Doherty증폭기를 이용한 Feedforward전력 증폭기의 효율 개선에 관한 연구

이택호,정성찬,박천석,Lee Taek-Ho,Jung Sung-Chan,Park Cheon-Seok 한국전자파학회 2005 한국전자파학회논문지 Vol.16 No.11

본 논문은 피드포워드 전력 증폭기의 효율 개선을 위한 도허티 증폭기의 적용에 관한 연구이다. 성능 분석을 위하여 중심 주파수 2.14 GHz의 WCDMA 4FA신호를 인가하여 평균 출력 전력 15 W에서 측정하였다. 적용한 도허티 증폭기는 동급 class AB 증폭기와 비교하여 고효율 저선형성의 특성을 나타내며 효율 개선을 위하여 피드포워드 전력 증폭기(FPA)의 주 증폭기로 사용되었다. 특성 변화를 분석하기 위해 선형성과 효율 특성이 다른 2가지 종류의 도허티 증폭기를 적용하였으며 각각의 FPA들은 평균 출력 15 W에서 효율은 $2\%$ 이상의 개선을 보였지만 선형성은 1.5 dBc 이상 저하되는 특성을 나타냈다. 저하된 선형성을 개선하기 위하여 부가적으로 오차 루프의 결합 계수(CF)와 오차 증폭기의 용량을 변화시켰다. CF와 오차 증폭기의 용량 변화로 효율 개선과 높은 선형성을 얻을 수 있었고 도허티 증폭기가 35 dBc 이상의 선형성을 유지하면 부가적인 변화 없이 평균 출력 전력 15 W에서 $2\%$ 이상의 효율 개선과 충분한 선형성을 얻을 수 있다. This paper reports an application of Doherty amplifier for efficiency improvement of feedforward power amplifier(FPA). For performance analysis, we measured 15 W average output power using WCDMA 4FA input signal with a center frequency 2.14 GHz. The applied Doherty amplifier presents the characteristics of high efficiency and low linearity in comparison to the class AB amplifier, and it was used as main amplifier of FPA fir efficiency improvement. To analyze the change of characteristic, tow Doherty amplifiers whose linearity and efficiency are different were applied. The applied FPAs are improved about $2\%$ or more performance in efficiency, but decreased in linearity on 15 W average output power. We additionally modified the coupling factor(CF) of the error loop and the error amplifier capacity for linearity improvement. Aa a result, the efficiency improvement and high linearity resulted from the change of CF and error amplifier capacity. However, we think if the linearity of Doherty amplifier were more than 35 dBc, the FPA would improve the performance about $2\%$ or more efficiency and maintain enough linearity.

전력증폭기의 효율 개선을 위한 도허티증폭기의 특성분석

이택호(Taek Ho Lee),정성찬(Sung Chan Jung),박천석(Cheon Seok Park) 한국정보통신설비학회 2004 한국정보통신설비학회 학술대회 Vol.2004 No.1

Prediction of diabetes occurrence using variable selection and classification methods

Taek-Ho Lee(이택호),Chi-Hyuck Jun(전치혁) 한국경영과학회 2016 한국경영과학회 학술대회논문집 Vol.2016 No.4

Diabetes is one of the major chronic diseases. The death rate from diabetes is more and more increasing, so causing the financial burdens of the nation to increase. Because chronic diseases, if occur, require continuous management and they are hard to be completely cured, it is important to predict its occurrence in advance. Our goal is to make diabetes risk prediction model based on machine learning techniques using database established by Korean National Health Insurance Corporation. The procedure to build the prediction model consists of two phases, i.e., ‘variable selection’ to find significant factors of diabetes and ‘learning classifier’ to learn a statistical risk prediction model. For the former, we apply correlationbased feature selection, minimum redundancy maximum relevance, classification and regression tree (CART) variable importance, and support vector machine (SVM)-recursive feature elimination. On the other hand, we apply logistic regression, linear discriminant analysis, CART, naïve Bayes (NB), and SVM for the latter. For the purpose of comparison, we conducted numerical experiments for the combinations of each variable selection method and classifier. As a result, the variable selection methods give somewhat consistent results. In the result of performance comparison, no significant difference has been observed among 5 classifiers except NB which showed poor performance.

메탈메쉬 터치스크린 제품의 품질보증시스템 인증을 위한 중소기업 대응방안 연구

이택호 ( Taek-ho Lee ),홍성훈 ( Sung-hoon Hong ),권혁무 ( Hyuck-moo Kwon ),이민구 ( Min-koo Lee ) 대한설비관리학회 2016 대한설비관리학회지 Vol.21 No.3

The purpose of this study is to investigate and systemize the evaluation items and criteria in terms of the product development, the quality, the reliability and the process management of global set makers in order to assure the quality and reliability of the Metal Mesh Touch Screen that PET(polyethylene terephthalate) films are applied. This study also suggests the countermeasures for small and medium enterprises to obtain the certification of the quality assurance system by identifying the quality evaluation items from the stage of product development of global set makers to their production. H company of the U.S, F company of Japan, and S company of South Korea are chosen as representatives.

Prediction of diabetes occurrence using variable selection and classification methods

Taek-Ho Lee(이택호),Chi-Hyuck Jun(전치혁) 대한산업공학회 2016 대한산업공학회 춘계학술대회논문집 Vol.2016 No.4

Diabetes is one of the major chronic diseases. The death rate from diabetes is more and more increasing, so causing the financial burdens of the nation to increase. Because chronic diseases, if occur, require continuous management and they are hard to be completely cured, it is important to predict its occurrence in advance. Our goal is to make diabetes risk prediction model based on machine learning techniques using database established by Korean National Health Insurance Corporation. The procedure to build the prediction model consists of two phases, i.e., ‘variable selection’ to find significant factors of diabetes and ‘learning classifier’ to learn a statistical risk prediction model. For the former, we apply correlationbased feature selection, minimum redundancy maximum relevance, classification and regression tree (CART) variable importance, and support vector machine (SVM)-recursive feature elimination. On the other hand, we apply logistic regression, linear discriminant analysis, CART, naïve Bayes (NB), and SVM for the latter. For the purpose of comparison, we conducted numerical experiments for the combinations of each variable selection method and classifier. As a result, the variable selection methods give somewhat consistent results. In the result of performance comparison, no significant difference has been observed among 5 classifiers except NB which showed poor performance.

청소년의 폭력비행 피해가 사이버 비행에 미치는 영향

이석영(Seok Young Lee),이택호(Taek Ho Lee),한윤선(Yoon Sun Han) 한국아동복지학회 2015 한국아동복지학 Vol.- No.50

선행연구에서는 폭력비행 피해를 받은 청소년이 가해자로 변할 수 있음을 시사한다. 그러나 오프라인 상의 청소년 피해경험이 사이버 비행에 영향을 주는지, 그리고 어떠한 경로로 영향을 주는지에 대해 구체적으로 밝혀진바가 없다. 따라서, 본 연구는 청소년의 폭력비행 피해가 사이버 비행 가해에 영향을 미치는지, 영향을 미친다면 그 경로에 공격성, 우울, 사회적 위축이 매개효과를 나타내는지 살펴보았다. 본 연구를 위해 한국청소년정책연구원(NYPI)에서 실시하는 한국아동·청소년 패널조사(KCYPS)의 중학교 1학년패널 2차년도(2011) 데이터(N =2,054)를 활용하였으며, 경로분석과 Sobel 검정등을 통해 통계분석을 실시하였다. 연구결과는 다음과 같다. 첫째, 학교 폭력비행 피해는 청소년의 사이버 비행 가해 행동에 영향을 준다. 둘째, 학교폭력 피해 경험이 사이버 비행에 미치는 영향에 있어 사회적 위축을 제외한 공격성, 우울이 모두 부분 매개하는 것으로 나타났다. 오프라인에서의 피해가 온라인상에서 가해로 이어질 가능성은 접근의 용이성과 익명성이라는 온라인 공간의 특성으로 설명할 수 있을 것이다. 그리고 본 연구의 결론에서 폭력비행 피해가 사이버 비행으로 이행되는 경로를 밝히고, 사이버 비행을 예방하기 위한 방안을 제안하였다. Literature suggests that youth victims of violence may subsequently develop into offenders. However, the exact mechanisms through which the victimization of youth offline affects their engaging in delinquent behavior online are relatively unknown. Thus, this study examined the relationship between violence victimization and cyber delinquency, investigated the mediating role of aggression, depression, and social withdrawal in this relationship. Data were obtained from the second wave of the middle school student cohort (N =2,054) of the Korean Children-Youth Panel Survey (KCYPS). Main analyses involved simple regression analysis, multivariate regression using path analysis and the Sobel test. The major findings are as follows: First, violence victimization was found to have a positive association with cyber delinquency. Second, the relationship between violence victimization and cyber delinquency was partially mediated by aggression and depression, but not by social withdrawal. The significant link between offline victimization and online perpetration may be explained by the unique features of online space that is easily accessible to anyone and preserves anonymity of the offender. The findings from this study highlight the importance of providing interventions for youth who are victims of violence and have symtoms of aggression and depression to prevent further cyber delinquency.

비정규직 종업원의 직무 및 조직 적합성과 직무태도가 자발적 이직에 미치는 영향

강성수(Kang, Seong Soo),이택호(Lee, Taek Ho) 한국국제회계학회 2013 국제회계연구 Vol.0 No.52

본 연구에서는 비정규직 종업원들을 대상으로 이들의 조직 환경과의 적합성이 직무태도와 자발적 이직의도에 어떠한 영향을 미치며 또한 그들 간에는 어떠한 차이를 보이고 있는가에 대해서 연구하였다. 본 연구에 대한 가설 검증 결과를 요약, 정리하면 다음과 같다. 첫째, 개인-조직적합성은 직무만족에 영향을 미치는 것으로 나타났다. 둘째, 개인-조직 적합성은 조직몰입에 영향을 미치는 것으로 나타났다. 셋째, 비정규직 종업원은 개인과 직무간의 적합성이 높을수록 이직의도가 높은 것으로 나타났다. 넷째, 개인과 조직 간의 적합성이 높을수록 이직의도를 억제하는 것으로 나타났다. 다섯째, 비정규직 종업원은 직무에 만족하게 되더라도 이직의도에는 아무런 영향을 주지 않는 것으로 나타났다. 여섯째, 비정규직 근로자는 조직에 대해 몰입하게 되더라도 이직의도에는 아무런 영향을 미치지 않는 것으로 나타났다. 본 연구가 다른 연구와의 차이는 조직의 구성원들이 직무와의 적합성에 따라 이직의도에 어떠한 영향이 있는가를 분석함에 있어서 비정규직만 분석했다는 점과 적합성과 이직의도 사이에 매개변수로서 직무태도를 추가하여 이들의 영향관계를 동시에 분석하였다는 점에서 시사점이 있다고 할 수 있다. Nowadays, companies are experiencing keen competition in the global market and learning that the human element may be competitiveness to accommodate the enterprise environmental changes. It has been asserted that the contingent workers have different job attitudes and behavior compared with full-time regular workers. So, the trend of increasing contingent workers demands a more effective management of human resources on the part of companies. The purpose of this study is to find the relationship between job fitness and voluntary turnover intention in contingent workers. To identify the these relationship, the past studies that related with job fitness and voluntary turnover intention was theoretically arranged and operation definitions were established. Using collected data, the theoretical proposed model to explain these relationship was executed. For the purpose of the research, this study were used to the structural equation model. The results of this study can be summarized as follows. First, person-job fitness and person-organization fitness had positive effect on job satisfaction. Second, person-organization fitness and job satisfaction had positive effect on organization commitment. Third, person-organization fitness had negative effect on voluntary turnover intention. But person-job fitness had positive effect on voluntary turnover intention.

잠재프로파일분석을 통한 청소년의 시민의식에 따른 유형 분류 및 영향 요인 탐색

김부경 ( Kim Bu-kyung ),이택호 ( Lee Taek-ho ) 한국청소년학회 2022 청소년학연구 Vol.29 No.11

The purpose of this study is to classify latent profiles based on the individual level(self-esteem) and the local level(sense of community, multicultural acceptance) civic consciousness of adolescent and to explore the school factors that affect the classified latent profiles. Through this, it was intended to suggest a direction for improving the civic consciousness of adolescent at the school level. The data were 2,390 third grade of middle school student from Busan Education Longitudinal Study(BELS) collected by Busan Educational Research. For analysing, latent profile analysis and logistic regression analysis were performed. As a result of the analysis, the latent profiles of adolescent's civic consciousness were classified most appropriately when there were three(high group, medium group, low group). Results from logistic regression are as follows. First, those who experienced multicultural education in the school were more likely to belong to the middle group and the high group than low-group. Second, the higher the level of discrimination experience, the higher the probability of belonging to the low and medium group than the high group. Third, the more positive the relationship with peers and teachers, the higher the probability of belonging to the medium group and the high group rather than the low group, and the high group rather than the medium group. Based on these results, policy and practical measures were suggested to improve the civic consciousness of adolescent.

IMT-2000 기지국용 고선형 고효율 도허티 파워 앰프의 설계 및 성능 분석

이우진(Woo-Jin Lee),이택호(Taek-Ho Lee),박천석(Cheon-Seok Park) 한국통신학회 2003 한국통신학회 학술대회논문집 Vol.2003 No.11

前腕部 遊離皮瓣術을 利用한 頸部의 肥厚性 瘢痕狗縮의 矯正

최준,李元鐘,李澤浩 大韓成形外科學會 1988 Archives of Plastic Surgery Vol.15 No.1

At present, there is a tendency in free flap transfer to look for neurovascular flap with standard anatomy and relatively large vessel to make the transfer easier and safer. In this regard, the free neurovascular forearm flap is a reliable and technically easy free or island flap that might provide good pliable skin with a thin layer of subcutaneous fat and sensation which based on the radial artery, one or two of the forearm vein, and one or two of the cutaneous nerve branch of the forearm. Because of the standard anatomy, the large caliber of the blood vessels, the good sensory supply, the quality and quantity of the forearm skin, and a thin layer of subcutaneous fat, the free forearm flap is a technically easy and safe flap for reconstruction of soft tissue defects, especially those in the head, neck and those area of the extremities where sensitive skin is desired. Adopting the idea of the forearm flap, we present our clinical experience of correction of the severe postburn scar contracture on neck with satisfactory restoration of sensation.