• Progress in Superconductivity and Cryogenics
• /
• v.25 no.3
• /
• pp.34-37
• /
• 2023

The practical application of REBCO coated conductor (CC) tapes, vital for energy transmission (e.g., cable application) and high-field magnets (e.g., coil application), necessitates efficient and simple quality assessment procedures. This study introduces a systematic approach to assess the electromechanical properties of REBCO CC tapes under 77 K and self-field conditions. The approach involves customized tensile and bending tests that clarify the critical current (I_c) response of the CC tapes under mechanical loads induced by tension and bending. This study measures the retained Ic values of commercially available GdBCO CC tapes under 250 MPa tensile stress and 40 mm bending diameter. Through experimentation, the study demonstrates the resilience of these tapes and their suitability for applications. By presenting a simplified stress-based analysis and a bending test of the tapes, the study contributes to effective quality assessment methods for the development of practical superconducting products.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.5
• /
• pp.521-524
• /
• 2015

This letter presents a selective wireless power transfer architecture using a reconfigurable multi-port amplifier. The proposed wireless power transfer architecture is composed of a phase shifter part controlled by FPGA, two class-E power amplifiers, a four-port power combiner and two coil loads. Depending on the phase control of FPGA, the power ratio of outputs at the two coil loads becomes 1:1, 2:0 and 0:2. The manufactured system has delivered 1W DC power to loads at 125 kHz. The total DC-to-DC conversion efficiency shows more than 40 % including PA efficiency of 79 %.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.6
• /
• pp.821-826
• /
• 2013

When the values of design variables change, mode switching can often occur. If the mode of interest is not tracked, the frequencies and modes for design optimization may be miscalculated owing to modes that differ from the intended ones. Thus, mode tracking must be employed to identify the frequencies and modes of interest whenever the values of design variables change during optimization. Furthermore, reliability-based design optimization (RBDO) must be performed for design problems with design variables containing uncertainty. In this research, we perform RBDO considering the mode tracking of a compressive coil spring, i.e., a component of the joint spring that supports a compressor, with design variables containing uncertainty by using only kriging metamodels based on multiple responses approach (MRA) without existing mode tracking methods. The reliability analyses for RBDO are employed using kriging metamodel-based Monte Carlo simulation.

• Progress in Superconductivity
• /
• v.13 no.1
• /
• pp.18-23
• /
• 2011

We developed a four-channel first order gradiometer system to measure magnetoencephalogram for mice. We used double relaxation oscillation SQUID (DROS). The diameter of the pickup coil is 4 mm and the distance between the coils is 5 mm. Coil distance was designed to have good spatial resolution for a small mouse brain. We evaluated the current dipole localization confidence region for a mouse brain, using the spherical conductor model. The white noise of the measurement system was about 30 fT/$Hz^{1/2}$/cm when measured in a magnetically shielded room. We measured magnetic signal from a phantom having the same size of a mouse brain, which was filled with 0.9% saline solution. The results suggest that the developed system has a feasibility to study the functions of brain of small animals.

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

• Nuclear Engineering and Technology
• /
• v.52 no.12
• /
• pp.2699-2708
• /
• 2020

Helical-coil steam generator (HCSG) technology is a major design candidate for small modular reactors due to its compactness and capability to produce superheated steam with high generation efficiency. In this paper, we investigate the feasibility of the passively autonomous power maneuvering by coupling the 3-D transient multi-physics of a soluble-boron-free (SBF) core with a time-dependent HCSG model. The predictor corrector quasi-static method was used to reduce the cost of the transient 3-D neutronic solution. In the numerical system simulations, the feedwater flow rate to the secondary of the HCSGs is adjusted to extract the demanded power from the primary loop. This varies the coolant temperature at the inlet of the SBF core, which governs the passively autonomous power maneuvering due to the strongly negative coolant reactivity feedback. Here, we simulate a 100-50-100 load-follow operation with a 5%/minute power ramping speed to investigate the feasibility of the passively autonomous load-follow in a 450 MW_th SBF PWR. In addition, the passively autonomous frequency control operation is investigated. The various system models are coupled, and they are solved by an in-house Fortran-95 code. The results of this work demonstrate constant steam temperature in the secondary side and limited variation of the primary coolant temperature. Meanwhile, the variations of the core axial shape index and the core power peaking are sufficiently small.

• Journal of the Optical Society of Korea
• /
• v.2 no.2
• /
• pp.74-79
• /
• 1998

The use of a fiber Fabry-Perot interferometer (FFPI) as an optical current transducer is demonstrated. A conventional inductive pickup coil converts the time-varying current I(t) being measured to a voltage waveform V(t) applied across a piezeolectric strip to which the FFPI is bonded. The strip experiences a longitudinal expansion and contraction, resulting in an optical phase shift ${\phi}(t)$ in the fiber proportional to V(t). This phase shift is measured using a frequency-modulated semiconductor light source, photodiodes to monitor the reflected light from the FFPI and the laser power, and a digital signal processor. Calibration routines compute V(t) and I(t) from the measured phase shift at a l KHz rate. Response to 60 Hz ac over the design range 0-1300A rms is characterized Transient response of the FFPI transducer is also measured.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.30 no.4
• /
• pp.59-68
• /
• 1998

This study was to investigate the effect of chitosan molecular weight, its charge density, and its surface coating treatment on the antibacterial properties of paper. For this study, E.coil was used for antibacterial experiment. Results obtained were as follows : 1. The antibacterial properties of chitosan was significant on the surface-treated sheet. 2. Antibacterial property surface treatment was appeared to be effective when film was formed on the paper surface. 3. The antibacterial properties of chitosan-treated paper was dependent on the amount and the molecular weight of chitosan used. The lower the molecular weight of the chitosan down to 30,000 the better the antibacterial properties in this experiment. 4. Determination of the degree of chitosan-deacetylation by colloidal titration method was consistent with the more complicated and conventional FT-IR method.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.12
• /
• pp.40-45
• /
• 1999

Electrical damages to critical parts in rotation machinery have caused may machinery failures and hours of costly downtime. The problem of shaft currents generated in non-electrical machines have puzzled both users and manufacturers of these machines. The main solution for preventing electro- magnetic type damage is to demagnetize all of the machinery parts, however this is costly and time consuming. Therefore a thorough investigation into the causes and physical characteristics of electro- magnetic shaft currents is needed. In this paper, the self excitation theory was developed for a simple model, and axial flux Faraday disk machine surrounded by a long solenoid. Experimental tests were conducted to investigate the physical characteristics on an electromagnetic self excitation rig. The theory showed that the directions of both the shaft rotation and the coil turns should e identical if self excitation is to occur. From the tests, the electromagnetic type shaft current had both AC and DC components occurred at all vibration frequencies. This could point to the way to detect small instabilities or natural frequency locations by monitoring shaft currents.

• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.573-576
• /
• 1992

This paper presents a method, which couples the boundary integral terms in the thin magnetic materials with standard FEM used to analyze the rest of it, for analyzing the magnetic fields. The proposed method retains the sparsity and symmetry of the final system matrix, the merits of standard FEM and eliminates the need for fininte elements in the thin magnetic materials, thereby reducing necessary capacity of computer memory and computing time. To verify the usefulness of the proposed alogorithmn, an examples, coil with source currents and thin magnetic materials, is chosen and analyzed. the results are compared with those of the standard FEM by coarse mesh and the proposed method, using standard FEM by fine mesh as a reference.