• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.311.1-311.1
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• 2013

건축물의 유리창을 통하여 유입되는 태양광을 조절하여 냉난방 부하를 절감하고자 사용하는 스마트 윈도우 필름(Electrochromic (EC), Polymer Dispersed Liquid Crystal (PDLC), Suspended Particle Display (SPD))의 방식이 있다. 이러한 스마트 윈도우 필름은 건물 외피에 적용할 때 여름철 태양으로부터 유입되는 열선 차폐만을 목적으로 유리를 완전히 불투명하게 가려버리는 것은 맑고 투명해야하는 창호의 기본적인 용도를 무시한 단편적 기술로서, 스마트 윈도우 필름을 작동하여 투명하게 할 경우 외부에서 열선이 유입되는 문제를 가지고 있다. 스마트 윈도우 필름을 만들 때 필수적으로 사용하는 전극필름으로 플렉서블 기판에 투명 전도막이 형성됨과 동시에 적외선만을 선택적으로 차단하는 기능을 가지는 필름을 제조하여 단열 성능 실험을 실시하였다. 아울러, 스마트 필름의 다양한 적용을 위한 발열 실험도 실시하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.3
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• pp.12-17
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• 2011

In this paper, we report on the improved electrical and optical characteristics for decreasing current crowding effect and uniform current distribution by designing octagonal finger type electrode pattern in large-scale lateral GaN (Gallium Nitride) LED (Light-emitting diode) with numerical 3-D simulator. Compared with the conventional electrode pattern, proposed electrode pattern was investigated to confirm the improvement of characteristics. From the simulation results of 3-D SpeCLED/RATRO simulator, we found that the forward voltage was decreased by 0.34 V and the light output power was improved by 7.72 mW at the same injection current condition in the LED with proposed octagonal finger type electrode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.18-18
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• 2009

본 논문은 X8R 온도 특성을 가지는 유전체 원료를 이용하여 고용량이면서 고압화가 가능한 적층 칩 캐패시터를 제작하였다. 대형 고압용 적층 칩 캐패시터를 위한 내부 전극 설계 및 외부 전극 형성 방법에 대한 연구도 함께 진행하였다. 적층 칩 캐패시터를 하이브리드 자동차 및 산업용 인버터의 DC-Link으로 사용하기 적합한 모듈을 제작하였으며 모듈 설계시 고유전율의 에폭시-세라믹 필름을 하였다. 본 모듈을 평가한 결과 기존 캐패시터 모듈에 비하여 2/3 크기의 소형화를 얻을 수 있었으며 ripple 전류 및 발열 특성이 매우 우수함을 확인하였다.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.114-121
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• 2016

This study investigates a CFD modeling of the charge-discharge behavior due to heat generation during charge-discharge cycles of a Li-ion secondary battery(LIB). Present LIB system adopted a current-density equation, heat and mass transfer governing equations upon the 1-dimensional system to the thickness direction for the rectangular pouch configuration. According to the 3-kinds of the charge-discharge current densities of 1C($17.5A/m^2$), 3C($52.5A/m^2$) and 5C($87.5A/m^2$) subject to a 3 V of cut-off voltage, a constant-temperature system at 298 K and three different heat generating systems were analyzed with comparison. Battery capacity decreases with increment of charge-discharge densities not only at the constant-temperature system but also at the heat-generating system. The time for charge-discharge cycles increases at the heat-generating system compare to the constant-temperature system. These trends are considered that the increase of temperature due to heat generation causes the decrement of equilibrium potential of electrodes and the increment of diffusivity of Li ions. Furthermore, cooling effects were discussed in order to control the influence of heat generation due to charge-discharge behavior of a Li-ion secondary battery.

• Resources Recycling
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• v.30 no.6
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• pp.19-27
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• 2021

Electrically conductive mortar used in industrial carbon material byproducts was manufactured and analyzed in this study. The contents of the carbon material and mixed water were controlled, and the distance between electrodes was set to 0.42 m and 0.88 m. The carbon material was graphite with a layered structure. The carbon material was used as fine powder and aggregate substitutes according to particle size. The average particle sizes of each materials were 18.4㎛ and 546.1 ㎛ and the electrical conductivities were 62.3 S/m and 32.5 S/m, respectively. To maintain similar mortar flow in each sample, the water content was increased with increasing carbon material, and accordingly, the porosity showed an increasing trend. When electrode distance of the mortar (week 6) was 0.42 m, the voltage-current values were 342 V-1.48 A (S20) and 349 V-1.44 A (S30). For electrode distance of 0.88 m, these values were 513 V-0.98 A (S20) and 500 V-1.01 A (S30). The exothermic properties improved with increasing carbon material content and decreasing electrode distance.

• Clean Technology
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• v.18 no.3
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• pp.320-324
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• 2012

In the present study, the discharge characteristics of a lithium-ion battery was evaluated to calculate the rate of heat generation under various discharge rates by mathematical modeling. The modeling and simulation of a pseudo-two dimensional ionic transport system for governing Butler-Volmer equation were carried out by using FEMLAB as a PDE (partial differential equation) solver, where the discharge rate was changed from 5 $A/m^2$ to 25 $A/m^2$. The computational results showed that the concentration of consumed solid-phase lithium at the surface of electrode was increased with increasing discharge rates. While the resulting diffusion limitation occurred shortly, it increased the rate of heat generation even more rapidly for the internal voltage to approach the cutoff voltage of the lithium-ion battery.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.688-697
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• 2014

In this study, electrode bonding technology needed for high density of rechargeable battery is studied, which is recently researched for electric vehicle, the small leisure vessel. For the alternative overcoming the limit of stacking amount able to be stacked by conventional ultrasonic welding, the low temperature bonding method, eligible for minimum of degeneration of chemical activator on the electrode surface which is generated by thermal effect as well as the increase of conductivity and tension strength caused by electrode bonding using filler metal, not using conventional direct heating on the electrode material method, is studied. Specifically to say, recently used more generally the ultrasonic welding and spot welding method are not usable for satisfying stable electric conductivity and bonding strength when much electrode is stacking bonded. If the electrical power is unreasonably increased for the welding, due to the effect of welding temperature, deformation of electrode and activating material degeneration are caused, and after the last packaging, decline of electrical output and generating heat cause to reduce stability of battery. Therefore, in this study, induction heating system bonding method using high frequency heating and differentiated electrode method using filler metal pre-treatment of hot dipping are introduced.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.2
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• pp.91-97
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• 2013

Self-heating effects during operation of high current AlGaN/GaN power transistors degrade the current-voltage characteristics. In particular, this problem becomes serious when a low thermal conductivity Si substrate is used. In this work, AlGaN/GaN-on-Si devices were fabricated with various channel widths and Si substrate thicknesses in which the structure dependent self-heating effects were investigated by temperature dependent measurements as well as thermal simulation. Accordingly, a device structure that can effectively dissipate the heat was proposed in order to achieve the maximum current in a multi-channel, large area device. Employing via-holes and common electrodes with a 100 ${\mu}m$ Si substrate thickness improved the current level by 75% reducing the channel temperature by 68%.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2206-2207
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• 2008

본 논문에서는 분전반에서의 화재 위험 요소와 화재위험 요소에 대한 현장 실태조사 결과를 분석하였다. 분전반에서의 화재 위험 요소는 크게 전기적 요인, 환경적 요인, 물리적 요인으로 나눌 수 있으며 전기적 요인으로는 단락, 과부하(과전류), 접촉불량, 전류 불평형 등이 있으며 환경적 요인으로는 수분(염분 등), 먼지(분진, 목분, 철분 등), 온도(고온) 등에 의한 절연파괴, 기기 손상, 오동작 등이 있다. 물리적 요인으로는 기계적인 진동이나 충격 등에 의한 전기적 접속부의 이완에 의한 발열 등을 들 수 있다. 이러한 화재 위험 요인에 대하여 현장실태조사를 실시한 결과, 일부 분전반에서 내부에 먼지 등 이물질이 차단기, 전선, 단자대 등의 표면에 부착되어 있음을 확인할 수 있었으며 수분이나 염분 등의 영향으로 전극간 절연물 표면의 열화로 화재가 발생할 가능성이 있다. 또한, 적외선 열화상 분석결과, 일부 차단기 단자에서 국부 발열이 관측되었으며, 부하 분담의 불평형에 의한 발열도 확인되었다. 이러한 위험요인에 의한 화재 예방을 위하여 규정된 전선 굵기의 사용과 적정 체결압력의 확보, 상간 전류 불평형을 줄이기 위한 부하 분담의 조정이 필요하다. 향후, 분전반에서의 전기화재, 감전사고 등 전기재해의 예방을 위하여 지속적이고 체계적인 유지관리는 물론 사고 발생 전에 이상 징후를 사전에 감지하여 조치를 취할 수 있도록 하는 기술의 개발과 현장 적용이 요구된다.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.940-946
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• 2015

In this paper, we study a method that amplifies the output gain of a high voltage pulse using 300 kHz or higher frequency. We conducted a study on a method for amplifying the output gain using the resonance between the capacitance components of the load and the parasitic components of the circuit, instead of the conservative method for amplifying the pulse-amplitude by raising the voltage of the power stage. In particular, the method simplifies the circuit configuration throughout the appliance of flyback-type topology instead of the bridge-type. There are advantages that prevent damage from overload and the heat in the output circuit through the hard switching by amplifying the gain of the output voltage applying to the load as given by the capacitance component of the output electrode to the output pulse waveform. This study proposed a method to enhance the spatial and electrical efficiency of the contact-type heating device through the dielectric heating method applied to the field of medical and industrial heating.