• Corrosion Science and Technology
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• v.8 no.2
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• pp.53-61
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• 2009

In this study, both evaluations by visual imaging for exterior view of coating and by EIS were executed for epoxy primer coated specimens deteriorated by accelerated test, and comparison and analysis were carried out for 2 evaluation methods. In the comparison between total damaged area ratio acquired by image processing method and deterioration point, higher deterioration points were appeared for rusted specimens than for non-rusted specimens. It is attributed that deterioration point per unit area ratio given for rust is higher than for peeling. In the comparison between total damaged area ratio and EIS result, impedance of coating was largely decreased as about TEX>$10^4{\Omega}{\cdot}cm^2$ or less when rust area ratio is more than about 0.1%, and blistering area ratio is more than about 3%. Charge transfer resistance ($R_{ct}$) and double layer capacitance ($C_{dl}$) values were appeared for all specimens except 2 ones, which shows that water is accumulated and steel substrate is corroded at coated film-steel interface. In the comparison between deterioration point and EIS result, more than 10 points as deterioration point were given for specimens of below $10^6{\Omega}{\cdot}cm^2$ of impedance at low frequency. For specimens deteriorated by NORSOK cyclic test, impedance was lowest of all, though deterioration point was not high. It is thought to be attributed that coating system and accelerated deterioration condition of cyclic tested specimens were different from those of main specimens. From the result, it is thought that coating resistance can be relatively more decreased than deterioration degree estimated from exterior view under more severe corrosion environment or in the present of more complex deterioration factors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5931-5936
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• 2012

This study was to evaluate the clinical usefulness of the PRESS technique based on the correlation between PRESS technique and biopsy results by applying 3.0T high magnetic field MRS technique for evaluation of non-alcoholic fatty liver disease patients. This experiment were carried out using a 3.0T magnetic resonance imaging equipment. The part data of each spectrum is taken by peak area integration. The part data of resonance peak was used to calculate relative ratio. MR spectral peak in patients with non-alcoholic fatty liver disease is from 0.9 to 1.6 ppm. According to MRS method study result, Patients with NAFLD were obtained with 94% sensitivity and 80% specificity(p=0.000). When compared to normal based on MRS and Biopsy results was valid correlation(r=0.79, p=0.04). Results for NAFLD(r=0.89, p=0.002) also showed a correlation. Therefore, PRESS technique to evaluate patients with non-alcoholic fatty liver disease, the distribution difference between normal liver and fatty liver part is significantly distinguished. Biopsy and MRS fatty liver peak ratio(%) proves high lipid over grade(r = 0.7).

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.2
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• pp.176-188
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• 2008

Anthropogenic emissions of nitrogen oxides and sulfur dioxide in Northeast Asia are of great concern because of their impact on air quality and atmospheric chemistry on regional and intercontinental scales. Satellite remote sensing based on DOAS (Differential Optical Absorption Spectroscopy) technique has been preferred to measure atmospheric trace species and to investigate their emission characteristics on regional and global scales. Absorption spectra obtained by the satellite-born instrument, SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) have been utilized to retrieve the information of $SO_2$ and $NO_2$ over Northeast Asia. $SO_2$ levels over Northeast Asia were in order of East China, Yellow Sea, South Sea and Korean Peninsula with mean vertical columns of $1.78({\pm}1.0){\times}10^{16}$, $1.11({\pm}0.67){\times}10^{16}$, $0.60({\pm}0.63){\times}10^{16}$, $0.71({\pm}0.65){\times}10^{16}\;molecules/cm^2$, respectively. $NO_2$ levels were in order of East China, Yellow Sea, Korean Peninsula, and South Sea with mean vertical columns of $1.2({\pm}0.56){\times}10^{16}$, $0.38({\pm}0.19){\times}10^{16}$, $0.48({\pm}0.28){\times}10^{16}$, $0.26({\pm}0.16){\times}10^{16}\;molecules/cm^2$, respectively. High levels of $SO_2$ and $NO_2$ were observed over East China, in particular in winter by the contribution of heating fuel combustion exhausts. The $SO_2$ and $NO_2$ levels over East China were the highest in January with 34% and 42% higher over the annual means. Low levels of $SO_2$ ranged over Korean peninsula, while $NO_2$ levels were relatively high, in particular in winter. The $SO_2$ and $NO_2$ levels over Yellow Sea were relatively higher compared to those over Korean peninsula and South Sea, which could be mainly attributed to their transport from East China.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.657-662
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• 2005

Iron sulfide(FeS) is significantly produced through both abiotic and biotic processes in natural sediments and pore waters. In this study, chromium(VI) reaction with iron sulfide at various initial concentrations and at pH values of 4 and 8 was conducted to better understand the interactions between Cr(VI) and Fe(II) species dissolved from iron sulfide in both the aqueous and solid phases. Also, the removal efficiency of iron sulfide was compared with zero valent iron and other iron bearing oxides such as ${\alpha}-Fe_2O_3$, ${\alpha}-FeOOH$ and $Fe_3O_4$. The Cr(VI) removal rate by iron sulfide was higher at pH 4 than at pH 8 because more dissolved Fe(II) existed at pH 4 than at pH 8. Chromium and iron(oxyhydroxide) could be identified on the iron sulfide surface with transmission microscopy imaging and energy dispersive spectroscopy. The removal capacity of iron sulfide was much higher than zero valent iron and other iron oxide minerals due to the synergic effect of hydrogen sulfide and ferrous iron.

• Journal of The Korean Astronomical Society
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• v.49 no.1
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• pp.25-35
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• 2016

Multiple color selection techniques are successful in identifying quasars from wide-field broadband imaging survey data. Among the quasars that have been discovered so far, however, there is a redshift gap at 5 ≲ z ≲ 5.7 due to the limitations of filter sets in previous studies. In this work, we present a new selection technique of high redshift quasars using a sequence of medium-band filters: nine filters with central wavelengths from 625 to 1025 nm and bandwidths of 50 nm. Photometry with these medium-bands traces the spectral energy distribution (SED) of a source, similar to spectroscopy with resolution R ~ 15. By conducting medium-band observations of high redshift quasars at 4.7 ≤ z ≤ 6.0 and brown dwarfs (the main contaminants in high redshift quasar selection) using the SED camera for QUasars in EArly uNiverse (SQUEAN) on the 2.1-m telescope at the McDonald Observatory, we show that these medium-band filters are superior to multi-color broad-band color section in separating high redshift quasars from brown dwarfs. In addition, we show that redshifts of high redshift quasars can be determined to an accuracy of Δz/(1 + z) = 0.002 - 0.026. The selection technique can be extended to z ~ 7, suggesting that the medium-band observation can be powerful in identifying quasars even at the re-ionization epoch.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.103-105
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• 2003

After fifteen years of development, Magnetic Resonance (MR) technology for human imaging and spectroscopy is reaching a refined state with FDA approved 3T clinical products from Siemens, GE, and Philips. Broker has cleared CE approval with a 4T system. Varian supports a 4T system platform as well. Shielded magnets are standard at 3T from GE, Oxford, Magnex, and IGC. A shielded 4T whole body magnet is available from Oxford. Stronger switched gradients and dynamic shim coils, desired at any field, areespecially useful at higher static magnetic fields B0. In addition to the higher currents required for higher resolution slice or volume selection afforded by higher SNR, whole body gradient coils will be driven at increasing slew rates to meet the needs of new cardiac applications and other requirements. For example 3T and 4T systems are now being equipped with 2kV, 500A gradient coils and amplifiers capable of generating 4G/cm in 200msec, over a 67+/-cm bore diameter. High field EPI applications require oscillation rates at 1 kHz and higher. To achieve a benchmark 0.2 ppm shim over a 30cm sphere in a high field magnet, at least four stages of shimming need to be considered. 1) A good high field magnet will be built to a homogeneity spec. falling in the range of 100 to 150 ppm over this 30cm spherical "sweet spot" 2) Most modern high field magnets will also have superconducting shim coils capable of finding 1.5 ppm by their adjustment during system installation. 3) Passive ferro-magnetic shimming combined with 4) active, high order room temperature shim coils (as many as five orders are now being recommended) will accomplish 0.2 ppm over the 30cm sphere, and 0.1 ppm over a human brain in even the highest field magnets for human studies. Safety concerns for strong, fast gradients at any B0 field include acoustic noise and peripheral nerve stimulation. One or more of the mechanical decoupling methods may lead to quieter gradients. Patient positioning relative to asymmetric or short gradient coils may limit peripheral nerve stimulation at higher slew rates. Gradient designs combining a short coil for local speed and strength with a longer coil for coverage are being developed for 3T systems. Local gradients give another approach to maximizing performance over a limited region while keeping within the physiologically imposed dB0/dt performance limits.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.324-325
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• 2014

Quantum wells infrared photodetectors (QWIPs) have been used to detect infrared radiations through the principle based on the localized stated in quantum wells (QWs) [1]. The mature III-V compound semiconductor technology used to fabricate these devices results in much lower costs, larger array sizes, higher pixel operability, and better uniformity than those achievable with competing technologies such as HgCdTe. Especially, GaAs/AlGaAs QWIPs have been extensively used for large focal plane arrays (FPAs) of infrared imaging system. However, the research efforts for increasing sensitivity and operating temperature of the QWIPs still have pursued. The modification of heterostructures [2] and the various fabrications for preventing polarization selection rule [3] were suggested. In order to enhance optical performances of the QWIPs, double barrier quantum well (DBQW) structures will be introduced as the absorption layers for the suggested QWIPs. The DBWQ structure is an adequate solution for photodetectors working in the mid-wavelength infrared (MWIR) region and broadens the responsivity spectrum [4]. In this study, InGaAs/GaAs/AlGaAs double barrier quantum well infrared photodetectors (DB-QWIPs) are successfully fabricated and characterized. The heterostructures of the InGaAs/GaAs/AlGaAs DB-QWIPs are grown by molecular beam epitaxy (MBE) system. Photoluminescence (PL) spectroscopy is used to examine the heterostructures of the InGaAs/GaAs/AlGaAs DB-QWIP. The mesa-type DB-QWIPs (Area : $2mm{\times}2mm$) are fabricated by conventional optical lithography and wet etching process and Ni/Ge/Au ohmic contacts were evaporated onto the top and bottom layers. The dark current are measured at different temperatures and the temperature and applied bias dependence of the intersubband photocurrents are studied by using Fourier transform infrared spectrometer (FTIR) system equipped with cryostat. The photovoltaic behavior of the DB-QWIPs can be observed up to 120 K due to the generated built-in electric field caused from the asymmetric heterostructures of the DB-QWIPs. The fabricated DB-QWIPs exhibit spectral photoresponses at wavelengths range from 3 to $7{\mu}m$. Grating structure formed on the window surface of the DB-QWIP will induce the enhancement of optical responses.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.441-450
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• 2005

The organic material is one of the most popular material for the satellites and the spacecrafts in order to perform the thermal management, and to protect direct exposure from the space environment. The present paper observes material property changes of organic material under the space environment by using ground facilities. One of the representative organic thermal management material of satellites, 2 mil ITO(Indium Tin Oxide) coated aluminized KAPTON was selected for experiments. In order to investigate the single parametric effect of protons in space environment, MC-50 cyclotron system in KIRAMS(Korea Institute of Radiological and Medical Science) was utilized for the ion beam irradiation of protons and ion beam dose was set to the Very Large August 1972 EVENT model, the highest protons occurrence near the earth orbit in history. The energy of ion beam is fixed to 30MeV(mesa electron volt), observed average energy, and the equivalent irradiance time conditions were set to 1-year, 3-year, 5-year and 10-year exposure in space. The procedure of analyses includes the measurement of the ultimate tensile strength for the assessment of quantitative degradation in material properties, and the imaging analyses of crystalline transformation and damages on the exposed surface by FE-SEM(Field Emission Scanning Electron Spectroscopy) etc.

• The Korean Journal of Nuclear Medicine
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• v.29 no.3
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• pp.328-331
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• 1995

$^{99m}Tc$ labeled PnAO(propylene amine oxime) derivatives have been widely studied as brain perfusion agents. We synthesized and characterized a PnAO derivative, (RR/SS/ meso)-4,8-diaza-3,9-dimethylundecane-2, 10-dione bisoxime(PRODD). Proton-NMR spectroscopy and thin layer chromatography(silica gel) were performed for its characterization. PRODD was labeled with $^{99m}Tc$ using stannous chloride as reducing agent. The labeling efficiency was determined to be about 85%. Brain uptakes of $4.16{\pm}0.42$ %ID/g and $3.24{\pm}0.13$ %ID/g were found after 10min and 30min after intravenous injection. Brain-to-blood ratios were 1.17 and 0.75 at 10 and 30 minutes, which were lower than 1.3 and 1.9 of the ratios with commercial ${\pm}$-HMPAO. Autoradiographs of rat brain sections showed the gray matter to white matter ratios of $1.13{\pm}0.10$ at 30 min after intravenous injection, which was lower than $1.94{\pm}0.19$ of commercial $^{99m}Tc$-HMPAO. With the above findings, we concluded that the lipophilic $^{99m}Tc$-PRODD complex was able to cross the blood-brain barrier, however the complex showed lower uptake than $^{99m}Tc$-HMPAO in mouse or rat brains. We could suggest possibility that PRODD could be used as another $^{99m}Tc$ chelator.

• Korean Journal of Remote Sensing
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• v.21 no.4
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• pp.341-369
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• 2005

Hyperspectral images have emerged as a new and promising remote sensing data that can overcome the limitations of existing optical image data. This study was designed to provide a comprehensive review on definition, data processing methods, and applications of hyperspectral data. Various types of airborne, spaceborne, and field hyperspectral image sensors were surveyed from the available literatures and internet search. To understand the current status of hyperspectral remote sensing technology and research development, we collected several hundreds research papers from international journals (IEEE Transactions on Geoscience and Remote Sensing, International Journal of Remote Sensing, Remote Sensing of Environment and AVIRIS Workshop Proceedings), and categorized them by sensor types, data processing techniques, and applications. Although several hyperspectral sensors have been developing, AVIRIS has been a primary data source that the most hyperspectral remote sensing researches were relied on. Since hyperspectral data have very large data volume with many spectral bands, several data processing techniques that are particularly oriented to hyperspectral data have been developed. Although atmospheric correction, spectral mixture analysis, and spectral feature extraction are among those processing techniques, they are still in experimental stage and need further refinement until the fully operational adaptation. Geology and mineral exploration were major application in early stage of hyperspectral sensing because of the distinct spectral features of rock and minerals that could be easily observed with hyperspectral data. The applications of hyperspectral sensing have been expanding to vegetation, water resources, and military areas where the multispectral sensing was not very effective to extract necessary information.