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Search Results: 1 - 10 of 21851 matches for " Jee Hyun Kim "
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Efficient Feedback via Subspace-Based Channel Quantization for Distributed Cooperative Antenna Systems with Temporally Correlated Channels
Jee Hyun Kim,Wolfgang Zirwas,Martin Haardt
EURASIP Journal on Advances in Signal Processing , 2008, DOI: 10.1155/2008/847296
Abstract: It is one of the biggest challenges of distributed cooperative antenna (COOPA) systems to provide base stations (BSs) with downlink channel information for transmit filtering (precoding). In this paper, we propose a novel feedback scheme via a subspace-based channel quantization method. The proposed scheme adopts the chordal distance as a channel quantizer criterion so as to capture channel characteristics represented by subspaces spanned by the channel matrix. We also propose a combined feedback scheme which is based on the hierarchical codebook construction method in an effort to reduce the feedback overhead by exploiting the temporal correlation of the channel. The proposed methods are tested for distributed COOPA systems in terms of simulations. Simulation results show that the proposed subspace-based channel quantization method outperforms the analog pilot retransmission method, and the combined feedback scheme performs as well as the permanent full-feedback scheme with a much smaller amount of uplink resources.
HIV-1 Tat Interacts with and Regulates the Localization and Processing of Amyloid Precursor Protein
Jiyoung Kim, Jee-Hyun Yoon, Yeon-Soo Kim
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0077972
Abstract: HIV-1 Tat protein plays various roles in virus proliferation and in the regulation of numerous host cell functions. Accumulating evidence suggests that HIV-1 Tat also plays an important role in HIV-associated neurocognitive disorders (HAND) by disrupting intracellular communication. Amyloid beta (Aβ) is generated from amyloid precursor protein (APP) and accumulates in the senile plaques of Alzheimer's disease patients. This study demonstrates that Tat interacts with APP both in vitro and in vivo, and increases the level of Aβ42 by recruiting APP into lipid rafts. Co-localization of Tat with APP in the cytosol was observed in U-87 MG cells that expressed high levels of Tat, and redistribution of APP into lipid rafts, a site of increased β- and γ-secretase activity, was demonstrated by discontinuous sucrose density gradient ultracentrifugation in the presence of Tat. Furthermore, Tat enhanced the cleavage of APP by β-secretase in vitro, resulting in 5.5-fold higher levels of Aβ42. This was consistent with increased levels of β-C-terminal fragment (β-CTF) and reduced levels of α-CTF. Moreover, stereotaxic injection of a lentiviral Tat expression construct into the hippocampus of APP/presenilin-1 (PS1) transgenic mice resulted in increased Tat-mediated production and processing of Aβ in vivo. Increased levels of Aβ42, as well as an increase in the number and size of Aβ plaques, were observed in the hippocampus following injection of Tat virus compared with mock virus. These results suggest that HIV-1 Tat may contribute to HAND by interacting with and modifying APP processing, thereby increasing Aβ production.
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.
Incomplete High Radial Nerve Palsy Due to Schwannoma of Radial Nerve in the Upper Arm—A Case Report  [PDF]
Hyun Seong Kang, Chen Tai Teong, Jee Eun Park, Sang Rim Kim, Kyu Bum Seo, Chang Lim Hyun, Kwang Hun Song
Open Journal of Orthopedics (OJO) , 2017, DOI: 10.4236/ojo.2017.72009
Abstract: A schwannoma is a benign soft tissue tumor composed of Schwann cells. Clinically, the tumor is slow-growing and usually asymptomatic, rarely developing neurological symptoms. We present a case of a 44-year-old female who was diagnosed with an incomplete high radial nerve palsy, showing a wrist drop and extension of fingers due to schwannoma on the radial nerve of the upper arm. The patient showed excellent result after excision of the schwannoma and neurorrhaphy of the radial nerve.
Pilot-Free Frequency Tracking Method for Ultra-Wideband Receivers
Jee-Hyun Kim;Young-Hwan You
PIER , 2008, DOI: 10.2528/PIER08021301
Abstract: This paper suggests a pilot-free frequency tracking scheme for ultra-wideband orthogonal frequency-division multiplexing (UWBOFDM) receivers. The proposed scheme uses a frequency-domain spreaded data symbols which is provided in the current UWB-OFDM system. Based on this property, we develop an improved frequency synchronization receiver without the use of pilot symbols. The simulation results indicate that the proposed scheme achieves much better performance than the conventional pilot-based schemes.
Characterization of Phase Transition in the Thalamocortical System during Anesthesia-Induced Loss of Consciousness
Eunjin Hwang, Seunghwan Kim, Kyungreem Han, Jee Hyun Choi
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050580
Abstract: The thalamocortical system plays a key role in the breakdown or emergence of consciousness, providing bottom-up information delivery from sensory afferents and integrating top-down intracortical and thalamocortical reciprocal signaling. A fundamental and so far unanswered question for cognitive neuroscience remains whether the thalamocortical switch for consciousness works in a discontinuous manner or not. To unveil the nature of thalamocortical system phase transition in conjunction with consciousness transition, ketamine/xylazine was administered unobtrusively to ten mice under a forced working test with motion tracker, and field potentials in the sensory and motor-related cortex and thalamic nuclei were concomitantly collected. Sensory and motor-related thalamocortical networks were found to behave continuously at anesthesia induction and emergence, as evidenced by a sigmoidal response function with respect to anesthetic concentration. Hyperpolarizing and depolarizing susceptibility diverged, and a non-discrete change of transitional probability occurred at transitional regimes, which are hallmarks of continuous phase transition. The hyperpolarization curve as a function of anesthetic concentration demonstrated a hysteresis loop, with a significantly higher anesthetic level for transition to the down state compared to transition to the up state. Together, our findings concerning the nature of phase transition in the thalamocortical system during consciousness transition further elucidate the underlying basis for the ambiguous borderlines between conscious and unconscious brains. Moreover, our novel analysis method can be applied to systematic and quantitative handling of subjective concepts in cognitive neuroscience.
Dipole Source Localization of Mouse Electroencephalogram Using the Fieldtrip Toolbox
Chungki Lee, Robert Oostenveld, Soo Hyun Lee, Lae Hyun Kim, Hokun Sung, Jee Hyun Choi
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0079442
Abstract: The mouse model is an important research tool in neurosciences to examine brain function and diseases with genetic perturbation in different brain regions. However, the limited techniques to map activated brain regions under specific experimental manipulations has been a drawback of the mouse model compared to human functional brain mapping. Here, we present a functional brain mapping method for fast and robust in vivo brain mapping of the mouse brain. The method is based on the acquisition of high density electroencephalography (EEG) with a microarray and EEG source estimation to localize the electrophysiological origins. We adapted the Fieldtrip toolbox for the source estimation, taking advantage of its software openness and flexibility in modeling the EEG volume conduction. Three source estimation techniques were compared: Distribution source modeling with minimum-norm estimation (MNE), scanning with multiple signal classification (MUSIC), and single-dipole fitting. Known sources to evaluate the performance of the localization methods were provided using optogenetic tools. The accuracy was quantified based on the receiver operating characteristic (ROC) analysis. The mean detection accuracy was high, with a false positive rate less than 1.3% and 7% at the sensitivity of 90% plotted with the MNE and MUSIC algorithms, respectively. The mean center-to-center distance was less than 1.2 mm in single dipole fitting algorithm. Mouse microarray EEG source localization using microarray allows a reliable method for functional brain mapping in awake mouse opening an access to cross-species study with human brain.
An Experiment on Power Properties in a Small-Scaled Wind Turbine Generator  [PDF]
Jee-Ho Kim, Hyun-Dai Yang, Kyu-Jin Lee, Sung-Do Song, Sung-Hoon Park, Joong-Ho Shin
Journal of Power and Energy Engineering (JPEE) , 2013, DOI: 10.4236/jpee.2013.17002
Abstract:

This study configures a simple wind tunnel using a blower for generating wind energy, which is equivalent to natural wind, and a test system that measures properties of power. Also, the mechanical and electrical power in a small-scaled wind turbine are empirically measured to analyze the relationship between the mechanical and electrical power.

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.

Role of ascites adenosine deaminase in differentiating between tuberculous peritonitis and peritoneal carcinomatosis
Seung Joo Kang,Ji Won Kim,Jee Hyun Baek,Se Hyung Kim
World Journal of Gastroenterology , 2012, DOI: 10.3748/wjg.v18.i22.2837
Abstract: AIM: To investigate the usefulness of tumor markers and adenosine deaminase in differentiating between tuberculous peritonitis (TBP) and peritoneal carcinomatosis (PC). METHODS: A retrospective analysis of data was performed on consecutive patients who underwent peritoneoscopic and abdominal computed tomography (CT) evaluations. Among 75 patients at the Seoul National University Hospital from January 2000 to June 2010 who underwent both tests, 27 patients (36.0%) and 25 patients (33.3%) were diagnosed with TBP and PC, respectively. Diagnosis was confirmed by peritoneoscopic biopsy. RESULTS: Serum c-reactive protein (7.88 ± 6.62 mg/dL vs 3.12 ± 2.69 mg/dL, P = 0.01), ascites adenosine deaminase (66.76 ± 32.09 IU/L vs 13.89 ± 8.95 IU/L, P < 0.01), ascites lymphocyte proportion (67.77 ± 23.41% vs 48.36 ± 18.78%, P < 0.01), and serum-ascites albumin gradient (0.72 ± 0.49 g/dL vs 1.05 ± 0.50 g/dL, P = 0.03) were significantly different between the two groups. Among tumor markers, serum and ascites carcinoembryonic antigen, serum carbohydrate antigen 19-9 showed significant difference between two groups. Abdominal CT examinations showed that smooth involvement of the parietal peritoneum was more common in the TBP group (77.8% vs 40.7%) whereas nodular involvement was more common in the PC group (14.8% vs 40.7%, P = 0.04). From receiver operating characteristic (ROC) curves ascites adenosines deaminase (ADA) showed better discriminative capability than tumor markers. An ADA cut-off level of 21 IU/L was found to yield the best results of differential diagnosis; sensitivity, specificity, positive predictive value, and negative predictive value were 92.0%, 85.0%, 88.5% and 89.5%, respectively. CONCLUSION: Besides clinical and radiologic findings, ascitic fluid ADA measurement is helpful in the differential diagnosis of TBP and PC.
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