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Search Results: 1 - 10 of 60693 matches for " Jae Hong Lee "
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Thermal Degradation Kinetics of iPP/Pd Nanocomposite Prepared by a Drying Process  [PDF]
Y Jae-Young Lee, Hong-Ki Lee, Sung-Wan Hong, Il-Yub Choi
Advances in Materials Physics and Chemistry (AMPC) , 2012, DOI: 10.4236/ampc.2012.24B030
Abstract: Palladium (Pd) nanoparticles were incorporated into isotactic polypropylene (iPP) film by a one-step dry process. iPP film was exposed to the sublimed Pd(acac)2 vapor in a glass vessel at 180oC. The Pd nanoparticles were observed by transmission electron microscope (TEM), and it was found that metallic nanoparticles were selectively loaded on the amorphous regions between the lamellae in iPP. Thermal degradation kinetics was investigated by introducing the data of thermogravimetric analysis (TGA) to Flynn & Wall equation. TGA data showed that thermal degradation temperature (Td) of the neat iPP was improved about 35oC by loading 0.27 wt% Pd nanoparticles. Thermal degradation activation energy (Ed) for iPP/Pd nanocomposite was 227.85 kJ/mol while that of neat iPP was 220.57 kJ/mol. These results meant that the Pd nanoparticles acted as a retardant in the thermal degradation of neat iPP polymer chain.
Power Law in Firms Bankruptcy
Byoung Hee Hong,Kyoung Eun Lee,Jae Woo Lee
Physics , 2007, DOI: 10.1016/j.physleta.2006.09.034
Abstract: We consider the scaling behaviors for fluctuations of the number of Korean firms bankrupted in the period from August 1 2002 to October 28 2003. We observe a power law for the distribution of the number of the bankrupted firms. The Pareto exponent is close to unity. We also consider the daily increments of the number of firms bankrupted. The probability distribution of the daily increments for the firms bankrupted follows the Gaussian distribution in central part and has a fat tail. The tail parts of the probability distribution of the daily increments for the firms bankrupted follow a power law.
Universality Class of Bak-Sneppen Model on Scale-Free Network
Kyoung Eun Lee,Byoung Hee Hong,Jae Woo Lee
Physics , 2005,
Abstract: We study the critical properties of the Bak-Sneppen coevolution model on scale-free networks by Monte Carlo method. We report the distribution of the avalanche size and fractal activity through the branching process. We observe that the critical fitness $f_c (N)$ depends on the number of the node such as $f_c (N) \sim 1/ \log (N)$ for both the scale-free network and the directed scale-free network. Near the critical fitness many physical quantities show power-law behaviors. The probability distribution $P(s)$ of the avalanche size at the critical fitness shows a power-law like $P(s) \sim s^{-\tau}$ with $\tau=1.80(3)$ regardless of the scale-free network and the directed scale free network. The probability distribution $P_f (t)$ of the first return time also shows a power-law such as $P_f (t) \sim t^{-\tau_f}$. The probability distribution of the first return time has two scaling regimes. The critical exponents $\tau_f$ are equivalent for both the scale-free network and the directed scale-free network. We obtain the critical exponents as $\tau_{f1} =2.7(1)$ at $t < t_c$ and $\tau_{f2} = 1.72(3)$ at $ t >t_c$ where the crossover time $t_c \sim 100$. The Bak-Sneppen model on the scale-free network and directed scale-free network shows a unique universality class. The critical exponents are different from the mean-field results. The directionality of the network does not change the universality on the network.
Biotransformation of endosulfan by the tiger worm, Eisenia fetida  [PDF]
Byeoung-Soo Park, Jae-Hong Yoo, Jeong-Han Kim, Sung-Eun Lee, Jang-Eok Kim
Journal of Agricultural Chemistry and Environment (JACEN) , 2012, DOI: 10.4236/jacen.2012.11004
Abstract: This study assesses the role of the earthworm, Eisenia fetida, in the breakdown of endosulfan in a soil environment. Two strains of E. fetida were used in this study to assess the effect of salinity on toxicity and metabolism of endosulfan in these earthworms. One strain of E. fetida (R) was reared in high salinity soil (over 2.0 dS/m of electric conductivity) from Shiwha lake, Korea. A control strain (W) was reared in pig manure compost. Acute toxicity of endosulfan was lower in the R strain when endosulfan was injected. In vitro metabolic studies of endosulfan based on microsomal preparations showed that both strains produced two major metabolites, endosulfan sulfate and endosulfan diol. The production rate of endodulfan sulfate was not significantly different between the strains, while endosulfan diol production was significantly different. In vivo metabolism studies showed only one primary metabolite, endosulfan sulfate, was produced by both strains. HPLC-MS/MS analysis showed annetocin was the indicative protein newly expressed in the R strain in relation to salinity exposure. These findings suggest salinity may induce hydrolyzing enzymes to produce endosulfan diol from endosulfan.
A Compact Vertical Scanner for Atomic Force Microscopes
Jae Hong Park,Jaesool Shim,Dong-Yeon Lee
Sensors , 2010, DOI: 10.3390/s101210673
Abstract: A compact vertical scanner for an atomic force microscope (AFM) is developed. The vertical scanner is designed to have no interference with the optical microscope for viewing the cantilever. The theoretical stiffness and resonance of the scanner are derived and verified via finite element analysis. An optimal design process that maximizes the resonance frequency is performed. To evaluate the scanner’s performance, experiments are performed to evaluate the travel range, resonance frequency, and feedback noise level. In addition, an AFM image using the proposed vertical scanner is generated.
Changes of empathy in medical college and medical school students: 1-year follow up study
Hong Minha,Lee Won,Park Jae,Yoon Tai
BMC Medical Education , 2012, DOI: 10.1186/1472-6920-12-122
Abstract: Background This study aims to determine the correlation between medical education systems, medical college (MC) and medical school (MS), and empathy by investigating the changes in empathy among students with each additional year of medical education. Methods The subjects were MC and MS students who had participated in the same study the previous year. All participants completed the same self-report instruments: a questionnaire on sociodemographic characteristics, and the Korean edition of the Student Version of the Jefferson Scale of Empathy (JSE-S-K), Among 334 students, the final analysis was conducted on the data provided by 113 MC and 120 MS students, excluding 101 with incomplete data. Results The age and sex did not affect the changes in empathy. Though the JSE-S-K score of MS was significantly higher than that of MC in initial investigation, this study found no difference of empathy between MC and MS. Conclusion Empathy increased significantly after one year of medical education. The difference between two education systems, MC and MS, did not affect the changes in empathy.
The Possibility of Inflation in Asymptotically Safe Gravity
Sungwook E. Hong,Young Jae Lee,Heeseung Zoe
Physics , 2011, DOI: 10.1142/S0218271812500629
Abstract: We examine the inflationary modes in the cubic curvature theories in the context of asymptotically safe gravity. On the phase space of the Hubble parameter, there exists a critical point which corresponds to the slow-roll inflation in Einstein frame. Most of the e-foldings are attained around the critical point for each inflationary trajectories. If the coupling constants $g_i$ have the parametric relations generated as the power of the relative energy scale of inflation $H_0$ to the ultraviolet cutoff $\Lambda$, a successful inflation with more than 60 e-foldings occurs near the critical point.
The Kepler Eclipsing System KIC 5621294 and its Substellar Companion
Jae Woo Lee,Kyeongsoo Hong,Tobias Cornelius Hinse
Physics , 2014, DOI: 10.1088/0004-6256/149/3/93
Abstract: We present the physical properties of KIC 5621294 showing light and timing variations from the ${\it Kepler}$ photometry. Its light curve displays partial eclipses and O'Connell effect with Max II fainter than Max I, which was fitted quite well by applying third-body and spot effects to the system. The results indicate that the eclipsing pair is a classical Algol-type system with parameters of $q$=0.22, $i$=76$^\circ$.8, and $\Delta$($T_{1}$--$T_{2}$)=4,235 K, in which the detached primary component fills about 77\% of its limiting lobe. Striking discrepancies exist between the primary and secondary eclipse times obtained with the method of Kwee \& van Woerden. These are mainly caused by surface inhomogeneities due to spot activity detected in our light-curve synthesis. The 1,253 light-curve timings from the Wilson-Devinney code were used for a period study. It was found that the orbital period of KIC 5621294 has varied due to a periodic variation overlaid on a downward parabola. The sinusoidal variation with a period of 961 d and a semi-amplitude of 22.5 s most likely arise from a light-time effect due to a third component with a mass of $M_3 \sin i_3$=46.9 M$\rm_{Jup}$, which is in good agreement with that calculated from the light curve itself. If its orbital inclination is larger than about 40$^\circ$, the mass of the circumbinary object would possibly match a brown dwarf. The parabolic variation could not be fully explained by either a mass transfer between the binary components or an angular momentum via magnetic braking. It is possible that the parabola may only be the observed part of a period modulation caused by the presence of another companion in a wider orbit.
On the Capacity of Doubly Correlated MIMO Channels
Hyundong Shin,Moe Z. Win,Jae Hong Lee,Marco Chiani
Mathematics , 2005,
Abstract: In this paper, we analyze the capacity of multiple-input multiple-output (MIMO) Rayleigh-fading channels in the presence of spatial fading correlation at both the transmitter and the receiver, assuming that the channel is unknown at the transmitter and perfectly known at the receiver. We first derive the determinant representation for the exact characteristic function of the capacity, which is then used to determine the trace representations for the mean, variance, skewness, kurtosis, and other higher-order statistics (HOS). These results allow us to exactly evaluate two relevant information-theoretic capacity measures--ergodic capacity and outage capacity--and the HOS of the capacity for such a MIMO channel. The analytical framework presented in the paper is valid for arbitrary numbers of antennas and generalizes the previously known results for independent and identically distributed or one-sided correlated MIMO channels to the case when fading correlation exists on both sides. We verify our analytical results by comparing them with Monte Carlo simulations for a correlation model based on realistic channel measurements as well as a classical exponential correlation model.
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
Abstract:

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.

 

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