Browsing by Author "Park, Saehan"
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Item The Interface Region Imaging Spectrograph (IRIS)(2014-02) De Pontieu, Bart; Title, Alan M.; Lemen, James; Kushner, G.D.; Akin, D.J.; Allard, A.; Berger, T.; Boerner, P.; Cheung, M.; Chou, C.; Drake, J.F.; Duncan, D.W.; Freeland, S.; Heyman, G.F.; Hoffman, C.; Hurlburt, Neal E.; Lindgren, R.W.; Mathur, D.; Rehse, R.; Sabolish, D.; Seguin, R.; Schrijver, C.J.; Tarbell, Ted D.; Wülser, J.P.; Wolfson, C.J.; Yanari, C.; Mudge, J.; Nguyen-Phuc, N.; Timmons, R.; van Bezooijen, R.; Weingrod, I.; Brookner, R.; Butcher, G.; Dougherty, B.; Eder, J.; Knagenhjelm, V.; Larsen, S.; Mansir, D.; Phan, L.; Boyle, P.; Cheimets, P.N.; DeLuca, E.E.; Golub, Leon; Gates, R.; Hertz, E.; McKillop, Sean; Park, Saehan; Perry, T.; Podgorski, W.A.; Reeves, Kathy K.; Saar, Steven; Testa, Paola; Tian, Hui; Weber, Mark A.; Dunn, C.; Eccles, S.; Jaeggli, Sarah; Kankelborg, Charles; Mashburn, K.; Pust, Nathan J.; Springer, LarryThe Interface Region Imaging Spectrograph (IRIS) small explorer spacecraft provides simultaneous spectra and images of the photosphere, chromosphere, transition region, and corona with 0.33 0.4 arcsec spatial resolution, twosecond temporal resolution, and 1 km s1 velocity resolution over a fieldofview of up to 175 arcsec × 175 arcsec. IRIS was launched into a Sunsynchronous orbit on 27 June 2013 using a PegasusXL rocket and consists of a 19cm UV telescope that feeds a slitbased dualbandpass imaging spectrograph. IRIS obtains spectra in passbands from 1332 1358 Å, 1389 1407 Å, and 2783 2834 Å, including bright spectral lines formed in the chromosphere (Mg ii h 2803 Å and Mg ii k 2796 Å) and transition region (C ii 1334/1335 Å and Si iv 1394/1403 Å). Slitjaw images in four different passbands (C ii 1330, Si iv 1400, Mg ii k 2796, and Mg ii wing 2830 Å) can be taken simultaneously with spectral rasters that sample regions up to 130 arcsec × 175 arcsec at a variety of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to emission from plasma at temperatures between 5000 K and 10 MK and will advance our understanding of the flow of mass and energy through an interface region, formed by the chromosphere and transition region, between the photosphere and corona. This highly structured and dynamic region not only acts as the conduit of all mass and energy feeding into the corona and solar wind, it also requires an order of magnitude more energy to heat than the corona and solar wind combined. The IRIS investigation includes a strong numerical modeling component based on advanced radiativeMHD codes to facilitate interpretation of observations of this complex region. Approximately eight Gbytes of data (after compression) are acquired by IRIS each day and made available for unrestricted use within a few days of the observation.Item Persulfate oxidation of MTBE- and chloroform-spent granular activated carbon(2011-09) Huling, S. G.; Ko, S.; Park, Saehan; Kan, E.Activated persulfate (Na2S2O8) regeneration of methyl tert-butyl ether (MTBE) and chloroform-spent GAC was evaluated in this study. Thermal-activation of persulfate was effective and resulted in greater MTBE removal than either alkaline-activation or H2O2–persulfate binary mixtures. H2O2 may serve multiple roles in oxidation mechanisms including Fenton-driven oxidation, and indirect activation of persulfate through thermal or ferrous iron activation mechanisms. More frequent, lower volume applications of persulfate solution (i.e., the persulfate loading rate), higher solid/solution ratio (g GAC mL−1 solution), and higher persulfate concentration (mass loading) resulted in greater MTBE oxidation and removal. Chloroform oxidation was more effective in URV GAC compared to F400 GAC. This study provides baseline conditions that can be used to optimize pilot-scale persulfate-driven regeneration of contaminant-spent GAC.Item Reducing the risk of well bore leakage using engineered biomineralization barriers(2011-04) Cunningham, Alfred B.; Gerlach, Robin; Spangler, Lee H.; Mitchell, Andrew C.; Park, Saehan; Phillips, Adrienne J.If CO2 is injected in deep geological formations it is important that the receiving formation hassufficient porosity and permeability for storage and transmission and be overlain by a suitable low-permeability cap rock formation. When the resulting CO2 plume encounters a well bore, leakage may occur through various pathways in the “disturbed zone†surrounding the well casing. Gasda et al.[9], propose a method for determining effective well bore permeability from a field pressure test. If permeability results from such tests prove unacceptably large, strategies for in situ mitigation of potential leakage pathways become important. To be effective, leakage mitigation methods must block leakage pathways on timescales longer than the plume will be mobile, be able to be delivered without causing well screen plugging, and be resistant to supercritical CO2 (ScCO2) challenges. Traditional mitigation uses cement, a viscous fluid that requires a large enough aperture for delivery and that also must bond to the surrounding surfaces in order to be effective. Technologies that can be delivered via low viscosity fluids and that can effectively plug small aperture pathways, or even the porous rock surrounding the well could have significant advantages for some leakage scenarios.We propose a microbially mediated method for plugging preferential leakage pathways and/or porous media, thereby lowering the risk of unwanted upward migration of CO2, similar to thatdiscussed by Mitchell et al.[12].We examine the concept of using engineered microbial biofilms which are capable of precipitating crystalline calcium carbonate using the process of ureolysis. The resulting combination of biofilm plus mineral deposits, if targeted near points of CO2 injection, may result in the long-term sealing of preferential leakage pathways. Successful development of these biologically-based concepts could result in a CO2 leakage mitigation technology which can be applied either before CO2 injection or as a remedial measure. Results from laboratory column studies are presented which illustrate how biomineralization deposits can be developed along packed sand columns at length scales of 2.54 cm and 61 cm. Strategies for controlling mineral deposition of uniform thickness along the axis of flow are also discussed.