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Articles 1 - 19 of 19
Full-Text Articles in Physics
Quantifying Complex Systems Via Computational Fly Swarms, Troy Taylor
Quantifying Complex Systems Via Computational Fly Swarms, Troy Taylor
Senior Theses
Complexity is prevalent both in natural and in human-made systems, yet is not well understood quantitatively. Qualitatively, complexity describes a phenomena in which a system composed of individual pieces, each having simple interactions with one another, results in interesting bulk properties that would otherwise not exist. One example of a complex biological system is the bird flock, in particular, a starling murmuration. Starlings are known to move in the direction of their neighbors and avoid collisions with fellow starlings, but as a result of these simple movement choices, the flock as a whole tends to exhibit fluid-like movements and form …
Manufacturing And Testing The Permanent Magnet Linear Motor, Renjie Kang
Manufacturing And Testing The Permanent Magnet Linear Motor, Renjie Kang
Senior Theses
Controlled mechanical motion is vital in many useful applications in technology. Among them, linear motors have advantages over traditional rotating motors. In this work, we built a permanent magnet linear motor to test and measure its energy efficiency. A maximum 29% total energy efficiency, and 67% energy transfer rate, were detected. In addition, a C-shape support structure was added to the moving part in order to increase the moving accuracy. The tests show that, with the support structure, the fluctuation in the vertical direction decreases significantly, but the friction of the system slightly increases.
Thermodynamic Properties Of Black Holes, Geoffrey Schulthess
Thermodynamic Properties Of Black Holes, Geoffrey Schulthess
Physics Capstone Projects
Black Holes are some of the most mysterious objects in the known universe. In 1975, Stephen Hawking stated that Black Holes can behave as thermodynamical objects with a finite mass, spin, angular velocity, temperature, and entropy. This has been one of the most fascinating yet perplexing breakthroughs in our understanding of these strongly gravitating objects. In this context, the purpose of this research was to use Wolfram Mathematica to create a program that would calculate the thermodynamic properties of a black hole, given a certain metric.
Parameter Of Elastic Anisotropy In Bismuth Silicate Crystals, F.R. Akhmedjanov, U.A. Saidvaliev, U.U. Tukxtaev, J.T. Nazarov
Parameter Of Elastic Anisotropy In Bismuth Silicate Crystals, F.R. Akhmedjanov, U.A. Saidvaliev, U.U. Tukxtaev, J.T. Nazarov
Scientific Journal of Samarkand University
The elastic anisotropy parameter of noncentrosymmetric cubic crystals of bismuth silicate has been investigated. It is shown that they belong to crystals with the negative anisotropy of elastic moduli of the second order. Comparison of the experimental results with the values of the velocities of acoustic waves calculated through the introduced anisotropy parameter shows a good agreement.
Solutions For Fermi Questions, October 2014: Question 1: Accelerating The Flash; Question 2: Flashing Through The Air, Larry Weinstein
Solutions For Fermi Questions, October 2014: Question 1: Accelerating The Flash; Question 2: Flashing Through The Air, Larry Weinstein
Physics Faculty Publications
The article provides answers to questions including the amount of force needed by The Flash as he accelerates and amount of force needed by The Flash to run at constant velocity near the Earth's surface.
A Correlation-Based Optical Flowmeter For Enclosed Flows, Naiqian Zhang, Joseph S. Dvorak, Yali Zhang
A Correlation-Based Optical Flowmeter For Enclosed Flows, Naiqian Zhang, Joseph S. Dvorak, Yali Zhang
Biosystems and Agricultural Engineering Faculty Publications
A low-cost flowmeter would be very useful in a wide variety of monitoring situations. This article discusses the development of such a flowmeter based on optical components and its testing with water in an enclosed flow system. The sensor consisted of two sets of LEDs and phototransistors spaced 4 cm apart, monitoring the optical properties of the fluid at upstream and downstream locations, respectively. A small amount of dye was injected into the flow, which caused a change in the optical properties of the fluid at both locations. The time required for this change to move from the upstream to …
Velocity Plateaus In Traveling-Wave Electrophoresis, R. Correll, Boyd F. Edwards
Velocity Plateaus In Traveling-Wave Electrophoresis, R. Correll, Boyd F. Edwards
All Physics Faculty Publications
One-dimensional models are used to study traveling-wave electrophoresis, a tunable method for separating charged analytes. A traveling-electrode model reveals the mechanism for longitudinal oscillations. A stationary-electrode model explains the origin of mode-locked plateaus in the average velocity, predicts devil's staircases with nested Farey sequences, and reduces to a continuum sinusoidal model in the high electrode-density limit. © 2012 American Physical Society.
Approach To Accurately Measuring The Speed Of Optical Precursors, Chuan-Feng Li, Zong-Quan Zhou, Heejeong Jeong, Guang-Can Guo
Approach To Accurately Measuring The Speed Of Optical Precursors, Chuan-Feng Li, Zong-Quan Zhou, Heejeong Jeong, Guang-Can Guo
Dartmouth Scholarship
Precursors can serve as a bound on the speed of information with dispersive medium. We propose a method to identify the speed of optical wavefronts using polarization-based interference in a solid-state device, which can bound the accuracy of the speed of wavefronts to less than 10−4 with conventional experimental conditions. Our proposal may have important implications for optical communications and fast information processing.
Molecular Interaction Studies In Binary Mixtures Containing Aniline, Toluene And N-Butanol, Palaniappan Lakshmanan, Mahendran Govindasamy
Molecular Interaction Studies In Binary Mixtures Containing Aniline, Toluene And N-Butanol, Palaniappan Lakshmanan, Mahendran Govindasamy
Turkish Journal of Physics
Ultrasonic velocity and density values have been measured at 303 K in binary mixtures containing aniline, toluene and n-butanol; and the thermodynamical approach is applied to evaluate the mixtures' molar volume, adiabatic compressibility, intermolecular free length and excess values. The observed results are interpreted in terms of molecular interaction between the components of the mixtures. Observed excess values and their fittings of R-K type equations lend further support to the observation made in the binary system.
Convective Inertia Effects On The Squeeze Film Between Rectangular Parallel Plates, Sikiru Adigun Sanni
Convective Inertia Effects On The Squeeze Film Between Rectangular Parallel Plates, Sikiru Adigun Sanni
Turkish Journal of Physics
This paper investigates the effects of convective inertia on the lubricating characteristics of the squeeze film between parallel rectangular plates. Relaxing a simplifying assumption of the conventional lubrication theory, the paper retains some terms of the convective inertia terms of the Navier-Stokes equations, leading to a derivation of a modified Reynolds equation. The introduction of the convective inertia terms induces two inversely related dimensionless parameters, m and R (the Reynolds number), into the characteristics of the flow behavior. The dimensionless normal (or squeezing) velocity increases monotonically from the lower plate to the upper plate for given value of R. At …
Ultracold Neutral Plasma Expansion In Two Dimensions, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson
Ultracold Neutral Plasma Expansion In Two Dimensions, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson
Faculty Publications
An isothermal model of ultracold neutral plasma expansion is extended to systems without spherical symmetry. It is used to interpret new fluorescence measurements on ultracold neutral calcium plasmas. For a self-similar expansion, the fluid equations are solved both analytically and numerically. The density and velocity solutions are used to predict fluorescence signals induced by a laser beam weakly focused into the plasma. Despite the simplicity of the model, predicted fluorescence signals reproduce major features of the experimental data
Mechanism For Carrier Velocity Saturation In Pure Organic Crystals, Vasudev M. Kenkre, Paul Ernest Parris
Mechanism For Carrier Velocity Saturation In Pure Organic Crystals, Vasudev M. Kenkre, Paul Ernest Parris
Physics Faculty Research & Creative Works
We present a possible mechanism for the saturation of the velocity of photoinjected charge carriers in pure organic crystals, the analysis having been motivated by observations in pentacene. The mechanism is based on the strong wave vector dependence of the damping coefficient appearing in the appropriate effective mass equation. Our primary goal is to explore this mechanism in general terms rather than to apply it to a specific system such as pentacene. Our analysis is based on a Fokker-Planck equation treatment. We indicate how the damping coeffcient is related to relaxation times in usual Boltzmann equations and how it can …
Saturation Of Charge Carrier Velocity With Increasing Electric Fields: Theoretical Investigations For Pure Organic Crystals, Vasudev M. Kenkre, Paul Ernest Parris
Saturation Of Charge Carrier Velocity With Increasing Electric Fields: Theoretical Investigations For Pure Organic Crystals, Vasudev M. Kenkre, Paul Ernest Parris
Physics Faculty Research & Creative Works
Should one expect injected charge carrier velocities to saturate as the applied electric field is increased simply because of the nonparabolicity of bands? Does the apparent saturation observed in recent experiments in hydrocarbon crystals signify, as supposed in some current interpretations of the data, that the carrier motion is coherent or bandlike and that the disappearance of the saturation at higher temperatures is indicative of a crossover from coherent to incoherent motion? These questions are addressed with the help of general theoretical investigations involving Drude-like considerations, quantum kinetic equations, and a Fokker-Planck analysis.
The Lunar Tide In The Equatorial F Region Vertical Ion Drift Velocity, R. J. Stening, Bela G. Fejer
The Lunar Tide In The Equatorial F Region Vertical Ion Drift Velocity, R. J. Stening, Bela G. Fejer
Bela G. Fejer
Vertical ion drift velocity data from Jicamarca have been analyzed for a lunar semidiurnal tide using a least squares fitting method. Amplitudes of up to 6 m s−1 are obtained with phases in agreement with lunar tidal determinations of other associated physical parameters. Variations between season, solar activity, and day to night are also examined. Generally, amplitudes are larger in the southern summer. Much of the phase variation with season is very similar for solar maximum and minimum years. There is a summer to winter phase change that is most distinct at solar maximum nighttime. A day-to-night phase reversal can …
Concept Of Local Polaritons And Optical Properties Of Mixed Polar Crystals, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky
Concept Of Local Polaritons And Optical Properties Of Mixed Polar Crystals, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky
Physics Faculty Research & Creative Works
The concept of local polaritons is used to describe the optical properties of mixed crystals in the frequency region of their restrahlen band. It is shown that this concept allows for a physically transparent explanation of the presence of weak features in the spectra of so-called one-mode crystals and for one-two mode behavior. The previous models Were able to explain these features only with the use of many fitting parameters. We show that under certain Conditions new impurity-induced polariton modes may arise within the restrahlen of the host crystals, and study their dispersion laws and density of states. Particularly, we …
Effects Of The Vertical Plasma Drift Velocity On The Generation And Evolution Of Equatorial Spread F, Bela G. Fejer, L. Scherliess, E. R. De Paula
Effects Of The Vertical Plasma Drift Velocity On The Generation And Evolution Of Equatorial Spread F, Bela G. Fejer, L. Scherliess, E. R. De Paula
Bela G. Fejer
We use radar observations from the Jicamarca Observatory from 1968 to 1992 to study the effects of the F region vertical plasma drift velocity on the generation and evolution of equatorial spread F. The dependence of these irregularities on season, solar cycle, and magnetic activity can be explained as resulting from the corresponding effects on the evening and nighttime vertical drifts. In the early night sector, the bottomside of the F layer is almost always unstable. The evolution of the unstable layer is controlled by the history of the vertical drift velocity. When the drift velocities are large enough, the …
Displacement, Velocity, And Frames Of Reference: Phenomenographic Studies Of Students’ Understanding And Some Implications For Teaching And Assessment, John Bowden, Gloria Dall'alba, Elaine Martin, D Laurillard, Ference Marton, Geoff Masters, Paul Ramsden, Andrew Stephanou, E Walsh
Displacement, Velocity, And Frames Of Reference: Phenomenographic Studies Of Students’ Understanding And Some Implications For Teaching And Assessment, John Bowden, Gloria Dall'alba, Elaine Martin, D Laurillard, Ference Marton, Geoff Masters, Paul Ramsden, Andrew Stephanou, E Walsh
Prof Geoff Masters AO
Student understanding of fundamental concepts in kinematics has been explored using the phenomenographic research method. University and high schoolphysics students were interviewed and their understandings of displacement, velocity, and frames of reference have been analyzed in particular problem contexts. Descriptions of the different ways students understand the concepts have been developed and relations between the different levels of understanding have been identified. The data highlight the contextual nature of learning and the need for teachers to focus on the nature of student understanding in specific contexts using questions that require qualitative explanation by students. In particular, it is demonstrated that …
Directional And Dynamic Variations Ofauroral Power Spectra Related To The Ionospheric Electron Drift Velocity, E. Nielsen, C. I. Haldoupis, Bela G. Fejer, H. M. Ierkic
Directional And Dynamic Variations Ofauroral Power Spectra Related To The Ionospheric Electron Drift Velocity, E. Nielsen, C. I. Haldoupis, Bela G. Fejer, H. M. Ierkic
Bela G. Fejer
Power spectral observations of auroral electron density fluctuations with a scale length of nearly 1 m have been made with the STARE system (Scandinavian twin auroral radar experiment). Simultaneous measurements of the mean radial Doppler velocities were used to derive estimates of the ionospheric electron drift velocity. The data were analyzed to determine the spectral dependence on the magnitude and direction of the electron drift velocity. The two spectral types, characterized as “narrow” and “broad,” were observed simultaneously from the same scattering volume. The width of the broad spectrum (up to about 1200 Hz) can be at least 3 times …
Radar Studies Of Anomalousvelocity Reversals In The Equatorial Ionosphere, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Radar Studies Of Anomalousvelocity Reversals In The Equatorial Ionosphere, Bela G. Fejer, D. T. Farley, B. B. Balsley, R. F. Woodman
Bela G. Fejer
Radar observations made at Jicamarca show that the equatorial electrojet current and the E and F region electric fields can reverse from their normal direction during the day or night and during magnetically quiet or disturbed conditions. The nighttime reversals can only be detected by such radar measurements. The observations support most of the current hypotheses concerning the electrojet plasma instabilities. The rapid reversals sometimes seen during disturbed conditions indicate that high-latitude currents and electric fields associated with substorm activity strongly perturb the dynamo current system at all latitudes.