Bulletin of the American Physical Society
Spring 2021 Meeting of the APS New England Section
Volume 66, Number 4
Friday–Saturday, April 16–17, 2021; Virtual; Eastern Daylight Time
Session A04: Poster Presentations I (3:30-4:30 PM, EDT) |
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A04.00001: Physical Processes Affecting the Electrical Conductivity of Liquid Crystals David Webb, Yuriy Garbovskiy Both display and non-display applications of thermotropic liquid crystals rely on an applied electric field influencing the orientation of anisotropic molecules. Small quantities of ions are typically present in liquid crystals and can alter the effect of the electric field. For example, a common screening effect can occur where the electric field induced by the ions diminishes the strength of the applied electric field. Therefore, an understanding of ion-related effects in liquid crystals is critical for the development of advanced liquid crystal devices. Measuring DC conductivity yields important information about the effect of ions on the behavior of molecular liquid crystals. An interpretation of the DC electrical conductivity data requires reasonable approximations. As a rule, a single type of dominant ions or two symmetric ions of the same mobility are assumed. In this presentation, the effects of several types of ions (characterized by different values of their mobility and interacting with substrates) on the measured DC electrical conductivity of liquid crystals are discussed. The substrates of the liquid crystal cell and their important role in ionic processes is also considered. . [Preview Abstract] |
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A04.00002: Nobel Prize for Lithium-Ion Battery: Electric Vehicles to Save our Planet. Paul Carr Whittingham, Goodenough, and Yoshino won the 2019 Nobel Prize for the now ubiquitous Lithium-Ion battery. In 1993, Whittingham's battery at Exxon had an inflammable lithium metal anode and a Lithium Titanium Disulfide cathode. This cathode intercalates Lithium ions between its layered structure, making the battery rechargeable. John Goodenough, who had researched magnetic oxides at the MIT Lincoln Laboratory, replaced the cathode with Lithium Cobalt Oxide, increasing the voltage from 2 to 4 volts. Yoshino used a non-flammable petroleum coke anode. In 1991, Sony commercialized Yoshino's battery for personal electronic devices. The cost of lithium batteries has decreased by more than a factor of six, making electric vehicles (EVs) viable for saving our planet. Electric motors have an order of magnitude lower moving parts and are more than twice as efficient as internal combustion engines. The equivalent gas mileage of EVs is over 100 miles per gallon. EVs have a quiet acceleration of at 0 to 60 miles/hour in less than 5 seconds, making them fun to drive. The EV range is now 250 to 400 miles. [Preview Abstract] |
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A04.00003: Using Ground-Based Particulate Matter Measurements from a PA-II Dual Laser Air Sensor to Estimate Aerosol Optical Depth Marcus Alcantara Silva, Alicja Urbanczyk, Nimmi Sharma Quantifying the aerosol optical depth (AOD) is important for a wide variety of applications such as studying correlations between air quality and adverse health effects and determining visibility of a particular area. Central Connecticut State University conducted a study to see if particulate matter data obtained using an inexpensive direct sampling sensor at ground level could be used to provide an estimate of the AOD in the region over time. In the study, data were obtained using a PA-II-SD air quality sensor manufactured by PurpleAir. As the air passes thru the sensor, laser light scattering is used to measure particulate matter of various sizes (1, 2.5, and 10 microns). Data were collected every 2 minutes for many days. These measurements provide particulate loading in the atmosphere at ground level. AOD is a total atmospheric column property, thus assumptions of uniform convective mixing in the atmospheric boundary layer and height of the boundary layer (where most aerosols reside) are needed to estimate AOD from the measurements. Balloon-borne radiosonde data launched from regionally nearby sites were used to estimate boundary layer height on the days data were collected, and AOD estimates were derived. The average derived AOD were compared to AOD estimates from satellites and ground-based photometers using data obtained from MODIS and AERONET. [Preview Abstract] |
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A04.00004: Study on the Time-scale Separation in Communities Networks with Consensus Dynamics Richard Kyung, Hyungsoon Henry Kim In this paper, dynamics, time-scales and communities were studied using graph theory. Simulations were performed by writing a code to simulate consensus dynamics on a network, and verify that the dynamics asymptotically converges towards a constant state. Adjacency matrix (unweighted) of a structured network with random groups was discussed in this research to study the consensus dynamics on this network which displays a time-scale separation. The presented code showed a plot of the vector set and x(t) and they converged to the average value after sufficient time steps. In contrast to the normal patterns, a greater time-scale separation was observed. This was because there were many less edges connecting the different communities: intuitively meaning the communities have less of an effect on each other, or that to have an effect it will take much more time. Increasing the number of random edges between communities— i.e. the magnitude of the perturbation to the adjacency matrix of the three separate communities—will reduce the time-scale separation, making it so that the communities reach the same consensus value at a certain time. Results show that until around t = 0:05, approximate consensus is reached within each group, then a consensus is reached between the groups. [Preview Abstract] |
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