Browsing by Author "Gavrin, Andrew"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Injection Current Modulated Parity-Time Symmetry in Coupled Semiconductor Lasers
    (2021-08) Thomas, Luke; Vemuri, Gautam; Gavrin, Andrew; Petrache, Horia; Wassall, Stephen
    This research investigates the characteristics of Parity Time symmetry breaking in two optically coupled, time delayed semiconductor lasers. A theoretical model is used to describe the controllable parameters in the experiment and intensity output of the coupled lasers. The PT parameters we control are the spatial separation between the two lasers, the frequency detuning, and the coupling strength. We find that the experimental data agrees with the predictions from the theoretical model confirming the intensity behaviors of the lasers, and the monotonic change in PT-threshold as a function of coupling scaled by the time delay
  • Thumbnail Image
    Item
    Preliminary efforts to evaluate an initiative introducing computation across the undergraduate physics curriculum
    (2021) Gavrin, Andrew; Vemuri, Gautam; Maric, Danka; Physics, School of Science
    We report our preliminary efforts to evaluate a departmental project: the inclusion of computational methods across our undergraduate curriculum. Our overarching goal is for students to consider computational approaches as a "normal" way to solve physics problems, on par with analytical approaches. In this paper, we focus on our efforts to evaluate the development of our students' attitudes and self-efficacy with respect to key computational methods. We describe our efforts to develop and deploy a survey instrument students complete each semester. This allows us to study, e.g., the points in the curriculum at which students gain confidence with particular methods, or adopt more expert-like attitudes regarding computation in general. We investigated the reliability of our instrument using a split-half process and found the Spearman-Brown coefficients for unequal length were r = 0.818, r = 0.895, and r = 0.917 for the three constructs in our survey. We also provide preliminary data from the early use of the survey and outline next steps for the project.
  • Thumbnail Image
    Item
    Short Range Probes to Extensions of the Standard Model
    (2023-08) Bsaibes, Thomas; Decca, Ricardo; Petrache, Horia; Cheng, Ruihua; Joglekar, Yogesh; Gavrin, Andrew; Michael, Snow
    As successful as the Standard Model has been in describing particle interactions, there are still many open questions it does not answer; the strong CP violation and the existence of dark matter among them. To address these issues many extensions to the Standard Model have been devised. Some of these extensions propose a new force mediating particle; a massive particle results in a potential described by a Yukawa-like interaction, while a massless exchange particle leads to power law type potentials. Limits on the strength of these interactions at the sub-micron range of separation between two particles are poorly characterized, but previous experiments conducted at IUPUI placed the best limits to date on the strength of a Yukawa-like interaction. Those experiments used a spherical test mass and a planar source mass. However, if a cylindrical test mass was used, the increased interaction volume of the cylinder would result in an increased sensitivity of about an order of magnitude over the spherical test mass experiment. Building such a system presents many challenges, namely the alignment of the cylinder with respect to the planar source mass. A capacitance based scheme to determine the alignment of a cylinder with respect to a plane will be discussed. The thesis concludes with an outline for a new type of measurement system. The new experiment attempts to induce a gravitational Π-pulse in a nanoshphere to probe extensions to the Standard Model.
  • Thumbnail Image
    Item
    Study of the Valence Tautomer Complex [Co(sq)(cat)(3-tpp)2] for Applications in Molecular Spintronics
    (2023-12) Phillips, Jared; Cheng, Ruihua; Gavrin, Andrew; Joglekar, Yogesh; Anasori, Babak; Kenning, Gregory
    Molecular materials exhibiting bistability between two states are intriguing candidates for next generation electronic devices. Two similar classes of materials, known as spin crossover (SCO) and valence tautomers (VT) respectively, are of particular interest due to their multifunctional properties, which are controllable via several external parameters, such as temperature, light irradiation, pressure, magnetic field, and electric field. In recent years, considerable research has been dedicated to better understanding the underlying principles that govern the behavior of these materials, so that their implementation into nano-based devices might be achieved. In this report, a systematic study of the valence tautomer molecule [Co(sq)(cat)(3-tpp)2] is presented. In the first chapter, the phenomenon of valence tautomerism (VT) occurring in coordination compounds is introduced and described from the perspective of Crystal Field Theory (CFT). Further, the molecular structure and physical properties of the [Co(sq)(cat)(3-tpp)2] molecule are explored. The properties of the ferroelectric material Polyvinylidene fluoride- hexafluoropropylene (PVDF-HFP), and the 2-D Mxene Ti3C2 are also discussed. The next section details equipment development and experimental methods. Thin films of VT molecules were prepared from solution via a drop-casting approach. For thin film analysis, we have developed a custom made, fully automated Vibrating Sample Magnetometer (VSM) with a sensitivity on the order of 1 × 10-5 emu, as well as a fully automated, variable temperature, under vacuum electron transport stage, and a magneto-optic Kerr effect apparatus (MOKE). Additional experimental methods used to characterize the VT thin films include X-ray Absorption Spectroscopy (XAS), UV-visible Spectrometry (UV-Vis) and Differential Scanning Calorimetry. Experimental results obtained from these techniques are discussed and analyzed in the third section. PVDF-HFP polarization dependent isothermal spin state switching of [Co(sq)(cat)(3-tpp)2] is also discussed as well as the effects of doping [Co(sq)(cat)(3-tpp)2] with Ti3C2, followed by a conclusion and an outline of future work.
  • Thumbnail Image
    Item
    Text Mining Online Discussions in an Introductory Physics Course
    (2018) Kelley, Patrick; Gavrin, Andrew; Lindell, Rebecca S.; Physics, School of Science
    We implemented a social networking platform called Course Networking (CN) in IUPUI’s introductory calculus based mechanics course and recorded three semesters of online discussions. We used the Syuzhet package in R to evaluate sentiment in the recorded discussions, and to quantify the incidence of eight basic emotions: anger, anticipation, disgust, fear, joy, sadness, surprise, and trust. We applied this text mining method to over nine thousand posts and replies to identify and analyze student sentiment during three semesters. We also investigated the variation of these emotions throughout the semester, the role played by the most vocal students as compared to the least frequent posters, and gender differences. With an abundance of students’ online discussions, text mining offers an expedient and automated means of analysis, providing a new window into students thinking and emotional state during semester-long physics courses