다층 진단 모델에 의한 광양만의 잔차류 수치 실험

추효상,이병걸,이규형 한국환경과학회 2002 한국환경과학회지 Vol.11 No.1

In order to estimate the quantitative roles of the tide induced residual currents, densisy currents and wind driven currents on the residual currents in Kwangynag Bay Korea, numerical experiments with a diagnostic multi-level model were carried out. Density currents were calculated from the temperature and salinity data observed in January, May, August and November 1998. Anti-clockwise circulations are formed at the western inner part of the bay, the location from the east of Myodo Is. to the south of POSCO Co. and the place between Yeosu peninsula and Namhae Is. from the calculation results of the tide induced residual currents. Velocities of the density currents are less than 3㎝/s at the western inner part of the bay and about 5㎝/s at the southern entrance of the bay. Density currents get strong in summer and weak in autumn. Wind driven currents at the surface layer flow in the directions of the given winds which are the daily mean winds when the temperature and salinity observations are carried out. In the middle and lower layers, however the wind driven currents flow in the opposite direction to the surface currents as supplementary currents. The surface wind driven currents are greater than the tide induced residual currents or the density currents. The calculated residual currents including the tide induced residual currents, density currents and wind driven currents agree with the results of the current observations approximately. In the Bay, the wind driven currents affect on the residual currents greatestly and tide induced residual currents and density currents do in the second place and the third place.

해양생태계모델에 의한 하계 진동만의 영양염변동

김동선,홍철훈 한국해양학회 2003 바다 Vol.8 No.2

하계 진동만에서 얻어진 영양염 DIN(dissolved inorganic nitrogen) 및 DIP(dissolved inorganic phosphate)의 분포는 이들 농도가 만안쪽에서 매우 높은 것이 특징이다. 또 표층(0∼1 m)과 저층(8 m∼bottom)은 만 안쪽이 고농도 이고 중층(1∼8 m)은 상대적으로 낮다. 이러한 영양염의 분포특성을 바람, 조류, 밀도의 수평경도력 및 잔차류를 고려한 생태계모델을 이용하여 조사하였다. 수치실험은 이들 조건들이 영양염에 각기 어떻게 영향을 미치는 가에 주목하여 실시되었다 조석잔차류를 고려한 경우는 전반적으로 관측값보다 저농도의 분포를 보였고, 바람, 조석잔차류 및 밀도의 수평경도력에 의한 효과를 포함한 경우는 보다 관측값에 근접한 결과를 얻었다 이러한 결과는 통계적 분석 방법에서도 잘 뒤받침된다. 본 연구결과는 하계 진동만에서 영양염의 분포변동에 조류효과 뿐만이 아니라 바람에 의한 취송류 및 밀도의 수평경도력에 의해 발생하는 밀도류의 효과가 매우 중요함을 시사한다. During summer, the DIN (dissolved inorganic nitrogen) and DIP (dissolved inorganic phosphate) observed in the Jindong Bay in the southern sea of Korea show much higher values in the inner area of the bay. In general, they have high values in the upper (0-1 m) and lower layers (8 m-bottom), but are relatively lower in the middle layer (1-8 m). These features in their distribution are examined using an ecosystem model with considering the wind, tidal current, horizontal gradient of water density and residual flow. The experiments were focused on how to influence nutrients associated with these conditions. In the experiment with tide-induced residual flow, the values of nutrients appeared lower than the observation, and were well corresponded to it when the effects of wind, tide-induced residual current and horizontal gradient of water density were additionally imposed. A statistical analysis identifies these results. This paper suggests that variation of nutrient in the Jindong Bay during summer should be seriously a(footed wind-driven current by the wind and density-driven current is induced by the horizontal gradient of water density as well as tidal current.

염해에 따라 콘크리트 속에서 부식된 철근의 반전지전위와 부식전류밀도의 상관관계에 관한 실험적 연구

조상현,김동원,기성훈 한국구조물진단유지관리공학회 2022 한국구조물진단유지관리공학회 논문집 Vol.26 No.6

This study aims to investigate the feasibility of the half-cell potential (HCP) measurements on the concrete surface for evaluation of corrosion rate (or corrosion levels) of reinforcing steel in concrete. A series of experimental study is performed to measure HCP (or corrosion potential, Ecorr ) and corrosion current density (icorr) of reinforcing steel in concrete cube specimens, with a side length of 200 mm. Various corrosion levels in a range of 0% to 20% of the test specimens are accelerated by impressing current to the reinforcing steel in concrete immersed in 3.0 % NaCl solution. HCP is measured in accordance with ASTM C876-15, and corrosion current density is determined by using the Stern-Geary equation and measured polarization resistance measured by electrochemical impedance spectroscopy (EIS). As a result, a numerical formula that relates HCP and icorr in the test specimen is established by a regression analysis of the measured data in this study. It is observed that HCP is linearly correlated with log(icorr) with a R2 greater than 0.87, which is less affected by the experimental variables such as concrete mixture proportion, diameter of reinforcing steel and the amount of applied current in this study. These results exhibit that HCP measurements could be effective for evaluation of corrosion rate (or corrosion levels) of reinforcing steel in concrete in the case of exposed to a certain consistent environment. 이 연구에서는 콘크리트 표면에서 측정된 반전지전위(half-cell potential, HCP)값을 활용하여 철근 부식 상태 및 부식속도의 정량적 평가 가능성을 논의하였다. 이 연구에서는 염수에 침지된 콘크리트 속 철근에 전류를 인가하여 다양한 부식상태의 철근 콘크리트 실험체(한 변의 길이가 200mm 인 정육면체)를 준비하였다. 부식촉진시험을 마치고, 염수 포화상태의 콘크리트 실험체 표면에서 HCP값을 측정하였고, 바로 이어서 동일한 조건의 실험체에서 전기화학적 임피던스 분광법을 활용하여 콘크리트 속 철근의 분극저항값을 측정하였다. 측정된 분극저항값을 Stern-Geary식에 대입하여 부식전류밀도(corrosion current density, icorr)를 계산하였다. 실험결과를 바탕으로 염해에 따라 다양한 부식상태의 철근이 매입된 철근 콘크리트 실험체의 염수 포화상태에서 HCP와 icorr의 상관관계를 도출하였다. 대체적으로 HCP와 icorr은 로그선형관계를 보였으며, R2값이 0.87이상의 높은 적합도를 확인하여 통계적인 유의함을 확인하였다. 이러한 결과는 일정한 환경에 노출된 철근 콘크리트일 경우 자연전위값을 측정함으로서 철근의 부식상태 및 속도를 평가할 수 있음을 실험적으로 확인하였다.

요실금 치료용 자기 자극기의 자속밀도 및 유도전류 측정

한병희,최경무,조민형,이수열,Han, Byung-Hee,Choi, Kyung-Moo,Cho, Min-Hyoung,Lee, Soo-Yeol 대한의용생체공학회 2009 의공학회지 Vol.30 No.4

A simple method for measuring magnetic flux and induced current in magnetic nerve stimulation for urinary incontinence treatment is proposed. Unlike electric nerve stimulation, direct measurement of the induced current in magnetic nerve stimulation is impossible. Since induced currents stimulate nerves or muscles in magnetic nerve stimulation, measuring induced current is very important in validating stimulation efficacy and securing safety. The magnetic flux measuring system is composed of 6 layers with pick-up coils of 7 by 7 in each layer, and the induced current measuring system is composed of 6 layers with 7 concentric circular coils in each layer. The proposed method can be used in the design or performance test of a magnetic nerve stimulator for many clinical applications such as urinary incontinence treatment, activation of peripheral nerves, and transcranial magnetic stimulation.

60Hz ELF 자계에 의한 인체내부 유도 전류밀도 해석

민석원,송기현,Min Suk-Won,Song Ki-Hyun 대한전기학회 2006 전기학회논문지C Vol.55 No.2

This paper analysed the characteristics of current density induced inside human body by 60 Hz extremely low frequency magnetic fields according to varying conductivities of human model. Human model was composed of several organs and other parts, whose shapes were expressed by spheroids or cylinders. Organs such as the brain, heart, lungs, liver and intestines were taken into account. Applying the boundary element method to the human model, we estimated effects on the induced current distribution due to differences of the organ conductivity and shape. We find organ conductivity influences most and a cross section area and a position of organ also gives effects.

60㎐ ELF 자계에 의한 인체내부 유도 전류밀도 해석

閔錫源(Suk-Won Min),宋棋鉉(Ki-Hyun Song) 대한전기학회 2006 전기학회논문지C Vol.55 No.2

This paper analysed the characteristics of current density induced inside human body by 60 ㎐ extremely low frequency magnetic fields according to varying conductivities of human model. Human model was composed of several organs and other parts, whose shapes were expressed by spheroids or cylinders. Organs such as the brain, heart, lungs, liver and intestines were taken into account. Applying the boundary element method to the human model, we estimated effects on the induced current distribution due to differences of the organ conductivity and shape. We find organ conductivity influences most and a cross section area and a position of organ also gives effects.

Artificial Crack Detection in Press fit Railway Axle for High Speed Train Using Induced Current Focusing Potential Drop

Seok Jin Kwon,Byeong Choon Goo 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8

Railway wheelsets are one of the most important components in railway vehicles with regard to safety. Since failure in railway vehicle wheelsets can cause a disaster, regular inspection of cracks in axles and wheels is mandatory. Fatigue cracks were initiated in press fit parts that suffer from fretting fatigue damage, such as the wheel seat, gear seat and brake disc seat. Railway axles in service are regularly checked by ultrasonic testing and magnetic particles inspection. However, due to noise echoes it is difficult to detect crack initiation clearly with ultrasonic testing. Therefore, it is necessary to develop a non-destructive technique that is superior to conventional NDT techniques in order to ensure the safety of high-speed wheelset. The induced current focusing potential drop (ICFPD) technique is a new non-destructive testing technique that can detect cracks in railway axles by applying on electro-magnetic field and potential measurement. In the present paper, the new concept ICFPD technique is applied to the detection in press fit crack of railway axles. To detect the crack, the pick-up pins must be located in the horizontal direction to the crack although it is general that the pick-up pins of potential drop are located in the vertical direction of crack. The crack detections in press fit railway axle by using ICFPD was carried out in the axial and azimuthally direction. The result show that the crack in press fit part could be detected by using this method at 10㎜ away from the crack. The ICFPD method is useful to detect the crack that initiated in the press fit railway axles.

유도가열 조리기의 EMF 기본한계 노출량 평가

장원용(Won-Yong Jang),박종원(Jong-Won Park),박재혁(Jae-Hyeok Park),변진규(Jin-Kyu Byun),김남(Nam Kim) 한국자기학회 2022 韓國磁氣學會誌 Vol.32 No.1

In this paper, the magnetic field of the domestic induction cooktop is measured according to the IEC standard and the values are compared with exposure limits in the international EMF (Electromagnetic Field) safety guidelines. Also, the equivalent coil of the induction cooktop is derived based on the measured magnetic field distribution using the magnetic dipole moment equation. The magnetic field by the equivalent coil is greater than the measured values at all distances considered and the conservative exposure assessment of the basic restrictions is possible. Next, the current density induced in the human model by the equivalent coil is calculated using the simulation software at various distances for the exposure assessment of the EMF basic restrictions. The exposure index of the induced current density with respect to the exposure limit in the ICNIRP (International Commission on Non-Ionizing Radiation Protection) 1998 guideline was less than 0.369 for all the cases considered.

에미터와 은 전극 계면에서 발생하는 금속 재결합 손실 분석

정명상(Myeong Sang Jeong),최성진(Sungjin Choi),민관홍(Kwan Hong Min),강민구(Min Gu Kang),박성은(Sungeun Park),정경택(Kyung Taek Jeong),이해석(Hae-Seok Lee),강윤묵(Yoonmook Kang),김동환(Donghwan Kim),송희은(Hee-eun Song) 한국태양에너지학회 2019 한국태양에너지학회 학술대회논문집 Vol.2019 No.10