다중 대역 전송 시스템을 위한 전치왜곡 알고리즘

최성호,이병환,이철수,정의림,Choi, Sung-Ho,Lee, Byung-Hwan,Lee, Chul-Soo,Jeong, Eui-Rim 한국정보통신학회 2012 한국정보통신학회논문지 Vol.16 No.1

본 논문에서는 다중 대역 전송 시스템에서 광대역 전력 증폭기의 선형화를 위한 새로운 전치왜곡 기법을 제안한다. 특히, 한 시스템에서 동시에 다중대역/다중모드 신호를 전송함에 있어 다중대역 신호가 하나의 전력 증폭기에 의해 증폭되어 전송되는 시스템을 고려한다. 상호 대역 간 비선형 왜곡을 포함한 비선형 특성을 보상하기 위하여, 본 논문에서는 다중 전치왜곡기 블록을 갖는 새로운 전치왜곡 구조를 제안하며, 다중 전치왜곡기의 계수를 동시에 갱신하는 적응 알고리즘을 제안한다. 제안하는 다중 대역 모델을 검증하기 위하여 상용 증폭기를 사용하여 증폭기 모델을 추출하였으며, 추출된 모델을 기반으로 제안한 알고리즘을 모의실험을 통해 검증하였다. 모의실험 결과는 제안 알고리즘이 효과적으로 다중 전치왜곡기의 계수를 구할 수 있으며, 다중 대역을 효과적으로 선형화 할 수 있음을 보여준다. New digital predistortion technique is proposed for power amplifier linearization in multi-band transmission systems. We consider a system where muli-band signals are combined and amplified by a single power amplifier (PA). In this system, the PA output is distorted by the nonlinear cross-products between different band signals as well as their own nonlinear self-products. To compensate these nonlinear effects, we propose a multiple PD structure. Each PD removes the nonlinear cross-products and self-products to mitigate the spectral regrowth for the corresponding band. Since the PD parameters for different bands are linked together, it is difficult to find the PD parameters separately. Thus, we propose an iterative method for finding the PD parameters jointly. For demonstration of the proposed method, multi-band characteristics of PA are extracted from a commercial power amplifier. Computer simulation was executed based on the PA parameters. The simulation results show that the proposed method can effectively linearize the PA and remove spectral regrowth at each signal band.

반복적인 펄스레이저 조사에 의한 알루미늄 합금의 표면상태 변화분석

최성호,김정석,장경영,신완순,Choi, Sung-Ho,Kim, Chung-Seok,Jhang, Kyung-Young,Shin, Wan-Soon 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.5

The objective of this study is to investigate the thermal behavior on material surface and the variation in the surface morphology of aluminum 6061 alloy by the Nd:YAG pulsed-laser irradiation. First, we predicted the surface temperature variation during pulsed-laser irradiation by using the two dimensional finite element analysis. When the pulsed-laser of 133 mJ energy and 5 ns pulse duration is irradiated on the surface of aluminum alloy, the material surface is thought to be melting because the surface temperature rises steadily up to about $660^{\circ}C$ exceeding the melting point. Also, the experimental results show that the solidification microstructure has been developed clearly after surface melting. Second, the diameter of melted zone was analysed by finite element analysis and measured by OM(Optical Microscopy). It increased logarithmically with increase in the number of laser irradiation. In addition, AFM(Atomic Force Microscopy) measurement showed an increase in the average surface roughness during pulsed-laser irradiation.

회원작품 - 담담헌(淡淡軒)

최성호,Choi, Sungho 대한건축사협회 2020 建築士 Vol.615 No.-

회원작품 - 화가당

최성호,Choi, Sungho 대한건축사협회 2022 建築士 Vol.639 No.-

성견 열개형 결손부에 DFDB이식과 Dura Mater막의 효과

최성호,김일영,김영희,서종진,정현철,조규성,채중규,Choi, Seong-Ho,Kim, Il-Young,Kim, Young-Hee,Suh, Jong-Jin,Jung, Hyun-Chul,Cho, Kyoo-Sung,Chai, Jung-Kiu 대한치주과학회 1998 Journal of Periodontal & Implant Science Vol.28 No.2

The present study invetigates the effects of root planing only(control group), DFDBA alone(test group 1) and combined use of DFDB and Dura mater(test group 2) in dehiscence defects in dogs. The results of 8weeks post-surgery by histological comparison between the three groups are as follows. 1. The contol group showed minimum regeneration of new cementum and new bone with limited migration of epitheilal cells, and healed by connective tissue attachment. 2. The test group 1 showed minimum regeneration of new cementum and new bone with limited migration of epitheilal cells, and healed by connective tissue attachment. 3. The test group 2 showed significant amount of the new cementum and new bone. 4. Both control and test groups healed without any observable root resorption and ankylosis. The above the results suggest that the use of resorbable Dura mater only does not improve the regeneration of new bone and periodontal ligament due to difficulties of space making, but the combined use with DFDB may be more effective.

가변 스펙트럼 할당을 지원하는 광대역 전력 증폭기를 위한 디지털 전치왜곡기

최성호,서성원,마백일,정의림,Choi, Sung-Ho,Seo, Sung-Won,Mah, Bak-Il,Jeong, Eui-Rim 한국정보통신학회 2011 한국정보통신학회논문지 Vol.15 No.2

인지통신(cognitive radio)과 같이 가변 스펙트럼 할당이 필요한 시스템을 위한 새로운 전치왜곡기를 제안한다. 본 논문에서 고려하는 시스템 모델에서 신호는 한 순간에는 작은 대역폭을 차지하지만 그 중심 주파수가 시간에 따라 변화할 수 있는 상황을 가정한다. 이러한 시나리오에서는 전력 증폭기 출력 단에 위치하는 종단 필터로는 전력증폭기에 의한 하모닉을 제거하지 못하는 상황이 발생할 수 있다. 제안된 전치왜곡기는 기본 주파수 (${\omega}_0$) 신호의 비선형 왜곡을 선형화할 뿐만 아니라, $2{\omega}_0$, $3{\omega}_0$, ...에서 발생하는 하모닉도 동시에 제거한다. 제안된 전치왜곡기는 ${\omega}_0$ 주파수의 정수배에 대응하는 여러 개의 전치왜곡기가 결합된 구조를 가지고 있다. 기본 주파수 ${\omega}_0$에 해당하는 전치왜곡기는 기본 주파수 신호의 선형화를 담당하며, 나머지 주파수에 대응하는 전치왜곡기는 하모닉을 제거하는 역할을 담당한다. 제안된 전치왜곡기에서 필요한 변수는 최소 평균 자승 에러 알고리즘에 의해 동시에 계산되며, 모의실험 결과에 따르면 제안된 방법을 이용하면 기본 주파수의 스펙트럼에 발생하는 스펙트럼 왜곡이 20dB 감소하며, 2차 및 3차 하모닉도 기본 신호의 전력대비 약 -70dB로 작아지는 것을 확인할 수 있다. A new predistortion technique for dynamic spectrum allocation systems such as cognitive radio (CR) is proposed. The system model considered in this paper occupies a small band at a time, but the center frequency can be changed in the wide range of frequency. In this scenario. the front-end filter may not eliminate the harmonics of the power amplifier (PA) output. The proposed PD reduces the spectral regrowth of the fundamental signal at the carrier frequency (${\omega}_0$) and removes the harmonics ($2{\omega}_0$, $3{\omega}_0$, ...) at the same time. The proposed PD structure is composed of multiple predistorters (PDs) centered at integer multiples of ${\omega}_0$. The PD at ${\omega}_0$ is for removing spectral regrowth of the fundamental signal, and the others are for harmonic reduction. In the proposed PD structure, parameters of PDs are found jointly. Simulation results show that the spectral regrowth can be reduced by 20dB, and the 2nd and 3rd harmonics can be reduced down to -70dB from the power of the fundamental signal.

초극소저출생체중아와 극소저출생체중아의 미숙아망막병증 발생 빈도와 위험 인자에 관한 연구

최성호,함돈일.Sung Ho Choi. M.D.. Don Il Ham. M.D. 대한안과학회 2006 대한안과학회지 Vol.47 No.6

Purpose: To evaluate the risk factors and prevalence of retinopathy of prematurity (ROP) in extremely low birth weight (ELBW) infants and very low birth weight (VLBW) infants. Methods: All babies were screened for ROP at a postconceptional age of 31 weeks or at 4 weeks of chronological age. We divided the infants into two groups according to birth weight < 1000 g (ELBW) and 1000~1500 g (VLBW), to compare the incidence of ROP and photocoagulation, and to retrospectively evaluate the risk factors. Results: Three hundred eight consecutive infants were included in the data analysis. The incidences of ROP were 70.5% (79/112) in ELBW infants and 36.7% (72/196) in VLBW infants (p<0.0001). 31 of 79 ELBW infants (39.2%) and 17 of 72 VLBW infants (23.6%) had undergone photocoagulation (p<0.0001). Among the various risk factors, mechanical ventilat6ion (p=0.039) and surfactant (p<0.000) were the independent risk factors associated with ROP in all infant groups by logistic regression analysis. In the ELBW group, however, surfactant injection was the only factor independently associated with ROP (p=0.008). The use of surfactant, the only risk factor in ELBW infants, was attributed with the initiation of ROP. However, it did not act as an aggravating factor. Conclusions: ELBW was associated with a higher incidence of ROP and laser photocoagulation. The results of this study emphasize that more special attention is needed for immature infants when ventilators and surfactants are used.

수종의 조직 양화재에서 탄성 변형과 복원에 관한 연구

최성호,심준성,문홍석,정문규,Choi Sung-Ho,Shim June-Sung,Moon Hong-Seok,Chung Moon-Kyu 대한치과보철학회 2003 대한치과보철학회지 Vol.41 No.1

The dimensional stability of tissue conditioners characterizes the ability of the materials to yield accurate functional impressions of oral mucosa. This study evaluated the viscoelastic property and the linear dimensional changes with the factor of time and thickness of tissue conditioners ($COE-COMFORT^{TM}$, Visco-gel. $COE-SOFT^{TM}$, Soft-Liner). The thickness of these materials were changed (1.5mm, 3.0mm) and the percentage changes in dimension were measured at 1h, 12h, 24h, 36h, 3day, 7day after specimen preparation. From the results large differences appear between the various tissue conditioners. The results suggest that the period recommended for forming functional impression would be 2-3days after insertion in the mouth. in addition. it is important to select tissue conditioners suitable for functional impression because of the wide range of dimensional stability among the materials.

증강현실을 활용한 홈 트레이닝에서 가상 참여자의 영향: 몰입, 인지된 경쟁, 그리고 정보 습득의 욕구를 중심으로

최성호,이원욱,김현주,원종서,이지항,이연주,김진우,Choi, Sungho,Lee, Wonouk,Kim, Hyunju,Won, Jongseo,Lee, Jeehang,Lee, Yeonjoo,Kim, Jinwoo 한국감성과학회 2017 감성과학 Vol.20 No.3

본 연구는 증강현실 홈 트레이닝 시스템을 통해 가상 참여자의 존자개 사용자에게 미치는 영향을 살펴보고자 한다. 구체적으로, 가상의 참여자가 제공되는 경우와 아닌 경우의 몰입, 인지된 경쟁, 그리고 정보 습득의 욕구의 차이에 대해 살펴보았다. 자동으로 실험 참여자들의 자세에 따른 정확도와 피드백을 제공하는 홈 트레이닝 시스템을 직접 개발하였고, 이를 활용하여 다음의 세 가지 가설을 실증하였다. 첫째, 가상의 참여자를 보며 트레이닝 시스템을 사용하면 그렇지 않은 경우보다 몰입이 더욱 높을 것이다. 둘째, 가상의 참여자를 보며 트레이닝 시스템을 사용하면 그렇지 않은 경우보다 인지된 경쟁이 더욱 높을 것이다. 셋째, 가상의 참여자를 보며 트레이닝 시스템을 사용하면 그렇지 않은 경우보다 정보 습득의 욕구가 더욱 높을 것이다. 실험을 통해 세 가지 가설이 모두 지지되었으며, 가상의 참여자가 이용자에 영향을 미침을 확인할 수 있었다. 기존 연구가 가상 트레이닝 시스템 그 자체에 대한 효과를 보는 것에 반해, 본 연구가 가상 트레이닝 시스템을 이용할 때 다른 운동 참여자가 나오는 영상을 보는 것이 유의한가에 대한 답을 하고 있다는 점에서 시사점을 제공한다. The purpose of the study is discovering the effects of virtual competitors on user in AR (Augment Reality) home training system. Specifically, the current research examined their effects on immersion, perceived competition, and leaning motivation. The paper tested three unexplored relationship. First, introducing virtual competitors in home training system will enhance user's immersion. Second, presenting virtual competitors in home training system will increase user's perceived competition. Third, virtual competitors in home training system will raise user's learning motivation. For empirical analysis, we developed home training system, which could check and give feedback automatically, based on user's posture. Using this AR home training system, the study empirically shows how and why virtual competitors affect users. The results give implications not only on service design; but also on the idea that virtual other could affect user's behavior.

디지털 데이터 가치의 정량적 측정에 대한 개념적 연구

최성호,이상곤,Choi, Sung Ho,Lee, Sang Kon 한국IT서비스학회 2022 한국IT서비스학회지 Vol.21 No.5

With the rapid development of computer technology and communication networks in modern society, human economic activities in the almost every field of our society depend on various electronic devices. The huge amount of digital data generated in these circumstances is refined by technologies such as artificial intelligence and big data, and its value has become larger and larger. However, until now, it is the reality that the digital data has not been clearly defined as an economic asset, and the institutional criteria for expressing its value are unclear. Therefore, this study organizes the definition and characteristics of digital data, and examines the matters to be considered when considering digital data in terms of accounting assets. In addition, a method that can objectively measure the value of digital data was presented as a quantitative calculation model considering the time value of profits and costs.