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평행평판 도파관의 주기적인 슬릿으로 구성된 PBG 구조
이종익,백운석 東洋大學校 産業技術硏究所 1999 東洋大學校 産業技術硏究所 論文集 Vol.1 No.1
In this study, both the infinite periodic strip gratings on a grounded dielectric slab are considered from the viewpoint of photonic band-gap(PBG) structure for TE polarization case. Parallel-plate waveguide(PPW) with finite number of periodic slits in its upper wall is considered as a finite periodic structure. Complex propagation constants(β-jα) of the infinite periodic structure against operating frequency are computed to show the effect of the geometric parameters such as dielectric constant, guide height, strip width on the bandwidth and center frequency of the PBG structure. Reflected and transmitted powers against the operating frequency in the practical finite periodic structure are also computed along with the results of complex propagation constants in the infinite periodic structure.
119구급대를 통한 서울지역 외상환자 진료체계에 대한 통계분석
서길준,이승한,조익준,권운용,송형곤,이중의,윤여규 대한응급의학회 2001 대한응급의학회지 Vol.12 No.2
Backgroud: Despite continous efforts to improve the prehospital trauma care system in Korea, the preventable death rate has been reported to be high. The purpose of this study was to evaluate the prehospital trauma care system in Seoul by analyzing 119 rescue databases. Methods: The 119 rescue data bases of 22,275 trauma patients, who were transported to the secondary and tertiary hospital in Seoul by Seoul 119 rescue services from January 1, 2000 to December 31, 2000, were analyzed. Results: The response time(mean 3.7 min.) showed no time, weekly, and regional variations. However, the transport time from field to hospital showed was high in the morning rush hour(7:00 to 10:00 am), and was gradually decreased and the lowest between 10:00 pm and 7:00 am. There was also a regional variation in the transport time, which was short in the central area and long in the peripheral area of Seoul. Prehospital cares were given to the 10,999 trauma patients(49.4%). Of the 464 unresponsive patients(2%), only 236 patients were identified in transported hospitals. The outcomes of these unresponsive patients were DOA(54%), survival(19%), death in ER(14%), transfer to other hospitals(8%), and death after admission(5%) in order. Conclusion: We suggest that this study may be helpful to the establishment and improvement of the prehospital trauma care system as well as the determination of the adequate numbers and locations of trauma center in Seoul.
Deep-Nanoscale Pattern Engineering by Immersion-Induced Self-Assembly
Park, Woon Ik,Kim, Jong Min,Jeong, Jae Won,Jung, Yeon Sik American Chemical Society 2014 ACS NANO Vol.8 No.10
<P>The directed self-assembly (DSA) of block copolymers (BCPs) is expected to complement conventional optical lithography due to its excellent pattern resolution and cost-effectiveness. Recent studies have shown that BCPs with a large Flory–Huggins interaction parameter (χ) are critical for a reduction of the thermodynamic defect density as well as an increase in pattern density. However, due to their slower self-assembly kinetics, high-χ BCPs typically necessitate solvent vapor annealing, which requires complex facilities and procedures compared to simple thermal annealing. Here, we introduce an immersion-triggered directed self-assembly (iDSA) process and demonstrate the combined advantages of excellent simplicity, productivity, large-area capability, and tunability. We show that the vapor-free, simple immersion of high-χ BCPs in a composition-optimized mixture of nonswelling and swelling solvents can induce the ultrafast (≤5 min) formation of nanoscale patterns with a pattern size ranging from 8–18 nm. Moreover, iDSA enables the reversible formation of seven different nanostructures from one sphere-forming BCP, demonstrating the outstanding controllability of this self-assembly route.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-10/nn504995c/production/images/medium/nn-2014-04995c_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn504995c'>ACS Electronic Supporting Info</A></P>
Enhancing the Directed Self-assembly Kinetics of Block Copolymers Using Binary Solvent Mixtures
Park, Woon Ik,Choi, Young Joong,Yun, Je Moon,Hong, Suck Won,Jung, Yeon Sik,Kim, Kwang Ho American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.46
<P>The rapid pattern formation of well-ordered block copolymer (BCP) nanostructures is practical for next-generation nanolithography applications. However, there remain critical hurdles to achieve the rapid self-assembly of BCPs with a high Flory–Huggins interaction parameter (χ), owing to their slow kinetics. In this article, we report that a binary solvent vapor annealing methodology can significantly accelerate the self-assembly kinetics of poly(dimethylsiloxane-<I>b</I>-styrene) (PDMS-<I>b</I>-PS) BCPs with a high-χ. In particular, we systemically analyzed the effects of the mixing ratio of a binary solvent composed of a PDMS-selective solvent (heptane) and a PS-selective solvent (toluene), showing an ultrafast self-assembly time (≤1 min) to obtain a well-ordered nanostructure. Moreover, we successfully accomplished extremely fast generation of sub-20 nm dot patterns within an annealing time of 10 s in a 300 nm-wide trench by means of binary solvent annealing. We believe that these results are also applicable to other solvent-based annealing systems of BCPs and that they will contribute to the realization of next-generation ultrafine lithography applications.</P><P>An extremely fast pattern generation (∼10 s) of PDMS-<I>b</I>-PS BCP with sub-20 nm was successfully accomplished by employing a binary solvent of PDMS-preferential (heptane) and PS-preferential (toluene). Furthermore, the use of binary solvent can also induce excellent tunability of the pattern size and period of BCPs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-46/acsami.5b08162/production/images/medium/am-2015-081629_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b08162'>ACS Electronic Supporting Info</A></P>
Park, Woon Ik,You, Byoung Kuk,Mun, Beom Ho,Seo, Hyeon Kook,Lee, Jeong Yong,Hosaka, Sumio,Yin, You,Ross, C. A.,Lee, Keon Jae,Jung, Yeon Sik American Chemical Society 2013 ACS NANO Vol.7 No.3
<P>Phase change memory (PCM), which exploits the phase change behavior of chalcogenide materials, affords tremendous advantages over conventional solid-state memory due to its nonvolatility, high speed, and scalability. However, high power consumption of PCM poses a critical challenge and has been the most significant obstacle to its widespread commercialization. Here, we present a novel approach based on the self-assembly of a block copolymer (BCP) to form a thin nanostructured SiO<SUB><I>x</I></SUB> layer that locally blocks the contact between a heater electrode and a phase change material. The writing current is decreased 5-fold (corresponding to a power reduction by 1/20) as the occupying area fraction of SiO<SUB><I>x</I></SUB> nanostructures is increased from a fill factor of 9.1% to 63.6%. Simulation results theoretically explain the current reduction mechanism by localized switching of BCP-blocked phase change materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-3/nn4000176/production/images/medium/nn-2013-000176_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn4000176'>ACS Electronic Supporting Info</A></P>
Park, Woon Ik,Kim, Jong Min,Jeong, Jae Won,Hur, Yoon Hyoung,Choi, Young Joong,Kwon, Se-Hun,Hong, Seungbum,Yin, You,Jung, Yeon Sik,Kim, Kwang Ho American Chemical Society 2015 Chemistry of materials Vol.27 No.7
<P>Phase change memory (PCM) is one of the most promising candidates for next-generation nonvolatile memory devices because of its high speed, excellent reliability, and outstanding scalability. However, the high switching current of PCM devices has been a critical hurdle to realize low-power operation. Although one solution is to reduce the switching volume of the memory, the resolution limit of photolithography hinders further miniaturization of device dimensions. In this study, we employed unconventional self-assembly geometries obtained from blends of block copolymers (BCPs) to form ring-shaped hollow PCM nanostructures with an ultrasmall contact area between a phase-change material (Ge<SUB>2</SUB>Sb<SUB>2</SUB>Te<SUB>5</SUB>) and a heater (TiN) electrode. The high-density (approximately 0.1 terabits per square inch) PCM nanoring arrays showed extremely small switching current of 2–3 μA. Furthermore, the relatively small reset current of the ring-shaped PCM compared to the pillar-shaped devices is attributed to smaller switching volume, which is well supported by electro-thermal simulation results. This approach may also be extended to other nonvolatile memory device applications such as resistive switching memory and magnetic storage devices, where the control of nanoscale geometry can significantly affect device performances.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-7/acs.chemmater.5b00542/production/images/medium/cm-2015-005424_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b00542'>ACS Electronic Supporting Info</A></P>
A Gateway to Effectiveness in Translation Class : Flip Classes
Cho Woon ik 한국통번역교육학회 2017 통번역교육연구 Vol.15 No.1
Currently, as digital natives are enrolling in universities, the teaching and learning environment is naturally flowing toward this new methodology. Such a methodology requires us to take deep considerations, and its possibility for success lies in cooperation between students and teachers. Different from the traditional translation class, this methodology can flip previous teacher-led classes. To conduct this flipped translation class successfully, three major stages should be created: Provide prior knowledge to students before the class, usually consisting of audiovisual teaching and learning materials uploaded onto the e-class/website; prepare a variety of class activities or peer group reviewing sessions; and assign students with after-class activities, possibly conducted among peer groups.