• Investigative Magnetic Resonance Imaging
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• 제20권2호
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• pp.132-135
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• 2016

We report the case of a 43-year-old male with both giant left atrial appendage (LAA) aneurysm and drug-refractory atrial fibrillation (AF). The patient was treated with percutaneous electrical isolation of cardiac arrhythmogenic substrate, and has been free of AF symptom over one year. Although the surgical resection of giant LAA aneurysm is mostly used to prevent systemic thromboembolism, we have performed follow-up of the giant LAA aneurysm using cardiac magnetic resonance (CMR) imaging and transesophageal echocardiography (TEE) after the successful catheter ablation of refractory AF. At one-year follow-up CMR, the giant LAA aneurysm showed remarkable enlargement as well as decreased contractility. Additionally, one-year follow-up TEE showed spontaneous echo contrast as an indicator of blood stasis in the giant LAA aneurysm. Those findings of giant LAA aneurysm suggest that the risk of thromboembolism may be high despite termination of AF.

• 한국전자통신학회논문지
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• 제8권9호
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• pp.1307-1312
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• 2013

본 논문에서는 알칼리성 또는 산성을 띠는 특정 용액 내에서 전기분해 원리를 이용하여 금속 표면을 산화시켜 절연피막을 형성하는 장치를 개발한다. 기존에는 주로 양극에만 펄스 형태로 전압을 인가하는 단극성(unipolar) 방식이지만 본 논문에서는 H-브리지를 이용하여 양극에 양(+)전압과 음(-)전압을 번갈아 가면서 전압을 공급하는 양극성(bipolar) 장치를 제작하였으며, 금속 시편의 특성에 맞는 다양한 전기적인 조건을 가지고 산화피막을 형성할 수 있는 장치를 개발하였다. 공급전류 가변은 PWM 변조를 이용하였으며, (+)와 (-)의 극성변화는 H-브리지를 이용하여 양극성 펄스전압을 공급할 수 있도록 하였다. 그 결과로써 단극성보다 균일한 기공을 갖는 피막이 형성되었다.

• Journal of information and communication convergence engineering
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• 제11권3호
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• pp.147-152
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• 2013

A novel balun being the structure of a Wilkinson power divider is suggested and fabricated. One of the power dividing paths in the suggested balun uses a conventional ${\lambda}/4$ transmission line for $-90^{\circ}$ phase shifting, and the other path uses a composite right/left-handed -${\lambda}/4$ transmission line for $+90^{\circ}$ phase shifting with four series capacitors and three parallel inductors. In addition, the suggested balun uses two $50-{\Omega}$ resistors and a conventional $50-{\Omega}$ transmission line of ${\lambda}/2$ electrical length between the two output ports, achieving good isolation and reflection values of two balanced ports. The suggested balun is simulated by the advanced design system simulation program and fabricated on TLX-9 20-mil substrate. The fabricated balun has a very good values of $S_{11}$ = -27.46 dB, $S_{21}$ = -3.40 dB, and $S_{31}$ = -3.28 dB, a phase difference of $-179.5^{\circ}$, a magnitude difference of 0.12 dB, and a delay difference of 0.1 ns, with $S_{22}$ = -36.28 dB, $S_{33}$ = -27.19 dB, and $S_{32}$ = -25.2 dB at 1 GHz, respectively.

• 한국재료학회지
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• 제15권9호
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• pp.613-619
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• 2005

The ever increasing popularity and acceptance in the market place of portable systems, such as cell phones, PDA, notebook PC, etc., are fueling effects in further miniaturizing and lowering power consumption in these systems. The dynamic power consumption due to the CPU activities and the static power consumption due to leakage currents are two major sources of power consumption. Smaller devices and a lower de voltage lead to reducing the power requirement, while better insulation and isolation of devices lead to reducing leakage currents. All these can be harnessed in the SOI (silicon-on-insulator) technology. In this study, the key aspects of the SOI technology, mainly device electrical properties and device processing steps, are briefly reviewed. The interesting materials issues, such as SOI structure formation and SOI wafer fabrication methods, are then surveyed. In particular, the recent technological innovations in two major SOI wafer fabrication methods, namely wafer bonding and SIMOX, are explored and compared in depth. The results of the study are nixed in that, although the quality of the SOI structures has shown great improvements, the processing steps are still found to be too complex. Between the two methods, no clear winner has yet emerged in terms of the product quality and cost considerations.

• 한국산업융합학회 논문집
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• 제20권2호
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• pp.115-124
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• 2017

This paper aims to develop an SMPS topology for handling a high range of input voltages based on a DC-DC flyback converter circuit. For this purpose, 2 capacitors of the same specifications were serially connected on the input terminal side, with a flyback converter of the same circuit configuration serially connected to each of them, so as to achieve high input voltage and an effect of dividing input voltage. The serially connected flyback converters have the transformer turn ratio of 1:1, so that each coil is used for the winding of a single transformer, which is a characteristic of doubly-fed configuration and enables the correction of input capacitor voltage imbalance. In addition, a pulse transformer was designed and fabricated in a way that can achieve the isolation and noise robustness of the PWM output signal of the PWM controller that applies gate voltage to individual flyback converter switches. PSIM simulation was carried out to verify such a structure and confirm its feasibility, and a 100W class stack was fabricated and used to verify the feasibility of the proposed high voltage SMPS topology.

• 전기전자학회논문지
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• 제23권2호
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• pp.474-478
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• 2019

본 논문에서는 휴대단말기 내의 디지털 노이즈와 안테나 사이의 결합(coupling)으로 인한 수신감도 저하 현상을 특성 모드(characteristic mode)를 사용해서 분석한다. 우선, 안테나와 디지털 잡음의 결합 메커니즘(mechanism)을 분석하고, 카메라 노이즈로 인한 안테나 수신감도 열화현상의 개선 방법 중 하나인 그라운드(ground) 선의 디커플링 커패시터(decoupling capacitor, decap)의 역할에 대해서도 분석한다. 분석을 위해서 카메라 모듈의 FPCB의 디지털 신호 선과 그라운드 선을 PCB 그라운드의 특성 모드를 여기(excitation) 시키는 루프(loop)형 피더(feeder)로 모델링 했고, 그라운드 선과 커패시터를 추가한 개선 모델에 대해서 분석을 했다.

• Journal of Electrochemical Science and Technology
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• 제10권2호
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• pp.244-249
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• 2019

SiO has a high theoretical capacity as a promising anode material candidate for high-energy-density Li-ion batteries. However, its practical application is still not widely used because of the large volume change that occurs during cycling. In this report, an active material containing a mixture of SiO and graphite was used to improve the insufficient energy density of the conventional anode with the support of multidimensional conducting agents. To relieve the isolation of the active materials from volume changes of SiO/graphite electrode, two types of conducting agents, namely, 1-dimensional VGCF and 0-dimensional Super-P, were introduced. The combination of VGCF and Super-P conducting agents efficiently maintained electrical pathways among particles in the electrode during cycling. We found that the electrochemical performances of cycleability and rate capability were greatly improved by employing the conducting agent combinations of VGCF and Super-P compared with the electrode using only single VGCF or single Super-P. We investigated the detailed failure mechanisms by using systematic electrochemical analyses.

• International Journal of Arrhythmia
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• 제19권3호
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• pp.235-284
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• 2018

In this part the writing group will cover strategies, techniques, and endpoints of atrial fibrillation (AF) ablation. Prior to all, electrical isolation of the pulmonary veins is recommended during all AF ablation procedures. In addition, techniques to be used for ablation of persistent and long-standing persistent AF, adjunctive ablation strategies, nonablative strategies to improve outcomes of AF ablation, and endpoints for ablation of paroxysmal, persistent, and long-standing persistent AF will be reviewed. Currently many technologies and tools are employed for AF ablation procedures. Radiofrequency energy, cryoablation, and other energy sources and tools are in various stages of development and/or clinical investigation. Finally, anticoagulation strategies pre-, during, and postcatheter ablation of AF and technical aspects of ablation to maximize safety are discussed in this section.

• 한국전자파학회논문지
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• 제16권7호
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• pp.732-739
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• 2005

본 논문에서는 E-평면 T형 분기 도파관을 갖는 Ka대역(20/30 GHz) 다이플렉서의 설계 및 구현에 관해 논하였다. 본 논문의 도파관 다이플렉서는 송신 필터 및 수신 필터를 E-평면 T형 분기 도파관으로 연결하여 E-평면으로 대칭이 되도록 하였다. T형 분기 도파관을 E-평면으로 선택한 이유는 제작시 생기는 절단면을 전류 밀도가 가장 낮은 지역에 두어 PIM(Passive Intermodulation) 레벨을 줄이기 위해서이다. 본 논문의 다이플렉서는 등가 모델을 사용하여 최적 설계를 수행함으로써 해석 시간을 줄이고자 하였다. 또한, 고전력 전송이 가능한 구조로 설계한 후 멀티팩션 해석을 수행하였으며, 해석 결과는 12 dB 마진을 확보하여 ESA/ESTEC 권고 사항을 만족함을 보였다. 제작된 다이플렉서는 전기적 성능 시험 결과를 통해 송수신 대역에서 반사 손실 22 dB 이상, 삽입 손실 0.20 dB 이하, 그리고 -40 dB 이하의 격리도 특성을 가져 요구 사항을 만족함을 보였고, 이로써 설계 결과가 검증되었다.

• 센서학회지
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• 제3권1호
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• pp.5-11
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• 1994

본 논문은 실리콘기판 직접접합기술과 에피택샬 성장법으로 각각 형성한 SOI구조, 즉 Si/$SiO_{2}$/Si 및 Si/$Al_{2}O_{3}$/Si 상에 제작한 압저항형 압력센서의 특성을 기술한다. SOI구조의 절연층을 압저항의 유전체 분리막으로 이용한 압력센서는 $300^{\circ}C$ 까지 사용 가능했다. SOI구조의 절연층을 박막 실리콘 다아어프램 형성시 에칭 중지막으로 이용한 경우, 제작된 압력센서의 200개 소자들에 대한 압력감도의 변화는 ${\pm}2.3%$ 이내로 제어 가능했다. 더구나 실리콘 기판 직접접합기술과 에피택샬 성장법의 결합으로 형성한 더불 SOI구조($Si/Al_{2}O_{3}/Si/SiO_{2}/Si$)상에 제작된 압력센서는 고온분위기에서 사용 가능할 뿐만 아니라 고분해 능력을 갖는 특성을 보였다.