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Search Results: 1 - 10 of 35763 matches for " Min-Su Hyon "
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Structural Analysis of Offshore Cofferdam Subjected to Wave Load and Suction Pressure  [PDF]
Jeongsoo Kim, Youn-Ju Jeong, Min-Su Park, Sunghoon Song
Open Journal of Civil Engineering (OJCE) , 2018, DOI: 10.4236/ojce.2018.84040
Abstract: This study presented a novel circular cofferdam for offshore bridges consisting of ring segments and investigated its structural behaviors using ANSYS Mechanical. Because the bottom segment of the cofferdam which has a double sleeve cross-section was installed by suction, contact behaviors of the cofferdam wall and the lid plate during installation are important for design and the behaviors were also analyzed. Prior to numerical investigation of the bottom segment and complete cofferdam after dewatering, a suction modeling for structural analysis was proposed and evaluate by seepage analysis. Hydrodynamic loads applied to the cofferdam were also evaluated using panel method based on the potential flow theory. Through numerical analyses, structural behaviors of the cofferdam during installation were then investigated. First, contact behaviors between the lid plate and the wall were analyzed using different contact conditions imposed on the interface. Sharp stress increases were shown while the stress jumps were limited to contact area. Next, structural behaviors were investigated by considering seepage pressure. Using an axisymmetric seepage model, the total water pressure considering seepage was estimated and applied to structural analysis. The analysis results showed that strong effects of seepage on the stress change in cofferdam occurred and the seepage effects are necessary to be considered in design of the cofferdam induced by suction.
Ram pressure stripping in elliptical galaxies: II. magnetic field effects
Min-Su Shin,Mateusz Ruszkowski
Physics , 2014, DOI: 10.1093/mnras/stu1909
Abstract: We investigate the effects of magnetic fields and turbulence on ram pressure stripping in elliptical galaxies using ideal magnetohydrodynamics simulations. We consider weakly-magnetised interstellar medium (ISM) characterised by subsonic turbulence, and two orientations of the magnetic fields in the intracluster medium (ICM) - parallel and perpendicular to the direction of the galaxy motion through the ICM. While the stronger turbulence enhances the ram pressure stripping mass loss, the magnetic fields tend to suppress the stripping rates, and the suppression is stronger for parallel fields. However, the effect of magnetic fields on the mass stripping rate is mild. Nevertheless, the morphology of the stripping tails depends significantly on the direction of the ICM magnetic field. The effect of the magnetic field geometry on the tail morphology is much stronger than that of the level of the ISM turbulence. The tail has a highly collimated shape for parallel fields, while it has a sheet-like morphology in the plane of the ICM magnetic field for perpendicular fields. The magnetic field in the tail is amplified irrespectively of the orientation of the ICM field. More strongly magnetised regions in the ram pressure stripping tails are expected to have systematically higher metallicity due to the strong concentration of the stripped ISM than the less magnetised regions. Strong dependence of the morphology of the stripped ISM on the magnetic field could potentially be used to constrain the relative orientation of the ram pressure direction and the dominant component of the ICM magnetic field.
Ram pressure stripping in elliptical galaxies: I. the impact of the interstellar medium turbulence
Min-Su Shin,Mateusz Ruszkowski
Physics , 2012, DOI: 10.1093/mnras/sts071
Abstract: Elliptical galaxies contain X-ray emitting gas that is subject to continuous ram pressure stripping over timescales comparable to cluster ages. The gas in these galaxies is not in perfect hydrostatic equilibrium. Supernova feedback, stellar winds, or active galactic nuclei (AGN) feedback can significantly perturb the interstellar medium (ISM). Using hydrodynamical simulations, we investigate the effect of subsonic turbulence in the hot ISM on the ram pressure stripping process in early-type galaxies. We find that galaxies with more turbulent ISM produce longer, wider, and more smoothly distributed tails of the stripped ISM than those characterised by weaker ISM turbulence. Our main conclusion is that even very weak internal turbulence, at the level of <15% of the average ISM sound speed, can significantly accelerate the gas removal from galaxies via ram pressure stripping. The magnitude of this effect increases sharply with the strength of turbulence. As most of the gas stripping takes place near the boundary between the ISM and the intraclustermedium (ICM), the boost in the ISM stripping rate is due to the "random walk" of the ISM from the central regions of the galactic potential well to larger distances, where the ram pressure is able to permanently remove the gas from galaxies. The ICM can be temporarily trapped inside the galactic potential well due to the mixing of the turbulent ISM with the ICM. The galaxies with more turbulent ISM, yet still characterised by very weak turbulence, can hold larger amounts of the ICM. [Abridged]
Detecting Variability in Massive Astronomical Time-Series Data I: application of an infinite Gaussian mixture model
Min-Su Shin,Michael Sekora,Yong-Ik Byun
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.15576.x
Abstract: We present a new framework to detect various types of variable objects within massive astronomical time-series data. Assuming that the dominant population of objects is non-variable, we find outliers from this population by using a non-parametric Bayesian clustering algorithm based on an infinite GaussianMixtureModel (GMM) and the Dirichlet Process. The algorithm extracts information from a given dataset, which is described by six variability indices. The GMM uses those variability indices to recover clusters that are described by six-dimensional multivariate Gaussian distributions, allowing our approach to consider the sampling pattern of time-series data, systematic biases, the number of data points for each light curve, and photometric quality. Using the Northern Sky Variability Survey data, we test our approach and prove that the infinite GMM is useful at detecting variable objects, while providing statistical inference estimation that suppresses false detection. The proposed approach will be effective in the exploration of future surveys such as GAIA, Pan-Starrs, and LSST, which will produce massive time-series data.
Feedback from central black holes in elliptical galaxies. II: Can purely mechanical energy feedback models work?
Min-Su Shin,Jeremiah P. Ostriker,Luca Ciotti
Physics , 2009, DOI: 10.1088/0004-637X/711/1/268
Abstract: By using high-resolution 1D hydrodynamical simulations, we investigate the effects of purely mechanical feedback from super massive black holes (SMBHs) in the evolution of elliptical galaxies for a broad range of feedback efficiencies and compare the results to four major observational constraints. In particular, we focus on 1) the central black hole to stellar mass ratio of the host galaxy, 2) the lifetime of the luminous quasar phase, 3) the mass of stars formed in the host galaxy within the last Gyr, and 4) the X-ray luminosity of the hot diffuse gas. As a result, we try to pin down the most successful range of mechanical feedback efficiencies. We find that while low feedback efficiencies result in too much growth of the SMBH, high efficiencies totally blow out the hot interstellar gas, and the models are characterized by very low thermal X-ray luminosity well below the observed range. The net lifetime of the quasar phase is strongly coupled to the mass ratio between SMBH and its host galaxy, while the X-ray luminosity is generally correlated to the recent star formation within the last Gyr. When considering the popularly adopted model of the constant feedback efficiency, the feedback energy deposited into the ambient medium should be more than 0.01% of the SMBH accretion energy to be consistent with the SMBH mass to stellar mass ratio in the local universe. Yet, the X-ray luminosity of the hot gas favors about 0.005% of the accretion energy as the mechanical AGN feedback energy. We conclude that the purely mechanical feedback mode is unlikely to be simultaneously compatible with all four observable tests, even allowing a broad range of feedback efficiencies, and that including both radiative and mechanical feedback together may be a solution to comply the observational constraints. [abridged]
Environmental effects on the growth of super massive black holes and AGN feedback
Min-Su Shin,Jeremiah P. Ostriker,Luca Ciotti
Physics , 2010, DOI: 10.1088/0004-637X/745/1/13
Abstract: We investigate how environmental effects by gas stripping alter the growth of a super massive black hole (SMBH) and its host galaxy evolution, by means of 1D hydrodynamical simulations that include both mechanical and radiative AGN feedback effects. By changing the truncation radius of the gas distribution (R_t), beyond which gas stripping is assumed to be effective, we simulate possible environments for satellite and central galaxies in galaxy clusters and groups. The continuous escape of gas outside the truncation radius strongly suppresses star formation, while the growth of the SMBH is less affected by gas stripping because the SMBH accretion is primarily ruled by the density of the central region. As we allow for increasing environmental effects - the truncation radius decreasing from about 410 to 50 kpc - we find that the final SMBH mass declines from about 10^9 to 8 x 10^8 Msol, but the outflowing mass is roughly constant at about 2 x 10^10 Msol. There are larger change in the mass of stars formed, which declines from about 2 x 10^10 to 2 x 10^9 Msol, and the final thermal X-ray gas, which declines from about 10^9 to 5 x 10^8 Msol, with increasing environmental stripping. Most dramatic is the decline in the total time that the objects would be seen as quasars, which declines from 52 Myr (for R_t = 377 kpc) to 7.9 Myr (for R_t = 51 kpc). The typical case might be interpreted as a red and dead galaxy having episodic cooling flows followed by AGN feedback effects resulting in temporary transitions of the overall galaxy color from red to green or to blue, with (cluster) central galaxies spending a much larger fraction of their time in the elevated state than do satellite galaxies.(Abridged)
Radio Emission and AGN Feedback in Post-starburst Galaxies
Min-Su Shin,Michael A. Strauss,Rita Tojeiro
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.17541.x
Abstract: We investigate radio-mode AGN activity among post-starburst galaxies from the Sloan Digital Sky Survey to determine whether AGN feedback may be responsible for the cessation of star formation. Based on radio morphology and radio-loudness from the FIRST and NVSS data, we separate objects with radio activity due to an AGN from ongoing residual star formation. Of 513 SDSS galaxies with strong A-star spectra, 12 objects have 21-cm flux density above 1 mJy. These galaxies do not show optical AGN emission lines. Considering that the lifetime of radio emission is much shorter than the typical time-scale of the spectroscopic features of post-starburst galaxies, we conclude that the radio-emitting AGN activity in these objects was triggered after the end of the recent starburst, and thus cannot be an important feedback process to explain the post-starburst phase. The radio luminosities show a positive correlation with total galaxy stellar mass, but not with the mass of recently formed stars. Thus the mechanical power of AGN feedback derived from the radio luminosity is related to old stellar populations dominating the stellar mass, which in turn are related to the masses of central supermassive black holes.
Efficacies of the new Paclitaxel-eluting Coroflex Please? Stent in percutaneous coronary intervention; comparison of efficacy between Coroflex Please? and Taxus? (ECO-PLEASANT) trial: study rationale and design
Jae-Bin Seo, Hui-Kyung Jeon, Kyung-Woo Park, Jong-Seon Park, Jang-Ho Bae, Sang-Wook Kim, Keon-Woong Moon, Jae-Woong Choi, Sang-Gon Lee, Woo-Young Chung, Tae-Jin Youn, Soo-Joong Kim, Doo-Il Kim, Byung-Ok Kim, Min-Su Hyon, Keum-Soo Park, Tae-Joon Cha, Hweung-Kon Hwang, Seung-Ho Hur, Hyo-Soo Kim
Trials , 2009, DOI: 10.1186/1745-6215-10-98
Abstract: In the comparison of Efficacy between COroflex PLEASe? ANd Taxus? stent(ECO-PLEASANT) trial, approximately 900 patients are being prospectively and randomly assigned to the either type of Coroflex Please? stent and Taxus Liberte? stent via web-based randomization. The primary endpoint is clinically driven target vessel revascularization at 9 months. The secondary endpoints include major cardiac adverse events, target vessel failure, stent thrombosis and angiographic efficacy endpoints.The ECO-PLEASANT trial is the study not yet performed to directly compare the efficacy and safety of the Coroflex Please? versus Taxus Liberte? stent. On the basis of this trial, we will be able to find out whether the Coroflex Please? stent is non-inferior to Taxus Liberte? stent or not.ClinicalTrials.gov number, NCT00699543.Previous randomized trials have shown the efficacy of a slow-release polymeric sirolimus-eluting stent (Cypher?, Cordis, Warren, NJ, USA), paclitaxel-eluting stent (Taxus?, Boston Scientific, Natick, MA, USA), and zotarolimus-eluting stent (Endeavor?, Medtronic, Minneapolis, MN, USA) over bare metal stents in reducing neointimal hyperplasia, late luminal loss, and angiographic restenosis leading to decreased target lesion revascularization [1-11] The Paclitaxel-eluting Coroflex Please? stent is a newly developed drug eluting stent using the Coroflex? stent platform combined with the drug paclitaxel contained in a polymer coating[12]In the PECOPS I, which was one-arm observational study, the results of Coroflex Please? stent were within the range of other Paclitaxel-eluting coronary stents [12,13] Compared with binary restenosis rate of 7.9% in Taxus IV trial, Coroflex? Please stent showed 7.8% of restenosis rate[7] The 3.1% of 30 day MACE rate is within the range of other trials with stents eluting Paclitaxel or Sirolimus. The 6 month MACE rates in PECOPS I were 8.0%, which was similar to 7.8%, and 8.5% in Taxus II MR and SR, respectively[6] In Taxus IV, 9 month f
Reliability of Reconstructed Breast Flap after Chemotherapy and Radiotherapy in Immediate Breast Reconstruction
Keun-Cheol Lee,Tae-Heon Kim,Su-Seong Park,Min-Su Kim
Archives of Plastic Surgery , 2012, DOI: http://dx.doi.org/10.5999/aps.2012.39.5.497
Abstract: Background Postmastectomy adjuvant therapy is used to prevent locoregional recurrenceand improve overall breast cancer specific survival rates. However, it can adversely affectthe cosmetic results of reconstruction. Therefore, the authors examined flap stability andpatients’ satisfaction with immediate breast reconstruction after adjuvant therapy.Methods We retrospectively reviewed the medical records of 204 patients from January2006 to November 2011. For complication rates, the authors categorized the patients whounderwent the immediate breast reconstruction into 4 groups: adjuvant chemotherapyand radiotherapy group, adjuvant chemotherapy only group, adjuvant radiotherapy onlygroup, and the group that did not undergo adjuvant therapy. For comparison of patients’satisfaction, the study was performed with an additional 16 patients who had undergonedelayed breast reconstruction.Results Regarding complication rates, the group that had undergone adjuvant therapyshowed no significant difference compared to the group that did not undergo adjuvanttherapy. In evaluating the patients’ satisfaction, there was no significant difference.Conclusions Even after adjuvant therapy, immediate breast reconstruction showed goodresults with respect to flap stability and patients’ satisfaction. Immediate breast reconstructionand adjuvant therapy is a safe and useful option for breast cancer patients.
Considerations for the Management of Cryptotia Based on the Experience of 34 Patients
Seok-Kwun Kim,Chung-Min Yoon,Myung-Hoon Kim,Min-Su Kim
Archives of Plastic Surgery , 2012, DOI: http://dx.doi.org/10.5999/aps.2012.39.6.601
Abstract: Background Cryptotia is a congenital ear deformity in which the upper pole appears buriedbeneath the mastoid skin. Cryptotia is a common auricular malformation among Asians. Theaim of this paper is to examine the surgical techniques for and complications of 34 cryptoticpatients.Methods Surgery was performed for 34 cryptotic deformities (January 2005 to January2012). Twenty-two patients (64.7%) were classified as having type I cryptotia, and 12 patients(37.5%) type II cryptotia. Among the type I cryptotia patients, 8 patients had mild deformityand 14 severe deformity. Among the type II cryptotia patients, 10 patients had mild deformityand 2 severe deformity.Results The mild deformities were corrected via Z-plasty, V-Y plasty, full-thickness skin graft,and transposition flap, while the severe deformities were corrected via cartilage graft orMedporfor the spread of cartilage adhesion of antihelix. There were two cases of reinvaginationin the autologous cartilage graft group. Implant exposure occurred with Medpor (two cases).There were two cases of hypertrophic scar on the previous surgical wound with Medpor. Therewere no complications in the 18 patients who had mild deformities.Conclusions The type I cryptotia patients had more severe deformities than the type IIcryptotia patients. As most of the type II cryptotia patients had only mild deformities, theirdeformities were corrected without using autologous conchal cartilage graft or Medpor,except for two patients. Through more case analyses, researchers should make an effort toidentify methods for recurrence and prevention of complication.
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