임의의 입ㆍ출구 위치를 가지는 소음기 해석을 위한 개선된 모드일치법

김봉준,정의봉,이정환,Kim, Bong-Jun,Jeong, Ui-Bong,Lee, Jeong-Hwan 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.5

The acoustic property of reactive type single expansion chamber can be analyzed by traditional plane wave theory. This theory can be applied in low frequency range and has good performance. But this theory can't include higher order modes, therefore another method is essential to analyze acoustic filter in high frequency range. Many researcher suggested the method that can concern higher order modes, and their methods are using mode matching technique. But there is no method that can be applied to the analysis of single expansion chamber with arbitrary inlet/outlet duct position and numbers of higher order modes of inlet/outlet duct and middle chamber. In this paper, the method which can analyze single expansion chamber with arbitrary inlet/outlet duct position and numbers of higher order modes of inlet/outlet duct and middle chamber using fundamental mode matching technique, was suggested and the predictions by this method was compared with those by the finite element method, and the influence of inlet/outlet location to acoustic performance of single expansion chamber is investigated and explained by higher order mode effects.

정신분열증으로 진단 받았던 양극성장에 환자의 특성에 관한 연구

김봉준(Bong Jun Kim),송인권(In Kuan Song),장동원(Dong Won Chang) 한국정신병리진단분류학회 1996 精神病理學 Vol.5 No.1

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빔 공간 MIMO 통신시스템에서 고레벨 변조 설계와 평가

김봉준(Bong-Jun Kim),유홍균(Heung-Gyoon Ryu) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.5(통신이론)

ESPAR(Electronically Steerable Parasitic Array Radiator) 안테나는 기존의 다중 안테나 시스템이 가지는 다중RF-체인으로 인한 공간적인 제한과 에너지 효율의 문제를 극복하는 기술이다. 다중 안테나와 다중 RF-체인을 사용함으로써 발생하는 문제를 해결하기 위해 단일 RF 체인을 갖는 ESPAR 안테나를 사용하여 다수의 데이터를 동시에 전송할 수 있는 빔 공간 MIMO 시스템이 제안되었다. 기존 연구에서는 PSK 변조 계열에서의 빔 공간MIMO 시스템에 대해 제안되었다. 본 논문에서는 1개의 능동소자와 2개의 기생소자를 가지는 ESPAR 안테나를 사용하여 PSK 변조뿐만 아니라 QAM 변조에서도 빔 공간 MIMO 시스템이 가능하다는 것을 밝히기 위해 16,64-QAM 변조방식을 이용한 2x2 빔 공간 MIMO 시스템을 제안하고 성능을 평가하였다. ESPAR 안테나의 기생소자의 리액턴스를 조절하여 리액턴스 셋을 생성하여 QAM 계열의 심볼을 생성할 수 있다는 것을 확인하고 시뮬레이션을 통해 이를 전송하여 빔 공간 MIMO 시스템의 통신성능이 기존의 MIMO 시스템과 유사하게 되는 것을 확인하였다. ESPAR(Electronically Steerable Parasitic Array Radiator) antenna is the technique for overcoming the problems of space limitation and energy efficiency due to the multiple RF-chain. Conventional MIMO system with multiple antenna requires a large number of RF-chain for transmitting the multiple data because it transmits the data in proportion to the number of antenna. Beamspace MIMO system using the ESPAR antenna which has single RF-chain was proposed for solving the problems caused by using the multiple antenna and RF-chain. In this paper, therefore we propose 2x2 beamspace MIMO system using the 16, 64-QAM modulation and evaluate the performance of this system to reveal that it is possible that beamspace MIMO system can use not only PSK modulation but also QAM modulation. We confirm that QAM symbol can be generated by adjusting reactance of parasitic elements and making reactance set and also we confirm that performance of beamspace MIMO system is similar to the conventional MIMO system by transmitting the QAM symbol made by reactance set through the simulation.

철도 운행효율성 향상을 위한 노선용량 산정모형 개발에 관한 연구

김봉준(Kim, Bong-Jun),김시곤(Kim, Si-gon) 대한토목학회 2021 대한토목학회논문집 Vol.41 No.1

지나친 도시화로 인한 차량증가로 도시교통 문제가 사회문제로 인식되고 있고 이로 인해 효과적인 도로계획과 설계는 더욱 중요하게 되었다, 이에 따라 기존 도로를 확장하거나 새로운 도로를 건설할 때 도로의 교통량 산정에 필요한 기준과 방법을 도로용량편람으로 제정하여 운영하고 있다. 하지만 철도 노선에는 이러한 중요성에 불구하고 체계적인 교통량 산정기준이나 방법이 없었다. 따라서 본 연구에서는 철도의 경쟁력 강화를 위해 철도에도 노선용량이란 개념을 도입하여 명확한 철도 노선용량의 산정기준과 방법을 제시 하였다. 그 결과를 바탕으로 국내 철도의 주요 선구별 노선용량을 산정하였다, 이에 따라 본 연구에서 제시한 노선용량 산정방법을 적용하면, 기존의 철도 노선 및 새롭게 확대되는 신규 노선의 용량에 대한 적정한 투자와 설계가 계획단계에서부터 이루어 질 수 있도록 체계적인 기준을 제공할 수 있게 되었으며, 향후 철도 운행효율성 향상에도 도움을 줄 수 있을 것으로 기대한다. Over-urbanization has contributed to the increase in traffic problems. This makes the need for effective road planning and design more important than ever. I have been able to learn how to build a new road, and how to use it. However, in spite of the importance of good road planning, there are no systematic standards or methods for calculating traffic volume on railroad routes. Therefore, in this study, to strengthen the competitiveness of railroads, the concept of line capacity is introduced to railroads, and a clear standard and method for calculating railroad line capacity are presented. Based on the results, the line capacity of main railway lines for domestic railways was calculated. By applying the method of calculating the line capacity presented in this study, the capacity of existing railway lines and newly expanded routes can be calculated. It is expected that our findings will be able to provide systematic standards that can be applied to yield a more effective investment and design planning stage; the findings will also help improve the efficiency of railroad operation.

신개념 휴대용가스렌지 디자인개발 사례연구

김봉준(Bong-Jun Kim) 산업기술교육훈련학회 2016 산업기술연구논문지 (JITR) Vol.21 No.4

Gas range industries are influenced by the factors of climate, food style and accommodation style of each countries. In special, the demands and supplies of portable gas range is rapidly increased by the luxurious accommodation, single family and urban life style. In addition, the portable gas ranges used for everywhere is required by leisure based outdoor activities and trends in life style. By effect of this phenomenon, many a middle sized companies are focusing on the development for its application but the lack of new technologies and information on the new materials, it is not easy for them. And so in this research, production issues in the manufacturer of portable gas range and status analysis are reviewed and the newly developed concept of portable gas range design for high ends is suggested.

터보등화기를 이용한 디지털 역지향성 안테나 시스템의 성능 개선

김봉준(Bong-Jun Kim),유흥균(Heung-Gyoon Ryu) 대한전자공학회 2014 전자공학회논문지 Vol.51 No.1

디지털 역지향성 안테나 시스템은 사전정보 없이 입사된 신호를 신호의 위상을 추정하여 추정한 각도만큼 다시 돌려서 신호가 수신된 방향으로 재전송하는 시스템이다. 디지털 역지향성 안테나는 모든 방향에 대해 전력을 송출해야 하는 무지향성 안테나에 비해 신호가 수신된 방향으로 신호를 재전송하기 때문에 입사된 방향으로 신호가 집중되어 지향성이 높아지므로 전력의 소모를 줄일 수 있다. 일반적으로 디지털 역지향성 안테나는 다중경로 환경에서 단일 안테나 시스템에 비해 좋은 성능을 보이는 것으로 알려져 있지만, 심각한 ISI의 영향에서는 성능의 저하가 일어난다. 본 논문에서는 이러한 문제점을 극복하기 위해 심각한 ISI의 보상이 가능한 터보등화기를 결합하여 역지향성 안테나를 제안하였다. 제안하는 터보등화기를 이용한 디지털 역지향성 안테나를 통해 심각한 ISI 환경에서의 BER 성능을 개선하였다. A digital RDA(Retrodirective Antenna) system is a retransmit system that received signal without prior information turn back by estimated phase of the signal to received direction. The RDA can decrease consumption of power by increase of directivity because signal concentrates on received direction compare to omni-direction antenna which transmit power all direction. Generally, the RDA is known to show better performance than the single-antenna system in multi-path environment. However, the RDA occurs performance degradation in serious ISI channel. In this paper, to solve this problem, we propose retrodirective antenna combined with turbo equalizer combined which can compensate serious ISI channel, we increase the BER performance through proposed retrodirective antenna combined with turbo equalizer in serious ISI channel.

군날개절제술 전후의 각막 고위수차 비교

김봉준(Bong Jun Kim),김선웅(Sun Woong Kim) 대한안과학회 2017 대한안과학회지 Vol.58 No.9

Purpose: To investigate the types of corneal higher-order aberration (HOA) induced by pterygium, residual corneal HOA after pterygium surgery, and correlations between corneal HOA and the length of the pterygium. Methods: Fifty-three patients who underwent pterygium excision with conjunctival autograft were enrolled. Corneal HOA was measured by Pentacam ?? (Oculus Inc., Wetzlar, Germany) preoperatively and 3 months postoperatively in the 6-mm optical zone. Preoperative and postoperative HOAs of eyes with pterygium were compared with HOAs of the fellow eye to evaluate HOAs induced by pterygium and residual HOAs after pterygium surgery. Partial correlation analysis was performed to investigate the relationship between HOAs and the length of pterygium. A postoperative HOA less than 0.35 μm in size was defined as a favorable surgical outcome and the surgical indications were estimated using receiver operator characteristic (ROC) curve. Results: Horizontal coma, root mean square (RMS) of coma, oblique trefoil, horizontal trefoil, RMS of trefoil, and total HOA were significantly greater in the eye with preoperative pterygium. Three months after pterygium excision, only RMS of coma and total HOA remained significantly greater in eyes with pterygium. Vertical coma, horizontal coma, RMS of coma, and oblique tetrafoil were correlated with pterygium length. Pterygium excision when pterygium length was less than 1.6 mm led to favorable surgical outcomes. Conclusion: Pterygium induced greater than third-order corneal HOAs and these HOAs were corrected via pterygium surgery. Longer pterygium length was associated with larger RMS of coma and larger coma RMS persisted after pterygium surgery. A pterygium length of 1.6 mm should be considered the cutoff for pterygium excision for reducing postoperative corneal HOA. J Korean Ophthalmol Soc 2017;58(9):1023-1030

고차모드를 고려한 사각형 단순 확장관의 간편음향해석법의 개선

김봉준(Bong-Jun Kim),정의봉(Weui-Bong Jeong),황상문(Sang-Moon Hwang) 한국소음진동공학회 1999 소음 진동 Vol.9 No.2

과학빅데이터 처리를 위한 클라우드 시스템 구조에 대한 연구

김봉준(Kim Bong-Jun),김이강(Kim Yi-Kang),조충호(Cho Choong Ho) 한국통신학회 2015 한국통신학회 학술대회논문집 Vol.2015 No.1

개선된 모드적합법을 이용한 사각단순확장형 소음기의 음향해석

김봉준(Bong-Jun Kim),이정환(Jeong-Hwan Lee),정의봉(Weui-Bong Jeong) 한국소음진동공학회 1999 한국소음진동공학회 학술대회논문집 Vol.1999 No.11