Analytical and Computational Studies of Magneto-Convection in Solidifying Mushy Layer

Natural convection in solidifying binary media is of great interest due to it\u27s applications in material processing and crystal growth industries. Convective flows between the layers of melt during alloy solidification is known to produce mechanical imperfections such as freckle\u27s. Hence it is important to investigate the criterion for freckling and discover the means of suppressing it. A mushy layer, which has both solid and fluid components and is formed between underlying solid and overlying liquid, is known to produce chimneys, which are narrow, vertical vents, devoid of solid. We consider the problem of magneto-convection in a horizontal mushy layer during the solidification of binary alloys. Both cases of permeable and impermeable mush-liquid interface were investigated. We carry out the numerical investigation for particular range of parameter values which cover those of available experimental studies. Cases of constant and variable permeability coupled with mush-liquid interface boundary conditions were included in the present study. The governing coupled non-linear partial differential equations are non-dimensionalized and solved to get steady basic state solution. Using multiple shooting technique we determine the steady state solutions in a range of critical Rayleigh number. We analyse the effect of, Chandrasekhar number Q, far-field temperature, permeability of the medium, mush-liquid interface condition, on the problem. The results of the analysis and computation indicate that increasing Q has the stabilizing effect on the solidification, because the critical Rayleigh number increases with increasing the strength of magnetic field. But permeable mush-liquid interface condition destabilizes the convection by reducing the critical Rayleigh number. It was also found that for moderate or small values of Robert\u27s number, the critical Rayleigh number is mostly insensitive. The most important finding of the present investigation is that the convection in a mushy layer decreases upon increasing the strength of externally imposed magnetic field and increasing far-field temperature. These theoretical results have been observed in related experiments of damped magneto-convection by Vives and Perry (1987)

1H and 19F NMR relaxation time studies in (NH4)2ZrF6 superionic conductor

1H and 19F spin-lattice relaxation times in polycrystalline diammonium hexafluorozirconate have been measured in the temperature range of 10–400 K to elucidate the molecular motion of both cation and anion. Interesting features such as translational diffusion at higher temperatures, molecular reorientational motion of both cation and anion groups at intermediate temperatures and quantum rotational tunneling of the ammonium group at lower temperatures have been observed. Nuclear magnetic resonance (NMR) relaxation time results correlate well with the NMR second moment and conductivity studies reported earlier

Study of molecular reorientation and quantum rotational tunneling in tetramethylammonium selenate by 1H NMR

1H NMR spin-lattice relaxation time measurements have been carried out in [(CH3)4N]2SeO4 in the temperature range 389-6.6 K to understand the possible phase transitions, internal motions and quantum rotational tunneling. A broad T1 minimum observed around 280 K is attributed to the simultaneous motions of CH3 and (CH3)4N groups. Magnetization recovery is found to be stretched exponential below 72 K with varying stretched exponent. Low-temperature T1 behavior is interpreted in terms of methyl groups undergoing quantum rotational tunneling. © 2007 Elsevier Inc. All rights reserved

H-1 NMR study of internal motions and quantum rotational tunneling in (CH3)(4)NGeCl3

(CH3)(4)NGeCl3 is prepared, characterized and studied using H-1 NMR spin lattice relaxation time and second moment to understand the internal motions and quantum rotational tunneling. Proton second moment is measured at 7 MHz as function of temperature in the range 300-77 K and spin lattice relaxation time (T-1) is measured at two Larmor frequencies, as a function of temperature in the range 270-17 K employing a homemade wide-line/pulsed NMR spectrometers. T-1 data are analyzed in two temperature regions using relevant theoretical models. The relaxation in the higher temperatures (270-115 K) is attributed to the hindered reorientations of symmetric groups (CH3 and (CH3)(4)N). Broad asymmetric T-1 minima observed below 115 K down to 17 K are attributed to quantum rotational tunneling of the inequivalent methyl groups. Copyright (c) 2007 John Wiley & Sons, Ltd

Cartoon Noir: A Comparative Study of Visual Parody

American film parody can be characterized as a distorted, comical and yet affectionate imitation of a given genre or specific work. Film noir as a genre with its distinct visual styles has been an easy target for such "creative criticism." Mel Brooks, famous for his series of successful parody films, has exhorted that the situation alone must be absurd while the actors must be serious, not funny to make a comedy funnier. He also said that funny is in the writing and not in the performance itself. Film noir through its unconventional visual styles and convoluted story lines engenders feelings of anxiety and paranoia in the audience, providing rich fodder for parody. The animated theatrical series Looney Tunes with its trademark slapstick style is well suited for making serious situations look absurd, affording "creative criticism". In this thesis I first analyze canonical examples to distill the distinct visual characteristics of these two different genres. I then employ the use of parody to bring together a few salient visual elements from each of these genres, thus enabling computer-generated visual parody. Finally, still image examples of such parody are produced by systematically combining visual elements from the two distinct genres, film noir for its expressionistic lighting and elliptical compositional elements, and Looney Tunes for its mischievous mise-en-scene and ingenuous characters

Study of molecular dynamics and cross relaxation in tetramethylammonium hexafluorophosphate (CH3)4NPF6 by 1H and 19F NMR

(CH3)4NPF6 is studied by NMR measurements to understand the internal motions and cross relaxation mechanism between the heterogeneous nuclei. The spin lattice relaxation times (T1) are measured for 1H and 19F nuclei, at three (11.4, 16.1 and 21.34 MHz) Larmor frequencies in the temperature range 350-50 K and 1H NMR second moment measurements at 7 MHz in the temperature range 300-100 K employing home made pulsed and wide-line NMR spectrometers. 1H NMR results are attributed to the simultaneous reorientations of both methyl and tetramethylammonium groups and motional parameters are evaluated. 19F NMR results are attributed to cross relaxation between proton and fluorine and motional parameters for the PF6 group reorientation are evaluated. © 2008 Elsevier Inc. All rights reserved

An efficient reconfigurable code rate cooperative low-density parity check codes for gigabits wide code encoder/decoder operations

In recent days, extensive digital communication process has been performed. Due to this phenomenon, a proper maintenance of authentication, communication without any overhead such as signal attenuation code rate fluctuations during digital communication process can be minimized and optimized by adopting parallel encoder and decoder operations. To overcome the above-mentioned drawbacks by using proposed reconfigurable code rate cooperative (RCRC) and low-density parity check (LDPC) method. The proposed RCRC-LDPC is capable to operate over gigabits/sec data and it effectively performs linear encoding, dual diagonal form, widens the range of code rate and optimal degree distribution of LDPC mother code. The proposed method optimize the transmission rate and it is capable to operate on 0.98 code rate. It is the highest upper bounded code rate as compared to the existing methods. The proposed method optimizes the transmission rate and is capable to operate on a 0.98 code rate. It is the highest upper bounded code rate as compared to the existing methods. the proposed method's implementation has been carried out using MATLAB and as per the simulation result, the proposed method is capable of reaching a throughput efficiency greater than 8.2 (1.9) gigabits per second with a clock frequency of 160 MHz

Preferential stiffness and the crack-tip fields of an elastic porous solid based on the density-dependent moduli model

In this paper, we study the preferential stiffness and the crack-tip fields for an elastic porous solid of which material properties are dependent upon the density. Such a description is necessary to describe the failure that can be caused by damaged pores in many porous bodies such as ceramics, concrete and human bones. To that end, we revisit a new class of implicit constitutive relations under the assumption of small deformation. Although the constitutive relationship \textit{appears linear} in both the Cauchy stress and linearized strain, the governing equation bestowed from the balance of linear momentum results in a quasi-linear partial differential equation (PDE) system. For the linearization and obtaining a sequence of elliptic PDEs, we propose the solution algorithm comprise a \textit{Newton\u27s method} coupled with a bilinear continuous Galerkin-type finite elements for the discretization. Our algorithm exhibits an optimal rate of convergence for a manufactured solution. In the numerical experiments, we set the boundary value problems (BVPs) with edge crack {under different modes of loading (i.e., the pure mode-I, II, and the mixed-mode). From the numerical results, we find that the density-dependent moduli model describes diverse phenomena that are not captured within the framework of classical linearized elasticity. In particular,numerical solutions clearly indicate that the nonlinear \textit{modeling} parameter depending on its sign and magnitude can control preferential mechanical stiffness along with the change of volumetric strain; larger the parameter is in the positive value}, the responses are such that the strength of porous solid gets weaker against the tensile loading while stiffer against the in-plane shear (or compressive) loading, which is vice versa for the negative value of it

Efficient Noise Filtration of Images by Low-Rank Singular Vector Approximations of Geodesics' Gramian Matrix

Modern society is interested in capturing high-resolution and fine-quality images due to the surge of sophisticated cameras. However, the noise contamination in the images not only inferior people's expectations but also conversely affects the subsequent processes if such images are utilized in computer vision tasks such as remote sensing, object tracking, etc. Even though noise filtration plays an essential role, real-time processing of a high-resolution image is limited by the hardware limitations of the image-capturing instruments. Geodesic Gramian Denoising (GGD) is a manifold-based noise filtering method that we introduced in our past research which utilizes a few prominent singular vectors of the geodesics' Gramian matrix for the noise filtering process. The applicability of GDD is limited as it encounters $\mathcal{O}(n^6)$ when denoising a given image of size $n\times n$ since GGD computes the prominent singular vectors of a $n^2 \times n^2$ data matrix that is implemented by singular value decomposition (SVD). In this research, we increase the efficiency of our GGD framework by replacing its SVD step with four diverse singular vector approximation techniques. Here, we compare both the computational time and the noise filtering performance between the four techniques integrated into GGD.Comment: 19 pages, 3 figures, submitted to ACM Transactions on Architecture and Code Optimizatio