• 대한원격탐사학회지
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• 제15권4호
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• pp.367-375
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• 1999

This paper describes the development, operations, and applications of ROCSAT-l and its Ocean Color Imager (OCI) remote-sensing payload. It is the first satellite program of NSPO. The satellite was successfully launched by Lockheed Martin's Athena on January 26, 1999 from Cape Canaveral, Florida. ROCSAT-l is a Low Earth Orbit (LEO) experimental satellite. Its circular orbit has an altitude of 600km and an inclination angle of 35 degrees. The satellite is designed to carry out scientific research missions, including ocean color imaging, experiments on ionospheric plasma and electrodynamics, and experiments using Ka-band (20∼30GHz) communication payloads. The OCI payload is utilized to observe the ocean color in 7 bands (including one redundant band) of Visible and Near-Infrared (434nm∼889nm) range with the resolution of 800m at nadir and the swath of 702km. It employs high performance telecentric optics, push-broom scanning method using Charge Coupled Devices (CCD) and large-scale integrated circuit chips. The water leaving radiance is estimated from the total inputs to the OCI, including the atmospheric scattering. The post-process estimates the water leaving radiance and generates different end products. The OCI has taken images since February 1999 after completing the early orbit checkout. Analyses have been performed to evaluate the performances of the instrument in orbit and to compare them with the pre-launch test results. This paper also briefly describes the ROCSAT-l mission operations. The spacecraft operating modes and ROCSAT Ground Segment operations are delineated, and the overall initial operations of ROCSAT-l are summarized.

• Steel and Composite Structures
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• 제31권3호
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• pp.291-301
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• 2019

Pure torsion loading conditions were not frequently occurred in practical engineering, but the torsional researches were important since it's the basis of mechanical property researches under complex loading. Then a 3D finite element model with precise material constitutive models was established, and the effectiveness was verified with test data. Parametric studies with varying factors as steel yield strength, concrete strength and sectional height-width ratio, were performed. Internal stress state and the interaction effect between encased steel tube and the core concrete were analyzed. Results indicated that due to the confinement effect between steel tube and core concrete, the torsional strength of CFT columns was greatly improved comparing to plain concrete columns. The steel ratio would greatly influence the torque share between the steel tube and the core concrete. Then the torsional strength calculation formulas for core concrete and the whole CFT column were proposed. The proposed formula could be simpler and easier to use with guaranteed accuracy. Related design codes were more conservative than the proposed formula, but the proposed formula presented more satisfactory agreement with experimental results.

• 한국기계가공학회지
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• 제18권5호
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• pp.90-95
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• 2019

This study aims to gain the design data through the process design of the organic Rankine cycle, which can produce 250kW of electric power through waste heat recovery. In this study, a simulation was conducted using APSEN HYSYS to make the model for the process design of the 250kW-class waste heat recovery system. For the thermodynamic model, the test was conducted with hot water as the heat source, the water steam as the cooling water for the cooler, and the refrigerant R245FA in the cycle. In the final design, it was expected and found from the simulation that the cycle efficiency was 12.62% and that 250kW of power was produced considering the margin of 80%.

• 생물정신의학
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• 제22권2호
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• pp.78-86
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• 2015

Objectives Although ginseng has been reported to protect neuronal cells and improve various cognitive functions, relationship between ginseng supplementation and response inhibition, one of the important cognitive domains has not been explored. In addition, effects of ginseng on in vivo human brain have not been investigated using the diffusion tensor imaging (DTI). The purpose of the current study is to investigate changes in intrusion errors and white matter microstructure after Korean Red Ginseng supplementation using standardized neuropsychological tests and DTI. Methods Fifty-one healthy participants were randomly allocated to the Korean Red Ginseng (n = 26) or placebo (n = 25) groups for 8 weeks. The California Verbal Learning Test was used to assess the number of intrusion errors. Intelligence quotient (IQ) was measured with the Korean Wechsler Adult Intelligence Scale. Depressive and anxiety symptoms were evaluated using Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale, and Hopkins Symptom Checklist-25. The fractional anisotropy (FA) was measured from the brain DTI data. Results After the 8-week intervention, Korean Red Ginseng supplementation significantly reduced intrusion errors after adjusting age, sex, IQ, and baseline score of the intrusion errors (p for interaction = 0.005). Change in FA values in the left anterior corona radiata was greater in the Korean Red Ginseng group compared to the placebo group (t = 4.29, p = 0.04). Conclusions Korean Red Ginseng supplementation may be efficacious for improving response inhibition and white matter microstructure integrity in the prefrontal cortex.

• 대한치과교정학회지
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• 제41권4호
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• pp.288-296
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• 2011

Objective: The purposes of this study were to evaluate the relationship between the dental and basal arch forms; to analyze their differences in the tapered, ovoid, and square arch forms in normal occlusion by using three-dimensional (3D) virtual models; and to test the hypothesis that the overjet and maxillomandibular basal arch width difference have a significantly positive correlation. Methods: Seventy-seven normal occlusion plaster casts were examined by 3D scanning. Facial axis (FA) and WALA points were digitized using the Rapidform 2006 software. The dimensions of the dental and basal arches and the overjet were measured. The samples were classified into 3 groups according to arch forms: tapered (n = 20), ovoid (n = 20), and square (n = 37). Analysis of variance (ANOVA) was used to compare the dental and basal arch dimensions. The Pearson correlation coefficients between the intercanine as well as the intermolar widths at the FA and WALA points were calculated. Results: With regard to the basal arch dimensions, the tapered arch form showed a larger mandibular intermolar depth than the ovoid. Strong correlations were noted between the basal and dental intermolar widths in both the upper and lower arches (r = 0.83 and 0.85, respectively). Moderate correlation was found between the upper and lower intercanine widths (r = 0.65 and 0.48, respectively). Conclusions: The 3 dental arch form groups differed only in some dimensions of the skeletal arch. Moderate correlations were found between the basal and dental intercanine widths. These findings suggest that the basal arch may not be a principle factor in determining the dental arch form.

• 콘크리트학회논문집
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• 제19권4호
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• pp.393-399
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• 2007

교량 바닥판은 공용 기간 동안 차량하중 및 다양한 환경 조건 (동결융해, 우수 및 융빙제)에 직접적으로 노출되어 있는 부재이다. 이로 인해, 교량 바닥판은 다른 주요부재에 비해서 다양한 결함 및 손상이 자주 발생하여 고속도로 상의 문제 교량은 대부분 바닥판에 결함을 지니고 있다. 따라서 교량 바닥판의 내구성을 확보하기 위한 방안으로 고성능콘크리트 (high performance concrete, HPC)가 대안으로 제시되었다. 교량 바닥판의 내구성을 향상하기 위해, 배합된 고성능콘크리트에 대한 내구성능 실험이 수행되었다. 본 연구에 사용된 배합 변수는 총 4가지로, 1) 보통시멘트 (OPC) 2) 시멘트 중량의 20%의 플라이애쉬 치환(FA), 3) 20%의 플라이애쉬와 4%의 실리카퓸 치환 (FS), 그리고 4) 40%의 고로슬래그미분말 치환 (BS)에 대해서 내구성 실험을 실시한 후 비교 평가를 실시하였으며, 사용된 설계 압축강도는 각각 27 MPa와 35 MPa이다. 고성능콘크리트를 시험 배합한 결과, 결합재의 양을 증가시켜 강도를 증진시키는 것보다는 혼화재를 사용하는 것이 내구 성능이 크게 향상되는 것으로 나타났다. 특히 혼화재 중, 플라이애쉬와 실리카퓸을 함께 결합재로 사용하는 경우가 균열 저감 및 내구 성능 증진에 가장 효율적인 것으로 나타났다.

• 대한디지털의료영상학회논문지
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• 제13권2호
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• pp.83-90
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• 2011

To prospectively determine the diagnostic performance a combination of standard bolus-chase magnetic resonance (MR) angiography and MR angiography with time-resolved imaging of contrast kinetics (TRICKS) for depicting severity of the head and neck vascular diseases. Over a period of two months, A total of 100 patients(average ages : $50{\pm}8$, male : 60, female : 40) with head and neck vascular diseases were performed on the GE excite 3.0 T units with 8-channel head coil and 4-channel NV coil. Imaging parameters for a typical study were as follow: SBC(TR/ TE/ FA/ SliceThicken./ Slab/ Freq./ FOV/ BW/Scan Time) = 5.4/ min/ 30/ 2/ zip2/ 70/ $224{\times}448$/ 30/ 62.50/ 28, TRICKS(TR/ TE/ FA/ Slice Thicken/Slab/ Freq./ FOV/ BW/ Temp Res./ Scan Time = 3.6/ min/ 25/ 4/ 30/ $160{\pm}384$, zip512/ 30/ 100/ 1 to 1.5/ 23). The analysis of all MR images, which have respect-ively classified two techniques into some diseases. The results of the former were divided into two groups(SBC, TRICKS)with 4 grading of two reader, respectively. Wilcoxon signed rank test was used to determine if a significant difference between imaging techniques existed(p < 0.05). In 33 of 100 patients, arterio-venous malformation was 11% at TRICKS, subclavian vein stenosis : 8%, fistular sinus : 4%, jugular vein stenosis:6%, Middle Cerebral Artery bypass surgery : 4%, p < 0.05). The rest of 67 patients were considered as the results of SBC(14% in the basilar artery stenosis, carotid stenosis : 16%, vertebral stenosis : 17%, central neuro-cytoma : 5%, meningioma : 5%, Not appliable : 10%, p < 0.05). Sensitivity and specificity of TRICKS MR angiography in SVS, FS, JVS, MCABS were improved compared with those at standard MR angiography. In SBS MR angiography which were improved in BAS, CS, VS, CN, Meningioma. In conclusion, TRICKS MR angiography of the SVS, FS, JVS, MCABS is superior to standard MR angiography regarding the number of diagnostic grading. The SBS MR angiography were improved in BAS, CS, VS, CN, Meningioma. and assessment of the degree of luminal narrowing on both TRICKS and SBS.

• 콘크리트학회논문집
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• 제23권3호
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• pp.311-320
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• 2011

화력발전 부산물 중 플라이애쉬는 포졸란 반응을 활용하여, 콘크리트 혼화재로 적극적으로 사용되고 있으나, 바텀애쉬는 주로 매립되어 재활용이 많이 요구되는 실정이다. 매립회에는 바텀애쉬와 플라이애쉬가 혼재되어 있는데, 이 연구에서는 국내 6개 발전소 매립회를 수집하고 5가지 치환율(10%, 20%, 30%, 50%, 70%)을 고려하여 매립회의 공학적 특성과 매립회 콘크리트의 역학적/내구 성능이 평가되었다. 골재 실험으로는 조립률, 밀도 및 흡수율, 안전성, 염화물 함유량, 유해이온 함유량, 알칼리 골재 반응 등이 수행되었으며, 매립회 콘크리트에 대해서는 경화 전 특성으로 슬럼프, 공기량 시험을, 경화된 콘크리트에 대해서는 압축강도, 건조수축, 염해 저항성 및 확산계수, 촉진 탄산화 실험, 동결 융해 실험 등이 수행되었다. 매립회는 일반 잔골재보다 큰 흡수율과 작은 밀도를 가지고 있었으나, 콘크리트 골재로 사용 가능하며, 매립회 콘크리트 역시 일반 콘크리트에 해당하는 적절한 성능을 확보하고 있었다. 특히 치환율이 증가함에 따라 강도는 증가하였으며, 우수한 탄산화 저항성을 확인하였다. 최종적으로 실험 결과를 정량적으로 등급화 하여 가장 우수한 매립회 및 매립회 콘크리트의 적용 제한 사항을 도출하였다. 이 연구는 매립회 및 매립회 콘크리트의 공학적 특성을 중심으로 다루고 있으며, 실제 구조물에 대한 모형 실험을 통한 적용성 평가가 추가로 진행될 것이다.

• 한국전자파학회논문지
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• 제19권10호
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• pp.1096-1103
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• 2008

본 논문에서는 개별 차수 혼변조 신호 발생기를 이용한 전치 왜곡 선형화기 구조를 제안하였다 혼변조 신호 발생기는 공통 에미터 증폭기의 에미터 단자에 쇼트키 다이오드를 삽입하여, 3차와 5차 혼변조 신호를 다이오드 바이어스 전압에 따라서 발생시킨다. 이렇게 만들어진 혼변조 신호는 다이오드의 직렬 궤환을 이용한 것으로, 다이오드 바이어스 제어에 따라서 혼변조 신호의 크기와 위상을 변화시킬 수 있다. 이러한 혼변조 발생기를 전치 왜곡 선형화기로 사용했을 때, 반송파 2톤 신호 인가 시 3차와 5차 혼변조 신호는 각각 13.5 dB, 0.9 dB의 개선을 보였고, 광 대역폭을 갖는 CDMA IS-95 2FA 신호를 인가하였을 경우, 중심 주파수로부터 ${\pm}0.885$ MHz, ${\pm}1.23$ MHz 떨어진 지점에서 ACLR이 각각 2.3 dB, 2.5 dB의 개선됨을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.837-840
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• 2008

본 논문에서는 압축강도가 $40{\sim}100MPa$인 3성분계 고강도콘크리트를 대상으로 혼화재의 대체율이 3성분계 고강도콘크리트의 유동성과 강도발현에 미치는 영향을 평가하기 위한 연구를 수행하고, 강도별 적정 혼화재 대체율을 제안하였다. 실험에 사용된 3성분계 고강도콘크리트의 배합 시 시멘트 대체재로써 고로슬래그가 0, 12, 25% 사용되었으며, 플라이 애시 대체율은 15%로 동일하게 계획하였다. 실험결과, 시멘트 대체재로써 고로슬래그를 플라이애시와 혼용하여 사용하는 경우 40MPa 시리즈에서 고로슬래그 대체율이 25%일때 슬럼프가 가장 우수하며, 압축강도 60, 80 MPa의 시리즈에서는 고로슬래그 대체율이 12%일때 슬럼프 플로우가 가장 우수한 것으로 나타났다. 반면 압축강도 100MPa의 경우 플라이 애시 15%만으로도 유동성이 가장 우수한 것으로 나타났다. 그리고 압축강도 40MPa의 경우 고로슬래그 대체율이 25%로 증가할 때까지 강도발현에 효과가 있는 것으로 나타났으며, 100MPa이상의 고강도콘크리트에서는 25% 이상의 고로슬래그 혼입률은 적합지 않은 것으로 나타났다.