• 대한기계학회논문집A
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• 제26권2호
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• pp.300-307
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• 2002

Partial penetration welding joint is defined as groove welds welded from one side, without steel backing or groove welds welded from both sides but without back gouging. So it has an unwelded portion at the root of the weld. Study of partial penetration weldment fracture behavior includes residual stress analysis and fracture analysis. The J-integral loses its path independency in residual stress field. Therefore, it is necessary to introduce a new J-integral, J, which is defined including the effect of plastic deformation and thermal strain. In this study, theoretical formulation and program were developed for the evaluation of J-integral for the crack tip located in the weldment. Evaluations of fracture behavior were performed for partial penetration multi-pass weldment of 25.4mm thick plate by J-integral. From a point of fracture in partial penetration multi-pass welding, it seemed to be better to control root face smaller than 6.35mm.

• 대한방사성의약품학회지
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• 제5권2호
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• pp.79-82
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• 2019

⁶¹Cu is a promising PET radiometal having favorable nuclear decay characteristics with appropriate half-life of 3.3 h. Owing its promising capabilities in radiopharmaceutical chemistry and its chemical similarities with its isotopes ⁶⁴Cu and ⁶⁷Cu, in this work we have tried to optimize the production and separation conditions of ⁶¹Cu. ⁶¹Cu was produced via (p, x) reaction with natural nickel which was electroplated on the high purity silver coated copper backing target holder. The optimization of target electrodeposition, beam energy and current modulation, target dissolution and separation were optimized in this study. Preliminary studies show that ⁶¹Cu was successfully produced and separated which can be further extended for the production of ⁶⁴Cu and ⁶⁷Cu.

• Journal of the Korean Wood Science and Technology
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• 제17권2호
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• pp.26-33
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• 1989

The acoustic absorption coefficient and acoustic impedance of 5 species of softwood(sonamoo, sam namoo, gusang namoo, hwaback, sitka spruce) and 5 species of hardwood (Mulgusul namoo, Italian popular, white meranti, red meranti, kalantas) were measured by the standing wave method. which is simple in the setup and gives more accurate result than does any other measuring method. The dependence of the absorption coefficient and complex acoustic impedance on the wood sections. thickness of the sample itself and the back air gap was investigated experimentally in the frequency range from 200Hz to 1800Hz, and the result are as follows: 1. The acoustic absorption coefficient of wood sections was higher on the cross section than radial and tangential sections. 2) The acoustic absorption coefficient were higher in the frequency range from 400Hz to 600Hz, but decreased in the frequency above 600Hz. 3. The genenal tendency of the variation of the normal acoustic impedance was increased according to the frequency. 4. The acoustic absortion coefficient was increased in the to 7mm-thick sample and decreased in 9mm-thick sample. 5. The higher acoustic absorption coefficient was shown in the case with the backing an gap than in the case without the gap.

• Journal of Biosystems Engineering
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• 제35권3호
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• pp.189-196
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• 2010

This study was conducted to develop an non-contact ultrasonic transducer for measurement of fruit firmness. The center frequency of non-contact ultrasonic transducer was 500 kHz. As an active element of non-contact ultrasonic transducer, the 1-3 piezoelectric composite material was selected. That material has high piezoelectric properties such as electro-mechanical coupling factor, $k_t$ and piezoelectric voltage constant, $d_{33}$ and also that material has low acoustical impedance which enables to matching the acoustical impedances between piezoelectric material and air. As a front matching material between 1-3 piezoelectric composite material and air, various kinds of paper with different thickness were tested. To control the dead-zone of the fabricated non-contact ultrasonic transducer, the backing material composed of epoxy resin and tungsten powder were made and evaluated. The fabricated non-contact ultrasonic transducer for fruit showed that the cneter frequency, bandwidth and beamwidth were approximately 480 kHz, 30 % and 12 mm, respectively. It was concluded that non-contact measurement of apple firmness would be possible by using the fabricated non-contact ultrasonic transducer.

• 한국진공학회지
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• 제16권6호
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• pp.405-413
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• 2007

진공시스템 최적화 설계를 위한 시스템 성능에 대한 설계인자 영향이 전산모사로 연구되었다. 본 연구로 상업화 전산모사기인 $VacSim^{Multi}$에 의한 진공시스템 모델링기구가 제시되었으며 진공시스템의 진공생성기구인 펌핑계 설계인자의 영향을 평가하여 향후 여러 설계인자들의 전산모사 연구 가능성이 확인되었다. $VacSim^{Multi}$의 저진공펌프 모델 전산모사 결과와 펌프사양에 의한 배기거동이 오차범위로 일치하였으며 부스터펌프의 사용이 중진공영역 응용에 효과적인 것으로 확인되었다. 또한 자체 배기능력이 없는 유확산펌프와 터보분자펌프 배기계의 최적화보조펌프 조합이 제시되었으며, 유확산 및 터보분자펌프 배기계의 시스템 공정응용특성도 확인되었다.

• 한국주조공학회지
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• 제29권1호
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• pp.45-51
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• 2009

Conventionally, Al-Sn bearing manufacturing involves casting the Al-Sn alloy and roll-bonding to a steel backing strip. This article will describe the microstructural control of Al-Sn metal bearing alloy following heat treatment. When the pure aluminum rod dipped in the melt of tin maintained below the melting point of aluminum, the melting of aluminum was accelerated with penetration of tin along the grain boundary of aluminum. The length of plate-shaped eutectic tin was decreased with heat treatment time. With even longer heat treatment time over 1 hour the length of eutectic tin didn't decrease any more, while resulting in coarsening of aluminum matrix. Exuded liquid of eutectic tin was formed at the surface of Al-Sn alloy after heat treatment even at below eutectic temperature.

• 한국항행학회논문지
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• 제12권2호
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• pp.164-169
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• 2008

본 논문에서는 영상분할에 의한 동작 추적 기법을 이용하여 침입자를 감시하고 관련 정보를 모바일 기반으로 확인하도록 하였다. 먼저, 탐지하고자 하는 일정한 영역을 촬영한 동영상에서 프레임을 추출하고, 인접한 두 프레임 사이의 이미지 차를 사용하여, 고정된 배경과 움직이는 대상을 분할한다. 분할된 전경 물체에서 에지를 검출하여 지정된 위치별로 추출된 에지의 중간 값을 추정하여 동작을 분석함으로써 침입자를 감시할 수 있도록 하였다. 동작이 검출되면, 영상은 WAP 풀 기반 영상 전송 방법을 사용하여 모바일 클라이언트로 전송한다.

• Progress in Superconductivity
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• 제12권2호
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• pp.110-113
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• 2011

We have grown a Nb/Gd bilayer on a$SiO_2$/Si substrate by using a DC magnetron sputtering system, which was fabricated in situ with silicon stencil masks. In order to investigate proximity effect of the Nb/Gd bilayer, we used a planar tunnel junction with an AlOx tunnel barrier by oxidizing the Al ground electrode at the bottom. A $Co_{60}Fe_{40}$ backing of Al was deposited so as to reduce the superconductivity of the Al, ensuring a normal counterelectrode. With a 50-nm-thick Nb layer, we have measured dI/dV (dynamic conductance) by varying the thickness of Gd, which can reveal the density of states (DOS) of the Nb/Gd bilayer as a function of the Gd thickness resulting from the proximity effect of a superconductor/ferromagnet bilayer (S/F). The SF proximity effect in Nb/Gd will be discussed in comparison to our previous results of the CoFe/Nb, Ni/Nb and CuNi/Nb proximity effect; Gd is expected to show different effects since Gd has f-electrons, while CoFe, Ni, and CuNi have only d-electrons. Our studies will focus on the triplet correlation in a superconducting pair.

• 한국정보통신학회논문지
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• 제6권2호
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• pp.282-287
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• 2002

본 논문에서는 모바일 인터넷을 기반으로 침입자를 감시하기 위하여 영상분할 기법에 의한 동작 추적 기법을 사용하였다. 먼저, 탐지하고자 하는 일정한 영역을 촬영한 동영상에서 프레임을 추출하고, 인접한 두 프레임 사이의 이미지 차를 사용하여, 고정된 배경과 움직이는 대상을 분할한다. 분할된 전경 물체에서 에지를 검출하여 지정된 위치별로 추출된 에지의 중간 값을 추정하여 동작을 분석함으로써 침입자를 감시할 수 있도록 하였다. 이러한 감시정보는 감지된 일련번호, 날짜, 시간의 기록과 함께 이미지 파일로 저장되어 서버에 저장되며 모바일 클라이언트에게 감시 장소의 상황에 대하여 SMS Message를 발송하도록 하였다.

• 전자공학회논문지CI
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• 제38권2호
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• pp.9-15
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• 2001

본 논문은 적응 피지 제어 시스템에 있어 유전자 알고리즘에 대한 새로운 방법을 제안한다. 다중개체군 유전자 알고리즘을 이용한 이전의 논문은 염색체를 두부분(제어규칙과 소속함수)으로 분할하였다. 그러나 이런 경우 좋지 못한 제어규칙은 좋은 제어규칙과 잘 진화된 소속함수의 최적화를 방해한다. 다중개체군 유전자 알고리즘에 대한 새로운 방법은 염색체를 세부분(좋은 제어규칙, 좋지 못한 제어규칙 및 소속함수)으로 분할하는 것이다. 이 방법에 대한 효율성을 입증하기 위해 트럭 배킹 문제에 적용하였다. 시뮬레이션 결과 다중개체군 유전자 알고리즘에 대한 제안된 방법이 좋은 적응성을 보여 주었다.