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Park, Seong Je,Lee, Ji Eun,Park, Jean Ho,Lee, Nak Kyu,Lyu, Min-Young,Park, Keun,Koo, Myung Sool,Cho, Sung Hwan,Son, Yong,Park, Suk-Hee Hindawi Limited 2018 Advances In Materials Science And Engineering Vol.2018 No.1
<P>Fused deposition modeling (FDM), one of the archetypal 3D printing processes, typically requires support structures matched to printed model parts that principally have undercut or overhung features. Thus, the support removal is an essential postprocessing step after the FDM process. Here, we present an efficient and rapid method to remove the support part of an FDM-manufactured product using the phenomenon of oxidative degradation of hydrogen peroxide. This mechanism was significantly effective on polyvinyl alcohol (PVA), which has been widely used as a support material in the FDM process. Compared to water, hydrogen peroxide provided a two times faster dissolution rate of the PVA material. This could be increased another two times by applying ultrasonication to the solvent. In addition to the rapidness, we confirmed that amount of the support residues removed was enhanced, which was essentially caused by the surface roughness of the FDM-fabricated part. Furthermore, we demonstrated that there was no deterioration with respect to the mechanical properties or shape geometries of the obtained 3D printed parts. Taken together, these results are expected to help enhance the productivity of FDM by reducing the postprocessing time and to allow the removal of complicated and fine support structures, thereby improving the design capability of the FDM technique.</P>
Yoon, Kyung Jean,Song, Seul Ji,Seok, Jun Yeong,Yoon, Jung Ho,Kim, Gun Hwan,Lee, Jong Ho,Hwang, Cheol Seong IOP Pub 2013 Nanotechnology Vol.24 No.14
<P>Various types of bipolar resistive switching (BRS) at the filament ruptured region by the unipolar resistive switching (URS) reset in the structure Pt/TiO<SUB>2</SUB>/Pt were categorized in terms of operation polarity and switching parameters. The differences in BRS behavior, even under identical current–voltage switching, are closely related to the previously performed URS reset parameter, especially the power consumed during the reset process. Various modes of BRS from the URS reset status in the structure Pt/TiO<SUB>2</SUB>/Pt are reported, and interpreted in terms of a distinct oxygen vacancy configuration in the ruptured region of a Magnéli filament.</P>
Kim, Gun Hwan,Lee, Jong Ho,Ahn, Youngbae,Jeon, Woojin,Song, Seul Ji,Seok, Jun Yeong,Yoon, Jung Ho,Yoon, Kyung Jean,Park, Tae Joo,Hwang, Cheol Seong WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.11
<P><B>Abstract</B></P><P>Various array types of 1‐diode and 1‐resistor stacked crossbar array (1D1R CA) devices composed of a Schottky diode (SD) (Pt/TiO<SUB>2</SUB>/Ti/Pt) and a resistive switching (RS) memory cell (Pt/TiO<SUB>2</SUB>/Pt) are fabricated and their performances are investigated. The unit cell of the 1D1R CA device shows high RS resistance ratio (≈10<SUP>3</SUP> at 1.5 V) between low and high resistance state (LRS and HRS), and high rectification ratio (≈10<SUP>5</SUP>) between LRS and reverse‐state SD. It also shows a short RS time of <50 ns for SET (resistance transition from HRS to LRS), and ≈600 ns for RESET (resistance transition from LRS to HRS), as well as stable RS endurance and data retention characteristics. It is experimentally confirmed that the selected unit cell in HRS (logically the “off” state) is stably readable when it is surrounded by unselected LRS (logically the “on” state) cells, in an array of up to 32 × 32 cells. The SD, as a highly non‐linear resistor, appropriately controls the conducting path formation during the switching and protects the memory element from the noise during retention.</P>
Optimization of Chemical Structure of Schottky-Type Selection Diode for Crossbar Resistive Memory
Kim, Gun Hwan,Lee, Jong Ho,Jeon, Woojin,Song, Seul Ji,Seok, Jun Yeong,Yoon, Jung Ho,Yoon, Kyung Jean,Park, Tae Joo,Hwang, Cheol Seong American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.10
<P>The electrical performances of Pt/TiO<SUB>2</SUB>/Ti/Pt stacked Schottky-type diode (SD) was systematically examined, and this performance is dependent on the chemical structures of the each layer and their interfaces. The Ti layers containing a tolerable amount of oxygen showed metallic electrical conduction characteristics, which was confirmed by sheet resistance measurement with elevating the temperature, transmission line measurement (TLM), and Auger electron spectroscopy (AES) analysis. However, the chemical structure of SD stack and resulting electrical properties were crucially affected by the dissolved oxygen concentration in the Ti layers. The lower oxidation potential of the Ti layer with initially higher oxygen concentration suppressed the oxygen deficiency of the overlying TiO<SUB>2</SUB> layer induced by consumption of the oxygen from TiO<SUB>2</SUB> layer. This structure results in the lower reverse current of SDs without significant degradation of forward-state current. Conductive atomic force microscopy (CAFM) analysis showed the current conduction through the local conduction paths in the presented SDs, which guarantees a sufficient forward-current density as a selection device for highly integrated crossbar array resistive memory.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-10/am301293v/production/images/medium/am-2012-01293v_0012.gif'></P>
김성규(Kim, Sung-Kyu),윤희성(yoon, Hee-Seong),김예진(Kim, Ye-Jean),전정환(Jeon, Jeong-Hwan) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.11
우리나라의 청년 실업자가 나날이 증가 하고 취업난이 지속됨에 따라 취업률이 대학평가에서 중요시 되고 있다. 지금까지 취업률 개선을 위해 학계 및 다양한 방면에서 연구가 진행되고 있으며, 여러 가지 활동들이 진행되어 왔다. 하지만 여전히 체계적이고 장기적인 지원 등에 있어서는 지속적인 개선 필요성이 제기 되고 있다. 이에 본 연구는 취업률 제고에 영향을 미치는 주요활동을 조사하고 중요도를 분석하고자 한다. 구체적으로 첫째, 주요 19개 대학에서 시행중인 취업지원 프로그램을 조사하였다. 둘째, 재학생과 취업지원관을 대상으로 AHP 분석을 통하여 취업지원 프로그램의 상대적 중요도를 분석하였다. 셋째, 재학생과 취업지원관간의 취업지원 프로그램에 대한 중요도 인식의 차이 여부를 분포 matrix를 구성하여 Portfolio 분석을 실시하였다. 본 연구의 결과는 향후 대학의 취업역량 강화 및 효율적인 취업지원정책수립에 도움이 될 수 있을 것으로 기대된다. The percentage of employment is getting important in the evaluation of university as the youth unemployment is increasing day by day and job shortage is followed. To improve the employment, several research from academy and various fields has been performed. However, systemic and long-term supports for improving the percentage of employment has been raised. Therefore, this study aims to survey the main activities for employment and analyse the importance of main activities. First, supporting activities for employment are surveyed about 19 universities. Second, the relative importance of supporting activities for employment are analysed to students and employment supporter by AHP. Third, portfolio analysis are conducted to analyse the difference of awareness on the employment supporting activities. This study is expected to strengthen the capability of university's employment and help to establish the policy for employment supporting activities.