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Dielectric Resonator의 마이크로파 유전 특성 측정에서 발생하는 오차요인 분석
박재환 한국교통대학교 2016 한국교통대학교 논문집 Vol.51 No.-
High-Q dielectric materials have been widely studied and used for the microwave passive devices such as resonators and filters. Transmission-mode cavity resonator method is very useful for the measurement of quality factor of the dielectrics. However, there could be some error factors in determining Q-factor measurement. In this paper, the effects of cavity material on the Q-factor measurement of microwave dielectric materials were studied by HFSS simulation. TE01δ mode resonant frequency was determined from the electric and magnetic field patterns and the loaded Q-factor was calculated from 3dB bandwidth of S21 spectrum. When the cavity metal materials were Cu and SUS, the level of Q-factor was similar. However, Q-factor was significantly decreased when the Cu metal was oxidized to CuO during 10 years.
박재환 韓國交通大學校 2022 한국교통대학교 논문집 Vol.57 No.-
Since the core concepts of the engineering certification system are competency-oriented education and continuous improvement of educational quality, it is very important to accurately evaluate the program utcomes according to program education. Course-embedded assessment can be a very useful tool for this purpose. In this study, we looked at some specific cases in the electronic engineering program of Korea National University of Transportation, step by step. By applying the course-embedded assessment, the administrative burden of the professor in charge of each subject may increase somewhat, but it is expected that more effective program outcomes evaluation will be possible for educational improvement.
네트웍분석기에 의한 PMN-PT 압전 레조네이터의 Q 측정
박재환 한국교통대학교 2020 한국교통대학교 논문집 Vol.55 No.-
In this study, the possibility of measuring the mechanical quality factor using a network analyzer was confirmed for piezoelectric samples of small size and thickness. The measurement result of the impedance spectrum-based mechanical quality factor using an impedance analyzer was 24. Using a network analyzer, the mechanical quality factor measured in reflection mode was calculated as 37, and the value measured in transmission mode was measured as 32. When the measurement equipment is changed or the measurement method is changed, errors in the measurement of the mechanical quality factor appear, which seems to be due to various factors. It seems to be due to the cable loss of each instrument and the pressure difference of the sampling fixture, and in this regard, various approaches and interpretations through subsequent studies are needed.
전계 및 응력 인가에 따른 PMN-PT 압전 단결정의 물리적 특성 변화
박재환 한국교통대학교 2021 한국교통대학교 논문집 Vol.56 No.-
A system measuring piezoelectric characteristics while varying pressure and temperature was constructed, and based on this, the electrical characteristics of PMN-PT-based piezoelectric materials were evaluated. Polarization and displacement characteristics of the sample were measured while applying a high voltage of 0 to 1.6 MV/m and a compressive stress in the range of 0 to 62 MPa. As the measurement temperature rose from 5oC to 60oC, the polarization tended to increase, and as the pressure applied to the sample increased, the polarization also increased. Strain of 0.1% or more was measured for the electric field application of 1MV/m.
HFSS 시뮬레이션에 의한 휴대폰 백커버 재질과 전파 방사특성의 상관관계 분석
박재환 한국교통대학교 2017 한국교통대학교 논문집 Vol.52 No.-
In this study, the effects of back cover materials on the electromagnetic properties of mobile phone were studied. As the efficiency of the PIFA antenna with plastic covers was 0.956 and the efficiency of the antenna with zirconia cover was 0.953, the antenna efficiency decrease was insignificant. The effect of zirconia cover on wireless power transmission also studied. When the cover material changes from plastic to zirconia, S21 parameter of 175 kHz Tx-Rx coil was reduced by approximately 1 dB.
SnO2 nanowire 기반 가스센서에서 귀금속 첨가제의 영향
박재환 한국교통대학교 2014 한국교통대학교 논문집 Vol.49 No.-
본 연구에서는 SnO2 나노선을 합성하고 이를 NOx 가스 센서로 제작한 후 저온에서의 가스 감응특성을 확인하고자 하였다. SnO2 나노선이 번들로 연결된 센서구조 아래에 에어홀을 형성 시켜줌으로써 SnO2 나노선이 공중에 들뜬 형태로 이루어 가스가 확산될 수 있는 통로를 만들어 줌으로써 흡탈착이 용이한 구조를 구현할 수 있었다. SnO2 나노선 조성에 대하여 귀금속 촉매를 도핑한 후 가스센서 감응성을 측정한 결과 NO2 가스에 대해서 높은 안정성, 높은 감도, 빠른 반응 및 회복 속도를 나타내었다. 200℃에서는 NO2 가스에 대하여 20 ppm에서 5 ppm까지 검출할 수 있었으며, 전체적으로 30~60초 내외의 90% 반응 속도 및 회복 속도를 얻을 수 있었다. Pd 귀금속 0.001M 첨가에 의해서 감도 20% 전후의 향상 효과를 얻을 수 있었다. 본 연구에서 구현시킨 센서구조는 100oC 전후의 저온에서도 센서 감응특성을 보임으로써 저비용, 고효율 가스 센서의 제작이 가능할 것으로 판단된다.
임재환,이기형,정인성 全北大學校 1994 論文集 Vol.37 No.-
The performance of ball bearing is evaluated by both the lubrication between ball and race and the condition of the contact mechanism. The contact between ball and race of bearing is considered as point contact, and point contact generally occurs in the condition of the contact between two spheres or between sphere and plane which is basic form. Therefore, first we have to define the contact mechanism of ball and race to know the performance of the ball bearing. By this reason, in the paper we defined the contact mechanism by using the actual surface parameters.
조재환,강승원 우송대학교 1997 우송대학교 논문집 Vol.2 No.-
The objective of this study is to find out the regional farmland price determination factors and their effects on farmland price fluctuatio. The study analyzes the long run equilibrium relationship and the innovation accounting analysis of regional farmland prices and its determinating factors. This empirical result will be helpful to set up the Farmland Utilization Inprovement Program for Korean agricltural structural adjustment in the future.