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Propulsion of Water-Floating Objects by Acoustically Oscillating Microbubbles
원정민,이정현,이경호,이계한,정상국 한국정밀공학회 2011 International Journal of Precision Engineering and Vol. No.
In this paper, novel propulsion of micro/millimeter-sized water-floating objects has been experimentally demonstrated. When an acoustic wave propagates onto air bubbles in a liquid medium, the bubbles oscillate and generate cavitational microstreaming flows; this can be used to propel small water-floating objects. This propulsion concept is simple, but the propulsion can provide sufficient force to propel the water-floating objects without electrical connecting wires and mechanical moving parts. In this study, we prepared open-box-type micro/millimeter-sized objects using a thin Al film. We then experimentally realized linear and rotational motions and two-dimensional maneuvers on the surface of water. The effects of the frequency of the acoustic wave and the applied voltage on the motions are quantified with the bubble oscillation amplitude using high speed images. Such water-floating objects propelled by oscillating microbubbles can be integrated with cameras and sensors and used in environment monitoring systems or surveillance security systems.
COVID-19에 따른 원격수업 시 교사들에게 필요한 사항
원정민 ( Jeongmin Won ),안성훈 ( Sung Hun Ahn ) 한국창의정보문화학회 2021 창의정보문화연구 Vol.7 No.3
본 연구에서는 COVID-19에 따른 원격수업 현황을 조사한 연구들로부터 효과적인 원격수업을 위해 교사들에게 필요한 사항들은 분석하였다. 그 결과, 원격수업 콘텐츠 관련 지원이 필요한 것으로 나타났다. 구체적으로는 원격수업 콘텐츠 제작에 특화된 플랫폼 구축 및 콘텐츠 제작·운영 관련 교원 연수의 확충, 콘텐츠 제작 관련 저작권 제도를 개선하는 방안이 필요하다고 판단된다. 또한 원격수업은 등교수업과 체계와 특징이 다르므로 원격수업을 위한 제도적 측면의 보완도 필요하다. 원격수업에 맞는 평가 방식, 교육과정 운영 권한, 학습관리 시스템 등에 대한 지원 필요하다고 판단된다. 아울러 원격수업을 위한 인프라 확충이 필요하며, 원격학습으로 인해 학습격차 문제가 반복되지 않도록 자기주도적 향상 프로그램 및 자기주도적 원격학습을 할 수 있는 구조 및 플랫폼도 필요한 것으로 분석되었다. In this paper, from the pervious studies investigating the current status of distance learning due to COVID-19, the needs of teachers for effective distance learning were analyzed. As a result, it was found that support related to distance learning contents was necessary. Specifically, it is necessary to establish a platform specialized for content production for distance learning, expand teacher training related to content production and operation, and improve the copyright system related to content production. In addition, since distance classes differ from those of back-to-school classes in system and characteristics, it is necessary to supplement the institutional aspects for distance classes. It is judged that it is necessary to support the evaluation method suitable for distance learning, the authority to operate the curriculum, and the learning management system. In addition, it was analyzed that it is necessary to expand the infrastructure for distance learning, and a structure and platform for self-directed improvement programs and self-directed distance learning are needed to prevent the learning gap problem from repeating due to distance learning.
송현석,원정민,정상국,Song, Hyeonseok,Won, Jung Min,Chung, Sang Kug 한국가시화정보학회 2020 한국가시화정보학회지 Vol.18 No.1
This paper presents a new type of electrowetting driven tandem light deflector for high performance optical application. To steer an incident light, the proposed light deflector deforms the fluid interface using electrowetting actuation. The performance of the light deflector was experimentally verified by using a prototype of the proposed light deflector. Single and tandem light deflectors were separately prepared using microfabrication processes. The optical tests of the deflectors were conducted using a laser light. The proposed tandem light deflector obtained a 45° beam steering angle with a 5.3° deflection angle while a single light deflector was required for a 10.9° deflection angle to obtain the same beam steering angle. The proposed tandem light deflector with high optical capability can be applied to various optical applications from camera modules in mobile smart devices to advanced future optical systems.
AEC 시설물의 프로덕트 모델기반 정보공유 기술 개발에 관한 연구
강병철,김인한,최삼락,김학두,권정민,김미희,원지선 한국CDE학회 2006 한국CDE학회 논문집 Vol.11 No.5
Currently, it is necessary to share and exchange drawing information between 2D and 3D data in AEC(Architecture, Engineering & Construction) fields. The authors suggest an information model framework to express IFC(Industry Foundation Classes)-based drawing of 3D AEC products as 2D drawing. In this study, 1)an information framework has been developed to enable sharing and exchange of AEC product model by adding various information factors, 2) standard APIs and an IFC2DBrowser are developed.
태아 선천성 갑상샘기능저하증에서 자궁 내로 티록신(thyroxine) 주입한
이미영 ( Mi Young Lee ),원혜성 ( Hye Sung Won ),김유진 ( Eu Gene Kim ),엄정민 ( Jeong Min Eom ),문제원 ( Jei Won Moon ),유래미 ( Ree Mi You ),이필량 ( Pil Ryang Lee ),김암 ( Ahm Kim ) 대한주산의학회 2009 Perinatology Vol.20 No.2
A 28-year-old primi gravida visited our department at 20 weeks gestation. The ultrasound screening revealed twin gestation, and follow up screening revealed a bilobed large fetal neck mass in the 1st twin. We measured thyroid volume with ultrasound which was 5.072 cm3. Other fetal organs appeared normal. Cordocentesis was performed for fetal thyroid function and congenital hypothyroidism was confirmed. In addition, maternal thyroid hormones were checked. The other fetus was normal. Thyroid stimulating hormone (TSH) in the maternal serum was increased, but thyroxine (T3) was (within normal range). Two weeks later, we checked TSH and free T4 in amniotic fluid and administered intra-amniotic thyroxine (200 μg). We repeated the procedures 2 more times in two consecutive weeks. After 3 intra-amniotic thyroxine injection, follow-up cordocentesis revealed euthyroid status of the fetus. Although the thyroid gland had decreased in size and volume, it was still goitrous. At 36 weeks of gestation, the patient was admitted for preterm premature rupture of the membranes and the twin was delivered vaginally. The 1st twin was proved as an euthyroid status and antithyroid antibody was not detected. During the 3 years follow up, the baby had no considerable developmental problem. The intrauterine recognition and treatment of congenital goitrous hypothyroidism may not only reduce the obstetric complications associated with large goiters, but possibly improve the prognosis for normal growth and mental development of affected fetuses.
케미칼 크랙킹 방법을 이용한 플라스틱 제품의 응력측정에 관한 연구
원시태 ( S. T. Won ),김태범 ( T. B. Kim ),이실 ( S. Lee ),원정민 ( J. M. Won ),차규호 ( K. H. Cha ),류민영 ( M. Y. Lyu ) 한국고무학회 2012 엘라스토머 및 콤포지트 Vol.47 No.4
사출성형품에서 잔류응력은 성형공정 중 열과 전단응력에 의해 형성된다. 잔류응력을 평가하는 방법은 여러 가지가 있는데, 불투명한 제품에서의 잔류응력은 케미칼 크랙킹 테스트 방법으로 측정 할 수 있다. 이 방법은 시편과 솔벤트가 반응하게 하여 측정하는 방법이다. 크랙은 응력의 크기에 따라 형성되기 때문에 크랙의 크기나 수를 측정하여 응력을 정량적으로 측정한다. 본 연구에서는 케미칼 크랙킹 방법으로 잔류응력을 측정하기 위한 기초자료인 응력과 크랙과의 관계를 규명하기 위한 실험을 수행하였다. 시편을 제작하기 위한 재료는 PC/PBT와 PC/ABS사용하였으며 지그를 이용하여 시편을 변형을 주고 이를 솔벤트에 담궈서 크랙을 유도하였다. 솔벤트는 tetrahydrofuran과 methyl alchol을 이용하여 제조하였다. 두 재료 모두 응력이 어느 정도 이상에서만 크랙이 형성되었으며, 크랙은 응력이 증가함에 따라 대략 2차함수로 증가하였다. Residual stress in the injection molded part is originated from thermal shrinkage and shear stress during injection molding process. There are many measurement methods of residual stress in the plastic part. Residual stress in opaque products can be measured by chemical cracking test. This method enables the solvent and specimen to react and to cause cracks. Cracks developed according to the level of residual stress. Thus the stresses in plastic part can be quantitatively measured by counting the number of cracks or measuring the size of cracks. Relationship between stress and number of cracks in a plastic specimen has been investigated in this study. Bergen jig was used to give a strain in the specimens those were molded using PC/PBT and PC/ABS. Solvent for the chemical cracking test was prepared using tetrahydrofuran and methyl alcol with the ratio of 1 to 3. Stresses in the specimen can be calculated by strains those were imposed by Bergen jig. Cracks were developed for stress higher than certain level. The number of cracks increased by second order function for stress.