Session B10: SPS Undergraduate Research I

Which String Breaks? Revisited

Many have seen the common introductory physics demonstration in which a heavy ball hangs from a string, with another identical string hanging freely from the ball. When the instructor pulls the bottom string slowly, the top string breaks. However, when the instructor pulls the bottom string very rapidly, the bottom string breaks. This simple experiment is used to demonstrate inertia and Newton's laws. In The Physics Teacher of November 1996, there is an article in which the authors create a model of this problem in an attempt to explain the outcomes quantitatively. However, their analysis gave strange results. Using an improved model, I will show that the results of this demonstration can be obtained using only simple calculations.   

Synchronization effects in chaotic oscillators with spatially dependent frequency mismatch

We investigate the phenomena of synchronization for two coupled chaotic oscillators with a frequency mismatch which is explicitly spatially dependent. We compute the frequency synchronization plot in the parameter space of coupling strength and frequency mismatch of the chaotic system. We find regimes where the system is frequency locked corresponding to a synchronous state and regimes of non-synchronous state. In the non-synchronous state the frequencies are either zero individually (quenched oscillations) or the difference between them is non-zero. We also find that the region with oscillation quenching is reduced compared to the case when the frequency mismatch is a constant.   

Rolling vs. Sliding: The inclusion of non-conservative work in the classic comparison

If a rolling and sliding object, each of the same material, were to race down the same incline plane, which would win? Last year, we presented a theoretical model with confirming experimental data which showed that the winning object depends on the angle, the effective coefficient of friction, C, and kinetic coefficients of friction: If C $< \quad \mu _{k\_block}$, the rolling object is faster, but if C $> \quad \mu _{k\_block}$, the sliding object is faster. Though the materials were the same, we previously reported that the $\mu _{s\_sphere }$was apparently not equal to $\mu _{s\_block}$. This year, we are directly determining the coefficients of friction using a force sensor, seeking to resolve this apparent discrepancy. We plan to report more accurate values of $\mu _{s\_sphere }$and $\mu _{s\_block}$ and, if they are found to be different, explain why. Steps will be taken to improve track uniformity. We will more precisely determine the transition angle, where the block becomes faster than the sphere, by taking data at smaller angular increments. In addition, we will incorporate results for rolling \textit{with} slipping, as it is expected that as slipping increases, so will linear velocity, as less energy is lost to rotational kinetic energy. Beyond this, we hope to extend the model to different geometries (with different moments of inertia).   

Is Ball Milling An Innovative Technique For the Production of Zn From ZnO?

The process of mechanical alloying using ball milling transfers mechanical energy to reactants in powder form, causing the particle size of the reactant powders to be reduced until defects in the lattice structure of the reactants are created. For reactions of sufficient exothermicity, this facilitates a complete mechanochemical reaction through self-heat propagating synthesis (SHS). The oxide reduction reaction of ZnO with Al, which yields pure Zn as a product, cannot be induced using ball milling alone because of its low exothermicity. This study used a systematic combination of ball milling and annealing in order to induce the reaction. Parameters tested were milling time, annealing time, and annealing temperature with the purpose of establishing the importance of each of these variables in inducing a complete reaction in the sample. The completeness of the reaction was determined using XRD analysis and inspection with an optical microscope. Results confirmed that neither ball milling nor heat treatment could induce the reaction individually; only ball milling followed by annealing could cause the reaction to take place. This study suggests that using ball milling in conjunction with heat treatment can produce Zn from ZnO in a less costly, more efficient, and less wasteful manner than traditional methods.   

Women in Physics: an Analysis of the Gender Gap

It is not a surprise that the number of women in physics is not impressive, and the reasons are diverse and well-known [1]. We conducted several surveys at SUNY Oswego regarding the gender gap. We examined the source of the problem and we developed possible solutions. We propose herein various strategies for short-term and long-term improvement of female representation in Physics. This insight will hopefully benefit other physics departments in which women are underrepresented. \\[4pt] [1] Rachel Ivie and Katie Stowe. June 2000. Women in Physics, 2000, AIP Publication Number R-430.   

STAIRSTEP -- a research-oriented program for undergraduate students at Lamar University

The relative low number of undergraduate STEM students in many science disciplines, and in particular in physics, represents a major concern for our faculty and the administration at Lamar University. Therefore, a collaborative effort between several science programs, including computer science, chemistry, geology, mathematics and physics was set up with the goal of increasing the number of science majors and to minimize the retention rate. Lamar's Student Advancing through Involvement in Research Student Talent Expansion Program (STAIRSTEP) is a NSF-DUE sponsored program designed to motivate STEM students to graduate with a science degree from one of these five disciplines by involving them in state-of-the-art research projects and various outreach activities organized on-campus or in road shows at the secondary and high schools [1]. The physics program offers hands-on experience in optics, such as computer-based experiments for studying the diffraction and interference of light incident on nettings or electronic wave packets incident on crystals, with applications in optical imaging, electron microscopy, and crystallography. The impact of the various activities done in STAIRSTEP on our Physics Program will be discussed. [1] Doerschuk P, Bahrim C, Daniel J, Kruger J, Mann J, and Martin Ch, \textit{39th ASEE/IEEE Frontiers in Education Conference,}\textbf{ }San Antonio 2009, M3F-1-2.   

Modeling Surface Acoustic Waves on Liquid Loaded Surfaces

Ultrasound excitation of crystals creates acoustic waves that propagate on the surface. The wave velocities vary with directions based on the properties of the crystal. Experiments typically use ultrasound transducers submerged in water. The water loading on the surface creates a perpendicular stress. This alters the boundary conditions of the surface waves, changing their propagation. We model the phase and group velocities of Rayleigh surface waves on water loaded Si (100) and CaWO$_{4}$. The addition of water loaded boundary conditions improves the match between model and experimental data.   

Characterization of a MEMS Actuator through Simulation

Simulations of a laterally shifting micro-electro-mechanical-system (MEMS) were performed to characterize the device for use in liquid $^{3}$He experimentation. Using the multiphysics software COMSOL, we were able to identify the relevant electrostatic and mechanical properties of our device, as well as its various vibrational modes. When actuated with a DC voltage, simulations demonstrated comparatively large out-of-plane displacements, which are in agreement with optical measurements taken from the actual device. New simulations were performed to test the effectiveness of possible efforts to dampen this displacement. Using the data collected from these simulations, future generations of the MEMS will be designed and improved for use in liquid $^{3}$He experiments.   

Scanning Tunneling Microscopy of Manganites

We have built a scanning tunneling microscope (STM) which employs a mechanical coarse approach mechanism. We have tested the mechanical and electronic components of the system and calibrated the piezoelectric scanning mechanism by imaging highly ordered pyrolytic graphite (HOPG) at room temperature. Atomic resolution HOPG images were obtained when the STM was placed inside a vibration isolated liquid helium dewar. We have also scanned single crystals and thin-films of hole-doped manganese oxides (manganites) and obtained images on the scale of about 100 nm to about 10 nm. After obtaining satisfactory images at room temperature, we will cool the apparatus first down to liquid nitrogen temperature (77 K) and then down to liquid helium temperature (4.2 K) to investigate micrometer and nanometer scale phase separation in manganites.   

Magnetic field dependence on neutrino-induced electron-positron creation rates

The study of neutrino processes in magnetic fields are immensely important for astrophysical phenomena where neutrino interactions are the dominant mode of energy loss and large fields exist. In this talk I will present a phenomenological relationship for the production rate of one such process, the creation of electron-positron pairs $\nu \to \nu \ e \ \bar{e}$, as a function of the magnetic field. I will show that above the critical magnetic field strength and at large neutrino energies there exists a power law dependence on the magnetic field.   

Emergent magnetic monopoles and their dynamics in artificial spin ice

Electrically charged particles such as electrons are common in our world. In contrast, no elementary particles with a net \textit{magnetic }charge have ever been observed. After a recent discovery that magnetic monopoles can emerge in a system of magnetic dipoles [1], much attention has been paid to the behavior of magnetic monopoles in artificial spin ice, arrays of nano-scale magnetic islands or wires that mimic the behavior of geometrically frustrated materials [2]. We have developed a theoretical model of magnetization dynamics in artificial spin ice under the action of an external magnetic field [3]. Magnetization reversal is mediated by the creation, propagation and absorption of domain walls carrying two units of magnetic. Domain walls are emitted from lattice junctions when the local field becomes large enough to overcome the Coulomb attraction between the magnetic charges of the domain wall and the junction. This interaction is also responsible for a positive feedback that triggers magnetic avalanches observed experimentally in artificial spin ice. \\[4pt] [1] C. Castelnovo, R. Moessner, and S. L. Sondhi, Nature \textbf{451}, 42 (2008). \\[0pt] [2] O. Tchernyshyov, Nat. Phys. \textbf{6}, 323 (2010). \\[0pt] [3] P. Mellado, O. Petrova, Y. Shen, and O. Tchernyshyov, Phys. Rev. Lett. \textbf{105}, 187206 (2010).   

Antihydrogen Production in a Paul Trap

We investigate the dynamics of anti-hydrogen production within a Paul trap through computational means with the intent to develop a strategy for confining the anti-atom for further experimentation. We obtained first preliminary results on the transient production of anti-hydrogen. We present these results, discuss the experimental implementation of our system, and suggest ways to lengthen the lifetime of anti-hydrogen in the trap.   

Effects of interactions on interference pattern formed after release and expansion of two identical Bose-Einstein condensates

We numerically simulate the expansion and interference of two adjacent, identical Bose-Einstein condensates initially trapped by harmonic potentials. We use explicit finite-difference methods to solve the Gross-Pitaevskii equation and time-evolve the condensates. We repeat the simulation, varying the interaction strength of the condensates, and analyze how the interactions affect the time-evolution of the interference pattern.   

Search for an Entanglement Measure for N-Qubit States via Phase Symmetry

While quantitative measures of entanglement exist for two-qubit systems, there are no equivalent measures for larger systems. Phase patterns within multi-qubit density matrices could yield clues to constructing quantitative measures for these larger systems. One such pattern within the N-qubit density matrix is observed by reordering the matrix according to the types of coherence terms in the first row and first column so the number of phases in each element increases from left to right in the first row, and from top to bottom in the first column. The resultant matrix contains blocks on its diagonal with elements having only bipartite entanglement. All remaining diagonal elements are part of GHZ-type states in this configuration. A benefit to this matrix structuring is the ability to apply concurrence, a measure of two-qubit entanglement, to the sub-matrix blocks formed on the diagonal. Exploring the meaning of these concurrences with regard to the entanglement of the whole system of N-qubits represented by the full density matrix is a possible next step toward finding a measure of N-qubit entanglement.   

Plasmon Enhancement of Organic Solar Cells using Embossed Gratings

Organic photovoltaic cells (OPV) are attractive because of their low cost and easy fabrication. However, because the diffusion length of excitons in most organic photovoltaic material is about 100 nm, the overall thickness and therefore the optical absorbance of the device is limited, reducing the overall efficiency. Surface plasmon excitations have been studied as a possible mechanism to increase the absorption of light in solar cell active layers because of their ability to manipulate and enhance local electromagnetic fields. This work focuses on using metal gratings as one electrode. Gratings support a broad range of surface plasmons that can be tuned by changing the incident angle of light, making them ideal to isolate the contribution of surface plasmons to increases in the quantum efficiency of solar cells. OPV cells are made using a conjugated polymer and fullerene-based active layer with either an aluminum or silver bottom electrode patterned with a grating through microcontact printing. By measuring the efficiency of the solar cells as a function of both incident angle and wavelength, we can match increases in efficiency with specific surface plasmon modes.