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Search Results: 1 - 10 of 1179 matches for " Chul Gwon "
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Physics of Solar Neutron Production: Questionable Detection of Neutrons from the 2007 December 31 Flare
Gerald H. Share,Ronald J. Murphy,Allan J. Tylka,Benz Kozlovsky,James M. Ryan,Chul Gwon
Physics , 2010, DOI: 10.1029/2010JA015930
Abstract: Spacecraft observations in the inner heliosphere offer the first opportunity to measure 1-10 MeV solar neutrons. We discuss the physics of low-energy neutron production in solar flares and show that, even at interacting-particle energies of 2 MeV/nucleon, neutrons with energies >10 MeV are produced. On the other hand, a significant fraction of 1-10 MeV neutrons result from interactions of >10 MeV/nucleon ions in typical flare spectra. We calculate the escaping neutron spectra for mono-energetic and power-law particle spectra at the Sun for the location and observation angle of MESSENGER at the time of its reported detection of low-energy neutrons associated with the 2007 December 31 solar flare. We detail concerns about this questionable observation of solar neutrons: 1. the inferred number of accelerated protons at the Sun for this modest M2-class flare was 10X larger than any flare observed to date, 2. the onset and duration of the 'solar' neutron count rate was similar to that of the solar energetic particles (SEPs), and 3. the authors' argument that the SEPs were dominated by electrons and so could not have produced the neutron counts locally in the spacecraft. In contrast we argue that solar energetic protons and alpha particles, through local neutron production and accidental coincidences, were the source of most of the reported 'solar-neutron' counts.
Remote Gaze Tracking System on a Large Display
Hyeon Chang Lee,Won Oh Lee,Chul Woo Cho,Su Yeong Gwon,Kang Ryoung Park,Heekyung Lee,Jihun Cha
Sensors , 2013, DOI: 10.3390/s131013439
Abstract: We propose a new remote gaze tracking system as an intelligent TV interface. Our research is novel in the following three ways: first, because a user can sit at various positions in front of a large display, the capture volume of the gaze tracking system should be greater, so the proposed system includes two cameras which can be moved simultaneously by panning and tilting mechanisms, a wide view camera (WVC) for detecting eye position and an auto-focusing narrow view camera (NVC) for capturing enlarged eye images. Second, in order to remove the complicated calibration between the WVC and NVC and to enhance the capture speed of the NVC, these two cameras are combined in a parallel structure. Third, the auto-focusing of the NVC is achieved on the basis of both the user’s facial width in the WVC image and a focus score calculated on the eye image of the NVC. Experimental results showed that the proposed system can be operated with a gaze tracking accuracy of ±0.737°~±0.775° and a speed of 5~10 frames/s.
Relationship between Insulin Resistance and Coronary Artery Calcium in Young Men and Women
Ki-Chul Sung, Jin-Ho Choi, Hyeon-Cheol Gwon, Seung-Hyuk Choi, Bum-Soo Kim, Hyon Joo Kwag, Sun H. Kim
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0053316
Abstract: Background The gender disparity in cardiovascular disease (CVD) risk is greatest between young men and women. However, the causes of that are not fully understood. The objective of this study was to evaluate the relationship between insulin resistance and the presence of coronary artery calcium (CAC) to identify risk factors that may predispose young men and women to CVD. Methodology/Principal Findings Insulin resistance and CVD risk factors were examined in 8682 Korean men and 1829 women aged 30–45 years old. Insulin resistance was estimated using the homeostasis model assessment of insulin resistance (HOMA-IR), and CAC was measured using computed tomography. Women were less likely to be insulin resistant (upper quartile of HOMA-IR, 18% vs. 27%, p<0.001) and had a lower prevalence of CAC (1.6% vs. 6.4%, p<0.001). Even when equally insulin resistant men and women were compared, women continued to have lower prevalence of CAC (3.1% vs. 7.2%, p = 0.004) and a more favorable CVD risk profile. Finally, after adjustment for traditional CVD risk factors, insulin resistance remained an independent predictor of CAC only in men (p = 0.03). Conclusions/Significance Young women have a lower risk for CVD and a lower CAC prevalence compared with men. This favorable CVD risk profile in women appears to occur regardless of insulin sensitivity. Unlike men, insulin resistance was not a predictor of CAC in women in this cohort. Therefore, insulin resistance has less impact on CVD risk and CAC in young women compared with men, and insulin resistance alone does not explain the gender disparity in CVD risk that is observed at an early age.
Multimodal sparse representation learning and applications
Miriam Cha,Youngjune Gwon,H. T. Kung
Computer Science , 2015,
Abstract: Unsupervised methods have proven effective for discriminative tasks in a single-modality scenario. In this paper, we present a multimodal framework for learning sparse representations that can capture semantic correlation between modalities. The framework can model relationships at a higher level by forcing the shared sparse representation. In particular, we propose the use of joint dictionary learning technique for sparse coding and formulate the joint representation for concision, cross-modal representations (in case of a missing modality), and union of the cross-modal representations. Given the accelerated growth of multimodal data posted on the Web such as YouTube, Wikipedia, and Twitter, learning good multimodal features is becoming increasingly important. We show that the shared representations enabled by our framework substantially improve the classification performance under both unimodal and multimodal settings. We further show how deep architectures built on the proposed framework are effective for the case of highly nonlinear correlations between modalities. The effectiveness of our approach is demonstrated experimentally in image denoising, multimedia event detection and retrieval on the TRECVID dataset (audio-video), category classification on the Wikipedia dataset (image-text), and sentiment classification on PhotoTweet (image-text).
AXTAR: Mission Design Concept
Paul S. Ray,Deepto Chakrabarty,Colleen A. Wilson-Hodge,Bernard F. Phlips,Ronald A. Remillard,Alan M. Levine,Kent S. Wood,Michael T. Wolff,Chul S. Gwon,Tod E. Strohmayer,Michael Baysinger,Michael S. Briggs,Peter Capizzo,Leo Fabisinski,Randall C. Hopkins,Linda S. Hornsby,Les Johnson,C. Dauphne Maples,Janie H. Miernik,Dan Thomas,Gianluigi De Geronimo
Physics , 2010, DOI: 10.1117/12.857385
Abstract: The Advanced X-ray Timing Array (AXTAR) is a mission concept for X-ray timing of compact objects that combines very large collecting area, broadband spectral coverage, high time resolution, highly flexible scheduling, and an ability to respond promptly to time-critical targets of opportunity. It is optimized for submillisecond timing of bright Galactic X-ray sources in order to study phenomena at the natural time scales of neutron star surfaces and black hole event horizons, thus probing the physics of ultradense matter, strongly curved spacetimes, and intense magnetic fields. AXTAR's main instrument, the Large Area Timing Array (LATA) is a collimated instrument with 2-50 keV coverage and over 3 square meters effective area. The LATA is made up of an array of supermodules that house 2-mm thick silicon pixel detectors. AXTAR will provide a significant improvement in effective area (a factor of 7 at 4 keV and a factor of 36 at 30 keV) over the RXTE PCA. AXTAR will also carry a sensitive Sky Monitor (SM) that acts as a trigger for pointed observations of X-ray transients in addition to providing high duty cycle monitoring of the X-ray sky. We review the science goals and technical concept for AXTAR and present results from a preliminary mission design study.
In vitro antagonistic potential of Streptomyces sp. AM-S1 against plant and human pathogens  [PDF]
Kandhasamy Sowndhararajan, Sun Chul Kang
Journal of Agricultural Chemistry and Environment (JACEN) , 2012, DOI: 10.4236/jacen.2012.11007
Abstract: In the present investigation, a total number of 132 different actinomycetes strains were isolated from the humus soil samples. Out of 132 isolates, 52 showed inhibitory activity against the fungal pathogen Rhizoctonia solani. Among the antagonists, the isolate designated as AM-S1 exhibited maximum inhibitory activity against the test pathogen R. solani (41 mm). Further, the light microscopic observations of the co-cultures showed severe structural alterations in the mycelia of R. solani near the zone of inhibition. The isolate AM-S1 was identified as Streptomyces sp. by morphological and 16S rDNA sequence analysis. The color of the aerial and substrate mycelia produced by the Streptomyces sp. AM-S1 varied with different media. The isolate Streptomyces sp. AM-S1 also effectively inhibited the growth of various plant and human pathogens. Further works are needed on optimization of this strain’s antagonistic activity, isolation and characterization of the antimicrobial metabolite.

Cognitive Profiles and Subtypes of Patients with Mild Cognitive Impairment: Data from a Clinical Follow-Up Study  [PDF]
Kyung Won Park, Eun-Joo Kim, Hwan Joo, Sung-Man Jeon, Seong-Ho Choi, Jay C. Kwon, Byoung Gwon Kim, Jae Woo Kim
International Journal of Clinical Medicine (IJCM) , 2012, DOI: 10.4236/ijcm.2012.35068
Abstract: Background: Mild cognitive impairment (MCI) is a heterogeneous condition with a variety of clinical outcomes, the presence of which correlates with risk of Alzheimer’s disease as well as pre-clinical stages of other dementia subtypes. The aims of this study were to assess the specific patterns of cognitive profiles and to identify changes from baseline to 24 weeks in patients with MCI using detailed neuropsychological testing. Methods: We consecutively recruited 120 MCI patients at baseline according to the Petersen’s clinical diagnostic criteria, who were admitted to the Dementia and Memory Clinics. We analyzed patients who fulfilled both inclusion and exclusion criteria for MCI and classified them into four subtypes according to deficits in major cognitive domains; amnestic MCI single domain (aMCI-s), amnestic multiple domain MCI (aMCI-m), non-amnestic single domain MCI (naMCI-s) and non-amnestic multiple domain MCI (naMCI-m). Four groups of MCI were evaluated by a detailed neuropsychological battery test. Results: 83 patients with MCI at the 24-week follow-up were classified into four subtypes. The most frequent subtype was amnestic multi-domain MCI, with the frequency of MCI subtypes as follows: aMCI-s (n = 21, 25.3%), aMCI-m (n = 53, 63.9%), naMCI-s (n = 5, 6.0%) and naMCI-m (n = 4, 4.8%). In the major cognitive items of the SNSB-D, there were significant changes between the initial and follow-up tests in the domains of language, memory and the fron-tal/executive function (p < 0.05), except for attention, in all MCI patient subtypes. At 24-weeks follow-up, the conversion rate to Alzheimer’s disease was 2.4% (n = 2) from a subtype of amnestic multi-domain MCI. Conclusions: Our study revealed the most frequent subtype of MCI to be multiple domain amnestic MCI, with this subtype having a higher tendency of conversion to Alzheimer’s disease.
Chemical composition, antioxidant and antibacterial activities of essential oil from Korean Citrus unshiu peel  [PDF]
Xiao Nan Yang, Sun Chul Kang
Journal of Agricultural Chemistry and Environment (JACEN) , 2013, DOI: 10.4236/jacen.2013.23007
Abstract: The chemical composition, antioxidant and antibacterial activities of essential oil from peel of Citrus unshiuwhich cultivated in South Korea were investigated. Eight compounds were identified as l-limonene (88.11%), γ-terpinene (4.66%), cyclohexane, 2,4-diisopropenyl-1-methyl-1-vinyl (1.82%), diethyl phthalate (1.02%), β-linalool (0.97%), β-myrcene (0.91%), α-farnesene (0.91%) and o-cymene (0.85%)
by GC-MS. The SC50values of this essential oil on DPPH and superoxide anion were 0.21 and 0.22% (v/v), respectively. The results of zone of inhibition, MIC, MBC and cell viability demonstrated the essential oil of-Citrus unshiupeel displayed antibacterial effect against B. cereus KCTC 14042, B. subtilis ATCC 6633 and S. aureusATCC 6538. The release of cell material and potassium ion from the B. subtilis ATCC 6633 cells treated with essential oil was further investigated. SEM observation also revealed the damaging effect of the essential oil on the morphology of B. subtilisATCC 6633 cells at minimum inhibitory concentration.

In vivo control of perilla rust disease by oak pyroligneous liquor  [PDF]
Anil Kumar Chauhan, Sun Chul Kang
Journal of Agricultural Chemistry and Environment (JACEN) , 2013, DOI: 10.4236/jacen.2013.24013
Abstract: Leaves of Perilla frutescens, commonly known as perilla are widely used in Korea, due to their medicinal properties. The rust disease of perilla interrupts its wide use every year. The present study was carried out to evaluate the control of perilla rust disease by using oak pyroligneous liquor having various biological properties. The rust disease infected perilla leaves were applied with 100 μl of oak pyroligneous liquor at different concentrations such as 6.25, 12.5, 25 and 50 μg/ml. Then the leaf samples were observed for the abortion of active rust pustules (yellow color) after 48 hours of incubation at 26?C. Further, inhibition of rust pustules development by oak pyroligneous liquor was evaluated on the leaves of artificially induced perilla rust disease. The best abortion of rust pustules by oak pyroligneous liquor was noticed at the concentration of 50 μg/ml, where 74.4% of the pustules were aborted. Discoloration of rust pustules was also observed in the treated leaves from yellow to white when compared with the untreated control. In addition, oak pyroligneous liquor completely inhibited the development of rust pustules in artificially induced leaves even at low concentration (6.25 μg/ml). The results clearly indicated that oak pyroligneous liquor is a good candidate for the management of Perilla rust disease.
Remote Operation SW for USV: Part II. Simulation Development  [PDF]
Jinyeong Heo, Kun Chul Hwang, Yongjin Kwon
World Journal of Engineering and Technology (WJET) , 2018, DOI: 10.4236/wjet.2018.64054
Abstract: For contingencies occurring in a complex marine environment, Unmanned Surface Vehicle (USV) has to recognize the situation and decide behaviors,?and?plan the following actions through the Integrated Mission Planning Process. Therefore, researches are actively being carried out about it. However, since it is difficult to test the actual USV with the mission planning process, it is necessary to develop a virtual experimental environment based on Modeling&Simulation (M&S). In this study, we developed an integrated simulation environment capable of simulating and analyzing the overall mission of USV. In Part?I, we modelled the USV Integrated Mission Planning Process and in Part?II, we developed an experimental framework and interface for loading them. In addition, we verified the suitability of this model through scenarios and defined the Mission of Effectiveness (MOE) concept for USV mission analysis.
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