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Search Results: 1 - 10 of 20994 matches for " Hyung Wook Kim "
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Numerical and Experimental Study on the Combustion and Emission Characteristics of a Dimethyl Ether (DME) Fueled Compression Ignition Engine études numériques et expérimentales sur les caractéristiques de combustion et d’émissions d’un éther diméthylique (EDM)- moteur à auto-allumage rempli de combustible
Kim Hyung Jun,Park Sung Wook,Lee Chang Sik
Oil & Gas Science and Technology , 2012, DOI: 10.2516/ogst/2011130
Abstract: A numerical investigation was carried out to study on the combustion and emission characteristics of dimethyl ether (DME) with wide ranges of injection timings in compression ignition engines. In order to simulate DME combustion processes, a KIVA-3V code coupled with a chemistry solver was used to solve the detailed chemical kinetics model of DME oxidation. In addition, the Kelvin-Helmholtz-Rayleigh-Taylor (KH-RT) hybrid breakup model and Renormalization Group (RNG) k-ε models were applied to analyze the spray characteristics and turbulent flow, respectively. To predict the NOx formation during DME combustion, a reduced Gas Research Institute (GRI) NO mechanism was used. From these results on the combustion and emission, the calculated results were compared with experimental ones for the same operating conditions. In the combustion characteristics, the calculated combustion pressure and heat release rates agreed well with experimental results. The levels of experimental NOx emissions was reduced as the start of the injection timing retarded, and also these trends appeared in calculated emission characteristics. Additionally, the calculated CO and HC emissions show an increasing trend as the start of the injection is retarded. Dans cette étude, nous considérons la simulation de la combustion du dimethyl ether (DME) dans un moteur à allumage par compression. Les caractéristiques de la combustion ainsi que les émissions polluantes sont analysées sur une large gamme d’avance à l’injection. Afin de simuler le processus de combustion du EDM, le code KIVA-3V couplé à un solveur chimique a été utilisé pour résoudre la cinétique détaillée de l’oxydation du EDM. Le modèle de rupture de Kelvin-Helmholtz-Rayleigh- Taylor (KH-RT) ainsi que le modèle de turbulence k-ε RNG ont été appliqués pour analyser respectivement les caractéristiques du jet et l’écoulement turbulent. Pour prévoir la formation de NOx pendant la combustion du EDM, le mécanisme réduit du GRI a été employé. Les résultats de simulation pour la combustion et les émissions polluantes ont été comparés aux résultats expérimentaux dans les mêmes conditions de fonctionnement. Concernant les calages de combustion, la pression moyenne simulée et les taux de chaleur dégagée sont en bon accord avec les résultats expérimentaux. Les niveaux d’émissions de NOx expérimentaux ont été réduits à mesure que l’injection est retardée; cette tendance est correctement reproduite par la simulation. Enfin, les prédictions sur les émissions en monoxyde de carbone et en hydrocarbure montrent une tendance croissante à mesure
Multifactorial, Site-Specific Recurrence Models after Radical Cystectomy for Urothelial Carcinoma: External Validation in a Cohort of Korean Patients
Hyung Suk Kim, Myong Kim, Chang Wook Jeong, Cheol Kwak, Hyeon Hoe Kim, Ja Hyeon Ku
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0100491
Abstract: Purpose The aim of this study was to evaluate the accuracy of site-specific recurrence models after radical cystectomy in the Korean population. Materials and Methods We conducted a review of an electronic medical record of 572 patients who underwent radical cystectomy for urothelial carcinoma of the bladder. Primary end point was the site-specific recurrence after radical cystectomy. Results The median follow-up in the validation cohort was 42.3 months (interquartile range: 23.0–89.3 months). During the follow-up period, there were 165 patients (28.8%), 85 (14.9%), 31 (5.4%), and 78 (13.6%) who recurred in abdomen/pelvis, thoracic region, upper urinary tract, and bone, respectively. The c-indices of abdomen/pelvis, thoracic region, upper urinary tract, and bone models 3 years after radical cystectomy were 0.69 (95% confidence interval [CI], 0.65–0.73), 0.69 (95% CI, 0.64–0.75), 0.61 (95% CI, 0.52–0.69), and 0.65 (95% CI, 0.59–0.71), respectively. Kaplan-Meier curves demonstrated that models discriminated well and log-rank test were all highly significant (all p<0.001), except upper urinary tract model (p = 0.366). Decision curve analysis revealed that the use of prediction models for abdomen/pelvis, thoracic region, and bone recurrence was associated with net benefit gains relative to the treat-all strategy, but not the model for upper urinary tract recurrence. Conclusions Abdomen/pelvis, thoracic region, and bone models demonstrate moderate discrimination, adequate calibration, and meaningful net benefit gains, whereas upper urinary tract model does not seem applicable to patients from Asia because it has suboptimal accuracy.
Schwannoma of ascending colon treated by laparoscopic right hemicolectomy
Hun Jin Kim, Chang Hyung Kim, Sang Woo Lim, Jung Wook Huh, Young Jin Kim, Hyeong Rok Kim
World Journal of Surgical Oncology , 2012, DOI: 10.1186/1477-7819-10-81
Molecular and Kinetic Properties of Two Acetylcholinesterases from the Western Honey Bee, Apis mellifera
Young Ho Kim,Deok Jea Cha,Je Won Jung,Hyung Wook Kwon,Si Hyeock Lee
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0048838
Abstract: We investigated the molecular and kinetic properties of two acetylcholinesterases (AmAChE1 and AmAChE2) from the Western honey bee, Apis mellifera. Western blot analysis revealed that AmAChE2 has most of catalytic activity rather than AmAChE1, further suggesting that AmAChE2 is responsible for synaptic transmission in A. mellifera, in contrast to most other insects. AmAChE2 was predominately expressed in the ganglia and head containing the central nervous system (CNS), while AmAChE1 was abundantly observed not only in the CNS but also in the peripheral nervous system/non-neuronal tissues. Both AmAChEs exist as homodimers; the monomers are covalently connected via a disulfide bond under native conditions. However, AmAChE2 was associated with the cell membrane via the glycophosphatidylinositol anchor, while AmAChE1 was present as a soluble form. The two AmAChEs were functionally expressed with a baculovirus system. Kinetic analysis revealed that AmAChE2 has approximately 2,500-fold greater catalytic efficiency toward acetylthiocholine and butyrylthiocholine than AmAChE1, supporting the synaptic function of AmAChE2. In addition, AmAChE2 likely serves as the main target of the organophosphate (OP) and carbamate (CB) insecticides as judged by the lower IC50 values against AmAChE2 than against AmAChE1. When OP and CB insecticides were pre-incubated with a mixture of AmAChE1 and AmAChE2, a significant reduction in the inhibition of AmAChE2 was observed, suggesting a protective role of AmAChE1 against xenobiotics. Taken together, based on their tissue distribution pattern, molecular and kinetic properties, AmAChE2 plays a major role in synaptic transmission, while AmAChE1 has non-neuronal functions, including chemical defense.
Chronic NMDA administration to rats increases brain pro-apoptotic factors while decreasing anti-Apoptotic factors and causes cell death
Hyung-Wook Kim, Yunyoung C Chang, Mei Chen, Stanley I Rapoport, Jagadeesh S Rao
BMC Neuroscience , 2009, DOI: 10.1186/1471-2202-10-123
Abstract: Using real time RT-PCR and Western blotting, chronic NMDA administration was shown to decrease mRNA and protein levels of anti-apoptotic markers Bcl-2 and BDNF, and of their transcription factor phospho-CREB in the cortex. Expression of pro-apoptotic Bax, Bad, and 14-3-3ζ was increased, as well as Fluoro-Jade B (FJB) staining, a marker of neuronal loss.This alteration in the balance between pro- and anti-apoptotic factors by chronic NMDA receptor activation in this animal model may contribute to neuronal loss, and further suggests that the model can be used to examine multiple processes involved in excitotoxicity.Glutamate is the major excitatory neurotransmitter in vertebrate brain. Glutamate acts on two different classes of receptors, ionotropic glutamatergic receptors and G-protein-coupled metabotropic receptors. The ionotropic receptors are further classified into α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA), kainate, and N-methyl-D-aspartate (NMDA) receptors [1]. Binding of glutamate to NMDA receptors (NMDAR) results in an influx of extracellular Ca2+ into the cell, which leads to the activation of many Ca2+-dependent enzymes such as calpain [2], calcineurin [3], inducible nitric oxide synthase (iNOS) expression [4] and arachidonic acid (AA, 20:4n-6) selective cytosolic phospholipase A2(cPLA2)[5,6]. NMDAR are present throughout the brain and predominantly in frontal cortex and hippocampal CA1 region [7]. Activation of NMDAR also induces signaling cascades involved in learning and memory, synaptic excitability and plasticity, and neuronal degeneration [8]. Overactivation of glutamate receptors can result in the death of neurons through a process termed excitotoxicity. Excitotoxicity has been implicated in several neurodegenerative diseases, including Alzheimer disease [9-11], Huntington disease [12], schizophrenia [13], and bipolar disorder [14-16]. Chronic NMDA administration to rats reduced NMDAR subunits and increased arachidonic acid cascade mar
Somatostatin adjunctive therapy for non-variceal upper gastrointestinal rebleeding after endoscopic therapy
Cheol Woong Choi,Dae Hwan Kang,Hyung Wook Kim,Su Bum Park
World Journal of Gastroenterology , 2011, DOI: 10.3748/wjg.v17.i29.3441
Abstract: AIM: To evaluate the effect of pantoprazole with a somatostatin adjunct in patients with acute non-variceal upper gastrointestinal bleeding (NVUGIB). METHODS: We performed a retrospective analysis of a prospective database in a tertiary care university hospital. From October 2006 to October 2008, we enrolled 101 patients with NVUGIB that had a high-risk stigma on endoscopy. Within 24 h of hospital admission, all patients underwent endoscopic therapy. After successful endoscopic hemostasis, all patients received an 80-mg bolus of pantoprazole followed by continuous intravenous infusion (8 mg/h for 72 h). The somatostatin adjunct group (n = 49) also received a 250-μg bolus of somatostatin, followed by continuous infusion (250 μg/h for 72 h). Early rebleeding rates, disappearance of endoscopic stigma and risk factors associated with early rebleeding were examined. RESULTS: Early rebleeding rates were not significantly different between treatment groups (12.2% vs 14.3%, P = 0.766). Disappearance of endoscopic stigma on the second endoscopy was not significantly different between treatment groups (94.2% vs 95.9%, P = 0.696). Multivariate analysis showed that the complete Rockall score was a significant risk factor for early rebleeding (P = 0.044, OR: 9.080, 95% CI: 1.062-77.595). CONCLUSION: The adjunctive use of somatostatin was not superior to pantoprazole monotherapy after successful endoscopic hemostasis in patients with NVUGIB.
Risk factors for rebleeding after angiographically negative acute gastrointestinal bleeding
Ijin Joo, Hyo-Cheol Kim, Jin Wook Chung, Hwan Jun Jae, Jae Hyung Park
World Journal of Gastroenterology , 2009,
Abstract: AIM: To identify possible predictive factors for rebleeding after angiographically negative findings in patients with acute non-variceal gastrointestinal bleeding.METHODS: From January 2000 to July 2007, 128 patients with acute non-variceal gastrointestinal bleeding had negative findings after initial angiography. Clinical and laboratory parameters were analyzed retrospectively.RESULTS: Among 128 patients, 62 had no recurrent gastrointestinal bleeding and 66 had recurrent gastrointestinal bleeding within 30 d. As determined by the use of multivariate analysis, an underlying malignancy, liver cirrhosis and hematemesis were significant factors related to recurrent gastrointestinal bleeding.CONCLUSION: Clinical factors including underlying malignancy, liver cirrhosis, and hematemesis are important predictors for rebleeding after angiographically negative findings in patients with acute non-variceal gastrointestinal bleeding.
Ruled minimal surfaces in the three dimensional Heisenberg group
Young Wook Kim,Sung-Eun Koh,Hyung Yong Lee,Heayong Shin,Seong-Deog Yang
Mathematics , 2009,
Abstract: It is shown that parts of planes, helicoids and hyperbolic paraboloids are the only minimal surfaces ruled by geodesics in the three dimensional Riemannian Heisenberg group. It is also shown that they are the only surfaces in the three dimensional Heisenberg group whose mean curvature is zero with respect to both of the standard Riemannian metric and the standard Lorentzian metric.
An Interesting Case of Cardiac Amyloidosis Initially Misdiagnosed as Syndrome X  [PDF]
Hyung Rae Sohn, Bong Gun Song, Eun Jin Kim, Seong Yeon Jeong, Su-Min Hong, Hyun Gul Jung, Hye-Jin Jung, Wook-Hyun Cho, Suk-Koo Choi
International Journal of Clinical Medicine (IJCM) , 2011, DOI: 10.4236/ijcm.2011.25102
Abstract: Cardiac infiltration of amyloid fibril results in progressive cardiomyopathy with a grave prognosis and results in cardiac diseases such as congestive heart disease, cardiomyopathy, valvular heart disease, and arrhythmias. We present a rare case of cardiac amyloidosis initially misdiagnosed as syndrome X in which recurrent chest pain and progressive heart failure could be managed finally by heart transplantation.
Associated factors for a hyperechogenic pancreas on endoscopic ultrasound
Cheol Woong Choi, Gwang Ha Kim, Dae Hwan Kang, Hyung Wook Kim, Dong Uk Kim, Jeong Heo, Geun Am Song, Do Youn Park, Suk Kim
World Journal of Gastroenterology , 2010,
Abstract: AIM: To identify the associated risk factors for hyperechogenic pancreas (HP) which may be observed on endoscopic ultrasound (EUS) and to assess the relationship between HP and obesity.METHODS: From January 2007 to December 2007, we prospectively enrolled 524 consecutive adults who were scheduled to undergo EUS. Patients with a history of pancreatic disease or with hepatobiliary or advanced gastrointestinal cancer were excluded. Finally, 284 patients were included in the analyses. We further analyzed the risk of HP according to the categories of visceral adipose tissue (VAT) and subcutaneous adipose tissue in 132 patients who underwent abdominal computed tomography scans.RESULTS: On univariate analysis, age older than 60 years, obesity (body mass index > 25 kg/m2), fatty liver, diabetes mellitus, hypertension and hypercholesterolemia were identified as risk factors associated with HP (P < 0.05). On multivariate analysis, fatty liver [P = 0.008, odds ratio (OR) = 2.219], male gender (P = 0.013, OR = 2.636), age older than 60 years (P = 0.001, OR = 2.874) and hypertension (P = 0.044, OR = 2.037) were significantly associated with HP. In the subgroup analysis, VAT was a statistically significant risk factor for HP (P = 0.010, OR = 5.665, lowest quartile vs highest quartile).CONCLUSION: HP observed on EUS was associated with fatty liver, male gender, age older than 60 years, hypertension and VAT.
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