Wyniki wyszukiwania - Biblioteka Nauki

1

Operation modes of the FALCON ion source as a part of the AMS cluster tool

100%

Girka O. , Bizyukov A. , Bizyukov I. , Gutkin M. , Mishin S.

Nukleonika

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2015

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tom 60

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nr 2

327-330

EN

The paper investigates the options to increase the production yield of temperature compensated surface acoustic wave (SAW) devices with a defined range of operational frequencies. The paper focuses on the preparation of large wafers with SiO2 and AlN/Si3N4 depositions. Stability of the intermediate SiO2 layer is achieved by combining high power density UV radiation with annealing in high humidity environment. A uniform thickness of the capping AlN layer is achieved by local high-rate etching with a focused ion beam emitted by the FALCON ion source. Operation parameters and limitations of the etching process are discussed.

2

Acoustic scattering from functionally graded cylindrical shells

100%

Jamali J. , Naei M. H. , Honarvar F. , Rajabi M.

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2011

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tom Vol. 63, nr 1

25-25

EN

In this paper, the method of wave function expansion is adopted to study the scattering of a plane harmonic acoustic wave incident upon an arbitrarily thick-walled, functionally graded cylindrical shell submerged in and filled with compressible ideal fluids. A laminate approximate model and the so-called state space formulation in conjunction with the classical transfer matrix (T-matrix) approach, are employed to present an analytical solution based on the three-dimensional exact equations of elasticity. Three models, representing the elastic properties of FGM interlayer are considered. In all models, the mechanical properties of the graded shell are assumed to vary smoothly and continuously with the change of volume concentrations of the constituting materials across the thickness of the shell. In the first two models, the rule of mixture governs. The main difference between them is the set of elastic constants (e.g., Lamé’s constants in model I and Young’s modulus and Poisson’s ratio in Model II) which are governed by the rule of mixtures. In the third model, an elegant self-consistent micromechanical model which assumes an interconnected skeletal microstructure in the graded region is employed. Particular attention is paid to backscattered acoustic response of these models in a wide range of frequency and for different shell wall-thicknesses. The results reveal a technical comparison between these models. In addition, by examining various cases (i.e., different shell wall-thicknesses, various profiles of variations and different volume concentration of constituents), the impact of the overall volume concentration of constituents and also the profile of variations, on the resonant response of the graded shell is investigated. Limiting cases are considered and good agreement with the solutions available in the literature is obtained.

3

Modelling flow in the porous bottom of the Barents Sea shelf

100%

Massel S. R.

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2013

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tom No. 55 (1)

129-146

EN

In their recent paper, Węsławski et al. (2012) showed that the Svalbardbanken area of the Barents Sea is characterized by a high organic carbon settlement to the permeable sea bed, which consists of gravel and shell fragments of glacial origin. In the present paper, which can be considered as a supplement to the Węsławski et al. paper, two potential hydrodynamic mechanisms of downward pore water transport into porous media are discussed in detail. In particular, estimated statistical characteristics of the pore water flow, induced by storm surface waves, indicate that the discharge of water flow can be substantial, even at large water depths. During stormy weather (wind velocity V=15 m s-1 and wind fetch X =200 km) as much as 117.2 and 26.1 m3 hour-1 of water filter through the upper 5 m of the shell pit at water depths of 30 and 50 m respectively. For a porous layer of greater thickness, the mean flow discharge is even bigger. The second possible mechanism of flow penetration in the porous layer is based on the concept of geostrophic flow and spiral formation within the Ekman layer. Assuming that the current velocity in the near-bottom water layer is u- = 1 m, the resulting mean discharge through this layer becomes as large as 0.99 and 0.09 m3 s-1 for downstream and transverse flows respectively.

4

Surface wave propagation in fiber-reinforced anisotropic elastic layer between liquid saturated porous half space and uniform liquid layer

100%

Samal S. , Chattaraj R.

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tom Vol. 59, no. 3

470-482

EN

Surface wave propagation in fiber-reinforced anisotropic elastic layer between a liquid saturated porous half space and a uniform liquid layer is considered. Equation of motion and suitable boundary conditions give rise to a dispersion equation in the form of a ninth order determinant. Phase velocity and group velocity of a particular model have been studied.

5

Detection of laser induced dielectric breakdown in water using a laser doppler vibrometer

88%

Saarela J. , Löfqvist T. , Ramser K. , Gren P. , Olson E. , Niemi J. , Sjödahl M.

Open Physics

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2010

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tom 8

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nr 2

235-241

EN

This study is focused on exploring the feasibility of an all-optic surface scanning method in determining the size and position of a submerged, laser generated, optoacoustic (OA) source. The optoacoustic effect in this case was generated when the absorption of a short electromagnetic pulse in matter caused a dielectric breakdown, a plasma emission flash and a subsequent acoustic wave. In the experiment, a laser pulse with λ = 1064 nm and 12 ns pulse length was aimed at a volume of deionized water. When the laser beam was focused by a f = 16 mm lens, a single dielectric breakdown spot occurred. When a f = 40 mm was used several breakdowns in a row were induced. The breakdowns were photographed using a double shutter camera. The acoustic wave generated by the dielectric breakdowns were detected at a point on the water surface using a laser Doppler vibrometer (LDV). First, the LDV signal was used to calculate the speed of sound with an accuracy of 10 m/s. Secondly, the location and length of the dielectric breakdown was calculated with an accuracy of 1 mm. The calculated position matched the breakdown location recorded by a camera. The results show that it is possible to use LDV surface measurements from a single spot to determine both the position and length of the OA source as well as the speed of sound in the medium. Furthermore, the LDV measurements also show a secondary peak that originates from the OA source. To unravel the origin and properties of this interesting feature, further investigations are necessary