• Progress in Superconductivity and Cryogenics
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• v.19 no.1
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• pp.26-29
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• 2017

We studied the distribution of the current density and its magnetic-field dependence in GdBCO coated conductors with AC bias currents using low temperature scanning Hall probe microscopy. We selectively measured magnetic field profiles from AC signal obtained by Lock-in technique and calculated current distributions by inversion calculation. In order to confirm the AC measurement results, we applied DC current corresponding to RMS value of AC current and compared distribution of AC and DC transport current. We carried out the same measurements at various external DC magnetic fields, and investigated field dependence of AC current distribution. We notice that the AC current distribution unaffected by external magnetic fields and preserved their own path on the contrary to DC current.

• Journal of Korean Association for Spatial Structures
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• v.2 no.1 s.3
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• pp.93-102
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• 2002

Pressure loads caused by gas, water and wind are the most important load cases in structural analysis. Often the pressure loads are approximated by constant directional loads since it is difficult to evaluate the exact value. However, the pressure load is defined as a displacement dependent one and it is necessary to consider the follower effects of the load in analysis procedure. In this study, the large deformation analysis considering geometrical nonlinearity for shell structures under pressure loads is presented. Finite element by using a three-node flat triangular shell element is formulated and the follower effects of the pressure load are included in the formulation. Some of results are presented for cantilevered beam under uniform external pressure and thin circular ring under non-uniform external pressure. The present results are in good agreement with the results available in existing literature and commercial software ABAQUS.

• Economic and Environmental Geology
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• v.32 no.3
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• pp.273-280
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• 1999

In order to protect inhabitans' health and to collect data for prediction of the effcts from accidental emission of rasioactive materials from nuclear power plant, exposed dose rate be monitored within the limit dose rate. This research was carried out to investigate the accumulation of environmental radioactivity around Younggwang Nuclear Power Plant, and to infer and in infer and assay the additional exposed dose rate of inhabitants in Younggwang site from the operation of nuclear plant operation. External radiation dose rate, radiation environmental samples, and exposed dose rate of inhabitants in Younggwang site were investigated for estimaing environment activity in the vicinity of the nuclear power plant area. For the external radiation dose rate, the result showed that range of normal variation was found and any artificial radioisotope was not deteted in the analysis of environmental samples. Exposed dose rate of inhabitants was lower than 0.4% of the limit value of ICRP and it may be concluded that there was no effect on inhabitants and environment from the operation of nuclear power plant.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.546-551
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• 2009

In this paper, we studied insulation characteristics of LED lamps for load and street lighting. LED lamps can be divided into internal type and external type according to converter type. In this study, we analyzed technology standard, K(Electrical Appliances Safety Standards) and KS(Korean Industrial Standards) about insulation resistance for LED lamps for load and street lighting, and measured insulation resistances for each measured point. Mostly, insulation resistances were measured high more than regulation value but some measured points were measured badly. We expect that the results of these experiments would be helpful for electrical safety of LED lighting installation, manufacture, construction and maintenance.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.695-698
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• 1999

Passive noise reduction is a classical approach to attenuate industrial noise. But Active noise cancellation has several advantages over the passive noise cancellation. Such a system offers a better low frequency performance with a smaller and lighter system. This paper presents an active closed loop control system which consists of an controller for inverting and compensating the phase delay, an microphone for picking up the external noise, and loudspeaker for radiating the acoustic anti-phase signal to reduce external noise. The noise in the phase delay covered from 80$^{\circ}$ to 270$^{\circ}$ tends to be reduced. The degree of noise cancellation obtainable with this system reaches value about 17㏈.

• Journal of the Korea Construction Safety Engineering Association
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• s.49
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• pp.84-91
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• 2009

By bond mechanism between the prestressing strand and the concrete surrounding it, the effective force of prestressing must be transferred to the concrete entirely. The distance required to transfer the effective force of prestressing is called the transfer length, and the development length is the bond length required to anchor the strand as it resists external loads on the member. Transfer length was determined from the concrete strain profile at the level of the strands at transfer and development length was determined from various external loading lengths and compared with current code equation. Through the test results, bond failure is predicted based on the distress caused by cracks when they propagate within the transfer zone of prestressing strand. The current code equation was found to be conservative in comparison with the measured value.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.4
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• pp.14-20
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• 2004

In this work, a new control methodology to achieve accurate position control of an AC servo motor subjected to external disturbance is proposed. Unlike conventional sliding mode controller which requires a prior knowledge of the upper bound of external disturbance, the proposed technique, called sliding mode controller with disturbance estimator (SMCDE), can offer robust control performances without a prior knowledge of the disturbance bound. The SMCDE is featured by an integrated average value of the imposed disturbance over a certain sampling period. By doing this, undesirable chattering phenomenon in the estimation process can be effectively alleviated. The benefits of the proposed control methodology are empirically demonstrated on AC servo motor and control responses are evaluated through a comparative work between the proposed and conventional control schemes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.6 no.1
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• pp.12-18
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• 1969

The characteristics of microwave reflection in the media of cold gaseous plasma is analysed to various external magnetic flux density. The DC discharge plasma is generated in the rectangular waveguide which contains two electrodes and helium gas at the pressure of 10-2mm Hg. The reflected and transmitted power of microwave is measured when the electric field is parallel to, and perpendicular to the external magnetic field. It shows that the reflected power is increased as the magnetic flux density is increased in the parallel case, but the maximum value of the reflected power is occured at the cyclotron resonance (3120 Gauss) in the perpendicular case.

• Journal of electromagnetic engineering and science
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• v.1 no.1
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• pp.37-42
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• 2001

This paper presents the basic characteristics of a cutoff cavity-hacked slot antenna, for the application of spacetenna, with a feed post and a parasitic post inserted parallel to the slot. This type of antenna might effectively excite the slot and forcibly resonate the cavity by adding external reactance to the parasitic post. The Galerkin\`s method of moments is used to analyze integral equations for the unknown electric current on each post and electric field in the slot. The value of external reactance for forced resonance is discussed by deriving a determining equation, the current distribution on each post and the radiation patterns are considered. The analysis is in excellent agreement with the experiment for the radiation patterns.

• Journal of Ocean Engineering and Technology
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• v.2 no.1
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• pp.95-105
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• 1988

This paper describes the development of a reliability-based optimum design technique for such three dimensional tubular frames as off shore structures. The objective function is formulated for the structural weight. Constraints that probability of failure for the critical sections does not exceed the allowable probability of failure are set up. In the evaluation of the probability of failure, fatigue as well as buckling and plasticity failure are taken into account and the mean-value first-order second-moment method(MVFOSM) is applied for its calculation. In order to reduce the computing time required for the repeated structural analysis in the optimization process, reanalysis method is also applied. Application to two and three dimensional simple frame structures is performed. The influence of material properties, external forces, allowable failure probabilities and interaction between external forces on the optimum design is investigated.