• Ocean and Polar Research
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• 제40권3호
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• pp.99-114
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• 2018

In the present study, we assess the GloSea5 (Global Seasonal Forecasting System version 5) near-surface ocean current forecasts using globally observed surface drifter dataset. Annual mean surface current fields at 0-day forecast lead time are quite consistent with drifter-derived velocity fields, and low values of root mean square (RMS) errors distributes in global oceans, except for regions of high variability, such as the Antarctic Circumpolar Current, Kuroshio, and Gulf Stream. Moreover a comparison with the global high-resolution forecasting system, HYCOM (Hybrid Coordinate Ocean Model), signifies that GloSea5 performs well in terms of short-range surface-current forecasts. Predictions from 0-day to 4-week lead time are also validated for the global ocean and regions covering the main ocean basins. In general, the Indian Ocean and tropical regions yield relatively high RMS errors against all forecast lead times, whilst the Pacific and Atlantic Oceans show low values. RMS errors against forecast lead time ranging from 0-day to 4-week reveal the largest increase rate between 0-day and 1-week lead time in all regions. Correlation against forecast lead time also reveals similar results. In addition, a strong westward bias of about $0.2m\;s^{-1}$ is found along the Equator in the western Pacific on the initial forecast day, and it extends toward the Equator of the eastern Pacific as the lead time increases.

• 에너지공학
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• 제11권3호
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• pp.230-236
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• 2002

전력계통 실시간 제어에서는 전압, 전류, 유효전력, 무효전력, 역률, 시스템 주파수 등 전력계통 변수들을 측정하는 것이 중요하다. 이 변수들은 전압과 전류의 동기화된 페이저 정보부터 추출할 수 있다. 따라서 전압 및 전류의 동기화된 페이저 측정은 실시간 전력계통 제어에서 매우 중요한 역할을 한다. 이런 이유로 동기위상측정장치가 개발되었고 본 논문에서는 동기위상측정장치의 설계와 구현한 것을 제시하였고 제작된 시작품을 RTDS(Real-time Digital Simulator)와 실험실에 있는 380 V 3상 배전계통에 적용하여 측정된 실험결과를 통해 개발된 시작품의 성능을 검증하였다.

• 한국환경과학회지
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• 제18권11호
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• pp.1225-1234
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• 2009

The aim of this research was to apply experimental design methodology in the optimization condition of electrochemical oxidation of Rhodamine B(RhB). The reactions of electrochemical oxidation were mathematically described as a function of parameters amounts of current, NaCl dosage, pH and time being modeled by the use of the central composite design, which was used for fitting quadratic response surface model. The application of response surface methodology using central composite design(CCD) technique yielded the following regression equation, which is an empirical relationship between the removal efficiency of RhB and test variable in actual variables: RhB removal (%) = 3.977 + 23.279$\cdot$Current + 49.124$\cdot$NaCI - 5.539$\cdot$pH - 8.863$\cdot$time - 22.710$\cdot$Current$\cdot$NaCl + 5.409$\cdot$Current$\cdot$time + 2.390$\cdot$NaCl$\cdot$time + 1.061$\cdot$pH$\cdot$time - $0.570{\cdot}time^2$. The model predicted also agree with the experimentally observed result($R^2$ = 91.9%).

• 전자공학회논문지A
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• 제30A권1호
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• pp.23-30
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• 1993

Hydrogenation on the top gate and bottom gate Poly-Si TET's was performed by using Nh$_{3}$ plasma and annealing SiN film deposited by PECVD and then the electric characteristics on Poly-Si TET were investigated. As the time of NA$_{3}$ plasma treatment increaes, on/off current ratio gradually increases and the swing value decreases. The trap densities of graim boundaries in Poly-Si decrease very much during the inital 20min of hydrogenation time, and the decreasing scale becomes smaller after 20 min. The electric characteristics of the top gate TFT are better than those of the bottom gate TFT, it is considered due to the defects at the interface between the Poly-Si and the underlayer, SiO$_{2}$. After NH$_{3}$ plasma was treated for 2 hours for the top gate TFT, as the aging time atroon temperature increases on current was not scacely changed and off current decreases more than 1 order. Gate current density recovers to original value after the aging treatment for 8 days and then the electric characteristics are finally improved. It is suggested that the degraded characteristics of gate oxide are improved, from the variations of C-V characteristics with aging time. For the hydrogenation of isothermal and isochronal annealing SiN film deposited by PECVD, the characteristics of Poly-Si TFT are improved with increasing annealing temperature and are not largely changed with increasing annealing time. This results is good in agreement with the hydrogen reduction in Sin film as variations of annealing temperature and time.

• Journal of Welding and Joining
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• 제17권5호
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• pp.61-68
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• 1999

For the last two decades, waveform control techniques have been successively developed and applied for the inverter welding machines resulting in the substantial reduction of spatter generated in CO₂ welding. One of the constituents commonly involved in those techniques is to delay the instant of current increase to some extent after the initiation of short-circuiting. Although this technique has been known to be quite effective in reducing the spatter generation through the suppression of is instantaneous short circuiting, the delay time necessary for minimum spatter has not been clearly understood. In this study, the control system for varying the delay time was constructed so that the spatter generation rates could be measured over a wide range of delay time, 0.29-2.0 msec. As a result of this study, it was demonstrated that spatter generation rate(SGR) sharply decreased at delay time of 0.6 msec and longer accompanied with the change in characteristics of short circuit mode from the instantaneous short-circuiting(ISC) dominant to normal short-circuiting(NSC) dominant. Another feature that have been found in current waveform of over 0.6msec was the creation of current pulse right after the arc reignition stage. Because of this current pulses weld pool oscillated in wave-like fashion and it looks like to play an important role in developing short circuiting between electrode and weld pool.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1106-1107
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• 2015

A flux pump (FP) can inject the DC current into high temperature superconducting (HTS) field coils of a HTS rotating machine without slip ring and current lead. However, it has limits to improve the value of DC current, and has time constants of DC current according to inductances of the HTS field coils. When a large-scale HTS generator with the FP is designed, a proper point about the inductance, field current, and time constant is demanded to decide parameters of the generator. In this paper, a parameter tuning skill of a large-scale superconducting wind power generator for applying a FP has been proposed. The design of the FP has been fixed, and 12 MW HTS generators have been variously designed by adjusting parameters related with the inductance of the HTS field coil. The induced current values have been calculated based on the FP design. The time constants of the induced currents depending on the DC current values and inductances of the generator have been represented. The results of the parameter tuning of the HTS generator have been discussed in detail.

• 한국표면공학회지
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• 제36권2호
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• pp.155-160
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• 2003

The effect of the temperature, current density and deposit time on hard chromium deposition in trivalent chromium bath was investigated. Cathode current efficiency increased with increasing current density. Increasing bath temperature from $20^{\circ}C$ to $50^{\circ}C$, chromium deposits were produced in higher current density and the maximum current efficiency was increased. At the plating conditions of $40^{\circ}C$, $30A/dm\m^2$, the deposition thickness increased in proportion to increasing electrolysis time The rate is$ 90\mu\textrm{m}$/hrs. for 2 hours. Microhardness of chromium deposits increased with increasing bath temperature and decreasing current density, and it was constant with electrolysis time. All of bath conditions, microstructure of chromium deposits has nodular structure with some cracking pattern and nodule size increased with increasing deposit thickness.

• 한국표면공학회지
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• 제52권2호
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• pp.72-77
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• 2019

To study the characteristics of AC driven OLED, we fabricated the fluorescent OLEDs and analyzed the electroluminescence characteristics of OLEDs with AC negative voltage. The luminance and the current density of the OLED decreased, and the number and size of the dark spots increased in proportion to the duration time and level of the applied AC negative voltage. The current efficiency of the OLED was improved when high AC negative voltage was applied within a short time. When the AC negative voltage of 10 V was applied for 1 minute, the efficiency was improved by 12.4%. Also, the degradation of luminance and current efficiency due to the duration of light emission was improved in the case of OLED applied for 1 minute with 10 V AC negative voltage. These are expected as a result of the improvement of the leakage current characteristics by eliminating the short-circuit region formed by the defect of the OLED at the AC negative high voltage. As a result, the continuous application of AC negative voltage reduced the luminance and the current density of OLED, but the temporary application of AC negative voltage with the proper time and voltage could improve the efficiency and lifetime of OLED.

• 한국표면공학회지
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• 제52권1호
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• pp.23-29
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• 2019

Electrolytic corrosion of the ship's hull can be occurred due to stray current during welding work using shore power and electrical leakage using shore power supply. The electrolytic corrosion characteristics were investigated for Al5083-H321 through potentiodynamic polarization and galvanostatic corrosion test in natural seawater. Experiments of electrolytic corrosion were tested at various current densities ranging from $0.01mA/cm^2$ to $10mA/cm^2$ for 30 minutes, and at various applied time ranging from 60 to 240 minutes. Evaluation of electrolytic corrosion was carried out by Tafel extrapolation, weight loss, surface analysis after the experiment. In the electrolytic corrosion characteristics of Al5083-H321 as the current density increased, the surface damage tended to proportionally increase. In the current density of $0.01mA/cm^2$ for a applied long time, the damage tended to grow on the surface. In the case of $10mA/cm^2$ current density for a applied long time, the damage progressed to the depth direction of the surface, and the amount of weight loss per hour increased to 4 mg/hr.

• KDI Journal of Economic Policy
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• 제34권3호
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• pp.187-214
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• 2012

우리나라 국민소득 통계는 한국은행에 의해 1953년부터 공식적으로 발표되고 있지만 UN이 제시한 매뉴얼인 "1993 SNA"에 의해 작성된 1970년 이후의 현행 계열과 "1953 SNA"에 의해 작성된 1953~70년의 구계열로 시계열이 단절되어 있다. 더구나 2009년에 한국은행이 1970년 이후 현행 계열에 연쇄가중법을 도입하면서 고정가중법에 의한 기존의 시계열과 더 큰 차이를 보이게 되었다. 본고에서는 UN이 발표한 각종 국민계정 매뉴얼, 우리나라의 과거 산업연관표 등을 활용하여 1953년부터 1970년까지의 구계열에도 포괄범위를 일치시키고 연쇄가중치를 적용하여 1953년부터 2010년까지의 장기 시계열을 일관된 기준으로 구해 보았다. 수정 계열은 구계열에 비해 1953년 경상 기초가격 GDP가 3.5% 높아졌고 성장률은 1953~70년 중 평균 1.5%p 상승한 것으로 나타났다. 한편, 수정 계열을 이용하여 지난 60년간의 우리 경제 변화상을 살펴본 결과 경제규모가 50배 이상 커진 것으로 나타났다. 산업별로는 제조업 및 SOC 산업은 크게 확대된 반면 서비스업은 상대적으로 확대 폭이 작았다.