• Proceedings of the Acoustical Society of Korea Conference
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• 1998.08a
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• pp.127-130
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• 1998

피치검색과 3-level clipping을 이용한 새로운 파형부호화법을 제안하고자 한다. 제안한 방법에서는 우선 피치를 검출하여 기준피치파형과 인근피치파형을 검색한다. 그 후 유사도 측정시 기준피치파형과 인근 피치파형에 대해 3-level clippng을 수행한다. 클리핑된 기준피치파형가 인근피치파형간의 유사도를 측정하여 유사성이 크다면 피치정보와 에너지 정보만을 전송하거나 저장하여 압축을 하고, 유사성이 적다면 인근피치파형을 압축을 하지 않고 저장한다. 그 후에 저장된 ？ㅇ을 기준 피치파형으로 재정의 하여 다시 반복적으로 압축을 수행한다. 압축된 음성신호를 다시 복원할 때에는 수신 또는 저장된 음성신호를 이용하여 PSOLA 방식으로 합성을 수행한다. 평균압축율이 약 65%일 경우에도, MOS 값이 4이상을 유지하였다.

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.77-84
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• 2009

Ground penetrating radar (GPR) is an effective tool for detecting shallow subsurface targets. In many GPR applications, these targets are veiled by the strong waves reflected from the ground surface, so that we need to apply a signal processing technique to separate the target signal from such strong signals. A pulse-compression technique is used in this research to compress the signal width so that it can be separated out from the strong contaminated clutter signals. This work introduces a filter algorithm to carry out pulse compression for GPR data, using a Wiener filtering technique. The filter is applied to synthetic and field GPR data acquired over a buried pipe. The discrimination method uses both the reflected signal from the target and the strong ground surface reflection as a reference signal for pulse compression. For a pulse-compression filter, reference signal selection is an important issue, because as the signal width is compressed the noise level will blow up, especially if the signal-to-noise ratio of the reference signal is low. Analysis of the results obtained from simulated and field GPR data indicates a significant improvement in the GPR image, good discrimination between the target reflection and the ground surface reflection, and better performance with reliable separation between them. However, at the same time the noise level slightly increases in field data, due to the wide bandwidth of the reference signal, which includes the higher-frequency components of noise. Using the ground-surface reflection as a reference signal we found that the pulse width could be compressed and the subsurface target reflection could be enhanced.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.265-268
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• 1998

일반적으로 음성 합성용 데이터 베이스에서는 고음질을 유지할 수 있는 파형 부호화법을 주로 사용한다. 그것은 파형 부호화법이 발성자의 개성과 메시지 정보를 보존하기 때문에 음질의 명료성이 우수하기 때문이다. 그러나 기존에는 파형 부호화법을 적용해서 음성 파형 자체의 잉여성분만을 제거한 후 합성용 데이터 베이스로 사용하기 때문에 음성 합성용 데이터 베이스의 크기가 커지는 단점을 가진다. 따라서 본 논문에서는 이러한 단점을 극복하기 위해서 기존의 운율조절법을 통해서 음성 합성용 데이터 베이스를 압축하는 방법을 제안한다. 결과적으로 제안한 방법을 사용함으로써 고음질을 갖는 음성 합성용 데이터 베이스를 가질 수 있었고 데이터 베이스의 크기도 줄일 수 있었다.

• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.522-533
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• 2019

The compressive sensing model for range-Doppler estimation can be expressed as an under-determined linear system y = Ax. To find the solution of the linear system with the compressive sensing method, matrix A should be sufficiently incoherent and x to be sparse. In this paper, we propose a transmission waveform design method that maintains the bandwidth required by the sonar system while lowering the mutual coherence of the matrix A so that the matrix A is incoherent. The proposed method combines two methods of optimizing the sensing matrix with the alternating projection and suppressing unwanted frequency bands using the DFT (Discrete Fourier Transform) matrix. We compare range-Doppler estimation performance of existing waveform LFM(Linear Frequency Modulated) and designed waveform using the matched filter and the compressive sensing method. Simulation shows that the designed transmission waveform has better detection performance than the existing waveform LFM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.3
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• pp.155-162
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• 2011

The structures that use the bridge plates are considered to have advantages such as short work term, excellent economical efficiency and low maintenance cost. Bridge plates are being widely used for water ducts and eco-corridors as replacements of reinforced concrete ducts. Bridge plates are deep and have greater pitch as compare to conventionally deep corrugated steel plate. They are expected to be increasingly used in the future. The structures that use bridge plates have two forms, such as arch type and box type. The arch type structures are designed based on the compressive strength, and the box type structures, based on the moment in the plate member. In this study, the ultimate strength and moment strength of the connection part of the specimens were examined by their thickness. Static and bending tests used to evaluate the performance of bridge plate. Finally, These results were used in the design process.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.3
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• pp.195-207
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• 2017

Recently, the SAR-GMTI mode is becoming increasingly essential in airborne radar systems. While SAR requires wideband waveforms for high resolution imaging, GMTI requires narrowband waveforms for doppler processing, which makes general LFM waveforms difficult to use for SAR-GMTI. This paper analyses the FJB(Frequency Jump Burst) waveform, which is studied for the SAR-GMTI waveform, and presents the method for the pulse compression and SAR image formation using FJB waveforms. Simulation results show that there is little difference in performances between the FJB waveform and the LFM waveform.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.13-17
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• 1991

고반복 레이저의 여기전원에 적합한 3단의 자기펄스 압축 시스템을 제작하고, 시스템의 특성을 고찰하였다. 자기 펄스 압축 시스템의 특성 파라메타는 펄스 변압기의 출력과 펄스파형에 대한 포화 인덕터의 단면적, 코일의 권수가 고려되었다. 실험 결과 3단의 자기 펄스압축 시스템의 최적 조건에서 펄스 압축비와 전류 이득은 각각 22,20 이었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.6
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• pp.661-670
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• 2013

In this paper, we propose the measurement techniques of mixed waveform. Mixed waveform has phase-continuous periodic waveform with fixed frequency signal and Linear Frequency Modulation(LFM) signal. This waveform is generated from a compact radar transmitter with frequency synthesizer and high power amplifier. Frequency synthesizer generates various signal waveform with continuos phase and high power amplifier amplify transmitting signal. First, we describe a compact radar transmitter with the phase-continuos signal and then verify the distortion characteristic of pulse compression by the mismatch of LFM waveform. Second, we describe three kinds of measurement techniques for measuring LFM waveform. These techniques include methods using signal analyzer, signal source analyzer and new methods using RF mixer and phase shifter. Finally, we verify the accuracy of the measurement technique from the pulse compression result of receiving signal.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.93-100
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• 2017

Four-stroke cycles in an automobile engine are suction stroke, compression stroke, combustion stroke and exhaustion stroke. A normal operation of engine in compression and power stroke must be processed in optimal fuel-air pressure. In this paper we describe a development of measuring equipment for engine cylinder pressure with observing supply current to self motor(start motor). By comparing the current wave on pressure of the 4 or 6 cylinder in engine, a abnormal cylinder state will be found. The validity of the proposed measuring equipment was shown by experiment for real automobile.

• Journal of the Korean GEO-environmental Society
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• v.2 no.4
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• pp.15-27
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• 2001

This paper proposes the force equations(thrust, moment) of corrugated steel culverts through the finite element method. The conditions for maximum thrust and maximum moment are determined from the analysis of soil-structure interaction during the three construction stages, such as backfill to the crown, backfill to the soil cover, and live loads. The proposed form of thrust and moment equations are deduced from the analysis of behaviour and the application of Castigliano's second theorem for the semi-arch structure. Finally, the coefficients used in the proposed equations are determined from a large number of analysis for the various geometries and the soil-structure relative stiffness under the conditions of maximum thrust and maximum moment.