• Title/Summary/Keyword: 열분석적 특성

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Replication Characteristics of Micropatterns According to Mold Temperature in Ultrasonic Imprinting (초음파 임프린팅에서 금형온도에 따른 미세패턴의 전사특성 연구)

  • Min, Kyeong Bin;Park, Jong Han;Park, Chang Yong;Park, Keun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.1
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    • pp.51-57
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    • 2014
  • Ultrasonic imprinting is a novel process for replicating micropatterns on thermoplastic polymer substrates with low energy consumption and short cycle time. The polymer substrate is softened by the frictional heat and repetitive deformation energy under ultrasonic excitation; thus, a number of micropatterns are replicated on the softened polymer substrate. In the present work, the effect of mold temperature on the replication characteristics of ultrasonic imprinting is investigated. The temperature change in the patterned region is measured by varying the mold temperature. Numerical simulation is then performed for investigating pattern replication characteristics under various mold temperatures. In addition, pattern replication ratio and uniformity are compared through various experimental measurements. Through the results of these comparisons, it is found that the mold temperature has a significant positive effect on the replication characteristics of ultrasonic imprinting.

이중 발광층을 가진 청색 유기발광소자의 발광효율 증가 메커니즘

  • Park, Seong-Jun;Jeon, Yeong-Pyo;Kim, Tae-Hwan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.479-479
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    • 2012
  • 유기발광소자는 낮은 구동전압, 저전력, 높은 명암비, 빠른 응답속도, 넓은 시야각 및 높은 박막의 특성을 가지고 있어서 차세대 평판 패널디스플레이 기술로 각광받고 있다. 하지만 청색 유기발광소자는 적색과 녹색 유기발광소자에 비해 낮은 신뢰성, 발광효율 및 색 순도의 문제점을 가지고 있어, 이를 개선하기 위한 연구가 다양하게 연구되고 있다. 청색 유기발광소자의 경우 발광층 내부로 주입되는 정공과 전자의 균형을 조절하기 위해 p-i-n 구조를 사용하거나 이리듐-유기물 합성물과 같은 인광물질의 적용하여 발광효율을 높이는 청색 유기발광소자에 대한 연구가 진행되고 있다. 하지만 정공 보조층과 청색 형광층의 도핑구조의 청색 유기발광소자에 대한 발광효율 증가 메커니즘에 관한 연구는 비교적 많이 이루어지지 않았다. 본 연구에서는 열 증착 방법을 이용하여 정공 보조층과 청색 형광층으로 구성된 이중 발광층을 사용한 청색유기발광소자의 발광효율 증가 메커니즘에 대해 연구하였다. 10%의 2,9-dimethyl-4,7-diphenyl-1,10-phenanthorlene (BCP)로 도핑된 2-methyl-9,10-bis(naphthalene-2-yl)anthracene (MADN)층을 발광층으로 사용한 유기발광소자, 5% MADN으로 도핑된 1, 3-bis(carbazol-9-yl)benzene (mCP) 층을 발광층으로 사용한 소자 및 10% BCP로 도핑 된 MADN 층과 5% MADN로 도핑 된 mCP층을 혼합하여 발광층으로 사용한 소자의 전류밀도-전압-발광 특성을 비교하여 청색 유기발광소자의 발광효율 증가 메커니즘을 분석하였다. 이중 발광층을 가지는 소자는 두 단일 발광층 중심부의 경계면에서 축적된 정공에 의해 발생한 쿨롱 인력으로 더 많은 전자들을 끌어들이게 되어 엑시톤 형성 및 빛 방출이 증가하였다. 이 실험의 결과는 MADN 형광물질을 가진 청색 유기발광소자의 발광효율 증가 메커니즘에 대한 이해를 높이는데 도움을 줄 수 있다.

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Fabrication and analysis of luminous properties of ceramic phosphor plate for high-power LED (High-power LED용 ceramic 형광체 plate 제조 및 발광 특성 분석)

  • Ji, Eun-Kyung;Song, Ye-Lim;Lee, Min-Ji;Song, Young-Hyun;Yoon, Dae-Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.25 no.1
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    • pp.35-38
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    • 2015
  • LEDs are considered to be an alternative for enhancement of energy efficiency, applied for numerous areas such as display, automotive headlight not only lights. Yellow phosphor is generally utilized with blue LEDs to generate WLED, $Y_3Al_{5}O_{12}:Ce^{3+}$ is typically used as the yellow phosphor. The phosphor, mixed with epoxy resin, has been used by being spread and hardened on the blue LED chip. This paste-based packaging gives rise to problems of degradation of phosphor by heat and decrease of luminous efficiency. Although phosphor plate is used instead of the epoxy-phosphor mixture to solve these problems, loss of luminous efficacy by total internal reflection inside the plate also should be solved. In this study, we coated the side of the plate with silver as one of the solution.

Basic Experimental Study on the Application of Biofuel to a Diesel Engine (바이오연료의 엔진 적용을 위한 실험적 기초연구)

  • Yeom, Jeong-Kuk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.11
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    • pp.1163-1168
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    • 2011
  • Compared with the spark-ignition gasoline engine, the compression-ignition diesel engine has reduced fuel consumption due to its higher thermal efficiency. In addition, this reduction in the fuel consumption also leads to a reduction in $CO_2$ emission. Diesel engines do not require spark-ignition systems, which makes them less technically complex. Thus, diesel engines are very suitable target engines for using biofuels with high cetane numbers. In this study, the spray characteristics of biofuels such as vegetable jatropha oil and soybean oil were analyzed and compared with those of diesel oil. The injection pressures and blend ratios of jatropha oil and diesel oil (BD3, BD5, and BD20) were used as the main parameters. The injection pressures were set to 500, 1000, 1500, and 1600 bar. The injection duration was set to $500{\mu}s$. Consequently, it was found that there is no significant difference in the characteristics of the spray behavior (spray angle) in response to changes in the blend ratio of the biodiesel or changes in the injection pressure. However, at higher injection pressures, the spray angle decreased slightly.

A Study on the molecular structure and molecular weight control of styrene films by plasma polymerization (플라즈마 중합법에 의한 스티렌 박막의 분자 구조 및 분자량 제어에 관한 연구)

  • 김종택;최충양;박종관;박응춘;이덕출
    • Journal of the Korean Vacuum Society
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    • v.6 no.3
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    • pp.213-219
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    • 1997
  • The plasma polymerized styrene films were prepared by using an inter-electrode capacitively coupled gas-flow-type reactor, and the effects of plasma polymerization condition on the molecular weight distribution were investigated by Fourier Transform Infrared (FT-IR), Pyrolysis Gas Chromatography(PyGC), Differential Scanning Calorimetry(DSC) and Gel Permeation Chromatography(GPC). From the above results, the very cross-linked films different from chemical characteristics of the starting monomer were taken out, and it is realized that the molecular structure, cross linking density, and molecular weight distribution could be controlled by changing the parameters such as deposition pressure, deposition power and gas flow rate. Accordingly, it is suggested that plasma polymerization method performed by inter-electrode capacitively coupled gas-flow-type reactor has good characteristics for manufacturing the functional organic thin films which can be applied in sensors, opto-electric device, photo-resist by changing the polymerization parameters.

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Post-cure Condition of a Silicone Rubber Material for a LCD Lamp Holder (LCD 램프홀더용 실리콘고무재료의 후가교 조건)

  • Ahn, Won-Sool;Lee, Joon-Man
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.7
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    • pp.1661-1667
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    • 2009
  • Post-cure characteristics of a silicone rubber material which is widely used for a LCD lamp holder were investigated using thermogravimetric analysis (TGA). Research was especially focussed on searching for the optimum post-cure conditions in relation to the practical operation environments. The results showed that incipient volatile temperature(Ti) during the process was considered as the most important factor and, thereby, post-curing for 2hrs at $250^{\circ}C$seemed to be a reasonable condition in the practical view-point. Arrhenius plot of shift factors which were empirically determined from the time-temperature-superposition-principle showed good linearity, exhibiting the post-cure mechanism might be proceeded through single mechanism with activation energy of 108.25kJ/mol.

Preparation and Properties of Antimicrobial Zinc Alginate Films according to Solution Concentration (용액 농도에 따른 항균성 알긴산 아연 필름의 제조 및 그 특성)

  • Lee, Ju-Hyun;Seo, Hye-Jin;Son, Tae-Won;Lim, Hak-Sang
    • Polymer(Korea)
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    • v.37 no.6
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    • pp.677-684
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    • 2013
  • Zinc alginate films were prepared by a film maker from sodium alginate solutions of different weight ratios and then they solidified into 3 wt% content $ZnCl_2$ coagulation solution and washed and dried at a $60^{\circ}C$ oven for 20 min. The characteristics were measured by several methods (antimicrobial activity, viscosity, FTIR, TGA, SEM, EDS, contact angle, tensile strength and solubility) and the film properties were investigated. The antimicrobial test showed that the zinc alginate films result in excellent antimicrobial activity in the two strains (Klebsiella pneumonia, Staphylococcus). The surface of zinc alginate film from the solution of 9 wt% sodium alginate showed more uniform shape than any other films and the cross-section were hard and rough when the films were well-solidified by the $ZnCl_2$ solution. The tensile strength of zinc alginate films increased along with the concentration of sodium alginate solution due to the cross-linking, and the initial thermal decomposition temperature increased gradually.

A Study on the Comparison of Explosive Lower Limit Concentration & Thermal Specific of Wheat Powder Dust & Salicylic Acid Dust (밀가루분진 및 살리실산분진의 폭발하한농도 및 열적특성 비교에 관한 연구)

  • Ko, Jae-Sun
    • Fire Science and Engineering
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    • v.26 no.4
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    • pp.1-9
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    • 2012
  • We have examined In order to compare each other from explosion and combustion characteristics about the dusts which collects from manufacturing process of wheat flour and cosmetics manufacturing process of functional Keratin removal soap at the small and medium enterprise style. We measured explosive pressure and explosive lower limit which follows in change of concentration change at the time of talc addition uses Hartman dust explosion apparatus, also measured weight loss and endothermic quantity uses DSC and TGA. The explosion test results show that increased explosive lower limit concentration and explosive pressure decreased by the increased ratio of the talc dust. And the DSC results show that heat flux and temperature decreased by the increased ratio of the talc dust. Also increased in raising temperature causes initial smoldering temperature to move towards low temperature section and the endothermic quantity increased on a large scale. Together the TGA results show that weight loss decreased by the increased ratio of the talc dust. From this research we have assured the successive dust explosion mechanism study will play a key role as a significant safety securing guideline against the dust explosion.

Synthesis and Characterization of Wholly Aromatic Polyester Liquid Crystalline Thermosets (전방향족 폴리에스터 열경화성 액정의 합성과 특성)

  • Moon, Hyun-Gon;Jung, Myung-Sup;Chang, Jin-Hae
    • Polymer(Korea)
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    • v.36 no.1
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    • pp.9-15
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    • 2012
  • We prepared a series of aromatic liquid crystals (LCs) based on wholly aromatic ester units with the reactive end group methyl maleimide by means of melt condensation method, and the resulting LCs were thermally crosslinked to produce liquid crystalline thermoset (LCT) films. The synthesized LCs and LCTs were characterized with Fourier transform infrared (FTIR) spectroscopy, wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomechanical analysis (TMA), and polarizing optical microscopy (POM) with a hot stage. The glass transition temperature ($T_g$) and coefficient of thermal expansion are strongly affected by the mesogen units in their main chain structures. The $p$-substituted biphenyl LC was found to have the highest thermal property value.

Controlling Factors of Open-Loop Combustion Response to Acoustic Pressures in Liquid Propellant Rocket Engine (강한 압력파동에 구속된 액체 추진제 연소응답의 지배인자)

  • Yoon Woongsup;Lee Gilyong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.10a
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    • pp.267-273
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    • 2004
  • This paper targets to define controlling factors of pressure-coupled combustion response and estimate their effects on droplet evaporation process. Dynamic characteristics of hydrocarbon propellant vaporization perturbed by acoustic pressure are numerically simulated and analyzed. 1-D droplet model including phase equilibrium between two phases is applied and acoustic wave is expressed by harmonic function. Effects of various design factors and acoustic pressure on combustion response are investigated with parametric studies. Results show that driving frequency of acoustic perturbation and ambient pressure have important roles in determining magnitude and phase of combustion response. On the other hand, other parameters such as gas temperature, initial droplet size and temperature, and amplitude of acoustic wave cause only minor changes to magnitude of combustion response. Resultant changes in phase of heat of vaporization and thermal wave in droplet highly influence magnitude and phase of combustion response.

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