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Search Results: 1 - 10 of 10924 matches for " Jeong Woo Park "
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Finite Element Analysis of Tire Traction Using a Rubber-Ice Friction Model  [PDF]
Hyun Chul Jung, Woo Cheol Park, Kyoung Moon Jeong
Open Journal of Applied Sciences (OJAppS) , 2018, DOI: 10.4236/ojapps.2018.811040
Abstract: The friction of road surface covered by snow or ice is very low and that results in reducing vehicle traction forces and potential traffic accidents. In general, to establish a master curve on a rubber-ice friction model is difficult because the ice surface, being not far removed from its melting point, reacts itself very sen-sitively to pressure, speed, and temperature changes. In this paper, an accepta-ble frictional interaction model was implemented to finite element method to rationally examine the frictional interaction behavior on ice between the tire and the road surface. The formula of friction characteristic according to tem-perature and sliding velocity on the ice surface was applied for tire traction analysis. Numerical results were verified by comparing the outdoor test data and it was confirmed to indicate similar correlation. It is found that the rub-ber-ice friction model will be useful for the improvement of the ice traction performance of tire.
Annexin A2 Binds RNA and Reduces the Frameshifting Efficiency of Infectious Bronchitis Virus
Hoyun Kwak, Min Woo Park, Sunjoo Jeong
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0024067
Abstract: Annexin A2 (ANXA2) is a protein implicated in diverse cellular functions, including exocytosis, DNA synthesis and cell proliferation. It was recently proposed to be involved in RNA metabolism because it was shown to associate with some cellular mRNA. Here, we identified ANXA2 as a RNA binding protein (RBP) that binds IBV (Infectious Bronchitis Virus) pseudoknot RNA. We first confirmed the binding of ANXA2 to IBV pseudoknot RNA by ultraviolet crosslinking and showed its binding to RNA pseudoknot with ANXA2 protein in vitro and in the cells. Since the RNA pseudoknot located in the frameshifting region of IBV was used as bait for cellular RBPs, we tested whether ANXA2 could regulate the frameshfting of IBV pseudoknot RNA by dual luciferase assay. Overexpression of ANXA2 significantly reduced the frameshifting efficiency from IBV pseudoknot RNA and knockdown of the protein strikingly increased the frameshifting efficiency. The results suggest that ANXA2 is a cellular RBP that can modulate the frameshifting efficiency of viral RNA, enabling it to act as an anti-viral cellular protein, and hinting at roles in RNA metabolism for other cellular mRNAs.
The Effect of Tire Design Parameters on the Force Transmissibility  [PDF]
Woo Cheol Park, Hee Kyu Lim, Kyoung Moon Jeong, Tan Wan Kim
Open Journal of Applied Sciences (OJAppS) , 2018, DOI: 10.4236/ojapps.2018.810035
Abstract: A finite element modeling technique is employed in this paper to predict the force transmissibility of tire-cavity-wheel assembly under a free-fixed condition. The tire and wheel force transmissibility is factor in structure borne road noise performance. In order to improve structure borne noise, it is required to lower the 1st peak frequency of force transmissibility. This paper presents an application of finite element analysis modeling along with experimental verification to predict the force transmissibility of tire and wheel assembly. The results of finite element analysis for force transmissibility are shown to be in good agreement with the results from the indoor test. In order to improve structure borne noise, it is required to lower the 1st peak frequency of force transmissibility. And, the effect of the tire design parameters such as the density and modulus of a rubber and the cord stiffness on the force transmissibility is discussed. It is found that the prediction of the force transmissibility model using finite element analysis will be useful for the improvement of the road noise performance of passenger car tire.
Vibration Electrochemical Micromachining Based on Coulostatic Analysis
Uk Su Kim,Yoon Jun Jung,Jeong Woo Park
International Journal of Applied Physics and Mathematics , 2013, DOI: 10.7763/ijapm.2013.v3.189
Abstract: One primary issue in pulse electrochemical micromachining is using pulses of electrical current to control precise machining resolution as well as the uniform electrolyte flow inside inter electrode gap between two electrodes. Periodical replacement of electrolyte flush away generated heat and gas bubbles which interrupt stable electrochemical reaction with uniform ionic charging in electrolyte. Though PECM require precise control of electrical parameters, such as pulse time, duty factor, applied current/voltage and total machining time, quantitative analysis of these parameter, especially pulse time, has not been introduced. This paper demonstrates rough prediction process of pulse time and machining resolution by analyzing high resolution pulse signals acquired from PECM operation. Additionally this research suggests vibration electrochemical polishing (VECP) assisted by ultrasonic vibration for enhancing electrochemical reaction and surface quality compared to the conventional ECP. The localized roughness of work material is measured by atomic force microscopy (AFM) for detailed information on surface. Besides roughness, overall surface quality and productivity etc. are compared with conventional ECP
Thermodynamic instability and first-order phase transition in an ideal Bose gas
Jeong-Hyuck Park,Sang-Woo Kim
Physics , 2008, DOI: 10.1103/PhysRevA.81.063636
Abstract: We conduct a rigorous investigation into the thermodynamic instability of ideal Bose gas confined in a cubic box, without assuming thermodynamic limit nor continuous approximation. Based on the exact expression of canonical partition function, we perform numerical computations up to the number of particles one million. We report that if the number of particles is equal to or greater than a certain critical value, which turns out to be 7616, the ideal Bose gas subject to Dirichlet boundary condition reveals a thermodynamic instability. Accordingly we demonstrate - for the first time - that, a system consisting of finite number of particles can exhibit a discontinuous phase transition featuring a genuine mathematical singularity, provided we keep not volume but pressure constant. The specific number, 7616 can be regarded as a characteristic number of 'cube' that is the geometric shape of the box.
Existence of a critical point in the phase diagram of the ideal relativistic neutral Bose gas
Jeong-Hyuck Park,Sang-Woo Kim
Physics , 2010, DOI: 10.1088/1367-2630/13/3/033003
Abstract: We explore the phase transitions of the ideal relativistic neutral Bose gas confined in a cubic box, without assuming the thermodynamic limit nor continuous approximation. While the corresponding non-relativistic canonical partition function is essentially a one-variable function depending on a particular combination of temperature and volume, the relativistic canonical partition function is genuinely a two-variable function of them. Based on an exact expression of the canonical partition function, we performed numerical computations for up to hundred thousand particles. We report that if the number of particles is equal to or greater than a critical value, which amounts to 7616, the ideal relativistic neutral Bose gas features a spinodal curve with a critical point. This enables us to depict the phase diagram of the ideal Bose gas. The consequent phase transition is first-order below the critical pressure or second-order at the critical pressure. The exponents corresponding to the singularities are 1/2 and 2/3 respectively. We also verify the recently observed `Widom line' in the supercritical region.
Two-dimensional Bose-Einstein condensate under pressure
Wonyoung Cho,Sang-Woo Kim,Jeong-Hyuck Park
Physics , 2014, DOI: 10.1088/1367-2630/17/1/013038
Abstract: Evading the Mermin-Wagner-Hohenberg no-go theorem and revisiting with rigor the ideal Bose gas confined in a square box, we explore a discrete phase transition in two spatial dimensions. Through both analytic and numerical methods we verify that thermodynamic instability emerges if the number of particles is sufficiently yet finitely large: specifically $N\geq 35131$. The instability implies that the isobar of the gas zigzags on the temperature-volume plane, featuring supercooling and superheating phenomena. The Bose-Einstein condensation then can persist from absolute zero to the superheating temperature. Without necessarily taking the large $N$ limit, under constant pressure condition, the condensation takes place discretely both in the momentum and in the position spaces. Our result is applicable to a harmonic trap. We assert that experimentally observed Bose-Einstein condensations of harmonically trapped atomic gases are a first-order phase transition which involves a discrete change of the density at the center of the trap.
Isobar of an ideal Bose gas within the grand canonical ensemble
Imtak Jeon,Sang-Woo Kim,Jeong-Hyuck Park
Physics , 2011, DOI: 10.1103/PhysRevA.84.023636
Abstract: We investigate the isobar of an ideal Bose gas confined in a cubic box within the grand canonical ensemble, for a large yet finite number of particles, N. After solving the equation of the spinodal curve, we derive precise formulae for the supercooling and the superheating temperatures which reveal an N^{-1/3} or N^{-1/4} power correction to the known Bose-Einstein condensation temperature in the thermodynamic limit. Numerical computations confirm the accuracy of our analytical approximation, and further show that the isobar zigzags on the temperature-volume plane if N is greater than or equal to 14393. In particular, for the Avogadro's number of particles, the volume expands discretely about 10^5 times. Our results quantitatively agree with a previous study on the canonical ensemble within 0.1% error.
Large-Scale Production of Microalgal Lipids Containing High Levels of Docosahexaenoic Acid upon Fermentation of Aurantiochytrium sp. KRS101  [PDF]
Won-Kyung Hong, Anna Yu, Baek-Rock Oh, Jang Min Park, Chul Ho Kim, Jung-Hoon Sohn, Akihiko Kondo, Jeong-Woo Seo
Food and Nutrition Sciences (FNS) , 2013, DOI: 10.4236/fns.2013.49A1001

In this study, large-scale production of microalgal lipid containing high levels of docosahexaenoic acid (DHA) by fermentation of Aurantiochytrium sp. KRS101 was performed. The microalgal strain yielded productivity of docosahex-aenoic acid (DHA) productivity of 1.08 and 1.6 g/L/d by fermentation at 300-L and 5000-L scale stirrer-type bioreactor. The productivity was significantly enhanced upto 5.6 g/L/d by fermentation at 6000-L scale airlift-type bioreactor, probably due to the reduced shearing force. The microalgal lipid could be efficiently recovered by safe extraction methods such as ethanol extraction, hot water extraction or supercritical fluid extraction, promising commercial potential of the microalgal DHA-rich lipid in the food and feed industry.

“Early Rupture of Membranes” during Induced Labor as a Risk Factor for Cesarean Delivery in Term Nulliparas
Seung Mi Lee, Jeong Woo Park, Chan-Wook Park, Bo Hyun Yoon
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039883
Abstract: Objective To determine if “early rupture of membranes” (early ROM) during induction of labor is associated with an increased risk of cesarean section in term nulliparas. Study Design The rate of cesarean section and the timing of ROM during the course of labor were examined in term singleton nulliparas whose labor was induced. Cases were divided into 2 groups according the timing of ROM: 1)“early ROM”, defined as ROM at a cervical dilatation<4 cm during labor; and 2) “late ROM”, ROM at a cervical dilatation≥4 cm during labor. Nonparametric techniques were used for statistical analysis. Results 1) In a total of 500 cases of study population, “early ROM” occurred in 43% and the overall cesarean section rate was 15.8%; 2) patients with “early ROM” had a higher rate of cesarean section and cesarean section due to failure to progress than did those with “late ROM” (overall cesarean section rate: 24%[51/215] vs. 10%[28/285], p<0.01; cesarean section rate due to failure to progress: 18%[38/215] vs. 8%[22/285], p<0.01 for each) and this difference remained significant after adjusting for confounding variables. Conclusion “Early ROM” during the course of induced labor is a risk factor for cesarean section in term singleton nulliparas.
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