• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.1988-1997
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• 2005

This study is concerned with structural integrity evaluations for the interference-fit flywheels in reactor coolant pumps (RCPs) of nuclear power plants. Stresses in the flywheel due to the shrinkage loads and centrifugal loads at the RCP normal operation speed, design overspeed and joint-release speed are obtained using the finite element method (FEM), where release of the deformation-controlled stresses as a result of structural interactions during rotation is considered. Fracture mechanics evaluations for a series of cracks assumed to exist in the flywheel are conducted, considering ductile (fatigue) and non-ductile fracture, and stress intensity factors are obtained for the cracks using the finite element alternating method (FEAM). From analysis results, it is found that fatigue crack growth rates calculated are negligible for smaller cracks. Meanwhile, the material resistance to non-ductile fracture in terms of the critical stress intensity factor (K$_{IC}$) and the nil-ductility transition reference temperature (RT$_{NDT}$) are governing factors for larger cracks.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.4
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• pp.463-473
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• 2011

The warm shrink fitting process is generally used to assemble automobile transmission parts (shaft/gear). But the fitting process can cause the dimensions of addendum and dedendum of the gear to change with respect to the fitting interference and the profile of the gear. As a result, there may be additional noise and vibration between gears. To address these problems, we analyzed the warm shrink fitting process according to process parameters; the fitting interference between the outer diameter of the shaft and the inner diameter of the gear, the inner diameter of the gear, addendum and dedendum of the gear, the heating temperature. In this study, a closed form equation for predicting the amount of deformation of addendum and dedendum in the R-direction was proposed. And the FEA method to analyze the cooling process was proposed for thermal-structural-thermal coupled field analysis of the warm shrink fitting process (heating-fitting-cooling process).

• Smart Structures and Systems
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• v.19 no.2
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• pp.137-149
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• 2017

Under the interference of the temperature effect, the alternation of cable force due to damages of a cable-stayed bridge could be difficult to distinguish. Considering the convenience and applicability in engineering practice, simple air or cable temperature measurements are adopted in the current study for the exclusion of temperature effect from the variation of cable force. Using the data collected from Ai-Lan Bridge located in central Taiwan, this work applies the ensemble empirical mode decomposition to process the time histories of cable force, air temperature, and cable temperature. It is evidently observed that the cable force and both types of temperature can all be categorized as the daily variation, long-term variation, and high-frequency noise in the order of decreasing weight. Moreover, the correlation analysis conducted for the decomposed variations of all these three quantities undoubtedly indicates that the daily and long-term variations with different time shifts have to be distinguished for accurately evaluating the temperature effect on the variation of cable force. Finally, consistent results in reducing the range of cable force variation after the elimination of temperature effect confirm the validity and stability of the developed method.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.872-876
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• 2006

This study was made to examine the electromagnetic interference(EMI) shielding effect (SE) of multilayered thin films in which indium-tin oxide(ITO) and Ag were deposited alternately from 3layer to 9 layer on Poly Methyl Meth Acrylate(PMMA) substrate at room temperature using a PF sputtering. We measured optical and electrical characteristics by UV-spectrometer and 4 point probe. The measurement of EMI SE in frequency range from 50MHz to 1.5GHz was performed by using ASTM D4935-89 method. We compared the measured EMI SEs with theoretical simulation data. We obtained relatively low resistivity and high transmittance from the EMI SE multilayers. In this study, we obtain good optical electrical characteristics with a minimun transmittance of about 60% at 550nm wavelength and sheet resistance of $2{\sim}3ohm/sq$., respectivity. Measured EMI SEs were over 50dB and similar to theoretical simulation data.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.33-36
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• 2003

AC and DC conductivity of the MWNT(Multi walled nanotubes)/polyurethane composites were investigated with respect to the various oxidative conditions, where these means acid concentration, treatment temperature, and treatment time. We suppose that the conditions of oxidation of the MWNTS have a certain influence on the degree of functionalization, damages, and dispersion of the MWNT themselves. Futhermore, the electrical properties of the resulting composites strongly depend on the oxidative conditions of MWNTS. The conductivity of the composites produced by using the optimal condition was measured as a function of frequency with volume content of MWNTS. These experimental results were analyzed using percolation theory Electromagnetic interference shielding effectiveness (SE) of the mixtures of polyurethane (PU), optimized MWNTs, and silver (Ag) is measured in the frequency range from 10 MHz to 6 ㎓ by using ASTM D4935-89. The measured SEs of the mixtures could be controlled from about 55 dB to 85 dB with the compositions of Ag/MWNT and compounding methods(C1, C2).

• Progress in Superconductivity and Cryogenics
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• v.16 no.4
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• pp.1-6
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• 2014

Superconducting quantum interference device (SQUID) is a sensitive detector of magnetic flux signals. Up to now, the main application of SQUIDs has been measurements of magnetic flux signals in the frequency range from near DC to several MHz. Recently, cryogenic low-noise radio-frequency (RF) amplifiers based on DC SQUID are under development aiming to detect RF signals with sensitivity approaching quantum limit. In this paper, we review the recent progress of cryogenic low-noise RF amplifiers based on SQUID technology.

• 연구논문집
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• s.33
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• pp.183-190
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• 2003

Today, We have used many electronic equipment such as computer, TV, cellular phone and so on. These equipment radiate a large amount of EMI(Electromagnetic interference) which is occurred trouble of airplane, medical equipment, communicate equipment, and especially, human health. So, Ni mesh fabrication for EMI shielding by continuous electroforming process was investigated. Continuous electroforming apparatus was made by means of rotating cathode drum. And We investigated the characteristics of two types of Ni electroforming solution. One was made by laboratory and the other was produced by M cooperation. The grain size increased with increasing current density and bath temperature, and decreasing rotating speed of cathode drum. EDX results indicate that the Ni mesh electroformed by the KIMM solution is composed of pure Ni. But the Ni mesh electroformed by the M cooperation solution has Ni and S element. The incorporation of S element in the Ni mesh has a profoundly effect on mechanical properties such as hardness, internal stress and so on.

• ETRI Journal
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• v.37 no.5
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• pp.906-916
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• 2015

High-speed I/O channels require adaptive techniques to optimize the settings for filter tap weights at decision feedback equalization (DFE) read channels to compensate for channel inter-symbol interference (ISI) and crosstalk from multiple adjacent channels. Both ISI and crosstalk tend to vary with channel length, process, and temperature variations. Individually optimizing parameters such as those just mentioned leads to suboptimal solutions. We propose a joint optimization technique for crosstalk cancellation (XTC) at DFE to compensate for both ISI and XTC in high-speed I/O channels. The technique is used to compensate for between 15.7 dB and 19.7 dB of channel loss combined with a variety of crosstalk strengths from $60mV_{p-p}$ to $180mV_{p-p}$ adaptively, where the transmit non-return-to-zero signal amplitude is a constant $500mV_{p-p}$.

• Korean Journal of Optics and Photonics
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• v.1 no.2
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• pp.204-209
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• 1990

The temperature variation at a laser rod center induced by high repetetion rate pumping was measured by counting the number of inteference frigne shift and found to be consistent with the theoretical value obtained from heat diffusion equation. The spatial homogeneity and energy transfer rate of flashlamp pumping by the single elliptical reflector plated with gold were evaluated by measuring interference fringes oever the cross section of a Nd:YAG laser rod.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.2
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• pp.1-5
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• 1985

In this paper, temperature-induced optical phase shifts in single-mode fibers are studied both analytically and experimentally. Temperature sensor using single-mode fiber interferometer is designed and the temperature sensitivity of the sensor system is investigated. This fiber-optic temperature sensor which employs the Mach-Zehnder arrangement is a high sensitivity sensor of phase detection type. In this type, temperature changes are ob-served as a motion of an optical interference fringe pattern. In the measurements using interferometer, one of the important problems is to detect simultaneously the number and direction of fringe displacement resulting from physical perturbations (temperature, pressure, etc.). To realize this, the array detector using multi-mode fiber is designed. By this array detector the number and direction of fringe displacement is Ineasured very conveniently.