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정병창,이두호,윤병동,이수범 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.8
The performance of surface damping treatments may vary once the surface is exposed to a wide range of temperatures, because the performance of viscoelastic damping material is highly dependent on operational temperature. In addition, experimental data for dynamic responses of viscoelastic material are inherently random, which makes it difficult to design a robust damping layout. In this paper a statistical modeling procedure with a statistical calibration method is suggested for the variability characterization of viscoelastic damping material in constrained-layer damping structures. First, the viscoelastic material property is decomposed into two sources: (i) a random complex modulus due to operational temperature variability, and (ii) experimental/model errors in the complex modulus. Next, the variability in the damping material property is obtained using the statistical calibration method by solving an unconstrained optimization problem with a likelihood function metric. Two case studies are considered to show the influence of the material variability on the acoustic performances in the structural-acoustic systems. It is shown that the variability of the damping material is propagated to that of the acoustic performances in the systems. Finally, robust and reliable damping layout designs of the two case studies are obtained through the reliability-based design optimization (RBDO) amidst severe variability in operational temperature and the damping material.
정병창,김현회,박용현 대한비뇨의학회 2009 Investigative and Clinical Urology Vol.50 No.10
Purpose: Recently, the whole DNA sequence of Bacillus subtilis (B. subtilis) was identified, revealing the existence of the YvrK gene encoding a 43 kD oxalate decarboxylase (OXDC), which degrades oxalate by a simple pathway. The objective of this study was to develop recombinant Escherichia coli (E. coli) expressing the Yvrk gene from B. subtilis. Materials and Methods: After the extraction of total DNA from B. subtilis, the YvrK gene was cloned by polymerase chain reaction. The cloned DNA encoding OXDC was inserted into the pBAD/gIII-A vector, downstream of the L-arabinose promotor. The plasmid vector was transformed into TOP 10 E. coli, and the transformants were selected with ampicillin. The recombinant E. coli, named pBy, was then analyzed by DNA sequencing and Western blot. To evaluate the oxalate-degrading function of pBy, pBy was cultured in LB broth containing oxalate, and then the amount of oxalate in the medium was assessed. The oxalate-degrading activity of homogenates of pBy was evaluated. Results: DNA sequencing showed the successful transformation of the YvrK gene into TOP 10 E. coli. Western blot analyses showed that pBy expressed OXDC. pBy removed oxalate during the overnight culture in oxalate-containing LB broth, and the homogenate of pBy degraded 90% of oxalate under acidic conditions. Conclusions: A recombinant E. coli expressing the YvrK gene was successfully produced. The bacteria showed potent oxalate-degrading activity. The results of this study will provide a solution to the treatment of calcium oxalate stones and hyperoxaluria, for which there are few medical treatment modalities. Purpose: Recently, the whole DNA sequence of Bacillus subtilis (B. subtilis) was identified, revealing the existence of the YvrK gene encoding a 43 kD oxalate decarboxylase (OXDC), which degrades oxalate by a simple pathway. The objective of this study was to develop recombinant Escherichia coli (E. coli) expressing the Yvrk gene from B. subtilis. Materials and Methods: After the extraction of total DNA from B. subtilis, the YvrK gene was cloned by polymerase chain reaction. The cloned DNA encoding OXDC was inserted into the pBAD/gIII-A vector, downstream of the L-arabinose promotor. The plasmid vector was transformed into TOP 10 E. coli, and the transformants were selected with ampicillin. The recombinant E. coli, named pBy, was then analyzed by DNA sequencing and Western blot. To evaluate the oxalate-degrading function of pBy, pBy was cultured in LB broth containing oxalate, and then the amount of oxalate in the medium was assessed. The oxalate-degrading activity of homogenates of pBy was evaluated. Results: DNA sequencing showed the successful transformation of the YvrK gene into TOP 10 E. coli. Western blot analyses showed that pBy expressed OXDC. pBy removed oxalate during the overnight culture in oxalate-containing LB broth, and the homogenate of pBy degraded 90% of oxalate under acidic conditions. Conclusions: A recombinant E. coli expressing the YvrK gene was successfully produced. The bacteria showed potent oxalate-degrading activity. The results of this study will provide a solution to the treatment of calcium oxalate stones and hyperoxaluria, for which there are few medical treatment modalities.
비침투식 밴드형 센서와 상호 상관함수를 이용한 배관 누설 탐지 기법의 실험적 고찰
정병창,노형주,박진우,정선아,엄성민,신윤호 한국비파괴검사학회 2023 한국비파괴검사학회지 Vol.43 No.2
At industrial sites, developing technologies that can rapidly detect pipe damage is crucial to minimize losses caused by pipe ruptures or leakages. Pipe damage can be categorized as either a rupture or a leakage depending on its size; various studies have been conducted to detect them. In this study, a non-intrusive pipe pressure monitoring sensor, wrapped around the pipe from the outside, was utilized to measure the internal pressure and fluid-structure coupled vibration. Based on the measured signals, a leak localization technique was proposed and examined experimentally. The proposed technique estimates the time difference between two signals measured by non-intrusive band-type sensors using cross-correlation functions and estimates the leakage location using the distance between the sensors and the wave propagation velocity. Experimental results demonstrated that the actual leakage location can be estimated within 8% accuracy using this method. 산업 현장에서 배관 손상 발생 시 신속하게 손상 위치를 탐지하거나 파악할 수 있는 기술의 개발은 배관 파손에 따른 사고의 확산 및 이에 따른 인적, 물적 손실을 감소시키기 위해 매우 중요하다. 배관의 손상은 그 크기에 따라 파열(rupture)과 누설(leakage)로 구분할 수 있으며, 다양한 방식으로 이들을 탐지하기 위한 연구가 진행되었다. 본 연구에서는 배관 외부에 감아 설치되어 배관 내부 압력과 유체-배관 연성 거동의 측정이 가능한 비침투식 밴드형 배관 압력 모니터링 센서(밴드형 센서)를 활용하여, 힘 신호 기반의 배관 누설 위치 탐지 기법을 제시하였다. 누설 탐지를 위해 상호상관함수를 활용하여 밴드형 센서 간 측정된 신호의 도달 시간 차이를 계산하였고, 센서 간 거리 및 전파 속도를 이용하여 누설 위치를 추정하였다. 밴드형 센서를 포함한 배관계를 대상으로 누설 탐지 가능성을 고찰하였으며, 누설 위치를 8% 이내의 오차로 추정할 수 있음을 실험적으로 확인하였다.