• 한국자기학회지
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• 제14권5호
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• pp.174-179
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• 2004

고주파 회로에서 발생하는 전도 노이즈의 흡수율을 측정하는 방안의 하나로 50 $\Omega$ 특성 임피던스의 마이크로스트립 선로를 제작하고, 순철 압분체로 구성되는 자기손실재의 전력 흡수율 측정을 통하여 측정 및 해석 방법의 타당성을 제시하였다 제작된 마이크로스트립 선로는 S$_{11}$ < -60 dB, S$_{21}$=0 dB의 반사/투과 특성을 보여 전도 노이즈 흡수율 측정에 이상적인 전송특성을 보였다. Attrition milling에 의해 순철 압분체를 제작하고, 이를 고무와 혼합하여 두께 1mm정도의 복합재 sheet를 제작하였다. 이 재료를 마이크로스트립 선로에 장착한 결과 2～8 GHz대역에서 전력흡수율이 80% 이상인 대역저지 필터와 유사한 특성을 얻을 수 있었다. 주파수, 흡수 sheet 크기에 따른 노이즈 흡수율에 관한 분석을 통하여, 노이즈 흡수율에 주된 영향을 주는 인자는 자기손실임을 제안하였다.

• 한국자기학회지
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• 제17권6호
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• pp.242-245
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• 2007

전자기적 해석 시뮬레이션 프로그램인 유한요소 방식의 HFSS(High Frequency Structure Simulation)를 사용하여, 전도 노이즈 흡수 sheet의 흡수특성을 해석하고 그 결과 값을 실측값과 비교함으로써 해석방법의 타당성을 검토하였다. 마이크로스트립 선로는 $S_{11}\simeq-30dB,\;S_{21}=0dB$의 반사투과 특성을 보여 전도 노이즈 흡수율 측정에 이상적인 전송특성을 보였다. 순철 압분체-고무 복합체 sheet의 복소비투자율과 복소비유전율을 입력하여 노이즈 흡수율을 계산한 결과 실측치와 비교적 잘 일치하는 해석결과를 얻었다. 주파수, 흡수계의 크기(특히 선로를 덮는 길이)에 따라 노이즈 흡수율은 현저한 변화를 보였으며, 이는 재료의 손실 특성과 밀접히 연관되어 있음을 제시하였다. 이러한 해석방법은 다양한 조성 및 크기의 전도 노이즈 흡수체의 설계에 유용히 사용될 수 있음을 제안할 수 있다.

• 전력전자학회논문지
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• 제27권2호
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• pp.85-91
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• 2022

This study proposes a high efficiency bridgeless Power Factor Correction (PFC) converter with improved common mode noise characteristics. Conventional PFC has limitations due to low efficiency and enlarged heat sink from considerable conduction loss of bridge diode. By applying a Common Mode (CM) coupled inductor, the proposed bridgeless PFC converter generates less conduction loss as only a small magnetizing current of the CM coupled inductor flows through the input diode, thereby reducing or removing heat sink. The input diode is alternately conducted every half cycle of 60 Hz AC input voltage while a negative node of AC input voltage is always connected to the ground, thus improving common mode noise characteristics. With the aim to improve switching loss and reverse recovery of output diode, the proposed circuit employs Critical Conduction Mode (CrM) operation and it features a simple Zero Current Detection (ZCD) circuit for the CrM. In addition, the input current sensing is possible with the shunt resistor instead of the expensive current sensor. Experimental results through 480 W prototype are presented to verify the validity of the proposed circuit.

• 한국음향학회지
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• 제32권5호
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• pp.423-429
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• 2013

본 논문은 소음 속에서 다양한 청력보호구 착용 시 청자의 두개골 위에 골진동체 자극을 이용하여 가장 민감한 어음인지 부위를 찾고자 하였다. 20명의 정상청력의 남성과 여성(각 10명)에게 강강격의 이음절어를 사용하여 네 종류의 청력보호구 (이어폼, 이어플러그, 이어머프, 이어폼과 머프 동시 착용)와 다섯 군데의 골진동체 위치 (하악골각, 관절구, 관자놀이, 유양돌기, 정수리)를 네가지의 소음 방향(0, 90, 180, 270도)에 따라 어음인지역치검사를 시행하였다. 연구 결과는 다음과 같다. 1) 골진동체의 위치 중 관절구가 가장 역치가 낮았으며, 2) 청력보호구 종류는 이어폼과 머프를 동시에 착용(이중 보호) 하였을 때 가장 역치가 낮았다. 3) 소음 방향에 따라서는 90도에서 소음이 제시되었을 때 가장 낮은 역치를 나타냈으나, 4) 실험 대상자의 성별에 따라서는 유의미한 차이가 없었다. 따라서 소음성난청을 예방하며 소음 속에서 원활한 의사소통을 위해서는 이중보호 청력보호구 착용 하에서 관절구를 통한 언어전달이 가장 효율적이다.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.1064-1069
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• 1994

In order to realize the function of human interface of telecommunications whose objective is to interchange useful information among persons, we developed a bone conduction telephone with which hearing impaired persons with conductive or noise-induced hearing loss and presbycusis can communicate with each other without any other additional devices such as hearing aids. The bone conduction telephone we developed has chatacteristics as follows : (i) a hearing impaired person and a normal hearing person can communicate by bone and air conduction hearings, respectively, using only this telephone set because, as its receiver, it uses a bone conduction vibrator with which we can realize such function with the voice coil and damper of a small speaker unit, the vibrating plate, etc., (ii) it has tone control function compensating hearing losses of hearing impaired persons according to their hearing loss/frequency chatacteristics. Using the tone control function together with a received volume control, it has the received volume range of 20dB in loudness rating; and (iii) it has the function of three emergency calls and a bell lamp as the visual display of a received call.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.794-796
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• 1993

This paper deals with the characteristic analysis of noise filter for the reduction of conduction noise, especially, common-mode noise. Attenuation in the system containing noise filter is analyzed and equivalent circuits for common- and differential- mode noise are derived. To clarify the effects by parasitic components of the inductor and capacitor, digital simulations using Design Center are carried out.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.613-617
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• 2008

One of the important parts on multimedia era is acoustic ones. With increased demand of smallest multimedia products such as personal digital assistant (PDA) and mobile phones, it is necessary to develop acoustic devices which have higher performance and smaller size. Acoustic parts with various function for hearing impaired persons. This paper introduces a bone conduction vibrator (BCV) for hearing impaired persons to use portable acoustic device without additional devices. For vibration analysis of the BCV, electromagnetic, mechanical and their coupling effects are considered for the analysis. This paper shows that the development of design and analysis technique by finite element method (FEM) of BCV.

• 비파괴검사학회지
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• 제31권6호
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• pp.665-670
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• 2011

In this paper, a new approach to detect surface cracks from a noisy thermal image in the infrared thermography is presented using an holomorphic characteristic of temperature field in a thin plate under steady-state thermal condition. The holomorphic function for 2-D heat flow field in the plate was derived from Cauchy Riemann conditions to define a contour integral that varies according to the existence and strength of a singularity in the domain of integration. The contour integral at each point of thermal image eliminated the temperature variation due to heat conduction and suppressed the noise, so that its image emphasized and highlighted the singularity such as crack. This feature of holomorphic function was also investigated numerically using a simple thermal field in the thin plate satisfying the Laplace equation. The simulation results showed that the integral image selected and detected the crack embedded artificially in the plate very well in a noisy environment.

• Journal of Power Electronics
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• 제19권1호
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• pp.296-306
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• 2019

The flyback topology is being widely used in power adapters. The coupling capacitance between primary and secondary windings of a flyback transformer is the main path for common-mode (CM) noise conduction. A Y-cap is usually used to effectively suppress EMI noise. However, this results in problems in space, cost, and the danger of safety leakage current. In this paper, the CM noise behaviors due to the electric field coupling of the transformer windings in a flyback adapter with synchronous rectification are analyzed. Then a scheme with balance winding is proposed to reduce the CM noise with a transformer winding design that eliminates the Y-cap. The planar transformer has advantages in terms of its low profile, good heat dissipation and good stray parameter consistency. Based on the proposed scheme, with the help of a full-wave simulation tool, the key parameter influences of the transformer PCB winding design on CM noise are further analyzed. Finally, a PCB transformer for an 18W adapter is designed and tested to verify the effectiveness of the balance winding scheme.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.288-288
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• 2009

Most of Static electricity forms part of our daily experience broadly. Most people have noticed from time to time electric shocks when closing of their car or after walking across a carpet, operating shredder in winter and touching a metal handle. This electrostatic discharge nuisance is normally a minor inconvenience, but in some cases static electricity can cause more serious problems. Static electricity can also be harnessed to good effect in Position Control System.