Papers by Arkadii Krokhin
arXiv (Cornell University), Oct 16, 2019
arXiv (Cornell University), Sep 22, 1999
Non-Linear Volt--Ampere Parameter of a Thin Metal Plate With Non-Diffuse Faces
Dr. Arkadii Krokhin. His invaluable guidance, academic expertise, enthusiasm, and kindness throug... more Dr. Arkadii Krokhin. His invaluable guidance, academic expertise, enthusiasm, and kindness throughout the course of my PhD as a research assistant for him have provided me a great platform for the learning of Physics. I am forever indebted to my family -my mother Sabitha Bai and my father Rama Raya Nayak, my brother Manu, and my sister Chandrika for their constant support throughtout my journey as a PhD student. It gives me immense pleasure to thank my best friends
Effects of viscous dissipation in propagation of sound in periodic layered structures
The Journal of the Acoustical Society of America/The journal of the Acoustical Society of America, Feb 1, 2024
Physical review, Oct 15, 1996
We study transport properties in the classical ballistic regime of a two-dimensional electron cha... more We study transport properties in the classical ballistic regime of a two-dimensional electron channel with sinusoideal ͑rippled͒ boundaries. We calculate the transmission coefficient, the average number of collisions, and the mean path length, as a function of ripple amplitude. The Poincare ´plots of the associated dynamical system ͑the infinitely long channel͒ exhibit the generic transition to chaos as the amplitude of the ripples is increased. The chaotic nature of the finite channel is manifested by the fractal character of a response function. Transport features and dynamical properties are correlated. We compare our results with those that consider collisions with random ͑rough͒ boundaries. A criterion is proposed to distinguish between regular and chaotic dynamics by measuring classical resistivity. ͓S0163-1829͑96͒02240-0͔
Diffraction-free propagation of acoustic bean through solid-fluid periodic lattice
We propose a simple solid-fluid layered structure where narrow Gaussian acoustic beam propagates ... more We propose a simple solid-fluid layered structure where narrow Gaussian acoustic beam propagates practically without spreading. It is demonstrated that the coefficient (so-called diffraction coefficient), which defines the rate of linear spreading, vanishes if a certain relation between frequency and direction of propagation is hold. Unlike nonspreading “light bullets” recently proposed in optics, acoustic monochromatic signal can propagate in diffraction-free regime without sophisticated modulation. In the experiment with steel-water layered structure we observe nonspreading propagation of a signal with frequency ~ 100 kHz at a distance ~ 1m. Such long-range collimation is accompanied by negative phase velocity refraction, anomalous dispersion, and very strong anisotropy of the effective mass density. Such long-range collimation is accompanied by negative phase velocity refraction, anomalous dispersion, and very strong anisotropy of the effective mass density.
Mobile Dislocations, Electrons, and Chaos*
APS, Mar 1, 2000
We show that the electron drag force on a dislocation moving in a magnetic field, H, introduces a... more We show that the electron drag force on a dislocation moving in a magnetic field, H, introduces a sharp maximum in the drag stress when H is parallel to the dislocation line (tilt-effect**). The angular width of this maximum, given by the radius of the effective electron-dislocation interaction is, in the linear approximation, of the order of w/R<<1, where w
Manifestations of quantum chaos in spectra of 2D photonic crystals
Physica E-low-dimensional Systems & Nanostructures, Mar 1, 2002
ABSTRACT An electromagnetic wave propagating in a 2D photonic crystal is considered as an example... more ABSTRACT An electromagnetic wave propagating in a 2D photonic crystal is considered as an example of a chaotic dynamical system. For a fixed Bloch vector , the photon frequencies form a discrete sequence , where n=1,2,3,… is the band index. We study the level spacing distribution at the center of the Brillouin zone . A square unit cell contains two “atoms”, that are circular cylinders with dielectric constant εa, arranged asymmetrically in order to break all the discrete symmetries. The level spacing distribution reveals a smooth transition from the Poisson to the Wigner distribution when εa increases. We show that the onset of chaos in the spectrum occurs at rather low values of the dielectric constant, 2<εa<5, but it reveals strong features of regularity when εa exceeds 10. The latter tendency is due to the modes, which propagate mostly inside the cylinders and do not undergo chaotic scattering.
Physical Review B, Mar 16, 2015
A fluid channel clad between two solid plates is an acoustic waveguide where excitation of elasti... more A fluid channel clad between two solid plates is an acoustic waveguide where excitation of elastic waves at the channel boundaries has been usually neglected. This work develops a rigorous theory of scattering of sound by a finite-length fluid channel which takes into account excitation of elastic eigenmodes of two plates acoustically coupled through a fluid channel. The theory predicts an evidently contradictory result that the transmission and reflection coefficients of a nondissipative channel do not sum up to one. Moreover, they both exhibit deep minima at the same series of frequencies. It is shown that conservation of acoustic energy occurs due to redirection of sound, since part of the acoustic flux escapes into the solid plates. This scattering becomes possible because the uniform flatness of the boundaries of a straight channel is broken by vibrations. Theoretical predictions are supported by the experiments with ultrasound transmission through a narrow slit obtained between two brass or aluminum plates submerged in water. Measured transmission spectra exhibit deep minima exactly at the frequencies where the theory predicts strong redirection of sound.
Applied Physics Letters, Jul 25, 2022
We designed and characterized a 3D printed acoustic shear wave polarization rotator (PR) based on... more We designed and characterized a 3D printed acoustic shear wave polarization rotator (PR) based on the specific nature of the fused-deposition-modeling (FDM) printing process. The principle of the PR is based on rotation of the polarization axis of a shear wave due to the gradual change in orientation of the axis of anisotropy along the direction of wave propagation of a printed layered structure. The component of the shear modulus parallel to the infilled lines within each layer is significantly higher than that in the perpendicular direction. As the PR was printing, a small angle between neighboring layers was introduced, resulting in a 3D helicoidal pattern of distribution of the axes of anisotropy. The polarization of the propagating shear wave follows this pattern leading to the rotation of the polarization axis by a desirable angle. The total rotation angle can be tuned by the number of printed layers. The fabricated 90° rotators demonstrate high performance that can be improved by changing the infill fraction settings. Additive manufacturing (AM) [1, 2] has undergone development and improvement for decades. Major technique categories in AM that are widely used in industrial fields [3] and research projects include plastic filament reformatting, liquid resin curing, and metal powder melting. These categories are often combined with the most commonly applied printing processes of FDM [4], stereolithography [5], and selective laser melting [6]. Digital printing [7], inkjets [8], and solid-state metal/alloy printing [9] are examples of recently developed printing techniques for current applications, and printable materials contain groups such as polymers [10], ceramics [11], metal/alloys [12], and even composites [3, 13]. Although the mechanical properties of materials produced using the current AM processes are inferior to conventionally manufactured products [14], the flexibility of AM techniques drives the interest in improvement and further investigation for next-generation manufacturing technology. Customized structures of complex geometric shape with specific material combinations that may be infeasible, costprohibitive, and/or very challenging to realize by conventional, subtractive manufacturing processes can be readily fabricated using AM. Additionally, unlike any other known manufacturing techniques, the unconventional methods of additive manufacturing allow the nature of the printing process to be used to design specific applications and devices. Manipulation of the various process parameters and mechanisms can produce structures with a very wide range of mechanical and physical properties from the same printing tool. For example, in laser-meltingbased AM techniques, ultrafine grain structures [1], alignment of anisotropic mechanical properties [15], and internal twinning textures were obtained without any additional post-processes. In direct energy deposition printers, dissimilar metals that are immiscible were joined together using a thin barrier material . Friction stir, another AM processing method, was used for local reconstruction of an existing complex structure . Motivated by these modern manufacturing process-based structures, we have utilized the nature of FDM printing to design a shear wave polarization rotator (PR).
Ultrasonic elastography for nondestructive evaluation of dissimilar material joints
Journal of Materials Processing Technology, 2022
Abstract Dissimilar material joints or multilayered metals have become inevitable in the manufact... more Abstract Dissimilar material joints or multilayered metals have become inevitable in the manufacturing industry due to the increasing demand for multifunctional materials with variable mechanical, thermal, or electrical characteristics in a single assembly. Lattice mismatch of materials at the interface of dissimilar materials leads to inferior mechanical characteristics. In particular, the mismatch in elastic properties indicated by a large initial elastic deformation is critical to determine the extent of variation in stress. However, nanoindentation, the most common and accepted technique to measure elastic modulus, is destructive, time-consuming, and can only examine mechanical properties within a limited area. A non-invasive elastographic mapping technique evaluates the mechanical properties using ultrasonic elastography to study incompressibility. The dissimilar joint between steel and copper was obtained via friction stir welding. The variation of the stress developed at the welded joint of the two different metals was evaluated from the dynamic bulk modulus map. A tensile test of the involved workpiece confirmed a good agreement with our analysis based on the dynamic bulk modulus elastographic mapping results. This study provides a rapid and non-invasive technique for the bulk metallurgic elastic modulus inspection to overcome the limitations of conventional methods.
Dislocation Motion At Low Temperatures
APS March Meeting Abstracts, Mar 1, 1997
Conversion of surface tension energy of carbon nanotubes into visible light using a microwave field
APS March Meeting Abstracts, Mar 1, 2004
Nonlinear Effect in the Electron Drag of Dislocations in Metals
APS, Mar 1, 1996
Introduction to Acoustics of Phononic Crystals. Homogenization at Low Frequencies
Springer eBooks, 2016
A short introduction to propagation of sound in phononic crystals is given. Special emphasis is p... more A short introduction to propagation of sound in phononic crystals is given. Special emphasis is put to the description of the properties of phononic crystals in the long-wavelength limit when periodic inhomogeneous medium can be replaced by a homogeneous one with effective parameters (speed of sound, elastic modulus, and mass density). Two approaches to calculate these effective parameters are given: the plane-wave method and the multiple-scattering method. Metafluid with anisotropic mass density is discussed.
Electrodynamics of superlattices with ultra-thin metal layers: quantum Landau damping and band gaps with nonzero density of states
Optical Materials Express, Jan 22, 2019
metal layers are calculated in the regime when size quantization of electron motion and their non... more metal layers are calculated in the regime when size quantization of electron motion and their nonlocal contribution to conductivity play an essential role. In the THz region and in helium temperatures, this regime is realized if the thickness of metal layers is comparable to the skin-depth and metal film becomes partially transparent. Due to size quantization, the Landau damping is also quantized, leading to new resonances in surface impedances of metal film. An avoided crossing of these resonances with Fabry-Perot photonic pass bands gives rise to narrow band gaps where, nevertheless, the density of photonic states does not vanish. Such dark photonic states populating the new band gaps exhibit strongly anomalous dispersion and strong decay, as it is required by the Kramers-Kronig relations. The decay is due to the quantized Landau damping and it remains finite even in the collisionless limit.
Physica D: Nonlinear Phenomena, Sep 1, 1998
We consider creep processes in plastically deformed materials as a critical process such as propo... more We consider creep processes in plastically deformed materials as a critical process such as proposed by Zaitsev (Physica A 189 (1992) 411). We give arguments that the low-temperature creep rate necessarily has two di erent modes. During the ÿrst (fast) stage of stress relaxation, dislocations surmount many barriers simultaneously due to their inertia and a low viscosity of the electron liquid. In the second (slow) stage the depinning of dislocations is mostly due to thermal activation. Our experiments on the mechanical relaxation process in lead alloys and zinc are consistent with the proposed mechanism of depinning of dislocations.
Surface absorption of electromagnetic waves in metals by random boundary inhomogeneities
Journal of Experimental and Theoretical Physics, Nov 1, 1980
Low-frequency limit for 2D photonic band structures
APS, Mar 1, 1997
ABSTRACT
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Papers by Arkadii Krokhin