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Effect of Rail Surface Damage on Contact Fatigue Life (레일표면손상이 접촉피로수명에 미치는 영향)

  • Seo, Jung-Won;Lee, Dong-Hyong;Ham, Young-Sam;Kwon, Sung-Tae;Kwon, Seok-Jin;Cho, Ha-Yong
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.6
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    • pp.613-620
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    • 2012
  • Rails are subjected to damage from rolling contact fatigue, which leads to defects such as cracks. Rolling contact fatigue damages on the surface of rail such as head check, squats are one of growing problems. Another form of rail surface damage, known as "Ballast imprint" has become apparent. This form of damage is associated with ballast particles becoming trapped between the wheel and the surface of rail. These defects are still one of the key reasons for rail maintenance and replacement. In this study, we have investigated whether the ballast imprint is an initiator of head check type cracks and effect of defect size using Finite element analysis. The FE analysis were used to investigate stresses and strains in subsurface of defects according to variation of defect size. Based on loading cycles obtained from FE analysis, fatigue analysis for each point was carried out.

Characteristics of the Contact Angle Using the Microwave Plasma Treatment on Scintillator Panel Substrates (마이크로웨이브 플라즈마 처리를 통한 섬광체 패널 기판의 접촉가 특성변화)

  • Kim, Byoungwook;Kim, Youngju;Ryu, Cheolwoo;Choi, Byoungjung;Kwon, Youngman;Lee, Youngchoon;Kim, Myungsoo;Cho, Gyuseong
    • Journal of Radiation Industry
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    • v.8 no.1
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    • pp.43-47
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    • 2014
  • By measuring decrease change of the contact angle after microwave plasma treatment on the glass and Al as a scintillator panel sample substrate, the adhesive performance of scintillator panel can be expected to improve. Also resolution and sensitivity of scintillator panel after microwave plasma treatment can be expected to maintain highly.

Characteristics of p-InGaN/GaN Superlattice structure of the p-GaN according to annealing conditions (p-InGaN/GaN 초격자구조에서 열처리 조건에 따른 오믹전극의 특성)

  • Jang, Seon-Ho;Kim, Sei-Min;Lee, Young-Woong;Lee, Young-Seok;Lee, Jong-Seon;Park, Min-Jung;Park, Il-Kyu;Jang, Ja-Soon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.160-160
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    • 2010
  • In this work, we investigate ohmic contacts to p-type GaN using a Pt/Cu/Au metallization scheme in order to achieve low resistance and thermally stable ohmic contact on p-GaN. An ohmic contact formed by a metal electrode deposited on a highly doped InGaN/GaN superlattice sturucture on p-GaN layer. The specific contact resistance is $1.56{\times}10^{-6}{\Omega}cm^2$ for the as-deposited sample, $1.35{\times}10^{-4}{\Omega}cm^2$ for the sample annealed at $250^{\circ}C$ and $6.88{\times}10^{-3}{\Omega}cm^2$ for the sample annealed at $300^{\circ}C$.

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Study on Non-contact Ultrasonic Transducer for Measurement of Fruit Firmness (과실 경도측정을 위한 비접촉 초음파 변환기 연구)

  • Lee, Sang-Dae;Ha, Tae-Hoon;Kim, Ki-Bok;Kim, Man-Soo
    • Journal of Biosystems Engineering
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    • v.35 no.3
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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.

Surgical Treatment of Vocal Cord Granuloma (성대돌기 육아종의 수술적 치료)

  • Yu, Myeong-Sang;Song, Hyung-Min;Roh, Jong-Lyel;Choi, Seung-Ho;Kim, Sang-Yoon;Nam, Soon-Yuhl
    • Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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    • v.17 no.1
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    • pp.49-52
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    • 2006
  • Background and Objectives: Vocal cord granuloma is a exophytic inflammatory mass and caused by gastroesophageal reflux, voice abuse, endotracheal intubation. There has been a controversy in the treatment of vocal cord granuloma. Our aim of study is to know the clinical characteristics and the results of surgical management for vocal cord granuloma. Materials and Methods: We have reviewed and analyzed medical records of 55 patients who were diagnosed and surgically treated as vocal cord granuloma in Asan medical center from 1997 to 2005 retrospectively. Results: 25 cases were intubation granuloma and 30 cases were contact granuloma. In intubation granuloma, the clinical manifestation was hoarseness(70%), foreign body sensation(44%), chronic cough(21%). In contact granuloma, the clinical manifestation was hoarseness(67%), foreign body sensation(60%), throat clearing(21%). The recurrence rate after surgery was 8% in intubation granuloma and 33% in contact granuloma. Mean recurrence time was 4.1months in intubation granuloma and 3.2months in contact granuloma. Conclusion: Although there is no significant difference, recurrence rate after surgery was high in contact granuloma compared to intubation granuloma(p=0.125). Although this study is retrospective, surgical management must be considered in resolving diagnostic doubt, treating airway obstruction, and failure in conservative treatments.

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Electrical properties of polyethylene composite films filled with nickel powder and short carbon fiber hybrid filler

  • Mironov, V.S.;Kim, Seong Yun;Park, Min
    • Carbon letters
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    • v.14 no.2
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    • pp.105-109
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    • 2013
  • Effects of the amount of nickel powder (Ni) in Ni-carbon fiber (CF) hybrid filler systems on the conductivity(or resistivity) and thermal coefficient of resistance (TCR) of filled high density polyethylene were studied. Increases of the resistivity and TCR with increasing Ni concentration at a given hybrid filler content were observed. Using the fiber contact model, we showed that the main role of Ni in the hybrid filler system is to decrease the interfiber contact resistance when Ni concentration is less than the threshold point. The formation of structural defects leading to reduced reinforcing effect resulted in both a reduction of strength and an increase of the coefficient of thermal expansion in the composite film; these changes are responsible for the increases of both resistivity and TCR with increasing Ni concentration in the hybrid filler system.

New Evaluation Method for The Particle Size and Morphology Via Change of Ground Particle During a Grinding Process (분쇄공정에서 변화된 입자크기 및 형상특성의 평가방법에 관한 새로운 제언)

  • Choi, Heekyu;Lee, Jehyun;Choi, Junewoo
    • Particle and aerosol research
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    • v.9 no.1
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    • pp.1-6
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    • 2013
  • New evaluation method for the particle size and morphology via change of ground particle during a grinding process was investigated. The grinding experiments were carried by a planetary ball mill. The relationship between the particle outline of the scanning electron microscopy photograph and measurement line, the measurement contact number was evaluated. The value of contact number decreased with the increase in the particle size of the ground sample, and varied with the experimental conditions. The value of contact number, which is related to the particle size of the raw sample, changed at the various experimental conditions.

Influence of a soft FGM interlayer on contact stresses under a beam on an elastic foundation

  • Aizikovich, Sergey M.;Mitrin, Boris I.;Seleznev, Nikolai M.;Wang, Yun-Che;Volkov, Sergey S.
    • Structural Engineering and Mechanics
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    • v.58 no.4
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    • pp.613-625
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    • 2016
  • Contact interaction of a beam (flexible element) with an elastic half-plane is considered, when a soft inhomogeneous (functionally graded) interlayer is present between them. The beam is bent under the action of a distributed load applied to the surface and a reaction of the elastic interlayer and the half-space. Solution of the contact problem is obtained for different values of thickness and parameters of inhomogeneity of the layer. The interlayer is assumed to be significantly softer than the underlying half-plane; case of 100 times difference in Young's moduli is considered as an example. The influence of the interlayer thickness and gradient of elastic properties on the distribution of the contact stresses under the beam is studied.

Over 8% efficient nanocrystal-derived Cu2ZnSnSe4 solar cells with molybdenum nitride barrier films in back contact structure

  • Pham, Hong Nhung;Jang, Yoon Hee;Park, Bo-In;Lee, Seung Yong;Lee, Doh-Kwon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.426.2-426.2
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    • 2016
  • Numerous of researches are being conducted to improve the efficiency of $Cu_2ZnSnSe_4$ (CZTSe)-based photovoltaic devices, which is one of the most promising candidates for low cost and environment-friendly solar cells. In this work, we concentrate on the back contact of the devices. A proper thickness of $MoSe_2$ in back contact structure is believed to enhance adhesion and ohmic contact between Mo back contact and absorber layer. Nevertheless, too thick $MoSe_2$ layers that are grown during high-temperature selenization process can impede the current collection, thus resulting in low cell performance. By applying molybdenum nitride as a barrier in back contact structure, we were able to control the thickness of $MoSe_2$ layer, which resulted in lower series resistance and higher fill factor of CZTSe devices. The phase transformation of Mo-N binary system was systematically studied by changing $N_2$ concentration during the sputtering process. With a proper phase of Mo-N fabricated by using an adequate partial pressure of $N_2$, the efficiency of CZTSe solar cells as high as 8.31% was achieved while the average efficiency was improved by about 2% with respect to that of the referent cells where no barrier layer was employed.

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