http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
하승훈,서영수 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
The aim of this study is to increase thermal conductivity of polyamideimide (PAI) composites filled with surface-modified hexagonal boron nitride (h-BN). Hexagonal boron nitride is exfoliated by horn-type sonication in five types of solvent such as ethanol, toluene, DMF, NMP, and MEK. The exfoliation of h-BN is effective to enhance thermal conductivity of the composite and to create hydroxyl functional group on the edge of BN. Surface modification has been done on exfoliated BN using different kinds of silane coupling agents having amino, phenyl, epoxide and alkane functional groups which were bonded to hydroxyl group formed on the BN surface. The thermal conductivity of PAI composites filled with 20 wt% surface-modified h-BN was increased up to 2 times.We will present optimal surface modification schemes for obtaining highest thermal conductivity and explain it with a chemical similarity between the functional group and polyamide-imide.
하승훈,서영수 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1
Polymer composite used for embedded capacitors should be considered to have high dielectric constant and low loss tangent. Loss tangent is strongly related to interfacial properties between dielectric materials and the polymer. BaTiO<sub>3</sub> particles are surface-modified by horn-type sonication and mixed with epoxy resin for preparing dielectric composite films. Dielectric properties of the films were measured by perturbation method with cavity resonance mode at 1 GHz. We found that loss tangent of the composite films using surface-treated BaTiO<sub>3</sub> particles kept a minimum value as low as the base resin film up to 70 wt%. SEM images of the composite film confirmed the dispersibility of BaTiO<sub>3</sub> particles.
자기공명미세영상 및 분광법을 위한 나선형 RF 표면코일의 감는 횟수에 따른 민감도 평가
우동철,하승훈,최치봉,최보영,Woo, Dong-Cheol,Ha, Seung-Hoon,Choi, Chi-Bong,Choe, Bo-Young 한국의학물리학회 2006 의학물리 Vol.17 No.3
본 연구의 목적은 고해상도 미세영상을 얻을 수 있는 기술을 확보하기 위하여 나선형 multi-turned RF 표면코일(surface coil)의 민감도(sensitivity)를 평가하고자 하였다. RF 코일의 자기장 분포를 시뮬레이션 함으로서 자기장의 불균질성 (inhomogeniety)을 조사하고, 그 결과를 토대로 개선된 RF 코일을 디자인할 수 있다. 1, 3, 5번씩 감은 나선형 코일을 조사 한 결과, 3번 감은 나선형 코일의 민감도가 가장 높은 것으로 나타났다. 이를 통하여 나선형 RF 코일의 감는 횟수를 조절함으로써 코일의 민감도를 향상시킬 수 있다는 것을 확인할 수 있었다. 그리고 지나치게 감는 횟수를 늘리면 오히려 코일의 impedance를 증가시키게 되어 민감도를 감소시키며, 동시에 matching이 어려워진다는 사실을 확인하였다. 본 연구의 결과로서 지름이 4 cm인 나선형 wire RF 표면코일의 최적의 감는 횟수를 발견하였다. 또한 나선형 표면코일에서 감는 횟수의 증가는 항상 민감도에 긍정적인 영향을 미치는 것이 아니며, 반드시 최적의 감는 횟수를 찾아야 한다는 것을 확인하였다. The purpose of this study was to improve the technique so as to develop an advanced sensitive RF surface coil for investigating the sensitivities of the multi-spiral surface coils, and we eventually wanted to achieve high resolution of the microscopic MR images and MR spectra. The magnetic field inhomogeneity and shape of a surface coil were statistically estimated by simulation of the magnetic field distribution. On the basis of the experimental results with single, 3 and S-turned spiral RF surface coils, we found that the 3-turned coil had the highest sensitivity. The present study showed that the sensitivity of the RF surface coil was improved by increasing the number of spiral coil turns, and also the SNR of the RF surface coil was dependent upon the number of spiral coil turns. However, we found, rather strikingly, that the sensitivity of excessive turns of the coils was decreased due to the rise of the coil's Impedance. Thus, the present results demonstrated that the sensitivity was not proportional to the number of a spiral RF coil's turns, and the number of spiral coil turns should be optimized for obtaining the highest sensitivity and SNR.