Browsing by Author "Kang, Hoyoung"
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Item Ghostly Stellar Halos in Dwarf Galaxies(2016-02-15) Kang, Hoyoung; Ricotti, Massimo; PhysicsOur study aims at probing the typical masses of the smallest and faintest galaxies that have ever formed in the universe. We carry out numerical simulations to characterize the size, stellar mass, and stellar mass surface density of stellar halos as a function of dark matter halo mass and a parameter that dictates the amount of stellar mass. We expect that for galaxies smaller than a critical value, these ghostly halos will not exist because the smaller galactic subunits that build it up, do not form any stars. Our results indicate the introduced parameter dominates the behaviors of stellar halos over dark matter mass. This indicates finding the appropriate parameter value is crucial to characterize these halos. We also find redshift contributes to the behavior of stellar mass but has no significant impact on the size of stellar halos.Item Laminar Free Convection from a Vertically-Oriented Concentrated Photovoltaic Cell with Uniform Surface Heat Flux(2013) Connolly, Jason; Fries, Kevin; Biswas, Sougata; Grant, Christopher; Hwang, Kevin; Kang, Hoyoung; Motabar, Donna; Carr, CharlieThis research project uses field measurements to investigate the cooling of a triple-junction, photovoltaic cell under natural convection when subjected to various amounts of insolation. The team built an experimental apparatus consisting of a mirror and Fresnel lens to concentrate light onto a triple-junction photovoltaic cell, mounted vertically on a copper heat sink. Measurements were taken year-round to provide a wide range of ambient conditions. A surface was then generated, in MATLAB, using Sparrow’s model for natural convection on a vertical plate under constant heat flux. This surface can be used to find the expected operating temperature of a cell at any location, given the ambient temperature and insolation. This research is an important contribution to the industry because it utilizes field data that represents how a cell would react under normal operation. It also extends the use of a well-known model from a one-sun environment to a multi-sun one.