• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.66 no.4
• /
• pp.200-205
• /
• 2017

In this paper, we propose a technique to determine the normal and arc of an alternating current using a mixed filter composed of an average filter and a band-pass filter and a frequency analysis. The proposed method uses the moving average filter of the FIR filter structure for noise removal and the band-pass filter of the IIR filter structure for detecting only specific frequency components after normalizing the measured current signal based on the maximum value. After performing Fast Fourier Transform (FFT) using the band-pass filtered signal, the total energy is calculated using the magnitude component of the frequency, and the arc is detected using the magnitude of the calculated energy. In order to show the validity of the proposed method, we experimented with various data and found that arc and steady state can be easily discriminated by calculating spectral energy. Therefore, it is considered that the proposed method can be applied to arc diagnosis of low voltage electric wire.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.19 no.2
• /
• pp.111-116
• /
• 2011

Three-dimensional finite element analyses have been performed to improve the durability of bulkhead. To keep pace with design changes and concentrate on regions of interest, SUBMODEL technique in ABAQUS was used for analysis. An analysis was conducted with following load cases: 1) Cap press-fit, 2) Bearing crush, 3) Bolt assembly, 4) Hot assembly, 5) Firing load, 6) Alternating firing load, 7) 2nd hot assembly. Fatigue analysis was done using commercial software FEMFAT and fatigue factors at the interested regions such as bolt tip area, counter bore, breathing hole, honing clearance were calculated and compared to aid design validation. Finite element modeling in the area of thread engagement used a simple constraint equations. Increasing bolt length, to a minimum of 39 mm above joint face gives a better fatigue resistance to the bulkhead. Breathing hole helps not only circulate the air in the crankcase but also fatigue resistance of bulkhead by relieving the stress at the critical locations.

• The Korean Journal of Ceramics
• /
• v.2 no.1
• /
• pp.1-10
• /
• 1996

Transparent conducting $SnO_2$-based thin films have been coated on float substrates such as fused quartz, and ceramic fiber cloths such as the Nexel and E-glass cloth from tin alkoxides by the sol-gel technique. Also, thin films of alternating layers of $SnO_2$ and $SiO_2$ have been fabricated by dip coating. The sheet resistance and average visible transmittance of the films were investigated in the aspect of the applications as transparent electrodes such as liquid crystal displays, photo-detectors and solar cells. The Nextel and E-glass cloths coated with antimony-doped tin oxide (ATO) had sheet resistance of as low as $20 \;ohm/{\Box}$ and $120ohm/\;{\Box}$, respectively. The promotion effects of additives as $La_2O_3$ and Pt on the ethanol gas sensing properties of the films were investigated in the aspects of the applications as an alcohol sensor and a breath alcohol checker. Possible evidence of quantum well effects in the oxide multilayers of $SnO_2$ and $SiO_2$ was investigated.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.1
• /
• pp.21-26
• /
• 2009

In order to determine the effective way of measuring the Mode I stress intensity factor($K_1$) by means of the alternating current potential drop(ACPD) technique for a material containing a two-dimensional surface crack, the change in magnetic flux in the air due to load was studied theoretically and experimentally. The magnetic flux in the air between crack surfaces is uniform and is not changed by increasing the load in the specimen and experimental results are the same as those obtained from theoretical analysis. Therefore, the change in potential drop due to load in the measuring system which was designed to induce a large amount of electro-motive force was caused by the change in internal inductance of material and the change in the mutual inductance concerned with internal inductance of material.

• Journal of Chest Surgery
• /
• v.31 no.7
• /
• pp.703-710
• /
• 1998

We treated 654 patients with simultaneous bilateral sympathectomy for essential hyperhidrosis from March 1989 to September 1997(354 males and 300 females). The exposure afforded by thoracoscopy is actually superior to that seen at the time of either thoracotomy or axillary thoracotomy. The use of single-lumen intubation with alternating partially collapsed lung by CO2 inflation resulted in shorter anesthesia, shorter operative time, and shorter hospitalization. 2-mm extended thoracoscopic T2-sympathectomy is not only a time-saving method but also a very simple and effective one in the treatment of hyperhidrosis by experienced surgeons. The modification on our technique of thoracoscopic sympathectomy as described allowed us to significantly improve our previous results. A majority of the patients were relieved, and over 95% were satisfied initially.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
• /
• v.26 no.1
• /
• pp.1-14
• /
• 1998

Various numerical methods for the two dimensional shallow water equations have been applied to the problems of flood routing, tidal circulation, storm surges, and atmospheric circulation. These methods are often based on the Alternating Direction Implicity(ADI) method. However, the ADI method results in inaccuracies for large time steps when dealing with a complex geometry or bathymetry. Since this method reduces the performance considerably, a fully implicit method developed by Wilders et al. (1998) is used to improve the accuracy for a large time step. Finite Difference Methods are defined on a rectangular grid. Two drawbacks of this type of grid are that grid refinement is not possibile locally and that the physical boundary is sometimes poorly represented by the numerical model boundary. Because of the second deficiency several purely numerical boundary effects can be involved. A boundary fitted curvilinear coordinate transformation is used to reduce these difficulties. It the curvilinear coordinate transformation is used to reduce these difficulties. If the coordinate transformation is orthogonal then the transformed shallow water equations are similar to the original equations. Therefore, an orthogonal coorinate transformation is used for defining coordinate system. A multigrid (MG) method is widely used to accelerate the convergence in the numerical methods. In this study, a technique using a MG method is proposed to reduce the computing time and to improve the accuracy for the orthogonal to reduce the computing time and to improve the accuracy for the orthogonal grid generation and the solutions of the shallow water equations.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.35 no.4
• /
• pp.258-267
• /
• 2015

Eddy current testing is widely used for inspecting steam generator tubing in nuclear power plants (NPPs). The inspection technique for steam generator tubing in NPPs should be qualified in accordance with examination guidelines. When the components of a qualified system such as eddy current tester, probe, and data analysis program, are changed, the equivalency of the modified system to the originally qualified system must be verified. The eddy current tester is the most important part of an eddy current testing system because it excites and transmits alternating currents to the probe, receives coil impedance of the probe and generates signals for anomalies. The Korea Hydro & Nuclear Power Co., Ltd. (KHNP) developed an eddy current testing system with an eddy current tester and data acquisition-analysis program for inspecting the steam generator tubing in NPPs; this system can be used for an array probe and as a bobbin and rotating probes. The equivalency assessment for the currently developed system was carried out, and we describe the results in this paper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.41-44
• /
• 1999

Displacement current was generated in the pressure stimulus and light stimulus. Solution of azobenzene molecules (8A5H) have to character trans-to-cis. Pressure stimulus generate in the pressure and current. light stimulus generate in the displasement current. The Maxwell displacement current measuring technique has been applied for the investigation of azobenzene organic thin films under alternating photoirradiation with ultraviolet(360nm) and visible (450nm) light. The displacement current was generated due to the trans-to-cis photoisomerization by irradiation with ultraviolet light(λ$_1$=360 nm) Whereas the displacement current was generated in the opposite direction due to the cis-to-trans photoisomerization by irradiation with visible light(λ$_2$=450nm). As result, To show twice reaction certainly phase transition in pressure. A first range generated from 24$\AA$$^2$ to 29$\AA$$^2$and second range generated from 20$\AA$$^2$to 24$\AA$$^2$. Also, cetainfy stimulus apper low pressure and high pressure in photoirradiation. To see different every moment phase transition.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.3
• /
• pp.866-872
• /
• 2014

The purpose of this paper was to find an effective method for measuring electromagnetic torque produced by a brushless DC motor with single-phase current sensing in real-time. A torque equation is derived from the theory of brushless DC motor. This equation is then validated experimentally with a motor dynamometer. A computer algorithm is also proposed to implement the electromagnetic torque estimation equation in real-time. Electromagnetic torque is a linear function of phase current. Estimating the electromagnetic torque in real-time using single-phase current is not appropriate with existing equations, however, because of the rectangular alternating-pulse nature of the excitation current. With some mathematical manipulation to the existing equations, the equation derived in this paper overcame this limitation. The equation developed is simple and so it is computationally efficient, and it takes only motor torque constant and single-phase current to evaluate the electromagnetic torque; no other parameters such as winding resistances, inductances are needed. The equation derived is limited to the three-phase brushless DC motor. It can, however, easily be extended to the multiphase brushless DC motor with the technique described in this paper.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.5
• /
• pp.1501-1510
• /
• 2014

Low voltage direct current (LVDC) distribution system is a suitable techno-economic candidate which can create an innovative solution for distribution network development with respect to rural electrification. This research focuses on the use of LVDC distribution system to replace some of KEPCO's existing traditional medium voltage alternating current (MVAC) distribution network for rural electrification in South Korea. Considering the technical and economic risks and benefits involved in such project, a comparative techno-economic analysis on the LVDC and the MVAC distribution networks is conducted using economic assessment method such as the net present value (NPV) on a discounted cash flow (DCF) basis as well as the sensitivity analysis technique. Each would play a role in an economic performance indicator and a measure of uncertainty and risk involved in the project. In this work, a simulation model and a computational tool are concurrently developed and employed to aid the techno-economic analysis, evaluation, and estimation of the various systems efficiency and/or performance.