• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.157-167
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• 1999

Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.6
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• pp.82-87
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• 2014

Dual pulse rocket motor has a rocket motor with different pulse grains divided by a pulse separation device such as a fragile bulkhead or a thermal barrier type. It distributes thrust energy very effectively via pulse separation device to improve range and terminal velocity of a missile. This paper contains the thermal barrier design and experimental analysis through ground firing tests of small dual pulse motors. The results will be applied to the design, test and evaluation of the scale up dual pulse rocket motor.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1355_1357
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• 2009

This paper describes the standard system for calibrating pulse generator of partial discharge(PD) and its uncertainty. The system is consisted of digital pulse generator, digital recorder and evaluation software. The uncertainty requirement of calibrator charge is less than $\pm$ (0.1pC + 0.03q) and that of pulse duration is less than $\pm$ 10 %. The system can generate various kind of calibration pulses such as single pulse, double pulses, oscillation pulse, long-duration pulse, random pulses and evaluate their uncertainty.

• Earthquakes and Structures
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• v.20 no.4
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• pp.457-471
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• 2021

This study aims at providing a simple and effective methodology to define a meaningful characteristic period for special class of earthquake records named "pulse-like ground motions". In the proposed method, continuous wavelet transform is employed to extract the large pulse of ground motions. Then, Fourier amplitude spectra obtained from the original ground motion and the residual motion is simply compared. This comparison permits to define a threshold pulse-period (Tp∗) as the threshold period above which the pulse component has negligible contributions to the Fourier amplitude spectrum. The effect of pulse on frequency content of motions was discussed on the light of this definition. The advantage and superior features of the new definition were related to the inelastic displacement ratio (IDR) for single-degree-of-freedom systems with period equal to one half of the threshold period. Analyses performed for the proposed period at three ductility levels u=2,4,6 were compared with the results obtained at half of pulse period derived from wavelet analysis, peak-point method and the peak of product of the velocity and the displacement response spectra (Sv x Sd). According to the results, pulse effects on inelastic displacement ratio seem to be more important when $\frac{T_p^*}{T}=2$ (T is the fundamental vibration period of system). The results showed that utilizing of the proposed definition could facilitate an enhanced understanding of pulse-like records features.

• Smart Structures and Systems
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• v.22 no.2
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• pp.223-230
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• 2018

This study examines a non-contact laser scanning-based ultrasound system, called an angular scan pulse-echo ultrasonic propagation imager (A-PE-UPI), that uses coincided laser beams for ultrasonic sensing and generation. A laser Doppler vibrometer is used for sensing, while a diode pumped solid state (DPSS) Q-switched laser is used for generation of thermoelastic waves. A high-speed raster scanning of up to 10-kHz is achieved using a galvano-motorized mirror scanner that allows for coincided sensing and for the generation beam to perform two-dimensional scanning without causing any harm to the surface under inspection. This process allows for the visualization of longitudinal wave propagation through-the-thickness. A pulse-echo ultrasonic wave propagation imaging algorithm (PE-UWPI) is used for on-the-fly damage visualization of the structure. The presented system is very effective for high-speed, localized, non-contact, and non-destructive inspection of aerospace structures. The system is tested on an aluminum honeycomb sandwich with disbonds and a carbon fiber-reinforced plastic (CFRP) honeycomb sandwich with a layer overlap. Inspection is performed at a 10-kHz scanning speed that takes 16 seconds to scan a $100{\times}100mm^2$ area with a scan interval of 0.25 mm. Finally, a comparison is presented between angular-scanning and a linear-scanning-based pulse-echo UPI system. The results show that the proposed system can successfully visualize defects in the inspected specimens.

• Journal of Sensor Science and Technology
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• v.21 no.2
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• pp.135-143
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• 2012

Arterial stiffness is causing the serious problems for human who is suffered from hypertension and metabolic syndrome. So it is important that measure the arterial stiffness for early prevention. Many researches point out that pulse wave velocity(PWV) is the reliable and simple method to predict arterial stiffness. In this paper, we developed the sensing parts that detect the pulse wave and ECG by using piezoelectric film and conductive textile with elastic band. Our system could detect 3ch pulse wave and ECG. Simultaneously, our algorithm extracts the features for calculating the delays among pulse waves. The delays are the significant parameter to estimate PWV, thus we design the experiment for evaluating the performance of our sensing parts. The reference is PP-1000(HanByul Meditech, Korea) that is good for performance evaluation. As a result, the start point of the pulse wave was the most reliable feature for comparing with PP-1000(r=0.691, P=0.00). The results between two operators showed that there is only a slight difference in the reproducibility of the devices. In conclusion, we assume that the suggested sensor could be more comfortable and faithful method for arterial stiffness.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.19 no.1
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• pp.47-54
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• 2015

Objective Wave reflection is an important factor that determines the shape of the pulse wave. The purpose of this study is to compare the conventional method used for estimating the reflection site of pulse with a cardiovascular simulator. Methods: In this study, cardiovascular simulator with one elastic tube was used. The pressure and flow was measured simultaneously at three different points. The measured data were used to the conventional methods to estimate the pulse wave reflection site. The results were compared with the known length which were the distances from the measured points to the end of tube. Results & Conclusions: There is a significant error with the time domain method. While, the reflection site with the frequency domain method was similar to the actual reflection site.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.210-211
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• 2018

In this study, the ultrasonic pulse velocity of the concrete cooled to room temperature after heating and the concrete during heating were evaluated. Also, the ultrasonic pulse velocity and mechanical properties of concrete were compared. As a result, the ultrasonic pulse velocity decreased when the concrete degraded during heating, and the ultrasonic pulse velocity of the cooled concrete decreased significantly. Which is consistent with the deterioration of mechanical properties of concrete.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2B
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• pp.151-161
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• 2009

The PULSE protocol can greatly reduce power consumption using a node's sleep state. But this protocol does not consider movement of a sink node in a sensor network. In the mobile sensor network a routing protocol must recover path error by movement of a sink node as quickly as possible. Therefore we have to achieve fast path recovery and power saving to support movement of a sink node in a sensor network. This paper proposes the Mobile PULSE protocol which is a improved routing protocol for a mobile sink node. And we evaluate Mobile PULSE and show that the Mobile PULSE reduces the recovery time about 40% compared with original PULSE protocol. Mobile PULSE increases energy consumption than PULSE as a maximum of 0.8%, which means Mobile PULSE is similar to PULSE in energy consumption. This paper shows mobile PULSE's capability in the mobile sensor network through evaluation of path recovery time and power consumption.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.9 no.1
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• pp.47-58
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• 2005

Background and purpose: The purpose of this study is to review the recent 10 year Chinese achievements on the objectification of traditional pulse diagnosis in clinical area. Methods: From the China Journal Full Text Database (中國學術期刊全文數据庫) we searched papers on pulse diagnosis by the keyword 'Maizhen'(脈診) Resulls: The researches are summarized into four parts; (1) the researches on the normal pulse in the physiological state (2) the clinical researches of pulse diagnosis on the symptom and disease diagnosis (3) the clinical researches of pulse diagnosis on the acupuncture treatment (4) the application of pulse diagnosis on the functional evaluation of the athlete. Conclusion: The undoubted principles of the traditional pulse diagnosis are evaluated by the objective clinical researches. And the researchers are trying to find a new application area over the traditional one.