High tensile strength of sputter-deposited ZrB₂ ceramic thin films measured up to 1016 K

Sim, G.D.,Choi, Y.S.,Lee, D.,Oh, K.H.,Vlassak, J.J. Elsevier Science 2016 Acta materialia Vol.113 No.-

<P>We report the results of tensile experiments on 900 nm sputter-deposited films of ZrB2, performed at temperatures ranging from ambient to 1016 K. The ZrB2 samples were tested using micromachined sample frames with integrated micro-heaters. Transmission electron microscopy shows that both as deposited films and films heated above 1000 K consist of two distinct layers, an amorphous layer and a crystalline layer with a very fine columnar structure. The ZrB2 films have a room-temperature tensile strength in excess of 1.2 GPa, far exceeding the tensile strength of bulk ZrB2, but their stiffness is lower and decreases significantly with increasing temperature. The reduction in stiffness is attributed to the presence of the amorphous phase and the high density of transverse grain boundaries in the crystalline region. The fracture toughness of the ZrB2 films was measured by introducing pre-cracks in the tensile specimens with a focused ion beam, and was found to be 2.57 +/- 0.03 MPa root m, similar to values reported for bulk ZrB2. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.</P>

Superconducting magnet system of in-flight separator for a heavy ion accelerator planned in Korea

Kim, J.W.,Kim, D.G.,Jo, H.C.,Choi, Y.S.,Kim, S.H.,Sim, K.D.,Sohn, M.H. The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.1

An in-flight fragment separator, which aims to produce and study rare isotopes, consists of superferric quadrupole triplets and $30^{\circ}$ dipole magnets to focus and bend the beams for achromatic focusing and momentum dispersion, respectively. The separator is divided into pre and main stages, and we plan to use superconducting magnets employing high-Tc superconductor (HTS) coils in the pre-separator area, where radiation heating is high. The HTS coils will be cooled by cold He gas in 20-50 K, and in the other area, superferric magnets using low-temperature superconductor (LTS) will be used at 4 K. A few LTS coils were wound and successfully tested in a LHe dewar, and the design of cryostat has been optimized. Development of the HTS coils is ongoing in collaboration with a group at KERI. An HTS coil of racetrack shape was wound and tested in a $LN_2$ bath and in a dewar with cryocooler. No degradation on critical current due to coil winding was found.

청소년의 근로 여부에 따른 신체활동 및 스트레스 비교

강지은,김혜원,백다인,신지원,신혜진,심지선,윤도연,이규리,이보라,이혜민,최주연 이화여자대학교 간호과학대학 2014 이화간호학회지 Vol.- No.48

Purpose: The purpose of this study was to investigate the stress and the physical activity according to working in Korean adolescents. Methods: Data were collected from 3 high schools in Seoul and Gyeonggi-do. The total number of four hundred twenty subjects were participated and they completed general questionnaire, International Physical Activity Questionnaire (Korean version) and adolescents stress scale. Data were analyzed by descriptive statistics and t-test using SPSS 21.0 program. Results: The number of employed was 151 (45.2%) and the number of unemployed was 183 (54.8%). Reasons for working were to earn money (44.0%) and to purchase significant product (35.6%). Moderate physical activities of employed students were more than them of unemployed students and there was significant difference (t=3.261, p˂.001). There was no significant difference between employed and unemployed students in the total score of stress. However, there were significant differences on school stress (t=2.854, p=.005) and economical stress (t=3.959, p˂.001) in the subcategory. The stress of employed was higher than the stress of unemployed. Conclusion: As shown in the above result, employed adolescents reported higher levels of both physical activity and stress than unemployed adolescents, thus indicating that employment status of adolescents has a significant impact on physical and mental health. Nursing implications include developing quality care for employed adolescents based on the community health nursing, and providing health education at schools in terms of adolescent employment.

간호 대학생의 성 지식, 성 태도와 성 건강 간호 장애감 간의 관계

김다연,김은아,노수경,류아인,박나은,박지혜,서정민,심효정,주성민,한진실,이건정,박수민 이화여자대학교 간호과학대학 2017 이화간호학회지 Vol.- No.51

Purpose: The purpose of this study was to investigate correlation among sexual knowledge, attitude and Barriers to patient’s sexual health of nursing undergraduate students and to provide objective data to promote sexual health-care. Method: Using a descriptive correlation, 304 nursing undergraduate students were recruited through convenience random sampling from August 1st to December 20th, 2016. Data were analyzed using average, standard deviation, percentage, t-test, ANOVA, Scheffe test, Pearson’s correlation and Multiple linear regression analysis using the SPSS 21.0 program. Results: The correlation between Sexual knowledge and Sexual attitude is statistically significant(r=.289, p<.01). As the level of sexual knowledge is higher, the sexual attitude is more open. And, Sexual knowledge(r=-.307,p<.01) and Sexual attitude(r=.180,p=.002) had a negative relationship with Barriers to patient’s sexual health. Also, Sexual knowledge was the greatest influencing factor on Barriers to patient’s sexual health. Conclusion: This study showed as the level of Sexual knowledge is higher, the Sexual attitude is more open. As the degree of Sexual knowledge is lower, the Sexual attitude is more conservative, and Barriers to patient’s sexual health is more higher. Also, Sexual knowledge is the most influential factor on Barriers to patient’s sexual health.

용접결함의 형상인식을 위한 신경회로망 알고리즘의 성능 비교

김재열,심재기,이동기,김창현,송경석,양동조 한국공작기계학회 2003 한국공작기계학회 추계학술대회논문집 Vol.2003 No.-

In this study, we compared backpropagation neural network(BPNN) with probabilistic neural network(PNN) as shape recognition algorithm of welding flaws. For this purpose, variables are applied the same to two algorithm. Here, feature variable is composed of time domain signal itself and frequency domain signal itself. Through this process, we comfirmed advantages/disadvantages of two algorithms and identified application methods of two algorithms.

GFRP 인장시험 시 적외선 열화상 계측

김진우,이동기,심재기,김재열,최승현 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-

Property of GFRP is naturally dependent on the property of matrix, but receives of temperature effects by external force. Therefore, determination of mechanical property by effect of temperature in GFRP is most crucial factor. In this paper, temperature distribution during crack propagation from temperature change under tensile test was proposed through IR thermography camera. Lock-in thermography method, which is one of technique in IR thermography camera to measure minute change in temperature, was utilized to monitor temperature distribution and change during crack propagation. Method to analyze temperature distribution during crack propagation under tensile test of GFRP via IR thermography camera was suggested. Anisotropy in fiber orientation showed longer fracture time and lower maximum temperature.

봉단 용접부 와전류탐상의 기초적인 연구

박춘호,권우주,서동만,심기섭,김정하 韓國非破壞檢査學會 1998 한국비파괴검사학회지 Vol.18 No.2

핵연료 제작과정에서 봉단마개 용접부는 완벽한 품질이 요구되고 있다. 본 연구에서는 와전류탐상방법을 이용하여 봉단마개 용접부의 검사를 위한 기초적인 방법을 연구하였다. 봉단마개 용접부 와전류검사를 위한 주사속도와 와전류신호의 최대주파수를 찾았고 잡음신호제거를 위해 대역통과여파기(0-250Hz)를 사용하였다. 이러한 와전류탐상방법은 직경 0.35mm의 작은 핀홀결함에서도 좋은 감도를 얻을 수 있었다. In nuclear fuel manufacturing process, end closure welding has long been recognized as requiring very high integrity. In this basic study, ECT(eddy current testing) method for end-closure welding has been developed to detect end cap weld discontinuities for nuclear fuel safety. In order to improve the inspection reliability, the maximum scanning speed and the maximum frequency is investigated for end-closure welding inspection. The bandpass filter(0-250Hz) is used for removing noise effects. This study shows that ECT method is effective and sensitive for the detection of small defect(0.35mm diameter).

Fabrication and device characterization of potassium fluoride solution treated CZTSSe solar cell

Rana, T.R.,Kim, J.,Sim, J.H.,Yang, K.J.,Kim, D.H.,Kang, J.K. Elsevier 2017 Current Applied Physics Vol.17 No.10

<P>Post deposition treatment (PDT) for Cu2ZnSn(S,Se)(4) (CZTSSe) was carried out by simply dipping the absorber into the KF solution at 80 degrees C. The dipping time of absorber in KF solution was found to be crucial to device parameters of CZTSSe solar cell. The K-doping improved the solar cell efficiency from 4.4% to 7.6% by 1 min dipping whereas the longer than 5 min dipping solar cells showed distorted kink J-V curves. The activation energy of CZTSSe solar cell was increased upto 1 min KF treatment from 0.83 eV to 0.92 eV which indicates interface recombination is reduced significantly. However, the activation energies of 5 min and 10 min dipping solar cells were found to be 0.81 eV and 0.63 eV where dominant recombination was interface recombination. Furthermore, trap energies of 49 meV and 298 meV of pristine CZTSSe solar cell were modified to 33 meV and 117 meV for 1 min treated CZTSSe solar cell. Trap energies of 5 min were calculated to be 112 meV and 147 meV. The proper KF doping passivated the shallow as well as deep defects of CZTSSe solar cell which is reflected in photovoltaic performances directly. (C) 2017 Elsevier B.V. All rights reserved.</P>

섬유강화 복합재료 사출성형품의 섬유배향상태

이정주,김진우,김혁,한길영,심재기,이동기 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-

Injection molding is the most widely used process for the industrial forming of plastic articles. During an injection molding process of composites, the fiber-matrix separation and fiber orientation are caused by the flow of molten polymer/fiber mixture. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation·orientation and injection molding conditions. So far, there is no research on the measurement of fiber orientation using image processing. In this study, the effects of fiber content ratio and molding condition on the fiber orientation-angle distributions are studied experimentally. Using the image processing method, the fiber orientation distribution of welding parts in injection-molded products is assessed. And the effects of fiber content and injection mold shapes on the fiber orientation in case of fiber reinforced polymeric composites are studied experimentally.

Porphyrins Bearing Stable<i>m</i><i>eso</i>-Alkylidenyl Double Bonds. A New Family of Nonplanar Porphyrinoids

Sim, E.-K.,Jeong, S.-D.,Yoon, D.-W.,Hong, S.-J.,Kang, Y.,Lee, C.-H. American Chemical Society 2006 Organic letters Vol.8 No.15