• The Journal of the Acoustical Society of Korea
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• v.22 no.4E
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• pp.167-175
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• 2003

Shear wave velocity was measured and grain size analysis was conducted on two core samples obtained in unconsolidated marine sediments of the western continental margin, the East Sea. A pulse transmission technique based on the Hamilton frame was used to measure shear wave velocity. Duomorph ceramic bender transducer-receiver elements were used to generate and detect shear waves in sediment samples. Time delay was calculated by changing the sample length from the transducer-receiver element. Time delay is 43.18 μs and shear wave velocity (22.49 m/s) is calculated from the slope of regression line. Shear wave velocities of station 1 and 2 range from 8.9 to 19.0 m/s and from 8.8 to 22 mis, respectively. Shear wave velocities with depth in both cores are qualitatively in agreement with the compared model〔1〕, although the absolute value is different. The sediment type of two core samples is mud (mean grain size, 8-9Φ). Shear wave velocity generally increases with sediment depth, which is suggesting normally consolidated sediments. The complicated variation of velocity anisotropy with depth at station 2 is probably responsible for sediment disturbance by possible gas effect.

• The Journal of the Acoustical Society of Korea
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• v.17 no.1E
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• pp.44-53
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• 1998

Bolt degradation has become a major issue in the nuclear industry since the 1980's due to failure during operation. If small cracks in stud bolt are not detected early enough, they grow rapidly and cause catastrophic disasters. Their detection, despite its importance, is known to be a very difficult problem due to the complicated structures of the stud bolts. This paper presents a method of detecting and sizing a small crack in the root between two adjacent crests in threads. The key idea is from the fact that the Rayleigh wave propagates slowly along a crack from the tip to the opening and is reflected from the opening mouth. When there exists a crack, a small delayed pulse due to the Rayleigh wave is detected between large regularly spaced pulses from the thread. The delay time is the same as the propagation delay time of the slow Rayleigh wave and is proportional to the size of the crack. To efficiently detect the slow Rayleigh wave, three methods based on digital signal processing are proposed : modified wave shaping, dynamic predictive deconvolution, and dynamic predictive deconvolution combined with wave shaping.

• Journal of the Korea Computer Industry Society
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• v.7 no.5
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• pp.563-572
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• 2006

Advantage that light transmission treatment way of most suitable through skin can investigate light directly in part ar there is difference in ability photoelectricity month by diverse complexion of horn character department which is branch or head of a family outside part of skin and treatment according to various patient can be inappropriate. By result that this research uses color information after search each color ingredient that ingredient of HIS and YIQ that use method, color information to use skin impedance way and color information through skin area ion and difference video to do fixed measuring by light investigation way by skin impedance corresponds to skin color in an experiment though is most universal result according to patient's skin model area detection each single person's skin model through videotex automatically create and because measuring, investigate skin color, energy, wave length, approximately, transmission time, model of most suitable that draw pulse delay and so on and want and special quality, and saved standard of disease treatment pulse modeling by skin impedance, and design and manufacture light investigation pulse modeling system of most suitable by skin subordinate, and constructed suitable treatment pulse database by skin color.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.3
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• pp.207-216
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• 1999

A phased array is a multi-element piezoelectric device whose elements are individually excited by electric pulses at programmed delay time. One of the advantages of using phased array in nondestructive evaluation (NDE) application over conventional ultrasonic transducers is their great maneuverability of ultrasonic beam. There are some parameters such as the number and the size of the piezoelectric elements and the inter-element spacing of the elements to design phased array transducer. In this study, the characteristic of ultrasonic beam for phased array transducer due to the variation of the number of elements has been simulated for ultrasonic SH-wave on the basis of Huygen's principle. Ultrasonic beam directivity and focusing due to the change of time delay of each element were discussed due to the change of the number of piezoelectric elements. It was found that ultrasonic beam was much more spreaded and hence its sound pressure was decreased as steering angle of ultrasonic beam was increased. In addition, the ability of ultrasonic bean focusing decreased gradually with the increase of focal length at the same piezoelectric elements. However, the ability of beam focusing was improved as the number of consisting elements was increased.

• Journal of Navigation and Port Research
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• v.36 no.6
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• pp.475-480
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• 2012

In order to establish eLoran (enhanced Long Range Navigation) system, it needs the advancement of receiver, transmitter, data channel addition for Loran information, differential Loran sites for compensating Loran-c signal and ASFs (Additional Secondary Factors) database, etc. In addition, the precise synchronization of transmitting station to the UTC (Coordinated Universal Time) is essential if Loran delivers the high absolute accuracy of navigation demanded for maritime harbor entrance. For better timing synchronization to the UTC among transmitting stations, it is necessary to measure and monitor the transmission delay of the station, and the correction information of the transmitting station should be provided to the user's receivers. In this paper we presented the measurement method of absolute delay of Pohang Loran transmitting station and developed a time delay measurement system and a phase monitoring system for Loran station. We achieved -2.23 us as a result of the absolute phase delay of Pohang station and the drift of Loran pulse of the station was measured about 0.3 us for a month period. Therefore it is necessary to measure the delay offset of transmitting station and to compensate the drift of the Loran signal for the high accuracy application of PNT (Positioning, Navigation and Timing).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.680-687
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• 2018

Borehole radar is a radar used for underground resources and geological exploration purposes. It needs a high-speed sampler to transmit electromagnetic waves with a pulse width of several ns and to receive reflected waves of several tens to several hundreds of MHz reflected from the object to be surveyed. ETS (Equivalent-Time Sampling), which can achieve sampling performance of several GHz with a sampling frequency of several tens of MHz, is suitable for use as a sampler of a borehole radar receiver. In this paper, we propose a method to control the sampling clock delay, which is the most important factor in ETS sampler design, using four clocks with phase difference of $90^{\circ}$ for one clock source. The proposed method can reduce the time required to acquire the data within the set interval by 1/25 than the conventional method using the delay generator. When the implemented sampler is applied to the receiver of existing borehole radar, it is possible to accumulate 58 additional times due to the shortened sampling time. In addition, by using one delay control logic compared with the conventional method using several sampling clock delay control logic in order to satisfy the target sampling range, it is possible to omit the correction process which was necessary in the past. As a result, the structure of the system can be simplified and a uniform sampler can be realized.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.6
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• pp.1-7
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• 2001

To analyze the driving principle of PDP, the influence on the discharge characteristics of space charge was researched. Space charge generated by the priming discharge shortens delay time of the discharge which happens as follows and shorts response time. Such influences are valid up to about 30㎲ after generating priming discharge. This space charge decreases dicharge ignition voltage of the cell near priming cell and the influences are most greatly alerted on the discharge of cell which is adjacent most. And the dependency to spare charge strengthens because discharge ignition voltage drop grows by narrowing of discharge pulse width. But the influence on space charge was observed very slightly in pulse width 1㎲ or more. Therefore, to cause a steady discharge, pulse width should become 1㎲ or more at least without being influenced for space charge of the adjoining discharge.

• Science of Emotion and Sensibility
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• v.11 no.4
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• pp.637-644
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• 2008

Human emotion has been tried to be recognized by physiological measurements in developing emotion machine enabling to understand and react to user's emotion. This study is to find the time-dependent physiological measurements and their variation characteristics for discriminating emotions according to dimensional emotion model. Ten university students were asked to watch sixteen prepared images to evoke different emotions. Their subjective emotions and autonomic nervous responses such as ECG (electrocardiogram), PPG (photoplethysmogram), GSR (Galvanic skin response), RSP (respiration), and SKT(skin temperature) were measured during experiment. And these responses were analyzed into HR(Heart Rate), Respiration Rate, GSR amplitude average, SKT amplitude average, PPG amplitude, and PTT(Pulse Transition Time). TDPs(Time dependent parameters) defined as the delay, the activation, the half recovery and the full recovery of respective physiological signal in this study have been determined and statistically compared between variations from different emotions. The significant tendencies in TDP were shown between emotions. Therefore, TDP may provide useful measurements with emotion recognition.

• Journal of Digital Convergence
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• v.16 no.12
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• pp.309-315
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• 2018

In this paper, propose an efficient arc detection and control method to achieve fast machining speed, improved precision and surface roughness in discharge machining, especially for carbide and hard material processing and metal processing using discharge phenomenon as energy. A single discharge waveform is divided into three sections of Td (Time-Delay), Ton (Time-on) and Toff (Time-off) and the gate control timing is simulated using the HDL language. In this paper, we analyze the effect of the gap between the electrode and the workpiece on the machining results by determining the operation of the servo mechanism by sampling the Td section through the comparator circuit. As a result of the analysis, the Td section of the formed waveform was more precisely sampled at a high speed and the results were improved when applied to the gap control between the electrode and the workpiece.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.274-277
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• 1999

The paper describes a implementation of space vector pulse-width modulation (SVPWM) voltage source inverter using Field Programmable Gate Array(FPGA) for a induction motor control system. The implemented chip is included logic circuits for SVPWM, dead time compensation and speed detection using Quick Logic, QL16X24B. The maximum operating frequency and delay time can be set to 110MHz and 6 nsec. The designed FPGA for SVPWM can be incorporated with a digital signal processing to provide a simple and effective solution for high performance voltage source inverter drives. Simulation and Implementation results are shown to verify the usefulness of FPGA as a Application Specific Integrated Circuit(ASIC) in power electronics applications