• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.291-296
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• 2006

The residual stress in shot-peened Al 7075 alloy was evaluated using surface acoustic wave (SAW). Shot peening was conducted to produce a variation in the residual stress with the depth below the surface under a shot velocity of 30 m/s. The SAW velocity was measured from the V(z) curve using a scanning acoustic microscopy (SAM). The Vickers hardness profile from the surface showed a significant work hardening near the surface layer with a thickness of about 0.25 mm. As the residual stress became more compressive, the SAW velocity increased, whereas as the residual stress became more tensile, the SAW velocity decreased. The variation in the SAW velocity through the shot peened surface layer was in good agreement with the distribution of the residual stress measured by X-ray diffraction technique.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.15-17
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• 2012

파, 해저지반 및 해안 해양구조물과의 관계는 해안공학뿐만 아니라 지반공학 분야에서도 중요한 이슈중의 하나이며, 파랑에 의한 해저지반 내부의 압력 및 응력의 파악은 다양한 해안 해양 구조물의 기초 설계 및 해저 연안 지반의 불안정성 검토에 있어서 중요한 과제이다. 해저 지반의 불안정에 대한 문제 중, 파랑에 의한 해저지반의 액상화는 기존의 연구를 통하여, 두개의 메커니즘이 존재한다는 것이 밝혀졌으며, 이는 각각 파랑에 의해 해저지반 내부에 발생하는 과잉간극수압의 변동 특성 및 잔류 특성에 따른 것이다. 이 연구에서는 중복파에 의해 해저지반 내부에 에 발생하는 과잉간극수압에 대하여 수치해석을 하였으며, 발생하는 과잉간극 수압 중 잔류 과잉간극수압의 발생 특성과 실험 결과를 비교 분석하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.43-50
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• 2012

The effects of parameters related to the finite element simulation of the laser shock peening(LSP) process on the residual stresses of Inconel alloy 600 steel are discussed. In particular, we focus on the maximum pressure, pressure pulse duration, laser spot size, and number of shots. It is found that certain ranges of the maximum pressure and pulse duration can produce the maximum compressive residual stresses near the surface, and thus proper choices of these parameters are important. The residual stresses are not affected by the laser spot size, provided it is larger than a certain size. The magnitudes of the compressive residual stresses and the plastically affected depths are found to increase with an increasing number of shots, but this effect is less pronounced for more shots.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.57-60
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• 1999

본 논문에서는 성문파에서 화자특성 계수를 추출하여 화자 인식기에 적용하고자 한다. 공분산 방법으로 음성의 잔류신호를 추정하고 이를 적분하여 성문파를 얻어낸다. 하나의 성문파 구간을 성문닫힘순간 사이가 아닌 잔류신호의 오차가 최대가 되는 순간 사이로 잡았다. 구해진 성문파를 M개의 데이터로 다시 샘플링하여 특성 벡터로 삼고 VQ기반 인식기를 사용하여 인식률을 측정하였다. 4초의 test data와 30차의 특성벡터를 사용한 경우 남성의 경우 평균 $96.08\%$, 여성에 대하여 $93.61\%$의 평균 인식률을 얻었다.

• Journal of Welding and Joining
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• v.15 no.3
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• pp.12-20
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• 1997

구조의 용접접합부에는 재료의 항복응력 크기의 용접잔류응력이 발생되고, 이 잔류응력 상태에서는 응력비(최소응력/최대응력)의 영향이 거의 없다는 것이 일정 진폭 하중조건의 피로실험결과로부터 알려져 있다. 이와 관련하여, 용접구조의 설계 단계에서는 초기 용접잔류응력이 그래도 잔류한 소형실험편의 일정진폭하중 상태의 피로실험 결과로부터 도출된 피로설계선도(S-N 선도)를 이용, 변동하중에 의한 응력 진폭의 밀도분포만으로 일생동안의 누적피해도를 구해 피로강도를 평가하는 것이 일 반적이다. 지금까지는 선박용접구조의 경우도 이러한 개념으로 피로강도 평가를 수행 하였으나, 일반적인 육상 또는 해상 용접구조물과는 달리, 화물의 적재 등의 정하중 이력에 의한 응력변동폭은 피로를 유발하는 파랑 응력변동폭보다 상당히 크다. 그리 고, 정하중에 의해 용접접합부에 인장응력을 발생시키는 하중이력을 받을 경우, 초기 용접잔류 응력은 상당히 저하될 것으로 생각된다. 본 연구에서는 인장응력을 유발하는 정하중 이력에 의해 저하된 용접잔류응력분포와 이러한 잔류응력분포를 가진 선측 종늑골 용접접합부의 피로강도를 검토한다.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.430-434
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• 2018

In this study, an effective diffusion coefficient and mass transfer coefficient were investigated in microwave-assisted drying of paclitaxel for removal of residual methylene chloride. At all the temperatures (35, 45, and $55^{\circ}C$), a large amount of the residual methylene chloride was initially removed during the drying, and the drying efficiency increased when increasing the drying temperature. The effective diffusion coefficient ($1.299{\times}10^{-13}{\sim}2.571{\times}10^{-13}m^2/s$) and mass transfer coefficient ($1.625{\times}10^{-11}{\sim}4.857{\times}10^{-11}m/s$) increased with increasing drying temperature. The small Biot number (0.0100~0.0151) indicated that the process of mass transfer was externally controlled.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.324-338
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• 2015

Analytical solutions for interaction between seabed and waves such as progressive wave or partial standing wave with arbitrary reflection ratio or standing wave have been developed by many researchers including Lee et al.(2014; 2015a; 2015b; 2015c; 2015d) and Yamamoto et al.(1978). They handled the pore-water pressure as oscillating pore-water pressure and residual pore-water pressure separately and discussed the seabed response on each pore-water pressure. However, based on field observations and laboratory experiments, the oscillating and residual pore-water pressures in the seabed do occur not separately but together at the same time. Therefore, the pore-water pressure should be investigated from a total pore-water pressure point of view. Thus, in this paper, the wave-induced seabed response including liquefaction depth was discussed among oscillating, residual, and total pore-water pressures' point of view according to the variation of wave, seabed, and flow conditions. From the results, in the field of flow with the same direction of progressive wave, the following seabed response has been identified; with increase of flow velocity, the dimensionless oscillating pore-water pressure increases, but the dimensionless residual pore-water pressure decreases, and consequently the dimensionless total pore-water pressure and the dimensionless liquefaction depth decrease.

• Journal of Ocean Engineering and Technology
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• v.17 no.1
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• pp.47-54
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• 2003

In this study, the residual stress and the acoustic emission Charactreistics from fatigue crack propagation were investigated, bused on the welded material of STS316L. The residual stress of welding locations could be evaluated by ultrasonic parameters, such as L$_{CR}$ wave velocity and L$_{CR}$ wave frequency； the residual stress between base metal and weld metal was evaluated. In the fatigue tests, three types of signals were observed, regardless of specimen condition, base metal, and weld metal. Based on NDE analysis of AE signals by the time-frequency analysis method, it should also be possible to evaluate, in real-time, the crack propagation and final fracture process, resulting from various damages and defects in welded structural members.

• Korean Journal of Environmental Agriculture
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• v.22 no.2
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• pp.130-136
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• 2003

An organophosphorus insecticide, chlorpyrifos and an arylnitrile fungicide, chlorothalonil commonly used far apple were subjected to a residual investigation under field conditions to ensure safety of terminal residues at harvest. After pesticides were applied at standard rate in apple tree fer 15 days for chlorpyrifos and 30 days far chlorothalonil, persistence of their residues in apple was investigated by several interval. At harvest, residual concentrations of chlorpyrifos and chlorothalonil in apple were 1.3 and 2.4mg/kg, respectively, and the residue levels were higher than MRL 1.0 mg/kg in Korea. As well fitted by the first-oder kinetics, biological half-lives of the pesticide residues in apple were 9.3 days for chlorpyrifos and 32.2 days for chlorothalonil. During the storage, half-lives of chlorpyrifos and chlorothalonil were 35.0 and 56.3days at room temperature, and 120.7 and 182.8 days at 412, respectively. Distribution of chlorpyrifos residue in flesh, fruit skin and stalk cavity of each apple corresponded to 0.1% 22.8% and 77.1%, respectively. In case of chlorothalonil, residue in flesh, fruit skin and stalk cavity was 4.4%, 10.4% and 85.2%, respectively.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2008.04a
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• pp.205-208
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• 2008

This paper propose a advanced technique for exciting and receiving the guided torsional wave to detect flaws in pipe systems. There are some difficulties in selecting and exciting of modes by using the nickel strip attached on pipe systems, such as qualification of residual magnetic field and multi-exciting of the unwanted modes etc. In order to there difficulties we propose the new sensor, so called Crossed-coils sensor. We will prove that it is possible to select the modes to be excited and to find a optimal excitation condition for torsional mode by using the proposed sensor.