• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1260-1261
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• 2008

Aluminium doped zinc oxide (ZnO:Al) thin film has emerged as one of the most promising transparent conducting electrode in flat panel displays(FPD) and in photovoltaic devices since it is inexpensive, mechanically stable, and highly resistant to deoxidation. In this paper ZnO:Al thin film was deposited on the polyethylene terephthalate(PET) substrate by the capacitively coupled r.f. magnetron sputtering method. Wide ranges of bias voltage, -30V${\sim}$45V, was applied to the growing films as an additional energy instead of substrate heating, and the effect of positive and negative bias on the film structure and electrical properties of ZnO:Al films was studied and discussed. The results showed that a bias applied to the substrate during sputtering contributed to the improvement of electrical properties of the film by attracting ions and electrons in the plasma to bombard the growing films. These bombardments provided additional energy to the growing ZnO film on the substrate, resulting in significant variations in film structure and electrical properties. The film deposited on the PET substrate at r. f. discharge power of 200 W showed the minimum resistivity of about $2.4{\times}10^{-3}{\Omega}-cm$ and a transmittance of about 87%.

• Journal of Power Electronics
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• 제16권5호
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• pp.1904-1917
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• 2016

The moving average filter (MAF) is widely utilized to improve the disturbance rejection capability of phase-locked loops (PLLs). This is of vital significance for the grid-integration and stable operation of power electronic converters to electric power systems. However, the open-loop bandwidth is drastically reduced after incorporating a MAF into the PLL structure, which makes the dynamic response sluggish. To overcome this shortcoming, some new techniques have recently been proposed to improve the transient response of MAF-based PLLs. In this paper, a comprehensive performance comparison of advanced MAF-based PLL algorithms is presented. This comparison includes HPLL, MPLC-PLL, QT1-PLL, and DMAF-PLL. Various disturbances, such as grid voltage sag, voltage flicker, harmonics distortion, phase-angle and frequency jumps, DC offsets and noise, are considered to experimentally test the dynamic performances of these PLL algorithms. Finally, an improved positive sequence extraction method for a HPLL under the frequency jumps scenario is presented to compensate for the steady-state error caused by non-frequency adaptive DSC, and a satisfactory performance has been achieved.

• 상하수도학회지
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• 제31권5호
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• pp.397-407
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• 2017

A dimensionally stable anode based on the $RuO_2$ electrocatalyst is an important electrode for generating chlorine. The $RuO_2$ is well-known as an electrode material with high electrocatalytic performance and stability. In this study, sonoelectrodeposition is proposed to synthesize the $RuO_2$ electrodes. The electrode obtained by this novel process shows better electrocatalytic properties and stability for generating chlorine compared to the conventional one. The high roughness and outer surface area of the $RuO_2$ electrode from a new fabrication process leads to increase in the chlorine generation rate. This enhanced performance is attributed to the accelerated mass transport rate of the chloride ions from electrolyte to electrode surface. In addition, the electrode with sonodeposition method showed higher stability than the conventional one, which might be explained by the mass coverage enhancement. The effect of sonodeposition time was also investigated, and the electrode with longer deposition time showed higher electrocatalytic performance and stability.

• Journal of Animal Science and Technology
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• 제48권2호
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• pp.315-324
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• 2006

This research was conducted to clarify the characteristics of electrochemical decolorization of effluent discharged from a biological animal wastewater treatment process and to finally establish parameters or mode for optimum operation of electrolysis system. Average color unit of wastewater was about 1,200 and DSA(Dimensionally Stable Anode) was used as electrode. Experiments were performed with two different operation conditions or modes, fixed voltage-free current(Run A) and free voltage-fixed current(Run B). Color removal rate was proportional to the electrode area and electrical conductivity, and an equation subject to them at a condition of fixed voltage was derived as follows; Ct=C0ekt, k=[{0.0121×ａ(dm2)× c(mS/cm)}+0.0288], [where, C0: initial color, Ct: color unit after treatment for t, k: reaction coefficient, t: time(min.), ａ: electrode area, c: conductivity]. From the study on the effects of current density on color removal, it was revealed that the removal efficiency of color was function of the current density, showing direct proportion. However, when considered energy consumption rate, maintenance of low current density was an economical way. Based on the obtained results, it was concluded that supplementation of electrolyte is not necessary for the removal of color from the effluent of secondary treatment process and operation with the mode of free voltage-fixed current, rather than operation with fixed voltage-free current mode, would be an efficient way to increase the removal performance and capacity per consumed energy.

• 한국태양에너지학회 논문집
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• 제32권4호
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• pp.43-50
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• 2012

Metal-metal oxide (M-M oxide) cermet solar selective coatings with a double cermet layer film structure were deposited on the Al-deposited glass substrate by using a directed current (DC) magnetron sputtering technology. M oxide (CrO and ZrO) was used as the ceramic component in the cermets, and Cr and Zr used as the metallic components. In addition, black Cr (Cr-$Cr_2O_3$ cermet) solar selective coatings were deposited on the Ni-plated Cu substrate by using a electroplating method for comparison. The thermal stability tests were carried out for performance evaluation of solar coatings. Reflectance measurements were used to evaluate both solar absorptance(${\alpha}$) and thermal emittance (${\epsilon}$) of the solar coatings before and after thermal testing by using a spectrometer. Optical properties of optimized cermet solar coatings were ${\alpha}{\simeq}0.94-0.96$ and ${\epsilon}{\simeq}0.1$ ($100^{\circ}C$). The results of thermal stability test of M-M oxide solar coatings showed that the Cr-CrO cermet solar selective coatings were more stable than the Zr-ZrO cermet selective coatings at temperature of both $400^{\circ}C$ in air and $450^{\circ}C$ in vacuum. The black Cr solar selective coatings were degraded in air at temperature of $400^{\circ}C$. The main optical degradation modes of these coatings were diffusion of metal atoms, and oxidation.

• 전기화학회지
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• 제16권3호
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• pp.157-161
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• 2013

다공성 $LiMn_{0.6}Fe_{0.4}PO_4$ (LMFP)를 졸-겔법을 이용하여 합성하였고, 원료물질을 양론비로 혼합한 후 혼합물을 $600^{\circ}C$에서 10시간 동안 가열하여 입자 표면 전체에 전도성 탄소물질이 균일하게 형성된 LMFP을 제조하였다. LMFP의 결정구조는 리트펠트법에 의해 조사하였고, 표면구조와 기공특성은 주사전자현미경, 투과전자현미경, BET로 분석하였다. 제조된 LMFP는 표면적이 크고, 입자 표면에는 웹(web) 형태의 다공성 탄소층이 균일하게 형성되어 있는 것을 확인하였다. 상온에서 LMFP를 양극으로 사용하여 0.1 C의 전류밀도에서 초기방전용량은 152 mAh/g, 에너지밀도는 570 Wh/kg로 높았고 사이클 성능도 장기적으로 안정적이었다. 졸-겔법에 의해 제조된 LMFP는 높은 기공도와 균일한 탄소코팅에 의한 시너지효과로 이온확산이 용이하여 우수한 전기화학적 특성을 나타내었다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제16권11호
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• pp.1081-1085
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• 2010

무선 센서 네트워크에서는 전송파워 제어를 이용하여 전력소비를 줄이고 채널간의 간섭을 줄일 수 있다. 무선 링크의 품질은 시간 및 공간적인 상황에 따라 변화하기 때문에 링크의 실패가 빈번하다. 기존의 전송파워 제어 기법은 링크 품질 변화에 적응할 수 있도록 주기적으로 이웃 노드와 비컨 패킷을 주고 받아 동적으로 전송파워를 조절하도록 하였다. 하지만 전송파워를 조절하는 주기에 따라서 링크 품질의 변화에 적용하는 시간과 트래픽 및 에너지 오버헤드에 영향을 줄 수 있다. 본 논문에서는 링크의 품질변화에 따른 동적인 전송파워 제어 기법과 전송파워 제어 주기를 변경하는 기법을 제안한다. 이를 통하여 링크가 불안정할 때에는 전송파워 제어 주기를 감소시켜 민첩하게 링크 품질을 유지하며, 링크가 안정할 때는 전송파워 제어 주기를 증가시켜 이에 따른 프로토콜의 오버헤드를 줄이고자 하였다.

• KIEAE Journal
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• 제17권5호
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• pp.69-76
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• 2017

Purpose: This study aimed at developing an Artificial Neural Network (ANN) model for predicting the amount of cooling energy consumption of the variable refrigerant flow (VRF) cooling system by the different set-points of the control variables, such as supply air temperature of air handling unit (AHU), condenser fluid temperature, condenser fluid pressure, and refrigerant evaporation temperature. Applying the predicted results for the different set-points, the control algorithm, which embedded the ANN model, will determine the most energy efficient control strategy. Method: The ANN model was developed and tested its prediction accuracy by using matrix laboratory (MATLAB) and its neural network toolbox. The field data sets were collected for the model training and performance evaluation. For completing the prediction model, three major steps were conducted - i) initial model development including input variable selection, ii) model optimization, and iii) performance evaluation. Result: Eight meaningful input variables were selected in the initial model development such as outdoor temperature, outdoor humidity, indoor temperature, cooling load of the previous cycle, supply air temperature of AHU, condenser fluid temperature, condenser fluid pressure, and refrigerant evaporation temperature. The initial model was optimized to have 2 hidden layers with 15 hidden neurons each, 0.3 learning rate, and 0.3 momentum. The optimized model proved its prediction accuracy with stable prediction results.

• 한국자기학회지
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• 제9권3호
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• pp.127-130
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• 1999

사각형구조를 갖는 Ru 단층에서 살창상수와 자성과의 관계를 총 에너지 총 퍼텐셜 보강 평면 파동(FLAPW) 에너지띠 방법에 의해 연구하였다. 반강자성상태를 고려하기 위해 2개의 원자를 포함하는 사각형에서 살창상수가 7.30a.u.보다 큰 경우는 강자성이었고 그 보다 작은 경우에는 상자성이었다. 반강자성상태도 고려하였으나 총 에너지 계산결과 그 가능성은 없었다. 총 에너지 최소값은 살창상수가 6.53a.u.인 경우로 이 때의 자기적 상태는 상자성이었다. Ag의 살창상수값 근처인 7.72a.u.에서 자기모멘트는 2.49$\mu$B로 계산되었다. 살창상수가 7.86a.u.인 경우에 자기모멘트가 거의 포화되었으며 그 때의 자기모멘트는 2.57$\mu$B이었다.

• Nuclear Engineering and Technology
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• 제16권3호
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• pp.169-179
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• 1984

FIPREL 전산코드를 사용하여 원자로 냉각수 내의 핵분열 생성물에 의한 방사능을 분석함으로써 PWR의 운전시에 발생하는 핵연료 피복관 파손을 평가할 수 있는 효과적인 절차를 모색하였다. 이 코드를 이용하여 핵연료의 농축도, 연소도, 가동온도 및 갭유출계수의 크기로 정량화되는 실제적 파손 크기등의 물리적 파라미터에 대해서 핵분열 생성물의 방사능이 나타내는 민감도에 대한 방대한 계산을 실시하였으며 그 결과는 PROFIP방법에 의한 것과 대체적으로 일치한다. 노출 우라늄이 존재하는 경우에는 옥소보다도 화학적으로 더 안정된 핵종간의 방사능비에 근거하여 반복계산을 실시함으로써 파손된 핵연료 봉에서 유출된 방사능만을 분리해 낸다. 개발된 전산코드로 파손 핵연료봉의 선형출력 밀도, 갯수, 실제적 파손 크기 및 노출우라늄의 질량등을 계산할 수 있다. 고리 1호기의 4주기에 걸친 운전 경험을 이 모텔에 의해 분석한 결과에 의하면 본 모델은 원자력발전소 정상운전시 핵연료봉의 상태를 감시·평가하는데 아주 적합한 것으로 판명되었다.