Anomalous attenuation effect on reflectivity of an ultrasonic wave from a thin layer between dissimilar materials

1997 ◽  
Vol 101 (6) ◽  
pp. 3405-3414 ◽  
Author(s):  
A. I. Lavrentyev ◽  
S. I. Rokhlin
Keyword(s):  
Thin Layer ◽  
Ultrasonic Wave ◽  
Dissimilar Materials ◽  
Attenuation Effect ◽  
Anomalous Attenuation

An electromagnetic wave attenuation superposition structure for thin-layer plasma

2022 ◽  
Author(s):  
Wenyuan Zhang ◽  
Haojun Xu ◽  
Binbin Pei ◽  
Xiaolong Wei ◽  
Pei Feng ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Thin Layer ◽  
Electromagnetic Scattering ◽  
Wave Attenuation ◽  
Control Method ◽  
Dispersion Model ◽  
Reflectance Measurement ◽  
Phase Gradient ◽  
Attenuation Effect ◽  
Stealth Technology

Abstract This work proposes a new plasma super-phase gradient metasurfaces (PS-PGMs) structure, owing to the limitations of the thin-layer plasma for electromagnetic wave attenuation. Based on the cross-shaped surface unit configuration, we have designed the X-band absorbing structure through the dispersion control method. By setting up the Drude dispersion model in the computer simulation technology, the designed phase gradient metasurfaces structure is superposed over the plasma, and the PS-PGMs structure is constructed. The electromagnetic scattering characteristics of the new structure have been simulated, and the reflectance measurement has been carried out to verify the absorbing effect. The results demonstrate that the attenuation effect of the new structure is superior to that of the pure plasma structure, which invokes an improved attenuation effect from the thin layer plasma, thus enhancing the feasibility of applying the plasma stealth technology to the local stealth of the strong scattering part of a combat aircraft.

TRAPPING CAPABILITY OF MICROLENS 2D ARRAY BY ACOUSTIC MODULATION

2014 ◽  
Vol 6 (2) ◽  
pp. 1072-1078
Author(s):  
Quang Quy Ho ◽  
Van Thinh Nguyen ◽  
Van Lanh Chu
Keyword(s):  
Refractive Index ◽  
Thin Layer ◽  
Ultrasonic Wave ◽  
Focal Length ◽  
Numerical Aperture ◽  
Optical Tweezer ◽  
Ultrasonic Waves ◽  
Optical Medium ◽  
Acoustic Modulation ◽  
2D Array

In this article, the microlens 2D array created in acoustic-optical medium by the ultrasonic wave modulation is proposed. The expression described the refractive index induced by cross-interference of two perpendicular ultrasonic waves is approximately derived. By simulation, the 2D array of the Graded–refractive index lenses are appeared in the thin layer with certain strain-acoutstic constant and thickness.  The  dependence of  focal length and the radius of lens, i.e. its numerical aperture (AN) on thickness and strain constant of layer, and ultrasonic wave intensity are simulated and trapping capability of optical tweezer array is discussed.

Applications of Photoelectron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 506-507
Author(s):  
William J. Baxter
Keyword(s):  
Electron Microscopy ◽  
Thermal Decomposition ◽  
Chemical Composition ◽  
Ultraviolet Radiation ◽  
Thin Layer ◽  
Edge Effects ◽  
Electron Optics ◽  
Surface Layers ◽  
Crystalline Orientation ◽  
Fluorescent Screen

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.

Analytical and High-Resolution EM Study of Crystalline Phases formed at Metal-Ceramic Interface

1990 ◽  
Vol 48 (2) ◽  
pp. 426-427
Author(s):  
N. Merk ◽  
A. P. Tomsia ◽  
G. Thomas
Keyword(s):  
Cross Section ◽  
Dissimilar Materials ◽  
Ceramic Materials ◽  
Electron Micrograph ◽  
Scanning Electron Micrograph ◽  
Structural Applications ◽  
Metal Ceramic ◽  
The Subject ◽  
Ceramic Compounds ◽  
Scanning Electron

A recent development of new ceramic materials for structural applications involves the joining of ceramic compounds to metals. Due to the wetting problem, an interlayer material (brazing alloy) is generally used to achieve the bonding. The nature of the interfaces between such dissimilar materials is the subject of intensive studies and is of utmost importance to obtain a controlled microstructure at the discontinuities to satisfy the demanding properties for engineering applications . The brazing alloy is generally ductile and hence, does not readily fracture. It must also wett the ceramic with similar thermal expansion coefficient to avoid large stresses at joints. In the present work we study mullite-molybdenum composites using a brazing alloy for the weldment.A scanning electron micrograph from the cross section of the joining sequence studied here is presented in Fig. 1.

Interfacial structures of dissimilar materials joined by capacitor-discharge welding

1994 ◽  
Vol 52 ◽  
pp. 534-535
Author(s):  
C. P. Doğan ◽  
R. D. Wilson ◽  
J. A. Hawk
Keyword(s):  
Rapid Solidification ◽  
Fusion Zone ◽  
Dissimilar Materials ◽  
Solidification Process ◽  
Weld Interface ◽  
Capacitor Discharge ◽  
Fine Grained ◽  
Iron Aluminum ◽  
Conductive Ceramics ◽  
Capacitor Discharge Welding

Capacitor Discharge Welding is a rapid solidification technique for joining conductive materials that results in a narrow fusion zone and almost no heat affected zone. As a result, the microstructures and properties of the bulk materials are essentially continuous across the weld interface. During the joining process, one of the materials to be joined acts as the anode and the other acts as the cathode. The anode and cathode are brought together with a concomitant discharge of a capacitor bank, creating an arc which melts the materials at the joining surfaces and welds them together (Fig. 1). As the electrodes impact, the arc is extinguished, and the molten interface cools at rates that can exceed 106 K/s. This process results in reduced porosity in the fusion zone, a fine-grained weldment, and a reduced tendency for hot cracking.At the U.S. Bureau of Mines, we are currently examining the possibilities of using capacitor discharge welding to join dissimilar metals, metals to intermetallics, and metals to conductive ceramics. In this particular study, we will examine the microstructural characteristics of iron-aluminum welds in detail, focussing our attention primarily on interfaces produced during the rapid solidification process.

Ultrasonic Wave Scattering by a Line Crack in a Solder Joint

1999 ◽  
Vol 11 (1) ◽  
pp. 117-135
Author(s):  
P. Dineva ◽  
D. Gross ◽  
T. Rangelov
Keyword(s):  
Solder Joint ◽  
Ultrasonic Wave ◽  
Wave Scattering ◽  
Line Crack

Efficiency of Lamb modes in the spatial and frequency acoustic signatures for a thin layer by the resonance theory

2000 ◽  
Vol 10 (2) ◽  
pp. 97-108
Author(s):  
A. Ramdani ◽  
F. Augereau ◽  
M. Sidki ◽  
G. Despaux
Keyword(s):  
Thin Layer ◽  
Resonance Theory ◽  
Acoustic Signatures

THE ANALYSIS OF ULTRASONIC WAVE ATTENUATION SPECTRA IN STEELS

1983 ◽  
Vol 44 (C9) ◽  
pp. C9-337-C9-340 ◽  
Author(s):  
R. L. Smith ◽  
W. N. Reynolds ◽  
S. Perring
Keyword(s):  
Ultrasonic Wave ◽  
Wave Attenuation
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