Search results

1

Particle tunneling and scattering in a three-dimensional potential with a barrier

100%

Olkhovsky V., Petrillo V., Jakiel J., Kantor W.

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vol. 6

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issue 1

122-127

EN

The particle tunneling through a 3-D rectangular potential barrier has been studied. The simplest model for multiple internal reflections has been assumed. The explicit expression for all the transmission and reflection probability amplitudes have been derived, as well as the tunneling and reflection phase times.

2

Threshold conditions and bound states for locally periodic delta potentials

100%

Dharani M., Sahu B., Shastry C.

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EN

We present a systematic study of the conditions for the generation of threshold energy eigen states and also the energy spectrum generated by two types of locally periodic delta potentials each having the same strength λV and separation distance parameter a: (a) sum of N attractive potentials and (b) sum of pairs of attractive and repulsive potentials. Using the dimensionless parameter g = λV a in case (a) the values of g = g n, n = 1, 2, …, N at which threshold energy bound state gets generated are shown to be the roots of Nth order polynomial D 1(N, g) in g. We present an algebraic recursive procedure to evaluate the polynomial D 1(N, g) for any given N. This method obviates the need for the tedious mathematical analysis described in our earlier work to generate D 1(N, g). A similar study is presented for case (b). Using the properties of D 1(N, g) we establish that in case (a) the critical minimum value of g which guarantees the generation of the maximum possible number of bound states is g = 4. The corresponding result for case (b) is g = 2. A typical set of numerical results showing the pattern of variation of g n as a function of n and several interesting features of the energy spectrum for different values of g and N are also described.

3

Conditions governing the generalisation of threshold bound states by N attractive delta potentials in one and three dimensions

100%

Dharani M., Sahu B., Shastry C.

Open Physics

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2013

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vol. 11

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issue 8

995-1005

EN

This paper proves that for N attractive delta function potentials the number of bound states (Nb) satisfies 1 ≤ N b ≤ N in one dimension (1D), and is 0 ≤ N b ≤ N in three dimensions (3D). Algebraic equations are obtained to evaluate the bound states generated by N attractive delta potentials. In particular, in the case of N attractive delta function potentials having same separation a between adjacent wells and having the same strength λV, the parameter g=λVa governs the number of bound states. For a given N in the range 1–7, both in 1D and 3D cases the numerical values of gn, where n=1,2,..N are obtained. When g=gn, Nb ≤ n where Nb includes one threshold energy bound state. Furthermore, gn are the roots of the Nth order polynomial equations with integer coefficients. Based on our numerical calculations up to N=40, even when N becomes large, 0 ≤ g n ≤ 4 and $\frac{{\Sigma g_n }} {N} \simeq 2 $ and this result is expected to be generally valid. Thus, for g > 4 there will be no threshold or zero energy bound state, and if g≈ 2 for a given large N, the number of bound states will be approximately N/2. The empirical formula gn = 4/[1+exp((N 0 − n)/β)] gives a good description of the variation of gn as a function of n. This formula is useful in estimating the number of bound states for any N and g both in 1D and 3D cases.

4

The Effect of Geometrical and Material Modification of Sound Diffusers on Their Acoustic Parameters

88%

Pilch A., Kamisiński T.

Archives of Acoustics

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2011

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vol. 36

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issue 4

5

Test Signal Selection for Determining the Sound Scattering Coefficient in a Reverberation Chamber

88%

Kamisiński T., Brawata K., Pilch A., Rubacha J., Zastawnik M.

Archives of Acoustics

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2012

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vol. 37

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issue 4

6

Sound Diffusers with Fabric Covering

88%

Kamisiński T., Brawata K., Pilch A., Rubacha J., Zastawnik M.

Archives of Acoustics

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2012

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vol. 37

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issue 3

7

Statistics of Envelope of High-Frequency Ultrasonic Backscatter from Trabecular Bone: Simulation Study

88%

Litniewski J.

Archives of Acoustics

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2010

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vol. 35

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issue 3

8

Einstein-Hopf drag, Doppler shift of thermal radiation and blackbody drag: Three perspectives on quantum friction

75%

Łach G., DeKieviet M., Jentschura U.

Open Physics

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2012

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vol. 10

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issue 4

763-767

EN

The thermal friction force acting on an atom moving relative to a thermal photon bath has recently been calculated on the basis of the fluctuation-dissipation theorem. The thermal fluctuations of the electromagnetic field give rise to a drag force on an atom provided one allows for dissipation of the field energy via spontaneous emission. The drag force exists if the atomic polarizability has a nonvanishing imaginary part. Here, we explore alternative derivations. The damping of the motion of a simple harmonic oscillator is described by radiative reaction theory (result of Einstein and Hopf), taking into account the known stochastic fluctuations of the electromagnetic field. Describing the excitations of the atom as an ensemble of damped harmonic oscillators, we identify the previously found expressions as generalizations of the Einstein-Hopf result. In addition, we present a simple explanation for blackbody friction in terms of a Doppler shift of the thermal radiation in the inertial frame of the moving atom: The atom absorbs blue-shifted photons from the front and radiates off energy in all directions, thereby losing energy. The original plus the two alternative derivations provide for additional confirmation of an intriguing quantum friction effect, and leave no doubt regarding its existence.

9

The Forces Driving Streaming in the Presence of Scatterers Mimicking the Blood Cells and the Contrast Agents

75%

Wójcik J., Secomski W., Wójcik J., Secomski W.

Archives of Acoustics

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2019

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vol. 44

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issue 4

10

Correction of Acoustics in Historic Opera Theatres with the Use of Schroeder Diffuser

63%

Kamisiński T.

Archives of Acoustics

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2012

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vol. 37

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issue 3

11

Full-wave Analysis of Periodic Baffle System in Beamforming Applications

51%

Tasinkevych Y., Danicki E.

Archives of Acoustics

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2010

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vol. 35

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issue 4

Refine search results

Particle tunneling and scattering in a three-dimensional potential with a barrier

Threshold conditions and bound states for locally periodic delta potentials

Conditions governing the generalisation of threshold bound states by N attractive delta potentials in one and three dimensions

The Effect of Geometrical and Material Modification of Sound Diffusers on Their Acoustic Parameters

Test Signal Selection for Determining the Sound Scattering Coefficient in a Reverberation Chamber

Sound Diffusers with Fabric Covering

Statistics of Envelope of High-Frequency Ultrasonic Backscatter from Trabecular Bone: Simulation Study

Einstein-Hopf drag, Doppler shift of thermal radiation and blackbody drag: Three perspectives on quantum friction

The Forces Driving Streaming in the Presence of Scatterers Mimicking the Blood Cells and the Contrast Agents

Correction of Acoustics in Historic Opera Theatres with the Use of Schroeder Diffuser

Full-wave Analysis of Periodic Baffle System in Beamforming Applications