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김근환,최창희,정세영,이동녕 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.4
In order to achieve good deep drawability it is imperative to obtain well developed {111}//ND texture which gives rise to the higher plastic strain ratios. However, it has been found that no {111} texture developed after a normal rolling process and subseguent annealing processe. Therefore an unconventional rolling process which causes shear deformation has been introduced for 99.99 pct aluminum and Al-1.2Mn-0.4Mg alloy. The effect of initial texture and microstructure on the shear texture has been studied. It is found that the rolling texture using asymmetric rolls could be characterized by α fibre and γ fibre. This experimental results were able to be explained by the Taylor-Bishop-Hill theory. The evolution of recrystallization texture from the specimen having the shear texture components was well predicted using the maximum energy release model suggested by Lee.
피드백 저항 제어에 의한 무선랜용 가변이득 저전압구동 저잡음 증폭기 MMIC
김근환,윤경식,황인갑,Kim Keun Hwan,Yoon Kyung Sik,Hwang In Gab 한국통신학회 2004 韓國通信學會論文誌 Vol.29 No.10A
본 논문에서 ETRI 0.5$\mu\textrm{m}$ MESFET 라이브러리 공정을 이용하여 동작 주파수 5GHz대 저전압구동 가변이득 저잡음 증폭기 MMIC를 설계 및 제작하였다. 이 저잡음 증폭기는 HIPERLAN/2의 Adaptive Antenna Arrays와 함께 사용할 수 있도록 이득조절이 가능하도록 설계하였다. 가변이득 저잡음 증폭기는 2단 캐스케이드 구조이며, 게이트전압에 따라 채널저항이 제어되는 증가형 MESFET과 저항으로 구성된 부귀환 회로를 제안하였다. 제작된 가변이득 저잡음 증폭기의 측정값은 $V_{DD}$ =1.5V, $V_{GG1}$=0.4V, $V_{GG2}$=0.5V일때 5.5GHz의 중심 주파수, 14.7dB의 소신호 이득, 10.6dB의 입력 반사손실, 10.7dB의 출력 반사손실, 14.4dB의 가변이득, 그리고 잡음지수 2.98dB이다. 또한, 가변이득 저잡음 증폭기는 -19.7dBm의 입력 PldB, -10dBm의 IIP3, 52.6dB의 SFBR, 그리고 9.5mW의 전력을 소비한다.다.다. A variable-gain low-voltage low noise amplifier MMIC operating at 5GHz frequency band is designed and implemented using the ETRI 0.5$\mu\textrm{m}$ GaAs MESFET library process. This low noise amplifier is designed to have the variable gain for adaptive antenna array combined in HIPERLAN/2. The feedback circuit of a resistor and channel resistance controlled by the gate voltage of enhancement MESFET is proposed for the variable-gain low noise amplifier consisted of cascaded two stages. The fabricated variable gain amplifier exhibits 5.5GHz center frequency, 14.7dB small signal gain, 10.6dB input return loss, 10.7dB output return loss, 14.4dB variable gain, and 2.98dB noise figure at V$\_$DD/=1.5V, V$\_$GGl/=0.4V, and V$\_$GG2/=0.5V. This low noise amplifier also shows-19.7dBm input PldB, -10dBm IIP3, 52.6dB SFDR, and 9.5mW power consumption.
A New Measurement to Understand Convergence Phenomenon
김근환 아시아기술혁신학회 2013 Asian Journal of Innovation and Policy Vol.2 No.1
Many scholars have persevered in understanding the convergence process by developing a measurement that reflects the characteristics of the convergence phenomenon as a process. Recently a series of studies suggested a framework in terms of diversity and coherence. However, an index for coherence is required to reflect the vital features of the conceptual definition, and thus a new index for coherence is proposed in this paper. Technology Convergence Index combines diversity and coherence and indicates the degree of the convergence in information computer technology (ICT), biotechnology (BT) and nanotechnology (NT) sectors. The index can not only be used to track each technology field that consists of a major technology sector, but also to compare other leading countries. Based on a comparison study between the United States and South Korea, the degrees of technology convergence of Korea in ICT, BT, and NT sectors have ameliorated.
Cystic Hygroma Occurring on the Left Side of Neck of an Adult : A Case Report and Literature Review
김근환,김진욱,최소영 대한구강악안면병리학회 2020 대한구강악안면병리학회지 Vol.44 No.3
With few reported cases, cystic hygroma is known to occur mainly in patients under the age of two years. Cystic hygroma can eventuate in any area; however, it mostly occurs in the cervicofacial area. If cystic hygroma occurs in this area, then the lesion may be related to the vital structures. Therefore, a complete surgical resection may be impossible and difficult to perform. This incident affects the high recurrence rate of cystic hygroma. The purpose of this report is to present a case of cystic hygroma occurring on the left side of the neck of a 47-year-old male patient as well as a review of literatures.
A New Approach to Estimating Product Lifetimes: A Case Study of an LED Based LCD TV
김근환 아시아기술혁신학회 2012 Asian Journal of Innovation and Policy Vol.1 No.2
Estimating the economic life of a technology is the first important prerequisite step in the feasibility analysis of technology-based business. Many empirical studies have concentrated on patents data to estimate the time period for a technology. However, it is recommended to estimate it along with qualitative considerations of future technological and market conditions. In this regard, little is known about how approaches are applied. This paper aims to establish a structural framework of estimating the lifetime of a technology by integrating the outputs of an analysis of the determinants in each transition of a product life cycle. We describe an illustrative case about a light emitting diode (LED) backlight unit (BLU) technology for the liquid crystal display (LCD) TV. The framework allows valuators and experts to estimate a technology lifetime by using multidimensional factors.
잔향환경에 강인한 Generalized Sinusoidal Frequency Modulated 펄스 생성 기법
김근환,윤경식,이동화,조점군,홍정표,이균경 한국산업정보학회 2019 한국산업정보학회논문지 Vol.24 No.5
본 논문에서는 잔향 환경에 강인한 GSFM(Generalized sinusoidal frequency modulated) 펄스를 설계하는 기법을 제안하였다. GSFM 펄스는 SFM(Sinusoidal frequency modulated) 펄스의 일반화한 형태로써 거리와 도플러 분해능이 모두 우수한 압정형태의 모호성 함수를 가지는 장점이 있다. 하지만 일반화를 하는 과정에서 주기성이 사라지기 때문에, 빗살형태의 스펙트럼을 가지는 SFM 펄스에 비해 잔향환경에서 탐지 성능이 저하된다. 본 논문에서는 GSFM 펄스의 파라미터 를 적절히 변화시켜 SFM 펄스의 잔향 제거 성능과 GSFM 펄스의 거리 분해능 성능 간에 트레이드오프(Trade-off)관계를 분석하고, 비교적 높은 성능을 동시에 만족할 수 있는 값을 제안하였다. 제안한 GSFM 펄스의 성능을 검증하기 위해 잔향환경을 모의하여 시뮬레이션을 수행하였으며, 제안한 GSFM 펄스가 저속의 도플러 표적을 탐지하면서 우수한 거리 분해능을 가지는 것을 확인할 수 있었다.