Discovering the Value of Multidisciplinary Approaches to Research: Insights from a Sabbatical

In this informal report, I outline my research efforts, collaborations, and other experiences while participating in the Naval Research Laboratory (NRL)'s Advanced Graduate Research Program (AGRP), aka Sabbatical, from October 2008 through September 2009. This report is in no way intended to present the technical details of the various research projects, but rather a broad overview of the small ways my efforts may have contributed to ongoing research. I wish to convey to the reader the value of multidisciplinary approaches to scientific research and how the AGRP facilitates these opportunities.Comment: 13 pages, 5 figure

Thermal Roughening and Deroughening at Polymer Interfaces in Electrophoretic Deposition

Thermal scaling and relaxation of the interface width in an electrophoretic deposition of polymer chains is examined by a three-dimensional Monte Carlo simulation on a discrete lattice. Variation of the equilibrium interface width $W_r$ with the temperature $T$ shows deroughening $W_r \propto T^{-\delta}$, with $\delta \sim 1/4$, at low temperatures and roughening $W_r \propto T^{\nu}$, with $\nu \sim 0.4$ at high temperatures. The roughening-deroughening transition temperature $T_t$ increases with longer chain lengths and is reduced by using the slower segmental dynamics.Comment: This is a work of the U.S. Government and is not subject to copyright protection in the United States. Foreign copyrights may appl

Almost rolling motion: An investigation of rolling grooved cylinders

We examine the dynamics of cylinders that are grooved to form N teeth for rolling motion down an inclined plane. The grooved cylinders are experimentally found to reach a terminal velocity. This result can be explained by the inclusion of inelastic processes which occur whenever a tooth hits the surface. The fraction of the angular velocity that is lost during an inelastic collision is phenomenologically found to be proportional to (2*sin^2*pi/N)-(alpha*sin^3*pi/N), and the method of least squares is used to find the constant alpha=0.98. The adjusted theoretical results for the time of rolling as well as for terminal velocity are found to be in good agreement with the experimental results.Comment: 8 pages, 6 figures http://link.aip.org/link/?AJPIAS/66/202/

Density and conformation with relaxed substrate, bulk, and interface electrophoretic deposition of polymer chains

Characteristics of relaxed density profile and conformation of polymer chains are studied by a Monte Carlo simulation on a discrete lattice in three dimensions using different segmental (kink-jump $K$, crank-shaft $C$, reptation $R$) dynamics. Three distinct density regimes, substrate, bulk, and interface, are identified. With the $KC$ segmental dynamics we find that the substrate coverage grows with a power-law, $d_s \propto t^{\gamma}$ with a field dependent nonuniversal exponent $\gamma = 0.23 + 0.7 E$. The bulk volume fraction $d_b$ and the substrate polymer density ($d_s$) increases exponentially with the field ($d_b \propto E^{0.4}$, $d_s \propto E^{0.2}$) in the low field regime. The interface polymer density $d_f$ increases with the molecular weight. With the $KCR$ segmental dynamics, bulk and substrate density decreases linearly with the temperature at high temperatures. The bulk volume fraction is found to decay with the molecular weight, $d_b \propto L_c^{-0.11}$. The radius of gyration remains Gaussian in all density regions.Comment: Changed double to single spacin

A Q-Ising model application for linear-time image segmentation

A computational method is presented which efficiently segments digital grayscale images by directly applying the Q-state Ising (or Potts) model. Since the Potts model was first proposed in 1952, physicists have studied lattice models to gain deep insights into magnetism and other disordered systems. For some time, researchers have realized that digital images may be modeled in much the same way as these physical systems (i.e., as a square lattice of numerical values). A major drawback in using Potts model methods for image segmentation is that, with conventional methods, it processes in exponential time. Advances have been made via certain approximations to reduce the segmentation process to power-law time. However, in many applications (such as for sonar imagery), real-time processing requires much greater efficiency. This article contains a description of an energy minimization technique that applies four Potts (Q-Ising) models directly to the image and processes in linear time. The result is analogous to partitioning the system into regions of four classes of magnetism. This direct Potts segmentation technique is demonstrated on photographic, medical, and acoustic images.Comment: 7 pages, 8 figures, revtex, uses subfigure.sty. Central European Journal of Physics, in press (2010

Interface relaxation in electrophoretic deposition of polymer chains: Effects of segmental dynamics, molecular weight, and field

Using different segmental dynamics and relaxation, characteristics of the interface growth is examined in an electrophoretic deposition of polymer chains on a three (2+1) dimensional discrete lattice with a Monte Carlo simulation. Incorporation of faster modes such as crankshaft and reptation movements along with the relatively slow kink-jump dynamics seems crucial in relaxing the interface width. As the continuously released polymer chains are driven (via segmental movements) and deposited, the interface width $W$ grows with the number of time steps $t$, $W \propto t^{\beta},$ ($\beta \sim 0.4$--$0.8)$, which is followed by its saturation to a steady-state value $W_s$. Stopping the release of additional chains after saturation while continuing the segmental movements relaxes the saturated width to an equilibrium value ($W_s \to W_r$). Scaling of the relaxed interface width $W_r$ with the driving field $E$, $W_r \propto E^{-1/2}$ remains similar to that of the steady-state $W_s$ width. In contrast to monotonic increase of the steady-state width $W_s$, the relaxed interface width $W_r$ is found to decay (possibly as a stretched exponential) with the molecular weight.Comment: 5 pages, 7 figure

Density and Conformation with Relaxed Substrate, Bulk, and Interface in Electrophoretic Deposition of Polymer Chains

Characteristics of relaxed density profile and conformation of polymer chains are studied by a Monte Carlo simulation on a discrete lattice in three dimensions using different segmental (kink-jump (K), crank-shaft (C), reptation (R)) dynamics. Three distinct density regimes, substrate, bulk, and interface, are identified. With the KC segmental dynamics, we find that the substrate coverage grows with a power law, ds∝tγ with a field (E) dependent non-universal exponent γ=0.23+0.7E. The bulk volume fraction db and the substrate polymer density (ds) increases with the field with power-laws (db∝E0.4, ds∝E0.2) in the low field regime. The interface polymer density df increases with the molecular weight. With the KCR segmental dynamics, bulk and substrate density decreases linearly with the temperature at high temperatures. The bulk volume fraction is found to decay with the molecular weight, db∝Lc−0.11. The radius of gyration remains Gaussian in all density regions