• 한국산업융합학회 논문집
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• 제25권6_2호
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• pp.1071-1081
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• 2022

As the demand for high-rise buildings increases, the demand for high-speed elevators is also increasing. In order to make a high-speed elevator, a method is needed to reduce the weight of the elevator's components, which is a constraint on the increase in speed. As a measure to reduce the weight, it is possible to remove the traveling cable for power and signal supply. Since the weight of the traveling cable varies depending on the position of the carriage, it is difficult to compensate the weight using the counter weight. The power supply is a structure in which a brush-rail type power input terminal is installed in the elevator hoistway to receive power in a contact-type manner while the carriage is moving. If a small-capacity ESS is installed in a passenger car, power can be supplied uninterruptedly inside the passenger car. A small-capacity ESS charging system to be applied to such an elevator system is required to perform several functions. First, the passenger Car must be able to charge as much as possible even during high-speed operation. A control algorithm with high responsiveness is required because charging starts and ends repeatedly by the partially installed input power stage. In addition, if the input-side line impedance is large due to the structure of the system and the response characteristic is increased, the stability of the system may be lowered. Accordingly, in this paper, we propose a control algorithm that has a stable steady-state output while having a fast response in a transient state. To verify the proposed control algorithm, simulation was conducted using PSIM, and the performance of the controller was verified by manufacturing a prototype buck conveter charger.

• 한국재료학회지
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• 제33권2호
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• pp.63-70
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• 2023

In this study, crystallization was effectively suppressed in Al-based metallic glasses (Al-MGs) during pulverization by cryo-milling by applying an extremely low processing temperature and using a surfactant. Before Al-MGs can be used as an additive in Ag paste for solar cells, the particle sizes of the Al-MGs must be reduced by milling. However, during the ball milling process crystallization of the Al-MG is a problem. Once the Al-MG is crystallized, they no longer exhibit glass-like behavior, such as thermoplastic deformation, which is critical to decrease the electrical resistance of the Ag electrode. The main reason for crystallization during the ball milling process is the heat generated by collisions between the particles and the balls, or between the particles. Once the heat reaches the crystallization temperature of the Al-MGs, they start crystallization. Another reason for the crystallization is agglomeration of the particles. If the initially fed particles become severely agglomerated, they coalesce instead of being pulverized during the milling. The coalesced particles experience more collisions and finally crystallize. In this study, the heat generated during milling was suppressed by using cryo-milling with liquid-nitrogen, which was regularly fed into the milling jar. Also, the MG powders were dispersed using a surfactant before milling, so that the problem of agglomeration was resolved. Cryo-milling with the surfactant led to D50 = 10 um after 6 h milling, and we finally achieved a specific contact resistance of 0.22 mΩcm² and electrical resistivity of 2.81 μΩcm using the milled MG particles.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
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• pp.152-154
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• 2001

Recently the extensive use of composite insulators for transmission lines can ultimately be justified only on long-term qualification tests. Especially, it is possible for the Polymer insulator to be aged in according to the environment in which it is used this may bring about the decrease of the duration of voltage application. So, this paper deals with aging property of the polymer insulator installed at real transmission line in the industry area. The contact angle, arc test, tracking test were measured for acquiring the degradation characteristics of silicone rubber and the SEM, XRF, FT-IR tests were measured for analyzing the crack and components. Also the surface leakage current of the polymer insulator was compared with that of the porcelain insulator. Finally, we knew that the aging property was not appeared during seven months at real transmission line in the industry area.

• ETRI Journal
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• 제37권2호
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• pp.387-394
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• 2015

A novel interconnection technology based on a 52InSn solder was developed for flexible display applications. The display industry is currently trying to develop a flexible display, and one of the crucial technologies for the implementation of a flexible display is to reduce the bonding process temperature to less than $150^{\circ}C$. InSn solder interconnection technology is proposed herein to reduce the electrical contact resistance and concurrently achieve a process temperature of less than $150^{\circ}C$. A solder bump maker (SBM) and fluxing underfill were developed for these purposes. SBM is a novel bumping material, and it is a mixture of a resin system and InSn solder powder. A maskless screen printing process was also developed using an SBM to reduce the cost of the bumping process. Fluxing underfill plays the role of a flux and an underfill concurrently to simplify the bonding process compared to a conventional flip-chip bonding using a capillary underfill material. Using an SBM and fluxing underfill, a $20{\mu}m$ pitch InSn solder SoP array on a glass substrate was successfully formed using a maskless screen printing process, and two glass substrates were bonded at $130^{\circ}C$.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.147-150
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• 2005

Low actuation voltage and no contact stiction are the important factors to apply MEMS RF switches to mobile devices. Conventional electrostatic MEMS RF switches require several tens of voltages for actuation. In this paper we propose PAS MEMS RF switch which adopt PZT actuators and seesaw cantilevers to meet the above requirements. The fundamental structures of PAS MEMS switch were designed, optimized, and fabricated. Through the developed processes PAS SPDT MEMS RF switches were successfully fabricated on 4" wafers and they showed good electrical properties. The driving voltage was less than 5 volts. And the insertion loss was -0.5dB and the isolation was 35dB at 5GHz. The switching speed was about 5kHz. So these MEMS RF switches can be applicable to mobile communication devices or wireless multi-media devices at lower than 6GHz.

• 대한화학회지
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• 제61권4호
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• pp.168-178
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• 2017

$La/TiO_2$ - graphene composites were synthesized in this study, and applied to the photocatalytic degradation of Rhodamine B (RhB) under UV-visible light irradiation. X-ray diffraction (XRD), surface analysis, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) analysis demonstrated that $La/TiO_2$ nanoparticles were well distributed on the surface of graphene, and formed the heterostructure of $La/TiO_2$-graphene. Compared to the pure $TiO_2$, $La/TiO_2$-graphene composites displayed much higher photocatalytic activities in RhB degradation under UV-visible light irradiation. The photocatalytic data of $La/TiO_2$-graphene composites exhibit extended light absorption in the visible light region, and possess better charge separation capability than that of pure $TiO_2$. The high photocatalytic activity was attributed to the composite's high adsorptivity, extended light absorption, and increased charge separation efficiency, due to the excellent electrical properties of graphene, and the large surface contact between graphene and $La/TiO_2$ nanoparticles.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.360.2-360.2
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• 2016

CuSn thin films were fabricated by rf magnetron co-sputtering method on the Si(100) substrate for evaluation of the antibacterial effect. The co-sputtering process was performed with different rf powers and sputtering times to regulate the thickness of the films and relative atomic ratio of Cu to Sn. The physicochemical properties of the CuSn thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES), Optical microscope (OM), 4-point probe, and antibacterial test. An antibacterial test was conducted with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as changing contact times between CuSn fillms and bacteria suspension. We compared to the crystalline structures of films before sterilization and after sterilization by XRD measurement. The changes of oxidation states of Cu and Sn and the chemical environment of films before and after antibacterial test were investigated with high resolution XPS spectra in the regions of Cu 2p, Cu LMM, and Sn 3d. After antibacterial test, the morphology of the films was checked with an OM images. The electrical properties of the CuSn films such as surface resistance and conductivity were measured by using 4-point probe.

• 전자공학회논문지 IE
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• 제44권3호
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• pp.6-11
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• 2007

본 연구는 플라즈마 처리한 고분자 복합재료 표면의 접촉각, X-선광전자분광법(XPS) 및 코로나 대전에 의한 표면 정전특성을 분석하여 발생된 화학적 변화와 정전적 특성 변화를 고찰하여 열화 메커니즘을 도출하였다. 플라즈마 처리된 시료의 접촉각 및 표면전위는 표면에 카르복실기 라디칼을 포함하는 다량의 측쇄화가 집중적으로 발생되어 처리시간에 따라 급격한 친수화가 진행되었다. 플라즈마 처리로 인한 화학적 변화에서 표면에 carboxyl 라디칼이 주로 형성되면서 급격히 표면 친수화로 변화하였다. 정전변화를 분석한 전위감쇠 결과에서 미처리 시료는 부극성 표면을 나타내었으나, 친수화 표면은 carboxyl 라디칼(-COO*)을 포함하는 정극성 라디칼로 인해 정극성 표면으로 변화하여 부극성 전하가 빠르게 감소하였다.

• 항공우주기술
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• 제9권2호
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• pp.57-62
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• 2010

저궤도 인공위성에서 SAR 위성 탑재체의 전류 소모량이 약 150A로 예측된다. 이러한 높은 전류 소모는 배터리-위성버스-탑재체로 이루어진 인터페이스에서 전압 강하를 유기하여 위성 본체의 전장품과 탑재체의 동작 전압을 낮추게 되어 정상 동작을 보장하지 못하게 된다. 따라서, 탑재체 동작에 따른 버스 전압과 탑재체 입력 전압 강하의 예측이 반드시 필요하다. 본 해석에서는 전압강하의 요인이 될 수 있는 하니스 및 접촉 저항에 대한 worst case analysis를 수행하여 탑재체 동작시 발생할 수 있는 전압 강하를 예측한다.

• Mass Spectrometry Letters
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• 제7권1호
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• pp.21-25
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• 2016

Dual-channel nano-electrospray has recently become an ionization technique of great promise especially in biological mass spectrometry. This unique approach takes advantage of the mixing processes that occurs during electrospray. Understanding in more detail the fundamental principles influencing spray formation further study of the origins of the mixing processes: (1) in a Taylor cone region, (2) in charged droplets or (3) in both environments. The dual-channel emitters were made from borosilicate theta-shape glass tubes (O.D. 1.2 mm) and had a tip diameters of less than 4 μm. Electrical contact was achived by deposition of a thin film of an appropriate metal onto the surface of the emitter. The experimental investigation of the Taylor cone formation in a dual-channel electrospray emitter has been carried out by injection of polystyrene beads (diameter 3 μm) at very low concentrations into one of the channels of the non-tapered theta-glass tubes. High-speed camera experiments were set up to visualize the mixing processes in Taylor cone regions for dual-channel emitters. Mass spectra from dual nano-electrospray are presented.