• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1320-1325
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• 2006

When the train running on the high-speed track, there is a speed band which track distortion is unusually increased according to the condition of track and roadbed. This speed is called critical velocity and physical parameter values are increased greatly. These phenomenon happened as high-speed train were developed, studied regularly through TGV 100 running test in France. As research result until now, the main reason is soft roadbed's bearing capacity. Wave propagation and track support capacity is varied by the ground characteristics. This paper achieved theoretical examination about resonance band(speed and frequency) that occurred in roadbed on the base rock in point of geotechnical engineering. The examination of resonance divides with ground response analysis, critical band analysis by the shear wave velocity of roadbed and train critical speed through the ground stratum.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 학술대회 논문집 전문대학교육위원
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• pp.85-88
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• 2000

This paper was development a discharge lamp ballast in order to wave improvement of high power factor and high efficiency. The discharge lamp ballast consists of a power factor correction circuit and a correction circuit on switching frequency of inverter. Instead of passive power factor circuit, active power factor circuit is adopted. Because it has the advantage of size, weight, total harmonic distortion, out DC voltage regulation, and power factor. The power factor circuit with MG34262 is controlled by variable frequency discontinuous mode. Results experiments, discharge lamp ballast is showed to have excellent for the proposed electronic ballast's operation and characteristics.

• 대한기계학회논문집B
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• 제29권8호
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• pp.921-926
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• 2005

In the idealized model problem of the interaction between a planar travelling shock and a symmetric vortex, the physics of shock distortion and quadrupole sound generation are well known to many researchers. However, the authors have distinguished the weak waves reflected and transmitted by the complicated photograph images obtained from a shock tube experiment. In this paper, we introduces a parametric study based on Navier-Stokes simulation and Rankin vortex model to see the difference of shock deformation shapes. Four combination of the strength of shock and vortex are respectively selected from a parameter plane of shock and vortex strength extended to the strong vortex region. The result shows clearly discernable wave morphology for the main parameters, which is not yet explicitly mentioned by other researchers.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1995년도 제12회 음성통신 및 신호처리 워크샵 논문집 (SCAS 12권 1호)
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• pp.123-126
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• 1995

The waveform coding are concerned with simply preserving the wave shape of speech signal through a redundancy reduction process. In the case of speech synthesis, the wave form coding with high quality are mainly used to the synthesis by analysis. However, because the parameters of this coding are not classified as either excitation and vocal tract parameters, it is difficult to applying the waveform coding to the synthesis by rule. In this paper, we proposed a new pitch alteration method that can change the pitch period in waveform coding by using scaling the time-axis and compensating the spectrum. This is a time-frequency domain method that is preserved in the phase components of the waveform and that has a little spectrum distortion with 2.5% and less for 50% pitch change.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.514-514
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• 2000

In this article, the realization of a precision full-wave rectifier circuit for analog signal processing, which operates throughout in the current domain, is presented. The circuit makes use of a MOS class B/AB configuration, and provides a wide dynamic range and wide-band capability. The rectifier has a simple circuit configuration and is suitable for implementing in CMOS integrated circuit form as versatile building block. The characteristic of the circuit exhibits a low distortion en the output signal at low level input signal. PSPICE simulation results demonstrating the characteristic of the proposed circuit are included.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.443-447
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• 2005

When the high-speed train running on the track, there is a speed band which track distortion is unusually increased according to the condition of track and roadbed. This speed is called critical velocity and physical parameter value increased greatly. These phenomenon happened as high-speed train were developed, studied regularly through TGV 100 running test in France. As research result until now, the main reason is soft roadbed's capacity. Wave propagation and track support capacity is varied by the site characteristics. This paper achieved theoretical examination about resonance band(speed and frequency) that occurred in roadbed on the base rock in point of geotechnical engineering. The examination of resonance divides with ground response analysis, critical band analysis by the shear wave velocity of roadbed, train critical speed through the ground stratum.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.389-393
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• 2005

When the high-speed train running on the track, there is a speed limit which track distortion is unusually increased according to condition of track and roadbed. This speed limit is called critical velocity, and physical parameter value increased very greatly. These phenomenon happened as high-speed train were developed, studied regularly through TGV 100 running test in France. As research result until now, the main reason is soft roadbed's capacity. Wave propagation and track support capacity is varied by the site characteristics. This paper achieved theoretical examination about resonance band(speed and frequency) that occurred in roadbed on the base rock in point of geotechnical engineering. The examination of resonance divides with ground response analysis, critical band analysis by the shear wave velocity of roadbed, train critical speed through the ground stratum.

• Computers and Concrete
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• 제8권5호
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• pp.563-581
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• 2011

The signal-based acoustic emission (AE) characterization of concrete fracture process utilizing home-programmed AE monitoring system was performed for three kinds of static loading tests (Cubic-splitting, Direct-shear and Pull-out). Each test was carried out to induce a distinct fracture mode of concrete. Apart from monitoring and recording the corresponding fracture process of concrete, various methods were utilized to distinguish the characteristics of detected AE waveform to interpret the information of fracture behavior of AE sources (i.e. micro-cracks of concrete). Further, more signal-based characters of AE in different stages were analyzed and compared in this study. This research focused on the relationship between AE signal characteristics and fracture processes of concrete. Thereafter, the mode of concrete fracture could be represented in terms of AE signal characteristics. By using cement-based piezoelectric composite sensors, the AE signals could be detected and collected with better sensitivity and minimized waveform distortion, which made the characterization of AE during concrete fracture process feasible. The continuous wavelet analysis technique was employed to analyze the wave-front of AE and figure out the frequency region of the P-wave & S-wave. Defined RA (rising amplitude), AF (average frequency) and P-wave & S-wave importance index were also introduced to study the characters of AE from concrete fracture. It was found that the characters of AE signals detected during monitoring could be used as an indication of the cracking behavior of concrete.

• 한국인터넷방송통신학회논문지
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• 제17권6호
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• pp.161-167
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• 2017

최근 소형 레이더는 다양한 운용환경에서 대응하기 위하여 소형화와 저전력화를 추진한다. 또한 한번의 타격으로 표적의 시스템을 무능화시키기 위해 높은 거리해상도를 갖는 소형 밀리미터파 레이더 개발을 요구한다. 본 논문에서는 소형 밀리미터파 레이더에서 사용할 수 있는 신호처리기를 설계하고 구현하였다. 소형 밀리미터파 레이더를 위한 신호처리기는 소형화와 저전력화를 위해 디지털 IF(Intermediate Frequency) 수신기와 실시간 FFT 연산이 가능한 DFT(Discrete Fourier Transform) 모듈을 설계하였다. 또한 소형 밀리미터파 레이더의 수신 경로에서 발생할 수 있는 신호의 왜곡을 보정하기 위한 수단으로 FPGA(Field Programmable Gate Array)와 DAC(Digital Analog Converter)를 활용하여 시스템에서 사용하는 RF(Radio Frequency) 신호를 생성할 수 있도록 하였다. 마지막으로 성능시험을 통해 구현한 신호처리기를 검증하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.361-365
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• 2002

Advancements in silicon phase control (SCR) technologies provide an arc welding power supply that has the capability to allow the alteration of the Alternating Current (AC) welding output. These technologies provide a square wave output involving sixteen frequency selections and multiple balance selections. While an AC out put is known to minimize magnetic disturbances associate with Direct Current (DC), the potentials of a non-sinusoidal waveform have not been explored. The focus of the paper is to determine the effects that the frequency and balance of an AC wave form output will have upon a high speed Submerge Arc (SAW) application. The test matrix of the project includes welding .250" steel plate. Joint type is square groove with a travel speed of 65 IPM. Each of the weld parameters was held constant, only the frequency and/or balance were altered between welds. Each frequency/balance combination involved three-gap spacing. Upon completion of the welds the bead profiles were measured and recorded. A relationships/trends were observed with various frequency and balance values. Optimum frequency and balance values were found for the .250" square groove application which permit consistent weld sizing, ease of slag removal, and minimal plate distortion.