• Investigative Magnetic Resonance Imaging
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• v.22 no.1
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• pp.26-36
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• 2018

Purpose: Children born with single ventricle physiology demonstrate poor growth rate and suffer from malnutrition, which lead to increased morbidity and mortality in this population. We assume that an anabolic steroid, oxandrolone, will promote growth in these infants by improving myocardial energy utilization. The purpose of this paper is to study the efficacy of oxandrolone on myocardial energy consumption in these infants. Materials and Methods: We modeled single ventricle physiology in a lamb by prenatally shunting the aorta to the pulmonary artery and then postnatally, we monitored cardiac energy utilization by quantitatively measuring the first order reaction rate constant, $k_f$ of the creatine-kinase reaction in the heart using magnetization transfer $^{31}P$ magnetic resonance spectroscopy, home built $^1H/^{31}P$ transmit/receive double tuned coil, and transmit/receive switch. We also performed cine MRI to study the structure and dynamic function of the myocardium and the left ventricular chamber. The spectroscopy data were processed using home-developed python software, while cine data were analyzed using Argus software. Results: We quantitatively measured both the first order reaction rate constant and ejection fraction in the control, shunted, and the oxandrolone-treated lambs. Both $k_f$ and ejection fraction were found to be more significantly reduced in the shunted lambs compared to the control lambs, and they are increased in oxandrolone-treated lambs. Conclusion: Some improvement was observed in both the first order reaction rate constant and ejection fraction for the lamb treated with oxandrolone in our preliminary study.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.222-225
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• 2001

The planar type inductors have a good potential for the application of miniaturized low power DC-DC converters. For those high quality application, the reduction of coil loss and also magnetic films which have good high frequency properties are required. Fabricated inductor was consisted of FeTaN/Ti magnetic film and electroplated Cu coil thickness of 100$\mu\textrm{m}$ and $SiO_2$ as a insulating layer. The inductor was designed double rectangular spiral shape for magnetic field highly confining within the device. The measured value of inductance and resistance were 980 nH and 1.7 $\Omega$ at 1 MHz as operating frequency of device. The Q factor is 3.55 at 1 MHz.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.407-410
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• 2002

As a part of electro-mechanical totally implantable artificial heart, a transcutaneous energy transmission system has been developed. By mutual magnetic induction between the first coil on the skin and the subcutaneously implanted second coil, the system transfers electrical power through the skin. This research aimed a minimizing the size of the implanted part as well as maximizing the transfer efficiency. When an air gap is 1$\sim$2cm, voltage gain and current gain low and it is hard to transfer energy due to large leakage flux. That is, the required input voltage and input current must be large compared with the output voltage and output current, respectively, This paper research the inverter topology and the control method in order to increase the voltage gain and the current gain. For this purpose, this inverter employs double tune to compensate the large leakage inductance of primary and secondary of the transcutaneous transformer. And the output energy of transcutaneous energy transmission system supply for Lithium-ion battery charger.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.123-125
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• 2003

We joined 19-multifilamentary (Bi, Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$_{x}$ Superconducting tapes and fabricated double-pancake coils by using resistive- and superconducting-joint methods. The joint resistance of the coils were characterized by the field decay technique and standard four-probe method. It was evaluated that joint resistance was 3.21$\times$10$^{-11}$ $\Omega$ in the superconducting-joint coil, which is approximately 4 orders of magnitude smaller than that in the resistive-joint coil (107$\times$10$^{-9}$ $\Omega$). The low value of joint resistance obtained by superconducting-joint is expected to be suitable for the practical applications in the persistent current mode.e.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.98-106
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• 1998

This paper shows the temperature distribution of double hull compartment and of cofferdam in a large LNG Carrier. In LNG Carrier, due to the lower cargo temperature($-163^{\circ}C$), structures are forced to lose their strength if additional heat is not supplied. So it is very important to estimate the temperature distribution and the heat flux needed to maintain the structure properly. The temperature of each compartment is obtained using 2-dimensional model analysis and compared with 3-dimensional results. And also this paper gives preliminary estimation of pipe length to supply necessary heat flux in bare pipe and finned pipe.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.233-234
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• 2007

We investigated the quench characteristics in integrated three-phase flux-lock type superconducting fault current limiter (SFCL), which consisted of three-phase flux-lock reactor wound on one iron core with the same turn's ratio between coil 1 and coil 2 for each single phase. To study the quench characteristics of the SFCL, the experiments was performed on various fault type such as the single line-to-ground fault, the double line-to-ground fault, the triple line-to-ground fault. From the experimental results, the generated point of element resistances was different on various fault type.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.39-40
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• 2007

The analysis of fault current limiting characteristics according to variation of fault current level in the integrated three-phase flux-lock type superconducting fault current limiter (SFCL), which consisted of three-phase flux-lock reactor wound on an iron core with the same turn's ratio between coil 1 and coil 2 for each single phase, was performed. To analyze the current limiting characteristics of this integrated three-phase flux-lock type SFCL, the short circuit experiments was carried out the various three-phase faults such as the single line-to-ground fault, the double line-to-ground fault, the triple line-to-ground fault. From the experimental results, the fault current limiting characteristic was improved according to increase of fault current level.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1491-1496
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• 2009

This paper presents an digital based input/output interface circuit for controlling and monitoring the Diesel Engine Generator for emergency. In order to monitor and control of the Emergency Diesel Engine Generator, controlling and monitoring circuits need 5 analog input channels, 2 pick-up coil measuring circuits, 10 digital input channels containing Broken Wire Detect function, and 7 relay control signal output channels. This system performs signal processing of input signal taking advantage of simple filter circuit, photo-coupler and comparator circuit at analog input parts, and output signals for main relay is designed acting by double control, so it prevents malfunction completely. And it improves accuracy of speed input signal by applying digital circuit that processes rick-up coil signal.

• Journal of Korean Neurosurgical Society
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• v.60 no.2
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• pp.262-268
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• 2017

Objective : Stents are widely used in coil embolization of intracranial aneurysms, but on occasion, a microcatheter must traverse a stented segment of artery (so-called trans-cell technique) to select an aneurysm, or double stenting may necessary. In such situations, microguidewire passage and microcatheter delivery through a tortuous stented parent artery may pose a technical challenge. Described herein is a microguidewire looping technique to facilitate endovascular navigation in these circumstances. Methods : To apply this technique, the microguidewire tip is looped before entering the stented parent artery and then advanced distally past the stented segment, with the loop intact. Rounding of the tip prevents interference from stent struts during passage. A microcatheter is subsequently passed into the stented artery for positioning near the neck of aneurysm, with microguidewire assistance. The aneurysm is then selected, steering the microcatheter tip (via inner microguidewire) into the dome. Results : This technique proved successful during coil embolization of nine saccular intracranial aneurysms (internal carotid artery [ICA], 6; middle cerebral artery, 2; basilar tip, 1), performing eight trans-cell deliveries and one additional stenting. Selective endovascular embolization was enabled in all patients, resulting in excellent clinical and radiologic outcomes, with no morbidity or mortality directly attributable to microguidewire looping. Conclusion : Microguidewire looping is a reasonable alternative if passage through a stented artery is not feasible by traditional means, especially at paraclinoid ICA sites.

• Progress in Superconductivity
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• v.13 no.1
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• pp.1-6
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• 2011

Measurement of magnetic signals generated from electric activity of myocardium provides useful information for the functional diagnosis of heart diseases. Key technical component of the magnetocardiography (MCG) technology is SQUID. To measure MCG signals with high signal-to-noise ratio, sensitive SQUID magnetic field sensors are needed. Present magnetic field sensors based on Nb SQUIDs have field sensitivity good enough to measure most of MCG signals. However, for accurate measurement of fine signal pattern or detection of local atrial fibrillation signals, we may need higher field sensitivity. In addition to field sensitivity, economic aspect of the SQUID system is also important. To simplify the SQUID readout electronics, the output voltage or flux-to-voltage transfer of SQUID should be large enough so that direct measurement of SQUID output can be done using room-temperature preamplifiers. Double relaxation oscillation SQUID (DROS), having about 10 times larger flux-to-voltage transfers than those of DC-SQUIDs, was shown to be a good choice to make the electronics compact. For effective cancellation of external noise inside a thin economic shielded room, first-order axial gradiometer with high balance, simple structure and long-baseline is needed. We developed a technology to make the axial gradiometer compact using direct bonding of superconductive wires between pickup coil and input coil. Conventional insert has mechanical support to hold the gradiometer array, and the dewar neck has equal diameter with the dewar bottom. Boiling of the liquid He can generate mechanical vibrations in the gradiometer array due to mechanical connection structure. Elimination of the mechanical support, and direct mounting of the gradiometer array into the dewar bottom can reduce the dewar neck diameter, resulting in the reduction of liquid He consumption.