• Progress in Superconductivity and Cryogenics
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• v.16 no.1
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• pp.1-5
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• 2014

We calculated the resonance tunneling energy band in the BCS gap for Type-II superconductor in which periodic potential is generated by external magnetic flux. In this model, penetrating magnetic flux was assumed to be in a fixed lattice state which is not moving by an external force. We observed the existence of two subbands when we used the same parameters as for the $Nd_{1.85}Ce_{0.15}CuO_X$ thin film experiment. The voltages at which the regions of negative differential resistivity (NDR) started after the resonant tunneling ended were in a good agreement with the experimental data in the field region of 1 T - 2.2 T, but not in the high field regions. Discrepancy occurred in the high field region is considered to be caused by that the potential barrier could not be maintained because the current induced by resonant tunneling exceeds the superconducting critical current. In order to have better agreement in the low field region, more concrete designing of the potential rather than a simple square well used in the calculation might be needed. Based on this result, we can predict an occurrence of the electromagnetic radiation of as much difference of energy caused by the 2nd order resonant tunneling in which electrons transit from the 2nd band to the 1st band in the potential wells.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.5
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• pp.481-487
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• 2013

This paper presents an FIR (Finite Impulse Response) fixed-interval smoothing filter for fast and exact estimating state variables of a discrete nonlinear system with modeling uncertainty. Conventional IIR (Infinite Impulse Response) filter and smoothing filter can estimate state variables of a system with an exact model when the system is observable. When there is an uncertainty in the system model, however, conventional IIR filter and smoothing filter may cause large errors because the filters cannot estimate the state variables corresponding to the uncertain model exactly. To solve this problem, FIR filters that have fast estimation properties and have robustness to the modeling uncertainty have been developed. However, there is time-delay estimation phenomenon in the FIR filter. The FIR smoothing filter proposed in this paper makes up for the drawbacks of the IIR filter, IIR smoothing filter, and FIR filter. Therefore, the FIR smoothing filter has good estimation performance irrespective of modeling uncertainty. The proposed FIR smoothing filter is applied to the integrated navigation system composed of a magnetic compass based DR (Dead Reckoning) and a GPS (Global Positioning System) receiver. Even when the magnetic compass error that changes largely as the surrounding magnetic field is modeled as a random constant, it is shown that the FIR smoothing filter can estimate the varying magnetic compass error fast and exactly with simulation results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.480-480
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• 2008

Vacuum circuit breaker(VCB) is now emerging as an alternative of gas circuit breaker(GCB) which uses SF6 gas as insulating material whose dielectric strength is outstanding. But we have to reduce SF6 gas because SF6 gas is one of greenhouse gas and efforts to reduce greenhouse gas are now trend of the world. Therefore, we can say VCB is the optimal alternative of GCB because vacuum is environmentally friendly. The vacuum interrupter is the core part of VCB to interrupt arcing current. There are mainly two methods to extinguish arc. One is radial magnetic field (RMF) method and the other is axial magnetic field (AMF) method. We deals with RMF method in this paper. Compared with AMP, RMF arc quenching method has different principle to extinguish arc. In case of RMF method, pinch effect is much larger than AMF method. Because of pinch effect RMF type contact electrodes have the single large spot which is severly damaged and melted while AMF type contact electrodes have small and multiple spots which are slightly damaged and melted. To prevent contact electrode being damaged and melted from high temperature-arc, RMF method uses Lorentz force to move arc. In this paper we calculated and compared the arc driving force of two cases and we analyzed the force acting on each part of arc by means of commercial finite element method software Maxwell 3D. They have 3petals and we considered two cases. One is the case when fixed(upper) and movable(lower) contacts are in mirror arrangement (Case 1). The other is the case when one of two contacts (movable contact) is revolved at maximum angle as possible as it can be (Case 2). And at each case above, we analyzed arc driving force at two positions, position 1 is the closest to the center of contact and position 2 is near the edge of petal on fixed contact. As a result we could find that Case 2 generated stronger arc driving force than Case 1 at position 1. But at position 2 Case 1 generated stronger arc driving force than Case 2. This simulation method can contribute to optimizing spiral-type electrode designs in a view of arc driving force.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.600-605
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• 2011

This paper shows field test and evaluation results for a wireless vehicle detector with anisotropic magneto-resistive (AMR) sensors. The detector consists of two AMR sensors and mechanical and electronic apparatuses. The AMR sensor senses disturbance of the earth magnetic field caused by a vehicle moving over the sensor and then produces an output indicative of the moving vehicle. In this paper, vehicle speeds are calculated by using two AMR sensors fixed on a board, with constant distance. To test and evaluate the accuracy of the detector in real traffic situations, the detector was installed on a local highway and vehicle speeds and volumes were measured both in a free running and a highly congested traffic. The measurements from the detector are compared with the reference measurements obtained from a traffic camera with the Mean Absolute Percentage Errors (MAPE), which has proved the usefulness of the detector in the field.

• Journal of Sensor Science and Technology
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• v.10 no.5
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• pp.292-303
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• 2001

This work reports the tunneling effects of the lateral field emitters. Tunneling effect is applicable to the VMFS(vacuum magnetic field sensors). VMFS uses the fact that the trajectory of the emitted electrons are curved by the magnetic field due to Lorentz force. Polysilicon was used as field emitters and anode materials. Thickness of the emitter and the anode were $2\;{\mu}m$, respectively. PSG(phospho-silicate-glass) was used as a sacrificial layer and it was etched by HF at a releasing step. Cantilevers were doped with $POCl_3(10^{20}cm^{-3})$. $2{\mu}m$-thick cantilevers were fabricated onto PSG($2{\mu}m$-thick). Sublimation drying method was used at releasing step to avoid stiction. Then, device was vacuum sealed. Device was fixed to a sodalime-glass #1 with silver paste and it was wire bonded. Glass #1 has a predefined hole and a sputtered silicon-film at backside. The front-side of the device was sealed with sodalime-glass #2 using the glass frit. After getter insertion via the hole, backside of the glass #1 was bonded electrostatically with the sodalime-glass #3 at $10^{-6}\;torr$. After sealing, getter was activated. Sealing was successful to operate the tunneling device. The packaged VMFS showed very small reduced emission current compared with the chamber test prior to sealing. The emission currents were changed when the magnetic field was induced. The sensitivity of the device was about 3%/T at about 1 Tesla magnetic field.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.73-77
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• 2005

Motivated by the enhanced magnetic properties of Mg-codoped GaMnN ferromagnetic semiconductors, Be-codoped GaMnAs films were grown via molecular beam epitaxy with varying Mn flux at a fixed Be flux. The structural, electrical, and magnetic properties were investigated. GaAs:(Mn,Be) films showed metallic behavior while GaAs:Mn films showed semiconducting behavior as determined by the temperature dependent resistivity measurements. The Hall-effect measurements with varying magnetic field showed clear anomalous Hall effect up to room temperature proving ferromagnetism and magnetotransport in the GaAs:(Mn,Be) films. Planar Hall resistance measurement also confirmed the properties. The dramatic enhancement of the Curie temperature in GaMnAs system was attributed to Be codoping in the GaMnAs films as well as MnAs precipitation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.28-36
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• 2020

As many types of magnetic sensors are widely applied in various industries, the analysis and processing of magnetic sensor data need to be accurate. On the other hand, owing to the complexity of the magnetic field line caused by a moving magnet, the magnetic data generated by magnetic sensors are unpredictably nonlinear. Many industry systems using magnetic sensors have struggled with the nonlinear nature of magnetic sensor data. To reduce the effect of the nonlinearity, they have the target objects fixed firmly. Therefore, to collect accurate and reliable data, considerable efforts have been made to resolve the issues with the expensive tools and systems required. Through this paper, to tackle the issues, the data analysis and methodologies, including intelligent algorithms, are presented for the wrist rehabilitation system using magnetic sensors while being implemented without using expensive tools or systems. On processing magnetic sensor data, this paper adopted an intelligent algorithm, fuzzy logic, and compared the performance of other algorithms for comparison.

• Journal of the Korean Institute of Navigation
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• v.13 no.3
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• pp.1-20
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• 1989

In order to provide a basic information to locate the sensor of remote-indicating magnetic compass onboard, an empirical model for the over-all ship's magnetism was developed based on the periodicity of the observed magnetic field around the vessels. The values of model parameters were determined by least-square method and optimum numbers of them were fixed using Akaike's information criterion theory, and also an approximation method to determine parameter was proposed based on the symmetrical characteristic of observed data versus ship's length. The confidence level of the newly developed models was tested by analysis of variance method. The agreement between the modelled and real values was found to be remarkably accurate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1873-1876
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• 2003

Magneto-rheological polishing is a new technology used in precision polishing. It utilizes magneto-rheological fluid. nonmagnetic polishing abrasive, aqueous carrier fluids in magnetic field to remove material from a part surface. Silicon micro channel as work piece is fixed in the slurry which is made of MR fluid and CeO$_2$(10 vol%) abrasive particles. And permanent magnet rotate in the slurry to transfers magnetic force to abrasive particles by increasing yield strength of MR fluid. so, the obtained bottom surface roughness of micro channel by experiment reduced to Ra 0.010 $\mu\textrm{m}$ Rmax 0.103 $\mu\textrm{m}$ and finwall surface roughness of micro channel reduced to Ra 0.018 $\mu\textrm{m}$ Rmax 0.468 $\mu\textrm{m}$. At optimum conditions of variables, the workpiece as silicon micro channel have about 24 times smaller surface roughness than before polishing.

• Journal of Magnetics
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• v.3 no.3
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• pp.92-95
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• 1998

In this paper we report the low and high angle diffraction results, and the magnetic and magnetroesistive characteristics of the spin valve multilayer structure prepared by the sputter machine Emerald II in the Balzers Laboratory. The investigated system consists of a ferromagnetic free layer (7 nm NiFe) and a ferromagnetic pinned layer (7 nm NiFe), separated from each other by a nonmagnetic (2.1 nm Cu) spacer. The NiFe pinned layer is fixed by the exchange coupling with an antiferromagnetic layer (10 nm FeMn). For such system the magnetoresistance ratio ΔR/R=3.58%, the interlayer exchange coupling $H_c=6.4$ Oe and the field sensitivity 1.15%/Oe were otained.