• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.7
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• pp.945-949
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• 2014

In cardiac magnetic resonance imaging (CMRI), heart and respiratory motions are one of main obstacles in obtaining diagnostic quality of images. To synchronize CMRI to the physiological motions, ECG and respiratory gatings are commonly used. In this paper multi-biological signal (ECG, respiratory, and SPO2) based smart trigger system is proposed. By using multi-biological signal, the proposed system is robust to the induced noise such as eddy current when gradient pulsing is continuously applied during the examination. Digital conversion of the multi-biological signal makes the system flexible in implementing smart and intelligent algorithm to detect cardiac and respiratory motion and to reject arrhythmia of the heart. The digital data is used for real-time trigger, as well as signal display, and data storage which may be used for retrospective signal processing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.671-674
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• 2004

This paper presents design and analysis of multi-layered ring-dot type piezoelectric transformer. These transformers are useful for step up and step down. The transformers consist of disk type multi-layered piezoelectric ceramic plates. The finite element method(FEM) was used for analysis transformer. Vibration mode, electric field and equivalent elastic strain of piezoelectric transformer were simulated by changing frequency. As results, the strain was distributed in isolation part entirely. We can get the operated in step up transformer when the inner side electrode using by input parts. Also we can get the step down transformers using by input Part as outer side electrode. The step up ratio and step down ratio was increased by decreasing inner side electrode. The resonance frequency was increased by increasing inner side electrode when the transformer was operated in step down transformer. But the step up one was decreased. From these results, we can expect to multi-layered ring-dot type piezo transformers as step up and step down transformers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4776-4783
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• 2014

Many studies have examined the reduction of primary noise sources, but quality-related noise, such as BSR, is rarely studied. This study describes the quantitative BSR test method using a multi-axial simulator. The sine sweep test was conducted to detect the system resonance and its relation to BSR noise with high frequency. This method is applied to the seat frame with/without the vibration durability test. The results showed that the $1^{st}$ lateral resonance leads to higher BSR frequency noise. In addition, the reduction of the lateral mode system stiffness after the durability test results in a decrease in the BSR noise in sine sweep test mode.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.12
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• pp.1064-1071
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• 2015

In this paper, the electrical characteristics of interdigital capacitor with single-layer and multi-layer graphene were compared and analyzed in the microwave region. In equivalent circuit, a capacitor coupled with graphene showed the clear difference in electrical components such as resistance, inductance, and capacitance. In particular, for the capacitor with single-layer graphene, additional inductance and resistance occurred and the electrode resistance was also increased. Meanwhile, the self-resonance frequency of capacitor was shifted toward lower frequency region and its transmitted characteristic was considerably improved at frequency ranging from 0.4 to 4 GHz. The electrical characteristics of the capacitor with multi-layer graphene were somewhat different than the bare capacitor. In conclusion, we could confirm that single-layer graphene greatly influenced the electrical characteristics and performances of interdigital capacitor compared to multi-layer graphene.

• Journal of Korea Multimedia Society
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• v.20 no.7
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• pp.1024-1029
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• 2017

A novel analytic solution has been derived for the bird-cage receiver coil of a magnetic resonance imaging (MRI) system, which is widely used in 3-dimensional medical imaging, by transforming the coil into an equivalent circuit model by using a transmission matrix-based circuit analysis. The bird-cage coil composed of N legs is divided into a cell for which input impedance is to be analyzed and the remaining N-1 cells, and then a transmission matrix corresponding to the N-1 cells is converted into a circuit to transform the 3-dimensional bird-cage coil into the 2-dimensional equivalent circuit model, which is suitable to derive the analytic solution for the input impedance. The proposed method derives directly the analytic solution for the input impedance at an arbitrary point of the coil unlike the conventional analytic solution of a bird-cage coil, so that it can be used not only for resonance frequency calculations but also for various coil characteristics analyses. Since the analytic solution agreed well with the results of computational simulations, it can be useful for the impedance matching of a coil and the analysis and the design of a multi-tune bird-cage coil.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1694-1706
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• 2017

Models and experiments for magnetic resonance coupling wireless power transmission (MRC-WPT) topologies such as the chain topology and branch topology are studied in this paper. Coupling mode theory based energy resonance models are built for the two topologies. Complete energy resonance models including input items, loss coefficients, and coupling coefficients are built for the two topologies. The storage and the oscillation model of the resonant energy are built in the time domain. The effect of the excitation item, loss item, and coupling coefficients on MRC systems are provided in detail. By solving the energy oscillation time domain model, distance enhancing models are established for the chain topology, and energy relocating models are established for the branch topology. Under the assumption that there are no couplings between every other coil or between loads, the maximum transmission capacity conditions are found for the chain topology, and energy distribution models are established for the branch topology. A MRC-WPT experiment was carried out for the verification of the above model. The maximum transmission distance enhancement condition for the chain topology, and the energy allocation model for the branch topology were verified by experiments.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.531-540
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• 2020

The whirl and generated forces of rotating cylinders with different diameters placed in still water and in flow are studied experimentally. For the rotating cylinders in still water, the Same Frequency Whirl (SFW) and Different Frequency Whirl (DFW) have been identified and illustrated. The corresponding SFW and DFW areas are divided. The Root Mean Square (RMS) values of the generated force coefficient dramatically increase in the defined ranges of Resonance I and Resonance II. For the rotating cylinders in flow, the hydrodynamics, SFW and DFW are illustrated. The hydrodynamic, SFW and DFW areas are divided. The RMS values of the generated forces in the range of Resonance II are much smaller than those in still water due to the generated lift forces. The discussion suggests that the frequency of the DFW may equal multiple times or one-multiple times that of the rotating frequency: the whirl direction of the DFW with multiple times the frequency of the rotating frequency is the same as the rotating direction. The whirl direction of the DFW with one-multiple times frequency of the rotating frequency is opposite to the rotating direction.

• The Korean Journal of Applied Statistics
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• v.34 no.2
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• pp.127-139
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• 2021

Independent Component Analysis is a popular statistical method to separate independent signals from the mixed data, and Group Independent Component Analysis is an its multi-subject extension of Independent Component Analysis. It has been applied Functional Magnetic Resonance Imaging data and provides promising results. However, classical Group Independent Component Analysis works poorly when outliers exist on data which is frequently occurred in Magnetic Resonance Imaging scanning. In this study, we propose a robust version of the Group Independent Component Analysis based on ROBPCA. Through the numerical studies, we compare proposed method to the conventional method, and verify the robustness of the proposed method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.123-128
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• 2022

Applying rigorous modal transmission-line theory (MTLT), the properties of resonant diffraction gratings under conical light incidence is investigated. The mode vectors pertinent to resonant diffraction under conical mounting vary less with incident angle than those associated with diffraction gratings in classical mounting. Furthermore, as the evanescent diffracted waves drive the leaky modes responsible for the resonance effects, the conical mounting imbues diffraction gratings with larger angular tolerance than their classical counterparts. Based on these concepts, the angular-spectral and wavelength-spectral performance of resonant diffraction gratings in conical and classical mounts by numerical calculations with spectra found for conical incidence are quantified. These results will be useful in various applications demanding resonant diffraction gratings that are efficient and physically sparse.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.429-435
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• 2015

The purpose of this study was to prospectively estimate the effectiveness of multi-transmit parallel technique in reduced FOV(Field of View) less than 26 cm. Homogeneity, SNR(signal to noise ratio) and acquisition time were measured and compared by setting FOV less than 26cm on the T1 and T2 weighted images using ACR phantom. The multi-transmit parallel technique resulted in significantly faster image acquisition by 46.8 % in T1 weighted images and 18.9% in T2 weighted images. The homogeneity and SNR values had no significant difference between pre and post application of the multi-transmit parallel technique. In conclusion, this study demonstrates the feasibility of multi-transmit parallel technique in FOV less than 26cm with a rapid acquisition and maintained image quality.