• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.52-54
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• 2005

In this paper, a new approach monitoring rotor vibrations in a squirrel-cage induction motor is proposed. The air-gap flux variation analysis was done using search coils inserted in stator slots when rotor vibration conditions occur. An accurate modelling and analysis of air-gap flux variation in the induction motor are developed using finite-element(FE) software packages, and measuring the flux are made using search coils. In the FE analysis, the three-phase squirrel-gage induction motor with 380 (V), 5 (HP), 4 Poles, 1,742 [rpm] ratings is used. The results of FE analysis can be useful for on-line vibration monitoring of the induction motors.

• Structural Engineering and Mechanics
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• v.55 no.1
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• pp.79-92
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• 2015

In this study, free vibration analyses of symmetric laminated cantilever and simply supported damaged composite beams are investigated by using finite element method (FEM). Free vibration responses of damaged beams are examined using Euler Bernoulli beam and classical lamination theories. A computer code is developed by using MATLAB software to determine the natural frequencies of a damaged beam. The local damage zone is assumed to be on the surface lamina of the beam by broken fibers after impact. The damaged zone is modeled as a unidirectional discontinuous lamina with $0^{\circ}$ orientations in this study. Fiber volume fraction ($v_f$), fiber aspect ratio ($L_f/d_f$), damage length ($L_D$) and its location (${\lambda}/L$), fiber orientation and stacking sequence parameters effects on natural frequencies are investigated. These parameters are affected the natural frequency values significantly.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.61-66
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• 2011

The purpose of this paper is to design a hydraulic actuator to operate under high pressure conditions. The flow characteristics under design conditions of hydraulic actuator were numerically conducted by commercial fluid dynamic code(ANSYS CFX V11). The numerical analysis was performed by transient technique according to the variation of stroke times, which was changed from 0 to 1 second by interval of 0.01. Turbulence model, $k-\omega$ SST was selected to secure more accurate prediction of hydraulic oil flow. The ICEM-CFD 11 and CFXMesher, reliable grid generation software was also adapted to secure high quality grid necessary for the reliable analysis. According to the simulation results, the flow rate which was supplied to the hydraulic actuator was 30.4l/min. These results are in good agreement with design results within 3.5% error.

• Current Optics and Photonics
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• v.2 no.3
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• pp.215-220
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• 2018

A novel porous-core hexagonal lattice photonic crystal fiber (PCF) is designed and analyzed for efficient terahertz (THz) wave propagation. The finite element method based Comsol v4.2 software is used for numerical analysis of the proposed fiber. A perfectly matched layer boundary condition is used to characterize the guiding properties. Rectangular air-holes are used inside the core to introduce asymmetry for attaining high birefringence. By intentionally rotating the rectangular air holes of porous core structure, an ultrahigh birefringence of 0.045 and low effective material loss of $0.086cm^{-1}$ can be obtained at the operating frequency of 0.85 THz. Moreover, single-mode properties, power fraction in air core and confinement loss of the proposed PCF are also analyzed. This is expected to be useful for wideband imaging and telecom applications.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.27-28
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• 2007

In this paper, the Wireless Sensor Network (WSN) based on ZigBee technology was devised and developed. Wireless communication was applied to petrochemical domain, like other industries. And sensor network of IEEE 802.15.4 protocol stack diagram was described. Then, by analyzing the protocol, the software systems included the communication Protocol and point-to-point network were implemented with Freescale Semiconductor's product MC13192-SARD DSK board. After that, the performance of this design system was evaluated, and finally, by using PC Graphic User Interface (GUI) and IDE CW08 V3.1 programming tool, the real time communication data and the curve function were displayed.

• Journal of the Korean Home Economics Association
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• v.42 no.3
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• pp.159-178
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• 2004

The purpose of this study was to investigate the effect of sexual messages in the media on adolescents' attitudes and behaviors toward sex. Subjects of this study consisted of 488 high school students in Cheong-ju City. The findings of this study were as follows; First, sexual messages in the media influenced-adolescents' attitudes toward sex. The more exposure to sexual messages adolescents had more liberal and permissive attitude toward sex. Secondly, sexual messages in the media also effected adolescents' behaviors toward sex, as well. The less sexual messages that they were exposed to, they displayed less sexual relations and behavior. In particular, the number of sexual materials in mass media, variety of sexual messages, and types of school were significant factors in predicting adolescents' sexual intercourse. The research suggested that sexual messages in the media definitely had an effect on adolescents' attitudes and behaviors toward sex. Therefore, it should be encouraged to take advantage of the television V chip and screening software for computers to reduce inappropriate access for adolescents.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.11-18
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• 2002

We proposed a new experimental method which is required to easily observe the growth behavior of fatigue cracks. In the proposed method, the image data of cracks were stored into the computer while the cyclic loading was interrupted. After testing, crack length was determined using an image processing software which was developed by authors. By comparing the data measured by the image processing system with those by the manual measurement with a microscope, the effectiveness of the image processing system was established. If the proposed method is used to monitor and observe the crack growth behavior automatically, the time and efforts for fatigue test could be dramatically reduced.

• Proceedings of the KIEE Conference
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• summer
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• pp.1127-1129
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• 2004

In this paper, a new approach detecting broken rotor bars in a squirrel-cage induction motor is proposed. The air-gap flux variation analysis was done using search coils inserted in stator slots when broken rotor bar conditions occur. An accurate modelling and analysis of air-gap flux variation in the induction motor are developed using finite-element(FE) software packages, and measuring the flux we made using search coils. In the FE analysis, the three-phase squirrel-gage induction motor with 380 [V], 5 [HP], 4 Poles, 1,742 [rpm] ratings is used.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.1
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• pp.20-25
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• 2006

We suggest a novel temperature detection method utilized in temperature monitoring system. Suggested method detects temperature variation by using $R_{ds(on)}$ characteristics of MOSFET, while conventional methods are using extra devices such as a temperature sensor or an over-temperature detection transistor. For voltage detection between drain and source, 10 bits resolution ADC is needed. Therefore possible measurement signal range is about ten mV. If detected temperature's voltage exceed protection temperature's voltage then controller generates OT (Over Temperature) signal to stop MOSFET's trigger signal. Whole process of measurement is controlled by software. Experimental results show that the developed temperature monitoring system can provide the suitable temperature monitoring method and difference between detected and data sheet value of the suggested system is about $3\%$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.130-131
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• 2006

In the present research work was searched the influence of severe plastic deformation (SPD) realized by ECAP (equalchannel angular pressing) on structural, mechanical and plastic properties of IF (interstitial free) steel. For physical simulation ECAP process with right angle channels $(90^{\circ})$ was used. The ECAP process was numerical simulated (namely its course of temperature, strain and stress fields and deformation forces) by FormFEM software, too.