• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.326-332
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• 1995

Using natural frequency measurement method, which is one of NDT method, natural frequency of the hot-rolled mild steel plate(specimen) under fatigue loading was measured. Between the degradation of the specimen under fatigue loading and the variation of the natural frequency of the specimen was investigated. As a result, the degradation of the specimen was described and monitored as variation of natural frequency of specimen. The natural frequency of specimen decreased gradually under fatigue loading. This means the variation of material properties of specimen. Especially. It means the variation of Young's modulus of specimen.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.6
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• pp.678-684
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• 2015

Near-threshold computing (NTC) is now regarded as a promising candidate for innovative power reduction, which cannot be achieved with conventional super-threshold computing (STC). However, performance degradation and vulnerability to process variation in the NTC regime are the primary concerns. In this paper, we propose a voltage- and frequency-tuning methodology for mitigating the process-variation-induced problems in NTC-based manycore architectures. To implement the proposed methodology, we build up multiple-voltage multiple-frequency (MVMF) islands and apply a voltage-frequency tuning algorithm based on the critical-path monitoring technique to reduce the effects of process variation and maximize energy efficiency in the post-silicon stage. Experimental results show that the proposed methodology reduces overall power consumption by 8.2-20.0%, compared to existing methods in variation-sensitive NTC environments.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1210-1216
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• 2014

This paper deals with an application of Teager Energy Operator (TEO) and Energy Separation Algorithm(ESA) to detect and determine various voltage waveform distortions like harmonics, inter-harmonics and frequency variation. Because the TEO and DESA algorithm was initially proposed for speech or communication analysis, its applications are limited to some types of waveform in the power quality analysis area. For example, an undistorted voltage signal is similar with a pure sinusoid. A voltage fluctuation is very similar with an amplitude-modulated signal, from the viewpoint of signal theory. And a continuous frequency variation is similar with a frequency-modulated signal, which is also known as a chirp signal. This paper is written to show that the TEO and DESA algorithm can be used for detecting occurrences of the representative waveform distortions and determining their instantaneous information of amplitude and frequency.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.371-375
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• 2014

In this paper, we compared the performances of the Right Handed Transmission Line (RHTL) and the Left Handed Transmission Line (LHTL) phase shifters as a frequency translator. Unlike other phase shifters, both phase shifters show a $0^{\circ}-360^{\circ}$ phase variation for a broadband frequency and compact in size which are ideal to use as a frequency translator. For the performance comparison, we fabricated both a RHTL and a LHTL phase shifter to cover 1.5 GHz - 2.4 GHz range with the whole $360^{\circ}$ phase variation. For the frequency range, a LHTL based frequency translator showed a much better performance whose Spurious Free Dynamic Range (SFDR) is 4dB - 17dB higher than the RHTL based frequency translator when the sawtooth modulation freqncy is 11 kHz. This is due to the linear phase-voltage variation of LHTL phase shifter. Furthermore, the LHTL phase shifter shows a less insertion loss and a insertion loss variation than the RHTL phase shifter. Overall, the LHTL based frequency translator outperformed RHTL based freqency translator.

• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.413-421
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• 2022

Modal parameters are the main dynamic characteristics of bridge. This study aims to propose an innovative route to estimate the modal parameters for bridges by using a parked vehicle in which mode shapes with high accuracy and spatial resolution are identified by frequency measurement. Based on the theory of dynamic modification and modal identification, the mathematical formulation between the parked mass induced frequency variation and the modal parameters of a bridge is derived. Then this mathematical formulation is extended to a parked vehicle-bridge system. The arithmetic and processes for estimating the modal parameters based on the identified frequency variation of the vehicle-bridge systems when the vehicle locates at sequentially arranged positions are presented. Finally the proposed method is applied to several simulated bridges of different types. The results indicate that it can estimate the modal parameters with high accuracy and efficiency.

• The Journal of the Acoustical Society of Korea
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• v.31 no.3
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• pp.197-204
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• 2012

In this thesis, studied the method to minimize the changes in frequency response and level due to the variation of the distance from the source to the microphone. selecting three microphones (omni directional, cardioid, super cardioid) which are being used generally, frequency responses were measured in accordance with the distance changes. Gotten the difference from the reference as the result of measurement, changed responses for each frequency range were compensated in comparison of the original human vocal source. In low frequency range, the low frequency boost caused by the proximity effect and decrease in accordance with the distance were compensated. The variation in mid-frequency range is comparatively small, however since the mid-range is the most important part of the human vocal signal, were compensated the mid-frequency range in comparison of the reference. The human vocal signal variation in high frequency range is extremely small and the high frequency is compensated close to the original source without difficulty. Understanding the microphone characteristics and compensations, this study showed that the response can be maintain among the change of the distance from the source to the microphone.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.770-772
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• 2002

In this paper, the eddy current sensor is develped for observing the ability of detecting defect with variation of frequency and velocity. The circuit designed for processing detected voltage and changing frequency is used for eddy current sensor to detect defect with variation of frequency. The ability of eddy current sensor to detect defects is studied with variation of velocity adjusted by rotating the circular plate. This study shows that the ability of eddy current sensor for detecting defect is increased and decreased by frequency. This fact means that the sensor has its best ability at a certain frequency. And the ability of eddy current sensor by velocity is decreased by increased velocity. Therefore, the eddy current sensor has to be developed with consideration of its operation velocity and frequency.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.563-565
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• 2002

The designed frequency compensator is proposed to make the estimation of amplitude of fundamental frequency immune to frequency variation. The designed method which has a simple structure and low calculation burden is proper to apply digital protective relay. The results of experimental demonstrate that the frequency compensator has good performance to the estimation of amplitude of fundamental frequency against frequency variation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.11
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• pp.1447-1454
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• 2018

In this paper, the design of robust DSC-PLL(Delayed Signal Cancellation Phase Locked Loop) is proposed for coping with frequency variation. This method shows significant performance for detection of fundamental positive sequence component voltage when the grid voltage is polluted by grid unbalance and frequency variation. The feedback frequency estimation of DSC-PLL is tracking the drift in the phase by unbalance and frequency variation. The robust DSC PLL is to present the analysis on method and performance under frequency variations. These compensation algorithms can correct for discrepancies of changing the frequency within maximum 193[ms] and improve traditional DSC-PLL. Linear interpolation method is adopted to reduce the discretized errors in the digital implementation of the PLL. For verification of robust characteristic, PLL methods are implemented on FPGA with a discrete fixed point based. The proposed method is validated by both Matlab/Simulink and experimental results based on FPGA(XC7Z030).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.375-378
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• 2000

This paper investigated that resonant frequencies of microstrip patch antenna were tunable when piezoelectric materials were used as the antenna substrates. The resonant frequencies of the microstrip antenna using the piezoelectric substrate, like PZT, LiNbO$_3$ were able to be controlled by applied DC voltage. The frequency variation of the air gap antenna was 29MHz when the voltage variation was 14[kV/cm], and the frequency variation of microstrip patch antenna made of LiNbO$_3$substrate was 29MHz when voltage variation was 6[kV/cm].