Bulletin of the American Physical Society
2017 Annual Spring Meeting of the APS Ohio-Region Section
Volume 62, Number 6
Friday–Saturday, May 5–6, 2017; Ypsilanti, Michigan
Session B6: Contributed Posters: General |
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Chair: Ernest Behringer, Eastern Michigan University Room: Pray-Harrold 221 |
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B6.00001: Tackling the Numerical Sign Problem: Complex Langevin Method Applied to the 2-D Repulsive Hubbard Model Mitchell Young One of the major unsolved dilemmas in physics today is the numerical sign problem. The sign problem involves the difficulty in numerically evaluating integrals of highly oscillatory multi-dimensional functions, plaguing many fields of physics from lattice QCD to condensed matter physics. For many particle systems, this generally occurs in the calculation of functional integrals without a positive definite measure. In this case, standard methods such as Monte Carlo Integration cannot be applied since the measure can no longer be interpreted as a probability distribution. One of the most promising approaches for tackling this sign problem is the Complex Langevin Method, which involves drawing the entire problem into the complex plane and evolving the solution according to the complex Langevin equation. Here we present the results of applying the Complex Langevin Method to the 2-D repulsive Hubbard model, the archetypal model for studying strongly interacting fermionic systems which exhibits the sign problem in the repulsive case. [Preview Abstract] |
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B6.00002: Molecular Mechanics of Bacterial Adhesion in the Dental Bacteria Biofilm Chai Rin Kim, Jehun Shin, Richard Kyung The cause of periodontal disease and dental caries is fundamentally different from other diseases caused by single pathogenic microorganisms. Oral fluids and small molecules make their way into enamel by slowly diffusing through a thin membrane, pellicle. If prophylaxis displaces pellicle, then pellicle immediately changes its form. Taking approximately seven days, pellicle incorporates bacterial elements and develops its reduced, mature structure. Examination of the plaque site determines either bacterial accumulation on teeth or bacterial removal. This paper examines the molecular mechanisms of bacterial adhesion in the dental bacteria biofilm. In this paper, a computational model displays the interaction of bacterial protein's side chain of a phenylalanine component through hydrophobic bonding with a salivary glycoprotein's side chain component in the acquired pellicle. In addition, electrostatic attraction explains the phenomenon of a bacterial protein's negatively charged carboxyl group being attracted to a positively charged calcium ion. Applying the attraction force, the salivary phosphoprotein's negatively charged phosphate group in the acquired pellicle is attracted to the calcium ion. [Preview Abstract] |
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B6.00003: Thermodynamic and Electrostatic Analysis of Flavonol and Tocopherol Analogues in Anti-Aging Products Yoojin Cho, Richard Kyung This research examined various physical electrostatic interactions and chemical conformations of the anti-aging products due to their ability to deactivate Reactive Oxidation Species (ROS) in the cells. ROS is highly reactive, causing cell's structural and genetic configurations which lead to cell aging or disease. By using the agents that can reduce ROS, cell aging can be delayed significantly. Examining stereo-chemistry and performing computational analysis of thermodynamic stability help determine which of the components in anti-aging antioxidants are most effective. In this research, the enthalpy and chemical safety of anti-aging antioxidants, such as flavonol, flavonoid, and other vitamin E derivatives were studied by calculating and analyzing the molecules’ thermodynamic stability. The thermodynamic stability was determined by using stereochemical analysis and calculating optimized enthalpy of the molecules. In addition, VES and α-TEA were investigated as vitamin E component together with enthalpies of tocopherols and tocotrienols. In this paper, Density Functional Theory (DFT) was used to assess the molecules’ electron properties. [Preview Abstract] |
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B6.00004: A Study about the steady-state regime on rotating compressible fluids and its application on a diffraction problem. Erick Muino-Garcia, Jose Marin-Antuna We develop a general study about the steady-state regime on rotating compressible fluids. We deduce an equation for the amplitude of the stabilized oscillations, and we obtain its fundamental solution. We establish the non-stationary problem for the field of velocities generated by the diffraction of an acoustic wave in a finite barrier within a rotating compressible fluid. We also solve analytically this problem and we study its behavior when the time tends to infinity. Then we apply the previously developed theory for the steady-state regime to obtain the mentioned field of velocities for big times, and by this way we obtain that the system reaches a steady-state regime and we verify that the same expressions of the limit amplitude are obtained. [Preview Abstract] |
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B6.00005: Runout Transition Bidimensional Dumbbell-Like Rock Avalanches Luis Armando Torres-Cisneros, Gabriel Perez-Angel, Yuri Nahmad-Molinari, Roberto Bartali, Gustavo Manuel Rodriguez-Linan Experimentally is found that a flow composed by monodisperse sample of rocks, for sizes ranging from 1mm to 2cm show an exponentially increasing behavior in runout vs particles size plot. Furthermore we show that this tendence is independent of the amount of falling matter, when it falls from the same heigth. Moreover we show using two-dimensional molecular-dynamics simulations, that the runout changes with the amount of matter falling, and there is a change from an exponentially increasing function to a constant one when we multiply by two the total mass, and multiplying again the total mass by two results in an exponentially decreasing behavior. This shows a well defined transition in the runout vs particle size plot when we increase the amount of matter in the flowing avalanche. The main hypothesis to explain this contradictory result is that the change of transversal length when the flow pass from the flume to the floor zone is not reproducible in a 2D simulation. We also characterize the flow computing the energy and the power dissipated. [Preview Abstract] |
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B6.00006: Impedance Spectroscopy Analysis of Fe doped Sr0.98Zn0.02TiO3 Ceramic Powders at Room Temperature Hemalatha B Rudramadevi, J Guravamma Fe doped Sr0.98Zn0.02TiO3 (Sr0.98 Zn0.02 Ti (1-x) Fe x O3) (x = 0.1) ceramics were prepared by standard solid-state reaction method. The structural and morphological properties of the ceramics were characterized by the XRD and SEM-EDS. The XRD results confirmed that the cubic structure of the host SrZnTiO3 and Fe doped Sr0.98Zn0.02TiO3 ceramic powders. The dielectric properties of these samples have also been measured as a function of frequency in the range of 1Hz – 1MHz at room temperature. The dielectric constant ($\epsilon$) and tangent loss (tan $\delta$) of all the samples are decreases while increasing the AC conductivity ($\sigma$ac) as a function of frequency. The cole-cole plots of all the samples studied show the bulk resistance (Rb) is decreasing with an increasing the concentration. The dc conductivity ($\sigma$dc) of all the samples increasing while increasing the Fe concentration. Improved conductivity values make them distinctive as potential materials in the fields of spintronics, electro ceramic applications, electromagnetic sensors, transducers and multiple state memory elements. Key words: Sr0.98Zn0.02TiO3, XRD, dielectric measurements, dc conductivity [Preview Abstract] |
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B6.00007: Thin film deposition using rarefied gas jet Dr. Sahadev Pradhan The rarefied gas jet of aluminium is studied at Mach number \textit{Ma }$=$\textit{ (U\textunderscore j / }$\backslash $\textit{sqrt\textbraceleft kb T\textunderscore j / m\textbraceright )}in the range \textit{.01 \textless Ma \textless 2}, and Knudsen number \textit{Kn }$=$\textit{ (1 / (}$\backslash $\textit{sqrt\textbraceleft 2\textbraceright }$\backslash $\textit{pi d\textasciicircum 2 n\textunderscore d H)} in the range \textit{.01 \textless Kn \textless 15}, using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations, to understand the flow phenomena and deposition mechanisms in a physical vapor deposition (PVD) process for the development of the highly oriented pure metallic aluminum thin film with uniform thickness and strong adhesion on the surface of the substrate in the form of ionic plasma, so that the substrate can be protected from corrosion and oxidation and thereby enhance the lifetime and safety, and to introduce the desired surface properties for a given application. Here, $H$is the characteristic dimension, \textit{U\textunderscore j}and \textit{T\textunderscore j}are the jet velocity and temperature, \textit{n\textunderscore d}is the number density of the jet, $m$and $d$ are the molecular mass and diameter, and \textit{kb}is the Boltzmann constant. An important finding is that the capture width (cross-section of the gas jet deposited on the substrate) is symmetric around the centerline of the substrate, and decreases with increased Mach number due to an increase in the momentum of the gas molecules. DSMC simulation results reveals that at low Knudsen number \textit{((Kn }$=$\textit{ 0.01);}shorter mean free paths), the atoms experience more collisions, which direct them toward the substrate. However, the atoms also move with lower momentum at low Mach number$,$which allows scattering collisions to rapidly direct the atoms to the substrate. [Preview Abstract] |
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B6.00008: Analysis of high-speed rotating flow inside gas centrifuge casing Dr. Sahadev Pradhan The generalized analytical model for the radial boundary layer inside the gas centrifuge casing in which the inner cylinder is rotating at a constant angular velocity $\Omega $\textit{\textunderscore i}while the outer one is stationary, is formulated for studying the secondary gas flow field due to wall thermal forcing, inflow/outflow of light gas along the boundaries, as well as due to the combination of the above two external forcing. The analytical model includes the sixth order differential equation for the radial boundary layer at the cylindrical curved surface in terms of master potential ($\chi )$, which is derived from the equations of motion in an axisymmetric $(r - z)$plane. The linearization approximation is used, where the equations of motion are truncated at linear order in the velocity and pressure disturbances to the base flow, which is a solid-body rotation. Additional approximations in the analytical model include constant temperature in the base state (isothermal compressible Couette flow), high aspect ratio (length is large compared to the annular gap), high Reynolds number, but there is no limitation on the Mach number. The discrete eigenvalues and eigenfunctions of the linear operators (sixth-order in the radial direction for the generalized analytical equation) are obtained. The solutions for the secondary flow is determined in terms of these eigenvalues and eigenfunctions. These solutions are compared with direct simulation Monte Carlo (DSMC) simulations and found excellent agreement (with a difference of less than 15{\%}) between the predictions of the analytical model and the DSMC simulations, provided the boundary conditions in the analytical model are accurately specified. [Preview Abstract] |
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B6.00009: Binary gas mixture in a high speed channel Dr. Sahadev Pradhan The viscous, compressible flow in a 2D wall-bounded channel, with bottom wall moving in the positive $x-$direction, simulated using the direct simulation Monte Carlo (DSMC) method, has been used as a test bed for examining different aspects of flow phenomenon and separation performance of a binary gas mixture at Mach number \textit{Ma }$=$\textit{ (U\textunderscore w / }$\backslash $\textit{sqrt(}$\gamma $\textit{ k\textunderscore B T\textunderscore w /m)) }in the range\textit{0.1 \textless Ma \textless 30}, and Knudsen number \textit{Kn }$=$\textit{ 1/(}$\backslash $\textit{sqrt(2) }$\pi $\textit{ d\textasciicircum 2 n\textunderscore d H)}in the range \textit{.1 \textless Kn \textless 10}. The generalized analytical model is formulated which includes the fifth order differential equation for the boundary layer at the channel wall in terms of master potential ($\chi )$, which is derived from the equations of motion in a 2D rectangular $(x - y)$coordinate. The starting point of the analytical model is the Navier-Stokes, mass, momentum and energy conservation equations in the $(x - y)$coordinate, where $x$and $y$are the streamwise and wall-normal directions, respectively. The linearization approximation is used ((Pradhan {\&} Kumaran\textit{, J. Fluid Mech -}); (Kumaran {\&} Pradhan, \textit{J. Fluid Mech -})), where the equations of motion are truncated at linear order in the velocity and pressure perturbations to the base flow, which is anisothermal compressible Couette flow. Additional assumptions in the analytical model include high aspect ratio \textit{(L \textgreater \textgreater H)}, constant temperature in the base state (isothermal condition), and low Reynolds number (laminar flow). The analytical solutionsare compared with direct simulation Monte Carlo (DSMC) simulations and found good agreement (with a difference of less than 10{\%}), provided the boundary conditions are accurately incorporated in the analytical solution. [Preview Abstract] |
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B6.00010: DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number Dr. Sahadev Pradhan The flow over a 2D leading-edge flat plate is studied at Mach number \textit{Ma }$= (U_{inf}/ \backslash $\textit{sqrt\textbraceleft k}$_{B}T_{inf}$\textit{/ m\textbraceright ) }in the range \textit{\textless Ma \textless 10}, and at Reynolds number number \textit{Re }$= (L_{T} U_{inf}$\textit{ rho}$_{inf\thinspace }$\textit{)/ mu}$_{inf\thinspace }$ equal to 10$^{\mathrm{\thinspace \thinspace }}$using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations to understand the flow phenomena of the leading-edge flat plate boundary layer at high Mach number. Here, $L_{T}$is the characteristic dimension, $U_{inf}$and $T_{inf}$are the free stream velocity and temperature, \textit{rho}$_{inf}$ is the free stream density, $m$is the molecular mass, \textit{mu}$_{inf\thinspace }$is the molecular viscosity based on the free stream temperature $T_{inf},$and $k_{B}$is the Boltzmann constant. The variation of streamwise velocity, temperature, number-density, and mean free path along the wall normal direction away from the plate surface is studied. The qualitative nature of the streamwise velocity at high Mach number is similar to those in the incompressible limit (parabolic profile). However, there are important differences. The amplitudes of the streamwise velocity increase as the Mach number increases and turned into a more flatter profile near the wall. There is significant velocity and temperature slip ((Pradhan and Kumaran, J. Fluid Mech-2011); (Kumaran and Pradhan, J. Fluid Mech-2014)) at the surface of the plate, and the slip increases as the Mach number is increased. It is interesting to note that for the highest Mach numbers considered here, the streamwise velocity at the wall exceeds the sound speed, and the flow is supersonic throughout the flow domain. [Preview Abstract] |
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B6.00011: DSMC Simulations of High Mach Number Taylor-Couette Flow Dr. Sahadev Pradhan The main focus of this work is to characterise the Taylor-Couette flow of an ideal gas between two coaxial cylinders at Mach number \textit{Ma }$=$\textit{ (U\textunderscore w / }$\backslash $\textit{sqrt\textbraceleft kb T\textunderscore w / m\textbraceright )}in the range 0.01 \textless Ma \textless , and Knudsen number \textit{Kn }$=$\textit{ (1 / (}$\backslash $\textit{sqrt\textbraceleft 2\textbraceright }$\backslash $\textit{pi d\textasciicircum 2 n\textunderscore d (r\textunderscore 2 - r\textunderscore 1))) }in the range 0.001 \textless Kn \textless , using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations. Here, \textit{r\textunderscore 1}and \textit{r\textunderscore 2}are the radius of inner and outer cylinder respectively, \textit{U\textunderscore w}is the circumferential wall velocity of the inner cylinder, \textit{T\textunderscore w}is the isothermal wall temperature, \textit{n\textunderscore d}is the number density of the gas molecules, $m$and $d$ are the molecular mass and diameter, and \textit{kb}is the Boltzmann constant. The cylindrical surfaces are specified as being diffusely reflecting with the thermal accommodation coefficient equal to one. In the present analysis of high Mach number compressible Taylor-Couette flow using DSMC method, wall slip in the temperature and the velocities are found to be significant. Slip occurs because the temperature/velocity of the molecules incident on the wall could be very different from that of the wall, even though the temperature/velocity of the reflected molecules is equal to that of the wall. Due to the high surface speed of the inner cylinder, significant heating of the gas is taking place. The gas temperature increases until the heat transfer to the surface equals the work done in moving the surface. The highest temperature is obtained near the moving surface of the inner cylinder at a radius of about (1.26 r\textunderscore 1). [Preview Abstract] |
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B6.00012: Neutrosophy and Physics Florentin Smarandache, Victor Christianto Using Neutrosophy, some known paradoxes in Quantum Physics could be solved in unique way. Some other neutrosophical predictions could find their way in experiments. It is known that there are numerous applications of Multi-Valued logic, which have become part of daily numerical tools for hardware designers and programmers alike. It is not difficult to expect that in the near future, applications of Neutrosophic Logic will also be found in the same way now electronic designers have made use Fuzzy Logic of L. Zadeh. In recent years, a few physicists have suggested that biological systems could be represented using Multi-Valued-logic. Therefore, it is very likely that study of Quantum Physics of biological systems will also find Neutrosophic Logic useful. Furthermore, it is also likely that Multi-Valued logic in particular Neutrosophy will improve various other branches of science, which have used mathematical methods extensively. [Preview Abstract] |
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B6.00013: Quantum potential Florentin Smarandache, Victor Christianto One of the deep questions related to the physical meaning of wavefunction of the Schr\"{o}dinger equation is whether there is neat linkage between Schr\"{o}dinger equation and classical wave dynamics. In other words, whether there is coherent picture to describe electron from these different approaches: quantum wave dynamics and classical electrodynamics. This question remains open for discussion, in particular in the context of plausible analogue between classical electrodynamics and non-local quantum interference effect, in particular via Aharonov effect. Hofer has also argued in the same direction, noting that it is possible to find physical meaning of wavefunction in classical electrodynamics sense. One could expect to find a neat link between Schr\"{o}dinger equation and classical wave dynamics. Another way to put forth the idea is to preserve that `particles' mean particles, regardless we use classical dynamics method or Schr\"{o}dinger equation; this lead us to introduce the `quantum potential' term. [Preview Abstract] |
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