• 대기
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• 제31권1호
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• pp.85-100
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• 2021

The necessity of accurate high-resolution meteorological forecasts becomes increasing in socio-economical applications and disaster risk management. The Korea Meteorological Administration Post-Processing (KMAPP) system has been operated to provide high-resolution meteorological forecasts of 100 m over the South Korea region. This study evaluates and improves the KMAPP performance in simulating wind speeds over complex terrain areas using the ICE-POP 2018 field campaign measurements. The mountainous measurements give a unique opportunity to evaluate the operational wind speed forecasts over the complex terrain area. The one-month wintertime forecasts revealed that the operational Local Data Assimilation and Prediction System (LDAPS) has systematic errors over the complex mountainous area, especially in deep valley areas, due to the orographic smoothing effect. The KMAPP reproduced the orographic height variation over the complex terrain area but failed to reduce the wind speed forecast errors of the LDAPS model. It even showed unreasonable values (~0.1 m s-1) for deep valley sites due to topographic overcorrection. The model's static parameters have been revised and applied to the KMAPP-Wind system, developed newly in this study, to represent the local topographic characteristics better over the region. Besides, sensitivity tests were conducted to investigate the effects of the model's physical correction methods. The KMAPP-Wind system showed better performance in predicting near-surface wind speed during the ICE-POP period than the original KMAPP version, reducing the forecast error by 21.2%. It suggests that a realistic representation of the topographic parameters is a prerequisite for the physical downscaling of near-ground wind speed over complex terrain areas.

• 자원환경지질
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• 제26권3호
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• pp.395-401
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• 1993

Lower Ordovician rock samples were collected from 23 sites located at the Okcheon non-metamorphic zone, near Taeback and Yeongweol areas, southern part of the Korean Peninsula. A characteristic magnetic component was obtained from four sites. This stable direction ($Dm=-19.4^{\circ}$, $Im=24.1^{\circ}$) which is carried by hematite of very high temperature $679^{\circ}C$), successfully pass both of reversal test and paleopole reliability test, and is regarded as a primary direction. The remagnetized components can be divided into three on the basis of their characteristic directions and magnetic minerals. The first which is carried by hematite, magnetite and pyrrhotite, is widely found at the whole sites. It shows syn- or post-tectonic remagnetization according to strongly negative fold test and distribution between Mesozoic and present field directions. The second, in situ, is distinguishable from the present field direction. After bedding correction, it is identical to Late Triassic to Early Jurassic direction. Its magnetic carrier is considered to be a single component hematite, which may be acquired by pre-tectonic CRM in the Okcheon orogenic zone. The third, which is carried by magnetite and hematite, is characterized by stable reversed direction. These minerals may be acquired by the thermal or chemical process in unknown period. Paleopole position is $169.2^{\circ}E$ in longitude and $59.9^{\circ}S$ in latitude, which indicates that the study area was located at $12.6^{\circ}S$ in paleo-latitude and belonged to northern end of the Gondwana in Early Ordovician.

• 한국해양학회지
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• 제22권3호
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• pp.143-152
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• 1987

SMS 960(Seafloor Mapping System) Side Scan Sonar에 자기테이프기록계 (Kennedy 900)를 연결하여 해저면 탐사자료를 수치적으로 처리할 수 있는 시스템을 개발, 이를 제주도 성산포 근해에서 시험적으로 적용하여 그 결과를 검토 하였다. 처리시스템은 주로 VAX 11/780 (4MB)를 사용하여 FORTRAN-77로 작성 되었으며 자료의 변환, 보정, 수치분석 및 도면제작 (cartography)을 주요기능으로 가지고 있다. SMS960에 의해 얻어진 수치자료는 특수한 형태를 가지고 있으므로 독자적으로 제작한 자료선별 계수기(Data Selecting Counter와 개인용 컴퓨터 personar computer을 사용하여 주처리 전산시스템에서 처리할 수 있도록 그 형태를 변환시켰으며, 경사거리(slant range)의 보정과 자료의 질적 개선을 위한 전처리 과 정을 거친 다음, 색상표현 으로 해저면 영상도면을 제작하였다. 후방산란 (backscattering) 음파자료를 통계처리하여 4가지 색상으로 제작된 영상도면을, 해저 퇴적물의 물성분포도와 비교해 본 결과 주로 평균입도와 분급도에 잘 대비되었다. 따라서 Side Scan Sonar에 의한 해저면 후 방상란 음향특성을 적절히 분석하므로 써 해저퇴적물의 퇴적상분포연구에 상당한 응용 효과가 있을 것으로 판단된다.

• 대한원격탐사학회지
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• 제39권6_2호
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• pp.1591-1604
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• 2023

해색 원격탐사에서 대기 보정은 자료의 정확도와 신뢰성 확보를 위해 반드시 수행해야하는 과정으로 높은 정확도가 요구된다. 또한 최근 원격 탐사 커뮤니티에서는 위성 자료의 오차에 대한 요구 사항이 증가함에 따라 대기 보정의 보조 자료로 사용되는 기상 변수(오존량, 기압, 바람장, 층적분 수증기량[total precipitable water, TPW])의 오차에 의해 발생하는 원격 반사도(remote sensing reflectance, R_rs)의 오차에 대한 연구가 진행되고 있지만 오차 요인으로 알려진 수증기 프로파일의 변동성에 의한 R_rs의 오차에 대한 연구는 수행되지 않았다. 본 연구에서는 Second Simulation of a Satellite Signal Vector version 2.1 모의를 통해 GOCI-II 관측 영역 내의 수증기 프로파일의 변동성에 따른 수증기 투과도의 오차를 계산하고 이로 인해 발생하는 해색 산출물의 오차에 대해 분석하였다. Radiosonde 관측 수증기 프로파일은 그 형태가 복잡할 뿐만 아니라 지표 부근의 큰 변동성으로 인해 기존 GOCI-II 대기 보정에서 사용하고 있는 US standard 62 수증기 프로파일과의 차이가 최대 0.007만큼 발생하였다. 이로 인해 발생한 수증기 투과도의 차이는 GOCI-II 대기 보정에서 에어로졸 반사도 추정의 차이를 발생시키고, 결과적으로 모든 밴드에서 R_rs의 오차가 발생하였다. 하지만 412-555 nm 밴드에서 수증기 프로파일 차이로 인한 R_rs 오차는 요구 정확도보다 낮은 2% 미만으로 나타났으며, 다른 해색 산출물인 클로로필(chlorophyll-a) 농도, 용존 유기물, 총 부유물 농도에서도 유사한 오차를 보이고 있다. 본 연구의 결과는 대기 보정 및 해색 산출물의 정확도에 있어 수증기 프로파일의 차이의 영향이 적다는 것을 의미한다. 하지만 추후 연구에서 수증기 흡광 보정 시 수증기 프로파일의 변동성을 고려할 경우 보다 높은 수준의 R_rs 정확도 확보를 기대할 수 있다.

• Journal of Astronomy and Space Sciences
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• 제27권2호
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• pp.153-160
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• 2010

We modified the optical system of 500 mm wide-field telescope of which point spread function showed an irregularity. The telescope has been operated for Near Earth Space Survey (NESS) located at Siding Spring Observatory (SSO) in Australia, and the optical system was brought back to Korea in January 2008. After performing a numerical simulation with the tested value of surface figure error of the primary mirror using optical design program, we found that the surface figure error of the mirror should be fabricated less than root mean square (RMS) $\lambda$/10 in order to obtain a stellar full width at half maximum (FWHM) below $28\;{\mu}m$. However, we started to figure the mirror for the target value of RMS $\lambda$/20, because system surface figure error would be increased by the error induced by the optical axis adjustment, mirror cell installation, and others. The radius of curvature of the primary mirror was 1,946 mm after the correction. Its measured surface figure error was less than RMS $\lambda$/20 on the table of polishing machine, and RMS $\lambda$/15 after installation in the primary mirror cell. A test observation performed at Daeduk Observatory at Korea Astronomy and Space Science Institute by utilizing the exiting mount, and resulted in $39.8\;{\mu}m$ of stellar FWHM. It was larger than the value from numerical simulation, and showed wing-shaped stellar image. It turned out that the measured-curvature of the secondary mirror, 1,820 mm, was not the same as the designed one, 1,795.977 mm. We fabricated the secondary mirror to the designed value, and finally obtained a stellar FWHM of $27\;{\mu}m$ after re-installation of the optical system into SSO NESS Observatory in Australia.

• 한국광학회지
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• 제9권3호
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• pp.134-141
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• 1998

원적외선인 7.6$\mu$m 과정대역에서 회절한계 성는을 만족하는 무초점 줌 망원경 광학계응 설계하였다. 기계보정식 4군 줌 방식을 적용하여 줌 대물부 설계하였으며 접안부는 고정초점 렌즈를 구성하였다. 망원경의 줌 비(zoom ratio)는 4.05로 배율을 2.0배에서 8.1배까지 연속적으로 가변할수 있으며, 총 5개의 렌즈군에 9매의 렌즈로 구성하였다. 줌 대물부는 F/1.3의 텔리포트 형태로 설계하여 최고배율 초점거리에 비해 광학계의 길이가 작아 시스템 적용성이 우수하도록 하였으며, 초점조절 렌즈를 줌밍 렌즈군의 뒤에 놓아 물체까지의 거리에 따라 초점을 조절하도록 설계하였다. 광학계에 사용된 재질은 색수차 보정을 위하여 대물부의 렌즈 1매만 ZnSe를 적용하고 나머지 헨즈는 모두 Ge을 적용하여\ulcorner며, 총 18면의 곡률중 1면만 비구면을 적용하고 나머지 면은 모주 구면을 적용하였다. 설계된 망원경의 8.1배율에서의 시야는 $\pm$2.31$^{\circ}$,대물부 유효구경은 163mm이며, 모든 배율에서 회절한계 성능을 만족하는 것으로 평가하였다.

• International Journal of Fluid Machinery and Systems
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• 제9권1호
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• pp.66-74
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• 2016

Concerning the numerical simulation of high-speed water jet with intensive cavitation this paper presents a practical compressible mixture flow method by coupling a simplified estimation of bubble cavitation and a compressible mixture flow computation. The mean flow of two-phase mixture is calculated by URANS for compressible fluid. The intensity of cavitation in a local field is evaluated by the volume fraction of gas phase varying with the mean flow, and the effect of cavitation on the flow turbulence is considered by applying a density correction to the evaluation of eddy viscosity. High-speed submerged water jets issuing from a sheathed sharp-edge orifice nozzle are treated when the cavitation number, ${\sigma}=0.1$, and the computation result is compared with experimental data The result reveals that cavitation occurs initially at the entrance of orifice and bubble cloud develops gradually while flowing downstream along the shear layer. Developed bubble cloud breaks up and then sheds downstream periodically near the sheath exit. The pattern of cavitation cloud shedding evaluated by simulation agrees experimental one, and the possibility to capture the unsteadily shedding of cavitation clouds is demonstrated. The decay of core velocity in cavitating jet is delayed greatly compared to that in no-activation jet, and the effect of the nozzle sheath is demonstrated.

• 한국산업보건학회지
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• 제33권2호
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• pp.93-102
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• 2023

Objectives: With the evolution of direct reading sensors, it is possible to monitor several substances through telecommunication. However, there are some limitations on the use of direct reading technologies in the Occupational Safety and Health Act in South Korea, which only applies to detector tubes, noise, heat, and carbon monoxides. The number of chemicals and their amount of use have been continuously increasing in South Korea. The Ministry of Employment and Labor (MoEL) has concerns about worker's health because exposure is only covered for about 1.2% of all distributed chemicals. Using a direct reading monitor with photoionization detectors (PID-DRMs), gases and vapors chemicals can be measured. Based on the data, business owners are able to create corrective strategies, provide better working routines, and select correct respiratory equipment. PID-DRMs are less expensive and easier to handle for an owner voluntarily controlling chemicals emitted in the workplace. However, there are several limitations on using these PID-DRMs to the degree that the MoEL has not been able to select a legal monitor. The aim of this study was to review previous studies related to PID-DRMs and identify the characterization and limitation on PID-DRMs. Methods: To search for related studies on PID-DRMs, key words were used including direct reading monitors/instruments and/or photoionization detectors. Through that, four domestic and 15 international studies were reviewed. Results: Studies on PID-DRMs were conducted by chamber (enclosed, dynamic, walk-in) and in the field (experimental environment, actual environment). The concentration of PID-DRMs and charcoal tubes were compared for a single substance or mixture, or within the PID-DRMs. There was a high correlation between the two concentrations, but it did not meet the accuracy criteria (95% confidence interval, within 25%) of the NIOSH technical report (2012). In addition, differences in measured values occurred according to environmental factors (temperature, humidity) and high concentration, and concentration values tended to be underestimated due to contamination of the sensor. As a way to improve the accuracy of PID concentration, it was proposed to use correction factors, charcoal tube-based correction factors, or to calibrate the PID-DRMs in the same environment as the workplace. Conclusions: PID-DRMs can likely be used by business owners for the purpose of voluntarily managing the workplace environment, and it is expected that it will be possible to use them as legal equipment if a PID sensor can be upgraded and the limitations of the sensor (temperature, humidity, high concentration evaluation, sensor pollution) can be overcome in the near future.

• 천문학회지
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• 제29권spc1호
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• pp.63-64
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• 1996

The nature of distant faint blue field galaxies remains a mystery, despite the fact that much attention has been devoted to this subject in the last decade. Galaxy counts, particularly those in the optical and near ultraviolet bandpasses, have been demonstrated to be well in excess of those expected in the 'no-evolution' scenario. This has usually been taken to imply that galaxies were brighter in the past, presumably due to a higher rate of star formation. More recently, redshift surveys of galaxies as faint as B$\~$24 have shown that the mean redshift of faint blue galaxies is lower than that predicted by standard evolutionary models (de-signed to fit the galaxy counts). The galaxy number count data and redshift data suggest that evolutionary effects are most prominent at the faint end of the galaxy luminosity function. While these data constrain the form of evolution of the overall luminosity function, they do not constrain evolution in individual galaxies. We are carrying out a series of observations as part of a long-term program aimed at a better understanding of the nature and amount of luminosity evolution in individual galaxies. Our study uses the luminosity-linewidth relation (Tully-Fisher relation) for disk galaxies as a tool to study luminosity evolution. Several studies of a related nature are being carried out by other groups. A specific experiment to test a 'no-evolution' hypothesis is presented here. We have used the AUTOFIB multifibre spectro-graph on the 4-metre Anglo-Australian Telescope (AAT) and the Rutgers Fabry-Perot imager on the Cerro Tolalo lnteramerican Observatory (CTIO) 4-metre tele-scope to measure the internal kinematics of a representative sample of faint blue field galaxies in the red-shift range z = 0.15-0.4. The emission line profiles of [OII] and [OIII] in a typical sample galaxy are significantly broader than the instrumental resolution (100-120 km $s^{-l}$), and it is possible to make a reliable de-termination of the linewidth. Detailed and realistic simulations based on the properties of nearby, low-luminosity spirals are used to convert the measured linewidth into an estimate of the characteristic rotation speed, making statistical corrections for the effects of inclination, non-uniform distribution of ionized gas, rotation curve shape, finite fibre aperture, etc.. The (corrected) mean characteristic rotation speed for our distant galaxy sample is compared to the mean rotation speed of local galaxies of comparable blue luminosity and colour. The typical galaxy in our distant sample has a B-band luminosity of about 0.25 L$\ast$ and a colour that corresponds to the Sb-Sd/Im range of Hub-ble types. Details of the AUTOFIB fibre spectroscopic study are described by Rix et al. (1996). Follow-up deep near infrared imaging with the 10-metre Keck tele-scope+ NIRC combination and high angular resolution imaging with the Hubble Space Telescope's WFPC2 are being used to determine the structural and orientation parameters of galaxies on an individual basis. This information is being combined with the spatially resolved CTIO Fabry-Perot data to study the internal kinematics of distant galaxies (Ing et al. 1996). The two main questions addressed by these (preliminary studies) are: 1. Do galaxies of a given luminosity and colour have the same characteristic rotation speed in the distant and local Universe? The distant galaxies in our AUTOFIB sample have a mean characteristic rotation speed of $\~$70 km $s^{-l}$ after correction for measurement bias (Fig. 1); this is inconsistent with the characteristic rotation speed of local galaxies of comparable photometric proper-ties (105 km $s^{-l}$) at the > $99\%$ significance level (Fig. 2). A straightforward explanation for this discrepancy is that faint blue galaxies were about 1-1.5 mag brighter (in the B band) at z $\~$ 0.25 than their present-day counterparts. 2. What is the nature of the internal kinematics of faint field galaxies? The linewidths of these faint galaxies appear to be dominated by the global disk rotation. The larger galaxies in our sample are about 2"-.5" in diameter so one can get direct insight into the nature of their internal velocity field from the $\~$ I" seeing CTIO Fabry-Perot data. A montage of Fabry-Perot data is shown in Fig. 3. The linewidths are too large (by. $5\sigma$) to be caused by turbulence in giant HII regions.

• 자원환경지질
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• 제40권2호
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• pp.191-207
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• 2007

경상분지 이외의 지역에 분포하는 백악기 암석에 대한 특성잔류자화 방향을 이해하기 위하여 한반도 남서부에 분포하는 부여분지와 함평분지의 백악기 암석에 대한 고지자기 연구를 수행하였다. 부여분지에 분포하는 퇴적암의 고지 자기 방향은 경사보정전의 방향$(D/I=356.5^{\circ}/61.5^{\circ},\;k=39.3\;\alpha_{95}=7.4^{\circ})$은 경사보정후의 방향$(D/I=25.0^{\circ}/60.6^{\circ},\;k=22.4,\;\alpha_{95}=9.9^{\circ})$보다 더 집중됨으로 습곡 이후 재자화된 것으로 볼 수 있으나, 경사보정후의 방향의 정밀도(k)와 신뢰도$(\alpha_{95})$ 경사보정 전의 값과 비교하여 신뢰할 수 있는 통계학적으로 여전히 양호한 값이며 경사보정 후의 극의 위치가 한반도 백악기의 극의 위치와 유사한 점 때문에 부여분지의 재자화 여부의 결정은 유보하였다. 경사보정 전의 고지자기극의 위치는 $(Lat./Long.=81.6^{\circ}N/106.9^{\circ}E,\;K=25.1\;A_{95}=9.3^{\circ})$는 유라시아 제3기의 고지자기 극과 유사하며, 경사보정 후의 고지자기극은 $(Lat./Long.=69.3^{\circ}N/186.7^{\circ}E,\;K=11.6\;A_{95}=14.0^{\circ})$로 한반도 후기 백악기의 극과 유사하다. 함평분지 퇴적암의 특성잔류자화 방향은 경사보정 후의 방향$D/I=32.5^{\circ}/55.4^{\circ},\;(k=35.6,\;\alpha_{95}=8.7^{\circ})$이 경사보정 전의 방향$D/I=18.3^{\circ}/62.5^{\circ},\;k=14.1,\;\alpha_{95}=14.2^{\circ})$보다 더 집중된다. 경사보정 후의 방향으로부터 계산된 고지자기극의 위치는 $Lat./Long.=63.9^{\circ}N/202.7^{\circ}E,\;(K=21.3,\;A_{95}=7.6^{\circ})$로 한반도 후기 백악기의 고지자기극$(Lat./Long.=70.9^{\circ}N/215.4^{\circ}E,\;A_{95}=5.3^{\circ})$의 위치와 유사하므로 암석의 생성 시기는 후기 백악기로 판단하였다. 한편 함평분지에 분포하는 백악기 화산암류에서는 한 개의 정자화 방향과 두 개의 역자화 방향이 확인되었다. 이들 특성잔류자화 방향은 백악기 화산암 형성 당시 암석에 기록된 성분으로써 당시 지구자기장의 상태를 기록한 것으로 해석하였으며, 이중 정자화 방향을 함평분지 화산암의 대표 방향으로 채택하였다 함평분지 화산암의 고지자기 극의 위치는 정자극의 경우는 $Lat./Long.=70.2^{\circ}N/199.5^{\circ}E,\;(K=18.1,\;A_{95}=9.6^{\circ})$ 이며 역자극의 경우는 $Lat./Long.=65.5^{\circ}S/251.3^{\circ}E,\;(K=7.1,\;A_{95}=20.7^{\circ})$이다. 이중 정자극의 위치는 한반도의 후기 백악기극의 위치와 통계적으로 동일한 것으로 나타나 함평분지 화산암의 형성 시기를 후기 백악기로 해석하였다.