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Search Results: 1 - 10 of 8462 matches for " Tae Hyun Choi "
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Automatic Classification for Various Images Collections Using Two Stages Clustering Method  [PDF]
Wan Hyun Cho, In Seop Na, Jun Yong Choi, Tae Hoon Lee
Open Journal of Applied Sciences (OJAppS) , 2013, DOI: 10.4236/ojapps.2013.31B010
Abstract: In this paper, we propose an automatic classification for various images collections using two stage clustering method. Here, we have used global and local image features. First, we review about various types of feature vector that is suita-ble to represent local and global properties of images, and similarity measures that can be represented an affinity be-tween these images. Second, we consider a clustering method for image collection. Here, we first build a coarser clus-tering by partitioning various images into several clusters using the flexible Mean shift algorithm and K-mean cluster-ing algorithm. Second, we construct dense clustering of images collection by optimizing a Gaussian Dirichlet process mixture model taking initial clusters as given coarser clustering. Finally, we have conducted the comparative experi-ments between our method and existing methods on various images datasets. Our approach has significant advantage over existing techniques. Besides integrating temporal and image content information, our approach can cluster auto-matically photographs without some assumption about number of clusters or requiring a priori information about initial clusters and it can also generalize better to different image collections.
Chromatin Assays for DNA Fragmentation Evaluation in Canine Sperm
Bum-Sul Choi,Tae-Koon Kim,Changbaig Hyun
Journal of Animal and Veterinary Advances , 2012, DOI: 10.3923/javaa.2011.1501.1503
Abstract: The aims of this study was to evaluate efficacy of detecting male infertility in dogs using conventional Computer Assisted Sperm Analysis (CASA) for morphological analysis of spermatozoa and the Sperm Chromatin Structure Assay (SCSA) for level of DNA fragmentation in the spermatozoa. This study found percentage of morphological abnormalities and motility in infertile dogs were statistically significantly poorer than those in healthy control (p<0.05). Also percent DNA Fragmentation Index (DFI%) were significantly higher in infertile dogs. There is correlation between morphological mortality indices and DFI%. This result strongly suggested that assays such as SCSA could be a good alternative test for canine male infertility and for evaluating quality of sperm before artificial insemination as reported previously.
Evaluation of an Amniotic Membrane-Collagen Dermal Substitute in the Management of Full-Thickness Skin Defects in a Pig
Hyunji Kim,Daegu Son,Tae Hyun Choi,Samhyun Jung
Archives of Plastic Surgery , 2013, DOI: http://dx.doi.org/10.5999/aps.2013.40.1.11
Abstract: Background To minimize the inflammatory reaction and improve healing, a new modifieddermal substitute composed of an atelocollagen, chondroitin-6-sulfate, and amnioticmembrane (AM) was applied to full-thickness skin defects in a pig. Atelocollagen was extractedfrom bovine skin, and two modified dermal substitutes were generated according to the crosslinkingtype.Methods The AM-collagen dermal substitutes were characterized and compared withcurrently used dermal substitutes in a pig skin defect model. There were five experimentalgroups: dehydrothermal (DHT) cross-linking atelocollagen with the AM on the top (AM-DHT),DHT and chemical cross-linking atelocollagen with the AM on the top (AM-DHT/chemical),Terudermis, Integra, and AlloDerm. After 3×3 cm full-thickness skin defects on the back ofa pig were created, each dermal substitutes dermal substitutes was randomly grafted on thedefects. Two weeks after grafting, autologous partial-thickness skin was over-grafted on theneodermis. The take rate of the dermal substitutes, skin, and histological sections were allassessed at 1, 2, and 4 weeks postoperatively.Results More rapid healing and a higher take rate were evident in the AM-DHT and Terudermisgroups. Histological examination revealed fewer inflammatory cells and more fibroblasthyperplasia in these two groups. Four weeks after surgery, the amount of newly formedcollagen was significantly more appropriate in the AM-DHT group.Conclusions These observations provide supporting evidence that a newly developed amnioticcollagendermal substitute may inhibit inflammatory reactions and promote wound healing.
Turbulent-Induced Noise around a Circular Cylinder Using Permeable FW-H Method  [PDF]
Woen-Sug Choi, Suk-Yoon Hong, Jee-Hun Song, Hyun-Wung Kwon, Chul-Min Jung, Tae-Gyoung Kim
Journal of Applied Mathematics and Physics (JAMP) , 2015, DOI: 10.4236/jamp.2015.32025
Abstract:

Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods: direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent- induced noise using permeable FW-H is established and its usability is shown.

Apoptosis Induction of Human Prostate Carcinoma DU145 Cells by Diallyl Disulfide via Modulation of JNK and PI3K/AKT Signaling Pathways
Dong Yeok Shin,Gi-Young Kim,Jun Hyuk Lee,Byung Tae Choi,Young Hyun Yoo,Yung Hyun Choi
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms131114158
Abstract: Diallyl disulfide (DADS), a sulfur compound derived from garlic, has various biological properties, such as anticancer, antiangiogenic and anti-inflammatory effects. However, the mechanisms of action underlying the compound's anticancer activity have not been fully elucidated. In this study, the apoptotic effects of DADS were investigated in DU145 human prostate carcinoma cells. Our results showed that DADS markedly inhibited the growth of the DU145 cells by induction of apoptosis. Apoptosis was accompanied by modulation of Bcl-2 and inhibitor of apoptosis protein (IAP) family proteins, depolarization of the mitochondrial membrane potential (MMP, ΔΨm) and proteolytic activation of caspases. We also found that the expression of death-receptor 4 (DR4) and Fas ligand (FasL) proteins was increased and that the level of intact Bid proteins was down-regulated by DADS. Moreover, treatment with DADS induced phosphorylation of mitogen-activated protein kinases (MAPKs), including extracellular-signal regulating kinase (ERK), p38 MAPK and c-Jun N-terminal kinase (JNK). A specific JNK inhibitor, SP600125, significantly blocked DADS-induced-apoptosis, whereas inhibitors of the ERK (PD98059) and p38 MAPK (SB203580) had no effect. The induction of apoptosis was also accompanied by inactivation of phosphatidylinositol 3-kinase (PI3K)/Akt and the PI3K inhibitor LY29004 significantly increased DADS-induced cell death. These findings provide evidence demonstrating that the proapoptotic effect of DADS is mediated through the activation of JNK and the inhibition of the PI3K/Akt signaling pathway in DU145 cells.
Autophagy Impairment Induces Premature Senescence in Primary Human Fibroblasts
Hyun Tae Kang,Ki Baek Lee,Sung Young Kim,Hae Ri Choi,Sang Chul Park
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0023367
Abstract: Recent studies have demonstrated that activation of autophagy increases the lifespan of organisms from yeast to flies. In contrast to the lifespan extension effect in lower organisms, it has been reported that overexpression of unc-51-like kinase 3 (ULK3), the mammalian homolog of autophagy-specific gene 1 (ATG1), induces premature senescence in human fibroblasts. Therefore, we assessed whether the activation of autophagy would genuinely induce premature senescence in human cells.
Transmesocolic hernia with strangulation in a patient without surgical history: Case report
Peel Jung,Min Dae Kim,Tae Hyun Ryu,Sung Ho Choi
World Journal of Gastroenterology , 2013, DOI: 10.3748/wjg.v19.i12.1997
Abstract: Transmesenteric hernias have bimodal distribution and occur in both pediatric and adult patients. In the adult population, the cause is iatrogenic, traumatic, or inflammatory. We report a case of transmesocolic hernia in an elderly person without any preoperative history. An 84-year-old Korean female was admitted with mid-abdominal pain and distension for 1 d. On abdominal computed tomography, we diagnosed transmesocolic hernia with strangulated small bowel obstruction, and performed emergency surgery. The postoperative period was uneventful and she was discharged 11 d after surgery. Hence, it is important to consider the possibility of transmesocolic hernia in elderly patients with signs and symptoms of intestinal obstruction, even in cases with no previous surgery.
Robust Depth Estimation and Image Fusion Based on Optimal Area Selection
Ik-Hyun Lee,Muhammad Tariq Mahmood,Tae-Sun Choi
Sensors , 2013, DOI: 10.3390/s130911636
Abstract: Mostly, 3D cameras having depth sensing capabilities employ active depth estimation techniques, such as stereo, the triangulation method or time-of-flight. However, these methods are expensive. The cost can be reduced by applying optical passive methods, as they are inexpensive and efficient. In this paper, we suggest the use of one of the passive optical methods named shape from focus (SFF) for 3D cameras. In the proposed scheme, first, an adaptive window is computed through an iterative process using a criterion. Then, the window is divided into four regions. In the next step, the best focused area among the four regions is selected based on variation in the data. The effectiveness of the proposed scheme is validated using image sequences of synthetic and real objects. Comparative analysis based on statistical metrics correlation, mean square error (MSE), universal image quality index (UIQI) and structural similarity (SSIM) shows the effectiveness of the proposed scheme.
Bipolar resistive switching characteristics of poly(3,4-ethylene-dioxythiophene): poly(styrenesulfonate) thin film
Hu Young Jeong,Jong Yun Kim,Tae Hyun Yoon,Sung-Yool Choi
Physics , 2009, DOI: 10.1016/j.cap.2009.12.011
Abstract: We investigated the reversible resistive switching of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) thin films sandwiched between Al electrodes. The J-V sweep curve showed a hysteretic behavior which depends on the polarity of the applied voltage bias. From the analysis of I-V curves, it was revealed that the charge transport through the junction was governed by the bulk space-charge-limited conduction (SCLC) model. Using transmission electron microscopy (TEM) analysis, it was confirmed that the initial high resistance state of PEDOT:PSS films is related with the segregation of PSS- chains induced by redox reaction between a Al metal electrode and PEDOT:PSS film. Positive space charges present on the top region of PEDOT:PSS films can be proposed as a possible trap centers of electron trapping and detrapping process.
Zn impurity induced moments and tunneling conductance asymmetry in cuprate superconductors
Jaesung Yoon,Tae-Hyoung Gimm,Hyun C. Lee,Han-Yong Choi
Physics , 2001,
Abstract: The effects of a non-magnetic Zn impurity substituting an in-plane Cu are studied by solving the Bogoliubov-de Gennes equation self-consistently which is derived from the \ttju Hamiltonian with all the allowed order parameters included. The Zn impurity, modeled in terms of a potential scatterer in unitary limit, induces local staggered magnetic moments around itself, and the calculated NMR shifts from the induced moments are in agreement with the experimental Cu NMR spectra. We also note that the experimentally observed negative slope of the tunneling conductance can result from the next-nearest hopping $t'$.
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