• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.835-838
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• 2002

An experiment has been performed using a facility, which simulates the safety depressurization system (SDS) and in-containment refueling water storage tank (IRWST) of APR1400, an advanced PWR being developed in Korea, to investigate the dynamic load resulting from the blowdown of steam from a steam generator through a sparser. The influence of the key parameters, such as air mass, steam pressure, submergence, valve opening time, and pool temperature, on frequency and peak toads was investigated. The blowdown phenomenon was analyzed to find out the real cause of the initiation of bubble oscillation and discrepancy in frequencies between the experiment and calculation by conventional equation for bubble oscillation. The cause of significant damping was discussed and is presumed to be the highly tortuous flow path around bubble. The Rayleigh-Plesset equation, which is modified by introducing method of image, reasonably reproduces the bubble oscillation in a confined tank. Right after the completion of air discharge the steam discharge immediately follows and it condenses abruptly to provide low-pressure pocket. It may contribute to the negative maximum being greater than positive maximum. The subsequently discharging steam does not play as at the driving force anymore.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.526-526
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• 2012

DC magnetron discharges were studied using three-dimensional self-consistent particle-in-cell and Monte Carlo collisional (PIC-MCC) simulation codes. Two rectangular sputter sources (120 mm * 250 mm and 380 mm * 200 mm target sizes) were used in the simulation modeling. The number of incident ions to the Cu target as a function of position and simulation time was obtained. The target erosion profile was calculated by using the incident ions and the sputtering yields of the Cu target calculated with SRIM codes. The maximum ion density of the ion density distribution in the discharge was about $10^{10}cm^{-3}$ due to the calculation speed limit. The result may be less than one or two order of magnitude smaller than the real maximum ion density. However, the target erosion profiles of the two sputter sources were in good agreement with the measured target erosion profiles except for the erosion profile near the target surface, in which which the measured erosion width was broader than the simulation erosion width.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.93-93
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• 2016

Large scale integrated circuits (LSIs) has been improved by the shrinkage of the circuit dimensions. The smaller chip sizes and increase in circuit density require the miniaturization of the line-width and space between metal interconnections. Therefore, an extreme precise control of the critical dimension and pattern profile is necessary to fabricate next generation nano-electronics devices. The pattern profile control of plasma etching with an accuracy of sub-nanometer must be achieved. To realize the etching process which achieves the problem, understanding of the etching mechanism and precise control of the process based on the real-time monitoring of internal plasma parameters such as etching species density, surface temperature of substrate, etc. are very important. For instance, it is known that the etched profiles of organic low dielectric (low-k) films are sensitive to the substrate temperature and density ratio of H and N atoms in the H2/N2 plasma [1]. In this study, we introduced a feedback control of actual substrate temperature and radical density ratio monitored in real time. And then the dependence of etch rates and profiles of organic films have been evaluated based on the substrate temperatures. In this study, organic low-k films were etched by a dual frequency capacitively coupled plasma employing the mixture of H2/N2 gases. A 100-MHz power was supplied to an upper electrode for plasma generation. The Si substrate was electrostatically chucked to a lower electrode biased by supplying a 2-MHz power. To investigate the effects of H and N radical on the etching profile of organic low-k films, absolute H and N atom densities were measured by vacuum ultraviolet absorption spectroscopy [2]. Moreover, using the optical fiber-type low-coherence interferometer [3], substrate temperature has been measured in real time during etching process. From the measurement results, the temperature raised rapidly just after plasma ignition and was gradually saturated. The temporal change of substrate temperature is a crucial issue to control of surface reactions of reactive species. Therefore, by the intervals of on-off of the plasma discharge, the substrate temperature was maintained within ${\pm}1.5^{\circ}C$ from the set value. As a result, the temperatures were kept within $3^{\circ}C$ during the etching process. Then, we etched organic films with line-and-space pattern using this system. The cross-sections of the organic films etched for 50 s with the substrate temperatures at $20^{\circ}C$ and $100^{\circ}C$ were observed by SEM. From the results, they were different in the sidewall profile. It suggests that the reactions on the sidewalls changed according to the substrate temperature. The precise substrate temperature control method with real-time temperature monitoring and intermittent plasma generation was suggested to contribute on realization of fine pattern etching.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 춘계학술대회
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• pp.288-290
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• 2022

최근 정부는 SOC디지털화 계획의 하나로 스마트 물관리 및 홍수 예방을 위해 배수시설 자동·원격제어체계를 국가하천 57%에 도입(1,800억원)하고 실시간 모니터링체계(300억원)를 구축하며, 댐 11개소에 빅데이터를 기반으로 한 스마트 댐 안전관리 체계(150억원)를 마련할 계획입니다. 이러한 스마트 물관리 및 홍수 예방을 위해서는 하천의 실시간 유속 측정을 통해 중간단면법을 적용하여 유량을 정확히 계산할 수 있는 시스템의 연구가 필요합니다. 이러한 시스템의 구현과 정확도를 높이기 위해서 가장 중요한 것은 실시간 유속 측정의 정확도를 확보하는 것입니다. 현재 실시간 유속 측정을 위해 미국, 유럽 등의 전자파 표면 유속 측정용 레이다 센서를 도입하여 시스템에 적용하고 있으나 고가의 가격, 유속 측정 범위의 한계 및 기술 지원 미흡 등의 문제로 인해 시스템의 개선 요구가 지속되고 있는 상황입니다. 따라서 실시간 유속 측정을 위한 전자파 표면 유속 측정용 레이다 센서를 자체 개발하여 개선된 유량 측정 및 홍수 예측 시스템을 제시하고자 합니다.

• Journal of Biosystems Engineering
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• 제36권1호
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• pp.15-22
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• 2011

An experimental variable rate nursery sprayer was developed to adjust application rates for canopy volume in real time. The sprayer consisted of two vertical booms integrated with ultrasonic sensors, and variable rate nozzles coupled with pulse width modulation (PMW) based solenoid valves. A custom-designed microcontroller instructed the sensors to detect canopy size and occurrence and then controlled nozzles to achieve variable application rates. A spray delivery system, which consisted of diaphragm pump, pressure regulator and 4-cycle gasoline engine, offered the spray discharge function. Spray delay time, time adjustment in spray trigger for the leading distance of the sensor, was measured with a high-speed camera, and it was from 50 to 140 ms earlier than the desired time (398 ms) at 3.2 km/h under indoor conditions. Consequently, the sprayer triggered 4.5 to 12.5 cm prior to detected targets. Duty cycles of the sprayer were from 20 to 34 ms for senor-to-canopy (STC) distance from 0.30 to 0.76 m. Outdoor test confirmed that the nozzles were triggered from 290 to 380 ms after detecting tree canopy at 3.2 km/h. The spray rate of the new sprayer was 58.4 to 85.2% of the constant application rate (935 L/ha). Spray coverage was collected at four areas of evergreen canopy by water sensitive papers (WSP), and ranged from 1.9 to 41.1% and 1.8 to 34.7% for variable and constant rate applications, respectively. One WSP area had significant (P < 0.05) difference in mean spray coverage between two application conditions.

• 대한공간정보학회지
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• 제14권2호
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• pp.15-22
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• 2006

지형학적순간단위유량도 및 지형기후학적단위유량도를 이용하여 미계측 소유역의 특성을 분석하였다. 경북 감포지역 $5km^2$ 미만의 소유역을 중심으로 GIS 기법으로 수문특성인자를 도출하고, 지형학적순간단위유량도의 동역학적 매개변수인 특성속도를 호우사상별로 추정하여 지형기후학적 순간단위유량도 및 기타 집중시간 경험식과 비교한 결과 Kerby 및 Brasby-Williams공식이 소유역의 특성속도 산정공식으로 제시될 수 있는 것으로 분석되었다. 또한 확률 강우량으로부터 지형기후학적순간단위유량도의 첨두유량과 확률홍수량을 비교하는 방법과 여러 단위유량도 및 지형기후학적순간단위유량도에서 산정된 첨두유량을 실측자료와 비교한 결과 미계측 소유역의 적용 타당성이 확인되어 향후 돌발홍수 등 방재계획 수립 시 기준우량을 산정하는데 활용될 수 있을 것으로 판단된다.

• Journal of Biosystems Engineering
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• 제26권2호
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• pp.147-154
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• 2001

In Korea and Japan, dried oak mushrooms are classified into 12 to 16 different categories based on its external visual quality. And grading used to be done manually by the human expert and is limited to the randomly sampled oak mushrooms. Visual features of dried oak mushrooms dominate its quality and are distributed over both sides of the gill and the cap. The 2nd prototype computer vision based automatic grading and sorting system for dried oak mushrooms was developed based on the 1st prototype. Sorting function was improved and overall system for grading was simplified to one stage grading instead of two stage grading by inspecting both front and back sides of mushrooms. Neuro-net based side(gill or cap) recognition algorithm of the fed mushroom was adopted. Grading was performed with both images of gill and cap using neural network. A real time simultaneous discharge algorithm, which is good for objects randomly fed individually and for multi-objects located along a series of discharge buckets, was developed and implemented to the controller and the performance was verified. Two hundreds samples chosen from 10 samples per 20 grade categories were used to verify the performance of each unit such as feeding, reversing, grading, and discharging unites. Test results showed that success rates of one-line feeding, reversing, grading, and discharging functions were 93%, 95%, 94%, and 99% respectively. The developed prototype revealed successful performance such as the approximate sorting capability of 3,600 mushrooms/hr per each line i.e. average 1sec/mushroom. Considering processing time of approximate 0.2 sec for grading, it was desired to reduce time to reverse a mushroom to acquire the reversed surface image.

• 대한토목학회논문집
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• 제29권4B호
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• pp.329-337
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• 2009

본 연구에서는 GPS와 RF 통신을 이용하여 개발한 전자부자 시스템을 간략하게 설명하고 현장 실측 결과를 분석하고 제시 하였다. 개발된 시스템은 15개의 전자부자를 동시에 이용하여 유량측정에 활용할 수 있다. 전자부자는 GPS를 이용하여 실제 유하경로를 측정할 수 있으며, 이를 통해 기존 부자법에 비해 10% 정도의 유속 측정 정확도의 개선이 가능하였다. 또한 ADCP와 유속 측정값을 비교한 결과 대체로 일치하는 결과를 보였다. 전자부자와 일반 부자법에 의해 계산된 소단면별 단면적 차이는 -79~71%에 달하였으며, 특히 부자의 중앙 수렴 경향으로 인해 좌우안 부근의 단면적 차이가 증가하였다. 부자의 유하경로와 단면의 배치가 불규칙한 지점에서 전자부자는 댐 방류량 대비 5~6%의 유량 개선 효과를 가지는 것으로 나타났다. 전자부자는 GPS에 기반한 측위 정보를 제공함으로써 정확한 유속과 단면적 산정이 가능하며, 현장 여건과 관계없이 적은 인력으로 측정과 분석, 유량계산을 신속하게 실시간으로 수행함으로써 홍수 유량측정의 효율성을 높일 수 있을 것으로 기대된다.

• Journal of Radiation Protection and Research
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• 제35권4호
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• pp.172-177
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• 2010

중수로원전에서 환경으로 배출되는 방사성유출물의 양은 경수로원전에 비해 상대적으로 많고, 방사성유출물을 계속적으로 배출하는 연속배출(Continuous release) 방식으로 운용되고 있다. 이 때문에 원자로건물 배기 굴뚝(Stack) 등 주요 배출지점에 방사선검출기(Radiation detector)를 설치하여 방사성유출물의 농도를 실시간으로 감시하고 있다. 또한 방사성핵종 별로 연간 배출 가능한 유도배출한계(Derived Release Limits: DRLs)를 정하고, 이들 설정 값을 초과하지 않도록 엄격하게 관리하고 있다. 본 논문은 중수로원전 방사성유출물에 대한 배출관리 방식, 유도배출한계의 설정기준, 설정 방법론과 설정 현황을 조사하여 검토하였다.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.739-742
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• 2008

표면영상유속계(SIV)는 기존의 입자영상유속계(PIV)의 원리를 이용하여 하천의 표면유속을 측정하는 방법이다. 본 연구에서는 경제적이고 효율적인 유속측정 기법인 SIV 기법을 이용하여 국내 3개 하천에 대하여 현장 유량측정에 적용하였다. 현장 영상분석은 다중카메라 방식을 이용하였고 영상분석과정에 필요한 참조점과 횡단면 자료는 측량을 통하여 획득하였다. SIV로 측정된 유속을 검증하는 수로 실험의 결과, 평균오차 10% 이내의 정확도를 보여 정확한 유속측정이 가능함을 확인하였다. 그러나, 실제 하천에의 적용에서는 저수위시와 악천후시에 대해서는 20 % 이내의 오차를 보이는 것으로 나타났다. 향후 SIV 기법의 문제점들을 해결한다면 언제 어디서나 효율적이고 경제적인 유량측정을 할 수 있을 것이다. 그리고 이를 활용하여 실시간 하천정보시스템으로 발전시킴으로써 하천 관리에 큰 도움이 될 것이라 판단된다.