien-Schlichting waves. The wave-packets have also been traced back to the leading edge and shown to be induced by interaction with strong free-stream voriticity.

Nagarajan, S.

25

Prediction of oscillatory leading-edge blowing  

NASA Astrophysics Data System (ADS)

Predictions of the effect of periodic leading-edge blowing on a NACA 0015 airfoil in turbulent flow were made using a compressible Navier-Stokes code with two-equation turbulence model. Such blowing has been demonstrated in experimental studies to delay separation at high angles of attack. The experiment (Seifert et al.) was a preliminary study to determine the sensitivity of instabilities in the flow to excitation. Predictions will be compared with experimental data.

Truman, C. Randall; Yazzie, Rufus; Salari, Kambiz

2001-11-01

26

Prediction of oscillatory leading-edge blowing  

Microsoft Academic Search

Predictions of the effect of periodic leading-edge blowing on a NACA 0015 airfoil in turbulent flow were made using a compressible Navier-Stokes code with two-equation turbulence model. Such blowing has been demonstrated in experimental studies to delay separation at high angles of attack. The experiment (Seifert et al.) was a preliminary study to determine the sensitivity of instabilities in the

C. Randall Truman; Rufus Yazzie; Kambiz Salari

2001-01-01

27

Influence of the composition of high-lead phosphate glasses on the location of the UV transmission edge and technological quality  

Microsoft Academic Search

This paper reports on the results of an investigation into the influence of the purity of the initial materials used for preparing\\u000a vitreous lead metaphosphate, the acidity of the phosphate matrix, and the contents of additives of Group I–III and V elements\\u000a and the second glass-former on the location of the UV transmission edge of simple binary and ternary lead

V. I. Arbuzov; M. V. Voroshilova; S. I. Nikitina; Yu. K. Fedorov

2006-01-01

28

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

29

Failure analysis of the space shuttle Columbia RCC leading edge  

Microsoft Academic Search

Failure analysis of the Columbia shuttle left T-seal 9 and an unidentified fragment of leading edge reinforced carbon-carbon (RCC) composite material was\\u000a carried out to determine the causes of failure. Standard metallographic and microscopy procedures were employed to identify\\u000a and characterize the failure mode. The results indicate that erosion and cracking occurred. Erosion was caused by the extreme\\u000a temperatures and

M. Bykowski; A. Hudgins; R. M. Deacon; A. R. Marder

2006-01-01

30

Early molecular events in the assembly of matrix adhesions at the leading edge of migrating cells  

Microsoft Academic Search

Cellular locomotion is driven by repeated cycles of protrusion of the leading edge, formation of new matrix adhesions and retraction of the trailing edge. In this study we addressed the molecular composition and dynamics of focal complexes, formed under the leading lamellae of motile cells, and their maturation into focal adhesions. We combined phase-contrast and fluorescence microscopy approaches to monitor

Ronen Zaidel-Bar; Christoph Ballestrem; Zvi Kam; Benjamin Geiger

2003-01-01

31

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

National Technical Information Service (NTIS)

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 a...

D. E. Glass M. A. Merrigan J. T. Sena R. S. Reid

1998-01-01

32

Effect of Leading Edge Tubercles on Marine Tidal Turbine Blades  

Microsoft Academic Search

This project investigated the impact that the addition of leading edge protuberances (tubercles) have on the effectiveness of marine tidal turbine blades, especially at lower flow speeds. The addition of leading edge tubercles to lifting foils has been shown, in previous research, to delay the onset of stall without significant hydrodynamic costs. The experimental results obtained utilizing three different blade

Mark Murray; Timothy Gruber; David Fredriksson

2010-01-01

33

Stall Delay by Leading Edge Tubercles on Humpback Whale Flipper  

Microsoft Academic Search

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

Mark Murray; David Miklosovic; Frank Fish; Laurens Howle

2003-01-01

34

Effect of Leading Edge Tubercles on Swept Humpback Whale Flipper  

Microsoft Academic Search

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

Mark Murray; David Miklosovic; Frank Fish; Laurens Howle

2004-01-01

35

Heat-Pipe-Cooled Leading Edges for Hypersonic Vehicles.  

National Technical Information Service (NTIS)

Heat pipes can be used to effectively cool wing leading edges of hypersonic vehicles. . Heat-pipe leading edge development. Design validation heat pipe testing confirmed design. Three heat pipes embedded and tested in C/C. Single J-tube heat pipe fabricat...

D. E. Glass

2006-01-01

36

Observations on the leading edge in lifted flame stabilization  

Microsoft Academic Search

The objective of this paper is to report some of the first experimental evidence for the “leading edge” flame as the stabilization mechanism in lifted jet diffusion flames [1–5]. CH fluorescence has been used to indicate the flame front location (i.e., region of chemical reaction) and thereby characterize features of the stabilization region [5, 6]. The “leading edge” flame phenomenon

K. A. Watson; K. M. Lyons; J. M. Donbar; C. D. Carter

1999-01-01

37

Leading edge design process using a commercial flow solver  

Microsoft Academic Search

A design process of an asymmetric leading edge, for laminar stability measurements in a flat plate boundary layer, is reported. The purpose is to minimize the leading edge pressure gradient region, which affects the stability characteristics of the flow. Finally, the design success is verified by wind tunnel testing.

Jens H. M. Fransson

2004-01-01

38

Towards a novel design method for impact on leading edges  

Microsoft Academic Search

Results of a parametric study concerning low velocity impact on leading edge profiles is presented. This work is the first part of a larger program on the development of an engineering design method for impact on Glare. In this first part, experimental tests and numerical simulations on two-dimensional aluminium leading edge profiles were carried out. An extensive parametric study was

Houten van M. H; H. Kaplan

2006-01-01

39

Leading edge design process using a commercial flow solver  

NASA Astrophysics Data System (ADS)

A design process of an asymmetric leading edge, for laminar stability measurements in a flat plate boundary layer, is reported. The purpose is to minimize the leading edge pressure gradient region, which affects the stability characteristics of the flow. Finally, the design success is verified by wind tunnel testing.

Fransson, Jens H. M.

2004-12-01

40

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. 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, Bernard (Palo Alto, CA)

1983-01-01

41

Design and development of a dynamically deforming leading edge airfoil for unsteady flow control  

Microsoft Academic Search

A novel approach to unsteady flow separation and dynamic stall control using a dynamically deforming leading edge airfoil is described. The design details of a carbon-fiber composite skin airfoil having a thickness of 0.002 in at the leading edge and capable of deforming at 20 Hz in unsteady flow at freestream Mach numbers of up to 0.45, are discussed. Implementation

M. S. Chandrasekhara; L. W. Carr; M. C. Wilder; G. N. Paulson; C. D. Sticht

1997-01-01

42

Columbia tragedy: High-temperature materials chemistry and thermodynamic considerations of the breached wing leading edge  

Microsoft Academic Search

Metallurgical analysis of debris from the leading edge of the breached left wing of the Columbia space shuttle demonstrated that the temperatures inside the leading edge structural subsystem exceeded 1760 ?C (3200 ?F).\\u000a A thin, relatively uniform deposit containing aluminum, Inconel, and Cerachrome was found inside most of the reinforced carbon-carbon\\u000a composite panels. Such deposition indicates the melting and concurrent

E. Opila; N. Jacobson; G. Jerman

2006-01-01

43

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

44

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

45

Heat pipes for wing leading edges of hypersonic vehicles  

Microsoft Academic Search

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

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

1990-01-01

46

Efficient Identification of Leading-Edge Expertise: Screening vs. Pyramiding  

Microsoft Academic Search

In order to find ideas for leading edge innovations, the lead user method recently gained much interest. A very important step in this method is the identification of lead users. Recently, there is a notable switch towards a technique we term \\

Eric von Hippel; Nikolaus Franke; R. Prugl

2006-01-01

47

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

48

Formation of Leading-Edge Pinholes in the Space Shuttle Wings Investigated.  

National Technical Information Service (NTIS)

The space shuttle wing leading edge and nose cap are composed of a carbon/carbon composite that is protected by silicon carbide. The coefficient of thermal expansion mismatch leads to cracks in the silicon carbide. The outer coating of the silicon carbide...

N. S. Jacobson

2000-01-01

49

Impact Damage on Titanium Leading Edges from Small Soft Body Objects.  

National Technical Information Service (NTIS)

Impact damage on titanium leading edge configurations was investigated by performing leading edge soft-body impacts on flat-edge and tapered-edge specimens. The objectives were to determine the laboratory specimen size, boundary condition, and test method...

R. S. Bertke J. P. Barber

1979-01-01

50

Effect of Leading Edge Tubercles on Marine Tidal Turbine Blades  

NASA Astrophysics Data System (ADS)

This project investigated the impact that the addition of leading edge protuberances (tubercles) have on the effectiveness of marine tidal turbine blades, especially at lower flow speeds. The addition of leading edge tubercles to lifting foils has been shown, in previous research, to delay the onset of stall without significant hydrodynamic costs. The experimental results obtained utilizing three different blade designs (baseline and two tubercle modified) are compared. All blades were designed in SolidWorks and manufactured utilizing rapid prototype techniques. All tests were conducted in the 120 ft tow tank at the U.S. Naval Academy using a specifically designed experimental apparatus. Results for power coefficients are presented for a range of tip speed ratios. Cut-in velocity is also compared between the blade designs. For all test criteria, the tubercle modified blades significantly outperformed the smooth leading edge baseline design blades.

Murray, Mark; Gruber, Timothy; Fredriksson, David

2010-11-01

51

Rarefaction effects in hypersonic flow about a blunted leading edge  

NASA Astrophysics Data System (ADS)

The rarefaction effects in the problem of hypersonic flow around a profile with blunted leading edge are studied in the flow regimes when the edge bluntness radius is comparable with the mean free path in the free stream. The flow around a cylindrically blunted thick plate at zero incidence was modelled numerically in the transitional regime by using the direct simulation Monte Carlo method, the finite-difference solution of the kinetic equation of the relaxation type (the ellipsoidal statistical model), and the solution of the Navier — Stokes equations. It is shown that for the Knudsen numbers in terms of the bluntness radius below 0.1, the Navier — Stokes equations can be applied successfully for viscous flow description behind the shock wave provided that the initial rarefaction effects are taken into account via the slip and temperature jump boundary conditions on the plate surface. For Knudsen number of about 0.5, the rarefaction effects are more appreciable; in particular, a substantial anisotropy of the distribution function takes place, but the Navier — Stokes equations yield, as before, a qualitatively correct result. The initial stage of the boundary layer development in the edge vicinity has been studied. In the considered range of Knudsen numbers, the entropy layer near the edge is comparable with the boundary layer thickness. As the distance from the leading edge increases one observes the absorption of the entropy layer by the boundary layer. In the studied parameter range, the interaction between the boundary and entropy layers leads to a flow stability increase.

Ivanov, M. S.; Khotyanovsky, D. V.; Shershnev, A. A.; Kudryavtsev, A. N.; Shevyrin, A. A.; Yonemura, S.; Bondar, Ye. A.

2011-12-01

52

Low Reynolds Number Low Aspect Ratio Leading Edge Separation Dynamics  

Microsoft Academic Search

The low Reynolds number flow conditions for a low aspect ratio wing are investigated using time resolved PIV with specific emphasis on the leading edge vortex generation at high angles of attack. The flow is highly three dimensional and the flow visualization shows very strong tip vortices which extend over a major portion of the wing. The separation bubble consists

Daniel Morse; James Liburdy

2008-01-01

53

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

54

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

55

The leading edge of production wafer probe test technology  

Microsoft Academic Search

Microelectronic wafer and die level testing have undergone significant changes in the past few years. This work's first section describes today's leading edge characteristics for numerous areas of this test technology including the minimum I\\/O pad pitch, advances in contactor technologies, maximum number of l\\/Os probed, maximum number of die tested in parallel, the largest prober and substrates, and the

W. R. Mann; Frederick L. Taber; Philip W. Seitzer; Jerry J. Broz

2004-01-01

56

The Leading Edge of Production Wafer Probe Test Technology  

Microsoft Academic Search

Microelectronic wafer and die level testing have undergone significant changes in the past few years. This paper's first section describes today's leading edge characteristics for numerous areas of this test technology including the minimum I\\/O pad pitch, advances in contactor technologies, maximum number of I\\/Os probed, maximum number of die tested in parallel, the largest prober and substrates, and the

William R. Mann; Frederick L. Taber; Philip W. Seitzer; Jerry J. Broz

2004-01-01

57

Combined overlay, focus and CD metrology for leading edge lithography  

Microsoft Academic Search

As leading edge lithography moves to 22-nm design rules, low k1 technologies like double patterning are the new resolution enablers, and system control and setup are the new drivers to meet remarkably tight process requirements. The way of thinking and executing setup and control of lithography scanners is changing in four ways. First, unusually tight process tolerances call for very

Martin Ebert; Hugo Cramer; Wim Tel; Michael Kubis; Henry Megens

2011-01-01

58

The artificially blunted leading edge concept for aerothermodynamic performance enhancement  

Microsoft Academic Search

An innovative aerothermodynamic performance enhancement concept for blunted geometries in hypervelocity flight is described. An Artificially Blunted Leading Edge (ABLE) is sought to be created by the use of a flow-through channel sized to choke at supersonic (in the normal direction) conditions. As a result, a normal shock stands off the channel but the high post-shock pressures have no wall

Anurag Gupta

1999-01-01

59

Making Use of Gestures, the Leading Edge in Literacy Development  

Microsoft Academic Search

Quantitative and qualitative studies of knowing and learning in science and mathematics show that gestures used in conjunction with utterances are the leading edge of cognitive development. That is, gestures express new levels of understanding before a student expresses this new understanding in words; more so, gestures express the new concepts although language still holds on to the old, incorrect

Wolff-Michael Roth

60

Leading-Edge Vortices Elevate Lift of Autorotating Plant Seeds  

Microsoft Academic Search

As they descend, the autorotating seeds of maples and some other trees generate unexpectedly high lift, but how they attain this elevated performance is unknown. To elucidate the mechanisms responsible, we measured the three-dimensional flow around dynamically scaled models of maple and hornbeam seeds. Our results indicate that these seeds attain high lift by generating a stable leading-edge vortex (LEV)

D. Lentink; W. B. Dickson; J. L. van Leeuwen; M. H. Dickinson

2009-01-01

61

Leading-edge correction for the supercavitating flat-plate hydrofoil  

Microsoft Academic Search

A leading-edge correction is obtained via the method of matched asymptotic expansions to the first-order linearized solution for the potential flow past a supercavitating flat-plate hydrofoil at zero cavitation number. The composite expansions for the pressure on the plate and the shape of the upper cavity are seen to compare well with the exact solution due to Rayleigh.

A. Plotkin

1978-01-01

62

CAD challenges for leading-edge multimedia designs  

Microsoft Academic Search

Multimedia designs are among the most complex leading-edge integrated circuits that are made today. In this session, CAD architects for three industry-leading multimedia products will discuss new challenges that arise across the CAD flow - from system and architecture level through physical implementation - as we approach billion-transistor devices.The first talk will focus on system-level specification and codesign of embedded

Andrew B. Kahng

2006-01-01

63

CAD Challenges for Leading-Edge Multimedia Designs  

Microsoft Academic Search

Multimedia designs are among the most complex leading-edge integrated circuits that are made today. In this session, CAD architects for three industry-leading multimedia products will discuss new challenges that arise across the CAD flow — from system and architecture level through physical implementation - as we approach billion-transistor devices. The first talk will focus on system-level specification and codesign of

A. B. Kahng

2006-01-01

64

Leading-edge receptivity for bodies with mean aerodynamic loading  

NASA Astrophysics Data System (ADS)

Boundary-layer receptivity in the leading-edge region of a cambered thin airfoil is analysed for the case of a low-Mach-number flow. Acoustic free-stream disturbances are considered. Asymptotic results based on large Reynolds number (U^2 / ? ? ? 1) are presented, supplemented by numerical solutions. The influence of mean aerodynamic loading enters the theory through a parameter ?, which provides a measure of the flow speed variations in the leading-edge region, due to flow around the leading edge from the lower surface to the upper. A Strouhal number based on airfoil nose radius, S = ? r_n/U, also enters the theory. The variation of the receptivity level as a function of ? and S is analysed. Modest levels of aerodynamic loading are found to decrease the receptivity level for the upper surface of the airfoil, while the receptivity is increased for the lower surface. For larger angles of attack close to the critical angle for boundary layer separation, a local rise in the receptivity occurs for the upper surface, while on the lower surface the receptivity decreases. These effects are more pronounced at larger values of S. While the Tollmien-Schlichting wave does not emerge until a downstream distance of O((U^2 / ? ?)^{1/3} U / ?), the amplitude of the Tollmien-Schlichting wave is influenced by the acoustic free-stream disturbances only in a relatively small region near the leading edge, of length approximately 4 U/?. The numerical receptivity coefficients calculated, together with the asymptotic eigenfunctions presented, provide all the necessary information for transition analysis from the interaction of acoustic disturbances with leading-edge geometry.

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

2005-07-01

65

Development of a Graphite/Bismaleimide Leading Edge for the F-111 (EF-111A) Horizontal Stabilizer.  

National Technical Information Service (NTIS)

The F-111 (EF-111A) horizontal stabilizer leading edge was selected as the baseline component to demonstrate the superior supportability characteristics of composites. The production component is a full-depth aluminum honeycomb sandwich construction that ...

J. A. Suarez S. C. Nolet M. Carteaux

1988-01-01

66

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

67

Computational aeroacoustic simulations of leading-edge slat flow  

Microsoft Academic Search

High-lift devices on modern airliners are a major contributor to overall airframe noise. In this paper the aeroacoustics of leading-edge slat devices in a high-lift configuration are investigated computationally. A hierarchical methodology is used to enable the rapid evaluation of different slat configurations. The overall goal is to gain a deeper understanding of the noise generation and amplification mechanisms in

K. Takeda; X. Zhang; P. A. Nelson

2004-01-01

68

Receptivity to surface roughness near a swept leading edge  

Microsoft Academic Search

The formation of stationary crossflow vortices in a three-dimensional boundary layer due to surface roughness located near the leading edge of a swept wing is investigated using numerical solutions of the compressible Navier{Stokes equations. The numerical solutions are used to evaluate the accuracy of theoretical receptivity predictions which are based on the parallel-flow approximation. By reformulating the receptivity theory to

S. S COTT C OLLIS; SANJIVA K. L ELE

1999-01-01

69

A high-performance, low-cost, leading edge discriminator  

Microsoft Academic Search

A high-performance, low-cost, leading edge discriminator has been designed with a timing performance comparable to state-of-the-art,\\u000a commercially available discriminators. A timing error of 16 ps is achieved under ideal operating conditions. Under more realistic\\u000a operating conditions the discriminator displays a timing error of 90 ps. It has an intrinsic double pulse resolution of 4\\u000a ns which is better than most

S. K. Gupta; Y. Hayashi; A. Jain; S. Karthikeyan; S. Kawakami; K. C. Ravindran; S. C. Tonwar

2005-01-01

70

Computational aeroacoustic simulations of leading-edge slat flow  

NASA Astrophysics Data System (ADS)

High-lift devices on modern airliners are a major contributor to overall airframe noise. In this paper the aeroacoustics of leading-edge slat devices in a high-lift configuration are investigated computationally. A hierarchical methodology is used to enable the rapid evaluation of different slat configurations. The overall goal is to gain a deeper understanding of the noise generation and amplification mechanisms in and around the slat, and the effects of slat system geometry. In order to perform parametric studies of the aeroacoustics, a simplified 2-D model of the slat is used. The flow and aeroacoustics are computed using a compressible, unsteady, Reynolds-Averaged Navier-Stokes code. A robust buffer zone boundary condition is used to prevent the reflection of outgoing acoustic waves from contaminating the long-time solution. A Ffowcs Williams-Hawkings solver is used to compute the far field acoustic field from the unsteady flow solution and determine the directivity. The spanwise correlation length used is derived from experimental data of this high-lift configuration. The effect of spanwise correlation length on the acoustic far field is examined. The aeroacoustics of the slat system are largely governed by the geometry, especially in terms of slat overlap. We perform a study of the effects of trailing edge thickness, horizontal and vertical overlap settings for the slat on near field wave propagation and far field directivity. The implications for low-noise leading edge slat design are discussed.

Takeda, K.; Zhang, X.; Nelson, P. A.

2004-02-01

71

Membrane and actin dynamics interplay at lamellipodia leading edge.  

PubMed

The multimolecular WAVE regulatory (WRC) and Arp2/3 complexes are primarily responsible to generate pushing forces at migratory leading edges by promoting branch elongation of actin filaments. The architectural complexity of these units betrays the necessity to impose a tight control on their activity. This is exerted through temporally coordinated and coincident signals which limit the intensity and duration of this activity. In addition, interactions of the WRC and Arp2/3 complexes with membrane binding and surprisingly membrane trafficking proteins is also emerging, revealing the existence of an 'endocytic wiring system' that spatially restrict branched actin elongation for the execution of polarized functions during cell migration. PMID:23639310

Bisi, Sara; Disanza, Andrea; Malinverno, Chiara; Frittoli, Emanuela; Palamidessi, Andrea; Scita, Giorgio

2013-04-29

72

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

73

Boundary Layer Leading Edge Receptivity to Sound at Incidence Angles.  

NASA Astrophysics Data System (ADS)

The leading edge receptivity to acoustic waves of two-dimensional parabolic bodies was investigated using a spatial solution of the Navier-Stokes equations in vorticity/stream function form in parabolic coordinates. The free-stream is composed of a uniform flow with a superposed periodic velocity fluctuation of small amplitude. The method follows that of Haddad & Corke(J. Fluid Mech.), 368, 1998 in which the solution for the basic flow and linearized perturbation flow are solved separately. We primarily investigated the effect of frequency and angle of incidence (-180^circ <= ? <= 180^circ) of the acoustic waves on the leading edge receptivity. The results at ?=0^circ were found to be in quantitative agreement with those of Haddad & Corke, and substantiated the Strouhal number scaling based on the nose radius. The results with sound waves at angles of incidence agreed qualitatively with the analysis of Hammerton & Kerschen (1992). These included a maximum receptivity at ?=90^circ, and an asymmetric variation in the receptivity with sound incidence angle, with minima at angles which were slightly less than ?=0^circ and 180^circ.

Erturk, E.; Corke, T. C.

1999-11-01

74

Leading Edge Vortex Detection Using On-Body Pressure Sensing  

NASA Astrophysics Data System (ADS)

Ongoing experiments within the Center for Environmental Sensing and Modeling (CENSAM) have shown that the low pressure region characteristic of a vortex allows for their detection and tracking using pressure sensors alone. While early experiments were conducted with wall mounted pressure sensors and externally generated vortices, a new series of experiments has succeeded in detecting separated flow generated by the sensing body. A combined pressure sensing and particle image velocimetry (PIV) approach was used to detect the leading edge vortex shed from a hydrofoil accelerated at a fixed angle of attack. A NACA 0018 foil was instrumented with four pressure sensors at discrete locations along the foil in the chord-wise direction. When accelerated from rest, the traces from each of the four pressure sensors displayed a distinctive, transient drop, consistent with results observed in previous experiments. From the pressure sensor results, it was theorized that a leading edge vortex was being created, and subsequently shed and convected along the foil chord. Two-dimensional PIV techniques were used to image the flow near the foil surface, allowing the anticipated vortex formation and shedding to be verified.

Dusek, Jeff; Dahl, Jason; Triantafyllou, Michael

2010-11-01

75

Numerical Simulation of Leading-Edge Receptivity to Freestream Vorticity  

NASA Astrophysics Data System (ADS)

The receptivity to freestream vorticity of the boundary layer over a flat plate with an elliptic leading edge is investigated numerically. The flow is simulated by solving the incompressible Navier-Stokes system in general curvilinear coordinates with the vorticity and stream function as dependent variables. A finite-difference scheme which is second-order accurate in both space and time is used. As a first step, the steady basic-state solution is computed. Then a small-amplitude vortical disturbance is introduced at the upstream boundary and the governing equations solved time accurately to evaluate the spatial and temporal growth of the perturbations leading to instability waves (Tollmien -Schlichting waves) in the boundary layer. Disturbance amplitude, orientation, the effect of the leading edge and of juncture curvature are investigated for the case of spanwise vorticity. Simulations reveal, for the conditions considered, a linear variation in the TS response with forcing amplitude for a perturbation of the freestream velocity which is either symmetrical or asymmetrical with respect to the basic-state stagnation streamline. The presence of a large transverse component of velocity along the basic-state stagnation streamline for the case of an asymmetrical perturbation of velocity results in the appearance of a superharmonic component near the nose. This superharmonic decays rapidly along the nose for the flow conditions considered. In all cases considered, the first clear appearance of the TS mode occurs aft of the surface pressure-gradient maximum in the juncture region. Changes to the geometry which increase the maximum in the basic-state pressure gradient near the juncture are found to increase receptivity.

Buter, Thomas Alan

76

Feasibility of Metallic Structural Heat Pipes as Sharp Leading Edges for Hypersonic Vehicles  

Microsoft Academic Search

Hypersonic flight with hydrocarbon-fueled airbreathing pr opulsion requires sharp leading edges. This generates high temperatures at the leading edge surface which cannot be sustained by most materials. By integrating a planar heat pipe into the structure of the leading edge, the heat can be conducted to large flat surfaces from which it can b e radiated out to the environ-

Craig A. Steeves; Ming Y. He; Scott D. Kasen; Lorenzo Valdevit; Haydn N. G. Wadley; Anthony G. Evans

2009-01-01

77

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

Microsoft Academic Search

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

Charles J. Camarda; David E. Glass

1992-01-01

78

Leading Edge Aerothermal Inverse Design of Hyersonic Vehicle Based on Homotopy Optimization Method  

Microsoft Academic Search

Blunt leading edge with profiles of circular or power law shape is often used to decrease the aerodynamic heating of a vehicle when it flights into hypersonic regime. In order to further reduce the peak of heat flux of the leading edge, an inverse shape design method is presented in this paper. The leading edge is parameterized by using B-spline

K. Cui; S. C. Hu; T. Y. Gao; X. P. Wang; G. W. Yang

2011-01-01

79

Centrifugal pump performance drop due to leading edge cavitation  

NASA Astrophysics Data System (ADS)

This paper deals with the leading edge cavitation of the impeller of a single stage centrifugal pump. A centrifugal pump with and without inducer is investigated by numerical simulation. The simulation results of the pump with inducer were compared with experimental data under cavitating and non-cavitating situation. An acceptable agreement has been obtained for the overall performance. Cavitation phenomena are found in varied area near the impeller inlet at the condition in the impeller flow passage and induce unexpected head drop and blade load for the pump without inducer. Violent excitement of cavitation appears at conditions of low partial flow rate and low inlet pressure. As to that with inducer, through obvious cavitation occurs in the inducer passage, no violent cavitation is found in the impeller passage. The overall performance curves are also different between the two conditions.

Li, X. J.; Pan, Z. Y.; Zhang, D. Q.; Yuan, S. Q.

2012-11-01

80

Managed aquifer recharge: rediscovering nature as a leading edge technology.  

PubMed

Use of Managed Aquifer Recharge (MAR) has rapidly increased in Australia, USA, and Europe in recent years as an efficient means of recycling stormwater or treated sewage effluent for non-potable and indirect potable reuse in urban and rural areas. Yet aquifers have been relied on knowingly for water storage and unwittingly for water treatment for millennia. Hence if 'leading edge' is defined as 'the foremost part of a trend; a vanguard', it would be misleading to claim managed aquifer recharge as a leading edge technology. However it has taken a significant investment in scientific research in recent years to demonstrate the effectiveness of aquifers as sustainable treatment systems to enable managed aquifer recharge to be recognised along side engineered treatment systems in water recycling. It is a 'cross-over' technology that is applicable to water and wastewater treatment and makes use of passive low energy processes to spectacularly reduce the energy requirements for water supply. It is robust within limits, has low cost, is suitable from village to city scale supplies, and offers as yet almost untapped opportunities for producing safe drinking water supplies where they do not yet exist. It will have an increasingly valued role in securing water supplies to sustain cities affected by climate change and population growth. However it is not a universal panacea and relies on the presence of suitable aquifers and sources of water together with effective governance to ensure human health and environment protection and water resources planning and management. This paper describes managed aquifer recharge, illustrates its use in Australia, outlining economics, guidelines and policies, and presents some of the knowledge about aquifer treatment processes that are revealing the latent value of aquifers as urban water infrastructure and provide a driver to improving our understanding of urban hydrogeology. PMID:21076220

Dillon, P; Toze, S; Page, D; Vanderzalm, J; Bekele, E; Sidhu, J; Rinck-Pfeiffer, S

2010-01-01

81

Subsonic Balance and Pressure Investigation of a 60-Deg delta Wing with Leading-Edge Devices (Data Report).  

National Technical Information Service (NTIS)

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 test...

D. M. Rao S. A. Tingas

1981-01-01

82

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

83

Structure of fractional edge states: A composite-fermion approach  

NASA Astrophysics Data System (ADS)

I study the structure of the two-dimensional electron-gas edge in the quantum Hall regime using the composite-fermion approach. The electron density distribution and the composite-fermion energy spectrum are obtained numerically in the Hartree approximation for bulk filling factors ?=1,1/3,2/3,1/5. For a very sharp edge of the ? =1 state the one-electron picture is valid. As the edge width a is increased the density distribution shows features related to the fractional states and new fractional channels appear in pairs. For a very smooth edge I find, by quasiclassical means, the number of channels p~ ?a/lH , where lH is the magnetic length.

Chklovskii, Dmitri B.

1995-04-01

84

The inception of leading-edge cavitation on thin hydrofoils  

NASA Astrophysics Data System (ADS)

The inception of leading-edge cavitation on smooth thin hydrofoils at moderate Reynolds number flows is investigated by an asymptotic approach and numerical simulations. The asymptotic theory is based on Rusak (1994) and demonstrates that the flow about a thin hydrofoil can be described in terms of an outer and inner regions that asymptotically match each other. The flow in the outer region is dominated by the classical thin hydrofoil theory. Scaled coordinates and a modified Reynolds number (Re_M) are used to correctly account for the nonlinear behavior around the nose. It results in a model problem of a uniform flow past a semi-infinite parabola with a far-field circulation governed by a parameter A that is related to the hydrofoil's angle of attack, nose radius of curvature, and camber. The model parabola problem consists of a viscous flow that is solved numerically to determine the minimum pressure coefficient and the angle of attack for the inception of cavitation as function of the flow Reynolds number and thermodynamic properties. The predictions according to this approach show good agreement with results from full numerical simulations and available experimental data. This simplified approach provides for the first time a universal criterion to determine the angle for the onset of cavitation on hydrofoils with a parabolic nose and the effect of hydrofoil's thickness ratio, nose radius of curvature, camber and flaps on this phenomenon.

Morris, Wallace J., II; Rusak, Zvi; Peles, Yoav

2004-11-01

85

Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 1: Material Modelling  

Microsoft Academic Search

Fibre Metal Laminates with layers of aluminium alloy and high strength glass fibre composite have been reported to possess excellent impact properties and be suitable for aircraft parts likely to be subjected to impacts from objects such as runway debris or birds. In a collaborative research project, aircraft wing leading edge structures with a glass-based FML skin have been designed,

M. A. McCarthy; J. R. Xiao; N. Petrinic; A. Kamoulakos; V. Melito

2004-01-01

86

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

87

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

Microsoft Academic Search

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

M. J. Stanway; A. H. Techet

2006-01-01

88

Experimental evaluation of joint designs for a space-shuttle orbiter ablative leading edge  

Microsoft Academic Search

The thermal performance of two types of ablative leading-edge joints for a space-shuttle orbiter were tested and evaluated. Chordwise joints between ablative leading-edge segments, and spanwise joints between ablative leading-edge segments and reusable surface insulation tiles were exposed to simulated shuttle heating environments. The data show that the thermal performance of models with chordwise joints to be as good as

S. S. Tompkins; W. P. Kabana

1975-01-01

89

The receptivity of laminar boundary layer flow to leading edge vibrations  

NASA Astrophysics Data System (ADS)

The receptivity of laminar boundary layer flow to leading edge vibrations has been studied experimentally. The experiments reported on in this paper include (1) a stable case and (2) an unstable case. These experiments identify the forcing field imposed by the vibrating leading edge and track the subsequent development of the unstable Tollmien-Schlichting waves. Detailed velocity measurements around the leading edge help in the identification of the source of such unstable boundary layer waves. The near-singular nature of the response of the fluid around the vibrating leading edge is found to be responsible for the generation of unstable boundary layer waves.

Chiu, W. K.; Norton, M. P.

1990-08-01

90

Effects of asymmetric leading edge flap deflection on delta wings  

NASA Astrophysics Data System (ADS)

Scope and method of study. The purpose of this study was to examine the effects that asymmetric flap deflection has on delta wings. The study was performed using computational and experimental methods. Computational studies were performed using an inviscid computer model that was coupled with the rigid body equation of motion in oscillations to simulate the fluid structure interaction. Investigation focuses on an isolation of quasi-steady effects on a delta wing through an application of the roll-rate boundary conditions. Spanwise camber changes through differential flap deflection was investigated. Experimental measurements on roll moment and pressure distribution over a 65sp° and 80sp° sweep angle wings. The effect of turbulent boundary layer has on the wings was investigated by placing trip wires over the wings. Findings and conclusions. Computational results indicate that quasi-steady effects have a damping effect on the motion primarily because of the hysteresis behavior of vortex position normal to the wing. Spanwise camber when applied proportional to roll rate has been shown to be capable controlling the wing when in roll. Experimental results indicated that asymmetric flap deflection (left flap downward, right flap upward) present 3 different behavior on the wings as the angle of attack changes. The 80sp° wing roll left for angles of attack between 0sp° to 4sp°. Does not move or 5sp° angle of attack. Rolls right for angles of attack higher than 6sp°. The same roll reversal phenomenon was observed for the 65sp° wing, but at different angles of attack. The reversal in roll moment can be explained by considering both the longitudinal and lateral flow effects. At low angles of attack the upward flap has a higher local angle of attack, and vice-versa on the downward flap. This increases the effective angle of attack, which increases the lift and generates a moment toward the downward flap. At large angles of attack, the crossflow becomes dominant due to the formation of the leading edge vortices. The downward deflected flap results in a stronger vortex closer to the wing, generating a roll moment in the direction of the upward flap. Trip wires shown to have a considerably effect on the flow over the wings.

Ize, Carlos

91

The Leading Edge Effect on the Flow over a Flat Plate at M = 10.  

National Technical Information Service (NTIS)

A study of the leading edge effects on the flow over a flat plate was made at a Mach number of 10. The Reynolds number based on free stream conditions and leading edge thickness varied from 115, where viscous effects predominated, to 14,550, where invisci...

J. C. Townsend W. R. Vollmar I. E. Vas

1966-01-01

92

Novel circuit design and process technology for leading-edge products  

Microsoft Academic Search

Achieving power, performance, yield and cost scaling targets at leading edge technology nodes has become significantly more challenging. Success is driven by making the optimal combination of process, design, and package decisions. In this paper, we report novel circuit design and process technologies for leading-edge products. We focus on two topics: (1) chip design optimization using extremely regular layout methodology,

K. Miyamoto; A. Strojwas; E. Hosomi; M. Ooida; H. Ezawa; M. Fukuda; Y. Matsubara; K. Numata

2010-01-01

93

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

Microsoft Academic Search

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

A. I. Kalfas; R. L. Elder

1993-01-01

94

Leading-edge adamantyl polymers designed for 193 nm lithography  

Microsoft Academic Search

There are some practical candidates for next generation lithography (NGL). However, many subjects are left behind and there is still no effective technique. One of those subjects is reduction of line edge roughness (LER)\\/line width roughness (LWR). As compared with 2-methyl-2-adamantyl methacrylate which is mostly used in 193nm lithography as acid cleavable monomer, it became clear that our new monomers

Kazuya Fukushima; Shinji Tanaka; Nobuaki Matsumoto; Hidetoshi Ohno; Naoya Kawano; Hideki Yamane; Naoyoshi Hatakeyama; Katsuki Ito

2008-01-01

95

Convergence of Strain Energy Release Rate Components for Edge-Delaminated Composite Laminates.  

National Technical Information Service (NTIS)

Strain energy release rates for edge delaminated composite laminates were obtained using quasi 3 dimensional finite element analysis. The problem of edge delamination at the -35/90 interfaces of an 8-ply composite laminate subjected to uniform axial strai...

I. S. Raju J. H. Crews M. A. Aminpour

1987-01-01

96

Bonded lap joints of composite laminates with tapered edges  

Microsoft Academic Search

This study presents a semi-analytical solution method to analyze the geometrically nonlinear response of bonded composite lap joints with tapered and\\/or non tapered adherend edges under uniaxial tension. The solution method provides the transverse shear and normal stresses in the adhesives and in-plane stress resultants and bending moments in the adherends. The method utilizes the principle of virtual work in

E. Oterkus; A. Barut; E. Madenci; S SMELTZERIII; D. R. Ambur

2006-01-01

97

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

98

Compositional variation in bullet lead manufacture.  

PubMed

The concentrations of antimony, copper, tin, arsenic, silver, bismuth, and cadmium in lead alloys produced by two smelters and one ammunition manufacturer were determined using inductively coupled plasma-atomic emission spectrometry. These element concentrations were used to measure the variations in composition of lead products that result from various processes involved in the manufacture of lead projectiles. In general, when a pot containing molten lead is used to cast a number of objects, these objects are similar, although not necessarily analytically indistinguishable in their elemental compositions. In each subsequent step in the processing of lead at the smelter and at the ammunition manufacturer, the size of an individual homogeneous melt of lead decreases as more distinct compositions are formed as a result of remelting and mixing of sources, including lead scrap. The ammunition manufacturer in this study produced at least 10 compositionally distinguishable groups of bullet wire in a 19.7-h period. The largest group could potentially be used to produce a maximum of 1.3 million compositionally indistinguishable 40 grain bullets. PMID:12353580

Koons, Robert D; Grant, Diana M

2002-09-01

99

On erosion issues associated with the leading edge of wind turbine blades  

NASA Astrophysics Data System (ADS)

The increasing developments in wind turbine technology, coupled with an unpredictable operating environment, present significant challenges regarding erosion issues on the leading edge of the blade tips. This review examines the potential degradation posed by the different environmental variables, with specific emphasis on both rain droplet and hailstone impact on the blade leading edge. Drawing on both the insights from experimental results and recent field data from the literature, the mechanisms of leading edge erosion are discussed. Meteorological tools that may enable rain and hailstone erosion prediction are addressed, as well as potential experimental and numerical approaches that may provide insight into the nature of impact and erosion on the blade surface.

Keegan, M. H.; Nash, D. H.; Stack, M. M.

2013-09-01

100

Direct simulation Monte Carlo of rarefied hypersonic flow on power law shaped leading edges  

NASA Astrophysics Data System (ADS)

A numerical study of several parameters that influence the flowfield structure, aerodynamic surface quantities and shock wave structure at rarefied hypersonic flow conditions is conducted on power law shaped leading edges. The calculations are performed with a detailed computer code that properly accounts for nonequilibrium effects and that has been demonstrated to yield excellent comparisons with flight- and ground-test data. The flowfield structure, aerodynamic surface quantities and shock wave structure of power law shaped leading edges are examined in order to provide information on how well these shapes could stand as possible candidates for blunting geometries of hypersonic leading edges. Newtonian flow analysis has shown that these shapes exhibit both blunt and sharp aerodynamic properties. Moreover, computational investigation of minimum-drag bodies at supersonic and moderate hypersonic speeds has indicated that power law shapes for certain exponents yield the lowest wave drag. These qualities make power law shapes strong candidates for leading edge design. A very detailed description of the impact on the flow properties, such as velocity, density, temperature and pressure, has been presented separately in the vicinity of the nose of the leading edges due to changes in their shapes. Numerical solutions show that the shape of the leading edge disturbed the flowfield far upstream, where the domain of influence decreased as the leading edge became aerodynamically sharp. A detailed procedure is presented to predict the pressure gradient along the body surface in a rarefied environment. Numerical solutions show that the pressure gradient behavior follows that predicted by Newtonian theory. It is found that the pressure gradient along the body surface goes to zero at the nose of the leading edge for power law exponents less than 2/3, a characteristic of a blunt body. It is finite for power law exponent of 2/3 and goes to minus infinite for power law exponents larger than 2/3, a characteristic of a sharp body. Numerical solutions show that the stagnation point heating for power law leading edges with finite curvature radius follows that for classical blunt body, i.e., the stagnation point heating is inversely proportional to the square root of the nose radius of the leading edge. For those power law leading edges with zero radius of curvature, the stagnation point heating is not a function of the radius of curvature in the vicinity of the leading edges, but agrees with the continuum prediction far from the stagnation point.

Santos, Wilson Fernando Nogueira Dos

101

Prediction of Unsteady Aerodynamic Loadings Caused by Leading Edge and Trailing Edge Control Surface Motions in Subsonic Compressible Flow: Analysis and Results.  

National Technical Information Service (NTIS)

A theoretical analysis and computer program was developed for the prediction of unsteady lifting surface loadings caused by motions of leading edge and trailing edge control surfaces having sealed gaps. The final form of the downwash integral equation was...

W. S. Rowe M. C. Redman F. E. Ehlers J. D. Sebastian

1975-01-01

102

Prediction of Unsteady Aerodynamic Loadings Caused by Leading Edge and Trailing Edge Control Surface Motions in Subsonic Compressible Flow: Computer Program Description.  

National Technical Information Service (NTIS)

A digital computer program has been developed to calculate unsteady loadings caused by motions of lifting surfaces with leading edge or trailing edge controls based on the 9subsonic kernel function approach. The pressure singularities at hinge line and si...

M. C. Redman W. S. Rowe

1975-01-01

103

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

104

Asymmetric distribution of Echinoid defines the epidermal leading edge during Drosophila dorsal closure.  

PubMed

During Drosophila melanogaster dorsal closure, lateral sheets of embryonic epidermis assemble an actomyosin cable at their leading edge and migrate dorsally over the amnioserosa, converging at the dorsal midline. We show that disappearance of the homophilic cell adhesion molecule Echinoid (Ed) from the amnioserosa just before dorsal closure eliminates homophilic interactions with the adjacent dorsal-most epidermal (DME) cells, which comprise the leading edge. The resulting planar polarized distribution of Ed in the DME cells is essential for the localized accumulation of actin regulators and for actomyosin cable formation at the leading edge and for the polarized localization of the scaffolding protein Bazooka/PAR-3. DME cells with uniform Ed fail to assemble a cable and protrude dorsally, suggesting that the cable restricts dorsal migration. The planar polarized distribution of Ed in the DME cells thus provides a spatial cue that polarizes the DME cell actin cytoskeleton, defining the epidermal leading edge and establishing its contractile properties. PMID:21263031

Laplante, Caroline; Nilson, Laura A

2011-01-24

105

Development of Advanced High Lift Leading Edge Technology for Laminar Flow Wings.  

National Technical Information Service (NTIS)

This paper describes the Advanced High Lift Leading Edge (AHLLE) task performed by Northrop Grumman Systems Corporation, Aerospace Systems (NGAS) for the NASA Subsonic Fixed Wing project in an effort to develop enabling high-lift technology for laminar fl...

A. Korntheuer J. C. Lin M. M. Bright S. Komadina

2013-01-01

106

Low Frequency Oscillation in the Flow over a NACA0012 Airfoil with an Iced Leading Edge.  

National Technical Information Service (NTIS)

The unusually low frequency oscillation in the wake of an airfoil is explored experimentally as well as computationally for a NACA0012 airfoil with a glaze ice accretion at the leading edge. Experimentally, flow oscillations were observed at low frequenci...

K. B. M. Q. Zaman M. G. Potapczuk

1989-01-01

107

On the stability of the swept leading-edge boundary layer  

Microsoft Academic Search

It has been acknowledged for a long time that the leading-edge boundary layer of a swept wing plays a critical role in the generation of skin friction. Instabilities in the swept leading-edge boundary layer can trigger the transition to a turbulent boundary layer already in the attachment-line region thereby increasing the overall skin friction substantially. Research has identified conditions for

Dominik Obrist

2000-01-01

108

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

Microsoft Academic Search

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

Derrick Custodio; Charles Henoch; Hamid Johari

2010-01-01

109

Static and dynamic leading-edge-flap effects on the vortex lift of a delta wing  

Microsoft Academic Search

Experiments were performed to determine the static and dynamic effects of leading edge flaps on the vortex lift of a delta wing. The flaps were linearly tapered, for a constant flap height to wing-span ratio of 0.33 or 0.22 and were able to pivot about the wing's leading edge. Experiments consisted mainly of pressure surveys, but also included flow visualizations

Thales Karagounis

1997-01-01

110

Small Leading-Edge Flap for Flow Control on a 45Deg Delta Wing  

Microsoft Academic Search

The characteristics of rolling moment in a 45-deg delta wing with a leading-edge flap were studied to examine its effects in pre- and post-stall regimes, where conventional control surfaces are ineffective. A small flap with a height of 2mm was employed to control the flow, which was placed on the round leading-edge of the delta wing from 10 to 75%

Takashi Matsuno; Shigeru Yokouchi; Yoshiaki Nakamura

2004-01-01

111

Prediction of leading-edge vortex behaviour to supplement the suction analogy  

Microsoft Academic Search

An analytical treatment is presented which permits the prediction of the strength and path of leading-edge vortices on thin wings of delta-like planform from a knowledge of the behaviour of the linearized approximation to the attached flow past the wing. This supplements the leading-edge suction analogy, which predicts the forces and moments acting on the wing from the same input.

N. Riley; J. H. B. Smith

1985-01-01

112

Method and equipment for induction surface hardening of the leading edges of turbine blades  

Microsoft Academic Search

Methodology and equipment for hardening the leading edges of blades for large nuclear reactor steam turbines was investigated using blades made of 15Kh11MF hardened and tempered steel. A machine was designed and built for hardening the blade leading edges with a vacuum-tube oscillator and 66,000 Hz frequency. The electrical parameters of the induction heating were recorded. Hardening of the actual

T. M. Sorokina; V. V. Dymchenko

1988-01-01

113

Aerodynamic Characteristics of Slender Star-Shaped Bodies with Supersonic Leading Edges  

Microsoft Academic Search

A theory of the flow around slender conical bodies with a star-shaped cross-section in regimes with shock attachment along the length of the leading edges is developed. The aerodynamic characteristics of the slender star body, a single cycle of which represents a V-shaped wing, are obtained for different numbers of reflections of the disturbances proceeding from the leading edges of

N. A. Ostapenko; A. M. Simonenko

2004-01-01

114

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades  

Microsoft Academic Search

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or

I. A. Hamakhan; T. Korakianitis

2010-01-01

115

Leading-edge redesign of a turbomachinery blade and its effect on aerodynamic performance  

Microsoft Academic Search

â–º We proposed a simple and practical blade leading edge direct design method. â–º Both RANS and LES were conduct to verify the effectiveness of the method. â–º We discussed the HD blade and a LP turbine at design and off-design conditions. â–º Detailed quantitative influence of leading edge on aerodynamic loss was analyzed. â–º About 10% decrease can be

Weihao Zhang; Zhengping Zou; Jian Ye

2012-01-01

116

Heat pipes for wing leading edges of hypersonic vehicles. Final report  

Microsoft Academic Search

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

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

1990-01-01

117

Boundary layer receptivity to free-stream sound on elliptic leading edges of flat plates  

NASA Astrophysics Data System (ADS)

The leading-edge receptivity to acoustic waves of two-dimensional bodies is investigated using a spatial solution of the Navier Stokes equations in vorticity/stream function form in general curvilinear coordinates. The free stream is composed of a uniform flow with a superposed periodic velocity fluctuation of small amplitude. The method follows that of Haddad & Corke (1998), in which the solution for the basic flow and the linearized perturbation flow are solved separately. The initial motivation for the work comes from past physical experiments for flat plates with elliptic leading edges, which indicated narrow frequency bands of higher neutral-curve Branch I receptivity. We investigate the same conditions in our simulations, as well as on a parabolic leading edge. The results document the importance of the leading edge, junction between the ellipse and flat plate, and pressure gradient to the receptivity coefficient at Branch I. Comparisons to the past experiments and other numerical simulations showed the influence of the elliptic leading-edge/flat-plate joint as an additional site of receptivity which, along with the leading edge, provides a wavelength selection mechanism which favours certain frequencies through linear superposition.

Wanderley, Juan B. V.; Corke, Thomas C.

2001-02-01

118

Hypersonic engine leading edge experiments in a high heat flux, supersonic flow environment  

NASA Astrophysics Data System (ADS)

A major concern in advancing the state-of-the-art technologies for hypersonic vehicles is the development of an aeropropulsion system capable of withstanding the sustained high thermal loads expected during hypersonic flight. Three aerothermal load related concerns are the boundary layer transition from laminar to turbulent flow, articulating panel seals in high temperature environments, and strut (or cowl) leading edges with shock-on-shock interactions. A multidisciplinary approach is required to address these technical concerns. A hydrogen/oxygen rocket engine heat source has been developed at the NASA Lewis Research Center as one element in a series of facilities at national laboratories designed to experimentally evaluate the heat transfer and structural response of the strut (or cowl) leading edge. A recent experimental program conducted in this facility is discussed and related to cooling technology capability. The specific objective of the experiment discussed is to evaluate the erosion and oxidation characteristics of a coating on a cowl leading edge (or strut leading edge) in a supersonic, high heat flux environment. Heat transfer analyses of a similar leading edge concept cooled with gaseous hydrogen is included to demonstrate the complexity of the problem resulting from plastic deformation of the structures. Macro-photographic data from a coated leading edge model show progressive degradation over several thermal cycles at aerothermal conditions representative of high Mach number flight.

Gladden, Herbert J.; Melis, Matthew E.

1994-10-01

119

Lead free tin based solder composition  

US Patent & Trademark Office Database

Lead-free solder alloys based on a Sn--Ag--Mg system are disclosed. The alloy compositions have a melting temperature close to 183.degree. C. and a similar surface tension to that of Sn--Pb solder, and can thus be a readily substituted for conventional Sn--Pb solders. P may be added to the alloy compositions to reduce its tendency of oxidation.

2004-11-30

120

The Three-Dimensional Leading-Edge Vortex of a "Hovering" Model Hawkmoth  

NASA Astrophysics Data System (ADS)

Recent flow visualization experiments with the hawkmoth, Manduca sexta, revealed a 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% of the wing length, its diameter increased approximately from 10 to 50% of the wing chord. The leading-edge vortex had a strong axial flow velocity, which stabilized it and reduced its diameter. The vortex separated from the wing at approximately 75% 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.

van den Berg, Coen; Ellington, Charles P.

1997-03-01

121

Receptivity to Sound of an Elliptic Leading Edge on a Flat Plate.  

NASA Astrophysics Data System (ADS)

The leading edge receptivity to acoustic waves of two-dimensional bodies is investigated using a spatial solution of the Navier-Stokes equations in vorticity/stream function form in general curvilinear coordinates. The free-stream is composed of a uniform flow with a superposed periodic velocity fluctuation of small amplitude. The method follows that of Haddad & Corke(J. Fluid Mech.), 368, 1998 in which the solution for the basic flow and linearized perturbation flow are solved separately. The motivation for the work comes from physical experiments by Wei(M.S. Thesis, Arizona State Univ., 1994) and Rasmussen(M.S. Thesis, Arizona State Univ., 1992) for flat plates with elliptic leading edges, which showed frequency bands of higher Branch I receptivity. We investigated the same conditions in our simulations, as well as on a parabolic leading edge. The numerical simulations documented higher receptivity in frequency bands which were similar to the experiments. These however did not appear for the parabolic body. The results suggest an influence of the elliptic leading-edge/flat-plate joint as an additional site of receptivity which, along with the leading edge, provides a wave-length selection mechanism which favors certain frequencies through linear superposition.

Wanderley, J.; Corke, T. C.

1998-11-01

122

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

123

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

124

Small Leading-Edge Flap for Flow Control on a 45-Deg Delta Wing  

NASA Astrophysics Data System (ADS)

The characteristics of rolling moment in a 45-deg delta wing with a leading-edge flap were studied to examine its effects in pre- and post-stall regimes, where conventional control surfaces are ineffective. A small flap with a height of 2mm was employed to control the flow, which was placed on the round leading-edge of the delta wing from 10 to 75% chord. Wind-tunnel experiments were carried out for static aerodynamic force measurements and flow visualization. In the pre-stall regime, it is observed that the single flap can produce about ±0.01 of rolling moment coefficient, which is sufficient for flight control. On the other hand, in the post-stall regime, its rolling moment characteristics are quite nonlinear and complex. The flap can basically reduce the unsteady moment by interfering with the development of a leading-edge vortex, or promoting the flow attachment to the wing surface.

Matsuno, Takashi; Yokouchi, Shigeru; Nakamura, Yoshiaki

125

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.

126

Low Reynolds Number Flow Dynamics of a Thin, Flat Airfoil with Elastically Mounted Leading Edge Actuator  

NASA Astrophysics Data System (ADS)

Direct numerical simulations are performed to investigate the effect of an elastically mounted leading edge actuator on the unsteady flow at high angles of attack over a flat, thin airfoil at Reynolds number of 14700 based on the chord length. The leading edge actuator is mounted with a torsion spring at one-third the chord length allowing dynamic variations in the effective angle of attack through flow-induced oscillations. The goal is to investigate potential benefits of flow induced flapping motion of the leading edge actuator to the lift and drag characteristics of thin airfoils. The structural model for the rigid actuator is based on a torsional spring-mounted compound pendulum. A fictitious-domain based finite volume approach [(Apte et al. (JCP 2009)] is used to compute this fluid-structure interaction problem on a fixed background mesh. It is shown that a lock-in region leading to limit cycle oscillations of the leading edge actuator can be achieved for certain spring parameters leading to improvements in mean lift-to-drag ratio.

Apte, Sourabh

2011-11-01

127

Image analysis tools to quantify cell shape and protein dynamics near the leading edge.  

PubMed

We present a set of flexible image analysis tools to analyze dynamics of cell shape and protein concentrations near the leading edge of cells adhered to glass coverslips. Plugins for ImageJ streamline common analyses of microscopic images of cells, including the calculation of leading edge speeds, total and average intensities of fluorescent markers, and retrograde flow rate measurements of fluorescent single-molecule speckles. We also provide automated calculations of auto- and cross-correlation functions between velocity and intensity measurements. The application of the methods is illustrated on images of XTC cells. PMID:23165752

Ryan, Gillian L; Watanabe, Naoki; Vavylonis, Dimitrios

2012-11-17

128

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

129

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

130

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

Microsoft Academic Search

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

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

1992-01-01

131

Finite Difference Treatment of Strong Shock over a Sharp Leading Edge with Navier-Stokes Equations.  

National Technical Information Service (NTIS)

The report develops finite difference techniques for computing with reasonable accuracy the static pressure field downstream of a strong shock wave, based on Navier-Stokes equations. The leading edge shock over a sharp flat plate in a Mach 20 uniform stre...

S. I. Cheng J. H. Chen

1972-01-01

132

Leading-edge tubercles delay stall on humpback whale ÑMegaptera novaeangliaeÖ flippers  

Microsoft Academic Search

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

D. S. Miklosovic; M. M. Murray; L. E. Howle

2004-01-01

133

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

Microsoft Academic Search

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

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

2004-01-01

134

First experimental assessment of RCS plume-flow field interaction on Hermes leading edge thruster configuration  

Microsoft Academic Search

Glow discharge flow visualization experiments are demonstrated which have been performed to enable a first assessment of the HERMES 1.0 leading edge thruster configuration concerning interference between the thruster plumes of the reaction control system (RCS) and the surrounding flow field. The results of the flow visualization tests are presented in exemplary selected photographs. Additional Pitot pressure measurements support assumptions

T. Poertner

1993-01-01

135

Investigation into the Failure Casue of a Double Acting, Leading Edge Groove, Tilting Pad Thrust Bearing.  

National Technical Information Service (NTIS)

This report describes the results of bench tests simulating operation and failure of a thrust bearing used in a gas turbine engine compressor development test rig. The bearing was a double acting, tilting pad with offset pivot, leading edge groove configu...

B. K. Peterson

1990-01-01

136

Integrin-mediated Protein Kinase A Activation at the Leading Edge of Migrating Cells  

PubMed Central

cAMP-dependent protein kinase A (PKA) is important in processes requiring localized cell protrusion, such as cell migration and axonal path finding. Here, we used a membrane-targeted PKA biosensor to reveal activation of PKA at the leading edge of migrating cells. Previous studies show that PKA activity promotes protrusion and efficient cell migration. In live migrating cells, membrane-associated PKA activity was highest at the leading edge and required ligation of integrins such as ?4?1 or ?5?1 and an intact actin cytoskeleton. ?4 integrins are type I PKA-specific A-kinase anchoring proteins, and we now find that type I PKA is important for localization of ?4?1 integrin-mediated PKA activation at the leading edge. Accumulation of 3? phosphorylated phosphoinositides [PtdIns(3,4,5)P3] products of phosphatidylinositol 3-kinase (PI3-kinase) is an early event in establishing the directionality of migration; however, polarized PKA activation did not require PI3-kinase activity. Conversely, inhibition of PKA blocked accumulation of a PtdIns(3,4,5)P3-binding protein, the AKT-pleckstrin homology (PH) domain, at the leading edge; hence, PKA is involved in maintaining cell polarity during migration. In sum, we have visualized compartment-specific PKA activation in migrating cells and used it to reveal that adhesion-mediated localized activation of PKA is an early step in directional cell migration.

Lim, Chinten J.; Kain, Kristin H.; Tkachenko, Eugene; Goldfinger, Lawrence E.; Gutierrez, Edgar; Allen, Michael D.; Groisman, Alex; Zhang, Jin

2008-01-01

137

SONIC BOOM TESTING OF ARTIFICIALLY BLUNTED LEADING EDGE (ABLE) CONCEPTS IN THE NASA AMES AEROBALLISTIC RANGE  

Microsoft Academic Search

Sonic boom signatures and aerodynamic drag from several configurations in supersonic free- flight at near sea level conditions have been recorded at the NASA Ames Research Center aeroballistic range. Several different Artificially Blunted Leading Edge (ABLE) configurations were successfully designed, fabricated, and launched at Mach 2.0 and 3x106 Reynolds number in the aeroballistic range to provide test data, outside the

Tim Tam; Stephen Ruffin; Peter Gage; David Bogdanoff; Leslie Yates; John Morgenstern

2000-01-01

138

PROFILED LEADING EDGE GROOVE TILTING PAD JOURNAL BEARING FOR LIGHT LOAD OPERATION  

Microsoft Academic Search

Optimization of a leading edge groove tilting pad journal bearing for application in a small, high speed, multistage steam turbine is described. Rotordynamics constraints to meet a design objective maximum operating speed of 18000 rpm resulted in a rotor with a 51.0 in bearing span and 5.0 in diameter tilting pad journal bearings. This configuration yielded a design with projected

Stephen L. Edney; John K. Waite

2003-01-01

139

Design and testing of a piezostack-actuated leading-edge flap  

Microsoft Academic Search

This paper presents the design and preliminary test results of a piezoelectric stack (piezostack) driven leading-edge flap actuator. The actuator uses six commercially available piezostacks with a curved contact tip for force and stroke profile tailoring. Force requirements were calculated using a quasi-steady aerodynamic model. Stroke amplification is achieved through a single lever. Initial results show that the current prototype

Mark C. Shaner; Inderjit Chopra

1999-01-01

140

Design of Subscale Airfoils with Full-Scale Leading Edges for Ice Accretion Testing  

Microsoft Academic Search

A design procedure for subscale airfoils with full-scale leading edges that exhibit full-scale water droplet impingement characteristics in an incompressible, inviscid è ow is presented. The design procedure uses validated airfoil design, è ow analysis, and water droplet impingement simulation codes to accomplish the task. To identify and isolate important design variables in the design, numerous trade studies were per-

Farooq Saeed; Michael S. Selig; Michael B. Bragg

1997-01-01

141

Development of a design model for airfoil leading edge film cooling  

Microsoft Academic Search

A series of experiments on scaled cylinder models having injection through holes inclined at 20, 30, 45, and 90 degrees are presented. The experiments were conducted in a wind tunnel on several stainless steel test specimens in which flow and heat transfer parameters were measured over simulated airfoil leading edge surfaces. On the basis of the experimental results, an engineering

A. R. Wadia; D. A. Nealy

1985-01-01

142

Closed-loop control of leading-edge and tip vortices for small UAV  

Microsoft Academic Search

Summary We present plans and preliminary results for a recently initiated multidis- ciplinary research effort aimed at closed-loop control of three-dimensional leading edge and tip vortices on low aspect ratio wings relevant to micro and small unmanned air vehicles. The goal of control is to extend the parameter space for which steady lift can be maintained at high angles of

Tim Colonius; Clarence W. Rowley; Gilead Tadmor; David R. Williams; Kunihiko Taira; Will B. Dickson; Morteza Gharib; Michael Dickinson

143

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

144

A design procedure for subscale airfoils with full-scale leading edges for ice accretion testing  

Microsoft Academic Search

A design procedure for subscale airfoils with full-scale leading edges that exhibit full-scale water droplet impingement characteristics in an incompressible inviscid flow is presented. The design procedure uses validated airfoil design, flow analysis, and water droplet impingement simulation codes to accomplish the task. To identify and isolate important design variables in the design, numerous trade studies were performed. The paper

Farooq Saeed; Michael S. Selig; Michael B. Bragg

145

Direct simulation Monte Carlo of rarefied hypersonic flow on power law shaped leading edges  

Microsoft Academic Search

A numerical study of several parameters that influence the flowfield structure, aerodynamic surface quantities and shock wave structure at rarefied hypersonic flow conditions is conducted on power law shaped leading edges. The calculations are performed with a detailed computer code that properly accounts for nonequilibrium effects and that has been demonstrated to yield excellent comparisons with flight- and ground-test data.

Wilson Fernando Nogueira Dos Santos

2002-01-01

146

Convective film cooling over a representative turbine blade leading-edge  

Microsoft Academic Search

Computations are performed to simulate a discrete hole film cooling flow over an experimental test geometry representative of the leading edge of turbine blades. A multiblock pressure correction algorithm is used for the computations, and both low-Reynolds number and wall function k–? models are used for turbulence closure. The flow through the coolant ducts, from the plenum to the blade

Siddharth Thakur; Jeffrey Wright; Wei Shyy

1999-01-01

147

Modeling and Control of Flexible Wing with Trailing and Leading Edge Control Surfaces  

Microsoft Academic Search

This paper investigates the problem of active flutter suppression for a one-dimensional two degrees of freedom airfoil with leading and trailing edge flap control. The goal is to design an active flaps control capability to suppress the flutter instability and enhance the sub critical aero elastic response to time-dependent external pulses. A new interpretation for the modeling of the airfoil

Dilmi Smain; Bouzouia Brahim

2010-01-01

148

Weak Force Stalls Protrusion at the Leading Edge of the Lamellipodium  

PubMed Central

Protrusion, the first step of cell migration, is driven by actin polymerization coupled to adhesion at the cell's leading edge. Polymerization and adhesive forces have been estimated, but the net protrusion force has not been measured accurately. We arrest the leading edge of a moving fish keratocyte with a hydrodynamic load generated by a fluid flow from a micropipette. The flow arrests protrusion locally as the cell approaches the pipette, causing an arc-shaped indentation and upward folding of the leading edge. The effect of the flow is reversible upon pipette removal and dependent on the flow direction, suggesting that it is a direct effect of the external force rather than a regulated cellular response. Modeling of the fluid flow gives a surprisingly low value for the arresting force of just a few piconewtons per micrometer. Enhanced phase contrast, fluorescence, and interference reflection microscopy suggest that the flow does not abolish actin polymerization and does not disrupt the adhesions formed before the arrest but rather interferes with weak nascent adhesions at the very front of the cell. We conclude that a weak external force is sufficient to reorient the growing actin network at the leading edge and to stall the protrusion.

Bohnet, Sophie; Ananthakrishnan, Revathi; Mogilner, Alex; Meister, Jean-Jacques; Verkhovsky, Alexander B.

2006-01-01

149

Diffraction of acoustic waves on the leading edge of a flat plate in a supersonic flow  

Microsoft Academic Search

A scheme is proposed for calculating the intensity of the acoustic wave field generated by diffraction of a beam of acoustic waves on a sharp leading edge of a flat plate in a supersonic flow. This wave field is shown to be a functional of the mass-flow amplitude distribution in the acoustic field at the level of the plate surface

S. A. Gaponov; B. V. Smorodsky

2005-01-01

150

Modelling bird impacts on an aircraft wing – Part 1: Material modelling of the fibre metal laminate leading edge material with continuum damage mechanics  

Microsoft Academic Search

In a collaborative research project, aircraft wing leading edge structures with a glass-based Fibre Metal Laminate (FML) skin have been designed, built, and subjected to bird strike tests that have been modelled with finite element analysis. Fibre Metal Laminates have layers of aluminium alloy and high strength glass fibre composite and have been reported to possess excellent impact properties. In

M. A. McCarthy; J. R. Xiao; N. Petrinic; A. Kamoulakos; V. Melito

2005-01-01

151

Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 2: Modelling of Impact with SPH Bird Model  

Microsoft Academic Search

Fibre Metal Laminates with layers of aluminium alloy and high strength glass fibre composite have been reported to possess excellent impact properties and be suitable for aircraft parts likely to be subjected to impacts such as runway debris or bird strikes. In a collaborative research project, aircraft wing leading edge structures with a glass-based FML skin have been designed, built,

M. A. McCarthy; J. R. Xiao; C. T. McCarthy; A. Kamoulakos; J. Ramos; J. P. Gallard; V. Melito

2004-01-01

152

A role for actin arcs in the leading edge advance of migrating cells  

PubMed Central

The migration of epithelial cells requires coordination of two actin modules at the leading edge: one in the lamellipodium and one in the lamella. How the two modules connect mechanistically to regulate directed edge motion is not understood. Using a combination of live-cell imaging and photoactivation approaches, we demonstrate that the actin network of the lamellipodium evolves spatio-temporally into the lamella. This occurs during the retraction phase of edge motion when myosin II redistributes to the cell edge and condenses the lamellipodial-actin into an arc-like bundle (i.e., actin arc) parallel to the edge. The newly formed actin arc moves rearward and couples to focal adhesions as it enters the lamella. We propose net edge extension occurs by nascent focal adhesions advancing the site at which new actin arcs slow down and form the base of the next protrusion event. The actin arc thus serves as a structural element underlying the temporal and spatial connection between the lamellipodium and lamella to drive directed cell motion.

Burnette, Dylan T.; Manley, Suliana; Sengupta, Prabuddha; Sougrat, Rachid; Davidson, Michael W.; Kachar, Bechara; Lippincott-Schwartz, Jennifer

2013-01-01

153

Flow field measurements of leading-edge separation vortex formed on a delta wing with vortex flaps  

Microsoft Academic Search

Wind tunnel tests are carried out using a 70 delta wing model with leading-edge vortex flaps. The structure of the leading-edge\\u000a separation vortex over the leading-edge vortex flap is measured by use of a 5 holes pitot probe, surface pressure measurement\\u000a technique and oil flow visualization technique. Separation vortices formed on a plain delta wing, on a vortex flap and

K. Rinoie

2001-01-01

154

ERK regulates Golgi and centrosome orientation towards the leading edge through GRASP65  

PubMed Central

Directed cell migration requires the orientation of the Golgi and centrosome toward the leading edge. We show that stimulation of interphase cells with the mitogens epidermal growth factor or lysophosphatidic acid activates the extracellular signal–regulated kinase (ERK), which phosphorylates the Golgi structural protein GRASP65 at serine 277. Expression of a GRASP65 Ser277 to alanine mutant or a GRASP65 1–201 truncation mutant, neither of which can be phosphorylated by ERK, prevents Golgi orientation to the leading edge in a wound assay. We show that phosphorylation of GRASP65 with recombinant ERK leads to the loss of GRASP65 oligomerization and causes Golgi cisternal unstacking. Furthermore, preventing Golgi polarization by expressing mutated GRASP65 inhibits centrosome orientation, which is rescued upon disassembly of the Golgi structure by brefeldin A. We conclude that Golgi remodeling, mediated by phosphorylation of GRASP65 by ERK, is critical for the establishment of cell polarity in migrating cells.

Bisel, Blaine; Wang, Yanzhuang; Wei, Jen-Hsuan; Xiang, Yi; Tang, Danming; Miron-Mendoza, Miguel; Yoshimura, Shin-ichiro; Nakamura, Nobuhiro; Seemann, Joachim

2008-01-01

155

Estimation of ground range on the sweep frequency backscatter leading edge  

NASA Astrophysics Data System (ADS)

The high frequency management system with backscatter radar supplies the real time ionosphere channel conditions to high frequency users, which leads to the demand for the ground range between the radar location and the scatters on the distant ground. The ionosphere electron density profile is usually inversed to obtain the ground range. An inversion algorithm, with which the ground range on the leading edge of the backscatter ionograms can be obtained without electron density, is presented in this paper. The ray path geometry of the backscatter sounding and the change in the group path on the leading edge with operating frequency are used to derive the ground range. Synthesized backscatter ionogram and experimental backscatter ionograms are processed to validate the algorithm. The results indicate that the algorithm is usable for high frequency management system.

Su, Fanfan; Zhao, Zhengyu; Deng, Feng; Li, Shipeng

2011-04-01

156

The effect of wavy leading edges on aerofoil–gust interaction noise  

NASA Astrophysics Data System (ADS)

High-order accurate numerical simulations are performed to investigate the effects of wavy leading edges (WLEs) on aerofoil–gust interaction (AGI) noise. The present study is based on periodic velocity disturbances predominantly in streamwise and vertical directions that are mainly responsible for the surface pressure fluctuation of an aerofoil. In general, the present results show that WLEs lead to reduced AGI noise. It is found that the ratio of the wavy leading-edge peak-to-peak amplitude (LEA) to the longitudinal wavelength of the incident gust (?g) is the most important factor for the reduction of AGI noise. It is observed that there exists a tendency that the reduction of AGI noise increases with LEA/?g and the noise reduction is significant for LEA/?g?0.3. The present results also suggest that any two different cases with the same LEA/?g lead to a strong similarity in their profiles of noise reduction relative to the straight leading-edge case. The wavelength of wavy leading edges (LEW), however, shows minor influence on the reduction of AGI noise under the present gust profiles used. Nevertheless, the present results show that a meaningful improvement in noise reduction may be achieved when 1.0?LEW/?g?1.5. In addition, it is found that the beneficial effects of WLEs are maintained for various flow incidence angles and aerofoil thicknesses. Also, the WLEs remain effective for gust profiles containing multiple frequency components. It is discovered in this paper that WLEs result in incoherent response time to the incident gust across the span, which results in a decreased level of surface pressure fluctuations, hence a reduced level of AGI noise.

Lau, Alex S. H.; Haeri, Sina; Kim, Jae Wook

2013-11-01

157

A computational investigation of receptivity in high-speed flow near a swept leading-edge  

NASA Astrophysics Data System (ADS)

Laminar-flow wings have the promise of reducing viscous drag forces in cruise for commercial aircraft. However, the success of a laminar-flow wing depends critically on the external disturbance environment and how these disturbances influence the transition from laminar to turbulent flow. The process by which external disturbances are converted into instability waves, which are the precursors to turbulence, is called receptivity. The research described in this thesis focuses on the receptivity of the three-dimensional boundary layer near the leading edge of a high-speed swept wing. In particular, the influence of surface roughness near the leading edge is examined as it relates to the formation of stationary crossflow vortices in the boundary layer. Recent experiments indicate that surface roughness is the primary cause of stationary crossflow vortices which are observed to dominate the laminar to turbulent transition process on swept wings. Therefore, the mechanisms responsible for the formation of crossflow vortices and the accurate prediction of their initial amplitude are essential for the development of laminar-flow wings. The receptivity and early evolution of stationary crossflow vortices is investigated through numerical solutions of the linearized Navier-Stokes equations for a swept leading-edge. Consistent with findings for other geometries, convex surface curvature stabilizes crossflow vortex growth while nonparallel effects are destabilizing. In contrast, the initial amplitude of crossflow vortices downstream of a localized surface roughness site is found to be greater in the presence of convex surface curvature, while the nonparallel meanflow near a leading-edge is found to strongly reduce the initial amplitude of crossflow vortices. These competing effects--curvature and nonparallelism--tend to counteract one another, but, for the conditions studied here, the nonparallel effect is dominant. Comparisons between linearized Navier-Stokes solutions and recent theoretical receptivity analysis, based on the parallel-flow equations, show that the theoretical method over-predicts the initial amplitude of stationary crossflow vortices by as much as 77% for long wavelength disturbances. The error in the theoretical prediction is reduced for shorter wavelengths, since nonparallel effects are relatively less important, but remains as high as 30% near the leading-edge. Although the parallel theory provides a conservative estimate of the initial amplitude of crossflow vortices, it is concluded that accurate theoretical prediction of crossflow receptivity near the leading-edge of a swept wing requires the inclusion of nonparallel effects.

Collis, Samuel Scott

158

Boundary Layer Resolved Measurements of Unsteady Leading Edge Separation on a Pitching Airfoil  

NASA Astrophysics Data System (ADS)

When an airfoil pitches rapidly to high angles of attack, the flow can remain attached well beyond the static stall angle. The flow will eventually separate from the leading edge culminating in the formation of the dynamic stall vortex. While this flow has been the subject of numerous studies, the details of the flow within the boundary layer at the onset of separation have not been captured experimentally to date. Using Molecular Tagging Velocimetry (MTV), we have obtained the first boundary layer resolved measurements of flow separation near the leading edge of a pitching airfoil. The data provide a detailed picture of the evolution of the velocity and spanwise vorticity for an airfoil executing a ramp motion trajectory. Results are compared with 2-D Navier-Stokes computations for flow conditions similar to our experiments. The experimental data suggest that the process of boundary layer separation occurs over a shorter time scale, and is more eruptive, than that captured by the computations.

Gendrich, Charles P.; Koochesfahani, Manoochehr

1998-11-01

159

Effect of Leading and Trailing Edge Geometry on the Aeromechanic Characteristics of Membrane Aerofoils  

NASA Astrophysics Data System (ADS)

The geometry of the rigid leading and trailing edges that hold the membrane could affect the aeromechanic performance of membrane wings. In this study the interaction between the supports and a membrane aerofoil is explored. Tests are performed at low Reynolds numbers, 4.3x10^4 - 1.1x10^5, and incidences of 0^o - 30^o. Four different leading and trailing edge geometries have been analysed focusing on the unsteady characteristics of the wake and the structural vibration of the membrane. Results indicate that aeroelastic coupling between vortex shedding and membrane vibration depends upon the type of membrane support. The wake's kinetic energy distribution has been found to be dependent on ? for round supports but independent of ? for rectangular supports. Finally,correlation between the membrane deflection and the lift generation has been found for all cases studied. Further analysis will be conducted and discussed.

Arbos, Sara; Pang, Zi; Ganapathisubramani, Bharathram; Palacios, Rafael

2010-11-01

160

Studies on laminar boundary-layer receptivity to freestream turbulence near a leading edge  

NASA Astrophysics Data System (ADS)

An experimental study of the generation of Tollmien-Schlichting waves and wave packets in a flat-plate boundary-layer by weak freestream turbulence has been conducted with the intent of clarifying receptivity mechanisms. Emphasis was placed upon the properties of such waves at stations as far forward as the minimum critical Reynolds number. It was found that alteration of the flow about the leading edge, due either to an asymmetry associated with lift, or due to a change of the fineness ratio of the leading edge, altered the T-S wave amplitude at early stations. The subsequent growth of the waves proceeded faster than expected according to certain stability theory results. Speculation regarding receptivity mechanisms is made.

Kendall, James M.

161

Leading-edge receptivity of a hypersonic boundary layer on a flat plate  

NASA Astrophysics Data System (ADS)

Experimental investigations of the boundary layer receptivity, on the sharp leading edge of a at plate, to acoustic waves induced by two-dimensional and three- dimensional perturbers, have been performed for a free-stream Mach number M[infty infinity] = 5.92. The fields of controlled free-stream disturbances were studied. It was shown that two-dimensional and three-dimensional perturbers radiate acoustic waves and that these perturbers present a set of harmonic motionless sources and moving sources with constant amplitude. The disturbances excited in the boundary layer were measured. It was found that acoustic waves impinging on the leading edge generate Tollmien Schlichting waves in the boundary layer. The receptivity coefficients were obtained for several radiation conditions and intensities. It was shown that there is a dependence of receptivity coefficients on the wave inclination angles.

Maslov, A. A.; Shiplyuk, A. N.; Sidorenko, A. A.; Arnal, D.

2001-01-01

162

Next-generation science information network for leading-edge applications  

Microsoft Academic Search

High-speed networks are definitely essential tools for leading-edge applications in many research areas, including nuclear fusion research. This paper describes a number of advanced features in the Japanese next-generation science information network, called SINET3, and gives researchers clues on the uses of advanced high-speed network for their applications. The network services have four categories, multiple layer transfer, enriched virtual private

S. Urushidani; J. Matsukata

2008-01-01

163

Aerothermal tests of a heat-pipe-cooled leading edge at Mach 7  

Microsoft Academic Search

A sodium-filled, Hastelloy X, heat-pipe-cooled leading-edge model, which had previously been tested in a radiant-heating environment, was subjected to steady-state, Earth-entry aerothermal loads (heat and pressure) in the Langley 8-foot high-temperature structures tunnel to verify performance in a realistic hypersonic environment. The model was tested at angles of attack of 0 deg, 10 deg, and 20 deg, angles of roll

C. J. Camarda

1978-01-01

164

The evolution of Tollmien-Schlichting waves near a leading edge  

Microsoft Academic Search

The method of matched asymptotic expansions is used to study the generation of Tollmien-Schlichting waves by free-stream disturbances incident on a flat-plate boundary layer. Near the leading edge, the motion is governed by the unsteady boundary-layer equation, while farther downstream it is governed (to lowest order) by the Orr-Sommerfeld equation with slowly varying coefficients. It is shown that there is

M. E. Goldstein

1983-01-01

165

Dynamic response of the leading edge wing under soft body impact  

Microsoft Academic Search

Soft body impact tests were conducted using an artificial bird of 0.2 kg with a striking velocity of 150 m·s on three different configurations of metallic wing leading edge (LE) structures. The objective of these experiments is to address the preliminary design of LE wing structures to soft body impact loads. The explicit finite element software PAM-CRASH was selected to

Sheikh Muhammad Zakir; Yulong Li

2012-01-01

166

CHARACTERIZATION OF UNSTEADY FLOW STRUCTURES NEAR LEADING-EDGE SLAT: PART I. PIV MEASUREMENTS  

Microsoft Academic Search

A comprehensive computational and experimental study has been performed at the NASA Langley Research Center as part of the Quiet Aircraft Technology (QAT) Program to investigate the unsteady flow near a leading-edge slat of a two-dimensional, high-lift system. This paper focuses on the experimental effort conducted in the NASA Langley Basic Aerodynamics Research Tunnel (BART) where Particle Image Velocimetry (PIV)

Luther N. Jenkins; Mehdi R. Khorrami; Meelan Choudhari

167

Exploration in optimal design of an airfoil with a leading edge rotating cylinder  

Microsoft Academic Search

Based on the theory of moving surface boundary layer control (MSBC), a concept of an airfoil having a rotating cylinder at\\u000a the leading edge has been developed and experimentally proven to have good aerodynamic performance even at large angles of\\u000a attack. Thus, this research aims to give guidance on optimizing the design of this kind of airfoil with high lift

Yuan-Yuan Zhang; Dian-Gui Huang; Xiao-Jing Sun; Guo-Qing Wu

2010-01-01

168

Towards Active Control of Leading Edge Stall by Means of Pneumatic Actuators  

Microsoft Academic Search

This contribution summarizes the flow control research results obtained at TU Braunschweig and their implication for control\\u000a on high-lift devices. The superordinate aim of the examination is the control of leading-edge stall on a two-element airfoil\\u000a by means of dynamic 3D actuators. This is of great practical interest in order to increase the maximum angle of attack and\\/or\\u000a the lift

C. J. Kahler; P. Scholz; J. Ortmanns; R. Radespiel

169

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

Microsoft Academic Search

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

Michael William Benner

2003-01-01

170

An experimental study of film cooling effectiveness near the leading edge of a turbine blade  

Microsoft Academic Search

A flame ionization technique based on the heat\\/mass transfer analogy has been used in a experimental investigation of film cooling effectiveness. The measurements were made over the surface of a turbine blade model composed of a semi-cylindrical leading edge bonded to a flat after-body. The secondary flow was injected into the boundary layer through four rows of holes located at

M. Salcudean; I. Gartshore; K. Zhang; I. McLean

1994-01-01

171

Numerical Study of the Effect of the Leading Edge Shape on Cavitation Around Inducer Blade Sections  

Microsoft Academic Search

A numerical study of the cavitation behaviour of two-dimensional hydrofoils simulating a section of an inducer blade is presented. Two leading edge shapes were chosen to approach rocket engine inducer designs. They were tested with respect to the development of sheet cavitation. The numerical model of cavitating flows is based on the 3D code FINE\\/TURBOTM, developed by NUMECA International. The

Olivier Coutier-Delgosha; Jean-Luc Reboud; Regiane Fortes-Patella

2002-01-01

172

Analysis and radiant heating tests of a heat-pipe-cooled leading edge  

Microsoft Academic Search

The performance of a heat pipe cooled leading edge was investigated experimentally and analytically. The test model and radiant heaters were positioned to simulate aerodynamic heating distributions and gravity effects at angles of attack of 0 deg, 10 deg, and 20 deg. Steady-state stagnation heating ranged from 239 kW\\/sq m to 395 kW\\/sq m with heat pipes operating at temperatures

C. J. Camarda

1977-01-01

173

Trypan blue capsular staining to “find” the leading edge of a “lost” capsulorhexis  

Microsoft Academic Search

PURPOSE: To describe an effective surgical technique to visualize an obscured leading edge of a capsulorhexis.DESIGN: Prospective, interventional case series.METHODS: In six eyes of six patients in which the capsulorhexis was started but could no longer be seen during surgery, the anterior chamber was irrigated to remove all viscoelastic, and 0.3-ml trypan blue 0.06% was applied onto the anterior lens

Peter W. T de Waard; Camille J Budo; Gerrit R. J Melles

2002-01-01

174

Roundtable: Design and CAD Challenges for Leading-Edge Multimedia Designs  

Microsoft Academic Search

Multimedia, game, and entertainment devices have pushed the leading edge of performance, complexity, power, form factor, design cycle time, and other key aspects of ASIC design for the past several technology nodes. This roundtable brings together experts who are defining the next generation of gaming, mobile-TV, digital-home, display, and multimedia-processing platforms. The discussion spans the underlying chip architectures and roadmaps,

Andrew B. Kahng; Ira Chayut; John M. Cohn; Toshihiro Hattori; Jeong-taek Kong; Pierre G. Paulin; Richard Tobias

2007-01-01

175

Delta Wing Steady Pressure Investigations for Sharp and Rounded Leading Edges  

Microsoft Academic Search

\\u000a The design, construction, manufacturing and geometric properties of a generic 65° Delta Wing for the International Vortex\\u000a Flow Experiment 2 are described. Briefly, the measurement equipment implemented in the model and the external sensors are\\u000a specified. A wind tunnel investigation has been performed and the results for two different leading edge geometries (sharp\\u000a and rounded) at three angles of attack

Andrej Furman; Christian Breitsamter

176

Predictive Digital-Controlled Converter With Peak Current-Mode Control and Leading-Edge Modulation  

Microsoft Academic Search

The main theme of this paper is to present the digital controller design of a power converter with predictive peak current-mode (PCM) control and leading-edge modulation. The advantages of the control and modulation technique include the reduction of the sampling frequency of the A\\/D converter, no need of slope compensation, and the provision of a fast dynamic current response. The

Yen-Shin Lai; Chia-An Yeh

2009-01-01

177

Dual leading-edge vortex structure for flow over a simplified butterfly model  

Microsoft Academic Search

The dye visualization experiments show that a dual leading-edge vortex (LEV) structure exists on the suction side of a simplified\\u000a butterfly model of Papilio ulysses at ? = 8°?12°. Furthermore, the results of particle image velocimetry (PIV) measurement indicate that the axial velocity of the\\u000a primary (outer) vortex core reaches the lower extreme value while a transition from a “wake-like” to a

Y. Hu; J. J. Wang

2011-01-01

178

Receptivity to Sound of an Elliptic Leading Edge on a Flat Plate  

Microsoft Academic Search

The leading edge receptivity to acoustic waves of two-dimensional bodies is investigated using a spatial solution of the Navier-Stokes equations in vorticity\\/stream function form in general curvilinear coordinates. The free-stream is composed of a uniform flow with a superposed periodic velocity fluctuation of small amplitude. The method follows that of Haddad & Corke(J. Fluid Mech.), 368, 1998 in which the

J. Wanderley; T. C. Corke

1998-01-01

179

Hypersonic engine leading edge experiments in a high heat flux, supersonic flow environment  

Microsoft Academic Search

A major concern in advancing the state-of-the-art technologies for hypersonic vehicles is the development of an aeropropulsion system capable of withstanding the sustained high thermal loads expected during hypersonic flight. Three aerothermal load related concerns are the boundary layer transition from laminar to turbulent flow, articulating panel seals in high temperature environments, and strut (or cowl) leading edges with shock-on-shock

Herbert J. Gladden; Matthew E. Melis

1994-01-01

180

Explanation of the effects of leading-edge tubercles on the aerodynamics of airfoils and finite wings  

Microsoft Academic Search

A computational study was conducted to explain the aerodynamic effect of leading edge tubercles on maximum lift coefficient, stall angle of attack (AoA), drag, and post stall characteristics for airfoils as well as finite wings. Past experiments demonstrated airfoils with leading edge tubercles do not improve Clmax, drag, or stall AoA but smoothen post stall characteristics to a great degree.

Mehdi Saadat; Hossein Haj-Hariri; Frank Fish

2010-01-01

181

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

182

Exploration in optimal design of an airfoil with a leading edge rotating cylinder  

NASA Astrophysics Data System (ADS)

Based on the theory of moving surface boundary layer control (MSBC), a concept of an airfoil having a rotating cylinder at the leading edge has been developed and experimentally proven to have good aerodynamic performance even at large angles of attack. Thus, this research aims to give guidance on optimizing the design of this kind of airfoil with high lift coefficients. Using computational fluid dynamics (CFD) technique, the CFD simulation results have been compared with the experimental results available in the literature, and then the SST two-equation model is selected as the appropriate turbulence model. At a given cylinder surface velocity ratio, the cylinder diameter d, the drop height of trailing edge ? and the curvatures of the pressure and suction surfaces of the airfoil are regarded as the optimal design parameters and the airfoil lift coefficient is considered as the optimization objective function. Therefore, using orthogonal optimization method, we herein develop a new design of airfoil favorable for having a rotating leading edge. It has been numerically proven that the resulting airfoil has good capability of achieving a substantially superior performance when compared to the airfoils of the prior art.

Zhang, Yuan-Yuan; Huang, Dian-Gui; Sun, Xiao-Jing; Wu, Guo-Qing

2010-08-01

183

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

184

Aerodynamic optimization of the flat-plate leading edge for experimental studies of laminar and transitional boundary layers  

NASA Astrophysics Data System (ADS)

This work is concerned with the design of a leading edge for a flat-plate model used to study laminar and transitional boundary layers. For this study, the flow over the complete boundary-layer model, including leading edge, flat section, and trailing-edge flap, is modeled. The effect of important geometrical features of the leading edge on the resulting pressure distribution, starting from the well-known symmetric modified super ellipse, is investigated. A minimal pressure gradient on the measurement side of the plate is achieved using an asymmetrical configuration of modified super ellipses, with a thickness ratio of 7/24. An aerodynamic shape optimization is performed to obtain a novel leading edge shape that greatly reduces the length of the non-zero pressure gradient region and the adverse pressure gradient region compared to geometries defined by ellipses. Wind tunnel testing is used to validate the numerical solutions.

Hanson, Ronald E.; Buckley, Howard P.; Lavoie, Philippe

2012-10-01

185

Dual modes of motility at the leading edge of migrating epithelial cell sheets  

PubMed Central

Purse-string healing is driven by contraction of actin/myosin cables that span cells at wound edges, and it is the predominant mode of closing small round wounds in embryonic and some adult epithelia. Wounds can also heal by cell crawling, and my colleagues and I have shown previously that the presence of unconstrained, straight edges in sheets of epithelial cells is a sufficient signal to induce healing by crawling. Here, it is reported that the presence of highly concave edges, which are free or physically constrained by an inert material (agarose), is sufficient to induce formation of purse strings. It was determined that neither of the two types of healing required cell damage or other potential stimuli by using the particularly gentle procedure of introducing gaps by digesting agarose blocks imbedded in the cell sheets. Movement by crawling depends on signaling by the EGF receptor (EGFR); however, this was not required for purse-string contraction. A migrating epithelial cell sheet usually produces finger-like projections of crawling cells. The cells between fingers contain continuous actin cables, which were also determined to contain myosin IIA and exhibit additional characteristics of purse strings. When crawling was blocked by inhibition of EGFR signaling, the concave regions continued to move, suggesting that both mechanisms contribute to propel the sheets forward. Wounding epithelial cell sheets causes activation of the EGFR, which triggers movement by crawling. The EGFR was found to be activated only at straight and convex edges, which explains how both types of movement can coexist at leading epithelial edges.

Klarlund, Jes K.

2012-01-01

186

Lead uptake in diverse plant families: a study applying X-ray absorption near edge spectroscopy.  

PubMed

The chemical environment of lead in roots and leaves of plants from four different plant families and a lichen from a former lead mining site in the Eifel Mountains in Germany was determined by Pb L3-edge XANES measurements using solid reference compounds and also aqueous solutions of different ionic strength simulating the plant environment. Pb(2+) ions in the plants were found to have two major coordinations, one with nine oxygen atoms in the first coordination shell similar to outer-sphere complexation and a second coordination with just three oxygen atoms similar to inner-sphere complexation. This can be interpreted assuming that lead is sorbed on the surface of cell walls depending on the concentration of lead in the soil solution. Pb L3-edge XANES spectra of dried and fresh plant samples are very similar because sorption does not change with removal of water but only because of the initial ionic strength. No bonding to biologically important groups (-S, - N) or precipitation (-PO4) was found. PMID:23517351

Bovenkamp, Gudrun L; Prange, Alexander; Schumacher, Wolfgang; Ham, Kyungmin; Smith, Aaron P; Hormes, Josef

2013-04-10

187

Low Reynolds Number Flow Dynamics of a Thin Airfoil with an Actuated Leading Edge using Direct Numerical Simulation  

NASA Astrophysics Data System (ADS)

Direct numerical simulations are performed to investigate the effect of a movable leading edge on the unsteady flow at high angles of attack over a flat, thin airfoil at Reynolds number of 14700 based on the chord length. The leading edge of the airfoil is hinged at one-third chord length allowing dynamic variations in the effective angle of attack through specified oscillations (or flapping). A fictitious-domain based finite volume approach [(Apte et al. (JCP 2009)] is used to compute the flow over an airfoil with a flapping leading edge on a fixed background mesh. Cases were run at 20 degrees angle of attack to study the drag and lift characteristics with sinusoidal flapping of the leading edge about the hinge over a range of reduced frequencies (k=?f c/U? = 0.57- 5.7). It is shown that high-frequency low amplitude actuation of the leading edge significantly alters the leading edge boundary-layer and vortex shedding and increases the mean lift- to-drag ratio. The concept of an actuated leading-edge flap has potential for development of control techniques to stabilize and maneuver low-Reynolds number micro-air vehicles in response to unsteady perturbations.

Drost, Kevin; Apte, Sourabh

2010-11-01

188

Leading Edge Receptivity to Sound at Incidence Angles on Parabolic Bodies at Mean Angles of Attack.  

NASA Astrophysics Data System (ADS)

The leading edge receptivity to acoustic waves of two-dimensional parabolic bodies was investigated using a spatial solution of the Navier-Stokes equations in vorticity/stream function form in parabolic coordinates. The free-stream is composed of a uniform flow with a superposed periodic velocity fluctuation of small amplitude. The method follows that of Haddad & Corke(J. Fluid Mech.), 368, 1998 in which the solution for the basic flow and linearized perturbation flow are solved separately. We primarily investigated the effect of the angle of incidence (-180^circ <= ?1 <= 180^circ) of the acoustic waves on the leading edge receptivity of parabolic bodies at mean angles of attack (0^circ <= ?2 <= 7^circ). The results at ?_1=?_2=0^circ quantitatively agree with those of Haddad & Corke, which showed an increase in the receptivity coefficient with increasing angle of attack. Of special interest is an asymmetry in the receptivity coefficient when determined by extrapolation to the leading from the lower or upper sides of the body, which is produced when the sound incidence angles and angles of attack are large.

Corke, T. C.; Erturk, E.

1999-11-01

189

Rarefaction and Non-equilibrium Effects in Hypersonic Flows about Leading Edges of Small Bluntness  

NASA Astrophysics Data System (ADS)

A hypersonic flow about a cylindrically blunted thick plate at a zero angle of attack is numerically studied with the kinetic (DSMC) and continuum (Navier-Stokes equations) approaches. The Navier-Stokes equations with velocity slip and temperature jump boundary conditions correctly predict the flow fields and surface parameters for values of the Knudsen number (based on the radius of leading edge curvature) smaller than 0.1. The results of computations demonstrate significant effects of the entropy layer on the boundary layer characteristics.

Ivanov, Mikhail; Khotyanovsky, Dmitry; Kudryavtsev, Alexey; Shershnev, Anton; Bondar, Yevgeniy; Yonemura, Shigeru

2011-05-01

190

Fracture of composite plates with periodical edge cracks  

Microsoft Academic Search

The elastostatic properties of two sets of periodically arranged and perfectly bonded strips are investigated under the assumption that every set of strips has edge cracks perpendicular to the interfaces, and that the external loads are applied parallel to the interfaces far away from the crack region. The problem is formulated in terms of a system of singular integral equations

M. Bakioglu

1980-01-01

191

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

National Technical Information Service (NTIS)

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 j...

M. V. Pulsonetti R. A. Thompson S. J. Alter

2004-01-01

192

High Mach Number Leading-edge Flow Separation Control using AC DBD Plasma Actuators  

NASA Astrophysics Data System (ADS)

Wind tunnel experiments were conducted to quantify the effectiveness of alternating current dielectric barrier discharge flow control actuators to suppress leading-edge stall on a NASA energy efficient transport airfoil at compressible freestream speeds. The objective of this research was to increase lift, reduce drag, and improve the stall characteristics of the supercritical airfoil near stall by flow reattachment at relatively high Mach and Reynolds numbers. In addition, the effect of unsteady (or duty cycle) operation on these aerodynamic quantities was also investigated. The experiments were conducted for a range of Mach numbers between 0.1 and 0.4. corresponding to a Reynolds number range of 560,000 through 2,260,000. Lift, drag, quarter chord moment, and suction side pressures were measured near stall for baseline, steady actuation, and a scan of nondimensional duty cycle frequencies. The results show that the plasma actuators were effective at reattaching the leading-edge separated flow as evidenced by the increase in maximum lift coefficient and stall angle (as much as 2.5 degrees). The experiment also showed that lift was increased the most when the plasma actuator was operated unsteady with a nondimensional frequency of unity.

Kelley, Christopher; Bowles, Patrick; Cooney, John; He, Chuan; Corke, Thomas; Osborne, Bradley; Silkey, Joseph; Zehnle, Joseph

2011-11-01

193

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

194

The leading-edge vortex and quasisteady vortex shedding on an accelerating plate  

NASA Astrophysics Data System (ADS)

A computational inquiry focuses on leading-edge vortex (LEV) growth and shedding during acceleration of a two-dimensional flat plate at a fixed 10°-60° angle of attack and low Reynolds number. The plate accelerates from rest with a velocity given by a power of time ranging from 0 to 5. During the initial LEV growth, subtraction of the added mass lift from the computed lift reveals an LEV-induced lift augmentation evident across all powers and angles of attack. For the range of Reynolds numbers considered, a universal time scale exists for the peak when ?>=30°, with augmentation lasting about four to five chord lengths of translation. This time scale matches well with the half-stroke of a flying insect. An oscillating pattern of leading- and trailing-edge vortex shedding follows the shedding of the initial LEV. The nondimensional frequency of shedding and lift coefficient minima and maxima closely match their values in the absence of acceleration. These observations support a quasisteady theory of vortex shedding, where dynamics are determined primarily by velocity and not acceleration. Finally, the nondimensional vortex formation time is found to be a function of the Reynolds number, but only weakly when the Reynolds number is high.

Chen, Kevin K.; Colonius, Tim; Taira, Kunihiko

2010-03-01

195

Reynolds number effects on leading edge vortex development on a waving wing  

NASA Astrophysics Data System (ADS)

The waving wing experiment is a fully three-dimensional simplification of the flapping wing motion observed in nature. The spanwise velocity gradient and wing starting and stopping acceleration that exist on an insect-like flapping wing are generated by rotational motion of a finite span wing. The flow development around a waving wing at Reynolds number between 10,000 and 60,000 has been studied using flow visualization and high-speed PIV to capture the unsteady velocity field. Lift and drag forces have been measured over a range of angles of attack, and the lift curve shape was similar in all cases. A transient high-lift peak approximately 1.5 times the quasi-steady value occurred in the first chord length of travel, caused by the formation of a strong attached leading edge vortex. This vortex appears to develop and shed more quickly at lower Reynolds numbers. The circulation of the leading edge vortex has been measured and agrees well with force data.

Jones, A. R.; Babinsky, H.

2011-07-01

196

Coronin 1B coordinates Arp2/3 complex and Cofilin activities at the leading edge  

PubMed Central

Summary Actin filament nucleation and turnover are interdependent processes in migrating cells, but the mechanisms coordinating these events are unknown. Coronin 1B influences motility, lamellipodial dynamics and actin filament architecture at the leading edge of Rat2 cells in a manner consistent with a role in coordinating filament formation and turnover. Coronin 1B interacts simultaneously with both Arp2/3 complex and Slingshot (SSH1L) phosphatase, two regulators of actin filament formation and turnover, respectively. Coronin 1B inhibits filament nucleation by Arp2/3 complex and this inhibition is attenuated by phosphorylation of Coronin 1B on Serine 2, a site targeted by SSH1L. Coronin 1B directs SSH1L to lamellipodia where it likely regulates Cofilin. Accordingly, depleting Coronin 1B increases phospho-Cofilin levels and expressing activated Cofilin partially suppresses the effects on lamellipodia dynamics of Coronin 1B depletion. Thus, Coronin 1B coordinates filament nucleation via Arp2/3 complex and turnover by Cofilin at the leading edge of migrating cells.

Cai, Liang; Marshall, Thomas W.; Uetrecht, Andrea C.; Schafer, Dorothy A.; Bear, James E.

2008-01-01

197

Boundary layer leading-edge receptivity to sound at incidence angles  

NASA Astrophysics Data System (ADS)

The leading-edge receptivity to acoustic waves of two-dimensional parabolic bodies was investigated using a spatial solution of the Navier Stokes equations in vorticity/streamfunction form in parabolic coordinates. The free stream is composed of a uniform flow with a superposed periodic velocity fluctuation of small amplitude. The method follows that of Haddad & Corke (1998) in which the solution for the basic flow and linearized perturbation flow are solved separately. We primarily investigated the effect of frequency and angle of incidence ([minus sign]180° [less-than-or-eq, slant] [alpha]2 [less-than-or-eq, slant] 180°) of the acoustic waves on the leading-edge receptivity. The results at [alpha]2 = 0° were found to be in quantitative agreement with those of Haddad & Corke (1998), and substantiated the Strouhal number scaling based on the nose radius. The results with sound waves at angles of incidence agreed qualitatively with the analysis of Hammerton & Kerschen (1996). These included a maximum receptivity at [alpha]2 = 90°, and an asymmetric variation in the receptivity with sound incidence angle, with minima at angles which were slightly less than [alpha]2 = 0° and [alpha]2 = 180°.

Erturk, Ercan; Corke, Thomas C.

2001-10-01

198

Myo1c facilitates G-actin transport to the leading edge of migrating endothelial cells.  

PubMed

Addition of actin monomer (G-actin) to growing actin filaments (F-actin) at the leading edge generates force for cell locomotion. The polymerization reaction and its regulation have been studied in depth. However, the mechanism responsible for transport of G-actin substrate to the cell front is largely unknown; random diffusion, facilitated transport via myosin II contraction, local synthesis as a result of messenger ribonucleic acid localization, or F-actin turnover all might contribute. By tracking a photoactivatable, nonpolymerizable actin mutant, we show vectorial transport of G-actin in live migrating endothelial cells (ECs). Mass spectrometric analysis identified Myo1c, an unconventional F-actin-binding motor protein, as a major G-actin-interacting protein. The cargo-binding tail domain of Myo1c interacted with G-actin, and the motor domain was required for the transport. Local microinjection of Myo1c promoted G-actin accumulation and plasma membrane ruffling, and Myo1c knockdown confirmed its contribution to G-actin delivery to the leading edge and for cell motility. In addition, there is no obvious requirement for myosin II contractile-based transport of G-actin in ECs. Thus, Myo1c-facilitated G-actin transport might be a critical node for control of cell polarity and motility. PMID:22778278

Fan, Yi; Eswarappa, Sandeepa M; Hitomi, Masahiro; Fox, Paul L

2012-07-01

199

Segregation of leading-edge and uropod components into specific lipid rafts during T cell polarization  

PubMed Central

Redistribution of specialized molecules in migrating cells develops asymmetry between two opposite cell poles, the leading edge and the uropod. We show that acquisition of a motile phenotype in T lymphocytes results in the asymmetric redistribution of ganglioside GM3- and GM1-enriched raft domains to the leading edge and to the uropod, respectively. This segregation to each cell pole parallels the specific redistribution of membrane proteins associated to each raft subfraction. Our data suggest that raft partitioning is a major determinant for protein redistribution in polarized T cells, as ectopic expression of raft-associated proteins results in their asymmetric redistribution, whereas non-raft-partitioned mutants of these proteins are distributed homogeneously in the polarized cell membrane. Both acquisition of a migratory phenotype and SDF-1?-induced chemotaxis are cholesterol depletion-sensitive. Finally, GM3 and GM1 raft redistribution requires an intact actin cytoskeleton, but is insensitive to microtubule disruption. We propose that membrane protein segregation not only between raft and nonraft domains but also between distinct raft subdomains may be an organizational principle that mediates redistribution of specialized molecules needed for T cell migration.

Gomez-Mouton, Concepcion; Abad, Jose Luis; Mira, Emilia; Lacalle, Rosa Ana; Gallardo, Eduard; Jimenez-Baranda, Sonia; Illa, Isabel; Bernad, Antonio; Manes, Santos; Martinez-A., Carlos

2001-01-01

200

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

201

Leading-edge modulation voltage-mode control with flux unbalance correction for push-pull converter  

Microsoft Academic Search

This paper presents a leading-edge modulation voltage-mode control scheme for a 3 kW, 96 V battery-backed-up DC-DC converter with 400 V\\/ 800 V output, which is developed to power a half-bridge inverter in an on-line sinewave UPS system. A new circuit scheme is proposed to implement pulse-by-pulse current limit and flux unbalance correction functions with a leading-edge modulation voltage-mode PWM

Xingsheng Zhou; Dan Chen; Clifford Jamerson

2000-01-01

202

Use of leading-edge modulation to transform boost and flyback converters into minimum-phase-zero systems  

Microsoft Academic Search

In leading-edge modulation, the pulsewidth-modulated (PWM) signal is turned off at the clock signal and turned on when the error signal crosses the ramp waveform. It is shown that the positive zero in the power stage transfer function of boost and flyback regulators can be shifted into the left-half-plane under suitable conditions. These conditions are as follows: (1) leading-edge modulation

Dan M. Sable; Bo H. Cho; Ray B. Ridley

1991-01-01

203

Evaluation of the 3D compositional heterogeneity effect on line-edge-roughness  

Microsoft Academic Search

The controlling factors in the formation of the compositional heterogeneity at the deprotection front were investigated using 3D computer simulation. The results illustrate that the chemical composition fluctuation (CCF) formed by the photoresist deprotection reaction is an important factor contributing to the line-edge-roughness (LER) in addition to the deprotection gradient (DG) of the reaction front. The magnitude of the chemical

Shuhui Kang; Wen-Li Wu; Vivek M. Prabhu; Bryan D. Vogt; Eric K. Lin; Karen Turnquest

2007-01-01

204

Subscale, hydrogen-burning, airframe-integrated-scramjet: Experimental and theoretical evaluation of a water cooled strut airframe-integrated-scramjet: Experimental leading edge  

Microsoft Academic Search

A water-cooled leading-edge design for an engine\\/airframe integrated scramjet model strut leading edge was evaluated. The cooling design employs a copper cooling tube brazed just downstream of the leading edge of a wedge-shaped strut which is constructed of oxygen-free copper. The survival of the strut leading edge during a series of tests at stagnation point heating rates confirms the practicality

S. Z. Pinckney; R. W. Guy; H. L. Beach Jr.; R. C. Rogers

1975-01-01

205

Measurements of heat transfer coefficients and friction factors in rib-roughened channels simulating leading-edge cavities of a modern turbine blade  

Microsoft Academic Search

Leading edge cooling cavities in modern gas turbine blades play an important role in maintaining the leading edge temperature at levels consistent with air foil design life. These cavities often have a complex cross-sectional shape to be compatible with the external contour of the blade at the leading edge. A survey of many existing geometries shows that, for analytical as

M. E. Taslim; T. Li; S. D. Spring

1997-01-01

206

Subscale, Hydrogen-Burning, Airframe-Integrated-Scramjet: Experimental and Theoretical Evaluation of a Water Cooled Strut Airframe-Integrated-Scramjet: Experimental Leading Edge.  

National Technical Information Service (NTIS)

A water-cooled leading-edge design for an engine/airframe integrated scramjet model strut leading edge was evaluated. The cooling design employs a copper cooling tube brazed just downstream of the leading edge of a wedge-shaped strut which is constructed ...

S. Z. Pinckney R. W. Guy H. L. Beach R. C. Rogers

1975-01-01

207

Optimal acceleration of ions by laser pulses with a sharp leading edge  

SciTech Connect

We consider acceleration of ions through the interaction of a laser pulse with a sharp leading edge with nanofilms. At sufficiently large amplitude of the pulse, all the electrons can be expelled from the film, which provides an effective regime of ion acceleration. Limiting the maximum energy of ions can result from the longitudinal reverse motion of electrons to the initial position and by the transverse motion of electrons along the nanofilm surface, which causes the ion charge compensation. The characteristic parameters of the dynamics of ions and electrons in the system are analytically evaluated, which agree well with the results of twodimensional numerical simulations by the particle-in-cell method. Optimisation of the acceleration process by using the analytical estimates makes it possible to select the optimal parameters of the laser pulse and nanofilm. Numerical simulation of ion acceleration at these parameters shows that the maximum energy of ions can be substantially increased.

Kulagin, V V; Kornienko, V N; Cherepenin, Vladimir A; Suk, Hyyong

2012-01-31

208

Manipulation of Laminar Separation Utilizing Dynamic Roughness at the Leading Edge of an Idealized Airfoil  

NASA Astrophysics Data System (ADS)

Low Reynolds number flow over a symmetric, idealized airfoil with a reasonably constant laminar separation point was manipulated using a leading edge roughness element with small, time-dependent amplitude. At a fixed height and low Reynolds number the roughness element was able to reduce the extent of laminar separation over the airfoil as compared to a smooth airfoil. Further reduction of the separation was achieved by dynamically oscillating the roughness element in an appropriate range of actuation frequencies. Proper orthogonal decomposition performed upon the flow over the airfoil for both the baseline and active open loop case shows the introduction of persistent structures within the flow due to the oscillating roughness element. The coupling of this small input perturbation with the flow and the resultant manipulation of the separation bubble will be discussed for a range of flow and roughness conditions. The support of NSF CAREER award #0747672 is gratefully acknowledged.

Wallace, Ryan; McKeon, Beverley

2011-11-01

209

a Spectral Multidomain Method in Generalized Curvilinear Coordinates with Application to Leading-Edge Receptivity  

NASA Astrophysics Data System (ADS)

A spectral method in generalized curvilinear coordinates is developed for studying the early stages of transition to turbulence on complex geometries. The earliest stage of transition is receptivity, the process by which small disturbances, originating in the free stream, penetrate the boundary layer and excite the boundary-layer instabilities. The spatial directions are discretized with a spectral collocation method using the Gauss-Lobatto points, with a choice of either Chebyshev or Legendre polynomials. A semi-implicit finite-difference scheme is utilized for the temporal discretization with the linear terms being treated implicitly and the nonlinear terms treated explicitly. The resulting algebraic system of equations is solved iteratively using a preconditioned truncated conjugate residual method. A multidomain method is also incorporated into the spectral method to aid in the resolution of the disparate length scales of the problem. In effect, it breaks the problem up into a set of sub-problems which are related through interface conditions. Two interface conditions are tested and evaluated for the two types of equations solved in this study, transport and Poisson equations, respectively. For those geometries examined that require an outflow boundary, a buffer domain technique has been developed for the vorticity-stream-function formulation that allows disturbances and vortex structures to pass out of the domain of interest without reflection. The spectral method is first tested using the shear-driven cavity, both standard and regularized. The multidomain method is also examined as to its performance with the shear-driven cavity problem. In particular, the proper choice of interface conditions is investigated for the two types of equations being used. Next, the simulation of the linear-stability problem on a flat plate boundary layer is examined to test the accuracy of the interface conditions with respect to the passage of small amplitude waves. In addition, this problem provides validation for the spectral multidomain method for use in studying receptivity and also introduces additional complexities such as grid stretching, and far-field and outflow boundary conditions. The present method is tested to insure that the base flow, the Blasius boundary-layer solution, is maintained in the absence of disturbances. Two cases of linear stability are simulated. Two additional geometries are examined that make use of the generalized curvilinear coordinates and for which leading-edge receptivity is investigated: the parabola, and the flat plate with an elliptic leading edge. Base flow results are obtained and excellent comparisons are obtained between the present parabola results and those of Davis. Good qualitative comparisons are obtained between the present method and the finite-difference results of Lin et al. A receptivity study was attempted on the parabola geometry, but, the problem when discretized proved to be ill-conditioned. However, receptivity to plane acoustic waves was successfully simulated for the flat plate with an elliptic leading-edge geometry. Favorable comparisons with the results of Lin et al. are obtained for two values of the leading-edge aspect ratio and two values of the forcing frequency. In all of the receptivity results, the Tollmien-Schlichting wave can be seen to appear downstream of the ellipse-plate juncture. (Abstract shortened by UMI.).

Blodgett, Keith Edward James

1995-01-01

210

A composite index of lead effects  

Microsoft Academic Search

Biological indicators of lead effects on the central nervous system (CNS), hematogenous bone marrow, and kidney function as measured by performance tests, hemoglobin (Hgb) and BUN levels respectively were combined in an integrative index (INDEX). Such an index was calculated by removing age effects in measures of performance and kidney function and then transforming all the variables to Z (standard)

José A. Valciukas; Ruth Lilis

1982-01-01

211

Static and dynamic leading-edge-flap effects on the vortex lift of a delta wing  

NASA Astrophysics Data System (ADS)

Experiments were performed to determine the static and dynamic effects of leading edge flaps on the vortex lift of a delta wing. The flaps were linearly tapered, for a constant flap height to wing-span ratio of 0.33 or 0.22 and were able to pivot about the wing's leading edge. Experiments consisted mainly of pressure surveys, but also included flow visualizations and lift force measurements. Flap deflections, for most static flap cases and all the moving flap cases, were from folded on to the upper (suction) wing surface to normal to it. At low angles of attack, the static flaps created strong separated vortices and a flap-angle controlled lift increment. The flow structure of the main vortices were no different from those of plain delta wings. At high angles of attack the flaps caused a decrease of lift, unless they were unfolded beyond the wing, forming a new, nearly planar, delta wing of reduced sweep, Asymmetric deployment of a single flap failed to control the rolling moment monotonicly. Rapid opening of the flaps, in the order of one convective time length, increased the vortex lift further, above its quasi steady value. Transient vortex-lift increments were typically of the order of 40% of the static flap increments, at low angles of attack. Rapid closing of the flaps diminished the vortex lift below its quasi steady value. The power needed to operate the flaps at such speeds was enormous, comparable to the propulsive power required by the wing. The data following the completion of flap motion had to be discarded, because the abrupt arrest of flap motion caused both structural and data interference problems. A co-planar delta wing with dynamically variable sweep angle is proposed to overcome the deficiencies of the present arrangement.

Karagounis, Thales

212

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

213

A simplified method for thermal analysis of a cowl leading edge subject to intense local shock-wave-interference heating  

Microsoft Academic Search

Type IV shock wave interference heating on a blunt body causes extremely intense heating over a very localized region of the body. An analytical solution is presented to a heat transfer problem that approximates the shock wave interference heating of an engine cowl leading edge of the National Aero-Space Plane. The problem uses a simplified geometry to represent the leading

David M. McGowan; Charles J. Camarda; Stephen J. Scotti

1992-01-01

214

Aluminium foams as a filler for leading edges: Improvements in the mechanical behaviour under bird strike impact tests  

Microsoft Academic Search

The use of aluminium foams as filler materials in aeronautical leading edges is investigated. Particularly, the improvement of the mechanical behaviour of the filled structure respect to the hollow one is analysed by means of standard bird strike impact tests. For this purpose, a collection of AlSi10 foams were fabricated using the powder metallurgical route (PM), and introduced into leading

J. A. Reglero; M. A. Rodríguez-Pérez; E. Solórzano; J. A. de Saja

2011-01-01

215

Teachers on the Leading Edge: A Place-Based Professional Development Program for K-12 Earth Science Teachers  

Microsoft Academic Search

Teachers on the Leading Edge (TOTLE) is an Earth Science teacher professional development program featuring Pacific Northwest active continental margin geology. To engage middle-school teachers and students, TOTLE workshops: (1) invite novice learners to geophysical studies of tectonics, earthquakes, and volcanoes; (2) provide access to EarthScope research; and (3) explain geologic hazards as understandable aspects of living on the ``leading

Robert Butler

2010-01-01

216

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.

Zhou, Feng-quan; Cohan, Christopher S.

2001-01-01

217

Spin-dependent transport for armchair-edge graphene nanoribbons between ferromagnetic leads.  

PubMed

We theoretically investigate the spin-dependent transport for the system of an armchair-edge graphene nanoribbon (AGNR) between two ferromagnetic (FM) leads with arbitrary polarization directions at low temperatures, where a magnetic insulator is deposited on the AGNR to induce an exchange splitting between spin-up and -down carriers. By using the standard nonequilibrium Green's function (NGF) technique, it is demonstrated that the spin-resolved transport property for the system depends sensitively on both the width of AGNR and the polarization strength of FM leads. The tunneling magnetoresistance (TMR) around zero bias voltage possesses a pronounced plateau structure for a system with semiconducting 7-AGNR or metallic 8-AGNR in the absence of exchange splitting, but this plateau structure for the 8-AGNR system is remarkably broader than that for the 7-AGNR one. Interestingly, an increase of the exchange splitting ? suppresses the amplitude of the structure for the 7-AGNR system. However, the TMR is much enhanced for the 8-AGNR system under a bias amplitude comparable to the splitting strength. Further, the current-induced spin-transfer torque (STT) for the 7-AGNR system is systematically larger than that for the 8-AGNR one. The findings here suggest the design of GNR-based spintronic devices by using a metallic AGNR, but it is more favorable to fabricate a current-controlled magnetic memory element by using a semiconducting AGNR. PMID:21415476

Zhou, Benhu; Chen, Xiongwen; Zhou, Benliang; Ding, Kai-He; Zhou, Guanghui

2011-03-17

218

Theory and experiment for flutter of a rectangular plate with a fixed leading edge in three-dimensional axial flow  

NASA Astrophysics Data System (ADS)

This paper explores cantilevered beam flutter for both clamped and pinned leading edge boundary conditions. Specifically, a three-dimensional vortex lattice panel method is coupled with a classical Lagrangian one-dimensional beam structural model to predict the linear flutter boundary for finite size rectangular plates. The paper explores the change in flutter characteristics as a function of the fluid to structure mass ratio and the structural aspect ratio. The paper also presents an exploration of the non-monotonic transition in flutter velocity between the pinned-free and clamped-free boundary conditions which is modeled using a leading edge torsional spring. The theoretical results are compared to vibration and aeroelastic test results collected in the Duke University wind tunnel as well as previous theoretical and experimental results for the leading edge clamped configuration. The aeroelastic experiments confirmed the validity of the three-dimensional vortex lattice aerodynamic model over a subset of mass ratios.

Chad Gibbs, S.; Wang, Ivan; Dowell, Earl

2012-10-01

219

Interlaminar strains at the free edge of a hole in laminated composites: An experimental study  

SciTech Connect

Free-edge effects in laminated composite materials were studied experimentally using high-sensitivity moire interferometry. Six laminates from two material systems were tested in uniaxial compression on an electro-mechanical testing machine. Interlaminar deformations were measured on a ply-by-ply basis at the straight free-edge and, for the first time, on the cylindrical surface of a hole. Strain distributions were determined with high fidelity for the hole surface and the straight free edge of the thick composite panels. Comparisons were made on a ply-by-ply basis for the transverse and tangential strains at the horizontal centerline of the hole (90{degree} location) and the corresponding plies at the straight boundaries.

Boeman, R.G. [Oak Ridge National Lab., TN (United States). Engineering Technology Div.

1993-12-31

220

Piezoelectric Properties of Polycrystalline Lead Titanate Zirconate Compositions  

Microsoft Academic Search

Detailed data are given for the piezoelectric, elastic, and dielectric properties of lead titanate zirconate ceramic compositions near the rhombohedral-tetragonal phase boundary. These compositions have markedly higher electromechanical coupling factors, remanent ferroelectric charge, and coercive field, than ceramic barium titanate. Another interesting feature is a pronounced change in the free permittivity ¿33T by the poling process; this change is in

D. A. Berlincourt; C. Cmolik; H. Jaffe

1960-01-01

221

Leading edge boundary layer receptivitivy to oblique free stream acoustic waves on parabolic bodies  

NASA Astrophysics Data System (ADS)

In this study, the effect of the incidence angle of free strewn acoustic waves on the leading edge boundary layer receptivity of a two dimensional laminar incompressible flow over parabolic bodies is investigated. For this, the full Navier-Stokes equations in parabolic coordinates in streamfunction and vorticity variables were solved numerically. For the receptivity problem a spatial approach is used. With this approach, the free stream flow variables are composed of a uniform flow with a superimposed perturbation fluctuations of small amplitude. Using Normal Mode form and linearization assuming that the perturbations are small, the unsteady governing equations are converted into two systems of equations; the steady nonlinear basic flow equations and the steady linear complex perturbation flow equations. For the solution of nonlinear basic flow equations, a new numerical technique is developed which provides very accurate solutions. The perturbation equations are solved using a direct linear solver (LINPACK subroutines). In the numerical calculations, the numerical domain extends downstream of Branch II predicted by the linear theory for Blasius flow, for the frequency of the free stream oscillations used in the problem. The numerical codes for the solution of both the basic flow and the perturbation flow equations are first tested extensively to validate the solutions. In order to determine the receptivity coefficient, KLE, three steps are followed. First the basic flow equations are solved. Second, using the basic flow solution, the perturbation equations are solved. Third, the Stokes wave solution is obtained and subtracted from the perturbation solution. Using this final solution, the receptivity coefficient is extrapolated to the leading edge. The results obtained are compared with the past numerical results of Haddad [17], where they were found to be in excellent quantitative agreement. Quantitative comparisons with the analytical results of Hammerton and Kerschen [20] could not be made because of differences between the semi-infinite geometry used here and the finite geometry used by them. However, we observed excellent qualitative comparisons which indicate that the essential physics were represented by our numerical approach.

Erturk, Ercan

222

Eddy-Current Nondestructive Detection of Delaminations Near Edges of Composite Materials  

Microsoft Academic Search

The paper reports on an investigation of the field generated by an eddy-current transducer placed over an edge surface of composite material with delaminations. The calculations have been performed by the finite difference method, and modulation characteristics of vector potential components have been determined. The effect of flaws has been determined on the complex plane of the vector potential at

V. S. Khandetskii; L. Ya. Martynovich

2001-01-01

223

Experimental analysis of vibration characteristics of an edge- cracked composite plate by ESPI method  

Microsoft Academic Search

In this paper, the amplitude fluctuation (AF) electronic speckle pattern interferometry (ESPI) method was adopted to investigate\\u000a the vibration characteristics of a composite plate containing an edge crack. The change of the modal shapes was discussed.\\u000a In addition, the stress intensity factors (SIFs) induced by the resonant vibration were evaluated.

Wei-Chung Wang; Chi-Hung Hwang

1998-01-01

224

The effects of chemical gradients and photoresist composition on lithographically generated line edge roughness  

Microsoft Academic Search

Previous work has demonstrated the dependence of photoresist line edge roughness (LER) on the image-log-slope of the aerial image over a wide range of conditions; however, this relationship does not describe the influence of other factors such as photoresist composition or processing conditions on LER. This work introduces the concept of chemical gradients in the photoresist film rather than gradients

Timothy B. Michaelson; Adam R. Pawloski; Alden Acheta; Yukio Nishimura; C. Grant Willson

2005-01-01

225

Giant microwave tunability in FeGaB/lead magnesium niobate-lead titanate multiferroic composites  

NASA Astrophysics Data System (ADS)

Giant magnetoelectric coupling at both microwave frequencies and dc was observed in an FeGaB/lead magnesium niobate-lead titanate microwave multiferroic composite. A record high microwave frequency tunability of ?f=900 MHz or ?f/f=58% was demonstrated with the change of an external electric field from -6 to +2 kV/cm. A strong electric field dependence of magnetic hysteresis loops was also observed. Such multiferroic composite provides great opportunities for electrostatically tunable microwave devices.

Lou, J.; Reed, D.; Pettiford, C.; Liu, M.; Han, P.; Dong, S.; Sun, N. X.

2008-06-01

226

NanoComposite Lead-Free Interconnect and Reliability  

Microsoft Academic Search

Lead free solder bumping requirements have challenged researchers to develop new technologies to achieve fine pitch interconnects. ITRS has predicts that by 2017 the industry will require 70 micron pitch area array lead free interconnects for flip chips. This paper describes bumping, assembly and reliability evaluation of a new nano composite 20 micron pitch interconnect technology. Nanoparticles are the most

Ravi Doraiswami; Rao Tummala

2005-01-01

227

Development of detectability limits for on-orbit inspection of space shuttle wing leading edge  

NASA Astrophysics Data System (ADS)

At the conclusion of the Columbia Accident Investigation, one of the recommendations of the Columbia Accident Investigation Board (CAIB) was that NASA develop and implement an inspection plan for the Reinforced Carbon-Carbon (RCC) system components. To address these issues, a group of scientists and engineers at NASA Langley Research Center proposed the use of an IR camera to inspect the RCC. Any crack in an RCC panel changes the thermal resistance of the material in the direction perpendicular to the crack. The change in thermal resistance can be made visible by introducing a heat flow across the crack and using an IR camera to image the resulting surface temperature distribution. The temperature difference across the crack depends on the change in the thermal resistance, the length of the crack, the local thermal gradient, and the rate of radiation exchange with the environment. The current paper describes how the authors derived the minimum thermal gradient detectability limits for a through crack in an RCC panel. This paper will also show, through the use of a transient, 3-dimensional, finite element model, that these minimum gradients naturally exist on-orbit. The results from the finite element model showed that there exists sufficient thermal gradient to detect a crack on 96% of the RCC leading edge.

Stephan, Ryan A.; Johnson, David G.; Mastropietro, A. J.

2005-03-01

228

Stroke plane angle controls leading edge vortex in a bat-inspired flapper  

NASA Astrophysics Data System (ADS)

The present interest in micro air vehicles has given the research on bat flight a new impulse. With the use of high speed cameras and improved PIV techniques, the kinematics and aerodynamics of bats have been studied in great detail. A robotic flapper makes it possible to do measurements by systematically changing only one parameter at a time and investigate the parameter space outside the natural flight envelope of bats without risking animal safety. For this study, a robotic flapper (RoBat), inspired by Leptonycteris yerbabuenae was developed and tested over the speed range 1-7 m/s, with variable maximum angles of attacks ( AoA=55° and 15°, respectively) and constant AoA=55°. These measurements show the presence of a leading edge vortex (LEV) for low speeds and a fully attached flow for high speeds at low AoA, which is in line with natural bat flight. A LEV occurs for AoA=55° throughout the complete flight speed range, and throughout which the LEV circulation coefficient remains rather constant. This implies that bats and micro air vehicles could use LEVs for high load maneuvers also at relatively high flight speeds. However, at high flight speeds the LEV bursts, which causes increased drag, most likely due to a decrease in Strouhal number.

Koekkoek, Gide; Muijres, Florian T.; Johansson, L. Christoffer; Stuiver, Melanie; van Oudheusden, Bas W.; Hedenström, Anders

2012-01-01

229

Airfoil Leading Edge Flow Separation Control using DBD Plasma Actuators driven by Nanosecond Pulses  

NASA Astrophysics Data System (ADS)

This work continues an ongoing exploration of the use of dielectric barrier discharge plasma actuators driven by repetitive nanosecond pulses (NS-DBD hereafter) for aerodynamic flow control. The NS-DBD transfers very little momentum to the neutral air, but generates compression waves that manipulate flow instabilities similar to localized arc filament plasma actuators. Such devices which are believed to function through thermal effects and instability manipulation could result in a significant improvement over conventional DBD (AC-DBD) plasmas that rely on momentum addition which limits their performance at high speeds. The efficacy of NS-DBDs has been demonstrated in our laboratory in a preliminary work on an airfoil leading edge up to Mach 0.17 and Re=1x106. The current work extends the investigation to higher Mach (0.27) and Re (1.15x106), the maximum operating conditions of our subsonic wind tunnel, using an 8 inch chord NACA 0015 airfoil. Results show the efficacy of the nanosecond pulse plasma discharge for attaching the nominally separated flow at various post stall angles of attack.

Little, Jesse; Rethmel, Chris; Takashima, Keisuke; Wiet, Chris; Adamovich, Igor; Samimy, Mo

2010-11-01

230

Dkk-1 Inhibits Intestinal Epithelial Cell Migration by Attenuating Directional Polarization of Leading Edge Cells  

PubMed Central

Wnt signaling pathways regulate proliferation, motility, and survival in a variety of human cell types. Dickkopf-1 (Dkk-1) is a secreted Wnt antagonist that has been proposed to regulate tissue homeostasis in the intestine. In this report, we show that Dkk-1 is secreted by intestinal epithelial cells after wounding and that it inhibits cell migration by attenuating the directional orientation of migrating epithelial cells. Dkk-1 exposure induced mislocalized activation of Cdc42 in migrating cells, which coincided with a displacement of the polarity protein Par6 from the leading edge. Consequently, the relocation of the microtubule organizing center and the Golgi apparatus in the direction of migration was significantly and persistently inhibited in the presence of Dkk-1. Small interfering RNA-induced down-regulation of Dkk-1 confirmed that extracellular exposure to Dkk-1 was required for this effect. Together, these data demonstrate a novel role of Dkk-1 in the regulation of directional polarization of migrating intestinal epithelial cells, which contributes to the effect of Dkk-1 on wound closure in vivo.

Koch, Stefan; Capaldo, Christopher T.; Samarin, Stanislav; Nava, Porfirio; Neumaier, Irmgard; Skerra, Arne; Sacks, David B.; Parkos, Charles A.

2009-01-01

231

Anodic corrosion of fiber reinforced lead composites for use in large lead-acid batteries  

Microsoft Academic Search

The corrosion resistance of lightweight, high strength lead metal matrix composites under conditions that simulate their use as grid materials in large lead-acid batteries has been studied. Constant potential testing provides an effective means for holding constant the oxidizing power of a metal-electrolyte system. Data are presented on corrosion currents, effect of exposure time on corrosion rates, dependence of the

C. M. Dacres; S. M. Reamer; R. A. Sutula; I. A. Angres

1981-01-01

232

A DYNAMIC EQUILIBRIUM ANALYSIS OF A LEADING EDGE THERMAL HEAT SPREADER USING A CUBIC EQUATION OF STATE  

Microsoft Academic Search

A new thermodynamic model for calculating the steady state behavior of a leading edge thermal heat spreader, which operates upon the principles of evaporation, convection, and condensation of a working fluid, is presented. The intense, localized impinging heat flux is balanced with the thermal capacitance of the container walls and working fluid. The thermophysical properties of the vapor-liquid equilibrium are

Scott D. Kasen

233

Correlation of laminar-turbulent transition data over flat plates in supersonic\\/hypersonic flow including leading edge bluntness effects  

Microsoft Academic Search

The paper discusses flat plate boundary layer transition in supersonic\\/hypersonic flow conditions. Examination of experimental infrared thermography data illustrates the importance of the leading edge thickness and (non-) uniformity to the transition process. Such observations have triggered the collection of a wide range of experimental data on supersonic\\/hypersonic flat plate boundary layer transition, and a number of attempts to correlate

G. A. Simeonides; Rio Patras

2003-01-01

234

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

National Technical Information Service (NTIS)

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 vehicl...

P. A. Gnoffo

2003-01-01

235

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

Microsoft Academic Search

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

Peter A. Gnoffo

236

Aerodynamic characteristics of V-shaped wings with shock waves detached from leading edges at hypersonic speeds  

Microsoft Academic Search

The direct problem of hypersonic flow past a V-shaped wing with a shock wave detached from the leading edges is solved. The reduced normal force coefficient and the lift-drag (L\\/D) ratio are calculated for a configuration with a lower part in the shape of a V-wing and a streamwise upper part.

N. A. Ostapenko

1993-01-01

237

Receptivity of the boundary layer over a flat plate with different leading-edge geometries: Numerical simulations  

NASA Astrophysics Data System (ADS)

The receptivity to freestream oscillations of the laminar boundary layer over a semi-infinite flat plate of finite thickness is simulated numerically. The incompressible flow past the flat plate is computed by solving the full Navier-Stokes equations in general curvilinear coordinates. A finite-difference method which is second-order accurate in space and time is used. Spatial and temporal developments of the Tollmien-Schlichting wave in the boundary layer, due to small-amplitude time-harmonic oscillations of the freestream velocity that closely simulate a sound wave traveling parallel to the plate for incompressible flow, are observed. The effect of leading-edge geometry is studied by using leading edges with different aspect ratios. The boundary layer over the flat plate with a sharper elliptic leading edge is found to be less receptive. A new leading-edge geometry, a modified super-ellipse, which provides continuous curvature at the juncture with the flat plate, is used to study the effect of continuous curvature and inherent pressure gradient on receptivity. It is found that receptivity magnitude depends on how rapid the pressure gradient changes along the wall, and for a given aspect ratio, there is an optimum variation of the leading-edge curvature for minimum receptivity. Moreover, the phase of the instability wave is determined by the location of the maximum adverse-pressure gradient along the wall. The threshold of linearity of the instability-wave response with respect to the freestream amplitude is investigated. The applicability of the linearized form of disturbance equations for this receptivity problem is also demonstrated.

Lin, Nay

238

Data acquisition electronics for gamma ray emission tomography using width-modulated leading-edge discriminators  

NASA Astrophysics Data System (ADS)

We present a new high-performance and low-cost approach for implementing radiation detection acquisition systems. The basic elements used are charge-integrating ADCs and a set of components encapsulated in an HDL (hardware definition language) library which makes it possible to implement several acquisition tasks such as time pickoff and coincidence detection using a new and simple trigger technique that we name WMLET (width-modulated leading-edge timing). As proof of concept, a 32-channel hybrid PET/SPECT acquisition system based on these elements was developed and tested. This demonstrator consists of a master module responsible for the generation and distribution of trigger signals, 2 × 16-channel ADC cards (12-bit resolution) for data digitization and a 32-bit digital I/O PCI card for handling data transmission to a personal computer. System characteristics such as linearity, maximum transmission rates or timing resolution in coincidence mode were evaluated with test and real detector signals. Imaging capabilities of the prototype were also evaluated using different detector configurations. The performance tests showed that this implementation is able to handle data rates in excess of 600k events s-1 when acquiring simultaneously 32 channels (96-byte events). ADC channel linearity is >98.5% in energy quantification. Time resolution in PET mode for the tested configurations ranges from 3.64 ns FWHM to 7.88 ns FWHM when signals from LYSO-based detectors are used. The measured energy resolution matched the expected values for the detectors evaluated and single elements of crystal matrices can be neatly separated in the acquired flood histograms.

Lage, E.; Tapias, G.; Villena, J.; Desco, M.; Vaquero, J. J.

2010-08-01

239

A numerical and experimental study of the effects of dynamic roughness on laminar leading edge separation  

NASA Astrophysics Data System (ADS)

The aircraft industry, as a whole, has been deeply concerned with improving the aerodynamic efficiency of current and future flight vehicles, particularly in the commercial and military markets. However, of particular interest to the field of aerodynamics is the elusive concept of a workable flow control mechanism. Effective flow control is a concept which if properly applied can increase aerodynamic efficiency. Various concepts and ideas to obtain successful flow control have been studied in an attempt to reap these rewards. Some examples include boundary layer blowing (steady and periodic), suction, and compliant walls for laminar flow control. The overall goal of flow control is to increase performance by increasing lift, reducing drag, and delaying or eliminating leading edge separation. The specific objectives of flow control are to (1) delay or eliminate flow separation, (2) delay boundary layer transition, and (3) and reduce skin friction drag. The purpose of this research is to investigate dynamic roughness as a novel method of flow control technology for external boundary layer flows. As opposed to standard surface roughness, dynamic roughness incorporates small time dependent perturbations to the surface of the airfoil. These surface perturbations are actual humps and/or ridges on the surface of the airfoil that are on the scale of the laminar boundary, and oscillate with an unsteady motion. Research has shown that this can provide a means to modify the instantaneous and mean velocity profile near the wall and favorably control the existing state of the boundary layer. Several flow control parameters were studied including dynamic roughness frequency, amplitude, and geometry. The results of this study have shown, both numerically and experimentally, that dynamic roughness can provide an effective means for eliminating both a short and long laminar separation bubble and possibly prove a viable alternative in effective flow control, hence reaping some of the rewards of an effective flow control system.

Gall, Peter D.

240

Influence of leading-edge geometry on profile losses in turbines at off-design incidence: Experimental results and an improved correlation  

Microsoft Academic Search

The most recent correlations for turbine profile losses at off-design incidence include the leading-edge diameter as the only aspect of the leading-edge geometry that influences the losses. Cascade measurements are presented for two turbine blades that differ primarily in their leading-edge geometries. The incidence was varied over a range of {+-}20 deg and the results show significant discrepancies between the

M. W. Benner; S. A. Sjolander; S. H. Moustapha

1997-01-01

241

Stochastic model of integrin-mediated signaling and adhesion dynamics at the leading edges of migrating cells.  

PubMed

Productive cell migration requires the spatiotemporal coordination of cell adhesion, membrane protrusion, and actomyosin-mediated contraction. Integrins, engaged by the extracellular matrix (ECM), nucleate the formation of adhesive contacts at the cell's leading edge(s), and maturation of nascent adhesions to form stable focal adhesions constitutes a functional switch between protrusive and contractile activities. To shed additional light on the coupling between integrin-mediated adhesion and membrane protrusion, we have formulated a quantitative model of leading edge dynamics combining mechanistic and phenomenological elements and studied its features through classical bifurcation analysis and stochastic simulation. The model describes in mathematical terms the feedback loops driving, on the one hand, Rac-mediated membrane protrusion and rapid turnover of nascent adhesions, and on the other, myosin-dependent maturation of adhesions that inhibit protrusion at high ECM density. Our results show that the qualitative behavior of the model is most sensitive to parameters characterizing the influence of stable adhesions and myosin. The major predictions of the model, which we subsequently confirmed, are that persistent leading edge protrusion is optimal at an intermediate ECM density, whereas depletion of myosin IIA relieves the repression of protrusion at higher ECM density. PMID:20195494

Cirit, Murat; Krajcovic, Matej; Choi, Colin K; Welf, Erik S; Horwitz, Alan F; Haugh, Jason M

2010-02-26

242

Measurement of Fuel Concentration Profile at Leading Edge of Lifted Flame with Acetone Laser-Induced Fluorescence  

NASA Astrophysics Data System (ADS)

This is a study of the leading-edge characteristics of a methane-air triple flame. Few experiment results are available for physical examination of such characteristics, so further experimental investigations are strongly needed to understand the stability mechanism in a mixture with a steep concentration gradient. To this end, we measured concentration profiles at the leading edge of a flame using acetone laser-induced fluorescence (acetone LIF). The results demonstrated that the lifted height of the flame changed when acetone was added to the mixture and correlated well with increased C2 radical behind the flame edge. However, the OH radical luminous intensity, measured with a spectroscope, did not change with addition of acetone. Moreover, the burning velocity obtained by the Bunsen-burner method remained constant when acetone was added to the mixture. Therefore, acetone had little influence on burning intensity. Acetone LIF can thus be employed to measure the local concentration gradient at the leading edge of a flame. The acetone LIF signals could be corrected to consider the thermal effect by using silicone oil vanishing-plane data. From the corrected acetone LIF data, the width between the lean and rich flammability limits (flammability limit width) in the flow upstream of the flame with a steep concentration gradient was clearly observed and could be quantitatively compared with the recent numerical results.

Hirota, Mitsutomo; Sekine, Kazushi; Hashimoto, Kouta; Saiki, Atsushi; Takahashi, Hidemi; Masuya, Goro

243

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

Microsoft Academic Search

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

I. Skrna-Jakl; F. G. Rammerstorfer

1993-01-01

244

Examination of free-edge crack nucleation around an open hole in composite laminates  

Microsoft Academic Search

The present work examines the free-edge crack nucleation around an open hole in composite laminates by applying a cohesive zone (CZ) model. The boundary-value problem of an open hole with interfacial damage and crack in an infinite laminate plate under far-field straining is considered. The problem has been solved numerically by applying a special single-domain dual boundary element method for

B. Yang

2002-01-01

245

Construction of composite leading indicator for the Slovak economy  

Microsoft Academic Search

Cyclical performance of economies in a turbulent environment is forcing researchers to search for early signals of turning points between the phases of slowdowns and accelerations. The most appropriate tool to solve this problem is the composite leading indicator (CLI), which is an aggregate index of several individual indicators proved to be statistical relevant for analyzing and forecasting of significant

Miroslav Klúcik; Ján Haluška

2008-01-01

246

Coordinated RhoA signaling at the leading edge and uropod is required for T cell transendothelial migration  

PubMed Central

Transendothelial migration (TEM) is a tightly regulated process whereby leukocytes migrate from the vasculature into tissues. Rho guanosine triphosphatases (GTPases) are implicated in TEM, but the contributions of individual Rho family members are not known. In this study, we use an RNA interference screen to identify which Rho GTPases affect T cell TEM and demonstrate that RhoA is critical for this process. RhoA depletion leads to loss of migratory polarity; cells lack both leading edge and uropod structures and, instead, have stable narrow protrusions with delocalized protrusions and contractions. By imaging a RhoA activity biosensor in transmigrating T cells, we find that RhoA is locally and dynamically activated at the leading edge, where its activation precedes both extension and retraction events, and in the uropod, where it is associated with ROCK-mediated contraction. The Rho guanine nucleotide exchange factor (GEF) GEF-H1 contributes to uropod contraction but does not affect the leading edge. Our data indicate that RhoA activity is dynamically regulated at the front and back of T cells to coordinate TEM.

Heasman, Sarah J.; Carlin, Leo M.; Cox, Susan; Ng, Tony

2010-01-01

247

Flow past a delta wing with a sinusoidal leading edge: near-surface topology and flow structure  

Microsoft Academic Search

The near-surface flow structure and topology on a delta wing of low sweep angle, having sinusoidal leading edges of varying\\u000a amplitude and wavelength, are investigated using a stereoscopic technique of high-image-density particle image velocimetry\\u000a at a Reynolds number of 15,000. Identification of critical points, in conjunction with surface-normal vorticity and velocity,\\u000a provides a basis for determining the effectiveness of a

T. Goruney; D. Rockwell

2009-01-01

248

Reynolds Stress Transport Modeling of Film Cooling at the Leading Edge of a Symmetrical Turbine Blade Model  

Microsoft Academic Search

This paper investigates the performance of the SSG (Speziale, Sarkar, and Gatski) Reynolds Stress Model for the prediction of film cooling at the leading edge of a symmetrical turbine blade model using the CFX 5.7.1 package from ANSYS, Inc. Using a finite-volume method, the performance of the selected turbulence model is compared to that of the standard k?? model. The

Fadela Nemdili; Abbes Azzi; Georgios Theodoridis; Bassam A. Jubran

2008-01-01

249

Cease-fire at the leading edge: new perspectives on actin filament branching, debranching and cross-linking  

PubMed Central

Membrane protrusion at the leading edge of migrating cells is driven by the polymerization of actin. Recent studies using advanced imaging techniques raised a lively controversy about the morphology of these filaments; however, common ground between the two sides now appears to have been found. Here we discuss how the controversy has led to a deeper consideration of the architecture of actin networks underlying cell migration, and has helped define new challenges that lie ahead.

Ydenberg, Casey A.; Smith, Benjamin A.; Breitsprecher, Dennis; Gelles, Jeff; Goode, Bruce L.

2011-01-01

250

Transfer of New Earth Science Understandings to Classroom Teaching: Lessons Learned From Teachers on the Leading Edge  

Microsoft Academic Search

Teachers on the Leading Edge (TOTLE) provided a field-based teacher professional development program that explored the active continental margin geology of the Pacific Northwest during a two-week field workshop that traversed Oregon from the Pacific Coast to the Snake River. The seventeen teachers on this journey of geological discovery experienced regional examples of subduction-margin geology and examined the critical role

R. Butler; C. Ault; E. Bishop; T. Southworth-Neumeyer; B. Magura; C. Hedeen; R. Groom; K. Shay; R. Wagner

2006-01-01

251

The Leading Edge of the Galapagos Hotspot: Geochemistry and Geochronology of Submarine Glasses Coupled to New Sidescan Sonar Imagery  

Microsoft Academic Search

Fernandina, the western-most volcano in the Galapagos archipelago, is at the leading edge of the hotspot with respect to plate motion. Recent mapping of the ocean floor west of Fernandina (on R\\/V Revelle, using the HMRG towed sidescan sonar MR1, and Simrad EM120 multibeam) provides a dramatic new view of the volcanic constructional processes that have created the islands. The

M. D. Kurz; D. J. Fornari; D. J. Geist; P. D. Johnson; J. M. Curtice; D. E. Lott; K. Harpp; A. E. Saal; U. G. Peckman

2001-01-01

252

Projection maskless patterning (PMLP) for the fabrication of leading-edge complex masks and nano-imprint templates  

Microsoft Academic Search

The reliable and cost-effective fabrication of 2D and 3D structured nano-surfaces is prerequisite for a number of industrial and emerging applications: (i) leading-edge complex masks, (ii) high precision nano-imprint templates, (iii) nano-functionalized surfaces and 3D structures for applications in nano-photonics, nano-magnetics, and nano-biotechnology. Projection Mask-Less Patterning (PMLP) is based on many hundred thousands of ion beams working in parallel. A

Elmar Platzgummer; Hans Loeschner; Gerhard Gross

2007-01-01

253

A receiver channel with a leading edge timing discriminator for a pulsed time-of-flight laser radar  

Microsoft Academic Search

An integrated receiver channel with a wide dynamic range for a pulsed time-of-flight (TOF) laser rangefinder has been designed and tested. The circuit uses leading edge timing discrimination. The bandwidth of the receiver channel is 250 MHz and the maximum transimpedance 40 k?. The single-shot distance measurement accuracy is 65 mm, taking into account walk error (input signal amplitude varies

T. Peltola; T. Ruotsalainen; P. Palojarvi; J. Kostamovaara

2000-01-01

254

Technical Report of National Aerospace Laboratory: Experimental Investigations on High Lift Devices for an SST Part 2. Effects of Rounded Leading-Edges.  

National Technical Information Service (NTIS)

The effects of rounded leading-edge vortex flaps were investigated on a cranked arrow wing SST configuration, using wind tunnel measurements. Differences in aerodynamic characteristics were discussed for the 'non-rounded' leading-edge flap-an original des...

K. Miyata K. Rinoie D. Y. Kwak M. Noguchi

2003-01-01

255

Caracteristiques d'Une Couche Limite en Aval d'UN Tourbillon de Bord d'Attaque (Characteristics of a Boundary Layer in a Leading Edge Vortex).  

National Technical Information Service (NTIS)

The boundary layer developing downstream of a leading edge vortex was investigated. This experiment is devoted to the understanding of the behavior of such a boundary layer submitted to the effects of a leading edge vortex developing on the suction side o...

G. Pailhas J. Cousteix

1991-01-01

256

A composite view on Windenburg's problem: Buckling and minimum stiffness requirements of compressively loaded orthotropic plates with edge reinforcements  

Microsoft Academic Search

This paper discusses the buckling behaviour of orthotropic composite plates under uniform uniaxial compression with one free reinforced unloaded edge. A typical application example for use of such a mechanical model is the web of stiffeners and frames attached to the fuselage skin of an aircraft. The considered plates are rectangular and simply supported at the loaded transverse edges. One

Christian Mittelstedt; Martin Schagerl

2010-01-01

257

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.

Portet, Thomas; Dimova, Rumiana

2010-01-01

258

Element migration from glass compositions containing no added lead.  

PubMed

Six crystal glass compositions without added lead were used to prepare standard beakers having a volume of ca. 240 ml. The experimentally determined concentrations of the elements in the glass beakers were in satisfactory agreement with the theoretically predicted values. The degree of leaching of selected elements from these beakers was determined using 4% acetic acid as described in the ISO 7086-1:2000 standard test. In addition, to the degree of leaching by 4% acetic acid, migration into cola, red wine, 40% ethanol and 0.3% citric acid was also determined. Elements tested included antimony, barium, bismuth and zinc as these were considered to be of most interest. The results show that it is possible to produce durable glass containing no added lead. The overall quality of the glasses was good and the concentrations of the various elements migrating (leaching) into the various test solutions used was very small and it is clear that they would not present a hazard to consumers in the event that they were to use glasses of any of these compositions for consumption of either alcoholic or non-alcoholic beverages. The original ISO7086-1:2000 test using a 4% acetic acid leaching solution was developed to test for lead migration from crystal containing added lead and ceramic ware containing lead glazes or colouring. This work also shows that it is an excellent leaching agent for assessing the safety of crystal containing no added lead as it gave the highest degree of migration for all the glass compositions and all the elements tested. In the case of glasses containing ZnO, it was shown that the degree of zinc migration was linearly related to the mole-% of ZnO in the glass. With respect to the durability of glasses, it was shown that the degree of attack increases when the degree of silica depolymerisation increases. PMID:14967500

Hynes, Michael J; Forde, Sean; Jonson, Bo

2004-02-01

259

Chemical resistant lead-free glass frit compositions  

SciTech Connect

Glass frit compositions for use in glazes or enamels have a fiber softening point of 535/sup 0/ C. or more and are free of cadmium, lead and arsenic and consist essentially of Bi/sub 2/O/sub 3/-B/sub 2/O/sub 3/-SiO/sub 2/ with R/sub 3/O being 2-8% and RO being 0-9% by weight.

Francel, T.

1985-11-19

260

Studies on lead-free multiferroic magnetoelectric composites  

NASA Astrophysics Data System (ADS)

Lead-free multiferroic magnetoelectric composites consisting of ferrimagnetic Ni0.93Co0.02Mn0.05Fe1.95O4 (NMF) and ferroelectric Na0.5Bi0.5TiO3 (NBT) phases were synthesized by the solid-state sintering method. The presence of constituent phases in composites was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A systematic study of dc conductivity as a function of temperature (RT -450 °C) revealed that the conduction is due to small polarons. The effect of constituent phase variation on the dielectric constant and piezoelectric strength (d33) was examined. The composites exhibited typical magnetic hysteresis (M-H) loops at room temperature. Furthermore, magnetoelectric (ME) output was evaluated as a function of applied magnetic field, which is a product property of the constituent phases. The compound 50% NMF-50%NBT is a new lead-free magnetoelectric composite with 155 ?V/cm ME output, which may have potential applications.

Babu, S. Narendra; Srinivas, K.; Bhimasankaram, T.

2009-11-01

261

Erythrocyte membrane microviscosity and phospholipid composition in lead workers.  

PubMed Central

The microviscosity and fluidity of erythrocyte ghost membranes from lead workers and control subjects was measured by fluorescence polarisation using the fluorophore, 1,6-diphenyl-1,3,5-hexatriene (DPH). Increased lead was associated with a significant decrease in the average microviscosity of resealed and unsealed erythrocyte membranes. Since DPH fluorescence reflects the organisation of lipids in the central core of the membrane, two aspects of phospholipid metabolism were investigated. Phospholipids were extracted from red blood cell ghost membranes and identified by high performance liquid chromatography. The ratio of phosphatidyl choline to phosphatidyl ethanolamine, an established correlate of membrane fluidity, was significantly increased in lead workers. This is attributed to the known increases in red blood cell cholesterol in lead workers and the structural incompatibility of phosphatidyl ethanolamine and cholesterol, which result in a compensatory increase of phosphatidyl choline. Erythrocyte ghost membranes from control subjects were resealed with the intermediates in phospholipid synthesis that increase with a lead inhibited decrease in red blood cell pyrimidine 5'-nucleotidase. Membrane fluidity was not modified by incubation with cytidine triphosphate, uridine triphosphate, cytidine diphosphate choline, or cytidine diphosphate ethanolamine. Alterations in the microviscosity of the lipid regions of the hydrophobic core of the erythrocyte membrane bilayer and in the phospholipid composition of the membrane may be defects which contribute to the clinical and biochemical instability of the red blood cell on exposure to lead.

Cook, L R; Stohs, S J; Angle, C R; Hickman, T I; Maxell, R C

1987-01-01

262

Co:GGG edge cladding with adjusted absorption coefficients in composite crystals  

NASA Astrophysics Data System (ADS)

Gadolinium Gallium Garnet single crystals doped with cobalt ions are used for suppression of parasitic as edge cladding layers in Nd:Gd3Ga5O12 (Nd:GGG) crystal amplifier plates for heat capacity and other high power solid-state laser applications. Co:GGG absorbs at the lasing wavelength of 1062 nm. Nd:GGG amplifier plates with edge cladding of Co:GGG of adjusted absorption coefficient at 1062 nm will be used as adhesive-free bonded (AFB) composite crystal components in a heat capacity laser system at Lawrence Livermore National Laboratory. Composite formation of Nd:GGG and Co:GGG involves heat treatment. The absorption coefficient of the as-grown Co:GGG single crystal changes as function of heat treatment. We report on a method of reversibly adjusting the absorption coefficient of Co:GGG in a certain range, e.g. for a specific Co ion concentration of 0.0046% between 0.45/cm and 0.95/cm. The interpretation of the reversible adjustment of absorption coefficients based on absorption spectra, site symmetry and cobalt ion valency will be presented

Lee, Huai-Chuan; Meissner, Helmuth E.; Meissner, Oliver R.

2004-07-01

263

Explanation of the effects of leading-edge tubercles on the aerodynamics of airfoils and finite wings  

NASA Astrophysics Data System (ADS)

A computational study was conducted to explain the aerodynamic effect of leading edge tubercles on maximum lift coefficient, stall angle of attack (AoA), drag, and post stall characteristics for airfoils as well as finite wings. Past experiments demonstrated airfoils with leading edge tubercles do not improve Clmax, drag, or stall AoA but smoothen post stall characteristics to a great degree. In contrast to airfoils, finite wings with L.E. tubercles improved all aerodynamic characteristics. We explain the stall mechanism of the tubercled wing by considering each L.E. tubercle as a combination of a swept forward and a swept backward wing.There are 3 mechanisms (streamline curvature, accelerated stall, and upwash) that cause Clmax of airfoils with L.E. tubercles always be lower than that of smooth airfoils. We also identify two additional mechanisms which are responsible for improved post-stall characteristics of airfoils with L.E. tubercles. Finally, we discuss why finite wings with L.E. tubercles have higher Clmax and lower drag than their smooth L.E. counterparts by studying effects of wing tip, sweep, and taper ratio.

Saadat, Mehdi; Haj-Hariri, Hossein; Fish, Frank

2010-11-01

264

A study of the effect of the temperature factor on pressure losses in the cooling system of the leading edge of a deflector vane  

Microsoft Academic Search

Reference is made to several earlier studies in which pressure losses associated with the use of single-row and multiple-row jet cooling of the leading edge of nozzle vanes of gas turbine engines have been estimated using independent models of the leading edge. Here, experiments are carried out on a specially designed high-temperature gasdynamic test bench in order to verify the

A. I. Arkhipov; A. S. Limanskii; V. V. Rumiantsev; M. M. Khasbiullin

1986-01-01

265

Landscape composition, patch size, and distance to edges: interactions affecting duck reproductive success  

USGS Publications Warehouse

Prairies and other North American grasslands, although highly fragmented, provide breeding habitat for a diverse array of species, including species of tremendous economic and ecological importance. Conservation and management of these species requires some understanding of how reproductive success is affected by edge effects, patch size, and characteristics of the landscape. We examined how differences in the percentage of grassland in the landscape influenced the relationships between the success of nests of upland-nesting ducks and (1) field size and (2) distance to nearest field and wetland edges. We collected data on study areas composed of 15DS20% grassland and areas composed of 45DS55% grassland in central North Dakota, USA during the 1996 and 1997 nesting seasons. Daily survival rates (DSRs) of duck nests were greater in study areas with 45DS55% grassland than with 15DS20% grassland. Within study areas, we detected a curvilinear relationship between DSR and field size: DSRs were highest in small and large fields and lowest in moderately sized fields. In study areas with 15DS20% grassland, there was no relationship between probability of hatching and distance to nearest field edge, whereas in study areas with 45DS55% grassland, there was a positive relationship between these two variables. Results of this study support the conclusion that both landscape composition and configuration affect reproductive success of ground-nesting birds. We are prompted to question conservation strategies that favor clustering moderately sized patches of nesting habitat within agricultural landscapes because our results show that such patches would have low nest success, most likely caused by predation. Understanding the pattern of nest success, and the predatorDSprey mechanisms that produce the pattern, will enable design of patch configurations that are most conducive to meeting conservation goals.

Horn, D. J.; Phillips, M. L.; Koford, R. R.; Clark, W. R.; Sovada, M. A.; Greenwood, R. J.

2005-01-01

266

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.

267

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.  

National Technical Information Service (NTIS)

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 appare...

W. A. Newsom D. R. Satran J. L. Johnson

1982-01-01

268

The endosomal adaptor protein APPL1 impairs the turnover of leading edge adhesions to regulate cell migration  

PubMed Central

Cell migration is a complex process that requires the integration of signaling events that occur in distinct locations within the cell. Adaptor proteins, which can localize to different subcellular compartments, where they bring together key signaling proteins, are emerging as attractive candidates for controlling spatially coordinated processes. However, their function in regulating cell migration is not well understood. In this study, we demonstrate a novel role for the adaptor protein containing a pleckstrin-homology (PH) domain, phosphotyrosine-binding (PTB) domain, and leucine zipper motif 1 (APPL1) in regulating cell migration. APPL1 impairs migration by hindering the turnover of adhesions at the leading edge of cells. The mechanism by which APPL1 regulates migration and adhesion dynamics is by inhibiting the activity of the serine/threonine kinase Akt at the cell edge and within adhesions. In addition, APPL1 significantly decreases the tyrosine phosphorylation of Akt by the nonreceptor tyrosine kinase Src, which is critical for Akt-mediated cell migration. Thus, our results demonstrate an important new function for APPL1 in regulating cell migration and adhesion turnover through a mechanism that depends on Src and Akt. Moreover, our data further underscore the importance of adaptor proteins in modulating the flow of information through signaling pathways.

Broussard, Joshua A.; Lin, Wan-hsin; Majumdar, Devi; Anderson, Bridget; Eason, Brady; Brown, Claire M.; Webb, Donna J.

2012-01-01

269

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

270

General Method for Determination of the Surface Composition in Bimetallic Nanoparticle Catalysts from the L Edge X-ray Absorption Near-Edge Spectra  

SciTech Connect

Bimetallic PtPd on silica nano-particle catalysts have been synthesized and their average structure determined by Pt L3 and Pd K-edge extended X-ray absorption finestructure (EXAFS) spectroscopy. The bimetallic structure is confirmed from elemental line scans by STEM for the individual 1-2 nm sized particles. A general method is described to determine the surface composition in bimetallic nanoparticles even when both metals adsorb, for example, CO. By measuring the change in the L3 X-ray absorption near-edge structure (XANES) spectra with and without CO in bimetallic particles and comparing these changes to those in monometallic particles of known size the fraction of surface atoms can be determined. The turnover rates (TOR) and neopentane hydrogenolysis and isomerization selectivities based on the surface composition suggest that the catalytic and spectroscopic properties are different from those in monometallic nano-particle catalysts. At the same neo-pentane conversion, the isomerization selectivity is higher for the PtPd catalyst while the TOR is lower than that of both Pt and Pd. As with the catalytic performance, the infrared spectra of adsorbed CO are not a linear combination of the spectra on monometallic catalysts. Density functional theory calculations indicate that the Pt-CO adsorption enthalpy increases while the Pd-CO bond energy decreases. The ability to determine the surface composition allows for a better understanding of the spectroscopic and catalytic properties of bimetallic nanoparticle catalysts.

Wu, Tiapin; Childers, David; Gomez, Carolina; Karim, Ayman M.; Schweitzer, Neil; Kropf, Arthur; Wang, Hui; Bolin, Trudy B.; Hu, Yongfeng; Kovarik, Libor; Meyer, Randall; Miller, Jeffrey T.

2012-10-31

271

Projection maskless patterning (PMLP) for the fabrication of leading-edge complex masks and nano-imprint templates  

NASA Astrophysics Data System (ADS)

The reliable and cost-effective fabrication of 2D and 3D structured nano-surfaces is prerequisite for a number of industrial and emerging applications: (i) leading-edge complex masks, (ii) high precision nano-imprint templates, (iii) nano-functionalized surfaces and 3D structures for applications in nano-photonics, nano-magnetics, and nano-biotechnology. Projection Mask-Less Patterning (PMLP) is based on many hundred thousands of ion beams working in parallel. A PMLP proof-of-concept tool has been realized as part of the European project CHARPAN (Charged Particle Nanotech; www.charpan.com). The novel ion beam projection optics with 200x reduction shows 16nm half pitch resolution. First results with a programmable aperture plate system have been achieved demonstrating high accuracy and flexible pattern fabrication.

Platzgummer, Elmar; Loeschner, Hans; Gross, Gerhard

2007-10-01

272

Syk-mediated translocation of PI3Kdelta to the leading edge controls lamellipodium formation and migration of leukocytes.  

PubMed

The non-receptor tyrosine kinase Syk is mainly expressed in the hematopoietic system and plays an essential role in beta(2) integrin-mediated leukocyte activation. To elucidate the signaling pathway downstream of Syk during beta2 integrin (CD11/CD18)-mediated migration and extravasation of polymorphonuclear neutrophils (PMN), we generated neutrophil-like differentiated HL-60 (dHL-60) cells expressing a fluorescently tagged Syk mutant lacking the tyrosine residue at the position 323 (Syk-Tyr323) that is known to be required for the binding of the regulatory subunit p85 of the phosphatidylinositol 3-kinase (PI3K) class I(A). Syk-Tyr323 was found to be critical for the enrichment of the catalytic subunit p110delta of PI3K class I(A) as well as for the generation of PI3K products at the leading edge of the majority of polarized cells. In accordance, the translocation of PI3K p110delta to the leading edge was diminished in Syk deficient murine PMN. Moreover, the expression of EGFP-Syk Y323F interfered with proper cell polarization and it impaired efficient migration of dHL-60 cells. In agreement with a major role of beta2 integrins in the recruitment of phagocytic cells to sites of lesion, mice with a Syk-deficient hematopoietic system demonstrated impaired PMN infiltration into the wounded tissue that was associated with prolonged cutaneous wound healing. These data imply a novel role of Syk via PI3K p110delta signaling for beta2 integrin-mediated migration which is a prerequisite for efficient PMN recruitment in vivo. PMID:17987119

Schymeinsky, Jürgen; Then, Cornelia; Sindrilaru, Anca; Gerstl, Ronald; Jakus, Zoltán; Tybulewicz, Victor L J; Scharffetter-Kochanek, Karin; Walzog, Barbara

2007-11-07

273

Isotopic composition of lead in soils and street dust in the Southeastern administrative district of Moscow  

NASA Astrophysics Data System (ADS)

The content and isotope ratios of lead were studied in soils, street dust, and snow sampled in the Southeastern administrative district of Moscow. The relationships between the lead isotope ratios and the content of different lead compounds in soils were revealed. It was shown that isotope ratios for the total lead have low information values upon low levels of lead contamination. The contribution of technogenic lead compounds to the isotopic composition of lead increases in the following sequence: total lead < acid-soluble lead < mobile lead. The effect of emissions from thermal power stations and vehicles’ exhaust on the isotopic composition of lead in the street dust and soils was estimated.

Ladonin, D. V.; Plyaskina, O. V.

2009-01-01

274

Compressive buckling of rectangular composite plates with a free-edge delamination  

Microsoft Academic Search

An experimental and analytical investigation is conducted on the compressive buckling behavior of orthotropic plates with a delamination. The plates, which have three simply supported edges and one free edge, are a simplified model of stiffener plates of a stiffened panel. A uniform width delamination is located at their free edges over the whole length. In the analysis, the Rayleigh-Ritz

Hiroshi Suemasu; Katsuhisa Gozu; Kunio Hayashi; Takashi Ishikawa

1995-01-01

275

Distinctive features of the transonic flow past a cone-cylinder body at small angles of the bend in the body generator at the leading corner edge  

Microsoft Academic Search

The distinctive features of the transonic flow past cone-cylinder bodies with small angles of the bend in the body generator\\u000a at the leading corner edge are considered. The mechanism of transonic flow restructuring downstream of the edge and the associated\\u000a variation of the gasdynamic parameters are studied, the reasons for the formation of aerodynamic hysteresis are established,\\u000a and the effect

B. N. Dan’kov; A. P. Kosenko; V. N. Kulikov; V. N. Otmennikov

2006-01-01

276

DQM large amplitude vibration of composite beams on nonlinear elastic foundations with restrained edges  

NASA Astrophysics Data System (ADS)

This paper presents an efficient and accurate differential quadrature (DQ) large amplitude free vibration analysis of laminated composite thin beams on nonlinear elastic foundation. Beams under consideration have elastically restrained against rotation and in-plane immovable edges. Elastic foundation has cubic nonlinearity with shearing layer. We impose the boundary conditions directly into the governing equations in spite of the conventional DQ method and without any extra efforts. A direct iterative method is used to solve the nonlinear eigenvalue system of equations after transforming the governing equations into the frequency domain. The fast rate of convergence of the method is shown and their accuracy is demonstrated by comparing the results with those for limit cases, i.e. beams with classical boundary conditions, available in the literature. Besides, we develop a finite element program to verify the results of the presented DQ approach and to show its high computational efficiency. The effects of different parameters on the ratio of nonlinear to linear natural frequency of beams are studied.

Malekzadeh, P.; Vosoughi, A. R.

2009-03-01

277

EDG-1 links the PDGF receptor to Src and focal adhesion kinase activation leading to lamellipodia formation and cell migration  

Microsoft Academic Search

Sphingosine-1-phosphate (SPP), formed by sphingosine kinase, is the ligand for EDG-1, a GPCR important for cell migration and vascular maturation. Here we show that cytoskeletal rearrangements, lamel- lipodia extensions, and cell motility induced by platelet- derived growth factor (PDGF) are abrogated in EDG-1 null fibroblasts. However, EDG-1 appears to be dis- pensable for mitogenicity and survival effects, even those induced

HANS M. ROSENFELDT; JOHN P. HOBSON; MICHAEL MACEYKA; ANA OLIVERA; VICTOR E. NAVA; SHELDON MILSTIEN; SARAH SPIEGEL

2001-01-01

278

First results from core-edge parallel composition in the FACETS project  

SciTech Connect

FACETS (Framework Application for Core-Edge Transport Simulations), now in its second year, has achieved its first coupled core-edge transport simulations. In the process, a number of accompanying accomplishments were achieved. These include a new parallel core component, a new wall component, improvements in edge and source components, and the framework for coupling all of this together. These accomplishments were a result of an interdisciplinary collaboration among computational physics, computer scientists, and applied mathematicians on the team.

Cary, John R. [Tech-X Corporation; Candy, Jeff [General Atomics; Cohen, Ronald H. [Lawrence Livermore National Laboratory (LLNL); Krasheninnikov, Sergei [University of California, San Diego; McCune, Douglas [Princeton Plasma Physics Laboratory (PPPL); Estep, Donald J [Colorado State University, Fort Collins; Larson, Jay [Argonne National Laboratory (ANL); Malony, Allen [University of Oregon; Pankin, A. [Lehigh University, Bethlehem, PA; Worley, Patrick H [ORNL; Carlsson, Johann [Tech-X Corporation; Hakim, A H [Tech-X Corporation; Hamill, P [Tech-X Corporation; Kruger, Scott [Tech-X Corporation; Miah, Mahmood [Tech-X Corporation; Muzsala, S [Tech-X Corporation; Pletzer, Alexander [Tech-X Corporation; Shasharina, Svetlana [Tech-X Corporation; Wade-Stein, D [Tech-X Corporation; Wang, N [Tech-X Corporation; Balay, Satish [Argonne National Laboratory (ANL); McInnes, Lois [Argonne National Laboratory (ANL); Zhang, Hong [Argonne National Laboratory (ANL); Casper, T. A. [Lawrence Livermore National Laboratory (LLNL); Diachin, Lori [Lawrence Livermore National Laboratory (LLNL); Epperly, Thomas [Lawrence Livermore National Laboratory (LLNL); Rognlien, T. D. [Lawrence Livermore National Laboratory (LLNL); Fahey, Mark R [ORNL; Cobb, John W [ORNL; Morris, A [University of Oregon; Shende, Sameer [University of Oregon; Hammett, Greg [Princeton Plasma Physics Laboratory (PPPL); Indireshkumar, K [Tech-X Corporation; Stotler, D. [Princeton Plasma Physics Laboratory (PPPL); Pigarov, A [University of California, San Diego

2008-01-01

279

Chronicling a century of lead pollution in Mexico: stable lead isotopic composition analyses of dated sediment cores.  

PubMed

Analyses of lead isotopic compositions (204Pb, 206Pb, 207Pb, and 208Pb) of dated sediment cores from two coastal estuaries and two inland lakes chronicle the predominance of industrial lead emissions in Mexico over the past century. These isotopic ratios exhibit a shift in composition from the turn of the previous century (1900) that corresponds with measurable increases (from 2- to 10-fold) in lead concentrations in the cores above their baseline values (3-22 microg/g)--both changes are consistent with the development of Mexican lead production for export and the manufacture of tetraethyl lead additives for Mexican gasolines. While subsequent changes in lead concentrations in the cores correspond with calculated emissions from the combustion of leaded gasoline in Mexico, isotopic compositions of the cores remain relatively constant throughout most of the 1900s (e.g., 206Pb/207Pb = 1.200 +/- 0.003; 208Pb/207Pb = 2.463 +/- 0.004). That isotopic constancy is attributed to the widespread pollution from lead production in Mexico and the dispersion of some of that lead used as an additive in Mexican gasolines. PMID:16509316

Soto-Jimenez, Martin F; Hibdon, Sharon A; Rankin, Charley W; Aggarawl, Jugdeep; Ruiz-Fernandez, A Carolina; Paez-Osuna, Federico; Flegal, A Russell

2006-02-01

280

Transition over C4 leading edge and measurement of intermittency factor using PDF of hot-wire signal  

SciTech Connect

The variation of intermittency factors in the transition region of a C4 leading edge flat plate is measured at three incidence angles in a low-turbulence free stream. During the determination of intermittency factor, the threshold value of the detector function and the validity of conditional averaging are verified by a method based on the direct application of PDF of the hot-wire output. As the angle of incidence is increased, the transition progressively moves through all the three modes on the suction surface: at zero incidence the bypass transition, at 2 deg incidence the natural transition, and at 4 deg incidence the separated-flow transition occur, respectively. All three modes of transition exhibited the chordwise intermittency factor variation in accordance with Narasinha`s universal intermittency distribution; thus, the method based on spot production rate is applicable to all the three modes of transition. In the transition zone of the attached boundary layers, the conditionally averaged interturbulent profiles are fuller than the Blasius profile, while the conditionally averaged turbulent profiles follow a logarithmic profile with a variable additive parameter.

Hazarika, B.K.; Hirsch, C. [Vrije Univ. Brussel, Brussels (Belgium). Dept. of Fluid Mechanics

1997-07-01

281

Smoke visualization of free-flying bumblebees indicates independent leading-edge vortices on each wing pair  

NASA Astrophysics Data System (ADS)

It has been known for a century that quasi-steady attached flows are insufficient to explain aerodynamic force production in bumblebees and many other insects. Most recent studies of the unsteady, separated-flow aerodynamics of insect flight have used physical, analytical or numerical modeling based upon simplified kinematic data treating the wing as a flat plate. However, despite the importance of validating such models against living subjects, few good data are available on what real insects actually do aerodynamically in free flight. Here we apply classical smoke line visualization techniques to analyze the aerodynamic mechanisms of free-flying bumblebees hovering, maneuvering and flying slowly along a windtunnel (advance ratio: -0.2 to 0.2). We find that bumblebees, in common with most other insects, exploit a leading-edge vortex. However, in contrast to most other insects studied to date, bumblebees shed both tip and root vortices, with no evidence for any flow structures linking left and right wings or their near-wakes. These flow topologies will be less efficient than those in which left and right wings are aerodynamically linked and shed only tip vortices. While these topologies might simply result from biological constraint, it is also possible that they might have been specifically evolved to enhance control by allowing left and right wings to operate substantially independently.

Bomphrey, Richard James; Taylor, Graham K.; Thomas, Adrian L. R.

2009-05-01

282

Smoke visualization of free-flying bumblebees indicates independent leading-edge vortices on each wing pair  

NASA Astrophysics Data System (ADS)

It has been known for a century that quasisteady attached flows are insufficient to explain aerodynamic force production in bumblebees and many other insects. Most recent studies of the unsteady, separated-flow aerodynamics of insect flight have used physical, analytical or numerical modeling based upon simplified kinematic data treating the wing as a flat plate. However, despite the importance of validating such models against living subjects, few good data are available on what real insects actually do aerodynamically in free flight. Here we apply classical smoke line visualization techniques to analyze the aerodynamic mechanisms of free-flying bumblebees hovering, maneuvering and flying slowly along a windtunnel (advance ratio: -0.2 to 0.2). We find that bumblebees, in common with most other insects, exploit a leading-edge vortex. However, in contrast to most other insects studied to date, bumblebees shed both tip and root vortices, with no evidence for any flow structures linking left and right wings or their near-wakes. These flow topologies will be less efficient than those in which left and right wings are aerodynamically linked and shed only tip vortices. While these topologies might simply result from biological constraint, it is also possible that they might have been specifically evolved to enhance control by allowing left and right wings to operate substantially independently.

Bomphrey, Richard James; Taylor, Graham K.; Thomas, Adrian L. R.

283

Influence of leading-edge lateral injection angles on the film cooling effectiveness of a gas turbine blade  

NASA Astrophysics Data System (ADS)

. Typical film-cooling configuration of a symmetrical turbine blade leading edge is investigated using a three-dimensional finite volume method and a multi-block technique. The computational domain includes the curved blade surface as well as the coolant regions and the plenum. The turbulence is approximated by a two layer k-? model. The computations have been performed using the TLV two-layer and the TLVA models. However, the utilization of the TLV and TLVA models has not improved the prediction of the lateral averaged film cooling effectiveness of gas turbine blades when compared with those obtained using wall function strategy. The general features of film cooling such as jet blow-off, high turbulence intensity in the shear layer, and secondary rotating vortices are captured in the present study. Comparison between predicted and experimental results indicates that the trends of the thermal field are well predicted in most cases. In the second part of this study, the influence of lateral injection angle on lateral averaged adiabatic film cooling effectiveness is investigated by varying the lateral injection angle around the experimental value (? = 25°, 30°, 35° and 60° spanwise to the blade surface). It was found that the best coverage and consequently, the maximum film cooling effectiveness are provided by the most extremely inclined injection angle, which is 25° in this investigation.

Azzi, Abbès; Ali Jubran, Bassam

284

CESA-1 project capabilities for high temperature material testing: Application to the HERMES wing leading edge tests  

SciTech Connect

This is a report on the activities carried out at the CESA-1 Facility of the Platforma Solar de Almeria within the framework of the HERMES Wing Leading Edge (W.L.E.) tests. It includes a description of the solar furnace, test procedure, instrumentation and test results, proving the capabilities of this facility in the field of high temperature material testing. It is not intended to compare the thermomechanical behavior of the materials tested. These tests to determine the thermomechanical behavior of two W.L.E.s (C-C and C-SiC) under simulated thermomechanical reentry conditions of the space vehicle HERMES, can be summarized as the performance of 1,550{degree} and 1,730{degree}C thermal cycles maintaining stationary conditions during 20 minutes. During this time a certain vertical temperature profile had to be reached on the W.L.E. and a set of mechanical tests (tension and compression) were carried out. Results demonstrate the flexibility of CESA-1 heliostat field control in tests of the nature. All heating and cooling rates, stationary conditions and temperature profile constraints imposed by the European Space Agency (E.S.A.) were satisfied successfully. The safety of the material was guaranteed and, finally, taking into account that the authors were using 55% of the total power of the heliostat field, material testing at even higher temperatures would seem to be possible.

Rosa, F.; Valverde, A.; Aranda, J.M.; Aranda, J.; Rodriguez, J. (Plataforma Solar de Almeria (Spain))

1991-01-01

285

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

286

Concentration of Uranium and Lead and the Isotopic Composition of Lead in Meteoritic Material  

Microsoft Academic Search

The cosmic abundance of lead and uranium have been determined by studying the lead and uranium contents of meteoritic materials. Lead is found to be present to 8×10-3 atom\\/10 000 atoms of silicon, and uranium to 1×10-4 atom\\/10 000 atom of silicon. The new value for lead removes the hump in the cosmic abundance curve in the 206-208 mass region.

C. Patterson; H. Brown; G. Tilton; M. Inghram

1953-01-01

287

Wind Tunnel Investigation of Effects of Variations in Reynolds Number and Leading-Edge Treatment on the Aerodynamic Characteristics of an Externally Blown Jet-Flap Configuration.  

National Technical Information Service (NTIS)

An investigation has been conducted in a full-scale tunnel to determine the effects of variations in Reynolds number and leading-edge treatment on the aerodynamic characteristics of an externally blown jet-flap transport configuration. The model had a dou...

L. P. Parlett C. C. Smith J. L. Megrail

1973-01-01

288

Investigation into the failure cause of a double-acting, leading-edge-groove, tilting-pad thrust bearing. Final report, Feb-Aug 90  

Microsoft Academic Search

This report describes the results of bench tests simulating operation and failure of a thrust bearing used in a gas turbine engine compressor development test rig. The bearing was a double acting, tilting pad with offset pivot, leading edge groove configuration using an AMS 4928 titanium collar and C18200 copper-chrome alloy pads with a No. 2 babbitt face. The bench

1990-01-01

289

Optimization of a Leading Edge Groove Tilting Pad Journal Bearing for Application in a Small, High Speed, MultiStage Steam Turbine  

Microsoft Academic Search

Optimization of a leading edge groove tilting pad journal bearing for application in a small, high speed, multi-stage steam turbine is described. Rotordynamics constraints to meet a design objective maximum operating speed of 18,000 rpm resulted in a rotor with a 5 1. 0 in. bearing span and 5. 0 in. diameter tilting pod journal bearings. This configuration yielded a

Stephen L. Edney; John K. Waite; Scan M. Decamillo

290

Studies of Interactive Procedures for Three-Dimensional Flows. 1. Separation and Reattachment Near the Leading Edge of a Thin Wing.  

National Technical Information Service (NTIS)

This report is concerned with the calculation of the leading-edge separation which occurs on thin wings with increasing angle of attack. To develop a general method and provide a basis for its evaluation, the simplified problem of a triaxial ellipsoid at ...

T. Cebeci K. Kaups A. A. Khattab

1985-01-01

291

Coupling of leading edge flames in the combustion zone of composite solid propellants  

Microsoft Academic Search

The burning rate trends of both pure binder sandwiches and those containing a mixture of binder with fine ammonium perchlorate particles are investigated over appreciable ranges of pressure and thickness of the middle lamina in the sandwich. The crucial aspect of this study is the wide variation of the fine ammonium perchlorate\\/binder ratio in the middle lamina of the sandwiches.

Mansu Navaneethan; Vishal Srinivas; Satyanarayanan R. Chakravarthy

2008-01-01

292

Calculated dielectric parameters of barium titanate-lead zirconate composites as a function of composition and frequency  

SciTech Connect

Some dielectric parameters e.g., dielectric constant, resistivity, dielectric strength, saturation polarization, loss tangent and coercive field of barium titanate-lead zirconate composites have been calculated as a function of composition and frequency. Most of the dielectric parameters have been found to vary linearly with composition and frequency. A 3-0 connectivity pattern of the composites has been assumed in calculating the dielectric parameters.

Sarkar, S.K. (Microelectronics Section, National Physical Laboratory, New Delhi 110012 (IN))

1990-03-01

293

Directional migration of leading-edge mesoderm generates physical forces: Implication in Xenopus notochord formation during gastrulation.  

PubMed

Gastrulation is a dynamic tissue-remodeling process occurring during early development and fundamental to the later organogenesis. It involves both chemical signals and physical factors. Although much is known about the molecular pathways involved, the roles of physical forces in regulating cellular behavior and tissue remodeling during gastrulation have just begun to be explored. Here, we characterized the force generated by the leading edge mesoderm (LEM) that migrates preceding axial mesoderm (AM), and investigated the contribution of LEM during Xenopus gastrulation. First, we constructed an assay system using micro-needle which could measure physical forces generated by the anterior migration of LEM, and estimated the absolute magnitude of the force to be 20-80nN. Second, laser ablation experiments showed that LEM could affect the force distribution in the AM (i.e. LEM adds stretch force on axial mesoderm along anterior-posterior axis). Third, migrating LEM was found to be necessary for the proper gastrulation cell movements and the establishment of organized notochord structure; a reduction of LEM migratory activity resulted in the disruption of mediolateral cell orientation and convergence in AM. Finally, we found that LEM migration cooperates with Wnt/PCP to form proper notochord. These results suggest that the force generated by the directional migration of LEM is transmitted to AM and assists the tissue organization of notochord in vivo independently of the regulation by Wnt/PCP. We propose that the LEM may have a mechanical role in aiding the AM elongation through the rearrangement of force distribution in the dorsal marginal zone. PMID:23933171

Hara, Yusuke; Nagayama, Kazuaki; Yamamoto, Takamasa S; Matsumoto, Takeo; Suzuki, Makoto; Ueno, Naoto

2013-08-06

294

Relationship between Arp2/3 Complex and the Barbed Ends of Actin Filaments at the Leading Edge of Carcinoma Cells after Epidermal Growth Factor Stimulation  

PubMed Central

Using both light and high resolution electron microscopy, we analyzed the spatial and temporal relationships between the Arp2/3 complex and the nucleation activity that is required for lamellipod extension in mammary carcinoma cells after epidermal growth factor stimulation. A rapid two- to fourfold increase in filament barbed end number occurs transiently after stimulation and remains confined almost exclusively to the extreme outer edge of the extending lamellipod (within 100–200 nm of the plasma membrane). This is accompanied by an increase in filament density at the leading edge and a general decrease in filament length, with a specific loss of long filaments. Concomitantly, the Arp2/3 complex is recruited with a 1.5-fold increase throughout the entire cortical filament network extending 1–1.5 ?m in depth from the membrane at the leading edge. The recruitment of the Arp2/3 complex at the membrane of the extending lamellipod indicates that Arp2/3 may be involved in initial generation of growing filaments. However, only a small subset of the complex present in the cortical network colocalizes near free barbed ends. This suggests that the 100–200-nm submembraneous compartment at the leading edge of the extending lamellipod constitutes a special biochemical microenvironment that favors the generation and maintenance of free barbed ends, possibly through the locally active Arp2/3 complex, severing or decreasing the on-rate of capping protein. Our results are inconsistent with the hypothesis suggesting uncapping is the dominant mechanism responsible for the generation of nucleation activity. However, they support the hypothesis of an Arp2/3-mediated capture of actin oligomers that formed close to the membrane by other mechanisms such as severing. They also support pointed-end capping by the Arp2/3 complex, accounting for its wide distribution at the leading edge.

Bailly, Maryse; Macaluso, Frank; Cammer, Michael; Chan, Amanda; Segall, Jeffrey E.; Condeelis, John S.

1999-01-01

295

Transfer of New Earth Science Understandings to Classroom Teaching: Lessons Learned From Teachers on the Leading Edge  

NASA Astrophysics Data System (ADS)

Teachers on the Leading Edge (TOTLE) provided a field-based teacher professional development program that explored the active continental margin geology of the Pacific Northwest during a two-week field workshop that traversed Oregon from the Pacific Coast to the Snake River. The seventeen teachers on this journey of geological discovery experienced regional examples of subduction-margin geology and examined the critical role of geophysics in connecting geologic features with plate tectonic processes. Two examples of successful transfer of science content learning to classroom teaching are: (1) Great Earthquakes and Tsunamis. This topic was addressed through instruction on earthquake seismology; field observations of tsunami geology; examination of tsunami preparedness of a coastal community; and interactive learning activities for children at an Oregon Museum of Science and Industry (OMSI) Science Camp. Teachers at Sunnyside Environmental School in Portland developed a story line for middle school students called "The Tsunami Hotline" in which inquiries from citizens serve as launch points for studies of tsunamis, earthquakes, and active continental margin geology. OMSI Science Camps is currently developing a new summer science camp program entitled "Tsunami Field Study" for students ages 12-14, based largely on TOTLE's Great Earthquakes and Tsunamis Day. (2) The Grand Cross Section. Connecting regional geologic features with plate tectonic processes was addressed many times during the field workshop. This culminated with teachers drawing cross sections from the Juan de Fuca Ridge across the active continental margin to the accreted terranes of northeast Oregon. Several TOTLE teachers have successfully transferred this activity to their classrooms by having student teams relate earthquakes and volcanoes to plate tectonics through artistic renderings of The Grand Cross Section. Analysis of program learning transfer to classroom teaching (or lack thereof) clearly indicates the importance of pedagogical content knowledge and having teachers share their wisdom in crafting new earth science content knowledge into learning activities. These lessons and adjustments to TOTLE program goals and strategies may be valuable to other Geoscience educators seeking to prepare K-12 teachers to convey the discoveries of EarthScope's USArray and Plate Boundary Observatory experiments to their students.

Butler, R.; Ault, C.; Bishop, E.; Southworth-Neumeyer, T.; Magura, B.; Hedeen, C.; Groom, R.; Shay, K.; Wagner, R.

2006-05-01

296

THE ISOTOPIC COMPOSITION OF LEAD IN MICROCLINES FROM THE LLANO UPLIFT, TEXAS  

Microsoft Academic Search

The isotopic composition of lead and the concentrations of lead and uranium in microclines were determined for some igneous and metamorphic rocks from the Llano uplift, Texas. At the time of their crystallization, all the microclines from the igneous rocks had rather similar lead isotopic compositions (Pbø6\\/Pb 2ø -- 16.6 to 17.0, Pbø7\\/Pb ø -- 15.4 to 15.5, Pbø8\\/Pbø --

Robert E. Zartman

1965-01-01

297

Isotopic Composition of Leads of Ancient Rocks (Izotopnyi Sostav Svintsa Drevneishilch Porod).  

National Technical Information Service (NTIS)

The study of the isotopic composition of lead(s) enclosed in various rocks is of considerable interest as regards the problems of geochronology. The dating of rocks and minerals by the ratio of lead isotopes opens new opportunities for application of the ...

E. V. Sobotovich S. M. Grashchenko A. V. Lovtsius

1968-01-01

298

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

299

British Airways Experience with Composite Repairs.  

National Technical Information Service (NTIS)

This paper describes British Airways experience with composite repairs since 1970. It includes the use of composite materials to repair metal structures such as Concorde wing leading edges and traces the repair of composite parts from Radomes starting in ...

K. B. Armstrong

1986-01-01

300

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

301

Three-dimensional flow and heat transfer calculations of film cooling at the leading edge of a symmetrical turbine blade model  

Microsoft Academic Search

Film cooling of a symmetrical turbine-blade model by lateral and non-lateral injection from one row of holes placed on each side near the leading edge is calculated with a 3D finite-volume method on multi-block grids. For various blowing rates, the flow and temperature fields are predicted, and in particular the contours of film-cooling effectiveness on the blade surface, which are

D. Lakehal; G. S. Theodoridis; W. Rodi

2001-01-01

302

Distinctive features of the transonic flow past a cone-cylinder body at large angles of the bend in the body generator at the leading corner edge  

Microsoft Academic Search

The results of an experimental investigation of the flow past cone-cylinder bodies with small angles of the bend in the body\\u000a generator at the leading corner edge (?s ? 20°) and the available data on the flow past cone-cylinder and segment-cylinder bodies with large angles of the bend in\\u000a the generator (?s, c ? 30°) are generalized. On the basis

B. N. Dan’kov; A. P. Kosenko; V. N. Kulikov; V. N. Otmennikov

2006-01-01

303

Mesoscale Structures of Air Flow in a Meiyu Front Leading Edge Observed by Aircraft off the East Coast of Taiwan during TAMEX IOP 9  

Microsoft Academic Search

In order to investigate the mesoscale structures and appropriate mechanisms for their maintenance in the Mei-yu front leading edge during the TAMEX (Taiwan Area Mesoscale EXperiment) IOP 9 (15 June 1987) off the east coast of Taiwan, we measured the fine-scale in-situ data by different sensors and sensed radar data by two airborne radars mounted on the NOAA P-3 research

Tai-Hwa Hor; Mou-Hsiang CHANG; Ben Jong-Dao Jou

1998-01-01

304

Integrated ablative and radiative heat shield panels and leading edges for high l\\/d reentry vehicles. Final technical report Jun 70Aug 73  

Microsoft Academic Search

This program analytically and experimentally investigates the design and thermostructural performance of integrated ablative\\/radiative thermal protection systems in two phases: CONCEPT DEVELOPMENT AND FULL-SCALE PANEL DEVELOPMENT. In Phase I, the program includes the investigation, analysis, and test of sub-scale specimens and various design concepts to determine design values for the full-scale panels and leading edges. Phase II covers the design

Kiger

1973-01-01

305

Magnetoelectric effect in lead-free BNKLBT ceramic/terfenol-D continue fiber composite laminates  

SciTech Connect

A magnetostrictive-piezoelectric laminated composite has been developed by sandwiching a lead-free BNKLBT ceramic plate polarized in the thickness direction between two terfenol-D continuous fiber composite plates. This lead-free magnetoelectric (ME) laminated composite has a large ME voltage sensitivity of 2.5 V/Oe at the resonance frequency of 130.9 kHz under a low magnetic bias field (H{sub Bias}) of 0.6 kOe. This work shows the potential of BNKLBT lead-free ceramics in ME sensing application.

Lo, C. Y.; Choy, S. H.; Or, S. W.; Chan, H. L. W. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University, Hunghom (Hong Kong)

2010-05-15

306

Optimum Material Composition for Minimizing the Stress Intensity Factor of Edge Crack in Thick-Walled FGM Circular Pipes Under Thermomechanical Loading  

NASA Astrophysics Data System (ADS)

This paper deals with the optimization problem of material composition for minimizing the stress intensity factor of radial edge crack in thick-walled functionally graded material (FGM) circular pipes under steady-state thermomechanical loading. Homogenizing the FGM circular pipes by simulating the inhomogeneity of thermal conductivity by a distribution of equivalent eigentemperature gradient and the inhomogeneity of Young's modulus and Poisson's ratio by a distribution of equivalent eigenstrain, we present an approximation method to obtain the stress intensity factor of radial edge crack in the FGM circular pipes. The optimum material composition for minimizing the stress intensity factor of radial edge crack is determined using a nonlinear mathematical programming method. Numerical results obtained for a thick-walled TiC/Al2O3 FGM circular pipe reveal that it is possible to decrease remarkably the stress intensity factor of radial edge crack by setting the optimum material composition profile.

Sekine, Hideki; Yoshida, Kimiaki

307

Board-Level Solder Joint Reliability of Edge- and Corner-Bonded Lead-Free Chip Scale Package Assemblies Subjected to Thermal Cycling  

NASA Astrophysics Data System (ADS)

In this paper, we present the results of thermal cycling test for edge- and corner-bonded lead-free chip scale packages (CSPs), which was carried out on the basis of the IPC-9701 test standard. Six materials were used in this study: four edge-bond adhesives and two corner-bond adhesives. These adhesives were compared with CSPs with full capillary flow underfill (FCFU) and without adhesives. The thermal cycling test results show that corner-bond adhesive has comparable solder joint reliability performance with CSP without adhesive, and is better than edge-bond adhesive, followed by CSPs with FCFU. In addition, the adhesives with a low coefficient of thermal expansion, a high glass transition temperature and a intermediate storage modulus yielded good performance. Results of detailed failure analysis indicate that the dominant failure mode is solder bulk fatigue cracking near package and/or printed circuit board (PCB) pads, and that the location of critical solder joints change from die edges to package corners with the introduction of adhesives.

Shi, Hongbin; Tian, Cuihua; Ueda, Toshitsugu

2012-04-01

308

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

2013-04-12

309

Compressive buckling of rectangular composite plates with a free-edge delamination  

NASA Astrophysics Data System (ADS)

An experimental and analytical investigation is conducted on the compressive buckling behavior of orthotropic plates with a delamination. The plates, which have three simply supported edges and one free edge, are a simplified model of stiffener plates of a stiffened panel. A uniform width delamination is located at their free edges over the whole length. In the analysis, the Rayleigh-Ritz approximation method is adopted. A constrained point is introduced to allow the contact between the two delaminated surfaces. Imaginary springs about relative displacement and two relative slopes are introduced at the constrained point. With the constraint, buckling loads of physically admissible buckling modes can be obtained by ordinary buckling analysis. The global buckling load reduction is found to be significant and almost proportional to the delamination width. Local delamination buckling is found to occur when the delamination is located near the surface and its size is relatively large compared with that of the plate. The local buckling mode is different from the global one, and more wave number in loading direction and constrained points are necessary to obtain physically admissible solutions. The analytical results agree well with the experimental ones.

Suemasu, Hiroshi; Gozu, Katsuhisa; Hayashi, Kunio; Ishikawa, Takashi

1995-02-01

310

The International Polar Year (IPY) Circumpolar Flaw Lead (CFL) system study: a focus on fast ice edge systems  

Microsoft Academic Search

The Circumpolar Flaw Lead (CFL) system study supported a large multidisciplinary overwintering in the Banks Island (NT) flaw lead over the period September 2007 to August 2008 as part of the International Polar Year (IPY). The CFL system is formed when the central pack ice (which is mobile) moves away from coastal fast ice, opening a flaw lead. The CFL

D. G. Barber; C. J. Mundy; T. N. Papakyriakou; R. W. MacDonald; Y. Gratton; L. Fortier; M. Gosselin; J. Hanesiak; J. Tremblay; S. Ferguson; G. Stern; S. Meakin; J. W. Deming; D. Leitch

2009-01-01

311

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.

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

2013-01-01

312

A metallurgical review of the interpretation of bullet lead compositional analysis  

Microsoft Academic Search

Comparison of the minor and trace element compositions of bullet lead alloys has been used by some forensic examiners to make definitive positive associations between bullets or lead fragments at a crime scene and samples of bullets linked to a suspect(s). Such conclusions have been based on the elemental analysis of isolated groups of bullets with no consideration of the

Erik Randich; Wayne Duerfeldt; Wade McLendon; William Tobin

2002-01-01

313

Lead uptake by algae Gelidium and composite material particles in a packed bed column  

Microsoft Academic Search

Biosorption of lead ions was studied in a flow-through column packed with red algae Gelidium and a composite material (industrial algal waste from the agar extraction process immobilized with polyacrylonitrile). Experiments were performed in order to study the effect of important design parameters such as flow rate and influent pH. The breakthrough curves for lead and proton concentrations were obtained

Vítor J. P. Vilar; Cidália M. S. Botelho; Rui A. R. Boaventura

2008-01-01

314

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

315

Isotope composition of Medieval lead glasses reflecting early silver production in Central Europe  

Microsoft Academic Search

The lead isotope composition of 32 lead glasses excavated from strata of the twelfth to early fifteenth century in six countries\\u000a of NW Europe made the predominance of the Harz Mountains in this period of the Medieval European lead and silver production\\u000a highly probable. Post-Variscan vein type galena, Devonian syngenetic hydrothermal ore (Rammelsberg) and blended ore from both\\u000a deposits in

K. H. Wedepohl; A. Baumann

1997-01-01

316

Leading Edge - Trailing Edge Airfoil Interactions  

Microsoft Academic Search

Computational aerodynamics predictions of airfoil drag and maximum lift continue to be a challenge to aerodynam- icists, even using large computer programs. The reliable calculation of the drag break and maximum lift, including the effects of Reynolds number, are simply not developed to the stage where they can be used routinely in aerody- namic design. This is especially troubling in

W. H. Mason

317

Regional variations in the lead isotopic composition of galena from southern Korea with implications for the discrimination of lead provenance  

NASA Astrophysics Data System (ADS)

This study presents a comprehensive database (n = 215) of lead isotopes in galena from the southern Korean peninsula using new and published data. Of the 69 metal mines examined, predominantly skarn- and hydrothermal-type Pb-Zn-Au-Ag-Cu deposits were observed and were associated with Mesozoic magmatic activities. Galena samples from each geotectonic unit showed discrete lead isotopic signatures. The Gyeongsang basin samples were characteristically unradiogenic and had restricted variations in lead isotopic composition (206Pb/204Pb = 18.16-18.59, 207Pb/204Pb = 15.48-15.64, 208Pb/204Pb = 37.87-38.77). Their 208Pb/204Pb range indicated an involvement of source materials less thorogenic than the associated granites. The galena samples from Cambro-Ordovician carbonate rocks of the northeastern Yeongnam massif and eastern Taebaeksan basin had the most radiogenic 206Pb/204Pb (19.28 ± 0.14) and 207Pb/204Pb (15.833 ± 0.027) ratios. Their lead isotopic trend indicated a combined contribution of ore lead from granitic magmas, Precambrian basements, and overlain host rocks. Less radiogenic galena samples from the middle to southwestern parts of the Yeongnam massif and Okcheon belt showed limited lead isotopic variations (206Pb/204Pb = 18.332 ± 0.065, 207Pb/204Pb = 15.693 ± 0.012, 208Pb/204Pb = 38.93 ± 0.07 on average), probably resulted from mixing with a common crustal basement. The differences in lead isotopes between the radiogenic and unradiogenic groups from the Yeongnam massif and Okcheon belt may reflect the spatial dissimilarity of involved crustal rocks. The old crust appears to have significantly contributed ore lead to galenas from the western Gyeonggi massif, but the geochronological meaning of their steep 207Pb/204Pb-206Pb/204Pb trend is not clear. The comprehensive database constructed by the present study suggests that lead province in the southern Korean peninsula may be subdivided into four discrete zones. Linear discriminant analysis showed that more than 90% of the compiled data were correctly reclassified within their a priori zones. Such discrimination may be useful for a wide range of applications, including mineral exploration, archaeological correlation, and environmental characterization.

Jeong, Youn-Joong; Cheong, Chang-sik; Shin, Dongbok; Lee, Kwang-Sik; Jo, Hui Je; Gautam, Mukesh Kumar; Lee, Insung

2012-11-01

318

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

Microsoft Academic Search

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

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

2009-01-01

319

Profilin1 regulates PI(3,4)P2 and lamellipodin accumulation at the leading edge thus influencing motility of MDA-MB-231 cells  

PubMed Central

Profilin1, a ubiquitously expressed actin-binding protein, plays a critical role in cell migration through actin cytoskeletal regulation. Given the traditional view of profilin1 as a promigratory molecule, it is difficult to reconcile observations that profilin1 is down-regulated in various invasive adenocarcinomas and that reduced profilin1 expression actually confers increased motility to certain adenocarcinoma cells. In this study, we show that profilin1 negatively regulates lamellipodin targeting to the leading edge in MDA-MB-231 breast cancer cells and normal cells; profilin1 depletion increases lamellipodin concentration at the lamellipodial tip (where it binds Ena/VASP), and this mediates the hypermotility. We report that the molecular mechanism underlying profilin1’s modulation of lamellipodin localization relates to phosphoinositide control. Specifically, we show that phosphoinositide binding of profilin1 inhibits the motility of MDA-MB-231 cells by negatively regulating PI(3,4)P2 at the membrane and thereby limiting recruitment of lamellipodin [a PI(3,4)P2-binding protein] and Ena/VASP to the leading edge. In summary, this study uncovers a unique biological consequence of profilin1-phosphoinositide interaction, thus providing direct evidence of profilin1’s regulation of cell migration independent of its actin-related activity.

Bae, Yong Ho; Ding, Zhijie; Das, Tuhin; Wells, Alan; Gertler, Frank; Roy, Partha

2010-01-01

320

Numerical analysis and PIV measurements of tip vortex in an axial rotor with Skewed-Swept blade at its leading edge  

NASA Astrophysics Data System (ADS)

Based on the characteristics of axial fans of outdoor units of centralized air-conditioners, using the finite-volume method, applying three-dimensional steady Reynolds-averaged Navier-Stokes equations coupled with Spalart-Allmaras turbulence model equation, and adopting SIMPLE algorithm, numerical analysis is made and applied to analyze the internal flow field of axial rotors with skewed-swept blade at its leading edge. This numerical simulation mainly investigates the formation and development of the tip vortex. Based on the tip vortex characteristics that have been captured, the internal flow numerical results are compared with those obtained by the PIV experiments. This comparison indicates a good agreement between numerical results and PIV results, thus proving the validity of the numerical simulation. In addition, based on the internal flow analyses of the axial rotor with skewed-swept blade at its leading edge, different flow phenomena features are presented. These flow features can be used for further improvements of the present rotor performance characteristics.

Wu, Guanghui; Zheng, Lijie; Wu, Keqi

2004-02-01

321

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 (V'') 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

322

Synthesis and thermoelectric properties of compositional-modulated lead telluride-bismuth telluride nanowire heterostructures.  

PubMed

We demonstrate the rational solution-phase synthesis of compositional modulated telluride nanowire heterostructures containing lead telluride (PbTe) and bismuth telluride (Bi2Te3). By tuning the ratio between PbTe and Bi2Te3 through adjusting the amount of critical reactants and precursors during the synthesis, the influence of composition on the thermoelectric properties of the nanowire heterostructures has been investigated in hot pressed nanocomposite pellets. Measurements of the thermoelectric properties show strongly reduced thermal conductivity that leads to an enhanced thermoelectric figure of merit (ZT) of 1.2 at 620 K. PMID:23586462

Fang, Haiyu; Feng, Tianli; Yang, Haoran; Ruan, Xiulin; Wu, Yue

2013-04-15

323

Lead  

Center for Food Safety and Applied Nutrition (CFSAN)

... Guidance for Industry: Lead in Candy Likely To Be Consumed Frequently by Small Children: Recommended Maximum Level and Enforcement ... More results from www.fda.gov/food/foodborneillnesscontaminants/metals

324

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

325

Spectral method of determining the isotopic composition of lead. Part I  

Microsoft Academic Search

An apparatus was developed for analyzing the isotopic composition of ; lead separated from geological samples. The light source was a water-cooled or ; liquid-air-cooled hollow cathode discharge tube. The high-resolution apparatus ; was a Fabry-Perot dielectric multilayer interferometer which was located in a ; pressure chamber and the scanning of isotope structure of the lead line PbI ; 4057.8

A. N. Zajdel; A. G. ZttIGLINSKI; J. ?ajko

1958-01-01

326

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

327

Optimum Material Composition for Minimizing the Stress Intensity Factor of Edge Crack in Thick-Walled FGM Circular Pipes Under Thermomechanical Loading  

Microsoft Academic Search

This paper deals with the optimization problem of material composition for minimizing the stress intensity factor of radial edge crack in thick-walled functionally graded material (FGM) circular pipes under steady-state thermomechanical loading. Homogenizing the FGM circular pipes by simulating the inhomogeneity of thermal conductivity by a distribution of equivalent eigentemperature gradient and the inhomogeneity of Young's modulus and Poisson's ratio

Hideki Sekine; Kimiaki Yoshida

2007-01-01

328

Forecasting malaysian business cycle movement: empirical evidence from composite leading indicator  

Microsoft Academic Search

Early detection of a turning point in a business cycle is crucial, as information about the changing phases in business cycles enables policy makers, the business community, and investors to cope better with unexpected events brought about by economic and business situations. The Malaysian economy is fortunate to own a publicly accessible composite of leading indicator (CLI) that is presumed

Shirly Siew-Ling Wong; Shazali Abu Mansor; Chin-Hong Puah; Venus Khim-Sen Liew

2012-01-01

329

A metallurgical review of the interpretation of bullet lead compositional analysis.  

PubMed

Comparison of the minor and trace element compositions of bullet lead alloys has been used by some forensic examiners to make definitive positive associations between bullets or lead fragments at a crime scene and samples of bullets linked to a suspect(s). Such conclusions have been based on the elemental analysis of isolated groups of bullets with no consideration of the metallurgical processes involved in the production and refining of the bullet lead alloys. An understanding of the metallurgy of lead refining reveals that the elements quantified in the forensic analysis are carefully controlled in the refining process and that there are logical reasons why some elements are more discriminatory than others. Data for lead alloys supplied to two major ammunition manufacturers confirm that multiple indistinguishable shipments of lead alloys from secondary lead refiners to the ammunition manufacturers are made each year and over a period of many years. The data also demonstrate that distinguishable compositions can come from the same melt or "source" of lead alloy. These results clearly indicate that bullets with indistinguishable compositions could have come from different lead "sources" produced in the same or different years. Furthermore, the observation that two bullets have a distinguishable composition does not necessarily mean that they came from a different "source". Our results show that the forensic examiner using a method of bullet lead alloy elemental analysis, which quantifies up to six elements is restricted to concluding only that indistinguishable bullets might have come from the same "source," not that they did come from the same "source". In addition, it is quite possible that multiple bullets with similar but distinguishable compositions could have come from the same "source". The authors therefore feel that there is no scientific validity to any conclusions more positive than attributing the possible association as to molten source among bullets from different samples. An understanding of the metallurgical principles operative in the melting/casting process as well as the data acquired for this study, indicate that any forensic conclusions which associate unknown bullets with the "same source", and/or "same box" should fail most or all Daubert criteria. PMID:12175947

Randich, Erik; Duerfeldt, Wayne; McLendon, Wade; Tobin, William

2002-07-17

330

Great Earthquakes and Tsunami Day for Teachers on the Leading Edge: Geologic Hazards and Links to EarthScope in a Field-Based Program  

NASA Astrophysics Data System (ADS)

Inviting K-12 science teachers into the field to observe the work of professional geologists and engage in learning that is scientifically important and socially relevant deepens their geologic understanding while instilling enthusiasm for inquiry-based instruction. "Teachers on the Leading Edge" (TOTLE) is a field-based and place-based teacher development program that features active continental margin geology of the Pacific Northwest. Program themes include: (1) Geophysics as fundamental to understanding plate tectonics and essential to deciphering Pacific Northwest geology that underlies a tree-covered landscape; and (2) Geologic Hazards as understandable and inevitable consequences of living on the leading edge of our continent. The two-week TOTLE 2005 field workshop traversed the active continental margin of Oregon from the Pacific Coast through the Cascade Range to accreted terranes along the Snake River. "Great Earthquakes and Tsunami Day" featured introductions to earthquake seismology and paleoseismology. Presentations on earthquake seismology with examples from the December 2004 Sumatra - Andaman earthquake and Indian Ocean tsunami provided context and background. During a morning low tide near Fort Clatsop south of Astoria, paleoseismologist Brian Atwater (USGS, Seattle) helped teachers observe and interpret drowned forests and tsunami deposits that mark four great Cascadia earthquakes of the past 2000 years. That afternoon, Darci Connor, former Tsunami Outreach Coordinator for the City of Seaside, helped teachers understand their critical role in educating K-12 students about natural hazard preparedness. In the evening, TOTLE teachers crafted their new understanding of great earthquakes and tsunami into interactive learning activities for Science Campers at Camp Kiwanilong operated by the Oregon Museum of Science and Industry. These experiences make frontier geophysical research, like GPS observations of slow earthquakes and seismic tomography of the subducting Juan de Fuca Plate, accessible to K-12 teachers and useful in their teaching of plate tectonics and earthquake seismology. Teachers on the Leading Edge is preparing K-12 teachers to convey the importance and discoveries of EarthScope's USArray and Plate Boundary Observatory experiments to their students.

Butler, R.; Bishop, E. M.; Ault, C.; Magura, B.; Hedeen, C.; Connor, D.; Southworth-Neumeyer, T.; Conrey, R.

2005-12-01

331

Metabolism of Antarctic micronektonic crustacea across a summer ice-edge bloom: respiration, composition, and enzymatic activity  

NASA Astrophysics Data System (ADS)

The Antarctic marginal ice zone is an important oceanic front separating the pack-ice and open-water environments. During summer, the retreating pack ice creates a meltwater lens in the euphotic zone, allowing primary producers and microheterotrophs to flourish in a discrete bloom just seaward of the retreating ice edge that lasts about 60 days. The purpose of the present study was to see if the ice-edge bloom had a discernible effect on the metabolism and physiological condition of Antarctic micronekton similar to that observed in zooplankton species. We also wished to assess the importance of the summer season to species' life cycles. Two major data sets were collected on 25 species in the following taxonomic groups: amphipods, cephalopods, decapods, euphausiids, isopods, mysids, ostracods, and polychaetes. The first data set described the metabolic rates of individuals in areas of the marginal ice zone with widely different levels of chlorophyll biomass to investigate the effect of the ice-edge bloom on metabolism. Additionally, summer metabolic rates were compared with data from other seasons. The second data set detailed the levels of protein, water, ash, RNA and DNA, and the activities of metabolic enzymes (citrate synthase and malate dehydrogenase) to examine the efficacy of biochemical indices as predictive tools for metabolism. Results suggested that the mobility of the micronektonic species eliminated most direct effects of the bloom on metabolism. Individuals captured in very different productivity regimes showed few significant differences in the metabolic indicators listed above. Isolated cases of changes in body composition and enzyme activity, however, implied that longer-term effects of the bloom may be exhibited. Seasonal increases in metabolism from winter to summer were observed in the euphausiids Euphausia superba, E. triacantha, and Thysanoessa macrura and the amphipod Vibilia stebbingi. It was concluded that the seasonal shifts were indicative of a "type 2" or compromise overwintering strategy whereby metabolism drops without an accompanying dormant state. Protein content and MDH activity were found to be the best predictors of respiration rate, while nucleic acid measures only correlated with respiration in immature specimens.

Donnelly, Joseph; Kawall, Helena; Geiger, Stephen P.; Torres, Joseph J.

2004-08-01

332

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

333

Lead-rich phases in partially processed Ag/Bi-2223 composite conductors  

SciTech Connect

The occurrence, composition, and melting behavior of lead-rich phases detected during the thermal processing of Ag/Bi-2223 composite conductors have been investigated by a combination of transmission electron microscopy (TEM), energy dispersive analysis (EDS), x-ray diffraction, differential thermal analysis, and Raman spectroscopy. A (Bi,Pb)-Sr-Ca-Cu-O composition with {open_quotes}4112{close_quotes} metal atom stoichiometry and Pb{approx_equal}Bi was detected during TEM/EDS examinations of partially processed/quenched Ag/Bi-2223 composites. An as-synthesized oxide mix with this stoichiometry was found to melt at a temperature <700{degrees}C. The lead-rich {open_quotes}3221{close_quotes} phase was found to have a wide range of compositional stability in terms of Pb/Bi ratio and Bi + Pb stoichiometry. Evidence was seen for the co-existence of this phase with (Ca,Sr){sub 2}PbO{sub 4} in partially processed Ag/Bi-2223 composites that were cooled slowly through the 800 to 600{degrees}C range.

Luo, J.S.; Merchant, N.; Maroni, V.A.

1996-02-01

334

Assessment of chemical species of lead accumulated in tidemarks of human articular cartilage by X-ray absorption near-edge structure analysis  

PubMed Central

A highly specific accumulation of the toxic element lead was recently measured in the transition zone between non-calcified and calcified normal human articular cartilage. This transition zone, the so-called ‘tidemark’, is considered to be an active calcification front of great clinical importance. However, little is known about the mechanisms of accumulation and the chemical form of Pb in calcified cartilage and bone. Using spatially resolved X-ray absorption near-edge structure analysis (µ-XANES) at the Pb L 3-edge, the chemical state of Pb in the osteochondral region was investigated. The feasibility of the µ-XANES set-up at the SUL-X beamline (ANKA synchrotron light source) was tested and confirmed by comparing XANES spectra of bulk Pb-reference compounds recorded at both the XAS and the SUL-X beamline at ANKA. The µ-XANES set-up was then used to investigate the tidemark region of human bone (two patella samples and one femoral head sample). The spectra recorded at the tidemark and at the trabecular bone were found to be highly correlated with the spectra of synthetic Pb-doped carbonated hydroxyapatite, suggesting that in both of these very different tissues Pb is incorporated into the hydroxyapatite structure.

Meirer, Florian; Pemmer, Bernhard; Pepponi, Giancarlo; Zoeger, Norbert; Wobrauschek, Peter; Sprio, Simone; Tampieri, Anna; Goettlicher, Joerg; Steininger, Ralph; Mangold, Stefan; Roschger, Paul; Berzlanovich, Andrea; Hofstaetter, Jochen G.; Streli, Christina

2011-01-01

335

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

336

Piezo-, pyro-, ferro-, and dielectric properties of ceramic/polymer composites obtained from two modifications of lead titanate  

NASA Astrophysics Data System (ADS)

Two modifications of lead titanate ceramic and the polyetherketoneketone polymer (PEKK) have been used to obtain two polymer/ceramic composites. The piezo-, pyro-, ferroelectric, and dielectric properties were studied. The calcium modified lead titanate/polyetherketoneketone (PTCa/PEKK) composite shows better piezo- and pyro-electric properties than that of the samarium and manganese modified lead titanate/polyetherketoneketone (PSTM/PEKK) composite. Also, a lower dielectric permittivity and remanent polarization values with a higher coercive field are obtained. The results are discussed considering the modifications made in the ceramic phases of each composite. The presented properties for both composites are still substantially lower than those in bulk ceramics.

Peláiz-Barranco, A.; Marin-Franch, P.

2005-02-01

337

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

338

Lead zirconate titanate fiber/polymer composites prepared by a replication process  

SciTech Connect

The woven replication process was used to fabricate lead zirconate titanate (PZT)/polymer composites with 1-3, 2-3, and 3-3 connectivities by starting with novoloid-derived carbon fiber, woven fabric, and nonwoven felt templates, respectively. Activated carbon-fiber template material was impregnated with PZT by soaking it in a solution containing stoichiometric amounts of dissolved lead, zirconium, titanium, and niobium ions. Heat treatment burned out the carbon, leaving a PZT replica with the same form as the template material. Replicas were sintered in a controlled atmosphere and back-filled with an epoxy polymer to form final composites. This method, which is believed to be adaptable for mass production, is capable of producing composites and extremely fine microstructures. Woven composite samples have fiber tow diameters of 200 to 250 {mu}m and spacings between tows of about 150 to 250 {mu}m. Average d{sub 33} = 90 pC/N, g{sub 33} = 211 mV {center dot} m/N, and d{sub h}g{sub h} hydrophone figure of merit of 2100 {times} 10{sup {minus}15} m{sup 2}/N values are reported for woven PZT/polymer composites.

Waller, D.J.; Safari, A. (Dept. of Ceramic Engineering, Rutgers, State Univ. of New Jersey, Piscataway, NJ (US)); Card, R.J.; O'Toole, M.P. (Chemical Research Div., American Cyanamid Co., Stamford, CT (US))

1990-11-01

339

Strong magnetoelectric coupling at microwave frequencies in metallic magnetic film/lead zirconate titanate multiferroic composites  

NASA Astrophysics Data System (ADS)

Strong magnetoelectric coupling was observed at microwave frequencies in metallic magnetic film/lead zirconate titanate [Pb(Zr,Ti)O3] multiferroic composites, in which the magnetic films were either FeCoB or FeGaB with relatively high saturation magnetostriction constants between 40 and 70 ppm and narrow ferromagnetic resonance linewidths of ~20 Oe at 10 GHz. Large electrostatically induced ferromagnetic resonance frequency shifts of 50-110 MHz at ~2.3 GHz were observed. These metallic magnetic film/Pb(Zr,Ti)O3 multiferroic composites with large electrostatic tunability of the ferromagnetic resonance frequency provide great opportunities for integrated microwave multiferroic devices.

Pettiford, C.; Lou, J.; Russell, L.; Sun, N. X.

2008-03-01

340

Next-to-leading QCD effect on the quark compositeness search at the LHC.  

PubMed

We present the exact next-to-leading order (NLO) QCD corrections to the dijet production induced by the quark contact interactions at the CERN Large Hadron Collider. We show that, as compared to the exact calculation, the scaled NLO QCD prediction adopted by the ATLAS Collaboration has overestimated the new physics effect on some direct observables by more than 30% and renders a higher limit on the quark compositeness scale. The destructive contribution from the exact NLO correction will also lower the compositeness scale limit set by the CMS Collaboration. PMID:21561184

Gao, Jun; Li, Chong Sheng; Wang, Jian; Zhu, Hua Xing; Yuan, C-P

2011-04-04

341

Current—voltage characteristics of lead zirconate titanate/nickel bilayered hollow cylindrical magnetoelectric composites  

NASA Astrophysics Data System (ADS)

Current-voltage measurements obtained from lead zirconate titanate/nickel bilayered hollow cylindrical magnetoelectric composite showed that a sinusoidal current applied to the copper coil wrapped around the hollow cylinder circumference induces voltage across the lead zirconate titanate layer thickness. The current-voltage coefficient and the maximum induced voltage in lead zirconate titanate at 1 kHz and resonance (60.1 kHz) frequencies increased linearly with the number of the coil turns and the applied current. The resonance frequency corresponds to the electromechanical resonance frequency. The current-voltage coefficient can be significantly improved by optimizing the magnetoelectric structure geometry and/or increasing the number of coil turns. Hollow cylindrical lead zirconate titanate/nickel structures can be potentially used as current sensors.

Pan, De-An; Zhang, Shen-Gen; Tian, Jian-Jun; Sun, Jun-Sai; Alex, Volinsky A.; Qiao, Li-Jie

2010-02-01

342

Retarding Electromigration in Lead-Free Solder Joints by Alloying and Composite Approaches  

NASA Astrophysics Data System (ADS)

The voids induced by electromigration (EM) can trigger serious failure across the entire cathode interface of solder joints. In this study, alloying and composite approaches showed great potential for inhibiting EM in lead-free solder joints. Microsized Ni, Co, and Sb particles were added to the solder matrix. Cu and Sn particles were added to the melting solder to form in situ Cu6Sn5, which formed a barrier layer in the underbump metallization of flip-chip solder joints. The polarity effect induced by EM was observed to be significantly inhibited in the alloyed and composite solder joints. This indicates that the Sn-Ni, Sn-Co, Sn-Sb, and Cu6Sn5 intermetallic compounds may act as barriers to obstruct the movement of the dominant diffusion species along phase boundaries, which in turn improves the resistance to EM. However, Sb particles could induce crack formation and propagation that might lead to joint fracture.

Zhao, Ran; Ma, Limin; Zuo, Yong; Liu, Sihan; Guo, Fu

2013-02-01

343

The leading edge during dorsal closure as a model for epithelial plasticity: Pak is required for recruitment of the Scribble complex and septate junction formation.  

PubMed

Dorsal closure (DC) of the Drosophila embryo is a model for the study of wound healing and developmental epithelial fusions, and involves the sealing of a hole in the epidermis through the migration of the epidermal flanks over the tissue occupying the hole, the amnioserosa. During DC, the cells at the edge of the migrating epidermis extend Rac- and Cdc42-dependent actin-based lamellipodia and filopodia from their leading edge (LE), which exhibits a breakdown in apicobasal polarity as adhesions are severed with the neighbouring amnioserosa cells. Studies using mammalian cells have demonstrated that Scribble (Scrib), an important determinant of apicobasal polarity that functions in a protein complex, controls polarized cell migration through recruitment of Rac, Cdc42 and the serine/threonine kinase Pak, an effector for Rac and Cdc42, to the LE. We have used DC and the follicular epithelium to study the relationship between Pak and the Scrib complex at epithelial membranes undergoing changes in apicobasal polarity and adhesion during development. We propose that, during DC, the LE membrane undergoes an epithelial-to-mesenchymal-like transition to initiate epithelial sheet migration, followed by a mesenchymal-to-epithelial-like transition as the epithelial sheets meet up and restore cell-cell adhesion. This latter event requires integrin-localized Pak, which recruits the Scrib complex in septate junction formation. We conclude that there are bidirectional interactions between Pak and the Scrib complex modulating epithelial plasticity. Scrib can recruit Pak to the LE for polarized cell migration but, as migratory cells meet up, Pak can recruit the Scrib complex to restore apicobasal polarity and cell-cell adhesion. PMID:20501591

Bahri, Sami; Wang, Simon; Conder, Ryan; Choy, Juliana; Vlachos, Stephanie; Dong, Kevin; Merino, Carlos; Sigrist, Stephan; Molnar, Cristina; Yang, Xiaohang; Manser, Edward; Harden, Nicholas

2010-06-01

344

Mode of lead addition and its effects on phase formation and microstructure development in ? composite conductors  

NASA Astrophysics Data System (ADS)

An extensive examination has been made of silver-sheathed 0953-2048/9/5/013/img11 (Bi-2223) composite conductors produced by the two-powder processing method, wherein single-phase 0953-2048/9/5/013/img12 (Bi-2212) is combined with a mix of Pb-Ca-Cu-O phases to give an overall stoichiometry of 0953-2048/9/5/013/img13. The principal variable is the proportioning of lead between the Bi-2212 phase and the Pb-Ca-Cu-O phases. X-ray diffraction measurements and scanning electron microscopy analyses have revealed that the length of the induction period prior to the onset of Bi-2223 formation decreases monotonically as the initial lead fraction in the Bi-2212 is increased up to a value of 0.3. The observed decrease in critical current density of fully processed composites with decreasing lead fraction in the Bi-2212 phase appears to be more closely related to the quantity of unconverted Bi-2212 than to the quantity of residual alkaline earth cuprate secondary phases. Transmission electron microscopy shows that the frequency of Bi-2212 intergrowths declines with increasing lead fraction in the starting Bi-2212 component.

Luo, J. S.; Dorris, S. E.; Fischer, A. K.; LeBoy, J. S.; Maroni, V. A.; Feng, Y.; Larbalestier, D. C.

1996-05-01

345

Leading Edge Design and Engineering  

NASA Website

Drawing from more than 50 years of spaceflight research and development, the Multi-Purpose Crew Vehicle (MPCV) is designed to meet the evolving needs of our nation's space program for decades to come.

346

Tasting edge effects  

NASA Astrophysics Data System (ADS)

We show that the baking of potato wedges constitutes a crunchy example of edge effects, which are usually demonstrated in electrostatics. A simple model of the diffusive transport of water vapor around the potato wedges shows that the water vapor flux diverges at the sharp edges in analogy with its electrostatic counterpart. This increased evaporation at the edges leads to the crispy taste of these parts of the potatoes.

Bocquet, Lydéric

2007-02-01

347

Near-Edge X-ray Absorption Fine-Structure, X-ray Photoemission, and Fourier Transform Infrared Spectroscopies of Ultrananocrystalline Diamond\\/Hydrogenated Amorphous Carbon Composite Films  

Microsoft Academic Search

The chemical bonding structure of ultrananocrystalline diamond (UNCD)\\/hydrogenated amorphous carbon (a-C:H) composite films prepared by pulsed laser deposition was examined by near-edge X-ray absorption fine-structure (NEXAFS), X-ray photoemission, and Fourier transform infrared (FTIR) spectroscopies. An intense sp3-CH peak was observed in the FTIR spectrum. This implies that the sp3-CH peak originates from the grain boundaries between UNCD crystallites, wherein dangling

Tsuyoshi Yoshitake; Akira Nagano; Shinya Ohmagari; Masaru Itakura; Noriyuki Kuwano; Ryota Ohtani; Hiroyuki Setoyama; Eiichi Kobayashi; Kunihito Nagayama

2009-01-01

348

Simulation of router action on a lathe to test the cutting tool performance in edge-trimming of graphite/epoxy composite  

NASA Astrophysics Data System (ADS)

The predominant machining application with graphite/epoxy composite materials in aerospace industry is peripheral trimming. The computer numerically controlled (CNC) high speed routers required to do edge trimming work are generally scheduled for production work in industry and are not available for extensive cutter testing. Therefore, an experimental method of simulating the conditions of periphery trim using a lathe is developed in this paper. The validity of the test technique will be demonstrated by conducting carbide tool wear tests under dry cutting conditions. The experimental results will be analyzed to characterize the wear behavior of carbide cutting tools in machining the composite materials.

Ramulu, M.; Rogers, E.

1994-04-01

349

High magnetoelectric effect in laminated composites of giant magnetostrictive alloy and lead-free piezoelectric ceramic  

NASA Astrophysics Data System (ADS)

Magnetoelectric (ME) laminated composites with all phases environmentally friendly were prepared by sandwiching one layer of thickness-polarized (Bi1/2Na1/2)TiO3-(Bi1/2K1/2)TiO3-BaTiO3 lead-free piezoelectric ceramic disk between two layers of thickness-magnetized Tb0.3Dy0.7Fe1.92 giant magnetostrictive alloy disk along the thickness direction. The composites exhibited the maximum ME voltage coefficient of 40.7 mV/Oe with a flat response in the measured frequency range of 0.1-20 kHz under a dc magnetic bias of 5 kOe. The induced ME voltage showed an extremely linear relationship to the applied ac magnetic field with amplitude varying from 3×10-5 to 10 Oe over a broad range of dc magnetic bias of 0-5.5 kOe. The high ME effect was analyzed and found to be comparable to most major lead-based ME composites. The present study opens up possibilities for developing green ME devices.

Jia, Yanmin; Or, Siu Wing; Wang, Jie; Chan, Helen Lai Wa; Zhao, Xiangyong; Luo, Haosu

2007-05-01

350

Surface injection effect on mass transfer from a cylinder in crossflow - A simulation of film cooling in the leading edge region of a turbine blade  

NASA Astrophysics Data System (ADS)

A naphthalene sublimation technique is used to study the effect of surface injection on the mass (heat) transfer from a circular cylinder in crossflow. Using a heat/mass transfer analogy the results can be used to predict film cooling effects in the leading edge region of a turbine blade. Air injection through one row of circular holes is employed in the stagnation region of the cylinder. Streamwise and spanwise injection inclinations are studied separately, and the effects of blowing rate and injection location relative to the cylinder front stagnation line are investigated. Streamwise injection produces significant mass transfer increases downstream of the injection holes, but a relatively small increase is observed between holes, normal to the injection direction. The mass transfer distribution, measured with spanwise injection through holes located near the cylinder front stagnation line, is extremely sensitive to small changes in the injection hole location relative to stagnation. When the centers of the spanwise injection holes are located 5 deg or more from the stagnation line, the holes lie entirely on one side of the stagnation line and the injection affects the mass transfer only on that side of the cylinder, approaching the pattern observed with streamwise injection.

Karni, J.; Goldstein, R. J.

1990-07-01

351

Effect of periodic wake passing on film effectiveness of inclined discrete cooling holes around the leading edge of a blunt body  

SciTech Connect

Detailed studies are conducted on film effectiveness of inclined discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a configuration similar to that of a typical turbine blade and are angled at 30 and 90 deg to the surface in the spanwise and streamwise directions, respectively. A spoked-wheel-type wake generator is used in this study to simulate periodically incoming wakes to turbine blades. In addition, two types of turbulence grid are used to elevate a free-stream turbulence intensity. The authors adopt three blowing ratios of the secondary air to the mainstream. Most of the dominant flow conditions are reproduced in this study, except for the air density ratio of the secondary air and the main stream. For each of the blowing ratios, wall temperatures around the surface of the test model are measured by thermocouples situated inside the model. The temperature is visualized using liquid crystals to obtain traces of the injected secondary air on the test surface, which consequently helps us interpret the thermocouple data.

Funazaki, K.; Koyabu, E. [Iwate Univ., Morioka (Japan). Dept. of Mechanical Engineering; Yamawaki, S. [Ishikawajima-Harima Heavy Industries Co., Tokyo (Japan). Aero-Engine and Space Operation

1998-01-01

352

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

SciTech Connect

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; constant hysteresis ({Delta}E) correlated with a constant temperature of the maximum dielectric constant (T{sub max}); a sharper dielectric-constant maximum peak; and increased room-temperature dielectric constant (K). Variations in the Zr:Sn ratio also were evaluated. Increased Zr{sup 4+} content produced the following: increased hysteresis with increased T{sub max}, decreased maximum dielectric constant, and decreased switching field with increased AFE-FE transition temperature (T{sub AFE-FE}). From these results, with respect to compositional modifications, the AFE-FE switching field (E{sub AFE-FE}) and {Delta}E were observed to be dependent strongly on T{sub AFE-FE} and T{sub max}, respectively. Negligible change existed in the strain achievable at the switching field, which remained constant for all compositions at {approximately}0.16%. The significance of this research was the ability demonstrated to tailor the properties of phase-change materials through compositional modifications.

Markowski, K.; Park, S.E.; Yoshikawa, Shoko; Cross, L.E. [Pennsylvania State Univ., University Park, PA (United States). Materials Research Lab.

1996-12-01

353

Mn and Sm doped lead titanate ceramic fibers and fiber/epoxy 13 composites  

NASA Astrophysics Data System (ADS)

Manganese and samarium doped lead titanate [Pb0.85Sm0.10(Ti0.98Mn0.02)O3, PSmT] fibers were prepared by sol-gel method. The micrographs obtained using scanning electron microscope show that PSmT ceramic fibers are round and dense. The diameter of the fibers was in the range of 30-35 ?m. The crystalline grains size is ~2.5 ?m. The micrographs obtained using transmission electron microscope also unveiled the layer-by-layer 90° domains in the grains. X-ray diffraction patterns of the fibers show that PSmT ceramics have a pure perovskite structure. The c/a ratio of the unit cell was 1.04. The PSmT fiber/epoxy 1-3 composites were fabricated by filling the ceramic fiber bundle with epoxy. The dielectric permittivity ?, electromechanical coefficient kt, and the piezoelectric constant d33 of PSmT fiber/epoxy 1-3 composites with 68% fiber loading were 118, 0.51, and 48 pC/N, respectively. The hysteresis loop of the composites was measured by the Sawyer-Tower method. It was also found that the composites could withstand an electric field of 15 kV/mm at room temperature.

Li, Kun; Pang, Geoffrey; Wa Chan, Helen Lai; Choy, Chung Loong; Li, Jin-Hua

2004-05-01

354

Effect of surface modification of lead zirconate titanate particles on the properties of piezoelectric composite sensors  

NASA Astrophysics Data System (ADS)

Piezoelectric composite sensors which consist of a ferroelectric ceramic phase and a polymer binder have been the center of interest for offering a distributed sensing mechanism in many industrial applications. This study investigates the effect of PZT surface modification on the mechanical and piezoelectric properties of PZT/epoxy composite sensors. Lead zirconate titanate ceramic powder (PZT-5H) was surface modified to prepare a high PZT content (0-3) piezoelectric composite sensor. Functional groups of the modifiers grafted onto the PZT particle surface served as a bridge into the epoxy matrix, thus creating strong bonds between the matrix and PZT particles. This noticeably improved the dispersion of the PZT phase, allowing the use of large fractions of piezoactive component in the composite. It is demonstrated that the produced piezo-film shows an enhanced poling behavior in that it can be poled with lower voltages under reduced poling times. This is caused by greater levels of microstructural homogeneity in the modified films as well as alteration of interfacial charge characteristics using modifiers' functional groups.

Saber, Nasser; Ma, Jun; Hsu, Hung-Yao; Lee, Sang-Heon; Marney, Donavan

2013-08-01

355

Electrical, Thermal and Mechanical Stability of AFM BSCCO-2223 Composite Conductors for Current Lead Applications  

NASA Astrophysics Data System (ADS)

In this work, the relevant properties of AFM BSCCO-2223/AgAu composite conductors and the most crucial technical problems faced in the design and manufacturing of current leads (CLs) are presented and discussed. Important issues such as thermal stability of AFM conductors, their effective mechanical reinforcement and the viable technical solutions for kA-class CLs are addressed. AFM BSCCO-2223 composite conductors and kA-class AFM bundles went through an extensive electrical, thermal and mechanical characterisation in order to evaluate and possibly improve their overall performances and to increase their potential and range of application. Experimental results on ageing tests on AFM specimens, with and without mechanical reinforcement, after thermal cycling in liquid nitrogen and quench experiments, induced by overcurrents and/or lacking of cooling, are reported and discussed in detail.

Martini, L.

356

Properties on the edge: graphene edge energies, edge stresses, edge warping, and the Wulff shape of graphene flakes  

NASA Astrophysics Data System (ADS)

It has been shown that the broken bonds of an unreconstructed graphene edge generate compressive edge stresses leading to edge warping. Here, we investigate edge energies and edge stresses of graphene nanoribbons with arbitrary orientations from armchair to zigzag, considering both flat and warped edge shapes in the presence and absence of hydrogen. We use the second generation reactive empirical bond order potential to calculate the edge energies and stresses for clean and hydrogenated edges. Using these energies, we perform a Wulff construction to determine the equilibrium shapes of flat graphene flakes as a function of hydrogen chemical potential. While edge stresses for clean, flat edges are compressive, they become tensile if allowed to warp. Conversely, we find that edge energies change little (~1%) with edge warping. Hydrogenation of the edges virtually eliminates both the edge energy and edge stresses. For warped edges an approximately linear relationship is found between amplitudes and wavelengths. The equilibrium shape of a graphene flake is determined by the value of the hydrogen chemical potential. For very small (and large) values of it the flakes have a nearly hexagonal (dodecagon) shape with zigzag oriented edges, while for intermediate values graphene flakes are found with complex shapes.

Branicio, Paulo S.; Jhon, Mark H.; Gan, Chee Kwan; Srolovitz, David J.

2011-07-01

357

Technical Report of National Aerospace Laboratory: Experimental Investigations on High Lift Devices for an SST. Part 3 Lift to Drag Ration Improvement by Leading-Edge Flap at Transonic Regions.  

National Technical Information Service (NTIS)

Wind tunnel tests were conducted to investigate lift to drag ratio improvement by the leading-edge flap of the outer wing on an SST model at transonic regions. Force measurements and surface pressure measurements were performed for the SST model with and ...

D. Y. Kwak K. Miyata M. Noguchi K. Yoshida K. Rinoie

2003-01-01

358

INVESTIGATION OF FEASIBILITY OF UTILIZING AVAILABLE HEAT-RESISTANT MATERIALS FOR HYPERSONIC LEADING-EDGE APPLICATIONS. VOLUME VI. DETERMINATION AND DESIGN APPLICATION OF MECHANICAL PROPERTIES OF BARE AND COATED GRAPHITE  

Microsoft Academic Search

The feasibility of utilizing available heat-resistant materials in the ; fabrication of leading edges for hypersonic boost-glide vehicles was investigated. ; The results of a study on the mechanical properties of a siliconized Grade ATJ ; graphite are presented. The mechanical properties were studied as functions of ; temperature (to 2950 deg F), strain rate, size, and stress state. Supplementary

A. Rudnick; R. L. Carlson; G. K. Manning

1960-01-01

359

19th Hot Chips Conference Meets on 19–21 August at Stanford University, Three days of Leading-Edge, Real-World Designs for High-performance Chips and Technologies  

Microsoft Academic Search

Three days of Leading-Edge, Real-World Designs for High-performance Chips and Technologies Newly cosponsored by SSCS this year, Hot Chips will offer nine technical sessions on topics such as the ultra-fast IBM Power6, the architecture of the NVIDIA GeForce 8800 chip, and Multi-terabit switch fabrics, a well as a panel entitled \\

Don Draper; John Sell; Allen Baum

2007-01-01

360

Study of Zinc and Niobium Modified Lead Zirconate Titanate Fiber/Epoxy 1-3 Composites  

NASA Astrophysics Data System (ADS)

Zinc and niobium modified lead zirconate titanate (PZN-PZT) fibers were prepared by the sol-gel method. After sintering at various temperatures the crystal structure of the ceramic fibers was determined by X-ray diffraction. The morphology of the ceramic fibers was studied using a scanning electron microscope. A bundle of ceramic fibers of 25 ?m diameter was placed in a plastic tube, which was then filled with epoxy. After curing, a PZN-PZT fiber/epoxy 1-3 composite rod was formed. The rod was sliced into disks which were then polished to a thickness of approximately 40 ?m. A composite disk with 0.62 ceramic volume fraction was poled under an electric field of 3.5 kV/mm at 120°C for 15 min. The electromechanical coupling coefficient kt, piezoelectric coefficient d33 and relative permittivity \\varepsilon of the disk were found to be 0.67, 403 pC/N and 1300, respectively. The hysteresis loop of the composite was also determined, and the remnant polarization Pr was found to be 12 ?C/cm2.

Li, Kun; Chan, Helen Lai-Wa; Choy, Chung-Loong

2002-11-01

361

Wear Behavior of the Lead-Free Tin Bronze Matrix Composite Reinforced by Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Copper-coated carbon nanotubes were prepared by the electroless plating route. The structure and component of copper/carbon tubes were characterized using a transmission electron microscope and energy dispersive spectrometer. The results show that the surface of the carbon tubes was covered by the copper particles. Copper/carbon tubes were used as the substitute of part of tin and all of lead in the tin bronze matrix, and the tribological properties of carbon nanotube-reinforced Cu-4 wt pct Sn-6 wt pct Zn composites were studied. The effects of the carbon nanotube volume fraction and sliding distance in unlubricated ball-on-disc wear test were investigated. The 3 vol pct carbon nanotube-reinforced Cu-4 wt pct Sn-6 wt pct Zn composite shows the Vickers hardness of 126.9, which is approximately 1.6 times higher than that of Cu-6 wt pct Sn-6 wt pct Zn-3 wt pct Pb tin bronze. The wear rate and average friction coefficients of 3 vol pct carbon nanotube-reinforced Cu-4 wt pct Sn-6 wt pct Zn composite were lower than those of the Cu-6 wt pct Sn-6 wt pct Zn-3 wt pct Pb tin bronze, respectively.

Zeng, Jun; Fan, Huiqing; Wang, Yangli; Zhang, Siquan

2011-12-01

362

Composite lead for conducting an electrical current between 75-80K and 4.5K temperatures  

Microsoft Academic Search

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 organizationl arrangements and

Yehia Negm; George O. Zimmerman; Powers Jr. Robert E; Randy J. McConeghy; Alvaro Kaplan

1994-01-01

363

Effect of the synthesis and annealing atmosphere composition on the fundamental absorption edge of ZnGA2O4 thin films  

NASA Astrophysics Data System (ADS)

We have used optical spectroscopy to study the region of the fundamental absorption edge of ZnGa2O4 thin films obtained by high-frequency RF ion plasma sputtering. We have established that the optical bandgap width E g increases from 4.55 eV to 4.81 eV when up to 20% oxygen is added to the sputtering argon atmosphere. An even greater increase in E g is observed when the films obtained are annealed in a hydrogen reducing atmosphere. We discuss the correlation between the value of E g and the composition of the sputtering and annealing atmosphere.

Bordun, O. M.; Kukharskyy, I. Yo.; Bihday, V. G.

2013-01-01

364

Microstructure Characterization Of Lead-Free Solders Depending On Alloy Composition  

NASA Astrophysics Data System (ADS)

Fatigue and crack nucleation in solder joints is basically associated with changes in the microstructure. Therefore the microstructure evolution of SnAgCu solder joints during solidification and subsequent application is an important subject for reliability investigations and physics of failure analysis. The scope of this study is a systematic overview of the as-cast microstructures in small sized lead-free SnAgCu solder spheres after solidification. A total of 32 alloy compositions have been investigated with varying Ag content from 0 to 5 wt.% and varying Cu content from 0 to 1.2 wt.%. The solder spheres had a diameter of approx. 270 ?m and were all manufactured under the similar conditions. Subsequent cross-sectioning was carried out in order to analyze the microstructure by optical and electron microscopy as well as Electron Backscatter Diffraction and Energy Dispersive X-ray Spectroscopy. The results allow a comprehensive overview of the dependence of the as-cast microstructure on the solder composition. It is shown that strong changes in microstructure can be caused by small changes in solder composition. In addition, a solidification phenomenon known as cyclic twinning has been found in the samples. Three different microstructures related to that phenomenon will be presented and detailed characterizations of these structures are given in this study. These microstructures differ in their appearance by solidification morphology, phase distribution as well as grain structure and can be described as follows: 1. large dentritic areas of different grain orientations which are characterized by approx. 60° twin boundaries; 2. areas of small ?-Sn cells with approx. 60° twin relation and larger intermetallic precipitates; 3. large grains consisting of a ?-Sn matrix with very fine intermetallic precipitates and high angle grain boundaries between adjacent grains.

Panchenko, Iuliana; Mueller, Maik; Wolter, Klaus-Juergen

2010-11-01

365

CUTTING EDGE PROFILE CHARACTERIZATIONS BY WHITE-LIGHT INTERFEROMETRY  

Microsoft Academic Search

Diamond coated cutting tools provide several advantages over traditional cutting tools, specifically in the machining of advanced materials such as composites. One of the main disadvantages of diamond coated cutting tools is the residual stresses induced from the diamond deposition, which lead to tool failure. Moreover, the cutting edge geometry can be critical to the deposition residual stresses of diamond

Andrew Ogilvie; Kevin Chou

366

Erosion resistance of needled carbon\\/carbon composites exposed to solid rocket motor plumes  

Microsoft Academic Search

The erosion resistance of the needled carbon\\/carbon composite leading edge was investigated by exposure to the solid rocket motor (SRM) plume. The erosion morphology and microstructure were examined and associated erosion mechanisms discussed. The composite leading edge was severely damaged with large recession and erosion rate after exposure. The results suggest that the erosion behavior was determined by the weak

Bo Chen; Li-Tong Zhang; Lai-Fei Cheng; Xin-Gang Luan

2009-01-01

367

EFFECTS OF ELASTIC EDGE RESTRAINTS AND INITIAL PRESTRESS ON THE BUCKLING RESPONSE OF COMPRESSION-LOADED COMPOSITE PANELS  

Microsoft Academic Search

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

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

368

Surface analyses of composites exposed to the space environment on LDEF. Technical report  

Microsoft Academic Search

We have conducted a series of surface analyses on carbon fiber\\/polyarylacetylene matrix composites that were exposed to the space environment on the Long Duration Exposure Facility (LDEF) satellite. 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

J. J. Mallon; J. C. Uht; C. S. Hemminger

1992-01-01

369

Electromigration and thermomigration studies in composite high lead and eutectic tin-lead flip chip solder joint  

NASA Astrophysics Data System (ADS)

The effect of thermomigration and the combination effect of thermomigration and electromigration have been studied in composite SnPb flip chip solder joints. Because Al line on the silicon chip side is the major heat source exerted on flip chip solder joint, temperature gradient across the joint is induced when a long Al line is stressed with high current density. Under a estimated temperature gradient of 1000°C/cm, Sn-rich and Pb-rich phase separation is found to occur. Experimental results have shown that Sn-rich phase accumulates at the hot side and Pb-rich phase accumulates at the cold side after thermomigration. When solder bumps are current high current density, thermomigration was found to accompany electromigration. Not only Pb-rich phase migrated toward the anode side and Sn-rich phase migrated toward the cathode side due to electromigration, Sn-rich phase was found to migrate along the top of solder joint due to thermomigration. It was found that as void propagates along the top of the solder joint, current crowding region shifts with the tip of the void. This created a local hot spot and thus a lateral temperature gradient was induced for thermomigration to occur. To isolate the thermal effect from the current effect, ac stressing at 60 Hz was also utilized. Interestingly, ac seems to have an effect other than thermal effect due to the difference in microstructure evolution between pure thermomigration and ac case after stressing. Further investigation at different frequency is needed to fully understand the effect of ac. Furthermore, analysis was performed to explain the phenomena of phase separation and phase reversal in the solder joint considering a constraint volume within underfill. Both Kirkendall effect and back stress were considered. Finally, detail morphological change after thermomigration and electromigration were investigated. Grain refinement was found to occur at a certain stressing condition. Production of entropy and morphological instability were utilized to explain the phenomenon.

Huang, Annie Tzuyu

370

Surface Plasmon Resonance Sensing Detection of Mercury and Lead Ions Based on Conducting Polymer Composite  

PubMed Central

A new sensing area for a sensor based on surface plasmon resonance (SPR) was fabricated to detect trace amounts of mercury and lead ions. The gold surface used for SPR measurements were modified with polypyrrole-chitosan (PPy-CHI) conducting polymer composite. The polymer layer was deposited on the gold surface by electrodeposition. This optical sensor was used for monitoring toxic metal ions with and without sensitivity enhancement by chitosan in water samples. The higher amounts of resonance angle unit (?RU) were obtained for PPy-CHI film due to a specific binding of chitosan with Pb2+ and Hg2+ ions. The Pb2+ ion bind to the polymer films most strongly, and the sensor was more sensitive to Pb2+ compared to Hg2+. The concentrations of ions in the parts per million range produced the changes in the SPR angle minimum in the region of 0.03 to 0.07. Data analysis was done by Matlab software using Fresnel formula for multilayer system.

Abdi, Mahnaz M.; Abdullah, Luqman Chuah; Sadrolhosseini, Amir R.; Mat Yunus, Wan Mahmood; Moksin, Mohd Maarof; Tahir, Paridah Md.

2011-01-01

371

Effects of compositional modification in lead lanthanum zirconate stannate titanate ceramics on electric energy storage properties  

NASA Astrophysics Data System (ADS)

The effects of compositional modifications on the antiferroelectric (AFE) to ferroelectric (FE) transition of lead lanthanum zirconate stannate titanate, (Pb1-3x/2Lax)(Zr1-v-zSnvTiz)O3 ceramics were used to optimize this material for energy storage. The experimental results show that an increase of Sn4+ respect to Ti4+ increases the coercive field of AFE-FE transition and keeps the hysteresis at the minimal level. This increases both the energy density of material and energy efficiency relative to a linear dielectric. Another advantage of Sn4+ addition was a polarization increase at the switching field. The substitution of Zn4+ for Sn4+ at fixed Ti4+ concentration of 0.1 was, however, undesirable for energy storage applications since this decreased the forward switching field and increased the hysteresis. This lowered both the energy density of the material and energy efficiency. Finally, addition of La3+ was performed and slim hysteresis loops were obtained resulting in energy efficiency of 80.1%. However, the slanted hysteresis behavior with La3+ results in a lower value of the maximum stored energy.

Jo, Hwan R.; Lynch, Christopher S.

2013-04-01

372

Surface plasmon resonance sensing detection of mercury and lead ions based on conducting polymer composite.  

PubMed

A new sensing area for a sensor based on surface plasmon resonance (SPR) was fabricated to detect trace amounts of mercury and lead ions. The gold surface used for SPR measurements were modified with polypyrrole-chitosan (PPy-CHI) conducting polymer composite. The polymer layer was deposited on the gold surface by electrodeposition. This optical sensor was used for monitoring toxic metal ions with and without sensitivity enhancement by chitosan in water samples. The higher amounts of resonance angle unit (?RU) were obtained for PPy-CHI film due to a specific binding of chitosan with Pb(2+) and Hg(2+) ions. The Pb(2+) ion bind to the polymer films most strongly, and the sensor was more sensitive to Pb(2+) compared to Hg(2+). The concentrations of ions in the parts per million range produced the changes in the SPR angle minimum in the region of 0.03 to 0.07. Data analysis was done by Matlab software using Fresnel formula for multilayer system. PMID:21931763

Abdi, Mahnaz M; Abdullah, Luqman Chuah; Sadrolhosseini, Amir R; Mat Yunus, Wan Mahmood; Moksin, Mohd Maarof; Tahir, Paridah Md

2011-09-09

373

Chip and built-up edge formation in the machining of in situ Al 4C 3–Al composite  

Microsoft Academic Search

As a consequence of widening range of applications of metal-matrix composites (MMCs), the machining of these materials has become a very important subject for research. This paper describes a study of chip formation during the machining of MMCs produced by the mechanical alloying (MA) technique. Aluminium based composite which contained various amounts of in situ Al4C3 particles, depending on MA

Yusuf Ozcatalbas

2003-01-01

374

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

DOEpatents

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

375

Magnetoelectric composite materials based on lead zirconate titanate and nickel ferrite  

Microsoft Academic Search

Composite materials that consist of a piezoelectric phase and a magnetostrictive ferrite exhibit a magnetoelectric effect. In composites, this effect is a consequence of the collective mechanical interaction of phases, and it manifests itself via electrical polarization or magnetization in magnetic or electric fields. At present, magnetoelectric composites are more promising materials than single-phase magnetoelectrics; most of the latter exhibit

T. G. Lupeiko; S. S. Lopatin; I. V. Lisnevskaya; B. I. Zvyagintsev

1994-01-01

376

Elastic buckling of unbalanced laminated fibre reinforced composite plates (rectangular plates of AsBtDs type, all edges simply-supported under biaxial loading)  

NASA Astrophysics Data System (ADS)

ESDU 94006 introduces a Fortran program, ESDUpac A9406, for calculating the buckling loading of composite plates for which in both the direct and flexural stiffness matrices the first two terms in the last column and last row are zero and in the coupling stiffness matrix the first two terms of the first two rows and the last term of the third row are zero. Such stiffness matrices arise when the fibers are all laid to make the same angle with a plate edge, but the angles are of opposite signs in each pair of laminae equidistant from the centre plane. The plate is assumed to be initial flat and rectangular, with loading applied uniformly along the edges. No account is taken of through-the-thickness shear deformation. Uniaxial or biaxial loading (in which one load can be tensile) is treated; under biaxial loading either one load may be fixed, and the other at buckling determined, or the ratio of the load may be fixed, and the loads in that ratio at buckling found. Example curves illustrate the variation of the buckling load with plate aspect ratio showing the influence of the coupling stiffness matrix. The full input and output to the program is explained and illustrated with worked examples. The program is provided on disc (uncompiled) in the software volume and compiled within ESDUview, a user-friendly shell running under MS DOS that prompts on screen for input data.

1994-04-01

377

Isotopic compositions of gangue versus ore minerals in the Upper Mississippi Valley zinc-lead district  

SciTech Connect

Four successive stages of gangue calcite occur after sulfide mineralization in the Upper Mississippi Valley zinc-lead district. These are commonly interpreted to represent the waning stage of MTV mineralization, because of spatial association and a smooth transition of decreasing fluid inclusion temperatures from late stage sphalerite through calcites 2 to 4. U-Pb systematics in two calcite 2 crystals suggests an age of 162 Ma, with [mu] values sufficiently great (1,175 and 1,611) that the indicated age is insensitive to initial [sup 206]Pb/[sup 204]Pb. This age for calcite formation is [approx] 100 Ma after that of sulfide mineralization and thus represents recurrent fluid activity along fracture zones. Initial [sup 87]Sr/[sup 86]Sr isotopic composition for three calcite 2 crystals range from 0.70956--0.70961, consist with initial [sup 87]Sr/[sup 86]Sr in the 270 Ma sphalerites. The initial [sup 87]Sr/[sup 86]Sr for two calcite 3 crystals and one calcite 4 crystal range from 0.70845--0.70875, consistent with mid-Ordovician seawater and the host carbonates of that age. The authors propose a hypothesis which is consistent with the Sr and U-Pb isotopic data. 162 Ma ago fluids flushed the existing pore fluids (left over from 270 Ma MVT event) from carbonate strata and deposited calcite 2. Subsequently, additional fluids containing [sup 87]Sr/[sup 86]Sr consistent with that derived from mid-Ordovician carbonates deposited calcite 3 and 4. If this hypothesis is correct the paragenetic connection between ore and gangue mineralization at UMV is weak and geochemical study of the gangue minerals may provide only limited information about the fluid which formed the ores.

Brannon, J.C.; Podosek, F.A. (Washington Univ., St. Louis, MO (United States). Dept. of Earth Planetary Sciences); McLimans, R.K. (E.I. DuPont de Nemours Co., Deepwater, NJ (United States). Jackson Research Lab.)

1993-03-01

378

E-field tuning microwave frequency performance of Co2FeSi/lead zinc niobate-lead titanate magnetoelectric coupling composites  

NASA Astrophysics Data System (ADS)

Nanocrystalline Co2FeSi Heusler alloy films were deposited on single crystal lead zinc niobate-lead titanate substrates. It is revealed that this multiferroic composite exhibits very strong continuously electric field (E-field) tunable microwave frequency characteristics. With an increase of the E-field intensity from 0 to 6 kV/cm, the ferromagnetic resonance field Hr shifts by 348 Oe along the easy axis direction, being equivalent to 58 Oe cm/kV, and the ferromagnetic resonance frequency fFMR dramatically increases from 2.2 to 6.1 GHz with an increment of 3.9 GHz or an increment ratio of 177% moreover, the damping constant ? decreases from 0.0150 to 0.0085. These features demonstrate that this multiferroic structure is promising in the fabrication of E-field tunable microwave components.

Li, Shandong; Liu, Ming; Lou, J.; Beguhn, Shawn; Wu, Jianpeng; Qiu, Jie; Lin, Jianhua; Cai, Zhiyi; Hu, Yi; Xu, Feng; Duh, Jenq-Gong; Sun, Nian X.

2012-04-01

379

Study on erosion resistance characteristics of Fe-MWCNT composite plating with respect to lead-free solder  

NASA Astrophysics Data System (ADS)

Sn-3mass%Ag-0.5mass%Cu lead-free solder causes strong erosion of Fe plating, which is used in hand soldering. In order to improve the durability of the soldering iron tip, we tried Fe-MWCNT (Multi-walled Carbon Nanotube) composite plating on the tip. Microstructures and the erosion resistance of the Fe-MWCNT composite plating under heating were examined. On the basis of the SEM/EDS analysis, it was confirmed that there were MWCNTs in the Fe-MWCNT composite plating. Even when heated to 673 K, MWCNTs were found to be present in the plating film under a stable condition. It was shown that the performance of erosion resistance for lead-free solders under high temperature (673 K) is improved due to the MWCNT addition to the Fe plating.

Watanabe, J.; Sekimori, N.; Hatsuzawa, K.; Uetani, T.; Shohji, I.

2012-08-01

380

Bending analysis of a laminated composite patch considering the free-edge effect using a stress-based equivalent single-layer composite model  

Microsoft Academic Search

The interlaminar stresses of a laminated composite patch, which is made up of reinforcing fibers (carbon\\/graphite) and epoxy matrix are analyzed using a stress-based equivalent single-layer model under a bending load. The composite patch is frequently used as reinforcement for a metallic adherend of mechanical\\/aerospace structures (i.e., aluminum alloy, etc) by attaching the film- or paste-type adhesive (i.e., epoxy, BMI,

Jaehun Lee; Maenghyo Cho; Heung Soo Kim

2011-01-01

381

Elastic buckling of cylindrically curved laminated fibre reinforced composite panels with all edges simply-supported under biaxial loading  

NASA Astrophysics Data System (ADS)

ESDU 94007 introduces a Fortran program, ESDUpac A9407, that calculates the buckling value of a uniform in-plane axial loading on the panel, with or without an additional circumferential loading due to normal pressure. Also output are the longitudinal buckle half wavelengths and, when pressure is considered, the circumferential buckle half wavelengths. The program applies to specially-orthotropic lay-ups, and will treat other lay-ups as if they were specially-orthotropic. It is based on elastic, thin plate, small deflection theory assuming the material to be homogeneous and orthotropic with the principal axes of orthotropy aligned with the rectangular plate edges. Through thickness shear is neglected. The equations on which the program is based are given, the input to the program is described in detail, its validation discussed, and specimen input and output of several worked examples are included. The program is provided on disc (uncompiled) in the software volume and compiled within ESDUview, a user-friendly shell running under MS DOS that prompts on screen for input data.

1994-04-01

382

Material nonlinear behavior of laminated metal–matrix composite plates supported at edges under uniform traverse loading  

Microsoft Academic Search

This paper deals with material non-linear behavior of steel fiber reinforced aluminum metal–matrix composite plates prepared by the squeeze casting process. By such an analysis it is intended to form an opinion about elastic–plastic behavior of laminated plates used in engineering problems associated with structural designs. Therefore, loads that begin plastic flow at any point of laminate for various stacking

Onur Sayman; Cesim Ata?; Hasan Çall?o?lu

2002-01-01

383

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

384

Impact of pH and Lead Composition on Metal Leached from Brass Coupons.  

National Technical Information Service (NTIS)

Water sampling and monitoring requirements under the Lead and Copper Rule specify one liter samples taken at the comsumers tap following at least 6 hours of stagnation. Probable direct sources of lead in the one liter water volume are lead/tin solder and ...

D. A. Lytle M. R. Schock

1993-01-01

385

Compositional dependence of the optical properties of bismuth doped lead-aluminum-germanate glass  

Microsoft Academic Search

We report the compositional dependence of absorption, emission, decay constant and quantum efficiency (QE) of GeO2:Al2O3:PbO:Bi2O3 glass with the aim of finding the composition most suitable for a laser gain medium. As the Bi2O3 content was varied we observed a non-monotonic variation in absorption spectrum. The optimized composition was 87.4GeO2:6Al2O3:6PbO:0.6Bi2O3 (% molar) which had a QE of 67% but low

M. A. Hughes; T. Suzuki; Y. Ohishi

2010-01-01

386

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

387

Compositional development of a plutonium surrogate glass without listed RCRA elements (lead and barium).  

National Technical Information Service (NTIS)

A lanthanide borosilicate (LaBS) glass composition, being evaluated by Savannah River Technology Center (SRTC) or plutonium disposition as part of the U.S. Department of Energy's (DOE) Office of the Fissile Materials Disposition (OFMD) program , has been ...

T. F. Meaker

1996-01-01

388

Mechanisms leading to nonlinear electrical response of a nano p-SiC\\/silicone rubber composite  

Microsoft Academic Search

It is well known that hopping of charge carriers via spatially and energetically distributed localized states is a primary transport mechanism in many disordered semiconductors and polymeric dielectrics. In this contribution, the nonlinear I-V physics of a 25 vol% 50 nm p-SiC\\/silicone rubber composite for high voltage field grading application was investigated, and a composite bulk hopping mechanism proposed. It

X. Wang; J. K. Nelson; L. S. Schadler; H. Hillborg

2010-01-01

389

Lead isotope composition of Central American volcanoes: Influence of the Galapagos plume  

Microsoft Academic Search

Lead isotopic analyses of lavas from Central America, both along and behind the volcanic arc, help to clarify source components in the mantle wedge. Analysis of previous Pb isotopic data had implied that little or no marine sediment lead was added to the Central American source region, as all samples fell within the MORB field, in contrast to other information

Mark D. Feigenson; Michael J. Carr; Susan V. Maharaj; Scott Juliano; Louise L. Bolge

2004-01-01

390

Development of composite materials for non-leaded glove for use in radiological hand protection  

Microsoft Academic Search

Lead is a hazardous material and US congress has mandated the rapid reduction of all hazardous waste generation as a matter of national policy. With the large amount of plutonium handling in numerous projects including the development of MOX fuel, power source etc., hand glove protection for the emitted alpha-beta- and low energy photons is an important issue. Leaded gloves

David Nii Amoo Dodoo-Amoo

2002-01-01

391

Phosphorus K-edge XANES spectroscopy of mineral standards  

PubMed Central

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.

Ingall, Ellery D.; Brandes, Jay A.; Diaz, Julia M.; de Jonge, Martin D.; Paterson, David; McNulty, Ian; Elliott, W. Crawford; Northrup, Paul

2011-01-01

392

Phosphorus K-edge XANES spectroscopy of mineral standards.  

PubMed

Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was performed on phosphate mineral specimens including (a) twelve specimens from the apatite group covering a range of compositional variation and crystallinity; (b) six non-apatite calcium-rich phosphate minerals; (c) 15 aluminium-rich phosphate minerals; (d) ten phosphate minerals rich in either reduced iron or manganese; (e) four phosphate minerals rich in either oxidized iron or manganese; (f) eight phosphate minerals rich in either magnesium, copper, lead, zinc or rare-earth elements; and (g) four uranium phosphate minerals. The identity of all minerals examined in this study was independently confirmed using X-ray powder diffraction. Minerals were distinguished using XANES spectra with a combination of pre-edge features, edge position, peak shapes and post-edge features. Shared spectral features were observed in minerals with compositions dominated by the same specific cation. Analyses of apatite-group minerals indicate that XANES spectral patterns are not strongly affected by variations in composition and crystallinity typical of natural mineral specimens. PMID:21335905

Ingall, Ellery D; Brandes, Jay A; Diaz, Julia M; de Jonge, Martin D; Paterson, David; McNulty, Ian; Elliott, W Crawford; Northrup, Paul

2010-12-02

393

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

394

Lead zirconate titanate-nickel zink ferrite thick-film composites: obtaining by the screen printing technique and magnetoelectric properties  

NASA Astrophysics Data System (ADS)

Layered thick-film composites containing one lead zirconate titanate (PZT) layer, one nickel zinc ferrite (NZF) layer, two PZT-NZF layers, or three PZT-NZF-PZT layers each 40-50 ?m thick are prepared. The layers are applied by screen printing on a ceramic aluminum oxide substrate with a preformed contact (conducting) layer. The dielectric properties of the composites are studied in the temperature interval 80-900 K and the frequency interval 25 Hz-1 MHz. Polarized samples exhibit piezoelectric, pyroelectric, and magnetoelectric effects. In tangentially magnetized two- and three-layer composites, the magnetoelectric conversion factor equals 57 kV/(m T) at low frequencies and reaches 2000 kV/(m T) at the mechanical resonance frequency.

Bush, A. A.; Shkuratov, V. Ya.; Chernykh, I. A.; Fetisov, Y. K.

2010-03-01

395

Magnetoelectric composite materials based on lead zirconate titanate and nickel ferrite  

SciTech Connect

Composite materials that consist of a piezoelectric phase and a magnetostrictive ferrite exhibit a magnetoelectric effect. In composites, this effect is a consequence of the collective mechanical interaction of phases, and it manifests itself via electrical polarization or magnetization in magnetic or electric fields. At present, magnetoelectric composites are more promising materials than single-phase magnetoelectrics; most of the latter exhibit magnetoelectric properties at temperatures of liquid helium or nitrogen. For the best single-phase ferromagnet Cr{sub 2}O{sub 3}, the magnetoelectric conversion factor if {Delta}E/{Delta}H = 25 x 10{sup {minus}3} V/A; the largest {Delta}E/{Delta}H ratios that were achieved for magnetoelectric ceramic materials prepared from powders of BaTiO{sub 3} and Ni{sub 0.97}Co{sub 0.03}Mn{sub 0.1}Fe{sub 1.9}O{sub 4} ferrite and for composites of the BaO-TiO{sub 2}-CoO-Fe{sub 2}O{sub 3} system prepared by unidirectional solidification of eutectic melts are 100 x 10{sup {minus}3} and 163 x 10{sup {minus}3} V/A, respectively. In addition to high {Delta}E/{Delta}H values, composites offer material designers the possibility of adjusting their piezoelectric and magnetostrictive components and of varying the ratios of these components over a wide range. This enables the design of magnetoelectric materials with controlled properties. In this paper, the authors report on the electrophysical and magnetoelectric properties of composites based on LZT and modified nickel ferrite and doped with bismuth, lanthanum, and niobium oxides.

Lupeiko, T.G.; Lopatin, S.S.; Lisnevskaya, I.V.; Zvyagintsev, B.I. [Rostov State Univ., Rostov-na-Donu (Russian Federation)

1994-11-01

396

Protist community composition during spring in an Arctic flaw lead polynya  

Microsoft Academic Search

The overwintering deployment of an icebreaker during the Canadian Flaw Lead study provided an opportunity to evaluate how\\u000a protist communities (phytoplankton and other single-celled eukaryotes) respond to changing spring irradiance conditions in\\u000a flaw lead polynyas, where open water persists between the central pack ice and land fast ice. We combined microscopic analysis\\u000a of the protist communities (all cell sizes) with

Ramon Terrado; Emmanuelle Medrinal; Cindy Dasilva; Mary Thaler; Warwick F. Vincent; Connie Lovejoy

397

Basanite–nephelinite suite from early Kilauea: carbonated melts of phlogopite–garnet peridotite at Hawaii’s leading magmatic edge  

Microsoft Academic Search

A basanite–nephelinite glass suite from early submarine Kilauea defines a continuous compositional array marked by increasing\\u000a 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,\\u000a 2006; Dixon et al. in J Pet 38:911–939, 1997), the early Kilauea basanite–nephelinite glasses are interpreted as

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

2009-01-01

398

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

399

Fabrication and Dielectric Properties of Lead-Free Inorganic Particles-Epoxy Resin Composites  

NASA Astrophysics Data System (ADS)

Inorganic-organic composites with a 0-3 connectivity are fabricated from inorganic particles with a high relative permittivity (\\varepsilonr) and a low dielectric loss (\\tan?), and epoxy resin. The compacted powder obtained by pulverizing BaZrO3-BaTiO3-Ba(Fe1/2Ta1/2)O3 (BZTFT) ceramics has 1/12th the \\varepsilonr and 72 times the \\tan? of the ceramics. On the basis of the relationship between \\varepsilonr and BZTFT filler content, the experimental values of the composites are determined to be in good agreement with theoretical values calculated by following Nielsen’s complex rule in the filler content range of 50-80 vol %. The temperature dependence of the dielectric properties of BZTFT powder/epoxy resin (90/10, v/v) composites measured at different frequencies suggests that the temperature characteristics of the present materials correspond to the Z8T characteristics [Z8T; Electronic Industries Association (EIA) standard: ? C/C25 {\\degC} is expressed as a rate of change within +22 and -33% in the temperature range from 10 to 150 °C] when represented by the temperature characteristics of surface-mounted capacitors. It is shown that the effect of the vacuum drying of the filler on the dielectric properties of the composites is larger than that of the silane coupling treatment and that the dielectric properties can be improved synergistically by performing both treatments.

Kobune, Masafumi; Takasaki, Keiko; Yazawa, Tetsuo

2006-09-01

400

The receptor for urokinase type plasminogen activator polarizes expression of the protease to the leading edge of migrating monocytes and promotes degradation of enzyme inhibitor complexes  

Microsoft Academic Search

Receptor-bound urokinase-type plasminogen activator (uPA) remains associated to the surface of human monocytes for many hours. Monocytes induced to migrate in a chemotactic gradient of f-Met-Leu-Phe rapidly polarize their uPA receptors to the leading front of the cells. Receptor-bound enzyme can be in- hibited by plasminogen activator inhibitor 2 (PAI-2), with a kinetics comparable to that determined for the free

Anne Estreicher; Judith Miihlhauser; Jean-Louis Carpentier; Lelio Orci; Jean-Dominique Vassalli

1990-01-01

401

Calculation of the composition dependence of the energy band gap in semiconducting solid solutions based on zinc, cadmium, and lead chalcogenides  

Microsoft Academic Search

Our study, based on interpolation methods, looked at the composition dependence of the energy band gap E\\/sub g\\/ in ternary and quaternary semiconducting solid solutions based on zinc, cadmium, and lead chalcogenides. Change in the energy band gap dependent on composition is not linear in most ternary systems. The nonlinear character of the composition dependent energy band gap for solid

F. U. Galeeva; K. D. Tarzimanov; I. K. Akhmetshin

1988-01-01

402

Effect of lead accumulation on growth and mineral composition of eggplant seedlings (Solarium melongena)  

Microsoft Academic Search

To examine lead (Pb) accumulation and distribution, and its effects on growth and nutrient content, Solanum melongena seedlings were grown in pot culture conditions in a glasshouse. The experiment was arranged in a randomised block design with 75, 150, and 300 mg litre Pb applications, and replicated 3 times. The highest Pb applications represent severely contaminated land, the lowest representing

Kadir Yilmaz; ?rfan Ersin Akinci; Sermin Akinci

2009-01-01

403

Snail ( Helix aspersa ) exposure history and possible adaptation to lead as reflected in shell composition  

Microsoft Academic Search

Lead sequestration in shell was examined for English and Welsh populations of the common garden snail (Helix aspersa) with different Pb exposure histories. Isotopic Pb ratios provided signatures for Pb source and a means of implying duration of population exposure from decades to millennia. Total Pb concentrations were used to quantify the intensity of exposure experienced by the populations. Snails

M. C. Newman; M. Mulvey; A. Beeby; R. W. Hurst; L. Richmond

1994-01-01

404

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)

1995-11-01

405

The Edge Current on Zigzag Graphene Nanoribbons  

Microsoft Academic Search

We have investigated the electron transport properties of zigzag graphene nanoribbons (GNRs) connected to one-dimensional leads on the edge. Transport properties are calculated using the nonequilibrium Green's function method with a tight-binding scheme. We revealed that an edge current originating in the edge states exists and found that the half width of the resonant peak of the transmission spectrum decays

Hirokazu Takaki; Nobuhiko Kobayashi

2010-01-01

406

Fabrication and Dielectric Properties of Lead-Free Inorganic Particles-Epoxy Resin Composites  

Microsoft Academic Search

Inorganic-organic composites with a 0-3 connectivity are fabricated from inorganic particles with a high relative permittivity (\\\\varepsilonr) and a low dielectric loss (\\\\tandelta), and epoxy resin. The compacted powder obtained by pulverizing BaZrO3-BaTiO3-Ba(Fe1\\/2Ta1\\/2)O3 (BZTFT) ceramics has 1\\/12th the \\\\varepsilonr and 72 times the \\\\tandelta of the ceramics. On the basis of the relationship between \\\\varepsilonr and BZTFT filler content, the

Masafumi Kobune; Keiko Takasaki; Tetsuo Yazawa

2006-01-01

407

Spectral method of determining the isotopic composition of lead. Part II  

Microsoft Academic Search

The paper describes different methods of isotopic spectral analysis of lead. Use was made of the apparatus described in ill. Analysis was carried out by measuring the intensities of the different components of hyperfine structure (hfs) of the line Phi 4057.8 A. Since we worked under conditions for which self-absorption was practically eliminated, we used the so-called method without standards.

A. N. Zajdel; A. G. Zhiglinski; J. ?ajko

1958-01-01

408

Edge conduction in vacuum glazing  

SciTech Connect

Vacuum glazing is a form of low-conductance double glazing using in internal vacuum between the two glass sheets to eliminate heat transport by gas conduction and convection. An array of small support pillars separates the sheets; fused solder glass forms the edge seal. Heat transfer through the glazing occurs by radiation across the vacuum gap, conduction through the support pillars, and conduction through the bonded edge seal. Edge conduction is problematic because it affects stresses in the edge region, leading to possible failure of the glazing; in addition, excessive heat transfer because of thermal bridging in the edge region can lower overall window thermal performance and decrease resistance to condensation. Infrared thermography was used to analyze the thermal performance of prototype vacuum glazings, and, for comparison, atmospheric pressure superwindows. Research focused on mitigating the edge effects of vacuum glazings through the use of insulating trim, recessed edges, and framing materials. Experimentally validated finite-element and finite-difference modeling tools were used for thermal analysis of prototype vacuum glazing units and complete windows. Experimental measurements of edge conduction using infrared imaging were found to be in good agreement with finite-element modeling results for a given set of conditions. Finite-element modeling validates an analytic model developed for edge conduction.

Simko, T.M.; Collins, R.E. [Sydney Univ., NSW (Australia). Dept. of Applied Physics; Beck, F.A.; Arasteh, D. [Lawrence Berkeley Lab., CA (United States)

1995-03-01

409

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

NASA Astrophysics Data System (ADS)

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.

1986-03-01

410

Ballistic parameters of .177 (4.5 mm) caliber plastic-sleeved composite projectiles compared to conventional lead pellets.  

PubMed

The capability of conventional air gun lead pellets (diabolo pellets) to cause severe injuries or fatalities even at low kinetic energy levels is well documented in medical literature. Modern composite hunting pellets, usually a metal core (made of steel, lead, zinc, or a zinc and aluminum alloy) encased in a plastic sleeve, are of special forensic and traumatological interest. These projectiles are advertised by the manufacturers to discharge at higher velocities than conventional air gun pellets, thus generating very high tissue-penetrating capabilities. Lack of experimental data on these uncommon air gun projectiles induced this work. Ballistic parameters of 12 different caliber .177 (4.5 mm) composite pellets, discharged from two spring-piston air guns (Weihrauch HW 35, Webley CUB) and three pneumatic air guns (Walther LGR, Walther LG400, Walther LP300), were investigated using a ballistic speed measurement system and compared to a conventional diabolo pellet (RWS Meisterkugel) as reference projectile. Although overall results were inconsistent, for some projectile-weapon combinations (particularly spring-piston air guns), a significant change of the kinetic energy (-53 up to +48 %) to the reference projectile was observed. The data provided in this work may serve as a basis for forensic investigation as well as traumatological diagnosis and treatment of injuries caused by these uncommon projectiles. PMID:23989221

Frank, Matthias; Schönekeß, Holger; Jäger, Frank; Herbst, Jörg; Ekkernkamp, Axel; Nguyen, Thanh Tien; Bockholdt, Britta

2013-08-29

411

Trace metal concentrations and lead isotopic composition in surface waters of the Northeast Pacific along the United States - Mexico boundary  

SciTech Connect

To evaluate the magnitude of heavy metal contamination along the United States - Mexico boundary, trace metal concentrations (Pb, Cd, Mn, Fe, and Zn) and lead isotopic composition ([sup 204]Pb, [sup 206]Pb, [sup 207]Pb, and [sup 208]Pb) were measured along four surface water transects across the continental shelf off the Baja California Coast. The stations were located between 2 to 45 km offshore, including both coastal and open ocean locations. All the metal distributions along the transects were characterized by offshore concentration gradients. The highest trace metal concentrations occurred in coastal waters in association with high salinities and nutrient concentrations. There was also a longshore gradient in trace metal concentrations. Trace element concentrations were lower in the southern locations than along the United States - Mexico boundary, and were comparable to typical open ocean values. The relative enrichment of metals in surface waters off the northern part of Baja California was primarily associated with advection/upwelling processes, not with anthropogenic inputs. Mass balance calculations indicated that about 1% of Cd and 13% of Zn were from urban discharges. The low metal levels measured in coastal waters off the central part of Baja California were attributed to the intrusion of open ocean waters, based on hydrographic data, satellite images and lead isotopic compositions.

Sanudo-Wilhelmy, S. (Inst. of Marine Science, Santa Cruz, CA (United States))

1990-01-09

412

Trace elements and lead isotopic composition of PM 10 in Lhasa, Tibet  

NASA Astrophysics Data System (ADS)

This paper presents the first detailed investigation on airborne trace metals and their potential major sources at Lhasa, the largest city in Tibetan Plateau (TP). The whole year PM 10 samples were collected during September 2007 and August 2008. The annual average concentration of PM 10 in Lhasa was 51.8 ± 42.5 ?g m -3, lower than those of major Asian cities. Distinct seasonal patterns were observed in PM 10 concentration, with higher concentrations in winter, and lower in summer. The mean elemental concentrations were generally comparable with other urban areas, but significantly higher than those from a remote site in TP (i.e., Nam Co). Crustal elements, including Na, Mg, Al, K, Ca, Sc, Ti, V, Mn, Fe, As and Ba, had similar seasonal patterns in PM 10, while other elements, such as Cr, Co, Ni, Cu, Zn, and Cd, had less distinct seasonal variations, suggesting more anthropogenic inputs of the latter group. The result of principle component analysis (PCA) on trace elements demonstrated that fugitive dusts, traffic emissions and waste incineration activities were probably the major sources of anthropogenic metals in the atmosphere at Lhasa. The Pb isotopic compositions revealed that the metal was mainly originated from nature background with a minor contribution from the cement factory. The data obtained in this study can be useful for making pollution control strategies in the city, and also valuable for trace element studies in other environmental medium, such as snow, ice core, and lake sediments in the TP region.

Cong, Zhiyuan; Kang, Shichang; Luo, Chunling; Li, Qing; Huang, Jie; Gao, Shaopeng; Li, Xiangdong

2011-11-01

413

Stable lead isotope compositions in selected coals from around the world and implications for present day aerosol source tracing  

SciTech Connect

The phasing out of leaded gasoline in many countries around the world at the end of the last millennium has resulted in a complex mixture of lead sources in the atmosphere. Recent studies suggest that coal combustion has become an important source of Pb in aerosols in urban and remote areas. Lead concentration and isotopic composition is reported for 59 coal samples representing major coal deposits worldwide in an attempt to characterize this potential source. The average concentration in these coals is 35 {mu}g Pb g{sup -1}, with the highest values in coals from Spain and Peru and the lowest in coals from Australia and North America. The {sup 206}Pb/{sup 207}Pb isotope ratios range between 1.15 and 1.24, with less radiogenic Pb in coals from Europe and Asia compared to South and North America. Comparing the Pb isotopic signatures of coals from this and previous studies with those published for Northern and Southern Hemisphere aerosols, we hypothesize that coal combustion might now be an important Pb source in China, the eastern U.S., and to some extent, in Europe but not as yet in other regions including South Africa, South America, and western U.S. This supports the notion that 'old Pb pollution' from leaded gasoline reemitted into the atmosphere or long-range transport (i.e., from China to the western U.S.) is important. Comparing the isotope ratios of the coals, the age of the deposits, and Pb isotope evolution models for the major geochemical reservoirs suggests that the lead isotope ratios (PbIC) in coals is strongly influenced by the depositional coal forming environment. 47 refs., 3 figs., 1 tab.

M. Diaz-Somoano; M.E. Kylander; M.A. Lopez-Anton; I. Suarez-Ruiz; M.R. Martinez-Tarazona; M. Ferrat; B. Kober; D.J. Weiss [Instituto Nacional del Carbon (INCAR-CSIC), Oviedo (Spain)

2009-02-15

414

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

415

Shifts in microbial community composition and function in the acidification of a lead/zinc mine tailings.  

PubMed

In an attempt to link the microbial community composition and function in mine tailings to the generation of acid mine drainage, we simultaneously explored the geochemistry and microbiology of six tailings collected from a lead/zinc mine, i.e. primary tailings (T1), slightly acidic tailings (T2), extremely acidic tailings (T3, T4 and T5) and orange-coloured oxidized tailings (T6). Geochemical results showed that the six tailings (from T1 to T6) likely represented sequential stages of the acidification process of the mine tailings. 16S rRNA pyrosequencing revealed a contrasting microbial composition between the six tailings: Proteobacteria-related sequences dominated T1-T3 with relative abundance ranging from 56 to 93%, whereas Ferroplasma-related sequences dominated T4-T6 with relative abundance ranging from 28 to 58%. Furthermore, metagenomic analysis of the microbial communities of T2 and T6 indicated that the genes encoding key enzymes for microbial carbon fixation, nitrogen fixation and sulfur oxidation in T2 were largely from Thiobacillus and Acidithiobacillus, Methylococcus capsulatus, and Thiobacillus denitrificans respectively; while those in T6 were mostly identified in Acidithiobacillus and Leptospirillum, Acidithiobacillus and Leptospirillum, and Acidithiobacillus respectively. The microbial communities in T2 and T6 harboured more genes suggesting diverse metabolic capacities for sulfur oxidation/heavy metal detoxification and tolerating low pH respectively. PMID:23574280

Chen, Lin-Xing; Li, Jin-Tian; Chen, Ya-Ting; Huang, Li-Nan; Hua, Zheng-Shuang; Hu, Min; Shu, Wen-Sheng

2013-04-09

416

Magnetohydrodynamic tokamak plasma edge stability  

NASA Astrophysics Data System (ADS)

The edge of a tokamak plasma is interesting due to its geometrical structure that is difficult to model mathematically and computationally, its tendency to form ‘transport barriers’ with increased confinement of energy and momentum, and the edge-localized instabilities associated with transport barriers that threaten the lifetime of components in large tokamaks. Ideal magnetohydrodynamics (MHD) is generally well understood, but only in the past decade has a good theoretical understanding emerged of MHD stability near the plasmas' separatrix when one or more X-points are present. By reviewing and discussing our theoretical understanding of ideal MHD stability of the plasma's edge, a clear picture emerges for its ideal stability. Conclusions are: ideal MHD will limit the width of strong transport barriers at the plasma's edge, a strong edge transport barrier will be associated with ELMs, ELMs will have a maximum toroidal mode number, will be preceded by smaller precursor instabilities, and can be triggered by sufficient changes to either the edge or the core plasma. Observations are made for the mechanisms responsible for edge transport barriers and ELMs, some leading to experimental predictions, others highlighting important open questions.

Webster, Anthony J.

2012-11-01

417

An analysis using the hobo genetic system reveals that combinatorial signaling by the Dpp and Wg pathways regulates dpp expression in leading edge cells of the dorsal ectoderm in Drosophila melanogaster.  

PubMed Central

Our laboratory has contributed to the development of a genetic system based upon the hobo transposable element in Drosophila melanogaster. We recently reported that hobo, like the better-known P element, is capable of local transposition. In that study, we mobilized a hobo enhancer trap vector and generated two unique alleles of decapentaplegic (dpp), a transforming growth factor-beta family member with numerous roles during development. Here we report a detailed study of one of those alleles (dpp(F11)). To our knowledge, this is the first application of the hobo genetic system to understanding developmental processes. First, we demonstrate that lacZ expression from the dpp(F11) enhancer trap accurately reflects dpp mRNA accumulation in leading edge cells of the dorsal ectoderm. Then we show that combinatorial signaling by the Wingless (Wg) pathway, the Dpp pathway, and the transcriptional coactivator Nejire (CBP/p300) regulates dpp(F11) expression in these cells. Our analysis of dpp(F11) suggests a model for the integration of Wg and Dpp signals that may be applicable to other developmental systems. Our analysis also illustrates several new features of the hobo genetic system and highlights the value of hobo, as an alternative to P, in addressing developmental questions.

Newfeld, S J; Takaesu, N T

2002-01-01

418

Retrograde Flow and Myosin II Activity within the Leading Cell Edge Deliver F-Actin to the Lamella to Seed the Formation of Graded Polarity Actomyosin II Filament Bundles in Migrating Fibroblasts  

PubMed Central

In migrating fibroblasts actomyosin II bundles are graded polarity (GP) bundles, a distinct organization to stress fibers. GP bundles are important for powering cell migration, yet have an unknown mechanism of formation. Electron microscopy and the fate of photobleached marks show actin filaments undergoing retrograde flow in filopodia, and the lamellipodium are structurally and dynamically linked with stationary GP bundles within the lamella. An individual filopodium initially protrudes, but then becomes separated from the tip of the lamellipodium and seeds the formation of a new GP bundle within the lamella. In individual live cells expressing both GFP-myosin II and RFP-actin, myosin II puncta localize to the base of an individual filopodium an average 28 s before the filopodium seeds the formation of a new GP bundle. Associated myosin II is stationary with respect to the substratum in new GP bundles. Inhibition of myosin II motor activity in live cells blocks appearance of new GP bundles in the lamella, without inhibition of cell protrusion in the same timescale. We conclude retrograde F-actin flow and myosin II activity within the leading cell edge delivers F-actin to the lamella to seed the formation of new GP bundles.

Anderson, Tom W.; Vaughan, Andrew N.

2008-01-01

419

Measurements in laminar regions of shock/shock and shock/boundary layer interaction over cylindrical leading edges, cone/cone and hollow cylinder flare configurations for DSMC/Navier-Stokes code validation  

NASA Astrophysics Data System (ADS)

Detailed measurements of the distribution of heat transfer and pressure, as well as Schlieren photographs, have been obtained in a series of experimental studies designed to provide measurements with which to evaluate the capabilities of the current numerical simulation techniques to predict the detailed characteristics of regions of shock/shock and shock/boundary layer interactions in laminar hypersonic flows. These experimental studies were conducted for a range of Mach numbers and Reynolds numbers to obtain fully laminar flows at conditions through the interaction regions that could be predicted with both DSMC and Navier-Stokes numerical schemes. In the first part of this paper, we present the model configuration, test condition and surface and flowfield measurements obtained in regions of shock/shock interaction over a highly instrumented cylindrical leading edge. In part two, only the model configurations, test conditions, and sample surface measurements are presented on two models-an axisymmetric cone/cone and a hollow cylinder flare configuration. The measurements that have been made on these configurations are being retained until the results of predictions with the DSMC and Navier-Stokes codes have been completed. .

Holden, Michael S.

2001-08-01

420

The localization of myosin VI at the golgi complex and leading edge of fibroblasts and its phosphorylation and recruitment into membrane ruffles of A431 cells after growth factor stimulation.  

PubMed

Myosin VI is an unconventional myosin that may play a role in vesicular membrane traffic through actin rich regions of the cytoplasm in eukaryotic cells. In this study we have cloned and sequenced a cDNA encoding a chicken intestinal brush border myosin VI. Polyclonal antisera were raised to bacterially expressed fragments of this myosin VI. The affinity purified antibodies were highly specific for myosin VI by immunoblotting and immunoprecipitation and were used to study the localization of the protein by immunofluorescence and immunoelectron microscopy. It was found that in NRK and A431 cells, myosin VI was associated with both the Golgi complex and the leading, ruffling edge of the cell as well as being present in a cytosolic pool. In A431 cells in which cell surface ruffling was stimulated by EGF, myosin VI was phosphorylated and recruited into the newly formed ruffles along with ezrin and myosin V. In vitro experiments suggested that a p21-activated kinase (PAK) might be the kinase responsible for phosphorylation in the motor domain. These results strongly support a role for myosin VI in membrane traffic on secretory and endocytic pathways. PMID:9852149

Buss, F; Kendrick-Jones, J; Lionne, C; Knight, A E; Côté, G P; Paul Luzio, J

1998-12-14

421

Propagating edge-flame response to multiple stoichiometry gradients  

SciTech Connect

A five-slot contoured nozzle burner was used to create multiple lifted partially premixed flames in close proximity. The burner permits the stoichiometry gradient below each edge flame and the separation distance between stabilization points of the flames to be separately controlled. In previous work, we showed that edge-flame interactions lead to a bifurcation in the flame stabilization, where the liftoff height of neighboring edge flames differs even in symmetric flow fields. As the composition gradient below each flame is decreased, the edge flames broaden. Flow around the edge flames leads to an aerodynamic interaction, where upstream conditions below one flame are modified by the neighboring flame. These interactions cause a liftoff height difference between the two flames. Further reduction of stoichiometry gradient causes the neighboring flames to merge and approach the structure of a single premixed flame. In this work, the equivalence ratio gradient and separation distance between stoichiometric points were varied by controlling the burner slot equivalence ratios, so that these interactions could be studied in greater detail. Rayleigh scattering was used to measure flame curvature and calculate local stoichiometry gradients below each flame stabilization point. Planar laser-induced fluorescence signals of hydroxyl and formaldehyde were measured to provide qualitative comparisons of relative reaction rates between flames. Neighboring edge flames were found to behave based solely on local conditions below each flame. Only aerodynamic interactions were observed and no chemical or thermal interactions, caused by heat or radical transport between flames, were observed. The bifurcated flame response can be described simply from the effects that flow around the flame structure has on local velocities and scalar dissipation rates. (author)

Kostka, Stanislav Jr.; Carnell, William F. Jr.; Renfro, Michael W. [Department of Mechanical Engineering, 191 Auditorium Rd, U-3139, University of Connecticut, Storrs, CT 06269 (United States)

2008-07-15

422

A comparison of procedures used in assessing the anodic corrosion of metal matrix composites and lead alloys for use in lead-acid  

Microsoft Academic Search

The anodic corrosion of lead at 70°C in sulfuric acid was studied at a potential of 1.226V vs. Hg\\/HgâSOâ where both the oxidation of lead to PbOâ and the oxidation of water are thermodynamically possible. These parallel anodic reactions can be the cause of a decrease in the faradaic efficiency. The faradaic corrosion current efficiency can be defined as a

C. M. Dacres; B. F. Larrick; R. A. Sutula

1983-01-01

423

Lead isotopic composition of trinitite melt glass: evidence for the presence of Canadian industrial lead in the first atomic weapon test.  

PubMed

The Pb isotopic compositions for 51 spots of melt glass in 11 samples of trinitite have been determined by laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Trinitite glass yields a large range of Pb isotopic compositions (i.e., (206)Pb/(204)Pb = 17.08-19.04), which reflect mixing between industrial Pb from materials used in the Trinity test and natural geologic components. Areas within trinitite melt glass containing high concentrations of both Cu and Pb, which are derived from the bomb and blast site-related components, were used for delineating the Pb isotopic composition corresponding to the anthropogenic Pb component. Comparison between the isotopic composition estimated here for the industrial Pb used in the Trinity test and those from known Pb deposits worldwide indicates close agreement with ore from the Buchans mine (Newfoundland, Canada). The Buchans mine was active during the time of the Trinity test and was operated by the American Smelting and Refining Company, which could have provided the Pb used in the test. The industrial Pb used in the Trinity test materials is not documented in the literature (or declassified) but could have been present in bricks, solder, pigs, or some other anthropogenic component related to the experiment. PMID:23829180

Bellucci, Jeremy J; Simonetti, Antonio; Wallace, Christine; Koeman, Elizabeth C; Burns, Peter C

2013-07-12

424

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.

425

Large converse magnetoelectric effect in Na0.5Bi0.5TiO3-CoFe2O4 lead-free multiferroic composites  

NASA Astrophysics Data System (ADS)

Lead-free multiferroic composites of ferroelectric, Na0.5Bi0.5TiO3 (NBT) and ferrimagnetic, CoFe2O4 (CFO) were synthesized by the solid-state sintering method and a systematic study of structural, magnetic, and magnetoelectric properties was undertaken. X-ray diffraction and field emission scanning electron microscopy displayed the formation of single phase for parent phases and the presence of both phases in the composites. Magnetic properties were investigated using a vibrating sample magnetometer (VSM) and ferromagnetic resonance (FMR) measurements at room temperature. Strong magnetoelectric (ME) coupling was demonstrated by an electric field tunable FMR field shift. A large value of converse ME coefficient 109 Oe-cm kV-1 was observed for NBT/CFO 70/30 composite. Furthermore, these lead-free multiferroic composites exhibiting a large converse magnetoelectric effect at room temperature provide great opportunities for electrostatically tunable devices at microwave frequencies.

Narendra Babu, S.; Malkinski, Leszek

2012-04-01

426

Edge foci interest points  

Microsoft Academic Search

In this paper, we describe an interest point detector using edge foci. Unlike traditional detectors that compute interest points directly from image intensities, we use normalized intensity edges and their orientations. We hypothesize that detectors based on the presence of oriented edges are more robust to non-linear lighting variations and background clutter than intensity based techniques. Specifically, we detect edge

C. Lawrence Zitnick; Krishnan Ramnath

2011-01-01

427

Visually significant edges  

Microsoft Academic Search

Numerous image processing and computer graphics methods make use of either explicitly computed strength of image edges, or an implicit edge strength definition that is integrated into their algorithms. In both cases, the end result is highly affected by the computation of edge strength. We address several shortcomings of the widely used gradient magnitude-based edge strength model through the computation

Tunç Ozan Aydin; Martin Cadík; Karol Myszkowski; Hans-Peter Seidel

2010-01-01

428

Magnetoelectric response in lead-free multiferroic NiFe2O4-Na0.5Bi0.5TiO3 composites  

NASA Astrophysics Data System (ADS)

Multiferroic composites that comprise NiFe2O4(NFO) and Na0.5Bi0.5TiO3(NBT) are synthesized using the sol-gel method. The results of XRD and scanning electron microscopy indicate the single-phase formation of NFO and NBT and the presence of two phases in the composites. The dielectric constant and dielectric loss are determined as functions of frequency over a wide range of frequencies from 40 Hz to 1 MHz. Room-temperature magnetization measurements show that these composites are soft magnetic. Further, the multiferroic character is confirmed by their magnetoelectric (ME) response at room temperature. The optimal ME response is 0.14% in a 67NFO-33NBT composite. The present study demonstrates that NFO-NBT could be effective as a lead-free multiferroic composite and provides an alternative for environmental-friendly ME devices.

Narendra Babu, S.; Hsu, Jen-Hwa; Chen, Y. S.; Lin, J. G.

2011-04-01

429

Containing Arsenic-Enriched Groundwater Tracing Lead Isotopic Compositions Of Common Arsenical Pesticides In A Coastal Maine Watershed Containing Arsenic-Enriched Ground Water  

Microsoft Academic Search

Arsenical pesticides and herbicides were extensively used on apple, blueberry, and potato crops in New England during the first half of the twentieth century. Lead arsenate was the most heavily used arsenical pesticide until it was officially banned. Lead arsenate, calcium arsenate, and sodium arsenate have similar Pb isotope compositions: 208Pb\\/207Pb = 2.3839-2.4722, and 206Pb\\/207Pb = 1.1035-1.2010. Other arsenical pesticides

Robert A. Ayuso; Nora K. Foley; Robinson Gilpin R. Jr; Anna S. Colvin; Gail Lipfert; Andrew S. Reeve

2012-01-01

430

Containing Arsenic-Enriched Groundwater Tracing Lead Isotopic Compositions Of Common Arsenical Pesticides In A Coastal Maine Watershed Containing Arsenic-Enriched Ground Water  

Microsoft Academic Search

Arsenical pesticides and herbicides were extensively used on apple, blueberry, and potato crops in New England during the first half of the twentieth century. Lead arsenate was the most heavily used arsenical pesticide until it was officially banned. Lead arsenate, calcium arsenate, and sodium arsenate have similar Pb isotope compositions: 208Pb\\/207Pb = 2.3839-2.4722, and 206Pb\\/207Pb = 1.1035-1.2010. Other arsenical pesticides

Robert A. Ayuso; Nora K. Foley; Robinson Gilpin R. Jr; Anna S. Colvin; Gail Lipfert; Andrew S. Reeve

2010-01-01

431

Composition and morphology of the film formed on a lead alloy under conditions typical of the electro-winning of copper  

Microsoft Academic Search

The composition and morphology of the anodic film formed on a lead alloy under conditions typical of copper electro-winning was studied with the aim of establishing the mechanism by which cobalt ions decrease the oxidation rate of lead. The film was characterized by scanning electron microscopy, X-Ray Diffraction (XRD) and X-Ray Photon Electron Spectroscopy (XPS). The anodic film formed in

T. Nguyen; A. Atrens

2009-01-01

432

Optimal Edge Detectors for Ramp Edges  

Microsoft Academic Search

It is argued that the best way to model an edge is by assuming all ideal mathematical function passed through a low-pass filter and and immersed in noise. Using techniques similar to those developed by J. Canny (1983, 1986) and L.A. Spacek (1986), optimal filters are derived for ramp edges of various slopes. The optimal nonrecursive filter for ideal step

Maria Petrou; Josef Kittler

1991-01-01

433

Luttinger liquids and composite fermions in nanostructures: what is the nature of the edge states in the fractional quantum Hall regime?  

Microsoft Academic Search

We study the Aharonov-Bohm conductance oscillations of a constriction with an antidot in the fractional quantum Hall regime using a recently proposed composite-fermion Fermi liquid theory, and also using Wen's chiral Luttinger liquid theory extended to include mesoscopic effects. The predictions of the composite-fermion Fermi liquid theory are very similar to standard Fermi liquid theory and are consistent with recent

Michael R Geller; Daniel Loss; George Kirczenow

1997-01-01

434

Teaching and Learning at the Leading Edge: Leading Edge Practitioners in Community Pharmacy.  

ERIC Educational Resources Information Center

|Focuses on pharmacists in Great Britain who have been identified as demonstrating more effective practices than others. Provides empirical evidence for the levels of organized teaching identified by French and Bazalgette. (Contains 25 references.) (DDR)|

Tann, Jennifer; Blenkinsopp, Alison; Platts, Adrian

2001-01-01

435

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

436

Door edge protection device  

US Patent & Trademark Office Database

A door edge protection device for a motor vehicle door which comprises a door edge protection member guided movably with respect to the door at at least two points lying one behind the other in a longitudinal direction of the door. The door edge protection member is driven via an eccentric lever mounted rotatably in the door.

Lichter; Martin (Erftstadt, DE); Benderoth; Thomas (Gummersbach, DE); Lopes dos Santos; Armando (Cologne, DE)

2012-11-06

437

Thermopower and Mott formula for a Majorana edge state  

NASA Astrophysics Data System (ADS)

We study the thermoelectric effect between a conducting lead and a Majorana edge state. In the tunneling limit, we first use the Landauer-Büttiker formalism to derive the Mott formula relating the thermopower and the differential conductance between a conducting lead and a superconductor. When the tunneling takes place between a conducting lead and a Majorana edge state, we show that a nonvanishing thermopower can exist. Combining measurements of the differential conductance and the voltage induced by the temperature difference between the conducting lead and the edge state, the Mott formula provides a unique way to infer the temperature of the Majorana edge state.

Hou, Chang-Yu; Shtengel, Kirill; Refael, Gil

2013-08-01

438

Measuring the vulnerability of populations susceptible to lead contamination in the Dominican Republic: evaluating composite index construction methods  

Microsoft Academic Search

There are several suspected sources of lead contamination in the Dominican Republic (DR) to which populations, to a greater\\u000a or lesser extent, may be exposed. These sources include: a lead battery recycling plant, a gold mine and vehicles using leaded\\u000a gasoline. In this paper we create and compare indices of spatial vulnerability using different index construction methods\\u000a including: the weighted

Samuel J. RatickJeffrey; Jeffrey P. Osleeb

439

Aerodynamics of flapping wings with fluttering trailing edges  

Microsoft Academic Search

Our previous work on the aerodynamics of passive flexible flapping wings showed that there is a strong relationship between the dynamics of trailing edge and the size of the leading edge vortex, therefore aerodynamic forces. Here we investigated the aerodynamic effects of active trailing edges. The experiments were conducted on a model flapping wing in an oil tank. During static

Liang Zhao; Zheng Hu; Jesse Roll; Xinyan Deng

2010-01-01

440

Edge stresses in alumina/zirconia laminates  

SciTech Connect

Using the technique of fluorescence piezospectroscopy, the authors determine the distribution of thermal residual stresses across the edges of three laminated alumina/zirconia composites. They develop a methodology for separating the measured stress state into microstresses that result from grain-to-grain thermal mismatch and macrostresses that result from lamination-induced thermal mismatch between individual plies. Comparison between the measured edge-stress distributions and those calculated based on a simple force-superposition model shows good agreement, indicating that the laminate system is well approximated as linear elastic. Given the experimental confirmation of significant edge stresses in multi-ply laminates, the possibility of failure initiating at composite edges must be considered in the design of surface-compressed laminate structures with the aim of mediating the detrimental effect of surface flaws.

Sergo, V. [Univ. di Trieste (Italy). Dipt. di Ingegneria dei Materiali; Lipkin, D.M.; Clarke, D.R. [Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Portu, G. de [CNR-IRTEC, Faenza (Italy)

1997-07-01

441

Influence of ceramic reinforcements on the wettability and mechanical properties of novel lead-free solder composites  

Microsoft Academic Search

In the present study, two sets of Sn–3.5 Ag–0.7 Cu solder-based composite materials were successfully synthesized using the powder metallurgy route of blending, compaction, sintering and extrusion. Varying amount of titanium diboride particulates and multi-walled carbon nanotubes were introduced respectively as reinforcements to obtain the two sets of composite solders. Following synthesis, the extruded materials were characterized in terms of

S. M. L. Nai; J. Wei; M. Gupta

2006-01-01

442

Near-Edge X-ray Absorption Fine-Structure Spectroscopic Study on Nitrogen-Doped Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared by Pulsed Laser Deposition  

NASA Astrophysics Data System (ADS)

Nitrogen-doped ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films, which possessed n-type conduction with enhanced electrical conductivity, were prepared by pulsed laser deposition. The film doped with a nitrogen content of 7.9 at. % possessed enhanced electrical conductivity of 18 ?-1\\cdotcm-1 at 300 K. The near-edge X-ray absorption fine-structure (NEXAFS) measurement indicated the appearance of additional peaks due to ?* C=N, ?* C=N, and ?* C--N bonds compared with the spectra of undoped films. The sp2 bonding fraction estimated from the NEXAFS spectra increased with the nitrogen content. The enhanced electrical conductivity is probably due to the formation of additional ?* and ?* states and the enhancement in the sp2 bonding fraction.

Al-Riyami, Sausan; Ohmagari, Shinya; Yoshitake, Tsuyoshi

2011-08-01

443

Projection Moire measurement of the deflection of composite plates subject to bird strike impact  

Microsoft Academic Search

For the new generation aircraft families, the use of fibre-reinforced plastics is considered for the leading edge of the wings. However, this leading edge is very prone to bird strike impact. This paper presents the use of the projection moire technique to measure the out-of-plane deflections of composite plates subject to bird strike. Very strict constraints with regard to: (i)

A. Shulev; W. Van Paepegem; J. Harizanova; A. Moentjens; J. Degrieck; V. Sainov

2007-01-01

444

Application of the method of equivalent edge currents to composite scattering from the cone-cylinder above a dielectric rough sea surface  

Microsoft Academic Search

Compared with scattering from a rough surface only, composite scattering from a target above a rough surface has become so practical that it is a subject of great interest. At present, this problem has been solved by some numerical methods which will produce an enormous calculation amount. In order to overcome this shortcoming, the reciprocity theorem (RT) and the method

Li-Xin Guo; Rui Wang; Zhen-Sen Wu

2010-01-01

445

Smart composite structures with embedded sensors  

Microsoft Academic Search

An overview of our developments toward fiber-optic-based smart composite structures is presented. This includes a review of our development of a full-scale fiber-optic damage assessment system for an aircraft composite leading edge and the confirmation of the feasibility of such a resident fiber-optic structural integrity monitoring system. We report on the development and characterization of fiber-optic strain gauges that have

Raymond M. Measures

1992-01-01

446

Aerodynamics of flapping wings with fluttering trailing edges  

NASA Astrophysics Data System (ADS)

Our previous work on the aerodynamics of passive flexible flapping wings showed that there is a strong relationship between the dynamics of trailing edge and the size of the leading edge vortex, therefore aerodynamic forces. Here we investigated the aerodynamic effects of active trailing edges. The experiments were conducted on a model flapping wing in an oil tank. During static tests, the trailing edge bending angle was held constant from the angle of attack of the upper portion of the rigid wing. For dynamic cases, the trailing edge was controlled to flutter with a prescribed frequency and amplitude. Force measurements and PIV results show that trailing edge flexion/camber strongly correlates with the leading edge vortex and the aerodynamic forces. In addition, large instantaneous force variations are observed in the dynamic fluttering cases, suggesting that trailing edge can be used for force modulation in MAVs.

Zhao, Liang; Hu, Zheng; Roll, Jesse; Deng, Xinyan

2010-11-01

447

Optical characteristic of sol-gel synthesized lead lanthanum titanate-cobalt iron oxide multiferroic composite thin film  

NASA Astrophysics Data System (ADS)

In the present work, we have investigated the optical characteristics of (1 - x) Pb0.85La0.15TiO3 (PLT15)-x CoFe2O4 (CFO) (x, volume fraction of CFO 0.0 <= x <= 0.12) composite multiferroic thin films. It has been demonstrated that the analysis of wavelength dispersion of refractive indices is an effective tool to comment on the magnetostrictive (CFO) phase distribution in perovskite (PLT15) matrix. Thus, in case of 0-3 type (1 - x) PLT15-x CFO composite films, it has been demonstrated that as long as CFO phase is distributed homogeneously in PLT15 matrix, the measured refractive indices follow Sellmeir dispersion formalism. Interestingly, for percolative magnetostrictive phase (CFO) distribution, the refractive index variation of the composite films deviates from the Sellmeir type dispersion. Absorption coefficient and the band gap energy are estimated for PLT15 and (1 - x) PLT15-x CFO composite films with varying CFO volume contents. Both refractive indices and packing fraction of (1 - x) PLT15-x CFO composite films are found to be marginally reduced with the increase in CFO volume contents. The band gap of these films is found to be systematically reduced with the increase in CFO volume contents. The change in band gap is argued to be due to cation/(s) diffusion across PLT15 and CFO interface.

Roy, Subhasis; Majumder, S. B.

2012-08-01

448

Microscale 1-3-type lead-free piezoelectric/ferrite composites fabricated by a modified dice-and-fill method  

NASA Astrophysics Data System (ADS)

This paper introduces a facile method to fabricate magnetoelectric (ME) composites with microscale lead-free piezoceramic pillars embedded in a ferrite matrix without high-temperature co-sintering. The microscale piezoceramic pillars with a sectional width of about 150 µm were obtained from lead-free piezoceramic discs by a dicing method. The spacing between the pillars was backfilled with cobalt ferrite (CFO) nanoparticles, and then a liquid epoxy was infiltrated into the backfilled spacing to bond the filled particles and the pillars. The ME property of the resultant 1-3-type piezoelectric/ferrite composites was verified and found to be significantly dependent on the filling density of the CFO powder, which could be adjusted by repeating the filling step. A maximum ME voltage response of up to 302 µV Oe-1 was obtained in a 700 µm high composite with pillars of 150 µm width and 200 µm spacing. The present method provides a potential way to fabricate finescale multiferroic composites for microdevice applications.

Xu, Ying; Li, Jing-Feng; Ma, Jing; Nan, Ce-Wen

2012-08-01

449

A comparison of lead-doped Bi-Sr-Ca-Cu-O superconductors at the '2223' and '2234' compositions  

Microsoft Academic Search

Superconducting Bi-Pb-Sr-Ca-Cu-O ceramics have been prepared at the Bi1.2Pb0.8Sr2Ca2Cu3Ox (2223) and Bi1.6Pb0.4Sr2Ca3Cu4Oy (2234) compositions. The properties and microstructures after sintering in air at 850 degrees C for times from 2 to 156 hours are described and compared. For the 2223 composition all heat treatment times result in multiphase samples. Bulk superconductivity giving zero resistance at 106 K and a maximum

T. W. Button; N. McN Alford; J. D. Birchall; F. Wellhofer; C. E. Gough; D. A. O'Connor

1989-01-01

450

The isotopic composition of lead in potassium feldspars from some 1.0-b.y. old North American igneous rocks  

USGS Publications Warehouse

The isotopic composition of lead and the uranium, thorium and lead concentrations in potassium feldspars are determined for more than 30 1.0-b.y. old North American igneous rocks. Samples representing a broad spectrum in petrographic type and mode of occurrence were chosen; an effort was made to include only rocks having well-documented ages from 950 to 1140 m.y. and showing minimal evidence of subsequent metamorphism. Most samples, including those from extensive terranes of contemporaneous age, have limited lead isotope variations ( Pb206 Pb204 = 16.74-17.38; Pb207 Pb204 = 15.39-15.59; Pb208 Pb204 = 36.38-37.10), which yield model ages close to the radiometric ages. Granite, pegmatite, and rhyolite from within the Grenville province of Canada and age-equivalent rocks of New York, Virginia, Texas, and Colorado and granophyric units associated with the Duluth Gabbro Complex of Minnesota are among the materials yielding this main isotopic spectrum. Several samples were encountered which had isotopic compositions very different from the above group. Lead showing a marked deficiency in radiogenic isotopes was found in two granitic bodies associated with older Labrador Trough rocks from Quebec, in a rapakivi granite from southern Nevada, and in a small granite stock from Mellen, Wisconsin. These occurrences all involve small intrusions of granite which lie near considerably older areas of basement rock. Model ages calculated from the Pb206 Pb204 ratio are older than the age of the intrusions and approach the age of the host basement rock. Several possible interpretations are offered to explain the isotopic behavior encountered in this study. In particular, a "vertically differentiated crust" model is proposed which will account for both the main spectrum and the anomalous lead. The significance of lead isotopic studies in understanding crustal structure in continental regions is discussed. ?? 1969.

Zartman, R. E.; Wasserburg, G. J.

1969-01-01

451

Effect of lead content on phase evolution and microstructural development in Ag-clad Bi-2223 composite conductors  

SciTech Connect

A two powder process was used to prepare silver-sheathed monofilamentary Bi{sub 1.8}Pb{sub x}Sr{sub 1.98}Ca{sub 1.97}Cu{sub 3.08}O{sub y} (Bi-2223) tapes with varying lead contents, x, from 0.2 to 0.5. The resulting tapes were subjected to thermomechanical processing and then characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray analysis (EDX). Layered phase texture was accessed using image analysis software on scanned SEM micrographs. Transport currents were measured at 77 K and zero field by the four-probe method. It was found that tapes with low lead content (X = 0.2 and 0.25) showed incomplete conversion to Bi-2223, had small grain size and poor c-axis texture. Tapes having higher lead content (x = 0.4 and 0.5) also showed incomplete conversion and the presence of lead-rich secondary phases. Tapes with lead content x = 0.3 and 0.35 showed complete conversion to Bi-2223, and had the least amount of secondary phases, the best c-axis texture, and the highest transport current (j{sub c}). The carbon content of the precursor powder also had a strong influence on secondary-phase chemistry.

Merchant, N.N.; Maroni, V.A.; Fischer, A.K.; Dorris, S.E.; Zhong, W.; Ashcom, N. [Argonne National Lab., IL (United States). Chemical Technology Div.

1997-02-01

452

Flexible and transparent nanogenerators based on a composite of lead-free ZnSnO3 triangular-belts.  

PubMed

A flexible and transparent lead-free triangular-belt ZnSnO(3) nanogenerator is demonstrated. When a mechanical deformation of ?0.1% is applied to the triangular-belt ZnSnO(3) nanogenerator, the output voltage and current reached 5.3 V and 0.13 ?A, respectively, which indicated a maximum output power density of ?11 ?W·cm(-3). This is the highest output power that has been demonstrated by lead-free ZnSnO(3) triangular-belts. PMID:22941870

Wu, Jyh Ming; Xu, Chen; Zhang, Yan; Yang, Ya; Zhou, Yusheng; Wang, Zhong Lin

2012-09-03

453

Lead in Three Peat Bog Profiles, Jura Mountains, Switzerland: Enrichment Factors, Isotopic Composition, and Chronology of Atmospheric Deposition  

Microsoft Academic Search

One metre cores were taken from three peat bogs in the Jura Mountains of Switzerland: Etang de la Gruère (EGr), La Tourbière des Genevez (TGe), and Praz Rodet (PRd). Dried peat samples were analyzed for lead (Pb) using the EMMA XRF and scandium (Sc) using INAA. Enrichment factors (EF) were calculated by normalizing to the background Pb\\/Sc ratio at EGr.

W. Shotyk; A. K. Cheburkin; P. G. Appleby; A. Fankhauser; J. D. Kramers

1997-01-01

454

Local recipes or distant commodities? Lead isotope and chemical compositional analysis of glaze paints from the Salinas pueblos, New Mexico  

Microsoft Academic Search

For nearly four hundred years, Pueblo potters in the Rio Grande Valley of New Mexico produced technologically innovative glaze-decorated bowls and exchanged them widely among different villages. While potential sources of lead ores used to make glaze paints are found throughout the Rio Grande Valley region, researchers have only recently begun to identify which ore sources potters exploited and to

Deborah L. Huntley; Katherine A. Spielmann; Judith A. Habicht-Mauche; Cynthia L. Herhahn; A. Russell Flegal

2007-01-01

455

Gyrokinetic Models for Edge Plasmas  

NASA Astrophysics Data System (ADS)

We have developed practical system of electromagnetic gyrokinetic equations for MFE edge simulations. This system 1) allows for large amplitude perturbations, 2) is consistent with energy conservation, and 3) minimizes the number of (difficult to implement) second-order terms needed. Because the relative perturbation amplitudes may be large, the operator in the gyrokinetic Poisson equation evolves with time, and the gyrocenter equations of motion used must retain specific second-order terms in order to maintain energy conservation. Methods for implementing the second-order terms in the equations of motion, and a useful finite-element discretization of the gyrokinetic Poisson equation have been developed. The latter results from a Galerkin approximation to Brizard's action variational principle. Because the magnetic field inhomogeneity scales are much longer than the radial plasma profile scales in the edge region, only the standard leading order terms (parallel streaming and magnetic drifts) need to be kept in the equilibrium portion of the gyrocenter equations of motion.

Dimits, A. M.; Cohen, R. H.; Xu, X. Q.

2008-11-01

456

Gyrokinetic Models for Edge Plasmas  

NASA Astrophysics Data System (ADS)

We have developed practical system of electromagnetic gyrokinetic equations for MFE edge simulations. This system 1) allows for large amplitude perturbations, 2) is consistent with energy conservation, and 3) minimizes the number of (difficult to implement) second-order terms needed. Because the relative perturbation amplitudes may be large, the operator in the gyrokinetic Poisson equation evolves with time, and the gyrocenter equations of motion used must retain specific second-order terms in order to maintain energy conservation. Methods for implementing the second-order terms in the equations of motion, and a useful finite-element discretization of the gyrokinetic Poisson equation have been developed. The latter results from a Galerkin approximation to Brizard's action variational principle. Because the magnetic field inhomogeneity scales are much longer than the radial plasma profile scales in the edge region, only the standard leading order terms (parallel streaming and magnetic drifts) need to be kept in the equilibrium portion of the gyrocenter equations of motion.

Dimits, A. M.; Cohen, R. H.; Xu, X. Q.

2009-05-01