CEO 9년 만에 사임 새 시대 여는 워싱턴포스트

윤홍우 한국언론진흥재단 미디어본부 2023 월간 신문과 방송 Vol.633 No.0

화이트칼라 노동조합원의 이중몰입에 관한 연구

윤홍우(Hong Woo Youn) 한국산학경영학회 1997 산학경영연구 Vol.10 No.-

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압전단결정을 이용한 소형 free-flooded ring 트랜스듀서의 성능 특성 예측 및 검증

임종범,윤홍우,권병진,김경섭,이정민,Im, Jongbeom,Yoon, Hongwoo,Kwon, Byungjin,Kim, Kyungseop,Lee, Jeongmin 한국음향학회 2022 韓國音響學會誌 Vol.41 No.3

In this study, a 33-mode Free-Flooded Ring (FFR) transducer was designed to apply piezoelectric single crystal PIN-PMN-PT, which has high piezoelectric constants and electromechanical coupling coefficient. To ensure low-frequency high transmitting sensitivity characteristics with a small size of FFR transducer, the commercial FFR transducer based on piezoelectric ceramics was compared. To develop the FFR transducer with broadband characteristics, a piezoelectric segmented ring structure inserted with inactive elements was applied. The oil-filled structure was applied to minimize the change of acoustic characteristics of the ring transducer. It was verified that the transmitting voltage response, underwater impedance, and beam pattern matched the finite element numerical simulation results well through an acoustic test. The difference in the transmitting voltage response between the measured and the simulated results is about 1.3 dB in cavity mode and about 0.3 dB in radial mode. The fabricated FFR transducer had a higher transmitting voltage response compared to the commercial transducer, but the diameter was reduced by about 17 %. From this study, it was confirmed that the feasibility of a single crystal-applied FFR transducer with compact size and high-power characteristics. The effectiveness of the performance prediction by simulation was also confirmed.

수치해석을 이용한 1-3 압전복합체 적용 판형 구조 수동센서의 음향특성 분석

오영식,박연수,윤홍우,이정현,권병진 한국소음진동공학회 2022 한국소음진동공학회 논문집 Vol.32 No.4

A hard baffle plate is typically chosen for a high receiving sensitivity gain effect of a plate structure passive sensor with 1-3 piezoelectric composites. However, the vibration modes of the baffle plate affect the response characteristics of the 1-3 piezoelectric composite. Therefore, analyzing the vibration modes of the baffle plate and designing it to not affect the reception characteristics of the sensor is important. In this paper, the acoustic characteristics of the plate structure passive sensor with a 1-3 piezoelectric composite are presented through numerical simulation. The frequency response characteristics, according to the width, thickness, and length of the baffle, were analyzed. In addition, the response characteristics in the baffle vibration mode through changes in the arrangement of the hydrophone were analyzed. Through the analyzed results, presenting a model with improved acoustic response characteristics compared to the existing model was possible.

압전 단결정을 이용한 고감도 광대역 링 트랜스듀서의수중 음향특성 분석

민승기,임종범,안병선,윤홍우,권병진,이정현 한국소음진동공학회 2022 한국소음진동공학회 논문집 Vol.32 No.4

In this study, the design and underwater acoustic characteristics of a ring transducer composed of a piezoelectric single crystal as the active material was reported. The PIN-PMN-PT piezoelectric single crystals with improved thermal durability have superior piezoelectric performance compared to PZT-4, widely used in underwater acoustic sensors. A 33-mode ring transducer was designed and its acoustic characteristics were estimated through electro-mechanical-acoustic coupled analysis. Furthermore, the acoustic characteristics of the ring transducers, composed of piezoelectric single crystals or PZT-4, were compared. The piezoelectric single crystals ring transducer is expected to have a higher transmitting voltage response (TVR) and receiving voltage sensitivity (RVS) compared to the PZT-4 ring transducer due to a high electro-mechanical coupling coefficient. It is also expected to have wideband performance due to a low mechanical quality factor. The acoustic characteristics of the fabricated piezoelectric single crystals ring transducer were measured and analyzed with the results of the electro-mechanical-acoustic coupled analysis. Upon applying piezoelectric single crystals as active materials, the ring transducer provided high sensitivity and broadband performance.

전자통신 시스템의 저소음 냉각 설계기술 개발

이정환(Jung-Hwan Lee),윤홍우(Hong-Woo Yoon),유성열(Seong-Ryoul Ryoo),김종만(Jong-Man Kim),전지환(Ji-Hwan Jun),김철주(Chul-Ju Kim),서명원(Myung-Won Suh) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

The purpose of this study is to investigate the cooling performance of heat sinks for telecommunication system by adequate natural convection. Heat generation rates of electronic components, temperature distributions of heat sinks and surrounding air are analyzed by experimental and numerical works. In order to perform the heat transfer analysis for the thermal design of telecommunication system, a program is developed. The program is capable of determining the arrangement of heat sources, interior fan capacity and configuration of the heat sink by graphic user interface environment. The simulation results indicate that a cooling capacity of up to 230W at a maximum temperature difference of 19℃ can be attainable. In order to verify the results from the numerical simulation, the experiment under the same condition is conducted, and their comparisons are made. Resulting, the design program can be a good tool to predict the effects of various parameters involved in the design of the heat sink for telecommunication system.

1-3형 압전복합재료 등가물성 직접 추출 기법의 정확도 분석

노응휘,김동현,문형민,장우석,윤홍우,표성훈,김경섭,조요한 한국음향학회 2023 韓國音響學會誌 Vol.42 No.5

본 논문에서는 1-3형 압전복합재료를 단일상의 균질 압전매질로 모델링하기 위해 필요한 등가의 물성을 유한요소 해석으로 직접 추출하는 기법의 정확도를 다룬다. 직접 추출 기법은 압전재료의 전기적, 기계적 거동과 상호 간커플링을 기술하는 구성방정식을 기반으로 물성 행렬의 개별 성분들을 직접적으로 산출하는 방법이다. 직접 추출에사용되는 두 가지 구성방정식 조합 간의 정확도를 비교하기 위하여 단일 1-3형 압전복합재료 하이드로폰을 대상으로등가물성과 수신감도를 산출하고 전체 영역에 대한 유한요소 해석 결과와 비교한다. 물성 추출의 정확도는 압전복합재료를 구성하는 폴리머의 탄성 특성과 밀접한 관련이 있음을 확인하고, 오차 원인을 분석하여 정확한 등가물성 산출을 위한 가이드라인을 제시한다. 압전복합재료 하이드로폰과 주변의 음향구조물을 포함하는 스테이브 규모에 대해서도 등가 모델링을 적용하여 추출된 물성의 정확도와 연산량 감소를 확인한다. This paper presents accuracy of a method that directly estimates equivalent properties of a 1-3 piezocomposite for modeling it into the single phase homogeneous piezomaterial. This direct estimation method finds individual components of a material property matrix based on the piezoelectric constitutive equations, which represent mechanical and electrical behaviors and their couplings. Equivalent properties on a single 1-3 piezocomposite hydrophone are derived, and their accuracy depending on pairing of the constitutive equations is investigated by comparing them with finite element analysis for the whole domain. The accuracy is related to elastic characteristics of a matrix polymer, and the error is analyzed so that some guidelines for correct estimation are suggested. Fidelity of estimated properties and equivalent modeling is shown in a stave scale including hydrophones and surrounding acoustic structures as well, and reduced computational cost is verified.

수중 음향 트랜스듀서의 임피던스 변화를 고려한 소나 송신기의 설계 및 출력 제어 기법

신창현,이윤호,안병선,윤홍우,권병진,김경섭,이정민 한국음향학회 2022 韓國音響學會誌 Vol.41 No.5

The active sonar transmission system consists of a transmitter that outputs an electrical signal and an underwater acoustic transducer that converts the amplified electrical signal into an acoustic signal. In general, the transmitter output characteristics are dependent on load impedance, and an underwater acoustic transducer, which is a transmitter load, has a characteristic that the electrical impedance varies largely according to frequency when driven. In such a variable impedance condition, the output of the active sonar transmission system may become unstable. Hence, this paper proposes a design and control technique of a sonar transmitter for transmitting a stable transmission signal even under variable impedance conditions of an underwater acoustic transducer in an active sonar transmission system. The electrical impedance characteristics of the underwater acoustic transducer are experimentally analyzed, and the sonar transmitter is composed of a single-phase full-bridge inverter, an LC filter, and a matching circuit. In this paper, the design and output control method of the sonar transmitter is proposed to protect the transmitter and transducer. It can secure stable output voltage characteristics even if it transmits the Linear Frequency Modulation (LFM) signal. The validity is verified through the simulation and the experiment. 능동 소나 송신시스템은 전기신호를 증폭하여 출력해주는 송신기와 증폭된 전기신호를 음향신호로 변환해주는 수중 음향 트랜스듀서로 구성된다. 일반적으로 송신기 출력 특성은 부하 임피던스에 의존적이며 송신기 부하인 수중 음향 트랜스듀서는 구동 시 전기적 임피던스가 주파수에 따라 크게 변화하는 특성을 갖는다. 이러한 가변 임피던스조건에서는 능동 소나 송신시스템의 출력이 불안정해질 수 있다. 이에 본 논문에서는 능동 소나 송신시스템에서 수중음향 트랜스듀서의 가변 임피던스 조건에서도 안정적인 송신 신호를 전송하기 위한 소나 송신기의 설계 및 제어 기법을 제안하였다. 수중 음향 트랜스듀서의 전기적 임피던스 특성은 실험적 방법으로 분석하였고, 소나 송신기는 단상 풀브릿지 인버터, LC 필터와 정합회로로 구성하였다. 실시간으로 부하 특성이 변하는 Linear Frequency Modulation (LFM) 신호를 송신하면서 송신기와 트랜스듀서를 보호하고 안정적으로 출력 전압 특성을 확보할 수 있는 소나 송신기의 설계 및 출력 제어 기법을 제안하였으며, 시뮬레이션과 실험을 통해 타당성을 검증하였다.

주파수 응답을 이용한 하이드로폰 수신감도의 비상관 잡음 저감

정인지(In-Jee Jung),조진석(Jin-Suk Cho),윤홍우(Hong-Woo Yoon),이학수(Hak-Su Lee),조완호(Wan-Ho Cho) 한국소음진동공학회 2017 한국소음진동공학회 논문집 Vol.27 No.7

Evaluation of the receiving voltage sensitivity (RVS) of a hydrophone by using frequency response is investigated for suppressing the RVS estimation error due to the un-correlated noise with transmit and receiving signals. The experiment to estimate the RVS of a hydrophone in a water tank is conducted with a reference projector in the frequency band of 250 to 1000 ㎐, and the experimental result using frequency response and the conventional method with root mean square (RMS) of the time domain signal are compared. The result with RMS method shows the RVS error occurs in the low frequency range due to the un-correlated noise. However, the result with frequency response shows the RVS error in the low frequency range can be reduced by suppressing the un-correlated noise, so that the flat RVS within 1 dB can be obtained in the measured frequency band.

고장물리 기반 수중 매설형 PBA에 대한 신뢰성 설계 연구

김지영(Ji-Young Kim),이기원(Ki-Won Lee),윤홍우(Hong-Woo Yoon),이승진(Seung-Jin Lee),허준기(Jun-Ki Heo),권형안(Hyeong-Ahn Kwon) 한국신뢰성학회 2017 신뢰성응용연구 Vol.17 No.4

Purpose: PBA buried in underwater requires high reliability because of its mission critical characteristic and harsh operational environment during its life cycle. Therefore, various reliability improvement activities are necessary. The defect on PBA manufacturing process have been studied, as a result, many activities and standards have been presented. However, there are less studies regarding failure pattern on physical features based on design. In this paper, we studied a possible failure patten based on physical features that is related with manufacturing process of PBA. And reliability improvement design based on PoF (Physical of Failure) were intruduced in this paper . Methods: A reliability prediction simulation were performed on the components A and B of the H system using Sherlock Software which is a PoF commercial tool from DFR solution. Solder fatigue and PTH fatigue analysis based on thermal cycling profiles and random vibration was analyzed on three earthquake response spectrum. Result: It was validated that life time and reliability improvement design through solder fatigue and PTH fatigue analysis in case of component. For compoenet B, random vibration fatigue was additionally analyzed and validated reliability for earthquakes profile. Conclusion: In design stage prior to manufacturing, PoF can be analyzed, and it is possible to make a reliability improvement/validated design using design data. This study can be applied in every design step and contribute to make more stable development product.