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Search Results: 1 - 10 of 25134 matches for " Hyun Sung Chang "
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Dramatic Improvement of Long Lasting Post-Inflammatory Hyperpigmentation by Oral and Topical Tranexamic Acid  [PDF]
Jae Kyung Kim, Sung Eun Chang, Chong Hyun Won, Mi Woo Lee, Jee Ho Choi, Kee Chan Moon
Journal of Cosmetics, Dermatological Sciences and Applications (JCDSA) , 2012, DOI: 10.4236/jcdsa.2012.22014
Abstract: Post-inflammatory hyperpigmentation is common problem, but its treatment still remains challenging. Tranexamic acid has been used to treat or prevent excessive bleeding loss in various medical conditions. There have been some reports of the effect of oral and topical tranexamic acid for treatment of pigmented disorder. Herein we report on a case of female patient who showed improvement of PIH after oral and topical tranexamic acid administration.
Laser induced birefringence in a wavelength-mismatched cascade system of inhomogeneously broadened Yb atoms
Tai Hyun Yoon,Chang Yong Park,Sung Jong Park
Physics , 2004, DOI: 10.1103/PhysRevA.70.061803
Abstract: We report the observation of laser induced birefringence (LIB) in a wavelength-mismatched cascade system (J=0 \leftrightarrow J=1 \leftrightarrow J=0 transitions) of inhomogeneously broadened ytterbium atoms with strong pump and probe fields. We investigate the transmission spectrum of two circular polarization (\sigma_p^+ and \sigma_p^-) components of strong probe field at fixed frequency, depending on the detuning of circularly polarized (\sigma_c^-) coupling field from two-photon resonance. We find that \sigma_p^+ (\sigma_p^-) polarized component exhibits a narrow electromagnetically induced absorption (transparency) spectrum. Numerical solutions of density matrix equations show qualitative agreement with experimental results. A Doppler-free dispersive LIB signal is obtained by detecting the Stokes parameter of the probe field, enabling us to stabilize the frequency of coupling laser without frequency modulation.
Informative Sensing
Hyun Sung Chang,Yair Weiss,William T. Freeman
Mathematics , 2009,
Abstract: Compressed sensing is a recent set of mathematical results showing that sparse signals can be exactly reconstructed from a small number of linear measurements. Interestingly, for ideal sparse signals with no measurement noise, random measurements allow perfect reconstruction while measurements based on principal component analysis (PCA) or independent component analysis (ICA) do not. At the same time, for other signal and noise distributions, PCA and ICA can significantly outperform random projections in terms of enabling reconstruction from a small number of measurements. In this paper we ask: given the distribution of signals we wish to measure, what are the optimal set of linear projections for compressed sensing? We consider the problem of finding a small number of linear projections that are maximally informative about the signal. Formally, we use the InfoMax criterion and seek to maximize the mutual information between the signal, x, and the (possibly noisy) projection y=Wx. We show that in general the optimal projections are not the principal components of the data nor random projections, but rather a seemingly novel set of projections that capture what is still uncertain about the signal, given the knowledge of distribution. We present analytic solutions for certain special cases including natural images. In particular, for natural images, the near-optimal projections are bandwise random, i.e., incoherent to the sparse bases at a particular frequency band but with more weights on the low-frequencies, which has a physical relation to the multi-resolution representation of images.
Development of a Consolidated Anaerobic Digester and Microbial Fuel Cell to Produce Biomethane and Electricity from Cellulosic Biomass Using Bovine Rumen Microorganisms  [PDF]
Rebecca Chung, Eunice Yujin Kang, Yun Jae Shin, Justin Jong Park, Peter Sang Park, Chang Hyun Han, Byungjun Kim, Seog In Moon, Jooheon Park, Paul Sung Chung
Journal of Sustainable Bioenergy Systems (JSBS) , 2019, DOI: 10.4236/jsbs.2019.92002
Abstract: Microbial fuel cells (MFCs) are bioelectrochemical systems that convert chemical energy contained in organic matter into electrical energy by using the catalytic (metabolic) activity of living microorganisms. Mediator-less two chamber H-type MFCs were constructed in the current study, using dairy digester microbial population as anode inocula to convert finely ground pine tree (Avicel) at 2% (w/v) to electricity. MFCs were placed at 37°C and after the circuit voltage was stabilized on d9, bovine rumen microorganisms cultured anaerobically for 48 hrs in cellulose broth media were added to treatment group of MFC at 1% v/v dosage. MFC power and current across an external resistor were measured daily for 10 d. At the end of incubation on d19 head space gas and anode chamber liquid solutions were collected and analyzed for total gas volume and composition, and volatile fatty acids, respectively. Addition of enriched rumen microorganisms to anaerobic anode chamber increased cellulose digestibility and increased both CO2 and methane production; however, it decreased the methane to CO2 ratio. Over the experimental period, electricity generation was increased with rumen microorganism addition, and power density normalized to anode surface area was 17.6 to 67.2 mW/m2 with average of 36.0 mW/m2 in treatment, while control group had 3.6 to 21.6 (AVE 12.0) mW/m2. These observations imply that biocatalysis in MFCs requires additional cellulolytic activities to utilize structural biomass in bioenergy production.
A Surface Plasmon Resonance Sensor for the Detection of Deoxynivalenol Using a Molecularly Imprinted Polymer
Sung-Wook Choi,Hyun-Joo Chang,Nari Lee,Hyang Sook Chun
Sensors , 2011, DOI: 10.3390/s110908654
Abstract: The aim of the present work was to investigate the feasibility of applying the molecular imprinting polymer technique to the detection of the mycotoxin deoxynivalenol (DON) using a surface plasmon resonance (SPR) transducer. A molecularly imprinted polypyrrole (MIPPy) film was prepared via electropolymerization of pyrrole onto a bare Au chip in the presence of a template DON molecule. Atomic force microscope SPR analysis showed that the MIPPy film was deposited homogeneously on the Au surface, with a thickness of 5 nm. The MIPPy–SPR sensor exhibited a linear response for the detection of DON in the range of 0.1–100 ng/mL (R2 = 0.988). The selectivity efficiency of the MIPPy film for DON and its acetylated analogs 3-ADON and 15-ADON was 100, 19, and 44%, respectively. The limit of detection for DON with the MIPPy–SPR for a standard solution was estimated at >1 ng/mL. These results suggest that the combination of SPR sensing with a MIPPy film as a synthetic receptor can be used to detect DON.
Differences between Sand and Gravel Bars of Streams in Patterns of Vegetation Succession
Lee, Chang-Seok,Yong-Chan Cho,Hyun-Cheol Shin,Sung-Ae Park
Journal of Ecology and Field Biology , 2009,
Abstract: We analyzed the factors driving succession and the structure, and dynamics of vegetation on sandand gravel bars in order to clarify the differences in vegetation succession in rivers with different river bed substrates.Woody plant communities (dominated by Salix), perennial herb communities (dominated by Miscanthus),and annual plant communities (dominated by Persicaria) appeared in that order from upstream to downstreamon the sandbar. The results of DCA ordination based on vegetation data reflected a successional trend. Thisresult suggests that sandbars grow in a downstream direction. Various vegetation types different in successionalstage, such as grassland, young stands of Korean red pine (Pinus densiflora), two-layered stands of young andmature pines, and mature pine stands also occurred on gravel bars, but the vegetation in earlier successionalstage was established upstream, which is the opposite to the direction found on sandbars. Those resultsdemonstrate that the dynamics of the bed load itself could be a factor affecting vegetation succession in rivers.In fact, sands suspended by running water were transported downstream over the vegetated area of sand barand thereby created new areas of sandbar on the downstream end of the sandbar. Meanwhile, gravel, whichis heavy and thereby is shifted by strong water currents, accumulated on the upstream end of the vegetatedarea, and thus created new areas of gravel bar in that direction. These results showed that allogenic processesdrive vegetation succession on sand and gravel bars in streams and rivers.
Understanding topological phase transition in transition metal dichalcogenides
Duk-Hyun Choe,Ha-Jun Sung,Kee Joo Chang
Physics , 2015,
Abstract: Despite considerable interest in layered transition metal dichalcogenides (TMDs), such as MX2 with M = (Mo, W) and X = (S, Se, Te), the physical origin of their topological nature is still poorly understood. In the conventional view of topological phase transition (TPT), the non-trivial topology of electron bands in TMDs is caused by the band inversion between metal d and chalcogen p orbital bands, where the former is pulled down below the latter. Here, we show that, in TMDs, the TPT is entirely different from the conventional speculation. In particular, MS2 and MSe2 exhibits the opposite behavior of TPT, such that the chalcogen p orbital band moves down below the metal d orbital band. More interestingly, in MTe2, the band inversion occurs between the metal d orbital bands. Our findings cast doubts on the common view of TPT and provide clear guidelines for understanding the topological nature in new topological materials to be discovered.
Plasma B-type Natriuretic Peptide Level in Patients with Acute Cerebral Infarction according to Infarction Subtype and Infarction Volume
Seo Hyun Kim, Ji-Yong Lee, Sang Hyun Park, Hyun-Chan Jang, Eun Ju Lim, Sei-Jin Chang, Sung-Soo Lee
International Journal of Medical Sciences , 2013,
Abstract: Background: Plasma B-type natriuretic peptide (BNP) is used as a diagnostic marker of cardiovascular diseases. BNP is secreted mainly from the myocardium and has been detected by immunoreactivity in brain and cerebral arteries. The aim of our study was to investigate plasma BNP in patients with acute cerebral infarction according to infarction subtype and infarction volume. Methods: We studied 141 patients with acute cerebral infarction, classified as large artery atherosclerosis (LAA), cardioembolism (CE), or small vessel disease (SA) according to the Trial of Org 10172 in Acute Stroke Treatment classification. Plasma BNP level was measured in patients and 61 healthy controls. We analyzed various clinical and laboratory variables of patients according to plasma BNP level. Results: Compared to controls, the patients had higher plasma BNP (11.9 ± 11.7 pg/mL versus 124.6 ± 228.8 pg/mL, p <0.01). The highest quartile BNP group was associated with advanced age, female gender, current non-smoker, atrial fibrillation, heart failure, CE group, increased white blood cell counts, increased high sensitivity C-reactive protein, increased left atrium size, decreased left ventricular ejection fraction, increased initial National Institute of Health Stroke Scale, and increased infarction volume. According to multiple regression analysis, CE group, female gender, and infarction volume were independently associated with plasma BNP. Plasma BNP level showed statistically significant differences among LAA (n = 71), CE (n = 50), and SA (n = 20) groups (p <0.001), and the expression decreased in order of CE (253.8 ± 337.1 pg/mL), LAA (61.6 ± 78.8 pg/mL), and SA (25.3 ± 24.8 pg/mL). Increased plasma BNP correlated with increased infarction volume (r = 0.42, p <0.001). Conclusions: Plasma BNP may be helpful for prediction of etiologic classification of acute cerebral infarction and infarction volume.
An Evaluation of Light Distribution in the Exhibition Areas of the Mimesis Art Museum Designed by Alvaro Siza  [PDF]
Chang Sung Kim
Journal of Building Construction and Planning Research (JBCPR) , 2014, DOI: 10.4236/jbcpr.2014.24021
Abstract: The works of Alvaro Siza have been referred that they were not the theoretical architecture but the sensual and experiential one. His works were designed on the base of their locality that each of them located. For the study, I selected a work of him, which was the Mimesis Art Museum at Paju in South Korea, and reviewed existing literatures to understand how he controlled the light and created the architectural spaces and forms in relation with the light, and I measured the illumination levels of the inside areas of the Mimesis Art Museum, and then, I surveyed the visitors’ responses on the lighting conditions of the Mimesis Art Museum. The results of the measurements showed that the illumination levels of the Mimesis Art museum on the first floor were effectively controlled to display the art works. The illumination levels on the third floor, however, were much higher than recommended illumination values for museum because of less controlled natural light. Therefore, more considerations to control the natural light are needed to secure stable environment in the exhibition spaces. Meanwhile, the answers of questionnaires concerning the quality of lighting conditions in the Mimesis Art Museum showed that the natural light was so effective to light the museum although the natural light illuminated some areas of the museum with high illumination levels.
Knowledge Discovery from Dynamic Data on a Nonlinear System  [PDF]
Chen-Sung Chang
Open Journal of Applied Sciences (OJAppS) , 2015, DOI: 10.4236/ojapps.2015.510056
Abstract: A method is presented for performing knowledge discovery on the dynamic data of a nonlinear system. In the proposed approach, a synchronized phasor measurement technique is used to acquire the dynamic data of the nonlinear system and a hyper-rectangular type neural network (HRTNN) is then applied to extract crisp and fuzzy rules with which to estimate the system stability. The effectiveness of the proposed methodology is verified using the dynamic data of a typical real-world nonlinear system, namely an AEP-14 bus, and the extracted rules are relating to the knowledge discovery of the stability levels for the nonlinear system. The discovered relationships among the dynamic data (i.e., the operating state), the extracted rules, and the system stability are confirmed by means of a two-stage confirmatory factor analysis.
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