• 대한의용생체공학회:의공학회지
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• 제23권5호
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• pp.375-383
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• 2002

코일을 이용한 동맥류 색전술은 동맥류 내부에 코일을 삽입하여 혈류 유동의 정체를 유도하여 혈전을 형성시키므로 동맥류를 폐색하는 방법이다. 코일을 이용하여 동맥류를 부분 폐색할 경우 동맥류의 폐색 위치에 따라 동맥류 내부의 유동 특성이 변하며, 이는 동맥류 내부의 현전 형성에 영향을 미칠 수 있다. 본 연구에서는 내경 동맥에서 발생한 측방 동맥류에 코일로 인한 부분 폐색이 발생할 경우, 부분 폐색 위치 및 내경 동맥의 곡률 반경의 변화에 따른 동맥류 내부 혈류 유동의 변화를 생체외 모델 실험을 이용하여 측정하여, 효율적인 동맥류 폐색 위치를 제시하고자한다. 내경동맥에서 발생한 측방 동맥류 내부에 코일을 동맥류 천정 근위부, 천정 원위부, 목 근위부 및 목 원위부에 각각 삽입하여 폐색 위치가 다른 모델을 제작하여, 입자영상속도계를 이용하여 속도장을 측정하였다. 동맥류 주머니의 원위부 폐색은 근위부 폐색에 비해 동맥류 내부고의 유입되는 유동이 적었으므로 동맥류 원위부 폐색이 혈전의 형성 및 동맥류 색전에 효율적임을 나타냈다. 동맥류 목 원위부 폐색은 천정 원위부 폐색에 비해 동맥류 내부로 혈류 유입을 효율적으로 차단하였으므로, 목 원위부 폐색이 동맥류 색전에 가장 효율적인 위치임을 알 수 있었다.

• 한국염색가공학회지
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• 제6권1호
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• pp.62-70
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• 1994

Silk fibroin was dissolved in 9.3 M LiBr aqueous solution at 4$0^{\circ}C$ for 1 hour. The dissolved silk fibroin was regenerated by casting the dialyzed solution into the membrane. The freshly prepared silk fibroin membrane was soluble in water and was. mainly consisted of random coil conformation. By the treatments in saturated water vapor at 3$0^{\circ}C$ and in 75% ethanolic aqueous solution (V/V), the insoluble membranes were obtained and the structure and morphology of those were investigated for the structure by means of X-ray diffraction analysis, infrared spectroscopy, thermal analysis. Rheovibron and scanning electron micrograph. Silk II type crystals were obtained by treating amorphous silk fibroin membrane in the random coil conformtion with 75% ethanol solution(V/V). Crystallization to silk II type crystals occured even after a few minutes, and a large number of silk II type crystals were formed after 30 mins. On the other and, the membrane treated in saturated water vapor was composed of the mixtures of silk I and silk II type crystals. A large number of silk I and silk II type crystals were formed after 24 hours. The micro brownian motion in the amorphous regions of silk fibroin membrane started at about 175~185$^{\circ}C$. $\alpha$ dispersion appeared at about 20$0^{\circ}C$ in the amorphous membrane, and at about 22$0^{\circ}C$ in the crystalline membrane. The crystallization of random coil conformation to silkII type crystals occured at about 215$^{\circ}C$. The surface, bottom and cross-section of the membranes were observed by scanning electrom microscope. Fine forms alike spherulites appeared at the surface of crystalline membrane.

• 한국전기전자재료학회논문지
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• 제22권11호
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• pp.918-924
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• 2009

In this paper, we designed micro-structured electromagnetic transducers for energy harvesting and verified the performance of proposed transducers using finite element analysis software, COMSOL Multiphysics. To achieve higher energy transduce efficiency, around the magnetic core material, three-dimensional micro-coil structures with high number of turns are fabricated using semiconductor fabrication process technologies. To find relations between device size and energy transduce efficiency, generated electrical power values of seven different sizes of transducers ($3{\times}3\;mm^2$, $6{\times}6\;mm^2$, $9{\times}9\;mm^2$, $12{\times}12\;mm^2$, $15{\times}15\;mm^2$, $18{\times}18\;mm^2$, and $21{\times}21\;mm^2$) are analyzed on various magnetic flux density environment ranging from 0.84 T to 1.54 T and it showed that size of $15{\times}15\;mm^2$ device can generate $991.5\;{\mu}W$ at the 8 Hz of environmental kinetic energy. Compare to other electromagnetic energy harvesters, proposed system showed competitive performance in terms of power generation, operation bandwidth and size. Since proposed system can generate electric power at very low frequency of kinetic energy from typical life environment including walking and body movement, it is expected that proposed system can be effectively applied to various pervasive computing applications including power source of embodied medical equipment, power source of RFID sensors and etc. as an secondary power sources.

• 대한기계학회논문집A
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• 제41권4호
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• pp.333-336
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• 2017

스피커 진동판은 고유 특성에 의해 분할진동을 발생 시킨다. 이 분할진동은 진동판의 형상 변화를 가져올 정도로 뚜렷한 영향을 주는데, 본 논문에서는 IT 분야의 첨병인 스마트 폰을 포함한 초박형 멀티미디어 기기에서 많이 사용되는 마이크로 스피커를 그 대상으로 삼는다. 마이크로 스피커는 일반적인 스피커와 다른 평판형의 구조적인 형태와 공간적인 제약이 존재한다. 특히 구동 공간이 밀폐형으로 설계되어 무빙 코일에서 발생하는 열의 냉각이 열악하고 보조적인 서스펜션 구조를 갖추기 어렵다. 본 연구에서는 진동판의 열전달과 분할진동 모드의 연관성을 연구한다. 이를 위해 진동판의 레이저 스캔을 통한 분할진동 측정과 열화상 카메라 촬영을 통한 열변화 측정의 두 단계로 나누어 실험을 진행한다. 이를 통해 특정 주파수 범위에서 분할진동 모드와 열전달 형태를 비교함으로써, 열화상 카메라를 통한 촬영 결과로 진동판 분할진동 모드의 경향성을 빠르게 예상할 수 있어, 마이크로 스피커의 최적 설계에 도움이 되는 지표를 제공할 수 있을 것으로 기대한다.

• KIEE International Transactions on Electrophysics and Applications
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• 제4C권4호
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• pp.176-180
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• 2004

This paper presents the fabrication and test of a micro cell exciter actuated by an electromagnetic force for the study on the chondrogenic differentiation of rabbit mesenchymal stem cells (MSCs). The micro cell exciter is designed to apply compressive loading to the alginate gel mixed with the MSCs. The magnetic cell exciter consists of an actuator component and a cartridge-type chamber component. An actuator is composed of a permanent magnet, a core and a coil. The chamber has seven PMMA wells and a cell culture Petri dish. Two types of alginate gels were stimulated by the cell exciters for 10 minutes every 12 hours for 7 days. In order to determine the expression of these matrix components during differentiation, RT-PCR analysis was performed. Collagen type II was expressed in the MSCs subjected to the compressive stimulation.

• International Journal of Precision Engineering and Manufacturing
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• 제2권3호
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• pp.54-60
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• 2001

A newly designed inductive micro displacement detecting system is presented. The proposed inductive system consists of driving coils, position-detecting coils, cores, and closed-loop formed magnetic blocks. The cores and magnetic blocks are made of Mn-Zn ferrite. When AC sine wave is applied to the driving coils, the time derivative flux is generated within the system, and then induced voltages arise in the position-detecting coils according to the core\`s position. Putting the cores to be moved proportionally to the input displacement, the induced voltage is proportional to input displacement. The parameters that affect the system characteristics are turn ratio, air-gap size, excitation frequency, overlap area, load resistance, capacitance effect, and so forth. Based on the experimental results, the system parameters are selected in such a way as to have high sensitivity ad stable responses. The sensitivity of the proposed inductive displacement-detecting system is greater than 2800mV.V-1mm-1 and the linearity error is below $\pm$0.10% in the range of $\pm$200㎛.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1641-1644
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• 2005

Magnetic actuation utilizes the mechanic torque that is the result of interaction of the current in a coil with an external magnetic field. A main obstacle is, however, that torques can only be produced perpendicular to the magnetic field. In addition, there is uncertainty in the Earth magnetic field models due to the complicated dynamic nature of the field. Also, the magnetic hardware and the spacecraft can interact, causing both to behave in undesirable ways. This actuation principle has been a topic of research since earliest satellites were launched. Earlier magnetic control has been applied for nutation damping for gravity gradient stabilized satellites, and for velocity decrease for satellites without appendages. The three axes of a micro-satellite can be stabilized by using an electromagnetic actuator which is rigidly mounted on the structure of the satellite. The actuator consists of three mutually-orthogonal air-cored coils on the skin of the satellite. The coils are excited so that the orbital frame magnetic field and body frame magnetic field coincides i.e. to make the Euler angles to zero. This can be done using a Neural Network controller trained by PD controller data and driven by the difference between the orbital and body frame magnetic fields.

• Journal of Advanced Marine Engineering and Technology
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• 제36권7호
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• pp.869-875
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• 2012

In the past decades, extensive studies on convection heat transfer on internal flow have been conducted by using high specific surface area, by increasing heat transfer coefficient and swirl flow, and by improving the transport properties. In this study, we applied a tangential slot swirl generator to improve heat transfer in a horizontal circular copper tube. The Al-Mg particles (approximately $100{\mu}m$ to $130{\mu}m$) were employed for this experimental work. The copper tube was heated uniformly by winding a heating coil with a resistance of 9 ohm per meter for heat transfer. Using Al-Mg particles, experiments were performed in the Reynolds number range of 5,000 to 13,130, with and without swirl. Experimental data transfers or comparisons between Nusselt numbers with and without swirl along the test tube and Reynolds numbers are presented. The Nusselt number is improved by increasing Reynolds numbers or swirl intensities along the test tube.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.511-517
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• 2016

This paper presents dynamic characteristics of a new actuator using magneto-rheological(MR) fluid between two electrode type coils. The concept of the actuator is to strengthen the force due to the magnetic field produced by the electrode-coil for MR fluid. The amount and direction of current input to the electrode-coils decide the characteristics of contraction-mode and extension-mode. For achieving the required actuating displacement and actuating force, the yield stress of the MR fluid between two electrode-coils is precisely changed by the input current. In this work, the MR fluid is operated in squeeze mode. The experimental results shown in this paper depict that it can be applied in the micro-level displacement and vibration control system.

• 한국가시화정보학회지
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• 제10권3호
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• pp.16-20
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• 2012

In the past decades, extensive studies on convection heat transfer on internal flow have been conducted by using high specific surface area, by increasing heat transfer coefficient and swirl flow, and by improving the transport properties. In this study, we applied a tangential slot swirl generator to improve heat transfer in a horizontal circular copper tube. The Al-Mg particles (approximately $100{\mu}m$ to $130{\mu}m$) were employed for this experimental work. The copper tube was heated uniformly by winding a heating coil with a resistance of 9ohm per meter for heat transfer. Using Al-Mg particles, experiments were performed in the Reynolds number range of 5,000 to 13,130, with and without swirl. Experimental data transfers or comparisons between Nusselt numbers with and without swirl along the test tube and Reynolds numbers are presented. The Nusselt number is improved by increasing Reynolds numbers or swirl intensities along the test tube.