• 한국가시화정보학회지
• /
• 제14권2호
• /
• pp.40-45
• /
• 2016

Magnetic resonance velocimeter (MRV) is a powerful tool to non-invasively measure the velocity of a fluid flow in various fields ranging from medicine to engineering. However, since the demands for accurate measurement in the solid/liquid interface for cardiovascular diseases and porous media increase, the improvement of spatial resolution is required. In this study, a solenoid RF coil is developed for high spatial resolution measurement. The signal-to-noise ratio in solenoid RF coil is increased seventeen times better than that in commercial coil. Moreover, the velocity distribution of Hagen-Poiseuille flow is measured with in-plane resolution of $36{\mu}m$ by $36{\mu}m$ and the accuracy of the measured velocity is compared with theoretical distribution of the laminar flow. Flow rate calculated by MRV is estimated with the flow rate injected by syringe pump.

• Journal of electromagnetic engineering and science
• /
• 제11권3호
• /
• pp.166-173
• /
• 2011

In this paper, we implemented and analyzed a wireless power transfer (WPT) system with a CSPR topology. CSPR refers to constant current source, series resonance circuit topology of a transmitting coil, parallel resonance circuit topology of a receiving coil, and pure resistive loading. The transmitting coil is coupled by a magnetic field to the receiving coil without wire. Although the electromotive force (emf) is small (about 4.5V), the voltage on load resistor is 148V, because a parallel resonance scheme was adopted for the receiving coil. The implemented WPT system is designed to be able to transfer up to 1 kW power and can operate a LED TV. Before the implementation, the EMF reduction mechanism based on the use of ferrite and a metal shield box was confirmed by an EM simulation and we found that the EMF can be suppressed dramatically by using this shield. The operating frequency of the implemented WPT system is 30.7kHz and the air gap between two coils is 150mm. The power transferred to the load resistor is 147W and the real power transfer efficiency is 66.4 %.

• Journal of Korean Neurosurgical Society
• /
• 제43권6호
• /
• pp.275-280
• /
• 2008

Objective : In order to assess the incidence of thromboembolic events and their clinical presentations, the present study prospectively examined routine brain magnetic resonance images (MRI) taken within 48 hours after a coil embolization of cerebral aneurysms. Methods : From January 2006 to January 2008, 163 cases of coil embolization of cerebral aneurysm were performed along with routine brain MRI, including diffusion-weighted magnetic resonance (DW-MR) imaging, within 48 hours after the embolization of the aneurysm to detect the silent thromboembolic events regardless of any neurological changes. If any neurological changes were observed, an immediate brain MRI follow-up was performed. High-signal-intensity lesions in the DW-MR images were considered as acute thromboembolic events and the number and locations of the lesions were also recorded. Results : Among the 163 coil embolization cases, 98(60.1%) showed high-signal intensities in the DW-MR imaging follow-up, 66 cases (67.0%) involved the eloquent area and only 6cases (6.0%) showed focal neurological symptoms correlated to the DW-MR findings. The incidence of DW-MR lesions was higher in older patients (${\geq}60$ yrs) when compared to younger patients (<60 yrs) (p=0.002, odd's ratio=1.043). The older patients also showed a higher incidence of abnormal DW-MR signals in aneurysm-unrelated lesions (p=0.0003, odd's ratio=5.078). Conclusion : The incidence of symptomatic thromboembolic attacks after coil embolization of the cerebral aneurysm was found to be lower than that reported in previous studies. While DW-MR imaging revealed a higher number of thromboembolic events, most of these were clinically silent and transient and showed favorable clinical outcomes. However, the incidence of DW-MR abnormalities was higher in older patients, along with unpredictable thromboembolic events on DW-MR images. Thus, in order to provide adequate and timely treatment and to minimize neurological sequelae, a routine DW-MR follow-up after coil embolization of cerebral aneurysms might be helpful, especially in older patients.

• 한국초전도ㆍ저온공학회논문지
• /
• 제18권1호
• /
• pp.46-49
• /
• 2016

The wireless power transfer (WPT) system using a magnetic resonance was based on magnetic resonance coupling of the transmission and the receiver coils. In these system, it is important to maintain a high quality-factor (Q-factor) to increase the transmission efficiency of WPT system. Our research team used a superconducting coil to increase the Q-factor of the magnetic resonance coil in WPT system. When the superconductor is applied in these system, we confirmed that transmission efficiency of WPT system was higher than normal conductor coil through a preceding study. The efficiency of the transmission and the receiver coil is affected by the magnetic shielding effect of materials around the coils. The magnetic shielding effect is dependent on the type, thickness, frequency, distance, shape of materials. Therefore, it is necessary to study the WPT system on the basis of these conditions. In this paper, the magnetic shield properties of the cooling system were analyzed using the High-Frequency Structure Simulation (HFSS, Ansys) program. We have used the shielding materials such as plastic, aluminum and iron, etc. As a result, when we applied the fiber reinforced polymer (FRP), the transmission efficiency of WPT was not affected because electromagnetic waves went through the FRP. On the other hand, in case of a iron and aluminum, transmission efficiency was decreased because of their electromagnetic shielding effect. Based on these results, the research to improve the transmission efficiency and reliability of WPT system is continuously necessary.

• International journal of advanced smart convergence
• /
• 제1권2호
• /
• pp.16-19
• /
• 2012

A modified 4-coil magnetic resonance wireless power transfer (MRWPT) system is proposed. Four coils based on 2-coil system with additional two matching coils were used in this topology. When Tx-Rx distance is changed, the input impedance is changed. However, it can be adjusted by coil parameters of matching coils to maintain impedance matching for maximum efficiency. The equivalent circuit of MRWPT system was analyzed for both transmission function and optimum coupling coefficient of the matching coils. By using four spiral resonant coils, these design considerations was experimentally verified. The measured data agreed well with the calculated data and the transmission function of the proposed system was more efficient than that of conventional 2-coil system.

• 한국정밀공학회지
• /
• 제31권6호
• /
• pp.527-534
• /
• 2014

The control system of human torso model and driving system of stethoscope for physical assessment trainer are developed. The detecting characteristics of circular pickup coil which is driven by square wave voltage signal with resonance frequency of LC circuits are investigated and it is confirmed that the pickup coil can detect the existence of chestpiece near the coil region. The control system of human torso model is composed of 8 channel pickup coils, Mp3 and Bluetooth module. The driving system of stethoscope is composed of chestpiece with contact switch and Bluetooth headset. The chestpiece detecting algorithm check the contact of chestpiece with human body model first and excite the pickup coil sequentially to find the location. The proposed system can be applied the physical assessment trainer.

• 대한자기공명의과학회:학술대회논문집
• /
• 대한자기공명의과학회 2003년도 제8차 학술대회 초록집
• /
• pp.74-74
• /
• 2003

목적： 피부표면에 가까운 고분해능 MR 영상을 얻기 위하여는 Surface RF Coil과 강력한 경사자계를 갖는 Gradient Coil이 필수적으로 요구된다. 본 연구에서는 High-Resolution MR Imaging을 위해 surface RF Coil과 Surface Gradient Coil을 제안하였다. Target Field Method를 사용하여 Gradient Coil의 전력 소모를 최소화하였으며 MR Microscopy가 가능한 50 mm∼100 mm의 해상도가 가능하도록 Coil을 설계하였다.

• Investigative Magnetic Resonance Imaging
• /
• 제25권4호
• /
• pp.229-251
• /
• 2021

Arteriosclerosis is the leading cause of stroke, with a fatality rate surpassing that of ischemic heart disease. High-resolution vessel wall magnetic resonance imaging is generally recognized as a non-invasive and panoramic method for the evaluation of arterial plaque; however, this method requires improved signal-to-noise ratio and scanning speed. Recent advances in high-density head and neck coil arrays are characterized by broad coverage, multiple channels, and closefitting designs. This review analyzes fast magnetic resonance imaging from the perspective of accelerated algorithms for vessel wall imaging and demonstrates the need for effective algorithms for signal acquisition using advanced radiofrequency system. We summarize different phased-array structures under various experimental objectives and equipment conditions, introduce current research results, and propose prospective research studies in the future.

• 대한자기공명의과학회:학술대회논문집
• /
• 대한자기공명의과학회 2001년도 제6차 학술대회 초록집
• /
• pp.177-177
• /
• 2001

목적： Head coil이나 Knee coil로 촬영하기에 부피가 작은 신체의 부위나 동물을 촬영하기 위하여 3T small birdcage coil을 개발하고 실험을 통해 코일의 효율성을 조사하였다. 대상 및 방법： 원통형 아크릴과 구리테이프를 사용하여 원통의 내경이 Knee coil보다 작은 8개의 elements를 가진 birdcage coil을 설계 제작하였고 팬톰, 지원자, 동물에 대한 MR 영상으로 그 가치를 평가하였다.

• 제어로봇시스템학회논문지
• /
• 제21권7호
• /
• pp.609-614
• /
• 2015

Implanted telemetry systems provide the ability to monitor different species of animals while they move within their cages. Species monitored include mice, rats, rabbits, dogs, pigs, primates, sheep, horses, cattle, and others. A miniature transmitter implanted in each animal measures one or more parameters. Parameters measured include arterial pressure, intra-pleural pressure, left ventricular pressure, intra-ocular pressure, bladder pressure, ECG, EMG, EEG, EOG, temperature, activity, and other parameters and transmits the data via radio frequency signals to a nearby receiver. Every conventional dedicated transmitter contains one or more sensors, cpu and battery. Due to the expected life of the battery, the measuring time is limited. To overcome these problems, electromagnetic inductive coupling based wireless power transmission technology using multiple transmit coils were proposed, with each coil having a different active area driven by the coil driver. In this research, a parallel resonance based coil driver and serial resonance based coil driver are proposed. From the experiments we see that the parallel coil driver shows better performance under a low impedance and multiple coils configuration. However, the serial coil driver is more efficient for high impedance transmit coils.