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Membrane-type Vibrational Energy Harvester Based on a Multi-layered Piezoelectric Membrane
류승환,김종훈,박석인,장철용,정학근 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.5
In this study, we fabricated a membrane-type vibrational energy harvester by using a conventionalmicro-electro-mechanical (MEMS) method. The membrane-type vibrational energy harvesterconsists of a multi-layered diaphragm for stable and flexible vibration, a piezoelectric ZnO film forresponding to the vibrational energy and for generating electric power, and a vibrator connectedto the bottom of multi-layered diaphragm for enhancing the vibrational displacement of the diaphragm. First, we characterized the quality of a ZnO film through scanning electron microscopy(SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD), which showed a preferredc-axis orientation, a hexagonal rod shape and a quite smooth surface. After the membrane-typevibrational energy harvester had been fabricated, we integrated it into a printing circuit board torealize piezoelectric generation and confirm its performance. Finally, under vibrational motion, weobtained a useful output voltage of 400 mV, and we estimated that the energy harvester generatedan actual output voltage of about 200 uV.
류승환,홍용기,고기혁,양희동,김종완 한국컴퓨터정보학회 2023 韓國컴퓨터情報學會論文誌 Vol.28 No.9
A privacy model is a technique that quantitatively restricts the possibility and degree of privacy breaches through privacy attacks. Representative models include k-anonymity, l-diversity, t-closeness, and differential privacy. While many privacy models have been studied, research on selecting the most suitable model for a given dataset has been relatively limited. In this study, we develop a system for recommending the suitable privacy model to prevent privacy breaches. To achieve this, we analyze the data features that need to be considered when selecting a model, such as data type, distribution, frequency, and range. Based on privacy model background knowledge that includes information about the relationships between data features and models, we recommend the most appropriate model. Finally, we validate the feasibility and usefulness by implementing a recommendation prototype system.
류승환,채수용,정학근,장철용,박형호 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.9
We report the direct patterning of diffractive optical elements (DOEs) on a flat conventionallateral-type light-emitting diode (LED) surface. Silicon dioxide, used as a diffractive optical element,was deposited on the flat surface of an LED by using plasma-enhanced chemical vapor depositionand was patterned by using nano-imprint lithography and ion-coupled plasma etching to producenanometer-scale DOEs. This method suggests a new approach for the mass production of DOEsby minimizing the size of the optical device through direct patterning on the LED surface. Theresulting DOEs also act as focal Fresnel lenses, leading to an enhancement of the external lightextractionefficiency of lateral-type LEDs based on the scattering effect and the concentration ofthe emitted light.
류승환,김인호,오경석,이상혁,설상영,정정명,최하진,최영길,한상석 인제대학교 1995 仁濟醫學 Vol.16 No.1
담낭 선종의 빈도는 드물지만 악성변이의 가능성을 가지고 있다. 저자들은 젊은 성인에게서 초음파로 진단된 다양한 크기(0.3-2.5cm)의 담낭용종을 악성종양으로 의심하여 외과적 절제술을 시행한 결과 악성의 증거가 없었던 담낭선종 1례를 경험하였기에 이에 보고하는 바이다. Gall bladder adenoma is very rare, but it has possibility of malignant transformation. We had experienced a case of large gall bladder adenoma in young adult, iris finding was multiple variable sized(0.3-2.5cm), fixed echogenic density without sonic shadow in ultra sonogram. Because it had been highly suspected malignancy, surgical intervention was done. Postoperative microscopic finding shows compact glandular structure intervening delicate fibrous stroma, and there is no evidence of malignant characteristics such as stromal invasion or anaplasia. So, we report one case of large gall bladder adenoma treated by surgical intervention.