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Search Results: 1 - 10 of 25665 matches for " Yeon-Gwan Lee "
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Parametric Study of the Reflective Periodic Grating for In-Plane Displacement Measurement Using Optical Fibers
Yeon-Gwan Lee,Dae-Hyun Kim,Chun-Gon Kim
Sensors , 2012, DOI: 10.3390/s120404265
Abstract: This paper presents a technique for a simple sensing principle that can be used for the measurement of displacement. The proposed sensor head is composed of a reflective grating panel and an optical fiber as a transceiver. The simplified layout contributes to resolving the issues of space restraints during installation and complex cabling problems in transmission fiber optic sensors. In order to verify the effectiveness of the proposed technique, it is important to obtain the sinusoidal signal reflected from the grating for reasonable phase tracking. In the numerical analysis, a real wave based optical beam model is proposed for the extraction of predicted signal according to the grating width and ratio of reflection bar width to spacing. The grating pattern design to obtain a sine wave reflected sensor signal was determined within an R-square value of 0.98 after sine curve fitting analysis. Consequently, the proposed sensor principle achieved the in-plane displacement measurement with a maximum accuracy error of 5.34 μm.
High Temperature Endurable Fiber Optic Accelerometer
Yeon-Gwan Lee,Jin-Hyuk Kim,Chun-Gon Kim
Shock and Vibration , 2014, DOI: 10.1155/2014/571017
Abstract: This paper presents a low frequency fiber optic accelerometer for application in high temperature environments of civil engineering structures. The reflection-based extrinsic fiber optic accelerometer developed in this study consists of a transmissive grating panel, reflective mirror, and two optical fiber collimators as the transceiver whose function can be maintained up to 130°C. The dynamic characteristics of the sensor probe were investigated and the correlation between the natural frequency of the sensor probe and temperature variation was described and discussed. Furthermore, high temperature simulation equipment was designed for the verification test setup of the developed accelerometer for high temperature. This study was limited to consideration of 130°C applied temperature to the proposed fiber optic accelerometer due to an operational temperature limitation of commercial optical fiber collimator. The sinusoidal low frequency accelerations measured from the developed fiber optic accelerometer at 130°C demonstrated good agreement with that of an MEMS accelerometer measured at room temperature. The developed fiber optic accelerometer can be used in frequency ranges below 5.1?Hz up to 130°C with a margin of error that is less than 10% and a high sensitivity of 0.18?(m/s2)/rad. 1. Introduction Over the past three decades, many types of fiber optic accelerometers (FOAs) have been developed because optical fibers (OFs) allow structural health monitoring within highly electromagnetic environments [1].Furthermore, optical fiber with fused silica is useful in a wide temperature range up to about 1000°C [2] although it depends on the optical fiber material such as fused silica and sapphire (Al2O3, single crystal alumina) [3, 4]. While most intensity-based fiber optic sensor systems are relatively low cost, fiber Bragg grating (FBG) sensor systems are rather higher cost wavelength shift interrogation equipment for high speed sampling frequency rates. Alternatively, intensity modulation techniques have been conducted on grating-based extrinsic type fiber optic sensors (FOSs) [5–7] because the grating-based sensors [8, 9] possess significant advantages [10]: simple mechanical structure and good reliability, among others. Therefore, research on grating-based fiber optic sensors has been conducted based on the shutter effect [9, 11] or the Moiré phenomenon techniques [7], which require four optical fiber lines and two grating panels. However, these transmission type FOSs [6, 7, 9, 11], including the Moiré fringe-based FOA, depending on the transmitted light
Hydrogen magnetic reaction gene regulation
Yeon Sook Kim,Dae Gwan Lee,Suk Keun Lee
Quantitative Biology , 2012,
Abstract: A new gene regulation system using weak magnetic field can induce the hydrogen magnetic reaction (HMR) in hydrogen atoms, and subsequently affect the electrostatic polarity of hydrogen bonds in DNA base pairs. The HMR can sequentially activate the DNA base pair polarities of target DNA. With the characteristic base pair polarities of DNA duplex the (pyrimidine)m-(purine)n DNA segment is a basic unit to maintain and to accumulate the electrostatic energy of DNA duplex (1). To enhance the polarities of objective DNA this HMR gene regulation (HMR-GR) uses the polarized magnetic field with optimal nucleotide exposure time for T:A and C:G base pairs (50 msec and 80 msec, respectively). The targeting efficiency of HMR-GR to the objective DNA is theoretically up to 25%. In the present study, the HMR-GR expanded the conformation of oligo-dsDNA in vitro, implicating the active state of DNA, and also enhanced the restriction endonuclease digestion, in vitro RNA transcription, and the production of green fluorescence protein and {\beta}-galactosidase by using each RE site sequence and relevant promoter sequence, respectively. Taken together, it is assumed that the HMR-GR is an effective and safe method to control the multiple genes sequentially by activating their specific DNA motifs.
South Korean Economic Miracle and Its Reflections in Los Angeles Times and New York Times, 1975-1979
Lee Young-gwan
Asian Social Science , 2012, DOI: 10.5539/ass.v8n7p91
Abstract: The major characteristics of South Korea’s economy had been set up during 1970s. The legacy of South Korea’s economic development model was created during the last half of 1970s. The export-oriented economy became the major characteristics of South Korea’s economy. Politically, the legacy of Park Chung-hee as a godfather figure developed the model led by a strong Presidential leadership. Economic initiatives introduced and carried out by a person not by the system. Socially, the sufficient distribution system of wealth was forced to be sacrificed for the economic development. The reports of Los Angeles Times and New York Times confirmed the facts. South Korea achieved its economic miracle. The legacy was established in the 1970s especially the late half of the decade. Through the reports of those two major American newspapers a new image of South Korea was created while they provided vivid American views on South Korea’s economic development of the period.
American Views on South Korea’s Economic Development in Los Angeles Times and New York Times, 1970-1974
Lee Young-gwan
Asian Social Science , 2011, DOI: 10.5539/ass.v7n5p85
Abstract: The first half of 1970s was one of the crucial periods to understand the South Korea’s economic success. South Korea achieved great economic success as President Park Chung-hee concentrated his effort to maintain economic development to consolidate his dictatorial power as well as to overcome North Korean threats. Los Angeles Times and New York Times dealt with the issues on the South Korea’s economy with considerable amount of reports. To do so, they helped to provide general views of Americans on South Korea’s economy of the time. According to them, South Korea’s economic development was comparatively successful during this period. Some of them even highly praised the economic success of this country. However, the lack of democracy made them to believe that South Korea’s economic success was fragile. They failed to understand the South Korean people’s will and desperation to survive after the long years of poverty. Still, the analyses and advices presented in the reports were very valuable to see South Korea’s economic structure and problem. The reports of both American major newspapers contributed to develop the American views on South Korea and its economic development of the period.
An evaluation of empirical regression models for predicting temporal variations in soil respiration in a cool-temperate deciduous broad-leaved forest
Na-Yeon Lee
Journal of Ecology and Field Biology , 2010,
Abstract: Soil respiration (RS) is a critical component of the annual carbon balance of forests, but few studies thus far haveattempted to evaluate empirical regression models in RS. The principal objectives of this study were to evaluate therelationship between RS rates and soil temperature (ST) and soil water content (SWC) in soil from a cool-temperatedeciduous broad-leaved forest, and to evaluate empirical regression models for the prediction of RS using ST and SWC.We have been measuring RS, using an open-flow gas-exchange system with an infrared gas analyzer during the snowfreeseason from 1999 to 2001 at the Takayama Forest, Japan. To evaluate the empirical regression models used for theprediction of RS, we compared a simple exponential regression (flux = aebt: Eq. [1]) and two polynomial multiple-regressionmodels (flux = aebt × (θν – c) × (d – θν)f: Eq. [2] and flux = aebt × (1 – (1 – (θν/c))2): Eq. [3]) that included two variables (ST:t and SWC: θν) and that utilized hourly data for RS. In general, daily mean RS rates were positively well-correlated withST, but no significant correlations were observed with any significant frequency between the ST and RS rates on periodsof a day based on the hourly RS data. Eq. (2) has many more site-specific parameters than Eq. (3) and resulted in somesignificant underestimation. The empirical regression, Eq. (3) was best explained by temporal variations, as it provideda more unbiased fit to the data compared to Eq. (2). The Eq. (3) (ST × SWC function) also increased the predictive abilityas compared to Eq. (1) (only ST exponential function), increasing the R2 from 0.71 to 0.78.
Numerical Model on Frost Height of Round Plate Fin Used for Outdoor Heat Exchanger of Mobile Electric Heat Pumps
Moo-Yeon Lee
Advances in Mechanical Engineering , 2012, DOI: 10.1155/2012/863731
Abstract:
Numerical Model on Frost Height of Round Plate Fin Used for Outdoor Heat Exchanger of Mobile Electric Heat Pumps
Moo-Yeon Lee
Advances in Mechanical Engineering , 2012, DOI: 10.1155/2012/863731
Abstract: The objective of this study is to provide the numerical model for prediction of the frost growth of the round plate fin for the purpose of using it as a round plate fin-tube heat exchanger (evaporator) under frosting conditions. In this study, numerical model was considering the frost density change with time, and it showed better agreement with experimental data of Sahin (1994) than that of the Kim model (2004) and the Jonse and Parker model (1975). This is because the prediction on the frost height with time was improved by using the frost thermal conductivity reflecting the void fraction and density of ice crystal with frost growth. Therefore, the developed numerical model could be used for frosting performance prediction of the round plate fin-tube heat exchanger. 1. Introduction Frost formation and growth of the evaporator operated under frosting conditions are very essential phenomena because it acts as a thermal resistance with decreasing the frosting heat transfer performances in many refrigeration systems, air conditioning systems, and heat pump systems [1, 2]. Especially, numerous experimental and numerical studies on frosting and its growth have been reported for a long time. Padhmanabhan et al. [3] studied the semiempirical model to predict the nonuniform frost growth on fin-tube heat exchangers and validated with the experimental data. The considered fin configuration is rectangular type. Hong et al. [4] studied frost growth on louvered folded fins of microchannel heat exchangers. They provided several new data for frost growth on louvered fins and experimentally demonstrated the feasibility of the frost mass and frost height measurements. Xia and Jacobi [5] studied exact solution to steady heat conduction in a two-dimensional slab on a one-dimensional fin for the purpose of application to frosted heat exchangers. They mentioned that the exact solution is useful in gaining physical insights into the problem, and it is simple, accurate, and less costly to use than numerical solutions. Shao et al. [6] showed the comparison of heat pump performance using fin and tube and microchannel heat exchangers under frosting conditions. Lee et al. [7] studied the air-side heat transfer characteristics of spirally-coiled circular fin-tube heat exchanger operating under frosting conditions. They suggested the useful heat transfer correlation to predict the frosting heat transfer coefficient of the fin-tube heat exchanger. In summary, frosting including the frost height and growing is a key factor related to the previously mentioned thermal systems because
Heat Transfer Enhancement of Cu-H2O Nanofluid with Internal Heat Generation Using LBM  [PDF]
Mohammad Abu Taher, Yeon Won Lee, Heuy Dong Kim
Open Journal of Fluid Dynamics (OJFD) , 2013, DOI: 10.4236/ojfd.2013.32A015
Abstract: Fluid flow and heat transfer analysis of Cu-H2O nanofluid in a square cavity using a Thermal Lattice Boltzmann Method (TLBM) have been studied in the present work. The LBM has built up on the D2Q9 model and the single relaxation time method called the Lattice-BGK (Bhatnagar-Gross-Krook) model. The effect of suspended nanoparticles on the fluid flow and heat transfer analysis have been investigated for different non dimensional parameters such as particle volume fraction (φ) and particle diameters (dp) in presence of internal heat generation (q) of nanoparticles. It is seen that flow behaviors and the average rate of heat transfer in terms of the Nusselt number (Nu) as well as the thermal conductivity of nanofluid are effectively changed with the different controlling parameters such as particle volume fraction (2% ≤ φ ≤ 10%), particle diameter (dp = 5 nm to 40 nm) with fixed Rayleigh number, Ra = 105. The present results of the analysis are compared with the previous experimental and numerical results for both pure and nanofluid and it is seen that the agreement is good indeed among the results.
Isolation and Characterization of Volatile Organic Compounds-Degrading Bacillus Strains from Loess  [PDF]
Soo Yeon Lee, Hye Yun Oh, Ok Bin Kim
Journal of Environmental Protection (JEP) , 2013, DOI: 10.4236/jep.2013.44A007
Abstract:

Volatile organic compounds (VOCs) are harmful to human health and the environment. Recently, loess (Hwangtoh) was used as an eco-friendly interior paint formulation in Korea. It is used even more commonly as a filter carrier to remove VOCs. In this study, we isolated Bacillus strains from a loess filter. The strains that were tolerant to VOCs were labeled according to the series VOC01 to VOC35. Four strains—VOC03, VOC11, VOC18, and VOC30—were investigated for their ability to degrade cyclohexane and toluene. Strain VOC18 best degraded both VOCs, whereas VOC03 demonstrated no ability to degrade VOCs. In keeping with this, VOC18 grew best on cyclohexane or toluene as the sole carbon source. The strains were identified by their physiochemical and phylogenetic characteristics. Strain VOC18 was determined as a strain of Bacillus cereus; VOC11 and VOC30 were determined as differentiated strains of B. thuringiensis. Strain VOC03, which demonstrated high tolerance but no ability to degrade VOCs, was identified as a strain of B. megaterium.

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