• Journal of Astronomy and Space Sciences
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• v.26 no.2
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• pp.229-236
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• 2009

KOorea Multi-purpose SATellite(KOMPSAT)-5 will be launched at 550km altitude in 2010. Accurate satellite position(20 cm) and velocity(0.03 cm/s) are required to treat highly precise Synthetic Aperture Radar(SAR) image processing. Ionosphere delay was eliminated using dual frequency GPS data and double differenced GPS measurement removed common clock errors of both GPS satellites and receiver. SAC-C carrier phase data with 0.1 Hz sampling rate was used to achieve precise orbit determination(POD) with ETRI GNSS Precise Orbit Determination(EGPOD) software, which was developed by ETRI. Dynamic model approach was used and satellite's position, velocity, and the coefficients of solar radiation pressure and drag were adjusted once per arc using Batch Least Square Estimator(BLSE) filter. Empirical accelerations for sinusoidal radial, along-track, and cross track terms were also estimated once per revolution for unmodeled dynamics. Additionally piece-wise constant acceleration for cross-track direction was estimated once per arc. The performance of POD was validated by comparing with JPL's Precise Orbit Ephemeris(POE).

• Restorative Dentistry and Endodontics
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• v.36 no.2
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• pp.98-107
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• 2011

Caries remains prevalent throughout modern society and is the main disease in the field of dentistry. Although studies of this disease have used diverse methodology, recently, X-ray microtomography has gained popularity as a non-destructive, 3-dimensional (3D) analytical technique, and has several advantages over the conventional methods. According to X-ray source, it is classified as monochromatic or polychromatic with the latter being more widely used due to the high cost of the monochromatic source despite some advantages. The determination of mineral density profiles based on changes in X-ray attenuation is the principle of this method and calibration and image processing procedures are needed for the better image and reproducible measurements. Using this tool, 3D reconstruction is also possible and it enables to visualize the internal structures of dental caries. With the advances in the computer technology, more diverse applications are being studied, such automated caries assessment algorithms.

• Journal of the Korean Vacuum Society
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• v.15 no.6
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• pp.581-586
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• 2006

We have generated the argon plasma in the diode chamber based on the established coaxial electrode type and investigated the emitted visible light for emission spectroscopy. We applied various voltages $2\sim3.5kV$ to the device by 0.5kV, and obtained the emission spectrum data for the focused plasma in the diode chamber on the argon pressure of 330 mTorr. The Ar I and Ar II emission line are observed. The electron temperature and ion density have been measured by the Boltzmann plot and Saha equation from assumption of local thermodynamic equilibrium (LTE) The Ar I and Ar II ion densities have been calculated to be $\sim10^{15}/cc\;and\;~10^{13}/cc$, respectively, from Saha equation.

• Korean Journal of Materials Research
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• v.7 no.3
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• pp.218-223
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• 1997

At the aim of finding a Fehased amorphous alloy with a wide supercooled liquid region (${\Delta}T_{x}=T_{x}-T_{g}$) before crystallization, the changes in glass transition temperatudfI$T_{g}$ and crystallization temperature ($T_{x}$) by the dissolution of additional M elements were examined for the $Fe_{80}P_{10}C_{6}B_{4}$(x~6at%. M= transition metals) amorphous alloys. The ${\Delta}T_{x}$ value is 27K for the Fe,,,P,,,C,,R, alloy and increases to 40K for the addition of M=4at%Hf, 4at%Ta or 4at%Mo. The increase in ${\Delta}T_{x}$ is due to the increase of $T_{x}$ exceeding the degree in the increase in $T_{g}$. The $T_{g}$ and $T_{x}$ increase with decreasing electron concentration (e/a) from about 7 38 to 7.05. The decrease of e/a also implies the increase in the attractive bonding state between the M elements and other constitutent elements. It is therefore said that $T_{g}$ and $T_{x}$ increase kith increasing attractive bonding force.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.1
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• pp.17-26
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• 2008

The 1st order level network of Korea was adjusted simultaneously in 1987. After that, the 1 st order level network of Korea was adjusted simultaneously by National Geographic Information Institute in 2006. The levelling data were acquired by digital level with invar staff from 2001 through 2006. The 1st order level network consists of 36 level lines. Among them, 34 level lines comprise 11 level loops. Among 36 level lines, 4 level lines have fore & back error larger than the regulations for the 1st order levelling of NGII, Korea. Also, the closing error of 3 loops of level network exceed the regulation for the 1st order levelling of NGII. The standard error of fore and back leveling between bench marks(${\eta}_1$) are distributed between 0.2 $mm/{\surd}km$ and 1.7 $mm/{\surd}km$. The standard error of loop closing(${\eta}_2$) is 2.0 $mm/{\surd}km$. This result means that the 1st order level network of Korea qualifies for the high precision leveling defined by International Geodetic Association in 1948. As the result of the 1st order level network adjustment, the reference standard error($\hat{{\sigma}_0}$) of the level network was 1.8 $mm/{\surd}km$, which is twice as good as that of the 1st adjustment of level networks in 1987.

• The Korean Journal of Malacology
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• v.9 no.1
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• pp.1-16
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• 1993

한국의 담수에 광범위하게 서식하고 있으면서 역학적으로 중요한 역할을 하고 있는 두 종의 복족류 즉 쇠우렁이(Parafossarulus manchouricus)와 물달팽이(Radix auricularia coreana)의 소화기관 중에서 식도, 소화선 및 장에 대한 미세구조 관찰을 시도하였다. 이 부위들은 간흡충(간디스토마)과간질(소간디스토마)의 유생들이 그들의 생활사 중 거쳐가는 곳으로 알려진 소화관들이어서 이후 흡충류의 유충들이 위의 소화관에 주는 영향을 연구하는데 필요한 기초자료를 얻고자 수행된 것이었다. 관찰해 본 결과 다음과 같은 결론을 얻을 수 있었다. 식도의 상피조직은 두 종류에서 공히 원주세포와 원주섬모세포 및 점액분비 세포로 이루어져 있었다. 식도강상피 내에서도 어느 정도의 흡수와 소화가 이루어 지고 있음은 특이한 현상이라 하겠다. 소화선은 두 종에서 공히 복분지 관상선으로서 그 상피는 micovilli를 선강 또는 도관에 연한 유리표면에 가지고 있어 brush boredr을 이루고 있는 원주세포과 원주섬모세포로 구성되어 있었다. 이들 세포들의 내부 구조로 보아 소화세포와 배석세포로 구분할 수 있었다. 장의 상피는 원주세포와 원주섬모세포로 구성되어 있었으며 이들도 장강에 연한 유리표면에는 brush border를 이루고 있었다. 흡수와 분비기능이 활발한 것으로 사료된다. 전반적으로 보아 본 연구에서 관찰한 두 복족류의 소화관은 모든 부위에서 세포의 유리표면에 microvilli를 가지고 있어 물질의 흡수기능을 가지고 있음을 시사해주고 있었고, 이들 세포 중에는 때로 밀집한 cilia를 가지고 있어 소화관 내의 액체물질이나 이에 내포된 미세입자들의 유동을 도와주고 있음을 추측할 수 있었다.)은 결합조직으로 이루어진 근육질의 두꺼운 벽을 가지고 있었으며 내강은 돌출부위에 의해 4부분으로 갈라져 있었다. 내강에 연한 상피는 원주세포로 되어 있었다. 상음경(epiphallus)의 벽은 근섬유 다발은 벽의 외곽으로 갈수록 밀도가 높아졌다. 상부에 내강과 연결되는 함입구조(groove)를 가지며, 내강에 연한 상피는 섬모가 없는 원주세포로 이루어져 있었다. 음경(penis)은 근섬유가 산재된 두꺼운 벽을 가졌으며 상음경보다 굵은 원통형이었다. 내강은 많은 돌출부에 의해 복잡하게 나뉘어 있으며 상피세포는 원주 세포로 이루어져 있었고 섬모는 관찰되지 않았다. 내강 내의 분비물과 세포의 형태로 보아 내강상피세포는 분비기능을 가진 것으로 사료된다.술적 문제가 적절히 해결되는 경우 비활성 가스 제너레이터는 민수용으로는 대형 빌딩, 산림, 유조선 등의 화재에 매우 적절히 사용되어 질 수 있을 뿐 아니라 군사적으로도 군사작전 중 및 공군 기지의 화재 그리고 지하벙커에 설치되어 있는 고급 첨단 군사 장비 등의 화재 뿐 아니라 대간첩작전 등에 효과적으로 활용될 수 있을 것으로 판단된다.가 작으며, 본 연소관에 충전된 RDX/AP계 추진제의 경우 추진제의 습기투과에 의한 추진제 물성 변화는 미미한 것으로 나타났다.의 향상으로, 음성개선에 효과적이라고 사료되었으며, 이 방법이 편측 성대마비 환자의 효과적인 음성개선의 치료방법의 하나로 응용될 수 있으리라 생각된다..7%), 혈액투석, 식도부분절제술 및 위루술·위회장문합술을 시행한 경우가 각 1례(2.9%)씩이었다. 13) 심각한 합병증은 9례(26.5%)에서 보였는데 그중 식도협착증이 6례(17.6%), 급성신부전증 1례(2.9%), 종격동기흉과 폐염이 병발한 경우와 폐염이 각

• Journal of Fisheries and Marine Sciences Education
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• v.3 no.2
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• pp.19-28
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• 1991

The United States has been developing a GPS(Global Positoning System), and now we can make use of it everywhere in the world. The author measured the usable time and took position fixes from three fixed stations in Japan in order to evaluate the positioning accuracy of GPS, firstly by the difference in the time of the year and, secondly by the difference in location between the stations in 1988. I was able to receive positioning signals from only 6 or 7 satellites, but in July 1991, 14 GPS satellites became available. The results obtained are summerized as follows: 1) The usable time was 7~9 hours from only 6~7 satellites. 2) In the case of the former, the time zone of position fixes varied with the time of the year and there were a little differences of the accuracy of position fixes except 3H(three dimensiomal high level positioning). In the case of the latter, there were not obvious locality differences in 3D(three dimensional positioning). But the positioning errors and number of data varied on each level in 2D(two dimensiomal positioning), although the positioning errors were smaller than 0.1 nautical mile. 3) Th standard deviations of Dep(departure) were larger than tat of D.lat(difference of latitude), and varied widely to the east and west. But the standard deviations were smaller than 100 meters.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.1
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• pp.50-63
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• 2021

Microcephalic osteodysplastic primordial dwarfism type II (MOPD II) is an autosomal recessive inherited disorder form of primordial dwarfism, caused by mutations in the pericentrin gene. The purpose of the study was to examine the clinical and radiological features, physicochemical properties and microstructures of the tooth affected with MOPD II. The mandibular 2nd molar was collected from the MOPD II patient. Micro-computerized tomography, scanning electron microscopy, energy dispersive spectrometry and Vickers microhardness analysis were performed on the MOPD II and the normal control. The morphology of the MOPD II tooth appeared to have malformed pulp and root and showed a small size. The mineral density measurement showed that the MOPD II tooth had similar scores in the enamel, but lower scores in the root 1/2 and apical dentin compared to the normal control. The microhardness values were smaller in the cusp enamel, root 1/2 dentin and apical dentin of the MOPD II compared to the normal control. In this study, the dental characteristics and the physicochemical properties of a tooth affected with MOPD II were analyzed to improve understanding of the oral manifestations of the disease and to assist in proper dental treatment by identifying precautions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.29-34
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• 2019

Silicon carbide is considered to be a potentially useful material for high-temperature electronic devices, as its large energy band gap and the p-type and/or n-type conduction can be controlled by impurity doping. Particularly, electric conductivity of porous n-type SiC semiconductors fabricated from ${\beta}-SiC$ powder at $2000^{\circ}C$ in $N_2$ atmosphere was comparable to or even larger than the reported values of SiC single crystals in the temperature region of $800^{\circ}C$ to $1000^{\circ}C$, while thermal conductivity was kept as low as 1/10 to 1/30 of that for a dense SiC ceramics. In this work, for the purpose of decreasing sintering temperature, it was attempted to fabricate porous reaction-sintered bodies at low temperatures ($1400-1600^{\circ}C$) by thermal decomposition of polycarbosilane (PCS) impregnated in n-type ${\beta}-SiC$ powder. The repetition of the impregnation and sintering process ($N_2$ atmosphere, $1600^{\circ}C$, 3h) resulted in only a slight increase in the relative density but in a great improvement in the Seebeck coefficient and electrical conductivity. However the power factor which reflects the thermoelectric conversion efficiency of the present work is 1 to 2 orders of magnitude lower than that of the porous SiC semiconductors fabricated by conventional sintering at high temperature, it can be stated that thermoelectric properties of SiC semiconductors fabricated by the present reaction-sintering process could be further improved by precise control of microstructure and carrier density.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.596-608
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• 2018

As urban infrastructure is aging, the possibility of accidents due to the failures or breakdowns of infrastructure increases. Especially, aging underground infrastructures like sewer pipes, waterworks, and subway have a potential to cause an urban ground sink. Urban ground sink is defined just as a local and erratic collapse occurred by underground cavity due to soil erosion or soil loss, which is separated from a sinkhole in soluble bedrock such as limestone. The conventional measurements such as differential settlement gauge, inclinometer or earth pressure gauge have a shortcoming just to provide point measurements with short coverage. Therefore, these methods are not adequate for monitoring of an erratic subsidence caused by underground cavity due to soil erosion or soil loss which occurring at unspecified time and location. Therefore, an alternative technology is required to detect a change of underground physical condition in real time. In this study, the feasibility of a novel magnetic resonance based monitoring method is investigated through laboratory tests, where the changes of path loss (S21) were measured under various testing conditions: media including air, water, and soil, resonant frequency, impedance, and distances between transmitter (TX) and receiver (RX). Theoretically, the transfer characteristic of magnetic field is known to be independent of the density of the medium. However, the results of the test showed the meaningful differences in the path loss (S21) under the different conditions of medium. And it is found that the reflection coefficient showed the more distinct differences over the testing conditions than the path loss. In particular, input reflection coefficient (S11) is more distinguishable than output reflection coefficient (S22).