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Search Results: 1 - 10 of 23077 matches for " Kim Won Ki "
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Optimizing of Iterative Turbo Equalizer for Underwater Sensor Communication
Ji Won Jung,Ki Man Kim
International Journal of Distributed Sensor Networks , 2013, DOI: 10.1155/2013/129781
Abstract: We presented an iterative turbo equalization to cope with intersymbol interference induced by reflection of sea level and sea bottom for underwater sensor communication channel. Iterative turbo equalizer consists of inner codes and outer codes; we employ decision feedback equalizer as an outer code and turbo codes as an inner code. Equalizer and decoder are connected through the interleaving and deinterleaving that update each other's information repeatedly. At the receiver side, we resort to powerful turbo equalization algorithms that iteratively exchange probabilistic information between inner decoder and outer decoder, thereby reducing the error rates significantly. Furthermore, we expand iterative turbo equalizer techniques for single-input-single-output (SISO) system to multiple-input-multiple-output (MIMO) system in order to increase data rates for underwater sensor communication channel. Based on experimental channel response, we confirmed that the performance is improved as iteration number is increased. The performance is improved by 3.5?[dB] compared to noniteration for SISO channel and by 1?[dB] for MIMO channel, respectively. We also decided that optimal iterations are 3. Very important for a successful decoding is the channel estimation, which is also discussed. 1. Introduction The excessive multipath encountered in underwater sensor communication (USC) channel is creating intersymbol interference (ISI), which is limiting factor to achieve a high data rate and bit error rate (BER) performance. Various different methods to cope with multipath situation have been developed. In addition to ISI, cochannel interference (CoI) is also occurred resulting from the use of multiple transmitters in UW communication. Removal of both CoI and ISI is a challenging problem in view of difficult channel conditions. The optimal detector is a maximum likelihood detector (MLD), which can be realized, for example, by the soft Viterbi algorithm. Due to the length of the impulse response in the UW channel, the number of states in the decoder will be increased. One well-proven method to counteract ISI is the decision feedback equalized (DFE), which has been used in many UW communication links [1, 2]. However, the use of DFE has difficulties when a multipath with a number of arrivals has equal strength or low SNR [3]. The other way to cope with ISI, iterative equalizer which constitutes an outer loop is used in the receiver. An inner loop consists of iterative decoder. The assembly utilizes the error correcting power of the iterative codes to get an efficient
Synthesis and Characterization of Poly (Methyl Methacrylate)/Polyethylenimine Grafting Core-Shell Nanoparticles for CO2 Adsorption Using Soap-Free Emulsion Copolymerization  [PDF]
Jun-Won Kook, Ji Young Lee, Ki Seob Hwang, In Park, Jung Hyun Kim, Jun-Young Lee
Advances in Materials Physics and Chemistry (AMPC) , 2016, DOI: 10.4236/ampc.2016.67022
Abstract: Unlike previous emulsion polymerization, we used grafting reactions in soap-free emulsion systems. In this study, we synthesized grafted PMMA/PEI core-shell nanoparticles by varying the MMA/PEI content and molecular weight of PEI (Mn = 600, 8000, and 10,000). The size and morphology of the core-shell nanoparticles were characterized by a particle size analyzer and scanning electron microscopy. The nanoparticles were 178 - 408 nm in diameter and swelled in water or methanol by 30 - 75 nm. The size of the nanoparticles increased with MMA contents, whereas the size distribution progressively became homogeneous with increasing molecular weight of PEI. Lastly, we measured CO2 adsorption capacity of the grafted PMMA/PEI core-shell nanoparticles, and we found the capacity to be limited at a level of 0.69 mg, which occurred for nanoparticles prepared from emulsions at a pH value of 11.
Duality of Quasilocal Gravitational Energy and Charges with Non-orthogonal Boundaries
Sung-Won Kim,Won Tae Kim,John J. Oh,Ki-Hyuk Yee
Physics , 2003, DOI: 10.1103/PhysRevD.67.104027
Abstract: We study the duality of quasilocal energy and charges with non-orthogonal boundaries in the (2+1)-dimensional low-energy string theory. Quasilocal quantities shown in the previous work and some new variables arisen from considering the non-orthogonal boundaries as well are presented, and the boost relations between those quantities are discussed. Moreover, we show that the dual properties of quasilocal variables such as quasilocal energy density, momentum densities, surface stress densities, dilaton pressure densities, and Neuve-Schwarz(NS) charge density, are still valid in the moving observer's frame.
Fixed Points and Random Stability of a Generalized Apollonius Type Quadratic Functional Equation
Min June Kim,Seung Won Schin,Dohyeong Ki,Jaewon Chang
Fixed Point Theory and Applications , 2011, DOI: 10.1155/2011/671514
Effect of Sodium Bicarbonate Administration on Mortality in Patients with Lactic Acidosis: A Retrospective Analysis
Hyun Jeong Kim, Young Ki Son, Won Suk An
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0065283
Abstract: Background Lactic acidosis is a common cause of high anion gap metabolic acidosis. Sodium bicarbonate may be considered for an arterial pH <7.15 but paradoxically depresses cardiac performance and exacerbates acidosis by enhancing lactate production. This study aimed to evaluate the cause and mortality rate of lactic acidosis and to investigate the effect of factors, including sodium bicarbonate use, on death. Methods We conducted a single center analysis from May 2011 through April 2012. We retrospectively analyzed 103 patients with lactic acidosis among 207 patients with metabolic acidosis. We used SOFA and APACHE II as severity scores to estimate illness severity. Multivariate logistic regression analysis and Cox regression analysis models were used to identify factors that affect mortality. Results Of the 103 patients with a mean age of 66.1±11.4 years, eighty-three patients (80.6%) died from sepsis (61.4%), hepatic failure, cardiogenic shock and other causes. The percentage of sodium bicarbonate administration (p = 0.006), catecholamine use, ventilator care and male gender were higher in the non-survival group than the survival group. The non-survival group had significantly higher initial and follow-up lactic acid levels, lower initial albumin, higher SOFA scores and APACHE II scores than the survival group. The mortality rate was significantly higher in patients who received sodium bicarbonate. Sodium bicarbonate administration (p = 0.016) was associated with higher mortality. Independent factors that affected mortality were SOFA score (Exp (B) = 1.72, 95% CI = 1.12–2.63, p = 0.013) and sodium bicarbonate administration (Exp (B) = 6.27, 95% CI = 1.10–35.78, p = 0.039). Conclusions Lactic acidosis, which has a high mortality rate, should be evaluated in patients with metabolic acidosis. In addition, sodium bicarbonate should be prescribed with caution in the case of lactic acidosis because sodium bicarbonate administration may affect mortality.
Scattering amplitudes and thermal temperatures of the Schwarzschild-de Sitter black holes
Won Tae Kim,John J. Oh,Ki Hyuk Yee
Physics , 2002, DOI: 10.1103/PhysRevD.66.044017
Abstract: We study thermodynamic evaporation of Schwarzschild-de Sitter black holes in terms of a low energy perturbation theory. A small black hole which is far from the cosmological horizon and observers at the spacelike hypersurface where black hole attraction and expansion of cosmological horizon balance exactly are considered. In the low energy perturbation, scalar field equations are solved in both regions of the hypersurface and scattering amplitudes are derived. And then the desired thermal temperatures from the two horizons are obtained as a ``minimal'' value of the statistical thermal temperature, and the fine-tuning between amplitudes gives a relation of the two temperatures.
Graph braid groups and right-angled Artin groups
Jee Hyoun Kim,Ki Hyoung Ko,Hyo Won Park
Mathematics , 2008,
Abstract: We give a necessary and sufficient condition for a graph to have a right-angled Artin group as its braid group for braid index $\ge 5$. In order to have the necessity part, graphs are organized into small classes so that one of homological or cohomological characteristics of right-angled Artin groups can be applied. Finally we show that a given graph is planar iff the first homology of its 2-braid group is torsion-free and leave the corresponding statement for $n$-braid groups as a conjecture along with few other conjectures about graphs whose braid groups of index $\le 4$ are right-angled Artin groups.
Fischer-Tropsch Synthesis of the Promoted Co/ZSM-5 Hybrid Catalysts for the Production of Gasoline Range Hydrocarbons  [PDF]
Suk-Hwan Kang, Jae-Hong Ryu, Jin-Ho Kim, Hyo-Sik Kim, Chan-Gi Lee, Yun-Jo Lee, Ki-Won Jun
Modern Research in Catalysis (MRC) , 2014, DOI: 10.4236/mrc.2014.33013

Fischer-Tropsch synthesis (FTS) reaction for the direct production of gasoline range hydrocarbons (C5-C9) from syngas was investigated on Ru, Pt, and La promoted Co/ZSM-5 (Si/Al = 25) catalysts. The hybrid catalysts were characterized by BET surface area, XRD, H2-TPR, NH3-TPD and XPS analyses. These physico-chemical properties were correlated with activity and selectivity of the catalysts. The promoted Co/ZSM-5 hybrid catalysts were found to be superior to the unpromoted Co/ZSM-5 catalyst in terms of better C5-C9 selectivity. Pt-Co/ZSM-5 exhibited the highest catalytic activity because of the small cobalt particle size.


Up-regulated expression of l-caldesmon associated with malignancy of colorectal cancer
Kim Kyung-Hee,Yeo Seung-Gu,Kim Won Ki,Kim Dae Yong
BMC Cancer , 2012, DOI: 10.1186/1471-2407-12-601
Abstract: Background Caldesmon (CaD), a major actin-associated protein, is found in smooth muscle and non-muscle cells. Smooth muscle caldesmon, h-CaD, is a multifunctional protein, and non-muscle cell caldesmon, l-CaD, plays a role in cytoskeletal architecture and dynamics. h-CaD is thought to be an useful marker for smooth muscle tumors, but the role(s) of l-CaD has not been examined in tumors. Methods Primary colon cancer and liver metastasis tissues were obtained from colon cancer patients. Prior to chemoradiotherapy (CRT), normal and cancerous tissues were obtained from rectal cancer patients. Whole-tissue protein extracts were analyzed by 2-DE-based proteomics. Expression and phosphorylation level of main cellular signaling proteins were determined by western blot analysis. Cell proliferation after CaD siRNA transfection was monitored by MTT assay. Results The expression level of l-CaD was significantly increased in primary colon cancer and liver metastasis tissues compared to the level in the corresponding normal tissues. In cancerous tissues obtained from the patients showing poor response to CRT (Dworak grade 4), the expression of l-CaD was increased compared to that of good response group (Dworak grade 1). In line with, l-CaD positive human colon cancer cell lines were more resistant to 5-fluorouracil (5-FU) and radiation treatment compared to l-CaD negative cell lines. Artificial suppression of l-CaD increased susceptibility of colon cancer cells to 5-FU, and caused an increase of p21 and c-PARP, and a decrease of NF-kB and p-mTOR expression. Conclusion Up-regulated expression of l-CaD may have a role for increasing metastatic property and decreasing CRT susceptibility in colorectal cancer cells.
Effect of the Collimator Angle on Dosimetric Verification of the Volumetric Modulated Arc Therapy
Yong Ho Kim,Ha Ryung Park,Won Taek Kim,Dong Won Kim,Yongkan Ki,Juhye Lee,Jinsuk Bae,Dahl Park
Physics , 2015,
Abstract: Collimator angle is usually rotated when planning volumetric modulated arc therapy (VMAT) due to the leakage of radiation between multi-leaf collimator (MLC) leaves. We studied the effect of the collimator angles on the results of dosimetric verification of the VMAT plans for head and neck patients. We studied VMAT plans for 10 head and neck patients. We made 2 sets of VMAT plans for each patient. Each set was composed of 10 plans with collimator angles of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45 degrees. Plans in the first set were optimized individually and plans in the second set shared the 30 degree collimator angle optimization. Two sets of plans were verified using the 2-dimensional ion chamber array MatriXX (IBA Dosimetry, Germany). The comparison between the calculation and measurements were made by the $\gamma$-index analysis. The $\gamma$-index (2\%/2 mm) and (3\%/3 mm) passing rates had negative correlations with the collimator angle. Maximum difference between $\gamma$-index (3\%/3 mm) passing rates of different collimator angles for each patient ranged from 1.46\% to 5.60\% with an average of 3.67\%. There were significant differences (maximum 5.6\%) in the passing rates of different collimator angles. The results suggested that the accuracy of the delivered dose depends on the collimator angle. These findings are informative when choosing a collimator angle in VMAT plans.
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