• 한국해안·해양공학회논문집
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• 제29권1호
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• pp.12-19
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• 2017

풍력 개발을 위한 해상기상탑은 초기 설치비와 유지보수비가 크기 때문에 윈드 라이다와 같은 원격관측장비를 이용하여 기상탑을 대체할 필요가 있다. 본 연구에서는 해상기상탑에서 윈드 라이다를 동시 운영하고 수집된 풍속 및 풍향의 관측결과를 상호 비교하여 윈드 라이다의 적용성을 검증하였다. 높이별 풍속 및 풍향 관측결과 두 자료간의 크기 및 경향 등의 통계적 특성 차이는 거의 없으며, 기상탑 관측자료는 구조물 차폐영향에 의한 오차가 발생하는 반면, 윈드 라이다는 오차가 없는 보다 정확한 자료를 얻을 수 있는 것을 확인하였다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
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• pp.308-311
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• 2005

[ $^{222}Rn\;and\;^{226}Ra$ ] in groundwater were determined simultaneously using a gamma-spectroscopy. A nitrogen flushing equipment has been used for elimination and stabilization of high and unstable background activity due to the radon and its progenies in counting shield and room. The aim of present work was to control the background activity for simultaneous measurement of radium$(^{226}Ra)$ and radon$(^{222}Rn)$ in groundwater using a gamma-spectrometry. Background activity was about 1.0dps and the standard deviation was about 50%, The background activity could be minimized using nitrogen flushing equipment in the range of 0.1 to 0.5 and the RSD was about 5% at the experimental condition. The detection limit of $^{222}Rn\;and\;^{226}Ra$ in groundwater was 0.5dps/L in the background control method. In most groundwater used in the work, radon activity was more than the detection limit. However, radium activity in some groundwater was less than the detection limit. If the low level radium in groundwater must be measured, preconcentration process such as concentration should be performed before measuring the groundwater.

• 한국가시화정보학회지
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• 제4권2호
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• pp.69-75
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• 2006

The microbubbles were used in various fields, such as turbulent control, drag reduction, material science and life science. The X-ray PTV using X-ray micro-imaging technique was employed to mea-sure the size and velocity of micro-bubbles moving in an opaque tube simultaneously. Micro-bubbles of $10{\sim}60{\mu}m$ diameter moving upward in an opaque tube (${\phi}$=2.7mm) were tested. Due to the different refractive indices of water and air, phase contrast X-ray images clearly show the exact size and shape of over-lapped microbubbles. In all of the working fluids tested (deionized water, tap water, 0.01 and 0.10M NaCl solutions), the measured terminal velocity of the microbubbles rising through the solution was proportional to the square of the bubble diameter. The rising velocity was increased with increasing mole concentration. The microbubble can be useful as contrast agent or tracer in life science and biology. The X-ray PTV technique should be able to extract useful information on the behavior of various bio/microscale fluid flows that are not amenable to analysis using conventional methods.

• 로봇학회논문지
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• 제12권4호
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• pp.385-394
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• 2017

Side scanning sonar (SSS) provides valuable information for robot navigation. However using the side scanning sonar images in the navigation was not fully studied. In this paper, we use range data, and side scanning sonar images from UnderWater Simulator (UWSim) and propose measurement models in a feature based simultaneous localization and mapping (SLAM) framework. The range data is obtained by echosounder and sidescanning sonar images from side scan sonar module for UWSim. For the feature, we used the A-KAZE feature for the SSS image matching and adjusting the relative robot pose by SSS bundle adjustment (BA) with Ceres solver. We use BA for the loop closure constraint of pose-graph SLAM. We used the Incremental Smoothing and Mapping (iSAM) to optimize the graph. The optimized trajectory was compared against the dead reckoning (DR).

• 한국자동차공학회논문집
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• 제2권5호
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• pp.11-22
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• 1994

The pupose of this study is to measure droplet size and velocity simultaneously for a transient diesel fuel spray in a quiescent chamber at atmospheric temperature and pressure. Generally, diesel combustion phenomena is mainly governed by characteristics of injection system and fuel spray. Therefore we need to clarify these characteristics for developing more economical diesel systems. In this study, correlation between droplet size and velocity was measured at downstream distance from nozzle. Governing parameters are pump speed and fuel quantity for the detailed nature in this transient diesel fuel spray. It is observed effect to the droplet size and velocity distribution. Velocity(peak, mean, rms), number density and droplet size were investigated simulaneously using PDA in the spray. Various results are presented to illustrate the effects of operation factors and correlation between the droplet diameter and velocity.

• 한국측량학회지
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• 제9권1호
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• pp.37-45
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• 1991

국내에 GPS 측지기준점을 설정하고 GPS의 장거리 측정 정밀도를 고찰할 목적으로 국내의 2개지 점과 일본의 1개지점에서 GPS 관측을 동시에 실시하여 자료처리방법에 따른 위치결정 정밀도를 비교 분석하였다. 그 결과 WGS 84 좌표계 내에서 국내 2지점의 3차원 좌표를 정확하게 설정할 수 있었고, GPS의 장거리 측정능력이 0.1 ppm에 달하는 것으로 입증되었다. 이 결과는 앞으로 국내의 GPS 측지기준점 확보를 위한 기초자료가 될 것으로 기대된다.

• Nuclear Engineering and Technology
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• 제45권1호
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• pp.61-66
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• 2013

Among the radioactive wastes generated from the nuclear power plant, a radioactive nuclide such as $^{129}I$ is classified as a difficult-to-measure (DTM) nuclide, owing to its low specific activity. Therefore, the establishment of an analytical procedure, including a chemical separation for $^{129}I$ as a representative DTM, becomes essential. In this report, the adsorption and recovery rate were measured by adding $^{125}I$ as a radio-isotopic tracer ($t_{1/2}$ = 60.14 d) to the simulation sample, in order to measure the activity concentration of $^{129}I$ in a pressurized-water reactor primary coolant. The optimum condition for the maximum recovery yield of iodine on the anion exchange resins (AG1 x2, 50-100 mesh, $Cl^-$ form) was found to be at pH 7. In this report, the effect of the boron content in a pressurized-water reactor primary coolant on the separation process of $^{129}I$ was examined, as was the effect of $^3H$ on the measurement of the activity of iodine. As a result, no influence of the boron content and of the simultaneous $^3H$ presence was found with activity concentrations of $^3H$ lower than 50 Bq/mL, and with a boron concentration of less than 2,000 ${\mu}g/mL$.

• 한국ITS학회 논문지
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• 제10권4호
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• pp.65-70
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• 2011

본 논문에서는 PIFA(Planer Inverted F Antenna)와 IFA(Inverted F Antenna)를 결합한 스마트 폰과 같은 데이터통신 단말기용 안테나를 설계하고 이를 제작하였다. 1개의 급전구조를 가지면서 PIFA와 IFA가 동시에 동작하도록 함으로써 다중대역특성을 갖도록 하였다. 베어보드에 제작된 안테나는 GSM900/USPCS/WCDMA 대역에서 VSWR 3:1 특성을 만족하였다. 평균이득과 효율은 GSM900 대역에서 -2.19~-3.63 dBi 및 43.31~60.33 %가 측정되었다. 또한 USPCS /WCDMA 대역에서는 -2.16~-10.67 dBi 및 8.56~60.78 %의 효율특성을 갖는다.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.449-453
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• 2009

A mesoporous assembly of layered titanate with well-dispersed Pt cocatalysts has been synthesized via a restacking of exfoliated titanate nanosheets and a simultaneous adsorption of Pt nanoparticles. According to powder X-ray diffraction analysis, the obtained mesoporous assembly shows amorphous structure corresponding to the disordered stacking of layered titanate crystallites. Field emission-scanning electron microscopy and $N_2$ adsorption-desorption isotherm measurement clearly demonstrate the formation of mesoporous structure with expanded surface area due to the house-of-cards type stacking of the titanate crystallites. From high resolution-transmission electron microscopy and elemental mapping analyses, it is found that Pt nanoparticles with the size of ~2.5 nm are homogeneously dispersed in the mesoporous assembly of layered titanate. In comparison with the protonated titanate, the present mesoporous assembly of layered titanate exhibits better photocatalytic activity for the photodegradation of organic molecules. This finding underscores that the restacking of exfoliated nanosheets is quite useful not only in creating mesoporous structure but also in improving the photocatalytic activity of titanium oxide.

• 한국수소및신에너지학회논문집
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• 제29권5호
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• pp.466-472
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• 2018

The investigation of cryogenic liquid pool spreading is an essential procedure to assess the hazard of cryogenic liquid usage. In this experimental study, to measure the evaporation velocity when the pool is spreading, liquid nitrogen was continuously released onto unconfined concrete ground. Almost all of the reported results are based on a non-spreading pool in which cryogenic liquid is instantaneously poured onto bounded ground for a very short period of time. A simultaneous measurement of the pool location using thermocouples and of the pool mass using a digital balance was carried out to measure the evaporation velocity and the pool radius. A greater release flow rate was found to result in a greater average evaporation velocity, and the evaporation velocity decreased with the spreading time and the pool radius.