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결합 및 교차 선로를 갖는 마이크로스트립 개방루프 공진기를 이용한 협대역 대역통과 여파기 설계
안승현,이영구,이문수 한국정보통신학회 2001 한국정보통신학회논문지 Vol.5 No.5
본 논문에서는 교차 및 결합 선로를 갖는 마이크로스트립 개방루프 공진기를 이용한 협대역 대역통과 여파기를 설계.제작하였다. 이 여파기는 크기가 작고 경량이며, 협대역 타원함수 대역통과 특성과 같은 우수한 특성을 가지고 있다. 여파기는 두 개의 동일한 마이크로스트립 개방루프 공진기와 교차 및 결합선로로 구성되어 있다. 개방루프 공진기를 사용함으로서 여파기 크기는 링 공진기와 비교하여 50% 정도가 축소된다. 교차선로는 억제대역에서 두 개의 노치를 제공하므로, 통과대역에서 예리한 선택도를 가진다. 중심주파수 2.455GHz로 설계된 마이크로스트립 대역통과 여파기는 1.22%의 대역폭을 가지며, 이는 무선LAN의 응용에 매우 적합하다. 여파기는 포토 에칭법으로 제작하였다 제작된 대역통과 여파기는 2.458GHz대에서 0.85%의 대역폭을 가지며 크기는 $2.6cm\times1cm$이다. In this paper, a narrow-band bandpass filter using microstrip open-loop resonators with coupled and crossing lines is designed and fabricated. This filter has many advantages such as compact in size, low weight and the characteristic of the elliptic-function narrow-band bandpass filtering. The configuration consists of two identical microstrip open loop resonators, coupled line and crossing line. By using open loop resonators, the size of the filter can be reduced about 50% compared with the ring resonators. A crossing line gives two notchs in the stopband, which have sharp selectivity in the passband. Centered at 2.455GHz, the calculated microstrip bandpass filter shows a bandwidth of 1.22%, which makes it very attractive for application in the wireless LAN. The filter is fabricated by photo-etching process. The fabricated bandpass filter shows that the bandwidth is 0.85% for 2.458GHz and the size is only $2.6cm\times1cm$.
체내 이식형 의료기기의 보안성 향상을 위한 3-Tier 보안 메커니즘 설계
안승현,박창섭,박주호 한국융합보안학회 2014 융합보안 논문지 Vol.14 No.3
의료기술 및 IT 기술의 급격한 발전으로 인해 체내 이식형 의료기기와 같은 융합 의료기술에 대한 관심이 날로 증 가하고 있다. 하지만, 체내 이식형 의료기기와 같은 새로운 형태의 의료서비스는 무선통신을 통해서 제공되고 있기 때 문에 무선통신에서 발생가능한 개인정보 위협을 포함한 다양한 보안 취약점에 관한 문제 역시 중요 이슈로 떠오르고 있다. 특히, 이러한 의료서비스에서의 보안상 취약점은 환자에게 치명적인 위협으로 다가갈 수 있기 때문에 더욱 안전 한 방식의 보안성 제공이 요구된다. 본 논문에서는 현재 제공되고 있는 체내 이식형 의료기기를 이용한 의료서비스에 서 발생할 수 있는 보안상 취약점들을 지적하고 이에 대응하기 위한 보안 메커니즘을 제안한다.
폴리우레탄 인공혈관에 대한 혈관내피세포의 친화성: 예비동물실험
안승현,전영민,장학,박정희,민경원 대한성형외과학회 2009 Archives of Plastic Surgery Vol.36 No.4
Purpose: Autologous vessels remain the gold standard for vascular grafts in microanastomoses. However, they are sometimes unavailable and have a limited long-term patency. Synthetic vessels have high success rates in large-diameter reconstructions but failed when used as small-diameter grafts due to graft occlusion. It has been proven that endothelial cell seeding improves prosthesis performance and long-term patency. Among polyurethane, PET and ePTFE, polyurethane has the best affinity to endothelial cells and mechanical properties closest to human vessels. We examined the ability of endothelial cells to attach to a polyurethane graft manufactured by the electrospinning method. Methods: Endothelial cells, which were cultured from porcine internal jugular veins, were attached to polyurethane grafts with an internal diameter of 3mm. The same cells were attached to allogeneic decellularized porcine internal carotid artery grafts as controls. Both of the 10mm-long grafts were exposed to endothelial cells in a well for 1 hour. Each well contained 2×105 endothelial cells. The graft materials were rotated through 90 degrees every 15 minutes in order to minimize the effect of gravity. The extent of cell attachment was examined with the MTT assay. Results: The MTT assay showed good incorporation of endothelial cells into both grafts. For the evaluation of affinity, the number of attached cells was counted at 10 fields of microscopic examination with×40 magnification. Endothelial cells adhered more to polyurethane grafts (mean, 127.4±6.2 cells) compared to porcine artery grafts (mean 45.8±5.1 cells)(p<0.05,Mann-Whitney test). Conclusion: In this study, we attached porcine endothelial cells to polyurethane grafts, manufactured by electrospinning. The grafts exhibited a better affinity to endothelial cells than allogeneic decellularized porcine internal carotid artery grafts. It is suggested that the time required for endothelial cells to attach to decellulized artery grafts may be longer than that which is required for attachment to polyurethane grafts.
등숙기 평균기온 상승에 따른 밀 종실의 이화학적 특성 변화
안승현,김대욱,이현석,정재혁,정한용,황운하,백정선,최경진,최인배,박홍규,윤종탁,김근중 한국국제농업개발학회 2017 韓國國際農業開發學會誌 Vol.29 No.1
We investigated the changes in the physicochemical properties of wheat grains during ripening stage to determine the effect of the rise in average temperature on that of wheat grains. The treated average temperatures were 18.3°C(control), 19.9°C(1.6°C increase), 21.5°C(3.2°C increase) in artificial climate room from heading time to harvest. Results showed that the ripening period from heading to maturity tended to be shorter during higher temperature treatment condition. The 1,000-grain weight, grain width, number of florets per spike, and number of grains per spike decreased as the ripening period was shortened. Gelatinization properties were affected by high temperature due to the reduction of starch and amylose contents. As the grain filling period was shortened by high temperature treatments, the crude protein content increased. As the grain filling period was shortened by 6 days, the starch and amylose contents decreased by 10.8% and 5.4%, respectively. However, the crude protein content increased by 1.7% in such a condition. Starch content showed positive correlations between amylose and breakdown. Meanwhile, it showed negative correlations between electric conductivity of leaching water from seeds, crude protein content, peak viscosity, trough viscosity, final viscosity, and setback.