• 전력전자학회논문지
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• 제6권5호
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• pp.438-445
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• 2001

본 논문은 메탈할라이드 램프용 고주파 변조방식 전자식 안정기에 관한 것이다. 제안한 안정기는 고주파 영역에서 동작되며 외부 점화기 없이 LC 공진회로를 이용하여 램프를 기동시키므로 매우 컴팩트하며, 통상의 저주파식 전자식 안정기에 비하여 효율이 좋다. 제안하는 안정기는 공명현상을 회피하기 위하여 20kHz에서 100kHz 범위 내에서 변조되는 주파수로 제어된다. 본 논문에서는 안정기 특성을 평가하기 위하여 새로운 실시간 공명현상 검출기를 제안하였다. 또한 직류단 전류 검출을 통한 무부하 검출 알고리즘 및 전력제어 알고리즘에 대하여 기술하였다. 그리고 제안하는 방법을 적용한 프로토타입의 150W 메탈할라이드 램프 안정기로 수행된 실험결과를 검토하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.180-180
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• 2000

Plasma source ion implantation is a new doping technique for the formation of shallow junction with the merits of high dose rate, low-cost and minimal wafer charging damage. In plasma source ion implantation process, the wafer is placed directly in the plasma of the appropriate dopant ions. Negative pulse bias is applied to the wafer, causing the dopant ions to be accelerated toward the wafer and implanted below the surface. In this work, inductively couples plasma was generated by anodized Al antenna that was located inside the vacuum chamber. The outside wall of Al chamber was surrounded by Nd-Fe-B permanent magnets to confine the plasma and to enhance the uniformity. Before implantation, the wafer was pre-sputtered using DC bias of 300B in Ar plasma in order to eliminate the native oxide. After cleaning, B2H6 (5%)/H2 plasma and negative pulse bias of -1kV to 5 kV were used to form shallow p+/n junction at the boron dose of 1$\times$1015 to 5$\times$1016 #/cm2. The as-implanted samples were annealed at 90$0^{\circ}C$, 95$0^{\circ}C$ and 100$0^{\circ}C$during various annealing time with rapid thermal process. After annealing, the sheet resistance and the junction depth were measured with four point probe and secondary ion mass spectroscopy, respectively. The doping uniformity was also investigated. In addition, the electrical characteristics were measured for Schottky diode with a current-voltage meter.

• 한국진공학회지
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• 제20권3호
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• pp.195-199
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• 2011

RF 마그네트론 스퍼터와 DC 마그네트론 스퍼터를 병행하여 ITO/Au/ITO, ITO/Cu/ITO, 그리고 ITO/Ni/ITO 박막을 유리기판 위에 증착하였다. 증착 후 진공열처리를 통하여 층간 금속 층이 ITO박막의 메탄올 검출 민감도에 미치는 영향을 분석하였다. 모든 박막센서의 두께는 100 nm로 동일하게 ITO 50 nm/metal 10 nm/ITO 40 nm로 제작되었고 메탄올 농도는 100에서 1,000 ppm까지 달리하였다. ITO/Au/ITO 박막센서가 가장 높은 민감도를 보임으로써 ITO/Au/ITO 다층박막이 기존의 ITO메탄올 센서를 대체할 수 있는 센서임을 확인하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.277-277
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• 2010

The capacity of the carbonaceous materials reached ca. $350\;mAhg^{-1}$ which is close to theorestical value of the carbon intercalation composition $LiC_6$, resulting in a relatively low volumetric Li capacity. Notwithstanding the capacities of carbon, it will not adjust well to the need so future devices. Silicon shows the highest gravimetric capacities (up to $4000\;mAhg^{-1}$ for $Li_{21}Si_5$). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. We focused on electrode materials in the multiphase form which were composed of two metal compounds to reduce the volume change in material design. A combination of electrochemically amorphous active material in an inert matrix (Si-M) has been investigated for use as negative electrode materials in lithium ion batteries. The matrix composited of Si-M alloys system that; active material (Si)-inactive material (M) with Li; M is a transition metal that does not alloy with Li with Li such as Ti, V or Mo. We fabricated and tested a broad range of Si-M compositions. The electrodes were sputter-deposited on rough Cu foil. Electrochemical, structural, and compositional characterization was performed using various techniques. The structure of Si-M alloys was investigated using X-ray Diffractometer (XRD) and transmission electron microscopy (TEM). Surface morphologies of the electrodes are observed using a field emission scanning electron microscopy (FESEM). The electrochemical properties of the electrodes are studied using the cycling test and electrochemical impedance spectroscopy (EIS). It is found that the capacity is strongly dependent on Si content and cycle retention is also changed according to M contents. It may be beneficial to find materials with high capacity, low irreversible capacity and that do not pulverize, and that combine Si-M to improve capacity retention.

• Journal of Power Electronics
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• 제17권6호
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• pp.1535-1544
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• 2017

Advances in FPGA technology have enabled fast real-time simulation of power converters, filters and loads. FPGA based HIL (Hardware-In-the-Loop) simulators have revolutionized control hardware and software development for power electronics. Common time step sizes in the order of 100ns are sufficient for simulating switching frequency current and voltage ripples. In order to keep the time step as small as possible, ideal switching function models are often used to simulate the phase legs. This often produces inferior results when simulating the discontinuous conduction mode (DCM) and disabled operational states. Therefore, the corresponding measurement and protection units cannot be tested properly. This paper describes a new solution for this problem utilizing a discrete-time PI controller. The PI controller simulates the proper DC and low frequency AC components of the phase leg voltage during disabled operation. It also retains the advantage of fast real-time execution of switch-based models when an accurate simulation of high frequency junction capacitor oscillations is not necessary.

• Bulletin of the Korean Chemical Society
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• 제15권2호
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• pp.122-126
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• 1994

Corrosion of brass coated steel cords in the acetonitrile solution of sulfenamide derivatives, N-Cyclohexylbenzothiazole-2-sulfenamide (CBTS), N,N'-Dicyclohexylbenzothiazole-2-sulfenamide (DCBS), N-tert-Butylbenzothiazole-2-sulfenamide (TBBS), N-tert-Amylbenzothiazole-2-sulfenamide (TABS), and N-Oxydiethylbenzothiazole-2-sulfenamide (OBTS) was investigated by potentiostatic anodic and cathodic polarization (Tafel plot), DC polarization resistance, and AC impedance measurements. The corrosion current densities and rates are 1.236 ${\mu}A /cm^2$ and 0.655 MPY for CBTS; 1.881 ${\mu}A/cm^2$ and 0.988 MPY for DCBS; 2.367 ${\mu}A/cm^2$ and 1.257 MPY for TBBS; 3.398 ${\mu}A /cm^2$ and 1.809 MPY for TABS, respectively. OBTS among derivatives under study shows the lowest corrosion density (0.546 ${\mu}A /cm^2$) and the slowest corrosion rate (0.288 MPY). Also, the charge transfer resistances and the double layer capacitances are 275.21 $k{\Omega}{\cdot}cm^2$ and 7.0 ${\mu}F{cdot}cm^{-2}$ for CBTS; 14.24 ${\mu}F{\cdot}cm^2$ and 26 ${\mu}F{\cdot}cm^{-2}$ for DCBS; 54.15 $k{\Omega}{\cdot}cm^2$ and 26 ${\mu}F{\cdot}cm^{-2}$ for TBBS; 0.96$k{\Omega}{\cdot}cm^2$ and 83 ${\mu}F{\cdot}cm^{-2}$ for TABS, respectively. The weaker the electron donating inductive effect of derivatives is and the smaller the effect of steric hindrance is, the more the corrosion of brass coated steel cords in the acetonitrile solution of sulfenamide derivatives is prevented. The above results agree with that observed in the field of tire industry.

• 한국태양에너지학회 논문집
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• 제37권4호
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• pp.23-33
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• 2017

A great deal of study for loss reduction of photovoltaic system is conducted currently. It is hard to distinct the fault of photovoltaic system with the naked eye. For that reason, it is essential to repair and maintain the PV system by monitoring the system. The fault of individual modules can cause the huge loss of the entire system because of the mismatch. Therefore, the method of diagnosing the PV array is necessary by measuring the multi-channel arrays simultaneously. In this paper, it is presented the method of measuring I-V curve of multi-channel arrays simultaneously by using the charge and discharge characteristics of capacitor. Generated DC power at PV arrays is charged and discharged at the capacitors in a moment. By measuring the charged voltage and current, it is possible to diagnose of performance of PV arrays.

• 한국표면공학회지
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• 제54권5호
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• pp.238-247
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• 2021

PEO (plasma electrolytic oxidation) was applied to modify the surface of AZ31 magnesium alloy in this study. The mixed solution of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) was used as the electrolyte, and 0 - 0.05 g/L of Ca-GP (Glycerol Phosphate Calcium salt) was added in the electrolyte as an additive. PEO treatment was conducted at a current density of 30mA/cm² for 5 minutes using a DC power supply. The surface properties were identified by SEM, XRD and surface roughness analyses, and the corrosion resistance was evaluated by potentiodynamic polarization and immersion tests. In addition, the biocompatibility was evaluated by immersion test in SBF solution. As the concentration of Ca-GP was increased, the surface morphology was denser and more uniform, and the amount of Ca and the thickness of oxide layer increased. Only Mg peak was observed in XRD analysis due to very thin oxide layer. The corrosion resistance of PEO-treated samples increased with the concentration of Ca-GP in comparision with the untreated sample. In particular, the highest corrosion resistance was identified at the group of 0.04g Ca-GP through potentiodynamic polarization and immersion tests in saline solution (0.9 wt.%NaCl). During the immersion in saline solution, pH rapidly increased at the beginning of immersion period due to rapid corrosion, and then increase rate of pH decreased. However, the pH value in the SBF temporarily increased from 7.4 to 8.5 during the day, then decreased due to the inhibition of corrosion with HA(hydroxyapatite) formation.

• 한국표면공학회지
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• 제55권6호
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• pp.363-367
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• 2022

Transparent ZnO/Ti/ZnO (ZTZ) tri-layered films were prepared with radio frequency (RF) and direct current (DC) magnetron sputtering on the glass substrate. The thickness of the ZnO and Ti films was kept at 50 and 10 nm to consider the effect of the electron irradiation on the crystallization and optoelectrical properties of the films. From the XRD spectra, post-depostion electron irradiated films showed the characteristic peaks of ZnO(002) and Ti(200), respectively. the observed grain size of the ZnO(002) and Ti(200) enlarged up to 18.27 and 12.16 nm at an irradiation condition of 750 eV. In the figure of merit which means an optoelectrical performance of the films, as deposited films show a figure of merit of 2.0×10^-5 𝛺^-1, while the films electron irradiated at 750 eV show a higher figure of merit of 5.7×10^-5 𝛺^-1.

• Current Photovoltaic Research
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• 제9권2호
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• pp.51-58
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• 2021

Solar water pumping system (SWPS) is reliable and beneficial for Indian farmers in irrigation and crop production without accessing utility. The capability of easy installation and deployment, makes it an attractive option in remote areas without grid access. The selection of portable solar based pumps is pertaining to its longer life and economic viability due to lower running cost. The work presented in this manuscript intends to demonstrate performance analysis of portable systems. Consequent investigation reveals PSWS as the emerging option for rural household and marginal farmers. This can be attributed to the fact that, a considerable portion (around 45.7%) of the country's land is farmland and irrigation options are yet to reach farmers who entirely rely on rain water at present for harvesting of the crops. According to census 2010-2011 tube wells are the main source for irrigation amongst all other sources followed by canals. Out of the total 64.57-million-hectare net irrigation area, 48.16% is accounted by small and marginal holdings, 43.77% by semi-medium and medium holdings, and 8.07% by large holdings. As per 2015-16 census data, nearly 100 million farming households would struggle to make ends meet. The work included in this manuscript, presents the performance of different commercial brands and different technologies of DC surface solar water micro pumping systems have been studied (specifically, the centrifugal and reciprocating type pumps have been considered for analysis). The performance of the pumping systems has been analyzed and data is evaluated in terms of quantity of water impelled for specific head. The reciprocating pump has been observed to deliver the best system efficiency.