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Search Results: 1 - 10 of 8394 matches for " Seung-Hyun Kong "
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Least-squares based iterative multipath super-resolution technique
Wooseok Nam,Seung-Hyun Kong
Mathematics , 2011,
Abstract: In this paper, we study the problem of multipath channel estimation for direct sequence spread spectrum signals. To resolve multipath components arriving within a short interval, we propose a new algorithm called the least-squares based iterative multipath super-resolution (LIMS). Compared to conventional super-resolution techniques, such as the multiple signal classification (MUSIC) and the estimation of signal parameters via rotation invariance techniques (ESPRIT), our algorithm has several appealing features. In particular, even in critical situations where the conventional super-resolution techniques are not very powerful due to limited data or the correlation between path coefficients, the LIMS algorithm can produce successful results. In addition, due to its iterative nature, the LIMS algorithm is suitable for recursive multipath tracking, whereas the conventional super-resolution techniques may not be. Through numerical simulations, we show that the LIMS algorithm can resolve the first arrival path among closely arriving independently faded multipaths with a much lower mean square error than can conventional early-late discriminator based techniques.
Experimental Study of the Fry-Drying Phenomena of Organic Wastes in Hot Oil for Waste-Derived Solid Fuel  [PDF]
Tae-In Ohm, Jong-Seung Chae, Seung-Hyun Moon
Journal of Environmental Protection (JEP) , 2014, DOI: 10.4236/jep.2014.57065
Abstract:

In sludge treatment, drying sludge using typical technology with high water content to a water content of approximately 10% is always difficult because of adhesive characteristics of sludge in drying. Many methods have been applied, including direct and indirect heat drying, but these approaches of reducing water content to below 40% after drying are very inefficient in energy utilization of drying sludge. In this study, fry-drying technology with a high heat transfer coefficient of approximately 500 W/m2·°C was used to dry swine excreta, sewage and industrial sludge. Also waste oil was used in the fry-drying process, and because the oil’s boiling point is between 240°C and 340°C and the specific heat is approximately 60% of that of water. In the fry-drying system, the sludge is input by molding it into a designated form after heating the waste oil at temperatures between 130°C and 150°C. At these temperatures, the heated oil rapidly evaporates the water contained in the sludge, leaving the oil itself. After approximately 8 - 10 min, the water content of the sludge was less than 10%, and its heating value surpassed 20,000 kJ/kg. Indeed, this makes the organic sludge appropriate for use as a solid fuel. The dried swine excreta, sewage and industrial sludge can be used in an incinerator like low-rank coal or solid fuel.

Abnormal Reorganization of Functional Cortical Small-World Networks in Focal Hand Dystonia
Seung-Hyun Jin, Peter Lin, Mark Hallett
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0028682
Abstract: We investigated the large-scale functional cortical connectivity network in focal hand dystonia (FHD) patients using graph theoretic measures to assess efficiency. High-resolution EEGs were recorded in 15 FHD patients and 15 healthy volunteers at rest and during a simple sequential finger tapping task. Mutual information (MI) values of wavelet coefficients were estimated to create an association matrix between EEG electrodes, and to produce a series of adjacency matrices or graphs, G, by thresholding with network cost. Efficiency measures of small-world networks were assessed. As a result, we found that FHD patients have economical small-world properties in their brain functional networks in the alpha and beta bands. During a motor task, in the beta band network, FHD patients have decreased efficiency of small-world networks, whereas healthy volunteers increase efficiency. Reduced efficient beta band network in FHD patients during the task was consistently observed in global efficiency, cost-efficiency, and maximum cost-efficiency. This suggests that the beta band functional cortical network of FHD patients is reorganized even during a task that does not induce dystonic symptoms, representing a loss of long-range communication and abnormal functional integration in large-scale brain functional cortical networks. Moreover, negative correlations between efficiency measures and duration of disease were found, indicating that the longer duration of disease, the less efficient the beta band network in FHD patients. In regional efficiency analysis, FHD patients at rest have high regional efficiency at supplementary motor cortex (SMA) compared with healthy volunteers; however, it is diminished during the motor task, possibly reflecting abnormal inhibition in FHD patients. The present study provides the first evidence with graph theory for abnormal reconfiguration of brain functional networks in FHD during motor task.
Insulin Receptor-Overexpressing β-Cells Ameliorate Hyperglycemia in Diabetic Rats through Wnt Signaling Activation
Mi-Hyun Kim, Seung-Hyun Hong, Moon-Kyu Lee
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067802
Abstract: To investigate the therapeutic efficacy and mechanism of β-cells with insulin receptor (IR) overexpression on diabetes mellitus (DM), rat insulinoma (INS-1) cells were engineered to stably express human insulin receptor (INS-IR cells), and subsequently transplanted into streptozotocin- induced diabetic rats. Compared with INS-1 cells, INS-IR cells showed improved β-cell function, including the increase in glucose utilization, calcium mobilization, and insulin secretion, and exhibited a higher rate of cell proliferation, and maintained lower levels of blood glucose in diabetic rats. These results were attributed to the increase of β-catenin/PPARγ complex bindings to peroxisome proliferator response elements in rat glucokinase (GK) promoter and the prolongation of S-phase of cell cycle by cyclin D1. These events resulted from more rapid and higher phosphorylation levels of insulin-signaling intermediates, including insulin receptor substrate (IRS)-1/IRS-2/phosphotylinositol 3 kinase/v-akt murine thymoma viral oncogene homolog (AKT) 1, and the consequent enhancement of β-catenin nuclear translocation and Wnt responsive genes including GK and cyclin D1. Indeed, the higher functionality and proliferation shown in INS-IR cells were offset by β-catenin, cyclin D1, GK, AKT1, and IRS-2 gene depletion. In addition, the promotion of cell proliferation and insulin secretion by Wnt signaling activation was shown by 100 nM insulin treatment, and to a similar degree, was shown in INS-IR cells. In this regard, this study suggests that transferring INS-IR cells into diabetic animals is an effective and feasible DM treatment. Accordingly, the method might be a promising alternative strategy for treatment of DM given the adverse effects of insulin among patients, including the increased risk of modest weight gain and hypoglycemia. Additionally, this study demonstrates that the novel mechanism of cross-talk between insulin and Wnt signaling plays a primary role in the higher therapeutic efficacy of IR-overexpressing β-cells.
Graphitic carbon grown on fluorides by molecular beam epitaxy
Sahng-Kyoon Jerng, Jae H Lee, Yong S Kim and Seung-Hyun Chun
Nanoscale Research Letters , 2013, DOI: 10.1186/1556-276X-8-11
Abstract: We study the growth mechanism of carbon molecules supplied by molecular beam epitaxy on fluoride substrates (MgF2, CaF2, and BaF2). All the carbon layers form graphitic carbon with different crystallinities depending on the cation. Especially, the growth on MgF2 results in the formation of nanocrystalline graphite (NCG). Such dependence on the cation is a new observation and calls for further systematic studies with other series of substrates. At the same growth temperature, the NCG on MgF2 has larger clusters than those on oxides. This is contrary to the general expectation because the bond strength of the carbon-fluorine bond is larger than that of the carbon-oxygen bond. Our results show that the growth of graphitic carbon does not simply depend on the chemical bonding between the carbon and the anion in the substrate.
An Elaborate Frequency Offset Estimation for OFDM Systems
Seung-Hyun Nam;Jae-Seon Yoon;Hyoung-Kyu Song
PIER Letters , 2008, DOI: 10.2528/PIERL08051204
Abstract: In this paper, a carrier frequency offset estimation scheme in orthogonal frequency division multiplexing is proposed. We focus on increasing the correlation of each PN sequence code repeated in one preamble. We aim at getting an efficiency like using many preambles. The proposed method can improve the performance of the system by estimating fine frequency offset. Also, the proposed method enhances reliability by maximizing the number of correlations compared with the established method in time domain.
Chest Wall Fibromatosis in the Axilla
Seung-Hyun Lee,Hye-Kyung Lee,Ji-Sun Song,Hii-Sun Jeong
Archives of Plastic Surgery , 2012, DOI: http://dx.doi.org/10.5999/aps.2012.39.2.175
Abstract:
Reply: Multiple Large Cysts Arising from Nevus Comedonicus
Hii-Sun Jeong,Hye-Kyung Lee,Seung-Hyun Lee,Hyoung-Suk Kim
Archives of Plastic Surgery , 2012, DOI: http://dx.doi.org/10.5999/aps.2012.39.3.261
Abstract:
Multiple Large Cysts Arising from Nevus
Hii-Sun Jeong,Hye-Kyung Lee,Seung-Hyun Lee,Hyoung-Suk Kim
Archives of Plastic Surgery , 2012, DOI: http://dx.doi.org/10.5999/aps.2012.39.1.63
Abstract: Nevus comedonicus is a type of hamartoma that arises from a developmental anomaly of themesodermal part of the pilosebaceous gland. In most cases of nevus comedonicus, an acnelikeskin condition develops. Repeated inflammation can cause a morphological change to thecyst, papule, to abscess. We experienced a case of congenital nevus comedonicus, which ledto the formation of large multiple cysts. A 50-year-old man was referred with a 12.5×10 cmlobulated mass on the posterior neck and upper back. The patient had a widespread presenceof nevus comedonicus in the region ranging from the right superior chest to the posteriorneck. The patient had a 30-year history of six prior excisions. A magnetic resonance imagingreview led to a diagnosis of nevus comedonicus. Surgical treatment consisted of excision ofthe mass and wide excision for the patch type of nevus comedonicus around the neck. Onhistopathology, multiple masses were diagnosed as typical cysts containing keratinized tissue.The diffuse comedone lesions were diagnosed as nevus comedonicus. This case shows thatlarge, multiple cysts can occur as a long-term complication of nevus comedonicus, and alsohighlights the importance of radical resection to prevent its further invagination.
Characterization of Bi and Fe co-doped PZT capacitors for FeRAM
Jeffrey S Cross, Seung-Hyun Kim, Satoshi Wada and Abhijit Chatterjee
Science and Technology of Advanced Materials , 2010,
Abstract: Ferroelectric random access memory (FeRAM) has been in mass production for over 15 years. Higher polarization ferroelectric materials are needed for future devices which can operate above about 100 °C. With this goal in mind, co-doping of thin Pb(Zr40,Ti60)O3 (PZT) films with 1 at.% Bi and 1 at.% Fe was examined in order to enhance the ferroelectric properties as well as characterize the doped material. The XRD patterns of PZT-5% BiFeO3 (BF) and PZT 140-nm thick films showed (111) orientation on (111) platinized Si wafers and a 30 °C increase in the tetragonal to cubic phase transition temperature, often called the Curie temperature, from 350 to 380 °C with co-doping, indicating that Bi and Fe are substituting into the PZT lattice. Raman spectra revealed decreased band intensity with Bi and Fe co-doping of PZT compared to PZT. Polarization hysteresis loops show similar values of remanent polarization, but square-shaped voltage pulse-measured net polarization values of PZT-BF were higher and showed higher endurance to repeated cycling up to 1010 cycles. It is proposed that Bi and Fe are both in the +3 oxidation state and substituting into the perovskite A and B sites, respectively. Substitution of Bi and Fe into the PZT lattice likely creates defect dipoles, which increase the net polarization when measured by the short voltage pulse positive-up-negative-down (PUND) method.
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